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A S I A P A C I F I CVol 57 No 1 March 2011

CASTING TECHNOLOGIES

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METAL Casting Technologies March 2011 1

18

CONTENTS

2216

06 EDITORIAL

10 BRIEFINGS

22 FEATURE STORY Sheet metal mould casting process – a new approach to produce castings By Dr P.C. Maity

28 TECHNICAL FEATURE Fatigue in metal castings By John Pearce

34 TECHNICAL FEATURE Foundry processing of aluminium chips by Electroslag Remelting By Amit M. Joshi

39 MCT MAGAZINE – PUBLICATION DEADLINES

40 FORTHCOMING EVENTS

42 BACK TO BASICS The effects of common elements in ductile iron By Jeff F. Meredith

46 BACK TO FLOOR Safety in induction furnace operations By Prof. John H. D. Bautista

48 WEBSITE SHOWCASE

PRINT + ONLINE EDITIONSEXCLUSIVE EMAIL BROADCASTS

POWERFULINTEGRATEDMEDIA

PLATFORM

2 www.metals.rala.com.au

Jimmy Loke Yoon CheeDirector, Yoonsteel Foundry MalaysiaRepresentative of FOMFEIA

Mr Gopal RamaswamiNational Secretary of the Institute of Indian Foundrymen, IndiaEmail: [email protected]

Jack FrostWorld Consulting Specialist Foundry Process [email protected]

Mr Zhang LiboExecutive Vice PresidentChina Foundry [email protected]

Mr Seksan TangkoblabPresident Thai Foundrymen’s Society

Dr John PearceMetals SpecialistMTEC National Metals and MaterialsTechnology Centre, Thailand

Industry AssociationsAustralian Foundry InstituteSouth Australia: The Secretary, PO Box 288, North Adelaide SA 5006Western Australia: The Secretary,[email protected] South Wales: The Secretary, Locked Bag 30, Bankstown NSW 2200, [email protected]: C/- PO Box 89, Acacia Ridge QLD 4110Victoria: PO Box 4284, Dandenong South VIC 3164

Casting Technology New Zealand Inc.PO Box 1925, Wellington, New ZealandTel: +64 4 496 6555, Fax: +64 4 496 6550

China Foundry Association3rd Floor, A-32 Zizhuyuan RdHaidian District, Beijing 100048, CHINATel: +86 10 6841 8899 Fax: +86 10 6845 8356Web: www.foundry-china.com

Federation of Malaysia Foundry & Engineering Industries Association(FOMFEIA), 8 Jalan 1/77B, Off Jalan Changi at Thambi Dollah 55100,Kuala Lumpur, MalaysiaTel: +603 241 8843, Fax: +603 242 1384

Institute of Indian FoundrymenIIF Center, 335 Rajdanga Main Road, East Kolkata Township P.O.Kolkata - 700107 IndiaTel: +91 33 2442 4489, +91 33 2442 6825Fax: +91 33 2442 4491

Japanese Association of Casting TechnologyNoboru Hatano, Technical Director, JACT,Nakamura Bldg, 9-13, 5-chome, Ginza,Chuo-ku, Tokyo, 104 JapanTel: +81 3 3572 6824, Fax: +81 3 3575 4818

Metalworking Industries Association of the Philippines Inc.Pacificador Directo, National President, MIAP, No. 55 Kanlaon St, Mandaluyong,1501 Metro Manila, PhilippinesTel: +632 775 391, Fax: +632 700 413

Philippine Iron & Steel Institute(PISI), Room 518, 5th Floor, Ortigas Building, Ortigas Avenue, Pasig, Metro ManilaTel: +632 631 3065, Fax: +632 631 5781

Philippine Metalcasting Association Inc.(PMAI), 1135 EDSA, Balintawak, Quezon City Metro Manila, PhilippinesTel: +632 352 287, Fax: +632 351 7590

South East Asian Iron & Steel Institute2E 5th Floor Block 2, Worldwide Business ParkJalan Tinju 13/50, 40675 Shah Alam, Selangor MalaysiaTel: +603 5519 1102, Fax: +603 5519 1159, Email: [email protected]

Thai Foundry Association86/8 1st Floor BSID BuildingBureau of Supporting Industries Development Soi Trimitr, Rama IV Road,Klongtoey, Bangkok 10110, ThailandTel: +662 712 2391, Fax: +662 712 2392www.thaifoundry.com

The Materials Process Technology CenterJapan. Kikai Shinko Bldg,3-5-8 Shiba-Koen, Minato-ku, Tokyo, 105 JapanTel: +81 3 3434 3907, Fax: +81 3 3434 3698

Publisher & Managing EditorBarbara CailEmail: [email protected]

Research and Technical Contributor Adjunct Professor Ralph TobiasEmail: [email protected]

Advertising and Production – GeneralAdam CailEmail: [email protected]

Advertising and Production – ChinaMs. Angela JiangTel: +86 15 801 748 090Email: [email protected]

Editorial and SubscriptionsMelinda CailEmail: [email protected]

Accounts PayableCheryl Welsh Email: [email protected]

DesignCraig O’NeillEmail: [email protected]

SUBSCRIPTION RATESAustralia $AUD 99.65 (Includes GST) Overseas $AUD 125.40 (Includes Mailing)

Published by RALA Information ServicesPostal: PO Box 134, Balmain

NSW 2041, AustraliaStreet: Rear of 205 Darling St, Balmain

NSW 2041, Australia (enter via Queens Place)

Phone: +61 2 9555 1944Fax: +61 2 9555 1496Web: www.metals.rala.com.au

Metal Casting Technologies is a technically based publication specifically for the Asia Pacific Region.The circulation reaches:• Foundries• Diecasters• Iron and steel mills• Testing labs• Planners & Designers – CIM-CAD-CAM

The Publisher reserves the right to alter or omit any article or advertisement submitted and requires indemnity from the advertisers and contributors against damages or liabilities that may arise from material published.

Copyright – No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without permission of the publisher.

Front Cover: SPECTRO Analytical Instruments GmbH. For further information see pages 4 and 5.

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powder or solution, with its unique product range of mobile and stationary metal analyzers, ICP and ICP-MS spectrometers as well as and X-ray fluorescence spectrometers, SPECTRO offers the optimum solution for any application. The smallest system barely weighs one kilogram while the largest fills a whole laboratory. All systems, however, are based on the most innovative technology, strictly geared towards specific user requirements, optimum configuration for the respective task and the worldwide recognized reliability that has made SPECTRO the leading supplier in the field of elemental analysis.

Mobile Metal Analyzers - MMAScrap sorting of production materials, identification of semi-finished products during processing and material testing of finished products are just some of the typical applications for SPECTRO portable and mobile metal analyzers. The applications are manifold: Pipes, forged parts, rods, valves, welds, containers and many other sample types can be tested both easily and effectively. Whether in production workshops, external stores, in places difficult to access or on components already mounted in industrial installations, the mobility of SPECTRO industrial spectrometers knows no limits. The range of SPECTRO portable and mobile metal analyzers extends from the small hand-held spectrometer weighting only one kilogram through to multi-matrix devices with on-site analysis performance features that are otherwise the realm of pure laboratory instruments.

Stationary Metal Analyzers - SMAStationary metal analyzers from SPECTRO are used wherever precision analysis of the chemical composition of metallic materials is required.

In all sectors of the metal producing and processing industry these analyzers control the alloying processes, monitor metal quality and rule out the use of incorrect materials and consequently the resulting production downtimes and safety risks.

XRF SpectrometersEnergy-dispersive X-ray fluorescence analysis technology is one of the simplest yet most efficient and economical analysis methods. With SPECTRO’s polarization technology it is also one of the most versatile and precise methods. Whether dealing with waste at an incinerator, raw materials in incoming goods inspection, petrochemical, chemical and pharmaceutical intermediate and finished products in manufacturing processes, soils in nature conservation or rocks in geology – SPECTRO X-ray fluorescence spectrometers are suitable for many thousands of applications.

ICP SpectrometersThe ICP spectrometers from SPECTRO are characterized by excellent measurement accuracy, maximum sensitivity and a high degree of flexibility. They are predestined for trace and ultra-trace analysis of solutions in environmental applications, for comprehensive analysis of foodstuffs, petrochemical products and for the monitoring of innumerable manufacturing processes in the chemical and pharmaceutical industry.

ICP-Mass SpectrometersThe SPECTRO MS is the first fully simultaneous measuring mass spectrometer with inductively coupled plasma in the world and offers a greatly increased sample throughput rate and much better precision and accuracy compared to sequential mass spectrometers. In addition to research laboratories, it is attractive for environmental, chemical, pharmaceutical and geology laboratories as well as many other branches of industry.

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Elemental Analysis for Every ApplicationSPECTRO offers a full range of metal analyzers as well as ICP and XRF spectrometers

SPECTRO Analytical Instruments (Asia-Pacific) Ltd Unit 1603, 16/F., Tower III Enterprise Square No. 9 Sheung Yuet Road Kowloon Bay, Kowloon Hong Kong Tel: +852.2976.9162 Fax: +852.2976.9542 [email protected] www.spectro.com

SPECTRO is one of the worldwide leading suppliers of analytical instruments for optical emission, ICP-mass and X-ray fluorescence spectrometry. As a member of the AMETEK Materials Analysis Division, SPECTRO manufactures advanced instruments, develops the best solutions for strongly varying applications and provides exemplary customer service. Innovation, instrument concerns and customer relations are its main activities. From its foundation in 1979 until today, more than 30,000 analytical instruments have been delivered to customers around the world.

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Please visit us at:Intermold Korea 2011, 16-20 March, Busan, KoreaAnalytica Vietnam 2011, 7-9 April, Ho Chi Minh City, VietnamShenyang Machine Tool and Mould Exhibition 2011, 25-27 April, Shenyang, ChinaNational Manufacturing Week 2011, 11 May, NSW, AustraliaBUTECH 2011, 25-29 May, Busan, Korea


The electric car is becoming inevitable

n this first edition of Metal Casting Technologies for 2011 it has a “technology” theme. In the process of my research for this column I finally decided that, once more, the Electric Vehicle is

claiming the high ground in driving new technologies: particularly battery technologies. How will this new world of electric vehicles impact on metal casters?

We are looking at a runway of 20-30 years for massive uptake of electric vehicles because their effectiveness and value will be dependent, mainly on a huge futuristic leap in battery technology. And, of course there are other technologies on the research agendas: fuel cell, hydrogen etc. It is therefore vital that this transitioning process to a new world order for cars enables the metal casters to be part of it and find their place within this new technology. The petrol engine and its attendant back-up systems have been the domain of the metal casting industry for most of last century and will remain so until the EV’s prove their place. But metal casters need to know how their role can capitalise and evolve at the same pace. There is no doubt that nearly every major automaker has an active program to develop and introduce EV’s.

As well as gearing up to training engineering graduates to meet the demand for extra engineering on EV’s, President Obama, in his 2011 State of the Union address, set a goal of one million electric vehicles to be on the road in the US by 2015.

The aim is to build U.S. leadership in technologies that reduce dependence on oil, enhance environmental stewardship, and promote transportation sustainability, while creating high quality jobs and economic growth. The million EV’s would include plug-in hybrids, extended range electric vehicles, and all-electric vehicles.

To reach this goal, President Obama has proposed to further support EV manufacturing by revised tax incentives plus greater research and development, investments, and programs to encourage communities to invest in infrastructure for EV’s. To further reinforce this vision, up to $5 million in funding has immediately been provided to support Graduate Automotive Technology Education (GATE) Centres of Excellence. The GATE Centres will focus on educating a future workforce of automotive

Barbara Cail

CON

TRIB

UTO

RS EDITORIAL

I

JOHN HERMES D. BAUTISTAPMAI Technical Consultant

DR. P. C. MAITYDr. P. C. Maity, Metal Casting and Materials Engineer

GOPAL PADKIGopal Padki is a senior executive member of HA in China. HA is committed to green, environment and energy efficient processes for the best performance of foundries worldwide.

JEFF F. MEREDITHCasting Solutions Pty Ltd

JOHN PEARCEMetals Specialist, MTEC National Metals and Materials Technology Centre, Thailand

engineering professionals who will gain experience in developing and commercialising advanced automotive technologies.

While all this visionary activity is gathering pace in the US, and boosted by tax incentives and other favorable policies, China’s auto market grew rapidly in the past two years and overtook United States to become the world’s largest auto market by selling 13.65 million vehicles, up 46 percent year-on-year. When the figures are finally analysed, China’s auto sales are expected to hit 18 million units for the year ended 2010 because the January to November sales reached 16.4 million. And China’s vision is firmly focused on the EV market for their own as well as the export market. As always, critical mass provides impetus and China is showing no signs of easing off in achieving full traction on the global EV market.

In our news section in this edition you will read about the fast emerging battery technology and, of course, the speed of its development will underpin and reinforce the race to the production of EV’s. However, all this news is about the manufacture of electric cars. There doesn’t seem to be too much real market analysis of who is going to buy them.

Many reports claim that consumers are ready for a change. The rationale being that high and rising oil prices have made them increasingly aware of the negative consequences of dependence on imported oil: economic instability at home and threats to global security (oil supply) abroad. This is combined with growing awareness of the environmental damage of oil dependency, including oil spills, air pollution and increased CO2 emissions that contribute to climate change.

And to further enhance the consumer’s case, the clear indication is that battery technology has improved dramatically, with significantly increased life spans and at the same time the cost is falling. The new lithium-ion battery chemistries are environmentally friendly, safe and more than 95% recyclable.

And a further claim to consumer’s likely take up of the EV’s is the emerging market for electric car infrastructure companies. They have emerged to ensure that electric cars can stay charged and on the road. And there is no doubt that governments around the world have got behind the transition to electric cars. They have set targets for production of electric cars and batteries, funded research and trials and are offering significant consumer incentives for early adopters. Capital markets have followed, investing billions of dollars in existing and new car, battery and infrastructure companies, creating thousands of jobs and new growth opportunities. So, the electric car is becoming inevitable.

What will metal caster’s role be in this rapidly emerging world? I would welcome some feedback on how the development of the electric vehicle impacts the market for metal casting technologies. I invite a discussion paper/s on this topic to be published in the next edition?

Please enjoy this edition.

Barbara Cail

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BRIEFINGS

China’s plan to control the electric car industry – battery technology

One of the great economic and technological battles over coming decades will be fought out in the area of battery technology. Batteries haven’t really changed much in decades. And it’s the limitations of the lithium-ion battery which many people believe has prevented the car industry’s move away from the combustion engine and all its related environmental problems.

China has made a commitment to the development of advanced batteries and the creation of an electric car industry. It wants to control the global electric car industry, and is in the process of rolling out 500,000 electric cars over the next two years.

Mr Steve Levine a contributing editor for the prestigious magazine Foreign Policy has written a story for that publication entitled ‘The Great Battery Race’. The story is about the quest to develop the next form of battery technology a race he says already involves many nations - South Korea and Japan for example - but which will ultimately be dominated and defined by the US-China rivalry.

Steve Levine claims that we’re not talking about something that’s happening in the next five years, we’re talking about a two-decade long runway. The outcome of this race, of the advanced battery race, and the enabling technologies - that’s the enabling technology for other big products like electric cars, “We’re talking the big hit in the late 2020s and the 2030s. And so what we are talking about is Advanced batteries, when they really hit their stride, they are going to be an industry the size of Exxon, of General Electric. This is going to be an economy-making industry of electric cars; the projection is that you’re going to have four or five companies the size of Exxon.”

How can the US compete against China in battery technology?This future scenario demands that the US sit up and take notice. It no longer has the sort of manufacturing base that it once had, that China now has, to support the development of advanced batteries. So the United States is at a serious disadvantage. However, it’s attempting to create some kind of a wedge in which it can compete in this field. Obama has put $2.4-billion into the creation of an advanced battery industry, but the US is very late and experts think that it really has got its work cut out. But this is where another idea comes into play, and that is, what can the United States do in order to get into this game in a big way?

Who are the big players? While Japan is a big player South Korea is going extremely big into advanced batteries. It has a manufacturing base and has an established learning curve. Interestingly, when Obama was handing out the $2.4-billion, the biggest single piece of it did not go to an American advanced battery maker, it went to a Korean L.G. A South Korean company was given $400-million to establish an advanced battery plant near Detroit for the Chevy Volt, and the smart thinking seems to be that what the United States will continue to do, is form a strategic partnership with South Korea. It will bring South Korean companies into the United States use US know-how, South Korean manufacturing, and suddenly they are in the game.

The observation is that the Japanese, when they’re working with other countries in the lab, they’re more takers than givers. As a rule, says Steve Levine, they want to collaborate up to a point, and at that point they go home and make it themselves. The South Koreans are very collaborative, it turns out. South Koreans aren’t trying to control everything, they simply want

to come into your market and make the product. So according to the labs, South Korea is seen as being an ideal strategic partner.This story is an extract from the recent article which Steve Levine wrote for the Foreign Policy magazine entitled The Great Battery Race. He is the author of The Oil and the Glory, a history of oil told through the 1990s-2000s oil rush on the Caspian Sea. He is also an adjunct professor at the Georgetown University School of Foreign Service, where he teaches energy and security in the Security Studies Program.

Thai auto-makers expected to export one million units in 2011Vehicle production in Thailand leapt to a record 1.65 million units in 2010, an increase of 64% over 2009. Thailand is now the 13th largest auto-maker in the world and has a current production capacity of nearly 2 million. During 2011production is expected to increase by around 9-10% over the 2010 level to 1.8 million vehicles, with at least 1 million of these to be exported. Exports in 2010 were a record 895,855 units, some 54% of total output, with just over 30% exported to countries in Asia. Toyota Motors Thailand, Mitsubishi, Honda, Ford and Mazda have all announced increases in investment and production capacity for these plants in Thailand. Sales of fuel efficient eco-cars such as the Nissan March, Honda Brio, Mazda 2 and Ford Fiesta have all showed rapid growth. Honda has built a new plant to build 240,000 Brios per year. Ford is building a new plant to produce the Focus in 2012. Toyota is to increase pick-up production at its Chachoengsao plant from 140,000 to 220,000 by August 2011.

Production of motor cycles in Thailand increased by 24% in 2010 with over 2 million complete units and assembly kits. Exports of complete motorcycles are expected to increase to 2.2 million units, a 9% increase.

According to the Thai Automotive Institute the automotive industry in Thailand employed 520,000 people in

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BRIEFINGS

2010 and this number needs to increase by 200,000 if the industry is to raise its production to 2.5 million vehicles per year. Shortages of skilled labour has been one of the concerns raised by car producers on the eastern seaboard such that both engineering craft and technician training in automotive and related supply industry, especially foundries, needs to be expanded and improved. Other concerns include the need to improve the road and communication infrastructure in Rayong province and for the vehicle excise tax structure to be overhauled such that the tax system was based on fuel economy and emissions.

Demand from the automotive industry, and from the electrical appliance & machine producers and construction, lead to a 40% increase in the steel market in Thailand during 2010 compared to 2009. The Iron & Steel Institute of Thailand has recommended that Thailand should set up co-operative steel production in nearby Myanmar or Cambodia or establish an eco-steel producing town in the south of Thailand. To date plans to develop liquid steel production in Thailand have drawn considerable opposition from Thai environmental groups.

CSIRO’s Simon McKeon named Australian of the yearCSIRO Chairman Simon McKeon was named Australian of the Year 2011 at a ceremony outside Parliament House in Canberra on Australia Day, 25 January 2011.

He was congratulated by Innovation Minister Senator Kim Carr who said. “I am delighted that Mr McKeon has been recognised for his contribution to Australia,”

“In his role as Chairman of the CSIRO, Mr McKeon plays a vital role in Australia’s scientific future and I am pleased to have the privilege to see firsthand his passion and commitment

to improving our country.”The Australian of the Year awards

recognises remarkable Australians who, through their actions and the way they lead their day to day lives inspire us all.

For more information on the Australian of the Year Awards and the recipients, visit www.australianoftheyear.org.au

For more information about the CSIRO, visit www.csiro.au to search for the latest information on Metals technologies. A sample follows.

A new technology developed by CSIROThe premier research organisation in Australia is about to deliver major improvements to an age-old die-casting process, making HPDC cheaper and improving the quality of the end product.Casting costs cutThe new process, Advanced Thixotropic Metallurgy (ATM), takes a new approach to HPDC by using a revolutionary feed system for forcing metal into the dies.

It is particularly suited to aluminium and magnesium alloys.

ATM is about 10 per cent cheaper to operate than conventional HPDC and does not require major investment in new equipment. ATM has the potential to give Australian manufacturers a competitive edge against imports by producing higher quality products.

Mr Lyndon Joss, managing director of Melbourne-based Excel Pacific Diecasting, says this is critical for local manufacturers. ‘Adopting best-practice die casting methods is crucial to the survival of die casting manufacturing in Australia. Using processes our grandfathers used and saying ‘that’ll be all right’ does not work anymore,’ says Mr Joss.A new feed approachConventional HPDC involves molten metal being forced into a cavity through small tunnels, or runners. During this

process, air can be trapped within the melt. This trapped air appears as porosity in the finished part and can be detrimental to its quality.

To exclude the worst of the affected metal and reduce porosity of the part, cavities usually have substantial overflow zones. Conventional feed systems can also contain pre-solidified grains that continue to grow while being forced into castings. Particularly large grains can seriously affect casting properties.

Dr Rob O’Donnell, project manager for ATM, says the feed system in the ATM process involves a radical redesign of the runners. This makes for a more uniform product with reduced porosity, and at a lower unit price than traditional casting.

The process has been in low-volume production since 2002. More than 15 manufacturers are now trialling the technology, and most are reporting immediate improvements.ATM advantagesATM has several advantages over traditional HPDC, including:● reduced rejection rates● reduced production time, which

lowers labour and machine costs● reduced wear on machines● negligible overflow zones, reducing

metal use and waste● more uniform distribution of

nucleation sites, leading to a more uniform product

● reduced energy costs, as less metal needs to be melted for casting, and dies do not need to be preheated to as high a temperature.According to Dr O’Donnell, ‘In a part

that normally costs one dollar, a die-caster can now save between 10 and 20 cents.’Low porosity also enables the end product to be heat-treated, which is impossible with conventional HPDC products. Heat treatments can significantly increase the metal’s pliability and can more than double product strength. This provides

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BRIEFINGS

the opportunity to manipulate the microstructure so that, where strength is critical, lighter parts can be designed to perform the same task. CSIRO is now introducing this development to component designers and showing them what can be done. It could mean thinner or lighter road wheels, for example.

Discover more about CSIRO’s work with Metals go to www.csiro.au/science/metals.html

Energy and the future of heat treatment and surface engineering Heat treatment and surface engineering needs energy: the IFHTSE Global 21 Project has shown that energy and environmental factors will significantly influence the future of heat treatment and surface engineering processes and that aside from governmental pressures most companies have a genuine interest in using less energy, producing less waste and being environmentally friendly.

Energy production needs heat treatment and surface engineering to ensure correct microstructures, properties and performance of parts and materials used in energy generating plants to give reliability and low maintenance.

Hence provisional plans are underway for a “1st International Conference on Energy and the Future of Heat Treatment and Surface Engineering” to be jointly organized by MTEC – the National Metals & Materials Centre in Thailand and IFHTSE – the International Federation for Heat Treatment & Surface Engineering and to be held during February 2012 in Bangkok.

The scope of the conference will include:● Energy management in heat

treatment and surface engineering● Heat treatment and surface

engineering in the manufacture of

clean mechanical energy generation and supply systems and in the processing of components needed for energy purposes.A recent 2010 IFHTSE meeting on

“Reduction of Energy Consumption in Heat and Thermo-mechanical Treatment Technologies and Installations” held in Brasov, Romania highlighted the need for a “first” international forum on this subject.

GIFA focus on energy efficiency and resource conservationIn view of global climate change, new approaches are called for in order to reduce the consumption of energy and natural resources. The GIFA/METEC/THERMPROCESS/NEWCAST trade fair quartet will be presenting especially sustainable innovations in the foundry industry within the new “ecoMetals” campaign. A special logo attracts visitors’ attention to the eco-eyecatchers.

When it comes to conserving raw materials, the foundry industry is a pioneer. More than 90 per cent of all the parts it produces are made by melting down scrap. At the four international trade fairs GIFA, METEC, THERMPROCESS and NEWCAST, Messe Düsseldorf is spotlighting the trend towards higher environmental awareness with the “ecoMetals” campaign. By participating in this initiative, exhibitors presenting substantially new developments in energy and resource efficiency from 28 June to 2 July 2011 will attract special attention – their exhibits and stands will be marked with the “ecoMetals” logo. Besides more efficient machines and systems, progressive processes and services are also needed. “All of the ecoMetals solutions being presented can claim to be groundbreaking in their respective markets, viable and sustainable,” says Friedrich-Georg Kehrer, Director of the trade fair quartet.

Bar set high“Demand for more energy-efficient products is a constantly recurring factor on the customer side as well,” says Kehrer. Resource-saving also pays off in terms of profitability, and manufacturers everywhere are therefore optimising their systems and processes – no matter whether their business is building energy-saving industrial furnaces, engineering new alloys, casting robust rotor hubs for wind-energy plants or designing rigid light-metal components for cars. “The economical use of energy and materials is becoming an increasingly important competitive factor,” says Max Schumacher, environment expert of the German Foundry Association (BDG). “The industry is part of the solution.”

One important building block for achieving climate protection is innovative light metals, such as those being researched at the Institute of Metallurgy of the Technical University of Clausthal. Lightweight constructions are becoming widespread in areas such as vehicle manufacture. At the same time, the power density of engines is increasing – and cast parts like cylinder heads are being designed with ever more complex geometries. “We are responding to these requirements by developing high-strength materials that cast well,” says Babette Tonn, professor of foundry technology.

Industrial furnaces, which are needed to manufacture and process metals, are also a focus of attention. 45 to 60 per cent of the overall costs for producing primary aluminium, for example, are accounted for by electricity. “If a furnace operator manages to cut electricity or gas consumption by ten per cent through intelligent upgrading of furnace controls, that can have a colossal impact on profitability,” says Heinz-Jürgen Büchner, an analyst at IKB Deutsche Industriebank.


Simulation technology avoids trial and errorSimulation techniques can also help to save energy. The Aachen-based company MAGMA Gießereitechnologie offers such software for simulating casting processes – and is presenting itself as a participant in the ecoMetals initiative. “Simulation makes it possible to design the casting technology to achieve the best results, both technically and economically,” says Jörg Sturm, head of sales and engineering at Magma. “This cuts expenditure in two areas – material input and smelting requirements.”

Materials research institutes get together in ThailandDuring November 2010 the National Metal and Materials Technology Center (MTEC) was the host for the 2nd Asia-Oceania Materials Research Institute Forum (WMRIF) at the Thailand Science Park near Bangkok. The delegates were executives from 11 leading material research institutes across 7 countries in the Asia-Oceania region, namely:● Central Iron and Steel Research

Institute (CISRI), China● Institute of Metal Research,

Chinese Academy of Sciences (IMR-CAS), China

● National Environmental Engineering Research Institute (NEERI), India

● Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), India

● National Research Institute for Materials Science (NIMS), Japan

● Korea Institute of Materials Science (KIMS), Korea

● Institute of Materials Research & Engineering (IMRE), Singapore

● Metal Industries Research & Development Centre (MIRDC), Taiwan

● Iron and Steel Institute of Thailand (ISIT), Thailand

● Metallurgy and Materials Science Research Institute (MMRI-CU), Thailand

● National Metal and Materials Technology Center (MTEC), ThailandThe main focus of the WMRIF is to

encourage international cooperation in materials research by bringing together research managers from the world’s leading materials research institutes to exchange information on research

priorities, management approaches and strategic directions. The Thailand meeting followed up on the progress of research collaboration in energy and environmental areas since the 1st Asia-Oceania WMRIF held in 2009.

Following presentations by each institute the main discussion

BRIEFINGS

“Ms. Seetala Jamrerkjang, MTEC International Officer, helps Prof. Hui-Ming Cheng, Deputy Director from IMR-CAS China Institute of Metal Research, Chinese Academy of Sciences to prepare his krathong”.

Dr. Dong Han, Vice President of CISRI, China Central Iron and Steel Research Institute, ready to honour the water spirits”.

Contact: (Mr.)Wu GuangChina Foundry AssociationAdd: A32#,Zizhuyuan Rd, Beijing, China Zipcode:100048T+8610-68418899 ext 665 T/F+8610-88514541Email: [email protected]

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BRIEFINGS

covered shared research experiences and preparation for the 4th WMRIF General Assembly meeting on “Materials Challenges for Safety and Reliability” which is due to be held in Shenyang, China from 22-26 May 2011. This event is being organized by the Institute of Materials Research, Chinese Academy of Sciences. Further details at http://english.www.imr.cas.cn

The conference was held during the Thai Loy Krathong festival in which, under the light of a full moon, small lotus shaped floats (krathongs) made of banana leaves decorated with flowers, incense sticks and candles are set afloat along waterways to honour the water spirits and to cleanse the mind of the previous year’s thoughts. The congress dinner was held on board a converted rice barge as it cruised on the river at Ayutthaya so that delegates could take part in this tradition. Ayutthaya was a fitting location since it was the capital of Thailand from 1350 to 1767 and was the first city in Thailand to develop as a centre for international exchange and trade, notably with Holland, Portugal, France and England.

$3.5M Green Car grant for cleaner LPG fuel systemAn innovative Melbourne company is developing a hi-tech new LPG liquid injection system for vehicles, thanks to a $3.54 million grant from the Australian Government.

The LPG Liquajet system will boost LPG power performance to match that of petrol-powered engines, whilst cutting average fuel costs by up to 50 per cent. It will lower the greenhouse gas emissions of individual vehicles by a minimum 10 per cent.

Liquajet’s developers, Alternative Fuel Innovations (AFI) Pty Ltd, will be supported through the Australian Government’s Green Car Innovation Fund.

Innovation Minister Senator Kim Carr said the Fund was equipping the Australian auto industry to compete in the carbon-constrained economy of the twenty-first century.

“Consumers in Australia and overseas are clearly looking for vehicles that are easier on the hip pocket and the environment. The Australian

Government is enabling firms like AFI to capitalise on that demand,’’ Senator Carr said.

“We are building high-wage, high-skill jobs in Australia, and making our manufacturers leading players in the global response to climate change.”

Senator Carr noted that the AFI project would facilitate wider uptake of the more environmentally friendly LPG as a fuel option.

“It is not only the big auto companies that are funded to achieve the objectives of A New Car Plan for a Greener Future,” he said.

“Our smaller companies and component producers have a role to play in making the world a more sustainable place for future generations.

“The Green Car Innovation Fund has already supported projects involving light-weight mirrors, more efficient batteries and better engine systems. Liquajet is another example of the incredible potential in our automotive sector.”

For more information on the Green Car Innovation Fund, visit www.ausindustry.gov.au, phone 13 28 46, or email [email protected]

Thailand Metallurgy Conference enjoys continued growthThe 4th Thailand Metallurgy Conference (TMETC4) was held from 17-19 November 2010 at the Greenery Resort in the Khao Yai National Park in Nakhon Ratchasima province. The conference was organized by the School of Metallurgical Engineering, Suranaree University of Technology with support from the Iron & Steel Institute of Thailand and MTEC - the National Metals & Materials Technology Centre plus a number of industrial sponsors. Seventy five oral papers were presented together with poster sessions. The main invited paper by Professors Gudenau and Senk from the Department of Ferrous Metallurgy at RWTH Aachen University, Germany Representatives of Asia-Oceania Research Institutes at the Thailand Science Park

BRIEFINGS

reviewed the “Evolution of Iron and Steelmaking and its Impacts on Global Environment”.

Since the first TMETC conference held in 2007 the event has grown steadily in terms of support and papers presented. Plans are well underway for TMETC5 with the theme “Metallurgy for Eco-Industry” which is scheduled

for 26-28 October 2011. This time the main organizer is the Dept. of Materials and Production Technology at King Mongkut’s University of Technology North Bangkok.

A number of awards for research achievement, technical performance and presentation were made during TMETC4. These included the Thailand

Metallurgy awards sponsored by Sahaviriya Steel Industry, the Thainox Stainless Steel awards, the Thai Tohken Thermo processing awards and the Thai Parkerising surface engineering prizes. The Thailand Metallurgist Award for 2010 was presented to Dr. Paritud Bhandhubanyong, Director of MTEC from 1999 to 2007 and currently Executive Director of the Technology Promotion Association (Thailand-Japan). Dr. Ekkarut Viyanit, leader of the research activities in corrosion and welding in the Materials Reliability Group at MTEC, received the Young Metallurgist Award for 2010.

TFA seminars at Metalex 2010 focus on pollution control and sand processesDuring the 24-27th November Metalex 2010 Trade Exhibition and Conference in Bangkok members of the Thai Foundry Association (TFA) attended seminars on air pollution and chemically bonded sands. Technical staff from Dantherm Filtration Thailand presented a session on Air Pollution Control for Manufacturing of Metal Castings covering general principles and pollution control systems with reference to a number of practical case studies. The basics of Furan No-bake and Alkaline Phenol sand processes together with a history of sand reclamation were covered by Mr. Yoshio Sato and Mr. Takeshi Nahayawa from Kao-Quaker.

The 2010 Metalex event, held at BITEC (Bangkok International Trade & Exhibition Centre), covered some 45,000m2 of exhibition space and was attended by around 66,000 visitors. The show covers a wide range of metal processing including metal working, foundry, welding, mould and die, machining, metrology, automation and handling, etc. Metalex 2011 is scheduled from 16-19 November 2011, again at BITEC. Further information at www.metalex.co.th ■

Dr. Paritud and Dr. Ekkarut with their Thailand Metallurgy awards at TMETC5

Dr. Ekkarut receives his Young Metallurgist 2010 award from Professor Prasart Suabka, Rector of Suranaree University of Technology


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SOLIDCast contains both Gating and Riser Design Wizards™, tools that allow you to rig new castings in just a few minutes, using actual simulation results, not guesses based on simple geometry. Since casting alloy, mold material and mold inserts are all considered, there is no more accurate way to rig a casting than with the Gating and Riser Design Wizards!

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SOLIDCast lets you see how your casting will solidify before you make patterns, dies and costly mistakes. Pour test castings on the computer, not the foundry floor! Design gating systems and test them out before making your first casting. Casting simulation helps you to shorten lead times, produce higher quality and improve yield. All of this means lower costs, higher profits and improved marketability for your foundry.

Optimization of casting process de-sign using SOLIDcast™ and HyperOpt®OPTICast™ is an amazing software tool that works in conjunction with the SOLIDCast™ solidification modeling system. OPTICast uses the HyperOpt® system from Altair Engineering, Inc., the leader in the field of optimization software.

What does OPTICast do?OPTICast actually automates the simulation process! Start with an initial design for a casting, with gating and risering, typically created in the SOLIDCast modeling system, using the Gating and Riser Design Wizards™. Then select the following elements:

Design Variables: Design elements that are allowed to vary. For example, the height and diameter of a riser. It could also be the metal pouring temperature, or the preheat temperature of an investment shell.

Constraints: Used to determine whether a particular design is acceptable. For example, the foundry engineer might specify a minimum acceptable yield percentage, or a maximum acceptable level of macroporosity.

The Objective Function: States what the foundry engineer is trying to achieve. Examples might be to maximize the yield, minimize shrinkage or minimize solidification time.

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Using OPTICast, the foundry engineer can start with an initial design and allow the computer to do the work of modifying the design and running simulations to achieve an optimum result.

Now the technology of automated design is brought to the foundry in the form of a practical and easy-to-use design tool. OPTICast can help you to improve your yield and your quality to an optimum point, while freeing design engineers from the repetitive task of trial-and-error design.

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t d

Introductionost of the castings are produced using sand mould, where sand

is mixed with a binder and the bonded sand is compacted around a pattern to form a mould cavity. The common binders are clay-water, sodium silicate, various types of resins, molasses etc. Sand-clay-water system is cheap, but can cause moisture related defects in castings. The cost of other binders is relatively high and varies over a wide range. Some of the binders, particularly the resins, pollute the moulding / core making shop and casting area. Therefore attempts have been made to produce castings from a mould made

with loose unbounded sand. There are mainly two moulding processes that use loose unbounded sand: Lost Foam Casting (LFC)[1-4] and Vacuum Moulding processes. In LFC, an expanded polystyrene pattern is coated with a thin layer of refractory and moulded in loose unbounded sand in a mould box. Liquid metal is poured in the mould during which the pattern burns and the pattern is replaced by liquid metal. In Vacuum moulding process, a thin plastic film forms the mould cavity by application of vacuum in loose unbounded sand. Due to various constraints, these two processes have found very limited adoption in foundries. In the present article, a new casting process

is proposed using sheet metal and loose unbounded sand. Steel casting have been attempted to produce by this process in the initial stage of the investigation.

Basic concept of the proposed casting processThe proposed Sheet Metal Mould Casting (SMMC) process presented in this article is based on the condition similar to LFC process, where loose unbounded sand is used as the mould material that surrounds a sheet metal body having shape and dimensions similar to that of the casting to be produced instead of an Expanded

FEATURE STORY

Sheet metal mould casting process – a new approach to produce castings

M

Dr. P. C. Maity Metal Casting and Materials Engineer E-Mail: [email protected]


Polystyrene Pattern used in LFC process. The schematic diagram of the SMMC mould is shown in Figure 1. The casting as well as the gating system is made of sheet metal and the assembly is embedded in loose unbounded sand contained in a mould box. Whereas the EPS pattern supports the loose sand before pouring, in case of the proposed SMMC process, the hollow structure made of sheet metal shaping the mould cavity supports the loose sand before pouring. During pouring, the liquid metal burns and displaces the EPS pattern in case of LFC process. However in the proposed SMMC process, the sheet metal is strong

enough just before filling the mould cavity to support the loose sand in the mould. Once the filling is complete, metallostatic pressure acts outward and progressive solidification is

expected to start at the mould- metal interface, which further supports the loose sand. On solidification and cooling, casting is to be taken out of the loose sand mould as usual.

FEATURE STORY


Figure 1. Schematic diagram showing the basic principle of SMMC process

FEATURE STORY

Experimental procedureTo validate the feasibility of producing castings by SMMC process, a sheet metal mould for gland casting was produced from 0.4 mm thick low carbon steel sheet, as shown in Figure 2. Steel sheet pieces were cut to required size as per the dimensions of Figure 2 and assembled manually to produce the mould of the casting including the gating system. The photograph of the mould is presented in Figure 3.

The assembly of the sheet metal mould was placed in a mould box above 2-3” loose unbounded silica sand at the bottom. The box was filled further with same sand gradually up to the top level of pouring cup with as maximum packing as possible.

Low carbon steel was melted in an induction furnace and poured into the mould at 16100C. On solidification and cooling, the casting was taken out of loose sand mould and was studied for various dimensions and defects, if any. To study the joining of sheet steel with the inner part of the casting, one piece was taken from it by sectioning.

Results and discussionPouring into sheet metal mould was observed to be safe. It was as smooth as pouring of conventional sand castings. The photograph of the gland casting is shown in Figure 4. The most important observation was that the shape of the gland casting was reproduced perfectly indicating the success of the newly proposed casting process. Dimensions of various parts of the casting was checked as per the drawing (Figure 2) of the gland casting. All the dimensions were found to be matching reasonably with the original dimensions of the drawing.

The surface of the casting was mostly free from adhered sand, since loose sand was used in the mould. In case of a binder used in a sand mould, the compounds from

binder and additives may react or fuse with the metal or sand. However these possibilities are eliminated when loose sand is used as mould material and the cleaning of casting becomes comparatively easier.

The sectioned sample taken out of the casting is shown in Figure 5. A narrow gap was found between the sheet metal mould and the casting indicating lack of fusion of steel sheet over the surface of casting. In spite of high metal temperature (16100C), the non-fusion of sheet with casting can be attributed to the following:● Quick drop in temperature at the sheet

metal – casting interface, since casting cools rapidly after pouring

● Shrinkage of casting directed towards the centre of sections of casting

● Presence of oxide layer over the inner surface of steel sheet mould or surface of liquid metal during fillingHence necessary steps are to be taken to

ensure complete fusion of the sheet metal over the casting to become a part of the latter. Another possibility is that the sheet metal mould not fused with the casting is to be taken out and these pieces are

either to be reused for mould production if possible or these are to be recycled.

It should be pointed out here that although the sheet metal mould for the experimental casting of this work was prepared manually, in actual production the sheet metal mould is to be divided suitably into a number of pieces and each piece is to be produced in sheet metal working machines using properly designed dies. Assembling these pieces would enable mass production of castings.

Advantages and Disadvantages/ Limitations of SMMC processAdvantagesThe SMMC process is similar to LFC Process and it has the following advantages:● No cores are required, since holes/

recesses in casting are parts of sheet metal mould. Hence castings can be produced without core binder and core making

● No binders are required in the moulding sand. The following advantages result from sand without binder:

● Cost of binder can be saved.● Easy shake out of casting and easy

removal of core sand

Figure 2. Drawing of gland casting. All dimensions are in mm

Figure 3. Photograph of Sheet Metal Mould for gland casting


FEATURE STORY

● Sand fusion over casting is expected to be minimum compared to some sand moulds containing binder such as sodium silicate, so cleaning of casting is easier

● Sand mixing/mulling are not needed and sand control is irrelevant

● No sand reclamation needed. Sand is reusable, so sand disposal problem is also minimised

● Moisture/binder related casting defects are eliminated

● No pollution in the moulding/core making shop and pouring area arising out of binder. It is true particularly for organic chemical binders

● No parting line defects such as mismatch /fins

● No chances of sand drop and sand inclusion during filling of mould

● Close tolerance casting, hence machining cost is minimised/eliminated

● All metals can be cast by SMMC process. For iron and steel casting low carbon steel sheet , for Al casting pure Al sheet and for Cu alloy casting Cu/brass sheet are to be used

● Possibility of producing bi-metallic casting with a wear/corrosion – resistant outer layer of different alloy

Disadvantages/limitationsThe following disadvantages and limitations are associated with the SMMC process:● Feasible only for mass production,

where sheet metal mould in parts can be produced with sheet metal working machines (Press)and dies

● Suitable for small and medium size castings only

● Only those shape of castings are possible that can be moulded by assembly of worked sheet metal

● Complete filling of mould with liquid metal is possible only in presence of proper venting

● Overall high installation cost associated with making and assembly of sheet metal mould

● Risk of mould collapse similar to LFC process, since no binder in sand mould

● Lack of fusion of sheet metal mould with body of casting

● The process appears to be economic only when the machining cost of casting is very high

ConclusionA new casting process has been demonstrated successfully, that uses a sheet metal mould having shape and dimensions similar to those of the casting to be produced, surrounded by loose unbounded sand in a mould box. The process has several advantages over conventional casting processes. However one problem of non-fusion of sheet metal with the casting was observed that needs to be solved.

AcknowledgementThe author is thankful to M/s. Leader Valves, Jalandhar for providing casting facility of this work. ■

Figure 4. Photograph of gland casting Figure 5. Photograph of sectioned sample from gland casting showing separation of sheet metal from casting due to incomplete fusion

A NEW CASTING PROCESS HAS BEEN DEMONSTRATED SUCCESSFULLY, THAT USES A SHEET METAL MOULD HAVING SHAPE AND DIMENSIONS SIMILAR TO THOSE OF THE CASTING TO BE PRODUCED, SURROUNDED BY LOOSE UNBOUNDED SAND IN A MOULD BOX.

ReferencesM. D. Lawrence, C. W. Ramsay and D. R. Askeland, AFS Transactions, Vol.106 (1998) p.349S. Bennett, T. Moody, A. Vrieze, M. Jackson, D. R. Askeland and C. W. Ramsay, AFS Transactions, Vol.108 (2000) p.795K. Kim and K. Lee, J. Mater. Sci. Technol., Vol.21 (2005) p.681N. Gupta, P. C. Maity, S. Choudhury and Santosh Kumar, Indian Foundry Journal, Vol.54 (2008) p.36.


AUSTIN FOUNDRY CORP., of Sheboygan WI, is a gray and ductile iron jobbing shop that has been producing quality castings ranging in size from one pound to 5,000 pounds for a wide variety of industries since 1946. Their molds are chemically bonded with Furan and some Pepset binders.

“We first considered a sand reclamation system a few years back, but with the recent downturn in the economy and our ever-increasing costs, becoming even more cost efficient became a priority. The cost savings potential of a DIDION® Sand Reclamation System became obvious”, says Sean Girdaukas, Vice President of AUSTIN FOUNDRY CORP.

“We sent sand samples to DIDION for test-ing, using their Rotary Lump Crusher/Sand Reclaimer System. DIDION’S patented design crushed the hard lumps, scrubbed the binder off the sand grains, screened the sand twice, recirculated the screen overs, and separated tramp metal. After evaluating the test results and their proposal, we purchased and installed a DIDION® Sand Reclamation System. Installation was fast and easy. We are very

pleased with the quality of the reclaimed sand and the system is extremely reliable.”

“In the first eight months of use, we reclaimed over four million pounds of spent sand which would previously have been sent to a landfill. We were able to dramatically reduce our new sand purchases and disposal costs. In addition, we have been able to cut back on binder and catalyst usage with no ill effect. We anticipate saving a quarter million dollars annually. Helping the environment is saving us money”, concludes Girdaukas.

The team at Austin Foundry was excited to reclaim a buried treasure. Turn a waste stream into a revenue stream and keep the EPA and DNR inspectors happy. Contact DIDION to help you become more efficient and more profitable.

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ADVANTAGES AND FEATURES✔ Patented multi-chamber design combines lump crushing, sand scrubbing, sand conditioning, dual sand screening, and metal separation for the fastest payback.✔ The time-tested design has the best performance/highest yield (up to 97%) in the industry.✔ Significant savings from reduced binder consumption, lower new sand purchases, and minimal disposal costs.✔ Additional savings from conditioned and higher quality reclaimed sand (which is more uniform/consistent) lowers finishing costs and reduces casting scrap.✔ The patented design has the lowest operating cost per ton in the industry worldwide, with system sizes from 1-100 TPH✔ Highly efficient air-wash separation removes binder, dust, debris, and excess fines.✔ Continuous improvement and development have made us the world leader in sand reclamation.

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TECHNICAL FEATURE

Introductionhe failure of metallic components under alternating stress conditions is known as “fatigue”. When stress is repeatedly applied or alternated such failure can occur

at much lower stress levels than when the stress is continually applied. Very few service failures result from static stress overload, nearly all mechanical failures occur as a result of fatigue damage.

Most foundries assess the mechanical property characteristics of their castings via routine tensile testing of specially cast test bars and hardness testing on the various casting sections with relatively few foundries becoming involved in fatigue or fracture toughness testing. The drive to lightweight components, especially in vehicle and aircraft parts, has resulted in ever increasing demands being made on the mechanical performance of all materials including metal castings. In recent years research, especially with regard to entrainment of oxide films [1], has highlighted how fatigue behaviour and reliability of castings can be seriously damaged by casting defects that can result from inadequate metal cleanliness, incorrect filling of moulds and insufficient feeding, etc. [e.g. 2-4]. This article is therefore intended to provide non-metallurgists with a brief overview of some aspects affecting fatigue behaviour in metal castings.

Characteristics of fatigue failureFatigue failures are most commonly observed in rotating parts such as drive shafts or gears and in parts in vehicle suspensions

and internal combustion engines. Fatigue failure begins when a crack is nucleated, usually at or near the surface of the component. Localized plastic deformation (slip) at stress raisers during alternating stresses leads to the development of fatigue cracks. Although stress may be reversed the structural effect of slip on two or more slip systems is not and this can result in slip band intrusions and extrusions at the surface which nucleate cracking. During further service this crack then grows, normally

Fatigue in metal castingsBy John Pearce

T

Figure 1. Example of a fatigue failure in a steel which was initiated at internal shrinkage porosity showing “beach” marks on the fracture surface.

Figure 2. Example of striations on a fatigue fracture surface (a) schematic (b) SEM view [5].

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at 90 degrees to the main tensile stress, step by step through the component reducing its effective load bearing cross section until complete failure occurs under a single tensile loading. Quite often more than one fatigue crack develops depending on the component design, its surface condition, distribution of defects and the environmental conditions and loading. The appearance of a fatigue fracture surface (Figure 1) is relatively smooth and may contain macroscopic “beach” marks which are formed when loading is intermittent or changed during service, or if there are changes in the environment at the crack tip. On the microscopic scale striations may also be seen on the fatigue fracture surface corresponding to the position of the fatigue crack after each stress cycle as shown in Figure 2 [5]. Although the overall deformation under load is elastic, fatigue cracks develop in a ductile manner with plastic deformation occurring in the zone around the growing crack tip. Propagation may be transgranular or follow interphase or grain boundaries. Any crack will follow the easiest route in the microstructure so the presence of any elongated inclusions, clusters of inclusions, oxide films, coarse second phases and intermetallics, and gas or shrinkage pores will allow faster growth. For example (Figure 3) AlFeSi plates facilitate fatigue fracture in Al alloy cylinder heads [6]. Second phases and intermetallics interact with freshly-formed oxide bifilms in Al alloys reducing tensile properties and fatigue resistance and limiting reliability [1].

Figure 3. Fatigue crack formation follows coarse platelets of Al5FeSi in an Al alloy cast cylinder head [6].


TECHNICAL FEATURE

Fatigue testingRotating cantilever beam tests (Figure 4), “push-pull” tests in a suitable tensile machine and torsion tests are the most common forms of fatigue testing. In the rotating beam test one revolution provides one complete stress cycle. A large number of specimens are tested at different applied loads and the data is plotted on S-N curves in terms of stress level against the number of cycles to failure (e.g. Figure 5). Ferrous alloys, steels and cast irons, exhibit a fatigue endurance limit which is the stress below which fatigue failure will not occur. Most non-ferrous alloys do not show an endurance limit and even at low stress levels may eventually fail by fatigue. In simple design considerations against fatigue failure a ferrous alloy must be loaded below its endurance limit whereas for a non-ferrous alloy a fatigue strength is specified as the stress below which failure will not occur within a given number of stress cycles (i.e. within the intended lifetime of the component) e.g. 108 cycles. In basic fatigue tests the mean stress is zero but in service the mean stress may be tensile or compressive. A mean tensile stress will reduce fatigue life, so static and fatigue data must be combined to avoid failure, for example as in Figure 6 [8]. In more detailed analysis information on fatigue crack growth rates can be combined with fracture toughness data to determine if a fatigue crack, or any other defect, will propagate in a catastrophic (fast fracture) manner [4, 9]. This means that increasing demands are being placed on NDT techniques to provide reliable information on the nature and distribution of defects, as in the case of shrinkage porosity in steel [4].

Some factors infl uencing the fatigue behaviour of castingsFatigue cracking is normally initiated at the surface of a component because:● Stresses are highest at the surface and local

plastic deformation is less restrained● Any surface roughness or imperfections

introduce notch (stress concentration) effects● Surfaces are in contact with the environment

and may become pitted by corrosion.

Figure 4. Schematic view of basic rotating bend fatigue test arrangement

Figure 5. Examples of stress –number of cycles to failure (S-N) curves for a tool steel and an aluminium alloy [7]. To prevent fatigue failure in the steel the applied stress must be below the endurance limit

Figure 6. Goodman type relationship for interaction between fatigue strength and mean tensile stress [8]

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Figure 7. Some effects of surface condition and imperfections on fatigue in pearlitic ductile iron [11]

In addition there may be undesirable variations in both composition and metallurgical structure in the surface regions, e.g. decarburization in a steel or cast iron, which may reduce fatigue resistance. Hence for all components whether cast or wrought, their surface condition and microstructure are both extremely important together with the component design. Any feature which causes a notch effect [10] (i.e. stress concentration) such as surface imperfections, rough machining marks or undercuts, scratching damage, and stamped identification marks must be avoided. Design and production must avoid sharp changes in section and fillet radii must be generous. Figure 7 illustrates the effects of surface condition on fatigue behaviour in a pearlitic ductile iron [11]. A study [3] of the effects of surface and internal defects in ferritic ductile iron has shown that, in both cases, the observed fatigue limit can be related

HENCE FOR ALL COMPONENTS WHETHER CAST OR WROUGHT, THEIR SURFACE CONDITION AND MICROSTRUCTURE ARE BOTH EXTREMELY IMPORTANT TOGETHER WITH THE COMPONENT DESIGN.


TECHNICAL FEATURE

to the area of each defect as measured on the fracture surface as shown in Figure 8. The surface defects are seen to be more damaging than internal defects. Likewise in a range of Al alloys containing 7-17%Si surface porosity was observed to be the most damaging defect in reducing fatigue resistance with fatigue life decreasing with increase in pore size [12].

Internal defects such as oxide films and inclusions [13] also provide sites and pathways for the nucleation and growth of fatigue cracks. Many of the recent process developments in casting of light alloys have involved improved melt preparation to provide cleaner liquid metal and reduced turbulence during liquid metal handling and mould filling to reduce the incidence of damaging folded over oxide films and bubble trails [1,14-16]. The tensile properties and fatigue resistance of Al base castings filled in a turbulent manner can be as variable as ceramic materials with Weibull Modulus values as low as 10. Campbell [1] has comprehensively reviewed and summarized the effects of oxide films on fatigue reliability (Figure 9). As well as significantly damaging mechanical properties folded over oxide films also encourage the formation of gas and shrinkage defects and reduce the pressure tightness of castings.

Moulds and dies must being filled with clean, suitably degassed metal with minimum turbulence and the castings must solidify with the correct microstructure. For example, as shown in Figure 10, in Al-Si alloys the eutectic Si must be effectively modified since fatigue life is reduced if the Si particles are large [17]. In Al cylinder heads where there is interaction between mechanical and thermal fatigue it has been found [6] that to minimize fatigue failure the key microstructural factors are: correct modification of eutectic Si, sufficiently high solidification rates to ensure a small secondary dendrite arm spacing, avoidance of coarse Al-Fe-Si compounds by limiting Fe level and using Mn for refinement.

All air-melted steels will contain inclusions as a result of deoxidation and re-oxidation during pouring. These inclusions will lower ductility, fatigue resistance and fracture

Figure 9. The effect of oxide bifilms and filling on fatigue lives of turbulently filled (containing young oxides) and better filled (old oxides) Al-7Si-0.4Mg alloy [1].

Figure 10. The effect of silicon particle size on fatigue life of Al-Si alloy [17].

Figure 8. The evolution of the fatigue limit with defect size for both surface and internal defects in ductile iron [3]


toughness and in general cause wide property variations. For improved cleanliness, integrity and reliability the steel for high strength investment castings must be melted and refined under vacuum or by using chemical fluxes in electroslag refining.

Fatigue resistance is increased by any alloy addition or treatment which raises the yield strength and is also improved by surface hardening treatments such as carburizing, nitriding, flame and induction hardening of ferrous alloys and by surface deformation such as shot peening. These surface treatments introduce residual compressive stresses into the surface layers which tend to oppose the formation of fatigue cracks.

Fatigue resistance will also be affected by any pre-loading effects from residual stresses or assembly stresses. Damaging residual tensile stresses can arise in Al alloys as a result of water quenching during solution treatment: to avoid this problem forced air in place of water as a quenchant has been recommended for some time [14]. In the work [6] on Al cylinder heads fatigue cracking was reduced when solution treatment was carried out using polymer-water quenching media rather than conventional water quenching.

Fatigue resistance of Al alloys can be improved by squeeze casting and by semi-solid processing [18, 19] both techniques providing finer dendrite arm spacings and improved soundness. Hot isostatic pressing (HIP) can also be used to remove internal porosity other than insoluble gas pores and thus improve densification in most types of casting alloys [20]. Castings are heated to a suitable temperature and then subjected to inert gas pressure to heal pores by plastic deformation. This gives significant improvements in ductility and in fatigue life. Although Hipping cannot remove oxides there is some evidence that it can deactivate entrained oxide bifilm defects as initiating sites for fatigue cracking in Al alloy [21]. However hipping will only provide maximum improvements in ductility and fatigue resistance in castings made from clean relatively oxide free metal.

It must be remembered that the combined effects of service stresses and corrosive environments can be very damaging. Tensile stresses can interact with specific ions to cause stress corrosion cracking e.g. the chloride ion in stainless steels. Fatigue life can be considerably reduced under corrosive conditions: corrosion produces pitting and certain ions can increase crack growth rates such that corrosion can remove the fatigue endurance limit in ferrous alloys. ■

References.“Entrainment Defects”. J. Campbell: Material Science & Technology 22 (2006) 127-145. “Casting defects and fatigue strength of a die cast aluminium alloy: a comparison between standard specimens and production components”. M. Avalle, G. Belingardi, M.P. Cavatorta, R. Doglione: International Journal of Fatigue 24 (2002) 1-9.“Influence of casting defects on the fatigue limit of nodular cast iron”. Y. Nadot, J. Mendez, N. Ranganathan: International Journal of Fatigue 26 (2004) 311-319.“Prediction of the Fatigue Life of Cast Steel Containing Shrinkage Porosity”. R.A. Hardin, C. Beckermann: Met. & Materials Transactions A 40A (2009) 581-597.“An Atlas of Metal Damage”. L. Engle & H. Klingele: (1981) Wolfe Publishing-Carl Hanser Verlag, Munich, Germany. “Critical material issues in cast aluminium cylinder heads”. Y. Birol & A.A. Ebrinc: Foundry Trade Journal 181 (2008) 196-199. “Mechanical Testing and Properties”, Ch.6: The Science & Engineering of Materials. D.R. Askeland (1989) Van Nostrand Reinhold International.“The use of fatigue data in the design of iron and steel castings” BCIRA Broadsheet 257-1 (1986). “An Introduction to Fracture Toughness”. J. Pearce: Metal Casting Technologies 52 (2006) 16-20. “Cast irons and steels in fatigue stress applications - effects of notches”. BCIRA Broadsheet 257-2 (1987)“Cast irons and steels in fatigue stress applications - effects of surface condition and treatments”. BCIRA Broadsheet 257-3 (1987). “Porosity and the fatigue behaviour of hypoeutectic and hypereutectic aluminium- silicon casting alloys”. H.R. Ammar, A.M. Samuel & F.H. Samuel: International Journal of Fatigue 30 (2008) 1024-1035. “Inclusions in Castings”. J. Pearce: Metal Casting Technologies 50 (2004) 17-22. “The Revolution in Casting Production”. J. Campbell: Foundryman 92 (1999) 313-317. “The Concept of the Fatigue Potential of Cast Alloy”. C. Nyahumwa & N. Green: Foundryman 93 (2000) 257-260. “Commentaries on ‘Entrainment defects’ by J. Campbell”. P.R. Beeley, J.R. Griffiths, N.R. Green & C.J. Newton: Material Science and Technology 22 (2006) 999-1008. “An Overview of the Development of Al-Si Alloy Based Material for Engine Applications”. H. Ye: Journal of Materials Engineering & Performance 12 (2003) 288-297.“Casting – current practice and future potential”. G.A. Chadwick: Metals & Materials (1986) 693-698. “Fatigue Properties of a semi-solid cast Al-7Si-0.3Mg-T6 alloy”. C.J. Davidson, J.R. Griffiths, M. Badiali & A. Zanada: Metallurgical Science & Technology 18 (2000) 27-31.“Fundamental Aspects of Hot Isostatic Pressing: An Overview”. H.V. Atkinson & S. Davies: Met. & Materials Transactions A 31A (2000) 2981-3000.“Influence of casting technique and hot isostatic pressing on the fatigue of an Al-7Si-Mg Alloy”. C. Nyahumwa, N.R. Green & J. Campbell: Met. & Materials Transactions A 32A (2001) 349-358.

CASTINGS ARE HEATED TO A SUITABLE TEMPERATURE AND THEN SUBJECTED TO INERT GAS PRESSURE TO HEAL PORES BY PLASTIC DEFORMATION.


TECHNICAL FEATURE

Introductionhe developments in nuclear, aerospace & automotive engineering demands materials with improved mechanical properties and

service reliability. Electroslag remelting (ESR) helps meet these stringent demands. Electroslag remelting (ESR) and vacuum arc remelting (VAR) are the two commonly used remelting processes. While both these processes can eliminate most of the in homogeneities and defects associated with the solidification process, their refining abilities are different. The equipment and operating costs of vacuum arc remelting are higher than the ESR process. It is a well known fact that ESR process produces high quality clean steels by improving the mechanical properties and eliminating inclusions. There is little published information available on ESR processing of aluminium and its alloys. The success of ESR of steels and super alloys has led to the interest in its application to non ferrous metals and alloys. High strength aluminium alloys which are used in aerospace applications would be benefited from the ESR process. In this experimental investigation ESR process is carried out on aluminium and its properties are determined. Conventionally cast aluminium has defects like porosity, segregation and pipe formation. In the ESR process these defects are eliminated.

The processESR process involves remelting of an electrode which is refined through a layer of molten slag. The metal to be refined is called an electrode. It can be cast or wrought and is known as consumable electrode. The electrode is melted by feeding its bottom end into a molten superheated slag layer. The slag temperature is higher than the melting point of the metal. The droplets of metal melting from the tip of electrode pass through the slag layer and join the molten pool of metal below the slag. The slag dissolves the inclusions from the molten metal and reacts chemically with the molten drops passing through it. Figure 1 shows the schematic diagram of the ESR process.

A water cooled mould holds the forming ingot and the slag. The heat required to maintain the slag layer in a molten condition

Foundry processing of aluminium chips by Electroslag RemeltingAmit Joshi Dept. of Metallurgical Engineering & Materials Science, Indian Institute of Technology – Bombay, India.Email: [email protected]

T

Figure 1. Schematic diagram of the ESR process

CONVENTIONALLY CAST ALUMINIUM HAS DEFECTS LIKE POROSITY, SEGREGATION AND PIPE FORMATION. IN THE ESR PROCESS THESE DEFECTS ARE ELIMINATED.

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is given by the resistance of the slag to the passage of an electric current through it. The ingot builds up in the mould and the slag is displaced in the upward direction. As the molten slag meets fresh surface of mould, a thin layer of slag adjacent to the surface solidifies to form a shell. The thin layer of solidified slag between the metal and mould wall produces a good ingot surface. The consumable electrode is thus changed into an ingot of refined metal with superior properties. A clean sound ingot is obtained as the inclusions are removed in the ESR process.

The important parts in an ESR unit consist of mould and the base plate; electrode feed arrangement, the power source. The ESR moulds are made of copper or steel. Steel moulds have a lesser life compared to the copper mould. The shape of the mould is decided by the shape of the ingot desired and can be square, rectangular or circular, etc. Static and moving type moulds can be employed in the ESR process. The moving type mould can produce a longer ingot. Both alternating and direct current can be used for the process. Usually AC is used as the equipment is cheaper and AC helps in stirring the slag metal interface due to electrocapillary action and creates better refining action.

The main problem in the ESR process is about the starting. Arcing, exothermic mixtures, solid conducting slags have been used. Arcing for a long time should be avoided. Premelted molten slag addition gives a smooth start for the ESR process. There is no arcing in molten slag addition. The molten slag has to be added rapidly at the base of the mould to prevent any loss of temperature. The electrode chemistry should be near to the desired ingot composition. Some elements have a tendency to oxidize and the loss can be compensated in the ESR process. The slag cover eliminates atmospheric contamination of the molten metal. ESR process removes defects like inclusions, porosities and segregation.

The set up consists of a vertical screw rotated by a dc motor through a reduction gear moves the electrode holder up and down between two vertical guides. Metallic mould and base plate are both water cooled in the ESR process. A fume extractor is fixed above the mould to drive off the fumes generated. Tapered mild steel moulds can be used in the ESR process to reduce the costs of a copper mould. The main variables in the ESR process are the slag composition, current and voltage. The slag chemistry is of the greatest importance as it is the main refining part. The liquidus temperature of the slag should be below than that of the metal to be refined. Since the melting point of aluminium is 6600 C, the slag used should have a lower melting point below this.


TECHNICAL FEATURE

Experimental procedureA hollow aluminium tube is used as the consumable electrode. The bottom end of the tube is made flat and sealed off by hammering. Aluminium chips produced during lathe machining were collected and rammed inside the hollow tube. The chips were rammed manually by a steel rod. The top end of the tube was made flat by hammering. This top end was attached to the electrode holder using nut bolt arrangement.

The slag contained 30% cryolite (Na3AlF6), 30% potassium chloride (KCl) and 40 wt % sodium chloride (NaCl) and had a melting point of around 6000C. Slag was made in an induction furnace in a graphite crucible. The molten slag was poured in a clay graphite crucible and allowed to solidify. The slag was later crushed and sieved into fine powder. The slag was stored in a desiccator. The mould is kept on the bottom plate and clamped tightly. The process is started by starting an arc between electrode tip and the bottom plate. Preheated slag was added immediately in the arc zone. It was observed that the slag melted partially and there was continuous arcing between electrode and base plate. The rest of the slag was added continuously in the arc zone.

The slag didn’t melt and the ingot produced was highly non uniform and unsatisfactory. Power was varied during arcing to make the slag molten but there was not much difference. This solid start arcing is a problem in aluminium ESR as the slag melting temperature is approximately near to the metal melting point. The slag may melt partially and remaining may not melt. There will be continuous arcing between electrode and bottom plate starting block. ESR melt of aluminium proved difficult to initiate by arcing due to the incomplete slag fusion.

As the solid slag with arcing failed molten slag addition was tried into the mould directly. This will give a quick smooth start of the process. The slag was kept ready in a molten condition in another furnace and added quickly in the mould through a transferring crucible ladle arrangement. The electrode end was kept about half inch above the base plate. As soon as the slag was poured the open circuit voltage reduced and the process started. The parameters were adjusted accordingly and the voltage was kept around 25 V. The process was stable throughout. At the end of the process hot topping was tried by reducing the voltage and current to give maximum yield. The ESR ingot was stripped out and analyzed.

Characterisation The ingot was cut to for determining mechanical properties. The other cut portion was macroetched using Tucker’s reagent to reveal the macrostructure. Samples were made from the bottom and the centre of ingot for checking the reproducibility of the results. All the tests were carried on transverse and longitudinal specimens. The chemistry of the ingot was checked in an optical emission spectrometer. Tensile samples were made according to ASTM E 8 specifications. The gauge length is kept at 20 mm and gauge diameter is 4 mm. Charpy impact samples with a V Notch (10 x 10 x 55mm) were made according to ASTM E 23. Vickers hardness values were taken at 100 gms load. Four hardness readings were taken for each sample and averaged. Two samples were made from transverse and longitudinal directions.

A part of the aluminium ESR ingot was cut for cold rolling. Cold rolling was done in a 75 tons capacity rolling mill. The starting thickness was 21 mm and it was rolled to 10.2 mm giving 51.42% reduction. Tensile and charpy impact samples were made from

Figure 2. Aluminium ingot prepared by ESR process using arcing method

THE PROCESS IS STARTED BY STARTING AN ARC BETWEEN ELECTRODE TIP AND THE BOTTOM PLATE. PREHEATED SLAG WAS ADDED IMMEDIATELY IN THE ARC ZONE. IT WAS OBSERVED THAT THE SLAG MELTED PARTIALLY AND THERE WAS CONTINUOUS ARCING BETWEEN ELECTRODE AND BASE PLATE.


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cold rolled ESR plate. The coefficients of thermal expansions (CTEs) of rolled aluminium were measured using a dilatometer. The linear thermal expansion tests were performed over the temperature range of 300C to 3000C. Scanning Electron Micrograph images were taken for the tensile fractured samples.

Results and discussions The ingots were examined visually for surface finish. Figure 2 shows the aluminium ingot prepared by ESR process using arcing method. It can be seen that the surface is totally non uniform and rough. The process has failed as the slag didn’t melt at all. There was no refining action. Unmelted slag can be seen on the ingot and there is absence of metallic shiny aluminium colour.

Figure 3 shows the ingot using liquid start method. The surface is far better than the earlier ingot. There is absence of shrinkage pipe at the top. The surface is bit irregular and is due to the varying power for Figure 3. An ingot using liquid start method


TECHNICAL FEATURE

achieving stability and for hot topping. Table 1 shows the chemical composition of the ESR ingot.

The sectioned ingot showed absence of any internal blowholes and porosities. Macrostructure confirmed the presence of equiaxed grains of about 1 mm uniformly distributed in the longitudinal section. Figure 4 shows the equiaxed macrostructure. There was an absence of columnar grains which is typically present in steels. It was due to the low temperature gradient in the liquid melt owing to higher thermal conductivity of the aluminium. The results of mechanical testing for the ESR ingot are given in Table 2.

The average impact strength is 68.218 KJ/m2 whereas the ultimate tensile strength is 117.5 MPa. The total elongation is 10.775% and the hardness value is 64.95.

Table 3 shows the properties of cold rolled ESR ingot.After rolling UTS increases from 117.5 MPa to 238.5 MPa. There

is an increase in hardness after cold rolling. The impact energy is reduced after rolling. Cold rolling decreases the impact toughness of alloys and makes the material brittle. Figure 5 shows the SEM image of tensile fractograph. The image shows the presence of cup shaped depressions called dimples throughout and are the result of microvoid coalescence. The fracture mode is dimple rupture.

Figure 4. Equiaxed macrostructure

ESR Ingot

Charpy ImpactEnergy

Impact StrengthKJ/m2

UTS, MPa Elongation %

Hardness

Transverse section (Ingot Bottom)

5.48 J 68.5 110 9 63.8

5.8 J 72.5 112 10.3 64.6

Longitudinal section(Ingot Centre)

5.38 J 67.25 117 10.8 65.1

5.17 J 64.625 131 13 66.3

Average 5.4575 J 68.218KJ/m2

117.5 MPa 10.775% 64.95

Table 2. Properties of aluminium ESR ingot

Rolled Impact Energy

J

Impact Strength

KJ/m2UTS, MPa

Elong-ation %

Hard-ness

CTE10-6 0C-1

Rolled Sample 1 4.12 51.5 242 MPa 7.9 69.1 22.7

RolledSample 2 4.8 60 235 MPa 6.5 73.2 23.2

Average 4.46 J 55.75 KJ/m2 238.5 MPa 7.2 % 71.15 22.95

Table 3 Properties of Rolled ESR

Elements wt %

Si 0.3

Fe 0.7

Cu 0.15

Mg 0.25

Zn 0.13

Al Bal.

Table 1. Chemical composition of Al ingot

Figure 5. The SEM image of tensile fractograph

Conclusions ESR is a well known process for steels and it can be concluded that it can be applied to aluminium and its alloys. From waste machined chips a sound ingot was produced using the ESR process. The ingot showed absence of internal porosities. There was no shrinkage in ESR ingot compared to a conventional casting. There was no slag entrapment in the metal. Macrostructure confirmed presence of equiaxed grains uniformly distributed in the longitudinal section. The ESR ingot showed good mechanical properties. ■

References G. Hoyle, Electroslag Processes: Principles and Practice, Applied Science Publishers London & NY. Medovar.B.I.et.al, ESR, Translated from the Russian book Elektroshlakovy Pereplav, Moscow, 1963, Office of technical services, Washington DC, USA.Rolland Kammel & H. Winter Hager, ATB Metallurgie, 1, 1970, 1 – 13. D.M.Rabkin, Ishchenko, Automet, Svarka, 19 (6), 1966, 75-6.M. Tajallya, Zainul Huda, and H.H. Masjuki, International Journal of Impact Engineering, Volume 37, Issue 4, April 2010, Pages 425-432

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EVENTS

115th Metalcasting CongressWhen: 5-8 April 2011 Where: Renaissance Schaumburg Hotel & Convention Center Schaumburg – IL USAThe Metalcasting Congress is North America’s largest annual event for the metalcasting industry, combining an exhibition of industry suppliers with technical, management and research presentations from the foremost experts around the world. Sponsored by the American Foundry Society (AFS), this year’s 115th event showcases the latest advancements in metalcasting. The exhibition is expected to draw more than 200 metalcasting industry suppliers. The Congress is expected to provide more than 100 technical presentations covering all facets of metalcasting from shop-floor production to management tactics to the latest research advancements.Web: http://www.afsinc.org/content/view/1005/308/

China Castpart Exhibition & 8th China International Non-Ferrous and Special Foundry ExhibitionWhen: 12-14 April 2011 Where: Nanjing International Expo Center, Nanjing – China In 2011, with innovative concept, China Caspart Exhibition, stemming from Casting China International will make its debut in Nanjing along with 8th China International Ferrous & Special Foundry Exhibition. Castpart mainly focuses on the integral production chain of foundry industry. Apart from conventional exhibits from castings, foundry equipment and consumable materials, Castpart introduce machine tools, hand tool and relevant finishedcasting proccessing equipment. Held concurrent to China International Marine, Port & Shipbuilding Fair, Global Clean Energy Congress and The 6th China Jiangsu International Agricultural Machinery Exhibition, Castpart and Non-ferrous and Special Foundry open to the production line of casting manufacturing, proccessing and application, a effective platform of trade opportunities.Web: www.foundry-china.com

SF EXPO ChinaWhen: 11-13 May 2011 Where: Guangzhou International Convention and Exhibition Center - ChinaSF EXPO 2011 will be committed to advancing the surface finishing industry entirely, through strengthening the cooperate with Powder Coating Institute and Metal Finishing News based on the cooperation with the Electroplating Branch of China Surface Finishing Engineering Association, Guangdong Electroplating Association and Guangdong Coating Industry Association, consolidating cooperation with previous partners such as Taiwan Surface Finishing Association, Korea Plating Industry Cooperative,

Japan Federation of Electro Plating Industry Association, Institute of Metal Finishing, Singapore Surface Finishing Society.Web: http://www.sf-expo.cn/en/

Dongguan International Exhibition on Foundry & Diecasting IndustriesWhen: 1-3 June 2011 Where: Dongguan International Conference & Exhibition Centre – Dongguan, ChinaThe Dongguan International Exhibition on Foundry and Diecasting Industries will provide you a timely and efficient, multi-faceted exchanges and cooperation platform for business interaction, enable you to seize new opportunities and win customers, further your understanding of the industry, consolidate and improve your favorable position and advantages in the world competition, and grasp the future.Email: [email protected]

The 12th China (Guangzhou) International Metal & Metallurgy ExhibitionWhen: 23-25 June 2011 Where: China Import & Export Fair Pazhou Complex, Guangzhou – ChinaThe 12th China (Guangzhou) International Metal & Metallurgy Exhibition will be a very important exhibition for the metal and metallurgy industry in China. The exhibition has been organized By Guangzhou Julang Exhibition Design Co. Ltd and will take place at the largest exhibition Centre in China. It will be a complete showcase of raw materials, processing technology, equipment and products. This three day exhibition will attract thousands of exhibitors from over 30 countries.The scale of the exhibition will be bigger than ever before as it is projected that over 300,000 purchasers are interested in doing business at the event. With such great trading opportunities this exhibition will act as the ideal platform for growth of metal and metallurgy industry in Asia.Web: http://www.julang.com.cn/english/index.asp

GIFA – The Bright World of MetalsWhen: 28 June – 2 July 2011Where: Exhibition Halls at Messe Düsseldorf – GermanyThe four international technology trade fairs GIFA, International Foundry Trade Fair, METEC, the International Metallurgical Technology Trade Fair, THERMPROCESS, the International Trade Fair for Thermo Process Technology, and NEWCAST, the International Castings Trade Fair, will be staged in Düsseldorf from 28 June to 2 July in 2011. Under the motto “The Bright World of Metals” such topics as castings, foundry technology, metallurgy and thermal


EVENTS

processing technology will be the focus of this entire world. All four technology trade fairs will place special emphasis on the topical issue of energy and resource efficiency. Again the events will be accompanied by a high-calibre fringe programme with numerous seminars, international congresses and lecture series.Web: www.gmtn.de, www.gifa.de www.metec.de www.thermprocess.de and www.newcast.de

ACHT2011When: 11–14 September 2011 Where: Sebel Albert Park Melbourne, AustraliaWith the support of the Australian and international aluminium industry, CAST CRC is organising the Aluminium Cast House Technology, 12th Australasian Conference & Exhibition. Invited and selected world recognised experts will be key speakers at the conference. Following the success of the previous eleven conferences, this conference will address the needs of the primary, secondary and recycling industries. A smelter plant tour will be held in conjunction with the conference. The Conference will also include a large trade exhibition, with major suppliers to the industry having booths to showcase their products and services.Web: http://www.aluminiumcasthouse.com/

MTM EXPO 2011 When: 26-28 September 2011 Where: The Theme Pavillion, Shanghai World ExpoOrganised by the Chinese Society for Metals, Baosteel Group Corporation and Shanghai Society of Metals, MTM EXPO 2011 will consist of Shanghai Metallurgy Expo, Shanghai Tube Expo and Shanghai Metal Expo.Email: [email protected]

New Zealand Foundry Conference - Adventure with Casting TechnologyWhen: 30 October – 2 November 2011 Where: Queenstown – New ZealandWeb: Coming Soon

CastExpo ‘13When: 6-9 April 2013Where: America’s Center in St. Louis, USAHeld every three years, CastExpo attracts thousands of decision-making metalcasters from around the world, all of whom are looking for the latest advancements in equipment, technology and services to advance their facilities.

The most recent show, CastExpo’10 held in Orlando, Florida in March, was a great success. The event attracted nearly 4,500 attendees and more than 350 companies from around the globe showcasing the latest technology, research and services available to the metalcasting industry. The attendees came with decision making power—27% were presidents, chief executive officers or owners, 22% were plant managers and 14% were vice presidents. The remaining 51% included engineers, sales representatives, and technical, production and maintenance personnel.

By popular demand, several of the new additions to CastExpo’10 will be included at CastExpo’13. The Cast in North America Pavilion on the CastExpo show floor allowed more than 40 metalcasting facilities (foundries and diecasters) to showcase their casting capabilities to buyers and designers in an unprecedented forum.

This area of the show was complemented by casting design and sourcing education in the Metalcasting Congress sessions. In addition, the Metalcasting Technology Theater, located on the exhibit floor provided practical shop-floor presentations for metalcasters.

Registration and exhibit information for CastExpo’13 will be available in 2012.Email: [email protected]

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Ductile iron grades

uctile iron is not a single material but is part of a group of materials which can be produced to have a wide range of properties through control of the

microstructure. The common defining characteristic of this group of materials is the graphite morphology. In ductile irons the graphite is in the form of spherical nodules rather than flakes (as in grey iron), thus inhibiting the creation of cracks and providing the enhanced ductility that gives the alloy its name. The formation of nodules is achieved by addition of nodularising elements, most commonly magnesium into the melt.

Besides the requirement that the graphite be in a spheroidal form, the ferrite and pearlite ratios can be controlled through alloying, cooling rate control or post-casting heat treatment to vary the relative amounts pearlite and ferrite from 0% pearlite and 100% ferrite, to 100% pearlite and 0% ferrite. The control of the pearlite and ferrite ratio manipulates the tensile, yield and elongation characteristics of the ductile iron to produce numerous standard grades of the material.

Primary elements in ductile ironThe primary elements in ductile irons are generally considered to be carbon, silicon, manganese, phosphorous, sulphur and magnesium.

CarbonWhile the carbon content in commercial ductile iron ranges from less than 3% to over 4%, it is more common for carbon to be within a range of 3.5% and 3.9%. As a general rule, the carbon equivalent has little effect on the mechanical properties of ductile iron. For this reason there is a tendency to use high carbon equivalent irons since this improves fluidity and reduces shrinkage tendency.

A combination of high carbon content and low solidification cooling rate can result in graphite floatation and the presence of degenerate graphite. For these reasons, it is necessary to adjust carbon equivalent according to section size. For thin sections (less than 12mm) a carbon equivalent of 4.6% is recommended, for intermediate sections (12 to 40mm) a carbon equivalent of 4.45% may be more appropriate whilst for heavy sections (greater than 50mm) it may be necessary to limit carbon equivalent to 4.3%.

Silicon

Typical silicon contents in ductile irons range from 1.80% to 2.80% although there are applications for lower and substantially higher levels. Some oxidation resistant alloys contain up to 6% silicon.

Silicon is a potent graphitiser, decreasing the stability of eutectic and pearlitic carbide. Silicon hardens and strengthens ferrite particularly in the annealed condition.

A potential adverse effect of increasing silicon in ferritic ductile irons is the raising of the ductile brittle impact transition temperature. For the low-temperature impact grades silicon contents are generally kept within a range of 1.7% to 2.2%.

ManganeseManganese is a pearlite stabilising element; however, it is also a moderately strong carbide promoter tending to form chill carbides in thin sections and intercellular carbides in heavy sections.

In as-cast ferritic grades and thin sections in any grade, it is preferable to maintain manganese below about 0.2%. Higher levels may be tolerated in heavier section pearlitic grades.

PhosphorusWhilst phosphorus must be considered as an undesirable element, it is present in most charge materials used in ductile iron production. The element forms a low melting point iron phosphide which segregates to cell boundaries resulting in deterioration in elongation and impact properties. It may also cause an increase in porosity.

Sulphur and magnesiumWhen magnesium is added to molten iron it acts to deoxidize and desulphurise the melt thereafter cause the graphite to precipitate and grow in a spheroidal form. If the base iron and treatment are not properly controlled, excessive oxygen and/or sulphur can consume the magnesium leaving an insufficient residual to spheroidise the graphite.

Excessively high magnesium contents tend to promote carbides.

Since sulphur readily combines with magnesium it has no effect on the matrix structure, however, high levels in the base iron are undesirable since magnesium yield is reduced.

The effects of common elements in ductile Iron J. F. Meredith Casting Solutions Pty Ltd

D

Common alloying elements in ductile ironDuctile iron is commonly alloyed at moderate levels for:● Promotion of pearlite● Enhancing elevated temperature properties

Pearlite promoting elementsPearlite promoting elements generally work by one of two fundamentally different mechanisms. One mechanism is by segregation of certain elements to the graphite/matrix phase boundary during solidification. These elements effectively act as barriers which inhibit diffusion of carbon from the matrix to the graphite spheroid. The second mechanism is by retarding the onset of the eutectoid transformation and decreasing the rate of diffusion of carbon in ferrite.

Most trace elements found in ductile irons have some pearlite stabilising effect, the potency of eight common elements are ranked in decreasing order in the following table.

Of these elements, pearlite promotion by either Mo or Ni is too expensive and the use of P, Ti, Mn and Cr is definitely advised against.

Tin and copper are most commonly used to stabiles pearlite in ductile iron. The pearlite promotion effect by the two elements is additive with tin being about ten times stronger than that of copper.

Tin additions in excess of about 0.07% can cause the iron to be embrittled due to the precipitation of tin to the grain boundaries.

Copper is widely used in amounts from about 0.2% to 1.5%

depending on the amount of pearlite required, the section size, and the levels of other pearlite stabilizing elements.

Enhanced elevated temperature propertiesMolybdenum is particularly useful in increasing elevated temperature tensile strength, stress-rupture and creep strength and thermal fatigue resistance and is added in amounts up to 2% for this purpose. Nickel acts in a similar manner and often accompanies molybdenum alloying.

Deleterious elements in ductile ironThe production of quality ductile iron involves treatment of the molten iron with sufficient magnesium in appropriate


Elements Relative pearlite promoting effect

Sn 39.00

Mo 7.90

P 5.60

Cu 4.90

Ti 4.40

Mn 0.44

Ni & Cr 0.37

Table 1. Relative pearlite promoting potency of common elements

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form shortly before casting to give residual magnesium content in excess of about 0.03% in the solidified casting. There are however, a number of elements, which may interfere with the development of acceptable spheroidal graphite structures. These elements are commonly referred to in various terms including deleterious and subversive.

Ductile irons are typically produced from mixed charges, which may contain pig iron, steel scrap from various sources, foundry returns and purchased cast iron scrap. As a result, impurity trace elements such as aluminium, antimony, arsenic, bismuth, lead, tellurium, titanium etc., may be introduced in small amounts. These elements can have a significant adverse effect on properties of the alloy by forming undesirable graphite and matrix forms in cast structures. Additionally, the effect of even trace amounts of these subversive elements can be cumulative when they are present in combination. For example, the presence of lead limits the tolerance for titanium, antimony and bismuth, and that the adverse effects of titanium are observed more strongly in copper alloyed irons. For this reason recommended “acceptable” levels of these elements must be treated with some caution.

The levels of such elements must therefore be minimised by avoiding contaminated scrap such as lead painted or enamelled material and automotive scrap containing aluminium components. In many cases, analysis of these elements is difficult without specialised equipment, however, based on the severity of the problems they can cause, concentrations should be periodically analysed by an outside laboratory.

Fortunately, the undesirable effect of many of these elements can be neutralised with the addition of some cerium either as mischmetal or as a cerium bearing magnesium ferrosilicon. The amount of cerium required to neutralise harmful effects will depend upon the effectiveness of the cerium and the sum of all the tramp elements present.

Typically, a residual cerium content of about 0.01% is usually sufficient for most situations.

Some of the more commonly experienced deleterious elements include:

Lead (Pb)Lead is perhaps one of the most common of the subversive elements found in charge materials. Lead may be introduced to the base iron through the melting of leaded (free-cutting) steel scrap, lead containing pig irons, steel scrap coated with lead based paints, leaded copper scrap which may be deliberately added to the charge to stabilise pearlite or contaminated melt stock such as shown in Figure 3.

As little as 0.002% lead in the base iron can neutralise the spheroidising effect of magnesium resulting in a flake form of graphite and dramatically reduced mechanical properties. Since such a small amount can have a dramatic effect on graphite shape, it can be difficult to monitor effects by chemical analysis.

The adverse effect of lead becomes more pronounced with heavier casting sections. The use of cerium or cerium

Figure 1. Well formed graphite nodules in ductile iron Figure 2. Undesirable graphite morphology

Figure 3. Lead insert in cast iron scrap

containing MgFeSi treatment alloy can help to neutralise its harmful effect believed to be by the preferential formation of a Ce-Pb compound.

Antimony (Sb)Antimony has a harmful effect similar to that of lead. It is considered that levels of over 0.004% antimony cannot be tolerated in ductile irons without a severe reduction in graphite quality and hence mechanical properties. The effect of antimony is also cooling rate sensitive, tending to segregate to the intercellular regions where it promotes the formation of a mesh-type flake graphite form.

Antimony can be introduced to the melt through the steel scrap or by intentional addition where small amounts such as 0.002% is sometimes used to promote a pearlitic matrix, particularly in heavy sections.

The subversive effects of antimony can be offset by the addition of cerium.

Bismuth (Bi)As little as 0.003% bismuth results in the formation of

significant amounts of flake graphite, whilst 0.005% bismuth will almost completely eliminate spheroidal graphite formation.

Bismuth is sometimes added to ductile irons in combination with cerium as a means of increasing nodule count. Bismuth and cerium additions can also help to reduce graphite floatation in heavy section ductile iron castings by producing a larger number of smaller nodules, which segregate more slowly towards cope surfaces during solidification.

Titanium (Ti)The effect of titanium in ductile iron is to counter the spheroidising action of magnesium and to cause vermicular graphite formation. Indeed, the balanced use of magnesium and titanium is the preferred method for producing compacted graphite cast irons. For general use, titanium levels should be limited to about 0.04%; however, the effect is again section size sensitive. Light section castings can tolerate higher levels, as much as 0.07%, whilst a little as 0.02% can have a subversive effect in heavy section castings.

Titanium is typically introduced into the iron through the melting of foundry pig irons, which possibly contain as much as 0.04% titanium, certain structural steels or compacted graphite iron scrap or returns. Where foundries produce both ductile and compacted graphite irons, segregation of scrap and returns is essential.

A small addition of cerium is capable of neutralising the subversive effects of titanium.

Aluminium (Al)Up to about 0.03% aluminium can be tolerated in ductile irons. Whilst aluminium is not as deleterious as titanium, aluminium

tends to promote the formation of vermicular graphite. The presence of aluminium in ductile iron also increases the sensitivity of the iron to hydrogen pinholing. This effect is most pronounced in small green sand moulded castings where as little as 0.01% aluminium can be enough to cause a severe outbreak.

Aluminium is introduced into the iron through charge and treatment materials such as steel scrap, ferroalloys and inoculants.

Tellurium (Te)Tellurium will react chemically with magnesium to form a telluride thus lowering the effective magnesium level and causing degradation in graphite shape. As little as 0.002% tellurium can cause graphite degradation, higher levels promote carbide formation. ■


ReferencesDuctile Iron Handbook – American Foundrymen’s Society Inc, 1993Metallurgy and Production of Grey and Ductile Irons – BCIRA, Alvechurch, Birmingham, UK

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Checking an induction furnace before operation General

hese are guidelines for checking induction furnaces before operation, especially newly installed units. There is no substitute for precautionary measures

being undertaken prior to operations.A thorough checking out of the system is required after

installation and prior to operation of the unit. If the system does not meet the specified standards, no attempt should be made to operate the unit until all faults have been corrected or defective parts replaced. The following check out procedures outline the steps to be followed prior to calling a Vendor’s service engineer.

It is important to recognize that most equipment is manufactured to operate at normal 440-460 volts, 3 phase, 50/60 cycle power systems. Higher power level furnaces are made to operate with a line voltage of 575 volts. Where the line voltage is 230 volts, 2,300 volts, or some other voltage, it will be necessary to supply a transformer (isolation or auto type) to step up or step down the voltage as required. These transformers are available from the Vendor. The supply voltage must be maintained within 5% below and 10% above the nominal rating. Should voltages be outside these levels, the power company should be contacted to change the appropriate taps on the transformers supplying this equipment.

The equipment would have been furnished with a circuit breaker in the cabinet to comply with various codes. In most units, a hole must be cut into the enclosure to facilitate the connection of the proper size of conduit. Refer to the wiring diagram supplied with the furnace for cable and conduit size recommended. Cables and conduit of equivalent voltage and current ratings may be substituted as desired and in accordance with local electrical codes. Proper electrical service installation is ultimately the responsibility of the installation contractor.Warning: Some furnace units require a dedicated line isolation transformer. No other equipment whatsoever may be connected to the secondary of this transformer.

Although the circuit breaker is provided in this equipment, the user should provide a means of protecting the incoming line.Note: The circuit breaker connection lugs will not necessarily accept all legal substitute cable. Be sure to check the compatibility of the circuit breaker connector before substituting cable sizes.Caution: Unless specified otherwise, disconnect incoming electrical power to all equipment until checking out procedures are completed.

Electrical1. Visually inspect all equipment for working condition or damage including:● Meters● Switches● Wiring● Cabinet door and hinge● Loose hardware and fasteners ● Signs of water leakage2. Circuit Breaker: Check for proper size. Check fuses (if installed ahead of unit electrical input) for proper service voltage and current rating.3. Bus Bars: Should be fastened with non-magnetic material such as:● Brass● Silicon Bronze● Aluminium

Do not connect bus bars with magnetic materials (iron or steel) for operation above 150 Hz.

Be sure that bus bars are adequately supported and secured against movement during operations.

Joints in aluminium bus bars or joints between aluminium and copper bus bars, must be carefully made using Electrical Joint Compound according to the manufacturer’s instructions.

Water CoolingA.Shut off supply and drain valves to equipment.B. Pressurize the lines external to the melting system and check for leaks.

Normal operating proceduresGeneralThis section outlines the normal operating procedure for starting up a furnace system, for making heats, and for shutting down. Because systems vary greatly in type of installation, type of furnace, and type of cooling system, this section is made very general to cover most installations.

Some operator procedures for abnormal conditions are suggested at the end of this section. However, each operator should review his own needs and develop specific emergency procedures based on his own unique installation and requirements.

Daily starting-up1. Turn the water on.2. Inspect the lining and patch it as necessary. When the lining is correct, charge the furnace.

Safety in induction furnace operations

T

By Prof. John H. D. Bautista, PEE, RMetE, MBA; Technical Consultant, Phil. Metalcasting Association., Inc.

– PART 1 –

Caution: a) Use only dry charge material.b) Inspect bundled or baled scrap for trapped moisture before

adding it to the melt.c) Avoid charging partially closed containers (soft drink bottles

or cans) that can contain trapped liquids. Liquids or pieces of combustible material can vaporize with explosive violence in the melt and cause an eruption of the molten metal.

d) Inspect spill pit and runout apron to ensure that they are clear of water and debris.

Warning: The failure to properly comply with these procedures may result in an explosion, with possible serious injuries to personnel and equipment.3. Set the furnace selector switches (if installed) for operation on the desired furnace.4. Turn the control power key switch ON and close the main circuit breaker.5. Push the RED STOP BUTTON to reset the AC Interrupter. (This step may be by-passed on systems without the ACI.) Reset the circuit monitor, then push the start button. Note: On units with remote controls, pushing the start button also resets the circuit monitor.6. Turn the control knob potentiometer to the full clockwise position for full power operation. The system will automatically maintain the highest allowable power without adjustment of the controls.7. If less than full power melting is needed, set the desired KW output by observing the KW meter as the control knob is turned.8. Check the panel indicator lights as follows:a) Main Power – RED light is ON.b) Furnace ON – The AMBER LIGHT is ON when the inverter is

running.c) Full Power – The GREEN LIGHT is ON when the inverter is at

full power.d) Normal Operation – With the system operating in a normal

melt cycle, all other panel lights are extinguished.9. Proceed with daily melting.10. Test the Ground Detector prior to every heat. Press, and hold in, the “TEST” pushbutton. The leakage meter reading should increase momentarily, the inverter will shut off, the red “CURRENT TRIP” light will turn on, and the green “GLD ON” light will turn off. A ground leakage reading of less than 2 ma. may indicate a problem with the detector. If the Ground Detector does not function properly, do not operate the power supply. Call the Vendor’s Service Department.

Shutting downWhen melting operations are finished:1. Turn the control knob to zero.2. Turn OFF the high-frequency control push button.3. Turn the circuit breaker OFF and turn OFF the control power key switch.4. Allow the cooling water to continue circulating through the furnace coils, to prevent thermal shock and coil damage, until the refractory has cooled down.Note: Observe all safety precautions. When melting

operations are finished, be sure that the main power red light is OFF. Refer to the troubleshooting section of this manual is faults are experienced. Cabinet doors should be kept locked during normal operation.

Abnormal operations1. Power Outage: The U.V. Trip on the circuit breaker will automatically shut down the furnace.2. Water Pressure Failure: The furnace will automatically shut down. If the furnace is hot, minmum water flow must be re-established within minutes in order to prevent damage to the equipment and possible personnel hazard from emitted steam.3, High Cooling Water Temperature: Try to reduce the power before the unit trips and then continue operations at reduced power while troubleshooting. After a “trip,” it may be necessary to allow a considerable period for the water to cool down.Troubleshooting and corrective procedures for other abnormal conditions are covered in the “Safety Precautions,” “Troubleshooting,” and “Maintenance” Sections. Generally, these procedures are to be undertaken only under the direction of qualified maintenance and supervisory personnel.

KWH counter operationMany systems are equipped with the optional microprocessor KWH Counter which offers even greater automation by allowing automatic melt cycling. The system consists of an LED digital display and four digital thumb switches mounted on the operator’s station. A blue warning beacon announces the end of each melt cycle and a single thumb switch controls the operation of the KWH Counter system.

Before operation, the system must be set up by making the following internal adjustments:

Set the full scale meter reading of the unit KW meter with the internal thumb switches on the back of the KWH counter.

Set the observed holding power loss in the other set of thumb switches. This quantity will be continually deducted from the furnace power so that the counter counts only the “net” melting power.

Set the desired holding power using the internal potentiometer. This is the power level at which the unit is to operate during “hold” periods.

For normal operation, the operator sets the KWH desired for each charge on the front panel of the counter. Melting is begun by moving the thumb switch to RESET and releasing it. After counting down the melt power, the unit automatically goes to “hold” power and lights the blue beacon.

To bypass KWH counting, the thumb switch is placed in the OFF position. This would typically be done during daily startup. ■

References1. Modern Casting Shopbook. ANSI Z241.2 – 1981 “Safety Requirements

for Melting and Pouring Metals in the Metalcasting Industry”. American Foundrymen’s Society, Inc., Golf and Wolf Roads, Des Plaines, IL 60016.

2. National Electrical Code (Latest Edition). National Fire Protection Association (NFPA) or NFPA No. 70-1978, 470 Atlantic, Avenue, Boston, MA 02210.


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