African Fusion August 2013

AFRICAN FUSION AUGUST 2013 1

AFRICAN FUSION AUGUST 20132


Contents

Published four times a year and

mailed out together with

Mechanical Technology by:

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Publisher: Jenny Warwick

Editor: Peter Middleton

Advertising: Jenny Warwick

Cover design: ESAB

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Reader enquiries: Radha Naidoo

Subscriptions: Wendy Charles

Printed by: Tandym Print Cape Town

The views expressed in this journal are not necessarily those of the publisher, the editor or the Institute of Welding.

August 2013

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FEATURES

4 SAIW celebrates South African welding successes SAIW held its 65th Annual Dinner and Awards Ceremony

at Gold Reef City Casino and Convention Centre on Friday, 16 August, 2013.

6 Steinmller Africa takes gold African Fusion takes a tour of Steinmller Africas ISO

3834-certified Pretoria West facilities, visits one of its technical training academies, and talks to Moso Bolofo, Gerrit Buitenbos, and Sonet Jordaan, group training administration manager.

16 The feasibility of utilising FHPP as a repair technique for incorrectly drilled holes

William Pentz outlines work done at the Nelson Mandela Metropolitan University on the use of Friction Hydro Pillar Processing (FHPP) for repair welding of low alloy forged steel (26NiCrMoV14-5).

24 Welding stainless steel using flux-cored wires In this paper, Wiehan Zylstra presents the case for using

flux-cored consumables for welding stainless steels, and highlights the advantages of bismuth-free stainless flux-cored wires.

30 Afrox reinvents the gas regulator At a glittering event at The Maslow in Sandton on 19

July, Afrox launched the most technologically advanced and engineered gas pressure regulator to hit the global industrial market.

34 GEA patents tube welding invention African Fusion visits GEAs Alrode facilities and talks to

the Angel Krustev, who has invented a new methodology and device for tube-to-tube butt-welding on air-finned fan coolers.

36 Reconditioning the Teebus sluice gate This article describes the reconditioning of the sluice gate

wheel, shaft and assembly at Teebus on the Orange-Fish Tunnel.ESAB Africa Welding and

Cutting, through its BBBEE channel partner, Xeon Gas and Welding, has been awarded the contract to supply a full turnkey fabrication solution for DCD Wind Towers R300-million factory currently under construction in the Coega Industrial Development Zone (IDZ). African Fusion talks to Chris Eibl and Tim Sivewright.

REGULARS3 Jims comment10 SAIW bulletin board12 Front cover story: Growing line concept for SAs wind

tower facility40 Welding and cutting forum44 Todays technology: Operating range extended for CMT

welding


Comment

Jims commentSAIW and SAIW CertificationSAIW President and Vice PresidentProf M du Toit - SAIW President, University of PretoriaMr M Maroga - Vice President and Eskom representative

Council membersMr JR Williamson - Personal memberMr T Rice - Personal memberMr DJ Olivier - Personal memberMr W Rankin - Personal memberMr P Viljoen - Stainless Steel FabricatorsDr A Koursaris - Personal memberMr F Buys - Sasol representativeMr G Joubert - SAISI representativeMr J Pieterse - Afrox representativeMr J Zinyana - Personal memberMr L Breckenridge - CEA representativeMr A Paterson - Personal memberMr W Scurr - SASSDA representativeMr J Botha - SAISI representative

Technology and Training Board Mr P Doubell - Chairperson, Eskom

SAIW Certification Governing Board Mr M Maroga - Chairperson, EskomDr A Koursaris - SAIWProf M du Toit - University of PretoriaMr F Buys - SAQCC IPEMr J Guild - SAIWMr D Olivier - SAQCC CPMr A Benade - Sasol TechnologyMr R Williamson - Consultant/Service IndustryMr J Peters - TV Rheinland & SAACBMr P Viljoen - Stainless Steel FabricatorsMr G Joubert - ArcelorMittal SteelMr W Rankin - VelosiMr J Zinyana - New Age Welding Solutions

Executive directorMr JC GuildTel: (011) 298-2101Fax: (011) [email protected]

Executive secretaryMs D KreouziTel: (011) 298-2102Fax: (011) [email protected]

Training services managerMr E NellTel: (011) 298-2135Fax: (011) [email protected]

SAIW and SAIW Certification representatives

Qualification and certification managerMr H PotgieterTel: (011) [email protected]

Technical services managerMr S BlakeTel: (011) 298-2103Fax: (011) [email protected]

Administration managerMrs M WarmbackTel: (011) 298-2125Fax: (011) [email protected]

Western Cape representativeMrs L BerryTel: 084 446 [email protected]

SAIW regional representatives

Durban branch chairmanMr T MonteTel: 082 577-6158Fax: (031) [email protected]

Our new company, SAIW Foundation, should be a reality in just a few weeks. If all goes to plan, and there is no reason to think it wont, SAIW Foundation will be a not for profit company with SARS Section 18 approval in effect, a charitable company.

This means that the company will be able to issue tax certificates for donations received, provided they are used for activi-ties falling within the remit of exemption.

What are the objectives of the com-pany? The intended scope of activities includes: Providing bursaries to needy students for welding, NDT or other

related technology courses. Conducting demonstrations and making presentations to schools and

colleges to promote careers in welding and inspection technologies. Training teachers and instructors from technical high schools and

further education and training (FET) colleges. Preparing DVDs and literature promoting careers in welding for

distribution to colleges and universities. Promotional events encouraging young people to take up careers in

the welding industry and to enter the annual Young Welder of the Year competition.

The Institute has provided start-up funding for the foundation and intends to continue to make contributions as and when it can, but the real key to success will be to get industry involved. This will grow the budget and allow the Foundation to make larger and more effective interventions. Initially SAIW Foundation will have an independent board made up of a maximum of eight directors.

We have great hopes that the Foundation will become a cornerstone of the welding industry and SAIW will be issuing invitations to companies to get involved in the very near future.

Excellence in welding, fabrication and NDT should be recognised and encouraged. Our Young Welder of the Year, Houston Isaacs, from Afrox, performed exceptionally well in the WorldSkills competition held in Leipzig in July, where he managed a creditable 23rd position, just a few marks short of a medal of excellence.

You may think this was not an exceptional performance, but remem-ber our winner comes from an open competition held just six months before the WorldSkills event. Houston is a top class welder, but we only had a few months to prepare our winner for the international competi-tion. The leading countries select a contestant at least two years before the event and use the years leading up to the competition for a training programme specifically aimed at WorldSkills. We want to be competitive, but we prefer an open competition that offers anyone capable a chance to win. In the future, we hope to hold the competition earlier so that there is more time between our national competition and WorldSkills and next time we should achieve that medal of excellence.

Inside this issue you will also see that the Institute has recognised our top trainees, Charl Brazelle and Khutso Moahloli who won awards at the annual dinner. Charl achieved distinctions in both his Level 1 and Level 2 welding inspector examinations and Khutso, an Eskom student, managed to achieve an incredible 90% average in the examinations for four surface and volumetric test methods at SAQCC NDT Level 1. The Harvey Shacklock Gold Medal award for research went to Corney van Rooyen, Herman Burger and our president Madeleine du Toit, for their paper on laser metal deposition of modified low-C martensitic stainless steel, which was presented at the IIW Regional Congress in November 2012.

Lastly, congratulations to Steinmuller Africa on being awarded the SAIW Gold Medal our top award for an outstanding contribution to welding and fabrication in the power generation and process industry fields.

Jim Guild


SAIW dinner and awards

Not only is tonight about entertain-ment, celebration, enjoying the company of friends, family and col-leagues and creating new networks, we are also here to honour and congratulate certain people in the welding industry: students who have done particularly well on SAIW courses; researchers who have contributed to the growing body of knowledge in the industry; and companies that have demonstrated no-table commitment to industry, begins Madeleine du Toit in her welcoming ad-dress. For your excellent performances, we honour and congratulate all of the award winners.

Among the notable guests in at-tendance were: Three past presidents: Robin Williamson, Willie Rankin; and Andy Koursaris; representatives from the Department of Labour and Depart-ment of Trade and Industry; Ben Beetge, the SAQCC NDT scheme committee chairperson; and Hennie de Clercq, the president of the South African Institute of Steel Construction (SAISC).

Lastly, I would like to honour the In-stitutes staff, which we dont do enough. The SAIW is well run, and that is down to what they do every day. So, thanks to them and to all others present who have contributed to the Institute's welfare over the past year, says Du Toit concluding her welcome.

The 2013 awardsThe first person to be honoured at the ceremony was the winner of the 2013 South African Young Welder of the Year competition, Houston Isaacs. We have the main sponsors for the YWOY competition here tonight, including rep-resentatives of merSETA, said Afroxs Johan Pieterse, the SAIW councillor designated to announce the awards on the night. Without the involvement of the sponsors, it would not be possible for the Institute to hold the competition, so we again say many thanks to you, Pieterse adds.

Introducing Isaacs, he adds that in January this young welder won prizes for best young welder in: carbon steel; stainless steel and aluminium as well as being the overall prize winner. Houston went on to represent South Africa at the WorldSkills competition in Germany last month, where he performed well, miss-ing out on a medal of excellence by just a few marks. In recognition of Houston Isaacs dedication and commitment, we have a token of our appreciation, says Pieterse, inviting Isaacs onto the stage to receive his gift from SAIW president,

Madeleine du Toit.The first official awards for the night

were presented to the best students on SAIW training courses. Describing these courses, Pieterse says that the Institute involves industry representatives in every aspect of the development of courses the syllabus, the training ma-terial and the examinations. It does this to ensure that its training programmes and qualifications are well-suited to real industry needs. Using this approach also helps to ensure that graduates from SAIW courses have good prospects of employment and that they will meet industry expectations, adds Pieterse.

Anyone attending SAIW courses will testify that they are very demand-ing. A lot of information has to be ab-sorbed in a short space of time. To be successful really takes a special effort and we aim to recognise the very best of our students through these training awards.

The winners receive a gift of top quality technical reference books and a voucher worth R20 000, which can be used for any Institute training course, seminar or conference.

The Presidents Award for NDTThe SAIW has been training NDT per-sonnel for more than 30 years, the same length of time that it has been training welders. This is a very important part of the Institutes activities and we want to encourage more young people to en-ter this field, which offers excellent ca-reer opportunities, continues Pieterse.

The Presidents Award, made in the name of all of the past presidents of the SAIW who have helped guide the Institute to becoming South Africas reference point for high quality training, recognises the top NDT student on an Institute course.

This years winner, Khutso Moahloli,

SAIW held its 65th Annual Dinner and Awards ceremony at Gold Reef City Casino and Convention Centre on Friday, 16 August, 2013. Guests and welding industry stalwarts, 360 of them, were entertained by the Nubia Girls and Mark Lottering, who compred the evening.

SAIW celebrates South African welding successes

Khutso Moahloli, an Eskom student, receives the Presidents Award for NDT from Madeleine du Toit, SAIW president.

The Phil Santilhano Award for the best student on an Institute Welding Inspector course, was won by Charl Brazelle.


SAIW dinner and awards

is an Eskom student, who achieved an average mark of over 90% in examina-tions for surface and volumetric testing methods at SAQCC NDT Level 1, Pieterse announces.

The Phil Santilhano Memorial AwardPhil Santilhano was one of South Africas leading welding technologists and is best remembered for the research work he did for Vecor on submerged-arc and electro-slag welding of heavy walled pressure vessels. When he was appointed technical director in 1977, he became the SAIWs first full-time employee.

This award goes to the best student on an Institute Welding Supervision and Inspection course. Since these courses began 30 years ago, over 6 000 inspec-tors and supervisors have been qualified to work in South Africas welding industry.

This years winer is Charl Brazelle, who achieved distinctions (over 80%) in his Welding Inspection Level 1 and Level 2 examinations, reveals Pieterse.

The Harvey Shacklock Gold Medal AwardThe Harvey Shacklock Award goes to the author of the best technical paper presented at an Institute event. Shack-lock was the MD of BOC, now Afrox and part of the global Linde Group. He was instrumental in establishing the SAIW and was its first president when it was founded in 1948. Afrox has donated a gold medal for this award since 1949.

This year, we are recognising Corney van Rooyen of the CSIRs National Laser Centre (NLC) and his co-authors, Herman Burger, also of the CSIR NLC and Mad-eleine du Toit, of the University of Pretoria for their paper: Laser metal deposition microstructure of modified low-carbon martensitic stainless steel which was presented at the IIW Regional Congress in November 2012, says Pieterse.

The Institutes Gold Medal AwardThe Gold Medal Award, which is the Institutes highest award, was intro-duced in 1966 and is made to either a company or an individual in recognition of outstanding contributions to welding technology or to the Institute.

This year we are recognising Stein-mller Africa, a multi-service provider of pressure piping, components and repair services to the power generation, petrochemical and allied industries.

In 2012, Steinmller Africa, now a member of the global Bilfinger Berger group celebrated 50 years in South Africa. The company has a relatively new fabrication facility in Pretoria West, which is currently primarily manufacturing boiler components for the Medupi and Kusile power stations and has recently expanded its local operations with the acquisition of KOG Fabricators in Alrode. Steinmller also played a leading role in the refurbish-ment and recommisioning of Eskoms Si-munye power stations Camden, Komati and Grootvlei returning them to service after many years of being mothballed.

The Gold Medal Award is made for the following contribution to the South African welding industry: For the companys commitment

to skills development: Steinml-ler has established three training academies in South Africa, all of which have full five year merSETA accreditation for the training of artisans. More than 32 artisans have been trained to date, includ-ing boilermakers and welders, who leave with coded welder qualifica-tions as well as Red Seal artisan certificates. There are currently 165 students in training and this is being extended to 180 for the 2014 year. In addition, Steinmller partly owns Eduardo Construction, which has a further two training centres that are both IIW approved facilities for training according to the IIW Inter-national Welders Scheme.

The implementation of ISO 3834: Along with its ISO 3834 accredita-tion for its Pretoria West and Alrode works, Steinmller Africa has offered all of its 12 construction sites to independent scrutiny by technical auditors, successfully, since all 12 are now certified.

The adoption of the latest welding equipment: Steinmller Africa has invested over R300-million in its Pretoria West facilities over the past five years.

The company has also demonstrated its commitment to disadvantaged communi-ties by setting up a welder training school in Diepsloot to provide sustainable skills to people seeking self-employment, adds Pieterse, before inviting Moso Bolofo, director of engineering and business proposals at Steinmller Africa, to collect the award.

African Fusion joins SAIW in con-gratulating all of these worthy winners.

The Harvey Shacklock Gold Medal Award for the best technical paper went to Corney van Rooyen of the CSIRs National Laser Centre (NLC) and his co-authors, Herman Burger, and Madeleine du Toit for their paper: Laser metal deposition microstructure of modified low-carbon martensitic stainless steel.

Moso Bolofo, director of engineering and business proposals at Steinmller Africa, collects the SAIW Gold Medal award from Madeleine du Toit.

SAIWs 65th Annual Dinner and Awards Ceremony was held at the Gold Reef City Casino and Convention Centre on Friday, 16 August, 2013.


Gold Medal Award: Steinmller Africa

In recognition of the companys commitment to training, quality of welded fabrications, the develop-ment of local and welding supervision personnel, and the implementation of ISO 3834 at its workshops and its site facilities, Steinmller Africa is the 2013 winner of the SAIWs Gold Medal Award.

Central to the SAIW Councils rea-sons for awarding the medal to Stein-mller Africa is the companys contribu-tions to training and skills development, which is, according to Jordaan a core pillar of the companys philosophy. People are a key ingredient for success. We have a unique approach to human capital management at Steinmller Africa: personnel and payroll on the administration side and two additional divisions: talent management and train-ing, she says.

Talent involves performance man-agement, careers and succession planning and incorporates recruitment. When we source talent, we look for very specific competencies. We also continuously review the competencies and skills of our people to support their development and to identify new career opportunities, Jordaan explains.

It is the success of her training and skills development portfolio that has attracted the recognition of the SAIW.

Jordaan joined Steinmller Africa two years ago and, within three months, had set up a technical skills develop-ment programme. In the past 15 months we have successfully put 36 artisans through the Red Seal tests. And today, we run three merSETA ac-credited Steinmller Africa Technical

On August 16, Steinmller Africa received the SAIWs Gold Medal Award at the 2013 Annual Dinner and Awards ceremony of the Southern African Institute of Welding. African Fusion takes a tour of the companys ISO 3834-certified Pretoria West facilities, visits one of its technical training academies, and talks to Moso Bolofo, director of business development; Gerrit Buitenbos, group quality assurance manager; and Sonet Jordaan, group training administration manager.

Steinmller Africa takes gold

Steinmller Africas Moso Bolofo, Gerrit Buitenbos, and Sonet Jordaan.

Trainees under instruction at the merSETA accredited Steinmller Africa Technical Training Academy (SATTAs), at the companys Pretoria Works.

A trainee artisan practices the special skill of welding boiler tubes in circumstances that simulate real boiler repair conditions.


Training Academies (SATTAs); one at our Pretoria Works; one at Bethal and one at the Vaal University of Technol-ogy (VUT) in Sebokeng, Jordaan tells African Fusion.

The Pretoria works with its 52 apprentices, focuses on boilermaking and welding; Bethal trains mechanical and pipe fitters as well as welders; and VUT is dedicated to welder training. We currently have 169 apprentices across the three academies and we expect 99% of them to graduate as Red Seal artisans, she continues.

The apprenticeships are 18 to 24 months in duration but we add three additional months for specialisations. The welders, for example, need to be coded and boilermakers or fitters also need to learn additional skills to get successfully integrated into the Stein-mller Africa workplace.

Where do the apprentices come from? We invite young people with Matric maths and science to send us their CVs, but most come through the Our Schools programme that we initiated last year. We have identified 12 partner schools, mostly technical schools from disadvantaged commu-nities that we work with. We start by going into Grade 7 classrooms to talk to learners before they choose between the academic and technical fields.

We tell them what it means to be an artisan, how much they can earn and the global opportunities that prac-tical qualifications can open up. We support and nurture these schools; se-curing equipment and material support from local industries; providing the basic curriculum to meet merSETAs minimum requirements; and provid-ing their teachers with some technical training and support to make sure they have skills to pass on in classrooms, Jordaan reveals.

As well as Red Seal artisan train-ing, Steinmller Africa is also proactive about upskilling its experienced work-ers. We have a significant number of skilled, experienced people and supervisors who do not have Red Seal qualifications. These people mean a lot to us and we cannot afford to lose them, Buitenbos reveals. Jordaan explains: Therefore, these people do an internal mini trade test that helps us to identify gaps in their knowledge.

Then we customise a training course to fill these gaps. After the course we issue them with a Certificate

of Competence, which allows them to apply to become fully qualified Red Seal artisans under Section 28.

These people are encouraged to apply to our service provider, the Ar-tisan Training Institute (ATI), to do the full trade test for themselves.

Jordaan continues: This is part of a companywide programme called Thuthuka, a Zulu word which means we grow. The programme is associat-ed with adult basic education (ABET)

in numeracy, literacy and soft skills such as business and personal finance. The idea is to uplift and open doors for our own people, not only in technical fields, but across the organisation.

We are introducing 24-month courses at all of our 16 sites nation-wide. Trainees are released from work for two hours a week, but then we ask them to commit to a further two hours of their own time every Friday afternoon.


Superheater elements loaded and ready for shipment to the Medupi Power station.

The tube bending shop at Steinmller Africas Pretoria West works.



of ISO 3884, along with the Eskom Rule Book, welding code requirements, client site requirements, the pressure equipment regulation (PER) and SANS 347, and its general commitment to the health of the South African weld-ing industry in general, the SAIW Gold Medal award is well deserved.

The commitment to quality of welded fabricationsBolofo assures African Fusion that in spite of recent criticisms of the contrac-tors on the Medupi and Kusile projects, Steinmller Africa has been audited by both Eskom and Hitachi and no problems with welding procedures, heat treatment or the qualifications of welders have ever been identified.

Over the past five years, we have invested over R300-million in our Preto-ria West facility, so the welding is being done using the very latest machines and technology available anywhere in the world, he points out. In fact, this plant in South Africa is now considered to be the global centre of competence for pressure parts for the entire Bilfinger Group.

Steinmller Africa is contracted to manufacture water-wall panels, head-ers, and superheater elements, amongst others, for the Medupi and Kusile power plants. We have extensive experience with all of the modern materials being used for these, Bolofo adds, with both the P91 and the new 12% Cr VM12 steel, which we are welding and heat treating successfully to the standards required.

As well as the Medupi and Kusile new build projects, which will be completed from a manufacturing point of view within two years, Steinmller Africa has also won an export tender for replacement headers and other pressure parts for a large 12-unit power plant in Poland. This is a modernisation programme to extend the life of 25 to 30 year old power boilers by a further 20 to 25 years, says Bolofo.

By using newer materials and designs, we have been able to increase the efficiency of these plants by more than 2%. For a power plant, this results in massive cost benefits over time. And we are fast approaching the time when we will need to do something similar here. Even Majuba, one of the younger power plants in the Eskom fleet, will get to the end of its life quicker than expected because it has been cycled a lot more than anticipated, he suggests.Despite coping with harsh conditions and high-ash coal in South Africa, we became very good at boiler mainte-nance, Bolofo continues. We are used to running excellent maintenance regimes and we are in the process of building that ability back up. We run service contracts, for example, for the

majority of the Eskom fleet. Many of these are performance-based, so we get paid based on meeting the shut-down times, weld repair rates and reliability indicators stipulated in the contracts, he says.

Gerrit Buitenbos, group quality assurance manager, cites Steinmller Africas certifications as evidence of the companys commitment to weld quality. We acknowledge welding as a special process that is critical to the success of our products and business, he says.

ISO 3834 offers a practical ap-proach to welding and everybody involved in fabrication processes is committed to maintaining the quality standards required.

The certifications of our Pretoria West and our Alrode manufacturing plants and all of our site-based opera-tions, ensure that qualified welding and supervisory staff are always available, following the required procedures, put-ting the necessary documentation in place and continually looking to achieve sound welding and product quality.ISO 3834 makes the welding require-ments very clear, which steers welders towards good practice and good quality work, which is the ultimate aim. Certifi-cation based on international standards puts us in a globally competitive posi-tion, Buitenbos suggests.

As a result of Steinmller Africas combined commitments in training and upskilling people, adopting the latest welding technology, the implementation

The CNC machining and nipple welding machine for boiler headers, one of the investments that has made this South African plant the Bilfinger Groups global centre of competence for pressure parts.

The Pema submerged-arc welding system for fabricating water-wall panels. Six submerged-arc welding seams are deposited simultaneously to join four water-tubes together with three connecting strips.


SAIW bulletin board

Materials Testing Laboratory officially opened

SAIWs new Materials Testing Laboratory was officially opened on Friday, 19 July, 2013 at an after-noon event at the Institutes City West premises. The journey towards this opening began back in 2006, while we were looking for ways to improve the quality of services offered to clients and members, says Jim Guild, SAIW executive director. After extending the building, we identified some under-utilised space and decided to make our Technology Centre more useful by adding metallurgical and weld testing capabilities, he adds.

Rising damp required that the en-tire floor had to be dug up and relaid, delaying completion of the project

by at least a year. So, thanks to the Institutes council for its ongoing sup-port and patience during this time and to our equipment suppliers, IMP, who willingly stored our equipment in their warehouses.

Finally, apart from one piece of preparation equipment and one final testing machine, we are good to go, Guild announces. We have a combina-tion of good equipment and good people and are finally able to support industry with the quality service that we origi-nally envisaged, he says, before hand-ing over to Sean Blake, SAIW technical services manager, who is responsible for the new laboratory.

Our core objective as SAIW is to improve the quality of welding in industry, so we have coined the tag line Testing for quality in welding for our Materials Testing Laboratory, says Blake. We have always offered a weld-ing consulting service, but in the past, we have never been able to test welds. We have always had to use third party inspection services.

Inspection reports give results, but you cant always get a feel for a weld from the results alone. Having our own lab allows us to look at the detail and interpret the results. If one Charpy result is a little lower than others, for example, even if it is still within specification, we can prepare a micrograph and look for

a reason and we recently did exactly that and discovered a layer of continu-ous martensite on one sample, while the other three showed martensite in-terspersed with ferrite. This allows us to make recommendations about welding that traditional testing houses could not have picked up, Blake reveals.

The SAIW facility is offering a specialist testing services for welds. If it has anything to do with welding, we are able to test, evaluate and give advice based on the results. If a weld fails, we can find out why. We can test welding consumables for mechanical strength, toughness and hardness. We can do welding procedure qualifications and welder qualifications, as well as positive material identifications to determine if the correct welding con-sumable has been used, for example, he explains.

The laboratory will also be used to improve the quality of the Institutes training courses. With our inspection and NDT courses, we can support classroom activities by showing stu-dents how to do tests and how poor control of weld quality will affect a weld, Blake continues. Year on year, we are seeing increasing numbers of students in welding engineering, weld-ing technology, weld inspection and NDT coming through and we want to support all of these training initiatives.

Madeleine du Toit, SAIW president, cuts the ribbon on the Materials Testing Laboratory, watched by Sean Blake and Jim Guild (foreground)

IIW 2013-Essen: The 66th IIW Annual Assembly and International ConferenceKlaus Middeldorf says that it is a great honour and privilege for DVS, the German Welding Society, to wel-come the IIW family to Germany for the fourth time. After Essen 1957, Ds-seldorf 1973 and Hamburg 1998, the IIW Annual Assembly and International Conference will return to Essen in the North Rhine-Westphalia region from 11-17 September for its 66th meet-ing, says the DVS general manager.

IIW2013-Essen will be unique compared to previous annual assem-blies. The usual Thursday to Saturday technical working group meetings are scheduled, but the event is destined to be a one-of-a-kind opportunity as it offers the added bonus of linking the IIWs family of science and technology with the world of joining applications, all under the same roof and at the same time. IIW attendees will be encouraged

to visit and network with over 1 000 exhibitors from more than 40 nations during Schweissen & Schneiden 2013, the international trade fair for the join-ing, cutting and surfacing industries taking place from 16-21 September. The overlapping of IIW2013-Essen with the worlds largest welding, joining, cutting and surfacing trade show will certainly add a new and unforgettable dimension to the IIWs world of joining experience.

The two-day IIW International Con-ference will focus on the globally trend-setting topic Automation in Welding and will feature invited speakers from the international scientific community and from industry. The current and future status of welding automation, as well as the present and projected world market situations, will be explored. Applications including the newest and

most emerging technologies, methods and processes, will be presented.

In addition to the stimulating techni-cal sessions, an interesting and varied programme of technical and sightseeing tours have been organised. As the lead-ing city of the Ruhr metropolis, Essen is home to many acknowledged cultural institutions, including a UNESCO World Heritage Site. Essen was nominated as a 2010 European Capital of Culture. The nearby cities of Cologne, Dssel-dorf, Aachen, Duisburg and Dortmund, as well as Mnster, Oberhausen and the former German capital city of Bonn, also have much to offer to delegates and ac-companying persons in terms of science and sightseeing.

DVS is pleased to be hosting the IIWs international materials joining fra-ternity in Essen, concludes Middeldorf.


SAIW bulletin board

Long service award for Johannes Msomi

Welding is a craft. Facets of both art and science are evident. Whilst we like the concept of science for its apparent predictability, the real-ity of welding cannot be modelled ex-actly. With a wide scope of applications and, in many cases, a significant cost of failure, a competent professional welding engineer is required.

Structures, large or small, are intended to achieve a purpose under certain operating conditions. The re-quirements may be described in terms of externally applied loads, and load effects that result in stresses in the structure. In most cases, the safety of many people depends on the integrity of the welds. The welding is a vital and enabling component of the structure.

If one considers the history of fail-ures, joints are high on the list. Who takes responsibility for such failures? The structural engineer signs drawings, taking legal responsibility for the integ-rity of the structure. Structural engineers are well trained to identify loads and load effects that affect structures and to determine models to characterise members of structures, but are not well trained to manage joints, particularly welded joints. Whilst the assumption of structural models is material homogene-ity, welded joints are not homogeneous and their analysis needs to integrate continuum and discrete material mod-els. Welding engineers are trained to manage the interface between the cast joint and the wrought structural ele-ments together with the effects of local geometric change.

So, where does the welding engi-neer fit in? Welding engineering is a relatively new postgraduate specialist qualification. It is the senior of three associated disciplines: the welding engi-neer, welding technologist and welding specialist. New procedures, such as ISO 3834, require that fabricators employ or have access to welding engineers, the requirements increasing as the impact of failure increases.

By its very nature, welding science and technology is multidisciplinary. It embraces the discrete theories of mate-rial chemistry and heat behaviour with the continuum theory used by structural engineers. Welding engineering is a postgraduate qualification. Candidates are drawn from graduate mechani-cal and metallurgical engineers with some experience. In this country, the qualifying authority is the International Institute of Welding (IIW).

The IIW differentiates between the international welding engineer (IWE) and the certified international welding engineer. The certification of the IWE is similar to a CPD system and has a period of validity of three years. Every three years, the certified IWE needs to document two recent years of experi-ence through relevant job content and demonstrate how technical knowledge has been maintained and developed.

In order to build a body of welding engineers in South Africa, both recog-nition of prior learning and a willing-ness to train graduate engineers and scientists without prior experience is required. Training with opportunity to

practice leads to com-petence. Competence is based in principles not rules first learn to question, to doubt. Maintaining compe-tence is a lifetime en-deavour. Competence is what enables the professional welding engineer to take legal responsibility for decisions.

The certificated IWE qualification is awarded to those who have passed the theory exam, have kept up with current theory and practice and who can document relevant experience. If the academic qualification and certifi-cation system cannot be administered by ECSA, as it is for other professional engineering disciplines, the local ANB, SAIW could take the lead.

Tony Patterson, associate professor for welding at Wits.

What we expect from a welding engineer by Tony Patterson

SAIW launches new safety courseA new five-day welding safety course will be presented by SAIW for all personnel carrying responsibility for safety in welding workshops and fa-cilities. The course is ideal for welding supervisors and safety officers.

Regulatory requirements of the OHS Act, and the Mines and Works Act, as well as SANS 10238: Weld-ing and thermal cutting processes Health and safety, will be dealt with in detail.

In summary, the five-day course syllabus will include: Welding theory in SMAW, GTAW,

GMAW and FCAW.

Practical welding in the above processes.

OHS Act Regulation IX and the Mines and Works Act.

A detailed look at SANS 10238. An Afrox presentation on oxyfuel

gas welding and cutting equip-ment and regulations.

The course will run from 30 Septem-ber to 4 October, 2013 and partici-pants will write an examination on the final day for certification purposes.

For further information contact Mi-chelle Warmback on 011 298-2100 or 298 2125.

[email protected].

Madeleine du Toit presents a long service award to SAIWs Johannes Msomi.

Johannes Msomi, who was recently appointed as the sample prepara-tion technician for SAIWs new Ma-terials Testing Laboratory, received a long service award from SAIW on July 19, 2013. Johannes has now been with the Institute for 30 years, and in recognition of that, we would like to present him with this long service award, said Jim Guild, the Institutes executive director.

Johannes is one of the Institutes most loyal, reliable and multi-skilled employees. For many years he travelled to work every morning from his home in Bronkhorstspruit, not something that anyone can now afford with fuel prices and toll fees where they are, he adds.

The award was presented by Mad-eleine du Toit, the Institutes president.


South Africas first wind tower fabrication facility, a 23 000 m2, ultra-modern production line capable of producing 120 m towers, is currently being built in Port Elizabeths Coega IDZ. The localisation of manu-facturing has got to be the right way to go, and now that wind tower volumes are here, this production facility will provide sustainable employment for more than 100 people in the Eastern Cape. This factory in Port Elizabeth is a major boost for the upliftment and upskilling of people in that region, says Sivewright.

The first round of the Independent Power Producer (IPP) bids had a 25% local content requirement, which is easily achieved during construction. So, at Jeffreys Bay and at Van Stadens, for example, tower sections are being

ESAB Africa Welding and Cutting, through its BBBEE channel partner, Xeon Gas and Welding, has been awarded the contract to supply a full turnkey solution, comprising cutting, welding, handling and rotating equipment and consumables for DCD Wind Towers a division of the DCD Group at its R300-million factory currently under construction in the Coega Industrial Development Zone (IDZ). African Fusion talks to Chris Eibl, MD of ESAB Africa, and Tim Sivewright of Xeon.

Growing line concept for SAs wind tower facility

Chris Eibl, MD of ESAB Africa, and Tim Sivewright, general sales manager of Xeon Gas and Welding.

At the start of the process are two ESAB SUPRAREX HD 6000 CNC-controlled flame cutting machines with 6,0 m width and 38 m length capacities. Insert: ESABs triple torch cutting heads enable I-, Y- and X-weld preparations to be cut in a single operation.

imported, shipped and bolted together on site, he continues. Bid Round 2, though, requires 40% local content. This means that the joint venture IPP companies and consortiums that have been awarded wind farm development contracts are going to have to get much more of the fabrication work done lo-cally, he explains.

To put the size of these wind towers in perspective, if you take the length of a rugby field and turn it upright, you will get a sense of just how tall they are! exclaims Eibl. A complete wind tower consists of three to five sections, giving a hub height of around 80-120 m. Each section is made up of individual cans 3,0 m in length and with diameters ranging from around 5,0 m at the base to about 2,5 m just below the turbine.

In a development that has been two years in the making, DCD and ESAB have planned and designed a complete cutting and welding production line to meet the high productivity and cost efficiency requirements of modern wind tower manufacturing. This line is a complete, innovative and turnkey solution. DCD has embraced ESABs growing line concept and, as the only original equipment manufacturer capable of supplying the equipment and consumables necessary to fabri-cate wind towers cutting machines, manipulators, columns and booms, welding equipment and consumables everything on the line will be supplied and integrated by ESAB, Eibl tells African Fusion.

Simply put, wind tower manufac-ture involves cutting plate, rolling it into cans and then joining cans until the length of the section is achieved.

Cover story


Each of the cans has to be perfectly aligned and welded. The old way of doing things was to use cranes, says Eibl. You would make a can, lift it into position and weld it onto the previ-ous can, and so on.

This factory will not use cranes for manipulation during the welding of the wind tower sections. Instead, roll-erbeds with built in manipulators are used to grow the line, he explains. A set of hydraulically driven transferring rollers lift the can clear of the rotating rollers and shuffle it along and onto a rollerbed further up the line. A new can is then loaded and welded, before the whole weldment is shuffled up a further 3,0 m. So you end up with a complete tower section of up to 38 m in length on a single growing line; and DCD Wind Towers has four of these lines, he says.

We have developed handling solu-tions to cater for most of the handling from the moment the plates arrive to the shot blasting and painting of the finished tower, says Siverwright. At the start of the process are two ESAB SUPRAREX HD 6000 CNC-controlled flame cutting machines with 6,0 m width and 38 m length capacities.

A key advantage is provided by the triple torch cutting heads that enable I-, Y- and X-weld preparations to be cut in a single operation and these heads will cut a perfect landing nose at the same time, continues Eibl.

Once profiled, the plate is rolled with equipment not supplied by ESAB, to form the can and the longitudinal seam is closed at the first welding sta-tion. DCD has decided to go for single wire submerged arc welding to start with, says Sivewright, but tandem, twin tandem and even ICE (integrated cold electrode) options are open to them should they need to increase throughput at a later stage.

The root runs are done from the inside at ground level. The can is then rotated through 180 to place the seam on top. The root is done with no back gouging as punch through is used be-fore the seam is filled and capped from the other side. On the thin sections, we are sometimes completing the seam in two runs, but on the 55 mm sec-tions, we might have to do 25 runs to completely close the joint.

ESAB Aristo 1000 AC/DC sub-merged arc power sources are being used, which use patent pending

technologies to deliver more welding per kilowatt hour. The primary input power requirement of these machines is lower than any equivalently rated

competitor machine and is the only power source on the market that can go from 100% dc to ac on the fly, claims Eibl.

Rollerbeds with built in manipulators are used to grow the line. A set of hydraulically driven transferring rollers lift the can clear of the rotating rollers and shuffle it along and onto a rollerbed further up the line.

ESABs flux feed and recovery system (FFRS) is being used to optimise flux use, temperature and humidity.

Cover story


channel partner that adds value for the end customer.

And we have committed to this project for the long term, Sivewright assures African Fusion. We will have dedicated specialists on call in Port Eliza-beth, 24/7, to go with our just-in-time deliv-e r y sys tem from our lo-cal warehouse to ensu re a secure supply of consumables.

This is a state-of-the-art factory and both Xeon and ESAB are determined to assist DCD in their quest to be a leader in wind tower manufac-turing in South Africa for many years to come, Eibl concludes.

The completed 3,0 m can is then shuffled along onto the next roller bed. There, a circular seam welding system joins it to the previously completed section. On the circs, we put the root in with dc-positive to get the required penetration and, without stopping the rotation, we switch to ac parameters, which give higher deposition rates, he adds.

Different welding procedures and parameters are required for each seam, but the ESABs PEK controller is able to store up to 255 pre-programmed procedures, so the parameters for every run at a station can be prepro-grammed.

As the tower grows, increasingly longer lengths have to be rotated. Two parallel rows of rollerbeds, all with pre-cisely synchronised speed control, and load capacities varying from 30-90 t, stretch the full length of the line. Once a tower is completed on one of the four growing lines, it is transferred across to a parallel line coming back down, where it is finished, shot blasted, and painted, explains Sivewright.

Highlighting the welding innova-tions embedded into the stations, Eibl says that ESAB GMH touch-probe seam tracking systems are being used to track the root seam and to control standoff. We also use a laser pointer when an edge for the touch probe to follow is unavailable. The operator uses a joystick to keep the laser on the required seam as welding progresses.

In addition, ESABs flux feed and recovery system (FFRS) is being used to optimise flux use, temperature and humidity. The quality and consistency of the flux is important for achieving the required weld toughness, Eibl reveals. This system not only recov-ers unused flux, but it ensures that the ratio of recovered flux to new flux is maintained. The flux is heated and dehumidified in a thermostatically controlled, 6,0 bar pressure vessel before use. This system, when used with our OK Flux 10.72 and OK Autrod 12.22 wire, enables us to guarantee the integrity of the weld and therefore the mechanical properties of the fin-ished seam.

From a business perspective, our partnership with Xeon was a key factor in securing this contract, Eibl continues. As a Level 1 BBBEE com-pany that has been properly funded and established, ESAB now has a

ESABs A6S Arc Master single-wire submerged are welding heads, complete with positioning, joint tracking, flux handling and a laser pointer system, are being used to automatically weld the horizontal and circumferential seams.

ESAB automatic welding heads on a three-section telescopic boom offer the operator safety, excellent reach and heavy loading capacity.

Cover story


FHPP

This paper reports on the findings of a study done to establish the feasibility of implementing Friction Hydro Pillar Processing (FHPP) as a repair technique for incor-rectly drilled or worn holes in high value components. FHPP is a solid state welding technique that utilises frictional heat generated by rotating a cylindrical consumable tool co-axially in a blind hole under an applied load. The resultant solidi-fied plasticised tool material then fills the hole. The first part of the paper reports results obtained from FHPP weld trials done on AISI 1018 material. Particular attention was given to evaluating the influence of axial force, rotational speed and consumable length on defect population and bonding.

The study showed that a good correlation exists between weld quality and the appearance of the primary and second-ary flash formation of a completed weld. A change in the axial force had a significant effect on weld time for a given consumable length. The weld quality was also significantly affected by the clearance between the consumable tool and the sidewall of the hole.

The second part of the paper discusses results obtained from FHPP welds made with 26NiCrMoV14-5. These welds were made considering some of the trends observed during the AISI 1018 weld investigation. The 26NiCrMoV14-5 material welds responded similarly to the AISI 1018 welds; however, the main difference being that fewer defects were observed at higher axial forces. The 26NiCrMoV14-5 FHPP welds produced bonding of 90% and above for the complete axial force range tested.

The study further showed that defects observed at the last shear interface decreased with an increase in forge force whereas excessive consumable length increased the amount of second phase particles in this same region.

Presenting at the SAIW-hosted International Institute of Weldings Regional Congress, 2012, William Pentz outlined work done at the Nelson Mandela Metropolitan University on the use of Friction Hydro Pillar Processing (FHPP) for repair welding of low alloy forged steel (26NiCrMoV14-5) used for components in turbine-generator installations.

William Pentz.

The feasibility of utilising FHPP

IntroductionFriction Taper Stud Welding (FTSW) and Friction Hydro Pillar Processing (FHPP) were first researched in the early 1990s by The Welding Institute (TWI)[1]. FHPP is a solid state welding process, where a load is applied to a rotating consumable tool in a co-axially aligned blind hole. The FHPP weld can be completed under water as researched by Ambroziak and Gul[2]. An example of utilising FHPP with a tapered geometry for the repair of a crack has been previously illustrated by Hattingh et al.[3]

The focus of this study is to evaluate FHPP as a potential repair procedure for damaged or incorrectly drilled holes in high value components. The work done was aimed to assist in creating an understanding of important considerations for producing an acceptable weld by FHPP in 26NiCrMoV14-5 materials. The proposed repair technique consists of six stages as shown in Figure 1. Firstly a sacrificial backing plate is placed below the hole and fastened to the component to be repaired.

The damaged hole is machined larger to remove the dam-aged circumference and into the backing plate. The machined hole is then repaired by FHPP and if required, post-weld heat treatment is performed. Excess material from the FHPP and backing plate is removed mechanically and a new hole re-drilled to complete the repair.

The quality of the bonding for this study refers to the degree of fusion achieved along the bond line between the sidewall and weld nugget. The bonding quality is expressed as a bonding percentage and will aid in establishing the feasibility of the repair technique. During FHPP welding the bottom corners and bottom surface of the hole presents the biggest challenge for achieving good bonding.

Figure 1: Proposed repair technique.

as a repair technique for incorrectly drilled holes


FHPP

To improve the bonding at the bottom of the hole to be repaired a sacrificial backing plate was introduced, which allowed the drilled hole to be extended into the backing plate. During removal of the backing plate, the inherent discontinuities are removed, resulting in a reduced risk of bonding defects at the bottom of the repaired hole.

Figure 2 shows a typical process torque curve of a AISI 1018 FHPP weld with the corresponding shear layers also visible on the macrograph as indicated.

Hasui and Fukushima were the first researchers to divide the torque curve of a friction weld into stages[4]. Later, Kimura et al[5] divided the first stage into two sub-stages, namely a wear stage and a seizure stage. With reference to Figure 2, the wear stage (a-b) commences as soon as contact is made between the tool and hole surfaces. This is also referred to as the dry friction stage and continues until frictional contact is established on the whole of the bottom interface surface.

Then the seizure stage starts (b-c). During this stage, fric-tional heat is generated while process torque continues to rise sharply, indicating that a pseudo-plasticised stage exists until torque starts to decrease. This is the second primary process stage where material is now fully plasticised and can no longer support an increase in torque due to a reduction in mechanical strength associated with the increase in temperature.

Torque will continue to decrease between the tool face and fused material until it can again support an increase in torque. This indicates the start of Stage 3 where the torque remains fairly constant. The torque increases during Stage 4 until the entire surface is plasticised again and can no longer support the increase in torque. It should be noted that a shear layer occurs when the torque drops during the welding process.

During Stage 5 (d-h) the torque continually increases and decreases cyclically as shear layers are formed. Stage 6 (h) occurs closer to the top of the weld when the weld interface area decreases, resulting in shear layers forming at lower torque values.

After the volume fill has been completed, the rotation stops and Stage 7 starts (i). During this stage an axial forge force is applied to allow for consolidation of the final plasticised mate-rial in the top region of the weld under a forge type set-up.

Figure 3 shows a cross-section of a FHPP weld that shows the weld nugget, heat-affected zone (HAZ), consumable tool, rotor block and backing plate. The primary flash is mainly formed from the solidified plasticised material originating from the consumable tool, while the secondary flash is formed from the rotor block material.

During this study, the fusion between the consumable tool and the side wall of the rotor block will be referred to as rotor bonding percentage whereas the fusion with the side wall of the backing plate will be referred to as the backing plate bonding and the bonding at the bottom surface of the hole will be referred to as bottom bonding.

The work done during this feasibility study was planned so as to assist in creating some understanding of the impor-tant considerations for producing acceptable FHPP welds in 26NiCrMoV145 materials.

Characterising the relationship between the process param-eters and their influence on the bond quality is considered a crucial contribution towards the development of an acceptable industrial FHPP repair technique. During the feasibility study there were no static or dynamic tests completed as good bond-ing was set as the first hurdle to cross.

Experimental setupFeedback data during welding is required to analyse the process and bonding. Torque and axial force were recorded by a calibrated load cell at 100 Hz, whereas the plunge depth and rotational speed was recorded at 1,0 Hz, due to platform limitations. The process parameters mentioned in this study refer to the values programmed into the control unit. All the welds were completed on the FHPP platform shown in Figure 4.

The consumable tool geometry and assembly of the work piece is shown in Figure 5. The assembly consists of the back-ing plate, holding block and the consumable block. Unless stated otherwise, all the welds were performed with a face diameter of 9,0 mm, tool diameter of 14 mm, chamfer angle and height of 45 and 2,5 mm respectively, hole diameter of 15 mm and a total hole depth of 25 mm. The depth of the hole in the backing plate was 7,0 mm.

FHPP as applied to AISI 1018Recognising that 26NiCrMoV14-5 low alloy steel is costly and difficult to source, AISI 1018 steel was selected for pre-liminary experimental development. Initially it was decided

Figure 2: The process torque curve for an AISI 1018 FHPP weld (left) and (right), the corresponding shear layers in macrograph.

Figure 3: Graphical representation of FHPP and associated micrograph.


FHPP

to set a rotor bonding criteria as an indicator and that a rotor bonding percentage lower than 80% would be considered unacceptable from a feasibility study point of view. All the AISI 1018 welds (22 in total) were completed with a constant forge force of 12 kN applied for 20 sec. It is important to note that the forge force relates to the axial downward force applied after completion of the weld, ie, with a stationary spindle.

The initial work indicated that the maximum tool face diameter had to be limited to 9,0 mm so as not to exceed the allowable motor start-up torque of the FHPP platform. To accommodate the larger tool diameter of 14 mm, a chamfer was machined onto the face of the consumable tool. Tool-hole clearance was initially evaluated followed by the two significant process parameters as identified by literature, namely axial force and rotational speed.

The volume fill was tested last, as it was believed to play a secondary role to bonding and was only beieved to be crucial in order to avoid underfill.

The initial tests, done at 9,0 kN to establish the effect of clearance between tool and hole, indicated a 10% variance in rotor bonding, with the 1,0 mm clearance achieving complete bonding. The only other noticeable difference was primary flash appearance, with the large clearance resulting in the flash rising along the tool shank as illustrated in Figure 6. Although con-sidered non-critical in the case where a sacrificial backing plate is used, it is important to note that this study showed a remarkable reduction in side wall backing plate bonding (90% to 2%) with an increase in clearance.

Figure 7 illustrates the effect of increased axial force with a pre-determined clearance of 1,0 mm. Externally there is a noticeable difference in the appearance of the flash, however more importantly, higher rotor force gives a 28% increase in rotor bonding. Poor bonding at lower axial forces can be at-tributed to the consumable tools tendency to plasticise and solidify onto itself, preventing it from transmitting sufficient heat to promote side wall bonding. An axial force of 9,0 kN was selected for use in further tests, as it gave a higher rotor bonding percentage (95%) and a last shear layer, which was closer to the top surface of the weld than the 12,0 kN weld.

Changing rotational speeds between 4 000 rpm, 5 000 rpm and 6 000 rpm had some effect on the flash formation as illustrated in Figure 8. More important to note is that at 9,0 kN of axial force, the higher rotational speeds achieved a substantial increase in rotor bonding percentage, most probably as a result of the greater heat input. It was also noticed that the primary flash tends to be smaller with higher rotational speed.

The FHPP platform could not maintain the rotational speed of 6 000 rpm during the weld, thus 5 000 rpm was selected, which had a rotor bonding percentage of 86%.

Increasing the volume fill at constant clearance (1,0 mm), axial force (9,0 kN) and rotational speed (5 000 rpm) resulted in a negligible change in rotor bonding, but 140% volume fill produced a more geometrically rounded flash as indicated in Figure 9. Volume fill of 120% was similar to the primary and secondary flash formation of 140%, however the bonding percentage was 95%.

From the analysis of all 22 welds made as part of this study, secondary and, to a lesser extent, primary flash forma-tion was identified as a potential early indicator of poor bond-ing. All welds that exhibited an identifiable lack or absence of secondary flash, or where the primary flash did not exhibit

Figure 4: The Friction Hydro Pillar Processing (FHPP) platform. Capabilities include: torque 100 Nm; axial and forge force 40 kN; rotational speed 6 000 RPM; sliding distance 95 mm.

Figure 5: Consumable Tool Geometry: left, consumable tool; right, workpiece.

Clearance 1,0 mm 3,0 mm

Axial force 9,0 kN 9,0 kN

Rotational speed 5 000 rpm 5 000 rpm

Volume fill [%] 100% 100%

Rotor bonding [%] 100% 91%

Backing plate bonding [%]

90% 2%

Visual appearance and macrograph

Figure 6: The effect of clearance between tool and hole indicated a 10% variance in rotor bonding, with the 1,0 mm clearance achieving complete bonding. A large clearance (3,0 mm) results in the flash rising along the tool shank.

Axial force 6,0 kN 12 kNClearance 1,0 mm 1,0 mmRotationalspeed

5 000 rpm 5 000 rpm

Volume fill 120% 120%Rotor bonding 67% 95%


Figure 7: The effect of increased axial force on bonding. The higher rotor force gives a 28% increase in rotor bonding.


FHPP

a rounded appearance, were associated with low rotor bond-ing percentages. Although more work needs to be done to definitively prove this, early indications are that a preliminary bond-quality screening model could be developed by com-bining external flash appearance with process torque data.

Figure 10 shows torque data of selected welds done with variation in clearance, axial force, rotational speed and volume fill for process conditions as indicated on each graph. The first graph shown in Figure 10 (a) was used to interpret the influence of clearance between the tool and hole. It was very clear from this study that there is a limit to clearance in both minimum and maximum directions. Evidence gathered indicated that the side wall must be close enough to the tool periphery for bonding, but far enough from the side wall so as not to interfere or bond prematurely, as this will result in uneven bonding and the formation of large voids.

Bonding percentage certainly improved as the clearance was reduced from 3,0 mm to 1,0 mm. If the clearance is too large, bonding with the sidewall is restricted as the plasticised material advances rapidly upwards along the shank and so-lidifies above the top of the hole around the consumable tool shank. Large clearance also resulted in smaller heat affected zones, indicating that the sidewall heating was less effective. As expected, Figure 10 (b) confirmed that increasing the axial force resulted in a corresponding torque increase over the first 5,0 sec, most probably due to increased frictional resistance caused by the larger applied axial force.

It is believed that optimal plasticising temperature is only obtained when the recorded torque starts to decrease. Evidence pertaining to shear-layer formation appears to be less prominent in high axial force torque curves; possibly suggesting that shear layer formation is rapidly interrupted or more continuous in nature. Macrographical evidence indi-cates that with high axial forces the last shear layer formed is more parabolic in shape with the lowest point well below the welds top surface. Since this phenomena reduces the hole volume to be filled by the plasticised tool material, it contributes to decreased welding time as was recorded for welds with higher axial forces.

With increased rotational speed, there was a significant decrease in the torque as shown in Figure 10 (c). The data tends to indicate that optimal plasticisation temperature is reached at lower torque values with a rotational speed of 5 000 rpm. The higher rotational speed certainly contributes to higher bonding percentages and evidence suggests that this is the result of increased shear layer interface temperatures, allowing shear layers to form more rapidly.

The data in Figure 10 (d) illustrates the relationship between process torque and volume fill. Recorded rotor bonding percentages were high and fairly constant between the 100 and 140% volume fill for the reported conditions. As expected, the HAZ at the top of the weld increased in width as volume fill increased. Preliminary interpretation of process parameter interaction tends to indicate that improved weld quality could be realised with lower process torque, reduced shear layer thickness and enough heat transfer between the plasticised tool material and the side wall of the hole.

FHPP of 26NiCrMoV14-5Based on the knowledge gained during the AISI 1018 weld trails, sixteen 26NiCrMoV14-5 welds were made and compared according to the matrixes shown in Table 1. This

analysis was done to identify process parameters that would contribute to increased bonding. This part of the paper will look at selected aspects of this study.

Considering the increased strength at elevated tempera-tures of 26NiCrMoV14-5 compared to the AISI 1018, it was decided to increase the forge force to 15 kN and the volume

Rotational Speed 4 000 rpm 6 000 rpmVolume fill 100% 100%Rotor bonding 58% 83%


Figure 8: The effect of varying rotational speeds between 4 000 rpm, 5 000 rpm and 6 000 rpm. At a 9,0 kN of axial force, the higher rotational speeds achieved a substantial increase in rotor bonding percentage.

Volume fill 100% 140%Rotor bonding 98% 99%


Figure 9: Increasing the volume fill at constant clearance (1,0 mm), axial force (9,0 kN) and rotational speed (5 000 rpm) resulted in a negligible change in rotor bonding.

Figure 10: Torque data of selected welds done with variations in clearance, axial force, rotational speed and volume fill.

Process parameters

Axial force [kN]

Rotational speed [rpm]

Forge force [kN]

Consumable length [mm]

Axial force matrix

9 5 000 15 1301215182124

Rotational speed matrix

21 3 000 15 1304 0005 000

Volume fill matrix

21 5 000 15 130170

Forge force matrix

21 5 000 15 13025

Table 1: Rotor material input process parameters and heat treatment.


fill from 100% to 130% to accommodate the expected higher axial forces required during welding. The forge time was kept constant at 15 sec for the duration of the 26NiCrMoV14-5 weld trials.

The consumable tool and the rotor block geometry were carried over from the AISI 1018 welds as illustrated in Figure 11, while the consumable tool tip run-out was kept within 0,15 mm. Considering the limits of the FHPP platform, it was decided to first vary the axial force from 9,0 to 21 kN in incre-ments of 3,0 kN. For the evaluation of varying axial forces, the

rotational speed, volume fill and forge force were kept constant as indicated in Table 1.

Increasing the axial force resulted in reduced weld time and a higher average torque, the same trend as was observed with the AISI 1018 welds. Important to note was that the bonding percentage was found to be independent on variation in axial force. Although 12 kN was sufficient to achieve maximum bonding, welds from 15-21 kN achieved bonding of 97% and higher. It was only the weld completed at the lowest axial force (9,0 kN), which produced lower bonding (93%).

One additional weld was completed at 24 kN to determine the maximum axial force of 26NiCrMoV14-5. It was found that an axial force of 24 kN was too high, as it produced a similar scenario as in AISI 1018, where the primary flash moved up along the consumable tool as shown in Figure 11. The rotor bonding of the 24 kN weld decreased compared to the 21 kN.

The effect of increasing the rotational speeds from 3 000 rpm to 4 000rpm and 5 000 rpm was evaluated with an axial force, volume fill and forge force kept constant as shown in Table 1. The weld performed at 3 000 rpm could not be completed due to platform constraints, however the other two welds indicated an increase in weld time and decrease in aver-age torque as rotational speed increased. Figure 12 shows the effect of rotational speed on the primary and secondary flash. The 5 000 rpm weld was the most promising and ensured lower process torque during the weld.

Areas of higher micro-hardness values were found around the shear layers of various welds as indicated by the arrows in Figure 13. The Vickers micro-hardness tests were performed with a 500 g load and a 15 sec dwell time. Inclusions with high percentages of chrome, manganese and sulphide were found at these areas. Further investigation showed manganese sulphide inclusions in the original parent material, accounting for the presences of the manganese sulphide inclusions in the weld nugget. The chrome could contribute to higher hardness values, however further investigation is required to determine the factors involved.

While completing the volume fill matrix, where the axial force and rotational speed were kept constant at 21 kN and 5 000 rpm respectively, the relationship between volume fill and rotor bonding percentage was investigated. When the volume fill was increased from 130% to 170%, the weld time, maximum torque, average torque and top HAZ were fairly constant, indicating that volume fill is not a major contributor in cases of weld overfill.

As expected, the primary flash moved further up along the consumable tool as shown in Figure 14, due to surplus displaced material. Additionally, the last shear layer did have a similar appearance to the above-mentioned welds as indi-cated by the arrow and the welds where the forge force was increased from 15 kN to 25 kN. Flaws in the top region of the weld nugget close to the fusion line were fewer as can be seen in Figure 15.

To investigate the effect of heat-treatment on the hardness, welds were performed with a rotor block pre-heating tempera-ture of 200C and post weld heat-treated at 740C. The input process parameters for the three welds were: 21 kN axial force, 5 000 rpm rotational speed, 25 kN forge force, 15 sec forge time and a volume fill of 130%. With the aid of pre-heat and a post weld heat treatment, the hardness of the weld nugget decreased to that of the parent material as shown in Figure 16.

Axial force 9,0 kN 21 kN 24 kN

Rotor bonding 93,4% 97,1% 91,4%

Visual appearance

Macrograph

Figure 11: The effect and visual appearance due to axial force variations in welds.

Rotational speed 3 000 rpm 4 000 rpm 5 000 rpm

Rotor bonding 44,3% 97,1% 97,1%

Visual appearance

Macrograph

Figure 12: The effect and visual appearance of rotational speed variation on welds.

Axial force 9,0 kN 12 kN 15 kN 18 kN 24 kNRotational speed 5 000 rpm 5 000 rpm 5 000 rpm 5 000 rpm 5 000 rpm

Volume fill 130% 130% 130% 130% 130%Chamfer angle 45 45 45 45 45

Bonding [%] 93,4% 98,8% 97,3% 97,1% 91,4%Macrograph

Arrow indicates the prominent shear layer

Figure 13: The effect of axial force on the prominent shear layer.

Volume fill 130% 170%

Rotor bonding 97,1% 96,6%

Visual appearance

Macrograph

Figure 14: Effects and visual appearance of volume fill variation on welds.

FHPP


ConclusionThe feasibility study showed that a 15 mm diameter hole, 25 mm deep can be filled successfully with an AISI 1018 tool at an axial force of 9,0 kN, rotational speed of 5 000 rpm, volume fill of between 120% and 140 %, with a forge force of 12 kN and a forge time of 20 sec. Evidence was found indicating that lower rotational speed and larger clearance adversely affect rotor bonding.

With the 26NiCrMoV14-5 material, it was found that the trends observed in the AISI 1018 welds could be transferred, although higher axial forces and forge forces were required to accommodate the higher strength of the material at elevated temperature.

While FHPP welding of the AISI 1018 and 26NiCrMoV14-5 materials, it was found that with increased axial force the volume of primary flash, torque, plunge rate and the dis-tance from the top surface to the last shear layer of the weld increased, whereas the weld time and top HAZ width de-creased. It was also found that a higher forge force improves weld consolidation.

Additionally, it was concluded that the combined analysis of torque, primary flash and secondary flash data can be used for preliminary screening to determine initial acceptable welding parameters.

Successful FHPP welds in 26NiCrMoV14-5 with similar geometry to AISI 1018 consumables can be produced using: an axial force of 21 kN, a rotational speed of 5 000 rpm, forge force of 25 kN and a volume fill of 130%.

Forge Force 15 kN 25 kNRotor bonding 94,9% 92,7%

Visual appearance

Figure 15: Effects and macrographs of varied forge force on welds.

References

1 Nicholas ED. Friction Process-

ing Technologies. Welding in the

World. 2003.

2 Ambroziak A, Gul B. Investigations

of underwater FHPP for welding

steel overlap joints. Archives of

Civil and Mechanical Engineering.

2007;: p. 67-76.

3 Hattingh DG, Steuwer A, James

MN, Wedderburn IN. Residual

Stresses in Overlapping Friction

Taper Stud Welds. In MACASENS;

May 2010.

4 Hasui A, Fukushima S. On the

Torque in Friction Welding. 1975;

44(12): p. 1005 - 1010.

5 Kimura M, Seo K, Kusaka M, Fuji

A. Observation of Joining Phenom-

ena in Friction Stage and Improving

Friction Welding Method. JSME

Interantional Journal. 2003.

6 Kimura M, Inoue H, Kusaka M,

Kaizu K, Fuji A. Analysis Method

of Friction Torque and Weld Inter-

face Temperature during Friction

Process of Steel Friction Welding.

Journal of Solid Mechanics and

Materials Engineering. 2010.

Figure 16:The effect of pre- and post-weld heat treatment on micro-hardness values.

AcknowledgementsI would like to thank THRIP and the National Research Foundation for financial assistance. Also to Eskom for the opportunity to do the research, and Phillip Doubell, Mark Newby and Ronnie Scheppers from Eskom for their assistance during the research.

FHPP


FCAW of SS

Stainless steel cored wires have existed for almost 50 years, but have only really taken off in the last twenty. The present state of evolution of stainless steel cored wires is highlighted by the appearance of the latest editions of EN ISO 17633 and AWS A-5.22 standards. These standards, if not exhaustive, nonetheless include almost as many filler

metal compositions as their counterparts for coated electrodes or solid wires.

Interesting advances and innovations have been made in all alloy classes: not only the well-known martensitic, ferritic, austenitic and austeno-ferritic stainless steels, but also special types for welding dissimilar materials, as well as compositions designed for high temperature service.

Stainless steel cored wires are commonly chosen nowa-days for cladding and for joining [1]-[4]. They are used in applications involving corrosion resistance and those involving service at elevated or cryogenic temperatures, applications that are far beyond the scope of low alloy steels. Stainless steel cored wires are available with or without slag, for weld-ing in all positions, with or without shielding gas. Products designed for submerged arc welding are also available.

This presentation describes the different products avail-able today and highlights one new trend, the use of bismuth-free cored wires for specific applications.

IntroductionAustenitic stainless steel flux-cored wires have been used in Europe since the beginning of the 1980s. At that time, products on offer consisted mainly of wires for welding in the flat and horizontal positions with an external active shielding gas. Only very common compositions were available.

Since then, choices have greatly evolved, not only with respect to the variety of compositions available, but also with the emergence and the optimisation of slag systems allowing improvements in productivity, quality and welder comfort.

The flux-cored arc welding (FCAW) technique has advan-tages that make it an attractive alternative to other common welding processes such as shielded metal arc welding, gas metal arc welding with solid wire or submerged arc welding and cladding with solid wire or strip.

The two main application fields for stainless steel cored wires are joining and cladding. In both cases, they present specific and useful characteristics. Hardfacing and cladding processes overlap when martensitic stainless steels are chosen for surfacing. Numerous proprietary compositions are available to cope with specific wear mechanisms and to meet the demands of end users.

Stainless steel cored wires are used today for cryogenic and high temperature applications, for the corrosion resistant properties conferred by their compositions and because of their ability to produce sound welds. They are also used for welding dissimilar materials, such as weld overlay cladding of a corrosion resistant material over a base material.

The Welding Alloys Group is a global manufacturer of flux-cored welding consumables for welding, hardfacing, joining and cladding applications, as well as automated welding equipment for surfacing and joining. In this paper, Wiehan Zylstra presents the case for using flux-cored consumables for welding stainless steels, and highlights the advantages of bismuth-free stainless flux-cored wires.

Welding stainless steel using flux-cored wires

Figure 1: Cross sections of 1,2 mm stainless steel flux-cored wires.

No Process

114 Self-shielded tubular-cored arc welding

125 Submerged arc welding with tubular-cored electrodes

132 MIG welding with flux-cored electrodes Gas metal arc welding using inert gas and metal-cored wire, USA.

133 MIG welding with metal-cored electrodes. Gas metal arc welding using inert gas and metal-cored wire, USA.

136 MAG welding with flux-cored electrodes. Gas metal arc welding using active gas and flux-cored electrodes, USA

138 MAG welding with metal-cored electrodes. Gas metal arc welding using active gas and metal-cored electrodes.

143 TIG welding with tubular-cored filler material Gas tungsten arc welding using inert gas and tubular-cored filler material.

Table 1: Cored wires EN ISO 4063 edition 2011 Numbering of the welding processes.

Figure 2: Open arc hardfacing with CHROMECORE 414N-O wire.


FCAW of SS

Stainless steel cored wires welding processes and core typesThe EN ISO 4063 edition 2011 [4] standard for stainless steel cored wires mentions seven processes (Table 1) where cored wires are used. It is important to differentiate clearly between these processes to realise the benefits that welding with stainless steel cored wires can offer.

Process 114: Open arc weldingThe most commonly used self-shielded (open arc) stainless steel wires are the martensitic or martensitic-ferritic grades used for hardfacing steel mill rolls or other parts requiring mechanical strength, hardness and moderate corrosion resistance.

Open arc stainless steel wires are also available for many austenitic grades. Some of these wires are approved for as-sembly work and their mechanical properties give no cause for complaint compared with gas-shielded wires. This solution is worth considering when the use of external gas protection is impractical or uneconomical.

Process 125: Submerged arc welding with cored wire.Stainless steel cored wires for submerged arc welding are essentially filled with metallic ingredients, though some ba-sic mineral additions may be added to improve weld metal soundness and toughness.

The interest in stainless steel cored wires for submerged arc welding is explained not only by the possibility of deposit-ing special compositions, but also by clear quality advantages, flexibility of use and productivity. [5]

The advantages of the tubular wire route may be sum-marised as follows: Increased productivity. Less warping of welded structures on account of increased

linear travel speeds. Attractive weldability, very good slag detachment even at

the root of the joint, neat beads with no adhering matter. Flexibility: tubular SAW wire is weldable over a wide

parameter range. It is therefore possible to weld a root pass at low current (eg, 250 A for 2,4 mm wire) and continue with the filling passes using the same wire at higher deposit rates (eg, 450 A for 2,4 mm).

Logistical advantages: a single diameter covers all ap-plications.

Processes 133 and 138: Welding with metal-cored wireMetal-cored wires may contain minor quantities of slag-forming additions. Their cores contain at least 95% metallic elements. A key advantage of metal-cored wires is the pos-sibility of offering alloys that cannot easily be manufactured as solid wires. [6]

The arc characteristics peculiar to the tubular construction of metal-cored wires offer other advantages as well. Compared with solid wires, when used at the same welding current, the higher current density flowing through the sheath of a metal-cored wire brings on a quicker transition to spray-arc conditions, giving better penetration, better wetting and less risk of weld defects. Deposit efficiency is comparable to that of solid wires, and deposit rates are often superior at a given diameter, stick out and current.

Pulsed arc welding allows stainless steel metal-cored

wires to be used for positional work, though at modest parameters when compared with all-positional flux-cored wires. With pulsed arc welding, it must be remembered that the requirements for metal-cored wire are slightly different to those of solid wire. As cored wires vary more widely in electrical and physical characteristics than solid wires, pre-programmed synergic parameters optimised for one brand may not work as well for another brand and some fine-tuning of the parameters may be needed. [1], [2], [6]

A slightly active gas such as M12 (an argon and CO2 mix) with or without helium (Process 138) is often preferred to favour arc stability and weld bead appearance. However, ex-perience shows that with cored wires, as distinct from GMAW with solid wires, pure argon (Process 133) is frequently the best choice to obtain the cleanest weld appearance and the best weld quality without impairing arc stability. Argon is recommended with most fully austenitic metal-cored wires, with superduplex metal-cored wires and, in some cases, with standard austenitic compositions.

Figure 3: Open arc cladding with TRI S 309L-O, E309LT0-3 wire.

Figure 4: A digester of a base metal composition of stainless steel A240 TP 304L is being submerged arc welded with EC308L wire.


FCAW of SS

Processes 132 and 136. Welding with flux-cored wire.Processes 132 and 136 relate to flux-cored wires. Three slag types are possible: rutile, slow freezing; rutile, fast freezing; and basic [1]-[6].

Rutile with slow freezing slag (Process 136) The flux in tubular wire is designed to function in almost the same way as that for stick electrodes. It can react with the molten droplets of metal as they transfer across the arc, with the slag refining and protecting the metal, but more importantly, it supports and smoothes the weld metal during solidification.

The melting point, viscosity and surface tension properties of the slag are optimised for welding in the flat and horizontal positions. [16]

The slow-freezing slag and the presence of arc stabilisers confer several advantages [1], [2]: Ease of use: Of all the arguments used for flux-cored wire,

ease of use is the least convincing in print and perhaps the most convincing on the shop floor.

Very pleasing arc characteristics with no spatter. Smooth clean bead with fine ripple, but with no silicate

surface layer. The result is comparable to that of high efficiency stainless steel stick electrodes, but without interruptions for electrode changes.

Self-detaching slag (or close to it), giving useful timesav-ings during weld finishing.

Wide tolerance to parameter settings that allow the weld quality to be maintained quite easily, even if the operator uses different parameters to those prescribed.

Wetting characteristics and a safe penetration profile allow welders to use faster travel speeds than with solid wires, and to get the most attractive bead appearance without using complex gas mixtures and sophisticated power sources.

Flat position stainless steel flux-cored wires can be a very productive, high quality substitute for GMAW and SMAW consumables. They are often used for welding vessels in the chemical, petrochemical, shipbuilding and food indus-tries. Base material thickness should be at least 3,0 mm to

benefit fully from their process advantages. They are especially recommended for fillet welds and are often a good choice for the filling and capping layers of butt weld joints.

Rutile fast freezing slag (process 136)The slag system used in flux-cored wires for downhand welding can be modified to obtain fast freezing. This gives a slag, which contains the weld pool well, allowing welding in any position with almost the same parameter settings.

Metal transfer via spray-arc assures excellent penetration, particularly in the vertical-up position where the productivity of this family is greatest. Excellent results are also obtained in the overhead, horizontal-vertical and vertical-down positions.

Compared to other manual arc welding processes, all-positional FCAW can provide significant productivity benefits, enabling considerable cost savings to be made during fabrica-tion. Rutile all-positional stainless steel wires provide excellent operability and the capability of producing high quality welds in all positions,

African Fusion August 2013

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