Strategic Basic Technology Advancement Supported Project “Development of molding technology for Advanced

Investment Casting”

Yukio Nasu King Parts, Ltd.

Japan Foundry Society, Inc.

13th WORLD CONFERENCE ON INVESTMENT CASTING

Paper: T2

Copyright reserved: Neither the Japan Foundry Society, Inc. nor its officers accept legal responsibility for information, advice given or opinions expressed.

Strategic Basic Technology Advancement Supported Project “Development of molding technology for Advanced Investment Casting”

Yukio Nasu*1, Kastunori Mishima*1, Toru Takahashi*1

Minoru Iwase*2, Yutaka Sato*2 Hideki Nakayama*3, Eiji Endo*3

Masazumi Kagawa*4 Takashi Yoneda*5 Masanobu Ezoe*6 Kiyotaka Katou*7 Yasuhiro Maeda*8

*1:Kingparts Ltd.

*2:Taenaka Kogyo Co., Ltd. *3:Castem Corporation

*4:Hitachi Metal Precision Co., Ltd. *5:Yoneda Advanced Casting Co., Ltd.

*6:Itochu Ceratech Corporation. *7:Advanced Industrial Science and Technology.

*8:Japan Coast Guard Academy Abstract A strategic basic technology advancement supported project named “Development of molding technology for Advanced Investment Casting” was accomplished from 2006 to 2009 under the monetary support by Japanese Ministry of Economy, Trade and Industry. Following these 3 years project term, this project had been continued for two more years for expanding their practical usage by the same project members.

This paper introduces R&D results which were established through this expanded project activity. 1. Project members and R&D theme

Expanded project was composed by 5 investment casting companies, 1 refractory material manufacturing company and 2 public research agents. These project members and their themes are introduced in Table 1.

Table.1 Project Members for Expanded Project

Team Theme

Material Team Development of synthetic refractory materials replacing Zircon Sand & Zircon Flour

Mold Team Development of molding technology using synthetic refractory materials replacing Zircon Sand

Ceramic Core Team Development of Ceramic core manufacturing technology using synthetic refractory materials

Simulation Team Application of casting simulation to ceramic mold with synthetic materials for replacing Zircon Sand

2. Developed technologies and their present status

Hereafter developed technologies and their present status are introduced one by one for each theme as follows: 2.1 Development of synthetic refractory materials replacing Zircon Sand & Zircon Flour

Zircon which is essentially natural resource is unevenly distributed in North America, Australia and South Africa in the whole world. We, Japanese manufactures, import all of our consumption mainly from Australia. Increasing demand for Zircon Sand in rapid developing countries including China caused sometimes tight delivery condition and hence the prices have been not stable in the last decade. According to market information, the price of Zircon Sand was increased by three times of that of 10 years ago as shown in Fig.1.

Fig.1 Zircon Sand price was increased by 3 times of that of 10 years ago During the 3 years’ R&D project from 2006, we grasped physical and chemical

characteristic of Zircon Sand and proceeded our project for finding or developing new synthetic refractory materials which are equal to or superior to that of Zircon Sand.

Fig.2 shows microscope image of typical Zircon Sand (imported from Australia) and they have almost spherical shapes. Typical grain size distribution curves are shown in Fig.3 and their physical characteristics are shown in Table 2.

Fig.2 Grain shape of Zircon Sand and existing synthetic material 0.2-0.1mm

*Test made by laser diffraction size distribution analyzer Fig.3 Size distribution of Zircon Sand

Table.2 Physical properties of Zircon Sand

Item Specific Gravity Refractoriness Thermal Conductivity (W/m・k)

Specific Heat (cal/g・K)

Packing Bulk Density

Zircon sand 4.6-4.8 *1 SK37 *2 0.8 *2 0.34 *2 2.99 *2 *1: Data from major zircon suppliers *2: Data from Itochu Ceratech Corp.

According to the information from mold developing team, semi- spherical shapes of

Zircon Sand may be important in making compact primary coating layer especially penetrating into inside of long hollow shapes and narrow channels. Our object was set to develop materials that have “①Equal or superior refractoriness to Zircon Sand, ②Similar grain shapes and ③Similar size distribution” Another point of view was “Recycling & Reusing” requirement. Used shell material is

not recycled & reused in the industry because we are using Zircon base materials in our ordinary shell system. We considered using “high purity Mullite”, which is similar material to current back up coat material, and easy to be recycled and reused after casting operation, as primary coat refractory replacing Zircon Sand.

Itochu Ceratech Corp. (one of the project members) developed newly designed synthetic refractory material by using “Spray Drying System” in achieving spherical shape and fine grains. These sprayed materials are sintered at around 1,780 °C in Rotary Kiln to adjust their physical property.

＊1 By microscope ＊2 By scanning electron microscope (×50)

Fig.4 shows the process diagram, -and Fig.5 and Fig.6 show the microscope image and grain size distribution curve respectively. At the R&D stage we called this material as “Synthetic Mullite Beads” and this material has physical properties indicated in Table 3 that is equivalent to natural Zircon Sand.

Fig.4 Production flow of crashed Sintered Alumina／Synthetic Mullite Beads

Average Particle size: 160μm Fig.5 Microscope photo of Synthetic Mullite Beads after sintering

Fig.6 Size Distribution of Synthetic Mullite Beads 212-75μm

Table.3 Physical Properties of Synthetic Mullite Beads 212-75μm

Sintering Temp. Water Absorption (%)

Apparent Specific Gravity

Bulk Density Apparent Porosity (%)

1780°C 2hours 3.50 2.99 2.70 9.50 ＊All data are from Itochu Ceratech Corp.

Based on the requests from mold developing team, Itochu Ceratec Corp. has also

developed new synthetic filler material for primary coat replacing Zircon Flour. Fig.7 shows binary phase diagram between Al2O3 and SiO2 and we chose a composition in the Mullite phase stable area to have better refractoriness. Itochu Ceratec Corp. developed “Synthetic Mullite Flour 85” which has richer Al2O3 composition than Mullite to achieve high property for using prime coat slurry filler.

Fig.7 Phase equilibrium diagram of Alumina-Silica and the developed Synthetic Material positioning

Through the expanded project interval, Itochu Ceratec Corp. established their manufacturing line in their Seto Factory and also reorganized their sales team. They named “Synthetic Mullite Beads” to “Wing Cerabeads” and “Synthetic Mullite Flour 85” to “Casfil 85” as their trade names. Itochu Ceratec Corp. has already furnished sample materials to many investment casting manufacturers all over the world and had lectures in made presentations at 58th ICI Technical Conference and Equipment Expo (1), at 159th Nation Wide Conference of Japanese Foundry Association (2), and at 4th Sokeizai New Technology Symposium 2011(3). 2.2 Development of molding technology using synthetic refractory material replacing

Zircon Sand In the mold developing team, we grasped physical properties of ordinary shell system

using Zircon Sand and Zircon Flour in primary coat and these values are adopted as base line of each manufacturer’s current shell system. After that we measured same properties for molds using various kinds of synthetic refractory materials as the above -and compared each other.

Table.4 shows the test results from the combination of synthetic Mullite or sintered Alumina and Zircon Sand.

Table.4 Sharing table of synthetic material test

Fig.8 Result of shell strength test

Fig.9 Result of permeability test

Compared to Zircon shells, synthetic material shells have relatively low permeability.

Fig.10 shows the casting surfaces of the test pieces using various synthetic material primary stuccos. According to the results above, molding development team has come to the following conclusions: ①“Synthetic Mullite Beads” was the best candidate in replacing Zircon Sand for

primary stucco. ②“Mullite Flour 85” showed good refractory performances, however, shell system using

this material showed rather less permeability and hence the castings tended to have miss run problems. We will continue to seek other solutions to increase their permeability.

Fig.10 Appearance of step block test specimens using various synthetic materials for primary stucco.

Through the expanded developing period, 5 investment casting manufacturers continued their R&D programs to adopt the technology to their main dipping systems. The present status in using synthetic refractory materials in their shell systems are shown in Table 5.

Table.5 Present status in using synthetic refractory materials in shell system Member Present status in using synthetic refractory materials Future plan

A

Al Alloy Casting : Using Wing Cerabeads for primary stucco Fe Alloy Casting : Testing in using Casfil85 for primary slurry filler

Wing Cerabeads for all kind of casting materials

B Al&Fe Alloys : Using Wing Cerabeads for primary stucco S/S Alloy casting : R&D for improving surface roughness

Wing Cerabeads for all kind of casting materials

C Al&Fe Alloys : Using Wing Cerabeads for primary stucco S/S Alloy casting : R&D for improving surface roughness

Wing Cerabeads for all kind of casting materials

D Ni base Alloy Casting : Using Wing Cerabeads for primary stucco

Wing Cerabeads for all shells

E Co base Alloy Casting : Using Sintered Alumina for primary stucco

Sintered Alumina for all shells

3-3 Development of Ceramic core manufacturing technology using synthetic refractory

materials Currently ceramic cores are manufactured by independent ceramic core manufacturers.

However, these ceramic core manufacturers have been merged into large investment casting manufacturers, and hence we, small investment casting manufacturers, are facing difficulties in purchasing ceramic cores from these core manufacturers.

Our goal is to manufacture ceramic cores internally and to develop core manufacturing technology not using Zircon Sand.

Fig.11 Casting process using the ceramic core

Fig.12 Surface roughness measurement

X-ray Inspection Inside observation of cut out sample casting Fig.13 Inside observation of cored casting

Castem Corp. has developed ceramic core manufacturing technology based on their

original Metal Injection Molding (MIM) technology. During the 3 year development duration, Castem Corp. manufactured 250mmL x 120mmW ceramic core for IGT turbine blade. These cores have been processed and poured Nickel base alloys, and the properties were evaluated (i.e. core strength, core leachability and casting surface etc.) Process flow at Castem Corp. is shown in Fig.11, and cut-out inspection of air flow passage was carried out as shown in Fig.12 and Fig.13.

Metal mold of wax injectionWax pattern

Dipping

250mm Casting product

Metal mold for core injectionInjected compact

DebindingSintering

Ceramic CoreSet ceram

ic core

Metal mold of wax injectionWax pattern

Dipping

250mm Casting product

Metal mold for core injectionInjected compact

DebindingSintering

Ceramic CoreSet ceram

ic core

On the other hand, Kingparts, Ltd. had developed ceramic core manufacturing technology based on their original “Slip Casting Technique”. During 3 year development duration, Kingparts, Ltd. manufactured 400mmL x 400mmW x 40mmt.max ceramic core for large size IGT turbine vane. Process flow is shown in Fig.14, and the ceramic core and the casting using the cores are shown in Fig.15. In 3 year duration, large size core manufacturing technology had not completed in terms of quality and productivity so that we continued to brush up our technology.

Order Process

Order 1 2 3

Rough sketch

Content Powder+Solvent Mixing Slurry

Order 4 5 6

Rough sketch

Content Slurry+Plaster mold Casting Mold Release

Order 7 8 9

Rough sketch

Content Air Dry Sintering Finished

Fig14 Process chart of ceramic core manufacturing with slip-casting method

ceramic core wax pattern tooling casting Fig15 Completed ceramics core and casting used it

Through the expanded development period, Castem continued R&D to improve core

quality for better dimensional stability and scrap rate. Castem also adopted their core technology for 2 new patterns successfully.

Kingparts, Ltd had developed a new tooling for large size turbine vane for steam turbine which will be used co-generation power plant system. For increasing total efficiency, turbine vane was designed to have hollow shape with slits to eliminate liquid water in their steam flow.

Fig.16 shows the -cores set inside the pattern tooling and Fig.17 shows the cast turbine vane.

Fig.16 Cores set inside the pattern tooling

Fig.17 Cast turbine vane

Both companies have strong desire to get into gas turbine and steam turbine industry

with these core manufacturing technologies.

2.4 Applying casting simulation to ceramic mold with synthetic materials for replacing to Zircon Sand

Various kinds of casting simulation software have been developed and used in casting industry. However main users of these simulations are limited to mass production makers such as sand casting manufactures and die casting manufacturers. The users in the field of investment casting are limited only the turbine blades & vanes manufacturers, who produce large volume of similarly configuration and material castings.

In the first development period of 3 years, 3 different simulation software were introduced into 3 different investment casting manufacturers respectively.

None of 3 investment casting manufacturers had any experience of casting simulation before participating the project. (Although they all had 3-D CAD systems and 3-D CAM systems for tooling design and manufacturing.) Table 6 shows the introduced software and corresponding casting manufactures to each.

Table6 Introduced Software and Investment Casting Manufacturers

Software Name Vender(Sales Agent) Investment Casting Manufacture

ADSTEFAN Ibaraki Hitachi Information Service Co., Ltd.

Taenaka Kogyo Co., Ltd.

JSCAST QUALICA Inc. Kingparts, Limited FLOW3D-CAST CFD Laboratory Inc. CASTEM Corp.

In three years of research and development, the manufactures of investment casting investigated the thermo-physical properties of the current shell system and the new system made of synthetic material, independently. The experiments were carried out to get the cooling curves during casting. Fig.18 shows an outline of measurement of cooling curve for the shell systems. The measurements were done at several points of the molds and castings using inserted thermo-couples. Then the simulation for parameter fitting was also repeated to obtain good simulation results. The parameter fitted by this operation was determined as a practical value unlike the original it of software.

Fig18 Temperature survey (Current Zircon mold)

Fig19 Nozzle ring for development with complicated geometry

Fig20 Comparison result between experiment and simulation Finally three manufactures of investment casting focused on the nozzle ring castings,

which are large castings with 600mm in diameter and complex shapes.Fig.19 shows a nozzle ring for development with complicated geometry. The casting design and plan are simulated and the casting was made with its conditions. Fig.20 shows the simulation and the real casting that has shrinkage defects. Both were able to get sound castings without the defect together.

Through the expanded development period, 3 manufactures adopted the improved simulations in order to be reduce the developing period of R&D stages to reduce the costs of its. Some examples are shown below.

Kingparts accepted an order of a large-sized hollow blade for steam turbine. Nine kinds of gating design plan were drafted, and mold filling and solidification simulations were executed. Fig.21 shows nine kinds of gating design plan and the simulation results are shown in Fig.22. One suitable gating design plan was chosen based on these simulation results, and the casting was done with the design. The sound casting without defects is obtained. Then, it was also possible to reduce the time for R&D and the cost of it.

Fig.21 Nine different types of gating design

Fig.22 Results of simulation

Taenaka Kogyo rebuilt R&D stage including the specification to execute the casting simulation for all items continuously in order to reduce the time and cost of research and development. Fig.23 shows the first tried result of the simulation, and the castings have shrinkage defects. By enlarging the gate area and minor modifications of the casting design, Taenaka Kogyo achieved good casting quality and yield, as shown in Fig.24, Fig.25 and Fig.26.

During the total 5 years, 3 software venders had closely cooperated with the investment casting manufactures and improved their own software for fitting to each casting process. Now three venders have multiple options to solve the unique issues arise from investment casting process.

Fig.23 The first try of simulation indicating shrinkage in the casting

Shrinkage

Fig.24 Design change of casting and gating system

Fig.25 Improved casting design

Fig.26 X-ray inspection results of improved castings 3. Summary

Through 5 year development duration, the following results were achieved by this project: (1) New synthetic refractory material replacing Zircon Sand was developed and

prepared to get distributed to all over the world.

Improved casting plan Result of solidification analysis

No shrinkage

(2) New shell system using synthetic materials is in the stage of pragmatic use for various material castings in Japan.

(3) A couple of investment casting manufacturers established their own manufacturing technologies of ceramic core at their own plants and started in production run.

(4) Various basic casting simulation software have been improved under cooperation between investment casting manufactures and software vendors.

We appreciate all the people who supported us in these 5 years.

References:

(1) E.Shimazaki, M.Ezoe “New Artificial Molding Material for Investment Casting” 58th Annual Technical Meeting: Investment Casting Institute 2011, Paper 8

(2) E.Shimazaki, M.Ezoe ”Properties of New Artificial Molding Material for Investment Casting” 159th JFS Meeting and FY23 JFS Autumn Lecture Meeting 2011

(3) E.Shimazaki “New Artificial Sand for Investment Casting” 4th Sokeizai New Technology Development Symposium

(4) M.Ezoe,S.Hidaka “Development of New Refractory Material for Primary Coating of Ceramic Shell Mold” 2009 JFS International Investment Casting Seminar Paper T-1

(5) T.Yoneda, M.Kagawa “Development of Molding Technology with Synthetic Material instead of Zircon Sand” 2009 JFS International Investment Casting Seminar Paper T-2

(6) M.Iwase, T.Takahashi “Application of Casting Simulation to Ceramic Mold with Synthetic Materials for a substitution of Zircon” 2009 JFS International Investment Casting Seminar Paper T-3

(7) H.Nakayama, K.Mishima “Development of Ceramic Core Processing Technology using Synthetic Materials” 2009 JFS International Investment Casting Seminar Paper T-4