Forging of Heat Resisting Alloy with Ceramic Dies

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This report describes a new forming method of heat resisting alloys in isothermal forging with ceramic dies.To develop a non-glass type lubricant suitable for ceramic dies, compression tests of ring-shape specimens of titanium alloys are carried out on a newly constructed apparatus at temperatures around 900゜C.From these results, it is found that a lubricant which consists of boric acid and boron nitride provides a very low friction for ceramic dies of <Al_2> <O_3> , SiC and <Si_3> <N_4> , when a ratio of boron nitride is in the range from 20 to 30%. Applying this lubricant with <Al_2> <O_3> dies, the lower friction than glass-type lubricant conventionally used in isothermal forging is obtained.By comparing the coefficients of friction for all the ceramic dies, it is clarified that <Al_2> <O_3> shows the lowest friction among the rest of ceramics.For confirming a principle of the new forming method, a mechanical press controlled by microcomputer is developed. Plasticine is formed to disk-shape product on the press. It is clarified that shape of product depends on forming conditions such as forming method, and it is necessary to determine shape of die teeth to finish surface of products smoothly. Deformation of plasticine is analyzed by using rigid-plastic finite element method and forging tests are carried out for various shapes of die teeth. The smooth surface is obtained by using dies with round corner.Conclusively, the feasibility of applying flexible forging system with ceramic dies to forming heat resisting alloys is clarified.