Preparation And Microstructure Design Of Gfr Alloy For Hot Working Mold With High Hardness And Wearability By Powder Metallurgy

The mould plays a decisive role in plastic shaping process. The longevity of a mold has an impact upon both quality and productivity of the products. It is desirable to improve the longevity of moulds which in generally have short service life in our country, especially the hot working moulds with the 1/5-1/3 or less time of that in developed countries. Among all the factors influencing longevity of the moulds, material is an important one.Good hot working moulds offer a much longer service period and capacity of being cold and hot machined. Consulting the development of material used in moulds, with powder metallurgy, we succeed in a new-style material-GFR alloy hot working mould material, which has higher hardness, wearability and heat-resistance than current-used hot working mould steel, has better toughness and capacity of being cold machined.In this paper, according to principle and characters of powder metallurgy, the method to produce the raw material of mould material with high strength, super wearability, and the optimized design and equipments to identify the content of hard phase, composition of binding phase of GRF alloy.1.The hard phase of GRF alloy is WC , with high melting point. The better stability of anti-tempering and toughness than TiC ensures higher capacity of being sintered, while lowprice than TiC, offers low cost to sinter. The amount of WC must insure both the high hardness and super wearability and pound toughness, cold and hot working. After repeating tests, 30%-35% WC were selected.2.CFR uses low carbon, medium alloy steel as the matrix. According to theory on alloy and composition peculiarity of hot working mould steel used at home and abroad, referencing to the status of sticking phase in existing steel bonded carbide hot working mould material, low carbon, medium alloy steel are chosen as the matrix, endowing the material with higher toughness, heat fatigue, working quality and relatively low cost than the existing. Proved elements are Fe, C, Cr, Mo, and Ni etc.3.Manufacturing process and heat treatment technology of GFR are also discussed in detail. Manufacturing technology is mixing powder, drying and sifting out, pressing to take shape, sintering and annealing.4.Heat treatment is an important means to improve internal quality of mould material. For GRF alloy steel matrix takes up 65%-70%, performance of alloy can also be improved through heat treatment. Alloy is suitable for heat treatment as being annealed, tempering and quenched. Changing technology of heat treatment can enable alloy to obtain performance to meet various requirements. This project has passed relatively systemic tests and the optimal criterion of heat treatment technology for GFR alloy has been attained.