Optimization Study Of The Composition And Process Of High Chromium Cast Iron

Wear-resistant materials were being used widely in different industry field like Machinery, building materials, cement, transportation and so on. For the reason of inadequate performed wear-resistant materials the economic losses of friction and wear is enormous. The purpose of this paper is to improve and enhance the mechanical and abrasion resistant performance. It aims to reduce the production costs and economic losses of the abrasion. This paper mainly discussed the high-chromium cast iron ball’s research of chemical composition and metamorphic treatment research of casting technology’s simulation and the late heat treatment research.0、0.3%、0.6% and 1.0% percentage content of Y-base heavy rare earth modificator was added for metamorphic treatment under certain chemical composition. The research result indicates that Y-base heavy rare earth modificator have a significant effect on the mechanical properties of materials. when 0.6% percentage content of Y-base heavy rare earth modificator was added the High-chromium cast iron ball can show excellent comprehensive mechanical properties.The average hardness of the cast sample reached 54.3HRC and impact toughness value reached 4.8 J/cm2.Which are 6.26% and 26.32% respectively higher than unmetamorphosed sample. Metamorphic treatment has no effect on macro hardness of the sample and micro hardness of the organization for heat treated sample, but it had a obvious promotion to impact toughness of the heat treated sample. With the process of 950℃ quenching temperature and 350℃ tempering temperature, impact toughness of the sample with 0.6% Y-base heavy rare earth modificator is about 18.0% higher than unmetamorphosed sample, the average hardness of the cast sample reached 63.3HRC and impact toughness value reached 5.9J/cm2.When other chemical constituents unchanged, with the increase of carbon content, hardness of Cast and heat treated material is gradually increasing and the impact toughness is gradually decreasing. The average hardness value of the cast sample with 1.3% copper and 0.9% molybdenum is about 7.8% lower and the impact toughness is about 18.0% higher than the sample which does not contain these elements. The strengthen role of copper and molybdenum for material is difficult to be reflected, but for larger high-chromium wear ball, copper and molybdenum can significantly enhance the hardenability of material.Casting technology’s simulation was conducted for high-chromium wear ball. Sand casting process、metal casting process and sand coated iron mold casting process were applied, it indicate that sand coated iron mold casting process can control coated sand thickness at different parts has the best comprehensive simulation results. The solidification time of different place of the ball can be controlled according to this process to achieve progressive solidification. The volume of distributed shrinkage reduced significantly, the forming defects contain the sinkhole and shrinkage porosity. Secondary dendrite arm spacing of the ball is about 0.045-0.07 millimeter. The maximum equivalent stress of the ball at 700℃ is about 292.368MPa, this stress is closed to the inherent strength of the material at this temperature. The possibility of cold cracking and thermal cracking were both very low. When the pouring temperature is 1440℃and the metal mold held temperature is 300℃ with sand coated iron mold casting process, the shrinkage probability of ball appears smaller and the grain size of ball is the best.Research result of heat treatment indicate that at same quenching temperature, the higher the tempering temperature, the lower the macro hardness、the micro hardness of microscopic matrix and the eutectic organization of the ball, but the impact toughness of the material is significantly increased. When the ball is only quenched and doesn’t been tempered, compared with cast sample the hardness of the ball increased significantly but the impact toughness value increases less. EDS composition analysis showed that the eutectic carbides type is a combination of M7C3 and M3C carbides. At destabilization time secondary carbide precipitation was M7C3 carbides. With the process of 950℃ quenching temperature and 350℃ tempering temperature, higher comprehensive mechanical properties can be obtained. the average hardness of the cast sample reached 59.2HRC and impact toughness value reached 5.1 J/cm2.Compared with the cast sample, the hardness and toughness were increased by 26% and 55% correspondingly.