Development Of Hi-chrome Cast Iron Compound Liners For Ball Mill

With the development of industry, the demand of wear-resisting metal became big. At the same time it also set the new request to the wear-resisting metal performance. However, it was difficult for a kind of material to have high toughness and hardness on actual condition. The bimetal composite was used to produce the important parts that were tougher and wearable on the face of it than using pure material.For the request of working condition of ball mill liners, using compounding cast processes made a kind of composite liners, which was made up of high chrome cast iron and ZG230/450 carbon steels. The purpose was that made the bimetal materials gain good wear-resisting, corrosion resistance, and with excellent mechanical properties, such as toughness, plastics, strength, ductility, and fracture.This paper's purpose is to investigate the compounding cast processes, Hi-chrome cast iron smelting and heat treatment processes of the ball mill composite liners by pilot trials and full scale testing, using metallographic structures examination and mechanical properties testing. The research results show as following:1. The Cr15 style Hi-chrome cast iron was chose for wear-resistance layer of compound liners, its casting microstructures were: the matrix metal was dendrite austenite and interdendritic eutectic carbide was M₇C₃ style and little ledeburite eutectic structures(M₃C style carbides and austenite), it had good wear-resistance.2. By modification for Hi-chrome cast iron, its crystal grains were refined, and ameliorated the distributing and morphology of the carbides, and increased the proportion of the M₇C₃ style carbides, also improved greatly the impact toughness.3. Using the compound cast process with horizontal clapboard in the casting box gained a good fusion face of Hi-chrome cast iron and low carbon steels.4. The optimized heat treatment processes with high strength and good toughness were that quenching: soaking temperature was 950℃, holding time was 60min, air cooling; Tempering: temper temperature was 200℃, holding time was 60min, air cooling.5. Having given the basic parameters of Hi-chrome cast iron in full scale testing:The compound liners were made up of Hi-chrome cast iron for wearing layer and ZG230/450 carbon steels for matrix;To add inoculation in smelting; The composite cast processes was with the horizontal clapboard in the casting box;The compositions of Cr15 Hi-chrome cast iron were that: C: 2.5%～3.0%,Si: 0.3%～0.8%, Mn: 0.5%～0.8%, P:≤0.04%, S:≤0.04%, Cr: 14%～16%, Mo: 1.5%～3.0%;The heat treatment processes of Hi-chrome cast iron: quenching: soaking temperature at 950℃, holding time by the thickness of actual parts (3min/mm) ,air cooling after wind cooling to 550～600℃; Tempering: temper temperature at 450℃, holding time by the thickness of actual parts (3min/mm) , air cooling.6. Having finished the full scale of Hi-chrome cast iron compound liners, its hardened layer excesses 70mm, increasing remarkably hardness after heat treatment, and also for impact toughness. There was as much as a good wearing surface after 5600 hours in actual using of ball mill.