Preparation Of Large Diameter Grinding Ball Of Medium Carbon Low Alloy Steel And Optimization Design Of Heat Treatment Process Parameters

With the development of the industrialization, the large semi autogenous are more and more widely used in the modern society. As the easy wear parts, the consumption of the large diameter grinding balls is huge. According to the strategy of sustainable development, it is necessary to produce a low energy consumption large diameter with high hardness and high toughness of grinding ball.Due to its good hardness and toughness, bainite/martensite multiphase steel has become an ideal material for the production of wear-resistant material. In this paper combined with the topic of actual production requirement, to 150mm diameter grinding ball as the research object, combined with the previous research was made in bainite/ martensite multiphase steel composition design aspects of research results and the results used in the actual production, to the composition of the alloy were optimized, and combined with the actual working condition, put forward a kind of preparation after the optimization of large diameter grinding ball forging process performance. In line with the purpose of reducing energy consumption, cost control, this paper presents a repeated water cooling and air cooling of new heat treatment process, through the numerical simulation technology of large diameter ball in water cooling air and cold alternating in the process of temperature field simulation, and verify the correctness of the simulation results. The reasonable heat treatment process parameters were determined by the determination of the CCT curve.The medium carbon low alloy steel by using large diameter 150mm diameter forging process for grinding ball and heat treatment process using the optimized parameters of large diameter grinding ball repeatedly cooling air cooling heat treatment technology, analysis by color metallography analysis and quantitative metallography, and the relative content of distinction bainite/martensite computing technology has different martensite, lower bainite/martensite multiphase, residual austenite, with performance testing, analysis of different contents of influence on properties of duplex phase steel, exploration of bainite, martensite and residual austenite ratio associated with the properties of the materials. To provide a theoretical basis for the high performance of bainite/martensite dual phase steel large diameter grinding ball control.Research results showed that the components of C-0.4～Si-1.8～Mn-2.3 (wt%) of steel for the forging method to manufacture large diameter grinding ball; forging billet size for phi 110 X 186mm, forging billet height to diameter ratio (H/D) is 1.69; pre forging blank were annealed at 900℃, with the furnace cooling and cooled to the 300℃ released air cooling; selection of die forging tonnage 1000kg of forging, forging heating rate was 3～4℃/s, initial forging temperature 1050℃, eventually forging temperature for 950℃, surface and internal no macro crack of large 150mm diameter grinding ball.The color metallographic technique can effectively distinguish the multiphase steel of lower bainite body, martensite and retained austenite, combined with quantitative metallographic analysis can calculate multiphase organization in the phase of the proportion of; through the analysis of microstructure and mechanical properties of, for the selected component for C-0.4-Si～1.8-Mn～2.2 medium carbon low alloy bainitic steel 150mm large diameter grinding ball optimal heat treatment process parameters: austenitizing temperature to 900℃, insulation 150min after repeated water-air-cooled alternating, after three circulation water-cooled 10s+ air-cooled 15s,340℃ salt bath isothermal quenching 3H. The large diameter grinding ball is obtained from the core to the surface, which has a good comprehensive mechanical properties. Also found that bainitic transformation is incomplete. By controlling the cooling air cooling time and cycle times and can not change the amount of bainite formation, and repeated water cooling and air cooling heat treatment process in martensitic transformation process quite in the gradient cooling process can break the austenite and martensite transformation of phase equilibrium, thus controlling martensite formation by different air cooling time.