Composition Design Of CADI Grinding Ball And Optimization Of It's Heat Treatment Process

Following the development of mining industry and the size of ball grinding mill become larger,the need of grinding ball increase by years,and the wear of the grinding ball increased,so the user of grinding ball demand the mechanical property of grinding ball to be better and better.Because of The carbidic austempered ductile iron(CADI)grinding ball has attacted the attention of the user for its outstanding performance advantage,But there are many problem of CADI grinding ball need to be solved.This thesis aims at the problem of spalling,roundless and broken of CADI grinding ball.Base on the previous research to study the influence of different content of Cr,Mn,Cu and different heating processing,By using the color metallography photo to statistical analysis the different phase,By studying the influence of the phase composition and phase morphology on the comprehensive mechanical properties of the CADI grinding ball.and optimizes the composition and heat treatment of the existing CADI grinding ball.The results of this study indicate that the CADI grinding ball is composed of bainite,martensite,carbide,retained austenite and graphite sphere.As the Cr content increases,the content of carbide in the CADI grinding ball increases.Gradually changing to continuous block structure,the hardness of the CADI grinding ball increases,and the toughness deteriorates sharply.With the increase of Mn element,the carbide content in the CADI grinding ball increases,and the stable retained austenite content also increases.The gradual increase and the toughness decrease;with the increase of Cu element,the bainite content in the CADI grinding ball increases,the toughness of the CADI grinding ball increases,and the hardness decreases.At the same austempering temperature,when the austenitizing temperature of 920 °C is used,the bainite content in the CADI grinding ball is higher than the austenitizing temperature at900 °C,and the carbonization is performed at the austenitizing temperature of 920 °C.The continuous structure of the material is destroyed,the carbide content is decreased,and the toughness of the CADI grinding ball increases as the austenitizing temperature increases,and the hardness decreases as the austenitizing temperature decreases.At the same austenitizing temperature,below 245 °C,as the isothermal temperature rises,the content of bainite and austenite in the CADI grinding ball increases,the carbide content decreases,the toughness of the CADI grinding ball increases,and the hardness decreases.Between 245 ° C and 260 ° C,as the austempering temperature increases,the carbide content in the CADI grinding ball increases,and the bainite and martensite change from fine needle-like structure to bamboo leaf-like structure,and the hardness increases.The resilience has declined.According to the study,the optimized CADI grinding ball has a chemical composition of C:2.5~3.8wt%,Si: 2.8~3.2%,Mn1.45wt%,Cr0.60wt%,Cu0.60wt%,P<0.03wt%,S.<0.03wt%,the hardness before work hardening is between 49.0HRC~49.5HRC,the hardness uniformity is improved,the impact toughness value is 9.2J/cm2,and the falling ball fatigue life is twice that of the original grinding ball,and the work hardening The capacity is double that of the original CADI grinding ball,and its hardness reaches 59.7HRC after work hardening.