基于响应面法的矿用高铬磨球热处理参数优化设计

Optimization Design of Heat Treatment Parameters of High Chromium Grinding Ball for Mining Based on Response Surface Method

为实现矿用磨球强韧性的进一步提升,本文采用Box-Behnken设计-响应面法(BBD-RSM),选择奥氏体化温度、奥氏体化保温时间、回火温度、回火保温时间为自变量影响因子,磨球的洛氏硬度和冲击韧性作为响应目标值,构建了多项式回归方程模型,同时利用OM、SEM、XRD等分析手段,研究了不同热处理条件下磨球的显微组织形貌及物相特征。结果表明,热处理参数对磨球洛氏硬度的显著性影响排序为回火温度>奥氏体化温度>奥氏体化保温时间>回火保温时间,对磨球冲击韧性的显著性影响排序为回火温度>回火保温时间>奥氏体化温度>奥氏体化保温时间。通过优化获得最佳热处理参数为奥氏体化温度885℃,奥氏体化保温时间4.8 h,回火温度400℃,回火保温时间3.5 h,其洛氏硬度为59.84HRC,冲击韧性为6.16 J,验证实验相对误差<5%,证实了响应面法优化磨球热处理参数的精确性和科学性。奥氏体中的合金元素含量,碳化物尺寸、形态和分布情况,残余奥氏体的转变行为及占比的共同作用,是磨球的洛氏硬度和冲击功呈现规律性变化的主要原因。

In order to further improve the strength and toughness of mining mill balls,Box-Behnken design-response surface method(BBD-RSM)was adopted in this paper.Austenitizing temperature,austenitizing holding time,tempering temperature and tempering holding time were selected as independent variable influencing factors,Rockwell hardness and impact toughness of mill balls were taken as response target values,and a polynomial regression equation model was established.At the same time,OM,SEM,XRD and other analytical methods were used to study the microstructure and phase characteristics of the grinding ball under different heat treatment conditions.The results show that the significant effects of heat treatment parameters on the hardness of the ball are in the order of tempering temperature>austenitizing temperature>austenitizing holding time>tempering holding time,and the significant effects on the impact toughness of the ball are in the order of tempering temperature>tempering holding time>austenitizing temperature>austenitizing holding time.The optimum heat treatment parameters were obtained as follows:austenitizing temperature 885℃,austenitizing holding time 4.8 h,tempering temperature 400℃,tempering holding time 3.5 h,Rockwell hardness of 59.84 HRC,impact toughness of 6.16 J,and the relative error of verification experiment was<5%.It is proved that the response surface method is accurate and scientific in optimizing the heat treatment parameters of grinding ball.The content of alloying elements in austenite,the size,shape and distribution of carbides,the transformation behavior and proportion of residual austenite are the main reasons for the regular change of Rockwell hardness and impact work of grinding ball.