立方氮化硼超硬磨料与45钢钎焊接头残余应力有限元分析

FINITE ELEMENT ANALYSIS ON RESIDUAL STRESSES IN BRAZED JOINT OF CBN SUPERABRASIVE AND 0.45%C STEEL

针对立方氮化硼(CBN)超硬磨料高温钎焊冷却过程中可能产生较大热应力而导致磨粒破碎和接头断裂的问题,利用弹塑性有限元法对Ag-Cu-Ti合金钎焊CBN磨粒与45钢基体时接头的残余应力进行模拟分析。结果表明;磨粒球体内部中心轴线、中心平面半径方向以及磨粒与钎料顶层圆形断面半径方向是磨粒内部残余应力变化最显著的区域,而圆形断面边缘部分为磨粒内部最大残余拉应力的存在区域。试验验证有限元分析结果与测试结果基本一致。基于磨粒内部的最大残余拉应力,为确保焊后磨粒强度和钎焊砂轮容屑空间,CBN磨粒在钎料层中的包埋深度宜控制在30%～40%之间。

For avoiding the grain microcrack and the joint rupture in the cooling stage during high temperature brazing, the residual stresses in the brazed joint of cubic boron nitride （CBN） superabrasive grain and 0.45%C steel with Ag-Cu-Ti alloy as filler metal is simulated by finite element method （FEM） according to the elastic-plastic theory. The results show that, several special zones, such as the center axis, the radius of the middle plane, and the radius of the section plane between the grain and the filler alloy, are the ones that have the most remarkable diversification of the residual stresses in the inner part of the brazed grain. Moreover, the margin of the section plane always endures the maximum tensile stresses. The corresponding experimental result indicates that the measured stresses are in accordance with the predicted ones. Based on the maximum tensile stress in the brazed grain, in order to ensure the grain strength and the storage space for chips, the embedding depth of the grains in the filler alloy is feasible to be controlled at 30%-40% of the whole grain crystal.