硬态车削轴承钢GCr15切屑形成机理分析

使用有限元仿真软件ABAQUS对硬态车削淬硬轴承钢GCr15（62HRC）的切削过程进行仿真，从切屑形态出发，结合切削力和切削温度等场量对切屑的形成过程进行分析.结果表明：在低速（60 m/min）切削时，没有形成明显的绝热剪切带而形成了连续切屑；在高速（181 m/min）切削时，形成了锯齿状切屑和绝热剪切带，且因绝热剪切区的热软化效应而使材料的承载能力下降，切削力发生波动；在高速切削时，工件与切屑自由表面处出现了微裂纹，并在一定程度上沿绝热剪切带而向刀尖方向扩展，使得锯齿更加明显，导致切削力“二次下降”并推迟了下一锯齿节块的形成；硬态车削淬硬轴承钢GCr15的绝热剪切是形成锯齿状切屑的前提，而周期性微裂纹的出现和扩展则是源于绝热剪切作用下材料发生的韧性断裂.

Finite Element Simulation of Chip Formation Mechanism in Hard Turning GCr15 Steel

 The formation of serrated chip in hard turning and tool life and the quality of the machined surface are closely related. Simulation experiments of hard turning hardened bearing GCr15 steel (62HRC) were conducted using finite element simulation software ABAQUS. According to chip morphology, combined with cutting force and temperature field, the formation process and mechanism were researched  and conclusions were obtained. Firstly, continuous chip is formed under relatively lower cutting speed (60 m/min), while under a higher speed of 181 m/min, serrated chip is formed with adiabatic shear band. The thermal softening effect of adiabatic shear band declines in the carrying capacity, and in turn results in fluctuates of cutting force. Secondly, under 181 m/min, micro-cracks appear on the connected surface between the workpiece and the chip and they extend along the adiabatic shear band to some extent. This not only makes the saw-tooth more apparent and results in “The 2th-Drop” of cutting force but also delays the formation of the next saw-tooth block. Thirdly, for hard turning hardened GCr15 steel, adiabatic shear theory is a precondition to form saw-tooth chips. The appearance and extension of the periodic micro cracks are also based on the ductile fracture of the shear adiabatic effect.