预应力淬硬磨削下强化层金相组织的转变机理

为了研究预应力淬硬磨削条件下工件表面强化层特征及金相组织形成变化机理,以45#钢为对象,进行了预应力淬硬磨削实验.获得了残余应力较小的表面强化层,测量得到了其表面硬度.通过观察表面强化层的金相组织特征,结合磨削温度场仿真,研究了磨削强化条件下预应力对马氏体等金相组织的影响机理.研究表明,磨削淬硬过程中产生的高温使45#钢的屈服强度大大降低,施加较小预应力会使材料发生塑性变形,由于塑性应变导致的母相强化和应变诱导相变两者的综合作用,该状态下预应力对马氏体相变的影响是先抑制再促进.

Transformation Mechanism of Microstructure in Hardening Layer Under the PSHG

In order to study the features of surface hardening layer and the formation and variation mechanism of metallographic structure under pre-stressed hardening grinding (PSHG)， the 45 steel was processed with the PSHG experiment. The surface hardening layer with little residual stress was obtained from it. The surface hardness was measured and its metallographic structure was observed. Combining experimental result with the simulation of grinding temperature field， we studied how the pre-stress influenced the metallographic structure such as martensite. It is shown that the high temperature in the grinding process largely weakens the yield limit of 45 steel. A smaller pre-stress would result in plastic deformation. The parent-phase-hardening and strain-inducing-phase-changing resulting from plastic deformation have comprehensive effect on the martensitic phase transformation. This indicates that the pre-stress restrains the phase transformation firstly and then promotes it.