Effects of Heating and Quenching Processing Parameters on Phase Transformation of 55CrMo Steel
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JMEPEG https://doi.org/10.1007/s11665-018-3637-7
Effects of Heating and Quenching Processing Parameters on Phase Transformation of 55CrMo Steel Haijuan Liu, Huiping Li, Zhichao Li, and Lianfang He (Submitted June 11, 2017; in revised form May 17, 2018) Microstructure and mechanical properties after induction hardening have a significant effect on the wear resistance performance and lifetime of 55CrMo steel ball screw. In the paper, the dilatometric curves were recorded at the different heating rate by a Gleeble-1500D thermo-mechanical simulator to determine the effect of heating rate on the austenitizing temperature of 55CrMo steel. Heat treatment of some specimens was performed by the Gleeble-1500D thermal simulator at the different heating temperature, holding time and cooling rate to investigate the effect of induction hardening parameters on the phase transformation, microstructure and microhardness of 55CrMo steel. Microstructure of specimen was analyzed using an optical microscope and a scanning electron microscope. Volume fraction of retained austenite was measured using an x-ray diffractometer. The mechanical properties were evaluated by a microhardness tester. The results show that the austenitizing temperature of 55CrMo steel increases with the increasing heating rate. Increasing the heating temperature, holding time and cooling rate of specimen is helpful in obtaining a uniform cryptocrystalline martensite. Volume fraction of retained austenite is less as the heating temperature is in the range of 900-950 °C. In the induction hardening of 55CrMo steel, the heating temperature should be in the range of 900-1000 °C. Keywords
dilatometric curve, microstructure, phase transformation, rapid heating
1. Introduction The precision ball screw is an important functional part in CNC (Computerized Numerical Control) machine tools, and its failure forms are generally wear and fatigue. Under certain conditions, hardness is directly related to the wear resistance of material (Ref 1). As a method to improve the strength and hardness of metals, martensite transformation is a more effective way, and hardness has become an important indicator to assess the wear resistance of the workpiece in many industries (Ref 2). At present, increasing the surface hardness of ball screw by induction hardening is the main method to improve the wear resistance of ball screw and prolong the lifetime of ball screw (Ref 3). However, it is prone to produce the non-uniform surface hardness, poor wear resistance or other problems during the induction hardening of ball screw. These problems severely hinder the development of CNC machine tools and manufacturing equipment (Ref 4). In order to attain the optimum processing parameters of heat treatment, several studies have been carried out to investigate the mechanical properties and phase transformation in the induction hardening (Ref 5-7). Kim et al. (Ref 8) studied the effects of induction hardening and tempering on the mechanical properties of medium-carbon SPS5 steel. Kristoffersen et al. (R
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