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采用膨胀法结合金相分析建立了P20钢的CCT曲线,根据动态CCT曲线,提出P20钢轧后控冷预硬化工艺.与常规热处理条件相比,形变热处理条件下的奥氏体具有较高的稳定性.变形后以0.2—0.02℃/s连续冷却时,主要发生贝氏体相交,而多边形铁素体相变被抑制.变形可使奥氏体机械稳定化,阿氏体相变推迟至较低温度下完成.P20钢轧后在贝氏体相变区缓冷获得粒状贝氏体组织,实现在线预硬化,硬度达到35—38.
The CCT curve of P20 steel was established by the expansion method combined with the metallographic analysis. According to the dynamic CCT curve, the pre-cooling controlled pre-hardening process of P20 steel was proposed. Compared with the conventional heat treatment conditions, the austenite under the condition of the deformation heat treatment has a higher stability. When the steel is continuously cooled at a temperature of 0.2-0.02 ° C / s after deformation, bainite mainly occurs and the polygonal ferrite The bulk change is inhibited. Deformation can austenite mechanical stabilization, delaying the phase transformation of the austenite to a lower temperature to complete.P20 steel after rolling in the bainite transformation zone slow cooling to obtain granular bainite, to achieve online pre-hardened, hardness reached 35-38.