热轧低碳钢高温变形行为与显微组织

采用 Gleeble-1500试验机对低碳钢进行热变形试验,获得了真应力-真应变曲线,进而研究了变形温度为900~1200℃,应变速率为0·1~10 s－1对材料热变形行为的影响。通过非线性回归获得了材料在不同变形条件下的材料常数,建立材料的热变形本构方程,进而分析了热变形低碳钢的微观组织演变及极限压缩率的变化规律。结果表明：基于热变形方程真应变为0·5时的热变形激活能Q为216·95 kJ/mol,利用该本构方程计算的峰值应力与试验得到的应力-应变曲线的峰值应力吻合较好；应变速率1 s－1,变形温度1100℃下的显微组织较其他温度相比都要细小、均匀,此时其极限压缩率最大可以达69％,可在此工艺条件下实现较大的塑性变形,且变形后具有较好的综合力学性能。

Hot deformation behaviors and microstructure of hot-rolled low-carbon steel

True stress-true strain curves of hot-rolled low-carbon steel were obtained by performing hot deformation experiments on a Gleeble-1500 thermal-mechanical simulator.The influences of hot deformation behaviors in the temperature range of 900-1 200℃ and strain rates of 0·1-10 s-1 were then investigated.The material constants of low-carbon steel in different deformation conditions were achieved by the non-linear regression and constitutive equation of low-carbon steel was established.Microstructural evolution of low-carbon steel and maximum com-pression ratio of specimens under different deformation conditions were analyzed.The results indicate that the de-formation activation energy (Q)of 216·95 kJ/mol based on the hot deformation equation was obtained at a strain of 0·5 and the peak stresses obtained by the non-linear regression were in good agreement with those of true stress-true strain curves.The microstructure of the steel is more uniform and grains are finer when deformed at 1 100℃ and 1 s-1 ,and the maximum compression ratio can reach 69%.Thus,larger plastic deformation can be realized.Furthermore,the steel after deformation has superior comprehensive mechanical properties.