基于热加工图的中碳钢加工性能分析

Processing properties analysis of medium carbon steel based on hot processing map

以LZ50钢为研究对象,分析了其热压缩应力应变曲线。运用线性回归方法建立了峰值应力应变、临界应力应变、稳态应力应变及材料发生最大软化时应力应变的数学模型。绘制了不同应变下LZ50钢的热加工图以预测锻造过程中组织演变行为,指导生产加工。结果表明,加工硬化率随温度降低或应变速率增加而升高。构建了基于Prasad准则、Murty准则及Poletti准则3种不同失稳判据下的热加工图,通过对比分析得出依据Murty准则的热加工图最适宜预测LZ50钢成形过程中的组织演变。研究发现高温高应变速率区域并没有明显组织缺陷,为"伪失稳区"。最适合LZ50钢锻造的区域为中等温度、中等应变速率区,如1 020℃、0.5s-1,该条件下锻后组织均匀,晶粒呈等轴状。

Taking LZ50 steel as deformation material,the stress-strain curves during hot compression was analyzed.The mathematical model of peak stress and strain,critical stress and strain,steady stress and strain as well as the stress and strain at which material exhibited maximum flow softening were established by liner regression method.The hot processing map of LZ50 steel under different strains was plotted to predict microstructure evolution behavior during forging process in order to guide production and processing.The results indicate that work hardening rate increases when temperature decreases or strain rate increases.The hot processing map of Murty criterion is optimum to predict the microstructure evolution of LZ50 steel during hot forming by comparing three different instability criterion′s hot processing maps(Prasad criterion,Murty criterion and Poletti criterion).The zone of high temperature and high strain rate hasn′t obvious microstructure defects,so it′s'false instability range'.The most optimum range for LZ50 steel deformation is zone of medium temperature and medium strain rate,such as 1 020℃and 0.5 s-1,where the structure is homogeneous and the grain keeps equiaxed after deformation.