Abstract: The growth behavior of austenite grain of non-quenching-tempering steel SG4201 for direct turning-cutting (/% : 0.42C, 0.50Si, 1.40Mn, 0.009P, 0.005S, 0.02Nb, 0.06V, 0.015N) heating at 1000-1250 T for 0-300 s has been tested and studied by using Gleeble 3500 thermal simulation test machine, and the growth model of austenite grain of steel has been established. Test results show that with heating for 30 s, the coarsening temperature of austenite grains with large amount niobium solving is about 1100 ℃； the activation energy of austenite grain growth is about 110.8 kJ； and the soaking temperature of steel SG4201 casting billet being no-more than 1150 °C is defined. The commercial production results show that with casting billet soaking heating at ≤1150℃, finished rolled at 800-850℃ , cooling speed after rolling 30-35℃/s, the mechanical properties of steel SG4201 are tensile strength 927 MPa, yield strength 687 MPa, elongation 23.5% , reduction of area 57% , U-impact energy 48 J and HBW hardness value 265.

Key words: Non-Quenching-Tempering Steel SG4201 for Turning-Cutting, Austenite, Grain Growth, Coarsening Temperature, Activation Energy

摘要： 采用Gleeble 3500热模拟试验机试验研究了直接车削用非调质钢SG4201（/%:0.42C，0.50Si，1.40Mn，0.009P，0.005S，0.02Nb，0.06V，0.015N）在1000~1250℃加热0~300 s的奥氏体晶粒长大行为,并建立了该钢奥氏体晶粒长大模型。试验结果表明,加热时间30 s时,奥氏体晶粒粗化温度和铌迅速大量固溶的温度为1100℃左右;奥氏体晶粒长大激活能约为110.8 kJ;确立SG4201钢铸坯均热不宜超过1150℃。工业生产结果表明,当铸坯均热温度≤1150℃,终轧温度800~850℃,轧后冷却速度30~35℃/s时,SG4201钢的力学性能为抗拉强度927 MPa,屈服强度687 MPa,延伸率23.5%,断面收缩率57%,U-冲击功48 J,HBW硬度值265。

关键词: 车削非调质钢SG4201, 奥氏体, 晶粒长大, 粗化温度, 激活能