TMCP工艺对Si--Mn系贝氏体钢组织与性能的影响

研究了轧后中温缓慢冷却与中温等温两种不同的热机械控制工艺( thermomechanical control process, TMCP)对硅锰系贝氏体钢的组织与性能的影响。通过拉伸试验机测试试验钢的力学性能,利用扫描电子显微镜、电子背散射衍射等分析手段对试验钢进行显微组织结构分析,并利用X射线衍射测定残余奥氏体含量。结果表明：随着轧后连续缓慢冷却开始温度的升高,贝氏体钢的抗拉强度、硬度及拉伸应变硬化指数n值有所提高,伸长率和冲击韧性降低,屈强比先降低后升高。随着轧后等温时间的延长,贝氏体钢的抗拉强度与屈强比先降低后升高,伸长率及冲击韧性先升高后降低。相对于等温制度,连续缓慢冷却可得到更好的综合力学性能,强塑积明显高于前者,伸长率比前者高20%以上。

Effect of TMCP on the microstructure and mechanical properties of Si--Mn series bainitic steel

The effects of two different thermomechanical control processes ( TMCP) including medium temperature slow cooling and medium temperature isothermal treatment after rolling on the microstructure and mechanical properties of Si-Mn series bainitic steel were investigated in this paper. The mechanical properties of the steel were studied by a tensile testing machine, the microstruc-ture was characterized by means of scanning electron microscopy and electron backscatter diffraction, and the amount of retained austenite in the steel was determined by X-ray diffraction analysis. The results show that, as the starting slow cooling temperature after rolling rises, the tensile strength, hardness and tensile strain hardening exponent n increase, the elongation rate and the impact tough-ness decrease, and the yield-strength ratio decreases first and then increases. When the isothermal time after rolling extends, the tensile strength and the yield-strength ratio of the steel first decrease and then increase, but the elongation and the impact toughness have a reverse trend. Compared with the isothermal regime, the continuous slow cooling can get better comprehensive mechanical prop-erties, the product of tensile strength and elongation is higher, and the elongation is 20% higher than that of the former.