汽车用低合金钢的索氏体化与组织性能研究

Study on Sorbite Transformation,Micro structure and Properties of Low Alloy Steel

采用扫描电镜、透射电镜和拉伸试验机等手段,研究了等温温度和等温保温时间对汽车用低合金钢显微组织和力学性能的影响。结果表明,等温温度为450℃及以上时,试验用钢的组织都为索氏体;随着等温保温时间延长或者等温温度升高,试验用钢的渗碳体片层厚度和索氏体片层间距呈现逐渐增加的趋势,尤其是等温温度600℃时的索氏体片层间距和渗碳体厚度增加较为明显。在等温温度为500℃和550℃时,试验用钢的显微硬度呈现先增加而后减小的特征,在等温保温时间为1000 s时取得最大值;试验用钢在等温温度500℃、等温保持时间1000 s时可以获得良好的强塑性结合,这主要与此时珠光体片层和渗碳体厚度较小以及基体中析出了大量起弥散强化作用的纳米级ε-Cu相有关。

The effects of isothermal temperature and holding time on the microstructures and mechanical properties of steel were studied by means of scanning electron microscopy (SEM),transmission electron microscopy (TEM) and tensile testing machine.The results show that the microstructure of test steel is sorbite when the isothermal temperature is 450 ℃ or above.With the prolongation of isothermal holding time or the increase of isothermal temperature,the thickness of cementite lamellae and the spacing of sorbite lamellae of test steel increase gradually,especially when the isothermal temperature is 600 ℃,the spacing of sorbite lamellae and the thickness of cementite increase obviously.At the isothermal temperatures of 500 ℃ and 550 ℃,the microhardness of the tested steel increases at first and then decreases,and reaches the maximum at 1 000 s.The steel for testing can obtain good strength-plasticity bonding at 500 ℃ and 1 000 s,which is mainly due to the smaller thickness of pearlite lamella and cementite,together with and the precipitation of a large number of particles in the matrix which can play a role in dispersion strengthening.