回火温度对1100 MPa钢组织和性能的影响

采用低碳+Nb、Ti、B、Cr、Mo、Ni成分体系,利用SEM、TEM等研究不同回火温度下试验钢的组织和力学性能变化。结果表明:220 ℃回火,马氏体发生分解,马氏体板条束变粗,束内板条逐渐合并,残留奥氏体逐渐分解,位错密度大幅度下降,淬火带来的内应力得到释放,试验钢具有最佳的综合力学性能。300 ℃回火,碳化物在奥氏体晶界或回火马氏体板条间大量聚集、长大,降低了晶界、板条间的结合力,出现了回火脆性。

Effect of tempering temperature on microstructure and properties of 1100 MPa steel

Microstructure and mechanical properties changes of the tested steel of low carbon and micro-alloyed with Nb, Ti, B, Cr, Mo, Ni tempered at different temperatures were systematically studied by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that the decomposition of martensite occurs after tempering at 220 ℃, the lath bundles of martensite become coarser, the laths in the bundles merge gradually, the retained austenite decomposes gradually, the dislocation density decreases greatly, and the internal stress caused by quenching is released. The tested steel has the best comprehensive mechanical properties. After tempering at 300 ℃, a large number of carbides gather and grow in austenite grain boundaries or between tempered martensite laths, which reduces the binding force between grain boundaries and laths, resulting in tempering embrittlement.