回火温度对低碳贝氏体高强度钢组织性能的影响

利用光学显微镜、扫描电镜、透射电镜和力学性能试验机等手段，系统研究了不同回火温度下低碳贝氏体高强度钢的组织及力学性能变化.结果表明:回火后位错密度的变化、析出相的形态、板条贝氏体的合并粗化和M/A岛的分解是导致力学性能变化的主要原因.600℃回火后屈服强度较热轧态强度提高了35MPa，-40℃冲击功提高了49J，此回火温度下实验钢具有最佳的强韧性配合.回火后低碳贝氏体高强度钢韧性改善主要是由于粗大M/A岛的分解，细小弥散分布的M/A岛可有效阻止裂纹扩展，改善低温冲击韧性.

Effects of Tempering Temperatures on Microstructure and Properties of Low Carbon High Strength Bainitic Steels

The variations of microstructure， mechanical properties of a low carbon high strength bainitic steel tempered at different temperatures were investigated with optical microscopy(OM)， SEM and TEM. The results showed that the appearance of variations of the dislocation density， morphology of the precipitates， merging and coarsening of lath bainite， and decomposition of M/A islands after tempring were the main reasons for the variations of mechanical properties. Compared with the as rolled steel， after tempered at 600℃， the yield strength of the tempered steel increased 35MPa， meanwhile， the impact absorbing energy at -40℃ enhanced 49J， thus the test steel obtained the best combination of the strength and toughness. The improvement of the low temperature impact toughness after tempering mainly relied on the decomposition of the bulk M/A islands. Fine and evenly dispersed M/A islands effectively prevented the propagation of cracks， thus improved the low temperature impact toughness.