两次淬火对HSLA钢组织和冲击韧性的影响

研究了两次淬火+回火和传统的一次淬火+回火热处理对HSAL钢的显微组织和力学性能的影响。结果表明，在不显著降低强度的条件下，两次淬火使实验钢的冲击功明显提高，还改善了低温韧性和稳定性。两次淬火回火热处理可细化钢的组织，使原始奥氏体晶粒的尺寸和有效晶粒尺寸减小、大角度界面的密度和解离裂纹的扩展偏折频率提高。组织的细化和大角度晶界的增多抑制了裂纹的扩展，使韧性大幅度提高。

Effect of Double Quenching on Microstructure and Impact Toughness of a High Strength Low Alloy Steel

The effect of double quenching and tempering (DQT) treatment as well as the conventional quenching and tempering (CQT) treatment on the microstructure and impact toughness of a high strength low alloy steel were investigated. The results show that compared with the CQT treatment, the impact toughness improved a lot, while the yield strength just slightly decreased for the DQT treated steel. These changes were characterized by optical microscope (OM), scanning electron microscope (SEM), electron back scatter diffraction (EBSD) and transmission electron microscope (TEM). It follows that in comparison to the CQT treatment, the DQT treatment led to a finer microstructure, namely, the size of prior austenite grain and the effective grain were refined, and the density of the high angle misorientation was increased, while the frequency of deflection for the crack propagation for the DQT treated steel was much higher than the CQT treated one. The superior toughness of the DQT treated steel can be attributed to the finer microstructure.