960 MPa级高强钢相变规律及热处理工艺探讨

借助DIL805A/D淬火变形膨胀仪，通过金相、透射电镜、室温拉伸、-40 ℃冲击测试等分析手段，研究了热处理工艺对960 MPa级高强钢组织与性能的影响。结果表明：在790～880 ℃温度范围内，试验钢随着淬火加热温度的提高，马氏体量逐渐增加，铁素体量逐渐减少，在850 ℃淬火，铁素体含量基本为零，组织最为均匀细小。随着回火温度从180 ℃提高到450 ℃，马氏体的板条逐渐分解，板条状的渗碳体开始聚集和球化。淬火加热温度高于850 ℃时，材料的屈服强度大于960 MPa；在450 ℃回火，材料具有更佳的冲击韧性。对本试验钢而言，采用850 ℃淬火+450 ℃回火，具有最佳的强韧性匹配。

Discussion about phase transformation and heat treatment

By means of DIL805A/D quenching deformation dilatometer, the influence of heat treatment process on the microstructure and properties of 960 MPa high strength steel was studied by optical microscopy (OM), transmission electron microscopy (TEM), tensile property at room temperature, and impact energy test at -40 ℃. The results showed that the content of martensite gradually increased and content of ferrite gradually decreased with the increase of quenching heating temperature in range of 790 880 ℃. The content of ferrite was nearly zero and the microstructure was the most uniform and small when quenched at 850 ℃. As the tempering temperature increased from 180 ℃ to 450 ℃, the lath of martensite gradually disintegrated and the lamellar cementite began to aggregate and spheroidize. When the quenching heating temperature was higher than 850 ℃, the yield strength of the material was over 960 MPa. When tempered at 450 ℃, the material had better impact toughness. For the steel in this study, the quenching at 850 ℃ and tempering at 450 ℃ enabled the best matching of strength and toughness.