热处理对不同碳含量3.5Ni钢力学性能和低温韧性的影响

利用光学显微镜及SEM进行组织观察,通过拉伸和低温冲击试验研究了热处理对两种不同碳含量3.5Ni钢的力学性能和低温韧性的影响。两种3.5Ni钢热轧板分别经860 ℃×1 h空冷的正火处理和860 ℃×1 h水淬+(580, 610, 640)×1 h回火的调质处理。结果表明:含碳量较高的3.5Ni钢热轧态强度低塑性高,但－100 ℃冲击吸收能量低,经正火处理后试验钢的整体性能降低,而调质处理后强度和低温冲击吸收能量均明显提升,塑性略有降低;含碳量较低的3.5Ni钢热轧态已经具有优异的拉伸性能和低温冲击性能,经热处理后拉伸性能和低温韧性没有得到明显提升。

Effect of heat treatment on mechanical properties and low temperature toughness of 3.5Ni steel with different carbon content

Effect of heat treatment on mechanical properties and low temperature toughness of two types of 3.5Ni steel with different carbon contents was studied by means of tensile testing and low temperature impact testing, and the microstructure of the steel was observed by means of optical microscope and SEM. The heat treatment of the two types of 3.5Ni steel hot-rolled plates were normalizing (860 ℃ for 1 h, air cooling) and quenching and tempering (860 ℃ for 1 h, water quenching and then tempering at 580, 610 and 640 ℃ for 1 h). The results show that the 3.5Ni steel with high carbon content has low strength and high absorbed plasticity after hot rolling, but low impact absorbed energy at －100 ℃. After normalizing treatment, the overall properties of the tested steel are decreased, while after quenching and tempering treatment, the strength and low temperature impact absorbed energy are significantly improved, while the plasticity is slightly reduced. The 3.5Ni steel with low carbon content has excellent tensile properties and low temperature impact properties after hot rolling, but the tensile properties and low temperature toughness have no significant improvement after heat treatment.