Cu对9Ni钢强度和低温韧性的影响

研究了Cu含量(质量分数)对9Ni钢强度和低温韧性的影响,并结合显微组织观察和精细结构分析了含铜9Ni钢的强韧化机理.结果表明,经过淬火+两相区淬火+回火(QLT)处理,Cu含量由0提高到1.5%,9Ni钢的室温屈服强度和抗拉强度分别提高约150和105 MPa;随着Cu含量的提高-196℃低温冲击功呈现先增加后降低的趋势,Cu含量为1.0%时达到最高值157 J,而所有含铜9Ni钢的冲击功均保持在较高的水平。随着Cu含量的增加,钢中二次回火马氏体增加而铁素体减少;颗粒或短杆棒状Cu析出物在基体上析出,组织强化与析出强化共同使钢的强度提高。同时,Cu的加入提高了二次回火马氏体板条边界上的逆转奥氏体含量,并富集于逆转奥氏体中提高其稳定性,从而提高了钢的低温韧性。

Effect of Copper on Strength and Cryogenic Toughness of 9Ni Steel

The effect of copper addition on the strength and cryogenic toughness of 9Ni steel was investigated and the mechanism of strengthening and toughening of Cu-bearing 9Ni steel was discussed in connection with the microstructure characteristics.The results show that the room-temperature yield strength and ultimate tensile strength of the 9Ni steels heat-treated by quenching + lamellarizing + tempering(QLT) process increase by about 150 and 105 MPa respectively when the copper content was increased from 0%to 1.5%.And the impact energy at -196℃increased as Cu content increases within 1%but decreased beyond 1%.At the same time,highest impact energy reaches to 157 J for Cu content of 1.0%though the steels with other Cu contents also have high level impact energy.The microstructure observation result reveals that,with increasing Cu,the strength increased due to increasing secondary tempered martensite and Cu particles precipitated finely.On the other hand,Cu addition increases the volume fraction of reversed austenite and improves the stability of formed reversed austenite resulting in cryogenic toughness improvement.