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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。
The effect of Cu content (mass fraction) on the strength and low temperature toughness of 9Ni steel was studied, and the strengthening and toughening mechanism of 9Ni steel with copper was analyzed by microstructure observation and fine structure.The results show that after quenching + two-phase quenching + Tempering (QLT), the content of Cu increased from 0 to 1.5%, the yield strength and tensile strength of 9Ni steel increased about 150 and 105 MPa, respectively. With the increase of Cu content, the impact energy at -196 ℃ increased first, The highest value of 157 J reached at the Cu content of 1.0%, while the impact energy of all the 9Ni steel containing copper was maintained at a high level. With the increase of Cu content, the secondary tempered martensite increases and the ferrite decreases in the steel. The precipitates of rod-shaped Cu or Cu rod-shaped particles precipitate on the matrix, and the strengthening of the microstructure and the precipitation strengthening together increase the strength of the steel. At the same time, the addition of Cu improves the reversed austenite content at the boundary of secondary tempered martensite lath and enriches in reverse austenite to improve its stability, thus improving the low temperature toughness of steel.