通过实验研究了Cu元素及热处理工艺对9Ni低温钢组织与力学性能的影响。结果表明,添加Cu元素后,材料的低温冲击韧性明显得到提升,而抗拉强度和屈服极限变化不大。调质热处理后,材料的力学性能及低温冲击性能均明显得到改善。通过光学显微镜观察发现,热轧态的9Ni钢微观组织主要为淬火马氏体,经热处理后则主要为回火马氏体;进一步通过扫描电镜观察可以发现,调质热处理后,材料的基体组织为回火马氏体,在基体上分布着白亮色的粒状和板条状的淬火马氏体和回转奥氏体混合物。通过X射线衍射检测发现,添加Cu元素后回转奥氏体的数量增加。Cu对9Ni钢低温韧性的改善主要有以下两方面原因:一是钢中Cu、Ni等元素的富集大大提高了回转奥氏体的稳定性并增加了其含量,二是Cu元素的添加使回转奥氏体在晶内、晶界的分布更加均匀、弥散,从而提高了9Ni钢的低温韧性。 The effects of Cu element and heat treatment process on microstructure and mechanical properties of 9Ni low temperature steel were studied experimentally. The results show that the addition of Cu element, the material low temperature impact toughness improved obviously, but the tensile strength and yield point little change. After quenching and tempering, the mechanical properties and low temperature impact properties of the materials are obviously improved. The microstructure of hot-rolled 9Ni steel was mainly quenched martensite by optical microscopy and mainly tempered martensite after heat treatment. Further observation by scanning electron microscopy revealed that the microstructure of 9Ni steel after hot- For the tempering martensite, the distribution of bright white granular and lath-shaped martensite and austenitic mixture on the matrix. It was found by X-ray diffraction test that the amount of austenite after the addition of Cu element increased. The improvement of low temperature toughness of Cu on 9Ni steel has the following two reasons: First, the enrichment of Cu, Ni and other elements in steel greatly improves the stability of the rotary austenite and increases its content; secondly, the addition of Cu Rotary austenite in the grain, the grain boundary distribution more uniform, dispersed, thereby increasing the low temperature toughness 9Ni steel.