热处理对9Ni钢焊接接头组织与性能的影响

Effect of heat treatment on microstructure and mechanical properties of 9Ni steel welded joint

对9Ni钢焊接接头分别进行了QT处理和IHT处理,采用拉伸、硬度、冲击试验,断口电镜扫描等方法研究了两种热处理对焊接接头显微组织及性能的影响。结果表明:未经热处理时焊缝的组织为细晶铁素体+针状铁素体;QT处理后焊缝的组织为马氏体+奥氏体;IHT处理后焊缝组织为马氏体+奥氏体+铁素体。QT与IHT处理均能使9Ni钢焊接接头的强度、硬度下降,塑性上升;IHT处理后焊接接头的伸长率达到29.0%,塑性优于QT态。经QT和IHT处理后,焊缝的低温冲击吸收能量分别从48 J上升至78 J和100 J;IHT处理可明显提升焊缝的低温韧性,其冲击断口为典型的韧性断裂。

QT treatment and IHT treatment for 9Ni steel welded joints were carried out. Effects of the two kinds of heat treatment on microstructure and properties of the welded joints were investigated by means of SEM observation, tensile test, hardness test and impact test. The results show that the microstructure of the weld consists of fine grain ferrite and acicular ferrite before heat treatment. The microstructure of the weld consists of martensite and austenite after QT treatment, and martensite, austenite as well as ferrite after IHT. Both QT and IHT can decrease the strength and hardness of 9Ni steel welded joints, but increase the ductility. The elongation of the welded joints after IHT treatment is 29.0%, which is superior to the QT. After QT and IHT, the low temperature impact energy of the weld increases from 48 J to 78 J and 100 J,respectively. The IHT treatment can significantly improve the low temperature toughness of the weld, and its impact fracture is a typical ductile fracture.