热处理对5Ni铸钢显微组织和低温韧性的影响

Effect of Heat Treatment on the Microstructure and Cryogenic Toughness for 5Ni Cast Steel

试验了三种热处理方式（ＱＬＴ、ＱＴ、ＬＴ）对５Ｎｉ铸钢组织及低温韧性的影响。结果表明，经ＱＬＴ、ＱＴ处理的钢组织均以铁素体为主，经ＱＬＴ处理的钢由于残余奥氏体稳定性好，分布均匀，故其低温韧性最佳（适在－９５℃下应用），ＱＴ处理的次之；ＬＴ处理的钢组织为板条状马氏体，只适在－４０℃以上使用。

Abstract The microstructure and cryogenic toughness of 5Ni cast steel in different heat treatment bave been investigated and the microstructure and the morphology of fracture were analysed by using metalloscope,X ray diffraction and SEM,the a k value of cast steel at several temperature was also measured using liquid nitrogen unit and shock test machine.The test results indicate that the microstructure of the steel is mainly compsed of ferrite,the test steel has the best toughness by QLT treatment at -95℃, and then by QT treatment,the minimum value meets the requirement of international standard about“work at tow temperature”.