预备热处理工艺对9Cr2Mo钢组织和硬度影响

利用金相显微镜、扫描电镜等试验手段，研究了经不同工艺预备热处理的9 Cr2 Mo钢的显微组织和碳化物形态、分布及大小，并测定了表面硬度。结果表明，9 Cr2 Mo钢淬火或正火态组织均为马氏体和下贝氏体，还有少量的未溶碳化物及残留奥氏体。钢的淬火组织中马氏体量要比正火组织中的多。经淬火＋高温回火或正火＋球化退火的9 Cr2 Mo钢，其组织均为铁素体基体和不同尺寸的碳化物颗粒，硬度基本能满足切削加工的要求。而经890℃×30 min油淬＋690℃×10 h回火的钢，其组织中碳化物颗粒较均匀细小，是一种良好的预备热处理组织。

Effect of Preliminary Heat Treating Cycle on Microstucture and Hardness of 9Cr2Mo Steel

Microstructure,morphology and distribution as well as size of carbides in 9Cr2Mo steel preliminary heat treated by different procedures were investigated by means of metallographic microscope and SEM , and its surface hardness was measured too .The results show that the microstructure of 9Cr2Mo steel after quenching or normalizing consists of martensite , lower bainite and small amount of undissolved carbide and retained austenite , and that amount of martensite in the as-quenched steel is more than that in the as-normalized steel .Furthermore , the microstructure of 9Cr2Mo steel hardened and high-temperature tempered or normalized and spheroidized is ferritic matrix with carbide particles different in size , and the resulting hardness is so low that the steel may be smoothly machined .After heating at 890 ℃for 30 min and oil quenching followed by tempering at 690 ℃for 10 h the steel offers fine and uniform carbides which is a proper microstructure developed by preliminary heat treating .