热处理工艺对中碳中合金钢显微组织的影响

Effect of heat treatment process on microstructure of medium carbon medium alloy steel

以国内某厂锻后退火态40CrNiMoV钢为研究对象,在实验室箱式热处理炉进行910℃正火+880℃淬火热处理,探究不同正火及淬火奥氏体化时间的中合金元素固溶与析出对40CrNiMoV钢显微组织的影响。结果表明:在910℃×1 h正火+880℃×1 h淬火工艺下,存在较多细小的VC钉扎在原奥氏体晶界,使奥氏体晶粒尺寸约为8μm。随正火及淬火奥氏体化时间的延长,VC逐渐长大,当大于80 nmVC约占15%时失去钉扎效应。当910℃×4 h正火+880℃×4 h淬火时,原奥氏体局部晶粒尺寸可达40μm,因此,奥氏体化时间不宜过长,910℃×2 h正火+880℃×2 h淬火为最佳热处理工艺,可保证合金元素充分回溶,同时利用细小第二相达到细化组织的目的。

Taking the annealed 40CrNiMoV steel after forging in a domestic factory as the research object,the 910℃normalizing+880℃quenching heat treatment was carried out in the laboratory box heat treatment furnace.The effects of solution and precipitation of medium alloy elements on the microstructure of 40CrNiMoV steel at different normalizing and quenching austenitizing times were investigated.The results show that under 910℃×1 h normalizing+880℃×1 h quenching process,more small VC is nailed to the grain boundary of the pre-austenite,and the grain size of austenite is about 8μm.With the extension of normalizing and quenching austenitizing time,VC gradually grew up,and the pinning effect is lost when the VC greater than 80 nm accounted for about 15%.When 910℃×4 h normalizing+880℃×4 h quenching,the local grain size of the original austenite can reach 40μm,therefore,austenitizing time should not be too long,910℃×2 h normalizing+880℃×2 h quenching is the best heat treatment process,which can ensure that the alloying elements are fully remelting,and the use of fine second phase to achieve the purpose of fine organization.