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本文用光学金相、电子金相、显微硬度、X射线衍射、磁性和膨胀等方法研究了中温和低温回火对18Cr2Ni4WA钢渗碳层中残余奥氏体(A_R)的影响。结果表明,220℃回火时A_R中的位错线上已可观察到碳化物(K)析出,350～480℃回火时A_R中析出大量的魏氏组织碳化物(K_W),520℃以上回火时K主要沿原奥氏体晶界析出,马氏体(M)对A_R向贝氏体(B)转变有明显促进作用,冰冷处理能增加这种转变,所形成的B的回火抗力很高,难以用高温回火工艺进行球化。
In this paper, the effects of medium and low temperature tempering on retained austenite (A_R) in carburized layer of 18Cr2Ni4WA steel were studied by means of optical metallography, electronic metallography, microhardness, X-ray diffraction, magnetic property and expansion. The results show that precipitation of carbides (K) can be observed on the dislocation line in A_R at 220 ℃ tempering. A large amount of Widmanstones (K_W) precipitated in A_R at 350 ~ 480 ℃ and above 520 ℃ During tempering, K mainly precipitates along the original austenite grain boundaries. Martensite (M) obviously promotes the transformation of A_R to bainite (B), and the cold treatment can increase this transformation. The tempering of B High resistance, it is difficult to temper the high temperature tempering process.