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30CrMnSiA钢经1250℃预先淬火后在慢速(0.5℃/min)加热过程中,奥氏体最先呈短针状在原马氏体板条界上渗碳体处形核,而后沿原板条界长大连接成针状,进一步长大连接呈网状且布满整个原板条界,最后,沿垂直于原板条界方向长大连接,使原奥氏体晶粒复原,保留了原粗大的条状特征.在奥氏体刚形成时,未溶渗碳体呈短棒状分布于原马氏体板条界上.且部分渗碳体具有相同的空间取向.在转变结束前,余下少量的铁素体呈菱形.奥氏体可能是以台阶机制形成的.
In the process of 30CrMnSiA steel pre-quenched at 1250 ℃ and heated slowly (0.5 ℃ / min), the austenite first appeared in the form of short-needle nuclei near the cementite in the original martensite slab boundary and then along the original slab boundary Grew up connected into a needle-like, and further growth of the network was connected and covered the entire original slab boundary, and finally, along the vertical growth of the original slab boundary connection, the original austenite grain recovery, retained the original thick bar Like features.In the early formation of austenite, undissolved cementite is short rod-like distribution in the original martensite slab boundary and some of the cementite with the same spatial orientation.At the end of the transition, the remaining small amount of iron The body is diamond-shaped. Austenite may be formed by a step mechanism.