20CrMnTi棒材表面混晶及消除方法

On Methods of Eliminating Mixed Crystal on 20CrMnTi Work Piece

大规格20CrMnTi棒材锻造之后,采用金相显微镜组织分析发现,表层组织不匀,表层晶粒尺寸相差悬殊,细晶粒中伴有粗大的珠光体团,局部混晶严重,为改善表层组织不均匀性,分别经多次正火及等温退火热处理,实验证实,多次正火可以消除局部混晶,并且细化组织;等温退火,也可以消除局部混晶,但偏析带仍较明显;比较而言,多次正火是锻造后较好的热处理工艺。

Through metallographic organization analysis, it is found that after forging, the large size round steels 20CrMnTi tend to have inhomogeneous surface tissue which are mainly mixed crystal. Repeated heat treatment test proves that repeated normalizing ean eliminate mixed grain, and refine grains; isothermal heat treatment can also elim-inate mixed crystal, but with obvious segregation. Comparatively speaking,repeated normalizing can eliminate mixed crystal with grain refinement, which is a superior technique.