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研究了四种高铬钢在恒温分解为珠光体时的碳化物形成过程。对所得结果和其他作者的结果进行了分析,得到统一的规律。 在铬钢中,珠光体转变时可以直接形成(Fe,Cr)_3C,(Cr,Fe)_7C_3或(Cr,Fe)_(23)C_6。但是,不同类型碳化物的形成并不决定于平衡图上所要求的碳化物类型,而决定于奥氏体中的Cr:C比值。Cr:C比值对碳化物成核的过程起着主导的作用。

The process of carbide formation during isothermal decomposition of austeniteinto pearlite in four chromium steels has been investigated by X-ray method. Theexperimental results are analysed and compared with results obtained by otherauthors on chromium steels of various compositions, and unified conclusions aredrawn. 1) Depending upon the composition of steels, the initial carbide formed duringisothermal formation of pearlite may be cementite, (Cr, Fe)_7C_3 or (Cr, Fe)_(23)C_6.That is, special carbides can be formed directly from austenite, and they are notalways products of secondary process as some authors believe. 2) Type of carbides to be formed directly from austenite is not determined bythe requirements of equilibrium diagram, but depends upon Cr: C ratio in austenite.When the atom ratio Cr: C is smaller than 2, the initial carbide is cementite; whenthe ratio lies between 2 and 13, the initial carbide is (Cr, Fe)_7C_3; when the ratiois larger than 13, it is (Cr, Fe)_(23)C_6. It seems that the Cr:C ratio in austenite hasdecided influence on the kinetics of nucleation of different carbides. 3) When the type of carbides formed directly from austenite is not that re-quired by the equilibrium diagram, carbide transformation takes place as a secondaryprocess. 4) When the directly formed carbide is an alloy carbide, i. e. (Cr, Fe)_7C_3 or(Cr, Fe)_23C_6, diffusion of chromium in austenite immediately in front of the growingnodules of pearlite is a necessary process during transformation.