Fe-C-Si合金固态脱碳实验

Experimental study on solid state decarburization of Fe-C-Si alloy

以1 mm厚的Fe-3.0%C-0.84%Si(质量分数,下同)合金薄带和Fe-4.0%C-xSi(x=0,0.84%,1.24%)合金薄带作为研究对象,分析了在H_(2)O-H_(2)气氛下Fe-C-Si合金薄带的脱碳行为,重点探究了脱碳过程中的脱碳速率、元素竞争氧化及相关反应动力学.结果表明:在脱碳过程中,试样表面主要为Fe,Si的选择性氧化,且Si优先氧化生成SiO2;随着φ(H_(2)O)/φ(H_(2))(即炉内水蒸气体积分数与H_(2)体积分数的比值)的升高,氧化物转变为Fe_(2)SiO_(4),当φ(H_(2)O)/φ(H_(2))=0.42时,脱碳效果最好;随着硅含量的增大,脱碳效果越好,说明硅可促进固态脱碳.通过对动力学的研究及计算可得,当φ(H_(2)O)/φ(H_(2))=0.42时,脱碳的宏观活化能为111.475 kJ/mol,低于碳在奥氏体中的扩散活化能,界面反应为脱碳的控速环节.

The decarbonization behavior of 1mm thick Fe-3.0%C-0.84%Si(mass fraction,same below)alloy strip and Fe-4.0%C-xSi(x=0,0.84%,1.24%)alloy strip in H_(2)O-H_(2)atmosphere was analyzed.The decarbonization rate,competitive oxidation of elements and related kinetics during solid state decarbonization of Fe-C-Si alloy thin strip were investigated.The results show that in the process of decarbonization,the surface of the sample is mainly Fe,Si is selectively oxidized,and Si is preferently oxidized to SiO2.With the increase ofφ(H_(2)O)/φ(H_(2)),the oxide changes into Fe_(2)SiO_(4),and the decarbonization effect is the best whenφ(H_(2)O)/φ(H_(2))=0.42.With the increase of silicon content,the decarbonization effect is better,indicating that silicon can promote solid decarbonization.According to the kinetic study and calculation,whenφ(H_(2)O)/φ(H_(2))=0.42,the macroscopic activation energy of decarbonization is 111.475 kJ/mol,which is lower than the diffusion activation energy of carbon in austenite,and the interfacial reaction is the speed control link of decarbonization.