稀土处理C-Mn钢显微组织和夹杂物演化

对稀土处理C-Mn钢的夹杂物和显微组织进行分析,统计稀土处理C-Mn钢中针状铁素体形核核心尺寸,并将稀土处理钢在不同温度下淬火,研究稀土夹杂物生成和长大过程.实验结果表明:C-Mn钢加入少量稀土后钢中夹杂物从MnS＋硅铝酸盐夹杂转变为La₂O₂S＋LaAlO₃＋MnS＋硅铝酸盐夹杂,尺寸得到细化,显微组织也从马氏体＋贝氏体组织变成侧板条铁素体、针状铁素体和块状铁素体组织;稀土处理C-Mn钢中针状铁素体有效形核核心的尺寸集中在1~4μm,主要是在钢液中形成,冷却和凝固过程形成的数量较少;稀土夹杂物在钢液温度和冷却及凝固过程容易碰撞黏合长大,上浮从钢液中去除,MnS能在稀土夹杂物颗粒间析出. 

Microstructure and inclusion evolution in rare earth treated C-Mn steel

The microstructure and inclusions in rare earth treated C-Mn steel were studied,the size distribution of the nuclei inducing acicular ferrite nucleation was subjected to statistical analysis,and the formation and growth processes of rare earth inclusions were discussed through quenching the treated samples at different temperatures. It is found that after a small amount of rare earth is added into the C-Mn steel,the inclusion composition changes from Mn S + aluminosilicate to La₂O₂S + LaAlO₃+ MnS + aluminosilicates,the inclusion size decreases,and the microstructure converts from martensite + bainite to ferrite side plate + acicular ferrite+ massive ferrite. The size of effective inclusions inducing acicular ferrite nucleation is mainly concentrated in 1-4 μm in the rare earth treated C-Mn steel,they primarily form in liquid steel,but little in the cooling and solidification processes. The rare earth inclusions are easy to coalesce and grow up at molten temperature and in the cooling and solidification processes,and Mn S can precipitate around the residual rare earth inclusion particles.