LF精炼渣碱度变化对304不锈钢夹杂物成分的影响

采用氧氮分析仪、扫描电镜、金相显微镜等分析手段,系统研究LF精炼渣系对304系不锈钢全氧质量分数wT[O]、夹杂物数量、尺寸及成分的影响。研究结果表明,当LF精炼渣碱度由1.5升高至2.6时,LF出站溶解氧质量分数w[O]由11.6×10~(-6)降低至4.8×10~(-6),铸坯wT[O]由47×10~(-6)降低至24×10~(-6),铸坯夹杂物总数量降低,但当量直径不大于10μm的夹杂物所占比率由77.7%增加至95.1%。热力学计算结果表明:在钢液中各元素达到平衡状态时,渣系碱度越高,低熔点夹杂物2MgO·2Al_2O_3·5SiO_2生成区域越小,MgO·Al_2O_3尖晶石类夹杂物生成区域越大,与生产试验结果一致。随着LF炉渣碱度升高,铸坯夹杂物成分中MgO和Al_2O_3的质量分数分别升高了14.4%和9.1%,当碱度不大于1.9时,铸坯中不会存在镁铝尖晶石。

Effect of LF refining slag basicity on composition of inclusions in 304 stainless steel

The effect of LF refining slag on number, size, composition of inclusions and T??O?? content in 304 stainless steel were analyzed by oxygen-nitrogen analyzer, scanning electronic microscopy and metallographic microscopy. The results indicate that mass fraction of dissolved oxygen in 304 stainless steel at LF tapping moment decreases from 11. 6??10-6 to 4. 8??10-6 with slag basicity in LF refining process increasing from 1. 5 to 2. 6, and mass fraction of T??O?? in 304 stainless steel continuous casting slab decreases from 47??10-6 to 24??10-6. The number of inclusions in slab decreases, but the proportion of inclusions which diameter less than 10??m increases from 77. 7% to 95. 1%. The thermodynamical calculation results show that under the condition of equilibrium state, with increasing slag basicity in LF refining process, the formation areas of 2MgO??2Al2O3??5SiO2 inclusions become smaller and the formation areas of MgO??Al2O3 become bigger, which have the same tendency with production test. The MgO and Al2O3 content of inclusions in slab increase 14. 4% and 9. 1% respectively with slag basicity in LF refining process increasing. There are no MgO??Al2O3 spinel inclusions in continuous casting slab when slag basicity in LF refining process is less than 1. 9.