LF精炼渣碱度变化对304不锈钢夹杂物成分的影响

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

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。

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 1.5to 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 10μm increases from77.7% 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·2Al_2O_3·5SiO_2inclusions become smaller and the formation areas of MgO·Al_2O_3become bigger,which have the same tendency with production test.The MgO and Al_2O_3 content of inclusions in slab increase 14.4%and 9.1%respectively with slag basicity in LF refining process increasing.There are no MgO·Al_2O_3spinel inclusions in continuous casting slab when slag basicity in LF refining process is less than 1.9.