钙镁复合处理20CrMnTi钢中硫化物夹杂

 20CrMnTi钢中添加硫可以改善切削性能，但也会带来力学性能变差的问题，Ca-Mg复合处理可减轻硫化物夹杂物的危害。通过实验室高温试验、电镜观察、能谱分析及统计方法，研究了对20CrMnTi钢中加硫后形成的硫化物进行Ca-Mg复合处理以及钙处理的效果。试验结果表明，复合处理可以使加硫钢中长条、链状的II类硫化物改性为球状单相或者包裹氧化物的复合夹杂物，处理后钢中夹杂物的平均长宽比、直径显著降低；复合处理时钙加入钢中形成的CaS与MnS固溶提高硫化物的球化率，镁主要形成MgO，使被包裹的氧化物核心更细小弥散，最终的夹杂物为MnS-CaS-MgO（-Al2O3-CaO）；若镁过量，则硫化物中会出现MgS，若钙过量，氧化物中出现CaO；加入镁使钙处理所需钙加入量变小，复合处理的效果优于单独的钙处理。

Modification of sulphide inclusions in 20CrMnTi steel by calcium-magnesium treatment

The resulphurized 20CrMnTi steel is with good machinability， but the mechanical property is poor. Ca-Mg duplex treatment can reduce the harm of sulphide in this steel. The effect of Ca-Mg duplex treatment with different proportions on resulfurized 20CrMnTi steel was studied through high temperature experiment and SEM-EDS analysis. The results show that the duplex treatment can modify the II type sulfide inclusion from strip and chain shapes to spherical shape or wrap on oxide inclusion core. The average aspect ratio and diameter decrease dominantly after treatment. During the duplex treatment， Ca mainly reacts with S in steel， which strengthens the spheroidization of sulfide inclusion， and Mg mainly reacts with O in steel， which generates diffusing oxide core of small size. The inclusion types are MnS-CaS-MgO（-Al2O3-CaO）after treatment.If adding superfluous Mg， MgS will show up insulfide inclusion and if adding superfluous Ca， CaO will show up in oxide inclusion. The Mg in the treatment strengthens the modification effect of Ca， which means that less Ca is needed to reach the same modification， and duplex treatment is better than Ca treatment.