高硫易切削H11模具钢点状偏析的形成机制

Forming Mechanism of Spot Segregation in High Sulfur Content Free Cutting Die Steel H11

采用光学显微镜、扫描电子显微镜及能谱仪等分析了高硫易切削H11模具钢中点状偏析缺陷的形成机制。结果表明:试验钢心部纵向带状偏析严重,偏析带中有较多的与偏析带方向平行的MnS夹杂物;部分MnS夹杂物内部包裹着Al_2O_3颗粒,有些Al_2O_3颗粒之间形成了孔隙性缺陷;点状偏析的形成与带状偏析及MnS夹杂物的偏聚有关,点状偏析的严重程度随着带状偏析严重程度的增加而增大;MnS夹杂物被热酸腐蚀后形成宏观可见的点状偏析;推荐采用稀土复合变质处理改善钢中的硫化物形态,进而减少点状偏析缺陷。

Forming mechanism of spot-segregation defect in high sulfur content die steel H11 was studied by means of optical microscopy,scanning electron microscopy and energy disperse spectroscopy.The results show that longtitudinal banded segregation in the core is serious and many MnS inclusions paralleled to the direction of segregated band can be observed in the segregated band.Part of the MnS inclusions contain Al2 O3 particles,and porosity defects may form between Al2 O3 particles.The formation of spot-segregation defect is related to banded segregation and segregation of MnS inclusions.Moreover,with the increase of the degree of banded segregation,the severity of spot-segregation is also increased.After hot acid corrosion,MnS inclusions were eroded leading to macroscopicly visible spot-segregation.It is recommended using rare earth compound modification to improve the shape of sulfide in high sulfur content steel,and then decrease spot segregation defect.