坩埚材质对55SiCr弹簧钢中夹杂物的影响

实验采用MoSi₂炉研究了MgO，MgO-CaO两种耐火材料对55SiCr弹簧钢中夹杂物的影响.结果表明，MgO，MgO-CaO两种坩埚冶炼均能使钢种成分控制在目标范围内，但与MgO坩埚相比，MgO-CaO坩埚净化钢液的效果更好:一方面，经MgO-CaO坩埚冶炼的55SiCr弹簧钢，钢中P，S，酸溶铝［Al］_s 以及全氧T.O质量分数分别降低至56×10^-6，10×10^-6，≤5 ×10^-6，以及4×10^-6;另一方面，钢中夹杂物的平均直径由1.376μm降低至1.222μm，夹杂物尺寸＜2μm的比例由79%上升至89%.这主要是因为碱性MgO-CaO坩埚兼具脱磷、脱硫、脱氧的作用，同时CaO还能与钢中的Al₂O₃夹杂物发生反应，生成熔点更低的复合夹杂物，因此更容易上浮去除，进一步净化钢液.

Effect of Crucible Material on Inclusions in 55SiCr Spring Steel

The effects of MgO and MgO-CaO refractories on inclusions in 55SiCr spring steel were studied in a MoSi₂ furnace. The results indicate that both MgO and MgO-CaO crucibles can adjust the composition of the steel within the aiming range. Moreover， compared with MgO crucible， MgO-CaO crucible is more effective in purifying the molten steel， in which the contents of P， S， ［Al］_s and T.O in 55SiCr spring steel smelted by MgO-CaO crucible are reduced to 56×10^-6， 10×10^-6， ≤5×10^-6 and 4×10^-6， respectively. The average diameter of inclusions in steel decreases from 1.376μm to 1.222μm， and the ratio of the inclusions with the size <2μm increased from 79% to 89%. This is mainly because the MgO-CaO crucible has not only the functions of dephosphorization， desulfurization and deoxidization， but also CaO reacts with Al₂O₃ inclusions in steel to form hybrid inclusions with lower melting point， which is easier to float and remove， so that the molten steel is further purified.