电渣重熔易切削钢中硫含量及夹杂物的控制

Sulfur content and inclusion control during electroslag remelting of die steel

基于热力学分析了电渣重熔中渣系及冶炼工艺对易切削钢AS136的夹杂物及硫均匀性的控制研究.实验采用4 t的非保护气氛电渣炉,分析了电渣锭中硫含量及夹杂物级别.实验结果发现:采用渣系S1 (质量分数为50%Ca F2+30%Al_2O_3+20%SiO_2)冶炼的电渣锭中硫质量分数为0. 066%～0. 075%,能够满足产品要求(产品中要求硫质量分数在0. 05%～0. 10%),但是B类和C类的夹杂物级别均达不到标准;在渣系S3 (质量分数为70%Ca F2+28%Al_2O_3+2%MgO)以及整个重熔中持续地加入质量分数4. 5%镁砂的冶炼工艺下,不仅可以使电渣锭中硫含量呈均匀分布,同时还能够改善夹杂物的分布和大小.分析结果表明:随着电渣重熔初期渣温的升高以及渣中SiO_2质量分数的增加,持续均匀地补加镁砂可以使得电渣锭中的硫沿轴向呈均匀分布.

Experimental and theoretical studies were carried out to investigate the effects of the slag and remelting process on sulfur content and steel cleanliness control during electroslag remelting ( ESR) process. AS136 die steel was used as the electrode and remelted under three different remelting conditions by using a 4 t ESR furnace. The contents of sulfur and inclusion along the axial direction of ingot products were analyzed. It was found that the sulfur content in ingot remelting with slag S1 ( 50% CaF2 + 30% Al2O3 + 20% SiO2 in mass fraction) ranges from 0. 066% to 0. 075% in mass fraction,which can satisfy the requirement of AS136 steel ( the sulfur content ranges from 0. 05% to 0. 1% in mass fraction) ,but the levels of B-alumina type and C-silicate type inclusions are higher than the standards. Under the condition of slag S3 ( 70% CaF2 + 28% Al2O3 + 2% MgO in mass fraction) combined with extra 4. 5% MgO in mass fraction continuously added into molten slag during the whole ESR process,the macrosegregation of sulfur along the height of ingot can be improved,the oxygen and inclusion contents reduce. Constant addition of extra amounts of MgO to the molten slag with the increase of slag temperature and SiO2 content in slag during the remelting process can improve the macrosegregation of sulfur distributed along the axial direction of ESR ingots.