Sulfur content and inclusion control during electroslag remelting of die steel

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%Ca F₂+30%Al₂O₃+20%Si O₂in 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%Ca F₂+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 Si O₂content in slag during the remelting process can improve the macrosegregation of sulfur distributed along the axial direction of ESR ingots.