Removing oxide and sulfide inclusions from molten steel by filtration

On the basis of thermodynamic calculations indicating that rare-earth sulfide inclusions may form in molten nonalloyed structural steel, the influence of filtration on the content of sulfur, oxygen, and nonmetallic inclusions in the steel is investigated. It is found that filtration removes the oxide phase and oxygen from 30Л steel. There is no change in the content of sulfide inclusions and sulfur. Filtration of steel preliminarily treated with 0.05–0.30% rare-earth metals removes 10–60% of the sulfur. Metallographic data show that the content of both oxide and sulfide inclusions is reduced here. Gray impressions of filter templates show that the sulfur-bearing phase is removed by an adhesive mechanism: this phase adheres to the filter surface, forming continuous borders around it.