X-ray observation of phosphorus vaporization from steelmaking slag and suppression method of phosphorus reversion in liquid iron

Abstract

The behavior of phosphorus in CaO-SiO₂-Al₂O₃-MgO-P₂O₅-Fe _t O slag systems during solid Al and carbon deoxidation was investigated at 1873 K. Furthermore, an X-ray apparatus (vertical resistancetube furnace equipped with an X-ray inspector system, which enhances the real-time observation of the generated gas in slag) was introduced to confirm the possibility of the vaporizing phenomena of phosphorus from slag. The X-ray-assisted observations proved that phosphorus gas is produced from P₂O₅-containing slag during the deoxidation process and can be applied to suppress the reversion of phosphorus into the liquid iron by removing it into the air. The results of experiments between slag and metal showed that Al decreased the Fe _t O and P₂O₅ contents in slag simultaneously because of the strong reducing power, but carbon decreased only the Fe _t O content in slag to a certain extent without reducing the P₂O₅. For the prevention of the phosphorus-content increment in liquid iron during the deoxidation process, it was ascertained that the Fe _t O content, the absorption site of phosphorus gas, should be decreased to some extent at the time of phosphorus generation. It could be proposed that it is the two-step deoxidation process that decreases the Fe _t O content by carbon while maintaining the P₂O₅ content in the slag at a nearly constant level and then decreases the remaining P₂O₅ content quickly by vaporizing as a gas phase by Al, without considerable reversion of the phosphorus in hot metal.