Slag Formation in the Basic Oxygen Steelmaking Process with Bottom Stirring by Inert Gas - Part 2: Investigation of Initial and Final Slags in the Basic Oxygen Steelmaking Process.

The results of microscopic, microanalytical and radiographic investigations of initial and final slags formed in the TBM process indicate that early liquid slags effect a primary precipitation of stable lime silicate phases. The remainder liquid slag phases are subject thereby to an enrichment with high-iron components. The precipitated lime silicates in the form of dicalcium silicate (C//2S) pick up a substantial amount of phosphorus and are depleted thereby of iron and manganese. At the same time, low silicon and phosphorus lime mixed crystals of the lime wuestite type featuring high iron contents are observed. The investigated final slags feature similarly phosphorus-enriched, low-iron lime silicate phases. However, high-iron lime solid solutions are found to an increasing extent here, especially in the form of lime ferrites with only small phosphorus and silicon contents. The high iron oxide and lime, active slags prevailing throughout the refining process result thus in a continuous removal of phosphorus from the metal and its pick-up by, and fixation in, the slag through the formation of stable silicophosphates.