Deoxidation of liquid steel

Rep] Repetylo, O., Olette, M., Kozakevitch, R, Deoxidation of Liquid Steel with Aluminum and Elimination of the Resulting Alumina , J. Metals, 45-49 (1967) (Experimental, 24) [1967Swi] Swisher, J.H., Note on the Aluminum-Oxygen Interaction in Liquid Iron , Trans. Met. Soc. AIME, 239, 123-124 (1967) (Experimental, 8)... 

Sulphide formation. As the tensile strength of steel increases, the harmful effect of sulphur increases. Sulphur is soluble in liquid steel, but on solidification it precipitates as MnS. Precipitates can take various forms and have different effects. The form of the sulphides is related to the residual aluminium content after deoxidation. The residual amount of A1 should allow the formation of type III sulphides. 

In conventional aluminum-deoxidized steels, the extra-low dissolved oxygen content maintains the sulfur in solution in the liquid stoel until the end of the solidification process. Since sulfur exhibits virtually no solubility in the solid steel — less than 0,001% in the bcc structure — a > iS-Fe eutectic suddenly precipitates at the as cast grain boundaries, the so called "Type II" structure described by Sims ( ). This weakens the as cast structure and also results in elongated MnS inclusions in the hot rolled steel plates, coils, sheets, bars, wires etc, as shown in Figure 5,... 

In conclusion, the commercial use that is now widely made of standard electrodes encased in solid-oxide electrolytes should be mentioned. Such electrodes are used to measure the concentration of oxygen in steel, for instance during deoxidation, and also in liquid copper and silver. Reference may be made to articles by Fitterer. ... 

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