Synopsis The relation between iron oxide ill slag and oxygen in lIletal ill 160-t LD converter are studied, and the lIlain results obtained are as follows : (1 ) During the period between end I)oint and tal)ping the oxygen COIltent in metal changes in a range of ± 150 Plmz in low carbon steel (0 .04 to O.OB% C). (2) Th is change of oxygen in lIletal delJelzds all the total FeO cOlltent of slag. When the total FeO content in slag is high, oxygen content in metal increases between end I)oint and

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... al)ping. On the other hand, wizen the total FeO content is low, the o:qgen content decreases. (3) At the end of oxygen blowing the slag temperature is higher than that oj metal. The difference in temperatures seems to be over 50' C. This difference, however, vanishes during the period between end point and tal)ping . Thi" decrease oj slag teml)eratllre aJter the end of blowin, t: reduces the degree of oxidation oj slog . (4) A s a consequence, the oxidi dng j)otential q( slag becomes lower than that oj metal at taj)I)ing. T his case occurs in aJ)p roximately one third oj the heats of low carbon steels. I n medium alld high carbon steels, however, this case scarcely occllrs.