within tolerable limits from the standpoint of controlling slopping and maintaining the oxygen utilization efficiency of the bof blowing cycle in order to make steel each bof shop has specified operating parameters for the oxygen blowing cycle establishing starting lance height lance height reduction rate oxygen flow rate and the like which typically vary from shop to shop in the practice of the invention the lance is initially adjusted to a height above the bath that is effective to create a foamy slag during the initial phase of the oxygen blowing cycle this initial lance height is preferably higher than the normal shop specification once the slag is made foamy during the initial stage of the oxygen blowing cycle the lance height is slowly reduced to further enhance and maintain the foam until the peak decarburization period of the blowing cycle in order to control the foamy slag produced by the high lance practice it is necessary to significantly reduce the oxygen flow rate at the appropriate time during the oxygen blowing cycle at the same time one must maintain an oxygen utilization efficiency sufficient to make steel by ensuring that the oxygen flow rate is at its minimum at or about the commencement of the peak decarburization period of the blowing cycle one can reduce the oxygen flow rate enough to controllably produce a sufficient amount of foamy slag to obtain post combustion heat transfer efficiencies on the order of 80 without jeopardizing the oxygen utilization efficiency in order to.