We' re looking at it in all the areas where we use gunning. The dissolution of refractories by slag is the major cause of refractory wear in any steelmaking furnace, says James Stendera, manager of research and technical services at Martin Marietta Magnesia Specialties in Baltimore. In the past few years, many mills have turned to slag splashing to counteract the effects of slag penetration. The splashed slag solidifies between heats, providing a disposable, protective coating to the lining. Nearly all BOFs in the country now use the procedure.
Mills can condition the slag with dolomitic lime or dolomite stone before blowing.
After blowing, any remaining slag is dumped. Bethlehem has used slag splashing to reach more than 10,000 heats between BOF relinings at its Burns Harbor, Ind., facility and up to 9,000 heats at the Sparrows Point, Md., mill, Beechan says. The average BOF-lining life in U.S. and Canadian mills currently is about 7,500 heats. Slag splashing also leads to significant savings in refractory-material costs. The steel industry's average consumption of refractory-maintenance products is 2.39 pounds per metric ton of steel produced.