Effects Of Scrap In The Blast-Furnace Burden

IN the preparation of this paper, the author has drawn upon experience with the operation of a blast furnace on 100 per cent scrap burden, which he believes was the first operation of its kind in the country. It is the writer's further belief that much of the controversy attending discussions of this subject may be obviated by the presentation of a group of facts that should be known by blast-furnace men and open-hearth men alike. The following question has been raised: "Is iron made with scrap in the blast-furnace charge as good iron as that made without scrap-made with straight ore?" This question may be answered in part by the fact that the open-hearth men of the Bethlehem Steel Co. who used pig iron from a blast furnace that operated on 100 per cent steel scrap found no difficulty in the processing of such iron other than that to be expected from the known analysis. OPERATION WITH 100 PER CENT STEEL SCRAP During World War I, there was accumulated at the Bethlehem plant of the Bethlehem Steel Co. some 22,000 tons of alloy-steel turnings and borings. This scrap material was highly corroded and, like alloy-steel turnings of that period, were as a drug on the market. There was also a small tonnage of scale, rich in valuable metal. If this scrap could be worked up into pig iron, it would become readily available for use in the open hearth. In order that the pig iron should contain the maximum percentage of nickel, permission was obtained from the Management to try a 100 per cent scrap operation. Accordingly, a blast furnace was swung over on July 25, 1919; the percentage of steel scrap increased more or less irregularly until July 29, when l00 per cent steel turnings were charged. Except for occasional charges of nickel scale as an "extra," the operation continued uninterruptedly until Aug. 27, when the furnace was swung back to the regular ore-ore and scrap-operation. During this period, the furnace production ranged from a low of 568.60 tons to a maximum of 766.07 tons. At the swing-over from i00 per cent scrap to the regular burden, the charge hung up rather severely. While the latter condition has nothing to do with the object of the paper, a brief discussion of the experience will appear later because of the interest it may have for blast-furnace operators. In Table I, results of the first and last days of the ore charge are shown, July 25 and July 29. The last column shows a summary for the period of maximum scrap charge. The furnace employed had a hearth 16 ft. 0 in., bosh 22 ft. 0 in., stock line 15 ft. 6 in., bell 11 ft. 6 in., batter ¾ in., bosh angle 73° 27' and a Baker-Neuman top, with gas-engine blowers. Analyses Range of Material Charged Gravel: Si02, 64.40 to .7o.54 per cent; A1203,3-52 to 4.58; CaO, 7.27 to 9.49; M90, 5.09 to 6.14; FeO, 1.67 to 3.34, ignition loss, 9.50 to 13.83.