I MARKETS

Slag Market Perks Up U.S. Steel steps up research to upgrade slag and uncork new markets as chemical raw material

B, JLAST-FURISACE SLAG, once a major nuisance by-product of steel, is big business today—and destined t o get a lot bigger. Some 30 to 35 million tons are produced annually, a rate of one third to one half ton of slag per ton of iron. And although the bulk of slag sold funnels into the booming construc­tion market (aggregate for portland cer.irit ooivruie, bituminous surface for non skid highways, concrete ma­sonry units, road fill, railroad ballast, fibers for mineral wool, and the like), newer and more sophisticated uses loom on the horizon. Two promising areas: raw material for glass fibers and soil-conditioning.

Total blast furnace slag sales have skidded badly, last year and this, from 1957's record $51.7 million, b u t only because of short supply (steel produc­tion cutback in 1958, strike this year). But when the current steel fiasco is finally settled, uses for slag will soar quickly to new highs, industry observ­ers predict. And U.S. Steel i s out to help trigger this sprint. Its answer: new products through research.

Object, says USS, is to upgrade slag's chemical potential—to tailor it to more refined markets. "Slag is now a full-fledged item on the company's research budget," USS's slag products manager, Stewart Steffey, says. Doubled in 1959, USS's slag marketing budget will double again for next year.

Chemistry of blast-furnace slag var­ies slightly from furnace to furnace, depending on the proportions and com­ponents of the raw materials, operating procedures, and the like. But for the most part it looks like this: silica (SiOo), 33 to 42 r r ; alumina (A1203), 10 to 16Γ*; lime ( C a O ) , 36 to 4 5 % ; magnesia ( M g O ) , 3 to 12%; sulfur, 1 to 37r; iron oxide ( F e O ) , 0.3 to 2%; and manganese oxide ( M n O ) , 0.2 to 1.5r*.

THE COYER. Molten slog from U.S. Steel's Pittsburgh furnaces flows f rom train of ladle cars into slag dump

As it happens, making good pig iron turns out a good slag for the major con­struction uses today. But for the more sophisticated uses USS is thinking about, it docs need to control composi­tion more closely. Among possibilities it sees:

• Selectively charge the blast furnace with raw materials (for example, use dolomite, (Ca, Mg)CO H , instead of limestone, CaCO s , to control the amount of lime and silica in the fin­ished product) .

• Separate the different composition slags from each furnace and sell each for specific end uses (e.g.: low sulfur content slag to glass fiber manufac­turers ) .

Slag is no newcomer to the glass industry. Many glass makers (Owens-Illinois and others) use slag to make amber glass, chiefly for the big beer-bottle market. Here the small amount of sulfur and iron in the slag is used to provide the amber color.

The glass fiber industry, too, has been toying with the idea of using slag

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Normal Steel Output Should Boost Slag Sales Blast Furnace Slag Sales

1949-53 a 1954 Source: U.S. Bureau of Mines

1955 1956 1957 1968 1959b 1960b *> C&EN estimates.

3 6 C & E N NOV. 30, I 9 5 9

Steel Production Cutback Steel Strike

The 194S-53 averaae widicatee saleai but doesn't refleel H * H r f ^ p / e ^ e l g ^ . teece»»*^^ Msurçgig those ~ yea r» . In.fançr^yesassi; production and ^saies W<*re more nearly «equal.

as a glass-batch raw material for a gcoci while. Advantages: improved melting and lower costs (it takes a lot less time to raise slag to the liquid state for glass making than it does to convert crystal­line silica sand to a l iquid). But slag for glass fibers must contain little sul­fur and iron.

Owens-Corning currently cooks up some 50,000 tons of slag a year for its Fiberglas. Source—Calumite Co. (Hamilton, Ohio) , working with sev­eral slag producers, and Way lite Co., (Bethlehem, Pa . ) . And now, O-C and USS have embarked on a joint research and development project to fashion USS's Orbitron slag as a glass-batch raw material. The potential market for slag in glass fibers next year is 100,000 tons; this should triple in 1965.

One long-standing, but generally lit­tle-known slag market is in mineral, or "rock," wool. About 85rv of all min­eral wool is made from blast-furnace slag fibers. Current market for slag here is one half million tons with an estimated value of $765,000, .This market is not expected to increase sig­nificantly by 1965.

• Fertilizer Uses Climbing. A good slug of USS's research budget for slag is ticketed for agricultural development. The company has given grants to sev­eral universities to pursue this goal. Some 50,000 tons of slag were sold last year as an agricultural liming material. Experts predict this figure will climb to a million tons by 1965. Open-hearth slag's importance as a soil conditioner is all the more striking considering that now it is shipped from Chicago to Florida where citrus fruit growers are singing its praises, Over all agricultural use of slag is expected to exceed 250,-O00 tons next year.

Slag also crops up in some unusual applications:

• Oysters, for a time, were not fair­ing too well along the Atlantic Coast. It seems they need oyster shell beds to lay their eggs in and for the young oysters to be protected from strong cur­rents and other sea life. Oystermen, however, cart off both shell and oyster when they harvest the beds. Someone dumped a barge-load of slag by acci­dent into Chesapeake Bay, a particu­larly troublesome area, and the oysters thrived. Since then, slag has been ap­plied regularly, and the area abounds in oysters once again.

• Rutgers University researchers tried it in the New Jersey cranberry bogs where acidity from the berries was

SLAG RECOVERY. Granulated slag is recovered from U.S. Steel's Peters Creek dump at Clairton, Pa. USS's Clairton Works is in background

raising havoc with berry-pickers and the wild-life in the area. Again, slag turned the trick.

• Open Hearth Slag. U.S. Steel alone produces some 6 million tons of slag yearly from its open-hearth opera­tions, a nice sized chunk of an industry-

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wide output of 18 to 20 million tons. This is not interchangeable with blast furnace slag and is largely experimental in application. Heavy (10 to 15%) in metallics, some of it is recycled to the blast furnaces for metal recovery. Also, some contractors take a portion to crush and recover the metals by magnetic means and then sell them back to the steel producer. Even so, over 50%, or 3 million tons, of O-H slag goes to waste stockpiles every year. But now USS is trying to uncover markets for it. Highway construction (as a fill mate­rial) is always a possibility. But the company has higher types of applica­tions in mind. For example, some O-H slag is high in phosphorus. This is be­ing marketed throughout the Southeast as a fertilizer and as a supplier of trace elements by USS's Tennessee Coal and Iron division.

• Seller 's Market . Slag salesmen are bubbling with enthusiasm, complain supply can't meet mount ing demands. Still, there's the old big-volume-low price problem overruling long-distance shipping costs. Heavy slag-producing areas such as Pittsburgh, Birmingham, and Gary still have their dwindling slag mountains, while nonproducing areas go begging for slag. But with research uncovering new and more re­fined uses for slag—where it can sell on quality rather than strictly on price— slag's future looks good, producers be­lieve. •

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