Sponge Iron

A strange wartime substitute was in the making last week--a substitute for scrap iron & steel. It is called sponge iron, and the U.S. Bureau of Mines has decided to risk $500,000 in hurry-up development of the hitherto unpractical process by which it is made.

To make sponge iron, ore is not smelted. It is mixed with pulverized coal (natural gas can also be used) and coke, then fed to a large rotary kiln. When the kiln is heated to 1,800DEGF., the powdered coal first robs the ore (iron oxide) of its oxygen, then turns into gas, leaving fairly pure iron granules which have a spongy texture. This stuff can then be fed to the steel furnaces.

Steelmakers watch the project with contending doubts and hopes. If sponge iron can be made, it will head off a decline in steel production caused by the ominous shrinking of U.S. scrap-iron resources. It may also cut the cost of steel by as much as $5 a ton.

In the last 90 years the steel industry has spent millions in futile efforts to make sponge iron. Catch in the process is selection of an ore which can yield high-grade sponge. Plants in Sweden and Finland are now turning it out profitably.

Until this summer scrap iron and steel have always been abundant, so steelmakers have relied on them for 40 to 60% of the charge in their furnaces. But now the U.S. needs scrap and needs it badly because there are not enough 1) open-hearth furnaces to produce steel at the slower rate required when higher percentages of pig iron are used, 2) blast furnaces to make pig for all the steel. The furnace handicap will be overcome if the sponge-iron process can 'be perfected, since sponge-iron plants can be built more quickly and cheaply than new blast furnaces, are cheaper to operate.

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