Technology: Tower of Steel

Though the U.S. is the world's largest steelmaker, most of the dramatic new techniques for better steelmaking have come from the other side of the Atlantic.

Austria's famed LD process, for example, has enabled U.S. steelmakers to make steel more quickly and at a lower cost by lacing their furnaces with liquid oxygen. Last week U.S. Steel, the biggest U.S. steelmaker, announced that it is borrowing yet another technique from Europe—one that may revolutionize the U.S. steel industry.

That technique is the continuous casting process, in which molten steel is formed into semifinished slabs in one unbroken step. Originally conceived by Sir Henry Bessemer, Britain's 19th century steelmaking genius, the process was developed in Germany in the 19305, but has been seriously put to use by European steelmakers only in the past year. The Soviet Union claims to have produced nearly one million tons of steel last year by continuous casting.

In the conventional method of making steel, molten steel is poured from the furnace into molds, forming ingots. After cooling, the ingots are placed in pit-type furnaces, reheated, and then put on blooming mills and rolled into semifinished slabs. All this takes hours, and sometimes days; continuous casting takes less than an hour. In it, the furnace is set on a tower directly above a tall, vertical mold, which is water-cooled. As the mol ten steel is poured into the mold, it solidifies and inches downward, emerging as a glowing sheet of steel at the bottom of the mold, where it is cooled further and chopped into slabs for convenient handling. Meanwhile, molten steel is steadily added from above so that a continuous ribbon of steel is produced. The continuous casting process can be almost completely automated, produces a uniform grade of steel, and in German plants has saved as much as $10 a ton in production costs of regular carbon steel. Though a handful of other U.S. steelmakers had already begun experimenting with continuous casting, U.S. Steel's adoption of the process means that it is sure to sweep the U.S. steel industry.