Technology: Tower of Steel

Though the U.S. is the world’s largeststeelmaker, most of the dramatic new techniques for better steelmakinghave come from the other side of the Atlantic.

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

That technique is the continuous casting process, in which molten steelis formed into semifinished slabs in one unbroken step. Originallyconceived by Sir Henry Bessemer, Britain’s 19th century steelmakinggenius, the process was developed in Germany in the 19305, but has beenseriously put to use by European steelmakers only in the past year. TheSoviet Union claims to have produced nearly one million tons of steellast year by continuous casting.

In the conventional method of making steel, molten steel is poured fromthe furnace into molds, forming ingots. After cooling, the ingots areplaced in pit-type furnaces, reheated, and then put on blooming millsand rolled into semifinished slabs. All this takes hours, and sometimesdays; continuous casting takes less than an hour. In it, the furnace isset on a tower directly above a tall, vertical mold, which iswater-cooled. As the mol ten steel is poured into the mold, itsolidifies and inches downward, emerging as a glowing sheet of steel atthe bottom of the mold, where it is cooled further and chopped intoslabs for convenient handling. Meanwhile, molten steel is steadilyadded from above so that a continuous ribbon of steel is produced. Thecontinuous casting process can be almost completely automated, producesa uniform grade of steel, and in German plants has saved as much as $10a ton in production costs of regular carbon steel. Though a handful ofother U.S. steelmakers had already begun experimenting with continuouscasting, U.S. Steel’s adoption of the process means that it is sure tosweep the U.S. steel industry.