Bessemer Eye

Up to about 1870 railroad rails were made of iron because the cost of making steel in quantity was prohibitive. Then the converters invented by Henry Bessemer got going and steel became much cheaper. In Bessemer converters--little changed after 70 years--a powerful blast of air is forced through molten pig iron as it lies in the converter's capacious belly. The air oxidizes impurities which form a slag or pass off as gases through the converter mouth. After the slag has formed, the steel is poured into molds to make ingots.

Since 1920 steelmaking has had a big swing to the open-hearth process. These furnaces, lined with dolomite (lime and magnesia oxide), are primed with plate scrap and limestone, then charged with pig iron, scrap and ore, and heated. Gas expelled from the limestone stirs the mixture, helps form the slag. A furnaceman spoons out samples, cools them to test quality, then adjusts the heat to get just the quality he wants. After about twelve hours the furnace is tapped, the steel ladled off. The Bessemer process is three times faster than the open-hearth, and correspondingly cheaper; but since the quality of the steel in a Bessemer "heat" must be judged by fallible human eyes, it is not so uniform--hence cannot be used for engineering jobs where high uniformity is necessary.

In recent months rumors have reached steelmakers that Pittsburgh's Jones & Laughlin Steel Corp., whose stockholders have fared thinly in recent years, had developed a photoelectric indicator ("robot eye") which, by judging the color and brilliance of a Bessemer heat better than human eyes can, made it possible to turn out steel with Bessemer rapidity but of a uniform quality comparable to that of the open-hearth product. The J. & L. researchers guarded their secret vigilantly, declared darkly not long ago that two other companies had tried to swipe it.

This week the public was told that J. & L. had indeed perfected photoelectric control for Bessemer converters. Though still chary of talking technical details, J. & L. disclosed that the indicator had been used on Bessemer heats for seven months. Patenting has not yet been completed; when it is, J. & L. expects other companies to pay for the privilege of using the new process, which it counts on to produce a revolution in steelmaking.

Photoelectrically controlled Bessemer steel is mainly due to a man with a jocular drawl, who likes to fish, take photographs of steel mills, put his feet on his desk. His name is Herbert W. Graham and J. & L. got him fresh from Lehigh University in 1914. He once told his research staff that, instead of 200 bright ideas a year, he would rather have two ideas that worked. In 1934 smart Metallurgist Graham persuaded J. & L. to let him build a complete miniature pilot mill to try out new metallurgical ideas. In this mill he developed a new way of getting manganese into steel to make it nonporous on cooling, then the Bessemer automatic eye.

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