Oxygen Steel-Making

Abstract

Prior to the invention of oxygen steel-making after World War II, there had been no major change since the last century in the processes of converting iron-ore into steel. Each of the conventional methods, the Bessemer, Thomas, open hearth and electric furnace, had drawbacks. In the Bessemer, air is blown through tuyeres (pipes) at the bottom of an acid-lined converter into a bath of molten pig-iron. Because of the converter's acid lining, phosphorus and sulphur impurities in the ore could not be removed. In addition, air-blowing yielded steel with an undesirable nitrogen content. The Thomas process, by substituting a basic lining for the acid, solved the problem of phosphorus and sulphur removal, but not that of high nitrogen content. The open hearth, where fuel oil or gas blown on the surface of the ore bath heats the pig-iron in a furnace, produces steel of excellent quality; however, it is slow and costly to install and operate. The electric furnace, relatively expensive to operate, is restricted primarily to specialty steels.