crucible process

crucible process

Technique for producing cast or tool steel. It was invented in Britain c. 1740 by Benjamin Huntsman, who heated small pieces of carbon steel in a closed fireclay crucible placed in a coke fire. This was the first process used in Europe in which the temperature (2,900°F, or 1,600°C) was high enough to melt the steel, producing a homogeneous metal of uniform composition. After 1870 the Siemens regenerative gas furnace replaced the coke-fired furnace. Capable of producing even higher temperatures, the Siemens furnace had a number of combustion holes, each holding several crucibles, and heated as many as 100 crucibles at a time. All high-quality tool steel and high-speed steel was long made by the crucible process. In the 20th century the electric furnace has replaced it in countries with inexpensive electric power. See also wootz.