Technique for producing cast or tool steel .
It was invented in Britain с 1740 by carbon steel in a closed fireclay crucible placed in a coke fire. This was the first process used in Europe in which the temperature (2,900kF, or 1,600kC) 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 {{link=wootz steel">wootz .