After smelting, the crucible is removed from the furnace and the steel is poured into ingot molds.
The term steel crucible can be somewhat misleading as it does not refer to a particular steel product, but rather to a specific steel production process. The steel crucible process involves smelting stock such as wrought iron, cast iron and bubble steel in small smelting crucibles for carburizing or decarburising. During these processes, carbon is diffused or removed from stock to produce optimal metallurgical qualities in the finished product. After smelting, the crucible is removed from the furnace and the steel is poured into ingot molds. The steel crucible process is one of the oldest documented methods of producing steel, and although it has been replaced by more efficient methods, it is still used to produce small quantities of high quality materials for specialized applications.
Coke can be used as a fuel source for creating crucible steel.
Steel is a combination of iron and small amounts of carbon. Combinations like these are known as alloys with additives, in this case carbon, which enhance the quality of the base material and give specific characteristics to the final product. Steel, for example, is harder than wrought iron, less brittle than cast iron, and has better wear and corrosion resistance qualities than either. Steel can be produced in a number of ways, most of which involve melting the iron stock in the presence of a carbon source. This process causes small amounts of carbon to diffuse into the cast iron with typical final carbon concentrations ranging from 0.2% to 2.1%, depending on the alloy’s intended use.
One of the oldest forms of steel production is the steel crucible process; The first reliable documentation of crucible-made steels is medieval Islamic records around 1050. The basic principle of crucible-made steel revolves around smelting metal stock into vessels or containers made of various refractory materials small enough to handle. by one or two people. Containers or crucibles are loaded with various metals, including wrought iron, cast iron or bubble steel, and fired in special furnaces to melt the charge. Low-carbon materials, such as wrought iron, are supplemented with a carbon source, such as coal, which cements or infuses carbon into the melt. In contrast, stock material with very high carbon content for general steelmaking is decarburized;
The process usually begins with the crucibles being heated to white heat in a coke or gas oven, at which point they are removed from the heat source, loaded with raw materials and returned to the oven. They are then left for several hours until the raw materials have completely melted. The crucibles are then removed from the furnace, any impurities on the surface of the molten steel are removed, and the steel is poured into ingots. This process is time-consuming and expensive and has largely been replaced by more cost-effective, high-capacity processes such as Bessemer ovens. The high quality of the crucible’s steel, however, means that the process is still used to produce small amounts of steel for specialized niche markets.