Cast steel is a type of metal created by heating iron using a crucible container. Cast steel allowed for a more uniform composition of, and fewer impurities in, steel than any previous manufacturing process. Since it is made in a crucible, cast steel is often called crucible steel.
Steel is made by combining iron with carbon or other alloys. Iron is a soft metal, so not ideal for many construction purposes. The creation of steel removes many of the impurities in iron, which allows steel to be harder and more durable. The better the steel, the more iron impurities that are removed.
Early steel was made by adding small amounts of carbon to iron. For example, blister steel was made by repeatedly heating wrought iron and charcoal together in a kiln. The charcoal's carbon transferred to the steel by the process of diffusion.
Cast steel was the first type of steel that allowed alloys to be added to the iron. Prior to this method, manufacturers had not been able to get steel hot enough to melt. By heating blister steel in a clay crucible placed directly into a fire, Huntsman allowed the metal to reach up to 2900°F (1600°C). Melting allowed other elements, such as nickel, to be mixed into the metal, thus strengthening the steel.