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The cementation process is a obsolete technique for making steel. It was developed in the 18th century from the crucible process.
Like making crucible steel the process begins with wrought iron and charcoal. Instead of crucibles, one or more long stone pots are used (typically, in Sheffield, each was 14 feet by 4 feet and 3.5 feet deep). Iron bars and charcoal are packed in alternating layers, with a top layer of charcoal and then refractory matter. Some manufacturers used a mix of powdered charcoal, soot and mineral salts, called cement powder - which gave the process its name. In larger works up to 16 tons of iron was treated in each cycle.
Depending on the thickness of the iron bars the pots were then heated from below for a week or more. Bars were regularly examined and when the correct condition was reached the heat is withdrawn and the pots are left until cool - usually around fourteen days. The iron had 'gained' a little over 1% in mass from the carbon in the charcoal, and had become hetrogenous bars of blister steel.
The bars were then shortened, bound, heated and hammered, pressed or rolled to become shear steel. Or broken up and heated in a reverberatory furnace with a flux to become cast steel.
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