CEMENTATION, a metallurgical term which describes processes by which one substance is, by exposure to great heat in a furnace, caused to interpenetrate and change the character of another. Although a high temperature is employed, the process is not one of melting materials together, but of combining them through contact at a temperature which is below their melting points. Thus, in the manufacture of blister steel by cementation, a rod of iron becomes steel because exposed at a temperature of about i,000°C. to carbon which penetrates its substance. (See BLISTER STEEL; IRON AND STEEL.)