Tempering
When steel is suddenly cooled from a high temperature it becomes hard and brittle, but when slowly cooled it is very tough and pliable. The process of bringing steel to the several degrees of hardness for use in the arts and manufactures is called tempering. This term is usually applied to mean a combination of the hardening and annealing processes. According to the temperature to which the hardened steel has been heated before annealing, so is the diminution of the hardness affected by the process. See STEEL; RESTORING BURNT STEEL; DIES, TO HARDEN; ANNEALING.