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- Stress Relieving: As the name implies, stress relieving is a heat treatment designed to relieve residual stresses in the steel. These stress may result from initial steel plate rolling, flame cutting, welding, forming or machining.
- Annealing: Annealing consists of heating the steel either in or near its critical temperature range followed by an extended slow furnace cooling. This allows for a softer steel more suitable for machining or severe forming.
- Normalizing: Normalizing is used to refine the grain structure left after mill rolling or forging. It provides uniform grain structure and improves toughness which is important in machining and roll forming or bending. In normalizing, the material is air cooled after heating to temperatures above the critical temperature.
- Quench & Temper: The steel is rapidly cooled from above its critical temperature range (austenitizing) to a temperature far below this range. Water or oil is used to accelerate the cooling. In the as-quenched condition, the product is not suitable for most commercial applications because of its lower ductility and high hardness. The steel must, therefore, be tempered in order to soften it somewhat to improve its ductility and toughness and relieve internal stresses. Tempering is a reheating treatment done in the range between 400°F and 1300°F.
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