44.1 HEAT TREATING

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Main processes include,

Annealing - The metal is heated enough to recrystallize and held at the temperature for hours normally. Parts are cooled slowly.

Stress Relieving - The part is held for hours at a lower temperature than annealing so that the metal properties remain the same, but residual stress is reduced. The part is also cooled slowly.

Quench Hardening - The part is heated to Austenetizing range and then cooled rapidly using oil, water, etc. This created a very hard metal structure. Parts can be hardened in locations using inductive coils for location specific heating.

Tempering - After a hardening process (such as quenching) the part may be heated to beneath the Austenite range. This can be used to soften the part to a desired hrdness.

Carburizing - Soft steel parts can be heated for hours while coated in carbon. Carbon is absorbed into the surface and then the part is quenched. This gives a hard outside case, but the inside remains more ductile.

Carbon Nitriding - Similar to carburizing, except nitrogen is also absorbed in the surface. These parts have better surface wear properties.

Age Hardening - These parts are heated, quenched and then held at relatively low temperatures so that grains precipitate. The process is stopped using refrigeration. The result is parts with higher strength.