44.1 HEAT TREATING
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.
