Metal Products Distributor Supplier
Metals and Materials Table of Contents
Heat Treating Metals - Basically, heat treatment of steel consists of raising the material some
specified temperature. The process is performed to change certain characteristics
of steel to make them more suitable for a particular kind of
service. Some of the reasons for heat treating are:
1. To soften a part so that it can be machined more easily
2. To relieve internal stresses so that a part will maintain its dimensional
stability (i.e., not warp or fail prematurely due to
3. To refine the grain structure so that the part will be less apt to
fracture abruptly (or to toughen)
4. To thoroughly harden a part so that it will be stronger
5. To case harden a part so that it will be more wear resistant
Heat Treatment Processes:
Annealing: Generally refers to the heating and controlled cooling
of a material to remove stresses, make it softer, refine its structure,
or change its ductility, toughness, or other properties.
Carburizing: Adding carbon to iron-base alloys by absorption
through heating the metal at a temperature below its melting
point in contact with carbonaceous materials. Such treatment
followed by appropriate quenching hardens the surface of the
metal. This is the oldest method of quenching.
Flame hardening: In this method of hardening, the surface layer
of a medium- or high-carbon steel is heated by a high-temperature
torch and then quenched.
Induction hardening: A hardening process in which the part is
heated above the transformation range by electrical induction.
Nitriding: Adding nitrogen to solid iron-base alloys by heating at
a temperature below the critical temperature in contact with ammonia
or other nitrogenous material.
Hardening (as applied to the heat treatment of steel): Heating and
quenching to produce increased hardness and increased
Normalizing: Heating to about 100°F above the critical temperature
and cooling to room temperature in still air. Provision is
often made in normalizing for controlled cooling at a slower
rate, but when the cooling is prolonged, the term used is annealing.
Stress relieving: Reducing residual stresses in a metal by heating
to a suitable temperature for a certain period. This method relieves
stresses caused by casting, quenching, normalizing, machining,
cold working, or welding.
Tempering: Reheating after hardening to a temperature below the
critical temperature and then cooling.