heat treatment

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heat treatment

[′hēt ‚trēt·mənt]
Heating and cooling a metal or alloy to obtain desired properties or conditions.

Heat treatment (metallurgy)

A procedure of heating and cooling a material without melting. Plastic deformation may be included in the sequence of heating and cooling steps, thus defining a thermomechanical treatment. Typical objectives of heat treatments are hardening, strengthening, softening, improved formability, improved machinability, stress relief, and improved dimensional stability. Heat treatments are often categorized with special names, such as annealing, normalizing, stress relief anneals, process anneals, hardening, tempering, austempering, martempering, intercritical annealing, carburizing, nitriding, solution anneal, aging, precipitation hardening, and thermomechanical treatment.

All metals and alloys in common use are heat-treated at some stage during processing. Iron alloys, however, respond to heat treatments in a unique way because of the multitude of phase changes which can be induced, and it is thus convenient to discuss heat treatments for ferrous and nonferrous metals separately.

Ferrous metals

Annealing heat treatments are used to soften the steel, to improve the machinability, to relieve internal stresses, to impart dimensional stability, and to refine the grain size.

Hardening treatments are used to harden steels by heating to a temperature at which austenite is formed and then cooling with sufficient rapidity to make the transformation to pearlite or ferrite unfavorable.

Some heat treatments are used to alter the chemistry at the surface of a steel, usually to achieve preferential hardening of a surface layer. Carburizing consists of subjecting the steel to an atmosphere of partially combusted natural gas which has been enriched with respect to carbon. In the nitriding treatment, nitrogen diffusing to the surface of the steel forms nitrides. Chromizing involves the addition of chromium to the surface by diffusion from a chromium-rich material packed around the steel or dissolved in molten lead.

Nonferrous metals

Many nonferrous metals do not exhibit phase transformations, and it is not possible to harden them by means of simple heating and quenching treatments as in steel. Unlike steels, it is impossible to achieve grain refinement by heat treatment alone, but it is possible to reduce the grain size by a combination of cold-working and annealing treatments.

Some nonferrous alloys can be hardened, but the mechanism is one by which a fine precipitate is formed, and the reaction is fundamentally different from the martensitic hardening reaction in steel. There are also certain ferrous alloys that can be precipitation hardened. However this hardening technique is used much more widely in nonferrous than in ferrous alloys. In titanium alloys, the β phase can transform in a martensitic reaction on rapid cooling, and the hardening of these alloys is achieved by methods which are similar to those used for steels.

heat treatment

Heating and cooling a solid metal or alloy in order to produce changes in its physical and mechanical properties.
References in periodicals archive ?
The company will also share its latest developments in furnace atmospheres - including plasma-activated case hardening of steels at atmospheric-pressure - and heat treating trends http://www.
The company will also share its latest developments in furnace atmospheres including plasma-activated case hardening of steels at atmospheric-pressure and heat treating trends as part of the conference s technical program.
All of their heat treating services is provided in the same Ajax, Ontario location to consolidate services, reduce costs and to avoid the hassle of forming partnerships with multiple businesses.
Improper placement of the castings in the furnace or inadequate furnace controls and temperature measurement can lead to inconsistent heat treating, variable mechanical properties and potential casting distortion.
Heat treating ginger, therefore, did not increase the analgesic benefit.
No relationship was found between responses to the question whether additional costs to treat WPM would be enough to allow alternative packaging materials more market share and the costs of treatment for heat treating ([chi square] = 3.
The only machine shop in the area with heat treating capability.
In 2006, TMK agreed to spend $6 million on Ajax's heating equipment for heat treating steel tubular products at TMK's Blytheville plant.
MME specialises in manufacturing and heat treating hydraulic motor drive components for tractor manufacturers, including Bosch, Case New Holland and Massey Ferguson.
Chapters cover fundamentals of heat treating steel, hardness and hardenability, furnaces and related equipment, instrumentation and control of heat treating processes, carbon steels, alloy steels, case hardening of steel, flame and induction hardening, stainless steels, tool steels, cast irons, nonferrous alloys, and quality assurance.
has selected Mobile, AL as the location to build its new continuous plate heat treating operation, which will be one of the most modern facilities of its kind in the world.