Heat Treatment

Heat Treating

Heat treatment is an essential step in precision machining. However, there is more than one way to accomplish it, and your choice of heat treatment depends on materials, industry and final application.

Heat Treating Services

Heat treating metalHeat treating is the process by which a metal is heated or cooled in a tightly controlled environment to manipulate physical properties such as its malleability, durability, fabricability, hardness, and strength. Heat-treated metals are imperative to many industries including the aerospace, automotive, computer, and heavy equipment industries. Heat treating metal parts (such as screws or engine brackets) creates value by improving their versatility and applicability.

Heat treatment is a three-step process. First, the metal is heated to the specific temperature needed to bring about the desired change. Next, the temperature is maintained until the metal has been evenly heated. The heat source is then removed, allowing the metal to cool completely.

Steel is the most common heat treated metal but this process is performed on other materials:

● Aluminum
● Brass
● Bronze
● Cast Iron

● Copper
● Hastelloy
● Inconel

● Nickel
● Plastic
● Stainless Steel

The Different Heat Treatment Options

Hardening

Hardening is performed to address metal’s deficiencies, especially those that affect overall durability. It is performed by heating the metal and quenching it quickly right when it reaches the desired properties. This freezes the particles so it gains new qualities.

Annealing

Most common with aluminum, copper, steel, silver or brass, annealing involves heating metal to a high temperature, holding it there and allowing it to slowly cool. This makes these metals easier to work into shape. Copper, silver and brass can be cooled quickly or slowly, depending on the application, but steel must always cool slowly or it will not anneal properly. This is normally accomplished before machining so materials do not fail during manufacturing.

Normalizing

Often used on steel, normalizing improves machinability, ductility and strength. Steel heats to 150 to 200 degrees hotter than metals used in annealing processes and is held there until the desired transformation occurs. The process requires steel to air cool in order to create refined ferritic grains. This is also useful for removing columnar grains and dendritic segregation, which can compromise quality while casting a part.

Tempering

This process is used for iron-based alloys, especially steel. These alloys are extremely hard, but often too brittle for their intended purposes. Tempering heats metal to a temperature just below the critical point, as this will reduce the brittleness without compromising the hardness. If a customer wishes for better plasticity with less hardness and strength, we heat metal to a higher temperature. Sometimes, though, materials are resistant to tempering, and it may be easier to purchase material that is already hardened or to harden it before machining.

Case hardening

If you need a hard surface but a softer core, case hardening is your best bet. This is a common process for metals with less carbon, like iron and steel. In this method, heat treatment adds carbon to the surface. You will normally order this service after pieces are machined so you can make them extra durable. It is performed by using high heat with other chemicals, as that reduces the risk of making the part brittle.

Aging

Also known as precipitation hardening, this process increases the yield strength of softer metals. If metal requires additional hardening beyond its current structure, precipitation hardening adds impurities to increase strength. This process usually happens after other methods were used, and it only raises temperatures to middle levels and cools material quickly. If a technician decides natural aging is best, materials are stored in cooler temperatures until they reach the desired properties.