All about Annealing Metals

Annealing metals is an excellent way to improve them and make them more usable. It takes a special process to change the structure of metal and this provides many different benefits. Here is more about the annealing process and some of the many good things it has to offer today.

What Does Anneal Mean?

In order to change the properties of some metals, they undergo a heat treatment process. In fact, when metals are heated to a specific point and then cooled slowly (annealed) it can change the structure on an atomic level. This can make a relatively hard metal, softer and easier to fabricate. It may also make metal much stronger and harder.

How Does Annealing Work?

Let’s take steel for an example. To change its properties, steel is heated until the metal is literally glowing red hot. The hot steel is then allowed to slowly cool. Other metals like brass or copper can be quenched or rapidly cooled in oil or water.

Why Does Annealing Metals Change Them?

When metals are heated the atoms begin to diffuse. This diffusion takes place on a greater scale as the temperature in the metal rises. In fact, intense heat can break the bonds holding atoms together and they are redistributed.

By changing the internal structure it makes some materials more ductile and easier to work with. Some metals become highly resistant to stress while others increase in hardness.

Controlled Environments

While metals are exposed to high heat they are vulnerable to oxidation from the atmosphere. This can cause scaling. In order to prevent scaling the process must be done in a special atmosphere with gases like hydrogen, nitrogen and carbon monoxide. This takes very large furnaces which operate under a vacuum so oxygen is not allowed to enter. In fact, some industrial furnaces also have special quenching chambers to complete the process. Some of the fastest quenching methods utilize saltwater because it does not form air bubbles like standard water quenching.

Stainless Steel Annealing

Stainless steel can be hard and brittle and annealing metals is an important process for many industries. In fact, there are four types of heat treatment processes used:

* Bright annealing – used to keep oxidation down during the process of heating and cooling. It provides a clean and bright surface.

* Normalizing – this heat treatment process heats steel beyond its critical temperature long enough to change its structure. It creates a uniform metal.
* Stress relief – internal metal stress is reduced during a special heating process.

* Tempering – to increase strength, steel is heated and then rapidly quenched.

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