What Happens When Metals Undergo Heat Treatment in Gastonia, NC?

Long before metalworkers used modern techniques to forge their items, blacksmiths used high degrees of heat to make the metal workable. Once they achieved the desired shape from the metal, they’d quickly cool it down to make the metal hard again.

Of course, today’s tactics are much more sophisticated and allow for more intricate designs and a wider variety of metalworking options. But the general idea is the same—heating and cooling metal at different points in the process to achieve a desired shape.

Here’s an overview of how heat treatment in Gastonia, NC affects metals of various types.

What happens when you heat up metal?

When metals are exposed to extreme heat, they begin to expand. The temperatures required to expand the metal vary depending on the type of the metal. In addition, the structure of the metal also changes at specific temperatures, a process referred to as “allotropic phase transformation.” During this process, the metal becomes softer, more ductile (able to be stretched) and weaker.

Metal’s electrical resistance can also be impacted by high degrees of heat. As the metal gets hotter, the electrons will scatter farther apart from each other, which actually results in the metal being more resistant to electricity.

Different types of heat treatment

Now that you have a general idea of what heat does to metal, here’s how heat affects metal in specific types of heat treatments:

  • Annealing: In annealing, the metal is brought closer to its so-called “equilibrium state.” The process makes the metal softer and more workable, allowing it to be shaped and stretched much more easily. The metal will be heated above its critical temperature to change its very microstructure, and will then be slow-cooled to be brought to shape.
  • Quenching: Quenching is a process that brings the metal back to room temperature very quickly after it’s heated past its upper critical temperature, versus the slow cooling of annealing. This can be done with oil, water or other media, but it does harden steel at the same temperature as annealing.
  • Precipitation hardening: This process results in a more uniform grain structure in the metal to create stronger materials. It involves heating up a solution treatment to extremely high temperatures after a fast cooling process. These temperatures can range from 900 to 1,150 degrees Fahrenheit, with the process taking anywhere from one to four hours, depending on the thickness of the metal and other such factors.
  • Tempering: This heat treatment process causes less stress on metals after they’ve been quenched or cast. It involves heating metal to temperatures lower than those required for transformation, then slowly cooling the metal. High temperatures and fast cooling create much more stress on the material.
  • Normalizing: This process eliminates impurities in the material and improves overall hardness and strength. The result is a more uniform grain size that comes from air-cooling the metal after it’s heated to a specific temperature.

For more information about heat treatment in Gastonia, NC, contact J. F. Heat Treating Inc. today.

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