The 3 Stages Of Heat Treatment

Overview of Heat Treatment

Whenever typical processes such as welding or cutting metals are performed, heat is generated and changing the metallographic structure and properties of the metal. At this time, if you want to restore the metal to its original form, you can be achieved by heat treatment. Heat treatment is the process of heating metal without letting it reach its molten, or melting, stage, and then cooling the metal in a controlled way to select desired mechanical properties. It can make metal stronger or more malleable, more resistant to abrasion or more ductile.

Stages of Heat Treatment

There are three stages of heat treatment: the heating stage, the soaking stage and the cooling stage.

During the heating stage, you get even heating by heating slowly. If the metal is not heats uniformly, it may cause one section expand faster than another, resulting in a distorted or cracked section of the metal. When choosing the heating rate, you can refer to heat conductivity of the metal, the condition of the metal, the size and cross-section of the metal, and several factors. For example, Metals with high heat conductivity heat faster than those with low conductivity. Tools and parts that have been hardened, or stressed, previously should be heated slower than tools and parts that haven’t. Larger parts or parts with uneven cross sections need to be heated more slowly than small parts to allow the inside temperature to be close to the surface temperature.

The purpose of the soaking stage is to keep the metal at the appropriate temperature until the desired internal structure takes shape. Be careful not to bring the temperature of the metal from room temperature to the soaking temperature in one step, but to heat the metal slowly to just below the temperature where the structure will change, and then hold it until the temperature is consistent throughout the metal. As for how long you need to keep the metal at the appropriate temperature, that requires the chemical analysis and mass of the metal, for uneven cross-sections, you can determine the soaking period using the largest section.

In the cooling stage, you’ll need to cool metal back to room temperature in different ways depending on the type of metal. It may need a cooling medium, a gas, liquid, solid, or combination thereof. The rate of cooling depends on the metal itself and the medium for cooling. It follows that the choices you make in cooling are important factors in the desired properties of the metal.

Ronsco supplies a variety of heat treated stainless steel sheet, plates, coils, strips. Contact Ronsco by email service@ronsteel.com for your heat treating needs.