Heat treatment is a crucial part of the metalworking process, being one of the final and most important steps in moulding materials so that they can be turned into products. Within the heat treatment process, there are a few different types of treatment that a material can go through. Special equipment such as conveyor ovens and annealing equipment are used during these processes.
Here are some of the most common heat treatment processes:
Hardening: this process improves the strength and hardness of the metal. Most metals, especially steels, are hardened by being heated to a specified temperature, before being cooled down by being soaked in a quenching medium.
Tempering: while steels’ strength is improved by hardening, this process will also make it more brittle. Tempering is used to reduce such brittleness by relieving the internal stresses. The specific temperatures employed during tempering are usually much less than the temperature used during hardening. The higher the temperature is during tempering, the softer the metal part will become.
Annealing: Much like tempering, metal parts are placed inside annealing equipment to reduce internal stresses and brittleness. However, annealing is also like heating wherein the metal is heated to a certain temperature, and that temperature is held for a prescribed time, thereby allowing the metal to cool down at a much slower rate. The cooling rate of the metal can vary greatly, depending on the desired properties of the material.
Normalizing: this process involves machining, forging, and welding to reduce the internal stresses that the metal experiences during heating. It is done by heating a metal part to a prescribed temperature, plunging it to achieve uniform heating, and cooling it down in still air. Typically, steels that have gone through normalizing are stronger and harder than the ones that have been processed in annealing equipment. In fact, normalizing a metal part before hardening it is very effective at attaining more hardness and brittleness.
At the end of the day, every process works for specific applications, so you will need to consult with an expert to figure out the right process for you.