Knowing the Difference between Tempering and Other Heat Treatment Methods

29 April 2021

Metal materials are typically processed out of various heat treatment methods. Heat treatment, in general, is the process of heating and cooling metal materials to effectively develop and achieve certain physical and mechanical properties. And through the heat treatment process, metal materials can expect significant changes to their softness or hardness. The electrical and heat conductivity of these materials are also altered once they are subjected to different heat treatment methods.

One heat treatment method that is often utilised in processing metal materials is tempering. Tempering is a heat treatment method wherein a metal material after hardening from a high temperature is then subsequently re-heated to a lower temperature than the hardening temperature and cooled slowly. Tempering is normally done to reduce hardness and brittleness and internal stresses, with increased toughness achieved. 

A General Overview of Tempering Process

As previously stated, tempering can reduce the brittleness and internal stresses of a metal material. The reduction of these elements allows the material to gain improved toughness and strength, allowing it to hold up and sustain the effects of other processes. The temperature for heating during tempering is typically below the hardening temperature of the material, which often ranges from 160 – 650 deg C.

The tempering process is conducted by heating the material to the mentioned temperatures and upholding the heating process for a certain amount of time. The values of both the heating temperature and the time needed for the heating are determined by the type of metal that is being processed. After the heating process, the metal material will be cooled. The cooling rate is likewise determined by the type of metal processed, impacting all the changes in the material’s overall mechanical properties. 

Comparing Tempering to Other Methods

There are other heat treatment methods that can be done to introduce changes to metal materials. Some of these methods are annealing and hardening. 

Annealing is a heat treatment method wherein a metal is heated and subsequently held to an ideal temperature at a predetermined time. The cooling will then be initiated gradually. With annealing, the metal material is expected to obtain an increase in ductility and a significant decrease in hardness, making it more workable for other processes.

Hardening, alternatively, is a heat treatment method that has the purpose of increasing the hardness of a metal material. This method is done by heating the metal material to a very high temperature for it to effectively disperse solute-rich precipitates. To avoid any reprecipitation, the metal material is then cooled at a rate which is material dependent, which is done by quenching it in inert gas, air, oil or water.

What makes tempering different from others is that it entails the reheating of metal materials to a temperature lower than hardening temperature, holding it for a certain time, and cooling it. Tempering likewise reduces the brittleness of the material, making it much easier to process. This specific process can also work on steels, while both annealing and hardening can be used for metals and metal alloys.

Tempering at Alpha Detroit Heat Treatment

If you need tempering services, feel free to call us at Alpha Detroit Heat Treatment. We provide a wide range of services for all your heat treatment needs. Our expertise allows us to suggest the most appropriate process for your heat treatment requirements.

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