There are several prominent heat treatment processes out there for steel and other types of metal, with the goal of altering various mechanical properties to change the way a metal operates. One such process is called tempering, which disperses carbon trapped in a metal’s microstructure and allows the release of internal stresses that often come from previous operations done on the metal.
At Wasatch Steel, we can help with tempering and several other processes as part of our steel services. How is tempering done, why is it done, and what are some of the common processes in the industry where tempering is used? Let’s take a look.
Tempering steel is a relatively simple process, one that begins by elevating the metal to a set temperature point that’s below its lower critical temperature. This is often done after a hardening operation. From here, the metal is held at the desired temperature for some set period of time, which will vary – along with the precise temperature number – depending on steel type, mechanical properties desired and a few other factors.
There are a few different devices that might be used to create the heat needed to raise the steel to just below its critical temperature. Gas furnaces, electrical furnaces, or even induction furnaces may be used for this purpose, which is often completed inside a vacuum or with an inert gas so as to protect from oxidization taking place. After the temperature is at the proper level, a dwell time takes place, after which the furnace is turned off and the steel cools.
For those looking for a solid combination of hardness and strength in their steel, the tempering process is often a good option. By allowing carbon diffusion to happen within the steel microstructure, it resists brittleness or strength issues that may take place on either side of the hardness spectrum. It can also improve the formability and machinability of steel, plus lower the risk of cracking or failing after internal stresses.
There are a few common applications and uses of tempered steel processes:
Quenching: The most common use of tempered steel is following a quenching operation. Normally, this quenching process can leave steel too hard and brittle for the desired effect due to the way it’s heated. Tempering improves the ductility that may have been lost here and stops the steel from being too brittle.
Welding: During some welding processes, a localized zone I created that’s hardened too far due to the heat applied to it. This leaves residual stress and may lead to hydrogen cracking, but tempering can prevent any of this from happening while reducing overall hardness.
Work-hardened materials: Punching, bending, forming, rolling or drilling processes generally come with high amounts of residual stress. Tempering alleviates much of this stress.
For more on the steel tempering process, or to view any of our other options and buy steel online, speak to the pros at Wasatch Steel today.