Many applications require metals to have different characteristics to their usual ones. This could be more tensile strength, better wear resistance, or many other things. One of the most popular ways to do this is to use a form of heat treatment. This can alter the grain structure and change the properties of the metal. However, it is important to use the right method for each metal and end use. It is also vital to test to make sure the treatments were successful. The best way to do this is with hardness testing.
Types of heat treatment
There are a number of different ways to treat metals to get the best results. The options include:
This is a relatively simple method which involves heating the metal, holding it at a temperature for a period of time, and then cooling it. The goal is to refine the grain structure so it is more uniform. That helps to improve ductility and machinability. There is also a specific option called solution annealing that is primarily for 300 series stainless steel.
Hardening or tempering
These processes can make steels lighter and stronger. Again the technique is to heat up the metal to the right temperature. Following this is rapid cooling or quenching. If the end use requires more ductility, a second heating and cooling cycle can temper the metal.
Carburising (or case hardening)
The goal here is to make the outer case of the metal harder to improve wear resistance while retaining the ductile core. The process is thermochemical and adds new alloying elements, usually nitrogen or carbon, to the surface of the metal.
Here the treatment uses a combination of inert gas, high pressure and a high temperature. This removes microporosity.
Some projects require ferrous metals with higher toughness and fewer internal stresses. This treatment is the best way to do that because it creates a more uniform grain structure and composition.
Talk to us about hardness testing
Format NDT Ltd knows just how useful heat treatment can be. However, we also appreciate that there can be cases when it is not as successful as it could have been. This could be because of a failure to hit the right temperature, cool the metal correctly, or many other things. Any of these issues could mean the final metal does not quite have the properties you were aiming for.
We always recommend hardness testing for metals following heat treatment. It is one of the most effective ways to determine how successful the process was. So, if you want to get a clearer idea of the properties of a metal after treating it, please contact us. We can arrange it for you.