How Heating Metals Can Change Their Properties

Industrial & Manufacturing Blog

When you're looking to have a project fabricated by a local machine shop like Create Cut Invent, they understand that most people aren't familiar with the different tools, materials, metals, and fabrication methods used to create various parts and products. However, gradually learning a little bit about metal fabrication can help both the fabricator and the customer. One area that is useful to understand is how metals can be treated prior to machining, changing the way the metal reacts and responds to stress. Here's what you need to know about heat treating, tempering, and annealing.

What Is Heat Treating?

Heating a metal will change its properties, and depending on what the project is, it's important to know how those changes could affect the final project. For example, if a forester designs a small bridge and culvert for a logging road, he's looking for a metal that is going to be strong enough to support processors, harvesters, and fully loaded log trucks routinely traversing.

Heat treating iron will displace its atoms, allowing for carbon to be introduced, which in turn will create a high carbon steel suitable for metal fabricators to construct the bridge trusses and suspension system. In addition to the normal expansion that occurs when heating most metals, heating a metal like nickel or iron to a certain temperature will lessen or eliminate its magnetism.  

A similar process is hardening. This is where steel or another alloy is heated up and kept at a high heat while the carbon is dissolved. The metal is then plunged into a cold liquid, a process called quenching. This hardened steel wouldn't be useful for engineering needs like a bridge, but it would be useful for knives and the cutting tools and blades a machinist would use.  

What Is Annealing?

Sometimes, a project requires a metal to be softer rather than harder. For example, when making stamped metal home décor products, super strength isn't required; flexibility is. Common decorative metals, like copper, silver, and brass, are good candidates for annealing, but the process can be done on steel and iron as well. These metals become more malleable and ductile, enabling them to be shaped and formed more easily. Annealing is also useful in electrical applications as conductivity is increased. The metal is heated and then is cooled very slowly according to the type of metal and its desired use.  


After a metal is hardened, if you want it to go back to having some malleability, it can be tempered. This is where it is heated to a low heat but then allowed to cool naturally. This provides a metal that is both strong and ductile.  


30 July 2018