The metal hardening process is very important. This is to increase the strength of metal. A hardened metal has a higher resistance in whatever application it is used than a less hardened metal. Metal hardening is done in large industrial complexes. There are many methods involve in hardening metal. During the hardening process, steel is treated by intense heat in order to give it different properties of hardness or softness. The whole process of metal hardening will depend on the amount of carbon in the steel. Steel with high carbon content can be easily hardened compared to those with low carbon content. This article highlights the importance of the metal hardening process.
Mild steel or steel with medium carbon content cannot be hardened easily. This is due to not having enough carbon content to change their crystalline structure. Medium carbon steel can become slightly tougher during the hardening process. But it cannot be hardened to a point where the metal cannot be cut with a hacksaw blade. In fact, this is a classic test to check whether the metal has been hardened enough or not.
When metal is heated to glow in red and immediately dumped in clean water, the metal becomes harder, but also brittle. Such metal can break or snap when placed under great pressure. But, when the red hot steel is allowed to cool down slowly, the resultant metal will be easier to cut, shape or file. The industrial heating process of steel is quite a complex process and it is a precise science.
There are five important methods of hardening metal. A short overview of these five methods will be discussed herewith. The Hall–Petch method a.k.a. grain boundary strengthening is a process of obtaining small grains of metal. These smaller grain sizes will obviously make the metal harder in the final analysis. The second method of metal hardening is called Work Hardening. It is also known as Cold Working or Strain Hardening. During this process, the material is strained past its yield point.
The third method of hardening metal is known as Solid Solution Strengthening. In this process, a soluble alloying element is added to the material that requires to be strengthened. Precipitation hardening is the fourth method used in hardening metal. The metal is first heated to a temperature where the elements forming the particles become soluble, and then quenching it. This will trap the particles in a solid solution. The fifth method of hardening metal is known as Martensitic transformation or Tempering or Quenching. In this method, the steel is heated to a temperature where the iron phase changes from ferrite into austenite.
Metal hardening is important to manufacture many applications useful for our day to day usage. Some construction materials are manufactured from hardened metal. High strength reduces the need for material thickness, which would reduce the cost and weight of the material. Knife blades are made from hardened steel. Hardened steel will produce a sharper edge. Bearings are made of hardened steel as well since a very hard surface is required to withstand continuous pressure on the parts.