What is a Heat Treatment Process ?
A Heat Treatment Process or Treating is nothing but heating the metal or material to change its physical properties, sometimes may be chemical and other properties. The most used common place for heat treatment is metallurgy. These are also used in manufacturing of glass with its process. Heat treatment involves the metal or material to be heated to the extreme points, i.e., to the extreme cold or the extreme heat positions. Heat treatment may also involve processes like softening or hardening the metal to the desired properties so that desired material with the desired shape will be prepared. Everything we do in the factory, in the companies, with the machines is only to obtain the desired output.
There are some heat treatment techniques and are described below –
Annealing is the most important and useful technique which primarily implements the heat treatment operation. Annealing is a process that we use Steel as the raw material. The main idea of the process is to convert the steel to austenite which can only be achieved when we heat the steel continuously but not to exceed the temperature of 50 degrees above its critical point. The steel is then allowed to cool down very slowly as a rate of 200 degrees in centigrade scale per hour.
Hardening is a heat treatment process used to impart certain selected mechanical properties to the materials. This helps the metal or material to be fit. Even in hardening, the metal is to be heated 50 degrees above the critical point of hypo-eutectoid and hyper-eutectoid steels. Then the steel is made to soak for some time such that the rest of the steels gets converted to austenite. The same way as Annealing, the steel is made to cool slowly and is also quenched to obtain desired shape and structure. The structure of the steel depends only on the cooling time and the type of cooling.
Tempering is a heat treatment process primarily used to remove the excess of brittleness from the material and also to impart toughness to the metal or material. The metal or material to made to heat above 200 degrees on the centigrade scale and the martensite is made to decompose to troostite which when again tempered at a temperature range of 500 to 600 degrees on the centigrade scale will lead to the formation of desired metal (Sorbite).
Normalizing is also a heat treatment process which include the metal or steel to be heated to 50 degrees on the centigrade scale above the critical temperature. We need to place the steel at that temperature for a short amount of time and must be continued with slow cooling with still air at the room temperature. This process of cooling is known as air quenching. Normalizing is used to reduce the internal stresses and also to improve the machinability of the steel.
Refining is the process of breaking down large and coarse grains formed by overheating of the metal steel. This process involves the heating of metal above critical temperature and then be quenched. This must be repeated several times so as to make it finer and also to obtain several desired shapes.