Everything About Heat Treatment
Heat treating or also known as heat treatment is a group of metalworking and industrial processes that are used to modify the physical and at times, the chemical properties of a particular material. A common application for this is metallurgical. There are different ways heat treatments are put into used like glass manufacturing.
Heat treating is involving the use chilling or heating to the most extreme temperature in an effort to achieve the desired result similar to softening or hardening of a material. Techniques that are used in heat treatment are quite a lot and this includes case hardening, annealing, precipitation strengthening, quenching, normalizing and tempering. It’s noteworthy that while this term is applicable to only processes where cooling and heating are done for specific purpose of intentionally modifying properties, cooling and heating typically take place incidentally throughout other manufacturing procedures like welding or hot forming.
Metallic materials consist of microstructure of small crystals also known as crystallites or grains. One of the most effective aspects to figure out the mechanical behavior of metal is seeing the nature of grains similar to its size or composition. With heat treatment, it offers an effective way to alter metal properties by means of controlling both the diffusion and cooling rate within microstructure. Most of the time, heat treatment is used to modify mechanical properties of metallic alloy, manipulating properties including toughness, strength, hardness, elasticity and ductility.
There are two mechanisms that could possibly change the properties of alloy during the heat treatment and it’s the diffusion mechanism which makes the changes in alloy’s homogeneity and formation of martensite that causes the crystals to deform intrinsically.
The structure of crystal includes atoms that are grouped in a particular arrangement that is referred as lattice. In other elements, this order rearranges itself depending on the conditions it is on like pressure and temperature. This said rearrangement is known as polymorphism or allotropy and it can occur several times, at different temperatures for certain kind of metal. Now in the subject of alloys, this rearrangement can make the element not dissolve normally into a base metal to be soluble while allotropy reversal can make the element to be either completely or partially insoluble.
When in soluble state, the diffusion process makes the atoms of dissolved element to spread while trying to form homogenous distribution within the base metal’s crystals. Now, when the alloy is cooled to insoluble state, the constituents of the dissolved atoms will move out of the solution. Precipitation is what’s called to the diffusion that lead to nucleation in which all migrating atoms are regrouping together at grain boundaries. This will create 2 or several distinctive phases when it forms into microstructure.