Everything About Heat Treatment
Heat treating or otherwise called as heat treatment is a group of metalworking as well as industrial processes being used for the modification of physical and chemical properties of a certain material. Metallurgical is the most common application. Heat treatments are used in the manufacturing of different materials similar to glass.
Heat treating involves the use of heating or chilling, commonly to extreme temperatures in order to attain the results desired such as softening or hardening of a material. Case hardening, annealing, precipitation strengthening, quenching, normalizing and tempering are only few of the many different techniques that are being used for heat treatment. It’s smart to put stress that while such term is only applicable to processes where cooling and heating are done for a particular purpose of modifying properties intentionally, the cooling and heating normally take place incidentally throughout other manufacturing procedures just like in welding or hot forming.
Metallic materials do consist of microstructure of small crystals otherwise referred to as crystallites or grains. Nature of grains such as composition or size is one of the effective factors that help in determining the overall mechanical behavior of metal. Heat treatment is providing an effective way of manipulating metal properties by controlling the diffusion rate as well as 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 2 mechanisms that might change the properties of alloy throughout heat treating and it is the formation of martensite causes crystals to deform intrinsically and diffusion mechanism that makes the changes in the alloy’s homogeneity.
The structure of crystal includes atoms that are grouped in a particular arrangement that is referred as lattice. In various elements, this said order is rearranging itself depending on the type of condition it is on similar to 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. In alloys, this rearrangement might lead to an element that won’t dissolve normally into base metal to become soluble while reversal of allotropy makes the element either completely or partially insoluble.
When it is in soluble state, diffusion process will make the dissolved atoms to spread while forming homogenous distribution within the base metal’s crystals. If ever the alloy is cooled to insoluble state, atoms of dissolved constituents might 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 form microstructure consisting of 2 or several distinctive phases.