Working with metals involves a few processes like extruding, forging, drawing, rolling, heading and spinning. These techniques can be summarized to one single process that covers all of them, and it's called annealing.
Annealing is studied in the fields of materials science and metallurgy. It pertains to a method in which heat is applied to materials to cause changes and changes to their properties. Metals are exposed to temperatures that are above their recrystallization points, and then they are left to cool down. The process causes the material to be ductile and soft. It also minimises the internal stress and refines its entire structure.
The most common metals used in annealing are silver, copper, brass and steel. The 1st 3 can be instantly soaked in water to chill them quicker, while ferrous metals have to be cooled down at a much slower pace. The final product can now go through a few more processes such as stamping, shaping and forming.
The term process hardening is also called in-process hardening, subcritical annealing and intermediate annealing. It is a kind of a treatment cycle that involves heat and attempts to prompt ductility into a piece of material to lessen its brittleness. Ductility is a very important property a material should possess for you to successfully use it for extruding, forging or drawing.
There are 3 phases in the annealing process. They are the recovery, recrystallization and grain growth phases. The first one is done to melt the metal. Imperfections and defects found on the crystals are removed. The second phase happens when new granulated crystals begin to grow. They are meant to be the replacements for those that were removed or deformed in the first phase. Finally, the last phase takes place when the grains or crystallites begin to grow in size.
Hardening also has specialized cycles and they are normalization, process annealing, full anneal and short cycle anneal. Process hardening has already been noted above so I'll move on to explain the other three. In normalization, after a metal is heated, it is cooled in air to relieve the stress produced. In full anneal, a metal is exposed to a temperature that is 50 degrees Celsius higher than the austenic temperature till austenites are formed. In short cycle anneal, normal ferrite is changed into malleable ferrite by heating the material first and then cooling it and then heating it again.
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