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Normalizing not only produces pearlite but also martensite and sometimes bainite, which gives harder and stronger steel but with less ductility for the same composition than full annealing. In the normalizing process the steel is heated to about 40 degrees Celsius above its upper critical temperature limit, held at this temperature for some ...
Tempering is a process of heat treating, which is used to increase the toughness of iron-based alloys. Tempering is usually performed after hardening, to reduce some of the excess hardness, and is done by heating the metal to some temperature below the critical point for a certain period of time, then allowing it to cool in still air. The exact ...
The high temperature of annealing may result in oxidation of the metal's surface, resulting in scale. If scale must be avoided, annealing is carried out in a special atmosphere, such as with endothermic gas (a mixture of carbon monoxide, hydrogen gas, and nitrogen gas). Annealing is also done in forming gas, a mixture of hydrogen and nitrogen.
As with conventional quench and tempering the material being heat treated must be cooled from the austenitizing temperature quickly enough to avoid the formation of pearlite. The specific cooling rate that is necessary to avoid the formation of pearlite is a product of the chemistry of the austenite phase and thus the alloy being processed.
Equipment. Consolidated Engineering Company Archived 2013-11-05 at the Wayback Machine Annealing furnaces cover a broad range of Steel and Aluminum applications including tempering, normalizing, and aging, and similar automated loading, unloading and natural or forced cooling is possible with roller hearth, tip-up or batch arrangements.
Deformation affects the critical temperature. Increasing the magnitude of prior deformation, or reducing the deformation temperature, will increase the stored energy and the number of potential nuclei. As a result, the recrystallization temperature will decrease with increasing deformation. Initial grain size affects the critical temperature.
Recovery is related to the similar processes of recrystallization and grain growth, each of them being stages of annealing. Recovery competes with recrystallization, as both are driven by the stored energy, but is also thought to be a necessary prerequisite for the nucleation of recrystallized grains.
The simplest phase diagrams are pressure–temperature diagrams of a single simple substance, such as water. The axes correspond to the pressure and temperature. The phase diagram shows, in pressure–temperature space, the lines of equilibrium or phase boundaries between the three phases of solid, liquid, and gas.