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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.
Differentially tempered steel. The various colors produced indicate the temperature the steel was heated to. Light straw indicates 204 °C (399 °F) and light blue indicates 337 °C (639 °F). [1] [2] Tempering is a process of heat treating, which is used to increase the toughness of iron-based alloys.
The quenched-steel is first sanded or polished, to remove any residual oxidation, revealing the bare metal underneath. The steel is then heated in a localized area, such as the hammering-end of a chisel or the handle-end of an axe. The smith then carefully gauges the temperature by watching the tempering colors of the steel. As the steel is ...
Tempering colors of steel. Steel that has been freshly ground or polished will form oxide layers when heated. At a very specific temperature, the iron oxide will form a layer with a very specific thickness, causing thin-film interference. This causes colors to appear on the surface of the steel.
The most common are annealing, quenching, and tempering. Annealing is the process of heating the steel to a sufficiently high temperature to relieve local internal stresses. It does not create a general softening of the product but only locally relieves strains and stresses locked up within the material. Annealing goes through three phases ...
The most notable difference between austempering and conventional quench and tempering is that it involves holding the workpiece at the quenching temperature for an extended period of time. The basic steps are the same whether applied to cast iron or steel and are as follows:
The rate of the microscopic mechanisms controlling the nucleation and growth of recrystallized grains depend on the annealing temperature. Arrhenius-type equations indicate an exponential relationship. Critical temperature. Following from the previous rule it is found that recrystallization requires a minimum temperature for the necessary ...
Soft (or ductile) copper tubing can be bent easily to travel around obstacles in the path of the tubing. While the work hardening of the drawing process used to size the tubing makes the copper hard or rigid, it is carefully annealed to make it soft again; it is, therefore, more expensive to produce than non-annealed, rigid copper tubing.