Tempering is a process of annealinga)Martensite at low temperaturesb)M...
Tempering is the process of annealing martensite at low temperature. Although martensite is strong and wear resistant, it is brittle. Its toughness is low, primarily because of residual stresses introduced by the transformation. When tempering is carried out at a occurs. The martensite grains retain their strength, but improve their toughness and donot change shape on storage.
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Tempering is a process of annealinga)Martensite at low temperaturesb)M...
Tempering of Martensite
Tempering is a heat treatment process that is performed on a martensitic steel to reduce its hardness and increase its toughness. It involves heating the steel to a temperature below the critical point, holding it at that temperature for a certain period of time, and then cooling it in still air.
Process of Tempering Martensite
The process of tempering martensite at low temperatures involves the following steps:
1. Heating: The martensitic steel is heated to a temperature between 150°C and 600°C, depending on the desired hardness and toughness. The higher the temperature, the lower the hardness and the higher the toughness.
2. Holding: The steel is held at the tempering temperature for a certain period of time, usually an hour or more, depending on the thickness of the steel and the desired properties.
3. Cooling: The steel is then cooled in still air, which allows it to reach a desired hardness and toughness.
Effect of Tempering
Tempering reduces the hardness of the martensitic steel and increases its toughness by causing the formation of small carbide particles in the steel. These carbide particles act as obstacles to the movement of dislocations in the steel, which makes it more difficult for the steel to deform under stress.
Conclusion
Tempering is a crucial process to achieve the desired properties of martensitic steel. It is done at low temperatures and reduces the hardness and increases toughness by formation of carbide particles in the steel.