The basic knowledge of heat treatment

12/07/2021
Understand the basics of heat treatment including Quenching, Normalizing, Annealing, Quenching and Tempering

Definition of heat treatment

* The process of processing metal parts by heat treatment, which includes heating to standard temperatures, holding heat and cooling at different rates.
 

Heat treatment of steel achieves 2 purposes

* Achieving desired quality (Hardness, permeability layer thickness, microstructure, etc.)
* In the same part when heat treatment mechanical properties another inner surface

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The iron-carbon phase diagram


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Basic heat treatment methods

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Normalizing
• Heat the part to a temperature 40-50oC above the upper critical point, hold that temperature, and then cool in still air.
Annealing
• Heat the part to a temperature between 40-50oC above the upper critical point, hold that temperature, and then cool in still air.
Austemper
• Heat the part to a temperature 40-50oC above the upper critical point, keep that temperature and then cool it at 232-427oC until it is completely transformed into Bainite
Isothermal annealing
• Heating the part to a temperature 40-50oC above the upper critical point, keeping it at that temperature and then cooling it to a temperature below the A1 line (50-100oC) keeping the heat and then cooling it in still air
Spheroidizing annealing
• Heating the part to the circulating temperature above and below the temperature of the A1 line forms a spherical Cemanite organization.

Methods of heat treatment and microstructure of metals

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Typical microstructure after quenching


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Change the microstructure of the part surface layer

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Change Layering improves the mechanical properties of steel


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