Explain the process of heat treatment

Heat treatment refers to the material in the solid state, through the means of heating, insulation and cooling, in order to obtain the expected structure and performance of a metal thermal processing process. Metal heat treatment is one of the important processes in mechanical manufacturing. Nantong heat treatment generally does not change the shape of the workpiece and the overall chemical composition, but by changing the internal microstructure of the workpiece, or change the chemical composition of the workpiece surface, give or improve the performance of the workpiece, nantong heat treatment is one of the important processes in mechanical manufacturing.

Metal heat treatment is a metal materials (including black metal and non-ferrous metal materials and its processed workpiece) within the scope of the solid state, through a certain heating, heat preservation and cooling, the metal or alloy internal organization change, can achieve the expected performance (such as mechanical properties, processing performance and physical and chemical properties), organization and structure of the floorboard of the process.

annealing

Concept: heat treatment method of heating steel to an appropriate temperature (generally above Ac1), holding it for a certain period of time, then cooling it slowly to obtain a near-equilibrium structure.

Objective:

1, reduce the hardness, to facilitate cutting;

2, improve the plasticity and toughness of steel, in order to facilitate cold deformation processing;

3, improve or eliminate the steel in the process of casting, rolling, forging and welding caused by various structural defects;

4. Refine grain, improve the morphology and distribution of carbide in steel, and prepare the structure for the final heat treatment;

5. Eliminate internal stress to reduce deformation and prevent cracking.

quenching

Concept: the steel is heated to the critical temperature (Ac3 or Ac1) above, after the austenitization of the steel is kept for a certain period of time, the steel is cooled at a cooling rate greater than the critical cooling rate to obtain the heat treatment process of high hardness martensite or lower bainite.

Objective:

1. Improve the hardness and wear resistance of the workpiece;

2, improve the comprehensive mechanical properties of the workpiece or the workpiece to obtain higher elasticity;

3. Obtain special physicochemical properties (magnetism, corrosion resistance, heat resistance, etc.).

tempering

Concept: a heat treatment process in which the workpiece is heated to a temperature below A1 of the steel, held for a period of time, and then cooled (generally to room temperature).

Objective:

1. Obtain the required mechanical properties of the workpiece;

2. Reduce or eliminate residual stress;

3. Stabilize the structure and size of the workpiece.

normalizing

Concept: heat treatment process in which steel is heated to an appropriate temperature above Ac3 or Acm for a certain period of time to homogenize the austenite and then cooled out of the oven by air cooling or by other suitable cooling methods.

Objective:

1. Steel with carbon content less than 0.5% is commonly used to normalize instead of annealing, which can not only save energy but also improve production efficiency;

2. For parts with low mechanical properties, normalizing can be used as the final treatment;

3. If net carbide exists in hypereutectoid steel, it must be normalized to eliminate net carbide and then spheroidized annealing;

4. Eliminate the hardening phenomenon after cutting and remove the internal stress;

5, fine grain, uniform organization.

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