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Heat treatment process - Part1
Date:2019-05-23      View(s):169      Tag:Heat treatment process

Annealing


Operation method:

After heating the steel to Ac3+30~50° or Ac1+30~50° or below Ac1 (you can refer to the relevant information), it will generally cool slowly with the furnace temperature.

Features:
1. Reduce hardness, improve plasticity, and improve cutting and press processing performance.
2. Refine the crystalline grains, improve the mechanical properties, and prepare for the next step.
3. Eliminate the internal stress generated by cold and hot processing.

Application:
1. Applicable to alloy structural steel, carbon tool steel, alloy tool steel, high speed steel forgings, welded parts and raw materials with unqualified supply conditions.
2. Generally annealing in the blank state.

Normalizing

Operation method:
The steel is heated to 30 to 50 degrees above Ac3 or Accm, and then cooled to a temperature slightly higher than the annealing cooling rate.

Features:
1. Reduce hardness, improve plasticity, and improve cutting and press processing performance.
2. Refine the grains, improve the mechanical properties, and prepare for the next step.
3. Eliminate the internal stress generated by cold and hot processing.

Application:
Normalizing is usually used as a pre-heat treatment process for forgings, weldments, and carburized parts. For low-carbon and medium-carbon carbon structural steels and low-alloy steels with low performance requirements, they can also be used as final heat treatment. For general medium and high alloy steels, air cooling can lead to complete or partial quenching and therefore cannot be used as the final heat treatment process.

Quenching

Method of operation: The steel is heated to a phase transition temperature of Ac3 or Ac1, held for a period of time, and then rapidly cooled in water, nitrate, oil, or air.

Features:
Quenching is generally used to obtain high-hardness martensite structure. Sometimes, when quenching some high-alloy steels (such as stainless steel and wear-resistant steel), it is to obtain a single uniform austenite structure to improve wear resistance and corrosive.

Application:
1. Generally used for carbon steel and alloy steel with carbon content greater than 0.3%.
2. Quenching can fully exert the strength and wear resistance potential of steel, but at the same time it will cause great internal stress and reduce the plasticity and impact toughness of steel. Therefore, tempering should be carried out to obtain better comprehensive mechanical properties.
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