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Research on Heat Treatment Quenching Process

Today I will share with you the views of heat treatment enthusiasts and researchers on the heat treatment quenching process. First, according to the different purposes of heat treatment, the heat treatment process can be divided into two categories: preliminary heat treatment and final heat treatment.
1. Preliminary heat treatment

    The purpose of preliminary heat treatment is to improve processing performance, eliminate internal stress and prepare a good metallographic structure for the final heat treatment. The heat treatment process includes annealing, normalizing, aging, quenching and tempering, etc.
Heat treatment quenching process
2. Final heat treatment

The purpose of the final heat treatment is to improve mechanical properties such as hardness, wear resistance and strength. The heat treatment quenching process we are going to mention belongs to the final heat treatment.

(1) Quenching

Quenching includes surface quenching and overall quenching. Among them, surface quenching is widely used because of small deformation, oxidation and decarburization, and surface quenching also has the advantages of high external strength and good wear resistance, while maintaining good internal toughness and strong impact resistance. In order to improve the mechanical properties of surface hardened parts, heat treatment such as quenching and tempering or normalizing is often required as a preliminary heat treatment. The general process route is: blanking-forging-normalizing (annealing)-rough machining-quenching and tempering-semi-finishing-surface quenching-finishing.

(2) Carburizing and quenching

Carburizing and quenching is suitable for low-carbon steel and low-alloy steel. First, increase the carbon content of the surface layer of the part. After quenching, the surface layer will obtain high hardness, while the core part still maintains a certain strength and high toughness and plasticity. Carburizing is divided into overall carburizing and partial carburizing. In the case of partial carburization, anti-seepage measures (copper plating or anti-seepage material plating) should be taken for the non-carburized part. Because the carburizing quenching deformation is large, and the carburizing depth is generally between 0.5~2mm, the carburizing process is generally arranged between semi-finishing and finishing.

The process route is generally: blanking-forging-normalizing-rough and semi-finishing-carburizing and quenching-finishing.

When the non-carburized part of the partial carburized parts adopts the process plan of removing the excess carburized layer after increasing the margin, the process of removing the excess carburized layer should be arranged after carburizing and before quenching.

(3) Nitriding treatment

Nitriding is a treatment method that allows nitrogen atoms to penetrate into the metal surface to obtain a layer of nitrogen-containing compounds. The nitriding layer can improve the hardness, wear resistance, fatigue strength and corrosion resistance of the surface of the part. Because the nitriding treatment temperature is low, the deformation is small, and the nitriding layer is thin (generally no more than 0.6~0.7mm), the nitriding process should be arranged as far as possible. In order to reduce the deformation during nitriding, it is generally required after cutting. Perform stress-relieving high-temperature tempering.