What is heat treatment - By changing the microstructure inside the workpiece, or changing the chemical composition of the workpiece surface, the performance of the workpiece is improved.
Heat treatment process classification - The heat treatment process includes quenching, tempering, nitriding, cryogenic, oxidation and other processes.
1. Quenching
1). What is quenching?
2->Improve the material properties or chemical properties of some special steels. Such as improving the corrosion resistance of stainless steel, increasing the permanent magnetism of magnetic steel, etc.
2. Tempering
1). What is tempering?
The quenched workpiece is heated to an appropriate temperature below the critical point AC1 for a certain period of time, and then cooled by a method that meets the requirements to obtain the required structure and properties of the heat treatment process.
2). The purpose of tempering?
1-> Reduce internal stress and brittleness. There is a lot of stress and brittleness in quenched parts. If they are not tempered in time, they will often deform or even crack.
2-> Adjust the mechanical properties of the workpiece. After the workpiece is quenched, the hardness is high and the brittleness is large. In order to meet the different performance requirements of various workpieces, the hardness, strength, plasticity and toughness can be adjusted by tempering.
3-> Stable workpiece size. The metallographic structure can be stabilized by tempering to ensure that no deformation will occur in the subsequent use process.
4-> Improve the cutting performance of some alloy steels.
3. Nitriding
1). What is nitriding?
Nitriding treatment refers to a chemical heat treatment process in which nitrogen atoms penetrate into the surface of the workpiece in a certain medium at a certain temperature.
2). The purpose of nitriding?
The products have excellent wear resistance, fatigue resistance, corrosion resistance and high temperature resistance.
4. Deep cold
1). What is deep cold?
Cryogenic treatment is to treat the metal below -160°C, so that almost all of the soft retained austenite is converted into high-strength martensite.
2). The purpose of deep cold?
Eliminate retained austenite (after quenching and tempering, the retained austenite is about 8~20%. Since austenite is very unstable, when it is subjected to external force or environmental temperature changes, it is easy to transform into martensite, while martensite is The volume is larger than the austenite, which will cause irregular expansion of the material and reduce the dimensional accuracy of the workpiece). After cryogenic cooling, the residual austenite is reduced to less than 2%, which reduces the residual stress, makes the metal matrix more stable, and improves the strength and toughness of the metal material. increased, the red hardness increased significantly.
5. Oxidation
What is oxidation?
The iron and steel parts are oxidized to form a dense and protective oxide film on the surface. The main component is magnetic iron oxide (Fe3O4), which has the effect of anti-bonding. The FeS film obtained by surface vulcanization can have both anti-wear and anti-bonding effects. Can improve corrosion resistance and high temperature oxidation resistance.
