Tempering of steel
Tempering
Tempering is a type of heat treatment that involves heating parts to temperatures below AC1, holding at specified temperatures and then cooling at a certain rate.
You can order several types of tempering from us. Low-temperature tempering of 250 ºС is suitable for measuring and cutting tools, medium-temperature tempering (350-500ºС) is required for springs, springs and dies, and the best combination of strength and toughness of steel can be achieved by high-temperature tempering at a temperature of 500-680ºС.
Tempering is the final operation of heat treatment, as a result of which the parts receive the required mechanical properties.
Depending on the temperature and purpose of the tempering, there are:
- Low-temperature (low) tempering is carried out at a temperature of up to 250ºС. In this case, quenching macrostresses are reduced, quenching martensite is converted to tempered martensite, strength increases and viscosity slightly improves without a noticeable decrease in hardness.
- Low-temperature tempering is used for cutting and measuring tools made of carbon and low-alloy steels, as well as for parts after high-frequency current quenching (surface hardening), carburization, cyanidation and nitrocarburizing.
- Medium-temperature (medium) tempering is carried out at a temperature of 350-500ºС and is used for springs, springs, and dies. Such tempering provides high elasticity and endurance limits, as well as relaxation resistance.
The structure of steel after medium tempering is tempered troostite or troostomartensite, the hardness of steel is 40-50HRC. - High-temperature (high) tempering is carried out at a temperature of 500-680ºС. The structure of steel after high tempering is sorbite tempering. High tempering creates the best combination of strength and toughness of steel.
Hardening with high tempering simultaneously increases the ultimate strength, yield strength, relative contraction and especially impact toughness. Heat treatment consisting of hardening with high tempering is often called — thermal improvement.
Stabilizing tempering is a special type of tempering, which is carried out in the process of manufacturing a hardened part to reduce and stabilize residual stresses caused by mechanical processing. The temperature of stabilizing tempering should be lower than the tempering temperature after hardening by 20-30° C.
In hardened steel, even at room temperature, and especially as a result of climatic temperature fluctuations, slow (over many years) processes of martensite decomposition, the transition of residual austenite to martensite, and stress relief occur. All these phenomena lead to a gradual change in the dimensions of the product. For such products as high-precision measuring instruments and precision bearings, changes in dimensions by even a few microns are unacceptable.
Stabilization of martensite and the stress state are achieved by low (stabilizing) tempering at 100-180 °C with a holding time of up to 30, and sometimes up to 150 hours.