时间：2013-11-20 09:25　作者：admin　点击： 次

1) Aging treatment.After solution treatment or quenching, the workpiece is kept at room temperature or an appropriate temperature higher than room temperature to achieve the purpose of precipitation hardening.The natural aging at room temperature is called natural aging, and the artificial aging at high temperature is called artificial aging.It can make small changes in the size and performance of parts, which affects its performance.
Natural aging is very slow, up to several years. Therefore, parts are often artificially aged to accelerate the aging process and stabilize the performance of the organization.Aging treatment is a treatment method in which the workpiece is heated to a lower temperature and kept for a long time and then slowly cooled.
For parts with low precision requirements, the aging treatment can be carried out simultaneously with low temperature tempering; for high-precision parts, it is often carried out after low temperature tempering and between rough and fine turning, or rough and fine grinding; particularly high precision requirements When there are more retained austenite, cold treatment and low temperature tempering should be performed after quenching, and then aging treatment should be performed.
2) Cold treatment.After the workpiece is quenched and cooled to room temperature, the process of cooling in general refrigeration equipment or low-temperature medium is continued.It is mostly used for high-precision measuring tools, rolling bearings and carburized parts.
Purpose of cold treatment:
① Improve the hardness and wear resistance of steel.
② Stabilize the size of the parts to prevent the parts from changing during storage and use.
③ Improve and stabilize the magnetic properties of steel.
④ The retained austenite in carburized parts and carbon tool steels is easy to stabilize at room temperature. Therefore, after quenching, cold treatment should be carried out quickly and then tempered; for high-temperature alloy steels with complex shapes, due to good hardenability, The residual austenitic body is unstable. Generally, it should be cold-treated after quenching and tempering, and then a low-temperature tempering. For high-precision parts such as standard gauges, in order to ensure the high stability of the structure and size, quenching-cold treatment-back Fire-cold treatment-aging process.
3) Surface hardening.Surface quenching is a local quenching method in which the surface of the workpiece is quenched to a certain depth while the core remains unquenched.It uses rapid heating to make the surface layer of steel parts reach the quenching temperature quickly, and quickly cools immediately before the heat is transmitted to the center to achieve surface quenching.
The purpose of surface quenching is to obtain a high-strength surface layer and favorable residual stress distribution to improve the wear resistance or fatigue strength of the workpiece.
4) Tempering brittleness.Tempering brittleness is a phenomenon in which the toughness of the workpiece decreases during the tempering process.Tempering generally increases the toughness of steel, but when tempered at 250~400℃, the impact toughness of steel decreases significantly. The temper brittleness in this temperature zone is called the first type of temper brittleness.For steels containing Mn, Ni, Cr, Si and other elements, there is also a second type of temper brittleness, that is, tempering at 450~650℃, and slow cooling, a low impact toughness zone will appear.If it cools quickly after tempering, this kind of temper brittleness can be avoided.