Heat treatment process of textile machinery accessories
The heat treatment process of textile machinery accessories generally includes three processes of heating, heat preservation and cooling, and sometimes there are only two processes of heating and cooling. These processes are connected and uninterrupted. H
The heat treatment process of textile machinery accessories generally includes three processes of heating, heat preservation and cooling, and sometimes there are only two processes of heating and cooling. These processes are connected and uninterrupted. Heating is one of the important processes of heat treatment.
There are many heating methods for the heat treatment of textile machinery parts. In the past, charcoal and coal were used as heat sources, and then liquid and gas fuels were used. The application of electricity makes heating easy to control without environmental pollution. These heat sources can be directly heated, or indirectly heated by molten salt or metal, or even floating particles.
When textile machinery parts are heated, the workpiece is exposed to the air, and oxidation and decarburization (that is, the carbon content on the surface of the steel parts is reduced) often occur, which has a very negative effect on the surface properties of the parts after heat treatment. Therefore, metals should usually be heated in a controlled atmosphere or protective atmosphere, molten salt and vacuum, and can also be heated by coating or packaging.
The heating temperature is one of the important process parameters of the heat treatment process. The selection and control of the heating temperature is the main issue to ensure the quality of the heat treatment. The heating temperature varies with the metal material being processed and the purpose of the heat treatment, but it is generally heated above a certain characteristic transition temperature to obtain a high-temperature structure.
In addition, the transformation takes a certain time. Therefore, when the surface of the metal workpiece reaches the required heating temperature, it must be maintained at this temperature for a certain period of time to make the internal and external temperatures consistent and complete the microstructure transformation. This time is called the holding time. When high-energy density heating and surface heat treatment are used, the heating speed is extremely fast and there is generally no holding time, while the holding time of chemical heat treatment is often longer.
Cooling is also an indispensable step in the heat treatment process. The cooling method varies from process to process, and the main thing is to control the cooling rate. Generally, the cooling rate of annealing is slow, the cooling rate of normalizing is faster, and the cooling rate of quenching is faster. But there are also different requirements due to different steel grades.