Process analysis of heat treatment of metal using medium frequency induction heating power supply

The process flow of heat treatment of metal using medium frequency induction heating power generally includes three processes: heating, insulation and cooling. Sometimes there are only two processes: heating and cooling. These processes are connected with each other and cannot be interrupted.

Heating is one of the important steps in heat treatment. There are many heating methods for metal heat treatment. Earlier, charcoal and coal were used as the heat source, and then liquid and gaseous fuels were used. The application of electricity makes heating easy to control and has no environmental pollution. The medium frequency induction heating power supply can be used for direct heating, or indirect heating through molten salt or metal to cause floating particles.

When the metal is heated, the workpiece is exposed to the air, and oxidation and decarburization often occur (that is, the carbon content on the surface of the steel part is reduced), which has a very adverse effect on the surface properties of the part after heat treatment. In order to prevent decarburization and oxidation, metals should usually be heated in a controlled atmosphere or protective atmosphere, in molten salt and in a vacuum, and protective heating can also be carried out by coating or packaging.

Heating temperature is one of important technical parameter of thermal treatment, selects and the control Heating temperature, and be the subject matter that guarantees thermal treatment quality. The heating temperature varies with the metal material being processed and the purpose of the heat treatment, but it is generally heated to above the phase transformation temperature to obtain the required structure. In addition, the transformation takes a certain amount of time, so when the surface of the metal workpiece reaches the required heating temperature, it needs to be maintained at this temperature for a certain period of time to make the internal and external temperatures consistent and the microstructure transformation to be complete. This period of time is called the holding time. When high-energy-density heating and surface heat treatment are used, the heating speed is faster, and generally there is no holding time or the holding time is very short, 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 is different due to different processes, mainly to control the cooling rate. General annealed speed of cooling is the slowest, normalizing speed of cooling is very fast, and quenching speed of cooling is faster. However, there are different requirements due to different steel types. For example, empty hard steel can be hardened at the same cooling rate as normalizing.

The heat treatment of metal using medium frequency induction heating power can be roughly divided into overall heat treatment, surface heat treatment, local heat treatment and chemical heat treatment. Depending on the heating medium, heating temperature and cooling method, each category can be divided into several different heat treatment processes. The same metal adopts different heat treatment processes to obtain different structures and thus have different properties. Steel is a metal that is widely used in industry, and the microstructure of steel is relatively complex, so there are many kinds of heat treatment processes for steel.