Tools industry vacuum heat treatment furnace

The heat treatment process generally consists of three processes: heating, heat preservation and cooling. Sometimes only two processes are heated and cooled. These processes are interconnected and uninterruptible.

Heating is one of the important processes of heat treatment. There are many heating methods of metal heat treatment, and the earliest use of charcoal and coal as heat source is used to apply liquid and gas fuel. The application of electricity makes heating easy to control and free of environmental pollution. These heat sources can be heated directly, or indirectly heated by molten salt or metal, or floating particles.

When the metal is heated, the workpiece is exposed to the air, which is often oxidized and decarburized, which can have a detrimental effect on the surface performance of the parts after heat treatment. Therefore, metals should usually be heated in a controlled atmosphere or in a protective atmosphere, in molten salt and in a vacuum, and can be protected by coating or packaging.

Heating temperature is one of the important process parameters of heat treatment process, and selecting and controlling the heating temperature is the main problem to ensure the quality of heat treatment. The heating temperature varies with the purpose of the treated metal material and heat treatment, but it is generally heated to the phase transition temperature to obtain the high temperature tissue. Another change will take time, so when the heating temperature of metal surface is achieved, still must in the temperature keeping time, make internal and external temperature, the microstructure change completely, this paragraph of time is called the heat preservation time.

With high energy density heating and surface heat treatment, the heating speed is very fast and there is no heat preservation time, while the heat preservation time of chemical heat treatment is usually longer. Cooling is an indispensable step in the process of heat treatment. The cooling method is different due to different processes, mainly controlling the cooling rate. Generally, the cooling rate of the annealing is the slowest, the cooling speed is fast, and the quenching speed is faster.