Austenitic
Duplex Steel
Nickel Alloy
Cobalt Alloy

Technological process

Heat treatment process generally includes three processes: heating, heat preservation and cooling. Sometimes there are only two processes: heating and cooling. These processes are interconnected and uninterrupted.

(heating)

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 steel parts is reduced), which has a very adverse impact on the surface properties of parts after heat treatment. Therefore, metals should usually be heated in controlled atmosphere or protective atmosphere, molten salt and vacuum, or protected by coating or packaging.

Heating temperature is one of the important process parameters of heat treatment process. Selecting and controlling heating temperature is the main problem to ensure the quality of heat treatment. The heating temperature varies with the treated metal materials and the purpose of heat treatment, but it is generally heated above the phase transformation temperature to obtain high-temperature microstructure. In addition, the transformation takes a certain time. Therefore, when the metal workpiece surface reaches the required heating temperature, it must be maintained at this temperature for a certain time to make the internal and external temperatures consistent and complete the transformation of microstructure. This period of time is called holding time.

(insulation)

When high-energy density heating and surface heat treatment are adopted, the heating speed is very fast, and generally there is no holding time, while the holding time of chemical heat treatment is often longer.

(cooling)

Cooling is also an indispensable step in the process of heat treatment. The cooling method varies with different processes, mainly controlling the cooling rate.

Process classification

Metal heat treatment process can be divided into three categories: overall heat treatment, surface heat treatment and chemical heat treatment. According to the different heating medium, heating temperature and cooling method, each category can be divided into several different heat treatment processes. Different structures can be obtained by different heat treatment processes for the same metal, so it has different properties. Steel is the most widely used metal in industry, and the microstructure of steel is also the most complex, so there are many kinds of steel heat treatment processes.

Integral heat treatment is a metal heat treatment process that heats the workpiece as a whole and then cools it at an appropriate speed to obtain the required metallographic structure and change its overall mechanical properties. The overall heat treatment of iron and steel roughly includes four basic processes: annealing, normalizing, quenching and tempering, namely the "four fires" of heat treatment.