According to the different steel types and process requirements, forgings often use the following heat treatment methods: annealing, normalizing, tempering, quenching and low-temperature tempering, quenching and aging, etc. Let's take a look at how it works:

1. Annealing:

The annealing process of forgings has various forms such as complete annealing, spheroidizing annealing, low-temperature annealing and isothermal annealing, which need to be selected according to the material and deformation of the forging.

After the forgings are annealed, the residual stress is eliminated or reduced due to the recrystallization of the grain, thereby reducing the hardness of the forging, improving its plasticity and toughness, and improving the cutting performance.

2. Normalizing:

Normalizing is generally to heat the forgings to 50-70 °C above the GSE line, and some high-alloy steel forgings are heated to 100-150 °C above the GSE line, and then cooled in air after proper insulation. If the hardness of the forgings is high after normalizing, in order to reduce the hardness of the forgings, high-temperature tempering should also be carried out, and the general tempering temperature is 560-660 °C.

3. Quenching and tempering:

Quenching is done to obtain an unbalanced structure to improve strength and hardness. Heat the steel forgings to 30-50°C above the Ac1 line. Quench after insulation.

Tempering is to eliminate the quenching stress, obtain a more stable structure, heat the forgings to a certain temperature below the Ac1 line, keep warm for a period of time, and then air cool or fast cool.

4. Quenching, aging:

Superalloys and alloys that can be strengthened by heat treatment are often quenched and aged after forging. Among them, quenching is to heat the alloy to an appropriate temperature, and after sufficient heat preservation, some of the tissue products in the alloy are dissolved into the matrix to form a uniform solid solution, and then quickly cooled to become a supersaturated solid solution, so it is also called solid solution treatment. Its purpose is to improve the plasticity and toughness of the alloy and to prepare the organization for further aging treatment. Aging treatment is to place the supersaturated solid solution or the alloy deformed by cold working at room temperature or heat it to a certain temperature, keep it warm for a period of time, so that the substances previously dissolved in the matrix can be uniformly dispersed and precipitated. The purpose of aging treatment is to improve the strength and hardness of the alloy.

The heat treatment of forgings is carried out according to certain heat treatment specifications, according to the steel type, section size and technical requirements of forgings, etc., and refer to relevant manuals and materials. Its contents include: heating temperature, holding time and cooling method. It is generally expressed by a temperature-time curve.