Pengsheng Forging Factory takes you through the requirements of forging for cooling.

The cooling of forging is more complicated and difficult to control. The development of a cooling process is much more important and complicated than a small piece. The key to determining the mechanical properties after forging tempering is the nature of the tissue obtained after cooling and its dispersion.

In general material manuals and factory standards, the normal mechanical properties of forgings of different diameters or normalized after normalizing are listed, and this is used as the delivery condition at the factory. However, there is no requirement for the state of the organization, and the organization is important for assessing properties such as high temperature creep strength and fracture enthalpy. In the development of the cooling process of forgings, not only the uniform mechanical properties of the entire section should be considered, but also the nature of the cooled structure and the distribution of the structure along the section.

The relationship between the forged cooling structure and the mechanical properties after tempering has been extensively tested and studied so far. The general conclusions are as follows:

1. If the martensite structure is obtained after cooling, it has high strength, hardness and low plasticity and toughness after low temperature tempering. The strength and hardness change with the increase of carbon content in the steel, and the plasticity and toughness decrease. The martensite structure decreases in strength and hardness with the change of tempering temperature, and the plasticity and toughness change accordingly. Normally, the alloying elements in the steel can reduce the strength and hardness of the steel when it is tempered, and the plasticity and toughness are also greatly improved. The martensite structure is tempered at a high temperature to obtain a uniform tempered sorbite structure. Its strength, plasticity and toughness can be well matched, that is, the comprehensive mechanical properties are obtained.

2. If the lower bainite structure is obtained after cooling, the mechanical properties after tempering are similar to those obtained after quenching the martensite at the same temperature and have high impact toughness.

3. If the upper bainite structure and the pearlite structure are obtained after cooling, the strength after the same fire is low, and the plasticity is not good, that is, the comprehensive mechanical properties are poor.

4. If ferrite is present in the cooled structure, the comprehensive mechanical properties after tempering are significantly deteriorated, mainly because the impacttoughness becomes low. It can be seen that the comprehensive mechanical properties after tempering deteriorate with the coarsening of the tissue obtained by cooling.

The task of forging the final heat treatment is to obtain the highest possible comprehensive mechanical properties that meet the requirements of the part by appropriate processing according to the steel grade used.