The heat treatment process of construction machinery forging die includes three processes: heating, insulation and cooling. For different materials and requirements, it is necessary to choose the appropriate temperature, holding time and cooling medium to achieve the ideal heat treatment effect.
Commonly used heat treatment processes include quenching, tempering and normalizing. Quenching is to heat the forgings above the critical temperature to quickly cool below room temperature, through this process can improve the hardness of the forgings, fine organization, but easy to produce internal stress and deformation. Tempering is to heat the forging again to a certain temperature after quenching, and then cool it after holding it for a period of time at this temperature, through which the internal stress can be reduced and the toughness of the forging can be improved. Normalizing is to heat the forging to a certain temperature, and then keep it for a certain time after natural cooling to improve the structure and performance of the forging.
The effect of heat treatment is mainly evaluated from two aspects: metallographic structure and mechanical properties. Metallographic structure can be determined by metallographic microscope observation, including grain size, precipitated phase, phase distribution, etc. The mechanical properties include hardness, tensile strength, yield strength, elongation, etc., which can be measured by corresponding test methods.
To evaluate the effectiveness of the heat treatment process, the following steps are required:
- Select the appropriate heat treatment process according to forging materials and requirements.
- Heat treatment test, after determining the process parameters, batch heat treatment of a small number of samples.
- Observe the microstructure of the sample through the metallographic microscope, and carry out the corresponding microhardness test.
- Mechanical properties test, including tensile test, impact test, etc., to obtain mechanical properties index.
- According to the test results of metallographic structure and mechanical properties, evaluate whether the heat treatment effect meets the requirements.
- If the effect is not ideal, it is necessary to adjust or improve the heat treatment process, and re-test and evaluate until the requirements are met.
It should be noted that different forging materials and requirements may require different heat treatment processes, so the specific operation needs to be selected and adjusted according to the specific situation. In addition, in order to ensure the stability and consistency of heat treatment, it is also necessary to control the temperature, time and rate of heating, holding and cooling.
