1. Properly put forward performance requirements according to the service conditions of parts
A machine part, according to its service conditions, may only have special requirements for some properties, while some properties are secondary or may not be considered. These important special requirements should be indicated in the technical requirements. For example, some transmission shafts bear the combined action of bending stress and torsional stress, and the maximum stress is in the outermost layer. Therefore, quenching is only required to be able to harden to 1/2 to 1/3 of the radius of the part.
For example, for gear parts, some gears have large transmission power and contact stress, but little friction and wear, so medium carbon steel quenching and tempering plus high-frequency heating and quenching of the gear part can meet the requirements.
2. The heat treatment requirements can only be set within the allowable range of hardenability and hardenability of the selected steel grade.
3. Heat treatment requirements should allow a certain amount of heat treatment deformation.
Because the microstructure of steel before and after quenching is different, its specific volume is also different, which will inevitably cause the size change of parts due to the change of specific volume. The size of each part is different, and the volume change caused by the change of specific volume is also different, which will not only cause the change of size, but also cause the change of shape, such as becoming oval or trumpet, etc.
When specifying the technical requirements for heat treatment, it is necessary to estimate or determine the change law of its geometric dimension and limit its deformation according to the steel grade used by the parts and the structural state before and after heat treatment. These deformations are corrected by retaining machining allowance and adjusting machining dimensions.
4. Economic effect
When putting forward the technical requirements for heat treatment of parts, we must comprehensively consider the actual economic effects such as the manufacturing cost and service life of such parts.
When formulating the requirements for heat treatment acceleration, the cost of the heat treatment process itself should be considered, such as equipment investment, man hours, material consumption, product repair rate and scrap rate after heat treatment. If the technical requirements of heat treatment are raised too high, the existing equipment and technical conditions are difficult to meet, which will inevitably lead to high repair rate and scrap rate of heat treatment products, waste a lot of man hours and materials, and increase the cost of heat treatment.