1. Overheating

The overheating phenomenon of the quenched mechanism can be observed from the blank holes of the bearing parts. However, in order to determine the degree of overheating, it is necessary to visit the micro layout. If there is coarse needle like martensite, it is a quenched and overheated structure. The reason may be that the quenching temperature is too high or the heating and holding time is too long, resulting in all overheating. It may also be that the original mechanism has severe banded carbides, and the low carbon region between the two bands forms all martensite needle like coarsening, resulting in all overheating. The amount of residual austenite increases and the dimensional stability decreases. Due to overheating of the quenched structure, the coarse grain size of the steel will reduce the toughness of the parts, reduce impact resistance, and reduce the handling life of the ina bearing. Overheating can even lead to quenching cracks.

2. Underheating

Lower quenching temperatures or poor cooling can produce toroidal structures that exceed the microstructure scale, known as ultra-low temperature structures. Reduced hardness, greatly reduced wear resistance, and affected the handling life of the bearing.

3. Quenching cracks

During the quenching and cooling process, cracks in the bearing components of the bearing adapter manufacturer caused by internal stress are called quenching cracks. The causes of such cracks are as follows: the quenching heating temperature is too high or the cooling is too fast, when the thermal stress and the volume change of the metal character are greater than the fracture toughness of the steel, the mechanism stress, the original defects in the mission details (such as detailed small cracks or scratches), or the internal defects of the steel (such as slag, severe non-metallic impurities, white spots, shrinkage residues, etc.) form a stress set during quenching; Severe details of decarburization and carbide segregation; No residual tempering or no tempering after quenching; Excessive cold impact stress caused by the previous process, forging folding, deep turning tool marks, sharp edges and corners of oil grooves, etc. In summary, the cause of quenching cracks can be one or more of the above components, and the presence of internal stress is an important cause of quenching cracks. The quenching crack is deep and elongated, the fracture is linear, and the fracture section has no oxidation color. The bearing ring has longitudinal straight cracks or annular cracks, and the shape of the bearing steel ball is S-shaped, T-shaped, or annular. The microstructure characteristic of quenching cracks is that there is no decarburization on both sides of the cracks, which is clearly incompatible with forging cracks and material cracks.

4. Heat treatment deformation

During heat treatment, there are thermal stresses and stresses in the bearing department, which can be superimposed or partially offset from each other. Due to its complexity as a function of heating temperature, heating speed, cooling, cooling rate, changes in shape components, and changes in size, thermal deformation is unavoidable. Understanding and controlling its changes can result in deformable INA bearing departments (for example, oval shaped collars, upward and large dimensions) being arranged within a controlled range, Production will be disadvantageous. After heat treatment of parts, there is a common moral defect: overheating and underheating of the hardening mechanism, quenching cracks, excessive hardness, thermal deformation, decarburization of details, and soft spots.