The rotary supporting bearing fault causes of quality defects

Rotary supporting bearing parts after heat treatment of the common quality defects are: quenching microstructure overheating, less heat, quenching crack, hardness is not enough, heat treatment deformation, surface decarburization, soft point. 1. Overheating from the mouth of the bearing parts rough can observe the microstructure after quenching overheat. But to correctly judge the degree of overheating must observe the microstructure. If appear in gcr15 steel quenching organization coarse acicular martensite, organization for quenching overheating. Reasons may be quenching heating temperature is too high or heating temperature time is too long cause comprehensive overheating; Also may be due to the original organization banded carbide, low carbon zone between two belts forming local martensite acicular bulky, cause local overheating. Overheating in the organization retained austenite increase, dimension stability. Overheating due to quenching organization, steel crystal bulky, to cause a decline in the toughness of the parts, the fight against performance degradation, the life of the joint bearing is also reduced. Serious overheating may even cause the quenching crack. 2. Owe heat quenching temperature is low or poor cooling will generate more than standard stipulated in the microstructure of austenite organization, called owe hot organization, it decreased hardness, wear resistance sharply reduced, affecting the service life of rotary supporting bearing. 3. Quenching crack bearing parts in the process of hardening cooling by internal stress of crack is called quenching crack. Of the cause of the crack are: due to quenching heating temperature is too high or cooling. The thermal stress and quality of metal volume change of the organization stress is greater than the fracture strength of steel; The original defects on the surface of the work ( Such as micro cracks or scratches on the surface of the) Or steel internal defects ( The non-metallic inclusions such as slag, serious, white spots, shrinkage residual, etc. ) When quenching form stress concentration; Serious surface decarbonization and carbide segregation; Parts fire or inadequate timely after quenching tempering; The previous process caused by salt stress, cold forging folding, deep oil turning tool and hook sharp edges, etc. 4. Rotary supporting bearing parts during heat treatment, heat treatment deformation are the thermal stress and organization stress, the internal stress can overlay or partially offset each other, is complex and changeable, because it can as the heating temperature, heating rate, cooling method and cooling rate, parts of the change of the shape and size changes, so the heat treatment deformation is inevitable. Understanding and mastering the change rule can make joint bearing parts deformation ( Such as sets of elliptic, large size up, etc. ) In the scope of the controllable, be helpful for production. , of course, in the process of heat treatment, mechanical collision also can make parts deformation, but the deformation can be used to improve operations to reduce and avoid. When the monitor to the rotary supporting bearing low frequency vibration is very large, in addition. Out of the unit, unbalanced, loose structure, basic resonance structural factors, even if no bearing characteristic frequency, should be decisive judgment bearing fault for maintenance. Bearing the kurtosis is not big, data collector used now is common. But pay attention to in the practical skills. With low vibration. Spectrum of complex vibration signals, the scene is difficult to determine a trouble-free, back to vibration signal acquisition, precision analysis to the computer. At this point, the conventional analysis, first check whether the bearing vibration velocity spectrum and kurtosis is close to the standard, and then use power spectrum to investigate excessive vibration energy, if the power spectrum is not big, all kinds of frequency component of the spectrum of observation. If the corresponding frequency spectral line power frequency times, should focus on find fault in the unit structure; For power frequency scores times, appears more small digital frequency, slaughter frequency should be focused on looking for bearing, if any, are bearing fault, if not, exclusion of other parts fault should be cause for alarm, strengthen monitoring. Actually find many not overweight, vibration and bearing failure. Once appear, bearing characteristic frequencies or close to the bearing characteristics of the frequency spectrum, should determine bearing fault, and then according to the size of amplitude, can make trend analysis or arrange maintenance.