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SKF Bearing parts heat treatment quality defects

Appropriateness of the selection is still bearing failure analysis must be considered. SKF Bearing failure analysis of the main task is based on a lot of background material, analysis of data and failure modes, find the cause of bearing failure of the main factors in order to have targeted improvements to extend bearing service period, to avoid bearing the occurrence of sudden of early failure.
    Installation conditions are the primary factors that one of the factors bearing is often caused by improper installation package SKF bearings between the various parts of the stress state changes, bearing in abnormal state of operation and early failure.
    SKF bearing parts from rough mouth after quenching can be observed on the microstructure overheating. But to determine the exact extent of overheating must observe the microstructure. If GCr15 steel hardened tissues appear coarse acicular martensite, was quenched overheating tissue. Formation may be due to the quenching temperature is too high or too long causing heat insulation comprehensive overheating; also may be due to the original organization carbon ribbon severe in the two areas with the formation of carbon between the local martensite needles thick, caused by local overheating. Overheating tissues residual austenite increases, dimension stability decreased. As quenching overheated steel coarse crystals, may cause parts of the decrease in toughness, impact resistance decreased, the bearing life is reduced. Even cause serious overheating quenching cracks.
    (2) less heat
    Quenching temperature is low or poor cooling in the microstructure produced more than the standard prescribed troostite organization called due to heat tissue, which decrease in hardness, wear resistance drastically reduced, affecting bearing life.
    3 quenching cracks
SKF Bearing parts in the quenching process due to the formation of stress cracks called quenching cracks. Cause such cracks reasons: because the quenching temperature is too high or too fast cooling, thermal stress and metal mass volume change when the stress fracture resistance than steel; work surface defects original (such as surface micro-cracks or draw marks) or steel internal defects (such as slag, severe non-metallic inclusions, white point, residual shrinkage, etc.) at a stress concentration quenching; severe surface decarburization and carbide segregation; parts after quenching and tempering insufficient or timely tempering; previous process caused by too much stress cold punching, forging folding, turning deep marks, oil, sharp edges, etc. ditch
    4 heat deformation
SKF bearing parts during heat treatment, the presence of thermal stress and stress, this stress can be superimposed on each other, or partially offset, is complex, because it along with the heating temperature, heating rate, cooling, cooling rate, parts shape and size changes, so the heat distortion is inevitable. Understand and grasp its variation can make the bearing part of the deformation (such as elliptical rings, rose and large size) placed controllable range, is conducive to the production of conduct. Of course, during the heat treatment the mechanical collision of parts also cause deformation, but this deformation can be used to reduce and improve operations avoided.
    5 surface decarburization
SKF bearing parts in the heat treatment process, if it is heated in an oxidizing medium, the surface oxidation occurs to parts of the surface carbon content reduced, resulting in surface decarburization. Surface decarburization depth over the last machining allowance will make parts scrapped. Determination of surface decarburization depth available in metallographic examination and microhardness metallographic method. In the surface layer microhardness distribution curve measurement prevail, do arbitration criterion.
    6 soft spots
Because insufficient heating and cooling is bad, improper operation and other causes hardening of SKF bearings parts of the surface hardness is not enough of the phenomenon known locally quenching soft spots. It is the same as the surface decarburization can cause surface wear resistance and fatigue strength of a serious decline
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