FAG bearing joints common parts after heat treatment quality defects

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The FAG bearing parts common quality defects after heat treatment: quenching microstructure overheating, due to thermal quenching cracks, hardness is not enough, heat treatment variant su rface the decarburization, soft point.thin ball bearings
1. Overheating
Overheated microstructure after quenching can be observed from the rough parts of FAG Bearings mouth.
But the right to judge the degree of overheating must observe the microstructure. If in gcr15 steel quenched structure in coarse acicular martensite, compared with quenching overheating organizations. Formation may be due to the quenching temperature is too high or a comprehensive overheating of the heating temperature is caused by too long; may be due to the original organization ribbon carbide serious, low-carbon zone between the two with the formation of local coarse martensitic acicular causing local overheating. Overheating organization residual austenite increases, the dimensional stability is lowered. Coarse crystals of steel due to overheating of the quenched structure cause parts of toughness decreases, the fight against performance degradation, the the joint bearing life also reduce. Severe or even cause overheating quenching cracks.
2. Due to heat
Low quenching temperature or cooling bad but in the microstructure than the standard the provisions troostite organization, called subcooled organizations, it is the decrease in hardness, wear resistance is drastically reduced, affecting the joints bearing life.deep groove ball bearing
3. Quenching cracks
The FAG bearing parts in the quenching process referred to as a quenching crack due to internal stress of the formed crack. This crack: hasty quenching temperature or cooling. The stress when the volume change of the thermal stress and the metal mass is greater than the anti-fracture strength of the steel; working surface of the original defect (such as a fine surface cracks or scratches) or steel internal defects (such as slag, severe nonmetallic inclusions matter, white point, residual shrinkage, etc.) formed in the quenching stress concentration; the surface decarburization severe carbide segregation; lack of parts after quenching fire or timely tempering; previous process caused by cold punching stress is too large, forging folding deep turning marks, oil hook sharp edges and corners.NSK bearings
4 heat treatment distortion
FAG bearing parts during heat treatment, the presence of thermal stress and stress, this internal stress can be superimposed on each other, or partially offset, is complex, because it as the heating temperature, heating rate, cooling method, the cooling rate, parts changes in the shape and size vary, so the heat treatment distortion is inevitable. Understanding and mastering the variation can be placed in a controlled range of deformation of the joint bearing parts (such as sets of oval, size up large, etc.), and is conducive to the production of the conduct. Of course, during the heat treatment, the mechanical collision also make parts generated deformation but such deformation can improve operation be reduced and avoided.
5. Surface decarburizationabec 7 bearings
FAG bearing parts in the heat treatment process, if it is heated in an oxidizing medium, surface oxidation occurs so that the decrease in the carbon mass fraction of the surface of the part, causing surface decarburization. Surface decarburized layer deeper than the final processing of the stay will make parts scrapped. Determination of surface decarburization depth available in metallographic method metallographic examination and microhardness method. Microhardness of the surface layer, announced curve measurements accurate, do arbitration Criterion.
6 soft spots
Due to lack of heating, cooling adverse improper operation quenching phenomenon causes loca l hardness of the articular surface of the bearing parts is not enough that this quenching soft point. It is like the surface decarburization surface wear resistance and fatigue can cause a serious decline.ball bearing suppliers