Common quality defects after heat treatment, the SKF bearing parts: quenching microstructure of overheating, lack of heat, quench cracks, hardness, heat treatment deformation and surface decarbonization, soft enough points, and so on.
1. overheating
From parts of deep groove ball bearings can be observed on the rough after quenching microstructure of overheating, but to exactly determine their degree of overheating must observe microstructures. If steel gcr15 quenched in an organization with needle-like martensite, to quench overheating organization. Causes may be hardening heating temperature is too high or full as a result of overheating heat insulation for too long; it may also be due to the original organization serious Ribbon carbide, in the formation of low carbon zone between two local Markov and body acupuncture-like thick, causing local overheating. Overheating increased residual austenite in organizations, dimensional stability decline. Overheating due to quenching organizations, large crystals of steel, will lower the parts of toughness, impact resistance reducing, SKF bearing life is also reduced. Overheating caused by serious or even quenching crack.
2. less heat
Quenching temperature on microstructure of low or poor cooling will be produced in excess of the standard troostite organization, known as the due to the heat organization, which degrade hardness, wear resistance sharply reduced, deep groove ball bearing life.
3. quenching crack
Components of deep groove ball bearing stress in quenching process for the formation of crack quench cracks. Caused this crack of causes has: due to quenching heating temperature high or cooling too anxious, hot stress and metal quality volume changes Shi of organization stress is greater than steel of anti-fracture strength; work surface of original defects (as surface micro-crack or is zoned trace) or steel internal defects (as clip slag, and serious of non-metallic clip debris, and white, and shrinkage residual,) in quenching Shi formed stress concentrated; serious of surface off carbon and carbide partial analysis of; parts quenching Hou tempered insufficient or is not timely tempered; front processes caused of cold rushed stress had large, and Forging collapse scar, oil trench, deep turning sharp corners, and so on. In short, resulting in quenching cracks can be caused by one or more of the above factors, there is the formation of quenching crack of main causes of stress. Quenching crack of deep and long, break straight, Fracture surface oxide-free color. It is often on a deep groove ball bearing vertical flat annular crack cracks or; in bearing steel ball on the shape of s-shaped, t-shaped or ring-shaped. Characteristics of quenching crack is cracked on both sides without removal, significant differences and forge cracks and cracks in materials.
4. heat treatment deformation
Deep groove ball bearing parts in heat treatment, there are thermal stress and the stress, this stress can overlay or partially offset each other, are complex and changing, because it can with the temperature, speed of heating, cooling, cooling rate, part shape and size changes, so heat treatment deformation is unavoidable. Understanding and mastering regularity of it enables SKF bearing deformation of parts (such as oval ring, size up, and so on) where it can control the scope of production. Mechanical collision course in the heat treatment process will make parts have the distortion, but this distortion can be reduced with improved operation and avoid.
5. surface decarburization
Deep groove ball bearing parts in the heat treatment process, if the heating in oxidizing medium, surface oxidation occurs so that spare parts surface mass fraction of carbon reduction, resulting in removal of carbon from the surface. Surface decarburized layer depth exceeds the final machining allowance for makes parts for scrap. Surface decarburization layer in metallographic test for determination of depth available in metallographic method and micro-hardness method. The distribution curve of surface layer hardness measurement shall prevail, may make the criterion of arbitration.

 


Other News:
After heat treatment, the deep groove ball bearing of common quality defects
The thrust ball bearings Timken the light usage considerations
How to choose a self-aligning ball bearing and precautions in use
SKF bearing analysis on causes of premature aging
Deep groove ball bearings Timken maintenance best practices
Self-aligning roller bearing life cycle extension method
Analysis of FAG bearings cause of defects in surface grinding
INA self-aligning ball bearings axial clearance adjustments should be noted