Bearing parts after the heat treatment of the common quality defects are as follows: hardened microstructure too hot, not hot, hardened cracks, hardness, heat treatment, surface deformation decarbonization, soft spots, and so on.
The hot 1 .
From the bearing part rough port that can be observed on the after quenching microstructure heat. However, to accurately judge the extent its hot microstructure must be observed. If the 15 steel hardened GCr organization appears in bold, maraging steel needle-hardened too hot for the organization. A reason could be hardened heating temperature is too high, or heating time is too long the FULL HOT; it is also possible that the original organization ribbon carbide, between the two with a low-carbon martensite formation of local district needle-like coarse, the hot spots. The residue of the austenitic hot organization increased stability, reduced size. As a hot, hardened steel, coarse crystals that will result in the part of the tough, impact-resistant performance, bearing life is reduced. Overheating and even hardened serious cracks.
2.The hot
Hardened temperature is low or poor cooling is the microstructure produced more than the standard organization of the Commonwealth's debt, known as the Organization, it dropped the hardness, abrasion resistance, impact dramatically reduce bearing life.
Hardened cracks 3 .
Bearing parts in the quench process because the stress cracks that formed by hardened cracks. This cracks the reasons are: the hardened heat temperature is too high or too cool, heat stress and metal quality volumetric change of Organization when stress greater than the resistance to tensile strength steel work surface; the original flaws (such as surface cracks or scratches) or steel internal defects (such as the standard chartered, non-metallic inclusions, white spots, such as a hole) in hardened remnants formed when the stress concentration; serious surface decarbonization and carbide to parse; part after quenching is not timely and tempered low or flash-back; the front operation caused by excessive stress cold punch and forging fold, deep cutting knife marks, oil and sharp edges, and so on. In short, the reason for hardened cracks could be one of the above factors of one or more of the stress, there is a quenching of the cracks. Hardened cracks deep and narrow, straight, and sedimentological intersection no carbon dioxide. In the bearing sleeve rings it is often the straight vertical cracks or ring cracks; in the bearing of ball-shape S T , or ring-shaped. Hardened cracks of organizational characteristics is decarbonization cracks both sides, no significant difference between the forging cracks and material cracks.
Heat-treated deformed 4 .
In bearing parts, heat-treated, there is a heat stress and strain relief, this strain can be mutually superimposed or offset, in part, is complex and changeable and because it moves with speed, the heating temperature, cooling, cooling, and part of the shape and size changes, so heat-treated distortion is inevitable. Understand and master the pattern of changes which can be part of the bearing deformation, such as collar of ellipse, Size Large, and so on) can be placed in control of the range, to production. Of course, in the heat treatment process mechanical collision parts also have a deformed, but this distortion can be used to improve operations and to avoid the reduction.
Decarbonization surface 5.
Bearing parts in the heat treatment process, if you are carbon dioxide, the heat in the media, surface oxidation will occur so that part of the carbon surface quality score resulted in surface decarbonization. decarbonization of the surface layer depth is greater than the final processing of scrap parts. decarbonization of the surface layer depth measured in Kim Kim Sang-test available in law and micro-hardness. In order to surface microhardness measurements distribution curve for the arbitration award may be made.
Soft point 6.
By heating, cooling, improper operation, such as hardened bearing cause the surface hardness is not part of the phenomenon known as hardened soft points. It is like a carbon scrubbers as surface can cause surface wear resistance and fatigue strength of serious decline.



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