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In order to ensure the performance requirements, SKF bearings with metallurgical quality of steel must ensure that the chemical composition of strict, especially high purity (non metallic inclusions in low level), oxygen content and residual element content is very low, low times microstructure strict and high times (micro) organization, carbon compounds strictly inhomogeneity, surface decarburization layer and internal porosity, segregation, microporosity and demanding; do not allow the existence of cracks, slag, burrs, folding, scarring, oxide skin, shrinkage, bubbles, since the point and the burning surface and internal defects.
Crack calcined fire crack of SKF bearing components in the forge fire cooling process due to the internal stress formed by calcining fire crack. Causes of the cracks are: because the calcining heat temperature is too high or cooling too quickly, the thermal stress resistance to fracture strength and metal quality of volume change stress greater than steel; the original defects of working surface (such as surface fine crack or scratch) or internal defects of steel (such as slag, serious non metal inclusion, white spots, shrinking hole remnant etc.) stress concentration is formed in the forge fire; surface decarburization and carbide segregation of SKF bearing serious; component calcined fire after tempering inadequate or not timely tempering; previous process caused by cold stress is too large, forging folding, turning deep marks, sharp edges and corners, oil groove.
SKF bearing assembly in the heat treatment process, if the heating in oxidizing medium, SKF bearing surface oxidation occurs so that the quality of fractional component surface carbon reduction, resulting in surface decarburization. The surface decarburized layer depth over the machining allowance will make component scrap. Determination of surface decarburized layer depth in the metallographic examination of available metallography and microhardness method. The microhardness distribution curve measurement method is accurate, can be used for arbitration criterion. Quality defects of SKF bearing assembly after heat treatment are common: Calcined fire microstructure, less heat, overheating quenching crack, the hardness is not enough, the heat treatment deformation, surface decarburization, soft point, maintenance and overhaul method of bearing. Overheating from SKF bearing assembly rough mouth can be observed in the microstructure of overheating calcined fire.
Usually, the operating temperature of the bearing is used in more than 150 ° is called high temperature bearing, the SKF bearing steel using chromium in temperature exceeds 150 °, its hardness will decline sharply, size is not stable, so that the bearing can not work normally. So for the working temperature of 350 DEG to the bearing working under the condition of 150 °, if the rings and rolling elements still use ordinary high carbon chromium bearing steel SKF manufacturing, it must be tempered with the special on SKF bearing components, in general should be tempered than working temperature of 50 °. Bearing steels after tempering treatment according to the above requirements, can use normally at operating temperature. But because after tempering hardness drops, bearing life decreased. When the operating temperature of the bearing is higher than that of 350 °, it must use the SKF bearing steel high temperature manufacturing.
| Product Model | Inside Diameter | Outside Diameter | Thickness |
| 7928A5DF NSK | 140 | 190 | 24 |
| 7326BDF NSK | 130 | 280 | 58 |