Three solutions for addressing the nonconformity of imported bearing raceways:

Three solutions for addressing the nonconformity of imported bearing raceways:

1. Center Offset Method:

   • For nonconforming dimensions (asymmetric defects) of the bearing raceway's inner and outer diameters, accurately measure the dimensions of the existing defects and calculate the small grinding allowance (the amount to be ground to achieve the final dimension), denoted as M. During the grinding process, offset the center of the workpiece towards the direction that increases the grinding allowance for the defect. The offset amount should be M/2, focusing on the grinding of the defect.
   • For the raceways' inner and outer surfaces, which are to be ground after the respective inner or outer diameter grinding, consider the example of the inner raceway. If there are asymmetric defects on the inner raceway, accurately measure the inner diameter dimension and calculate the maximum grinding allowance, denoted as M1, for the defect. If M1 < M, offset the center of the inner raceway during the grinding of the inner diameter by an amount equal to M1/2. This will pre-increase the grinding allowance for the defect, enabling focused grinding during the grinding of the inner raceway and salvaging the defective parts. If M1 ≥ M, normal grinding will not remove the defect. In such cases, refer to the method described in section 1.1 for salvage options.
   • Center offset grinding should be performed while ensuring the hardness and carburized layer depth of the workpiece. The total offset amount cannot be achieved in a single grinding operation and is usually divided into several grinding stages. The process involves trial grinding with offset - measurement - adjustment of the offset amount - repeated grinding. Once the defect is ground away, return to proper alignment and perform normal grinding to correct the ellipticity. This method has a lower efficiency and requires operators with a high level of technical expertise. However, it has a higher success rate for salvage in single-machine, single-piece production, without delaying production schedules. It has been proven effective through several years of practice.

2. Thermal Treatment Swelling Method:

   • The microstructure of imported bearing steel after quenching consists of quenched martensite, a small amount of undissolved secondary carbides, and residual retained austenite, which accounts for approximately 12% to 14% of the structure. Both the quenched martensite and residual retained austenite are unstable. During the tempering process, the decomposition of martensite causes the steel to shrink, while the decomposition of residual retained austenite causes the steel to swell.
   • By increasing the tempering temperature, the decomposition of residual retained austenite increases. Under the condition of ensuring the required hardness, a suitable increase in the tempering temperature promotes the decomposition of residual retained austenite into martensite with a larger volume. This leads to an increase in the overall volume of the workpiece, specifically increasing the outer diameter grinding allowance. This method enables the salvage of defective sections of imported bearing raceways under normal grinding conditions.
   • This method yields significant results for thick and heavy-duty workpieces with a higher content of retained austenite, especially for self-aligning roller bearings. Different tempering processes are developed for various specifications, sizes, and thicknesses of components in actual production. By ensuring hardness and minimizing deformation, the microstructure transformation is maximized, resulting in significant swelling and corresponding grinding allowance increase to salvage defective parts.

3. Chemical Deposition Method:

   • For imported bearing components with dimensional tolerances exceeding design standards, chemical deposition can be used for salvage. The principle of chemical deposition involves chemical reactions among various chemical reagents, which uniformly produce a metal coating with a certain thickness on the surface of the component. Additional tempering