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Reasons And Countermeasures For Fracture Of FAG Bearing Ring

Source:  skf bearing  Time:  2021-04-29

    Ring fracture is one of the problems that plague the quality of FAG spherical roller bearings. Defect fracture is the main form of ring fracture. The main cause is the problem of the raw material itself or improper production operation, and the equipment cannot operate normally. The actual analysis is as follows.


    1. Raw materials

    When raw material inclusions, looseness, brittle element segregation or carbide liquefaction, network, ribbon, unfortunately free uniform segregation and other defects are not eliminated or improved during processing, they will cause stress concentration, weaken the basic strength of the ferrule, and become cracks source. The preventive measures are to adhere to the main channels for supply, try to purchase steel with stable and reliable quality, strengthen the inspection of the purchased steel, and check it from the source.


    2. Production and equipment


    (1) Forging: The toughness and strength of the ferrule will be reduced if overburning, overheating, internal cracking into network carbides are produced during the forging process. Therefore, the processing temperature, circulating heating and calcining heat dissipation conditions (such as spray cooling) must always be strictly controlled, especially after the final forging of larger varieties of ferrules, the temperature is above 700 ℃, and they shall not be stacked.


    (2) Heat treatment: close monitoring of heat treatment equipment is an important job in the workshop.

    Monitor the reliability of the equipment. Important temperature control instruments such as meters and thermocouples must be closely monitored to ensure that the measurement data is accurate and reliable; those with excessive errors must be replaced in time, and operation with diseases is strictly prohibited.

    Record of monitoring data. The temperature recording device of each heat treatment equipment must be restored in order to effectively monitor the whole process of equipment work (night shift is the focus), so that the heat treatment quality has strong traceability, to prevent false records and randomness, and to provide a complete ISO9000 quality system Data.

    Quench cooling conditions. In order to solve the defects such as soft spots of medium and large FAG spherical roller bearing rings, the composition and performance of the quenching oil should be measured. Those that do not meet the requirements should be replaced in advance and replaced with rapid quenching oil to enhance the quenching capacity of the quenching medium. Improve quenching cooling conditions.

    Strictly tempering process. For the varieties with more fracture phenomena, the second tempering is performed after rough grinding of the ferrule, which can further stabilize the structure and size of the ferrule, reduce the grinding stress, and improve the performance of the grinding metamorphic layer. Recently, two types of 22328/02 and 22236/02 have been implemented a secondary tempering process, which needs to be verified by after-sales follow-up feedback.


    (3) Monitoring of grinding process. The finished FAG spherical roller bearing rings are not allowed to have grinding burns and grinding cracks, especially on the mating surface of the inner ring screwdriver. If the ferrule is pickled, it should be fully inspected to remove the burned product. If it is severely burned, it should not be repaired or repaired unqualified should be scrapped. Ferrules with grinding burns are not allowed to enter the assembly process.


    (4) Identification management. After the steel is put into storage and before the ferrule is ground, each process must be strictly managed, and the two different materials and products of GCr15 and GCr15SiMn must be strictly distinguished.

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    3. The possibility of overload fracture and fatigue fracture of the ferrule exists at the same time.

    The research on the ring fracture phenomenon should not only consider the defects generated in the material and the production process, but also the structural dimensions, processing measurement methods, processing technology, and FAG spherical rollers of FAG spherical roller bearing parts. Research and analysis of bearing service conditions and other factors.

    (1) FAG spherical roller bearing structure and service conditions. Different structures are suitable for different service conditions; FAG spherical roller bearing parts have different structures and their processing technology is different, which affects its quality. Therefore, we should develop new structure products to adapt to different service conditions, and can indicate their suitable service conditions or performance on the FAG spherical roller bearing operating instructions to facilitate customer choice.


    (2) Strengthen process research, improve processing technology, improve processing quality, and reduce the possibility of defects in processing. For heat treatment, for larger varieties of inner and outer rings, try to use the middle and lower quenching heating temperature to adapt to prolong the holding time to increase the alloying concentration, increase the martensite fracture strength, and choose higher under the premise of ensuring quality Tempering temperature to enhance the impact toughness of the workpiece.


    (3) Improve processing monitoring methods and promote the improvement of processing quality. Such as improving the monitoring of the curvature position of the flow channel, improving the overall performance of FAG spherical roller bearings after assembly, and improving the working conditions of FAG spherical roller bearings.