Ferrule fracture is one of the problems that plague the quality of bearings. Defect fracture is the main form of ferrule 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.
一. Raw materials
When raw material inclusions, looseness, brittle element segregation or carbide liquefaction, mesh, ribbon, unfortunately free uniform segregation and other defects are not eliminated or improved in the processing work, they will cause stress concentration and weaken the basic strength of the ferrule. Crack source. The preventive measure is to adhere to the main channel for supply, try to purchase steel with stable and reliable quality, strengthen the inspection of the purchased steel, and check it from the source.Eric Bearing Limited provides FAG 51105, contact us to buy it.
二. Production and equipment
1. Forging: The toughness and strength of the ferrule will be reduced if overburning, overheating, and internal cracking into network carbides occur during the forging process. Therefore, it is necessary to strictly control the processing temperature, circulating heating and heat dissipation conditions after forging (such as spray cooling), etc., especially after the final forging of larger varieties of ferrules, the temperature is above 700 ℃, and shall not be stacked.
2. Heat treatment: close monitoring of heat treatment equipment is an important job in the workshop.
Monitor the reliability of equipment. Important temperature control instruments such as instruments 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 entire process of the equipment work, so that the heat treatment quality has strong traceability, to prevent false records and randomness, and to provide complete data for the ISO9000 quality system.
Quench cooling conditions. In order to solve the defects such as soft spots of medium and large types of bearing rings, the composition and performance of the quenching oil should be measured. Those that do not meet the requirements should be replaced with rapid quenching oil to enhance the quenching capacity of the quenching medium and improve the quenching cooling conditions.
Strictly tempering process. For varieties with more fracture phenomena, the ferrule is subjected to secondary tempering after rough grinding, 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 is subject to after-sale tracking feedback verification.
3. Monitoring of grinding process. The finished bearing ring is 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 cannot be repaired or if it is unqualified, it 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.Need FAG Bearing 32311-A, click here to contact us for more details.
三. The possibility of overload fracture and fatigue fracture of the ferrule exists at the same time, especially for bearings with poor service conditions (such as 22328, etc.). The research on the ring fracture phenomenon should not only consider the defects produced in the material and production process, but also study and analyze the structural dimensions of the bearing parts, the processing measurement methods, the processing technology, and the bearing service conditions.
1. Bearing structure and service conditions. Different structures are suitable for different service conditions; the processing technology of bearing parts is different, which affects its quality. Therefore, we should develop new structural products to adapt to different service conditions, and indicate their suitable service conditions or performance in the bearing 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 the bearing after assembly, and improving the working condition of the bearing.
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