Causes and Prevention of Fractures in Rolling Bearing Rings

Sep 19, 2023

For bearings, ring breakage is one of the problems that plague bearing quality, and defective breakage is the main form of ring breakage. The main causes are problems with the raw materials or improper production operations, and the equipment cannot operate normally. Today, we will analyze the reasons for this phenomenon.

Based on the actual use of bearings, our FV analyzed the following reasons:

1. The raw materials of the bearings are not pure enough. When defects such as raw material inclusions, looseness, segregation of brittle elements or carbide liquidation, mesh, band, and unavoidable uniform segregation are not eliminated or improved during processing, they will cause stress concentration, weaken the basic strength of the ferrule, and become Source of cracks. 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 purchased steel at the warehouse, and check it from the Source. FV bearings use high-quality steel. The steel raw materials we choose are consistent with world-class brands, which is the basis for ensuring the quality of our products.

2. Bearing production and equipment

Forging: During the forging process, overburning, overheating, internal cracking into network carbides, etc., will reduce the toughness and strength of the ferrule. Therefore, the processing temperature, circulating heating, and post-forging heat dissipation conditions (such as spray cooling) must always be strictly controlled. They must not be piled up, especially for larger-sized ferrules with temperatures above 700°C after final forging.

Heat treatment: Close monitoring of heat treatment equipment is an important task in the workshop. To monitor the reliability of equipment, such as temperature control equipment, such as meters and thermocouples, must be closely monitored to ensure accurate and reliable measurement data; those with excessive errors must be replaced promptly, and operation while sick is strictly prohibited. At the same time, standardize the recording of monitoring data. The temperature recording devices of each heat treatment equipment must be restored to effectively monitor the entire process of equipment work (focusing on night shifts) so that the heat treatment quality has strong traceability, eliminates false records and randomness, and at the same time provides a complete system for the ISO9000 quality system. Data information. Quenching cooling conditions: to solve defects such as soft spots in medium and large-size bearing rings, the composition and performance of the quenching oil should be measured. If it does not meet the requirements, it should be replaced in advance and replaced with rapid quenching oil to enhance the quenching medium quenching ability and improve Quenching cooling conditions. At the same time, the tempering process is strict. After rough grinding of the ferrules, a secondary tempering process can further stabilize the structure and size, reduce grinding stress, and improve the properties of the metamorphic layer.

Monitoring of the grinding process. Grinding burns and cracks are prohibited on the bearing rings, especially on the inner ring and taper mating surface. If the ferrules are pickled, they should be fully inspected to remove burned products. Severely burned ones cannot be repaired, or those that fail to be repaired should be scrapped. Rings with grinding burns are not allowed to enter the assembly process.

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

3. The possibility of overload fracture and fatigue fracture of the ferrule exists simultaneously, especially for bearings with poor working environment. The study of the ring fracture phenomenon must not only consider the defects caused by materials and production processes but also study and analyze the structural dimensions of bearing parts, processing and measurement methods, processing technology, bearing service conditions, and other factors. Bearings are designed to work in specific conditions, meaning that different bearing structures may be more suitable for different environments. 

Additionally, the quality of bearings can be affected by the processing techniques used to create them. With this in mind, it is important to constantly develop new structural products that can adapt to different working environments. We are excited to guide our customers in selecting the perfect bearings with comprehensive instructions on performance and conditions. At the same time, our FV strengthens process research, improves processing technology, improves processing quality, and reduces the possibility of defects during processing. 

The following is the optimized design of cylindrical roller bearings. The original design is four-row cylindrical roller bearings. Our designer changed it to the six-row cylindrical roller bearing, which makes the bearings have better impact resistance and load capacity.

To improve the strength of martensite during heat treatment, use middle and lower limits of quenching heating temperature for larger inner and outer rings. Increase the alloying concentration by extending the holding time and consider higher quenching temperatures while maintaining quality. Optimize workpiece toughness by tempering at the right temperature, which improves processing quality, flow channel monitoring, bearing performance, and working conditions.