Cross roller bearing is widely used in the joints of various mechanical arms and the spindle of machine tools. However, in actual use, the problem of bearing ring fracture is occasionally encountered. The fracture of the bearing ring directly affects the operation of machinery, resulting in the production quality problems. Therefore, it is necessary to check the operation of bearings frequently. What is the reason for the fracture of cross roller bearing?
1、 Caused by improper processing
1）. The raw material quality of ferrule is poor
When the defects of raw materials such as inclusions, looseness, brittle element segregation or carbide liquidus, reticulation, banded and unfortunately uniform segregation are not eliminated or improved in the machining process, they will cause stress concentration, weaken the basic strength of ferrule and become the source of cracks. The preventive measures are to adhere to the main channel supply, try to purchase stable and reliable steel products, strengthen the warehousing inspection of purchased steel, and control the quality from the source.
2）. Improper grinding
The race grinding is an important process to ensure its accuracy, but the grinding process has strict requirements for processing tools, equipment speed, etc. improper process selection may lead to grinding burn and cracks of the ring. The monitoring of the grinding process should be strengthened. Grinding burn and grinding crack is not allowed in finished bearing rings, especially on the fitting surface of inner ring taper modification. If the ferrule is pickled, it should be fully inspected and the burned products should be removed. The severely burned rings should not be repaired or the unqualified ones should be scrapped. The rings with grinding burns are not allowed to enter the assembly process.
3）. Improper heat treatment
Heat treatment can eliminate the stress inside the ring and improve the strength of the ring. However, if the heat treatment temperature and quenching process are not selected properly, the ring will have structural defects or size defects. In order to solve the defects of bearing rings such as soft spots, the composition, and properties of quenching oil should be determined. The unqualified ones should be replaced by quick quenching oil to enhance the hardenability of the quenching medium and improve the quenching cooling conditions. Strict tempering process. In view of the varieties with more fracture phenomena, the secondary tempering is carried out after rough grinding, which can not only further stabilize the structure and size of rings but also reduce the grinding stress and improve the performance of grinding metamorphic layer.
2、 Incorrect use of bearings
The ring of cross roller bearing will also fracture in the process of use, which mainly has three forms: fatigue fracture, overload fracture, and thermal fracture.
1. Fatigue fracture
Under the alternating load and impact load, the stress of the bearing ring (especially the outer ring) continuously exceeds the fatigue strength limit of the material, which leads to the generation of fatigue crack, and the crack eventually extends to a certain extent, which leads to the fracture of the part at the stress. It usually occurs in the bearing area of the outer ring of the bearing. Because the outer ring usually fits with the bearing housing hole for clearance, and the bearing housing is a changeable and elliptical part, it is easy to cause fatigue fracture under alternating load and impact load.
2. Overload fracture
Similar to fatigue fracture, when the stress acting on the bearing is greater than the tensile strength of the material, the inner ring will crack, which is usually caused by improper installation, such as bearing inclination, resulting in bearing partial overload and fracture; in addition, improper knocking during installation causes bearing cracking and block falling, which is also classified as overload cracking category. There are also common bearing fit size interference installation, too large interference will also lead to bearing ring cracking, too large interference will lead to greater stress in the inner ring, especially for the inner ring with thin section thickness (section thickness < 12mm), too large interference often leads to axial cracking of inner ring.
3. Thermal fracture
Thermal fracture is mainly due to sliding friction between the parts matching with the end face of the bearing ring. Under the action of axial force, the friction produces high heat, resulting in the end face accompanied by burn and discoloration. Friction and high heat cause cracks on the end face of the bearing ring. The characteristics of the cracks are perpendicular to the direction of friction operation. Similarly, the end face cracks also have a negative effect on the section thickness (section thickness < 12mm)。 The influence of the inner ring is greater.
Luoyang TEDIN Bearing Co., Ltd.， after years of technical development and improvement, the production of cross roller bearings using advanced process technology, avoid the ring fracture caused by processing. Welcome to leave a message on our website or call for a detailed consultation.
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