The reason and countermeasures of ferrule cracking

Source: China Bearing Network Time: 2014-03-25

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The cracking of the ferrule is one of the problems that confuse the quality of the bearing; and the cracking of the shortcoming is the primary way of cracking the ferrule; the cause of the attack is that the original data itself is difficult or the production operation is not proper; the equipment can not be formed normally. .
First, the original data of the original data noisy, loose, brittle element segregation or carbide liquid analysis, mesh, band, do not escape uniform segregation and other shortcomings are not eliminated or improved during processing; will form stress gathering; weaken The basic strength of the ferrule; the source of the crack. The precautionary measure is to insist on the supply of the main channel; try to acquire the steel with good quality and stability; strengthen the warehousing view of the purchased steel;
Second, production and equipment 1. Casting: If the burning, overheating, and internal cracking into mesh carbides during the casting process will reduce the resistance and strength of the ferrule, it is necessary to strictly control the processing temperature, circulating heating and post-forging heat dissipation conditions (such as spray cooling). Etc.; especially after the larger types of ferrules are finally forged; the temperature is above 700 Â°C;
2. Heat treatment: close monitoring of heat treatment equipment is an important job in the workshop.
The reliability of the monitoring equipment. The important temperature control tools such as external watches and thermocouples must be closely monitored; the measurement data should be accurate and reliable, and the errors should be replaced in time; the disease operation is prohibited.
Recording of monitoring data. It is necessary to recover the temperature recording equipment of each heat treatment equipment; in order to perform useful monitoring on the whole process of equipment operation (the night shift is the main point); to make the heat treatment quality have strong traceability; to eliminate false records and randomness; Providing good data for the ISO9000 quality system.
Quenching and cooling conditions. It is a disadvantage to deal with the soft points of large and medium-sized bearing rings; the composition and function of quenching oil should be determined; the replacement of the demand should be replaced; the quenching oil should be replaced; the hardening medium can be strengthened; Quenching and cooling conditions.
Severe tempering process. Align the cracking appearance with more types of attack; perform secondary tempering after rough grinding of the ferrule; this can further stabilize the arrangement and scale of the ferrule; reduce the grinding stress; improve the grinding and tamping Layer function. Recently, the second tempering process has been carried out on 22328/02 and 22236/02; there is verification of tailing reaction after sale.
3. Monitoring of the grinding process. The bearing ring of the product is not allowed to have grinding burns and grinding cracks; in particular, there should be no burns on the cooperation surface of the inner ring taper. If the ferrule is pickled, it should be fully inspected; Product; severe burns that cannot be repaired or returned unqualified should be voided; ferrules that have burned burns are not allowed to enter the installation process.
4. Marking processing; steel after storage into the ferrule before grinding; each process must be strictly handled; severely distinguish between GCr15 and GCr15SiMn two different raw materials and products.
Third, the possibility of ferrule overload cracking and fatigue cracking together; especially for bearings with poor operating conditions (such as 22328, etc.). Discussion on the cracking appearance of the ferrule; not only the shortcomings from the data and the production process To think about; to analyze the layout dimensions of the bearing parts, processing measurement methods, processing technology, bearing conditions and other factors.
1. Bearing layout and service conditions. Different layouts are suitable for different conditions of service. The layout of bearing parts is different, and the processing technology is not the same; it affects its quality. Therefore, we should develop new layout products; Different qualification conditions; and indicate the appropriate conditions or functions of the bearing on the bearing instructions; to facilitate customer selection.
2. Strengthen process research; improve processing technology; improve processing quality; reduce the possibility of shortcomings in processing. For example, in heat treatment; for larger types of inner and outer rings; try to use medium and lower limit quenching heating temperature; moderately extend heat preservation time to improve alloying concentration Adding the cracking strength of martensite; and using a higher tempering temperature to enhance the impact resistance of the workpiece under the premise of ensuring the quality.
3. Improve the processing monitoring method; promote the improvement of processing quality. For example, improve the monitoring of the curvature direction of the flow channel; improve the overall function of the bearing after installation; improve the bearing operation.

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