Bearing ring inner surface defect factors and treatment measures

As one of the important parts of mechanical equipment, bearing work on bearing surface has the high requirements, such as smoothness, strength and wear resistance, it will involve the bearing material and bearing processing technology, such as bearing ring inner surface pitting, indentation crack defects such as will seriously affect the bearing performance. Below the bearing network ( Hereinafter referred to as:) According to the understanding of the knowledge of bearing, are related in the manufacturing process of bearing ring common instances of some surface defects, and make corresponding measures to this defect. 1, bearing ring, inner ring surface defects, for example in the production of bearing ring, the need for bearing ring forging processing, and bearing ring forging processing, find bearing ring inner surface defects such as cracks, pits ( As shown in figure 1) , this kind of defect caused by bearing scrap rate is very good. Figure 1 bearing ring inner surface defect 2, bearing ring, inner ring surface defect analysis 1) Composition analysis for defect bearing ring back analysis, the results are shown in table 1. 2) Gas analysis the material of the bearing ring is used GCr15 round steel, GCr15 round steel treated with RH vacuum degassing during smelting, trace gas defect products leave the factory inspection records, inspection. Gas analysis for defect product sample preparation, as shown in table 2. This shows the defects of subcutaneous bubble defect. 3) Metallographic analysis through metallographic analysis ( As shown in figure 2) Found near the pits and crack defects without big particle inclusions, tin oxide both exist, complete decarburization layer defect. Including crack defects hypodermic and there are many similar crack, crack in the tin oxide both exist. It can judge the defect before heating, is a raw material defect. Figure 2 GCr15 bearing ring inner surface microstructure defect parts can be seen, all the defects arise from the inner surface bearing ring forging process and principle of metal plastic, boldly to judge the defects for external surface of the round steel defect as metal deformation in the process of forging hole extends to the inner surface of the bearing ring, due to the inner surface machining allowance is lesser, no clear exposed in the process of grinding on the surface, causing parts scrap. In order to test, the view is correct, simulation experiment. 3, simulation analysis of 1) Validation of bearing ring processing test purposes, the round steel outer surface defects such as cracks, pitting, indentation, etc will cross section to the round steel billet in the process of stamping, and under the stamping punch edge and below the surface of the bearing ring parts, lead to the unqualified products. 2) Through experimental design and user technical personnel communication, determine the compression ratio, the size of the raw materials, in the process of forging blank, punch and other key parameters ( Table 3) And processing technology. Use of existing resources to make the mould, punch, such as experiments, tool as shown in figure 3. Figure 3 bearing ring test tool (3) Experiment process, mark a sample for a sample, the sample of 50 mm diameter GCrl5 round steel, 55 mm sample height. Annular groove in the sample end face and surface processing, is advantageous for the experiment to observe the annular groove position, as shown in figure 3. B, experiment steps in order to protect the equipment, box-type resistance furnace heating up to 850 °, insulation in the sample after 30 min. Ready at the beginning of composition and upsetting machine, into the specimen, stamping, to remove the sample after cooling. Heat the cylindrical sample again, use the punch hole and forging die forging hole. The sample after finish stamping experiment, cut section observation. C, after forging experiment, at the beginning of the conclusion on the surface of the round steel ring mark all rise in forging parts on the surface at the beginning of place, as shown in figure 4, figure 5. Figure 4 round steel forging parts forging at the beginning of sample figure 5 hole, annular tag in the punch under enormous pressure, signs of inner hole edge to the mobile, as shown in figure 6. Figure 6 hole forging parts 1 1 the tiny crack were found at the edge of the specimen, the crack down to the bottom of the tag in the sample surface, is now moving to the end of the sample above. If the cracks occur near the end of the sample position, it is possible to move to the edge of bearing ring, as shown in figure 7. Figure 7 forging 2 restricted by equipment spare parts, this experiment USES 500 t hydraulic upsetting machine instead of customers stamping equipment, is far less than the impact of the customers using air hammer, due to the impact of increased metal fluidity in theory, circular mark signs of leaning to inner hole edge mobile will be more obvious. If the round steel outer surface cracks, scratches, pits, pitting, inclusion and other defects, the thermal deformation under the action of impact force in the process, will flow to the edge of bearing ring surface, in the subsequent grinding exposed on the surface of the parts in the process of scrap. 4, 1) improvement measures The supplier to enhance the surface quality of round steel, the surface should not have crack, scratch, pitting and defects such as inclusions, should keep clear of in time if you have the above defects. 2) The blank bearing ring outer surface machining allowance is 0. 6 mm, surface defects in the process of grinding are all clear, did not find the surface defects; The inner surface of the machining allowance is 0. 3 mm, should increase grinding machining allowance, clear the inner surface of defects. 3) At the beginning of bearing ring in forging process are all made of the free forging process. In the design process, according to the parts of forging hole size, and compression ratio in parts, on the basis of using the constant volume principle, with 52 mm round steel instead of 55 mm or phi phi phi 50 mm round steel, avoid round steel outer surface metal into the inner surface in the process of hot deformation.