Experimental Research on Removal of Scale in Hollow Roller Hole by Abrasive Flow

Aiming at the problem of descaleing the inner hole of the hollow roller of the rolling bearing, the silicon carbide viscoelastic fluid abrasive with the particle size of 46 and 220 was used to remove the inner hole of the hollow roller of the extrusion rolling mill bearing. The results show that: using the abrasive flow The processing method can effectively remove the oxide scale in the inner hole of the hollow roller; under the same abrasive flow processing parameters, different machined surfaces can be obtained by using silicon carbide abrasive grains of different particle sizes, and the machined surface should match the silicon carbide abrasive grains used. , the machined surface with thick scale should be processed in stages to achieve good scale removal effect. 1. Overview At present, the large-scale rolling bearings used in the rolling mill field are subjected to large loads during the steel rolling process, resulting in large forces on the rolling elements that are mainly carried in the bearings. In order to improve the bearing capacity of the bearing, hollow rollers are mostly used, which are passed through the hollow rollers through the struts, and are connected with the cage by welding. Fatigue failure of the rolling element or raceway surface of the pillar welded cage will occur under heavy load conditions. In addition to the uneven drilling of the cage and the deflection of the pillar caused by the welding stress, the inner surface of the pillar hole connected with the hollow roller is oxidized. Peeling and surface wear caused by unclean skin removal can also cause bearing fatigue failure. In order to reduce the damage of sliding friction to the rollers, sandblasting or manual methods are usually used to remove the oxide scale in the inner holes of the hollow rollers, but the processing efficiency is low, it is difficult to achieve uniform removal, and it also has a bad impact on workers and the environment. The abrasive flow machining method was first proposed by American researchers. This method uses a hydraulic press as a power transmission system to repeatedly extrude viscoelastic fluid abrasives in one or two directions, so that the abrasives quickly rub against the surface of the workpiece under the action of pressure. The grinding and polishing of the workpiece surface, the processing principle is shown in Figure 1. In this paper, the abrasive flow technology is mainly used to remove the oxide scale on the inner hole surface of the bearing hollow roller. 1—fixture; 2—loading cylinder; 3—workpiece; 4—viscoelastic abrasive; 5—unloading cylinder; 6—extrusion piston. Fig. 1 Machining principle of abrasive flow machining method Fig. 1 Machining principle of abrasive flow machining method Before adjustment and cross-section matching tests, appropriate abrasive grains should be selected according to different machined surfaces. Literature [8-10] selected viscoelastic abrasives with different particle sizes and concentrations to extrude and remove the oxide scale on the surface of workpieces with different materials. The results of the study on the abrasive characteristics of the abrasive flow showed that the workpiece surfaces obtained by different processing methods should choose different particle sizes. Abrasive particles remove the oxide scale; the abrasive flow machining method is the best for the removal of the oxide scale formed on the surface of the workpiece after EDM. In addition, with the increase of the number of cycles, the surface roughness Rα tends to be constant. 2. Test In view of the difficulty in removing oxide scale from the inner hole of a super-large rolling mill bearing hollow roller after heat treatment, the self-developed abrasive flow machine tool was used to conduct the grinding test. The processing principle of the abrasive flow processing equipment is shown in Figure 2. The abrasive flow processing mainly relies on two hydraulic cylinders to symmetrically reciprocate the semi-solid fluid abrasive medium, passing through the sealed flow channel formed by the workpiece and the fixture, and the abrasive and the surface of the workpiece produce Relative friction, so as to achieve grinding and polishing. In the process of processing, the workpiece is fixed by the upper and lower platens, and the number of workpieces can be changed by adjusting the distance between the upper and lower platens. The equipment can process up to 7 workpieces of the same model at a time. 1—lower hydraulic cylinder; 2—lower abrasive cylinder; 3—lower platen; 4—7 workpieces; 5—upper platen; 6—abrasive; 7—upper hydraulic cylinder; 8—piston; 9—upper abrasive cylinder; 10— hydraulic station. Fig. 2 Diagram of abrasive flow equipment and principle Due to the protective atmosphere in the heat treatment process, the black oxide scale with uneven thickness can be clearly seen after heat treatment, and it is difficult to remove. The main dimensions of the hollow roller and the oxide scale on the inner hole surface after wire cutting are shown in Figure 3. Fig.3 Main sizes and bore surface of hollow roller after heat treatment Based on the material removal characteristics of the above four abrasives, silicon carbide viscoelastic abrasive was selected as the grinding medium for the experiment. In order to verify the processing effect of the abrasive particle size on the machined surface, silicon carbide abrasives of 220 mesh (particle size 65 μm) and 46 mesh (particle size 330 μm) were selected. Extrusion of the type, and no back pressure (no pressure at the end of the workpiece opposite to the flow direction of the abrasive flow).