Effect of finishing rolling process of pushing the end face quality of the crank
First, the rack to the rotational position of the crankshaft, steeple on both ends of the center hole coarse location, this time in the axial direction of the crankshaft is still floating in the action of the spring force. Rolling head into the end face of the thrust to open files, rolling head to the center axis rotated counterclockwise at an angle, the roller contact side wall, and adjust the axial position of the crankshaft until both sides by Yan. Second, the top ends of the hydraulic unit will crank locking piece perfectly positioned axially, while the left jaw clamping shaft head, as shown. When the workpiece rotation, up knife device operation, both from the swollen nose, turning forward to, finishing side walls. Upon completion, the tip is retracted, the knife body return to the starting position. Then, rolling head into the open file again (Figure 2), rolling wheel rotates clockwise around the shaft, respectively, abut the side walls, with the rotation of the crankshaft, rolling wheels grind thrust follower end face, Rolling push to achieve the end face of the stop. Here, one of the main purpose is to make the finishing thrust distance between the end faces close to the design standards, and the other is to provide a smaller roughness next roll is to make rolling to achieve more good results. Crankshaft fillet rolling and rolling the purpose here is different. The main purpose is to increase the fillet rolling compressive residual stress at the fillet to offset part of the crankshaft tensile stress at work, in order to delay the expansion of fillet cracks, thereby increasing the fatigue strength of fillet. The purpose is to improve the finishing rolling surface roughness, thereby reducing the rate of formation of cracks. At the same time, but also improve the thrust rolling end surface hardness, surface abrasion resistance also will increase; generating a certain amount of residual compressive stress on the fatigue life of push end face only have a positive effect. Finishing rolling process, finishing blade center must be consistent with the center of the roll, there would be inconsistent on both sides of the rolling capacity, affecting rolling effect. After rolling surface quality significantly better thrust end face grinding on surface quality, especially dense tissue is improved, greatly improving its abrasion strength. Finishing rolling after the completion of the entire process to push the end face of the stop. Effect of rolling fatigue life of ductile iron push the end face of the stop before rolling 83HRB 23HRC 49MnVS3 rolling 98HRB 26HRC after finishing rolling around before and after change in hardness finishing rolling hardness are shown in Table 1. As can be seen from Table 1, the hardness after rolling nodular cast iron crankshaft improved 18.1%, 49MnVS3 crankshaft hardness increased by 13%. The vast majority of information, improve the surface hardness can enhance the wear resistance of the surface to varying degrees. Thus, these two materials to improve the surface hardness, have enhanced wear resistance of the thrust end face in varying degrees. Before and after finishing roughness change before and after rolling finishing rolling roughness change as shown in Table 2. From Table 2, after finishing rolling surface roughness values ??decreased significantly decreased by about an order of magnitude, which undoubtedly greatly improve the fatigue strength of the surface. According to fracture mechanics, the larger the surface roughness, the greater the effect of the cut, so the fatigue performance worse. This is because there is always a rugged machined surface machining marks such as marks, cracks (Figure 3), which traces the equivalent of many tiny gap, the parts work surface stress concentration, it can represent theoretical stress concentration factor Kt. Namely Kt = 1 + 2 (ghr) (1) where, h is the microscopic roughness height; r is the radius of curvature of the trough, g is the correlation coefficient unevenness spacing to height ratio. 4 3 finishing rolling analysis machined surface (80 ×) after rolling FIG
