我厂有15吨、25吨门座起重机共五台。这些起重机的旋转机构采用了转盘滚轮式支承装置,如图1所示。这些起重机在使用五、六年之后,旋转环形轨道表面出现了磨损凹陷,局部还有深度达2～3毫米的龟裂剥落,严重影响了旋转机构的正常运行,需要对上、下环形轨道进行加工修复。从图1可以看出,上、下环形轨道是分别 I plant 15 tons, 25 tons of portal cranes a total of five. The slewing mechanism of these cranes uses a turntable roller support, as shown in Figure 1. After these cranes have been used for five or six years, the surface of the rotating annular track has worn depressions, and local cracks of 2 to 3 mm in depth have seriously affected the normal operation of the rotating mechanism. The upper and lower annular tracks need to be carried out Processing repair. As can be seen from Figure 1, the upper and lower annular tracks are respectively