Repair of broken steering wheel shaft heads of forklifts

(1) On a lathe, remove the broken end of the shaft head, bore a counterbore with a diameter of φ35mm and a depth of 15mm on its cross-section, and then make a 10×60° chamfer on its outer circle. According to the calculation, the bending moment M of this section is 1410N·m and the tensile force S is 7030N, both of which are not large. However, its cross-sectional area is relatively large, so the force on the section is relatively small.

(2) Make the shaft head fitting as shown in Figure 2 with 45# steel, and press its round boss into the counterbore of the original shaft head. The fit relationship is H7/S6.

(3) Weld the steering wheel shaft and shaft head accessories. Select 607 welding rods (ensuring that the strength of the weld seam is equal to that of the base electrode). The drying temperature before welding is 350-450℃. Heat up with the furnace and hold for 1-2 hours. Take them out as needed. Preheat the base material to around 250℃. Weld with a DC welding machine at a small current. After each layer is welded, tap the weld seam on the cross-section with a small hammer to eliminate internal stress. At the same time, only after observing that there are no cracks at the welding area can the next layer be welded to ensure the welding quality.

(4) Precisely process the welded parts in accordance with the technical requirements of the components, and pay attention to the tolerances of the bearing fit parts. The strength of the weld seam has been verified to meet the usage requirements. The repaired shaft head has been in use for over a year and everything is normal.