The frame of forklift mainly adopts two kinds of structure: side beam type and box type. Frame is a welded structure, box frame is welded into a box with steel plate, no obvious longitudinal beam, high rigidity. It connects all parts of the forklift together. The front end of the frame is rigidly installed and fixed to the drive axle, and the rear end is supported on the steering axle through the middle hinge. The drive axle and the steering axle together support the whole car. During the operation, the drive axle will bear most of its weight, so the front of the frame is symmetrically welded with the reinforcing ribs of the side force plate, and the front panel is welded between the side beam bodies, so that the frame forms a solid whole.
1. Common faults of frame
In the process of using the frame, the frame structure of forklift truck will be damaged. The common damage is the frame deformation and cracks. In case of the following conditions, the frame shall be removed and replaced:
1) As a result of corrosion, more than 50% of the initial section has been lost.
2) There are more than two serious fatigue cracks with large length and dangerous location.
3) Fatigue cracks appear again in or near the repaired area.
4) The frame structure of forklift truck which has cracks or can not reach the required bearing capacity after repair due to accident cracks shall also be replaced.
5) In a node, when the number of defects is large, it should be replaced.
2. Frame repair
1) The frame body, side plate and edge are dented or deformed. When the deformation is not more than 6mm, it can be corrected by cold rectification method. However, the cold correction can only be used at air temperature. But the cold correction can only be done in the air temperature
Above 0 ℃. Bow calipers, jacks and other tools can be used for calibration.
When the depression and deformation are large, the large deformation can be eliminated by heating to 700-1100 ℃ or 900-1150 ℃.
In all cases, when the temperature is lower than 700 ℃, the correction work should be stopped immediately, and the deformed part should be heated along the convex surface with a nozzle at the place with large deformation. After correction, the component should be cooled at ambient temperature above 0 ℃.
2) Inspection and repair of Frame Crack
Most of the cracks occur in the components with drastic changes in cross-section, the connection points of components and the nodes with too many welds. During the inspection, the paint, dust and soil can be removed from the places where cracks may occur to expose the metallic luster. The cracks can be inspected with a 6-8 times magnifying glass, and the distribution of cracks can also be shown by immersion hammering.
For the detected cracks, a hole with a diameter of 8-25 mm can be drilled 10-15 mm from both ends of the visible cracks to control the development of cracks. Before repair welding, the groove should be ground along the crack, and e4315 or e4316 electrodes should be used for carbon structural steel and e5015-a1 or e5016-a1 electrodes for low alloy structural steel.
After welding, check whether there are cracks in the welding. If there are cracks, grind off the welded joint with grinding wheel and re weld it. The worn length should be 50-100 mm longer than the tail of the obvious crack. The new weld should be straight, dense, and the transition between base metal and new weld should be smooth.
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