Loaders, bulldozers and other engineering machinery work in bad conditions, complex and changeable force, serious wear, especially the hinge pin, pin sleeve and pin sleeve seat, are often the most serious parts of friction damage (see the attached figure). Taking the repair of the friction damage of the pin seat under the bucket of a certain type loader as an example, this paper introduces the replacement and welding repair methods of this kind of damage parts.
Replacement and welding repair method for bucket pin seat of loader
1. Analyze the wear condition
Before repair should record the wear condition of hinge pin, pin sleeve and pin sleeve seat hole, measure the clearance of the lower hinge pin and shaft sleeve, and the maximum use limit, if the wear exceeds the maximum use limit, it should be repaired in time.
2. Measure and determine the pin holder size
When repairing the pin block by welding, the damaged pin block must be cut down and re-welded to the newly processed pin block. The new pin block processing needs to ensure accurate size data, which requires data measurement of the old pin block. However, after long-term use, the old lower pin holder is generally seriously damaged and has lost its original dimensional accuracy and external shape, which affects the accuracy of the measurement data.
This can take the following methods: one is to find the technical drawings of the product; The second is to find the same model of the newer machine for comparison measurement; Third, use vernier caliper to measure the size of the lower pin holder with the lightest wear condition, and calculate the wear amount accordingly, adjust the measured data. If the measured thickness of the lower pin holder is 35mm, the thickness can be adjusted to 45mm when determining the new size of the lower pin holder. There are four reasons for adjustment: one is based on the measurement of axial clearance of the lower pin seat and the estimation of axial wear; Two, the lower arm of the lower pin seat on both sides of the wear thinning, not in the lower arm of the pin seat on both sides of the welding thickening, by appropriately thickening the bucket pin seat, can make up for the lower arm pin hole on both sides of the wear, so that the axial gap back to normal; Three is easy to weld, ensure firm; Fourth, the new pin seat of the thickened bucket is not restricted in the space position, so it will not cause other adverse effects.
3. Make new lower pin holder and mandrel
Make new lower pin holder according to the size determined. Considering the requirements of strength and weldability, the material can be 40Cr or 45# steel.
The core shaft is mainly used to avoid the deviation of the new pin seat in the welding process, so as to ensure the coaxiality of the four new pin seat on the bucket after welding. The length of the mandrel varies depending on the size and size of the loader bucket, but the width of the loader bucket is generally not more than 3000mm, and the distance between the upper and lower pins of the bucket is generally 2 500mm~2600mm, so the length of the mandrel is better than this value. The diameter of the mandrel should be based on the aperture of the lower pin seat to ensure that proper force can be inserted into the seat hole. The mandrel should be straightened on the lathe and rounded to 50mm.
4. Cut off the damaged lower pin holder
Put the bucket flat so that the lower pin holder on both sides is in a natural state for easy operation. First choose 4 lower pin seat hole in the most serious wear 1, with oxygen acetylene flame will be the old lower pin seat from the bucket reinforcement plate cut. Gas cutting should be carried out along the original weld as far as possible, the diameter of the cutting hole is slightly greater than the outer diameter of the new pin seat.
5. Place the new lower pin holder and insert the mandrel
Put the new lower pin holder into the cutting hole, and pass the mandrel from the 4 lower pin holder holes to ensure that the lower pin holder to be welded and fixed is on the same axis with the other 3.
6. Weld new pin holder
The new pin seat welded on the bucket rib plate, to be completely cooled after gently tapping the mandrel, before complete cooling do not pull out the mandrel, the purpose is to resist the weld cooling shrinkage deformation of the mandrel, in order to ensure that the new pin seat hole and other pin seat holes coaxial.
After the newly welded pin block is completely cooled, gently tap the mandrel. Then replace other lower pin holder with severe partial wear according to the above method.