Usage:
776B (6JC1-103) Tractors;
777B (4YC1-1803) Trucks
Small cracks around holes in the front wheel can be repaired by welding. The weld repair will close the holes.
Location of the holes (1 and 2) to be repaired.
The procedure must be followed when making repairs to the holes in the front wheels. Because of the relatively high alloy content, cooling cracks and "hard spots" may be encountered and "hard spots", which can lower casting fatigue life. Using the following procedure will reduce the risks associated with welding on this type of material.
Repair cracks that are no longer than 6.0 mm (.2362 in) in length, around the two holes in the wheel are covered in this procedure. Any cracks longer than 6.0 mm (.24 in) results in a component that cannot be repaired.
Welding Operator Qualifications
All repair welding operators must be qualified for fillet and/or groove welding as outlined in the current ANSI.AWS D1.1 or D14.3 specifications.
The qualification will be for groove welding, as outlined in the current ANSI/AWS D1.1, D14.3 or Caterpillar Manufacturing Practices MC1000-105 for the shielded metal arc welding process in the position used for repairing the front wheels. The welding operator must also have used the welding process within the past six months prior to wheel assembly salvage or be requalified. Documentation must be maintained of the weld operators qualifications.
Weld Parameters
The shielded metal arc welding (SMAW) process shall be used with E7018 (AWS 5.5) welding consumables. The weld deposited by these electrodes will have the following minimum mechanical properties:
-
- * 62 ksi tensile strength.
- * 50 ksi yield strength.
- * 22% elongation in 50.80 mm (2.0 in).
- * 20 ft lb notch toughness at -28 C° (-20 F°).
- * 62 ksi tensile strength.
These are sow hydrogen electrodes that must be stored in a 121 C° (250 F°) rod oven when not being used. The electrodes should be scraped if they become damp.
The chart that follows gives the electrode diameter and current setting for welding a groove weld in the flat (horizontal) position.
Use the direct current electrode positive (DCEP) polarity setting. Weld slag should be removed after every pass.
NOTE: Welding operator personal protection should be provided to assure that total weld fume in the operator's breathing zone does not exceed OSHA limits.
Repair Procedure
1. Clean a minimum area of 304.80 mm (12.0 in) around the hole. The area should be free of any oil, grease, paint or other contaminants.
NOTE: Weld repairs should not be made in area (A).
Illustration 2. Location of Area (A).
2. If a crack is present in the casting, extending no more than 6.0 mm (.24 in), remove the crack by boring the hole to a larger diameter to eliminate the discontinuity.
NOTE: Do not attempt to repair the wheel if a crack extends beyond 6.0 mm (.24 in).
3. Visually inspect the inside and surface area of the holes for other damage or cracks before welding.
Illustration 3. Fabricated plug for filling the holes in the front wheels. The Angle (B) is 45°.
4. Fabricate a steel plug to fit within the holes to be filled. Fabricate the plugs from weldable grade steel using Illustration 3 as a guide for forming the plug. Weld groove preparation should include an angle of approximately 45° at the root for good weld penetration and to minimize root defects.
5. Preheat the front wheel. Heat the entire wheel to evenly distribute the heat and to equalize stresses. Preheat the area around the hole to a temperature of 232 C° (450 F°).
Use a 121 C° (250 F°) Templestick® or other device to measure the surface temperature while heating the wheel.
6. Tack weld the fabricated plug in position. Use a temporary back-up strip if necessary to hold the plug in position.
7. Place the wheel in a flat position. Weld the plug in place.
Each weld pass should not exceed 8.0 mm (.31 in) fillet weld volume at any time. The temperature between passes should be kept at 121 to 232 C° (250 to 450 F°) to minimize distortion. Remove the weld slag after each pass.
8. After the groove on the front side has been completed, turn the wheel over to allow access to the back side.
9. Use an air carbon arc torch, or other suitable tool, to remove weld material to a depth of 2.4 mm (.09 in) beyond the bottom of the weld joint deposited on the front side of the wheel. Use a rotary file to dress the surfaces left by the carbon arc torch. The completed weld joint must result in 100% weld penetration.
10. After each hole has been welded, control the cooling rate by covering the welded ares with lime, blankets or other methods.
11. After the welds have cooled, grind the welded area flush with the surrounding casting surface. A hard grinding disk, or stone, may be used to remove the majority of the excess weld cap. Remove all grinding marks to produce a smooth casting surface.
The completed weld repair area should be free of cracks, porosity, undercut and incomplete fusion. All weld quality should conform to ANSI/AWS D1.1, D14.3 or Caterpillar Manufacturing Practices MC1000-901.