Usage:
793 (3SJ),
793B (1HL),
793C (4AR) Off-Highway Trucks
- SUPPLEMENT: JANUARY 25, 1999
Service Magazine SEPD0447, Article 16, Page 15, December 7, 1998; "Prevention Of Cracking Of 125-6961 A-Frame Support Assembly".
Disregard this article and refer to Service Magazine SEPD0453, Article 24, Page 12 with the same title.
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Description of Change: The position of weld block (not serviced) causes overlapping of welds on the 8X-1464 Yoke Assembly of the A-Frame. This can result in cracking in the yoke weld.
Illustration 1.
Block position dimensions.
The weld block (not serviced) should be located to the new dimensions using the weld specifications listed below. The previous location was 200 mm (7.9 in) from the centerline of the 8X-1464 Yoke Assembly. The new location is 175 mm (6.9 in) from centerline of the Yoke Assembly. This moves the weld block away from the welded joint of the support assembly. Weld only from point A to point B 112 mm (4.4 in) using the given fillet specifications.
Welding OperatorsQualifications
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 qualifications, or Caterpillar Manufacturing Practices MC1000-105. The qualification will be for the SMAW (Shielded Metal Arc Welding) process in the vertical welding positions. The alternate process for this repair is FCAW (Flux Cored Arc Welding). The welding operator must also have used the welding process within the last six months or be re-certified for this process before welding. Documentation must be maintained of the weld operators qualifications.
Weld Procedure
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Protect yourself and others; read and understand this warning. Fumes and gases can be dangerous to your health. Ultraviolet rays from the weld arc can injure eyes and burn skin. Electric shock can kill.
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Read and understand the manufacturer's instructions and your employer's safety practices. Keep your head out of the fumes. Use ventilation, exhaust at the arc, or both, to keep fumes and gasses from your breathing zone and the general area. Wear correct eye, ear and body protection. Do no touch live electrical parts.
Refer to American National Standard Z49.1 "Safety in Welding and Cutting" published by the American Welding Society, 2501 N.W. 7th Street, Miami, Florida 33125; OSHA Safety and Health Standards, 29 CFR 1910, available from U.S. Dept. of Labor, Washington, D.C. 20210.
NOTE: Welding operator personal protection should be provided to assure that total weld fumes in the operators breathing zone does not exceed OSHA limits.
Weld Process
When the base metal temperature is below 0°C (32°F), the base metal shall be preheated to at least 21°C (70°F) and this minimum temperature maintained through the weld repair procedure.
NOTE: Since weld distortion is a possibility, minimizing the heat into the metal is important.
The SMAW process shall be used with E7018 (ANSI/AWS A5.1) welding electrode. The weld deposited by these electrodes will have the following minimum mechanical properties:
- 500 MPa (72 KSI) Tensile Strength
- 420 MPa (60 KSI) Yield Strength
- 13% Elongation
- 18% Reduction of Area
- 420 MPa (60 KSI) Yield Strength
These are low hydrogen electrodes and must be stored in an electrode oven at 121°C (250°F) when not in use. If the electrodes get damp, scrap or recondition them to the manufacturer's specifications.
Use the direct current positive (DC reverse polarity) setting and remove the slag after every pass. The weld pass size shall not exceed two times the electrode diameter.
As an alternate process the FCAW process may be used with E71T-I (ANSI/A5.20) welding electrode and the manufacturer's specified shielding gas(es). The weld deposited by three electrodes will have the following minimum properties.
- 500 MPa (72 KSI) Tensile Strength
- 420 MPa (60 KSI) Yield Strength
- 13% Elongation
- 18% Reduction of Area
- 420 MPa (60 KSI) Yield Strength
NOTE: This type of electrode has limitations if it is used to carry larger weld pass volumes in the flat welding position. Due to the fast freezing characteristics of this electrodes slag system, there is a chance of trapping evolving gases in the weld melt. Precaution should be taken by controlling weld pass size.
Weld Parameters
Welding parameters will vary due to weld position and manufacturer of the welding electrode. For 1.30 mm (.052 in) diameter electrode typical welding parameters should be:
Use the direct current electrode positive (DC reverse polarity) polarity setting and remove the slag after every pass. The weld pass size shall not exceed 8.0 mm (.31 in) fillet volume.
Clean the casting of oil, grease, paint, and dirt in the area to be welded. Attach the welding ground cable directly to the area to be welded. Protect all machined surfaces from sparks or splatter produced by the welding, chipping, and/or grinding operations.
The welds shall be free from cracks, porosity, undercut, and incomplete fusion. All weld quality shall conform to ANSI/AWS D14.3 or 1E99 specifications.
Adaptable To: 793 (3SJ-Up), 793B (1HL-Up), 793C (4AR-Up)