05/13/2026
A 190-ton haul truck front A-frame came in with a crack at the ball joint socket weld on the lower right arm. The ball joint socket is a forged insert welded into the fabricated A-frame, and the weld between the forging and the high-strength A-frame plate had cracked 210 degrees around the circumference — more than half the weld gone. The remaining 150 degrees was carrying the full suspension load and was showing fatigue pitting at the toe. The A-frame is T-1 equivalent high-strength plate and the socket insert is 4140 forged steel — a dissimilar joint that requires a careful buttering sequence before the filler rod can bridge the two materials. I removed the socket insert completely by cutting the remaining weld, cleaned both mating faces to bright steel, and ran PT on the A-frame socket opening to confirm no cracking had extended into the plate. Clean. I buttered the 4140 forging face with two layers of E309L MIG wire to provide a compatible buffer deposit, then refitted the socket with the correct gap and alignment. Preheat was 400°F across the full A-frame arm section, maintained with induction coils and thermocouple data logging. I welded the full circumference joint with E11018-M, GTAW root pass at 90 amps for maximum root control on the dissimilar joint, then E11018-M SMAW fill and cap in the 2G position, walking 90-degree segments. Post-weld PWHT was performed at 1,100°F for 2 hours using resistance heating pads, ramp rates controlled at 150°F per hour. Phased array UT on the completed circumferential weld showed full fusion at 360 degrees with zero indications. The A-frame was load tested on a ramp fixture at 120 percent of rated suspension load and held for 30 minutes with a load cell recording. No movement, no indication of distortion. The truck returned to haul duty loaded on the next shift.