Aluminum Sheet Welding Deformation Control & Joint Integrity Assurance

1. Pre-Weld Preparation

   • Surface Treatment: Mechanically clean with dedicated stainless brushes to remove oxide layers (Al₂O₃), followed by alkaline degreasing (pH 9-11)
   • Edge Preparation: Apply 30°-45° beveling for sheets >3mm thickness to ensure full penetration

2. Process Optimization

   • **Welding Method Selection
     • TIG welding with pulsed current (2-5Hz frequency) for heat-sensitive applications
     • Robotic welding for long seams to maintain consistent travel speed (8-15cm/min)
   • Parameter Control
     • Current: 80-180A (adjusted per 1.5-6mm thickness)
     • Interpass temperature: <150°C monitored via infrared thermometer
     • Intermittent welding pattern: 50mm weld/100mm gap alternation

3. Deformation Mitigation

   • Fixture Design: Modular clamping systems with 3D-angled vises maintain <0.5mm/m alignment tolerance
   • Welding Sequence: Implement symmetric skip-welding technique (backstep sequence)
   • Thermal Management: Use copper chill bars behind weld joints for rapid heat dissipation

4. Post-Weld Treatment

   • Mechanical Correction:
     • Cold straightening with hydraulic presses (≤3mm/m correction capacity)
     • Localized peening (0.3-0.6mm indent depth) using pneumatic needle scalers
   • Surface Finishing:
     • Grinding sequence: 80→120→240 grit abrasives with ≤Ra 1.6μm final finish
     • Stress relief: Vibration aging treatment (30-50Hz, 2-4 hours)

5. Quality Verification

   • Non-Destructive Testing:
     • Penetrant testing (ASTM E1417) for surface defects
     • Ultrasonic inspection (AWS D1.2 Class B) for internal flaws
   • Mechanical Validation:
     • Tensile testing: ≥85% base metal strength retention
     • Macro-etch examination: Full penetration verification

This methodology achieves <1.5mm/m² distortion rate while maintaining weld shear strength ≥140MPa for 6061-T6 aluminum, compliant with AWS D1.2 structural requirements.