Weld crack prevention and post-heat treatment process for 5456 aluminum plate for ship deck applications

Welding Process Optimization: Use 5356 aluminum-magnesium welding wire to match the composition of the 5456 base metal. TIG welding parameters are controlled within a range of 90-120A, 10-12V, and a welding speed of 15-20cm/min to minimize heat input. Preheat to 150-200℃ before welding to reduce temperature gradients. Immediately after welding, perform stress relief using a flame heater (300-350℃ for 30 minutes), focusing on eliminating residual stress in the weld and heat-affected zone (HAZ).

Post-Heat Treatment Improvement: For thick 5456 plate (>10mm), adopt a stepped heating cycle (200℃ → 300℃ → 350℃ for 2 hours), combined with forced air cooling to maintain a cooling rate of ≤50℃/min. The treatment effect is verified through hardness testing (target HV80-90) and metallographic analysis (grain size ≤50μm) to ensure that no low-melting-point eutectic remains. If microcracks are present, they can be repaired through additional local pulse annealing (350℃ x 1h).