A423 weathering steel may require preheating and post-weld heat treatment (PWHT) depending on thickness, joint restraint, and service conditions. Here's a concise guide:
1. Preheating Recommendations
When Required:
Thickness > 20–25mm: Preheat to 100–150°C (212–302°F) to avoid hydrogen-induced cracking (HIC).
Low Ambient Temperatures (<5°C/41°F): Preheating is mandatory.
Purpose: Reduces thermal stress and slows cooling rates.
2. Post-Weld Heat Treatment (PWHT)
Typically Not Required for thin sections (<25mm) or non-critical structures.
Recommended When:
Thickness > 25mm: Stress relief at 550–600°C (1022–1112°F) for 1 hour per 25mm thickness.
High-Restraint Joints (e.g., thick plates, dynamic loads).
Harsh Environments (coastal, cyclic loading) to enhance toughness.
3. Key Considerations
Low-Hydrogen Electrodes: Always use (e.g., E7018 for SMAW) to minimize cracking risk.
Interpass Temperature: Maintain ≤250°C (482°F) to prevent HAZ softening.
