Whether Q460NH weathering steel requires post-weld heat treatment (PWHT) depends on several factors, including material thickness, welding method, and application requirements. Here's a concise guideline:
1. When PWHT is Typically Required
Thick Sections (≥25–30mm):
PWHT (e.g., stress relieving at 550–650°C) may be needed to reduce residual stresses and avoid cold cracking, especially in high-restraint joints.
Critical Applications:
For structures subject to fatigue loads or low-temperature service (e.g., bridges, offshore platforms), PWHT improves toughness in the heat-affected zone (HAZ).
2. When PWHT Can Be Omitted
Thin Sections (<20mm):
Preheating (150–200°C) and controlled interpass temperatures often suffice to prevent cracking.
Standard Atmospheric Use:
If welding follows qualified procedures (e.g., low-hydrogen electrodes, proper preheat), PWHT may not be mandatory for non-critical structures.
3. Key Considerations
Material Certification: Check if the Q460NH supplier specifies PWHT requirements.
Standards Compliance: Refer to codes like AWS D1.1, EN 1011-2, or project specifications.
