Q1: Why does A312 TP347 require Nb-stabilized filler?
A1: Nb (niobium) stabilization prevents chromium carbide formation in HAZ, maintaining corrosion resistance.
Q2: What preheat/PWHT is needed for A335 P11 welded pipes?
A2: Preheat to 150–200°C; PWHT at 650–700°C for 1 hour per inch thickness.
Q3: How to weld A335 P91 for high-temperature service?
A3: Use matching filler ER90S-B9, strict control of preheat (200°C), interpass temp (300°C max), and mandatory PWHT at 760°C.
Q4: What is the risk of cold cracking in A335 P22 welds?
A4: High due to Cr-Mo content; use low-hydrogen processes, preheat to 175°C minimum, and immediate PWHT after welding.
Q5: How to maintain ferrite-austenite balance in A790 S31803 welds?
A5: Use over-alloyed filler (e.g., ER2209), control heat input 0.5–1.5 kJ/mm, and avoid interpass temperature above 150°C.
