Q1: What preheat is required for welding P91 (A335 P91) alloy pipes?
A: Minimum 400°F (204°C) to prevent cold cracking due to high hardenability.
Q2: Why is post-weld heat treatment necessary for AISI 4340 tubing?
A: PWHT at 1100-1200°F reduces residual stresses and restores toughness in HAZ.
Q3: What filler metal is used to weld 2205 duplex to API 5L X60?
A: ER309L or E2209 filler with proper dilution control to maintain corrosion resistance.
Q4: How is bending radius limited for DOM 1026 hydraulic tubing?
A: Minimum bend radius = 3× OD for thin-wall tubes to avoid wall collapse or wrinkling.
Q5: What causes sensitization in 304H during welding and how is it mitigated?
A: Chromium carbide precipitation at grain boundaries; mitigated by using 347 (Nb-stabilized).
