Why this matters
Heat treatment determines whether a buttweld fitting reaches its specified tensile, yield and toughness numbers, and whether it stays inside the allowable hardness window for sour service. ASTM A234 leaves the choice between annealing, normalizing, normalizing and tempering, or quench and temper open to the manufacturer for many size and grade combinations, which is exactly why procurement engineers need to understand the trade-offs.
Key technical facts
For ASTM A234 (covering WPB, WPC, WP1, WP5, WP9, WP11, WP12, WP22 and similar carbon and low-alloy buttweld fittings):
- Hot-formed fittings finished above approximately 980 degC (1800 degF) shall be subsequently annealed, normalized, or normalized and tempered.
- WPB and WPC fittings above NPS 12 produced by locally heating the stock for forming shall be subsequently annealed, normalized, or normalized and tempered.
- Cold-formed WPB fittings whose final forming is below approximately 620 degC (1150 degF) shall be normalized, or stress-relieved at 595-690 degC (1100-1275 degF).
For low-alloy grades (WP11, WP22, WP91), the standard typically requires normalizing and tempering; quench and temper is also permitted with documented temperatures.
