ASTM A234

Covers — wrought carbon- and alloy-steel butt-welding fittings (elbows, tees, reducers, caps): grades WPB/WPC (carbon) and WP1/WP11/WP22/WP5/WP9/WP91 (alloy) for moderate and elevated temperature.

Does NOT cover (exclusions) — the following are governed elsewhere:

• Austenitic stainless butt-weld fittings → ASTM A403.
• Low-temperature (impact-tested) fittings → ASTM A420 (WPL6).
• Forged (socket-weld/threaded) fittings → ASTM A105 + ASME B16.11.
• Fitting dimensions and ratings → ASME B16.9.

A234 is the material; the buttweld-fitting dimensions/ratings come from ASME B16.9.

A234 sets minimum requirements for the fitting material:

• Chemistry — carbon or chrome-moly composition per grade (WPB carbon; WP11/WP22 = 1¼Cr/2¼Cr-Mo).
• Mechanical Properties — grade tensile/yield/elongation.
• Heat Treatment — required post-forming heat treatment (normalize/temper or anneal) to restore properties, mandatory for alloy grades.
• Testing — tension testing and, where specified, hardness and NDE; heat certification with PMI for alloys.

ASTM A234 is the standard material for wrought carbon- and alloy-steel butt-welding fittings — the elbows, tees, and reducers that make up a welded piping system. WPB is the carbon-steel default; WP11/WP22/WP91 match the chrome-moly A335 pipe grades for high-temperature service.

Because fittings are hot- or cold-formed, the specified post-forming heat treatment is essential to restore mechanical properties, particularly for alloy grades. Fitting dimensions and ratings come from ASME B16.9.

Engineering Note: Match the fitting grade to the pipe: a WP22 fitting on A335 P22 pipe keeps the weld and the base metal compatible for creep service.