ASTM A234 Grade WPB is the world's most widely used buttweld fitting material. This complete guide covers everything — chemical composition, mechanical properties, temperature range, dimensions, and applications.
ASTM A234 is the American Society for Testing and Materials standard covering wrought carbon steel and alloy steel fittings for moderate and elevated temperature service. Grade WPB (Wrought Pipe, Grade B) is the most commonly specified grade — covering general service carbon steel buttweld fittings from -29°C to 427°C (-20°F to 800°F).
WPB fittings are manufactured by forging, extrusion, or forming from seamless or welded pipe or plate. Every fitting is marked with manufacturer's name, material grade, size, schedule, and heat number for traceability.
| Element | Requirement |
|---|---|
| Carbon (C) | 0.30% max |
| Manganese (Mn) | 0.29–1.06% |
| Phosphorus (P) | 0.050% max |
| Sulfur (S) | 0.058% max |
| Silicon (Si) | 0.10% min |
| Chromium (Cr) | 0.40% max |
| Molybdenum (Mo) | 0.15% max |
| Nickel (Ni) | 0.40% max |
| Copper (Cu) | 0.40% max |
| Vanadium (V) | 0.08% max |
| Property | Requirement |
|---|---|
| Tensile Strength (min) | 415 MPa (60,000 psi) |
| Yield Strength (min) | 240 MPa (35,000 psi) |
| Elongation (min) | 22% in 2 inches |
| Reduction of Area (min) | 30% |
| Hardness (max) | 197 HBW |
| Parameter | Value |
|---|---|
| Material Standard | ASTM A234 / ASME SA234 |
| Grade | WPB |
| Dimensional Standard | ASME B16.9 |
| Min Design Temperature | -29°C (-20°F) |
| Max Design Temperature | 427°C (800°F) |
| Size Range | ½" NB to 48" NB |
| Schedules Available | Sch 10 to XXS |
| Certificate | EN 10204 3.1 MTC |
| Heat Treatment | Normalized or as-rolled |
| Service Condition | WPB Suitable? | Alternative |
|---|---|---|
| -29°C to 427°C general service | ✓ Yes — ideal | — |
| Below -29°C | ✗ No | LTCS WPL6 (-46°C) or WPL3 (-73°C) |
| Above 427°C | ✗ No | WP11, WP22, or WP91 |
| Corrosive fluid service | ✗ No | SS 304L or SS 316L |
| Seawater service | ✗ No | CuNi 90/10 or Duplex S31803 |
| H₂S sour service | Conditional — NACE MR0175 | Duplex or SS 316L |
| Dry gas, steam, water pipelines | ✓ Yes — standard choice | — |
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