SS 347 is stabilized with niobium (columbium) and tantalum, offering improved high-temperature strength compared to SS 321. SS 347H (higher carbon variant) provides enhanced creep resistance, making i...
SS 347 is stabilized with niobium (columbium) and tantalum, offering improved high-temperature strength compared to SS 321. SS 347H (higher carbon variant) provides enhanced creep resistance, making it the preferred choice for refinery and petrochemical high-temperature piping. Widely specified in ASTM A358 welded pipe and A403 fittings for hydrogen reformers.
| Property | Value |
|---|---|
| Grade | SS 347 / 347H |
| ASTM / ASME | ASTM A403 WP347 / WP347H |
| UNS Number | S34700 / S34709 |
| Chromium (Cr) | 17–19% |
| Nickel (Ni) | 9–13% |
| Molybdenum (Mo) | — |
| Max/Min Service Temp | 950°C |
| Fitting Standard | ASME B16.9 / MSS SP-43 |
| Size Range | ½" NB to 48" NB |
| Certificate | EN 10204 3.1 MTC |
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