Specification reference for wrought ferritic-austenitic stainless steel piping fittings
ASTM A815 / A815M covers wrought ferritic, ferritic-austenitic, and martensitic stainless steel piping fittings produced by hot-forming or cold-forming from pipe, tube, plate, or bar feedstock. The standard accepts Ferralium 255 (UNS S32550) under the WP-S32550 grade designation, alongside standard duplex (WP-S32205, WP-S31803), super duplex 2507 (WP-S32750), and Zeron 100 (WP-S32760). Buttweld dimensional follows ASME B16.9 and socketweld follows ASME B16.11 class 3000 / 6000 / 9000. Each fitting is supplied solution-annealed at 1040 to 1120 °C with rapid water quench, hardness ≤ 32 HRC for NACE MR0175 sour-service compliance, ferrite content within 35 to 55% per ASTM E562. The standard explicitly requires that the supplier verify that hot-forming did not push the fitting through the sigma-phase precipitation window without subsequent re-solution-anneal.
| Test | Method | Frequency |
|---|---|---|
| Chemistry | Heat analysis | Per heat |
| Tensile | ASTM A370 / E8 | Per heat per fitting type per finishing lot |
| Hardness | ASTM E18 (HRC) | Per heat per finishing lot |
| Microstructure / ferrite content | ASTM E562 point count | Per heat per fitting type |
| S2 intergranular corrosion (supplementary) | ASTM A262 method E | Per heat where specified |
| S5 NDE | UT, MT, PT, RT (per supplementary requirement) | Per finishing lot |
| S7 Charpy V-notch (supplementary) | ASTM E23, qualifying temperature | Per heat where specified |
| S58 NACE MR0175 conformance documentation | Per Table A.10 | Where sour service is the project requirement |
Hot-forming for super duplex fittings (elbow drawing, tee branching, reducer expansion) is performed in the 1050 to 1200 °C austenitisation range with finish-form temperature held above 950 °C. The 600 to 950 °C window is the sigma-phase precipitation range, and any fitting that dwells in that window during forming or cooling without subsequent re-solution-anneal will fail the ferrite-content acceptance and the intergranular corrosion supplementary test. The standard supply route is: form at temperature, transfer to solution-anneal furnace at 1080 °C for 30 minutes per inch of cross-section, water quench within 90 seconds. The MTC documents the heat-treat record including time-at-temperature and quench-completion time.
