ASTM A815 / A815M — Wrought Duplex and Ferritic Stainless Steel Piping Fittings
ASTM A815/A815M (latest edition: A815M-23) is the primary specification for wrought ferritic, ferritic-austenitic (duplex), and martensitic stainless steel butt-welding pipe fittings. The ASME counterpart SA-815 is adopted in BPVC Section II Part A. A815 is the duplex companion to ASTM A403 (austenitic SS) — together they cover the full stainless steel fitting range. Products include elbows (LR/SR), tees, reducers, and caps to ASME B16.9 dimensions.
1. Scope
A815 covers three microstructural families: ferritic-austenitic (duplex) — the dominant group, comprising grades with 40–60% ferrite; ferritic — body-centred cubic (BCC) alloys without nickel; and martensitic grades (410, 420). The duplex grades provide approximately twice the yield strength of austenitic grades (ASTM A403) combined with superior resistance to chloride stress corrosion cracking (SCC).
2. Grade Designations
| Grade |
UNS No. |
Type |
PREN |
Typical Application |
| WP2304 |
S32304 |
Lean Duplex |
~26 |
Mildly corrosive service, cost-sensitive duplex applications |
| WP2205 (WP31803) |
S32205 / S31803 |
Standard Duplex |
~35 |
Seawater, desalination, chemical processing, offshore |
| WP2507 |
S32750 |
Super Duplex |
~43 |
FGD, highly aggressive chloride media, deep-sea umbilicals |
| WP2101 |
S32101 |
Lean Duplex (Mn) |
~26 |
Structural applications, cost-optimised with Mn replacing Ni |
| WP446 |
S44600 |
Ferritic |
~23 |
High-temperature oxidation resistance, NO₂ environments |
| WP430 |
S43000 |
Ferritic |
~18 |
Automotive, general corrosion-resistant service |
3. Chemical Composition
| Grade |
C max |
Cr |
Ni |
Mo |
N |
Others |
| WP2304 |
0.030 |
21.5–24.5 |
3.0–5.5 |
0.05–0.60 |
0.05–0.20 |
— |
| WP2205 |
0.030 |
21.0–23.0 |
4.5–6.5 |
2.5–3.5 |
0.08–0.20 |
— |
| WP2507 |
0.030 |
24.0–26.0 |
6.0–8.0 |
3.0–5.0 |
0.24–0.32 |
Cu 0.50 max |
| WP2101 |
0.040 |
19.5–21.5 |
1.35–1.70 |
0.10–0.80 |
0.20–0.25 |
Mn 4.0–6.0 |
| WP446 |
0.20 |
23.0–27.0 |
— |
— |
0.25 max |
N+C ≤0.25 |
4. Mechanical Properties
| Grade |
UTS min (MPa) |
YS min (MPa) |
Elong. min (%) |
Hardness max (HBW) |
| WP2304 |
600 |
400 |
25 |
290 |
| WP2205 |
620 |
450 |
25 |
293 |
| WP2507 |
795 |
550 |
15 |
310 |
| WP2101 |
655 |
450 |
30 |
290 |
| WP446 |
483 |
276 |
20 |
217 |
5. Heat Treatment — Solution Annealing
| Grade |
Solution Temp (°C) |
Cooling |
Target Ferrite % |
| WP2304 |
980–1080 |
Water quench |
40–65% |
| WP2205 |
1020–1100 |
Water quench (mandatory) |
40–60% |
| WP2507 |
1050–1150 |
Water quench (mandatory) |
40–60% |
| WP446 |
760–830 (anneal) |
Air cool |
N/A (fully ferritic) |
Duplex caution: Do not hold duplex grades in the 600–1000 °C range during cooling — sigma (σ) phase and chi (χ) phase precipitate rapidly, causing embrittlement and dramatic loss of corrosion resistance. Verify per ASTM A923 Practice A (sodium hydroxide etch) and Practice B (ferric chloride corrosion test).
6. Testing and Inspection
| Test |
Requirement |
| Tensile |
One test per heat or heat-treatment lot |
| Hardness |
Spot check per lot; 100% on WP2507 for critical service |
| Ferrite Content (duplex) |
ASTM A923 Practice A — magnetic or metallographic; ferrite ≥ 25% |
| Corrosion Test |
ASTM A923 Practice B (ferric chloride) — supplementary when specified |
| Impact Test (Charpy) |
ASTM A923 Practice C — ≥ 54 J at –40 °C for WP2205/WP2507 |
| Chemical Analysis |
One ladle analysis per heat |
| Visual & Dimensional |
100%; per ASME B16.9 / B16.28 |
7. Applications
| Industry |
Grade |
Reason |
| Seawater / offshore |
WP2205, WP2507 |
PREN ≥ 35, SCC resistance, high strength (weight saving) |
| Desalination (RO, MSF) |
WP2205, WP2507 |
Chloride pitting resistance at elevated temperature |
| Flue Gas Desulfurisation (FGD) |
WP2507 |
PREN > 40 required; sulphur-chloride combined attack |
| Oil & gas (subsea) |
WP2205, WP2507 |
High pressure, CO₂/H₂S, chloride SCC resistance |
| High-temperature oxidising |
WP446 |
Good oxidation resistance to 1100 °C, no creep requirement |
8. Related Standards
| Standard |
Description |
| ASTM A789 / ASME SA-789 |
Duplex SS seamless and welded tubing (companion tube specification) |
| ASTM A790 / ASME SA-790 |
Duplex SS seamless and welded pipe (companion pipe specification) |
| ASTM A182 F51/F53 |
Forged duplex SS flanges and fittings |
| ASTM A403 |
Wrought austenitic SS butt-welding fittings (companion austenitic spec) |
| ASTM A923 |
Detecting detrimental intermetallic phase in duplex stainless steels |
9. How to Order
| # |
Item |
Example |
| 1 |
Standard |
ASTM A815M-23 or ASME SA-815 |
| 2 |
Grade |
WP2205 or WP2507 |
| 3 |
Fitting type & NPS |
90° LR Elbow, NPS 6, Sch 40S |
| 4 |
Dimensional standard |
ASME B16.9 |
| 5 |
Heat treatment |
Solution annealed + water quenched (mandatory) |
| 6 |
Test requirements |
ASTM A923 ferrite check; Charpy –40 °C if required |
| 7 |
Certificate |
EN 10204 3.1 MTR with full chemical, mechanical, heat treatment record |
HT PIPE supplies ASTM A815 duplex stainless steel fittings in WP2205 and WP2507, NPS ½–48, solution-annealed with EN 10204 3.1 and NACE MR0175 compliance.
10. Frequently Asked Questions
Q1: Why is WP2507 harder to weld than WP2205?
WP2507's higher alloy content (Cr 25%, Mo 4%, N 0.28%) narrows the welding process window. Excessive heat input causes sigma-phase precipitation in the HAZ; insufficient heat input produces excess ferrite. AWS D10.18 and NORSOK M-601 set strict heat input limits (0.5–1.5 kJ/mm). Filler metal must be over-alloyed (e.g. ER2509 for 2507 base metal) to compensate for nitrogen loss in the arc.
Q2: Is A815 WP2205 suitable for H₂S sour service?
WP2205 is conditionally permitted for sour service per NACE MR0175/ISO 15156 Part 3, with hardness ≤ 310 HBW and operating temperature ≤ 232 °C. The duplex microstructure is susceptible to hydrogen embrittlement above 232 °C or under high H₂S partial pressures. Confirm with MR0175 Part 3 Table A.3 for exact temperature and H₂S limits before specifying.
