Duplex Stainless Steel Pipes
A duplex stainless steel pipe with dual-phase ferrite-austenite structure, double the strength of 304/316L, excellent chloride and SCC resistance, for oil and gas, marine, and chemical applications.
Product Introduction
1. Brief Introduction
Duplex Stainless Steel (DSS) possesses a dual-phase microstructure (approx. 50% ferrite + 50% austenite). It combines the advantages of ferritic stainless steel (high strength, SCC resistance) and austenitic stainless steel (toughness, weldability). Duplex pipes feature double yield strength compared with 304 / 316L, excellent resistance to chloride pitting, crevice corrosion and stress corrosion cracking.
Main Application: Oil & gas, seawater desalination, marine engineering, chemical processing, flue gas desulfurization (FGD), heat exchangers, pulp & paper industry.
2. Global Executed Standards for Duplex Steel Pipes
ASTM / ASME Standards (Most widely used for international trade)
- ASTM A790 / ASME SA790: Seamless & welded duplex stainless steel PIPE (for pipeline, large diameter)
- ASTM A789 / ASME SA789: Seamless & welded duplex stainless steel TUBING (heat exchanger tubes, small bore)
- ASTM A928 / ASME SA928: Electric-fusion welded duplex pipe with filler metal
- ASME B36.19M: Stainless steel pipe dimensions (NPS, Schedule OD & WT)
European EN Standards
- EN 10216-5: Seamless pressure tubes of stainless steel
- EN 10217-7: Welded pressure tubes of stainless steel
Chinese Standard
- GB/T 21833: Austenitic-ferritic duplex stainless steel seamless pipes
3. Common Commercial Duplex Grades & Equivalent Designations
| Common Name | UNS No. | EN No. | EN Material Designation | Grade Category | PREN Value |
|---|---|---|---|---|---|
| 2304 | S32304 | 1.4362 | X2CrNiN23-4 | Lean Duplex | 24~26 |
| 2205 | S32205 (S31803) | 1.4462 | X2CrNiMoN22-5-3 | Standard Duplex | 30~35 |
| 2507 | S32750 | 1.4410 | X2CrNiMoN25-7-4 | Super Duplex | >40 |
| 2760 | S32760 | 1.4501 | X2CrNiMoCuWN25-7-4 | Super Duplex | >40 |
Definition:
- Lean Duplex: Low Mo, cost-effective for mild chloride environment
- Standard Duplex (2205): The most popular universal grade
- Super Duplex (2507 / 2760): For severe seawater & high chloride corrosive conditions
4. Chemical Composition (Max %, Heat Analysis)
| Element | S32304 (2304) | S32205 (2205) | S32750 (2507) | S32760 (2760) |
|---|---|---|---|---|
| C | ≤0.03 | ≤0.03 | ≤0.03 | ≤0.03 |
| Si | ≤1.00 | ≤1.00 | ≤0.80 | ≤1.00 |
| Mn | ≤2.00 | ≤2.00 | ≤1.20 | ≤1.00 |
| P | ≤0.040 | ≤0.035 | ≤0.035 | ≤0.030 |
| S | ≤0.030 | ≤0.015 | ≤0.020 | ≤0.010 |
| Cr | 21.5–24.5 | 21.0–23.0 | 24.0–26.0 | 24.0–26.0 |
| Ni | 3.0–5.5 | 4.5–6.5 | 6.0–8.0 | 6.0–8.0 |
| Mo | 0.05–0.60 | 2.5–3.5 | 3.0–5.0 | 3.0–4.0 |
| N | 0.05–0.20 | 0.08–0.20 | 0.24–0.32 | 0.20–0.30 |
| Cu | — | — | — | 0.50–1.00 |
| W | — | — | — | 0.50–1.00 |
| Fe | Balance | Balance | Balance | Balance |
5. Room Temperature Mechanical Properties (Solution Annealed Condition)
| Property | Unit | S32304 | S32205 | S32750 | S32760 |
|---|---|---|---|---|---|
| Tensile Strength, Rm ≥ | MPa | 600 | 620 | 800 | 750 |
| Yield Strength Rp0.2 ≥ | MPa | 400 | 450 | 550 | 550 |
| Elongation A5 ≥ | % | 25 | 25 | 25 | 25 |
| Max Brinell Hardness | HB | 260 | 290 | 310 | 310 |
| Charpy V-notch Impact (-46°C) ≥ | J | 60 | 100 | 100 | 100 |
Delivery Status: Solution annealed + water quenched
Heat treatment temperature range: 1020 ~ 1100 ℃
6. Pipe Dimension & Production Scope
Form: Seamless Pipe / Welded Pipe
- Outer Diameter Range: 6 mm ~ 610 mm
- Wall Thickness: 1.0 mm ~ 30 mm
- Standard Schedule: SCH10, SCH20, STD, SCH40, SCH80, SCH160, XXS
- Standard Length: 6 m / 12 m fixed length or random length
- Tolerance: Compliant with ASME B36.19, ASTM A790