ASTM A789 UNS S31803 S32750 S32760 Duplex Stainless Steel Tubing
What is ASTM A789?
ASTM A789/A789M covers the nominal wall thickness grades and standard requirements for stainless steel pipe for general corrosion-resistant applications, with particular emphasis on resistance to stress corrosion cracking. These steels are susceptible to embrittlement when subjected to prolonged use at elevated temperatures.
ASTM A789 specifies duplex and austenitic-ferritic stainless steel tubing for services requiring general corrosion resistance, particularly against stress corrosion cracking (SCC). The listed UNS grades S31803 (standard duplex), S32750, and S32760 (super duplex) are specific alloys with high strength, good toughness, and excellent resistance to pitting and crevice corrosion. They are used in harsh environments such as chemical processing, oil and gas, and seawater applications where high pressure, corrosive elements, and high temperatures may be present.
ASTM A789 Duplex Stainless Steel Tubing Specifications
| Type | Seamless Tubing |
|---|---|
| Specification | ASTM A789, ASME SA789 |
| Grades | UNS S31803, S32750, S32760 |
| Outside Diameter | 6 – 610 mm |
| Wall Thickness | 0.5 – 30 mm, Average Wall Or Minimum Wall |
| Length | Specific or Rando, standard 6000 mm length |
| Condition | Annealing Pickling, Beight Annealing |
| Form: | Round, Coiled Tubing |
| Application | Heat Exchanger, Boiler, Water, High Pressure, Ornamental Purpose |
| Manufacturing Method | Cold Rolling, Cold Drawn |
SA789 Duplex Steel Chemical Composition
| UNS Designation | C | Mn | P | S | Si | Ni | Cr | Mo | N | Cu | Others |
|---|---|---|---|---|---|---|---|---|---|---|---|
| S31803 | 0.030 | 2.00 | 0.030 | 0.020 | 1.00 | 4.5–6.5 | 21.0–23.0 | 2.5–3.5 | 0.08–0.20 | . . . | . . . |
| S32205 | 0.030 | 2.00 | 0.030 | 0.020 | 1.00 | 4.5–6.5 | 22.0–23.0 | 3.0–3.5 | 0.14–0.20 | . . . | . . . |
| S32750 | 0.030 | 1.20 | 0.035 | 0.020 | 0.80 | 6.0–8.0 | 24.0–26.0 | 3.0–5.0 | 0.24–0.32 | 0.50 |
Heat Treatment
| UNS Designation | Temperature °F [°C] | Quench |
|---|---|---|
| S31803 | 1870–2010 [1020–1100] | Rapid Cooling In Air Or Water |
| S32205 | 1870–2010 [1020–1100] | Rapid Cooling In Air Or Water |
| S32750 | 1880–2060 [1025–1125] | Rapid Cooling In Air Or Water |
| S32760 | 1960–2085 [1070–1140] | Rapid Cooling In Air Or Water |
ASTM A789 Duplex Stainless Steel Tubing Mechanical Properties
| Grade | Tensile Strength (MPa) | Yield Strength 0.2% (MPa) | Elongation (%) | Hardness, HB (max) | Hardness, HRB (max) |
|---|---|---|---|---|---|
| UNS S31803 | ≥ 620 | ≥ 450 | ≥ 25 | 290 | 97 |
| UNS S32750 | ≥ 795 | ≥ 550 | ≥ 25 | 310 | 100 |
| UNS S32760 | ≥ 750 | ≥ 550 | ≥ 25 | 310 | 100 |
What is the difference between uns S31803 and uns S32760?
UNS S31803 have a tensile strength of around 620 MPa and yield strength of 450 MPa. Super Duplex Steel S32760 possess a tensile strength of 750 MPa and yield strength of 550 MPa and thus they are suited for high pressure applications.
What's the difference between S31803 and S32205?
S32205 is an improved version of S31803, containing higher levels of chromium, molybdenum, and nitrogen to enhance mechanical properties such as corrosion resistance and strength. Both grades are duplex stainless steels with a 22% chromium content, but S32205's higher alloy content offers improved performance, especially in harsh environments, and it can be dual-certified with S31803. While S31803 is generally less expensive, S32205 is often preferred for demanding applications such as chemical processing and papermaking.
We offer ASTM A789, UNS S31803, S32750, and S32760 duplex stainless steel pipe in various sizes. ASTM A789 is the standard for duplex steel piping, including both welded and seamless stainless steel pipe. Duplex steels offer high strength and excellent corrosion resistance, making them suitable for harsh environments. UNS S32750 and S32760 are superduplex steels with excellent mechanical properties, often allowing thinner-walled duplex steels to achieve the same design strength as thicker-walled nickel alloys.
