What is ASTM A789 UNS S31803 Duplex Steel Seamless Tube?
ASTM A789 S31803 is the standard specification for seamless and welded ferritic/austenitic stainless steel pipe for general purpose use. S31803 is a duplex stainless steel, meaning it has a dual-phase microstructure consisting of austenite and ferrite phases. ASTM A789 covers pipe with an outside diameter range of 1/8 inch to 5 inches and a wall thickness range of 0.015 inch to 0.500 inch.
GNEE supplies ASTM A789 UNS S31803 duplex steel seamless tubes, a standard duplex stainless steel material formed through hot piercing or hot extrusion followed by cold rolling/cold drawing and solution annealing treatment. These tubes are available in outer diameters of 12.7–114.3 mm (1/2"–4 1/2") (with options for larger custom sizes) and wall thicknesses of 0.89–3.0 mm. They are particularly suitable for high-temperature, high-pressure, and highly corrosive fluid environments containing chlorides or sulfides in boiler systems, such as boiler feedwater pipes, steam condensate return lines, and heat exchanger connection pipes.
ASTM A789 UNS S31803 Duplex Steel Seamless Tube For Boiler Specification
| Product Name: | Boiler Tube | Standard: | ASTM A789 / ASME SA789 |
|---|---|---|---|
| Material: | Duplex Steel | End: | Plain Ends/ Beveled Ends |
| Form: | Straight &U Bend | Type: | Seamless &Welded |
| Packing: | Plywood Case,Bundle | ||
| High Light: |
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Chemical Composition of ASTM A789 S31803
| Grade | C | Mn | S | P | Si | Ni | Cr | Mo | N | |
| S31803 | Min | 4.5 | 21.0 | 2.5 | 0.08 | |||||
| Max | 0.03 | 2.0 | 0.02 | 0.03 | 1.0 | 6.5 | 23.0 | 3.5 | 0.20 |
Mechanical Properies of ASTM A789 S31803
| Grade | Tensile Str Ksi(Mpa) | Yield Str Ksi(Mpa) | Elongation(%) | Brinell(HBW) | Rockwell C(HRC) |
| S31803 | ≥90(620) | ≥65(450) | ≥25 | ≥290 | ≥30 |
Wall Thickness Tolerance of ASTM A789
| OD Range | TYPE | Wall Thickness Tolerance | |
| Average | Mln. | ||
| 0~12.7mm (Incl.) | SMLS&WLD | (+/-15%) | (0,+30%) |
| 12.7~38.1mm (Incl.) | SMLS&WLD | (+/-10%) | (0,+20%) |
| 38.1~88.9mm (Incl.) | SMLS&WLD | (+/-10%) | (0,+20%) |
| 88.9~139.7mm(Incl.) | SMLS&WLD | (+/-10%) | (0,+20%) |
| 139.7~203.2mm(Incl.) | SMLS&WLD | (+/-10%) | (0,+20%) |
Length Tolerance of ASTM A789
| Length Tolerance | |||
| Range(m) | TYPE | OD range | Tolerance |
| 0~24ft (7.3m Incl.) | SMLS+Hot Finished | All Sizes | 0,+5mm |
| 0~24ft (7.3m Incl.) | SMLS+Cold Finished | <50.8mm | 0,+3mm |
| 0~24ft (7.3m Incl.) | SMLS+Cold Finished | 50.8mm(Incl.) to Up | 0,+5mm |
| 0~24ft (7.3m Incl.) | WLD | <50.8mm | 0,+3mm |
| 0~24ft (7.3m Incl.) | WLD | 50.8mm(Incl.) to Up | 0,+5mm |
Why Choose Gnee
Gnee is a leading manufacturer and exporter of UNS S31803 Duplex Steel Seamless Tube, supplying over 1,000 tons annually to chemical, marine, and aerospace industries.
Our Advantages:
✅ ISO, SGS, and BV certified production
✅ Customized dimensions and surface finishes
✅ Advanced TIG and plasma welding lines
✅ Competitive factory prices and fast delivery (7–15 days)
✅ Export packaging: wooden cases, moisture-proof wrapping, and pallet protection
Packaging & Delivery
Each pipe is packed with:PE plastic film and moisture-proof treatment,Bubble wrapping and wooden box reinforcement,Clear labeling with grade, dimensions, and heat number.
