Duplex stainless steel pipe generally refers to a steel composed of 50% Ferritic and 50% Austenitic phase structure. This composition gives them a better strength than either Ferritic or Austenitic steels. Duplex stainless steel has excellent pitting corrosion resistance and is also a nickel-saving stainless steel.
HT PIPE supplys the ASME SA789 and ASME SA790 Duplex Stainless Steel Pipe and tube materials for the Oil and Gas, Refinery, Petrochemical and Power Industries as S31803 Duplex steel Pipe, 2205 Duplex steel Pipe, S32750 Super Duplex steel Pipe, S32760 Super Duplex steel Pipe.
ASME SA789 /ASTM A789: Standard for Seamless and Welded Ferritic/Austenitic Stainless Steel Tubing for General Service.
ASME SA790 /ASTM A790: Standard Specification for Seamless and Welded Ferritic/Austenitic Stainless Steel Pipe.
Duplex and super duplex stainless steels are weldable.
Standard duplex: UNS S31803, S32205
Super duplex: S32750 (2507), UNS S32760
The differences between duplex/super duplex pipes:
WHAT IS DUPLEX STEEL?
Duplex stainless steel (UNS S31803/UNS S32205) has been developed to overcome the issues of the 300 series stainless steels, it has stronger resistance to seawater corrosion compared to stainless steel 316.
Note that, despite Duplex stainless steel shows good high-temperature oxidation resistance, 2205 suffers from embrittlement if kept at temperatures above 300ºC for some period of time. (a situation that can be rectified only by a full solution annealing treatment). For this reason, Duplex stainless steels are never used for temperatures in excess of 300ºC.
UNS2205 duplex steel finds application in marine projects, oil & gas exploration, closed loops water systems, desalinization plants, hydrocarbons storage and transportation, downstream refining, pulp, and paper.
SUPER DUPLEX PIPE, WHAT IS SUPER DUPLEX?
Super duplex stainless steel is a variation of the duplex steel alloy which is used in the oil & gas, chemical, power generation, mechanical and desalination industries. The higher chromium and molybdenum content of Super Duplex compare to Duplex makes it extremely resistant to uniform corrosion by organic acids like formic and acetic acid. Super Duplex also provides excellent resistance to inorganic acids, especially those containing chlorides.
 A790 S32750 Super Duplex Pipe |
 A789 S31803 Tube |
 A790 UNS S31803 Pipe |
 Seamless Duplex SS Tube |
 Super Duplex S32205 Pipe |
 Super Dupex S32760 Pipe |
Duplex steel Pipe & Tube Chemical Composition:
| Grade |
C≤ |
Mn≤ |
P≤ |
S≤ |
Si≤ |
Ni |
Cr |
Mo |
N |
Cu |
| S31803 |
0.03 |
2.00 |
0.03 |
0.02 |
1.00 |
4.5–6.5 |
21.0–23.0 |
2.5–3.5 |
0.08–0.20 |
- |
| S32205 |
0.03 |
2.00 |
0.03 |
0.02 |
1.00 |
4.5–6.5 |
22.0–23.0 |
3.0–3.5 |
0.14–0.20 |
- |
| S32750 |
0.03 |
1.20 |
0.035 |
0.02 |
0.80 |
6.0-8.0 |
24.0-26.0 |
3.0-5.0 |
0.24-0.32 |
0.5 |
| S32760 |
0.05 |
1.00 |
0.03 |
0.01 |
1.00 |
6.0-8.0 |
24.0-26.0 |
3.0-4.0 |
0.20-0.30 |
0.50–1.00 |
Duplex steel Pipe & Tube Mechanical Properties:
| Mechanical properties |
Tensile,min,ksi[MPa] |
Yield,min,ksi[MPa] |
Elongation,%(min) |
Hardness,HB(max) |
| S31803 |
90 [620] |
65 [450] |
25 |
290 |
| S32205 |
95 [655] |
65 [450] |
25 |
290 |
| S32750 |
116 [800] |
80 [550] |
15 |
300 |
| S32760 |
109 [750] |
80 [550] |
25 |
300 |
Duplex Stainless steel pipes are manufactured according to the ASME B36.19 standard.
DUPLEX PIPE：S31803 Pipe, S32205 Pipe
SUPER DUPLEX PIPES: S32750 Pipe, S32760 Pipe
Duplex pipes and Super Duplex pipes match the following fittings materials: ASTM A815 (butt weld fittings) and ASTM A182 F51 / F53 / F55 / F60 (flanges / forged socket weld and threaded fittings).
Tension Test, Flattening Test, Hardness Test, or Bend Test; Hydrostatic Test or nondestructive electric test.
Applications:
Chemical processing, transport and storage, Oil and gas exploration and processing equipment, Effluent scrubbing systems, Food processing equipment, Cargo tanks for ships and trucks, Biofuels plants
