DUPLEX SEAMLESS TUBES
- PRODUCT DETAIL
PRODUCT DESCRIPTION
ASME SA790 /ASTM A790: Standard Specification for Seamless and Welded Ferritic/Austenitic Stainless Steel Pipe.
ASME SA928 /ASTM A928 ：Standard Specification for Ferritic/Austenitic (Duplex) Stainless Steel Pipe Electric Fusion Welded with Addition of Filler Metal
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.
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.
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 |
Test:
Tension Test, Flattening Test, Hardness Test, or Bend Test; Hydrostatic Test or nondestructive electric test.