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ASTM A790 S31803 / S32750 / S32205 / S31254 Duplex Steel Pipes for Industrial Application
This standard is the standard specification for ferritic austenitic stainless steel pipes used in corrosive environments. ASTM A790 specifies the elements and requirements for the manufacturing of seamless and welded pipes, and requires the welding of dual phase steel and super dual phase steel pipes without adding any filler metal.
When using UNS S31803, S32205, S32750, S32760, and S32520 duplex steel materials to produce steel pipes, corrosion testing should be supplemented. The ASTM A790 standard covers steel pipes with diameters ranging from 1/8 "(10.29mm) to 30" (762.0mm) and wall thicknesses ranging from 1.24mm to 12.7mm. Based on ANSI B36.10 for steel pipes, larger diameter steel pipes can be provided according to the A790 standard.
What material is S31803?
S31803 is the Unified Numbering System (UNS) name for the original duplex stainless steel. The UNS system was jointly created by multiple trading groups in the 1970s to reduce confusion caused by the same alloy being referred to as different things, and vice versa. Each metal is represented by a letter followed by five numbers, where the letter represents the metal series and S represents stainless steel.
Duplex stainless steel was developed in the 1930s for use in Paper mill where lower alloy grades are not required to have adequate corrosion resistance. Based on a 22% chromium content, they have a combination of austenite and ferrite microstructures, providing higher strength, corrosion resistance, and cost-effectiveness.
The UNS S31803 (ASTM F51) specification has been largely replaced by UNS S32205 (1.4462, ASTM F60). This reflects their desire to maximize the corrosion performance of the alloy, thanks to the development of AOD steelmaking technology, which allows for stricter control of composition. In addition, it also allows for the addition level of nitrogen to be affected, rather than simply being present as a background element. Therefore, the highest performing dual phase steel seeks to maximize the content of chromium (Cr), molybdenum (Mo), and nitrogen (N).In most environments (including seawater), S31803 has better corrosion resistance than austenitic grades (such as alloy 316L). This brand has excellent resistance to intergranular corrosion, pitting and Crevice corrosion, and resistance to chloride stress corrosion cracking at temperatures up to 150 º C.UNS S31803 is a ferritic austenitic stainless steel that combines many beneficial characteristics of ferrite and austenitic steel. Due to the high content of chromium and molybdenum, this steel has excellent pitting corrosion and uniform resistance to stress corrosion cracking corrosion, as well as high mechanical strength.UNS S31803 has good weldability and can be welded using most welding techniques of stainless steel. Due to the balanced composition, when welding correctly, the heat affected zone contains sufficient austenite to avoid the risk of local corrosion.
ASTM A789/A789M-20 Standard Specification for Seamless and Welded Ferritic/Austenitic Stainless Steel Tubing for General Service.
| Specifications | ASTM A790 / ASME SA790, ASTM A789 / ASME SA A789 |
| Standards | ASTM, ASME and API |
| Size | 1/2″NB TO 12″NB IN |
| Schedule | SCH20, SCH30, SCH40, STD, SCH80 |
| Type | Seamless / ERW / Welded / Fabricated |
| Form | Round Tubes, Custom Tubes, Square Tubes, Rectangular Tubes, “U” Shape, Hydraulic Tubes |
| Length | Single Random, Double Random & Cut Length. |
| End | Plain End, Beveled End, Treaded |
Chemical Composition
| Grade | C | Mn | Si | P | S | Cr | Mo | Ni | N | |
| 2205 (UNS S31803) | Min Max | – 0.030 | – 2.00 | – 1.00 | – 0.030 | – 0.020 | 21.0 23.0 | 2.5 3.5 | 4.5 6.5 | 0.08 0.20 |
| 2205 (UNS S32205) | Min Max | – 0.030 | – 2.00 | – 1.00 | – 0.030 | – 0.020 | 22.0 23.0 | 3.0 3.5 | 4.5 6.5 | 0.14 0.20 |
Mechanical Properties
| Grade | Tensile Strength (MPa) min | Yield Strength 0.2% Proof (MPa) min | Elongation (% in 50mm) min | Hardness | |
| Rockwell C (HR C) | Brinell (HB) | ||||
| UNS S31803 / 2205 | 621 | 448 | 25 | 31 max | 293 max |
| UNS S32205 / 2205 | 621 | 448 | 25 | 31 max | 293 max |
ASTM A790 Duplex Steel Pipes Applications
1. Chemical processing, Transport and Storage.
2. Oil and gas exploration and offshore rigs.
3. Oil and gas refining.
4. Marine environments.
5. Pollution control equipment.
6. Pulp and paper manufacturing.
7. Chemical process Plant.
