What is A790 pipe?
ASTM is the American Society for Testing and Materials, and A790 is the 'Standard Specification for Seamless and Welded Ferritic/Austenitic Stainless Steel Pipe'. This general specification for supply defines the composition and mechanical property requirements for seamless and straight seam-welded steel pipe.
What is ASTM A790 UNS S31803 material?
ASTM A790 S31803 (Duplex 2205) pipe is a duplex stainless steel. UNS S31803 duplex stainless steel pipe offers excellent corrosion resistance, far exceeding that of grade 316. It resists localized corrosion types such as intergranular, crevice, and pitting corrosion. With a sustained ignition temperature (CPT) of approximately 35°C, this type of stainless steel is well-suited for use in harsh environments such as the oil and gas, chemical, and marine industries.
EN 10204 3.2 certification indicates that the material has been third-party inspected and certified to meet the specified standard. This means that a certified inspector (independent of the manufacturer) has verified that the pipe meets the chemical, mechanical, and dimensional requirements of the ASTM A790 standard and EN 10204 3.2.
Chemical Composition (Wt. %) – Optimized for Corrosion Resistance
Table: Balanced Chemistry of S31803 Duplex Steel Pipe
| Element | Min | Max | Target | Role in Performance |
|---|---|---|---|---|
| Cr | 21.0 | 23.0 | 22.0 | Pitting/Corrosion Resistance |
| Ni | 4.5 | 6.5 | 5.5 | Austenite Stability |
| Mo | 2.5 | 3.5 | 3.0 | Chloride Resistance |
| N | 0.08 | 0.20 | 0.15 | Strength & PRE Boost |
| Mn | - | 2.0 | 1.2 | Deoxidation |
| C | - | 0.030 | 0.02 | Weldability |
| S | - | 0.020 | 0.001 | Machinability |
| P | - | 0.030 | 0.025 | - |
| Fe | Balance |
Equivalent Grades – Global Compliance
Table: Cross-Standard Material Equivalents
| Standard | Grade | Common Name | Similarity |
|---|---|---|---|
| UNS | S31803 | Duplex 2205 | Identical |
| EN | 1.4462 | X2CrNiMoN22-5-3 | Direct Equivalent |
| ASME | SA790 | - | Parent Spec |
| GOST | 03Kh22N6M2 | - | Comparable |
| JIS | SUS 329J3L | - | Near Match |
Mechanical Properties – Engineered for Extreme Service
Table: Room-Temperature Mechanical Properties per ASTM A790
| Property | Requirement | Typical Value | Advantage vs. 316L |
|---|---|---|---|
| Tensile Strength | ≥ 620 MPa | 750-895 MPa | +40% Higher |
| Yield Strength (0.2%) | ≥ 450 MPa | 550-625 MPa | 2x Higher |
| Elongation (%) | ≥ 25% | 28-35% | Superior Ductility |
| Hardness (Rockwell C) | ≤ 32 HRC | 28-32 HRC | Optimal for Sour Service |
| Impact Toughness | ≥ 100 J (-50°C) | ≥140 J | Arctic Readiness |
Dimensional Tolerances – Precision Manufacturing
Table: Permissible Variations per ASTM A790/ASME B36.19
| Parameter | Tolerance (Seamless Pipe) | Critical Application Focus |
|---|---|---|
| OD (Outer Diameter) | ±0.8% or ±0.2mm* | Fitting Compatibility |
| Wall Thickness | +20% / -12.5% | Pressure Integrity |
| Straightness | ≤ 0.2% of length | Offshore Installation |
| Cut Length | +3mm / -0mm | Welding Efficiency |
Application Domains – Where S31803 Duplex Excels
Corrosion-Demanding Environments:
Offshore Oil & Gas: Seawater injection lines, risers, umbilicals
Chemical Processing: Acid coolers, chloride-bearing reactors
Power Generation: FGD (Flue Gas Desulfurization) systems
Pulp & Paper: Bleach plants, digesters
Desalination Plants: High-salinity brine heaters
GNEE offers high-quality ASTM A790 S31803 welded and seamless pipes, featuring precise dimensional accuracy and a superior surface finish. S31803 welded and seamless pipes conform to ANSI B36.19 standards, with outside diameters ranging from NPS 1/8 to NPS 30 and wall thicknesses including Sch 5S, Sch 10S, Sch 40S, and Sch 80S. Other sizes are available upon request. ASTM A790 pipes are subject to external and wall thickness tolerances in accordance with ASTM A999. The pipes should be free of scale after pickling. Bright annealing eliminates the need for pickling.Mail:es@gescosteel.com
