ASTM A790 S31803 Duplex Stainless Steel Pipe for Oil and Gas
Product Overview
ASTM A790 S31803 duplex stainless steel pipe is manufactured from UNS S31803, a ferritic-austenitic stainless steel commonly associated with Duplex 2205. Its dual-phase microstructure combines austenitic and ferritic structures, providing a balance of mechanical strength and corrosion resistance.
With approximately 22% chromium, 5% nickel, and 3% molybdenum, S31803 offers good resistance to general corrosion, pitting, crevice corrosion, and chloride-induced stress corrosion cracking.
ASTM A790/A790M covers seamless and straight-seam welded ferritic/austenitic stainless steel pipe intended for general corrosive service. S31803 is commonly used in oil and gas facilities, chemical processing plants, marine engineering, and industrial piping systems.
Technical Specifications
| Item | Description |
|---|---|
| Product Name | Duplex Stainless Steel Pipe |
| Material Grade | S31803 |
| UNS | S31803 |
| Common Grade Name | Duplex 2205 |
| Material Classification | Duplex Stainless Steel |
| Standard | ASTM A790/A790M |
| ASME Standard | ASME SA790/SA790M, when specified |
| Manufacturing Type | Seamless or Straight-Seam Welded |
| Manufacturing Process | Hot Finished or Cold Finished, as applicable |
| Size | As per customer requirements |
| Outer Diameter | As per applicable pipe dimensions |
| Wall Thickness | As per schedule or customer requirements |
| Length | Random or specified length |
| Heat Treatment | Solution annealing |
| Surface Finish | Pickled or as agreed |
| Inspection | Applicable mechanical, dimensional, and nondestructive tests |
| Documentation | Material Test Certificate (MTC) |
Chemical Composition of UNS S31803
The chemical composition of ASTM A790 S31803 is controlled to maintain its duplex structure and corrosion-resistant properties.
| Element | Composition (%) |
|---|---|
| Carbon (C) | ≤ 0.030 |
| Manganese (Mn) | ≤ 2.00 |
| Silicon (Si) | ≤ 1.00 |
| Phosphorus (P) | ≤ 0.030 |
| Sulfur (S) | ≤ 0.020 |
| Chromium (Cr) | 21.0–23.0 |
| Nickel (Ni) | 4.5–6.5 |
| Molybdenum (Mo) | 2.5–3.5 |
| Nitrogen (N) | 0.08–0.20 |
Mechanical Properties
Typical minimum mechanical property requirements for ASTM A790 S31803 pipe are listed below.
| Property | Requirement |
|---|---|
| Tensile Strength | ≥ 620 MPa |
| Yield Strength (0.2% Offset) | ≥ 450 MPa |
| Elongation | ≥ 25% |
| Hardness | ≤ 290 HBW |
| Hardness | ≤ 30 HRC |
Key Characteristics of ASTM A790 S31803
High Mechanical Strength
S31803 offers higher yield strength than conventional austenitic stainless steel grades such as 304L and 316L. This property can provide design flexibility in applications where mechanical strength and pressure requirements are important.
Resistance to Chloride Stress Corrosion Cracking
The combination of ferritic and austenitic phases contributes to resistance against chloride-induced stress corrosion cracking. This makes S31803 a candidate material for selected industrial and marine environments.
Resistance to Pitting and Crevice Corrosion
Chromium, molybdenum, and nitrogen improve resistance to localized corrosion. S31803 is commonly selected for applications involving chloride-containing process fluids, although its suitability depends on actual operating conditions.
Duplex Microstructure
The material consists of both ferritic and austenitic phases. Proper solution heat treatment and controlled fabrication are important to maintain the intended microstructure and mechanical properties.
Manufacturing Process
ASTM A790 S31803 pipe can be manufactured through seamless or straight-seam welded processes.
Typical production and quality control stages include:
Raw material selection and chemical composition verification.
Pipe forming through the applicable manufacturing process.
Solution heat treatment according to the applicable specification.
Pickling or other agreed surface treatment.
Dimensional inspection and mechanical testing.
Applicable nondestructive examination and hydrostatic testing.
Final inspection, marking, and preparation of material documentation.
Actual manufacturing processes and inspection capabilities should be confirmed with the supplier before being stated as guaranteed services.
Applications of S31803 Duplex Stainless Steel Pipe
Oil and Gas: Process piping, production facilities, and selected corrosive service environments.
Chemical Processing: Pipelines and equipment handling compatible corrosive chemicals.
Marine Engineering: Selected piping systems exposed to chloride-containing environments.
Water Treatment: Industrial water treatment and selected desalination-related systems.
Pulp and Paper: Process equipment and pipelines exposed to corrosive chemicals.
Power Generation: Selected industrial process and utility systems.
Material selection should consider temperature, pressure, chloride concentration, chemical composition, and other operating conditions.
ASTM A790 S31803 vs. S32205
S31803 and S32205 are closely related duplex stainless steel grades commonly associated with Duplex 2205. However, their specified chemical composition limits differ.
| Comparison | S31803 | S32205 |
|---|---|---|
| Material Family | Duplex Stainless Steel | Duplex Stainless Steel |
| Common Name | Duplex 2205 | Duplex 2205 |
| Chromium | 21.0–23.0% | 22.0–23.0% |
| Nickel | 4.5–6.5% | 4.5–6.5% |
| Molybdenum | 2.5–3.5% | 3.0–3.5% |
| Nitrogen | 0.08–0.20% | 0.14–0.20% |
| Minimum Tensile Strength | 620 MPa | 655 MPa |
| Minimum Yield Strength | 450 MPa | 450 MPa |
S32205 has tighter minimum requirements for chromium, molybdenum, and nitrogen, as well as a higher minimum tensile strength. Although both grades are commonly referred to as Duplex 2205, they should not be treated as automatically interchangeable. The specified UNS grade and material test certificate should be checked against the project requirements.
S31803 vs. S32750 Super Duplex Stainless Steel
| Comparison | S31803 | S32750 |
|---|---|---|
| Material Category | Duplex | Super Duplex |
| Common Name | 2205 | 2507 |
| Chromium | 21.0–23.0% | 24.0–26.0% |
| Nickel | 4.5–6.5% | 6.0–8.0% |
| Molybdenum | 2.5–3.5% | 3.0–5.0% |
| Nitrogen | 0.08–0.20% | 0.24–0.32% |
| Minimum Yield Strength | 450 MPa | 550 MPa |
| Typical Selection | General duplex applications | More demanding chloride environments |
S32750 generally provides higher strength and localized corrosion resistance than S31803. The appropriate grade depends on the actual service environment, design requirements, and material cost.
