Home / Products / Stainless Steel Pipe / UNS S31803 Seamless Pipe ASTM A789 4" Schedule 40 Stainless Steel Pipe
Quality UNS S31803 Seamless Pipe ASTM A789 4" Schedule 40 Stainless Steel Pipe factory
Quality UNS S31803 Seamless Pipe ASTM A789 4" Schedule 40 Stainless Steel Pipe factory

UNS S31803 Seamless Pipe ASTM A789 4" Schedule 40 Stainless Steel Pipe

Basic Properties
Place of Origin: MADE IN CHAINA
Brand Name: Baosteel，TISCO
Certification: EN 10204 Type 3.1 / 3.2 available
Model Number: 201 / 202 / 301 / 302 / 303 / 304 / 304L / 305 / 309S / 310S / 316 / 316L / 317 / 317L / 321 / 347 / 409L / 410 / 420 / 430 / 440C / 2205 / 2507
Trading Properties
Minimum Order Quantity: 100kg
Price: Negotiable (Request a Quote)
Payment Terms: T/T，D/P，D/A，Western Union，PayPal
Supply Ability: 10000tons
Tags

Molybdenum Alloy Stainless Steel Pipe

Stainless Steel Pipe Chloride Resistance

S31803 Seamless Pipe Sch 40
Product Summary
UNS S31803 duplex stainless steel pipe is a widely used duplex grade that offers a balanced mix of good strength, excellent corrosion resistance, and cost-effectiveness. It is the original standard duplex stainless steel, commonly specified in ASTM A790 and ASTM A789 for both seamless and welded ...

Product Details

Highlight:

S31803 Seamless Pipe Sch 40

,

S31803 Seamless Pipe ASTM A789

,

4" Schedule 40 Stainless Steel Pipe
Country Of Origin: MADE IN CHAINA
Brand: Baosteel，TISCO
Certifications: ISO/EN 10204 Type 3.1 / 3.2 Available
Grade: 201 / 202 / 301 / 302 / 303 / 304 / 304L / 305 / 309S / 310S / 316 / 316L / 317 / 317L / 321 / 347 / 409L / 410 / 420 / 430 / 440C / 2205 / 2507 / 630 (17-4PH)
MOQ: 100kg
Price: Negotiable (Request A Quote)
Packaging: Wooden Case / Wooden Pallet / Steel Frame / Carton / Woven Bag
Delivery Time: 15-25days
Payment Terms: T/T，D/P，D/A，Western Union，PayPal
Supply Capacity: 10000tons
Product Description

UNS S31803 duplex stainless steel pipe is a widely used duplex grade that offers a balanced mix of good strength, excellent corrosion resistance, and cost-effectiveness. It is the original standard duplex stainless steel, commonly specified in ASTM A790 and ASTM A789 for both seamless and welded pipe applications.
With a dual-phase microstructure (austenite + ferrite), UNS S31803 provides approximately twice the yield strength of 304 or 316L austenitic stainless steels, while maintaining good weldability and fabricability.

Available Sizes – UNS S31803 Pipe
Parameter Range
Outer Diameter (OD) 6.0 mm – 610 mm (1/4″ – 24″)
Wall Thickness (WT) 0.5 mm – 50 mm (Schedule 5S – XXS)
Length Customized (up to 12 meters or as required)
Type Seamless / Welded
End Finish Plain end, beveled end, threaded, or grooved
Key Features of UNS S31803 Duplex Pipe
FeatureDescription
High Yield StrengthMinimum 450 MPa (65 ksi) – 2x stronger than 316L
Good Corrosion ResistanceResistant to pitting, crevice corrosion, and stress corrosion cracking (SCC)
Chloride ResistanceSuitable for brackish water, seawater, and high-chloride environments
WeldableCan be welded using standard methods with proper filler (e.g., 2209)
Cost-EffectiveLower cost than super duplex grades (e.g., 2507) and nickel-based alloys
Wide Temperature RangeServiceable from -50°C to 300°C depending on conditions
UNS S31803 vs UNS S32205
Comparison: S31803 vs S32205 (2205)
ElementUNS S31803UNS S32205 (Enhanced 2205)
Chromium (Cr)21.0 – 23.022.0 – 23.0
Nickel (Ni)4.5 – 6.54.5 – 6.5
Molybdenum (Mo)2.5 – 3.53.0 – 3.5
Nitrogen (N)0.08 – 0.200.14 – 0.20
PREN30 – 3433 – 37

Which one to choose?

  • S31803 is suitable for most general duplex applications and is often more available and cost-effective.

  • S32205 is preferred for slightly more aggressive environments or when better weldability and higher pitting resistance are required.

  • Many ASTM A790 pipes today are dual-certified as S31803 / S32205, meeting both specifications.

Chemical Composition (%, ASTM A790 / A789)
ElementUNS S31803 Requirements
Carbon (C)≤ 0.030
Silicon (Si)≤ 1.00
Manganese (Mn)≤ 2.00
Chromium (Cr)21.0 – 23.0
Nickel (Ni)4.5 – 6.5
Molybdenum (Mo)2.5 – 3.5
Nitrogen (N)0.08 – 0.20
Phosphorus (P)≤ 0.030
Sulfur (S)≤ 0.020
Iron (Fe)Balance
Mechanical Properties (Typical)
PropertyValue
Tensile Strength≥ 620 MPa (90 ksi)
Yield Strength (0.2% offset)≥ 450 MPa (65 ksi)
Elongation≥ 25%
Hardness (HRC)≤ 30
Density7.8 g/cm³
Pitting Resistance Equivalent Number (PREN)

PREN = %Cr + 3.3 × %Mo + 16 × %N
UNS S31803 PREN Range: 30 – 34

Applicable Standards
StandardDescription
ASTM A790Seamless and welded ferritic/austenitic stainless steel pipe
ASTM A789Seamless and welded ferritic/austenitic stainless steel tubing
ASME SA790 / SA789Boiler and pressure vessel code
EN 10216-5European standard for duplex steel tubes
EN 10217-7Welded duplex steel tubes
NACE MR0175 / ISO 15156Suitable for sour service (H₂S environments)
Common Applications for UNS S31803 Duplex Pipe
IndustryTypical Applications
Oil & GasFlowlines, gathering lines, process piping, and offshore platforms
Chemical ProcessingHeat exchangers, pressure vessels, and reactor piping
Marine EngineeringSeawater cooling systems, ballast lines, and desalination plants
Pulp & PaperDigesters and bleach plant equipment
Water TreatmentReverse osmosis (RO) high-pressure piping
ConstructionStructural components in coastal or de-icing salt environments
FAQ – UNS S31803 Duplex Stainless Steel Pipe

Q: What is the difference between UNS S31803 and UNS S32205?
A: S32205 has tighter limits on Cr, Mo, and N, giving it slightly higher pitting resistance (PREN 33-37 vs 30-34). Many pipes today are dual-certified as both S31803 and S32205.
Q: Is UNS S31803 suitable for seawater applications?
A: Yes, S31803 offers good resistance to seawater and brackish water. For continuous immersion in aggressive seawater, super duplex (e.g., UNS S32750) may be recommended.
Q: Can UNS S31803 pipe be welded to 316L?
A: Yes, but proper filler metal (e.g., 309L or 2209) and welding procedure are required. Consult our technical team for specific cases.
Q: Is UNS S31803 magnetic?
A: Yes, due to its ferrite content, S31803 is slightly magnetic – unlike fully austenitic grades like 304 or 316.
Q: Do you provide cutting and threading services?
A: Yes, we offer custom cutting, beveling, threading, and grooving per your requirements.

Request a Quote for UNS S31803 Duplex Stainless Steel Pipe

Please provide your required size (OD × WT), quantity, standard, and delivery port. We will reply within 24 hours with a competitive price.

Related Products
  • Quality Precision 301 304 316 430 Cold Rolled Stainless Steel Strip 2B BA No.4 Finish factory

    Precision 301 304 316 430 Cold Rolled Stainless Steel Strip 2B BA No.4 Finish
    Precision cold rolled stainless steel strip is a narrow, thin-gauge stainless steel product manufactured to significantly tighter thickness and width tolerances than standard cold-rolled sheet. Unlike standard sheet (typically 1000mm or 1219mm wide), precision strip is produced in narrow widths — usually less than 600mm — and thin gauges from 0.05mm up to 3.0mm. The key differentiator is the tolerance : the precision strip holds thickness variations to as low as ±0.005mm,
  • Quality High Precision 304 Stainless Steel Seamless Pipe Cold Rolled Corrosion Resistance factory

    High Precision 304 Stainless Steel Seamless Pipe Cold Rolled Corrosion Resistance
    304 Stainless Steel Seamless Pipe The 304 stainless steel seamless pipe is a globally recognized standard grade in the stainless steel family. With a chemical composition of 18% chromium and 8% nickel, it offers excellent corrosion resistance, high toughness, and outstanding formability. Manufactured using precision seamless cold-rolling technology, this pipe delivers a superior surface finish, tight dimensional tolerances, and consistent mechanical properties — making it the
  • Quality UNS N06022 Hastelloy C-22 Alloy Corrosion Resistant ASTM B622 factory

    UNS N06022 Hastelloy C-22 Alloy Corrosion Resistant ASTM B622
    UNS N06022 is a nickel-chromium-molybdenum alloy renowned for its exceptional resistance to both oxidizing and reducing corrosive media. With a higher chromium content than C-276, plus controlled additions of tungsten, this alloy offers superior resistance to pitting, crevice corrosion, and stress-corrosion cracking in aggressive environments. UNS N06022 provides outstanding performance in wet chlorine, hydrochloric acid, sulfuric acid, and mixed acid solutions where many
  • Quality Austenitic Corrosion Resistant Hastelloy C-22 Nickel Alloy For Harsh Chemical Processing factory

    Austenitic Corrosion Resistant Hastelloy C-22 Nickel Alloy For Harsh Chemical Processing
    Hastelloy C-22: Ultimate Corrosion-Resistant Nickel Alloy Hastelloy C-22 is a fully austenitic, advanced corrosion-resistant nickel-chromium-molybdenum-tungsten alloy. It offers outstanding resistance to both uniform corrosion in oxidizing media and localized attack (pitting, crevice corrosion) in reducing environments. Unlike standard alloys, C-22 provides exceptional resistance to stress corrosion cracking (SCC), intergranular attack, and weld heat-affected zone (HAZ)

Send An Inquiry