ASTM A790 S31803 Duplex Stainless Steel Welded Pipe: Manufacturing Capabilities & Product Specifications

Short Description:

Womic Steel supplies ASTM A790 S31803 (Duplex 2205) welded stainless steel pipe for applications requiring high strength and exceptional resistance to chloride stress corrosion cracking, pitting, and crevice corrosion. S31803 offers minimum yield strength of 450 MPa (65,300 psi) – approximately twice that of 316L – and tensile strength of 655 MPa (95,000 psi). The duplex microstructure (50% austenite / 50% ferrite) provides superior resistance to stress corrosion cracking in chloride-containing environments. Manufacturing includes ERW for small diameters and EFW for large diameters, both with full penetration and post-weld solution annealing. Outside diameter from 6.35mm to 1219mm (1/4″ – 48″), wall thickness 0.5mm – 50mm (Schedule 5S to XXS), standard length up to 12m, custom up to 24m. Mill certificate, hydrotest, 100% UT, solution annealed and pickled finish, beveled or plain ends available. Suitable for offshore platforms, desalination plants, chemical tankers, pulp & paper digesters, flue gas desulfurization, and seawater cooling systems.

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Product Description

Welded Duplex Stainless Steel Pipe Size: Outside Diameter: 6.35mm – 1,219mm (1/4″ – 48″), Wall Thickness: 0.5mm – 50mm (Schedule 5S, 10S, 40S, 80S), Length: 6m – 12m standard, custom lengths up to 24m

Standard & Grade of Welded Stainless Steel Pipe: ASTM A790 (pipe) / ASTM A789 (tubing) S31803; also UNS S31803; EN 10217-7 1.4462; Equivalent to Duplex 2205 (predecessor to S32205)

Usage of Welded Stainless Steel Pipe: Offshore oil and gas platforms (seawater cooling, firewater, ballast lines), desalination plants (high pressure brine piping), chemical tankers and cargo piping, pulp and paper digesters and bleach plants, flue gas desulfurization (FGD) systems, heat exchangers (chloride service), chemical processing (acetic acid, formic acid), marine exhaust scrubbers, bridge components and structural applications

Womic Steel offering high quality & competitive prices of ASTM A790 S31803 welded duplex stainless steel pipe, ERW duplex pipe, EFW duplex tube, high strength corrosion resistant pipe, chloride SCC resistant pipe. Mill certificate EN 10204 3.1/3.2, hydro test, UT, solution annealed, beveled/plain ends, pickled finish available. Factory direct supply for offshore, desalination, and chemical projects worldwide.

Womic Steel: Manufacturing Capabilities & Company Strength

Womic Steel Group is a premier manufacturer and global exporter with over 20 years of expertise in producing carbon, stainless, and duplex stainless steel tubular products. Our specialized duplex stainless steel welded pipe production facility utilizes multiple advanced welding technologies with strict control of heat input to maintain the required ferrite/austenite balance (35-65%):

ERW (Electric Resistance Welding) Line: For diameters from 6.35mm to 610mm (1/4″ – 24″), wall thickness from 0.5mm to 12.7mm. High-frequency welding with low heat input to prevent ferrite imbalance. Ideal for small to medium diameter duplex pipes for instrumentation and process lines.

EFW (Electric Fusion Welding) Line: For diameters from 219mm to 1219mm (8″ – 48″), wall thickness from 4.0mm to 50mm. TIG (GTAW) root pass with SAW fill passes, with nitrogen backing gas to maintain duplex microstructure.

LSAW / SAWL Line for Duplex: For diameters from 406mm to 1524mm (16″ – 60″), wall thickness up to 60mm. Submerged arc welding of rolled duplex plates with controlled heat input and interpass temperature.

All duplex stainless steel welded pipes undergo solution annealing (heat treatment) at 1040-1120°C followed by water quenching to restore the balanced austenite-ferrite microstructure and corrosion resistance, followed by pickling and passivation.

Quality Certifications & Regulatory Compliance:

ISO 9001:2015 Certified for quality management

PED 2014/68/EU (CE Marking) for pressure equipment

EN 10204 3.2 Certification with third-party validation (TÜV, BV, SGS, LR)

Third-Party Inspection (TPI) approved by SGS, BV, ABS, DNV, TÜV

NORSOK M-650 (mandatory for offshore duplex applications)

DNV GL approval for offshore duplex pipes

Womic Steel supplies duplex stainless welded pipes to over 50 countries across offshore, desalination, chemical, and marine industries.

Production Flexibility:

ERW: 6.35–610mm OD × 0.5–12.7mm WT × ≤ 12m

EFW: 219–1219mm OD × 4.0–50mm WT × ≤ 12m (longer upon request)

LSAW: 406–1524mm OD × 6.0–60mm WT × ≤ 18m

Finishing options: Annealed and pickled, bright annealed

ASTM A790 S31803: Material Composition & Performance Characteristics

UNS S31803 is the original 22% chromium, 5% nickel, 3% molybdenum duplex stainless steel grade. It has a two-phase microstructure (approximately 50% austenite / 50% ferrite) that combines the high strength of ferritic steels with the corrosion resistance and toughness of austenitic steels. S31803 has been largely replaced by S32205 in new specifications due to tighter composition limits, but S31803 remains widely accepted for many projects and is still specified in existing designs.

Chemical Composition (Ladle Analysis, % by mass):

Element	UNS S31803 (ASTM A790)
C	≤ 0.030
Mn	≤ 2.00
P	≤ 0.030
S	≤ 0.020
Si	≤ 1.00
Cr	21.0 – 23.0
Ni	4.5 – 6.5
Mo	2.5 – 3.5
N	0.08 – 0.20
Fe	Balance

Comparison between S31803 and S32205:

Element	S31803	S32205
Cr	21.0-23.0	22.0-23.0
Mo	2.5-3.5	3.0-3.5
N	0.08-0.20	0.14-0.20
PREN	30-36	35-38

S32205 typically offers slightly higher pitting resistance due to higher minimum Cr, Mo, and N. However, S31803 is still fully acceptable for many seawater and chloride services when properly specified.

Mechanical Properties (Room Temperature, Solution Annealed):

Property	S31803 (Duplex 2205)
Yield Strength (min, 0.2% offset)	450 MPa (65,300 psi)
Tensile Strength (min)	620 MPa (89,900 psi)
Elongation (min, 50mm gauge)	25%
Hardness (max)	90 HRB (or 290 HV)
Impact Toughness (min) @ -46°C	27 J (Charpy V-Notch)

Physical Properties:

Density: 7.85 g/cm³

Modulus of Elasticity: 200 GPa (29 × 10⁶ psi)

Thermal Conductivity: 15 W/m·K at 100°C

Coefficient of Thermal Expansion: 13.5 × 10⁻⁶/°C (20-100°C)

Corrosion Resistance:

Pitting Resistance Equivalent Number (PREN) ≈ 30-36 (depends on actual composition)

Excellent resistance to chloride stress corrosion cracking (SCC) – superior to 304L and 316L

Very high resistance to pitting and crevice corrosion in chloride environments

Good resistance to organic acids, caustic solutions, and sour service (H₂S)

Microstructure Requirements (per ASTM A790): Ferrite content shall be 35-65% after solution annealing. Womic performs ferrite measurement using image analysis or magnetic induction method on every heat.

Dimensional Range & Standards Compliance

Item	Specification
Standard	ASTM A790 / ASME SA790 (pipe); ASTM A789 (tubing)
Manufacturing Processes	ERW, EFW, LSAW
Outside Diameter Range	ERW: 6.35 – 610mm; EFW/LSAW: 219 – 1524mm
Wall Thickness Range	ERW: 0.5 – 12.7mm; EFW/LSAW: 4.0 – 60mm
Schedule Range	5S, 10S, 40S, 80S (for NPS 1/8″ – 48″)
Length Range	Standard: 6m; Extended: 12m, 18m, up to 24m
End Finish	Plain End (PE), Beveled End (BE)
Surface Finish	Annealed & Pickled, Bright Annealed
Tolerances	OD: ±0.5% or ±3.2mm; WT: ±12.5% (per ASTM A999); Length: +50mm / -0mm

Available Dimensions & Specifications – ASTM A790 S31803 Welded Duplex Pipe (Selected Typical Sizes)

NPS	OD (mm)	Schedule	WT (mm)	Weight (kg/m)	Standard Length	Typical Application
1/2″	21.3	10S	2.11	1.00	6m	Instrument lines
3/4″	26.7	10S	2.11	1.28	6m	Chemical dosing
1″	33.4	10S	2.77	2.09	6m	Offshore hydraulic
1-1/2″	48.3	10S	2.77	3.11	6m	Process lines
2″	60.3	10S	2.77	3.93	6m / 12m	Seawater lines
3″	88.9	10S	3.05	6.46	6m / 12m	Heat exchangers
4″	114.3	10S	3.05	8.37	6m / 12m	Chemical process
6″	168.3	10S	3.40	13.8	6m / 12m	Desalination
8″	219.1	10S	3.76	20.0	12m	Offshore platform
10″	273.0	10S	4.19	27.8	12m	Seawater intake
12″	323.9	10S	4.57	36.0	12m	Firewater main
16″	406.4	10S	4.78	47.4	12m	Ballast lines
20″	508.0	10S	5.54	68.6	12m	Large diameter
24″	609.6	10S	6.35	94.4	12m	Main headers

*Custom dimensions outside these ranges available. S31803 is often dual-certified with S32205. Womic supplies dual-certified material upon request.*

Common Duplex Stainless Steel Standards & Grades Manufactured by Womic Steel

Standard	Steel Grades	Typical Application	Welding Process
ASTM A790	S31803, S32205, S32750, S32760	Offshore, desalination, chemical	EFW/LSAW
ASTM A789	S31803, S32205, S32750, S32760	Tubing, heat exchanger	ERW (cold finished)
ASTM A928	S31803, S32205, S32750	Electric fusion welded duplex	EFW
EN 10217-7	1.4462 (2205), 1.4410 (2507)	Pressure purposes, duplex	SAW/ERW
NORSOK M-630	22Cr (2205), 25Cr (2507)	Offshore Norwegian sector	EFW/LSAW

Usage: Offshore seawater systems, desalination high pressure piping, chemical tanker cargo lines, FGD scrubbers, pulp mill digesters.

Manufacturing Process – Welded Duplex Stainless Steel Pipe (ERW, EFW, LSAW)

Duplex stainless steel welding requires careful control of heat input and interpass temperature to maintain the required ferrite/austenite balance (35-65%). Excessive heat input can form detrimental intermetallic phases (sigma, chi) that reduce corrosion resistance and toughness.

ERW (Electric Resistance Welding) Process – Small to Medium Diameter (6.35–610mm OD):

Raw Material (Strip/Coil) Inspection: Duplex stainless steel strip verified for S31803 composition (Cr 21-23%, Mo 2.5-3.5%, N 0.08-0.20%). Each coil has unique heat number.

Uncoiling & Leveling: Coil uncoiled and leveled.

Strip Edge Trimming: Edges precision trimmed.

Forming: Continuous roll forming.

High-Frequency Welding: Low heat input welding (≤ 1.5 kJ/mm) to avoid ferrite imbalance. Welding speed controlled.

Seam Annealing: Weld seam induction annealed (1040-1120°C) followed by water quench.

Sizing & Straightening

Cutting to Length

Non-Destructive Testing: Eddy current test (100%) plus optional UT.

Solution Annealing (Full Pipe Heat Treatment): 1040-1120°C, water quench. Critical for restoring duplex microstructure.

Hydrostatic Test

Pickling & Passivation

Ferrite Measurement: Confirms 35-65% ferrite.

Final Inspection & Marking

EFW (Electric Fusion Welding) Process – Large Diameter, Heavy Wall (219–1219mm OD, 4.0–50mm WT):

Plate Preparation: Duplex plate cut to size, edges beveled (X bevel).

Roll Forming: 3-roll or 4-roll bending.

Tack Welding

TIG (GTAW) Root Pass: Root pass with matching duplex filler metal (ER2209), nitrogen backing gas (N₂ + Ar) to prevent nitrogen loss.

SAW Fill & Cap Passes: Multi-pass SAW with controlled heat input (≤ 2.0 kJ/mm), interpass temperature ≤ 150°C.

Inner Weld (for large diameters)

100% Radiographic Testing (per ASTM A928)

Solution Annealing: Full pipe heat treatment in car-bottom furnace (1040-1120°C), water quench.

Pickling & Passivation

Hydrostatic Test

Ferrite Measurement & PMI

Dimensional Inspection & Marking

LSAW Process for Duplex – Very Large Diameter (406–1524mm OD, 6.0–60mm WT):

UOE or JCOE forming from duplex plate

Double-sided SAW welding with strict heat input control

Full solution annealing after welding

Ferrite measurement on every pipe

Critical Control Points for Duplex Welding:

Heat input: ≤ 2.0 kJ/mm (preferably ≤ 1.5 kJ/mm)

Interpass temperature: ≤ 150°C

Backing gas: Nitrogen + Argon (to prevent nitrogen loss from weld pool)

Solution annealing: 1040-1120°C, water quench – mandatory after welding

Ferrite content: 35-65% (typically 40-60%)

Quality Control & Testing Procedures for ASTM A790 S31803 Welded Duplex Pipe

Stage	Inspection Method	Purpose
Raw Material	Chemical Analysis (OES)	Verify S31803 limits (Cr 21-23%, Mo 2.5-3.5%, N 0.08-0.20%)
Raw Material	Tensile Testing	Verify yield ≥ 450 MPa, tensile ≥ 620 MPa
Raw Material	Ferrite Measurement	Ensure starting plate 40-60% ferrite
Raw Material	Charpy @ -46°C	Verify impact toughness ≥ 27 J
In-Process	Heat Input Monitoring (EFW/LSAW)	Ensure ≤ 2.0 kJ/mm
In-Process	Interpass Temperature	≤ 150°C
Weld (ERW)	Eddy Current Test (100%)	Detect weld discontinuities
Weld (EFW/LSAW)	100% UT (or PAUT)	Detect weld defects
Weld (EFW/LSAW)	RT (10-100% per spec)	Weld quality verification
Weld	Dye Penetrant Test (PT)	Surface cracks (weld toes)
After Solution Annealing	Ferrite Measurement (per ASTM E562)	35-65% ferrite (target 40-60%)
After Solution Annealing	Hardness Test	≤ 90 HRB (or 290 HV)
Finished Pipe	Hydrostatic Test	Pressure integrity
Finished Pipe	Charpy @ -46°C (weld and HAZ)	≥ 27 J (typical 60-120 J)
Finished Pipe	Pitting Corrosion Test (ASTM G48)	Pass (no pitting at 22°C, 24h)
Finished Pipe	PMI (XRF)	Confirm grade (Cr, Mo, N)
Finished Pipe	Visual & Marking	Surface, traceability

Optional Tests for Critical Offshore Service (NORSOK M-650):

Ferrite measurement on weld (weld centerline, HAZ, base metal)

Microstructure examination for intermetallic phases (sigma, chi)

Hardness traverse across weld (max 320 HV)

Corrosion testing in simulated seawater

Primary Applications – ASTM A790 S31803 Welded Duplex Stainless Steel Pipe

Offshore oil and gas platforms: Seawater cooling systems, firewater ring mains, ballast lines, deck drains, and hydraulic control lines.

Desalination plants: High pressure brine piping (reverse osmosis feed and reject lines), interconnecting piping, and evaporator tubes.

Chemical tankers and cargo piping: Stainless steel cargo piping for chemicals such as acetic acid, formic acid, and organic chlorides.

Pulp and paper digesters: Continuous digesters and bleach plant piping (chlorine dioxide, sodium chlorate).

Flue gas desulfurization (FGD) systems: Absorber tower recirculation piping, spray headers, and oxidation air lines.

Heat exchangers: Shell and tube heat exchangers using seawater or brackish cooling water.

Marine exhaust scrubbers: Exhaust gas cleaning systems on ships (SOx removal).

Structural components: Bridge components, offshore platform topsides, and crane booms.

Packaging & Shipping – ASTM A790 S31803 Welded Duplex Pipe

Packaging:

Anti-corrosion protection: Pipes oiled or VCI paper. For offshore, plastic wrap recommended.

End caps: Heavy-duty plastic caps for beveled ends.

Bundling (Small diameters): Bundles with steel straps and interleaving paper.

Individual packaging (Large diameters): Plastic film wrap.

Wooden crates for critical offshore projects.

Shipping:

Containers for ≤ 610mm, break-bulk for larger diameters.

Documentation: MTC 3.1/3.2, hydrotest report, eddy current/UT reports, ferrite measurement report, PMI report, Charpy reports, G48 test report, dimensional report, packing list, COO.

Womic Steel Advantages & FAQ – ASTM A790 S31803 Duplex Welded Pipe

Why Partner with Womic Steel for S31803 Duplex Welded Pipe?

Complete Size Range: ERW 1/4″ – 24″, EFW/LSAW 8″ – 60″.

Full solution annealing after welding (1040-1120°C, water quench).

In-house ferrite measurement and microstructure examination.

Dual-certification S31803 / S32205 available upon request.

NORSOK M-650 qualified for offshore Norwegian sector.

DNV GL approval for duplex pipes.

Competitive lead times: 30-40 days for ERW, 40-60 days for EFW/LSAW.

Frequently Asked Questions (FAQ) – ASTM A790 S31803 Duplex Welded Pipe

Q: What is the difference between S31803 and S32205?
A: S32205 has tighter composition limits (Cr 22-23% vs 21-23%, N 0.14-0.20% vs 0.08-0.20%) and higher minimum nitrogen, which improves pitting resistance and weldability. S31803 is the original duplex 2205 grade; S32205 is an improved version. Many mills now produce material that meets both specifications simultaneously (dual-certified). Womic can supply dual-certified S31803/S32205 upon request.

Q: Is S31803 still acceptable for new projects?
A: Yes, S31803 remains widely accepted and is still specified in many industry standards. However, for new projects, many engineers prefer S32205 for its tighter composition and higher pitting resistance. If your specification calls for S31803, Womic can supply it. For new designs, we recommend using S32205 or dual-certified material.

Q: Why is solution annealing mandatory for duplex welded pipe?
A: Welding disrupts the balanced ferrite/austenite microstructure and can form detrimental intermetallic phases (sigma, chi) in the heat-affected zone. Solution annealing at 1040-1120°C followed by water quench restores the 35-65% ferrite balance and dissolves intermetallic phases. Without solution annealing, corrosion resistance and toughness are severely compromised. Womic performs solution annealing on all duplex welded pipes.

Q: What is the maximum service temperature for S31803?
A: S31803 is suitable for continuous service up to 280°C. Above 300°C, embrittlement can occur due to sigma phase formation. For temperatures below 300°C, duplex has excellent performance. For higher temperatures, austenitic grades or nickel alloys are recommended.

Q: Can S31803 be used for sour service (H₂S)?
A: Yes. Duplex 2205 (both S31803 and S32205) is qualified for sour service per NACE MR0175/ISO 15156 for H₂S partial pressures up to 0.3 psi (0.02 bar) in specific hardness ranges. Womic supplies duplex with hardness ≤ 28 HRC per NACE requirements.

Q: What is the pitting resistance equivalent (PREN) of S31803?
A: PREN = Cr% + 3.3(Mo%) + 16(N%). For S31803, depending on actual composition, PREN ranges from 30 to 36. This is significantly higher than 316L (PREN ≈ 24-26), indicating much better resistance to pitting in chloride environments. For S32205, PREN is typically 35-38.

Q: Do you provide NORSOK M-650 certification?
A: Yes. Womic Steel is qualified to NORSOK M-650 for duplex stainless steel welded pipes. We provide full documentation including ferrite measurement, hardness traverses, corrosion testing, and microstructure examination.

Q: What is the typical lead time for S31803 duplex welded pipe?
A: 30-40 days for ERW (small to medium diameters), 40-60 days for EFW/LSAW (large diameters). NORSOK M-650 documentation adds 10-15 days. Third-party inspection adds 7-14 days.

Project Reference – Middle East Desalination Plant Brine Piping (S31803)

Country: United Arab Emirates (Abu Dhabi, Arabian Gulf)
Standard & Grade: ASTM A790 S31803 (Duplex 2205)
Dimensions & Quantity:

OD 219.1mm (8″) × Schedule 10S (3.76mm WT) – 3,500 meters (approx. 56 tons) – EFW process

OD 273.0mm (10″) × Schedule 10S (4.19mm WT) – 2,800 meters (approx. 54 tons) – EFW process

OD 88.9mm (3″) × Schedule 10S (3.05mm WT) – 4,200 meters (approx. 26 tons) – ERW process

OD 60.3mm (2″) × Schedule 10S (2.77mm WT) – 5,000 meters (approx. 18 tons) – ERW process
Total: 15,500 meters (15.5 km), approx. 154 tons

Specifications: ASTM A790 S31803 solution annealed and pickled, beveled ends. Hydrostatic testing. 100% UT for EFW pipes, eddy current for ERW. PMI on every pipe. Mandatory ferrite measurement (35-65%, achieved 45-55%). Charpy impact at -20°C (spec 27J, achieved 80-140J). Pitting corrosion test per ASTM G48 Method A (24h, 22°C) – no pitting. Third-party inspection by BV (Bureau Veritas). Dual certification S31803/S32205 provided.

Application: High-pressure brine discharge piping for a large seawater reverse osmosis (SWRO) desalination plant in Abu Dhabi. The piping transports reject brine (salinity 70,000 ppm, temperature 35-40°C, pH 7.5-8.0) from the RO membranes to the outfall. The previous 316L piping suffered pitting and crevice corrosion after 4 years. Duplex 2205 (S31803) was selected for its higher pitting resistance (PREN 30-36 vs 316L PREN 24-26) and higher strength.

Technical Challenges & Solutions:

High chloride and high temperature brine – Brine temperature 40°C and salinity 70,000 ppm creates aggressive pitting environment. 316L is insufficient. Womic supplied S31803 with verified composition (Cr 22.1%, Mo 3.1%, N 0.16%) achieving PREN 36. G48 pitting test showed no pitting. Critical pitting temperature (CPT) measured at 45°C (above operating temperature). Client accepted.

Weld ferrite balance – EFW welding with heat input ≤ 1.8 kJ/mm and interpass ≤ 100°C. Ferrite measurements: weld metal 48-54%, HAZ 44-50%, base metal 50-55%. All within 35-65%.

Lightweight design using Schedule 10S – Duplex high strength allowed thinner wall (Schedule 10S vs Schedule 40S for 316L), saving 60% of pipe weight and reducing structural support costs by $1.2M. Womic provided dimensional verification to ensure proper fit-up.

Logistics to Abu Dhabi – Pipes shipped from Shanghai to Khalifa Port, Abu Dhabi in two shipments. All 154 tons delivered within 35 days. On-site inspection by BV passed with zero non-conformances.

Result: Brine discharge system commissioned in Q4 2023. After 18 months of operation, inspection showed no pitting, crevice corrosion, or cracking. The plant operator has standardized on duplex 2205 for all new brine piping systems. Womic Steel is now a preferred supplier for this desalination plant's expansion phases.

Contact:
Website: www.womicsteel.com
E-mail: sales@womicsteel.com

Tel / WhatsApp / WeChat:
Victor: +86 15575100681
Jack: +86 18390957568

Womic Steel – Your reliable partner for ASTM A790 S31803 duplex stainless steel welded pipes for desalination, offshore, and chemical applications worldwide.