ASTM B673 UNS N08904 (904L) Welded Stainless Steel Pipe: Manufacturing Capabilities & Product Specifications

Short Description:

Womic Steel supplies ASTM B673 UNS N08904 (904L) welded stainless steel pipe for highly aggressive corrosive environments including sulfuric acid, phosphoric acid, and high-chloride seawater. 904L is a super austenitic stainless steel with high nickel (23-28%), high chromium (19-23%), and molybdenum (4-5%), plus copper (1-2%) for exceptional resistance to reducing acids. Minimum yield strength 220 MPa (31,900 psi), tensile strength 490 MPa (71,100 psi). The alloy offers pitting resistance equivalent (PREN) of 35-40, significantly higher than 316L, and excellent resistance to stress corrosion cracking. 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 – 40mm, standard length up to 12m, custom up to 18m. Mill certificate, hydrotest, 100% UT, solution annealed and pickled finish, beveled or plain ends available. Suitable for sulfuric acid plants, phosphoric acid production, flue gas desulfurization (FGD), seawater cooling systems (elevated temperature), chemical tankers, offshore platforms (sour service), and pharmaceutical equipment.

Welded Stainless Steel Pipe Size: Outside Diameter: 6.35mm – 1,219mm (1/4″ – 48″), Wall Thickness: 0.5mm – 40mm (Schedule 5S, 10S, 40S), Length: 6m – 12m standard, custom lengths up to 18m

Standard & Grade of Welded Stainless Steel Pipe: ASTM B673 (welded pipe) / ASTM B674 (seamless) / ASTM B677 (seamless tube); UNS N08904; EN 10217-7 1.4539; Equivalent to 904L

Usage of Welded Stainless Steel Pipe: Sulfuric acid plants (concentrated and dilute acid service, acid coolers), phosphoric acid production (wet process evaporators, transfer lines), flue gas desulfurization (FGD) absorber outlet ducts and stack liners, seawater cooling systems with elevated temperatures (30-50°C), chemical tankers and cargo piping (aggressive chemicals), offshore oil and gas (sour service with high H₂S and chlorides), pulp and paper bleach plants (high chloride environments), pharmaceutical equipment, textile dyeing equipment, food processing (high chloride brines), heat exchangers for aggressive cooling water

Womic Steel offering high quality & competitive prices of ASTM B673 UNS N08904 welded stainless steel pipe, 904L super austenitic pipe, ERW stainless pipe, EFW stainless pipe, acid resistant pipe, seawater 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 chemical, marine, and offshore projects worldwide.

Send email to us Product Specifications

Product Detail

Product Tags

1. Womic Steel: Manufacturing Capabilities & Company Strength

Womic Steel Group is a premier manufacturer and global exporter with over 20 years of expertise in producing corrosion resistant alloy pipes. Our specialized 904L welded pipe production facility utilizes multiple advanced welding technologies with strict control of heat input and post-weld heat treatment:

● 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 (≤ 1.2 kJ/mm) to avoid segregation of high alloy content. Ideal for small to medium diameter 904L pipes.

● EFW (Electric Fusion Welding) Line: For diameters from 219mm to 1219mm (8″ – 48″), wall thickness from 4.0mm to 40mm. TIG (GTAW) root pass with SAW fill passes, using matching filler metal (ERNiCrMo-3 or ER385).

● LSAW / SAWL Line for High Alloy: For diameters from 406mm to 1219mm (16″ – 48″), wall thickness up to 40mm. Submerged arc welding of rolled 904L plates with controlled heat input.

All 904L welded pipes undergo solution annealing (heat treatment) at 1050-1150°C followed by water quenching to dissolve any secondary phases and restore corrosion resistance, followed by pickling and passivation with specialized acid mixtures.

Quality Certifications & Regulatory Compliance:

● ISO 9001:2015 Certified

● 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

● NACE MR0175 / ISO 15156 for sour service (H₂S) upon request

● ASME Boiler and Pressure Vessel Code (Section VIII, Div. 1) upon request

Womic Steel supplies 904L welded pipes to over 30 countries across chemical, marine, and offshore industries.

Production Flexibility:

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

● EFW: 219–1219mm OD × 4.0–40mm WT × ≤ 12m (longer upon request)

● LSAW: 406–1219mm OD × 6.0–40mm WT × ≤ 18m

● Finishing options: Annealed and pickled, bright annealed (for small tubing)

2. ASTM B673 UNS N08904: Material Composition & Performance Characteristics

UNS N08904 (904L) is a super austenitic stainless steel with high nickel (23-28%), high chromium (19-23%), molybdenum (4-5%), and copper (1-2%). The copper addition provides exceptional resistance to reducing acids such as sulfuric and phosphoric acid. The high molybdenum and chromium provide excellent pitting resistance in chloride environments. 904L is often used as a cost-effective alternative to nickel alloys in moderately aggressive conditions.

Chemical Composition (Ladle Analysis, % by mass):

Element	UNS N08904 (904L)	316L (for comparison)
C	≤ 0.020	≤ 0.030
Mn	≤ 2.00	≤ 2.00
P	≤ 0.040	≤ 0.045
S	≤ 0.030	≤ 0.030
Si	≤ 1.00	≤ 1.00
Cr	19.0 – 23.0	16.0 – 18.0
Ni	23.0 – 28.0	10.0 – 14.0
Mo	4.0 – 5.0	2.0 – 3.0
Cu	1.0 – 2.0	—
Fe	Balance	Balance

Mechanical Properties (Room Temperature, Solution Annealed):

Property	UNS N08904 (904L)
Yield Strength (min, 0.2% offset)	220 MPa (31,900 psi)
Tensile Strength (min)	490 MPa (71,100 psi)
Elongation (min, 50mm gauge)	35%
Hardness (max)	90 HRB

Physical Properties:

Density: 8.00 g/cm³

Modulus of Elasticity: 195 GPa (28.3 × 10⁶ psi)

Thermal Conductivity: 12.0 W/m·K at 100°

Coefficient of Thermal Expansion: 15.4 × 10⁻⁶/°C (20-100°C)Corrosion Resistance:

Pitting Resistance Equivalent Number (PREN) = Cr% + 3.3(Mo%) + 16(N%) ≈ 35-40 (vs 316L PREN 24-26)

Excellent resistance to sulfuric acid across a wide concentration range (up to 90% at moderate temperatures)

Outstanding resistance to phosphoric acid (wet process) containing chlorides and fluorides

Excellent resistance to pitting and crevice corrosion in chloride environments

Good resistance to intergranular corrosion after welding (low carbon)

Suitable for sour service (NACE MR0175) with proper heat treatment

Corrosion Limits (Approximate):

● Sulfuric acid (H₂SO₄): up to 90% at 50°C; up to 70% at 100°C

● Hydrochloric acid (HCl): limited to dilute (< 5%) at room temperature

● Phosphoric acid (H₃PO₄): excellent up to 85% at 100°C

● Acetic acid: excellent at all concentrations

● Seawater: excellent at temperatures up to 50°C

3. Dimensional Range & Standards Compliance

Item	Specification
Standard	ASTM B673 / ASME SB-673 (welded pipe)
Manufacturing Processes	ERW, EFW, LSAW
Outside Diameter Range	ERW: 6.35 – 610mm; EFW/LSAW: 219 – 1219mm
Wall Thickness Range	ERW: 0.5 – 12.7mm; EFW/LSAW: 4.0 – 40mm
Schedule Range	5S, 10S, 40S (for NPS 1/8″ – 48″)
Length Range	Standard: 6m; Extended: 12m, 18m, up to 18m
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 B775); Length: +50mm / -0mm

4. Available Dimensions & Specifications – ASTM B673 UNS N08904 Welded Stainless Steel 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	Chemical dosing
3/4″	26.7	10S	2.11	1.28	6m	Instrument line
1″	33.4	10S	2.77	2.09	6m	Acid feed
1-1/2″	48.3	10S	2.77	3.11	6m	Sulfuric acid line
2″	60.3	10S	2.77	3.93	6m / 12m	Process line
3″	88.9	10S	3.05	6.46	6m / 12m	Acid transfer
4″	114.3	10S	3.05	8.37	6m / 12m	Phosphoric acid
6″	168.3	10S	3.40	13.8	6m / 12m	Seawater cooling
8″	219.1	10S	3.76	20.0	12m	Offshore sour line
10″	273.0	10S	4.19	27.8	12m	FGD outlet
12″	323.9	10S	4.57	36.0	12m	Chemical main
16″	406.4	10S	4.78	47.4	12m	Large diameter

*Custom dimensions outside these ranges available. 904L welded pipes require longer lead times (minimum 60 days) due to specialized strip/plate sourcing.*

5. Common Super Austenitic Standards & Grades Manufactured by Womic Steel

Standard	Steel / Alloy Grades	Typical Application	Welding Process
ASTM B673	UNS N08904 (904L)	Sulfuric/phosphoric acid, seawater	EFW/LSAW/ERW
ASTM B674	UNS N08904 (seamless)	Pressure tubing	-
ASTM B677	UNS N08904	Seamless pipe	-
EN 10217-7	1.4539 (904L)	Pressure purposes, super austenitic	SAW/ERW
ASTM A312	UNS N08367 (AL-6XN), S31254 (254 SMO)	Seawater, FGD	EFW/LSAW

Usage: Sulfuric acid plants, phosphoric acid production, FGD systems, seawater cooling (elevated temp), chemical tankers, offshore sour service.

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

904L welding requires careful control of heat input and post-weld heat treatment due to its high alloy content. The copper and molybdenum make the alloy prone to segregation if cooling is too slow.

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

● Raw Material (Strip/Coil) Inspection: 904L strip verified for composition (Ni 23-28%, Cr 19-23%, Mo 4-5%, Cu 1-2%). Each coil has unique heat number.

● Uncoiling & Leveling

● Strip Edge Trimming

● Forming: Continuous roll forming.

● High-Frequency Welding: Low heat input (≤ 1.2 kJ/mm) to avoid Cu/Mo segregation. Welding in inert atmosphere.

● Seam Annealing: Induction annealing followed by water quench.

● Sizing & Straightening

● Cutting to Length

● NDT: Eddy current test (100%) + optional UT.

● Solution Annealing (Full Pipe): 1050-1150°C, water quench. Mandatory for dissolving secondary phases.

● Hydrostatic Test

● Pickling & Passivation (special mixed acid for high alloy)

● PMI (XRF) & Hardness check

● Final Inspection & Marking

EFW (Electric Fusion Welding) Process – Large Diameter (219–1219mm OD, 4.0–40mm WT):

● Plate Preparation: 904L plate, edges beveled (X bevel).

● Roll Forming

● Tack Welding

● TIG (GTAW) Root Pass: Matching filler (ERNiCrMo-3 or ER385), argon backing gas.

● SAW Fill & Cap Passes: Heat input ≤ 1.5 kJ/mm, interpass temperature ≤ 120°C. Special low-sulfur flux.

● Inner Weld

● 100% Radiographic Testing + UT (per ASTM B775)

● Solution Annealing: Full pipe heat treatment (1050-1150°C), water quench.

● Pickling & Passivation

● Hydrostatic Test

● PMI & Dimensional Inspection

● Marking

LSAW Process for High Alloy – Very Large Diameter (406–1219mm OD, 6.0–40mm WT):

● UOE or JCOE forming from 904L plate

● Double-sided SAW welding with strict heat input control

● Full solution annealing after welding

Critical Control Points for 904L Welding:

● Heat input: ≤ 1.5 kJ/mm (target ≤ 1.2 kJ/mm)

● Interpass temperature: ≤ 120°

● Shielding gas: 100% Argon with oxygen getter

● Solution annealing: 1050-1150°C, water quench – mandatory

● Pickling: Special acid mixture for high chromium/nickel alloys

7. Quality Control & Testing Procedures for ASTM B673 UNS N08904 Welded Stainless Steel Pipe

Stage	Inspection Method	Purpose
Raw Material	Chemical Analysis (OES or ICP)	Verify N08904 (Ni 23-28%, Cr 19-23%, Mo 4-5%, Cu 1-2%)
Raw Material	Tensile Testing	Yield ≥ 220 MPa, Tensile ≥ 490 MPa
Raw Material	Corrosion Test (ASTM G28)	Intergranular corrosion resistance (for acid service)
Raw Material	PREN Calculation	Ensure PREN ≥ 35
In-Process	Heat Input Monitoring	≤ 1.5 kJ/mm
In-Process	Interpass Temperature	≤ 120°C
Weld (ERW)	Eddy Current (100%)	Weld integrity
Weld (EFW/LSAW)	100% UT (or PAUT)	Detect weld defects
Weld (EFW/LSAW)	RT (10-100% per spec)	Weld quality
Weld	Dye Penetrant (PT)	Surface cracks
After Solution Annealing	Hardness Test	≤ 90 HRB
After Solution Annealing	Microstructure (ASTM E407)	No sigma, chi, or secondary phases
Finished Pipe	Hydrostatic Test	Pressure integrity
Finished Pipe	PMI (XRF)	Confirm grade (Ni, Cr, Mo, Cu)
Finished Pipe	Pitting Corrosion Test (ASTM G48)	Verify pitting resistance (if specified)
Finished Pipe	Visual & Marking	Traceability

Optional Tests for Critical Service:

● ASTM G28 Practice A (ferric sulfate-sulfuric acid) for intergranular corrosion

● ASTM G48 pitting test in FeCl₃ (6% at 40°C) for seawater service

● HIC/SSC testing for sour service (NACE TM0284, TM0177)

● Copper sulfate test for reducing acid resistance

8. Primary Applications – ASTM B673 UNS N08904 Welded Stainless Steel Pipe

● Sulfuric acid plants: Handling concentrated acid (90-98% H₂SO₄) at moderate temperatures, dilute acid (5-10%) at elevated temperatures, and acid cooler piping. Replaces 316L and 317L.

● Phosphoric acid production (wet process): Evaporators, flash coolers, and transfer lines handling phosphoric acid with chlorides and fluorides. 904L is standard for wet process phosphoric acid.

● Flue gas desulfurization (FGD) absorber outlet ducts: Downstream of absorbers where wet chloride-rich acidic gases are present. 904L is used for outlet ducting and stack liners where 317L is insufficient.

● Seawater cooling systems (elevated temperature): Coastal cooling water systems where seawater temperature exceeds 40°C. 904L resists pitting at temperatures where 316L and even super duplex may fail.

● Chemical tankers (IMO Type II): Cargo piping for aggressive chemicals including sulfuric acid, phosphoric acid, and organic acids. 904L is approved by many chemical shipping companies.

● Offshore sour service: Oil and gas production with high H₂S and high chlorides, especially where temperature is moderate but corrosion demands exceed duplex.

● Pulp and paper bleach plants: Chlorine dioxide and sodium hypochlorite service where 317L is insufficient.

● Pharmaceutical equipment: Reactors and piping for processes involving strong acids.

● Textile dyeing equipment: Dyeing machines handling chlorinated dyebaths.

● Food processing: High chloride brines, pickle liquor, and acidic food products.

9. Packaging & Shipping - JIS A5525 SKK490 SSAW Steel Pipe Pile

Packaging:

● Anti-corrosion protection: Plastic wrap or VCI paper. No oil residue for chemical service.

● End caps: Heavy-duty plastic caps (color-coded – typically blue for 904L).

● Bundling (Small diameters): Each pipe individually wrapped, then bundled with non-metallic straps.

● Individual packaging (Large diameters): Plastic film wrap with foam rings.

● Wooden crates for critical chemical and offshore projects.

Shipping:

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

Documentation: MTC 3.1/3.2, hydrotest report, UT/RT reports, PMI report, corrosion test report (if specified), dimensional report, packing list, COO. Full traceability from heat number to finished pipe.

10. Womic Steel Advantages & FAQ – ASTM B673 UNS N08904 Welded Pipe

Why Partner with Womic Steel for 904L Welded Pipe?

● Complete Size Range: ERW 1/4″ – 24″, EFW/LSAW 8″ – 48″.

● Full solution annealing after welding (1050-1150°C, water quench).

● In-house corrosion testing (ASTM G28, G48) for acid and seawater service.

● PREN ≥ 35 – excellent pitting resistance.

● Competitive lead times: 60-75 days for ERW, 75-90 days for EFW/LSAW.

● Global Certification: ISO 9001, PED (CE), EN 10204 Type 3.2.

Frequently Asked Questions (FAQ) – ASTM B673 UNS N08904 Welded Pipe

Q: What is the difference between 904L and 316L?
A: 904L has significantly higher nickel (23-28% vs 10-14%), higher chromium (19-23% vs 16-18%), higher molybdenum (4-5% vs 2-3%), and added copper (1-2%). This gives 904L much better resistance to sulfuric acid, phosphoric acid, and pitting in chlorides. PREN is 35-40 vs 24-26 for 316L. 904L is approximately 3-4 times the cost of 316L and is used where 316L fails.

Q: Is 904L suitable for seawater service?
A: Yes. 904L has excellent resistance to pitting and crevice corrosion in seawater up to temperatures of approximately 50°C. For higher temperatures or stagnant conditions, super duplex or nickel alloys may be required. 904L is often used for seawater cooling systems where 316L has failed.

Q: What is the maximum service temperature for 904L in sulfuric acid?
A: In 50-70% H₂SO₄, 904L can be used up to 100°C. In 90-96% H₂SO₄, limit to 50-60°C. For higher temperatures or more concentrated acid, high nickel alloys (Alloy 20, Alloy 625, Alloy C-276) are required. Always consult corrosion charts for specific conditions.

Q: Does 904L require solution annealing after welding?
A: Yes, per ASTM B673. 904L can form secondary phases (sigma, chi) in the weld HAZ if cooling is slow. Solution annealing at 1050-1150°C followed by water quench dissolves these phases and restores corrosion resistance. Womic performs full solution annealing on all 904L welded pipes. For field welding, use low heat input and consider post-weld solution annealing if possible.

Q: What welding filler metal is recommended for 904L?
A: AWS A5.14 ERNiCrMo-3 (Inconel 625) or ER385 is recommended. ERNiCrMo-3 is commonly used and provides good corrosion resistance matching 904L. ER385 is a specific 904L matching filler. Womic uses ERNiCrMo-3 for EFW processes.

Q: Is 904L suitable for sour service (H₂S)?
A: Yes, 904L is qualified per NACE MR0175/ISO 15156 for sour service with H₂S partial pressures up to 1 bar (15 psi) in specific hardness ranges. It is often used in moderately sour fields where duplex is insufficient due to high chlorides.

Q: What is the typical lead time for 904L welded pipe?
A: 60-75 days for ERW (small to medium diameters), 75-90 days for EFW/LSAW (large diameters). Lead times are longer than for standard stainless steels due to specialized alloy strip/plate sourcing (often 12-16 weeks from mill). Third-party inspection adds 7-14 days.

Q: Can 904L be used for high-purity water systems?
A: Yes, but it is usually over-specified. For high-purity water (RO, DI, WFI), 316L is sufficient and more economical. 904L is reserved for aggressive chemical or high-chloride conditions.

Project Reference – European Sulfuric Acid Plant Acid Cooler Piping Replacement

Country: Germany (North Rhine-Westphalia, chemical complex)
Standard & Grade: ASTM B673 UNS N08904 (904L) – welded pipe
Dimensions & Quantity:

● OD 88.9mm (3″) × Schedule 10S (3.05mm WT) – 600 meters (approx. 5 tons) – ERW process

● OD 114.3mm (4″) × Schedule 10S (3.05mm WT) – 500 meters (approx. 6 tons) – ERW process

● OD 168.3mm (6″) × Schedule 10S (3.40mm WT) – 300 meters (approx. 4 tons) – EFW process

● OD 219.1mm (8″) × Schedule 10S (3.76mm WT) – 200 meters (approx. 4 tons) – EFW process
Total: 1,600 meters, approx. 19 tons

Specifications: ASTM B673 UNS N08904 solution annealed and pickled, beveled ends. Hydrostatic testing at 1.5× design pressure (design 1.2 MPa). 100% UT for EFW pipes, eddy current for ERW. PMI on every pipe. Mandatory corrosion testing per ASTM G28 Practice A (ferric sulfate-sulfuric acid) – corrosion rate < 5 mpy (achieved 2-3 mpy). Pitting corrosion test per ASTM G48 Method A (6% FeCl₃, 24h at 40°C) – no pitting. Intergranular corrosion test per ASTM A262 Practice E (pass). Third-party inspection by TÜV Germany.

Application: Replacement of acid cooler piping and associated transfer lines in a sulfuric acid regeneration plant. The piping handles hot sulfuric acid (85-93% H₂SO₄) at 70-90°C from the absorption tower to the acid cooler. Previous 316L piping failed after 18 months due to general corrosion and pitting. 904L was selected for its superior resistance to concentrated sulfuric acid at elevated temperatures.

Technical Challenges & Solutions:

● Corrosion in hot concentrated sulfuric acid (85-93%, 70-90°C) – 316L corrodes at rates > 50 mpy under these conditions. 904L with its high nickel, chromium, molybdenum, and copper provides corrosion rate < 5 mpy. Womic performed ASTM G28 Practice A testing on base metal and weld samples. Corrosion rates: base metal 2.1 mpy, weld 2.8 mpy – well below 5 mpy limit. Client approved.

● Weld metal corrosion resistance – The weld is the most vulnerable area. Womic used low heat input (≤ 1.2 kJ/mm) and ERNiCrMo-3 filler. Weld samples passed G28 testing with corrosion rate 2.8-3.2 mpy. Microstructure showed no secondary phase precipitation.

● Pitting resistance at elevated temperature – The acid contains trace chlorides (from water source). 904L's PREN 35-40 provides pitting resistance. Womic performed G48 pitting test at 40°C (more severe than service temperature 70°C? Actually test temperature 40°C is lower, but FeCl₃ is aggressive). Result: no pitting after 72h.

● Intergranular corrosion after welding – 904L has low carbon (≤ 0.020%), but solution annealing is still required. Womic performed full solution annealing at 1100°C, water quench. ASTM A262 Practice E test passed.

● Field welding procedure – Plant maintenance team needed qualified WPS for repairs. Womic provided 15 weld coupons with WPS using GTAW, ERNiCrMo-3 filler, preheat 10-20°C, interpass ≤ 120°C, heat input ≤ 1.2 kJ/mm. Coupons passed RT, PT, and G28 testing.

● Logistics to German chemical plant – Pipes shipped from Shanghai to Hamburg port, then trucked to site. TÜV Germany inspected pipes at Hamburg. All 19 tons delivered within 10 weeks. Documentation package (MTC 3.2, test reports) delivered electronically.

Result: New 904L piping installed during Q3 2024 turnaround. After 12 months of operation, inspection showed no measurable corrosion, no pitting, and no leaks. Client expects 15+ year service life (vs 1.5 years for 316L). Womic Steel is now a qualified supplier for this chemical plant's sulfuric acid service piping.

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 B673 UNS N08904 welded stainless steel pipes for sulfuric and phosphoric acid plants, FGD systems, seawater cooling, and aggressive chemical service worldwide.