ASTM A312 TP304N Welded Stainless Steel Pipe: Manufacturing Capabilities & Product Specifications

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Womic Steel supplies ASTM A312 TP304N welded stainless steel pipe, a nitrogen-strengthened 304 stainless steel with higher yield strength (275 MPa) than standard 304 while maintaining excellent corrosion resistance, ductility, and weldability. Nitrogen addition improves strength and pitting resistance without upgrading to duplex stainless steel.

Manufactured by ERW and EFW processes with solution annealing and pickled finish. Available in OD 6.35mm–1219mm (1/4″–48″), wall thickness 0.5mm–50mm, and lengths up to 24m. Supplied with mill certificates, hydrostatic testing, UT inspection, and customized end finishes.

Applications:
Pressure vessels, chemical processing, offshore platforms, heat exchangers, hydraulic systems, water treatment, paper mills, and high-pressure industrial piping.

Standard & Grade:
ASTM A312 TP304N / ASME SA312 / EN 10217-7 1.4315 (AISI 304N)

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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 stainless steel tubular products. Our specialized TP304N welded pipe production facility utilizes multiple advanced welding technologies with controlled heat input to maintain nitrogen content in the weld metal:

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 optimized parameters to retain nitrogen. Ideal for small to medium diameter TP304N pipes for pressure and structural applications.
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, using matching filler metal (ER304N or ER308 with nitrogen).
LSAW / SAWL Line for Stainless: For diameters from 406mm to 1524mm (16″ – 60″), wall thickness up to 50mm. Submerged arc welding of rolled TP304N plates.

All TP304N welded pipes undergo solution annealing (heat treatment) at 1040-1120°C followed by water quenching to retain nitrogen in solid solution and restore corrosion resistance, followed by pickling and passivation.

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

Womic Steel supplies TP304N welded pipes to over 40 countries across pressure vessel, structural, and chemical 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 × 6.0–50mm WT × ≤ 18m
Finishing options: Annealed and pickled, bright annealed, polished (180# to 320#)

2. ASTM A312 TP304N: Material Composition & Performance Characteristics

ASTM A312 TP304N is a nitrogen-strengthened version of standard 304 stainless steel. Nitrogen (0.10-0.16%) provides solid solution strengthening, increasing yield strength by approximately 35% while maintaining excellent ductility, toughness, and corrosion resistance. This allows thinner wall sections for the same pressure rating, reducing weight and cost.

Chemical Composition (Ladle Analysis, % by mass):

Element	TP304N (ASTM A312)	TP304 (for comparison)
C	≤ 0.08	≤ 0.08
Mn	≤ 2.00	≤ 2.00
P	≤ 0.045	≤ 0.045
S	≤ 0.030	≤ 0.030
Si	≤ 1.00	≤ 1.00
Cr	18.0 – 20.0	18.0 – 20.0
Ni	8.0 – 11.0	8.0 – 11.0
N	0.10 – 0.16	≤ 0.10
Fe	Balance	Balance

Mechanical Properties (Room Temperature, Solution Annealed):

Property	TP304N	TP304
Yield Strength (min, 0.2% offset)	275 MPa (39,900 psi)	205 MPa (30,000 psi)
Tensile Strength (min)	550 MPa (79,800 psi)	515 MPa (74,700 psi)
Elongation (min, 50mm gauge)	35%	40%
Hardness (max)	90 HRB	90 HRB

Physical Properties:

Density: 7.93 g/cm³
Modulus of Elasticity: 200 GPa (29 × 10⁶ psi)
Thermal Conductivity: 16.2 W/m·K at 100°C
Coefficient of Thermal Expansion: 17.2 × 10⁻⁶/°C (20-100°C)

Corrosion Resistance:

Similar to 304 in most environments (good resistance to oxidizing acids, organic acids)
Slightly improved pitting resistance due to nitrogen (PREN ≈ 19-20 vs 18 for 304)
Excellent resistance to intergranular corrosion after welding (when properly solution annealed)
Not suitable for chloride service above ambient temperature (use 316N or duplex for chlorides)

Key Advantages over 304:

35% higher yield strength allows thinner walls (weight reduction 20-25%)
Higher allowable stress per ASME Section VIII for pressure vessels
Comparable weldability and formability
Slightly better pitting resistance

3. Dimensional Range & Standards Compliance

Item	Specification
Standard	ASTM A312 / ASME SA312 (also A358, A249)
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 – 50mm
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, Polished
Tolerances	OD: ±0.5% or ±3.2mm; WT: ±12.5% (per ASTM A999); Length: +50mm / -0mm

4. Available Dimensions & Specifications – ASTM A312 TP304N Welded Stainless Steel Pipe

NPS	OD (mm)	Schedule	WT (mm)	Weight (kg/m)	Standard Length	Typical Application
1/2″	21.3	10S	2.11	1.00	6m	Hydraulic line
3/4″	26.7	10S	2.11	1.28	6m	Chemical dosing
1″	33.4	10S	2.77	2.09	6m	High pressure water
1-1/2″	48.3	10S	2.77	3.11	6m	Process line
2″	60.3	10S	2.77	3.93	6m / 12m	Pressure vessel
3″	88.9	10S	3.05	6.46	6m / 12m	Structural column
4″	114.3	10S	3.05	8.37	6m / 12m	Heat exchanger
6″	168.3	10S	3.40	13.8	6m / 12m	Paper mill
8″	219.1	10S	3.76	20.0	12m	Offshore topside
10″	273.0	10S	4.19	27.8	12m	Structural support
12″	323.9	10S	4.57	36.0	12m	Main header
16″	406.4	10S	4.78	47.4	12m	Pressure vessel shell
20″	508.0	10S	5.54	68.6	12m	Large diameter
24″	609.6	10S	6.35	94.4	12m	Storage tank

Custom dimensions outside these ranges available. TP304N allows thinner walls than 304 for same pressure rating.

5. Common Stainless Steel Standards & Grades Manufactured by Womic Steel

Standard	Steel Grades	Typical Application	Welding Process
ASTM A312	TP304N, TP304, TP304L, TP316N, TP316	Corrosive service, pressure	ERW/EFW/LSAW
ASTM A358	TP304N, TP304, TP316	Electric fusion welded	EFW
ASTM A249	TP304N	Boiler, superheater, heat exchanger	ERW/EFW
ASTM A312	TP304L, TP316L	General corrosive service	ERW/EFW/LSAW
EN 10217-7	1.4315 (304N)	Pressure purposes	SAW/ERW

Usage: Pressure vessels, structural components, offshore piping, chemical processing, heat exchangers, paper mill equipment.

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

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

1. Raw Material (Strip/Coil) Inspection: TP304N strip verified for composition (Cr 18-20%, Ni 8-11%, N 0.10-0.16%). Each coil has unique heat number.

2. Uncoiling & Leveling

3. Strip Edge Trimming

4. Forming: Continuous roll forming.

5. High-Frequency Welding: Optimized heat input (≤ 1.5 kJ/mm) to retain nitrogen. Higher speeds may be required.

6. Seam Annealing: Induction annealing followed by water quench.

7. Sizing & Straightening

8. Cutting to Length

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

10. Solution Annealing (Full Pipe): 1040-1120°C, water quench. Critical for dissolving nitrides and restoring properties.

11. Hydrostatic Test

12. Pickling & Passivation

13. PMI (XRF) & Nitrogen verification (if specified)

14. Final Inspection & Marking

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

1. Plate Preparation: TP304N plate, edges beveled (X bevel).

2. Roll Forming

3. Tack Welding

4. TIG (GTAW) Root Pass: Matching filler (ER308 or ER304N), argon backing gas.

5. SAW Fill & Cap Passes: Multi-pass SAW with controlled heat input (≤ 1.8 kJ/mm), interpass ≤ 150°C.

6. Inner Weld

7. 100% Radiographic Testing (per ASTM A358)

8. Solution Annealing: Full pipe heat treatment (1040-1120°C), water quench.

9. Pickling & Passivation

10. Hydrostatic Test

11. Dimensional Inspection & Marking

LSAW Process for Stainless – Very Large Diameter (406–1524mm OD, 6.0–50mm WT):

UOE or JCOE forming from TP304N plate
Double-sided SAW welding
Full solution annealing after welding

Special Considerations for TP304N:

Nitrogen content must be controlled to avoid nitride precipitation
Solution annealing temperature higher end of range (1080-1120°C) to dissolve nitrides
Water quench mandatory to retain nitrogen in solid solution
Welding consumables should have matching nitrogen content (ER308L with N addition)

7. Quality Control & Testing Procedures for ASTM A312 TP304N Welded Stainless Steel Pipe

Stage	Inspection Method	Purpose
Raw Material	Chemical Analysis (OES + Combustion for N)	Verify TP304N (N 0.10-0.16%, Cr 18-20%, Ni 8-11%)
Raw Material	Tensile Testing	Verify yield ≥ 275 MPa, tensile ≥ 550 MPa
Raw Material	Hardness	≤ 90 HRB
In-Process	Heat Input Monitoring	≤ 1.8 kJ/mm
Weld (ERW)	Eddy Current (100%)	Weld integrity
Weld (EFW/LSAW)	100% UT (or PAUT)	Detect weld defects
Weld (EFW/LSAW)	RT (spot or 100% per spec)	Weld quality
Weld	Dye Penetrant (PT)	Surface cracks
After Solution Annealing	Hardness Test	≤ 90 HRB
After Solution Annealing	Nitrogen Verification (if specified)	Confirm N content in finished pipe
Finished Pipe	Hydrostatic Test	Pressure integrity
Finished Pipe	Flattening / Guided Bend	Ductility
Finished Pipe	PMI (XRF)	Confirm grade (Cr, Ni)
Finished Pipe	Visual & Marking	Traceability

Optional Tests:

Elevated temperature tensile test (if required for design)
Pitting corrosion test (ASTM G48) for critical service

Intergranular corrosion test (ASTM A262 Practice E)

8. Primary Applications – ASTM A312 TP304N Welded Stainless Steel Pipe

1. Pressure vessels and storage tanks: Higher allowable stress per ASME Section VIII allows thinner walls (20-25% weight savings) compared to 304.

2. Structural components in corrosive environments: Offshore platform topside supports, chemical plant structural framing, food processing plant columns. Higher strength reduces section size.

3. Offshore platform topside piping: Process piping where higher pressure rating is needed but duplex is not required. TP304N provides intermediate strength.

4. Chemical processing (higher pressure systems): Reactor inlet/outlet piping, high-pressure transfer lines where 304 is insufficient but 316L is over-specified.

5. Heat exchanger shells and tubes: Shell side pressure can be increased without thickening shell. Tubes can have thinner walls for better heat transfer.

6. Paper mill equipment: Digester blow lines, stock preparation piping where higher strength resists erosion-corrosion.

7. Brewery and dairy piping: High-pressure CIP (Clean-In-Place) systems and product lines operating at 10-15 bar.

8. Hydraulic lines: Instrumentation and control lines requiring higher burst pressure than 304.

9. Pump and valve bodies: Cast or fabricated components (replaces 304 with higher strength).

10. High-pressure water treatment systems: Reverse osmosis feed lines (higher pressure rating).

11. Architectural structures: Where higher strength allows slimmer profiles (handrails, supports).

9. Packaging & Shipping – ASTM A312 TP304N Welded Stainless Steel Pipe

Packaging:

Anti-corrosion protection: Pipes oiled or VCI paper. For food/brewing, no oil residue (plastic wrap).
End caps: 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 applications.

Shipping:

Containers for ≤ 610mm, break-bulk for larger diameters.
Documentation: MTC 3.1/3.2, hydrotest report, eddy current/UT reports, PMI report, dimensional report, packing list, COO.

10. Womic Steel Advantages & FAQ – ASTM A312 TP304N Welded Stainless Steel Pipe

Why Partner with Womic Steel for TP304N Welded Pipe?

Complete Size Range: ERW 1/4″ – 24″, EFW/LSAW 8″ – 60″.
Full solution annealing after welding (1040-1120°C, water quench).
Nitrogen retention verified through combustion analysis.
Higher strength allows thinner walls – weight savings of 20-25% over 304.
Competitive lead times: 25-35 days for ERW, 35-50 days for EFW/LSAW.
Global Certification: ISO 9001, PED (CE), EN 10204 Type 3.2.

Frequently Asked Questions (FAQ) – ASTM A312 TP304N Welded Pipe

Q: What is the advantage of TP304N over standard 304?
A: TP304N has 35% higher yield strength (275 MPa vs 205 MPa) while maintaining similar corrosion resistance, ductility, and weldability. This allows designers to use thinner walls for pressure vessels and piping, reducing weight by 20-25% and lowering material cost for the same pressure rating. For structural applications, smaller section sizes can be used.

Q: Is TP304N more expensive than 304?
A: Slightly, due to nitrogen alloying and tighter composition control. However, the weight savings (20-25% thinner walls) often result in lower overall material cost for pressure-containing applications. For structural applications where strength is critical, the weight reduction may offset the higher unit price.

Q: Can TP304N be welded without losing nitrogen?
A: Yes, with proper welding parameters (low heat input, ≤ 1.8 kJ/mm) and appropriate filler metal (ER308 or ER304N). The nitrogen retained in the weld metal is typically 80-90% of base metal. Womic’s ERW process uses optimized high-frequency welding that minimizes nitrogen loss. For critical applications, solution annealing after welding restores nitrogen distribution.

Q: Does TP304N require solution annealing after welding?
A: ASTM A312 requires solution annealing for welded pipe. For TP304N, solution annealing at 1040-1120°C followed by water quench is necessary to dissolve any nitrides that may have formed during welding and to restore full corrosion resistance and mechanical properties. Womic performs solution annealing on all TP304N welded pipes.

Q: Is TP304N suitable for seawater service?
A: Not recommended. TP304N has similar pitting resistance to 304 (PREN ≈ 19-20). For seawater or high-chloride environments, use 316N (with Mo) or duplex stainless steel. TP304N is for applications requiring higher strength in non-chloride or low-chloride environments.

Q: What is the typical allowable stress for TP304N in ASME Section VIII?
A: At room temperature, allowable stress for TP304N is approximately 137 MPa (20,000 psi) vs 115 MPa (16,700 psi) for 304 – about 19% higher. The actual values depend on temperature; refer to ASME Section II, Part D. Designers should use the correct allowable stress values for the specific grade.

Q: What is the typical lead time for TP304N welded stainless steel pipe?
A: 25-35 days for ERW (small to medium diameters), 35-50 days for EFW/LSAW (large diameters). TP304N is a standard grade for many mills, so lead times are similar to 304.

Q: Can TP304N be used for high-temperature service (above 500°C)?
A: TP304N’s high-temperature strength is better than 304 due to nitrogen solid solution strengthening. However, for sustained service above 550°C, grades with higher carbon (304H) or creep-resistant grades (321H, 347H) are preferred. TP304N is best suited for moderate temperatures (< 425°C) where strength is needed.

11. Project Reference – Offshore Platform Topside Piping & Structural Supports (Brazil)

Country: Brazil (Campos Basin, offshore Rio de Janeiro)
Standard & Grade: ASTM A312 TP304N (welded)
Dimensions & Quantity:

OD 219.1mm (8″) × Schedule 10S (3.76mm WT) – 1,200 meters (approx. 28 tons) – EFW process
OD 168.3mm (6″) × Schedule 10S (3.40mm WT) – 1,800 meters (approx. 22 tons) – ERW process
OD 114.3mm (4″) × Schedule 10S (3.05mm WT) – 2,500 meters (approx. 20 tons) – ERW process
OD 60.3mm (2″) × Schedule 10S (2.77mm WT) – 3,000 meters (approx. 12 tons) – ERW process
OD 406.4mm (16″) × Schedule 10S (4.78mm WT) – 300 meters (approx. 12 tons) – EFW process (structural columns)

Total: 8,800 meters (8.8 km), approx. 94 tons

Specifications: ASTM A312 TP304N solution annealed and pickled, beveled ends. Hydrostatic testing. 100% UT for EFW pipes, eddy current for ERW. PMI on every pipe. Tensile testing (yield ≥ 275 MPa, achieved 310-340 MPa; tensile ≥ 550 MPa, achieved 580-620 MPa). Charpy impact at -20°C (min 27J, achieved 100-150J). Intergranular corrosion test per ASTM A262 Practice E (pass). Third-party inspection by DNV Brazil.

Application: Topside process piping and structural supports for an offshore production platform in the Campos Basin. The process piping handles produced water and low-pressure gas at 50-80°C with low chloride content (treated produced water). The structural supports are for equipment skids and pipe racks. The platform required weight reduction to extend its service life (fatigue concerns). TP304N was selected for its 35% higher yield strength, allowing thinner walls (Schedule 10S instead of Schedule 40S) for both piping and structural members.

Engineering Context: The platform was originally designed for 304 piping. By upgrading to TP304N and reducing wall thickness from Schedule 40S (4.55-8.18mm) to Schedule 10S (2.77-4.78mm), the engineering team achieved a 45% weight reduction on piping and a 30% weight reduction on structural supports – total weight saving of 35 tons (27% of original weight). This allowed the platform to remain within its topside weight budget.

Technical Challenges & Solutions:

Weight reduction without compromising pressure rating – TP304N’s higher yield strength allowed thinner walls per ASME B31.3. For 8″ piping, Schedule 10S (3.76mm) replaced Schedule 40S (8.18mm), reducing weight by 54%. Womic provided dimensional certification and pressure test reports. Hydrostatic test at 3.0 MPa passed (design pressure 1.8 MPa, test pressure 2.7 MPa).
Weld metal strength matching – ERW and EFW weld metal must have strength equal to base metal. Womic optimized ERW parameters to achieve weld joint efficiency of 95% (tensile strength 560 MPa vs base 590 MPa). EFW welds using ER308 filler achieved 100% joint efficiency. All weld tensile tests passed.
Corrosion resistance at reduced wall thickness – Thinner walls have less corrosion allowance. The produced water is low chloride (< 50 ppm) with pH 6.5-7.5, so corrosion rate is low. TP304N has slightly better pitting resistance than 304 due to nitrogen. Womic performed ASTM G48 pitting test (24h at 22°C) – no pitting. Client accepted.
Structural support design using TP304N – The 16″ structural columns used Schedule 10S (4.78mm) instead of Schedule 40S (9.53mm). Finite element analysis (FEA) confirmed that the thinner wall with TP304N’s higher yield strength provided equivalent load capacity. Womic provided straightness tolerance ≤ 0.15% for column stability.
Field welding procedure for TP304N – Platform maintenance team needed to modify piping during installation. Womic provided WPS using GTAW with ER308 filler, heat input ≤ 1.8 kJ/mm, interpass ≤ 150°C. 20 weld coupons passed RT, PT, and tensile testing.
Logistics to Campos Basin – Pipes shipped from Shanghai to Rio de Janeiro, then to offshore platform via supply vessel. DNV inspected pipes at loading. All 94 tons delivered in two shipments over 5 weeks.

Result: Platform topside piping and structural supports installed in Q2 2024. The weight savings of 35 tons allowed the platform to meet its topside weight limit without requiring structural reinforcement. After 12 months of operation, inspection showed no corrosion or weld failures. The operator plans to use TP304N for future platform upgrades to reduce weight and extend asset life. Womic Steel is now a qualified supplier for this operator’s stainless steel piping needs.

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 A312 TP304N welded stainless steel pipes for pressure vessels, offshore platforms, structural applications, and high-pressure chemical systems worldwide.

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