Product Introduction
Seamless Austenitic Steel 304L Pipe is a low-carbon variant of the widely used 304 stainless steel, engineered to eliminate intergranular corrosion risks during welding while maintaining excellent general corrosion resistance. This austenitic alloy features an 18-20% chromium and 8-13% nickel composition, with carbon content restricted to ≤0.035%—a critical modification that prevents chromium carbide precipitation at grain boundaries (sensitization), a common issue in standard 304 (≤0.08% C).
The alloy's microstructure offers a balance of ductility, formability, and corrosion resistance, making it ideal for applications requiring hygienic standards, weldability, and durability. Its austenitic structure provides inherent non-magnetic properties and good low-temperature toughness, while the addition of nickel enhances resistance to reducing acids and chloride environments. TP304L’s versatility is further amplified by its ease of fabrication—capable of being welded, machined, and formed without specialized processes, making it a cost-effective solution across diverse industries.
Manufactured via seamless extrusion or welding, TP304L pipes undergo solution annealing to refine grain structure and remove residual stresses, ensuring uniform performance. Optional surface treatments like pickling, polishing, or electropolishing enhance corrosion resistance and meet strict hygienic requirements, solidifying its role as a go-to material in critical sectors such as food processing, pharmaceuticals, and chemical manufacturing.
Key Product Parameters
Material Grades & Specifications
ASTM A312: Seamless/welded austenitic stainless steel pipes for high-pressure applications.
ASTM A213: Boiler, superheater, and heat-exchanger tubes.
EN 10216-5: European standard for seamless steel tubes in pressure systems.
JIS G3459: Japanese standard for stainless steel pipes.
Chemical Composition (wt.%)
| Grade | C | Si | Mn | Cr | Ni | S | P |
| 304L | ≤0.035 | ≤1.00 | ≤2.00 | 18.0-20.0 | 8.0-13.0 | ≤0.03 | ≤0.045 |
| 304 | ≤0.08 | ≤1.00 | ≤2.00 | 18.0-20.0 | 8.0-11.0 | ≤0.03 | ≤0.045 |
| 304H | 0.04-0.10 | ≤1.00 | ≤2.00 | 18.0-20.0 | 8.0-11.0 | ≤0.03 | ≤0.045 |
Mechanical Properties
| Property | 304L | 304 | 304H |
| Tensile Strength | ≥70 ksi (485 MPa) | ≥75 ksi (515 MPa) | ≥75 ksi (515 MPa) |
| Yield Strength | ≥25 ksi (170 MPa) | ≥30 ksi (205 MPa) | ≥30 ksi (205 MPa) |
| Elongation | ≥35% | ≥35% | ≥35% |
| Hardness (HRB) | ≤90 | ≤90 | ≤90 |
| Impact Toughness | ≥100 J/cm² at 20°C | ≥100 J/cm² at 20°C | ≥100 J/cm² at 20°C |
Dimension Range
Outer Diameter (OD): 6 mm to 1016 mm (0.24" to 40")
Wall Thickness: 1 mm to 65 mm (0.04" to 2.56")
Length: Customizable up to 12 meters (standard: 6 meters)
Corrosion Resistance
Media Resistance:
Organic acids (acetic, formic) at moderate temperatures.
Salt solutions (sulfates, sulphites).
Caustic solutions (NaOH, KOH) at low concentrations.
Oxidizing acids (nitric acid) up to 60% concentration.
Limitations:
Poor resistance to reducing acids (hydrochloric, sulfuric) at high concentrations.
Susceptible to pitting in stagnant chloride solutions (>200 ppm Cl⁻).
Surface & Testing
Surface Treatments:
Pickled & Annealed: Removes scale, ideal for general corrosion resistance (Ra ≤1.6μm).
Polished: Ra ≤0.8μm for hygienic applications (food, pharmaceuticals).
Electropolished: Ra ≤0.2μm for ultra-clean surfaces (semiconductor, medical).
Quality Control:
100% Eddy Current Testing (ET) for surface defects.
Hydrostatic Pressure Testing (1.5x design pressure).
Intergranular Corrosion (IGC) Testing per ASTM A262 Practice E.
Application Scenarios
Food & Beverage Industry
Processing Equipment: Milk processing lines, brewery tanks, and juice extraction systems, meeting 3-A Sanitary Standards.
Packaging Machinery: Conveyor rails, filling nozzles, and sterilization chambers, ensuring product safety and hygiene.
Storage & Transport: Stainless steel tubing for edible oil pipelines and beverage distribution networks.
Pharmaceutical & Biotechnology
Cleanroom Infrastructure: Welded pipe systems for purified water (PW) and water-for-injection (WFI), complying with cGMP.
Drug Manufacturing: Reactors, distillation columns, and API transfer lines, resisting corrosion from aggressive chemicals.
Medical Devices: Sterilizable components for autoclaves and pharmaceutical filling machines.
Chemical Processing
Acid Handling: Nitric acid transport lines (≤60% concentration) and mild alkali systems.
Petrochemical Refining: Heat exchangers in hydrocarbon processing and fuel distribution pipelines.
Waste Treatment: Corrosion-resistant pipes for acidic effluent neutralization and chemical storage tanks.
Architectural & Structural
Building Envelopes: Decorative handrails, curtain wall systems, and outdoor cladding, resisting atmospheric corrosion.
Marine Architecture: Coastal bridges, piers, and waterfront structures, withstanding salt-laden air.
Interior Design: Kitchen countertops, elevator panels, and sanitary fixtures, combining aesthetics with durability.
Automotive & Aerospace
Exhaust Systems: Mufflers, catalytic converters, and exhaust pipes, enduring high temperatures and moisture.
Aerospace Components: Non-magnetic brackets, fuel lines, and cabin interiors for commercial aircraft.
FAQ (Frequently Asked Questions)
Q: How does TP304L differ from TP304 in welding applications?
A: TP304L’s lower carbon content (≤0.035%) prevents intergranular corrosion after welding, whereas TP304 (≤0.08% C) may develop chromium carbide precipitation in the heat-affected zone (HAZ), compromising corrosion resistance.
Q: Can TP304L be used in seawater environments?
A: TP304L offers limited resistance to seawater (high chloride content). For marine applications, consider 316L (with molybdenum) or duplex steels. TP304L is suitable for intermittent seawater exposure but not for submerged or stagnant conditions.
Q: What is the maximum service temperature for TP304L?
A: TP304L performs reliably up to 425°C in continuous service. For higher temperatures (540–870°C), use TP304H, which maintains strength via higher carbon content (0.04–0.10%).
Q: How to prevent pitting corrosion in TP304L?
A: Avoid stagnant chloride solutions (>200 ppm Cl⁻). For aggressive environments, specify electropolished surfaces to reduce surface roughness, or use corrosion inhibitors to minimize chloride concentration.
Q: Is TP304L magnetic?
A: No, TP304L is austenitic and non-magnetic in its as-annealed condition. Cold working may induce slight magnetism, but it can be eliminated via annealing.
Q: What is the lead time for custom TP304L orders?
A: Standard sizes are available within 1–2 weeks. Custom dimensions, special finishes (e.g., electropolishing), or certifications (e.g., 3.2 Certification) require 3–4 weeks, including testing and documentation.
