316L stainless steel welded pipe (UNS S31603 / SUS316L / 1.4404) is a low-carbon molybdenum-bearing austenitic stainless steel tube manufactured by high-frequency longitudinal welding, continuous forming, internal weld bead leveling, solution annealing, pickling and precision sizing. The letter “L” stands for ultra-low carbon content (C ≤0.03%), which effectively prevents intergranular corrosion after welding and long-term high-temperature service.

With molybdenum alloy addition, 316L welded pipe delivers outstanding resistance to chloride ions, salt spray, seawater, mild acid and alkali media, far superior to standard 304 welded tubes. It features smooth inner and outer surfaces, precise dimensional tolerance, uniform wall thickness, excellent weld integrity, good ductility, weldability and machinability. Widely adopted in marine, chemical, food & beverage, pharmaceutical, water treatment, HVAC, desalination and coastal anti-corrosion pipeline systems.

2. Global Equivalent Grade Cross Reference

Remark: All equivalent grades share unified low-carbon & molybdenum design, fully interchangeable for fluid delivery, structural and sanitary pipeline applications.

3. Chemical Composition (wt%, Standard Specification Limits)

Core Composition Advantages

Ultra-low carbon (C ≤0.03%): Suppresses chromium carbide precipitation at grain boundaries, eliminates intergranular corrosion after welding without post-weld solution annealing.

2.00–3.00% molybdenum: The core anti-corrosion element, greatly improves resistance to pitting corrosion, crevice corrosion and chloride ion erosion in seawater, salt fog and chemical brine environments.

16–18.5% chromium: Forms dense self-repairing chromium oxide passive film for oxidation and atmospheric corrosion protection.

10–14% nickel: Stabilizes full austenite microstructure, maintains excellent toughness and non-magnetic performance under annealed state.

Strict low sulfur & phosphorus control: Avoids weld cracking during high-frequency welding, bending and flanging processing.

4. Physical & Mechanical Properties

4.1 Basic Physical Properties (Room Temperature, Solution Annealed Condition)

Density: 7.98 g/cm³
Melting range: 1370 ~ 1400 ℃
Thermal conductivity (20℃): 15.9 W/m·K
Specific heat capacity: 500 J/kg·K
Resistivity: 0.74 Ω·mm²/m
Linear thermal expansion coefficient (20–200℃): 16.0 ×10⁻⁶ /℃
Elastic Modulus E: 193 GPa
Shear Modulus G: 71 GPa
Poisson’s Ratio: 0.24
Magnetism: Fully non-magnetic after full solution annealing; slight weak magnetism generated after cold forming, bending or drawing
Continuous long-term service temperature: ≤600℃

4.2 Room-Temperature Mechanical Properties (Annealed Welded Pipe, Minimum Standard Values)

Key Weld Performance

Internal weld bead is fully leveled after welding; uniform metallurgical structure at weld seam, consistent mechanical strength with base metal, passing hydraulic pressure test, eddy current and ultrasonic non-destructive testing.

5. Outer Diameter & Wall Thickness Tolerance Range

5.1 Outer Diameter Tolerance

Small OD tube (OD ≤ 50.8 mm): ±0.10 mm
Medium OD tube (50.8 mm ＜ OD ≤ 168.3 mm): ±0.15 mm
Large OD tube (OD ＞ 168.3 mm): ±0.20 ~ ±0.30 mm Sanitary thin-wall precision tubes can provide tighter tolerance ±0.05 mm on custom demand.

5.2 Wall Thickness Tolerance

Standard industrial welded pipe: ±10% of nominal wall thickness
Sanitary precision thin-wall tube: ±5% of nominal wall thickness
Heavy-wall structural pipe: ±8% of nominal wall thickness

5.3 Standard Size Range

Outer Diameter: 6 mm ~ 610 mm
Wall Thickness: 0.3 mm ~ 12.0 mm
Standard fixed length: 3000 mm / 6000 mm; custom cut-to-length service available
Supply forms: Straight fixed-length tubes, coil welded tubes (small OD thin wall)

6. Common Surface Finishes for 316L Welded Pipe

2B Pickled Matte Surface (Industrial General Grade) Uniform silver-gray matte surface after annealing and pickling, clean inner and outer walls, low cost, widely used for chemical fluid pipelines, water treatment and structural frames.

BA Bright Annealed Surface Semi-bright smooth finish without oxide layer, smooth inner bore, suitable for general sanitary equipment and heat exchange pipelines.

No.4 Brushed Hairline Surface Fine linear grain outer surface, fingerprint-resistant optional coating, for architectural decorative handrail tubes and outdoor decorative piping.

8K Mirror Polished Surface High-gloss mirror finish on inner & outer walls, ultra-smooth, no dead angle residue, used for high-end food, pharmaceutical sanitary pipelines.

Electro-Polished EP Surface (Premium Sanitary Grade) Electrochemical polishing treatment, ultra-low surface roughness Ra ≤0.8μm, superior anti-staining performance, dedicated to biopharmaceutical, beverage, pure water ultra-clean piping systems.

7. Core Product Features

Outstanding Chloride Corrosion Resistance Molybdenum alloy design resists seawater, salt spray, coastal humidity and mild acid & alkali media; service life is 3–5 times longer than 304 welded pipe in corrosive environments.

Ultra-Low Carbon Anti-Sensitization Property No intergranular corrosion risk after repeated welding; no need for post-weld heat treatment, greatly reducing construction processing cost.

Smooth Inner Wall & Low Fluid Resistance Leveled internal weld bead eliminates welding protrusions, reduces pipeline fluid resistance, avoids medium residue and bacterial breeding, meets sanitary standards.

Excellent Formability & Weldability High ductility supports bending, flanging, rolling and secondary welding; compatible with TIG, MIG, orbital automatic welding for sanitary engineering.

Wide Temperature Adaptability Stable mechanical performance from -196℃ cryogenic environment up to continuous working temperature 600℃.

Sanitary & Biocompatible Non-toxic, no heavy metal precipitation, complies with food contact, pharmaceutical and medical pipeline global standards.

Long Service Life & Maintenance-Free Self-healing passive anti-rust film, no painting required, wear-resistant and aging-resistant for indoor and coastal outdoor long-term use.

8. Typical Application Fields

8.1 Marine & Coastal Engineering

Seawater desalination pipelines, ship fluid delivery tubes, offshore platform support pipes, coastal factory cooling water piping, salt fog workshop anti-corrosion pipelines.

8.2 Chemical & Environmental Protection Industry

Chemical acid & alkali medium conveying pipes, sewage treatment equipment pipelines, waste gas desulfurization piping, brine circulation system tubes.

8.3 Food, Beverage & Dairy Industry

Edible liquid transmission pipelines, beverage production lines, dairy processing equipment tubes, food sterilization circulating pipes, sanitary tank connecting pipes.

8.4 Pharmaceutical & Medical Equipment

Pure water pipeline for pharmaceutical workshops, sterile production delivery tubes, medical equipment support piping, laboratory anti-corrosion fluid pipes.

8.5 HVAC, Heat Exchange & Water Supply

Heat exchanger tubes, central air conditioning anti-corrosion piping, domestic pure water supply pipelines, boiler low-pressure fluid circulation tubes.

8.6 Architectural & Municipal Decoration

Coastal building handrail tubes, outdoor landscape decorative pipes, municipal coastal guardrail structural tubes, public facility anti-rust piping.

9. Grade Comparison Chart

10. Usage Notes

Not suitable for long-term service in concentrated strong acid or high-concentration chloride solution; select higher grade alloy such as 904L for heavy corrosive working conditions.

Slight magnetism after cold bending and forming is normal physical characteristic, which does not affect corrosion resistance and structural strength; demagnetization annealing can be provided upon request.

Continuous working temperature cannot exceed 600℃; long-term high temperature will cause surface oxidation and reduce anti-corrosion performance.

For sanitary pipelines transporting pure water and pharmaceutical media, EP electro-polished surface is recommended to avoid medium adhesion and bacterial growth.

After field welding of thick-wall pipes used in corrosive environment, pickling and passivation treatment is required to restore full anti-corrosion performance.

11. Executive Standards & Export Supporting Certifications

Comply with ASTM A249, ASTM A269, ASTM A312, EN 10217-7, JIS G3447, GB/T 12771. Available documents: MTC material test certificate, SGS third-party composition inspection, RoHS environmental compliance report, food-grade contact safety test report, hydraulic pressure & NDT test records, fully meet global industrial, sanitary and marine engineering export procurement standards.

Contact Us

ALLIN METAL GROUP is a professional manufacturer specialized in premium 316L stainless steel welded pipes, covering industrial pickled tubes, BA bright tubes, No.4 brushed tubes, 8K mirror tubes and EP electro-polished sanitary tubes. We own full production lines including high-frequency forming, internal weld leveling, continuous annealing, precision sizing and multi-channel non-destructive testing, capable of customizing outer diameter, wall thickness, length and surface treatment to match marine, chemical, food, pharmaceutical and water treatment projects worldwide. With stable monthly output, strict full-process quality control and flexible delivery schedules, we supply cost-effective anti-corrosion welded tubes for global buyers. If you have any procurement requirements, please feel free to contact our professional sales team to obtain technical datasheets, factory quotations and bulk order support.