What is 304 Stainless Steel Aircraft Tubing?
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What is 304 Stainless Steel Aircraft Tubing?
304 stainless steel aircraft tubing is a high-performance austenitic stainless steel tube used in aircraft structures, hydraulic systems, and support assemblies where strength, corrosion resistance, and weldability are essential. With its balanced chemical composition and proven reliability, 304 tubing is one of the most widely used materials in the aerospace and aviation industries.
Key Characteristics of 304 Stainless Steel Aircraft Tubing
304 stainless steel (UNS S30400) is an iron-based alloy containing approximately 18% chromium and 8% nickel, making it highly corrosion-resistant and mechanically stable across a wide temperature range.
304 Stainless Steel Corrosion Resistant Tubing
Excellent Corrosion Resistance to atmospheric conditions, mild chemicals, and oxidizing environments
Good Strength-to-Weight Ratio, suitable for non-critical load-bearing components
304 stainless steel annealed tube
Outstanding Weldability and Formability, enabling complex fabrication without cracking
Non-Magnetic in Annealed Condition, a benefit in aerospace electrical or sensor environments
Where is 304 tubing for aerospace used?
Hydraulic Lines: High-pressure fluid transport in aircraft.
Fuel Systems: Corrosion-resistant fuel delivery lines.
Structural Support: Airframe components where weight and strength are balanced.
Instrumentation: Pitot tubes and sensor housings.
Aircraft-grade 304 stainless steel tubing Specifications
| Item | Description |
| Product Name | Aerospace Grade 304 Stainless Steel Tubing |
| Grade | Type 304 (Austenitic Stainless Steel) |
| Construction | Seamless (SML) or Welded and Drawn (W&D) |
| Condition | Annealed (Soft), 1/8 Hard, or Full Hard (as specified) |
| Finish | Bright Annealed or Passivated |
Applicable Aerospace Standards
| Standard | Description |
| AMS 5560 | Seamless 18Cr-8Ni (304) Tubing |
| AMS 5566 | Seamless or Welded & Drawn (High Pressure/Hydraulic) |
| MIL-T-8504 | Military Specification for Stainless Steel Tubing |
| ASTM A269 | General Service Tubing (often used as a baseline) |
Chemical Composition
Per AMS 5560/5566 Standards (wt%)
| Element | Min (%) | Max (%) |
| Carbon (C) | - | 0.08 |
| Chromium (Cr) | 18.00 | 20.00 |
| Nickel (Ni) | 8.00 | 11.00 |
| Manganese (Mn) | - | 2.00 |
| Silicon (Si) | - | 1.00 |
| Phosphorus (P) | - | 0.040 |
| Sulfur (S) | - | 0.030 |
Mechanical Properties
Values based on Annealed Condition; cold-worked tubes will have higher strength.
| Property | Value (Imperial) | Value (Metric) |
| Tensile Strength (Rm) |
≥ 75,000 psi |
≥ 515 MPa |
| Yield Strength (Rp0.2) |
≥ 30,000 psi |
≥ 205 MPa |
| Elongation (in 2") |
≥ 35% |
≥ 35% |
| Hardness (Rockwell) |
≤ 90 HRB |
≤ 90 HRB |
Precision Tolerances
Aircraft tubing requires tighter tolerances than standard commercial tubing.
| Nominal OD Range | OD Tolerance | Wall Thickness Tolerance |
| Up to 0.500" |
± 0.003" |
± 10% |
| 0.501" to 1.000" |
± 0.005" |
± 10% |
| 1.001" to 1.500" |
± 0.010" |
± 10% |
304 vs. 321 vs. 316 Aircraft Tubing
| Grade | Corrosion resistance | Temperature resistance | Typical use |
|---|---|---|---|
| 304 | Very good | Up to ~870°C (intermittent) | General tubing, support frames |
| 316 | Excellent (chloride) | Up to ~870°C | Marine, high-corrosion zones |
| 321 | Very good | 900°C+ (Ti stabilized) | High-temperature aerospace systems |
If you're working on a project, tell me:
What specific part are you building?
Do you need seamless or welded tubing?
I can help you pick the right size or grade.
Required Testing & Quality Control
| Test Item | Description |
| Hydrostatic Test | 100% tested at high pressure to ensure no leakage. |
| Eddy Current Test | Non-destructive test (NDT) to detect internal/surface flaws. |
| Flaring Test | Tube must expand (usually 1.15x OD) without cracking. |
| Flattening Test | Tube is flattened to a specific height to test ductility/weld integrity. |
| Intergranular Corrosion | Tested per ASTM A262 Practice E to ensure corrosion resistance. |
| Cleanliness | ID (Internal Diameter) must be free from oil, grease, and metallic particles. |
Things to Consider When Buying 304 Stainless Steel Aircraft Tubing
Confirm Aerospace Specification Compliance (AMS 5566, ASTM A269, etc.)
Choose Seamless for Critical Applications where leakage or vibration is a concern
Check Surface Finish and ID Cleanliness for hydraulic or fuel line compatibility
Request Material Test Reports (MTRs) or traceability for aerospace certifications
FAQ
Q: Is 304 tubing magnetic?
A: In the annealed condition 304 is essentially non-magnetic; cold working can induce slight magnetism.
Q: When should 321 be used instead of 304?
A: For service in the carbide-precipitation range (about 425-870°C) or above 870°C, titanium-stabilized 321 is the better choice.
Q: What standard covers 304 aircraft tubing?
A: AMS 5566 covers welded 304 aircraft tubing; ASTM A269 covers general seamless and welded austenitic tubing.
