Round tube
Extruded seamless or porthole tube from about 20 mm to 250 mm OD. Even stress distribution for members loaded in several directions.
High-strength 6xxx structural tube
6066-T6 Aluminium Tube
6066-T6 is the strongest of the common 6xxx extrusion alloys, with a typical yield strength around 350 MPa, roughly 25 % more than 6061-T6. It is chosen for extruded tube and hollow sections that must carry high loads in thin walls, where 7xxx alloys would be too costly or difficult. Metline supplies 6066 tube in round, square, rectangular and custom hollow sections to customers worldwide.
- Alloy
- 6066 (Al-Mg-Si-Cu-Mn)
- Tempers
- T6, T6511, T4, O
- Typical yield
- ≈ 350 MPa (T6)
- Standards
- ASTM B221 · AMS-QQ-A-200/10
What is 6066 aluminium tube?
6066 is an aluminium-magnesium-silicon alloy with deliberate additions of copper and manganese. The extra silicon, copper and manganese raise its T6 strength well above 6061 and 6082, while the alloy can still be extruded into tubes and hollow sections and heat-treated like other 6xxx grades.
The alloy fills a gap between general structural grades and the high-strength aerospace alloys. 6061-T6 tube has a typical yield of about 276 MPa; 7075-T6 reaches about 505 MPa but is hard to extrude into hollows, difficult to weld and sensitive to stress corrosion. 6066-T6 sits at about 350 MPa, so designers can reduce wall thickness by around a fifth compared with 6061 for the same bending stress, without moving to a 7xxx alloy.
The price of that strength is in fabrication and corrosion. 6066 extrudes more slowly than 6061, it is more prone to weld cracking, and its copper content (0.7 – 1.2 %) makes it more susceptible to intergranular corrosion in aggressive environments. Used where those limits are understood, it is an efficient structural tube for frames, booms, vehicle members and forged or extruded load-bearing parts.
6066 chemical composition (wt %)
| Element | Min | Max | Role |
|---|---|---|---|
| Silicon (Si) | 0.90 | 1.80 | Excess Si above Mg2Si balance boosts ageing response |
| Iron (Fe) | — | 0.50 | Impurity |
| Copper (Cu) | 0.70 | 1.20 | Adds strength; reduces corrosion resistance |
| Manganese (Mn) | 0.60 | 1.10 | Strength and grain control |
| Magnesium (Mg) | 0.80 | 1.40 | Strengthening with Si |
| Chromium (Cr) | — | 0.40 | Grain structure control |
| Zinc (Zn) | — | 0.25 | |
| Titanium (Ti) | — | 0.20 | Grain refiner |
| Others each / total | — | 0.05 / 0.15 | |
| Aluminium | Remainder |
These are the registered Aluminum Association limits. Some published sources show lower copper and manganese ranges for 6066; those figures do not match the registered alloy, so always check composition against the mill certificate and your order specification.
Mechanical properties of 6066 tube
| Temper / basis | Tensile strength | Yield strength (0.2 %) | Elongation | Hardness |
|---|---|---|---|---|
| O, typical | 150 MPa / 22 ksi | 83 MPa / 12 ksi | 18 % | 43 HB |
| T4, typical | 360 MPa / 52 ksi | 207 MPa / 30 ksi | 18 % | 90 HB |
| T6, typical | 390 – 395 MPa / 57 ksi | 350 – 360 MPa / 51 – 52 ksi | 12 % | 120 HB |
| T6 extruded, ASTM B221 minimum | 345 MPa / 50 ksi | 310 MPa / 45 ksi | 8 % | — |
Physical properties
- Density
- 2.72 g/cm³
- Elastic modulus
- about 69 GPa
- Thermal conductivity (T6)
- about 147 W/m·K
- Electrical conductivity (T6)
- about 37 % IACS
- Thermal expansion
- about 23 µm/m·°C
- Melting range
- about 563 – 645 °C
Stiffness is the same as other aluminium alloys, so 6066 does not reduce deflection; its benefit is higher allowable stress. If a 6061 tube fails on deflection rather than strength, increase the section depth instead of changing alloy.
6066 standards and designations
| System | Designation / standard |
|---|---|
| Aluminum Association | 6066 |
| UNS | A96066 |
| ASTM | B221 (extruded bar, rod, profiles and tube) |
| Aerospace / military | AMS-QQ-A-200/10 (extrusions), forgings to AMS-QQ-A-367 |
| ISO name | AlSi1Mg1CuMn (descriptive) |
6066 is not listed in EN 573-3, so European projects normally specify 6082-T6 or a 7xxx weldable grade such as 7020 for similar duties.
6066 tube forms, sizes and weights
Square and rectangular tube
Flat faces for bolting and brackets; rectangular sections aligned with the main load path.
Structural hollow profiles
Multi-cavity and ribbed sections designed to the load; send a drawing for die review.
Oval and special sections
Oval, hexagonal or D-shaped tubes for directional stiffness or anti-rotation.
Weight in kg/m = π × (OD − wall) × wall × 2.72 / 1000 for round tube. Typical structural sizes:
| OD × wall (mm) | kg/m | I (cm⁴) | Z (cm³) |
|---|---|---|---|
| 25 × 3 | 0.56 | 1.3 | 1.02 |
| 30 × 3 | 0.69 | 2.3 | 1.56 |
| 40 × 4 | 1.23 | 7.4 | 3.71 |
| 50 × 5 | 1.92 | 18.1 | 7.25 |
| 60 × 5 | 2.35 | 32.9 | 10.98 |
| 80 × 6 | 3.79 | 96.1 | 24.03 |
| 100 × 8 | 6.29 | 246.5 | 49.30 |
| 120 × 10 | 9.40 | 527.0 | 87.83 |
| 150 × 12 | 14.15 | 1247.8 | 166.38 |
| 200 × 15 | 23.71 | 3754.2 | 375.42 |
Machining, welding, forming and finishing
Machining
Machines well in T6, with better chip breaking than 6061 thanks to higher hardness. Use carbide tools and flood coolant.
Welding
Weldability is rated only fair: the alloy is more susceptible to hot cracking than 6061. Use 4xxx filler (ER4043 or ER4145) and expect a large strength loss near the weld; mechanical fastening or bonding is often preferred.
Forming
Limited ductility in T6. Bend in O or T4 and then age, or use large radii.
Corrosion protection
Copper lowers resistance to intergranular corrosion. Anodise, paint or powder coat tube used outdoors or near the sea.
Heat treatment
Solution treat at about 530 °C, quench, and age at about 175 °C for T6; follow the governing specification for exact cycles.
Temperature
Like other 6xxx alloys, prolonged service above about 150 °C over-ages the material and reduces strength.
Applications of 6066 tube
- Transport structures: vehicle frame members, trailer cross-members and suspension parts
- Lifting and access: booms, ladders, telescopic masts and lightweight beams
- Sport and leisure: highly stressed frame tubes and components where weight matters
- Aerospace ground equipment and defence: extruded and forged structural parts to AMS-QQ-A-200/10
- Industrial equipment: machine frames, conveyor structures and handling equipment
- Modular structures: staging, temporary structures and prefabricated frames
6066 vs 6061, 6063 and 6082 tube
| 6063-T6 | 6061-T6 | 6082-T6 | 6066-T6 | |
|---|---|---|---|---|
| Typical tensile | 241 MPa | 310 MPa | 310 – 340 MPa | 390 – 395 MPa |
| Typical yield | 214 MPa | 276 MPa | 260 – 310 MPa | 350 – 360 MPa |
| Extrudability | Excellent | Good | Good | Fair |
| Weldability | Good | Good | Good | Fair |
| Corrosion resistance | Very good | Good | Good | Fair |
| Best for | Appearance | General structures | European structures | Highest-strength 6xxx sections |
How to order 6066 tube
- SpecifyAlloy and temper (for example 6066-T6, 50 × 5 mm round), section size and wall thickness, length, quantity and the governing standard (ASTM B221 or AMS-QQ-A-200/10). A drawing helps for cut parts.
- QuoteWe confirm availability, tolerances, certification and delivery terms (EXW, FOB, CIF or DAP) for your destination.
- ProcessMaterial is cut to length, de-burred and, if you ask, bent, machined or finished before packing.
- DocumentEach shipment carries a mill test certificate to EN 10204 3.1 with chemistry and tensile results, plus the packing list. Third-party inspection can be arranged.
- ShipBundled with end caps and interleaving or packed in seaworthy wooden cases, then shipped by sea or air.
References and standards
- ASTM B221 – Aluminum and Aluminum-Alloy Extruded Bars, Rods, Wire, Profiles, and Tubes
- SAE AMS-QQ-A-200/10 – Aluminum Alloy 6066, Bar, Rod, Shapes, Tube and Wire, Extruded
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits (Teal Sheets)
- ASM Handbook, Vol. 2 – Properties and Selection: Nonferrous Alloys and Special-Purpose Materials
6066 aluminium (aluminum) tube: frequently asked questions
How strong is 6066-T6 compared with 6061-T6?
Typical yield strength is about 350 – 360 MPa for 6066-T6 against 276 MPa for 6061-T6, roughly 25 – 30 % higher. Guaranteed minimums under ASTM B221 are 310 MPa yield for 6066-T6 and 240 MPa for 6061-T6 extrusions.
Can 6066 tube be welded?
It can, but it is more crack-prone than 6061 and loses much of its strength near the weld. Use 4xxx filler, qualify the procedure, and consider bolted or bonded joints for highly stressed parts.
Is 6066 corrosion resistant?
Less so than 6061 or 6063, because of its copper content. It performs well when anodised, painted or used indoors; avoid bare 6066 in marine or industrial atmospheres.
Is there a European equivalent of 6066?
No direct EN equivalent is listed. European designs usually use 6082-T6 for slightly lower strength or 7020-T6 where a weldable higher-strength alloy is needed.
Can 6066 be supplied as drawn tube?
6066 is normally supplied extruded. Drawn tube and special sizes can be discussed on enquiry; send the dimensions and tolerances you need.
Need high-strength 6066 tube?
Send the section, wall, length, temper and destination, and we will reply with availability, certification and a delivered price.
