6061 T6 Aluminum Tube
6061 aluminum seamless tube has good mechanical properties, corrosion resistance, and weldability, making it an ideal material for various industrial applications.
1. Material Composition & Standards
Conforming to ASTM B210, AMS 4151, and ISO 6361-2 standards, 6061-T6 aluminum tubing features a magnesium-silicon alloy formulation optimized for structural applications:
Primary Elements:
Magnesium (Mg): 0.8-1.2% (forms Mg₂Si precipitates)
Silicon (Si): 0.4-0.8% (enhances strength and fluidity)
Copper (Cu): 0.15-0.40% (improves machinability)
Base Material:
Aluminum (Al): ≥97.0% (balance)
Impurity Limits:
Iron (Fe): ≤0.70%
Chromium (Cr): 0.04-0.35%
Zinc (Zn): ≤0.25%
Manganese (Mn): ≤0.15%
Third-party verification per NADCAP AC7117 ensures chemical consistency with max 5% deviation in key elements. The balanced Mg:Si ratio (1.73:1) enables optimal precipitate formation during T6 heat treatment. Complies with SAE J454, AMS-QQ-A-200/2, and ASTM B241 for pressure applications.
2. Strength Performance
6061-T6 demonstrates superior structural efficiency for load-bearing applications:
| Property | Value | Test Standard |
|---|---|---|
| Tensile Strength (Rm) | 310-330 MPa | ASTM E8 |
| Yield Strength (Rp0.2) | 275-290 MPa | ASTM E8 |
| Elongation at Break (%) | 10-15% | ASTM E8 |
| Shear Strength | 207 MPa | ASTM B769 |
| Compressive Yield | 285 MPa | ASTM E9 |
| Fatigue Endurance (10⁷ cycles) | 95-110 MPa | ISO 1099 |
| Fracture Toughness | 29 MPa√m | ASTM E399 |
| Hardness (Rockwell B) | 60-65 HRB | ASTM E18 |
Maintains 85% room temperature strength at 150°C and exhibits excellent impact toughness of 20J at -40°C.
3. Heat Treatment Process
The T6 temper sequence follows precisely controlled parameters:
Solution Treatment:
530°C ±10°C for 60-90 minutes (homogenization)
Atmosphere: Nitrogen-protected furnace (±5°C uniformity)
Rapid Quenching:
Water quenching at >200°C/sec cooling rate
Quench delay: <15 seconds maximum
Artificial Aging:
175°C ±5°C for 8-10 hours
Cooling method: Forced air (≥10°C/min rate)
Microstructural Features:
Grain size: ASTM 5-6 (20-50μm)
Precipitate distribution: β" (Mg₅Si₆) phase dominant
Dislocation density: 10⁸/cm²
Secondary phase particles: <0.5% volume fraction
Reheating above 250°C causes overaging with 15% strength reduction. Stress relief required after severe forming: 345°C for 1 hour + re-aging.
4. Dimensions & Customization
Manufactured to structural engineering tolerances:
| Parameter | Standard Range | Precision Tolerance | Custom Options |
|---|---|---|---|
| Outer Diameter | 6-500 mm | ±0.1% OD | Rectangular profiles |
| Wall Thickness | 0.8-25 mm | ±7% WT | Variable wall transitions |
| Length | 1-12 m | +0/-3 mm | Up to 20m lengths |
| Straightness | - | 0.5 mm/m max. | ±0.2 mm/m |
| Ovality | - | ≤0.75% TIR | ≤0.3% TIR |
| Bend Radius (min) | 2.0× OD | - | Tight radius: 1.2× OD |
Fabrication Services:
Precision rotary draw bending (max 180°)
CNC end forming for complex joints
Hydroforming for non-circular sections
Notching and coping for truss systems
Anodizing per MIL-A-8625 Type II
5. Corrosion Resistance Properties
Environmental Performance Data
| Environment | ISO 9223 Rating | Corrosion Rate (μm/yr) | Protection Recommendation |
|---|---|---|---|
| Rural Atmosphere | RC2 (Good) | <3 μm/yr | Architectural anodizing |
| Coastal Exposure | RC3 (Fair) | 10-15 μm/yr | PVDF coating systems |
| Industrial Area | RC4 (Moderate) | 15-30 μm/yr | Ceramic-epoxy lining |
| Alclad 6061 | RC1 (Excellent) | <1 μm/yr | 10% clad layer |
Protection Methods:
Anodizing:
Sulfuric acid (Type II): 15-25μm thickness
Hard anodizing (Type III): 50-70μm (>60 HRC)
Organic Coatings:
Fluoropolymer coatings: 25-50μm DFT
Polyester powder coating: 60-80μm
Chemical Treatments:
Chromate conversion (MIL-DTL-5541)
Plasma electrolytic oxidation (PEO)
6. Machinability Characteristics
Optimization Parameters
| Operation | Tool Material | Speed (m/min) | Feed (mm/rev) | Notes |
|---|---|---|---|---|
| Turning | Carbide K10 | 300-500 | 0.15-0.30 | 7° positive rake |
| Milling | Carbide K20 | 250-450 | 0.06-0.18 | Climb milling |
| Drilling | TiAlN Coated | 60-100 | 0.05-0.12 | 140° point angle |
| Tapping | HSS-Co8 | 10-15 | Pitch matched | 70% thread depth |
Machining Performance:
Machinability rating: 80% (baseline: 2011-T3=100%)
Surface finish achievable: Ra 0.4μm
Built-up edge tendency: Low (Grade 2 per ISO 3685)
Chip characteristics: Continuous chips requiring breakers
Coolant requirements: Soluble oil 5-8% concentration
Dimensional stability: <0.02mm thermal expansion at 100°C
7. Weldability & Joining Methods
Gas Tungsten Arc Welding (GTAW) Recommended
Requires strict heat control to preserve properties:
Fusion Welding Parameters
Filler alloys: ER4043 (AlSi5) or ER5356 (AlMg5)
Interpass temperature: <65°C
Preheat: Optional for >6mm thickness
Post-weld aging: 175°C/4hrs to restore properties
Alternative Joining
Friction Stir Welding:
Rotation: 800-1200 RPM
Traverse: 50-200 mm/min
Adhesive Bonding:
Epoxies: FM73 (22-28 MPa shear)
Surface prep: Chromate conversion
Mechanical Fastening:
Blind rivets: Stainless steel mandrel
Flow drill screws: Up to 800N axial load
Joining sleeves: 150% tube strength retention
8. Physical Properties
| Property | Value | Test Standard |
|---|---|---|
| Density | 2.70 g/cm³ | ASTM B311 |
| Thermal Conductivity (25°C) | 167 W/m·K | ASTM E1461 |
| CTE (20-100°C) | 23.6 μm/m·°C | ASTM E228 |
| Electrical Resistivity | 42 nΩ·m | ASTM B193 |
| Modulus of Elasticity | 68.9 GPa | ASTM E111 |
| Fatigue Strength Coefficient | 0.56 | ASTM E739 |
| Specific Heat (100°C) | 960 J/kg·K | ASTM E1269 |
| Recrystallization Temp | 290°C | ASTM E112 |
9. Surface Quality Standards
Surface finishes:
As-drawn: Ra 0.8-1.6μm
Cold-finished: Ra 0.4-0.8μm
Mirror polish: Ra <0.1μm achievable
Inspection criteria (ASTM B241):
Scratch depth: <0.5% WT
Surface inclusions: <0.25mm
Discoloration: None
Die lines: <0.1mm height
Cleaning protocols:
Alkaline degreasing to AMS 2646
Acid etching for adhesives
Electropolishing for sanitary applications
10. Certifications & Testing
Quality Assurance Protocols
Chemical Analysis:
Spectrometry per ASTM E1251
ICP verification for trace elements
Mechanical Testing:
Transverse tensile testing (ASTM E8)
Flattening test to 75% OD reduction
NDT Methods:
Ultrasonic testing: 5-10MHz probes
Hydrostatic testing: 2× working pressure
Eddy current per ASTM E309
Industry Certifications
AS9100 Aerospace Quality
ISO 9001:2015 Quality Management
PED 2014/68/EU Annex I Category II
TÜV SÜD Pressure Vessel Certification
Lloyds Register Type Approval
FDA CFR 21.177.1500 (Food contact compliant)
Structural Applications: Roll cages, space frames, hydraulic cylinders, robotic arms, structural trusses, and architectural elements where strength/weldability balance is critical.
Packaging: VCI paper interleaving + shrink-wrap bundles, wooden crates with desiccant. Standard lead time: 6 weeks.
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