1. Material Composition & Manufacturing Process
7050 (AMS 4050M, ASTM B247) large diameter pipes feature copper-zinc-magnesium alloying system optimized for high-strength structural applications:
- Alloy Chemistry:
- Zinc (Zn): 5.7-6.7% (primary strengthening)
- Magnesium (Mg): 1.9-2.6% (precipitation hardening)
- Copper (Cu): 2.0-2.6% (stress corrosion resistance)
- Trace Elements:
- Zirconium (Zr): 0.08-0.15% (grain refinement)
- Iron (Fe): ≤0.15% max
- Silicon (Si): ≤0.12% max
- Manganese (Mn): ≤0.10% max
Advanced Manufacturing Process:
- Billet Pre-heating: 430-480°C (Argon atmosphere)
- Hot Extrusion: 315-410°C at 100-350 MN press force
- Cold Draw Sizing: 15-30% reduction
- Stretch Straightening: 1-3% permanent elongation
- Heat Treatment: T7451/T7651 proprietary aging
- Calibration: 3-roll planetary sizing system
- Surface Finish: Micro-peening (0.5-1.2μm Ra)
Certified to AMS-QQ-A-200/11 and EN 754 standards with full digital material traceability.
2. Mechanical Properties for Heavy Structures
| Property | T7451 Temper | T7651 Temper | Test Standard |
| Ultimate Tensile Strength | 510-550 MPa | 530-570 MPa | ASTM E8 |
| Yield Strength (Rp0.2) | 455-495 MPa | 470-510 MPa | ASTM E8 |
| Elongation (%) | 9-12% | 7-10% | ASTM E8 |
| Fracture Toughness KIC | 32 MPa√m | 29 MPa√m | ASTM E399 |
| Compression Yield | 480-520 MPa | 500-540 MPa | ASTM E9 |
| Shear Strength | 300-335 MPa | 310-345 MPa | ASTM B565 |
| Fatigue Strength (10⁷) | 160-185 MPa | 180-205 MPa | ASTM E466 |
| Bearing Strength | 840-890 MPa | 860-910 MPa | ASTM E238 |
Maintains ≥90% mechanical properties at temperatures from -55°C to +125°C per ASTM E21.
3. Heat Treatment & Microstructural Control
Proprietary Aging Sequence:
- Solution Treatment: 477°C ±5°C for 2-4 hours
- Controlled Quenching: Polymer quench at 40-60°C/sec
- Stress Relief: 3% stretch deformation
- Aging Protocol:
- T7451: 107°C/8hr + 163°C/30hr
- T7651: 121°C/6hr + 177°C/20hr
Microstructural Characteristics:
- Grain Size: ASTM 6-7 (25-40μm)
- Precipitate Structure:
- η’ (MgZn₂) phase: 10-30nm
- Al₃Zr dispersoids: 5-15nm
- Dislocation Density: 4-6×10¹⁰/cm²
- Grain Boundary Structure: Discrete η-phase
- Recrystallization: ≤15%
- Texture Index: <1.5 random multiples
4. Dimensional Specifications for Large Pipes
| Parameter | Standard Range | Precision Tolerance | Special Capabilities |
| Outer Diameter | 200-1200 mm | ±0.15% OD | Up to 2500 mm |
| Wall Thickness | 8-80 mm | +10%/-5% WT | 3-150 mm available |
| Length | 3-20 m | +10mm/-0mm | Up to 30m sections |
| Ovality | ≤0.8% | ≤0.3% (critical) | – |
| Straightness | 1.0 mm/m | 0.3 mm/m | – |
| Perpendicularity | ≤0.5° | ≤0.2° | – |
| Wall Uniformity | ±7% | ±3% | – |
Advanced Forming Technologies:
- Spin Forming for end configurations
- Flow Turning for thickness variation
- Explosive Expansion for size transitions
- Mandrel Forging for flanged ends
- Localized Solution Heat Treatment
5. Environmental Durability Performance
| Condition | Performance Rating | Key Metrics | Protection Methods |
| Salt Spray Exposure | Excellent | <0.002 mm/yr corrosion rate | Alodine 1200 treatment |
| Stress Corrosion Cracking | Good | Threshold >150 MPa | T7451 overaged temper |
| Galvanic Corrosion | Moderate | <0.003 mm/yr when isolated | Fiberglass isolation |
| Atmospheric Exposure | Excellent | 0.0001 mm/yr rural environment | Chromate conversion coating |
| High Humidity | Good | No pitting after 3000hr | Anodizing (Type II) |
Surface Enhancement Options:
- Hard Anodizing (50-70μm, 500-600 HV)
- Plasma Electrolytic Oxidation (PEO)
- HVOF WC-Co Coating (1200-1400 HV)
- Electroless Nickel Plating (ENP)
- Thermal Spray Aluminum (TSA)
6. Machining & Fabrication Properties
| Operation | Tool Material | Recommended Parameters | Dimensional Precision |
| Deep Hole Drilling | Carbide gundrills | 25-45 m/min, 0.05-0.12 mm/rev | ±0.05 mm |
| End Milling | TiAlN coated carbide | 250-400 m/min, 0.1-0.3 mm/tooth | Ra 0.8-1.6μm |
| Tapping | Coated HSS-E taps | 8-15 m/min, spiral point | 6H tolerance |
| Boring | CBN-tipped bars | 150-250 m/min, 0.05 mm/rev | IT7 grade |
| Trepanning | PCD cutters | 60-100 m/min | Wall runout ±0.1 mm |
Machinability Advantages:
- Chip Formation: Short breaking chips
- Built-up Edge Tendency: Low (Class B per ISO 3685)
- Cutting Force Requirements: 20-30% lower than steel
- Residual Stress Control: Cryogenic machining capable
- Typical Surface Finish: Ra 0.4-1.6 μm achievable
7. Welding & Joining Technologies
Optimal Welding Processes:
- Variable Polarity PAW (VPPAW):
- Current: 180-300A
- Travel Speed: 100-250 mm/min
- Filler: ER7037 (Al-Zn-Mg)
- Friction Stir Welding:
- Spindle Speed: 350-600 RPM
- Traverse: 80-200 mm/min
- Down Force: 12-20 kN
Specialized Joint Designs:
- High-Strength Mechanical Joints:
- Swaged collars with 1:15 taper
- Interference fit bushings
- Adhesive Bonding Systems:
- Epoxy novolac: 25 MPa at 100°C
- Polyurethane methacrylate: 18 MPa
- Double-Welded Joints:
- Root gap: 0.8-1.5mm
- Groove angle: 60°±5°
- Back-gouging: Full penetration
8. Physical Properties for Structural Applications
| Property | Value | Structural Significance |
| Density | 2.83 g/cm³ | 60% weight savings vs steel |
| Young’s Modulus | 71 GPa | Stiffness-to-weight ratio |
| Poisson’s Ratio | 0.33 | Stress distribution |
| CTE (20-150°C) | 23.6 μm/m·°C | Thermal compatibility |
| Thermal Conductivity | 130 W/m·K | Heat dissipation |
| Electrical Resistivity | 41.5 nΩ·m | Static discharge |
| Damping Capacity | 0.002 | Vibration reduction |
| Magnetic Permeability | 1.00002 | EMI protection |
9. Testing & Certification
Rigorous Testing Protocols:
- Ultrasonic Testing: 5-15 MHz probes, AWS D1.2 standards
- Eddy Current Inspection: 1-3% sensitivity
- Hydrostatic Testing: 1.5x design pressure
- Fracture Toughness: ESIS TC24 protocol
- Fatigue Testing: 10⁷ cycles minimum
- Residual Stress Analysis: X-ray diffraction method
Comprehensive Certification:
- NADCAP AC7108 Accreditation
- ISO 9001/AS9100 Quality Systems
- PED 2014/68/EU Compliance
- DNV GL Type Approval
- ABS Material Certification
- MIL-DTL-45225 Inspection
10. Industrial Applications
Primary Application Sectors:
- Aerospace structural frameworks
- Missile launch tube systems
- Industrial hydraulic cylinders
- Energy sector gas injection pipes
- Heavy machinery booms and arms
- Marine propulsion shafting
- High-pressure gas storage
- Telescope structural components
Handling & Storage:
- VCI coating with desiccant packs
- Non-metallic end protectors
- Wooden saddles in storage racks
- Never-stack direct contact policy
- ISO container transport systems
