GR2 Titanium Thin-Walled Tube Manufacturing Process
1. GR2 titanium tube material selection and pretreatment
GR2 titanium alloy characteristics: industrial pure titanium (Grade 2), moderate strength (tensile strength ≥ 345 MPa), excellent corrosion resistance (especially chloride ion corrosion resistance), good weldability and cold forming ability.
Raw material inspection: ensure that the titanium coil or tube blank meets the ASTM B338/B861 standard, and control the content of impurities such as oxygen and iron (O≤0.25%, Fe≤0.30%).
Surface cleaning: Removal of the oxide layer by pickling (HNO₃+HF mixture) to avoid contamination in subsequent processing.
2. GR2 titanium tube forming process
Cold rolling/cold drawing: through multi-pass cold working (wall reduction rate of 10%-30%), the wall thickness is gradually thinned (up to 0.5mm), and intermediate annealing (650-750°C vacuum annealing) is required to eliminate work hardening.
Spinning forming: suitable for complex curved surfaces (such as reducers), through high-speed rotation and mold extrusion to achieve thin-wall uniformity (wall thickness tolerance±0.05mm).
Welding process:
TIG welding: high-purity argon protection (purity ≥ 99.999%), the welding wire is made of ERTi-2 matching material, and the heat input is controlled to prevent grain roughening.
Laser welding: suitable for precision welds (melting width ≤1mm), small heat affected zone, weld strength coefficient ≥ 90%.
3. Post-processing and testing
Heat treatment: vacuum annealing (700-800°C/1-2h) to eliminate residual stress and restore plasticity.
Surface treatment: Electrolytic polishing or sandblasting (Al₂O₃ abrasives) to improve the surface finish (Ra≤0.8μm) and enhance the resistance to high-temperature oxidation.
Non-destructive testing:
Eddy current testing (ET): Detects surface cracks and wall thickness uniformity.
Ultrasonic Testing (UT): 99% internal defect detection rate≥
Helium Mass Spectrometry Leak Detection: Ensure air tightness (leak rate≤ 1×10⁻⁶ Pa·m³/s).
GR2 Titanium Thin-Walled Pipes Are At The Heart Of Automotive Exhaust Systems
1. Application Scenarios and Advantages
Component Position:
Head/Manifold: Resistant to 900°C high temperature exhaust gas, avoid creep problems of stainless steel.
Mid-section silencer: resistant to condensation acid corrosion (pH 2-4), the service life is extended by 3-5 times.
Tailend/tailpipe: 40%-50% weight reduction (compared to 304 stainless steel) to improve the thrust-to-weight ratio of the vehicle.
Performance Advantages:
Weight reduction effect: mass density 4.51g/cm³ (stainless steel 7.93g/cm³), the vehicle weight reduction of 8-15kg, reduce fuel consumption by 2%-5%.
Temperature resistance: GR2 titanium has a strength retention rate of >80% at 600°C, which is better than stainless steel (strength drops sharply after 500°C).
Corrosion resistance: 1000 hours salt spray test (5% NaCl) without pitting, suitable for coastal/snow melting agent environment.
2. Technical challenges and solutions
High Temperature Oxidation Protection: Surface aluminization treatment (formation of TiAl₃ layer) reduces the oxidation rate by 70% at 1000°C.
Vibration fatigue: Finite element analysis is used to optimize the piping structure (wall thickness gradient design) so that the resonant frequency avoids the common speed range of the engine (2000-6000 RPM).
Cost control: The use of "titanium-steel composite structure" (titanium only for high-temperature sections) reduces material costs by 30%.
3. Typical application cases
High-performance model: The Porsche 911 GT3 RS features an all-titanium exhaust system, which reduces weight by 11kg and increases horsepower by 7%.
New energy range extender: In Li Auto's range extender electric vehicle, titanium exhaust reduces the impact of heat radiation on the battery pack.
In the field of racing: the exhaust system of the F1 car has a wall thickness of only 0.3mm, and the specific strength of titanium is used to achieve extreme weight reduction.
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