Here we provide a detailed analysis of the titanium 6Al4V (Ti-6Al-4V) tube. It is currently the most widely used α+β dual-phase titanium alloy tube material, featuring high specific strength, excellent corrosion resistance and good processability. It is indispensable in high-end fields such as aviation, chemical industry and medicine.
Manufacturing process and specifications, standards, seamless pipe (mainstream): hot rolling / extrusion + cold rolling / cold drawing + vacuum annealing; specifications cover φ3–φ180 mm, wall thickness ranging from 0.2 to 30 mm; high precision, good pressure resistance, suitable for aviation and high-pressure systems. Welded pipes are mostly argon arc welding / plasma welding, suitable for medium-sized diameters, low-pressure conditions; strict control of weld quality and protective atmosphere is required. Core standards: ASTM B338 (seamless), ASTM B861 (welded); aviation-specific AMS 4928. Preferentially select seamless pipes for high-pressure, vibration conditions; welded pipes are suitable for low-pressure, large-diameter, cost-sensitive scenarios. Welding must be protected by high-purity Ar throughout (backside + front side), to prevent weld oxidation and embrittlement; recommend using ERTi-5 welding wire. Cutting requires carbide tools, low cutting speed + sufficient cooling to avoid surface hardening and tool wear. Surface treatment can be acid washing, sandblasting, anodizing; strictly prohibit long-term immersion in hydrochloric acid / sulfuric acid.
Seamless pipes are the most common form. For small-diameter pipes (such as aerospace hydraulic pipelines), usually a composite processing technique such as extrusion, precision forging, rolling, and drawing is adopted. For large-diameter thick-walled pipes (such as vertical pipes for deep-sea oil and gas extraction), methods like inclined rolling and piercing or forging plus ring rolling may be used to form a dense structure and continuous fiber flow lines, thereby enhancing the circumferential mechanical properties of the pipe. The manufacturing size range: According to the data from domestic research institutions, through the composite process, the inner diameter range of the pipes that can be manufactured is 5 to 60 mm, and the wall thickness range is 0.5 to 10 mm. For special-purpose large-sized pipes, through hot extrusion or diameter forging technology, the outer diameter can even reach over 800 mm. The processing difficulty is high because of its poor thermal conductivity and its tendency to react with cutting tools, making it a typical difficult-to-machine material. Special processing equipment and techniques are required. Poor room-temperature formability, especially for large-diameter seamless pipes, has poor bending formability at room temperature, which is a challenge in their application. The risk of high-temperature hydrogen embrittlement exists in a hydrogen-rich environment above 150°C, which may lead to a decline in material performance.
Seamless Precision Manufacturing (The Only Reliable Route): Vacuum Self-Consumption / Cold Bed Melting of Ingots → Hot Extrusion / Piercing for Blank Making → Multi-Stage Cold Rolling / Cold Drawing (with Special Dies and Lubrication) → Vacuum Tempering (to Eliminate Residual Stress and Control Bimetallic Structure) → Precise Cutting, Edge Deburring, Inner/Outer Surface Polishing; Welding is strictly prohibited (Welds are prone to causing blockages and uneven strength). Surface and Cleanliness: Ra often reaches 0.4–0.8 μm, Medical grade can be polished to Ra < 0.1 μm; Remove Oxide Skin by Acid Washing / Electro-polishing; 100% Eddy Current / Ultrasonic Testing, Air Tightness Test, and when necessary, Helium Leak Testing.
Typical application scenarios: medical intervention cardiovascular stent tubes, endoscope catheters, orthopedic guide pins, dental implant components (ELI low-oxygen version); aerospace engine fuel/hydraulic micro-piping, sensor capillaries, satellite thermal control loops; chemical/analytical gas chromatography (GC) sample tubes, corrosive trace medium transportation, seawater desalination micro heat exchange tubes; precision instruments pressure/level sensors' pressure-measuring capillaries, vacuum system fine tubes. Selection and procurement suggestions: choose Grade 5 (industrial) or Grade 5 ELI (medical implant) based on the working conditions; must provide material certification + non-destructive testing report + full size inspection data; distinguish between precision grade and ordinary grade tolerances; thin-walled tubes should avoid excessive bending to prevent flattening; storage should be isolated from carbon steel and humid environment to prevent galvanic corrosion; strictly prohibit long-term immersion in hydrochloric acid/sulfuric acid for degreasing or acid washing.
