Custom Gr5 Titanium Fasteners

Gr5 titanium (Ti-6Al-4V), the most widely used grade in the titanium alloy family, is the material of choice for custom fastener manufacturing. Composed of 6% aluminum, 4% vanadium, and the balance titanium, Gr5 titanium alloy inherits the low density (approximately half that of steel) and excellent corrosion resistance of pure titanium. However, alloying significantly enhances its strength (tensile strength exceeding 860 MPa) and high-temperature stability (capable of long-term operation at 300-400°C), achieving a perfect balance between the two core requirements of lightweight and high strength. Custom manufacturing of Gr5 titanium fasteners requires more than simply following a drawing; rather, it requires comprehensive optimization of the entire process, from materials and design to manufacturing and quality control, taking into account the specific load conditions, environmental media, and installation requirements of the application scenario.

Threads are the core of titanium fastener connections, requiring guaranteed profile accuracy, pitch tolerance, and surface roughness. Gr5 titanium alloy thread machining is challenging, requiring special attention to the following technical key points:

Thread Machining

Small-size threads (M2-M8): The “thread rolling” process, using a rolling plate for extrusion, is highly efficient and can achieve a thread surface roughness of Ra 1.6μm.

Large-size or fine-pitch threads (M10 and above, pitch ≤1mm): The “turning + tapping” or “rolling” process is employed. Turning requires carbide tools (such as WC-Co tools) at a cutting speed of 5-10 m/min (to avoid tool wear due to excessive temperatures). Tapping requires specialized titanium alloy taps and the application of extreme-pressure cutting fluid to reduce tool sticking.

Shank Machining: For shanks requiring high precision (e.g., h6 tolerance), a grinding process is required using a cubic boron nitride (CBN) grinding wheel at a controlled grinding speed of 30-40 m/s. This ensures a shank roundness of ≤0.005 mm and a straightness of ≤0.01 mm/m.

Heat Treatment

Heat treatment is the core process that determines the mechanical properties of Gr5 titanium fasteners. Annealing or solution aging should be selected based on application requirements.

Annealing: Suitable for normal load applications, it aims to reduce hardness, eliminate machining-induced stresses, and stabilize the microstructure. Parameters: Temperature 650-700°C, hold for 2-4 hours, followed by furnace cooling (cooling rate ≤50°C/hour). The annealed material has a hardness of approximately HB 300-320 and good toughness (impact energy ≥30 J).

Solution aging: Suitable for high-load applications (e.g., aerospace structural parts) to increase strength. Parameters: First step: solution treatment (temperature 950-980℃, holding time 30-60 minutes, water quenching). Second step: aging treatment (temperature 500-550℃, holding time 4-8 hours, air cooling). After treatment, the tensile strength can reach 1100-1200MPa and the hardness is about HB 380-400, but the toughness will be slightly reduced (impact energy ≥ 20J).