How To Analyze Precision Manufacturing Process Of Titanium Bolts?

Gr5 titanium alloy  is applied to aerospace fasteners; Gr2 pure titanium serves for chemical anti-corrosion and general medical applications; ELI high-purity titanium is used to fabricate precision medical connecting components.

High-precision titanium bolts require twelve sequential processes including raw material inspection, forging, heat treatment, precision grinding, thread rolling, non-destructive testing and surface treatment.

1. Melting and Rolling of Titanium Materials

High-end titanium ingots undergo triple vacuum arc melting to strictly control oxygen and hydrogen impurities, eliminating pores and component segregation.

• Gr5 aerospace titanium: Oxygen ≤ 0.18%, Hydrogen ≤ 0.012%
• Gr2 pure titanium: Excellent plasticity, suitable for low-load anti-corrosion scenarios
• Ti-6Al-4V ELI: Low impurity grade, dedicated to medical implants

2. Full Inspection of Incoming Materials

Each batch is tested for chemical composition, ultrasonic testing (UT) and magnetic particle testing (MT), as well as dimensional and hardness inspection. Diameter tolerance is controlled within ±0.05 mm, straightness ≤ 0.2 mm, and non-conforming products are directly scrapped.

3. Surface Pre-Treatment

Pickling removes oxide scale, followed by coating with high-temperature special lubricant to prevent die adhesion and surface cracking during forging.

1.Mass standard parts

CNC high-speed sawing with titanium-specific saw blades and cooling oil, length tolerance ±0.3 mm, burr-free cutting surfaces with automatic deburring.

2.High-precision special parts

Aerospace and medical special-shaped workpieces are cut by lathe, length tolerance ±0.05 mm, cutting surface perpendicularity ≤ 0.01 mm; thin stocks adopt wire electrical discharge machining (WEDM) to avoid extrusion deformation.

3.Post-cutting cleaning

Ultrasonic high-pressure cleaning to remove debris and oil stains, followed by drying and classified storage to prevent interlayer defects of forgings induced by impurities.

1.Gr5 process

Medium-frequency heating under argon shielding to avoid oxidation, isothermal heading and forging at 850–900 °C with preheated dies at 800 °C. Large-tonnage multi-station CNC equipment and cemented carbide dies are adopted for low-speed forming, with single deformation ≤ 40% to avert folding and cracking.

2.Advantages

Cutting breaks metal fibers and causes stress concentration; integrated warm heading delivers continuous grain structure with density ≥ 99.5%, doubling fatigue strength and achieving material utilization over 80%.

3.Defect control

Real-time infrared temperature control and regular die polishing. Forgings are air-cooled after forging to prevent grain coarsening, then subject to magnetic particle inspection to detect microcracks and folding defects on bolt heads.

1.Low-pressure white corundum negative-pressure sandblasting eliminates thick oxide scale and refines surface texture; pressure is controlled to avoid surface pits.

2.Special mixed hydrofluoric-nitric acid pickling removes residual oxide contaminants, followed by multi-stage pure water rinsing and drying to prevent cracking caused by residual acid corrosion.

• Process parameters: Vacuum solution treatment at 920–950 °C, quenching under argon protection, then low-temperature aging at 480–520 °C for 4 hours to enhance material properties.
• Finished mechanical properties: Tensile strength ≥ 1100 MPa, yield strength ≥ 1000 MPa, shear strength ≥ 670 MPa, meeting the standard for Grade 10.9 aerospace fasteners.
• Quality control: Furnace temperature deviation limited to ±5 °C; test bars are sampled for each furnace batch, and entire batches are reworked if unqualified.

1.CNC precision turning

Titanium-specific PCBN cutting tools paired with high-flow cooling to prevent tool adhesion; step-by-step precision finishing of outer profiles. Total length tolerance ±0.02 mm, shank diameter tolerance ±0.008 mm.

2.Centerless precision grinding

CBN grinding wheels polish smooth shanks to eliminate tool marks and micro-stress defects, surface roughness Ra ≤ 0.8 μm, coaxiality between head and shank ≤ 0.02 mm to reduce crack risks.

3.Fillet strengthening

Roll finishing is applied to the under-head fillets prone to stress concentration, generating compressive stress on the surface layer and cutting stress concentration factor by 30%, effectively preventing bolt fracture failure.

Cold thread rolling replaces cutting threading. Instead of material removal, plastic forming refines thread grains and boosts hardness by 15%–20%. Complete metal flow lines at thread roots deliver fatigue life 2–3 times that of cut threads, achieving aerospace Class 6g precision with Ra ≤ 1.6 μm and outstanding anti-thread-stripping and anti-loosening performance.

Process control: Pre-matching of blank shank diameter, secondary low-speed rolling to avoid thread tearing. Finished products undergo full inspection with go/no-go gauges to strictly control thread form and pitch diameter; fine threads receive additional calibration of helix angle.

Fluorescent Penetrant Testing: Detects surface microcracks, pores and folding defects of workpieces.

Magnetic Particle Testing: Identifies hidden cracks at under-head fillets and thread roots.

Sampling Ultrasonic Testing: Batch sampling to inspect internal micropores and delamination defects inside workpieces.

 

 

 

Ruihang, as a direct manufacturer of titanium products, supply optimal quality raw materials for your precision components production. Please feel free to contact us via email: Sam.Rui@bjrh-titanium.com