Medical Grade Gr5 ELI (Ti-6Al-4V ELI, UNS R56401) titanium bars and plates require strict production and testing processes to meet standards like ASTM F136 (for surgical implants) and ISO 5832-3. Below is a detailed breakdown of production steps, required equipment, testing stages, and corresponding equipment.
Production Processes & Corresponding Equipment
1.1 Raw Material Preparation (Raw Material Smelting & Ingots)
Process Objective: Produce high-purity Ti-6Al-4V ELI alloy ingots with extra low interstitial(ELI) elements (O≤0.13%, C≤0.08%, N≤0.05%, H≤0.0125%).
Key Steps:
Batching: Mix sponge titanium (≥99.7% purity), aluminum ingots (≥99.95% purity), and vanadium alloy (V-Ti master alloy) per Ti-6Al-4V ELI composition ratio.
Vacuum arc remelting (VAR): Melt the batch 2-3 times in a vacuum to eliminate impurities (e.g., gas, inclusions) and ensure uniform composition.
Required Equipment:
Vacuum Arc Remelting Furnace (VAR Furnace): With vacuum degree ≤1×10⁻³ Pa, temperature control accuracy ±5℃, to achieve high-purity melting.
Ingredient Mixer: For precise proportioning of sponge Ti, Al, and V alloys (error ≤±0.1%).
Ingot Molding Die: Heat-resistant graphite or copper die, customized for ingot size (e.g., Φ300-800mm, length 1000-3000mm).
1.2 Hot Working (Forming Bars & Plates)
1.2.1 Forging (Ingot to Semi-Finished Products)
Process Objective: Break ingot coarse grains, improve material density (relative density ≥99.5%), and form initial shapes (billets for bars/plates).
Key Steps:
Ingot heating: Heat ingots to 950-1050℃ (α+β phase region of Ti-6Al-4V ELI) and hold for 2-4 hours for uniform temperature.
Hot forging: Use press forging to shape ingots into bar billets (Φ50-200mm) or plate billets (thickness 20-100mm, width 300-1000mm).
Required Equipment:
Electric Resistance Heating Furnace: With temperature control range 800-1200℃, suitable for large ingot heating.
Hydraulic Forging Press: 1000-5000 tons, with precision position control (error ≤±0.5mm) for uniform forging.
Forging Dies: Heat-treated H13 steel dies, with cooling systems to prevent die wear.
1.2.2 Rolling (Semi-Finished Products to Final Bars/Plates)
Process Objective: Refine grains, control final dimensions (e.g., bar diameter tolerance ±0.1mm, plate thickness tolerance ±0.05mm), and improve surface quality.
Key Steps for Bars:
Hot rolling: Roll bar billets at 850-950℃ to reduce diameter step-by-step (e.g., Φ100mm → Φ50mm).
Cold drawing (optional): For high-precision bars (e.g., Φ10-30mm), perform cold drawing at room temperature to improve dimensional accuracy.
Key Steps for Plates:
Hot rolling: Roll plate billets at 850-950℃ to reduce thickness (e.g., 50mm → 10mm) and expand width.
Cold rolling (optional): For thin plates (thickness ≤5mm), cold roll to achieve Ra≤0.8μm surface roughness.
Required Equipment:
Hot Rolling Mill:
For bars: Multi-stand continuous rolling mill (3-5 stands), with roll diameter 200-500mm.
For plates: Four-high reversible rolling mill, with work roll diameter 150-300mm and width 1000-2000mm.
Cold Drawing Machine (for bars): With drawing force 50-200kN, equipped with die lubrication system.
Cold Rolling Mill (for plates): Two-high or four-high mill, with precision roll gap control (±0.01mm).
1.3 Heat Treatment (Performance Optimization)
Process Objective: Adjust mechanical properties (tensile strength ≥860MPa, yield strength ≥795MPa, elongation ≥10%) and eliminate internal stress.
Key Steps:
Annealing: Heat bars/plates to 700-750℃, hold for 1-2 hours, then cool in air (for stress relief) or furnace-cool (for softer properties).
Solution treatment + aging (optional): For high-strength applications, heat to 920-950℃ (solution), water quench, then age at 500-550℃ for 4-8 hours.
Required Equipment:
Vacuum Heat Treatment Furnace: With vacuum degree ≤5×10⁻³ Pa, to avoid oxidation (medical Ti requires no surface oxide scale).
Temperature Controller: With PID control, accuracy ±2℃, to ensure uniform heat treatment.
Quenching Tank: For water quenching (solution treatment), with temperature control (20-30℃) to prevent material deformation.
1.4 Surface Treatment (Hygiene & Biocompatibility)
Process Objective: Remove surface defects (e.g., scale, scratches), improve corrosion resistance, and meet medical hygiene standards.
Key Steps:
Pickling: Immerse in mixed acid (HNO₃ + HF) to remove oxide scale and surface impurities (pickling time 5-15 minutes).
Passivation: Treat with nitric acid (20-30% concentration) to form a dense TiO₂ film (thickness 5-10nm) for corrosion resistance.
Polishing (optional): For implant-grade products, perform mechanical polishing (Ra≤0.2μm) or electrochemical polishing.
Required Equipment:
Pickling Tank: Acid-resistant PP or titanium tank, with ventilation system to remove acid fumes.
Passivation Tank: Same material as pickling tank, with temperature control (25-40℃).
Polishing Machine:
Mechanical: Belt grinder (for bars) or plate polisher, with abrasive belts (800-1200 grit).
Electrochemical: Titanium electrode polishing equipment, with voltage control (10-30V).
Products Description
2. Testing Processes & Corresponding Equipment
2.1 Chemical Composition Testing
Test Objective: Verify compliance with Gr5 ELI composition (Al:5.5-6.75%, V:3.5-4.5%, interstitial elements ≤ limits) and detect harmful impurities (e.g., Fe≤0.25%).
Testing Methods & Equipment:
Optical Emission Spectrometry (OES):
Equipment: OES Spectrometer (e.g., Bruker Q4 TASMAN), tests 20+ elements in 1-2 minutes, accuracy ±0.01%.
Inert Gas Fusion (IGF):
Equipment: IGF Analyzer (e.g., LECO TC600), measures O, N, H content (detection limit 0.1ppm).
Carbon/Sulfur Analyzer:
Equipment: CS Analyzer (e.g., LECO CS844), tests C content (detection limit 0.001%).
2.2 Mechanical Property Testing
Test Objective: Ensure tensile strength, yield strength, elongation, and hardness meet ASTM F136 requirements.
Testing Methods & Equipment:
Tensile Test:
Equipment: Universal Testing Machine (e.g., Instron 5982), with load capacity 100-500kN, measures stress-strain curve and calculates tensile/yield strength, elongation.
Sample: Dumbbell-shaped specimens (ASTM E8 standard).
Hardness Test:
Equipment: Vickers Hardness Tester (e.g., Wilson VH1102), tests HV hardness (load 10kgf, dwell time 10s), requirement HV 280-340.
Impact Test (optional):
Equipment: Charpy Impact Tester (e.g., Instron CEAST 9050), measures impact toughness (≥10J/cm² at room temperature).
2.3 Microstructure Testing
Test Objective: Check grain size (≤50μm), phase distribution (uniform α+β phase), and absence of defects (e.g., inclusions, cracks).
Testing Methods & Equipment:
Metallographic Preparation:
Equipment: Grinding Machine (for sample grinding), Polishing Machine (with diamond paste, 1-0.25μm), Etching Tank (etchant: Kroll's reagent - 1-3% HF + 2-6% HNO₃+ H₂O).
Microstructure Observation:
Equipment: Optical Microscope (e.g., Olympus BX53M), with 100-1000× magnification; Scanning Electron Microscope (SEM, e.g., Zeiss Sigma 300) for high-resolution observation (optional).
2.4 Dimensional & Surface Quality Testing
Test Objective: Ensure dimensions meet tolerance requirements and surface is free of defects (e.g., scratches, pits).
Testing Methods & Equipment:
Dimensional Measurement:
For bars: Digital Caliper (accuracy ±0.01mm) for diameter; Laser Diameter Gauge (e.g., Keyence LS-9000) for continuous measurement (speed 1000 times/second).
For plates: Thickness Gauge (e.g., Mitutoyo ID-C112) for thickness; Coordinate Measuring Machine (CMM, e.g., Hexagon Global S) for 3D dimensional accuracy (error ≤±0.005mm).
Surface Roughness Test:
Equipment: Surface Roughness Tester (e.g., Mitutoyo SJ-210), measures Ra, Rz values (detection range 0.001-20μm).
Visual Inspection:
Equipment: High-Definition Camera or Microscope, checks for surface defects (defect size ≤0.1mm is acceptable).
2.5 Corrosion Resistance Testing (Critical for Medical Use)
Test Objective: Verify resistance to body fluid corrosion (simulate in-vivo environment).
Testing Methods & Equipment:
Potentiodynamic Polarization Test:
Equipment: Electrochemical Workstation (e.g., Gamry Reference 600), tests in simulated body fluid (SBF solution, 37℃), measures corrosion current density (≤1×10⁻⁶ A/cm²).
Neutral Salt Spray Test (NSS):
Equipment: Salt Spray Chamber (e.g., Q-FOG CRH), sprays 5% NaCl solution (35℃), requires no corrosion for ≥200 hours.
2.6 Non-Destructive Testing (NDT, for Internal Defects)
Test Objective: Detect internal cracks, inclusions, or pores (no defects ≥0.5mm allowed).
Testing Methods & Equipment:
Ultrasonic Testing (UT):
Equipment: Ultrasonic Flaw Detector (e.g., Olympus EPOCH 650), with probe frequency 2-5MHz, tests internal defects (detection limit 0.1mm).
Radiographic Testing (RT, optional for thick products):
Equipment: X-ray Radiography Machine (e.g., YXLON Cheetah EVO), detects internal inclusions (sensitivity ≥2% of thickness).
Magnetic Particle Testing (MPT, for surface cracks):
Equipment: Magnetic Particle Tester (e.g., Eriez 6200), detects surface cracks (length ≥0.2mm) on ferromagnetic parts (rare for Ti, but used if iron contamination is suspected).
Monica
Position:Manager
WhatsApp: +86 182 9270 2722
E-mail:Cr-Re@titanmsgp.com
