As experts in CNC machining, Hansheng Automation has extensive experience machining titanium in our CNC machining centers (with ultra-mirror finishes to ±0.002mm accuracy). Below is an introduction to titanium, a material suitable for CNC machining.
What is titanium?
Ti (atomic number 22) is a silvery-white transition metal discovered in 1790 and industrialized in 1948. Titanium's most important characteristic is its allotropy: the same element exhibits different properties due to its internal crystal structure. For example, below 882°C, it exhibits a close-packed hexagonal α structure (excellent plasticity), while above 882°C, it exhibits a body-centered cubic β structure (high strength). Alternatively, by alloying with elements such as Al, V, and Sn, the α/β phase ratio can be manipulated to create titanium alloys with varying properties.
What are the types of titanium (classified by ISO/ASTM standards)?
| Category | Typical Grades | Core Characteristics | Typical Applications |
|---|---|---|---|
| Commercially Pure Titanium | JIS Grades 1-4 / ASTM Grades 1-4 | Purity >99%, strength increases with oxygen content (Grade 1: most ductile; Grade 4: highest strength) | Heat exchangers (Grade 2), low-temperature vessels (Grade 4) |
| Alpha Titanium Alloys | Grade 23 (Ti-6Al-4V ELI) | Single α-phase structure, high temperature resistance (>500℃), excellent weldability | Aerospace structural parts, medical implants (Grade 23) |
| Alpha + Beta Titanium Alloys | Grade 5 (Ti-6Al-4V, classic grade) | Dual-phase structure, balanced comprehensive performance, heat-treatable for strengthening | Aircraft engine blades, automotive fasteners |
| Beta Titanium Alloys | TB Series (e.g., Ti-15V-3Al-3Cr-3Sn) | High strength (>1300MPa), good cold formability, requires thermal stability control | Springs, aerospace fasteners |
What are the properties of titanium (compared to steel/aluminum)?
| Property | Titanium (Grade 5) | 304 Stainless Steel | 6061 Aluminum | Application Value |
|---|---|---|---|---|
| Density (g/cm³) | 4.47 | 7.9 | 2.7 | Lightweighting (43% weight reduction vs. steel) |
| Tensile Strength (MPa) | 950 | 515 | 276 | Specific strength (212 MPa·cm³/g) is 2.7x that of steel |
| Modulus of Elasticity (GPa) | 113.8 | 193 | 69 | Easy to bend, suitable for complex structures |
| Thermal Conductivity (W/m·K) | 6.7 | 16.2 | 167 | Requires high-pressure cooling to prevent thermal deformation |
| Seawater Corrosion Rate (mm/year) | <0.001 | 0.1-0.5 | 0.5-1.0 | First choice for marine equipment |
| Biocompatibility | No ion leaching (ISO 5832) | Requires coating protection | Not applicable | Only "biophilic metal" for orthopedic implants |
What are the key points of CNC machining titanium?
First, we need to understand the challenges of machining titanium. First, titanium's thermal conductivity is only one-third that of steel. This means that during machining, the material itself has low thermal conductivity, and heat is primarily concentrated on the cutting tool, resulting in high tool wear. Second, at high temperatures, it easily reacts with oxygen or nitrogen, causing overall performance changes. This requires the use of argon shielding or high-pressure coolant (>7MPa). Finally, titanium is prone to deformation during remachining, requiring the use of rigid fixtures and short-edged cutting tools to ensure machining integrity.
CNC Machining Process Optimization for Titanium
| Process Step | Parameters/Solutions | Objectives |
|---|---|---|
| Tool Selection | Carbide tools with TiAlN coating (sharp cutting edges) | Reduce tool adhesion (titanium's stickiness is 2x that of steel) |
| Cutting Speed | Roughing: 40-60 m/min; Finishing: 80-120 m/min | Control heat input to avoid annealing softening |
| Feed Rate | 0.05-0.15 mm/tooth (30% lower than steel) | Reduce cutting force and vibration |
| Cooling System | Internal coolant spindle + high-pressure coolant (>7MPa, with extreme pressure additives) | Chip flushing & cooling, 200% longer tool life |
| Post-Processing | Sandblasting (Ra 3-5 μm) + mixed acid etching (for medical parts) | Improve bone-bonding ability (ASTM F67 certified) |
Is titanium safe?
Professor of Materials Science and Engineering Andrew Minow stated, "If you want the strongest material at the lowest weight, titanium is it. If we could, we'd make everything out of titanium." This speaks volumes about the safety of titanium. Furthermore, titanium is 100% biocompatible. The naturally formed TiO₂ passivation film (5-10nm thick) on its surface isolates metal ions from release and is non-allergenic. Clinical data shows that titanium implants have a 5-year survival rate of over 98%, and are widely used in artificial joints and heart stents.
Where can CNC machined titanium parts be used?
Titanium parts have a wide range of applications, and the following are the most common ones.
| Industry | Typical Components | Irreplaceable Advantages of Titanium |
|---|---|---|
| Aerospace | Engine blades, landing gear | weight reduction, withstands long-term operation at 300℃ |
| Medical | Hip prostheses, orthodontic brackets | No rejection reaction, direct bonding with bone tissue |
| Marine Engineering | Submarine hulls, seawater valves | Corrosion resistance is 100x that of stainless steel |
| Automotive | Turbocharger impellers, suspension links | High specific strength, resistance to high-temperature fatigue |
| High-End Manufacturing | Semiconductor jigs, vacuum chambers | Non-magnetic, resistant to extreme environments (-200℃ to 500℃) |
FAQ
Q: Do CNC parameters need to be adjusted when machining different titanium grades (such as Gr2 pure titanium and Gr5 alloy)?
A: Yes, they do. For example, for Gr2 pure titanium (high ductility, low strength, tensile strength 345 MPa), the feed rate can be appropriately increased (0.12-0.2 mm/tooth), and the cutting speed can be relaxed to 60-80 m/min (for finishing). Tool wear is slow, making conventional carbide tools suitable.
For Gr5 alloy (high strength, medium ductility, tensile strength 950 MPa), the feed rate needs to be reduced (0.05-0.15 mm/tooth), and the roughing speed should be controlled at 40-60 m/min. Diamond-coated or TiAlN-coated tools must be used, and enhanced cooling (such as high-pressure internal coolant >10 MPa) is required to prevent material hardening and tool chipping.
Q: Are there any special handling requirements for chips/waste generated by titanium machining? Are there any safety risks?
A: Yes, because titanium shavings pose a risk of spontaneous combustion, they should be handled as follows:
First, store them in sealed metal containers, taking care to avoid excessive stacking. Then, they should be recycled by a qualified titanium scrap recycling company.
Q: Do titanium parts require heat treatment after machining? When is heat treatment necessary?
A: This requires a case-by-case analysis. For example, landing gear joints in aerospace load-bearing parts require a vacuum stress relief annealing at 650°C for 2 hours after machining to eliminate internal stresses. Medical implants require a low-temperature annealing at 550°C for 1 hour to stabilize the material structure. Applications that do not require heat treatment include decorative titanium parts and housings.