Tungsten (W)
Tungsten has the highest melting point (3,422°C) and highest tensile strength of any pure metal, making it essential for extreme-temperature applications. As tungsten carbide, it dominates the cutting tool and mining drill bit industries. Its exceptional density (19,250 kg/m³) also makes it valuable for radiation shielding and counterweights.
Properties
- Density
- 19,250 kg/m³
- Melting Point
- 3,422 °C
- Boiling Point
- 5,555 °C
- Thermal Conductivity
- 173 W/(m·K)
- Electrical Resistivity
- 5.28 × 10⁻⁸ Ω·m
- Tensile Strength
- 980–1,510 MPa
- Yield Strength
- 750 MPa
- Hardness
- 350–450 HV (pure) / 1,300–1,800 HV (WC)
- Elongation
- 0–4%
- Crystal Structure
- BCC
Common Grades
- W 99.95%: Pure tungsten. Furnace elements, electron emitters, electrical contacts.
- WC-Co (6% Co): Tungsten carbide with cobalt binder. Cutting tools, mining bits, wear parts.
- W-La₂O₃ (1–2%): Lanthanum oxide dispersion-strengthened. TIG welding electrodes (gold tip).
- W-Re (3–25% Re): Tungsten-rhenium alloy. Thermocouples, rocket nozzles, extreme-temperature components.
- Heavy alloy (W-Ni-Fe): 90–97% W with Ni-Fe binder. Radiation shielding, counterweights, kinetic penetrators.
Applications
- Cutting Tools: Cemented carbide inserts, drill bits, end mills, mining bits, rock drilling
- Lighting & Electronics: Incandescent filaments, electron emitters, X-ray targets, electrical contacts
- Welding: TIG welding electrodes (thoriated, lanthanated, ceriated), plasma cutting electrodes
- Aerospace & Defense: Rocket nozzles, turbine blades, kinetic penetrators, counterweights
- Medical: Radiation shielding, X-ray collimators, brachytherapy containers
FAQ
Why does tungsten have the highest melting point?
Tungsten's extremely high melting point (3,422°C) results from very strong metallic bonding due to half-filled 5d electron shells and large atomic mass. The BCC crystal structure and high bond energy per atom make it the most thermally stable metal — only carbon (which sublimes) has a higher effective 'melting' temperature.
What is tungsten carbide and why is it so hard?
Tungsten carbide (WC) is a compound of tungsten and carbon with hardness approaching diamond (9–9.5 on Mohs scale vs. diamond's 10). Cemented carbide tools use WC particles bonded with cobalt, combining extreme hardness for cutting with enough toughness to resist fracture. They revolutionized metalworking productivity.
Is tungsten toxic?
Tungsten metal is generally considered low-toxicity and is not classified as carcinogenic. However, tungsten carbide cobalt (WC-Co) dust is classified as possibly carcinogenic (IARC Group 2A) due to the cobalt binder. Proper dust control and PPE are essential when grinding or machining tungsten carbide.
What is the difference between thoriated and lanthanated TIG electrodes?
Both are tungsten TIG welding electrodes with oxide additions for improved arc starting. Thoriated (2% ThO₂, red tip) offers excellent performance but is mildly radioactive. Lanthanated (1.5–2% La₂O₃, gold/blue tip) provides equivalent performance without radioactivity and is now preferred in most applications.