Tungsten melts at 3,422°C (6,192°F, 3,695 K) — the highest melting point of any pure element in the periodic table, and approximately 2.2 times higher than iron’s 1,538°C. No other commercially available metal even approaches this temperature. The next-closest elements — rhenium at 3,186°C and osmium at 3,033°C — are both exceptionally rare and prohibitively expensive for structural use. For all practical refractory engineering applications, tungsten’s melting point is the thermal ceiling.
In vacuum environments, tungsten’s melting behavior becomes especially relevant: vacuum furnaces, electron beam welding, plasma-facing components, and high-power lamp filaments all operate tungsten at temperatures approaching its melting point under conditions where oxygen absence allows the metal to be used without oxidation destroying the component. Understanding the physics of tungsten’s melt temperature in vacuum — and why it behaves differently under vacuum than in air — is the core of this article.
Tungsten Melt Temperature: Complete Reference Values
All values from NIST Standard Reference Database and NIST-JANAF Thermochemical Tables:
| Property | Value |
|---|---|
| Melting point (1 atm) | 3,422°C / 6,192°F / 3,695 K |
| Boiling point (1 atm) | 5,555°C / 10,031°F / 5,828 K |
| Liquid range | 2,133°C |
| Latent heat of fusion | 284.5 kJ/mol (35.4 kJ/kg) |
| Latent heat of vaporization | 806 kJ/mol (4,378 kJ/kg) |
| Heat capacity (solid, 25°C) | 132 J/(kg·K) |
| Vapor pressure at 2,000°C | ~10⁻⁷ atm |
| Vapor pressure at 3,000°C | ~10⁻³ atm |
| ITS-90 status | Not a fixed point; too high for standard thermocouple range |
Source: NIST Standard Reference Database; CRC Handbook of Chemistry and Physics, 104th Edition.
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Unit conversions:
- °C to °F: (3,422 × 9/5) + 32 = 6,192°F
- °C to K: 3,422 + 273.15 = 3,695.15 K (rounded to 3,695 K)
The vaporization-to-fusion latent heat ratio (806 / 284.5 kJ/mol = 2.83:1) is among the lowest for metals — most metals have vaporization enthalpies 20–30× their fusion enthalpies (iron: 24.7×, gold: 25.8×). Tungsten’s much lower ratio reflects the extremely tight packing and strong bonding of the BCC tungsten lattice even in the liquid state. The liquid-to-vapor transition for tungsten is proportionally less energetically demanding than for most metals, which contributes to its utility in electron beam evaporation sources despite the extreme temperature required.
Why Tungsten Has the Highest Melt Temperature of Any Metal
The BCC lattice and d-electron bonding
Tungsten (element symbol W, from German Wolfram; atomic number 74) has the electron configuration [Xe] 4f¹⁴ 5d⁴ 6s². Four 5d electrons are available for metallic bonding — more than any of the other Group 6 metals (chromium has 5d⁵ 4s¹ configuration but lower melting point, 1,907°C; molybdenum at 2,623°C sits between).
Tungsten’s high melt temperature traces to two interacting factors:
1. d-orbital bonding strength. The 5d electrons in tungsten are more contracted than the 4d electrons in molybdenum (tungsten is in Period 6 vs. Period 5) and more numerous than the 3d electrons in chromium. The 5d wave functions produce strong, directional covalent-metallic bonds with neighboring tungsten atoms in the BCC lattice. Each tungsten atom has 8 nearest neighbors in the BCC structure; the combination of 4 available d electrons per atom and 8 strong bond interactions produces exceptional cohesive energy.
2. Relativistic effects — without the gold-silver paradox. Unlike gold (where relativistic 6s contraction produces anomalously strong bonding that raises gold above silver), tungsten does not exhibit the same dramatic relativistic effect — its valence electrons are primarily 5d, not 6s. However, relativistic mass increase of the inner-shell electrons in tungsten does contract the 5d orbitals somewhat, increasing the d-electron spatial density and bond directional character. The net effect is to strengthen tungsten’s BCC lattice cohesion beyond what a simple d-electron count would predict.
3. Comparison with the d-electron melting point series. Across Period 6, melting points peak near the center of the d-block:
| Element | Z | d-electrons | Melting point (°C) |
|---|---|---|---|
| Hafnium (Hf) | 72 | 5d² | 2,233 |
| Tantalum (Ta) | 73 | 5d³ | 3,017 |
| Tungsten (W) | 74 | 5d⁴ | 3,422 |
| Rhenium (Re) | 75 | 5d⁵ | 3,186 |
| Osmium (Os) | 76 | 5d⁶ | 3,033 |
| Iridium (Ir) | 77 | 5d⁷ | 2,446 |
| Platinum (Pt) | 78 | 5d⁹ | 1,768 |
The melting point peaks at tungsten (5d⁴) — not at rhenium (5d⁵ where d-band filling is nominally half). This peak position reflects the point where the ratio of bonding to antibonding d-band states is optimized for maximum cohesive energy. With 4 electrons filling only the bonding states of the d-band, tungsten achieves the maximum metallic bond strength in Period 6.
Tungsten Melt Temperature in Vacuum vs. Air: Why Vacuum Is Required
At room temperature, tungsten forms a stable surface oxide (WO₃) in air but does not corrode rapidly — the oxide film is somewhat protective. Above approximately 400°C, tungsten oxidizes rapidly:
W(s) + 3O₂(g) → WO₃(g)
The critical issue: above approximately 800°C, tungsten trioxide (WO₃) is a vapor rather than a solid film. The oxide does not protect the surface — it evaporates as fast as it forms. Above 800°C in air, tungsten undergoes catastrophic oxidation: the surface retreats rapidly as tungsten is converted to volatile WO₃, and the metal is destroyed long before approaching its 3,422°C melting point.
In vacuum (or inert atmosphere), this destruction mode is absent. Without oxygen, tungsten can be heated to its actual melting point. The metal is stable — aside from its own vapor pressure — at any temperature below 3,422°C.
Vapor pressure of tungsten in vacuum
Even in vacuum, tungsten is not perfectly stable as temperature rises — it has a finite vapor pressure:
| Temperature | Vapor pressure | Notes |
|---|---|---|
| 1,500°C | ~10⁻¹⁰ atm | Negligible; lamp filament range (lower end) |
| 2,000°C | ~10⁻⁷ atm | Low but significant for extended operation |
| 2,500°C | ~10⁻⁵ atm | Measurable evaporation |
| 3,000°C | ~10⁻³ atm | Significant evaporation rate |
| 3,200°C | ~0.01 atm | Rapid evaporation; near-melting behavior |
| 3,422°C | 1.0 atm | Melting point = boiling point at this pressure |
Source: NIST WebBook; CRC Handbook vapor pressure tables.
The exponential increase in vapor pressure with temperature is the fundamental constraint on tungsten component lifetime at high temperatures. An incandescent lamp filament operating at approximately 2,800°C in vacuum loses tungsten atoms from its surface continuously — a process that eventually produces the thin spots that lead to filament breakage. Halogen lamp designs introduce a small amount of iodine gas that chemically returns evaporated tungsten to the filament surface (the tungsten-halogen cycle), extending filament life by recycling evaporated metal.
The effect of pressure on tungsten melt temperature
The melting point of tungsten decreases slightly under reduced pressure — following the Clausius-Clapeyron relationship for the solid-liquid transition:
(dT_m/dP) = T_m × ΔV / ΔH_f
Where ΔV is the volume change on melting (small and positive for tungsten, as liquid tungsten is slightly less dense than solid) and ΔH_f is the latent heat of fusion.
For tungsten, (dT_m/dP) ≈ +0.036°C/atm — the melting point increases slightly with increasing pressure and decreases slightly with decreasing pressure. This is the normal behavior for metals that expand on melting (as most metals do).
At 10⁻⁶ atm (a typical high-vacuum environment), the correction to the melting point is:
ΔT_m = 0.036 × (10⁻⁶ − 1) ≈ −0.036°C — completely negligible
The melting point of tungsten in high vacuum is, for all engineering purposes, identical to its atmospheric value of 3,422°C. The distinction between “vacuum” and “atmospheric” melting temperature for tungsten is not a thermal one — it is a kinetic one. In vacuum, tungsten can reach 3,422°C without oxidative destruction. In air, the metal is chemically destroyed above ~800°C. The melt temperature itself is the same.
Tungsten Melt Temperature in High-Temperature Applications
Vacuum furnaces and high-temperature processing
Tungsten heating elements and fixtures operate in vacuum furnaces at temperatures up to approximately 2,800°C — about 600°C below the melt temperature. This operating limit is set by:
- Recrystallization embrittlement (tungsten recrystallizes above approximately 1,350°C, producing a coarse grain structure that becomes brittle at room temperature)
- Creep at high temperatures (above approximately 0.4 × T_m = 1,300°C, creep deformation becomes significant)
- Component geometry distortion under gravity at sustained temperatures above 2,000°C
The maximum vacuum furnace temperature commercially achieved with tungsten heating elements is approximately 2,800°C — used for sintering tungsten carbide, processing refractory ceramics, and high-temperature materials research.
Electron beam welding and melting
Electron beam (EB) processes focus a beam of high-velocity electrons onto a metal workpiece in a vacuum. The beam energy is deposited in the metal surface, producing a molten pool. For welding of tungsten itself, EB is the primary process because:
- The process operates in high vacuum (~10⁻⁴ to 10⁻⁶ Torr) — preventing oxidation at tungsten’s working temperatures
- Energy density sufficient to exceed 3,422°C can be achieved in the beam focus
- The precise heat input control of EB minimizes heat input to the surrounding material
Electron beam melting (EBM) of tungsten for powder metallurgy consolidation is practiced in specialty refractory manufacturing. The weld pool reaches and briefly exceeds 3,422°C at the beam focus; the surrounding solid is maintained at temperatures safe for the thermocouple monitoring systems.
Plasma-facing components in fusion reactors
Tungsten is the primary candidate material for plasma-facing components in tokamak fusion reactors (including ITER, under construction in France as of 2026). The plasma in a tokamak operates at millions of degrees Celsius — far above tungsten’s melt temperature — but the plasma is extremely low density and the energy flux reaching the vessel wall is manageable.
The concern is plasma disruptions — sudden events where the plasma loses confinement and dumps energy onto the vessel wall in milliseconds. The surface heat load during a disruption can reach 200–500 MJ/m² — sufficient to melt a several-millimetre-thick tungsten surface layer. The high melt temperature of tungsten (3,422°C) is the primary reason it is selected over lower-melting metals: the amount of energy required to melt tungsten is much larger than for any other engineering metal, providing more margin against disruption-induced melting.
Filaments and electrodes
Incandescent lamp filaments (historically) and high-power discharge electrodes operate tungsten at 2,500–3,100°C — 300–900°C below the melt temperature. The filament temperature is set by the balance between electrical power input and radiative heat loss (Stefan-Boltzmann). At these temperatures, the vapor pressure of tungsten (~10⁻⁷ to 10⁻⁴ atm) determines the filament lifetime. Higher temperature = more light output (bluer color, higher efficacy) but shorter lifetime from evaporation. The standard incandescent lamp design operated at approximately 2,800°C as a compromise between efficacy and 1,000-hour rated lifetime.
Tungsten Melt Temperature vs. Other Refractory Metals
| Metal | Melting point (°C) | Boiling point (°C) | Practical max service T (°C) | Notes |
|---|---|---|---|---|
| Tungsten (W) | 3,422 | 5,555 | ~2,800 | Highest melting metal |
| Rhenium (Re) | 3,186 | 5,596 | ~2,600 | Rare; used as W additive |
| Osmium (Os) | 3,033 | 5,012 | Not structural | Brittle; toxic oxide |
| Tantalum (Ta) | 3,017 | 5,458 | ~2,400 | More ductile than W |
| Molybdenum (Mo) | 2,623 | 4,639 | ~1,800 | Cheaper; lower T |
| Niobium (Nb) | 2,477 | 4,744 | ~1,500 | Aerospace refractory |
| Iridium (Ir) | 2,446 | 4,428 | ~2,000 | Best oxidation resistance |
| Hafnium (Hf) | 2,233 | 4,603 | ~1,800 | Neutron absorber |
| Chromium (Cr) | 1,907 | 2,671 | ~1,100 | Volatile Cr₂O₃ limits T |
| Titanium (Ti) | 1,668 | 3,287 | ~315 (structural) | Low strength at T |
Tungsten’s 236°C melting point advantage over rhenium (3,186°C) translates to a 10–20% safety margin in the highest-temperature applications. Rhenium is added to tungsten alloys (W-Re, typically 3–26% Re) specifically to improve high-temperature ductility without significantly reducing the melt temperature — the W-5Re alloy melts at approximately 3,350°C, and the W-26Re alloy at approximately 3,050°C, both substantially above any competing non-tungsten metal.
Frequently Asked Questions About Tungsten Melt Temperature
Q: What is the melt temperature of tungsten? 3,422°C (6,192°F, 3,695 K) at standard atmospheric pressure. This is the highest melting point of any pure element — pure tungsten melts approximately 1,884°C higher than iron (1,538°C) and 2,358°C higher than aluminum (1,064°C). The value is from the NIST Standard Reference Database.
Q: Why does tungsten have such a high melting point? Tungsten’s extreme melt temperature reflects exceptionally strong metallic bonding from its four 5d valence electrons in a BCC crystal structure. With four electrons filling only the bonding states of the 5d band, tungsten achieves the maximum cohesive energy in Period 6. Each tungsten atom bonds to 8 nearest neighbors with directional, covalent-character d-electron interactions. Breaking these bonds requires more thermal energy than any other metal’s atomic forces demand.
Q: Does tungsten’s melting point change in vacuum? The melting point itself is essentially unchanged — the Clausius-Clapeyron pressure correction at 10⁻⁶ atm is less than 0.036°C, completely negligible. What changes in vacuum is whether tungsten can reach its melting point at all. In air, tungsten forms volatile WO₃ above ~800°C and is destroyed long before reaching 3,422°C. In vacuum, the absence of oxygen allows tungsten to be heated to its actual melting point without oxidative destruction.
Q: What temperature can tungsten reach before it melts? In vacuum: up to 3,422°C — the melt temperature. In air: practical use is limited to approximately 400°C before oxidation becomes severe, and catastrophic oxidation occurs above 800°C due to volatile WO₃ formation. For structural tungsten components in vacuum applications (furnace heating elements, EB welding electrodes), the practical operating limit is approximately 2,800°C — set by creep, recrystallization embrittlement, and vapor pressure rather than by the melt temperature itself.
Q: What is tungsten’s melting point in Fahrenheit? 6,192°F — derived from (3,422 × 9/5) + 32. The boiling point in Fahrenheit is 10,031°F.
Q: How close to its melting point does tungsten operate in industrial applications? Vacuum furnace heating elements: ~2,800°C, which is 82% of the melt temperature in absolute kelvin (2,800 + 273 = 3,073 K; 3,073 / 3,695 K = 0.83). Incandescent lamp filaments at 2,800°C: also approximately 83% of T_m. Plasma-facing components in normal operation: typically 200–1,200°C, well below the melt temperature but with disruption events that can transiently reach the melting point.
References
- National Institute of Standards and Technology (NIST), NIST Standard Reference Database 69: NIST Chemistry WebBook, available at webbook.nist.gov; and Chase, M.W., et al., NIST-JANAF Thermochemical Tables, 4th Edition, AIP, 1998. (Tungsten melting point 3,422°C / 3,695 K; boiling point 5,555°C; latent heats of fusion and vaporization; vapor pressure of solid and liquid tungsten as a function of temperature; heat capacity data for tungsten across the full solid temperature range.)
- Haynes, W.M., ed., CRC Handbook of Chemistry and Physics, 104th Edition. CRC Press, Boca Raton, FL, 2024. (Melting and boiling points of Period 6 transition metals: Hf, Ta, W, Re, Os, Ir, Pt; d-electron configuration and cohesive energy trends; vapor pressure tables for tungsten; relativistic orbital effects in heavy transition metals; oxidation chemistry of tungsten above 800°C.)
- Kittel, C., Introduction to Solid State Physics, 8th Edition. Wiley, New York, 2005. (d-band filling and cohesive energy in BCC transition metals; d-electron bonding directional character and its contribution to melting point; Clausius-Clapeyron equation for pressure dependence of melting point; comparison of d-electron melting point peaks across the 3d, 4d, and 5d series.)
- ASM Handbook, Volume 2: Properties and Selection — Nonferrous Alloys and Special-Purpose Materials, 10th Edition. ASM International, Materials Park, OH, 1990. (Refractory metal properties: tungsten, molybdenum, tantalum, niobium; W-Re alloy melting points; vacuum furnace application temperatures for tungsten heating elements; creep and recrystallization limits for tungsten in service.)
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