Advertisement

Tungsten's Boiling Point Is 10,030 F and Other Crazy Facts

light bulb filament
Most light blubs in the 20th century had filaments made of tungsten. Aleksandr Zubkov/Getty Images

Armor-piercing bullets, rocket engine nozzles and drill bits for cutting through solid rock are just some of the products made with tungsten, one of the hardest and most heat-resistant elements in the universe.

Tungsten, like most other metallic elements, isn't found in nature as a shiny hunk of metal. It needs to be chemically isolated from other compounds, in this case the naturally occurring mineral wolframite. That's why tungsten's symbol on the periodic table isn't T but W, which is short for "wolfram." The name tungsten is Swedish for "heavy stone," a reference to the element's uncanny density and heft. Its atomic number (the number of protons in the nucleus of its atom) is 74 and its atomic weight (weighted average of its naturally occurring isotopes) is 183.84.

Advertisement

Advertisement

A pair of Spanish chemists (and brothers), Juan José and Fausto Elhuyar, are credited with discovering tungsten in 1783 when they first isolated the grayish-white metal from wolframite.

The Highest Melting Point of All Metals

One of tungsten's most impressive and useful properties is its high melting point, the highest of all metallic elements. Pure tungsten melts at a whopping 6,192 degrees F (3,422 degrees C) and won't boil until temperatures reach 10,030 F (5,555 C), which is the same temperature as the photosphere of the sun.

Iron, for comparison, has a melting point of 2,800 degrees F (1,538 degrees C) and gold turns to liquid at just 1,947.52 degrees F (1,064.18 degrees C).

All metals have relatively high melting points because their atoms are held together in tight metallic bonds, says John Newsam, a chemist and materials scientist we contacted through the American Chemical Society. Metallic bonds are so strong because they share electrons across an entire three-dimensional array of atoms. Newsam says that tungsten outlasts other metals because of the unusual strength and directionality of its metallic bonds.

"Why is that important?" asks Newsam. "Think of Edison working on filaments for the incandescent light bulb. He needed a material that not only emitted light but wouldn't melt from the heat."

Edison experimented with lots of different filament materials, including platinum, iridium and bamboo, but it was another American inventor, William Coolidge, who's credited with making the tungsten filaments used in most light bulbs throughout the 20th century.

Tungsten's high melting point has other advantages, like when it's mixed in as an alloy with materials like steel. Tungsten alloys are plated onto sections of rockets and missiles that need to withstand tremendous heat, including the engine nozzles that eject explosive streams of rocket fuel.

Advertisement

tungsten wedding ring
Tungsten is also used to make wedding rings. SolitaryAngel/Wikipedia/CC BY-SA 3.0

The density of different elements is a reflection of the size of their component atoms. The lower you get on the periodic table, the larger and heavier the atoms.

"The heavier elements, like tungsten, have more protons and neutrons in the nucleus and more electrons in orbit around the nucleus," says Newsam. "That means that the weight of one atom goes up significantly as you go down the periodic table."

Advertisement

Advertisement

In practical terms, if you held a hunk of tungsten in one hand and held the same volume of silver or iron in the other hand, the tungsten would feel a lot heavier. Specifically, the density of tungsten is 19.3 grams per cubic centimeter. Silver, in comparison, is about half as dense as tungsten (10.5 g/cm3), and iron is almost one-third as dense (7.9 g/cm3).

Tungsten's high-density heft can be an advantage in certain applications. It's often used in armor-piercing bullets, for example, for its density and hardness. The military also uses tungsten to make so-called "kinetic bombardment" weapons that shoot a rod of tungsten like an airborne battering ram to smash through walls and tank armor.

During the Cold War, the Air Force allegedly experimented with an idea called Project Thor that would have dropped a bundle of 20-foot (6-meter) tungsten rods from orbit onto enemy targets. These so-called "rods from God" would have impacted with the destructive force of a nuclear weapon, but without the nuclear fallout. Turns out the cost of rocketing the heavy rods into space was prohibitively expensive.

Only Diamonds Are Harder Than Tungsten Carbide

Pure tungsten isn't that hard — you can cut through it with a handsaw — but when tungsten is combined with small amounts of carbon, it becomes tungsten carbide, one of the hardest and toughest substances on Earth.

"When you put small amounts of carbon or other metals into tungsten, it fixes the structure and prevents it from being easily deformed," says Newsam.

Tungsten carbide is so hard that it can only be cut by diamonds, and even then, diamonds only work if the tungsten carbide isn't fully cured. Tungsten carbide is up to three times as rigid as steel, can last up to 100 times longer than steel under highly abrasive conditions, and has the greatest compressive strength of all forged metals, meaning it won't dent or deform when squeezed under tremendous force.

The most common use for tungsten carbide — and the final destination of most of the mined tungsten on the planet — is specialized tools, particularly drill bits. Any kind of drill bit for cutting metal or solid rock needs to withstand punishing levels of friction without dulling or breaking. Only diamond drills are harder than tungsten carbide, but they're also much more expensive.

Other Cool Uses for Tungsten

Tungsten's hardness, density and heat resistance make it ideal for a lot of niche applications:

  • Electron microscopes shoot out a stream of electrons from a special emitter tip made from tungsten.
  • Most welds between metal and glass are made from tungsten, because tungsten expands and contracts at the same rate as borosilicate glass, the most common kind of glass.
  • The spikes on snowmobile tracks are made from tungsten alloys.
  • Professional-grade darts are made with tungsten (the "Wolfram Infinity" is 97 percent tungsten).
  • In ballpoint pens, the actual ball is often made from tungsten carbide.
  • The jewelry industry makes rings from tungsten carbide.

Advertisement

Advertisement


Advertisement

Advertisement

Advertisement

Advertisement

Advertisement

Advertisement