By: Dave Ross | September 22, 2020

Armour-piercing bullets, rocket engine nozzles and drill bits used to cut solid rocks are just some of the products made of tungsten, which is one of the hardest and most heat-resistant elements in the universe.

Like most other metal elements, tungsten is not like a shiny metal in nature. It needs to be chemically separated from other compounds, in this case the naturally occurring mineral wolframite. This is why the symbol for tungsten on the periodic table is not T but W. W is the abbreviation of "wolfram". The name tungsten means "heavy stone" in Swedish, referring to the incredible density and weight of this element. Its atomic number (the number of protons in its nucleus) is 74, and its atomic weight (the weighted average of its natural isotopes) is 183.84.

In 1783, a pair of Spanish chemists (and brothers) Juan José and Fausto Elhuyar separated the off-white metal from wolframite for the first time, and thus discovered tungsten.

One of the most impressive and useful properties of tungsten is its high melting point, which is the highest of all metal elements. Pure tungsten melts at temperatures as high as 6,192 degrees Fahrenheit (3,422 degrees Celsius) and does not boil until the temperature reaches 10,030 degrees Fahrenheit (5,555 degrees Celsius), which is the same temperature as the solar photosphere.

In contrast, iron has a melting point of 2,800 degrees Fahrenheit (1,538 degrees Celsius), while gold only becomes liquid at 1,947.52 degrees Fahrenheit (1,064.18 degrees Celsius).

John Newsum, a chemist and materials scientist we contacted through the American Chemical Society, said that all metals have relatively high melting points because their atoms are held together by tight metal bonds. Metal bonds are so strong because they share electrons throughout the three-dimensional array of atoms. Newsam said that tungsten is more durable than other metals because of its unusual strength and directionality of metal bonds.

"Why is this important?" Newsum asked. "Think of Edison working on filaments for incandescent light bulbs. He needed a material that not only emits light, but does not melt due to heat."

Edison experimented with many different filament materials, including platinum, iridium, and bamboo, but another American inventor, William Coolidge, was praised for making the tungsten filament used in most light bulbs throughout the 20th century.

The high melting point of tungsten has other advantages, such as when it is mixed with materials such as steel. Tungsten alloys are plated on rocket and missile components that need to withstand huge heat, including engine nozzles that spray explosive rocket fuel streams.

The density of different elements is a reflection of the size of their constituent atoms. The lower your position on the periodic table, the larger and heavier the atom.

"Heavier elements, such as tungsten, have more protons and neutrons in the nucleus and more electrons in orbits around the nucleus," Newsum said. "This means that as you go down the periodic table, the weight of an atom increases significantly."

In fact, if you hold a large piece of tungsten in one hand and the same volume of silver or iron in the other, the tungsten will feel a lot heavier. Specifically, the density of tungsten is 19.3 grams per cubic centimeter. In contrast, the density of silver is about half that of tungsten (10.5 g/cm3), and the density of iron is almost one-third of that of tungsten (7.9 g/cm3).

The high density and weight of tungsten may be an advantage in certain applications. For example, due to its density and hardness, it is often used for armor-piercing bullets. The military also uses tungsten to make so-called "kinetic bombardment" weapons, shooting a tungsten rod like an aerial siege hammer to smash walls and tank armor.

During the Cold War, the Air Force reportedly experimented with an idea called "Project Thor", which dropped a bundle of 20-foot (6 m) tungsten rods from orbit onto enemy targets. These so-called "sticks of God" will be affected by the destructive power of nuclear weapons, but they will not produce nuclear radiation. Facts have proved that the cost of sending a heavy-rod rocket into space is prohibitively high.

Pure tungsten is not that hard—you can cut it with a hand saw—but when tungsten is combined with a small amount of carbon, it becomes tungsten carbide, which is one of the hardest and toughest substances on the planet.

"When you put a small amount of carbon or other metal into tungsten, it will fix the structure and prevent it from deforming easily," Newsum said.

Tungsten carbide is very hard and can only be cut with diamonds. Even so, diamonds can only function if the tungsten carbide is not fully cured. The hardness of tungsten carbide is three times that of steel, the service life under high wear conditions is 100 times that of steel, and it has the greatest compressive strength among all forged metals, which means that it will not sink or sink under huge pressure. Deformed.

The most common use of tungsten carbide-and the ultimate destination for most tungsten mining on the planet-is special tools, especially drill bits. Any type of drill bit used to cut metal or solid rock needs to withstand harsh friction without becoming dull or broken. Only diamond bits are harder than tungsten carbide, but they are also much more expensive.

The hardness, density and heat resistance of tungsten make it ideal for many niche applications:

Counterfeiters have discovered that the density of tungsten is almost the same as that of gold a long time ago, and sometimes try to fake gold-plated tungsten bars as pure gold bars.

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