Strength is an important quality in the use of metals. This is especially true in construction, transportation, heavy industry and tool making. Metal alloys are often stronger than a metal in their pure form. In discussing the strongest metals, we should first consider what we mean by strength.
Differences in types of strength
There are a number of different measures of strength of a metal:
l Yield strength measures the lowest stress that will result in permanent deformation.
l Compressive strength measures the amount of squeezing stress that will cause defects.
l Tensile strength measures the amount of pulling stress that will cause defects.
l Impact strength measures the amount of impact energy that will cause a fracture.
The importance of the different types of strength depends on the intended use of the metal.
The strongest metals
There are a number of metals which can be considered “the strongest”. Of course, this depends greatly on the intended application of the metal. Another consideration is the various alloys that can be formed with each metal.
That said, four metals stand out as being the strongest: Steel, Titanium, Tungsten and Inconel.
Steel is an alloy of iron and carbon, often in combination with other elements. It is made by heating iron ore in furnaces where impurities are removed and carbon is added. Raw iron is ductile and weak, but the addition of other elements such as manganese, niobium, or vanadium gives steel strength and hardness. However, it is important to remember that these additional elements also impact other properties, such as toughness and ductility.
Steel is one of the most common materials of the modern world – with more than 1.3 billion tons of steel are produced every year. It is widely used in the transportation, infrastructure, building, and weapons industries. Most large modern buildings – including skyscrapers, airports and bridges – are held up by steel structures. In the automotive industry, steel is still the principal material, although aluminum is increasingly popular. Steel is also used in smaller items such as screws, nails and kitchen utensils.
There are many forms of steel alloys:
Stainless steel is a corrosion resistant alloy containing a minimum of 11% chromium.
Tool steels are alloyed with tungsten and cobalt and are notable for their hardness. Tool steel can retain a sharp cutting edge and is used in axes and drills.
Maraging steel is alloyed with nickel and other elements. It has a low carbon content and is extremely strong. Maraging steel is used in rocket and missile skins, gas centrifuges for uranium enrichment, and fencing blades.
Titanium is a silvered colored metal with low density and high strength. It is notable for having the highest tensile strength-to-density ratio of any metallic element. However, it’s not as hard as some varieties of heat-treated steel.
Titanium is commonly alloyed with a range of elements including iron, aluminum, and vanadium. Titanium alloys are strong and lightweight making them ideal for automotive, aerospace, military and industrial applications. Two-thirds of all titanium metal produced is used for aircraft parts. Titanium is also highly resistant to seawater corrosion making it perfect for propeller shafts and rigging as well as divers’ knives.
Tungsten is a rare metal found on Earth in the form of chemical compounds. It has a metallic grey color, is brittle and hard to work. If refined to its purest form, it has a hardness that exceeds that of most steels. Of all the pure metals, tungsten has the highest melting point, lowest vapor pressure and highest tensile strength. It has the lowest coefficient of thermal expansion of any pure metal.
Tungsten’s toughness is greatly enhanced by alloying it with steel.
Around half of all tungsten is used for the production of hard materials, principally tungsten carbide. Tungsten carbide is used to make knives, drills, circular saws, and lathes. The metalworking, mining, construction, and petroleum industries rely heavily on tungsten carbide tools. Tungsten is also used to make alloys. The high melting point of tungsten makes it ideal for rocket and missile manufacture.
Inconel is a type of superalloy made from austenite, nickel, and chromium. It is distinguished by its high strength which is not diminished at high temperatures. It’s also highly oxidation and corrosion resistant.
Inconel’s properties make it suitable for service in extreme environments. It’s commonly used in gas turbine blades, well pump motor shafts, chemical processing plants, and nuclear-pressurized water reactors.