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Metals: From Raw Strength to Practical Use

Metals: From Raw Strength to Practical Use

Metals: From Raw Strength to Practical Use

In theory, science appears to be a concrete practice. Facts, figures, conclusions, analyses- these processes don’t leave a lot of room for creative interpretation. There are, however, some subjects where science can become more speculation than fact. Take metals, for example. You’d think if someone asked what the strongest metal was there’d be an easy answer or even an NBA-style ranking of strongest to weakest ones. But, like in the NBA or NFL, the idea of the ‘best’ is debatable because there are different ways to measure ‘quality’.

To even begin to talk about the strongest metal, you must first understand the four different types of strength.

Strengths

One type of strength is called Yield Strength, which measures how well the material resists being bent or deformed. This is a particularly important factor for structural engineers, who will ideally want to build with a material that won’t bend when more weight is added. You don’t want your building to end up looking like the Leaning Tower of Pisa.

The next type of strength is Tensile Strength, which measures how much strength it would take to pull the metal apart. While a substance like cookie dough, for example, has a low tensile strength, something like graphene has one of the highest tensile strengths ever recorded.

There’s also Compressive Strength, which is how well the material withstands to being squeezed together or compacted. Styrofoam, as one example, has very little compressive strength and will break apart easily if squeezed or flattened. Compressive strength can be measured using Moh’s scale which measures relative hardness and resistance to scratching.

Finally there’s Impact Strength which measures the material’s ability to resist sudden force or impact without breaking. While bulletproof materials wouldn’t be a perfect ten in every category, they would have a high level of Impact Strength. On the other hand, while a diamond may score a 10 on Moh’s scale, it will shatter if struck by a hammer.

Welding Metal Beam

While it would be really convenient for there to be a metal that was a perfect ten in all four categories, unfortunately there isn’t one. Therefore, when choosing a metal you have to make a decision based on your particular project and determine which type of strength is most needed.

Scientists have, however, found a way to cheat the system a bit by creating alloys (or combinations of metals) that produce an even stronger metal. This process may sound a bit like a Marvel movie, but it has helped create extremely useful building materials.

Steel

One metal that makes the cut is steel, which is an alloy of iron and carbon (often in combination with other elements as well). It’s created by heating iron ore in furnaces where impurities are removed and carbon is added.

According to Metal Supermarkets, steel is one of the most common materials in modern day society with more than 1.3 billion tons produced each year. Most large buildings like skyscrapers, airports and bridges are held up by steel in some capacity. It’s the primary source for the automotive, infrastructure, building and weapons industries.

There are a few different types of steel, each with their own types of strength. Carbon Steel is the first, which combines carbon and iron and scores high on all four types of strength. It has a high level of yield and tensile strength with an overall score of 6.0 on the Mohs scale.

The next type of steel is Maraging Steel, which combines nickel and elements such as cobalt, titanium, molybdenum or aluminum. With a lower carbon content, this type of steel is known for its high yield strength, being anywhere between 1,400 and 2,400 MPa. It’s often used in rocket and missile skins, gas centrifuges for uranium enrichment, and fencing blades.

Another type is Stainless Steel, an alloy of steel, chromium, and manganese. This combination creates a corrosion-resistant material which has high amounts of tensile and yield strength. The corrosion-resistant element makes stainless steel a commodity for everything from kitchen accessories and cutlery to medical instruments to even ship containers and refuse vehicles.

The last type of steel is Tool Steel which, shockingly enough, is primarily used to make tools. This is steel alloyed with cobalt and tungsten and is used for its hardness and its ability to retain a sharp cutting edge. This is why it’s largely used for axes and drills.

Chrysler Building New York

In terms of practical use, carbon steel and stainless steel are most often used in the construction industry. Carbon steel is primarily used to make beams for structural framework, bridges, and plates for highway construction. Stainless Steel is one of the oldest known building materials: there are structures made centuries ago that still stand today. Many famous buildings (the Chrysler Building in New York, for example) rely on stainless steel. This metal is often found on roofing, structural applications, handrails and balustrade, architectural cladding and in drainage components.

It may be surprising to learn that steel is often used by Green builders on eco-friendly construction projects. According to How Stuff Works, this is partly because steel is long-lasting and durable; it doesn’t lose any quality each time it’s recycled. There is also less waste with steel projects compared to wood projects because you can weld small ‘offcuts’ together to use for smaller jobs.

Inconel

Another alloy known for its strength is Inconel. In fact, it’s not just an alloy- it’s a superalloy, combining austenite, nickel and chromium. This metal is known for its ability to withstand extremely high temperatures and harsh conditions. As a result, it’s primarily used in gas turbine blades, well pump motor shafts, chemical processing plants and nuclear pressurized water reactors.

Tungsten

One naturally occuring metal to make the list is tungsten, which has the highest tensile strength of any naturally occuring metal. It’s extremely rare and usually found in the form of chemical compounds. Of all natural metals, tungsten has the highest melting point and lowest vapor pressure. However, tungsten is brittle and has a lower impact strength, so it’s often used as an alloy rather than in its natural state.

Around half of all tungsten is used for the production of hard materials- primarily tungsten carbide, which is an alloy of tungsten and carbon. 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. The high melting point of tungsten makes it perfect for rocket and missile manufacturing.

Titanium

Also naturally occurring, Titanium has the highest tensile strength to density ratio of any metal. Though it is very corrosion-resistant, it scores lower on Moh’s scale of hardness so it’s often used as an alloy. It’s commonly alloyed with a range of elements, including iron, aluminum, and vanadium. Alloys made using titanium are strong and lightweight, which makes them perfect for the automotive, aerospace, military and industrial industries. A total of two thirds of the titanium produced is used for aircraft parts and, because titanium is also resistant to seawater corrosion, it can be used for propeller shafts and rigging.

While not commonly ranked among the strongest metals, there are a few others that are quite commonly used for their significant amount of strength and additional benefits in the construction industry.

Aluminum

While aluminum itself doesn’t often make the list of strongest metals, it’s often used as an alloy in order to increase the strength of a metal. Some common elements with which aluminum is combined are silicon, magnesium and copper. Aluminum-zinc alloys are some of the strongest alloys available today and are often used in the automotive and aerospace industries.

Aluminum can also be made stronger through processing- by using hot rolling or cold rolling- which is heat treating followed by rapid cooling. This process freezes the atoms in place, strengthening the metal. The other process is “cold worked” or rolling, stretching, forging or drawing to make the metal stronger. This inhibits the movement of atoms relative to each other.

Aluminum has appeal because it’s about one-third the weight of steel, meaning parts can be made thicker and stronger while still reducing the weight of a vehicle. It’s the second most used material by auto-makers according to The Aluminum Association. It’s also commonly used in window frames, streetlights, doors, planes, trains, buses, trucks and ocean liners. The metal is also used by the U.S. Army, NASA and U.S. Air Force.

Copper

As the oldest known metal used by man–dating back to ancient Egypt–there are many benefits to copper. It has a lower tensile strength, is extremely corrosion-resistant and is a super conductor for electricity. Copper is often used for refrigeration, air conditioning, cookware, computers, medicines, and piping.

There are two types of copper tubing. Rigid copper tubing is ideal for hot and cold tap water pipes in buildings. Soft copper, on the other hand, is frequently used to make refrigerant lines in HVAC systems and heat pumps. Copper ductile, a malleable metal, is resistant to corrosion from water and soil, and is also recyclable. Copper tubing is also easily soldered, forming lasting bonds.

This metal is also alloyed with brass and used in musical instruments, jewelry, construction and artwork.

Iron
The comic book nerds out there may automatically think of Iron Man, but fun fact: Iron Man’s suit isn’t actually made of iron. Speculations say it’s most likely made out of some kind of nickel and titanium alloy.

There are two different types of iron: cast and wrought iron. Essentially, cast iron is rolled, pour and molded while wrought iron is only rolled in the final stages of production. Cast iron is used in architectural projects (like the dome of the U.S. Capitol) while wrought is used for things like beams, trusses and girders.

From constructing the Empire State Building to making modifications to your home, knowing your metals is crucial. Even if you’re not a builder, this knowledge can allow you to find a new appreciation for buildings in your hometown.