What is Metal?
A metal is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typically malleable or ductile. Metal may be a chemical element such as iron; an alloy such as stainless steel; or a molecular compound such as polymeric sulfur nitride.
In physics, metal is generally regarded as any substance capable of conducting electricity at a temperature of absolute zero. Many elements and compounds that are not normally classified as metals become metallic under high pressures.
For example, the nonmetal iodine gradually becomes a metal at a pressure of between 40 and 170 thousand times atmospheric pressure. Equally, some materials regarded as metals can become nonmetals. Sodium, for example, becomes a nonmetal at a pressure of just under two million times atmospheric pressure.
In chemistry, two elements that would otherwise qualify (in physics) as brittle metals arsenic and antimony are commonly instead recognized as metalloids due to their chemistry (predominantly non-metallic for arsenic, and balanced between metallicity and no metallicity for antimony).
Around 95 of the 118 elements in the periodic table are metals (or are likely to be such). The number is inexact as the boundaries between metals, nonmetals, and metalloids fluctuate slightly due to a lack of universally accepted definitions of the categories involved.
Different Types of Metal
Metals can be divided into two main groups: ferrous metals are those which contain iron and non-ferrous metals are those which contain no iron. There are thousands of different types and grades of metal out there, and each one is developed for very specific applications.
Steel is an iron alloy enriched with around 1% carbon and it is generally free of the impurities and residues that can otherwise be found in iron. While iron itself is stronger than other metals, it is remarkably heavy, dense, and prone to corrosion. For these reasons, purely iron structures can be difficult to build and maintain.
Not only does adding carbon to iron mitigate these vulnerabilities, but it also makes the material stronger. Additionally, steel has a rather high strength-to-weight ratio compared to other types of metals, which enables the manufacturing of small yet strong steel parts.
With over 3500 different grades and almost 2 billion tons of steel manufactured globally each year, steel is the most commonly used metal in the world. With the number of different elements and varying qualities of those elements being added to create steel alloys, there is a multitude of different types of steel. Without further ado, let’s dig deeper into the world of steel!
Alloy steel is made by combining elements such as chromium, manganese, nickel, tungsten, or vanadium with iron. Each of the alloying elements brings different properties to the mix, thus making the alloy steel highly customizable.
Depending on the needs of the project, the specific alloy can be modified to produce many desired qualities, a couple of which might be a higher material strength or a product that is more resistant to wear and corrosion. Alloy steel can be relatively inexpensive to produce, making it very widely used.
Stainless steel is a highly corrosion-resistant alloy steel that consists of iron, carbon, significant amounts of chromium, and residues of other metals.
It is a versatile material widely applied in many households. From kitchen utensils to tables, sinks, and other furniture, stainless steel is perfect for the manufacturing of anything that comes into contact with food because it doesn’t rust easily.
Carbon steel is an alloy made of iron and carbon, sometimes with residues of other elements. It is commonly categorized into three groups (low, medium, and high carbon steel) based on the amount of carbon the alloy contains.
The more carbon is used to manufacture steel, the harder the alloy will be. On the other hand, small amounts of carbon make for an alloy that is easier and cheaper to manufacture. Carbon steel is often used to produce tools and mechanical elements but is best known as a structural building material.
Due to its hardness, tool steel is used for the manufacturing of cutting, drilling, and other shock-resistant tools. The hardness comes from alloying iron with elements such as cobalt, molybdenum, tungsten, or vanadium.
Tool steel has a wide variety of applications, including construction, shipbuilding and automotive industries. It is primarily used to machine and make changes to different kinds of steel.
With around 5% of the Earth’s crust and as the 6th most common element in the universe, iron is a highly abundant and immensely popular metal. Unalloyed iron is an unstable element that easily reacts with the oxygen from the air and forms iron oxide.
In order to make it more stable, it is commonly alloyed with other elements to create steel. Iron finds its application in cookware because its porous surface combined with hot oil prevents sticking. Due to its remarkably high melting point, cast iron is used for the production of wood stoves.
Being a heavy metal, iron provides rigidity and reduces vibrations, which is why it is often used for the manufacturing of heavy machinery frames and bases.
Aluminum is a highly durable, lightweight, and corrosion-resistant metal derived from its ore bauxite. First made in the 19th century, aluminum found widespread use due to its machinability, electrical conductivity, and inability to magnetize.
It is the most common non-ferrous metal on Earth, known for its malleability and ability to form alloys with almost all other metals. Aluminum has an impressive strength-to-weight ratio, and even though it doesn’t rust, it oxidizes and corrodes when it is exposed to salt. Its applications are wide: from cans and household appliances to airplanes.
Zinc is a common metal with a low melting point. Because it flows smoothly in its melted form, it is easy to cast and recycle. The end product is quite strong and has low electrochemical potential.
Zinc is used to coat and protect other metals, as well as to prevent rusting in galvanized steel. Its applications include the industrial, marine, and medical sectors, as well as hardware, electrical and automotive industries.
Bronze is made by alloying copper and tin, and often small amounts of elements such as aluminum, manganese, silicon, or phosphorus. As the first human-made alloy, bronze is incredibly historically significant – thus the “Bronze Age.”
Even though it is brittle, bronze is a hard element known to resist fatigue that doesn’t bend or crack. Due to its high corrosion resistance and solid thermal and electrical conductivity, it is used for the manufacturing of electrical connectors, church bells, ship parts, and reflectors.
In addition to the five most popular metals outlined above, Texas Iron & Metal offers a large inventory of materials that may be suitable for your next project.
Magnesium is a really cool metal. It’s about 2/3rds the weight of aluminum, and it has comparable strength. It’s becoming more and more common because of this.
Most commonly, you’ll see this as an alloy. That means that it’s mixed with other metals and elements to make a hybrid material with specific properties. This can also make it easier to use for manufacturing processes.
One of the most popular applications of magnesium is in the automotive industry. Magnesium is considered a step up from aluminum when it comes to high-strength weight reduction, and it’s not astronomically more expensive.
Some places where you’ll see magnesium on a performance car is in the wheel rims, engine blocks, and transmission cases. There are disadvantages to magnesium, though. Compared to aluminum, it will corrode more easily. For example, it will corrode when in contact with water, where aluminum will not. Overall, it’s about double the price of aluminum, but it’s generally faster to deal with in manufacturing.
Fun fact: Magnesium is really flammable, and it burns super-hot. Metal chips, filings and powder need to be carefully disposed of to prevent explosions.
Copper is another old-fashioned metal. Today you’ll see it often as an alloy (more on that later) or in a reasonably pure state.
Common applications include electronics, water pipes, and giant statues that represent liberty. Copper will form a patina, or an oxidized layer, that will actually prevent further corrosion. Essentially, it’ll turn green and stop corroding. This can make it last for centuries.
If you want some more info on why this metal turns green, then you might find this article I wrote to be an interesting read.
Brass is actually an alloy of copper and zinc. The resulting yellow metal is really useful for a number of reasons. Its goldish color makes it really popular for decorations. It’s common to see this metal used in antique furniture as handles and knobs.
It’s also extremely malleable, meaning that it can be hammered out and formed. This is why it’s what’s used for brass instruments like tubas, trumpets, and trombones. They’re easy to hammer into shape (relatively speaking) and they’re durable.
Another really cool property of brass is that it will never spark. A steel hammer, for example, can make a spark if you hit it a certain way. A brass hammer doesn’t do that. This means that brass tools are great for areas that might be around flammable gases, liquids or powders.
This is a really amazing modern metal. It was first discovered in 1791, first created in its pure form in 1910, and first made outside of a laboratory in 1932.
Titanium is actually really common (the 7th most abundant metal on Earth), but it’s really hard to refine. This is why this metal is so expensive. It’s also really worthwhile:
- Titanium is biocompatible, meaning that your body won’t fight and reject it. Medical implants are commonly made from titanium.
- Its strength to weight ratio is higher than any other metal. This makes it extremely valuable for anything that flies.
- It’s really corrosion resistant
- Titanium nitride (titanium that’s reacted with nitrogen in a high energy vacuum) is an insanely hard and low-friction coating that’s applied to metal cutting tools.
Fun fact: The reason that titanium resists corrosion is that it instantly reacts with oxygen, creating a really thin, hard barrier that protects the metal. If you scrape off the barrier, a new one instantly forms. It’s kind of like its self-healing.
Bonus fun fact: Titanium isn’t found naturally on its own. It’s always bonded to another element.
Tungsten has the highest melting point and the highest tensile strength of any of the pure metals. This makes it extremely useful.
About half of all tungsten is used to make tungsten carbide. This is an insanely hard material that’s used for cutting tools (for mining and metalworking), abrasives, and heavy equipment. It can easily cut titanium and high-temperature superalloys.
It gets its name from the Swedish word “tungsten“, which means “heavy stone”. It’s about 1.7 times the density of lead. Tungsten is also a popular alloying element. Since its melting point is so high, it’s often alloyed with other elements to make things like rocket nozzles that have to be able to handle extreme temperatures.
Nickel is a really common element that’s used all over. Its most common application is in making stainless steel, where it boosts the metal’s strength and corrosion resistance. Actually, almost 70% of the world’s nickel is used to make stainless steel.
Interestingly, nickel only makes up 25% of the composition of the five-cent American coin.
Nickel is also a common metal to use for plating and alloying. It can be used to coat lab and chemistry equipment, as well as anything that needs to have a really smooth, polished surface.
Fun fact: Nickel gets its name from medieval-era German folklore. Nickel ore looks a lot like copper ore, but when the old miners couldn’t get copper from it they blamed a mischievous sprite named Nickel.
This is a metal that has been used for a long time to make blue pigment in paints and dyes. Today, it’s primarily used in making wear-resistant, high-strength steel alloys.
Cobalt is very rarely mined by itself, it’s actually a by-product of the production of copper and nickel.
Tin is really soft and malleable. It’s used as an alloying element to make things like bronze (1/8th tin and 7/8ths copper). It’s also the primary ingredient in pewter (85-99%).
Fun fact: When you bend a bar of tin, you can hear something called a “tin cry”. This is a twanging sound of the crystal structure reorganizing itself (called twinning).
Lead is really soft and malleable, and it’s also very dense and heavy. It’s got a really low melting point, too.
In the 1800s it was discovered that lead is actually pretty toxic stuff. That’s why it’s not so common in modern times, although it wasn’t all that long ago that it was still found in things like paints and bullets.
Lead is a neurotoxin that can cause brain damage and behavioral problems, among other things.
That said, it still does have modern uses. For example, it’s great for radiation shielding. It’s also occasionally added to copper alloys to make them easier to cut. The copper-lead mix is often used to improve the performance of bearings.
Technically speaking, silicon is a metalloid. This means that it has both metallic and non-metallic qualities.
For example, it looks like a metal. It’s solid, shiny, bendable, and has a high melting point. However, it does a terrible job of conducting electricity. This is partly why it’s not considered a full metal.
Even still, it’s a common element to find in metals. Using it for alloying can change the metal’s properties quite a bit. For example, adding silicon to aluminum makes it easier to weld.