Introduction

Rocks are all around us. They are the ground that we walk on and the building blocks of our homes and organizations. Every metal is derived from the minerals and ores that are located in the ground. Luckily for civilization today we have the technology to extract the raw materials found in the earth’s crust and process them into a variety of alloys. Alloys are a combination of metals or metals that are combined with other elements.

The different types of metals can be classified as either hard or soft. A few examples of soft metals are gold, silver, bronze, brass, magnesium, and copper. While Inconel, cobalt, titanium, steel, and stainless steel are categorized as hard metals.

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Soft Metals: Aluminum, Magnesium, Brass, and Copper

Aluminum

The most plentiful metal found in the earth’s crust and the third most common element after oxygen and silicon is aluminum. This metal accounts for about 8 percent of the earth’s crust by its weight is the second most malleable metal. It is often used as an alloy because aluminum on its own is not incredibly strong. Typically, aluminum is mixed with a wide variety of elements like copper, magnesium, zinc, and silicon. Then it is heated to make it more durable and lightweight.

Advantages:

  • Aluminum-zinc alloys are some of the strongest alloys obtainable today.
  • Relatively soft, durable, lightweight, ductile, and malleable.
  • Good thermal and electrical conductor.
  • Fairly corrosion resistant.

Disadvantages:

  • Elemental aluminum is a poor option for machine-driven purposes because it is soft and extremely malleable.
  • Weak and expensive compared to steel of the same strength.

Applications:

  • Generally used by the automotive, construction, packaging, and aerospace industries.

Magnesium

Magnesium is another lightweight material that a lot of people are familiar with. Magnesium is the fourth most abundant element that can be found within the crust of the earth and is the lightest of all structural metals.

Advantages:

  • Magnesium is the desired material when lightweight and good strength is desired.
  • Magnesium is two-thirds the weight of 6061 and just about as strong.

Disadvantages:

  • Biggest issue is its tendency to corrode.
  • When exposed to high temperatures its strength diminishes.
  • Lower ductility, toughness, strength, and fatigue life compared to aluminum alloys.

Applications:

  • In items such as cameras, mobile devices, laptop computers, and in other electronic devices.
  • Magnesium is used in the automotive industry because of its lightweight. It is 36 percent lighter per unit in volume than aluminum.

Brass

Brass is an alloy of copper, which is made by adding zinc. Brass can have various amounts of zinc and other elements added. By mixing brass with other elements, it can have a wide range of properties and can vary in color. If the zinc content in brass is about 32 to 39 percent is can have increased hot-working abilities, but the cold-working will be more limited. However, if the zinc content in brass is more than 39 percent it will have more strength and less ductility.

Advantages:

  • Widely versatile due to its low boiling point and durability. This makes it able to be used for a lot of different uses.
  • Great option because it comes in many different shapes, widths, sizes, and fittings that make it very malleable.
  • Brass is extremely durable, can withstand high temperatures, and is resistant to corrosion.

Disadvantages:

  • Due to its ability to develop blackish tarnish, it requires a lot of maintenance.

Applications:

  • Brass alloy is a great option for rivets, screws, locks, gears, bearings, zippers, plumbing, and musical instruments like horns and bells.

Copper

Copper was one of the first metals extracted by humans from the earth. Copper alloys primary ingredient is brass. Copper was first used to make coin and other items years ago due to how the element copper can be found in nature. Copper tools enabled civilization to emerge from the Stone Age. Today, copper is an ingredient in more than 570 various metallic alloys. A few examples of these are tellurium copper, nickel copper, gunmetal, aluminum, bronze, and steel alloys.

Advantages:

  • Copper is the second most conductive material next to silver.
  • High electrical and thermal conductivities, ductility, and is corrosion-resistant.

Disadvantages:

  • Copper on its own has horrible machinability. It is about five times worse than brass and the vast majority of machinists avoid it because of it is difficult to weld.

Applications:

  • Commonly used in wiring and plumbing.
  • Used in glass-to-metal seals like those used in vacuum tubes, in semiconductor manufacturing as an element of high-temperature superconducting and is used in hospitals and public areas as an antimicrobial surface.
  • Used for electrodes in electrical discharge machining (EDM), a technology often seen in injecting molding and metal stamping.

Hard Metals: Steel, Stainless Steel, Inconel, Chrome, and Titanium

Steel

Just like with soft metal, adding even the tiniest bit of alloying elements can make a huge impact on steel’s properties. For example, adding less than 1 percent of carbon and manganese with a pinch of metallurgical legerdemain is what turns brittle iron into the strongest 1018 steel. By combining a tiny amount of chromium with a small amount of molybdenum, 4140 alloy steel is created. Steel is most commonly mixed with iron.

Advantages:

  • Adds strength and durability to the items people use every day.
  • Temperature resistant. Able to withstand temperatures of more than 2,700 degrees Fahrenheit.
  • Carbon steels can be hardened and are effortlessly welded.
  • Stainless steel was invented by rising the amount of chromium to about 10.5 percent, enabling corrosion resistance to be improved.

Disadvantages:

  • The issue with these carbon steels is that they rust. Therefore, a requirement when using carbon steel is that they must be plated or painted before they can be used.

Applications:

  • Can be found in a lot of different everyday items such as cars, cruise ships, bridges, homes, office buildings, cables, and crescent wrenches.
  • 4140 alloy steel is used in the formation of aircraft.
  • Stainless steel is often used in the chemical industry, textile processing, and marine equipment.

Inconel

Inconel is a material that is used for the toughest conditions found in manufacturing. It is a nickel and chromium alloy.

Advantages:

  • Made up of about 50 percent nickel making it an excellent strength at a range of temperatures.
  • Compared to stainless steel, Inconel has a super high tolerance for extreme heat and doesn’t lose much tinsel strength at 2,000 degrees Fahrenheit.
  • Strong corrosion resistance to chemicals, heat, and other agents like seawater.

Disadvantages:

  • High nickel content makes it difficult to machine.
  • Requires wear-resistant coated carbide and rigid machine tools.
  • Expensive material.

Applications:

  • Extreme demands such as gas turbine blades, jet engines compressor discs, nuclear reactors, and jet engine combustion chambers.

Cobalt

Like nickel, cobalt is found in the earth’s crust. Cobalt can be obtained through mining nickel, lead, silver, copper, and iron.

Advantages:

  • The main ingredient in cobalt is chrome alloy making it wear-resistant.
  • Human biocompatibility, meaning it is not harmful to living tissue.
  • Produces strong, corrosion, and heat resistant alloys.
  • High melting point meaning it retains strength at high temperatures.

Disadvantages:

  • Brittle metal on its own.

Applications:

  • Ideal for magnets, metallic cathodes of rechargeable batteries, dental implants, hip and knee replacements, and arterial stents.

Titanium

Titanium is the ninth most abundant metal found in the earth’s crust. Titanium is a transition metal, which means it can form bonds using electrons from more than one of its shells. Other metals that are transition metals are gold, copper, and mercury.

Advantages:

  • Lightweight element commonly alloyed with aluminum and vanadium to provide strong, corrosion-resistant material.
  • Unalloyed it is as strong as some steels.
  • Human biocompatible.
  • Tensile strength almost twice that of any mild steel and weighs half as much making it appealing to the aerospace industry and high-performance vehicle manufactures.
  • Relatively high melting point of more than 3,000 degrees Fahrenheit.

Disadvantages:

  • High reactivity meaning it needs to be treated differently during each of the different stages of production.
  • Unalloyed, it is less dense steel.
  • Costly and laborious process is needed to extract titanium.

Applications:

  • Ideal for bone screws, pins, and plates due to its human biocompatibility.
  • When alloyed with iron, aluminum, vanadium, and molybdenum it is used in aerospace, aircraft, the military, industrial process, medical industries, and engines due to its strong, lightweight, and temperature resistance capabilities.

All these elements listed about provide hundreds of essential materials. They would not be worth a thing without the means to shape them into valuable items used today. Over the past 1,050 years, machine tools have evolved from the basic pulley and steam-driven devices to high-tech, precise computer numerical control (CNC) equipment that is seen today.

Machining centers work by rotating a cutting tool like an end mill or drill in order to remove material. The material is then gripped in a vise or comparable clamping instrument and moved on one or more axes against the cutter. This movement creates multifaceted geometries. Five-axis machining centers typically used all axes at the same time to create the free-form shapes that are typically used in artificial knees and propellers. They can also be indexed to machine multiple sides of the work piece in a single clamping.

CNC lathes use a chuck (collet) to grip the work piece and change the direction of it against a fixed cutting device. Lathes can cut a set of candlestick holders or even a fitting for a garden hose. Mill-turn machines use lathes along with rotating tools and secondary spindles, which were once secondary machining operations.