What it is
Steel is something we surround ourselves with every single day. Knives, hammers and other tools, but also jewelery, cutlery and your car.
But what is it?
Steel is an alloy of iron and carbon, along with a small proportion of other elements.
The reason steel was invented was that iron contains impurities, such as phosphor, mangan, silicon and sulfur. The process of making steel removes these elements, and gives the opportunity to add other elements to the iron, opening a chance of making new materials.
Some history and the making of steel
In the beginning, steel was made via a process called cementation. This involved heating iron with charcoal in a closed furnace as an extension of the process of making iron.
Today, we use something called the Bessemer process or the oxygen process.
The latter was developed in the 1950s. The furnace in which this process happened was redesigned, and oxygen was added so the fuel (charcoal) would burn away more cleanly, producing cleaner (i.e more high grade) steel.
The latest developments in steel processing is the electric arc furnace - it has the advantage of not having to include a fuel with the iron, thereby making it possible to make an even cleaner and better form of steel.
For commercial use, most steel is rolled into the shape needed - usually steel plates that later are cut and formed further into the correct shapes. However, the infamous T-girders and I-girders are often rolled to that shape in the factory.
The earliest steel roller mill was built in Pittsburgh in 1811.
The classification of steel types is often done by carbon content. If a steel has a lot of carbon, it becomes very hard and brittle, good for cutting tools, but this steel can break.
Steel with less carbon is often used in construction for strength. Think about it: It would be better if a girder bent, so you at least had a chance to get out of the house, than if it broke, crashing down.
By adding various elements to the steel, you get steel with special properties.
Aluminium in the steel makes it smooth and gives it a high tensile strength.
Chrome in steel makes it hard, strong and elastic (or "bouncy"), and is therefore good for use in aeroplanes and cars. If there is a lot of chrome in the steel, it prevents rust, and becomes stainless steel
Chrome Vanadium has a similar effect as chrome, but is harder.
Nickel in steel makes it extremely hard, but it also makes the steel non-magnetic and less brittle.
Steels used in knives
Steels that are used in knives get a special scale. You might have heard about the 440c, but the rest is usually unknown to the layman. Not anymore!
0-1 is excellent quality - very tough and hard through repeated heat treatments.
0-6 is the next step up from 0-1 - it is even harder and definitely tougher. It has a strange orangish spark, and a knife edge made with 0-6 stays sharp for a LONG time.
5160 steel is often used in springs, and can be used in swords, axes or other high-impact tools.
52100 is ball bearing steel - extremely hard and tough, but very difficult to shape
L-6 is the steel most often used in lumber mills as the saw blades. Flexible and quite hard, but this steel rust easily.
D-2 is a beast - it contains 12 % chrome and is often used in sawing and grinding tools.
D-4 and D-7 are often used in good cutlery.
440C is one of the few steel types you are likely to know - this is one of the most popular steels used by knife makers, because it is easy to work with and gives strong, reliable blades. This steel was first used by Gil Hibben
DAMASCUS steel is one of the other steel types you might have heard of. It comes in many different forms, and is considered nearly legendary.
There are hundreds of variations of knife steels, this is merely an introduction. Expert knife makers will often have their own personal steel types that they order from steel mills.