Steel

Steel: an alloy of iron and carbon

Steel is one of the most widely used materials in the modern world.

It can be found in buildings, tools and countless everyday objects.

This ubiquity is due to a set of rare qualities. It is strong, durable, versatile and relatively easy to produce.

Steel is an alloy, which means a combination of several elements.

The two main components are iron and carbon. Iron is abundant in the Earth’s crust, but it is found in the form of oxides that must be purified before use.

Carbon can be added in different ways to modify the properties of the metal.

When these two elements are combined, even in very small proportions, they profoundly change the internal structure of iron.

How does carbon content define the different types of iron

The amount of carbon contained in iron determines its nature and behaviour.

If iron contains almost no carbon, it is considered pure iron.

If the carbon content varies roughly between 0.1 per cent and 2 per cent, the result is steel.

Above 2 per cent, the metal becomes cast iron, which is more brittle and less malleable.

This simple classification helps explain why each type of metal is used differently.

Pure iron is malleable but not very strong.

Steel offers an ideal balance between hardness and elasticity. Cast iron is valued for its resistance to compression but is fragile when subjected to shocks.

What is non alloy steel

Non alloy steels contain only iron and carbon, with no deliberate addition of other elements.

This group is very broad, since even an extremely small change in carbon content creates a new material.

• Extra mild steels, very low in carbon, are easy to work, weld and shape.

They are used for sheet metal, folded parts and decorative elements.

Steels with a higher carbon content become harder and stronger.

They can be hardened by heating followed by rapid cooling to increase their hardness further.

These steels form the basis of many fields, such as ironwork, construction, simple tools, general mechanics and traditional craftsmanship.

What is alloy steel

In some cases, steel is deliberately enriched with other elements.

Even very small additions change its properties significantly.

• Chromium makes it possible to obtain stainless steels that resist corrosion.
• Nickel improves strength and the ability to withstand low temperatures.
• Molybdenum, vanadium, tungsten and cobalt increase strength, hardness or resistance to heat.

Thanks to these added elements, there is a wide variety of specialised steels suited to precise applications, ranging from aerospace to knife making, and from springs to cutting tools and engine components.

Uses and advantages of steel

Steel is used in an enormous range of fields. It can be found in building frames, bridges, rails, mechanical parts, knives, springs, gears, kitchen utensils, sculptures and scientific instruments.

Its advantages are numerous.

• It can be adjusted to be very hard or more flexible depending on its composition.
• It withstands tension, compression and bending extremely well.
• It can be forged, rolled, drawn, heated or shaped cold.
• It keeps its form and returns to its original position even under significant stress.
• It can be recycled indefinitely without major loss of quality, which makes it an essential material for an environmentally responsible approach.