What is Chemical Composition? 2022

Chemical composition is the DNA or source code of steel.

Steel is a metal alloy that contains iron and carbon as the main constituents (i.e., in its chemical composition).

Carbon can have concentrations of 0.008 to 2.11% of the metal alloy.

What is iron? What is carbon?

Iron and carbon are chemical elements of the periodic table. Remember the periodic table?

I circled below the elements Iron (Fe) and Carbon (C) in the figure below.

Iron is found in nature as iron ore (Fe2O3) but after a metallurgical process it is reduced to iron which is used in steel production.

Steel difference to cast iron

The differentiation of cast iron is made by the concentration of carbon in the alloy. Any additional carbon at 2.11%, then the alloy is considered a cast iron. Example:

• Iron with 2.5% carbon is cast iron;
• Iron with 3% carbon is cast iron.

Alloy elements

Steels can have other alloying elements, as required by the user. Some elements typically added to steel are

• Chrome
• Nickel
• Molybdenum
• Copper
• Silicon
• Nitrogen
• Titanium
• Niobium
• Aluminum
• Cobalt
• Vanadium
• Tungsten
• Cerium

Other elements that are controlled (more can be added):

• Manganese
• Phosphorus
• Sulfur

Note that all of these elements can be found in the periodic table.

Learn more: What is the function of each element in steel?

Classification of chemical composition

You may have heard that steel can be "carbon" or "stainless steel", isn't it?

In practice chemical composition can go much further than that. Here are some examples:

• Carbon steel
• Nickel Steel
• Steel-Nickel-Chromium
• Steel-Molybdenum
• Steel-Chromium
• Chromium-Vanadium Steel
• Tungsten-Chromium Steel
• Steel-Nickel-Chromium-Molybdenum
• Silicon-Manganese Steel
• Steel-Nickel-Chromium-Molybdenum

Learn more: Steel classification

Practical Examples

There are several types of steel and therefore there are different chemical compositions as well:

• 1020 Steel
• 4340 Steel
• A36 Steel
• 8620 Steel