Carbon steel, on the other hand, has far lower chromium levels, and is instead a carbon-iron alloy with only a few other materials, if any, as part of its makeup. As a result, it can be referred to as ‘low-alloy’ steel. Both stainless steel and carbon steel feature this basic composition, but carbon steel can be defined by its carbon content. This is normally around 2-2.5%, however this often varies. Though susceptible to rust unlike stainless steel, carbon steel is often cheaper and has its own varying mechanical properties based on carbon content.

Low-carbon steels are weaker and softer, but can be machined and welded easily; while high-carbon steel is stronger, but significantly harder to process.

Types of Carbon Steel

The defining element of any carbon steel alloy is its carbon content, and so this is how the various types of carbon steel are ordered and categorised.

Low-carbon steel: the most widely used form of carbon steel, with a carbon content of less than 0.25% - they are usually relatively weaker and softer but more easily welded and ductile, and so are often used to machine and weld for a low cost

Medium-carbon steel: with a carbon content of 0.25-0.6%, and a manganese content of 0.6-1.65%, these metals can be improved via heat treatment, though this can only be performed on very thin sections unless additional alloying elements are added – these steels are stronger but less ductile than lower-carbon steels

High-carbon steel: this is the hardest and toughest carbon steel, with the lowest ductility, very wear-resistant and almost always hardened and tempered – they tend to have a carbon content from 0.6-1.25% and a manganese of 0.3-0.9%