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  • Writer's pictureNur Izzah Jamaluddin


Why do metal manufacturers add carbon to iron? The process actually solidifies the metal’s interior structures, which strengthens it. Carbon is also one of the cheapest alloys, widely available.

Carbon steel is a metal alloy that is formed as a result of combining iron and carbon. Steel typically is considered to be carbon steel when the proportions of other trace elements in it do not exceed certain percentages.


The more carbon there is in steel, the harder and stronger it gets when heat treated. But it also becomes less ductile, which means it loses strength when deformed and isn’t as malleable. With or without heat treatment, a higher carbon content in steel makes the metal less weldable, and the more carbon there is, the lower the melting point.

1. Carbon steel is often simply a steel alloy containing anything from 0.12% to 2% carbon

2. Steel is also classified as carbon steel when there’s no official minimum amount of key substances like chromium, cobalt, molybdenum, nickel, niobium, titanium, tungsten, vanadium, zirconium or any other alloy

3. Carbon steel can also be any steel where the minimum amount of copper is less than 0.4%

4. It is also defined as steel with a maximum content of 1.65% manganese or 0.6% copper

5. The term can even be used for any steel that isn’t stainless steel, including alloy steels


1. Low-carbon steel contains a maximum of 0.3% carbon

2. Medium-carbon steel contains 0.3% to 0.6% carbon

3. High-carbon steel contains 0.6% to 1% carbon

4. Ultra-high-carbon steel contains 1.25% to 2% carbon

Low-carbon steel is strong and tough but doesn’t temper easily. It’s the most popular type with a relatively low price and a plethora of applications. It’s both malleable and ductile, has a comparatively low tensile strength, and the hardness of the metal’s surface can be improved by carburising, a heat treatment process. It’s easier to cold-form and handle than other grades.

Higher-carbon steels are happy under heat treatment. But they don’t like trace impurities, which can dramatically affect the quality of the metal. Sulphur is the biggest culprit, making the steel brittle and crumbly when worked.


LOW CARBON STEEL is also called mild steel and comes in the widest choice of shapes, everything from flat sheets to structural beams.

Low Carbon Steel is usually made into flat-rolled sheets and strips, used for shipbuilding, wire, vehicle bodies and domestic appliances. It’s widely used for fabrication and panelling because it can’t be altered by heat treatment.

Carbon steel with the lowest possible amount of carbon is called ‘wrought iron’, used for fencing, gates and railings, hard but not brittle.

MEDIUM CARBON STEEL is stronger than low carbon and trickier to form, weld and cut. It’s often hardened and tempered with heat treatment. Medium-carbon steels are similar to low-carbon steels except they contain carbon from 0.30% to 0.60% and manganese from 0.60% to 1.65%. Increasing the carbon content to approximately 0.5% with an accompanying increase in manganese allows medium-carbon steels to be used in the quenched and tempered condition.

These steels are mainly used for making shafts, axles, gears, crankshafts, couplings, and forgings. Steels with carbon ranging from 0.40% to 0.60% are used for rails, railway wheels, and rail axles.

Medium Carbon Steel is a lot easier to machine and adding small amounts of silicon and manganese improves the quality. Also called mild steel, it’s commonly used structurally in buildings and bridges, axles, gears, shafts, rails, pipelines and couplings, cars, fridges and washing machines.

HIGH CARBON STEEL is also called carbon tool steel, and is very difficult to cut, bend and weld. When heat treated it becomes very hard and extremely brittle.

Due to their workability, hardenability, product performance, affordability, and other characteristics, carbon tool steels are the most widely used cold-rolled special steel strips.

Carbon tool steel is used in a wide range of fields from hard applications including blades, cutting tools, and regular tools to applications that require elasticity and toughness including regular springs, spiral springs, knitting needles, horns, measuring tapes, and washers.

High Carbon Steel has a much better tensile strength, used to make cutting tools, blades, punches, dies, springs and high-strength wire.

ULTRA HIGH CARBON STEEL is brittle and very hard, and can’t be cold-worked. It’s used to make extremely hard components like blades, cutting tools and large machine parts, hot water radiators, industrial castings and metal lamp posts.

It’s also called ‘cast iron’, and it’s the material used to make old fashioned cooking pots.

When it comes to an excellent combination of mechanical properties such as tensile strength, shear strength, toughness, hardness, and ductility, it is hard to beat carbon steel.

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