Or are they the same?

Is carbon steel better than mild steel? Trick question! Mild steel is a type of carbon steel. The element carbon is present in all steel. Whenever this carbon is the main alloying element, the alloy is considered a carbon steel. “Low-carbon” steel is another name for mild steel. There are other carbons steels, of different carbon contents. Which one is better depends on the application the steel will be used for.

Over 1.5 billion tons of steel are produced every year to make products as diverse as sewing needles and structural beams for skyscrapers. Carbon steels are the most commonly used steel alloys, making up approximately 85% of all production in the US. The carbon content of the product is in the 0–2% range. This carbon affects the microstructure of the steel, giving it legendary strength and toughness. These alloys also contain small amounts of manganese, silicon, and copper. Mild steel is a commercial term for low carbon steel, where the carbon content is in the 0.04–0.3% range.

Mild steel has exceptional ductility and are used for pipelines that transport oil, gas, or water.

Carbon steel categories

Carbon steel can be categorized depending on the chemical composition and characteristics of the product. Mild steel also falls under the low carbon steel category as it is comprised of similar carbon content. Plain carbon steel is free from alloys and can be placed in four categories:

1. Low carbon steel or mild steel

Low carbon steel has 0.04–0.3% carbon content and is the most common grade of carbon steel. Mild steel is also considered low carbon steel as it is defined as having a low carbon content of 0.05–0.25%. Mild steel is ductile, highly formable, and can be used for automobile body parts, plates, and wire products. At the higher end of the low carbon content range, and with the addition of manganese of up to 1.5%, mechanical properties are suitable for stampings, forgings, seamless tubes, and boiler plates.

2. Medium carbon steel

Medium carbon steel has a carbon range of 0.31–0.6% and a manganese range of 0.6–1.65%. This steel can be heat treated and quenched to further adjust the microstructure and mechanical properties. Popular applications include shafts, axles, gears, rails, and railway wheels.

3. High carbon steel

High carbon steel has a carbon range of 0.6–1% with a 0.3–0.9% manganese content. Properties of high carbon steels make them suitable for use as springs and high-strength wires. These products cannot be welded unless a detailed program of heat treatment is included in the welding procedure. High carbon steel is used for edged tools, high-strength wires, and springs.

4. Ultra-high carbon steels

Ultra-high carbon steel has a carbon range of 1.25–2%, and are known as an experimental alloy. Tempering can produce a steel with a great hardness level, which is useful for applications like knives, axles, or punches.