Steel is graded as a way of classification and is often categorized into 4 groups:

• Carbon Steels only contain trace amounts of elements besides carbon and iron. This group is the most common, accounting for 90% of steel production. Carbon Steel is divided into three subgroups depending on the amount of carbon in the metal: Low Carbon Steels/Mild Steels (up to 0.3% carbon), Medium Carbon Steels (0.3–0.6% carbon), and High Carbon Steels (more than 0.6% carbon).

• Alloy Steels contain alloying elements like nickel, copper, chromium, and/or aluminum. These additional elements are used to influence the metal’s strength, ductility, corrosion resistance, and machinability.

• Stainless Steels contain 10–20% chromium as their alloying element and are valued for their high corrosion resistance. These steels are commonly used in medical equipment, piping, cutting tools, and food processing equipment.

• Tool Steels make excellent cutting and drilling equipment as they contain tungsten, molybdenum, cobalt, and vanadium to increase heat resistance and durability.

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Structural Mild Steel

In the UK, we follow the a grading system introduced by the EU.

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• ‘S’ denotes the fact that it is structural steel;

• ‘235’ which relates to the minimum yield strength of the steel (tested at a thickness of 16mm);

• ‘J2’, ‘K2’, ‘JR’, and ‘JO’ all demonstrate the material toughness in relation to the Charpy impact or ‘V’ notch test methodology;

• ‘W’ is weathering steel (atmospheric corrosion-resistant);

• ‘Z’ represents structural steel with improved strength perpendicular to the surface, and

• ‘C’ is cold-formed.

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Depending on the manufacturing process, chemical composition and relevant application, further letters and classifications might be used to reference particular grades or products of structural steel.

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See the images to see how grade names correspond across the pond.