Glossary

Alloy steel is a type of steel that has been intentionally mixed with one or more alloying elements—such as chromium, nickel, molybdenum, vanadium, manganese, or tungsten—to improve its mechanical and physical properties beyond those of plain carbon steel. These added elements enhance characteristics like strength, hardness, toughness, wear resistance, and corrosion resistance, depending on the specific combination and percentage used.

At its core, all steel is primarily iron (Fe) with a small amount of carbon (C)—usually less than 2%. In carbon steel, carbon is the main hardening element, but in alloy steels, other elements are added (typically between 1% and 5%, though sometimes higher) to achieve specialized performance.

Different alloying elements serve specific purposes:

- Chromium (Cr): Improves hardness, corrosion resistance, and wear resistance.

- Nickel (Ni): Increases toughness and impact resistance.

- Molybdenum (Mo): Enhances strength at high temperatures and resists softening.

- Vanadium (V): Refines grain structure and increases toughness and fatigue strength.

- Manganese (Mn): Boosts strength and hardness while aiding deoxidation.

- Tungsten (W): Increases hot hardness and high-temperature strength.

Alloy steels are broadly classified into two groups:

- Low-alloy steels, with total alloying content below about 5%, used for general engineering and structural applications.

- High-alloy steels, with more than 5% total alloying elements, designed for highly specialized uses such as tool steels, heat-resistant steels, and stainless steels.

Common uses of alloy steels include gears, axles, crankshafts, fasteners, tools, high-strength structural components, and pressure vessels. Their ability to combine strength, toughness, and resistance to fatigue and corrosion makes them essential in automotive, aerospace, oil and gas, and heavy machinery industries.