Brief Description for Alloy Steel and Alloying Element

Alloy steel is steel that is alloyed with a variety of elements in total amounts between 1.0% and 50% by weight to improve its mechanical properties. The alloying elements are added to produce specific properties that are not found in regular carbon steel such as manganese, silicon, nickel, titanium, copper, chromium and aluminum. These elements are added in varying proportions (or combinations) making the material take on different aspects such as increased hardness, increased corrosion resistance, increased strength, improved formability (ductility); the weldability can also change.

The most important and desired changes in alloy steel are:

Increased hardenability.

Increased corrosion resistance.

Retention of hardness and strength.

Nearly all alloy steels require heat treatment in order to bring out their best properties. 

Below is the alloying elements added Alloying Elements & Their Effects

Chromium - Adds hardness. Increased toughness and wear resistance.

Cobalt - Used in making cutting tools; improved Hot Hardness (or Red Hardness).

Manganese - Increases surface hardness. Improves resistance to strain, hammering & shocks.

Molybdenum - Increases strength. Improves resistance to shock and heat.

Nickel - Increases strength & toughness. Improves corrosion resistance.

Tungsten – Adds hardness and improves grain structure. Provides improved heat resistance.

Vanadium - Increases strength, toughness and shock resistance. Improved corrosion resistance.

Chromium-Vanadium - Greatly improved tensile strength. It is hard but easy to bend and cut.

By these properties, alloy steels are found in various applications like in the turbine blades of jet engines, in spacecraft, and in nuclear reactors.