These steels have various elements added in small quantities to improve the material strength, hardenability, temperature resistance, corrosion resistance, and other properties. Any level of carbon can be combined with these alloying elements.

• Chro­mium is added to improve strength, ductility, toughness, wear resistance and hardenability.
• Nickel is added to improve strength without loss of ductility, and it also enhances case hardenability.
• Molybdenum, used in combination with nickel and/or chromium, adds hardness, reduces brittleness, and increases toughness.

Many other alloys in vari­ous combinations are used to achieve specific properties. The ultimate tensile strength of alloy steels can vary from about 80 to 300 kpsi depending on its alloying elements and heat treatment.