A2 Steel Composition

AISI A2 tool steel is an air-hardening, medium-alloy cold-work steel widely recognized for its balanced wear resistance and toughness. This guide provides a technical breakdown of its typical elemental makeup. At the bottom of the page, you can download the A2 steel composition PDF for free.

What is A2 Tool Steel

A2 tool steel is specifically classified for cold-work applications. Its defining characteristic is the combination of good wear resistance and toughness, achieved through its specific alloying and air-hardening capability.

Key Alloying Elements in A2 Steel Composition¹

The typical chemical A2 steel composition, by weight percentage, based on industry specifications, is as follows:

Element	Symbol	Typical Range (%)	Primary Contributions
Carbon	C	0.95 – 1.05	Critical for hardness and carbide formation for wear resistance
Manganese	Mn	Up to 1.00	Contributes to hardenability
Silicon	Si	Up to 0.50	Primarily a deoxidizer
Chromium	Cr	4.75 – 5.50	Essential for air-hardening and wear resistance
Molybdenum	Mo	0.90 – 2.20	Enhances hardenability and wear resistance
Vanadium	V	Up to 0.50	Contributes to wear resistance by forming hard carbides

Nominal values often observed include: Carbon ~1.00%, Manganese ~0.60-0.62%, Silicon ~0.17-0.25%, Chromium ~5.00-5.31%, Molybdenum ~1.00-1.20%, and Vanadium ~0.20-0.32%.

Elements such as Phosphorus (P) and Sulfur (S), while always present in steel, are maintained at low maximum levels in the A2 steel composition. This is crucial as they can have detrimental effects on toughness and hot working characteristics. Standard specifications for similar steels often limit Phosphorus to below 0.04% and Sulfur to below 0.05%.

The specific elemental balance in the A2 steel composition dictates its characteristic performance attributes.

Wear Resistance and Toughness

A2 tool steel offers a good combination of wear resistance and toughness.

• Compared to S-series (shock-resistant) steels, A2 provides greater abrasion resistance.
• Compared to D-series (high-carbon, high-chromium) steels like D2, A2 exhibits better toughness and ductility, although D2 has very high wear resistance. D2 has poorer machinability and toughness relative to A2.

Dimensional Stability in Heat Treatment

A2 tool steel has good dimensional stability during air quenching in heat treatment. It expands approximately 0.001 in./in. (0.001 mm/mm). This minimal distortion is a key reason A2 is preferred for applications where maintaining tight tolerances after heat treatment is critical. For more information, please click A2 steel heat treatment guide.

Summary

The typical A2 steel composition is engineered to deliver a reliable balance of wear resistance, toughness, and dimensional stability through air hardening, making it a staple for many cold-work tooling applications.

1. Bringas, J. E. (Ed.). (2004). Handbook of Comparative World Steel Standards (3rd ed., p. 433). ASTM International. ↩︎