air-hardening

[air-hahr-dn-ing]

adjective Metallurgy.

noting any metal, especially alloy steel, that can be hardened from above its transformation point by cooling in air.

Origin of air-hardening

First recorded in 1905–10

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

This alloy, because hardened simply in air, was called “air-hardening” or “self-hardening.”
Inventors at Work
George Iles