Hardened steel

The quenching results in the formation of metastable martensite, the fraction of which is reduced to the desired amount during tempering.

If a metal does not contain the necessary quantity of carbon, then its crystalline structure cannot be broken, and therefore the physical makeup of the steel cannot be altered.

A talented smith or metalworker can fine-tune the performance of a steel tool or item to precisely what is required based solely on careful observation of temper colours.

It is not easy to determine if steel has undergone the hardening and tempering process by simply looking at it, but there is a reliable and simple test.

If the metal has been hardened, the file fails to cut into the sample and glances off with little visible effect.