How to Make Steel Hard
Ideally, steel should be in its softest form when being machined. This state, known as the annealed state, shortens the time required to machine the steel while reducing the amount of wear on the cutting blade. Once machined, most applications require steel to be hardened to make it useful. Hardening steels locks in a predetermined crystalline structure making the steel much harder. Tempering steel after it is hardened reduces the stress produced during the hardening process. Just as various steel differs in its chemical composition, the temperatures at which they are hardened differ as well but the all follow a similar process.