Hardening and Tempering is a thermal process that strengthens steel through a controlled heating and cooling process.
This process will result in improved mechanical properties and give a tougher more durable product. The hardening process involves heating the steel to above the critical temperature for the given grade and then rapidly cooling. Whilst this process achieves the highest mechanical stengths and hardness’s, steel in this condition is extremely brittle and therefore requires further treatment in the form of tempering. This consists of reheating the steel to a lower temperature and holding the steel at the given temperature for a given period of time. As with traditional annealing (used to soften steels) this process is conducted in an inert atmosphere to avoid oxidation.
The exact temperature and processing times vary with given grades of steel and the process is very specialized.