Hardening and tempering

Hardening and tempering essentially refers to hardening with subsequent tempering, usually carried out high temperatures. This results in a high tenacity at a specific tensile strength. Hardening and tempering delivers increased tensile strength, yield stress, lateral contraction and impact strength in comparison to standard annealed characteristics.
Many steels are supplied by steelworks in the form of rolled or forged parts and are pre-hardened and tempered. Depending on the cross-section, the tensile strength usually lies somewhere between 700 and 1000 N/mm². Machining is still possible without any great difficulty. A disadvantage of hardening and tempering lies in the fact that it is not always possible to attain optimum uniform microstructures because relatively large batches are treated in furnace systems and quenching baths at the same time. With unit hardening and tempering the process is carried out on parts spaced at a distance (low-density batches). This allows for an even heating and quenching. The costs of unit hardening and tempering lie considerably higher than for parts hardened and tempered by steel manufacturers.