Heat-treated bearing steel is the most widely used category. It has a martensitic and/or bainitic microstructure at room temperature and its final hardness after adequate heat treatment can reach a range of 60-64 HRC and is practically homogeneous throughout the entire section. Internationally, the best-known steel of this category is 100Cr6, an alloy which contains approximately 1% Carbon and 1.5% Chromium and which is used in the construction of standardized elements for molds such as punches, extractors, plugs, sockets, columns etc.