This study describes laser heat treatment of steels using a YAG laser beam on-the-machine tools. An optical fiber has been used in order to transmit the laser light from a source to workpieces at this system. In the present report, experiments were carried out to research the quenching characteristics of various die steels using a YAG laser beam. As.a result, the influence of carbon and chromium in materials on hardening was clarified. Additionally, it is shown that laser heat treatment of pre-hardened steels is effective to increase the hardness of these materials. Tempering hardness of hot die steels is confirmed after laser hardening.
