The heat treatment of the cutting edge and stamping surface of cast iron dies was studied using a 808 nm wavelength diode laser. The irradiated energy was absorbed effectively by the cast iron dies without any coating. Rectangular laseer scanning at 1000w, over an area of 13mm × 5mm, and at the speed of 3.3mm/s resulted in 600HV hardness on the surface of spheroidal graphite cast iron with pearlite matrix and bull's eye structure to a depth of 0.5mm and width of 10mm. Conventional flame hardening has historically not been able to generate the required hardness on bull's eye structures (JIS FCD600.) The localized and rapid heating of laser irradiation triggered carbon diffusion from graphite nodules into the austenitic matrix, thereby producing the desired hardness. Trimming edges tend to melt easily due to their relatively small mass for thermal diffusion. In this study, three different laser irradiation methods were tested to clarify the optimum toughness and hardness of cast iron trimming edges. It was successfully demonstrated that “Two Pass Simultaneous Irradiation” can generate 600HV hardness on the whole area of the trimming edge to a width of 5mm.
