Electric furnace are builted on a steel frame. They have a programmer to step with ramp and soak temperature control digital and PID control. The electrical resistance of the furnace is controlled by an SSR (solid state relay) which allows to obtain a precise power management and temperature. The furnace insulation with ceramic panels with high thermal coefficient of the latest generation and a forced ventilation to the exterior surfaces of the furnace, the power employed ensures optimal speed of ascent of the furnace.