The plug hardening heat treatment is carried out after cementing, in order to guarantee the geometry of delicate pieces and the consequent dimensional precision. This operation consists of introducing the piece to be worked, previously austenitized in a continuous oven, into a calibrated pad (plug) and then soaking it in a tank of hardening oil. The range of pieces to which this process is focused is very wide and starts from the sleeve and ends to the synchronizer ring and other pieces having a broached hole or a diameter whose precision and dimensional consistency must be guaranteed.
DEMM is equipped with a continuous furnace system.