TREATMENT FOR SURFACE CHILLING OF STEEL

PURPOSE:To perform a titled treatment without spoiling mechanical workability except the part to be treated by enclosing the optional part on the surface of a steel part with carburizing gas, subjecting the part to high temp. carburization at a high carbon concn. then melting only the surface and cooling quickly the same. CONSTITUTION:A steel part which is a material 4 to be treated is set in the holding jig 3 in a furnace body 1 and thereafter carburizing gas is supplied through a carburizing gas feed port 5. On the other hand, high frequency current is conducted from a high frequency oscillator 7 to a high frequency heating coil 2 and after a carburization treatment is performed for a prescribed time at a prescribed high temp., the temp. is further increased to melt only the surface and is then the surface is cooled quickly to chill the surface. The carburizing gas after the reaction is discharged through a discharging port 6. A carburizing agent may be coated on the surface in place of the carburizing gas in this case. When the surface of the steel part is chilled in such a manner, the double hardened layers consisting of a chilled layer 8 and a carburized layer 9 is formed in a suitable form on the material 4.