PURPOSE: To improve the productivity of a bar-like parts and to reduce production cost by quenching whole sectional area of raw bar material by rapidly heating and cooling, executing the temp. up and rapid cooling under the specific condition and executing at the same time, temper of the core part and quench-hardening of the surface layer.
CONSTITUTION: The raw bar material W is continuously carried to the axial direction and after rapidly heating by induction heating, etc., through a rapid heating means 11 of quenching device 1, it is rapidly cooled by a rapid cooling means 12 to execute the whole sectional area quenching of the bar material W. Next, the temp. of the surface of the bar material W is raised to the prescribed temp. more than the Ac1 transformation point under the prescribed heating condition in accordance with steel kind of the bar material W diameter, required hardness at the core part by the induc tion heating coil 2. At the time of passing the prescribed time T after heating, it is rapidly cooled by cooling jacket 3, the tempering at the core part of the bar material and forming of quench-hardened layer having controlled depth of the surface layer are executed at the same time. By this method, the bar material W making fine sorbitic structure with good toughness in the core part and martensitic structure with high hardness and excellent wear resistance from the surface to the prescribed depth, is obtd.
YAMASHITA EIJI
SUGA TAKIO
Next Patent: RADIANT TUBE HEATER FOR VACUUM HEAT TREATMENT FURNACE