Patent ID: 7220327

Claim:
A method for manufacturing a kick-down drum comprising fine ferrite and microdispersion spheroidized cementite prepared by cooling a carbon steel at a rate of 150–200 ° C./s, said carbon steel comprising Fe as a major component, about 0.32 to about 0.38 wt % of C, about 0.15 to about 0.35 wt % of Si, about 0.60 to about 0.90 wt % of Mn, about 0.03 wt % or less of P, about 0.035 wt % or less of S, about 0.02 wt % or less of Cr and other impurities, said method comprising steps of: (a) leading-in a heating coil into a space of internal circumference of a spline member while concurrently covering a heat sealing cap on top of said spline member of the kick-down drum; (b) water-cooling said kick-down drum while concurrently heating at 900–950° C. for 3–5 sec under 100 kHz and 94 kW; and (c) tempering at 140–150° C. for 1 hr in an electric furnace.