Medium carbon steel sheet for cold working, and method for producing same

A medium carbon steel sheet for cold working has a hardness of 500 to 900 HV inclusive when the steel sheet is subjected to a high-frequency quenching in such a manner that the temperature of the steel sheet is raised at an average heating rate of 100 DEG C/sec, the temperature of the steel sheet is then held at 1000 DEG C for 10 seconds and the steel sheet is then rapidly cooled to room temperature at an average cooling rate of 200 DEG C/sec, and comprises, in mass%, 0.30 - 0.60% of C, 0.06 - 0.30% of Si, 0.3 - 2.0% of Mn, 0.03% or less of P, 0.0075% or less of S, 0.005 - 0.10% of Al, 0.001 - 0.01% of N, 0.001 - 0.10% of Cr, and a remainder made up by Fe and unavoidable impurities, wherein the average diameter (d) of a carbide is 0.6 mum or less, the spheroidizing ratio (p) of the carbide is 70% or more and less than 90%, and the average diameter (d) (mum) of the carbide and the spheroidizing ratio (p) (%) of the carbide fulfill the following formula: d <= 0.04*p-2.6.