| abstract |
The medium-carbon steel sheet for cold working is heated at an average heating rate of 100 ° C./sec, held at 1000 ° C. for 10 seconds, and has a hardness of 500 HV or more when high-frequency quenching is performed to quench to room temperature at an average cooling rate of 200 ° C./sec. A medium-carbon steel sheet for cold working to be 900 HV or less, in mass%, C: 0.30 to 0.60%, Si: 0.06 to 0.30%, Mn: 0.3 to 2.0%, P: 0.03% or less, S: 0.0075% or less, Al: 0.005 to 0.10%, N: 0.001 to 0.01%, Cr: 0.001 to 0.10%, the remainder contains Fe and unavoidable impurities, the average diameter d of the carbide is 0.6 µm or less, and the spheroidization rate of the carbide is 70 % Or more and less than 90%, and the average diameter d micrometer of the said carbide and the spheroidization rate p% of the said carbide satisfy | fill d <= 0.04 * p-2.6. |