| abstract |
This carbon steel sheet for cold working has a hardness of not less than 500 HV when it is heated at an average heating rate of 100 占 폚 / sec, then maintained at 1000 占 폚 for 10 seconds and then quenched to room temperature at an average cooling rate of 200 占 폚 / Wherein said carbon steel sheet has a composition of C: 0.30-0.60%, Si: 0.06-0.30%, Mn: 0.3-2.0%, P: 0.03% or less, S: 0.0075% or less, Al: 0.001 to 0.10% of N, 0.001 to 0.01% of N, 0.001 to 0.10% of Cr, the balance of Fe and inevitable impurities, the average diameter d of the carbides is 0.6 탆 or less, % And less than 90%, and the average diameter d 탆 of the carbide and the spheroidizing rate p% of the carbide satisfies d? 0.04 x p-2.6. |