Production manner and high carbon cold rolling steel sheet null mass of the high carbon cold rolling steel sheet which is superior

摘要

PROBLEM TO BE SOLVED: To provide a high-carbon cold-rolled steel sheet which can be efficiently manufactured through a continuous annealing process and is superior in workability.;SOLUTION: This method for manufacturing the high-carbon cold-rolled steel sheet comprises the steps of: hot-rolling a steel slab having a predetermined composition at a finishing temperature of (Ar3 transformation temperature -20°C) or higher; primarily cooling the plate to a cooling-stopping temperature in between 500°C and 650°C (both inclusive) at a cooling rate of higher than 120°C/second; holding the plate at the temperature in between 500°C and 650°C (both inclusive) by secondary cooling; winding it at 600°C or lower; acid-pickling it; spheroidizing-annealing it at a temperature in between 600°C and the Ac1 transformation temperature (both inclusive) with a core box annealing method; subsequently cold-rolling the plate at a cold rolling rate of 30% or higher; annealing the sheet at a temperature in between (Ac1-50°C) and the Ac1 transformation temperature (both inclusive), for a soaking period of 100 to 600 seconds with a continuous annealing method. Thus manufactured high-carbon cold-rolled steel sheet has a structure in which an average particle diameter of ferrites is 2.0 μm or more, an average particle diameter of carbides is 0.10 μm to 2.0 μm, and a ferrite grain containing the carbide of 10% or less by a volume rate therein occupies 50% or more by the volume rate.;COPYRIGHT: (C)2007,JPO&INPIT