| 摘要 |
A high-carbon hot-rolled steel sheet with excellent width-direction homogeneity is provided. The steel sheet contains 0.2% to 0.7% carbon, 0.01% to 1.0% silicon, 0.1% to 1.0% manganese, 0.03% or less phosphorus, 0.035% or less sulfur, 0.08% or less aluminum, and 0.01% or less nitrogen, and the balance is iron and incidental impurities. The structure is such that the average ferrite grain size of edge parts of the steel sheet is less than 35 mum, the average ferrite grain size of a part closer to the center of the steel sheet than the edge parts is less than 20 mum, and the average carbide grain size is 0.10 mum or more and less than 2.0 mum. The steel sheet is produced by roughly rolling the steel, finish-rolling the steel at a finishing temperature of more than (Ar3+40° C.), cooling the steel at a cooling rate of more than 120° C./s within two seconds after the finish rolling to a cooling termination temperature of more than 550° C. and less than 650° C., coiling the steel at a temperature of 550° C. or less, pickling the steel, and subjecting the steel to spheroidizing annealing at a temperature of 670° C. to the Ac1 transformation point by a batch annealing method.
|
