| 摘要 |
PROBLEM TO BE SOLVED: To provide a hot-rolled high-carbon steel sheet excellent in uniformity in the width direction. SOLUTION: The steel sheet contains C: 0.2 to 0.7%, Si: 0.01 to 1.0%, Mn: 0.1 to 1.0%, P: 0.03% or below, S: 0.035% or below, Al: 0.08% or below and N: 0.01% or below with the balance consisting of Fe and unavoidable impurities. The texture of the sheet is characterized by a mean ferrite grain size in the sheet edge of less than 35μm, a mean ferrite grain size in the central area of less than 20μm, and a mean carbide grain size of 0.10μm to less than 2.0μm. The steel sheet of the invention is manufactured by rough rolling, finish rolling at a finishing temperature of (Ar3+40°C) or above, cooling initiated within two seconds after the finish rolling at a cooling rate exceeding 120°C/s until a cooling stop temperature exceeding 550°C and below 650°C, coiling at a temperature of 550°C or below, pickling, and then spheroidizing at a temperature of 670°C to Ac1 transformation point. COPYRIGHT: (C)2008,JPO&INPIT |
