The excellent cold-forming property of high-carbon hot rolled steel sheet and its manufacturing method

摘要

PROBLEM TO BE SOLVED: To provide a method for producing a high carbon hot-rolled steel sheet having cold workability, particularly, cold forgeability, in which a production process is reduced to remarkably reduce production cost, and further, excellent cold workability (cold forgeability) is imparted to a high carbon hot-rolled steel sheet.SOLUTION: Provided is a high carbon hot rolled steel sheet excellent in cold workability, being a high carbon hot-rolled steel sheet finished with hot rolling in the temperature range of 600 to 750°C, having a structure including ferrite having a volume fraction of 60% or higher and the balance carbide or a structure including carbide, in which the average r value (r-m) is 0.7 or lower and Δr value is -0.2 to 0.1. The high carbon hot rolled steel sheet is produced in such a manner that the high carbon hot rolled steel sheet finished with hot rolling in the above temperature range is (a) immediately cooled to 300°C or lower in a cooling zone, is heated directly above an A1 point directly before coiling, and is coiled as it is or is (b) immediately cooled to 300°C or lower in a cooling zone, is coiled, is thereafter rewound, is heated to directly above an A1 point, and is coiled as it is.SELECTED DRAWING: Figure 1