Abstract: A method for manufacturing a steel sheet for cold rolling, including hot-rolling a slab so that an outlet temperature of a finishing rolling mill is 800° C. or higher and 940° C. or lower, cooling at least a portion of the hot-rolled steel sheet, at a water volume density of 100 L/min/m2 or more for 0.1 seconds or more, within 3.0 seconds after passing through a final stand of the finishing rolling mill and being sent out on a run-out table, and coiling, at a coiling temperature of 550° C. or higher, the cooled hot-rolled steel sheet.

Abstract: A method for producing a hot-rolled steel sheet which enables predicting a temperature history of unevenness of the end face of a coil includes: measuring a surface temperature of hot-rolled strip-shaped steel; calculating a temperature history in a natural cooling state after coiling, assuming that the strip-shaped steel has been coiled without unevenness on an end face, based on the surface temperature measured in the measurement step; actually coiling the strip-shaped steel after the measurement step; scanning with a displacement meter, an end face of a coil formed in the coiling step, and deriving a size of the unevenness of the end face over a radius of the coil; and predicting a temperature history of the unevenness in a natural cooling state using: the temperature history calculated in the first calculation step; and the size of the unevenness derived in the derivation step.

Abstract: Disclosed is a high-strength steel sheet having predetermined chemical components, and microstructures of the steel sheet satisfies that: a fraction of MA in all steel microstructures being more than 0% and 15.0% or less by area ratio; a fraction of a soft ?-phase microstructure in the all steel microstructures being 0% or more and 50% or less by area ratio; and a standard deviation of an equivalent circle diameter of retained austenite being greater than 0.155 ?m.