HOT ROLLED STEEL STRIP, COLD ROLLED STEEL STRIP, AND PRODUCTION METHOD OF HOT ROLLED STEEL STRIP

摘要

PROBLEM TO BE SOLVED: To provide a hot rolled steel strip whose intensity, hardness, internal oxidation thickness are uniform over whole width and longitudinal directions of the hot rolled steel strip, a cold rolled steel strip formed by cold rolling the hot rolled steel strip, and a production method for producing the hot rolled steel strip while suppressing increase of production cost.;SOLUTION: The present invention relates to the hot rolled steel strip comprising by mass%, Mn:2.0-3.0%, Si:0.01-3.0%, C:0.03-0.3%, and comprising following characteristics. The characteristics are: when Vickers hardness, tension strength, and internal oxidation thickness are measured at total 9 measurement points, in which, in a center of a longitudinal direction, a tip end and tail end of the hot rolled steel strip which is unwound from a coil, the respective width direction center and both ends of the width direction are measurement points, difference between a maximum value and a minimum value of the Vickers hardness is less than 50 HV, difference of a maximum value and a minimum value of the tension strength is less than 100 MPa, and difference between a maximum value and a minimum value of the internal oxidation thickness is less than 3 μm.;SELECTED DRAWING: Figure 2;COPYRIGHT: (C)2016,JPO&INPIT