Patent ID: 9732405
Date: 2017-08-15
CPC Classifications: C21D,C22C

Claim:
1. A hot rolled steel sheet comprising, as a chemical composition, by mass %, as a metallographic structure, wherein: amounts expressed in mass % of each element in the chemical composition satisfy a following Expression 1; an average grain size of the ferrite which is the primary phase is 2 μm to 10 μm; an area fraction of the ferrite which is the primary phase is 90% to 99%; an area fraction of the martensite and the residual austenite which are the secondary phase is 1% to 10% in total; an average of a maximum of a ratio of a major axis to a minor axis of each of the inclusions observed in each of 30 visual fields being 0.0025 mm a group of inclusions in which a major axis of each of the inclusions is 3 μm or more and an interval in a rolling direction between the inclusions is 50 μm or less are defined as inclusion-cluster, an inclusion in which the interval is more than 50 μm are defined as an independent-inclusion, a total length in the rolling direction of both the inclusion-cluster whose length in the rolling direction is 30 μm or more and the independent-inclusion whose length in the rolling direction is 30 μm or more is 0 mm to 0.25 mm per 1 mm a texture satisfies that an X-ray random intensity ratio of a {211} plane which is parallel to a rolling surface is 1.0 to 2.4; and a tensile strength is 590 MPa to 980 MPa,