HOT-ROLLED STEEL SHEET

Abstract: in this hot-rolled steel sheet, a microstructure at a � position from a surface includes, by area %, ferrite: 2.0% to 30.0%, bainite: 60.0% to 93.0%, and martensite: 5.0% to 20.0%, an area ratio of martensite, which is in contact with a 30� grain boundary, when a maximum value of a gaiq value of the ferrite is indicated as i�, which has a relative gaiq value of i�/3 or less, and which has a grain size of 2.0 �m or more, is 5.0% or more, and a tensile strength is 980 mpa or more.

Inventor(s): Shohei YABU, Takuya KUWAYAMA

CPC Classification: C21D9/46 (MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class and at least one process covered by this subclass ; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials ))

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