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Area factor of the ferrite phase which the tensile strength which is superior in extension and extension flange property mannered null systematic
Area factor of the ferrite phase which the tensile strength which is superior in extension and extension flange property mannered null systematic
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机译：延伸性和延伸凸缘性优异的抗拉强度推定为无系统的铁素体相的面积因数
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摘要
PROBLEM TO BE SOLVED: To produce an inexpensive high strength hot rolled steel sheet excellent in elongation and stretch flange properties and having a TS of ≥780 MPa, and a method for producing it.;SOLUTION: The high strength hot rolled steel sheet has a composition composed of, by mass, 0.06 to 0.15% C, ≤1.2% Si, 1.0 to 1.8% Mn, ≤0.04% P, ≤0.005% S, ≤0.05% Al and 0.06 to 0.13% Ti, and the balance Fe with inevitable impurities, and has a microstructure in which the area ratio of a ferrite (F) phase is ≥85%, the area ratio of a bainite phase is 2 to 9%, and the F phase satisfies the following conditions (i) to (iii): (i) the area ratio of the crystal grains with an aspect ratio of 3.0 occupied in the F phase is ≥80%; (ii) the total ratio of the content of the Ti in the precipitates of 20 nm to the total of the content of the Ti in all the precipitates in the steel is ≥70%; and (iii) the area ratio of the crystal grains in which the precipitates of 20 nm are present is occupied in the F phase is ≥50%.;COPYRIGHT: (C)2011,JPO&INPIT
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