HIGH-STRENGTH ALLOYED HOT-DIP GALVANIZED STEEL SHEET AND MANUFACTURING METHOD THEREFOR
摘要:
A high-strength hot-dip galvannealed steel sheet may include a plating layer on a surface of a base steel sheet. The base steel sheet may satisfy a predetermined chemical composition, in a metallographic structure of the base steel sheet, wherein a volume ratio of martensite (including tempered martensite and self-tempered martensite) is 82 vol % or more, a volume ratio of ferrite, pearlite and bainite is 13 vol % or less in total, and volume ratio of retained austenite is 5 vol % or less, in an image obtained by observing the metallographic structure of the base steel sheet with a scanning electron microscope, the number of laths at a total length of 300 μm, the number being measured by an intercept method is 200 or more, a yield strength is 970 MPa or more, and a tensile strength is 1,470 MPa or more.
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