Patent classifications
C21D2221/02
High-strength hot-dip galvanized steel sheet having excellent surface quality and electric resistance spot weldability, and manufacturing method therefor
A hot-dip galvanized steel sheet according to one aspect of the present invention comprises a base steel sheet and a hot-dip galvanized layer formed on the surface of the base steel sheet, wherein the difference between the average of the Mn/Si values of surface oxides present on a surface portion, which is the region from the interface between the hot-dip galvanized layer and the base steel sheet to a depth of 15 nm, and the average of the Mn/Si values of internal oxides, which are present in the region from the interface to a depth of 50-100 nm, can be 0.5 or more. Mn and Si of each oxide mean the amounts (wt %) of Mn and Si components in the oxide, which are measured by EDS, and the average of Mn/Si values means the averaged value of the Mn/Si values measured for each oxide.
HIGH-STRENGTH HOT-DIP GALVANIZED STEEL SHEET HAVING EXCELLENT SURFACE QUALITY AND ELECTRIC RESISTANCE SPOT WELDABILITY, AND MANUFACTURING METHOD THEREFOR
A hot-dip galvanized steel sheet according to one aspect of the present invention comprises a base steel sheet and a hot-dip galvanized layer formed on the surface of the base steel sheet, wherein the difference between the average of the Mn/Si values of surface oxides present on a surface portion, which is the region from the interface between the hot-dip galvanized layer and the base steel sheet to a depth of 15 nm, and the average of the Mn/Si values of internal oxides, which are present in the region from the interface to a depth of 50-100 nm, can be 0.5 or more. Mn and Si of each oxide mean the amounts (wt %) of Mn and Si components in the oxide, which are measured by EDS, and the average of Mn/Si values means the averaged value of the Mn/Si values measured for each oxide.
High strength member, method for manufacturing high strength member, and method for manufacturing steel sheet for high strength member
A high strength member according to the present invention is the high strength member having a bending ridge line portion formed from a steel sheet, the member having a tensile strength of 1470 MPa or higher, a residual stress of 300 MPa or lower in an end surface of the bending ridge line portion, and a Vickers hardness (HV) of 200 or higher and 450 or lower in the end surface of the bending ridge line portion.