TH182448B - Steel plate, hot dip galvanized steel plate, galvanized steel plate, and methods. - Google Patents

Abstract

1 page of the number 1 page summary of the invention Steel sheet, according to the nature of the present invention, has a chemical composition. That was predetermined Where a structure at 1/4 part thickness includes in terms of volume ratio, 30% to 70% quenched martensite, and one or both ferrites and benite: 20% to 70 total. %, In a structure at 1/4 part thickness, by volume ratio of austenite. Less than 10% residual, volume by volume ratio of new martensite is 10% or less, perlite's volume ratio is 10% or less, and total by volume ratio. The residual austenite, new martensite, and perlite are 15% or less, density by number of carbides based on iron with a core of 5 nm or more. In the quenched martensite at 1/4 part thickness is 5x107 particles / square millimeter or more, the ratio by the number of formula-type carabytes in the number of carabytes on the basis of core iron. 5nm or more where a thickness of 1/4 part is 20% or more, and tensile strength is 780Mpa or higher:

Claims (1)

Page 1 of the number 3 pages. Claims 1. Steel sheet that is included. As chemical composition by% by mass C: 0.05% to 0.40%, Si: 0.05% to 3.00%, Mn: 1.50% or more or less 3.50%, P: 0.04% or less, S: 0.01% or less. Over, N: 0.01% or less, 0: 0.006% or less, A1: 0% to 2.00%, Cr: