Patent ID: 9702035
Date: 2017-07-11
CPC Classifications: B21B,B32B,C21D,C22C,C23C,Y10T

Claim:
1. A manufacturing method of a hot-dip galvanized steel sheet, comprising: a step of obtaining a base steel sheet, the step comprising: a plating step of making the base steel sheet to be immersed in a plating bath in which an effective Al amount is 0.01 to 0.18 mass % to form a hot-dip galvanized layer on a surface of the base steel sheet to produce a hot-dip galvanized steel sheet: wherein in Expression 1, N indicates a total number of passes from a start of the hot rolling to a completion of the hot rolling, i indicates an order of pass, T wherein the base steel sheet has a steel sheet structure in a range of ⅛ thickness to ⅜ thickness centered around ¼ thickness of a sheet thickness from a surface, in which a volume fraction of a retained austenite phase is 5% or less, and a total volume fraction of a bainite phase, a bainitic ferrite phase, a fresh martensite phase and a tempered martensite phase is 40% or more; an average effective crystal grain diameter and a maximum effective crystal grain diameter in the range of ⅛ thickness to ⅜ thickness centered around ¼ thickness of the sheet thickness from the surface are 5.0 μm or less and 20 μm or less, respectively; and the decarburized layer has a thickness of 0.01 μm to 10.0 μm and is formed on a surface layer portion, in which a density of oxides dispersed in the decarburized layer is 1.0×10