Alloyed hot-dip galvanized steel plate and manufacturing method therefor

Abstract

This alloyed hot-dip galvanized steel plate comprises a steel plate, a galvanization layer on the surface thereof, and a mixed layer formed between the steel plate and the galvanization layer. The mixed layer contains the following: a ferrite part that has microscopic crystal grains that are more than 0 µm but no more than 2 µm in size; a zinc-iron alloy phase; and an oxide that contains one or more elements selected from among manganese, silicon, aluminum, and chromium. Said oxide and zinc-iron alloy phase are present at the grain boundaries of the microscopic crystal grains in the mixed layer, and tendrils of the zinc-iron alloy phase extend into the ferrite part. (1) [Mn]+[Si]+[Al]+[Cr] ≥ 0.4

Description

Technical field [0001] The present invention relates to an alloyed hot-dip galvanized steel sheet with excellent coating adhesion and a manufacturing method thereof. Background technique [0002] In recent years, particularly in the field of automobile technology, the demand for high-strength steel sheets has been increasing from the viewpoint of weight reduction for the purpose of improving combustion efficiency and energy saving. In response to such a demand, for example, Patent Document 1 discloses a steel sheet in which the structure of the steel sheet is formed into a structure in which three phases of a ferrite phase, a bainite phase, and an austenite phase are mixed. In addition, it is disclosed that the steel sheet is a steel sheet that utilizes transformation-induced plasticity that exhibits high ductility by transforming retained austenite into martensite during forming processing. [0003] For this type of steel sheet, for example, it contains C: 0.05-0.4% by mass, Si: ...

AI Technical Summary

Problems solved by technology

Therefore, only by controlling the maximum penetration depth of the Zn-Fe intermetallic compound, it is difficult to ensure the adhesion of the coating that can withstand severe processing

For example, when performing severe molding using a mold, powdering called peeling of the surface coating may occur, and it has been difficult to prevent powdering from occurring in the past.

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