Method for manufacturing hot-dip galvanized steel sheet

Abstract

Provided is a method for manufacturing a hot-dip galvanized steel sheet, whereby high plating adhesion and a good plating appearance can be obtained even when performing hot-dip galvanization of a steel strip including 0.2% by mass or more of Si. In the present invention, a steel strip is sequentially conveyed in a heating zone, a soaking zone, and a cooling zone inside an annealing furnace, annealing of the steel strip is performed, and hot-dip galvanization is then performed on the steel strip discharged from the cooling zone. A reducing gas or a non-oxidizing gas supplied to the soaking zone is a humidified gas and a dry gas. Fluctuation of the pressure in the annealing furnace is suppressed by adjusting the flow rate of the dry gas while the width and the sheet passing speed of the steel strip passing through the soaking zone are constant, whereas the fluctuation range of the amount of moisture supplied to the soaking zone by the humidified gas is set to 20% or less.

Description

technical field [0001] The invention relates to a method for manufacturing hot-dip galvanized steel sheets, which uses a continuous hot-dip galvanizing device with an annealing furnace and hot-dip galvanizing equipment. The above-mentioned annealing furnace is arranged in sequence with a heating zone, a soaking zone and a cooling zone. A hot-dip galvanizing plant adjoins the aforementioned cooling zone. Background technique [0002] In recent years, demand for high-tensile steel sheets (high-strength steel sheets) that contribute to weight reduction of structures has been increasing in the fields of automobiles, home appliances, and building materials. As a high-strength steel material, for example, it is known that a steel sheet with good hole expandability can be produced by including Si in the steel, and a steel sheet with good ductility can be produced by easily forming residual γ by containing Si and Al. [0003] However, when a galvannealed steel sheet is manufactured...

AI Technical Summary

Problems solved by technology

In addition, even if it is not serious enough to cause non-plating, there is a problem of poor plating adhesion

Furthermore, if Si in the steel is selectively oxidized and enriched on the surface of the steel sheet, a significant alloying delay occurs in the alloying process after hot-dip galvanizing, and there is a problem that the productivity is significantly hindered.

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