Method for manufacturing high-strength hot-dip galvanized steel sheet, method for manufacturing hot-rolled steel plate for high-strength hot-dip galvanized steel sheet, method for manufacturing cold-rolled steel plate for high-strength hot-dip galvanized steel sheet, and high-strength hot-dip galvanized steel sheet

Abstract

Provided is a method for manufacturing a high-strength hot-dip galvanized steel sheet, a method for manufacturing a hot-rolled steel plate for a high-strength hot-dip galvanized steel sheet, a methodfor manufacturing a cold-rolled steel plate for a high-strength hot-dip galvanized steel sheet, and a high-strength hot-dip galvanized steel sheet, the high-strength hot-dip galvanized steel sheet having exceptional molding properties, outer surface appearance, and plating adhesion. The Mn content is 2.00 to 10.00%. The concentration of solid-solution Mn within a depth of 5 [mu]m from the steel plate surface is 1.50% by mass or less, and the value obtained by dividing the average Mn mass percentage in the residual austenite by the average Mn mass percentage in the ferrite is 2.0 or greater. Afirst heat treatment is performed for holding said sheet in a temperature range of 650 to 850 DEG C for 600 to 21600 s while the steel plate surface is exposed in an atmosphere having an H2 concentration of 0.1 to 25.0 vol% and a dew point of -45 to 0 DEG C, and a second heat treatment is performed for holding said sheet in a temperature range of 650 to 830 DEG C for 20 to 900 s in an atmosphere having an H2 concentration of 0.05 to 25.0 vol% and a dew point of -10 DEG C or less.

Description

technical field [0001] The present invention relates to a method for manufacturing a high-strength hot-dip galvanized steel sheet suitable for use in automotive components, a method for manufacturing a hot-rolled steel sheet for a high-strength hot-dip galvanized steel sheet, and a method for manufacturing a cold-rolled steel sheet for a high-strength hot-dip galvanized steel sheet Manufacturing method and high-strength hot-dip galvanized steel sheet. Background technique [0002] In recent years, due to the increasing awareness of the protection of the global environment, there has been a strong demand for CO 2 Fuel consumption improvement due to emission reduction. At the same time, there is an active movement toward increasing the strength of steel sheets used as materials for body parts, thereby reducing the thickness of body parts and reducing the weight of the body. However, increasing the strength of steel sheets leads to a reduction in formability, and therefore, d...

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Problems solved by technology

[0008] However, in these methods, in order to improve the appearance of plating, it is necessary to add an oxidation process, an equipment for reducing the oxygen potential energy, or a re-annealing process for plating treatment, etc., which requires a large amount of equipment modification and an additional heat treatment process, resulting in The cost of the final product rises

In addition, it cannot cope with a large increase in the amount of Mn added.

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