High-strength hot-dip galvanized steel sheet having excellent surface quality and resistance spot weldability, and method for manufacturing same

Abstract

The present invention relates to a high-strength hot-dip galvanized steel sheet having excellent surface quality and resistance spot weldability, and a method for manufacturing the same. A galvanized steel sheet according to one aspect of the present invention may comprise a base steel sheet and a zinc-based plating layer formed on the surface of the base steel sheet, wherein the ratio (a/b) of the surface layer hardness (a) to the internal hardness (b) of the base steel sheet may be less than 0.95.

Description

technical field [0001] The invention relates to a high-strength hot-dip galvanized steel sheet with excellent surface quality and resistance spot weldability and a manufacturing method thereof. Background technique [0002] Due to problems such as environmental pollution, the control of vehicle exhaust and fuel efficiency is increasingly strengthened. Therefore, the demand for reducing fuel consumption by reducing the weight of automobile steel sheets is increasing, and thus various high-strength steel sheets with high strength per unit thickness have been developed and launched. [0003] High-strength steel usually refers to steel with a strength of 490 MPa or more, but it is not necessarily limited to this, transformation-induced plasticity (TRIP) steel, twin-induced plasticity (TWIP) steel, dual-phase (Dual Phase, DP) steel, complex phase (Complex Phase, CP) steel, etc. may belong to high-strength steel. [0004] In addition, in order to ensure corrosion resistance, aut...

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Problems solved by technology

[0005] However, when galvanizing the surface of a high-strength steel sheet, there is a problem that spot weldability deteriorates

That is, in the case of high-strength steel, the tensile strength is high and the yield strength is also high, so it is difficult to eliminate the tensile stress generated during welding by plastic deformation, so there is a high possibility of microcracks on the surface

When welding high-strength galvanized steel sheets, zinc with a low melting point penetrates into the fine cracks in the steel sheets. As a result, a phenomeno

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