STEEL SHEET HOT-DIP-COATED WITH Zn-Al-Mg-BASED SYSTEM, AND PROCESS OF MANUFACTURING SAME

[Problem] To provide a steel sheet hot-dip-plated with a Zn-Al-Mg-based alloy coating, which is remarkably improved in point of all the burring workability, the liquid metal embrittlement cracking resistance and the corrosion resistance in the welded part thereof, as a steel material favorable for arc-welded structural members. [0002] [Means for Resolution] A plated steel sheet having a Zn-Al-Mg-based alloy coating layer formed by hot-dipping on the surface of a base steel sheet for welded structural members, wherein the base steel sheet has a specific chemical composition and has a metallographic structure of such that Ti-containing precipitates having a mean particle diameter of at most 20 nm are dispersed in the matrix formed of a ferrite phase therein, and wherein the liquid metal embrittlement cracking sensitivity index H3 value of the base steel sheet represented by the following formula (3) and indicating the relationship between the contents of the steel components and the thickness t (mm) of the steel sheet is at most 2.90: