Mg-based alloy plated steel material

1. A Mg-based alloy plated steel material characterized by being provided with a hot dip Mg-based alloy plating layer containing

Zn: 15 atm % or more,

Mg: over 35 atm %, and

further containing

Ca and optionally one or more elements selected from the group of elements B: Al, and Y in a total of 0.03 to 15 atm %,

wherein said hot dip Mg-based alloy plating layer comprises only crystal phase, and contains an intermetallic compound Zn 3 Mg 7 , wherein an X-ray intensity ratio of diffraction peak intensity of Zn 3 Mg 7 relative to the sum of all diffraction peak intensities appearing at diffraction plane spacing of 0.1089 to 1.766 nm is 10% or more, wherein diffraction peak of diffraction plane spacing of 0.233 nm is excluded from determining said X-ray intensity ratio.

2. An Mg-based alloy plated steel material as set forth in claim 1 , characterized in that said hot dip Mg-based alloy plating layer containing Mg: 85 atm % or less.

3. The Mg-based alloy plated steel material as set forth in claim 1 , characterized in that said hot dip Mg-based alloy plating layer contains Mg: 55 to 80 atm %.

4. The Mg-based alloy plated steel material as set forth in claim 1 characterized in that said hot dip Mg-based alloy plating layer further contains one or more elements selected from the group of elements A: Si, Ti, Cr, Cu, Fe, Ni, Zr, Nb, Mo, and Ag in a total of 0.03 to 5 atm %.

5. The Mg-based alloy plated steel material as set forth in claim 1 , characterized in that said hot dip Mg-based alloy plating layer containing

Zn: 20 atm % or more,

Mg: 50 atm % to 75 atm %, and

further containing

Ca and optionally one or more elements selected from the group of elements B: Al, and Y in a total of 0.03 to 12 atm %, here when said total is 1 to 12 atm %, containing Al: 1 atm % or more.

6. The Mg-based alloy plated steel material as set forth in claim 5 , characterized in that said hot dip Mg-based alloy plating layer is a single Zn 3 Mg 7 phase.

7. The Mg-based alloy plated steel material as set forth in claim 1 , characterized in that said hot dip Mg-based alloy plating layer is subject to holding said plating layer at a temperature of a melting point of the Mg-based alloy plating to melting point of Mg-based alloy plating +100° C. for 1 minute or less, then rapidly cooling it.

8. The Mg-based alloy plated steel material as set forth in claim 7 , characterized in that said rapid cooling is water cooling or mist water cooling.

9. The Mg-based alloy plated steel material as set forth in claim 1 , characterized in that the interface between said hot dip Mg-based alloy plating layer and steel material is provided with a preplating layer comprised of one or more elements selected from Ni, Cu, Sn, Cr, Co, and Ag.

10. The Mg-based alloy plated steel material as set forth in claim 1 , characterized in that said hot dip Mg-based alloy plating layer contains a balance of Mg and unavoidable impurities.