Multi-layered zinc alloy plated steel having excellent spot weldability and corrosion resistance

1. A multilayer zinc alloy plated steel material comprising:

a base steel material having a thickness; and

multiple plating layers formed on the base steel material,

wherein a ratio of a total Mg content in the multiple plating layers to a total weight of the multiple plating layers is from 0.13 to 0.24,

wherein the multiple plating layers comprise: a first plating layer formed on the base steel material and having a Mg content of 7 wt % or less; and a second plating layer formed on the first plating layer, and

wherein the first plating layer comprises: a Zn single phase, and the second plating layer comprises: a Zn—Mg alloy phase, or

wherein the first plating layer comprises: a Zn single phase and a Zn—Mg alloy phase, and the second plating layer comprises: a Zn—Mg alloy phase, and

wherein grains of the multiple plating layers have an average diameter of 100 nm or less (excluding 0 nm).

2. The multilayer zinc alloy plated steel material of claim 1 , wherein, when a GDS profile is measured at a thicknesswise center portion of the each of the multiple plating layers, a Mg content in the each of the multiple plating layers deviates within a range of ±5%.

3. The multilayer zinc alloy plated steel material of claim 1 , wherein a total plating amount of the multiple plating layers is 40 g/m 2 or less (excluding 0 g/m 2 ).

4. The multilayer zinc alloy plated steel material of claim 1 , wherein, when spot welding is performed on the multilayer zinc alloy plated steel material, the multiple plating layers are configured to be changed to a single alloy layer in a weld zone, and the single alloy layer comprises: a MgZn 2 alloy phase in an area fraction of 90% or greater (including 100%).

5. The multilayer zinc alloy plated steel material of claim 1 , wherein, when spot welding is performed in accordance with SEP 1220-2, an average length of type B cracks is equal to or less than 0.1 times the thickness of the base steel material.

6. The multilayer zinc alloy plated steel material of claim 1 , wherein the base steel material comprises, by wt %, C: 0.10% to 1.0%, Si: 0.5% to 3%, Mn: 1.0% to 25%, Al: 0.01% to 10%, P: 0.1% or less (excluding 0%), S: 0.01% or less (excluding 0%), and a balance of Fe and inevitable impurities, and

wherein the contents of C, Si, Mn, P, and S satisfy Condition 1 below:

[C]+[Mn]/20+[Si]/30+2[P]+4[S]≥0.3  Condition 1:

where each of [C], [Mn], [Si], [P], and [S] refers to a content (wt %) of a corresponding element.

7. The multilayer zinc alloy plated steel material of claim 6 , wherein the base steel material comprises: a microstructure including at least one of austenite and retained austenite.

8. The multilayer zinc alloy plated steel material of claim 1 , wherein a total plating amount of the first laying layer and the second plating layer is 40 g/m 2 or less (excluding 0 g/m 2 ), and a plating amount of the first plating layer is 3 g/m 2 or greater.

9. The multilayer zinc alloy plated steel material of claim 1 , wherein, in the first plating layer comprising the Zn single phase and the Zn—Mg alloy phase, the Zn—Mg alloy phase comprises: a Mg 2 Zn 11 alloy phase.

10. The multilayer zinc alloy plated steel material of claim 1 , wherein the multiple plating layers further comprise: a third plating layer formed on the second plating layer and having a Mg content of 2 wt % or less, and

wherein the third plating layer comprises: a Zn single phase, or a Zn single phase and a Zn—Mg alloy phase.

11. The multilayer zinc alloy plated steel material of claim 10 , wherein a total plating amount of the first playing layer, the second plating layer and the third plating layer is 40 g/m 2 or less (excluding 0 g/m 2 ), a plating amount of the first plating layer is 3 g/m 2 or greater, and a plating amount of the third plating layer is 2 g/m 2 or greater.

12. A multilayer zinc alloy plated steel material comprising:

a base steel material having a thickness; and

multiple plating layers formed on the base steel material,

wherein a ratio of a total Mg content in the multiple plating layers to a total weight of the multiple plating layers is from 0.13 to 0.24,

wherein the multiple plating layers comprise: a first plating layer formed on the base steel material and having a Mg content of 7 wt % or less; and a second plating layer formed on the first plating layer, and

wherein the first plating layer comprises: a Zn single phase, and the second plating layer comprises: a Zn—Mg alloy phase, or

wherein the first plating layer comprises: a Zn single phase and a Zn—Mg alloy phase, and the second plating layer comprises: a Zn—Mg alloy phase, and

wherein, when spot welding is performed on the multilayer zinc alloy plated steel material, the multiple plating layers are configured to be changed to a single alloy layer in a weld zone, and the single alloy layer comprises: a MgZn 2 alloy phase in an area fraction of 90% or greater (including 100%).

13. A multilayer zinc alloy plated steel material comprising:

a base steel material having a thickness; and

multiple plating layers formed on the base steel material,

wherein a ratio of a total Mg content in the multiple plating layers to a total weight of the multiple plating layers is from 0.13 to 0.24,

wherein the multiple plating layers comprise: a first plating layer formed on the base steel material and having a Mg content of 7 wt % or less; and a second plating layer formed on the first plating layer, and

wherein the first plating layer comprises: a Zn single phase, and the second plating layer comprises: a Zn—Mg alloy phase, or

wherein the first plating layer comprises: a Zn single phase and a Zn—Mg alloy phase, and the second plating layer comprises: a Zn—Mg alloy phase, and

wherein, when spot welding is performed in accordance with SEP 1220-2, an average length of type B cracks is equal to or less than 0.1 times the thickness of the base steel material.