Technical field [0001] 　The present invention, Zn-Al-Mg plated steel sheet, and a method of manufacturing a Zn-Al-Mg plated steel sheet. Background technique [0002] 　For the consumer and building materials, Zn, and Al as a main component and Mg, hot-dip plated steel sheet of the composition was added an additive element such as Si as required, widely used, or have been proposed. These plating, as compared with Zn plating or Al plating, has corrosion resistance superior to the influence of alloying elements. [0003] 　In recent years, in order to further improve the corrosion resistance and the like and appearance uniformity, defined particle size by optimization of the bath composition, the provisions of the existing form of the cooling method defined particle size by other compounds due to differences in the pre-plating process, cooling optimization of phase by the control of the method, device and the like is added. [0004] 　For example, the following Patent Document 1, MgZn the plating layer 2 and Mg 2 Zn 11 1 kind or two kinds of single phase are precipitated by the size of the above particle size 0.5 [mu] m, unpainted processing unit and invention has been disclosed about the excellent hot-dip Zn-Al-Mg plated steel corrosion resistance of the coating end face. [0005] 　The invention has revealed the presence form of excellent corrosion resistance Mg. Specifically, Mg, rather than present in finely distributed in the ternary eutectic in the form of intermetallic compounds, MgZn above particle size 0.5μm in size 2 or Mg 2 Zn 11 single of better to present in the plating layer independently to form a phase indicating that good corrosion resistance improvement. [0006] 　The following Patent Document 2, the plating layer of the molten zinc plated steel sheet, Al phase magnitude is microcrystalline following granular 0.3 [mu] m, Zn phase, MgZn 2 , Mg 2 Zn 11 1 kind or two kinds of above are dispersed, the invention relates to an excellent hot-dip galvanized steel sheet corrosion resistance after processing is disclosed. [0007] 　In the present invention, the cooling conditions of 40 ~ 100 ° C. / sec, the fine crystals having a 0.3μm or less of the average particle size of the phase and the compound that becomes the dispersed structure randomly reduces the machining cracks, machining It is the excellent corrosion resistance after. [0008] 　The following Patent Document 3, has at least one surface plated layer of the steel sheet, Mg-Zn-based compounds contained in the plating layer is not present in bulk, plated surface from the vicinity of the interface between the plated layer and the base steel grown into columnar direction, present in columnar exposed on the plating layer surface is the 15 to 60% exposed area of ​​the plating layer surface, the invention has been disclosed about the Zn-Al-Mg plated steel sheet. [0009] 　The present invention, such as by Ni plating as a pretreatment, that the Mg-Zn-based compound is grown in a columnar shape, Mg-Zn-based compound until the entire plating disappears from corrosion initial gradually dissolves at a constant rate, appropriate amount of Mg which can contribute to corrosion is to be supplied to the plating surface. Then, it was confirmed the effect in a stable corrosion resistance in wet and dry repetition environment. [0010] 　The following Patent Document 4, during solidification of Zn-Al-Mg plated, MgZn 2 system and Mg 2 Zn 11 to system phases improves uneven appearance due to crystallization in a mixed, unsolidified respect of the plating layer over the entire surface, until completion from the solidification start, invention relates to a technique for spraying water or an aqueous solution in droplet form is disclosed [0011] 　In the present invention, the above spray chilling, Al / Zn / Mg 2 Zn 11 by Al primary crystal or Al primary crystal and Zn single phase in the matrix of the ternary eutectic structure is present the metal structure mixed, uniform It is set to become appearance. [0012] 　The following Patent Document 5, characterized in that more than 60% of the crystals of a ternary eutectic structure of Al / Zn / MgZn alloy plating layer per unit area is equivalent circle diameter 100μm or more, good appearance dip plated steel sheet is disclosed Do. [0013] 　In the present invention, by defining the cooling conditions by reducing the supercooling part, Mg 2 Zn 11 to suppress the formation of phases, and with preventing poor appearance. [0014] 　Other, for tissue of the plating layer of Zn-Al-Mg plated steel sheet, various disclosures have been made in Patent Document 6 to 12. [0015] 　Patent Document 1: JP 2001-20050 JP 　Patent Document 2: JP 2003-147500 Patent Publication 　Patent Document 3: JP 2010-100897 Patent Publication 　Patent Document 4: JP-A 10-265926 JP 　Patent Document 5: JP 2006-283155 JP 　Patent Document 6: International Publication WO2007 / 108,496 discloses 　Patent Document 7: JP 2004-68075 JP 　Patent Document 8: JP-A-10-265926 　Patent Document 9: JP-A-10-226865 JP 　Patent Document 10: JP 2002-047549 JP 　Patent Document 11: JP 2002-047548 JP 　Patent Document 12: JP 2002-030405 JP Summary of the Invention Problems that the Invention is to Solve [0016] 　However, these prior art has the following problems. [0017] 　For example, Patent Document 1 and Patent Document 2 defines with respect to the particle size of the product. Specifies the Patent Document 1, the plating composition range, MgZn particle size of more than 0.5 [mu] m 2 or Mg 2 Zn 11 that is present as a "single phase", stable corrosion products of Mg serving as a high concentration of zinc is a corrosion resistance effect can be greatly improved to reduction, cooling rate shows that slow better in the description. On the other hand, by cooling in Patent Document 2 the freezing point ± 20 ℃ 40 ℃ / sec or more, all of Al phase, Zn phase, MgZn 2 or Mg 2 Zn 11 dispersed in the plating layer in the particle size of 0.3μm or less and, no cracks during processing, although the excellent processability after corrosion resistance and more improved corrosion resistance, even better. [0018] 　Patent Documents 1 and 2 is greatly different from the prescribed range with respect to particle size, portions common to the manufacturing conditions no. However, a large Mg anticorrosion action positively to generate and grow a Mg-Zn alloy containing a high concentration is to try to improve the corrosion resistant capability itself is Patent Document 1. On the other hand, by the form and hardness are not allowed to coexist different particles, preventing physical cracks in the plating layer processing is Patent Document 2 for illustrating a method for preventing the factors that corrosion resistance is greatly degraded. [0019] 　Thus, each of the advantages is also the other problem. That is, in Patent Document 1, the physical properties difference between the remaining phases increases by growing the single-phase structure, cracks during processing is an issue that is likely to occur. In other words, the refrigerator, such as looking at air conditioning, consumer electronics such as video equipment, outdoor equipment frame, outer wall buildings, an example in building materials such as a cable rack, as the processed products, it is difficult to very easy to use material. On the other hand, in Patent Document 2, is a problem that at the expense of average corrosion resistance. [0020] 　Patent Document 3, the provisions of the existing forms of the compounds according to the difference in plating pretreatment is illustrated. Plating the columnar crystals of Zn-Mg phase - from base steel interface is grown in a vertical direction (surface direction), bringing to the surface (usually grown in the horizontal direction) very specific organizational structure in order to generate, prior to the Ni plating was applied by electroplating the steel sheet surface as a treatment after the immersion treatment in an aqueous acid solution, under non-oxidizing or reducing atmosphere, and heated at base iron not alloyed with temperature (500 ° C. or less), must be subjected to plating there is. Typical plating line, holds the material making inclusive annealing furnace (maximum temperature of about 800 ° C.) in a plating process preceding a special condition that can not be realized with such a line. The corrosion resistance, the present invention comparable corrosion loss (JASO test) is presented. In addition, Ni plating is a pre-processing, equipment costs and operating costs are expensive, low-cost consumer electronics, difficult to use in building applications. 　Further to produce a columnar grain from subjected to the Ni plating Patent Document 3. When Ni plating is less than a predetermined amount is described to be inferior corrosion resistance is not a columnar crystal. When Ni plating is not considered to have the same corrosion resistance and US Pat. [0021] 　Patent Document 4 and Patent Document 5, a method to improve the appearance optimization of phase by control of the cooling method is illustrated. In this method, Mg as MgZn alloy in Patent Document 4, Al / Zn / MgZn alloy quenching by spraying water or an aqueous solution (ternary eutectic) 2 Zn 11 is set to generate only. Common liquid spray methods including plating process, there is a fluid nozzle for spraying a gas-liquid nozzle for entrained liquid to the jet of gas, the liquid by pressure atomized. Both use a number of nozzles, a number of droplets dispersed in the range of the cross-sectional shape of an oval with one single nozzle (including circular) collides with the steel plate heat exchanger to cool the steel plate. And, it is known that water density distribution in the spray elliptical range, water density difference or the like between the nozzle portion and the nozzle occurs. Therefore, the uniformity in the 1μm wide range be secured, it is difficult to ensure the same cooling conditions in the range of 0.5 ~ 2m is a common plate width in the plating process. Furthermore, because of concerns such as nozzle clogging, resulting in a high-maintenance load equipment. In order to cover the non-uniformity, there is a case of spraying a liquid or gas and liquid at a high pressure. In this case, if the above pressure wiping determining the basis weight, non-uniformity of the shape becomes a problem. 　In Patent Document 4, Mg-Zn alloys of the present invention similar ternary in eutectic (Mg 2 Zn 11 ) is produced is observed, to achieve the appearance improved by cooling as a method for appearance improvements with water or an aqueous solution spray and, although there is no description with respect to corrosion resistance, (up to 20 degrees / sec in the embodiment) since the cooling rate is low, generally considered a Mg-Zn-Al-based order of plating. [0022] 　On the other hand, in Patent Document 5, Mg generated by supercooling by slow secondary cooling Conversely 2 Zn 11 to a focus on eliminating, as in the case of Patent Document 1, difference in physical properties between the plurality of phases to generate cracking after processing is likely to occur by, there is a high possibility that the corrosion resistance is impaired. Although there is no description with respect to corrosion resistance, the cooling rate be lower, generally considered a Mg-Zn-Al-based order of plating. [0023] 　Other, even Patent Documents 6-12 have been studied corrosion resistance of Zn-Al-Mg plated, at present, further improvement is desired. [0024] 　The present invention has been made in view of the above problems. Then, it is an object of the present invention, while a conventional composition, than conventional products typified by Patent Documents 1 to 2 and 4 to 12, excellent corrosion resistance, and excellent formability microcrystalline structure made, is that further corrosion resistance to provide a method of manufacturing a stably Zn-Al-Mg plated steel sheet is maintained, and Zn-Al-Mg plated steel sheet. Further, in Patent Document 3, the equivalent corrosion resistance and corrosion resistance obtained by a special pretreatment and equipment configurations, by a general plating line configuration, can be easily obtained, and further corrosion resistance is maintained stably method for producing a Zn-Al-Mg plated steel sheet, and Zn-Al-Mg plated steel sheet is to provide. Means for Solving the Problems [0025] 　The present inventor has manufacturing conditions of the plating layer, to investigate the relationship between the solidification structure and the product and corrosion resistance, excellent corrosion resistance, and corrosion resistance is improved over the prior art, Zn-Al this is stably maintained -Mg-plated steel sheet, and to obtain a method of manufacturing a Zn-Al-Mg plated steel sheet. [0026] 　The present invention has been completed based on the above findings, the gist of the invention is as follows. [0027] 　(1) Al and 4 to 22 wt%, Mg 1.0 to 6.5 wt% and wt% of Al of 1/2 or less, 0.001 to 1.000 mass% of Si, as well as, Zn as the balance and has a plating layer containing an impurity, 　the tissue of the plating layer, an area ratio of 30-70%, and the cellular dendrites of the second shaft spacing 0.5 ~ 2.0 .mu.m first Al primary crystal If, summed area ratio is 30 to 70%, the main shaft length of 5 ~ 10 [mu] m, the second Al primary crystal and the main shaft length of the small equiaxed dendrite second axis spacing 0.5 ~ 2.0 .mu.m It has an Al primary crystal comprising a third Al primary crystal Saga 0.5 ~ 3.0 [mu] m petaloid, wherein the Al primary crystal other than the organization, Al and Zn and Mg 2 Zn 11 third and Zn-Al-Mg plated steel sheet is composed of a terpolymer crystal structure. [0028] 　(2) the plating layer further, Ti, Nb, Fe, Ni, Cr, Sn, Mn, and one or two or more selected from B, and either alone or combined, from 0.0001 to 1.0000 mass Zn-Al-Mg plated steel sheet according to% containing (1). [0029] 　(3) tissue of the plating layer, Mg 2 contains no Si (1) or (2) Zn-Al-Mg-based plated steel sheet according to. [0030] 　(4) Al a 4 to 22 mass%, Mg 1.0 to 6.5 wt% and wt% of Al of 1/2 or less, 0.001 to 1.000 mass% of Si, as well as, Zn as the balance and molten zinc containing impurities, plated on at least one surface of the steel sheet, 　a plated steel sheet the molten zinc, and a temperature of + 30 ° C. or higher 520 ° C. below the temperature at which Al primary crystal to initiate clotting, and 370 ° C. from the temperature made of to a temperature 500 ° C. / sec or more cooling rate, and the overall heat transfer coefficient during cooling 1000 ~ 3000W / (m 2 Zn-Al-Mg-based method for producing a plated steel sheet is cooled in the · K). [0031] 　(5) the cooling method of the Zn-Al-Mg plated steel sheet according to do (4) submerged cooling. Effect of the invention [0032] 　According to the present invention, excellent corrosion resistance, corrosion resistance can be provided a method of manufacturing a Zn-Al-Mg plated steel sheet, and Zn-Al-Mg plated steel sheet is stably maintained. Then, the plated steel sheet of the present invention, the use household electrical appliances, building materials, etc., can be a product to withstand long-term use. BRIEF DESCRIPTION OF THE DRAWINGS [0033] FIG. 1 is a schematic plan view showing the shape of the Al primary crystal in the plating layer of the Zn-Al-Mg plated steel sheet of the present invention. [2] is an SEM photograph obtained by observing the plated layer from the surface of the Zn-Al-Mg plated steel sheet of the present invention. 3 is a diagram showing the observed SEM photograph the cross section of the plating layer of Zn-Al-Mg plated steel sheet of the present invention. 4 is a view showing an SEM photograph obtained by observing the plated layer from the surface of the Zn-Al-Mg plated steel sheets of the comparative examples. [FIG 5A] is a diagram showing the intensity of the X-ray diffraction spectrum in the plating layer of the Zn-Al-Mg plated steel sheet of the present invention (coated steel sheet produced in Example (5)). [FIG. 5B] is a diagram showing the intensity of the X-ray diffraction spectrum in the plating layer of the Zn-Al-Mg plated steel sheets of the comparative examples (coated steel sheet produced in Example (10)). 6 is a diagram showing a cross-sectional measurements of the component distribution of elements of the plating layer of Zn-Al-Mg plated steel sheets of the comparative examples. 7 is a diagram showing the measurement results of the component element distribution of the surface of the plating layer of Zn-Al-Mg plated steel sheet of the present invention. 8 is a graph showing measurement results of components elemental distribution of the surface of the plating layer of Zn-Al-Mg plated steel sheets of the comparative examples. [FIG 9A] is a schematic perspective view showing the shape of a cellular dendritic Al primary crystal. [FIG 9B] photograph showing the cellular dendritic Al primary crystal (Reference Photo by "B. Chalmers, Principles of Solidification (1964 ) " T.Bower, 165 pages). FIG. DESCRIPTION OF THE INVENTION [0034] 　The following is a detailed description of the present invention. [0035] 　The present inventor relates to a Zn-Al-Mg plated steel sheet, in view of enhancing the uniformity of the solidification structure were investigated in consideration of the component elements or cooling system or the like of the plating layer. Thereby, excellent corrosion resistance, as an organization of the plating layer corrosion resistance is stably maintained, 1) fine Al primary crystal conventionally no different solidification structure shape is present in more than certain ratio, 2) Al first as tissues other than crystal is composed of a predetermined ternary eutectic structure, manufacturing has been found to be important. The excellent corrosion resistance, and corrosion resistance has reached a plated steel sheet of the present invention to be stably maintained. [0036] (Component elements of the Zn-Al-Mg plated layer) 　First, the present invention will be described component elements of the Zn-Al-Mg plated layer of interest. [0037] 　Plating layer, a Zn-based, but with improved corrosion resistance Al, the content of Mg. Furthermore, the plating layer, the content of Si, in which increased adhesion of the plated layer and the steel sheet. 　Specifically, the plating layer, the Al 4 ~ 22 wt% 1.0 to 6.5 wt% of Mg and 1/2 or less of Al by mass%, the Si 0.001 ~ 1.000 wt% as well, including Zn and impurities as the balance. However, the plating layer, Al, Mg and Si include the above content may be the balance of the plating layer composed of Zn and impurities. [0038] 　The content of Al is in the 4 to 22 wt%. Content is less than 4 mass% of Al, the corrosion resistance improving effect is insufficient. When the content of Al exceeds 22 mass%, it is impaired sacrificial protection effect of Zn, the corrosion resistance of the machined portion and the end face is reduced. Incidentally, from the same viewpoint, the content of Al is preferably 5 to 15 wt%. [0039] 　The content of Mg is 1.0 to 6.5 wt%. Content is less than 1.0 mass% of Mg, the corrosion resistance improving effect is insufficient. When the content of Mg exceeds 6.5 mass%, the amount of Mg oxide in the plating bath becomes excessive, plating appearance is degraded. Incidentally, from the same viewpoint, the content of Mg is preferably 2 to 5 wt%. [0040] 　The content of Mg is in 1/2 or less of Al by mass%. That is, the ratio of the content of Mg to the content of Al (the content of the content / Al of Mg) is 1/2 or less. When the content of Mg exceeds 1/2 of the Al (the content of Al), equilibrium on, Al primary crystal is not generated hardly or generated, in order to allow an average Mg composition by fine crystalline structure of cellular dendritic Al primary crystal, fine equiaxed dendrite Al primary crystal, petaloid Al primary crystal, and takes hardly or not taking the structure of the Al primary crystal of another shape. Further, Mg 2 Si is produced, it will take a non-uniform structure. Incidentally, from the same viewpoint, the content of Mg is 1/3 or less is preferably an Al mass%. [0041] 　The content of Si is set to 0.001 to 1.000 wt%. The Si content is less than 0.001% by mass, excessive growth of the plating layer and interface at an Fe-Al alloy layer between the steel sheet occurs, the adhesion of the plated layer and the steel sheet becomes insufficient. When the content of Si is more than 1.000 mass%, in addition to generating inhibitory effect of Fe-Al alloy layer is saturated, resulting in deterioration of workability of the plated steel sheet. Incidentally, from the same viewpoint, the content of Si is preferably from 0.100 to 0.500 wt%. 　Incidentally, Si is, Mg on the composition 2 there is a case where Si is precipitated preferentially on equilibrium, in the present invention range, a solid solution in tissues other than Al primary crystal or Al primary crystal, or in finely precipitated state , contained in the plating layer. [0042] 　Impurities, or contained in the steel sheet itself, attached to the steel plate before the plating step, components or mixed with diffused in the plating layer after the plating, or contained in the plating bath, it plating in the course of the plating a component remaining in the layer, refers to not intended to be contained intentionally plating layer component. Specifically, as the impurity, for example, Pb, Sb, Co, Cu, In, Bi, Be, Zr, Ca, Sr, Y, Ce, Hf and the like. The content of impurities may be less 0.0010 mass%. [0043] 　Here, Zn-Al-Mg-based plating layer further one or two or more selected elements, either alone or combined, may contain from 0.0001 to 1.0000 wt%. Specifically, the plating layer, Ti, Nb, Fe, Ni , Cr, Sn, Mn, and one or two or more selected from B, and either alone or combined, from 0.0001 to 1.0000 wt% it may contain. 　Among these selected elements, and eluted into the plating layer side of a steel plate at a plating bath immersion, also because the diffusion to a predetermined temperature even during the cooling is continued, in terms of composition early stabilization in the vicinity of the interface between the plated layer and the steel sheet it is preferred that Fe in the plating layer is present about the saturation dissolution amount. [0044] 　Selection elements other than Fe also, although the amount is less than Fe, and a component type and amount determined for each steel type is contained in the steel sheet, it is preferable to target the Fe composition similar early stabilization. These optional elements, while influence on the generation of dendrite structures, such as the Al primary crystal is small, since if the amount is large may inhibit the diffusion of Al or Mg, the content of these elements, 0.0005 ~ 0.2000 wt% is preferred. [0045] 　These optional elements are solid-solved in tissues other than Al primary crystal or Al primary crystal, or finely precipitated state, contained in the plated layer. [0046] 　The content of the selection element is the total amount of the selected element contained in the plating layer. Also, the plating layer, and the content of the optional elements in the composite, indicating that the selection element is contained in the plating layer as a compound containing two or more selected elements. [0047] 　Adhesion amount of a plating made of such component elements is appropriately determined depending on the application, usually per side, for example, 30 ~ 150 g / m 2 is. [0048] (Organizations Zn-Al-Mg plated layer) 　Next, the present invention will be described tissue Zn-Al-Mg plated layer of interest ( "plating layer of the present invention"). [0049] 　Organization of the plating layer of the present invention is constituted by the Al primary crystal, and tissue other than Al primary crystal. Incidentally, the Al primary crystal, in addition to Al, an Al primary crystal that contains Mg, Si and Zn. [0050] 　It will be described Al primary crystal. 　In tissues of the plating layer of the present invention, Al primary crystal, an area ratio of 30-70%, and the first Al primary crystal (hereinafter the second axis spacing like cellular dendrites of 0.5 ~ 2.0 .mu.m " a cellular dendrites also referred to as Al primary crystal "), a 30-70% summed area ratio, major axis length 5 ~ 10 [mu] m, fine equiaxed dendritic second axis spacing 0.5 ~ 2.0 .mu.m second Al primary crystal (hereinafter referred to as "fine equiaxed dendrite Al primary crystal") and the main shaft length of 0.5 ~ 3.0 [mu] m petaloid third Al primary crystal (hereinafter "petaloid Al primary crystal includes a "and also referred to), the. The area ratio of each Al primary crystal is a ratio by volume of the total Al primary crystal. [0051] 　The Al primary crystal of the present invention, as a crystal of a shape without a conventional plating layer, belong cellular dendrites Al primary crystal, fine equiaxed dendrite Al primary crystal, petaloid Al primary crystal, and the above three types of Al primary crystal blocks like include Al primary crystal other shapes (bulk) and the like. Other shapes of Al primary crystal, for example, Al primary crystal of the conventional equiaxed, if it contains block-like (bulk) or the like, the area ratio of the Al primary crystal other shapes may be less than 40%. 　Note that the Al primary crystal of another shape, the second axis spacing of the columnar structure seen from the prior art which does not satisfy the above range Al primary crystal, spindle length and the second-axis distance does not satisfy the above range shaft organizations It is included in the Al primary crystal. [0052] 　Cellular dendrite Al primary crystal, for example, as shown in FIG. 1, a plurality of spindle grown in parallel, and has a structure having a plurality of second axis perpendicular to the main axis (see FIGS. 9A and 9B ). The second axis spacing cellular dendrites Al primary crystal shows a distance D12 of the central axes of the second shaft adjacent. 　Fine equiaxed dendrite Al primary crystal, for example, as shown in FIG. 1, has a main shaft grown radially from the central portion, the structure having a second axis grown branch from the main axis. The major axis length of the micro equiaxed dendrite Al primary crystal indicates the length D21 from the tip of the center side to the other. The second center distance of the fine equiaxed dendrite Al primary crystal shows a distance D22 of the central axes of the second shaft adjacent. 　Petaloid Al primary crystal, for example, as shown in FIG. 1 has a structure having a principal axis grown radially from the center. Petaloid Al primary crystal is considered axed crystal such that the secondary shaft (2 Tsugieda) is not developed. The major axis length of the petal-like Al primary crystal indicates the length D31 from the tip of the center side to the other. 　Incidentally, FIG. 1 is a schematic plan view showing the shape of an Al primary crystal of the plating layer of the present invention. [0053] 　Here, in FIG. 2, SEM of the Zn-Al-Mg plated layer of the present invention was observed from the surface (Scanning Electron Microscope: scanning electron microscope) shows an example of a photograph. The 2, 100-fold magnification, and shows a magnification of 1000 × SEM photograph of. 　3, SEM observing a cross section of Zn-Al-Mg plated layer of the present invention (Scanning Electron Microscope: scanning electron microscope) shows an example of a photograph. 3 shows a SEM photograph of 1000 magnifications. [0054] 　On the other hand, in FIG. 4, SEM observed Zn-Al-Mg plated layer of comparative example (plating layer of Comparative Example) from the surface (Scanning Electron Microscope: scanning electron microscope) shows an example of a photograph. 4 shows a magnification of 100, and shows a magnification of 1000 × SEM photograph of. 　Incidentally, the plating layer of the comparative example, by using the molten zinc of the same components as the present invention is the plating layer when producing a plated steel sheet in the usual method of cooling the plating to the gas cooling and steam cooling and the like in steel . [0055] 　As shown in FIG. 4, the plating layer of the comparative example, the main shaft length has a 50 ~ 200 [mu] m, Al primary crystal equiaxed second axis interval 5 ~ 20 [mu] m. In contrast, as shown in FIGS. 2-3, the plating layer of the present invention, compared to the Al primary crystal of the plating layer of the comparative example, the size of the cellular dendrites Al primary crystal, fine equiaxed above size dendrite Al primary crystal, and it is found to have Al primary crystal fine solidification structure comprising petaloid Al primary crystal of the size. In other words, it petaloid Al primary crystal micro equiaxed dendrite Al primary crystal and the size of the size in the plating layer of the present invention is a tissue of fine Al primary crystal, coarse equiaxed in the plating layer of Comparative Example the of Al primary crystal is distinguished. [0056] 　Here, in FIG. 2, a region surrounded by a solid line shows a region with a cellular dendrites Al primary crystal (cellular dendritic Al primary crystal). Region surrounded by one-dot chain line indicates a region having a fine equiaxed dendrite Al primary crystal. Area surrounded by two-dot chain line indicates a region with an Al primary crystal petals Al primary crystal and other shapes (block shape, etc.). [0057] 　The Zn-Al-Mg plated layer mainly by the cooling start temperature and cooling rate, changes the structure of the resulting Al primary crystal. Corrosion resistance of the Zn-Al-Mg plated layer is due to the effect of Mg, in order to maintain a stable corrosion resistance, it has been found that the shape and distribution of the Al primary crystal to first generation is influenced . Then, the present inventors have found that including the Al primary crystal, the size of the cellular dendrites Al primary crystal, fine equiaxed dendrite Al primary crystal of the size, and the three types of Al primary crystal petals Al primary crystal of the size to include Al primary crystal fine solidification structure with a predetermined area ratio, excellent corrosion resistance, corrosion resistance (corrosion loss) was found to be stably maintained. 　Specifically, as shown in examples described later, in the present invention, compared with the comparative example, the corrosion resistance (corrosion loss) becomes apparent advantage has been found that can be secured than 2/3 of corrosion resistance as corrosion weight loss . [0058] 　In Al primary crystal, improved corrosion resistance, from the viewpoint of maintaining the corrosion resistance stably, the area ratio of the cellular dendrites Al primary crystal is preferably 40 to 70%, more preferably 50-70%. From the same point, the area ratio of the combined micro equiaxed dendrite Al primary crystal and a petal-shaped Al primary crystal is preferably 30 to 60%, more preferably 30-40%. Further, these organizations may include together. [0059] 　Incidentally, the cellular dendrites Al primary crystal dendrite shapes can be discriminated by the whether developed in view the 90 degree direction from the top (see Figure 2). Since the second shaft of the dendrite in cross-section (secondary branch) is perpendicular to the first axis (primary branch), it can be confirmed cellular dendrite shape (see FIG. 3). However, sometimes oblique section appears on the surface, a diamond shape in this case. 　Further, when viewed in cross section perpendicular to the surface, it can be seen that the second shaft to the first shaft (primary branch) (secondary branch) is developed vertically. On the other hand, the tissue of the same cross-section of a conventional coated steel sheet, the second shaft to the first shaft (primary branch) (secondary branch) is that is perpendicular not developed understood from FIG. 　Segregation of cellular dendrite Al HatsuAkirama Since variations in comparison with fine equiaxed dendrite Al primary crystal and petals Al primary crystal is small, to include cellular dendrites Al primary crystal in a predetermined range, to that corrosion resistance is further excellent It is considered to be. Incidentally, fine equiaxed dendrite Al primary crystal, there is the main shaft (stem), the second axis (primary branch), third axis (secondary branch) have developed, seen from the top when the 90-degree direction of the cell Jo to never develop, also great variation in segregation between trees. Petaloid Al primary crystal, there is only the main shaft, the second shaft, but not the third shaft is present, is developed in micro equiaxed dendrite Al primary crystal as well as 90-degree directional cellular when viewed from above and not without, also similarly large variation in the trunk. In the method of manufacturing a cooling rate range of the present invention, although the small equiaxed dendrite Al primary crystal and petal-shaped Al primary crystal can be clearly form distinct and defined, as in some of the comparative example, in the case of low cooling rate conditions, the main shaft as well as the second shaft, becomes the third axis is likely to develop, the distinction between the two types of Al primary crystal becomes difficult. Therefore, in the comparison of the area ratio of the Al primary crystal in the present invention, different cellular dendrites Al primary crystal of the sum of the area ratio, clearly structure a combination of the fine equiaxed dendrite Al primary crystal and petal Al primary crystal and it was decided to compare the area ratio of Al primary crystal other shapes. [0060] 　Here, the cellular dendrites Al primary crystal, fine equiaxed dendrite primary crystal, petaloid Al primary crystal, and the area ratio of the Al primary crystal other shapes, a value determined by the following method. 　Area ratio of Al primary crystal, using SEM 1000 times image 5 fields in each sample using (N number = 5), by a commercially available image analysis software, to identify Al primary crystal of each shape, the area that determined by the following calculation formula from. · Formula: Cellular dendrite Al primary crystal area ratio of = cellular dendrites Al primary crystal total area / Al primary crystal total area × 100 in -formula: fine equiaxed dendrite Al primary crystal area ratio of = fine equiaxed dendrite Al primary crystal total area × 100 of the total area / Al primary crystal -type: the area ratio of the petal-like Al primary crystal = petaloid Al primary crystal total area / Al total area × 100 of primary crystal -type: Al's first other shapes crystal area ratio = other shapes total area × 100 of the total area / Al primary crystal Al primary crystal 　Incidentally, the area of each Al primary crystal is a area of a region Al primary crystal is present, Al primary crystal and an area including the eutectic structure that exist between trees of Al primary crystal (between axes) and. That is, the area ratio of each Al primary crystal is the area ratio of the region including the eutectic structure existing between trees Al primary crystal and Al primary crystal (between axes). [0061] 　Al primary crystal other tissues will be described. 　In tissues of the plating layer of the present invention, tissues other than Al primary crystal, Al and Zn and Mg 2 Zn 11 is composed of a ternary eutectic structure with. However, this ternary eutectic structure, MgZn traces (5 vol% or less) 2 , may also be included. 　Incidentally, the structure of the plating layer of the present invention, Mg 2 preferably contains no Si. In the present specification, "Mg 2 includes no Si", Specifically, for example, the measurement results shown in FIG. 5A (measurement of the intensity of X-ray diffraction spectrum of the plating layer), with respect to strength 35,000CPS of the maximum peak, Mg 2 Si peak is below the noise (about 50 cps) could not have detected. 　Incidentally, in the conventional plating Mg 2 By containing Si, had improved corrosion resistance, since the plating crystals unprecedented in the present invention is to further enhance corrosion resistance, Mg 2 Si in the corrosion resistance is better not exist but rather affect it is considered that there is no. [0062] 　Here, using the molten zinc of the same components as the present invention, the plated steel sheet to produce a coated steel sheet in the usual cooling method such as a gas cooling and steam cooling, for example, the spindle length 50 ~ 200 [mu] m, the second equiaxed dendritic Al primary crystal axis spacing 5 ~ 20 [mu] m is, Zn, Al and MgZn 2 generates in a state of being dispersed in configured eutectic product with (see Figure 4). This is a clotting sequence, first high Al primary crystal solidification starting point is precipitated and grown everywhere in the plating layer, then Al and MgZn after starting cooling 2 eutectic structure of precipitates around the Al primary crystal further when cooled Zn, Al and MgZn 2 is because the ternary eutectic structure and generates, MgZn clearance around the Al primary crystal 2 is considered to be a structure that meets the and Mg. [0063] 　For the Mg-Zn compound, the ternary equilibrium diagram Mg 2 Zn 11 , but it should be stabilized generated as equilibrium composition, sometimes the driving force of precipitation is short, usually, the fast nucleation and growth rate MgZn is 2 is produced preferentially. In the operating condition shown in Patent Document 4 using the liquid spray cooling, to lower the influence of the relatively nucleation and growth rate by solidification rate increases, Mg near the equilibrium composition 2 Zn 11 is liable to generate a think. In Patent Document 5, the degree of supercooling is at a high partial Mg 2 Zn 11 has a occurs when could uniformly cooled to avoid uneven cooling, MgZn 2 may be considered to occur. 　Furthermore, with regard to Mg-Si compound, which contains the Si in the molten zinc, in normal Mg 2 but Si is produced, in the case of the present invention is the compound deviated from the equilibrium phase diagram is generated it is considered Mg 2 believed often Si does not generate. [0064] 　Meanwhile, in order to investigate the composition of the plating layer of the present invention, it was examined the intensity of X-ray diffraction spectrum using Cu radiation source. Figure 5A, the intensity of X-ray diffraction spectrum of the plating layer (plated steel sheet used in Example (5)) The present invention, shown in association with the diffraction angle 2 [Theta]. Further, in FIG. 5B, the intensity of X-ray diffraction spectrum of the plating layer of Comparative Example (plated steel sheet used in Example (10)), shown in association with the diffraction angle 2 [Theta]. ● (black circle) represents the peak of Zn, in each case ▼ (closed inverted triangles) showed a peak of Al, ■ (filled square) is MgZn 2 showed a peak of, ◆ (black diamonds) Mg 2 Zn 11 It shows the peak. Incidentally, Si, the concentration is X-ray diffraction intensity due to the low small peak was not obtained. 　The intensity of X-ray diffraction spectrum using a Rigaku RINT2000, at Cu (K [alpha) radiation source, a tube voltage 40 kV, measured under the conditions of a tube current 150 mA. [0065] 　Here, in the plating layer of the comparative example was examined Mg, Al, for each of the elemental distribution of Zn and Si, as shown in FIG. 6, high density distribution of Mg and Si in the same area (white), and Al and Zn is not distributed (black) portion there is a plurality, the presence of Mg-Si compound is confirmed. Thereby, the plating layer of Comparative Example, Mg 2 it was found that there is a high possibility that Si exists. 6, SEM observing the cross section of the plating layer of Comparative Example: with (Scanning Electron Microscope SEM) photograph, EDS (Energy Dispersive X-ray Spectrometer) in accordance Mg, Al, each element distribution of Zn and Si It shows the measurement results. In each element, bright it is, the concentration is high. [0066] 　As shown in FIGS. 5B and 6, the plating layer of the comparative example was produced in the usual method of cooling, Zn, Al, Si, MgZn 2, Mg 2 While likely composed of Si, the present invention plating layer, Al, Zn, Si, Mg 2 Zn 11 is composed of. That is, in the structure of the plating layer of the present invention, Mg 2 contains no Si, tissue other than Al primary crystal, Al and Zn and Mg 2 Zn 11 is composed of a ternary eutectic structure with, the conventional the different organizations. Incidentally, in the plating layer of the present invention, Si is, Al and Zn and Mg 2 Zn 11 in ternary eutectic structure in the considered to be included as a solid solution, or other fine precipitates. [0067] 　The Zn-Al-Mg plated layer mainly by the cooling start temperature and cooling rate also changes the structure of the tissues other than Al primary crystal to produce. Corrosion resistance of the Zn-Al-Mg plated layer, the composition distribution and Mg-Zn compound and Mg affects. Then, the present inventors have found that in Zn-Al-Mg plated layer, the Al primary crystal on which the said tissue, the tissue other than Al primary crystal Al and Zn and Mg 2 Zn 11 ternary eutectic with by configuring organization, excellent corrosion resistance, corrosion resistance (corrosion loss) it was found to be stably maintained. [0068] 　That is, since the plating structure of the present invention is a conventional plating tissue is another organization, the organization of the Zn-Al-Mg plated layer, Mg 2 preferably be configured without the Si, [0069] (Element distribution of Zn-Al-Mg plated layer) 　is described element distribution of the plating layer of the present invention. 　Mg in Zn-Al-Mg plated layer of the present invention, Al, were examined for each of the elemental distribution of Zn and Si. 7, the plating layer SEM observed from the surface of the present invention: together with (Scanning Electron Microscope SEM) photograph, EDS (Energy Dispersive X-ray Spectrometer) in accordance Mg, Al, each element distribution of Zn and Si It shows the measurement results. In each element, bright it is, the concentration is high. 　Similarly, examined Mg in Zn-Al-Mg plated layer of comparative example, Al, each element distribution of Zn and Si. 8, shown with SEM photograph obtained by observing the plated layer of the Comparative Example from the surface, Mg by EDS, Al, the measured results of distribution of elements Zn and Si. Incidentally, the plating layer of the comparative example, by using the molten zinc of the same composition as the present invention, after the plated steel sheet, plating layer when producing a plated steel sheet in the usual cooling method such as a gas cooling and steam cooling is there. [0070] 　As shown in FIG. 8, a plating layer of the comparative example, Mg is distributed in the three-way eutectic structure other than equiaxed dendrite Al primary crystal, Zn, except equiaxed dendrite Al primary crystal It is distributed unevenly distributed in the ternary eutectic organization. [0071] 　In contrast, as shown in FIG. 7, the plating layer of the present invention, Mg and Zn, are both distributed throughout the plating layer. Other, Al concentration (component element ratio of Al) of a cellular dendrites Al primary crystal, fine equiaxed dendrite Al primary crystal (center) and lower than the Al concentration of the petal-like Al primary crystal. [0072] 　Thus, the plating layer of the present invention, varies element distribution state and the plating layer of the comparative example. Then, the present inventors have found that elemental distribution of the plating layer is also considered to contribute to the improvement and maintenance of corrosion resistance. [0073] (Zn-Al-Mg-based ratio of the component elements of each tissue in the plating layer) 　next examined for the ratio of the component elements of each tissue in Zn-Al-Mg plated layer of the present invention (mass ratio). Table 1, in the plating layer of the present invention, 1A) cellular dendrites Al primary crystal of the principal axes of the cellular dendrite structure, 2A) central small equiaxed dendrite Al primary crystal, 3A) fine equiaxed dendrite Al primary crystal of the spindle, 4A) petaloid Al primary crystal, 5A) shows the measurement results of the ratio of component elements of the tissues other than Al primary crystal (mass ratio). 　Similarly, it was examined for the ratio of the component elements of the organization of the structures in Zn-Al-Mg plated layer of Comparative Example (weight ratio). Table 2, in the plating layer of Comparative Example, 1B) equiaxed tissue Al primary crystal of the spindle, the central portion of the Al primary crystal 2B) equiaxed structure, the root between the main shaft of the Al primary crystal 3B) equiaxed tissue tissues other than Al primary crystal located, 4B) equiaxed tissue tissues other than Al primary crystal located at the top between the main axis of the Al primary crystal, situated outside between the main shaft of the Al primary crystal 5B) equiaxed tissue the measurement results of the ratio of component elements other than the organization Al primary crystal (mass ratio) to. 　In Table 1 and Table 2, "-" indicates that below a measurement limit value, were treated as "0% by weight". [0074] 　Here, the ratio of the component elements (mass ratio), using a JSM Co. 7000F, by SEM-EDS, the acceleration voltage = 15V, was measured under the conditions of the electron beam diameter = 10 [mu] m. [0075] [Table 1] [0076] [Table 2] [0077] 　Unlike plated layer of comparative example, the plating layer of the present invention, except for small Si absolute amount is small variations in component element ratio of tissue for each structure. Further, in the plating layer of the present invention, component element ratio Al cellular dendrite Al primary crystal is lower than the center portion of the fine equiaxed dendrite Al primary crystal. [0078] 　That is, the component element ratio of the tissue of the plating layer of the present invention, the maximum mass ratio, Zn, Al, value obtained by dividing the difference between the maximum value and the average value of the ratio of the component elements of Mg in the average value, and Si value it is possible to following ranges. Note that these maximum value and the average value is a measurement point of said 1A) ~ 5B), the value calculated when measuring the ratio of the component elements. The value obtained by dividing the average value of the difference between the maximum value and the average value of the component element ratio of Zn is more than 20% (preferably 15% or less) the average difference between the average value and the maximum value of the component element ratio, Al a value obtained by dividing the 75% or less in value (preferably 60% or less) · Mg of the maximum value of the component element ratio between the average value and the difference between the value obtained by dividing the average value of 60% or less (preferably not more than 30%) , the maximum value of the component element ratio of Si below 0.2 wt% [0079] 　Then, the present inventors have found that in Zn-Al-Mg plated layer, Zn, Al, maximum value and a value obtained by dividing the difference between the average value by the average value of the ratio of the component elements of Mg, and a maximum value of Si a range from, are considered to contribute to the improvement and maintenance of corrosion resistance. [0080] (The present production of plated steel sheet of the present invention (forming of the plating layer)) 　plated steel sheet of the present invention, for example, prepared as follows. 　First, on at least one surface of the steel sheet (Motoita), plating the molten zinc comprising the component element. Plating molten zinc, for example, it is carried out by immersing the steel sheet in a plating bath of molten zinc. Next, by performing the wiping to remove excess molten zinc adhering to the steel sheet, the basis weight of the predetermined plating layer. Then, the plated steel sheet hot-dip zinc was cooled and solidified plating components, to form a plating layer. [0081] 　Then, in order to obtain a plated layer having the above structure, from the state in which the composition of the plating layer was uniformly melted, to a temperature change of the tissue Al primary crystal is eliminated, it is possible to rapidly cool. On the other hand, in order to a state of homogeneously melt the composition of the plating layer, if excessively raising the temperature, reacts with the metal of the composition of the base steel and the plating layer of the steel plate, the interface between the plated layer and the steel sheet to, Fe-Al alloy layer (e.g., Fe 2 Al 5 layer) is excessively formed, the corrosion resistance of the plated steel sheet may be deteriorated. [0082] 　In addition, the generation of cellular dendrite Al primary crystal (transition to cellular dendrites Al primary crystal Al primary crystal), the solidification rate of the Al primary crystal is affected. Specifically, a temperature gradient during Al primary crystal solidification, form is determined by the balance of the growth rate of the Al primary crystal organization. We, the generation of cellular dendrite Al primary crystal is strongly influenced by temperature gradients, some cellular dendrites Al primary crystal at a specific quenching conditions found that easily generated. 　Here, the temperature gradient indicates a temperature gradient in the solidification interface of the Al primary crystal, the temperature gradient is determined in relation to the latent heat of solidification and cooling (heat removal). Then, the temperature gradient is large, is that in a state that winning is greater heat removal than persistently latent heat of solidification. In other words, the temperature gradient during cooling is large, the overall heat transfer coefficient at the time of refrigerant [alpha: W / (m 2 · K)] may be'll enhanced. [0083] 　Therefore, in order to obtain a plated layer having the above structure, the plated steel sheet melted zinc (its surface), Al primary crystal temperature to initiate clotting + 30 ° C. or higher 520 ° C. or less of the temperature (cooling start temperature before) and then, at a cooling rate of up to a temperature from the temperature becomes 370 ° C. 500 ° C. / sec or more (preferably 800 ° C. / sec or higher 2000 ° C. / sec or less), and cooling time of overall heat transfer coefficient 1000 ~ 3000W / ( m 2 · K) (preferably ~ 3000W 2000 / (m 2 · K) it is preferred to carry out the cooling, such as a). Further, if the cooling conditions, the plating layer obtained, cellular dendrites Al primary crystal is generated by amorphous structure does not generate. 　3000W / (m 2 when · K) implementing the cooling in the cooling system of the overall heat transfer coefficient greater than, the amorphous phase is generated, the cellular dendrites Al primary crystal, fine equiaxed dendrite Al primary crystal, the ratio of the petaloid Al primary crystal well be decreases, amorphous structure has no particular crystalline structure, that dissolution of Mg component is promoted, because the corrosion resistance is remarkably lowered, which is not preferable. 　Note that the overall heat transfer coefficient, heat transfer surfaces (i.e., work rate required to change the 1 ℃ temperature per unit area of the surface of the plating layer of the plated steel sheet hot-dip zinc (W / (m 2 · K) ) means. 　it is also contemplated that fine equiaxed dendrite Al primary crystal and petals Al primary crystal is also formed by cooling substantially under the same overall coefficient of heat transfer. [0084] 　Then, to achieve the cooling of the above conditions, it submerged cooling such cooling submerged steel sheet (for example, steel sheet having a thickness of 0.5 ~ 4 mm) in water are preferred. Then, in the submerged cooling of the present invention, using an area of the film boiling from the transition boiling for heat transfer control. On the other hand, further as a method of increasing the cooling efficiency, to prevent low temperature (circulating cooling water of the aquarium, for example, chillers maintain a low temperature by low temperature) and the heat transfer inhibition by transition boiling to destroy the boiling film there is a method and the like. However, these methods, 3000W / (m in overall heat transfer coefficient 2 when · K) exceeds, as described above amorphous phase is produced, since the corrosion resistance is deteriorated to the contrary, a thick steel plate (e.g. when using the plate thickness 4mm beyond steel), or is used such as when the width direction of the steel sheet desired average cooling. A method of destroying a boiling film, there is a method of applying a water spray to the steel sheet in water, it is possible to implement the water temperature and water flow as the operation range. Further, the water temperature is preferably less than 10 ° C. greater than 95 ° C., water is preferably velocity component of the water flow impinging vertically on the steel sheet has a range of 100 m / s from 1 m / s. [0085] 　Furthermore, the overall heat transfer coefficient at the submerged cooling, a thermocouple welded and installed on the steel sheet, to calculate the amount of heat exchange from the temperature change and the specific heat property value of the steel sheet was measured by heating and cooling, the sheet passing speed, the plate width, based on the strip thickness, unit time, unit area, and is calculated as a moving amount of heat per unit temperature change. Cooling rate, the steel sheet temperature and time at the time of submersion, the temperature and time at which the steel sheet temperature is less than 100 ° C., calculated as a temperature difference per unit time. Time difference of the two points of time measured was about 0.01-0.10 seconds. [0086] 　When not using circulating water cooling (cooling tower, chiller, etc.), the water temperature is lowered to rise to the cooling rate to near 100 ° C., the corrosion resistance is deteriorated if less than 500 ° C. / sec. After Other rapid cooling method, the plated steel sheet molten zinc, which is Tsuban between the one or more metal roll pair water cooling (e.g. during three copper roll pairs) by internal circulation cooling water, air-water There is a roll / steam cooling method for cooling by blowing, it can be cooled about 400 ° C. / sec close to the cooling rate, but easily uneven cooling occurs, to produce a new problem that deformation of the steel sheet, the present invention it can not be said that is an effective method. [0087] 　Here, in the submerged cooling in the temperature range of the present invention occurs film boiling during submerged, is cooled in a stable state where the boiling film was present was carried out between the plating layer and the water of the steel sheet. That is, in the submerged cooling, large heat removal vaporization, continuously solidifying latent cooling while maintaining the state that the heat loss is superior to that performed, the overall heat transfer coefficient during cooling, for example, 2000 ~ 3000W / ( M 2 · K) and higher. Note that the overall heat transfer coefficient at the air-water cooling, for example 300 ~ 900 W / (m 2 a · K) or so, the overall heat transfer coefficient at the time of gas cooling, for example 0.99 ~ 400W / (m 2 is a · K) degrees . Therefore, in the submerged cooling, higher overall heat transfer coefficient during cooling, and cooling the cooling rate and the temperature gradient is large, are realized, plated steel sheet can be easily obtained with a plating layer having the tissue. [0088] 　On the other hand, a conventional cooling means, laminar flow water cooling, spray cooling, or the steam-water cooling, the film boiling is intermittently performed, also state that the heat removal is superior to latent heat of solidification becomes intermittent Summary it is not possible to increase the heat transfer coefficient sustained. Further, in the gas cooling, even lower the temperature of the gas, it persistently the overall heat transfer coefficient can not increase to make a state in which heat removal is superior to the solidification latent heat for heat extraction amount is small intermittent It can not be. [0089] 　The cooling rate and temperature gradient during cooling, the surface temperature of the plated steel sheet after cooling and before the start cooling measures, determined by the temperature analysis by calculation. In this case, the temperature of the plated steel sheet before cooling and measurement in the temperature of the base steel and the plating layer of the steel sheet are substantially constant temperature, the surface temperature of the plated steel sheet after cooling of the cellular dendrites Al primary crystal to a temperature which does not affect the generation measured in a sufficiently cooled location. However, it may be corrected by calculation. Furthermore, the overall heat transfer coefficient is also determined simultaneously by unsteady heat conduction analysis calculations. [0090] 　Further, in the state of the plating layer surface temperature higher than the same or plating bath temperature and plating bath temperature of the steel sheet before the start of cooling, the cooling is started, easily, temperature Al primary crystal to initiate clotting + 30 ° C. or higher 520 ℃ is preferred because it can implemented cooling from a temperature below. When carrying out this cooling, prior to cooling, electromagnetic induction heating, heating by combustion gases, it is possible to heat the steel plate by electrical heating or the like. [0091] 　Here, the cooling below 370 ° C., is not particularly limited. In less than 370 ° C. cooling, because the variation in the tissue of Al primary crystal is eliminated. In other words, the organization of Al primary crystal is determined depending on a start of cooling to 370 ° C.. However, for example, when in cooling of less than 370 ° C. cooling, MgZn between up to 336 ° C. from 370 ° C. 2 and additional precipitation, then, MgZn 2 becomes large particle size, decreases the corrosion resistance of the plated steel sheet there is a possibility. Therefore, the entire cooling process is preferably carried out at a cooling under the above conditions. [0092] 　Incidentally, plated steel sheet of the present invention, the interface between the plated layer and the steel sheet, alloy layer (e.g., Fe 2 Al 5 layer, etc. Fe-Al alloy layer) may but have a, Fe-Al-based sometimes the alloy layer is excessively generated by the drop in corrosion resistance and coating adhesion deterioration occurs. Therefore, plated steel sheet of the present invention, the interface between the plated layer and the steel sheet, it is preferable that no alloy layer. Example [0093] 　Hereinafter, the present invention will be described more specifically by way of Examples. However, these examples are not intended to limit the present invention. [0094] (Production of plated steel sheet) 　in accordance with various conditions shown in Tables 3 and 4, as the plating of the original sheet (steel sheet as a base material of the plated steel sheet), hot-rolled steel sheet having a thickness of 0.8 mm (carbon content: 0.2 mass %) it was carried out plating with. The processing of pre-plating, degreasing, pickling, is annealed, not performed special pretreatment particularly affect the effect of the present invention. While using the hot rolled steel sheet in the embodiment, normally used for plating, cold-rolled steel sheet annealing been cold-rolled steel plate or the like, no particular constraint is not as long as the steel sheet in the state suitable for plating. The thickness is, for example, if the steel sheet having a thickness of 0.5 ~ 4 mm, no problem. Further, in the embodiment, the plated directly without subjected Ni plating on the steel plate. However, although it is not necessarily to eliminate the Ni plating, it does not mean much required. [0095] 　After dipping the master plate 3 seconds in a molten zinc plating bath of a given component and temperature, per side 140 g / m by nitrogen wiping 2 was adjusted to basis weight of about plating layer. Thereafter, the ultrashort surface temperature (cooling temperature before) a predetermined temperature of the plating layer of the steel sheet, i.e., after the temperature of + 30 ° C. or higher 520 ° C. below the temperature at which Al primary crystal to initiate clotting, and the steel plate from the temperature rapidly cooling time up to a temperature below 370 ° C., to form a plating layer on the steel sheet. Through this process, No. 1 ~ No. Obtain each Zn-Al-Mg plated steel sheet 21. Note that the entire cooling process of the plating layer of the plated steel sheet was carried out according to various conditions shown in Table 4. [0096] 　In Table 3, the column of "Al primary crystal solidification temperature" of the components of the galvanizing bath (D), MgZn 2 shows the solidification temperature of the. In Table 3, column "impurities" indicates a portion of the detected impurities. 　In Table 4, in the column of the cooling process, denoted with "submerged cooling" indicates a cooling method of immersing the steel sheet in water 45 ° C. water temperature 35 ° C.. Water temperature in the submerged cooling, by circulating water, cooled in cooling tower, and a predetermined temperature by adjusting the circulating amount of water. The submerged cooling, using a region of the film boiling from the transition boiling for heat transfer control. 　Notation as "roll cooling + steam cooling", after Tsuban between three copper roll pairs steel sheet shows a roll / air-water cooling method of cooling by blowing steam. The roll / steam cooling method, during three copper roll pairs cooled by internal circulation cooling water, and strip passing the steel sheet at a high speed of about 2m / sec, to quench the very surface of the plated layer and the steel sheet plated to solidify the layer. Further third attach the air-water nozzle on the outlet side of the copper roll pair, blowing steam, prevents the plating layer by heat from the hot steel plate center part is highest melting, coagulation component of the plating layer fixed. 　Notation as "roll strong cooling + steam cooling" is, 5 ° C. ~ 10 ° C. The internal circulation cooling water in chiller cooled to (inlet side coolant temperature), shows a cooling method with increased cooling capacity. 　Notation as "submerged cooling (low water temperature, water spray)" is circulated and cooled by using the chiller, keeping the water temperature 5 ~ 10 ° C., and branches the circulating water, in water, a plate 50mm of distance shows a cooling method of blowing water flow vertically from the nozzle of each fifteen sides at one per 20L / min. 　Notation as "submerged cooling (high water temperature)", the water of the aquarium was used without being cooled, shows a cooling method that rises to 95 ° C.. [0097] 　Here, in the preparation of coated steel sheet, (in Table 4, indicated as "before-cooling temperature") rapid cooling prior to the plating layer surface temperature of the steel sheet equal to or bath temperature is higher than the bath temperature at the induction heating the heating was carried out. [0098] (Various measurements) 　for the plating layer of the produced plated steel sheet structure (Al primary crystal, tissue other than Al primary crystal) was measured according to the method described above. 　Further, the tissue for the plating layer of the plated steel sheet produced, the peak distribution of the X-ray diffraction spectrum using Cu-ray source, and identified by analyzing the SEM-EDS elemental distribution, material constituent of the tissues other than Al primary crystal It was confirmed. 　Further, the element distribution of the plating layer of the plated steel sheet produced, investigated and determined according to the method described above, Zn, Al, maximum value and a value obtained by dividing the difference between the average value by the average value of Mg, the maximum value of the Si It was. [0099] (Corrosion resistance evaluation) 　The evaluation of the corrosion resistance, by sampling from the plating layer of the plated steel sheet after cooling, performed in dry-wet combined cycle testing using 5% -NaCl (JASO test), the plating corrosion weight loss after 60 cycles investigated. The results were evaluated as follows. 　Note that the JASO test is that of JASO (Japanese Automotive Standards Organization) JASO M610 salt dry-wet cycle test stipulated by (equivalent to JIS H 8502). 　○: corrosion weight loss 20 g ≦ / m 2 　△: 20 g / m 2