Plated steel sheet having excellent degreasing properties and method for producing same

Abstract

The present invention relates to a magnesium-containing highly corrosion-resistant alloy-plated steel sheet, and relates to a plated steel sheet having excellent degreasing properties and a method for manufacturing the same.

Description

Technical Field

[0001] The present invention relates to a magnesium-containing highly corrosion-resistant alloy-coated steel sheet, and also to a coated steel sheet having excellent degreasing properties and a method for manufacturing the same. Background Art

[0002] When a galvanized steel sheet is exposed to a corrosive environment, zinc with a redox potential lower than that of iron will corrode first, thus having the sacrificial anti-corrosion property of inhibiting the corrosion of steel. In addition, the zinc in the coating forms a dense corrosion layer on the surface of the steel while oxidizing, isolating the steel from the oxidizing atmosphere, thereby improving the corrosion resistance of the steel. Due to the above-mentioned advantageous properties, the application range of galvanized steel sheets has been continuously expanding in recent years, covering building materials, household electrical appliances, and automotive steel sheets.

[0003] However, due to the increase in air pollution caused by the high degree of industrialization, the corrosive environment is gradually deteriorating, and due to strict regulations on resource and energy conservation, the demand for developing steel materials with more excellent corrosion resistance than existing galvanized steel sheets is increasing day by day.

[0004] To improve this problem, various studies are being conducted on the manufacturing technology of zinc alloy-based coated steel sheets with high corrosion resistance by further improving the corrosion resistance of steel by adding elements such as aluminum (Al) and magnesium (Mg) to the zinc plating bath. As a representative example, there is an Al-Mg-Zn-based highly corrosion-resistant alloy-coated steel sheet containing zinc (Zn), magnesium (Mg), and aluminum (Al).

[0005] However, in the case of such highly corrosion-resistant alloy-coated steel sheets, poor degreasing occurs after applying rust preventive oil, which becomes a problem in subsequent treatment processes such as phosphate treatment and Zr treatment. So far, no technology has been developed that can meet the high-end demand for excellent degreasing properties as an Al-Mg-Zn-based highly corrosion-resistant alloy-coated steel sheet.

[0006] [Prior Art Documents]

[0007] [Patent Documents]

[0008] (Patent Document 1) Korean Patent Publication No. 2013-0133358 Summary of the Invention

[0009] (I) Technical Problems to be Solved

[0010] An object of one aspect of the present invention is to provide a coated steel sheet having excellent degreasing properties and a method for manufacturing the same.

[0011] Alternatively, an object of another aspect of the present invention is to provide a coated steel sheet having excellent degreasing properties and high corrosion resistance, and a method for manufacturing the same.

[0012] The technical problems of the present invention are not limited to the above. Those skilled in the art to which the present invention pertains can easily understand the additional technical problems of the present invention based on the entire text of the specification of the present invention.

[0013] (II) Technical Solution

[0014] One aspect of the present invention provides a coated steel sheet, which includes: a base steel sheet; a surface coating provided on at least one surface of the base steel sheet; and an Al-Mg-Zn-based coating provided between the base steel sheet and the surface coating, wherein the surface coating is a metal coating composed of one or more selected from Fe, Zn, Al, and Si, or the surface coating is an aqueous coating containing one or more components selected from P, Zn, Mn, Mo, and B.

[0015] In addition, another aspect of the present invention provides a method for manufacturing a coated steel sheet, the manufacturing method including the following steps: immersing a base steel sheet in an Al-Mg-Zn-based plating bath to form an Al-Mg-Zn-based coating on the surface of the base steel sheet; and forming a surface coating on the surface of the Al-Mg-Zn-based coating, wherein in the step of forming the surface coating, a metal coating composed of one or more selected from Fe, Zn, Al, and Si is formed by one method selected from physical vapor deposition method, electroplating method, and electroless plating method using a substance composed of one or more selected from Fe, Zn, Al, and Si, or an aqueous coating is formed by coating a coating solution on the Al-Mg-Zn-based coating and then heating and drying, the coating solution containing: oxides, hydroxides, and water-soluble salts of one or more components selected from P, Zn, Mn, Mo, and B; and a solvent.

[0016] (III) Beneficial Effects

[0017] According to one aspect of the present invention, a coated steel sheet with excellent degreasing property and a method for manufacturing the same can be provided.

[0018] In addition, according to another aspect of the present invention, a coated steel sheet with excellent degreasing property and high corrosion resistance and a method for manufacturing the same can be provided.

[0019] The various beneficial advantages and effects of the present invention are not limited to the above, and the various beneficial advantages and effects of the present invention will be more easily understood during the process of describing the specific embodiments of the present invention. Best Embodiment

[0020] Hereinafter, the preferred embodiments of the present invention will be described. However, the embodiments of the present invention can be deformed into various other embodiments, and the scope of the present invention is not limited to the following embodiments. In addition, the embodiments of the present invention are provided to more completely describe the present invention to those skilled in the art.

[0021] As used in the specification, the meaning of "comprising" or "including" is used to specifically describe the composition and does not exclude the existence or addition of other components.

[0022] Unless otherwise defined, all terms, including technical and scientific terms used in this specification, have the same meaning as commonly understood by those skilled in the art. Terms defined in a dictionary are interpreted to conform to the meaning in the relevant technical literature and the currently disclosed content.

[0023] Hereinafter, a plated steel sheet according to one aspect of the present invention will be described in detail. In the present invention, unless otherwise defined, the content of each element is expressed in weight %.

[0024] Existing Al-Mg-Zn series plated steel sheets have more excellent corrosion resistance than Zn series plated steel sheets, but the Al-Mg-Zn series plating has a problem of poor degreasing property. Specifically, in the case of Al-Mg-Zn series plating, there are problems in subsequent chemical conversion treatment processes such as phosphate treatment and Zr treatment after applying rust preventive oil and poor degreasing.

[0025] It was confirmed that one of the reasons for this degreasing problem is that in order to improve corrosion resistance, magnesium (Mg) is added to the coating, and oxides generated by the strong oxygen affinity of Mg and surfactant components in the rust preventive oil are adsorbed, resulting in poor degreasing property.

[0026] Therefore, if direct contact between magnesium oxide and the rust preventive oil can be prevented, the degreasing problem of the high corrosion resistance alloy plated steel sheet can be solved. However, when applied to conventional automotive steel sheets, the contact between magnesium oxide and the rust preventive oil must be blocked by a method that does not affect subsequent processes such as phosphate treatment and Zr treatment.

[0027] Therefore, the inventors of the present invention conducted in-depth research to solve the above problems and found that by forming a surface coating on the surface of the Al-Mg-Zn series coating that can act as a barrier layer to prevent the interaction between the Mg component in the coating and the rust preventive oil, the above problems can be solved, thus completing the present invention. Hereinafter, the composition of the present invention will be specifically described.

[0028] The plated steel sheet according to one aspect of the present invention includes: a base steel sheet; a surface coating provided on at least one surface of the base steel sheet; and an Al-Mg-Zn series coating provided between the base steel sheet and the surface coating.

[0029] In the present invention, the type of the base steel plate is not particularly limited. For example, the base steel plate may be an Fe-based base steel plate used as a base steel plate for a general galvanized steel plate, that is, it may be a hot-rolled steel plate or a cold-rolled steel plate, but is not limited thereto. Alternatively, the base steel plate may be carbon steel, extra-low carbon steel, high manganese steel, stainless steel, etc. used as building materials, household appliance materials, or automotive materials. In addition, in the case of the carbon steel, extra-low carbon steel, medium-low carbon steel, low carbon steel, and carbon steel all exhibit similar effects, and there is no special limitation on the steel composition, so it is hardly affected by a large amount of added components such as Mn, Si, Ti, Nb, and B components in high-strength steel and ultra-high-strength steel. In addition, as an example of the base steel plate, it may include, by weight%: C: more than 0% and 0.18% or less, Si: more than 0% and 1.5% or less, Mn: 0.01-2.70%, P: more than 0% and 0.07% or less, S: more than 0% and 0.015% or less, Al: more than 0% and 0.5% or less, Nb: 0.06% or less (including 0%), Cr: 1.1% or less (including 0%), Ti: 0.06% or less (including 0%), B: 0.03% or less (including 0%), and the balance of Fe and other inevitable impurities. Or, as another example of the base steel plate, it may include, by weight%: C: more than 0% and 0.18% or less, Si: more than 0% and 1.5% or less, Mn: 0.01-2.70%, P: more than 0% and 0.07% or less, S: more than 0% and 0.015% or less, Al: more than 0% and 0.5% or less, Nb: more than 0% and 0.06% or less, Cr: more than 0% and 1.1% or less, Ti: more than 0% and 0.06% or less, B: more than 0% and 0.03% or less, and the balance of Fe and other inevitable impurities.

[0030] According to one aspect of the present invention, at least one surface of the base steel plate may be provided with the following surface coating. The surface coating may be formed only on one surface of the base steel plate, or may also be formed on both surfaces of the base steel plate.

[0031] In addition, according to one aspect of the present invention, an Al-Mg-Zn-based coating may be provided between the base steel plate and the surface coating. Although not particularly limited, in this specification, the Al-Mg-Zn-based coating refers to a coating containing Mg and Al but having Zn as the main component (that is, more than 50% by weight).

[0032] Although not particularly limited, according to one aspect of the present invention, by weight%, the Al-Mg-Zn-based coating may include: Mg: 0.1-15.0%, Al: 1.5-15.0%, and the balance of Zn and other inevitable impurities.

[0033] Mg: 0.1-15.0%

[0034] Magnesium (Mg) is an element that plays a role in improving the corrosion resistance of the coated steel sheet. To ensure the high corrosion resistance desired in the present invention, the content of Mg in the coating can be set to 0.1% or more. However, when the content of added Mg is too high, scum may be generated, so it can be set to 15.0% or less.

[0035] Al: 1.5 - 15.0%

[0036] Generally, when Mg is added, the effect of improving corrosion resistance is exerted. As the content of Mg increases, due to the oxidation of Mg, the generation of scum in the plating bath increases, so there is a problem that scum must be removed frequently. To solve this problem, 1.5% or more of Al can be added to the coating. However, to suppress scum, when too much Al is added, the melting point of the plating bath rises, and thus due to the too high operating temperature, problems caused by high-temperature operation may occur, for example, erosion of the plating bath structure and deformation of the steel, etc., and the content of Al can be 15.0% or less.

[0037] The balance of Zn and other unavoidable impurities

[0038] In addition to the composition of the above coating, the balance can be Zn and other unavoidable impurities. Unavoidable impurities can include any substances that may be undesirably mixed in the manufacturing process of conventional hot-dip galvanized steel sheets, and those skilled in the art can easily understand its meaning.

[0039] According to an embodiment of the present invention, the Al-Mg-Zn based coating may further contain any one or more selected from the following groups (a) to (h).

[0040] However, the elements in the following groups are not essential elements for solving the technical problems of the present invention, so the lower limit of their content is not limited. Therefore, even if not specifically mentioned below, the lower limit of the content of each element can be 0%.

[0041] (a) One or more of Si: 0.5% or less, Ni: 0.5% or less

[0042] (b) One or more of Ca: 1.0% or less, La: 0.1% or less, Ce: 0.1% or less, Y: 0.1% or less, Sr: 1.0% or less

[0043] (c) Ti: 0.1% or less

[0044] (d) W: 0.5% or less

[0045] (e) Cu: 2.0% or less

[0046] (f) One or more of Fe: 1% or less, Cr: 0.5% or less, Mn: 0.5% or less, V: 0.5% or less

[0047] (g) One or more of B: 0.1% or less, P: 0.1% or less

[0048] (h) One or more of Sn: 1% or less, Sb: 1% or less, Bi: 1% or less

[0049] (a) One or more of Si: 0.5% or less, Ni: 0.5% or less

[0050] Si has the effect of preventing Fe-Zn alloying by generating interfacial Mg2Si and can prevent the excessive formation of Fe-Al alloy phases. However, when the content of Si exceeds 0.5%, the melting point of the plating bath rises, and brittleness may increase due to the formation of too much Mg2Si. Ni has the effect of preventing Fe diffusion by generating Al-Ni alloy phases, but when the content of Ni exceeds 0.5%, there may be a problem of excessive increase in the cost of auxiliary materials.

[0051] (b) One or more of Ca: 1% or less, La: 0.1% or less, Ce: 0.1% or less, Y: 0.1% or less, Sr: 1% or less

[0052] Ca, La, Ce, Y, and Sr have the effect of preventing the oxidation of plating bath Mg by forming an oxide film. However, when their contents exceed 1%, 0.1%, 0.1%, 0.1%, and 1% respectively, there may be a problem of increased dross due to the increase in Ca oxide, and there may be a problem of reduced plating performance due to the increase in the viscosity of the plating bath for La, Ce, Y, and Sr.

[0053] (c) Ti: 0.1% or less

[0054] Ti acts as a nucleation point for Ti-Al intermetallic compounds and has the effect of refining the grains (spangle). However, when the content of Ti exceeds 0.1%, the melting point of the plating bath rises, and there is a problem of increased dross.

[0055] (d) W: 0.5% or less

[0056] W forms W oxide on the surface and has the effect of improving corrosion resistance. However, when the content of W exceeds 0.5%, there may be a problem of rising melting point of the plating bath.

[0057] (e) Cu: 2% or less

[0058] Cu forms an Al-Cu eutectic structure and has the effect of reducing the hardness of the coating. However, when the content of Cu exceeds 2%, there is a problem of coarsening of the spangle.

[0059] (f) One or more of Fe: 1% or less, Cr: 0.5% or less, Mn: 0.5% or less, V: 0.5% or less

[0060] Fe, Cr, Mn, and V have the effect of preventing electrode deterioration by suppressing the alloying of zinc and the welding electrode due to the fast liquid loss rate. However, when their contents exceed 1.0%, 0.5%, 0.5%, and 0.5% respectively, there may be a problem of excessive increase in the melting point of the plating bath.

[0061] (g) One or more of B: 0.1% or less, P: 0.1% or less

[0062] B and P have the effect of suppressing LME cracks in the welded part. However, when their contents exceed 0.1% respectively, there may be a problem of increased generation of dross.

[0063] (h) One or more of Sn: 1% or less, Sb: 1% or less, Bi: 1% or less

[0064] Sn, Sb, and Bi have the effect of homogenizing the zinc flower and improving the durability of the plating bath (pot) by reducing the plating bath temperature. However, when their contents exceed 1.0% respectively, there may be a problem of coarsening of the zinc flower.

[0065] In order to effectively exert the function of the above-mentioned barrier layer, the surface coating can be a metal coating or a water-based coating. The following will be described separately.

[0066] First, in order to effectively exert the function of the barrier layer of the metal coating to prevent the interaction between Mg in the coating and the rust preventive oil, the metal coating can be composed of one or more selected from Fe, Zn, Al, and Si. That is, since the metal coating is a barrier layer for preventing the interaction between Mg and the rust preventive oil, it is preferably free of Mg and can be composed of one or more selected from Fe, Zn, Al, and Si, or more preferably can be an Fe coating, a Zn coating, or an Al coating.

[0067] Although there is no particular limitation, according to one aspect of the present invention, the average thickness of the metal coating can be 10 - 3000 nm. As a barrier layer that effectively blocks the interaction between the oxide caused by Mg in the coating and the rust preventive oil, in order to effectively exert the function of the metal coating, the average thickness of the metal coating can be 10 nm or more. On the other hand, when the thickness of the metal coating is too thick, considering the coating time and the usage amount of the coating material, it may be disadvantageous in terms of economy, and the corrosion resistance may also be insufficient. Therefore, the upper limit of its average thickness can be set to 3000 nm.

[0068] In addition, in terms of further improving the above effects, the lower limit of the average thickness of the metal coating can be 20 nm, or the upper limit of the average thickness of the metal coating can be 1000 nm.

[0069] Although not particularly limited, according to one aspect of the present invention, the metal coating can satisfy the following relational expression 1.

[0070] [Relational expression 1]

[0071] 0.003 ≤ Ts / Tp ≤ 0.400

[0072] (In the relational expression 1, Tp represents the average thickness of the Al-Mg-Zn based plating layer, and Ts represents the average thickness of the metal coating.)

[0073] At this time, in the relational expression 1, as long as the units of Tp and Ts are the same, the units are not particularly limited.

[0074] Although not particularly limited, according to one aspect of the present invention, the metal coating can be formed by a method selected from physical vapor deposition, electroplating, and electroless plating using a substance composed of one or more selected from Fe, Zn, Al, and Si. However, as a preferred example, the metal coating can be formed by physical vapor deposition (PVD) sputtering method, whereby a thin metal coating with an average thickness in the range of 10 - 3000 nm can be easily formed.

[0075] According to one aspect of the present invention, as described above, by providing a metal coating on at least one surface of the Al-Mg-Zn based plating layer, not only can the interaction between Mg in the plating layer and the rust preventive oil be effectively prevented, but also subsequent chemical conversion treatments such as phosphate treatment or Zr treatment become possible.

[0076] In addition, in order for the above water-based coating to effectively function as a barrier layer for preventing the interaction between Mg in the plating layer and the rust preventive oil, the water-based coating can contain one or more components selected from P, Zn, Mn, Mo, and B. At this time, the water-based coating can refer to a coating having hydrophilicity. That is, as described below, it can refer to a coating that can be dissolved in hydrophilic solvents such as aqueous solutions and alkaline solutions, whereby the water-based coating can be stripped by treatment with the hydrophilic solvents such as aqueous solutions and alkaline solutions.

[0077] Although there is no particular limitation, according to one aspect of the present invention, the water-based coating can be formed by applying a coating solution onto the Al-Mg-Zn based plating and heating and drying it. The coating solution contains: oxides, hydroxides, and water-soluble salts of one or more components selected from P, Zn, Mn, Mo, and B; and a solvent. Specifically, the coating solution can be applied onto the Al-Mg-Zn based plating and then heated and dried at 80-100°C for less than 10 seconds (except 0 seconds) to form the water-based coating.

[0078] For example, the water-based coating can be formed by applying a coating solution onto the Al-Mg-Zn based plating and heating and drying it. The coating solution contains the boric acid-based oxides, hydroxides, and water-soluble salts, or contains phosphoric acid-based oxides, hydroxides, and water-soluble salts and a solvent.

[0079] Although there is no particular limitation, according to one aspect of the present invention, the water-based coating can contain one or more components selected from P and B, or, by weight%, the water-based coating can contain 5-45% of one or more components selected from P and B.

[0080] Alternatively, although there is no particular limitation, according to one aspect of the present invention, the water-based coating can contain: one or more components selected from P and B; and one or more components selected from Zn, Mn, and Mo.

[0081] Although there is no particular limitation, according to one aspect of the present invention, by weight%, the water-based coating can contain 5-45% of one or more components selected from P and B, and / or, by weight%, can contain 2.5-30.0% of one or more components selected from Zn, Mn, and Mo.

[0082] Although there is no particular limitation, according to one aspect of the present invention, the adhesion amount per side of the water-based coating can be 100.0-900.0 mg / m 2 . By making the adhesion amount per side of the water-based coating reach 100.0 mg / m 2 or more, the contact between the rust preventive oil and the plating can be effectively prevented, thereby ensuring good degreasing property. However, when the adhesion amount per side of the water-based coating exceeds 900.0 mg / m 2 , problems may occur in weldability or problems in economy may be caused by an increase in the amount of raw materials used.

[0083] Although there is no particular limitation, in terms of further improving the above effects, when the water-based coating contains P, B, and Mo, the adhesion amount per side can be 100.0-900.0 mg / m 2Similarly, when the water-based coating contains P, Mn, and Zn, the adhesion amount per side can be 100.0 - 900.0 mg / m 2 .

[0084] In addition, the water-based coating is a water-soluble film containing one or more components selected from P, Zn, Mn, Mo, and B, with a pH of 2 or more. The coating solution can be formed by the above method. In the coating solution, the amount of phosphoric acid or boric acid that reacts with the plating layer is 20% or less (except 0%). The water-based coating thus formed is a water-soluble coating and must be soluble in an aqueous solution or an alkaline solution for chemical conversion treatment in subsequent processes. The removal rate during dissolution can be 80% or more.

[0085] According to one aspect of the present invention, as described above, by providing a water-based coating on at least one side of the Al-Mg-Zn-based plating layer, not only can the interaction between Mg in the plating layer and the rust preventive oil be effectively prevented, but the water-based coating can also be demembraned in the water washing process or the degreasing process. Thus, after the degreasing process, by removing the above water-based coating through demembraning, a plated steel sheet using a demembraning type coating that is not affected by subsequent chemical conversion treatments such as phosphate treatment or Zr treatment can be provided.

[0086] A method for manufacturing a plated steel sheet according to another aspect of the present invention will be described.

[0087] The base steel sheet is immersed in an Al-Mg-Zn-based plating bath to form an Al-Mg-Zn-based plating layer on the surface of the base steel sheet. At this time, the composition and the content of each component of the Al-Mg-Zn-based plating bath are the same as those of the above Al-Mn-Zn-based plating layer. Therefore, the description of the reasons for adding each component and the reasons for limiting the content of the above plating layer can be equally applicable to the Al-Mg-Zn-based plating bath.

[0088] Next, a surface coating is formed on the surface of the Al-Mg-Zn-based plating layer.

[0089] When forming the surface coating, a substance composed of one or more selected from Fe, Zn, Al, and Si can be used, and a metal coating composed of one or more selected from Fe, Zn, Al, and Si can be formed by one method selected from physical vapor deposition method, electroplating method, and electroless plating method, or a coating solution can be coated on the Al-Mg-Zn-based plating layer and then heated and dried to form a water-based coating. The coating solution contains: oxides, hydroxides, and water-soluble salts of one or more components selected from P, Zn, Mn, Mo, and B; and a solvent. In addition, the solvent is a water-soluble solvent, and all conventional solvents in the technical field can be used, so there is no particular limitation thereto, and water, etc. can be typically exemplified.

[0090] At this time, the above description of the plated steel sheet is equally applicable to the said surface coating.

[0091] In addition, although not particularly limited, according to one aspect of the present invention, when forming the water-based coating, the coating solution is applied to the Al-Mg-Zn-based plating, and then heat-treated at 80-100 °C for less than 10 seconds (except 0 seconds) for heating and drying. Detailed implementation mode

[0092] (Example)

[0093] Hereinafter, the present invention will be described in more detail by way of examples. However, it should be noted that the following examples are only used to illustrate the present invention for more detailed description, and are not used to limit the scope of the rights of the present invention. This is because the scope of the rights of the present invention is determined by the content recorded in the claims and the content reasonably deduced therefrom.

[0094] (Experimental example 1)

[0095] An Al-Mg-Zn-based plating with an average thickness of 8 μm was formed on the surface of a base steel sheet. The Al-Mg-Zn-based plating consisted of 1.2% Mg, 1.7% Al, and the balance of Zn and other inevitable impurities. Then, on the surface of the Al-Mg-Zn-based plating, a metal coating as a surface coating was formed under the conditions recorded in Table 1 below by physical vapor deposition (PVD) sputtering method. At this time, as recorded in Table 1 below, test pieces with adjusted average thickness of the surface coating were manufactured by controlling the coating time.

[0096] Next, in order to evaluate the degreasing property, it was immersed in the 90EG rust preventive oil of Buhmwoo Company, and the oil-coated test piece was placed upright for 72 hours, and then degreased in the degreasing solution EC-90 of Japan's FATE Company for 90 seconds, so as to evaluate the water wettability of the test piece surface. When the water wettability of the surface was 80% or more and less than 90%, it was evaluated as "Δ", when the water wettability of the surface was 90% or more (including 100%), it was evaluated as "○", and in other cases it was evaluated as "X", and it is shown in Table 1 below.

[0097] In addition, in order to evaluate the phosphating property, each test piece was surface-adjusted and phosphated according to the standards of a conventional automobile company, and then the uniformity of the phosphate was evaluated. The case where it was uniformly formed was evaluated as "○", and the case where it was non-uniformly formed was evaluated as "X".

[0098] [Table 1]

[0099]

[0100] As can be seen from the results in Table 1, in the case of Invention Examples 1 to 8 where a metal coating is provided as the surface coating according to the present invention, compared with Comparative Examples 1 to 3, it was confirmed that the degreasing property was more excellent. In particular, in the case of Invention Examples 2 to 4 and Invention Examples 6 to 8 where the average thickness of the metal coating satisfied 20 nm or more, compared with Invention Examples 1 and 5, it was confirmed that the degreasing property was more excellent.

[0101] On the other hand, in the case of Comparative Example 1 where no surface coating was formed on the surface of the Al-Mg-Zn-based plating layer, it was confirmed that the degreasing property and the phosphate treatment property were very poor.

[0102] In addition, in the case of Comparative Examples 2 and 3 where a Ni metal layer was provided as the metal coating, although the thickness of the surface coating increased, the adsorption of the Al-Mg-Zn-based plating layer and the rust preventive oil was not prevented, so it was confirmed that the degreasing property deteriorated.

[0103] (Experimental Example 2)

[0104] Similar to Experimental Example 1, an Al-Mg-Zn-based plating layer was formed on the surface of the base steel plate. On the surface of the Al-Mg-Zn-based plating layer, in order to form an aqueous coating as the surface coating, an aqueous phosphoric acid-based solution 1 containing hypophosphorous acid solution, ethanol, zinc oxide and manganese and an aqueous boric acid-based solution 2 containing ammonium pentaborate, ammonium molybdate and ethanol were prepared. As recorded in Table 2 below, using each of the aqueous phosphoric acid-based solution 1 or the aqueous boric acid-based solution 2, on the surface of the Al-Mg-Zn-based plating layer, it was coated by roll coating with the coating amount recorded in Table 2 below and heat-dried to 80 °C within 10 seconds based on the surface temperature of the plated steel sheet, thereby forming an aqueous coating containing one or more components selected from P, Zn, Mn, Mo and B.

[0105] Then, the degreasing property and the phosphate treatment property were evaluated in the same manner as in Experimental Example 1 above and are shown in Table 2 below.

[0106] [Table 2]

[0107]

[0108] As can be seen from the results in Table 2, in the case of Invention Examples 9 to 18 where a water-based coating is provided as the surface coating according to the present invention, compared with Comparative Example 4, it was confirmed that one or more of the degreasing property and phosphate treatment property were excellent. In addition, in the case of Invention Examples 9 to 18, when treated with an aqueous solution or an alkaline solution, the water-based coating was removed (stripped), and the removal rate was confirmed to be 80% or more (including 100%). In addition, in the case of the plated steel sheets obtained from Invention Examples 9 to 18, it was confirmed that the water-based coating contained 5-45% by weight of one or more components selected from P and B, and 2.5-30.0% by weight of one or more components selected from Zn, Mn, and Mo.

[0109] Particularly, in Invention Examples 9 to 13 containing B, Mo, and an amine compound as the water-based coating, the adhesion amount per side satisfied 100.0-900.0 mg / m 2 In Invention Examples 10 to 13 compared with Invention Example 9, the contact between the rust preventive oil and the surface of the plating layer was prevented, and thus it was confirmed that the effect of improving the degreasing property was more excellent.

[0110] In addition, in Invention Examples 14 to 18 containing P, Mn, and Zn as the water-based coating, the adhesion amount per side satisfied 100.0-900.0 mg / m 2 In Invention Examples 16 to 18 compared with Invention Examples 14 and 15, the contact between the rust preventive oil and the surface of the plating layer was prevented, and thus it was confirmed that the effect of improving the degreasing property was more excellent.

[0111] On the other hand, in the case of Comparative Example 4 where no surface coating was formed on the surface of the Al-Mg-Zn-based plating layer, it was confirmed that the degreasing property and phosphate treatment property were very poor.

Claims

1. A coated steel sheet, comprising: A base steel sheet; A surface coating provided on at least one surface of the base steel sheet; And An Al-Mg-Zn based coating provided between the base steel sheet and the surface coating, wherein the surface coating is a metal coating composed of one or more selected from Fe, Zn, Al, and Si, or the surface coating is an aqueous coating containing one or more components selected from P, Zn, Mn, Mo, and B.

2. The coated steel sheet according to claim 1, wherein, By weight%, the Al-Mg-Zn based coating contains: Mg: 0.1 - 15.0%, Al: 1.5 - 15.0%, the balance of Zn and other inevitable impurities.

3. The plated steel sheet according to claim 2, wherein, The coating further contains any one or more selected from the following groups (a) to (h): (a) One or more of Si: 0.5% or less and Ni: 0.5% or less; (b) One or more of Ca: 1.0% or less, La: 0.1% or less, Ce: 0.1% or less, Y: 0.1% or less, Sr: 1.0% or less; (c) Ti: 0.1% or less; (d) W: 0.5% or less; (e) Cu: 2.0% or less; (f) One or more of Fe: 1.0% or less, Cr: 0.5% or less, Mn: 0.5% or less, V: 0.5% or less; (g) One or more of B: 0.1% or less and P: 0.1% or less; (h) One or more of Sn: 1.0% or less, Sb: 1.0% or less, Bi: 1.0% or less.

4. The coated steel sheet according to claim 1, wherein, The average thickness of the metal coating is 10 - 3000 nm.

5. The plated steel sheet according to claim 1, wherein, The metal coating satisfies the following relational expression 1, [Relational expression 1] 0.003 ≤ Ts / Tp ≤ 0.4 In the relational expression 1, Tp represents the average thickness of the Al-Mg-Zn based coating, and Ts represents the average thickness of the metal coating.

6. The plated steel sheet according to claim 1, wherein, The coating amount per side of the water-based coating is 100.0 - 900.0 mg / m 2 .

7. The plated steel sheet according to claim 1, wherein, The aqueous coating contains one or more components selected from P and B.

8. The plated steel sheet according to claim 1, wherein, By weight%, the aqueous coating contains 5 - 45% of one or more components selected from P and B.

9. The plated steel sheet according to claim 1, wherein, The aqueous coating includes: One or more components selected from P and B; and One or more components selected from Zn, Mn, and Mo.

10. The plated steel sheet according to claim 1, wherein, By weight%, the aqueous coating contains 2.5 - 30.0% of one or more components selected from Zn, Mn, and Mo.

11. The plated steel sheet according to claim 1, wherein, The metal coating is formed using a substance composed of one or more selected from Fe, Zn, Al, and Si, and by one method selected from physical vapor deposition method, electroplating method, and electroless plating method.

12. The plated steel sheet according to claim 1, wherein, The aqueous coating is formed by coating a coating solution on the Al-Mg-Zn based coating and heating and drying, The coating solution contains: oxides, hydroxides, and water-soluble salts of one or more components selected from P, Zn, Mn, Mo, and B; and a solvent.

13. The coated steel sheet according to claim 1, wherein, The water-based coating contains P, B and Mo, and the adhesion amount per side is 100.0 - 900.0 mg / m 2 .

14. The plated steel sheet according to claim 1, wherein, The water-based coating contains P, Mn, and Zn, and the adhesion amount per side is 100.0 - 900.0 mg / m 2 .

15. The plated steel sheet according to claim 1, wherein, When the aqueous coating is treated with an aqueous solution or an alkaline solution, the removal rate is 80% or more and includes 100%.

16. A method for manufacturing a coated steel sheet, comprising the following steps: Immersing a base steel sheet in an Al-Mg-Zn based plating bath to form an Al-Mg-Zn based coating on the surface of the base steel sheet; And A surface coating is formed on the surface of the Al-Mg-Zn series coating, wherein, in the step of forming the surface coating, a metal coating composed of one or more selected from Fe, Zn, Al, and Si is formed by using a substance composed of one or more selected from Fe, Zn, Al, and Si through a method selected from physical vapor deposition method, electroplating method, and electroless plating method, or a coating solution is coated on the Al-Mg-Zn series coating and then heated and dried to form an aqueous coating, and the coating solution contains: oxides, hydroxides, and water-soluble salts of one or more components selected from P, Zn, Mn, Mo, and B; and a solvent.

17. The method for manufacturing a plated steel sheet according to claim 16, wherein, The heat drying is carried out at 80-100 °C for heat treatment for less than 10 seconds and excluding 0 seconds.

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