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    • 专利摘要:
    GALVANIZED STEEL SHEET IN BLACK COLOR. The black galvanized steel sheet has a Zn coating layer that contains molten Al and Mg, containing Al in an amount of 1.0 to 22.0% by weight, containing Mg in an amount of 1.3 to 10 , 0% by mass and which has a black Zn oxide distributed in a lamellar pattern in the coating layer. Black Zn oxide is a Zn oxide derived from a Zn2Mg phase. The surface gloss of the Zn coating layer containing the molten Al and Mg has an L * value of 60 or less.
    公开号:BR112014026678B1
    申请号:R112014026678-6
    申请日:2012-06-29
    公开日:2020-11-24
    发明作者:Masaya Yamamoto；Tadashi Nakano；Hirofumi Taketsu
    申请人:Nisshin Steel Co., Ltd；
    IPC主号:
    专利说明:

    TECHNICAL FIELD
    [001] The present invention relates to a sheet of black galvanized steel sheet. BACKGROUND OF THE TECHNIQUE
    [002] In the field such as roofing materials and materials for the exterior of a building, appliances and automobiles, the needs for steel sheets that have a dark appearance from the design points of view etc. are increasing. The surface of a steel sheet can be darkened by applying a black coating material to the surface of a steel sheet to form a black coating film. In the field described above, however, coated steel sheets such as the galvanized Zn steel sheet containing Al and the galvanized Zn steel sheet containing Al and Mg in terms of corrosion resistance are used in many cases. The coated steel sheet has a metallic shiny surface with a silvery gray color. Consequently, to achieve a dark appearance of quality design by applying a black coating material, a thick coating film is required to hide the color of the coated steel sheet, which results in high coating costs. In addition, the thick coating film makes resistance welding as well as spot welding impossible, which is another disadvantage.
    [003] As a process to hide the metallic silver-gray luster of a coated steel sheet without the formation of a black coating film, a process has been proposed for the darkening of a coating layer itself (for example, with reference to PTL 1). PTL 1 describes a process for the formation of a thin black layer on the surface of the coating layer by insufflation of water vapor at a high temperature on a galvanized Zn steel sheet containing Al for 24 hours or more. The black galvanized steel sheet according to PTL 1 has a coating layer layer that contains elements to accelerate the darkening such as Mg, Cu and Bi. According to the specification, however, with an element content to accelerate blackening of more than 1%, the blackening acceleration effect on the contrary decreases due to the suppression of Zn oxidation. CITATION LISTING PATENT LITERATURE PTL 1
    [004] Open Japanese Patent Application No. SHO 64-56881 SUMMARY OF THE INVENTION TECHNICAL PROBLEM
    [005] The sheet of galvanized steel sheet in black according to PTL 1 presents a problem that a thick black layer cannot be formed due to the reduction of adhesion, since the blackening in the entire total thickness of a layer of layer of coating causes the coating layer to weaken. Consequently, the black galvanized sheet steel sheet has no resistance for powerful processing, as the scratches to be formed on the surface of the coating layer by processing ruin the appearance of the surface due to the exposure of the silver gray color of the coating layer itself. In addition, the black galvanized steel sheet according to PTL 1 requires a long time for blackening treatment, which is another problem.
    [006] An objective of the present invention is to provide a sheet of galvanized steel sheet in black color that has excellent retention of black appearance after processing and can be produced by blackening treatment in a short period of time. SOLUTION TO THE PROBLEM
    [007] The present inventors have discovered that the problem can be solved by contacting an original sheet of the galvanized Zn steel sheet containing Al and Mg that includes 1.0 to 22.0% by weight of Al and 1.3 to 10 , 0% by mass of Mg, which includes Zn2Mg phases distributed in a coating layer, with water vapor in a closed container and carried out further investigations to complete the present invention.
    [008] More specifically, the present invention relates to the following black galvanized steel sheet metal: [1] A black galvanized steel sheet metal that includes a layer of galvanized Zn steel sheet containing Al and Mg containing 1.0 to 22.0% by weight of Al and 1.3 to 10.0% by weight of Mg, with a black Zn oxide distributed in the coating layer, the galvanized Zn steel sheet containing Al and Mg which has a luminosity on the surface represented by the L * value of 60 or less. [2] The black galvanized steel sheet according to [1], in which the black Zn oxide is distributed in a lamellar form in the layer of the galvanized Zn steel sheet containing Al and Mg. [3] The black galvanized steel sheet according to [1] or [2], in which the Zn oxide is a Zn oxide derived from a Zn2Mg phase. [4] The black galvanized steel sheet according to any of [1] to [3], which also includes an inorganic coating film on the galvanized Zn layer containing Al and Mg [5] The steel sheet galvanized in black according to [4], in which the inorganic coating film includes one or more compounds selected from the group consisting of a metal oxide for a valve, a metal oxoate for a valve, a metal hydroxide for a valve, a metal phosphate for valve and a metal fluoride for valve. [6] The black galvanized steel sheet according to [5], where the valve metal is one or more metals selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, W, Si and Al. [7] The galvanized steel sheet in black according to any of [1] to [3], which also includes a film for coating organic resin in the galvanized Zn layer containing Al and Mg. [8] The black galvanized steel sheet according to [7], in which an organic resin consisting of the coating film of the organic resin is urethane-based resin obtained by the reaction of polyols consisting of a polyol based of ether and in an ester-based polyol with polyisocyanate, a proportion of the ether-based polyol in the polyols being 5 to 30% by weight. [9] The black galvanized steel sheet according to [8], in which the organic resin coating film also includes a polyvalent phenol. [10] The black galvanized steel sheet according to any of [7] to [9], in which the organic resin coating film includes a lubricant. [11] The black galvanized steel sheet according to any of [7] to [10], in which the organic resin coating film includes one or more compounds selected from the group consisting of a metal oxide for valve, metal valve oxoate, metal valve hydroxide, metal valve phosphate and metal valve fluoride. [12] The black galvanized steel sheet according to [11], where the metal for the valve is one or more metals selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, W, Si and Al. [13] The black galvanized steel sheet according to any of [7] to [12] in which the organic resin coating film is a laminate layer or a coating layer. [14] The black galvanized steel sheet according to any of [7] to [13], where the organic resin coating film is a transparent coating film. ADVANTAGE EFFECTS OF THE INVENTION
    [009] According to the present invention, a black galvanized steel sheet that has a black appearance with quality design and excellent retention of black appearance after processing can be produced by blackening treatment in a short period of time. The black galvanized steel sheet produced by the present invention is excellent in design, maintenance of appearance, ability to be molded by a press and corrosion resistance and can be applied as a coated steel sheet, for example, roofing materials and materials to the outside of a building, appliances and automobiles. BRIEF DESCRIPTION OF THE DRAWINGS
    [0010] Figure 1A is an image obtained in an optical microscope of the cross section of the coating layer of a galvanized Zn steel sheet containing Al and Mg after treatment with water vapor;
    [0011] Figure 1B is a scanning image with an electron microscope of a cross section in the same visual field as in Figure 1A;
    [0012] Figure 2A is a scanning image with an optical microscope of the region indicated by the dotted lines in Figure 1A and Figure 1B;
    [0013] Figure 2B is a scanning image with an electron microscope of the region indicated by dotted lines in Figure 1A and Figure 1B;
    [0014] Figure 2C is a schematic diagram that illustrates a microstructure of the region indicated in Figure 2A and Figure 2B;
    [0015] Figure 3 illustrates images of element distribution in the coating layer layer of a galvanized Zn steel sheet containing Al and Mg before and after treatment with water vapor;
    [0016] Figure 4A is an electron rotation resonance (ESR) spectrum for a powder sample prepared on the surface of a Zn2Mg plate before treatment with water vapor;
    [0017] Figure 4B is an electron rotation resonance (ESR) spectrum for a powder sample prepared on the surface of a Zn2Mg plate after treatment with water vapor;
    [0018] Figure 5 is a graph that illustrates the results of an XPS analysis of the coating layer of a galvanized Zn steel sheet containing Al and Mg before and after treatment with water vapor;
    [0019] Figure 6A is a photograph that illustrates the surface of a galvanized Zn steel sheet containing Al and Mg after treatment with water vapor in an open system and
    [0020] Figure 6B is a photograph illustrating the surface of a galvanized Zn steel sheet containing Al and Mg after treatment with water vapor in a closed system. DESCRIPTION OF THE MODALITIES
    [0021] 1. Galvanized steel sheet in black color
    [0022] The black galvanized steel sheet of the present invention includes a steel substrate and a galvanized Zn coating layer containing Al and Mg (hereinafter also referred to as "coating layer"). The black galvanized steel sheet of the present invention can also include an inorganic coating film or an organic resin film for coating on the coating layer.
    [0023] The black galvanized steel sheet of the present invention has a characteristic that includes: 1) a black Zn oxide that is distributed in the coating layer and 2) the surface of the coating layer that has a luminosity value L * 60 or less (preferably 40 or less, more preferably 35 or less). The luminosity (L * value) of the coating layer surface is measured by spectral reflectance with a color difference spectroscopic meter, according to JIS K 5600.
    [0024] [Steel substrate]
    [0025] The type of steel substrate is not specifically limited. Examples of the steel substrate for use include a low carbon steel sheet steel, medium carbon steel, high carbon steel or steel alloy. When it is necessary that the steel substrate has a good ability to be molded in a press, it is preferred to use a steel sheet for deep drawing made, for example, of steel with the addition of low carbon Ti or of steel with addition of low carbon Nb. Alternatively, a high-strength steel plate can be used with the addition of P, Si and Mn etc.
    [0026] [Galvanized Zn coating layer containing Al and Mg]
    [0027] As the original sheet for black galvanized steel sheet of the present invention, a galvanized Zn steel sheet containing Al and Mg is used, which includes a layer of galvanized Zn containing Al and Mg which contains 1.0 up to 22.0% by weight of Al and 1.3 to 10.0% by weight of Mg, with Zn2Mg phases distributed in the coating layer. More preferably, a galvanized Zn steel sheet containing Al and Mg is used, including a galvanized Zn coating layer containing Al and Mg which also contains a single Al phase as the microstructure of the coating layer. The term "single Al phase" means an Al phase that has no eutectic structure such as Al phase "with Zn in solid state. The only Al phase is, for example, a primary Al". Al and Mg, that is, elements for improving the corrosion resistance of a Zn-based steel plate, are essential elements for blackening the present invention as described below. With an Mg content or an Al content less than the lower limit in the range, sufficient corrosion resistance cannot be achieved. In contrast, with a content greater than the upper limit, a beautiful coated steel sheet cannot be obtained due to excessive generation of oxides (waste) on the surface of the coating bath during the production of the coated steel sheet.
    [0028] The galvanized Zn coating layer containing Al and Mg which has the composition described above includes a ternary eutectic structure of AI / Zn / Zn2Mg. When the cross section of the coating layer is observed, for example, as in Figures 2A to 2C, the proportion of the AI / Zn / Zn2Mg ternary eutectic structure in the entire cross section, however, is different depending on a coating composition. In the ternary Zn-AI-Mg system, the eutectic composition includes approximately 4 wt% Al and approximately 3 wt% Mg. In the case of a coating composition close to the eutectic composition, the AI / Zn / Zn2Mg ternary eutectic structure is consequently a phase that has the largest area in the coating cross section, having an area ratio of approximately 80%. The area ratio, however, decreases when the composition was due to a eutectic composition, so that the phase other than the AI / Zn / ZnzMg ternary eutectic structure may have the largest area ratio in some cases. Depending on a coating composition, the galvanized Zn coating layer containing Al and Mg also includes a primary Al ". A schematic cross-sectional view of the coating layer that has a coating composition with an Al concentration of 6.0 % by mass, an Mg concentration of 3.0% by mass and a remainder of Zn are illustrated, for example, in Figure 2C. In the coating layer, the ternary eutectic structure of AI / Zn / ZnsMg (represented as "Zn phase" and "Zn2Mg phase (which include fine Al phase and Zn phase) in the drawing) and the primary crystal structure of Al (represented as" primary "Al" in the drawing). The primary "Al" can be clearly discriminated against the Al phase of the ternary eutectic under observation under a microscope. Depending on a coating composition, the primary crystal of the coating layer can be formed from a Zn phase, a Zn2Mg phase or an Mg2Si phase, instead of the Al phase.
    [0029] In Figure 2C, each of the phases (an Al phase, a Zn phase and a Zn2Mg phase) of a ternary AI / Zn / ZtoMg eutectic structure is of irregular size and shape, having a lamellar structure . The lamellar structure means a state that has phases alternately arranged to form the eutectic structure, respectively.
    [0030] The Al phase in the ternary eutectic structure is derived from an Al "phase (a solid solution of Al with dissolved Zn, containing a small amount of Mg) at high temperature in a ternary phase diagram in Al-equilibrium Zn-Mg. The Al "phase at high temperature usually forms in thin phases of Al phases and in thin phases of Zn, which are separated from each other, at normal temperature. The thin phases of Al phases and the thin phases of Zn are dispersed in a phase of ZnzMg (In Figure 2C, the thin phases of Al and the thin phases of Zn dispersed in a phase of Zn2Mg are not shown in the drawing). The Zn phase in the ternary eutectic structure is a solid solution of Zn that dissolves a small amount of Al and also dissolves Mg in some cases. The ZnzMg phase in the ternary eutectic structure is an intermetallic compound phase that exists in the vicinity of a point corresponding to approximately 84% by weight of Zn in the binary equilibrium phase diagram of the Zn-Mg system. As shown in Figure 2C, the Zn2Mg phases are distributed in a lamellar form throughout the coating layer. Although the Zn2Mg phase distributed in the coating layer of the galvanized Zn steel sheet containing Al and Mg, that is, the black galvanized steel sheet of the present invention, has been described so far in the case of a phase to form the AI / Zn / Zn2Mg ternary eutectic structure, the phase can emerge to form a binary AI / Zn2Mg eutectic structure or a binary Zn / Zn2Mg eutectic structure in the coating layer of the present invention in some cases. Even in the case of a Zn2Mg phase derived from them, the present invention can achieve the effect as long as the Zn2Mg phase forms an eutectic structure. Depending on the cooling conditions and the coating composition of the coating layer, the ZnnMg2 phase may exist in the coating layer in some cases. The presence of the ZnnMg2 phase in the coating layer of the galvanized Zn steel sheet containing Al and Mg, that is, the original black galvanized steel sheet plate of the present invention, does not cause any problem. The present invention can obtain the advantageous effect, even in the case, for example, where a part of the AI / Zn / Zn2Mg ternary eutectic structure is an AI / Zn / ZnnMg2 ternary eutectic structure.
    [0031] In this specification, oxides and hydrated oxides are collectively referred to as an oxide. In this specification, the content of each component in the coating layer is represented by the percentage of the mass of each metal component contained in the coating layer divided by the total mass of metals contained in the coating layer. Consequently, the mass of oxygen and water contained in the oxides is not included in the components in the coating layer. When there is no elution of the metal components during the treatment with water vapor, the content of each component in the coating layer is therefore kept constant before and after the treatment with water vapor.
    [0032] The galvanized Zn coating layer containing Al and Mg for use may include, for example, from 1.0 to 22.0% by weight of Al, from 1.3 to 10.0% by weight of Mg, and the rest of Zn and unavoidable impurities. To improve the adhesion between the steel substrate and the coating layer, Si, which can suppress the growth of the Al-Fe alloy layer at the interface between the steel substrate and the coating layer, can be added to the coating layer in the range of 0.005% by mass to 2.0% by mass. A Si concentration greater than 2.0% by mass can cause the generation of Si-based oxides to block blackening on the surface of the coating layer. Ti, B, a Ti-B alloy, a compound containing Ti or a compound containing B can be added to the coating layer. The amount of the compounds to be added is preferably adjusted such that the Ti content is from 0.001% by weight to 0.1% by weight and the content of B is from 0.0005% by weight to 0.045% by weight. An excessive amount of Ti or B addition can cause precipitates to grow on the coating layer. Incidentally, the addition of Ti, B, a Ti-B alloy, a compound containing Ti or a compound containing B to the coating layer hardly affects blackening by treatment with water vapor.
    [0033] The thickness of the coating layer is not specifically limited, preferably in the range of 3 to 100 pm. With a coating layer thickness of less than 3 pm, scratches easily reach the Durant steel substrate and manipulation, which can decrease maintenance of black appearance and resistance to corrosion. In contrast, with a coating layer thickness greater than 100 pm, the coating layer can detach from the steel substrate in a processed part due to the difference in ductility between the coating layer and the compressed steel substrate.
    [0034] [Black oxides]
    [0035] The black galvanized steel sheet of the present invention contains black Zn oxides distributed in the coating layer (refer to Figure 1 A, Figure 2A and Figure 3). The term "in the coating layer" includes both the surface of the coating layer and the interior of the layer.
    [0036] Figure 1A is an image of an optical microscope showing a cross section of the layer applied as a coating of the black galvanized steel sheet of the present invention. Figure 1B is an image of a scanning electron microscope of a cross section in the same visual field as in Figure 1A. Figure 2A is an image of an optical microscope of the region indicated by the dotted lines in Figure 1A and Figure 1B. Figure 2B is an image of a scanning electron microscope for the region indicated by the dotted lines in Figure 1A and Figure 1B. Figure 2C is a schematic diagram that illustrates the microstructure of the region indicated in Figure 2A and Figure 2B. In Figure 2C, for convenience of description, the oxidized metal region is classified in the same group as before oxidation (a Zn phase, a Zn2Mg phase and a primary Al) in the drawing.
    [0037] As illustrated in the drawings, the black galvanized steel sheet of the present invention includes black Zn oxides derived from the Zn2Mg phases. The black Zn oxides are distributed in a lamellar form (black Al oxides derived from a primary Al "need to be described below). The mechanism for the generation of black Zn oxides can be simulated as follows.
    [0038] The galvanized Zn steel sheet containing Al and Mg is in contact with water vapor in a closed container, so that the oxide layer on the surface of the coating layer first reacts with H2O to form hydrated oxide, while H2O passing through the oxide layer reacts with the metal in the coating layer. On this occasion, the Zn contained in the Zn2Mg phase to constitute the ternary eutectic structure is preferentially oxidized. As time passes, the oxidation of Zn contained in the Zn2Mg phase proceeds towards the depth of the coating layer. Under a water vapor atmosphere with low oxygen potential, Mg in the vicinity of Zn oxides, which has a high reactivity with oxygen, steals Zn oxides from oxygen in order to form Mg oxides. Zn oxides are believed to vary to oxygen-deficient oxides with a non-stoichiometric composition (for example, ZnOi-x). In this way, the generation of oxygen-deficient oxide allows light to be trapped at the level of the defect, so that the oxide has a black appearance. The black galvanized steel sheet of the present invention, therefore, allows the acceleration of blackening when the Mg content in the coating layer increases, which is different from the black PTL 1 galvanized steel sheet. On the other hand, the oxidation reaction of Zn contained in a Zn phase proceeds slowly, so that most of the Zn remains as a metal. As a result, the coating layer of a black galvanized steel sheet obtained by the present invention includes the microstructure of black Zn oxides derived from the Zn2Mg phases. The black Zn oxides are distributed in a lamellar form. Depending on a coating composition and the cooling conditions of the coating layer, ZnnMg2 phases may also exist in the coating layer in some cases. In this case, the Zn contained in the ZnnMg2 phase is also oxidized and the Mg in the circumference is stolen from oxygen, in order to form oxygen-deficient Zn oxides that have a black color.
    [0039] In the case of a coating layer that has primary Al crystals, black Zn oxides develop within the coating layer in a shorter period of time. Al has higher reactivity with H2O compared to Zn and Mg. As a result, Al metal that comes in contact with water vapor at high temperature quickly forms oxides. After the Al contained in the primary "Al" is rapidly oxidized, the oxidation of the Zn contained in the Zn2Mg phase located there proceeds towards the depth of the coating layer. passage "to accelerate the oxidation of Al within the coating layer. As a result, the presence of a single Al phase such as primary Al "in the coating layer allows the formation of black Zn oxides in the coating layer over a shorter period of time. It is assumed that Al in a eutectic ternary also functions as a "passageway" to accelerate the oxidation of Zn. With reference to Figure 2A, it is shown that the depth at which black Zn oxides exist is different between a region that has the primary Al "and a region that does not has primary "Al. As also shown in Figure 2A, the primary" Al has a blackish appearance, since the Zn dissolved in the solid solution state in the primary "Al is oxidized and the oxidized Zn allows oxygen to be stolen by Al at the circumference of in order to form ZnOi-x.
    [0040] In the black galvanized steel sheet described in PTL 1, the surface of a coating layer is only blackened due to the generation of ZnOi-x needle crystals. In contrast, on the black galvanized steel sheet of the present invention, a black oxide layer is formed on the surface of the black Zn oxide coating layer which is distributed within the coating layer, based on the reaction mechanism described above. . Consequently, the black galvanized steel sheet of the present invention can maintain the black appearance even when the coating layer is scratched in processing. The blackened oxides inside the coating layer can be confirmed by observation with an optical microscope of a cross section of the coating layer (with reference to Figure 1A and Figure 2A) or by amalgam of the metals Zn, Al and Mg in the coating layer with saturated HgCh solution to remove and collect only oxides. The interior of black oxides in a coated layer may be blackened or alternatively the surface may be blackened only.
    [0041] Figure 4A is an electron rotation resonance (ESR) spectrum for a powder sample prepared from the surface of a ZnsMg plate before treatment with water vapor. Figure 4B is an electron rotation resonance (ESR) spectrum for a powder sample prepared from the surface of a Zn2Mg plate after treatment with water vapor. The Zn2Mg plate after treatment with water vapor has a black appearance.
    [0042] With reference to Figure 4A, no ESR spectrum is observed from Zn2Mg. In contrast, with reference to Figure 4B, six large peaks are observed. From the peak positions, it is discovered that Zn2Mg after treatment with water vapor has electrons not paired with a nuclear rotation of 5/2. The presence of unpaired electrons with a nuclear rotation of 5/2 means the presence of defective crystal structure. From the results presented in Figure 4B, it was discovered that the Zn2Mg plate that has a black appearance after treatment with water vapor includes oxides with oxygen deficiency. It is also suggested that the steam treatment of the coating layer containing Zn2Mg generates blackened oxides with Zn oxygen deficiency as in the present invention.
    [0043] Figure 5 is a graph illustrating results of X-ray photoelectron spectroscopy (XPS) analysis of the coating layer of a galvanized Zn steel sheet containing Al and Mg before and after water vapor treatment . The cross sections of the coating layer before and after the water vapor treatment were exposed by an oblique cut to inspect the binding state of Zn, Al and Mg in a region with a diameter of 10 pm approximately in the center of the coating layer. coating. As a result, it was confirmed that the oxides (oxides and hydrated oxides) of the respective elements were generated by treatment with water vapor as shown in Figure 5.
    [0044] [Inorganic coating film and organic resin film for coating]
    [0045] The coating layer surface of the black galvanized steel sheet of the present invention can be applied with an inorganic coating film or with an organic resin film for coating. The inorganic coating film and the organic resin coating film improve the corrosion resistance and abrasion resistance (maintaining the black appearance) of a black galvanized steel sheet.
    [0046] (Inorganic coating film)
    [0047] The inorganic coating film preferably includes one or more compounds (hereinafter referred to as "valve metal compound") selected from the group consisting of a valve metal oxide, a valve metal oxoate, a hydroxide metal for valve, metal phosphate for valve and metal fluoride for valve. The inclusion of a metal valve compound reduces an environmental load and provides an excellent barrier function. Valve metal means a metal whose oxide exhibits high insulation resistance. Examples of the valve metal include one or more metals selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, W, Si, and Al. A known compound can be used as the valve metal compound.
    [0048] The inclusion of a soluble metal fluoride for valve in an inorganic coating film can confer a self-repair function. The metal fluoride for valve dissolved in moisture in the atmosphere forms oxides or hydroxides that have low solubility, reprecipitation on the exposed steel plate of the defective regions in a coating film in order to bury the defective regions. For the inclusion of soluble metal fluoride for valve in an inorganic coating film, a soluble metal fluoride for valve can be added to the inorganic material for coating or a soluble fluoride such as (NH4) F can be added in addition to a compound of metal for valve.
    [0049] The inorganic coating film may also include a soluble or poorly soluble metal phosphate or a complex phosphate. The soluble phosphate eluted from the inorganic coating film to the defective regions in a coating film reacts with the metal of a coated steel plate to form an insoluble phosphate, which complements the metal self-repair function for the valve conferred by the soluble fluoride . The poorly soluble phosphate is dispersed in the inorganic coating film in order to improve the resistance of the coating film. Examples of the metal contained in the soluble metal phosphate or in the complex phosphate include an alkali metal, an alkaline earth metal and Mn. Examples of poorly soluble metal phosphate or complex phosphate include Al, Ti, Zr, Hf and Zn.
    [0050] (Film for organic resin coating)
    [0051] The organic resin to constitute the coating film of the organic resin can be a urethane-based resin, an epoxy-based resin, an olefin-based resin, a styrene-based resin, a resin-based resin polyester, an acrylic-based resin, a fluorine-based resin, a combination of these resins or a copolymer or a modified product of these resins. The use of these organic resins that have flexibility avoids the occurrence of cracks during the formation of a galvanized steel sheet in black, improving resistance to corrosion. In addition, the metal valve compounds included in the organic resin film can be dispersed in the organic resin film (organic resin matrix), as described below.
    [0052] Preferably the organic resin coating film includes a lubricant. The inclusion of a lubricant reduces the friction between a mold and the surface of a coated steel sheet during processing such as pressing so that the abrasion of the coated steel sheet can be suppressed (improved resistance to abrasion). The type of lubricant is not specifically limited and can be selected from known lubricants. Examples of lubricants include an organic wax such as a fluorine-based wax, a polyethylene-based wax and a styrene-based wax and an inorganic lubricant such as molybdenum disulfide and talc.
    [0053] Similar to an inorganic coating film, the organic resin coating film preferably includes the valve metal compounds described above. The inclusion of a metal valve compound reduces an environmental load and provides excellent barrier function.
    [0054] Similar to an inorganic coating film, the organic resin coating film may also include a soluble or poorly soluble metal phosphate or a complex phosphate. The soluble phosphate eluted from the organic coating film to the defective regions in a coating film reacts with the metal of a coated steel plate to form an insoluble phosphate, complementing the self-repairing function of the metal for the valve conferred by the soluble fluoride. The poorly soluble metal phosphate is dispersed in the organic coating film in order to improve the resistance of the coating film.
    [0055] The organic resin coating film that includes a metal valve compound and a phosphate usually allows the formation of a reaction layer at the interface between a coated steel sheet and the organic resin coating film. The reaction layer at the interface is a dense layer formed of zinc fluoride, zinc phosphate and metal valve fluoride or a phosphate which are products of the reaction of a fluoride or phosphate contained in an organic material for coating with metals contained in the coated steel plate or a valve metal. The reaction layer at the interface has an excellent ability to block the environment, preventing corrosive components in the atmosphere from reaching the coated steel plate. Meanwhile, the organic resin coating film includes particles of metal oxide for valve, metal hydroxide for valve, metal fluoride for valve and phosphate, which are dispersed in an organic resin matrix. Since the metal oxide particles for the valve are dispersed three-dimensionally in an organic resin matrix, corrosive components such as moisture passing through the organic resin matrix can be captured. As a result, the organic resin coating film substantially reduces the corrosive components that reach the reaction layer at the interface. Due to the coating film of the organic resin and the reaction layer at the interface, excellent anti-corrosion can be achieved.
    [0056] The organic resin coating film can be, for example, a urethane-based coating film that contains urethane-based resin that has excellent flexibility. The urethane-based resin to form the film for coating urethane-based resin can be obtained by reacting polyol with polyisocyanate. In the case of black water treatment after formation of the urethane-based resin coating film, the polyol for use preferably includes a combination of an ether-based polyol (polyol that has an ether bond) and an ester-based polyol (polyol that has an ester bond) at a predetermined ratio.
    [0057] A film for coating urethane-based resin formed only from ester-based polyol, as the polyol allows ester bonds in the urethane-based resin to be hydrolyzed by water vapor, so that resistance to corrosion cannot be sufficiently improved. On the other hand, a film for coating urethane-based resin formed only of ester-based polyol, since the polyol has insufficient adhesion to a coated steel sheet, so that the corrosion resistance cannot be sufficiently improved. In contrast, the present inventors have found that the use of the combination of an ether-based polyol and an ester-based polyol at a predetermined ratio dramatically improves the corrosion resistance of a coated steel sheet, making effective use of the advantages of both an ether-based polyol as well as an ester-based polyol and complementing the disadvantages with each other. The effect of the urethane-based resin coating film to improve corrosion resistance can thus be maintained even when treated with water vapor to impart a black color (described below) after the formation of the resin coating film on urethane base. Thus, a black galvanized steel sheet can be produced, which has black color and excellent resistance to corrosion.
    [0058] The type of the ether-based polyol is not specifically limited and can be selected appropriately from those known. Examples of the ether-based polyol include polyethylene glycol, polypropylene glycol and a straight chain polyalkylene polyol such as an ethylene oxide or propylene oxide glycerin adduct.
    [0059] The type of the ester-based polyol is also not specifically limited and can be selected appropriately from known ones. The ester-based polyol for use may, for example, be a linear polyester having a hydroxyl group in a molecular chain that is obtained by reacting dibasic acid with a low molecular weight polyol. Examples of dibasic acid include adipic acid, azelaic acid, dodecanedioic acid, dimer acid, isophthalic acid, hexahydro phthalic anhydride, terephthalic acid, dimethyl terephthalate, itaconic acid, fumaric acid, maleic anhydride and esters of each of the acids.
    [0060] The ratio of the ether-based polyol to polyol formed from a combination of an ether-based polyol and an ester-based polyol is preferably in the range of 5 to 30% by weight. The proportion of the ether-based polyol less than 5% by weight results in an excessively increased proportion of the ester-based polyol, so that the urethane-based resin is easily hydrolyzed. Consequently, corrosion resistance may not be sufficiently improved. On the other hand, the proportion of the ether-based polyol greater than 30% by weight results in an excessively increased proportion of the ether-based polyol, so that adhesion to a coated steel sheet is reduced. Consequently, corrosion resistance may not be sufficiently improved.
    [0061] The type of polyisocyanate is not specifically limited and can be selected appropriately from known ones. The polyisocyanate for use can be, for example, a polyisocyanate compound that has an aromatic ring. Examples of polyisocyanate compounds that have an aromatic ring include hexamethylethylene diisocyanate, o-, m-, or p-phenylene diisocyanate, 2, 4- or 2,6-tolylene diisocyanate 2, 4- or 2,6-tolylene isocyanate having a hydrogenated aromatic ring, 4'-4'-diphenylmethane diisocyanate, 3'-3'-dimethyl-4,4-biphenylene diisocyanate, ω , ω'-diisocyanate-1,4-dimethylbenzene, and ω, ω'-diisocyanate-1,3-dimethylbenzene. These can be used alone or in combination of two or more.
    [0062] Preferably the urethane-based resin coating film also includes a polyvalent phenol. A film for coating urethane-based resin that includes a polyvalent phenol allows the formation of a layer of polyvalent phenol concentrated at the interface between a coated steel sheet and the film for coating urethane-based resin in order to obtain a strong adhesion between them. Consequently, the blend of polyvalent phenol in the urethane-based resin coating film also improves the corrosion resistance of the urethane-based resin coating film.
    [0063] The type of polyvalent phenol is not specifically limited and can be appropriately selected from known ones. Examples of the polyvalent phenol include tannic acid, gallic acid, hydroquinone, catechol and floroglucinol. The amount of polyvalent phenol mixed in the urethane-based resin coating film is preferably in the range of 0.2 to 30% by weight. An amount of the mixed polyvalent phenol less than 0.2 mass% has insufficient effect of the polyvalent phenol. On the other hand, with an amount of the mixed polyvalent phenol greater than 30% by mass, the stability of the coating material can be reduced.
    [0064] The organic resin coating film can be a coating layer or a laminate layer. The organic resin coating film is preferably a transparent coating film to take advantage of the black appearance of the black galvanized steel sheet.
    [0065] The black galvanized steel sheet of the present invention includes black oxides to impart black color not only to the surface of a coating layer, but also inside. Consequently, the black galvanized steel sheet of the present invention can maintain the black appearance even when the surface is scraped, showing excellent retention of the black appearance.
    [0066] The black galvanized steel sheet of the present invention includes black oxides to impart the black color that are dispersed in a coating layer without the formation of a coating film. As a result, the black galvanized steel sheet of the present invention has excellent press-molding ability without reducing the adhesion of the coating layer. Of course, the black galvanized steel sheet of the present invention also has excellent corrosion resistance similar to that of a normal galvanized Zn steel sheet containing Al and Mg.
    [0067] The black galvanized steel sheet of the present invention does not have a coating film, to which a weld point so similar to a normal galvanized Zn steel sheet containing Al and Mg can be applied.
    [0068] The process for producing the present invention is not specifically limited and the black galvanized steel sheet of the present invention can be produced, for example, by the following process.
    [0069] 2. Process of black galvanized steel sheet
    [0070] The production process of a black galvanized steel sheet of the present invention includes: 1) a first stage of preparing a galvanized Zn steel sheet containing Al and Mg and 2) a second contact stage of a galvanized Zn steel plate containing Al and Mg with water vapor in a closed container. The process may also include: 3) a third step of forming an inorganic coating film or an organic resin coating film on the surface of the galvanized Zn steel sheet containing Al and Mg, before or after the second step as an optional step.
    [0071] [First stage]
    [0072] In the first stage, the galvanized Zn steel sheet containing Al and Mg is prepared.
    [0073] The galvanized Zn steel sheet containing Al and Mg can be produced by galvanization using an alloy coating bath that includes, for example, 1.0 to 22.0% by weight of Al, 1, 3 to 10.0% by weight of Mg and the remainder substantially of Zn. The coating layer formed from 1.0 to 22.0% by weight of Al, 1.3 to 10.0% by weight of Mg and the rest of Zn and unavoidable impurities, with Z ^ Mg phases distributed in the layer of coating can thus be formed. To the alloy coating bath, Si, Ti, B, a Ti-B alloy, a compound containing Ti or a compound containing B can be added. The galvanized Zn steel sheet containing Al and Mg can be produced using, for example, a coating bath at a temperature of 430 ° C, with an air cooling process after the coating application at a rate average cooling of 11 ° C / s from the bath temperature for coating application to the solidification temperature of the coating layer.
    [0074] [Second stage]
    [0075] In a second stage, the coated steel sheet prepared in the first stage is in contact with the water vapor in a closed container, so that the coated layer is blackened. The process allows the luminosity (L 'value) of the coating surface layer to be reduced to 60 or less (preferably 40 or less, more preferably 35 or less). The luminosity (L 'value) of a coating layer surface is measured with a color difference spectroscopic meter.
    [0076] In the second stage, the presence of oxygen in the atmosphere for treatment with water vapor prevents the coating layer from being sufficiently blackened. It is assumed that the treatment with water vapor in an oxygen-rich atmosphere allows the basic zinc and aluminum carbonate to show a gray color in the surface layer to be more preferably formed compared to the oxides with Zn oxygen deficiency that have black color. In the second stage, therefore, it is necessary to reduce the concentration of oxygen in the atmosphere (partial pressure of oxygen) for treatment with water vapor. More specifically, the oxygen concentration in the water vapor treatment is preferably 13% or less. The process for decreasing the oxygen concentration in the atmosphere is not specifically limited. For example, the water vapor concentration (relative humidity) can be increased, the air in a container can be replaced with an inert gas, or the air in a container can be removed with a vacuum pump. In any case, it is necessary that the treatment with steam is carried out in a closed container.
    [0077] In the production process of a black galvanized steel sheet described in PTL 1, water vapor at a high temperature is sprayed on the surface of a coated steel sheet. Consequently, it is believed that the steam treatment is carried out in an open system whose oxygen concentration cannot be adjusted. The coating layer, however, cannot be sufficiently blackened by the water vapor treatment of the galvanized Zn steel sheet containing Al and Mg prepared in step 1 in an open system whose oxygen concentration cannot be adjusted. Figure 6A and Figure 6B are photographs illustrating the results of water vapor treatment of a galvanized Zn steel sheet containing Al and Mg that has a coating composition with an Al concentration of 6.0% by weight , a Mg concentration of 3.0% by weight and the rest of Zn. Figure 6A is a photograph illustrating the galvanized Zn steel sheet containing Al and Mg after spraying with water vapor at 98 ° C for 60 hours in an open system with an oxygen concentration greater than 13% (value L *: 62). Figure 6B is a photograph illustrating the galvanized Zn steel sheet containing Al and Mg after contact with water vapor at 140 ° C for 4 hours in a closed system with an oxygen concentration of 13% or less (value of L *: 32). The photographs indicate that it is necessary that the treatment with water vapor be carried out in a closed system whose oxygen concentration can be adjusted for sufficient blackening of the galvanized Zn layer containing Al and Mg.
    [0078] (Treatment temperature)
    [0079] The temperature for the treatment with water vapor is preferably in the range of 50 ° C or higher and 350 ° C or lower. In the case of a temperature for treatment with water vapor below 50 ° C, productivity is decreased due to a slow blackening rate. More preferably, the temperature for the treatment with water vapor is 100 ° C or higher, as the oxygen concentration in the atmosphere can be easily decreased when the water is heated to 100 ° C or higher in a closed container. having a pressure in the container of 1 atmospheric pressure or higher. In contrast, in the case of a temperature for treatment with water vapor above 350 ° C, control is difficult due to an extremely high blackening rate. In addition, not only is a large appliance required for processing, but also an extended total processing time that includes the time required to increase and decrease the temperature, which is impractical. Consequently, a temperature for the treatment with water vapor in the range of 105 ° C or higher and 200 ° C or lower is particularly preferred, from the point of view of removing oxygen in the atmosphere and controlling the blackening rate. .
    [0080] When a temperature of less than 100 ° C is required for treatment with water vapor, an inert gas at atmospheric or higher pressure may be contained in the container in order to prevent the air from being mixed. The type of inert gas is not specifically limited as long as it does not involve the blackening reaction. Examples of the inert gas include Ar, N2, He, Ne, Kr and Xe. Among these, Ar, N2 and He are preferred, being available at low cost. Alternatively, the steam treatment can be carried out after removing air from the container by a vacuum pump or similar.
    [0081] (Relative humidity)
    [0082] In the treatment with water vapor, the relative humidity of water vapor is preferably in the range of 30% or more and 100% or less, more preferably in the range of 30% or more and less than 100 %. A relative humidity of water vapor less than 30% reduces productivity due to a low blackening rate. A relative humidity of 100% water vapor can easily cause defects in appearance due to the adhesion of dew condensation water to the surface of a coated steel sheet.
    [0083] The processing time for 0 water vapor treatment can be adjusted appropriately depending on the conditions for water vapor treatment (temperature, relative humidity, pressure and the like), the amount of Al and Mg in the water layer. coating and the necessary brightness.
    [0084] (Preheating)
    [0085] Before treatment with water vapor, the coated steel sheet can be heated to form ZnnMg2 starting from Zn2Mg in the coating layer, so that the time for treatment with water vapor to obtain a black appearance of the layer coating can be abbreviated. The heating temperature of the coated steel sheet is preferably in the range of 150 to 350 ° C. A heating temperature less than 150 ° C prolongs the processing time to form ZnnMg2 starting from Zn2Mg by preheating, so that the advantage of shortening the treatment time with water vapor cannot be obtained. In contrast, although a heating temperature higher than 350 ° C allows the change from Zn2Mg to ZnnMg2 in a short period of time, further reaction progress can form a coating layer that has less resistance to corrosion due to the separation of each of the phases with progress of the variation in the state of the coating layer, so that the preheating cannot be easily controlled. The processing time for preheating can be appropriately adjusted depending on the processing temperature and the amount of Al and Mg in the coating layer. Preheating can typically be carried out at 250 ° C for approximately 2 hours.
    [0086] Water vapor treatment can be applied to any of a coated steel plate wound in a spiral shape wound in a coil shape, a flat coated steel plate before processing and a coated steel plate after molding or welding.
    [0087] [Optional step]
    [0088] In an optional step performed optionally before or after the second step, an inorganic coating film or an organic resin coating film is formed on the surface of a galvanized Zn steel sheet containing Al and Mg.
    [0089] The inorganic coating film can be formed by a known process. For example, an organic coating material that contains a valve metal can be applied to the surface of a galvanized Zn steel sheet containing Al and Mg before or after contact with water vapor and then dried without washing with water. Examples of the application process include a roller coating process, a rotary coating process and a spray coating process. In the case of adding a metal valve compound to an inorganic coating material, an organic acid that has a chelating function can be added to the inorganic coating material so that the metal valve compound can exist stably in the inorganic material for coating. Examples of organic acid include tannic acid, tartaric acid, citric acid, oxalic acid, malonic acid, lactic acid and acetic acid.
    [0090] An organic resin coating film can also be formed by a known process. In the case of an organic resin coating film formed, for example, from a coating layer, an organic coating material containing an organic resin can be applied and a metal valve can be applied to the surface of a steel sheet. Galvanized Zn containing Al and Mg before or after contact with water vapor and then dried without washing with water. Examples of the application process include a roller coating process, a rotary coating process and a spray coating process. In the case of adding a metal valve compound to an organic coating material, an organic acid that has a chelating function can be added to the organic coating material so that the metal valve compound can exist stably in the organic material for coating. In the case of application of an organic coating material that contains an organic resin, a metal valve compound, a fluoride and a phosphate on the surface, a coated steel sheet, a coating film (reaction layer at the interface) that includes a product of the reaction of negative inorganic ions such as fluorine ions and phosphorus ions with metals contained in the coated steel sheet or a valve metal is preferably formed and densely formed on the surface of the coated steel sheet, on which is formed a organic resin coating film that includes dispersed particles of metal oxide for valves, metal hydroxides for valves, metal fluorides for valves and phosphates. In contrast, in the case of the organic resin coating film formed from a laminate layer, an organic resin film containing a valve metal or the like can be laminated on the surface of a coated steel sheet.
    [0091] In the case of forming a film for coating organic resin on the surface of a galvanized Zn steel sheet containing Al and Mg before the contact of the galvanized Zn steel sheet containing Al and Mg with water vapor, the The organic resin coating film is preferably the urethane-based resin coating film. The urethane-based resin coating film formed from polyol that includes a combination of an ether-based polyol and an ester-based polyol at a predetermined ratio can maintain the effect to improve corrosion resistance even when treated with water vapor. A black galvanized steel sheet that has a black color and excellent resistance to corrosion can therefore be produced, even when the second stage is performed after any stage.
    [0092] According to the procedures described above, the coating layer can be blackened to produce a black galvanized steel sheet excellent in retaining the black appearance and being able to be formed in a press.
    [0093] The production process of the present invention uses water vapor for blackening, so that the galvanized steel sheet in black color can be produced without placing a load on the environment.
    [0094] Examples
    [0095] The following examples also illustrate the present invention, however the scope of the present invention is not limited to the examples.
    [0096] [Example 1]
    [0097] The galvanized Zn steel sheet containing Al and Mg which has a coating layer with a thickness of 3 to 100 pm was prepared starting from an SPCC substrate with a thickness of the plate of 1.2 mm. The composition of the coating bath (concentration of Zn, Al and Mg) was changed to prepare 20 species of coated steel sheets, each of which had a coating layer with a different composition and a different thickness. The composition of the coating bath and the thickness of the coating layer for each of the 20 species of prepared coated steel sheets are shown in Table 1. The composition of the coating bath and the composition coating layer are the same. [Table 1]

    [0098] A cross section of the coating layer was observed by a scanning electron microscope and analyzed by X-ray diffraction to identify phases for each of the coated steel sheets Nos. 1 to 16. As a result, the AI / Zn / Zn2Mg ternary eutectic structure was discovered in any of the coating textures. A primary Al crystal was also discovered in the texture of the Nos coating. 2 to 5. The primary crystal of coated steel sheets No. 1 and Nos. 7 to 9 was Zn and the primary crystal of the coated steel plate No. 6 was from Zn2Mg. The AI / Zn / Zn2Mg ternary eutectic structure was discovered only on coated steel plate No. 10. In contrast, the AI / Zn / Zn2Mg ternary eutectic, the primary Zn crystal and a binary Zn / Zn2Mg eutectic structure were found on coated steel plate No. 17. The AI / Zn / Zn2Mg ternary eutectic structure was found on each of the Nos coated steel sheets. 18 to 20. The primary crystal was from Al nos Nos. 18 and 19 and the Zn2Mg phase at No. 20.
    [0099] The prepared coated steel sheet was placed in an apparatus for treatment with high humidity at high temperature and high pressure (obtained by Hisaka Works, Ltd.) and the coating layer was put in contact with water vapor under the conditions presented in Table 2.
    [00100] Figure 1A is an image of an optical microscope of a cross section of the coated steel sheet layer after treatment with water vapor in Example 21. Figure 1B is a scanning electron microscope image of a section transversal in the same visual field as in Figure 1A. Figure 2A is an image of an optical microscope of the region indicated by dotted lines in Figure 1A and Figure 1B. Figure 2B is a scanning electron microscope image of the region indicated by the dotted lines in Figure 1A and Figure 1B. Figure 2C is a schematic diagram that illustrates the microstructure of the region indicated in Figure 2A and Figure 2B. In Figure 2C, for convenience of description, the oxidized metal region is also classified in the same group as before oxidation (a Zn phase, a Zn2Mg phase and a primary "Al" in the drawing. As illustrated in the photographs, the phase of Zn2Mg distributed in a lamellar form is blackened It was observed that in each of the coating layers of the steel sheets coated in other Examples (Examples 1 to 20 and 22 to 23), the Zn2Mg phases distributed in a lamellar form were also blackened inside the coating layer.
    [00101] In Figure 1A, the blackened part has a depth of approximately 8 pm, so it was confirmed that the blackening reached a deeper layer in the coating layer. In other Examples, the blackening also reached a deeper layer of the coated steel sheet. To examine the adhesion of the black galvanized steel sheet after processing, a 180 degree bending test was also carried out for each coated steel sheet after treatment with water vapor (Examples 1 to 23). In the 180-degree bending test, a specimen cut out of each of the coated steel sheets was flexed to 180 degrees (3 t) and a cellophane tape peeling test was performed for the folded part. As a result, peeling was not found for anyone in Examples 1 to 23. It was therefore shown that the black galvanized steel sheet of the present invention has excellent adhesion even when processed. It was also confirmed that the Zn2Mg phases dispersed in the coating layer in Comparative Examples 1 to 4 were blackened.
    [00102] Figure 3 illustrates images of element distribution of the coated steel plate before and after treatment with water vapor in Example 20 (coated steel plate No. 13) analyzed by electron probe micro analyzer (EPMA) . In the top row, the cross sections of the coated steel sheet No. 13 are shown before the steam treatment and in the bottom row, the cross sections of the coated steel sheet are shown after the steam treatment in the Example 20. The visual field in the photographs is different between before and after the treatment with water vapor. "SEI" represents secondary electronic images, "Zn" represents images of Zn distribution, "Al" represents images of Al distribution, "Mg" represents images of Mg distribution and "O" represents images of O distribution. , it was found that the Zn contained in the primary Al "and Zn contained in the Zn2Mg phase were mainly oxidized. In steel sheets coated in other Examples (Examples 1 to 19 and 21 to 23), the Zn contained in the Zn2Mg phase and the Zn contained in the primary Al "were also oxidized. On the other hand, also in Comparative Examples 1 to 4, O (oxygen) was distributed after the treatment with water vapor and it was confirmed that the Zn contained in Al "and the Zn contained in the Zn2Mg phase were oxidized.
    [00103] The luminosity (L 'value) of the coating layer surface was measured for each of the coated steel sheets after treatment with water vapor (Examples 1 to 23 and Comparative Examples 1 to 4) by spectral reflectance with a spectroscopic color difference meter (TC-1800, obtained by Tokyo Denshoku Co. Ltd.), according to JIS K 5600. The measurement conditions are presented below: Optical conditions: d / 8 ° method (optical system double-beam) Visual field: 2 degrees Measurement method: reflectometry Standard light: C Color system: CIELAB Wavelength measurement: 380 to 780 nm Wavelength range measurement: 5 nm Spectroscope: 1,200 diffraction grid / mm Lighting: halogen lamp (voltage: 12 V, power: 50 W, duration: 2,000 hours) Measurement area: diameter = 7.25 mm Detection element: photomultiplier (R928 obtained by Hamamatsu Photonics KK) Reflectance: 0 at 150% Temperature measurement: 23 ° C Standard plate: white
    [00104] For each of the coated steel sheets after treatment with water vapor (Examples 1 to 23 and Comparative Examples 1 to 4), which have an L * value of 35 or less was rated as "A", more than 35 and 40 or less than "B", more than 40 and 60 or less like "C" and more than 60 like "D".
    [00105] Corrosion resistance was assessed for each of the coated steel sheets after treatment with water vapor (Examples 1 to 23 and Comparative Examples 1 to 4). After sealing the end faces of a specimen (150 mm long and 70 mm wide) cut out of each of the coated steel sheets, the specimen was subjected to repeated cycles that include a salt water spray stage , a drying step and a wetting step in one cycle (8 hours). The assessment was made based on the number of cycles when the proportion of red rusted area reached 5%. In the salt water spraying stage, a 5% aqueous solution of NaCI at 35 ° C was sprayed on the same specimen for 2 hours. In the drying step, the specimen was left to rest for 4 hours in an environment at an atmospheric temperature of 60 ° C and a relative humidity of 30%. In the wetting stage, the specimen was left to stand for 2 hours in an environment at an atmospheric temperature of 50 ° C and a relative humidity of 95%. The specimen that requires more than 120 cycles for a proportion of red rusty area to reach 5% was rated as "A", more than 70 cycles and 120 or less as "B" and 70 cycles or less as "D" ".
    [00106] The luminosity and the results of the corrosion resistance test for the surface of the coating layer of each of the coated steel sheets after treatment with water vapor are shown in Table 2. [Table 2]

    [00107] As shown in Table 2, the steel sheets coated in Comparative Examples 1 and 3 had a coating layer with reduced corrosion resistance due to the Al or Mg content in the coating layer beyond the appropriate range. The steel sheets coated in Comparative Examples 2 and 4 were coated beautifully, as the excessive generation of oxides (waste) on the surface of the coating bath during the production of the coated steel sheet causes the adhesion of the waste to the surface of the coating layer .
    [00108] The results proved that the black galvanized steel sheet of the present invention has a high degree of black color, which is excellent for corrosion resistance and for retaining the black appearance after processing.
    [00109] [Example 2]
    [00110] A steel plate immersed in liquid Al and the galvanized Zn steel plate containing Al and Mg which has a coating layer with a thickness of 10 pm was prepared starting from an SPCC substrate with a thickness of the sheet of 1.2 mm. The composition of the coating bath (concentration of Zn, Al, Mg, Si, Ti and B) was varied to prepare 35 types of coated steel sheets, each of which had a coating layer with a different composition. The composition of the coating bath and the thickness of the coating layer for each of the 35 types of prepared coated steel sheet are shown in Table 3. The composition of the coating bath and the composition of the coating layer are the same. [Table 3]

    [00111] The prepared coated steel sheet was placed in an apparatus for treatment with high humidity at high temperature and high pressure and the coating layer was put in contact with water vapor under the conditions presented in Table 4.
    [00112] The cross section of the coating layer was observed for each of the coated steel sheets after treatment with water vapor (Examples 24 to 58) with an optical microscope. It was observed that the Zn2Mg phases distributed in the coating layer were blackened even inside the coating layer.
    [00113] The luminosity (L * value) of the coating layer surface was measured for each of the coated steel sheets after treatment with water vapor (Examples 24 to 58) with an electroscope color difference meter. Corrosion resistance testing was also carried out for each of the coated steel sheets after treatment with water vapor (Examples 24 to 58). The luminosity measurement and the corrosion resistance testing were carried out in the same way as in Example 1. The luminosity and corrosion resistance testing results for the surface of the coating layer of each of the coated steel sheets after treatment with water vapor are shown in Table 4. [Table 4]

    [00114] As shown in Table 4, the steel sheets coated in Examples 24 to 58 were sufficiently blackened and had good results in corrosion resistance of the coating layer. A 180 degree bending test was also carried out for each of the coated steel sheets after treatment with water vapor (Examples 24 to 58).
    [00115] In the 180-degree bending test, a specimen cut out of each of the coated steel sheets was flexed to 180 degrees (3 t) and a cellophane strip stripping test was performed for the folded part. As a result, peeling was not found for anyone in Examples 24 to 58.
    [00116] The results proved that the black galvanized steel sheet of the present invention has a high degree of black color, which is excellent for corrosion resistance and for retaining the black appearance after processing.
    [00117] [Example 3]
    [00118] A coated steel plate No. 36 or 52 in Table 3 was coated with an inorganic liquid for chemical treatment presented in Table 5 and placed in an electric oven without washing with water in order to be heated and dried under conditions so that the temperature of the plate reached 120 ° C. Consequently, an inorganic coating film was formed on the surface of the coated steel sheet. [Table 5]

    [00119] The prepared coated steel sheet that has the inorganic coating film was placed in an apparatus for treatment with high humidity at high temperature and high pressure and the coating layer was put in contact with water vapor under the conditions presented in Tables 6 and 7.
    [00120] A cross section of the coating layer was observed for each of the coated steel sheets after treatment with water vapor (Examples 59 to 90) with an optical microscope. It was observed that the ZnsMg phases distributed in a lamellar form mainly in the ternary eutectic structure were blackened. It was confirmed that the ZnzMg phases partially crystallized phases and the ZnaMg phases of the AI / Zn2Mg binary eutectic were also blackened.
    [00121] The luminosity (L * value) of the coating layer surface was measured for each of the coated steel sheets after treatment with water vapor (Examples 59 to 90) with an electroscopic color difference meter. same as in Example 1. Corrosion resistance testing was also carried out for each of the coated steel sheets after treatment with water vapor (Examples 59 to 90). In testing for corrosion resistance, the aqueous solution of NaCI at 35 ° C was sprayed onto the specimen for 12 hours in accordance with JIS Z 2371. The specimen with the proportion of white rusty area after spraying 0% was rated as "A", more than 0% and less than 5% as "B", 5% or more and less than 10% as "C" and 10% or more as "D".
    [00122] The luminosity and the results of the corrosion resistance test for the surface of the coating layer of each of the coated steel sheets after treatment with water vapor are presented in Tables 6 and 7. [Table 6]
    [Table 7]

    [00123] By Tables 6 and 7, it has been proved that the corrosion resistance of a black steel sheet can be further improved by the formation of the inorganic coating film. A 180 degree bending test was also carried out for each of the coated steel sheets after treatment with water vapor (Examples 59 to 90). In the bending test at 180 degrees, a specimen cut out of each of the coated steel sheets was bent to 180 degrees (3 t) and the peeling test with cellophane tape was performed for the flexed part. As a result, peeling was not found for anyone in Examples 59 to 90.
    [00124] [Example 4]
    [00125] A black galvanized steel sheet in Example 39 (L 'value: 32) and a black galvanized steel sheet in Example 55 (L * value: 30) in Table 4 were coated with a substance liquid organic chemical for treatment presented in Table 8 and placed in an electric oven without washing with water in order to be heated and dried under conditions for the plate temperature to reach 160 ° C. Consequently, an organic resin coating film was formed on the surface of the black galvanized steel sheet. The urethane resin for use was APX-601 (obtained from DIC Corporation). The epoxy resin for use was EM-0718 (obtained from ADEKA Corporation). The acrylic resin for use was SFC-55 (obtained from DIC Corporation). [Table 8]

    [00126] A test for corrosion resistance and a test for abrasion resistance were carried out for each of the coated steel sheets that have the organic resin coating film (Examples 91 to 122). Corrosion resistance testing was carried out according to JIS Z 2371 in the same way as in Example 3. In the test for abrasion resistance, a 30 mm by 250 mm specimen was subjected to a ball stretch test ( ball height: 4 mm, applied pressure: 3.0 kN), and the sliding surface was observed visually after testing. The specimen with a proportion of scratched area on the sliding surface of 0% (without scratch) was rated as "A", more than 0% and less than 5% as "B", 5% or more and less than 10% as "C" and 10% or more as "D".
    [00127] The results of a corrosion resistance test of an abrasion resistance test for each coated steel sheet are shown in Table 9. [Table 9]

    [00128] By Table 9, it was proved that the corrosion resistance and abrasion resistance of a black galvanized steel sheet can also be improved by the formation of the organic resin coating film.
    [00129] [Example 5]
    [00130] The coated steel plate No. 36 or 52 in Table 3 was coated with a liquid organic chemical for treatment presented in Table 10 and placed in an electric oven without washing with water in order to be heated and dried under conditions for the plate temperature reaches 160 ° C. Consequently, an organic resin coating film (urethane-based resin coating film) was formed on the surface of the coated steel sheet. The ether-based polyol for use was polypropylene glycol. The ester-based polyol for use was adipic acid. The polyisocyanate for use was hydrogenated tolylene diisocyanate.
    [00131] [Table 10]

    [00132] The coated steel sheet that has the organic resin coating film was placed in an apparatus for treatment with high humidity at high temperature and high pressure and the coating layer was put in contact with water vapor under the conditions presented in Tables 11 and 12.
    [00133] A cross section of the coating layer was observed for each of the coated steel sheets after treatment with water vapor (Examples 123 to 172) with an optical microscope. It was observed that the Zn2Mg phases distributed in a lamellar form, mainly in the ternary eutectic, partially crystallized the Zn2Mg phases and the Zn2Mg phases of AI / Zn2Mg were blackened.
    [00134] The measurement of the luminosity of the coating layer surface and the corrosion resistance testing were carried out for each of the coated steel sheets after treatment with water vapor (Examples 123 to 172). The measurement of the surface luminosity of the coating layer was performed in the same manner as in Example 1. The corrosion resistance testing was carried out in the same manner as in Example 3.
    [00135] The luminosity and the results of the corrosion resistance test for the surface of the coating layer of each of the coated steel sheets after treatment with water vapor are presented in Tables 11 and 12. [Table 11]
    [Table 12]

    [00136] In the present example, after a film for coating organic resin was formed on a galvanized Zn steel sheet containing Al and Mg, the coated steel sheet containing the organic resin coating film was brought into contact with water vapor so as to be blackened. In this case, the formation of an organic resin coating film insufficiently improved the corrosion resistance in some cases (with reference to Examples 139 to 147 and 164 to 172). The formation of the inorganic coating film or the organic coating film of the present invention on the coating layer did not interfere with blackening. In contrast, the black galvanized steel sheet in Examples 123 to 138 and 148 to 163 which has a urethane-based resin coating film in combination with an ether-based polyol and an ester-based polyol with the proportion of the ether-based polyol of 5 to 30% has sufficient corrosion resistance. It was also found that the addition of an organic acid to the urethane-based resin coating film also improved corrosion resistance compared to the addition of a metal valve compound or a phosphate (with reference to Examples 133, 138, 158 and 163). A 180 degree bending test was also carried out for each of the coated steel sheets after treatment with water vapor (Examples 123 to 172). In the bending test at 180 degrees, a specimen cut out of each of the coated steel sheets was bent at 180 degrees (3 t) and the cellophane tape was peeled off for the flexed part. As a result, peeling was not found for any of Examples 123 to 172.
    [00137] [Example 6]
    [00138] A black galvanized steel sheet in Example 39 (L * value: 32) and a black coated steel sheet in Example 55 (L 'value: 30) in Table 4 were coated with a liquid chemical for treatment presented in Table 5 and placed in an electric oven without washing with water in order to be heated and dried under conditions for the plate temperature to reach 140 ° C. Consequently, an inorganic coating film was formed on the surface of the black galvanized steel sheet.
    [00139] Corrosion resistance testing was performed for each of the coated steel sheets that have the inorganic coating film (Examples 173 to 204). Corrosion resistance testing was carried out according to JIS Z 2371 in the same manner as in Example 3. The results of corrosion resistance testing for each coated steel sheet are shown in Table 13. [Table 13]

    [00140] By Table 13, it was proved that the formation of an inorganic coating film also improves the corrosion resistance of a black galvanized steel sheet.
    [00141] A 180 degree bending test was also carried out for each of the coated steel sheets after treatment with water vapor (Examples 173 to 204). In the bending test at 180 degrees, a specimen cut out of each of the coated steel sheets was bent to 180 degrees (3 t), the cellophane strip stripping test was performed for the flexed part. As a result, no stripping was found for any of Examples 173 to 204.
    [00142] This patent application claims priority based on Japanese Patent Application No. 2012-100437 filed on April 25, 2012 and Japanese Patent Application No. 2012-134807 filed on June 14, 2012. The description in descriptive report and drawings of patent applications are hereby incorporated by reference in their entirety. INDUSTRIAL APPLICABILITY
    [00143] The black galvanized steel sheet of the present invention is of excellent design, retention of black appearance and the ability to be formed in a press, being applicable as a coated steel sheet, for example, for roofing materials and materials to the outside of a building, for appliances and automobiles.
    权利要求:
    Claims (11)
    [0001]
    1. Black galvanized steel sheet comprising a layer of galvanized Zn containing Al and Mg, which comprises 1.0 to 22.0% by weight of Al and 1.3 to 10.0% by weight of Al Mg, with a black Zn oxide distributed in a lamellar form in the coating layer, characterized by the fact that the galvanized Zn layer containing Al and Mg has a luminosity on the surface represented by the L * value of 60 or less.
    [0002]
    2. Black galvanized steel sheet according to claim 1, characterized by the fact that the black Zn oxide is a Zn oxide derived from a Zn2Mg phase.
    [0003]
    3. Black galvanized steel sheet according to claim 1 or 2, characterized by the fact that it still comprises an inorganic coating film on the galvanized Zn layer containing Al and Mg.
    [0004]
    4. Black galvanized steel sheet according to claim 3, characterized in that the inorganic coating film comprises one or more compounds selected from the group consisting of a valve metal oxide, a valve metal oxoate , a metal hydroxide for valve, a metal phosphate for valve and a metal fluoride for valve, and the metal for valve being one or more metals selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, W, Si and Al.
    [0005]
    5. Black galvanized steel sheet according to claim 1 or 2, characterized by the fact that it still comprises a film for coating organic resin on the galvanized Zn layer containing Al and Mg.
    [0006]
    6. Black galvanized steel sheet according to claim 5, characterized by the fact that an organic resin comprised in the coating film of the organic resin is a urethane-based resin obtained by the reaction of polyols consisting of a polyol to ether-based and an ester-based polyol with polyisocyanate, the proportion of the ether-based polyol in the polyols being 5 to 30% by weight.
    [0007]
    7. Black galvanized steel sheet according to claim 6, characterized in that the organic resin coating film also comprises a polyvalent phenol.
    [0008]
    8. Black galvanized steel sheet according to any one of claims 5 to 7, characterized in that the coating film of the organic resin comprises a lubricant.
    [0009]
    9. Black galvanized steel sheet according to any one of claims 5 to 8, characterized in that the organic resin coating film comprises one or more compounds selected from the group consisting of a metal oxide for valve, a valve metal oxoate, a valve metal hydroxide, a valve metal phosphate and a valve metal fluoride, and the valve metal being one or more metals selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, W, Si and Al.
    [0010]
    10. Black galvanized steel sheet according to any one of claims 5 to 9, characterized in that the coating film of the organic resin is a laminate layer or a coating layer.
    [0011]
    Black galvanized steel sheet according to any one of claims 5 to 10, characterized in that the organic resin coating film is a transparent coating film.
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    同族专利:
    公开号 | 公开日
    WO2013160973A1|2013-10-31|
    BR112014026678A2|2017-06-27|
    AU2012378606B2|2016-07-07|
    KR101537345B1|2015-07-16|
    TWI558846B|2016-11-21|
    EP2857544A4|2016-01-13|
    EP2857544A1|2015-04-08|
    AU2012378606A1|2014-11-13|
    JP2013241666A|2013-12-05|
    CN104245997A|2014-12-24|
    CN104245997B|2016-06-22|
    RU2605050C2|2016-12-20|
    TW201343963A|2013-11-01|
    MX2014012951A|2015-04-08|
    MY170885A|2019-09-11|
    PH12014502343A1|2014-12-22|
    JP2013241665A|2013-12-05|
    NZ701240A|2016-03-31|
    PH12014502343B1|2014-12-22|
    CA2871226C|2017-05-30|
    KR20140128464A|2014-11-05|
    RU2014142992A|2016-06-20|
    US20150072166A1|2015-03-12|
    CA2871226A1|2013-10-31|
    IN2014MN02123A|2015-09-11|
    US9863027B2|2018-01-09|
    JP5097305B1|2012-12-12|
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    法律状态:
    2018-04-03| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|
    2019-08-20| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|
    2020-05-19| B06A| Patent application procedure suspended [chapter 6.1 patent gazette]|
    2020-09-08| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|
    2020-11-24| B16A| Patent or certificate of addition of invention granted [chapter 16.1 patent gazette]|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 29/06/2012, OBSERVADAS AS CONDICOES LEGAIS. |
    优先权:
    申请号 | 申请日 | 专利标题
    JP2012-100437|2012-04-25|
    JP2012100437|2012-04-25|
    JP2012-134807|2012-06-14|
    JP2012134807A|JP5097305B1|2012-04-25|2012-06-14|Black plated steel plate|
    PCT/JP2012/004254|WO2013160973A1|2012-04-25|2012-06-29|Black-plated steel sheet|
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