JP2017218647A - MOLTEN Zn-BASED PLATED STEEL SHEET HAVING LINEAR PATTERN - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel sheet having high designability in which a silver linear pattern is mixed in a black ground, which is manufacturable more inexpensively than a design steel sheet mechanically polished after generating chemical color development on the surface of a stainless steel sheet.SOLUTION: A molten Zn-Al-Mg-based alloy plated steel sheet is subjected to steam oxidization, to thereby form a black ground having little metallic sheen by forming oxide and/or hydroxide on a surface layer of a plating layer, and thereafter, mechanical polishing is performed to remove a part of the black ground by cutting, and to thereby expose a silver part having an original tone of a molten plating layer as a linear pattern.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a hot-dip Zn-based plated steel sheet having a linear pattern having a beautiful appearance in harmony with interior materials and exterior materials such as buildings and vehicles, and furniture furniture.

  In recent elevator industry and construction industry, materials such as interior materials and exterior materials having a color pattern suitable for a black-colored fantastic atmosphere are demanded. In order to meet this demand, Patent Document 1 discloses that a stainless steel plate is immersed in a hexavalent chromic acid-sulfuric acid mixed aqueous solution to forcibly oxidize the surface of the stainless steel plate to have a black color of any color from light black to dark black. After forming a colorable film, the surface of the colored film is roughened by mechanical polishing to correspond to a predetermined pattern, so that the black color appearance due to the color development film and the white or silver color appearance that is the material color of the stainless steel plate A method for forming a surface pattern of a metal plate is disclosed in which a stainless steel plate having a color tone mixed with is obtained.

Japanese Patent Laid-Open No. 61-213380

A stainless steel plate is a suitable material in that it maintains a strong metallic luster over a long period of time and is excellent in corrosion resistance, but has a problem that the cost of the steel material is high. For this reason, the stainless steel sheet provided with mechanical polishing is restricted in use for economic reasons. In general, a stainless steel plate is harder than a steel plate of ordinary steel, so that the burden on polishing work for applying a necessary pattern is large.
Therefore, if a method that can give the appearance of a linear pattern suitable for a fantastic atmosphere with a mixture of black and silver was developed, it was excellent in design. It becomes possible to provide inexpensive interior materials and exterior materials.

In order to solve the above-described problems, the present invention has the following configuration.
(1) A molten Zn system in which a molten Zn-based plating layer and a black layer containing an oxide and / or a hydroxide are provided on the surface of the molten Zn-based plating layer on at least one surface of a base steel sheet It is a plated steel plate, and when the surface of the hot-dip Zn-based plated steel plate is measured in the range of 200 μm × 280 μm using a Keyence Corporation shape analysis laser microscope, model VK-9700, the width is 5 μm or more and the depth is observed. There are three or more linear patterns in the range of 1 mm × 1 mm on the surface of the hot-dip Zn-plated steel sheet, each of which is a recess portion of 3 μm or more, and the ratio of the length / width of the recess portion is three times or more. The shape pattern is a molten Zn-based plated steel sheet having a linear pattern in which the molten Zn-based plating layer is exposed and the surface brightness L ^* is 55 or less.
(2) The hot-dip Zn-based plated steel sheet of (1) has Zn, Al: 0.1 mass% to 22.0 mass%, and Mg: 0.1 mass% or more on at least one surface of the steel sheet. And a molten Zn—Al—Mg-based plating layer comprising 10.0% by mass or less is provided, and one or more selected from the group consisting of Zn, Al, and Mg on the surface layer of the molten Zn—Al—Mg-based plating layer A hot-dip Zn-plated steel sheet having a linear pattern as described in (1), characterized in that a blackened oxide and / or hydroxide is present.
(3) Moreover, you may have the chromate film | membrane or chromate free film | membrane which has chromium as a main component in the surface layer of the hot-dip Zn type plated steel plate which has the linear pattern of (1).
(4) In the present invention, the base steel sheet contains Zn, Al: 0.1% by mass or more and 22.0% by mass or less, and Mg: 0.1% by mass or more and 10% by mass or less. Preparing a molten Zn-Al-Mg-based plated steel sheet having a Zn-Al-Mg-based plating layer, contacting the molten Zn-Al-Mg-based plated steel sheet with water vapor in a sealed container, and And a step of removing a part of the plating layer by mechanical polishing after the contact, and a method for producing a hot-dip Zn-based plated steel sheet having a linear pattern.
(5) Preferably, after the step of removing a part of the plating layer by mechanical polishing in (4), a step of forming a chromate film or a chromate-free film mainly composed of chromium on the surface layer.
(6) Moreover, this invention is a decorative board which consists of a hot-dip Zn type plated steel plate which has the linear pattern as described in (1).

  According to the present invention, with the appearance of blackened by oxidizing the hot-dip plating layer by bringing it into contact with water vapor, white or silver which is the color tone of the hot-dip plating layer itself is mixed in as a linear pattern. It is possible to provide a hot-dip Zn-plated steel sheet having a color pattern suitable for a fantastic atmosphere and having a linear pattern, and a method for producing the same.

FIG. 1A is a diagram showing a measurement result of hydroxide by TOF-SIMS for a hot-dipped layer in an example of a hot-dipped steel sheet (before water vapor treatment), and FIG. 1B shows water vapor with respect to the hot-dipped steel sheet of FIG. It is a figure which shows the measurement result of the hydroxide by TOF-SIMS about the hot-dip plated layer after giving a process. FIG. 2A is a diagram showing a measurement result of oxide by TOF-SIMS for a hot-dip plated layer in an example of the same hot-dip steel sheet (before steam treatment) as in FIG. 1A, and FIG. 2B is the same as FIG. It is a figure which shows the measurement result of the oxide by TOF-SIMS about the hot-dipped layer after performing a steam process with respect to a hot-dipped steel plate. FIG. 3A is a view showing an X-ray diffraction chart of a hot dipped layer in an example of the same hot dipped steel sheet (before water vapor treatment) as in FIG. 1A, and FIG. 3B is a water vapor treatment for the hot dipped steel sheet of FIG. It is a figure which shows the chart of the X-ray diffraction about the hot-dip plated layer after giving. FIG. 4A is a diagram showing an ESR spectrum of a hot-dip plated layer in an example of the same hot-dip plated steel sheet (before water vapor treatment) as in FIG. 1A, and FIG. 4B is obtained by subjecting the hot-dip steel sheet of FIG. It is a figure which shows the ESR spectrum about the subsequent hot dipping layer. FIG. 5 is an optical micrograph of the same cross section after black oxidation as in FIG. 1B. FIG. 6 is an example of a vibration polishing apparatus. FIG. 7 is an example of an image of a two-dimensional image in which the shape of the recess by vibration polishing is evaluated using a shape analysis laser microscope. FIG. 8 is an example of an image of a two-dimensional image in which the shape of the dent by vibration polishing is evaluated using a shape analysis laser microscope. FIG. 9 shows the result of measuring the depth of the dent along the line segment shown in FIG.

  The present inventors have made various steel materials from the viewpoint of a material that can be given a polishing pattern relatively easily, and a method that can give an appearance of a linear pattern suitable for a fantastic atmosphere in which black and silver are mixed. Various methods for obtaining a black appearance color were investigated and examined. As a result, hot-dip galvanized steel sheet and hot-dip galvanized steel sheet were selected as materials that can be easily provided with a polishing pattern in addition to the stainless steel sheet, and the condition of the polishing pattern was investigated. As a result, it was found that when a hot-dip Zn-Al-Mg alloy-plated steel sheet in which a spangle pattern does not appear on the surface of the plating layer is used as a material, a polished pattern with extremely high visibility can be applied. On the other hand, in the hot-dip galvanized steel sheet and other hot-dip galvanized steel sheets, the visibility of the polished pattern is reduced because the spangle pattern remains on the surface layer of the plating layer.

The appearance color of the hot-dip Zn—Al—Mg alloy-plated steel sheet is silver. Therefore, in order to obtain a black appearance, black coating and a method of blackening by oxidizing the plating layer in contact with water vapor were examined. As a result, it was found that when the plating layer itself was steam-oxidized to give a black appearance, it had a deep visual effect in which the shades of black color oozed out subtly and had a natural color tone. On the other hand, in the case of black paint, there is no difference in hue and contrast, and a uniform black appearance can be obtained, but there is some kind of blurring and it is not suitable for a use environment where a calm atmosphere is required.
In the present specification, hereinafter, the treatment for blackening the contact by oxidizing the plating layer with water vapor may be referred to as “water vapor treatment”.

  Furthermore, by removing a part of the plating layer that has been blackened by contacting the plating layer with water vapor and removing it by mechanical polishing, black and silver are mixed, visibility is high, and the line is rich in change. A hot-dip Zn-plated steel sheet having a pattern was obtained, and a material having high design properties and applicable as an inexpensive interior material, exterior material or the like was obtained. Further, after applying the linear pattern, an inorganic or organic film may be laminated on the surface of the hot-dip Zn-based plating layer having the linear pattern.

The inventors of the present invention have a low metallic luster if the molten Zn-based plated steel sheet is brought into contact with water vapor to form an oxide or hydroxide having a lattice defect for a part of the metal on the surface layer side of the plating layer. It has been found that a black appearance can be obtained.

  However, generally oxides and hydroxides are hard and brittle. Therefore, if the original plating layer is uniform, the oxide or hydroxide layer is only formed on the surface of the plated steel sheet. As a result, when the oxide and hydroxide layers are mechanically polished, adjacent convex portions of the concave portions formed by polishing are likely to fall off when rubbed with a finger or the like.

  Therefore, as a result of further studies, the inventors have performed steam treatment on a molten Zn-Al-Mg alloy-plated steel sheet having a plating layer structure composed of a plurality of intermetallic compound phases. It has been found that the oxide and / or hydroxide protrusions can be reduced even after polishing.

Moreover, although this plating layer is hard, it is easy to have a polishing pattern with high visibility. The ease of attaching the texture pattern is that the primary eutectic Al, Zn single phase, Zn ₂ Mg ternary eutectic structure becomes oxide and / or hydroxide with lattice defects by steam oxidation, and each adjacent phase It is presumed that the bonding force is reduced, so that it is easy to be cut. When the polishing is further performed in the depth direction, a plating layer having a silver appearance, which is the original color tone of the molten Zn—Al—Mg based steel sheet, is exposed. Therefore, by adjusting the polishing conditions, it is possible to obtain a hot-dip Zn-based plated steel sheet having a linear pattern in which black and silver are mixed and have a contrast contrast as the appearance of the plating layer.

After applying a linear pattern, providing an inorganic or organic clear coating on the surface of the hot dipped layer improves corrosion resistance, fingerprint resistance, and discoloration resistance, and protects the polished pattern with a clear coating. The plating layer can be prevented from discoloring over a long period of time, and a highly visible polished pattern can be maintained.

Embodiments of the present invention will be described below.

[Base steel sheet]
Various steel plates can be used as the base steel plate. Examples of the base steel plate include low carbon steel, medium carbon steel, high carbon steel, alloy steel, high strength steel plate, and stainless steel. When good press formability is required, the base steel plate is preferably a deep drawing steel plate, examples of which include low carbon Ti-added steel and low carbon Nb-added steel. . Further, the base steel sheet may be electroplated before the hot-dip plating is performed for reasons such as improved plating properties. Examples of the electroplating include plating of Ni or Fe.

[Hot Zn-based plating layer]
The molten Zn-based plating layer is disposed on at least one surface or both surfaces of the base steel plate. The molten Zn-based plating layer contains Zn, Al, and Mg. The Al content in the molten Zn-based plating layer is 0.1 to 22.0 mass%. Moreover, content of Mg in the said hot-dip Zn type plating layer is 0.1-10.0 mass%. The content of Zn in the molten Zn-based plating layer may be the remaining, for example, 68 to 99.8% by mass.

  When the Mg content is smaller than the lower limit of the above range, a black appearance may not be obtained even if steam treatment is performed. On the other hand, when the Al content is out of the above range or the Mg content is larger than the upper limit of the above range, a large amount of oxide called dross is generated on the surface of the plating bath (molten metal). Since this adheres to the surface of the hot dip galvanized steel sheet when the hot dip galvanized steel sheet is manufactured, a beautiful appearance may not be obtained.

The hot-dip plated layer has a plurality of alloy phases. Therefore, the oxide and / or hydroxide portion after performing the steam treatment can prevent the protrusions of the hot-dip plated layer from falling off even after mechanical polishing. The hot-dip plated layer usually has an Al—Zn—Zn ₂ Mg ternary eutectic structure. The hot-dip plated layer only needs to have a eutectic structure as long as the above oxide and / or hydroxide is prevented from falling off, and a binary co-structure such as Al—Zn or Zn—Zn ₂ Mg. A crystal structure may be included, or Zn ₁₁ Mg ₂ may be included instead of Zn ₂ Mg. The Zn ₁₁ Mg ₂ phase can be formed according to conditions such as the cooling rate of the molten metal during the production of the hot dipped layer.

  Moreover, the said hot-dip Zn type plating layer may further contain other metals or inorganic components other than Zn, Al, and Mg in the range in which the effect of this embodiment is acquired. For example, the molten Zn-based plating layer may further contain 2.0% by mass or less of Si, or may further contain 0.1% by mass or less of Ti, or 0.045% by mass. % Or less B may further be contained. Moreover, when manufacturing the said hot-dip Zn type plating layer, since the said steel plate is immersed in the said molten metal and let it pass through, the metal component in the said steel plate may generally mix in the said hot-dip plating layer. Therefore, the molten Zn-based plating layer may further contain up to approximately 2.0 mass% of Fe.

  The thickness of the hot-dip Zn—Al—Mg-based alloy-plated steel sheet plating layer can be determined within a range in which the effect of the present embodiment can be obtained, and is preferably 3 to 100 μm, for example. When the thickness of the hot-dip plating layer is less than 3 μm, the design properties may be impaired because red rust is generated from the scratched portion early by reaching the steel plate by mechanical polishing. On the other hand, when the thickness of the hot-dip plating layer exceeds 100 μm, the hot-dip plating layer and the steel plate are easily separated from each other in the processed portion because the hot-dip plating layer and the steel plate have different ductility when subjected to compression during processing. The thickness of the hot-dip plated steel sheet is more preferably 3 to 50 μm, and even more preferably 5 to 30 μm, from the viewpoint of preventing a decrease in design properties and peeling of the hot-dip plated layer.

[Oxides and hydroxides produced by steam treatment]
The molten Zn—Al—Mg-based alloy plating layer contains one or both of an oxide and a hydroxide. The oxide or hydroxide is distributed in the hot-dip plated layer. Here, “in the hot-dip plating layer” includes both the surface of the hot-dip plating layer and the inside of the hot-dip plating layer.

  One or both of the oxide and hydroxide (hereinafter, also referred to as “oxide or the like”) is produced by bringing the hot-dip plated steel sheet into contact with water vapor.

  The oxide or the like is, for example, one or more oxides or hydroxides selected from the group consisting of Zn, Al, and Mg. The oxides and the like can be identified by time-of-flight secondary ion mass spectrometry (TOF-SIMS) or X-ray photoelectron spectroscopy (ESCA, XPS) analysis. Since the oxide or the like is a reaction product of the metal component in the hot-dip plating layer and water vapor, it is considered that the hot-dip plating layer contains both oxide and hydroxide. . Moreover, metal ions, such as the said oxide, originate in the metal component in the said molten Zn-Al-Mg type alloy plating layer. The fact that the hot-dip plating layer contains the oxide or the like substantially means that any oxide and hydroxide of Zn, Al, and Mg are present in the hot-dip plating layer.

An example of the TOF-SIMS analysis result is shown in FIGS. FIG. 1A shows the hot-dip plated steel plate No. 1 in Table 1 in Examples described later. FIG. 1B is a diagram showing the measurement results of hydroxide by TOF-SIMS of a hot-dip coating layer of 3 (hot-plated steel sheet before steaming treatment, hereinafter sometimes referred to as “before black oxidation”). FIG. It is a figure which shows the measurement result of the hydroxide by TOF-SIMS of the hot-dipped layer of Example 3 (The hot-dipped steel sheet after steam treatment, which may be referred to as “after black oxidation” hereinafter) in Table 2.
FIG. 2A is a diagram showing a measurement result of oxide by TOF-SIMS of a hot-dip plating layer before black oxidation, and FIG. 2B shows a measurement result of oxide by TOF-SIMS of a hot-dip plating layer after black oxidation. FIG.
In FIG. 1, the one-dot chain line represents HOZn, the solid line represents HOAl, and the broken line represents HOMg. Similarly, in FIG. 2, the alternate long and short dash line represents OZn, the solid line represents OAl, and the broken line represents OMg. The measurement conditions are such that Ga + is used as the primary ion species, the primary acceleration voltage is 15 kV, and the primary ion current is 0.6 nA. The raster area is 20 μm × 20 μm, and the measurement range is 0.5 to 2000 m / z. The “secondary ion intensity” in FIGS. 1 and 2 represents the number of secondary ions detected in 30 seconds, and “sputtering time” is the sputtering time. That means

  Before and after black oxidation, the surface of the hot-dip plating layer and the vicinity thereof (also referred to as “surface layer”) are oxidized by the atmosphere, and the secondary ions derived from oxide and hydroxide Both secondary ions are detected. However, secondary ions are not detected in the hot dipped layer before the steam treatment in the hot dipped layer (also referred to as “lower layer”) rather than the surface layer. That is, in the lower layer of the hot dip plating layer, neither oxide nor hydroxide is present, and it is shown that all are in a metal state (FIGS. 1A and 2A). However, OAl in FIG. 2A is also detected in the lower layer. Since Al is a metal having a higher ionization efficiency than Zn and Mg, it is considered that the strength is increased even in the lower layer. Further, the present inventors have found that OZn and OMg are not substantially present in the lower layer and that the strength in FIG. 2A is sufficiently low compared to those in FIG. 2B described later for Zn and Mg. Believes that the detection of Al in the lower layer is due to measurement errors and does not indicate the presence of oxide.

  On the other hand, in the plated layer after black oxidation, both secondary oxide ions and hydroxide ions are detected in the lower layer. Further, as described above, the OAl in FIG. 2B clearly shows a higher strength than that in FIG. 2A, and therefore the presence of an oxide of Al can be confirmed. It can be seen that the oxide has a large number of secondary ions derived from the oxide of Al, and the hydroxide has a large number of secondary ions derived from the hydroxide of Mg (FIGS. 1B and 2B).

About the kind of oxide and hydroxide in a hot dipping layer, it can judge by analyzing the sample after said black oxidation by X-ray diffraction. An example is shown in FIG. FIG. 3A is a diagram showing an X-ray diffraction chart of a hot-dip plating layer before black oxidation, and FIG. 3B is a diagram showing an X-ray diffraction chart of a hot-dip plating layer after black oxidation. In FIG. 3, “●” indicates Zn ₂ Mg, “▼” indicates ZnO, “▲” indicates Zn (OH) ₂ , “◯” indicates Zn, “Δ” indicates Al, and “▽” indicates Each represents Fe.

Looking at the diffraction intensity before and after the water vapor treatment, the peak intensities of Zn, Zn ₂ Mg, and Al are large before the water vapor treatment (before black oxidation). However, after steam treatment (after black oxidation), their peak intensities decrease, and instead the ZnO and Zn (OH) ₂ peak intensities increase. From the change in the peak intensity, it can be confirmed that oxides and hydroxides are generated in the hot-dip plating layer by the steam treatment.

  However, the peaks of Al and Mg oxides are likely to be broad and difficult to judge. Even in that case, these can be determined by the above-described TOF-SIMS or ESCA. For simplicity, oxides of Al and Mg are subjected to element mapping in the cross section of the heat absorbing and radiating steel plate using an electron beam microanalyzer (EPMA) and the like, and are determined from the distribution of each metal component and oxygen in the cross section. It is also possible.

  Whether or not the oxide or the like has a lattice defect can be determined by the presence or absence of a peak by an electron spin resonance (ESR) spectrum. An example is shown in FIG. FIG. 4A is a diagram showing an ESR spectrum before black oxidation, and FIG. 4B is a diagram showing an ESR spectrum after black oxidation. In FIG. 4, the horizontal axis represents the magnetic flux density (mT) and the g factor (symbol: g), and the vertical axis represents the strength.

  When comparing the ESR response before and after steaming, the ESR response is only observed after steaming. Therefore, it can be determined that the oxide or the like generated by the steam treatment has lattice defects. The cause of the lattice defect is not necessarily clear, but because it is a reaction with water vapor, Zn, Al, and Mg are substituted with each oxide or hydroxide or arranged as an interstitial atom, or This is probably because oxygen-deficient oxides or hydroxides of Zn, Al, and Mg are generated.

  Whether the various alloy layers are distributed can be determined by observing a cross-sectional structure with an optical microscope or a scanning electron microscope. For example, when observed from a cross section, the metal is observed as a whitish portion, and the oxide or the like is observed as a gray portion or a darker portion. An example is shown in FIG. FIG. 5 is an optical micrograph of a cross section after black oxidation.

  The amount of the oxide or the like can be determined by measuring the thickness of the relevant part by observing the cross-sectional structure with an optical microscope.

The oxidation rate of the molten Zn—Al—Mg-based plating layer (the rate at which the appearance seen from the surface of the plating layer becomes black) can be arbitrarily adjusted depending on the conditions of the steam treatment. As the conditions of the steam treatment are high temperature and high humidity and for a long time, the appearance seen from the surface of the plating layer becomes black and the lightness is lowered. However, when the lightness L ^* is lowered to a range of 20 to 25, the appearance is lowered. Never do. However, even if there is no change in the color tone of the appearance, the oxidation of the molten Zn-Al-Mg-based plating layer that has been blackened due to the progress of oxidation from the surface side in the molten Zn-Al-Mg-based plating layer toward the steel substrate. The thickness increases and eventually the entire plating layer is oxidized.

In order to make the appearance color of the molten Zn-Al-Mg-based plated steel sheet treated with water vapor, that is, the molten Zn-Al-Mg-based plated steel sheet before mechanical polishing, lightness L ^* 50 or less, an oxidized black plated layer The average thickness of the film must be 1.0 μm or more. The average thickness of the black plating layer described above is a site where the cross section of the molten Zn-Al-Mg plating layer after oxidation with water vapor is observed with an optical microscope at a magnification of 500 times and blackened from the surface layer to the depth direction. The average thickness in the depth direction was measured for three fields and averaged.

The hot-dip Zn-based plated steel sheet having the linear pattern of the present invention is cut to a depth at which the original silver portion of the plated layer is linearly removed by removing a part of the black plated layer on the surface of the plated layer by mechanical polishing. Therefore, it is necessary to leave an unoxidized part even after steam oxidation. Moreover, when the quantity which cuts the oxide layer blackened with the method of mechanical polishing increases, it is necessary to adjust an upper limit thickness according to the cutting quantity. However, as the amount of cutting increases, the energy, processing time, cutting time, and cutting waste generated by cutting increase in order to oxidize the plating layer and blacken, resulting in decreased production efficiency and increased costs. Therefore, the upper limit thickness of the blackened plating layer is preferably 10 μm.

Depending on the composition of the molten Zn-based plating layer, Al, Zn, or Zn ₂ Mg may be precipitated as the primary crystal. The primary crystal portion is observed as a blackened portion in the above-described cross-sectional observation as in the oxide portion. Therefore, the presence of primary crystals is not substantially a problem in the hot-dip Zn-based plated steel sheet having the linear pattern of the present invention. Rather, the primary crystal serves as a path for promoting oxidation inside the hot-dip plating layer, and as a result, the processing time of the water vapor treatment of the hot-dip Zn-based plating layer tends to be shortened.

[Mechanical polishing]
For mechanical polishing, hairline polishing or No. 1 polishing using polishing paper in one direction. There are 4 mat finish polishing, vibration finish, and the like, but they are not particularly specified, and the polishing conditions may be adjusted by appropriately selecting the type of polishing method to obtain a linear pattern according to the application. In addition, mechanical polishing needs to be performed so that a part of the plating layer blackened by steam oxidation is removed so that the original color tone of the molten Zn—Al—Mg alloy plating layer before the steam treatment is exposed. There is.

  The machine-polished hot-dip galvanized steel sheet has an active surface, is easily contaminated with various kinds of dirt including fingerprints, and is susceptible to white rust. Therefore, in order to prevent this, a chromate film or a chromate-free film may be provided after the molten Zn—Al—Mg alloy plating layer is mechanically polished.

  The film may be an inorganic film or an organic film, and an organic film may be formed after the inorganic film is formed.

  As long as the above treatment can be further improved by a combination with the polished Zn-Al-Mg alloy-plated steel sheet, the color tone of the treatment film may be arbitrarily adjusted, but preferably clear. System processing is good. Moreover, it is preferable that the thickness of the film is a thickness that does not impair the appearance of the hot-dip plated steel sheet. In the case of organic processing, when the film thickness is increased, the surface of the hot dip plated steel sheet is smooth and smooth, and as a result, the gloss tends to increase.

In the case of inorganic chromate treatment, a known chromate treatment, for example, a chromate treatment with a chromate treatment solution containing trivalent chromium oxide, hexavalent chromic acid and silica, phosphoric acid or the like as a main component is applied. The chromate adhesion amount is 1 to 100 mg / m ² .

If the amount of chromate attached is less than 1 mg / m ² , sufficient fingerprint resistance and rust preventive effect will not be obtained. If it exceeds 100 mg / m ² , the color tone will change and the design will deteriorate and the rust preventive effect will be saturated. Costly. More desirably, 5 to 50 mg / m ² is good.

Similar effects to the chromate-free treatment of the inorganic treatment can be obtained as well as the chromate treatment. The chromate-free treatment does not contain environmentally harmful hexavalent chromium in the treatment solution. For example, there are treatment solutions containing Zr and Ti salts, treatment solutions containing silane coupling agents, etc. Free processing solution can be used. In the chromate-free treatment, one or two kinds selected from the group consisting of valve metal oxide, valve metal oxyacid salt, valve metal hydroxide, valve metal phosphate and valve metal fluoride. The valve metal is a chromate-free treatment layer containing one or more metals selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, W, Si and Al. The adhesion amount is preferably ¹ to 200 mg / m ² .

If the adhesion amount of chromate-free treatment is less than 1 mg / m ² , sufficient fingerprint resistance and rust preventive effect cannot be obtained, and if it exceeds 200 mg / m ² , not only the unevenness formed by mechanical polishing becomes inconspicuous. The rust prevention effect is saturated and the cost is increased economically. More preferably, 10 to 200 mg / m ² is good.

In the organic treatment, if the clear resin coating layer is formed with a thickness of 0.1 to 100 μm, fingerprint resistance, scratch resistance and corrosion resistance can be improved. For the clear resin coating layer, a conventionally known organic clear paint can be used. Specific examples of such an organic resin-based baking clear paint include acrylic resin-based, urethane resin-based, epoxy resin-based, polyester-based, melamine alkyd-based, and fluororesin-based. Of these, acrylic resin, urethane resin, polyester, and fluororesin are preferably used.

In order to improve the rust-prevention effect, the above organic treatment is made from valve metal oxide, valve metal oxyacid salt, valve metal hydroxide, valve metal phosphate, and valve metal fluoride in an organic resin. You may mix | blend the 1 type, or 2 or more types of compound chosen from the group which consists of. The valve metal is one or more metals selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, W, Si, and Al.

Examples of the method for applying the treatment liquid include a roll coater method, a curtain coater method, a spin coat method, a spray method, and an electrostatic method. Among these, the roll coater method and the spray method are preferable. In addition, the shape of the coating formed on the surface of the hot-dip Zn—Al—Mg alloy-plated steel plate may be either a continuous coating in the width direction and the length direction of the steel plate or a state distributed in islands.
[Production method]

The hot-dip Zn-based plated steel sheet having the linear pattern of the present invention is a hot-dip Zn-based plated steel sheet, which is blackened by bringing the hot-dip Zn-based plated steel sheet into contact with water vapor in a sealed container and then blackened. It can be produced by removing part of the layer by mechanical polishing.

(1) Preparation of hot-dip Zn-plated steel sheet The hot-dip Zn-plated steel sheet has, for example, Al of 1.0 to 22.0 mass%, Mg of 1.3 to 10.0 mass%, and the balance substantially Zn. It is manufactured by a hot dipping method using a hot metal (alloy plating bath). The hot dip plating layer may be formed on one surface of the base steel plate, or may be formed on both surfaces.

The plated structure of the molten Zn—Al—Mg-based plated steel sheet usually has a lamellar ternary eutectic structure of Al—Zn—Zn ₂ Mg. By performing the water vapor treatment described later, the ternary eutectic structure can be made into a structure having an oxide or the like in a lamellar shape. The oxides and the like are distributed in a lamellar form on the micro order, and as a result, they are difficult to peel off even after processing of a hot-dip Zn-based plated steel sheet. However, if Al and Mg contained in the plating structure are not contained in a certain amount of mass%, oxides or the like may not be observed as a lamellar structure even if the steam treatment described later is performed.

In addition, the above-described molten Zn—Al—Mg-based plated steel sheet has a microscopic Al—Zn—Zn ₂ Mg ternary eutectic structure, and the formation reaction of oxides and the like by steam treatment described later is Compared to plated steel sheets with different types of plating layers, it is faster and takes less time. The reason for this is not necessarily clear, but since Al, Zn, and Zn2Mg are finely distributed, it may be caused by the promotion of oxidation of each metal component due to a potential difference between the metal components. They speculate.

You may further add other elements, such as Si, Ti, or B, to the said alloy plating bath. The hot-dip plated steel sheet has, for example, a temperature of the alloy plating bath of 400 ° C., cooling after hot dipping is an air cooling system, and an average cooling rate from the temperature of the alloy plating bath to solidification of the hot-dip plating layer is 10 ° C./second. By setting it as a grade, it can manufacture as a hot-dip Zn-Al-Mg alloy plating steel plate.

(2) Implementation of water vapor treatment In the water vapor treatment, the hot-dip plated steel sheet is brought into contact with water vapor to change a part of the metal component in the hot-dip plating layer into an oxide or hydroxide having lattice defects. In the water vapor treatment, it is preferable that the amount of oxygen in the atmosphere is adjusted to be lower than the normal concentration in the atmosphere from the viewpoint of uniformly generating a reaction for obtaining the oxide or the like. This is presumably because when oxygen is large, the generation of oxides and hydroxides having no lattice defects is promoted. Therefore, the oxygen concentration in the atmosphere in the steam treatment is preferably 13% or less. In order to prevent intrusion of oxygen in the atmosphere, it is preferable to use a sealed container or a semi-sealed container that can be held in a state where the pressure inside the container is raised for the steam treatment. A semi-hermetic container is a container that can maintain its internal pressure higher than atmospheric pressure by supplying water vapor. Specifically, it is a container to which more water vapor is constantly or appropriately supplied than leaks.

The treatment temperature of the steam treatment is preferably 50 to 350 ° C. When the treatment temperature is lower than 50 ° C., the reaction rate is extremely reduced, and productivity may be reduced. When the treatment temperature is higher than 350 ° C., the speed of the reaction becomes extremely fast, but the alloying of the hot-dip plating layer and the steel sheet proceeds in the temperature rising process, and the lamellar structure in the hot-dip plating layer May collapse, and as a result, the yield may be extremely reduced. In view of the reaction rate of the steam treatment, the treatment temperature is more preferably 105 to 200 ° C.

The relative humidity in the steam treatment atmosphere is preferably 30 to 100%. When the relative humidity is less than 30%, the rate of the reaction may be extremely reduced, and productivity may be reduced.

The treatment time for the water vapor treatment is appropriately set according to the treatment temperature and relative humidity, the composition of the hot-dip plating layer, or the like. For example, the processing time can be appropriately determined from the range of 0.017 to 120 hours.

The shape of the hot dip plated steel sheet to be subjected to the steam treatment can be appropriately determined within a range where the steam treatment is sufficiently performed. For example, the hot dip galvanized steel sheet to be subjected to the steam treatment can be any of the coiled galvanized steel sheet, the cut plate shaped hot dip plated steel sheet, and a product after the hot dip plated steel sheet is processed. When the hot dip plated steel plates are in contact with each other, it is preferable to arrange a spacer between the hot dip plated steel plates from the viewpoint of sufficiently bringing the hot dip plated layer into contact with the water vapor. Examples of the spacer include a nonwoven fabric, a mesh-like resin, and a metal wire.

Examples will be described below, but the present invention is not limited to these examples.

[Production of Hot Dipped Steel Plates 1 to 20]
A cold-rolled steel plate (SPCC) having a thickness of 1.2 mm is formed with a plated layer (hot-plated layer) made of a molten metal containing Al, Mg and Zn and having a thickness of 1 to 100 μm. Was made. The composition of the hot-dip plating layer was adjusted by changing the composition of the molten metal (the concentrations of Zn, Al, and Mg). Moreover, the thickness of the hot dipping layer was adjusted by the amount of adhesion of the hot metal. In addition, the remainder in the composition of the molten metal described in Table 1 is substantially zinc. Further, the composition of the molten metal and the composition of the produced hot-dip plating layer are substantially the same.

Table 1 shows the composition of the molten metal, the thickness (t _D ) of the molten plating layer, and the lightness L ^* in the hot dip plated steel sheets 1 to 20.

About the hot dip plated steel plates 1-20, the lightness (L ^* value) of the plating layer surface was measured with a spectroscopic color difference meter (TC-1800; Tokyo Denshoku Co., Ltd.) by a spectral reflection measurement method based on JISK5600. The measurement conditions are shown below.
Optical conditions: d / 8 ° method (double beam optical system)
Field of view: Twice field of view Measurement method: Reflected light measurement Standard light: C
Color system: CIELAB
Measurement wavelength: 380 to 780 nm
Measurement wavelength interval: 5 nm
Spectrometer: Diffraction grating 1200 / mm
Lighting: Halogen lamp (voltage 12V, power 50W, rated life 2000 hours)
Measurement area: 7.25mmφ

  In the hot dip plated steel sheets No. 17, 18, and 20 in Table 1, the dross generated on the surface of the hot dip plating bath adheres to the surface of the hot dip plated steel sheet, and the hot dip galvanized steel sheet is inferior in appearance and thus has a linear pattern. It was difficult to apply as a plated steel sheet.

  The hot dip plated steel sheets No. 1 to 16 and 19 in Table 1 were placed in a high-temperature and high-pressure moist heat treatment apparatus (manufactured by Nisaka Manufacturing Co., Ltd.), and the hot dip plated steel sheet was brought into contact with water vapor. A black-plated steel sheet was created. The respective steam treatment conditions are shown in Table 2. In Table 2, T1 is the treatment temperature (° C.), Hr is the relative humidity (%), Co is the oxygen concentration (%), and t1 is the treatment time (hours).

Table 2 also shows the lightness L ^* after the steam treatment. Method of measuring lightness L ^* is the same as the lightness L ^* measurement methods shown in Table 1. In addition, when the lightness L ^* value is 35 or less, it is evaluated as “◎”, when it is over 35 and 40 or less, “◯”, when it is over 40 and 50 or less, “△”, and when it exceeds 50, it is evaluated as “×”. did.

In Examples 18 and 19, the relative humidity was low, in Example 21, the oxygen concentration was high, and in Example 24, the treatment time was short, so a good black appearance was not obtained. In Comparative Example 1, a good black appearance was not obtained because the amount of Mg in the hot dipped layer was small. In Examples 1 to 17, 20, 22, 23, 25 to 30 other than those, the lightness L ^* value was 50 or less, and a good black appearance was obtained.

  Mechanical polishing for giving a linear pattern was implemented about Examples 1-17, 20, 22, 23, 25-30 of Table 2 with which the favorable black external appearance was obtained.

An outline of the vibration polishing apparatus used for mechanical polishing is shown in FIG. The vibration polishing apparatus includes a main shaft 1, a motor 3 attached so that the rotation shaft 2 thereof is in an eccentric position with respect to the main shaft 1, a disc-like sponge 4 attached to the motor 3, and a surface of the sponge 4. And a disc-shaped non-woven pad 5 attached thereto. For the nonwoven fabric pad 5, trade name “Scotch Bright # 180” (grain size 180) manufactured by Sumitomo 3M Co. was used. Reference numeral 6 is a blackened hot-dip Zn-based plated steel sheet used for mechanical polishing.

The conditions for vibration polishing are as follows.
Pressure: 20 g / cm ²
Spindle speed: 1000 rpm,
Spindle speed: 10m / min
Feed pitch: 50 mm,
Number of scans: 1 or 2 times

After performing vibration polishing, the ratio of the width and depth of the dent and the width and length of the dent was determined by the following method, and the number of effective linear patterns effective in the present invention was evaluated. Further, the lightness L ^* was measured by the method described above. The results are shown in Table 3.

[Evaluation A: Effective linear pattern evaluation method]
FIG. 7 to FIG. 9 show an example of the results of measurement using the following shape analysis laser microscope for the sample of Example 3 of Example 3 with two scans.
7 and 8 are uneven 2D image images. It can be seen from FIG. 8 that a range of 200 μm long × 280 μm wide was observed per screen.
FIG. 9 shows the result of measuring the depth of the recess along the line segment AB shown in FIG. A dent corresponds to the linear pattern of the present invention.
Apparatus: Shape analysis laser microscope manufactured by Keyence Corporation Model: Model VK-9700
・ Measurement range: 200μm × 280μm
-Effective linear pattern conditions: The depth of the recess is 3 μm or more and the width is 5 μm or more.
The ratio of width to length is 3 times or more ・ Evaluation criteria: The number of effective linear patterns in the range of 1 mm x 1 mm is 3 or more ○ 2 △ 1 piece ×

[Evaluation B: Method for measuring the number of effective linear patterns by visual observation]
-The number of linear patterns was measured visually within a range of 10 mm x 10 mm.
・ Effective linear pattern conditions to be measured: Length 5 mm or more ・ Evaluation criteria: Number of effective linear patterns 5 or more ○ 2 or more and less than 5 △ <2 or less ×
[Evaluation C: Lightness]
Evaluation criteria: 55 or less: ○, more than 55: ×
[Comprehensive evaluation]
Based on the three evaluation results of Evaluation A to Evaluation C, comprehensive evaluation was performed. The evaluation criteria were as follows: number of ◯: 3; ◯, 2: Δ, 1: x.

  For the samples of Examples 1, 9, 20 to 23, 30 with a single scan number of Examples 2 to 8, 10 to 17, and 25 to 29 with a total number of scans of “◯” shown in Table 3, A water-based urethane resin (manufactured by ADEKA, product name: HUX232) was applied to the surface with a bar coater so as to be a constant dry film thickness of 0.5 μm, and dried at an ultimate plate temperature of 160 ° C. to form a clear film. In all samples, it was found that the traces of fingerprints were hardly recognized due to the formation of a clear film.

  From the results shown in Table 3, it is possible to obtain a black-silver-colored Zn-based plated decorative board having a good black-silver appearance by adjusting the vibration polishing conditions according to the black state of the hot-dip plating layer in Examples 1 to 30. all right.

As described above, the hot-dip Zn-Al-Mg alloy-plated steel sheet is steam-oxidized to form oxides and hydroxides on the surface layer side of the plated layer of the hot-dip plated steel sheet, resulting in a black appearance with less metallic luster. A base is formed. Thereafter, by mechanical polishing, a part of the black hot-dip plated layer is cut to expose the silver portion which is the original color tone of the hot-dip plated layer, thereby obtaining a black silver Zn-based plated decorative board having a black silver appearance. Can do. Since this decorative board has a design appearance, it can be used for home appliances, architectural interior materials, furniture, decorative boards, etc. In comparison, it can be provided at a low cost.

Claims (6)

A molten Zn-based plated steel sheet in which a molten Zn-based plated layer and a black layer containing an oxide and / or hydroxide are provided on the surface of the molten Zn-based plated layer on at least one surface of the base steel sheet There,
Indentations with a width of 5 μm or more and a depth of 3 μm or more observed when the surface of the molten Zn-based plated steel sheet is measured in the range of 200 μm × 280 μm using a shape analysis laser microscope manufactured by Keyence Corporation, model VK-9700 And there are three or more linear patterns in the range of 1 mm × 1 mm of the surface of the hot-dip Zn-based plated steel sheet, wherein the ratio of the length / width of the recesses is 3 times or more,
The linear pattern is one in which the molten Zn-based plating layer is exposed,
The surface brightness L ^* is 55 or less.
A hot-dip Zn-based plated steel sheet having a linear pattern. The hot-dip Zn-based plated steel sheet having the linear pattern is
On at least one surface of the steel plate, Zn, Al: 0.1% by mass to 22.0% by mass, Mg: 0.1% by mass to 10.0% by mass, and molten Zn—Al— Mg-based plating layer is provided,
One or more blackened oxides or hydroxides selected from the group consisting of Zn, Al, and Mg are present on the surface layer of the molten Zn—Al—Mg-based plating layer,
A hot-dip Zn-based plated steel sheet having the linear pattern according to claim 1. Of the hot-dip Zn-based plated steel sheet having the linear pattern,
Furthermore, the surface layer has a chromate film or a chromate-free film mainly composed of chromium.
A hot-dip Zn-based plated steel sheet having the linear pattern according to claim 1. Molten Zn-Al having a molten Zn-Al-Mg-based plating layer containing Zn, Al: 0.1 mass% or more and 22.0 mass% or less, and Mg: 0.1 mass% or more and 10 mass% or less -Preparing a Mg-based plated steel sheet;
Contacting the molten Zn-Al-Mg-based plated steel sheet with water vapor in a sealed container;
After contacting the water vapor, removing a part of the plating layer by mechanical polishing;
A method for producing a hot-dip Zn-based plated steel sheet having a linear pattern. After the step of removing a part of the plating layer by mechanical polishing,
And a step of forming a chromate film or a chromate-free film mainly composed of chromium on the surface layer,
The manufacturing method of the hot-dip Zn-plated steel plate which has a linear pattern of Claim 4. A decorative board made of a hot-dip Zn-plated steel sheet having a linear pattern according to claim 1.