WO2025121108A1 - 溶融Ｚｎ－Ａｌ－Ｍｇ系めっき鋼板 - Google Patents

溶融Ｚｎ－Ａｌ－Ｍｇ系めっき鋼板 Download PDF

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WO2025121108A1
WO2025121108A1 PCT/JP2024/040735 JP2024040735W WO2025121108A1 WO 2025121108 A1 WO2025121108 A1 WO 2025121108A1 JP 2024040735 W JP2024040735 W JP 2024040735W WO 2025121108 A1 WO2025121108 A1 WO 2025121108A1
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Prior art keywords
steel sheet
hot
dip
plated steel
plating film
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English (en)
French (fr)
Japanese (ja)
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昌浩 吉田
章一郎 平
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JFE Steel Corp
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JFE Steel Corp
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C18/00—Alloys based on zinc
    • C22C18/04—Alloys based on zinc with aluminium as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/06—Zinc or cadmium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D

Definitions

  • the present invention relates to hot-dip Zn-Al-Mg plated steel sheets with excellent corrosion resistance and plating adhesion.
  • Hot-dip galvanized steel sheets have excellent corrosion resistance and have conventionally been widely used as rust-resistant steel sheets in the fields of automobiles, electrical machinery, building materials, and the like.
  • a hot-dip Zn-based plating coating is composed of an interfacial alloy layer present at the interface with the base steel sheet and a main layer present on the interfacial alloy layer, and exhibits superior corrosion resistance compared to cold-rolled steel sheets and hot-rolled steel sheets, mainly due to the sacrificial corrosion protection ability of the Zn present in the main layer against Fe.
  • the above-mentioned interface alloy layer contains as its constituents an Fe-Al alloy or an Fe-Zn alloy formed by the reaction between the Fe in the base steel sheet and the Zn or Al in the coating bath.
  • Patent Document 1 discloses a hot-dip Zn-Al-Mg plated steel sheet having a plating film composition of 4.0 to 10 wt % Al, 1.0 to 4.0 wt % Mg, and the remainder being Zn and unavoidable impurities.
  • Patent Document 2 discloses a hot-dip Zn-Al-Mg plated steel sheet having a plating film composition consisting of 2 to 19 wt % Al, 1.0 to 10 wt % Mg, 0.01 to 2 wt % Si, with the balance being Zn and unavoidable impurities, with the total content of Al and Mg being 20 mass % or less.
  • hot-dip Zn-Al-Mg plated steel sheets as disclosed in Patent Documents 1 and 2, complex solidification reactions occur during the film formation process, resulting in a plated film with a complex and non-uniform structure. Due to this non-uniform structure, hot-dip Zn-Al-Mg-plated steel sheets have a problem in that the adhesion between the base steel sheet and the plating film (hereinafter referred to as "plating adhesion”), in particular the adhesion between the interface alloy layer and the main layer, is unstable and low compared to conventional hot-dip Zn-plated steel sheets.
  • plating adhesion the adhesion between the base steel sheet and the plating film
  • the present invention aims to provide a hot-dip Zn-Al-Mg plated steel sheet that combines high levels of corrosion resistance and coating adhesion.
  • the plating film has a composition containing 10 to 22 mass% Al, 0.01 to 2 mass% Si, and 3 to 10 mass% Mg, with the remainder being Zn and unavoidable impurities;
  • a Zn-Al-Mg-based hot-dip plated steel sheet characterized in that, when a cross section of the plating film in a thickness direction is observed, needle-shaped inorganic compounds having a major axis of 1 ⁇ m or more and an aspect ratio (minor axis/major axis) of 0.2 or less are formed on the interfacial alloy layer.
  • the hot-dip Zn-Al-Mg plated steel sheet according to 1 above characterized in that, when a cross section of the plating film is observed in a thickness direction, the needle-like inorganic compounds extend from a surface of the interface alloy layer into the main layer. 3.
  • the present invention provides hot-dip Zn-Al-Mg plated steel sheets that combine high levels of corrosion resistance and coating adhesion.
  • FIG. 2 is an enlarged schematic view of a cross section of the hot-dip Zn-Al-Mg plated steel sheet of the present embodiment.
  • the hot-dip Zn-Al-Mg plated steel sheet of the present invention has a plating film 20 on a base steel sheet 10, and the plating film 20 comprises an interfacial alloy layer 22 present at the interface with the base steel sheet 10 and a main layer 21 present on the interfacial alloy layer.
  • the plating film 20 has a composition containing 10 to 22 mass % Al, 0.01 to 2 mass % Si, 3 to 10 mass % Mg, with the remainder being Zn and unavoidable impurities. Note that, while FIG. 1 shows an enlarged cross section of the hot-dip Zn-Al-Mg plated steel sheet of the present embodiment, the dimensions and shapes of the components are shown diagrammatically for the sake of convenience of explanation and differ from the actual ones.
  • Zn the main component of the plating film
  • the plating layer is composed of elements with low specific gravity such as Al and Mg, so that Zn must be the main component in terms of atomic composition ratio as well. Therefore, the Zn content in the plating film must be 60 mass% or more, and preferably 70 mass% or more.
  • the upper limit of the Zn content is the content that is the remainder other than elements other than Zn and impurities.
  • Al in the plating film is an essential element for forming an Al phase in the main layer and obtaining excellent corrosion resistance.
  • the Al content of the plating film exceeds 5 mass%, an Al phase can be formed in the plating film, and the amount of Al phase formed increases with an increase in the Al content.
  • the Al content in the plating film may be 10 mass% or more. Therefore, the lower limit of the Al concentration is set to 10 mass%.
  • the Al concentration in the plating film increases, the sacrificial corrosion protection tends to deteriorate. Therefore, the upper limit of the Al concentration needs to be 22 mass% or less.
  • the Al content in the plating film is preferably 12 to 20 mass %, and more preferably 15 to 19 mass %.
  • the Si in the plating film is used to suppress the abnormal growth of the Fe-Al interfacial alloy layer that is generated mainly at the interface with the base steel sheet, and to ensure the workability of the plating film.
  • the base steel sheet is immersed in a molten Zn-Al-Mg plating bath containing the Si, the Fe on the surface of the base steel sheet reacts with the Al and Si in the bath to form an Fe-Al and/or Fe-Al-Si intermetallic compound layer at the interface between the base steel sheet and the plating film.
  • the Si content in the plating film must be 0.01 mass% or more.
  • the Si content in the plating film exceeds 2 mass%, not only will the effect of suppressing the growth of the interfacial alloy layer described above saturate, but the presence of excess Si in the plating film will also promote corrosion, so the Si content is set to 2 mass% or less.
  • Mg in the plating film has a function of stabilizing the corrosion products formed during corrosion, and is an essential element for obtaining excellent corrosion resistance.
  • the Mg content in the plating film needs to be 3 mass% or more, and to obtain a more reliable effect, it is preferable that the Mg content is 5 mass% or more.
  • the Mg content in the plating film exceeds 10 mass %, the plating film becomes hard and brittle, and the workability deteriorates, so the upper limit of the Mg content is set to 10 mass %.
  • the Mg content in the plating film is preferably 5 to 8 mass %, and more preferably 6 to 8 mass %.
  • the plating film contains unavoidable impurities.
  • the unavoidable impurities include Fe.
  • This Fe is inevitably contained in the plating film as a result of dissolution of the steel sheet or bath-immersed equipment into the plating bath, and as a result of being supplied by diffusion from the base steel sheet when the interfacial alloy layer is formed.
  • the Fe content in the plating film is usually about 0.1 to 0.5 mass%.
  • the plating film preferably further contains, as necessary, one or more elements selected from the group consisting of B, Ca, Ti, V, Cr, Mn, Co, Ni, Sr, In, Sn, Sb, Ce, Pb and Bi in a total amount of 0.1 to 5 mass %.
  • elements selected from the group consisting of B, Ca, Ti, V, Cr, Mn, Co, Ni, Sr, In, Sn, Sb, Ce, Pb and Bi in a total amount of 0.1 to 5 mass %.
  • the plating film is composed of an interface alloy layer 22 present at the interface with the base steel sheet 10 and a main layer 21 present on the interface alloy layer 22 .
  • Figure 1 shows a schematic cross-section of the base steel plate 10, the main layer 21 and the interface alloy layer 22 for ease of explanation, and the actual shapes, dimensions, etc. differ from those shown in Figure 1.
  • the interfacial alloy layer is formed in the plating process by the reaction of the base steel sheet with bath components such as Zn, Al, Mg, and Si in the plating bath, and is generally an Fe-Al and/or Fe-Al-Si intermetallic compound.
  • the base steel sheet may be pre-plated with Ni, Fe, or the like before the plating process in order to ensure wettability.
  • Ni-Al and/or Fe-Ni-Al intermetallic compounds containing Ni are formed as the interface alloy layer.
  • the interfacial alloy layer exists with an average thickness of 0.1 to 1 ⁇ m, a stable main layer can be formed on the interfacial alloy layer.
  • the average thickness is less than 0.1 ⁇ m, the interfacial alloy layer may not be formed over the entire plating film, i.e., the base steel sheet and the plating bath may not react, which may result in a stable plating adhesion and film formation.
  • the average thickness exceeds 1 ⁇ m, the interfacial alloy layer may crack during processing, causing the plating to peel off. Therefore, it is preferable that the average thickness of the interfacial alloy layer is 0.1 to 1 ⁇ m.
  • the plating bath components that were not consumed in the formation of the interface alloy layer 22 are solidified in the main layer, and thus mainly an Al phase, a Zn phase, and MgZn2 are formed.
  • the Al phase is a necessary structure for obtaining stable and excellent corrosion resistance, and when observing a cross section of the plating film in the thickness direction, the area ratio occupied by the Al phase is preferably 30% or more, and more preferably 40% or more.
  • the MgZn2 has the function of stabilizing the corrosion products formed by preferentially dissolving in the initial stage when the plating film corrodes.
  • MgZn2 is a hard intermetallic compound, its presence in the plating main layer can improve the scratch resistance of the plating film.
  • the area ratio of the MgZn2 in the main layer is preferably 10% or more, more preferably 30% or more.
  • the Zn phase mainly exerts a sacrificial corrosion protection ability against Fe together with the MgZn2 , and has an effect of improving the corrosion resistance of the end surface where Fe is exposed. In order to stably obtain such an effect, it is preferable that the area ratio of the Zn phase and the MgZn2 in the main layer is 30% or more in total when observing a cross section in the thickness direction of the plating film.
  • the hot-dip Zn-Al-Mg plated steel sheet of the present invention is characterized in that, when a cross section of the plating film is observed in the thickness direction, needle-shaped inorganic compounds having a major axis of 1 ⁇ m or more and an aspect ratio (minor axis/major axis) of 0.2 or less are formed on the interfacial alloy layer.
  • needle-shaped inorganic compounds 23 are formed on the interface alloy layer 22, and an anchor effect can be exerted between the interface alloy layer 22 and the main layer 21. This makes it possible to obtain a high level of plating adhesion while obtaining excellent corrosion resistance as a hot-dip Zn-Al-Mg plated steel sheet.
  • the long diameter of the acicular inorganic compounds 23 is determined by observing a cross section of the plating film 20 in the thickness direction in a range of 2 mm or more in a direction parallel to the surface of the base steel sheet, measuring the long diameter L of each of 10 or more randomly selected acicular inorganic compounds 23, and averaging the measured values, as shown in Fig. 1.
  • the short diameter of the acicular inorganic compounds 23 is determined by measuring the short diameter D of each of the acicular inorganic compounds 23 in the same measurement range and for the same number of compounds as the long diameter. If the long diameter of the needle-shaped inorganic compound 23 is less than 1 ⁇ m, a sufficient anchor effect may not be obtained, and the desired plating adhesion may not be obtained.
  • the long diameter of the needle-shaped inorganic compound 23 is preferably 10 ⁇ m or less, and more preferably 5 ⁇ m or less.
  • the method for observing a cross section of the plating film 20 in the thickness direction is not particularly limited as long as it allows for observing the presence or absence of the acicular inorganic compounds 23 and the major axis L and minor axis D.
  • the cross section can be observed and measured by SEM-EDX (energy dispersive X-ray analysis using a scanning electron microscope).
  • the aspect ratio of the needle-shaped inorganic compound 23 is the ratio of the short diameter to the long diameter of the needle-shaped inorganic compound 23 (short diameter D/long diameter L) as shown in FIG. 1.
  • the aspect ratio of the needle-shaped inorganic compound 23 exceeds 0.2, a sufficient anchor effect may not be obtained, and the desired plating adhesion may not be obtained.
  • the aspect ratio of the needle-shaped inorganic compound 23 is less than 0.05, the needle-shaped inorganic compound 23 penetrates deeply into the main layer 21, which may deteriorate the processability and the corrosion resistance of the processed part.
  • the aspect ratio of the needle-shaped inorganic compound 23 is preferably 0.05 to 0.2, and more preferably 0.10 to 0.15.
  • the average aspect ratio of each aspect ratio of the needle-shaped inorganic compounds 23 selected at random from a cross section of the plating film 20 in a range of 2 mm or more in a direction parallel to the surface of the base steel sheet is 0.2 or less.
  • the average aspect ratio of the needle-shaped inorganic compounds 23 is 0.2 or less, stable and excellent adhesion can be obtained.
  • the average aspect ratio of the needle-shaped inorganic compounds 23 is less than 0.05, the needle-shaped inorganic compounds 23 penetrate deeply into the main layer 21, which may deteriorate the workability and the corrosion resistance of the processed part.
  • the average aspect ratio of the needle-shaped inorganic compounds 23 is preferably 0.05 to 0.2, and more preferably 0.10 to 0.15.
  • the acicular inorganic compounds 23 preferably extend from the surface of the interface alloy layer 22 into the main layer 21 when observing a cross section of the plating film 22 in the thickness direction. This is because the acicular inorganic compounds 23 increase the adhesive strength between the interface alloy layer 22 and the main layer 21, thereby making it possible to obtain better plating adhesion.
  • the constituent components of the acicular inorganic compound preferably further contain Ni in addition to the above-mentioned Si.
  • the needle-shaped inorganic compound extending from the interface alloy layer contains Ni.
  • the coating weight of the plating film is preferably 30 to 300 g/ m2 per side.
  • the coating weight of the plating film is 30 g/ m2 or more, sufficient corrosion resistance is obtained for applications requiring long-term corrosion resistance, such as building materials, while when the coating weight of the plating film is 300 g/m2 or less , excellent corrosion resistance can be achieved while suppressing the occurrence of plating cracks during processing.
  • the coating weight of the plating film is more preferably 50 to 150 g/ m2 .
  • the amount of plating adhesion can be calculated, for example, by dissolving and peeling off a specific area of the plating film in a mixture of hydrochloric acid and hexamethylenetetramine as specified in JIS H 0401:2013, and calculating the difference in the weight of the steel sheet before and after peeling. To determine the amount of plating adhesion per side using this method, the non-target side is sealed with tape so that the plated surface is not exposed, and then the dissolution described above is carried out.
  • a plating film 20 is formed on a base steel sheet 10, but an intermediate layer or a coating film can also be further formed on the plating film, if necessary.
  • the type of the coating film and the method for forming the coating film are not particularly limited and can be appropriately selected depending on the required performance.
  • the coating film can be formed by a method such as roll coater coating, curtain flow coating, spray coating, etc. After coating the coating material containing an organic resin, the coating film can be formed by heating and drying the coating film by means of hot air drying, infrared heating, induction heating, etc.
  • the intermediate layer is not particularly limited as long as it is a layer formed between the plating film of the hot-dip Zn-Al-Mg-plated steel sheet and the coating film.
  • examples include a chemical conversion coating film and a primer such as an adhesive layer.
  • the chemical conversion coating film can be formed, for example, by a chromate treatment or a chromium-free chemical conversion treatment in which a chromate treatment liquid or a chromium-free chemical conversion coating liquid is applied, and then dried at a steel sheet temperature of 80 to 300°C without rinsing with water.
  • These chemical conversion coating films may be single-layered or multi-layered, and in the case of multi-layered films, multiple chemical conversion treatments may be performed sequentially.
  • the method for producing the hot-dip Zn-Al-Mg plated steel sheet of the present invention is not particularly limited.
  • the plating film of the hot-dip Zn-Al-Mg plated steel sheet obtained by the present invention has a composition generally equivalent to that of the plating bath. Therefore, the present invention includes a step of forming the plating film on the base steel sheet using a plating bath whose composition is controlled to contain 10-22 mass% Al, 0.01-2 mass% Si, 3-10 mass% Mg, with the balance being Zn and unavoidable impurities.
  • the step of forming the plating film is not particularly limited except for the composition of the plating bath described above.
  • the steel sheet can be produced by cleaning, heating, and immersing the base steel sheet in a coating bath in a continuous hot-dip galvanizing facility.
  • recrystallization annealing or the like is performed to control the structure of the base steel sheet itself, and heating in a reducing atmosphere such as a nitrogen-hydrogen atmosphere is effective in preventing oxidation of the steel sheet and reducing a small amount of oxide film present on the surface.
  • the temperature of the plating bath is not particularly limited, but is preferably in the range of (melting point + 20°C) to 550°C.
  • the reason why the lower limit of the bath temperature is set to the melting point + 20° C. is that the bath temperature needs to be equal to or higher than the solidification point in order to perform hot-dip plating, and by setting the temperature to the melting point + 20° C., solidification due to a local drop in the bath temperature of the plating bath is prevented.
  • the reason why the upper limit of the bath temperature is set to 550° C. is that if the bath temperature exceeds 550° C., rapid cooling of the plating film becomes difficult, and there is a risk that the interfacial alloy layer formed between the plating film and the steel sheet will become thick.
  • the method for forming the acicular inorganic compound on the interface alloy layer is not particularly limited.
  • the acicular inorganic compound can be formed by adding the acicular inorganic compound to a plating bath and performing a hot-dip plating process.
  • the acicular inorganic compound added has a major axis of 1 ⁇ m or more and an aspect ratio (minor axis/major axis) of 0.2 or less.
  • the base steel sheet constituting the Zn-Al-Mg-plated steel sheet of the present invention is not particularly limited, and a cold-rolled steel sheet, a hot-rolled steel sheet, or the like can be used as appropriate depending on the required performance and specifications.
  • the base steel sheet is also not particularly limited.
  • the method for obtaining the base steel sheet is not particularly limited.
  • the hot-rolled steel sheet one that has been subjected to a hot rolling process and a pickling process can be used, and in the case of the cold-rolled steel sheet, it can be manufactured by further adding a cold rolling process.
  • a pre-plated steel sheet may be used as the base steel sheet.
  • the pre-plated steel sheet is plated, for example, by an electrolytic treatment method or a displacement plating method.
  • the base steel sheet may be immersed in a sulfate bath or a chloride bath containing metal ions of various pre-plating components to perform electrolytic treatment.
  • the displacement plating method the base steel sheet may be immersed in an aqueous solution containing metal ions of various pre-plating components and having a pH adjusted with sulfuric acid to cause displacement precipitation of metal.
  • a representative example of a pre-plated steel sheet is a Ni pre-plated steel sheet.
  • Ni pre-plated steel sheet it is particularly preferable to subject a Ni pre-plated steel sheet to hot-dip plating in a bath containing the above-mentioned needle-shaped inorganic compounds, since the needle-shaped inorganic compounds tend to extend from the surface of the interface alloy layer into the main plating layer, improving the adhesion of the resulting hot-dip Zn-Al-Mg plated steel sheet.
  • Examples 1 to 3 (Manufacturing method A:) A cold-rolled steel sheet having a thickness of 0.8 mm, manufactured by a conventional method, was used as a base steel sheet, and annealing and plating were performed using a hot-dip plating simulator manufactured by Rhesca Corporation to produce hot-dip Zn-Al-Mg plated steel sheet samples 1 to 3 under the conditions shown in Table 1.
  • Table 1 shows the composition and bath temperature of the plating bath used in the production of the hot-dip Zn-Al-Mg plated steel sheets, and the composition and coating weight of the plating film of each sample.
  • Example 4 to 9 (Manufacturing method B:) A cold-rolled steel sheet having a thickness of 0.8 mm, manufactured by a conventional method, was used as a base steel sheet, and annealing and hot-dip plating were performed using a hot-dip plating simulator manufactured by Rhesca Corporation, to produce samples 4 to 9 of hot-dip Zn-Al-Mg plated steel sheets under the conditions shown in Table 1.
  • Table 1 shows the composition and bath temperature of the plating bath used in the production of the hot-dip Zn-Al-Mg plated steel sheets, and the composition and coating weight of the plating film of each sample.
  • an acicular inorganic compound was added to the plating bath in an amount of 0.1% based on the total weight of the plating bath.
  • the type, average major axis, and aspect ratio of the acicular inorganic compound are shown in Table 1.
  • the Ni pre-plating treatment of the cold-rolled steel sheet was performed using a plating bath with a NiSO4.6H2O concentration of 300 g/L, a H3BO3 concentration of 40 g/L, a Na2SO4 concentration of 100 g/L, and a pH of 2.7, with a bath temperature of 60°C and a current density of 50 A/ dm2 , and controlled so that the Ni deposition weight was 1 g/ m2 .
  • Table 1 also shows the composition and bath temperature of the plating bath used in the production of the hot-dip Zn-Al-Mg plated steel sheets, as well as the composition and coating weight of the plating film of each sample.
  • an acicular inorganic compound was added to the plating bath in an amount of 0.1% relative to the total weight of the plating bath for each of Samples 10 to 14.
  • the type, average major axis, and aspect ratio of the acicular inorganic compound are shown in Table 1.
  • Needle-like inorganic compounds For each sample of hot-dip Zn-Al-Mg-plated steel sheet thus prepared, a cross section was observed and analyzed at one random location by scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX). For each sample, the presence or absence of needle-shaped inorganic compounds observed in the cross section of the plating film in the thickness direction, the components contained in the needle-shaped inorganic compounds, the average size (long diameter, aspect ratio) of the needle-shaped inorganic compounds, and the presence or absence of any of the needle-shaped inorganic compounds extending from the interfacial alloy layer were measured and calculated, and the results are shown in Table 1.
  • ⁇ No peeling of plating film (no cracks or only cracks)
  • the plating film is slightly peeled off (the total diameter of the peeled part is less than 5 mm)
  • ⁇ Plating film is clearly peeled off (total diameter of peeled off area is 5mm or more)
  • Table 1 show that the samples of the present invention have a good balance of corrosion resistance and plating adhesion compared to the samples of the comparative examples.
  • the present invention provides hot-dip Zn-Al-Mg plated steel sheets that combine high levels of corrosion resistance and coating adhesion.
  • Base steel sheet 20
  • Plating film 21
  • Main layer 22
  • Interface alloy layer 23
  • Needle-shaped inorganic compound L
  • Long diameter of needle-shaped inorganic compound D

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PCT/JP2024/040735 2023-12-04 2024-11-15 溶融Ｚｎ－Ａｌ－Ｍｇ系めっき鋼板 Pending WO2025121108A1 (ja)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016140370A1 (ja) * 2015-03-02 2016-09-09 Ｊｆｅ鋼板株式会社 溶融ＡＩ－Ｚｎ－Ｍｇ－Ｓｉめっき鋼板とその製造方法
WO2018169085A1 (ja) * 2017-03-17 2018-09-20 新日鐵住金株式会社 めっき鋼板
WO2021215421A1 (ja) * 2020-04-21 2021-10-28 日本製鉄株式会社 溶融めっき鋼板、及びその製造方法

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016140370A1 (ja) * 2015-03-02 2016-09-09 Ｊｆｅ鋼板株式会社 溶融ＡＩ－Ｚｎ－Ｍｇ－Ｓｉめっき鋼板とその製造方法
WO2018169085A1 (ja) * 2017-03-17 2018-09-20 新日鐵住金株式会社 めっき鋼板
WO2021215421A1 (ja) * 2020-04-21 2021-10-28 日本製鉄株式会社 溶融めっき鋼板、及びその製造方法

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