WO2025017974A1 - 表面処理鋼材 - Google Patents

表面処理鋼材 Download PDF

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Publication number
WO2025017974A1
WO2025017974A1 PCT/JP2024/012767 JP2024012767W WO2025017974A1 WO 2025017974 A1 WO2025017974 A1 WO 2025017974A1 JP 2024012767 W JP2024012767 W JP 2024012767W WO 2025017974 A1 WO2025017974 A1 WO 2025017974A1
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Prior art keywords
compound
plating layer
plated
compounds
less
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English (en)
French (fr)
Japanese (ja)
Inventor
慎平 ▲徳▼田
義勝 西田
浩雅 莊司
晋 上野
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Nippon Steel Corp
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Nippon Steel Corp
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Priority to AU2024291770A priority Critical patent/AU2024291770A1/en
Priority to JP2024548529A priority patent/JP7684623B1/ja
Publication of WO2025017974A1 publication Critical patent/WO2025017974A1/ja
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    • 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
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/26—After-treatment
    • 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
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
    • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
    • C23C22/48—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 not containing phosphates, hexavalent chromium compounds, fluorides or complex fluorides, molybdates, tungstates, vanadates or oxalates
    • C23C22/50—Treatment of iron 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
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
    • C23C22/68—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous solutions with pH between 6 and 8
    • 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
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent

Definitions

  • the present invention relates to a surface-treated steel material.
  • This application claims priority based on Japanese Patent Application No. 2023-116278, filed on July 14, 2023, the contents of which are incorporated herein by reference.
  • the plated steel materials disclosed in the above Patent Documents 1 to 4 are excellent in long-term corrosion resistance of flat surfaces. However, when the plated steel materials are used, they may be cut to a predetermined size. In this case, the plated layer is not formed on the cut surface (cut end surface). Even on plated surfaces, there may be unplated areas, or areas where the plated layer is not formed (where the steel sheet is exposed) due to scratches causing the plated layer to peel off or cracks caused by cutting, punching, bending, drawing, or the like.
  • the present invention aims to provide a surface-treated steel material, such as a surface-treated steel sheet having a Zn-based plating layer containing Mg, in which the formation of red rust in non-plated areas is suppressed.
  • the inventors have investigated the above-mentioned problem. As a result, they have found that the formation of red rust can be suppressed by having a compound containing a specific amount of Mg present on the surface of the steel sheet in the non-plated areas where no plating layer is formed.
  • a surface-treated steel material has a steel material and a plating layer formed on at least a part of a surface of the steel material, the plating layer being a Zn-based plating layer containing 0.3 to 12.5 mass% Mg, and when a part of the surface of the steel material where the plating layer is not formed is defined as a non-plated part, at least a part of the non-plated part contains one or more compounds selected from the group consisting of Compound A, Compound B, Compound C, Compound D, Compound E, Compound F, Compound G, Compound H, Compound I, and Compound J.
  • Compound A MgO
  • Compound B Mg(OH) 2
  • Compound C MgCO3
  • Compound D Mg 4 Al 2 (OH) 12 CO 3.3H 2 O
  • Compound E Mg 6 Al 2 (OH) 16 CO 3.4H 2 O
  • Compound F Zn6Al2 ( OH ) 16CO3.4H2O containing Mg
  • Compound G 4MgCO3.Mg ( OH)2.5H2O
  • Compound H Zn5 ( CO3 ) 2 (OH) 6 containing Mg
  • Compound I Zn5 (OH) 8Cl2.H2O containing Mg
  • Compound J NaZn4 ( SO4 )Cl(OH) 6.6H2O containing Mg .
  • the plating layer may contain 4.0 to 25.0 mass % Al.
  • the surface-treated steel material according to [1] or [2] may be covered with the compound over an area ratio of 50% or more.
  • the compound may include one or more selected from the group consisting of compound D, compound E, compound F, compound H, and compound I, and one or more selected from the group consisting of compound A, compound B, compound C, compound G, and compound J.
  • the compound may include two or more selected from the group consisting of compound B, compound D, compound G, compound H, and compound I.
  • the total composition ratio of one or two of the compounds H and I among the compounds may be 10% or more in terms of molar ratio.
  • the above aspect of the present invention makes it possible to provide a surface-treated steel material that inhibits the formation of red rust in non-plated areas.
  • FIG. 1 is a schematic diagram showing an example of a surface-treated steel sheet, which is one form of a surface-treated steel material according to the present embodiment.
  • FIG. FIG. 1 is a diagram showing an image of normalization of an XAFS spectrum.
  • a surface-treated steel material according to one embodiment of the present invention (surface-treated steel material according to this embodiment) will be described using a surface-treated steel sheet as an example.
  • a surface-treated steel sheet 1 (hereinafter, surface-treated steel sheet according to this embodiment), which is an example of a surface-treated steel material according to this embodiment, has a steel sheet (base steel sheet) 11 and a plating layer 12 formed on at least a part of a surface 101 of the steel sheet 11, as shown in FIG. 1 , and when a part of the surface 101 of the steel sheet 11 where the plating layer 12 is not formed is defined as a non-plated portion 41, a predetermined compound 31 containing Mg is present in at least a part of the non-plated portion 41 of the steel sheet 11.
  • the surface of the surface 101 that comes into contact with the plating bath and on which a plating layer is formed is the plated surface 103, and the surface that is exposed when the product is pulled up from the plating bath and cut to a predetermined size is the end surface 102.
  • the end surface 102 is in a direction that intersects with the plated surface 103, and in many cases, is in a direction that is approximately perpendicular to the plated surface 103.
  • the shape of the surface-treated steel material according to the present embodiment is not limited to a steel plate.
  • it may be a shape obtained by bending a steel plate, a shape like a steel pipe, a shape like a steel bar or steel wire, or a shape like a steel section having an H-shape or T-shape.
  • the surface-treated steel material according to this embodiment will be described in detail below, taking a surface-treated steel sheet as an example.
  • a numerical range expressed using “to” means a range that includes the numerical values before and after "to” as the lower and upper limits. However, when the numerical values before and after "to” are followed by "more than” or “less than,” the numerical range does not include these numerical values as the lower or upper limit.
  • the surface-treated steel sheet 1 according to this embodiment is characterized by the plating layer 12 and the compound 31. Therefore, the steel sheet 11 is not particularly limited.
  • the steel sheet 11 may be determined according to the product to which it is applied and the required strength and sheet thickness, and may be, for example, a hot-rolled steel sheet described in JIS G 3131:2018, JIS G 3113:2018, or a cold-rolled steel sheet described in JIS G 3141:2021, JIS G 3135:2018, or the like.
  • steel materials such as steel pipes, steel wires, and various members made of steel other than steel sheets can be used.
  • the plate thickness is not limited, but the preferred range of the plate thickness is 1.0 to 9.0 mm.
  • a plating layer 12 is formed on at least a part of the surface of a steel sheet 11.
  • the plating layer 12 is a Zn-based plating layer containing 0.3 mass% to 12.5 mass% Mg.
  • the plating layer may further contain 4.0 mass% to 25.0 mass% Al.
  • the Zn-based plating layer is a plating layer having a Zn concentration of 50.0 mass % or more.
  • Zn and Mg, or Zn, Mg and Al often form an alloy in the plating layer, but the state in which Zn, Mg and Al are present is not limited.
  • the plating layer 12 may be formed on the entire (100% by area) plating surface 103 (front and back surfaces (in the case of a cut plated steel sheet, this will often be the surface other than the end faces)) of the steel sheet 11, but there may be portions (non-plated portions 41) that are not formed due to non-plating or peeling due to scratches, etc.
  • the area ratio of the non-plated portions 41 is preferably 10% or less of the entire plating surface.
  • the area ratio of the non-plated portions 41 on the plating surface 103 may be 0%.
  • the plating layer 12 may be formed on a part of the surface 101 other than the plated surface 103 (end surface 102 in FIG.
  • the area ratio of the non-plated portion 41 may be more than 0% of the entire surface including the surface other than the plated surface 103.
  • the plating layer 12 is made into a Zn-based plating layer 12 containing Mg, and then a specific treatment described below is performed, so that the formation of red rust is suppressed even in the non-plated portion 41 (red rust resistance is improved).
  • a specific treatment Mg contained in the Zn-based plating layer 12, which dissolves through sacrificial corrosion protection, generates a compound, described later, in the non-plated portion 41.
  • the plating layer 12 is not a Zn-based plating layer containing Mg, the effect of forming the compounds 31 cannot be sufficiently obtained. Even if the steel sheet 11 contains Mg, the amount of Mg contained in the steel sheet 11 is very small and the amount of Mg eluted from the steel sheet 11 is small, so that the same effect cannot be obtained.
  • the Mg concentration (content) in the Zn-based plating layer 12 is set to 0.3 mass% or more and 12.5 mass% or less. If the Mg concentration (content) is less than 0.3 mass%, compounds containing Mg are not formed. Therefore, the Mg concentration is set to 0.3 mass% or more. On the other hand, if the Mg concentration is more than 12.5 mass%, the workability decreases. Therefore, the Mg concentration is set to 12.5 mass% or less.
  • the concentrations (contents) of elements other than those mentioned above are not limited.
  • the chemical composition of the plating layer 12 is, in mass %, Mg: 0.3-12.5%, Al: 0-25.0%, Sn: 0-20.0%, Bi: 0-less than 5.0%, In: 0-less than 2.0%, Ca: 0-3.0%, Y: 0-0.5%, La: 0-less than 0.5%, Ce: 0-less than 0.5%, Si: 0-less than 2.5%, Cr: 0-less than 0.25%, Ti: 0-less than 0.25%, Ni: 0-less than 0.25%, Co: 0-0.
  • V 0-0.25%
  • Nb 0-0.25%
  • Cu 0-0.25%
  • Mn 0-0.25%
  • Fe 0-5.0%
  • Sr 0-0.5%
  • Sb 0-0.5%
  • Pb 0-0.5%
  • B 0-0.5%
  • Zn and impurities This is preferable because it provides excellent corrosion resistance for the surface-treated steel sheet 1, including the portion where the plating layer 12 is formed.
  • the percentages for the concentration (content) of each element in the chemical composition of the plating layer 12 are mass percentages.
  • the Mg concentration is 0.3% or more.
  • Mg is also an element that has the effect of improving the corrosion resistance of the plating layer 12.
  • the Mg concentration is The Mg concentration is preferably 0.5% or more, more preferably 1.0% or more, and further preferably 3.0% or more.
  • the Mg concentration exceeds 12.5%, the effect of improving corrosion resistance becomes saturated and the workability of the coating layer may decrease.
  • the Mg concentration is set to 12.5% or less, more preferably 10.0% or less, and further preferably 8.0% or less.
  • Al is an element effective for improving the corrosion resistance of the plating layer (Zn-based plating layer) 12. Therefore, although the lower limit of the Al concentration is 0%, Al may be contained. In order to obtain a sufficient amount of Al, the Al concentration is preferably 2.0% or more or 4.0% or more. If necessary, the Al concentration may be 6.0% or more or 8.0% or more. On the other hand, if the Al concentration exceeds 25.0%, the sacrificial anticorrosive effect of the plating layer 12 decreases. Therefore, the Al concentration is preferably 25.0% or less. It may be 0% or less or 16.0% or less.
  • the concentration of these elements contribute to improving corrosion resistance and sacrificial corrosion protection. Therefore, although the lower limit of the concentration of these elements is 0%, any one or more of them may be contained. When such a solution is obtained, the concentration of each is preferably 0.05% or more. Among these, Sn is preferred because it is a low melting point metal and can be easily incorporated into the plating bath without impairing the properties of the bath. On the other hand, if the Sn concentration exceeds 20.0%, the Bi concentration is 5.0% or more, or the In concentration is 2.0% or more, the corrosion resistance decreases. It is preferable that the Al concentration is less than 5.0% and the In concentration is less than 2.0%.
  • Ca is an element that reduces the amount of dross that is easily formed during operation and contributes to improving plating manufacturability. Therefore, although the lower limit of the Ca concentration is 0%, Ca may be contained. In order to obtain the desired effect, the Ca concentration is preferably 0.1% or more. On the other hand, if the Ca concentration is high, the corrosion resistance of the flat portion of the plating layer 12 itself tends to deteriorate, and the corrosion resistance around the welded portion may also deteriorate. Therefore, the Ca concentration is preferably 3.0% or less. .
  • Y, La, and Ce are elements that contribute to improving corrosion resistance.
  • the lower limit of the concentration of these elements is 0%, but to obtain this effect, one or more of these elements should be 0.05% each. It is preferable that the content is more than 1.
  • the concentrations of these elements are excessive, the viscosity of the plating bath increases, and the preparation of the plating bath itself often becomes difficult, and there is a concern that it may not be possible to produce steel products with good plating properties.
  • the Y concentration is 0.5% or less
  • the La concentration is less than 0.5%
  • the Ce concentration is less than 0.5%.
  • Si is an element that contributes to improving corrosion resistance.
  • Si is also an element that has the effect of suppressing the formation of an excessively thick alloy layer between the surface of the steel sheet 11 and the plating layer 12 when forming the plating layer 12 on the steel sheet 11, thereby enhancing the adhesion between the steel sheet 11 and the plating layer 12.
  • the lower limit of the Si concentration is 0%, but to obtain these effects, it is preferable to set the Si concentration to 0.1% or more.
  • the Si concentration is more preferably 0.2% or more.
  • the Si concentration is less than 2.5%.
  • the Si concentration is more preferably 1.5% or less.
  • the concentrations of these elements are excessive, the viscosity of the coating bath increases, making it difficult to prepare the coating bath itself, and there is a concern that it may not be possible to produce steel products with good coating properties. Therefore, it is preferable to set the concentration of each element to less than 0.25%.
  • Fe may be mixed into the plating layer 12 during the production of the plating layer 12.
  • the content of Fe may be up to about 5.0%.
  • the adverse effect on the effect is small. Therefore, it is preferable to set the Fe concentration to 5.0% or less.
  • the inclusion of Fe is not essential.
  • the lower limit of the Fe concentration is 0%.
  • the concentration of these elements is 0%, but to obtain this effect, the concentration of one or more of Sr, Sb, and Pb is preferably 0.05% or more, and more preferably 0.1% or more.
  • the concentrations of these elements are excessive, the viscosity of the coating bath increases, making it difficult to prepare the coating bath itself, and there is a concern that it may not be possible to produce steel products with good coating properties. Therefore, it is preferable to set the concentration of each element to less than 0.5%.
  • B is an element that, when contained in the plating layer 12, combines with Zn, Al, Mg, etc. to form various intermetallic compounds. These intermetallic compounds have the effect of improving LME.
  • the lower limit of the B concentration is 0%, but to obtain this effect, the B concentration is preferably 0.05% or more, and more preferably 0.1% or more.
  • the B concentration is preferably less than 0.5%.
  • the elements other than those mentioned above may be Zn and impurities.
  • the concentration of Zn in the plating layer 12 is 50.0% or more, preferably 62.5% or more, more preferably 70.0% or more, and even more preferably 85.0% or more.
  • the Zn-based plating layer means that the concentration of Zn in the plating layer 12 is 50.0% or more.
  • Impurities are elements that are mixed in from raw materials during the manufacturing process. The total concentration of impurities is usually 0.5% or less, but it is preferable if the total concentration is 0.1% or less.
  • raw materials containing relatively large amounts of elements other than the above elements, including Zn may be used intentionally. Therefore, in this embodiment, these elements (elements other than the above elements, including Zn) are all considered to be impurity elements, regardless of whether they are mixed in or intentionally added. For this reason, it is preferable that the total concentration of these elements is 0.5% or less.
  • the coating weight of the plating layer 12 is not limited, but is preferably 10 g/ m2 or more per side to improve corrosion resistance. If necessary, it may be 20 g/m2 or more , 40 g/m2 or more , or 60 g/m2 or more per side to further improve corrosion resistance. On the other hand, if the coating weight exceeds 400 g/ m2 per side, the corrosion resistance will saturate and it will be economically disadvantageous. Therefore, it is preferable that the coating weight per side is 400 g/ m2 or less. If necessary, it may be 350 g/m2 or less , 300 g/m2 or less, or 250 g/m2 or less per side to further improve economic efficiency.
  • the chemical composition of the plating layer 12 can be measured by the following method. First, the plating layer 12 is peeled off and dissolved with an acid containing an inhibitor that suppresses corrosion of the base steel (steel sheet 11) (for example, an acid obtained by adding 1% Hibilon (A-6) (manufactured by Sugimura Chemical Industry Co., Ltd.) to 10% hydrochloric acid) to obtain an acid solution. Next, the chemical composition of the plating layer 12 can be obtained by measuring the obtained acid solution by ICP analysis.
  • an acid containing an inhibitor that suppresses corrosion of the base steel for example, an acid obtained by adding 1% Hibilon (A-6) (manufactured by Sugimura Chemical Industry Co., Ltd.) to 10% hydrochloric acid
  • the amount of adhesion of the plating layer 12 is determined by measuring the change in mass (weight) of a sample (a sample taken from the surface-treated steel sheet 1) before and after the plating layer 12 is peeled and dissolved by an acid containing an inhibitor using the method described above, and calculating the amount of adhesion from the results.
  • a compound 31 containing Mg is present in at least a part of the non-plated portion 41 of the surface 101 (plated surface 103, end surface 102) of the steel sheet 11.
  • This compound contains one or more compounds selected from the following (consists essentially of one or more compounds selected from the following, but is permitted to contain trace amounts of other compounds):
  • Compound D Mg 4 Al 2 (OH) 12 CO 3.3H 2 O
  • Compound E Mg 6 Al 2 (OH) 16 CO 3.4H 2 O
  • Compound F Zn6Al2 (OH)16CO3.4H2O containing Mg
  • Compound G 4MgCO3.Mg ( OH ) 2.5H2O
  • Compound H Zn5 ( CO3 ) 2 (OH) 6 containing Mg
  • the Mg concentration (Mg content) of compound F, compound H, compound I, and compound J prepared by the reagent preparation procedure described below is 0.1% or more by mass.
  • the Mg content of these compounds can be easily measured by a known ICP atomic emission spectrometry test. The presence of these compounds improves the corrosion resistance of the non-plated portion 41 and suppresses the formation of red rust.
  • the present inventors performed electrochemical measurements on the end surface and found that when these compounds are present, the current value is suppressed on both the cathode side and the anode side (especially the anode side) compared to when these compounds are not present. From this, it is believed that this is due to the physical protective effect (cathode reaction suppression) of the presence of these compounds and the passivation effect (anode reaction suppression) caused by the increase in pH near the surface that occurs when these Mg-containing compounds dissolve in the moisture in the environment.
  • the compound preferably contains one or more compounds selected from the following group a and one or more compounds selected from group b: Group a: a group consisting of compound D, compound E, compound F, compound H, and compound I; Group b: a group consisting of compound A, compound B, compound C, compound G, and compound J.
  • the compounds in group a are highly effective in improving red rust resistance due to the physical protective action (inhibition of cathodic reaction) provided by the presence of these compounds, while the compounds in group b are highly effective in improving red rust resistance due to the passivation action (inhibition of anodic reaction) caused by the increase in pH near the surface that occurs when these Mg-containing compounds dissolve in moisture in the environment.
  • a synergistic effect is achieved, resulting in a more excellent red rust inhibiting effect than when only a compound of one group is contained.
  • the compound preferably contains two or more compounds selected from the group consisting of compound B, compound D, compound G, compound H, and compound I.
  • the compound may essentially consist of two or more compounds selected from the above group.
  • the total composition ratio of compound H and one or two of compound I is preferably 10% or more in terms of substance amount ratio (molar ratio).
  • an area ratio of 50% or more of the non-plated portion 41 where the plating layer 12 is not formed is covered with the above compounds.
  • the covered area ratio may be 100%.
  • the compounds present in the non-plated portion 41 are identified by performing X-ray absorption fine structure analysis (hereinafter, referred to as XAFS analysis) and performing fitting processing of the XAFS spectrum. Specifically, it can be obtained by the following method. First, a sample, for example, of sheet thickness x 7 mm x 7 mm, including the non-plated portion 41 to be measured, is cut out from the surface-treated steel sheet 1. XAFS analysis is performed on the non-plated portion 41 (for example, in a range of 1.0 mm x 1.2 mm) of the sample to obtain an XAFS spectrum. The obtained spectrum is fitted with a linear combination of the spectra of standard samples of each compound using Athena (analysis software), thereby identifying the compounds.
  • XAFS analysis X-ray absorption fine structure analysis
  • the measurement conditions for the XAFS analysis are as follows. ⁇ Measurement of Mg K absorption edge ⁇ Measurement atmosphere: High vacuum ⁇ Measurement temperature: Room temperature ⁇ Energy range: 1250 eV to 1540 eV (step: 0.2 eV)
  • the incident X-ray intensity I0 is determined from the sample current of the Au mesh.
  • the detected X-ray intensity I is determined by the fluorescence yield method (SDD detector) and the total electron yield method (sample current method).
  • the XPS Au4f peak position is measured before measuring the sample. To improve the signal-to-noise ratio, measurements are taken three times and the average spectrum is used for analysis.
  • the fitting is carried out as follows: The energy is corrected based on the Au4f peak position of XPS. As shown in Figure 2, the background is subtracted and the overall intensity is normalized so that the difference in intensity between the pre-edge and post-edge is 1. - The spectrum obtained from the sample is fitted with a linear combination of the spectra of standard samples of each compound. The R-factor is used to confirm the validity of the fitting, and if the R-factor is 5% or less in the region from 1300 to 1380 eV, it is judged to be valid, and if the R-factor is more than 5%, it is judged that the fitting was not possible. If fitting using standard samples of compounds A to J was not possible, it means that it cannot be determined that at least one compound among compounds A to J is present.
  • the R-factor is calculated using the following formula.
  • d' in the formula represents the fitting data (spectral data when the spectra of each compound are linearly combined), and d represents the measurement data.
  • R factor ⁇ (d'-d) 2 / ⁇ d 2 When the sum of the constituent ratios of each compound is 100%, a compound with a constituent ratio of 1% or more is judged to be "present".
  • Each of these coefficients is the constituent ratio of each compound.
  • the units of a, b, c, ..., j are the molar ratios of compounds A, B, C, ..., J, respectively.
  • Compound E ( Mg6Al2 (OH) 16CO3.4H2O ): (commercially available reagent ) manufactured by Fujifilm Wako Pure Chemical Industries , Ltd., product name: Hydrotalcite Compound F ( Zn6Al2 ( OH ) 16CO3.4H2O containing Mg): Preparation procedure: 0.2M ZnCl2 -0.1M AlCl3 -0.050M MgCl2 solution (however, the amount of MgCl2 is within the range of 0.045M to 0.055M MgCl2 ) is dropped into 0.1M Na2CO3 , the pH is adjusted to 10 , and the solution is left for 24 hours, then suction filtered and dried.
  • Compound G ( 4MgCO3.Mg (OH) 2.5H2O ): (commercially available reagent ) manufactured by Kanto Chemical Co., Ltd., product name: magnesium hydroxide carbonate
  • Compound H ( Zn5 ( CO3 ) 2 (OH) 6 containing Mg):
  • Preparation procedure 0.1M Na2CO3 is added dropwise to a 0.1M ZnCl2-0.050M MgCl2 solution (however, the amount of MgCl2 is within the range of 0.045M to 0.055M MgCl2 ) to adjust the pH to 10, and then the solution is left to stand for 24 hours, after which it is suction filtered and dried.
  • the coverage (coverage area) of the compound in the non-plated portion 41 is determined by the following method.
  • a Mg mapping analysis is performed by ⁇ -XRF (micro-X-ray fluorescence) on the portion where the plating layer 12 is not formed (non-plated portion 41), the intensity of the ⁇ -XRF spectrum is measured, and the ratio of the area of the region where the Mg concentration is 0.5 atomic % or more to the area of the non-plated portion 41 where the plating layer 12 is not formed is defined as the "compound coverage rate.”
  • the ⁇ -XRF measurement conditions are as follows: Measurement atmosphere: vacuum Acceleration voltage: 15 kV Current value: 50 ⁇ A Tube: Rh tube Scan speed: 4.00 mmS -1 Polymeter: 30 ⁇ m
  • the surface-treated steel sheet 1 according to the present embodiment can obtain its effects as long as it has the above-mentioned characteristics regardless of the manufacturing method, but it can be manufactured by a manufacturing method including the following steps.
  • III A compound forming step of forming a predetermined compound containing Mg on the end surface and/or the non-plated portion 41 of the plated surface. Preferable conditions for each step will be described.
  • plating process In the plating process, a steel material such as a steel sheet is immersed in a plating bath containing Mg and Zn, or is electroplated to form a plating layer 12 on the surface. There are no particular limitations on the conditions for forming the plating layer 12. A normal method may be used so as to obtain sufficient plating adhesion. In addition, the steel material to be subjected to the plating process and its manufacturing method are not limited.
  • a hot-rolled steel sheet described in JIS G 3113:2018 or JIS G3131:2018 or a cold-rolled steel sheet described in JIS G 3141:2021 or JIS G 3135:2018 can be used as the steel sheet to be immersed in the plating bath.
  • steel materials such as steel pipes, steel wires, and various members made of steel other than steel sheets can be used.
  • the composition of the plating bath may be adjusted according to the chemical composition of the plating layer 12 desired to be obtained. After the steel material is pulled out of the plating bath, the amount of coating of the plating layer 12 can be adjusted by wiping, if necessary.
  • the plated steel sheet is cut and/or punched to have any shape.
  • an end surface on which the plated layer 12 is not formed is formed at the cut portion.
  • An end surface is also formed in the punched portion.
  • the shape may be changed by bending, drawing, etc. In this case, a non-plated portion 41 may be generated on the plated surface.
  • a predetermined compound containing Mg is formed in the non-plated portion 41 (the non-plated portion 41 of the end face and/or the plated surface) where the plating layer 12 is not formed.
  • the steel sheet after the processing step is brought into contact with the plating layer 12 and the non-plated portion 41 on which the plating layer 12 is not formed, for 1 to 20 minutes , with a solution containing Cl - : 1.0 to 100.0 mM, SO 4 2- : 0.1 to 10.0 mM, Na + : 1.0 to 100.0 mM, and CO 3 2- : 1.0 to 100.0 mM, the solution having a pH of 4.5 to 7.0 and a liquid temperature of 25 to 60°C.
  • the steel sheet is thoroughly dried for 5 to 20 minutes in an inert atmosphere of nitrogen gas or argon gas or the like at a temperature of 40 to 60° C. and a relative humidity of 20 to 40%. If the concentrations of Cl - , SO 4 2- , Na + , and CO 3 2- in the solution and the pH of the solution are outside the above ranges, the adhesion between the compounds formed in the non-plated portion 41 and the steel sheet 11 (base material) will be poor, and the specified compounds will not be sufficiently formed in the non-plated portion 41. Furthermore, if the contact time is shorter than the above range, the specified compounds will not be sufficiently formed in the non-plated portion 41.
  • the contact time exceeds 20 minutes, corrosion of the plated portion will progress and the corrosion resistance of the plated portion may decrease. Furthermore, if the temperature of the solution is less than 25° C. or more than 60° C., the formation of the desired compounds in the non-plated areas will be insufficient. Furthermore, if the drying atmosphere is other than an inert atmosphere such as nitrogen gas or argon gas, red rust may occur in the non-plated portions. If the drying temperature is less than 40° C. or more than 60° C., the formation of the specified compounds in the non-plated parts may be insufficient, and if it exceeds 60° C., the drying proceeds too quickly and the compounds may not remain in the non-plated parts.
  • the specified compounds may not be formed, and red rust may occur in the non-plated parts.
  • the relative humidity is less than 20% or more than 40%, the formation of the specified compounds in the non-plated parts will be insufficient, and as a result, the specified compounds will not be formed and red rust may occur in the non-plated parts.
  • the drying time is less than 5 minutes or more than 20 minutes, the formation of the specified compounds in the non-plated parts will be insufficient, and as a result, the specified compounds will not be formed and red rust may occur in the non-plated parts.
  • a hot-rolled steel plate having a thickness of 4.5 mm satisfying JIS G 3131:2018 was prepared.
  • This steel sheet was subjected to hot-dip plating to form a Zn-based plating layer having the chemical composition shown in Tables 1 to 6.
  • the concentration (content) of impurities in the plating layer was 0.1% or less.
  • the coating weight of the plating layer was 135 g/ m2 on both the front and back plated surfaces.
  • the obtained plated steel sheet (surface-treated steel sheet) was cut with an electric shear to form an end surface having a portion with a plated layer and a portion without a plated layer (where the steel sheet was exposed). No non-plated portion was formed on the plated surface.
  • the end surface was brought into contact with the solutions shown in Tables 7 to 12. Thereafter, the end surface was dried in a nitrogen gas atmosphere or in an atmosphere shown in Tables 13 to 18.
  • compounds were formed by any of the following methods.
  • Compound formation method 1 Immersed in 5 mass% NaCl aqueous solution (pH: 5-6, solution temperature: 30°C) for 20 minutes.
  • Compound formation method 2 Immersed in 5 mass% NaCl aqueous solution (pH: 5-6, solution temperature: 25°C) for 72 hours.
  • Compound formation method 3 28.6 g of magnesium ethoxide was diluted with pure water to 200 cc, and then further diluted with ethylene glycol monoethyl ether to 1 L in a bath, which was then applied by the pulling method, dried, and then heat-treated at 100-400°C.
  • Compound formation method 4 Using a molten salt containing 60 mol% MgCl2 , 20 mol% NaCl, and 20 mol% KCl, which was heated and dissolved at 500°C, a cathodic electrolysis treatment was performed in an atmosphere with a partial pressure of H2O of 16 mmHg, with a current density of 20 A/ dm2 and a current flow time of 5 seconds.
  • Compound formation method 5 Mg Cathodic electrolysis was carried out in an aqueous solution containing 0.3 g/L of 2+ and 0.5 g/L of NO 3 - with a pH of 7.0, at a current density of 50 A/dm 2 and a current application time of 5 seconds.
  • the compounds present on the end faces were identified and the coverage rate on the end faces was measured in the manner described above. When multiple compounds were present, their abundance ratios were also determined.
  • the thickness of the compounds was set to about 10 nm to 30 ⁇ m by changing the time for which the steel sheet was in contact with the solution.
  • no compound detected means that none of the compounds A to J were detected. More specifically, in fitting with the standard samples of compounds A to J, the R factor exceeded 5% in the region from 1300 to 1380 eV, meaning that fitting with the standard samples of compounds A to J was not possible and it was not possible to determine the presence of at least one of compounds A to J.
  • an exposure test was carried out on the surface-treated steel sheets after contact with the solution and drying, and the area ratio of red rust on the end face after 50 days was determined.
  • the exposure conditions were as follows: The steel sheet samples were inclined 30° from the horizontal so that the treated cut end surface was at the top, and were placed facing south to conduct the atmospheric exposure test. After exposure, the samples were evaluated as follows based on the ratio of the area where red rust occurred to the area where the plating layer was not formed.
  • SS 70% or less
  • S More than 70% to 80% or less
  • AA More than 80% to 90% or less
  • A More than 90% to 100% or less
  • B More than 100% to 115% or less
  • C More than 115% Those with a red rust area rate of SS, S, AA, or A after 50 days of exposure were judged to have excellent red rust resistance. When the percentage of the area where red rust occurred exceeded 100%, red rust occurred not only in the areas where the plating layer was not formed but also in the surrounding areas.
  • the present invention provides a surface-treated steel material that inhibits the formation of red rust in non-plated areas, and therefore has high industrial applicability.

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JP7769282B1 (ja) * 2024-05-16 2025-11-13 日本製鉄株式会社 表面処理鋼材
WO2025238907A1 (ja) * 2024-05-16 2025-11-20 日本製鉄株式会社 表面処理鋼材

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JP2006193791A (ja) 2005-01-14 2006-07-27 Nippon Steel Corp 表面外観に優れた溶融Ｚｎ−Ａｌ−Ｍｇ−Ｓｉめっき鋼板及びその製造方法。
JP2009078450A (ja) * 2007-09-26 2009-04-16 Kobe Steel Ltd 端面耐食性に優れた非クロム系樹脂塗装金属板
WO2011001662A1 (ja) 2009-06-30 2011-01-06 新日本製鐵株式会社 Ｚｎ－Ａｌ－Ｍｇ系溶融めっき鋼板とその製造方法
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JP2023116278A (ja) 2022-02-09 2023-08-22 富士フイルムビジネスイノベーション株式会社 定着ベルト、定着装置、及び画像形成装置

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JPS59166568A (ja) * 1983-03-10 1984-09-19 Toyota Central Res & Dev Lab Inc 耐糸状腐食性塗料組成物
JP2006193791A (ja) 2005-01-14 2006-07-27 Nippon Steel Corp 表面外観に優れた溶融Ｚｎ−Ａｌ−Ｍｇ−Ｓｉめっき鋼板及びその製造方法。
JP2009078450A (ja) * 2007-09-26 2009-04-16 Kobe Steel Ltd 端面耐食性に優れた非クロム系樹脂塗装金属板
WO2011001662A1 (ja) 2009-06-30 2011-01-06 新日本製鐵株式会社 Ｚｎ－Ａｌ－Ｍｇ系溶融めっき鋼板とその製造方法
JP2017122186A (ja) * 2016-01-08 2017-07-13 新日鐵住金株式会社 塗料組成物およびそれを用いた塗装部材
WO2020008753A1 (ja) * 2018-07-02 2020-01-09 日本電信電話株式会社 塗料
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JP2023116278A (ja) 2022-02-09 2023-08-22 富士フイルムビジネスイノベーション株式会社 定着ベルト、定着装置、及び画像形成装置

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP7769282B1 (ja) * 2024-05-16 2025-11-13 日本製鉄株式会社 表面処理鋼材
WO2025238907A1 (ja) * 2024-05-16 2025-11-20 日本製鉄株式会社 表面処理鋼材

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