WO2024018723A1 - Tôle d'acier traitée en surface et son procédé de production - Google Patents

Tôle d'acier traitée en surface et son procédé de production Download PDF

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Publication number
WO2024018723A1
WO2024018723A1 PCT/JP2023/016772 JP2023016772W WO2024018723A1 WO 2024018723 A1 WO2024018723 A1 WO 2024018723A1 JP 2023016772 W JP2023016772 W JP 2023016772W WO 2024018723 A1 WO2024018723 A1 WO 2024018723A1
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Prior art keywords
chromium
steel sheet
containing layer
treated steel
steel plate
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PCT/JP2023/016772
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English (en)
Japanese (ja)
Inventor
卓嗣 植野
方成 友澤
祐介 中川
真司 大塚
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Ｊｆｅスチール株式会社
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Priority to JP2023544609A priority Critical patent/JP7401033B1/ja
Publication of WO2024018723A1 publication Critical patent/WO2024018723A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/38—Chromatising
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D9/00—Electrolytic coating other than with metals
    • C25D9/04—Electrolytic coating other than with metals with inorganic materials
    • C25D9/08—Electrolytic coating other than with metals with inorganic materials by cathodic processes
    • C25D9/10—Electrolytic coating other than with metals with inorganic materials by cathodic processes on iron or steel

Definitions

  • the present invention relates to a surface-treated steel sheet, and in particular to a surface-treated steel sheet that has excellent corrosion resistance in BPA (bisphenol A)-free painted areas.
  • the surface-treated steel sheet of the present invention can be suitably used for containers such as cans.
  • the present invention also relates to a method for manufacturing the surface-treated steel sheet.
  • tinplate Sn-plated steel sheets
  • TFS tin-free steel sheets
  • Tinplate and TFS are coated with organic resins such as epoxy paints and PET films in order to accommodate a variety of contents.
  • organic resins such as epoxy paints and PET films
  • the oxidized Cr layer formed on the outermost surface by electrolytic treatment or immersion treatment of the steel plate in an aqueous solution containing hexavalent Cr has excellent adhesion with the organic resin coating layer. Demonstrate your sexuality. Therefore, the deformation of the organic resin coating layer follows the deformation of the steel sheet during can manufacturing, ensuring corrosion resistance against various contents even after can manufacturing.
  • a surface treatment layer is formed by performing electrolytic treatment in an electrolytic solution containing a trivalent chromium compound such as basic chromium sulfate.
  • a surface treatment layer can be formed without using hexavalent chromium.
  • a surface-treated steel sheet that has excellent adhesion to an epoxy paint can be obtained by the method described above. Further, according to Patent Documents 3 and 4, it is possible to obtain a surface-treated steel sheet that exhibits excellent corrosion resistance even after being coated with an epoxy paint and deformed.
  • the present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide a surface-treated steel sheet that can be manufactured without using hexavalent chromium and has excellent corrosion resistance in BPA-free painted areas. be.
  • the inventors of the present invention conducted intensive studies to achieve the above object, and as a result, they obtained the following findings (1) and (2).
  • the number of linear regions enriched with elements with a lower atomic number than chromium that are observed when the chromium-containing layer is observed from the surface direction is determined within a specific range. By controlling this, it is possible to obtain a surface-treated steel sheet with excellent corrosion resistance in the BPA-free painted portion.
  • the above-mentioned surface-treated steel sheet is produced by bringing the steel sheet into contact with an aqueous solution containing sulfate ions, and applying 0.1 to 20.0 g/m 2 of the aqueous solution on the surface of the steel sheet. After holding the steel plate for seconds, the steel plate can be produced by cathodic electrolysis treatment in an electrolytic solution containing 0.05 mol/L or more of trivalent chromium ions.
  • the present invention has been completed based on the above findings.
  • the gist of the present invention is as follows.
  • a surface-treated steel sheet comprising a chromium-containing layer disposed on at least one surface of the steel sheet, When the chromium-containing layer is observed from the surface direction, there is a linear region where elements with a smaller atomic number than chromium are concentrated, A surface-treated steel sheet in which the number of linear regions is 5.0 lines/100 nm or more.
  • a method for producing a surface-treated steel sheet comprising a steel sheet and a chromium-containing layer disposed on at least one surface of the steel sheet, the method comprising: A steel plate surface conditioning step in which the steel plate is brought into contact with an aqueous solution containing sulfate ions, and the aqueous solution is held on the surface of the steel plate for 0.1 to 20.0 seconds in a state where the aqueous solution is present at 1.0 to 30.0 g/ m2 .
  • a method for producing a surface-treated steel sheet comprising a cathodic electrolytic treatment step of cathodic electrolyzing the steel sheet in an electrolytic solution containing 0.05 mol/L or more of trivalent chromium ions.
  • the electrolytic solution is prepared by mixing a trivalent chromium ion source, a carboxylic acid compound, and water, adjusting the pH to 4.0 to 7.0, and adjusting the temperature to 40 to 70 ° C. 8.
  • the present invention it is possible to provide a surface-treated steel sheet that is BPA-free and has excellent corrosion resistance in painted areas without using hexavalent chromium.
  • the surface-treated steel sheet of the present invention can be suitably used as a material for containers and the like.
  • the surface-treated steel sheet in one embodiment of the present invention is a surface-treated steel sheet that has a chromium-containing layer on at least one side of the steel sheet.
  • a chromium-containing layer on at least one side of the steel sheet.
  • any steel plate can be used without particular limitation, but it is preferable to use a steel plate for cans.
  • a steel plate for example, an ultra-low carbon steel plate or a low carbon steel plate can be used.
  • the method of manufacturing the steel plate is not particularly limited, and steel plates manufactured by any method may be used, but usually cold-rolled steel plates may be used.
  • the cold-rolled steel sheet can be manufactured by a general manufacturing process that includes, for example, hot rolling, pickling, cold rolling, annealing, and temper rolling.
  • the composition of the steel plate is not particularly limited, but may contain C, Mn, P, S, Si, Cu, Ni, Mo, Al, and inevitable impurities within a range that does not impair the effects of the present invention.
  • a steel plate having a composition specified in ASTM A623M-09 can be suitably used as the steel plate.
  • C in mass %, C: 0.0001 to 0.13%, Si: 0 to 0.020%, Mn: 0.01-0.60%, P: 0 to 0.020%, S: 0 to 0.030%, Al: 0-0.20%, N: 0 to 0.040%, Cu: 0 to 0.20%, Ni: 0 to 0.15%, Cr: 0 to 0.10%, Mo: 0 to 0.05%, Ti: 0 to 0.020%, Nb: 0 to 0.020%, B: 0 to 0.020%, Ca: 0-0.020%, Sn: 0 to 0.020%, Sb: 0 to 0.020%, It is preferable to use a steel plate having a composition consisting of Fe and the remainder Fe and unavoidable impurities.
  • the lower the content of Si, P, S, Al, and N the more preferable the components are.Cu, Ni, Cr, Mo, Ti, Nb, B, Ca, Sn, and Sb are optional. It is a component that can be added.
  • the thickness of the steel plate is not particularly limited, but is preferably 0.60 mm or less.
  • the lower limit of the plate thickness is not particularly limited either, but it is preferably 0.10 mm or more.
  • steel plate is defined here to include “steel strip.”
  • a chromium-containing layer is present on at least one side of the steel plate.
  • the components constituting the chromium-containing layer are not particularly limited, but may include metallic chromium and chromium compounds.
  • the chromium compound is not particularly limited and may include any chromium compound.
  • the chromium compound may include, for example, at least one selected from the group consisting of chromium oxide, chromium carbide, chromium sulfide, chromium nitride, chromium chloride, chromium bromide, and chromium boride. Further, the chromium-containing layer may contain impurities in addition to the metal chromium and the chromium compound.
  • the impurities include metal elements such as Ni, Cu, Sn, and Zn mixed as impurities into the electrolytic solution, which will be described later.
  • the metal element is typically considered to be present in the chromium-containing layer in a metallic state, but may also be present as a compound.
  • the chromium-containing layer preferably has a total content of chromium metal and elements constituting the chromium compound of 90 atomic % or more.
  • the total content is expressed as a percentage of the ratio of the total number of atoms of the metal chromium and the elements constituting the chromium compound to the total number of atoms of all elements other than Fe.
  • the total content can be determined by measuring the content (atomic %) of each of the metal chromium contained in the chromium-containing layer and the elements constituting the chromium compound by X-ray photoelectron spectroscopy (XPS) and summing the results. can.
  • XPS X-ray photoelectron spectroscopy
  • the content (atomic ratio) of each element can be calculated from the integrated intensity of the peak corresponding to each element by the relative sensitivity coefficient method.
  • the content of Cr 2 O 3 can be determined from the integrated intensity of the peak of 2p oxide of Cr that appears around 576.7 eV. Further, the content of CrO 3 can be determined from the integrated intensity of the peak of the 2p oxide part of Cr that appears around 579.2 eV.
  • the content of metallic chromium can be determined by calculating the Cr content from the integrated intensity of the 2p peak of Cr that appears around 573.8 eV, and subtracting the content of Cr atoms contained as chromium compounds from the chromium content. It is determined by
  • the total content of metallic chromium and the elements constituting the chromium compound can be determined.
  • the above-mentioned total content refers to the value at 1/2 the thickness of the chromium-containing layer.
  • the 1/2 position can be determined by the following procedure. First, while sputtering the chromium-containing layer from its outermost surface, the total content of metal chromium and the elements constituting the chromium compound and the Fe content are measured using the method described above. The position (depth) where the measured total content of metal chromium and elements constituting the chromium compound and Fe content are equal is defined as the interface between the chromium-containing layer and the steel plate. The thickness from the outermost surface of the chromium-containing layer to the interface is defined as the thickness of the chromium-containing layer, and a half position thereof is determined.
  • a scanning X-ray photoelectron spectrometer PHI X-tool manufactured by ULVAC-PHI can be used.
  • the X-ray source is a monochrome AlK ⁇ ray
  • the voltage is 15 kV
  • the beam diameter is 100 ⁇ m ⁇
  • the extraction angle is 45°
  • the sputtering conditions are Ar ion acceleration voltage 1 kV
  • the sputter rate is 1.50 nm/min in terms of SiO 2 .
  • the spatial structure of the components constituting the chromium-containing layer is not particularly limited, and for example, they may be separated as separate layers within the chromium-containing layer, or may be mixed throughout the chromium-containing layer. That is, the spatial structure of the components constituting the chromium-containing layer can include one or both of separate layers and mixed layers.
  • the amount of chromium deposited in the chromium-containing layer is not particularly limited. However, if the amount of chromium deposited in the chromium-containing layer is excessive, cohesive failure may occur in the chromium-containing layer during processing of the surface-treated steel sheet. Therefore, from the viewpoint of more stably ensuring corrosion resistance of BPA-free painted parts, it is preferable that the amount of chromium deposited in the chromium-containing layer be 500.0 mg/m 2 or less per side, and 450.0 mg/m 2 or less. More preferably, it is 2 or less.
  • the amount of chromium deposited in the chromium-containing layer is preferably 40.0 mg/m 2 or more per side, and 50.0 mg/m 2 or more. It is more preferable to do so.
  • the "chromium adhesion amount” refers to the total adhesion amount of chromium present in various forms.
  • the amount of chromium deposited can be measured by fluorescent X-ray analysis. More specifically, the amount of chromium deposited is measured by the following procedure. First, the amount of Cr (total amount of Cr) in the surface-treated steel sheet is measured using a fluorescent X-ray device. Next, using a fluorescent X-ray device, the amount of Cr (original Cr amount) in the steel sheet before forming the chromium-containing layer or the steel sheet after the chromium-containing layer is peeled off is measured. The value obtained by subtracting the original Cr amount from the total Cr amount is defined as the chromium adhesion amount of the chromium-containing layer. Note that, for example, a commercially available hydrochloric acid-based chromium plating remover can be used to remove the chromium-containing layer.
  • Chromium oxide may be present in the chromium-containing layer.
  • the location of chromium oxide is not particularly limited, but it may be present in a form where O is concentrated in a linear region, which will be described later.
  • the location of O can be determined, for example, by compositional analysis using energy dispersive X-ray spectroscopy (EDS) or wavelength dispersive X-ray spectroscopy (WDS) attached to a scanning electron microscope (SEM) or transmission electron microscope (TEM), or by three-dimensional This can be confirmed by three-dimensional composition analysis using an atom probe (3DAP).
  • EDS energy dispersive X-ray spectroscopy
  • WDS wavelength dispersive X-ray spectroscopy
  • SEM scanning electron microscope
  • TEM transmission electron microscope
  • the amount of chromium oxide deposited in the chromium-containing layer is not particularly limited. However, if the amount of chromium oxide deposited in the chromium-containing layer is excessive, cohesive failure may occur starting from Cr oxide in the chromium-containing layer when processing the surface-treated steel sheet, and the corrosion resistance of the BPA-free painted part may deteriorate. There is. Therefore, from the viewpoint of more stably ensuring corrosion resistance of BPA-free painted parts, the amount of chromium oxide deposited in the chromium-containing layer is preferably 40.0 mg/m 2 or less per side, and 35.0 mg/m 2 or less. It is more preferable that it is less than m2 .
  • the chromium-containing layer may be completely free of chromium oxide. Therefore, the lower limit of the amount of chromium oxide deposited on the chromium-containing layer is not particularly limited, and may be 0.0 mg/m 2 per side.
  • the amount of chromium oxide attached can be measured by fluorescent X-ray analysis. More specifically, the amount of chromium oxide deposited is measured by the following procedure. First, the Cr content (total Cr content) of the surface-treated steel sheet is measured. Next, the surface-treated steel sheet is subjected to an alkaline treatment by immersing it in 7.5N-NaOH at 90° C. for 10 minutes to remove chromium oxide. After thoroughly washing the surface-treated steel sheet after the alkali treatment with water, the amount of Cr (the amount of Cr after the alkali treatment) is measured again using a fluorescent X-ray device. The value obtained by subtracting the amount of Cr after alkali treatment from the total amount of Cr is defined as the amount of chromium oxide deposited in the chromium-containing layer.
  • the chromium-containing layer may be amorphous or crystalline. That is, the chromium-containing layer can contain one or both of amorphous and crystalline materials.
  • the chromium-containing layer produced by the method described below generally contains an amorphous layer, and may further contain a crystalline layer. Although the formation mechanism of the chromium-containing layer is not clear, it is thought that crystallization progresses partially when an amorphous phase is formed, resulting in a chromium-containing layer containing both an amorphous phase and a crystalline phase.
  • the area ratio of the crystalline region is not particularly limited, it is preferably 30% or less when the chromium-containing layer is observed from the surface direction. On the other hand, since the crystal region does not need to exist, the lower limit of the area ratio of the crystal region may be 0%.
  • the crystalline region in the chromium-containing layer can be confirmed by removing the base steel sheet part from the surface-treated steel sheet to prepare a single-layer chromium-containing layer sample, and observing the single-layer chromium-containing layer sample from the surface side using TEM or STEM. can.
  • the method for producing the chromium-containing single layer sample is not particularly limited, but it can be produced, for example, by irradiating an ion beam of Ar or the like from the base steel plate side and ion milling the steel plate.
  • the ion beam is irradiated at an accelerating voltage of 5 kV or less and at an incident angle of 1 degree to 5 degrees relative to the underlying steel plate, thereby forming a layer of several ⁇ m.
  • a view of two or more chromium single layer regions can be secured.
  • the bottom part of the chromium-containing layer is also milled to some extent, and the thickness of the chromium-containing layer may become thinner, but this does not affect the measurement results of the crystalline region.
  • the area ratio of crystalline regions in the chromium-containing layer can be measured by TEM. Specifically, first, a diffraction pattern of the chromium-containing layer is obtained by selected area diffraction using a TEM. Next, a dark-field image is obtained for all of the diffraction spots in the diffraction pattern, and a region displayed with high brightness in the dark-field image is defined as a crystal region. The area of the obtained crystalline region is calculated by image processing, and the area ratio of the crystalline region is calculated by dividing it by the area of the chromium-containing layer within the selected area aperture. For example, image analysis software such as image-J can be used to calculate the area ratio.
  • the chromium-containing layer may contain C.
  • the upper limit of the C content in the chromium-containing layer is not particularly limited, the atomic ratio to Cr is preferably 50% or less, more preferably 45% or less.
  • the chromium-containing layer does not need to contain C, and therefore, the lower limit of the atomic ratio of C to Cr contained in the chromium-containing layer is not particularly limited and may be 0%.
  • the C content in the chromium-containing layer can be measured by XPS. That is, the content of C in the Cr oxide layer is determined by sputtering from the outermost layer to a depth of 0.2 nm or more in SiO 2 terms, and quantifying the atomic ratio by the relative sensitivity coefficient method of the integrated intensity of the narrow spectrum of Cr2p and C1s. , and calculate the C atomic ratio/Cr atomic ratio.
  • XPS measurement for example, a scanning X-ray photoelectron spectrometer PHI X-tool manufactured by ULVAC-PHI can be used.
  • the X-ray source is a monochrome AlK ⁇ ray, the voltage is 15 kV, the beam diameter is 100 ⁇ m ⁇ , the extraction angle is 45°, the sputtering conditions are Ar ion acceleration voltage 1 kV, and the sputter rate is 1.50 nm/min in terms of SiO 2 .
  • the location of C in the chromium-containing layer is not particularly limited, but C may be present in a concentrated form in the linear region described below.
  • the location of C can be determined, for example, by compositional analysis using energy dispersive X-ray spectroscopy (EDS) or wavelength dispersive X-ray spectroscopy (WDS) attached to a scanning electron microscope (SEM) or transmission electron microscope (TEM), or by three-dimensional This can be confirmed by three-dimensional composition analysis using an atom probe (3DAP).
  • EDS energy dispersive X-ray spectroscopy
  • WDS wavelength dispersive X-ray spectroscopy
  • SEM scanning electron microscope
  • TEM transmission electron microscope
  • the chromium-containing layer may contain Fe.
  • the upper limit of the Fe content in the chromium-containing layer is not particularly limited, it is preferably 100% or less as an atomic ratio to Cr.
  • the chromium-containing layer does not need to contain Fe, so the lower limit of the atomic ratio to Cr is not particularly limited and may be 0%.
  • the content of Fe in the chromium-containing layer can be measured by XPS similarly to the content of C. The narrow spectra of Cr2p and Fe2p may be used to calculate the atomic ratio.
  • the chromium-containing layer contains metal impurities such as K, Na, Mg, and Ca contained in water, Sn, Ni, Cu, and Zn contained in an aqueous solution, S, N, Cl, Br, etc. may be included.
  • the presence of these elements may reduce the corrosion resistance of the BPA-free painted area. Therefore, the total amount of elements other than Cr, O, Fe, and C is preferably 3% or less as an atomic ratio to Cr, and more preferably not contained at all (0%).
  • the content of the above elements is not particularly limited, and can be measured by XPS, for example, similarly to the content of C.
  • the number of the linear regions is 5.0. /100 nm or more.
  • the number of the linear regions is preferably 7.0 lines/100 nm or more, and more preferably 10.0 lines/100 nm or more.
  • the upper limit of the number of linear regions is not particularly limited, but may be, for example, 50.0 lines/100 nm or less, 45.0 lines/100 nm or less, and 40.0 lines/100 nm or less. There may be.
  • a typical chromium-containing layer formed from a hexavalent Cr bath or a trivalent Cr bath is composed of metallic chromium or chromium oxide.
  • Such a surface-treated steel sheet having a chromium-containing layer is generally processed into cans and the like after an organic resin coating is formed on the surface.
  • metallic chromium has poor workability, the chromium-containing layer cannot completely follow the deformation of the steel sheet due to processing, and as a result, the organic resin coating existing on the chromium-containing layer is damaged. As a result, the corrosion resistance after processing decreases.
  • chromium oxide has excellent adhesion with epoxy paint, so even if the metal chromium is unable to follow the deformation of the underlying steel plate, the chromium-containing layer and epoxy paint will adhere firmly, and the coating with the epoxy paint will continue. The properties can be maintained even after canning.
  • the present invention is based on a completely different technical idea from the conventional ones, which is to improve the deformability of the chromium-containing layer itself rather than the adhesion with the paint.
  • the EDS quantitative map obtained by STEM/EDS analysis of the chromium-containing layer elements with an atomic number smaller than chromium are detected in an amount of 20 atomic % or more more than the average composition of the chromium-containing layer.
  • the region is defined as "a linear region in which elements with an atomic number smaller than chromium are concentrated.”
  • the STEM/EDS analysis is performed using a chromium-containing monolayer sample.
  • the chromium-containing single layer sample can be created by the method described above.
  • the number of linear regions can be determined, for example, from the EDS quantitative map of the chromium-containing layer. Ten 100 nm lines are arbitrarily drawn on the map image, the intersections with the intersecting linear regions are counted, and the arithmetic average value can be measured as the number of linear regions.
  • the element concentrated in the linear region is not particularly limited, and may be any element as long as it has a smaller atomic number than chromium.
  • the element may include at least one selected from the group consisting of O, C, N, and S.
  • the linear regions may be isolated one by one, may intersect, or may be connected in a mesh pattern, but preferably have a structure in which they are connected in a mesh pattern.
  • the size, number, and shape of the mesh are not limited, but from the viewpoint of further improving the corrosion resistance of the BPA-free painted part, the standard circle equivalent diameter of the mesh
  • the deviation is preferably 30 nm or less, more preferably 20 nm or less.
  • the lower limit of the standard deviation is not particularly limited either, but may be, for example, 0.5 nm or more, or 1.0 nm or more.
  • the equivalent circle diameter of the mesh can be calculated by image analysis of the STEM/EDS map. Specifically, from a STEM/EDS map observed at a magnification of 450,000 times, the number of pixels in the area surrounded by mesh is calculated using image analysis software such as image-J, and multiplied by the area per pixel. Calculate the area of the mesh. Then, the equivalent circle diameter is calculated from the obtained area. The standard deviation of the equivalent circle diameter is calculated from data of a total of 100 equivalent circle diameters.
  • the shape of the mesh is not particularly limited, but it is desirable that it be close to a perfect circle. Specifically, it is preferable that the average value of the circularity of the mesh is 0.5 or more. When the shape of the mesh is a perfect circle, the circularity is 1. Therefore, the average value of the roundness may be 1.0 or less.
  • the circularity of the mesh can also be calculated by image analysis of a STEM/EDS map. Specifically, a STEM/EDS map observed at a magnification of 450,000 times is analyzed using image analysis software such as image-J, and circles inscribed and circumscribed in the mesh are drawn. The roundness is determined by dividing the diameter of the inscribed circle by the diameter of the circumscribed circle. The roundness is calculated for a total of 100 inscribed circles, and the average value is taken as the roundness of the mesh.
  • a surface-treated steel sheet having the above characteristics can be manufactured by the method described below.
  • a method for manufacturing a surface-treated steel sheet in an embodiment of the present invention is a method for manufacturing a surface-treated steel sheet having a chromium-containing layer on at least one side of the steel sheet, and includes a steel sheet surface conditioning step and a cathodic electrolytic treatment step. Each step will be explained below.
  • the steel plate surface is prepared by bringing the steel plate into contact with an aqueous solution containing sulfate ions, and holding the steel plate in a state in which a predetermined amount of the aqueous solution is present on the surface of the steel plate for a predetermined period of time. It is important to carry out the process.
  • Amount of aqueous solution 1.0-30.0g/m 2 Holding time: 0.1 to 20.0 seconds
  • sulfate ions must be contained in the steel sheet surface conditioning process. It is necessary to bring the aqueous solution into contact with the steel plate and hold the aqueous solution in a state of 1.0 g/m 2 to 30.0 g/m 2 on the surface of the steel plate for 0.1 seconds or more and 20.0 seconds or less.
  • the Fe ions are oxidized to become oxidized Fe, which is deposited in a very small amount on the surface of the steel sheet.
  • a trace amount of deposited Fe oxide is reduced and a chromium-containing layer is formed.
  • the surface potential is microscopically different between a portion where a small amount of deposited Fe oxide is present and a portion where no Fe oxide is present. As a result, it is estimated that a linear region is formed in which elements with an atomic number smaller than chromium are concentrated.
  • the amount of the aqueous solution is preferably 2.0 g/m 2 or more, and 3.0 g/m 2 It is more preferable to set it as above. From the same viewpoint, the amount of the aqueous solution is preferably 28.0 g/m 2 or less, more preferably 25.0 g/m 2 or less.
  • the holding time is preferably 0.2 seconds or more, and is preferably 0.3 seconds or more. It is more preferable. From the same viewpoint, the holding time is preferably 18.0 seconds or less, more preferably 15.0 seconds or less.
  • the amount of aqueous solution present on the surface of the steel plate can be measured with a moisture meter using a filter type infrared absorption method. Specifically, the absorbance on the surface of the steel plate is measured using a moisture meter using a filter type infrared absorption method, and the amount of the aqueous solution is determined from the absorbance using a calibration curve determined in advance.
  • the said calibration curve can be created by the following procedure. First, a steel plate is placed on an electronic balance. An aqueous solution is dropped onto the steel plate using a pipette to form a liquid film over the entire surface of the steel plate.
  • the weight of the aqueous solution present on the steel plate is determined from the weight of the steel plate before dropping the aqueous solution and the weight of the steel plate after dropping the aqueous solution.
  • the amount of aqueous solution per unit area is determined by dividing the weight of the obtained aqueous solution by the area of the steel plate.
  • the absorbance on the steel plate surface is measured using a moisture meter using a filter type infrared absorption method. The above measurements are performed multiple times while changing the amount of the aqueous solution, and a calibration curve representing the correlation between the amount of the aqueous solution and the absorbance is created. As the calibration curve, a linear approximation of the correlation between the amount of the aqueous solution and the absorbance can be used.
  • the method for adjusting the amount of aqueous solution present on the surface of the steel plate is not particularly limited, and any method can be used.
  • a method such as squeezing the liquid with a ringer roll or wiping may be used.
  • the composition of the aqueous solution is not particularly limited, it is preferably a sulfuric acid aqueous solution such as dilute sulfuric acid.
  • the sulfuric acid aqueous solution means an aqueous solution of sulfuric acid, and includes cases where components other than sulfuric acid are contained.
  • the pickling solution can also be used as the aqueous solution in the steel plate surface conditioning step.
  • pickling inhibitors, pickling accelerators, and the like are generally added to the pickling solution, these components do not particularly hinder the formation of linear regions. Therefore, even if a pickling inhibitor, a pickling accelerator, or the like is added to the pickling solution, the pickling solution can be used as the aqueous solution in the steel plate surface conditioning step.
  • the lower limit of the concentration of sulfate ions contained in the aqueous solution is not particularly limited, but is preferably 3 g/L or more, more preferably 5 g/L or more.
  • the upper limit of the concentration of sulfate ions contained in the aqueous solution is not particularly limited, but is preferably 200 g/L or less, more preferably 150 g/L or less.
  • the lower limit of the temperature of the aqueous solution is not particularly limited, but is preferably 10°C or higher, more preferably 15°C or higher.
  • the upper limit of the temperature of the aqueous solution is not particularly limited, but is preferably 70°C or lower, more preferably 60°C or lower.
  • the steel plate is subjected to cathodic electrolysis treatment in an electrolytic solution containing 0.05 mol/L or more of trivalent chromium ions.
  • a chromium-containing layer can be formed on the steel plate by the cathodic electrolytic treatment.
  • the trivalent chromium ion source any compound that can supply trivalent chromium ions can be used.
  • the trivalent chromium ion source for example, at least one selected from the group consisting of chromium chloride, chromium sulfate, and chromium nitrate can be used.
  • the temperature of the electrolytic solution during the cathodic electrolytic treatment is not particularly limited, but is preferably 40° C. or higher in order to efficiently form the chromium-containing layer. For the same reason, it is preferable that the temperature of the electrolytic solution be 70° C. or lower. From the viewpoint of stably manufacturing the above-mentioned surface-treated steel sheet, it is preferable to monitor the temperature of the electrolytic solution in the cathodic electrolytic treatment step and maintain the temperature of the electrolytic solution in a temperature range of 40 to 70°C.
  • the pH of the electrolyte during cathodic electrolytic treatment is not particularly limited, but is preferably 4.0 or higher, more preferably 4.5 or higher. Further, the pH is preferably 7.0 or less, more preferably 6.5 or less. From the viewpoint of stably manufacturing the above-mentioned surface-treated steel sheet, it is preferable to monitor the pH of the electrolytic solution and maintain it within the above pH range in the cathodic electrolytic treatment step.
  • the current density in the cathodic electrolytic treatment is not particularly limited, and may be adjusted as appropriate so that a desired surface treatment layer is formed. However, if the current density is excessively high, the load placed on the cathode electrolytic treatment apparatus becomes excessive. Therefore, the current density is preferably 200.0 A/dm 2 or less, more preferably 100 A/dm 2 or less. Further, there is no particular restriction on the lower limit of the current density, but if the current density is too low, hexavalent Cr may be generated in the electrolyte, which may disrupt the stability of the bath. Therefore, the current density is preferably 5.0 A/dm 2 or more, more preferably 10.0 A/dm 2 or more.
  • the number of times the steel plate is subjected to cathodic electrolysis treatment is not particularly limited, and can be any number of times.
  • cathodic electrolytic treatment can be performed using an electrolytic treatment apparatus having an arbitrary number of passes of one or more.
  • the electrolysis time per pass is not particularly limited. However, if the electrolysis time per pass is too long, the conveyance speed (line speed) of the steel plate decreases, resulting in a decrease in productivity. Therefore, the electrolysis time per pass is preferably 5 seconds or less, more preferably 3 seconds or less.
  • the lower limit of the electrolysis time per pass is not particularly limited either, but if the electrolysis time is excessively shortened, it becomes necessary to increase the line speed accordingly, making control difficult. Therefore, the electrolysis time per pass is preferably 0.005 seconds or more, more preferably 0.01 seconds or more.
  • the amount of Cr deposited in the chromium-containing layer formed by cathodic electrolytic treatment can be controlled by the total electricity density expressed as the product of current density, electrolysis time, and number of passes. As mentioned above, if the amount of Cr deposited is too small, the corrosion resistance of the BPA-free painted part will be impaired, and if the amount of Cr deposited is too large, it may cause cohesive failure within the chromium-containing layer during processing, so it will be more stable. From the viewpoint of ensuring corrosion resistance of the BPA-free painted part, it is preferable to control the total electricity density so that the amount of Cr deposited on one side of the steel plate in the chromium-containing layer is within an appropriate range.
  • the type of anode used when performing cathodic electrolysis treatment is not particularly limited, and any anode can be used.
  • the anode it is preferable to use an insoluble anode.
  • the insoluble anode it is preferable to use at least one selected from the group consisting of an anode in which Ti is coated with one or both of a platinum group metal and an oxide of a platinum group metal, and a graphite anode. More specifically, examples of the insoluble anode include an anode in which the surface of a Ti substrate is coated with platinum, iridium oxide, or ruthenium oxide.
  • the concentration of the electrolyte constantly changes due to the formation of a chromium-containing layer on the steel plate, the removal or introduction of the liquid, the evaporation of water, etc.
  • the concentration of the electrolyte in the cathodic electrolytic treatment process varies depending on the equipment configuration and manufacturing conditions, so from the perspective of producing surface-treated steel sheets more stably, the concentration of the components contained in the electrolyte in the cathodic electrolytic treatment process is It is preferable to monitor and maintain the concentration within the range described below.
  • the steel plate after the cathodic electrolytic treatment step is preferably washed with water at least once. By washing with water, the electrolyte remaining on the surface of the steel plate can be removed.
  • the washing with water can be performed by any method without particular limitation.
  • a water washing tank can be provided downstream of a dipping tank for performing dipping treatment, and the steel plate after dipping can be continuously dipped in water.
  • water washing may be performed by spraying water onto the steel plate after immersion.
  • the water used for the washing is not particularly limited, but it is preferable to use at least one of reverse osmosis water (RO water), ion exchange water, and distilled water.
  • the electrical conductivity of the water used for the washing is not particularly limited, but is preferably 100 ⁇ S/m or less, more preferably 50 ⁇ S/m or less, and even more preferably 30 ⁇ S/m or less.
  • the temperature of the water used for the washing is not particularly limited and may be any temperature. However, since an excessively high temperature places an excessive burden on the washing equipment, it is preferable that the temperature of the water used for washing is 95° C. or lower. On the other hand, the lower limit of the temperature of the water used for washing is also not particularly limited, but it is preferably 0° C. or higher. The temperature of the water used for the washing may be room temperature.
  • drying may be optionally performed.
  • the drying method is not particularly limited, and for example, a normal dryer or an electric oven drying method can be applied.
  • the temperature during the drying treatment is preferably 100° C. or lower from the viewpoint of suppressing deterioration of the surface treated film. Note that the lower limit is not particularly limited, but is usually about room temperature.
  • the steel plate prior to the steel plate surface conditioning step, the steel plate can be optionally pretreated.
  • the pretreatment it is preferable to perform at least one of degreasing, pickling, and water washing.
  • degreasing rolling oil, rust preventive oil, etc. attached to the steel plate can be removed.
  • the degreasing can be carried out by any method without particular limitation. After degreasing, it is preferable to wash the steel plate with water to remove the degreasing solution adhering to the surface of the steel plate.
  • the natural oxide film present on the surface of the steel plate can be removed, so the surface can be effectively adjusted in the later steel plate surface conditioning process.
  • the pickling can be carried out by any method without particular limitation. After the pickling, it is preferable to wash with water to remove the pickling solution adhering to the surface of the steel plate. When an aqueous solution containing sulfate ions is used as the pickling treatment liquid, it is preferable to use the aqueous solution as it is in the steel plate surface conditioning step.
  • the method for preparing the electrolytic solution used in the cathodic electrolytic treatment step is not particularly limited, but by going through the electrolytic solution adjusting step described below, it can be stably used in the cathodic electrolytic treatment process for a long period of time.
  • Electrode preparation process (i) Mixing In the electrolyte solution preparation step, first, a trivalent chromium ion source, a carboxylic acid compound, and water are mixed to form an aqueous solution.
  • trivalent chromium ion source any compound that can supply trivalent chromium ions can be used.
  • the trivalent chromium ion source for example, at least one selected from the group consisting of chromium chloride, chromium sulfate, and chromium nitrate can be used.
  • the content of the trivalent chromium ion containing source in the aqueous solution needs to be 0.05 mol/L or more in terms of trivalent chromium ions, preferably 0.08 mol/L or more, and 0.10 mol/L. It is more preferable that it is above.
  • the upper limit of the content of the trivalent chromium ion-containing source is not particularly limited, but it is preferably 1.50 mol/L or less, more preferably 1.30 mol/L or less in terms of trivalent chromium ions.
  • As the trivalent chromium ion source Atotech's BluCr (registered trademark) TFS A can be used.
  • the carboxylic acid compound is not particularly limited, and any carboxylic acid compound can be used.
  • the carboxylic acid compound may be at least one of a carboxylic acid and a carboxylate salt, and is preferably at least one of an aliphatic carboxylic acid and a salt of an aliphatic carboxylic acid.
  • the aliphatic carboxylic acid preferably has 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms. Further, the number of carbon atoms in the aliphatic carboxylate is preferably 1 to 10, more preferably 1 to 5.
  • the content of the carboxylic acid compound is not particularly limited, it is preferably 0.1 mol/L or more and 5.5 mol/L or less, and more preferably 0.15 mol/L or more and 5.3 mol/L or less.
  • the carboxylic acid compound Atotech's BluCr (registered trademark) TFS B can be used.
  • Water can be used as a solvent for preparing the aqueous solution.
  • As the water it is preferable to use at least one of ion-exchanged water and distilled water.
  • the aqueous solution further contains at least one type of halide ion.
  • the content of halide ions is not particularly limited, but is preferably 0.05 mol/L or more and 3.0 mol/L or less, more preferably 0.10 mol/L or more and 2.5 mol/L or less.
  • Atotech's BluCr (registered trademark) TFS C1 and BluCr (registered trademark) TFS C2 can be used.
  • hexavalent chromium is not added to the above aqueous solution. Although it has been confirmed that hexavalent chromium is not formed in principle during the cathode electrolytic treatment process, even if a small amount of hexavalent chromium were to be formed at the anode, it would be immediately reduced to trivalent chromium, so the electrolyte solution The concentration of hexavalent chromium in it does not increase.
  • metal ions other than trivalent chromium ions are not intentionally added to the above-mentioned aqueous solution.
  • the above-mentioned metal ions are not limited, but include Cu ions, Zn ions, Fe ions, Sn ions, Ni ions, etc., and each is preferably 0 mg/L or more and 40 mg/L or less, and 0 mg/L or more and 20 mg/L. It is more preferably below, and most preferably 0 mg/L or more and 10 mg/L or less.
  • Fe ions are dissolved in the above-mentioned electrolytic solution in the cathodic electrolytic treatment step and the immersion step, and may be eutectoid in the film, but this does not affect the corrosion resistance of the BPA-free painted part.
  • the Fe ion concentration is within the above range at the time of bath preparation, it is also preferable to maintain the Fe ion concentration in the electrolytic solution within the above range during the cathodic electrolytic treatment process and the immersion process. If Fe ions are controlled within the above range, the formation of the chromium-containing layer will not be inhibited, and a necessary amount of the chromium-containing layer can be formed.
  • the electrolytic solution is prepared by adjusting the pH of the aqueous solution to 4.0 to 7.0 and adjusting the temperature of the aqueous solution to 40 to 70°C.
  • the pH and temperature As mentioned above, in order to stably use the cathode electrolytic treatment process for a long period of time, it is necessary not only to simply dissolve the trivalent chromium ion source and the carboxylic acid compound in water, but also to appropriately control the pH and temperature as described above. It is preferable.
  • the pH of the mixed aqueous solution is adjusted to 4.0 to 7.0.
  • the pH is preferably 4.5 or higher. Further, the pH is preferably 6.5 or less.
  • Any reagent can be used to adjust the pH.
  • the temperature of the aqueous solution after mixing is adjusted to 40 to 70°C. Note that the holding time in the temperature range of 40 to 70°C is not particularly limited.
  • the electrolytic solution obtained by the above procedure can be stably used in the cathode electrolytic treatment process for a long period of time. Note that the electrolytic solution produced by the above procedure can be stored at room temperature.
  • the use of the surface-treated steel sheet of the present invention is not particularly limited, it is particularly suitable as a surface-treated steel sheet for containers used for manufacturing various containers such as food cans, beverage cans, pail cans, and 18-liter cans.
  • a surface-treated steel sheet was manufactured according to the procedure described below, and its characteristics were evaluated.
  • electrolytic solutions having compositions A to G shown in Table 1 were prepared under the conditions shown in Table 1. That is, each component shown in Table 1 was mixed with water to form an aqueous solution, and then the aqueous solution was adjusted to the pH and temperature shown in Table 1.
  • the electrolytic solution G corresponds to the electrolytic solution used in the example of Patent Document 6.
  • Ammonia water was used to raise the pH, and to lower the pH
  • sulfuric acid was used for electrolytes A, B, and G
  • hydrochloric acid was used for electrolytes C and D
  • nitric acid was used for electrolytes E and F, respectively.
  • Pretreatment for steel plate A cold-rolled steel plate was used as the steel plate. More specifically, a steel plate for cans (T4 original plate) having a plate thickness of 0.17 mm was used. The steel plate was sequentially subjected to electrolytic degreasing, water washing, and pickling as pretreatment. For the pickling, a sulfuric acid aqueous solution having a sulfate ion concentration shown in Table 2 was used, and the steel plate was immersed in the aqueous solution. The steel plate after the pickling was subjected to the next steel plate surface conditioning step without being washed with water.
  • Step plate surface conditioning process Next, the steel plate after pickling was subjected to surface conditioning. Specifically, by squeezing the pickling solution remaining on the surface of the steel plate with a ringer roll, the amount of the pickling solution adhered to is adjusted to the amount shown as "amount of aqueous solution" in Table 2. did. Thereafter, after maintaining the amount of adhesion for the holding time shown in Table 2, the pickling solution was removed by washing with water.
  • the amount of chromium deposited per one side of the steel sheet and the amount of chromium oxide deposited per one side of the steel sheet of the chromium-containing layer were measured using the method described above.
  • the number of linear regions enriched with elements having an atomic number smaller than chromium, the presence or absence of a network structure, the standard deviation of the network, and the circularity of the network were measured using the methods described above. The measurement results are shown in Table 3.
  • the chromium-containing layer obtained by cathodic electrolytic treatment contained chromium compounds such as chromium oxide and chromium carbide in addition to metallic chromium.
  • the total content of metal chromium and elements constituting the chromium compound in the chromium-containing layer was 90% by mass or more.
  • at least one selected from the group consisting of O, C, N, and S was concentrated in the linear region. In particular, O was observed to be enriched in the linear regions in all examples.
  • a BPA-free coated steel plate was prepared by coating the surface of a surface-treated steel plate with a BPA-free paint.
  • a BPA-free paint a polyester paint for the inside of a can (BPA-free paint) was used.
  • the BPA-free paint was applied to the surface of the surface-treated steel plate, and then baked at 80° C. for 10 minutes. The amount of coating applied was 60 mg/dm 2 .
  • a cross cut penetrating the base steel plate was made on the obtained BPA-free coated steel plate, and then an overhang of 4 mm in height was formed around the intersection of the cross cuts using an Erichsen tester to form a test piece.
  • a corrosion resistance test was conducted using the test piece according to the following procedure.
  • a test piece was immersed in a Teflon (registered trademark) container containing a test solution, and the container was covered with a lid. In this state, retort treatment was performed at a temperature of 121° C. for 1 hour. Thereafter, the test piece was taken out from the container, washed with water to remove the test liquid, and then dried with a blower.
  • Teflon registered trademark
  • any surface-treated steel sheet that satisfies the conditions of the present invention can be manufactured without using hexavalent chromium, and has superior properties equivalent to or better than conventional TFS. It has BPA-free paint and corrosion resistance.
  • (4) retort treatment with a test solution of common salt and acetic acid is a very harsh corrosive environment, so as with conventional TFS, the score of a surface-treated steel sheet that meets the conditions of the present invention is less than 3.0. was. Therefore, when applying the surface-treated steel sheet of the present invention to contents containing acetic acid in particular, it is necessary to double-coat with BPA-free paint and optimize retort processing conditions. It should be noted that the same precautions should be taken when using it.

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  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
  • Laminated Bodies (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)

Abstract

La présente invention concerne une tôle d'acier traitée en surface qui peut être produite sans l'utilisation de chrome hexavalent, et qui présente une excellente résistance à la corrosion dans une partie revêtue exempte de BPA La présente invention concerne une tôle d'acier traitée en surface qui comprend une tôle d'acier et une couche contenant du chrome qui est disposée sur au moins une surface de la tôle d'acier, si la couche contenant du chrome est observée à partir de la direction de surface, il existe des régions linéaires dans lesquelles un élément ayant un nombre atomique inférieur à celui du chrome est enrichi, et le nombre des régions linéaires est de 5,0 pour 100 nm ou plus.
PCT/JP2023/016772 2022-07-19 2023-04-27 Tôle d'acier traitée en surface et son procédé de production WO2024018723A1 (fr)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06108265A (ja) * 1992-09-29 1994-04-19 Nippon Steel Corp 塗装鋼板用下地塗布クロメート処理方法
JPH06340998A (ja) * 1993-06-01 1994-12-13 Nippon Parkerizing Co Ltd 陰極電解樹脂クロメート型金属表面処理方法
JPH10130891A (ja) * 1996-09-05 1998-05-19 Teikoku Piston Ring Co Ltd 複合Ｃｒめっき皮膜およびこれを有する摺動部材
JP2021038429A (ja) * 2019-09-02 2021-03-11 オテック株式会社 複合化クロムめっき物品

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06108265A (ja) * 1992-09-29 1994-04-19 Nippon Steel Corp 塗装鋼板用下地塗布クロメート処理方法
JPH06340998A (ja) * 1993-06-01 1994-12-13 Nippon Parkerizing Co Ltd 陰極電解樹脂クロメート型金属表面処理方法
JPH10130891A (ja) * 1996-09-05 1998-05-19 Teikoku Piston Ring Co Ltd 複合Ｃｒめっき皮膜およびこれを有する摺動部材
JP2021038429A (ja) * 2019-09-02 2021-03-11 オテック株式会社 複合化クロムめっき物品

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