Surface-treated steel sheet for container material, precoated steel sheet for container material, laminated steel sheet for container material, method for producing surface-treated steel sheet for container material, method for producing precoated steel sheet for container material, and method for producing laminated steel sheet for container material

Abstract

This surface-treated steel sheet for a container material comprises a steel sheet and a coating that includes Zr, O, P, and F provided on the steel sheet and that comprises unavoidable impurities, wherein: the adhered amount of the coating is more than 5.0 mg / m2 and no more than 200.0 mg / m2 in terms of Zr; the F / Zr atomic concentration ratio in the surface layer of the coating is 0-0.30, inclusive; and in an image obtained by observing a cross-section in the thickness direction with a transmission electron microscope, x as calculated by a prescribed formula is 3.0-10.0 nm, inclusive.

Description

Surface-treated steel sheet for container material, painted precoated steel sheet for container material, laminated steel sheet for container material, manufacturing method of surface-treated steel sheet for container material, manufacturing method of painted precoated steel sheet for container material, and manufacturing method of laminated steel sheet for container material

[0001] The present invention relates to a surface-treated steel sheet for use as a container material that achieves chromate-free properties, a painted precoated steel sheet for use as a container material, a laminated steel sheet for use as a container material, a manufacturing method for a surface-treated steel sheet for use as a container material, a manufacturing method for a painted precoated steel sheet for use as a container material, and a manufacturing method for a laminated steel sheet for use as a container material. This application claims priority based on Japanese Patent Application No. 2024-032658, filed on March 5, 2024, the contents of which are incorporated herein by reference.

[0002] Chromate treatment, phosphate treatment, treatment with silane coupling agents, etc. have been known as treatments for improving the adhesion between metal materials such as steel sheets, zinc-plated steel sheets, zinc alloy sheets, tin-plated steel sheets, and aluminum alloy sheets and organic films. Of these, chromate treatment has been widely used in fields such as home appliances, building materials, vehicles, and metal containers due to its excellent corrosion resistance and adhesion. However, it has been pointed out that hexavalent chromium, a hazardous substance, may leach into soil and cause contamination when discarded, and therefore chromate treatment is already being phased out, mainly in Europe.

[0003] For metal materials for containers, chromate treatments are used in which tin-plated steel sheets are subjected to cathodic electrolysis in an aqueous solution of sodium dichromate, or steel sheets are subjected to cathodic electrolysis in an aqueous solution of fluoride-containing chromic anhydride, resulting in no residual hexavalent chromium in the coating. However, since the treatment solution itself, which is the raw material, contains hexavalent chromium, it is necessary to render the hexavalent chromium harmless before disposing of it in wastewater or exhaust gas. From the perspective of environmental impact, a surface treatment method in which the treatment solution does not contain hexavalent chromium is more desirable.

[0004] One of the measures to reduce the burden on the environment is to eliminate chromate by using alternative elements. As a chromate-free surface treatment for container materials, Patent Document 1 discloses a method in which the surface of a tin-plated steel sheet is subjected to cathodic electrolysis in an aqueous zirconium sulfate solution to form a chromium-free coating made of a zirconium compound. However, if it becomes possible to apply a chromate-free coating directly to the surface of a steel sheet without tin plating, it would be possible to reduce costs.

[0005] As an example of a chromate-free coating applied directly to the steel sheet surface without tin plating, a coating containing Zr, O, and F as its main components was formed by cathodic electrolysis to a Zr content of 5 to 300 mg / m ２ Patent Document 2 provides an example of a coating formed so that the film has a thickness of 100 μm or more. This invention states that P contained in the coating is preferably not contained because it reduces film adhesion, and also states that an excessive F / Zr atomic ratio in the surface layer of the coating reduces film adhesion, but does not mention a method for controlling the F / Zr atomic ratio.

[0006] In Patent Document 3, the amount of Zr is 80 to 200 mg / m ２ The amount of F is adjusted on both the inner and outer surfaces of the can, but it is necessary to use different processes to control the amount of F on the inner and outer surfaces, which is thought to be problematic from the viewpoint of productivity.

[0007] In addition, Patent Document 4 discloses a method for producing a silicon nitride film with a Zr content of 1 to 200 mg / m ２ After the film formation, the coating is washed with warm water at 40°C or higher for 0.5 seconds or more to reduce the F content to 0.1 mg / m ２ Although the following examples show controlled conditions, there is no mention of the effects that the morphology and composition distribution in the coating surface layer have on film adhesion and corrosion resistance.

[0008] Japanese Patent No. 5091803 Japanese Patent No. 4492103 Japanese Patent No. 5886919 Japanese Patent No. 4886811

[0009] The present invention has been made in consideration of the above circumstances, and aims to provide a surface-treated steel sheet for use as a container material, a painted precoated steel sheet for use as a container material, a laminated steel sheet for use as a container material, a method for manufacturing a surface-treated steel sheet for use as a container material, a method for manufacturing a painted precoated steel sheet for use as a container material, and a method for manufacturing a laminated steel sheet for use as a container material, which are chromate-free, have a low environmental impact, have excellent adhesion to films and corrosion resistance, and can be manufactured at low cost.

[0010] In order to solve the above problems, the present invention proposes the following means: (1) A surface-treated steel sheet for use as a container material according to aspect 1 of the present invention comprises a steel sheet and a coating film formed on the steel sheet, the coating film containing Zr, O, P, F and unavoidable impurities, and the coating film has a coating weight of 5.0 mg / m2 in terms of Zr. ２ Over 200.0 mg / m ２ and the F / Zr atomic concentration ratio in the surface layer of the coating is 0 or more and 0.30 or less, and in an image obtained by observing a cross section in the thickness direction with a transmission electron microscope, the direction perpendicular to the thickness direction is defined as an evaluation direction, the length of an evaluation range of the image along the evaluation direction is defined as a reference length L, and the thickness of the coating at an i-th position when the evaluation range is divided into n equal intervals along the evaluation direction is defined as x ｉ nm, and the x ｉ The average value of x ａｖｅ When x is calculated from the following formula (1), it is 3.0 nm or more and 10.0 nm or less. (2) Aspect 2 of the present invention relates to the surface-treated steel sheet for container material of Aspect 1, wherein the F / Zr atomic concentration ratio at a depth from the surface of the coating in the thickness direction to half the thickness of the coating is 0.10 or more and 0.80 or less. (3) Aspect 3 of the present invention relates to the precoated painted steel sheet for container material, which uses the surface-treated steel sheet for container material of Aspect 1 or 2. (4) Aspect 4 of the present invention relates to the laminated steel sheet for container material, which uses the surface-treated steel sheet for container material of Aspect 1 or 2. (5) A manufacturing method of a surface-treated steel sheet for use as a container material according to Aspect 5 of the present invention is the manufacturing method of a surface-treated steel sheet for use as a container material according to Aspect 1, comprising: a coating step of forming a pre-cleaning coating on the steel sheet to obtain a coated steel sheet, a primary cleaning step of cleaning the coated steel sheet with warm water of 80°C or higher for 0.5 to 5 seconds after the coating step, and a secondary cleaning step of cleaning the coated steel sheet with water below 40°C for 0.5 to 5 seconds after the primary cleaning step. (6) Aspect 6 of the present invention is the manufacturing method of a surface-treated steel sheet for use as a container material according to Aspect 5, wherein in the coating step, the pre-cleaning coating is formed by immersing the steel sheet in a treatment solution and performing cathodic electrolysis, and the Zr concentration in the treatment solution is 1,000 ppm by mass or more and 15,000 ppm by mass or less, and the P concentration in the treatment solution is 100 ppm by mass or more and 2,000 ppm by mass or less. (7) Aspect 7 of the present invention relates to the method for producing a surface-treated steel sheet for container material according to Aspect 5, wherein the F / Zr atomic concentration ratio in the surface layer of the pre-cleaning coating is 0.40 or more and 1.10 or less, and the F / Zr atomic concentration ratio at a position half the thickness of the pre-cleaning coating from the surface of the pre-cleaning coating in the thickness direction is 0.30 or more and 0.90 or less. (8) Aspect 8 of the present invention relates to the method for producing a surface-treated steel sheet for container material according to Aspect 5, wherein the primary cleaning step involves spray cleaning with hot water of 80°C or more for 0.5 seconds or more and 5 seconds or less. (9) Aspect 9 of the present invention relates to the method for producing a surface-treated steel sheet for container material according to Aspect 5, wherein the primary cleaning step involves immersion in hot water of 80°C or more for 1.0 seconds or more and 5 seconds or less. (10) Aspect 10 of the present invention relates to the method for producing a painted precoated steel sheet for container material, wherein the surface of the surface-treated steel sheet for container material produced by the method for producing a surface-treated steel sheet for container material according to Aspect 5 or 6 is further painted.(11) A method for producing a laminated steel sheet for use as a container material according to aspect 11 of the present invention further comprises laminating a film on the surface of the surface-treated steel sheet for use as a container material produced by the method for producing a surface-treated steel sheet for use as a container material according to aspect 5 or 6.

[0011] According to the above-mentioned aspects of the present invention, it is possible to provide a surface-treated steel sheet for use as a container material, a painted precoated steel sheet for use as a container material, a laminated steel sheet for use as a container material, a method for manufacturing a surface-treated steel sheet for use as a container material, a method for manufacturing a painted precoated steel sheet for use as a container material, and a method for manufacturing a laminated steel sheet for use as a container material, which are chromate-free, have a low environmental impact, and have excellent adhesion to films and corrosion resistance.

[0012] 1 is a schematic cross-sectional view of a surface-treated steel sheet for container material;

[0023] FIG. 1 is a diagram illustrating a method for measuring the roughness parameter x of a coating surface;

[0024] FIG. 2 is a diagram illustrating the influence of the Zr deposition amount and the F / Zr atomic concentration ratio in a coating surface layer on film adhesion and corrosion resistance;

[0025] FIG. 3 is a diagram illustrating the influence of the roughness parameter x of a coating surface and the F / Zr atomic concentration ratio in a coating surface layer on film adhesion and corrosion resistance;

[0026] FIG. 4 is a diagram illustrating the relationship between time at each hot water washing temperature in spray cleaning and the F / Zr atomic concentration ratio in the coating surface layer;

[0027] FIG. 5 is a diagram illustrating the relationship between time at each hot water washing temperature in spray cleaning and the roughness parameter x of the coating surface;

[0028] FIG. 6 is a diagram illustrating the relationship between time at each hot water washing temperature in immersion cleaning and the F / Zr atomic concentration ratio in the coating surface layer;

[0029] FIG. 7 is a diagram illustrating the relationship between time at each hot water washing temperature in immersion cleaning and the roughness parameter x of the coating surface;

[0029] FIG. 8 is a diagram illustrating the influence of the secondary cleaning temperature and the F / Zr atomic concentration ratio in the coating surface layer on retort resistance.

[0013] The following describes the surface-treated steel sheet for container material, the painted precoated steel sheet for container material, the laminated steel sheet for container material, the manufacturing method of the surface-treated steel sheet for container material, the manufacturing method of the painted precoated steel sheet for container material, and the manufacturing method of the laminated steel sheet for container material. FIG. 1 is a schematic cross-sectional view of the surface-treated steel sheet for container material of the present disclosure. The surface-treated steel sheet for container material 100 of the present disclosure comprises a steel sheet 10 and a coating 20 formed on the steel sheet 10, the coating 20 containing Zr, O, P, and F and containing inevitable impurities. Specifically, after the process of forming the Zr-based coating, the steel sheet is subjected to a process of spray cleaning or immersion treatment with warm water, followed by a water rinsing process, which sufficiently removes F present in the surface layer of the coating, further roughens the surface, and produces a coating 20 with excellent film adhesion and corrosion resistance. Details are described below.

[0014] (Steel Plate 10) The steel plate 10 used in the present disclosure is not particularly limited, and may be tinplate, tin-free steel base plate, or the like, which has been conventionally used for steel plates for container materials.

[0015] (Coating 20) The coating 20 is disposed so as to contact the surface of the steel sheet 10. In the present invention, a coating (chromate-free coating) 20 containing Zr, O, P, and F as its main components is formed by cathodic electrolysis in an aqueous solution containing Zr ions, F ions, phosphate ions, and Fe ions eluted from the steel sheet. Here, "containing Zr, O, P, and F as its main components" means that the total content of Zr, O, P, and F is 50 mass% or more relative to the total mass of the coating 20. Examples of unavoidable impurities in the coating 20 include Fe, C, N, Al, Si, Mn, S, Ti, Nb, Cu, Ni, and Mo.

[0016] When Zr is used as a component in the coating 20, the surface of the steel sheet 10 is covered with a hydrated oxide of Zr (ZrO ２ ) is coated. This allows the formation of ZrO ２ Hydrogen bonds are formed between the hydroxyl groups in the laminate film and the resin film, which is expected to improve adhesion.

[0017] ZrO ２The metal salts used in the method of depositing by cathodic electrolysis include carbonates, sulfates, and halide salts, but the method of cathodic electrolysis in an aqueous solution of zirconium fluoride compound is easy and can be carried out at low cost. ２ ＋ It exists as a metal salt and is stable in the low pH range. However, when cathodic electrolysis is performed, hydrogen gas is generated at the interface between the steel sheet and the metal salt-added aqueous solution on the steel sheet side of the cathode, and OH － As a result, the pH at the interface between the steel sheet and the metal salt-added aqueous solution increases, and ZrO ２ ＋ It is believed that the stability of SiO2 decreases and it precipitates as a hydrated oxide.

[0018] The amount of Zr deposited in the coating 20 is 5.0 mg / m in terms of Zr. ２ In the following cases, the coating is too thin, which is undesirable as it reduces corrosion resistance. ２ More preferably, it is greater than 40.0 mg / m ２ or more, more preferably 50.0 mg / m ２ The upper limit of the Zr coating amount is 200.0 mg / m in terms of Zr. ２ If the amount exceeds this, the occurrence of uneven deposition in the coating film becomes significant, and the coating film may become significantly brittle, which is undesirable because it reduces the film adhesion. In order to avoid these, the upper limit of the Zr coating amount is preferably 200.0 mg / m in terms of Zr. ２ , more preferably 100 mg / m ２ , more preferably 80 mg / m ２ is.

[0019] O is ZrO in the coating 20 ２ It is preferable that the O / Zr atomic concentration ratio in the surface layer of the coating 20 is 2.00 to 5.00. If the O / Zr atomic concentration ratio is within this range, ZrO in the coating 20 ２ Since the ratio is in an appropriate range, corrosion resistance can be improved.

[0020] The O / Zr atomic concentration ratio in the surface layer of the coating 20 can be measured by the following method. The atomic ratio of the surface layer can be measured by measuring the surface of the sample with an X-ray photoelectron spectrometer (e.g., PHI5800 manufactured by ULVAC-PHI, Inc.) (X-ray source: Mg-Kα, X-ray diameter: 800 μmφ, measurement area: 800 μmφ, detection angle: 45°). When the sum of the atomic concentrations of the main elements (e.g., Zr, P, C, O, F, and Fe) detected by the X-ray photoelectron spectrometer is taken as 100%, impurities and contaminants adhering to the surface are removed by Ar sputtering, and the point at which the atomic concentration of C is 10% or less is defined as the surface layer. The O / Zr atomic concentration ratio can be measured by determining the atomic concentrations of Zr, P, O, and F at this point.

[0021] When P is used as a coating component, the PO present in the aqueous solution is ４ ３－ is the aforementioned ZrO ２ Zirconium phosphate (Zr(HPO ４ ) ２ ・H ２ O, etc.) and ZrO ２ This improves the corrosion resistance and film adhesion of the surface-treated steel sheet for container material 100, and therefore it is preferable that the coating 20 contain the above.

[0022] The P / Zr coating weight ratio is preferably 0.50 or more. If the P / Zr coating weight ratio is 0.50 or more, the adhesion to the resin film can be further improved. Here, the P / Zr coating weight ratio is a value obtained by dividing the P coating weight (P conversion) by the Zr coating weight (Zr conversion). There is no particular upper limit for the P / Zr coating weight ratio, but if the P / Zr coating weight ratio is too large, ZrO, which becomes the matrix of the coating, may be formed. ２ Therefore, it is preferable that the ratio is less than 1.00, and more preferably 0.80 or less.

[0023] The P / Zr atomic concentration ratio (surface layer atomic concentration ratio) in the surface layer of the coating 20 is preferably 0.60 or more. If the P / Zr atomic concentration ratio is 0.60 or more, the adhesion to the resin film can be further improved. There is no particular upper limit for the P / Zr atomic concentration ratio, but if the P / Zr atomic concentration ratio is too large, the P / Zr atomic concentration ratio may be increased by 0.60 or more. ２ Therefore, the P / Zr atomic concentration ratio is preferably less than 1.00, and more preferably 0.80 or less.

[0024] The Fe ions are eluted from the steel sheet and inevitably incorporated, and may diffuse and be incorporated into the coating 20 .

[0025] In addition, F contained in the metal salt of Zr - is irreversibly incorporated into the coating 20. The F / Zr atomic concentration ratio in the surface layer of the coating 20 exceeding 0.30 is undesirable because it reduces the resin film adhesion. Here, the F / Zr atomic concentration ratio is the value obtained by dividing the atomic concentration of F by the atomic concentration of Zr. There is no lower limit for the F / Zr atomic concentration ratio, and F may be completely removed. Therefore, the appropriate range for F / Zr is 0 or more and 0.30 or less. More preferably, the F / Zr atomic concentration ratio in the surface layer of the coating 20 is 0.10 or less. The surface layer of the coating 20 refers to the depth of 15 nm from the outermost surface layer of the sample. The measurement point is a point located within that range, and is defined as the point at which impurities and dirt adhering to the surface are removed by Ar sputtering to remove C at an atomic concentration of 10% or less, when the sum of the atomic concentrations of major elements such as Zr, P, C, O, F, and Fe detected by an X-ray photoelectron spectrometer (for example, PHI5800 manufactured by ULVAC-PHI, Inc.) is taken to be 100%.

[0026] The F / Zr atomic concentration ratio at a position (half depth position) from the surface of the coating 20 in the thickness direction is preferably 0.10 or more and 0.80 or less. When the F / Zr atomic concentration ratio at a position (half depth position) from the surface of the coating 20 in the thickness direction is 0.10 or more and 0.80 or less, the effect of exhibiting excellent workability can be obtained. Note that the F / Zr atomic concentration ratio at the half depth position is lower than the F / Zr atomic concentration ratio in the surface layer of the coating 20.

[0027] (Adhesion Mass) The adhesion mass of each element (adhesion mass of the coating 20 converted into each element) can be measured by punching out a specimen having a diameter of 5 cm from the steel sheet sample after electrolytic treatment and using a fluorescent X-ray absorption spectrometer (for example, ZSX Primus II manufactured by Rigaku).

[0028] (Surface Layer Atomic Concentration) The atomic concentration of the surface layer can be measured by the following method. The atomic ratio of the surface layer can be measured by measuring the surface of a sample using an X-ray photoelectron spectrometer (e.g., a PHI5800 manufactured by ULVAC-PHI, Inc.) (X-ray source: Mg-Kα, X-ray diameter: 800 μmφ, measurement area: 800 μmφ, detection angle: 45°). When the sum of the atomic concentrations of the main elements (e.g., Zr, P, C, O, F, and Fe) detected by the X-ray photoelectron spectrometer is taken as 100%, impurities and contaminants adhering to the surface are removed by Ar sputtering, and the point at which the atomic concentration of C is 10% or less is defined as the surface layer. By determining the atomic concentrations of Zr, P, O, and F at this point, the F / Zr atomic concentration ratio, the O / Zr atomic concentration ratio, and the P / Zr atomic concentration ratio can be measured.

[0029] The atomic concentration in the surface layer is a value found by dividing the area intensity when the background is removed from the peak of each element by the relative sensitivity coefficient set for each device, and can be calculated using analysis software. It can also be found by manually measuring the area, but care must be taken as errors can occur depending on how the background is subtracted.

[0030] (Atomic Concentration at Half Depth) The atomic concentration at a position from the surface of the coating 20 to a depth of half the thickness of the coating 20 in the thickness direction can be measured by the following method. The atomic ratio at the half depth position can be measured by measuring the surface of the sample with an X-ray photoelectron spectrometer (e.g., PHI5800 manufactured by ULVAC-PHI, Inc.) (X-ray source: Mg-Kα, X-ray diameter: 800 μmφ, measurement area: 800 μmφ, detection angle: 45°). When the sum of the atomic concentrations of the main elements (e.g., Zr, P, C, O, F, Fe) detected by the X-ray photoelectron spectrometer is taken as 100%, the F / Zr atomic concentration ratio can be measured by determining the atomic concentrations of Zr, P, O, and F at the half depth position while performing Ar sputtering. The half depth position is determined by calculating the time required to reach the half depth from the sputtering rate of Zr, and then determining the position after sputtering for that calculated time.

[0031] (Roughness parameter x) In an image (for example, an image as shown in FIG. 2 ) obtained by observing a cross section in the thickness direction with a transmission electron microscope, the direction perpendicular to the thickness direction is defined as the evaluation direction, the length of the evaluation range of the image along the evaluation direction is defined as the reference length L, and the film thickness of the coating 20 at the i-th position when the evaluation range is divided into n equal intervals along the evaluation direction is defined as x ｉ nm, and x ｉ The average value of x ａｖｅ When x is 3.4 nm or more and 9.0 nm or less, x (roughness parameter x) calculated from the following formula (1) is 3.0 nm or more and 10.0 nm or less. By setting x to 3.4 nm or more and 9.0 nm or less, adhesion to the resin film can be further improved. The roughness parameter x of the coating 20 is more preferably 4.0 nm or more. The roughness parameter x of the coating 20 is even more preferably 5.0 nm or more. The roughness parameter x of the coating 20 is more preferably 9.0 nm or less. The roughness parameter x of the coating 20 is even more preferably 8.0 nm or less.

[0032]

[0033] Here, we will explain how to measure the roughness parameter x of the coating surface layer. The roughness parameter x is on the order of nanometers, making it difficult to measure using a typical stylus roughness meter. Instead, it is manually measured and calculated using an electron microscope image. First, the sample to be measured is cut into pieces approximately 10 mm x 10 mm in size. A cross section approximately 50 μm wide and 30 μm deep is then machined using a focused ion beam-scanning electron microscope (e.g., a Hitachi NB5500) combined instrument. The cross section is then observed at 200,000x magnification with a 10 nm beam diameter and an acceleration voltage of 200 kV using a field emission transmission electron microscope (FE-TEM) (e.g., a JEOL JEM-1200F). In TEM images, elements with large atomic weights are observed with bright contrast (white), and this contrast difference allows the steel sheet and the coating formed on top to be distinguished. If it is difficult to distinguish the interface between the steel sheet 10 and the coating 20, the composition may be analyzed and determined using EDX (for example, JED-2300T manufactured by JEOL).

[0034] Next, a method for measuring the roughness parameter x on the surface of the coating 20 will be described. First, a reference length (for example, 227.5 nm) is determined in the TEM image observed at a magnification of 200,000 times as described above, and the thickness x of the coating is measured in a direction parallel to the steel sheet. ｉ (nm) are measured at equal intervals. Then, the roughness parameter x can be calculated using the above formula (1). Here, L is the reference length (for example, the above-mentioned 227.5 nm), and xave is the average value of x1 to xi.

[0035] Next, a method for measuring the roughness parameter x on the surface of the coating 20 will be described with reference to Figure 2. To improve the measurement accuracy of the roughness parameter x, the number of measurement points i is preferably 20 or more, more preferably 30 or more (i = 1 to 36 in Figure 2). Furthermore, x is measured in multiple visual fields, preferably three or more visual fields, and the average value is used.

[0036] Next, the method for producing the surface-treated steel sheet for container material of the present invention will be described.

[0037] "Coating Formation Step" A steel sheet is immersed in a treatment solution and subjected to cathodic electrolysis to form a pre-cleaning coating. The treatment solution has a Zr concentration of 1,000 to 15,000 ppm by mass, a P concentration of 100 to 2,000 ppm by mass, and an F concentration of 1,300 to 19,700 ppm by mass. The F / Zr atomic concentration ratio in the surface layer of the pre-cleaning coating formed by cathodic electrolysis is 0.40 to 1.10, and the F / Zr atomic concentration ratio at a depth from the surface of the pre-cleaning coating in the thickness direction to a depth of half the thickness of the pre-cleaning coating is 0.30 to 0.90. The conditions for the coating formation step are not particularly limited as long as the F / Zr atomic concentration ratio in the surface layer of the pre-cleaned coating is 0.40 or more and 1.10 or less, and the F / Zr atomic concentration ratio at a depth of half the thickness of the pre-cleaned coating from the surface of the pre-cleaned coating in the thickness direction is 0.30 or more and 0.90 or less. An example of the conditions for the coating formation step will be described below.

[0038] Zr Concentration in Treatment Solution If the Zr concentration is less than 1000 ppm by mass, it is difficult to deposit a coating during cathodic electrolysis, and the Zr deposition amount cannot be ensured, which is undesirable. Furthermore, if the Zr concentration exceeds 15000 ppm by mass, uneven deposition of the coating 20 is likely to occur. In addition, the apparent Zr consumption increases due to liquid carryover during continuous sheet threading, which is uneconomical, and therefore undesirable. For these reasons, the Zr concentration in the aqueous solution is preferably 1000 ppm by mass or more and 15000 ppm by mass or less, more preferably 1200 ppm by mass or more and 13000 ppm by mass or less.

[0039] P concentration in treatment solution When the P concentration is less than 100 mass ppm, ZrO precipitated by cathodic electrolysis ２ If the P concentration is too high, the P content of the ZrO film, which forms the matrix of the coating, becomes too high. ２ For the above reasons, the P concentration in the aqueous solution is preferably 100 ppm by mass or more and 2000 ppm by mass or less, and more preferably 200 ppm by mass or more and 1800 ppm by mass or less.

[0040] F concentration in the treatment solution When the F concentration is less than 1,300 mass ppm, ZrO precipitated by cathodic electrolysis ２ In addition, if the F concentration exceeds 19,700 mass ppm, the ZrO ２ For the above reasons, the F concentration in the aqueous solution is preferably 1,300 ppm by mass or more and 19,700 ppm by mass or less, and more preferably 1,500 ppm by mass or more and 17,000 ppm by mass or less.

[0041] pH of treatment solution: By subjecting a steel sheet to cathodic electrolysis in an aqueous solution containing Zr ions and Fe ions eluted from the steel sheet, the pH of the steel sheet surface increases, and Zr is converted into ZrO. ２ However, if the pH of the aqueous solution exceeds 3.8, the solubility of the zirconium compound decreases, and a large amount of the zirconium compound precipitates as sludge during cathodic electrolysis, which is undesirable. Furthermore, if the pH of the aqueous solution is 3.0 or less, the zirconium compound is less likely to precipitate, which is also undesirable. In order to adjust the lower limit of the pH of the aqueous solution, K ＋ , Na ＋ , N.H. ４ ＋ , Mg ２ ＋ Alternatively, an alkaline compound having a cationic species such as an amine may be added. The upper limit of the pH may be adjusted by adding an appropriate amount of nitric acid or ammonia.

[0042] (Electrode) The counter electrode plate corresponding to the anode side can be made of a platinum-coated titanium plate, a stainless steel plate, a lead oxide plate, etc. As for the conditions for the counter electrode plate, it is desirable that the counter electrode material does not dissolve in the treatment solution during electrolysis and that it is an insoluble anode with a small oxygen overvoltage.

[0043] (Bath Temperature) The temperature of the treatment solution (electrolytic treatment aqueous solution) is preferably in the range of about 40°C to 70°C, in which case there are no problems with the deposition of the coating or workability. However, a temperature in the range of 50°C to 60°C is preferred, as this will result in higher deposition efficiency of the coating and less fluctuation in concentration due to evaporation.

[0044] (Power Supply Interruption Time) The cathodic electrolytic treatment method in the coating formation step may be either a continuous electrolysis method in which there is no section where power supply is interrupted during the cathodic electrolytic treatment of the steel sheet, or an intermittent electrolysis method in which power supply is temporarily interrupted in a portion where the steel sheet is not immersed in the aqueous solution, such as between line tanks, during the cathodic electrolytic treatment in which the steel sheet is passed through a plurality of line tanks in a plating line, and power supply and interruption are repeated multiple times.

[0045] When using the intermittent electrolysis method, there is no particular lower limit on the total current interruption time during the cathodic electrolysis treatment section, i.e., the time from entering the first electrode to passing through the last electrode (i.e., it approaches the continuous electrolysis method).

[0046] If the total current-off time exceeds 7.6 seconds, coatings 20 with different compositions will be stacked before and after the current-off time between individual line plating tanks, which is undesirable. Therefore, the total current-off time is preferably 7.6 seconds or less, more preferably 3.8 seconds or less, and even more preferably 2.9 seconds or less. Furthermore, the number of current-on and current-off cycles is not limited, but it is preferable to perform 2 to 10 cycles with a current-on time in the range of 0.1 to 0.6 seconds and a current-off time in the range of 0.1 to 0.8 seconds.

[0047] Current Flow Time and Current Density There are no particular limitations on the total current flow time, but if it is too short, the current density in the coating 20 will be 5.0 mg / m ２ Since it is not possible to ensure a Zr deposition amount exceeding 0.2 seconds, it is preferable to set the time to 0.2 seconds or more. If the time is too long, the line speed will slow down and productivity will decrease, so it is preferable to set the time to 2.4 seconds or less, and more preferably to 0.9 seconds or less. The current density during cathodic electrolysis treatment is set to 0.1 to 120 A / dm according to the total current application time. ２ It may be set appropriately within the range.

[0048] (Cleaning Step) The present invention is characterized in that, following the coating formation step, a hot water washing step is carried out as a primary washing, followed by a water washing step as a secondary washing. A water washing step may be carried out before the hot water washing step as the primary washing. The water washing time is not particularly limited, but is preferably 0.5 seconds or more and 3 seconds or less. The water temperature during washing is also not particularly limited, but is preferably 20°C or more and less than 40°C due to the cooling or heating costs.

[0049] The hot water washing method as the primary cleaning includes a method of irradiating the steel sheet 10 on which the pre-cleaning film has been formed with a spray, and a method of immersing the steel sheet 10 on which the pre-cleaning film has been formed in hot water. Each method will be described in detail below.

[0050] (Primary Cleaning: Spray) The lower limit of the hot water washing temperature is preferably 80°C or higher, more preferably 90°C or higher, because if it is below 80°C, F is not sufficiently removed and the F / Zr atomic concentration ratio exceeds 0.30. The upper limit of the hot water washing temperature is preferably 100°C or lower, more preferably 95°C, because if it is above 100°C, the solution evaporates and becomes inefficient. Furthermore, the lower limit of the hot water washing time is preferably 0.5 seconds or higher, more preferably 3.0 seconds or higher, because if it is less than 0.5 seconds, F in the surface layer of the coating 20 is not sufficiently removed and the F / Zr atomic concentration ratio in the surface layer of the coating 20 exceeds 0.30. Although a hot water washing time of more than 5 seconds does not cause any performance problems, productivity decreases, so 5 seconds or less is preferable. The spray may be applied either in air or in water.

[0051] The lower limit of the hot water rinsing temperature is preferably 80°C or higher, more preferably 90°C or higher, because if it is lower than 80°C, the coating surface will not be sufficiently roughened and the roughness parameter x will be less than 3.0 nm. The upper limit of the hot water rinsing temperature is preferably 100°C or lower, more preferably 95°C, because if it is higher than 100°C, the solution will evaporate, making the process inefficient. The lower limit of the hot water rinsing time is preferably 0.5 seconds or higher, because if it is lower than 0.5 seconds, the coating surface will not be sufficiently roughened and the roughness parameter x will be less than 3.0 nm. The upper limit of the hot water rinsing time is preferably 5 seconds or lower, because if it exceeds 5 seconds, productivity will decrease. The strength of the spray rinsing can be controlled by the flow rate. If the flow rate is too low, the roughening effect will not be obtained, so a flow rate of 300 L / min or higher is preferred, and if the flow rate is too high, cost issues will arise, so a flow rate of 600 L / min or lower is preferred. Furthermore, spray rinsing may be performed either with the steel sheet submerged in water or in the air (in contact with air).

[0052] From the above, when a surface-treated steel sheet for use as a container material having excellent retort resistance is produced by primary cleaning with a spray, the hot water washing temperature should be 80°C or higher and 100°C or lower, and the hot water washing time should be 0.5 seconds or higher and 5 seconds or lower.

[0053] (Primary cleaning: immersion) The lower limit of the hot water cleaning temperature is preferably 80°C or higher, because if it is lower than 80°C, F will not be sufficiently removed even if the hot water cleaning time is extended, and the F / Zr atomic concentration ratio will exceed 0.30. A more preferred temperature is 90°C or higher. The upper limit of the hot water cleaning temperature is preferably 100°C or lower, more preferably 95°C or lower, because if it is higher than 100°C, the solution will evaporate and become inefficient. Furthermore, the lower limit of the hot water cleaning time is preferably 1.0 second or higher, because if it is less than 1.0 second, F will not be sufficiently removed and the F / Zr atomic concentration ratio will exceed 0.30. There is no particular upper limit to the hot water cleaning time, but if it exceeds 5 seconds, productivity will decrease, so 5 seconds or less is preferred.

[0054] The lower limit of the hot water washing temperature is preferably 80°C or higher, more preferably 90°C or higher, because if it is lower than 80°C, the coating surface will not be sufficiently roughened and the roughness parameter x will be less than 3.0 nm. The upper limit of the hot water washing temperature is preferably 100°C or lower, more preferably 95°C, because if it is higher than 100°C, the solution will evaporate and the process will be inefficient. The lower limit of the hot water washing time is preferably 1 second or higher, because if it is lower than 1.0 second, the coating surface will not be sufficiently roughened and the roughness parameter x will be less than 3.0 nm. The upper limit of the hot water washing time is preferably 5 seconds or lower, because if it exceeds 5 seconds, productivity will decrease.

[0055] From the above, when a surface-treated steel sheet for use as a container material having excellent retort resistance is produced by primary washing by immersion, the hot water washing temperature should be 80° C. or higher and the hot water washing time should be 1.0 second or longer.

[0056] (Secondary Cleaning) Although the detailed mechanism has not been elucidated, when secondary cleaning was not performed or when the temperature of secondary cleaning was 40°C or higher, part of the coating dissolved and remained on the sample surface in a viscous state, and the F / Zr atomic concentration ratio exceeded 0.30, resulting in poor retort resistance.

[0057] The secondary cleaning method includes a method of spraying the coated steel sheet or a method of immersing the coated steel sheet in warm water, and either method is acceptable. In the spraying method, the spray may be applied in either air or water. The water temperature during cleaning is not particularly limited to a lower limit, but is preferably 20°C or higher because cooling costs are high when the water temperature is below 20°C. The upper limit is preferably less than 40°C because the performance described above cannot be achieved when the water temperature is above 40°C. The cleaning time is not particularly limited, but is preferably 0.5 seconds or more and 5 seconds or less because, as with the hot water cleaning in the primary cleaning, the desired effect cannot be achieved when the water temperature is less than 0.5 seconds, and productivity decreases when the water temperature is more than 5 seconds.

[0058] When a surface-treated steel sheet for use as a container material having excellent retort resistance is produced by primary cleaning with a spray, the hot water cleaning temperature should be 80° C. or higher and the hot water cleaning time should be 0.5 seconds or longer.

[0059] Drying Step After the steel sheet surface has been subjected to electrolytic treatment and the surface of the coating 20 has been cleaned, it is preferable to dry the steel sheet to evaporate the water. The drying method may be natural drying or heat drying.

[0060] <Coated precoated steel sheet for container material> The steel sheet for container material of the present invention can also be used as a coated precoated steel sheet for container material. The configuration of the coated precoated steel sheet for container material using the steel sheet for container material of the present invention is not particularly limited, but it is preferable to use a coated precoated steel sheet for container material that includes at least the steel sheet for container material 100 of the present disclosure and an organic resin coating (i.e., an organic resin coating arranged in the form of coating 20) disposed on the surface of the surface-treated steel sheet for container material 100. The organic resin coating can be formed by applying a coating (precoat) to the surface of the surface-treated steel sheet for container material 100 under known conditions.

[0061] <Laminated steel sheet for container material> The steel sheet for container material of the present invention can also be used for a laminated steel sheet for container material. The configuration of the laminated steel sheet for container material using the steel sheet for container material of the present invention is not particularly limited, but it is preferable that the laminated steel sheet for container material includes at least the steel sheet for container material 100 of the present disclosure and a laminate film arranged on the surface of the surface-treated steel sheet for container material 100 (i.e., a laminate film arranged on the coating 20). The laminated steel sheet for container material can be produced by further laminating a film on the surface of the surface-treated steel sheet for container material 100 under known conditions.

[0062] "Evaluation of Coating Weight" The coating weight of the coating and the coating before cleaning described below was measured by the following method. A specimen with a diameter of 5 cm was punched out from the steel sheet sample after electrolytic treatment or secondary cleaning, and a specimen with a diameter of 3 cm (area 7.07 cm) was measured using a fluorescent X-ray absorption spectrometer (Rigaku ZSX Primus II). ２ ) within the range, the amount of Zr, the amount of F, and the amount of P in the coating were measured, and the amount per unit area (mg / m ２ The results are shown in Tables 1B and 2B.

[0063] "Surface Layer Atomic Concentration Ratio" The surface layer atomic concentration ratio was measured by the following method for measuring the coating weight of the coating and the coating before cleaning, which will be described later. The surface of the steel sheet sample after electrolytic treatment or secondary cleaning was measured using an X-ray photoelectron spectrometer (PHI5800, manufactured by ULVAC-PHI, Inc.). The measurement conditions were: X-ray source: Mg-Kα, X-ray diameter: 800 μmφ, measurement area: 800 μmφ, detection angle: 45°. The obtained results are shown in Tables 1B and 2B.

[0064] "1 / 2 Depth Atomic Concentration Ratio" The 1 / 2 depth atomic concentration ratio can be measured by measuring the surface of a sample using an X-ray photoelectron spectrometer (e.g., PHI5800 manufactured by ULVAC-PHI, Inc.) (X-ray source: Mg-Kα, X-ray diameter: 800 μmφ, measurement area: 800 μmφ, detection angle: 45°) to determine the atomic ratio at the 1 / 2 depth position. When the sum of the atomic concentrations of the major elements (e.g., Zr, P, C, O, F, and Fe) detected by the X-ray photoelectron spectrometer is taken as 100%, Ar sputtering was performed, and the F / Zr atomic concentration ratio was measured by determining the atomic concentrations of Zr, P, O, and F at the 1 / 2 depth position. Similarly, the P / Zr and O / Zr ratios were determined. The results are shown in Tables 1B and 2B.

[0065] (Retort Treatment) The adhesion and corrosion resistance after retort treatment were evaluated by the following method. In the case of laminated steel sheets for container materials, a 19 μm-thick IA-PET film was used on the evaluation side, and a 13 μm-thick IA-PET (white film) film was used on the non-evaluation side. The washed sample (surface-treated steel sheets for container materials) and the above film were laminated at a laminating roll temperature of 260° C. and a laminating roll pressure of 20 kgf / cm. ２ The film laminating device used for heat sealing was designed so that the steel sheet before lamination was passed between a pair of heating rolls to heat it to a predetermined temperature, and then the pre-resin-coated steel sheet was fed between the laminating rolls, and simultaneously, front and back films were fed from the front and back sides of the pre-resin-coated steel sheet and pressed by the rolls, and then water-cooled after about 1 second.

[0066] Thereafter, the prepared film-laminated steel sheet was dried in a heating oven at 180° C. for 20 minutes, simulating the baking step after printing in the can manufacturing process.

[0067] For can manufacturing, a wax-based lubricant was applied to both sides of a film-laminated steel sheet, and a disk with a diameter of 155 mm was punched out using a press to obtain a shallow-drawn cup. This shallow-drawn cup was then stretch-ironed to obtain a cup with a cup diameter of 52 mm, a cup height of 138 mm, and an average thickness reduction rate of 18% at the can sidewall. This cup was heat-treated at 215°C to remove film distortion, and then further heat-treated at 200°C, equivalent to print baking, to prepare a sample for can property evaluation.

[0068] The retort treatment of the canned products was carried out by placing the film-laminated steel sheet in a steam oven for retort treatment and performing retort sterilization at 125°C for 90 minutes, and then evaluating the adhesion of the film and the presence or absence of discoloration.

[0069] "Evaluation of the relationship between the Zr deposition amount of the coating, the F / Zr atomic concentration ratio, and the adhesion and corrosion resistance" Total current application time (0.4 to 0.8 seconds), total current stop time (0 to 2.4 seconds), current density (25 to 50 A / dm ２ The steel sheets on which the pre-cleaning coating was formed were subjected to a primary cleaning (spray: 30-100°C for 0.2-5.0 seconds, immersion: 50-100°C for 0.5-5.0 seconds) and a secondary cleaning (25-50°C), and the resulting samples were subjected to a retort test to evaluate the film adhesion and corrosion resistance.

[0070] The relationship between the amount of Zr deposited on the surface layer of the coating obtained using the above aqueous solution containing zirconium fluoride as the Zr metal salt, and the F / Zr atomic concentration ratio, and the film adhesion and corrosion resistance is shown in Figure 3. In Figure 3, ◎ indicates no film peeling or discoloration, ○ indicates slight film peeling or no discoloration, ◇ indicates slight film peeling or slight discoloration, △ indicates partial film peeling or significant discoloration, and × indicates complete film peeling or significant discoloration. In Figure 3, ◎, ○, and ◇ are considered to be acceptable, while △ and × are considered to be unacceptable.

[0071] As shown by the dotted line in Figure 3, when the F / Zr atomic concentration ratio was 0.30 or less, the corrosion resistance and adhesion were excellent. However, there were some cases where the coating failed even when the F / Zr atomic concentration ratio in the surface layer was 0.30 or less. When investigating whether there was a level at which the retort performance was poor, it was found that the roughness parameter x in the surface layer of the coating did not satisfy the requirement of 3.0 nm or more and 10.0 nm or less.

[0072] "Evaluation of the relationship between the roughness parameter x and the F / Zr atomic concentration ratio of the coating and adhesion" Next, we evaluated the relationship between the total current application time (0.4 to 0.8 seconds), the total current stop time (0 to 2.4 seconds), the current density (25 to 50 A / dm ２ ) were changed to prepare samples with different coating roughness parameter x and F / Zr atomic concentration ratios. The samples were prepared by primary cleaning (spraying at 30-100°C for 0.2-5.0 seconds, immersion at 50-100°C for 0.5-5.0 seconds) and secondary cleaning (25-50°C). The obtained samples were then subjected to retort treatment, and the film adhesion and corrosion resistance were evaluated.

[0073] The results are shown in Figure 4. In Figure 4, ◎ means no film peeling and no discoloration, ○ means slight film peeling and no discoloration, ◇ means slight film peeling and slight discoloration, △ means partial film peeling and significant discoloration, and × means complete film peeling and significant discoloration. In Figure 4, ◎, ○, and ◇ were considered to be pass marks, while △ and × were considered to be fail marks.

[0074] In Figure 4, the reason why the film adhesion improves as the F / Zr atomic concentration ratio decreases is thought to be because, in a coating that exists in a structure such as ZrOx(OH)y-zFz, the value of z in the molecular formula of the compound is small and the value of y is large, resulting in an increase in the number of OH groups that are exposed on the surface of the coating and form hydrogen bonds with the film.Furthermore, the reason why the film adhesion improves as x increases is thought to be due to the anchor effect, i.e., the effect of the fine irregularities on the surface of the coating being embedded in the film.

[0075] "Evaluation of the effect of primary cleaning" A steel plate with a thickness of 0.2 mm was immersed in a treatment solution (pH: 3.4, bath temperature: 60°C), and the electrolytic treatment conditions were: total current application time: 0.8 seconds, total current stop time: 0 seconds, current density: 25 A / dm ２(surface layer F / Zr: 1.02, 1 / 2 depth F / Zr: 0.79) The steel sheets on which the pre-cleaning coatings were formed were cleaned under different conditions for the primary cleaning, and then subjected to secondary cleaning at 25°C. The F / Zr atomic concentration ratios of the obtained samples were evaluated.

[0076] The relationship between the time for each hot water washing temperature in spray cleaning and the F / Zr atomic concentration ratio in the coating surface is shown in Figure 5. In Figure 5, the horizontal axis represents time, and the vertical axis represents the F / Zr atomic concentration ratio. Figure 6 shows the relationship between the time for each hot water washing temperature in spray cleaning and the roughness parameter x of the coating surface. In Figure 6, the horizontal axis represents time, and the vertical axis represents the roughness parameter x. Figure 7 shows the relationship between the time for each hot water washing temperature in immersion cleaning and the F / Zr atomic concentration ratio in the coating surface. In Figure 7, the horizontal axis represents time, and the vertical axis represents the F / Zr atomic concentration ratio. Figure 8 shows the relationship between the time for each hot water washing temperature in immersion cleaning and the roughness parameter x of the coating surface. In Figure 8, the horizontal axis represents time, and the vertical axis represents the roughness parameter x.

[0077] 5, in the case of spraying, F was not sufficiently removed at temperatures below 80° C., resulting in an F / Zr atomic concentration ratio exceeding 0.30. When the hot water rinsing time was less than the lower limit of 0.5 seconds, F in the surface layer of the coating 20 was not sufficiently removed, resulting in an F / Zr atomic concentration ratio exceeding 0.30.

[0078] 6, in the case of spraying, the coating surface was not sufficiently roughened at temperatures below 80° C., and the roughness parameter x was less than 3.0 nm. When the hot water washing time was less than the lower limit of 0.5 seconds, the coating surface was not sufficiently roughened, and the roughness parameter x was less than 3.0 nm.

[0079] 7, in the case of immersion, F was not sufficiently removed when the temperature was less than 80° C., and the F / Zr atomic concentration ratio exceeded 0.30. When the hot water rinsing time was less than the lower limit of 0.5 seconds, F in the surface layer of the coating 20 was not sufficiently removed, and the F / Zr atomic concentration ratio in the surface layer of the coating 20 exceeded 0.30.

[0080] 8, in the case of immersion, the coating surface was not sufficiently roughened and the roughness parameter x was less than 3.0 nm when the temperature was less than 80° C. As for the lower limit of the hot water washing time, when the time was less than 0.5 seconds, the coating surface was not sufficiently roughened and the roughness parameter x was less than 3.0 nm.

[0081] "Evaluation of the effect of secondary cleaning" A steel plate with a thickness of 0.2 mm was immersed in a treatment solution (pH: 3.4, bath temperature: 60°C), and the electrolytic treatment conditions were: total current application time: 0.8 seconds, total current stop time: 0 seconds, current density: 25 A / dm ２ A pre-cleaning coating was formed using a temperature-controlled process (surface layer F / Zr: 1.02, 1 / 2 depth F / Zr: 0.79). The steel sheets on which the pre-cleaning coating was formed were subjected to a primary cleaning (spray or immersion, 80°C, 5 seconds), followed by a secondary cleaning at different temperatures. The F / Zr atomic concentration ratio of the resulting samples was evaluated. Figure 9 shows the relationship between the secondary cleaning temperature, the F / Zr atomic concentration ratio in the coating surface layer, and retort resistance. The horizontal axis of Figure 9 represents the cleaning temperature, and the vertical axis represents the surface layer F / Zr atomic concentration ratio.

[0082] As shown in Figure 9, when the secondary cleaning temperature was 40°C or higher and the cleaning time was less than 0.5 seconds, the F / Zr atomic concentration ratio in the surface layer exceeded 0.3. Although the detailed mechanism by which the F / Zr concentration increased after primary cleaning is unknown, this is thought to be because part of the coating dissolved and remained on the sample surface in a viscous state.

[0083] Next, with reference to the conditions obtained above, surface-treated steel sheets for container materials of Examples and Comparative Examples were produced and evaluated under the conditions shown in Tables 1A and 2A. Steel sheets with a thickness of 0.185 mm were used as test materials. For reference, steel sheets with a thickness of 0.185 mm and a chromate coating weight of approximately 110 mg / m were used. ２ Evaluation was also carried out using general tin-free steel material.

[0084] The electrolytic treatment solution is zirconium fluoride (ZrF ６ ) and phosphoric acid (H ３ P.O. ４The treatment solution used was a solution containing 1,400 to 7,000 mass ppm of Zr and 200 to 1,800 mass ppm of P. The pH of the solution was adjusted appropriately using nitric acid and ammonia to the values ​​shown in Tables 1A and 2A. The electrolysis conditions were as shown in Tables 1A and 2A.

[0085] The electrolytically treated steel sheets were subjected to primary cleaning under the conditions shown in Tables 1A and 2A. The primary cleaned steel sheets were subjected to secondary cleaning under the conditions shown in Tables 1A and 2A to obtain surface-treated steel sheets for container materials of Examples and Comparative Examples.

[0086] The surface-treated steel sheets for container materials were coated with an epoxy paint on the steel sheet surface after electrolytic treatment and evaluated in a corrosion resistance test. The epoxy paint for cans was applied using a bar coater to a target film thickness of 5 μm, and cured by baking in a baking and drying oven at 210°C for 10 minutes twice. General tin-free steel materials were also coated in the same way.

[0087] (Corrosion Resistance) The corrosion resistance test was carried out by cutting a surface-treated steel sheet for container material coated with an epoxy paint for cans into 100 mm x 50 mm strips, making cross-cut scratches, processing the strips to a height of 3 mm using an Erichsen processing tester, and applying tape seals to the end faces and back faces. After spraying 5% NaCl aqueous solution for 1 hour using a salt spray tester, the strips were left to stand for 10 days under constant temperature and humidity conditions of 40°C temperature and 85% humidity, and evaluated on a four-point scale, with only A and B being considered pass. The results are shown in Tables 1B and 2B. <Evaluation method> A: No change B: Partial discoloration C: Partial rust D: Rust over the entire surface

[0088] (Peel Test) The coating adhesion test is performed by preparing a T-peel test piece. First, the painted surfaces of two pre-coated steel sheets are hot-pressed together via an ethylene acrylic acid (EAA) adhesive film (0.1 mm thick) (200°C, preheating for 30 seconds, pressure time for 30 seconds, 1 MPa). After hot-pressing, the test piece is again heat-cured in a baking oven at 210°C for 20 minutes and then removed and cooled. An adhesion test piece 10 mm wide and 150 mm long is then cut out, and a portion of the adhesion test piece approximately 50 mm long is peeled off in advance to serve as a gripping margin for the tensile test, to prepare a T-peel test piece.

[0089] The previously peeled gripping portion was clamped in the grip of a tensile tester, and the T-peel strength of 100 mm of the adhesive portion was measured at room temperature at a pulling speed of 20 mm / min. The paint adhesion was evaluated as follows, with only A and B being considered acceptable. The results are shown in Tables 1B and 2B. Evaluation method: A: 25 N / 15 mm or more; B: More than 10 N / 15 mm but less than 25 N / 15 mm; C: 10 N / 15 mm or less.

[0090] In the case of pre-coated steel sheets for container materials, an epoxy paint for cans is applied to the surface of the steel sheet after electrolytic treatment using a bar coater to a target film thickness of 5 μm, and then baked in a baking and drying oven at 210° C. for 10 minutes.

[0091] Furthermore, corrosion resistance tests and paint adhesion tests for surface-treated steel sheets for container materials are tests that simulate the painting conditions at the user's site, while paint adhesion tests for pre-coated steel sheets for container materials are tests that test the product before shipping after painting. The only difference is where the painting (pre-coating) is done, but the evaluations can be carried out in essentially the same way.

[0092] (Retort Treatment) A film was laminated onto the evaluation sample to prepare a laminated steel sheet for container material, and the laminated steel sheet for container material was subjected to retort treatment to evaluate the film adhesion and corrosion resistance. A 19 μm-thick IA-PET film was used on the evaluation side, and a 13 μm-thick IA-PET (white film) film was used on the non-evaluation side.

[0093] The film lamination method was performed by laminating the prepared electrolytically treated plate and the above film at a lamination roll temperature of 260°C and a lamination roll pressure of 20 kgf / cm. ２ The film was heat-sealed for 60 seconds at 100°C and then cooled with water to obtain a film-laminated steel sheet.

[0094] Thereafter, the prepared film-laminated steel sheet was dried in a heating oven at 180° C. for 20 minutes, simulating the baking step after printing in the can manufacturing process.

[0095] For can manufacturing, a wax-based lubricant was applied to both sides of a film-laminated steel sheet, and a disk with a diameter of 155 mm was punched out using a press to obtain a shallow-drawn cup. This shallow-drawn cup was then stretch-ironed to obtain a cup with a cup diameter of 52 mm, a cup height of 138 mm, and an average thickness reduction rate of 18% at the can sidewall. This cup was heat-treated at 215°C to remove film distortion, and then further heat-treated at 200°C, equivalent to print baking, to prepare a sample for can property evaluation.

[0096] For the retort treatment of canned products, the film-laminated steel sheet was placed in a steam oven for retort treatment and retort sterilization was carried out at 125°C for 90 minutes. Performance was evaluated as follows, and only those with a grade of C or higher were deemed to have passed. The results are shown in Tables 1B and 2B. <Evaluation method> A: No film peeling, no discoloration B: Minor film peeling, no discoloration C: Minor film peeling, slight discoloration *Indicated as ◇ on the graph D: Partial film peeling, significant discoloration E: Complete film peeling, significant discoloration

[0097] Tables 1B and 2B show examples and comparative examples, and their evaluations. Steel sheets that satisfy the requirements of the present invention show good results as chromate-free surface-treated steel sheets for container materials, pre-painted steel sheets for container materials, and laminated steel sheets for container materials.

[0098]

[0099]

[0100]

[0101]

[0102] The surface-treated steel sheet for container materials of the present disclosure is chromate-free, has a low environmental impact, and has excellent adhesion to films and corrosion resistance, and therefore has high industrial applicability.

[0103] 10 Steel plate, 20 Coating, 100 Surface treated steel plate for container materials

Claims

1. A steel sheet comprising: a coating containing Zr, O, P, F, and unavoidable impurities, the coating having a coating weight of 5.0 mg / m2 in terms of Zr; ２ Over 200.0 mg / m ２ and the F / Zr atomic concentration ratio in the surface layer of the coating is 0 or more and 0.30 or less, and in an image obtained by observing a cross section in the thickness direction with a transmission electron microscope, the direction perpendicular to the thickness direction is defined as an evaluation direction, the length of an evaluation range of the image along the evaluation direction is defined as a reference length L, and the thickness of the coating at an i-th position when the evaluation range is divided into n equal intervals along the evaluation direction is defined as x ｉ nm, and the x ｉ The average value of x ａｖｅ wherein x calculated from the following formula (1) is 3.0 nm or more and 10.0 nm or less:

2. The surface-treated steel sheet for container material according to claim 1, characterized in that the F / Zr atomic concentration ratio at a position at a depth of 1 / 2 the thickness of the coating from the surface of the coating in the thickness direction is 0.10 or more and 0.80 or less.

3. A pre-painted steel sheet for use as a container material, characterized in that the surface-treated steel sheet for use as a container material according to claim 1 or 2 is used.

4. A laminated steel sheet for container material, characterized in that the surface-treated steel sheet for container material according to claim 1 or 2 is used.

5. A method for manufacturing a surface-treated steel sheet for use as a container material according to claim 1, comprising: a coating formation step of forming a pre-cleaning coating on the steel sheet to obtain a coated steel sheet; a primary cleaning step of cleaning the coated steel sheet with warm water of 80°C or higher for 0.5 to 5 seconds after the coating formation step; and a secondary cleaning step of cleaning the coated steel sheet with water below 40°C for 0.5 to 5 seconds after the primary cleaning step.

6. A method for manufacturing a surface-treated steel sheet for container material as described in claim 5, characterized in that in the coating formation process, the steel sheet is immersed in a treatment solution and subjected to cathodic electrolysis to form the pre-cleaning coating, the Zr concentration in the treatment solution is 1,000 mass ppm or more and 15,000 mass ppm or less, and the P concentration in the treatment solution is 100 mass ppm or more and 2,000 mass ppm or less.

7. A method for manufacturing a surface-treated steel sheet for container materials according to claim 5, characterized in that the F / Zr atomic concentration ratio in the surface layer of the pre-cleaning coating is 0.40 or more and 1.10 or less, and the F / Zr atomic concentration ratio at a position at a depth of 1 / 2 the thickness of the pre-cleaning coating from the surface of the pre-cleaning coating in the thickness direction is 0.30 or more and 0.90 or less.

8. The method for manufacturing a surface-treated steel sheet for container materials according to claim 5, wherein in the primary cleaning step, the steel sheet is spray-cleaned with hot water of 70°C or higher for 0.5 to 5 seconds.

9. The method for manufacturing a surface-treated steel sheet for use as a container material according to claim 5, characterized in that in the primary cleaning step, the steel sheet is immersed in hot water of 80°C or higher for 1.0 second to 5 seconds.

10. A method for producing a painted precoated steel sheet for use as a container material, which comprises further applying a coating to the surface of the surface-treated steel sheet for use as a container material produced by the method for producing a surface-treated steel sheet for use as a container material according to claim 5 or 6.

11. A method for producing laminated steel sheets for container materials, characterized in that a film is further laminated on the surface of the surface-treated steel sheets for container materials produced by the method for producing surface-treated steel sheets for container materials according to claim 5 or 6.

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