Method of producing coated metal material

Abstract

Provided is a method of producing a coated metal material less susceptible to visual defects in chemical conversion by batch processing. The method of producing a coated metal material includes a (a) coating chemical conversion step and a (b) water rinsing step in this order. The (a) coating chemical conversion step and the (b) water rinsing step are performed in batches, and the number of metal materials treated in one batch is 100 to 1,000,000. Formula (1) is satisfied where A [minutes] is the length of time between the (a) coating chemical conversion step and the (b) water rinsing step and B (pieces) is the number of metal materials treated in one batch.　Formula (1): A6.5 × log(B) × 0.00001 < 118

Description

Method for manufacturing coated metal material

[0001] The present disclosure relates to a method for producing a coated metal material.

[0002] Conventionally, chemical conversion treatments such as phosphate treatment and zirconium chemical conversion treatment have been used as a paint base for automobile bodies, etc., to improve functions such as adhesion to a paint film and corrosion resistance after painting. For example, Patent Document 1 discloses a chemical conversion treatment method for a paint base for an automobile body.

[0003] Japanese Patent Application Publication No. 2-277781

[0004] In recent years, chemical conversion coatings have been increasingly applied for purposes other than coating substrates, such as imparting insulation. Chemical conversion coatings for the purpose of imparting insulation may be performed in a batch process, in which a large number of small metal materials are placed in a container and chemical conversion treatment is performed on each container. However, batch processing presents new challenges, such as poor appearance of the chemical conversion coating, due to the simultaneous chemical conversion treatment of a large number of small metal materials in a single container.

[0005] Therefore, an object of the present disclosure is to provide a method for producing a coated metal material that is less likely to suffer from poor appearance when subjected to chemical conversion treatment by batch processing.

[0006] As a result of extensive research into solving the above problems, the present inventors have discovered that poor appearance of chemical conversion coatings can be suppressed by appropriately managing the batch chemical conversion coating process.

[0007] That is, the present disclosure provides: (1) a method for producing a coated metal material, the method comprising (a) a coating chemical conversion treatment step and (b) a water-rinsing treatment step in this order, the (a) coating chemical conversion treatment step and the (b) water-rinsing treatment step being carried out by batch treatment, the number of metal materials treated in one batch treatment being 100 or more and 1,000,000 or less, and satisfying the following formula (1) when the time between the (a) coating chemical conversion treatment step and the (b) water-rinsing treatment step is A [minutes] and the number of metal materials treated in one batch treatment is B [pieces]; ６．５× log(B) × 0.00001 < 118 ... formula (1); (2) The method for producing a coated metal material according to (1) above, in which the chemical conversion treatment in the (a) coating chemical conversion treatment step includes a phosphate treatment; (3) The method for producing a coated metal material according to (1) or (2) above, in which the (b) water-washing treatment step is followed by a (c) drying step, and the time between the (b) water-washing treatment step and the (c) drying step is 30 minutes or less; and the like.

[0008] According to the present disclosure, it is possible to provide a method for producing a coated metal material that is less likely to suffer from poor appearance during chemical conversion treatment by batch processing.

[0009] <Metallic Material> The metallic material used in the method for producing a coated metallic material according to this embodiment will now be described. The metallic material according to this embodiment is not particularly limited as long as it is a metallic material capable of forming a chemical conversion coating. However, it may be entirely composed of metal, or may be combined with other materials as long as at least a portion of the surface is metallic. Examples of metals include metals containing at least one element selected from the group consisting of Fe, Al, Si, Cr, Zn, Cu, Ni, Sn, Co, Pb, Pt, Ag, Au, Mg, and B. Furthermore, examples of alloys include iron alloys, zinc alloys, aluminum alloys, and magnesium alloys. Examples of iron alloys include carbon steel, Fe—Si alloys, Fe—Si—Cr alloys, Fe—Al alloys, Fe—Ni alloys, Fe—Co alloys, Fe—Si—Al alloys, and Fe—Si—B—Cr alloys. Examples of aluminum alloys include 1000 series aluminum alloys, 2000 series aluminum alloys, 3000 series aluminum alloys, 4000 series aluminum alloys, 5000 series aluminum alloys, 6000 series aluminum alloys, 7000 series aluminum alloys, 8000 series aluminum alloys, aluminum castings, aluminum alloy castings, and die-cast materials. Examples of magnesium alloys include AZ91, AZ61, and AZ31. The metal may be a plated material. Examples of plated materials include zinc-based plated materials and aluminum-based plated materials. Examples of zinc-based plated materials include electrogalvanized materials, hot-dip galvanized materials, hot-dip zinc-aluminum plated materials, hot-dip zinc-aluminum-magnesium plated materials, and alloyed hot-dip galvanized materials. The metal may be in the form of a metal oxide, as long as it can form a chemical conversion coating. Examples of metal oxides include zinc oxide, alumina, zirconia, cordierite, ferrite, barium titanate, lead zirconate titanate, forsterite, zircon, mullite, steatite, etc. Other materials include, but are not limited to, resins, ceramics, etc. Examples of resins include epoxy resins, polyamide resins, phenolic resins, acrylic resins, silicone resins, polyimide resins, polyamideimide resins, etc.Examples of ceramics include metal nitrides and metal carbides. Examples of metal nitrides include silicon nitride, aluminum nitride, and titanium nitride. Examples of metal carbides include silicon carbide.

[0010] When the metal material is a metal, it is presumed that the pH near the surface of the metal material increases due to an etching reaction of the metal, and the film is formed accordingly. On the other hand, when the metal material is a metal oxide, it is presumed that the metal oxide on the surface is dissolved by an acid, and the dissolved metal ions and the acid form an insoluble salt, forming the film. For example, in the phosphate treatment of a metal oxide, when the metal oxide is zinc oxide, it is presumed that an insoluble zinc phosphate film is formed by the following chemical reaction: 3ZnO + 2H ３ P.O. ４ → Zn ３ (P.O. ４ ) ２ ↓ + 3H ２ O

[0011] The size of the metal material is not particularly limited, but the volume per piece is 1.0 × 10 －８ cm ３ 1.0cm or more ３ Preferably, it is 1.0 x 10 or less. －７ cm ３ Above 1.0 x 10 －１ cm ３ More preferably, it is 1.0 × 10 or less. －６ cm ３ Above 1.0 x 10 －２ cm ３ It is even more preferable that:

[0012] The shape of the metal material is not particularly limited, and may be, for example, a sphere, a cylinder, or a polygonal prism. It may also have a complex shape. Examples of polygonal prisms include cubes and rectangular parallelepipeds. Rectangular parallelepipeds may be, for example, plate-shaped. Examples of plate-shaped metal materials include cold-rolled steel plates, hot-rolled steel plates, and high-tensile steel plates. Other shapes of metal materials include tool steel, alloy tool steel, spheroidal graphite cast iron, and gray cast iron.

[0013] (Method for manufacturing a coated metal material) <(a) Chemical conversion coating step> The method for manufacturing a coated metal material according to this embodiment includes (a) a chemical conversion coating step. The (a) chemical conversion coating step is a step of performing a chemical conversion treatment on a metal material. The chemical conversion treatment is not particularly limited, and examples thereof include phosphate treatment and zirconium chemical conversion treatment. Examples of phosphate treatment include zinc phosphate treatment, manganese phosphate treatment, iron phosphate treatment, and zinc calcium phosphate treatment. The chemical conversion treatment includes a step of contacting the metal material with a chemical conversion treatment solution.

[0014] The chemical conversion treatment solution may be, for example, a known phosphate treatment solution or zirconium chemical conversion treatment solution. The phosphoric acid treatment solution is not particularly limited, but may be, for example, a zinc phosphate treatment solution, a manganese phosphate treatment solution, an iron phosphate treatment solution, or a zinc calcium phosphate treatment solution.

[0015] The concentration of phosphate ions in the phosphate treatment solution is not particularly limited, but can be, for example, 10 mmol / L or more and 850 mmol / L or less. When the phosphate treatment solution is a zinc phosphate treatment solution, the molar ratio of zinc ions to phosphate ions in the treatment solution (Zn / PO ４ When the phosphate treatment solution is a manganese phosphate treatment solution, the molar ratio of manganese ions to phosphate ions in the treatment solution (Mn / PO ４ When the phosphate treatment solution is a zinc calcium phosphate treatment solution, the molar ratio of calcium to phosphate ions in the treatment solution (Ca / PO ４ ) can be, for example, 0.02 or more and 2.0 or less.

[0016] The pH of the phosphate treatment solution is not particularly limited, but can be 1.0 or more and 7.0 or less. Note that the pH in this disclosure is a value at 25°C, and was measured using a pH meter (IM-32P) manufactured by Toa DKK (the pH of the zirconium chemical conversion treatment solution described below was also measured under the same conditions).

[0017] The zirconium concentration in the zirconium chemical conversion treatment solution is not particularly limited, but can be, for example, 0.02 g / L or more and 2.0 g / L or less. The zirconium chemical conversion treatment solution is a treatment solution in which a zirconium compound is dissolved, and examples of the zirconium compound include, but are not limited to, zirconium sulfate, ammonium zirconium sulfate, zirconium nitrate, ammonium zirconium nitrate, zirconium chloride, zirconium acetate, zirconium lactate, ammonium zirconium carbonate, potassium zirconium carbonate, and sodium zirconium carbonate.

[0018] The pH of the zirconium chemical conversion treatment solution is not particularly limited, but can be, for example, 3.0 or more and 7.0 or less.

[0019] The time for which the metal material is brought into contact with the chemical conversion treatment solution is not particularly limited, but may be, for example, 0.5 minutes to 30 minutes. The temperature of the chemical conversion treatment solution when the metal material is brought into contact is not particularly limited, but may be, for example, 20°C to 100°C.

[0020] The method for bringing the metal material into contact with the chemical conversion treatment solution is not particularly limited, but examples thereof include immersion treatment, spray treatment, pouring, and combinations of these.

[0021] <(b) Water-Rinsing Treatment Step> In the method for producing a coated metal material according to this embodiment, the (a) chemical conversion coating step is followed by the (b) water-rinsing treatment step. In the (b) water-rinsing treatment step, the metal material subjected to the (a) chemical conversion coating step is brought into contact with water. The water is not particularly limited, and industrial water, city water, deionized water, distilled water, etc. can be used. The method for bringing the metal material into contact with water is not particularly limited, and examples thereof include immersion treatment, spray treatment, pouring, and combinations thereof. The time for which the metal material is brought into contact with water is not particularly limited, and can be, for example, 10 seconds or more and 300 seconds or less. Furthermore, the temperature of the water when the metal material is brought into contact is not particularly limited, and can be, for example, 0°C or more and 40°C or less.

[0022] The time between (a) the film conversion treatment step and (b) the water washing treatment step is not particularly limited as long as it satisfies the formula (1) described below, but for example, it is preferably within 10 minutes and more preferably within 5 minutes.

[0023] <Batch Treatment> In the method for producing a coated metal material according to this embodiment, (a) the chemical conversion coating step and (b) the water washing step are performed in a batch process. Batch treatment is a treatment method in which a container containing multiple metal materials is subjected to treatment. The size of the container is not particularly limited, but is preferably 100 cm ３ More than 50000cm ３ The material of the container is not particularly limited, but may be, for example, a stainless steel material, an iron material, an iron alloy material, or a resin material.

[0024] The number of metal materials processed in one batch processing is from 100 to 1,000,000, more preferably from 1,000 to 800,000, and more preferably from 5,000 to 500,000. In the batch processing, the metal materials are stacked in a dense state.

[0025] In the method for producing a coated metal material according to this embodiment, when the time between (a) the coating chemical conversion treatment step and (b) the water rinsing treatment step is A [minutes] and the number of metal materials treated in one batch treatment is B [pieces], the following formula (1) is satisfied. In formula (1), log means common logarithm. ６．５ ×log(B)×0.00001<118...Formula (1)

[0026] When metal materials are filled in a container as described above and the (a) chemical conversion coating step is performed in a batch process, it is presumed that the gaps between the metal materials are reduced, making it easier for the chemical conversion coating agent to remain between the (a) chemical conversion coating step and the (b) water rinsing step. Because the chemical conversion coating agent has a neutral to acidic pH range, if it remains on the metal surface for a long time, it is presumed that the coating formed by the reaction will be redissolved, ultimately causing unevenness in the coating and resulting in poor appearance. This phenomenon is presumed to occur more easily the greater the number of metal materials. This is presumed to be because it becomes difficult to drain the chemical conversion coating agent adhering to the metal material. When draining is difficult, a high concentration of acid component is sequentially supplied to the coating surface from the large amount of remaining chemical conversion coating agent, making the coating more likely to redissolve. The uneven redissolution of the coating is presumed to cause unevenness and increase the incidence of poor appearance.

[0027] In the method for producing a coated metal material according to this embodiment, the (b) water-washing step may be followed by the (c) drying step. The (c) drying step may be performed as a batch process. The drying temperature in the (c) drying step is not particularly limited, but may be 40°C or higher and 200°C or lower. The drying time is also not particularly limited, but may be 1 minute or higher and 30 minutes or lower.

[0028] The time between the (b) water washing step and the (c) drying step is not particularly limited, but is preferably within 30 minutes, more preferably within 10 minutes.

[0029] In the method for producing a coated metal material according to this embodiment, a cleaning step may be carried out before the (a) chemical conversion coating step. A known method can be used for the cleaning step, such as an acid pickling step, a degreasing step, or an alkaline cleaning step. Only one of the above-mentioned steps may be carried out as the cleaning step, or two or more steps may be combined and carried out sequentially. When a cleaning step is carried out, a water rinsing step may be carried out after the cleaning step. When multiple cleaning steps are carried out, a water rinsing step may be carried out after each cleaning step or after some of the cleaning steps. The cleaning step and the accompanying water rinsing step may be carried out as a batch process.

[0030] In the method for producing a coated metal material according to this embodiment, a surface conditioning step may be carried out before the (a) chemical conversion coating step and after the cleaning step. A known method may be used for the surface conditioning step. After the surface conditioning step, it is preferable to carry out the (a) chemical conversion coating step without carrying out a water washing step, a drying step, or the like. The surface conditioning step may be carried out as a batch process.

[0031] Examples and comparative examples of the present disclosure will be described below, but the present disclosure is not limited to these examples.

[0032] (Metallic Material) In Examples 1 to 20 and Comparative Examples 1 to 8, the metallic material was a cold rolled steel plate (SPCC) conforming to the standard of JIS G3141:2011, with a length and width of 1 mm and a height of 0.3 mm (volume of 3 × 10 －４ cm ３ In Example 21, a hot-dip galvanized steel sheet (SGCC) conforming to the standard of JIS G3302:2019 was cut into a rectangular parallelepiped shape of 1 mm in length and 0.8 mm in height (volume: 8 × 10 －４ cm ３ ) and used as test materials.

[0033] Example 1 One hundred metal materials were placed in a 500 mL SUS mesh basket and degreased by immersion in a degreasing agent (an aqueous solution of FC-E6400 manufactured by Nihon Parkerizing Co., Ltd. dissolved in water to a concentration of 20 g / L) at 60°C for 120 seconds. The materials were then immersed at 25°C for 30 seconds and rinsed with water. Subsequently, in the (a) chemical conversion coating step (referred to as step (a) in Table 1), the materials were immersed in a chemical conversion coating agent (zinc phosphate treatment solution, PB-L3020 manufactured by Nihon Parkerizing Co., Ltd.) at 40°C for 10 minutes to form a chemical conversion coating on the surface of the metal material. The zinc ion concentration in the zinc phosphate treatment solution was 0.02 mol / L, and the phosphate ion concentration was 0.16 mol / L. Furthermore, the molar ratio of zinc ions to phosphate ions in the zinc phosphate treatment solution (Zn / PO ４) was 0.13. The surface of the metal material having the obtained chemical conversion coating was washed with tap water and then deionized water at 25°C. The time from the end of the (a) chemical conversion coating process to the start of the (b) water washing process (referred to as process (b) in Table 1) was 10 minutes. Thereafter, in the (c) drying process (referred to as process (c) in Table 1), the water was dried in a hot air drying oven at 100°C. The time from the end of the (b) water washing process to the start of the (c) drying process was 5 minutes. The metal material with the coating of Example 1 was manufactured by the above series of processes. The value of the left side of the following formula (1) for the manufactured metal material is shown in Table 1. A ６．５ ×log(B)×0.00001<118...Formula (1)

[0034] (Example 21) 1,000,000 metal materials were placed in a 1,300 mL SUS mesh basket and degreased by immersion in a degreasing agent (a 20 g / L aqueous solution of FC-E6400 manufactured by Nihon Parkerizing Co., Ltd.) at 60°C for 120 seconds. The materials were then immersed in a chemical conversion treatment agent (zinc phosphate treatment solution, PB-L3020 manufactured by Nihon Parkerizing Co., Ltd.) at 40°C for 10 minutes, forming a chemical conversion coating on the surface of the metal material. The zinc ion concentration in the zinc phosphate treatment solution was 0.02 mol / L, and the phosphate ion concentration was 0.16 mol / L. In addition, the molar ratio of zinc ions to phosphate ions in the zinc phosphate treatment solution (Zn / PO ４ ) was 0.13. The surface of the metal material having the obtained chemical conversion coating was washed with tap water and then deionized water at 25°C. The time from the end of the (a) chemical conversion coating process to the start of the (b) water washing process (referred to as process (b) in Table 1) was 9 minutes. Thereafter, in the (c) drying process (referred to as process (c) in Table 1), the water was dried in a hot air drying oven at 100°C. The time from the end of the (b) water washing process to the start of the (c) drying process was 30 minutes. The metal material with a coating of Example 21 was produced by the above series of processes. The value of the left side of the following formula (1) for the produced metal material is shown in Table 1. A ６．５×log(B)×0.00001<118...Formula (1)

[0035] Examples 2 to 21 and Comparative Examples 1 to 8 The coated metal materials of Examples 2 to 21 and Comparative Examples 1 to 8 were produced in the same manner as in Example 1 except for the conditions shown in Table 1.

[0036] (Appearance Defect Rate) One hundred metal materials (test pieces) having a chemical conversion coating obtained in each Example and Comparative Example were sampled and their appearances were checked using a microscope. Each test piece was visually inspected for the presence or absence of coating unevenness, and the appearance defect rate (%) was calculated according to the following formula: Appearance Defect Rate (%) = 100 × (number of metal materials with coating unevenness) / 100. An appearance defect rate of 10% or more was considered a failure, and an appearance defect rate of less than 10% was considered a pass.

[0037] Details of the treatments (solutions) listed in Table 1 are as follows: SPCC: SPCC-SD, manufactured by Standard Test Piece Co., Ltd. SGCC: Untreated SGCC, manufactured by Standard Test Piece Co., Ltd. Iron phosphate treatment: PF-1077, manufactured by Nihon Parkerizing Co., Ltd. Zinc calcium phosphate treatment: FT-7, manufactured by Nihon Parkerizing Co., Ltd. Manganese phosphate treatment: PF-M1A, manufactured by Nihon Parkerizing Co., Ltd. Zirconium conversion treatment: PLC-1500, manufactured by Nihon Parkerizing Co., Ltd.

[0038] As described above, the present invention can provide a method for producing a coated metal material that is less likely to suffer from poor appearance in chemical conversion treatment by batch processing, and is therefore extremely useful and has high industrial applicability. CROSS-REFERENCE TO RELATED APPLICATIONS

[0039] This application claims priority based on Japanese Patent Application No. 2024-147749, filed with the Japan Patent Office on August 29, 2024, the entire disclosure of which is incorporated herein by reference in its entirety.

Claims

1. A method for producing a coated metal material, comprising (a) a coating chemical conversion treatment step and (b) a water washing treatment step in this order, wherein the (a) coating chemical conversion treatment step and the (b) water washing treatment step are carried out in a batch process, the number of metal materials treated in one batch process is 100 or more and 1,000,000 or less, and the following formula (1) is satisfied when the time between the (a) coating chemical conversion treatment step and the (b) water washing treatment step is A [minutes] and the number of metal materials treated in one batch process is B [pieces]. A ６．５ ×log(B)×0.00001<118...Formula (1) 2. The method for producing a coated metal material according to claim 1, wherein the chemical conversion treatment in the (a) chemical conversion coating step includes phosphate treatment.

3. A method for producing a coated metal material according to claim 1 or 2, comprising (c) a drying step after (b) the water washing step, and the time between (b) the water washing step and (c) the drying step is 30 minutes or less.

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