JP5648522B2 - Manufacturing method of surface-treated steel sheet - Google Patents

Description

  The present invention is a surface-treated steel sheet mainly used for containers such as cans after the surface is coated (laminated) with a resin film such as a plastic film, in particular, adhesion with a resin coated in a high-temperature and humid environment ( Hereinafter, the present invention relates to a method for producing a surface-treated steel sheet that is excellent in wet resin adhesion) and exhibits excellent corrosion resistance even when the coated resin is missing.

  For various metal cans such as beverage cans, food cans, pail cans and 18 liter cans, electrolytic chromic acid treated steel plates called tin-plated steel plates or tin-free steel plates are used. Among these, tin-free steel sheets are manufactured by electrolytically treating steel sheets in a plating bath containing hexavalent Cr, and are characterized by excellent wet resin adhesion to resins such as paints.

  In recent years, due to the increasing awareness of the environment, the use of hexavalent Cr has been regulated worldwide, and there is an alternative material for tin-free steel plates manufactured using a hexavalent Cr plating bath. It has been demanded.

  On the other hand, various metal cans have traditionally been manufactured by coating tin-free steel sheets, etc., and then processing them into cans. A method of processing a laminated steel sheet laminated with a resin film such as a plastic film into a can body is frequently used. In this laminated steel sheet, it is necessary that the resin is strongly adhered to the steel sheet. Especially, the laminated steel sheet used as a beverage can or a food can may undergo a retort sterilization process after filling the contents, Excellent wet resin adhesion that prevents the resin from peeling even in a high temperature wet environment, and even if the resin is partially missing due to scratching, it does not cause holes due to being attacked by the contents of the can. Excellent corrosion resistance is required.

  In response to such a request, the inventors of the present invention in Patent Document 1, on at least one surface of the steel plate, among Ni layer, Sn layer, Fe-Ni alloy layer, Fe-Sn alloy layer and Fe-Ni-Sn alloy layer After forming a corrosion-resistant film consisting of at least one layer selected from the above, it contains Ti-containing ions, and further contains at least one metal selected from Co, Fe, Ni, V, Cu, Mn and Zn It was proposed that a surface-treated steel sheet having extremely excellent wet resin adhesion and excellent corrosion resistance can be produced without using Cr by forming an adhesive film by cathodic electrolysis in an aqueous solution containing ions.

JP 2009-155665 A

  However, in the method for producing a surface-treated steel sheet described in Patent Document 1, the resin film has a biaxial orientation degree (BO value: Degree of Degree of) so that it can be used for applications that require higher impact resistance of the resin film after lamination. There is a problem in that excellent wet resin adhesion cannot always be obtained when lamination is performed under a condition of increasing the biaxial orientation (for example, at a lower temperature).

  An object of the present invention is to provide a method for producing a surface-treated steel sheet that does not use Cr, has excellent corrosion resistance, and provides excellent wet resin adhesion even when laminated under the condition of increasing the BO value of a resin film. To do.

The present inventors diligently studied to achieve the above object, and in the manufacturing method of the surface-treated steel sheet disclosed in Patent Document 1, the current density is the current density at which Ti precipitates and the current density at which Ti does not precipitate. Electricity at the current density at which the number of cycles is 10 or more and Ti is deposited, using a current with a period of 0.005 to 0.2 seconds at a current density at which the Ti does not precipitate per period, with a period of 0.01 to 0.4 seconds. It has been found that cathodic electrolysis is effective under the electrolysis conditions where the quantity density is 4 C / dm ² or more.

The present invention has been made based on such knowledge, and at least one surface of a steel plate is selected from a Ni layer, a Sn layer, a Fe—Ni alloy layer, a Fe—Sn alloy layer, and a Fe—Ni—Sn alloy layer. After forming a corrosion-resistant film composed of at least one layer, Ti is contained at 0.008 to 0.07 mol / l (l: liter), and at least one selected from Co, Fe, Ni, V, Cu, Mn and Zn In an aqueous solution containing a total of 0.01 to 10 molar ratios of seed metals to Ti, the current density changes between a current density at which Ti precipitates and a current density at which Ti does not precipitate in a period of 0.01 to 0.4 seconds, Using a current with a current density of 0.005 to 0.2 seconds at a current density at which Ti does not precipitate per cycle, the number of cycles is 10 or more, and the total electric density at the current density at which Ti precipitates is 4 C / dm ² or more. Provided is a method for producing a surface-treated steel sheet, characterized by forming an adhesive film by cathodic electrolysis under electrolysis conditions Here, the upper limit of the current density at which Ti does not precipitate is a value that depends on the composition and pH of the aqueous solution used for the cathodic electrolysis.

In the method for producing a surface-treated steel sheet of the present invention, a current whose current density changes to a binary value of a current density at which Ti precipitates and a current density at which Ti does not precipitate can be used. At this time, the current density at which Ti does not precipitate is preferably 0 A / dm ² .

  According to the present invention, it is possible to produce a surface-treated steel sheet that is excellent in corrosion resistance without using Cr, and that can obtain excellent wet resin adhesion even when laminated under the condition that the BO value of the resin film is increased. The surface-treated steel sheet produced by the production method of the present invention can be used as a substitute for conventional tin-free steel sheets without any problem and without being coated with a resin on a container containing oil, organic solvent, paint, or the like. Moreover, even if the resin is coated to form a resin-coated steel sheet, processed into a can or can lid and exposed to a retort atmosphere, the resin does not peel off, and even in a missing part of the resin such as a scratch, Fe Is significantly less dissolved and has excellent corrosion resistance.

FIG. 3 is a graph showing the relationship between the current density and the amount of Ti deposited in an aqueous solution of pH 3.5 containing potassium fluorinated titanate 10.6 g / l and cobalt sulfate heptahydrate 5 g / l. FIG. 3 is a graph showing the relationship between the current density and the amount of Ti deposited in an aqueous solution at pH 4.5 containing potassium fluorinated titanate 10.6 g / l and cobalt sulfate heptahydrate 4 g / l. It is a figure explaining a 180 degree peel test.

1) Formation of corrosion-resistant film As a material, a low-carbon cold-rolled steel sheet for cans is used as a raw material. First, the steel sheet surface is first firmly bonded to the base steel sheet to form a resin-coated steel sheet. In order to give excellent corrosion resistance to the steel sheet even if the material is missing, a single layer of Ni layer, Sn layer, Fe-Ni alloy layer, Fe-Sn alloy layer and Fe-Ni-Sn alloy layer or a multilayer thereof can be used. A corrosion resistant film is formed. This corrosion-resistant film can be formed by a known method according to the contained metal element.

In the case of the Ni layer, the amount of Ni deposited on one side of the steel sheet may be about 100 mg / m ² , but is preferably 200 mg / m ² or more. In the case of the Fe—Ni alloy layer, it is preferable that the Ni adhesion amount per one side of the steel sheet is 60 mg / m ² or more. In the case of the Sn layer or the Fe—Sn alloy layer, it is preferable that the Sn adhesion amount per one side of the steel sheet is 100 mg / m ² or more. In the case of the Fe—Ni—Sn alloy layer, it is preferable that the Ni adhesion amount per side of the steel sheet is 50 mg / m ² or more and the Sn adhesion amount is 100 mg / m ² or more. Here, the measurement of the adhesion amount of Ni or Sn can be performed by surface analysis using fluorescent X-rays.

2) Formation of adhesion film Next, in order to give excellent wet resin adhesion, on the above corrosion-resistant film, Ti is contained 0.008 to 0.07 mol / l, and Co, Fe, Ni, V, Cu, The adhesive film is formed by cathodic electrolysis in an aqueous solution containing at least one metal selected from Mn and Zn in a total molar ratio of 0.01 to 10 with respect to Ti. At this time, when the cathode electrolysis treatment is carried out intermittently using a current that periodically changes between a current density at which Ti is deposited and a current density at which Ti is not deposited, a resin film Excellent wet resin adhesion can be obtained even when laminated under the condition of increasing the BO value.

To that end, it is necessary to secure a certain amount of Ti adhesion, but in order to secure the necessary amount of Ti adhesion for productivity (line speed) riding on a commercial base, the cycle is 0.01 to 0.4 seconds, per cycle. Cathode under electrolysis conditions using current of 0.005-0.2 seconds for current density at which Ti does not precipitate, cycle number 10 or more, and total electric density at current density at which Ti precipitates is 4 C / dm ² or more It is necessary to perform electrolytic treatment. In addition, by carrying out electrolytic treatment under these conditions, the current density at which Ti does not precipitate promotes the re-dissolution of the precipitated Ti rather than the precipitation of Ti. It is considered that excellent wet resin adhesion is obtained.

The upper limit of the current density at which Ti does not precipitate, that is, the boundary current density when Ti does not precipitate and when Ti precipitates, was selected from Ti, Co, Fe, Ni, V, Cu, Mn, and Zn Depends on the composition and pH of the aqueous solution containing at least one metal. For example, FIG. 1 shows the relationship between the current density and the amount of Ti deposited in an aqueous solution at pH 3.5 containing 10.6 g / l of potassium fluorinated titanate and 5 g / l of cobalt sulfate heptahydrate. In this case, it is understood that Ti precipitation does not occur at 4 A / dm ² or less. In addition, FIG. 2 shows the relationship between the current density and the amount of Ti adhesion in an aqueous solution containing potassium fluoride titanate 10.6 g / l and cobalt sulfate heptahydrate 4 g / l and pH 4.5. In this case, it can be seen that Ti precipitation does not occur at 1 A / dm ² or less. Thus, since the upper limit of the current density at which Ti does not precipitate depends on the composition and pH of the aqueous solution used for the cathodic electrolysis treatment, it is necessary to obtain in advance according to the aqueous solution used.

The current that periodically changes between the current density at which Ti precipitates and the current density at which Ti does not precipitate includes an alternating current that periodically changes like a sine curve, and the current density and Ti that precipitate Ti. It is possible to use a pulse current that changes in binary with a current density that does not. In addition, a current obtained by superimposing an alternating current or a pulse current on a direct current can also be used. In addition, when using a pulse current that changes to a binary value of a current density at which Ti precipitates and a current density at which Ti does not precipitate, the current density at which Ti does not precipitate can be 0 A / dm ² depending on the aqueous solution used. This is more preferable because it is not necessary to obtain the upper limit of the current density at which Ti does not precipitate.

  As the aqueous solution containing Ti, an aqueous solution containing fluorotitanate ions or an aqueous solution containing fluorotitanate ions and a fluorine salt is suitable. As the compound that gives fluorotitanate ions, fluorinated titanate, ammonium fluoride titanate, potassium fluoride titanate, and the like can be used. As the fluorine salt, sodium fluoride, potassium fluoride, silver fluoride, tin fluoride, or the like can be used. In particular, the method of cathodic electrolysis of a steel sheet after the formation of a corrosion-resistant film in an aqueous solution containing potassium fluoride titanate or an aqueous solution containing potassium fluoride titanate and sodium fluoride forms an efficient uniform film It is possible and preferable. The concentration of Ti needs to be 0.008 to 0.07 mol / l, more preferably 0.02 to 0.05 mol / l. This is because when the Ti concentration is less than 0.008 mol / l, the Ti coating amount of the obtained Ti film is insufficient, and wet resin adhesion cannot be obtained, and when it exceeds 0.07 mol / l, the cost increases. .

  The compounds that give Co, Fe, Ni, V, Cu, Mn and Zn ions include cobalt sulfate, cobalt chloride, iron sulfate, iron chloride, nickel sulfate, copper sulfate, vanadium oxide sulfate, zinc sulfate, manganese sulfate, etc. Can be used. The total concentration of these metals needs to be 0.01 to 10 in terms of molar ratio to Ti, but is more preferably 0.1 to 2.5. If the total concentration of these metals is less than 0.01 or exceeds 2.5 in terms of molar ratio to Ti, excellent wet resin adhesion cannot be obtained.

The adhesion amount of Ti in the adhesive film is preferably 3 to 200 mg / m ² per one side of the steel sheet. This is because excellent wet resin adhesion can be sufficiently obtained when the Ti adhesion amount is 3 mg / m ² or more, and when it exceeds 200 mg / m ² , the effect is saturated and the cost is increased.

The amount of at least one metal selected from Co, Fe, Ni, V, Cu, Mn and Zn contained in the adhesive film is 0.01 to mass ratio (M / Ti) to Ti in total. 10 is preferable. More preferably, it is 0.1-2.5. This is because, within this range, an adhesive film having a denser and more evenly distributed surface irregularity is formed, and excellent wet resin adhesion can be obtained. A mass ratio of 0.01 to 10 of the total amount of metal to Ti corresponds to an adhesion amount of 10 to 200 mg / m ² per one surface of the total metal plate.

  The adhesive film preferably further contains O (oxygen). This is because the inclusion of O makes the film mainly composed of Ti oxide, which is more effective in improving wet resin adhesion.

  Note that the amount of adhesion of Ti, Co, Fe, Ni, V, Cu, Mn, and Zn on the adhesive film can be measured by surface analysis using fluorescent X-rays. The amount of O is not particularly defined, but its presence can be confirmed by surface analysis using XPS (X-ray photoelectron spectroscopy analyzer).

  A laminated steel sheet can be obtained by laminating a resin film on the surface-treated steel sheet on which the corrosion-resistant film and the adhesive film are formed by the method of the present invention. As described above, since the surface-treated steel sheet produced by the method of the present invention has excellent wet resin adhesion, this laminated steel sheet has excellent corrosion resistance and workability.

  The resin film laminated on the surface-treated steel sheet of the present invention is not particularly limited, and examples thereof include films made of various thermoplastic resins and thermosetting resins. For example, polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic ester copolymer, olefin resin film such as ionomer, polyester film such as polybutylene terephthalate, or nylon 6 A non-stretched or biaxially stretched thermoplastic resin film such as a polyamide film such as nylon 6,6, nylon 11, or nylon 12, a polyvinyl chloride film, or a polyvinylidene chloride film can be used. When an adhesive is used in the lamination, a urethane adhesive, an epoxy adhesive, an acid-modified olefin resin adhesive, a copolyamide adhesive, a copolyester adhesive, or the like is preferable.

  Furthermore, modified epoxy paint such as phenol epoxy, amino-epoxy, vinyl chloride-vinyl acetate copolymer, saponified vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, epoxy-modified- , Epoxyamino-modified, Epoxyphenol-modified Vinyl paint or Modified vinyl paint, Acrylic paint, Synthetic rubber paint such as styrene-butadiene copolymer, etc. alone or in combination of two or more Can be used.

  The thickness of the resin laminate layer is preferably 3 to 50 μm. This is because if the thickness is less than the above range, the corrosion resistance becomes insufficient, and if the thickness exceeds the above range, problems are likely to occur in terms of workability.

  The resin laminate layer can be formed on the surface-treated steel sheet by any means. For example, it can be performed by an extrusion coating method, a cast film thermal bonding method, a biaxially stretched film thermal bonding method, or the like.

Using plating baths a and b shown in Table 1 on both sides of cold-rolled cold-rolled steel sheets (thickness 0.2 mm) as cold-rolled steel used for the production of tin-free steel sheets (TFS), A corrosion-resistant film is formed by the methods A to D.
A: Cold rolled steel sheet was annealed at about 700 ° C in a 10 vol% H ₂ +90 vol% N ₂ atmosphere, subjected to temper rolling with an elongation of 1.5%, alkaline electrolytic degreasing, and sulfuric acid After washing, Ni plating treatment is performed using a plating bath a to form a corrosion-resistant film composed of a Ni layer.
B: Cold-rolled steel sheet is alkaline electrolytically degreased and Ni-plated using plating bath a, then annealed at about 700 ° C in a 10 vol% H ₂ +90 vol% N ₂ atmosphere, and then Ni-plated After diffusing and infiltrating, temper rolling with an elongation of 1.5% is performed to form a corrosion-resistant film composed of an Fe—Ni alloy layer.
C: Alkaline electrolytic degreasing of cold-rolled steel sheet, Ni plating using plating bath a, and then annealing at 700 ° C in 10 vol% H ₂ +90 vol% N ₂ atmosphere After diffusing and penetrating and temper rolling with an elongation of 1.5%, degreasing, pickling, Sn plating using the plating bath b, and heating and melting treatment for heating and holding above the melting point of Sn are performed. By this treatment, a corrosion-resistant film composed of an Fe—Ni—Sn alloy layer and an upper Sn layer is formed.
D: Alkaline electrolytic degreasing of the cold-rolled steel sheet, annealing and temper rolling in the same manner as in Condition A, followed by Sn plating using the plating bath b, followed by a heat-melting treatment that heats and maintains the melting point of Sn or higher . By this treatment, a corrosion-resistant film composed of the Fe—Sn alloy layer and the upper Sn layer is formed.

  In the treatment of C and D, a part of Sn plating is alloyed by heat melting treatment. Tables 2 to 5 show the amount of pure Sn remaining without alloying.

Next, on the corrosion-resistant film formed on both surfaces of the steel sheet, cathodic electrolysis treatment was performed under the conditions of cathodic electrolysis shown in Tables 2 to 6, and dried to form an adhesive film to form surface-treated steel sheets No. 1 to 40. Make it. At this time, the pH of the treatment bath is adjusted with an alkaline solution such as potassium hydroxide or an acidic solution such as sulfuric acid. The pH of the treatment bath of the surface-treated steel sheets No. 31 to 40 is in the range of 3 to 5. In the surface-treated steel plates No. 1 to 25 and 31 to 40, pulse current is used, and the current density at which Ti does not precipitate is 0 A / dm ² . On the other hand, in the surface-treated steel plates No. 26 to 30, using pulse current, based on the results of FIGS. 1 and 2, the current density at which Ti does not precipitate is not 0 A / dm ² (No. 26, 28, 29) and Examples (No.27, 30) exceeding the upper limit are given. Among these surface-treated steel sheets, Nos. 5, 6, 13 to 15, 20, 25, 27, 28, and 30 are comparative examples in which the electrolysis conditions for cathodic electrolysis are outside the scope of the present invention. In particular, Nos. 6 and 15 correspond to the invention example of Patent Document 1 in which cathodic electrolysis is performed using a plurality of electrodes. That is, in this example, the current density at which Ti does not precipitate is 0 A / dm ² between the electrodes, but the time and the number of cycles for maintaining the current density are outside the scope of the present invention.

  Then, the Ni and Sn adhesion amounts of the corrosion-resistant film and the Ti adhesion amount of the adhesive film are obtained by fluorescent X-ray analysis in comparison with a calibration plate obtained by chemical analysis of the adhesion amount in advance. In addition, the adhesion amount of Co and Fe is determined by selecting an appropriate measurement method from the same fluorescent X-ray analysis method as that of Ti, chemical analysis, Auger electron spectroscopic analysis, and secondary ion mass spectrometry. Further, O can be confirmed by XPS surface analysis for all of Nos. 1 to 40.

The BO value of the resin film was used on both surfaces of these surface-treated steel plates No. 1 to 40, using an isophthalic acid copolymerized polyethylene terephthalate film having a draw ratio of 3.1 × 3.1, a thickness of 25 μm, a copolymerization ratio of 12 mol%, and a melting point of 224 ° C. Laminating conditions such that the steel sheet feed rate is 40 m / min, the nip length of the rubber roll is 17 mm, and the time until water cooling after crimping is 1 second. No.1 to 40 are produced. Here, the nip length is the length in the transport direction of the portion where the rubber roll and the steel plate are in contact. The BO value of the resin film is the X-ray diffraction intensity of the PET (100) plane observed in the vicinity of 2θ = 26 ° measured using a Cu tube as the X-ray source. And about the produced laminated steel plates No. 1-40, wet resin adhesiveness and corrosion resistance are evaluated by the following method.
Wet resin adhesion: Wet resin adhesion is evaluated by a 180 ° peel test in a retort atmosphere at a temperature of 130 ° C. and a relative humidity of 100%. The 180 ° peel test is a test piece (size: 30 mm x 100 mm, with both sides on the front and back sides set to n = 1, leaving a film 2 as shown in Fig. 3 (a) and cutting out part 3 of the steel sheet 1 , N = 2 for each laminated steel sheet), as shown in Fig. 3 (b), attach a weight 4 (100g) to one end of the test piece, turn it 180 ° to the film 2 side, and leave it for 30 min. This is a film peeling test. Then, the peel length 5 shown in (c) of FIG. 3 is measured and evaluated, and the average of the peel lengths (n = 2) on the front and back surfaces of each laminated steel sheet is obtained. The smaller the peel length 5, the better the wet resin adhesion, but when the BO value is 150, the peel length 5 is less than 10 mm, and when the BO value is 250, the peel length 5 is less than 20 mm, It is evaluated that the excellent wet resin adhesion intended by the present invention is obtained.
Corrosion resistance: Cut the laminate surface of the laminated steel plate to reach the steel plate substrate using a cutter knife, and immerse it in 80 ml of a test solution in which the same amount of 1.5% by weight NaCl aqueous solution and 1.5% by weight citric acid aqueous solution are mixed. And left for 9 days to evaluate the corrosion resistance of the cut part (where both the front and back surfaces are n = 1 and n = 2 for each laminated steel sheet) as follows. And
○: No corrosion at n = 2 ×: Corrosion at 1 or more of n = 2 Table 7 shows the results. Laminated steel sheets No. 1 to 4, 7 to 12, 16 to 19, 21 to 24, 26, 29, and 31 to 40 using surface-treated steel sheets produced by the production method according to the present invention are all excellent wetness. It shows resin adhesion and corrosion resistance. On the other hand, laminated steel sheets No.5, 6, 13-15, 20, 25, 27, 28, 30 as comparative examples are excellent in wet resin adhesion and corrosion resistance when the BO value is 150. When the BO value is 250, the wet resin adhesion is poor.

1 Steel plate
2 film
3 Parts cut from steel plate
4 weights
5 Peel length

Claims (3)

After forming a corrosion-resistant film consisting of at least one layer selected from Ni layer, Sn layer, Fe-Ni alloy layer, Fe-Sn alloy layer and Fe-Ni-Sn alloy layer on at least one side of the steel plate, Ti is added. It contains 0.008 to 0.07 mol / l (l: liter), and further contains at least one metal selected from Co, Fe, Ni, V, Cu, Mn and Zn in a total molar ratio of 0.01 to 2.5 with respect to Ti. In the aqueous solution containing, the current density changes between the current density at which Ti precipitates and the current density at which Ti does not precipitate at a period of 0.01 to 0.4 seconds, and the time at which the current density at which no Ti is deposited per period is 0.005 Form an adhesive film by cathodic electrolysis under electrolysis conditions using a current of ~ 0.2 seconds and a cycle number of 10 or more and a total electric density at a current density of Ti of 4 C / dm ² or more. The upper limit of the current density at which Ti does not precipitate is used for cathodic electrolysis. Is a value that depends on the composition and pH of the aqueous solution that. 2. The method for producing a surface-treated steel sheet according to claim 1, wherein the current density is a current that changes into a binary value of a current density at which Ti precipitates and a current density at which Ti does not precipitate. 3. The method for producing a surface-treated steel sheet according to claim ² , wherein the current density at which Ti does not precipitate is 0 A / dm ² .

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