TW201600638A - Steel sheet for containers - Google Patents

Abstract

Provided is a steel sheet for containers, which has excellent film adhesion. This steel sheet for containers comprises: a plated steel sheet that has a plating layer containing a Sn layer on at least part of the surface of a steel sheet; and a surface treatment film that contains Ti and Ni, and is disposed on the plating-layer-side surface of the plated steel sheet. The developed area ratio (Sdr) of the surface-treatment-film-side surface of this steel sheet for containers, as calculated from the surface area determined by a measurement using a scanning electron microscope, is 0.25% or more.

Description

Steel plate for containers

The present invention relates to a steel sheet for containers.

According to the metal container for beverages or foods, it has been used all over the world since the contents can be stored for a long time. The metal container is composed of a deep-drawn 2-piece can body or a welded 3-piece can body and a can lid wound around the can body.

For the above metal containers, the coating step and the baking step before and after the can making are indispensable. In these steps, the waste liquid of the paint or the VOC (volatile organic compound) at the time of baking and the carbon dioxide which is one of the greenhouse gases are produced in large quantities. In recent years, based on the view of global environmental protection, there has been a mechanism for reducing such waste or carbon dioxide. Further, BPA (bisphenol A), which is a raw material of an epoxy resin as a component of a coating, is an environmental hormone, and its use is regulated in some countries for use in contact with a human body. As a substitute for the above-described coating step and baking step, a container using a steel sheet in which an organic resin film such as PET (polyethylene terephthalate) is laminated is currently attracting attention, and this is Technology is rapidly expanding.

On the other hand, on the steel sheet for laminating the film, a chromate film subjected to electrolytic chromate treatment is generally used. However, in recent years, in Europe and the United States, based on restrictions on the use of harmful substances such as lead, cadmium, and chromium, and concerns about the manufacturing environment, the industry is currently pursuing a film that is not treated with chromate.

For example, Patent Document 1 discloses: "A surface-treated steel sheet characterized in that it has a corrosion-resistant film on at least one side of a steel sheet, and the corrosion-resistant film is selected from the group consisting of a Ni layer, a Sn layer, and an Fe-Ni alloy. At least one of a layer, an Fe-Sn alloy layer, and an Fe-Ni-Sn alloy layer, the corrosion-resistant film has an adhesive film, and the adhesive film contains Ti, and further contains a relative value. At least one selected from the group consisting of Co, Fe, Ni, V, Cu, Mn, and Zn has a mass ratio of Ti of 0.01 to 10.

[Advanced technical literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2010-031348

The inventors of the present invention have studied the steel sheet for a container (surface-treated steel sheet) described in Patent Document 1, and found that the adhesion to the PET film (hereinafter referred to as "film adhesion") is insufficient.

The present invention has been developed in view of the above points, and an object thereof is to provide a steel sheet for containers excellent in film adhesion.

As a result of intensive studies to achieve the above object, the inventors have found that a steel sheet for a container having a specific surface shape has excellent film adhesion, and the present invention has been completed.

Specifically, the present invention provides the following (1) to (4).

(1) A steel sheet for a container, comprising: a plated steel sheet having a plating layer containing a Sn layer on at least a part of a surface of the steel sheet; and a surface containing Ti and Ni disposed on a surface of the plating layer on the plating layer side The surface area of the surface of the steel sheet for the container, which is calculated from the surface area obtained by measurement using a scanning electron microscope, has a developed area ratio Sdr of 0.25% or more.

(2) The steel sheet for a container according to the above (1), wherein the plating layer further contains at least a group selected from the group consisting of a Ni layer, a Ni-Fe alloy layer, an Fe-Sn alloy layer, and an Fe-Sn-Ni alloy layer. 1 story.

(3) The steel sheet for a container according to the above (1) or (2), wherein the surface-treated film has an adhesion amount of 5 to 30 mg/m ² in terms of Ti on each side of the plated steel sheet. The Ni-conducted adhesion amount of each side of the coated steel sheet is 1 to 30 mg/m ² .

(4) The steel sheet for containers according to any one of the above (1) to (3), wherein the surface area obtained by measurement using a scanning probe microscope The calculated area ratio Sdra of the surface of the surface treatment film side of the steel sheet for a container is 5.00% or more.

According to the invention, it is possible to provide a steel sheet for a container excellent in film adhesion.

1‧‧‧ steel plate

2‧‧‧ plating

3‧‧‧Surface treatment film

4‧‧‧Protective film

5‧‧‧The surface of the coating

Fig. 1 is a graph showing a plot of the relationship between the developed area ratio Sdr and the film adhesion (evaluation 1).

Fig. 2 is a view showing a reflected electron image of a 45° section of the test material No. 10.

Fig. 3 is a view showing a reflection electron image of a 45° section of the test material No. 15.

[Steel plate for containers]

The steel sheet for a container of the present invention has a plated steel sheet and a surface-treated film disposed on the surface of the plating layer of the plated steel sheet, and has a specific developed area ratio Sdr.

Hereinafter, after the specific aspects of the plated steel sheet and the surface treated film are described in detail, the expanded area ratio Sdr will be described. First of all, the plating steel The details of the board are detailed.

[plated steel plate]

The plated steel sheet has a steel sheet and a plating layer covering at least a part of the surface of the steel sheet, and the plating layer contains at least a Sn layer.

As the steel plate of the material, a general steel plate for cans can be used. The plating layer may be a continuous layer or a discontinuous island shape. Further, the plating layer may be provided on at least one side of the steel sheet, or may be provided on both sides. The formation of the plating layer can be carried out by a known method of blending the metal elements contained.

Hereinafter, preferred aspects of the steel sheet and the plating layer will be described in detail.

<Steel plate>

The type of the steel sheet is not particularly limited, and a steel sheet (for example, a low carbon steel sheet or an extremely low carbon steel sheet) which is used as a container material can be generally used. The method for manufacturing the steel sheet, the material, and the like are not particularly limited, and the steps are the steps of manufacturing a common steel sheet by hot rolling, pickling, cold rolling, annealing, temper rolling, and the like. Manufacturing.

If necessary, a nickel (Ni)-containing layer may be formed on the surface of the steel sheet, and a Sn-containing plating layer to be described later may be formed on the Ni-containing layer. By using Sn in a steel sheet having a Ni-containing layer, a plating layer containing island-shaped Sn can be formed, and the weldability is improved.

The Ni-containing layer may contain nickel, and examples thereof include a Ni plating layer (Ni layer), a Ni-Fe alloy layer, and the like.

There is no particular limitation on the method of imparting a Ni-containing layer to a steel sheet. For example, a known method such as electroplating can be mentioned. Moreover, when a Ni-Fe alloy layer is provided as a Ni-containing layer, Ni-Fe alloy layer can be formed by alloying with Ni on the surface of the steel sheet and then coordinating the Ni diffusion layer by annealing.

The amount of Ni attached to the Ni-containing layer is not particularly limited, and the amount of metal Ni per side is preferably 50 to 2000 mg/m ² . If it is within the above range, it is also advantageous at the cost level.

Further, the amount of Ni attached can be measured by surface analysis on a fluorescent X-ray. In this case, the Ni adhesion sample, which is known as the Ni adhesion amount, is used, and the calibration curve for the Ni adhesion amount is specified in advance, and the Ni adhesion amount is relatively specified using the calibration curve.

When Ni is contained in the film described later, it is difficult to measure only the amount of Ni deposited in the Ni-containing layer by surface analysis using the above-described fluorescent X-ray. In this case, the Ni adhesion amount in the Ni-containing layer can be obtained by subtracting the Ni adhesion amount contained in the film described later from the Ni adhesion amount determined by the fluorescent X-ray.

<plating>

The plated steel sheet has a plating layer containing a Sn layer on at least a part of the surface of the steel sheet. The plating may be provided on at least one side of the steel sheet or on both sides. Further, the plating layer is a layer covering at least a part of the surface of the steel sheet, and may be a continuous layer or a discontinuous island shape.

The amount of Sn deposited on each side of the steel sheet is preferably 0.1 to 15.0 g/m ² . When the Sn adhesion amount is within the above range, the steel sheet for a container is excellent in appearance characteristics and corrosion resistance. In particular, it is more preferably 0.2 to 15.0 g/m ² based on the characteristics of these characteristics, and more preferably 1.0 to 15.0 g/m ^{2 from} the viewpoint of excellent workability.

Further, the Sn adhesion amount can be measured by surface analysis on a fluorescent X-ray. In the case of the fluorescent X-ray, the Sn-attached sample of the Sn amount can be used, and the calibration curve for the amount of Sn can be specified in advance, and the amount of Sn can be relatively specified using the calibration curve.

In addition to the plating layer containing the Sn layer obtained by plating Sn, the plating layer is heated and melted by energization heating or the like, and the lowermost layer (Sn layer/steel plate interface) of the Sn layer is obtained by heating. A portion of the Fe-Sn alloy layer is formed by plating.

In addition, as a plating layer, a steel sheet having a Ni-containing layer on the surface is subjected to Sn plating, and the Sn is heated and melted by electric heating or the like to form a Fe in the lowermost layer (Sn layer/steel plate interface) of the Sn layer. a plating layer of a Sn-Ni alloy layer, an Fe-Sn alloy layer, or the like.

Further, in the present invention, the Ni-containing layer (Ni layer or Ni-Fe alloy layer) is also included in the plating layer of the plated steel sheet.

As a method of producing the plating layer, a well-known method (for example, a plating method or a method of immersing in molten Sn and plating) can be mentioned.

For example, after using a phenolsulfonic acid Sn plating bath, a methanesulfonic acid Sn plating bath, or a halogen-based Sn plating bath, after plating the Sn on the surface of the steel sheet in such a manner that the adhesion amount per surface becomes a specific amount (for example, 2.8 g/m ² ), The heat-melting treatment is carried out at a temperature equal to or higher than the melting point of Sn (231.9 ° C), and a plating layer of an Fe-Sn alloy layer is formed on the lowermost layer (Sn layer/steel plate interface) of the plating layer (Sn layer) of the Sn monomer. In the case where the heat-melting treatment is omitted, a plating layer (Sn layer) of the Sn monomer can be produced.

Further, when the steel sheet has a Ni-containing layer on the surface thereof, if Sn is plated on the Ni-containing layer and then subjected to heat-melting treatment, Fe is present in the lowermost layer (Sn layer/steel plate interface) of the Sn-based plating layer (Sn layer). A Sn-Ni alloy layer, an Fe-Sn alloy layer, or the like is formed.

In the present invention, the area ratio of the Sn layer (pure Sn layer) (the ratio of the area of the Sn layer to the entire area of the plating layer) is at least from the viewpoints of corrosion resistance, weldability, and excellent film adhesion described later. Should be more than 10%.

In addition, the "Sn layer" in the area ratio may be an Sn layer (pure Sn layer) as the outermost layer, and may include an Fe-Sn-Ni alloy layer or an Fe-Sn alloy layer in the lowermost layer.

The method for measuring the area ratio of Sn will be described in the section of [Examples] to be described later.

[surface treatment film]

Next, the surface treatment film disposed on the surface on the plating side of the plated steel sheet will be described. The surface-treated film is, in general, a film containing Ti (titanium element) and Ni (nickel element) as components thereof, and is formed using a treatment liquid described later.

In the case of the surface-treated film, the adhesion of the steel sheet for a container according to the present invention is more excellent, and the amount of adhesion in terms of Ti (hereinafter referred to as "Ti adhesion amount") on each side of the plated steel sheet is preferably 5 ~30mg/m ² . The Ti adhesion amount is more preferably 7 to 25 mg/m ^{2 for} the reason that the film adhesion is more excellent.

In addition, the surface-treated film is preferably made of a Ni-based adhesion amount (hereinafter referred to as "Ni adhesion amount") on each side of the plated steel sheet, because the film adhesion property of the steel sheet for containers of the present invention is more excellent. It is 1~30mg/m ² . The Ni adhesion amount is preferably 1 to 10 mg/m ^{2 for} the reason that the adhesion between the film and the plated steel sheet is excellent.

The Ti adhesion amount and the Ni adhesion amount were measured by surface analysis using fluorescent X-rays.

Ti, Ni, and the like in the surface treatment film are each contained in various titanium compounds and nickel compounds, and the kind or aspect of these compounds is not particularly limited.

Further, the fluorescent X-ray analysis is carried out, for example, under the following conditions.

‧Device: Rigaku's fluorescent X-ray analyzer System 3270

‧Measurement diameter: 30mm

‧ Determination of atmosphere: vacuum

‧Spectrum: Ti-Kα, Ni-Kα

‧Slot: COARSE (standard)

‧Special crystallization: TAP

The peak count values of Ti-Kα and Ni-Kα were analyzed by fluorescence X-ray analysis of the surface-treated film measured under the above conditions. Further, using a standard sample having a known adhesion amount, a calibration curve for Ti adhesion amount and Ni adhesion amount is specified in advance, and Ti adhesion amount and Ni adhesion amount are relatively obtained using the calibration curve.

When Ni is contained in the plating layer, it is difficult to measure only the amount of Ni adhering to the surface treatment film by the surface analysis using the above-described fluorescent X-ray.

In this case, the cross-sectional observation by scanning electron microscopy (SEM) or transmission electron microscope (TEM) and glow discharge luminescence analysis can be used to distinguish the surface treatment film. The amount of Ni attached and the amount of Ni contained in the plating layer.

Specifically, the cross-section of the surface-treated film and the plating layer was exposed by a focused ion beam (FIB), and the thickness of the surface-treated film was calculated from a cross-sectional observation by SEM or TEM. Then, the relationship between the sputtering depth and the sputtering time was obtained by glow discharge luminescence analysis. Then, the cumulative value of the luminescence count derived from the Ni element of the glow discharge luminescence analysis corresponding to the sputtering time of the surface treatment film thickness was determined. From the cumulative value of the luminescence count derived from the Ni element, the amount of Ni adhesion can be obtained by using a calibration curve obtained in advance.

Here, the calibration curve is created by the following method.

First, a plurality of samples having different Ni adhesion amounts on the Ni-containing plating layer are subjected to glow discharge luminescence analysis, and the luminescence count derived from the Ni element is determined to be an undetected sputtering time. The cumulative value of the count. Next, the Ni adhesion amount of these samples was obtained by surface analysis using fluorescent X-rays. Thus, a calibration curve of the Ni count integrated value and the Ni adhesion amount according to the glow discharge luminescence analysis was prepared.

[Expanded area ratio Sdr]

The steel sheet for containers of the present invention is obtained by measurement using a scanning electron microscope (SEM). The developed area ratio Sdr of the surface on the surface of the surface treatment film calculated from the surface area was 0.25% or more.

The expanded area ratio Sdr (hereinafter, or simply "Sdr") can be expressed by the following equation.

Expanded area ratio Sdr={(A-B)/B}×100[%]

A: Surface area (expansion area) of the actual unevenness of the measurement area

B: area of the plane of the measurement area without unevenness

In the steel sheet for a container of the present invention, it is conceivable that the surface having the uneven shape on the surface exhibits an effect of increasing the effective surface area (expanded area ratio) of the adhesion and the anchoring effect of the unevenness itself, and the film adhesion is excellent.

Moreover, such a surface uneven shape can be obtained by an electroless immersion step which will be described later before the surface treatment film forming step to be described later.

Therefore, the larger the Sdr is, the higher the film adhesion is. In the present invention, in order to provide good film adhesion, the Sdr is set to 0.25% or more. The Sdr is preferably 0.50% or more, more preferably 0.85% or more. Further, the upper limit of Sdr is preferably 1.0% or less, more preferably less than 1.0%.

Further, Sdr, which is calculated from the conditions described below, reflects the surface unevenness of the steel sheet for a container having a plating layer and a surface-treated film, and particularly reflects the shape of the surface of the Sn layer. It is conceivable that the surface of the Sn layer is a film. Adhesion has an impact.

In the present invention, Sdr is calculated from the surface area obtained by measurement using a scanning electron microscope (SEM). In more detail, an electron line three-dimensional scanning electron microscope (3D-SEM) is used. The three-dimensional surface shape (3D-SEM image) of the surface on the surface of the surface of the steel sheet for a container was measured, and the distortion of the measured three-dimensional surface shape data was calculated.

In the Sdr of the present invention, the average value of the field of view (measurement region) of any five parts on the Sn layer of each sample is taken.

Here, the distortion of the measured three-dimensional surface shape data refers to a parabolic distortion represented by a quadratic equation which overlaps with the original three-dimensional shape on the principle of 3D-SEM measurement. Therefore, in the present invention, the quadratic surface shape data of the measured three-dimensional surface shape data is excluded from the quadratic surface of the quadratic surface to which the least square method is applied, and the rough surface data is obtained.

In addition, the rough surface data obtained by performing the quadratic curve returning process is formed by superposing the shape of the fine plating on the giant relief of the plated original plate (the steel plate of the material), and then plating the original plate (the plate of the material) The mega-concave convexity does not contribute to the improvement of film adhesion. Therefore, in the present invention, the data of the shape of the fine plating layer obtained by the high-pass filter processing is further calculated from the rough surface data obtained by the quadratic method, and the Sdr is calculated.

The cutoff wavelength of the high-pass filter processing is a cutoff wavelength set to 1/2 of the measurement length in the longitudinal direction of the obtained 3D-SEM image. Specifically, in the present invention, the 3D-SEM image is set to 3 μm × 4 μm, and the cutoff wavelength is 2 μm which is 1/2 of the longitudinal direction (4 μm) of the 3D-SEM image.

Moreover, in the present invention, it is made of ELIONIX. Decomposition energy 3D-SEM ERA-8800FE. The electron gun is a field emission type. The 3D-SEM has four secondary electron detectors facing the sample direction, and can represent an image in which the sum signal of the secondary electrons or the difference signal emphasizes a composition or an image reflecting the unevenness in a specific direction. In the present invention, the acceleration voltage is 5 kV, the irradiation current is pA grade, and the magnification is 30,000 times, and a 3D-SEM image is obtained.

In addition, from the 3D-SEM image obtained, Sdr was obtained using the three-dimensional surface shape analysis software "SUMMIT" developed by the research laboratory of Nagaoka University of Science and Technology.

[Expanding area ratio Sdra]

In the steel sheet for a container of the present invention, the surface area ratio Sdra of the surface of the surface treatment film side calculated from the surface area obtained by measurement using a scanning probe microscope (SPM) is preferably 5.00% or more.

The developed area ratio Sdra (hereinafter, simply referred to as "Sdra") is the same as the above-described developed area ratio Sdr and can be expressed by the following equation.

Expanded area ratio Sdra={(C-D)/D}×100[%]

C: Surface area (expansion area) of the actual unevenness of the measurement area

D: area of the plane of the measurement area without unevenness

A scanning electron microscope (SEM) was used for the developed area ratio Sdr, and a scanning probe microscope (SPM) was used for the developed area ratio Sdra. By scanning a probe microscope which can obtain atomic level fine concavity and convexity information, the developed area ratio Sdra can reflect the fine uneven shape of the nanometer level on the outermost surface of the surface treated film.

Further, the fine concavo-convex shape of the surface-treated film as reflected by the area of Sdra can be obtained by a surface-treating film forming step under an appropriate electrolytic current density condition to be described later, and is not affected by the electroless impregnation step described later.

As with Sdr, the larger the Sdra, the higher the film adhesion. In the present invention, Sdra is preferably 5.00% or more, more preferably 10.00% or more, still more preferably 20.00% or more, from the viewpoint of good film adhesion. Further, the upper limit of Sdra is not particularly limited, and is, for example, less than 50.00%.

As described above, Sdra is obtained by measurement using a scanning probe microscope (SPM). More specifically, the SPM-4500 of the field of view (measurement area) (2 μm × 2 μm) on the Sn layer of the sample was measured using SFT-4500 manufactured by SHIMADZU Co., Ltd., and the morphology analysis (surface area analysis) was performed using the SPM analysis software. That is, based on the image information of the three-dimensional image, the surface area is obtained by statistical processing, and Sdra is calculated using the above formula.

The cantilever beam used in the measurement was a cantilever beam having a low spring constant, specifically, an OMCL-AC240TS manufactured by Olympus Corporation or a cantilever beam equivalent thereto. The measurement point was 2 μm × 2 μm with respect to the measurement area, and was 512 points in length and 512 points in width. The scanning speed can be appropriately changed as long as it is within the range in which the uneven shape can be followed. It is preferable to adjust the scanning speed within a range of about 5 minutes to 10 minutes in the measurement time of the standard one field of view.

The Sdra of the present invention is taken from any three parts of the Sn layer of each sample. The average value of the field of view (measurement area).

[Method for Producing Steel Sheet for Containers and Treatment Liquid]

The method for producing a steel sheet for a container according to the present invention is preferably a method comprising at least the following steps (hereinafter, referred to as "the production method of the present invention"): a surface treatment film forming step, and a treatment liquid to be described later (hereinafter, a plated steel sheet immersed in a convenient or referred to as "treatment liquid of the present invention") is subjected to cathodic electrolysis to form the surface treatment film; and an electroless immersion step is performed before the surface treatment film forming step. In the treatment liquid of the invention, the plated steel sheet is immersed in an electroless state.

Hereinafter, the production method of the present invention will be described, and the treatment liquid of the present invention will be described in the same description.

[Surface treatment film formation step]

The surface treatment film forming step is a step of forming the surface treatment film on the surface of the plating layer of the plated steel sheet by subjecting the plated steel sheet immersed in the treatment liquid of the present invention to be described later to a cathodic electrolysis treatment. Further, alternate electrolysis in which cathodic electrolysis treatment and anode electrolysis treatment are alternately performed may be performed.

Hereinafter, the conditions of the treatment liquid or cathodic electrolysis treatment of the present invention to be used will be described in detail.

<treatment liquid>

The treatment liquid of the present invention contains the same for supplying the surface treatment film Ti component (Ti compound) of Ti (titanium element).

The Ti component is not particularly limited, and examples thereof include titanium alkoxide, titanyl oxalate, potassium oxytitanate dihydrate, titanium sulfate, titanium lactate, and titanium hydrofluoride (H ₂ TiF ₆ ). / or its salt and so on. Further, examples of the salt of titanium hydrofluoride include potassium hexafluorophosphate (K ₂ TiF ₆ ), sodium hexafluorophosphate (Na ₂ TiF ₆ ), and ammonium hexafluorophosphate ((NH). ₄ ) ₂ TiF ₆ ) and so on.

Among these Ti components, titanium hydrofluoride and/or a salt thereof is preferred from the viewpoints of stability of the treatment liquid, ease of availability, and the like.

The content of Ti in the treatment liquid of the present invention is not particularly limited, and when titanium hydrofluoride and/or a salt thereof is used, the amount of titanium hexafluoride ion (TiF ₆ ^2- ) is preferably 0.004 to 0.4 mol/ L, more preferably 0.02 to 0.2 mol/L.

Further, the treatment liquid of the present invention contains a Ni component (Ni compound) for supplying Ni (nickel element) to the surface treatment film.

The Ni component is not particularly limited, and examples thereof include nickel sulfate (NiSO ₄ ), nickel sulfate hexahydrate, nickel chloride (NiCl ₂ ), nickel chloride hexahydrate, and the like.

The Ni content in the treatment liquid of the present invention is not particularly limited, and the amount converted to Ni ions (Ni ²⁺ ) is preferably 0.002 to 0.04 mol/L, more preferably 0.004 to 0.02 mol/L.

Further, as the solvent in the treatment liquid of the present invention, water is usually used, but an organic solvent may be used in combination.

The pH of the treatment liquid of the present invention is not particularly limited, and is preferably pH 2.0 to 5.0. If it is within this range, the processing time can be shortened, and the treatment liquid is safe. Excellent qualitative. For the adjustment of the pH, a known acid component (for example, phosphoric acid or sulfuric acid) and an alkali component (for example, sodium hydroxide or ammonia water) can be used.

Further, the treatment liquid of the present invention may contain a surfactant such as sodium lauryl sulfate or acetylene glycol as necessary. Further, the treatment liquid may contain a condensed phosphate such as pyrophosphate based on the viewpoint of the stability of adhesion behavior.

Here, return to the description of the surface treatment film forming step.

The liquid temperature of the treatment liquid at the time of the treatment is preferably 20 to 80 ° C, more preferably 40 to 60 ° C.

In addition, the electrolysis current density at the time of performing the cathodic electrolysis treatment is based on the fact that Ti and Ni in the surface-treated coating film are formed in an appropriate amount, and the formation of the fine uneven shape in the surface-treated film is promoted, and the film adhesion is further improved. It is suitably 1.0 ~ 20.0A / dm ^2, more preferably 3.0 ~ 15.0A / dm ^2, no matter how good is 6.0 ~ 10.0A / dm ^2.

At this time, the energization time of the cathodic electrolysis treatment is preferably 0.1 to 5 seconds, more preferably 0.3 to 2 seconds, for the same reason as the preferred electrolysis current density.

Further, the electric charge density at the time of the cathodic electrolysis treatment is a product of the current density and the energization time, and can be appropriately set.

Further, based on the reason for lowering the F contained in the film, after the cathodic electrolysis treatment, the obtained steel sheet is preferably subjected to a water washing treatment.

The method of the water washing treatment is not particularly limited, and examples thereof include a method of providing a water washing tank after the treatment liquid tank, and continuously immersing in water after the cathode electrolytic treatment, for example, in the case of manufacturing in a continuous production line. Washing treatment The temperature (water temperature) of the water used in the medium should be 40 to 90 °C.

At this time, the reason why the washing time is more excellent based on the effect of the washing treatment is preferably more than 0.5 second, more preferably 1.0 to 5.0 seconds.

Further, it may be dried instead of the water washing treatment or after the water washing treatment. The temperature and the manner of drying are not particularly limited, and for example, a general dryer or an electric furnace drying method can be applied. The temperature at the time of the drying treatment is preferably 100 ° C or lower. If it is in the above range, the oxidation of the surface treatment film can be suppressed, and the stability of the surface treatment film composition can be maintained. Further, the lower limit is not particularly limited, and is generally about room temperature.

[No electric immersion step]

The electroless impregnation step is a step of performing electroless immersion treatment of immersing the plated steel sheet in an electroless state in the treatment liquid of the present invention before the surface treatment film formation step.

In the steel sheet for a container of the present invention, as described above, the developed area ratio is more than 0.25% of the Sdr, and the surface of the surface-treated coating layer has an uneven shape. In order to obtain such a surface shape, in the present invention, the electroless immersion treatment is applied in this step before the cathodic electrolysis treatment is carried out in the surface treatment film forming step. That is, the plated steel sheet is impregnated in the treatment liquid of the present invention in an electroless state. Thereby, the surface of the plating layer (particularly, the Sn layer) is corroded to form a concavo-convex shape. Then, a surface treatment film is formed on the plating layer having the uneven shape, whereby the surface of the surface treatment film also reflects the uneven shape of the plating layer.

As the impregnation condition for forming a suitable uneven shape, the bath temperature is preferably 20~80 °C, more preferably 40~60 °C.

The longer the immersion time, the more the corrosion of the surface of the Sn layer progresses, and the uneven shape becomes severe. The electroless immersion time can be appropriately set in accordance with the desired uneven shape of the surface of the Sn layer, and the immersion time is preferably 0.1 to 5.0 seconds, more preferably 0.6 to 5.0 seconds, and even more preferably 1.0 second to 5.0 seconds. If it is 0.1 second or more, the immersion time is not too short, so that the corrosion of the surface of the Sn layer is easy to proceed. On the other hand, when it is 5.0 seconds or less, the uneven shape of the surface of the Sn layer is not easily deviated from an appropriate range, and deterioration in performance such as weldability or corrosion resistance can be avoided.

[pre-processing step]

The manufacturing method of the present invention may have the previous processing steps described below before the electroless immersion step and the surface treatment film forming step.

The pretreatment step is a step of subjecting the plated steel sheet to a cathodic electrolysis treatment in an aqueous alkaline solution (particularly an aqueous solution of sodium carbonate).

Usually, when the plating layer is formed, its surface is oxidized to form tin oxide. By subjecting the plated steel sheet to cathodic electrolysis, unnecessary tin oxide can be removed to adjust the amount of tin oxide.

The solution used in the cathodic electrolysis treatment as the pretreatment step may be an alkaline aqueous solution (for example, an aqueous sodium carbonate solution). The concentration of the alkali component (for example, sodium carbonate) in the alkaline aqueous solution is not particularly limited, and is preferably 5 to 15 g/L, more preferably 8 to 12 g/L, from the viewpoint that the removal of the tin oxide can be carried out efficiently. .

The liquid temperature of the alkaline aqueous solution at the time of cathodic electrolysis treatment is not particularly limited. It should be 40~60 °C. The electrolysis conditions (current density, electrolysis time) of the cathodic electrolysis treatment can be appropriately adjusted. Further, after the cathodic electrolysis treatment, a water washing treatment may be applied as necessary.

The steel sheet for containers of the present invention obtained by the production method of the present invention can be used, for example, in the production of a two-piece can body such as a food can, a beverage can, or the like, a three-piece can body, and a can lid.

[Examples]

Hereinafter, the present invention will be specifically described by way of examples. However, the invention is not limited by the examples.

<Manufacture of plated steel sheets>

A plated steel sheet was produced based on the following method.

First, a steel plate (T4 original plate) having a thickness of 0.22 mm was electrolytically degreased, and a nickel plating layer was formed on both surfaces of the Ni adhesion amount on each side shown in Table 3 using a Watt plating bath. Then, annealing is performed at 700 ° C in an atmosphere of 10 vol.% H ₂ +90 vol.% N ₂ to diffuse and impregnate the plated nickel, thereby forming an Fe-Ni alloy layer (Ni containing layer) on both sides (Table 3) The Ni adhesion amount shown).

Then, the above-mentioned surface layer was provided with a steel sheet containing a Ni-containing layer, and an Sn plating bath was used to form an Sn layer on both surfaces of Sn on each side as shown in the third table. Then, heat fusion treatment is performed at a temperature equal to or higher than the melting point of Sn, and the plating layer is formed on both surfaces of the T4 original plate. Thus, a plating layer containing a Ni—Fe alloy layer/Fe—Sn—Ni alloy layer/Sn layer was sequentially formed on both sides from the lower layer side.

Further, a plated steel sheet containing no Ni-containing layer was produced. Specifically, in the same manner as described above, a steel sheet (T4 original plate) having a thickness of 0.22 mm was electrolytically degreased, and a Sn layer was formed on both surfaces with a Sn deposition amount on each side shown in Table 3 using a Sn plating bath. Then, heat fusion treatment is performed at a temperature equal to or higher than the melting point of Sn, and the plating layer is formed on both surfaces of the T4 original plate. Thus, a plating layer containing an Fe-Sn alloy layer/Sn layer was sequentially formed on both sides from the lower layer side.

<area ratio of the Sn layer>

The area ratio of the Sn layer (pure Sn layer) on the surface of the plated steel sheet produced was measured. Specifically, the surface of the produced plated steel sheet was observed at a voltage of 15 kV using a scanning electron microscope at a magnification of 500 times. Next, after confirming the pure Sn portion by elemental analysis, the contrast between the pure Sn portion and the non-pure Sn portion of the plating layer was made to be binarized by image processing, and the area ratio (unit: %) of the Sn layer was calculated. The average value of the field of view (measurement area) of any five parts was obtained. The results are shown in Table 3 below.

<Formation of the film>

The plated steel sheet was immersed in a sodium carbonate aqueous solution having a bath temperature of 50 ° C and 10 g/L, and subjected to cathodic electrolysis treatment (pretreatment step) under the conditions shown in Table 2.

Next, the obtained steel sheet was washed with water, and a treatment liquid (solvent: water) having a pH adjusted to a composition shown in Table 1 of 4.0 was used, and electroless immersion treatment and cathodic electrolysis treatment were carried out according to the conditions shown in Table 2. Then, the office The obtained steel sheet was washed with water and dried by using a fan at room temperature to form a film on both sides (electroless impregnation step and film formation step). Further, in the case of the water washing treatment, the obtained steel sheet was immersed in a water bath at 85 ° C in the water washing time shown in Table 3.

Thereby, the test material of the steel plate for containers was produced.

Then, with respect to the test material for the steel sheet for containers to be produced, the developed area ratio Sdr and the developed area ratio Sdra were obtained by the above method, and the film adhesion was evaluated by the following method. The results are shown in Table 3 below.

Further, the Ni adhesion amount, the Sn adhesion amount, the Ti adhesion amount, and the Ni adhesion amount were also measured and calculated according to the above method, and the results are shown in Table 3 below.

<Film Adhesion (Evaluation 1)>

The surface of the test piece of the steel plate for the container was prepared by pressing a roller at 4 kgf/cm ² , a plate feed speed of 40 mpm, and a surface temperature of the plate after the roll was passed at 160 ° C. A commercially available PET film (Melinex 850: DuPont) The company made a hot melt, and then post-heated in a batch furnace (to reach a plate temperature of 210 ° C for 120 seconds) to produce a laminated steel plate.

For the laminated steel sheet to be produced, a punch having a front end radius of 3/16 inch was used, and a weight of 1 kg was dropped from a height of 40 cm, and DuPont impact processing was performed so that the surface side to which the film was attached was convex. Four such test pieces were prepared and placed in a distillation tank apparatus with a convex upward facing surface, and were taken out in a 130 ° C distillation tank environment for 30 minutes, and then taken out. The degree of film peeling of the processed portion was evaluated by visual observation in five stages, and the average value of the four test pieces (one place below the decimal point (the second decimal place was rounded off) was used to evaluate the film adhesion. Practically, when the result is 3.0 or more, it is evaluated that the film adhesion is excellent.

5: no peeling

4: The area of the processing department is less than 5%.

3: 5% or more of the area of the processing part and less than 20% peeling

2: 20% or more of the area of the processing part and less than 50% of the peeling occurs

1: 50% or more of the area of the processing part is peeled off

<Film Adhesion (Evaluation 2)>

The surface of the test piece of the steel plate for the container was prepared by pressing a roller at 4 kgf/cm ² , a plate feed speed of 40 mpm, and a surface temperature of the plate after the roll was passed at 160 ° C. A commercially available PET film (Melinex 850: DuPont) The company made a hot melt, and then post-heated in a batch furnace (to reach a plate temperature of 210 ° C for 120 seconds) to produce a laminated steel plate.

For the laminated steel sheet to be produced, a punch having a front end radius of 3/16 inch was used, and a weight of 1 kg was dropped from a height of 60 cm, and DuPont impact processing was performed so that the surface side to which the film was attached was convex. Four such test pieces were prepared, placed in a distillation pot apparatus with a convex surface upward, and taken out in a 130 ° C distillation tank environment for 30 minutes, and then taken out to visually evaluate the film peeling of the processed portion in a five-stage process. The degree of film adhesion was evaluated using the average of four test pieces (one place below the decimal point (the second decimal place was rounded off)). Practically, if the result is 2.0 On the other hand, it was evaluated that the film adhesion was excellent.

5: no peeling

4: The area of the processing department is less than 5%.

3: 5% or more of the area of the processing part and less than 20% peeling

2: 20% or more of the area of the processing part and less than 50% of the peeling occurs

1: 50% or more of the area of the processing part is peeled off

Fig. 1 is a plot showing the relationship between the developed area ratio Sdr and the film adhesion (evaluation 1), which is obtained by plotting the results of the test materials No. 1 to 22, and the horizontal axis representing the expanded area ratio Sdr [ %], the vertical axis indicates the evaluation result of the film adhesion (evaluation 1).

As a result of the plots of the above-described first to third tables and the first graph, it is understood that the developed example (test materials No. 1 to 14 and 19 to 22) having an expanded area ratio Sdr of 0.25% or more is confirmed. Film adhesion (Evaluation 1) Excellent.

On the other hand, in the comparative example (test materials No. 15 to 18) in which the developed area ratio Sdr was 0.25% or more, it was confirmed that the film adhesion (evaluation 1) was poor.

In addition, the examples of the present invention (test materials No. 1 to 14 and 19 to 22) were compared with each other, and the test materials No. 1 to 14 and 19 having an area ratio Sdra of 5.00% or more were developed, and the film adhesion was evaluated (evaluation 2). It is better than the test material No. 20~22 which is less than 5.00% of the unfolded area.

Next, in the test materials of the steel sheets for containers, the surface irregularities of the plating layers were directly confirmed for the test materials Nos. 10 and 15.

Specifically, first, a FIB (Focused Ion Beam) method was used to perform a milling process by irradiating an ion beam from an angle of 45° on the surface of the plating layer, and the cross section was observed by SEM. At this time, the surface of the surface-treated film is processed after forming a protective film made of carbon. The machining position is arbitrary, and the direction of machining and milling is also arbitrary, and the cross section is observed based on the reflected electron image of the acceleration voltage of 5 kV. Also, the height direction is longer than the actual length due to the 45° section. Times, so take 1 Double the correct.

Fig. 2 is a reflection electron image of a 45° section of the test material No. 10, and Fig. 3 is a reflection electron image of a 45° section of the test material No. 15. In Figs. 2 and 3, reference numeral 1 denotes a steel plate, reference numeral 2 denotes a plating layer, reference numeral 3 denotes a surface treatment film, reference numeral 4 denotes a protective film, and reference numeral 5 denotes a surface of the plating layer.

As shown in Fig. 2 and Fig. 3, in the case of the test material No. 10 of the invention example excellent in film adhesion, the uneven shape of the surface of the plating layer (Sn layer) In the case of the test material No. 15 which is a comparative example in which the film adhesion was poor, the shape of the unevenness could not be confirmed.

Claims (5)

A steel sheet for a container, comprising: a plated steel sheet having a plating layer containing a Sn layer on at least a part of a surface of the steel sheet; and a surface treatment film containing Ti and Ni disposed on a surface of the plating layer on the plating layer side; The developed area ratio Sdr of the surface of the surface-treated film side of the steel sheet for a container calculated from the surface area obtained by measurement using a scanning electron microscope was 0.25% or more. The steel sheet for containers according to claim 1, wherein the plating layer further contains at least 1 selected from the group consisting of a Ni layer, a Ni-Fe alloy layer, an Fe-Sn alloy layer, and an Fe-Sn-Ni alloy layer. Floor. The steel sheet for containers according to claim 1 or 2, wherein the surface-treated film has an adhesion amount of 5 to 30 mg/m ² in terms of Ti on each side of the plated steel sheet, and is applied to the plated steel sheet. The amount of Ni conversion per side is 1 to 30 mg/m ² . The steel sheet for a container according to the first or second aspect of the invention, wherein the surface area ratio of the surface of the steel sheet for the container to be measured by the surface area obtained by the scanning probe microscope is 5.00. %the above. The steel sheet for a container according to the third aspect of the invention, wherein the surface area ratio Sdra of the surface of the steel sheet for a container obtained by measuring using a scanning probe microscope is 5.00% or more. .