JP2843274B2 - Surface treated steel sheet for welding cans with excellent surface color after coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-treated steel sheet used as a material for forming a can body by a welding can manufacturing method. More specifically, in the coating process using an organic resin or the like, the surface color of the coated surface layer is bright even after heat treatment is applied, and the surface treatment for a welding can is excellent in the surface color after coating, which can obtain a high whiteness state. Related to steel plate.

[0002]

2. Description of the Related Art Conventionally, the development of surface-treated steel sheets for welding cans has been
It has been promoted mainly for the purpose of improving the weldability. For steel sheets with tin plating layers, the weldability is determined by the amount of residual metallic tin after the coating heat treatment, so that both the economic effect of reducing the amount of tin deposited and the securing of residual metallic tin to guarantee weldability are to be achieved. For this reason, a technique typified by the invention described in JP-B-62-54399 (hereinafter referred to as island-shaped LTS, Lightly
Tin-Coated Steel). Since the surface-treated steel sheet manufactured by this technology can make weldability and coating film adhesion practically compatible,
In recent years it has been used in large quantities. However, island LTS
Had a structure in which metallic tin was dispersed on an Fe-Sn-Ni alloy, and thus the appearance color tone was different from that of a normal tin plate whose surface was completely covered with tin. That is, the color tone was lower in brightness and whiteness than in a normal tinplate.

[0003] Empty cans used for beverage cans, food cans, and the like manufactured using island-like LTS as a material are used by painting and printing. In promoting the sales of canned products, the appeal of consumption becomes a problem, so the quality of the printed state on the surface is regarded as an important function of the can. Adjustment of color matching is indispensable to keep coating quality constant, but the surface tone of the steel plate,
If the whiteness is high, the lightness in the state of paint print finish,
Saturation can be easily increased, the thickness of the white base coat in the color matching process can be reduced, and the burden of fine adjustment of the paint composition can be reduced.

[0004] Under the above circumstances, the island-like LTS has a lightness,
The whiteness is inevitably lower than that of ordinary tinplate, and tin baking gradually proceeds from the tin metal layer to the alloy layer due to baking, resulting in a decrease in the metal tin coating surface area and the overall color tone of the alloy layer becomes higher. There was a feature approaching. Also, as a means of rationalizing the paint baking process, increasing the baking temperature for the purpose of shortening the baking time accelerates the reduction of the alloy tin layer, resulting in a change in the color tone of the finish compared to ordinary tinplate. This was an unstable factor in process management.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problem of the surface color tone of the island-shaped LTS by controlling the island-shaped tin shape within a certain range to obtain the same surface color as that of a normal tin plate. In particular, it is an object of the present invention to provide a surface-treated steel sheet for a welding can which has a lightness and a whiteness, and at the same time has a small change in color tone due to a heat treatment for paint baking.

[0006]

Means for Solving the Problems The inventors of the present invention have developed the above-described surface color tone, the change due to the heat treatment, and the island-like LTS.
The relationship between the shape of the island-shaped metal tin was investigated, and the following findings were obtained.
That is, by controlling the shape of the island-shaped metal tin to a certain range, it is possible to obtain the same surface brightness and whiteness as the tin coated with 100% tin. Specifically, a metal tin layer is dispersed in an island shape on at least one surface of the steel plate, and the shape of the island-shaped metal tin is taken as a 50 μm square field, and the x and y axes are perpendicular to the steel plate plane, With the thickness direction of the steel sheet as the z axis, x
= Y = 50 μm, when the maximum peak in the height direction (z direction) of the measurement space is set to the coordinate Z _max on the Z axis and the minimum peak is set to the coordinate Z _min on the Z axis, the minimum and the maximum are obtained. 50% the height of the contour of the peak heights, i.e., the _{Z = (Z max + Z min} ) / 2 ····· formula [1] cross-sectional area S _m of the measurement curved surface is cut at the plane of the measurement curved surface Is 50% depth area ratio S _r defined as a percentage of the xy plane projected area S ₀ (50 μm square) as follows: S _r = 100 × S _m / S ₀ ≧ 15 Equation (2) ] It is the surface-treated steel sheet for welded cans excellent in surface color after coating, characterized by the following.

[0007] The surface-treated steel sheet for a welding can may further include a Sn-Fe alloy layer between the island-shaped metal tin layer and the steel sheet base layer. Further, the surface-treated steel sheet for a welding can further includes a Sn layer between the island-shaped metal tin layer and the steel sheet base layer.
-The Fe-Ni alloy layer and the Fe-Ni alloy layer are Fe-N
The i-alloy layer may be present on the iron underlayer side. further,
In the surface-treated steel sheet for a welding can, a Cr oxide layer may be present in the outermost layer in an amount of ² to 20 mg / m ^{2 in} terms of metallic Cr. In addition, the surface-treated steel sheet for a welded can may have a metal Cr layer of ² to 20 mg / m ² directly below the outermost Cr oxide layer.

Hereinafter, the present invention will be described in detail. The present invention has a metal tin layer having island-shaped metal tin having a specific shape on at least one surface on a steel plate. There may or may not be another metal plating layer between the metal tin layer and the steel sheet base. The metal plating layer may be a single metal layer or an alloy layer. In the case of an alloy layer, it may be formed by alloy plating, or after a single metal layer is plated, a melting treatment may be performed together with the underlying metal to form an alloyed layer. Another embodiment of the present invention further includes a Cr oxide layer on the surface of the metal tin layer having island-shaped metal tin having a specific shape. A metal Cr layer may further be present between the Cr oxide layer and the metal tin layer. The steel sheet used as the material of the surface-treated steel sheet of the present invention is not particularly limited as long as it can withstand processing as a normal steel sheet for cans. In addition, the method of coating Ni, Sn, Cr, and a compound thereof with Fe, O, and the like to be coated on the surface of the steel sheet can be performed by known means such as plating, and any means may be used.

When the steel sheet has a Ni plating layer, the steel sheet table
The adhesion amount of the Ni plating layer on one side hit one side from the point of corrosion resistance.
10mg / m^TwoIt is preferable that there be the above. Adhesion amount is 30
0mg / m^TwoWhen the value exceeds, the effect is saturated.
mg / m^TwoMore than 300mg / m^TwoThe following is more preferable
Is 50 mg / m^Two200 mg / m or more^TwoThe following ranges and
Good to do. The Sn layer on the steel plate is a metal Sn layer, Sn-
Fe layer, Sn—Fe—Ni layer, etc.
n-plated adhesion amount is 0.05 g / m per side of steel sheet^Two
The above is preferred. 0.05g / m^TwoIf less, the weldability
Insufficient storage, 2.5 g / m^TwoBeyond the weldability
Since the good effect is saturated, 0.05 g / m^Two2.5g or more
/ M^TwoOr less, more preferably 0.1 g / m^TwoAbove 1.
6g / m^TwoThe following range is preferred. Chrome steel plate
Oxide layer and metal obtained by heat treatment
The Cr layer affects the coating adhesion of the surface-treated steel sheet of the present invention.
It is especially applied when excellent coating film adhesion is required.
Things. The amount of adhesion depends on weldability, coating film adhesion,
What is necessary is just to determine in consideration of surface color tone and economy. Like
As a new range of the adhesion amount, the Cr oxide layer was hit on one side.
2mg / m in terms of metal^TwoMore than 20mg / m^TwoBelow, gold
For the Cr layer, 2 mg / m2 per metal equivalent per side
^TwoMore than 20mg / m ^TwoIt is as follows. 2mg / m
^TwoIs the limit at which the effect of improving coating film adhesion is exhibited, and the upper limit
Is limited by the saturation point of the effect. More preferably,
3 mg / m in terms of metal per side for Cr oxide layer^Two
More than 15mg / m^TwoHereinafter, for the metal Cr layer, one side
3mg / m in metal conversion^Two17 mg / m or more^TwoLess than
It is.

The shape of the island-shaped tin of the steel sheet can be easily measured by measuring the surface shape using a commercially available scanning tunnel microscope, atomic force microscope, scanning electron microscope for three-dimensional shape analysis, or the like.

Means for obtaining the above-mentioned island-like tin include, for example, the composition of an electrolytic solution in electroplating, the setting of electrolytic conditions, the setting of heat treatment conditions such as melting treatment, the mechanical control of steel sheet and plating layer roughness, and the basis of vacuum deposition. Pretreatment, control of vapor phase growth conditions such as temperature and atmosphere, or thermal spraying,
There is no particular limitation on the contents, such as mechanical plating and other conditions control. As a method of obtaining the island-like tin, for example, after applying flat electrolytic tin plating on the surface of the steel sheet, after applying a flux which is an aqueous solution of ZnCl ₂ , NH ₄ Cl or the like in an arbitrary distribution state on the surface, There is a method of performing molten tin treatment to obtain island-shaped metal tin. When this method is used, as shown in FIG. 1, the island-shaped metal tin 1 is formed on the steel sheet base layer 3, and between the steel sheet base layer 3 and the island-shaped metal tin 1, Fe— The Sn alloy layer 31 can be formed.

Further, a method of obtaining an island-shaped metal tin by subjecting a steel sheet surface to a passivation treatment against molten tin wetting (diffusion treatment of Ni, etc.), followed by flattening an electric tin plating and a molten tin treatment. There is. Using this method, as shown in FIG.
Between the steel sheet base layer 3 and the island-shaped metal tin 1, the island-shaped metal tin 1
The Sn-Fe-Ni alloy layer 33 can be formed on the steel sheet base 3 side and the Fe-Ni alloy layer 32 can be formed on the steel sheet base 3 side by molten tin treatment. The steel sheet in which the metal tin layer obtained as described above is dispersed in an island shape is subjected to a chromate treatment by an ordinary method to form a chromate layer on the island-shaped metal tin layer 1.

The amount of each metal layer on the surface-treated steel sheet obtained as described above is as described above, and the shape of the island-shaped metal layer is as follows. Specifically, when observing the shape of the island-shaped metal tin of the present invention in a 50 μm square visual field, that is, 50 μm in each of the x-axis direction and the y-axis direction, the 50% depth area ratio of the island-shaped metal tin is as follows. It satisfies Expression [2]. S _r = 100 × S _m / S ₀ ≧ 15 Formula [2] Sr is preferably 15% or more and less than 100%, more preferably 20-70%. Here, S ₀ is the xy plane projected area of the measured curved surface, and S _m is the cross-sectional area of the measured curved surface cut by a contour line having a height of 50% of the maximum peak-to-peak height determined by the following equation [1]. . Z = (Z _max + Z _min ) / 2 Formula [1] When the shape of the island-shaped metal tin is represented by the above formulas [1] and [2], welding having excellent surface color after coating is performed. A surface-treated steel sheet for cans can be obtained.

[0014]

EXAMPLES Examples of specific embodiments of the present invention are shown below together with comparative examples. Embodiments of the present invention are not particularly limited to the embodiments described herein.

(Production Examples) The surface-treated steel sheets of Examples 1 to 3 and the steel sheets of Comparative Examples 1 to 4 were produced as follows.
The steel plate was subjected to Ni plating of 80 mg / m ² per side, and then diffusion annealing was performed in a reducing atmosphere to form a NiFe alloy plating layer. After the steel sheet is degreased and pickled, tin-plated at 0.8 to 1.6 mg / m ² per side, then immersed in aqueous solutions of various ammonium chloride (NH ₄ Cl) concentrations and dried, and then the steel sheet is dried. Heat treatment was applied to the molten tin, immediately followed by water cooling, and further, the steel sheet was subjected to cathodic treatment with an aqueous solution containing CrO ₃ to cover Cr ^M (metallic chromium) and chromium hydrated oxide. A part of the comparative example was plated in the same manner as in the example except that the molten tin treatment was not performed after tin plating with a metal tin adhesion amount of 2.9 g / m ² . Table 1 shows these conditions for the surface-treated steel sheets of Examples 1 to 3 and the steel sheets of Comparative Examples 1 to 4.

[0016]

[Table 1]

(Evaluation Method) (1) Measurement of Color Tone The following measurement was carried out using an integrating sphere color difference meter SM-3 manufactured by Suga Test Instruments, and was shown as an L value. 1) The measurement was performed while the original plate was plated. 2) A 25 μm thick TiO ₂ mixed PET (polyethylene terephthalate) film is heat-sealed to the original plate (about 250 μm).
C) after adhesion. 3) Whiteness is 210 ° C after white coating using PET resin.
And measured after baking for 20 minutes.

(2) Observation of surface structure Nanoscope IISPM manufactured by Digital Instruments Co., Ltd.
The following measurements were made using the system. Quantification of the island-shaped Sn shape using an atomic force microscope (AFM) (50 μm
Angle field observation). The quantification of the shape is shown schematically in FIG. In Figure 3, S ₀ represents the the x-y plane projected area of the measuring curved, S _m denotes a contour cutting area corresponding to the z-axis coordinate median of the measurement surface. 50% depth area ratio ( _Sr )
It was determined by _{S r (%) = S m} / S 0 × 100. Table 1 shows the S _r of the steel sheet of the surface-treated steel sheets and Comparative Examples 1 to 4 of Examples 1 to 3.

[0019]

According to the present invention, a surface-treated steel plate for an island-shaped tin-type welded can having a surface color similar to that of a normal tin plate, in particular, lightness and whiteness, and having a small color change due to heat treatment of paint baking is obtained. Can be This simplifies the management of the coating and printing process during can making, and reduces the color change even when baking is performed at a temperature higher than the conventional baking temperature of about 220 ° C. Is achieved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a state in which island-shaped metal tin is formed on a steel plate.

FIG. 2 is a diagram showing a state in which island-shaped metal tin is formed on a steel plate.

FIG. 3 is a schematic diagram of surface structure quantification showing how to determine a 50% depth area ratio (S _r ).

[Explanation of symbols]

REFERENCE SIGNS LIST 1 metal tin 3 base steel sheet 31 Fe-Sn layer 32 Fe-Ni-Sn layer 33 Fe-Ni layer S ₀ : xy plane projected area of measured curved surface S _m : contour line cut area corresponding to z-axis coordinate median of measured curved surface Z _max : the coordinate on the Z axis of the maximum peak in the z direction Z _min : the coordinate on the Z axis of the minimum peak in the z direction

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-156294 (JP, A) JP-A-63-76896 (JP, A) JP-A-61-139694 (JP, A) JP-A-4- 128386 (JP, A) JP-A-6-173035 (JP, A) JP-A-6-293996 (JP, A) JP-A-4-2211096 (JP, A) JP-B-62-54399 (JP, B2) (58) Field surveyed (Int. Cl. ⁶ , DB name) C25D 5/00-7/12 C23C 28/00 C23C 30/00

Claims (5)

(57) [Claims] 1. A metal tin layer is dispersed in an island shape on at least one surface of a steel plate, and the shape of the island-shaped metal tin is taken as a 50 μm square field of view, taking x and y axes perpendicular to the steel plate plane. When observing at x = y = 50 μm with the steel sheet thickness direction as the z-axis, the coordinate _Zmax of the maximum peak in the height direction (z-direction) of the measurement space on the Z-axis and the coordinate of the minimum peak on the Z-axis Z _{mi n}
, The contour line having a height of 50% of the height between the minimum and maximum peaks, that is, Z = (Z _max + Z _min ) / 2... Traversing the measurement curved surface cut by the plane of the formula [1] area S _m, 50% depth area ratio S _r is defined by the percentage of the the x-y plane projected area S ₀ of the measurement curved _{surface, S r = 100 × S m} / S 0 ≧ 15 ····· A surface-treated steel sheet for a welded can excellent in surface color after coating, characterized by the following formula [2]. 2. The surface-treated steel sheet for a welded can according to claim 1, wherein Sn- is provided between said island-shaped metal tin layer and said steel sheet base layer.
A surface-treated steel sheet for a welded can excellent in surface color after coating, characterized by having an Fe alloy layer. 3. The surface-treated steel sheet for a welded can according to claim 1, wherein Sn- is provided between said island-shaped metal tin layer and said steel sheet base layer.
The Fe-Ni alloy layer and the Fe-Ni alloy layer are present with the Fe-Ni alloy layer being on the steel sheet base layer side,
Surface treated steel sheet for welding cans with excellent surface color after coating. 4. The surface-treated steel sheet for a welding can according to claim 1, wherein a Cr oxide layer is a metal C
A surface-treated steel sheet for welded cans having an excellent surface color after coating, characterized by being present at 2 to 20 mg / m ^{2 in} terms of r. 5. A method according to claim 1, wherein said chromium oxide layer is located just under the outermost Cr oxide layer.
Characterized in that the 0 mg / m ² of metallic Cr layer is present, welded cans for surface-treated steel sheet excellent in surface color after coating of claim 4.