JPH06142704A - Steel sheet-for di-can excellent in corrosion resistance, image clarity after coating and di-workability - Google Patents

Abstract

PURPOSE:To obtain a steel sheet for DI-can excellent in corrosion resistance of the inside surface of can, image clarity after coating of the outside surface of can and DI-workability by stipulating the microscopic shape which compose the surfaces of the steel sheet corresponding to the inside and outside surfaces of can. CONSTITUTION:(1) Recessed parts 1 and flat parts 2 are approximately uniformly composed on both surface and back faces of the steel sheet, the average diameter of the outer edge of the recessed part on both the faces is 10-500mum, the area rate of the recessed part on the surface corresponding to the inside surface of can is 0.6-45% and the area rate of recessed part on the surface corresponding to the outside surface of can is 1-30%. (2) The average center distance between the nearest adjacent recessed parts 1 on both the surface and back faces of the steel sheet is 1.73-10 in the ratio to the average diameter of the outer edge of the recessed part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel sheet for DI can which is excellent in corrosion resistance, image clarity after coating, and DI processability.

[0002]

2. Description of the Related Art DI cans are used for filling beverages such as carbonated drinks, and the plated steel sheet for DI cans is a steel plate after cold rolling, which is annealed and temper-rolled by a dull roll. And then tin-plated.

In the manufacturing process of a DI can, a drawing process, a drawing process, and an ironing process are performed.
And a subsequent two-piece can formed in the order of punch extraction (strip-out). This drawing, ironing and strip-out are collectively referred to as DI.
It is called processing.

Usually, the ironing process is performed in three stages by dividing the ironing amount into three. The easiness of DI processing described above is called DI processing property, and is generally evaluated by the processing energy of strip-out and third squeezing (hereinafter, 3rd squeezing). The smaller the processing energy, the better the DI processability.

The plating layer such as tin plating imparts corrosion resistance especially to the inner surface of the can, and acts as a lubricant during the DI processing and as a high reflectance agent for improving the post-painting clarity of the outer surface of the can. However, due to the recent demand for steel plate cost reduction for cost reduction in the production of DI cans, the amount of tin plating is being reduced, and there is concern that the DI processability will be greatly deteriorated. Further, regarding the corrosion resistance, due to severe DI processing (particularly, strip-out), the coating of the tin plating is peeled off on the inner surface side of the can and the base metal is exposed, so that the corrosion resistance is deteriorated. Therefore, it is the current situation that desired corrosion resistance is ensured by performing the inner coating twice (for example, Japanese Patent Application Laid-Open No. 1-111883), which, on the contrary, brings about a significant increase in can manufacturing cost. There is.

On the surface of the steel plate used for the outer surface of the can,
The ironing workability and the image clarity after painting are required. Regarding the post-painting image clarity, the tin plating on the outer surface of the can is removed by severe DI processing, and the base metal is exposed, so the light reflectance is low. Has a poor color tone, resulting in poor appearance.

As measures against this, for example, Japanese Patent Publication No. 60-2
As disclosed in Japanese Patent No. 8917 and Japanese Patent Laid-Open No. 63-45045, by plating a tin-plated base with a metal having a high light reflectance, it is possible to suppress the exposure of the base metal after DI processing and to increase the metal plating. There is a method to secure the reflectance and improve the image clarity after painting on the outer surface of the can. Further, recently, as in Japanese Patent Laid-Open No. 2-142624, directly irradiating a roll surface with a laser beam in a pulsed manner to form irregularities regularly, and transferring the shape to a steel plate (hereinafter referred to as laser dull processing) Therefore, there is a method of improving the post-painting clarity of the outer surface of the can.

[0008]

However, in the prior art, because of the reduction of the plating amount for the low cost and the DI processing accompanied by the reduction of the plate thickness from the original plate by 60% or more,
The base metal is exposed on the inner and outer surfaces of the can during the I process, and the desired DI processability, corrosion resistance, and clearness after painting have not been obtained.

The object of the present invention, therefore, is to provide a steel sheet for DI cans which solves such problems.

[0010]

The present invention has been made in order to advantageously solve such a problem, and is characterized by (1) a recess and a flat portion on both the front and back surfaces of a steel sheet. Are distributed almost evenly, the average diameter D1 of the outer edge of the recess is 10 μm ≦ D1 ≦ 500 μm on one side which is the inner surface of the can, and the area ratio of the recess is 0.6% or more and 45% or less, and the outer surface of the can is On the other side, the average diameter D2 of the outer edge of the recess is
A steel sheet for a DI can excellent in corrosion resistance, image clarity after coating, and DI processability, characterized in that 10 μm ≦ D2 ≦ 500 μm and the area ratio of recesses is 0.6% or more and 30% or less.

(2) The concave portions and the flat portions are almost evenly distributed,
When the average diameters of the recesses closest to and adjacent to each other are D1 and D2, the average center distances L1 and L2 of the recesses are 1.
73D1 ≦ Ll ≦ 10D1 and 1.73D2 ≦ L2 ≦ 1
A steel sheet for a DI can excellent in corrosion resistance, image clarity after coating and DI processability according to the item (1), which satisfies 0D2.

[0012]

The present invention provides a steel sheet for a DI can which is excellent in corrosion resistance of the inner surface of the can, image clarity after coating of the outer surface of the can, and DI processability by completely preventing the exposure of the base metal on the inner surface of the can by DI processing. I will get it. That is, in order to prevent galling and to completely prevent the exposure of the base metal, various studies have been made, and the idea is to perform DI processing, and there is no convex portion on the front and back surfaces of the steel sheet, This is a specific distribution in which the flat portions and the concave portions are almost even.

However, since the concave portions having a specific size and area ratio are substantially evenly distributed at specific intervals, contact with the mold is reduced, and galling does not occur.

In addition, since the front and back surfaces of the steel sheet consist of concave portions and flat portions and there are no convex portions, when the inner and outer surfaces of the can are smoothed by DI processing (cup-shaped deep drawing and ironing of the can wall), Since there is no place that should be the starting point for exposure of the ground iron,
The exposure of the ground iron is completely prevented. That is, the inner surface of the can and the outer surface of the can are sufficiently covered with the plating layer even after DI processing, so that the corrosion resistance of the inner surface of the can is extremely good.
The image clarity after painting after I processing is equivalent to that of aluminum DI cans, and is extremely excellent. Further, the processing energy of DI processing is significantly suppressed, and the DI processing property is greatly improved.

Next, the reasons for limiting the scope of the claims of the present invention will be described.

As described above, in order to improve the corrosion resistance, it is necessary that the concave portions and the flat portions are substantially evenly distributed on either one of the front and back surfaces of the steel sheet which is the inner surface of the can. For this purpose, it is necessary that the concave portions and the flat portions are substantially evenly distributed on either one of the front and back surfaces of the steel plate that is the outer surface of the can. Since the concave portions and the flat portions are substantially evenly distributed on the front and back surfaces, the contact resistance with the die is significantly reduced, the processing energy can be reduced, and the DI processing can be significantly improved.

In the present invention, the shape of the recess to be used may be an arbitrary shape such as a circle (FIGS. 1 and 2), an ellipse and a polygon, and the same steel plate may have a plurality of shapes. An example of a substantially uniform distribution pattern (distribution pattern) of concave portions is shown in FIG.
Any shape such as a square (b), a rectangle, an isosceles triangle (c), a regular polygon (eg, a regular hexagon (d)) having a concave portion at its apex may be used, or a combination of a plurality of distribution patterns may be used. . Furthermore, the distribution may differ between the front and back surfaces of the steel sheet.

The shape of the recess is arbitrary, but its size is such that the average diameters D1 and D2 of the can inner surface and the can outer surface are 10 μm or more, respectively, when the area covered by the outer edge of the recess is converted into an equivalent circle. And 500 μm or less.

If the thickness is less than 10 μm, it is difficult at present because of the mechanical light collection limit of the laser beam and the mechanical chopper for processing the roll for transferring the recess of the steel plate. Fifty
If it exceeds 0 μm, it is determined to be a defective product by visual inspection of the surface at the time of shipping.

The diameters of the recesses are calculated by converting the outer edges into circles and satisfying the average diameters of 10 μm ≦ D1 ≦ 500 μm (inner surface of the can) and 10 μm ≦ D2 ≦ 500 μm (outer surface of the can), but the distribution of the diameters of the individual recesses. As 6 out of the entire recess
It is preferable that 0% or more satisfies 10 μm or more and 500 μm or less.

Further, the area ratio of the recesses is 0.6% on the inner surface of the can.
It is 45% or less and 0.6% or more and 30% or less on the outer surface of the can. If the area ratio of the concave portion on the inner surface of the can is less than 0.6, DI
After processing, the contact surface with the mold is too wide and the contact resistance is large, the plating layer is removed and the base iron is exposed, so the corrosion resistance is insufficient. On the other hand, if it exceeds 45%, the area of the flat portion is too small, and the flat portion functions similarly to the convex portion, so that it becomes a starting point of exposed base metal as a protrusion during DI processing.

Next, when the area ratio of the concave portion on the outer surface of the can is less than 0.6%, the contact resistance is too large as described above, the plating layer is removed and the base metal is exposed. Therefore, the exposed portion is directly coated. As a result, the image clarity after coating is significantly deteriorated. on the other hand,
If it exceeds 30%, the number of recesses is too large to obtain a high light reflectance and the image clarity after coating is not good.

In ironing, the outer surface of the can is subjected to a greater amount of processing than the inner surface of the can. Therefore, as a matter of course, the upper limit of the area ratio of the recesses is smaller on the outer surface of the can than on the inner surface of the can.

Next, the concave portions and the flat portions are almost evenly distributed,
The relationship between the average center distances L1 and L2 of the most adjacent adjacent recesses and the average diameters D1 and D2 of the outer edges of the recesses is 1.73D ≦ L1 ≦ 10D1, 1.73D2 ≦ L2 ≦ 1.
It satisfies 0D2. However, L1, D1 is the inner surface of the can, L2,
D2 is the value on the outer surface of the can.

The circles having the diameters D1 and D2 are densely distributed when the centers of the circles are arranged at the vertices of an equilateral triangle and the circles having the same diameter are arranged at the centers of the equilateral triangles.
Therefore, when the center distances of adjacent recesses are L1 and L2 and the diameters are D1 and D2, the lower limit of D1 and D2 is L.
1 = 2D1 × cos 30 ° = 1.73D1 and L2 = 2
D2 × cos 30 ° = 1.73 D2. On the other hand, D
With the increase of 1 and D2, the interval of the flat portion between the adjacent recesses becomes wider, the local contact area to the die at the time of DI processing becomes wider, and the “gnazing” is caused by adhesion during the processing. It tends to occur. L1> 10D1 or L1> 10D1
In this case, the processing energy becomes high, galling occurs, the corrosion resistance of the inner surface of the can deteriorates, and the image clarity after coating of the outer surface of the can remarkably deteriorates.

The depth of the recess is preferably deep, but is preferably 1 μm or more and 8 μm or less after plating or before DI processing. If it exceeds 8 μm, the DI workability is saturated and only the manufacturing cost of the steel sheet increases, which is not preferable.

The steel sheet of the present invention is used for DI processing by plating the surface of the steel sheet after applying the surface shape of the claims, but the type of the plating is not particularly limited, and the DI film is formed by a good lubricating film or the like. There is no restriction on the type of lubricating film even when it is processed. That is, the steel sheet for DI cans according to the present invention is characterized by the steel sheet surface shape itself as described in the claims, and the surface treatment performed after the steel sheet is manufactured is not particularly limited. .

[0029]

EXAMPLES normal cold rolling the Al-killed steel sheet used for DI cans with the actual device, after continuous annealing, temper degree 4 in the temper rolling _{(T-4CA, H R 30T} = 60) Material of those with It was used as (plate thickness = 0.245 mm). For the work roll used for temper rolling, a dull roll is manufactured by photoetching (used for making the steel sheet of the present invention) and laser beam processing (used for making the steel sheet having convex portions).
By transferring dullness to the inner and outer surfaces of the can of the above material, a steel plate corresponding to the steel plate for DI can was obtained.
Further, a DI steel sheet having flat front and back surfaces was manufactured even with an ordinary bright roll. Both sides in these DI steel sheet for cans ^#
25 (2.8 g / m ² ) of tin was applied to obtain a tin-plated steel sheet for DI cans. The tin-plated steel sheet prepared this time is not reflowed, but may be lightly reflowed. Then, each of the tin-plated steel plates punched into a disk shape is subjected to a drawing process, and subsequently, the can wall plate thickness = 0.
A can body was created by ironing up to 1 mm.

The characteristics of these steel plates and cans are shown in Table 1 together with those of the comparative examples. In each of the examples of the present invention, the DI processing energy is low and the visual evaluation of the steel sheet before DI processing is good.

On the other hand, in the comparative example, any one of the average diameter, the area ratio and the center-to-center distance of the recesses is inappropriate, or
Since the convex portion is present or the concave portion is not present, the DI processing energy is high, the base metal is exposed in a large amount after the DI processing, and the visual evaluation of the steel sheet is insufficient.

[0032]

[Table 1]

[0033]

[Table 2]

Description of Table 1 (Note 1) Method for measuring D and L: The steel sheet surface is highly magnified (50 times to
Take a photograph at 1000 times), measure D and L, and measure the diameter and distance by converting the magnification.

(Note 2) Recess area ratio method: The area ratio of the recess on the surface of the steel sheet was measured by binarizing the recess and the flat portion on the surface of the steel sheet with an image analyzer.

(Note 3) Convex area ratio method: The convex portion on the surface of the steel sheet and other portions (concave portion and flat portion) are binarized by an image analyzer, and the area ratio occupied by the convex portion on the surface of the steel sheet is measured. .

(Note 4) Measuring method of exposure rate of base steel: 1 / side of inner surface of can
Line strength analysis of the tin strength at 2 can heights and measuring distance of 10 mm by EPMA showed that the tin analytical strength was 1500 cp at all measuring distances.
Ratio (%) occupying s or less EPMA analysis conditions: Acc. V = 1.5 kV, S.V. C.
= 0.015 μmA, analysis speed 100 μm / min. Lα of Sn is measured at full scale 5000cps (Note 5) 3rd ironing and stripping-out processing energy measurement method: 3rd ironing die used for DI processing and strain gauge attached to punch, 3rd ironing,
Measures processing energy when stripping out.

[0038]

EFFECT OF THE INVENTION According to the present invention, a steel sheet for DI can having excellent corrosion resistance on the inner surface of the can, sharpness after painting on the outer surface of the can and DI processability can be obtained.

[Brief description of drawings]

FIG. 1 is a bird's-eye view showing an example of a flat portion and a concave portion on the surface of a steel plate which is the inner surface of a DI can according to the present invention.

FIG. 2 is a bird's-eye view showing an example of a flat portion and a concave portion on the surface of a steel plate which is the outer surface of a DI can according to the present invention.

3 (a), (b), (c) and (d) are surface views showing an example of a distribution form of recesses.

FIG. 4 is a schematic comparison diagram of steel plate cross-sectional views.

FIG. 5 is a diagram showing the influence of DI processing energy on the existence of concave portions and flat portions on one side and both sides.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Steel plate recessed part 2 ... Steel plate flat part, D1 ... Average diameter of recessed part outer edge of can inner surface side L1 ... Average center distance of recessed part of can inner surface side D2 ... Average diameter of recessed part outer edge of can outer surface side L1 ... Average recess part of can outer surface side Center distance

Claims (2)

[Claims] 1. On both front and back surfaces of a steel sheet, concave portions and flat portions are substantially evenly distributed, and the average diameter D1 of the outer edge of the concave portion on one side which is the inner surface of the can is 10 μm ≦ D1 ≦ 500 μm,
In addition, the area ratio of the recesses is 0.6% or more and 45% or less, and the average diameter D2 of the outer edge of the recesses is 10 μm ≦ D2 ≦ 500 μm and the area ratio of the recesses is 0.6% on the other surface that is the outer surface of the can. As described above, a steel sheet for a DI can excellent in corrosion resistance, image clarity after coating, and DI processability, which is 30% or less. 2. When the recesses and the flats are substantially evenly distributed and the average diameters of the closest and adjacent recesses are D1 and D2, the average center distances L1 and L2 of the recesses are 1.73D.
1 ≦ Ll ≦ 10D1 and 1.73D2 ≦ L2 ≦ 10D2
The steel sheet for a DI can excellent in corrosion resistance, image clarity after coating, and DI processability according to claim 1.