JPH06146072A - Steel plate for di can with superior corrosion resistance - Google Patents

Abstract

PURPOSE:To provide a steel plate for DI can with superior corrosion resistance for a DI can inner surface by regulating microshape which comprises a steel plate surface corresponding to a can inner surface side. CONSTITUTION:(1) This steel plate is the one for DI can with superior corrosion resistance comprised in such a way that a recessed part and a flat part are distributed almost uniformly on either one surface of the front surface or the back surface of a steel plate, and the means diameter D of the outer edge of the recessed part is set between 10mum and 500mum, and the area ratio of the recessed part is set between 15% and 45%. (2) The steel plate for DI can with superior corrosion resistance described in (1) comprised in such a way that the mean center distance L between the nearest recessed parts is set between, 1.73D and 10D (D: the means diameter of the outer edge of the recessed part) can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel plate for a DI can having excellent corrosion resistance on the inner surface of the can, and more particularly to a steel plate for plating the same to obtain the above-mentioned plated steel plate for a DI can. is there.

[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.

[0003] The DI can is a two-piece can that is formed in the manufacturing process in the order of drawing, ironing, and then punching (strip-out). , Ironing and strip-out are collectively called DI processing.

The plating layer such as tin plating not only provides corrosion resistance but also acts as a lubricant at the time of DI processing. However, tin plating has been demanded in order to reduce the cost in the recent DI can manufacturing in order to reduce the cost. The amount is being reduced, and it is feared that the lubricity is constant and the corrosion resistance is deteriorated in DI processing. Further, regarding the corrosion resistance, the coating of the plating layer such as tin plating is peeled off on the inner surface side of the can due to severe DI processing, and the base metal is exposed, so that the corrosion resistance deteriorates.
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.

Several techniques have already been disclosed for improving the above characteristics.

Regarding the improvement of corrosion resistance, for example, JP-A-54-150331 and JP-A-55-158838.
A method of defining the surface shape (surface irregularities, the number of peaks per inch, etc.) as disclosed in Japanese Patent Laid-Open Publication No. 55-50485. Further, as in JP-A-2-142624 and JP-A-2-36679, a method of irradiating a laser beam on the roll surface to form irregularities regularly and transferring the shape to the steel sheet surface by temper rolling. (Hereinafter referred to as laser dull method) and a steel sheet for DI can in which the shape is transferred.

However, in the prior art, since there is a convex portion, the base metal is exposed from the convex portion as a starting point when the inner surface of the can is smoothed during DI processing, and if the surface roughness is reduced, the ground surface may be "galled". When the iron is exposed and DI processing is performed,
It has not been possible to completely prevent the exposure of the base metal, and the corrosion resistance is insufficient as described above.

[0008]

As described above, the base metal is exposed during DI processing, and in the above disclosed technique, the cost reduction and the high corrosion resistance of the DI steel sheet are insufficient, and these are satisfied. The development of a steel sheet that can be used is an issue.

The present invention has been made to solve this problem, and an object of the present invention is to provide a steel plate for a DI can having excellent corrosion resistance on the inner surface of the can by safely preventing the exposure of the base metal due to the DI processing. I am trying.

[0010]

The present invention has been made in order to advantageously solve such a problem, and is characterized in that (1) a recess is formed on either one of the front and back surfaces of a steel sheet. And the flat portion are distributed almost evenly, and the average diameter D of the outer edge of the recess is 1
0 μm ≦ D ≦ 500 μm, and the area ratio of the recesses is 15%
A steel sheet for DI cans having excellent corrosion resistance, which is not less than 45%. (2) The concave portions and the flat portions are almost evenly distributed, and the relationship between the average center distance L of the concave portions that are closest to and adjacent to each other and the average diameter D of the outer edge of the concave portions satisfies 1.73D ≦ L ≦ 10D. A steel sheet for a DI can having excellent corrosion resistance according to the item (1).

[0011]

The present invention is to obtain a steel plate for a DI can which is excellent in corrosion resistance by completely preventing the exposure of the base metal due to the DI processing. In other words, in order to prevent galling and to completely prevent the exposure of the base metal, various investigations were carried out, and the flat part and the concave part were almost evenly distributed on either one of the front and back surfaces of the steel plate which became the inner surface of the can. , Based on the finding that it can completely prevent the exposure of the ground iron.

However, since the concave portions having the specific area ratio are almost evenly distributed at the specific intervals, galling due to contact with the mold does not occur, and the concave portions and the flat portions do not have the convex portions.
At the time of surface smoothing by the I processing (cup-shaped deep drawing processing and can wall ironing processing), there is no portion that should be the starting point of the base iron exposure, so that the base iron is not exposed at all. That is, since the inner surface of the can is sufficiently covered with the plating layer and the like even after DI processing, even if it is immersed in a carbonated beverage or the like, iron elution can be prevented by the corrosion resistance of the plating layer and the like, and the corrosion resistance can be improved. Are better.

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 of the inner surface of the can, 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 which is the inner surface of the can.

In the present invention, the recess used may have any shape such as a circle (FIG. 1), an ellipse and a polygon, and the same steel plate may have a plurality of shapes. As a substantially uniform distribution form (arrangement form) of the equilateral triangle (a), square (b),
Any shape such as a rectangle, an isosceles triangle (c), a regular polygon (eg, a regular hexagon (d)) having a concave portion at its apex may be used.

The shape of the recess is arbitrary, but its size is such that the average diameter D when the area taken by the outer edge of the recess is converted into an equivalent circle is 10 μm or more and 500 μm or less.

If the thickness is less than 10 μm, it is difficult at present due to the mechanical light collection limit of the laser beam and the mechanical chopper which are roll processing methods as described below. 500μ
If it exceeds m, it is determined to be defective by visual inspection of the surface at the time of shipping.

Regarding the diameter of the concave portion, the outer edge is converted into a circle equivalent and the average diameter satisfies 10 μm ≦ D1 ≦ 500 μm.
Regarding the distribution of the diameter of each recess, it is preferable that 60% or more of the recesses satisfy 10 μm or more and 500 μm or less.

Furthermore, the area ratio of the outer edge of the recess is 15% or more and 45% or less. If it is less than 15%, the flat part is too wide and the inner surface of the can is exposed to the metal mold during galvanizing to expose the base metal. On the other hand, if it exceeds 45%, since the flat portion is too small, the flat portion becomes substantially the same as the convex portion, and the DI
Since it becomes the starting point for exposing the base metal during processing, naturally the corrosion resistance of the inner surface of the can also deteriorates. Even after the plating, the steel sheet of the present invention has flat portions and recesses substantially evenly distributed on one of the front and back surfaces of the plated steel sheet, as in the case of the steel sheet before plating. Therefore, on either one of the front and back surfaces of the steel plate that will be the inner surface of the DI can, even after plating, sound recesses and flat parts are almost evenly distributed, and it is the inner surface of the can that contacts the die during DI processing. It is a flat part.

Next, the substantially uniform distribution of the concave portions and the flat portions satisfies the relation of 1.73D≤L≤1D in the relationship between the average center distance L of the closest adjacent concave portions and the average diameter D of the outer edges of the concave portions.

According to various studies, the inventors have found that the circles having the diameter D are most closely and effectively distributed by arranging the centers of the circles at the vertices of the regular triangle and arranging them at the centers of the regular triangle. It turned out to be the case when placing the same circle. Therefore, when the center distance between adjacent recesses is L and the diameter is D, the lower limit value of L is L = 2D cos 30 ° = 1.73D.
On the other hand, as L increases, the distance between the flat portions between the adjacent recesses increases, which increases the local contact area with the mold during DI processing, causing sticking during processing and “galling”. It tends to occur. If L exceeds 10D, galling occurs,
Moreover, the inner surface of the can is scratched and the corrosion resistance of the inner surface of the can is significantly deteriorated.

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 corrosion resistance is saturated and the manufacturing cost of the steel sheet is excessively increased, which is not preferable.

The steel sheet according to 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 plating is not particularly limited, and the DI coating is performed 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. .

[0025]

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 the dull to the material by them,
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 of these steel sheets for DI cans are ^# 25 (2.8
g / m ² ) was tin-plated 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, a disk-shaped punched piece of each tin-plated steel sheet was subjected to a drawing process, and then ironed to a can wall plate thickness of 0.1 mm to prepare a can body.

Properties 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 visual evaluation of the steel sheet before DI processing was good, and the iron elution amount after carbon dioxide immersion after DI processing was 0 ppm, which is extremely excellent in corrosion resistance. On the other hand, in the comparative example, any one of the average diameter of the concave portion, the area ratio, or the center-to-center distance is inappropriate, or there is a convex portion or there is no concave portion, so that the visual evaluation and / or the iron elution amount is 20 ppm. As above, corrosion resistance is insufficient.

[0027]

[Table 1]

Description of Table 1 (Note 1) Method for measuring D and L: The surface of the steel sheet is photographed at high magnification (100 to 1000 times), D and L are measured, and the diameter and distance are converted by magnification. Measurement.

(Note 2) Recessed area ratio method: The recessed portion and the flat portion on the steel plate surface were binarized by an image analyzer, and the area ratio occupied by the recessed portions on the steel plate surface was measured.

(Note 3) Convex area ratio method: The convex portion on the surface of the steel sheet and other portions (recessed portion and flat portion) are binarized by an image analyzer to measure the area ratio of the convex portion on the surface of the steel sheet. .

(Note 4) Steel plate visual evaluation method: After the tin plating, the steel plate surface was visually evaluated, and those in which the recesses could be easily confirmed were marked with X, and the others were marked with O.

(Note 5) Method of measuring 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. Sn Lα is measured at full scale of 5000 cps (Note 6) Iron elution amount measurement method: A sample of 60 mmφ is taken from the side wall after can making, and the other side is completely sealed leaving 50 mmφ at the inside of the can at 50 ° C. It was immersed in 100 ml of the carbonated drink (cola) heated to 10 hours, and the amount of eluted iron was measured by argon plasma spectroscopic analysis.

[0033]

According to the present invention, a DI can steel sheet having excellent corrosion resistance on the inner surface of the can 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.

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

FIG. 3 is a schematic comparison diagram of steel plate cross-sectional views.

FIG. 4 is a diagram showing a change over time in the amount of iron eluted from the inside surface of a can by a carbonated beverage.

[Explanation of symbols]

1 ... Steel plate recessed part 2 ... Steel plate flat part, D ... Average diameter of recessed part outer edge L ... recessed part average center distance

Claims (2)

[Claims] 1. A recess and a flat portion are distributed substantially evenly on one of the front and back surfaces of a steel sheet, and the average diameter D of the outer edge of the recess is 1.
0 μm ≦ D ≦ 500 μm, and the area ratio of the recesses is 15%
A steel sheet for DI cans having excellent corrosion resistance, which is not less than 45%. 2. The recesses and the flat parts are substantially evenly distributed, and the relationship between the average center distance L of the closest adjacent recesses and the average diameter D of the outer edge of the recesses satisfies 1.73D ≦ L ≦ 10D. The steel plate for a DI can having excellent corrosion resistance according to claim 1.