JP3517532B2 - Method for forming uneven pattern on seamless can side wall - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an uneven pattern on a side wall of a seamless can. The seamless can is a seamless can in which the bottom and the body are integrated.

[0002]

2. Description of the Related Art Conventionally, in beverage cans, a tin-plated steel plate or an aluminum plate is deep-drawn into a cylindrical shape with a bottom, and further,
Seamless cans are generally manufactured by ironing. However, since these beverage cans have almost the same shape, they can be mass-produced at low cost, but on the other hand, the shapes of these seamless cans have no individuality. Therefore, a beverage maker that fills and sells beverages in beverage cans is demanding inexpensive cans with a unique shape for the purpose of individualizing and differentiating products.

As one of the forming methods of the can body for individualization and differentiation, an elastic body such as liquid, gas or rubber which is largely deformed by swelling process or pressure using an expanding die is used. Bulging processing is known.

[0004] Further, the body of a can, which is usually used for beverage cans, is ironed and stretched to the ironing limit to be thinned to reduce the wall thickness, save materials, and be hardened by work hardening. .

For this reason, since a large residual stress remains in the can body of the conventional beverage can, if the conventional beverage can is subjected to the bulging process as it is, the can body portion is obtained before the desired uneven pattern is obtained. A fracture may occur in the.

Therefore, in order to prevent breakage of the can body,
It is necessary to perform molding with a reduced amount of bulging, or to perform annealing treatment before bulging to remove residual stress and increase the elongation of the material. However, if the amount of bulging is reduced and the bulging is performed as in the former case, there is a drawback in that the height difference of the unevenness is small and a unique design surface cannot be obtained. On the other hand, when the seamless can is annealed like the latter, the can strength and withstand pressure decrease, and the can body part buckles due to the neck-in processing force during can-neck-in processing and the lifter pressure during can lid winding. Alternatively, there is a drawback that the bottom of the can buckles due to the internal pressure of the can after the can is filled with the beverage and sealed. In order to eliminate these drawbacks,
If the wall thickness of the can body is made thicker to make up for the lack of strength, extra material is required, resulting in higher material cost and uneconomical.

For the above reasons, conventionally, the swelling process and the swelling process for the ironing cans have been hardly carried out. However, proposals for swelling and swelling of ironing cans are disclosed in Japanese Patent Publication No. 59-18261 and Japanese Patent Publication No. 61-27124. The former is by printing and painting on the inner and outer surfaces of a can formed by drawing and ironing, and then using a drying oven to dry this, after reducing the residual stress generated during drawing and ironing, Put the can in the split mold, then insert the elastic body into the can, and bulge and deform this elastic body in the direction orthogonal to the can axis by the pressure from above, and by the pressing force of this elastic body, the can A bulging process corresponding to the inner surface shape of the mold is performed by applying a pressing force in a direction orthogonal to the can axis to the body. In the latter, after the incomplete annealing treatment is performed by high-frequency induction heating for a single hour only on the part of the can body where bulging is to be performed, the can is placed in a split mold and subsequently the can is elasticized. The body is inserted, and this elastic body is bulged and deformed in the direction orthogonal to the can axis by pressure from above, and the pressing force of this elastic body applies a pressing force in the direction orthogonal to the can axis to the can body. The bulging process is performed according to the inner surface shape of the mold.

[0008]

However, the former molding method has a problem in that a sufficient amount of bulging cannot be processed. If you raise the heating temperature to increase the amount of swelling,
There is a problem that the pressure resistance of the bottom of the can is reduced.

On the other hand, the latter molding method has a problem that the processing cost is increased because it is necessary to add not only the bulging processing step but also a special heat treatment step to the processing step of the ordinary drawn and ironed can. Moreover, there is a problem that an expensive high-frequency induction heating device is required, the manufacturing cost is higher than that of the former, and it is not practical.

SUMMARY OF THE INVENTION An object of the present invention is to provide a bulging method in which a seamless can is subjected to a large amount of bulging and a difference in height of unevenness is large without performing annealing treatment.

[0011]

A method for forming a concavo-convex pattern on a side wall portion of a seamless can according to the present invention relates to a method for forming a concavo-convex bottomed cylindrical can which has not been annealed. It is placed in a mold, and then at least one member selected from a fluid and an elastic body is introduced into the seamless can to pressurize the member, so that the side wall of the seamless can is pressured by the member. In the method of bulging the inner wall side of the split mold into close contact with the side wall of the seamless can by pressing the inner wall of the split mold into contact with the inner wall of the split mold. As a mold, the inner surface of the bottom portion has a shape corresponding to the shape of the can bottom of the seamless can to be arranged, and the inner surface of the body portion includes a convex portion having a diameter smaller than the outer diameter of the can body of the seamless can before the expansion process. Use the one with unevenness and the bill Then, the seamless can is placed between the split molds, then the split mold is closed, and the convex portion on the inner surface of the split mold is brought into contact with the body of the seamless can. Press, dent a part of the body of the seamless can, then, at the same time or after introducing the member into the seamless can, press the member,
Swell the side wall of the seamless can to the inner surface of the split mold,
It is characterized in that the side wall of the seamless can is pressed against and closely adhered to the inner surface of the split mold to form a concavo-convex pattern having a projecting protrusion and a recessed recess on the side wall of the seamless can.

According to the second aspect of the method for forming a concavo-convex pattern on a side wall of a seamless can according to the present invention, the seamless can arranged between the split molds is formed by drawing and ironing. It is characterized by being a can.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A method for forming a concavo-convex pattern on a side wall portion of a seamless can according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view through the axis of a seamless can. The seamless can 1 has a bottomed cylindrical shape including a can bottom portion 101 and a can body portion 102. As the seamless can, a plate having a thickness of 0.3 mm of aluminum alloy 3004-H191 is used, and the height of the can is 134 mm, the thickness of the body is 0.155 mm, and the neck (the opening 103 in FIG. 2 and the inclined portion below the neck 103). ) Prepared a squeezed and ironed can having a thickness of 0.165 mm and an outer diameter of 60 mm (comparative example) and a squeezed and ironed can (example) which is the same as the comparative example except that the outer diameter of the can body is 62 mm. did. The seamless can may be a deep-drawn can that has been drawn twice or more (including when stretched), and the material of the can is a tin-plated steel plate, an electrolytic chromic acid-treated steel plate, or the like. Treated steel sheets can also be used.

Since it is difficult to print on a can body having irregularities, it is desirable to print on the outer surface of the can body in the state of the seamless can shown in FIG. 1 before bulging.
In addition, when a printed thermoplastic synthetic resin film is attached to the outer surface of the can body, it is difficult to attach the synthetic resin film to the can body with unevenness after the bulging process, so bulge It is desirable that a synthetic resin film is previously attached to the outer surface of the can body in advance in the state of the seamless can shown in FIG.
In any case, since the split mold is used for bulging, from the viewpoint of preventing the occurrence of scratches on the outer surface of the can body and the inner surface of the mold,
It is not preferred that the outer surface of the can directly contact the inner surface of the mold. From this viewpoint as well, it is preferable to apply a paint or attach a synthetic resin film to the can body of the seamless can before the bulging process.

Further, when the can body of a seamless can is bulged, the material of the opening 103 of the can is pulled in, but the amount of pulling in is uneven in the circumferential direction of the can (rolling of metal sheet). In order to prevent the height of the can from being varied due to the unevenness of the elongation in the rolling direction and the elongation in the direction of 45 ° with respect to the rolling direction), the opening 103 is formed before the expansion process.
It is preferable to neck-in the opening so as to work harden. FIG. 2 is a sectional view through the axis of a neck-in processed can. The opening 103 of the seamless can 1 is narrowed, and the outer diameter of the opening 103 is smaller than the outer diameter of the can body.

Further, the knockout punch is inserted into the can during the neck-in process, but paint is applied to the inner surface of the can in advance so that the knockout punch and the metal base of the can do not come into direct contact with each other. Alternatively, a thermoplastic synthetic resin film may be previously attached to a plate material for forming a seamless can, and a seamless can is manufactured by drawing so that the synthetic resin film-attached surface is the inner surface of the can. It is desirable to form a synthetic resin film on the inner surface.

In this embodiment, the outer surface of the can is printed / painted, dried at 250 ° C. for 6 seconds, and the inner surface of the can is spray-painted with an epoxy-phenol-based paint.
It was dried at 30 ° C. for 60 seconds and then necked in.

FIG. 3 is a front sectional view of a split mold used in the method for forming a concavo-convex pattern on the side wall of a seamless can according to the embodiment of the present invention. The split mold 2 is a two-split mold, one of which is shown in FIG. The split mold 2 includes a body portion 201, a bottom portion 202, and an assembly portion 203. Bottom 20 of split mold 2
The shape of 2 is a female type corresponding to the shape of the bottom of the can. The barrel 201 of the split mold 2 has a cylindrical female shape divided into two parts that substantially match the shape of the can barrel, and has a convex portion 210 and a concave portion 211 extending substantially in the direction parallel to the central axis thereof. An alternating pattern of protrusions and recesses is formed on the female mold (both the convex portion 210 and the concave portion 211 have a shape in which the central portion of the body portion 201 is constricted). The tip diameter of the convex portion 210 having an uneven pattern (the diameter of a virtual circle connecting the tips of the respective convex portions 210) is 6
The bottom diameter of the concave and convex portions 211 (the diameter of a virtual circle connecting the bottoms of the respective concave portions 211) is 64.6 mm. That is, the minimum diameter of the body 201 of the split mold 2 is 60.7 mm at the tip of the convex portion 210 having an uneven pattern,
The maximum diameter of the body of the split mold 2 is 64.6 mm at the bottom of the concave portion 211 having an uneven pattern. Therefore, the diameter (62 mm) of the can body of the seamless can of the embodiment is larger than the minimum diameter of the body 201 of the split mold 2, but the body 20 of the split mold 2 is larger.
It is smaller than the maximum diameter of 1. On the other hand, the diameter (60 mm) of the can body portion of the seamless can of the comparative example is the body portion 201 of the split mold 2.
Not only smaller than the maximum diameter, but also the body 201 of the split mold 2.
Smaller than the minimum diameter of.

The split mold 2 is opened, and the seamless can 1 of the embodiment is inserted into one of the split molds 2. At that time, a part of the can barrel portion 102 of the seamless can 1 on the side facing the split mold 2 into which the seamless can is inserted is a body portion 201 of the split mold 2.
Of the can body 102 of the seamless can 1 is in contact with the convex portion 210 of the concave mold 21 of the split mold 2.
There is a gap without contacting with 1. Further, half of the can bottom portion 101 of the seamless can 1 is the bottom portion 202 of the inserted split mold 2.
And the half of the necked-in inclined portion of the seamless can 1 and the opening 103 above it is in contact with the inner surface of the inserted split mold 2. Next, split mold 2
Closed, the convex portion 2 of the concave-convex pattern of the body portion 201 of the split mold 2 is closed.
Since 10 pushes a part of the can body portion 102 of the seamless can 1 of the embodiment inward, the recess 110 is formed in a part of the can body portion 102 of the seamless can 1. FIG. 5 (a) shows a method for forming a concavo-convex pattern on a side wall portion of a seamless can according to an embodiment of the present invention, in which the split mold is opened and the seamless can of the example is placed between the split molds. FIG. 5B is a front sectional view showing a state where the mold is closed and pressed, and FIG. 5B is a partial sectional view thereof. Each recess 110 has a shape extending in a direction parallel to the can axis. But these dimples 110
Is not a shape with a clear contour.

In the case where these recesses are continuously formed on the entire circumference of the can body or the size and design are such that the marks of these recesses cannot be removed by the subsequent swelling process, the present invention It is impossible to form an uneven pattern for the purpose. That is, the dents formed in this step must be such that the outer peripheral length of the can body does not change and that no dent traces remain after the bulging process.

On the other hand, FIG. 4 is a front sectional view showing a state where the split mold is opened and the seamless can of the comparative example is placed between them, and then the split mold is closed and pressed. Since the can body portion 302 of the seamless can 3 of the comparative example does not come into contact with the convex portion 210 of the uneven pattern of the body portion 201 of the split mold 2 and is not pressed, the can body portion 302 of the seamless can 3 of the comparative example has an indentation. Does not occur at all.

FIG. 6 is a front sectional view of a bulge forming apparatus used in the bulging step in the method for forming a concavo-convex pattern on the side wall of a seamless can according to the embodiment of the present invention. It is a figure which shows the state before applying.
By the convex portion 210 of the split mold 2 which is closed, the depression 11 is formed.
An elastic bag 4 inside the seamless can 1 formed with 0
To place. The bag 4 has a bottomed cylindrical shape made of neoprene rubber, and an edge 401 at the upper end thereof is attached to the fixture 5. The fixture 5 is a bottom portion 202 of the body 201 of the split mold 2.
It is closely attached to the other end 204 facing the attachment end. A pipe 7 is connected to the center of the fixture 5, and water pressurized by a compressor (not shown) is supplied into the bag 4, and the bag 4 is filled with water 6. Water pressure is 40 kg /
cm ² and the elastic bag 4 is inflated, and the expanded bag 4 causes an outward pressing force to act on the inner wall of the can body 102 of the seamless can 1 to bulge the can body 102 and break it. It is brought into close contact with the inner surface of the body portion 201 of the mold 2 to form a concavo-convex pattern on the can body portion 102 that matches the shape of the inner surface of the body portion 201 of the split mold 2.

Here, a member selected from the fluid and the elastic body used in the swelling process of the present invention will be described. Examples of the member selected from the fluid and the elastic body used for the bulging process include liquids such as water and oil, gases such as air, and solids having an elastic body such as rubber. Liquid or gas can be directly introduced under pressure into a seamless can inserted into a split mold. Also, liquid or gas can be used with an elastic bag, in which case the seamless can is first inserted into the split mold, and then the elastic can is placed into the seamless can inside the split mold. Insert the bag made of
Liquid or gas is supplied into this bag while being pressurized to inflate the bag, or as described in Japanese Patent Publication No. 51-41147, the liquid is sealed in advance in an elastic bag and the bag is In the liquid inside, insert the lower part of the operating rod that can move up and down, and prepare the one with the pressing plate attached to the outer surface of the upper part of the bag, first insert the seamless can into the split mold, Next, most of the elastic bag is inserted into the seamless can in the split mold, and then the operating rod is pushed down to press the bag from above by the pressing plate to push the entire bag into the seamless can. By pressing the bag in the axial direction to expand the bag and pushing the operating canister into the bag, the liquid in the bag is compressed and the bag swells in the lateral direction (direction orthogonal to the can axis). May be. Further, when an elastic body such as rubber is used, JP-B-59-53129 and JP-A-5-53129.
As described in JP-A No. 7-28739, JP-A No. 61-27124, etc., first, a seamless can is inserted into a split mold, and then an elastic body is inserted into the seamless can, and thereafter. The elastic body is laterally deformed by pressing the elastic body from above with a rod or a cylinder. There is no problem when introducing air directly into the seamless can, but when introducing water directly into the seamless can,
The inner surface of the seamless can needs to be dried later, and when oil is directly introduced into the seamless can, the inner surface of the seamless can needs to be washed and then dried.

FIG. 7 is a front cross-sectional view of the seamless can after bulging in the method for forming a concavo-convex pattern on the side wall of the seamless can according to the embodiment of the present invention. Seamless can 1
In the can body portion 102, the recess 105 is formed on the recess formed in the previous step, and the recess mark is completely disappeared. In addition, the can body 102 of the seamless can 1 has a recess 1
The convex portion 106 is formed adjacent to 05. Figure 8
It is an AA sectional view of the seamless can of FIG. Each recess 10
5 and the wall thickness of each convex portion 106 is substantially constant at any position, and the diameter of the virtual circle connecting the bottom portions of the respective concave portions 105 is 60.7 mm, and the diameter of the virtual circle connecting the tip portions of the respective convex portions 106. Is 64.6 mm, and the convex portion 106 and the concave portion 105 are
And the difference in height is 1.95 mm. It is formed from a hard aluminum alloy plate, has undergone ironing with an ironing rate of 48.3%, has undergone considerable work hardening, and even if this swelling process is applied to a drawn and ironed can that has not been annealed, A rugged pattern can was obtained in which no breakage occurred in the can body 102, and the height difference was large and the appearance was good.

In order to express the amount of work in the bulging process, it is often measured how much the peripheral length is extended. However, the elongation of the material depends on the fact that it is a seamless can in which the body and the bottom are integrally formed, and the pattern. Since it is not uniform, it is more practical to measure the ratio of the can outer diameter before and after deformation,
It can also be broken. The bulge ratio R is the outer diameter (r
₁ ) and the original outer diameter (r ₂ ), that is, R = r ₁ / r ₂ , the aluminum alloy 3004 having a plate thickness of 0.3 mm
In the case of drawn and ironed cans made of H191 and having a can body wall thickness of 0.15 mm, R
It was found that when R = 1.16 or more, fracture occurs, but when annealing treatment is performed, fracture occurs when R = 1.11 or more.

When the can to be bulged is not annealed, the bulging amount is relatively small and limited in order to prevent the can from breaking. Therefore, in the unannealed can, conventionally, the height difference of the uneven pattern cannot be obtained, and as a result, the design in which the uneven pattern is emphasized cannot be expressed.

Of course, also in the present invention, since the concavo-convex pattern is formed on the side wall of the seamless can which is not annealed, the amount of protrusion is limited. However, in the concavo-convex pattern forming method of the present invention, as in the conventional method, due to the difference in height between the high bulge processed portion and the low bulge processed portion, or between the bulged processed portion and the unbulged processed portion. The height difference of the unevenness is not formed by the height difference, but the height difference of the unevenness is formed by the indenting process and the subsequent bulging process. Therefore,
In the uneven pattern forming method of the present invention, an uneven pattern having a large height difference can be obtained without causing breakage, and a design in which the uneven pattern is emphasized can be expressed.

Moreover, in the method of forming a concavo-convex pattern according to the present invention, after the can is placed in the open split mold, the split mold is closed and pressed to form a partial depression (or Dent) is formed, and subsequently at least one member selected from the fluid and the elastic body inserted into the can is pressed or deformed by pressure, and the pressed or deformed member is applied to the wall of the can body. Applying a pressing force to the outside to bring the wall of the can body into close contact with the inner surface of the split mold, and to bulge into a shape that corresponds to the inner surface of the split mold, so the recesses and protrusions are clean and clear. It is formed. That is, a desired sharp uneven pattern or a conspicuous pattern can be obtained.

The minimum diameter of the body of the split mold used in the method of the present invention is such that when the split mold is closed and pressed, a hollow is formed in the barrel of the can and the hollow disappears completely by the subsequent bulging process. It must be a value that does not leave a mark. The minimum diameter value of the body of the split mold depends on the material of the seamless can for which an uneven pattern is to be formed, the drawing degree, the ironing degree, and the stretching degree.

In the method of the present invention, it is only necessary to add a step (pushing step and swelling step) for forming a concavo-convex pattern to the conventional seamless can manufacturing process, and a concavo-convex pattern forming device is also incorporated as a manufacturing apparatus. Since the manufacturing cost is low, and the can manufactured by the method of the present invention is not subjected to the annealing treatment, there is no decrease in the strength of the can and the pressure resistance of the bottom of the can, and conversely by the work hardening. Since the hardness of the can body is further increased, the pressure resistance of the can is higher than that of the one subjected to the annealing treatment (depending on the shape of the uneven pattern to be formed, the resistance to the vertical load of the can is higher than that before forming the uneven pattern. Although the force may decrease, even in that case, the can formed by the present invention has a higher vertical strength than the can formed by the annealing treatment and then the uneven pattern.).

[0032]

According to the method for forming a concavo-convex pattern on the side wall portion of a seamless can according to the first aspect of the invention, after the can is placed in the split mold, the split mold is closed and pressed to perform the can body. A dent is partially formed in the can, and then at least one member selected from the fluid or the elastic body inserted into the can is pressed or deformed to the outside of the can body wall. Since the can body wall is brought into close contact with the inner surface of the split mold by applying a pressing force and bulging is performed into a shape corresponding to the inner surface shape of the split mold, the first is that the rupture occurs even though no annealing treatment has been performed. There is an effect that a large unevenness pattern of height difference can be obtained without causing it, and it becomes possible to express a design emphasizing the unevenness pattern. Secondly, the concave portion and the convex portion are formed neatly and clearly, Thirdly, there is an effect that a desired sharp uneven pattern and a conspicuous pattern can be obtained. Forming an uneven pattern on seamless can manufacturing process of the (push-machining process and bulge processing step)
Since it is only necessary to add the above, and as the manufacturing apparatus, it is only necessary to incorporate the concavo-convex pattern forming apparatus, so that the manufacturing cost is low.

According to the method for forming a concavo-convex pattern on the side wall portion of a seamless can according to claim 2, the seamless can arranged between the split molds is subjected to severe processing such as drawing and ironing. Even can be obtained can have a large uneven pattern of height difference, and since the seamless can before bulging has not been subjected to annealing treatment, there is no decrease in can strength and can bottom withstand pressure, On the contrary, since the hardness of the can body wall increases due to work hardening, there is an effect that the pressure resistance of the can is higher than that of the one subjected to the annealing treatment.

[Brief description of drawings]

FIG. 1 is a cross-sectional view taken along the axis of a seamless can.

FIG. 2 is a cross-sectional view passing through the shaft of a neck-in processed can.

FIG. 3 is a front cross-sectional view of a split mold used in a method for forming a concavo-convex pattern on a side wall portion of a seamless can according to an embodiment of the present invention.

FIG. 4 is a front cross-sectional view showing a state where the split mold is closed after the split mold is opened and the seamless can of the comparative example is arranged therebetween.

FIG. 5 is a view showing a method of forming a concavo-convex pattern on a side wall of a seamless can according to an embodiment of the present invention, in which a split mold is opened, the seamless can of the embodiment is placed between them, and then the split mold is closed and pressed. 3A is a front sectional view thereof, and FIG.

FIG. 6 is a front cross-sectional view of a bulge forming device used in the bulging step in the method for forming an uneven pattern on the side wall of a seamless can according to the embodiment of the present invention.

FIG. 7 is a front cross-sectional view of the seamless can after bulging in the method for forming an uneven pattern on the side wall portion of the seamless can according to the embodiment of the present invention.

8 is a cross-sectional view taken along the line AA of the seamless can of FIG.

[Explanation of symbols]

1,3 seamless cans 101 can bottom 102 can body 103 opening 105 recess 106 convex 110 hollow 2 mold 201 body 202 bottom 203 Assembly Department 210 convex 211 recess 3 Seamless cans of comparative example 302 Can body 4 Elastic body bag 401 Edge of bag 4 5 fittings 6 water 7 piping

Continuation of front page (51) Int.Cl. ⁷ Identification code FI B21D 22/30 B21D 22/30 Z 26/02 26/02 B // B65D 1/14 B65D 1/14 1/26 1/26 (56) References JP-A 7-242226 (JP, A) JP-A 61-56736 (JP, A) JP-A 50-101181 (JP, A) JP-A 57-28739 (JP, A) JP-A 55 -45546 (JP, A) JP-A-48-25667 (JP, A) Actual development 3-62644 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) B21D 51/26 B21D 22/02 B21D 22/10 B21D 26/02 B21D 22/30 B65D 1/14 B65D 1/26

Claims (2)

(57) [Claims] 1. A bottomed substantially cylindrical seamless can that has not been annealed is placed in a split mold, and then at least one member selected from a fluid and an elastic body is introduced into the seamless can. Then, by pressing the member, the side wall portion of the seamless can is bulged toward the inner surface of the split mold by the pressure of the member to press the side wall portion of the seamless can against the inner surface of the split mold to be in close contact, In the method of bulging the seamless can side wall portion into the inner shape of the split die, the split die has a shape corresponding to the shape of the can bottom of the seamless can to be placed on the inner surface of the bottom, and the inner surface of the body has Use a seamless can before and after bulge processing that has irregularities that include a convex portion with a diameter smaller than the outer diameter of the can body, open the split mold, and then place the seamless can between the split molds. Then, close the split mold and The convex portion of the inner surface of the mold is brought into contact with the body of the seamless can and pressed, and a part of the body of the seamless can is recessed, and thereafter, the member is introduced into the seamless can or at the same time. After pressing the member, the side wall of the seamless can is bulged to the inner surface of the split mold, and the side wall of the seamless can is pressed against the inner surface of the split mold to be in close contact,
A method for forming a concavo-convex pattern on a side wall portion of a seamless can, which comprises forming a concavo-convex pattern having an overhanging convex portion and a recessed concave portion on a side wall portion of the seamless can. 2. The seamless can side wall portion according to claim 1, wherein the seamless can arranged between the split molds is a can formed by drawing and ironing. Uneven pattern forming method.