JP5471182B2 - Method for manufacturing metal can body - Google Patents

Description

  The present invention relates to a method of manufacturing a rectangular tube-shaped metal can body, and more particularly to a manufacturing method suitable for obtaining a rectangular tube-shaped can body made of an ultrathin metal plate.

The rectangular tube type container is advantageous in terms of space saving because, for example, when a plurality of containers are packed in a box and packed or displayed at a storefront, the gap between the containers can be reduced. In the case of a beverage container having an inner volume of about 400 mL or less, conventionally, paper has been used as a material for such a rectangular tube type container. Paper containers have the advantage of being light, but have a disadvantage that they are small in strength and easily deform when pressed or dropped.
On the other hand, metal cans are widely used for beverage containers. Metal has a higher strength than paper and is advantageous for deformation of the container. However, in the past, metal was rarely used as a material for a rectangular tube type beverage container. This is probably because the metal can is heavier than the paper container. To lighten the metal can, it is effective to reduce the thickness of the material metal plate.

Patent Document 1 discloses a method of forming a rectangular tube-shaped metal can using a material having a thin plate thickness. In this method, a rectangular material sheared to a predetermined dimension is formed into a cylindrical body by seam welding, and a square tube is formed by squaring (molding corners). The cornering is performed by using a plurality of sets of inner molds and outer molds corresponding to the number of corners to be molded, and the corners are further grooved. According to this method, a steel plate having a thickness of up to 0.1 mm can be formed into a rectangular tube-shaped metal can.
Patent Document 2 discloses a square can in which a concave portion recessed inward is formed on a side wall portion of a can body and a molding method thereof.

Japanese Patent Publication No.61-34891 Japanese Patent Application Laid-Open No. 2002-211559

  However, as a result of experiments conducted on the method of Patent Document 1 by using the ultrathin steel plate having a thickness of 0.1 mm, the inventors found that the following problems occur. First, when squaring and grooving were performed, breakage occurred at the grooving portion. Since this breakage occurred in the grooved portion, when the molding was performed without grooving, the corner portion did not become a predetermined angle (approximately 90 °), and as a result, the side wall portion curved toward the outside of the cylinder. As a result, the result was that the square tube was not properly shaped. That is, in forming a square tube having four corners and side walls, as shown in FIG. 3 (a plan view of the can body seen from the height direction), the side walls 1 are substantially flat and the corners 2 are formed. In this case, an attempt was made to obtain a shape having an angle α (corner angle) of approximately 90 °, but actually, as shown in FIG. 4 (a plan view of the can body seen from the height direction), the side wall portion 1 is outside. And the angle α of the corner portion 2 becomes considerably larger than 90 °, and it has been found that an appropriate shape as a square tube cannot be obtained. In such a shape, the advantage as a rectangular tube type container that the space | gap between containers can be made small is not acquired. Here, the angle α of the corner 2 described above is defined as follows. That is, as shown in FIG. 19, assuming a circle 20 (virtual circle) having a radius of curvature b of the corner 2 and in contact with the corner 2, circles at points 21 and 22 where the circle 20 and the corner 2 are separated from each other. When 20 tangent lines 23 and 24 are determined, an angle formed by the tangent line 23 and the tangent line 24 is defined as an angle α of the corner 2.

Further, as in Patent Document 2, by forming a concave portion recessed inward in the side wall portion of the can body, it is possible to avoid the outward bending of the side wall portion, but when the side wall portion is recessed inward. The content of the square can will be reduced. Since Patent Document 1 and Patent Document 2 are intended for cans having a relatively large internal volume such as an 18L can, a decrease in the internal volume due to the inward depression of the side wall is not a big problem. However, in a can with a relatively small internal volume of about 400 mL, which is the main object of the present invention, the decrease in the internal volume due to the inward depression of the side wall cannot be overlooked. Moreover, since the method of patent document 2 is what shape | molds into a rectangular tube and then shape | molds and forms a recessed part in a side wall part, the formation process of a can body increases and manufacturing cost becomes high.
As described above, a manufacturing technique for a rectangular tube can body using a thin metal plate as a raw material has not yet been established.
Accordingly, an object of the present invention is to provide a method for manufacturing a metal can body that can efficiently manufacture a square-shaped can body having an appropriate shape even when a thin metal plate is used as a raw material. .

［2］上記［1］の製造方法で得られた金属缶胴の少なくとも一方の端部に蓋を固定し、金属缶とすることを特徴とする金属缶の製造方法。 The gist of the present invention for solving the above problems is as follows.
[1] An outer mold that uses a cylindrical body of a metal plate as a material to be molded, has an outer mold having a cross-sectionally shaped machining surface, and an inner mold having a machining surface having an arc-shaped cross section at the tip, and is located outside the cylindrical body By pressing the cylindrical portion that becomes the side wall portion of the square tube in the direction toward the inside of the cylindrical body, the side wall portion is molded, and the cylindrical portion that becomes the corner portion of the square tube is formed into a cylinder by the inner mold located inside the cylindrical body. It is a manufacturing method of a square tube type can body that presses in the body outer side direction to mold a corner part,
The opening angle θ (°) of the outer die machining surface, the radius of curvature R (mm) of the top of the outer die machining surface, the radius of curvature r (mm) of the inner die machining surface, the thickness t (mm) of the metal plate, and the metal plate The can body is formed by the outer mold and the inner mold under the condition that the yield strength σ (N / mm ² ) satisfies the following formulas (1) and (2): Method.

[2] A method for producing a metal can, characterized in that a lid is fixed to at least one end of the metal can body obtained by the production method of [1] to obtain a metal can.

  According to the present invention, using a thin metal plate as a raw material, an appropriately shaped rectangular tube can body having a side wall portion that is substantially flat and a corner portion angle (corner angle) of approximately 90 ° is efficiently produced. Can be manufactured.

It shows an example of the implementation status of the production method of the present invention, (A) is before molding, (B) is during molding, (C) is a plan view showing each state after molding Plan view showing the structure of the outer mold and the inner mold used in the present invention Explanatory drawing which shows the proper can body shape (planar shape of the can body seen from the height direction) obtained by the formation process of a square tube type can body Explanatory drawing which shows the improper can body shape (planar shape of the can body seen from the height direction) obtained by the formation process of a rectangular tube type can body In the method of Patent Document 1, a material (cylindrical body) before molding and a molding means (inner mold, outer mold) when performing a molding test for squaring without grooving the corners are shown. Plan view of the trunk as seen from the height direction FIG. 5 is a plan view showing one set of inner mold and outer mold used in the molding test of FIG. In the method of Patent Document 1, the angle α of the can barrel corner obtained when a forming test for cornering is performed without grooving the corner, in relation to the curvature radius r of the inner die machining surface. Graph showing 7 is an explanatory diagram for explaining a phenomenon in which the angle α of the can barrel corner becomes 95 ° or more in the molding test of FIG. FIG. 7 is a graph in which the results of FIG. 7 are arranged by the relationship between σ · r / (1000 · t) and the angle α of the can barrel corner. The top view which shows the inner type | mold and outer type | mold used in the molding test of the can body performed in order to obtain this invention Explanatory drawing which shows the shape of the square cylinder type can body obtained by the shaping | molding test using the inner type | mold and outer type | mold shown in FIG. A graph showing the angle α of the can body corner portion obtained when the can body is molded with the open angle θ of the outer mold processing surface being 120 to 175 ° in relation to the open angle θ of the outer mold processing surface. Based on the results of FIG. 12, a graph in which the condition that the angle α of the can barrel corner is 90 ° is arranged in relation to the open angle θ of the outer die machining surface and σ · r / (1000 · t). The displacement h of the side wall portion obtained when the can body is molded with the curvature radius R of the top portion of the outer die machining surface being 4 to 16 mm is shown in relation to the curvature radius R of the top portion of the outer die machining surface. Graph Based on the result of FIG. 14, a graph in which the condition that the displacement amount h of the side wall portion is 0 mm is arranged by the relationship between the radius of curvature R of the top portion of the outer die machining surface and (t · 10 ⁴ ) / σ. Based on the result of FIG. 12, a graph in which the condition that the angle α of the can body corner portion is 85 ° to 93 ° is arranged by the relationship between the open angle θ of the outer die machining surface and σ · r / (1000 · t). Based on the results of FIG. 14, a graph in which the condition that the displacement amount h of the side wall portion is ± 1 mm is arranged by the relationship between the radius of curvature R of the top portion of the outer die machining surface and (t · 10 ⁴ ) / σ. Sectional drawing of forming means (inner mold, outer mold) for grooving corners in the method of Patent Document 1 Explanatory diagram for defining the angle α of the corner

In the method of manufacturing a rectangular tube can body according to the present invention, a cylindrical body of a metal plate is used as a material to be molded, and the corner portion of the rectangular tube is formed by an inner mold positioned inside the cylindrical body and an outer mold positioned outside the cylindrical body. The cylindrical body part and the cylindrical part serving as the side wall part are pressed from outside the cylindrical body, respectively, to form the cylindrical body into a rectangular tube.
FIG. 1 shows an example of the implementation status of the production method of the present invention, where (A) is before molding, (B) is during molding, and (C) is a plan view showing each state after molding. In the figure, a is a cylindrical body which is a material to be molded, and is obtained by joining opposite end edges of a rectangular metal plate deformed into a cylindrical shape by seam welding or the like. A is a molded square tube. 3 is an inner mold located inside the cylindrical body a, and 4 is an outer mold located outside the cylindrical body a. The inner mold 3 and the four outer molds 4 are provided, and these constitute molding means. ing.

FIG. 2 is a plan view showing one inner mold 3 and two outer molds 4 that mold the side wall portions 1 on both sides of the corner 2 formed by the inner mold 3.
The outer mold 4 has a machining surface 40 having a cross-sectional mountain shape (a loose mountain shape in a horizontal cross section) having a predetermined opening angle θ. The outer mold 4 is located outside the cylindrical body, and at the time of molding, the side wall portion is formed by pressing the cylindrical body portion whose processed surface 40 becomes the side wall portion of the square tube in the inner side of the cylindrical body. The cross-sectional mountain shape of the processing surface 40 is configured such that both inclined portions 400 are configured in a straight line and the top portion 401 is formed in an arc shape having a predetermined radius of curvature R. The open angle θ of the processed surface 40 of the outer mold 4 is an inner angle of a corner (an angle) formed by an extension line of both inclined portions 400 as shown in FIG.
The inner die 3 has a processing surface 30 having a circular arc shape (arc shape in a horizontal cross section) having a predetermined radius of curvature r at the tip. The inner mold 3 is located inside the cylindrical body, and at the time of molding, the corner portion is formed by pressing a cylindrical body portion whose processing surface 30 is a corner portion of the rectangular tube in the outer direction of the cylindrical body.

In the manufacturing method of the present invention, as shown in FIG. 1 (a), four inner molds 3 and four outer molds 4 are arranged on the cylindrical body a so as to be equally spaced in the circumferential direction of the cylindrical body a. In this state, as shown in FIG. 1B, the inner mold 3 and the outer mold 4 are used to press the cylindrical portion serving as the corner portion of the rectangular tube and the cylindrical portion serving as the side wall portion into and out of the cylindrical body. Forming a square tube. As a result, a square tube A having a corner portion 2 and a side wall portion 1 as shown in FIG.
In the present invention, in such a molding process, the open angle θ (°) of the outer die machining surface, the curvature radius R (mm) of the top of the outer die machining surface, the curvature radius r (mm) of the inner die machining surface, metal The forming is performed under the condition that the plate thickness t (mm) and the yield strength σ (N / mm ² ) of the metal plate satisfy the expressions (1) and (2) described later. Hereinafter, the details of the production method of the present invention and the results of the study that led to the present invention will be described.

When the present inventors formed an ultrathin steel sheet by the method of Patent Document 1, as described above, breakage occurs due to grooving, and the side wall portion curves toward the outside of the can body, and has an appropriate shape. The reason why it was not a square tube was examined in detail.
First, it is considered that the rupture caused by grooving is due to the following reasons. Grooving in the method of Patent Document 1 is performed by forming a material 14 (metal plate) with a punch 12 provided in the outer mold 11 and a recess 13 provided in the inner mold 10 as shown in FIG. . At this time, the material 14 constrained by the inner mold 10 is pushed into the recess 13 by the punch 12 and stretched. There is no problem as long as the material 14 has sufficient elongation that can withstand such molding, but if the elongation is inferior, it is considered that the material cannot withstand molding and breaks. The elongation of the material is a material property determined by its chemical composition, manufacturing method, metal structure, etc., but on the other hand, it is greatly influenced by the plate thickness, and the elongation decreases as the plate thickness decreases. Conventionally, an ultra-thin steel sheet having a thickness of about 0.1 mm that has not been used in the can manufacturing field has a low elongation even if the material characteristics are equivalent compared to a steel sheet having a larger thickness. Therefore, it is considered that the fracture occurred at the grooved portion.

Breaking the material is a phenomenon that should not occur because it leads to leakage of the contents in the beverage container. Therefore, it is desirable not to perform grooving which is a cause of breakage. Therefore, an experiment was conducted in which the inner mold and the outer mold were squared without grooving.
In this experiment, specimens A to D (tinned steel sheets) having a thickness t and a yield strength σ shown in Table 1 were used. The test material was formed into a cylindrical body a having an outer diameter of 52.4 mm and a height of 136.7 mm by seam welding, and an inner mold 5 (processing with an arc-shaped cross section at the tip) arranged as shown in FIG. A corner portion was formed by an outer mold 6 (an outer mold having a surface 50) and an outer mold 6 (an outer mold having a corner-shaped processed surface 60) to form a rectangular tube-shaped can body. Although the opening angle β of the machining surface 60 of the outer mold 6 shown in FIG. 6 is not described in Patent Document 1, it is the same here because it is 90 ° when measured in the drawing of the same document. Moreover, as for the curvature radius r of the processing surface 50 of the inner mold 5 shown in FIG. 6, 22 mm is exemplified for the 18 L can in Patent Document 1, but the present invention mainly uses a small can of about 400 mL or less. Since it is assumed, the thickness is set to 2 to 8 mm in this experiment in consideration of the difference in size. The four sets of the inner mold 5 and the outer mold 6 were arranged so that each set was equally spaced in the circumferential direction of the cylindrical body a. About the can body after shaping | molding, the angle (alpha) (corner angle) of the corner | angular part 2 was measured.

  FIG. 7 shows the result of arranging the angle α of the can barrel corner 2 with the radius of curvature r of the inner mold processed surface 50. According to the figure, the angle α of the can body corner portion 2 is 95 ° or more, and the side wall portion 1 is curved toward the outside of the tube under any condition, so that it does not become a square tube of an appropriate shape. It was. The reason is considered as follows. An outline of molding in this experiment is shown in FIG. As shown in FIG. 8 (a), when the cylindrical body (material to be molded) is sandwiched between the inner mold 5 and the outer mold 6, the side wall 1 of the square tube A is flat while the mold is in contact. In other words, the angle of the corner portion 2 is 90 ° along the opening angle β of the outer die machining surface 60. However, as shown in FIG. 8 (b), in the can body A released from the mold after molding, the corner portion 2 is opened by the spring back, so that the angle α becomes larger than 95 °, thereby the side wall portion 1. Is curved toward the outside of the cylinder. In the method of Patent Document 1, since the groove is formed, that is, the two inner mold tip portions (processed surfaces) having a small radius of curvature are bent at two locations, the spring back of the corner portion 2 is suppressed by the effect. It is considered to be done.

  Therefore, in order to suppress the curvature of the side wall surface, the angle α of the can barrel corner after being released from the mold should be close to 90 °. Therefore, when the experimental result is examined again in order to find a method for controlling the angle α, the larger the yield strength σ of the material and the larger the radius of curvature r of the inner working surface, the more the thickness t of the material. Is smaller, the angle α is larger. In other words, the angle α of the can barrel corner is proportional to the yield strength σ of the material and the radius of curvature r of the inner surface, and inversely proportional to the thickness t of the material. Accordingly, FIG. 9 shows the relationship between σ · r / (1000 · t) and the angle α of the can body corner portion, with respect to the experimental results described above. Here, the thickness t is multiplied by 1000 in order to simplify the calculation by setting the absolute value of σ · r / (1000 · t) to the same value as the angle α. . According to FIG. 9, it can be understood that the angle α of the can barrel corner can be unified by using σ · r / (1000 · t) as an index. That is, in order to control the angle α of the can body corner portion, it is understood that the relationship between the yield strength σ of the material, the plate thickness t, and the curvature radius r of the inner die machining surface may be adjusted.

In order to reduce the angle α of the can barrel corner, it is better that the plate thickness t of the material is thicker, the yield strength σ is lower, and the radius of curvature r of the inner die working surface is smaller. However, in order to obtain a lightweight can body aimed by the present invention, the thickness t of the material is preferably thin, and is preferably about 0.10 to 0.15 mm. Further, from the viewpoint of securing the strength of the can body, in order to compensate for the thin plate thickness, the material should have a high yield strength σ, preferably about 300 to 750 N / mm ² . Further, the radius of curvature r of the inner die working surface is preferably large so as not to damage the material when the inner die contacts, and is preferably approximately 2 mm or more. Thus, the desirable conditions for the material thickness t, yield strength σ, and radius of curvature r of the inner working surface are all the conditions necessary to reduce the angle α of the can barrel corner and approach 90 °. Are in a conflicting relationship. Moreover, the angle α of the can barrel corner obtained in such a range of the desired thickness t, yield strength σ, and radius of curvature r of the inner working surface is at least 95 ° in the experimental results of FIG.

As described above, the angle α of the can barrel corner portion is brought close to 90 ° by the method of forming the corner portion by pressing the material between the inner mold and the outer mold, which is a conventional technique, thereby eliminating the curvature of the side wall portion. That is practically difficult. In addition, the method of correcting the curvature of the side wall after first forming the corner by this method is not desirable because it increases the number of steps.
Therefore, the inventors of the present invention are methods other than the method of forming the corner portion by clamping the material between the inner mold and the outer mold as in the prior art, and the can body corner portion is set to an appropriate angle in one step. As a result, the material (cylindrical portion that becomes the corner of the square tube) is formed on the outside of the cylindrical body by the inner mold 3 as shown in FIG. In addition to forming the corners by pressing in the direction, a method of forming the side walls by pressing the material (cylindrical body portion serving as the side wall portion of the square tube) with the outer mold 4 in the direction toward the inner side of the cylinder was devised. In this molding method, the corner of the square tube is molded so as to have an angle of less than 90 ° while being constrained by the outer die 4 and the inner die 3, and the angle of the corner becomes approximately 90 ° after the spring back. In this way, corner forming and side wall correction are achieved in one step. In order to confirm the effectiveness of this method, the following experiment was conducted.

  Using test materials (i) to (iv) (tin-plated steel plates) having a thickness t and a yield strength σ shown in Table 2, the test materials were seam welded to have an outer diameter of 52.4 mm and a height of 136. A cylindrical body of 7 mm was formed, and corners and side walls were formed using the inner mold 3 and the outer mold 4 arranged as shown in FIG. As the inner mold 3, one having a radius of curvature r of the processed surface 30 at the tip of 2 mm and 4 mm was used. In addition, the outer mold 4 used was one in which the radius of curvature R of the top 401 of the processed surface 40 was 4 mm and the open angle θ of the processed surface 40 was 120 to 175 °. The molded can body was released from the mold, and the angle α of the can body corner was measured. FIG. 12 shows the relationship between the open angle θ of the outer mold processed surface and the angle α of the can barrel corner.

The appropriate opening angle θ of the outer die machining surface 40 depends on the conditions (i) to (iv) in Table 2, that is, the combination of the material thickness t, the yield strength σ, and the curvature radius r of the inner die machining surface 30. Different. Therefore, based on the results of FIG. 12, the conditions in which the angle α of the can barrel angle portion is 90 ° are arranged in relation to the open angle θ of the outer mold processed surface 40 and σ · r / (1000 · t). FIG. That is, by forming the can body under the condition satisfying the relationship between the opening angle θ of the outer mold processed surface and σ · r / (1000 · t) shown in FIG. A can body having a flat side wall surface at 90 ° is obtained.
12 and 13 correspond to the specimens in Table 2, respectively. As shown in FIG. 13, the angle α of the can barrel corner can be set to a value close to 90 ° by appropriately setting the opening angle θ of the outer mold processing surface 40 for molding the side wall. However, as shown in FIG. 11, the angle α of the can barrel corner is a value close to 90 ° by simply press-molding the corner with the inner mold 3 and press-molding the side wall with the outer mold 4. Even if it is possible, the shape of the side wall portion is indented as in Patent Document 2 (h in FIG. 11: the amount of displacement of the central portion of the side wall portion due to the depression), which is not desirable. Therefore, as a result of examining the molding conditions that do not cause such a shape defect of the side wall portion, it has been found that the shape of the outer mold processing surface 40 that presses the side wall portion may be optimized.

  Using test materials (v) to (vii) (tin-plated steel plates) having a thickness t and a yield strength σ shown in Table 3, the test materials were seam-welded to have an outer diameter of 52.4 mm and a height of 136. A cylindrical body of 7 mm was formed, and corners and side walls were formed using the inner mold 3 and the outer mold 4 arranged as shown in FIG. The curvature radius r of the inner die machining surface 30 and the opening angle θ of the outer die machining surface 40 were values shown in Table 3, and the curvature radius R of the top 401 of the outer die machining surface 40 was 4 to 16 mm. The molded can body was released from the mold, and the displacement h (see FIG. 11) at the center of the side wall was measured. FIG. 14 shows the relationship between the radius of curvature R of the apex 401 of the outer die machining surface 40 and the amount of displacement h at the center of the side wall. The amount of displacement h of the side wall portion in FIG. 14 is shown as positive when the dent is inside the can and minus when it protrudes outside the can. According to FIG. 14, it can be seen that by optimizing the radius of curvature R of the top 401 of the outer mold processing surface 40, the displacement of the side wall due to the dent and overhang can be suppressed. However, the optimum radius of curvature R of the apex 401 of the outer die machining surface 40 differs depending on the conditions (v) to (vii) in Table 3, that is, the combination of the plate thickness t of the material and the yield strength σ.

From the result of FIG. 14, the curvature radius R that brings the displacement amount h due to the depression or overhanging of the side wall portion closer to 0 is smaller as the plate thickness t is thicker and smaller as the yield strength is larger. Therefore, based on the result of FIG. 14, the condition in which the displacement amount h of the side wall portion becomes 0 is arranged by the relationship between the radius of curvature R of the top portion 401 of the outer die machining surface 40 and (10 ⁴ · t) / σ. FIG. Here, multiplied by 10 ⁴ in the thickness t is, (10 4 · ^t) / sigma of the absolute value by the magnitude of the value comparable to the radius of curvature R, in order to calculate the simplified is there. That is, when the can body is molded under the condition that satisfies the relationship between the radius of curvature R of the apex 401 of the outer die machining surface 40 and (10 ⁴ · t) / σ shown in FIG. A can body with h = 0 is obtained.

As described above, in the can barrel forming method using the inner mold 3 and the outer mold 4 as shown in FIG. 10, the angle α of the can barrel corner is set to 90 °, and the amount of displacement due to the depression or overhang of the side wall. It was found that there exist molding conditions that can make h 0.
In order to use the can body manufactured according to the present invention as a rectangular tube-shaped container, after providing flange portions at both ends (both openings) of the can body, similarly, a lid provided with the flange portions is mounted and both flanges are mounted. The lid is attached and fixed by tightening the part. Here, the advantage of the rectangular tube container that the gap between the containers can be reduced is that the side wall portion of the can body is strictly planar and the angle α of the can body corner portion is not 90 °, that is, the can body If the side wall portion of the can is substantially planar and the angle α of the can barrel corner portion is an angle close to 90 °, substantially no problem is obtained.
Specifically, if the angle α of the can body corner portion is 85 to 93 °, the displacement amount h due to the depression or overhanging of the sidewall portion can be reduced by optimizing the conditions for pressing the sidewall portion with an outer mold. It can be within 1 mm.

Therefore, based on the result of FIG. 12, the condition that the angle α of the can barrel angle portion is 85 ° to 93 ° is arranged by the relationship between the open angle θ of the outer mold processed surface 40 and σ · r / (1000 · t). FIG. 16 shows the result. That is, by forming the can body under the condition of the following formula (1) that satisfies the relationship between the opening angle θ of the outer mold processing surface 40 shown in FIG. 16 and σ · r / (1000 · t), A can body having an angle α of the can body corner portion of 85 ° to 93 ° is obtained.
Further, based on the result of FIG. 14, the condition that the amount of displacement of the central portion of the side wall portion is within ± 1 mm is based on the relationship between the radius of curvature R of the top portion 401 of the outer die machining surface 40 and (10 ⁴ · t) / σ. FIG. 17 shows the arrangement. That is, the can body is molded under the condition of the following formula (2) that satisfies the relationship between the radius of curvature R of the top 401 of the outer die machining surface 40 shown in FIG. 17 and (10 ⁴ · t) / σ. Thus, a can body having a displacement amount of the central portion of the side wall portion within ± 1 mm is obtained.
Therefore, in the present invention, the opening angle θ (°) of the outer die machining surface 40, the curvature radius R (mm) of the top 401 of the outer die machining surface 40, the curvature radius r (mm) of the inner die machining surface 30, the metal plate The can body is formed by the outer mold 4 and the inner mold 3 under the conditions that the sheet thickness t (mm) and the yield strength σ (N / mm ² ) of the metal sheet satisfy the following expressions (1) and (2): Do.

  As a material of the can body manufactured by the present invention, a steel plate subjected to various surface treatments for ensuring corrosion resistance is desirable. As such a surface-treated steel plate, one or more of tin, zinc, nickel, chromium, etc. are plated on the surface of the steel plate, and further, the chromate treatment or phosphate treatment is applied to the upper layer of the plated layer. Those subjected to various chemical conversion treatments are suitable. Among these, tin-plated steel plates (baffle) and electrolytic chromate-treated steel plates (tin-free steel) conventionally used for beverage containers are suitable. Moreover, the laminated steel plate which coat | covered the organic resin film on various surface treatment steel plates is especially suitable from viewpoints, such as corrosion resistance and environmental compatibility.

Although there is no special restriction | limiting in the plate | board thickness of a metal plate, 0.095-0.155mm is suitable from a viewpoint of weight reduction of a container. The yield strength σ of the metal plate is particularly preferably about 360 to 650 N / mm ² .
In order to obtain a cylindrical body a which is a material to be molded, the opposite end edges of a rectangular metal plate deformed into a cylindrical shape are usually joined to form a cylindrical body. The method for joining both edge portions of the metal plate is not particularly limited as long as sufficient joining strength is obtained, but a welding method, an adhesion method, a solder method, or the like can be used. Among these, a welding method with particularly high joint strength is suitable. As the welding method, current welding such as seam welding, laser welding, or the like can be applied.

Since the inner mold 3 and the outer mold 4 need to accurately mold the can body, it is necessary that the mold itself does not deform when the material is molded. Therefore, it is desirable to be a rigid body, and it is desirable to use a material such as a metal used in normal metal processing.
There is no particular limitation on the size of the rectangular tube can body manufactured according to the present invention, the size of the rectangular tube container using the can body, or the internal capacity, but a particularly preferable rectangular tube can body and rectangular tube container The size between the side walls is about 4 cm to 5 cm, the can height is about 5 cm to 15 cm, and the internal volume is about 80 to 400 mL. In addition, a rectangular tube can body and a rectangular tube container having a square cross section are manufactured according to the present invention.
The can body manufactured according to the present invention has a lid attached to at least one end to form a rectangular tube-shaped metal can. The attachment of the lid is usually performed by providing flange portions on the periphery of the end of the can body and the periphery of the cover, and winding both flange portions in a state where the cover is attached to the end of the can body.

A tin-plated steel sheet having a thickness t and a yield strength σ shown in Tables 4 to 6 was used as a test material. After this test material was formed into a cylindrical body having an outer diameter of 52.4 mm and a height of 136.7 mm by a seam welding method, the curvature radius r of the inner die machining surface and the open angle of the outer die machining surface shown in Tables 4 to 6 were used. Each of the four inner molds and outer molds each having θ and a radius of curvature R was molded into a rectangular tube can body. With respect to the can body thus obtained, the angle α of the corner portion and the displacement amount h due to the depression or overhang of the side wall portion were measured. The displacement amount h of the side wall portion is shown as positive when the dent is inside the can and as minus when the bulge is outside the can. The results are also shown in Tables 4 to 6.
As shown in Tables 4 to 6, in all examples of the present invention, the angle α of the can barrel corner is in the range of 85 ° to 93 °, and the displacement amount h of the side wall is within ± 1 mm.

In Tables 4 to 6, f1 and f2 indicate the left and right sides of the expression (1) of the present invention as follows, and f3 and f4 indicate the left and right sides of the expression (2) of the present invention as follows. Indicates.

DESCRIPTION OF SYMBOLS 1 Side wall part 2 Corner | angular part 3 Inner type | mold 4 Outer type | mold 30 Inner type | mold processing surface 40 Outer type | mold processing surface 400 Inclination part 401 Top part a Cylindrical body A Square cylinder

Claims (2)

A metal plate cylinder is used as a material to be molded, and an outer mold having a cross-sectionally mountain-shaped machining surface and an inner mold having a cross-section arc-shaped machining surface at the tip, and an outer mold positioned outside the cylinder, The cylindrical portion that becomes the side wall portion of the cylinder is pressed toward the inner side of the cylindrical body to form the side wall portion, and the cylindrical portion that becomes the corner portion of the square tube is moved outward from the cylindrical body by the inner mold positioned inside the cylindrical body. A method of manufacturing a rectangular tube can body that is pressed into a corner portion,
The opening angle θ (°) of the outer die machining surface, the radius of curvature R (mm) of the top of the outer die machining surface, the radius of curvature r (mm) of the inner die machining surface, the thickness t (mm) of the metal plate, and the metal plate The can body is formed by the outer mold and the inner mold under the condition that the yield strength σ (N / mm ² ) satisfies the following formulas (1) and (2): Method.

  A metal can manufacturing method, wherein a lid is fixed to at least one end of a metal can body obtained by the manufacturing method according to claim 1 to form a metal can.

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