JPH09285832A - Seamless can and its forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the remarkably improved pressure-proof strength and corrosion resistance while a stock is of thin-walled structure, and to control the deformation of a container by the pressure to be on a low level. SOLUTION: A seamless can is provided with a cylindrical body part 2, a circumferential ground part 4, an outer circumferential bottom part 5 to connect the cylindrical body part 2 with the circumferential ground part 4, a riser part 6 on the inner side to the circumferential ground part 4, and a dome part 7 connected to the riser part 6. The circumferential ground part 4 comprises annular parts of small intervals provided with an inner circumferential edge part 9 continuous to an inner circumferential connection part 8 extending from the circumferential ground part 4 at acute angle and an outer circumferential edge part 11 continuous to an outer circumferential connection part 10 extending from the circumferential ground part 4 at the obtuse angle, and the inner circumferential side connection part 8 to the riser part 6 are of the inversely tapered shape in which the diameter is increased in the height direction, and the shape of a bottom part has the dimension in the prescribed range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seamless can and a method for forming the seamless can, and more particularly to a seamless can capable of maintaining an excellent pressure resistance even when the material is thin. The present invention also relates to a method for efficiently manufacturing the seamless can using a relatively thin metal material.

[0002]

2. Description of the Related Art A can body obtained by drawing and redrawing a metal material between a punch and a die or further ironing it is used in a can body portion and a connecting portion between the can body portion and a can bottom portion. It has no seams, has a good appearance, does not require operations such as tightening the bottom lid and forming seams, and has the advantage that the side wall of the can body is thin and the amount of metal material can be small. From
Widely used for applications such as beverage canning.

Since such a two-piece can is used for contents such as beer and carbonated beverages having an autogenous pressure, and for applications such as nitrogen-filled cans, pressure resistance is required, and in particular, buckling at the bottom of the can is required. In order to prevent this, many proposals regarding the bottom shape have been made, such as providing an upward rising portion and a dome portion on the bottom portion of the can.

In Japanese Utility Model Laid-Open No. Hei 1-130916, a base portion having a substantially V-shaped cross section is provided around the lower end portion of the can body, and a bottom portion of the can body connected to the base portion is formed with an inner recess. In the spherical dome, the structure of the bottom of the DI can is described, which is characterized in that the inner side wall of the base part is recessed toward the side wall. While the internal pressure resistance strength is 7 kgf / cm ² ,
When the side wall is recessed by 1 °, the internal pressure resistance is 7.8.
It has been shown to be kgf / cm ² .

Further, in Japanese Patent Laid-Open No. 4-267733, the bottom dent portion includes a center panel and a dome positioning portion for disposing the center panel above a supporting surface, and the dome positioning portion is located at a first radial distance from a vertical axis. A first portion arranged and an adjoining portion arranged at a radial distance different from the first radial distance from the vertical axis, and a plurality of adjoining portions are arranged in an arcuate shape with a circumferential gap therebetween, The shape of the can bottom having excellent pressure resistance in which a plurality of first parts are arranged is described, and FIGS. 7 and 11 thereof describe that the dome positioning part is recessed outward in the adjacent part. ing.

[0006]

The former conventional technique is based on V
Although it is significant to find that the pressure resistance can be improved by recessing the V-shaped base portion, that is, the rising portion toward the outside, the pressure resistance is improved by about 10%. However, I am still not completely satisfied.

In the latter prior art, the dome positioning portion is recessed to the outside and adjacent portions are arranged in an arc shape at intervals, and the outer edge of the dome portion is arranged inside the adjacent portion. As a result, the improvement in pressure resistance is still not fully satisfactory.

In recent years, in order to reduce the cost of canned products, efforts have been made to reduce the cost of metal materials without substantially lowering the strength of cans and the like. In order to reduce the cost of metal materials, it is effective to use materials with small thickness and relatively large strength, but in this case, processing to increase pressure resistance and drop strength becomes severe. , Not only the appearance is poor due to wrinkles on the bottom, but the prescribed drop strength and pressure resistance cannot be obtained due to the occurrence of wrinkles, and corrosion resistance due to poor adhesion of the coating film at the wrinkles Cause problems such as a decrease in

Therefore, an object of the present invention is to make a seamless can whose material has a reduced thickness but has remarkably improved pressure resistance and corrosion resistance and whose deformation due to the pressure of the container is suppressed to a small level. And to provide a manufacturing method thereof.

Another object of the present invention is to form a bottom shape having excellent pressure resistance without reducing the thickness of the machined portion of the bottom, and to form the bottom efficiently with a simple tool and a small number of steps. It is to provide a manufacturing method of a seamless can that is possible.

[0011]

According to the present invention, a tubular body portion, a circumferential grounding portion, an outer peripheral bottom portion connecting the tubular body portion and the circumferential grounding portion, and an inner side of the circumferential grounding portion. In a seamless can comprising a rising part of the above and a dome part connected to the rising part, the circumferential grounding part is an inner peripheral end edge part connected to the inner peripheral side connecting part extending at an acute angle from the grounding part. ,
It consists of an annular portion with a small interval provided with an outer peripheral end edge portion that is continuous with an outer peripheral side connecting portion whose angle from the ground portion extends at an obtuse angle, and the inner peripheral side connecting portion or rising portion has a diameter in the height direction. It has an increasing inverse taper shape, and the radius of the inner peripheral edge is R
R _M / R, where _E and the maximum radius of the dome are R _M
The ratio of _E is in the range of 1.015 to 1.150, and the radius of curvature R _{1 of} the inner peripheral side edge is 1 to 7 times the plate thickness (t),
The radius of curvature R ₂ of the outer peripheral side edge portion is 3 to 20 of the plate thickness (t).
And a radius of curvature R ₃ of the ground contact portion is in the range of 3.5 times or more of the plate thickness (t), and a seamless can having excellent internal pressure resistance is provided.

According to the present invention, a material for a seamless can is formed from a tubular body portion, a circumferential lower end portion, an outer peripheral bottom portion connecting the tubular body portion and the circumferential lower end portion, and a circumferential lower end portion. Also a step of press-molding into a cup having a substantially vertical rising portion on the inner side and a dome portion connected to the rising portion; and controlling the dome portion while downwardly and radially inwardly the circumferential lower end portion. And a circumferential grounding portion having a diameter smaller than that of the circumferential lower end portion, a projecting portion formed of an inner circumferential side connecting portion with the rising portion and an outer circumferential side connecting portion with the outer circumferential bottom portion, and the circumferential grounding portion. Of a seamless can with excellent pressure resistance, characterized in that the inner taper portion and the dome portion are pressed to form an inverse taper whose diameter increases in the height direction at the inner peripheral side connecting portion or rising portion. A method is provided. With respect to the pushing of the circumferential lower end portion, the outer peripheral bottom portion of the cup is held by the tapered support portion of the holddown ring, and the dome portion is held by the dome holding tool coaxial with the holddown ring to press both, It is preferable to guide it into a groove that is continuous with the tapered support portion and has a diameter smaller than that of the circumferential lower end portion.

In the present invention: 1. The reverse taper portion of the rising portion has an angle of 4 ° to 50 ° with respect to the height direction; The height of the maximum diameter portion of the dome portion (H _M) in the range of 10 to 40% of the maximum height of the dome portion (H _D), 3. 3. The plate thickness (t ₁ ) of the inner peripheral side connection part or the rising part is maintained at 0.9 times or more of the plate thickness (t ₀ ) at the center of the dome part. 4. When the radius of the inner peripheral edge is R _E and the radius of the tubular body is R, the ratio R _E / R is in the range of 0.60 to 0.85. 5. The outer peripheral bottom portion forms a taper portion whose diameter decreases toward the bottom. Of the reverse taper portion of the inner peripheral side connection portion or the rising portion, the portion closest to the outer peripheral bottom portion has a dimension (F) of not more than 15 times the plate thickness in the radial direction with respect to the outer peripheral bottom portion. , 7. It is preferable that the seamless can is formed by drawing a metal laminate plate having at least an inner surface coated with an organic resin.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 showing the overall structure of an example of a seamless can according to the present invention, the can body 1 comprises a tubular body portion 2 and a can bottom portion generally designated by 3. The can bottom portion 3 is connected to the circumferential grounding portion 4, the outer circumferential bottom portion 5 that connects the tubular body portion 2 and the circumferential grounding portion 4, the rising portion 6 inside the circumferential grounding portion 4, and the rising portion 6. And the dome portion 7 that is formed.

In FIG. 2 for enlarging and showing the main part of the bottom of the can and for explaining various dimensions, the peripheral grounding part 4 is connected to the outer peripheral side connecting part 8 whose angle from the grounding part 4 is α. End edge portion 9 and inner peripheral side connecting portion 10 whose angle from the ground portion 4 is β
And an inner peripheral edge portion 11 continuous with the inner peripheral edge portion 11 and a small interval annular portion. In addition, the inner peripheral side connecting portion 10 and the rising portion 6 may be located on the same straight line or the same curved line in the cross section, and are respectively located on different straight lines or curved lines and are connected via the curvature change points. May be. This also applies to the relationship between the outer peripheral side connecting portion 8 and the outer peripheral bottom portion 5.

In FIG. 1, the inner peripheral edge 11 has a radius R _E.
And a connection portion 1 between the dome portion 7 and the rising portion 6
2 has a maximum radius R _M. Also, the body 2 has a radius R
have.

In FIG. 2, the inner peripheral edge portion 11 of the ground contact portion is shown.
Has a radius of curvature R ₁ and the outer edge 9 has a radius of curvature R ₂
And the ground portion 4 has a radius of curvature R ₃ . Also,
1 and 2, the connecting portion 12 has a radius of curvature R ₄ and the dome portion 7 has a radius of curvature R ₅ .

The dome portion 7 has a maximum height H _D at the center thereof.
And has a height H _M of the maximum diameter portion 12.

Further, the inner peripheral side connecting portion 10 or the rising portion 6 and the outer peripheral bottom portion 5 to the outer peripheral side connecting portion 8 have a dimension F in the radial direction at the portion 13 closest to each other. On the other hand, the inner peripheral edge portion 11 and the outer peripheral edge portion 9 have a G dimension (spacing) in the radial direction.

The plate thickness of the material is t, while the dome portion has a plate thickness t ₀ and the rising portion 6 has a plate thickness t ₁ .

In the can bottom portion 3 of the seamless can of the present invention, the circumferential grounding portion 4 is formed as a small-interval annular portion having an inner peripheral edge portion 11 and an outer peripheral edge portion 9; While connecting the outer peripheral side connecting portion 8 via the outer peripheral edge portion 9,
The angles α are made obtuse, the circumferential grounding portion 4 and the inner peripheral side connecting portion 10 are connected via the inner peripheral end edge portion 11, and the angles β are made acute; inner peripheral side connection Part 1
0 has an inverse taper shape in which the diameter increases in the height direction; when the radius of the inner peripheral edge portion 11 is R _E and the maximum radius of the dome portion 7 or its connecting portion 12 is R _M , R _M /
The ratio of R _E is set to 1.015 to 1.150, particularly preferably 1.050 to 1.100; the radius of curvature R ₁ of the inner peripheral side edge portion 11 is set to the plate thickness (t). 1 to 7 times,
Especially 1.5 to 2.5 times, the radius of curvature R ₂ of the outer peripheral edge
Is 3 to 20 times the plate thickness (t), particularly 4 to 10 times, and the radius of curvature R ₃ of the ground contact portion is 3.5 times or more the plate thickness (t), particularly 10 to 30 times. Is a characteristic
As a result, buckling of the bottom of the can can be prevented and the pressure strength can be significantly increased.

Please refer to FIG. 3 of the accompanying drawings. FIG.
Conventional bottom shape, that is, a bottom shape seamless can whose rising part is almost vertical (chin-free steel, thickness 0.1
8 mm) and a bottom shape as shown in FIGS. 1 and 2 and a seamless can in which the dimensions of each part are within the following ranges (see the example described later for detailed data), the pressure and the displacement of the bottom of the can It is a plot of the relationship. α = 120 °, β = 67 °, R _M / R _E = 1.05,
R ₁ = 3.0t, R ₂ = 5.0t, R ₃ = 15.0t.

According to the above results, the conventional bottom-shaped can has a pressure resistance of 7 kgf / cm ² as shown by the curve A.
While the bottom deformation is remarkable, the bottom-shaped can of the present invention has a compressive strength of 11 kgf / cm ² or more, which is improved by about 50%, as shown by the curve B, and the bottom deformation is high. Reveals the surprising fact that is suppressed to a small extent.

FIG. 4 is an enlarged view showing the actual change of the bottom shape when internal pressure is applied to the bottom-shaped can of the present invention. In FIG. 4, a solid line indicates respectively the shape is not applied pressure, state chain line applying a pressure of 8 kgf / cm ^2, a broken line indicates a state of applying a higher pressure of 11 kgf / cm ² . This result shows the following very interesting fact.

That is, as the internal pressure increases, the inner peripheral edge 1
1 deforms so that its radius R _E increases and the angle β of the inner peripheral side connecting portion 10 also increases, but in the bottom shape of the present invention,
At the same time, (1) the radius of curvature R ₂ of the outer peripheral edge portion 9 increases, and (2) the annular grounding portion 4 has a sufficient width G,
The inner peripheral edge portion 11 is deformed so as to extend downward, and (3) the dome portion or the connecting portion 12 thereof has a maximum radius R
_{Since M is} also drawn radially outward so as to increase, the maximum radius R _{M of the} dome portion, which is larger than the radius R _E of the inner peripheral edge 11 of the ground contact portion, is maintained, and a large pressure resistance against buckling is exerted. Is obtained.

In the present invention, the ratio R _M / R of the maximum radius R _M of the dome part or its connecting part and the radius R _E of the inner peripheral edge part 11
It is important that _E is in the above range, and if this ratio is lower than the above range, it tends to be difficult to maintain the state of R _M > R _E when the internal pressure is applied. On the other hand, making this ratio larger than the above range has processing restrictions.

Further, the reverse taper portion of the inner peripheral side connecting portion 10 is
The angle (γ = 90 ° -β) to the height direction is preferably 4 ° to 50 °, and particularly preferably 15 ° to 30 ° from the same viewpoint.

The inner radius of curvature R ₁ of the end edge 11, each of the radius of curvature R ₃ of the curvature radius R ₂ and the circumferential ground portion 4 of the outer peripheral edge portion 9 is also important to be in the above range, R _{If 1} is larger than the above range, it becomes difficult to form an inverse taper portion that satisfies the above conditions, and the pressure resistance decreases. If R ₁ is smaller than the above range, the corrosion resistance of the can will be significantly reduced. On the other hand, if R ₂ is larger than the above range, it becomes difficult to sufficiently extend the grounding portion downward when the internal pressure is applied, and the pressure resistance is lowered, and if R ₂ is smaller than the above range, the corrosion resistance of the can still remains. Is reduced. Further, if R ₃ is smaller than the above range, stability, slipperiness, and impact resistance when placed on the ground or the like deteriorates. In this connection, the width G of the inner peripheral edge 11 and the outer peripheral edge 9 in the circumferential grounding portion 4 is determined by the body radius R.
It is preferable that the width is 0.07 to 0.16 times.

In the present invention, the height of the maximum radius portion 12 of the dome portion 7 (H _M) is the maximum height of the dome portion 7 (H _D)
In the range of 10 to 40%, especially 15 to 25%, it is preferable from the viewpoint of preventing buckling.

Further, the seamless can of the present invention is also characterized in that the inner peripheral side connecting portion or the rising portion 10 is not substantially thinned by the processing, which results in excellent pressure resistance and content resistance. A combination is obtained. The plate thickness (t ₁ ) of the inner peripheral side connecting portion is 9 of the plate thickness (t ₀ ) at the center of the dome portion.
It is preferably maintained at 0% or more.

The position of the circumferential grounding portion 4 provided on the bottom of the can relates to both the upright stability during transportation and the pressure resistance, but the radius of the inner peripheral edge edge is R _E and the cylindrical body is When the radius is R, the ratio R _E / R is 0.60 to 0.85, especially 0.6
It is preferable for these properties that it is in the range of 5 to 0.80.

It is preferable in view of stackability of the can that the outer peripheral bottom portion 5 has a tapered portion whose diameter decreases toward the bottom (downward), and the angle with respect to the vertical direction is generally 10
It is preferably in the range of 45 °.

Further, in the inverse taper portion of the inner peripheral side connecting portion 11, a portion F closest to the outer peripheral side connecting portion 8 to the outer peripheral bottom portion 5 and a radial dimension F formed by the outer peripheral side connecting portion to the outer peripheral bottom portion.
Is preferably not more than 15 times the plate thickness in order to deform the dome portion or the connecting portion 12 thereof radially outward so as to increase the maximum radius R _M thereof.

The seamless can of the present invention can be manufactured by drawing a metal plate and then painting it. However, in view of corrosion resistance, at least the inner surface of the metal laminated plate of the organic laminate is coated. It is preferably formed by drawing. That is, the circumferential grounding portion 4 and the like of the seamless can of the present invention have a very small structure, but by using a laminate coated beforehand, the coating of the fine inner surface portion is also complete. .

[Material] In the present invention, as the metal for the seamless can, various surface-treated steel plates and light metal plates such as aluminum are used.

As the surface-treated steel sheet, a cold rolled steel sheet is annealed.
After that, 0.1 to 30% temper rolling or secondary cold rolling
Galvanized, tin plated, nickel plated, electrolytic black
One or two types of surface treatment such as mumic acid treatment and chromic acid treatment
What was performed above can be used. Suitable surface treatment
An example of a steel sheet is an electrolytic chromic acid treated steel sheet, and particularly 10
To 200 mg / m^Two 1 ~ 50mg with metallic chromium layer
/ M^Two With a chromium oxide layer (converted to metallic chromium)
This is a combination of coating adhesion and corrosion resistance.
It ’s excellent. Other examples of the surface-treated steel sheet include 0.5 to
11.2 g / m ^Two With a hard tin plate with the tin plating amount of
is there. This tin plate has a chromium content in terms of metal chromium.
1 to 30 mg / m^Two Chromic acid treatment or
It is desirable that chromic acid-phosphoric acid treatment is performed.

As still another example, an aluminum-coated steel plate plated with aluminum, pressure-welded with aluminum, or the like is used.

As the light metal plate, an aluminum alloy plate is used in addition to the so-called aluminum plate. An aluminum alloy plate excellent in corrosion resistance and workability has a Mn: 0.
2 to 1.5% by weight, Mg: 0.8 to 5% by weight, Z
n: 0.20 to 0.3% by weight, Cu: 0.15 to 0.45% by weight, and the balance is Al. It is desirable that these light metal plates have also been subjected to a chromic acid treatment or a chromic / phosphoric acid treatment such that the chromium amount becomes 20 to 300 mg / m ^{2 in} terms of chromium metal.

The thickness of the metal plate, that is, the thickness of the bottom of the can (t
B) generally has a thickness of 0.10 to 0.50 mm, though it varies depending on the type of metal, the use or size of the container, and in the case of the surface-treated steel sheet, 0.1) to 0. It is preferable to have a thickness of 0.30 mm, and in the case of a light metal plate, a thickness of 0.15 to 0.40 mm.

The material (blank) used for the seamless can according to the present invention is preferably a laminate in which at least the inner surface of the can is previously coated with an organic resin, from the viewpoint of resistance to contents.

Examples of the thermoplastic resin forming the side wall resin layer on the inner surface of the can include low-density polyethylene, high-density polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene or ethylene, pyropyrene, 1-butene, 4 -Polyolefin such as random or block copolymers of α-olefins such as methyl-1-pentene, ethylene / vinyl acetate copolymer, ethylene / vinyl alcohol copolymer, ethylene / ethylene / vinyl chloride copolymer, etc. Vinyl compound copolymer, polystyrene,
Acrylonitrile / styrene copolymer, ABS, styrene resin such as α-methylstyrene / styrene copolymer,
Polyvinyl chloride, polyvinylidene chloride, polyvinyl chloride / vinylidene chloride copolymer, polyvinyl compounds such as polymethyl acrylate and polymethyl methacrylate, nylon 6,
It may be a resin such as polyamide such as nylon 6-6, nylon 6-10, nylon 11 or nylon 12, thermoplastic polyester such as polyethylene terephthalate or polybutylene terephthalate, polycarbonate, polyphenylene oxide or the like, or a mixture thereof.

Among these thermoplastic resins, polyester resins are particularly suitable from the viewpoints of processability, corrosion resistance, and flavor retention of the contents.

The polyester resin used in the present invention is preferably a homopolyester or a copolyester derived from a dibasic acid mainly containing terephthalic acid and a diol mainly containing ethylene glycol.

As dibasic acids other than terephthalic acid, isophthalic acid, P-β-oxyethoxybenzoic acid, naphthalene-2,6-dicarboxylic acid, diphenoxyethane-
4,4'-dicarboxylic acid, 5-sodium sulfoisophthalic acid, hexahydroterephthalic acid, adipic acid, sebacic acid and the like can be mentioned.

Examples of diol components other than ethylene glycol include propylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexylene glycol, diethylene glycol, triethylene glycol, cyclohexanedimethanol, and ethylene oxide of bisphenol A. Mention may be made of glycol components such as adducts.

It is particularly preferable that the acid content of the copolyester is composed of terephthalic acid and isophthalic acid from the viewpoint of processability and mechanical properties, and from the viewpoint of flavor retention.
As the acid component, a small amount of another dibasic acid component, for example, an amount of 1 mol% or less is allowed to be contained, but it prevents adsorption of the flavor component and suppresses elution of the polyester component. It is desirable that at least the polyester layer on the inner surface of the container does not contain an aliphatic dibasic acid. The polyester containing isophthalic acid as an acidic component is characterized by having a large barrier effect against various components, flavor components and corrosive components, and having a small adsorptivity.

The diol component of the copolyester is preferably one mainly composed of ethylene glycol.
It is preferable that 95 mol% or more, particularly 98 mol% or more of the diol component is composed of ethylene glycol from the viewpoint of molecular orientation, barrier properties against corrosive components and odor components, and the like.

The homopolyester or copolyester should have a molecular weight in the range of film formation,
The intrinsic viscosity [η] measured using a phenol / tetrachloroethane mixed solvent as a solvent is 0.5 to 1.5,
Particularly, it is preferable that it is in the range of 0.6 to 1.5.

The polyester layer preferably used as the thermoplastic resin layer may be a layer composed of a homopolyester or a copolyester alone, a layer composed of a blend of two or more kinds thereof, or a polyester layer composed of two or more kinds. It may be a laminated body of.

The thickness of the thermoplastic resin layer used in the present invention is generally 2 to 100 μm, particularly 5 to 50 μm.
The range of m is good in terms of the metal protection effect and workability.

Of course, in this thermoplastic resin layer, a compounding agent known per se, for example, an antiblocking agent such as amorphous silica, a pigment such as titanium dioxide (titanium white), various antistatic agents, lubricants, Antioxidants, stabilizers and the like can be added according to a known formulation.

The laminate used in the present invention can be produced by thermally adhering the above-mentioned metal substrate and the thermoplastic resin film, or can be produced by extrusion coating the thermoplastic resin on the metal substrate. In order to enhance corrosion resistance and adhesiveness, in the case of a laminating method, a metal substrate or a thermoplastic resin film can be previously coated with an adhesive primer, and also in the case of an extrusion coating method,
An adhesion primer can be applied to the metal substrate in advance.

Thermoplastic resin films such as polyester films should generally be biaxially stretched. This is because the use of the biaxially stretched film improves the workability of the laminate and improves the heat resistance and barrier properties of the inner surface coating. The degree of biaxial orientation is determined by the X-ray diffraction method,
It can also be confirmed by a polarized fluorescence method, a birefringence method, a density gradient tube method, or the like.

Although not generally required, when a bonding primer is used, it is generally necessary to subject the surface of the biaxially stretched polyester film or the like to corona discharge treatment in order to enhance the adhesion to the film. desirable. The degree of corona discharge treatment is such that the wetting tension is 44 dy.
It is desirable that it be ne / cm or more.

In addition, it is also possible to subject the film to plasma treatment, flame treatment, or other known adhesion-improving surface treatment, or urethane resin-based or modified polyester resin-based adhesion-improving coating treatment. .

For example, when a thermoplastic resin film such as polyester-metal laminate is manufactured, a metal plate is used.
It is heated to a temperature (T ₁ ) higher than the melting point (T _m ) of the polyester to be used with a heating roll or the like and supplied between the laminating rolls. On the other hand, the polyester film is unwound from a supply roll and supplied in a positional relationship in which a metal plate is sandwiched between laminating rolls. The laminating roll is kept at a temperature (T ₂ ) slightly lower than that of the heating roll, and the polyester film is heat-bonded to both surfaces of the metal plate. A water tank containing cooling water for rapidly cooling the formed laminate is provided below the laminating roll, and a guide roller for guiding the laminate is arranged in the water tank. It is also possible to form a gap at a constant interval between the laminating roll and the cooling water, and to provide a heat-retaining mechanism in this gap so as to maintain the temperature within a constant temperature range (T ₃ ).

The heating temperature (T ₁ ) of a metal plate is generally T _m
-50 ° C. to Tm + 100 ° C., in particular the temperature of T _m -50 ° C. to T _m + 50 ° C. is appropriate, while the temperature T ₂ of the laminate roll, T ₁ -300 ° C. to T ₁ -10 ° C., in particular T ₁ range of -250 ° C. to T ₁ -50 ° C. is suitable.

In the case of the extrusion coating method, instead of pulling out the polyester film from the supply roll, the molten polyester may be pulled out from the extrusion die in the form of a film, and the same lamination may be performed by a laminating roll. In this extrusion coating method, the thermoplastic resin layer of the manufactured laminate is naturally in an unoriented state.

In the case of the extrusion coating method, the heating temperature (T ₁ ) of the metal plate is generally _Tm −150 ° C. to T _m + 50 ° C., while the temperature T of the laminating roll is T.
₂ is preferably in the range of 20 ° C to _Tm ° C.

The adhesive primer, which is optionally provided between the film such as polyester and the metal material, exhibits excellent adhesion to both the metal material and the film. A typical example of a primer coating having excellent adhesion and corrosion resistance is a phenol epoxy-based coating composed of a resol-type phenol aldehyde resin derived from various phenols and formaldehyde, and a bisphenol-type epoxy resin. In particular, phenol resin and epoxy resin
0:50 to 5:95 weight ratio, especially 40:60 to 1
It is a coating material contained in a weight ratio of 0:90.

The adhesive primer layer is generally provided in a thickness of 0.01 to 10 μm. The adhesive primer layer may be previously provided on the metal material or may be previously provided on the film such as polyester.

In the laminate used in the present invention, the inner surface of the seamless can is provided with the above-mentioned film of polyester or the like, and the outer surface of the seamless can is the inner surface. The same kind of film may be provided, or a can coating material known per se may be provided.

The external protective coating film is a thermosetting resin coating material such as phenol-formaldehyde resin, furan-formaldehyde resin, xylene-formaldehyde resin, ketone-formaldehyde resin, urea-formaldehyde resin, melamine-formaldehyde resin, alkyd resin, Unsaturated polyester resin, epoxy resin, bismaleimide resin, triallyl cyanurate resin, thermosetting acrylic resin, silicone resin, oily resin, or thermoplastic resin paint, for example, vinyl chloride-vinyl acetate copolymer, vinyl chloride -Maleic acid copolymer, vinyl chloride-
Examples thereof include maleic acid-vinyl acetate copolymer, acrylic polymer, saturated polyester resin and the like. These resin coatings may be used alone or in combination of two or more.

[Manufacture of Seamless Can] The seamless can of the present invention comprises a material for a seamless can, including a tubular body, a circumferential lower end, and an outer peripheral bottom connecting the tubular body and the circumferential lower end.
A step of press-molding into a cup provided with a rising portion that is substantially vertical inside the circumferential lower end portion and a dome portion connected to the rising portion; and while lowering the circumferential lower end portion while restricting the dome portion, Inward and radially inward, to form a circumferential grounding portion having a smaller diameter than the circumferential lower end portion, a projection portion composed of an inner circumferential side connecting portion with a rising portion and an outer circumferential side connecting portion with an outer circumferential bottom portion, In addition, it is manufactured by pressing the circumferential grounding portion and the dome portion to form an inverse taper in which the diameter increases in the height direction at the inner peripheral side connection portion or the rising portion.

The process up to the first stage in the manufacturing method of the present invention is the same as the conventional method for forming a can bottom, but the circumferential lower end obtained in this process is pushed downward and radially inward to form a circumferential shape. Forming a protrusion composed of a circumferential grounding portion having a smaller diameter than the lower end portion, an inner circumferential side connecting portion with the rising portion and an outer circumferential side connecting portion with the outer circumferential bottom portion, and the circumferential grounding portion and the dome portion formed. It is a remarkable feature to press and to form an inverse taper in which the diameter increases in the height direction at the inner peripheral side connection portion or the rising portion.

According to the present invention, not only can the seamless can having the above-mentioned unique bottom shape be manufactured by a simple process such as indentation, but also the respective parts of the bottom to be formed are not thinned. It has the advantage of being not only excellent in pressure resistance but also excellent in corrosion resistance. Further, there is also an advantage that the existing press equipment can be used for efficient production with only a slight modification of the tool or the like.

The tubular body of the seamless can of the present invention is formed by drawing the above-mentioned material between the punch and the die into a cup with a bottom and deep-drawing, and if necessary, bending and stretching in the deep-drawing stage. Alternatively, it is performed by further thinning the side wall portion of the cup by ironing. Drawing-redrawing is carried out by forming the material into a large diameter shallow drawing cup and then forming this shallow drawing cup into a small diameter deep drawing cup. That is, this drawing is carried out several times while gradually reducing the diameters of the punch and the die until the desired shape and the desired height / diameter ratio are obtained. At this time, the following equation So that the drawing ratio defined by is from 1.20 to 2.10, particularly from 1.30 to 1.90 by one-step drawing.
Further, it is desirable that the overall aperture ratio is set to 1.50 to 4.00, and particularly 1.80 to 3.80. When ironing the side wall, The ironing rate as defined by is 10 to 50%, especially 1
5 to 45%, and 40 to 80% as a whole, particularly 45 to 75%, are preferable.

In FIG. 5 showing an example of draw-ironing forming, a front draw cup 30 formed from a coated metal plate has an annular holding member 31 inserted into this cup and a re-draw ironing located below it. It is held by the die 32. Retaining member 31 and redrawing-redrawing coaxially with the ironing die 32 so that the holding member 31 can be moved in and out.
An ironing punch 33 is provided. The redrawing-ironing punch 33 and the redrawing-ironing die 32 are moved relative to each other so as to mesh with each other.

The redrawing-ironing die 32 has a flat surface portion 34 at the upper part thereof, and a working corner portion 35 having a small radius of curvature at the periphery of the flat surface portion, and is provided downward in the periphery connected to the working corner portion. Tapered approach portion 36 with decreasing diameter toward
Following the approach portion, a cylindrical ironing land portion (ironing portion) 38 is provided via a small curvature portion 37. Below the land portion 38, a reverse tapered relief 3
9 are provided.

The side wall portion of the front throttle cup 30 is bent radially inward from the outer peripheral surface 40 of the annular holding member 31 through its curvature corner portion 41, and is rejoined with the annular bottom surface 42 of the annular holding member 31. The corner portion 35 of the redrawing die 32 passes through a portion defined by the flat surface portion 34 of the drawing die 32.
Is bent almost perpendicular to the axial direction by the front squeezing cup 30.
Is formed into a deep drawn cup with a smaller diameter. At this time, in the working corner portion 35, the portion on the side opposite to the side in contact with the corner portion 35 is stretched by bending deformation, while the portion on the side in contact with the working corner portion 35 is the working corner portion 3.
After leaving 5, the sheet is stretched by the return deformation, whereby the side wall is bent and stretched to reduce the wall thickness. In FIG. 5 showing an example of drawing-ironing forming, a front drawing cup 30 formed from a coated metal plate includes an annular holding member 31 inserted in the cup and a re-drawing ironing die 32 located below the holding member 31. Held in. A redrawing-ironing punch 33 is provided coaxially with the holding member 31 and the redrawing-ironing die 32 so that the holding member 31 can move in and out. The redrawing-ironing punch 33 and the redrawing-ironing die 32 are moved relative to each other so as to mesh with each other.

The redrawing-ironing die 32 has a flat surface portion 34 at the upper part thereof, and a working corner portion 35 having a small radius of curvature at the periphery of the flat surface portion, and is provided downward in the periphery connected to the working corner portion. Tapered approach portion 36 whose diameter increases toward
Following the approach portion, a cylindrical ironing land portion (ironing portion) 38 is provided via a small curvature portion 37. Below the land portion 38, a reverse tapered relief 3
9 are provided.

The side wall portion of the front throttle cup 30 is bent from the outer peripheral surface 40 of the annular holding member 31 through its curvature corner portion 41 to the inside in the vertical direction, and is rejoined with the annular bottom surface 42 of the annular holding member 31. The corner portion 35 of the redrawing die 32 passes through a portion defined by the flat surface portion 34 of the drawing die 32.
Is bent almost perpendicular to the axial direction by the front squeezing cup 30.
Is formed into a deep drawn cup with a smaller diameter. At this time, in the working corner portion 35, the portion on the side opposite to the side in contact with the corner portion 35 is stretched by bending deformation, while the portion on the side in contact with the working corner portion 35 is the working corner portion 3.
After leaving 5, the sheet is stretched by the return deformation, whereby the side wall is bent and stretched to reduce the wall thickness.

The side wall portion thinned by bending and stretching is
Its outer surface comes into contact with the approach portion 36 having a small taper angle whose diameter gradually increases, and its inner surface is guided to the ironing portion 38 in a free state. The process of passing the side wall portion through the approach portion is a stage prior to the subsequent ironing process, and stabilizes the laminate after bending and stretching, and slightly reduces the diameter of the side wall portion to prepare for ironing. That is, the laminate immediately after bending and stretching has the effect of vibration due to bending and stretching, and distortion remains inside the film, which is still in an unstable state, and when this is immediately subjected to ironing, Although smooth ironing cannot be performed, according to this processing method, the outer surface side of the side wall portion is brought into contact with the approach portion 36 to reduce the diameter thereof, and the inner surface side is freed so that vibration It prevents the influence and alleviates the non-uniform strain inside the film, and enables smooth ironing.

The side wall passing through the approach portion 36 is introduced into the gap between the landing portion (ironing portion) 38 for ironing and the redrawing-ironing punch 33, and is rolled to a thickness regulated by this gap (C1). It The thickness C1 of the final side wall is determined to be 30 to 85% of the original thickness (t) of the laminate. The small curvature part 37 on the ironing part introduction side smoothly introduces the material to the ironing part 38 while effectively fixing the ironing start point, and the reverse tapered relief under the land part 38. 39 is for preventing an excessive increase in processing force.

The radius of curvature Rd of the curvature corner portion 35 of the redrawing / ironing die 32 should be 2.9 times or less of the wall thickness (t) of the material for effective bending and stretching. If the radius of curvature becomes too small, the laminate will break, so the thickness should be at least 1 time the wall thickness (t) of the laminate material.

The approach angle (1/2 of the taper angle) α of the tapered approach portion 37 should be 1 to 8 °. If this approach angle is smaller than the above range, orientation relaxation of the polyester film layer and stabilization before ironing will be insufficient, and if the approach angle is larger than the above range, bending and stretching will be uneven (return The deformation is insufficient), and in any case, the ironing process for giving the above-mentioned specific orientation to the polyester film becomes difficult without causing cracking or peeling of the film.

The radius of curvature Ri of the small curvature portion 37 should be not less than 0.3 times and not more than 20 times the wall thickness (t) of the material in order to effectively fix the ironing start point. If the radius of curvature becomes too large, the laminate will be scraped.

Although the clearance between the land portion 38 for ironing and the re-drawing-ironing punch 33 is within the range described above,
Generally, the land length L is preferably 0.5 to 3 mm. If this length is larger than the above range, the working force tends to be excessively large, while if it is smaller than the above range, the return after ironing is large, which is not preferable in some cases.

In the seamless can manufacturing method of the present invention, the bottom of the can can be molded by a two-step method or a one-step method.
The one-step method can be advantageously applied to a cup formed of a laminate material in which at least the inner surface of the can is coated with an organic resin. On the other hand, the two-step method can be advantageously applied to a case where a metal material is subjected to a high degree of ironing, and the ironing cup after the processing is subjected to degreasing cleaning, inner surface coating, and the like. In the case of the one-step method, a cylindrical punch, a dome holding tool that is accommodated in the cylindrical portion of the punch so as to be coaxially slidable and biased toward the tip of the punch, and can be moved in and out of the cylindrical punch. A doming die and a hold-down ring coaxial with the doming die and provided on the outer periphery of the doming die, the punch and the hold-down ring hold the outer peripheral bottom portion and relatively lower the peripheral lower end portion, rising portion, and The bottom of the dome is molded, and then the punch and hold down ring hold the outer peripheral bottom and raise it relatively, so that the lower peripheral edge is in the groove defined by the hold down ring and the outer surface of the doming die. It is preferable to push it in to form the ground portion and the inner and outer peripheral side connecting portions.

Further, in the two-step method, the push molding of the circumferential lower end portion is performed in a step different from the bottom molding step of the circumferential lower end portion, the rising portion and the dome portion. In this case, a dome holding tool that can be engaged with the dome portion of the cup, a cup outer peripheral side holder having a tapered support portion, and a bottom holder that forms a groove connected to the tapered outer peripheral side holder together with the cup outer peripheral side holder are prepared. It is preferable that the dome pressing tool is relatively lowered to press the peripheral lower end portion into the groove to form the ground contact portion and the inner peripheral side and outer peripheral side connecting portions. First, bottom molding by the two-step method will be described, and then bottom molding by the one-step method will be described.

The bottom forming apparatus used in the first step of the two-step method is, as shown in FIG. 6, a punch 5 inserted into and supported by a deep drawing cup or a deep drawing-ironing cup 50.
1, a hold-down ring 52 that supports the outer peripheral bottom of the cup 50 in cooperation with the punch, and a doming die 53. The punch 51 is cylindrical and has an outer surface 5
4, an inner surface 55, a tip 56 provided at the lower end on the inner surface side, and a taper portion 57 extending from the tip to the outer surface. The hold-down ring 52 has a tapered support portion 58 corresponding to the tapered portion of the punch, and an introduction portion 59 having a taper angle smaller than that of the tapered support portion on the outer peripheral side of the support portion. An extension portion 60 having a taper angle smaller than that of the tapered support portion is provided on the circumferential side. The doming die 52 has a dome portion forming surface 61 having a predetermined radius of curvature and an outer surface 62. Further, the doming die 53 uses the punch 5
It is provided inside the 1 and the hold-down ring 52 and can be freely inserted into and taken out of them. Punch 51
It should be understood that there is a clearance between the inner surface 55 of the cup and the outer surface 62 of the doming die 53 that is slightly larger than the wall thickness of the cup 50. Punch 5
It should be understood that at least one of 1 and the doming die 53 are connected to a hydraulic mechanism and a cam mechanism (neither shown), are axially drivable, and interengageable with each other. is there. Further, it should be understood that the hold down ring 52 is also supported by a spring, an air cushion mechanism, or the like, so that a constant pressing load is maintained between the hold down ring 52 and the punch 51.

The bottom portion of the outer periphery of the cup 50 is held by the taper portion 57 of the punch 51 and the taper support portion 58 of the hold-down ring 52 with a force (wrinkle pressing force) sufficient to prevent the generation of wrinkles. 51 and the doming die 53 are driven so as to mesh with each other. Thus, as shown in FIG. 7, the bottom of the cup is connected to the lower end 13 corresponding to the punch tip 56, the substantially vertical rising portion 6 connected to the inside of the lower end, and the inside of the rising portion. And the dome portion 7 is formed.

The bottom forming means in the first step is the same as the normal bottom forming, but the radius of curvature R _{pr of the tip} end portion 13 is formed in order to suppress the reduction of the thickness of the lower end portion 13 as much as possible. _The difference is that _e is taken large. In general, R
_It is appropriate that _pre is about 3 to 10 times, especially about 5 to 8 times the plate thickness t. The wrinkle holding force varies depending on the material and plate thickness, but is usually set to 300 to 2000 kg. Further, the portion of the holddown ring corresponding to the punch tip 56 is the extension portion 60 having a small taper angle, and since there is no restraint of the cup, the tip portion 13 is smoothly formed and the rising portion of the plate is also formed. Withdrawal is also effectively performed. Moreover, (the distance from leading edge portion to the dome vertex) bottom sink is effective to take a little deeper than the final shape of the dome height H _D of the final seamless can 1.
It is preferably about 1 to 1.4 times.

In the first step, the cup having the primary bottom shape is subjected to the second step after completion of various steps such as degreasing and cleaning, inner surface coating and baking. The bottom forming device used in the second step is, as shown in FIG. 7, a cup outer peripheral side holder 63, a bottom holder 64 and a dome pushing down tool 6.
It consists of five. The holder 63 on the outer peripheral side of the cup is
It is similar to the holddown ring 52 in the process,
A tapered support portion 58 corresponding to the tapered outer peripheral bottom portion 5 of the cup is provided, an introduction portion 59 having a taper angle smaller than that of the tapered support portion is provided on the outer peripheral side of the support portion, and an inner peripheral side of the support portion is provided. Extension 6 with a smaller taper angle than the tapered support
It has 0.

The bottom holder 64 has a horizontal portion 66 and a small-sized rising portion 67, which are spaced a small distance from the outer peripheral side. The horizontal portion 66 and the rising portion 67 are tapered extensions of the cup outer peripheral side holder 63. A groove 68 is formed in combination with the portion 60. Dome pushing tool 65
Is a concave support 6 that fits into the dome 7 of the cup
9, a falling portion 70 with a small interval smoothly connected to the end of the supporting portion, and a taper portion 71 outside the falling portion.
And consists of

The operation of bottom molding in the second step will be understood with reference to FIGS. 7 to 11.

First, in FIG. 7, the cup 72 formed in the first step of FIG. 6 is placed on the cup outer peripheral holder 58. At this point, the dome pushing tool 65 starts to descend.

In FIG. 8, the dome depressing tool 65 descends, and the supporting portion 69 contacts the dome 7.

In FIG. 9, the dome pushing tool 65,
Therefore, when the dome 7 is lowered, the most distal end portion 13 and the rising portion 6 of the cup 72 are guided by the extension portion 60 of the cup outer peripheral side holder 63 to start pushing so as to protrude into the groove 68.

In FIG. 10, the dome pushing tool 65
Is further lowered, and the tip end portion 13 pushed into the groove 68 reaches the flat surface portion 66 of the bottom holder 64.

In FIG. 11, the dome pushing down tool 65
Lowers to the lowest position and pushes down the dome 7 with the tool 65
The outermost diameter of the dome increases along the falling surface 70 of the dome, and the taper angle of the reverse taper portion of the inner peripheral side connection portion also increases.

With the above, since the final forming into the bottom shape is completed, the dome pushing down tool 65 may be raised and the processed cup may be taken out from the cup outer peripheral side holder 63 and the bottom holder 64. The bottom holder 64
The cup outer peripheral holder 63 and the cup outer peripheral side holder 63 may be formed separately or may be integrated.

Extension part 60 of cup outer holder 63
Is the groove 68 for the bottom tip 13 formed in the first step.
Although it acts as a guide for smoothly pushing in, it also defines the angle α (FIG. 2) of the outer peripheral side connecting portion 8 at the same time. On the other hand, the flat surface portion 66 of the bottom holder 64 defines the gap G between the inner peripheral edge portion 11 and the outer peripheral edge portion 9 and the radius R _E of the inner peripheral edge portion 11 (FIG. 2) in the circumferential ground contact portion 4. To do. Also, the fall portion 70 of the tool 65 depressed dome is to define the maximum radius R _M of the dome portion. Further, by adjusting the lowest point of the stroke of the dome pushing tool 65, the reverse taper angle β of the inner peripheral side connecting portion 10 can be defined, and the closest approach distance between the inner peripheral side connecting portion and the outer peripheral side connecting portion. It will be understood that F can also be defined.

As shown in FIG. 12, the bottom forming apparatus used in the one-step method comprises a punch 51 inserted into and supported by a deep-drawing cup or a deep-drawing-ironing cup 50, and a punch on the outer peripheral bottom of the cup 50. It comprises a holddown ring 52 that cooperates and supports it, a doming die 53 for forming a dome portion on the bottom of the can, and a dome pushing tool 65. The punch 51 has a cylindrical lower portion, and includes an outer surface 54, an inner surface 55, a tip 56 provided at a lower end on the inner surface side, and a taper portion 57 extending from the tip to the outer surface. The dome push-down tool 65 includes a concave support portion 69 that fits the dome portion 7 of the cup, and is provided so as to be able to move in and out of the space 75 in the cylindrical portion of the punch 51. That is, a bearing 76 is formed on the punch 51, and a bolt 77 passing through this bearing is embedded in the pushing-down tool 65. Thus, the push-down tool 65 is
Is slidable in the axial direction, and the sliding distance is regulated by the bolt head 78 and the stem 79. A push spring 80 is provided between the punch 51 and the push-down tool 65, and always pushes the push-down tool 65 downward.

The hold-down ring 52 has a tapered support portion 58 corresponding to the tapered portion of the punch, and has an introduction portion 59 having a taper angle smaller than that of the tapered support portion on the outer peripheral side of this support portion. On the inner peripheral side of the portion, an extension portion 60 having a taper angle smaller than that of the tapered support portion and a grounding portion forming portion 81 having a downward convex surface are provided. The hold-down ring 52 is supported on an elastic support mechanism such as the air cushion mechanism 82, and can follow the punch 52 under a certain pressure or more.

The doming die 53 has a dome portion forming surface 61 having a predetermined radius of curvature and an outer surface 62.
Further, the doming die 53 is provided inside the punch 51 and the hold-down ring 52, and is also capable of being put in and taken out relative to these. It should be understood that there is a clearance between the inner surface 55 of the punch 51 and the outer surface 62 of the doming die 53 that is slightly larger than the wall thickness of the cup 50. At least one of the punch 51 and the doming die 53 is connected to a hydraulic mechanism or a cam mechanism (neither is shown), can be driven in the axial direction, and can be engaged with each other.

The outer peripheral bottom of the cup 50 is held by the taper portion 57 of the punch 51 and the tapered support portion 58 of the hold-down ring 52 with a force (wrinkle pressing force) sufficient to prevent the generation of wrinkles, and the punch is punched. 51 and the doming die 53 are driven so as to mesh with each other. As a result, FIG.
The bottom 50 'of the cup and the doming die 5 as shown in
3 and 3 start to engage.

In the specific example shown in FIG. 12, the punch 51 and the hold-down ring 52 continue to descend while sandwiching the outer peripheral bottom of the cup. The supporting force of the hold-down ring 52 is a wrinkle pressing force in draw forming, and is generally set to 300 to 2000 kg, though it depends on the material and plate thickness. The dome pushing-down tool 65 inside the punch 51 is preloaded with about 200 kg by the spring 80. This spring can be replaced by an air cylinder, a nitrogen cylinder, an elastic body such as urethane rubber, or the like.

FIG. 13 shows a state in which the apparatus of FIG. 12 is at the bottom dead center of the press. In the steps up to this point, the bottom of the cup has a lower end 13 corresponding to the punch tip 56, a substantially vertical rising portion 6 connected to the inside of the lower end, and a dome portion connected to the inside of the rising portion. And 7 are formed. The molding up to this point is the same as that in FIG. 6, but there is a slight difference in that the inner surface side of the dome portion is pressed by the dome pushing tool 65. As in the case of the two-step method, by setting the radius R _pre of the bottom tip portion 13 to be as large as possible, the thinning of the rising portion 6 is suppressed, which is advantageous for pressure resistance. The radius of curvature R _pre and the bottom sink (the distance from the most distal end to the dome apex) of the tip portion 13 are the same as in the two-step method.

FIG. 14 shows the device of FIG. 12 just past the bottom dead center of the press. The bottom of the outer periphery of the cup is sandwiched between the punch 51 and the hold-down ring 52, and rises. After separating from 51, molding of the grounding portion of the cup and the connecting portions on the inner peripheral side and the outer peripheral side is started.

The hold-down ring 52 has a grounding portion forming portion 81 and a tapered extension portion 60, which are spaced a small distance from the outer peripheral side, and is combined with the outer surface 62 of the doming die 53 to form a groove 68. There is. The bottom portion of the outer periphery of the cup held by the punch 51 and the hold down ring 52 rises, and the dome 7 supported by the dome pushing down tool 65 is maintained in the original position, whereby the tip portion 1 of the cup 1
3 and the rising portion 6 are guided by the tapered extension portion 60 of the hold-down ring 52, and the pushing is started so as to protrude into the groove 68.

In FIG. 15, the bottom of the outer periphery of the cup is sandwiched between the punch 51 and the hold-down ring 52 and further raised, and the pushing process proceeds to the final stage, and the tip end portion 13 pushed into the groove 68 is The hold-down ring 52 reaches the grounded portion forming portion 81. At the same time, the rising portion 6 is deformed into a reverse taper shape, and the dome 7 is punched 5
Processing is performed so that the outermost diameter of the dome increases along the inner surface 55 of No. 1.

With the above, since the final forming into the bottom shape is completed, as shown in FIG. 16, the punch 51 and the dome pushing-down tool 65 may be raised and the processed cup may be taken out from the hold-down ring 52.

Extension 60 of hold down ring 52
Serves as a guide for smoothly pushing the bottom tip portion 13 formed in the step of FIG. 13 into the groove 68, and at the same time, the angle α of the outer peripheral side connection portion 8 (FIG. 2).
Is defined. On the other hand, hold down ring 5
Second grounding portion forming portion 81 and outer surface 62 of the doming die 53
In combination with, the inner peripheral edge portion 1 in the circumferential grounding portion 4
The distance G between 1 and the outer peripheral edge 9 and the radius R _E (FIG. 2) of the inner peripheral edge 11 are defined. In addition, the punch 51
Inner surface 55 defines the maximum radius R _M of the dome portion. Further, by adjusting the difference in stroke between the punch 51 and the dome pushing-down tool 65, the reverse taper angle β of the inner peripheral side connecting portion 10 can be defined, and the maximum difference between the inner peripheral side connecting portion and the outer peripheral side connecting portion can be defined. It will be understood that the approach distance F can also be defined.

According to the invention, the cans after draw forming and bottom forming can then be subjected to at least one heat treatment. This heat treatment has various purposes, and mainly includes removing residual strain of a film generated by processing, volatilizing a lubricant used for processing from a surface, and drying and curing a printing ink printed on the surface. Is the purpose. For this heat treatment, a heating device known per se, such as an infrared heater, a hot air circulation furnace, and an induction heating device, can be used. In addition, this heat treatment may be performed in one stage, or may be performed in two or more stages. The heat treatment temperature is suitably in the range of 180 to 240 ° C. The heat treatment time is generally on the order of 0.5 to 5 minutes.

If desired, the obtained can is subjected to one-step or multi-step neck-in processing and flange processing to obtain a can for tightening.

[0107]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the following examples.

Example 1 By heat-bonding a 0.020 mm-thick polyester film on both sides of a tin-free steel (electrolytic chromic acid treated steel plate) having a thickness of 0.18 mm and a tensile strength of 52 kgf / mm ^2. Punching the produced laminated steel plate into a circular blank with a diameter of 179 mm,
By a conventional method, a shallow drawing cup having a diameter of 115 mm and a depth of 42 mm was produced. The cup was thinned and redrawn as disclosed in JP-A-2-58822 twice to produce a cup having a diameter of 66 mm and a height of 126 mm and a flat bottom. This cup was press-molded in the first step of the bottom of the cup using a mold having the configuration shown in FIG. At this time, the hold down ring is supported from below by an air cushion, and its supporting force (wrinkle pressing force) is set to 1000 kgf. The main dimensions of the cup bottom thus formed are shown in FIG. Next, the second stage press molding was performed using the mold having the configuration shown in FIG. 7. The main dimensions of the cup bottom thus formed are as follows, which is the bottom shape in the final product. _{R = 33mm R E = 22.8mm R} M = 24mm R 1 = 0.6mm R 2 = 1.0mm R 3 = 3.0mm α = 40 ° beta = 23 DEG _{H M = 2.3mm H D = 12} . 0 mm F = 1.9 mm R _PRE = 15.5 mm Further, when the plate thickness t ₁ of the inner peripheral side edge portion was measured by the cutting method, it was about 101% of the blank plate thickness t ₀ , and the plate thickness reduction in this portion Was not seen. As a result of a pressure resistance test with this cup, the pressure resistance was 11.3 kgf / cm ² , which was higher than the guaranteed value (7.5 kgf / cm ² ).

Example 2 An aluminum alloy plate having a thickness of 0.26 mm (A3004H19; tensile strength of about 31 kg)
f / mm ² ) is punched out into a circular blank with a diameter of 140 mm, and the diameter is 85 m with a drawing punch and a drawing die according to a conventional method.
m cup was molded. This cup has a diameter of 66 mm and a height of 126 m by one-stage redrawing and three-stage ironing.
A cup for squeezing and ironing cans (DI cans) of m was produced. The punch in this step has a cylindrical tip portion and has a shape shown in FIG. Further, a hold-down ring and a doming die are arranged in front of the end of the stroke of this process as shown in FIG. The punch and doming die were engaged with each other to form the cup bottom. The hold down ring is supported from below by an air cushion, and its supporting force (wrinkle pressing force) is 500 kgf.
Set to. The shape of the molded cup bottom portion is the same as the shape after press molding of the first step in Example 1 (FIG. 1).
7). The open end of this cup was cut with a rotary blade to a height of 124 mm. Next, through the steps of degreasing, washing, and surface treatment, the outer surface of the can was painted / printed and the inner surface of the can was spray-painted by a known method. The same operation as in the second-stage molding in Example 1 was carried out except that this cup was used to obtain a cup having a bottom of a final shape. As a result of pressure resistance test with this cup, the pressure resistance is 8.4 kgf.
/ Cm ^2, which is higher than the guaranteed value (7.5 kgf / cm ² ). [Example 3] The blank thickness is 0.15 mm and the tensile strength is 50.
A cup having a final can bottom shape was obtained in the same manner as in Example 1 except that tin-free steel of kgf / mm ² was used. As a result of pressure resistance test with this cup, the pressure resistance is 8.0 kgf / cm ^2, which is a guaranteed value (7.5 kgf / cm ^2).
Values higher than cm ² ) were obtained.

[Example 4] The cup having a diameter of 66 mm, a height of 126 mm and a flat bottom, which was produced in the first half of Example 1, was press-molded by a mold having a structure shown in FIG. The preload applied to the dome pushing tool was set to about 250 kgf. The main dimension of the cup bottom formed by this is the same as the dimension after press-forming the second step in Example 1, and is the bottom shape of the final product. When the plate thickness t ₁ of the inner peripheral edge portion was measured by the cutting method, it was about 101% of the blank plate thickness t ₀ , and no decrease in plate thickness was observed at this portion. As a result of a pressure resistance test performed on this cup, the pressure resistance was 11.3 kgf / cm ² , which was higher than the guaranteed value (7.5 kgf / cm ² ).

[Comparative Example 1] A cup having a diameter of 66 mm and a height of 126 mm and a flat bottom, which was produced in the first half of Example 1, was cupped with a hold-down ring and a punch by using a mold having the structure shown in FIG. The punch and the doming die were meshed with each other while sandwiching the outer peripheral bottom to form a cup bottom. The hold down ring is supported from below by an air cushion, and its supporting force (wrinkle pressing force) is set to 1000 kgf. The main dimensions of the cup bottom thus formed are as shown in FIG. 18, which is the bottom shape of the final product. When the plate thickness t ₁ of the rising portion was measured by the cutting method, it was found that the thickness was reduced in this portion at about 85% of the raw plate thickness t ₀ . As a result of pressure resistance test with this cup, the pressure resistance is 7.1 kgf / c.
It was m ² and did not satisfy the guaranteed value (7.5 kgf / cm ² ).

[Comparative Example 2] Aluminum alloy plate having a thickness of 0.26 mm (A3004H19; tensile strength of about 31 kg)
f / mm ² ) is punched out into a circular blank with a diameter of 140 mm, and the diameter is 85 mm with a drawing punch and drawing die according to a conventional method.
Molded cup. This cup has a diameter of 66 mm and a height of 126 mm by one-stage redrawing and three-stage ironing.
A cup for squeezing and ironing (DI) can was prepared. The punch in this step has a cylindrical shape at the tip portion and has a shape shown in FIG. Further, a holddown ring and a doming die are arranged in front of the end of the stroke of this process as shown in FIG. The punch and doming die were engaged with each other to form the cup bottom. The hold down ring is supported from below by an air cushion, and its supporting force (wrinkle pressing force) is 500 kgf.
Set to. The shape of the molded cup bottom is the same as the bottom shape of the final product in Comparative Example 1 (FIG. 1).
8). The open end of this cup was cut with a rotary blade to a height of 124 mm. Next, through the steps of degreasing, washing, and surface treatment, the outer surface of the can was painted / printed and the inner surface of the can was spray-painted by a known method. As a result of a pressure resistance test with this cup, the pressure resistance was 6.1 kgf / cm ² , which did not satisfy the guaranteed value (7.5 kgf / cm ² ).

[Pressure resistance test method] With the cup filled with water, the open end is sealed with a plug provided with a water supply pipe. Next, pressurized water is sent from the water pump through the water pipe into the cup. The internal pressure of the cup rises, and at a certain point, the dome part instantly jumps and deforms so as to flip outward. Usually, the internal pressure of the can rapidly decreases at the same time as this jumping deformation. The maximum value of the internal pressure of the can during this period is the withstand pressure.

[0114]

According to the present invention, the grounding portion is formed at the bottom of the can via the inversely tapered connecting portion having a specific dimension, so that the material can be made thin and the pressure resistance can be remarkably excellent. It was possible to provide a seamless can having strength and corrosion resistance, and suppressing deformation of the container due to pressure to a small level, and a method for producing the same. Further, according to the present invention, by using the indentation molding, it is possible to mold a bottom shape having excellent pressure resistance without reducing the thickness of the bottom processed portion. Moreover, the molding of the bottom can be performed with a simple tool and a small number of steps. It became possible to do it efficiently.

[Brief description of drawings]

FIG. 1 is a sectional view showing a structure of a can bottom portion of an example of a seamless can according to the present invention.

FIG. 2 is a cross-sectional view showing an enlarged main part of a can bottom portion of the seamless can of FIG. 1 and explaining various dimensions.

FIG. 3 shows a conventional bottom-shaped seamless can (chin-free steel, thickness 0.18 mm) in which the rising portion is almost vertical, and a seamless can whose bottom is shown in FIGS. 1 and 2. It is the graph which plotted the relationship between the pressure and the displacement of the can bottom part.

FIG. 4 is a cross-sectional view showing, in an enlarged manner, an actual change in the bottom shape when internal pressure is applied to the bottom-shaped can of the present invention.

FIG. 5 is a cross-sectional view showing an example of an apparatus used for drawing-ironing.

FIG. 6 is a layout cross-sectional view of a bottom forming device used in the first step of the two-step method.

FIG. 7 is a layout cross-sectional view of the bottom forming device used in the second step of the two-step method, showing the first operation.

8 is a cross-sectional view showing a state where the dome pushing-down tool is lowered and the dome is brought into contact with the support portion in the apparatus of FIG. 7.

9 is a cross-sectional view showing a state in which, in the apparatus of FIG. 7, the tip of the cup and the rising portion of the cup have started to be pushed in so as to protrude into the groove when the dome pushing-down tool is lowered.

FIG. 10 is a cross-sectional view showing a state in which the dome pushing-down tool is further lowered in the apparatus of FIG. 7 and the leading end portion pushed into the groove reaches the flat surface portion of the bottom holder.

FIG. 11 is a cross-sectional view showing a state where the dome pushing-down tool is lowered to the lowest position in the apparatus shown in FIG.

FIG. 12 is a cross-sectional view of a bottom forming device used in the one-step method.

FIG. 13 is a cross-sectional view showing a state in which the punch has descended to the bottom dead center and the dome formation has ended in the apparatus of FIG.

14] In the apparatus of FIG. 12, the punch moves up a little from the bottom dead center, and
FIG. 6 is a cross-sectional view showing a state in which pushing has started so as to project into a groove.

FIG. 15 is a cross-sectional view showing a state where the punch further rises in the apparatus of FIG. 12 and the leading edge portion pushed into the groove reaches the flat surface portion of the groove.

16 is a cross-sectional view showing a state in which the punch is separated from the cup after the bottom molding is completed in the apparatus shown in FIG.

FIG. 17 is a cross-sectional view of the cup bottom portion showing the shape and dimensions of the cup bottom portion after the first-stage press molding in Example 1.

FIG. 18 is a cross-sectional view of the cup bottom portion showing the shape and dimensions of the cup bottom portion formed in Comparative Example 1.

FIG. 19 is a cross-sectional view of a cup bottom molding apparatus in Comparative Examples 1 and 2.

[Explanation of symbols]

 1 Seamless Can Body 2 Cylindrical Body Part 3 Can Bottom Part 4 Circumferential Grounding Part 5 Outer Perimeter Bottom Part 6 Rising Part 7 Dome Part 8 Inner Circumferential Side Connection Part 9 Inner Peripheral End Edge Part 10 Outer Circumferential End Part 11 Outer Peripheral Edge Part 12 Dome Part of the bottom part before final molding 13 Bottom end before final forming 30 Front draw cup 31 Ring holding member 32 Redrawing-ironing die 33 Redrawing-ironing punch 34 Plane part 35 Working corner part 36 Approach part 37 Small curvature Portion 38 land portion for ironing 39 reverse tapered relief 40 outer peripheral surface of annular holding member 41 curvature corner portion 42 annular bottom surface of annular holding member 50 deep drawing cup or deep drawing-ironing cup 51 punch 52 hold down ring 53 doming die 54 punch outer surface 55 inner surface 56 tip provided at the lower end on the inner surface side 57 taper portion 58 hold down refill Tapered support part 59 Introductory part 60 Extension part 61 Doming part dome part forming surface 62 Outer surface 63 Cup outer peripheral side holder 64 Bottom holder 65 Dome pushing tool 66 Bottom holder horizontal part 67 Rising part 68 Push-in groove 69 Concave support part of the dome pushing tool 70 Falling part 71 Outside taper part 75 Space inside the cylindrical part of the punch 76 Bearing 77 Bolt 78 Bolt head 79 Stem 80 Push spring 81 Grounding part forming part 82 Air cushion mechanism

Claims (16)

[Claims] 1. A tubular body portion, a circumferential grounding portion, an outer peripheral bottom portion connecting the tubular body portion and the circumferential grounding portion, a rising portion inside the circumferential grounding portion, and a rising portion. In the seamless can having a dome portion, the circumferential grounding portion has an inner peripheral end edge portion connected to an inner peripheral side connecting portion extending at an acute angle from the grounding portion and an obtuse angle at an angle from the grounding portion. It is composed of a small-interval annular portion having an outer peripheral edge portion that is continuous with the outer peripheral side connecting portion, and the inner peripheral side connecting portion or rising portion has an inverse taper shape whose diameter increases in the height direction, When the radius of the inner peripheral edge is R _E and the maximum radius of the dome is R _M , the ratio of R _M / R _E is 1.015 to 1.150.
, The radius of curvature R _{1 of} the inner peripheral edge portion is 1 to 7 times the plate thickness (t), and the radius of curvature R ₂ of the outer peripheral edge portion is 3 to 20 times the plate thickness (t). A seamless can having excellent internal pressure resistance, in which the radius of curvature R ₃ of the ground contact portion is in the range of 3.5 times or more of the plate thickness (t). 2. The seamless can according to claim 1, wherein the reverse taper portion of the inner peripheral side connection portion or the rising portion has an angle of 4 ° to 50 ° with respect to the height direction. Wherein the height of the maximum radius of the dome portion (H _M) is seamless can according to claim 1 or 2, wherein a 10 to 40% of the maximum height of the dome portion (H _D). 4. The plate thickness (t ₁ ) of the inner peripheral side connection part or the rising part is maintained at 0.9 times or more of the plate thickness (t ₀ ) at the center of the dome part. Seamless can described in either. 5. When the radius of the inner peripheral edge is R _E and the radius of the tubular body is R, the ratio R _E / R is 0.60 to 0.
The seamless can according to any one of claims 1 to 4, which is within a range of 85. 6. The seamless can according to claim 1, wherein the outer peripheral bottom portion forms a taper portion whose diameter decreases toward the bottom. 7. A portion (F) of the inverse tapered portion of the inner peripheral side connecting portion or rising portion that is closest to the outer peripheral bottom portion has a dimension (F) of 15 times or less the plate thickness in the radial direction with respect to the outer peripheral bottom portion. The seamless can according to any one of claims 1 to 6, which has. 8. The seamless can according to claim 1, wherein the seamless can is formed by drawing a metal laminate plate having at least an inner surface coated with an organic resin. 9. A material for a seamless can is provided with a tubular body portion, a circumferential lower end portion, an outer peripheral bottom portion connecting the tubular body portion and the circumferential lower end portion, and a substantially vertical portion inside the circumferential lower end portion. The peripheral lower end is press-molded into a cup having a rising portion and a dome portion connected to the rising portion, and the peripheral lower end portion is pushed downward and radially inward while regulating the dome portion. A circumferential grounding portion having a diameter smaller than that of the portion, an inner circumferential side connecting portion with the rising portion and an outer circumferential side connecting portion with the outer circumferential bottom portion, and a pressing portion pressing the circumferential grounding portion and the dome portion. Then, a method for forming a seamless can having excellent pressure resistance is characterized in that an inverse taper whose diameter increases in the height direction is formed on the inner peripheral side connecting portion or the rising portion. 10. The pressing of the peripheral lower end portion is held by holding the outer peripheral bottom portion of the cup by the tapered support portion of the holddown ring and the dome portion by a dome holding tool coaxial with the holddown ring. 10. The method according to claim 9, which is carried out by pressing and guiding into a groove that is continuous with the tapered support and has a diameter smaller than that of the lower circumferential end. 11. The method according to claim 9, wherein the push-molding of the circumferential lower end portion is performed in the same step after the bottom molding step of the circumferential lower end portion, the rising portion and the dome portion. 12. A cylindrical punch, a dome holding tool which is coaxially slidably accommodated in the cylindrical portion of the punch and is biased toward the tip of the punch, and can be moved in and out of the cylindrical punch. A doming die and a hold-down ring coaxial with the doming die and provided on the outer periphery of the doming die, the punch and the hold-down ring hold the outer peripheral bottom portion and relatively lower the peripheral lower end portion, rising portion, and The bottom of the dome is molded, and then the punch and hold down ring hold the outer peripheral bottom and raise it relatively, so that the lower peripheral edge is in the groove defined by the hold down ring and the outer surface of the doming die. The method according to claim 11, wherein the grounding portion and the inner and outer peripheral side connecting portions are formed by pushing. 13. The method according to claim 9, wherein the push-molding of the circumferential lower end portion is performed in a step different from the step of molding the circumferential lower end portion, the rising portion and the bottom of the dome portion. 14. A dome holding tool capable of engaging with a dome portion of a cup, a cup outer peripheral side holder having a tapered support portion, and a bottom holder forming a groove connecting to the tapered outer peripheral side holder together with the cup outer peripheral side holder. 14. The method according to claim 13, wherein the method is prepared, and the dome pressing tool is relatively lowered to push the lower circumferential end portion into the groove to form a grounding portion and inner and outer peripheral side connecting portions. 15. The lower circumferential edge has a thickness of 3 to 1 of the original thickness of the material.
The method according to any one of claims 9 to 14, which has a radius of curvature of 0 times. 16. The method according to claim 9, wherein the dome portion before the extrusion molding has a bottom sink of 1.1 to 1.4 times the bottom sink of the final seamless can.