JP2019001500A - Pure-aluminum-made seamless can - Google Patents

Abstract

To provide a pure-aluminum-made seamless can which includes both properties of a can obtained through drawing and ironing processing and a can obtained through impact molding.SOLUTION: In a pure-aluminum-made seamless can 50 which has an aluminum content of 99.0 mass% or more, provided are a bottom part 53 and a trunk part 51. The standard deviation of Vickers hardness in the circumferential direction at the trunk part 51 is 1.4 or less, and/or the 60 degree specular glossiness at the outer surface of the trunk part 51 is 300% or more.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for producing a metal container.

Conventionally, drawn ironing (DI molding) has been widely adopted as a method for producing aluminum cans (for example, Patent Document 1).
This method uses a metal plate, punches this metal plate to produce a circular blank, and after drawing and redrawing the blank, ironing is performed to reduce the thickness, thereby forming a can body. It is a technique to do.

  This method has the advantage that the can body side wall and the bottom can be thinned, a can excellent in lightness can be obtained, and furthermore, a can with a high height and a glossy outer surface can be obtained. However, there is a drawback that punching waste is generated and material loss is large.

In addition to DI molding, a technique called impact molding is also widely adopted (see, for example, Patent Document 2). This method uses a thin disk-shaped slag, puts this slag between a die (female) and a punch (male), and extrudes metal (slag) by pressing, so it cans at once There is a merit that a can body can be obtained in one step per mold, but there is a drawback that the skin of the can body wall is extremely rough and it is difficult to obtain a glossy outer surface. In producing various can molds having different can diameters and heights by impact molding, two conventional methods can be exemplified. One is a method in which the diameter of the slag is set approximately equal to the diameter of the can, and the thickness of the slag is precisely set to a value calculated from the target can height and diameter. For this reason, there are disadvantages that a punching die is required for each diameter of the slag, and various types of base plates having different thicknesses need to be prepared.
Another way is to make a can-type slag with the highest can height among the cans with the same can diameter, then make an elementary can and trim it to the required height. This is a method of producing a can having a height, and there is a drawback that a can shape having a lower can height has a significant material loss.
In any case, punching waste is generated in the process of punching slag from the base plate, resulting in a large material loss.

  As described above, all the manufacturing methods have advantages and disadvantages, and the improvement is demanded at present.

By the way, as a manufacturing method in which the above problems are solved, the present applicant uses a metal rod, cuts the rod at a certain height, and produces a container slag. A method for producing a seamless container was proposed by impact molding, then drawing or redrawing as appropriate, and further ironing (Japanese Patent Application No. 2015-243928).
Such a manufacturing method has an advantage that containers of various sizes can be obtained according to the diameter and length of the obtained container with little material loss.

  As a result of further pursuing the above-described production method, the present inventors have investigated a can obtained by so-called squeezing and ironing, and a can obtained by impact molding, when producing a pure aluminum seamless can using such a method. It has been found that a unique seamless can with the characteristics of can be obtained.

Japanese Patent Publication No. 2-30930 JP-A-6-279888

  Accordingly, an object of the present invention is to provide a pure aluminum seamless can having the characteristics of a can obtained by drawing ironing and a can obtained by impact molding.

According to the present invention, in a seamless can made of pure aluminum having an aluminum content of 99.0% by mass or more,
It has a bottom part and a body part, the standard deviation in the circumferential direction of Vickers hardness at the body part is 1.4 or less, and / or the 60-degree specular gloss on the outer surface of the body part is 300% or more. A seamless can characterized by the above is provided.

The pure aluminum seamless can of the present invention (hereinafter simply referred to as a pure aluminum seamless can) is usually
(1) An inflection point existing at a boundary portion between the outer surface of the body portion and the outer surface of the bottom portion is a reference position, and the body portion has a tapered region in which the thickness gradually decreases upward from the reference position; A straight region that is continuous with the tapered region and has a constant thickness;
It has the form.

  The pure aluminum seamless can of the present invention is made of pure aluminum having an aluminum content of 99.0% by mass or more, but as one characteristic, the 60-degree specular gloss on the outer surface of the trunk is 300% or more, It has extremely high gloss. Such high gloss indicates that it is manufactured through drawing and ironing in addition to being formed from pure aluminum. That is, in the can obtained by impact molding, the outer surface becomes rough and such high glossiness cannot be obtained.

In addition, another characteristic of the pure aluminum seamless can of the present invention is that the standard deviation in the circumferential direction of the Vickers hardness at the trunk is 1.4 or less, and the variation in strength in the circumferential direction is extremely small and high. It is to show isotropic properties. Such isotropy is a property which is not recognized at all in a seamless can obtained by a conventionally known drawing and ironing process.
That is, in a seamless can obtained by using a rolled plate as a base material, punching out and drawing and squeezing it, the can body has anisotropy with respect to the rolling direction. It shows variations in strength. Therefore, there is little variation in the strength in the circumferential direction of the trunk, and the fact that it has isotropic properties means that the pure aluminum seamless can of the present invention is made of a slag produced by cutting a rod, not from a rolled plate. This means that impact molding was performed, and drawing and ironing was performed after this impact molding. This is because the circumferential direction of the body portion of the seamless can obtained by such a method does not show anisotropy.

As described above, the pure aluminum seamless can of the present invention has both a unique metallic luster obtained by drawing and ironing and a unique property of strength isotropic obtained by impact molding.
Further, such a pure aluminum seamless can has an advantage that it is manufactured with extremely little material loss.

The figure which shows to the process by which a cup-shaped molded object is produced when manufacturing the pure aluminum seamless can of this invention. The figure which shows the process of redrawing and ironing a cup-shaped molded object when manufacturing the pure aluminum seamless can of this invention. The schematic side sectional view and principal part expanded sectional view which show an example of the form of the pure aluminum seamless can of this invention. The schematic sectional side view and the principal part expanded sectional view which show the other example of the form of the pure aluminum seamless can of this invention.

<Manufacture of pure aluminum seamless cans>
Referring to FIGS. 1 and 2 showing the manufacturing process of the pure aluminum seamless can of the present invention, this seamless can uses a rod 1 (see FIG. 1 (a)), which is cut to a predetermined length. A disk-shaped slag 3 is produced (see FIG. 1 (b)), this slag 3 is subjected to impact molding (see FIG. 1 (c)), and finally obtained by redrawing and ironing (FIG. 1). 2).
In addition, the seamless can finally obtained is shown by 50 in FIG.

In the present invention, the rod 1 shown in FIG. 1A is manufactured by, for example, hot forging, cold forging, hot rolling, cold rolling, extrusion molding, pultrusion molding, casting, or the like. It has a round bar shape and is made of pure aluminum having an aluminum content of 99.0% by mass or more, such as A1070.
By using the rod 1 made of such pure aluminum, it is possible to develop an excellent high metallic luster by molding in the following steps, and the seamless can 50 obtained has excellent corrosion resistance. Become.

  The pure aluminum rod 1 (the diameter is indicated by t) is first cut at a position of height h as shown in FIG. A disc-shaped blank (slag) 3 having a bottom diameter t ′ and a height h ′ is formed.

In addition, as a means for cutting the rod 1, it can be performed by a known cutting method. For example, although not shown, a cutting method such as shearing that does not generate chips is preferable because of less material loss.
The diameter t ′ of the blank 3 is set slightly smaller than the inner diameter of the die 21 for impact molding which will be the next step.

When changing the dimensions of the target seamless can 50, the material can be changed by changing the cutting height h with the same rod, in addition to changing the diameter of the rod.
As a result, material loss can be greatly reduced, molding can be performed at a material utilization rate close to 100%, and can types can be easily changed.
If the height h is excessively large, plastic processing in the next step may be difficult, so the diameter t of the rod 1 is also an appropriate size according to the size of the seamless can 50 finally obtained. It is desirable that the height h be about twice or less the diameter t of the rod 1.

  Moreover, in order to produce the disk-shaped slag 3, the member to which the rod 1 is cut may be pressed in the height direction. For example, in the case of a rectangular container (not shown), the pressing direction may be changed. . In addition to the power press, a rolling machine, a forging machine, or the like can be used as an apparatus for pressing depending on the shape and dimensions of the slag.

  The slag 3 produced as described above is subjected to plastic working. Prior to this plastic working, annealing is performed to remove residual stress, recover coarse grains, and recover work hardened structure. For example, the slag 3 made of pure aluminum is softened by heating to about 350 to 500 ° C. and then gradually cooling. In addition, annealing can also be performed in the middle of the process of producing slag as needed.

The slag 3 produced as described above is subjected to impact molding.
In this impact molding, as shown in FIG. 1 (c), a cup-shaped molded body 11 is molded by impact extrusion of the slag 3 in the die 21 using a female die 21 and a punch 23. To do.
The outer diameter of the obtained cup-shaped molded body 11 is the same as the diameter t ′ of the slag 3.

  In this method, the cup-shaped molded body 11 can be used as a container as it is, but there are problems of surface roughness and surface smoothness, and metal gloss cannot be expressed. For this reason, as shown in FIG. 2, further drawing and ironing are performed, whereby the diameter is reduced and the thickness is reduced, and a high metallic luster can be realized.

  In addition, when the drawing is performed directly on the slag 3 described above, severe surface pressure is applied and it may be difficult to form. However, once the cup is formed into a cup shape by impact molding, the cup is drawn. By performing (redrawing molding), molding defects can be reliably avoided.

  In such drawing, as shown in FIG. 2A, a die 31 having an opening 25a having a diameter t1 (t1 <t ′) is used, and held by the redraw die 31 by a holder 35. By using the punch 37 to push the cup-shaped molded body 11 into the opening 25 a of the die 31, the bottomed cylindrical drawn molded body 13 is obtained. The outer diameter of the drawn body 13 obtained by this drawing is equivalent to the diameter t1 of the opening 25a and is smaller than the diameter t 'of the cup-shaped body 11 (or slag 3).

In the above-mentioned drawing, a rounded portion (curvature portion) is formed at the corner portion (the side holding the cup-shaped molded body 11) of the upper end of the opening of the die 31, and the cup-shaped molded body 11 is quickly formed. The punch 37 is pushed into the opening 25a of the die 31 without breaking, and the outer diameter of the punch 37 is equivalent to 2.5 times the thickness of the cup-shaped molded body 11, and the opening 25a It is set smaller than the diameter t1. In other words, thinning is hardly performed in this drawing process.
Such redrawing is performed a plurality of times as necessary, and further diameter reduction can be performed.

  The drawn compact 13 thus obtained is subjected to ironing as shown in FIG.

  In the ironing process, a plurality of ironing dies 33 a to 33 c are provided below the redraw die 31, and ironing using the ironing punch 37 is performed on the drawn compact 13 formed by drawing.

A stripper finger 39 and a doming die 43 are disposed below the final stage ironing die 33c, and the compacted body passes through the stripper finger 39 and is subjected to doming by the doming die 43. Thereby, a dome-shaped bottom is formed, and the intended pure aluminum seamless can 50 of the present invention is obtained.
The obtained pure aluminum seamless can 50 is pulled out from the punch 37 by the stripper finger 39 when the punch 37 is raised (not shown).

In the ironing process as described above, in FIG. 2, three ironing dies are arranged, and ironing is performed in three stages, but the number of ironing dies is limited to three. Rather, it can be an appropriate number depending on the desired degree of thinning, and can be ironed in one step with one die, or two or more dies can be formed. Arrangement and ironing can be performed in multiple stages. Of course, when a plurality of ironing dies are arranged along the machining direction and the ironing is performed in multiple stages, the inner diameter (machining diameter) becomes smaller as it goes downstream in the machining direction.
In any case, in the pure aluminum seamless can 50 of the present invention, the inner diameter of the last ironing die (die 33c in the example of FIG. 2) is substantially equivalent to the outer diameter t2 (t2 <t1) of the thinnest barrel part. To do.

In the ironing process, the lower portion of the punch 37 has a tapered shape, and the ironing process and the doming process using the punch 43 have a stable upright form in a grounded state. The bottom can be dome-shaped to be retained.
In the ironing process, an emulsion of a lubricating liquid or the like is used as a coolant, and the ironing process is performed while cooling with such a coolant flowing.

  As shown in FIG. 3, the pure aluminum seamless can 50 of the present invention thus obtained has a trunk portion 51 and a bottom portion 53.

The bottom 53 is thicker than the body 51, has a convex shape (that is, a dome shape), has a central portion 53a bulging upward, and a peripheral portion thereof. Is a grounding portion 53b, and an outer peripheral side of the grounding portion 53b is a slightly curved curvature surface 53c.
Since the bottom 53 has such a configuration, the pure aluminum seamless can 50 can be installed so that the upright state can be stably maintained.
In the present invention, the shape of the bottom 53 is not limited to the mode shown in FIG. 3. For example, as shown in FIG. 4, a chime portion 53 d may be formed between the grounding portion 53 b and the curvature surface 53 c. It is possible to think about this type of configuration as well.

The body 51 is a region whose outer surface rises upward from the bottom 53, and a boundary portion X (corresponding to the upper end of the curvature surface 53c) with the bottom 53 is an inflection point.
The body 51 has a tapered region Y in which the thickness gradually decreases from the reference position with the boundary X (inflection point) as a reference position, and this tapered region is formed. A straight region Z having a constant thickness is formed continuously to Y.
That is, the straight region Z is the thinnest portion, and the outer diameter t2 substantially corresponds to the inner diameter of the last ironing die (die 33c in FIG. 2) as described above. Yes.

The tapered region Y formed in the body portion 51 is unique to ironing processing performed by arranging ironing dies in multiple stages, and the ironing rate and die-punch clearance (gap) set in each stage. However, the straight region Z of the trunk portion 51 is usually thinned so that it is about 5 to 40 mm in length and about 10 to 60% of the thickness at the reference position X. Yes. If it is necessary to provide a plate thickness change in the straight region Z, it is also possible to provide a plate thickness change by slightly increasing or decreasing the diameter of the ironing punch at the corresponding position.
When the container is molded only by impact molding, such a tapered region Y is not formed, and the thickness of the trunk portion 51 is uniform.

The pure aluminum seamless can 50 of the present invention thus obtained is made of high purity pure aluminum having an aluminum content of 99.0% by mass or more, and is formed through drawing and ironing processing. The 60 degree specular glossiness on the outer surface of the body portion 51 (particularly, the outer surface in the straight region Z) is 300% or more, particularly 350% or more. Such high specular gloss is that the aluminum surface has a surface roughness represented by arithmetic mean roughness Ra (JIS B-0601: 2013) of 0.3 μm or less, particularly 0.1 μm or less, This is because the surface represented by the root mean square inclination angle Δq has an extremely smooth surface with an inclination of 6 ° or less, particularly 3 ° or less.
As described above, such a high metallic luster does not appear in a can obtained only by impact molding.

  Furthermore, the pure aluminum seamless can 50 of the present invention is not obtained by drawing and ironing using a rolled plate, but impact molding is performed on the slag obtained by cutting the rod 1 as a base material. It is obtained by drawing and ironing after being performed. Therefore, the trunk | drum 51 of this can 50 shows isotropic, and the standard deviation about the circumferential direction of the Vickers hardness measured about the trunk | drum 51 is 1.4 or less. In the seamless can obtained by squeezing and squeezing using a rolled plate, the circumferential direction of the body portion 51 exhibits anisotropy with respect to the rolling direction, so for such Vickers hardness, the variation in the circumferential direction is large, The standard deviation is large.

  As described above, the pure aluminum seamless can 50 of the present invention has high metallic luster and isotropic property, and variation in physical properties in the circumferential direction of the body portion 51 is extremely small.

  Such a pure aluminum seamless can 50 of the present invention can be applied as a can for soft drinks, beers, foods, aerosol products, etc., and trimming, inner / outer surface coating, outer surface printing, decorative processing as necessary. Neck-in processing, flange processing, bead molding, nozzle screw molding, and the like are performed, the contents are filled and the lid is attached, and the resulting product is commercially available.

<Experimental example>
A rod made of pure aluminum A1070 (20 mm diameter, 4 m length) with an aluminum content of 99.7% by mass or more is prepared, and this rod is cut and pressed to a length of about 20 mm, the diameter is 48 mm, the thickness Obtained a disk-shaped slag of about 3.5 mm.
This disk-shaped slag was annealed at 350 ° C. for 1 hour. The hardness of the annealed disc slag was HV20 in terms of Vickers hardness. This disk-shaped slag is impact molded to form a cup-shaped molded body having a bottom diameter of 48 mm, a bottom thickness of about 0.9 mm, an average side wall thickness of about 1.3 mm, and a height of about 27 mm. did. In molding, a draw forming lubricant was used.
The side wall of this cup had rough skin peculiar to impact molding.
Next, without removing the lubricant adhering to the cup-shaped molded body obtained above, it was drawn by a redraw mold, the bottom diameter was about 36 mm, the side wall thickness was about 1.4 mm, and the height was About 38 mm bottomed cylindrical drawn product was obtained.
Next, iron forming is performed in three stages using a water-based emulsion coolant and a die for ironing having a diamond film formed on the processed surface, the bottom diameter is about 35 mm, the side wall thickness is about 0.35 mm, and the height. Obtained a seamless can made of pure aluminum having a thickness of about 150 mm.

The obtained pure aluminum seamless cans were subjected to a hardness test at an intermediate position in the height direction of the trunk, and the average value obtained by performing a 32-point test at equal intervals in the circumferential direction of the Vickers hardness was HV40. 0, the standard deviation is 1.2 (test machine: MVK-G3, manufactured by AKASHI), and the 60-degree specular gloss on the outer surface of the body is 320 to 410% (measurement device: colorimetric color difference manufactured by Suga Test Instruments Co. Total SM-4).
Furthermore, using the remaining pure aluminum rod after the molding, a pure aluminum drawn iron can was repeatedly molded by the same operation. As a result, about 99% of the previously prepared pure aluminum rod could be used for the production of a pure aluminum seamless can, and material loss could be effectively avoided.

1: pure aluminum rod 3: slag 11: cup-shaped molded body 13: drawn molded body 15: ironed molded body 50: pure aluminum seamless can 51: trunk 53: bottom X: boundary between the trunk and bottom (reference) position)
Y: Taper area Z: Straight area

Claims (3)

In a seamless can made of pure aluminum having an aluminum content of 99.0% by mass or more,
A seamless can having a bottom part and a body part, wherein a standard deviation in a circumferential direction of Vickers hardness at the body part is 1.4 or less. In a seamless can made of pure aluminum having an aluminum content of 99.0% by mass or more,
A seamless can having a bottom part and a body part, and having a 60-degree specular gloss on the outer surface of the body part of 300% or more.   The inflection point existing at the boundary between the outer surface of the body part and the outer surface of the bottom part is used as a reference position, and the body part has a tapered region in which the thickness gradually decreases upward from the reference position, and the tapered region. The seamless can according to claim 1, wherein the seamless can has a straight region with a constant thickness.