EP3096897A1 - Method for producing a beverage can, a bottle-can or an aerosol can from aluminium alloy - Google Patents

Abstract

The invention relates to a method for producing a beverage can, a bottle or an aerosol can from aluminium alloy, by means of drawing and ironing using a non-circular blank, in which: the metal strip from which each blank is taken is divided virtually into identical regular hexagons of which two opposing sides are substantially perpendicular to the rolling direction of the strip, forming a compact flat hexagonal system; the periphery of the blank is calculated by adjustment starting with a concentric circle having a radius smaller than that of the inscribed circle of the corresponding hexagon, so as to compensate for the anisotropy of the metal during drawing, using a method known to persons skilled in the art; at least four ears are added, extending from and beyond the periphery in the free zones of the hexagon, of which the main axis forms an angle of substantially 35°, 145°, 215° and 325° with the rolling direction. The invention also relates to a beverage can, a bottle-can or an aerosol can made from a flank having the aforementioned features, including a shaped bottle-can or aerosol can, i.e. the main walls of which are not strictly cylindrical.

Description

 Process for manufacturing a beverage can, metal bottle or aluminum alloy aerosol can

Field of the invention

The invention relates to the field of aluminum alloy beverage cans, still known to those skilled in the art under the name "cans" or "beverage cans", but also metal bottles or "bottle-cans" and aerosol containers, manufactured by stamping-drawing, that is to say according to a process including in particular these two basic steps.

 The invention more particularly relates to a stamping process optimized for this type of application and having the particular advantage of avoiding the phenomenon called "pinched horns", well known to those skilled in the art, with the risk of breakage that it involves during subsequent stretching.

State of the art Aluminum alloys are increasingly used in the manufacture of beverage cans, also known as "cans" or "beverage cans", but also metal bottles or "bottle-cans" and aerosol containers, because of their very good aesthetic appearance, especially with respect to plastics and steels, their recyclability and their good resistance to corrosion.

All aluminum alloys referred to in the following are designated, unless otherwise indicated, in accordance with the designations defined by "Aluminum Association" in the "Registration Record Series" which it publishes regularly.

Beverage cans, or cans, still known to those skilled in the art under the name of "cans" or "beverage cans", are usually manufactured by drawing-drawing from alloy plates of the type 3104 in the state metallurgical H19. The sheet undergoes a first operation of cutting into blanks and stamping cups or "cups"; more specifically, during this step, the sheet metal coil feeds a press, also called "cupper", which cuts disks called blanks and performs a first stamping operation to produce cups also known as "cups"". This is the stage primarily concerned by the invention.

 The cups are then conveyed to a second press or "bodymaker" where they undergo at least a second stamping and several successive draws; these consist of passing the stamped blank by stretching rings in order to lengthen the metal and thin it.

 Boxes whose walls are thinner than the bottom are thus progressively obtained. These boxes are then processed in a machine that prints a rotary motion while a shear cuts at the desired height.

These are then washed in several cleaning and rinsing baths and dried.

 After coating, the beverage cans are then conveyed to a necking and edging station (or edging) also known as a "necker flanger" where the upper part of the preform undergoes several successive diameter narrowing and a border for the subsequent installation of the lid.

Metal cylinders and aerosol cans or aerosol cans, made of aluminum alloy, are traditionally made by shock spinning, from pawns from wheel casting.

 The first bottles of aluminum alloy, or "bottle-cans", made by drawing-drawing and then shrinking or "necking", appeared in Japan in 1993 and in Europe in 1995.

 This is evidenced by patent applications JP 7060386 of Toyo Rikagaku Kenkyusho of 1993 and EP 0740971 of Hoogovens under priority of 1995.

These bottles are however not monobloc structure. Indeed, the vertical walls and neck of the bottle are made from the bottom of the preform and a cover is crimped on the top of the preform. So is it also in the case of the application WO 01 15829, Daiwa Can in 2000 under priority of 1999, which claims an aluminum alloy bottle manufactured by hot forming with complex tooling.

 The manufacture of beverage cans, "bottle can" type bottles or aluminum alloy aerosol cans by essentially stamping-drawing and necking requires in fact a material capable in particular of:

 - Deep drawing, that is to say the formation of vertical wall cups and horizontal bottom, with stamping ratios, ie the ratio of the diameter of the blank to the diameter of the punch, up to 1.9 or more, with high necking deformations, in order to obtain a large diameter reduction in two press passes (stamping and re-stamping),

- And especially, object of this invention, provide cups or "cups" of good quality, that is to say, having no defects known to those skilled in the art under the name of "pinched horns" or folds, to avoid any breakage during subsequent stretching.

The first bottles of aluminum alloy, or "bottle-cans", of monobloc structure, and manufactured mainly by stamping-drawing then narrowed or "necking", were born in Japan in the 2000s. 2003082429 of Kobe Steel under 2001 priority.

 The same applies to the application EP 1870481 under priority of 2005 of the same Kobe Steel.

 This type of solution is also used in series, in particular in the United States.

However, it has the disadvantage of a non-optimal formability vis-à-vis the stamping, and also the necking or "necking".

 In particular, after stamping the cups or "cups" from circular blanks, the shape of the developed perimeter, known to those skilled in the art under the name of "horn profile", is not favorable.

This is indeed a six-horn profile, two positioned respectively at 0 and 180 ° of the rolling direction and four at 45 ° on either side of said direction, according to Figure 1. It happens that such a configuration, because of the horns at 0 and 180 °, presents a serious risk of giving rise to the so-called phenomenon "pinched horns" well known to those skilled in the art, with the risk of breakage during subsequent stretching.

To overcome this problem, the design and use in production of non-circular blanks for the manufacture of beverage cans are part of the state of the art. In this context, the objective is to compensate for the anisotropy of the metal by varying the diameter of the blank according to its orientation with respect to the rolling direction. This technology is advantageous because it increases the ratio between the amount of metal actually used in the beverage can and the amount of metal engaged on the flat metal, or strip.

 Such a typical design is perfectly described in particular in the article "Convolute Cut-Edge Design for an Earless Cup in Cup Drawing" by R. E. Dick, J. W. Yoon and F. Barlat, CP778 Volume A, Numishet 2005. Problem raised

The use of this type of non-circular blank unfortunately has the major disadvantage of making the stamping process much more sensitive to the less variability of metal anisotropy. Indeed, the cup or "cup" stamped, made from a non-circular blank, theoretically has a "flat" profile because the hollows and bumps were offset by the diameter variations of the starting blank. In this case, any variation in the anisotropy of the metal will inevitably generate a profile with uncontrolled horns of size and orientation. Thus, a modification of the anisotropy of the metal along the axis of rolling or orthogonally to this axis, will promote the appearance of 2 diametrically opposed horns, which is conducive to the phenomenon of "pinched horns" that the skilled person seeks absolutely to avoid.

Thus, the profile of the cup always has hollows and horns at the expense of the ratio between the amount of metal actually used in the beverage can and the amount of initial metal on the flat metal. The invention aims to solve these difficulties by providing a non-circular blank eliminating any risk of horn (s) pinch (s) during the stamping cups or "cups". Object of the invention

The subject of the invention is a method for manufacturing a beverage can, a bottle or an aluminum alloy aerosol can, by drawing-drawing followed by shrinking and / or folding, starting from a blank circular, according to which:

 The metal strip in which each blank is taken is virtually divided into identical regular hexagons, two opposite sides of which are substantially perpendicular to the rolling direction of said strip and constituting a flat compact hexagonal system,

 - The perimeter of said blank is calculated by adjusting from a concentric circle and radius less than that of the inscribed circle of the corresponding hexagon, to compensate, during stamping, the anisotropy of the behavior of the metal, according to a method known to those skilled in the art, typically as described in the article "Convolute Cut-Edge Design for an Earless Cup in Cup Drawing" by Dick RE, JW Yoon and F. Barlat, CP778 Volume A, Numishet 2005

 and characterized in that

 At least four horns are added beyond and from said perimeter, in the zones of the hexagon left free, or the main axis of which forms an angle of approximately 35 °, 145 °, 215 ° and 325 ° respectively with the rolling direction, each of a relative height of 0.3 to 0.8% relative to said concentric circle of departure, and a maximum width in view of the available space, is typically corresponding, halfway up the said horn , at a minimum angular sector of substantially 25 ° having at the top the center of the blank. The invention also relates to a beverage can draw blank, metal bottle or aerosol can manufactured by a method as described above.

It also relates to a drink-box or metal bottle, still known to those skilled in the art under the repetitive designations of "can" or "beverage can" and "bottle can" or "bottle type beverage can", made from a blank having the aforementioned characteristics, including a metal bottle called shape, that is to say whose main walls are not strictly cylindrical. It also relates to an aerosol can, also known to those skilled in the art under the name of "aerosol can" or "aerosol dispenser", made from said blank having the aforementioned characteristics, including an aerosol case said shape, that is to say whose main walls are not strictly cylindrical.

Description of figures

FIG. 1 represents the "horn profile", that is to say the shape of the developed perimeter of the top of the "cups" at the end of the first embossing, with, on the ordinate, the ratio of the horn height to the average height of the cup and, as abscissa, the angle a with respect to the rolling direction.

This profile, with horns in particular for a = 0 and 180 °, corresponds to a cup of the prior art without optimization. This is indeed a six-horn profile, two positioned respectively at 0 and 180 ° of the rolling direction and four at 45 ° on either side of said direction. FIG. 2 represents the starting metal band A as well as its virtual division into regular hexagons B in which the C blanks are taken.

The direction of rolling bears the mark D while the bandwidth bears the mark E. Figure 3 provides the same indications, with, in addition, the zones of the hexagon left free in F, G, H and I.

FIG. 4 represents a curve of the flat outer profile of the uniform circular blank with a radius of 69.3 mm (solid line) and optimized non-circular to take into account the anisotropic behavior of the metal according to the prior art (curve in dashed lines). On the ordinate, the radius R in mm and, on the abscissa, the angle formed with the rolling direction. FIG. 5 represents a curve (continuous with added cross patterns) of the flat outer profile of the noncircular blank according to the invention, designed by adding to the above variant four horns with a relative height equal to 0.35% of the radius of said variant.

 The variant with constant radius is always represented in a solid line and the blank of the prior art said optimal in dashed lines as in FIG.

FIG. 6 represents a curve (continuous plus cross-patterned) of the flat outer profile of the non-circular blank according to the invention, designed by adding to the "optimized" variant of FIG. 4, four horns of equal relative height at 0.57% of the radius of said variant.

 The variant with constant radius is always represented in a solid line and the blank of the prior art said optimal in dashed lines as in Figure 5.

FIG. 7 represents the profile curves of the cups obtained from the 4 blank variants, with, on the ordinate, the height H of the cup at the corresponding point with a pitch of 0.1 mm and in abscissa the angle formed with the rolling direction. : In solid curve, the profile of the cups obtained with a uniform circular blank of radius equal to 69.3 mm,

 Dashed curve, the profile of the cups with a noncircular blank of the prior art said "optimal",

 In curve with cross, the profile of the cups with an optimized non-circular blank according to the invention with 4 horns at 0.35%,

Curved with circles, the profile of the cups with an optimized non-circular blank according to the invention with 4 horns at 0.57%.

DESCRIPTION OF THE INVENTION The invention consists in a judicious choice of the non-circular blank design, optimized in two steps:

A first step of compensation of the anisotropy according to the prior art: It consists in compensating the effect of the anisotropy of the metal by varying the diameter of the blank according to its orientation with respect to the rolling direction, typically, and schematically, by increasing the radius of the blank along the directions corresponding to hollows on the profile of the cup, due to the anisotropy of the behavior of the metal during the first stamping step, and reducing it in the directions corresponding to horns or bumps on said profile. Such a typical design is perfectly described in particular in the article "Convolute Cut-Edge Design for an Earless Cup in Cup Drawing" by Dick RE, JW Yoon and F. Barlat, CP778 Volume A, Numishet 2005.

 A second step in which at least four horns are added beyond and from said perimeter, by increasing the radius of the blank in the areas beyond the additional hornless blanks and within the corresponding hexagon, following four directions symmetrical with respect to the rolling direction, as shown in FIG. 3 (zones F, G, H and I).

 More specifically, if virtually the metal strip in which each blank is taken into identical regular hexagons whose two opposite sides are substantially perpendicular to the rolling direction, thereby forming a planar hexagonal system, as shown in FIG. four horns are added beyond and from the perimeter, in the zones of the hexagon left free, or whose principal axis forms an angle respectively of approximately 35 °, 145 °, 215 ° and 325 ° with the direction of rolling, as shown in Figure 3, each of a relative height of 0.3 to 0.8% with respect to said concentric circle of departure, and a maximum width given the available space, typically corresponding to half-height said horn to a minimum angular sector of substantially 25 ° having the top of the center of the blank.

More specifically, the typical width at half height is equal to the length of the segment perpendicular to the radius joining the center of the blank and the top of the horn, and delimited by the intersection of the horn with a corner sector of substantially ° from the center of the flan. The Applicant has found that this optimization had the effect of repetitive to minimize the risk of defects known to the skilled person under the name of "pinched horns" and folds, to avoid any breakage during subsequent stretching. In its details, the invention will be better understood with the aid of the following examples, which are however not limiting in nature.

Examples

A Type 3104 alloy plate was continuously vertically cast. It was scalped and then homogenized at a temperature of about 580 ° C for about 3 hours before being hot-rolled and then cold-rolled. the final thickness of 0.264 mm is in the metallurgical state H19.

 "Cups" were made from this plate with a stamping cup diameter of 88.9 mm from flat profile blanks according to the following variants, all cut by laser:

Variants 1 and 2 outside the invention:

Variant 1 corresponds to a constant blank radius of 69.3 mm as shown in solid lines in FIG. 4, ie a circular blank without any optimization.

Variant 2 corresponds to a so-called "optimal" blank, that is to say "perfectly" compensating for the anisotropy of the behavior of the metal, according to a method known to those skilled in the art, such as that mentioned above reported in the article "Convolute Cut-Edge Design for an Earless Cup in Cup Drawing" by Dick RE, JW Yoon and F. Barlat, CP778 Volume A, Numishet 2005.

 It is represented in this same figure 4 by a curve in dashed lines.

Variant 3 according to the invention:

Variant 3 corresponds to a blank according to the invention, designed by adding to the above variant 2 four horns at 35 °, 145 °, 215 ° and 325 °, of a relative height equal to 0.35% of the radius of said variant 2 and a width at mid-height corresponding to a sector of 30 °.

It is shown in Figure 5 by a curve in a continuous line with added cross patterns. Variant 1 is always shown in a solid line and the blank of the prior art said optimum in dashed lines as in Figure 4.

Variant 4 according to the invention:

Variant 4 corresponds to a blank according to the invention, designed by adding to the above variant 2 four horns at 35 °, 145 °, 215 ° and 325 °, of a relative height equal to 0.57% of the radius of said variant 2 and a width at mid-height corresponding to a sector of 30 °.

It is shown in Figure 6 by a curve in a continuous line with added cross patterns.

 Variant 1 is always shown in a solid line and the blank of the prior art said optimum in dashed lines as in Figure 4. Results:

From these four variants of blanks, we made stamping cups with a stamping punch diameter of 88.9 mm for an average cup height of 32 mm.

Figure 7 shows the profile curves of the cups obtained from the 4 variants of blank:

 In a solid curve, the profile of the cups obtained with a uniform circular blank of radius equal to 69.3 mm.

 Dashed curve, the profile of the cups with a non-circular blank of the prior art said "optimal".

 In curve with cross, the profile of the cups with an optimized non-circular blank according to the invention with 4 horns at 0.35% according to variant 3.

Curved with circles, the profile of the cups with an optimized non-circular blank according to the invention with 4 horns at 0.57% according to variant 4. It is unambiguously observed that the blank of the prior art called "optimal" (dashed curve) compensates for the anisotropy of the metal because the amplitude of the profile curve goes from about 0.9 mm to less than 0.2 mm.

 On the basis of optimized profiles according to the invention, the additional 4 horns are clearly visible on the profile curves with cross and with round. The difference in height of the additional horns is correctly related to the difference in the initial horn heights.

 We also observe that the height of the artificial horns, in the case of the horn profile at 0.57% (curve with circles), largely exceeds the height of the horns related to the anisotropy (solid curve) and also reaches it in the case of the horns at 0.35% (curve with cross). Thus, the risk of seeing a 2-horn system appear, a system more sensitive to the phenomenon of "pinched horns", is clearly reduced, including with respect to the case corresponding to the dotted curve of the optimization according to the prior art, but also, negative values (hollow of the upper cup profile) are not recorded.

Claims

claims A method of manufacturing a canister, bottle or aluminum alloy aerosol can by drawing and drawing followed by shrinking and / or folding from a non-circular blank, wherein:  - The metal strip in which each blank is taken is virtually divided into identical regular hexagons whose two opposite sides are substantially perpendicular to the rolling direction of said strip and constituting a compact hexagonal planar system  - The perimeter of said blank is calculated by adjusting from a concentric circle and radius less than that of the inscribed circle of the corresponding hexagon, to compensate, during stamping, the anisotropy of the behavior of the metal, according to a method known to those skilled in the art,  and characterized in that  At least four horns are added beyond and from said perimeter, in the zones of the hexagon left free, or the main axis of which forms an angle of approximately 35 °, 145 °, 215 ° and 325 ° respectively with the rolling direction, each of a relative height of 0.3 to 0.8% relative to said concentric circle of departure, and a maximum width in view of the available space, is typically corresponding, halfway up the said horn , at a minimum angular sector of substantially 25 ° having at the top the center of the blank. 2. Bottle for drawing a beverage can, metal bottle or aerosol can, characterized in that it is manufactured by a process according to claim 1.