FR2773819A1 - Aluminum-copper-manganese alloy for impact extruded and drawn aerosol can manufacture - Google Patents

Abstract

An aluminum alloy, having copper and manganese contents lying within a defined polygonal area in a compositional diagram having the Mn content as the abscissa and the Cu content as the ordinate, is new. An aluminum alloy has copper and manganese contents within the polygon ABCD defined, in a coordinate axis system with the Mn content (wt.%) as the abscissa (x) and the Cu content (wt.%) as the ordinate (y), by the points A: x = 0.075, y = 0.65; B: x = 0.50, y = 0.65; C: x = 0.35, y = 0.4; and D: x = 0.25, y = 0.4. An Independent claim is also included for aerosol cans of the above alloy made by impact extrusion, optionally followed by drawing, of blanks produced from continuously cast strip.

Description

i

  ALUMINUM ALLOY FOR AEROSOL CASE

FIELD OF THE INVENTION

  The invention relates to the field of aluminum alloys, and more particularly those

  intended for the manufacture of aerosol cans.

STATE OF THE ART

  Already known, in particular from Japanese application 1-149939 / 89, aluminum alloys comprising from 0.05 to 0.8% by weight of Cu and from 0.05 to 0.8% by weight of Mn. These alloys are suitable for the manufacture of aerosol packages spun by impact (impact extrusion) from pins, and which have improved resistance to pitting corrosion. According to this state of the art, the pins are obtained from strip by rolling to

hot, then cold rolling.

  In a manner known per se, the impact spun housings are then typically degreased, internally varnished and / or externally printed, treated in an oven so as to

  bake the inks and dry the varnishes, and finally conified.

PROBLEMS POSED

  The Applicant has searched for aluminum alloys which present an improvement

  mechanical properties, with a view to reducing the wall thickness of the aerosol cans.

  Furthermore, it sought alloys, preferably suitable for the manufacture of pins by continuous casting, and no longer by rolling alone, and preferably adapted to the

  manufacture of spun and drawn aerosol cans, not just spun.

DESCRIPTION OF THE INVENTION

  According to a first subject of the invention, the aluminum alloy, intended for the manufacture of aerosol cans obtained by impact spinning of pions of said alloy or by impact spinning of these pions followed by drawing, comprises copper and manganese, whose composition in Cu and Mn is located inside the defined polygon ABCD, in a system of coordinate axes with the content of Mn (% by weight) on the abscissa and that of Cu (% in weight) on the ordinate, by the coordinates of points A, B, C and D: abscissa (Mn%) ordinate (Cu%)

A 0.075 0.65

B 0.50 0.65

C 0.35 0.4

D 0.25 0.4

  the remainder being constituted by Ai and the inevitable impurities.

  This alloy composition has been found particularly suitable for the manufacture of

  pawns from continuous casting tape.

  With regard to the Mn contents, they above all aim to reduce the softening of the metal during the annealing of lacquers and varnishes of aerosol cans. The tests conducted by the applicant have shown that an Mn content situated below the limit imposed by the straight line AD would lead to a too large-grained pawn, ultimately leading to the formation of

  folds during conformation of the final aerosol. Furthermore, an Mn content of between

  below the limit imposed by the straight line AD would lead in addition to an aerosol of insufficient mechanical characteristics taking into account in particular the need to reduce the thickness of the walls of aerosol cans to significantly reduce the

metal costs.

  In particular when the Mn content is between 0.2 and 0.4% by weight, a strong anti-softening effect of Mn has been observed, which results in a very marked increase in mechanical characteristics. This effect is particularly remarkable in the case of alloys also containing Cu; indeed, these aluminum alloys with Cu soften very quickly: we can thus consider that the addition of 0.3% of Mn to an aluminum alloy 1050 (designation of the Aluminum Association) saves 15 MPa, while the same addition to a 1050 alloy containing 0.5% Cu saves 30 MPa. So, he

  a strong synergy between the Cu and Mn elements was observed.

  For high Mn contents, typically greater than 0.5%, the additional addition of Mn brings nothing because the alloy hardly softens anymore during the annealing of lacquers or varnishes of aerosol cans, and generally moreover, an addition of Mn above

  0.5% by weight only degrades the structure of the metal.

  With regard to the copper contents, the tests showed that it was advantageous, in order to obtain a high resistance to corrosion, for the Cu content to be less than 0.65% (ordinate of the line AB) , but that it is greater than 0.4% (ordinate of the straight line CD) to obtain a final aerosol with high mechanical characteristics in order to be able to reduce the thickness of the walls of aerosol cans.

DESCRIPTION OF THE FIGURES

  FIG. 1 represents the diagram of the compositions in the plane Ox, y, where the abscissa Ox represents the percentage by weight in Mn of the alloy of Al, and where the ordinate Oy

  represents the percentage by weight of Cu of the alloy of Al.

  The polygon ABCD delimits the domain of the Mn and Cu compositions of the alloys

aluminum according to the invention.

  The polygon EFGH delimits the preferred domain of the Mn and Cu compositions of

  aluminum alloys according to the invention.

  FIG. 2 is a qualitative illustration of the variation of the mechanical characteristics Rm (on the ordinate), as a function of the height H (on the abscissa) of the aerosol can obtained for the same starting pin, on the left part A of the diagram, as a function of the heat treatment time for baking varnishes and inks (on the abscissa), on the right-hand side B. Curve I corresponds to the impact spinning process, while curve II corresponds

  at a first stage Fi, of impact spinning, followed by a second stage of stretching EJ].

  Figure 3 is a sectional view of a continuous casting device "4R"> (1), supplied with liquid metal (2), for the manufacture of strip (3) intended for manufacture, by

  stamping, pins (4) having substantially the same thickness as said strip (3).

  FIGS. 4a to 4c are a schematic illustration of the preferred method according to the invention, comprising the transformation of a starting pin (4) (FIG. 4a) into a spun blank (5) (FIG. 4b), and the transformation of this rough (5) in an aerosol can (6) by

  drawing with reduction in thickness of the wall (7) of the blank (5).

  DETAILED DESCRIPTION OF THE INVENTION

  Preferably, the aluminum alloy according to the invention has a composition of Cu and Mn which is located inside the polygon EFGH defined by the coordinates of the points E, F, G and H (% by weight): abscissa ( % Mn) ordered (% Cu)

E 0.25 0.6

F 0.45 0.6

G 0.4 0.5

H 0.3 0.5

as shown in figure 1.

  The alloy compositions according to the invention are particularly advantageous when, on the one hand, the pins (4) are obtained from continuously cast strip (3) as illustrated in FIG. 3, and when, on the other hand , the pins are transformed into aerosol cans by a first step of impact spinning, followed by a second step

  drawing, as shown diagrammatically in FIGS. 4a to 4c.

  Figure 2 illustrates the advantages of this process on the mechanical characteristics (Rm).

  It should also be noted that the alloys according to the invention are less sensitive than the standard alloys or the alloys outside the invention, to the effects of the heat treatment (part B of FIG. 2) and to the reduction in the mechanical characteristics which results from this treatment. . Thus, the invention makes it possible to obtain aerosol cans having, as desired, either better mechanical characteristics and therefore resistance to higher internal pressure,

  or a smaller wall thickness, which corresponds to a saving of metal.

  The alloy according to the invention may, in addition to the elements Cu and Mn, comprise other elements: 0.005 to 0.05% by weight of Ti, from 0.2 to 0.5% by weight of Fe, and less than 0.2

% by weight of Si.

  The use of titanium is aimed at obtaining relatively fine-grained casting tape (3).

  As for the elements Fe and Si, they are most often impurities from aluminum. The Fe content results from the fact that this element, at a content greater than 0.2% by weight, plays a role in reducing the size of the grains, while beyond a content of 0.5% in weight, its effect is negative, because it annihilates the effect of manganese by trapping this element. Silicon is a simple impurity, the content of which must be kept below 0.2% by weight, otherwise the solubility of manganese will be reduced, which in particular leads to

larger grains.

  A second subject of the invention relates to the use of the alloys according to the invention for obtaining aerosol cans produced by shock spinning of pawns (4) of said alloy,

  said pins being obtained from continuously cast strip.

  Preferably, this second object relates to the use of the alloys according to the invention for obtaining aerosol cans produced by shock impact spinning (4) of said alloy and subsequent drawing of the blank (5) obtained, said pawns being obtained from

continuous casting strip.

  i As already indicated, the selection of alloys according to the present invention is particularly suitable in the case of pions obtained from continuously cast strip, and more particularly advantageous when these pions are transformed into

  aerosol cans by impact spinning followed by a stretching step.

  A third object of the invention consists of the aerosol canisters of an alloy according to the invention, obtained by impact spinning of pins (4) of said alloy, said pins being

  obtained from continuous casting tape.

  Preferably, this third object is constituted by aerosol canisters made of an alloy according to the invention, obtained by impact spinning of pions of said alloy followed by at least one step

  drawing, said pins being obtained from continuously cast strip.

EXAMPLES OF REALIZATION

  Pawns were produced in different aluminum alloys, as well as the corresponding drawn spun housings. The enclosures obtained have the following dimensions: - diameter: 45 mm - height: 290 mm - wall thickness: 0.28 mm e j. Weight composition Mechanical resistance Raw mechanical resistance of spinning after annealing of lacquers Fe Mn% Cu% Si% Rm (MPa) R0,2 MPa Rm (MPa) R0,2 MPa

1 0.24 0.5 0 0.15 188 175 184 172

2 0.22 O 0 0.16 165 150 148 136

3 0.26 0 0.55 0.12 201 186 180 167

4 0.3 0 0.25 0.14 190 175 168 149

0.35 0 0.1 0.18 173 161 157 142

6 0.28 0.3 0 0.12 178 164 172 160

7 0.26 0 0.7 0.13 210 196 188 172

8 0.38 0.5 0.5 0.18 208 194 204 190

  9 0.41 0.18 0.54 0.16 207 193 200 187

0.35 0.36 0.54 0.17 209 196 206 191

- - - - - _ _... L

  12 0.29 0.3 0.45 0.17 204 192 201 190

  Only tests 9 to 12 are in accordance with the invention.

  Ref. Corrosion resistance Shaping (spinning + drawing) Grain size, im Conformation aptitude! IcommeAI 1050 300 Folds 2 same 50 No folds 3 | idem 30 No pleats 4 idem 40 No pleats idem 40 No pleats 6 idem 220 Beginning of pleats 7 Stitching 30 No pleats 8 like AI 1050 300 Pleats 9 like AI 1050 70 No pleats like AI 1050 120 No pleats 11 as AI 1050 135 No folds 12 as AI 1050 120 No folds These comparative tests clearly show the advantage of the selection according to the invention since the alloy field alone makes it possible to obtain both high mechanical characteristics for the aerosol can after annealing of lacquers and varnishes, an absence of folds at conification, and good corrosion resistance, similar to that of an aluminum alloy casing little loaded with elements other than Ai, the 1050 alloy ( standard designation according to the Aluminum Association), the benchmark alloy for this type of application.

Claims (6)

  1. Aluminum alloy, intended for the manufacture of aerosol cans obtained by shock spinning of pions of said alloy or by shock spinning followed by drawing, comprising copper and manganese, whose composition in Cu and Mn is located inside the polygon ABCD defined, in a system of coordinate axes with the content of Mn (% by weight) on the abscissa and that of Cu (% by weight) on the ordinate, by the coordinates of the points A, B, C and D: ordered abscissa A 0.075 0.65 B 0.50 0.65 C 0.35 0.4 D 0.25 0.4   the rest being made up of AI and unavoidable impurities.   2. Aluminum alloy according to claim 1, the composition of Cu and Mn of which is located inside the polygon EFGH defined by the coordinates of the points E, F, G and H: ordered abscissa E 0.25 0.6 F 0.45 0.6 G 0.4 0.5 H 0.3 0.5   3. Alloy according to any one of claims 1 and 2 comprising from 0.005 to 0.05%   by weight of Ti, from 0.2 to 0.5% by weight of Fe, and less than 0.2% by weight of Si.   4. Use of the alloys according to any one of claims 1 to 3 for obtaining   aerosol cans manufactured by impact spinning of pions of said alloy, said pions   being obtained from continuous casting tape.   Use of the alloys according to any one of Claims 1 to 3 for obtaining   aerosol cans manufactured by shock spinning of pawns of said alloy and subsequent drawing of the blank obtained, said pawns being obtained from continuously cast strip.   6. Alloy aerosols according to any one of claims 1 to 3, obtained by spinning   by impact of pawns of said alloy, said pawns being obtained from continuously cast strip.   7. Alloy aerosols according to any one of claims 1 to 3, obtained by spinning   by impact of pawns of said alloy followed by at least one drawing step, said pawns being   obtained from continuous casting tape.