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Publication numberUS3032448 A
Publication typeGrant
Publication dateMay 1, 1962
Filing dateMay 13, 1959
Priority dateMay 17, 1958
Publication numberUS 3032448 A, US 3032448A, US-A-3032448, US3032448 A, US3032448A
InventorsErich Tragner, Gustav Siebel, Karl Broockmann
Original AssigneeAluminium Walzwerke Singen
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Method for producing lacquered thin sheets of aluminum
US 3032448 A
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Description  (OCR text may contain errors)

It is well known to use sheets of aluminum or aluminum alloy in lacquered or unlacquered state as a substitute material for tin plate. ample of the fabrication of cans or boxes or bottle caps of the crown cork type, sheets of a thickness of at most 0.8 mm. and at least 0.1 mm., preferably between 0.25' and 0.35 mm, are required. The aluminum sheets which have been furnished till now for such purposes and which are produced in the form of a rolled strip have a mechanical strength below that of the tin plate, especially if they were used lacquered- If a hard rolled sheet of aluminum or an aluminum alloy with only a little amount of alloying constituents is used lacquered, whereby the varnish serves as protection against corrosion or as a priming coat for a plastic coating, the metal looses its mechanical strength during heating for drying or baking the varnish, so that its strength is not sufiicient for cans and crown corks. Sheets of highly alloyed aluminum, for example with magnesium, which have also in the annealed state considerable tensile strength, yield strength, elongation and hardness, are not suitable as a substitute material for tin plate in the making of mass produced articles such as cans and crown corks because of their higher price. The material of the sheet should not cost sensibly more than pure aluminum.

Our present invention relates to a method for producing lacquered thin sheets of aluminum, the mechanical properties of which correspond to those of tin plate of the same thickness and which may also compete in price with tin plate.

According to our invention an aluminum alloy containing at most 1.5% of one or more of the alloying constituents Mg, Si, Zn, Cr, Mn and Ti is solution annealed and quenched at least at the double end thickness, preferably at the 3- to 5-fold and thickness, is aged at roomtemperature or slightly increased temperature, for example at 40 to 60 C., in order to attain a natural aging effect, then rolled to end thickness, thereafter coated with the solution of a varnish giving a coating suitable for deep-drawing and finally heated for drying or baking the varnish, whereby in comparison to the cold rolled state not only the malleability but also the mechanical strength of the sheet is increased.

It the solution annealing is carried out at the double end thickness, the sheet becomes then cold rolled with a deformation degree of 50%; if the solution treatment is carried out at the fivefold end thickness, the cold rolling degree will be 80%. This value may be exceeded if the desired mechanical strength is still reached. 1

The aging for attaining a natural aging effect is preferably carried out until practically the state of full agehardening is reached. For example with an alurninum alloy with 0.4% Mg and 0.6% Si it is recommendable to choose an aging period of at least two days at room temperature, respectively somewhat shorter at a slightly increased temperature.

Preferably this alloy is aged at room temperature during 3 to 4 days. Of course a longer aging period is not detrimental as the material remains unchanged after aging. 7

There may be considered many aluminum alloys with If it is the question for eX- of crown corks.

strength and the hardness.

3,032,448 Patented May 1, 1962 a low content of alloying constituents, but for the practice of the present invention they must be harde-nable by a heat treatment. Very good results are obtained with sheets of an aluminum alloy containing about 0.3- to 0.7% Mg and 0.3 to 0.7% Si. The aluminum with a low content of alloying constituents may of course contain beside Mg, Si, Zn, Cr, Mn and Ti some; other elements in a low amount, provided that these other elements do not impair the result of the method according to the invention.

The sheet of aluminum alloy is preferably rolled and worked subsequently as a strip. After drying or stoving the varnish the sheet is cut, punched, divided in several increase results during cold rolling, but simultaneously the elongation is decreased. With an aluminum alloy containing 0.4% Mg and 0.6% Si the elongation drops to 6 t0 3%. In this state the malleability is not sufiicient for example for the deep drawing of cans or for the making But when the cold rolled sheet has been lacquered and is heated during 10 minutes, to 30 seconds at a temperature of 120 to 240 C. for drying or stoving the varnish it is subjected at the same time to a re laxation of the crystalline structure resulting in an increase of the elongation for example up to 10-15% and a subsequent increase of the tensile strength, the yield The improvement of the mechanical properties of the cold rolled sheet is combined with the drying or stoving of the lacquer coating.

It was already known to lacquer after solution annealing and quenching articles made of an aluminum alloy containing 0.6 to 1.4% Mg, 0.8 to 1.2% Si, 0.6 to 1.0% Mn and up to 0.3% Cr (known in Europe as AlMgSi) and to heat them thereafter in order to stove the varnish and to age the alloy at the same time. But it was the question neither of an aluminum alloy with a low content of alloying constituents nor of the lacquering and arof the several working steps: solution annealing, quenching, natural aging, cold rolling, artificial aging together withdrying and stoving the lacquer, it was possible to increase the tensile strength, the yield strength, the hardness and the elongation and also to dry the varnish. Without the natural aging after the solution annealing and quenching it is not possible to obtain a sufficient mechanical strength by artificially aging a sheet of an end thickness of for example 0.25 to 0.45 mm. if the sheet should be used for the fabrication of cans or crown corks.

The methodaccording to our invention presents besides the already mentioned advantages (steady improvement of the mechanical strength during the last working steps, combination of the artificial aging with the drying and stoving of the varnish) further advantages:

(1) The solution annealing and the quenching have not to be carried out at the end thickness of the sheet, but can be done at a considerable higher thickness. A hardening by solution annealing and quenching at an end thickness of for example 0.25 to 0.45 mm. is uneconomical, technically difiicult to be carried out and does not give the maximal values for the mechanical strength.

(2) Generally the surface of the hardenable aluminum alloys, even of the alloys with a low content of alloying constituents, shows a grey colour after solution annealing and quenching, which colour does not disappear during aging. But during the cold rolling of the aged material according to our invention the surface becomes bright again, what is very advantageous for the use of the material.

Example.--A strip of aluminum containing 0.4% Mg and 0.6% Si is solution annealed at an intermediate thickness of 1 to 1.5 mm. quenched in cold water and naturally aged, whereby the yield strength is increased from 4-6 kg./mm. up to 8-15 kg./mm. the tensile strength from about 10 up to about kgjmm. and the Brinell hardness from 20-30 up to -60 kg/rnmfi. During the following cold rolling to the end thickness of 0.3 mm. (deformation degree of to the yield strength rises to 2834 kg./mm. the tensile strength to 30-35 kg./mm. and the Brinell'hardness to -100 kg./rnm. In this state the elongation is only 3 to 4%, that means the malleability is insutiicient for example for the manufacture of crown corks. It now such a cold rolled sheet is then lacquered according to any known method and the varnish is dried by heating at a temperature between and 240 C., the elongation becomes considerably increased; its value may rise up to 15%, whereas yield strength and tensile strength do not decrease, but increase further by about 6 to 8% respectively 8 to 10%. The mechanical strength of the material obtained in this way corresponds to the strength of the usual tin plate of the same thickness.

What we claim is:

1. The method for producing lacquered thin, deformable sheets of aluminum with high mechanical strength comprising the steps of solution annealing and quenching to room temperature a rolled sheet of an aluminum alloy containing at least one of the constituents selected from a group consisting of Mg, Si, Zn, Cr, Mn and Ti, in an amount not to exceed 1.5% by weight, the said constituents being in such combination and amount that the alloy is hardenable by heat treatment, these annealing and quenching steps taking place at a thickness at least twice the desired ultimate thickness of the sheet; aging the sheet for attaining a natural aging effect; cold rolling the sheet to end thickness; covering the sheet with the solution of a varnish giving a coating suitable for deepdrawing and heating the lacquered sheet to 120 to 240 C. for drying or stoving the varnish, whereby not only the malleability but also the mechanical strength of the sheet become increased in comparison to the mechanical strength of the sheet in the cold-rolled state.

2. The method according to claim 1, in which the sheet is worked in strip form.

3. The method according to claim 1, in which the sheet is made from an alloy consisting of aluminum, 0.3 to 0.7% Mg and 0.3 to 0.7% Si.

4. The method according to claim 1, in which the sheet is cold rolled to a thickness of 0.8 to 0.1 mm.

References Cited in the file of this patent UNITED STATES PATENTS 1,083,903 Wilm Jan. 6, 1914 1,472,739 Archer et a1 Oct. 30, 1923 2,394,546 Harrington Feb. 12, 1946 2,695,253 Schaaber Nov. 23, 1954 2,837,450 Moore et a1. June 3, 1958 2,877,195 McNa-bb Mar. 10, 1959

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US1083903 *Mar 15, 1910Jan 6, 1914Alfred WilmProcess of improving alloys.
US1472739 *Dec 20, 1921Oct 30, 1923Aluminum Co Of AmericaAluminum-base alloy
US2394546 *Mar 28, 1942Feb 12, 1946Gen ElectricAluminum base alloy containing copper and beryllium and method of making the same
US2695253 *May 6, 1949Nov 23, 1954Otto SchaaberHeat treatment of aluminum alloys
US2837450 *Oct 26, 1953Jun 3, 1958Ici LtdMethod of bonding parts of light alloy heat exchangers
US2877195 *Apr 29, 1954Mar 10, 1959American Can CoVinylate fatty acid esters
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3314825 *May 20, 1963Apr 18, 1967Nat Res DevComposite metal structural components
US3935007 *Nov 13, 1974Jan 27, 1976Sumitomo Light Metal Industries, Ltd.Aluminum alloy of age hardening type
US4000007 *May 7, 1975Dec 28, 1976Cegedur Societe De Transformation De L'aluminium PechineyMethod of making drawn and hemmed aluminum sheet metal and articles made thereby
US4039355 *Feb 18, 1975Aug 2, 1977Riken Light Metal Industries Company, Ltd.Aluminum alloy shapes
US4174232 *Dec 22, 1977Nov 13, 1979Swiss Aluminium Ltd.Method of manufacturing sheets, strips and foils from age hardenable aluminum alloys of the Al-Si-Mg-type
US4457965 *Feb 4, 1982Jul 3, 1984Hunter Douglas International N.V.Process for lacquering articles & articles lacquered therewith
US4617339 *May 10, 1984Oct 14, 1986Hunter Douglas International N.V.Wear-resistant coating having plastic particles partially projecting; anticracking agents; flexibility
US5614037 *May 1, 1995Mar 25, 1997Mcdonnell Douglas CorporationCuring phenolic resin
US5858133 *Apr 26, 1996Jan 12, 1999Mcdonnell Douglas CorporationMethod for preparing pre-coated aluminum alloy articles and articles prepared thereby
US5894879 *Aug 5, 1997Apr 20, 1999Kaiser Aluminum & Chemical CorporationContinuous, one step process, strip/slab casting aluminum alloy feedstock, rolling, no intermediate heating, no recrystallization, rapid cooling to prevent precipitation of alloying elements, beverage cans and cups
US5922472 *Jan 12, 1998Jul 13, 1999Mcdonnell Douglas CorporationMethod for preparing pre-coated aluminum alloy articles and articles prepared thereby
US5944918 *Oct 7, 1996Aug 31, 1999Mcdonnell Douglas CorporationAircraft; applying phenolic resin, curing
US6221177May 5, 1999Apr 24, 2001Mcdonnell Douglas CorporationProviding aluminum-alloy article precursor; anodizing article precursor; applying curable organic coating material; heat-treating coated aluminum article precursor to its final heat-treated state
US6403230May 15, 2000Jun 11, 2002Mcdonnell Douglas CorporationAnodizing with chromic acid; solution treatment, annealing, deformation, and aging; heat treating curable, crosslinked phenolic resin
Classifications
U.S. Classification148/537, 427/388.1, 427/388.2, 148/697
International ClassificationC22C21/08, C22C21/06
Cooperative ClassificationC22C21/08
European ClassificationC22C21/08