CA1235361A - Production of aluminum alloy sheet and articles fabricated therefrom - Google Patents
Production of aluminum alloy sheet and articles fabricated therefromInfo
- Publication number
- CA1235361A CA1235361A CA000476424A CA476424A CA1235361A CA 1235361 A CA1235361 A CA 1235361A CA 000476424 A CA000476424 A CA 000476424A CA 476424 A CA476424 A CA 476424A CA 1235361 A CA1235361 A CA 1235361A
- Authority
- CA
- Canada
- Prior art keywords
- article
- gauge
- sheet
- alloy
- aging
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Abstract
Production of Aluminum Alloy Sheet and Articles Fabricated Therefrom Abstract A process for producing Al-Mg-Si alloy sheet in T8 temper, including the steps of providing a sheet article of an intermediate gauge, solution heat treat-ing the article, naturally aging the article for at least one day, cold rolling the article to final gauge, and artificially aging it, wherein the artificial aging step is performed by heating the cold rolled sheet at final gauge to a predetermined temperature for a time shorter than that at which maximum yield strength would be achieved. The intermediate gauge is selected such that a reduction between about 25% and about 71% there-from is required to achieve the final gauge. The T8 sheet is characterized by strength and formability pro-perties suitable for production of one piece drawn and ironed can bodies and lids therefor, and for other purposes.
Description
~353~L
Production of Aluminum Alloy Sheet and Articles Fabricated Therefrom Background of the Invention This invention relates to processes for producing Al-Mg-Si alloy sheet and articles fabricated therefrom, and to the products of such processes.
Al-Mg-Si alloys as herein contemplated are alloys having a major content of Al and a minor content of My and Six and are exemplified by known alloys identified by Aluminum Association designations in the 6000 series, e.g. the alloys having Aluminum Association BAA) de-signa~ions 6009, 6010, 6011, 6061, and 6063. The term "sheet" is broadly used herein to mean rolled products, without limitation to any particular gauge;
thus it includes products at plate and foil gauges as well as products at conventional sheet gauges.
More particularly, the invention is directed to processes for producing Al-Mg-Si sheet in so-called To temper, which-is the temper achieved by performing sue-cessively the steps of solution heat treatment, quenching, cold working, and artificial aging, some-times with a natural aging period interposed between the quench after solution heat treatment and the following cold working step. It has heretofore been known to provide Al-Mg-Si products, including sheet, in To temper, for various purposes.
In one important specific aspect, to which de-tailed reference will be made herein for purposes of illustration, the invention is dlrecte~ to the pro-diction of aluminum alloy can body and lid stock, viz.
aluminum alloy sheet for forming one-piece drawn and ironed can bodies and can lids for such bodies, as well as to the formation of can bodies and lids from such sheet and to the articles thus formed.
- --353~
Presented metal cans as used for beverages such as soft drinks, beer and the like are commonly keenest-tuned of a seamless one-piece body (which includes the bottom end and cylindrical side wall of the can) and a top end bearing a ring or other opening device. The body is produced from a blank of cold-rolled aluminum alloy sheet (having a gauge, for example, of about 0.014 inch) by a now-conventional forming technique known as drawing and ironing, which involves drawing the blank into a cup and then passing it through a sue-cession of dies to achieve the desired elongated cry-lindrical body configuration, with a side wall of no-duped thickness relative to the bottom end. The top end is separately produced from another sheet aluminum alloy blank, by different but also conventional forming operations, and is secured around its circumference to the top edge of the side wall of the body to provide a complete can.
The severity of the forming procedure employed in producing a drawn-and-ironed can body as described above, and in particular the reduction in thickness of the can side wall (which must nevertheless be able to withstand the internal and external forces exerted on it in use), as well as the fact that the formed can is usually lacquered in an operation necessitating a strength-reducing exposure to heat, require a special combination of strength, formability, and tool wear properties in the alloy sheet from which the can body is made. Significant among these properties are multi-mate tensile strength, yield strength, elongation, endearing. Attainment of the requisite combination of properties is dependent on alloy composition and on the processing conditions used to produce the sheet.
Heretofore, a conventional sheet for can body blanks has been constituted of the alloy having the SLY
Aluminum Association designation AYE, and has been produced from conventionally direct-chill-cast ingot up to 24 inches thick by scalping and homogenizing the ingot, and successively hot roiling and cold rolling to the desired final gauge; often an anneal treatment is used between the hot and cold rolling operations, with the annealing gauge so selected that the amount of cold reduction to final gauge after annealing is about 85%, thereby to provide can body blanks in Hl9 (extra hard) temper. This practice imparts the combination of pro-parties currently required for commercial can body stock. The aluminum alloy designated AA 5182 is ox-pensively used for the manufacture of the can top ends or lids, can lid stock (sheet) of such alloy being pro-duped in a manner similar to that described above for production of AYE on body stock in that similar steps of direct chill casting; homogenization, hot rolling, annealing and cold rolling to the Hl9 temper are employed; cold rolling may also be performed be tweet the hot rolling and annealing steps. The final can lid stock, ego at a gauge of about 0.013 inch, is fag-queued and when formed into lids the lacquering operation again involving a stowing (heating) step.
Although satisfactory cans are provided my the foregoing conventional procedures utilizing different alloys for the body and lid respectively, it would be desirable to produce cans having both body and lid formed of the same alloy, to facilitate recovery and reuse of the metal when the cans are recycled. Such an alloy requires a combination of high strength and good formability. Aluminum alloy sheet having such a combination of strength and formability properties would be advantageous for use, at various gauges, in a wide variety of other applications as well.
~L%3S3~l Summary of the Invention .
The present invention broadly contemplates the provision ox a process for producing aluminum alloy sheet of predetermined final gauge, comprising the steps of ~rovidlng a sheet article of a heat-treatable Al-Mg-Si alloy (having a composition as defined below) at an intermediate gauge from which a reduction of be-tweet about 25% and about 71~ is required to achieve the predetermined final gauge; solution-heat-treating the sheet article at the intermediate gauge by heating and ~enc~g, for effecting it least Shelley ~n~lete Lyon of ye My Ed So therein; aster quenching, and without intervening heat treatment, naturally aging the sheet article by maintaining it at ambient temperature for at least about one day; a~tPr natural aging, and without intervening heat treatment, cold rolling the sheet article to the final gauge (i.e. with a reduction ox between about 25% and about 71~); and artificially aging the sheet article at the final gauge or increasing the yield strength thereof by heating the article to a prude-termined temperature for a time shorter than that no-squired to achieve the maximum yield strength attainable by artificial aging of the article at that predetermined temperature, and such that the % elongation value ox the article after artificial aging is within 20~ ox the maximum value attainable by artificial aging OX the sheet article at that temperature following the same extent of cold reduction performed after solution heat treatment. The alloys used in the process, in its broad-eat aspects, are those having a major content of I
and a minor content of jig and available So such that on a rectangular graph of % My slotted against % avail able Six the point representing tune lug and available at content lies within the area of a pentagon defined by the coordinates 0.2% Six I lug 0.2~ Six 0.9~ lug ~2353~i~
0~4% Six Lo lug 1.2~ Six 1.2~ go and 1.2% Six 0.4~~g, all composition percentages here and elsewhere set forth in the present specification being expressed as percentages by weight. As used herein, the term "avail-able Six means So which has not been taken up by Fish is ordinarily present in the alloy. It is usual to assume that a percentage of So equal to one third or the Fe content is lost to the inter metallic compounds.
Thus, with this assumption made, the available So con-tent of an alloy (in weight percent) is equal to teetotal So content of the alloy (in weight percent) less one-third of the Fe content (in weight percent).
The process of the invention differs from pro-seeders heretofore known (for producing Alms So en-tides in To temper) in that, in the artificial aging step, heating is terminated before the article attains its maximum yield strength. Specifically, it has now been found that when a solution-heat-treated and worn-hardened Al-Mg-Si sheet is heated to effect artificial aging, the formability (represented by % elongation) as well as the yield strength initially increases at-though with continued heating, the % elongation begins to decrease at a time when the yield strength is still increasing. Thus, termination OX artificial aging be-fore the peak yield strength is reached affords beneficial improvement in strength without substantial imp paramount of formability, and indeed, in many cases, with actual enhancement of formability.
More particularly, the steps of natural aging after solution heat treatment, subsequent cold rolling between about 25% and about 71%, and artificial aging with observance of the special conditions just de-scribed, cooperatively provide artificially aged sheet having a superior combination of strength and format ability properties. In one specific sense, the process ..
~23S36~
of the invention further includes the step of forming the artificially aged sheet article into a component of a can, viz. a one-piece drawn and ironed can body have in an open end or a lid for closing the open end. In some instances, the stowing (heating) operation per-formed after lacquering of the lid stock may be con-dueled under conditions selected to constitute the anti-filial aging step of the present process, although it is at present preferred to perform the artificial lo aging on the sheet stock prior to lacquering. As will be understood, in these embodiments of the process of the invention, tile predetermined final gauge to which the sheet is reduced before artificial aging is a de-sired and e.g. conventional gauge for can body or lid stock. Advantageously, the invention can be embodied in a process for the production of cans wherein both lid and body are fabricated of sheet of the same alloy produced by the foregoing sequence of steps so that the metal of the can (when recycled) may be remelted and reused to produce new can bodies and lids without major adjustment of alloy composition.
In a broader sense, the sheet products of the in-mention may be produced at various final gauzes, since the combination of strength and formability achieved by the present process is beneficial for diverse uses.
A preferred upper limit of final sheet gauge for pro-ducts of the present process is l/2 inch.
Preferably, the alloy composition employed in the practice of the invention is selected to have at least a slight excess of available So over that statue-metrically required for combination (as Mg2Si) with all the 21g present, and (especially for production of can body or lid stock) the amount of My in the alloy it selected to insure a total Mg2Si content between about 1.35 and about 1.50~. Preferably also, the amount of -`
~23S3~
cold reduction between solution heat treatment and artificial aging is at least about 35~, and most pro-fireball (again, for production of can body and lid stock) the amount of such cold reduction is between about 50 and about 71%, this condition being provided by appropriate selection of the aforementioned inter-mediate gauge with reference to the desired predetex-mined final gauge.
The invention also embraces sheet articles, and lo can components, produced by the foregoing process, and possessing the advantageous combination of mechanical properties thereby achieved.
Further features and advantages of the invention will be apparent from the detailed description herein-below set forth, together with the accompanying draw-ins.
Brief Description of the Drawings Fig. 1 is a rectangular graph on which % My is plotted against available Six in illustration of the ; My and available So content of alloys suitable for the practice of the present invention;
Fig. 2 is a rectangular graph of ultimate tensile strength (US), yield strength (YE), elongation and Erickson cup depths of artificially aged (To temper) AYE alloy sheet, plotted against artificial aging time, for sheet subjected to 35~ cold reduction after solution heat treatment, to a final gauge of 0.030 inch, and then artificially aged at 160C.
Fig. 3 is a graph similar to jig. 2 for AWAIT
sheet subjected to 71% cold reduction after solution heat treatment, to a final gauge of 0.0135 inch, and then artificially aged at 160C: and Fig. 4 is a graph similar to Figs 2 and 3 for AYE (To) sheet subjected to 71% cold reduction after solution heat treatment, to a final gauge of 0.0135 inch, and then artificially aged at 185%C.
Detailed Description The invention will ye described, with reverence to the drawings, as embodied in a process for product in Al-Mg-Si alloy sheet from reroll stock by the sue-cessive steps of providing a sheet article of inter-mediate gauge, solution heat treating, natural aging, - cold rolling, and artificial aging, and in the pro-ducts. of that process. Par oculars of the alloys em-plowed, the preparation of the reroll stock, the per-pheromones of each of the aforementioned steps, and their combination in the complete. process, are set forth below.
35.3~S~
g Alloy Composition , . . . .
Alloys suitable for the practice of the present invention broadly include Al-Mg-Si alloys having a minor content of My and available So such that on a S rectangular graph of % My plotted against available So (i.e. the graph of Fig. 1) the point representing the My and available So content of the alloy lies within the area of pentagon 10 in Fig. 1, Vim. a pentagon de-fined by the coordinates 0.2% Six 0.4~ My; 0.2~ Six C.9~ My; 0~4~ Six 1.2~ My; 1.2% Six 1.2% My; and 1.2~
Six 0.4~ My. referred alloy compositio~s,within this broad definition, are those or which the point repro-setting My and available So content lies not only within the aforesaid pentagon but also to the right of a line 12 which represents the theoretical Mg2Si weight ratio, i.e. McCoy = 1.73/1. Preferably, also, the alloy con-sits essentially of My and available So in amounts (~) defined by pentagon 10, optionally also containing up to 0.9% Cut up to lo Fe, up to 0.8~ Len, up lo 0.35% Or, up to 0.25% Zen, up to 0.20% Tip balance essentially Al with usual impurity levels not materially affecting the combination of strength and formability properties with - which the present invention is concerned Specific examples of known alloys within the foregoing broad definition, and suitable for the pray-lice of the invention are the alloys having the Aluminum Association designations AA 6009, 6010, 6011, 6061, and 6063, the registered compositions of which are as follows:
~2353~
Range or Maximum (% by weight) __ . . _ . _ . .
AYE AYE AYE AYE AYE
. . _ So 0.6-L.0 0.8-1.2 0.40-0.8 aye Fe 0.50 0.50 0.7 0.35 1.0 Queue 0.15-0.6 0.15-0.40 0.100.40-0.9 My 0.20-0.8 0.20-0.8 Owls 0.10 0.8 My 0.40-0.8 0.6-1.0 0.8-1.2 0.45-0.90.6-1.2 Or 0.10 0.10 0.04-0.35 0.100.30 Zen 0.25 0.25 0.~5 0.10 1.5 1.0 To 0.10 0.10 0.15 0.100.20 No - - - - 0.20 other (each/
total) 0.05/0.15 0.05/0.15 0.05/0.15 0.15/0.15 0.05/0.15 Al balance balance balance balance balance Alloys with the composition limits of AYE as given above are particularly-preferred, especially for em-bodiments of the invention providing drawn-and-ironed- --can body stock and can lid stock; currently most pro-furred for these embodiments is an alloy having the nominal composition 0.25% Fe, 0.30% Cut 0.65~ Six 0.05~ (max.) I, 0.90~ My, Mecca.) Zen, 0.17~ Or, 0.25~ (max.) Tip other 0.10% (max.), balance aluminum, the designation "(Mecca' being used to indicate that the value given is a maximum and that the element so design noted is merely optional or tolerable as an impurity up to the stated maximum. For good age-hardening response, the alloy should contain a slight excess of available So (at least about OOZE) over that needed to statue-metrically form Mg2Si with a weight ratio McCauley of 1.73/1; as mentioned above, when making this calculi-lion, it is usual to assume that a percentage of the total So content equal to 1/3 of the Fe content is lost to the inter metallic compounds It is also usual with AYE to ensure a total Mg2Si content between about lo 35 and about 1.50.
. ' .
353~1 A further example of alloys suitable for can stock are those having a minor content of My and available So such that on the graph of Pig. 1, the joint repro-setting the go and available So content ox the alloy lies within the area of a parallelogram defined by the coordinates 0.3% Six 0.8~ My; 0.5S% Six 1.2~ My; 1.05 Six 1.2~ My; and 0.8% Six 0.8% My, this parallelogram being represented in Fig. 1 by the chain lines 14 and a portion of the top horizontal) line ox pentagon 10.
Preferred alloy compositions within this parallelogram are those. for which the point representing My and avail-able So content lies to the right of the aforementioned line 12; of these, the most preferred compositions are those (again within the parallelogram) for which the point representing My and available So content lies above and to the left of the dotted lines 16 and to the right of line 12, i.e. within the quadrilateral defined by the coordinates 0.7% Six 0.9~ My; 0.875% Six 1.2% My; 0.69% Six 1.2% My; 0.52~ Six owe% My.
Preparation of Reroll Stock The starting material for the practice of the present process, in illustrative embodiments thereof, is a Dow of an alloy having a composition as defined above, in the form or a strop of appropriate gauge or the initial cold-rolling step ox the process, such strip being herein termed "reroll stock." Typically, the reroll stock is prepared my casting a convention-ally dimensioned sheet ingot of the alloy, e.g. by so-30 called direct chill casting, scalping and homogenizing the ingot, and hot rolling to the reroll gauge, all in accordance with well-known and wholly conventional procedures. Alternatively, the reroll stock can be produced by continuous strip casting techniques, viz.
: 35 by casting the alloy as a continuous, relatively thin : .. .:
~23S3~
strip in a casting cavity defined between chilled end-less moving steel bolts, between chilled rolls, or be-tweet chilled walls of a stationary mold, again as is well-known in the art. Such continuously cast strip either can be cast sufficiently thin to enable direct cold rolling, or can be hot-rolled to reroll gauge.
The reroll stock, however produced, is cooled and or-dinarily coiled; thus, preferably in at least most instances, the reroll gauge is sufficiently thin to lo enable direct coiling.
Provision of Intermediate Gauge Sheet Article In specific exemplary embodiments of the invention, reroll stock prepared as described above is cold roiled (employing procedure entirely conventional for cold roll-in of Al-Mg-Si alloys to reduce it to strip of an inter-mediate gauge at which the strip is to be solution heat treated. This intermediate or solution-heat-treatment gauge is selected, with reference to the predetermined desired final gauge of the sheet to be produced, such that a reduction of between about 25% and about 71%
from the intermediate gauge is required to achieve the final gauge. That is to say, the intermediate gauge is selected to provide for further cold reduction of about 25% to about 71% by cold rolling after solution heat treatment, as described below; preferably, the amount of cold reduction after solution heat treatment is be-tweet about 35% and about 71% and indeed most prefer-`
ably (especially for production of can body or can lid stock) between about 50% and about 71%, and for such preferred practice the intermediate gauge is selected accordingly. The reason for selecting the intermediate gauge to provide for the specified amount of cold no-diction after solution heat treatment is to enable de-US velopment of desired properties in the strip by post-~23S3~
solution-heat-treatment cold work. Selection of a particular intermediate gauge Raytheon the stated ranges is dependent on the specific properties sought to be attained in the final product.
It will be appreciated that the reroll gauge is not critical but is conveniently selected to be appear-. privately larger than the aforementioned intermediate gauge so that a substantial amount of reduction will be performed in the initial cold rolling step. Merely by way of illustration, in one example of production of can lid stock of 0.013 inch final gauge by the process of the invention, the intermediate (soluti.on-heat-treat-mint) gauge is selected to be between 0.0~6 and 0.045 inch, such that the cold reduction to final gauge after solution heat treatment is between 50% and about 71~, depending upon the particular final properties desired;
the reroll gauge in this instance it conveniently between about 0.120 inch and about C.160 inch.
It will be also be appreciated that, in its broader aspects, the invention does not require that - the sheet article be brought to intermediate gauge by cold rolling, but embraces the provision of the sheet article in intermediate gauge in other ways as well;
25 for example, in some instances the intermediate gauge can be attained directly by hot rolling, without any cold rolling before solution heat treatment.
~3~i3~
Solution float Treatment The initially cold-rolled strip article, at the aforementioned intermediate gauge, its solution heat treated (by heating and quenching) under conditions selected to effect at least substantially complete solution of the My and So therein. I've steps and conditions employed may, again, be entirely conventional, and as such are well known to persons of ordinary skill in the art. ~atch-type solution heat treatment may be used; although the time/temperature conditions are dependent on the coarseness of the Mg2Si phase, a batch process wherein the strip is heated for one hour at 530C is completely satisfactory. Alternatively and preferably, continuous solution heat treatment of the intermediate gauge strip (e.g. performed on a continuous annealing line) may be employed, a high temperature being required in view of the short soaking time involved. For instance, in continuous solution heat treatment a peak metal temperature of 570C, with a very short soak period of less than one minute, has been found adequate.
high temperature being required in view of the short soaking time involved. For instance, in continuous solution heat treatment a peak metal temperature of 570C, with a very short soak period of less than one minute, has been found adequate.
To retain the My and So in solution, the metal must be rapidly cooled to room temperature (quenched) from the solution heat treatment temperature, viz. in a time of no more than 60 seconds, and preferably less than 30 seconds. If the intermediate gauge is suffix ciently small, air quenching can be em Poe us water quenching is necessary for heavier gauges and is suitable lo r all gauges.
Nature Aging - Aster solution heat treatment and quenching, and without any intervening subsequent heat treatment, the as-cuenched strip article at the intermediate gauge is subjected to natural axing by standing at ambient tempera-lure (ens. about 0 to about 40C) for at least about ~;~353~
one day, and preferably for a-t least about three days.
Natural aging periods in excess of three days (regardless OX how long) are also acceptable.
The reason for performing this natural aging step, in the process of the invention, is to attain a state wherein the strength of the strip becomes relatively stable owing to the formation of lattice coherent nuclei of the ~g2Si phase.
Cold Rolling to Final Gauge After natural aging, and again without any inter-vexing heat treatment, the strip is subjected to cold rolling to effect work hardening while reducing it to the predetermined final gauge. The extent of cold reduction in this cold rolling step, in act cordons with the invention, is between about 25~ and about 71%, preferably at least about 35% and, as at-ready stated, most preferably (especially for product lion of can body or lid stock) between about 50% and about 71~, the intermediate gauge being selected to provide for thy extent of cold reduction after solution heat treatment and natural aging. As before, the equipment and procedures employed to perform the cold reduction may be entirely conventional for cold rolling of aluminum alloy strip. This cold roll-in operation after solution heat treatment produces a strip or sheet article which is at the final gauge and has been enhanced in strength by work hardening tithe as-rolled final gauge sheet being in To temper), and which has not been subjected to any applied heat treatment following the quench from the solution heat -treatment. Typical or exemplary final gauges are 0.013 inch for can lid stock and 0.014 inch for can body stock, or higher gauges (e.g. 0.040 inch) for other end products.
;
~l~3S36~
Between this step of cold rolling to final gauge and the subsequent artificial eying step described be-low, there is almost inevitably some further natural aging, since in the ordinary course of commercial opera-Tony the cold-rolled strip article is not immediately ; artificially aged but sits for some period at ambient temperature. Such further natural aging, of whatever duration, is not material to. the process of the in-mention.
~ti:ficial Aging Further in accordance with the invention, and as a particular feature thereof, the as-rolled strip at final gauge (usually, as noted, after some further in-cidental natural aging) is subjected to artificial aging, for increasing the yield strength thereof, by heating the strip to a predetermined elevated tempera-lure for a time shorter than that required to achieve the maximum yield strength attainable by heating the same strip to the same temperature, and such that the elongation of the strip aster artificial aging is within 20% of the maximum value atonal by heating the same strip to. the same temperature. The expression "heating to,`' as used herein, will be understood to em-brace both raising the strip to, and maintaining the strip at, the predetermined elevated temperature.
In this connection it may be explained that the yield strength and % elongation (as well as other prop-reties) of Al-Mg-Si strip artificially aged from To temper are both dependent on time of heating to elevated them-orator, for any given elevated temperature, in the artificial aging step. More particularly, it has now been found that during such heating, the % elongation (a measure of formability) as well as the yield strength ' ' ~.%353~
initially increases to a maximum and when declines, although the peak elongation is achieved earlier than the peak yield strength. Thus, by the present step ox artificially aging the strip by heating to an elevated temperature for a time shorter than that required to achieve peak yield strength (in contrast to the prior conventional practice of heating at least long enough to achieve peak yield strength), there is provided an advantageous combination of high strength and good formability. the relatively short heating time of-feats beneficial enhancement of yield strength (as compared to the yield strength in To temper) without undue impairment of % elongation (as compared to the % elongation in To temper). Fully adequate enhancement of strength for such purposes as the fabrication of drawn-and-ironed cans can be achieved by artificial aging for a time such that the % elongation is within 20% of the maximum value attainable upon artificially aging the same strip at the same temperature. Indeed, preferably in many cases, the artificial aging time can be selected to provide an actual increase in elongation (as compared to the % elongation of the strip in To temper, viz. just before artificial aging) as well as a satisfac tory enhancement ox yield strength. Other pertinent mock-apical properties are also wound to be at suitable levels (e.g. for can stock and other uses) in To strip after sub- -section to this duration of artificial aging.
The relationship between aging time and yield strength and % elongation is illustrated, for exemplary treatments, in Figs. 2-4. These figures show properties obtained upon artificial aging of strip of an PA 6061 alloy having the hollowing composition: 0.26% Cut 0.26% Fe, 0.89% My, 0.04% My, 0.64% Six 0.027% Tip 0.20% Or, balance essentially - aluminum. The strip was produced from a direct chill cast ingot which was homogenized, hot rolled and coiled at 0.13 in. (reroll gauge), cold rolled to an intermediate gauge of 0.046 in., and solution heat treated on a continuous ~3S3~
annealing line t60 seconds, 570C). Thereafter, the strip was naturally aged at ambient temperature for at least one day, and cold rolled to final gauges of 0.030 in. strip sample ox Fig. 2) or 0.0135 in. (strip samples of Figs 3 and 4). The 0.030 in. final gauge strip sample was ax-tificially aged at 160~C, different portions of the sample being thus heated for different times; the ~.0135 in.
final gauge samples were artificially aged a-t 160C (Fig.
3) or 185C (Fig. 4), with different portions of these lo samples again being heated for different times. The curves shown in Figs. 2-g represent the values of the indicated properties, measured in the transverse direction, for the strip portions in To temper after various dip-fervent artificial aging times. The values of properties lo indicated at 0 aging time ("as ruler) are the values measured for each sample in To temper, before artificial aging. For all aging times, strengths measured in a longitudinal direction are generally higher than the transverse values represented in the figures, but exhibit essentially the same dependence on heating time. These and other properties of the samples of Figs. 2-4 are summarized in Table I.
It will be seen that for each of the samples rep-resented by Figs. 2-4, both yield strength and elongation exhibit an initial increase (compared to the To temper values) during artificial aging. As the aging (heating) treatment continues, elongation begins to decrease, while yield strength continues to increase for some further period before starting to decline. In each instance, it is possible to select a time at which the elongation is within 20% of its maximum value and yet the yield strength is greater than that of To temper, although this time varies depending on such factors as artificial aging them-portray and % cold reduction (35% in Fig. 2; 71% in jigs.
3 and 4) after solution heat treatment.
By way of specific example, for 0.013 in. gauge strip of AA 6061 alloy work hardened by cold reduction of 71% after solution heat treatment, an aging time of ::.
.
:
~%353~L
. o on o a so co Al l l ~'~
..... l l ..... 1, I l l l l l l h O Al rJ I rJ Jo En . _ __ _ .... _ Jo . o I or us o or o o I rJ r I:: or I I I o lo l l l l l l I: O ..... II ..... II IIIIIII
o rJ I
_ ,. _ or o I o ED u) o or I o o I ~7 I a: ox co co a Jo co a I a a rJ I I I I I I I I I
l Al I owe owe _ . . . _ _ __ _ _ _ co us o o o Ox u in o Us O O
..~ UP . . . . . . . . . . . . . .
ED O Clue 1` I 1` or I I
Jo _ - . _ _ __ _ _ -I
I I co a a o I o or Jo o Jo co or O In a Jo o o (D
us in ...... ....... .......
ED r- I go I
. I_ Lo on Lo In Lo Lo Lam Jo O _ .- __ _. _ Ski r I o cry or or CO
O En us ....... ....... .......
us: 0 I I Jo co us O _ or us us Lo In Us Lo Lo n Lo r h _ , _ . --H . _ Lo o o o co us o o us o o o o okay O ............ ....... .......
I_ Jo It Us no us l - - - - -----En En '? .. ,.~ I I I LO a o o co o Clue Us Us Us ....... ....... .......
I: X co Lo I a n I
h _ or r n u En _ _ _ . , Us or o co In on I I co 0 ~1~1 rJ
En us ....... ....... .......
X a I o I o o I us I_ I Us .__ . _ . _ .
. . .
I h h h .,~ I Lo Us rl En h h a pa 0 h h 0 h h 0 0 0 h O S S 5 o I a O (I S S
fix .
Jo or co r . . _ _ .
a a) I I
I I I
~l~rl 111 Jo V to h h .' try h try to pa o a) a I I
. a Jo :: ~1 I I
I I
_, _ --us a) I I
I I o o Jo o o O o o I) o o LO
e . .. ,, . . .,, I . . ,, co O O O
an . _ . .
~23S3~
three hours at 160C (or a shorter aging time at a higher temperature) produces a significant in-crease in both elongation and yield strength (as compared to the values in To temper) as well as achieving satisfactory levels of such other prop-reties as Erickson Cup height and ultimate tensile strength. More generally, the times to peak % slog anion and peak yield strength during artificial aging are dependent on alloy composition; efficiency of soul-lion heat treatment, as affected by time, -temperature, quenching rate, and prior influence from homogenization treatment of the ingot (e.g., whether the homogenization treatment dissolved all coarse Mg2 So); % of cold no-diction following solution heat treatment; extent of natural aging, and whether natural aging precedes or follows the cold reduction after solution heat treatment;
and aging temperature. The above factors, and also the final gauge, affect the magnitude of the peak elonga-lion during artificial aging. Accordingly, in the practice of the invention, the proper heating time for the artificial aging step is determined, after selection of the foregoing factors, by aging for different periods a series of samples of strip for which all these factors are nerd constant, thereby to establish the artificial aging time dependency of the yield strength and % elongation of such strip. An aging time at which suitable values of yield strength and % elongation are achieved can then be immediately determined, and employed as the artificial aging time for commercial production of the same strip. The procedure involved in thus establishing the aforementioned time dependency is simple and straightforward and can readily be practiced by -persons of ordinary skill in the art.
Conveniently, the artificial aging step of the present process can be performed US a batch artificial aging treatment, by heaving a coil of the strip at final :. :
-- , .
, .
~23S3fii~
gauge (and initially in To temper) to a temperature in the range of, say, 160C for a period of 1-3 hours.
Alternatively, aging can be performed by stowing the To strip for a much shorter time at a substantially higher temperature, e.g., by stowing for about 10 to about 20 minutes at about 200C. In particular in-stances, such a stowing step may also be used to perform some other function; for example, in the production of can lids, the stowing of the lid stock after lacquering 10 can be performed under the just-mentioned conditions so as to constitute the artificial aging step OX the present process. gain, in this rapid stowing treatment, the artificial aging step effects. an increase in yield strength and provides a % elongation (in the artificially aged strip) within 20~ of the maximum value attainable during stowing at the selected temperature, such value being commonly or preferably higher than the % elongation of the To temper strip before stowing.
The product of the present process, after completion of the artificial aging step, is a sheet article of Alms So alloy in To temper, exhibiting a combination of high strength and good formability achieved by the above described succession of steps, in particular including the artificial aging step performed under the specified conditions of aging for a time less than that required to achieve peak yield strength Such sheet may be produced in various final gauges, for a wide variety of different end uses for which this combination of strength and formability properties is necessary or advantageous.
Production of Cans - In specific and presently preferred embodiments of the process of the invention as employed for the production of components of cans (viz. drawn-and-ironed can bodies or lids therefore), the final gauge of the To strip resulting from the practice of the above-described steps is selected ~23S3~
to be appropriate for direct formation of can bodies (e.g. 0.014 inch final gauge strip) or lids (e.g.
0.013 inch final gauze strip), and the artificial ago in treatment is hollowed by a step of forming the To strip into a one-piece can body or a can lid, in act cordons with forming procedures now wholly conventional for forming such bodies and lids. Ordinarily the process in each instance (bodies and lids) will include a lacquer-in step, followed by stowing.
It is conventional, in the case of lids, to lacquer and stove the sheet stock from which the lid is made prior to the lid-forming operation. The lacquer in such case may be applied while the sheet is in To temper and as already stated, the subsequent stowing of the lacquered sheet may be performed under conditions (e.g. heaving for about 10-20 minutes at about 200C) selected to effect the special artificial aging treatment of the invention. Thereafter, the lacquered and stowed (To temper) sheet is conventionally wormed into can lids. Alternatively, the To temper sheet may first be artificially aged in accordance with the in-mention and subsequently lacquered, stowed, and formed into lids.
In the case of can body stock, the forming (drawing and ironing operations precede lacquering and 25 stowing, and the stock in final gauge is subjected to the artificial aging step of the invention before be-in wormed into can bodies, i.e. the stowing after lacquering is a separate heat treatment performed sub-sequent to artificial aging. Where stowing after lacquering 30 is performed as a separate treatment, it ordinarily coca-sons some reduction in strength, but causes relatively less .
.;"
' ~L~3~;3~
strength reduction than is caused by stowing of AA 3004 lacquered cans.
The products of these embodiments of the present process are, respectively, a drawn-and-ironed can body and a can lid of Alex alloy having the beneficial properties developed by the combination of treatments described above. Lucite advantageously, a lid and body of the same alloy composition are produced and assembled to provide a can wherein both components (lid and body) lo are constituted of a single composition as desired to facilitate recycling and reuse of the metal.
The invention affords further important advantages, as well, for the production of can lids and bodies. Con-lain of these advantages will be apparent from the compare iron of AA 6061 can stock prepared in accordance with the present process, and conventional AA 3004 and A 5182 can body and lid stock, set forth in Table II
wherein the AA 6061 stock at To temper (which is at a gauge of 0.013 inch) represents the product ox the invention:
.
. .
~L23S3~i~
-- I --Jo \
I 11; Lo O on I I
l l l l l l o o o o I, us o own Lo Jo aye I_ . I I I I
o o o o o out I
.,, I t ^
o I_ o I out O O do --H
a I I_ a) so u~coco kiwi En I X I
.
rî I` In r-- o En Us--Us I) a) o a a a) a a) o o so x 3 o o o o . do 3 o a o Q
or co I I
-I_ G' O O CO CO
O OWE
ED ED Us ., Lo The AA 6061 stock represented in the foregoing table was produced by successively direct chill casting and homogen-icing an ingot, hot rolling, cold rolling to an intermediate gauge, solution-heat-treating and quenching, natural aging for at least one day, and cold rolling (with 50-71% reduction) to final gauge, followed by artificial aging, as indicated for 3 hours at 160C. The lacquering treatment referred to in the table followed artificial aging (in the case of the AA 6061 stock and in each instance involved stowing the lacquered metal at SKYE for 10 minutes.
As is apparent from the table, the AA 6061-~r8 strip produced by the invention has earing and Erickson values comparable to conventional AA 3004 body stock, better bend-ability, and yield strength 14 ski (thousands of pounds per square inch) higher than the AA 3004 body stock before lacquer-in; after lacquering, though yield strength falls in both instances, the yield strength differential is even greater (17 ski in favor of the AA 6061-T8 stock. This lacquered strength is particularly important for can bodies as it directly affects the pressure at which the bottom of the filled can will buckle outwardly. Because of pasteurization after filling, a minimum bottom buckle pressure of 90 pi is commonly required for drawn-and-ironed can bodies. 3004-Hl9 can bodies generally develop buckle pressures between 95 and 110 pi in one test, 6061-T8 can bodies were shown to develop bottom buckle pressures in excess of 130 pi Thus, 6061-T8 can body stock produce by the process of the invention may be reduced in gauge, as compared to 3004-H19 stock, with consequent reduction in metal cost per can, and still exceed buckle pressure requirements.
Compared to 5182-Hl9 can lid stock, lacquered 6061-T8 stock produced in accordance with the invention has higher yield strength (7 ski higher, in the example represented by the table), higher Erickson cup values, and the same bendability, although the 6061-T8 stock may be slightly less formable than 5182-Hl9 stock under severe draw conditions, and the higher 'foe yield strength of 6061-T8 does not provide improved buckle pressure performance, owing to the higher work hardening rate of the 5182 alloy, which results in a strength equivalent to 6061 in the formed areas of the lid which actually control buckle performance. Never-the less, as the comparison of properties in the table illustrates the properties exhibited by the 6061-T8 sheet are fully adequate for use as both lid and body stock, and are generally equivalent to or better than the properties of the conventional alloys used for lids and bodies.
It is to be understood that the invention is not limited to the features and embodiments hereinabove specifically set forth but may be carried out in other ways without departure from its spirit.
Production of Aluminum Alloy Sheet and Articles Fabricated Therefrom Background of the Invention This invention relates to processes for producing Al-Mg-Si alloy sheet and articles fabricated therefrom, and to the products of such processes.
Al-Mg-Si alloys as herein contemplated are alloys having a major content of Al and a minor content of My and Six and are exemplified by known alloys identified by Aluminum Association designations in the 6000 series, e.g. the alloys having Aluminum Association BAA) de-signa~ions 6009, 6010, 6011, 6061, and 6063. The term "sheet" is broadly used herein to mean rolled products, without limitation to any particular gauge;
thus it includes products at plate and foil gauges as well as products at conventional sheet gauges.
More particularly, the invention is directed to processes for producing Al-Mg-Si sheet in so-called To temper, which-is the temper achieved by performing sue-cessively the steps of solution heat treatment, quenching, cold working, and artificial aging, some-times with a natural aging period interposed between the quench after solution heat treatment and the following cold working step. It has heretofore been known to provide Al-Mg-Si products, including sheet, in To temper, for various purposes.
In one important specific aspect, to which de-tailed reference will be made herein for purposes of illustration, the invention is dlrecte~ to the pro-diction of aluminum alloy can body and lid stock, viz.
aluminum alloy sheet for forming one-piece drawn and ironed can bodies and can lids for such bodies, as well as to the formation of can bodies and lids from such sheet and to the articles thus formed.
- --353~
Presented metal cans as used for beverages such as soft drinks, beer and the like are commonly keenest-tuned of a seamless one-piece body (which includes the bottom end and cylindrical side wall of the can) and a top end bearing a ring or other opening device. The body is produced from a blank of cold-rolled aluminum alloy sheet (having a gauge, for example, of about 0.014 inch) by a now-conventional forming technique known as drawing and ironing, which involves drawing the blank into a cup and then passing it through a sue-cession of dies to achieve the desired elongated cry-lindrical body configuration, with a side wall of no-duped thickness relative to the bottom end. The top end is separately produced from another sheet aluminum alloy blank, by different but also conventional forming operations, and is secured around its circumference to the top edge of the side wall of the body to provide a complete can.
The severity of the forming procedure employed in producing a drawn-and-ironed can body as described above, and in particular the reduction in thickness of the can side wall (which must nevertheless be able to withstand the internal and external forces exerted on it in use), as well as the fact that the formed can is usually lacquered in an operation necessitating a strength-reducing exposure to heat, require a special combination of strength, formability, and tool wear properties in the alloy sheet from which the can body is made. Significant among these properties are multi-mate tensile strength, yield strength, elongation, endearing. Attainment of the requisite combination of properties is dependent on alloy composition and on the processing conditions used to produce the sheet.
Heretofore, a conventional sheet for can body blanks has been constituted of the alloy having the SLY
Aluminum Association designation AYE, and has been produced from conventionally direct-chill-cast ingot up to 24 inches thick by scalping and homogenizing the ingot, and successively hot roiling and cold rolling to the desired final gauge; often an anneal treatment is used between the hot and cold rolling operations, with the annealing gauge so selected that the amount of cold reduction to final gauge after annealing is about 85%, thereby to provide can body blanks in Hl9 (extra hard) temper. This practice imparts the combination of pro-parties currently required for commercial can body stock. The aluminum alloy designated AA 5182 is ox-pensively used for the manufacture of the can top ends or lids, can lid stock (sheet) of such alloy being pro-duped in a manner similar to that described above for production of AYE on body stock in that similar steps of direct chill casting; homogenization, hot rolling, annealing and cold rolling to the Hl9 temper are employed; cold rolling may also be performed be tweet the hot rolling and annealing steps. The final can lid stock, ego at a gauge of about 0.013 inch, is fag-queued and when formed into lids the lacquering operation again involving a stowing (heating) step.
Although satisfactory cans are provided my the foregoing conventional procedures utilizing different alloys for the body and lid respectively, it would be desirable to produce cans having both body and lid formed of the same alloy, to facilitate recovery and reuse of the metal when the cans are recycled. Such an alloy requires a combination of high strength and good formability. Aluminum alloy sheet having such a combination of strength and formability properties would be advantageous for use, at various gauges, in a wide variety of other applications as well.
~L%3S3~l Summary of the Invention .
The present invention broadly contemplates the provision ox a process for producing aluminum alloy sheet of predetermined final gauge, comprising the steps of ~rovidlng a sheet article of a heat-treatable Al-Mg-Si alloy (having a composition as defined below) at an intermediate gauge from which a reduction of be-tweet about 25% and about 71~ is required to achieve the predetermined final gauge; solution-heat-treating the sheet article at the intermediate gauge by heating and ~enc~g, for effecting it least Shelley ~n~lete Lyon of ye My Ed So therein; aster quenching, and without intervening heat treatment, naturally aging the sheet article by maintaining it at ambient temperature for at least about one day; a~tPr natural aging, and without intervening heat treatment, cold rolling the sheet article to the final gauge (i.e. with a reduction ox between about 25% and about 71~); and artificially aging the sheet article at the final gauge or increasing the yield strength thereof by heating the article to a prude-termined temperature for a time shorter than that no-squired to achieve the maximum yield strength attainable by artificial aging of the article at that predetermined temperature, and such that the % elongation value ox the article after artificial aging is within 20~ ox the maximum value attainable by artificial aging OX the sheet article at that temperature following the same extent of cold reduction performed after solution heat treatment. The alloys used in the process, in its broad-eat aspects, are those having a major content of I
and a minor content of jig and available So such that on a rectangular graph of % My slotted against % avail able Six the point representing tune lug and available at content lies within the area of a pentagon defined by the coordinates 0.2% Six I lug 0.2~ Six 0.9~ lug ~2353~i~
0~4% Six Lo lug 1.2~ Six 1.2~ go and 1.2% Six 0.4~~g, all composition percentages here and elsewhere set forth in the present specification being expressed as percentages by weight. As used herein, the term "avail-able Six means So which has not been taken up by Fish is ordinarily present in the alloy. It is usual to assume that a percentage of So equal to one third or the Fe content is lost to the inter metallic compounds.
Thus, with this assumption made, the available So con-tent of an alloy (in weight percent) is equal to teetotal So content of the alloy (in weight percent) less one-third of the Fe content (in weight percent).
The process of the invention differs from pro-seeders heretofore known (for producing Alms So en-tides in To temper) in that, in the artificial aging step, heating is terminated before the article attains its maximum yield strength. Specifically, it has now been found that when a solution-heat-treated and worn-hardened Al-Mg-Si sheet is heated to effect artificial aging, the formability (represented by % elongation) as well as the yield strength initially increases at-though with continued heating, the % elongation begins to decrease at a time when the yield strength is still increasing. Thus, termination OX artificial aging be-fore the peak yield strength is reached affords beneficial improvement in strength without substantial imp paramount of formability, and indeed, in many cases, with actual enhancement of formability.
More particularly, the steps of natural aging after solution heat treatment, subsequent cold rolling between about 25% and about 71%, and artificial aging with observance of the special conditions just de-scribed, cooperatively provide artificially aged sheet having a superior combination of strength and format ability properties. In one specific sense, the process ..
~23S36~
of the invention further includes the step of forming the artificially aged sheet article into a component of a can, viz. a one-piece drawn and ironed can body have in an open end or a lid for closing the open end. In some instances, the stowing (heating) operation per-formed after lacquering of the lid stock may be con-dueled under conditions selected to constitute the anti-filial aging step of the present process, although it is at present preferred to perform the artificial lo aging on the sheet stock prior to lacquering. As will be understood, in these embodiments of the process of the invention, tile predetermined final gauge to which the sheet is reduced before artificial aging is a de-sired and e.g. conventional gauge for can body or lid stock. Advantageously, the invention can be embodied in a process for the production of cans wherein both lid and body are fabricated of sheet of the same alloy produced by the foregoing sequence of steps so that the metal of the can (when recycled) may be remelted and reused to produce new can bodies and lids without major adjustment of alloy composition.
In a broader sense, the sheet products of the in-mention may be produced at various final gauzes, since the combination of strength and formability achieved by the present process is beneficial for diverse uses.
A preferred upper limit of final sheet gauge for pro-ducts of the present process is l/2 inch.
Preferably, the alloy composition employed in the practice of the invention is selected to have at least a slight excess of available So over that statue-metrically required for combination (as Mg2Si) with all the 21g present, and (especially for production of can body or lid stock) the amount of My in the alloy it selected to insure a total Mg2Si content between about 1.35 and about 1.50~. Preferably also, the amount of -`
~23S3~
cold reduction between solution heat treatment and artificial aging is at least about 35~, and most pro-fireball (again, for production of can body and lid stock) the amount of such cold reduction is between about 50 and about 71%, this condition being provided by appropriate selection of the aforementioned inter-mediate gauge with reference to the desired predetex-mined final gauge.
The invention also embraces sheet articles, and lo can components, produced by the foregoing process, and possessing the advantageous combination of mechanical properties thereby achieved.
Further features and advantages of the invention will be apparent from the detailed description herein-below set forth, together with the accompanying draw-ins.
Brief Description of the Drawings Fig. 1 is a rectangular graph on which % My is plotted against available Six in illustration of the ; My and available So content of alloys suitable for the practice of the present invention;
Fig. 2 is a rectangular graph of ultimate tensile strength (US), yield strength (YE), elongation and Erickson cup depths of artificially aged (To temper) AYE alloy sheet, plotted against artificial aging time, for sheet subjected to 35~ cold reduction after solution heat treatment, to a final gauge of 0.030 inch, and then artificially aged at 160C.
Fig. 3 is a graph similar to jig. 2 for AWAIT
sheet subjected to 71% cold reduction after solution heat treatment, to a final gauge of 0.0135 inch, and then artificially aged at 160C: and Fig. 4 is a graph similar to Figs 2 and 3 for AYE (To) sheet subjected to 71% cold reduction after solution heat treatment, to a final gauge of 0.0135 inch, and then artificially aged at 185%C.
Detailed Description The invention will ye described, with reverence to the drawings, as embodied in a process for product in Al-Mg-Si alloy sheet from reroll stock by the sue-cessive steps of providing a sheet article of inter-mediate gauge, solution heat treating, natural aging, - cold rolling, and artificial aging, and in the pro-ducts. of that process. Par oculars of the alloys em-plowed, the preparation of the reroll stock, the per-pheromones of each of the aforementioned steps, and their combination in the complete. process, are set forth below.
35.3~S~
g Alloy Composition , . . . .
Alloys suitable for the practice of the present invention broadly include Al-Mg-Si alloys having a minor content of My and available So such that on a S rectangular graph of % My plotted against available So (i.e. the graph of Fig. 1) the point representing the My and available So content of the alloy lies within the area of pentagon 10 in Fig. 1, Vim. a pentagon de-fined by the coordinates 0.2% Six 0.4~ My; 0.2~ Six C.9~ My; 0~4~ Six 1.2~ My; 1.2% Six 1.2% My; and 1.2~
Six 0.4~ My. referred alloy compositio~s,within this broad definition, are those or which the point repro-setting My and available So content lies not only within the aforesaid pentagon but also to the right of a line 12 which represents the theoretical Mg2Si weight ratio, i.e. McCoy = 1.73/1. Preferably, also, the alloy con-sits essentially of My and available So in amounts (~) defined by pentagon 10, optionally also containing up to 0.9% Cut up to lo Fe, up to 0.8~ Len, up lo 0.35% Or, up to 0.25% Zen, up to 0.20% Tip balance essentially Al with usual impurity levels not materially affecting the combination of strength and formability properties with - which the present invention is concerned Specific examples of known alloys within the foregoing broad definition, and suitable for the pray-lice of the invention are the alloys having the Aluminum Association designations AA 6009, 6010, 6011, 6061, and 6063, the registered compositions of which are as follows:
~2353~
Range or Maximum (% by weight) __ . . _ . _ . .
AYE AYE AYE AYE AYE
. . _ So 0.6-L.0 0.8-1.2 0.40-0.8 aye Fe 0.50 0.50 0.7 0.35 1.0 Queue 0.15-0.6 0.15-0.40 0.100.40-0.9 My 0.20-0.8 0.20-0.8 Owls 0.10 0.8 My 0.40-0.8 0.6-1.0 0.8-1.2 0.45-0.90.6-1.2 Or 0.10 0.10 0.04-0.35 0.100.30 Zen 0.25 0.25 0.~5 0.10 1.5 1.0 To 0.10 0.10 0.15 0.100.20 No - - - - 0.20 other (each/
total) 0.05/0.15 0.05/0.15 0.05/0.15 0.15/0.15 0.05/0.15 Al balance balance balance balance balance Alloys with the composition limits of AYE as given above are particularly-preferred, especially for em-bodiments of the invention providing drawn-and-ironed- --can body stock and can lid stock; currently most pro-furred for these embodiments is an alloy having the nominal composition 0.25% Fe, 0.30% Cut 0.65~ Six 0.05~ (max.) I, 0.90~ My, Mecca.) Zen, 0.17~ Or, 0.25~ (max.) Tip other 0.10% (max.), balance aluminum, the designation "(Mecca' being used to indicate that the value given is a maximum and that the element so design noted is merely optional or tolerable as an impurity up to the stated maximum. For good age-hardening response, the alloy should contain a slight excess of available So (at least about OOZE) over that needed to statue-metrically form Mg2Si with a weight ratio McCauley of 1.73/1; as mentioned above, when making this calculi-lion, it is usual to assume that a percentage of the total So content equal to 1/3 of the Fe content is lost to the inter metallic compounds It is also usual with AYE to ensure a total Mg2Si content between about lo 35 and about 1.50.
. ' .
353~1 A further example of alloys suitable for can stock are those having a minor content of My and available So such that on the graph of Pig. 1, the joint repro-setting the go and available So content ox the alloy lies within the area of a parallelogram defined by the coordinates 0.3% Six 0.8~ My; 0.5S% Six 1.2~ My; 1.05 Six 1.2~ My; and 0.8% Six 0.8% My, this parallelogram being represented in Fig. 1 by the chain lines 14 and a portion of the top horizontal) line ox pentagon 10.
Preferred alloy compositions within this parallelogram are those. for which the point representing My and avail-able So content lies to the right of the aforementioned line 12; of these, the most preferred compositions are those (again within the parallelogram) for which the point representing My and available So content lies above and to the left of the dotted lines 16 and to the right of line 12, i.e. within the quadrilateral defined by the coordinates 0.7% Six 0.9~ My; 0.875% Six 1.2% My; 0.69% Six 1.2% My; 0.52~ Six owe% My.
Preparation of Reroll Stock The starting material for the practice of the present process, in illustrative embodiments thereof, is a Dow of an alloy having a composition as defined above, in the form or a strop of appropriate gauge or the initial cold-rolling step ox the process, such strip being herein termed "reroll stock." Typically, the reroll stock is prepared my casting a convention-ally dimensioned sheet ingot of the alloy, e.g. by so-30 called direct chill casting, scalping and homogenizing the ingot, and hot rolling to the reroll gauge, all in accordance with well-known and wholly conventional procedures. Alternatively, the reroll stock can be produced by continuous strip casting techniques, viz.
: 35 by casting the alloy as a continuous, relatively thin : .. .:
~23S3~
strip in a casting cavity defined between chilled end-less moving steel bolts, between chilled rolls, or be-tweet chilled walls of a stationary mold, again as is well-known in the art. Such continuously cast strip either can be cast sufficiently thin to enable direct cold rolling, or can be hot-rolled to reroll gauge.
The reroll stock, however produced, is cooled and or-dinarily coiled; thus, preferably in at least most instances, the reroll gauge is sufficiently thin to lo enable direct coiling.
Provision of Intermediate Gauge Sheet Article In specific exemplary embodiments of the invention, reroll stock prepared as described above is cold roiled (employing procedure entirely conventional for cold roll-in of Al-Mg-Si alloys to reduce it to strip of an inter-mediate gauge at which the strip is to be solution heat treated. This intermediate or solution-heat-treatment gauge is selected, with reference to the predetermined desired final gauge of the sheet to be produced, such that a reduction of between about 25% and about 71%
from the intermediate gauge is required to achieve the final gauge. That is to say, the intermediate gauge is selected to provide for further cold reduction of about 25% to about 71% by cold rolling after solution heat treatment, as described below; preferably, the amount of cold reduction after solution heat treatment is be-tweet about 35% and about 71% and indeed most prefer-`
ably (especially for production of can body or can lid stock) between about 50% and about 71%, and for such preferred practice the intermediate gauge is selected accordingly. The reason for selecting the intermediate gauge to provide for the specified amount of cold no-diction after solution heat treatment is to enable de-US velopment of desired properties in the strip by post-~23S3~
solution-heat-treatment cold work. Selection of a particular intermediate gauge Raytheon the stated ranges is dependent on the specific properties sought to be attained in the final product.
It will be appreciated that the reroll gauge is not critical but is conveniently selected to be appear-. privately larger than the aforementioned intermediate gauge so that a substantial amount of reduction will be performed in the initial cold rolling step. Merely by way of illustration, in one example of production of can lid stock of 0.013 inch final gauge by the process of the invention, the intermediate (soluti.on-heat-treat-mint) gauge is selected to be between 0.0~6 and 0.045 inch, such that the cold reduction to final gauge after solution heat treatment is between 50% and about 71~, depending upon the particular final properties desired;
the reroll gauge in this instance it conveniently between about 0.120 inch and about C.160 inch.
It will be also be appreciated that, in its broader aspects, the invention does not require that - the sheet article be brought to intermediate gauge by cold rolling, but embraces the provision of the sheet article in intermediate gauge in other ways as well;
25 for example, in some instances the intermediate gauge can be attained directly by hot rolling, without any cold rolling before solution heat treatment.
~3~i3~
Solution float Treatment The initially cold-rolled strip article, at the aforementioned intermediate gauge, its solution heat treated (by heating and quenching) under conditions selected to effect at least substantially complete solution of the My and So therein. I've steps and conditions employed may, again, be entirely conventional, and as such are well known to persons of ordinary skill in the art. ~atch-type solution heat treatment may be used; although the time/temperature conditions are dependent on the coarseness of the Mg2Si phase, a batch process wherein the strip is heated for one hour at 530C is completely satisfactory. Alternatively and preferably, continuous solution heat treatment of the intermediate gauge strip (e.g. performed on a continuous annealing line) may be employed, a high temperature being required in view of the short soaking time involved. For instance, in continuous solution heat treatment a peak metal temperature of 570C, with a very short soak period of less than one minute, has been found adequate.
high temperature being required in view of the short soaking time involved. For instance, in continuous solution heat treatment a peak metal temperature of 570C, with a very short soak period of less than one minute, has been found adequate.
To retain the My and So in solution, the metal must be rapidly cooled to room temperature (quenched) from the solution heat treatment temperature, viz. in a time of no more than 60 seconds, and preferably less than 30 seconds. If the intermediate gauge is suffix ciently small, air quenching can be em Poe us water quenching is necessary for heavier gauges and is suitable lo r all gauges.
Nature Aging - Aster solution heat treatment and quenching, and without any intervening subsequent heat treatment, the as-cuenched strip article at the intermediate gauge is subjected to natural axing by standing at ambient tempera-lure (ens. about 0 to about 40C) for at least about ~;~353~
one day, and preferably for a-t least about three days.
Natural aging periods in excess of three days (regardless OX how long) are also acceptable.
The reason for performing this natural aging step, in the process of the invention, is to attain a state wherein the strength of the strip becomes relatively stable owing to the formation of lattice coherent nuclei of the ~g2Si phase.
Cold Rolling to Final Gauge After natural aging, and again without any inter-vexing heat treatment, the strip is subjected to cold rolling to effect work hardening while reducing it to the predetermined final gauge. The extent of cold reduction in this cold rolling step, in act cordons with the invention, is between about 25~ and about 71%, preferably at least about 35% and, as at-ready stated, most preferably (especially for product lion of can body or lid stock) between about 50% and about 71~, the intermediate gauge being selected to provide for thy extent of cold reduction after solution heat treatment and natural aging. As before, the equipment and procedures employed to perform the cold reduction may be entirely conventional for cold rolling of aluminum alloy strip. This cold roll-in operation after solution heat treatment produces a strip or sheet article which is at the final gauge and has been enhanced in strength by work hardening tithe as-rolled final gauge sheet being in To temper), and which has not been subjected to any applied heat treatment following the quench from the solution heat -treatment. Typical or exemplary final gauges are 0.013 inch for can lid stock and 0.014 inch for can body stock, or higher gauges (e.g. 0.040 inch) for other end products.
;
~l~3S36~
Between this step of cold rolling to final gauge and the subsequent artificial eying step described be-low, there is almost inevitably some further natural aging, since in the ordinary course of commercial opera-Tony the cold-rolled strip article is not immediately ; artificially aged but sits for some period at ambient temperature. Such further natural aging, of whatever duration, is not material to. the process of the in-mention.
~ti:ficial Aging Further in accordance with the invention, and as a particular feature thereof, the as-rolled strip at final gauge (usually, as noted, after some further in-cidental natural aging) is subjected to artificial aging, for increasing the yield strength thereof, by heating the strip to a predetermined elevated tempera-lure for a time shorter than that required to achieve the maximum yield strength attainable by heating the same strip to the same temperature, and such that the elongation of the strip aster artificial aging is within 20% of the maximum value atonal by heating the same strip to. the same temperature. The expression "heating to,`' as used herein, will be understood to em-brace both raising the strip to, and maintaining the strip at, the predetermined elevated temperature.
In this connection it may be explained that the yield strength and % elongation (as well as other prop-reties) of Al-Mg-Si strip artificially aged from To temper are both dependent on time of heating to elevated them-orator, for any given elevated temperature, in the artificial aging step. More particularly, it has now been found that during such heating, the % elongation (a measure of formability) as well as the yield strength ' ' ~.%353~
initially increases to a maximum and when declines, although the peak elongation is achieved earlier than the peak yield strength. Thus, by the present step ox artificially aging the strip by heating to an elevated temperature for a time shorter than that required to achieve peak yield strength (in contrast to the prior conventional practice of heating at least long enough to achieve peak yield strength), there is provided an advantageous combination of high strength and good formability. the relatively short heating time of-feats beneficial enhancement of yield strength (as compared to the yield strength in To temper) without undue impairment of % elongation (as compared to the % elongation in To temper). Fully adequate enhancement of strength for such purposes as the fabrication of drawn-and-ironed cans can be achieved by artificial aging for a time such that the % elongation is within 20% of the maximum value attainable upon artificially aging the same strip at the same temperature. Indeed, preferably in many cases, the artificial aging time can be selected to provide an actual increase in elongation (as compared to the % elongation of the strip in To temper, viz. just before artificial aging) as well as a satisfac tory enhancement ox yield strength. Other pertinent mock-apical properties are also wound to be at suitable levels (e.g. for can stock and other uses) in To strip after sub- -section to this duration of artificial aging.
The relationship between aging time and yield strength and % elongation is illustrated, for exemplary treatments, in Figs. 2-4. These figures show properties obtained upon artificial aging of strip of an PA 6061 alloy having the hollowing composition: 0.26% Cut 0.26% Fe, 0.89% My, 0.04% My, 0.64% Six 0.027% Tip 0.20% Or, balance essentially - aluminum. The strip was produced from a direct chill cast ingot which was homogenized, hot rolled and coiled at 0.13 in. (reroll gauge), cold rolled to an intermediate gauge of 0.046 in., and solution heat treated on a continuous ~3S3~
annealing line t60 seconds, 570C). Thereafter, the strip was naturally aged at ambient temperature for at least one day, and cold rolled to final gauges of 0.030 in. strip sample ox Fig. 2) or 0.0135 in. (strip samples of Figs 3 and 4). The 0.030 in. final gauge strip sample was ax-tificially aged at 160~C, different portions of the sample being thus heated for different times; the ~.0135 in.
final gauge samples were artificially aged a-t 160C (Fig.
3) or 185C (Fig. 4), with different portions of these lo samples again being heated for different times. The curves shown in Figs. 2-g represent the values of the indicated properties, measured in the transverse direction, for the strip portions in To temper after various dip-fervent artificial aging times. The values of properties lo indicated at 0 aging time ("as ruler) are the values measured for each sample in To temper, before artificial aging. For all aging times, strengths measured in a longitudinal direction are generally higher than the transverse values represented in the figures, but exhibit essentially the same dependence on heating time. These and other properties of the samples of Figs. 2-4 are summarized in Table I.
It will be seen that for each of the samples rep-resented by Figs. 2-4, both yield strength and elongation exhibit an initial increase (compared to the To temper values) during artificial aging. As the aging (heating) treatment continues, elongation begins to decrease, while yield strength continues to increase for some further period before starting to decline. In each instance, it is possible to select a time at which the elongation is within 20% of its maximum value and yet the yield strength is greater than that of To temper, although this time varies depending on such factors as artificial aging them-portray and % cold reduction (35% in Fig. 2; 71% in jigs.
3 and 4) after solution heat treatment.
By way of specific example, for 0.013 in. gauge strip of AA 6061 alloy work hardened by cold reduction of 71% after solution heat treatment, an aging time of ::.
.
:
~%353~L
. o on o a so co Al l l ~'~
..... l l ..... 1, I l l l l l l h O Al rJ I rJ Jo En . _ __ _ .... _ Jo . o I or us o or o o I rJ r I:: or I I I o lo l l l l l l I: O ..... II ..... II IIIIIII
o rJ I
_ ,. _ or o I o ED u) o or I o o I ~7 I a: ox co co a Jo co a I a a rJ I I I I I I I I I
l Al I owe owe _ . . . _ _ __ _ _ _ co us o o o Ox u in o Us O O
..~ UP . . . . . . . . . . . . . .
ED O Clue 1` I 1` or I I
Jo _ - . _ _ __ _ _ -I
I I co a a o I o or Jo o Jo co or O In a Jo o o (D
us in ...... ....... .......
ED r- I go I
. I_ Lo on Lo In Lo Lo Lam Jo O _ .- __ _. _ Ski r I o cry or or CO
O En us ....... ....... .......
us: 0 I I Jo co us O _ or us us Lo In Us Lo Lo n Lo r h _ , _ . --H . _ Lo o o o co us o o us o o o o okay O ............ ....... .......
I_ Jo It Us no us l - - - - -----En En '? .. ,.~ I I I LO a o o co o Clue Us Us Us ....... ....... .......
I: X co Lo I a n I
h _ or r n u En _ _ _ . , Us or o co In on I I co 0 ~1~1 rJ
En us ....... ....... .......
X a I o I o o I us I_ I Us .__ . _ . _ .
. . .
I h h h .,~ I Lo Us rl En h h a pa 0 h h 0 h h 0 0 0 h O S S 5 o I a O (I S S
fix .
Jo or co r . . _ _ .
a a) I I
I I I
~l~rl 111 Jo V to h h .' try h try to pa o a) a I I
. a Jo :: ~1 I I
I I
_, _ --us a) I I
I I o o Jo o o O o o I) o o LO
e . .. ,, . . .,, I . . ,, co O O O
an . _ . .
~23S3~
three hours at 160C (or a shorter aging time at a higher temperature) produces a significant in-crease in both elongation and yield strength (as compared to the values in To temper) as well as achieving satisfactory levels of such other prop-reties as Erickson Cup height and ultimate tensile strength. More generally, the times to peak % slog anion and peak yield strength during artificial aging are dependent on alloy composition; efficiency of soul-lion heat treatment, as affected by time, -temperature, quenching rate, and prior influence from homogenization treatment of the ingot (e.g., whether the homogenization treatment dissolved all coarse Mg2 So); % of cold no-diction following solution heat treatment; extent of natural aging, and whether natural aging precedes or follows the cold reduction after solution heat treatment;
and aging temperature. The above factors, and also the final gauge, affect the magnitude of the peak elonga-lion during artificial aging. Accordingly, in the practice of the invention, the proper heating time for the artificial aging step is determined, after selection of the foregoing factors, by aging for different periods a series of samples of strip for which all these factors are nerd constant, thereby to establish the artificial aging time dependency of the yield strength and % elongation of such strip. An aging time at which suitable values of yield strength and % elongation are achieved can then be immediately determined, and employed as the artificial aging time for commercial production of the same strip. The procedure involved in thus establishing the aforementioned time dependency is simple and straightforward and can readily be practiced by -persons of ordinary skill in the art.
Conveniently, the artificial aging step of the present process can be performed US a batch artificial aging treatment, by heaving a coil of the strip at final :. :
-- , .
, .
~23S3fii~
gauge (and initially in To temper) to a temperature in the range of, say, 160C for a period of 1-3 hours.
Alternatively, aging can be performed by stowing the To strip for a much shorter time at a substantially higher temperature, e.g., by stowing for about 10 to about 20 minutes at about 200C. In particular in-stances, such a stowing step may also be used to perform some other function; for example, in the production of can lids, the stowing of the lid stock after lacquering 10 can be performed under the just-mentioned conditions so as to constitute the artificial aging step OX the present process. gain, in this rapid stowing treatment, the artificial aging step effects. an increase in yield strength and provides a % elongation (in the artificially aged strip) within 20~ of the maximum value attainable during stowing at the selected temperature, such value being commonly or preferably higher than the % elongation of the To temper strip before stowing.
The product of the present process, after completion of the artificial aging step, is a sheet article of Alms So alloy in To temper, exhibiting a combination of high strength and good formability achieved by the above described succession of steps, in particular including the artificial aging step performed under the specified conditions of aging for a time less than that required to achieve peak yield strength Such sheet may be produced in various final gauges, for a wide variety of different end uses for which this combination of strength and formability properties is necessary or advantageous.
Production of Cans - In specific and presently preferred embodiments of the process of the invention as employed for the production of components of cans (viz. drawn-and-ironed can bodies or lids therefore), the final gauge of the To strip resulting from the practice of the above-described steps is selected ~23S3~
to be appropriate for direct formation of can bodies (e.g. 0.014 inch final gauge strip) or lids (e.g.
0.013 inch final gauze strip), and the artificial ago in treatment is hollowed by a step of forming the To strip into a one-piece can body or a can lid, in act cordons with forming procedures now wholly conventional for forming such bodies and lids. Ordinarily the process in each instance (bodies and lids) will include a lacquer-in step, followed by stowing.
It is conventional, in the case of lids, to lacquer and stove the sheet stock from which the lid is made prior to the lid-forming operation. The lacquer in such case may be applied while the sheet is in To temper and as already stated, the subsequent stowing of the lacquered sheet may be performed under conditions (e.g. heaving for about 10-20 minutes at about 200C) selected to effect the special artificial aging treatment of the invention. Thereafter, the lacquered and stowed (To temper) sheet is conventionally wormed into can lids. Alternatively, the To temper sheet may first be artificially aged in accordance with the in-mention and subsequently lacquered, stowed, and formed into lids.
In the case of can body stock, the forming (drawing and ironing operations precede lacquering and 25 stowing, and the stock in final gauge is subjected to the artificial aging step of the invention before be-in wormed into can bodies, i.e. the stowing after lacquering is a separate heat treatment performed sub-sequent to artificial aging. Where stowing after lacquering 30 is performed as a separate treatment, it ordinarily coca-sons some reduction in strength, but causes relatively less .
.;"
' ~L~3~;3~
strength reduction than is caused by stowing of AA 3004 lacquered cans.
The products of these embodiments of the present process are, respectively, a drawn-and-ironed can body and a can lid of Alex alloy having the beneficial properties developed by the combination of treatments described above. Lucite advantageously, a lid and body of the same alloy composition are produced and assembled to provide a can wherein both components (lid and body) lo are constituted of a single composition as desired to facilitate recycling and reuse of the metal.
The invention affords further important advantages, as well, for the production of can lids and bodies. Con-lain of these advantages will be apparent from the compare iron of AA 6061 can stock prepared in accordance with the present process, and conventional AA 3004 and A 5182 can body and lid stock, set forth in Table II
wherein the AA 6061 stock at To temper (which is at a gauge of 0.013 inch) represents the product ox the invention:
.
. .
~L23S3~i~
-- I --Jo \
I 11; Lo O on I I
l l l l l l o o o o I, us o own Lo Jo aye I_ . I I I I
o o o o o out I
.,, I t ^
o I_ o I out O O do --H
a I I_ a) so u~coco kiwi En I X I
.
rî I` In r-- o En Us--Us I) a) o a a a) a a) o o so x 3 o o o o . do 3 o a o Q
or co I I
-I_ G' O O CO CO
O OWE
ED ED Us ., Lo The AA 6061 stock represented in the foregoing table was produced by successively direct chill casting and homogen-icing an ingot, hot rolling, cold rolling to an intermediate gauge, solution-heat-treating and quenching, natural aging for at least one day, and cold rolling (with 50-71% reduction) to final gauge, followed by artificial aging, as indicated for 3 hours at 160C. The lacquering treatment referred to in the table followed artificial aging (in the case of the AA 6061 stock and in each instance involved stowing the lacquered metal at SKYE for 10 minutes.
As is apparent from the table, the AA 6061-~r8 strip produced by the invention has earing and Erickson values comparable to conventional AA 3004 body stock, better bend-ability, and yield strength 14 ski (thousands of pounds per square inch) higher than the AA 3004 body stock before lacquer-in; after lacquering, though yield strength falls in both instances, the yield strength differential is even greater (17 ski in favor of the AA 6061-T8 stock. This lacquered strength is particularly important for can bodies as it directly affects the pressure at which the bottom of the filled can will buckle outwardly. Because of pasteurization after filling, a minimum bottom buckle pressure of 90 pi is commonly required for drawn-and-ironed can bodies. 3004-Hl9 can bodies generally develop buckle pressures between 95 and 110 pi in one test, 6061-T8 can bodies were shown to develop bottom buckle pressures in excess of 130 pi Thus, 6061-T8 can body stock produce by the process of the invention may be reduced in gauge, as compared to 3004-H19 stock, with consequent reduction in metal cost per can, and still exceed buckle pressure requirements.
Compared to 5182-Hl9 can lid stock, lacquered 6061-T8 stock produced in accordance with the invention has higher yield strength (7 ski higher, in the example represented by the table), higher Erickson cup values, and the same bendability, although the 6061-T8 stock may be slightly less formable than 5182-Hl9 stock under severe draw conditions, and the higher 'foe yield strength of 6061-T8 does not provide improved buckle pressure performance, owing to the higher work hardening rate of the 5182 alloy, which results in a strength equivalent to 6061 in the formed areas of the lid which actually control buckle performance. Never-the less, as the comparison of properties in the table illustrates the properties exhibited by the 6061-T8 sheet are fully adequate for use as both lid and body stock, and are generally equivalent to or better than the properties of the conventional alloys used for lids and bodies.
It is to be understood that the invention is not limited to the features and embodiments hereinabove specifically set forth but may be carried out in other ways without departure from its spirit.
Claims (17)
1. A process for producing aluminum alloy sheet of predetermined final gauge, comprising the steps of:
(a) providing a sheet article, at an inter-mediate gauge from which a reduction of between about 25% and about 71% is re-quired to achieve said final gauge, of a heat-treatable Al-Mg-Si alloy having a major content of Al and a minor con-tent of Mg and available Si such that on a rectangular graph of % Mg plotted against % available Si the point repre-senting said minor content lies within the area of a pentagon defined by the coordinates 0.2% Si, 0.4% Mg; 0.2% Si, 0.9% Mg; 0.4% Si, 1.2% Mg; 1.2% Si, 1.2%
Mg; and 1.2% Si, 0.4% Mg;
(b) solution-heat-treating the sheet article at said intermediate gauge by successively heating and quenching the article, for effecting at least substantially complete solution of the Mg and Si therein;
(c) after quenching, and without intervening heat treatment, naturally aging the sheet article by maintaining the sheet article at ambient temperature for at least about one day;
(d) after natural aging, and without interven-ing heat treatment, cold rolling the sheet article to said final gauge; and (e) artificially aging the cold rolled sheet article at said final gauge for increas-ing the yield strength thereof by heating the article to a predetermined temperature for a time shorter than that required to achieve the maximum yield strength attain-able by artificial aging of said final gauge cold rolled sheet article at said temper-ature, and such that the % elongation value of the article after artificial aging is within 20% of the maximum value attainable by artificial aging of said final-gauge cold rolled sheet article at said temperature following the extent of cold reduction per-formed in step (d).
(a) providing a sheet article, at an inter-mediate gauge from which a reduction of between about 25% and about 71% is re-quired to achieve said final gauge, of a heat-treatable Al-Mg-Si alloy having a major content of Al and a minor con-tent of Mg and available Si such that on a rectangular graph of % Mg plotted against % available Si the point repre-senting said minor content lies within the area of a pentagon defined by the coordinates 0.2% Si, 0.4% Mg; 0.2% Si, 0.9% Mg; 0.4% Si, 1.2% Mg; 1.2% Si, 1.2%
Mg; and 1.2% Si, 0.4% Mg;
(b) solution-heat-treating the sheet article at said intermediate gauge by successively heating and quenching the article, for effecting at least substantially complete solution of the Mg and Si therein;
(c) after quenching, and without intervening heat treatment, naturally aging the sheet article by maintaining the sheet article at ambient temperature for at least about one day;
(d) after natural aging, and without interven-ing heat treatment, cold rolling the sheet article to said final gauge; and (e) artificially aging the cold rolled sheet article at said final gauge for increas-ing the yield strength thereof by heating the article to a predetermined temperature for a time shorter than that required to achieve the maximum yield strength attain-able by artificial aging of said final gauge cold rolled sheet article at said temper-ature, and such that the % elongation value of the article after artificial aging is within 20% of the maximum value attainable by artificial aging of said final-gauge cold rolled sheet article at said temperature following the extent of cold reduction per-formed in step (d).
2. A process according to claim 1, wherein the available Si content of said alloy is in excess of that required to.
combine completely with the Mg content present as Mg2Si.
combine completely with the Mg content present as Mg2Si.
3. A process according to claim 2, wherein the available Si content is greater, by an amount of at least 0.05%
of the weight of said alloy, than that needed to combine completely with the Mg content of said alloy as aforesaid.
of the weight of said alloy, than that needed to combine completely with the Mg content of said alloy as aforesaid.
4. A process according to claim 3, wherein said alloy contains Fe, and wherein the Si content of said alloy is greater than that needed to combine completely with the Mg content of said alloy by an amount equal to at least 0.05% of the weight of said alloy plus at least about 1/3 of the weight % of Fe present in said alloy.
5. A process according to claim 4, wherein the Mg content of said alloy is selected to provide a total Mg2Si content between about 1.35% and about 1.50%.
6. A process according to claim 1, wherein the natural aging step is performed by maintaining the sheet article at ambient temperature for at least about 3 days.
7. A process according to claim 1, wherein said intermediate gauge is such that a reduction of at least about 35% therefrom is required to achieve said final gauge.
8. A process according to claim 7, wherein said intermediate gauge is such that a reduction of at least about 50% therefrom is required to achieve said final gauge.
9. A process according to claim 1, wherein the artificial aging step is performed by heating the article to a predetermined temperature for a time at which the % elongation value of the article is greater than the %
elongation value of the article immediately prior to the artificial aging step.
elongation value of the article immediately prior to the artificial aging step.
10. Aluminum alloy sheet produced by the process of claim 1.
11. A process according to claim 1, further includ-ing the step of forming the sheet article into a component of a can, said can consisting essentially of a one piece drawn and ironed body having an open end and a lid for closing the open end, said body and said lid being the components of said can.
12. A process according to claim 11, wherein said component is a can lid, wherein said sheet article, after rolling to said final gauge, is coated with lacquer and stoved under conditions selected to effect arti-ficial aging of the article as aforesaid, and wherein the step of forming the sheet article into the lid is performed after stoving.
13. A process according to claim 11, wherein said component is a one-piece drawn and ironed can body, and wherein the step of forming the sheet article into the body is performed after said artificial aging step.
14. A can component produced by the process of claim 11.
15. A process according to claim 1, wherein said alloy consists essentially of about 0.2% to about 1.2%
available Si, about 0.4% to about 1.2% Mg, up to 0.9%
Cu, up to 1.0% Fe, up to 0.8% Mn, up to 0.35% Cr, up to 0.25% Zn, up to 0.20% Ti, balance Al.
available Si, about 0.4% to about 1.2% Mg, up to 0.9%
Cu, up to 1.0% Fe, up to 0.8% Mn, up to 0.35% Cr, up to 0.25% Zn, up to 0.20% Ti, balance Al.
16. A process for producing an aluminum alloy can consisting essentially of a one-piece drawn and ironed body having an open end, and a lid for closing the open end, said process comprising:
(a) preparing a first sheet article, in T3 temper, of a heat-treatable Al-Mg-Si alloy;
(b) preparing a second sheet article, in T3 temper, of the same Al-Mg-Si alloy;
(c) artificially aging each said sheet ar-ticle for increasing the yield strength thereof by heating the article to a pre-determined temperature for a time shorter than that required to achieve the maximum yield strength attainable by artificial:
aging of the same article at said tempe-rature, and such that the % elongation value of the article after artificial aging is within 20% of the maximum value attainable by artificial aging of the same article at said temperature;
(d) forming one of said articles into a one piece drawn and ironed can body having an open end;
(e) forming the other of said articles into a lid for closing said open end; and (f) assembling said body and said lid to produce a closed can.
(a) preparing a first sheet article, in T3 temper, of a heat-treatable Al-Mg-Si alloy;
(b) preparing a second sheet article, in T3 temper, of the same Al-Mg-Si alloy;
(c) artificially aging each said sheet ar-ticle for increasing the yield strength thereof by heating the article to a pre-determined temperature for a time shorter than that required to achieve the maximum yield strength attainable by artificial:
aging of the same article at said tempe-rature, and such that the % elongation value of the article after artificial aging is within 20% of the maximum value attainable by artificial aging of the same article at said temperature;
(d) forming one of said articles into a one piece drawn and ironed can body having an open end;
(e) forming the other of said articles into a lid for closing said open end; and (f) assembling said body and said lid to produce a closed can.
17. A process for producing aluminum alloy sheet of predetermined final gauge, comprising the steps of:
(a) providing a sheet article, at an inter-mediate gauge from which a reduction of between about 25% and about 71% is required to achieve said final gauge, of a heat-treatable Al-Mg-Si alloy having a major content of Al and a minor content of Mg and available Si such that on a rectangular graph of % Mg plotted against % available Si the point representing said minor content lies within the area of a pentagon defined by the coordinates 0.2% Si, 0.4% Mg; 0.2% Si, 0.9% Mg; 0.4%
Si, 1.2% Mg; 1.2% Si, 1.2% Mg; and 1.2%
Si, 0. 4% Mg;
(b) solution-heat-treating the sheet article at said intermediate gauge by succes-sively heating and quenching the article, for effecting at least substantially complete solution of the Mg and the Si therein;
(c) after quenching, and without intervening heat treatment, naturally aging the sheet article by maintaining the sheet article at ambient temperature for at least about one day;
(d) after natural aging, and without inter-vening heat treatment, cold rolling the sheet article to said final gauge; and (e) artificially aging the cold rolled sheet article at said final gauge for increasing the yield strength thereof by heating the article to a predetermined temperature, beginning at a time T0, under conditions such that (i) achievement of the maximum yield strength attainable by artificial aging of said final gauge cold rolled sheet article at said temperature requires continuing the heating until a time T2 later than T0, and (ii) the maximum value of % elongation attainable by artificial aging of said final-gauge cold rolled sheet article at said temperature following the extent of cold reduction performed in step (d) would be achieved by continuing the heating until a time T1 later than T0 but earlier than T2 and terminating the heating at T1;
wherein improvement comprises:
(f) continuing the heating in step (e) at:
least until T1 and terminating the heating at a time prior to T2 and such that the % elongation value of the article after artificial aging is within 20% of said maximum value of %
elongation.
(a) providing a sheet article, at an inter-mediate gauge from which a reduction of between about 25% and about 71% is required to achieve said final gauge, of a heat-treatable Al-Mg-Si alloy having a major content of Al and a minor content of Mg and available Si such that on a rectangular graph of % Mg plotted against % available Si the point representing said minor content lies within the area of a pentagon defined by the coordinates 0.2% Si, 0.4% Mg; 0.2% Si, 0.9% Mg; 0.4%
Si, 1.2% Mg; 1.2% Si, 1.2% Mg; and 1.2%
Si, 0. 4% Mg;
(b) solution-heat-treating the sheet article at said intermediate gauge by succes-sively heating and quenching the article, for effecting at least substantially complete solution of the Mg and the Si therein;
(c) after quenching, and without intervening heat treatment, naturally aging the sheet article by maintaining the sheet article at ambient temperature for at least about one day;
(d) after natural aging, and without inter-vening heat treatment, cold rolling the sheet article to said final gauge; and (e) artificially aging the cold rolled sheet article at said final gauge for increasing the yield strength thereof by heating the article to a predetermined temperature, beginning at a time T0, under conditions such that (i) achievement of the maximum yield strength attainable by artificial aging of said final gauge cold rolled sheet article at said temperature requires continuing the heating until a time T2 later than T0, and (ii) the maximum value of % elongation attainable by artificial aging of said final-gauge cold rolled sheet article at said temperature following the extent of cold reduction performed in step (d) would be achieved by continuing the heating until a time T1 later than T0 but earlier than T2 and terminating the heating at T1;
wherein improvement comprises:
(f) continuing the heating in step (e) at:
least until T1 and terminating the heating at a time prior to T2 and such that the % elongation value of the article after artificial aging is within 20% of said maximum value of %
elongation.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US588,945 | 1984-03-13 | ||
| US06/588,945 US4637842A (en) | 1984-03-13 | 1984-03-13 | Production of aluminum alloy sheet and articles fabricated therefrom |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1235361A true CA1235361A (en) | 1988-04-19 |
Family
ID=24355973
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000476424A Expired CA1235361A (en) | 1984-03-13 | 1985-03-13 | Production of aluminum alloy sheet and articles fabricated therefrom |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS63162844A (en) |
| CA (1) | CA1235361A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4012216A1 (en) * | 1990-04-14 | 1991-10-17 | Boehringer Mannheim Gmbh | TEST CARRIER FOR THE ANALYSIS OF LIQUIDS |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61288056A (en) * | 1985-06-13 | 1986-12-18 | Sumitomo Light Metal Ind Ltd | Manufacture of aluminum alloy sheet for deep drawing |
-
1985
- 1985-03-13 CA CA000476424A patent/CA1235361A/en not_active Expired
-
1986
- 1986-12-19 JP JP30357386A patent/JPS63162844A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPS63162844A (en) | 1988-07-06 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4637842A (en) | Production of aluminum alloy sheet and articles fabricated therefrom | |
| US5106429A (en) | Process of fabrication of aluminum sheet | |
| US4605448A (en) | Aluminum alloy forming sheet and method for producing the same | |
| US5104465A (en) | Aluminum alloy sheet stock | |
| US4318755A (en) | Aluminum alloy can stock and method of making same | |
| US5110545A (en) | Aluminum alloy composition | |
| EP0672758A1 (en) | Method of manufacturing canning steel sheet with non-aging property and superior workability | |
| EP0786535A1 (en) | Method of manufacturing aluminum alloy plate for molding | |
| US4517034A (en) | Strip cast aluminum alloy suitable for can making | |
| US4284437A (en) | Process for preparing hard tempered aluminum alloy sheet | |
| JPS6330368B2 (en) | ||
| US5616190A (en) | Process for producing a thin sheet suitable for making up constituent elements of cans | |
| US5913989A (en) | Process for producing aluminum alloy can body stock | |
| US4838955A (en) | Method for the manufacture of hard steel sheet from Al-killed continuous-cast carbon-manganese steel | |
| CA1235361A (en) | Production of aluminum alloy sheet and articles fabricated therefrom | |
| US3772091A (en) | Very thin steel sheet and method of producing same | |
| US6156131A (en) | Process for manufacturing a strip of steel sheet for the production of metal packaging by drawings and steel sheet obtained | |
| AU659099B2 (en) | Al base - Mn-Mg alloy for the manufacture of drawn and ironed container bodies | |
| JPS6339655B2 (en) | ||
| EP0269773B1 (en) | Production of aluminum alloy sheet and articles fabricated therefrom | |
| US5746847A (en) | Aluminum alloy sheet for easy-open can ends having excellent corrosion resistance and age softening resistance and its production process | |
| WO1992004477A1 (en) | Aluminum alloy composition | |
| US5704997A (en) | Process for preparing a steel strip and novel steel strip | |
| JPH01123054A (en) | Hard-baked-type high-strength can material and its production | |
| EP0801141A1 (en) | Method for the manufacture of aluminium alloy sheet |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |