CA1193524A - Process for preparing low earing aluminum alloy strip on strip casting machine - Google Patents
Process for preparing low earing aluminum alloy strip on strip casting machineInfo
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- CA1193524A CA1193524A CA000436945A CA436945A CA1193524A CA 1193524 A CA1193524 A CA 1193524A CA 000436945 A CA000436945 A CA 000436945A CA 436945 A CA436945 A CA 436945A CA 1193524 A CA1193524 A CA 1193524A
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Abstract
ABSTRACT OF THE DISCLOSURE
There is described a process for fabricating high strength, improved formability, low earing aluminum strip stock from hot rolled aluminum strip. According to this process, the hot rolled strip is cold rolled in a first series of passes to an intermediate gauge. Then, it is flash annealed for not more than 90 seconds at a temperature of from about 350°C to 500°C. Finally, the flash annealed strip is cold rolled in a second series of passes to final gauge.
There is described a process for fabricating high strength, improved formability, low earing aluminum strip stock from hot rolled aluminum strip. According to this process, the hot rolled strip is cold rolled in a first series of passes to an intermediate gauge. Then, it is flash annealed for not more than 90 seconds at a temperature of from about 350°C to 500°C. Finally, the flash annealed strip is cold rolled in a second series of passes to final gauge.
Description
A
~ACKGROUND OF THE INVENTION
The present invention teaches a process for preparing strip stock from aluminum and aluminurn alloys, preferably Al-Mg-Mn alloys, by means o~ strip casting machinesg wherein the strip exhibits low earing properties and is suitable for use in the manufacture o~ deep drawn and ironed hollow articles such as cans or the like.
In recent years Al-Mg-Mn alloys, in the form of cold rolled strip, have been success~ully processed into beverage cans by deep drawing and ironing. A number of processes are known for the production of aluminum strip for use in these beverage cans.
Typically, aluminum is cast by known methods such as horizontal and vertical direct chill casting, or strip casting for fur~her treatment. One such known process is disclosed in U.S. Patent 3,787,248 to Setzer et al. and assigned to the Assignee of the present invention. The process comprises casting an Al-Mg-Mn alloy, homogenizing this alloy at a temperature of between 455C
to 620C for 2 to 24 hours, hot rolling from a starting temperature Or 3115C to 510C with a total reduction in thickness of at least 20%, subsequent rolling, starting from a temperature Or 205C to 430C with reduction Or at least 20%, subsequent rolling, starting ~rom a temperature Or less than 205C with reduction o~ at least 20%, heating the alloy between 95C and 230C ror at least 5 seconds but no longer than a time determined by the equation T(10 t log t) - 12,500, T standing for degrees Kelvin and t for maxirnum time in minutes.
While the process disclosed in the aforenoted patent has been used successfully ror making rnetal strip to be used in the manufacture of cans, it has been found that strip produced by said process is not completely satisfactory in that the material experiences a high degree of earing.
A further known process for ~he production of strip is disclosed in Light' ~et'aI'Age, Volume 33, 1975g December, ;' Pages 28-33. In the aforenoted ar~icle the strip was prepared '` by a strip casting process and was thereafter treated so as to be useful in the manufacture of cans. One basic problem which arises in the production of strip via strip casting machines as disclGsed in the above-noted article is that the dendritic arm spacing or cell size at the surface of the strip is too large.
As a result of this large dendritic arm spacing, the strip exhibits extensive surface porosity which leads to cracks in the ~inal rolled strip. In addition, when the dendritic arm spacing is too large, there is a danger of surface segregation which can lead to poor quality in the final rolled strip which in turn causes difficulties during the drawing and ironing operation.
~ ccordingly, it is a principal object of the present invention to provide a process for preparing alwninum alloy strip stock by means of a continuous strip casting machine which exhibits properties favorable for further processing by cold rolling~
It is a further object of the present invention to provide an improved process for cold rolling continuous strip cast stock to thereby :Lmprove the earing properties thereof.
It is still a further object of the present invention to provide the process as aforesaid which enables t'he aluminum alloy strip to be used in the production of cans and the llke.
~ urther objects and advantages will appear hereinbelow.
s~
UMMAR~ OF THE INVENTION
In accordance with the present invention, the foregoing objects and advantages may be readily obtained.
In accordance with one embodiment of the invention, there is provided a multi-stepped process for fabricating high strength, improved formability, low earing aluminum strip stock from an aluminum melt comprising: A) continuously casting said aluminum melt in strip form; B) holding said casting strip at casting speed after the start of solidifica-tion at a ternperature be-tween 400C and the liquidus te~pera-ture of the alloy for about 2 to 15 minutes prior to hot rolling so as to obtain a preferred dendritic arm spacing;
C) continuously hot rolling the cast strip at casting speed at a temperature range betwee~ 300C and the non-equilibrium solidus temperature of the alloy to a total reduction of at least 7~/0; and D) hot coiling said hot rolled strip wherein said coiled strip is allowed to cool in air to room temperature prior to further worklng.
In accordance with another embodiment of the invention, there is provided a multi-stepped process for fabricating high strength, improved formability, low earing aluminum strip stock from an aluminum melt comprising:
A) continuously casting said aluminum melt in strip form so as to obtai.n a preferred dendritic arrn spacing B) continuous-ly hot rolling the cast stri.p at casting speed at a tempera-ture range between 300C and the non-equilibrium solidus ternperature of the alloy to a total reduction of at least 70/0, C) hot coiling said hot rolled strip wherein said coiled str.ip is allowed to cool in air to room ternperature prior to further working; D) cold rolling said cooled hot rolled strip il~ a first series of passes to a strip of intermediate gauge;
E) flash annealing said cold rolled strip for not more than 90 seconds at a temperature of from about 350C to about 500C, and F) cold rolling said annealed strip in a second series oE passes to final gauge.
In accordance with yet another embodiment of the invention, there is provided a process for fabricating high strength, improved formability, low earing aluminum strip stock from hot ro:Lled aluminum strip comprising: A) cold rolling said hot rolled strip in a first series of passes to an intermediate gauge, B) flash annealing said cold rolled strip for not more than 90 seconds at a temperature of from about 350C to 500C, and C) cold rolling said flash annealed strip in a second series of passes to final gaugeO
In accordance with yet another embodiment of the invention the cast strip may be held at casting speed after the start of solidification at a temperature between 500C and the ]iquidus temperature of the alloy for frorn about 10 to 50 seconds prior to hot rolling.
In accordance with a broad embodiment of the invention, there is provided a multi-stepped process for fabricating high strength, improved formability, low earing aluminum strip stock from an aluminum melt. According to this broad embodiment the aluminum melt is cast continuously in strip form. Then the cast strip is continuously hot rolled at casting speed, at a tempera-ture range between 300C and the non-equilibrium solidus temp-erature of the alloy to a total reduction of at least 70%.
Finally, the hot rolled strip is hot coiled and then the coiled strip is allowed to cool in air at room temperature prior to further working.
In accordance with yet another embodiment of the present invention, there is provided a high strength aluminum - 4a -: base alloy particularly Al-Mg-Mn alloys having improved earing properties which comprises: A) continuously casting said alloy melt in strip forrn on a strip casting machine so as to obtain a dendritic arm spacing in the region of the surface of the as-cast strip from about 2 to 25 ~m, preferably from about 5 to 15 ~m and the dendritic arm spacing in the center of the strip is from about 20 to 120 ~m, preferably from about 50 to 80 ~rn' B) continuously hot rolling the cast strip at casting speed at a temperature range between 300~C and the non- -equilibrium solidus temperature of the alloy to a total reduction of at least 70~/O~ whereby the temperature of the strip at the start of hot rolling is between said non-equilibrium solidus temperature and a temperature of about 150C below said non-equilibrium solidus temperature wherein the temperature of the strip at the end of the hot rolling is at least 280C; C) hot coili.ng said strip whereby said coiled strip is allowed to cool to room temperature in air, D) cold rolling said cooled strip in a first series of passes with a total reduction of at least 50%, preferably at least 65%, E) Elash annealing said cold rolled strip for not more than 90 seconds at a temperature of from about 350C to 500C, and - 4b -F. cold rolling said strip in a second series of passes with a total reduction not to exceed 75%, preferably not to exceed 70%.
In the preferred embodiment, the cast strip of the present invention is cast on a strip casting machine having a plurality of continuously moving chilling blocks, as is kno~n in the art, such that the cast strip arter the start o~ solidification is held at a temperature between 400C and the liquidus temperature of the alloy for 2 to 15 minutes, preferably above 500C for preferably 10 to 50 seconds. By controlling the solidification rate the desired dendritic arm spacing-as well as optimum distribution of insoluble heterogeneities is achieved. In addition, by controlling the cooling rate, homogenization treatments required in conventional processes can be eliminated due to the uniformity of composition of the as-cast strip.
The present invention resides in an improved process ~or casting aluminurn and aluminum alloys, and in particular Al-Mg-Mn alloys wherein the total concentration of magnesium and manganese is from 2.0 to 3.3%, the ratio of magnesium 20 to rnanganese is from 1.4:1 to 4.4:1 and the total concentration of other alloying elements and impurities is 1.5% maximum.
The process of the present invention lowers the cost of rnanu~facturing aluminum strip by eliminating ingot casting, su~sequent hornogenization treatment, and the additional cost of hot rolling the large ingots.
_RIEF DESCR:~PTlON OF THR DRAWING
Figure 1 is a schematic illustration Or the strip casting machine used in the process of the present invention.
r~
DE~AILED DESCRIPTION
. ~
As indicated hereinabove; the present invention comprises a process for producing hot rolled aluminum sheet by a strip casting machine which is characterized by a preferred dendritic arm spacing and insoluble heterogeneity distribution which structures are essentially desirable when the strip is to be further processed by subsequent cold rolling operations.
rrhe present invention further comprises an improved cold rolling process for further processing the hot rolled strip which improves the earing properties thereof thus making the strip stock especially suitable for use in the proauction of deep drawn and ironea articles such as cans'or the like.
Figure 1 is a schematic illustration of the strip caster employed in the process of the present invention. ~he details of the strip caster employed in the present invention can be found in U.S. Patents 3,709,281, 3,744,545, 3,759,313 3,77~670 and 3~835,917. With reference to Figure 1, two sets of chilling blocks are employed and rotate in opposite senses to form a casting cavity into which the aluminum alloy is brought through a thermally insulated nozzle system, not shown.
rrhe liquid metal upon contact with the chilling blocks is cooled and solidified. The strip of metal travels during this cooling and solidifying phase along with the chilling blocks ulltil the strip exits the casting cavity where the chilling blocks lift off the cast strip and start the return path to a cooler where the chi]ling blocks are cooled before returning to the casting cavity.
It has been found that by controlling the cooling rate and thereby the rate of solidification of the cast strip as it passes through the casting cavity the desired dendritic and heterogeneity C~U ~ A
structure can be obtained. On cooling the aluminum alloy from the liquid state there are two important ternperature ranges.
The first temperature range being that temperature between the liquidus and the solidus of the aluminum alloy. The second temperature range being between the solidus and a temperature 100C below the solidus. The time taken to cool through the li~uidus to solidus temperature range controls the average secondary dendrite arm spacing. While the time taken to cool în the range of the solidus temperature to a point 100C below the solidus ternperature eliminates to-a large extent nonunifor-mities in the as-cast strip by controlling the rounding of the heterogeneities in the as-cast structure, the equalization or distribution of the heterogeneities and the transformation of non-equilibrium phases to equilibrium phases.
The rate of cooling as the cast strip passes through the casting cavity of the strip casting machine illustrated in Figure 1 is controlled by controlling various process and product parameters. These parameters include material cast, strip gauge~
chill block material, length of casting cavity, casting speed and efflciency of the chill block cooling system.
It is a surprising advantage of the process of the present invention that this process imparts significant improved physical characteristics to the aluminum material processed characterized by improved stren~th arld earing properties. These characteristics will be discussed in greater detail hereinbelow.
As an example Or the foregoing, conventional materials currently used in the production of strip include Aluminum Alloy 3004. Alloy 3004 having the following composition has been found to be particularly suitable ~or use in the process of the present invention: magnesium from o.8 to 1.3%, magnanese
~ACKGROUND OF THE INVENTION
The present invention teaches a process for preparing strip stock from aluminum and aluminurn alloys, preferably Al-Mg-Mn alloys, by means o~ strip casting machinesg wherein the strip exhibits low earing properties and is suitable for use in the manufacture o~ deep drawn and ironed hollow articles such as cans or the like.
In recent years Al-Mg-Mn alloys, in the form of cold rolled strip, have been success~ully processed into beverage cans by deep drawing and ironing. A number of processes are known for the production of aluminum strip for use in these beverage cans.
Typically, aluminum is cast by known methods such as horizontal and vertical direct chill casting, or strip casting for fur~her treatment. One such known process is disclosed in U.S. Patent 3,787,248 to Setzer et al. and assigned to the Assignee of the present invention. The process comprises casting an Al-Mg-Mn alloy, homogenizing this alloy at a temperature of between 455C
to 620C for 2 to 24 hours, hot rolling from a starting temperature Or 3115C to 510C with a total reduction in thickness of at least 20%, subsequent rolling, starting from a temperature Or 205C to 430C with reduction Or at least 20%, subsequent rolling, starting ~rom a temperature Or less than 205C with reduction o~ at least 20%, heating the alloy between 95C and 230C ror at least 5 seconds but no longer than a time determined by the equation T(10 t log t) - 12,500, T standing for degrees Kelvin and t for maxirnum time in minutes.
While the process disclosed in the aforenoted patent has been used successfully ror making rnetal strip to be used in the manufacture of cans, it has been found that strip produced by said process is not completely satisfactory in that the material experiences a high degree of earing.
A further known process for ~he production of strip is disclosed in Light' ~et'aI'Age, Volume 33, 1975g December, ;' Pages 28-33. In the aforenoted ar~icle the strip was prepared '` by a strip casting process and was thereafter treated so as to be useful in the manufacture of cans. One basic problem which arises in the production of strip via strip casting machines as disclGsed in the above-noted article is that the dendritic arm spacing or cell size at the surface of the strip is too large.
As a result of this large dendritic arm spacing, the strip exhibits extensive surface porosity which leads to cracks in the ~inal rolled strip. In addition, when the dendritic arm spacing is too large, there is a danger of surface segregation which can lead to poor quality in the final rolled strip which in turn causes difficulties during the drawing and ironing operation.
~ ccordingly, it is a principal object of the present invention to provide a process for preparing alwninum alloy strip stock by means of a continuous strip casting machine which exhibits properties favorable for further processing by cold rolling~
It is a further object of the present invention to provide an improved process for cold rolling continuous strip cast stock to thereby :Lmprove the earing properties thereof.
It is still a further object of the present invention to provide the process as aforesaid which enables t'he aluminum alloy strip to be used in the production of cans and the llke.
~ urther objects and advantages will appear hereinbelow.
s~
UMMAR~ OF THE INVENTION
In accordance with the present invention, the foregoing objects and advantages may be readily obtained.
In accordance with one embodiment of the invention, there is provided a multi-stepped process for fabricating high strength, improved formability, low earing aluminum strip stock from an aluminum melt comprising: A) continuously casting said aluminum melt in strip form; B) holding said casting strip at casting speed after the start of solidifica-tion at a ternperature be-tween 400C and the liquidus te~pera-ture of the alloy for about 2 to 15 minutes prior to hot rolling so as to obtain a preferred dendritic arm spacing;
C) continuously hot rolling the cast strip at casting speed at a temperature range betwee~ 300C and the non-equilibrium solidus temperature of the alloy to a total reduction of at least 7~/0; and D) hot coiling said hot rolled strip wherein said coiled strip is allowed to cool in air to room temperature prior to further worklng.
In accordance with another embodiment of the invention, there is provided a multi-stepped process for fabricating high strength, improved formability, low earing aluminum strip stock from an aluminum melt comprising:
A) continuously casting said aluminum melt in strip form so as to obtai.n a preferred dendritic arrn spacing B) continuous-ly hot rolling the cast stri.p at casting speed at a tempera-ture range between 300C and the non-equilibrium solidus ternperature of the alloy to a total reduction of at least 70/0, C) hot coiling said hot rolled strip wherein said coiled str.ip is allowed to cool in air to room ternperature prior to further working; D) cold rolling said cooled hot rolled strip il~ a first series of passes to a strip of intermediate gauge;
E) flash annealing said cold rolled strip for not more than 90 seconds at a temperature of from about 350C to about 500C, and F) cold rolling said annealed strip in a second series oE passes to final gauge.
In accordance with yet another embodiment of the invention, there is provided a process for fabricating high strength, improved formability, low earing aluminum strip stock from hot ro:Lled aluminum strip comprising: A) cold rolling said hot rolled strip in a first series of passes to an intermediate gauge, B) flash annealing said cold rolled strip for not more than 90 seconds at a temperature of from about 350C to 500C, and C) cold rolling said flash annealed strip in a second series of passes to final gaugeO
In accordance with yet another embodiment of the invention the cast strip may be held at casting speed after the start of solidification at a temperature between 500C and the ]iquidus temperature of the alloy for frorn about 10 to 50 seconds prior to hot rolling.
In accordance with a broad embodiment of the invention, there is provided a multi-stepped process for fabricating high strength, improved formability, low earing aluminum strip stock from an aluminum melt. According to this broad embodiment the aluminum melt is cast continuously in strip form. Then the cast strip is continuously hot rolled at casting speed, at a tempera-ture range between 300C and the non-equilibrium solidus temp-erature of the alloy to a total reduction of at least 70%.
Finally, the hot rolled strip is hot coiled and then the coiled strip is allowed to cool in air at room temperature prior to further working.
In accordance with yet another embodiment of the present invention, there is provided a high strength aluminum - 4a -: base alloy particularly Al-Mg-Mn alloys having improved earing properties which comprises: A) continuously casting said alloy melt in strip forrn on a strip casting machine so as to obtain a dendritic arm spacing in the region of the surface of the as-cast strip from about 2 to 25 ~m, preferably from about 5 to 15 ~m and the dendritic arm spacing in the center of the strip is from about 20 to 120 ~m, preferably from about 50 to 80 ~rn' B) continuously hot rolling the cast strip at casting speed at a temperature range between 300~C and the non- -equilibrium solidus temperature of the alloy to a total reduction of at least 70~/O~ whereby the temperature of the strip at the start of hot rolling is between said non-equilibrium solidus temperature and a temperature of about 150C below said non-equilibrium solidus temperature wherein the temperature of the strip at the end of the hot rolling is at least 280C; C) hot coili.ng said strip whereby said coiled strip is allowed to cool to room temperature in air, D) cold rolling said cooled strip in a first series of passes with a total reduction of at least 50%, preferably at least 65%, E) Elash annealing said cold rolled strip for not more than 90 seconds at a temperature of from about 350C to 500C, and - 4b -F. cold rolling said strip in a second series of passes with a total reduction not to exceed 75%, preferably not to exceed 70%.
In the preferred embodiment, the cast strip of the present invention is cast on a strip casting machine having a plurality of continuously moving chilling blocks, as is kno~n in the art, such that the cast strip arter the start o~ solidification is held at a temperature between 400C and the liquidus temperature of the alloy for 2 to 15 minutes, preferably above 500C for preferably 10 to 50 seconds. By controlling the solidification rate the desired dendritic arm spacing-as well as optimum distribution of insoluble heterogeneities is achieved. In addition, by controlling the cooling rate, homogenization treatments required in conventional processes can be eliminated due to the uniformity of composition of the as-cast strip.
The present invention resides in an improved process ~or casting aluminurn and aluminum alloys, and in particular Al-Mg-Mn alloys wherein the total concentration of magnesium and manganese is from 2.0 to 3.3%, the ratio of magnesium 20 to rnanganese is from 1.4:1 to 4.4:1 and the total concentration of other alloying elements and impurities is 1.5% maximum.
The process of the present invention lowers the cost of rnanu~facturing aluminum strip by eliminating ingot casting, su~sequent hornogenization treatment, and the additional cost of hot rolling the large ingots.
_RIEF DESCR:~PTlON OF THR DRAWING
Figure 1 is a schematic illustration Or the strip casting machine used in the process of the present invention.
r~
DE~AILED DESCRIPTION
. ~
As indicated hereinabove; the present invention comprises a process for producing hot rolled aluminum sheet by a strip casting machine which is characterized by a preferred dendritic arm spacing and insoluble heterogeneity distribution which structures are essentially desirable when the strip is to be further processed by subsequent cold rolling operations.
rrhe present invention further comprises an improved cold rolling process for further processing the hot rolled strip which improves the earing properties thereof thus making the strip stock especially suitable for use in the proauction of deep drawn and ironea articles such as cans'or the like.
Figure 1 is a schematic illustration of the strip caster employed in the process of the present invention. ~he details of the strip caster employed in the present invention can be found in U.S. Patents 3,709,281, 3,744,545, 3,759,313 3,77~670 and 3~835,917. With reference to Figure 1, two sets of chilling blocks are employed and rotate in opposite senses to form a casting cavity into which the aluminum alloy is brought through a thermally insulated nozzle system, not shown.
rrhe liquid metal upon contact with the chilling blocks is cooled and solidified. The strip of metal travels during this cooling and solidifying phase along with the chilling blocks ulltil the strip exits the casting cavity where the chilling blocks lift off the cast strip and start the return path to a cooler where the chi]ling blocks are cooled before returning to the casting cavity.
It has been found that by controlling the cooling rate and thereby the rate of solidification of the cast strip as it passes through the casting cavity the desired dendritic and heterogeneity C~U ~ A
structure can be obtained. On cooling the aluminum alloy from the liquid state there are two important ternperature ranges.
The first temperature range being that temperature between the liquidus and the solidus of the aluminum alloy. The second temperature range being between the solidus and a temperature 100C below the solidus. The time taken to cool through the li~uidus to solidus temperature range controls the average secondary dendrite arm spacing. While the time taken to cool în the range of the solidus temperature to a point 100C below the solidus ternperature eliminates to-a large extent nonunifor-mities in the as-cast strip by controlling the rounding of the heterogeneities in the as-cast structure, the equalization or distribution of the heterogeneities and the transformation of non-equilibrium phases to equilibrium phases.
The rate of cooling as the cast strip passes through the casting cavity of the strip casting machine illustrated in Figure 1 is controlled by controlling various process and product parameters. These parameters include material cast, strip gauge~
chill block material, length of casting cavity, casting speed and efflciency of the chill block cooling system.
It is a surprising advantage of the process of the present invention that this process imparts significant improved physical characteristics to the aluminum material processed characterized by improved stren~th arld earing properties. These characteristics will be discussed in greater detail hereinbelow.
As an example Or the foregoing, conventional materials currently used in the production of strip include Aluminum Alloy 3004. Alloy 3004 having the following composition has been found to be particularly suitable ~or use in the process of the present invention: magnesium from o.8 to 1.3%, magnanese
2~
from 1.0 to 1. 5% a iron up to 0.7%, silicon up to O.3%, copper up to 0.25%, zinc up to 0.25%, balance essentially aluminum.
The processing o~ the present invention achieves superior properties in 3004 than that obtained by conventional processes.
A particular ad~antage of the material processed in accordance with the present invention is its superior strength and improved earing properties over the same material processed in a conventional manner.
Other alloys which are particularly suitable for use in the process of the present inYention are characterized by having a total concentration of magnesium and manganese from 2 0 to 3.3%
while maintaining the ratio of magnesium to manganese rrom 1.4:1 to 4.4:1 and maintaining the total concentration of other alloying elements to 1.5% maximum. It has been found that when these alloys are processed in accordance with the present invention, they exhibit superior earing properties as well as deep drawing properties at least as good as conventional A1-Mg-Mn alloys in spite Or the high concentration o~ solid solution strengthening elements, magnesium and manganese. It is prererred that the total magnesium and manganese concentration be between 2.3 and 3.0% thus resulting in the combined solid solution strengthening influence Or magnesium and manganese to approximate that Or the magnesium addition in the 5000 series aluminum alloy.
In addltlon, it is prererred that the ratio Or magnesium to manganese is kept in the range of 1.8:1 to 3.0:1. Prererred add-ltlonal alloy~ng elements include copper up to 0.3%, silicon from 0.1 to 0.5%, iron from 0.1 to 0.65%, titanium and/or vanadium up to 0.15%, with the totai additional alloying elernents and irnpurities not to exceed 1.5%.
The surprising advantage Or the present invention is that it enables strip stock to be -nade ~rom alloys containi.ng a high concentration of solid solution strengthening elements while maintaining excellent deep drawing properties as well as improving the earing properties thereof~ It is a particular advantage that material processed in accordance with the present invention exhibit superior earing, strength and deep drawing properties over the same material processed in a conventional ]nanner.
In accordance with the process of the present invention~
the aluminum alloys utilized herein are continuously cast into strip rorm on a strip casting machine having continuously moving chilling blocks such that the dendritic arm spacing in the region of the as-cas~ strip is between 2 and 25 ~m, pre.ferably between and 15 ym~ and the den~ritic arm spacing in the center region of the strlp ~s between 20 to 120 ~m, preferably between 50 and 80 ~m.
In.accordance with the process of the present invention, in order to achieve the aforenoted preferred dendritic structure as well as uniformity in the composition of the cast strip in the alloys utilized herein, it has been found ~avorable in the process of the present :Invention to keep the cast strip arter the start o~
solidi~ication to the start of hot rolling at a temperature o~
between ll00C and the liquidus temperature of the cast alloy ~or 2 to 15 m:lnute~s, preferably above 500C for pre~erably 10 to 50 seconds. By controlling the cooling rate at the start Or solidi~ication of`the cast strip, the desired dendrltic arm spacing~is readily obtained~ It has also been fourld that as a result Or the relativelg slow cooling rate achieved by the process of the present invention there ls an optimum distribut:lon of insoluble heterogeneities within the _ g _ cast strip~ a feature which is favorable in connection with subsequent cold rolling. As a result of the relatively long time the solidified strip spends at high temperatures-the heat contained ~n the as-cast strip promotes diffus~on controlled processes in khe structure which results in eliminating non~
uniformities by spheroidication and rounding Or the heterogeneities, equalization of the micro-segregation, ~.e., coring and transformation of non-equilibrium phases to equilibrium phases.
Thus, by the strip casting process of the present invention the normal homogenization treatment required in conventional processes can be eliminated.
The process o~ the present invention comprises a series of hot rolling steps which fall into critical temperature limits.
In accordance with the process of the present invention the cast strip is hot rolled continuously at the casting speed, with additional heating being applied thereto ir desired, in a temperature range between 300C and the non-equilibrium solidus temperature o~ the alloy with a total reduction of thickness of at least 70%, whereby the temperature o~ the strip at the start of hot rolling is between the non-equilibrium solidus temperature and a temperature 150C below the non-equilibrium solidus temperature and the temperature Or the strip at the end o~ hot rolling is at least 280C. It has been found in order to minimize undesirable properties, particularly excessive earing which would result from direct processing of the cast strip into fin~shed products such as cans or the like, special attention must be given to insure that the hot working takes place at a sufficiently hlgh temperature, prererably above 440C and ideally about 490C.
Only hot worklng in accordance with the process of the present invention at the required temperature and with the requlred -- 10 .--t~
amount of formlng will guarantee adequate working of the strip materlal so as to enable the elimination Or a homogenization strip without impairing the quality Or the end product. As previously noted, only an amount of hot forming of at least 70%
can guarantee the same favorable products in the end product, i.e., strip stock as can be achieved with conventional methods.
One of the essential steps in the process according to the present invention .i5 the hot coiling of the cast strip after it has been hot worked, and the cooling down of the hot rolled coil in air to room temperature. As previously noted above, the temperature of the strip at the end of hot rolling should be at least 2~0C and preferably at least 300C. It has been found that when the hot strip is coiled and allowed to cool in air to room temperature, the heat stored ~n the coils allows precipitation of the intermetallic phases whlch slowly precipitate out and at the same time brings about a softening of the strip which is favorable for subsequent cold rolling. In addition, a certain degree of recrystallization-occurs.in this stage of the process which, due to a reduction in the amount of rolling texture, has a favorable effect in reducing the earing at ~5 to the rolling direction when the strip is further processed into cans or the like.
The coiled strip as cast according to the process of the present invention as described above is at a gauge selected to give the finished gauge after appropriate rolling. ~The cold rolling operation may be carried out in any known manner.
In accordance with the process Or the present inventiong it has been found particularly advantageous to introduce an intermediate flash anneal at 350C to 500C during cold rolling whereby in the cold rolling to final thickness after the intermediate anneal a reduction of at rnost 75%, preferably at most 70% is carried out. The-process comprises the following A. cold rolling in a first series of passes with a total reduction of at least 50%,- preferably at least 65%;
B. subjecting the cold rolled strip to a brief flash anneal at a temperature between 350C to 500~C for not more than 90 seconds;~and C. cold rolling in a second series of passes with a total reduction of at most 75%, preferably at most 70%.
It has been round that due to the brief flash anneal, in particular with strip produced by strip casting as described above, the amount Or earing at 45~ to the rolling direction in the finished strip is substantially reduced. A decrease in the amount o~ earing during subsequent drawing and ironing operations is particularly advantageous in that the ironing step can proceed symmetrically and is not influenced by asy~netry due to excessive earing.
It has been round that the intermediate flash anneal in accordance with the process of the present invention is superior when compared with the normal conventional anneal lnvolving slow heating up, slow cooling down, and long holding times. It has been ~ound that the brief flash anneal, A) reduces the rolling texture in the cold rolled strlp to a greater extent than is accomplished with conventlonal annealing and, B) at the s~ne time results in a smaller loss Or strength than that which occurs ~rom the conventional processing. As a result o~ feature A described above, the second series Or cold rolling passes which brings the strip to final gauge is carrled out with less pronounced rolling texture and can, 2~
as a result o~ feature B, be carried out with less hard working thus resulting in an overall less pronounced rolling texture.
As is well known~ a smaller amount of rolling texture results in a smaller amount of earing at 45 to the rolling direction.
In accordance with the process of the present- inven~ion the time and temperature of i~termediate flash anneal are inter-dependent. It can be determined in accordance with the equation lnt = AT ~ C where, ~ is the time and seconds, T is the temperature degrees Kelvin and A and C are constants. The interdependency between the time and temperature is such that the higher the temperature of the flash anneal the shorter the amount of time required. In the preferred embodiment o~
the present invention, the duration of the intermediate ~lash anneal is pre~erably at most 90 seconds including heating up~
holding at temperature and cooling down. It is preferred thak when carrying out the intermediate anneal in the process of the present invention heat up be not more than 30 seconds and preferably 4 to 15 seconds~ holding the strip at temperature for prererably between 3 to 33 seconds and cooling the strip to room temperature within 25 seconds.
The process o~ the present invention will be more readily understandable from a consideration of the ~ollowing illustrative examples.
EXAMPLE I
As previously noted~ on cooling ~rom the liquid state there are two -lmportant temperature ranges, the temperature between ~the liquidus and solidus, ~TL/S, and the temperature range between the solidus and a temperature 100C below the solidus ATS/s lOO~c. The time taken to cool through the range ATL/S controls average dendritic arm spacing while the time ~ ~ r ~
spent in the region ATSjs 100C controls the rounding of the heterogeneities in the as-cast structure, equalization Or the microstructure and the transformation of non-equilibrium phases to equilibrium phases.
Aluminum Alloy 3004 was provided and was cast in accordance with both the strip casting process according to the present invention and conventional direct chill casking. In accordance with the present invention the strip was cast on a casting machine similar to that shown in Figure 1 wherein the casting speed was 3 meters per minute. The temperature Or the strip at the start of solidification was 650C, the temperature falling to 500C after 35 seconds and reaching a temperature of 400C
after 6 minutes. The cell size Or the strip as cast is illustrated in Table I, the times spent in each Or the temperature ranges listed in Table I was roughly estimated from the measurement of the cell size. Another melt Or Alloy 3004 was cast by the conventional direct chill casting method. The surface o~ the direct chilled cast lngots was scalped so as to remove non-unirormities in the compositlon from the outer surface of the ingot. As previous notedg Table I set forth below was the dendritic arm spacing obtained on the surface and in the center Or the as~cast alloy for both the process Or the present invention and the conventional direct chill cast process. The QTL/S and ~TS/s 100C values have been calculated from the measurement Or the dendritic arm spacing.
TABLE I
Cel~ Slze ~TL/s ~Ts/s-loooc - Sample (~m) (sec) (sec) Surface of strip cast in accordance with the present 15 5 120 invention Center of strip cast in accordance with the present 50 20 120 invention Direct chill cast, surface30 15 5 Direct chill cast~ center 70 80 15 As can be seen from Table I, the strip cast in accordance with the process of-the present invention spends a longer time in temperature range where diffusion controlled transforma-tions are possible than is the case with conventional direct chill casting. For this reason~ the transformations involved pro~ressed much more in the structure of the strip casting than in the structure produced by conventional direct chill casting.
In addition, the strip cast in accordance wlth the process of the present invention has undergone a larger amount Or homogenization than the direct chill cast. In particular, at the surface of the as-cast strip, the diffusion controlled transformations effectlng the equalization Or concentration differeIlces is especially advanced since these transformations proceed faster the finer the dendritic arm spacing. This distlnguishes the final dendritic arm spacing of the strip Or the present invention from the coarser structure obtained from direct chill casting.
EXAMPLE II
Two Al-Mg-Mn alloys were provided having the compositions set forth in Table II below.
t~
TABLE II
Mg Mn 'Cu 'S~ Fe ''Al A ,`0.90%0.96% 0.90% 0.18% o.58% Balance B 1.86% o.66% 0.04% 0.23% 0~39% Balance , Two samples of both Alloys A and E were cast as 20 mm thick strip in a strip casting machine, hot rolled in two passes in line with the caster and then coiled hot in accordance with the process of the present invention. The first pass was made at a starting temperature of 550C to a finished temperature of 440C with reduction o~ thickness o~ the strip from 20 mm to 6 mm. The second pass was made at a starting temperature of 360C to a finished temperature of 320C with a reduction in thickness from 6 mm to 3 mm. Table III below lists the 0~2%
offset yield strength and the ultimate tensile strength for the hot rolled strip for both Alloys A and B.
TABLE 'III
Ultimate 0.2% Tenslle ';Yi'e'l'd 'Strength ''Stren~
A130 MPa 210 MPa B140 MPa 220 MPa Strip A was then cold rolled with reduction from 3 mm to 1.05 mm and Strip B was cold rolled with reduction from 3 mm to 0.65 mm. Both str:lps were given an intermediate anneal at 425C before being cold rolled to a final gauge of 0~31l mm.
One sample Or each Alloy A and B were subjected to conventional intermecl:late anneal where heat up time was approximately 10 hours and the strip was held for one hour at 425C with a coollng down of 3 hours. The second samples o~ each alloy were f'lash annealed in accordance with the process of the present invention. The alloy strips were held for 10 seconds at 425C with a heat up time of 15 seconds and a cooling down time of 15 seconds. Both annealing treatments as set forth above produce complete recrystallizat~on of the strip. Table IV below lists the 0.2% yield strength and earing values obtained for each of the samples after annealing and prior to cold rolling to final thickness Or 0.34 mm.
TABLE_IV
~0.2% Yield Strength_ Before cold After cold Intermediate rolling torolling to Anneal 0.34 mm 0.34 mm Earin~
A a)71 MPa 261 MPa 3.0%
b)87 MPa 274 MPa 2.4g B a)88 MPa 266 MPa 1.8%
b)104 MPa 278 MPa 1.2~
It is clearly seen from Table IV that the brief flash anneal ln accordance with the process of the present invention produces lower earing values in spite of higher strength than does the conventional anneal.
EXAMPLE III
The cold rolling passes were chosen such that after the flash anneal treatment of the present invention the same final strength was obtained as arter the conventional intermediate anneal so as to show that the reduction in the earing by the process of the present lnvention is even more striking.
To illustrate this point Strip A was cold rolled from 3 mm to o.8 mm and Strlp B from 3 mm to 0.52 mm. Both strips were then sub;ected to the flash anneal treatment described above ln accordance with the present invention. Strips A and B
were then cold rolled to a final thickness of 0.34 mm. The results that are set forth in Table V show ~hat when the cold
from 1.0 to 1. 5% a iron up to 0.7%, silicon up to O.3%, copper up to 0.25%, zinc up to 0.25%, balance essentially aluminum.
The processing o~ the present invention achieves superior properties in 3004 than that obtained by conventional processes.
A particular ad~antage of the material processed in accordance with the present invention is its superior strength and improved earing properties over the same material processed in a conventional manner.
Other alloys which are particularly suitable for use in the process of the present inYention are characterized by having a total concentration of magnesium and manganese from 2 0 to 3.3%
while maintaining the ratio of magnesium to manganese rrom 1.4:1 to 4.4:1 and maintaining the total concentration of other alloying elements to 1.5% maximum. It has been found that when these alloys are processed in accordance with the present invention, they exhibit superior earing properties as well as deep drawing properties at least as good as conventional A1-Mg-Mn alloys in spite Or the high concentration o~ solid solution strengthening elements, magnesium and manganese. It is prererred that the total magnesium and manganese concentration be between 2.3 and 3.0% thus resulting in the combined solid solution strengthening influence Or magnesium and manganese to approximate that Or the magnesium addition in the 5000 series aluminum alloy.
In addltlon, it is prererred that the ratio Or magnesium to manganese is kept in the range of 1.8:1 to 3.0:1. Prererred add-ltlonal alloy~ng elements include copper up to 0.3%, silicon from 0.1 to 0.5%, iron from 0.1 to 0.65%, titanium and/or vanadium up to 0.15%, with the totai additional alloying elernents and irnpurities not to exceed 1.5%.
The surprising advantage Or the present invention is that it enables strip stock to be -nade ~rom alloys containi.ng a high concentration of solid solution strengthening elements while maintaining excellent deep drawing properties as well as improving the earing properties thereof~ It is a particular advantage that material processed in accordance with the present invention exhibit superior earing, strength and deep drawing properties over the same material processed in a conventional ]nanner.
In accordance with the process of the present invention~
the aluminum alloys utilized herein are continuously cast into strip rorm on a strip casting machine having continuously moving chilling blocks such that the dendritic arm spacing in the region of the as-cas~ strip is between 2 and 25 ~m, pre.ferably between and 15 ym~ and the den~ritic arm spacing in the center region of the strlp ~s between 20 to 120 ~m, preferably between 50 and 80 ~m.
In.accordance with the process of the present invention, in order to achieve the aforenoted preferred dendritic structure as well as uniformity in the composition of the cast strip in the alloys utilized herein, it has been found ~avorable in the process of the present :Invention to keep the cast strip arter the start o~
solidi~ication to the start of hot rolling at a temperature o~
between ll00C and the liquidus temperature of the cast alloy ~or 2 to 15 m:lnute~s, preferably above 500C for pre~erably 10 to 50 seconds. By controlling the cooling rate at the start Or solidi~ication of`the cast strip, the desired dendrltic arm spacing~is readily obtained~ It has also been fourld that as a result Or the relativelg slow cooling rate achieved by the process of the present invention there ls an optimum distribut:lon of insoluble heterogeneities within the _ g _ cast strip~ a feature which is favorable in connection with subsequent cold rolling. As a result of the relatively long time the solidified strip spends at high temperatures-the heat contained ~n the as-cast strip promotes diffus~on controlled processes in khe structure which results in eliminating non~
uniformities by spheroidication and rounding Or the heterogeneities, equalization of the micro-segregation, ~.e., coring and transformation of non-equilibrium phases to equilibrium phases.
Thus, by the strip casting process of the present invention the normal homogenization treatment required in conventional processes can be eliminated.
The process o~ the present invention comprises a series of hot rolling steps which fall into critical temperature limits.
In accordance with the process of the present invention the cast strip is hot rolled continuously at the casting speed, with additional heating being applied thereto ir desired, in a temperature range between 300C and the non-equilibrium solidus temperature o~ the alloy with a total reduction of thickness of at least 70%, whereby the temperature o~ the strip at the start of hot rolling is between the non-equilibrium solidus temperature and a temperature 150C below the non-equilibrium solidus temperature and the temperature Or the strip at the end o~ hot rolling is at least 280C. It has been found in order to minimize undesirable properties, particularly excessive earing which would result from direct processing of the cast strip into fin~shed products such as cans or the like, special attention must be given to insure that the hot working takes place at a sufficiently hlgh temperature, prererably above 440C and ideally about 490C.
Only hot worklng in accordance with the process of the present invention at the required temperature and with the requlred -- 10 .--t~
amount of formlng will guarantee adequate working of the strip materlal so as to enable the elimination Or a homogenization strip without impairing the quality Or the end product. As previously noted, only an amount of hot forming of at least 70%
can guarantee the same favorable products in the end product, i.e., strip stock as can be achieved with conventional methods.
One of the essential steps in the process according to the present invention .i5 the hot coiling of the cast strip after it has been hot worked, and the cooling down of the hot rolled coil in air to room temperature. As previously noted above, the temperature of the strip at the end of hot rolling should be at least 2~0C and preferably at least 300C. It has been found that when the hot strip is coiled and allowed to cool in air to room temperature, the heat stored ~n the coils allows precipitation of the intermetallic phases whlch slowly precipitate out and at the same time brings about a softening of the strip which is favorable for subsequent cold rolling. In addition, a certain degree of recrystallization-occurs.in this stage of the process which, due to a reduction in the amount of rolling texture, has a favorable effect in reducing the earing at ~5 to the rolling direction when the strip is further processed into cans or the like.
The coiled strip as cast according to the process of the present invention as described above is at a gauge selected to give the finished gauge after appropriate rolling. ~The cold rolling operation may be carried out in any known manner.
In accordance with the process Or the present inventiong it has been found particularly advantageous to introduce an intermediate flash anneal at 350C to 500C during cold rolling whereby in the cold rolling to final thickness after the intermediate anneal a reduction of at rnost 75%, preferably at most 70% is carried out. The-process comprises the following A. cold rolling in a first series of passes with a total reduction of at least 50%,- preferably at least 65%;
B. subjecting the cold rolled strip to a brief flash anneal at a temperature between 350C to 500~C for not more than 90 seconds;~and C. cold rolling in a second series of passes with a total reduction of at most 75%, preferably at most 70%.
It has been round that due to the brief flash anneal, in particular with strip produced by strip casting as described above, the amount Or earing at 45~ to the rolling direction in the finished strip is substantially reduced. A decrease in the amount o~ earing during subsequent drawing and ironing operations is particularly advantageous in that the ironing step can proceed symmetrically and is not influenced by asy~netry due to excessive earing.
It has been round that the intermediate flash anneal in accordance with the process of the present invention is superior when compared with the normal conventional anneal lnvolving slow heating up, slow cooling down, and long holding times. It has been ~ound that the brief flash anneal, A) reduces the rolling texture in the cold rolled strlp to a greater extent than is accomplished with conventlonal annealing and, B) at the s~ne time results in a smaller loss Or strength than that which occurs ~rom the conventional processing. As a result o~ feature A described above, the second series Or cold rolling passes which brings the strip to final gauge is carrled out with less pronounced rolling texture and can, 2~
as a result o~ feature B, be carried out with less hard working thus resulting in an overall less pronounced rolling texture.
As is well known~ a smaller amount of rolling texture results in a smaller amount of earing at 45 to the rolling direction.
In accordance with the process of the present- inven~ion the time and temperature of i~termediate flash anneal are inter-dependent. It can be determined in accordance with the equation lnt = AT ~ C where, ~ is the time and seconds, T is the temperature degrees Kelvin and A and C are constants. The interdependency between the time and temperature is such that the higher the temperature of the flash anneal the shorter the amount of time required. In the preferred embodiment o~
the present invention, the duration of the intermediate ~lash anneal is pre~erably at most 90 seconds including heating up~
holding at temperature and cooling down. It is preferred thak when carrying out the intermediate anneal in the process of the present invention heat up be not more than 30 seconds and preferably 4 to 15 seconds~ holding the strip at temperature for prererably between 3 to 33 seconds and cooling the strip to room temperature within 25 seconds.
The process o~ the present invention will be more readily understandable from a consideration of the ~ollowing illustrative examples.
EXAMPLE I
As previously noted~ on cooling ~rom the liquid state there are two -lmportant temperature ranges, the temperature between ~the liquidus and solidus, ~TL/S, and the temperature range between the solidus and a temperature 100C below the solidus ATS/s lOO~c. The time taken to cool through the range ATL/S controls average dendritic arm spacing while the time ~ ~ r ~
spent in the region ATSjs 100C controls the rounding of the heterogeneities in the as-cast structure, equalization Or the microstructure and the transformation of non-equilibrium phases to equilibrium phases.
Aluminum Alloy 3004 was provided and was cast in accordance with both the strip casting process according to the present invention and conventional direct chill casking. In accordance with the present invention the strip was cast on a casting machine similar to that shown in Figure 1 wherein the casting speed was 3 meters per minute. The temperature Or the strip at the start of solidification was 650C, the temperature falling to 500C after 35 seconds and reaching a temperature of 400C
after 6 minutes. The cell size Or the strip as cast is illustrated in Table I, the times spent in each Or the temperature ranges listed in Table I was roughly estimated from the measurement of the cell size. Another melt Or Alloy 3004 was cast by the conventional direct chill casting method. The surface o~ the direct chilled cast lngots was scalped so as to remove non-unirormities in the compositlon from the outer surface of the ingot. As previous notedg Table I set forth below was the dendritic arm spacing obtained on the surface and in the center Or the as~cast alloy for both the process Or the present invention and the conventional direct chill cast process. The QTL/S and ~TS/s 100C values have been calculated from the measurement Or the dendritic arm spacing.
TABLE I
Cel~ Slze ~TL/s ~Ts/s-loooc - Sample (~m) (sec) (sec) Surface of strip cast in accordance with the present 15 5 120 invention Center of strip cast in accordance with the present 50 20 120 invention Direct chill cast, surface30 15 5 Direct chill cast~ center 70 80 15 As can be seen from Table I, the strip cast in accordance with the process of-the present invention spends a longer time in temperature range where diffusion controlled transforma-tions are possible than is the case with conventional direct chill casting. For this reason~ the transformations involved pro~ressed much more in the structure of the strip casting than in the structure produced by conventional direct chill casting.
In addition, the strip cast in accordance wlth the process of the present invention has undergone a larger amount Or homogenization than the direct chill cast. In particular, at the surface of the as-cast strip, the diffusion controlled transformations effectlng the equalization Or concentration differeIlces is especially advanced since these transformations proceed faster the finer the dendritic arm spacing. This distlnguishes the final dendritic arm spacing of the strip Or the present invention from the coarser structure obtained from direct chill casting.
EXAMPLE II
Two Al-Mg-Mn alloys were provided having the compositions set forth in Table II below.
t~
TABLE II
Mg Mn 'Cu 'S~ Fe ''Al A ,`0.90%0.96% 0.90% 0.18% o.58% Balance B 1.86% o.66% 0.04% 0.23% 0~39% Balance , Two samples of both Alloys A and E were cast as 20 mm thick strip in a strip casting machine, hot rolled in two passes in line with the caster and then coiled hot in accordance with the process of the present invention. The first pass was made at a starting temperature of 550C to a finished temperature of 440C with reduction o~ thickness o~ the strip from 20 mm to 6 mm. The second pass was made at a starting temperature of 360C to a finished temperature of 320C with a reduction in thickness from 6 mm to 3 mm. Table III below lists the 0~2%
offset yield strength and the ultimate tensile strength for the hot rolled strip for both Alloys A and B.
TABLE 'III
Ultimate 0.2% Tenslle ';Yi'e'l'd 'Strength ''Stren~
A130 MPa 210 MPa B140 MPa 220 MPa Strip A was then cold rolled with reduction from 3 mm to 1.05 mm and Strip B was cold rolled with reduction from 3 mm to 0.65 mm. Both str:lps were given an intermediate anneal at 425C before being cold rolled to a final gauge of 0~31l mm.
One sample Or each Alloy A and B were subjected to conventional intermecl:late anneal where heat up time was approximately 10 hours and the strip was held for one hour at 425C with a coollng down of 3 hours. The second samples o~ each alloy were f'lash annealed in accordance with the process of the present invention. The alloy strips were held for 10 seconds at 425C with a heat up time of 15 seconds and a cooling down time of 15 seconds. Both annealing treatments as set forth above produce complete recrystallizat~on of the strip. Table IV below lists the 0.2% yield strength and earing values obtained for each of the samples after annealing and prior to cold rolling to final thickness Or 0.34 mm.
TABLE_IV
~0.2% Yield Strength_ Before cold After cold Intermediate rolling torolling to Anneal 0.34 mm 0.34 mm Earin~
A a)71 MPa 261 MPa 3.0%
b)87 MPa 274 MPa 2.4g B a)88 MPa 266 MPa 1.8%
b)104 MPa 278 MPa 1.2~
It is clearly seen from Table IV that the brief flash anneal ln accordance with the process of the present invention produces lower earing values in spite of higher strength than does the conventional anneal.
EXAMPLE III
The cold rolling passes were chosen such that after the flash anneal treatment of the present invention the same final strength was obtained as arter the conventional intermediate anneal so as to show that the reduction in the earing by the process of the present lnvention is even more striking.
To illustrate this point Strip A was cold rolled from 3 mm to o.8 mm and Strlp B from 3 mm to 0.52 mm. Both strips were then sub;ected to the flash anneal treatment described above ln accordance with the present invention. Strips A and B
were then cold rolled to a final thickness of 0.34 mm. The results that are set forth in Table V show ~hat when the cold
3~
rolling passes are chosen so as to obtain the same yield strength as was obtained by conventlonal processing as set forth in Example II, Table I of the improvement in earing values of the material processed in accordance with the present invention, is even more striking.
TABLE V
0.2% Yield Strength (After cold rolling to 0.3 mm) E.aring A 261 MPa 1.9%
B 266 MPa 0.9%
_AMPLE IV
Three samples of the same alloy designated Alloy B in Table II of Example II were processed in accordance with Example II to produce a 3 mm thick hot rolled strip. The strip was then cold rolled with reduction from 3 mm to 0.65 mm. Each sample was then annealed using three different treatments after which each sample was cold rolled to an 85% reduction to final thlckness. One sample was treated at 350C for 20 seconds, the second was treated at 425C for 20 seconds and the third was treated at 425C for one hour. Table VI below llsts the 0.2% yield strength and tensile strength of the material for the three different anneal treatments.
TABLE VI
Ultimate 0.2% Tensile Intermed _te Anneal Yield Strength Strength 350C/20 s 336 MPa 341 MPa 425C/20 s 331 MPa 339 MPa 425C/1 h 334 MPa 340 MPa ~ ~ ~
1~ IIA b~ ~ 3 ~ :It Finally, ln order to simulate stove lacquering, i.e., when stock for can bodies are coated with a polymeric layer to prevent direct contact between the alloy container and the material contained therein, each sample of the material was given a treatment at a-temperature of l90~C for 8 minutes which is typical for curing the polymeric coating. This heat treatment tends to produce a partial softening in the alloy.
The strength losses after this treatment are given in Table VII hereinbelow with details of the corresponding intermediate anneal.
~ABLE VII
IntermediateLoss of 0.2% -L~ss of Ultimate Anneal Yield StrengthTensile Strength 350C/20 s 18 MPa 0 MPa 425C/20 s 40 MPa 15 MPa 425C/1 h 55 MPa 40 MPa As can be seen from Table VII the brief heat treatments in accordance with the process of the present invention produce a much smaller loss of strength than the conventional inter-mediate anneals which are at 45C.
This invention may be embodied in other forms or carried out ln other ways without departing from the spirit or essentlal characteristics thereof. The present embodiment is therefore to be cons:ldered as in all respects illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and all changes which come within the meaning and range Or equivalency are intended to be embraced therein.
ThiS i5 a division of application Serial No. 333,160, filed on August 3, 1979.
rolling passes are chosen so as to obtain the same yield strength as was obtained by conventlonal processing as set forth in Example II, Table I of the improvement in earing values of the material processed in accordance with the present invention, is even more striking.
TABLE V
0.2% Yield Strength (After cold rolling to 0.3 mm) E.aring A 261 MPa 1.9%
B 266 MPa 0.9%
_AMPLE IV
Three samples of the same alloy designated Alloy B in Table II of Example II were processed in accordance with Example II to produce a 3 mm thick hot rolled strip. The strip was then cold rolled with reduction from 3 mm to 0.65 mm. Each sample was then annealed using three different treatments after which each sample was cold rolled to an 85% reduction to final thlckness. One sample was treated at 350C for 20 seconds, the second was treated at 425C for 20 seconds and the third was treated at 425C for one hour. Table VI below llsts the 0.2% yield strength and tensile strength of the material for the three different anneal treatments.
TABLE VI
Ultimate 0.2% Tensile Intermed _te Anneal Yield Strength Strength 350C/20 s 336 MPa 341 MPa 425C/20 s 331 MPa 339 MPa 425C/1 h 334 MPa 340 MPa ~ ~ ~
1~ IIA b~ ~ 3 ~ :It Finally, ln order to simulate stove lacquering, i.e., when stock for can bodies are coated with a polymeric layer to prevent direct contact between the alloy container and the material contained therein, each sample of the material was given a treatment at a-temperature of l90~C for 8 minutes which is typical for curing the polymeric coating. This heat treatment tends to produce a partial softening in the alloy.
The strength losses after this treatment are given in Table VII hereinbelow with details of the corresponding intermediate anneal.
~ABLE VII
IntermediateLoss of 0.2% -L~ss of Ultimate Anneal Yield StrengthTensile Strength 350C/20 s 18 MPa 0 MPa 425C/20 s 40 MPa 15 MPa 425C/1 h 55 MPa 40 MPa As can be seen from Table VII the brief heat treatments in accordance with the process of the present invention produce a much smaller loss of strength than the conventional inter-mediate anneals which are at 45C.
This invention may be embodied in other forms or carried out ln other ways without departing from the spirit or essentlal characteristics thereof. The present embodiment is therefore to be cons:ldered as in all respects illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and all changes which come within the meaning and range Or equivalency are intended to be embraced therein.
ThiS i5 a division of application Serial No. 333,160, filed on August 3, 1979.
Claims (8)
1. A process for fabricating high strength, improved formability, low earing aluminum strip stock from hot rolled aluminum strip comprising:
A) cold rolling said hot rolled strip in a first series of passes to an intermediate gauge;
B) flash annealing said cold rolled strip for not more than 90 seconds at a temperature of from about 350°C to 500°C, and C) cold rolling said flash annealed strip in a second series of passes to final gauge.
A) cold rolling said hot rolled strip in a first series of passes to an intermediate gauge;
B) flash annealing said cold rolled strip for not more than 90 seconds at a temperature of from about 350°C to 500°C, and C) cold rolling said flash annealed strip in a second series of passes to final gauge.
2. The process of claim 1 wherein said cold rolling to said intermediate gauge comprises at least a 50% reduction in thickness.
3. The process of claim 1 wherein said cold rolling to said final gauge comprises a total reduction of at least 65%.
4. The process of claim 1 wherein said cold rolling to said final gauge comprises a total reduction not to exceed 75%.
5. The process of claim 1 wherein said cold rolling of said strip to said final gauge comprises a total reduction not to exceed 70%.
6. The process of claim 1 wherein said flash anneal comprises a heat-up time not to exceed 30 seconds, holding the strip at temperature for between about 3 to 30 seconds and cooling the strip to room temperature within 25 seconds.
7. The process of claim 6 wherein said heat-up is between 4 to 15 seconds.
8. The process of claim 1 wherein said cold rolling to said final gauge comprises a total reduction of from about 65% to 70%.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/931,037 US4238248A (en) | 1978-08-04 | 1978-08-04 | Process for preparing low earing aluminum alloy strip on strip casting machine |
| US931,037 | 1978-08-04 | ||
| CA000333160A CA1171235A (en) | 1978-08-04 | 1979-08-03 | Process for preparing low earing aluminum alloy strip on strip casting machine |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000333160A Division CA1171235A (en) | 1978-08-04 | 1979-08-03 | Process for preparing low earing aluminum alloy strip on strip casting machine |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1193524A true CA1193524A (en) | 1985-09-17 |
Family
ID=25668947
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000436945A Expired CA1193524A (en) | 1978-08-04 | 1983-09-16 | Process for preparing low earing aluminum alloy strip on strip casting machine |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1193524A (en) |
-
1983
- 1983-09-16 CA CA000436945A patent/CA1193524A/en not_active Expired
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