RU2181149C2 - Method for manufacture of sheet material for production of cans for drinks - Google Patents

Abstract

FIELD: manufacture of sheets of aluminum alloy. SUBSTANCE: the process is conducted in the form of two successions of continuous operations within the line including the continuous hot rolling of a hot aluminum blank within the limits of the first succession for reducing its thickness and rolling-up, and unreeling of the rolled-up blank and hardening to a temperature required for cold rolling within the limits of the second continuous succession of operation within the line; after the continuous hot rolling within the limits of the first continuous succession hardening of the hot blank is accomplished for reduction of its temperature, the cooled-down blank is rolled up, and hardening within the limits of the second continuous succession is accomplished with a preliminary quick heating of the blank for annealing and recrystallization without an intensive precipitation of elements in the form of intermetallic compounds carried out after unreeling of the blank and by a immediate quick cooling of the annealed blank for prevention of precipitation of alloys. EFFECT: improved mouldability of cans from the obtained sheets and enhanced strength. 2 cl, 8 dwg, 3 tbl, 8 ex

Description

BACKGROUND OF THE INVENTION
The present invention relates to a process for manufacturing containers of aluminum alloys for beverages, and more particularly, to a method for manufacturing lids and ears of such containers with greater cost-effectiveness and efficiency.

Prior art
The use of aluminum alloys in the manufacture of containers for beverages is today quite a traditional practice. First, the aluminum alloy sheet is given a circular shape, and then a cup-shaped blank is obtained from it. The side walls of such a cup are thinned, passing it through a series of matrices with successively decreasing points. Due to thinning in the matrices, the length of the side wall increases, resulting in a can body with a thickness less than that of the bottom.

 Thus, the formability of the aluminum alloy cans used to make cans is crucial. Most often, such cans are made of aluminum alloys of the 3000 group. These alloys include both magnesium and manganese alloying elements. As a rule, manganese and magnesium used in raw materials for can cases are present in amounts of less than 1 wt.%.

 In the manufacture of such beverage containers, it has become common practice to form separately, on the one hand, the top cover of such cans and, on the other, ears that serve to facilitate the opening of these covers, using different alloys. Next, the lids with ears are fed to the filling machine and immediately after filling the containers they are placed on a jar. The requirements for lids and ears of cans, as a rule, differ significantly from the requirements for their bodies. In general, more stringent strength requirements are imposed on caps and ears, which necessitated their manufacture from an aluminum alloy. One of the most common alloys of this kind is AA5182 alloy, which contains relatively large amounts of magnesium, which allows for additional strength required for lids and ears of cans. The amount of magnesium in this alloy usually reaches values greater than 4.4 weight. %, which leads to a rise in the cost of raw materials used for lids and ears of cans.

 It was proposed to use any alloy from the group 3000, in particular AA3104 alloy, as an aluminum alloy for the manufacture of lids and ears of cans. Since such alloys usually have worse strength characteristics in comparison with AA5187 alloy, it was necessary to manufacture can lids from AA3104 with a larger thickness, which leads to their cost increase.

 Thus, one of the objectives of the present invention is to obtain such a rental for lids and ears of cans, as well as the manufacture of this hire such lids and ears that would be free from the aforementioned disadvantages.

 One of the more specific objectives of the invention is to obtain lids and ears of cans, as well as to develop a method for their manufacture by using aluminum alloys with a lower content of alloying elements without reducing the strength of the products.

 Another more specific objective of the invention is to obtain lids for cans and ears for them, as well as the development of a method for their manufacture, which can be implemented using aluminum alloys containing less than 2% magnesium without reducing the necessary strength of the lids and ears of cans.

 These and other objectives and advantages of the invention are more clearly apparent from the following detailed description.

Summary of the invention
The fundamental principle of the present invention is based on the discovery that aluminum alloys containing smaller amounts of alloying elements can nevertheless be used to make lids and ears of cans without reducing their strength due to the application of a process in which an aluminum alloy containing preferably less than 2 weight. % magnesium as an alloying element, is molded in the form of sheet metal, which serves to obtain such products. In accordance with the invention, the production of aluminum alloy sheet metal is carried out in the form of two sequences of continuous operations as part of a line, moreover, in the framework of the first sequence, continuous hot rolling of a hot aluminum billet is carried out to reduce its thickness and coils it, and as part of a second continuous sequence of operations as a part of the line, unwinding a billet rolled into a roll and hardening to the temperature necessary for cold rolling is carried out. After continuous hot rolling, in the framework of the first continuous sequence, the hot billet is quenched to lower its temperature, rolled into a cooled billet, and quenched in the second continuous sequence is pre-heated with preliminary heating of the billet for annealing and recrystallization without intensive deposition of alloying elements in the form of intermetallic compounds carried out after unwinding the workpiece, and immediate rapid cooling of the annealed workpiece for prevent intensive precipitation of alloying elements.

 It was unexpectedly discovered that a similar process allows to obtain aluminum billets with the same or better metallurgical characteristics compared to aluminum alloys, traditionally used for forming lids and ears of cans.

 It was also found that the processes in accordance with the present invention can be applied to alloys of the group 3000, for example AA3104, without resorting to an increase in the thickness of the lids and ears of the cans to obtain strips with comparable parameters. Not limited to the theoretical aspects of the present invention, it can be assumed that strip casting methods followed by rapid hardening make it possible to obtain sheet metal products of alloy having increased strength due to the presence of eutectic components. In addition, it can be considered, again, not limited to the theoretical side, that the formability of the sheet metal according to the invention used in the formation of lids and ears of cans is improved compared to aluminum alloys with a higher content of alloying elements, since the implementation of the invention eliminates the need for an annealing step traditionally included in the process in accordance with the prior art. Thus, the present invention allows to obtain lids and ears of cans of less expensive aluminum alloys without compromising the metallurgical properties of the more expensive alloys mentioned.

 Carrying out a continuous process as part of a single production line provides an additional advantage, which consists in eliminating the stages of processing and transportation of materials traditionally included in the process in accordance with the prior art. Casting can be used to obtain strips with a thickness of 25.4 mm and preferably in the range from 0.254 to 5.08 mm. In addition, in accordance with the most preferred embodiment of the invention, the bandwidth is smaller compared with known practice. This facilitates refueling and processing in the production line and makes it possible to physically place the can and lid production lines of cans nearby or as part of can manufacturing equipment. In addition, due to the placement of the filling machine, which gives an additional advantage of eliminating the additional costs of the processing and transportation operations, the overall cost-effectiveness of the entire can manufacturing process is increased.

 In accordance with another embodiment of the invention, the production of aluminum alloy sheet metal is carried out by two sequences of continuous operations as part of a line, moreover, in the first sequence, the aluminum alloy billet is continuously cast in the form of a strip between two moving endless tapes to produce a hot aluminum alloy billet and, as part of the second continuous sequence of operations as part of the line, the workpiece is quenched to a temperature, In winter the cold rolling. After continuous casting, within the first continuous sequence, the preform is quenched to lower its temperature, and the second sequence is quenched with preliminary rapid heating of the preform for annealing and its recrystallization without intensive deposition of alloying elements in the form of intermetallic compounds and immediate rapid cooling of the preform to prevent deposition alloying elements.

 It was found that the intermediate stages of annealing and hardening contribute to a significant increase in the formability of the workpieces while maintaining extremely high metallurgical properties, including tensile strength and yield strength.

 The exclusion of the first hardening stage gives a more efficient use of energy, since there is no need to heat the workpieces to the desired annealing temperature after cooling as a result of the initial hardening. It was also found that such an exception to the first hardening step also contributes to a more efficient application of the principles of the present invention with a continuous sequence of operations in the line. This, in turn, provides significant economic benefits when implementing the method according to the invention.

 It was also found that a similar process allows to obtain billets from aluminum alloys with the same or better metallurgical properties and formability characteristics compared to aluminum alloys traditionally used for forming lids and ears of cans.

Brief Description of the Drawings
FIG. 1 is a schematic diagram of a continuous flow of operations as part of a production line carried out in accordance with a first embodiment of the invention.

 FIG. 2 is a schematic representation of a continuous line flow of operations carried out in accordance with a second embodiment of the invention.

 FIG. 3 is a schematic representation of a continuous line flow of operations carried out in accordance with a third embodiment of the invention.

 FIG. 4 is a schematic illustration of a preferred embodiment of a strip casting plant in accordance with the invention.

 FIG. 5 is a generalized isothermal transformation diagram for aluminum alloys, which shows that rapid heating and rapid cooling help eliminate or at least significantly reduce the deposition rate of alloying elements in the form of intermetallic compounds.

 FIG. 6 is a schematic diagram of a process using a continuous sequence of steps in a line to produce aluminum alloy sheet metal.

 FIG. 7 is a drawing of a workpiece obtained using a curved matrix for controlling festoon formation (tongue formation) according to the invention.

 FIG. 8 is a schematic representation of two continuous sequences of steps used in accordance with another embodiment of the invention.

Detailed Description of Drawings
The sequence of steps used in accordance with one embodiment of the invention is shown in FIG. 1. One of the achievements provided by the present invention is that the processing steps necessary to obtain sheet metal can be organized in the form of two continuous sequences in a production line, within which these steps are performed in a specific order. Due to the small strip width adopted, according to the invention, for example 305 mm, it is possible to conveniently and economically place this line inside or next to the user equipment of sheet metal. Under these conditions, the process according to the invention can be implemented in accordance with the specific technical needs of the user of sheet metal and the required performance.

 According to a preferred embodiment, the molten metal is supplied from a furnace not shown in the drawing to a metal degassing and filtering device (also not shown) in order to reduce the content of dissolved gases and particles in the liquid metal. This liquid metal immediately turns into a cast billet, or strip, 4 in the casting device 3.

 The preform used in accordance with the invention can be obtained by any of a number of casting methods well known to those skilled in the art, including the use of foundry machines with two conveyor belts of the type described in US Pat. No. 3,937,270 and other patents indicated therein. In a number of practical cases, it may be appropriate to apply the method and installation for casting aluminum strip described in pending applications with registration numbers 08/184581, 08/173663 and 07/173369, which are described here by reference.

 The strip casting method described in the aforementioned applications, which can be successfully applied with the implementation of the present invention, is illustrated in FIG. 2. As you can see, the installation contains two endless conveyor belts 10 and 12, mounted on two upper pulleys 14 and 16, as well as two corresponding lower pulleys 18 and 20. Each pulley is rotatably mounted and heat-resistant. Any or both of the upper pulleys 14 and 16 are driven by a corresponding engine or similar drive mechanism, which is not shown in the drawing for simplification. The same applies to the lower pulleys 18 and 20. Each of the belts 10 and 12 is an endless conveyor belt and is preferably made of metal exhibiting low reactivity when interacting with cast aluminum. Mild steel or copper is often used as the preferred material for endless tapes.

 As shown in FIG. 2 pulleys are located one above the other with maintaining a molding gap between them corresponding to the desired thickness of the cast aluminum strip.

 The molten metal to be cast is fed into the molding gap by means of a special distributing means such as an intermediate casting device 28. The width of the internal volume of the intermediate device 28 practically coincides with the width of the strips 10 and 12; it includes a pouring cup 30, providing the supply of liquid metal in the molding gap between the belts 10 and 12.

 The casting device also contains two cooling means 32 and 34, mounted opposite the contact point of the endless tape with the cast metal in the molding gap between the tapes. Thus, the cooling means 32 and 34 serve to cool the belts 10 and 12, respectively, before they come into contact with the liquid metal. According to the preferred embodiment shown in FIG. 2, coolers 32 and 34 are located, as shown in the drawing, on the return branches of the belts 10 and 12, respectively. In this embodiment, the cooling means 32 and 34 can be made in the form of conventional coolers such as spray nozzles installed with the possibility of spraying the cooling medium directly on the inner and / or outer surface of the belts 10 and 12 in order to cool these belts throughout their thickness. Further information on the design of the hollow molding device can be found in the applications mentioned above.

 Returning to the consideration of FIG. 1, it can be seen that the workpiece 4 coming from the strip casting device 3 is fed through an optional trimming and stripping section 5 into one or more hot rolling stands 6, where its thickness is reduced. Immediately upon completion of the hot rolling operation in stands 6, the workpiece passes to the quenching section 7, where, while maintaining the high temperature obtained during the casting operation, it is brought into contact with the cooling medium. When implementing the invention, any of a wide variety of quenching agents can be used. As a rule, the hardening section is constructed in such a way that a cooling medium in liquid or gaseous form is sprayed onto a hot billet in order to quickly reduce its temperature. As a cooling medium, water, air, liquefied gases such as carbon dioxide or nitrogen, etc. can be used. It is important that the hardening is carried out quickly enough to ensure a rapid decrease in the temperature of the hot billet and thereby prevent the intensive deposition of alloying elements from solid solution.

 It will be apparent to those skilled in the art that some slight precipitation of intermetallic compounds can be expected, which will not ultimately have undesirable effects on product properties. The absence of an adverse effect of such an insignificant precipitation on the final properties is explained, firstly, by the fact that intermetallic compounds are present in small quantities and, in any case, are re-dissolved at the stage of rapid annealing, and secondly, by the fact that both their volume and species have only a negligible effect on the final properties. In this description, referring to "intensive" deposition, we mean one that entails a deterioration in the final properties of sheet metal.

Typically, a decrease in temperature occurs from values in the range of 315.6-510 ^{° C.} to values below 287.8 ^{° C.} , preferably below 232.2 ^° C. The importance of rapid cooling after hot rolling is shown in FIG. 5, which is a generalized graphical representation of the formation of the distinguished phases of alloying elements as a function of time and temperature. Similar curves, known in the art as “isothermal transformation diagrams,” or “C curves,” show the formation of large and small particles resulting from the deposition of alloying elements as intermetallic compounds during heating or cooling of an aluminum alloy. Thus, the cooling obtained as a result of the quenching operation immediately after hot rolling is carried out at such a speed that the temperature-time line corresponding to the quenching of the aluminum alloy retains the position between the ordinates and the curves. Due to this, a sufficiently high cooling rate is achieved, which allows to practically prevent the deposition of such alloying elements in the form of intermetallic compounds.

According to one of the preferred embodiments of the invention, the billet comes after the hardening step to one or more cold rolling sections 19, where it is processed in order to increase the hardness of the alloy and reduce the thickness of the strip to a final gauge. According to a preferred embodiment of the invention, it is sometimes desirable to perform, after cold rolling, curing the cold-rolled strip at a high temperature, preferably in the range of 148.9-190.6 ^{° C.} for about 1-10 hours. Given that the strip is quenched immediately after hot rolling in order to significantly reduce the deposition rate of alloying elements in the form of intermetallic compounds, the cast strip will be characterized by an unusually high level of supersaturation with dissolved substances. Thus, the holding stage of aging (aging) contributes not only to the improvement of formability, but also to increase the tensile strength and yield strength.

 Further, the aged cast strip can either be rolled up awaiting further use or immediately formed into cans and / or ears into cans using conventional methods.

 As is quite obvious to specialists, the present invention can be advantageously used without performing the cold rolling step in the rolling mill 19, which is an integral part of the production line. Thus, the application of the cold rolling stage can only be considered as an optional process, which can either be excluded as a whole or performed offline offline, depending on the end use of the alloy being processed. As a rule, the autonomous execution of the cold rolling stage is associated with a decrease in economic benefits compared with the preferred embodiment of the invention, according to which all process steps are performed as part of the line.

 It has become common practice in the aluminum industry to use wide enough strips or slabs for reasons of economy. However, according to a preferred embodiment of the present invention, in contrast to such a traditional approach, it was decided that more significant savings are achieved when the cast billet 4 is made in the form of a narrow strip, which facilitates processing and allows the use of small decentralized workshops to obtain a strip rental. Good results were obtained with a cast billet width of less than 609 mm, more preferably between 50.8 and 508 mm. Thanks to the use of such a narrow cast strip, costs can be significantly reduced by using small two-roll rolling mills and other equipment as part of the production line. Such small and economical miniature mills according to the invention can be placed in areas where there is a need for them, for example, near canning plants. This, in turn, gives an additional advantage, consisting in minimizing the costs associated with packaging, as well as with the transportation of products and waste generated by the consumer. In addition, it is possible to achieve exact coordination of the volume of equipment for the manufacture of cans and its need for metal with the performance of the adjacent miniature rolling mill.

In accordance with the principles of the invention, the temperature at the outlet of the hot rolling process is usually maintained in the range from 148.9 to 537.8 ^° C. Hot rolling is carried out, as a rule, in the temperature range from 148.9 ^{° C.} to the solidus temperature of the workpiece.

 It will be apparent to those skilled in the art that the degree of thickness reduction achieved by the hot and cold rolling operations of the invention is subject to significant fluctuations depending on the type of alloys used, their chemical composition, and the method of production thereof. For this reason, the percentage reduction in thickness for each of the hot and cold rolling operations according to the invention is not considered as a decisive factor for its practical implementation. However, if we talk about a specific product, then you should set certain boundaries for reducing the thickness and temperature used. As a rule, good results can be obtained by reducing the thickness after hot rolling in the range of 15-99% and after cold rolling in the range of 10-85%. As it should be clear to those skilled in the art, strip casting, carried out in accordance with the most preferred embodiment of the invention, allows the preparation of blanks that do not require the hot rolling step described above.

 As was shown, in accordance with the fundamental principle of the invention, aluminum alloys with a lower content of alloying elements can be used as raw materials for the manufacture of lids and ears of cans in comparison with known systems. As a general recommendation, it can be proposed to apply the idea of the invention to aluminum alloys containing less than 2% magnesium. Suitable for these purposes aluminum alloys can be considered alloys of group 3000, in particular AA3004 and AA3104. Due to the original combination of processing steps used in accordance with the essence of the invention, it becomes possible, using similar aluminum alloys with a low content of alloying elements, to achieve strength values that will be comparable or better than for the previously used more expensive alloys. Typically, such alloys contain from 0 to about 0.6 wt.% Silicon, from 0 to about 0.8 wt.% Iron, from 0 to about 0.6 wt.% Copper, from about 0.2-1.5 wt.% manganese, about 0.2-2 wt.% magnesium and about 0-0.25 wt.% zinc, the rest is aluminum with its usual impurities.

Typically, such aluminum alloys subjected to processing according to the present invention exhibit values of tensile strength and yield strength above 3515.5 kg / cm ² .

 Now, having completed the description of the fundamental ideas of this embodiment of the invention, we turn to the examples below, which are given only by way of illustration, in no way limiting the legal scope of the invention.

Example 1
Cast strips with a thickness of 2.03 mm are obtained from an aluminum alloy with the following composition:
Element - Weight.%
Si - 0.3
Fe - 0.45
Cu - 0.2
Mn - 0.90
Mg - 0.80
Alumina - Else
The hot cast strip was hot rolled to a thickness of 0.94 mm and then quenched in water. After that, it was cold rolled to a final thickness of 2.9 mm. Next, the strip was cooled and aged for several hours at a temperature of 160 ^o C. Then, the values of tensile strength (PPR), yield strength (PT) and elongation in percent (% Elongation), which are summarized in Table 1, were determined.

Example 2
In this example, an aluminum alloy with the following composition was used:
Element - Weight.%
Si - 0.3
Fe - 0.45
Cu - 0.2
Mn - 0.94
Mg - 0.92
Alumina - Else
In this example, the described aluminum alloy was cast to form 2.03 mm thick strips and then rapidly air-hardened. After that, hot rolling of the strips was carried out until a final thickness of 2.79 mm was achieved and stabilizing heat treatment was performed at a temperature of 160-171.1 ^o C. The properties obtained are also given in Table 1.

Example 3
Using the same alloy as in Example 2, it was cast to form strips 2.03 mm thick, and then quenched in water. After that, cold rolling of the strips was carried out until a final thickness of 0.279 mm was reached and curing for several hours at a temperature of 160-171.1 ^o C. The properties obtained are shown in Table 1.

 By way of comparison, Examples A and B are given below, where, for Example A, the traditionally obtained aluminum alloy AA5182 with a final caliber of 0.284 mm is taken, and for Example B, another, standard aluminum for can lids. Their compositions and the corresponding physical properties are summarized in Table 2. It can be seen from the above data that when implementing the invention, an alloy with a low content of alloying elements can be used as an aluminum alloy for the manufacture of lids and ears of cans, without completely compromising its metallurgical properties.

 In FIG. 2 shows a second embodiment of the invention, according to which an intermediate annealing step is applied. The strip casting operations of the casting machine 3, optional hot rolling 6 and hardening 7 are the same as those shown in FIG. 1.

 After quenching, the workpiece can be rolled and then stored until the need arises. According to another embodiment, it can be continuously fed into the stand 15 of the cold rolling mill and then to the annealing furnace 17, in which the billet in a coiled or strip form is subjected to rapid heating. This stage of rapid annealing provides the best combination of metallurgical properties such as grain size, strength and formability. In addition, due to the rapid heating of the workpiece, the precipitation of alloying elements in any significant quantities is prevented. Thus, heating operations should be carried out until the desired annealing and recrystallization temperature is reached, at which the temperature-time line corresponding to the aluminum alloy does not intersect with the C-curves shown in FIG. 5, so as to cause intense precipitation.

 Immediately after the heating furnace 17, there is a hardening section 18, on which the strip is subjected to rapid cooling or hardening using a conventional cooling medium to a temperature suitable for cold rolling. As a result of rapid cooling of the workpiece at the hardening stage 18, there is not enough time for any intensive extraction of alloying elements from the solid solution.

According to a preferred embodiment of the invention, after passing through the hardening step, the workpiece is fed into one or more stands 19 of the cold rolling mill, where it is processed in order to increase the hardness of the alloy and reduce the thickness of the strip to a final thickness. According to a preferred embodiment of the invention, it is sometimes desirable to carry out, after cold rolling, curing the cold-rolled strip at a high temperature, preferably in the range of 104.4-204.4 ^{° C.} for about 1-10 hours. Given that the strip was quenched immediately after hot rolling with a minimum of deposition of alloying elements in the form of intermetallic compounds, the cast strip is characterized by an unusually high level of supersaturation with dissolved substances. Thus, the aging stage leads not only to an improvement in formability, but also to an increase in the tensile strength and yield strength.

 After this, the aged strip can either be rolled up until it becomes necessary, or immediately molded into lids and / or ears of cans using traditional methods.

 As is quite obvious to specialists, the present invention can be advantageously used without performing the cold rolling step in the rolling mill 19, which is an integral part of the production line. Thus, the application of the cold rolling stage can only be considered as an optional process, which can either be excluded as a whole or performed offline offline, depending on the end use of the alloy being processed. As a rule, the autonomous execution of the cold rolling stage is associated with a decrease in economic benefits compared with the preferred embodiment of the invention, according to which all process steps are performed as part of the line.

In accordance with the principles of the invention, the temperature at the outlet of the hot rolling process is usually maintained in the range from 148.9 to 537.8 ^° C. Hot rolling is carried out, as a rule, in the temperature range from 148.9 ^{° C.} to the solidus temperature of the workpiece.

The annealing step, during which the preform undergoes heat treatment for solid solution in order to obtain recrystallization, is carried out at temperatures in the range of 315.6-648.9 ^o C for a time of less than 120 seconds, preferably from 0.1 to 10 seconds. Immediately after heat treatment, the preform in the form of strip 4 is quenched in water to the temperatures necessary to hold the alloying elements in the solid solution as before, i.e., as a rule, at temperatures less than 204.4 ^o C.

 It will be apparent to those skilled in the art that the degree of thickness reduction achieved by the hot and cold rolling operations of the invention is subject to significant fluctuations depending on the type of alloys used, their chemical composition, and the method of production thereof. For this reason, the percentage reduction in the thickness of each of the hot and cold rolling operations according to the invention is not considered as a decisive factor for its practical implementation. As a rule, good results can be obtained by reducing the thickness after hot rolling in the range of 15-99% and after cold rolling in the range of 10-85%. As should be clear to those skilled in the art, strip casting performed in accordance with the most preferred embodiment of the invention allows the preparation of blanks that do not require the hot rolling step described above to be carried out.

 As was shown, in accordance with this embodiment of the invention, aluminum alloys with a lower content of alloying elements can be used as raw materials for the manufacture of lids and ears of cans compared to known systems. As a general recommendation, it can be proposed to apply the idea of the invention to aluminum alloys containing less than 2% magnesium. Suitable for these purposes aluminum alloys can be considered alloys of group 300, in particular AA3004 and AA3104. Due to the original combination of processing steps used in accordance with the invention, it is possible, using similar aluminum alloys with a low content of alloying elements, to achieve strength and formability values that will be comparable or better than for previously used more expensive alloys. Typically, such alloys contain from 0 to about 0.6 wt.% Silicon, from 0 to about 0.8 wt.% Iron, from 0 to about 0.6 wt.% Copper, from about 0.2-1.5 wt.% manganese, approximately 0.2-2 weight. % magnesium and approximately 0-0.25 wt.% zinc, the rest is aluminum with its usual impurities.

 Now, having completed the description of the fundamental ideas of this embodiment of the invention, we turn to the examples below, which are given only by way of illustration, in no way limiting the legal scope of the invention.

Example 4
Strip castings with a thickness of 2.29 mm are obtained from an aluminum alloy with the following composition:
Element - Weight.%
Si - 0.3
Fe - 0.45
Cu - 0.2
Mn - 0.90
Mg - 0.80
Alumina - Else
Then the hot cast strip was immediately rolled to a thickness of 1.14 mm and heated for five seconds at a temperature of 537.8 ^o C, and immediately after that - quenching in water. Then it was rolled to a thickness of 0.29 mm and stabilizing heat treatment at a temperature of 160 ^o C for two hours with a final size. The workpiece was characterized by a tensile strength of 3937 kg / cm ² , a yield strength of 3558 kg / cm ² and an elongation of 7.2%.

 In FIG. 3 shows a third embodiment of the invention, according to which an annealing step is carried out before quenching. As before, the strip casting operation 3 and the optional hot rolling operation 6 are here the same as those described with respect to FIG. 1 and 2.

 Immediately after the optional operation of hot hardening in stands 6, the preform is fed into an annealing furnace 7, in which, while maintaining the high temperature acquired during casting, it is subjected to annealing with rapid heating. This stage of rapid annealing provides the best combination of metallurgical properties such as grain size, strength and formability. Due to the rapid heating of the workpiece, the precipitation of alloying elements in any significant quantities is prevented.

 Immediately after the heating furnace 7, there is a hardening section 8, in which the billet is subjected to rapid cooling or hardening using a conventional cooling medium to a temperature suitable for cold rolling. As a result of rapid cooling of the workpiece in the quenching section 8, in the same way, there is not enough time left for any intensive extraction of alloying elements from the solid solution. As before, it is important that the hardening is carried out quickly enough in order to ensure a rapid decrease in the temperature of the hot billet and thereby prevent the intensive deposition of alloying elements from the solid solution.

 The importance of rapid heating and quenching is illustrated in FIG. 3, which is a generalized graphical representation of the formation of the distinguished phases of alloying elements as a function of time and temperature. Thus, the heating carried out at the annealing stage and the cooling obtained as a result of the quenching operation immediately after annealing are performed at such a speed that the temperature-time line corresponding to the heating and quenching of the aluminum alloy maintains the position between the ordinate and the curves. Due to this, a sufficiently high heating and cooling rate is achieved, which prevents the intensive deposition of such alloying elements in the form of intermetallic compounds.

According to this embodiment of the invention, after passing through the hardening step, the workpiece is fed into one or more stands 19 of the cold rolling mill, where it is processed in order to increase the hardness of the alloy and reduce the thickness of the strip to a final thickness. According to a preferred method, it is sometimes desirable to carry out, after cold rolling, curing the cold-rolled strip at a high temperature, preferably in the range of 104.4-204.4 ^{° C.} for about 1-10 hours. Considering that the strip was quenched immediately after annealing, with almost the minimum deposition of alloying elements in the form of intermetallic compounds, the cast strip is characterized by an unusually high level of supersaturation with dissolved substances. Thus, the aging stage leads not only to an improvement in formability, but also to an increase in the tensile strength and yield strength.

 After this, the aged strip can either be rolled up until it becomes necessary, or immediately molded into lids and / or ears of cans using traditional methods.

 As is quite obvious to specialists, the present invention can be advantageously used without performing the cold rolling step in the rolling mill 19, which is an integral part of the production line. Thus, the application of the cold rolling stage can only be considered as an optional process, which can either be excluded as a whole or performed offline offline, depending on the end use of the alloy being processed. As a rule, the autonomous execution of the cold rolling stage is associated with a decrease in economic benefits compared with the preferred embodiment of the invention, according to which all process steps are performed as part of the line.

In accordance with the principles of the invention, the temperature at the outlet of the hot rolling process is usually maintained in the range from 148.9 to 537.8 ^° C. Hot rolling is carried out, as a rule, in the temperature range from 148.9 ^{° C.} to the solidus temperature of the workpiece.

The annealing step, during which the preform undergoes heat treatment for solid solution in order to obtain recrystallization, is carried out at temperatures in the range of 315.6-648.9 ^o C for a time of less than 120 seconds, preferably from 0.1 to 10 seconds. Immediately after heat treatment, the preform in the form of strip 4 is hardened to the temperatures necessary to hold the alloying elements in the solid solution, i.e., as a rule, at temperatures less than 287.8 ^o C.

 It will be apparent to those skilled in the art that the degree of thickness reduction achieved by the hot and cold rolling operations of this embodiment of the invention is subject to significant fluctuations depending on the type of alloys used, their chemical composition and the method for their preparation. For this reason, the percentage reduction in thickness for each of the hot and cold rolling operations according to the invention is not considered as a decisive factor for its practical implementation. As a rule, good results can be obtained by reducing the thickness after hot rolling in the range of 15-99% and after cold rolling in the range of 10-85%. As should be clear to those skilled in the art, strip casting performed in accordance with the most preferred embodiment of the invention allows the preparation of blanks that do not require the hot rolling step described above to be carried out.

 As was shown, in accordance with the essence of the present invention, aluminum alloys with a lower content of alloying elements can be used as raw materials for the manufacture of lids and ears of cans in comparison with known systems. As a general recommendation, it can be proposed to apply the idea of the invention to aluminum alloys containing less than 2% magnesium. Suitable for these purposes aluminum alloys can be considered alloys of group 300, in particular AA3004 and AA3104. Due to the original combination of processing steps used in accordance with the invention, it is possible, using similar aluminum alloys with a low content of alloying elements, to achieve strength and formability values that will be comparable or better than for previously used more expensive alloys. Typically, such alloys contain from 0 to about 0.6 wt.% Silicon, from 0 to about 0.8 wt.% Iron, from 0 to about 0.6 wt.% Copper, from about 0.2-1.5 wt.% manganese, about 0.2-2 wt.% magnesium and about 0-0.25 wt.% zinc, the rest is aluminum with its usual impurities.

 Now, having completed the description of the fundamental ideas of this embodiment of the invention, we turn to the examples below, which are given only by way of illustration, in no way limiting the legal scope of the invention.

Example 5
Cast strips with a thickness of 2.29 mm are obtained from an aluminum alloy with the following composition:
Element - Weight.%
Si - 0.3
Fe - 0.45
Cu - 0.2
Mn - 0.90
Mg - 0.80
Alumina - Else
Then the hot cast strip was immediately rolled to a thickness of 1.14 mm and heated for five seconds at a temperature of 537.8 ^o C, and immediately after that - quenching in water. Then it was rolled to a thickness of 0.29 mm and stabilizing heat treatment at a temperature of 160 ^o C for two hours with a final size. The workpiece was characterized by a tensile strength of 3937 kg / cm ² , a yield strength of 3558 kg / cm ² and an elongation of 7.2%.

 All the technical solutions described above relate to the caps and lugs of containers for drinks made of aluminum alloys, the manufacture of which is fraught with slightly different problems than the production of raw materials for cans made of aluminum alloys, which is used for the manufacture of side walls and bottoms of such containers. It was also indicated above that it often turns out to be expedient to apply a continuous sequence of the described operations as part of the technological line when processing an aluminum alloy in the process of manufacturing raw materials for cans of such an alloy.

 A pending application with registration number 07/902936, filed June 23, 1992, the contents of which are given here by reference, describes a new approach to the problem of processing aluminum alloys in the manufacturing process of raw materials for cans. It was found that a combination of casting, hot rolling, annealing, solid solution heat treatment, quenching, and cold rolling can be achieved in one continuous operation as part of a production line for the production of raw materials for aluminum alloy can cases. One of the advantages obtained through the process described in the aforementioned application is that it is possible to carry out a continuous sequence of steps in a line with exceptionally high speeds of the order of hundreds of meters per minute. The disadvantage of this process is that the intermediate stage of annealing, which ensures re-dissolution of soluble elements and control of feston formation by recrystallization of sheet material, can play the role of a factor limiting the possible speed of the process. Indeed, the greater the speed of the process, the greater the length and the higher energy level the continuous annealing furnace should work, preferably used in the process described in the aforementioned application, which leads to an increase in the cost of the main equipment and operating costs process. Therefore, it seems more advantageous to eliminate the indicated continuous annealing step.

 It is possible to obtain rolled sheets of aluminum alloy, preferably similar rolled products for can bodies having the required metallurgical properties, by carrying out, in one continuous sequence, the steps of producing a hot billet of aluminum alloy, which is subjected to a series of rolling operations for the purpose of its quick and continuous cooling to obtain the desired thickness and the required metallurgical properties without the need for an annealing step, traditionally used earlier. In some well-known processes of this kind, for example, described in U.S. Pat. No. 4,282,044, it has been proposed to produce rolled products for can bodies of aluminum alloys by strip casting, after which rolling and rolling are performed, as a result of which the billet rolled and rolled up undergoes slow cooling. After that, the roll is subjected to further annealing to improve the metallurgical properties of sheet metal.

 In the framework of the present invention, it was found that in the case of rapid cooling of the preform after casting, there is no need for annealing steps to obtain the desired metallurgical properties resulting from the dissolution of soluble elements. Not limited to the theoretical aspects of the present invention, it can be assumed that rapid cooling, carried out as part of a continuous rolling process as part of the production line, is carried out for a sufficiently short time to avoid deposition of alloying elements contained in aluminum raw materials in the form of intermetallic compounds. This deposition is a diffusion-controlled reaction that takes some time to pass. However, with quick cooling of the workpiece during rolling, there is not enough time for the appearance of diffusion-controlled deposition. At the same time, in turn, not only the operational processing of aluminum alloy is facilitated by minimizing the number of material processing steps, but also due to rapid cooling, the intensive deposition of alloying elements is really prevented, which eliminates the use of the high-temperature annealing step to achieve the required strength of the final product ( banks).

 The billet obtained by the proposed method is characterized in that it is manufactured with high profitability, without the need for an expensive annealing step. As it should be clear to specialists, the need for this stage was determined in known systems by the desire to minimize feston formation. When implementing this invention, it was found that to control festoon formation, it is possible to use the conditions (time and temperature) of hot rolling, the thickness of the strip cast from the alloy, and the speed at which casting is performed. So, for example, it can be considered that a strip with a smaller thickness cast from an aluminum alloy helps to reduce festoon formation; likewise, it can be reduced by casting at higher speeds. Nevertheless, in cases where, under the processing conditions, a strip of aluminum alloy is obtained, which exhibits a tendency to increase festoon formation, this phenomenon can still be controlled using any other means.

 In accordance with another embodiment of the invention, the intense feston formation observed in the preforms can be eliminated by cutting the processed preform before forming the cups into non-circular blanks using a device called the “curved matrix” in the art. Thanks to the use of such a matrix, the smallest phenomena of festoon formation in sheet metal are eliminated due to the removal of metal from those peripheral sections of the disc which, when the cups are drawn, could take the form of festoons (tongues). Thus, the curved matrix negates the slightest feston formation, which otherwise could have arisen as a result of the exclusion of high-temperature annealing.

 According to a preferred embodiment, the strip is obtained by casting to obtain a thickness of less than 25.4 mm, preferably in the range of 0.254 to 5.08 mm.

 In accordance with another preferred embodiment, the width of the strip, slab or plate is made insignificant, in contrast to conventional practice, which facilitates refueling and processing as part of the production line, minimizes equipment costs and reduces the cost of operations for converting molten metal into billets for cases of cans.

The preferred process according to the invention involves the use of a new method of manufacturing cups and cases of cans of aluminum alloy, comprising the following steps in a single continuous sequence in the composition of the line:
(a) in the first step, a hot aluminum billet is obtained, preferably by strip casting, after which
(b) the billet in accordance with a preferred embodiment is subjected to rolling in order to quickly and continuously cool sheet metal to obtain the desired thickness and achieve the desired strength properties.

 Then, the chilled billet can either be molded into a roll for its subsequent use, or further processed to obtain non-circular blanks using a curved matrix in order to eliminate festoon formation according to a known technique.

 In this embodiment of the invention, it is important that the rolling of the just cast strip is carried out quickly before sufficient time passes for the diffusion-controlled reaction to occur, as a result of which the alloying elements are released from the solid solution in the form of intermetallic compounds. Subject to this condition, the process according to the invention eliminates the stage of high-temperature annealing, which was necessary in known systems to ensure the dissolution of soluble alloying elements. Typically, the cast billet should be cooled to cold rolling temperatures in less than 30 seconds, and preferably less than 10 seconds.

According to a preferred embodiment, the entire process according to the invention is characterized by the following features different from traditional processes:
(a) a small rolling width was adopted for can bodies;
(b) hire for can cases is obtained using low-power simple equipment as part of the production line;
(c) the tendency to intense festoon formation, manifested by unannealed aluminum alloy, is eliminated by using a curved matrix while maintaining the required strength properties;
(d) the indicated low-power cans production facilities are located within or close to the cans production facilities, thereby eliminating the need for packaging and transportation operations.

 Thanks to the organization of the processing steps as part of the production line with the production of a narrow strip (for example, 305 mm), it is possible to conveniently and economically place the equipment involved in the process either inside or near the equipment for making cans. As a result, it is possible to carry out the process according to the invention, based on the specific needs of the equipment for the production of cans in the rental, both technologically and in terms of productivity.

 In FIG. 6 shows a flowchart used in accordance with a preferred embodiment of the invention. One of the achievements of the invention is that the processing steps used to produce sheet metal for can bodies can be arranged in a single continuous line, as a result of which various process steps will be performed in a specific sequence. Thus, many loading and moving operations are excluded.

 According to a preferred embodiment, the molten metal is fed from the furnace 1 to a metal degassing and filtering device 2 in order to reduce the content of dissolved gases and particles in the liquid metal, as shown in FIG. 1. This liquid metal immediately turns into a cast billet 4 in the casting device 3. The term "billet" as used herein refers to any of a wide variety of billets in the form of ingots, plates, slabs and strips supplied to the hot rolling step at the required temperature. An aluminum ingot is typically about 152-762 mm thick and is usually obtained by die casting or electromagnetic casting. By "plate" here is meant an aluminum alloy product of a thickness of about 12.7-152 mm, obtained, as a rule, only by chill or electromagnetic casting, or such casting in combination with hot rolling of an aluminum alloy. The term "slab" is applied to an aluminum alloy product with a thickness of from 9.5 mm to about 76 mm, i.e. here there is a partial coincidence with the range of thicknesses for the plates. Finally, the term “strip” refers to an aluminum alloy product with a thickness typically of less than 9.5 mm. In the most typical case, both slabs and strips are produced by continuous casting, well known to those skilled in the art.

 The preform used in accordance with the invention can be obtained by any of a number of casting methods well known to those skilled in the art, including the use of foundry machines with two conveyor belts of the type described in US Pat. No. 3,937,270 and other patents indicated therein. In a number of practical cases, it may be appropriate to apply the method and installation described for applications with registration numbers 184581 (filed June 21, 1994) 173663 (filed December 23, 1993) and 173369 (filed December 23) for casting an aluminum strip 1990), the description of which is given here by reference. The strip casting technique described in the aforementioned applications, which can be successfully applied within the framework of the present invention, is shown in FIG. 4 discussed above.

 The workpiece 4 is moved through the optional pulling rollers 5 in one or more stands of hot rolling 6, where there is a decrease in its thickness. In addition, the stands of the rolling mill serve to quickly cool the workpiece in order to prevent or stop the deposition of hardening alloying components such as manganese, copper, magnesium and silicon included in the aluminum alloy.

It will be apparent to those skilled in the art that one or more rolling steps can be envisaged to reduce the thickness of the strip 4 while cooling it rapidly to prevent deposition of alloying elements. The temperature at the outlet of the strip casting machine 3 varies from 371 ^{° C.} to the solidus temperature of the alloy. The rolling operations provide quick cooling of the cast strip 4 to the temperatures necessary for cold rolling, typically below 177 ^{° C.} , for a time of less than 30 seconds, preferably less than 10 seconds; as a result of such rapid cooling, it is possible to prevent or significantly reduce the intensity of the release of alloying elements from the solid solution. The effect of rapid cooling can be illustrated using FIG. 5, which shows the formation of intermetallic phases released in aluminum as a function of temperature and time. According to the invention, it is important to achieve rapid cooling of the workpiece during rolling operations so that strip 4 is cooled along the temperature-time line, which does not intersect with the curves shown in FIG. 5. When using well-known methods that allow slow cooling, for example, of a roll, a temperature-time line is obtained that intersects these curves, as a result of which the conditions are maintained under which alloying elements are deposited in the form of intermetallic compounds.

 The degree of reduction in thickness achieved in a similar way as a result of rolling operations can vary within a fairly wide range depending on the type of workpieces used, their chemical composition and the method of their preparation. For this reason, the percentage reduction in thickness during rolling operations is not considered as a decisive factor for the practical implementation of the invention. As a rule, good results can be obtained by reducing the thickness after the rolling operation within 40-99% of the original thickness of the cast strip.

 According to another methodology, instead of cooling the strip or slab 4, it is expedient to immediately cut the blanks with the help of a curved matrix and produce cup-shaped blanks for the production of cans. Such curved matrices are well known in the art; they are described, for example, in US Pat. Nos. 4,711,611 and 5,095,733. The curved matrices used in accordance with the invention can be used to form the non-circular blanks shown in FIG. 7, from which, in turn, it is possible to obtain cups with the configuration shown in the same drawing. Thus, a curved matrix can be used, if necessary, to minimize the tendency to scalloping in sheet metal.

 As it should be clear to specialists, it is also possible before rolling sheet using a curved matrix to roll it into a roll.

 The principles underlying the invention are applicable to a wide variety of aluminum alloys used in the manufacture of can bodies. Typically, such alloys within the scope of the invention can be used those that contain from 0 to about 0.6 wt.% Silicon, from 0 to about 0.8 wt.% Iron, from 0 to about 0.6 wt. % copper, about 0.2-1.5 wt.% manganese, about 0.2-4 wt.% magnesium and about 0-0.25 wt.% zinc, the rest is aluminum with its usual impurities. Examples of alloys suitable for these purposes are aluminum alloys of groups 3000 and 5000, in particular AA 3004, AA 3104 and AA 5017.

 Now, having completed the description of the fundamental ideas of this embodiment of the invention, we turn to the examples below, which are given only by way of illustration, in no way limiting the legal scope of the invention.

Example 6
Finished sheet metal sheets for cans that were not annealed were formed into cups using a conventional round die. The measured value of festoon formation was 6.6%.

 Another adjacent sheet that underwent the same processing operations (also without annealing) was formed on a blank matrix in the form of a cup with an edge having a curved section. The measured value of festoon formation was 3.1%.

Example 7
A thin strip of metal (2.3 mm thick) was cast at a speed of 91.4 m per minute and immediately after that it was rolled at high speed in three passes with a decrease in thickness from 2.3 mm to 0.29 mm, while the temperature decreased in the process rolling from 482 ^o C to 149 ^o C. The measured value of feston formation in the sheet obtained in this way was 3.8%. The tensile strength of the sheet was 3 kg / cm ² and the elongation was 4.4%.

 US Pat. No. 5,356,495 claims and describes one of the modifications to the continuous rolling process for cans of aluminum alloy as part of a production line in accordance with which two sequences of such processing are provided. In the first sequence, the aluminum alloy billet is first subjected to hot rolling, cooling and self-annealing in rolls, and the second sequence provides for continuous operations in the line, including unwinding the coil, quenching without intermediate cooling, cold rolling and coiling. An advantage of the process described in the said patent is that in the absence of costs for operating the annealing furnace, it is nevertheless possible to obtain aluminum sheet metal and raw materials for cans with sufficient strength corresponding to the heat treatment of the aluminum alloy.

 In this regard, it was possible to establish that aluminum alloys and raw materials for cans can be obtained by using two different sequences of continuous operations as part of a production line, of which the first sequence includes a hardening step, and the second is a quick annealing step, to produce sheet metal from aluminum alloys and raw materials for cans with exceptionally high metallurgical properties. It was found that rapid hardening in the first sequence of steps and fast heating with subsequent hardening in the second sequence prevent the intensive deposition of alloying elements included in the alloy, and thus make it possible to obtain sheet metal and raw materials for cans of aluminum alloys with exceptionally high metallurgical properties.

 It is possible to bring together casting, hot rolling and rapid hardening into the first continuous sequence of steps, in which the specified quick hardening prevents the intensive release of alloying elements from the solid solution, as a result of which they are retained in this solution. After that, in the second sequence of continuous operations as part of the line, the aluminum alloy sheet metal can be annealed with rapid heating and rapid hardening in order to ensure that alloying elements are retained in solid solution. Due to the annealing with the subsequent hardening included in the second sequence of steps, it is possible to maximize the content of alloying elements in the solid solution, which allows to increase the strength of the final product.

 In this description, the terms "annealing" and "annealing with rapid heating" refer to a heating process that recrystallizes the grains of an aluminum alloy in order to obtain uniform formability and eliminate festoon formation. By quick heating annealing referred to here is meant a fast annealing process that aims to recrystallize aluminum grains without causing intense deposition of intermetallic compounds. As is known, slow heating and cooling of an aluminum alloy is accompanied by intensive deposition of intermetallic compounds. Thus, in accordance with the essence of the invention, it is important that heating, annealing with heating and hardening are carried out quickly enough. In contrast to the "batch" processing method, the continuous process facilitates the precise control of technological conditions and, therefore, control over metallurgical properties. In addition, due to the continuous processing stages as part of a single line, it is possible to eliminate the expensive stages of loading and transporting materials, as well as reduce the working capital involved in the process and reduce losses associated with starting and stopping operations.

So, the process according to the present invention provides for the creation of a method of manufacturing sheet metal and raw materials for can bodies of aluminum alloys using the following process steps in two continuous sequences in a single line. During the first sequence, the following operations are performed continuously and as part of the line:
(a) hot aluminum billet is subjected to hot rolling to reduce its thickness;
(b) then the hot billet with reduced thickness is subjected to rapid hardening without intensive deposition of alloying elements such as manganese to the temperature necessary for cold rolling;
(c) in accordance with a preferred embodiment of the invention, the hardened billet is cold rolled to obtain a sheet with an intermediate size;
(g) the preform is rolled up for subsequent processing.

After that, in the second sequence, the following operations are carried out continuously and as part of the production line:
(a) the rolled preform is unwound, after which it can be cold rolled if necessary in order to further reduce the thickness of the rolled product;
(b) the billet is subjected to annealing with fast heating to obtain recrystallization of aluminum grains at a sufficiently high rate to prevent intensive deposition of alloying elements in the form of intermetallic compounds, and then fast hardening, also carried out at high speed, in order to practically eliminate the precipitation of alloying elements in the form of intermetallic compounds;
(c) thereafter, the hardened billet is subjected to additional cold rolling and rolling up to a final thickness.

 According to the essence of the invention, it is important to ensure that the annealing operations with heating and hardening are carried out quickly enough to ensure that alloying elements, in particular manganese, as well as copper, silicon, magnesium and aluminum compounds are retained in the solid solution. As is well known in the art, precipitation hardening of aluminum is a diffusion phenomenon that is a function of time. Therefore, it is important that heating annealing and hardening operations, which are part of the second sequence of steps, be carried out rather quickly, so that there is not enough time left for intensive deposition of alloying elements in the form of intermetallic compounds of copper, silicon, magnesium, iron, aluminum, and manganese. At the same time, annealing and hardening operations, which are part of the second stage, help minimize feston formation. This is especially important in cases where the aluminum alloy is used as a raw material for the manufacture of cans, since the phenomenon of festoon formation is often observed precisely in the process of forming cans from workpieces of cases, when the plastic deformation that the aluminum alloy undergoes is uneven. Thus, by minimizing the deposition of intermetallic compounds, an increase in strength occurs, the possibility of recrystallization at a smaller size is created, and the final cold deformation is minimized, which reduces the intensity of feston formation.

 According to a preferred embodiment of the invention, the strip is obtained by casting to obtain a casting thickness of less than 25.4 mm, preferably in the range of 1.5 to 5.1 mm. According to another preferred embodiment, the width of the strip, slab or plate is chosen, rather than traditional practice, rather small. This facilitates refueling and processing in the production line, and also reduces the investment in equipment and the cost of converting liquid metal into sheet metal.

 The sequence of steps adopted according to this embodiment is shown in FIG. 8. One of the achievements provided by the present invention is that the processing steps necessary to obtain sheet metal can be organized in the form of two continuous sequences in a production line, within which these steps are performed in a specific order. Due to the small strip width adopted, according to the invention, for example 305 mm, it is possible to conveniently and economically place this line inside or next to the equipment of a user of sheet metal. Under these conditions, the process according to the invention can be implemented in accordance with the specific technical needs of the user of sheet metal and the required performance.

 According to a preferred embodiment, molten metal is supplied from a furnace not shown in the drawing to a metal degassing and filtering device (also not shown) in order to reduce the content of dissolved gases and particles in the liquid metal. This liquid metal immediately turns into a cast billet 4 in the casting device 3.

 The strip casting method described in the above applications pending simultaneously with this one, which can be successfully applied to the implementation of the present invention, is illustrated in FIG. 4 mentioned above. The workpiece 4 is moved from the device for casting strips 3 through the optional section of trimming and stripping 5 into one or more stands 6 of the hot rolling mill, where its thickness is reduced. Immediately after the end of the hot rolling operation in stands 6, the workpiece is moved to the quenching section 7, where, while maintaining the high temperature obtained during casting, it is brought into contact with the cooling fluid. In carrying out the invention, any of a wide variety of quenching devices can be used. Typically, a quenching unit is used in which a cooling fluid in liquid or gaseous form is sprayed onto a hot billet in order to quickly reduce its temperature. Suitable for these purposes are such media as water, liquefied gases such as carbon dioxide or nitrogen, etc. It is important that the hardening is carried out at a sufficiently high speed in order to achieve a rapid decrease in the temperature of the hot billet, which will prevent the intensive release of alloying elements from solid solution.

 It will be apparent to those skilled in the art that some slight precipitation of intermetallic compounds can be expected, which will not ultimately have undesirable effects on product properties. The absence of an adverse effect of such an insignificant precipitation on the final properties is due, firstly, to the fact that intermetallic compounds are present in small quantities and, in any case, are re-dissolved at the stage of rapid annealing, and secondly, that their volume and appearance only render negligible effect on the final properties. In this description, referring to "intensive" deposition, we mean one that entails a deterioration in the final properties of sheet metal.

Typically, a decrease in temperature occurs from values in the range of about 315.6-510 ^{° C.} to values below 287.8 ^{° C.} , preferably below 232.2 ^° C. After that, the workpiece can be rolled up in a coiling device 8 using a conventional for such technical purposes. According to another embodiment, before rolling into a roll, the preform 4 can be cold rolled, which should be considered as an optional step preceding cooling.

 The importance of rapid cooling following hot rolling is illustrated in FIG. 5, which is a generalized graphical representation of the formation of the distinguished phases of alloying elements as a function of temperature and time. Similar curves, known in the art as “isothermal transformation diagrams,” or “C curves,” show the formation of large and small particles resulting from the deposition of alloying elements as intermetallic compounds during heating or cooling of an aluminum alloy. Thus, the cooling obtained as a result of the quenching operation immediately after hot rolling is carried out at such a speed that the temperature-time line corresponding to the quenching of the aluminum alloy maintains a position between the ordinate and the curves. Due to this, a sufficiently high cooling rate is achieved, which prevents the intensive deposition of such alloying elements in the form of intermetallic compounds.

 At the end of coagulation, the chilled billet can be deposited until it becomes necessary. Given that previously the temperature of the workpiece was quickly reduced in the hardening section 7 to prevent intensive deposition of alloying elements and their compounds, the roll can be stored for an unlimited time.

 During the second sequence, when it becomes necessary to obtain a final processed alloy, the stored coil can be subjected to the following continuous processing operations as part of the production line shown in FIG. 8. The previously formed roll is placed in the unwinder 13, from which it enters the optional cold rolling section 15, and then into the annealing furnace 17, where the roll is quickly heated. This fast heating annealing step allows for a better combination of metallurgical properties, including grain size, strength and formability. Thanks to the rapid heating of the workpiece, it is also possible to prevent the intensive deposition of alloying elements. Thus, the heating operation should be carried out until the desired annealing or recrystallization temperature is obtained, at which there will be no such intersection of the temperature-time line corresponding to the aluminum alloy with curve C shown in FIG. 5, when intense precipitation may occur. Immediately after the heater 14, there is a quenching section 15, on which the strip is rapidly cooled using a conventional cooling medium to the temperature necessary for cold rolling. Since the preform is rapidly cooled in the quenching section 15, there is not enough time left for any noticeable separation of the alloying elements from the solid solution to occur. This makes it easier to achieve strengths that exceed traditionally obtained values. As a result, the volume of hardening operations required for cold processing is reduced, and cold processing itself reduces the intensity of feston formation.

 According to a preferred embodiment of the invention, the workpiece arrives after the hardening step at one or more cold rolling sections 19, where it is processed in order to increase the hardness of the alloy and reduce the thickness of the strip to a final thickness. After cold rolling, the workpiece 4 is rolled up in a coiler 21.

 As is quite obvious to specialists, this embodiment of the invention can be advantageously used without performing the cold rolling step in the rolling mill 19, which is an integral part of the production line. Thus, the application of the cold rolling stage can only be considered as an optional process, which can either be excluded as a whole or performed offline offline, depending on the end use of the alloy being processed. As a rule, the autonomous execution of the cold rolling stage is associated with a decrease in economic benefits compared with the preferred embodiment of the invention, according to which all process steps are performed as part of the line.

 It is quite possible, and sometimes desirable, to use appropriate automatic control equipment. So, for example, often there is a need for a device for operational control of surface quality. In addition, a thickness measuring device traditionally used in the aluminum industry can be used, which will be included in the feedback loop in order to monitor the progress of the process.

When implementing this embodiment, the temperature at the outlet of the hot rolling process is usually maintained in the range from 148.9 to 537.8 ^° C. Hot rolling is carried out, as a rule, in the temperature range from 148.9 ^{° C.} to the solidus temperature of the workpiece. Annealing and heat treatment for solid solution are carried out at temperatures in the range of 315.6-648.9 ^o C for a time of less than 120 seconds, preferably from 0.1 to 10 seconds. Immediately after heat treatment at these temperatures, the preform in the form of strip 4 is quenched in water to the temperatures necessary to keep the alloying elements still in solid solution and for cold rolling (usually at temperatures less than 204.4 ^o C).

 It will be apparent to those skilled in the art that the degree of thickness reduction achieved by the hot and cold rolling operations of the invention is subject to significant fluctuations depending on the type of alloys used, their chemical composition, and the method of production thereof. For this reason, the percentage reduction in the thickness of each of the hot and cold rolling operations according to the invention is not considered as a decisive factor for its practical implementation. However, if we talk about a specific product, then you should set certain boundaries for reducing the thickness and temperature used. As a rule, good results can be obtained by reducing the thickness after hot rolling in the range of 15-99% and after cold rolling in the range of 10-85%. As it should be clear to those skilled in the art, strip casting, carried out in accordance with the most preferred embodiment of the invention, allows the preparation of blanks that do not require the hot rolling step described above. In cases where blanks are obtained by similar casting methods in the form of strips, the hot rolling step can be completely excluded, therefore, when implementing the invention, it should be considered only as optional.

 The ideas of the present invention are applicable to a wide range of aluminum alloys used in the manufacture of a wide variety of products. As a rule, for these purposes it is advisable to use alloys of groups 1000, 2000, 3000, 4000, 5000, 6000, 7000 and 8000.

 Now, having completed the description of the fundamental principles of this embodiment, let us turn to the example below, which is given only by way of illustration. As a test blank, we took a blank obtained by casting from an aluminum alloy and subjected to sufficiently fast hardening so that the distance between the secondary axes of the dendrites was less than 10 microns.

Example 8
During Tests 1 and 2, an aluminum alloy was taken with the composition shown in Table 3, and one of the known alloys and each of them was processed in a strip casting machine with two conveyor belts, in which the belts are cooled during the period when they do not touch with liquid metal, or with a cast strip, to obtain a finished strip with a thickness of 0.254 mm Then, in each of the samples, the cast strip was subjected to the processing indicated in Table 3 to obtain products whose characteristics are given in the same table. The well-known process taken here corresponds to that described in US Pat. this description for AA3104 and AA5182, which are obtained by the traditional ingot method with an ingot thickness of 660 mm. The values of the strength of the cans for longitudinal bending are given for all alloys, with the exception of 5182, and for the convenience of comparison, a correction for the caliber of 0.284 mm was introduced.

 The reviewed tests clearly demonstrate the unexpected results provided by the invention. The rapid quenching used in accordance with the invention instead of the slow cooling allows a much higher strength to be achieved both in the case of hot rolling and without it. As can be seen from the results obtained, the strength values obtained here for aluminum alloys with a low content of alloying elements are close to the data for the alloy AA5182, characterized by a high content of alloying elements, which is used for the manufacture of lids and ears of cans. The process used according to the invention allows not only to achieve higher strength, but also to maintain the intensity of festoon formation at the same or lower level.

 It is quite obvious that a wide variety of changes can be made to the specific features of the methodology, compositions and application, provided that the essence and scope of the invention are determined by the points of the following formula.

Claims (20)

 1. A method of manufacturing a rolled sheet of aluminum alloy, in accordance with which the process is carried out in the form of two sequences of continuous operations as part of a line, comprising, within the first sequence, continuous hot rolling of a hot aluminum billet to reduce its thickness and rolling it into a roll, and within the second continuous sequence of operations as part of the line - unwinding rolled billet and hardening to the temperature required for cold rolling, characterized in that after intermittent hot rolling in the framework of the first continuous sequence, the hot billet is quenched to reduce its temperature, coiled into a coil of the cooled billet, and quenching in the second continuous sequence is carried out with preliminary quick heating of the billet for annealing and recrystallization without intensive deposition of alloying elements in the form of intermetallic compounds carried out after unwinding the workpiece and immediately rapidly cooling the annealed workpiece to prevent ascheniya intensive precipitation of alloying elements.  2. The method according to p. 1, characterized in that the preform is obtained by continuous casting of a strip or slab.  3. The method according to p. 2, characterized in that the continuous casting during molding of the preform is carried out by feeding a liquid aluminum alloy to an endless conveyor belt made of heat-conducting material, as a result of which the molten metal solidifies with the formation of a cast strip, and the endless belt is cooled in the period when it does not come into contact with metal.  4. A method of manufacturing a rolled sheet of aluminum alloy, in accordance with which the process is carried out in the form of two sequences of continuous operations as part of a line, comprising, within the first sequence, continuous casting of an aluminum alloy billet in the form of a strip between two moving endless tapes to produce a hot billet of aluminum alloy, and as part of a second continuous sequence of operations as part of the line, the workpiece is quenched to the temperature necessary for cold rolling, characterized in that after continuous casting within the first continuous sequence, the billet is quenched to lower its temperature, and quenching in the second continuous sequence is carried out with preliminary quick heating of the billet for annealing and its recrystallization without intensive deposition of alloying elements in the form of intermetallic compounds and immediate fast cooling the annealed billet to prevent the deposition of alloying elements.  5. The method according to p. 4, characterized in that in the framework of the first sequence carry out the rolling of the hardened workpiece into a roll.  6. The method according to p. 4, characterized in that in the framework of the first sequence carry out the step of continuous hot rolling of a billet of aluminum alloy in the composition of the line immediately after casting the strip.  7. The method according to any one of paragraphs. 1-3 and 6, characterized in that the hot rolling of the workpiece is carried out with a decrease in the thickness of the workpiece by a value of 15 - 99%. 8. The method according to any one of paragraphs. 1-3 and 6, characterized in that the hot rolling of the workpiece is carried out at a temperature in the range from 149 ^o With up to the solidus temperature of the workpiece. 9. The method according to any one of paragraphs. 1-3 and 6, characterized in that the temperature at the outlet of the hot rolling process is in the range of 149 - 538 ^o C.  10. The method according to any one of paragraphs. 1-9, characterized in that in the framework of the first sequence is carried out as a stage of continuous processing as part of the line cold rolling of the workpiece after hardening.  11. The method according to any one of paragraphs. 1-10, characterized in that the billet of aluminum alloy is a sheet metal for can bodies.  12. The method according to any one of paragraphs. 1-11, characterized in that in the framework of the second sequence is carried out as a stage of continuous processing in the composition of the line cold rolling of the workpiece immediately after annealing and hardening.  13. The method according to any one of paragraphs. 1-11, characterized in that they carry out additional cold rolling of the annealed billet as an autonomous stage outside the line.  14. The method according to any one of p. 11 or 13, characterized in that they carry out coagulation of the workpiece after cold rolling.  15. The method according to any one of paragraphs. 11-14, characterized in that it includes an additional step of forming cups of cold rolled sheet metal. 16. The method according to any one of paragraphs. 1-15, characterized in that the heating of the preform for annealing is carried out in the range 316 - 649 ^o C.  17. The method according to any one of paragraphs. 1-16, characterized in that the annealing is carried out for a time of less than 120 s.  18. The method according to p. 17, characterized in that the annealing is carried out for a time of less than 10 s. 19. The method according to any one of paragraphs. 1-18, characterized in that the hardening of the workpiece with a reduced thickness is carried out to a temperature of less than 288 ^o C.  20. The method according to any one of paragraphs. 1-19, characterized in that the resulting sheet metal is suitable for the manufacture of sheets or ingots for housings used in the production of cups.

Images