Method for producing aluminum can plate

Abstract

A method of producing an aluminum can panel comprising the steps of: providing a body made of an aluminum alloy of AA3004 type, AA3104 type or another aluminum alloy suitable for making an aluminum can panel; homogenizing the body at a homogenization temperature of about 525 DEG C or less; hot-rolling the homogenized body in a single stand hot mill to produce a hot-rolled sheet, the hot-rolled sheet exiting the single stand hot mill at a hot mill exit dimension at a hot rolling exit temperature below a hot rolling onset temperature; annealing the sheet to form a recrystallized hot rolled sheet; and cold-rolling the recrystallized annealed sheet to apply cold compression to produce a cold-rolled sheet of final scale.

Description

[0001] Technical field and prior art

[0002] The present invention relates to a method for producing aluminum can sheet.

[0003] When aluminum can sheet is formed into a cup-shaped article, a phenomenon known as "earing" usually occurs to some extent. Earing can be observed as a wavy appearance around the top edge of the formed cup. The wavy protrusions, also known as "ears", are formed during the deep drawing step in cup manufacturing and represent an undesirable feature of the article. In the aluminum can body stock (CBS), the cup is then punched into multiple rings, which can highlight the wavy ears. High earing can cause transportation problems for the cups, as well as insufficient trimming after punching, truncated ears and trimmer clogging. These artifacts are undesirable in aluminum can manufacturing. Therefore, there is a need to minimize earing in order to avoid these problems and improve the quality of the cup.

[0004] Known can stock materials such as AA3004, AA3104 or other aluminium alloys are generally suitable for producing aluminium can sheet with low earing characteristics, provided that a suitable manufacturing process can be established.

[0005] A well-known process is established in the aluminum industry for producing aluminum strip suitable for can stock. The process involves hot rolling an aluminum ingot through a roughing mill and subsequently through a multi-stand hot rolling mill, usually leaving at high temperature to ensure that a fully recrystallized material is obtained through an autoannealing process. This well-known method produces a final product with low earing and desirable mechanical properties. However, the installation and operation of such hot continuous rolling mills requires a large capital expenditure.

[0006] Modifications have been proposed in the past to produce can plate with commercially acceptable earing characteristics by a single-stand reversing mill (see, for example, US 5,362,340 and US 5,362,341). According to the method of US 5,362,340, an aluminum alloy ingot is provided and heated to a temperature between about 527°C and 571°C. Thereafter, the ingot is hot rolled in a single-stand reversing hot rolling mill to produce an intermediate gauge (thickness) plate. The self-annealed or batch-annealed intermediate gauge plate is then cold rolled to produce a final gauge aluminum can plate with low earing characteristics. This relatively low temperature homogenization (527°C to 571°C, preferably 543°C to 566°C) is applied in order to avoid uncontrolled recrystallization during hot rolling in a single-stand reversing mill.

[0007] Document EP3875692A1 discloses a method for producing aluminum can plates, wherein a body made of an aluminum alloy of the AA3004 type, AA3104 type or other aluminum alloy suitable for making aluminum can plates is heated to a homogenization temperature in the range of about 500°C to 595°C and then hot rolled in a hot rolling mill to produce a hot rolled plate, which leaves the hot rolling mill at a hot rolling exit temperature selected to substantially avoid recrystallization of the hot rolled plate. The hot rolling can be carried out in a single-stand reversing mill. The hot rolled plate is then cold rolled in a cold rolling mill to apply cold compression to produce a cold rolled plate having a cold rolling mill exit dimension that is smaller than the hot rolling mill exit dimension, followed by annealing the cold rolled plate in an intermediate temperature range selected to allow recrystallization of the cold rolled plate to obtain a recrystallized annealed plate. The recrystallized annealed plate is then cold rolled to apply cold compression to produce a cold rolled plate having a final dimension.

[0008] Reducing carbon emissions has become a central task for aluminum producers over the past few years. Towards this direction, the industry has increased its demand for higher recycle content and lower CO2 footprint for can sheet production. One possible way to do this is to increase the post-consumer scrap used for the production of can sheet. The standard practice in the industry is mainly to use UBC (old beverage cans) as the main source of post-consumer scrap, which is mixed with very low amounts of primary aluminum. Moreover, in addition to UBC type scrap, there are some other post-consumer scrap types (mainly from aluminum foil recycling, such as household foil, yogurt lids, etc.) which can be another possible addition in order to increase the recycle content. Summary of the invention

[0009] The object of the present invention is to provide a method for producing aluminum can sheet suitable for manufacturing aluminum cans using a single-stand reversing hot rolling mill, wherein the aluminum sheet has a higher recycled aluminum content and lower energy consumption, and exhibits favorable ear-making characteristics after the deep drawing step, and also allows the production of stable cans with thin wall thickness.

[0010] This object is achieved by a method comprising the features of claim 1. Preferred embodiments are defined in the dependent claims.

[0011] According to the method for producing aluminum can plate, a body (also referred to as an ingot) made of an aluminum alloy is provided. The aluminum alloy is selected so that it is suitable for manufacturing aluminum can plate. Specifically, the aluminum alloy can be based on AA3004 type, AA3104 type or other aluminum alloy suitable for manufacturing aluminum can plate, such as AA3204 alloy.

[0012] The body may be made of cast aluminum, which is then peeled to obtain a body suitable for further processing. The body is homogenized for a period of time at a homogenization temperature within a certain temperature range, and then cooled to a hot rolling start temperature below the homogenization temperature, followed by hot rolling the homogenized body in a single-stand hot rolling mill to produce a hot rolled plate, which leaves the single-stand hot rolling mill at a hot rolling exit temperature below the hot rolling start temperature with a hot rolling mill exit dimension. Depending on the hot rolling exit temperature (i.e., the exit temperature of the last hot rolling coiling pass), the plate is annealed by self annealing or batch annealing to form a recrystallized hot rolled plate. After annealing, the recrystallized annealed plate is cold rolled to apply cold compression to produce a cold rolled plate with a final dimension.

[0013] Typical requirements for aluminum alloys suitable for making aluminum can plates are described, for example, in the article "AlMn1Mg1 for Beverage Cans" in J. Hirsch's "Virtual Fabrication of Aluminium Products", Wiley-VCH 2006 (ISBN: 3-527-31363-X), Chapter I-4. In general, the material must provide an optimal combination of strength and sufficient forming properties. For aluminum (aluminum / aluminum), strength is achieved by a combination of appropriate alloy additions (e.g., by Mg and Mn) for optimal solid solution hardening and pre-deformation (i.e., highly rolled plates). In addition, the strength must also remain sufficiently high after subsequent paint baking cycles. Good formability is achieved by an optimal combination of alloy additions for good work hardening (Mg) and certain particle strengthening effects (Mn). The latter also maintains uniform deformation and even provides a cleaning effect on the mold, preventing harmful oxide accumulation and scratches. Therefore, common aluminum alloys used to produce can bodies are AlMg1Mn1=EN-AW 3004 and AlMg1Mn1(Cu)=EN-AW 3104, which best meet the requirements of can strength and formability.

[0014] The inventors have recognised that recycling traditional post-consumer scrap sources of aluminium materials (e.g. UBC (waste beverage cans) and aluminium foil recycling such as household aluminium foil, yoghurt lids etc.) tends to result in relatively high Fe content in the alloy compared to using non-recycled base materials.

[0015] It was observed that with increasing Fe content in the alloy, the cubic texture developed after intermediate annealing weakens, thereby producing high 45° in the final product. The final product with higher 45° ears increases the tear-off can and also has low performance at the canmaker.

[0016] The method of the present invention takes this undesirable tendency into account and overcomes this problem.A significant contribution to the technical solution is the step of homogenizing the ingot at a homogenization temperature of about 525°C or less, which is lower than the homogenization temperature of the related prior art.

[0017] In other words: reducing the homogenization temperature to significantly below the minimum temperature currently considered necessary to obtain low-earing aluminum materials appears to be an effective measure to offset the negative impact of the relatively high Fe content in the alloy caused by the use of scrap materials.

[0018] Homogenization should preferably be performed in a temperature range of 460-525° C. For example, the holding time may preferably be in the range of about 1 hour to about 22 hours holding time.

[0019] Lowering the homogenization temperature ensures that the material does not recrystallize in the coiling pass in a single stand reversing mill. On the other hand, after annealing, the undesirable effect of a lower cubic density due to a higher Fe content is partially or completely compensated in terms of texture development by the effect obtained using a lower homogenization temperature.

[0020] Homogenizing the ingots at lower temperatures also helps reduce the CO2 footprint, as the preheating furnace uses less energy than the high temperature homogenization (600°C) required by existing technologies and the conventional process of producing can plate via tandem hot rolling mills.

[0021] The inventors currently believe that the following mechanism may contribute to this surprisingly positive result.

[0022] The earing of the material at the final dimension is caused by the texture developed after annealing the hot strip and the amount of cold working to reach the final dimension. The latter also controls the strength of the final product and requires a minimum amount of cold working. Therefore, the earing of the final product is mainly affected by the earing obtained after annealing (i.e. the texture developed on the annealed hot strip).

[0023] The earing obtained after annealing is a result of the orientation of the newly recrystallized grains. Generally speaking, cubically oriented grains will produce 0-90° earing, while rolled and randomly textured grains will produce 45° earing. The balance between these orientations will determine the amount of 0 / 90° earing in the annealed hot strip.

[0024] For can plate material, this amount is very important and must be well controlled. If the 0 / 90° lug is too low in the annealed hot strip, the 45° lug will be very strong in the final product and the formed can will have a profile with four high 45° lugs. On the other hand, if the 0 / 90° lug is too high, the final product will have a profile with 8 or 6 lugs, with the two 0-180° lugs being significantly higher. Both of these situations are well known in the can industry and can require over-trimming and will result in broken cans and should be avoided.

[0025] According to the document, cubic texture grains are generally nucleated at microstructural heterogeneities (such as transition zones and flat cubic grains retained during hot deformation), which are considered to be constant as a first approximation. However, grains nucleated at second phase particles larger than about 2 μm will promote the development of random texture at the expense of cubic texture, and its mechanism is described as PSN (particle stimulated nucleation). Therefore, the greater the amount of second phase particles, the greater the number of recrystallized grains with random orientation, and the higher the 45° earing of the final can plate.

[0026] The amount of second phase particles is affected by the alloy composition and the homogenization treatment. Increasing the Fe content and / or using high temperature homogenization increases the number of second phase particles that can generate PSN mechanisms through particle coarsening and will (i) produce higher 45° lugs as described above, and (ii) promote recrystallization during the coiling pass. Similarly, the second phase particles will coarsen under high temperature homogenization.

[0027] Therefore, the particle coarsening is suppressed by adopting a lower temperature for homogenization, and the effectiveness of the PSN mechanism is reduced.

[0028] The homogenization treatment also affects the size of the second phase particles and dispersoids (i.e. fine particles of about 0.1 μm in size that precipitate during the homogenization process). Dispersoids play a crucial role in the growth of nucleated grains through the pinning effect. Depending on the size of the dispersoids and the spacing between them, they can act as obstacles to the movement of new grain boundaries, prevent the growth of new grains, and inhibit recrystallization during the coiling pass. According to the literature, the pinning effect is stronger when the number of dispersoids is high (enclosed spaces) and small. Using a lower homogenization temperature is beneficial to meet these two conditions.

[0029] Lowering the homogenization temperature seems to help obtain smaller dispersoid size and spacing, thus enhancing the pinning effect.

[0030] Generally, the chemical composition of AA3004, AA3104, AA3204 or other aluminum alloys suitable for making aluminum can sheet, as well as other aluminum alloys, are known to those skilled in the art and can be obtained, for example, from the Aluminum Association's Teal Table.

[0031] On the other hand, many aluminum alloys optimized for other purposes are considered unsuitable for making aluminum can sheet in the context of the present application. These include, for example, 1XXX series alloys (essentially pure aluminum, with a minimum aluminum content of 99% by weight), 2XXX series alloys alloyed with copper as a base alloying element and capable of precipitation hardening to strengths comparable to steel, 4XXX series alloys alloyed with silicon as a base alloying element, 5XXX series alloys alloyed with magnesium as a base alloying element to provide excellent corrosion resistance, 6XXX series alloys alloyed with magnesium and silicon as base alloying elements, 7XXX series alloys alloyed with zinc as a base alloying element and capable of precipitation hardening, or 8XXX series alloyed with other elements not covered by the other series (e.g., aluminum-lithium alloys).

[0032] In a preferred embodiment, an aluminum alloy containing the following chemical composition can be used (all quantities are in wt %): about 0.05-0.60 wt % Si (silicon), preferably 0.15-0.5 wt % Si; about 0.10-0.80 wt % Fe (iron), preferably 0.45-0.70 wt % Fe; about 0.70-1.50 wt % Mn (manganese), preferably 0.80-1.40 wt % Mn; about 0.80-1.50 wt % Mg (magnesium), preferably 0.90-1.30 wt % Mg; about 0.05-0.25 wt % Cu (copper), preferably 0.10-0.25 wt % Cu; up to 0.10 wt % Ti (titanium); up to 0.25 wt % Zn (zinc); and up to 0.15 wt % impurities, preferably each impurity is less than 0.05 wt %; the balance is Al (aluminum).

[0033] In preferred embodiments the Fe content is at the upper end of the above range, wherein the Fe content may be at least 0.6 wt%, preferably greater than 0.60 wt% Fe to 0.80 wt% Fe and / or 0.61 wt% Fe or more.

[0034] In some embodiments the aluminum alloy comprises: about 0.20-0.40 wt % Si, preferably about 0.30 wt % Si; about 0.80-1.20 wt % Mn, preferably about 0.90 wt % Mn; about 0.90-1.40 wt % Mg, preferably about 1.20 wt % Mg; about 0.10-0.25 wt % Cu, preferably about 0.17% Cu, and about 0.55-0.70 wt % Fe, preferably about 0.60 wt % Fe.

[0035] As mentioned above, this method may be particularly useful if the alloy contains a relatively high amount of Fe. High amounts of Fe may be present in all types of post-consumer scrap recycled aluminum materials. Those materials can be recycled and used to make alloys. In some embodiments, the step of providing a body made of an aluminum alloy includes forming an aluminum alloy based on a composition comprising 80% or more aluminum scrap, and using this alloy in a solidified form as an ingot. Therefore, the final product may contain a high percentage of recycled aluminum material.

[0036] The annealing step may include auto-annealing. Auto-annealing may be caused by a significantly rapid and large reduction in thickness mechanically during the final coiling pass in a single-stand reversing hot rolling mill, thereby increasing the temperature relative to the temperature level in the previous coiling pass without applying additional thermal energy. The temperature of the plate material may thereby be raised from a level low enough to prevent recrystallization (e.g., a temperature of about 260° C. or less) to a higher temperature sufficient to initiate nucleation and growth of new grains (e.g., a temperature of about 330° C. or more).

[0037] In some cases, annealing is performed exclusively by autoannealing, saving the cost of a separate batch furnace.

[0038] In a preferred embodiment, the annealing step comprises batch annealing, which allows for better control of the annealing effect. Batch annealing of the coiled material can be carried out in a batch furnace. In this case, it is not necessary to obtain autogenous annealing conditions in the final stages of hot rolling. In some cases, autogenous annealing and subsequent batch annealing can be combined.

[0039] In some embodiments, the step of annealing the plate includes selectively self-annealing or furnace annealing the plate to form a recrystallized hot rolled plate, wherein (i) if the hot rolling exit temperature is equal to or exceeds a threshold temperature, the plate is self-annealed to a recrystallized annealed state while being coiled in a single stand reversing mill, and (ii) if the hot rolling exit temperature is below the threshold temperature, the hot rolled plate is transferred from the single stand reversing mill to a batch furnace and annealed in the batch furnace at an annealing temperature within the range of the hot rolling exit temperature or higher to allow the hot rolled plate to recrystallize, obtaining a recrystallized annealed plate. In some cases, the threshold temperature is 330°C.

[0040] With regard to the temperature range, it has been observed that it is beneficial in many cases if the material temperature after the last flat rolling pass is between 290° C. and 350° C. Alternatively or additionally, it has been found that good results are more prominent if the material temperature ranges between about 220° C. and about 280° C. in all coiling passes. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the entire drawings, the same elements will be represented by the same reference numerals.

[0042] Figure 1 shows a schematic diagram of a portion of an apparatus configured to manufacture aluminum can sheet suitable for making cup-shaped articles;

[0043] Figure 2 A diagram illustrating the earing of the final product for different production processes is shown, with negative earing values ​​corresponding to 45° earing and positive earing values ​​corresponding to 0-90° earing relative to the rolling direction. DETAILED DESCRIPTION

[0044] Sufficiently high strength and formability (including limited earing) are among the main requirements for aluminum can body plate. High strength is needed to achieve sufficient structural stability and avoid buckling of the can bottom under high internal pressure (dome inversion). High strength is also needed in order to obtain a stable can with very thin can walls after ironing. Good formability is required because the material is subjected to a large number of forming operations. The anisotropic material flow caused by the texture of the plate - controlled by balancing the hot strip cubic and cold rolled textures - always forms an uneven can rim during deep drawing and ironing operations. This unevenness is also called "earing". Highly uneven cup rims are not conducive to the transportation of cans, or when the ears are stretched and sheared off during ironing, the entire process is affected, resulting in machine downtime and reduced efficiency.

[0045] Embodiments of the present invention are able to address both of these requirements in a satisfactory manner using an economically viable production process.

[0046] Figure 1 A schematic diagram of a portion of an apparatus 100 configured to manufacture aluminum can sheet suitable for making cup-shaped articles is shown. The schematic diagram shows only some of the devices used in the production line.

[0047] The production equipment usually includes a casting device to produce a large ingot from an aluminum alloy melt. The ingot usually consists of coarse grains with a dendritic structure and a random texture. Precipitates containing aluminum and other components (such as Fe, Mn and Si) are usually unevenly distributed in the ingot.

[0048] In some embodiments, the aluminum alloy contains a significant amount of traditional post-consumer scrap sources of recycled aluminum materials, such as UBC (waste beverage cans) and aluminum foil recycling (e.g., household aluminum foil, yogurt lids, etc.). This tends to result in a relatively high amount of Fe in the alloy compared to using non-recycled base materials.

[0049] In the next step, the ingot is preheated and thereby homogenized in a homogenizing furnace 110, also called a preheating furnace 110. The homogenization process is usually accompanied by characteristic changes in the solute content and the precipitate microstructure, which subsequently affect recrystallization, grain size and texture during plate production.

[0050] The homogenized ingot is then transferred to the hot rolling stage. In the equipment, a single-stand reversing rolling mill 120 is used for hot rolling. The single-stand reversing rolling mill 120 can be schematically Figure 1 120 ). In a first operating mode HR-FP (shown on the left-hand side of the single-stand reversing mill 120 ), the thickness of the input ingot is reduced using several flat rolling passes, in which the material is rolled back and forth without being coiled on either side of the rolls. In a second operating mode HR-CP (shown on the right-hand side of the figure representing the single-stand reversing mill 120 ), the coiling reels CR on both sides of the mill stand MS are used to coil the sheet SH between coiling passes carried out in mutually opposite rolling directions. In any coiling pass, one reel operates as an unwinder, supplying the input strip to the rolling gap formed in the mill stand. The other reel serves as a tension reel, coiling the output strip after the rolling path. Since single-stand reversing mills are generally known in the art, it is not considered necessary to describe them in detail in the present application.

[0051] The process does not require a cold rolling step immediately following the hot rolling step. Instead, the further processing steps depend on certain conditions that determine the recrystallization characteristics of the material in the process.

[0052] Specifically, the plate is selectively subjected to self-annealing or furnace annealing to form a recrystallized hot-rolled plate. If the hot rolling exit temperature is equal to or exceeds a threshold temperature (e.g., 330°C), the plate is self-annealed to a recrystallized annealed state while being coiled in a single-stand reversing mill. On the other hand, if the hot rolling exit temperature is lower than a threshold temperature (e.g., 330°C), the hot-rolled plate is transferred from the single-stand reversing mill 120 to a batch furnace 140 and annealed in the batch furnace, with the annealing temperature being within a range of or higher than the hot rolling exit temperature or the threshold temperature to allow the hot-rolled plate to recrystallize and obtain a recrystallized annealed plate.

[0053] In an embodiment, a batch furnace 140 is arranged downstream of the hot rolling stage 120. The batch furnace is configured to receive a plurality of coils CL after cold rolling and to perform annealing of the material received from the hot rolling stage to achieve complete recrystallization of the plate material.

[0054] The cold rolling stage 150 is arranged downstream of the annealing batch furnace 140 in order to apply cold rolling to the recrystallized material to obtain a cold rolled material in the final dimensions required for further processing steps. Figure 1 In the embodiment of the present invention, the cold rolling mill 150 comprises a single stand.

[0055] An exemplary process for producing aluminum can sheet on the apparatus 100 may be performed as follows.

[0056] Casting aluminum alloy AA3004 or AA3104 or (other aluminum alloys suitable for making aluminum can plate) ingots. The aluminum alloy used in this process may contain about 0.30% Si, about 0.90% Mn, about 1.20% Mg, about 0.17% Cu. The Fe content can be about 0.60% or higher to increase the use of post-consumer scrap. The alloy with a Fe content of 0.61% is produced using post-consumer scrap aluminum.

[0057] After casting, the ingot is peeled to remove surface irregularities and shell areas produced during the DC casting process.

[0058] The next step is a preheating step or homogenization step of the ingot in a preheating furnace 110. Homogenization may be performed at a temperature of about 520°C with a holding time of about 6 hours.

[0059] Then, the preheated (homogenized) ingot is transferred to the hot rolling single stand reversing mill 120. Hot rolling can start at about 500°C, and the ingot thickness can be reduced from 600mm to about 30mm through several flat rolling passes. The ingot temperature after the last flat rolling pass can be about 310°C.

[0060] After the flat rolling pass, the thickness reduction can be achieved in the same single-stand reversing mill 120, but this time the material can be coiled after each pass (see Figure 1 For example, the finished thickness of the hot-rolled material may be about 2 mm. The plate outlet thickness after hot rolling may preferably be between about 1.7 mm and about 5 mm.

[0061] The hot rolling exit temperature (after the last coiling pass) can be different. If the exit temperature is above 330°C, the coil can be self-annealed. If the exit temperature is below 330°C, a batch annealing process can then be performed in a batch furnace 140 to ensure that the material is in a soft state (fully recrystallized) before cold rolling. The batch annealing temperature can be around 390°C, with a holding time of 3 hours at this temperature.

[0062] The main purpose of the hot rolling process is to ensure that there is no recrystallization during the coiling pass. Therefore, the temperature during the coiling pass, except for the last one, can be around 270°C. As for the last coiling pass, the absence of recrystallization is not so important and the material can also become partially recrystallized (due to the exit temperature <330°C) because the next step is batch annealing, where recrystallization can be completed.

[0063] The recrystallized annealed coil may then be transferred to a cold rolling mill 150 for cold rolling where the material is cold rolled to final gauge with a total cold reduction of about 90%.

[0064] Industrial tests were carried out with the recommended homogenization parameters (520°C-6 hours) and Fe contents exceeding 0.6 wt% (particularly about 0.61 wt% Fe). For comparative purposes, the following combinations of homogenization treatments and Fe contents were also produced:

[0065] (A) Typical homogenization (540-560℃–12 hours) / Typical Fe (about 0.50%)

[0066] (B) Typical homogenization / high Fe

[0067] (C) Low temperature homogenization / high Fe

[0068] In typical homogenization, typical homogenization temperatures are selected within the conventional temperature ranges disclosed, for example, in US 5,362,340.

[0069] Figure 2 The graphs in illustrate the final earing obtained for each combination. The vertical axis (y-axis) represents the type and amount of earing (in percentage) at the final thickness. The area above the baseline (dashed line for 0% earing) corresponds to 0-90° earing, while the area below the baseline represents 45° earing. The absolute distance of a data point from the baseline in the y-axis direction of the graph represents the amount or intensity of the corresponding earing, which means that the points on the baseline correspond to panels that show no earing at all. Figure 2 The schematic box plots in represent the results of industrial trials.

[0070] Result A is considered to represent many conventional cases where the Fe content used in the alloy is not too high and the homogenization temperature is relatively high (540°C or higher) resulting in very good earing behavior.

[0071] Result B seems to indicate that conventional, relatively high homogenization temperatures (homogenization temperatures of about 540°C or higher) may not result in good ear-forming properties if the Fe content in the alloy is within the higher allowable range of about 0.6 wt% Fe.

[0072] Result C seems to indicate that low temperature homogenization as proposed in this application may result in good earing behavior if the Fe content in the alloy is within the higher permissible range of about 0.6 wt% Fe. For high Fe alloys, low temperature homogenization produces significantly better earing behavior than high temperature homogenization.

[0073] Therefore, from the results shown in the graph, it can be concluded that, without changing the homogenization conditions, only increasing the Fe content, the final earing will shift to significantly higher values ​​of earing in the 45° direction, which may lead to a decrease in the performance of the can making machine. On the contrary, by adopting a lower homogenization temperature (here below 520°C), the final earing will shift to lower values, close to the typical values ​​of can plate.

Claims

1. A method for producing aluminum can sheet, comprising: Providing a body made of aluminum alloy type AA3004, type AA3104 or other aluminum alloy suitable for manufacturing aluminum can plate; homogenizing the body at a homogenization temperature of about 525° C. or less; hot rolling the homogenized body in a single stand hot rolling mill to produce a hot rolled plate, the hot rolled plate leaving the single stand hot rolling mill at a hot rolling exit temperature below a hot rolling start temperature and at a hot rolling mill exit dimension; annealing the sheet to form a recrystallized hot rolled sheet, The recrystallized annealed sheet is cold rolled to apply cold compression to produce a cold rolled sheet of final size.

2. The method according to claim 1, wherein the homogenization is carried out in a homogenization temperature range of 460°C to 525°C, preferably with a holding time in the range of about 1 hour to about 22 hours holding time.

3. The method according to claim 1 or 2, wherein the aluminum alloy comprises the following chemical composition (all quantities are in wt%): about 0.05-0.60 wt% Si (silicon), preferably 0.15-0.5 wt% Si; about 0.10-0.80 wt% Fe (iron), preferably 0.45-0.70 wt% Fe; about 0.70-1.50 wt% Mn (manganese), preferably 0.80-1.40 wt% % Mn; about 0.80-1.50wt% Mg (magnesium), preferably 0.90-1.30wt% Mg; about 0.05-0.25wt% Cu (copper), preferably 0.10-0.25wt% Cu; up to 0.10wt% Ti (titanium); up to 0.25wt% Zn (zinc); and up to 0.15wt% impurities, preferably each impurity is less than 0.05wt%; the balance is Al (aluminum).

4. The method according to claim 3, wherein the aluminum alloy comprises at least 0.6 wt% Fe, preferably more than 0.6 wt% Fe and / or 0.61 wt% Fe or more.

5. The method according to one of claims 1 to 4, wherein the aluminum alloy comprises: about 0.20-0.40 wt% Si, preferably about 0.30 wt% Si; about 0.80–1.20 wt % Mn, preferably about 0.90 wt % Mn; about 0.90-1.40 wt % Mg, preferably about 1.20 wt % Mg; about 0.10-0.25 wt% Cu, preferably about 0.17% Cu, and About 0.55-0.70 wt% Fe, preferably about 0.60 wt% Fe.

6. The method according to one of claims 1 to 5, wherein the step of providing a body made of an aluminum alloy comprises forming the aluminum alloy based on a composition comprising 80% or more aluminum scrap.

7. The method according to claim 1, wherein the step of annealing the sheet comprises selectively self-annealing or furnace-annealing the sheet to form a recrystallized hot rolled sheet, wherein (i) if the hot rolling exit temperature is equal to or exceeds the threshold temperature, the plate is self-annealed to a recrystallized annealed state while being coiled in a single stand reversing mill; (ii) if the hot rolling exit temperature is lower than the threshold temperature, the hot rolled sheet is transferred from the single stand reversing mill to a batch furnace, and annealed in the batch furnace at an annealing temperature within the range of the hot rolling exit temperature or higher to allow the hot rolled sheet to recrystallize, obtaining a recrystallized annealed sheet. The method of claim 7 , wherein the threshold temperature is 330° C. 9 .

9. The method according to one of claims 1 to 8, wherein the hot rolling comprises a number of flat rolling passes followed by a number of coiling passes.

10. The method of claim 9, wherein the material temperature after the final flat rolling pass is between 290°C and 350°C.

11. The method of claim 9 or 10, wherein the material temperature is in the range of about 220°C to about 280°C in all coiling passes.

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