Can lids for food and beverages

Abstract

The present invention relates to a can lid for food or drink, the can lid being composed of an end and a tab for opening a score that is formed in the end. By forming the end and / or the tab from an aluminum alloy that contains 0.5 to 1.4% by mass of Mn, 2.0 to 4.5% by mass of Mg, 0.6% by mass or less of Si, 0.8% by mass or less of Fe, 0.25% by mass or less of Cu, 0.10% by mass or less of Cr, 0.25% by mass or less of Zn and 0.10% by mass or less of Ti, the present invention is able to provide a can lid which comprises an end and / or a tab that has adequate properties such as pressure-resisting strength required for can lids even in cases where the end and / or the tab contains a recycled aluminum alloy that uses aluminum UBC as a starting material.

Description

Technical Field

[0001] The present invention relates to an aluminum alloy can lid comprising an end and a tab for tearing and opening a score formed on the end. More specifically, the present invention relates to a can lid for food and beverages having the required performance for the end and the tab while using a recycled material made from an aluminum can after the contents have been consumed.

Background Art

[0002] As a can for filling beverages and foods such as beer and soft drinks, a food and beverage can is widely used, which is formed by attaching an aluminum can lid to a can body made of a metal such as aluminum or steel. Such an aluminum can lid generally comprises an end and a tab for tearing a score formed on the end and forming an opening partitioned by the score. The materials used for the can lid are required to have strength, formability, corrosion resistance, etc. That is, the end is required to have excellent pressure resistance such that the can lid does not deform even in the case of a positive pressure can containing a carbonated beverage or the like as the content, or in the case of a negative pressure can where the pressure is reduced due to a temperature drop caused by high-temperature filling of the content, and toughness such that the score does not break unintentionally. On the other hand, the tab is required to have a breaking strength and toughness such that no breakage or tearing occurs when forming the opening.

[0003] As an aluminum alloy used for the can lid, for example, in Patent Document 1 below, an aluminum-magnesium alloy containing no beryllium is proposed, which contains 0.8 to 15% by mass of Mg, 0.2 to 0.6% by mass of Fe, the total content of Al and Mg is 90% by mass or more, and the content of P as an impurity is 0.001% by mass or less, which is a molten oxidation-inhibiting aluminum-magnesium alloy. Furthermore, Patent Document 2 below describes a cold-rolled sheet material with a thickness of 0.22 to 0.25 mm, containing, by mass, Mg: 0.80 to 1.50%, Mn: 0.80 to 1.20%, Fe: 0.40 to 0.60%, Si: 0.20 to 0.40%, and Cu: 0.15 to 0.25%, satisfying the content relationships Mn / Fe = 1.5 to 2.5 and Mg / Mn ≥ 1.0, with the remainder being aluminum and an aluminum alloy, which is an unavoidable impurity. An aluminum alloy sheet for negative pressure can lids has been proposed, characterized in that one or both sides are coated with an organic resin film, and after paint curing, the 45° edge ratio is 1.5 to 3.0%, the 0-180° edge ratio is 1.0 to 2.5%, satisfying the formula: -0.6% ≤ (45° edge ratio) - (0-180° edge ratio) ≤ 1.5%, and further having a tensile strength of 270 to 300 MPa and a yield strength of 240 to 270 MPa in the direction 0° with respect to the rolling direction. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 5920705 [Patent Document 2] Patent No. 5898426 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Incidentally, used beverage cans (UBCs) are collected at a rate of nearly 100%, and in the case of aluminum beverage cans, they are recycled into aluminum ingots. The can body is generally made of 3000 series aluminum alloy, which has a high Mn content, but the can lid (end and tab) is made of 5000 series aluminum alloy, which has a higher Mg content and is stronger than 3000 series aluminum alloy, from the viewpoint of strength, formability, and corrosion resistance. Therefore, recycled aluminum alloys made from UBC have a composition similar to 3000 series aluminum alloys, which account for a large proportion of the total weight of aluminum beverage cans. Compared to 5000 series aluminum alloys, they have a higher Mn content and a lower Mg content, making them unsuitable for use in can lids. Consequently, new aluminum ingots had to be used for can lids. However, the production of new aluminum ingots requires a large amount of electricity and the resulting carbon dioxide emissions are significant. From an environmental perspective, there is a demand for the use of recycled materials in can lids as well.

[0006] Furthermore, in aluminum alloys with a high Mn content using recycled aluminum alloys made from UBC, the strength of the score formed at the end decreases due to an increase in Al-Fe-Mn-Si precipitates. As a result, the score may unintentionally fracture when subjected to impact such as dropping, potentially leading to leakage of the contents. It was also found that microcracks may occur in the organic coating on the inner surface of the score processing area (inner surface of the end) and in the rivet forming area for tab attachment, potentially leading to metal exposure and corrosion of the end due to storage over time. Moreover, aluminum alloys with increased Al-Fe-Mn-Si precipitates have reduced toughness, making them more prone to cracking. When the score fractures to form an opening, there is a risk of derailment and fracture from the score. Furthermore, the tabs attached to the ends are generally made of thin sheet metal for ease of opening formation and tab strength, and their ends are formed by bending the gripping portion for the fingers and curling the rest. In this case, if an aluminum alloy with increased Al-Fe-Mn-Si precipitates is used, there is a risk of tab breakage or cracks occurring on the metal surface of the processed part.

[0007] Therefore, the object of the present invention is to provide a can lid equipped with ends and / or tabs that have the required performance, such as pressure resistance, even when containing a recycled aluminum alloy made from aluminum UBC. Another object of the present invention is to provide a can lid with an end and / or tab that, even when molded from a material containing a recycled aluminum alloy made from aluminum UBC with a high Mn content and a large amount of Al-Fe-Mn-Si precipitates, has high score strength, effectively prevents leakage of contents due to unintended breakage of the score and the occurrence of microcracks in the organic coating due to score processing, and effectively prevents breakage at locations other than the score. [Means for solving the problem]

[0008] According to the present invention, a can lid for food and beverages is provided, comprising an end and a tab for opening a score formed on the end, characterized in that the end and / or tab are made of an aluminum alloy containing Mn: 0.5 to 1.4 mass%, Mg: 2.0 to 4.5 mass%, Si: 0.6 mass% or less, Fe: 0.8 mass% or less, Cu: 0.25 mass% or less, Cr: 0.10 mass% or less, Zn: 0.25 mass% or less, and Ti: 0.10 mass% or less.

[0009] In the food and beverage can lid of the present invention, (1) The aluminum alloy contains Mn: 0.5 to 1.0 mass%, Mg: 3.0 to 4.5 mass%, Si: 0.60 mass% or less, Fe: 0.8 mass% or less, Cu: 0.25 mass% or less, Cr: 0.10 mass% or less, Zn: 0.25 mass% or less, and Ti: 0.10 mass% or less. (2) The aluminum alloy contains Mn: 0.5 to 1.0 mass%, Mg: 3.0 to 4.5 mass%, Si: 0.35 mass% or less, Fe: 0.6 mass% or less, Cu: 0.25 mass% or less, Cr: 0.10 mass% or less, Zn: 0.25 mass% or less, and Ti: 0.10 mass% or less. (3) The aluminum alloy contains Mn: 0.5 to 1.0 mass%, Mg: 2.0 to 3.0 mass%, Si: 0.60 mass% or less, Fe: 0.8 mass% or less, Cu: 0.25 mass% or less, Cr: 0.10 mass% or less, Zn: 0.25 mass% or less, and Ti: 0.10 mass% or less. (4) The aluminum alloy contains Mn: 0.5 to 1.0 mass%, Mg: 2.0 to 3.0 mass%, Si: 0.35 mass% or less, Fe: 0.6 mass% or less, Cu: 0.25 mass% or less, Cr: 0.10 mass% or less, Zn: 0.25 mass% or less, and Ti: 0.10 mass% or less. (5) The Mg content in the aluminum alloy is 2.0 to 3.0 mass%, and the remaining thickness of the score in the initial opening portion of the score is 71% or less of the original plate thickness. (6) The tensile strength of the aluminum alloy plate in the 0° rolling direction after paint curing is 350 to 410 MPa. (7) The thickness of the unprocessed portion of the end is 0.19 to 0.30 mm, and the thickness of the unprocessed portion of the tab is 0.24 to 0.35 mm. (8 )before The aluminum alloy contains recycled material from used aluminum beverage cans. ( 9 The Mn content of the aluminum alloy is 0.8 to 1.4% by mass. ( 10 The breakable score has, in a vertical cross-section in the width direction of the score, opposing inclined surfaces and a bottom surface, the score width decreasing as it goes downwards, and at least a portion of the bottom surface has a width that is 65% or less of the width of the virtual bottom surface defined by the virtual extension line of the inclined surface and the virtual extension line passing through the center of the bottom surface. ( 11 ) The inclined surface and the bottom surface are continuous via a curved surface. ( 12 ) A flat portion is formed in the center of the bottom surface, and the width of the flat portion is 65% or less of the width of the virtual bottom surface. ( 13 The width defined by the virtual extension line of the inclined surface and the virtual extension line passing through the center of the bottom surface is 15 to 40 μm. ( 14 ) The score angle formed by the inclined surface is 40 to 60 degrees. ( 15) The breakable score is the main score, and it has an auxiliary score adjacent to the main score and located inward of the main score. In the vertical cross-section in the width direction of the score, the metal repulsion amount S0 due to the auxiliary score processing is 25% or more of the metal repulsion amount S1 due to the main score processing. ( 16 ) The main score has a high score remaining thickness portion where the score remaining thickness with respect to the virtual thickness when the score is not formed in the score processing portion is larger than the main score remaining thickness rate and 85% or less. ( 17 ) The breakable score is the main score, and it has an auxiliary score adjacent to the main score and located inward of the main score. In the vicinity of the initial opening portion of the main score, a score for preventing ejection close to the main score is formed, and the score remaining thickness of the score for preventing ejection is 70 to 90% of the original plate thickness. ( 18 ) A rivet forming portion for tab attachment is formed at the end, and the processing rate with respect to the original plate thickness at the center portion in the rivet forming portion is 70% or less of the original plate thickness. ( 19 ) The ratio of the diameter of the coining processing region on the top surface of the rivet forming portion to the inner diameter of the side wall portion in the rivet forming portion at the end is 40 to 95%. ( 20 ) In the tab, at the finger-touching portion, the ratio of the thickness of the finger-touching portion to the original plate thickness (thickness of the finger-touching portion / original plate thickness) is 2 or more and is less than or equal to the value of the ratio of the thickness of the curled portion of the tab to the original plate thickness (thickness of the curled portion / original plate thickness). is preferable.

[0010] According to the present invention, there is also provided a method for manufacturing the lid for a food or beverage can, wherein the score forming blade used for forming the breakable score comprises opposing inclined side surfaces whose blade width decreases as going towards the tip and a tip portion located at the lower end of the inclined side surfaces in the vertical cross-section in the width direction of the score forming blade, and at least a part of the tip portion has a width that is 65% or less of the width of the virtual tip surface defined by the virtual extension line of the inclined side surface and the virtual extension line passing through the center of the tip portion.

[0011] In the method for manufacturing the end of the present invention, (1) Both sides of the tip portion are continuously connected by the inclined side surfaces and curved surfaces, (2) A flat portion is formed at the center of the tip portion, and the width of the flat portion is 65% or less of the width of the virtual tip surface, is preferable.

[0012] According to the present invention, there is further provided a canned food filling can characterized in that the above-mentioned canned food lid is applied to a can filled with canned food.

Effects of the Invention

[0013] According to the canned food lid of the present invention, even when a recycled material of aluminum UBC is used, since each main component of the alloy elements is within the above range, an end having excellent pressure resistance and a tab having excellent fold resistance can be obtained. As a result, it becomes possible to reduce the amount of newly used aluminum with a large carbon dioxide emission. Also, in the canned food lid of the present invention, even when the amount of Mg in the recycled material of aluminum UBC is in a range different from that of the 5000 series aluminum alloy, the strength can be obtained by Mn contained in the recycled material, and by defining the original plate thickness (non-processed part) of the end and the remaining thickness at the initial opening part of the score processed part, it is possible to provide a canned food lid that does not impair the performance required for the canned food lid, such as pressure resistance and opening property.

[0014] In this invention, by improving the form (shape, dimensions, etc.) of the breakable score (main score) formed at the end, even in ends made of recycled aluminum alloy using aluminum UBC as a raw material, where Al-Fe-Mn-Si precipitates increase, high score strength is achieved, and unintended fracture of the score is effectively prevented even when subjected to impact from dropping, etc. Furthermore, the occurrence of microcracks in the organic coating on the back surface (inner surface side of the end) of the score processing area and the top surface of the rivet is effectively prevented, providing an end with excellent corrosion resistance. Moreover, when the score fractures, fracture (derailment) of areas other than the score does not occur, and the so-called pop missile phenomenon during initial opening does not occur, resulting in excellent openability. Furthermore, by improving the thickness of the curled and bent finger rest portions of the tabs attached to the score as described above, it is possible to effectively prevent cracks from occurring on the metal surface of the tabs and damage to the rivets when attaching the tabs to the ends, while maintaining excellent opening ability.

[0015] Furthermore, according to the end manufacturing method of the present invention, even when using aluminum UBC, which has a high Mn content and is prone to an increase in Al-Fe-Mn-Si precipitates, it is possible to form scores with high score intensity as described above. [Brief explanation of the drawing]

[0016] [Figure 1] This figure shows an example of a can lid of the present invention, where (A) is a plan view and (B) is a cross-sectional view. [Figure 2] This is a partially enlarged cross-sectional view illustrating the score processing section at the end. [Figure 3] This diagram illustrates the scoring section of the end, and is a partially enlarged cross-sectional view of the axial cross-section in the width direction of the score. [Figure 4] This is a partially enlarged cross-sectional view illustrating the amount of metal rejected by the main score and auxiliary score. [Figure 5] This is a partially enlarged cross-sectional view showing the axial cross-section in the length direction of the score. [Figure 6]This is a partially enlarged plan view illustrating the score formed near the tab attachment area using rivets. [Figure 7] This figure shows an enlarged cross-sectional view of the rivet forming section. [Figure 8] This is a cross-sectional photograph of the tab mounting area. [Figure 9] This figure shows an example of a tab used in the present invention, where (A) is a plan view and (B) is a cross-sectional view. [Figure 10] This figure illustrates a score-forming blade used in the end manufacturing method of the present invention, and is an enlarged cross-sectional view of the score-forming blade in the width direction. [Modes for carrying out the invention]

[0017] (Aluminum alloy) An important feature of the food and beverage can lid of the present invention is that the aluminum alloy constituting the end and / or tab of the can lid contains Mn: 0.5 to 1.4 mass%, Mg: 2.0 to 4.5 mass%, Si: 0.6 mass% or less, Fe: 0.8 mass% or less, Cr: 0.10 mass% or less, Zn: 0.25 mass% or less, Ti: 0.10 mass% or less, and Cu: 0.25 mass% or less. As mentioned above, recycled materials made from aluminum UBC have an alloy composition similar to that of 3000 series aluminum alloys, as can bodies made from 3000 series aluminum alloys with low Mg content and high Mn content make up the majority of these recycled materials. However, in the can lid ends and tabs of the present invention, even when such recycled materials are used, the aluminum alloy has the above-mentioned alloy composition with adjusted Mg content. Therefore, even when recycled materials made from 3000 series UBC are included, there is no reduction in pressure resistance, and it is possible to provide a can lid that effectively prevents deformation of the lid and breakage of the tab when opening.

[0018] In the aluminum alloy constituting the end and / or tab, the amount of Mn is preferably in the range of 0.5 to 1.4 mass%, and particularly 0.5 to 1.0 mass%. In other words, while Mn is an essential element for improving the strength of aluminum alloys, an increase in Mn content leads to an increase in Al-Fe-Mn-Si precipitates, which reduces toughness. This can result in reduced score strength at the end, potentially causing unintended fracture of the score, and in the tab, the tab may break or crack during opening formation, as well as reduced repeated bending resistance. Furthermore, magnesium (Mg) is an essential element for obtaining the strength required for can lids, including tensile strength, yield strength, and elongation. If the amount of Mg is low, the end may deform when subjected to positive pressure cans or sterilization treatments, and the tab may have reduced tab break strength. If the amount of Mg is higher than the above range, it may cause ingot cracking, as well as cracking during hot rolling and can lid forming. Therefore, even when the Mn and Mg content is within the above range, if the Mn content is high and Al-Fe-Mn-Si precipitates tend to be abundant, setting the Mg content to 2.0-3.0 mass% appropriately complements the tensile strength of the aluminum alloy, making it possible to have excellent compressive strength while suppressing cracking during forming. On the other hand, in aluminum alloys with a relatively low Mn content, a Mg content of 3.0-4.5 mass% similarly makes it possible to have excellent compressive strength.

[0019] Si and Fe form the Al-Fe-Mn-Si precipitates described above, acting as recrystallization nuclei during hot rolling to form crystal grains of various orientations, thereby suppressing concentration towards the Cube orientation at the end of hot rolling. From this viewpoint, it is preferable that the Si content be 0.6 mass% or less, particularly 0.35 mass% or less, and the Fe content be 0.8 mass% or less, particularly 0.6 mass% or less. Furthermore, while Cu and Cr are included to increase the strength of aluminum alloys, if the amount of Cu exceeds the above range, cracking may occur during hot rolling, and if the amount of Cr exceeds the above range, coarse intermetallic compounds may be formed. Furthermore, Zn and Ti are impurities that are inevitably present in aluminum alloys, and if their levels are below the above values, they will not affect the can lid of the present invention.

[0020] Furthermore, in the can lid of the present invention, as described above, by appropriately adjusting the amount of Mg according to the amount of Mn, it is possible to ensure strength with Mn contained in the recycled material, and, as described later, by adjusting the remaining thickness of the score in the initial opening portion of the score processing part formed at the end, it is possible to use the lid without causing unintended score breakage or tab breakage.

[0021] The aluminum alloy constituting the ends and / or tabs is prepared by adding Mg to recycled aluminum UBC and, if necessary, incorporating new aluminum to achieve the alloy composition. As mentioned above, the recycled aluminum UBC mainly consists of the 3000 series aluminum alloy that made up the can body, and therefore contains Mn in an amount of 0.5 to 1.4 mass%. In addition to recycled aluminum UBC, scrap materials discharged from the aluminum alloy sheet manufacturing process and the aluminum can manufacturing process can also be used as recycled aluminum materials.

[0022] As described above, the aluminum alloy sheet used for forming the end and / or tab of the can lid of the present invention is manufactured by melting recycled aluminum, and if necessary, new aluminum, adjusting the amount of alloying components such as Mg, and then performing hot rolling and cold rolling. Intermediate annealing during cold rolling is preferable. The above-mentioned aluminum alloy plate can be subjected to various surface treatments as necessary by conventionally known methods, and then an organic coating such as a thermoplastic resin coating or paint film can be formed on it by conventionally known methods. Examples of surface treatments, though not limited to those mentioned above, include conventionally known surface treatments such as chromate phosphate treatment and chemical conversion treatments mainly composed of zirconium and / or titanium oxides.

[0023] Examples of thermoplastic resin coatings include olefin resin films such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic ester copolymer, and ionomer; polyester films such as polyethylene terephthalate; polyamide films such as nylon 6, nylon 6,6, nylon 11, and nylon 12; polyvinyl chloride films; and polyvinylidene chloride films. Such thermoplastic resin films may be unstretched or biaxially stretched. Examples of coatings capable of forming a film include modified epoxy coatings such as phenol-epoxy and amino-epoxy coatings, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate copolymer saponified products, vinyl chloride-vinyl acetate-maleic anhydride copolymers, epoxy-modified, epoxy-amino-modified, epoxy-phenol-modified vinyl coatings or modified vinyl coatings, acrylic coatings, and synthetic rubber coatings such as styrene-butadiene copolymers.

[0024] The aluminum alloy sheet used for forming the end and / or tab of the can lid of the present invention is preferably a painted aluminum alloy sheet with an epoxy-based paint, polyester-based paint, or the like, and has a tensile strength of 350 to 410 MPa, particularly 370 to 400 MPa, in the 0° rolling direction. Having a tensile strength within this range makes it possible to use it as a can lid for positive-pressure cans. The thickness of the aluminum alloy sheet is not limited to this, but the sheet thickness for end material is preferably in the range of 0.19 to 0.30 mm, and the sheet thickness for tab material is preferably in the range of 0.24 to 0.35 mm. In the present invention, it is most preferable that both the end and the tab be made of an aluminum alloy having the above-described composition, but it is preferable that at least the end be made of an aluminum alloy having the above-described composition. Furthermore, the end and the tab do not necessarily have to be made of the same composition, but it is preferable from the viewpoint of productivity and economy that they be made of aluminum alloys of the same composition.

[0025] (Ends and tabs) The can lid of the present invention is not limited in form and can take various forms, as long as it has an end and a tab for breaking the score formed at the end to form an opening. Figure 1 shows an example of a can lid according to the present invention, where (A) is a plan view and (B) is a cross-sectional view. The can lid, represented as 1 in its entirety, is a stay-on tab can lid consisting of an end 2 and a tab 4 fixed to this end 2 with rivets 3. End 2 has a circular center panel 21, a chuck wall radius 22 projecting downward from the periphery of the center panel 21, a chuck wall 23 rising from the outer wall of the chuck wall radius 22, and a seaming panel 24 formed continuously with the chuck wall 23. A score 25 is formed on the center panel 21, and this score 25 consists of a main score 25a and an auxiliary score 25b provided inside the main score 25a. The auxiliary score 25b is for preventing cracking of the main score during machining and does not fracture more shallowly than the main score 25a. On the other hand, the tab 4 comprises a tab body 41, an arc-shaped tab nose portion 42 formed on the side facing the direction of dispensing the contents, a finger rest portion (grip portion) 43 formed on the opposite side of the tab nose portion 42, and a fixing portion 44 to which the tab body 41 is fixed with a rivet 3. Furthermore, the tab body 41 is bent at the outer peripheral edge 45 of the grip portion 43, and a downwardly folded curl portion 46 is formed around the entire circumference of the outer peripheral edge other than the grip portion 43.

[0026] As mentioned above, in the can lid of the present invention, in order to achieve the required pressure resistance strength for the end and tab, it is effective to adjust the amount of Mg in the aluminum alloy constituting the end and tab according to the amount of Mn. Furthermore, by adjusting the remaining thickness of the score in the initial opening portion of the score processing part formed on the end, it is possible to suppress unintended score breakage and improve opening properties, thereby effectively preventing tab tearing and other problems. In other words, since the initial opening of the score-processed section is located directly below the tab, water droplets may adhere to it. Conventional 5000 series aluminum alloys used for can lids have a high Mg content, making them highly susceptible to moisture, and reducing the score thickness could lead to stress corrosion cracking. However, with aluminum alloys where the Mg content is within the above range, there is no risk of stress corrosion cracking, making it possible to reduce the score thickness at the initial opening and enabling opening formation with light force. On the other hand, aluminum alloys with a high Mn content and many Al-Fe-Mn-Si precipitates tend to have poor toughness, making them prone to tab cracking when the tab is opened. However, as described above, opening formation with light force is now possible, making it possible to effectively prevent tab cracking even with aluminum alloys with low Mg content.

[0027] Figure 2 is a schematic cross-sectional view of the score-forming portion of the end. Specifically, as shown in Figure 2, it is desirable to form the score such that the ratio of the remaining score thickness (thickness of the score-forming portion) t1 in the initial opening of the score-forming portion where the score 25 is formed, relative to the unprocessed portion (original plate thickness) t0 of the center panel 21 of end 2, is 71% {(t1 / t0) × 100 (%)}. The ratio of the score remaining thickness to the original plate thickness t0 at the end varies depending on the original plate thickness. As the original plate thickness increases, the ratio decreases. Specifically, within the range of 0.19mm to 0.30mm for the original plate thickness at the end, the ratio is 71% or less when the original plate thickness is greater than 0.190mm and 0.200mm or less, 68% or less when it is greater than 0.200mm and 0.210mm or less, 64% or less when it is greater than 0.210mm and 0.220mm or less, 61% or less when it is greater than 0.220mm and 0.230mm or less, and 0. It is preferable that the ratio be 59% or less when the length is greater than 230 mm and less than or equal to 0.240 mm, 56% or less when the length is greater than 0.240 mm and less than or equal to 0.250 mm, 54% or less when the length is greater than 0.250 mm and less than or equal to 0.260 mm, 52% or less when the length is greater than 0.260 mm and less than or equal to 0.270 mm, 50% or less when the length is greater than 0.270 mm and less than or equal to 0.280 mm, 48% or less when the length is greater than 0.280 mm and less than or equal to 0.290 mm, and 47% or less when the length is greater than 0.290 mm and less than or equal to 0.300 mm.

[0028] Furthermore, auxiliary scores, which are formed together with the fractureable main score and are adjacent to and inward of the main score, are preferably in a range of 90% or more of the remaining thickness ratio of the main score relative to the original plate thickness, and their width is preferably in the range of 50 to 110 μm. Furthermore, the remaining thickness and width of the score do not necessarily have to be the same from the beginning to the end of the score; they can be appropriately changed depending on the initial opening and the position of the score.

[0029] In the end caps used for food and beverage can lids of the present invention, as described above, by improving the remaining thickness and shape of the breakable score (main score) formed on the end cap, it is possible to improve the score strength even in ends made of recycled aluminum alloy using aluminum UBC as a raw material, which has an increased amount of Al-Fe-Mn-Si precipitates. As described later, this makes it possible to effectively prevent the occurrence of microcracks in the organic coating on the back surface (inner surface side of the end cap), derailment when the score breaks, or the so-called pop missile phenomenon when the can is first opened.

[0030] [Score Shape] In the end of the present invention, as is clear from Figure 3 which shows an axial cross-section in the width direction of the score, at least a portion of the main score 25a has opposing inclined surfaces 26a, 26b whose score width decreases as it goes downwards, and a bottom surface 27 having a flat surface 27a in the center, the inclined surfaces 26a, 26b and the bottom surface 27 are continuous via a curved surface R, and it is preferable that at least a portion of the bottom surface has a width W1 of the flat surface 27a that is 65% or less of the width W0 of the virtual bottom surface 27 defined by the virtual extensions La, Lb of the inclined surfaces 26a, 26b and the virtual extension Lc passing through the center of the bottom surface 27. Thus, by forming the main score that can be broken in such a way that the inclined surface and the bottom surface are continuous via a curved surface, and the width of the bottom surface (the width of the flat section 27a in the specific example shown in Figure 2) is 65% or less of the virtual bottom surface, it is possible to improve the score strength, and even when the contents are filled and subjected to impact from dropping or vibration during transport, the breakage of the score can be effectively prevented. In other words, as is clear from the results of the embodiments described later, if the width W1 of the flat surface becomes larger than the above range, there is a risk of leakage of contents from the score. Furthermore, the width of the base mentioned above is the distance at the center of the base, excluding the curved surface connecting the inclined surface and the base. As shown in Figure 2, if there is a flat surface in the center, it is the width of the flat surface, but this width includes cases where it is as close to zero as possible. In such cases, the base becomes a roughly arc shape continuous with the curved surface. Furthermore, in a preferred embodiment of the present invention shown in the figure, the inclined surface and the bottom surface of the score are continuous via a curved surface. However, even if the inclined surface and the bottom surface are not connected via a curved surface, the same effect as when connected via a curved surface may be obtained if the remaining thickness of the score is thick, or depending on the angle formed by the inclined surface and the bottom surface. In the end of the present invention, the portion of the main score where the flat surface of the bottom surface is within the above numerical range is preferably formed over the entire area of ​​the main score from the viewpoint of improving score strength, but it may also be formed partially in thin-walled portions with less remaining score thickness, such as the latter half of the opening.

[0031] Furthermore, the width W0 of the virtual base surface of the score bottom surface is preferably in the range of 15 to 40 μm. This prevents microcracks from occurring in the organic coating (thermoplastic resin coating or paint film) on the inner surface side of the score portion (back side of the end), effectively preventing metal exposure on the inner surface of the end, and making it possible to provide an end with excellent corrosion resistance. If the width W0 of the virtual base is smaller than the above range, stress corrosion cracking may occur, depending on the material used. On the other hand, if it is larger than the above range, microcracks may occur on the inner surface of the score compared to when it is within the above range.

[0032] Furthermore, the score angle Θ formed by the inclined surfaces 26a and 26b of the score is preferably in the range of 40 to 60 degrees. By having the score angle Θ within this range, microcracks do not occur in the organic coating on the inner surface of the score (the back side of the end), metal exposure on the inner surface of the end is effectively prevented, and an end with excellent corrosion resistance can be provided. If the score angle is larger than the above range, microcracks may occur in the organic coating on the inner surface of the score (the back side of the end). If the score angle is smaller than the above range, the score forming blade may suffer damage such as chipping of the cutting edge or chipping / cracking from the base due to prolonged use.

[0033] [Score Metal Removal Amount] In the end used in the present invention, as shown in Figure 1, it is preferable to have an auxiliary score adjacent to the main score and located inward from the main score, along with the fractureable main score. This auxiliary score is provided to prevent cracking of the main score during processing and is not fractured itself, so it has a higher score remaining thickness ratio than the main score. In the present invention, in particular, from the viewpoint of preventing the occurrence of microcracks in the organic coating on the inner surface side of the main score (inner surface side of the end), it is desirable to form the auxiliary score such that the amount of metal repelled by the scoring of the auxiliary score S0 in the cross section perpendicular to the width direction of the score is 25% or more of the amount of metal repelled by the scoring of the main score S1.

[0034] In other words, as shown in Figure 4, the cross-sectional areas S0 and S1 of the main score 25a and auxiliary score 25b in the widthwise perpendicular section are defined as the metal repulsion amount, and it is preferable to form the main score and auxiliary score such that the ratio [(S1 / S0) × 100] of the metal repulsion amount S1 of the auxiliary score 25b to the metal repulsion amount S0 of the main score 25a is 25% or more, particularly in the range of 25 to 200%. If the metal repulsion amount of the auxiliary score is smaller than the above range, microcracks may occur in the organic coating on the inner surface side (end inner surface side) of the main score. If it is larger than the above range, no defects will occur at the end, but the molding load will increase, and there is a risk of damage to the score forming tool. Furthermore, the rejection amounts for the primary and secondary scores do not need to be constant from the beginning to the end of the score; they may vary depending on the location. Furthermore, as long as the proportion of the rejected material falls within the above range, the cross-sectional shape of the score is not a concern.

[0035] [High score remaining portion] As mentioned above, when the contents are such as beer or carbonated beverages, creating positive pressure inside the can, the initial opening of the score can cause the intended opening to be rapidly pushed upward by the gas pressure as the internal pressure is released. This can cause the score to break, and depending on the force, the intended opening may separate from the panel and be blown away, resulting in a phenomenon known as a "pop missile." This pop missile phenomenon can be prevented by providing a high score remaining thickness section in a part of the main score. In the present invention, as shown in Figure 5 which shows the axial cross-section of the main score 25a in the score length direction, the main score 25a has a high score remaining thickness portion 2 which has a larger score remaining thickness than the main score. 8 This is partially formed, and this high score remaining thickness portion 2 8 It is preferable that the remaining thickness ratio of the score is higher than the remaining thickness ratio of the main score and is 85% or less. That is, as shown in FIG. 5, the score remaining thickness ratio R1 of the main score 25a is the ratio [(t1 / t0)×100(%)] of the main score remaining thickness (t1: the thickness of the score processing part) to the virtual thickness (t0) when the score 25a is not formed. On the other hand, the score remaining thickness ratio R2 of the high score remaining thickness part 2 8 is represented by the ratio [(t2 / t0)×100(%)] of the remaining thickness (t2) in the high score remaining thickness part. In the present invention, the high score remaining thickness part is formed so that R1 < R2 ≦ 85%. In addition, the high remaining thickness score part does not matter the relationship with the main score remaining thickness as long as it is higher than the score remaining thickness rate of the main score and 85% or less. However, if the step amount from the main score (remaining thickness difference (t2 - t1) in FIG. 2) is too large, the opening operation does not proceed smoothly and the force required for opening increases. Therefore, the remaining thickness difference from the main score is preferably 50 μm or less.

[0036] It is clear from the results of the examples described later that when the score remaining thickness ratio is within the above range, the score can be smoothly broken without deviating. That is, when a high score remaining thickness part with a score remaining thickness ratio of 85% or less is formed, even at the end made of an aluminum alloy containing aluminum UBC with a large Mn content and where Al-Fe-Mn-Si-based crystallized products are likely to increase, the score is smoothly broken without the other parts except the score being broken. On the other hand, when the score remaining thickness ratio of the high score remaining thickness part is larger than the above range, the score breakage stops at the high score remaining thickness part 2 8 and there is a risk that the breakage of the end will proceed deviating from this part instead. In addition, the length in the score length direction of the high score remaining thickness part (indicated by L in FIG. 5) can be appropriately changed depending on the remaining thickness ratio, formation position, required anti-pop missile effect, etc. of the high score remaining thickness part, but it is preferably in the range of 3 to 10 μm.

[0037] Figure 6 is a partially enlarged plan view illustrating the score formed near the tab attachment area by rivet 3 in Figure 1. In Figure 6, area A, indicated by the dotted line on the outer edge, is the coining area associated with rivet forming, and the plate thickness in this area is reduced due to the coining process compared to other areas. As is clear from Figure 6, a main score 25a and an auxiliary score 25b are formed within the coining area A, and a high score remaining thickness portion is formed in the main score 25a within the coining area A. 6 Inside 2 8 a to 2 8 b is where a high score remaining thickness portion is formed. The high score remaining thickness portion is formed up to position 26b, which is located outside the coining process area A, and 2 8 b is the portion of the aluminum alloy plate that makes up the end where the original plate thickness is maintained. Furthermore, in this invention, the remaining thickness ratio of the high-score remaining thickness portion is based on the virtual thickness that would occur if no score were formed in the area where the high-score remaining thickness portion is formed, as shown in Figure 6 Even when high-scoring residual thickness portions are formed at locations where the reference virtual thickness (t0) differs, as shown above, it is possible to form high-scoring residual thickness portions that are effective with respect to the main score. In other words, high-scoring residual thickness portion Starting point 2 8 a may be inside or outside region A. This high residual thickness score portion The location and number of these devices are not specified, but it is preferable to place them in the initial opening area or around the coining area.

[0038] [Score for preventing eruption] As mentioned above, when the contents are such as beer or carbonated beverages, which create positive pressure inside the can, the initial opening of the score can cause the opening to be rapidly pushed upward by the gas pressure as the internal pressure is released, potentially causing the score to break. Depending on the force of the rupture, the opening may even separate from the panel and be blown away, resulting in what is known as a "pop missile" phenomenon. In the end used in the present invention, by forming a score (anti-ejection score) that crosses the auxiliary score and is close to the main score in the vicinity of the initial opening portion of the score, with a score remaining thickness ratio of 70-90% of the original plate thickness, it is possible to prevent such pop missile phenomena. That is, the auxiliary score is provided to prevent cracking of the main score during processing and is not fractured itself, and the score that crosses this auxiliary score extends in a direction that blocks the progression of fracture of the main score due to the release of internal pressure and the rise of the planned opening portion, thereby effectively preventing the pop missile phenomenon. If the score remaining thickness of this anti-ejection score is smaller than the above range, there is a risk of microcracks occurring in the organic coating on the inner surface side of the anti-ejection score (inner surface of the end), while if the score remaining thickness ratio of the anti-ejection score is larger than the above range, the anti-pop missile effect cannot be sufficiently obtained. Furthermore, the ejection prevention score is provided in close proximity to the main score and may be provided in a position that does not cross the auxiliary score, i.e., outside the main score. Its location is not limited, but it is preferable to form it in the vicinity of the initial opening portion of the score.

[0039] [rivet] In the end used in the present invention, as described later, a rivet-formed portion is formed on a shell made by press-forming an aluminum alloy plate by rivet forming, then a tab is fitted into the rivet-formed portion, and the tab is attached by rivet by riveting the rivet-formed portion while pressing the top surface of the rivet-formed portion. In the end of the present invention, as shown in Figure 7, it is preferable that the thickness at the center of the rivet-formed portion 30 (i.e., the thickness t3 at the center of the rivet-formed portion after riveting) is 30% or more of the original plate thickness t0. This effectively prevents the occurrence of microcracks in the organic coating at the center of the top surface of the rivet.

[0040] As described above, in the end to which the tab is attached by crimping the rivet-formed portion, as shown in Figure 8, an enlarged cross-sectional photograph of the tab attachment portion, the top surface 31 of the rivet-formed portion 30 of end 1 has a central region (indicated by diameter D1 in Figure 8) that has been coined, and this region is thinner than the surrounding area. In the present invention, it is preferable that the ratio of the diameter D1 of this central region to the inner diameter D2 of the side wall portion 32 of the rivet-formed portion 30 [(D2 / D1) × 100] is 40 to 95%. This effectively prevents the occurrence of microcracks in the organic coating in the rivet-formed portion. If the proportion of the central region D1 is less than the range described above, microcracks may occur in the organic coating in the central region. Conversely, if the proportion of the central region is greater than the range described above, microcracks may occur in the organic coating at the outer edge of the central region D1.

[0041] [tab] In the can lid of the present invention, the tab can be formed from a 5000 series aluminum alloy or the aforementioned aluminum alloy, as described above. In the finger-grip portion of the can lid of the present invention, it is preferable that the ratio of the thickness of the finger-grip portion to the original plate thickness (thickness of the finger-grip portion / original plate thickness) is 2 or more, and that the ratio of the thickness of the curled portion of the tab to the original plate thickness (thickness of the curled portion / original plate thickness) is less than or equal to the value of the ratio of the curled portion to the original plate thickness. In other words, Figure 9 shows an example of a tab applied to a can lid of the present invention, where (A) is a plan view and (B) is a cross-sectional view. As shown in Figure 9(B), the thickness t4 of the finger rest portion (grip portion) 43 and the thickness t5 of the curl portion 46 in the tab nose 42, formed by bending, are such that (thickness of finger rest portion t4 / original plate thickness t0) is 2 or more, and the ratio of the thickness of the curl portion of the tab to the original plate thickness (thickness of curl portion t5 / original plate thickness t0) is less than or equal to the value of the ratio of the thickness of the curl portion of the tab to the original plate thickness. If the value of t4 / t0 is less than 2, there is a risk of cracks occurring on the metal surface during bending. On the other hand, if it is greater than t5 / t0, the position of the tab may shift when crimping the rivet forming portion during tab attachment, preventing the tab from being inserted all the way to the base of the rivet, which may result in molding defects such as scratches on the rivet.

[0042] (Manufacturing method for end caps) The end manufacturing method of the present invention is the same as conventional end manufacturing methods known, except that a specific score-forming blade described later is used. That is, although not limited thereto, a metal sheet such as an aluminum alloy sheet is punched into a circular shape in a press forming process and formed into the shape of a shell having the aforementioned seaming panel portion and chuck wall radius portion, and a compound is applied to the groove of the seaming panel portion in a lining process. Next, a cylindrical rivet projection is formed and a score is engraved from the outer surface of the end in a score-forming process. Finally, after fitting the tab onto the rivet projection, the head of the rivet projection is crimped to attach the tab, thereby manufacturing an end that can be attached to a can body.

[0043] In the present invention, a key feature is that the score forming blade used in the score forming step of the above manufacturing method, as shown in Figure 10, consists of opposing inclined sides 51a, 51b and a tip portion 52 located at the lower end of the inclined sides 51a, 51b, with the blade width decreasing towards the tip in a vertical cross section in the width direction of the score forming blade 50, and at least a portion of the tip portion 52 has a width w1 that is 65% or less of the width W0 of the virtual tip surface defined by the virtual extension lines La, Lb of the inclined sides 51a, 51b and the virtual extension line Lc passing through the center of the tip portion 52. Furthermore, the width of the tip portion described above is the distance at the center of the tip portion, excluding the curved surface connecting the inclined side surface and the tip portion. As shown in Figure 10, if there is a flat surface 52a in the center, it is the width of the flat surface, but this width includes cases where it is as close to zero as possible. In such cases, the tip portion becomes a roughly arc shape continuous with the curved surface. Furthermore, in the preferred embodiment shown in Figure 10, both sides of the tip portion 52 are continuous with the inclined sides 51a and 51b via a curved surface R. However, even if both sides of the tip portion are not connected by an inclined side or a curved surface, the same effect as when connected by a curved surface may be obtained if the remaining score thickness is increased, or depending on the angle formed by the inclined side and the tip portion. By using a score-forming blade having the above-described characteristics when scoring the end, scores are formed that reflect the characteristics of the score-forming blade as described above. This makes it possible to form scores with improved score strength as described above, and also prevents the occurrence of microcracks on the inner surface of the scored area.

[0044] Furthermore, the virtual tip width W0, defined by the virtual extension lines La and Lb of the inclined sides 51a and 51b of the score-forming blade shown in Figure 10, and the virtual extension line Lc passing through the center of the tip portion 52 of the score-forming blade, is preferably in the range of 15 to 40 μm. This prevents microcracks from occurring in the organic coating (thermoplastic resin coating or paint film) on the inner surface side of the score portion (back side of the end), effectively prevents metal exposure on the inner surface of the end, and makes it possible to form an end with excellent corrosion resistance. If the virtual tip width W0 is smaller than the above range, stress corrosion cracking may occur at the end, depending on the material used. On the other hand, if it is larger than the above range, microcracks may occur on the inner surface of the score compared to when it is within the above range.

[0045] Furthermore, it is preferable that the angle Θ of the score-forming blade formed by the inclined sides 51a, 51 of the score-forming blade shown in Figure 10 be between 40 and 60 degrees. Because the angle Θ of the score-forming blade is within the above range, microcracks do not occur in the organic coating on the inner surface of the score (the back side of the end), metal exposure on the inner surface of the end is effectively prevented, and it becomes possible to form an end with excellent corrosion resistance. If the angle of the score-forming blade is greater than the above range, microcracks may occur in the organic coating on the inner surface of the score (the back side of the end). If the score angle is smaller than the above range, the score-forming blade may suffer damage such as chipping of the cutting edge or chipping / cracking from the base due to prolonged use.

[0046] In the rivet forming process, as shown in Figure 7, after fitting the tab 4 to the shell 2 in which the rivet forming portion 30 has been formed, the tab is attached to the shell by rivets by riveting the rivet forming portion while pressing the top surface of the rivet forming portion 30 from above. In this case, in the present invention, it is preferable to process the rivet so that the processing rate of the rivet center relative to the original plate thickness is 70% or less, and in particular, in the range of 40 to 70%. Also, as shown in Figure 8, in the coining process of the rivet top surface, it is preferable to coin the rivet so that the ratio [(D2 / D1) × 100] of the diameter D1 of the central region of the top surface 31 of the rivet forming portion 30 to the inner diameter D2 of the side wall portion 32 of the rivet forming portion 30 is 40 to 95%. This effectively prevents the occurrence of microcracks in the organic coating in the rivet forming portion. [Examples]

[0047] (Experimental Example 1) Using aluminum alloy sheets No. 1 to 7 with the compositions shown in Table 1, and 5182 material, a general-purpose material for end tabs (all are aluminum alloy sheets with a thickness of 0.235 mm that underwent intermediate annealing during cold rolling), as well as 3104 material, a general-purpose material for can bodies (thickness of 0.235 mm), 204 diameter shells were created, and scores were formed using a scoring tool with a score-forming blade (blade width 35 μm, inclination angle 50 degrees) to create the ends. Similarly, using aluminum alloy plates No. 1-7, 5182 material, and 3104 material (each with a plate thickness of 0.235 mm) with the compositions shown in Table 1, tabs with the shape shown in Figure 9 were created and attached to the above ends to create a can lid. The resulting can lid was attached to the opening of a seamless can, and 350 ml of beer chilled to 5°C was filled inside.

[0048] [Evaluation of end and tab molding] For each end obtained as described above, end molding defects were evaluated by marking those with cracks on the surface of the chuck wall radius as "×" and those without cracks as "〇". The results are shown in Table 1. The surface of the finger rest of each tab obtained as described above was observed under a microscope, and those with cracks were marked with "×" and those without cracks were marked with "○" to evaluate the defects in the tab's molding. The results are shown in Table 1.

[0049] [Pressure resistance measurement] A hole is made in the can body of the beer-filled can obtained as described above, a tube is connected, and air is used to increase the pressure at a rate of approximately 0.33 kgf / cm² per second. 2 The pressure was increased, and the peak value was observed when the lid inverted. 5.5 kgf / cm² 2 Pressure resistance strength was evaluated by indicating whether the value exceeded the specified threshold ("○") or fell below it ("×"). The results are shown in Table 1.

[0050] [Table 1]

[0051] (Experimental Example 2) A 204mm diameter shell was fabricated using an aluminum alloy plate S (Mn: 0.9 mass%, Mg: 2.3 mass%, Si: 0.3 mass%, Fe: 0.5 mass%, Cu: 0.2 mass%, Cr: 0.01 mass%, Zn: 0.14 mass%, Ti: 0.01 mass%) with a thickness of 0.235mm. Scores were formed on the resulting shell according to a conventional method, and tabs were attached to create a can lid. The can lid obtained above was attached to the opening of a seamless can, and 350 ml of beer chilled to 5°C was filled inside.

[0052] [Vibration Test] For beer-filled cans with the score retention rates at the initial opening shown in Table 2, a vibration test was conducted using a vibration testing machine (electric vibration testing machine manufactured by Shinken Co., Ltd.) under the following conditions. Vibration direction: Can axis, Vibration frequency: 10Hz, Vibration time: 60 minutes, Amplitude: 5mm, Stacking: 3 cases of 24 cans, Can temperature: 30℃, Internal pressure: Approximately 300kPa We evaluated instances where no data leaks occurred from the score section as "○" and instances where leaks occurred as "×".

[0053] [Inverted drop test] For beer-filled cans with the score retention rate at the thinnest wall section shown in Table 3, the cans were dropped from a height of 150 cm with the end side facing down under conditions of a can temperature of 30°C and an internal pressure of approximately 300 kPa, and leakage of beer from the score section was checked. Cans that did not leak were evaluated as "○", and those that leaked were evaluated as "×".

[0054] [Opening test] For the beer-filled cans shown in Tables 2 and 3, openings were formed, and a "○" was rated if the can opened normally, and a "×" was rated if it did not open normally (e.g., initial opening failed, derailment occurred, or it only opened partway).

[0055] [Table 2]

[0056] [Table 3]

[0057] (Experimental Example 3) In Experimental Example 2, a 204mm diameter shell (aluminum alloy plate S) was obtained, and a 204mm diameter shell made of 5182 material with a plate thickness of 0.235mm was used to form the main score using a scoring tool with a W0 value shown in Figure 3 and a value shown in Table 4. The ratio of the flat portion to the cutting edge bottom surface (cutting width) was 65%. The surface of the back of the main score portion of the end was examined, and the presence or absence of microcracks in the organic coating was confirmed by microscopic observation. Table 4 shows that samples without microcracks are marked with "○" and samples with microcracks are marked with "×". Furthermore, a can lid with a tab attached to the end after score formation was fitted onto the opening of a seamless can, and 350 ml of beer cooled to 5°C was filled inside. The cans were then stored for two weeks in an environment of 37°C and 80% RH. Cans that did not leak were marked with "○" indicating resistance to stress corrosion cracking, while those that leaked were marked with "×" indicating resistance to stress corrosion cracking, as shown in Table 4.

[0058] [Table 4]

[0059] (Experimental Example 4) In Experimental Example 2, a 204mm diameter shell was used to form the main score using a scoring tool with a score angle Θ value shown in Figure 3 and a score value shown in Table 5. The ratio of the flat portion to the cutting edge bottom surface (cutting width) was 65%. The surface of the back of the main score portion of the end was examined, and the presence or absence of microcracks in the organic coating was confirmed by microscopic observation. Table 5 shows that samples without microcracks are marked with "○" and samples with microcracks are marked with "×".

[0060] [Table 5]

[0061] (Experimental Example 5) In Experimental Example 2, a 204mm diameter shell (aluminum alloy plate S) was formed on the shell using a scoring tool, with main and auxiliary scores having the respective rejection amounts shown in Table 6. A tab made of 5000 series aluminum alloy plate (5182 material) was then attached to create a can lid. The surface of the back of the main score portion of the end was examined, and the presence or absence of microcracks in the organic coating was confirmed by microscopic observation. Table 6 shows that samples without microcracks are marked with "○" and samples with microcracks are marked with "×".

[0062] [Table 6]

[0063] (Experimental Example 6) In Experimental Example 2, a 204mm diameter shell (aluminum alloy plate S) was formed with auxiliary and main scores (50% score retention rate) for ejection prevention, with the score retention rates shown in Table 7. A tab made of 5000 series aluminum alloy plate (5182 material) was also attached to create a can lid. To evaluate the pop missile resistance of the resulting can lids, the lids were attached to seamless cans, holes were drilled in the can bodies, tubes were connected, and compressed air was used to increase the pressure at a rate of approximately 0.33 kgf / cm² per second. 2 Pressurize the device and check the pressure gauge reading until it reaches 5.5 kgf / cm². 2 Internal pressure was applied up to this point. The opening was then opened to check if it opened normally. A "○" indicates that no pop missile occurred, and a "×" indicates that a pop missile occurred. The results are shown in Table 7.

[0064] [Table 7]

[0065] (Experimental Example 7) For the 204mm diameter shell (aluminum alloy plate S) obtained in Experimental Example 2, rivet forming was performed using a press forming machine so that the processing rate of the rivet top surface was the value shown in Table 8. Microscopic observation was performed to check for the occurrence of microcracks in the organic coating at the center of the rivet top surface. Table 8 shows "○" for those without microcracks and "×" for those with microcracks.

[0066] [Table 8]

[0067] (Experimental Example 8) For the 204mm diameter shell (aluminum alloy plate S) obtained in Experimental Example 2, a lid was formed using a tool designed so that the D2 / D1 values ​​shown in Figure 8 were in the ratio shown in Table 9. The organic coating at the center and outer edge of the D1 region in Figure 8 was confirmed by microscopic observation. Table 9 shows "○" for those without microcracks and "×" for those with microcracks.

[0068] [Table 9]

[0069] (Experimental Example 9) Using aluminum alloy plates S with thicknesses of 0.330 mm and 0.279 mm, tabs were formed in the shape shown in Figure 9 by keeping the thickness of the tab nose constant and varying the thickness of the finger rest (grip) portion, as shown in Tables 10 and 11. These tabs were attached to the 204 mm diameter shell (aluminum alloy plate S) obtained in Experimental Example 1 to create a can lid. The presence or absence of microcracks in the organic coating of the tab finger rest was confirmed by microscopic observation. Those without microcracks were evaluated as "○" and those with microcracks as "×", as shown in Tables 10 and 11. We also checked for scratches on the rivets and for any molding defects. Items without molding defects are marked with "○", while those with scratches or other defects are marked with "×", as shown in Tables 10 and 11.

[0070] [Table 10]

[0071] [Table 11]

[0072] The information disclosed above allows those who access this disclosure to select and use elements as appropriate to obtain benefits corresponding to the selected elements, and to obtain synergistic benefits by using multiple elements in combination. [Industrial applicability]

[0073] Even when using recycled aluminum UBC material, the can lid of the present invention has an adjusted amount of alloying elements, resulting in an end with excellent pressure resistance, a tab with excellent bending and tearing resistance, and can be used for positive-pressure cans. Furthermore, since it is possible to obtain a can lid for food and beverages that is the same as when using new aluminum, it can be suitably used in applications where a reduction in carbon dioxide emissions is required. Furthermore, by improving the morphology (shape, dimensions, etc.) of the fractureable score (main score) formed at the end, it is possible to provide an end with high score strength, effective prevention of microcracks in the organic coating, and excellent corrosion resistance, even in ends made of recycled aluminum alloy using aluminum UBC as a raw material, which has an increased amount of Al-Fe-Mn-Si precipitates. [Explanation of symbols]

[0074] 1 Can lid, 2 End, 3 Rivet, 4 Tab, 21 Center panel, 22 Chuck wall radius, 23 Chuck wall, 24 Seaming panel, 25 Score, 26 Score inclined surface, 27 Score bottom surface, 41 Tab body, 42 Tab nose section, 43 Gripping section, 44 Fixing section, 46 Curl section.

Claims

1. A can lid for food and beverages, comprising an end and a tab, wherein the end has a breakable score formed therein that defines the intended opening, and the tab is attached by a rivet, The end is made of an aluminum alloy containing Mn: 0.5 to 0.9 mass%, Mg: 2.0 to 4.5 mass%, Si: 0.2 to 0.3 mass%, Fe: 0.4 to 0.5 mass%, Cu: 0.1 to 0.2 mass%, Cr: 0.10 mass% or less, Zn: 0.25 mass% or less, and Ti: 0.10 mass% or less, and the aluminum alloy contains recycled material from used aluminum beverage cans. A can lid for food and beverages, characterized in that the remaining thickness of the score in the initial opening portion of the score is 43-51% of the original plate thickness, and the remaining thickness of the score in the thinnest part is 34-41% of the original plate thickness, and is used for positive-pressure cans.

2. The can lid for food and beverages according to claim 1, wherein the aluminum alloy plate made of the aforementioned aluminum alloy has a tensile strength in the 0° rolling direction after paint and baking, which is 350 to 410 MPa.

3. The can lid for food and beverages according to claim 1, wherein the thickness of the unprocessed portion of the end is 0.19 to 0.30 mm.

4. The can lid for food and beverages according to any one of claims 1 to 3, wherein the breakable score has, in a vertical cross section in the width direction of the score, opposing inclined surfaces and a bottom surface, the score width decreasing as it goes downwards, and at least a portion of the bottom surface has a width that is 65% or less of the width of the virtual bottom surface defined by the virtual extension line of the inclined surface and the virtual extension line passing through the center of the bottom surface.

5. The can lid for food and beverages according to claim 4, wherein the inclined surface and the bottom surface are continuous via a curved surface.

6. The can lid for food and beverages according to claim 4, wherein a flat portion is formed in the center of the bottom surface, and the width of the flat portion is 65% or less of the width of the virtual bottom surface.

7. The can lid for food and beverages according to claim 4, wherein the width defined by the virtual extension line of the inclined surface and the virtual extension line passing through the center of the bottom surface is 15 to 40 μm.

8. The can lid for food and beverages according to claim 4, wherein the score angle formed by the inclined surface is 40 to 60 degrees.

9. A can lid for food and beverages according to any one of claims 1 to 3, wherein the breakable score is a main score, and the lid comprises an auxiliary score adjacent to the main score and located inward from the main score, and in a cross section perpendicular to the width direction of the score, the amount of metal ejected by processing the auxiliary score S0 is 25% or more of the amount of metal ejected by processing the main score S1.

10. A can lid for food and beverages according to any one of claims 1 to 3, wherein the breakable score is the main score, and the lid has a high score remaining thickness portion in which the score remaining thickness relative to the virtual thickness when no score is formed in the score processing portion is greater than the main score remaining thickness ratio and is 85% or less.

11. A can lid for food and beverages according to any one of claims 1 to 3, wherein the breakable score is a main score, and the lid comprises an auxiliary score adjacent to the main score and located inward from the main score, and an anti-ejection score is formed near the initial opening portion of the main score, and the remaining thickness of the anti-ejection score is 70 to 90% of the original plate thickness.

12. The end is formed with a rivet forming portion for tab attachment, and the processing rate of the rivet forming portion with respect to the original plate thickness in the center is 70% or less of the original plate thickness, according to any one of claims 1 to 3.

13. The can lid for food and beverages according to any one of claims 1 to 3, wherein the ratio of the diameter of the coining process area on the top surface of the rivet forming portion to the inner diameter of the side wall portion of the rivet forming portion at the end is 40 to 95%.

14. The can lid for food and beverages according to any one of claims 1 to 3, wherein the tab has a finger rest portion, and the ratio of the thickness of the finger rest portion to the original plate thickness (thickness of the finger rest portion / original plate thickness) is 2 or more, and the ratio of the thickness of the curled portion of the tab to the original plate thickness (thickness of the curled portion / original plate thickness) is less than or equal to the value of the ratio of the thickness of the curled portion to the original plate thickness.

15. A food and beverage can characterized by applying a food and beverage can lid according to any one of claims 1 to 3 to a can filled with beer.

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