Patent Application
20240229198
This international application claims the benefit of Japanese Patent Application No. 2021-79212 filed on May 7, 2021 with the Japan Patent Office, and the entire disclosure of Japanese Patent Application No. 2021-79212 is incorporated herein by reference.
The present disclosure relates to an aluminum alloy sheet for a beverage can body.
Beverage cans made of aluminum alloys include two-piece cans. The bodies of two-piece cans are produced by performing a drawing process, a redrawing process, and an ironing process on aluminum alloy sheets for beverage can bodies.
In recent years, due to need for cost reduction of beverage cans, thinning of side walls of can bodies, sheet metal thinning, and high strengthening of the sheet metal are required. However, sheet metal thinning tends to cause defects in shape called chime wrinkling.
In the redrawing process, as the amount of a material flowing into a chime portion increases, circumferential compressive stress increases due to reduction in diameter, and chime wrinkling is more likely to occur. Occurrence of chime wrinkling is a buckling phenomenon. Thus, as a metal sheet of the sheet metal is thinned, chime wrinkling is more likely to occur. Ironing formability refers to resistance to tear-off and unlikelihood of defects in appearance during an ironing.
Patent Documents 1 to 3 propose techniques to increase the work hardening exponent n-value of aluminum alloy sheets for beverage can bodies to thereby improve chime wrinkling. However, if the work hardening exponent n-value alone is improved in accordance with the methods disclosed in Patent Documents 1 to 3, stress on the sidewalls of cans becomes high in the ironing. As a result, rupture (that is, tear-off) is more likely to occur in the sidewalls of cans, and ironing formability is reduced.
Patent Document 4 proposes a technique to increase the work hardening exponent n-value of aluminum alloy sheets for beverage can bodies and keep the amounts of increases in work hardening rate and in tensile strength at respective specified values or less to thereby achieve both chime wrinkling resistance and ironing formability.
However, the technique disclosed in Patent Document 4 is insufficient for aluminum alloy sheets for beverage can bodies with high strength, and there is need for further improvement in chime wrinkling resistance and ironing formability. It is preferable that one aspect of the present disclosure provides an aluminum alloy sheet for a beverage can body that is excellent in chime wrinkling resistance and ironing formability.
One aspect of the present disclosure provides an aluminum alloy sheet for a beverage can body. The aluminum alloy sheet is made of an aluminum alloy comprising Si: 0.10 mass % or more and 0.70 mass % or less, Fe: 0.10 mass % or more and 0.80 mass % or less, Cu: 0.10 mass % or more and 0.30 mass % or less, Mn: 0.50 mass % or more and 1.50 mass % or less, Mg: 1.20 mass % or more and 1.50 mass % or less, and a balance comprising Al and inevitable impurities. The aluminum alloy sheet comprises an n-value of 0.049 or greater in an equivalent plastic strain range of 0.01 to 0.03 and an n-value of 0.063 or less in an equivalent plastic strain range of 0.3 to 1.1.
The aluminum alloy sheet for a beverage can body according to one aspect of the present disclosure is high in strength and excellent in chime wrinkling resistance and ironing formability.
Another aspect of the present disclosure provides an aluminum alloy sheet for a beverage can body. The aluminum alloy sheet is made of an aluminum alloy comprising Si: 0.10 mass % or more and 0.70 mass % or less, Fe: 0.10 mass % or more and 0.80 mass % or less, Cu: 0.10 mass % or more and 0.30 mass % or less, Mn: 0.50 mass % or more and 1.50 mass % or less, Mg: 1.20 mass % or more and 1.50 mass % or less, and a balance comprising Al and inevitable impurities. The aluminum alloy sheet comprises a tensile strength of 315 MPa or greater and 350 MPa or less, an n-value of 0.049 or greater in an equivalent plastic strain range of 0.01 to 0.03, and an n-value of 0.063 or less in an equivalent plastic strain range of 0.3 to 1.1.
The aluminum alloy sheet for a beverage can body according to another aspect of the present disclosure is high in strength and excellent in chime wrinkling resistance and ironing formability.
Another aspect of the present disclosure provides an aluminum alloy sheet for a beverage can body. The aluminum alloy sheet is made of an aluminum alloy comprising Si: 0.10 mass % or more and 0.70 mass % or less, Fe: 0.10 mass % or more and 0.80 mass % or less, Cu: 0.10 mass % or more and 0.30 mass % or less, Mn: 0.50 mass % or more and 1.50 mass % or less, Mg: 1.20 mass % or more and 1.50 mass % or less, and a balance comprising Al and inevitable impurities. The aluminum alloy sheet comprises an n-value of 0.049 or greater in an equivalent plastic strain range of 0.01 to 0.03, an n-value of 0.063 or less in an equivalent plastic strain range of 0.3 to 1.1, and a Mg solid solution content of 1.20 mass % or more that is calculated from a specific resistance difference between the aluminum alloy sheet for a beverage can body after a rolling with an equivalent plastic strain of 0.3 to 1.1 and a hot-rolled aluminum alloy sheet cooled immediately after a hot finishing rolling.
The aluminum alloy sheet for a beverage can body according to another aspect of the present disclosure is high in strength and excellent in chime wrinkling resistance and ironing formability.
Another aspect of the present disclosure provides an aluminum alloy sheet for a beverage can body. The aluminum alloy sheet is made of an aluminum alloy comprising Si: 0.10 mass % or more and 0.70 mass % or less, Fe: 0.10 mass % or more and 0.80 mass % or less, Cu: 0.10 mass % or more and 0.30 mass % or less, Mn: 0.50 mass % or more and 1.50 mass % or less, Mg: 1.20 mass % or more and 1.50 mass % or less, and a balance comprising Al and inevitable impurities. The aluminum alloy sheet comprises a tensile strength of 315 MPa or greater and 350 MPa or less, an n-value of 0.049 or greater in an equivalent plastic strain range of 0.01 to 0.03, an n-value of 0.063 or less in an equivalent plastic strain range of 0.3 to 1.1, and a Mg solid solution content of 0.96 mass % or more that is calculated from a specific resistance difference between the aluminum alloy sheet for a beverage can body and a hot-rolled aluminum alloy sheet cooled immediately after a hot finishing rolling. The aluminum alloy sheet further comprises a Mg solid solution content of 1.20 mass % or more that is calculated from a specific resistance difference between the aluminum alloy sheet for a beverage can body after a rolling with an equivalent plastic strain of 0.3 to 1.1 and a hot-rolled aluminum alloy sheet cooled immediately after a hot finishing rolling.
The aluminum alloy sheet for a beverage can body according to another aspect of the present disclosure is high in strength and excellent in chime wrinkling resistance and ironing formability.
Example embodiments of the present disclosure will be described.
An aluminum alloy sheet for a beverage can body of the present disclosure contains 0.10 mass % or more and 0.70 mass % or less of Si. Si contributes to formation of a Mg—Si based intermetallic compound, an Al—Mg—Cu—Si based intermetallic compound, and an Al—Mn—Fe—Si based intermetallic compound. The Al—Mn—Fe—Si based intermetallic compound inhibits the aluminum alloy sheet for a beverage can body from adhering to a metal die during an ironing. The Al—Mn—Fe—Si based intermetallic compound is an alpha-phase compound. The Al—Mn—Fe—Si based intermetallic compound is an intermetallic compound with an extremely high hardness. The Al—Mn—Fe—Si based intermetallic compound exerts, in a DI forming, effect of improving the surface texture of the material of the can body due to solid lubrication effect.
The Si content of 0.10 mass % or more sufficiently forms the Al—Mn—Fe—Si based intermetallic compound. The Si content of 0.70 mass % or less can inhibit excessive increases in the amounts of the Mg—Si based intermetallic compound, the Al—Mg—Cu—Si based intermetallic compound, and the Al—Mn—Fe—Si based intermetallic compound. As a result, the Mg solid solution content increases in the aluminum alloy sheet for a beverage can body, and thus material strength thereof becomes high. In addition, the Mg solid solution content after a rolling equivalent to an ironing being performed on the aluminum alloy sheet for a beverage can body increases, a second n-value becomes low, and thus ironing formability is improved. The rolling equivalent to an ironing refers to a rolling with an equivalent plastic strain of 0.3 to 1.1. The second n-value refers to an n-value in an equivalent plastic strain range of 0.3 to 1.1.
The aluminum alloy sheet for a beverage can body of the present disclosure contains 0.10 mass % or more and 0.80 mass % or less of Fe. Fe contributes to formation of the Al—Mn—Fe—Si based intermetallic compound. The Fe content of 0.10 mass % or more sufficiently forms the Al—Mn—Fe—Si based intermetallic compound.
The Fe content of 0.80 mass % or less can inhibit excessive increases in size and amount of the Al—Mn—Fe—Si based intermetallic compound, and thus inhibit cracking due to a coarse Al—Mn—Fe—Si based intermetallic compound during the ironing. As a result, the ironing formability of the aluminum alloy sheet for a beverage can body is improved.
The aluminum alloy sheet for a beverage can body of the present disclosure contains 0.10 mass % or more and 0.30 mass % or less of Cu. Cu is an element that contributes to material strength.
The Cu content is determined to be 0.10 mass % or more. The Cu content of 0.10 mass % or more can optimize the Cu solid solution content. An optimized Cu solid solution content improves the material strength of the aluminum alloy sheet for a beverage can body. The Cu content is also determined to be 0.30 mass % or less. The Cu content of 0.30 mass % or less hinders the material strength of the aluminum alloy sheet for a beverage can body from being excessively high. As a result, the ironing formability of the aluminum alloy sheet for a beverage can body is improved.
The aluminum alloy sheet for a beverage can body of the present disclosure contains 0.50 mass % or more and 1.50 mass % or less of Mn. Mn contributes to improvement in strength of the aluminum alloy sheet for a beverage can body and formation of the Al—Mn—Fe—Si based intermetallic compound.
The Mn content of 0.50 mass % or more further improves the strength of the aluminum alloy sheet for a beverage can body and sufficiently forms the Al—Mn—Fe—Si based intermetallic compound. In addition, the Mn content of 1.50 mass % or less can inhibit excessive formation of a coarse Al—Mn—Fe—Si based intermetallic compound. As a result, the ironing formability of the aluminum alloy sheet for a beverage can body is improved.
The aluminum alloy sheet for a beverage can body of the present disclosure contains 1.20 mass % or more and 1.50 mass % or less of Mg. Mg in solid solution contributes to improvement in strength of the aluminum alloy sheet for a beverage can body. The Mg content of 1.20 mass % or more can optimize the Mg solid solution content. An optimized Mg solid solution content improves the material strength of the aluminum alloy sheet for a beverage can body. In addition, the Mg solid solution content after the rolling equivalent to an ironing being performed on the aluminum alloy sheet for a beverage can body becomes sufficiently high, and thereby the second n-value becomes low. As a result, the ironing formability is improved. The rolling equivalent to an ironing refers to a rolling with the equivalent plastic strain of 0.3 to 1.1.
The Mg content of 1.50 mass % or less hinders the material strength of the aluminum alloy sheet for a beverage can body from being excessively high. As a result, the ironing formability of the aluminum alloy sheet for a beverage can body is improved.
In the aluminum alloy sheet for a beverage can body of the present disclosure, the n-value in an equivalent plastic strain range of 0.01 to 0.03 is referred to as a first n-value. The first n-value is 0.049 or greater. The first n-value of 0.049 or more renders the radial tension in a tapered chime portion at the can bottom high. As the radial tension becomes higher in the tapered chime portion at the can bottom, tensile deformation is promoted, producing radial elongation of the material circumferentially compressed, thereby improving chime wrinkling resistance.
If the first n-value is less than 0.049, the above-described effect cannot be sufficiently achieved, and thus the chime wrinkling resistance is reduced.
In the aluminum alloy sheet for a beverage can body of the present disclosure, the second n-value is 0.063 or less. In the DI forming, tensile stress acts on the sidewall of the can. A higher tensile stress is more likely to cause tear-off. The second n-value of 0.063 or less renders the tensile stress applied on the sidewall of the can in the ironing low, improving the ironing formability. If the second n-value exceeds 0.063, the tensile stress applied on the sidewall of the can in an ironing process becomes high, reducing the ironing formability.
The aluminum alloy sheet for a beverage can body of the present disclosure is produced by sequentially performing, for example, a casting process, a homogenizing treatment process, a hot rolling process, and a cold rolling process. The following describes the optimum production conditions for each process in the present disclosure.
An aluminum alloy ingot having a composition comprising 0.10 mass % or more and 0.70 mass % or less of Si, 0.10 mass % or more and 0.80 mass % or less of Fe, 0.10 mass % or more and 0.30 mass % or less of Cu, 0.50 mass % or more and 1.50 mass % or less of Mn, 1.20 mass % or more and 1.50 mass % or less of Mg, and a balance comprising Al and inevitable impurities. The technical significance of the numerical range of each component is as described above.
Al is the principal component of the aluminum alloy ingot. Al contained in the aluminum alloy ingot is, for example, the balance other than Si, Fe, Cu, Mn, Mg, and the inevitable impurities. In the aluminum alloy ingot, the total content of the inevitable impurities is preferably 0.5 mass % or less.
The aluminum alloy ingot can be obtained by melting and casting the raw materials in a conventional manner. Casting speed is preferably 10 mm/min or greater and 70 mm/min or less. When the casting speed is 10 mm/min or greater, it is possible to inhibit crystallization of a coarse intermetallic compound in the ingot. An example of the intermetallic compound may be Al6Mn. When the casting speed is 70 mm/min or less, occurrence of ingot cracking is inhibited, and thus casting yield is improved.
The temperature of the homogenizing treatment is preferably 550° C. or higher and 620° C. or lower. When the temperature of the homogenizing treatment is 550° C. or higher, a fine Al—Mn—Fe—Si based intermetallic compound is sufficiently formed, thus improving the ironing formability. When the temperature of the homogenizing treatment is 620° C. or lower, it is possible to inhibit occurrence of swelling on the ingot surface and local melting of the ingot, and thus inhibit degradation of the surface quality.
The duration of the homogenizing treatment is preferably one hour or longer. When the duration of the homogenizing treatment is one hour or longer, homogenization is sufficiently done, the Mg—Si based intermetallic compound crystallized in the casting process is sufficiently re-solidified, and the Mg solid solution content in a sheet metal to be obtained in the final process becomes high. As a result, it is possible to inhibit reduction in strength of an aluminum alloy sheet to be obtained. Hereinafter, the aluminum alloy sheet may be abbreviated as a sheet.
A hot rolling consists of, for example, a hot rough rolling and a hot finishing rolling. The ingot after the homogenizing treatment can be, for example, subjected directly to the hot rough rolling process without a reheating. The hot rough rolling can be performed using, for example, a reversing mill.
A hot rough rolling starting temperature is preferably 550° C. or higher and 600° ° C. or lower. When the hot rough rolling starting temperature is 550° C. or higher, it is possible to inhibit excessive precipitation of the Al—Mn—Si based intermetallic compound. As a result, the Mn solid solution content becomes high, and thus it is possible to inhibit reduction in strength of a sheet to be obtained. When the hot rough rolling starting temperature is 600° C. or lower, it is possible to inhibit excessive growth of an oxide film to be formed, and thus inhibit degradation of the surface quality.
It is preferable that a duration of keeping the sheet at the temperature of 300° C. or higher after the hot finishing rolling is ten hours or shorter. When the duration of keeping is ten hours or shorter, the amount of precipitated Mg2Si is controlled, thereby rendering the Mg solid solution content in the sheet high. Mg2Si is the Mg—Si based intermetallic compound. As a result, the tensile strength is improved. In addition, the Mg solid solution content after the rolling equivalent to an ironing being performed on the aluminum alloy sheet for a beverage can body becomes high. As a result, the second n-value becomes low, and thus the ironing formability is improved. The rolling equivalent to an ironing refers to a rolling with the equivalent plastic strain of 0.3 to 1.1.
For example, after the hot finishing rolling, a hot rolled sheet can be subjected to the cold rolling process. In the cold rolling, a rolling ending temperature of the pass before the final pass is preferably 110° C. or higher and 180ºC or lower. It is preferable, in the cold rolling, that a duration of keeping the sheet at the temperature of 100° C. or higher after a completion of the rolling of the pass before the final pass is 15 hours or shorter. When the duration of keeping is 15 hours or shorter, the amount of precipitated Mg2Si is controlled, thereby rendering the Mg solid solution content in the sheet high. As a result, the tensile strength is improved. In addition, the Mg solid solution content after the rolling equivalent to an ironing being performed on the aluminum alloy sheet for a beverage can body becomes high. As a result, the second n-value becomes low, and thereby the ironing formability is improved. The rolling equivalent to an ironing refers to a rolling with the equivalent plastic strain of 0.3 to 1.1.
When the rolling ending temperature of the pass before the final pass is 180° C. or lower, it is possible to inhibit excessive precipitation of the Mg—Si based intermetallic compound. Thus, it is possible to inhibit excessive reduction in the Mg solid solution content after the rolling equivalent to an ironing being performed on the aluminum alloy sheet for a beverage can body. As a result, the second n-value becomes low, and thereby the ironing formability is improved. The rolling equivalent to an ironing refers to a rolling with the equivalent plastic strain of 0.3 to 1.1.
It is further preferable, in the cold rolling, that a rolling ending temperature of the final pass is 140° C. or higher and 180ºC or lower. When the rolling ending temperature of the final pass is 140° ° C. or higher, dislocation is sufficiently restored, the first n-value becomes high, and thus the chime wrinkling resistance is improved.
When the rolling ending temperature of the final pass is 180° C. or lower, it is possible to inhibit microscopic precipitation of the Mg—Si based intermetallic compound. Thus, it is possible to inhibit excessive reduction in the Mg solid solution content after the rolling equivalent to an ironing is performed on the aluminum alloy sheet for a beverage can body. As a result, the second n-value becomes low, and thereby the ironing formability is improved. The rolling equivalent to an ironing refers to a rolling with the equivalent plastic strain of 0.3 to 1.1. In addition, when the rolling ending temperature of the final pass is 180° C. or lower, it is possible to inhibit excessive restoration of dislocation, and as a result the material strength is improved.
Aluminum alloy sheets for beverage can bodies S1 to 8 were produced under the production conditions shown in Table 1. All of the aluminum alloy sheets for beverage can bodies S1 to 8 have a composition comprising 0.25 mass % of Si, 0.30 mass % of Fe, 0.22 mass % of Cu, 1.19 mass % of Mn, 1.34 mass % of Mg, and a balance comprising Al and inevitable impurities.
All of S1 to 8 have in common that an aluminum alloy sheet for beverage can body is produced by the following method. First, an aluminum alloy ingot was cast by a semicontinuous casting method. Next, the surface of the ingot was grinded, and then the ingot was subjected to the homogenizing treatment process at 600° ° C. for three hours. The ingot was then subjected to the hot rough rolling process with a single stand reversing mill to obtain a hot rolled sheet. The hot rolled sheet was then subjected to the hot finishing rolling process with a four-stand tandem mill to obtain a further hot rolled sheet. A hot rolling starting temperature was 580° C. Finally, the hot rolled sheet was subjected to the cold rolling process to obtain an aluminum alloy sheet for a beverage can body.
Other conditions in the production of S1 to S8 are as shown in Table 1.
The following evaluations were conducted on each of the aluminum alloy sheets for beverage can bodies S1 to 8.
The aluminum alloy sheet for a beverage can body was used as a sheet for evaluation. The sheet was subjected to a tensile test in the rolling direction in accordance with JIS Z 2241 to measure the tensile strength of the sheet. Measurement was performed using an N number of three. The arithmetic mean among the measured values of three sheets was defined as the tensile strength of the aluminum alloy sheet for a beverage can body. The measurement results of the tensile strength are shown in the column “Tensile strength” in Table 1.
(ii) Evaluation of First n-Value
Using the measurement results of the tensile strength in (i) mentioned above, the first n-value in the equivalent plastic strain range of 0.01 to 0.03 was obtained in accordance with JIS Z 2253. The first n-value was obtained for each of the three sheets, and the arithmetic mean thereof was defined as the first n-value of the aluminum alloy sheet for a beverage can body. The measurement results of the first n-value are shown in the column “n-Value E=0.01-0.03” in Table 1.
(iii) Evaluation of Second n-Value
The aluminum alloy sheet for a beverage can body was used as a sheet for evaluation. First, the sheet was plastically deformed by the rolling so that the equivalent plastic strain thereof was at a specified value. The specified value of the equivalent plastic strain was 0.3, 0.6, and 1.1. Three sheets of the same equivalent plastic strain at each of the specified values were made.
Next, the tensile test was conducted on the plastically deformed sheet to measure yield stress. Then, a log-log graph of the equivalent plastic strain and the yield stress was created. Then, in the created graph, an approximate straight line that represents the relationship between the equivalent plastic strain and the yield stress was estimated by linear approximation. Then, the slope of an approximate curve was calculated. From the calculated slope, the second n-value was then calculated. The calculation results of the second n-value are shown in the column “n-Value ε=0.3-1.1” in Table 1.
The Mg solid solution content was evaluated for each of the aluminum alloy sheet for a beverage can body without the rolling equivalent to an ironing and the aluminum alloy sheet for a beverage can body after the rolling equivalent to an ironing being performed. The method for evaluating the Mg solid solution content is as follows.
The electrical conductivity of the aluminum alloy sheet for a beverage can body was measured with an eddy current conductivity meter, and the specific resistance p of the aluminum alloy sheet for a beverage can body was calculated in accordance with Formula (1) below. Measurement frequency was 960 kHz. If the thickness of the sheet to be measured was 0.6 mm or less, several sheets were stacked so that the thickness was made to be 0.6 mm or greater and measured.
A hot rolling processed sheet was prepared. The hot rolling processed sheet refers to a semi-produced sample that was produced by the same production method as for the aluminum alloy sheet for a beverage can body, which is the subject of evaluation of the Mg solid solution content, up to the hot finishing rolling and then cooled without the keeping, and that has not been subjected to a subsequent process such as the cold rolling. The aluminum alloy sheet for a beverage can body, which is the subject of evaluation of the Mg solid solution content, refers to the aluminum alloy sheet for a beverage can body without the rolling equivalent to an ironing, or the aluminum alloy sheet for a beverage can body after the rolling equivalent to an ironing being performed. The specific resistance ρ0 of the hot rolling processed sheet was measured in the same way as the measuring method of the specific resistance ρ. The unit of the specific resistance ρ0 is μΩ-cm.
In accordance with Formula (2) below, a specific resistance difference Δp was calculated. The unit of the specific resistance difference Δρ is μΩ-cm.
The calculated specific resistance difference Δρ was assumed to be due to precipitation of Mg2Si. With the constants of the specific resistances of Si and Mg, a Mg solid solution content difference ΔMgin was calculated in accordance with Formula (3) below. ΔMgin means a value obtained by subtracting the Mg solid solution content in the hot rolling processed sheet from the Mg solid solution content in the aluminum alloy sheet for a beverage can body, which is the subject of evaluation of the Mg solid solution content.
The meaning of each term in Formula (3) is as follows.
The value of XMgin is 0.54 μΩ-cm/mass %. The value of XMgout is 0.22 μΩ-cm/mass %. The value of XSiin is 1.02 μΩ-cm/mass %. The value of XSiout is 0.088 μΩ-cm/mass %. The value of YMg2Si is 1.73.
Using the Mg in solid solution difference ΔMgin and the Mg solid solution content Mgin0 in the hot rolling processed sheet, a Mg solid solution content Mgin was calculated in accordance with Formula (4) below.
The Mg solid solution content Mgin0 in the hot rolling processed sheet was assumed to be a solid solution content in equilibrium at 350° C. The Mg solid solution content Mgin0 in the hot rolling processed sheet was calculated by JMatPro-v10.1. JMatPro-v10.1 is a metal property calculation software made by Sente Software Ltd.
In calculation, Aluminum alloy was selected for MATERIALS TYPES, and the mass fractions (mass %) of Cu, Fe, Mg, Mn, Si, Cr, Ti, and Zn among the elements contained in the hot rolling processed sheet were entered. The mass fractions (mass %) of Cu, Fe, Mg, Mn, and Si were rounded to be numerical values with two decimal places, and the mass fractions (mass %) of Cr, Ti, and Zn were rounded to be numerical values with three decimal places.
The Mg solid solution content Mgin in the aluminum alloy sheet for a beverage can body without rolling equivalent to an ironing is shown in the column “Mg solid solution content ε=0” in Table 1. The Mg solid solution content Mgin in the aluminum alloy sheet for a beverage can body after the rolling equivalent to an ironing being performed is shown in the column “Mg solid solution content ε=1.1” in Table 1.
The aluminum alloy sheet for a beverage can body was subjected to a cup forming and then a drawing to be shaped into a redrawn can. A blank diameter before the cup forming was 140 mm. A cup diameter after the cup forming was 87 mm. A redrawn diameter of the redrawn can was 66 mm. For the drawing, a DI punch for a 202 diameter was used.
The undulation amplitude of the tapered chime portion at the can bottom was measured along the entire circumference using a shape measuring instrument to determine the maximum value of the undulation amplitude. Measurement of the maximum value of the undulation amplitude was performed using an N number of five. The arithmetic mean of the maximum values of the undulation amplitudes among five samples (hereafter referred to as mean maximum value of undulation amplitude) was calculated.
If the mean maximum value of undulation amplitude is 500 μm or less, the chime wrinkling resistance was determined to be good. If the mean maximum value of undulation amplitude exceeds 500 μm, the chime wrinkling resistance was determined to be poor. The mean maximum value of undulation amplitude is shown in the column “Mean maximum value of undulation amplitude” in Table 1. The results of evaluating the chime wrinkling resistance are shown in the column “Chime wrinkling resistance” in Table 1. “∘” means that the chime wrinkling resistance is good. “x” means that the chime wrinkling resistance is poor.
Out of the aluminum alloy sheet for a beverage can body, a disc with a blank diameter of 140 mm was made. The disc was subjected to the DI forming to create a can with an inner diameter of 66 mm. Then, using a punch that renders the external diameter of the can larger from the can bottom toward the opening of the can, a severe ironing test was performed that forces to cause cut-off of the can during the third ironing. Measurement was performed of a thickness a at the thinnest portion in the sidewall of the can before the third ironing, and a thickness b of the sidewall of the can at the time of cut-off of the can.
The thickness a was measured for each of ten cans. The average of the measured thicknesses a of the ten cans was denoted by A. The thickness b was also measured for each of the ten cans. The average of the measured thicknesses b of the ten cans was denoted by B.
A limit ironing rate R was calculated in accordance with Formula (5) below. The limit ironing rate R is an index of the ironing formability.
Cans with a limit ironing rate R of 50.7% or greater were determined to be good, and cans with a limit ironing rate of less than 50.7% were determined to be defective. The limit ironing rate R is shown in the column “Limit ironing rate” in Table 1. The determination results of the ironing formability are shown in the column “Ironing formability” in Table 1. “∘” means that the ironing formability is good. “x” means that the ironing formability is poor.
The results of overall evaluation are shown in Table 1. If the chime wrinkling resistance and the ironing formability are good, the overall evaluation result was considered good. “∘” in Table 1 means that the overall evaluation result is good. If the tensile strength, the chime wrinkling resistance, and the ironing formability are good, the overall evaluation result was considered particularly good. “⊚” in Table 1 means that the overall evaluation result is particularly good.
In S2 and S4, the tensile strength was 315 MPa or greater and 350 MPa or less, the first n-value was 0.049 or greater, and the second n-value was 0.063 or less. As a result, the chime wrinkling resistance and the ironing formability were good.
In S1, 3, and 7, the rolling ending temperature of the final pass in the cold rolling was too low, and thus restoration of dislocation was insufficient. As a result, the first n-value was low, and the chime wrinkling resistance was poor.
In S5, the rolling ending temperature of the final pass in the cold rolling was higher than the optimum temperature. Thus, the precipitation amount of the Mg—Si based intermetallic compound increased, and the Mg solid solution content in the sheet was low. As a result, the tensile strength was relatively low compared with others.
In S6, the duration of keeping at 110° C. or higher was too long after a completion of the rolling of the pass before the final pass in the cold rolling. Thus, the precipitation amount of the Mg—Si based intermetallic compound increased, and the Mg solid solution content was low in the sheet after the rolling equivalent to an ironing was performed on the sheet. As a result, the second n-value was high, and the ironing formability was poor. The rolling equivalent to an ironing refers to a rolling with the equivalent plastic strain of 0.3 to 1.1.
In S8, the duration of keeping at 300° ° C. after the hot finishing rolling was too long. Thus, the precipitation amount of the Mg—Si based intermetallic compound increased, and the Mg solid solution content was low in the sheet. As a result, the tensile strength was low.
In S2, S4, and S5, the chime wrinkling resistance and the ironing formability were good. In S2 and S4, the tensile strength, the chime wrinkling resistance, and the ironing formability were good.
Although some embodiments of the present disclosure have been described above, the present disclosure is not limited to the aforementioned embodiments and may be implemented in variously modified forms.
(1) A function of a single element in each of the aforementioned embodiments may be distributed to a plurality of elements, or a function of a plurality of elements may be achieved by a single element. A part of the configuration in each of the aforementioned embodiments may be omitted. At least a part of the configuration in each of the aforementioned embodiments may be added to, replaced with the configuration of other aforementioned embodiments.
(2) In addition to the aluminum alloy sheet for a beverage can body described above, the present disclosure can also be achieved in various forms, such as products including the aluminum alloy sheet for a beverage can body as a component, methods for producing aluminum alloy sheets for beverage can bodies, methods for producing beverage cans, and methods for producing can bodies.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-079212 | May 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/014983 | 3/28/2022 | WO |
