JP2008144221A - Aluminum alloy sheet for cap and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum alloy sheet for an explosion-protection cap, which shows satisfactorily excellent mechanical properties and formability as a cap material particularly of a bottle type can that may cause a high pressure, and to provide a manufacturing method therefor. <P>SOLUTION: This aluminum alloy sheet has a composition comprising, by mass%, 1.1 to 1.5% Mg, 0.03% or less Cu, 0.10% or less Mn, 0.04% or less Cr, 0.3% or less Zn, 0.35% or less Si, 0.40% or less Fe, 0.20% or less Ti, and the balance Al with unavoidable impurities, and has a tensile strength of 185 to 205 MPa, a yield strength of 155 to 195 MPa and an elongation of 6 to 11%; and shows an earing rate of 2% or less when a drawing ratio is 2 or less. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an aluminum alloy plate for a cap of a bottle can and a method for producing the same.

  Threaded caps are widely used as caps for glass bottles and plastic containers. Recently, aluminum alloy bottle cans with threaded caps have also been developed. As a material for such a bottle can, for example, an Al—Mn-based aluminum alloy such as JIS3004 (AA3004) or JIS3104 (AA3104) is used. On the other hand, as a material for the cap, for example, an Al—Mg-based aluminum alloy such as JIS5154 is used (see, for example, Patent Documents 1 to 3).

The quality characteristics required for bottle caps are diverse, including pressure resistance, corrosion resistance, low ears, sealing properties, explosion-proof properties, and deep drawability, and these properties must be stable. Don't be. Further, since this type of cap is mass-produced, it is desirable that no material is wasted during manufacture. For example, when forming a cap by deep drawing, how much ears are wasted of materials depending on the composition and manufacturing conditions of the aluminum alloy plate, and how good the workability is with a low ear rate An important issue is whether high tensile strength can be secured.
JP 2005-2464 A JP 2004-353079 A JP 2005-126664 A

  By the way, since the bottle can provided with the screw cap mentioned above can close the cap again after opening the cap, it is very convenient. However, when the bottle can is left in a state where the contents remain, gas may be generated in the bottle can due to proliferation of germs mixed in the bottle can, thereby increasing the internal pressure of the bottle can. For example, when the content of the bottle can is a carbonated beverage or the like, the pressure in the bottle can is usually about 0.2 MPa, but there is also a knowledge that a higher pressure is generated depending on the use environment, temperature conditions, and the like.

  Therefore, an explosion-proof cap has been developed in which the screw part of the cap has enough strength to withstand the increase in the internal pressure of the bottle can so that the cap will not come off and the contents will not pop out when the internal pressure of the bottle can rises. . In addition, an explosion-proof cap having a structure in which a slit is formed in the knurled portion of the cap and the cap is deformed when the internal pressure of the bottle can becomes abnormally high and gas is released from the slit of the knurled portion has been developed. Therefore, it is necessary to use a cap material having particularly high strength and elongation for a cap for a bottle can in which such a high pressure may occur.

  The present invention has been proposed in view of such conventional circumstances, and particularly as a cap material for bottle cans that may generate high pressure, satisfying excellent mechanical properties and moldability, An object of the present invention is to provide an aluminum alloy plate for an explosion-proof cap that can be thinned by further improving the strength and a method for producing the same.

  In order to achieve this object, the invention according to claim 1 is, in mass%, Mg: 1.6 to 2.0%, Cu: 0.10% or less, Mn: 0.30% or less, Cr: A composition comprising 0.30% or less, Zn: 0.4% or less, Si: 0.5% or less, Fe: 0.50% or less, Ti: 0.40% or less, the balance being Al and inevitable impurities. And having a tensile strength of 210 to 250 MPa, a yield strength of 170 to 220 MPa, and an elongation of 7 to 13%, a tensile strength after baking of 210 to 250 MPa, a yield strength of 160 to 210 MPa, and an elongation of 7 to 13 %, And the ratio of the tensile strength to the yield strength after baking is 1.1 to 1.4, and the shape of the ears generated in the opening of the cup by the deep drawing test is 0 with respect to the rolling direction. 6 ° ears appearing at 6 ° in 45 ° direction, or 0 ° 45 °, a Happo ear that occurs eight of 90 ° direction, noted and an aluminum alloy plate for a cap, wherein the ear rate in drawing ratio 1.97 is not more than 2.0%.

  The invention according to claim 2 is a method for producing an aluminum alloy plate for a cap according to claim 1, wherein the slab is hot-rolled and cold-rolled, and the final cold rolling rate exceeds 40% and 80%. %, The final plate thickness is 0.210 to 0.260 mm, and final temper annealing at 205 to 245 ° C. is performed after the final cold rolling.

  As described above, according to the present invention, since it has a good mechanical strength as a cap material particularly excellent in explosion-proof property, the cap is removed and the contents pop out when the internal pressure of the bottle can rises. Can be prevented. Moreover, the thickness can be reduced by further improving the strength. In addition, because it has good elongation, it has excellent workability, and furthermore, the ear rate can be lowered while satisfying these mechanical properties, so that waste of materials at the time of production is reduced and low when mass-produced. Cost reduction can be realized.

  Hereinafter, an aluminum alloy plate for a cap to which the present invention is applied and a manufacturing method thereof will be described in detail.

First, an aluminum alloy plate for a cap to which the present invention is applied will be described.
The aluminum alloy plate for a cap to which the present invention is applied is in mass%, Mg: 1.6 to 2.0%, Cu: 0.10% or less, Mn: 0.30% or less, Cr: 0.30% or less Zn: 0.4% or less, Si: 0.5% or less, Fe: 0.50% or less, Ti: 0.40% or less, having a composition consisting of the balance Al and inevitable impurities, tensile strength Is 210 to 250 MPa, proof stress is 170 to 220 MPa, elongation is 7 to 13%, tensile strength after baking is 210 to 250 MPa, proof stress is 160 to 210 MPa, elongation is 7 to 13%, and The ratio of the tensile strength to the yield strength after baking is 1.1 to 1.4, and the shape of the ears generated in the opening of the cup by the deep drawing test is 0 ° and 45 ° directions with respect to the rolling direction. The hexagonal ears that occur at 6 locations, or 0 °, 5 °, a Happo ear that occurs eight of 90 ° direction, noted and, is characterized in that the ear rate in drawing ratio 1.97 is not more than 2.0%.

  Hereinafter, the reasons for defining each composition element added to the aluminum alloy plate for a cap of the present invention and the amount of addition and the specific matters of the aluminum alloy of the present invention will be described.

(Mg: 1.6-2.0%)
Mg is an element necessary for improving the strength of the aluminum alloy. However, if Mg is less than 1.6%, the effect of improving the strength of the aluminum alloy for an explosion-proof cap is insufficient, and if Mg exceeds 2.0%, workability deteriorates. Therefore, Mg is preferably contained in the range of 1.6 to 2.0%, more preferably in the range of 1.75 to 1.90%.

(Cu: 0.10% or less)
Cu is an element that improves the strength of the aluminum alloy. However, if Cu exceeds 0.10%, the corrosion resistance of the aluminum alloy deteriorates. Therefore, Cu is preferably added in a range of 0.10% or less, and more preferably in a range of 0.03 to 0.07%.

(Mn: 0.30% or less)
Mn is an element that improves the strength of the aluminum alloy. However, if Mn exceeds 0.30%, workability deteriorates. Therefore, it is preferable to contain Mn in the range of 0.30% or less, and more preferably in the range of 0.1 to 0.2%.

(Cr: 0.30% or less)
Cr is an element that reduces the ear rate. However, if Cr exceeds 0.30%, the strength of the aluminum alloy becomes too high and the formability deteriorates. Therefore, Cr is preferably added in the range of 0.30% or less, and more preferably in the range of 0.1 to 0.2%.

(Zn: 0.4% or less)
Zn is an element that improves crystal formability and improves formability. However, when Zn exceeds 0.4%, the strength of the aluminum alloy becomes too high, and the formability deteriorates. Therefore, Zn is preferably added in a range of 0.4% or less, and more preferably in a range of 0.2 to 0.3%.

(Si: 0.5% or less)
Si is an element that improves deep drawability. However, when Si exceeds 0.5%, the deep drawability is deteriorated. Therefore, Si is preferably added in the range of 0.5% or less, more preferably in the range of 0.3 to 0.4%.

(Fe: 0.50% or less)
Fe is an element that improves the strength of the aluminum alloy. However, if Fe exceeds 0.50%, deep drawability and corrosion resistance deteriorate. Therefore, Fe is preferably added in a range of 0.50% or less, and more preferably in a range of 0.2 to 0.4%.

(Ti: 0.40% or less)
Ti is an element that achieves finer crystal grains and improves formability. However, when Ti exceeds 0.40%, the surface state of the aluminum alloy deteriorates due to rough skin or the like. Therefore, Ti is preferably added in a range of 0.40% or less, and more preferably in a range of 0.2 to 0.3%.

(mechanical nature)
The aluminum alloy plate for a cap of the present invention preferably has a tensile strength of 210 to 250 MPa, a proof stress of 170 to 220 MPa, and an elongation of 7 to 13%.
If the tensile strength is less than 210 MPa, the strength as a cap for a bottle can will be insufficient, and if it exceeds 250 MPa, it will be difficult to mold the screw part formed on the cap. Therefore, the tensile strength is preferably in the range of 210 to 250 MPa, and more preferably in the range of 220 to 235 MPa.
When the proof stress is less than 170 MPa, appearance defects such as wrinkles are likely to occur during deep drawing, and when it exceeds 220 MPa, cracks are likely to occur during deep drawing. Therefore, the proof stress is preferably in the range of 170 to 220 MPa, and more preferably in the range of 180 to 205 MPa.
If the elongation is less than 7%, the formability of the cap by the deep drawing process deteriorates. If the elongation exceeds 13%, the cap shape after the deep drawing process becomes unstable. Therefore, the elongation is preferably in the range of 7 to 13%, more preferably in the range of 10 to 12%.

The aluminum alloy plate for a cap of the present invention preferably has a tensile strength of 210 to 250 MPa, a proof stress of 160 to 210 MPa, and an elongation of 7 to 13% after being baked at 200 ° C. for 10 minutes.
If the tensile strength after baking is less than 210 MPa, the strength as a cap for a bottle can is insufficient, and if it exceeds 250 MPa, it is difficult to form a screw part formed on the cap. Therefore, the tensile strength is preferably in the range of 210 to 250 MPa, and more preferably in the range of 220 to 235 MPa.
If the yield strength after baking is less than 160 MPa, appearance defects such as wrinkles are likely to occur during deep drawing, and if it exceeds 210 MPa, cracks are likely to occur during deep drawing. Therefore, the yield strength is preferably in the range of 160 to 210 MPa, and more preferably in the range of 170 to 195 MPa.
If the elongation after baking is less than 7%, the formability of the cap by deep drawing deteriorates, and if it exceeds 13%, the cap shape after deep drawing becomes unstable. Therefore, the elongation is preferably in the range of 7 to 13%, more preferably in the range of 10 to 12%.

  Furthermore, in the aluminum alloy plate for caps of the present invention, the ratio of the tensile strength to the proof stress after baking is preferably 1.1 to 1.4. If this ratio is less than 1.1, the strength becomes too low to withstand the internal pressure of the bottle can, or the yield strength becomes too high and the moldability deteriorates. On the other hand, if this ratio exceeds 1.4, the strength becomes too high and it is difficult to open the cap, or the proof stress becomes too low and the cap shape becomes unstable. Therefore, the ratio of the tensile strength to the yield strength after baking is preferably in the range of 1.1 to 1.4, and more preferably in the range of 1.2 to 1.3.

(Deep drawing test)
In the aluminum alloy plate of the present invention, the shape of the ears generated at the opening of the cup by the deep drawing test is 0 ° (180 °), 45 ° (135 °, 225 °, 315 °) direction with respect to the rolling direction. 6-point ears that occur at 6 points, or 8-point ears that occur at 8 points in the directions of 0 ° (180 °), 45 ° (135 °, 225 °, 315 °), 90 ° (270 °), In addition, it is preferable that the ear ratio at the aperture ratio of 1.97 is 2.0% or less. By making the ear rate 2.0% or less, it is possible to reduce the waste of materials during manufacturing.

  Here, the deep drawing test is a method of punching a disc (blank) of a predetermined diameter from a material and drawing it into a cylinder with a flat bottom (called a drawing cup) using a punch and a die. This refers to a test for determining the deep drawability of a material by measuring the height of the ear generated in the opening. The ear rate was determined by performing a deep drawing test using a die having a die diameter of 33.7 mm, a punch diameter of 33 mm, and a punch shoulder R of 4 mm under the conditions of a blank diameter of 65 mm and a drawing ratio of 2 or less. Calculated from

Next, the manufacturing method of the aluminum alloy plate for caps which applied this invention is demonstrated.
The manufacturing method of the aluminum alloy plate for caps to which the present invention is applied can be manufactured by using an aluminum alloy having the above composition components and combining conventional methods applied when manufacturing this type of aluminum alloy. That is, after obtaining a slab from the molten metal, the slab is subjected to hot rolling and cold rolling a plurality of times, and before and after the rolling, homogenization treatment and intermediate annealing are performed as necessary, and further cooling is performed after the intermediate annealing. The rolling process is performed a plurality of times, and the cold rolling rate (referred to as the final cold rolling rate) from the last intermediate annealing is set to more than 40% and not more than 80%, and the final adjustment at 205 to 245 ° C. after the final cold rolling. It is a feature of the present invention to perform quality annealing. The final plate thickness is preferably in the range of 0.210 to 0.260 mm.

  Specifically, when the final cold rolling rate is 40% or less, the strength is insufficient, and when it exceeds 80%, the ear rate is increased. For example, the final cold rolling rate when processed from a thickness of 0.6 mm to 0.25 mm is 58%, and the final cold rolling rate when the thickness is changed from 0.8 mm to 0.25 mm is 69%. Even in this case, the tensile strength is improved when the ear rate is lower and the cold rolling rate is higher. Therefore, the final cold rolling rate is preferably in the range of more than 40% and 80% or less, and more preferably in the range of 55 to 70%. Thereby, the form of the above-mentioned ear can be a hexagonal ear or an eight-sided ear, and the tensile strength can be improved while maintaining a low ear rate.

  The desired tensile strength can be finally obtained by final cold rolling. On the other hand, if the final temper annealing is not performed after the final cold rolling, elongation does not occur. Specifically, if the final temper annealing is less than 205 ° C, the elongation is insufficient, and if it exceeds 245 ° C, the strength of the material is lowered. Therefore, the final temper annealing is preferably performed in the range of 205 to 245 ° C, and more preferably in the range of 220 to 235 ° C. The heating method may be a batch type or a rapid heating method. The heating time is about 1 to 10 hours for the batch method and about 1 to 60 seconds for the rapid heating method.

  Since the aluminum alloy plate of the present invention produced as described above has a good mechanical strength as a cap material particularly excellent in explosion-proof property, when the internal pressure of the bottle can rises, the cap comes off and the contents pop out. This can be prevented in advance. Moreover, the thickness can be reduced by further improving the strength. In addition, because it has good elongation, it has excellent workability, and furthermore, the ear rate can be lowered while satisfying these mechanical properties, so that waste of materials at the time of production is reduced and it is low when mass-produced. Cost reduction can be realized.

  In addition, the aluminum alloy plate of the present invention can be used as an explosion-proof cap material that vents gas between the cap and the bottle mouth at high pressure, and of course, as a cap material that does not require pressure resistance as much as an explosion-proof cap. Can also be used, and the range of use as a cap material is very wide.

  Hereinafter, the effects of the present invention will be made clearer by examples. In addition, this invention is not limited to a following example, In the range which does not change the summary, it can change suitably and can implement.

  In this example, the difference in physical properties when the contents of Mn and Si were changed as an aluminum alloy plate for an explosion-proof cap was examined. Specifically, first, by mass, Mg: 1.8%, Cu: 0.05%, Cr: 0.15%, Zn: 0.2%, Fe: 0.25%, Ti: 0.00. An aluminum alloy containing 2%, Mn: 0.005 to 0.3%, Si: 0.15 to 0.5% and having a composition composed of the balance Al and inevitable impurities was melted and cast into a slab. Next, homogenization treatment was performed at 560 ° C. for 4 hours, and the thickness was 6 mm by hot rolling. Next, cold rolling and intermediate annealing were performed in a continuous annealing furnace (460 ° C.), and cold rolling was performed to a final sheet thickness of 0.25 mm at a final cold rolling rate of 65%. Finally, temper annealing was performed at 225 ° C. for 4 hours. 1 to 12 aluminum alloy plates were obtained.

  And the obtained No. About the aluminum alloy board of 1-12, each measurement of tensile strength, yield strength, elongation, and ear rate was performed. The measurement results are shown in Table 1. The ear rate was determined by performing a deep drawing test using a die having a die diameter of 33.7 mm, a punch diameter of 33 mm, and a punch shoulder R of 4 mm under the conditions of a blank diameter of 65 mm and a drawing ratio of 2 or less. Calculated from No. The aluminum alloy plates 1 to 12 were each measured for tensile strength, yield strength, and elongation after baking at 200 ° C. for 10 minutes. The measurement results are shown in Table 1. Furthermore, the ratio TS / YS (A / B) of the tensile strength (A) to the yield strength (B) after baking was calculated. The calculation results are shown in Table 1.

  As shown in Table 1, no. In the case of the aluminum alloy plates 1 to 3 having a Mn content of 0.2% and a Si content of 0.3 to 0.5%, No. 1 to 3 were used. When the Mn content is 0.3% and the Si content is 0.3 to 0.5%, the aluminum alloy plates 4 to 6 are No. When the Mn content is 0.25% and the Si content is 0.15 to 0.25% (less than 0.3%), the aluminum alloy plates 7 to 9 are No. 7-9. The 10 to 12 aluminum alloy sheet is a case where the Si content is 0.4% and the Mn content is 0.005 to 0.15% (less than 0.2%).

  From the measurement results shown in Table 1, no. Each of the aluminum alloy sheets 1 to 12 uses an aluminum alloy within the composition range of the present invention, the final cold rolling rate is set to 40 to 80% and the final tempering is performed in the range of 205 to 245 ° C. after the final cold rolling. Annealed.

  These aluminum alloy plates have a tensile strength before baking of 210 to 250 MPa, a yield strength of 170 to 220 MPa, and an elongation of 7 to 13%, a tensile strength after baking of 210 to 250 MPa, a yield strength of 160 to 210 MPa, It can be seen that the elongation is 7 to 13%, and the ratio of the tensile strength to the proof stress after baking is 1.1 to 1.4, and good mechanical properties are maintained after baking. Of these, No. Since the aluminum alloy sheet of No. 6 showed the best results, the contents of Mn and Si should be as high as possible within the numerical range of the present invention, thereby improving the formability while maintaining the strength. Is possible.

Claims (2)

In mass%, Mg: 1.6 to 2.0%, Cu: 0.10% or less, Mn: 0.30% or less, Cr: 0.30% or less, Zn: 0.4% or less, Si: 0 0.5% or less, Fe: 0.50% or less, Ti: 0.40% or less, and having a composition comprising the balance Al and inevitable impurities,
Tensile strength is 210-250 MPa, yield strength is 170-220 MPa, elongation is 7-13%, tensile strength after baking is 210-250 MPa, yield strength is 160-210 MPa, elongation is 7-13% And the ratio of tensile strength to yield strength after baking is 1.1 to 1.4,
The shape of the ears generated at the opening of the cup by the deep drawing test is six hexagonal ears generated at 0 ° and 45 ° directions with respect to the rolling direction, or 8 at 0 °, 45 ° and 90 ° directions. An aluminum alloy plate for a cap which is an eight-sided ear generated at a location and has an ear rate of 2.0% or less at a drawing ratio of 1.97. It is a manufacturing method of the aluminum alloy plate for caps according to claim 1,
The slab is hot-rolled and cold-rolled, the final cold rolling rate exceeds 40% and is 80% or less, the final sheet thickness is 0.210 to 0.260 mm, and the final tempering at 205 to 245 ° C. after the final cold rolling. A method for producing an aluminum alloy plate for a cap, which comprises annealing.