JP4393949B2 - High strength aluminum alloy plate for wide-mouth bottle can cap - Google Patents

Description

  The present invention relates to an Al—Mg—Mn (aluminum-magnesium-manganese) based alloy plate suitably used for a PP (pilfer proof) cap for a wide-mouth bottle can.

  PP caps are generally coated and printed on an aluminum alloy plate that is a material, then a plurality of cylindrical cups are formed at the same time, the ears of each cup are trimmed, and perforations are processed in the hem. It is manufactured by the process. The cap formed in this way is filled with the contents in the beverage container, wound around the threaded portion of the container, and put on the market.

  Until now, Al-Mn 3105 alloy (see Patent Document 1) or Al-Fe 8011 alloy has been mainly used for PP caps with a diameter of 28 mm or less (see Non-Patent Document 1). . On the other hand, Al-Mg-based 5151 alloy (Al-1.5 to 2.1% Mg alloy) is used for a wide-mouth cap having a diameter of 38 mm or the like because it needs to have higher strength. However, a plate with higher strength and better openability is expected for contents that require a higher internal pressure or for gauge down (reduction in plate thickness).

  As an alloy that can meet the expectation of such high strength and good openability, there is an Al-Mg-Mn alloy. In the prior art (refer to Patent Document 2) in which the final cold rolling rate and the crystal grain size of the Al—Mg—Mn alloy plate are limited, there is an example of 263 MPa as a tensile strength of 200 MPa or more. Is 2%, and PP caps for wide-mouth bottle cans may cause problems such as cracking during molding.

Moreover, in the prior art (refer patent document 3) which limited the conditions from the homogenization process of Al-Mg-Mn type alloy to finish annealing (refer patent document 3), the tensile strength is 141 MPa in an example at the maximum, and 152 MPa in a comparative example, The strength is too low to apply to PP caps for wide-bottle cans.
Furthermore, even in the prior art (see Patent Document 4) in which the final annealing conditions by rapid heating and cooling are limited (see Patent Document 4), the maximum tensile strength is 185 MPa, and the strength is too low.

  On the other hand, as an example of an Al-Mg-Mn alloy having high tensile strength, there is a prior art (see Patent Document 5) showing an example exceeding 200 MPa, but it is not for a PP cap by deep drawing but by a ring pull. It is for shallow-drawn wide-mouthed caps that are opened by tearing, and emphasizes the tearability of the score processing part, and is used differently from the present invention.

Japanese Patent No. 3153541 JP 58-224142 A Japanese Patent Laid-Open No. 9-25546 JP 2000-282195 A JP 2000-282164 A Sumitomo Light Metal Technical Report, vol. 23 (1982), p. 36.

  The present invention has been made in view of such conventional problems. By increasing the strength of the squeezed cup within a range where the ear ratio is low and the moldability is not impaired, the rigidity of the threaded portion of the manufactured cap can be improved. Provided is a high-strength aluminum alloy plate for Al-Mg-Mn-based wide-mouth bottle can caps, which can improve the pressure resistance so that surface doming can be prevented.

The present invention, after painting / printing, is formed into a cylindrical cup having a diameter of more than 28 mm, trims the ear of the cup, then processes the perforation at the hem, and then the beverage container filled with the contents An aluminum alloy plate for a wide-mouth bottle can cap that is wound around the screw part of
Mg: more than 0.8% (weight%, the same applies hereinafter), less than 2.5%, and Mn: not less than 0.3% and less than 0.8%, and further Cu: 0.01 to 0.24% Cr: 0.01-0.05%, Zn: 0.01-0.25%, Si: 0.01-0.30%, Fe: 0.01-0.50%, Ti: 0.005 It contains one or more of 0.05%, and the balance has a chemical composition consisting of inevitable impurities and aluminum ,
The tensile strength of the base plate of the aluminum alloy plate is 200 to 300 MPa, the proof stress is 150 to 250 MPa,
And the tensile strength of the blank board which gave the heat processing hold | maintained for 10 minutes at the temperature of 200 degreeC with respect to the said base plate is 200-300 MPa, yield strength is 140-240 MPa, elongation is 5% or more, It is characterized by the above-mentioned. It is in the high intensity | strength aluminum alloy plate for wide-mouth bottle can caps made into (1).

First, the reason for limiting the chemical composition in the present invention will be described.
Mg is an essential component of the present invention. By limiting the content to more than 0.8% and less than 2.5%, the strength and formability can be kept good.
When the Mg content is 0.8% or less, the strength is insufficient to cope with high internal pressure contents or gauge down, so that a predetermined pressure resistance is obtained as a wide-mouth bottle can cap (hereinafter simply referred to as a cap). I can't. In addition, there is a problem that the rigidity of the threaded portion in the molded cap and the effect of preventing doming on the top surface cannot be sufficiently obtained. In addition, four ears in the 0 °, 90 °, 180 °, and 270 ° directions with respect to the rolling direction are easily developed, so it is difficult to stably obtain a material with a low ear rate, and it is difficult to bend characters. It is not easy to mass-produce. Character bending referred to here is a phenomenon in which printed pictures and characters are bent and displayed depending on how the material is deformed due to the characteristics of the method of manufacturing a cap that is molded into a cup shape after printing in a flat state. That means.
The larger the Mg content, the finer the crystal grains. By increasing the Mg content and enhancing the crystal grain refining effect, it becomes easy to suppress rough skin during cup molding.

  On the other hand, when the Mg content is 2.5% or more, the strength is too high, and a great deal of force is required at the time of opening, which makes it difficult to open. Therefore, the Mg content is preferably less than 2.5%. The Mg content is preferably more than 1.3%, less than 2.2%, more preferably more than 1.5%, in order to satisfy the above-described anisotropy and strength in a balanced manner and facilitate production. Less than 2.0% is good.

Mn is an essential component of the present invention in order to maintain good strength and moldability. In addition, by using Mn as an essential component, for example, can body material 3004 alloy and 3104 alloy can be recycled and used as the raw material. The Mn content is limited to 0.3% or more and 1.5% or less. When the Mn content is less than 0.3%, it is difficult to obtain a predetermined performance as a cap due to insufficient strength, and it is difficult to use a lot of recycled materials. On the other hand, if it exceeds 1.5%, the strength is so high that a large amount of force is required at the time of opening and it is difficult to open, or a huge intermetallic compound is easily produced at the time of casting together with elements such as Fe.
The Mn content is preferably 0.3% or more and less than 0.8%. The reason for suppressing the upper limit of the amount of Mn is that the higher the Mg content, the higher the strength while maintaining the formability, but the ingot cannot be homogenized at high temperature, and the Mn-based precipitates that affect the ear rate are affected. This is because it becomes difficult to control.

  The generation state and strength characteristics of the ear rate can be adjusted not only by the contents of Mg and Mn but also by other manufacturing conditions.

  The above-mentioned base plate refers to the aluminum alloy plate of the present invention itself, that is, the state as manufactured and the state before being supplied to the cap manufacturing process. The blank plate is a plate in which the base plate is subjected to the heat treatment as described above, and the state after printing in the cap manufacturing process is reflected to some extent for convenience.

The strength of the base plate is limited to a tensile strength of 200 to 300 MPa and a proof stress of 150 to 250 MPa. And the intensity | strength of the said baked board is limited to the range whose tensile strength is 200-300 MPa, proof stress is 140-240 MPa, and elongation is 5% or more.
If the tensile strength and proof stress of the base plate are not within the above ranges, it will be difficult to obtain the desired strength after baking.
When the tensile strength of the blank plate is less than 200 MPa and the proof stress is less than 140 MPa, a predetermined pressure resistance cannot be obtained in the molded cap. On the other hand, when the tensile strength of the blank plate exceeds 300 MPa and when the proof stress exceeds 240 MPa, there is a problem that it is difficult to open the molded cap. When the elongation of the blank plate is less than 5%, there is a problem that molding defects such as cracks are likely to occur during cap molding.

In the present invention, according to the specifications of the cap to be obtained, the Mg content can be limited to a narrower range and adjusted to a more optimal strength characteristic.
That is, when emphasizing the ease of opening the cap, the Mg content is more than 1.3% and less than 2.2%, the tensile strength of the base plate is 210 to 280 MPa, and the proof stress is In addition to 160 to 250 MPa, it is preferable that the blank plate has a tensile strength of 210 to 280 MPa, a proof stress of 150 to 240 MPa, and an elongation of 5% or more.

Moreover, the chemical composition of the said aluminum alloy plate is further Cu: 0.01-0.24%, Cr: 0.01-0.05%, Zn: 0.01-0.25%, Si: 0.01 One type or two or more types are included among -0.30%, Fe: 0.01-0.50%, and Ti: 0.005-0.05% .

Cu: 0.01 to 0.24%;
Cu is an element that affects the material strength. If it is less than 0.01%, not only the effect cannot be obtained, but it is necessary to use a high purity metal, resulting in an increase in cost. Addition exceeding 0.24% makes rolling difficult.

Cr: 0.01-0.05%, Zn: 0.01-0.25%, Fe: 0.01-0.50%;
Cr, Zn, and Fe are elements that affect the formability by crystal grain refinement. If each of these is less than the above lower limit, not only the effect cannot be obtained, but it is necessary to use a high purity metal, resulting in an increase in cost. On the other hand, when the above upper limit is exceeded, the crystal grain refining effect is saturated. Therefore, the upper limit is preferably taken into consideration in view of the cost increase required for addition.

Si: 0.01-0.30%;
Si is an element that forms a compound with Mn and Fe and forms a crystallized product such as an Al-Mn-Fe-Si-based or Al-Fe-Si-based compound during casting. If it is less than 0.01%, it is necessary to use high purity metal, which increases costs. When it exceeds 0.30%, the crystallized matter increases and the cap moldability is deteriorated.

Ti: 0.005 to 0.05%;
Ti is an element that affects the improvement of formability by refining the ingot structure. If it is less than 0.005%, the effect cannot be obtained. If it exceeds 0.05%, an insoluble Al—Ti compound tends to appear as a surface defect in the final product.
In addition, when adding an Al-Ti-B intermediate alloy as an ingot structure | tissue refiner, B contains, but it is preferable to add B in 0.02% or less of range.

Next, the aluminum alloy plate has four locations (45 °, 45 ° in the rolling direction) with respect to the rolling direction among the ears generated in the opening portion of the drawn cup used for the ear rate test of the base plate or the blank plate. 135 °, 225 °, four points of 315 ° direction), and 0 °, 90 °, 180 ° , and the ear ear rate occurring at four positions 270 ° direction of 2.5% or less, and the rolling direction it is preferable 0 ° and ears ears rates occurring in two places in the 180 ° direction against the 2.0% or less (claim 3).

  When the ear rate of the four ears in the 45 ° direction exceeds 2.5%, bending of printed characters or the like at the skirt portion of the molded cap becomes noticeable in the 45 ° direction and is difficult to prevent. The smaller the ear ratio, that is, the lower limit is preferably 0%, but it is difficult due to the nature of the metal plate. Actually, an ear rate of 0.5% to 2.0% is more preferable.

  Further, even when the ear rate of the ears occurring at the four locations in the 0 °, 90 °, 180 °, and 270 ° directions exceeds 2.0%, the ear rate at the four locations in the 45 ° direction is 2.0%. As in the case of exceeding, bending of printed characters or the like becomes remarkable.

  Furthermore, even when the ear-ear ratio occurring at two locations in the 0 ° and 180 ° directions with respect to the rolling direction exceeds 2.0%, it is possible to prevent bending of printed characters and the like on the molded cap hem portion. It becomes difficult. In the case of drawing of an Al-low Mg alloy, ears in the directions of 0 ° and 180 ° are particularly likely to occur with respect to the rolling direction, and it is important to control the ears in this direction. And in order to suppress the bending of printed characters and the like more reliably, it is preferable to set the ear ratio of the ears generated at 0 ° and 180 ° with respect to the rolling direction to 1.5% or less.

  Here, the drawn cup is a cup-shaped test material obtained by drawing a blank cut out from the cap Al—Mg alloy plate under predetermined conditions. At the opening end of the throttle cup, the portion protruding in the axial direction is called an ear, and the most depressed portion between the ears is called a valley. The distance from the bottom of the squeeze cup to the tip of the ear is defined as the ear height, and the distance from the bottom of the squeeze cup to the tip of the valley is defined as the valley height. The ear rate can be calculated as follows.

<Ear rate of ears at 45 points in 45 ° direction>
45 ° ear height = A, 135 ° ear height = B, 225 ° ear height = C, 315 ° ear height = D,
Minimum valley height between 45 ° and 135 ° = E,
Minimum valley height between 135 ° and 225 ° = F,
Minimum valley height between 225 ° and 315 ° = G,
Minimum valley height between 315 ° and 45 ° = H,
Ear average: M45 = (A + B + C + D) / 4,
Average valley: V45 = (E + F + G + H) / 4
Ear rate = [(M45−V45) / {(M45 + V45) / 2}] × 100 (%)

<Ear rate of ears at 4 locations in 0 °, 90 °, 180 °, 270 ° direction>
0 ° ear height = A ′, 90 ° ear height = B ′, 180 ° ear height = C ′, 270 ° ear height = D ′, minimum valley height between 0 ° and 90 ° = E ',
Minimum valley height between 90 ° and 180 ° = F ′,
Minimum valley height between 180 ° and 270 ° = G ′,
Minimum valley height between 270 ° and 0 ° = H ′,
Ear average: M ′ = (A ′ + B ′ + C ′ + D ′) / 4
Average valley: V ′ = (E ′ + F ′ + G ′ + H ′) / 4
Ear rate = [(M′−V ′) / {(M ′ + V ′) / 2}] × 100 (%)

<Ear ratio of ears at two locations at 0 ° and 180 °>
Average height of cup = P (average height obtained by measuring the height of the open end at 1000 points),
0 ° ear height = Q, 180 ° ear height = R,
Ear average: S = (Q + R) / 2,
Ear rate = {(SP) / P} × 100 (%)

<Cup drawing molding conditions>
Using a die with a die diameter of 33.6 mm, a punch diameter of 33 mm, and a punch shoulder R of 1.5 mm, a cup blank was carried out with a drawing material blank diameter of 55 mm and a drawing ratio of 1.67.

Further, the aluminum alloy plate preferably has a thickness is 0.20～0.26Mm (claim 4).
That is, the thickness of the aluminum alloy plate for the wide-mouth bottle can cap affects the pressure resistance of the cap, which is the subject of the present invention. The thicker the plate, the greater the pressure resistance, but the thinner the plate is preferable from the viewpoint of resource saving. In the present invention, by increasing the strength as described above, it becomes possible to reduce the plate thickness while maintaining a predetermined pressure strength. Conventionally, a plate thickness of less than 0.25 mm has been difficult from the viewpoint of pressure resistance, but in the present invention, sufficient pressure resistance can be obtained even when a plate thickness of 0.20 mm or more and less than 0.25 mm is applied. It is. Further, in the case of 0.25 to 0.26 mm, it is possible to further increase the strength with respect to the demand for a high breakdown voltage. When the plate thickness is less than 0.20 mm, the current cap shape does not provide a predetermined pressure strength. However, when the cap shape is improved by technological advancement, the material of the present invention can be put to practical use. Conceivable.

Next, preferable production conditions for obtaining the aluminum alloy plate of the present invention will be described.
The basic manufacturing process is to homogenize and heat the ingot, then hot-roll to form a plate, and then anneal, cold-roll, anneal, and cold-roll sequentially to obtain the product thickness, and finally strength In order to stabilize the heat treatment, stabilization heat treatment is performed. In many cases, surface treatment such as degreasing and chemical conversion treatment is performed before or after the stabilization heat treatment.

  The said homogenization heat processing is the conditions which hold | maintain an ingot at the temperature of 450-550 degreeC for 1 to 24 hours. If the holding temperature is less than 450 ° C. or the holding time is less than 1 hour, the ear formation becomes unstable and control becomes difficult. When the holding temperature exceeds 550 ° C. or the holding time exceeds 24 hours, Mg easily diffuses on the surface, the Mg oxide layer on the surface becomes thick, and the amount of chamfering needs to be excessively increased, which is uneconomical.

Subsequently, for example, hot rolling, annealing, cold rolling, annealing, cold rolling, and stabilizing heat treatment are sequentially performed. In this step, a predetermined strength and ear rate can be obtained.
In the said annealing 1 and 2, it carries out on the conditions hold | maintained at the temperature of 300-550 degreeC. When the holding temperature is less than 300 ° C., a predetermined ear ratio cannot be obtained with the final plate, and the strength becomes too high and the moldability is poor. When the holding temperature exceeds 550 ° C., the surface tends to be oxidized, which is not preferable. The holding time is not particularly limited, but when annealing at a relatively high temperature such as rapid heating / cooling using a continuous annealing line or the like, holding is performed for 0 to 20 seconds, holding when annealing at a relatively low temperature using a batch annealing furnace. 30 minutes to 5 hours is appropriate.

  What is necessary is just to perform the cold rolling 2 after the said annealing 2 in 30 to 70% of range. When the rolling rate is less than 30%, it is difficult to obtain a predetermined strength, and it becomes difficult to obtain a predetermined ear rate. If the rolling rate exceeds 70%, the formability is lowered, the strength is too high and it is difficult to open the plug, and the rolling texture is developed so much that the ears in the 45 ° direction become large.

  The performance as a cap material is almost achieved with cold rolling, but in the case of an Al-Mg alloy, when the cold rolling is left at room temperature, a phenomenon in which the strength gradually decreases occurs. In order to prevent this and stabilize the strength, a heat treatment (stabilized heat treatment) for heating at a temperature of 100 to 300 ° C. for 30 minutes or more is necessary. If it is less than 100 ° C., the strength is not stable, and if it exceeds the upper limit of 300 ° C., softening increases and a predetermined strength cannot be obtained.

The contents of the present invention will be described with reference to specific examples, but the following shows one embodiment of the present invention and the present invention is not limited thereto.
Example 1
Aluminum alloy ingots containing the chemical components shown in Table 1 are ingoted by semi-continuous casting, and after the segregation layer on the surface is cut, homogenized heat treatment is maintained at 500 ° C. for 6 hours, and then removed from the homogenized heat treatment furnace. Hot rolling was started immediately. Hot rolling is finished at a sheet thickness of 3 mm, and after recrystallization is obtained by annealing, cold rolling is performed to a predetermined sheet thickness, and further intermediate annealing is performed to obtain a recrystallized structure. The specimens were cold-rolled to the product thickness at the cold working degree and subjected to stabilization heat treatment.

The following evaluation tests were performed using the obtained seven types of test materials E1 to E7. Some specimens were observed for material structure.
<Mechanical properties>
A tensile test was performed using a JIS No. 5 test piece.

<Ear rate>
Using a die with a die diameter of 33.6 mm, a punch diameter of 33 mm, and a punch shoulder R of 1.5 mm, a cup blank was carried out with a drawing material blank diameter of 55 mm and a drawing ratio of 1.67.
The ear rate is calculated based on the above-mentioned conditions, and the ear rate of ears at 45 locations in the 45 ° direction (A direction) or 4 locations at 0 °, 90 °, 180 °, and 270 ° directions (B The ear rate of the ears in the direction) and the ear rates of the ears at two locations in the 0 ° and 180 ° directions were measured.

<Crystal grain size>
The plate surface of the test material was electropolished and the crystal grains were observed with a polarizing microscope. The crystal grain size was determined from the comparative method using an ASTM card.

<Character bending>
10 characters are printed on the blank before drawing so that the character comes to a position 3 to 5 mm from the cap opening end, and a 28 mm diameter PP cap cup with a stricter drawing ratio than 38 mm is drawn, Character bending was visually observed and evaluated.
<Cap formability>
The appearance of the cap cup after molding was visually confirmed for the presence of defects such as cracks, wrinkles, and rough skin.

  Table 2 shows the evaluation results. The test materials E1 to E7 of this example have good results as cap materials for wide-mouth bottle can caps in all the evaluation items of mechanical properties, ear ratio, crystal grain size, letter bending, and cap moldability. Indicated.

(Comparative Example 1)
An aluminum alloy ingot having a component whose Mg content shown in Table 3 is outside the scope of the present invention was manufactured under the same conditions as in Example 1 to obtain specimens C1 and C2.

These evaluation results are shown in Table 4.
As can be seen from Table 4, the sample material C1 has an Mg amount and an Mn amount that are less than the lower limit of the present invention, so that high strength cannot be obtained, and it is not suitable for a product with high pressure resistance.
Since the amount of Mg exceeds the upper limit of the present invention, the sample material C2 is not suitable because the strength is too high and the cap is difficult to open.

Claims (4)

After painting and printing, the cup is molded into a cylindrical cup with a diameter of more than 28 mm, the ears of the cup are trimmed, the perforations are processed in the hem, and then the beverage container filled with contents is threaded An aluminum alloy plate for a wide-mouth bottle can cap to be wound,
Mg: more than 0.8% (weight%, the same applies hereinafter), less than 2.5%, and Mn: not less than 0.3% and less than 0.8%, and further Cu: 0.01 to 0.24% Cr: 0.01-0.05%, Zn: 0.01-0.25%, Si: 0.01-0.30%, Fe: 0.01-0.50%, Ti: 0.005 It contains one or more of ~ 0.05%, the balance has a chemical composition consisting of inevitable impurities and aluminum ,
The tensile strength of the base plate of the aluminum alloy plate is 200 to 300 MPa, the proof stress is 150 to 250 MPa,
And the tensile strength of the blank board which gave the heat processing hold | maintained for 10 minutes at the temperature of 200 degreeC with respect to the said base plate is 200-300 MPa, yield strength is 140-240 MPa, elongation is 5% or more, It is characterized by the above-mentioned. High-strength aluminum alloy plate for wide-mouth bottle can caps.   In Claim 1, Mg content is more than 1.3% and less than 2.2%, the tensile strength of the said base plate is 210-280MPa, proof stress is 160-250MPa, and the said baked board A high-strength aluminum alloy plate for a wide-mouth bottle can cap, characterized by having a tensile strength of 210 to 280 MPa, a proof stress of 150 to 240 MPa, and an elongation of 5% or more.   In Claim 1 or 2, out of the ear | edge which generate | occur | produces in the opening part of the draw cup used for the ear | edge rate test of the said base plate or the said unglazed board, four places of 45 degree direction with respect to a rolling direction, and 0 degree, 90 The ear rate of ears occurring at four locations in the directions of °, 180 °, and 270 ° is 2.5% or less, and the ear rate of ears occurring at two locations in the directions of 0 ° and 180 ° with respect to the rolling direction is 2. A high-strength aluminum alloy plate for a wide-mouth bottle can cap, characterized by being 0.0% or less.   The high-strength aluminum alloy plate for wide-mouth bottle can caps according to any one of claims 1 to 3, wherein the aluminum alloy plate has a thickness of 0.20 to 0.26 mm.