JP2011219870A - Aluminum alloy sheet for pp cap - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy sheet for a PP cap which can suppress a change of an earing ratio to be low even if recrystallization annealing is not performed, and also possesses proper strength.SOLUTION: The aluminum alloy sheet for the PP cap is an aluminum alloy sheet which includes Cu 0.3 mass% or less Cu, 0.2-0.5 mass% Mn, 0.2-0.6 mass% Mg, 0.1-0.3 mass% Si, and 0.2-0.7 mass% Fe, and the balance being Al and inevitable impurities where a crystal particle size on a sheet surface of this aluminum alloy sheet is equal to or smaller than 50 μm in a rolling parallel direction in parallel to a rolling direction, and equal to or smaller than 30 μm in a rolling vertical direction vertical to the rolling direction, the tensile strength of the aluminum alloy sheet is equal to or larger than 150 MPa, and the earing ratio computed by the predetermined equation from an ear height of a drawn cup in which the aluminum alloy sheet is drawn at a drawing ratio of 48% is 0% or more and less than +3%.

Description

  The present invention relates to an aluminum alloy plate for a PP (Pilfer Proof) cap used for a bottle-shaped packaging container made of metal or glass.

  The PP cap has a function to guarantee that the product is not opened until the product arrives at the consumer after the content is sealed, and can protect the content and prevent theft. It is widely used as a lid for containers such as drinks and drinks.

  For conventional PP caps, 3000, 5000, or 6000 series aluminum alloy sheets that have been tempered appropriately to be hardened or softened are cut into sheets of any size and printed with trademarks, letters, arrows, etc. Or, after coating for surface protection, punching to make a blank of a predetermined size and shape, forming a cup by drawing such a blank, opening the cup in the opening of the packaging container It is manufactured by press-fitting a rotating roll into the outer peripheral portion of the cup along the screw portion formed in the opening of the packaging container to form the screw portion of the PP cap.

As an aluminum alloy plate used for PP cap, what was manufactured by the manufacturing method of the aluminum alloy plate for PP caps described in patent document 1, for example can be used conveniently.
The manufacturing method of the aluminum alloy plate for PP cap is Cu: 0.03 to 0.30 wt%, Mn: 0.3 to 0.8 wt%, Mg: 0.2 to 0.5 wt%, Si: 0.1 to 0.4 wt% and Fe: 0.1 to 0.7 wt%, Cr: 0.4 wt% or less, Zn: 0.5 wt% or less, and Ti: 0.2 wt% Homogenization treatment for heat-treating an Al alloy ingot containing one or more elements selected from the group consisting of the following, with the balance being Al and inevitable impurities at a temperature of 570 to 610 ° C. for 1 hour or more 10 to 10 steps, a rolling step for hot rolling and cold rolling the Al alloy ingot after homogenization treatment to obtain a rolled plate, an annealing step for recrystallizing the rolled plate, and a rolled plate after annealing. A finish cold rolling process in which a product sheet is obtained by cold rolling at a processing rate of 30%; It is characterized in that it has a final annealing step of annealing the serial product plate at a temperature of 230 to 260 ° C..

  If the aluminum alloy plate for PP cap manufactured by such a manufacturing method is used, even if the pressure input of a rotary roll is enlarged, a crack will not occur in a screw part, it is excellent in unplugging property, and is usable. The mechanical properties that can be tolerated and the value of the ear rate were also excellent in that an appropriate PP cap could be manufactured.

Japanese Patent No. 2942172 (Claim 1, paragraphs 0009 to 0050)

Here, recent PP caps are required to have higher strength than before, and in order to meet such demand, the strength has been increased by increasing the rolling reduction of cold rolling.
However, when the strength is increased by such a method, the change in the ear rate tends to be large due to the high reduction rate, and this causes the trademark or the trademark applied to the PP cap when the blank is drawn into a cup. An arrow or the like sometimes deviated from a predetermined position.

Therefore, for the purpose of reducing the change in the ear rate, recrystallization annealing is usually performed after hot rolling at 350 to 550 ° C. for 0 second to 10 hours. However, when recrystallization annealing is performed, an oxide is generated. In some cases, a desired surface finish cannot be obtained or an edge mark may be generated by subsequent cold rolling.
In addition to recrystallization annealing, it is necessary to perform intermediate annealing and finishing annealing for strength adjustment and suppression of thermal softening deformation during sheet coating, which complicates the manufacturing process and hinders improvement in production efficiency.

  The present invention has been made in view of the above problems, and can provide an aluminum alloy plate for PP caps that can suppress a change in the ear rate low without performing recrystallization annealing and has an appropriate strength. provide.

  The aluminum alloy plate for PP cap according to the present invention that has solved the above problems is Cu: 0.3% by mass or less, Mn: 0.2-0.5% by mass, Mg: 0.2-0.6% by mass, An aluminum alloy plate containing Si: 0.1 to 0.3% by mass, Fe: 0.2 to 0.7% by mass, the balance being made of Al and inevitable impurities, The crystal grain size on the surface is 50 μm or less in the rolling parallel direction parallel to the rolling direction, 30 μm or less in the rolling vertical direction perpendicular to the rolling direction, and the tensile strength of this aluminum alloy sheet is 150 MPa or more. The ear ratio calculated from the following formula 1 is 0% or more and less than + 3% based on the height of the ear of the drawn cup in which the aluminum alloy plate is drawn at a drawing ratio of 48%.

  As described above, the aluminum alloy plate for PP cap of the present invention limits the composition of the aluminum alloy to a specific range and crystals in the rolling parallel direction and the rolling vertical direction over the entire width / length direction of the aluminum alloy plate. By limiting the particle size to a specific range, the ear rate can be stabilized without intermediate annealing. In addition, since the crystal grains could stabilize the recrystallized structure over the entire plate surface, it was possible to improve the molding quality and the productivity.

  According to the aluminum alloy plate for PP cap of the present invention, the change in the ear ratio can be suppressed to a low level without performing recrystallization annealing, and suitable strength is achieved. Therefore, when the PP cap is manufactured, the printed trademark or arrow does not deviate from a predetermined position. Moreover, since recrystallization annealing after hot rolling can be omitted and growth of the surface oxide film can be suppressed, productivity can be improved and a suitable surface form can be easily obtained.

It is a flowchart which shows the flow of the manufacturing method of the aluminum alloy plate for PP caps of this invention.

  Next, with reference to FIG. 1, the aluminum alloy plate for PP caps which concerns on this invention, and its manufacturing method are demonstrated in detail. In addition, FIG. 1 is a flowchart which shows the flow of the manufacturing method of the aluminum alloy plate for PP caps of this invention.

[Aluminum alloy plate for PP cap]
The aluminum alloy plate for PP cap of the present invention has Cu: 0.3 mass% or less, Mn: 0.2 to 0.5 mass%, Mg: 0.2 to 0.6 mass%, Si: 0.1 to 0.1 mass%. 0.3% by mass, Fe: 0.2 to 0.7% by mass, the balance being an aluminum alloy plate composed of Al and inevitable impurities, the crystal grain size on the surface of the aluminum alloy plate is The rolling parallel direction parallel to the rolling direction is 50 μm or less, and the rolling vertical direction perpendicular to the rolling direction is 30 μm or less.
Below, each alloy component contained in the aluminum alloy plate for PP caps concerning this invention and the reason which limited the crystal grain diameter in the plate | board surface of this aluminum alloy plate are demonstrated.

(Cu: 0.3% by mass or less)
Cu plays a role of increasing the strength of the aluminum alloy plate. However, when the content of Cu exceeds 0.3% by mass, the strength becomes too high, and the cap-clamping formability is lowered, and the unplugging property is also lowered.

(Mn: 0.2 to 0.5% by mass)
Mn plays a role of improving the strength of the aluminum alloy sheet and improving the crack propagation property by generating an intermetallic compound, that is, the bridge fracture property when the cap is formed and opened after winding. When the content of Mn is less than 0.2% by mass, it is difficult to ensure sufficient strength, and the intermetallic compound is insufficient, and the bridge breakability is lowered, so that the plug-openability is lowered. On the other hand, if the content of Mn exceeds 0.5% by mass, the strength becomes too high, the cap winding formability is lowered, and it causes a plug opening failure.

(Mg: 0.2-0.6% by mass)
Mg plays the role which improves intensity | strength improvement and work hardenability like Cu. That is, the addition of Mg is effective for accumulating processing strain due to recrystallization. If the Mg content is less than 0.2% by mass, sufficient strength cannot be ensured. On the other hand, if the Mg content exceeds 0.6% by mass, the strength becomes too high, the cap winding formability deteriorates, and it causes a plug opening failure.

(Si: 0.1 to 0.3% by mass)
When Si is added appropriately, drawability can be improved, and it plays a role of adjusting the ear ratio and also affects recrystallization behavior and strength characteristics. If the Si content is less than 0.1% by mass, the effect of improving drawability cannot be exhibited, and the ear rate tends to become unstable. On the other hand, when the content of Si exceeds 0.3% by mass, cap drawability and cap winding formability deteriorate.

(Fe: 0.2-0.7 mass%)
Fe combines with Al, Mn and Si to form an intermetallic compound, improves crack propagation, that is, bridge breakability when opening after cap molding and tightening, and is effective in refining crystal grains At the same time, it plays the role of adjusting the ear rate according to the state of solute iron. If the Fe content is less than 0.2% by mass, the crystal grains are likely to be coarsened, it becomes difficult to adjust the appropriate ear ratio, and the pluggability is also lowered. On the other hand, if the Fe content exceeds 0.7% by mass, not only does a rough intermetallic compound form and the cap drawability and cap tightening formability deteriorate, but the ear growth increases and the ear rate increases. Adjustment becomes difficult.

(Inevitable impurities)
Inevitable impurities include Cr, Zn, Ti, Zr, etc., but these elements do not impede the effects of the present invention as long as the content is 0.05% by mass or less and are allowed. .

(The crystal grain size on the surface of the aluminum alloy sheet is 50 μm or less in the rolling parallel direction parallel to the rolling direction over the entire width / length direction of the aluminum alloy sheet, and 30 μm or less in the rolling vertical direction perpendicular to the rolling direction. )
In the present invention, it is important to control the crystal grain size. The crystal grain size at the plate surface of the aluminum alloy plate directly contributes to formability and indirectly contributes to the ear rate due to recrystallization behavior. The crystal grain size was measured based on the method of JIS H0501.
When the crystal grain size in the rolling parallel direction of the aluminum alloy plate exceeds 50 μm in the rolling parallel direction parallel to the rolling direction, or the crystal grain size exceeds 30 μm in the rolling vertical direction perpendicular to the rolling direction, PP In deep drawing at the time of making a cap, it breaks or the surface of the processed surface becomes rough.

[Method for producing aluminum alloy plate for PP cap]
Next, the manufacturing method of the aluminum alloy plate for PP caps of this invention is demonstrated, referring the flowchart of FIG.
As shown in FIG. 1, the manufacturing method of the aluminum alloy plate for PP caps of the present invention uses a pre-homogenization heat treatment step S1 using the aluminum alloy slab having the specific composition described above, Each step including a cutting step S2, a homogenizing heat treatment step S3, a hot rolling step S4, a cold rolling step S5, an intermediate annealing step S6, a finishing cold rolling step S7, and a finishing annealing step S8. An aluminum alloy plate for PP cap can be manufactured by carrying out the process contents of.
Below, the process content of each process in the manufacturing method of the aluminum alloy plate for PP caps which concerns on this invention is demonstrated in detail.

(Preliminary homogenization heat treatment process)
The preliminary homogenization heat treatment step S1 is performed in order to appropriately grow precipitates necessary for homogenization and recrystallization of the cast segregation component of the aluminum alloy sheet to be manufactured. Therefore, in this preliminary homogenization heat treatment step S1, preliminary homogenization heat treatment is performed on the aluminum alloy slab having the above-described composition under the conditions of holding temperature: 550 to 630 ° C. and holding time: 1 to 10 hours.
Here, if the treatment temperature of the preliminary homogenization heat treatment is less than 550 ° C., the formation of intermetallic compounds becomes insufficient, which adversely affects recrystallization and cap opening properties. Further, if the pre-homogenization heat treatment time is less than 1 hour, sufficient homogenization cannot be performed, resulting in large variations in characteristics.
On the other hand, if the treatment temperature of the preliminary homogenization heat treatment exceeds 630 ° C., Mg causes burning, which causes a problem in product surface quality. Also, if the pre-homogenization heat treatment time exceeds 10 hours, the intermetallic compound grows over the precipitate size and becomes coarse due to recrystallization, resulting in variations in crystal grains and ear ratios, and the productivity is hindered. It is.

(Chamfering process)
The chamfering step S2 is performed to remove segregation generated on the surface of the slab subjected to the preliminary homogenization heat treatment. The amount of chamfering on the slab surface in the chamfering step S2 varies depending on the component composition of the aluminum alloy, the processing conditions of the preliminary homogenization heat treatment, and the like, and it is preferable to set appropriate conditions in advance through experiments or the like.

(Homogenization heat treatment process)
The homogenizing heat treatment step S3 is performed for heating to the hot rolling temperature. Therefore, in this homogenization heat treatment step S3, the homogenization heat treatment is performed on the slab whose surface has been chamfered in the above-described chamfering step S2 under the conditions of holding temperature: 450 to 530 ° C. and holding time: 1 to 10 hours. .
Here, when the processing temperature of the homogenization heat treatment is less than 450 ° C., the rolling load increases, and the number of hot rolling passes must be increased, which is economically disadvantageous. Further, if the treatment time for the homogenization heat treatment is less than 1 hour, it is difficult to make the temperature uniform throughout the entire ingot, and the characteristics are likely to vary.
On the other hand, when the processing temperature of the homogenization heat treatment exceeds 530 ° C., a surface oxide film grows and adversely affects the product surface quality. Further, even if the treatment time for the homogenization heat treatment is carried out for 10 hours or more, the effect remains unchanged, and the productivity is lowered, which is not suitable.

(Hot rolling process)
The hot rolling step S4 is performed for reducing the sheet thickness to the cold rolling thickness and for controlling to the optimum internal structure. The hot rolling step S4 is usually a hot rough rolling in which the plate thickness is reduced to a predetermined thickness by a reverse rolling mill, and a hot hot rolling at a high pressure using a tandem rolling mill to a hot coil thickness at once after hot rough rolling. It is divided into finish rolling. In the hot rough rolling, control is performed in consideration of the structure change in the middle stage so that the final structure becomes an appropriate recrystallization state.
In this hot rolling step S4, a hot rolled sheet is obtained by performing hot rolling on the slab obtained in the above-described homogenizing heat treatment step S3 at a rolling end temperature of 300 to 380 ° C.
In addition, by carrying out the above-mentioned preliminary homogenization heat treatment step S1, precipitates of an appropriate size contributing to recrystallization are dispersed throughout the slab, so hot rolling is performed over the entire plate surface. The recrystallized structure after the completion of step S4 becomes stable.
If the rolling end temperature in the hot rolling step S4 is less than 300 ° C, a sufficient recrystallization state cannot be obtained. On the other hand, when the rolling end temperature in the hot rolling step S exceeds 380 ° C., the surface quality deteriorates.

(Cold rolling process)
Cold rolling process S5 is performed in order to reduce plate | board thickness to intermediate annealing thickness. Therefore, this cold rolling process S5 performs cold rolling on the hot rolled sheet obtained in the above-described hot rolling process S4 under the condition of a rolling reduction: 50 to 90%, thereby cold rolling sheet. Get.
Here, if the rolling reduction of cold rolling is less than 50%, the strain introduced by cold rolling is insufficient, and coarse recrystallization is likely to occur during intermediate annealing, which is not suitable. On the other hand, if the rolling reduction of cold rolling exceeds 90%, the number of cold rolling passes up to the intermediate annealing thickness increases, and the productivity decreases.

(Intermediate annealing process)
The intermediate annealing step S6 is performed for the purpose of refining crystal grains by recrystallization and maintaining the strength after baking coating by solid solution hardening. Therefore, this intermediate annealing step S6 is carried out under the conditions of temperature rising rate: 10 ° C./second or more, holding temperature: 400 to 530 ° C., holding time: 0 to 10 seconds, temperature decreasing rate: 10 ° C./second or more. Intermediate annealing is performed on the cold rolled sheet obtained in the cold rolling step S5.
Here, if the rate of temperature rise is less than 10 ° C./second, crystal grains are likely to grow and become coarse.
Further, if the holding temperature is less than 400 ° C., thermal energy necessary for recrystallization cannot be obtained, and unrecrystallized grains may remain even after intermediate annealing.
On the other hand, if the holding temperature exceeds 530 ° C., the risk of causing burning increases.
In addition, it is sufficient if the cold rolled sheet can be processed at the above holding temperature, and the holding time is not particularly limited, but is preferably within 10 seconds. Even if the holding time exceeds 10 seconds, the effect on the solid solution hardening does not change, and the processing time is prolonged and the productivity is lowered.
And when temperature-fall rate is less than 10 degree-C / sec, since precipitation arises during temperature-fall, sufficient solid solution hardening cannot be obtained.

(Finish cold rolling process)
The finish cold rolling step S7 is performed to reduce the sheet thickness to the product thickness and to adjust the ear rate and strength. Therefore, the finish cold rolling step S7 is performed by performing the finish cold rolling on the cold rolled sheet subjected to the intermediate annealing in the above-described intermediate annealing step S6 under the condition of a reduction ratio of 10 to 60%. A finished cold rolled sheet is obtained.
Here, when the reduction ratio of finish cold rolling is less than 10%, sufficient strength cannot be obtained.
On the other hand, when the reduction ratio of finish cold rolling exceeds 60%, the rolling texture develops and the ear ratio increases.

(Finish annealing process)
The finish annealing step S8 is performed for the purpose of adjusting the strength of the aluminum alloy plate for PP cap and preventing thermal deformation of the plate in the coating baking furnace in the coating / printing process performed after the production of the aluminum alloy plate for PP cap. The aluminum alloy plate for PP cap is usually cut in the longitudinal direction after being manufactured in the form of a coil, and the coating and printing process is performed in the form of a sheet.
In the painting and printing process, a heat treatment for baking (a temperature of about 150 to 200 ° C. for 20 minutes × multiple times) is performed, but at that temperature, the aluminum alloy plate for PP cap undergoes thermal softening and warpage occurs. Then, there is a risk of causing poor coating appearance by contacting the front and rear plates in the baking furnace. Finish annealing is a necessary process from the viewpoint of preventing deformation of the plate due to thermal softening.

Therefore, this finish annealing process S8 carries out finish annealing with respect to the finish cold-rolled sheet obtained by finishing cold rolling process S7 mentioned above on the conditions of holding temperature: 200-260 degreeC and holding time: 1-4 hours. By performing, the aluminum alloy plate for PP caps of this invention is manufactured.
Here, when the holding temperature of finish annealing is less than 200 ° C., a sufficiently softened state cannot be obtained, and there is a risk of causing plate warpage in the sheet printing process.
On the other hand, when the holding temperature of finish annealing exceeds 260 ° C., the strength is excessively lowered and the metal structure may be completely softened.
Moreover, when the holding time of finish annealing is less than 1 hour, the metal structure of a homogeneous state cannot be obtained over the full length of the aluminum alloy plate for PP caps.
On the other hand, even if the holding time of finish annealing exceeds 4 hours, the degree of softness does not change. On the contrary, the surface oxide film grows, and the surface quality may be deteriorated.

  In addition, the aluminum alloy plate for PP caps of the present invention is usually subjected to a finish annealing treatment and may be subjected to distortion correction treatment, degreasing, etching treatment, and base conversion treatment for coating as necessary. Not too long.

  Next, the aluminum alloy plate for PP cap of this invention and its manufacturing method are demonstrated concretely comparing the Example which satisfy | fills the requirements of this invention, and the comparative example which does not satisfy the requirements of this invention.

First, the component composition of the aluminum alloy plate for PP caps of the present invention was examined.
Aluminum alloy slabs having component compositions as shown in Examples 1 to 5 and Comparative Examples 1 to 9 in Table 1 were prepared, and the slabs were preliminarily maintained under conditions of holding temperature: 600 ° C. and holding time: 4 hours. Homogenization heat treatment was performed, and the surface of the slab subjected to the preliminary homogenization heat treatment was chamfered by 8 mm. And after performing the homogenization heat processing of holding temperature: 500 degreeC and holding time: 2 hours, the said slab is hot-rolled by carrying out hot rolling of rolling completion temperature: 340 degreeC, and carrying out the hot rolling sheet | seat. did. Then, the hot-rolled sheet is subjected to cold rolling at a reduction rate of 80% to obtain a cold-rolled sheet, and then the cold-rolled sheet is heated at a rate of temperature increase of 20 ° C./second or more, and a holding temperature: Intermediate annealing was performed at 450 ° C., holding time: 1 second, and cooling rate: 20 ° C./second or more. Next, the cold-rolled sheet subjected to the intermediate annealing is subjected to finish cold rolling at a reduction ratio of 50% to obtain a finished cold-rolled sheet, and the finished cold-rolled sheet is maintained at a holding temperature of 220 ° C. and a holding time. : The aluminum alloy plate provided with the component composition shown in Examples 1-5 and Comparative Examples 1-9 was manufactured by finishing annealing in 3 hours. In addition, the underline in Table 1 indicates that the requirements of the present invention are not satisfied.

  As shown in Table 1, Examples 1 to 5 all satisfy the requirements for the component composition defined in the present invention. On the other hand, Comparative Examples 1-9 do not satisfy any of the component composition requirements defined in the present invention.

Specifically, in Comparative Example 1, the Cu content exceeds the upper limit defined in the present invention.
In Comparative Example 2, the Mn content is less than the lower limit defined in the present invention, and in Comparative Example 3, the Mn content exceeds the upper limit defined in the present invention.
In Comparative Example 4, the Mg content is less than the lower limit defined in the present invention, and in Comparative Example 5, the Mg content exceeds the upper limit defined in the present invention.
In Comparative Example 6, the Si content is less than the lower limit defined in the present invention, and in Comparative Example 7, the Si content exceeds the upper limit defined in the present invention.
In Comparative Example 8, the Fe content is less than the lower limit defined in the present invention, and in Comparative Example 9, the Fe content exceeds the upper limit defined in the present invention.

  And about the obtained aluminum alloy plate of Examples 1-5 and Comparative Examples 1-9, (a) Crystal grain size in the rolling parallel direction on the plate surface (shown as “rolling parallel direction” in Table 2) and rolling vertical Evaluation was made on the crystal grain size in the direction (shown as “rolling vertical direction” in Table 2), (b) tensile test, (c) ear ratio, and (d) cap property evaluation. In addition, (d) Cap characteristic evaluation evaluated three items, (d-1) cap drawability, (d-2) cap winding property, and (d-3) cap openability.

(A) Crystal grain size in the rolling parallel direction on the plate surface and crystal grain size in the rolling vertical direction Crystal grain size in the rolling parallel direction on the plate surface of the aluminum alloy plates of Examples 1 to 5 and Comparative Examples 1 to 9 and rolling perpendicular The crystal grain size in the direction was measured based on the method of JIS H0501. That is, the aluminum alloy plate was polished to a mirror finish, the surface was etched, and the metal structure was observed and photographed with a metal microscope having a magnification of 100 times. At this time, a line segment of a known length (for example, 1 mm) is drawn in a direction parallel and perpendicular to the rolling direction, and the length of the line segment is divided by the number of crystal grains cut by the line segment, The crystal grain width per crystal grain was determined (cutting method). The same measurement was repeated at different locations (5 locations), and the average value was taken as the average crystal grain size in each direction. Those having a crystal grain size of 50 μm or less in the rolling parallel direction on the plate surface were evaluated as suitable, and those exceeding 50 μm were evaluated as inappropriate. Those having a crystal grain size of 30 μm or less in the vertical direction of rolling on the plate surface were evaluated as suitable, and those exceeding 30 μm were evaluated as inappropriate.

(B) Tensile test First, No. 5 test pieces defined in JIS Z 2201 were prepared from the aluminum alloy plates of Examples 1 to 5 and Comparative Examples 1 to 9.
And the tension test was done based on the metal material tension test method prescribed | regulated to JISZ2241 using this test piece. The tensile strength of 150 MPa or higher was evaluated as suitable based on the increase in the strength of the top surface and the improvement in internal pressure resistance, which are now required for PP caps.

(C) Ear rate The ear rate is a blank with a diameter of 40 mm made from the aluminum alloy plates of Examples 1 to 5 and Comparative Examples 1 to 9, and is drawn with a punch with a diameter of 76.9 mm (drawing rate is 48%). It was calculated from the ear height of the squeezed cup. That is, the average difference between the eight peaks and valleys that normally occur is divided by the average height of the cup (see the following formula 2). The 90-degree ear (mountain) is a minus sign and the 45-degree ear is a plus sign. In the present invention, it was evaluated that the ear rate of 0% or more and less than + 3% is suitable for use as a PP cap. In addition, when the ear ratio exceeds the above range, there is a strong concern that the side face of the PP cap is bent when the PP cap is manufactured by drawing after printing on a blank, which is not preferable.

In the evaluation of the following (d-1), (d-2), and (d-3) among the cap characteristic evaluations, a conventional chemical conversion treatment (phosphorus) is applied to the aluminum alloy plate for PP caps produced by the above production method. Acid chromate treatment) to achieve a coating amount of about 10 mg / m ^{2 in} terms of Cr, and then use a commercially available PP cap paint in accordance with a conventional method to apply the size coat and top coat of the inner and outer surfaces to each paint. The coating was baked in a BOX oven in an optimum baking temperature range (150 to 190 ° C. × 15 minutes). For the printing and top coat, clear paints such as polyester and epoxy phenol containing no pigment were used in order to facilitate observation of the molded state.

(D-1) Cap drawability The cap drawability was evaluated for capshell molding of a conventional 28-diameter PP cap. The cap size was an inner diameter of φ28 mm and the height was 17 mm. This was molded from a blank having a size of 55 mm by one drawing.
If the crystal grain size is large, the strength is excessive, or the ear rate is excessive, cracks or missing circles may occur during drawing.
Evaluated as “○” when cap shell molding was successful, “△” when chipping or rough surface due to draw molding occurred, “X” when molding was not possible due to cracking or breaking did.

(D-2) Cap wrapping formability Evaluation of the wrapping property of the cap is an extremely important characteristic for maintaining the sealing property and the opening property. After the cap shell was formed, knurling was performed on the side wall near the top surface of the cap by a conventional method, and perforation processing and score processing were performed on the side wall near the opening, followed by mounting a resin mold on the inner surface. After that, the glass bottle of a size suitable for the cap shell was subjected to winding molding using a dedicated winding machine.
At this time, when the crystal grain size is large or the strength is excessive, roughening of the thread portion may occur when the rotary roll is pressed. On the other hand, if the strength is excessive, there is a risk that the screw will not be fully inserted and the sealing will be incomplete, or the screw portion will be cracked.
When the cap is tightened, the thread depth can be sufficiently secured and the sealability can be secured with “○”, and the thread with rough skin is “△”. A case where the thread portion was incomplete or a crack occurred in the screw portion, or a case where the perforation was broken by roll press-fitting at the time of winding was evaluated as “x”.

(D-3) Cap openability The cap openability was measured after tightening using a torque meter. The opening torque is usually evaluated in three stages. In other words, the torque that causes the cap and the bottle to slide relative to each other (first torque), the perforation breaking torque (second torque), and the ring detachment torque (third torque) due to score breakage are maximum values during the opening process. As measured and evaluated.
Of these, the second torque is particularly important when the perforation breaks, which are affected by the cap-clamping formability of the cap, and requires screw formability and appropriate breaking characteristics of the material. The appropriate value of the second torque varies depending on the application, but any consumer cannot easily open it if it exceeds 1 Nm.
“○” when the second torque is 1 Nm or less with good opening behavior, and the cap is not able to open due to insufficient thread forming depth, or the second torque exceeds 1 Nm Evaluated as “x”. In addition, when evaluation of "x" was obtained by cap winding formability, since evaluation of cap opening ability cannot be performed, this evaluation was not performed ("-").

  Table 2 shows the evaluation results of the items (a) to (d) described above. In Table 2, “o” indicates that the overall evaluation as a PP cap by the evaluations (a) to (d) was good, and “x” indicates that the overall evaluation was poor.

As shown in Table 1 and Table 2, since Examples 1 to 5 all satisfy the requirements of the present invention, good evaluation results could be obtained for the items (a) to (d). .
On the other hand, Comparative Examples 1 to 9 did not satisfy any of the requirements defined in the present invention, and therefore, good evaluation results could not be obtained in any of the items (a) to (d).

Specifically, in Comparative Example 1, since the Cu content exceeds the upper limit defined in the present invention, the results of unsatisfactory cap winding and cap opening properties were obtained.
In Comparative Example 2, the content of Mn was less than the lower limit specified in the present invention, so that the strength and the ear ratio were not preferable.
In Comparative Example 3, the content of Mn exceeded the upper limit defined in the present invention, so that the results of unsatisfactory cap winding and cap opening were obtained.
In Comparative Example 4, since the Mg content was less than the lower limit defined in the present invention, the crystal grain size and strength in the rolling parallel direction on the plate surface were undesirable.
In Comparative Example 5, since the Mg content exceeds the upper limit defined in the present invention, the crystal grain size in the rolling parallel direction of the plate surface, the cap winding formability, and the cap opening performance are unfavorable results. It was.
In Comparative Example 6, since the Si content was less than the lower limit specified in the present invention, the cap drawability was not preferable.
In Comparative Example 7, since the Si content exceeds the upper limit defined in the present invention, the ear ratio, cap drawing formability, and cap winding formability were not preferable.
In Comparative Example 8, since the Fe content is less than the lower limit specified in the present invention, the crystal grain size in the rolling flat direction on the plate surface, the crystal grain size in the rolling vertical direction on the plate surface, the ear ratio, cap drawing The results were unfavorable with respect to the properties and cap-clamping formability.
In Comparative Example 9, since the Fe content exceeded the upper limit defined in the present invention, unfavorable results were obtained with respect to the ear ratio, cap drawing formability, and cap tightening formability.

  Next, using the aluminum alloy slab having the component composition of Example 3 for which good evaluation results could be obtained, the contents of each step were performed under the conditions shown in Table 3 to produce an aluminum alloy plate for PP cap. did.

As shown in Table 3, Comparative Examples 10 to 30 do not satisfy any of the requirements in the method for producing the aluminum alloy plate for PP cap of the present invention.
Specifically, in Comparative Example 10 or Comparative Example 11, the treatment temperature of the preliminary homogenization heat treatment (indicated as “preliminary soaking” in Table 3) deviates from the upper limit value or the lower limit value defined in the present invention.
In Comparative Example 12 or Comparative Example 13, the pre-homogenization heat treatment time deviates from the upper limit value or the lower limit value defined in the present invention.
In Comparative Example 14 or Comparative Example 15, the treatment temperature of the homogenization heat treatment is outside the upper limit value or the lower limit value defined in the present invention.
In Comparative Example 16 or Comparative Example 17, the processing time of the homogenization heat treatment is outside the upper limit value or the lower limit value defined in the present invention.
In Comparative Example 18 or Comparative Example 19, the rolling end temperature of hot rolling (shown as “hot rolling end temperature” in Table 3) deviates from the upper limit value or the lower limit value defined in the present invention.
In Comparative Example 20 or Comparative Example 21, the rolling reduction of cold rolling (shown as “cold rolling ratio” in Table 3) deviates from the upper limit value or the lower limit value specified in the present invention.
In Comparative Example 22 or Comparative Example 23, the holding temperature of the intermediate annealing (shown as “medium annealing” in Table 3) deviates from the upper limit value or the lower limit value defined in the present invention.
In Comparative Example 24, the holding time of the intermediate annealing is out of the upper limit defined in the present invention.
In Comparative Example 25, the temperature increase rate of the intermediate annealing is outside the lower limit value defined in the present invention.
In Comparative Example 26, the temperature decrease rate of the intermediate annealing is outside the lower limit value defined in the present invention.
In Comparative Example 27 or Comparative Example 28, the reduction ratio of finish cold rolling (indicated as “finishing cold rolling ratio” in Table 3) deviates from the lower limit value or the upper limit value defined in the present invention.
In Comparative Example 29 or Comparative Example 30, the finish annealing holding temperature (indicated as “finish annealing temperature” in Table 3) deviates from the lower limit value or the upper limit value defined in the present invention.
Note that the effect of holding time for finish annealing affects the variation within the lot in coil processing and the material surface oxide film, and is not directly related to the cap characteristics that are being evaluated this time. Time was not evaluated.

  When the aluminum alloy plate for PP cap was manufactured under each condition shown in Table 3, the case where the aluminum alloy plate for PP cap could be manufactured without any problem without considering the characteristic evaluation was evaluated as “◯”. Moreover, although it can manufacture without a problem, the case where productivity fell remarkably was evaluated as "(triangle | delta)". And the case where there was a problem in manufacture of the aluminum alloy plate for PP caps by the case where it cannot manufacture or surface quality abnormality etc. was evaluated as "x". Such evaluation is also shown in Table 3.

In addition, since the examples of “×” and “Δ” in the evaluation of manufacturability do not meet the gist of the present invention, the characteristic evaluation shown in Table 4 was not performed. Examples corresponding to such an example include Comparative Examples 10, 12, 14 to 16, 18, 20, 22, 24, and 29.
In other words, the same characteristic evaluation as described above was performed only for an example in which an aluminum alloy plate for PP cap can be produced without problems and the evaluation of manufacturability is “◯”.

About Example 3 manufactured on the conditions shown in Table 3, and the example in which the manufacture availability in Table 3 was evaluated as “◯”, (a) the crystal grain size in the rolling parallel direction of the plate surface and Evaluation was made on each item of crystal grain size in the vertical direction of rolling, (b) tensile test, (c) ear ratio, and (d) cap property evaluation. Table 4 shows the evaluation results of the items (a) to (d).
In addition, when evaluation of "x" was obtained by cap drawability, since evaluation of cap winding formability and evaluation of cap openability cannot be performed, these evaluations were not performed (" − ”).

As shown in Table 3 and Table 4, since Example 3 satisfied the requirements of the present invention, good evaluation results could be obtained for the items (a) to (d).
On the other hand, Comparative Examples 11 to 30 do not satisfy any of the requirements defined in the present invention, so that a good evaluation result is obtained in any of the items of surface quality, productivity, and (a) to (d). I could not.

In Comparative Example 11, the treatment temperature of the preliminary homogenization heat treatment is outside the lower limit specified in the present invention, so the crystal grain size in the rolling parallel direction on the plate surface, the crystal grain size in the rolling vertical direction on the plate surface, and the ear The rate resulted in an unfavorable result. Further, the cap drawability and the cap tightening moldability were not preferable.
In Comparative Example 13, since the processing time of the pre-homogenization heat treatment is outside the lower limit specified in the present invention, the crystal grain size in the rolling parallel direction on the plate surface, cap drawing formability, and cap winding formability are preferable. No results.
In Comparative Example 17, the processing time of the homogenization heat treatment was out of the lower limit specified in the present invention, and the ear rate was not preferable.
In Comparative Example 19, the rolling end temperature of the hot rolling is outside the lower limit defined in the present invention, so that unrecrystallized grains remain, and the ear ratio and cap drawability are unfavorable. became.
In Comparative Example 21, the rolling reduction of the cold rolling is out of the lower limit defined in the present invention, so the crystal grain size in the rolling parallel direction on the plate surface, the crystal grain size in the rolling vertical direction on the plate surface, and the ear rate Resulted in an undesirable result. Further, the cap drawability and the cap tightening moldability were not preferable.
In Comparative Example 23, since the holding temperature of the intermediate annealing is out of the lower limit specified in the present invention, unrecrystallized grains are not left, and the ear rate and cap drawability are unfavorable. .
In Comparative Example 25, the temperature increase rate of the intermediate annealing was out of the lower limit defined in the present invention, so that the crystal grain size and the edge ratio in the rolling parallel direction on the plate surface were not preferable. Further, the cap drawability was unfavorable.
In Comparative Example 26, the temperature decrease rate of the intermediate annealing was out of the lower limit value defined in the present invention, so the strength was low and the result was not preferable.
In Comparative Example 27, the reduction ratio of the finish cold rolling was out of the lower limit value defined in the present invention, so that the strength and the ear ratio were not preferable. Further, the cap drawability was unfavorable.
In Comparative Example 28, the reduction ratio of the finish cold rolling was outside the upper limit defined in the present invention, so that the crystal grain size and the edge ratio in the rolling parallel direction on the plate surface were not preferable. In addition, cap drawing formability, cap roll-tightening formability, and cap openability were unfavorable results.
In Comparative Example 30, since the holding temperature of the finish annealing is outside the upper limit specified in the present invention, the crystal grain size in the rolling parallel direction on the plate surface, the crystal grain size in the rolling vertical direction on the plate surface, and the strength are preferable. No results.

  As mentioned above, although the aluminum alloy plate for PP caps of this invention and its manufacturing method were concretely demonstrated by the best embodiment and Example of this invention, the content of this invention is limited to these description However, it goes without saying that various changes and modifications can be made without departing from the spirit of the present invention.

  For example, for the purpose of obtaining an effect such as strength improvement, an element such as Cr can be contained within a range not impairing the effect of the present invention.

S1 Preliminary homogenization heat treatment process S2 Facing process S3 Homogenization heat treatment process S4 Hot rolling process S5 Cold rolling process S6 Intermediate annealing process S7 Finish cold rolling process S8 Finish annealing process

Claims (1)

Cu: 0.3 mass% or less, Mn: 0.2-0.5 mass%, Mg: 0.2-0.6 mass%, Si: 0.1-0.3 mass%, Fe: 0.2 An aluminum alloy plate comprising ~ 0.7 mass%, the balance being composed of Al and inevitable impurities,
The crystal grain size on the surface of the aluminum alloy plate is 50 μm or less in the rolling parallel direction parallel to the rolling direction, and 30 μm or less in the rolling vertical direction perpendicular to the rolling direction,
The tensile strength of this aluminum alloy plate is 150 MPa or more,
An aluminum alloy plate for PP caps characterized in that the ear ratio calculated from the following formula 1 is 0% or more and less than + 3% based on the height of the ear of the drawn cup obtained by squeezing the aluminum alloy plate with a drawing ratio of 48%.

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