JP4846457B2 - Manufacturing method of aluminum alloy plate for caps with excellent bending workability - Google Patents

Description

The present invention relates to a method for producing an aluminum alloy plate for a cap suitable for a wide mouth PP (pillar proof) cap.

  In recent years, as caps made of aluminum alloys such as bottle cans, PP caps that can be re-sealed after being opened once and that can be easily identified once opened have been widely used. . As a method of manufacturing this type of PP cap, generally, an aluminum alloy plate that has been painted and letter-printed is drawn into a cup shape, and then the opening end is trimmed to further facilitate the opening of the skirt. It is usual to make a perforation and to form a screw groove in the body part. In such a PP cap, it is usual to make it possible to easily identify the presence or absence of the opening history once it is opened by forming the perforations across the printed characters. .

  By the way, as an aluminum alloy for this type of PP cap, JIS A1100 alloy and A3105 alloy, which are generally excellent in formability, have been used conventionally. High-strength Al—Mg alloys have begun to be used to compensate for the decrease in strength. As such a high-strength Al—Mg alloy for PP caps, for example, those shown in Patent Document 1, Patent Document 2, or Patent Document 3 have been proposed. On the other hand, the present inventors have already proposed the one shown in Patent Document 4 as a relatively low strength Al-Mg alloy for caps.

JP 2004-353079 A JP 2004-353080 A JP 2003-328062 A JP 2006-45638 A

  The aluminum alloy plate for caps of Patent Document 1 has a high strength of 215 to 270 MPa in tensile strength, and the aluminum alloy plate for caps of Patent Literature 2 has a high strength of 215 to 265 MPa in the same manner. However, when the material is strengthened in this way, it is effective for improving the strength of the top surface, but the bending workability of the material is reduced, and severe processing is added like the threaded part after drawing. The problem that the adhesiveness of a coating film falls in a location arises. If the adhesion of the coating film is reduced in this manner, the identification function of the important opening history in the PP cap may be impaired due to the peeling of the coating film. Therefore, the PP cap has excellent bending workability. Therefore, it is strongly desired that the adhesion of the coating film is good. However, such a request could not be satisfactorily satisfied with the aluminum alloy plate for caps of Patent Documents 1 and 2.

  In addition, the Al-Mg alloy plate for caps of Patent Document 3 also has the same problem of deterioration of coating film adhesion as described above because sufficient consideration is not given to bending workability as in Patent Documents 1 and 2. In addition, as a manufacturing method thereof, it is necessary to increase the temperature of the hot rolling in order to make the hot rolled plate into a recrystallized structure, and therefore, the surface quality is likely to cause a problem.

  Furthermore, the aluminum alloy plate for caps of Patent Document 4 aims at a comparatively low strength of 179 to 201 MPa in the embodiment, and the manufacturing method thereof is as follows. Since the recrystallization rate is 80% or more, a problem is likely to occur in the surface quality as in the case of Patent Document 3, and sufficient consideration has not been given to the ear rate. That is, when the aluminum alloy plate for caps has a high ear rate, there is a strong possibility that the characters printed in advance will be bent when drawing into a cup shape. However, no positive consideration is given to the aluminum alloy for caps of Patent Document 4 in this regard, and it has been difficult to reliably and stably prevent bending of printed characters on the caps.

This invention was made against the background described above, and as an aluminum alloy plate mainly used for wide-mouth PP caps, it has excellent bending workability, and as a result, has excellent coating film adhesion in parts to which severe processing is applied. Furthermore, it is an object of the present invention to provide a method for producing an aluminum alloy plate for a cap that is excellent in surface quality, has a high ear rate, does not easily bend printed characters, and has a good opening performance. To do.

As a result of intensive experiments and examinations to solve the above-mentioned problems, the present inventors appropriately controlled the end temperature of hot rolling, and obtained a hot rolled sheet having a completely non-recrystallized structure after hot rolling. In addition, by appropriately regulating the conditions of subsequent cold rolling, intermediate annealing, and finish cold rolling, thereby obtaining an aluminum alloy plate having appropriate strength and appropriate ear ratio, aluminum for PP cap It has been found that the above-mentioned problems can be solved as a method for producing an alloy plate, and the present invention has been made.

Specifically, the manufacturing method of the aluminum alloy plate for a cap excellent in bending workability of the invention of claim 1 is Mg1.5-2.1%, Fe0.1-0.3%, Mn0.1% or less In addition, when the ingot of aluminum alloy containing 0.05 to 0.25% of Si and the balance being made of Al and inevitable impurities is subjected to homogenization, hot rolling is performed at an end temperature of 280. The temperature of the hot rolled sheet after the hot rolling is completely non-recrystallized by restricting to ℃ or lower, and then cold rolling is performed on the hot rolled sheet at a rolling rate of 70 to 85%, and then 400 to 550 Intermediate annealing within 2 minutes is performed at a temperature of ° C., finish cold rolling is performed at a rolling rate of 25 to 50%, and then stabilization treatment is performed, whereby the tensile strength is within the range of 170 to 200 MPa and 45 ° ears. Aluminum alloy with a rate of 2% or less It is characterized in that to obtain a plate.

Since the aluminum alloy plate for caps obtained by the production method of the present invention is excellent in bending workability, the adhesiveness of the coating film is inferior even in a severely processed part such as a threaded part after drawing. Therefore, even when used as a PP cap, the opening history identification function is not impaired by the peeling of the coating film, and the ear rate is good and can prevent bending of printed characters, Furthermore, since the surface quality is excellent and the strength is not excessively high, the cap-opening property is also good as a cap. Therefore, it can be suitably used for a cap, particularly a PP cap.

  First, the reasons for limiting the component composition of the aluminum alloy in the present invention will be described.

Mg:
Mg is an indispensable element for imparting necessary strength as an Al—Mg-based aluminum alloy for caps. If the Mg content is less than 1.5%, the effect of imparting strength cannot be sufficiently obtained. On the other hand, if the Mg content exceeds 2.1%, the strength becomes too high and it is difficult to open the cap as a cap. . Therefore, the Mg content is set in the range of 1.5 to 2.1%.

Fe:
Fe forms a crystallized substance and contributes to the improvement of the openability as a cap. If the amount of Fe is less than 0.1%, the effect cannot be obtained sufficiently, and the openability may be deteriorated. On the other hand, if the Fe content exceeds 0.3%, the ears in the 45 ° direction (45 ° ear rate) become high, and the printed characters may be bent. Therefore, the amount of Fe is set in the range of 0.1 to 0.3%.

Mn:
Mn is an element that contributes to strength improvement. If the amount of Mn exceeds 0.1%, the 45 ° ear becomes high, and there is a risk of causing bending of printed characters. The following regulations were decided.

Si:
Si also forms a crystallized product and contributes to the improvement of the opening performance as a cap. If the amount of Si is less than 0.05%, the effect of improving the openability cannot be sufficiently obtained. On the other hand, if the amount of Si exceeds 0.25%, 45 ° ears may be generated and the printed characters may be bent. . Therefore, the Si amount is set in the range of 0.05 to 0.25%.

  In addition to the above elements, basically, Al and inevitable impurities may be used. However, Ti, B, or Cr, V, Zr, Cu, Zn, etc., which are often added in ordinary Al alloys, are used. It is permissible for the elements to be contained within a range that does not significantly affect the characteristics. For example, Ti and B, which are often added as a finer during casting, are allowed to be 0.05% or less and 0.01% or less, respectively, and Cr and V are considered to be effective in increasing the strength. , Zr is 0.1% or less, Cu is 0.25% or less, and Zn is 1.0% or less, respectively.

Furthermore, in the manufacturing method of the aluminum alloy plate for caps of this invention, it is required that the tensile strength (tensile strength) of the product plate is within a range of 170 to 200 MPa. When the tensile strength of the product plate is less than 170 MPa, the top surface strength of the cap becomes insufficient, making it unsuitable as a wide-mouth PP cap. On the other hand, if the tensile strength of the product plate exceeds 200 MPa, not only the opening performance deteriorates but also the bending workability deteriorates, so that there is a possibility that the coating film may be peeled off at a portion where severe processing is applied such as a threaded portion. For example, there is a problem of adhesion of the coating film. Therefore, in this invention, while maintaining the top surface strength necessary as a PP cap for a wide mouth, not only improving the plug-opening property but also focusing on improving the bending workability, and consequently the adhesion of the coating film. The tensile strength of the product plate is regulated within the range of 170 to 200 MPa.

In addition, in the method for producing an aluminum alloy plate for a cap according to the present invention, the ear rate (45 ° ear) in the 45 ° direction of the product plate needs to be 2% or less. If the 45 ° ear exceeds 2%, the printed character may be bent as a cap. The reason why the 45 ° ear is defined as 2% or less is that even if the ear rate is 2% or less as a whole, if the 0-180 ° ear becomes strong, the printed characters may be bent. Because there is.

  Next, the manufacturing method of the aluminum alloy plate for caps of this invention is demonstrated.

  First, an aluminum alloy having the above-described component composition is cast according to a conventional method such as a DC casting method, and the resulting ingot is homogenized. There are no particular restrictions on the conditions for the homogenization treatment, but it is preferable to carry out the conditions at a temperature of 450 ° C. or higher (usually 550 ° C. or lower) for 1 hour or longer (usually within 12 hours) to eliminate casting segregation. is there.

  Although hot rolling is performed after the homogenization treatment, this hot rolling may be started immediately without cooling after the homogenization treatment, or may be performed by reheating after the homogenization treatment. It is important that this hot rolling is carried out so as to have a completely non-recrystallized structure in the state after the hot rolling (usually, after being wound on a coil and cooled by being left at room temperature). Therefore, in the method of the present invention, the hot rolling end temperature needs to be a low temperature of 280 ° C. or lower.

  If the hot rolling end temperature exceeds 280 ° C., it becomes difficult to make the hot rolled end plate completely non-recrystallized, so that it becomes a strong 0-180 ° ear tendency as a product plate ear as described later. This may increase the risk of bending the printed characters as a cap. In addition, by setting the hot rolling end temperature to a low temperature of 280 ° C. or lower, a product plate having excellent surface quality can be easily obtained. From the standpoint of improving the surface quality, it is sufficient that the hot rolling end temperature is 330 ° C. or lower. However, by setting it to 280 ° C. or lower, the surface quality can be improved more reliably. Since it is difficult to obtain a complete non-recrystallized structure at a hot rolling end temperature near 330 ° C., the hot rolling end temperature is defined as 280 ° C. or lower in the present invention.

  Here, the necessity of making the hot-rolled finished plate into a completely non-recrystallized state and the hot-rolling conditions necessary for that will be described in more detail.

  If the recrystallized part is mixed in the hot rolled finished plate, the cube orientation (cube orientation) develops excessively during the subsequent intermediate annealing, and the 0-180 ° ear of the product plate becomes strong, resulting in processing into a cap. Cause the printed characters to bend. Therefore, it was decided to control so as to obtain a completely non-recrystallized structure at the stage of the hot rolled plate.

  The most significant influence on the recrystallized state in the process of winding from the hot rolling and cooling is the end temperature of the hot rolling. Can do. In general, hot rolling is generally performed by combining hot rough rolling and hot finish rolling, and the conditions of temperature and rolling reduction in each pass of hot finish rolling are also in a recrystallized state. Although it has an effect, in a normal hot finish rolling process using a tandem hot finish rolling mill, if finish rolling is performed at a total rolling reduction of 85% or more, which is a general rolling reduction condition, the end If the temperature is 280 ° C. or lower, a completely non-recrystallized structure can be obtained with certainty.

  After hot rolling is completed as described above, cold rolling (primary cold rolling) is performed at a rolling rate of 70 to 85% to obtain an intermediate plate thickness. Here, if the rolling ratio of primary cold rolling is less than 70%, the cube orientation develops excessively during the subsequent intermediate annealing, and the 0-180 ° ear of the product plate becomes strong. On the other hand, if the rolling ratio of the primary cold rolling exceeds 85%, the cube orientation is not sufficiently developed during the intermediate annealing, and a strong 45 ° ear is generated on the product plate. It becomes difficult to achieve a value of 0% or less. Therefore, in order to appropriately control the ears of the product plate, it is necessary to regulate the primary cold rolling rate within a range of 70 to 85%.

  After the primary cold rolling, intermediate annealing is performed at a temperature within a range of 400 to 550 ° C. under a condition within 2 minutes. Such intermediate annealing for a short time at a high temperature is usually performed using a continuous annealing furnace. If the temperature of the intermediate annealing is less than 400 ° C., it is difficult to obtain a recrystallized state by annealing in a continuous annealing furnace, in which case the strength of the product plate becomes abnormally high, so that the unplugging property deteriorates and bending The processability is remarkably deteriorated and the coating film adhesion is inferior. Further, since the cube orientation to be developed by the intermediate annealing is not sufficiently developed, the 45 ° ear of the product plate may be strengthened. On the other hand, if the temperature of the intermediate annealing exceeds 550 ° C. or the holding time exceeds 2 minutes, the recrystallized grains may be coarsened, resulting in rough skin after molding, and such recrystallized grains may be coarsened. Along with this, the cube orientation becomes too strong, and the 0-180 ° ears of the product plate become strong, and there is a possibility that the printed characters are bent as a cap.

  After the intermediate annealing, finish cold rolling (final cold rolling) is performed to the final product sheet thickness. This finish cold rolling needs to be performed within a rolling rate of 25 to 50%. If the rolling rate of finish cold rolling is less than 25%, the strength of the product sheet is insufficient, and a rolling texture that is a 45 ° ear component sufficient to meet the cube orientation developed by intermediate annealing cannot be developed. As a result, the 0-180 ° ear and the 90-270 ° ear of the product plate become high. On the other hand, if the rolling ratio of finish cold rolling exceeds 50%, the strength of the product plate becomes too high, the bending workability deteriorates, and the rolling texture develops too much, and the 45 ° ear becomes strong. As a result, the printed character is bent as a cap.

  Stabilization processing is performed on the rolled sheet having the final sheet thickness by finish cold rolling as described above. This stabilization treatment may be performed under the same conditions as those conventionally used for Al-Mg alloy sheets, and is not particularly limited. The heating may be performed for 5 to 6 hours.

  As described above, the hot rolling finish temperature is regulated to a low temperature of 280 ° C. or lower to obtain a complete non-recrystallized structure after hot rolling, and further each of the following primary cold rolling, intermediate annealing, and finish cold rolling By appropriately regulating the conditions, bending workability, and consequently coating film adhesion, is good, the ear rate is low, printing characters do not bend easily, surface quality is good, and strength is appropriate. Thus, it is possible to obtain an aluminum alloy plate for a cap that can secure the top surface strength necessary for a PP cap for a wide mouth and at the same time does not impair the openability.

  Examples of the present invention will be described below.

  Alloys having respective component compositions shown in alloy codes A to I in Table 1 were melt-cast by a conventional method to obtain a slab (plate ingot) having a thickness of 500 mm. The obtained ingot was subjected to a homogenization treatment of 500 ° C. × 4 hr, and then the production number No. 1-No. Hot rolling, primary cold rolling, intermediate annealing, and finish cold rolling (final cold rolling) were performed under the conditions shown in No. 18, and stabilization treatment (final annealing) was performed. Here, for hot rolling, rough rolling was performed with a single reverse rolling mill at a starting temperature of 470 ° C., and finish rolling was performed with a four-stand tandem rolling mill. Moreover, the continuous annealing furnace (CAL) was used for the intermediate annealing. Further, for the final annealing, a box-type annealing furnace (batch furnace) was used, and the conditions were 220 ° C. × 2 hr. The final plate thickness was 0.25 mm.

  During the manufacturing process as described above, a sample is cut out from a hot rolled plate that has been wound after hot rolling and cooled to room temperature, and the recrystallization rate of the hot rolled plate is examined, and the surface quality of the hot rolled plate is examined. Therefore, the results are shown in Table 3. Here, the recrystallization rate of the hot-rolled sheet was measured by taking a photo with the Barker method after polishing the cross section and measuring the ratio of the recrystallized portion in the total thickness.

  Further, the product plate obtained as described above was subjected to a tensile test to examine the tensile strength, and the ear rate was measured. The results are shown in Table 3. The tensile test and the method of measuring the ear rate are as follows.

Tensile test:
A tensile test was performed in the direction parallel to the rolling direction using JIS No. 5 test pieces.

Ear rate:
A cup was formed with a punch diameter of 33 mm, a punch shoulder R of 1.5 mm, a blank diameter of 57 mm, and a wrinkle presser of 250 kgf, and calculation was performed using the following formula.
Ear rate = (mountain average-valley average) / cup average height x 100 (%)
When the 0 ° and 90 ° positions are compared with the 45 ° position, the case where the 0 ° and 90 ° positions are high is indicated by minus, and the case where the 45 ° position is high is indicated by plus. Here, the 45 ° ear rate needs to be 2.0% or less, and the case where the 0-90 ° ear is high (minus ear) is not allowed.

  Further, the product plate obtained as described above was examined for bending workability, and the product plate was subjected to a coating treatment, and a cap having a diameter of 38 mmφ was produced by pressing and roll forming, and then the appearance was observed for forming. After confirming that there was no problem, the container was wrapped around a container and its opening torque was measured. The results are shown in Table 3.

  The bending processability, cap appearance quality, opening torque measuring method, and evaluation method are as follows.

Bending workability:
The surface state of the base plate was observed after 2T bending so that the base plate was folded in parallel with the rolling direction. A sample in which no constriction or crack was generated was indicated as “◯”, and a sample in which constriction or micro crack was generated was defined as “X”.

Appearance observation:
A sample having no particular problem was marked with ◯, and a sample having rough skin or a flow mark was marked with ×.

Opening torque:
Under the condition that the bridge width of the 38 mmφ cap (the width of the portion that can be cut when the cap is opened) is 1 mm, ◯ is 16 kgf · cm or less, and × is the case that exceeds this.

  As apparent from Table 3, the production number No. 1-No. It was confirmed that all the characteristics within the scope of the present invention of 4 were good.

  On the other hand, the production number No. in which the alloy component composition deviated from the range specified in the present invention. 5-No. No. 9 and production number No. in which the manufacturing process condition was out of the condition range of the present invention. 10-No. In 18 comparative examples, it was found that at least one of the various required characteristics was inferior.

  That is, first, the production number No. No. 5 was found to have a high ear rate in the 45 ° direction of the final plate due to an excessive amount of Si in the alloy, causing bending of printed characters. The production number No. No. 6 has an excessive Fe content, so the final plate has a high ear rate in the 45 ° direction, and it has been found that the printed characters are bent. Further, the production number No. No. 7 was found to have a strong 45 ° ear due to an excessive amount of Mn in the alloy, resulting in bending of printed characters. The production number No. No. 8 has a low strength because the Mg content of the alloy is too small. Further, the production number No. No. 9 has an excessive amount of Mg and Mn in the alloy, so that the strength is too high, the bending workability is lowered, and the opening force is increased.

  On the other hand, the production number No. No. 10 has a high hot rolling end temperature, and therefore there is a portion that is recrystallized after hot rolling. Therefore, the cubic orientation develops excessively during intermediate annealing, and the ear of the final plate becomes negative, 0-180 °. It was found that the printed characters were bent at the position. The production number No. In No. 11, the hot finish rolling finish temperature was too high, the surface quality of the hot rolled sheet was lowered, and a flow mark was generated in the molded product of the final sheet. Further, it was found that the cube orientation was excessively developed during the intermediate annealing, so that the ear of the final plate became negative and the printed characters were bent at 0-180 ° position. Further, the production number No. No. 12, the cold rolling rate before the intermediate annealing is too low, the cube orientation is excessively developed during the intermediate annealing, so the ear of the final plate becomes negative, and the printed characters are bent at 0-180 ° position. There was found. The production number No. No. 13, the cold rolling rate before intermediate annealing is too high, the cube orientation does not develop sufficiently during intermediate annealing, a strong 45 ° ear is produced on the final plate, and the printed characters are bent at the 45 ° position. found. Further, the production number No. No. 14 cannot be completely recrystallized because the intermediate annealing temperature is too low. Therefore, the strength becomes too high and the opening torque becomes high, and the bending workability also deteriorates, and further 45 °. It has been found that the ears are remarkably developed and the printed characters are bent at 45 °.

  And production number No. No. 15, since the intermediate annealing temperature was too high and the crystal grain size became coarse, the surface of the molded product was roughened, and the cube orientation became stronger during the intermediate annealing, and the ear of the final plate became negative, 0-180 ° It was found that the printed characters were bent at the position. The production number No. In No. 16, since the holding time of the intermediate annealing was too long and the crystal grain size became coarse, the surface of the molded product was roughened, and the cube orientation became strong during the intermediate annealing, and the ear of the final plate became negative. It has been found that the printed characters are bent at the 180 ° position. Further, the production number No. In No. 17, the final cold rolling rate was too low, the ear rate became negative, the printed characters were bent at 0-180 ° position, and the strength was insufficient. The production number No. No. 18 was found that the final cold rolling rate was too high, the 45 ° ear was too high, the strength was too high and the opening torque was increased, and the bending workability was also deteriorated.

Claims (1)

Contains Mg 1.5 to 2.1% (mass%, the same shall apply hereinafter), Fe 0.1 to 0.3%, Mn 0.1% or less, Si 0.05 to 0.25%, the balance being Al and inevitable impurities subjected to a homogenization treatment to an ingot of more Na Ru aluminum alloy, when performing hot rolling, the hot rolling finishing temperature was regulated to 280 ° C. or less, the structure of the hot rolled sheet hot rolling up After making it into a completely non-recrystallized state and then cold rolling the hot rolled sheet at a rolling rate of 70 to 85%, intermediate annealing is performed at a temperature of 400 to 550 ° C. within 2 minutes, and further a rolling rate of 25 to 50 Bending process, characterized in that a finish cold rolling is performed at a percentage, followed by a stabilization treatment, thereby obtaining an aluminum alloy sheet having a tensile strength within a range of 170 to 200 MPa and a 45 ° ear ratio of 2% or less. Excellent aluminium for caps Manufacturing method of the non-alloy plate.