JP2007100182A - Aluminum alloy sheet for cap and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an Al alloy sheet for a PP (pilfer proof) cap having satisfactory cap openability in spite of its extremely high strength, having satisfactory earing rates, free from curving of a printing character and having excellent surface quality as well. <P>SOLUTION: The Al alloy sheet comprises >3.0 to 5.0% Mg, 0.1 to 0.3% Fe, 0.05 to 0.5% Mn and 0.05 to 0.2% Si, and in which the area ratio of all crystallized products is 1.0 to 2.0%, and tensile strength is 300 to 350 MPa. Regarding its production method, hot finish rolling is performed under the conditions satisfying a starting temperature of ≤450°C, a finishing temperature of 260 to 330°C, the total draft of ≥85% and a draft in the final pass of ≥40%, thus the hot rolled sheet is made into a recrystallized state, next, primary cold rolling is performed, thereafter, process annealing is performed at 400 to 550°C without performing holding or under holding within 2 min, then, finish cold rolling is performed at the total draft of 25 to 50%, and next, stabilization treatment is performed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing an aluminum (Al) alloy plate having excellent drawability suitable for a wide mouth PP (pilfer proof) cap and the like.

  The PP cap is made, for example, by drawing an Al alloy plate that has been painted and printed on a letter in the shape of a cup, trimming the ears at the open end, and putting perforations on the hem to facilitate opening. It is manufactured with a thread groove in the part. The perforation is inserted across printed characters so that the presence or absence of opening can be identified. As materials, JIS A1100 and A3105 alloys, which are generally excellent in formability, are used, but with the widening of caps in recent years, high-strength Al—Mg-based alloys that compensate for the reduction in top surface strength have begun to be used.

  By the way, in general, if the strength of the material is increased to increase the strength of the top surface, there is a problem that the opening torque is excessively increased. Therefore, there has been a demand for a material that has high strength but good tearability and good openability.

As a high-strength PP cap material, an invention as disclosed in Patent Document 1 is disclosed, but the strength is not sufficient.
JP 2003-328062 A

Aiming to achieve both higher strength and openability, the present inventors have further improved the Mg content and Mn content of the Al-Mg alloy material, so that the openability is good while having higher strength. The present invention has been completed through headings and further studies.
An object of the present invention is to produce an aluminum alloy plate for PP caps that is extremely high in strength, has good openability, has excellent ear coverage, does not bend printed characters, and has excellent surface quality.

  According to the present invention, Mg is more than 3.0 and 5.0% or less, Fe is 0.1 to 0.3%, Mn is 0.05 to 0.5%, Si is 0 0.05 to 0.2%, a cap comprising Al and inevitable impurities, a total crystallized area ratio of 1.0 to 2.0%, and a tensile strength of 300 to 350 MPa Aluminum alloy plate for

    Moreover, the manufacturing method is as described in claim 2, Mg is more than 3.0 and 5.0% or less, Fe is 0.1 to 0.3%, Mn is 0.05 to 0.5%, Si is In carrying out hot rolling with a hot rough rolling mill and a hot finish rolling mill after homogenizing the Al alloy ingot containing 0.05 to 0.2% and the balance being Al and inevitable impurities. The finish rolling start temperature is 450 ° C. or less, the end temperature is 260 to 330 ° C., the total rolling reduction is 85% or more, and the final pass rolling reduction is 40% or more, and the hot rolled sheet is recrystallized, Next, after subjecting the hot-rolled sheet to primary cold rolling, intermediate annealing is performed at a temperature of 400 to 550 ° C. without holding or within 2 minutes, and then finish cold rolling is performed at a total rolling rate of 25 Aluminium for caps, characterized in that it is applied at -50%, followed by a stabilization treatment. This is a method for producing a copper alloy plate.

  According to the present invention, it is possible to provide an aluminum alloy plate for a PP cap that has an extremely high strength, a low opening force, a good ear rate, no printed character bending, and excellent surface quality.

  Hereinafter, the reason for adding the alloy components will be described first.

  In the present invention, Mg contained in the aluminum alloy contributes to improving the strength of the aluminum alloy plate for cap. The reason why the Mg content is specified to be more than 3.0 and 5.0% or less is that the effect cannot be obtained sufficiently if it is 3.0% or less. This is because it may be difficult to plug.

  Fe forms a crystallized product and contributes to the improvement of the pluggability. If the Fe content is less than 0.1%, the effect cannot be obtained sufficiently, and the opening performance deteriorates. However, if it exceeds 0.3%, the ears in the 45 ° direction become high and the printed characters are bent. There is.

  Mn imparts strength and further contributes to the improvement of pluggability by forming a crystallized product. However, if it is less than 0.05%, there is no effect. May worsen and the ears in the 45 ° direction become higher, which may cause the printed characters to be bent.

Si also contributes to the formation of Mg ₂ Si crystals and contributes to the improvement of the plug-opening property. However, if it is less than 0.05%, there is no effect, and if it exceeds 0.25%, Mg ₂ Si crystals are increased too much. ° Ears develop, causing printed characters to bend.

  Other elements are allowed as long as they do not significantly affect the properties. For example, Ti or B added as a refining material during casting is 0.05% or less and 0.01% or less, respectively, Cr, V or Zr is 0.1% or less, Cu is 0.25% or less, Zn If it is 1% or less, there is no problem.

  Next, the crystallized area ratio has a role of maintaining good opening performance even in a high-strength material, but the range of 1.0 to 2.0% is less than 1.0%. This is because the properties are not good, and if it exceeds 2.0%, the development of the cube orientation at the time of intermediate annealing is suppressed, the 45 ° ear becomes strong, and the printed characters are bent.

  When the tensile strength of the final plate is set to 300 to 350 MPa, the top surface strength is not sufficient when the tensile strength is less than 300 MPa, and when the tensile strength exceeds 350 MPa, the plug opening property is deteriorated.

  Next, a manufacturing method is demonstrated.

  An ingot produced by normal semi-continuous casting is homogenized under normal conditions and faced as necessary.

Next, hot rolling is performed by a rolling mill composed of rough rolling and finish rolling.
In contrast to rough rolling, which is intended to efficiently reduce the plate thickness with a large amount of processing, finish rolling has a greater effect on the quality of hot-rolled plates.
Although it does not specifically limit about rough rolling conditions, it starts from about 450-550 degreeC which is a temperature range which is high to some extent and local melting does not occur from the problem of the reduction of deformation resistance, and the temperature ensuring after finish rolling.

  Here, if the total rolling reduction of finish rolling is 85% or more, if it is less than 85%, the recrystallization state cannot be achieved at the rolling end temperature of the present invention.

  When the hot finish rolling start temperature is set to 450 ° C. or lower, when the temperature exceeds 450 ° C., a part of the roll coating formed on the surface of the roll is peeled off during hot finish rolling, and defects are embedded in the surface of the plate frequently. Decreases. In this case, a flow mark may appear on the final product.

  When the hot rolling end temperature is set to 280 to 330 ° C., if it is less than 280 ° C., cracks at the end of the hot rolled end plate become severe, and subsequent rolling is impossible. If the temperature exceeds 330 ° C., part of the roll coating formed on the surface of the rolling roll at the time of hot finish rolling is peeled off, resulting in frequent defects that are embedded in the plate surface, and the surface quality is deteriorated. In this case, a flow mark may appear on the final product.

  The reason why the rolling reduction of the final stand of hot finish rolling is 40% or more is to sufficiently accumulate distortion and ensure recrystallization even at the low temperature of hot rolling as in the present invention, and less than 40% Then, the crack at the end of the hot-rolled finished plate becomes so severe that rolling after that becomes impossible.

  Subsequently, it is necessary to perform primary cold rolling to sufficiently accumulate strain. Thereby, the crystal grain at the time of intermediate annealing is refined. It is desirable to perform cold rolling with a cold rolling rate of 30% or more.

  Next, annealing is performed as intermediate annealing at 400 to 550 ° C. without holding or within 2 minutes. In this case, the annealing is performed in a continuous annealing furnace. If it is less than 400 ° C., it is difficult to obtain a recrystallized state in the case of a continuous annealing furnace, and the strength of the final plate becomes abnormally high and the plug-opening property becomes poor. Furthermore, the rolling texture develops and the 45 ° ear becomes stronger. If it exceeds 550 ° C. or held for 2 minutes or longer, the recrystallized grains become coarse and rough after molding.

  Subsequently, finish cold rolling is performed, but if the rolling rate is set to 25 to 50%, the strength is insufficient if it is less than 25%. On the other hand, if it exceeds 50%, the strength becomes too high and the opening performance deteriorates. Also, the rolling texture becomes too developed and the 45 ° ear becomes strong.

  Then, industrially, stabilization treatment is performed, but this condition is not particularly limited, but it is usually performed at 140 to 250 ° C. for about 0.5 to 12 hours.

  The present invention will be specifically described below with reference to examples.

  The alloy components shown in Table 1 were melted and cast by a conventional method to obtain a slab (plate ingot) having a thickness of 500 mm. Next, the final plate was manufactured under the conditions shown in Table 2.

  In addition, about the hot rolling after the homogenization process of 500 degreeC * 4hr, rough rolling was performed with the single reverse type rolling mill, and was performed at the starting temperature of 470 degreeC. For the finish rolling, a 4-stand tandem rolling mill was used. The end plate thickness was 2.5 mm. For the intermediate annealing, a continuous annealing furnace (CAL) was used. Finish annealing was performed using a box-type annealing furnace (batch furnace) at 220 ° C. × 2 hr. The final plate thickness was 0.25 mm.

  The product plate thus obtained was subjected to a tensile test, ear ratio measurement, and image analysis of the crystallized product.

<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 (%)
The 0 ° and 90 ° positions were compared with the 45 ° position, and the 0 ° and 90 ° positions were indicated as minus, and the 45 ° position was indicated as plus.
The ear rate needs to be 2.5% or less, and negative ears are not acceptable.

<Crystal image analysis>
After the cross section of the plate was polished to a mirror surface, it was photographed 400 times with an optical microscope, and the area ratio of the crystallized substance having a size of 1 μm or more was measured by image analysis. The measurement area was 0.5 mm ² .
At this time, Fe and Mn crystallized products and Mg ₂ Si crystallized products are observed, but the total value of both is adopted here.

  Further, the product plate was subjected to a coating treatment, a cap having a diameter of 38φ was produced by press and roll molding, and the appearance was observed to confirm that there was no molding problem, and then the container was tightened and its opening torque was measured.

Appearance observations were marked with o for those with no particular problems, and x for those with flow marks or rough skin.
The opening torque was ○ when 7.5 kgf · cm or less, and x when exceeding this.

  The results are shown in Table 3.

  As apparent from Table 3, No. The inventive examples 1 to 4 are all good in properties.

On the other hand, the comparative example which is outside the scope of the present invention has the following problems.
No. 5 has an excessive amount of Fe and Si, and thus has a high crystallized area ratio and a high ear ratio in the 45 ° direction of the final plate, which causes bending of printed characters.
No. 6 has too much Mn, so the strength is too high and the opening torque is also high. Furthermore, the crystallized area ratio is too high and the 45 ° ears are strong and the printed characters are bent.
No. In No. 7, since the amount of Mn is too small, the crystallized area ratio is low and the opening torque is high.
No. No. 8 has a low strength due to an excessive amount of Mg.
No. No. 9 has an excessive amount of Mg, so that the strength is too high and the opening force is high.
No. No. 10 could not be cold-rolled because the hot finish rolling end temperature was too low and the cracks at the end of the hot-rolled sheet were severe and there was a risk of sheet breakage.
No. In No. 11, the hot finish rolling start temperature and end temperature were too high, the surface quality of the hot rolled sheet was lowered, and a flow mark was generated in the final molded product.
No. No. 12 could not be cold-rolled because the total hot rolling reduction ratio was low and the cracks at the end of the hot-rolled sheet were severe and there was a risk of sheet breakage.
No. No. 13 could not be cold-rolled because the rolling reduction of the final stand of hot finish rolling was too low and the cracks at the end of the hot-rolled sheet were severely broken.
No. In No. 14, the intermediate annealing temperature was too low to completely recrystallize, so the strength was too high and the opening torque was high. In addition, the 45 ° ear is remarkably developed, and the printed character is bent at the 45 ° position.
No. In No. 15, since the intermediate annealing temperature was too high and the crystal grain size became coarse, the surface of the molded product was rough.
No. In No. 16, since the intermediate annealing retention time was too long and the crystal grain size became coarse, the surface of the molded product was rough.
No. The final cold rolling rate of 17 is too low and the strength is insufficient.
No. No. 18 has a final cold rolling rate that is too high, the 45 ° ear becomes too high, and the strength is too high to increase the opening torque.

Claims (2)

Mg exceeds 3.0 and is 5.0% or less (mass%, the same applies hereinafter), Fe is 0.1 to 0.3%, Mn is 0.05 to 0.5%, and Si is 0.05 to 0. .2% content, balance of Al and inevitable impurities, total crystallized area ratio of 1.0 to 2.0%, tensile strength of 300 to 350 MPa, aluminum alloy plate for cap . Mg is more than 3.0 and 5.0% or less, Fe is 0.1 to 0.3%, Mn is 0.05 to 0.5%, Si is 0.05 to 0.2%, and the balance is After performing homogenization on an Al alloy ingot composed of Al and inevitable impurities, when performing hot rolling with a hot rough rolling mill and a hot finish rolling mill, the finish rolling start temperature is 450 ° C. or less and finished. The temperature is 260 to 330 ° C., the total rolling reduction is 85% or more, and the final pass rolling reduction is 40% or more. The hot rolled sheet is recrystallized, and then the hot rolled sheet is subjected to primary cold rolling. After application, intermediate annealing is performed at a temperature of 400 to 550 ° C. without holding or within 2 minutes, then finish cold rolling is applied at a total rolling rate of 25 to 50%, and then a stabilization treatment is performed. The manufacturing method of the aluminum alloy plate for caps characterized by these.