JP2006077278A - Aluminum alloy sheet for bottle type can - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent wrinkling and cracking at necking for a mouth part and subsequent threading and curl forming while satisfactorily securing the strength after baking (pressure resistance of cans) of bottle type cans. <P>SOLUTION: The aluminum-base alloy has a composition containing 0.1 to 0.5% Si, 0.8 to 1.5% Mg, 0.7 to 1.5% Mn, 0.05 to 0.5% Cu and 0.2 to 0.7% Fe and further containing either or both of 0.01 to 0.3% Cr and 0.01 to 0.3% Ti. Moreover, the number of secondary-phase particles with ≥15μm diameter is ≤3 pieces/mm<SP>2</SP>and the number of secondary-phase particles with 0.75 to 2μm diameter is ≥10,000 pieces/mm<SP>2</SP>, and tensile proof stress after treatment at 210°C for 10 min ranges from 230 to 260 N/mm<SP>2</SP>. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

    TECHNICAL FIELD The present invention relates to an aluminum alloy plate for a bottle-shaped beverage can in which a resealable bottom, body, and mouth part are integrally formed, and in particular, aluminum excellent in necking, curl and threading of the mouth. It relates to alloy plates.

  Conventional beverage cans are mainly so-called two-piece cans composed of a can lid and a can body, but recently, bottle-type beverage cans that can be resealed have been developed. This bottle can is shaped like a normal two-piece can body by blanking a base plate into a circular shape, making it a primary squeeze cup, then having a body part and a bottom part by redrawing and ironing. After trimming this and aligning the can height, the diameter of the opening is reduced, and the threaded portion is further processed at this portion to further curl the drinking mouth.

Such a bottle-type can with a screw is required to have a high drawability since the drawing ratio of necking molding at the mouth is larger than that of a conventional DI can. In addition, the strength after necking is higher because it is stronger, but in the subsequent process, there is a more stringent molding than the conventional DI can, such as threading and bending the flange part in a curled shape, and the strength is increased. There is a problem that cracks are likely to occur. If the pre-molding strength is lowered as a countermeasure, the strength of the mouth portion is lowered and the moldability is improved, but a strength higher than a certain level is necessary for ensuring the pressure resistance, and it is difficult to achieve both strength and moldability.

The following techniques have been proposed as aluminum alloy materials for such bottle-shaped cans.
JP 2002-256366 A JP 2003-82429 A JP 2003-306750 A

  Patent Document 1 (Japanese Patent Application Laid-Open No. 2002-256366) and Patent Document 2 (Japanese Patent Application Laid-Open No. 2003-82429) disclose aluminum plates for bottle cans having excellent necking properties. Even if it is low, sufficient necking moldability cannot be obtained with a material that has a large work hardening during DI molding or necking molding.

  Further, Patent Document 3 (Japanese Patent Laid-Open No. 2003-306750) discloses a method for producing an aluminum alloy plate for a bottle-type beverage can having a high necked neck and neck strength and excellent curl processability. This is disadvantageous in cost because it requires two intermediate annealings during cold rolling.

  In the present invention, these conventional techniques are insufficient, and sufficient strength after baking (can pressure resistance) is ensured, while the neck formation of the mouth and subsequent threading and curling do not cause wrinkles and cracks. Is an issue.

  The inventors have found that it is possible to obtain an aluminum alloy sheet satisfying the above characteristics by setting the alloy composition within a specific range and specifying the post-baking proof stress and the distribution density of the second phase particles on the sheet surface, Further studies have been made to complete the present invention.

That is, according to the first aspect of the present invention, Si: 0.1 to 0.5% (mass%, the same shall apply hereinafter), Mg: 0.8 to 1.5%, Mn: 0.7 to 1. as essential elements. 5%, Cu: 0.05-0.5%, Fe: 0.2-0.7%, Cr: 0.01-0.3%, Ti: 0.01-0.3% It is an aluminum-based alloy containing one or two of them, the second phase particles having a diameter of 15 μm or more are 3 / mm ² or less, and the second phase particles of 0.75 to 2 μm are 10,000 / mm ² or more. Aluminum for bottle-type cans having a draw ratio of 30% or more with respect to the body, characterized by being present and having a tensile strength after treatment at 210 ° C. × 10 minutes in the range of 230 to 260 N / mm ² Alloy plate.

  The bottle can material of the present invention is suitably used as a plate for a bottle can body, because the strength and ductility are sufficiently secured and the required piercing strength is satisfied by the definition of the aluminum alloy component.

  First, the reason for limiting the components of the aluminum alloy in the present invention will be described.

Si is an element necessary for generating an α phase effective in preventing baking. If it is less than 0.1%, the amount of α phase sufficient to prevent baking cannot be obtained. Moreover, when there is little Si, the amount of Mn solid solution will increase, strength after necking will also become large, and the moldability of a mouth part will fall. When it exceeds 0.5%, the amount of precipitated Mg ₂ Si increases, and the formability deteriorates due to high strength and embrittlement.

  Mg is a constituent element of precipitates that contributes to solid solution strengthening and contributes to improvement in strength during paint baking. If it is less than 0.8%, the effect is insufficient, and if it exceeds 1.5%, the strength after necking molding increases due to cracking during rolling and an increase in the amount of solid solution, and the moldability of the mouth part decreases.

  Mn is essential for improving strength and forming α-Al (Fe, Mn) Si phase during homogenization to ensure lubricity during ironing and prevent seizure to the mold. It is an element. If Mn is less than 0.7%, the above-mentioned lubricity cannot be ensured. In addition, the number of second phase particles is reduced and moldability is lowered. On the other hand, if it exceeds 1.5%, the moldability deteriorates due to the increase of the second phase particles. Furthermore, the strength after necking increases due to the increase in the amount of solid solution, and the moldability of the subsequent mouth portion decreases.

  Cu is an element necessary for strength improvement by Al—Mg—Cu-based precipitation during coating baking. If it is less than 0.05%, the effect is not obtained, and if it exceeds 0.5%, the corrosion resistance is lowered and the moldability of the mouth is lowered due to the increase in the amount of solid solution.

  Fe is an element necessary for α-phase formation and distribution density control. If it is less than 0.2%, the seizure prevention effect and the necessary distribution of the second phase particles cannot be obtained. If it exceeds 0.7%, an Al—Fe—Mn-based giant intermetallic compound is produced, and the moldability is lowered.

Ti improves formability through refinement of crystal grains. If it is less than 0.01%, the effect cannot be obtained. Moreover, when it exceeds 0.3%, a coarse intermetallic compound will arise and a moldability will fall.

Cr also improves formability through crystal grain refinement. If it is less than 0.01%, the effect cannot be obtained. Moreover, when it exceeds 0.3%, a coarse intermetallic compound will arise and a moldability will fall.

  However, excellent formability cannot be obtained only by limiting the alloy composition as described above, and the following two metal structure controls are indispensable.

One is to make the Al—Mn second phase particles having a diameter of 15 μm or more 3 particles / mm ² or less.

The Al—Mn crystallized product is necessary for preventing seizure during DI molding. However, if it exceeds 15 μm, strain concentrates during DI processing, necking, threading, and curl bending molding, and tends to be the starting point of fracture. If the distribution density exceeds 3 pieces / mm ² , molding cracks become prominent.

The other is to make the Al-Mn type second phase particles having a diameter of 0.75 to 2 μm 10000 particles / mm ² or more.

  The body part for threaded cans has a higher necking ratio than normal DI cans, and is followed by threading, curl bending of the openings, and strong processing, making it higher than DI cans. Sex is required. For threading and curl bending, a material with little increase in strength is preferred because dislocations are easily arranged during necking and subsequent strong processing.

In the vicinity of particles having a diameter of about 0.5 to 3 μm, dislocations concentrate at the time of DI or at the initial stage of necking. Therefore, as the processing proceeds further, dislocations are easily organized and the increase in strength is small. The inventors investigated the relationship between the particle distribution density and the formability of the mouth part, and in particular, the arrangement of dislocations in a wide range if the number of second phase particles having a diameter of 0.75 to 2 μm, which has a large effect, is 10000 particles / mm ² or more. It has been found that sufficient formability can be obtained. If the number of particles is less than that, the number of particles having a diameter that does not promote dislocation rearrangement increases, or the amount of solid solution increases, and the formability decreases. This is because solid solution atoms hinder the rearrangement of dislocations, so that the strength is increased after necking, and cracking is likely to occur during curl forming and threading.

Furthermore, the following are required as material characteristics.
-Tensile strength (ABYS) after treatment at 210 ° C for 10 minutes is 230 to 260 N / mm ²
If it is less than 230 N / mm ² , sufficient pressure resistance cannot be obtained, and if it exceeds 260 N / mm ² , the mouth moldability becomes difficult.

  In order to achieve the above characteristics, homogenization treatment conditions are particularly important among the normal steps of casting, homogenization treatment, hot rolling, and cold rolling.

Homogenization treatment conditions The ingot homogenization treatment is necessary not only for the homogenization of the components but also for the alpha conversion of the Al-Fe-Mn intermetallic compound in order to obtain good ironing properties. For this purpose, treatment at 500 ° C. or higher is generally required, but a large amount of fine precipitates of about 0.2 μm or less are generated during the temperature rise. In order to set the distribution state of the second phase particles to 10000 / mm ² or more for particles having a diameter of 0.75 to ² μm, the fine precipitates are once solid-dissolved to obtain a larger precipitate of 0.5 μm or more. Growth and generation are required.

for that purpose,
A Treatment at 580 to 615 ° C. for 2 hours or longer is required. In this temperature range, solid precipitates are dissolved, and a residence time of 4 hours or more is required including the temperature rising process. In the treatment at a temperature lower than 580 ° C., it is necessary to carry out a long-time treatment that is not practically industrialized or is not practical. Further, there is a possibility of burning at 615 ° C. or higher.
However, in the state of A, the number of intermetallic compounds of 0.75 to 2 μm is insufficient at 10,000 pieces / mm ² . Further, since the amount of the solid solution is large, the work hardenability is greatly increased during molding, and the moldability is lowered.

Therefore,
B Precipitation treatment for retaining at 400 to 550 ° C. for 2 hours or more is required. This process may be performed after the process A and before hot rolling of the next process. For example, the heat treatment may be started from the process A to the start of hot rolling, the cooling during cooling to room temperature, or the continuous cooling, or the temperature may be raised to the hot rolling start temperature after cooling to room temperature.

Hereafter, the process of hot rolling and cold rolling may be a normal and widely performed method.
In addition, even if it anneals after hot rolling, in the middle of cold rolling, and at the end of cold rolling, it does not prevent obtaining a desired metal structure.

Hereinafter, the present invention will be described in detail with reference to examples.
Aluminum alloy having the alloy composition shown in Table 1 is melt-cast into a 500 mm thick ingot, homogenized at 590 to 630 ° C. for 6 hours, and the ingot surface cooled to room temperature is chamfered about 5 to 8 mm on one side. did. The ingot after chamfering is reheated to 400 to 550 ° C. and subjected to hot rough rolling of 10 to 30 passes at a rolling rate of 10 to 30% per pass using a reverse hot rough rolling machine, and finished plate A hot rough rolled plate having a thickness of 20 to 30 mm is used. Subsequently, hot finish rolling was performed using a four-stage tandem hot finish rolling mill so that the end plate thickness was 2 to 4 mm and the end temperature was 330 to 350 ° C. After hot rolling is completed, cold rolling is performed at a rolling rate of 40 to 60% and a total number of passes of 3 passes, and final cold rolling (total rolling rate of 85 to 90%) is performed to a plate thickness of 0.4 mm. An alloy plate was obtained.

The following measurements were performed on the aluminum alloy plate produced as described above.
0.2% proof stress after baking: Instron type tensile tester, using JIS No. 5 test piece, tensile speed 10 mm / min. The 0.2% yield strength after baking at 210 ° C. for 10 minutes was determined.
Second-phase particle distribution measurement: The equivalent-circle diameter distribution of the second-phase particles on the surface of the final plate after cold rolling was measured and evaluated using an image analyzer.

Moreover, can moldability evaluation was performed as follows.
A large number of DI cans having an inner diameter of 66 mmφ were manufactured, and subjected to trimming and baking treatment corresponding to a drying step of 210 ° C. × 10 minutes. Then, necking molding and curl molding were performed and evaluated.
-DI property: In case of breaking and goling (scratches) during DI, X was marked with no occurrence.
-Necking moldability: Necking was performed so that the diameter of the mouth portion was 40 mmφ. Evaluation was made by visually observing the absence of wrinkles as ◯, a slight occurrence as Δ, and a large number of wrinkles as x.
-Curl moldability: After necking, curling was performed, and the wrinkles and cracks of the curled portion were visually confirmed. In the evaluation, “O” indicates no cracking, and “X” indicates that cracking occurred.

  The measurement results and evaluation results are shown in Table 1 together with the alloy composition.

An alloy within the composition range of the present invention has sufficient strength after baking and good formability.
On the other hand, No. which is a comparative example. Nos. 5, 7, and 9 each had a large amount of Si, Cu, and Mg, so that the strength after baking increased, and the neck formability and curl bendability decreased. No. In Nos. 6 and 8, since Fe and Mn exceeded the specified amounts, Al-Fe-Mn coarse crystals were increased and the moldability was poor. No. Since 10, 11, and 13 have few Si, Fe, and Mn, they are inferior to DI moldability. Further, the distribution of the second phase particles of 0.75 to 2 μm is small and the curl moldability is poor. No. Since Nos. 12 and 14 are low in Cu and Mg, the strength after baking is lowered.

Claims (1)

As essential elements, Si: 0.1 to 0.5% (mass%, the same applies hereinafter), Mg: 0.8 to 1.5%, Mn: 0.7 to 1.5%, Cu: 0.05 to 0.5%, Fe: 0.2-0.7%, Cr: 0.01-0.3%, Ti: 0.01-0.3% one or two of them contained It is an aluminum-based alloy, the number of second phase particles having a diameter of 15 μm or more is 3 / mm ² or less, and the number of second phase particles of 0.75 to 2 μm is 10,000 / mm ² or more, and is treated at 210 ° C. for 10 minutes. An aluminum alloy plate for a bottle-type can having a drawing ratio of the mouth portion to the body portion of 30% or more, characterized in that the later tensile yield strength is in the range of 230 to 260 N / mm ² .