JP2001152271A - Aluminum hard sheet for can cover and producing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an aluminum hard sheet small in the anisotropy of strength and small in the generation of cracking caused by blistering when used to a positive pressure can cover material for carbonated beverages, beer or the like and to provide a method for producing the same. SOLUTION: This sheet has a composition composed of 3.5 to 5.0% Mg, 0.15 to 0.6% Mn, 0.02 to 0.20% Si, 0.01 to 0.20% Cu, <=0.40% Fe, <=0.03% Ti, also (Fe+Mn)/Si<=20, and the balance Al with inevitable impurities, in which the ratio between the total of the orientational density from the Cu orientation to the S orientation (Cu to S) belonging to beta fiber among the components with a rolled texture in the center of the sheet thickness and the total of the orientational density from the S orientation to the Brass orientation (Brass to S), i.e., (Cu to S)/(Brass to S) is <=5.0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a 5000 series alloy used for cans having a high internal pressure such as for carbonated beverages and beer, and more particularly to controlling the size, dispersion state and texture of crystallized substances. By reducing the anisotropy of strength, even if the lid swells due to internal pressure, it will expand evenly in each direction, so that local stress concentration does not occur and cracks do not easily occur during deformation. It concerns the manufacturing method.

[0002]

2. Description of the Related Art Generally, can lid materials having a high internal pressure for carbonated beverages and beer are JIS-5 from the viewpoint of strength and moldability.
182 alloy is mainly used, and properties such as strength after baking, bulging, scoring, rivet forming, and crimping are required. In recent years, the demand for further thinning of materials has been increasing more and more, and there has been a demand for materials having even better properties than conventional materials.

[0003]

When a material containing a crystallized material is cold-rolled, a large number of dislocations introduced by the rolling are accumulated around the crystallized material to form a high dislocation density region. When such a large number of regions are formed, the dislocation density becomes uneven between the matrix and the periphery of the crystallized substance, and the strength anisotropy becomes remarkable. When the strength anisotropy is large, the lid does not swell evenly due to the internal pressure, but preferentially swells in a direction of low strength, and at the time of the deformation, a local stress concentration occurs and a crack is easily generated. is there. At the same time, when molded for can lids, if the rivet moldability is poor, there is also a problem that cracks occur during molding. It is also necessary to have a sufficient strength, but on the other hand, it is also required to be tearable when opening the can. To solve these problems, it is necessary to develop a material that satisfies the required characteristics and a method of manufacturing the material.

[0004]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted various experiments and studies, and as a result, have obtained new findings and arrived at the present invention.

That is, according to the present invention, 3.5 to 5.0% of Mg (% by mass, the same applies hereinafter), 0.15 to 0.6% of Mn,
02 to 0.20%, Cu 0.01 to 0.20, Fe0.
40% or less, Ti 0.03% or less, and (Fe + M
n) / Si is 20 or less, the balance has a composition consisting of Al and unavoidable impurities, and the sum of the orientation densities from the Cu orientation belonging to the beta fiber to the S orientation belonging to the beta fiber among the rolling texture components in the center of the plate thickness ( Bra from Cu to S) and S orientation
The aluminum hard plate for a can lid with small strength anisotropy, wherein the ratio (Cu-S) / (Brass-S) of the sum of the orientation densities up to the ss orientation (Brass-S) / (Brass-S) is 5.0 or less. It is. In the second invention, Mg 3.5 to 5.5.
0%, Mn 0.15-0.6%, Si 0.02-0.2
0%, Cu 0.01 to 0.20, Fe 0.40% or less,
Ti not more than 0.03% and (Fe + Mn) / Si is 20
And the remainder is A composed of Al and unavoidable impurities.
1 Hold the ingot in a temperature range of 400 to 550 ° C.
After performing the heat treatment for a long time, hot rolling is performed so that the initial crystal grain size before final cold rolling is 250 μm or less, and final cold rolling is performed at a rolling reduction of 40 to 95%. 0.5-1 in the temperature range of 100-240 ° C after cold rolling
Finish annealing is performed for 0 hour, and the ratio of the sum of the orientation densities from the Cu orientation to the S orientation belonging to the beta fiber and the sum of the orientation densities from the S orientation to the Brass orientation (Cu ~ S) / (Bras
s to S) is 5.0 or less, which is a method for producing an aluminum hard plate for a can lid having low strength anisotropy.

In the present invention, the strength anisotropy is evaluated by the maximum value of the difference in proof stress in the 0, 45, and 90 ° directions with respect to the rolling direction. If this value is 25 MPa or less, the aluminum alloy for can lids is used. It can be said that the plate has low strength anisotropy.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the reasons for limiting the composition of the aluminum alloy used in the present invention will be described.

Mg: The addition of Mg has the effect of improving the strength due to the solid solution of Mg itself, and can be expected to improve the strength by work hardening due to the large interaction with dislocations. Is an indispensable element for obtaining
However, if the Mg content is less than 3.5%, the strength is insufficient for use in lids for carbonated drinks, beer, etc., while 5.0 is used.
%, The workability is reduced and cracking during hot rolling is caused. Therefore, the amount of Mg was set in the range of 3.5 to 5.0%.

Mn: Al-M formed by adding Mn
The n- (Si) and Al-Fe-Mn- (Si) -based crystallized substances are indispensable crystallized substances for enhancing the tearability of the score portion. Further, Mn contributes to the improvement of the strength similarly to Mg. If the Mn content is less than 0.15%, the effect is small.
On the other hand, if it exceeds 0.6%, these crystallized substances are coarsened, and a high dislocation density region is formed around the crystallized substances during rolling to increase the strength anisotropy. In addition, cracks are generated and propagated at the interface between Al and these crystallized substances at the time of rivet forming and deterioration of workability, which easily causes cracking of the material. Therefore, the Mn content is set in the range of 0.15 to 0.6%.

[0010] Si: The crystallized Mg ₂ Si formed by Si has the effect of improving the openability, like Mn. However, when the amount of addition is as high as less than 0.02%, the regulation at the time of casting becomes strict and the productivity is reduced. On the other hand, if it exceeds 0.20%, the number of crystallized substances increases, or Al—Mn— (Si), Al—Fe—Mn
-The (Si) crystallized material becomes large, and a high dislocation density region is formed around the crystallized material during rolling to increase the strength anisotropy and reduce the rivet forming. Therefore, the Si content is set to 0.02 to 0.20% or less.

Cu: Cu is an element contributing to the improvement of strength, but its effect is not exhibited if the added amount is less than 0.01%. On the other hand, if it exceeds 0.20%, rivet formability may be impaired. Therefore, the amount of Cu is 0.01 to 0.2.
The range was 0%.

Fe: Al—F formed by adding Fe
The e-Mn- (Si) -based crystallized material is important for improving the openability. However, when the Fe content exceeds 0.40%, the crystallized material becomes coarse, and high rolling around the crystallized material occurs during rolling. A dislocation density region is formed to increase strength anisotropy and decrease rivet formability. Therefore, the Fe content is set to 0.40% or less.

Ti: Ti is an element effective for refining crystal grains. However, if the amount of Ti is large, the ingot structure is less likely to become feather-like crystals, and it is easy to form granular crystals. In the case of granular crystals,
Since the size of the crystallized substance that is crystallized at the grain boundary is larger than that of the feathered crystal, it is a harmful element for reducing the diameter of the crystallized substance. In addition, Ti itself produces a giant crystallized substance to lower the formability. If the amount of Ti is regulated to 0.03% or less, the area ratio of the feathered crystals in the cross section of the ingot becomes 10% or more, and the crystallized product can be reduced in diameter. For this reason, the Ti content is set to 0.1.
Restricted to less than 03%.

(Fe + Mn) / Si ≦ 20: If this condition is satisfied, the crystallized material will not be coarsened and Al—
Promotes the formation of Fe-Mn-Si crystallization,
The size of the crystallized product can be smaller than that of the Mn crystallized product. If the size of the crystallized material becomes smaller, it becomes difficult for the kinetic dislocations generated during rolling to form a high dislocation density region around the crystallized material. Will not be.

Next, the ratio of the sum of the orientation densities from the Cu orientation to the S orientation when the texture is measured at the center of the sheet thickness and the sum of the orientation densities from the S orientation to the Brass orientation (Cu to
The reason why (S) / (S to Brass) is 5.0 or less will be described. The Euler space showing the crystal orientation distribution is shown in FIG.
Shown in Orientation components from the Cu orientation to the S orientation belonging to the beta fiber develop into non-uniform deformation regions such as shear bands. The dislocation density in such a non-uniform deformation region is S
The dislocation density is considerably higher than the dislocation density in the uniform deformation region that develops to the azimuth component from the azimuth to the Brass azimuth. For this reason, the density between the dislocation density in the region having the orientation from the Cu orientation to the S orientation and the dislocation density in the region having the orientation from the S orientation to the Brass orientation is generated, and the strength anisotropy is remarkable. In order to reduce the strength anisotropy, it is necessary to increase the uniform deformation region, that is, the azimuth density from the S azimuth to the Brass azimuth as much as possible. However, as a result of repeated experiments, it has been found that if the ratio (Cu to S / S to Brass) is 5.0% or less, the strength anisotropy can be reduced to a level that does not cause a problem.

Strength anisotropy (0, 45,
The fact that the maximum proof stress difference in the 90 ° direction) is 25 MPa or less will be described. If the strength anisotropy is greater than 25 MPa, the lid does not swell evenly due to internal pressure, but preferentially swells in the direction of lower strength. More likely to occur.
However, it has been found that such a phenomenon is unlikely to occur when the strength anisotropy is 25 MPa or less.

If the proof stress is less than 270 MPa, the pressure resistance is practically insufficient, and a positive pressure can such as a carbonated beverage can or a beer can cause distortion. Therefore, the proof stress needs to be 270 MPa or more.

Next, the manufacturing process of the present invention will be described.

The Al ingot is heated at a temperature of 400 to 550 ° C. for 1 to 10 hours. If the heating temperature is lower than 400 ° C., the hot workability is reduced.
The oxidation of g is promoted, and the surface properties are reduced. Further, if the holding time is less than 1 hour, a homogeneous effect of the tissue cannot be obtained, and
Exceeding the time causes a decrease in productivity and increases the size of the crystallized material, so that when forming a plate, a large number of high dislocation density regions, that is, non-uniform deformation regions are formed around the crystallized material, and the strength anisotropy increases. . Therefore, the heating temperature is 400 to 550
° C, and maintained for 1 to 10 hours.

Subsequently, hot rolling is performed and final cold rolling is performed. Before the final cold rolling, if necessary, continuous annealing (hereinafter abbreviated as CAL) or batch annealing is performed after hot rolling, or primary cold rolling is performed after hot rolling to perform CAL.
Alternatively, batch annealing may be performed. In that case, the primary cold rolling reduction is desirably 55% or more in order to control the size of the recrystallized grains formed by annealing. In the case where continuous annealing is performed at a temperature lower than 320 ° C., an unrecrystallized structure is formed, and the effect of CAL does not appear. On the other hand, when the temperature exceeds 550 ° C., the recrystallized grains become coarse and the formability is reduced, or the strength anisotropy of the product plate is increased. For this reason, the continuous annealing condition is set to a temperature range of 320 to 550 ° C. and a holding time of 10 minutes or less that does not cause a decrease in productivity. In the case of batch annealing, if the temperature is lower than 250 ° C., a non-recrystallized structure is formed, and the effect of batch annealing does not appear. On the other hand, if the temperature exceeds 500 ° C., the recrystallized grains become coarse and the formability is reduced, or the strength anisotropy in the product plate is increased. Therefore, the conditions of batch annealing are such that the average temperature rise of 10 to 50 ° C./hour does not cause a decrease in productivity in the temperature range of 250 to 500 ° C.
Heat treatment is performed at a cooling rate for 0.5 hours or more.

Annealing or rolling must be controlled so that the initial average grain size at the time of final cold rolling (the grain size at the start of rolling) is 250 μm or less. If final cold rolling is performed immediately after hot rolling, 220 to 3
Hot rolling must be terminated in the range of 90 ° C.
When the hot rolling is completed at a temperature lower than 220 ° C., the edge cracks of the sheet become remarkable and the productivity is reduced. On the other hand, if hot rolling is completed at a temperature exceeding 390 ° C., recrystallized grains may become coarse and the average crystal grain size may exceed 250 μm. When the average crystal grain size is exceeded, the shear band is remarkably developed by the subsequent rolling, the orientation density of the Cu to S orientation is increased, and coarse old crystal grains remain to exhibit a function like a single crystal. For,
Increase the strength anisotropy of the product plate.

The final cold rolling is performed at a rolling reduction of 40 to 95%. If the final cold rolling reduction is less than 40%, the required strength as a can lid material cannot be obtained. On the other hand, if it exceeds 95%, the non-uniform deformation region increases and the strength anisotropy increases, or the dislocation density becomes high, so that the rivet formability decreases. Therefore, the final cold rolling reduction was set to 40 to 95%.

[0023] After the final cold rolling, a further finish annealing at a temperature in the range of 100 to 240 ° C for 0.5 to 10 hours reduces the strength anisotropy. If the finish annealing temperature is less than 100 ° C., the effect is not remarkably exhibited. On the other hand, if the temperature exceeds 240 ° C., the material may be softened and the strength may be insufficient. If the time is less than 0.5 hour, the effect is hard to appear, while
If it exceeds 10 hours, the productivity will be reduced. In addition, when the sheet temperature after the final cold rolling reaches 100 to 240 ° C., and when the same temperature and time conditions as the above annealing conditions are satisfied in the subsequent cooling process, the same effect is finally obtained. Therefore, it is not always necessary to perform the finish annealing again by the annealing furnace.

[0024]

EXAMPLE An ingot of an Al alloy having various chemical components shown in Table 1 was subjected to a heat treatment at 500 ° C. for 6 hours and hot-rolled.
And finished to a final plate thickness of 0.26 mm. Only production code A is annealed after hot rolling and before cold rolling. During the production process, the initial average grain size before the final cold rolling was observed. When the grain size was 250 μm or less, it was described as ○, and when it exceeded 250 μm, it was described as x.

[0025]

[Table 1]

[0026]

[Table 2]

Various measurements and evaluations were performed using the finished plate. The manufactured plate is subjected to 2
Measure the proof strength by painting and baking at 70 ° C x 20s,
The texture at the center of the plate thickness was measured. The azimuth density was determined by measuring incomplete pole figures of {200}, {220}, and {111}, and using them to calculate and evaluate a three-dimensional azimuth distribution function. The rivet formability was evaluated by covering the material subjected to the paint baking treatment, dropping about 10 ml of a 1% NaCl solution, and measuring the current flowing after applying a voltage of 6 V for 3 seconds. The larger the degree of cracking, the higher the energizing current value. Therefore, the case where the energizing current value was 15 mA or more was rejected (x). Further, the plate subjected to the paint baking treatment was torn along the rolling direction, and the tearing load at that time was compared with that of the conventional material to evaluate the tearability. The case where the material was superior or equal to the conventional material was evaluated as ○, and the case where the material was inferior to the conventional material was evaluated as ×. Table 3 shows the results.

[0028]

[Table 3]

As shown in the table, all of the inventive examples show excellent characteristics. That is, the production codes A and C were excellent in strength anisotropy and good in rivet formability and tearability because they were manufactured by the process of the present invention using the alloy of the present invention. On the other hand, the alloys of the present invention were used for B, D, E, F, and G. However, since the manufacturing process did not satisfy any of the conditions, the proof stress was insufficient or the strength anisotropy was out of the specified value. Also, the rivet formability was poor and the test was rejected. H, I, J, K, L, M, and N were manufactured by the process of the present invention, but because the alloy of the present invention was not used, strength, strength anisotropy, rivet formability and tearability were inferior. Rejected.

[0030]

As described in detail above, according to the present invention,
When used for cans with high internal pressure such as for carbonated drinks and beer, even if the lid expands due to internal pressure, local stress concentration does not occur, cracks are less likely to occur during deformation, and rivet forming It is possible to obtain an aluminum hard plate having excellent tearability and good tearability.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an Euler space showing a crystal orientation distribution in a texture of aluminum.

[Explanation of symbols]

 ψ1, ψ2, φ ‥‥‥ Euler angle coordinates Cu, S, Brass ‥‥‥ Each crystal orientation

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22F 1/00 691 C22F 1/00 691B 691C 694 694A

Claims (2)

[Claims] 1. Mg 3.5-5.0% (mass%, the same applies hereinafter), Mn 0.15-0.6%, Si 0.02-0.2
0%, Cu 0.01 to 0.20, Fe 0.40% or less,
Ti not more than 0.03% and (Fe + Mn) / Si is 2
0 or less, the balance having a composition consisting of Al and inevitable impurities, and the sum of the orientation densities (Cu to S) from the Cu orientation to the S orientation belonging to the beta fiber among the rolling texture components at the center of the plate thickness. Ratio of total (Brass to S) of orientation densities from S orientation to Brass orientation (Cu to S) /
(Brass-S) is 5.0 or less, The aluminum hard plate for can lids with small strength anisotropy characterized by the above-mentioned. 2. Mg 3.5-5.0%, Mn 0.15-
0.6%, Si 0.02 to 0.20%, Cu 0.01 to
0.20, Fe 0.40% or less, Ti 0.03% or less, (Fe + Mn) / Si is 20 or less, and the balance is A
1 and an ingot of Al inevitable impurities
After performing heat treatment at a temperature range of 50 ° C. for 1 to 10 hours, hot rolling is performed so that the initial crystal grain size before final cold rolling is 250 μm or less, and a rolling reduction of 40 to 95%. The final cold rolling is performed, and after the final cold rolling, 100 to 2
Finish annealing is performed at a temperature range of 40 ° C. for 0.5 to 10 hours, and among the rolling texture components in the center of the sheet thickness, the sum of the orientation densities from the Cu orientation to the S orientation belonging to the beta fiber and the Brass orientation from the S orientation. A ratio (Cu to S) / (Brass to S) of the sum of the orientation densities up to 5.0 is not more than 5.0.