JP2017222918A - Aluminum alloy sheet for can top - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy sheet for a can top jointly having high strength, bending workability and can operability.SOLUTION: The high strength, bending workability and can operability are jointly imparted, as the texture measured by the X-ray diffraction using a Cr light source of a 5,000 series aluminum alloy sheet having a specified composition, regarding the total of the orientation density in the Brass orientation, S orientation and Copper orientation, that of the central position of the sheet thickness of made higher than that of the surface layer of the sheet, and further, regarding the total of the orientation density of γ fiber, that of the surface layer of the sheet is made higher than that of the central position of the sheet thickness of the sheet.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an aluminum alloy plate for can lids, and relates to an aluminum alloy plate for easy open can lids having high strength, bending workability, and can openability.

  At present, as one of the packaging containers widely used for beverages and foods, the bottom and side walls are sealed at the bottomed cylindrical body (can body, can body) and the opening of this body part. A two-piece all-aluminum can having a disk-shaped lid (can lid, can end) on the upper surface is well known.

  As materials for such aluminum cans, due to differences in strength and formability required for each, the can body is made of AA to JIS3000 (Al-Mn) aluminum alloy plate, and the can lid is made of AA to JIS5000. (Al—Mg-based) aluminum alloy plates and the like are properly used.

  Among these, the important characteristics required for 5000 series aluminum alloy plates for can lids are cracking even if they are deformed due to formability that can withstand lid processing and pressure strength that can withstand the internal pressure of beverages after filling beverages, or changes in internal pressure. Crack resistance (these characteristics are combined and hereinafter referred to as pressure resistance), can openability so that the lid can be opened normally and easily by the attached tab.

  In recent years, from the viewpoint of cost reduction of cans, these can lids, that is, 5000 series aluminum alloy plates for can lids, are also required to have a thickness of about 0.2 mm. Examples of problems with such thinning include a decrease in pressure strength and a decrease in moldability. Among these, the decrease in the pressure strength can be compensated by increasing the material strength of the aluminum alloy plate. However, with such an increase in strength, there arises a problem that the formability decreases. For this reason, in order to reduce the thickness of the aluminum alloy plate for can lids, it is necessary to improve both strength and formability.

  For this reason, as a technique for improving the formability while maintaining the material strength even if the thickness of the 5000 series aluminum alloy plate for can lids is reduced, the amount of alloy element solid solution, intermetallic compound, crystal grain size, aggregate Various control of the structure such as the structure, subgrain, precipitate, shear band (shear band) has been performed.

  For example, Patent Document 1 describes an aluminum alloy plate for an Al—Mg can lid containing Mn, Fe, Si, and Ti. This document describes that this aluminum alloy plate is excellent in formability, pressure strength and can openability.

  Patent Document 2 describes an aluminum alloy plate for an Al—Mg-based can lid containing Mn, Si, Cu, Fe, and Ti. In the same document, the strength anisotropy is obtained when the sum of the orientation densities of the Cu, S, and Brass orientations is less than 50 times the random orientation among the rolling texture components of the 1/4 thickness portion. It is described that it is small, the ear rate is stably lowered, and is excellent in moldability and can openability.

  In Patent Document 3, as the texture of an aluminum alloy plate for can lids containing Mg, Fe, Si, Mn, and Cu, X-ray diffraction intensities I (200) and (220) from the (200) plane of the plate surface are disclosed. The ratio to the X-ray diffraction intensity I (220) from the surface, I (200) / I (220) is described to be less than 0.6. This document solves the problems of the above-mentioned Patent Documents 1 and 2 and improves the can openability without impairing the pressure resistance and formability of the Al-Mg alloy plate for can lids (open can) The load can be reduced).

JP 2001-164347 A JP 2002-105574 A Japanese Patent Laying-Open No. 2015-189997

  As described above, the requirements for formability and pressure resistance of the 5000 series aluminum alloy plate for can lids are becoming higher as the thickness is reduced.

  As an index for comprehensively evaluating severe formability and pressure resistance during such thinning, there is evaluation of bending workability by a push bending method (roller bending method) described later with reference to FIG. This push-bending method is stricter than other winding methods and bending test methods such as the V-block method with a bending angle of 90 °. If the bending workability evaluated by this push-bending method is improved, the can lid 5000 Even if the formability of the aluminum alloy plate is improved and thinned, it can withstand lid processing and is not easily broken, and coating film defects due to lid processing are less likely to occur. In addition, cracks are less likely to occur during deformation due to changes in internal pressure after beverage filling, and pressure resistance increases as a lid after being attached to a can.

  The conventional 5000 series aluminum alloy plate for can lids still has the problem that the rivet formability is good, but the bending workability by the push bending method is not always good. This means that the conventional 5000 series aluminum alloy plate for can lids does not necessarily have a comprehensive combination of properties such as formability and pressure resistance on the premise that it has high material strength.

  In response to such a problem, the present invention is excellent in formability and pressure resistance represented by the bending workability by the above-described bending method, while maintaining the strength of the 5000 series aluminum alloy plate for can lids, and is open. An object of the present invention is to provide an aluminum alloy plate for can lids (which has high strength, bending workability, and can openability) excellent in can properties.

The gist of the aluminum alloy plate for can lids having high strength, bending workability, and can openability of the present invention for solving the above problems is as follows: Mg: 3.8 to 5.5 mass%, Fe: 0.00. 10 to 0.50 mass%, Si: 0.05 to 0.30 mass%, Mn: 0.01 to 0.60 mass%, Cu: 0.01 to 0.30 mass%, the balance being Al And an aluminum alloy plate made of inevitable impurities,
As a texture measured by X-ray diffraction using a Cr light source,
The total βc of the azimuth densities of the Brass azimuth, S azimuth, and Copper azimuth at the center of the thickness of the plate is 20 or more and 40 or less, and the Brass azimuth and S azimuth of the surface layer of the plate with respect to the total βc of the azimuth density The ratio βs / βc of the total density βs of Copper orientations is less than 1.0,
Further, the total γs of γ fibers on the surface layer of the plate is 3 or more and 10 or less, and the γ fibers on the surface layer of the plate with respect to the total γc of γ fibers at the center position of the plate thickness. The ratio γs / γc of the sum γs of the azimuthal densities exceeds 1.0.

  As described above, the structure of the plate defined in the present invention is an aluminum alloy plate for a can lid, an aluminum alloy plate after a cold-rolled plate is subjected to coating and paint baking treatment, or a can lid formed with this plate. It is prescribed as an organization. Moreover, the structure of the board after performing the heat processing on the specific conditions mentioned later which simulated the coating baking process to the said cold-rolled board may be sufficient.

  The present invention balances the surface layer of the plate and the plate thickness center position (plate thickness center position) in a specific range for a specific texture of the aluminum alloy plate for can lids, and the orientation of the Brass, S, and Copper orientations. The plate thickness center position is made larger than the surface layer of the plate as the sum of the density, and the surface layer of the plate is made larger than the plate thickness center position of the plate as the sum of the orientation density of the γ fibers.

  As a result, the present invention does not need to reduce the material strength in order to obtain excellent moldability as in the prior art, and even when the plate thickness is reduced to about 0.2 mm, there is no shortage of pressure strength, and high An aluminum alloy plate for can lids having strength, bending workability, and can openability can be provided.

It is a front view which shows the outline | summary of the testing apparatus of bending workability. It is a top view of the can lid used for the can open test. It is sectional drawing of the score 3 of the can lid used for the can open test. It is a schematic diagram of the can opening load measuring machine which measures the load at the time of can opening.

  The form for implementing the aluminum alloy plate for can lids which concerns on this invention is demonstrated below.

(Aluminum alloy composition)
As described above, the aluminum alloy plate for can lids must satisfy the formability, pressure resistance, and can openability as the characteristics required for the can lid.

  Therefore, the alloy composition of the aluminum alloy plate for can lids according to the present invention also satisfies these required characteristics from the aspect of the alloy composition, Mg: 3.8 to 5.5% by mass, Fe: 0.10 to 0.00. 50% by mass, Si: 0.05 to 0.30% by mass, Mn: 0.01 to 0.60% by mass, Cu: 0.01 to 0.30% by mass, the balance being Al and inevitable impurities It shall consist of Hereinafter, the significance of each element contained will be described in order.

Mg: 3.8 to 5.5% by mass
Mg has the effect of improving the strength of the aluminum alloy plate. When the content of Mg is less than 3.8% by mass, the strength of the aluminum alloy plate is insufficient, and the pressure strength when formed into a can lid is insufficient. On the other hand, when the Mg content exceeds 5.5% by mass, the strength of the aluminum alloy plate becomes excessive, and the bending workability is lowered. Therefore, the Mg content is 3.8 to 5.5% by mass, preferably 3.8 to 5.0% by mass.

Fe: 0.10 to 0.50 mass%
Fe forms Al-Fe (-Mn) -based and Al-Fe (-Mn) -Si-based intermetallic compounds in the aluminum alloy plate, and improves the tearability of the score part when it is molded into a can lid. There is an effect of improving canability. If the Fe content is less than 0.10% by mass, the tearability of the score part does not improve, and score derailment occurs when the can is opened (the crack propagates to other than the score part when the can is opened) and the opening force increases. Opening defects such as tab breakage are likely to occur. On the other hand, when the Fe content exceeds 0.50% by mass, the number density and volume ratio of the intermetallic compound produced during casting or hot rolling in the aluminum alloy plate increase, and the bending workability decreases. Therefore, the Fe content is 0.10 to 0.50 mass%, preferably 0.10 to 0.30 mass%.

Si: 0.05-0.30 mass%
Si forms Mg-Si-based and Al-Fe (-Mn) -Si-based intermetallic compounds in an aluminum alloy plate, improves the tearability of the score part when molded into a can lid, and improves can openability There is an effect to make. When the Si content is less than 0.05% by mass, the can opening property is not improved as in the case of Fe. Moreover, since the required purity of the aluminum ingot used for the raw material of an aluminum alloy plate becomes high, cost increases. On the other hand, when the Si content exceeds 0.30% by mass, the number density and volume ratio of the intermetallic compound produced during casting or hot rolling in the aluminum alloy plate increase, and the bending workability decreases. Accordingly, the Si content is 0.05 to 0.30 mass%, preferably 0.05 to 0.20 mass%.

Mn: 0.01-0.60 mass%
Mn has the effect of improving the strength of the aluminum alloy sheet, and when Al-Fe-Mn and Al-Fe-Mn-Si intermetallic compounds are formed in the aluminum alloy sheet and formed into a can lid. There is an effect of improving the tearability of the score part and improving the can openability. When the content of Mn is less than 0.01% by mass, the effect of improving the strength of the aluminum alloy plate or the effect of improving the openability when formed into a can lid cannot be obtained. On the other hand, when the content of Mn exceeds 0.60% by mass, the number density and volume ratio of the intermetallic compound produced during casting or hot rolling in the aluminum alloy plate increase, and the bending workability decreases. Therefore, the Mn content is 0.01 to 0.60 mass%, preferably 0.30 to 0.50 mass%.

Cu: 0.01-0.30 mass%
Cu has the effect of improving the strength of the aluminum alloy plate. Moreover, work hardening characteristics improve by making it dissolve. When the Cu content is less than 0.01% by mass, the solid solution amount is small and the strength is lowered. On the other hand, when the Cu content exceeds 0.30% by mass, the strength of the aluminum alloy plate becomes excessive, and the bending workability decreases. Therefore, the Cu content is 0.01 to 0.30 mass%, preferably 0.05 to 0.20 mass%.

Inevitable Impurities The aluminum alloy according to the present invention comprises the balance Al and inevitable impurities in addition to the essential components. Inevitable impurities are Cr 0.3 mass% or less, Zn 0.3 mass% or less, Ti 0.1 mass% or less, Zr 0.1 mass% or less, B 0.1 mass% or less, Other elements are allowed within a range of 0.05% by mass or less. If the content of inevitable impurities is within this range, the characteristics of the aluminum alloy plate according to the present invention are not affected.

(Aluminum alloy plate texture)
In the present invention, with the above-described alloy composition, the central position of the plate thickness is more than the surface layer of the plate as the total orientation density of the Brass, S, and Copper orientations for a specific texture of the aluminum alloy plate for can lids. And the surface layer of the plate is made larger than the central position of the plate thickness as the sum of the orientation density of the γ fibers.
In this way, by controlling the total sum of specific orientation densities so that they are balanced between the surface layer of the plate and the plate thickness center position (plate thickness center position), the strength is not lowered (while the strength is maintained). , Improve bending workability (formability and pressure resistance).

  Here, the specific texture is the sum of the orientation densities of the Brass, S, and Copper orientations as β fibers (β fiber texture), and {111} <112> or {111} <110> And the sum of orientation density of γ fibers (γ fiber texture).

More specifically, the total βc of the density of Brass, S, and Copper at the center of the thickness of the plate is set to 20 to 40 and the surface layer of the plate with respect to the total βc of the orientation density. The ratio βs / βc of the total βs of the azimuth densities of the Brass, S, and Copper orientations is less than 1.0.
At the same time, the total γs of γ fibers on the surface layer of the plate is set to 3 or more and 10 or less, and the γ fibers on the surface layer of the plate with respect to the total γc of γ fibers at the center position of the plate thickness. It is assumed that the ratio γs / γc of the sum γs of the azimuthal densities exceeds 1.0.

In the aluminum alloy sheet, the texture of the rolled sheet is the β fiber (β fiber texture, β-fiber) including the Brass, S, and Copper orientations, {111} <112> and {111} <110> is known to exist as γ fibers (γ fiber texture, γ-fiber). And it has been known so far that the β fiber component is poor in bending workability and the γ fiber component is relatively good in bending workability.
However, until now, no more facts could be recognized, and on the basis of the above recognition, the manufacturing conditions were controlled so as to reduce the degree of accumulation of the β fiber component having poor bending workability. However, the strength was reduced.

In this situation, when the texture is measured by X-ray diffraction (XRD), if the Cr light source is used instead of the commonly used Cu light source, the texture information of the plate surface layer can be obtained more accurately. It became clear.
In the present invention, using such a measurement technique, the investigation is conducted by paying attention to the mutual relationship between the texture of the plate surface that greatly affects the bending workability and the texture of the central position of the plate thickness that affects the strength. did.
As a result, for the β fiber and γ fiber, the balance of orientation density at the surface layer and plate thickness center position of each plate greatly affects the bending workability, and if these are balanced to a specific range, It has been found that the bending workability can be improved without reducing the strength.

Sum of azimuth density of Brass azimuth, S azimuth, and Copper azimuth If strength sum βc of azimuth density of Brass azimuth, S azimuth, and Copper azimuth at the center position of the plate thickness is less than 20, the strength decreases. On the other hand, if this βc exceeds 40, the bending workability deteriorates. Therefore, the total βc of the azimuth densities is in the range of 20 to 40.

  Further, the ratio βs / βc of the sum βs of the azimuthal density of the Brass azimuth, S azimuth, and Copper azimuth of the surface layer of the plate to the total azimuthal density βc of the Brass azimuth, S azimuth, and Copper azimuth at the center of the plate thickness is 1. When it is 0.0 or more, the bending workability is lowered. Accordingly, the ratio βs / βc of the sum of the orientation densities is less than 1.0.

Sum of γ fiber orientation density At the same time, if the sum γs of γ fiber orientation densities on the surface layer of the plate is less than 3, bending workability is lowered. On the other hand, when γs exceeds 10, the strength decreases. Therefore, the total sum γs of the azimuth densities of γ fibers on the surface layer of the plate is in the range of 3 to 10.

  Further, when the ratio γs / γc of the total γs of azimuth densities of γ fibers on the surface layer of the plate to the total γc of γ fibers at the center of the plate thickness is 1.0 or less, the bending workability is increased. descend. Accordingly, the ratio γs / γc of the sum γc of the γ fibers at the center of the plate thickness to the sum γs of the γ fibers on the surface layer of the plate exceeds 1.0.

  Here, the bending workability is evaluated by the presence or absence of cracks or rough skin at the apex of the test piece bent by the push bending method of FIG. Based on such evaluation, in order to improve the bending workability, it is usual to suppress and control a coarse intermetallic compound that is likely to be the starting point of the cracks and rough skin, thereby improving the bendability. . And the existence state of such a coarse intermetallic compound is controllable with the said alloy composition or a normal manufacturing method.

In this respect, the present invention also presupposes suppression of such a coarse intermetallic compound by a conventional method. However, in the present invention, in addition to this, by controlling the specific texture of the aluminum alloy plate for can lids so that the surface layer of the plate and the center of the plate thickness are balanced, the cracks and rough skin are prevented. It is made difficult to occur and the bending workability is further improved.
As a result, the present invention can achieve both bending workability and high strength, which has been difficult to achieve in the past. That is, as a characteristic of the aluminum alloy plate for can lids, the 0.2% proof stress of the aluminum alloy plate for can lids after being baked and coated after cold rolling and the bending workability of this plate are both high. can do. More specifically, as in the examples described later, even when the 0.2% proof stress is 300 MPa or more, it has high bending workability and can have high strength and high formability.

Measurement of texture by X-ray diffraction method:
The orientation density of the texture between the surface layer of these plates and the center position of the plate thickness (Orientation Density) is measured and calculated by the surface layer of the test material (the region from the outermost surface of the test material to the penetration depth of X-ray diffraction) ) Or the center position of the plate thickness obtained by polishing, can be performed by X-ray diffraction using a Cr light source instead of a commonly used Cu light source.
In this Cr light source, the X-ray tube of the X-ray diffractometer is a Cr tube (chrome tube), and a complete pole figure or incomplete pole figure (Pole Figure) is measured by the chromium Kα ray from the Cr tube. If this Cr light source is used, since the penetration depth of the X-ray becomes shallower than that of the conventional Cu light source, information on the outermost layer can be obtained. Moreover, if it measures after grind | polishing to the plate | board thickness center, only the plate | board thickness center part information will be obtained and the difference with surface layer structure | tissue can be clarified.

  The orientation density of each orientation defined in the present invention is determined by measuring the complete pole figure or the incomplete pole figure of the surface layer of the plate or the central position of the plate thickness by an X-ray diffraction method using a Cr light source. It is obtained using an orientation distribution function (ODF). The orientation density of each orientation thus obtained is calculated as a ratio to the orientation density of a standard sample having a random texture without orientation orientation in which aluminum powder is sintered.

  Specific measurement and analysis methods of the texture using these X-ray diffraction and analysis methods are known per se, and are described in, for example, “Cross texture” written by Shinichi Nagashima, published by Maruzen Co., Ltd., 1984, P8-44, etc. ing.

(Bending test)
As an evaluation index of the bending workability of the aluminum alloy plate for can lids, there is the push bending method (roller bending method) shown in FIG. In this push-bending method, a plate-shaped test piece is placed on two supporting rotating rolls spaced apart, and a load is applied from above to the center of the plate with a pressing metal, and the plate is bent downward. Bend into a letter shape.

This push-bending method is a severe test method among bending work tests. If the bending workability evaluated by this push-bending process is improved, the formability of a 5000 series aluminum alloy plate for can lids is improved and the wall thickness is reduced. Even if it is done, it will endure lid processing and it will be hard to break, and it will become difficult to produce the coating-film defect by lid processing. In addition, cracks are less likely to occur during deformation due to changes in internal pressure after beverage filling, and pressure resistance increases as a lid after being attached to a can.
That is, according to this push-bending method, whether the conventional 5000 series aluminum alloy plate for can lids has comprehensive properties such as formability and pressure resistance on the premise of having high material strength. Can be evaluated. In other words, even if individual or individual evaluation of specialized formability such as rivet formability is good, if the bending workability by this push bending method is not excellent, as a 5000 series aluminum alloy plate for can lids, This means that it does not always have characteristics such as moldability and pressure resistance.

  As described above, the structure of the plate defined in the present invention as described above is the aluminum alloy plate after the cold-rolled plate (the plate after cold-rolling) is subjected to painting and baking treatment as the aluminum alloy plate for can lids. It is the structure of a (pre-coated board) or the structure of a can lid formed from this board. In addition, the plate after the heat treatment under the specific conditions described later was performed on the cold-rolled plate, which was not subjected to such painting or paint baking treatment, or formed into a can lid, simulating the paint baking treatment. It may be an organization. These structures are the same or can be regarded as the same by a slight difference if the conditions of the paint baking process and the heat treatment are the same.

(Production method)
Next, the manufacturing method of the aluminum alloy plate for can lids in this invention is demonstrated.
The production process of the aluminum alloy sheet of the present invention itself includes, as usual, a casting process in which an aluminum alloy having the above composition is melted and cast to form an ingot, and a homogenization heat treatment process in which the ingot is homogenized by heat treatment. A hot rolling process in which a homogenized ingot is hot-rolled to form a hot-rolled sheet, a primary cold-rolling process in which the hot-rolled sheet is cold-rolled, and an intermediate annealing of the primary cold-rolled sheet The intermediate annealing process is performed, and the secondary cold rolling process is performed to cold-roll the intermediate annealed plate. Hereinafter, it demonstrates in order of a process.

  First, an aluminum alloy is melted, and an aluminum alloy having the above composition is cast by a known semi-continuous casting method such as a DC casting method. Incidentally, in continuous (CC) casting, the size of the intermetallic compound is small and the volume ratio is also small, so there is a possibility that the openability of the can deteriorates (the open load becomes high), and it is better to use the DC casting method. preferable.

Homogenization heat treatment:
Next, after removing the area | region used as an inhomogeneous structure | tissue of an ingot surface layer by chamfering, homogenization heat processing is performed. As a result, internal stress is removed, solute elements segregated during casting are homogenized, and intermetallic compounds crystallized during casting are diffused and solidified to homogenize the structure. Therefore, the homogenization heat treatment is preferably maintained at a temperature of 450 ° C. or higher for 1 hour or longer.

  When the homogenization heat treatment temperature is less than 450 ° C. or the holding time is less than 1 hour, the homogenization effect may be reduced, and the mechanical properties and can openability may be reduced. The upper limit of the holding time is 20 hours, and even if it exceeds this, there is no great difference in the homogenizing effect, and the productivity may decrease.

Hot rolling:
After this homogenization heat treatment, the ingot is continuously cooled or cooled to a predetermined starting temperature, first hot rough rolled, and further hot finish rolled to hot-roll aluminum alloy having a predetermined thickness. A board. In the hot rough rolling, the temperature at which the rough rolled plate is minimum between passes is preferably 450 ° C. or higher.
Subsequent to this hot rough rolling, hot finish rolling is performed without delay or continuously to obtain a hot rolled sheet. At this time, it is preferable to finish the finish hot rolling at 300 ° C. or higher.

Cold rolling and intermediate annealing:
Subsequently, this hot-rolled sheet is subjected to primary cold rolling (primary cold rolling), intermediate annealing, secondary cold rolling (secondary cold rolling) to obtain a cold rolled sheet (cold rolled sheet).
Since the surface roughness of the roll used for cold rolling, including these primary and secondary, affects bending workability, Ra is preferably 0.5 μm or more, more preferably 0.8 μm or more, and still more preferably Is roughened to 1.0 μm or more. If this roll roughness is large, the friction increases and the amount of shear strain introduced into the surface layer of the plate during rolling increases, so that the γ fiber component containing {111} <112> or {111} <110> in the surface layer The bending workability is improved. The upper limit of the roll roughness is not particularly defined, but is set to 3.0 μm or less in order not to make the surface roughness of the plate too rough. These roll roughnesses are measured according to JIS B 0601-2001.

  Conventionally, the surface roughness of rolls used for cold rolling, including primary and secondary, is made fine by setting Ra to be less than 0.5 μm, and the surface roughness of the plate is made as fine as possible. I tried to improve the properties. However, if Ra is set too low, such as less than 0.5 μm, bending workability is lowered.

  The total rolling ratio of the primary cold rolling is preferably 60% or more, more preferably 70% or more. When the total rolling rate is less than 60%, the accumulated strain due to rolling becomes insufficient, the recrystallized grain size becomes large in the subsequent intermediate annealing, and the bending workability may be deteriorated.

  The primary cold-rolled cold-rolled sheet is preferably annealed and recrystallized, and the solid solution amount of the alloy element is increased. This intermediate annealing is performed in a continuous annealing process (equipment), and is preferably performed in the shortest possible time of the maximum attainable temperature of 400 ° C to 550 ° C and the holding time at the maximum attainable temperature of 60s or less. It is preferable that both the heating rate up to and the cooling rate from the maximum temperature reached 100 ° C./min or more. When the heating rate is less than 100 ° C./min, the holding temperature exceeds 550 ° C., the holding time exceeds 60 s, and the cooling rate is less than 100 ° C./min, growing. For this reason, moldability may be reduced. Moreover, when the highest temperature of intermediate annealing is less than 400 degreeC, while a process structure | tissue will remain in the aluminum alloy plate after completion | finish of an annealing process, the solid solution amount of an alloy element may reduce.

In the secondary cold rolling, the number of rolling is preferably 2 passes or more, and the roll roughness used is preferably the roll roughness in all passes other than the final pass. However, the roll roughness of the final pass may be adjusted according to the required quality of the product, and Ra may be less than 0.5 μm.
Further, the rolling allowance for the first pass is preferably 0.3 mm or more, more preferably 0.4 mm or more. If this rolling allowance is too low, bending workability will be reduced. The upper limit of the rolling allowance for the first pass is not particularly defined, but is about 0.6 mm.
When the rolling allowance of the first pass of secondary cold rolling is increased in this way, the amount of shear strain introduced into the surface layer of the plate during rolling increases in addition to increasing the surface roughness of the roll as described above. The gamma fiber component containing {111} <112> and {111} <110> on the surface layer of the plate increases, and the bending workability is improved.

  The aluminum alloy plate for can lids manufactured by the above process is subjected to a surface treatment such as a chromate type or a zircon type, and an organic paint such as an epoxy resin, a vinyl chloride sol type, or a polyertel type is applied, and PMT (Peak Metal Temperature: After the metal baking temperature is 200 to 280 ° C. and a pre-coating plate is formed, it is formed into a can lid. In the present invention, the heat treatment simulating a paint baking process for evaluation of strength, bending workability, and can openability is 260 ° C. × 20 seconds in order to provide reproducibility from this paint baking process condition range. Is selected as one point.

(Production method of can lid)
An example of a known method for producing a can lid from a material aluminum alloy plate (cold rolled plate) will be described below.

As described above, a blank material obtained by punching (blanking) a blank aluminum alloy plate (pre-coated plate), which has been pre-painted and baked, is drawn with a press to curl the outer periphery. After that, a sealing compound is applied to the curled portion to make a shell.
Thereafter, the following molding is performed as conversion molding. Using a press machine, rivet forming is performed to form a protrusion for attaching a tab to the center of the shell. This rivet molding is composed of a bubble molding process for projecting the central portion of the can lid and a button molding process for reducing the diameter of the projecting section (bubble) in 1 to 3 steps and making a sharp projection.

Next, a die having a cutting edge with a V-shaped cross-section is pressed to form a score 3 in FIG. 3 which is a groove of the drinking mouth, and to form irregularities and characters for increasing the rigidity of the panel.
Further, a tab formed separately is caulked and integrated with the convex portion processed at the center of the shell (this is called a stake process). A plan view of this integrated can lid is shown in FIG.
Then, the can lid is wound and sealed from the opening to the opening of the can body filled with the contents (beverage, food) from the opening.

  As mentioned above, although the form for implementing this invention was described, the Example which confirmed the effect of this invention is demonstrated concretely compared with the comparative example which does not satisfy | fill the requirements of this invention below. In addition, this invention is not limited to this Example.

(Sample aluminum alloy plate)
Each aluminum alloy having the composition shown in Table 1 was cast by a semi-continuous casting method (DC), and in common with each example, the ingot surface layer was chamfered to produce a slab. The slab was subjected to a homogenization heat treatment of 500 ° C. × 4 hours in common with each example, and then hot rough rolling was started at the temperature of 500 ° C., and the end temperature of the subsequent hot finish rolling was set to 330 ° C. As a hot rolled plate having a thickness of 3 mm.

The hot rolled sheet was subjected to primary cold rolling at various roll roughnesses (μm) shown in Table 1. However, in order to obtain the same final sheet thickness in each example while changing the secondary cold rolling rate, the rolling rate was performed at various rolling rates of 60% or more.
Thereafter, in each example, intermediate annealing was performed with continuous annealing equipment at a maximum material temperature of 400 ° C. and a holding time of less than 1 minute. The heating rate up to the holding temperature and the cooling rate from the holding temperature during the intermediate annealing were both set to 100 ° C./min or more in common.

  After that, secondary cold rolling was performed with the total rolling rate (%), roll roughness (μm) in the first pass (μm), and rolling reduction in the first pass (mm) as shown in Table 1, with two rolling cycles. It was. However, only in Invention Example 13 and Comparative Example 31, the number of rolling was set to 3 times. The roll roughness (μm) in the second pass or the third pass was commonly set to 0.3 μm. By this secondary cold rolling, an aluminum alloy plate for can lids having a plate thickness of 0.2 mm was produced in common with each example.

  The aluminum alloy plate produced in this way was simulated by a paint baking process, and in common, without being painted, only subjected to heat treatment at 260 ° C. for 20 seconds in an oil bath, with the following structure and characteristics: Samples for measurement and evaluation were used. These results are shown in Table 2.

(Measurement of texture by X-ray diffraction)
The texture of the specimen was measured by X-ray diffraction using a Cr light source. At this time, by measuring the cut specimen as it is (without removing the oxide film), first obtain information on the texture of the surface layer, and then measure after polishing to the center of the plate thickness Thus, information on the texture at the center position of the plate thickness was obtained.
Then, the sum of the azimuth densities of the Brass azimuth, S azimuth, and Copper azimuth at the center of the plate thickness β, and the total azimuth density βs of the Brass azimuth, S azimuth, and Copper azimuth of the surface layer of the plate to be defined relative to the sum of the azimuth densities βc. The ratio βs / βc was measured and analyzed.
Further, the total γc orientation density γc at the center position of the plate thickness of the specified plate, and the ratio γs / γc of the total γs orientation density γs of the surface layer of the plate to the total γc of this orientation density, Analyzed.

  These textures were measured using a Rigaku X-ray diffraction apparatus RINT2100 using the Cr light source (target) and a target output (tube voltage-tube current) of 40 kV-30 mA.

0.2% Yield Strength A JIS-5 tensile test piece was prepared from the specimen so that the tensile direction was parallel to the rolling direction. Using this test piece, a tensile test was performed according to JIS-Z2241, and a 0.2% yield strength was obtained. An appropriate range of 0.2% proof stress is 300 MPa or more, and within this range, even a thin can lid satisfies the compressive strength.

Bending workability The bending workability is obtained by processing the sample material into a plate-like test piece having a length of 80 mm and a width of 25 mm, and then pressing the plate-like test piece by a press bending method (roller bending method) shown in FIG. Placed on two supporting rotating rolls spaced 0.95 mm apart, bent from the top to the center of the plate by applying a load with a pusher with a tip of R of 0.2 mm from the top. It was bent into an acute V shape with an angle of 15 °.
And, by observing the surface of the tip part, it is evaluated as ◯ that there is no rough skin or cracking, or there is rough skin but no crack (crack) is good for bending workability and can be used for can lids did.
In addition, a sample having rough skin and having cracks with a width of less than 150 μm was evaluated as Δ for being usable as a can lid depending on conditions.
Furthermore, those having large cracks with a width of 150 μm or more were evaluated as x because the bending workability was inferior and they could not be used for can lids.

Can Opening Load The test material was subjected to shell molding, conversion molding, and tab stake using a 204-diameter full-form end mold, and then a can opening test was performed.
FIG. 2 is a plan view of the can lid used in the can open test.
FIG. 3 is a cross-sectional view of the score 3 of the can lid used in the can open test.
FIG. 4 is a schematic view of a can opening load measuring machine for measuring the load at the time of opening the can. Among these, FIG. 4A is a perspective view of the can opening load measuring device 5. FIG. 4B is a schematic cross-sectional view of the vicinity of the can lid 1 when measured by the can opening load measuring device 5. FIG. 4C is a schematic front view showing the direction of the can lid 1 when the can lid 1 is installed in the can opening load measuring device 5.

  Specifically, the can lid 1 is placed on the can opening load measuring machine 5 so that the tab 4 is located above the score 3 with respect to the score 3 (FIG. 4C). A latch 6 is hooked on the tab 4 of the can lid 1 to form a latch 7 (FIG. 4B). The latch 6 was pulled in the horizontal direction to apply a 3N tensile load, and the latch 6 was stationary in that state, and then the can lid 1 was rotated in the X direction. The load was measured with a load cell, and the highest load was taken as the can open load. The appropriate range of the can opening load was 21 N or less.

As shown in Table 1, the inventive examples have a component composition within the scope of the invention and are all manufactured under preferable manufacturing conditions.
Therefore, as shown in Table 2, as a texture, the total density βc of the plate thickness center position, the ratio of the total density βs / βc, the total surface density γs of the plate surface, the direction density Respectively satisfying the ratio γs / γc of the sum.
As a result, as shown in Table 2, the invention examples have appropriate 0.2% proof stress and can open load, and are excellent in bending workability. That is, the strength is increased while maintaining the moldability, and both the moldability and the strength can be achieved. Therefore, although the aluminum alloy plate of an Example is as thin as 0.2 mm, it can be used conveniently for an easy open can lid.

On the other hand, as shown in Table 1, Comparative Examples 18 to 27, as shown in Table 1, although the component composition is not within the specified range of the present invention and all are manufactured under preferable manufacturing conditions, Any of 2% proof stress, bending workability, and can open load does not meet the appropriate values.
Comparative Example 18 has too little Mg.
Comparative Example 19 has too much Mg.
Comparative Example 20 has too little Fe.
Comparative Example 21 has too much Fe.
Comparative Example 22 has too little Si.
Comparative Example 23 has too much Si.
The comparative example 24 has too little Mn.
Comparative Example 25 has too much Mn.
Comparative Example 26 has too little Cu.
Comparative Example 27 has too much Cu.

In Comparative Examples 28 to 31, as shown in Table 1, the composition of the components is within the specified range of the present invention, but the production conditions are not in the preferred range. Any one of the total orientation density βc at the position, the total orientation density ratio βs / βc, the total orientation density γs of the plate surface, and the total orientation density ratio γs / γc is out of the specified range.
As a result, in these comparative examples, as shown in Table 2, any of 0.2% yield strength, bending workability, and can open load does not satisfy the appropriate value.
In Comparative Example 28, the roll roughness of the primary cold rolling is too small.
In Comparative Example 29, the total rolling reduction of the secondary cold rolling is too low.
In Comparative Example 30, the roll roughness of the first pass of secondary cold rolling is too small.
In Comparative Example 31, the rolling allowance in the first pass of secondary cold rolling is too small.

  The above results support the significance of each requirement and preferred production conditions of the present invention for combining high strength, bending workability, and can openability.

  As described above, the present invention provides a can lid aluminum alloy plate that has high strength, bending workability, and can openability without the need to reduce material strength to obtain formability as in the prior art. it can. For this reason, it is optimal for an aluminum alloy plate used for a can lid that is thinned and strengthened, and that requires high formability under more severe conditions and can openability.

1 Can Lid 2 Rivet 3 Score 4 Tab 5 Opening Load Measuring Machine 6 Hook 7 Hook

Claims (1)

Mg: 3.8 to 5.5% by mass, Fe: 0.10 to 0.50% by mass, Si: 0.05 to 0.30% by mass, Mn: 0.01 to 0.60% by mass, Cu: An aluminum alloy plate containing 0.01 to 0.30 mass%, with the balance being Al and inevitable impurities,
As a texture measured by X-ray diffraction using a Cr light source,
The total βc of the azimuth densities of the Brass azimuth, S azimuth, and Copper azimuth at the center of the thickness of the plate is 20 or more and 40 or less, and the Brass azimuth and S azimuth of the surface layer of the plate with respect to the total βc of the azimuth density The ratio βs / βc of the total density βs of Copper orientations is less than 1.0,
Further, the total γs of γ fibers on the surface layer of the plate is 3 or more and 10 or less, and the γ fibers on the surface layer of the plate with respect to the total γc of γ fibers at the center position of the plate thickness. The aluminum alloy plate for can lids, wherein the ratio γs / γc of the total γs of the azimuthal density exceeds 1.0.