WO2012043582A1 - Cold-rolled aluminum alloy sheet for bottle can - Google Patents

Abstract

The present invention reduces the cost of production of a cold-rolled aluminum alloy sheet to be used as a material for bottle cans and reduces the width-direction unevenness of earing. This cold-rolled aluminum alloy sheet for bottle cans has a specific composition and has a structure which contains a small amount of dispersed particles having a center-of-gravity diameter less than 1 µm, which represent an α phase, and in which the ratio of the amount of the β phase that is an Al₆(Fe,Mn)-based intermetallic compound to the amount of the α phase that is an Al-Fe-Mn-Si-based intermetallic compound is 0.50 or more in terms of the ratio of the maximum height Hβ of the X-ray diffraction peaks and the maximum height Hα of the X-ray diffraction peaks, Hβ/Hα. Thus, the hot-rolled sheet in the invention has an even degree of recrystallization in the sheet-width direction, and the cold-rolled aluminum alloy sheet has low width-direction unevenness of earing.

Description

Aluminum alloy cold rolled sheet for bottle cans

The present invention relates to a material plate for bottle cans, and more particularly to an aluminum alloy cold-rolled plate for bottle cans. The aluminum cold-rolled alloy sheet in the present invention is a rolled sheet (cold-rolled sheet) that has been rolled through hot rolling-cold rolling, and has been cold-rolled or further subjected to heat treatment. It is a tempered board. Hereinafter, the aluminum alloy is also referred to as an Al alloy.

As an aluminum beverage can, a two-piece aluminum can obtained by seaming a can body and a can lid (can end) is often used. The can body is made by DI processing (Drawing and Ironing) of an aluminum cold-rolled plate, trimming to a predetermined size, degreasing and washing, and painting and printing. The can body is baked (baked), and the can body edge is necked and flanged. Hereinafter, the can thus produced is also referred to as a DI can.

Conventionally, hard plates such as JIS 3004 alloy and 3104 alloy, which are Al—Mg—Mn alloys, have been widely used as cold rolled plates for the can body. These JIS3004 alloy and 3104 alloy are excellent in ironing workability, and exhibit relatively good formability even when cold rolling is performed at a high rolling rate in order to increase the strength. From these facts, these alloys are considered suitable as materials for DI can bodies.

Among the beverage cans, in order to produce bottle cans (aluminum bottles, bottle cans) having a threaded mouth, a resin coating (resin coating or film laminating) is carried out on an aluminum alloy plate after a ground treatment (chromate, etc.). ). Subsequently, the aluminum alloy plate with the resin coating is punched into a circular blank and formed into a cup shape. As described above, the manufacturing process of the bottle can (three-piece type described later) was slightly different from the manufacturing process of the DI can, and a thermoplastic resin coating layer (resin coating or film lamination) was formed on both surfaces of the aluminum alloy plate. Done above.

After forming into this cup shape, bottle cans are manufactured through each process of drawing ironing, top dome molding, trimming, printing and painting, screw / curl molding, and neck flange molding. In the drawing and ironing process (DI process), the cup-shaped molded product is redrawn and stretched or ironed to reduce the body diameter, thereby reducing the thickness of the bottomed cylindrical can. Is formed. Thereafter, the bottom side of the bottomed cylindrical can is drawn a plurality of times to form a shoulder portion and an unopened mouth portion. The printing / coating on the can body is performed after washing and trimming. Next, after opening the mouth portion, the curl portion and the screw portion are formed (screw / curl molding). Furthermore, after the neck-in process and the flange process are performed on the part on the opposite side of the screw part (neck flange molding), a bottle can is obtained by tightening a separately formed bottom lid with a seamer (Patent Document) 1).

In recent years, the wall thickness of both bottle cans and DI cans is about 110 μm, and there is a demand for further thinning to reduce weight. In order to achieve such thinning, it is important to increase the strength of the material so that the buckling strength of the can does not decrease. In addition, a low earing during ironing is also strongly required. By reducing the ear rate at the time of ironing, the yield at the time of ironing can be increased, and furthermore, the can body can be prevented from being broken due to the ear cut of the can body.

Generally, when manufacturing a can body, can blanks are respectively collected from a plurality of different positions (portions) in the plate width direction of an aluminum alloy plate as a material (original plate). On the other hand, depending on the manufacturing process of the aluminum alloy plate used as a material, a plate having uniform characteristics in the plate width direction is not always obtained. Usually, variations in characteristics often occur in the plate width direction. Therefore, even if the ear rate of the material plate is low on average, the size of the ear rate may vary at each position in the plate width direction. Thus, it becomes difficult to obtain a can body having a high yield.

Various techniques for reducing the ear rate itself have been proposed. Many of them are subjected to homogenization heat treatment at a relatively high temperature in a process consisting of homogenization heat treatment (hereinafter also referred to as homogenization treatment, soaking heat treatment), hot rough rolling-hot finish rolling, and the hot rolling is finished. This is common in that the recrystallization of the hot-rolled plates is uniformly progressed in the plate width direction, and a plate having a uniform recrystallization state in the plate width direction is obtained.

For example, Patent Document 2 proposes a technique for reducing the ear ratio of an aluminum alloy plate for a can body by sufficiently generating a texture in which the cube orientation is prioritized in hot rolling. For this reason, it is proposed in Patent Document 2 to perform a homogenization heat treatment at a high temperature of 530 to 630 ° C., and particularly the hot finish rolling conditions are defined in detail.

Patent Document 3 describes that ears are generated due to the crystallographic anisotropy of the rolled material. Patent Document 3 further describes a texture component (mainly 0 ° -90 ° ears) of cubic-oriented crystal grains formed by recrystallization that proceeds after hot rolling and a rolling texture formed by cold rolling. It is described that the height of the ear is determined by the balance between the component (45 ° ear). In this patent document 3, in order to realize the reduction in the ear rate that is strictly required as the can diameter is reduced, it is assumed that the soaking condition as the upper process is important in addition to the hot rolling condition, 560 to 620 A method for producing an aluminum alloy cold-rolled sheet for can bodies that has been subjected to soaking at a relatively high temperature of 0 ° C. has been proposed.

Also, even if the ear rate itself is lowered, the ear rate is not always a good material unless the ear rate of the cold-rolled plate is suppressed in the width direction. For this reason, proposals have conventionally been made for suppressing variations in the ear rate.

For example, in Patent Document 4, the ingot is subjected to homogenization heat treatment at a high temperature of 540 to 610 ° C. This is because if the temperature of the homogenization heat treatment is less than 540 ° C., the distribution of precipitates becomes dense and the structure becomes difficult to recrystallize after hot rolling. Moreover, in patent document 4, it is proposed that the completion | finish temperature of hot rough rolling shall be 430 degreeC or more. Thereby, in patent document 4, until the subsequent hot finishing rolling process is started, the temperature is relatively high and the plate width central portion where recrystallization is likely to proceed, and the temperature is relatively low and recrystallization hardly occurs. Variation in the progress of recrystallization in the plate width direction that can occur between the plate width ends is suppressed. Further, in Patent Document 4, in order to reduce the ear rate itself by developing a proper cubic orientation during intermediate annealing in the middle of cold rolling after the hot rolling, and in a recrystallized state after hot rolling. The finishing temperature of finish rolling is in the range of 330 to 360 ° C.

In Patent Document 5, by reducing the difference in the area ratio of the Cube-oriented crystal grains in the region from the plate surface to the plate thickness center in the cross section of the aluminum alloy hot rolled plate, the ear rate is stabilized in the plate width direction. It has been proposed to obtain good materials. For this reason, Patent Document 5 provides a homogenization treatment at a high temperature of about 600 to 620 ° C. to provide Al—Mn—Fe—Si intermetallic compound phases and nucleus of Cube orientation crystal grains in a hot rolling process. The non-precipitation zone (PFZ) is distributed uniformly. Further, in this document, after the above-mentioned soaking (first soaking), a second homogenizing heat treatment is performed, which is once cooled and reheated to a temperature equal to or slightly higher than the hot rough rolling start temperature and held for several hours. It is recommended to perform two homogenization heat treatments called soaking twice.

In Patent Document 6, the average solid solution amount of Mn in the hot-rolled sheet is controlled in the range of 0.12 to 0.38% by mass, the average solid solution amount of Cu is controlled in the range of 0.01 to 0.3% by mass, and the like. It has been proposed to do. Thereby, in patent document 6, even if it manufactures a cold rolled sheet without carrying out intermediate annealing, the ear rate when this cold rolled sheet is DI-formed is made small. According to the same literature, if the average solid solution amount of Mn and Cu increases, the Cube orientation (cube orientation) tends to develop during recrystallization, and the average ear ratio of the hot-rolled sheet tends to decrease. It is a thing. Conventionally, in the method of performing the intermediate annealing after the hot rolling, the ear rate was stabilized by temporarily canceling the variation in the internal structure by the intermediate annealing. The average ear rate can be stabilized without performing the above. However, even in this document, the homogenization heat treatment temperature is still relatively high at about 550 to 650 ° C., and this homogenization heat treatment is performed in a plurality of stages such as twice soaking.

In Patent Document 7, it is proposed to perform homogenization at a high temperature of about 550 to 650 ° C., then cool and then reheat and then perform hot soaking twice. Thus, in Patent Document 7, the Mn average solid solution amount and crystal grain size of the hot-rolled sheet are controlled within a predetermined range, and the ear ratio of the hot-rolled sheet is stably -3 to -6%. . Further, in Patent Document 7, it is proposed that the hot rolled sheet is cold rolled without intermediate annealing so that the obtained cold rolled sheet has a stable ear ratio of 0 to 2%. Yes.

In addition to this, although it relates to DI cans instead of bottle cans, in Patent Document 8, β ₆ which is an Al ₆ (Mn, Fe) phase crystallized product produced at the time of casting at a high homogenization temperature of 600 to 640 ° C. It has also been proposed to increase the area ratio of the α phase to 50% or more by transforming the phase into an α phase (Al—Mn—Fe—Si compound). In Patent Document 8, this α phase is used to prevent seizure at the time of ironing on a DI can.

Japanese Unexamined Patent Publication No. 2001-162344 Japanese Unexamined Patent Publication No. 9-268355 Japanese Unexamined Patent Publication No. 10-310837 Japanese Unexamined Patent Publication No. 2008-156710 Japanese Unexamined Patent Publication No. 2004-244701 Japanese Patent No. 4205458 Japanese Unexamined Patent Publication No. 2003-342657 Japanese Unexamined Patent Publication No. 2000-248326

In the bottle cans, a two-piece bottle can (“two-piece type” consisting of an integrally formed can body and cap) manufactured by coating the inner and outer surfaces of a molded aluminum plate, There are three-piece bottle cans ("three-piece type" composed of a can body, a bottom lid, and a cap) manufactured by forming a film-laminated material into a can body. The present invention is a technique applied to the latter. In this three-piece type, the flange of the bottom part of the bottom of the can body remaining at the time of forming the cup-shaped can body in the previous stage is left during the ironing process for further forming the drinking mouth part on the upper part of the can body formed in the cup shape. It is processed as follows. And after shaping | molding this drinking part (after the said ironing process), this flange is removed by trimming.

In the three-piece type bottle can, if the ear rate itself can be lowered and the variation of the ear rate in the plate width direction can be suppressed, the amount of flange removed by trimming (trimming amount) can be reduced. The yield of materials can be improved. In addition to this, recently, in order to reduce the thickness of the bottle can for weight reduction, not only the improvement of the characteristics to suppress the variation of the ear rate in the plate width direction but also the production cost of the material plate is reduced. It is also necessary to reduce it. In other words, even if we review the manufacturing conditions that have been adopted in the past in order to suppress the variation of the ear rate in the plate width direction, the manufacturing cost of the can material cold-rolled plate can be reduced and the variation of the ear rate in the plate width direction can be reduced. There is a difficult problem of control.

The above-mentioned conventional technology cannot respond to the required issues of reducing the manufacturing cost and improving the ear rate. In the prior art, as described above, it has also been proposed to cold-roll a hot-rolled sheet without intermediate annealing. However, in these prior arts, for example, the temperature at which the homogenization heat treatment is performed remains the same as the high temperature, and the earring rate of the can material cold-rolled plate is reduced, such as the homogenization heat treatment being performed twice. This has not led to a full-scale reduction in manufacturing cost while suppressing variations in the plate width direction.

The present invention has been made in view of such problems, and aims to reduce the manufacturing cost of an aluminum alloy cold-rolled sheet, which is a material of a bottle can, and to suppress variations in the edge ratio in the sheet width direction. And

In order to achieve this object, the gist of the aluminum alloy cold-rolled sheet for bottle cans of the present invention is as follows.
(1) Mn: 0.3 to 1.2% by mass, Mg: 1.0 to 3.0% by mass, Fe: 0.3 to 0.7% by mass, Si: 0.1 to 0.5% by mass An aluminum alloy for a bottle can having a composition in which the mass composition ratio of Fe and Mn (Fe / Mn) is in the range of 0.45 to 1.5, and the balance is composed of Al and inevitable impurities. A plate,
In the structure of the aluminum alloy cold-rolled sheet for bottle cans, the average number density of dispersed particles having a gravity center diameter of less than 1 μm that can be measured with a transmission electron microscope at a magnification of 20000 is less than 3 / mm ² ,
A β phase that is an Al ₆ (Fe, Mn) intermetallic compound, and an α phase that is an Al—Fe—Mn—Si intermetallic compound,
The maximum height Hβ of the X-ray diffraction peak in the range of 2θ = 20.5 to 21.5 °, which can be regarded as the diffraction peak of the β phase, measured by the X-ray diffraction analyzer, and the diffraction peak of the α phase For bottle cans characterized in that the ratio (Hβ / Hα) of the maximum height Hα of the X-ray diffraction peak in the range of 2θ = 25.5 to 26.5 °, which can be regarded as 2θ, is 0.50 or more Aluminum alloy cold rolled sheet.
(2) One or more selected from Cu: 0.05 to 0.5% by mass, Cr: 0.001 to 0.3% by mass, Zn: 0.05 to 0.5% by mass (1) ) Aluminum alloy cold-rolled sheet for bottle cans.
(3) Aluminum for bottle can according to (1) or (2), further containing Ti: 0.005 to 0.2% by mass alone or in combination with B: 0.0001 to 0.05% by mass Alloy cold rolled sheet.

Incidentally, what is controlled in the present invention, as will be described later, is the dispersed particles (α phase, β phase) of the ingot structure after soaking and before hot rolling. It is about. These dispersed particles, of course, depend on the production conditions, but within the production conditions of the present invention, even after hot rolling or cold rolling, the state of the ingot structure after soaking is maintained as it is, There is almost no change even with rolled or cold rolled sheets. Therefore, in the present invention, the ingot structure after soaking and before hot rolling is not an intermediate product such as an ingot or hot-rolled plate that is difficult to analyze, but is a cold-rolled material that is the final bottle can material that is easy to analyze. It defines the board.

The present invention is the same as the conventional one in that it guarantees uniform recrystallization in the sheet width direction of the hot-rolled sheet structure in order to suppress variation in the edge ratio in the sheet width direction. However, contrary to the prior art, in the present invention, the soaking temperature is set as low as possible. That is, the present invention is characteristic in that a certain amount of coarse dispersed particles that promote recrystallization are present in the ingot structure after soaking and before hot rolling.

The cause of variation in the edge width ratio of the ear ratio is variation in the progress of recrystallization after the hot rolling (hot rolling) of the can material plate is completed. In this hot rolling process, recrystallization proceeds on the end side in the plate width direction of the can raw material plate (hot rolled plate) with a relatively high strain introduced, whereas the strain introduced is low. Recrystallization is less likely to occur at the center in the plate width direction of the can material plate (hot rolled plate), particularly at the center of the plate thickness. This phenomenon influences after the subsequent cold rolling, resulting in a large variation as the ear of the final plate (molded can).

On the other hand, in the present invention, in order to reduce the variation in the edge ratio of the final plate in the plate width direction, the dispersed particle state of the ingot after the homogenization heat treatment (soaking) and before hot rolling is controlled. To do. Then, the proportion of the β phase, which is a relatively coarse Al ₆ (Fe, Mn) intermetallic compound that promotes recrystallization, is increased, and a relatively fine Al—Fe—Mn—Si that inhibits recrystallization. Reduce the abundance ratio of α-phase, which is an intermetallic compound. By controlling the abundance ratio of the β phase and the α phase as described above, the β phase is increased, and the center portion in the plate width direction of the above-described can material plate (hot rolled plate), in particular, the central portion of the plate thickness is restored. Crystallization is promoted, the recrystallization rate in the plate width direction of the hot-rolled plate is made uniform, and as a result, the variation in the ear rate of the final plate in the plate width direction is reduced. At the same time, the fine α-phase is restricted, but the relatively coarse α-phase should not be too small.

Therefore, in the present invention, the soaking temperature is as low as possible below 550 ° C., and the hot rolling (particularly rough rolling) conditions are adjusted. As described above, in the present invention, the existence ratio of the fine α phase that inhibits recrystallization is increased while the existence ratio of the β phase that promotes recrystallization is increased by devising the manufacturing process of the hot-rolled sheet in particular. Control to reduce.

On the other hand, in the above-described prior art, since the soaking process at a relatively high temperature of 520 ° C. or higher is generally performed or the soaking process is performed twice, the β phase generated during casting is dissolved. In addition, the amount of solute Fe and the amount of solute Mn increase, and a structure in which recrystallization of the hot-rolled sheet is difficult to proceed is obtained. For example, Patent Document 4 is directed to a structure that is easily recrystallized, and despite the attempt to prevent a structure that is difficult to recrystallize with a dense distribution of precipitates, it is 540 to 610 ° C. with respect to the ingot. Homogenized heat treatment is performed at high temperature. Also in Patent Document 8, the homogenization treatment temperature is set to a high temperature of 600 to 640 ° C., and the β phase generated during casting is positively transformed into the α phase so that a large amount of the α phase is present. The amount of dissolved Mn is also increasing, and a structure that is difficult to recrystallize is obtained.

Therefore, in the conventional manufacturing method, the manufacturing cost of the material plate is reduced by omitting the process such as performing the homogenization heat treatment only once and lowering the soaking temperature, and the ear rate of the can material plate itself. It is impossible to achieve both reduction and suppression of variation in the width direction of the ear rate. As a result, the conventional manufacturing method cannot reduce the amount (trimming amount) of the flange of the bottom portion of the bottom of the can body remaining in the can body molding of the three-piece type can among the bottle cans.

On the other hand, in the present invention, the process is omitted such as performing the homogenization heat treatment only once, and the soaking temperature is lowered to reduce the manufacturing cost of the material plate. The rate itself can be reduced, and variations in the ear rate in the plate width direction can be suppressed. As a result, it is possible to reduce the amount of trimming when molding a three-piece type can body among bottle cans.

It is explanatory drawing which shows distribution of the diffraction peak of the X-ray-diffraction line measured with the X-ray-diffraction analyzer about the cold rolled sheet of this invention.

(Al alloy cold-rolled sheet composition)
First, the chemical component composition of the aluminum alloy cold-rolled sheet (ingot) according to the present invention will be described below, including reasons for limiting each element.

The chemical component composition of the aluminum alloy cold-rolled sheet in the present invention satisfies the necessary characteristics such as formability and strength to the above-mentioned can as a material for a bottle can, and the structure specified by the present invention has a chemical component composition. It is necessary to satisfy from the point of. For this reason, the aluminum alloy cold-rolled sheet according to the present invention has Mn: 0.3 to 1.2% by mass, Mg: 1.0 to 3.0% by mass, Fe: 0.3 to 0.7% by mass, Si: 0.1 to 0.5% by mass, the mass composition ratio of Fe and Mn (Fe / Mn) is in the range of 0.45 to 1.5, and the balance is from Al and inevitable impurities. It has the composition which becomes.

In addition to the above composition, the aluminum alloy cold rolled sheet according to the present invention has Cu: 0.05 to 0.5 mass%, Cr: 0.001 to 0.3 mass%, Zn: 0.05 to 0.5 mass%. One or more selected from mass% and / or 0.005 to 0.2 mass% Ti alone or in combination with 0.0001 to 0.05 mass% B may be further contained. good. The significance of the definition of each element will be described below in order.

(Mn: 0.3 to 1.2% by mass)
Mn is an effective element that contributes to improvement in strength and further contributes to improvement in formability. In particular, in the can body material (cold rolled plate) of the present invention, Mn is extremely important because ironing is performed during DI molding. Mn forms various Mn-based intermetallic compounds such as a coarse β phase. The coarse compound contributes to the promotion of recrystallization of the hot-rolled sheet and is also effective for increasing the strength of the product sheet. If the Mn content is too small, the above effect cannot be exhibited. For this reason, content of Mn is 0.3 mass% or more, Preferably it is 0.4 mass% or more. On the other hand, when Mn is excessive, the amount of Al—FeMn—Si intermetallic compound (α phase) produced increases, making recrystallization on a hot-rolled sheet difficult. Moreover, the primary crystal giant metal compound of Mn and Al is easily crystallized, and the moldability is also lowered. Therefore, the upper limit of the Mn content is 1.2% by mass, preferably 1.1% by mass, and more preferably 1.0% by mass.

(Mg: 1.0-3.0% by mass)
Mg is effective in that the strength can be improved by solid solution strengthening alone. In addition, when the Mg content is low, the amount of MgSi compound generated decreases and Si remains excessively, so that the amount of Al—Fe—Mn—Si intermetallic compound (α phase) increases. The Mg content for this purpose is 1.0% by mass or more, preferably 1.2% by mass or more. On the other hand, when Mg is excessive, work hardening is likely to occur, and thus formability is remarkably lowered. Therefore, the upper limit of the amount of Mg is 3.0% by mass, preferably 2.5% by mass.

(Fe: 0.3 to 0.7% by mass)
Fe has the effect of refining crystal grains, and further increases the amount of coarse β phase formed, contributing to the promotion of recrystallization of hot-rolled sheets. Fe is also useful in that it promotes crystallization and precipitation of Mn, and controls the Mn average solid solution amount in the aluminum matrix and the dispersion state of the Mn-based intermetallic compound. For this reason, content of Fe is 0.3 mass% or more, Preferably it is 0.4 mass% or more. On the other hand, when the Fe content is excessive, a huge primary intermetallic compound having a diameter exceeding 15 μm is likely to be generated, and the moldability is lowered. Therefore, the upper limit of the Fe content is 0.7% by mass, preferably 0.6% by mass.

Here, in order to reduce the number density of fine particles (α phase) having a diameter of less than 1 μm and increase the amount of coarse β phase that becomes a nucleation site for recrystallization, the mass composition ratio of Fe and Mn (Fe / Mn) is set to 0.45 to 1.5, preferably 0.6 to 1.4. When this ratio is smaller than 0.45, the content of Fe with respect to Mn is too small, so the amount of β-phase generated is reduced, and the number density of particles (α-phase) having a diameter of less than 1 μm is increased. On the other hand, if this ratio exceeds 1.5, the amount of α-phase produced becomes too small, and the ironing processability is lowered.

(Si: 0.1-0.5% by mass)
Si forms an Al—Fe—Mn—Si intermetallic compound (α phase). As the α phase is appropriately distributed, the moldability is improved. For this reason, content of Si is 0.1 mass% or more, Preferably it is 0.2 mass% or more. On the other hand, when Si is excessive, recrystallization of the hot-rolled sheet is suppressed, and the variation in the ear ratio increases. For this reason, the upper limit of Si content is 0.5 mass%, Preferably it is 0.4 mass%.

(Cu: 0.05 to 0.5% by mass)
Cu increases the strength by solid solution strengthening. For this reason, the lower limit in the case of selectively containing Cu is 0.05% by mass or more, preferably 0.1% by mass or more. On the other hand, if Cu is excessive, high strength can be easily obtained, but it becomes too hard, so that formability is lowered and corrosion resistance is also deteriorated. For this reason, the upper limit of Cu content is 0.5 mass%, preferably 0.4 mass%.

In addition to Cu, Cr, Zn and the like can be cited as elements for improving the strength of the same effect. Therefore, in addition to Cu, you may selectively contain 1 type or 2 types of Cr and Zn further.

(Cr: 0.001 to 0.3% by mass)
Cr is also an effective element for improving the strength. The amount of Cr is, for example, 0.001% by mass or more, preferably 0.002% by mass or more. On the other hand, when Cr becomes excessive, a giant crystallized substance is generated and formability is lowered. The upper limit of the Cr amount is, for example, about 0.3% by mass, preferably about 0.25% by mass.

(Zn: 0.05 to 0.5% by mass)
Zn is also an element effective for improving the strength. The amount of Zn is 0.05% by mass or more, preferably 0.06% by mass or more. On the other hand, when Zn becomes excessive, corrosion resistance will fall. The upper limit of the Zn content is about 0.5% by mass, preferably about 0.45% by mass.

(Ti: 0.005 to 0.2% by mass)
Ti is a grain refinement element. Therefore, Ti is preferably selectively contained when it is desired to exert the effect of crystal grain refinement. In this case, the Ti content is 0.005% by mass or more, preferably 0.01% by mass or more. When Ti is excessive, a huge Al—Ti intermetallic compound is crystallized to hinder formability. Therefore, the upper limit of the Ti content is 0.2% by mass, preferably 0.1% by mass.

Ti may be contained alone, but may be contained together with a small amount of B. When B is used in combination, the effect of crystal grain refinement is further improved. For this reason, the content of B when selectively contained is 0.0001% by mass or more, preferably 0.0005% by mass or more. On the other hand, when B is excessive, Ti—B-based coarse particles are generated and formability is lowered. Therefore, the upper limit of the B content is 0.05% by mass, preferably 0.01% by mass.

Other than the elements described above are inevitable impurities. In order not to impede the above plate characteristics, the content of inevitable impurities is basically preferably low, but there is also a balance with refining costs for reducing impurities in the aluminum alloy melting step. Therefore, the inclusion of inevitable impurities up to the upper limit value of each element of the 3000 series aluminum alloy described in the JIS standard or the like is allowed within a range that does not impair the plate characteristics.

(Cold rolled sheet structure)
Next, the cold rolled sheet structure of the present invention will be described below. In the present invention, in addition to the component composition, in order to ensure uniform recrystallization in the sheet width direction of the hot-rolled sheet structure, the main elements (Mn, Fe, Cu) of the ingot after soaking and before hot-rolling are used. ) And the amount of β phase, which is coarse dispersed particles that promote recrystallization of the structure, are guaranteed in relation to the α phase to be regulated. However, what is controlled in the present invention is the structure of the ingot after soaking and before hot rolling. As described above, in the present invention, these are defined in the state of cold-rolled sheets.

Here, again, the β phase, which is an intermetallic compound composed of Al ₆ (Fe, Mn) as defined in the present invention, is a coarse crystallized product produced during casting, and the second phase during hot rolling. It becomes a recrystallization nucleation site as dispersed particles and promotes recrystallization of the hot-rolled sheet structure. On the other hand, the α phase, which is an intermetallic compound composed of Al—FeMn—Si, has two types, one that transforms from the β phase during the soaking (coarse) and one that newly nucleates and precipitates (fine). is there.

As in the prior art described above, the higher the soaking condition is, the higher the temperature and the longer the time, the easier the transformation from the β phase to the α phase proceeds, and the α phase existing after soaking is transformed from this β phase to the α phase. Many things originate from transformation. However, because the soaking temperature under the optimum production conditions of the present invention is low (less than 550 ° C.), the α phase in the structure after soaking (cold rolled sheet) in the present invention is transformed from the β phase during soaking. It is thought that there are few, and many are fine particles that are newly nucleated and precipitated during soaking. Further, the β phase is a coarse crystallized product, and there is no fine one having a center of gravity diameter of less than 1 μm. Therefore, when the cold-rolled sheet structure in the present invention is observed with a transmission electron microscope, the observed particles having a center-of-gravity diameter of less than 1 μm are considered to be α phases that are newly nucleated and precipitated during soaking. It is done.

Dispersed particles:
In the present invention, first, this average number density is defined as less than 3 / mm ² in order to regulate fine dispersed particles having a large effect of inhibiting recrystallization of hot-rolled sheets and having a center of gravity diameter of less than 1 μm. Most of the fine dispersed particles having a diameter of the center of gravity of less than 1 μm are α phases newly nucleated and precipitated during soaking or hot rolling. The phase is substantially defined. This reduces the particularly fine α phase itself that hinders recrystallization, promotes recrystallization at the center in the width direction of the can material plate (hot rolled plate), particularly in the center of the plate thickness, The recrystallization rate in the plate width direction of the plate is made uniform, and as a result, variation in the ear rate of the final plate in the plate width direction is reduced. If this average number density is 3 pieces / mm ² or more, particularly fine α phase is increased, recrystallization of the hot-rolled sheet is hindered, and variation in the edge width ratio of the final sheet cannot be reduced. .

In the present invention, the number of fine dispersed particles having a center-of-gravity diameter (size) of less than 1 μm is specified. However, the transmission-type electron microscope (hereinafter referred to as “Transmission Electron Microscope”) is limited only to the upper limit of the center-of-gravity diameter. , Also referred to as TEM), the range may include finely dispersed particles that cannot be observed or measured. For this reason, in the present invention, by defining the magnification of TEM and further defining that measurement is possible at this magnification, it is clarified that only the finely dispersed particles that can be measured are included. The lower limit of the center-of-gravity diameter (size) of the dispersed particles that can be objectively measured with good reproducibility using a TEM with a magnification of 20000 times is about 30 nm. In the preferred soaking and hot rolling temperature range defined in the present invention, the atomic diffusion rate is large and the growth rate of the dispersed particles is large. Therefore, fine particles of 30 nm or less at the time of recrystallization in hot rolling. Is very unlikely to be dispersed. Therefore, in the present invention, actually, fine dispersed particles having a centroid diameter of 30 nm or more and less than 1 μm are measured and defined.

In TEM observation, the average number density of dispersed particles is usually defined per mm ³ considering the volume of the thin film sample. In the present invention, the average number density of dispersed particles is defined per mm ² . The reason for this is that while the TEM observation sample is a thin film having a thickness of about 100 μm, the dispersed particles (precipitates) targeted by the present invention observed in the TEM image are three-dimensionally formed on the entire thin film. Due to being dispersed. For this reason, even if a plurality of particles are dispersed in a state of being overlapped in the thickness direction of the thin film, only a single particle is seen (not observed) in the TEM image, and thus the number of particles that are three-dimensionally accurate is counted. That is impossible in principle. Further, the thickness of the thin film is not necessarily completely the same over the observation visual field. Therefore, in the present invention, for the sake of convenience, the number of dispersed particles per mm ² is calculated, and this number is defined as the number density of dispersed particles.

Here, the center-of-gravity diameter is the equivalent circle diameter (equivalent circle diameter) when the maximum length of the irregularly dispersed particles is regarded as the diameter of the circle. For example, Japanese Patent Application Laid-Open No. 2009-191293 JP2009-215643, JP2009-228111, JP2009-242904, JP2008-266684, JP2007-126706 As disclosed in Japanese Laid-Open Patent Publication No. 2006-104561, Japanese Laid-Open Patent Publication No. 2005-240113, and the like, it is widely used as a definition of the size of dispersed particles and the like in the field of aluminum alloys.

Measurement of the number density of dispersed particles:
The average number density of dispersed particles having a centroid diameter of less than 1 μm is measured by observing the cold-rolled plate structure with a transmission electron microscope. More specifically, the specimen at the center of the plate thickness and the upper surface of the rolling surface is mirror-polished, and the structure of the polished surface is observed with 10 fields of view with a transmission electron microscope of 20000 times, and the average number density per 1 μm ² is calculated. did. At this time, the number of particles observed in a range of 8 μm × 8 μm was measured, and the number of particles per 1 μm ² was calculated. Further, since the film thickness greatly affects the average number density, the film thickness at the time of TEM observation is constant at 100 nm, and the film thickness error is within an allowable range of ± 20 nm.

X-ray diffraction peak height:
In the present invention, the amount of β phase is increased to promote recrystallization of the hot rolled sheet. In order to ensure this, in addition to regulating the fine α phase that precipitates due to new nucleation during soaking, the α phase that is generated by transformation from the β phase during soaking is also the β phase. Regulate in relation to That is, the amount of β phase is ensured by controlling the balance of the existence ratio of these β phase and α phase and relatively increasing the β phase. This promotes the recrystallization of the above-mentioned can material plate (hot rolled plate) in the center portion in the plate width direction, particularly the center portion of the plate thickness, and uniformizes the recrystallization rate in the plate width direction of the hot rolled plate, The variation in the edge ratio of the final plate in the plate width direction is reduced. At the same time, the fine α phase newly precipitated by nucleation or the like during soaking is regulated, but the relatively coarse α phase generated by transformation or the like from the β phase during soaking should not be too small. Incidentally, since the α phase transformed from the β phase is as coarse as the β phase, it is a dispersed particle having a centroid diameter of less than 1 μm, which is subject to the regulation, and is newly nucleated and precipitated during soaking. It is not included in the α phase.

Α When the α phase decreases, the lubricity of ordinary DI cans decreases and ironing processability decreases. However, as described above, the bottle can is slightly different from the manufacturing process of the DI can. The bottle can is formed after forming a thermoplastic resin coating layer (resin coating or film lamination) on both sides of an aluminum alloy plate (cold rolled plate). Is done. For this reason, the moldability to the can is greatly improved by the role of the thermoplastic resin coating layer as a lubricant during molding.

In addition to the lubrication effect of the thermoplastic resin film layer formed before molding, the present invention minimizes the deterioration of the can moldability of the material plate by minimizing the relatively coarse α phase. is doing. That is, the prescription of the existence ratio of the β phase and the α phase according to the present invention is not to restrict only the β phase side or only the α phase side, but to suppress an excessive decrease of the α phase and By controlling the balance of the abundance ratio with the α phase, the can moldability is prevented from being lowered and the moldability of the can when the thermoplastic resin coating layer is formed before molding is ensured.

In the present invention, the diffraction peak intensity measured by the X-ray diffraction analyzer is used to define the abundance ratio (balance control) of these β phase and α phase. Identification (qualification and quantification) of the type and amount of the compound (intermetallic compound, etc.) as the second phase particles in the metal matrix (structure) based on the position and height of the X-ray diffraction peak measured by X-ray diffraction analysis Possible). Therefore, the method using the diffraction peak intensity in the present invention is optimal for discrimination (distinguishment) and quantification of the β phase and the α phase as the second phase particles in the present invention, that is, for defining the existence ratio.

FIG. 1 shows the distribution of diffraction peaks of X-ray diffraction lines measured by an X-ray diffraction analyzer for the cold-rolled sheet of the present invention (Invention Example 7 in Table 2 in Examples described later). The β phase as the second phase particle in the aluminum alloy structure by the position (horizontal axis position) of the diffraction peak shown in FIG. 1 and the height H (intensity (unit: CPS)) of the diffraction peak shown on the vertical axis. And the abundance ratio of the α phase can be identified.

In FIG. 1, the diffraction peak distribution is shown in the range where the measurement range 2θ on the horizontal axis is 10 ° to 100 °. Below this diffraction peak distribution (below the 0 position on the vertical axis), the diffraction peaks of the crystallized product and Al are shown as thin bar lines (bar graphs) for each position on the horizontal axis in order from the top. ing. In these bar graphs, the crystallized substances on the right side are listed in order from the top, α phase (described as (α-Al ₁₂ (Fe, Mn) ₃ Si)), β phase (Al ₆ (Fe, Mn)). And an intermetallic compound (denoted as: Mg ₂ Si), and the bottommost is Al described as a base material component at the right end.

In FIG. 1, it can be seen from the comparative comparison between the diffraction peak distribution and the bar graph that the large intensity peaks with 2θ of 45 ° or more are all Al of the base material component (matrix). In addition, the α phase and the β phase can be seen from the comparative comparison of each diffraction peak distribution and each bar graph that the peaks overlap with each other at almost the horizontal axis position.

In such a factual relationship, a relatively large discriminable diffraction peak that does not overlap each other and exists only in either the α phase or the β phase and can measure the height with high reproducibility is obtained. Search based on a comparison between each diffraction peak distribution and each bar graph. As a result, such a β-phase diffraction peak is a bar indicated by the left arrow of the two arrows shown in FIG. 1, and 2θ is within the range of 20.5 to 21.5 ° ( It can be seen that this is the maximum X-ray diffraction peak (around 21 °). Further, such an α-phase diffraction peak is a bar indicated by a right arrow of the two arrows shown in FIG. 1, and 2θ is within the range of 25.5 to 26.5 ° (26 It can be seen that it is the maximum height X-ray diffraction peak (near °). That is, the X-ray diffraction peaks at positions other than these overlap with each other in the α phase and the β phase or are small (low) without overlapping, and the height cannot be measured with good reproducibility. Accordingly, each X-ray diffraction peak (X-ray diffraction peak having the maximum height within the range) specified within the range indicated by the horizontal axis position described above defines the abundance of the β phase and the α phase, respectively. Each can be regarded as a unique diffraction peak.

X-ray diffraction peak height ratio (Hβ / Hα):
For this reason, in the present invention, the maximum height Hβ of the X-ray diffraction peak in the range of 2θ = 20.5 to 21.5 °, which can be regarded as the diffraction peak of β phase, and the diffraction peak of the α phase can be regarded. The maximum height Hα of the X-ray diffraction peak in the range of 2θ = 25.5 to 26.5 ° is used, and the ratio of β phase and α phase is defined by these ratios (Hβ / Hα). . This ensures the abundance of the β phase and ensures uniform recrystallization of the hot rolled sheet.

In the present invention, the lower limit of the X-ray diffraction peak height ratio Hβ / Hα is 0.50 or more. When this ratio is less than 0.50, the β phase is too small, and the recrystallization suppression effect by the α phase is too large compared to the recrystallization promotion effect by the β phase. For this reason, it becomes impossible to guarantee uniform recrystallization in the plate width direction of the hot-rolled plate structure in order to suppress variations in the ear rate in the plate width direction. Incidentally, too much α phase (too little β phase) is due not only to soaking conditions, but also to the time to start hot rough rolling and the steady speed in hot rough rolling, as will be described later. This is also due to manufacturing conditions.

On the other hand, in the present invention, although the quantitative ratio is smaller than that of the β phase, a certain amount of α phase is necessarily present. As disclosed in Patent Document 8 and the like, generally, ironing processability is improved by the dispersion of the α phase. For this reason, if the amount of the α phase is too small, even in the present invention, even if the thermoplastic resin coating layer is pre-coated, the lubrication in the can molding is insufficient, and the galling or seizure called goling is caused. Such appearance defects may occur. Therefore, the upper limit of the X-ray diffraction peak height ratio (Hβ / Hα) is 1.8 in order to allow the presence of a certain α phase so that there is no reduction in can moldability until such a problem occurs. In the following, it is preferable to set it to 1.6 or less. Further, by allowing the presence of the α phase, there is an advantage that a decrease in can moldability due to the β phase can be minimized. However, when the α phase is excessive, such as when the X-ray diffraction peak height ratio (Hβ / Hα) exceeds the above upper limit, the can moldability is improved, while the ear ratio, which is the main object of the present invention. It itself goes down. The definition based on the X-ray diffraction peak height ratio (Hβ / Hα) of the present invention, that is, the definition of the abundance ratio of the β phase and the α phase of the present invention is not limited only to the β phase side. It is also meaningful to ensure can moldability by controlling the balance of the proportion of β phase and α phase while suppressing the decrease of α phase.

By the way, in the aluminum alloy field, the method of identifying and defining the α phase and β phase as the second phase particles in the aluminum alloy structure with such X-ray diffraction peak height or height ratio by X-ray diffraction is as follows. For example, it is known in Japanese Unexamined Patent Publication No. 2010-116594. In this patent document, the proportion of α-phase crystallized material existing in an Al-Mg-Si-based Al-Mg-Si-based AA or JIS 6000-based aluminum alloy plate is increased, and the entire existing crystallized material is refined. And spheroidizing to improve bending workability (hem workability) under severe conditions for automobile panels.

X-ray diffraction peak measurement method:
The X-ray diffractometer used to measure the X-ray diffraction peak height, Hβ and Hα is, for example, a Rigaku Electric X-ray diffractometer (model: RAD-RU300), using a Co target, Measurement is performed at a voltage of 40 kV, a tube current of 200 mA, a scanning speed of 1 ° / min, a sampling width of 0.02 °, and a measurement range (2θ) of 10 ° to 100 °. Then, the maximum X-ray diffraction peak height Hβ (around 21 °) in the range of 2θ = 20.5 to 21.5 ° that can be regarded as a β-phase diffraction peak, and 2θ = can be regarded as an α-phase diffraction peak. The maximum X-ray diffraction peak height Hα (in the vicinity of 26 °) within the range of 25.5 to 26.5 ° is obtained. Each of these maximum peak heights is determined by subtracting the background from the X-ray diffraction profile.

Production method:
According to the method of manufacturing an aluminum alloy cold-rolled sheet, which is a material for a bottle can in the present invention, it can be manufactured without greatly changing the conventional soaking, hot-rolling, and cold-rolling manufacturing processes, and the manufacturing cost is reduced. In addition, it is possible to suppress the variation of the ear rate in the plate width direction.

However, in order to make the structure defined in the present invention and reduce the variation in the ear rate of the final plate, it is necessary to set the soaking condition and the hot rolling condition to the following conditions. That is, in the present invention, the aluminum alloy ingot having the above composition is subjected to homogenization heat treatment only once at a temperature of 450 ° C. or more and less than 550 ° C., and then the hot rough rolling is quickly started. And hot rough rolling is completed rapidly.

Soaking conditions:
In order to reduce the manufacturing cost, the soaking process is performed only once. The soaking temperature at this time is in a relatively low temperature range of 450 ° C. or higher and lower than 550 ° C., preferably 460 ° C. or higher and lower than 530 ° C. As described above, in the present invention, the presence state of the β phase of the ingot after the homogenization heat treatment (soaking) and before hot rolling is controlled in order to reduce the variation in the edge ratio of the final plate in the plate width direction. To do. In particular, in the present invention, this β phase is maintained in a relatively coarse state without undergoing α transformation. For this reason, the temperature of the soaking is set as low as possible at a temperature lower than 550 ° C., so that the crystallized β phase is not so dissolved, and the β-phase transformation is suppressed. This also reduces the amount of solid solution Fe and solid solution Mn, and positively increases the amount of β phase, which is a relatively coarse dispersed particle having a diameter of 2 to 15 μm, which serves as a nucleation site for recrystallization of the hot-rolled sheet. Increase.

As a result, recrystallization at the central portion in the plate width direction of the can material plate (hot rolled plate) described above, particularly the central portion of the plate thickness, is promoted, and the recrystallization rate in the plate width direction of the hot rolled plate is made uniform. As a result, the variation in the ear width of the final plate in the plate width direction is reduced. However, if the soaking temperature is too low and less than 450 ° C., the ingot cannot be homogenized or hot rolled.

On the other hand, in the prior art, as described above, since the soaking process at a relatively high temperature of 520 ° C. or higher is performed, the soaking temperature is too high, the crystallized product is dissolved, or the β phase is transformed into α. Therefore, the relatively coarse dispersed particles that promote the recrystallization of the hot-rolled sheet as defined by the present invention are insufficient. Moreover, in the said prior art, the amount of solid solution Fe and the amount of solid solution Mn increase, and it becomes a structure | tissue in which recrystallization of the said hot rolled sheet does not advance easily. Furthermore, in the prior art, since the soaking process is preferably performed twice, the manufacturing cost cannot be reduced.

The soaking time (homogenization time) is preferably as short as possible so that the ingot can be homogenized, for example, 12 hours or less, preferably 6 hours or less.

Hot rolling conditions:
The hot rolling is a rough rolling step of the ingot (slab) after the soaking performed according to the thickness of the rolled sheet, and a thickness of about 40 mm or less after the rough rolling is about 4 mm or less. And a finish rolling step of rolling to a maximum. In these rough rolling process and finish rolling process, a reverse type or a tandem type rolling mill is used as appropriate, and rolling consisting of a plurality of passes is performed.

Hot rough rolling:
In the present invention, after the soaking process is completed, the soaking process is not performed twice or two steps so as to be cooled and reheated once, but the soaking process is performed only once. Therefore, in the present invention, hot rough rolling is started at a soaking temperature in a temperature range of 450 ° C. or higher and lower than 550 ° C. When this rough rolling start temperature is too lower than 450 ° C., recrystallization of the hot rolled sheet is suppressed. On the other hand, the upper limit of the rough rolling start temperature is determined by the soaking temperature (upper limit 550 ° C.). If hot rolling is started from a temperature of 550 ° C. or higher, seizure of the plate and the work roll occurs during hot rolling, and surface defects of the plate are likely to occur.

This hot rough rolling is performed promptly (without time delay) immediately after the soaking. By performing hot rough rolling promptly, generation of particles (α phase) having a diameter of less than 1 μm from the end of soaking to the start of hot rough rolling can be suppressed. As a measure of this point, hot rough rolling is started within 15 minutes, preferably within 10 minutes, on the aluminum alloy sheet after the soaking.

In this hot rough rolling, the lowest steady speed is set to 50 m / min or more among all the steady speeds of a pass of several to several tens of times in the case of a reverse rolling mill. Here, the steady speed means a rolling speed (line speed) that is maximum and constant per pass. If the steady speed at which all the passes in hot rough rolling are the lowest is less than 50 m / min, the rolling time becomes longer, the amount of α-phase is increased, and the hot-rolled sheet is recrystallized. It is suppressed.

The end temperature of hot rough rolling is preferably 400 ° C. or higher. In the present invention, hot rolling is divided into rough rolling and finish rolling, and these are carried out continuously, so if the end temperature of hot rough rolling becomes too low, in the hot finish rolling of the next step The rolling temperature is lowered and edge cracking is likely to occur. In addition, if the end temperature of hot rough rolling is too low, the self-heating necessary for recrystallization after finish rolling tends to be insufficient, so it becomes unnecessary to recrystallize the hot-rolled sheet, and recrystallization in the sheet width direction. The uniformity of is impaired.

Hot finish rolling:
For the aluminum alloy sheet that has been subjected to hot rough rolling, hot finish rolling is performed, for example, continuously and quickly (immediately without any time delay). By rapid hot finish rolling, it is possible to prevent the strain accumulated in the hot rough rolling from recovering, and the strength of the cold-rolled sheet obtained thereafter can be increased. As a measure of this point, it is preferable to hot finish and roll the aluminum alloy sheet after the hot rough rolling within 5 minutes, preferably within 3 minutes.

The finishing temperature of hot finish rolling is preferably 300 to 360 ° C. The hot finish rolling step is a step of finishing the plate to a predetermined size. Since the structure after the end of rolling becomes a recrystallized structure due to self-heating, the end temperature affects the recrystallized structure. If the finish temperature of hot finish rolling is 300 ° C. or higher, the structure of the final plate can be easily made into a uniform recrystallized structure in the plate width direction together with the subsequent cold rolling conditions. When the finish temperature of hot finish rolling is less than 300 ° C., it is difficult to obtain the structure of the present invention. On the other hand, when the finish temperature of hot finish rolling exceeds 360 ° C., a coarse MgSi compound or the like precipitates to hinder formability, and further, the crystal grains become coarse and the plate surface becomes rough. Therefore, the lower limit of the finish temperature of hot finish rolling is 300 ° C. or higher, preferably 310 ° C. or higher. Moreover, the upper limit of the finish temperature of hot finish rolling is 360 ° C. or lower, preferably 350 ° C. or lower.

As the hot finish rolling mill, it is preferable to use a tandem hot rolling mill having three or more stands. When the number of stands is 3 or more, the rolling rate per stand can be reduced, and strain can be accumulated while maintaining the surface properties of the hot-rolled sheet. For this reason, the intensity | strength of a cold-rolled board and its DI molded object can further be raised. The thickness of the alloy plate after hot (finish) rolling is desirably about 1.8 to 3 mm. If the plate thickness after the end of hot (finish) rolling is 1.8 mm or more, the surface properties (seizure, rough surface, etc.) of the hot-rolled plate and deterioration of the plate thickness profile can be prevented. On the other hand, if the sheet thickness after hot (finish) rolling is 3 mm or less, the rolling rate when manufacturing a cold rolled sheet (usually about 0.28 to 0.35 mm) becomes too high. Can be prevented, and the ear rate after DI molding can be suppressed.

Cold rolling:
In the cold rolling process, it is desirable that rolling is performed directly by a plurality of passes without intermediate annealing, and the total rolling ratio is 77 to 90%. The plate thickness after cold rolling is about 0.28 to 0.35 mm in terms of forming into a bottle can. In the cold rolling process, it is desirable to use a tandem rolling mill in which two or more rolling stands are arranged in series. By using such a tandem rolling mill, compared to a single rolling mill that repeatedly performs a pass (through plate) in a single-stage rolling stand and cold-rolls to a predetermined plate thickness, even with the same total cold rolling rate, The number of passes (passing plates) can be reduced, and the rolling rate in one pass can be increased.

Conditioning treatment:
After cold rolling, a tempering treatment such as finish annealing (final annealing) at a temperature lower than the recrystallization temperature may be performed as necessary. However, cold rolling by the tandem rolling mill described above can generate subgrains at a lower temperature and continuously, so that such finish annealing is basically unnecessary.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples, and is implemented with appropriate modifications within a range that can meet the purpose described above and below. Of course, any of these is also included in the technical scope of the present invention.

In addition to aluminum bullion, can scrap and other materials are used as melting raw materials to melt a 3000 series Al alloy melt having the composition shown in Table 1 below, and an ingot having a thickness of 600 mm and a width of 2100 mm is obtained by DC casting. Manufactured. In Table 1, “-” indicates that the content of the corresponding element is below the detection limit.

The ingot having such a component composition was subjected to soaking and hot rolling according to the conditions shown in Table 2. The soaking process was performed only once, and each treatment temperature shown in Table 2 was held for 4 hours in common with each ingot of each example. After this soaking, hot rolling was performed. A reverse hot rough rolling mill with one stand was used for hot rough rolling, and a tandem hot rolling mill with four stands was used for hot finish rolling. At that time, as shown in Table 2, the start temperature of hot rough rolling, the time from the end of soaking to the start of hot rough rolling, the lowest steady time in all passes of hot rough rolling (the lowest in all passes) Steady time), hot rough rolling finish temperature (approximately equal to hot finish rolling start temperature), hot finish rolling finish temperature, and the like were variously changed. In this way, an aluminum alloy hot-rolled sheet having a thickness of 2.5 mm in common after hot finish rolling was obtained.

Here, in the hot rough rolling, the rolling reduction was changed according to the plate thickness. In areas where the thickness of the ingot is from the initial plate thickness of 600 mm to 100 mm or more, and the plate thickness is relatively large, the reduction is relatively light. Was roughly 20%, less than 25%, and rough rolled in 15 passes. Further, in the rough rolling region where the thickness of the ingot is less than 100 mm, the number of passes is 4 in each example.

The obtained hot-rolled sheet was cold-rolled (directly-rolled) with only one pass through a two-stage tandem rolling mill without intermediate annealing. Thus, in common with each example, a plate material for a bottle can body (cold rolled plate) having a final plate thickness of 0.3 mm is manufactured.

The test piece mentioned later was extract | collected from the cold rolled sheet (coil) for bottle can bodies after cold rolling. And the mechanical characteristic of the test piece was measured with the above-mentioned measuring method. Further, in the measurement method described above, the average number density (particles / mm ² ) of dispersed particles having a centroid diameter of less than 1 μm as the structure of the test piece, and 2θ = 20.5 to 21 which can be regarded as a β-phase diffraction peak. The maximum height Hβ of the X-ray diffraction peak in the range of .5 ° and the maximum height Hα of the X-ray diffraction peak in the range of 2θ = 25.5 to 26.5 ° which can be regarded as the diffraction peak of the α phase. The ratio (Hβ / Hα) was measured. Furthermore, the ear rate of the test piece was measured and evaluated. These results are also shown in Table 2.

(Mechanical properties)
The tensile test for measuring the mechanical properties (tensile strength, 0.2% proof stress) is performed according to JIS Z 2201, and the test piece shape is a JIS No. 5 test piece, and the longitudinal direction of the test piece coincides with the rolling direction. A test piece was prepared as described above. The crosshead speed was 5 mm / min, and a tensile test was performed at a constant speed until the test piece broke.

(Ear rate)
First, blanks were collected from a total of two locations, that is, the central portion in the width direction of the cold rolled sheet for the bottle can body and one of the end portions. The lubricating oil [D. A. The blank coated with Stuart's Nalco 147] was subjected to a 40% deep drawing test with an Erichsen tester and molded into a cup shape, and the ear rate was examined. The test conditions are blank diameter = 66.7 mm, punch diameter = 40 mm, die side shoulder R = 2.0 mm, punch shoulder R = 3.0 mm, and wrinkle holding pressure = 400 kgf. 8 directions of the opening peripheral edge of the cup thus obtained (0 ° direction, 45 ° direction, 90 ° direction, 135 ° direction, 180 ° direction, 225 ° direction, 270 ° direction, assuming the rolling direction as 0 °, And 315 ° direction) were measured, and the average ear rate was calculated.

In the present invention, the average ear rate is in the range of 0% to + 3.5%. The calculation of the average ear rate was performed by a known method disclosed in the prior art based on the developed view of the cup obtained by DI molding a plate material for a bottle can body. That is, the height of the ears (T1, T2, T3, T4; referred to as minus ears) measured in the directions of 0 °, 90 °, 180 °, and 270 ° is measured with the rolling direction of the development view of the cup as 0 °. In addition, the heights of the ears (Y1, Y2, Y3, Y4; referred to as plus ears) occurring in the 45 °, 135 °, 225 °, and 315 ° directions are measured. The heights Y1 to Y4 and T1 to T4 are heights from the bottom of the cup. Then, the average ear rate is calculated from each measured value based on the following equation.
Average Ear Ratio (%) = [{(Y1 + Y2 + Y3 + Y4) − (T1 + T2 + T3 + T4)} / {1/2 × (Y1 + Y2 + Y3 + Y4 + T1 + T2 + T3 + T4)}] × 100

Invention Examples 1 to 12 in Table 2 have the composition of the present invention (Alloy Nos. 1 to 10 in Table 1), and are TEMs having a magnification of 20000 times in the cold rolled sheet structure of Invention Examples 1 to 12. The average number density of dispersed particles having a center of gravity diameter of less than 1 μm, which can be measured at 1 is less than 3 particles / mm ² , and the ratio of the maximum height Hα of the X-ray diffraction peaks of the β phase and the α phase ( (Hβ / Hα) is 0.50 or more. As a result, as is apparent from Table 2, in the inventive examples 1 to 10, the average ear rate itself is low even in a low-cost production method of only one time and low-temperature soaking and no intermediate annealing. The variation in the ear rate in the width direction is small.

On the other hand, Comparative Examples 13 to 17 and 21 in Table 2 are manufactured under preferable manufacturing conditions as in the invention examples. However, since the aluminum alloy composition (alloy Nos. 11 to 16 in Table 1) deviates from the composition of the present invention, the structure deviates from the definition of the present invention. As a result, in a low-cost manufacturing method in which only one-time low-temperature soaking and intermediate annealing are not performed, the average ear rate itself is high and the variation in the ear rate in the plate width direction is also large.

For Comparative Example 13, the alloy no. 11, since the amount of Si is too large, the average number density of dispersed particles having a centroid diameter of less than 1 μm is too large, and the ratio between the maximum height Hα of the X-ray diffraction peaks of the β phase and the α phase ( Hβ / Hα) is too low.
For Comparative Example 14, alloy no. As shown in FIG. 12, the amount of Fe is too small, and the mass composition ratio (Fe / Mn) between Fe and Mn is too low. For this reason, the ratio (Hβ / Hα) of the maximum height Hα of the X-ray diffraction peak between the β phase and the α phase is too low.
For Comparative Example 15, alloy no. As shown in FIG. 13, both the Fe amount and the Mn amount are too large. For this reason, the average number density of dispersed particles having a centroid diameter of less than 1 μm is too large, and the ratio (Hβ / Hα) of the maximum height Hα of the X-ray diffraction peak between the β phase and the α phase is too low.
For Comparative Example 16, alloy no. As shown in FIG. 14, the individual Fe and Mn amounts are within the scope of the present invention, but the mass composition ratio (Fe / Mn) between Fe and Mn is too low. For this reason, the average number density of dispersed particles having a centroid diameter of less than 1 μm is too large, and the ratio (Hβ / Hα) of the maximum height Hα of the X-ray diffraction peak between the β phase and the α phase is too low.
For Comparative Example 17, alloy no. As shown in FIG. 15, the amount of Mg is too small. For this reason, the average number density of dispersed particles having a centroid diameter of less than 1 μm is too large, and the ratio (Hβ / Hα) of the maximum height Hα of the X-ray diffraction peak between the β phase and the α phase is too low.
For Comparative Example 22, alloy no. As shown in FIG. 16, the mass composition ratio (Fe / Mn) of Fe and Mn is too low, and only this condition deviates from the composition of the present invention. Nevertheless, since the Fe content with respect to Mn is too small, as described above, the amount of β-phase generated is reduced, and the number density of particles (α-phase) having a centroid diameter of less than 1 μm is increased. As a result, as shown in Table 2, the average number density of dispersed particles having a centroid diameter of less than 1 μm is too large, and the ratio between the maximum height Hα of the X-ray diffraction peaks of the β phase and the α phase (Hβ / Hα). Is too low.

Further, although Comparative Examples 18 to 21 have the composition of the present invention (alloy No. 2 in Table 1), the conditions such as the soaking temperature only once and the end temperature of hot rough rolling are the above-mentioned preferable conditions. In order to deviate, the organization deviates from the provisions of the present invention. As a result, in a low-cost manufacturing method in which low-temperature soaking and intermediate annealing are performed only once, the average ear rate itself is high, and the variation in the ear rate in the plate width direction is also large.

About Comparative Example 18, since the soaking temperature was too low and hot rolling cracks occurred, the test was interrupted in the middle of hot rolling as shown by the hatched lines in Table 2.
In Comparative Example 19, the finish temperature of hot finish rolling was too high, and surface defects were caused by rough skin. Therefore, cold rolling after hot rolling was not performed as shown by the diagonal lines in Table 2.
For Comparative Example 20, the end temperature of hot rough rolling and the end temperature of hot finish rolling are too low, the average number density of dispersed particles having a centroid diameter of less than 1 μm is too high, and the β phase and α phase The ratio Hβ / Hα to the maximum height Hα of the X-ray diffraction peak is too low.
In Comparative Example 21, the soaking temperature was too high, and surface defects due to seizure occurred during hot rolling, so that cold rolling after hot rolling was not performed as shown by the oblique lines in Table 2.

From the above results, the critical significance of each specified requirement of the present invention and preferable manufacturing conditions can be understood.

As described above, according to the present invention, it is possible to reduce the manufacturing cost of an aluminum alloy cold-rolled sheet, which is a material of a bottle can, and to suppress variations in the edge ratio in the sheet width direction. Further, in the three-piece type bottle can, the amount of the flange (trimming amount) to be removed particularly by trimming is reduced by lowering the ear rate itself and suppressing the variation of the ear rate in the plate width direction. Therefore, the yield of the material can be improved. Therefore, the present invention is suitable for use in manufacturing a three-piece type bottle can among the bottle cans.

Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims. is there. This application is based on a Japanese patent application filed on September 30, 2010 (Japanese Patent Application No. 2010-221623) and a Japanese patent application filed on September 5, 2011 (Japanese Patent Application No. 2011-192510). Incorporated by reference.

Claims (3)

1. Mn: 0.3 to 1.2% by mass, Mg: 1.0 to 3.0% by mass, Fe: 0.3 to 0.7% by mass, Si: 0.1 to 0.5% by mass An aluminum alloy cold-rolled sheet for bottle cans, wherein the mass composition ratio (Fe / Mn) of Fe to Mn is in the range of 0.45 to 1.5, and the balance is composed of Al and inevitable impurities. There,
   In the structure of the aluminum alloy cold-rolled sheet for bottle cans, the average number density of dispersed particles having a gravity center diameter of less than 1 μm that can be measured with a transmission electron microscope at a magnification of 20000 is less than 3 / mm ² ,
   A β phase that is an Al ₆ (Fe, Mn) intermetallic compound, and an α phase that is an Al—Fe—Mn—Si intermetallic compound,
   The maximum height Hβ of the X-ray diffraction peak in the range of 2θ = 20.5 to 21.5 °, which can be regarded as the diffraction peak of the β phase, measured by the X-ray diffraction analyzer, and the diffraction peak of the α phase For bottle cans characterized in that the ratio (Hβ / Hα) of the maximum height Hα of the X-ray diffraction peak in the range of 2θ = 25.5 to 26.5 °, which can be regarded as 2θ, is 0.50 or more Aluminum alloy cold rolled sheet.
2. 2. The composition according to claim 1, further comprising at least one selected from Cu: 0.05 to 0.5 mass%, Cr: 0.001 to 0.3 mass%, and Zn: 0.05 to 0.5 mass%. Aluminum cold-rolled plate for bottle cans.
3. The aluminum alloy cold-rolled sheet for bottle cans according to claim 1 or 2, further containing Ti: 0.005 to 0.2 mass% alone or in combination with B: 0.0001 to 0.05 mass%.

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