WO2015125791A1

WO2015125791A1 - Aluminum alloy plate for can lids

Info

Publication number: WO2015125791A1
Application number: PCT/JP2015/054340
Authority: WO
Inventors: 友己田中; 有賀　康博; 正浩山口
Original assignee: 株式会社神戸製鋼所
Priority date: 2014-02-18
Filing date: 2015-02-17
Publication date: 2015-08-27
Also published as: CN106029923B; CN106029923A

Abstract

The purpose of the present invention is to provide an aluminum alloy plate for can lids, which achieves excellent rivet formability without lowering the material strength. One embodiment of the present invention provides an aluminum alloy plate for can lids, which contains 3.8-5.5% by mass of Mg, 0.1-0.5% by mass of Fe, 0.05-0.3% by mass of Si, 0.01-0.6% by mass of Mn and 0.3% by mass or less of Cu, with the balance made up of Al and unavoidable impurities, and which is characterized in that: the number density of intermetallic compounds having circle-equivalent diameters of from 10 nm to 300 nm (inclusive) is 80 compounds/μm³ or less; and the area ratio of intermetallic compounds having circle-equivalent diameters of more than 300 nm is from 0.3% to 2.0% (inclusive).

Description

Aluminum alloy plate for can lid

The present invention relates to an aluminum alloy plate for can lids, and more particularly to an aluminum alloy plate for easy open can lids having a good balance between material strength and rivet formability.

Properties required for the aluminum alloy plate for can lids include formability that can withstand lid processing, pressure resistance that can withstand internal pressure after beverage filling, and can openability for normal and easy opening.
On the other hand, in recent years, thinning of the aluminum alloy plate for can lids is required from the viewpoint of cost reduction. However, when the aluminum alloy plate is thinned, the pressure resistance of the can lid decreases. As one of the methods for suppressing the decrease in the pressure resistance of the can lid, it is conceivable to increase the strength of the aluminum alloy itself. However, there arises a problem that the formability decreases as the strength is increased. For this reason, in order to reduce the thickness of the aluminum alloy plate for can lids, it is necessary to improve the balance between strength and formability.

As one of the techniques to improve the formability while maintaining the material strength of the aluminum alloy plate for can lids (Al-Mg alloy plate for can lids) It has been done to control the existence state and texture.
For example, Patent Document 1 discloses a can in which the number of particles of an intermetallic compound having a diameter of 3 μm or more existing in a visual field having a diameter of 50 μm and the number of particles of an intermetallic compound having a diameter of 1 μm or more existing in 0.2 mm ² are defined. An aluminum alloy plate for the lid is described. Patent Document 2 describes an aluminum alloy plate for can lids that defines the number of intermetallic compound particles having a length of 1 μm or more existing in 1 mm ² and the rolling texture component in a portion in the plate thickness direction 1/4. Has been. Patent Document 3 describes an aluminum alloy plate for a can lid that defines the number of particles of an intermetallic compound having an equivalent circle diameter of 0.7 μm or more present in 1 mm ² and the proof stress after the coating film is formed.

Japanese Unexamined Patent Publication No. 05-302139 Japanese Unexamined Patent Publication No. 2002-105574 Japanese Unexamined Patent Publication No. 2007-277694

The intermetallic compounds having the sizes described in Patent Documents 1 to 3 (equivalent circle diameter of 0.7 μm or more) serve as starting points for cracking during rivet molding. For this reason, as described in Patent Documents 1 to 3, by reducing the number of particles per unit area of an intermetallic compound of this size or by reducing the area ratio, cracks that occur during rivet molding Can be suppressed.
However, even if cracks do not occur during rivet molding, if constriction occurs, cracks may occur during stake (processing to strike the rivet portion to attach the tab to the lid). In the conventional technique, the constriction at the time of rivet forming cannot be controlled, and better rivet formability with reduced constriction is required.

An object of the present invention is to provide an aluminum alloy plate for can lids having excellent rivet formability without reducing the material strength.

It is generally considered that an Al—Mg-based alloy forms a microband as the deformation progresses, and the microband develops to cause constriction. The present inventors presume that the starting point of the microband is a submicron-sized intermetallic compound, and for an intermetallic compound having a size smaller than the conventionally controlled size (equivalent circle diameter is 0.7 μm or more), We thought to control the occurrence of constriction by controlling the distribution state. Based on this idea, the present inventors have conducted experiments and examinations. As a result, the inventors have found an optimal distribution state of submicron-sized intermetallic compounds and have achieved an embodiment of the present invention.

That is, the aluminum alloy plate for a can lid according to an embodiment of the present invention has Mg: 3.8 to 5.5% by mass, Fe: 0.1 to 0.5% by mass, Si: 0.05 to 0.00%. 3% by mass, Mn: 0.01 to 0.6% by mass, Cu: 0.3% by mass or less, the balance consisting of Al and inevitable impurities, and the equivalent circle diameter of 10 to 300 nm. The area ratio of an intermetallic compound having a number density of 80 / μm ³ or less and an equivalent circle diameter exceeding 300 nm is 0.3% or more and 2.0% or less. In the aluminum alloy plate for can lids, the number density of intermetallic compounds having an equivalent circle diameter of 10 nm to 300 nm is preferably 60 / μm ³ or less.

In addition, as a means to improve the rivet formability without reducing the material strength of the aluminum alloy plate for can lids (Al-Mg alloy plate), the amount of solid solution strengthening by increasing the concentration of solid solution elements, and work hardening characteristics An improvement in (uniform deformation ability) can be considered. Solid solution strengthening and work hardening occur because dislocation movement is hindered by the interaction between dislocations and solute atoms. In an aluminum alloy, it is said that the difference in atomic radius between the parent phase (Al) and the solute atoms (Mg, Cu, Mn) dominates the magnitude of the interaction. Mg, Cu, and Mn have a large atomic radius difference from the parent phase (Al) and a large amount of solid solution strengthening, but Mg and Mn increase not only the amount of solid solution but also the amount of crystallized matter. Formability decreases due to an increase in the amount of products. For this reason, the present inventors paid attention to an increase in the solid solution amount of Cu, and decided to improve the formability without reducing the material strength, and particularly to suppress the occurrence of necking during rivet forming.

That is, the aluminum alloy plate for can lids according to another embodiment of the present invention has Mg: 3.8 to 5.5% by mass, Fe: 0.1 to 0.5% by mass, Si: 0.05 to An aluminum alloy plate containing 0.3% by mass, Mn: 0.01 to 0.6% by mass, Cu: 0.06 to 0.3% by mass or less, and the balance being Al and inevitable impurities, The solid solution concentration is 0.06% by mass or more, and the area ratio of the intermetallic compound having an equivalent circle diameter exceeding 300 nm is 0.3% to 2.0%.

Previously, aluminum alloy plates for lid materials have deteriorated rivet formability when increased in strength. Conversely, in order to obtain excellent rivet formability, it has been necessary to reduce material strength. On the other hand, the aluminum alloy plate for a lid material according to the present invention has excellent rivet formability despite having high material strength. According to the present invention, even when the aluminum alloy plate for can lids is thinned, there is provided an aluminum alloy plate for can lids that has no deficiency in pressure resistance after beverage filling and is excellent in rivet formability and can openability. be able to.

FIG. 1 is a plan view of a can lid made of an aluminum alloy plate. FIG. 2 is a cross-sectional view of the score of the can lid used when evaluating the can opening property. 3 (a) to 3 (c) are schematic views of a can opening load measuring machine used when evaluating the can opening ability. FIG. 3A is a perspective view of an open load measuring machine. FIG.3 (b) is a cross-sectional schematic diagram of can-lid vicinity at the time of the measurement of an open can load measuring machine. FIG.3 (c) is a front schematic diagram which shows the direction of a can lid when installing a can lid in a can opening load measuring machine.

Hereinafter, the aluminum alloy plate for can lids and the manufacturing method thereof according to the present invention will be described in detail. In the present specification, the percentage based on mass (% by mass) is the same as the percentage based on weight (% by weight).

<First Embodiment>
First, an aluminum alloy plate for a can lid according to an embodiment of the present invention (hereinafter also referred to as a first embodiment) and a manufacturing method thereof will be described in detail.
The aluminum alloy plate for can lids according to the first embodiment of the present invention has Mg: 3.8 to 5.5% by mass, Fe: 0.1 to 0.5% by mass, Si: 0.05 to 0.00%. 3% by mass, Mn: 0.01 to 0.6% by mass, Cu: 0.3% by mass or less, the balance consisting of Al and inevitable impurities, and the equivalent circle diameter of 10 to 300 nm. The area ratio of an intermetallic compound having a number density of 80 / μm ³ or less and an equivalent circle diameter exceeding 300 nm is 0.3% or more and 2.0% or less.

(Component composition of aluminum alloy)
Mg: 3.8 to 5.5% by mass
Mg has the effect of improving the strength of the aluminum alloy plate. However, when the Mg content is less than 3.8% by mass, the strength of the aluminum alloy plate is insufficient, and the pressure resistance 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 rivet formability decreases. Accordingly, the Mg content is set to 3.8 to 5.5% by mass.

Fe: 0.1 to 0.5% by mass
Fe forms Al—Fe (—Mn) -based and Al—Fe (—Mn) -Si-based intermetallic compounds in an aluminum alloy plate to improve the tearability of the score part when it is molded into a can lid, and it can be opened. There is an effect of improving canability. However, if the Fe content is less than 0.1% by mass, the tearability of the score part does not improve, and score derailment at the time of can open (crack propagates to other than the score part at the time of can open) and can opening force Opening defects such as tab breakage due to increase are likely to occur. On the other hand, when the Fe content exceeds 0.5% by mass, the area ratio of intermetallic compounds exceeding 300 nm in the aluminum alloy plate is larger than a predetermined range, and the rivet formability is lowered. Therefore, the Fe content is 0.1 to 0.5 mass%.

Si: 0.05 to 0.3% by mass
Si forms Mg—Si, Al—Fe (—Mn), and Al—Fe (—Mn) —Si intermetallic compounds in an aluminum alloy plate, and tears the score when molded into a can lid It has the effect of improving the performance and improving the can openability. However, when the Si content is less than 0.05% by mass, the openability is not improved as in the case of Fe. In addition, the amount of scrap that can be used as the raw material for the aluminum alloy plate is reduced, and the required purity of the aluminum ingot is increased, which increases the cost. On the other hand, when the Si content exceeds 0.3% by mass, the area ratio of the intermetallic compound exceeding 300 nm in the aluminum alloy plate becomes larger than the predetermined range, and the rivet formability decreases. Therefore, the Si content is set to 0.05 to 0.3% by mass.

Mn: 0.01 to 0.6% by mass
Mn has the effect of improving the strength of the aluminum alloy sheet, and when the 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. However, 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 0.6% by mass, the area ratio of intermetallic compounds exceeding 300 nm in the aluminum alloy plate becomes larger than a predetermined range, and the rivet formability decreases. Therefore, the Mn content is set to 0.01 to 0.6% by mass.

Cu: 0.3% by mass or less Cu has an effect of improving the strength of the aluminum alloy plate. However, when the Cu content exceeds 0.3% by mass, the strength of the aluminum alloy plate becomes excessive, and the rivet formability decreases. Therefore, the Cu content is set to 0.3% by mass or less.

Inevitable Impurities The aluminum alloy according to the present embodiment contains the balance Al and inevitable impurities in addition to the additive components. Inevitable impurities are 0.3 mass% or less for Cr, 0.3 mass% or less for Zn, 0.1 mass% or less for Ti, 0.1 mass% or less for Zr, 0.1 mass% or less for B, etc. Are permitted 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 this embodiment are not affected.

(Intermetallic compounds in aluminum alloy plates)
The effect of increasing the tearability of the score part when aluminum alloy plates are molded into can lids and improving the can openability by appropriately distributing intermetallic compounds with equivalent circle diameters exceeding 300 nm in aluminum alloy plates Is obtained. On the surface of the aluminum alloy plate, when the area ratio of the intermetallic compound having an equivalent circle diameter of more than 300 nm is smaller than 0.3%, the tearability of the score portion is lowered and the openability is deteriorated. On the other hand, when the area ratio of the intermetallic compound with an equivalent circle diameter exceeding 300 nm exceeds 2.0% on the plate surface, cracks are generated by the intermetallic compound during rivet forming, and it is easy to propagate and formability. Decreases. Therefore, the area ratio of the intermetallic compound having an equivalent circle diameter exceeding 300 nm is set to 0.3% or more and 2.0% or less. The upper limit of this area ratio is preferably 1.0%, and the lower limit is preferably 0.4%.

On the other hand, among the submicron-sized intermetallic compounds, intermetallic compounds having an equivalent circle diameter of 10 nm or more and 300 nm or less become the starting point of a microband during rivet molding, and the microband develops and becomes constricted. If the number density of the intermetallic compounds having an equivalent circle diameter of 10 nm to 300 nm exceeds 80 / μm ³ , a large number of microbands are generated during rivet forming, and it tends to develop and necking occurs. Therefore, the number density of intermetallic compounds having a circle-equivalent diameter of 10 nm to 300 nm is 80 / μm ³ or less. The smaller the number density of intermetallic compounds having an equivalent circle diameter of 10 nm or more and 300 nm or less, the better, preferably 60 pieces / μm ³ or less.

(Aluminum alloy plate manufacturing method)
The aluminum alloy plate according to the present embodiment can be produced by the steps of casting, homogenizing heat treatment, hot rolling, primary cold rolling, intermediate annealing, and secondary cold rolling. In casting, homogenization heat treatment, hot rolling, intermediate annealing, etc., an intermetallic compound of Al- (Fe, Mn) and Mg ₂ Si is generated, and in self-annealing or coiling annealing by winding after cold rolling. , Precipitates such as Al—Cu—Mg are formed. The size of the precipitate generated by self-annealing or baking finish annealing is several nm, and it is considered that it does not become a starting point of cracks or microbands during rivet forming. Therefore, in order to control the size, number density, and area ratio of the intermetallic compound within the above-mentioned specific range and to develop an excellent can openability and an improved balance between strength and rivet formability, the process up to intermediate annealing is performed. Is important.
The method for producing an aluminum alloy sheet according to the present embodiment is particularly characterized in that the homogenization heat treatment is maintained at a temperature range of 400 ° C. to 550 ° C. for 1 to 10 hours, and the intermediate annealing is performed twice in succession. . Hereinafter, each step will be described.

First, an aluminum alloy is cast by a known semi-continuous casting method such as a DC casting method.
Next, after removing the area | region used as an inhomogeneous structure | tissue of an ingot surface layer by chamfering, homogenization heat processing is performed. The homogenization heat treatment is held in a temperature range of 400 to 550 ° C. for 1 to 10 hours. When the homogenization heat treatment temperature is less than 400 ° C. or the holding time is less than 1 hour, the area ratio of the intermetallic compound having an equivalent circle diameter of more than 300 nm is smaller than a predetermined range, and the openability is lowered. When the homogenization heat treatment temperature exceeds 550 ° C., burning occurs during hot rolling. Moreover, when holding time exceeds 10 hours, productivity will fall.
After the homogenization heat treatment, the hot rolling is continued without cooling, and the hot rolling is preferably finished at 300 ° C. or higher. The produced hot rolled material has a recrystallized structure.

The hot-rolled sheet is cold-rolled (primary cold-rolling) at a total rolling rate of 50 to 80%. When the total rolling rate is less than 50%, the accumulated strain due to rolling becomes insufficient, the recrystallized grain size becomes large in the subsequent intermediate annealing, and the formability including the rivet formability is deteriorated. On the other hand, when the total rolling rate exceeds 80%, the number of rolling passes increases and productivity decreases.

Next, the cold-rolled sheet is subjected to intermediate annealing and recrystallization, and the number density of intermetallic compounds of 300 nm or less is reduced. This intermediate annealing is performed twice continuously. The first intermediate annealing is performed under conditions where the material temperature is in the range of 380 ° C. to 550 ° C. and the holding time is within 10 minutes, and after cooling to room temperature, reheating is performed to perform the second intermediate annealing. Similarly, the second intermediate annealing is performed under the condition that the material temperature is in the range of 380 ° C. to 550 ° C. and the holding time is within 10 minutes. The cooling rate after the second intermediate annealing is set to 100 ° C./min or more. When the holding temperature of the intermediate annealing is less than 380 ° C., the number density of the intermetallic compound having an equivalent circle diameter of 10 to 300 nm becomes larger than a predetermined range, and the rivet formability is lowered. When holding temperature exceeds 550 degreeC or holding time exceeds 10 minutes, the effect of reducing an intermetallic compound will be saturated, and cost will become high. In addition, when the number of intermediate annealing is one or when the second cooling rate is less than 100 ° C./min, the number density of the intermetallic compound having an equivalent circle diameter of 10 to 300 nm becomes larger than a predetermined range, and the rivet Formability is reduced.

Subsequently, the annealed cold rolled sheet is cold rolled again (secondary cold rolling) at a total rolling rate of 50 to 85%, whereby the aluminum alloy sheet according to the present embodiment can be manufactured. . When the total rolling rate is less than 50%, the work hardening by rolling is small and the strength is lowered, and the pressure strength when formed into a can lid is insufficient. On the other hand, when the total rolling rate exceeds 85%, the strength of the aluminum alloy plate for can lids becomes too high, and the formability of the product plate including the rivet formability is lowered. Therefore, the total rolling rate is 50 to 85%.

The aluminum alloy plate for can lids manufactured by the above process is subjected to a surface treatment such as chromate or zircon, applied with an organic paint such as epoxy resin, vinyl chloride sol or polyertel, and PMT (Peak Metal Temperature: After being baked at a metal arrival temperature of about 230 to 280 ° C., it is formed into a can lid.

<Second Embodiment>
Next, an aluminum alloy plate for can lids and a method for manufacturing the same according to another embodiment of the present invention (hereinafter also referred to as a second embodiment) will be described in detail.
The aluminum alloy plate for can lids according to the second embodiment of the present invention has Mg: 3.8 to 5.5% by mass, Fe: 0.1 to 0.5% by mass, Si: 0.05 to 0.00%. 3% by mass, Mn: 0.01 to 0.6% by mass, Cu: 0.06 to 0.3% by mass or less, the balance being an aluminum alloy plate made of Al and inevitable impurities, The area ratio of the intermetallic compound having a concentration of 0.06% by mass or more and an equivalent circle diameter exceeding 300 nm is 0.3% to 2.0%.

(Component composition of aluminum alloy)
In the component composition of the aluminum alloy in the aluminum alloy plate for can lids according to the second embodiment, Mg (3.8 to 5.5% by mass), Fe (0.1 to 0.5% by mass), Si (0 .05-0.3% by mass), Mn (0.01-0.6% by mass), and the balance (Al and inevitable impurities), the contents of these components and the reasons for their control are the first. Since it is the same as that of embodiment, the detail is abbreviate | omitted here. Hereinafter, the Cu content and the reason for its control will be described.

Cu: 0.06 to 0.3% by mass
Cu has the effect of improving the strength of the aluminum alloy plate. Moreover, a moldability improves also by making it dissolve. However, when the Cu content is less than 0.06% by mass, the amount of solid solution in the parent phase is small, the balance between strength and formability is lowered, and rivet formability is not improved. On the other hand, when the Cu content exceeds 0.3% by mass, the strength of the aluminum alloy plate becomes excessive, and the rivet formability decreases. Accordingly, in this embodiment, the Cu content is 0.06 to 0.30 mass%.

(Cu solid solution concentration)
As described above, when the Cu solid solution concentration in the parent phase (Al) is large, the material strength is increased due to the increase in the solid solution strengthening amount, and the work hardening characteristics (uniform deformation ability) are improved. Constriction can be suppressed. However, if the Cu solid solution concentration is less than 0.06% by mass, the effect is insufficient. Therefore, the Cu solid solution concentration is 0.06% by mass or more, preferably 0.09% by mass or more, and more preferably 0.12% by mass or more. In addition, the ratio of the solid solution amount to the added amount of Cu (Cu solid solution concentration / Cu content) is preferably 0.75 or more, and more preferably 0.87 or more.

(Intermetallic compounds in aluminum alloy plates)
The effect of increasing the tearability of the score part when aluminum alloy plates are molded into can lids and improving the can openability by appropriately distributing intermetallic compounds with equivalent circle diameters exceeding 300 nm in aluminum alloy plates Is obtained. On the surface of the aluminum alloy plate, when the area ratio of the intermetallic compound having an equivalent circle diameter of more than 300 nm is smaller than 0.3%, the tearability of the score portion is lowered and the openability is deteriorated. On the other hand, when the area ratio of the intermetallic compound with an equivalent circle diameter exceeding 300 nm exceeds 2.0% on the plate surface, cracks are generated by the intermetallic compound during rivet forming, and it is easy to propagate and formability. Decreases. Therefore, the area ratio of the intermetallic compound having an equivalent circle diameter exceeding 300 nm is set to be 0.3% or more and 2.0% or less. The upper limit of this area ratio is preferably 1.0%, and the lower limit is preferably 0.4%.

(Aluminum alloy plate manufacturing method)
The aluminum alloy plate according to the present embodiment can be produced by the steps of casting, homogenizing heat treatment, hot rolling, primary cold rolling, intermediate annealing, and secondary cold rolling. The method for producing an aluminum alloy sheet according to the present embodiment is particularly characterized in that the homogenization heat treatment is maintained at a temperature range of 400 ° C. to 550 ° C. for 1 to 10 hours, and the intermediate annealing is performed twice in succession. . Here, each process (casting, homogenization heat treatment, hot rolling, primary cold rolling, and secondary cold rolling) other than intermediate annealing in the method for producing an aluminum alloy according to the present embodiment is the first implementation. Since it is the same as the embodiment, the details are omitted here. Hereinafter, the intermediate annealing in the manufacturing method of the aluminum alloy which concerns on this embodiment is demonstrated.

In the manufacturing method according to the present embodiment, after obtaining a cold rolled sheet by casting, homogenizing heat treatment, hot rolling and cold rolling (primary cold rolling) as in the first embodiment, The cold-rolled sheet is annealed and recrystallized, and the solid solution concentration of Cu is increased. This intermediate annealing is performed twice continuously. The first intermediate annealing is performed under conditions where the material temperature is in the range of 380 ° C. to 550 ° C. and the holding time is within 10 minutes, and after cooling to room temperature, reheating is performed to perform the second intermediate annealing. Similarly, the second intermediate annealing is performed under the condition that the material temperature is in the range of 380 ° C. to 550 ° C. and the holding time is within 10 minutes. The cooling rate after the second intermediate annealing is set to 100 ° C./min or more. When the holding temperature of the intermediate annealing exceeds 550 ° C., or when the holding time exceeds 10 minutes, the recrystallized grains after the annealing process are finished, and the formability of the product plate is lowered. When the holding temperature of the intermediate annealing is less than 380 ° C., the solid solution concentration of Cu does not fall within a predetermined range, and the rivet formability is not improved. In addition, when the number of intermediate annealing is one or when the second cooling rate is less than 100 ° C./min, the solid solution concentration of Cu does not fall within a predetermined range and the rivet formability is not improved.

Subsequently, the annealed cold-rolled sheet is cold-rolled (secondary cold-rolling) again at a total rolling ratio of 50 to 85%, as in the first embodiment, to thereby relate to the present embodiment. Aluminum alloy plates can be manufactured.

Hereinafter, examples in which the effects of the present invention have been confirmed will be specifically described in comparison with comparative examples that do not satisfy the requirements of the present invention. In addition, this invention is not limited to this Example.

(Example according to the first embodiment)
Aluminum alloys shown in Table 1 (except No. 32) were cast by a semi-continuous casting method (DC), and the ingot surface layer was faced to produce a slab. After subjecting this slab to homogenization heat treatment, it is hot-rolled to form a hot-rolled sheet. The hot-rolled sheet is subjected to primary cold rolling (rolling rate 70%), intermediate annealing, and secondary cold. Rolling (rolling rate 79%) was sequentially performed to produce an aluminum alloy plate for can lids having a plate thickness of 0.215 mm. However, no. The aluminum alloy No. 33 was subjected to only primary cold rolling (rolling rate: 93%) after hot rolling, and no intermediate annealing was performed. No. In order to simulate the invention of Patent Document 1, the 32 aluminum alloy was cast by a continuous casting method (CC), and a primary cold rolling (rolling rate 70%) and intermediate annealing were performed without homogenizing the continuous cast plate. Secondary cold rolling (rolling rate 79%) was sequentially performed to produce an aluminum alloy plate for can lids having a plate thickness of 0.215 mm. Tables 1 and 2 show the homogenization heat treatment and intermediate annealing conditions.

No. manufactured 1 to 33 aluminum alloy sheets as test materials, number density of intermetallic compounds with equivalent circle diameters of 10 nm to 300 nm, area ratio of intermetallic compounds with equivalent circle diameters exceeding 300 nm, 0.2% yield strength, rivets The moldability and can open load were measured as follows. The results are shown in Table 2.

(Number density of intermetallic compounds with equivalent circle diameter of 10 nm to 300 nm)
After mechanically polishing the surface of the aluminum alloy plate to a thickness of 0.1 mm, a thin film having a thickness of 100 nm is formed by a twin jet electrolytic polishing method, and this thin film is subjected to 500,000 with a transmission electron microscope (TEM). 4 fields of view were taken. Transfer only the intermetallic compound from the photographed image to the transparent film, and measure the number of intermetallic compounds in the photographing range and the particle area of each using the image analysis software Image-Pro Plus. The number density of particles having an equivalent circle diameter of 10 nm to 300 nm was determined.

(Area ratio of intermetallic compound with equivalent circle diameter exceeding 300 nm)
A parallel section in the rolling direction of the aluminum alloy plate is mirror-finished by buffing, and 20 views of a composition image (COMPO image) at an acceleration voltage of 15 kV and a magnification of 500 times are obtained on this mirror-finished surface with a scanning electron microscope (SEM). (Total area 0.75 mm ² or more) Photographed. Of these composition images, particles obtained with white contrast from the parent phase are regarded as Al—Fe (—Mn) -based and Al—Fe (—Mn) —Si-based intermetallic compounds, and particles obtained with black contrast are regarded as Mg—. It was regarded as a Si-based intermetallic compound. From this composition image, the area ratio (percentage of the photographing area) of the intermetallic compound exceeding the equivalent circle diameter of 300 nm was calculated by image processing.

(0.2% yield strength)
The aluminum alloy sheet was subjected to a heat treatment at 255 ° C. for 20 seconds using an oil bath simulating a painting / baking process, and then a JIS-5 tensile test piece was prepared 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.

(Rivet formability)
The rivet forming process includes a bubble forming process for projecting the central part of the can lid, a button forming process for reducing the diameter of the projecting part (bubble) in 1 to 3 processes and making a sharp protrusion, and a tab on the protrusion (button). And a stake process in which the protrusion is crushed and the tab is crimped. In order to fix the tab normally, it is necessary to ensure the size of the rivet diameter after stake. Therefore, an aluminum alloy plate that can be formed with a sufficiently high protrusion (button) height after the button forming process is required. It is done.
Here, rivet formability was evaluated by a test simulating a bubble process. That is, after the aluminum alloy sheet was heat-treated at 255 ° C for 20 seconds using an oil bath simulating the painting and baking process, a micro-extrusion test of φ6 mm was performed, and the limit overhang height at which no constriction or cracking occurred Asked. The appropriate range of the limit overhang height was 1.45 mm or more. If the limit overhang height of the aluminum alloy plate is 1.45 mm or more, a button having a sufficient height can be formed during actual forming.

(Opening load)
After aluminum alloy plate is heat treated at 255 ° C for 20 seconds using an oil bath that simulates the painting and baking process, after shell molding, conversion molding, and tab stake using a 204-diameter full-form end mold A can open test was conducted. FIG. 1 is a plan view of a can lid used in a can open test. FIG. 2 is a cross-sectional view of the score 3 of the can lid used in the can open test. 3 (a) to 3 (c) are schematic views of a can opening load measuring machine for measuring the load at the time of opening the can. FIG. 3A is a perspective view of the can opening load measuring machine 5. FIG. 3B is a schematic cross-sectional view of the vicinity of the can lid 1 at the time of measurement by the can open load measuring device 5. FIG. 3C 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. The can lid 1 is placed on the can opening load measuring device 5 so that the tab 4 is located above the score 3 with respect to the score 3 (FIG. 3C). A hook 6 is hooked on the tab 4 of the can lid 1 to form a hook 7 (FIG. 3B). 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 25 N or less. For aluminum alloys whose limit overhang height is less than 1.45 mm in the micro overhang test, the necessary protrusion (button) height cannot be obtained and the tab cannot be properly attached. There was no test to measure.

As shown in Tables 1 and 2, the component composition, the number density of intermetallic compounds having an equivalent circle diameter of 10 nm to 300 nm (hereinafter referred to as the number density of intermetallic compounds of 10 nm to 300 nm), and the equivalent circle diameter exceeding 300 nm The area ratio of the intermetallic compound (hereinafter referred to as the area ratio of the intermetallic compound of more than 300 nm) is No. within the specified range of the first embodiment. Nos. 1 to 17 (Examples) have appropriate 0.2% proof stress and opening load, and excellent rivet formability. Therefore, no. The aluminum alloy plates 1 to 17 have a thin thickness of 0.215 mm, but can be suitably used for easy open can lids.

On the other hand, no. 18 to 33 (comparative example), any of the component composition, the number density of the intermetallic compound of 10 nm to 300 nm, and the area ratio of the intermetallic compound of more than 300 nm are not within the specified range of the first embodiment. As shown, any one of 0.2% proof stress, can open load and rivet formability does not satisfy the appropriate value.
No. No. 18 has a low 0.2% yield strength due to insufficient Mg content. No. 19 is inferior in rivet formability because the Mg content is excessive.
No. Since the Fe content of 20 is insufficient, the area ratio of intermetallic compounds exceeding 300 nm is small and the can opening load is large. No. Since No. 21 has an excessive Fe content, the area ratio of intermetallic compounds exceeding 300 nm is large and the rivet formability is poor.
No. No. 22 has an insufficient Si content, so the area ratio of the intermetallic compound exceeding 300 nm is small and the can opening load is large. No. In No. 23, since the Si content is excessive, the area ratio of the intermetallic compound exceeding 300 nm is large and the rivet formability is inferior.

No. No. 24 has a low Mn content, so the 0.2% yield strength is low, the area ratio of intermetallic compounds exceeding 300 nm is small, and the opening load is large. No. Since No. 25 has an excessive Mn content, the area ratio of intermetallic compounds exceeding 300 nm is large and the rivet formability is poor.
No. No. 26 is inferior in rivet formability because the Cu content is excessive.
No. No. 27 has a low intermediate annealing retention temperature, so that the number density of intermetallic compounds of 10 nm to 300 nm is high and the rivet formability is poor. No. Since No. 28 has a low cooling rate after the second intermediate annealing, the number density of the intermetallic compound of 10 nm to 300 nm is high and the rivet formability is poor. No. In No. 29, since the intermediate annealing is performed only once, the number density of the intermetallic compound of 10 nm to 300 nm is high and the rivet formability is inferior.

No. Since No. 30 has a low holding temperature in the homogenization treatment, the area ratio of the intermetallic compound exceeding 300 nm is small and the can opening load is large. No. Since No. 31 has a short homogenization holding time, the area ratio of the intermetallic compound exceeding 300 nm is small and the can opening load is large. No. Since No. 32 is not homogenized, the area ratio of intermetallic compounds exceeding 300 nm is small and the can opening load is large.
No. Since No. 33 is not subjected to intermediate annealing, the number density of the intermetallic compound of 10 nm to 300 nm is high and the rivet formability is poor.

(Example according to the second embodiment)
Aluminum alloys shown in Table 3 (except for No. 60) were cast by a semi-continuous casting method (DC), and the ingot surface layer was chamfered to produce a slab. After subjecting this slab to homogenization heat treatment, it is hot-rolled to form a hot-rolled sheet. The hot-rolled sheet is subjected to primary cold rolling (rolling rate 70%), intermediate annealing, and secondary cold. Rolling (rolling rate 79%) was sequentially performed to produce an aluminum alloy plate for can lids having a plate thickness of 0.215 mm. No. In order to simulate the invention of Patent Document 1, 60 aluminum alloy was cast by a continuous casting method (CC), primary cold rolling (rolling rate 70%), intermediate annealing without homogenizing the continuous cast plate. Secondary cold rolling (rolling rate 79%) was sequentially performed to produce an aluminum alloy plate for can lids having a plate thickness of 0.215 mm. Tables 3 and 4 show the homogenization heat treatment and intermediate annealing conditions.

No. manufactured 34-66 aluminum alloy plates were used as test materials, the solid solution concentration of Cu, the area ratio of intermetallic compounds with an equivalent circle diameter exceeding 300 nm, 0.2% proof stress, rivet formability and can open load were as follows: Measured as indicated. The results are shown in Table 4.

(Cu solid solution concentration)
After the aluminum alloy plate is decomposed with phenol, it is filtered using a 0.1 μm pore filter, and the filtrate is introduced into an ICP (Inductively Coupled Plasma) emission spectrophotometer, and is nebulized with a nebulizer so that only a small mist is contained in the plasma. The solid solution concentration of Cu was measured. In addition, even if the filtrate contains a precipitate of less than 0.1 μm, it is discharged without being analyzed as a large mist when it is atomized. Not included.

(Area ratio of intermetallic compound with equivalent circle diameter exceeding 300 nm, 0.2% yield strength, rivet formability and can open load)
For the area ratio, 0.2% proof stress, rivet formability and can open load of intermetallic compounds having an equivalent circle diameter of more than 300 nm, see “No. Measurements were performed in the same manner as in 1-33.

As shown in Tables 3 and 4, the composition ratio, the solid solution concentration of Cu, and the area ratio of intermetallic compounds having an equivalent circle diameter exceeding 300 nm (hereinafter referred to as the area ratio of intermetallic compounds exceeding 300 nm) are the second. No. within the prescribed range of the embodiment. Nos. 34 to 49 (Examples) have appropriate 0.2% proof stress and opening load, and excellent rivet formability. Therefore, no. The aluminum alloy plates 34 to 49 have a thin thickness of 0.215 mm, but can be suitably used for easy open can lids.

On the other hand, no. 50 to 66 (comparative examples) were not any of the component composition, the solid solution concentration of Cu, and the area ratio of the intermetallic compound exceeding 300 nm within the specified range of the second embodiment. Any of 2% yield strength, can open load, and rivet formability does not satisfy the appropriate values.
No. No. 50 has an excessive Mg content, so the rivet formability is inferior. No. 51 has a low 0.2% yield strength due to insufficient Mg content.
No. No. 52 has an excessive Fe content, so that the area ratio of intermetallic compounds exceeding 300 nm is large and the rivet formability is poor. 53 has an insufficient Fe content, so the area ratio of intermetallic compounds exceeding 300 nm is small and the can opening load is large.
No. No. 54 has an excessive Si content, so that the area ratio of intermetallic compounds exceeding 300 nm is large and the rivet formability is inferior. Since No. 55 has insufficient Si content, the area ratio of intermetallic compounds exceeding 300 nm is small and the opening load is large.

No. No. 56 has an excessive Mn content, so that the area ratio of intermetallic compounds exceeding 300 nm is large and the rivet formability is inferior. No. 57 has a low Mn content, so the 0.2% yield strength is low, the area ratio of intermetallic compounds exceeding 300 nm is small, and the can opening load is large.
No. No. 58 has an excessive Cu content, so the rivet formability is inferior. No. 59 has a low Cu content, so the Cu solid solution concentration is low and the rivet formability is poor.
No. Since No. 60 was not subjected to homogenization heat treatment, the area ratio of the intermetallic compound exceeding 300 nm was small and the can opening load was large. No. No. 61 has a low holding temperature in the homogenization treatment, so that the area ratio of the intermetallic compound exceeding 300 nm is small and the can opening load is large. No. No. 62 has a short holding time of the homogenization treatment, so that the area ratio of the intermetallic compound exceeding 300 nm is small and the can opening load is large.

No. No. 63 has a low intermediate annealing holding temperature, so that the solid solution concentration of Cu does not increase and the rivet formability is poor. No. In 64 and 65, since the intermediate annealing is performed only once, the solid solution concentration of Cu does not increase and the rivet formability is inferior. No. No. 66 has a low cooling rate after the second intermediate annealing, so that the solid solution concentration of Cu is low and the rivet formability is poor.

Although the invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application is based on Japanese Patent Application (Japanese Patent Application No. 2014-028184) filed on February 18, 2014 and Japanese Patent Application (Japanese Patent Application No. 2014-028185) filed on February 18, 2014. Which is incorporated by reference in its entirety.

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

Claims

Mg: 3.8 to 5.5% by mass, Fe: 0.1 to 0.5% by mass, Si: 0.05 to 0.3% by mass, Mn: 0.01 to 0.6% by mass, Cu: An aluminum alloy plate containing 0.3% by mass or less, with the balance being Al and inevitable impurities, the number density of intermetallic compounds having an equivalent circle diameter of 10 nm or more and 300 nm or less is 80 pieces / μm 3 or less, An aluminum alloy plate for a can lid, wherein the area ratio of an intermetallic compound having an equivalent diameter exceeding 300 nm is 0.3% or more and 2.0% or less.
2. The aluminum alloy plate for can lid according to claim 1, wherein the number density of intermetallic compounds having an equivalent circle diameter of 10 nm to 300 nm is 60 / μm 3 or less.
Mg: 3.8 to 5.5% by mass, Fe: 0.1 to 0.5% by mass, Si: 0.05 to 0.3% by mass, Mn: 0.01 to 0.6% by mass, Cu: An aluminum alloy plate containing 0.06 to 0.3% by mass or less, the balance being Al and inevitable impurities, the Cu solid solution concentration being 0.06% by mass or more, and the equivalent circle diameter exceeding 300 nm An aluminum alloy plate for can lids, wherein the area ratio of the intermetallic compound is 0.3% or more and 2.0% or less.