KR20170038908A - Aluminum alloy sheet for can body - Google Patents

Abstract

There is provided an aluminum alloy plate for a can body in which a can wall after DI processing and baking processing is uniformly deformed by secondary processing and subsequent plastic deformation to suppress a local plate thickness reduction of the can wall. Wherein the composition of the aluminum alloy sheet contains 0.1 to 0.5 mass% of Si, 0.3 to 0.6 mass% of Fe, 0.1 to 0.35 mass% of Cu, 0.5 to 1.2 mass% of Mn and 0.7 to 2.5 mass% of Mg, The remainder is made of Al and inevitable impurities. The aluminum alloy plate was subjected to baking at 200 占 폚 for 20 minutes after DI molding with an internal strength of 240 to 290 MPa after baking at 200 占 폚 for 20 minutes and a processing rate of the can wall of 60 to 70% , A 1% stretch is applied, and the increment of the 0.2% proof stress when subjected to a 90 ° V bending-bending recovery process at a bending radius of 0.1 mm in the circumferential direction of the can is at least 10 MPa.

Description

ALUMINUM ALLOY SHEET FOR CAN BODY}

The present invention relates to an aluminum alloy plate used for forming a can body of two-piece can by performing DI (draw & ironing) molding. More particularly, the present invention relates to an aluminum alloy plate for DI- It is about the plate.

In order to improve the designability of the aluminum can, there is a growing demand for providing DI-molded can walls with secondary processing such as embossing or diamond cut patterns, and thus an aluminum alloy plate for a can body having excellent secondary workability is required. Further, in order to reduce the environmental load, the thinning of the aluminum alloy plate for the can body and the thinning of the can wall after DI molding are also progressing.

For example, Patent Document 1 discloses that the breaking limit cycle is 6 cycles or more when a 90 degree bending with a bending radius of 1.0 mm is performed on a can wall in a state of adding about 15% of a 0.2% proof stress, There is disclosed an aluminum alloy plate for a can body which is excellent in secondary workability of a can wall.

Japanese Patent Application Laid-Open No. 2005-248275

The can which has been subjected to secondary processing such as embossing processing or diamond cutting pattern on the can wall has been modified in the manufacturing step including the filling of the contents, the distribution step after filling, the step transferred to the consumer, There is a case where a hard and sharp foreign object repeatedly comes in contact with the outside to cause plastic deformation at that portion. When the plate is locally decreased in thickness by the secondary processing and subsequent plastic deformation (when a constricted portion is formed), a portion where the plate thickness is decreased, for example, when the can is impacted or foreign matter is contacted with the can wall An excessive stress may be applied, and the can wall may be broken to cause leakage of the contents.

It is said that the evaluation method of Patent Document 1 assumes that the can wall is locally reduced in thickness due to the secondary processing and subsequent plastic deformation, and the can wall is broken due to excessive stress applied thereto I can not. Even after plastic deformation corresponding to a stricter condition (small bending radius) than the evaluation method of Patent Document 1 after secondary processing is applied to the can wall, the can wall is uniformly deformed, and local plate thickness reduction is suppressed Is required.

The present invention has been made on the basis of such a request, and it is an object of the present invention to provide an aluminum alloy for a can body in which a can wall after DI processing and baking treatment is uniformly deformed by secondary processing and subsequent plastic deformation, It is intended to provide a plate.

The aluminum alloy plate for a can body according to the present invention comprises 0.1 to 0.5 mass% of Si, 0.3 to 0.6 mass% of Fe, 0.1 to 0.35 mass% of Cu, 0.5 to 1.2 mass% of Mn, 0.7 to 2.5 mass% of Mg %, And the balance of Al and inevitable impurities, and after DI molding with a proof stress of 200 to 290 MPa after baking at 200 占 폚 for 20 minutes and a processing rate of 60 to 70% 0.2% strength increment when a 90% V bending-bending recovery process was performed at a bending radius of 0.1 mm in the circumferential direction of the can after the 1% stretch was applied to the can above the can of the can which was baked for 20 minutes (Also referred to as work hardenability) is 10 MPa or more.

The aluminum alloy may further contain, if necessary, at least one of Cr: 0.10 mass% or less, Zn: 0.40 mass% or less, and Ti: 0.10 mass% or less.

The aluminum alloy sheet for a can body according to the present invention exhibits excellent DI workability and can wall secondary workability when the can wall is subjected to secondary processing such as embossing or diamond cut after DI processing and baking processing. In addition, the aluminum alloy plate for a can body according to the present invention has a high work hardening ability, and when the can wall subjected to the secondary processing is further subjected to plastic deformation, the can wall is uniformly deformed and local plate thickness reduction ) Is suppressed. Therefore, it is possible to prevent a large amount of local stress from being applied to the can wall, for example, when the can is impacted or when the can is contacted with the can wall, so that breakage of the can wall after filling can be prevented and leakage can be prevented.

Fig. 1 is a conceptual diagram of a test for measuring the reduction rate of the cross-sectional plate thickness after 90 ° V bending-bending recovery processing of the can wall.
2A is a view for explaining a procedure of a pressure resistance test of a can, and is a side view of a can used in a pressure resistance strength test.
Fig. 2B is a view for explaining the procedure of the pressure resistance strength test of the can, and is a side view of a main portion of the pressure resistance tester.
FIG. 2C is a view for explaining the procedure of the pressure resistance strength test of the can, and is a plan view of a main part of the pressure resistance tester. FIG.
Fig. 3A is a view for explaining the procedure of the pressure resistance strength test of the can, and is a side view when the can is fixed to the holder. Fig.
FIG. 3B is a view for explaining the procedure of the pressure resistance strength test of the can, and is a side view when the bottom of the can is buckled by the internal pressure.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an aluminum alloy sheet for a can body according to the present invention and a method for producing the same will be described in detail.

<Composition of Aluminum Alloy>

(Si: 0.1 to 0.5% by mass)

If the Si content is less than 0.1% by mass, the ear becomes 0-180 占 at the time of DI molding, and ear cutting and tail-off due to this are liable to occur at the time of ironing. On the other hand, when the Si content exceeds 0.5% by mass, since the non-recrystallized grains remain in the hot coil, the ear is raised by 45 ° at the time of DI molding, and ear cutting and tail- .

(Fe: 0.3 to 0.6% by mass)

If the Fe content is less than 0.3% by mass, unrecrystallization remains in the hot coil, so that the ear is raised by 45 ° at the time of DI molding, and ear cutting and tail-off due to this are likely to occur at the time of ironing. On the other hand, if the Fe content exceeds 0.6% by mass, the Al-Fe-Mn intermetallic compound increases and tear-off easily occurs during ironing. Further, cracks are likely to occur starting from the intermetallic compound at the time of secondary processing of the can wall.

(Cu: 0.1 to 0.35 mass%)

If the Cu content is less than 0.1 mass%, the strength is insufficient and the strength of the internal pressure of the can is insufficient. On the other hand, if the Cu content exceeds 0.35 mass%, the strength becomes excessive, and the tail-off tends to occur at the time of ironing.

(Mn: 0.5 to 1.2% by mass)

If the Mn content is less than 0.5% by mass, the strength is insufficient and the strength of the internal pressure of the can is insufficient. On the other hand, if the Mn content exceeds 1.2% by mass, the Al-Fe-Mn intermetallic compound increases, and the tail-off tends to occur at the time of ironing. Further, cracks are likely to occur starting from the intermetallic compound at the time of secondary processing of the can wall.

(Mg: 0.7 to 2.5 mass%)

If the Mg content is less than 0.7 mass%, the strength is insufficient, and the strength of the internal pressure of the can is insufficient. Further, the work hardening ability of the aluminum alloy plate is insufficient, and a constricted portion is likely to occur at the time of secondary processing of the can wall. On the other hand, if the Mg content exceeds 2.5 mass%, the strength becomes excessive, and the tail-off tends to occur at the time of ironing.

(Cr: 0.10 mass% or less)

If the content of Cr is 0.10 mass% or less, the material properties of the aluminum alloy plate and the can characteristics after the DI molding are not affected. Cr is an inevitable impurity. However, in order to reduce the cost, for example, Cr may be positively added within the above range by increasing the blending ratio of scrap into the raw material (scrap containing a large amount of Cr). However, when the Cr content exceeds 0.10% by mass, the hot recoil remains in the hot coil, and the ear is raised by 45 ° in the DI molding, and ear cutting and tail-off due to this are likely to occur at the time of ironing. Therefore, the Cr content in the aluminum alloy is limited within the above range. On the other hand, the content of Cr is inevitably 0.050 mass% or less.

(Zn: 0.40 mass% or less)

If the content of Zn is 0.40 mass% or less, the material properties of the aluminum alloy plate and the can characteristics after the DI molding are not affected. Zn is an inevitable impurity. However, in order to reduce the cost, for example, Zn may be positively added within the above range by increasing the blending ratio of scrap into the raw material (scrap of the clad for heat exchanger, etc.). On the other hand, the content of Zn inevitably is usually 0.30 mass% or less.

(Ti: 0.10 mass% or less)

Ti is added as necessary for the purpose of miniaturization of the ingot crystal grains. When the ingot texture is refined at the time of casting, the casting is improved and high-speed casting becomes possible. The effect is obtained by adding 0.01% by mass or more. On the other hand, when Ti is added in an amount exceeding 0.10 mass%, clogging of the filter is accelerated, and the molten metal gradually passes through the filter during casting, and casting must be stopped in the end. Therefore, the Ti content in the aluminum alloy is limited within the above range. On the other hand, when Ti is added, since the ingot finishing agent (Al-Ti-B) having a mass ratio of Ti and B of 5: 1 is added to the molten metal before casting in the form of waffles or rods, B is inevitably added. On the other hand, the content of Ti is inevitably 0.050 mass% or less.

(Other inevitable impurities)

, 0.1% or less, preferably 0.05% or less, and in total 0.30% or less, preferably 0.15% or less, of the inevitable impurities (V, Na, Zr, Ni, It does not hinder the effect of On the other hand, with respect to these elements, if the content is not exceeded, not only the case of being contained as an inevitable impurity but also the effect of the present invention can be obtained even when the content is intentionally added such as intentionally increasing the compounding ratio of scrap containing these elements Do not interfere.

<Characteristics of aluminum alloy plate>

(Strength after baking: 240 to 290 MPa)

If the tensile strength of the aluminum alloy sheet after baking at 200 占 폚 for 20 minutes is less than 240 MPa, the strength is insufficient and the strength of the internal pressure of the can after DI molding and baking is insufficient. On the other hand, if the proof strength of the aluminum alloy sheet after baking exceeds 290 MPa, the strength is excessively excessive, and the tail-off occurs frequently during the ironing process, thereby deteriorating the productivity. On the other hand, the strength after baking is interlocked with the strength before baking, and the strength of the aluminum alloy sheet after baking is high before baking (ironing).

(Work hardenability: 10 MPa or more)

In the present invention, after DI molding with a processing rate of the can wall of 60 to 70%, a further 1% (permanent deformation) stretch is applied to the can wall of the can which is baked at 200 占 폚 for 20 minutes, , And the increment of the 0.2% proof stress when the 90 ° V bending-bending recovery process is performed at a bending radius of 0.1 mm is defined as the work hardening ability. On the other hand, the processing rate of 60 to 70% by DI molding is a standard processing rate in DI molding of can.

When the 0.2% proof stress of the can wall after the DI forming and baking is σ ₁ , and the 0.2% proof stress of the can wall after the stretch and V bending-bending restoration is σ ₂ , the work hardening ability is represented by σ ₂ -σ ₁ . When the work hardening ability ( _{2 -} ? ₁ ) is 10 MPa or more, the can wall is uniformly deformed by the secondary working and subsequent plastic deformation, and the local plate thickness reduction of the can wall is suppressed. On the other hand, when the work hardening ability is less than 10 MPa, the can wall is difficult to be uniformly deformed by secondary processing and subsequent plastic deformation, and the can wall is locally reduced in plate thickness, and a constricted portion is apt to occur. Therefore, an excessive stress is applied to a thinned portion such as when the can is impacted or when the can is contacted with the can wall, and the can wall is broken, so that leakage of the contents tends to occur.

&Lt; Production method of aluminum alloy plate >

The aluminum alloy sheet according to the present invention can be produced by respective steps of casting, homogenizing heat treatment, hot rolling, and cold rolling. Intermediate annealing after hot rolling and finish annealing after cold rolling are not performed. The method of producing an aluminum alloy sheet according to the present invention is characterized in that cold rolling is performed under a predetermined condition.

Hereinafter, each step will be described.

First, an aluminum alloy may be cast by a known semi-continuous casting method such as a direct-chill (direct-chill) casting method.

Next, after the area of the uneven texture of the surface layer of the ingot is removed by sawing, a homogenizing heat treatment is performed based on a conventional method. In this case, a two-step homogenization heat treatment or a two-times homogenization heat treatment may be employed. Here, the two-step homogenization heat treatment refers to a process in which the ingot is maintained at a high temperature for a predetermined time (first-stage homogenization heat treatment), and then the cooling is stopped at a temperature exceeding 200 캜 without cooling to room temperature, Second-stage homogenization heat treatment). The homogenization heat treatment twice is a process in which the ingot is maintained at a high temperature for a predetermined time (first homogenization heat treatment), then cooled to a temperature of 200 DEG C or lower including the room temperature, reheated and maintained at a predetermined homogenization treatment temperature for a predetermined time (Second homogenization heat treatment).

After the homogenization heat treatment, the temperature of the ingot is not cooled to less than 450 캜, but the hot rolling is continued, and the hot rolling is preferably finished at 300 캜 or higher. In the case where the two-step homogenization heat treatment is performed, after the second-stage homogenization heat treatment, if necessary, it is heated to a higher temperature and then hot-rolled. The produced hot rolled material becomes a recrystallized structure.

Subsequent cold rolling is done with a tandem mill. By performing cold rolling with a tandem rolling mill, the rolling rate in a single transfer plate can be increased. As a result, the machining heat generation is increased, and the dynamic recovery of the cold rolled steel sheet and the recovery after winding are promoted. As a result, the work hardening ability of the can wall is improved in the can which the cold rolled steel material (the aluminum alloy sheet according to the present invention) is subjected to DI molding and baking.

The total rolling rate of cold rolling is 80 to 90%. This rolling rate is achieved with a single pass through the tandem mill. If the total rolling ratio in the cold rolling is less than 80%, the strength of the aluminum alloy sheet is insufficient and the strength of the internal pressure of the can after the DI forming and baking is insufficient. On the other hand, if the total rolling ratio exceeds 90%, the strength becomes excessive, and the 45-degree ear is increased, and it is likely to cause ear cutting and tail-off caused by the ear cutting at the time of ironing.

The coiling temperature after cold rolling is set in the range of 120 to 180 캜. By bringing the coiling temperature within the above temperature range, the dynamic recovery of the aluminum alloy plate (cold rolled steel sheet) and the recovery after winding are promoted, and the work hardening ability of the can wall at the time of final can is improved.

If the coiling temperature is less than 120 캜, the effect of recovery is insufficient, the work hardening ability of the can wall is insufficient, and it is difficult for uniform deformation due to secondary processing and subsequent plastic deformation, and the can wall locally decreases in plate thickness, easy. The lower limit of the coiling temperature is preferably 150 占 폚.

If the coiling temperature exceeds 180 캜, the softening of the aluminum alloy sheet due to the heat generated by machining becomes large, and plate cutting tends to occur during rolling. As a result, the productivity of the aluminum alloy sheet is greatly reduced, which is not preferable for practical use.

Coil after winding is kept at a temperature of 120 ° C or more for 4 hours or more. As a result, the recovery of the aluminum alloy plate (cold rolled steel sheet) is promoted, and the work hardening ability of the can wall in the can after DI forming and baking is improved. On the other hand, if the holding time at the temperature of 120 占 폚 or more is less than 4 hours, recovery of the aluminum alloy plate (cold rolled steel sheet) is insufficient and does not contribute to improvement of work hardening ability of the can wall.

Example

Hereinafter, examples in which the effects of the present invention are confirmed will be specifically described in comparison with comparative examples which do not satisfy the requirements of the present invention. On the other hand, the present invention is not limited to this embodiment.

An aluminum alloy having the composition shown in Tables 1 and 2 was melted and an ingot having a thickness of 600 mm was produced by using a semi-continuous casting method (except No. 12 in the comparative example). The surface layer of the ingot was ground and subjected to a homogenizing heat treatment, followed by hot rolling. Thereafter, cold rolling (tandem rolling mill or single rolling mill) was performed on the hot rolled material without intermediate annealing, and an aluminum alloy sheet having a thickness of 0.30 mm was formed and wound. Finish annealing after cold rolling was not performed (except No. 20 in the comparative example). On the other hand, 12 could not be cast due to clogging of the filter.

Tables 1 and 2 describe the type of rolling mill used in cold rolling, the total rolling rate of cold rolling, the coiling temperature after cold rolling, the time when the coils after winding were maintained at 120 DEG C or more, the presence or absence of finishing annealing after cold rolling, .

The produced Example No. 1 was obtained. 1 to 19 and Comparative Example No. 1. 1 to 11 and 13 to 20 aluminum alloy plates were used as test materials, and the post-baking strength was measured in the following manner.

Subsequently, 1 to 19 and Comparative Example No. 1. 1 to 11 and 13 to 20 aluminum alloy plates were used to prepare DI cans. As a manufacturing method, first, a blank having a diameter of 140 mm was punched out from an aluminum alloy plate, and this blank was formed by drawing to produce a cup having a diameter of 90 mm. The resulting cup was subjected to DI molding with a general-purpose aluminum can body molding machine (consisting of four steps of redrawing, one new ironing, two new ironing and three new ironing) to prepare a DI can. On the other hand, the third ironing processing rate was 40%. This ironing processing rate is a stricter condition than the general annealing processing rate of 35 to 38%.

Fig. 1 (a) shows a side view of the manufactured can (after trimming the opening). The outer diameter of the can was 66.3 mm, the height was 124 mm, the width of the bottom of the canvas was the largest (60 mm from the can bottom), and the processing rate of the copper was 68.3% (original thickness: 0.3 mm).

10000 cans of each of the examples and comparative examples were continuously molded by the above-mentioned aluminum can body molding machine, and the ironing processability was evaluated by the following procedure. Subsequently, using the formed can, the work hardening ability of the can wall, the reduction rate of the cross-sectional plate thickness after 90 ° V bending-bending restoration of the can wall, and the pressure resistance strength were measured in the following manner. Table 3 shows the above results.

(Strength after baking of aluminum alloy plate)

The test piece (aluminum alloy plate) was baked at 200 占 폚 for 20 minutes and then JIS No. 5 test pieces were taken in the rolling parallel direction and subjected to a tensile test in accordance with JIS Z 2241 (revised in 2011) 0.2% proof stress was measured. When the 0.2% proof stress was within the range of 240 to 290 MPa, it was evaluated as acceptable.

(Ironing processability)

Of the 10000 cans that were continuously molded, those that had problems such as tear-off were 3 cans or less and those that were 4 cans or more were judged to be unacceptable (x).

(Work hardening ability of can wall)

After baking at 200 DEG C for 20 minutes, the prepared can was subjected to baking along the circumference of the can so that the height of 60 mm from the bottom of the can becomes the center of the width direction and the 0 DEG direction of rolling becomes the center of the length direction. 13 No. B test piece (first test piece) was collected.

After baking at 200 占 폚 for 20 minutes, the produced can was subjected to baking at 200 占 폚 for 20 minutes so that the height of 60 mm from the bottom of the can becomes the center in the width direction and the 0 占 direction of rolling is the center in the longitudinal direction. Therefore, a test piece of a desk having a width of 20 mm and a length of 100 mm was cut out (see Fig. 1 (a)). The test piece of the desk was subjected to a 90 ° V bending process using a jig having a bend radius R of 0.1 mm at the tip after applying a 1% stretch with a tensile tester (see Fig. 1 (b)) 1 (c)). Then, bending recovery processing was performed in the opposite direction (see Fig. 1 (d)). JIS No. 13 B test piece (second test piece) was taken from the test piece of the desk. The V-bending-bending recovery part was positioned in the longitudinal center of this JIS 13 B test piece.

On the other hand, the first test piece and the second test piece are different from each other in that the former is not subjected to a 1% stretch and V-bend-bending recovery process, and the latter is subjected to their processing.

Subsequently, the first and second test pieces were subjected to a tensile test in accordance with JIS Z 2241 (revised in 2011), and their 0.2% proof stresses were determined. The original plate thickness of the second test piece was regarded as 95 탆 as in the first test piece. When the 0.2% proof stress of the first test piece is σ ₁ and the 0.2% proof stress of the second test piece is σ ₂ , the difference (σ ₂ -σ ₁ ) between the _two is 0.2% of the post-bending stress- The increment was defined as the work hardening ability of the can wall. It was evaluated that the work hardenability (σ ₂ -σ ₁ ) of 10 MPa or more was acceptable. As described above, if the work hardening ability of the can wall is high, the can wall is uniformly deformed during the secondary processing and subsequent plastic deformation, and the local plate thickness reduction (formation of the constricted portion) of the can wall is suppressed, It is possible to prevent a large amount of local stress from being applied to the can wall, such as when it is received or when foreign matter comes into contact with the can wall.

On the other hand, the stretch giving a permanent deformation of 1%, which is performed in this measurement test, simulates the secondary processing (embossing processing or diamond cutting processing) performed on the can wall. However, the permanent deformation of 1% is larger than the permanent deformation applied to the can wall due to the processing of the actual diamond cut pattern, and this stretch can be said to be a fairly strict process as compared with the actual embossing process or diamond cut pattern process. In addition, the V-bending-bending recovery process simulates plastic deformation that is accidentally applied to the can in a manufacturing step including charging of contents, a distribution step after filling, and a step over to the consumer. This V-bending-bending recovery process can be said to be conditionally stricter than the evaluation method (bending radius of 1 mm) of Patent Document 1 in that the bending radius is extremely small at 0.1 mm.

(Reduction rate of sheet thickness after 90 ° V bending-bending recovery of can wall)

The prepared can was subjected to baking at 200 ° C for 20 minutes and then the height of 60 mm from the bottom of the can was set as the center in the width direction and the width in the circumferential direction of the can A 20 mm x 100 mm long step test specimen was cut out (see Fig. 1 (a)). (See Fig. 1 (b)) was subjected to a 90 ° V bending process using a jig having a bending radius R of 0.1 mm at the tip, (See Fig. 1 (c)), and then bending recovery processing was performed in the opposite direction (see Fig. 1 (d)). 1 (e)), a bending-bending recovery portion (a portion surrounded by a dashed line in Fig. 1 (e)) at the center in the width direction of the test piece was fabricated, Was observed to measure the plate thickness reduction rate relative to the original plate thickness (95 mu m). And the case where the reduction rate of the section plate thickness is 5% or less was evaluated as acceptable.

(Withstand pressure strength of cans)

The internal pressure was applied to the baked can by using a hydrostatic pressure tester (a hydraulic pressure increasing / decreasing pressure buckling test apparatus, type name: WBT-500, manufactured by Ace Tech Co., Ltd.) Pressure strength.

2A to 2C, the internal pressure tester includes a base plate 2 provided on a base 1, a cylindrical holder 3 provided on the base plate 2, And a pair of fixing members 4, 4 arranged. An O-ring 5 is provided at an intermediate position in the height direction of the holder 2. The rubber tube 6 is provided inside the holder 2 and the rubber tube 6 extends downward through the base plate 2 and is connected to the water pipe so as to interpose the water pressure meter, And communicated with the water pressure pump (all not shown). A hole 7 is formed in the base plate 2 and the hole 7 is connected to the ventilation duct so as to communicate with the vacuum pump through a switching valve or the like (all not shown). The fixing members 4 and 4 are advanced and retracted by hydraulic cylinders, not shown, respectively.

The withstand pressure test is performed as follows.

(1) As shown in Figs. 2A to 2C, a can 8 having a height of 100 mm by trimming an opening portion is inserted into the holder 3 with the bottom of the can placed upright, and then the fixing members 4, . The front ends of the fixing members 4 and 4 press the can walls of the can 8 from both sides at slightly lower positions of the O-ring 5 when the fixing members 4 and 4 reach a predetermined position , The can 8 is fixed to the holder 3. Thus, the inner surface of the can 8 of the can 8 is brought into close contact with the periphery of the O-ring 5 and the inside of the holder 3 (inside the can 8) except for the location of the rubber tube 6 and the hole 7, Is sealed.

(2) The vacuum pump is operated to evacuate the inside of the holder 3 (in the can 8) through the hole 7 to 9.8 kPa (0.1 kgf / cm ² ) or less, and then the ventilation channel is closed.

(3) The water pressure pump is operated to supply water from the rubber tube 6 to the holder 3 (in the can 8). The water pressure (measured by the hydraulic pressure meter) in the holder 3 (in the can 8) rises almost in proportion to the elapsed time from the start of the supply and decreases at the moment when buckling of the can bottom occurs. The maximum internal pressure when buckling of the can bottom occurred was taken as the internal pressure strength of the can. The state when the buckling of the can bottom occurred is shown in Fig. 3B.

When the internal pressure strength was 618 kPa or more (6.3 kgf / cm ² or more), it was evaluated as acceptable.

As shown in Tables 1 and 3, the composition of the aluminum alloy plate, the strength of the aluminum alloy plate after baking, and the work hardenability of the can wall are within the range specified in the present invention. 1 to 19 are excellent in ironing workability and have a small reduction rate of the cross-sectional plate thickness of the can wall after the stretch and V-bending-bending recovery processing, and have a high withstand pressure strength. The fact that the above-mentioned section reduction rate is small means that the can wall is not reduced in the plate thickness locally (occurrence of the constricted portion is suppressed), which means that the can wall is uniformly deformed by the stretch and V bending-bending recovery processing. Example No. 2. All of 1 to 19 were subjected to cold rolling within the range of the conditions described above.

On the other hand, as shown in Tables 2 and 3, when the composition of the aluminum alloy plate, the strength of the aluminum alloy plate after baking, and the work hardening ability of the can wall were outside the specified range of the present invention, 1 to 11 and 13 to 20 do not satisfy the criteria of the present invention, either of the ironing processability, the cross-sectional plate thickness reduction rate of the can wall, and the pressure resistance strength.

Comparative Example No. 1 1 and 2 are inferior in the ironing processability because the Si content is outside the specified range of the present invention. Comparative Example No. 1 3, and 4, iron content falls outside the specified range of the present invention, resulting in poor ironing processability. Comparative Example No. 1 5, 7, and 9 have insufficient Cu, Mn, and Mg contents, respectively, the strength of the aluminum alloy plate after baking is insufficient and the strength of the internal pressure of the can is inferior. Comparative Example No. 1 6, and 10 have an excessive Cu and Mg content, respectively, so that the strength of the aluminum alloy sheet after baking is excessive, and the ironing workability is poor. Comparative Example No. 1 8, and 11 have excessive Mn and Cr contents, respectively, so that the ironing processability is poor. On the other hand, 12 had excessive Ti content, so that casting could not be carried out as described above.

Comparative Example No. 1 13, since the total rolling ratio of the cold rolling was insufficient, the strength of the aluminum alloy plate after baking was insufficient and the strength of the pressure resistance was poor. Comparative Example No. 1 14, the total rolling ratio is excessive, so that the proof stress of the aluminum alloy sheet is excessive, and the ironing workability is poor. Comparative Example No. 1 15 has a low coiling temperature, and the dynamic recovery and recovery after winding are insufficient, the work hardening ability of the can wall is low, and the reduction rate of the cross sectional plate thickness of the can wall is large.

Comparative Example No. 1 16 shows that the holding time at the temperature of 120 DEG C or more of the coil after being wound is insufficient and the recovery after winding is insufficient and the work hardening ability of the can wall is not improved and the cutting rate of the cross section of the can wall is large. Comparative Example No. 1 17, and 19, cold rolling was carried out with a single rolling mill. Therefore, the coiling temperature was low, the dynamic recovery and the recovery after winding were insufficient, the strength of the aluminum alloy sheet was excessive, and ironing workability was poor. In addition, 17 and 19, the work hardening ability of the can wall is low, and the reduction rate of the cross-sectional plate thickness of the can wall is large. On the other hand, 17 is based on the composition of the alloy e5 of the example of Patent Document 1. [ No. 18 is cold rolled by a single rolling mill, the coiling temperature is low, the dynamic recovery and the recovery after winding are insufficient, the work hardening ability of the can wall is low, and the reduction rate of the cross sectional plate thickness of the can wall is large. No. Since the coiling temperature is low due to cold rolling performed by a single rolling mill, the dynamic recovery and the recovery after winding are insufficient, the effect of finish annealing is small, the work hardening ability of the can wall is low, and the reduction rate of the cross-

This application is a continuation-in-part of Japanese Patent Application No. 2014-184681 filed on Sep. 10, 2014, which is incorporated herein by reference, and Japanese Patent Application No. 2014-184681, which is incorporated herein by reference.

Claims (2)

Wherein the alloy contains 0.1 to 0.5% by mass of Si, 0.3 to 0.6% by mass of Fe, 0.1 to 0.35% by mass of Cu, 0.5 to 1.2% by mass of Mn and 0.7 to 2.5% by mass of Mg, the balance being Al and inevitable impurities , And the can was subjected to baking at 200 占 폚 for 20 minutes after DI molding with a proof stress of 240 to 290 MPa after baking at 200 占 폚 for 20 minutes and a processing rate of 60 to 70% Wherein an increment of a 0.2% proof stress when subjected to a 90 DEG V bending-bending recovery process at a bending radius of 0.1 mm in a circumferential direction of the can after applying 1% of a stretch is 10 MPa or more. The method according to claim 1,
0.10 mass% or less of Cr, 0.40 mass% or less of Zn, and 0.10 mass% or less of Ti.

Images