JPH046456B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD This invention relates to a method for manufacturing cans made of aluminum alloy, and more particularly to a method for manufacturing a flanged can body of a so-called three-piece can in which the joints of can bodies are bonded or welded. Conventional technology Conventionally, cans made of aluminum alloy generally include:
Many so-called two-piece cans are manufactured using the DI method, which combines deep drawing and ironing. however
When manufacturing cans using the DI method, ironing often becomes difficult if the can body is made thicker, and if the can body is made thicker, the can bottom becomes thicker than necessary, making it uneconomical. For this reason, cans manufactured using the DI method are limited to those with thin can bodies. Therefore, the two-piece can using the DI method is
Although it is widely used in applications where internal pressure is applied, such as beer and other carbonated beverages, in applications where internal pressure is not applied, such as coffee beverage cans, non-carbonated beverage cans, and food cans, the wall thickness of the can body is too thin, resulting in poor strength. It is considered inappropriate on the surface. Therefore, for applications where no internal pressure is applied, it may be possible to use a so-called three-piece can in which not only the can lid but also the can bottom and can body are processed separately. 3
Piece cans allow the thickness of the can bottom and can body to be changed individually, and are relatively easy to process. By the way, as a method for manufacturing the can body of a three-piece aluminum alloy can, it has been considered that a thin aluminum alloy plate as a material is formed into a cylindrical shape by roll forming, and the opposing sides are joined by welding or adhesive. There is. In this case, since three-piece cans generally have a relatively thin plate thickness of 0.1 to 0.3 mm, they are formed into a cylindrical shape by roll forming, etc. as described above, and their opposing sides are overlapped and joined as a lap joint or pine room joint. It is normal to do so. After the overlapping parts are joined in this manner, flanges for attaching a can lid are formed at both open ends thereof. The flange forming process includes a roll forming method in which the open end is pressed against a roll and the can is rotated or a roll is rotated in the circumferential direction of the can, and a die method in which the open end of the can is pressed against a die. Problems to be Solved by the Invention As mentioned above, when the body of a three-piece aluminum alloy can is manufactured by joining, the joint is usually a lap joint or a pine seam joint. As shown in the figure, the joint 2 of the can body 1 has a step d equal to or slightly smaller than the thickness of the plate. On the other hand, when attaching the can lid and can body to the can body after joining, it is normal to apply seaming, so after joining as described above, the upper and lower open ends are fixed as shown in Figure 5. Section 3 is flange-processed. In this flange processing, cracks may occur in the joint 2 due to the step d of the joint 2 as described above. That is, when flanging a cylindrical can body, not only tensile-compressive stress in the plate thickness direction but also tensile stress in the circumferential direction occurs, and especially in the joint 2 described above, as shown in FIG. A portion 23 in contact with the ends 21 and 22 of the plate superimposed on the
Stress concentration occurs at 24, and cracks may occur in those portions 23 and 24. As a general method for preventing flange cracking during flanging of the can body of a three-piece can, as already shown in Japanese Patent Application Laid-Open No. 52-58062, the portion of the can body that should become the open end (flange A method has been proposed in which the entire can body is heated and softened in the form of a band before forming and joining the can body. However, this proposed method does not specifically focus on the level difference at the joint, but is generally aimed at preventing flange processing cracks.
Since the entire portion of the can body that is supposed to be the open end is heated, the heat input tends to be large, and because aluminum alloy has good heat conduction, it is possible to heat only the portion where flange cracks are likely to occur. First, there is the problem that other parts of the can tend to soften, resulting in insufficient strength as a can. To avoid this, it may be possible to apply forced cooling to areas other than the necessary parts, but in that case, new problems such as complicating the equipment and impairing workability will arise. On the other hand, in the production of can bodies for two-piece aluminum alloy cans, a method for heating and softening the entire open end of the can body after DI processing is disclosed in Japanese Patent Application Laid-Open No. 53-71338 to prevent flange cracking. However, when this method is applied to the manufacture of the body of a three-piece can, the same problems as the method of JP-A-52-58062 may occur. It was hot. This invention was made against the background of the above-mentioned circumstances, and focused on the fact that flange processing cracks are likely to occur at the joint part in the manufacture of jointed can bodies, and developed a simple method that does not reduce the strength of the can body. It is an object of the present invention to provide a method for manufacturing a joined can body made of an aluminum alloy, which prevents flange processing cracks from occurring. Means for Solving the Problems In order to achieve the above-mentioned object, the inventors of the present invention have carried out extensive experiments and studies, and have determined that the elongation of the aluminum alloy thin plate is within a predetermined range, and that the material is lap-bonded. The above objective is achieved by locally heating and softening only the required areas before or after joining the joint so that the required elongation according to the size of the step formed in the part can be secured during flange processing. They discovered that it could be done and came up with this invention. That is, the method of the first invention involves bending a rectangular aluminum alloy thin plate into a cylindrical shape and forming two opposing
After overlapping the sides and joining the overlapped parts, flanging is performed on both open ends to produce a flanged joint can body made of aluminum alloy.
~20%, and is characterized by locally heating and softening the four corners of the aluminum alloy thin plate so as to satisfy the following formula before joining the overlapping parts: . El/d≧80 (%/mm) However, El: Elongation of the heated part after heating (%) d: Difference in thickness of lap joint (mm) In addition, the method of the second invention uses a rectangular aluminum alloy thin plate. When manufacturing a flanged joint can body made of aluminum alloy by bending it into a cylindrical shape, overlapping two opposing sides, joining the overlapping parts, and then flanging both open ends, the material aluminum The elongation is 5 as an alloy thin plate.
~20%, and after joining the overlapped parts, both ends of the overlapped joint are locally heated and softened so as to satisfy the above formula, and then flanged. This is a characteristic feature. Effect As shown in FIG. 1, the method of the first invention locally applies only the four corner portions 5a, 5b, 5c, and 5d of the rectangular aluminum alloy thin plate 5, which is the raw material, from the front side or the back side at the stage before joining. is subjected to heat softening treatment. Thereafter, it is curved into a cylindrical shape by roll forming or the like, and the opposing sides are overlapped and joined to obtain the joined can body 1. In the state after joining, the portions 5a to 5d that have been heat-softened as described above are located at both ends 2a and 2b of the lap joint portion 2, and these portions are in the same position as the portion to be subjected to subsequent flange processing. corresponds to a part. Therefore, in the case of the method of the first invention, heating and softening the four corners 5a to 5d of the rectangular aluminum alloy thin plates at the stage before joining means that the parts that are to become both ends of the lap joint 2, in other words, This means that of the entire circumference of both open ends of the can body to be flanged, only the part that is to become the joint part is subjected to heat softening treatment. As already mentioned, in the case of a joined can body, cracking during flanging is particularly likely to occur at the overlapped joint of the entire circumference of both open ends where flanging is applied. Flange processing cracks can be prevented by preheating and softening the part, especially the part that will become the lap joint. On the other hand, in the method of the second invention, as shown in FIG. 2, at the stage after the overlap joint, heat softening treatment is performed locally only on both end portions 2a and 2b of the overlap joint 2 of the can body 1 on the surface side in the axial direction of the can. Or apply from the back side. Both end portions 2a and 2b of the lap joint 2 each occupy a part of both open ends of the can body 1 to which flanging is to be performed, as described above, and among the open ends, the flanging cracks are the least likely to occur. Since this is a part where cracks are likely to occur, flange processing cracks can be effectively prevented as in the case of the method of the first invention. As mentioned above, in both the methods of the first invention and the second invention, the entire part to be flanged is not heated, but the part to be flanged is particularly prone to cracking due to flange processing. Since only the lap joint (or the equivalent part) is locally heated, less heat is required, and there is less risk of reducing the strength of areas other than those that require heating and softening. A simple method is sufficient. If the elongation of the aluminum alloy thin plate used as the material is less than 5%, the ductility of the base plate is too low.
Flange processing cracks are more likely to occur in areas that are not subjected to heat softening treatment, that is, areas other than lap joints, while 20%
For materials with an elongation exceeding The strength of the board is also low, making it impractical. Therefore, the elongation of the aluminum alloy sheet used as the material is 5 to 20%.
Must be less than or equal to The composition of the aluminum alloy is not particularly limited, and it has traditionally been used for cans.
3000 series alloys (Al-Mn alloys) such as 3004 alloys,
Or 5000 series alloys such as 5182 alloy (Al-Mg
alloys), etc. can be used. In addition, specific joining methods for joining the overlapping parts after forming rectangular aluminum alloy thin plates into a cylindrical shape include bonding using an adhesive, ultrasonic welding, electric resistance seam welding, or electric resistance pine seam welding. is applicable and is not particularly limited. However, in the case of bonding, if heat softening treatment is performed after bonding, there is a risk that the adhesive will melt or deteriorate. It is preferable to apply it. On the other hand, in the case of welding, heat softening treatment may be performed either before joining (first invention) or after joining (second invention), but if there is a risk of hardening during welding, heat softening treatment may be performed after joining (after welding). It is preferable to perform treatment. As a specific heating means for the heat softening treatment, any means such as gas burner, laser, high frequency induction heating, etc. may be used, and either method requires spot-like local heating, so it is extremely easy to carry out. However, from a cost standpoint, it is preferable to use simple and inexpensive burner heating. The degree of heat-softening treatment must be determined so that the elongation El (%) of the heat-treated part after heating and the step d (mm) of the overlapped joint satisfy El/d≧80 (%/mm). . That is, the heat softening treatment is performed so as to obtain an elongation El corresponding to the step difference d of the lap joint. Such a conditional expression was derived through experiments by the inventors, and
If the above conditional expression is not satisfied, flange processing cracks are likely to occur at the lap joint, and only when the above conditional expression is satisfied can the effect of preventing flange cracking be obtained. In this way, the jointed can body obtained by locally applying heat softening treatment to predetermined areas before or after joining effectively prevents flange cracking during flange processing, and also reduces strength. There are also few. Examples Example 1 As a test material, H38, a JIS A 5182 alloy, was treated with phosphochromic acid (metallic chromium amount: 20 mg/m ² ).
Thickness made of H18 material and JIS A 3004 alloy
Two types of aluminum alloy thin plates of 0.23 mm, width 200 mm, and length 130 mm were prepared, and the four corners of each thin plate were subjected to heat softening treatment from the front side using an oxygen-acetylene burner under various conditions shown in Table 1. After that, each thin plate is formed into a cylindrical shape by roll forming, and both sides are coated with a primer.
A polyamide adhesive was placed between the overlapping edge parts, and then the adhesive was melted, and the adhesive was cooled and solidified under pressure to obtain a can body. Both open ends of the can body thus obtained were flanged using a roll flange, and the flanging properties were examined. The results are also shown in Table 1. In addition, test pieces were cut from both open ends of the can body manufactured under the same conditions as the can body manufactured as described above, and a local elongation test was conducted at the overlap joint. (%) and
The level difference d (mm) was examined and the value of El/d was determined. The results are also shown in Table 1. As a comparison material, Table 1 also shows the case where a thin plate of JIS A 3003 alloy H19 material whose elongation of the original plate was less than 5% was used. Example 2 JIS A 5052 alloy H38 material (elongation 8
A thin aluminum alloy plate with a thickness of 0.3 mm, a width of 200 mm, and a length of 130 mm is prepared, and after roll-forming it into a cylindrical shape, the overlapping portion is welded using an ultrasonic welder with an output of 1200 W. Ultrasonic seam welding was performed under the conditions shown in Table 2 to obtain a can body. Both ends of the welded portion of this can body were locally heated from the front side using an oxygen-acetylene burner under various conditions shown in Table 2. After that, both open ends of this can body are flanged with a roll flange,
Flange crackability was investigated. The results are shown in Table 2. In addition, test pieces were cut from both open ends of a can body (after local heating) produced under the same conditions as the can body produced as described above, and a local elongation test was performed on the overlap joint. Elongation El (%) of step part)
At the same time, the step difference d (mm) was also investigated, and the value of El/d was determined. The results are also shown in Table 2.

【table】

[Table] As is clear from Tables 1 and 2, when local heating treatment is performed before joining and joining with adhesive (Example 1), and after joining by ultrasonic seam welding, local In both cases where heat treatment was performed (Example 2), the value of El/d was
It was found that when local heating was performed to achieve a heating rate of 80%/mm or more, flange cracking did not occur and the flange formability was excellent. On the other hand, even if local heat treatment is performed, the heating time is insufficient and the value of El/d decreases.
In both the comparative example where the heat treatment was less than 80%/mm and the comparative example where local heat treatment was not performed, flange cracking occurred at the stepped portion of the lap joint. In Table 1 of Example 1, the comparative example using 3003 alloy H19 material is an example in which the elongation of the original plate was less than 5%, but in this case, flange cracking occurred in the base material other than the lap joint. It was. From this, it can be seen that in the case of the method of this invention, the condition that the elongation of the base plate is 5% or more is required. Effects of the Invention According to the method for manufacturing a bonded can body made of aluminum alloy of the present invention, it is possible not only to obtain a bonded can body that is resistant to flange cracking during flange processing but also has excellent resistance to flange cracking. Because the softening treatment only needs to be performed spot-on to a limited number of local areas, the process is simple and workability is good, and an inexpensive and simple gas burner can be used as a heating source. Therefore, there is no risk that the strength of the entire can body will decrease, and cooling around the heating part is not required, so there is no risk of increasing equipment costs for cooling or reducing work efficiency. Therefore, according to the method of the present invention, a joined can body with excellent flange resistance can be obtained simply and easily without causing a decrease in strength.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the parts to be heat-softened in the method of the first invention, FIG. 2 is an explanatory diagram to show the parts to be heat-softened in the method of the second invention, and FIG. 3 is a general diagram. FIG. 4 is a cross-sectional view showing an enlarged overlap joint of the can body in FIG. 3, and FIG. 5 is a vertical cross-sectional view showing the flanged can body. . 1... Can body, 2... Overlap joint, 2a, 2b
. . . Both end portions of the lap joint, 5 . . . Aluminum alloy thin plate, 5a to 5d . . . Four corner portions of the aluminum alloy thin plate.

Claims (1)

[Claims] 1. A rectangular aluminum alloy thin plate is curved into a cylindrical shape, two opposing sides are overlapped, and after the overlapping parts are joined, flanges are formed on both open ends to create an aluminum alloy product. In manufacturing the flanged joint can body, the material is an aluminum alloy thin plate with an elongation of 5 to 20.
%, and before joining the overlapping parts, the four corners of the aluminum alloy thin plate are locally heated and softened so as to satisfy the following formula. A method for manufacturing a jointed can body. El/d≧80 (%/mm) However, El: Elongation of heated part after heating (%) d: Thickness difference in lap joint (mm) 2 A rectangular aluminum alloy thin plate is curved into a cylindrical shape. When producing a flanged joint can body made of aluminum alloy by overlapping two opposing sides and joining the overlapping parts, flanging is performed on both open ends, the elongation of the raw aluminum alloy thin plate is 5 to 5.
20%, and after joining the overlapped parts, locally heat soften the ends of the overlapped parts so as to satisfy the following formula, and then perform flange forming. A method for manufacturing a flanged aluminum alloy jointed can body. El/d≧80 (%/mm) However, El: Elongation of heated part after heating (%) d: Difference in thickness of lap joint (mm)