JPH07232230A - Method for manufacturing thin-walled DI can - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a method for manufacturing a container that enables the weight of the bottom of a DI can to be reduced without impairing the pressure resistance and enabling weight reduction. A method for producing a thin-walled DI can, characterized in that, when a DI can is produced, an overhanging process with a plate thickness reduction of 15% or more and 50% or less is performed on a portion of the can bottom before the second drawing. [Effect] The thickness of the DI can (in particular, the thickness of the bottom of the can) can be reduced without impairing the pressure resistance, which can contribute to resource saving of the container.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a squeezed / ironed can, which is generally called a DI can, which is used as a container for selling beverages and the like.

[0002]

2. Description of the Related Art A method of manufacturing a DI can is as follows.
And a redrawing (hereinafter referred to as a second drawing) to form a cylindrical cup having a drawing ratio of about 2, and subsequently, several side walls of the cup are installed in series with the punch without changing the diameter of the cup. It is a method of making a can by squeezing between ironing dies (that is, performing ironing processing) to reduce the wall thickness and make the height of the can high, for example, Journal of Japan Society of Mechanical Engineers, Vol. 84, No. 74.
No. 8, pages 256-260, it is already well known, and USP128
With 13 as the basic patent, various innovations have been made. For example, in JP-A-3-27828 and JP-A-3-71938, the formation of wrinkles during molding is prevented and the pressure resistance is improved by devising the shape of the can bottom.

[0003]

In the case of a DI can, the side wall portion of the can is squeezed and thinned, but the can bottom portion is slightly overhanged (the plate thickness reduction of the portion corresponding to the can bottom is 3% or less. ) Is applied, the thickness of the original plate remains almost unchanged. At present, the plate thickness is about 0.08 mm at the side wall, but 0.22 mm at the bottom of the can.
It is 0.25 mm. Even if the thickness of the DI can is reduced in order to reduce the weight of the DI can, the thickness of the side wall has reached a limit where it cannot be further reduced. Therefore, it suffices to reduce the thickness of the bottom of the can, but if the thickness of the original plate is reduced, the pressure resistance of the bottom of the can will be insufficient, and the function as a can will not be sufficiently obtained. In Japanese Patent Laid-Open No. 3-71938, it is possible to improve the pressure resistance by devising the shape of the can bottom, but this is not a technology that satisfies the weight reduction of DI cans. The present invention solves this problem and provides a manufacturing method that satisfies the contradictory characteristics of reducing the weight of a DI can (reducing the thickness of the bottom of the can) and improving the pressure resistance.

[0004]

The present invention has been made to solve the above problems, and the gist thereof is D
In the production of the I can, there is provided a method for producing a thin-walled DI can, which is characterized by subjecting the bottom of the can to overhanging with a thickness reduction of 15% or more and 50% or less before the second drawing.

The feature of the present invention resides in that the portion corresponding to the bottom of the DI can is subjected to an overhanging process to be cured. As a method of this hardening, a projecting process is applied to the portion that contacts the bottom of the can. The overhanging process may be performed before the second drawing process, but considering the current normal line configuration, the overhanging process is performed simultaneously with the first drawing process.
And or, it is desirable to perform after the first aperture stop and before the second aperture stop because the line configuration is less changed. In addition, the overhang processing is
It may be performed once, or may be performed twice.
The bottom portion of the first squeezing cup overhangs as shown in FIG. The processing amount is 15% or more and 50% or less in terms of the reduction in plate thickness. If the working amount is less than 15%, the work hardening amount is small and the effect of increasing the pressure resistance of the can is small.
Was set as the lower limit. If it exceeds 50%, the possibility of breakage during processing increases, and the plate thickness corresponding to the bottom of the can decreases too much compared to the increase in the amount of work hardening. 50% because the effect of increasing the product of the strength and the yield strength of the material) decreases
Is the upper limit. When the projecting process is performed twice, it is desirable from the viewpoint of productivity that the processing amount be at least 7% or more in one process. The shape of the processed part is as shown in FIG.
It may be spherical or any other shape.

The chemical composition of the raw material may be any as long as it is usually used for DI cans. Since the compressive strength is proportional to the yield stress of the material after forming, it is necessary to increase the sum of the yield strength and the work hardening amount of the material in order to secure the compressive strength. On the other hand, in order to secure the formability of drawing, it is desirable to reduce the C content in the case of a steel material. Therefore, it is possible to make the carbon content extremely low and contain one or more of Ti, Nb, and B to improve the yield strength and ductility, increase the processing amount of the can bottom equivalent portion, and further reduce the weight.

After the portion corresponding to the bottom of the can is overhanged as described above, it is molded according to a normal can manufacturing process. Second
The squeezing can be formed without problems if the wrinkle holder is adapted to the shape of the can bottom of the first squeezing.

The material to which the manufacturing method of the present invention can be applied may be a usual material for DI cans, for example, a tin-plated metal strip, a chrome-plated metal strip, or a tin-plated layer whose upper layer is chrome-plated. A metal strip, a chrome oxide film formed on the metal strip, or a metal strip (with or without plating) coated with resin on both sides or one side (for the metal strip, the above-mentioned Plated metal strips are also applicable), as the material of the metal strips, any steel can be used as long as it is a steel normally used in containers, such as aluminum killed steel and IF steel, aluminum (usually used in containers) Any aluminum may be used, for example, 30
00 series, 5000 series aluminum alloy, etc.), etc. are applicable.

[0009]

[Example] The steel for cans shown in Table 1 was manufactured by a conventional method. The temper degree is T4-CA. Using each can steel in Table 1,
I made a can.

A disk having the diameter shown in Table 2 was punched, and at the same time as the punching, the first drawing and the overhanging process were performed. As for the overhanging method, the wrinkle holding pressure in the initial stage of forming was increased, and the wrinkle holding pressure was lowered in the latter half of forming to increase the inflow amount of the flange portion and perform draw forming. The diameter of the first squeezing cup is 87 mm, and the protruding height of the cup bottom is 15 mm ~
30 mm, various thickness reduction amounts were processed. Also,
As a comparative example, a can that was not subjected to the overhanging process within the scope of the present invention was also molded. Subsequently, a second product having a diameter of 66 mm, ironing, and doming were performed to obtain a final product. The height required for the final product is 125 mm.

The formed can is processed according to the actual can manufacturing process.
Paint baking was performed at 05 ° C for 10 minutes to obtain a finished product. Using this can, pressure resistance was measured. The compressive strength was defined as the compressive strength when the internal pressure was applied to the can and the can bottom started buckling. Table 2 shows examples of the present invention and comparative examples.

In Examples 17, 18 and 19 in which the overhanging process is not performed before the second drawing, the desired DI can cannot be manufactured due to inability to reduce the weight, insufficient pressure resistance and insufficient shape. Further, in Examples 20, 21 and 22 in which the amount of overhanging processing is out of the range of the present invention, the desired DI can cannot be obtained due to breakage during processing or insufficient pressure resistance. Further, also in the case of aluminum, Example 23 in which the overhanging process is not performed before the second drawing is performed.
Is not light enough. On the other hand, in each of Examples 1 to 16 which are the methods of the present invention, it can be seen that the pressure resistance is high and the weight reduction is sufficiently achieved.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

As described above, the thickness of the DI can (in particular, the thickness of the bottom of the can) can be reduced without impairing the pressure resistance, which contributes to resource saving of the container.

[Brief description of drawings]

FIG. 1 (a) is a view showing a cross section of a cup after drawing in a first step of a DI can manufacturing process according to the method of the present invention, and (b) is a drawing in a first step of a DI can manufacturing process by a comparative proportional method. The figure which shows the cross section of a rear cup.

FIG. 2 (a) is a schematic view showing an example of a cross section of a cup after overhanging by the method of the present invention, and (b) is a schematic view showing an example of a cross section of a cup after overhanging by the method of the present invention.

Claims (1)

[Claims] 1. A thin-walled DI, which is characterized in that, when a DI can is manufactured, an overhanging process is performed on the bottom of the can before the second squeezing with a plate thickness reduction of 15% or more and 50% or less.
Can manufacturing method.