JPH0584524A - Manufacture of draw-ironed can - Google Patents

Abstract

PURPOSE:To provide a draw-ironing method capable of reducing cracks in the draw-ironing process without damaging the surface property of a can and further shortening a movable distance of a shell body forming machine. CONSTITUTION:In a working process of an Al-alloy cylindrical draw-ironed can having a final shape of a diameter-to-height ratio >=1.8, as the ratio of the outer diameter of a blank to an initial drawn core diameter is given by >=1.6 and <=1.8, and the ratio of the core diameter at the initial drawing time to the continued redrawn core diameter is given by >=1.3 and <=1.5, two stages of drawing are carried out. In this case, the difference between the outer diameter of the core and its inner diameter in time of drawing is given by >=2.1 times and <=2.3 times to the thickness of the blank and after it is drawn, the reduction percentage of the plate thickness of the wall part on the can side in time of the initial ironing to the plate thickness of the blank is given by >=25% and <=40%, the reduction of the plate thickness of the side wall part on the followed ironed can is given by >=40% and <=50% and two stages of ironing is carried out continuously to obtain the final side wall thickness of the can.

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 DI can for producing a cylindrical molded body such as a beer or beverage can.

[0002]

2. Description of the Related Art A deep cylindrical molded body such as a beer or a beverage can is usually formed by a blanking process and a cupping process for initial drawing, followed by a redrawing process and a three-stage ironing process for forming a body of a can. It is molded.
On the other hand, in the can manufacturing industry, the can forming speed is increasing year by year in order to improve the productivity, and a molding machine capable of reaching 300 cans per minute is now being developed.

[0003]

By the way, the speed of a molding machine is limited in terms of maintaining its output as well as its accuracy. Needless to say, the accuracy is more advantageous as the movable distance (stroke) of the punch is shorter. At present, the can body processing machine requires a movable distance of 600 mm or more in order to continuously perform redrawing and three-stage ironing, which is one of the restrictions for improving the productivity by increasing the can forming speed.

As a countermeasure against this, it is conceivable to shorten the distance between the dies or reduce the number of steps. Regarding the former, the current process is performed, but the next process begins, which imposes a heavy burden on the formability of the material. On the other hand, in the latter case, the processing rate in one process becomes large, and the crushing occurs. Japanese Unexamined Patent Publication No. 2-303634 discloses a squeezing ironing can in which the reduction rate of the thickness in the ironing process is controlled within a predetermined range from the lower part to the upper part of the cup side wall to prevent cracks during subsequent processing. Is disclosed. However, this alone cannot reduce the ironing process. Further, this method causes wear of the drawing tool or deterioration of the surface properties of the can, and is not yet a satisfactory method.

In view of the above problems, an object of the present invention is to reduce a crack in a drawing and ironing process without deteriorating the surface properties of a can, and to provide a drawing and ironing method capable of shortening a movable distance of a can body forming machine. To provide.

[0006]

The present inventor has conducted extensive studies to overcome the above-mentioned drawbacks of the conventional method for producing a squeezed ironing can, and as a result, in particular, a final height-diameter ratio of 1.8 or more was obtained. When manufacturing a cylindrical drawn ironing can made of aluminum alloy, which is shaped, the drawing process is performed in two steps, and the ratio of the pipe diameter before processing to the core diameter after processing in each drawing process falls within the predetermined range. It has been found that the objects can be achieved by carrying out the ironing process in two steps by accommodating each of them, and based on this knowledge, the present invention has been accomplished.

That is, according to the present invention, in the processing step of a cylindrical drawn ironing can made of an aluminum alloy having a final shape in which the ratio of height to diameter is 1.8 or more, (a) the punching plate with respect to the initial drawn core diameter is used. Outer diameter ratio is 1.6 or more and 1.8
Less than 1 and the ratio of the core diameter at the time of initial drawing to the core diameter of the re-drawing process to be continuously performed is 1.3 or more and less than 1.5 in two stages, and (b) the core at the time of drawing. The difference between the outer diameter and the inner diameter of the die should be 2.1 times or more and less than 2.3 times the material plate thickness, and (c) the plate of the side wall of the can at the time of initial ironing to the plate thickness after drawing. 25% reduction in thickness
The final can side wall thickness is obtained by continuously performing a two-stage ironing process in which the plate thickness reduction rate of the can side wall part of the ironing process is 40% or more and less than 50%. A method for producing a squeezed ironing can.

The aluminum alloy used in the present invention is not particularly limited. For the improvement of aluminum alloys for drawing and ironing, the development of materials with good formability, which emphasizes productivity as well as higher strength for weight reduction of cans, is underway. it can.

A cylindrical can made of an aluminum alloy formed by the method of the present invention is shown in FIG. The ratio of height (H) to diameter (D) is H / D ≧ 1.8. 2 of this cylindrical can
The state of the step drawing is shown in FIGS. 2 (A), (B), and (C). (A) is a punched plate, (B) is an initial drawn can, and (C) is a redrawn can. The total drawing ratio during drawing is determined by the size of the final can and the plate thickness of the can bottom and the can side wall. Two
In the case of step drawing, it is desirable to set the first step draw ratio to the maximum in order to maximize the total draw ratio. However, with this setting, initial drawing cracks frequently occur due to changes in material characteristic values and molding conditions. Considering the above, the ratio D ₀ / D ₁ of the outer diameter of the punched plate to the diameter of the initial drawing core is 1.6 or more.
It is less than 8, and the ratio D ₁ / D ₂ of the core diameter at the time of initial drawing to the core diameter of the subsequent redrawing is 1.3 or more.
A drawing process of less than 5 is preferable. Here, the initial drawing ratio is 1.65 or more and less than 1.75 and the redrawing ratio is 1.35.
It is preferably not less than 1.4 and less than 1.4. Thereby, the ironing formability can be further enhanced.

Further, it is desirable to reduce the plate thickness of the raw plate during the drawing process as in the case of the ironing process. However, if the plate thickness is excessively reduced during the drawing process, the forming load at that time increases and cracks and surface defects occur. As a result, the durability of the drawing die is significantly deteriorated. Therefore, the difference between the outer diameter of the core and the inner diameter of the die during drawing is suppressed to 2.1 times or more the material plate thickness.
If it is 2.3 times or more, the effect of improving the ironing property is lost.

In order to suppress the increase in plate thickness during drawing as described above, it is necessary to reduce the load applied to the die. The conditions relating to the die will be described with reference to FIGS. 3 and 4. FIG. 3 is a sectional view showing a state of drawing, and FIG.
It is an enlarged view of the R part of the die. In the figure, 1 is a die,
2 is an aluminum alloy plate and 3 is a core. A straight portion having a length (L) of 0.2 mm or more and less than 1.5 mm having a clearance angle α of 30 seconds or more and less than 3 degrees from the smallest position 1a corresponding to the end portion of the shoulder radius in the cross-sectional shape passing through the center line of the die 1. It is necessary to use a drawing die with 1b. Furthermore, the clearance angle α is 1 minute or more and less than 1 degree, and 0.5
The performance can be further improved by forming a straight line portion having a length (L) of not less than 1.0 mm and less than 1.0. The presence of the straight line portions having these clearance angles makes it possible to make the plate thickness distribution of the draw-formed product uniform and to suppress an unnecessary increase in load caused by the plate thickness returning after passing through the die.

FIG. 5 shows the forming process of the drawn and ironed can according to the method of the present invention. In the present invention, ironing is performed after drawing, but the plate thickness reduction rate of the can side wall part during the initial ironing process is 25% or more and less than 40% with respect to the base plate thickness, and the plate thickness reduction of the can side wall part of the subsequent ironing process is performed. 40% or more 50
The final can side wall thickness is obtained by continuously performing a two-step ironing process in which the percentage is less than%. Development of the high molding material and oil of high lubricity obtained here and development of the molding conditions to optimize molding conditions makes it possible to obtain a molded product equivalent to that of three stages by ironing in two stages.

The improvement in productivity in the molding process is proportional to the increase in molding speed. The impediment to improving the molding speed here is the accuracy of the molding machine. As a method of increasing accuracy, it is possible to increase the rigidity of the machine and shorten the movable distance. For this reason, currently three-stage ironing is generally used, but after drawing this as described above, the plate thickness reduction rate of the can side wall part at the time of initial ironing with respect to the base plate thickness is 25% or more 40% or more.
%, The can forming by continuous two-stage ironing that could not be performed until now because cracking occurred by setting the plate thickness reduction rate of the can side wall part of the ironing process to be continued to 40% or more and less than 50%. Is possible. Here, in the initial ironing process, there is an influence of nonuniformity of the plate thickness due to the drawing process, so that cracks partially occur at a plate thickness reduction rate of 40% or more. On the other hand, if it is less than 25%, the thickness of the final product is fixed, so the reduction rate of the thickness at the time of ironing in the next process is 5
It exceeds 0%.

[0014]

EXAMPLES The present invention will be described in more detail based on examples. AA30 having a composition shown in Table 1 with a plate thickness of 0.30 mm
A DI can having a capacity of 350 ml was produced according to the conditions shown in Table 2 using 04 alloy. The crack occurrence rate in this case is also shown in Table 2.
Are also shown. As is clear from the table, in the case of the production according to the present invention, the defective crack hardly occurs and the movable distance required for the molding machine can be shortened.

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

INDUSTRIAL APPLICABILITY By the DI molding according to the method of the present invention, it is possible to suppress the occurrence of cracks during drawing and ironing, and it is possible to perform molding at a higher speed by reducing the number of ironing steps. According to the method of the present invention, the productivity of the squeezed ironing can can be remarkably increased.

[Brief description of drawings]

FIG. 1 is a perspective view of a molded cylindrical can.

FIG. 2 is a perspective view of a drawn can. (A) is a punched plate, (B) is an initial drawn can, and (C) is a redrawn can.

FIG. 3 is a cross-sectional view showing a state of drawing processing.

4 is a partially enlarged cross-sectional view of a die used for drawing in FIG.

FIG. 5 is a manufacturing process drawing of a squeezed ironing can according to the method of the present invention.

[Explanation of symbols]

 1 die 2 aluminum alloy plate 3 core 1a minimum position of inner diameter of die 1b linear portion of die L length of linear portion of die

Claims (2)

[Claims] 1. In a process of processing a cylindrical drawn and ironed can made of an aluminum alloy having a final shape in which the ratio of height to diameter is 1.8 or more, (a) the outer diameter of the punched plate with respect to the initial drawn core diameter. Performing two stages of drawing with a ratio of 1.6 or more and less than 1.8, and a ratio of the core diameter at the time of initial drawing to the core diameter of redrawing that is subsequently performed is 1.3 or more and less than 1.5, (B) The difference between the outer diameter of the core and the inner diameter of the die during drawing is 2.1 times or more and less than 2.3 times the material plate thickness, and (c) after drawing, the initial thickness relative to the plate thickness. Plate thickness reduction rate of can side wall during ironing is 25% or more and less than 40%, and plate thickness reduction rate of can side wall during subsequent ironing is 40%
A method for producing a drawn and ironed can, wherein the final can side wall thickness is obtained by continuously performing a two-step ironing process in which the above is less than 50%. 2. The end portion of the shoulder radius in the sectional shape passing through the center line of the die in the process of processing a cylindrical drawn and ironed can made of an aluminum alloy having a final shape in which the ratio of height to diameter is 1.8 or more. 0.2mm or more with a clearance angle of 30 seconds or more and less than 3 degrees from the position with the smallest inner diameter corresponding to 1.
The method for producing a drawn and ironed can according to claim 1, wherein drawing is performed using a drawing die having a straight portion of less than 5 mm.