JP5630621B2 - Resin-coated seamless can body - Google Patents

Description

  The present invention relates to a resin-coated seamless can body, and more particularly to a resin-coated seamless can body formed by a drawing and ironing method from a resin-coated metal plate in which at least one surface of a metal plate is coated with an organic resin.

  In recent years, resin-coated seamless cans, which have been proposed from the viewpoint of environmental conservation and can-material saving, are formed by drawing and ironing a resin-coated metal plate. When the ironing rate is 15% or more, there is a tendency that organic resin thread-like cutting waste (hereinafter referred to as resin hair) is likely to occur. When the resin hair is generated, the resin hair adheres to the punch or die, so that there is a problem that the coating resin on the surface of the can body subjected to the ironing process is damaged.

  As a means for solving this problem, as shown in FIG. 7, the cup 25 after drawing is attached to a punch 20 having a relief surface 21 at the rear end of the small diameter portion, and two ironing dies are connected in series. A method has been proposed in which a can body is obtained by inserting into an ironing die placed in this manner, performing ironing, reducing the side wall thickness of the drawn cup, and increasing the height of the cup (see Patent Document 1). ). In this processing method, the first die 10 and the second die 11 are connected in series, so that the forming stress in the axial direction generated by the ironing by the first die 10 at the preceding stage is reduced when ironing by the second die 11 at the latter stage. Effectively used as a back tension, it has the advantage that the ironing rate is improved more than the one-step ironing with a single die. Further, by using a punch having a punch relief inclined surface 21, it is possible to prevent the occurrence of resin hair by a device that does not perform the ironing process of the end portion of the can body opening.

  However, when the above-mentioned continuous die is used, the amount of ironing changes significantly when shifting from the ironing process of the side wall part to the ironing process of the flange forming part, and a thin part (shock line) is generated in a part of the side wall part. When the ironing rate is increased in order to obtain a thin-walled can, a broken case may occur. As a countermeasure for this, there is provided a drawing ironing method that can suppress the destruction of the side wall portion by forming a taper having a length longer than the distance between lands in the first die and the second die in the large diameter portion of the punch. (See Patent Document 2). In this case, by forming a taper in the large-diameter portion of the punch, the thickness of the side wall near the stepped portion gradually increases in the axial direction (to the opening), so that a thin portion (shock line) is generated. Can be prevented.

JP 2006-68779 A WO2007-052364

  However, in the ironing method using the above-described continuous die, the amount of ironing changes greatly even when the ironing process of the flange forming part is shifted to the ironing process end, and a thin part (similar to the above) is formed in part of the flange forming part. Shock line) occurs. In the case of a general positive pressure can, the flange forming portion is thicker than the side wall portion because post-processing such as neck-in processing and flange processing for winding is performed. As shown in detail in FIG. 8, the details of the flange forming portion include a phenomenon in which a thin portion Z is locally generated in the circumferential direction, and a variation in thickness at a height after the thin portion is increased. Is seen. The graph shown in FIG. 9 shows the change in thickness in the height direction from the bottom of the can in which the proposed first die and the second die are connected to each other with a distance of 10 mm between the lands and the can body ironed by a conventional punch. Was measured at intervals of 45 ° in the circumferential direction and at intervals of 2.5 mm in the height direction. In this way, a decrease in wall thickness is observed locally at a certain height from the bottom of the can (160 mm in the example of FIG. 9), and there is a large variation in wall thickness at subsequent heights. I understand.

  If the thickness of the flange forming portion is non-uniform, a problem of wrinkles 45 (circumferential buckling) occurs during neck-in processing as shown in FIG. This problem can be solved by increasing the thickness of the flange forming portion. However, since the material cost is increased, it is required to suppress the generation of wrinkles with the smallest possible thickness. In order to make this possible, there is little variation in the plate thickness, and a more uniform thickness is required. However, in the case of resin-coated seamless cans, if a squeezing method using a continuous die is used to prevent the occurrence of resin hair, it will inevitably cause local thickness reduction at the flange forming part, resulting in unevenness. There was a tendency to become thin, wrinkles were generated during the neck-in processing described above, and remained after the flange processing, and double winding was not performed normally and leakage occurred. As proposed in Patent Document 2, a taper is applied to the large-diameter portion of the punch as a measure for preventing a thin portion (shock line) from being formed in a part of the side wall portion when ironing using a continuous die. Is formed. Due to the taper, the thickness of the side wall portion in the vicinity of the stepped portion gradually increases in the axial direction (to the opening portion), so that the occurrence of a thin portion (shock line) can be prevented.

When the above method is applied to the ironing of the flange forming part and the taper is formed in the small diameter part of the punch, the thickness of the flange forming part gradually increases in the axial direction (to the opening), so that the thin part Can be prevented. However, the wall thickness at the open end increases too much, and the molding load during neck-in processing and flange processing becomes excessive, causing problems such as buckling of the can body, and more wasteful amount of metal is required. Cost up.
Then, an object of this invention is to provide the seamless can body which solved the two said problems.

  As a result of earnest experiments to solve the above-mentioned problems, the present inventor performs ironing with a second die following ironing with a first die in ironing with a continuous die. It was found that the occurrence of the thickness reduction in the formation portion is a portion where the land of the second die is located at the end of the processing by the first die. In the ironing process using the connecting die, while the ironing process using the first die is performed, the back tension acts on the ironing process using the second die. When the back tension changes, the ironing process using the second die is performed. Since the processing load also changes, the wall thickness after ironing changes as a result. The cause of the reduction in the thickness is considered to be that the back tension temporarily increases when the top edge of the inclined surface of the punch relief reaches the rear end of the land of the first die. Thereafter, the ironing process by the first die is performed on the inclined surface of the punch relief, so that the ironing amount is drastically reduced and finally becomes zero. After this, since the back tension in the ironing process with the first die disappears, the ironing process with the second die alone will be performed, but it is found that the variation in the wall thickness increases due to the influence of the above-mentioned thickness reduction occurrence. did.

  As a result of further research based on this knowledge, by providing a circumferential groove on the outer peripheral surface of the punch small-diameter portion where thickness reduction occurs, it becomes possible to prevent thickness reduction due to a temporary increase in back tension, The present inventors have found that variations in thickness can be suppressed and have reached the present invention.

That is, a resin-coated seamless can body according to the invention of claim 1 of the present application is a drawn cup comprising a resin-coated metal plate in which at least one surface of a metal plate is coated with an organic resin and at least one surface of which is coated with an organic resin. Is a resin-coated seamless can body comprising a bottom part, a side wall part, and a flange forming part, which is made by passing through a continuous die in which a plurality of dies are stacked and ironed, and by the ironing process using the connecting die The thickness reduction part locally generated in the flange forming part is corrected by a circumferential groove formed in the outer periphery of the small-diameter part of the punch, and the circumferential thickness deviation of the flange forming part is at each height position. The average wall thickness is within 5% .
In the ironing process in which a punching cup made of a resin-coated metal plate made by coating an organic resin on at least one surface of a metal plate is attached to a punch and passed through a continuous die, the limit ironing rate is higher than the one-step iron forming with a single die. However, a local thickness reduction portion is generated in the flange forming portion due to the use of the continuous dies. As a countermeasure against this, a decrease in thickness can be corrected by forming a circumferential groove on the outer peripheral surface of the punch having a small diameter as described above and appropriately selecting the width and depth of the circumferential groove. A portion corresponding to the circumferential groove position of the punch small diameter portion in the flange forming portion is referred to as a thickness correction region.
In the can body of the present invention, the thickness of the flange forming portion can be eliminated by correcting the thickness reduction by appropriately increasing the thickness of the thickness correction area, so that the thickness of the flange forming portion is substantially uniform. It is characterized by.
As a result, in the can body of the present invention, the amount of uneven thickness in the circumferential direction of the flange forming portion is within 5% with respect to the average thickness at each height position . Accordingly, a can body having a uniform thickness in the circumferential direction of the flange forming portion can be obtained as compared with a conventional can body, and the above-described neck-in process and flange process can be performed more favorably.

  Since the resin-coated seamless can body of the present invention has less variation in the thickness of the flange forming portion, wrinkles during neck-in processing can be suppressed without making the flange forming portion thicker than before. As a result, the can body can be reduced in weight (reducing material costs).

It is a principal part schematic sectional drawing which shows the state which the top end edge of the punch relief inclined surface reached | attained the 1st die | dye in the ironing process of the resin-coated seamless cup by the ironing apparatus of the resin-coated seamless can of this invention. It is a schematic sectional drawing which shows the ironing process of the can body side wall part in the ironing process of the resin-coated seamless cup by the ironing apparatus of the resin-coated seamless can body of the present invention. It is a schematic sectional drawing which shows completion | finish of the ironing process of the resin-coated seamless cup by the ironing apparatus of the resin-coated seamless can of this invention. It is a principal part expanded sectional view of the flange formation part vicinity of the resin-coated seamless can which concerns on embodiment of this invention. It is a graph which shows the thickness distribution of the circumferential direction and the height direction of the can body flange formation part after the ironing process in the Example of this invention. It is a graph which shows the thickness distribution of the circumferential direction and height direction of the can body flange formation part after the ironing process in an Example. It is a principal part cross-sectional schematic diagram which shows the flange formation part ironing process in the comparative example by the continuous die using the conventional punch. It is a principal part expanded sectional view of the flange formation part vicinity of the resin-coated seamless can which concerns on a comparative example. It is a graph which shows the thickness distribution of the circumferential direction of the can body flange formation part after ironing in a comparative example, and a height direction. It is a schematic diagram showing the occurrence of wrinkles (buckling in the circumferential direction) when neck-in processing is performed on a conventional can body flange forming portion.

FIG. 1 is an enlarged view of a main part showing the ironing process by the ironing apparatus for the resin-coated seamless can shown in FIG.
An ironing device 1 for a resin-coated seamless can according to an embodiment of the present invention includes a continuous die 2 having an annular ironing surface and a punch 5, and a cup 25 formed by drawing as shown in FIG. 2. The ironing process is performed by inserting the punch 5 into the punch 5 and allowing the machined surface of the continuous die 2 to pass through the pressed state.

  As shown schematically in FIGS. 2 and 3, the punch 5 in the apparatus is subjected to post-processing such as a large-diameter portion 5a for ironing the side wall of the can body, neck-in or flange processing. The flange forming portion to be applied has a small-diameter portion 5c for ironing, and the large-diameter portion 5a and the small-diameter portion 5c are connected via a connecting inclined surface 5b. The small-diameter portion 5c is further connected to the rod 6 via a punch escape inclined surface 5d. Therefore, in the ironing process at the large diameter portion 5a, the thickness of the can body is thin, and in the ironing process at the small diameter portion 5c, the clearance with the die processing surface increases and the amount of ironing decreases as the punch outer diameter decreases. The thickness of the can body increases. Furthermore, if the can barrel opening end is moved to the punch relief inclined surface 5d and the ironing process is continued, the amount of ironing gradually decreases and finally becomes zero, thereby generating resin hair at the can barrel opening end. Can be prevented. In the punch having such a structure, the present invention is characterized in that a circumferential groove 7 to be described later is formed at a position indicated by hatching of the small diameter portion 5c.

  On the other hand, the continuous die 2 is formed by connecting the first die 10 and the second die 11, and each die has a shape having approach portions 10a and 11a, land portions 10b and 11b, and relief portions 10c and 11c. Is formed. The land portion inner diameter of the second die is smaller than the land portion inner diameter of the first die so that the first die 10 performs the preceding ironing process and then the second die 11 performs the subsequent ironing process. Further, the ironing process is further performed by the second die, but by forming the first die 10 and the second die 11 in series, the axial forming stress generated by the first die during the ironing process by the second die in the subsequent stage. Is effectively used as back tension. As a result, the one-step iron forming by the continuous die composed of the first die and the second die has an effect of improving the limit ironing rate, rather than the one-step iron forming by the single die. Note that the continuous arrangement means that the first die and the second die are provided continuously in a state where they are simultaneously inserted into a portion where punching is performed, and the first die and the second die are separated. However, it is also possible to form a unitary structure or install two dies with a spacer interposed therebetween.

  The inter-land distance between the land portions 10b and 11b of the first die 10 and the second die 11 differs depending on the material, thickness and size of the can body, and is not necessarily uniform. From the standpoint of improving the limit ironing rate by the effective use of the back tension by the processing part, it is more effective that the distance L between the lands of the first die and the second die is shorter, and the distance L between the lands should be 40 mm or less. preferable. Preferably, it is in the range of 3 to 40 mm.

  As described above, the circumferential groove 7 having a very small depth is formed on the outer peripheral surface of the small diameter portion 5c of the punch 5 used in combination with the continuous die 2 as described above. The circumferential groove 7 is for suppressing a reduction in thickness locally generated when ironing the flange forming portion. In the present embodiment, the deepest portion is the land portion 7b, and both walls thereof are provided. The inclined surfaces 7a and 7c are not necessarily limited to such shapes, but can be formed in any shape such as a circular arc whose curvature changes continuously.

Circumferential groove 7, the land portion rear end 10d of the first die 10, when the distance t ₁ to land center of the second die 11 from the top edge 9 of the punch flank inclined surface 5d, the distance t ₁ It is desirable to form the center of the circumferential groove 7 at a distance substantially equal to.

  The size of the circumferential groove 7 is such that when ironing with the second die, the amount of ironing with the second die increases as the back tension temporarily increases, and the resulting reduction in the wall thickness of the can body can be prevented. The total width s is preferably in the range of 5 to 15 mm, although it depends on the land width of the second die and the clearance between the land and the small diameter portion of the punch. Moreover, the depth h of the circumferential groove is a minute depth and is preferably in the range of 1 to 10 μm. If the width s of the circumferential groove is small and the depth is particularly shallower than the above range, the thickness reduction generated in the second die cannot be prevented. On the other hand, if the width s of the circumferential groove is large or the depth h is too deep, the amount of ironing at that portion is excessively reduced and the thickness is increased, and the thickness of the flange forming portion is not uniform. From such a viewpoint, the above range is desirable.

  The ironing method is an organic resin made of thermoplastic resin such as polyester resin, polyolefin resin, polyamide resin on both surfaces of various plated steel plates such as tinplate, surface-treated steel plates, stainless steel plates, aluminum plates and aluminum alloy plates. When squeezing and squeezing a metal plate coated with metal, a coated metal plate coated with a thermoplastic or thermosetting resin, or an organic resin-coated metal plate containing pigments or fillers in the organic resin Is particularly effective. The thickness of the organic resin film is preferably 5 to 100 μm. As the resin film applied to the present invention, either a single-layer film or a multilayer film having two or more layers can be applied, and a film made of a thermoplastic resin, particularly a polyester resin is preferable.

  In the case of a single layer film, the thickness of the resin film is preferably 5 to 100 μm, and more preferably 10 to 40 μm. When the thickness is less than 5 μm, the operation of laminating the surface-treated steel sheet becomes extremely difficult, and the resin layer after drawing or ironing is likely to be defective, and it is molded into a can and filled with the contents. However, the permeation resistance to corrosive components is not sufficient. When the thickness is increased, the permeation resistance is sufficient, but it is economically disadvantageous to have a thickness exceeding 100 μm. In the case of a multilayer film, the ratio of the thickness of each layer varies from the viewpoint of molding processability, permeation resistance, or the effect on the flavor of the contents, but each layer has a total thickness of 5 to 60 μm. Adjust the thickness.

[Example]
Used ironing equipment:
In the ironing apparatus shown in FIG. 1 to FIG. 3, the land portion width of the first die 10 is 1.0 mm, the land width of the second die 11 is 1.0 mm, the land end of the first die and the second die as continuous dies. The distance t ₁ between 11 land centers (inter-land distance + half the land width of the second die) was set to 10.5 mm. The punch has a circumferential groove 7 with an overall width s of 9 mm, a deepest flat portion width w of 2 mm, and a deepest portion depth h of 5 μm. The distance from the edge 9 to the center of the circumferential groove was set to 10.5 mm.
Test cup:
A circular blank having a diameter of 165 mm is obtained from a resin-coated steel plate having a thickness of 0.254 mm, in which a polyester film having a thickness of 28 μm is coated on the inner surface portion and a polyester film having a thickness of 16 μm is coated on the outer surface portion. Was drawn with a cupping press to obtain a cup having a diameter of 91 mm. The cup is fitted to the punch of this processing apparatus and redrawn, and then ironed with the above-mentioned continuous die to obtain a seamless can with a capacity of 500 ml, a diameter of 66 mm, and a thickness of the body side wall of the body 0.095 mm Then, ironing was performed with a target of a flange forming portion plate thickness of 0.172 mm. The canning speed of the ironing apparatus was 200 cpm continuous molding.

  FIG. 4 shows a plate thickness cross-sectional view of the main part from the side wall portion of the obtained can body to the flange forming portion. Table 1 shows that the can body, which was trimmed at position 31 in FIG. 4 to a height of 168.0 mm, was divided into 8 equal parts in the circumferential direction at intervals of 2.5 mm from the position 150 mm from the can bottom. This is data obtained by measuring the thickness of the can body at each position and examining the distribution of the thickness of the can body. FIG. 5 is a graph showing the results. Moreover, the change of the average value of can body plate | board thickness in the perimeter at each said 2.5 mm space | interval is shown by the continuous line in FIG.

[Comparative example]
As a comparative example, as shown in FIG. 7, except that the circumferential groove is not formed in the small-diameter portion of the punch 20, the same conditions are used by using the ironing apparatus and the test cup having the same conditions as in the above-described example. The ironing process was performed. And the thickness of the obtained can body was measured similarly to the Example, and thickness distribution was investigated. The results are shown in Table 2 and FIG. FIG. 6 shows, along with the example, the change in the average value of the can body thickness on the entire circumference measured at intervals of 2.5 mm from the height of 150 mm from the bottom of the can by broken lines.

  As shown in Table 2 and the graphs of FIGS. 6 and 9, in the comparative example, the can body was locally thinned at a height of 160 mm, and the thickness variation in the circumferential direction increased at the subsequent height. Recognize. On the other hand, in the can body of the example, as shown in the table 1 and the graphs of FIGS. 5 and 6, the thickness reduction portion at a height of 160 mm in the flange forming portion (range from 155 to 168 mm from the bottom). Although there was some variation in the thickness after that, the variation in thickness could be suppressed as compared with the comparative example. Further, in the examples and comparative examples, the circumferential thickness deviation (maximum wall thickness-minimum wall thickness) in the flange forming portion (in the range of 13 mm from the trimming end) is 0.004 to 0.007 mm in the embodiment, and the average is 0. 0.006 mm. And the maximum amount of thickness deviation in the circumferential direction for each height was 4.1% with respect to the average value at a height of 162.5 mm, and was within a range of 5%. Further, the thickness average value in the height direction of the flange forming portion is 0.1713 mm as clearly shown in the graph of FIG. 6, the maximum thickness is 0.1716 mm, and the minimum thickness is 0.1708 mm (bottom). 160mm height position), the axial thickness deviation is 0.0008mm, 0.5% of the circumferential average thickness at the height position, that is, within 1%, and there is almost no variation, In particular, it can be seen that the thinness at the position of 160 mm from the bottom, which is the maximum thinness, is almost eliminated.

  On the other hand, in the can of the comparative example, the amount of uneven thickness in the circumferential direction is 0.004 to 0.016 mm and an average of 0.010 mm, and the maximum amount of uneven thickness with respect to the average thickness in the circumferential direction at each height position is 0.016 mm, and 9.3% relative to the circumferential average thickness. On the other hand, the thickness variation in the height direction is large, and the maximum thickness is 0.1718 mm and the minimum thickness is 0.1664 mm and the height is 160.0 mm with respect to the average thickness of 0.1695 mm of the flange forming portion. The thickness is extremely thin, and the axial thickness deviation is 0.0054 mm, which is 3.2% larger than the axial average thickness. From the above, the thickness of the embodiment is significantly smaller than that of the comparative example in both the circumferential direction and the axial direction (height direction), and the superiority of the can body of the present invention is significant. confirmed.

  As described above, according to the can body of the present invention, it has been confirmed that the variation in the thickness of the flange forming portion and the amount of uneven thickness can be effectively reduced. That is, according to the can body of the present invention, the thickness reduction portion generated by ironing with the conventional connecting die and punch does not occur, and this portion becomes the thickness correction region, and the thickness of the flange forming portion is uniform. It becomes possible to. As a result, it was possible to obtain a can body that does not wrinkle even if the portion is subjected to neck-in processing or flange processing in post-processing.

  The processing method of the resin-coated seamless can body according to the present invention is to prevent the flange forming portion from partially reducing the thickness in the ironing processing of the flange forming portion and to suppress the variation in the thickness. Since processing etc. can be performed satisfactorily and resin hair does not occur, it can be suitably used for the production of various steel and aluminum resin-coated seamless cans. And since the obtained can of this invention is excellent in resource saving and environmental conservation, and is excellent in sealing performance, it can be applied to various contents and has high industrial applicability.

DESCRIPTION OF SYMBOLS 1 Ironing apparatus 2 Consecutive die 5a Large diameter part 5b Connection inclined surface 5c Small diameter part 5d Relief inclined surface 6 Rod 7 Circumferential groove 9 Top edge 10 1st die 11 2nd die 20 Punch 25 Cup 30 Flange formation part ironing End position 31 Trimming position

Claims (1)

Forming the bottom, side wall, and flange by attaching a squeezing cup made of a resin-coated metal plate coated with an organic resin on at least one side of the metal plate to the punch and passing through a continuous die in which a plurality of dies are stacked. A resin-coated seamless can body comprising parts,
The thickness reduction part locally generated in the flange forming part by ironing by the connecting die is corrected by a circumferential groove formed on the outer periphery of the small diameter part of the punch,
The resin-coated seamless can body, wherein the amount of uneven thickness in the circumferential direction of the flange forming portion is within 5% with respect to the average thickness at each height position .

Images