JP4112941B2 - Method of processing metal strip for paint cans with excellent formability - Google Patents

Description

【００１６】
【発明の効果】
以上述べたように、本発明による多段加工に際しての金型の温度を制御することで、多段の絞り加工やしごき加工を行うに際して、優れた潤滑性が確保できる成形性に優れた塗装缶用金属帯を得ることができた。
【図面の簡単な説明】
【図１】本発明の対象とする金属帯の１例の断面を示す図である。
【符号の説明】
１ 金属帯
２ 表面処理層
３ 塗料
４ 塗料またはラミネートフィルム[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multistage can manufacturing method for a metal strip for cans coated with a paint containing an inner wax on the side corresponding to the outer surface of the can.
[0002]
[Prior art]
Conventionally, metal cans for beverages have been widely used for drawing and ironing cans because they are inexpensive and easy to mass-produce. As a method for producing these cans, generally, from the viewpoint of ensuring workability, a method of processing a tin-plated steel plate or an aluminum plate while applying a lubricant to the surface is generally used. However, in order to prevent external rust and to ensure internal corrosion resistance, it is necessary to coat and coat after ironing molding. After molding, the lubricant is washed with water with a detergent such as an alkali after the molding process, and then coated after chemical conversion treatment. There was a problem of having to go through.
[0003]
As a technique for improving productivity by omitting the low productivity process of the can process, for example, a method of laminating a resin film on both surfaces of a metal band in advance before processing disclosed in Patent Document 1, or coating with a resin-based paint A method has been proposed.
Among the above methods, when applying with a resin-based paint, an inner wax may be added as a lubricant to the paint to ensure workability after coating.
[0004]
However, since drawing and ironing are generally multistage processes, the lubricating effect tends to disappear at the initial stage of the first stage or the second stage, and it is difficult to fully exhibit the effect of the inner wax throughout the entire stage. . If processing is performed with insufficient lubrication, the can body breaks or a flaw called galling occurs on the surface, so that mass production of metal cans by the above method has not been carried out so far.
[0005]
[Cited document]
(A) Patent Document 1 (Japanese Patent Laid-Open No. 10-46101)
[0006]
[Problems to be solved by the invention]
The present invention provides a method of processing a metal strip for improving the above-mentioned drawbacks of the prior art and sufficiently exerting a lubricating effect on drawing and ironing of an inner wax added to a resin-based paint. .
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the present inventors have found that by controlling the temperature of the mold during multi-stage processing, excellent lubricity can be ensured when performing multi-stage drawing and ironing. The present invention has been completed.
The gist is that
When a metal strip coated with a paint containing an inner wax on the side corresponding to the outer surface of the can metal strip is to be made into a multistage can, the temperature Tn (° C.) of the n-th mold contacting the side corresponding to the outer surface of the can , 20 ≦ Tn ≦ (n−1) × 20 + 60 (° C.) , and the temperature of the mold is made higher in the subsequent stage than in the previous stage, and the punch temperature Tp (° C.) in contact with the can inner surface side is set to Tp ≦ 150 It is in the processing method of the metal strip for coating cans excellent in the moldability characterized by setting it as ° C.
[ 0008 ]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described by taking the case of ironing as an example.
First, the metal strip of the present invention will be described. FIG. 1 is a view showing a surface cross-sectional structure of a metal strip according to the present invention. As shown in this figure, the metal strip 1 serving as a base material is provided with a surface treatment layer 2 subjected to various types of plating and surface treatment as necessary, and a paint 3 is applied to the surface which becomes the outer surface side of the can after the can manufacturing process. The surface which becomes the inner surface side has a structure having a paint or laminate film 4.
[ 0009 ]
Next, canning process conditions, which are the greatest feature of the present invention, will be described.
In the present invention, the temperature Tn (° C.) of the n-th mold is defined as 20 ≦ Tn ≦ (n−1) × 20 + 60 (° C.), and the punch temperature Tp (° C.) is defined as Tp ≦ 150 (° C.). Note that the mold temperature refers to the temperature of the mold surface that contacts the outer surface of the can used for drawing or ironing, and the punch temperature refers to the temperature of the mold surface that contacts the surface corresponding to the inner surface of the can. Point to. These temperatures can be measured by inserting a thermocouple or performing image analysis with a thermoviewer, but the simplest method is to estimate the cooling water temperature of the mold or punch. is there.
[ 0010 ]
The reason why good lubrication can be obtained when the temperature of the mold and punch is defined in this way is not clear, but the mold can be considered as follows.
When subjected to severe processing such as drawing or ironing, heat is generated between the metal strip and the mold due to processing or friction, but when the mold exceeds a certain temperature, the inner wax in the paint that comes into contact has a melting point. It melts over, moves to the surface layer of the resin, and is consumed by contact with the mold. That is, if the temperature of the mold is high in the pre-processing stage, the lubrication effect is consumed and lost in the pre-stage of the multi-stage processing, resulting in insufficient lubrication in the post-stage and causing problems.
[ 0011 ]
In the first stage of processing, it is necessary to process at a temperature as low as possible in order to maintain the lubrication effect in the subsequent stage, and in the latter stage, the mold temperature is higher than that in the previous stage because wax is quickly supplied to the resin surface. This is very important.
However, in a low temperature range, the resin has a high hardness and lacks fluidity, and therefore does not exhibit good lubricating performance. Therefore, the mold temperature needs to be 20 ° C. or higher.
[ 0012 ]
In some cases, the paint may contain a metal filler such as aluminum or aluminum alloy filler to control the color tone of the outer surface of the can of the metal strip. In that case, the effect of the present invention is particularly remarkably exhibited. The reason for this is not clear, but it is estimated that the paint containing the metal filler is poor in ductility, so that the part depending on the lubrication effect by the inner wax is large.
[ 0013 ]
Next, regarding the punch temperature, unlike the above-mentioned molds divided into multiple stages, there is a feature that the heat input is large because it is always in contact with the can during processing, and the heat escapes due to the structure of the processing machine. Because it is difficult, it becomes hotter than the mold. However, the processing is almost done by friction between the mold and the outer paint layer, and furthermore, heat transfer is hindered between the inner paint layer (or laminate layer) and the metal strip, and further the outer paint layer. Does not affect the lubricity. As a result of various tests, it has been found that if the punching temperature is 150 ° C. or lower, it is possible to further prevent processing defects. Note that the mold and punch can be controlled within the specified temperature range by adjusting the cooling water temperature and flow rate of the mold and punch.
In addition, although this invention is a technique applied to the metal strip in general, it is preferable that the metal strip is a plate of aluminum, an aluminum alloy, or steel from the viewpoint of workability, cost, and the like.
[ 0014 ]
【Example】
Steel plates containing the filler and inner wax shown in Table 1 were canned at the mold and punch temperature shown in Table 1. The results are also shown in Table 1.
[ 0015 ]
[Table 1]

[ 0016 ]
【The invention's effect】
As described above, by controlling the temperature of the mold in the multi-stage processing according to the present invention, when performing multi-stage drawing and ironing, the metal for coating cans with excellent formability that can ensure excellent lubricity I was able to get a belt.
[Brief description of the drawings]
FIG. 1 is a diagram showing a cross section of an example of a metal strip that is an object of the present invention.
[Explanation of symbols]
1 Metal strip 2 Surface treatment layer 3 Paint 4 Paint or laminate film

Claims (1)

When a metal strip coated with a paint containing an inner wax on the side corresponding to the outer surface of the can metal strip is to be made into a multistage can, the temperature Tn (° C.) of the n-th mold contacting the side corresponding to the outer surface of the can 20 ≦ Tn ≦ (n−1) × 20 + 60 (° C.), and the temperature of the mold is made higher in the subsequent stage than in the previous stage , and the punch temperature Tp (° C.) contacting the inner surface of the can is set to Tp ≦ 150 ° C. A method for processing a metal strip for a paint can having excellent formability.

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