The present invention relates to a mold used for shaping a blank to be drawn. More specifically, the present invention relates to a mold that is used for shaping a blank to be drawn and that has a peripheral end face communicated indirectly with a top face.
A metal can is usually manufactured by blanking a metal plate to a suitable shape for making a blank, and by subjecting the blank with working such as drawing. In blanking the metal plate, a blank-shaping punch (male mold) and a blank-shaping die (female mold) of desired shapes are prepared in advance. Then, the metal plate is set between the punch and the die, and either the punch or the die is moved to make the punch pass through the die.
Recently, demand for reducing frequency of mold maintenance, demand for improvement in press quality, demand for reducing loads on environment, restriction on chemical ingredients and the like have become more severe. In order to cope with such demand, there has been a necessity of imparting higher hardness or lubricity to a mold so as to decrease breakage in the mold during pressing or to decrease the amount of lubricant or to avoid use of lubricant.
For enhancing the hardness or lubricity of the mold, techniques to cover the mold surface with a surface treatment film of diamond or the like have been developed keenly. However, in the mold such as a blank-shaping punch or a blank-shaping die to be used for blanking a metal plate, a strong impact load may be applied to the cutting edge part. Further, the surface treatment film on the cutting edge part tends to be thicker due to the sharp shape of the cutting edge part. These factors may cause degradation in adhesiveness of the surface treatment film at the cutting edge part, and often results in chipping and scaling of the surface treatment film during polishing or pressing. When the surface treatment film has chipping and scaling, the chipping or scaling originates peeling of the surface treatment film that may progress even to other parts.
In order to solve the chipping and scaling problem, non-patent document 1 proposes diamond coating of a blank-shaping punch and a blank-shaping die both used for blanking a metal plate, where the punch and the die have chamfered corners. However, as specified in Non-patent document 1, the blank-shaping punch or the blank-shaping die having chamfered corners cannot effectively avoid peeling of the diamond film.
Non-patent document 1: Research and Development Report “Development of boron-doped diamond-coated high toughness cemented carbide alloy tool for dry pressing” in the year of 2011 by Strategic Core Technology Advancement Supporting Program
Therefore, an object of the present invention is to provide a mold used for blanking a plate material like a metal plate so as to shape a blank to be drawn, where progress of peeling of a surface treatment film on the mold is prevented or controlled effectively.
The present invention provides a mold that can be used for blanking a plate material like a metal plate for shaping a blank to be drawn. The mold comprises a top face to be brought into contact with the plate material and a peripheral end face communicated indirectly with the top face, and at least the top face is coated with a surface treatment film.
It is preferable in the mold of the present invention that:
Further, the present invention provides a method for manufacturing a drawn can. The method comprises: preparing an annular mold with a through hole, having a top face to be brought into contact with a plate material, and a peripheral end face communicated indirectly with the top face, and at least the top face being coated with a surface treatment film; blanking the plate material to form a blank by using the mold as a punch; and drawing subsequently the blank by using the mold as a die.
The mold of the present invention has a peripheral end face communicated indirectly with the top face. Therefore, even if chipping or scaling occurs on the surface treatment film due to strong shearing force applied to the corners of the outer edge of the mold at the time of blanking the metal plate, the peeling of the surface treatment film may be stopped at the peripheral end face without spreading to the area of the surface treatment film on the top face.
Hereinafter, the mold of the present invention will be explained in detail with reference to the attached drawings. In the present specification, a ‘punch’ indicates a mold used as a male mold, and a ‘die’ indicates a mold used as a female mold. Aside of the mold of the present invention on which the metal plate is to be placed is determined as the upper side, and the opposite side is determined as the lower side.
There is no particular limitation on the entire shape of the mold 1 of the present invention as long as the outer periphery of the mold 1 corresponds to the shape of the target blank to be drawn. For instance, in a case of drawing the blank to be circular, the outer periphery of the mold 1 also may be formed circular. Further, as described below in detail, in a case of allowing the mold 1 to function not only as a blank-shaping punch but also as a die during drawing, the mold 1 can have a doughnut-shape with a through hole to pass the drawing punch.
Examples of the surface treatment film 17 used to coat at least the top face 11 include a carbon-based rigid film such as a diamond-like carbon (DLC) film and a diamond film, and further, any known surface treatment film such as a ceramic coating film and a fluororesin coating film. Among these films, a carbon-based rigid film tends to be peeled from the mold surface particularly noticeably. Therefore, the present invention may be applied effectively to the carbon-based rigid film, in particular, the diamond film. Here, the diamond-like carbon (DLC) is a generic name for incomplete diamond structure as a mixture of diamond and carbon, and its mixing ratio is not particularly limited.
The surface treatment film 17 has an average thickness usually in a range of 0.1 to 30 μm, and in most cases, 5 to 15 μm. When the surface treatment film is excessively thin, it might be difficult to coat the mold uniformly with the film. When the surface treatment film is excessively thick, the peeling resistance might be degraded.
From the viewpoint of durability, the surface treatment film 17 preferably has Vickers hardness of 2000 or more.
It is preferable that the top face 11 of the mold of the present invention has the surface treatment film 17 which is smooth, and specifically, the surface roughness Ra is 0.1 μm or less. The surface roughness Ra can be measured in compliance with JIS B0601-2001.
For a corner Y formed by the peripheral wall face 15 and the peripheral end face 13, it is preferable that the radius of curvature of the corner Y is as small as possible for preventing reliably the surface treatment film from further scaling. Specifically, the radius of curvature of the corner Y is preferably 1 mm or less. The corner Y preferably has also an angle θ1 in a range of 90 to 150° from the viewpoint of processability and from the viewpoint of keeping the maximum surface area of the top face. Further, as shown in
A corner Z in
Returning to
The difference in height between the surface of the peripheral end face 13 and the top face 11 is preferably in a range of 0.1 to 5 mm, and particularly preferably 0.1 to 2 mm in order to avoid the following problems: a metal plate may be bent during blanking and may be caught between the punch and the die, or an indentation may remain on the metal plate to cause product failure.
The outer periphery on the peripheral end face 13, which serves as a cutting edge, is preferably not covered with the surface treatment film 17 as shown in
In
As shown in
The peripheral end face 13 preferably has a shape corresponding to the shape of the outer edge of the mold 1. For instance, when the mold outer edge is circular, preferably the peripheral end face 13 is shaped annular. When the outer edge of the mold is rectangular, the peripheral end face 13 preferably is also shaped as a rectangular ring. As mentioned above, the peripheral end face is provided on the outer edge of the mold, imparting an important feature of the present invention.
In a conventional technique, a mold is coated with a surface treatment film such as a carbon-based rigid film. When the mold is polished or used as a blank-shaping punch, shearing force may be intensively applied to the corners of the outer edge of the mold, thereby causing chipping and scaling of the surface treatment film at the part for coating the mold outer edge corners. Starting from the chipping and scaling, peeling progresses to the remaining part of surface treatment film on the other parts of the mold, thereby shortening the life of the mold. In contrast, in the mold of the present invention, even when chipping or scaling occurs in the surface treatment film at the part covering the outer edge corner of the mold, the peeling of the film is limited to the peripheral end face but it may not spread further. In addition to that, the peripheral end face imposes substantially no influence on the final state of the blank to be drawn. Therefore, with the mold of the present invention, which has a peripheral end face, a high-quality blank to be drawn can be shaped without concern for chipping or scaling of the surface treatment film.
The above descriptions with reference to
A plate material is blanked out to a predetermined shape by use of the mold of the present invention having the aforementioned features, whereby a blank to be drawn is obtained. Specific examples of the plate material to be blanked include a plate of metal such as aluminum, copper, iron or an alloy containing any of these metals, and further a surface-treated steel plate such as a tin-plated steel plate like a tinned steel plate. Similarly to the metal plates, composite plates such as a resin plate, paper, and a fiber sheet can be used preferably. The thus obtained blank to be drawn is then subjected to drawing, and further subjected to bending, ironing or the like if necessary to make a finally shaped article.
As described above, the mold of the present invention is formed in advance with a through hole to pass a drawing punch, so that the mold of the present invention can be used as a punch for shaping a blank to be drawn and further as a drawing die. The mold can be used to conduct blanking and drawing consecutively (hereinafter, this consecutive working may be called blank-drawing), and thus, it has industrial advantages.
When the mold of the present invention is used as a blank-shaping punch and also as a drawing die, the blank-drawing is conducted according to the following process, for instance. First, as shown in
As mentioned above, when the mold of the present invention is used also as a drawing die, the peripheral end face of the mold may not cause any product failures such as indentations and wrinkles of the obtained drawn cans, as evidently shown in Examples below. Namely, it is possible to obtain a high-quality drawn can by use of the mold of the present invention as the blank-shaping punch and also as the drawing die.
The mold of the present invention can be manufactured by any conventional manufacturing method as long as at least the top face is coated with the surface treatment film and the mold has a peripheral end face.
The mold is manufactured by, for instance, preparing a substrate of any known material, and the substrate is worked to have a desired shape. In the working, the thickness of the surface treatment film is taken into consideration.
Specific examples of the materials for the substrate include: a cemented carbide alloy obtained by sintering a mixture of tungsten carbide (WC) and a metal binder such as cobalt; and a cermet obtained by sintering a mixture of a metal carbide such as titanium carbide (TiC) or a titanium compound such as titanium carbonitride (TiNC) and a metal binder such as nickel or cobalt.
Next, the surface treatment film is formed by use of any known film formation process suitable for the composition of the surface treatment film, and the surface of the film may be polished as required by any known method.
For instance, when the surface treatment film is a diamond film, the film may be formed by any known method such as a plasma CVD method like a microwave plasma CVD method or a high frequency plasma CVD method, or a hot filament CVD method. The plasma CVD method is carried out in the following manner. For preparing the material gas, a hydrocarbon gas such as methane, ethane, propane, or acetylene is diluted with a hydrogen gas. This material gas may be mixed suitably with a small amount of gas such as oxygen, carbon monoxide, or carbon dioxide in order to adjust the film quality and film formation rate. The substrate is heated using the material gas, so that plasma is generated by microwave, high frequency or the like. The material gas is decomposed in the plasma to generate active species, and to grow diamond crystals on the substrate, whereby a diamond film can be formed.
In a case where the surface treatment film is a DLC film, the film can be formed by any known film formation methods such as a high frequency plasma CVD method, an ECRCVD method, an ICP method, a DC sputtering method, an ECR sputtering method, an ionization vapor deposition method, an arc vapor deposition method, a laser vapor deposition method, an electron beam vapor deposition method, and a resistance heating vapor deposition method. In the high frequency plasma CVD method, for instance, a glow discharge generated by the high frequency between electrodes decomposes the material gas (hydrocarbon gas such as methane) to form a DLC film on the substrate.
In a case of not coating the peripheral wall face with the surface treatment film in the present invention, the aforementioned film formation may be carried out after masking the region corresponding to the peripheral wall face. Alternatively, the surface treatment film on the peripheral wall face may be removed after formation of the surface treatment film. The same holds true for a case where the peripheral end face is not coated with the surface treatment film.
After formation of the surface treatment film, the surface of the mold is polished if necessary by any known method, whereby the mold of the present invention is manufactured.
Hereinafter, the present invention will be explained with reference to Experimental Examples below.
In these Experimental Examples, the surface roughness and waviness were measured by the methods as described below. Namely, arithmetic mean roughness Ra and the maximum height waviness Wz were measured by using a surface texture and contour measuring instrument (SURFCOM 2000SD3 supplied by TOKYO SEIMITSU CO., LTD.) and in compliance with JIS-B-0601.
The mold to be subjected to the experiment was prepared by coating diamond on a substrate of cemented carbide alloy by a hot filament CVD method.
Diamond films were provided on a conventional mold without peripheral end face (hereinafter, this may be called simply a conventional mold) and on a mold with peripheral end face of the present invention (hereinafter, this may be called simply as a mold of the present invention). The molds were coated completely with the films, excepting the bottom parts. Some regions (i.e., top face and the inner diameter part) to be brought into contact with the metal plate were polished with a grindstone containing diamond abrasive grains until the arithmetic mean roughness Ra became 0.03 μm.
The thus obtained molds have shapes as described below. Conventional mold and mold of the present invention;
Outer diameter: 140 mm
Inner diameter: 90 mm
Average thickness of surface treatment film 17: 10 μm Mold of the present invention;
Radius of curvature of corner X: 0.2 mm
Radius of curvature of corner Y: 0.1 mm
Angle of corner Y: 90°
Width in circumferential direction of peripheral end face 13: 0.5 mm
Difference in height between surface of peripheral end face 13 and top face 11: 0.2 mm
Distance between groove 19 and outer edge of peripheral end face 13: 0.25 mm
Depth of groove 19: 0.1 mm
In the conventional mold without peripheral end face, chipping occurred at the outer edge corner of the mold during polishing. When polishing was continued further, peeling of the diamond film progressed from the chipped part. In contrast, neither chipping nor peeling occurred in the mold having a peripheral end face, namely, the mold of the present invention.
A metal plate was blanked and drawn by use of the mold that had been polished in Experimental Example 1. As the metal plate, A3104 material having a plate thickness of 0.27 mm was used. As shown in
The maximum height waviness Wz in the vicinity of the open end of each of the drawn cans obtained in Experimental Example 2 was measured to evaluate the wrinkles of the drawn cans. The values were about 1.6 μm in both the conventional mold and the mold of the present invention. The peripheral end face did not cause any wrinkles.
1 mold
3 blank-shaping die
3′ tip end of die
5 metal plate
7 blank
11 top face
13 peripheral end face
15 peripheral wall face
17 surface treatment film
19 groove
20 upper mold
21 drawpad
23 drawing punch
30 drawn can
Number | Date | Country | Kind |
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2015-234527 | Dec 2015 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2016/084541 | 11/22/2016 | WO | 00 |