Fabrication mold with surface treatment film

Abstract

To provide a fabrication mold having a surface treatment film formed on a machining surface, in which no surface treatment film is present on a fitting surface formed on a non-machining surface connected to the machining surface to a fabrication device.SOLUTION: In a fabrication mold (ironing die) 50 having a machining surface A on which a surface of a workpiece is machined by friction with the workpiece, the machining surface A has the following forms (a)-(d) when seen in a side cross section which becomes a side surface: (a) the machining surface is positioned within a plane extending in a height direction; (b) a pair of non-machining surfaces facing each other in the height direction are provided; (c) a step which becomes a barrier in the extending direction continuing from the machining surface is formed on at least one of the pair non-machining surfaces; and (d) a surface treatment film is formed on the machining surface, and the surface treatment film extends to the non-machining surface.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a forming die provided with a surface treatment film, and more particularly to a forming die used in plastic working of metals and the like. [Background technology]

[0002] Conventionally, known methods of plastic processing of metals include rolling, bending, shearing, drawing, and ironing. Such plastic processing is carried out by bringing a jig made of a rigid substrate, for example, made of cemented carbide, into contact with the metal being processed.

[0003] In the above-mentioned plastic forming processes, lubricants such as oil are generally used to prevent direct contact between the workpiece and the processing jig. However, in the case of plastic forming processes under high surface pressure, such as ironing, the lubricating film cannot be maintained locally, resulting in direct contact between the workpiece and the processing jig, which can cause the workpiece to seize on the processing surface and result in surface roughness of the formed product. Furthermore, when sintered bodies such as cemented carbide are used as processing dies, microscopic voids are inevitably present within the sintered body, and even if the cemented carbide surface is polished to a mirror finish, these voids remain exposed on the surface. When soft metals, such as aluminum, are processed using jigs with such voided surfaces, wear particles from the soft metal can accumulate on the processing surface. Such seizure and accumulation not only cause surface roughness in the formed product, but also significantly reduce tool life due to wear on the processing die surface (processing surface) and dimensional changes caused by re-polishing.

[0004] Therefore, in the case of forming dies used in the plastic processing of metals, a method of providing a hard surface treatment film such as a carbon film (diamond film) on the processing surface is widely adopted, mainly for the purpose of wear resistance and seizure resistance (see, for example, Patent Documents 1 and 2).

[0005] While it would be ideal if the above-mentioned surface treatment film could be selectively formed only on the processing surface of the mold, in practice, such selective film formation is difficult, resulting in the inconvenience of the surface treatment film being formed on the part (mounting surface) that is attached to the molding machine. If a surface treatment film is formed on such a mounting surface, the dimensional accuracy of the molding mold deteriorates, adversely affecting the quality of the molded product. Therefore, polishing or grinding is required to remove the surface treatment film formed on the mounting surface, resulting in reduced productivity and increased costs.

[0006] Also, in order to prevent the formation of a surface treatment film on the mounting surface, a method is known in which a masking is attached to the mold, the mounting surface is covered with the masking, and film formation is carried out in this state (for example, Patent Document 3). By carrying out film formation using such a masking, it is possible to avoid film formation on the mounting surface, and therefore it is possible to effectively avoid inconveniences such as a decrease in mold accuracy due to film formation on unnecessary parts.

[0007] However, if the mounting surface is covered with a masking jig as described above and film formation is carried out in this state, there is a risk of productivity decreasing due to the work of attaching and removing the masking, and the quality of the masked surface decreasing due to deterioration of the masking jig, and costs increasing due to replacement of the masking jig.

[0008] In addition, during film formation, the surface treatment film will also adhere to the surface that was masked in the pretreatment process. However, since this surface has not been pretreated by masking, the adhesion is much weaker than that of the non-masked surface, and it can be easily removed using commercially available diamond or ceramic grinding stones, sponge abrasives, etc. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 2783746 [Patent Document 2] WO2017 / 033791 issue [Patent Document 3] Patent Publication No. 2021-191592 Summary of the Invention [Problem to be solved by the invention]

[0010] Therefore, an object of the present invention is to provide a molding die having a surface treatment film formed on the processing surface, in which the formation of the surface treatment film on the non-processing surface adjacent to the processing surface is limited, and in which the surface treatment film (or its residue) is completely absent on certain non-processing surface portions (for example, the attachment surface to the molding device formed on the non-processing surface). Another object of the present invention is to provide a method for forming a surface treatment film on the working surface of a molding die without carrying out a polishing treatment after the formation of the surface treatment film.

[0011] According to the present invention, there is provided a molding die having a processing surface that processes the surface of a workpiece by rubbing against the workpiece, There is provided a molding die characterized by having the following configurations (a) to (d) when viewed in cross section, where the processed surface is the side surface: (a) The processed surface is located within a plane extending in the height direction. (b) It has a pair of non-machined surfaces facing each other in the height direction. (c) At least one of the pair of non-machined surfaces has a step formed thereon that acts as a barrier in the direction of extension continuing from the machined surface. (d) A surface treatment film is formed on the processed surface, and the surface treatment film extends to the non-processed surface.

[0012] In the molding die of the present invention, the following aspects are preferably adopted. (1) The mold has a circular ring shape, and the processing surface is present within the inner surface of the circular ring shape. (2) The non-machined surface extends in a direction perpendicular to the height direction. (3) The step is larger than the thickness of the surface treatment film. (4) The surface treatment film is a carbon film. (5) Used as a drawing die or an ironing die.

[0013] According to the present invention, there is provided a method for forming a surface treatment film on a processing surface of a molding die having a processing surface that processes the surface of a workpiece by rubbing against the workpiece, the method comprising the steps of: (A) The molding die is prepared to have the following shapes (a) to (c) when viewed in cross section with the processing surface as a side surface: (a) the processed surface is located within a plane extending in the height direction; (b) having a pair of non-machined surfaces facing each other in the height direction; (c) At least one of the pair of non-machined surfaces facing each other in the height direction has the machining A step is formed that acts as a barrier in the direction of extension from the surface. (b) performing a film formation operation on the molding die, and forming the surface treatment film on the processed surface as a film base surface and on the non-processed surface as a film base surface in a portion that is continuous from the processed surface to the step; The present invention provides a method for forming a surface treatment film, characterized by the steps of:

[0014] In such a method, the following means are preferably employed. (1) Prior to the film forming operation in the step (b), at least the surface of the film substrate is pretreated. (2) Prior to the film formation operation in step (b), a masking jig is attached to the molding die so as to cover the non-processed surface except for the film base surface, and the masking jig is removed after film formation. (3) The film formation process in the step (b) is vapor deposition, and a carbon film is formed as the surface treatment film. (4) Prior to the film-forming operation, pretreatment is carried out by immersing the substrate in an alkaline solution and an acid solution. The pretreatment process involves, for example, etching the WC present in the cemented carbide substrate with an alkaline solution such as Murakami's reagent when the carbon film is a diamond film, followed by removing the Co with an acid solution such as nitric acid. This process removes Co from the substrate surface, which inhibits diamond film formation, and also improves adhesion through an anchoring effect. [Effects of the Invention]

[0015] In the molding die of the present invention, when viewed in a side cross-sectional view, the height direction is the processing direction, and at least one of a pair of surfaces that are continuous with the processing surface and face each other in the height direction has a portion where the formation of a surface treatment film, such as a mounting surface, should be avoided. For example, the mounting surface is a surface for fixing the position of the die, and is formed with a surface that comes into contact with a position fixing jig. The fact that such a surface, such as a mounting surface, where the formation of a surface treatment film should be avoided is formed via a step is a notable feature of the present invention.

[0016] In the present invention, it is desirable to form the surface treatment film continuously in the processing direction, which is the height direction when viewed in a side cross-sectional view, and up to a pair of surfaces that are connected to the processing surface and face each other in the height direction, in order to maintain the adhesion of the surface treatment film. In other words, by forming a step that acts as a barrier against the extension direction of the surface that is connected to the processing surface and faces in the height direction, even after the surface treatment film that has adhered to the mounting surface, which is the masking surface, is removed, the surface treatment film is formed in the processing direction, which is the height direction, and up to a pair of surfaces that are connected to the processing surface and face in the height direction, so that adhesion can be maintained. On the other hand, if there is no such step, the surface treatment film on the pair of surfaces that are connected to the processing surface and face each other in the height direction must all be removed to ensure the mounting surface, which raises concerns that the surface treatment film may peel off in the processing direction (height direction) during the removal work.Furthermore, since the surface treatment film is formed only in the processing direction (height direction), there is a risk of reduced adhesion.

[0017] In this way, the present invention not only reliably prevents the presence of a surface treatment film on the mounting surface of a molding die, but also ensures the dimensional accuracy of the die at low cost by eliminating the need for polishing or grinding processes after the formation of the surface treatment film while maintaining the adhesion of the surface treatment film formed in the processing direction, which is the height direction when viewed in a side cross-sectional view.

[0018] The forming die of the present invention is particularly suitable as a die for the severe ironing process performed on relatively soft metals or alloys such as aluminum and aluminum alloys, and is most suitable for forming can bodies made of these metals or alloys. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a diagram showing an example of a molding process using ironing to which the molding die of the present invention is suitably applied. [Figure 2] FIG. 2 is a side cross-sectional view showing the installation state of the ironing die in the process of FIG. 1. [Figure 3] FIG. 2 is a plan cross-sectional view showing the installation state of the ironing die in the process of FIG. 1. [Figure 4] FIG. 2 is a diagram for explaining the state of processing by the ironing die in the process of FIG. 1. [Figure 5] 1A and 1B are half cross-sectional side views of a molding die according to the present invention and diagrams showing examples of step shapes that can be adopted by the present invention. [Figure 6] 6 is a schematic plan view of a masking jig used to form a surface treatment film on the molding die of FIG. 5. DETAILED DESCRIPTION OF THE INVENTION

[0020] The forming die of the present invention is used for forming various hard materials, specifically for plastic forming. Prior to a detailed description of the configuration of this die, the forming (ironing) process from a metal plate to a seamless metal can, to which the forming die of the present invention is most suitably applied, will be described as an example.

[0021] Referring to FIG. 1 showing the above-mentioned forming process, a raw plate (e.g., an aluminum plate) 1 used for forming is first subjected to a punching process, thereby obtaining a disk 3 for drawing and ironing (see FIG. 1(a)).

[0022] In this punching process, a punch 5 having an outer diameter corresponding to the diameter of the disk 3 and a die 7 that holds the blank 1 and has an opening corresponding to the diameter of the disk 3 are used. That is, by punching the blank 1 held on the die 7 with the punch 5, a disk 3 of a predetermined size is obtained, and punching waste 9 having processing corresponding to that of the disk 3 is generated.

[0023] Depending on the shape of the molded product produced in this manufacturing process, the blank 1 may be punched out into other shapes (for example, a rectangular shape).

[0024] The disk 3 obtained as described above is subjected to drawing, thereby obtaining a low-height drawn can (bottomed cylindrical body) 11 (see FIG. 1(b)). In this drawing process, the punched disk 3 is held on a die 13, and the periphery of this disk 3 is held by a clamping jig 15. An opening is formed in the die 13, and the disk 3 is forced into the opening of the die 13 using a drawing punch 17, thereby obtaining a drawn can 11.

[0025] The upper corner of the opening of the die 13 (the side holding the disk 3) is rounded (curved), so that the disk 3 can be quickly pushed into the opening of the die 13 without breaking, and the outer diameter of the punch 17 is set smaller than the diameter of the opening of the die 13 by an amount roughly equivalent to the thickness of the disk 3. In other words, this drawing process hardly results in thinning. Furthermore, the drawing process may be performed multiple times depending on the shape of the molded product.

[0026] Next, the drawn can 11 obtained above is subjected to an ironing process, whereby a metal can base 21 having a large height and a thin wall is formed (see FIG. 1(c)).

[0027] In this process, the drawn can 11 obtained by the drawing process described above is held by the die 23 and the presser foot 25, and the ironing punch 27 is inserted into the drawn can 11 thus held and then lowered to perform the ironing process.

[0028] That is, in this ironing process, in addition to the die 23 (drawing die), an ironing die 29 is attached and fixed in position to a die mounting tool 31 and a die-fixing spacer ring 33 of the forming apparatus. The die 29 and punch 27 work together to iron the drawn can 11. For example, in the example shown in FIG. 1 , three dies 29 (29-1, 29-2, 29-3) with different inner diameters are attached along the processing direction (the direction in which the punch 27 descends). Each time the punch 27 (drawn can 19) passes through these dies 29-1, 29-2, 29-3, the sidewall of the drawn can 19 is thinned, resulting in a metal can base (ironed can) 21 with a height that increases depending on the degree of thinning. The number and inner diameter of the dies 29 can be changed as needed depending on the desired degree of thinning.

[0029] Referring to Figs. 2 and 3, which show a side cross-sectional view and a plan cross-sectional view showing the mounting configuration of the ironing dies, the above-mentioned various dies 23, 29 (29-1, 29-2, 29-3) all have an annular shape, and the above-mentioned spacer rings 33 are provided between them, respectively, and the dies 23, 29 are positioned so that the interval between them is within a certain range.

[0030] The metal can substrate 21 obtained after passing through the lowest die 29-3 and completing the thinning process by ironing is then usually extruded by a punch 27 through a hold-down ring 35 onto a doming device 40, where the bottom is processed (domed) into a shape that allows the bottom to stand upright stably. After doming, post-processing such as necking and flanging is performed, followed by printing and other processes, and the can is then sold commercially.

[0031] As shown in Figure 4, the ironing process performed by the ironing die 29 described above involves the outer surface of the sidewall of the drawn can 11 rubbing against the processing surface A of the ironing die 29 and moving in the processing direction together with the punch 27, thereby thinning the sidewall of the drawn can 11. Therefore, to ensure smooth ironing (thinning) by processing surface A of the die 29, processing surface A is a flat surface extending parallel to the processing direction, and both sides of this processing surface are tapered inclined surfaces B to ensure rapid introduction into and rapid discharge from the annular space of the die 29. Opposing flat surfaces C, C extend from the end of inclined surface B (the end opposite processing surface A), and these flat surfaces C, C are connected to the back surface D.

[0032] In this type of die 29, first, a portion of inclined surface B (B1) located upstream in the processing direction (the side connected to processing surface A) is in contact with the outer surface of the side wall of the drawn can 11, which is the workpiece, but the remaining portion of inclined surface B1 (the portion not in contact with the outer surface of the side wall of the drawn can 11), the mutually opposing flat surfaces C, C, and back surface D are non-processing surfaces that do not come into contact at all with the outer surface of the side wall of the drawn can 11. Of course, the entire inclined surface B1 can also be a processing surface that contacts the outer surface of the side wall of the drawn can 11 (see particularly Figure 4).

[0033] As can be seen from the above embodiment, the mutually opposing flat surfaces C, C and back surface D have portions, i.e., mounting surfaces, that come into contact with members for stably fixing the die 29, such as the spacer ring 33 and tool 31. Therefore, the flat surfaces C, C having the mounting surfaces that come into contact with the spacer ring 33 are surfaces that are perpendicular to the machining direction, and the back surface D having the mounting surface that comes into contact with the tool 31 is a surface that is parallel to the machining direction and the machining surface A, thereby allowing the die 29 to be positioned and fixed with high precision, and enabling stable ironing to be performed.

[0034] However, in the ironing die 29 (hereinafter sometimes simply referred to as the ironing die), ironing can cause problems such as the buildup of soft metal wear powder on the work surface A or wear of the work surface A, both of which shorten the tool life. To avoid these problems, the ironing die 29 is made of a material with rigidity and heat resistance, such as a so-called cemented carbide obtained by sintering a mixture of tungsten carbide (WC) and a metal binder such as cobalt, a cermet obtained by sintering a mixture of a metal carbide such as titanium carbide (TiC) or a titanium compound such as titanium carbonitride (TiCN) with a metal binder such as nickel or cobalt, or a hard ceramic such as silicon carbide (SiC), silicon nitride (Si3N4), alumina (Al2O3), or zirconia (ZrO2).

[0035] However, even if the ironing die 29 is made of a material with the above-mentioned rigidity and heat resistance, when the ironing process is severe and a high degree of thinning is required, it is still impossible to ignore the wear of the processing surface A and the adhesion of wear powder to the processing surface A. As a result, a method is adopted in which a hard surface treatment film is provided on at least the processing surface A of the ironing die 29.

[0036] Typical surface treatment films with excellent wear resistance, seizure resistance, etc. are hard films such as TiC, TiN, TiAlN, CrN, and diamond-like carbon (DLC), and among these, carbon films containing diamond crystals, such as DLC and polycrystalline diamond, are particularly suitable.

[0037] The carbon film (i.e., the surface treatment film) is a carbon nanotube having a structure represented by the following formula (1): I D / I G (1) During the ceremony, I D is the Raman spectrum of the carbon film surface at 1333±10 cm -1 in is the maximum peak intensity of I Gis the Raman spectrum of the carbon film surface at 1500±100 cm -1 is the maximum peak intensity at It is preferable that the intensity ratio represented by the following formula is in the range of 0.5 to 10.0, particularly 0.8 to 3.0.

[0038] The above 1333±10cm -1 Maximum peak intensity at I D is due to the diamond component in the film, and is 1500±100cm -1 Maximum peak intensity at I G is derived from the graphite component in the film. The smaller the peak intensity ratio, the greater the graphite content, and the greater the peak intensity ratio, the closer the film resembles diamond crystals. A carbon film suitable for surface treatment contains a graphite component that satisfies the above intensity ratio, which ensures excellent hardness and adhesion to the underlying rigid substrate (ironing die 29), and exhibits good impact resistance. For example, even when subjected to severe ironing, peeling of the film can be effectively prevented, thereby achieving a long service life for the processing jig.

[0039] The above-mentioned carbon film is produced by forming a film on at least the processing surface A of the die 29 using a known method such as a hot filament CVD method or a plasma CVD method, for example, a microwave plasma CVD method, a high frequency plasma CVD method, or a thermal plasma CVD method, and then polishing the surface.

[0040] In film formation, the source gas generally used is a hydrocarbon gas such as methane, ethane, propane, or acetylene diluted with hydrogen gas to about 1%. Small amounts of oxygen, carbon monoxide, carbon dioxide, or other gases may be mixed into this source gas as appropriate to adjust the film quality and film formation rate.

[0041] Using the above-mentioned raw material gas, the ironing die 29 having the processing surface A is heated to a high temperature of 700 to 1000°C, plasma is generated by microwaves, high frequency waves, etc., the raw material gas is decomposed in the plasma to generate active species, and diamond crystals are grown on the processing surface A, thereby forming a film. During this film formation, hydrogen atoms dissociated in the plasma selectively etch the graphite and amorphous carbon formed on the processing surface A, resulting in a film with a high diamond content and a peak intensity ratio in the Raman spectroscopy spectrum within the aforementioned range.

[0042] Although the manufacturing method for the carbon film has been shown, when forming a surface treatment film using inorganic oxides of other materials, the film can also be formed on the processing surface A by a conventionally known method such as CVD or PVD, as described above.

[0043] However, the surface of the above-mentioned surface-treated films, especially those formed by CVD, is likely to become rough because it is selectively etched as necessary during film formation to promote crystal growth. For this reason, it is desirable to smooth the surface by polishing after film formation.

[0044] The surface of the surface-treated film can be polished by a known method. For example, it may be a mechanical polishing method using a grinding stone such as diamond abrasive grains, or a polishing method utilizing chemical action. A polishing method that combines these mechanical and chemical techniques is also acceptable. By using these polishing methods, it is optimal to adjust the arithmetic mean surface roughness Ra (JIS-B-0601) of the film to 0.1 μm or less, especially 0.05 μm or less.

[0045] Incidentally, the above-mentioned surface treatment film basically needs to be formed only on the work surface A (and part of the inclined surface B1) that comes into contact with the outer surface of the side wall of the drawn can 11, which is the workpiece. However, in this case, the film is likely to peel off from its edges as the ironing process continues. For this reason, such a surface treatment film is generally formed not only on the work surface A, but also on the inclined surfaces B1 and B2 and the opposing flat surfaces C and C.

[0046] However, extending the area where the surface treatment film is formed beyond the processing surface A and forming the surface treatment film on the non-machined surface, which is not machined, creates a new problem. Specifically, the pair of flat surfaces C, C and the back surface D, which are the non-machined surfaces, have mounting surfaces that come into contact with components for stably fixing the die 29, such as the spacer ring 33 and the tool 31, as can be seen particularly from Figures 2 and 3. Therefore, if the surface treatment film is formed on these surfaces C and D, the mounting accuracy of the die 29 will be reduced, and the accuracy of the ironing process will be impaired. Therefore, after the surface treatment film is formed, it is necessary to remove the surface treatment film formed on the mounting surfaces by polishing or grinding, which results in inconveniences such as reduced productivity, increased production costs, and reduced adhesion of the processing surface A.

[0047] In the present invention, it is possible to reliably avoid the formation of the above-mentioned surface treatment film on the mounting surface, and to eliminate the need for steps such as polishing after the formation of the surface treatment film.

[0048] <Configuration of ironing die to which the present invention is applied> 5, an ironing die 50 to which the present invention is applied has a circular ring shape, similar to the ironing die 29 described above, and has a processing surface A extending parallel to the processing direction (height direction), which is continuous with an inclined surface B, which has a pair of flat surfaces C (the upstream side with respect to the processing direction is indicated as a top surface C1 and the downstream side as a bottom surface C2) perpendicular to the processing direction, and further has a back surface D extending parallel to the processing surface A. This configuration is basically the same as the ironing die 29 described above.

[0049] 5, the inclined surface B on the upstream side in the processing direction relative to the processing surface A is indicated by B1, while the inclined surface B on the downstream side in the processing direction is indicated by B2. Of course, the downstream inclined surface B2 can be formed in two or more stages. However, from the viewpoint of preventing peeling of the surface treatment film on the inclined surface B1, which is subjected to the greatest molding pressure, it is preferable to form at least one of the inclined surfaces B1 or B2 on the upstream or downstream side in the processing direction as multi-stages, and to reduce the inclination angle relative to the processing surface A.

[0050] In the ironing die 50 of this type, in the present invention, a step 51 is formed on the top surface C1 extending from the inclined surface B (particularly the inclined surface B1 on the upstream side in the processing direction), and a surface on which the formation of a surface treatment film is to be avoided, such as the mounting surface X, is formed on either side of this step 51. That is, as can be seen from Fig. 5, a major feature of the present invention is that the step 51 is formed so as to act as a barrier against the extension direction of the top surface C1 extending from the inclined surface B (B1).

[0051] That is, such a step 51 is formed, and further, a surface treatment film 53 is formed on the processing surface A and the inclined surface B (B1, B2), but this surface treatment film 53 is not formed at all on the mounting surface X because the step 51 acts as a barrier. Moreover, this configuration can be obtained without performing a polishing process or the like after the surface treatment film 53 is formed.

[0052] When forming the surface treatment film 53 in the above manner, for example, the pretreatment work is performed while covering the mounting surface X with a masking jig, and then the masking jig is removed and the surface treatment film 53 is formed. After the film formation, the surface treatment film also adheres to the mounting surface X, but since its adhesion is weaker than that of the non-masked surface, it can be easily removed with commercially available diamond or ceramic grinding stones, sponge abrasives, etc. This makes it possible to avoid the formation of the surface treatment film on the mounting surface X.

[0053] The shape of the step 51 is not particularly limited as long as it is a shape that acts as a barrier against the extension direction of the top surface C1 extending from the inclined surface B (B1) (i.e., a shape that can prevent the extension of the surface treatment film).For example, a vertical shape (see Figure 5(a)) is most preferable, but it may also be a tapered (inclined) shape (see Figure 5(b)), an R-shape (see Figure 5(c)), or other shapes.

[0054] Furthermore, the height of the step 51 needs only to be less than the thickness of the surface treatment film 53. If this height is greater than the film thickness, the dimensional accuracy of the mounting surface cannot be obtained. For example, if the thickness of the surface treatment film 53 is 5 to 50 μm, a height of 51 μm for the step 51 is sufficient.

[0055] 6, the ironing die 50 is sandwiched between masking jigs 60a and 60b, which cover the mounting surface X of the top surface C1 on the upstream side in the processing direction and the entire bottom surface C2 on the downstream side in the processing direction, and then perform surface treatment to form the surface treatment film 53. At this time, no step is formed on the bottom surface C2, but because the masking jig 60b covers the entire bottom surface C2, the end of the surface treatment film 53 is located at the end of the inclined surface B2. However, because it is located on the downstream side in the processing direction, the problem of film peeling during ironing can be ignored.

[0056] 6 shows plan views of masking jigs 60a and 60b. As can be seen from these figures, these jigs 60a and 60b are ring-shaped and can be fastened with screws 63 through screw holes 65, thereby clamping the ironing die 50 and forming the surface treatment film 53. Although not shown in FIG. 6, by providing a cylindrical side wall of an appropriate size on one of the jigs 60a and 60b, the back surface D (the outer peripheral surface of the mold) can be masked.

[0057] The masking jigs 60a, 60b and screws mentioned above are made of materials with excellent chemical resistance, such as stainless steel (SUS), polypropylene (PP) and polytetrafluoroethylene (PTFE), which allows them to be repeatedly used in pretreatment processes such as Co removal using alkaline solutions such as Murakami's reagent or acidic solutions containing nitric acid.

[0058] In the present invention, the ironing process using the ironing die 50 described above can be applied to various metals or alloys, such as aluminum, copper, iron, or alloys containing these metals, as well as surface-treated steel sheets such as tin-plated steel sheets and aluminum sheets that have been subjected to a chemical conversion treatment, and pre-coated metal sheets having an organic coating on at least one surface, and severe ironing processes with a high ironing rate can be repeatedly performed. In particular, ironing using the annular ironing die 50 can be suitably used in ironing when producing metal can bodies by the process shown in FIG. 1, and is most suitably applied to the production of aluminum cans. [Explanation of symbols]

[0059] 50: Ironing die (molding die) 51: Step 53: Surface treatment film A: Machining surface B: Inclined surface continuing to machining surface A C, C: A pair of unmachined surfaces facing each other in the vertical direction D: Back side of the processed surface 60a, 60b: Masking jig 63: Bis 65:Screw hole

Claims

1. A molding die having a processing surface that processes the surface of a workpiece by rubbing against the workpiece, A molding die having the following shapes (a) to (d) when viewed in cross section, in which the processed surface is a side surface: (a) the processing surface is located within a plane extending in the height direction; (b) having a pair of non-machined surfaces facing each other in the height direction; (c) a step is formed on at least one of the pair of non-machined surfaces to serve as a barrier in an extension direction continuing from the machined surface; (d) A surface treatment film is formed on the processed surface, and the surface treatment film extends to the non-processed surface.

2. 2. The molding die according to claim 1, wherein the die has a circular ring shape, and the processing surface is present within the inner surface of the circular ring shape.

3. The molding die according to claim 1 or 2, wherein the non-processing surface extends in a direction perpendicular to the height direction.

4. 4. The molding die according to claim 1, wherein the step is larger than the thickness of the surface treatment film.

5. 5. The mold for molding according to claim 1, wherein the surface treatment film is a carbon film.

6. 3. The molding die according to claim 1, which is used as a drawing die or an ironing die.

7. A method for forming a surface treatment film on a processing surface of a molding die having a processing surface that processes the surface of a workpiece by rubbing against the workpiece, comprising: (A) The molding die is prepared to have the following shapes (a) to (c) when viewed in cross section with the processed surface as a side surface: (a) the processing surface is located within a plane extending in the height direction; (b) having a pair of non-machined surfaces facing each other in the height direction; (c) At least one of the pair of non-machined surfaces facing each other in the height direction has the machining A step is formed that acts as a barrier in the direction of extension from the surface. (b) performing a film formation operation on the molding die, and forming the surface treatment film on the processed surface as a film base surface and on the non-processed surface as a film base surface in a portion that is continuous from the processed surface to the step; A method for forming a surface treatment film, characterized by:

8. 8. The method according to claim 7, wherein at least the surface of the film substrate is pretreated prior to the film formation operation in step (b).

9. 8. The method according to claim 7, wherein, prior to the film formation operation in step (b), a masking jig is attached to the molding die so as to cover the non-processed surface except for the film base surface, and the masking jig is removed after the film formation.

10. 8. The method according to claim 7, wherein the film formation in step (b) is vapor deposition, and a carbon film is formed as the surface treatment film.

11. 8. The method according to claim 7, wherein a pretreatment is carried out by immersing the substrate in an alkaline solution and an acid solution prior to the film-forming operation.

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