JP2011200912A - Method and die for pressing metallic member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a die for pressing a metallic member, which are suitable to press the metallic member which is difficult to work, such as a titanium member and a magnesium member.SOLUTION: The die for pressing has a fine recessed and projection part which includes fine recesses and projections which are formed in at least a part of a portion which is brought into contact with the metallic member and have maximum surface roughness of 3-25 μm and a fluororesin film which is formed in the fine recessed and projection part so that only a part of a plurality of top parts included in the fine recessed and projection part is exposed, and the fluororesin film is adhered closely to the surface of the fine recessed and projection part.

Description

  The present invention relates to a method of pressing a metal member such as drawing, bending, and forging, and a press working die used for the pressing.

  2. Description of the Related Art Conventionally, a mold is used for pressing a member made of a metal such as titanium, magnesium, and aluminum (hereinafter referred to as “metal member”), and molding a resin product, a rubber product, or the like. When performing press processing or molding using a mold, lubrication and releasability (ease of peeling) between the mold and a metal member or resin product is required, and the mold is a metal member or resin product. It is desirable that it is easily peeled off.

  Conventionally, with regard to making a mold easily peeled off from a metal member, a resin product, etc., for example, a technique for forming an ultra-hard film such as DLC (Diamond Like Carbon) on a mold (for example, see Patent Document 1), a fluororesin A technique for forming a fluororesin film on a mold by applying a paint or the like (see, for example, Patent Documents 2, 3, and 4) has been known. Since the fluororesin film is flexible and is likely to be peeled off or damaged by repeatedly using a mold, the techniques described in Patent Documents 2 to 4 increase the durability of the fluororesin film.

JP 2003-154418 A JP 2004-74646 A JP-A-9-193164 JP-A-5-245848

  According to each prior art described in Patent Documents 2 to 4, the strength of the fluororesin film itself can be increased.

  However, these conventional technologies are technologies for molds used for molding of resin products, rubber products, etc., and are applicable to molds used for press processing of metal parts such as drawing, bending and forging. It was difficult to do. A mold used for molding a resin product, a rubber product, or the like is used as a so-called mold for pouring resin or the like into a space (gap) formed by the mold to form a desired shape.

  For example, if there are molds 100 and 101 as shown in FIG. 19, in these molds 100 and 101, a fluororesin film 102 is formed on the surface of the inner part in contact with the resin or the like. Then, the fluororesin film 102 receives a pressure f1 in a direction intersecting the inner surfaces of the molds 100 and 101 from the resin 103.

  On the other hand, it is assumed that there are dies 200, 201, and 202 as shown in FIG. When the metal member 203 is bent using these molds 200, 201, and 202, the mold 202 moves in the direction of the arrow P. At this time, the molds 200, 201, and 202 are in contact with the metal member 203. It is strongly pressed or rubbed against the surface. Therefore, the molds 200, 201, and 202 receive not only the pressure f2 in the direction intersecting the surface of the mold but also the pressure f3 in the direction along the surface from the metal member 203.

  The pressure f2 in the direction intersecting the surface acts to press against the surface of the mold against the fluororesin film, but the pressure f3 in the direction along the surface follows the surface of the mold against the fluororesin film. Acts like scraping. Therefore, even if a fluororesin film having increased strength as in the prior art is formed on the surfaces of the molds 200, 201, 202, a strong pressure in the direction along the surface such as the pressure f3 is applied, The fluororesin film is easily scraped off in the direction along the surface of the mold, and the fluororesin film is easily peeled off from the surface of the mold. For this reason, there is a problem that press working cannot be repeatedly performed in a mold in which a fluororesin film is used as a film (lubricant film) in order to improve lubricity and releasability between the mold and the metal member.

  On the other hand, among metal members, metal members made of pure titanium or titanium alloys (hereinafter referred to as “titanium members”) and metal members made of magnesium alloys (hereinafter referred to as “magnesium alloy members”) are likely to be welded to the mold. Conventionally, press working has been performed using a lubricant such as lubricating oil, and it has been extremely difficult to work in a dry environment without using a lubricant.

  In order to press the titanium member and the magnesium alloy member in a dry environment without using a lubricant, it is desirable to form a fluororesin film as a lubricant film on the mold.

  However, as described above, since the fluororesin film has poor durability and the mold having the fluororesin film cannot be repeatedly pressed, conventionally, a sheet-like member such as a Teflon sheet (Teflon is a registered trademark) is used. As a result, processing was performed in a dry environment. In such a dry environment, there is a problem that, for example, in the case of drawing, drawing cannot be repeated, and complicated shapes cannot be machined.

  Therefore, the present invention has been made to solve the above problems, and in a metal member pressing method and a pressing mold used for the pressing, the pressing process is repeated even if the fluororesin film is used as a lubricating film. In addition to improving the durability of the mold so that it can be performed, it is possible to process metal parts that are difficult to process (hard metal parts) such as titanium members and magnesium alloy members in a dry environment without using sheet-like members such as Teflon sheets. It aims to be able to do.

  In order to solve the above-mentioned problems, the present invention is a method of pressing a metal member using a mold, wherein a fine uneven portion having a fine unevenness having a maximum surface roughness of 3 μm or more and 25 μm or less is formed on the surface of the mold. A fluororesin film having a thickness exceeding the maximum surface roughness is formed on at least a part of the portion in contact with the metal member, and a pressing mold is manufactured. The fluororesin film is directly connected to the metal member. The metal member is pressed using a pressing mold so as to be in contact with the metal member.

  In this pressing method, since the fine irregularities are formed on the surface of the pressing mold, the surface area of the mold is enlarged, and the fluororesin film is formed on the surface of the fine irregularities. The resin film is caught by the unevenness of the fine uneven part, and the fine uneven part holds the fluororesin film so as not to be displaced along the surface. Further, the fluororesin film is in direct contact with a wide range of the metal member, and the coefficient of friction is kept low. The fluororesin film penetrates into the concave portions of the fine irregularities, and the fluororesin film becomes a lubricant during press working. Therefore, by pressing using a pressing mold so that the fluororesin film is in direct contact with the metal member, it is possible to press difficult-to-process metal members without using sheet-like members such as lubricants and Teflon sheets. Can be processed.

  In the above press working method, when the mold is made of cemented carbide steel, the fine irregularities are formed so that the maximum surface roughness is 3 μm or more and 10 μm or less, and the mold is steel other than cemented carbide steel. It is preferable that the fine irregularities be formed so that the maximum surface roughness is 10 μm or more and 25 μm or less.

  By keeping the maximum surface roughness in the above range, the effect of preventing the fluororesin film from being joined by the fine unevenness can be obtained while keeping the friction coefficient at a low value.

  Furthermore, in the above press working method, it is preferable to apply a fluororesin to the fine irregularities when the press work is repeated.

  If it does in this way, a fine uneven part will be replenished with the fluororesin which the fluororesin film | membrane lost by press work apply | coated.

  In the above-mentioned press working method, it is preferable to perform the press working in the warm range from the normal temperature set in the range of 10 ° C. to the maximum continuous use temperature of the fluororesin. In this temperature range, the spreadability of the titanium member and the magnesium member is particularly enhanced and the molding becomes easy.

  And this invention is a metal mold | die for press work used for the press work of a metal member, Comprising: The largest surface roughness formed in at least one part of the part which contact | connects a metal member was equipped with the fine unevenness | corrugation of 3 micrometers or more and 25 micrometers or less. There is provided a press working die having a fine uneven portion and a fluororesin film formed on the fine uneven portion, wherein the fluororesin film is in close contact with the surface of the fine uneven portion.

  In this mold, since the fine irregularities are formed on the surface, the surface area of the mold is enlarged, and the fluororesin film is formed on the surface of the fine irregularities. The fine irregularities are stuck to the fluororesin film so as to catch on the irregularities and not shift along the surface. Further, the fluororesin film is in direct contact with a wide range of the metal member, and the coefficient of friction is kept low. The fluororesin film penetrates into the concave portions of the fine irregularities, and the fluororesin film becomes a lubricant during press working.

  In the case of this press working mold, the fine irregularities are formed so that the maximum surface roughness is 3 μm or more and 10 μm or less when the mold is made of cemented carbide steel, and the mold is made of steel other than cemented carbide steel. In some cases, the maximum surface roughness is preferably 10 μm or more and 25 μm or less.

  As described above in detail, according to the present invention, the metal member press working method and the press working die used for the press working can be used so that the press work can be repeated even if the fluororesin film is a lubricating film. While improving the durability of the mold, it is possible to perform dry processing on difficult-to-work metal members such as titanium members and magnesium alloy members.

It is a figure which shows schematic structure of the press work apparatus which concerns on embodiment of this invention. FIG. 4 is a cross-sectional view schematically showing the surface of the blank holder including the fine irregularities and the fluororesin film, taken along the line 2-2 in FIG. It is a top view which shows the surface of a blank holder typically. It is sectional drawing which shows typically the part which the fine uneven | corrugated | grooved part of a blank holder, the fluororesin film | membrane, and the metal plate are contacting. It is sectional drawing which shows typically a mode that a fluororesin film | membrane deform | transforms in the case of press work. It is sectional drawing which shows typically the fine uneven | corrugated | grooved part and fluororesin film | membrane after press work. It is sectional drawing which shows another fluororesin film | membrane and a fine uneven | corrugated | grooved part typically. BRIEF DESCRIPTION OF THE DRAWINGS It is a side view which shows typically the manufacturing process of the metal mold | die for press work, (A) is a metal mold | die before manufacture, (B) is a metal mold | die after forming a fine uneven part on the surface, (C) is a fine unevenness | corrugation. The metal mold | die after forming the fluororesin film | membrane on the surface of a part is shown. It is the photograph which showed an example of the molded article manufactured by drawing. The experimental result which investigates the change of a friction coefficient in case the maximum surface roughness is 0.5 micrometer is shown, (A) shows the photograph which image | photographed the base-material surface with the microscope, (B) is a graph which investigates the change of a friction coefficient. is there. The experimental result which investigates the change of a friction coefficient in case the maximum surface roughness is 5 micrometers is shown, (A) shows the photograph which image | photographed the base-material surface with the microscope, (B) is a graph which investigates the change of a friction coefficient. The experimental result which investigates the change of a friction coefficient in case the maximum surface roughness is 14.8 micrometers is shown, (A) shows the photograph which image | photographed the base-material surface with the microscope, (B) is a graph which investigates the change of a friction coefficient. is there. The experimental result which investigates the change of a friction coefficient in case the maximum surface roughness is 33 micrometers is shown, (A) shows the photograph which image | photographed the base-material surface with the microscope, (B) is a graph which investigates the change of a friction coefficient. The experimental result for confirming that the durability is improved is shown. (A) shows a case where a fluororesin film is formed by a fluororesin coating technique using no primer, and (B) shows a fluororesin film made of PTFE. In the case, (C) shows a case where the fluororesin film is formed by one coat. It is a graph which shows the change of the original friction coefficient before the friction coefficient of a test piece (TF50) rises. (A) is a graph showing the change of the friction coefficient when the friction test is performed at 200 N (5 minutes) after the friction coefficient of the test piece (TF50) is increased, and (B) is the friction coefficient after repainting. It is a graph which shows the change of. (A) is a graph which shows the change of the friction coefficient of another test piece (TF50) before repainting, (B) is a graph which shows the change of the friction coefficient after repainting. (A) is a photograph of the mold surface when only a part of the top is exposed without being covered with the fluororesin film, and (B) is that more tops are covered with the fluororesin film. It is a photograph of the mold surface when it is completely exposed. It is sectional drawing which shows an example of the conventional metal mold | die for resin molding, and resin. It is sectional drawing which shows an example of the metal mold | die for a conventional press work, and a metal member.

  Embodiments of the present invention will be described below. In addition, the same code | symbol is used for the same element and the overlapping description is abbreviate | omitted.

(Structure of press processing equipment)
First, the press working apparatus 10 will be described with reference to FIG. FIG. 1 is a diagram showing a schematic configuration of a press working apparatus according to an embodiment of the present invention. The press working apparatus 10 is an apparatus for performing the press working method according to the embodiment of the present invention, and is a device that performs press working of a metal member by dry pressing. In the present embodiment, the press work means that a metal member is deformed by a machine using a tool such as a mold, and plasticity such as shearing, drawing, bending, overhanging, forging, extrusion, and coining. It means the whole processing. The dry press means press working in a dry environment in which no sheet-like member such as a lubricant and a Teflon sheet is used.

  As shown in FIG. 1, the press working apparatus 10 includes a die 1 and a blank holder 2 as a press working die according to the present invention, and a punch 3. The press working apparatus 10 is an apparatus that presses a metal plate 11 that is a plate-like metal member sandwiched between the die 1 and the blank holder 2 to process it into a desired molded product.

  The die 1 and the blank holder 2 have fine uneven portions 1a, 2a and a fluororesin film 5, respectively, and the fluororesin film 5 is formed as a lubricating film. In FIG. 1, fine uneven portions 1a and 2a are formed on the portions of the die 1 and the blank holder 2 with dots, and a fluororesin film 5 is formed on the surface thereof. In the press processing apparatus 10, dry pressing is performed and no sheet-like member such as a lubricant and a Teflon sheet is used at the time of press processing. Therefore, the die 1 and the blank holder 2 are in direct contact with the metal plate 11.

  In the press working apparatus 10, the main configuration of the portion in contact with the metal plate 11 in the die used for press working is divided into a die 1, a blank holder 2, and a punch 3. Among them, the fluororesin film 5 is essential for the die 1 and the blank holder 2 that requires a blank holding force. Since the punch 3 requires friction holding force, the fluororesin film 5 is not required.

  For this reason, as shown in FIG. 1, the die 1 is formed with the fine concavo-convex portions 1 a and the fluororesin film 5 on and around the portion in contact with the metal plate 11 at the start of pressing, and the blank holder 2 The fine concavo-convex portion 2a and the fluororesin film 5 are formed on the portion in contact with the metal plate 11 at the start of press working.

  As described above, the fine uneven portions 1 a and 2 a are formed on a part of the surfaces of the die 1 and the blank holder 2. The die 1 and the blank holder 2 are in contact with the metal plate 11 at a part of the entire surface of the die 1 and the blank holder 2, and during the press working in the portion in contact with the metal plate 11, strong pressure is applied from the metal plate 11. The fine irregularities 1a and 2a are formed in a portion that can be received.

  The fine uneven portions 1a and 2a are so fine that the shape and size cannot be clearly recognized with the naked eye, that is, they are very fine and have irregular and complicated uneven portions. As shown in FIG. 2, the irregularities of the fine irregularities 2a (same for 1a) mean irregularities in the surface with irregular sizes and intervals and including many tops, bottoms and depressions, which will be described later. It is. Here, FIG. 2 is a cross-sectional view schematically showing the surface of the blank holder 2 including the fine irregularities 2 a and the fluororesin film 5, and is a cross-sectional view taken along line 2-2 in FIG. 3. FIG. 2 and 3 show the fine uneven portion 2a of the blank holder 2, the fine uneven portion 1a of the die 1 has the same structure as the fine uneven portion 2a, although not shown.

  The fine uneven portion 2a has a large number of tops including a plurality of tops P1, P3, P5, P7, P9, P11 and a large number of bottoms including a plurality of bottoms P2, P4, P6, P8, P10. Yes. The fine uneven portion 2a (same for the fine uneven portion 1a) is subjected to surface treatment such as blasting on the surface of the blank holder 2 (die 1) to obtain the maximum surface roughness (in this embodiment, the maximum height roughness). The thickness Rz is also set to 3 μm or more and 25 μm or less. Note that, in the fine uneven portion 2a, the top is the tip, the periphery, and the bottom of the portion protruding outside the reference line L that is the reference of the height of the fine uneven portion 2a than the reference line L. The tip of the part recessed inside and its periphery are meant, and the concave means a part other than the top.

  For example, in the fine uneven portion 2a shown in FIG. 2, the maximum surface roughness is the summit portion (the top portion P5 in FIG. 2) that protrudes to the outermost side among the plurality of top portions and the plurality of bottom portions. The surface roughness is evaluated using the height difference h1 from the most concave bottom (bottom P4 in FIG. 2). That is, the maximum surface roughness (maximum height roughness Rz) being 3.0 μm means that h1 is 3.0 μm. Although there is a method of evaluating the surface roughness by taking the average of the height differences of the plurality of bottom portions or the top portions P1 to P11, in this embodiment, the maximum height roughness Rz is adopted.

  The die 1 and the blank holder 2 are formed using a metal such as steel, but the maximum surface roughness needs to be set to a certain size in order to make the recesses to a certain size. By forming the fine irregularities 1a and 2a on the surfaces of the die 1 and the blank holder 2, as shown in FIG. 2, a large number of concave portions having irregular sizes and shapes appear on the surfaces of the die 1 and the blank holder 2, A part of the fluororesin film 5 enters the recess so as to block all the recesses.

  In order to make the volume of the fluororesin film 5 entering the recesses to some extent and to make the structure of the unevenness of the fine unevenness 2a intricately complicated, at least the maximum surface roughness is preferably 3 μm or more. . On the other hand, if the maximum surface roughness is increased, the volume of the fluororesin film 5 entering the recesses also increases. However, since the fine irregularities 2a can receive a strong pressure from the metal plate 11 during the press working, the maximum surface roughness is reduced. If it exceeds 25 μm, the portion protruding from the reference line L is not preferred because it tends to be broken or broken during press working. Further, the friction coefficient of the die 1 and the blank holder 2 may be too high.

  Therefore, it is preferable that the maximum surface roughness of the fine irregularities 1a and 2a be 3 μm or more and 25 μm or less. For example, when manufacturing the die 1 and the blank holder 2 using a steel other than the cemented carbide steel, it is preferable that the maximum surface roughness is slightly larger than 10 μm to 25 μm. More preferably, the maximum surface roughness is about 14.8 to 15 μm. In addition, since cemented carbide steel is harder and stronger than steels other than cemented carbide steel, when manufacturing die 1 and blank holder 2 using cemented carbide steel, the maximum surface roughness is slightly smaller than 3 μm. The thickness is preferably 10 μm or less.

  Next, the fluororesin film 5 is formed on the respective surfaces of the fine irregularities 1a and 2a. The fluororesin film 5 has such a thickness that only a part of the tops included in the fine irregularities 1 a and 2 a is exposed without being covered by the fluororesin film 5. In the case of the fine concavo-convex portion 2a, as shown in FIG. 3, in the fluororesin film 5, only the most protruding top portion P5 is exposed among the plurality of top portions P1, P3, P5, P7, P9, P11, and the other portions The top is thick enough to be covered. Therefore, the fluororesin film 5 has a thickness slightly smaller than the maximum surface roughness of each of the fine uneven portions 1a and 2a.

The fluororesin film 5 is formed in close contact with the surfaces of the fine concavo-convex portions 1a and 2a and entering the concave portions so as to block all the concave portions.
The fluororesin film 5 can be formed by coating a fluororesin such as polytetrafluoroethylene (PTFE), perfluoroethylene propene copolymer (FEP), perfluoroalkoxyalkane (PFA), for example. In the present embodiment, in consideration of the direct coating of the fluororesin and the fact that the fluororesin is easily peeled off, the surface of the fine irregularities 1a and 2a is coated with a mixed fluororesin mixed with a primer to obtain a fluororesin film. 5 (details will be described later).

(Operation details of the press machine)
Then, the operation | movement content of the press work apparatus 10 which has the above structure is demonstrated with reference to FIGS. 4-7 with FIG. FIG. 4 is a cross-sectional view schematically showing a portion where the fine uneven portion 2a and the fluororesin film 5 of the blank holder 2 are in contact with the metal plate 11, and FIG. 5 is a diagram illustrating the deformation of the fluororesin film 5 during press working. It is sectional drawing which shows a mode typically. FIG. 6 is a cross-sectional view schematically showing the fine uneven portion 2a and the fluororesin film 5 after pressing, and FIG. 7 is a cross-sectional view schematically showing another fluororesin film and the fine uneven portion 2a.

  In the press working device 10, for example, a circular metal plate 11 is sandwiched between the die 1 and the blank holder 2 and pressed by pressing the punch 3 against the metal plate 11 with a hydraulic device (not shown) from one side. Processing.

  As the punch 3 enters, the metal plate 11 is pushed and deformed. At that time, the metal plate 11 is deformed while moving in the approach direction of the punch 3 while being strongly pressed against the die 1 and the blank holder 2.

  Then, the fluororesin film 5 is formed to a thickness that exposes only the most projecting apex P5, and all other apexes are covered with the fluororesin film 5. Therefore, the fluororesin film 5 is in direct contact over a wide range of the metal plate 11 and acts as a lubricant that keeps the coefficient of friction between the die 1 and the blank holder 2 and the metal plate 11 low and improves slipping. .

  Moreover, the fluororesin film 5 is in close contact with the surfaces of the fine irregularities 1a and 2a. The surface area of the die 1 and the blank holder 2 is enlarged by forming the fine irregularities 1a and 2a on the surface. In addition, irregularities and irregularities with irregular shapes and sizes are formed, and the fluororesin film 5 enters into a large number of depressions with irregular shapes and sizes, so that the fluororesin film 5 has fine irregularities. It is firmly stuck to the unevenness of 1a and 2a. For this reason, the fine uneven portions 1a and 2a exert an action of firmly connecting the fluororesin film 5 so as not to be displaced along the surface.

  On the other hand, since only the top P5 is exposed without being covered with the fluororesin film 5 among the plurality of tops, the entire thickness direction of the fluororesin film 5 is formed by any top including the top P5. It is supposed to be accepted.

  During the press working, a pressure in the direction along the surface of the blank holder 2 (pressure F2 in FIG. 4) acts on the fluororesin film 5 from the metal plate 11. The pressure F2 acts so as to scrape the fluororesin film 5 in the direction along the surface of the die 1 or the blank holder 2, but the recess and the top are formed in a direction intersecting the direction of the pressure F2. The concave portion and the top portion obstruct the movement of the fluororesin film 5 due to the pressure F2, and try to prevent the fluororesin film 5 from peeling off.

  In addition, the irregularities of the fine irregularities 1a and 2a are irregular and complex in size and shape, and fine irregularities are also formed on the surface of each depression as shown in FIG. . Therefore, the degree to which the fluororesin film 5 is in close contact with the fine irregularities 1a and 2a is higher than when regular irregularities are formed.

  Therefore, the fluororesin film 5 tends to stay on the surfaces of the die 1 and the blank holder 2 during the press working, and as a result, the function as a lubricant that suppresses the friction coefficient generated between the fluororesin film 5 and the metal plate 11. Is effective. Therefore, the die 1 and the blank holder 2 have high durability so that the press working can be repeated even if the fluororesin film 5 is a soft lubricating film.

  Here, as shown in FIG. 7, the fluororesin film 105 having a thickness sufficient to cover all the tops including the top P5 (that is, a thickness larger than the maximum surface roughness) is the surface of the mold. Consider the case where it was formed. In the case of this mold, a part of the fluororesin film 105 becomes the surface layer part 106 (the part to which the dots of FIG. Since the top portion of the surface layer portion 106 does not exist at all in the direction along the surface, it cannot receive any tethering by the top portion. For this reason, when pressure is applied in the direction along the surface during press working, it is easily peeled off.

  If the fine irregularities 1a and 2a are formed on the surface of the die 1 and the blank holder 2, the effect of preventing the connection to the fluororesin film 5 can be expected, but the thickness of the fluororesin film to be formed is limited to a part of the top. If the thickness is not exposed, it is not preferable because the fluororesin film is likely to be wasted because it does not function as a lubricant.

  On the other hand, as shown in FIG. 4, during the press working, the fine irregularities 1a and 2a and the fluororesin film 5 are applied to the surface together with the pressure F1 in the direction intersecting the surfaces of the fine irregularities 1a and 2a from the metal plate 11. A pressure F2 in the direction along is received. Since the fluororesin film 5 is flexible, it is deformed by the pressures F1 and F2 as shown in FIG. 5, for example. Among the portions entering the recess, the upper portion is received by the recess relative to the lower portion. It is difficult

  For example, as shown in FIG. 2, the portion of the fluororesin film 5 that has entered the recess 2b increases the distance between the top portions P1 and P3 and the bottom portion P2 toward the upper portion and moves to the surface of the fine uneven portions 1a and 2a. , And the pressure from the metal plate 11 is more easily received by the pressures F1 and F2. Therefore, a part of the fluororesin film 5 may be peeled off in the direction along the surfaces of the fine irregularities 1a and 2a by press working.

  As a result, as shown in FIG. 6, the thickness of the fluororesin film 5 is slightly reduced, and the top portions P3 and P7 protruding next to the top portion P5 may be exposed in addition to the top portion P5. However, the fluororesin film 5 still remains in the recess between the two adjacent tops while being in close contact with the surfaces of the fine uneven portions 1a and 2a. The fluororesin film 5 remaining in the concave portion is deformed by the pressure F1 during the press working and enters between the surface of the fine concave and convex portions 1a and 2a and the metal plate 11 to reduce the friction coefficient of both. Acts as a lubricant to improve slipping. Therefore, by using the die 1 and the blank holder 2, the metal plate 11 can be repeatedly pressed with high lubricity.

  In this way, the press working apparatus 10 can perform dry pressing while fully utilizing the good lubricity of the fluororesin film 5, and therefore presses metal members that are likely to be welded to a mold such as a titanium member or a magnesium alloy member. It is extremely good for processing.

  On the other hand, when the press processing of the metal plate 11 is repeatedly performed by the press processing apparatus 10, the fluororesin film 5 gradually entering the concave portion is lost. Then, since the lubricant gradually decreases, the coefficient of friction between the die 1, the blank holder 2, and the metal plate 11 increases, and in particular, welding with a mold such as a titanium member or a magnesium alloy member. An unfavorable situation may occur in the press working of a metal member that is liable to cause erosion.

  When repeatedly performing such pressing, preferably at least fine irregularities of the die 1 and the blank holder 2 by spraying a liquid fluororesin with a spray when the coefficient of friction exceeds a predetermined specified value. It is preferable to apply a fluororesin to the surfaces of the parts 1a and 2a. By doing so, the fluororesin film 5 lost by repeated pressing is replenished to the fine irregularities 1a and 2a by the sprayed fluororesin, so that the lubricity by the fluororesin film 5 can be revived. By doing so, the press working apparatus 10 can further repeatedly press the metal member. Note that the specified value in this case can be set to about 0.2 in view of examples described later.

  In particular, when pressing a titanium member or a magnesium member by the press processing apparatus 10, the temperature range is from a normal temperature warm set to a range of 10 ° C. to the maximum continuous use temperature of the fluororesin (288 ° C.). It is preferable to perform press working in the region. This is because, in this temperature range, the spreadability of the titanium member and the magnesium member is particularly enhanced and the molding becomes easy.

(Manufacturing method of press mold)
Next, as a manufacturing method of the press working mold, the manufacturing method of the blank holder 2 described above will be described as an example with reference to FIG. FIG. 8 is a side view schematically showing a manufacturing process of a press working mold, (A) is a mold before manufacturing, (B) is a mold after forming fine irregularities on the surface, (C). Indicates a mold after a fluororesin film is formed on the surface of the fine irregularities.

  As shown in FIG. 8A, when the die 1 and the blank holder 2 are manufactured, first, a mold 22 having a desired shape is formed using a metal such as steel. Next, as shown in FIG. 8 (B), at least a part of the surface of the mold 22 in contact with the metal plate 11 is subjected to blasting to roughen the surface, thereby forming the fine uneven portion 2a. At this time, when the mold is made of steel other than cemented carbide steel, the maximum surface roughness is set to 10 μm or more and 25 μm or less. When the mold is made of cemented carbide steel, the maximum surface roughness is set to 3 μm or more and 10 μm or less.

  Subsequently, undercoating is performed, followed by drying and firing. After that, the fluororesin is repeatedly applied to the mold 22 by repeating the process of firing and cooling after performing fluorine resin coating including dispersion coating, electrostatic powder coating, fluidized immersion coating, spray coating and the like. Do. In this way, as shown in FIG. 8C, a fluororesin film 15 having a thickness larger than the maximum surface roughness is formed on the surface of the fine irregularities 2a. In this case, a mixed paint of a primer and a fluororesin can be applied, but after applying the primer, the fluororesin may be applied.

  Then, pressing is performed in advance by using the die 22 with the fluororesin film 15 as the die 1 and the blank holder 2 by the press processing apparatus 10, or the fluororesin film 15 is removed along the surface by other means. As a result, the aforementioned fluororesin film 5 is formed. At this time, only a part of the tops including the highest top among the plurality of tops included in the fine concavo-convex portion 2 a is exposed so as not to be covered with the fluororesin film 5. By executing the steps so far, the blank holder 2 as a press working mold provided with the fluororesin film 5 can be manufactured.

  As the pressing process proceeds, the surface of the mold is, for example, as shown in FIG. 18A, and most of the top is covered with the fluororesin film 5, but only a part of the top is covered. It is exposed without being covered with the fluororesin film 5. When further pressing is performed, a part of the fluororesin film 5 is peeled off along the surface thereof, so that a larger portion of the top is exposed. In this case, the surface of the press working die is as shown in FIG.

  Next, the Example regarding the press processing apparatus 10 is described. In this example, a 0.8 mm-thick plate material made of pure titanium was used as the metal plate 11, and this was formed into a cup shape by deep drawing. Pure titanium exhibits sufficient ductility even at room temperature, and is a metal material suitable for press working in terms of properties.

  However, since pure titanium is an active metal, if the press working is performed without forming the fine irregularities 1a, 2a and the fluororesin film 5 on the die 1 and the blank holder 2, the metal plate 11 and the die 1 are seized. Occurs, and it is difficult to mold into a cup shape. In the press working apparatus 10, since the fine uneven portions 1a, 2a and the fluororesin film 5 are formed on the die 1 and the blank holder 2, the fluororesin film 5 acts as a lubricant, and as a result, the metal plate 11 is illustrated in FIG. 9 could be formed into a cup shape.

  On the other hand, when the metal plate 11 made of pure titanium is pressed, an oxide film is formed on the surface of the metal plate 11, and a molybdenum dioxide solid lubricant, which has a high effect of preventing seizure, is used. , 2a and the die 1 and the blank holder 2 on which the fluororesin film 5 is not formed can be formed into a cup shape. However, if the oxide film is formed, the metal plate 11 is damaged and it is expensive to form the oxide film. Depending on the product, the problem that the oxide film has to be peeled after pressing remains unsolved. . Further, when the solid lubricant is used dispersed in oil or grease, cleaning may be required. All such problems can be solved by using the press working apparatus 10 without remaining unsolved.

  Subsequently, a plurality of base materials having different maximum surface roughness sizes were prepared, and an experiment was conducted to examine the change in the friction coefficient. The base material is prepared with four plate-like materials made of steel other than cemented carbide steel, and each has four different values of maximum surface roughness of 0.5 μm, 5 μm, 14.8 μm, and 33 μm. Fine irregularities were formed, and the same fluororesin film 5 was formed on each surface. The experiment was performed using a ball-on-disk type friction tester (not shown) and increasing the load in order of 100 N, 200, 400, 600, 800, 1000 N every 5 minutes. The results of this experiment are as shown in FIGS. In each figure, (A) shows a photograph of the surface of the substrate taken with a microscope, and (B) is a graph for examining changes in the friction coefficient (the vertical axis is the friction coefficient, and the horizontal axis is the friction distance (m)).

  As shown in FIG. 10, when the maximum surface roughness is 0.5 μm, the friction coefficient exceeds 0.2 only when the friction distance becomes several meters. In addition, as shown in FIG. 11, when the maximum surface roughness is 5 μm, the friction coefficient exceeds 0.2 when the friction distance is around several 50 m, but the friction coefficient is about 0.1 until about 40 m. ing. Furthermore, as shown in FIG. 12, when the maximum surface roughness is 14.8 μm, the friction coefficient is consistently kept at about 0.1 until the friction distance becomes about 60 m. As shown in FIG. 13, when the maximum surface roughness is 33 μm, the friction coefficient exceeds 0.2 only when the friction distance becomes several meters.

  As a result, in view of the fact that the coefficient of friction is consistently about 0.1, it is most preferable to set the maximum surface roughness to 14.8 μm among the four types of maximum surface roughness, It was confirmed that 5 μm was preferable. Further, it was confirmed that the friction coefficient was not within about 0.1 when the maximum surface roughness was 0.5 μm and 33 μm.

  Furthermore, an experiment was conducted to confirm that durability was improved by forming various fluororesin films 5 on the fine irregularities. The experiment was performed in the same manner using the same testing machine as in Example 2. The result of the experiment is as shown in FIG. (A) is a fluororesin film formed by a fluororesin coating technique (hypercoat) that does not use a primer, (B) is a fluororesin film made of PTFE, (C) is a fluororesin film with one coat The case where is formed is shown. In any case, since the friction coefficient was consistently kept at about 0.1 until the friction distance became about 60 m, it was confirmed that the durability was improved.

  Next, an experiment was conducted to confirm that the durability in the fine irregularities was regenerated by applying a liquid fluororesin. In the experiment, a part of the fluororesin film was peeled off in the experiment of Example 3 and a liquid fluororesin was applied to the test piece (TF50) having an increased friction coefficient by spraying (also referred to as spray coating). A similar experiment was conducted using the same testing machine. Prior to the experiment, the test piece was subjected to a friction test at 200 N (5 minutes) to confirm the coefficient of friction before repainting, then spray-coated, and dried with a hand dryer. In the experiment, 200 N (15 minutes), 400 N (10 minutes), 600 N (5 minutes), and 800 N (5 minutes) friction endurance tests were performed on the samples repainted by spraying.

  Here, FIG. 15 is a graph showing a change in the original friction coefficient before the friction coefficient of the test piece (TF50) increases. FIG. 16A is a graph showing a change in the friction coefficient when the friction test is performed at 200 N (5 minutes) after the friction coefficient of the test piece (TF50) is increased, and FIG. It is a graph which shows the change of the subsequent friction coefficient. As is clear from FIGS. 15 and 16, it was confirmed that repainting exhibited a good coefficient of friction lower than the original value and improved durability. FIG. 17A is a graph showing a change in the friction coefficient of another test piece (TF50) before repainting, and FIG. 17B is a graph showing a change in the friction coefficient after repainting. is there. As is clear from FIG. 17, it was confirmed that another test piece showed a good friction coefficient by repainting. Further, it is considered that the specified value of the coefficient of friction when repainting is preferably about 0.15 to 0.18 as seen from FIG.

  The above description is the description of the embodiment of the present invention, and does not limit the apparatus and method of the present invention, and various modifications can be easily implemented. In addition, an apparatus or method configured by appropriately combining components, functions, features, or method steps in each embodiment is also included in the present invention.

  By applying the present invention, a fluororesin film is used as a lubricating film to improve the durability of the mold so that the press process can be repeated, and it is possible to perform dry processing on difficult-to-process metal members such as titanium members and magnesium alloy members. become.

  DESCRIPTION OF SYMBOLS 1 ... Die, 2 ... Blank holder, 3 ... Punch, 5 ... Fluororesin film, 10 ... Press processing apparatus, 11 ... Metal plate, 1a, 2a ... Fine uneven part, P1, P3, P5, P7, P9, P11 ... Top, P2, P4, P6, P8, P10 ... bottom.

Claims (6)

A method of pressing a metal member using a mold,
Forming a fine concavo-convex portion having fine concavo-convex having a maximum surface roughness of 3 μm or more and 25 μm or less on at least a part of a portion in contact with the metal member on the surface of the mold
A fluororesin film having a thickness exceeding the maximum surface roughness is formed on the fine concavo-convex portion to produce a pressing mold,
A pressing method for a metal member, wherein pressing is performed using the pressing die so that the fluororesin film is in direct contact with the metal member.   When the mold is made of cemented carbide steel, the fine irregularities are formed so that the maximum surface roughness is 3 μm or more and 10 μm or less, and when the mold is made of steel other than the cemented carbide steel 2. The metal member pressing method according to claim 1, wherein the fine irregularities are formed so that the maximum surface roughness is 10 to 25 [mu] m.   The metal member pressing method according to claim 1 or 2, wherein a fluororesin is applied to the fine irregularities when the pressing process is repeated.   The metal member according to any one of claims 1 to 3, wherein the pressing is performed in a warm range from a normal temperature set in a temperature range of 10 ° C to the maximum continuous use temperature of the fluororesin. Press working method. A metal mold for press working used for pressing metal members,
A fine concavo-convex portion having a fine concavo-convex portion having a maximum surface roughness of 3 μm or more and 25 μm or less formed on at least a part of a portion in contact with the metal member;
A fluororesin film formed on the fine irregularities;
A pressing mold, wherein the fluororesin film is in close contact with the surface of the fine irregularities.   The fine irregularities are formed so that the maximum surface roughness is 3 μm or more and 10 μm or less when the mold is made of cemented carbide steel, and the maximum surface roughness is formed when the mold is made of steel other than the cemented carbide steel. The metal mold for press working according to claim 5, wherein the thickness is 10 μm or more and 25 μm or less.