Method and punch for punching amorphous metal foil

Abstract

The present invention addresses the problem of providing a method and a punch for punching an amorphous metal foil with which a greater reaction force is prevented from acting on the punch in a short period of time, a great impact is prevented from being imparted to a press machine, and loud processing sound or great vibrations are prevented from being produced, during punching of an amorphous metal foil in press working.　The present invention provides a method for punching an amorphous metal foil that is punched into a prescribed shape by a press machine, the method including a step for placing the amorphous metal foil on a die, and a step for punching out, by using a punch, a portion of the amorphous metal foil placed on the die, the distal-end surface of the punch being an inclined surface that is inclined in one direction with respect to a plane orthogonal to the direction of movement of the punch. The present invention also provides a punch applied in punching of an amorphous metal foil that is punched into a prescribed shape by a press machine, the punch being configured such that the distal-end surface of the punch is an inclined surface inclined in one direction with respect to a plane orthogonal to the direction of movement of the punch.

Description

Amorphous metal foil punching method and punching punch

[0001] The present invention relates to a method for punching an amorphous metal foil and a punch for punching.

[0002] In recent years, Fe-based amorphous alloys have attracted attention as excellent soft magnetic materials due to their properties such as high corrosion resistance and high strength, as well as high magnetic conductivity and low loss factor, and their foils (Fe-based amorphous foils) are used in the iron cores of motors and transformers. Fe-based amorphous foils need to be processed into various shapes depending on the application, and are cut by punching using a press (see Patent Documents 1 and 2).

[0003] JP 2020-44635 A Patent No. 7129048 A

[0004] In conventional punching processes for amorphous metal foil using a press, the tip surface of the punch used in the punching process is formed into a plane perpendicular to the direction of punch movement. In conventional punching processes, the amorphous metal foil material is instantaneously cut along the entire outer periphery of the tip surface of the punch. Although amorphous metal foil material is thin, approximately 0.01 mm to 0.1 mm thick, it is a hard material with a Vickers hardness of 1000 HV or more. Therefore, during punching (cutting) using the press, a large reaction force is applied to the punch in a short period of time, causing a large impact on the press and resulting in loud processing noise and vibration. The large reaction force applied to the punch can cause distortion or damage to the punch itself, and the large impact applied to the press can cause distortion or damage to various parts of the press. Furthermore, the loud processing noise and vibration significantly degrade the environment around the press. The cutting process includes punching, which cuts out unnecessary parts from the sheet material, and punching, which cuts out parts to become products from the sheet material.

[0005] Therefore, an object of the present invention is to solve the above problems and to provide an amorphous metal foil punching method and a punch for punching that do not apply a large reaction force to the punch in a short period of time, do not give a large impact to the press machine, and do not generate large processing noise or vibration during amorphous metal foil punching in press working.

[0006] In order to solve these problems, the present invention has the following configuration: A method for punching amorphous metal foil into a predetermined shape using a press, comprising the steps of placing amorphous metal foil on a die, and punching a portion of the amorphous metal foil placed on the die with a punch, wherein the tip surface of the punch is an inclined surface that is inclined in one direction with respect to a plane perpendicular to the moving direction of the punch. The present invention also has the following configuration: A punch for punching amorphous metal foil, used for punching amorphous metal foil into a predetermined shape using a press, wherein the tip surface of the punch is an inclined surface that is inclined in one direction with respect to a plane perpendicular to the moving direction of the punch.

[0007] By using a punch whose tip surface is inclined in one direction relative to a plane perpendicular to the moving direction of the punch, it is possible to provide an amorphous metal foil punching method and a punch for punching that do not apply a large reaction force to the punch in a short time, do not give a large impact to the press machine, and do not generate large processing noise or vibration.

[0008] FIG. 1 is a diagram showing the state of punching of an amorphous metal foil according to an embodiment of the present invention. FIG. 2 is a diagram of a punch 4 for an amorphous metal foil according to an embodiment of the present invention. FIG. 3 is a diagram showing the dimensions of a punch 4 for an amorphous metal foil according to an embodiment of the present invention. FIG. 4 is a graph showing the relationship between punch stroke and shear load during punching of an amorphous metal foil according to an embodiment of the present invention and a conventional method. FIG. 5 is a diagram showing a crack C that occurs during punching of an amorphous metal foil. FIG. 6 is a table showing experimental results of punching of an amorphous metal foil. FIG. 7 is a diagram showing warpage that occurs during punching of an amorphous metal foil. FIG. 8 is a diagram showing a specific example using punching of an amorphous metal foil according to an embodiment of the present invention.

[0009] [Embodiment] Hereinafter, an amorphous metal foil punching method and a punching punch according to an embodiment of the present invention will be described with reference to the drawings. In the following description, the same reference numerals in different drawings indicate parts with the same function, and duplicated descriptions in each drawing will be omitted as appropriate.

[0010] [Embodiment] The press used in the embodiment of the present invention is a known press, and includes a die 2 (also referred to as a die) on which an amorphous metal foil to be processed, typically a long amorphous metal sheet 1, is placed; a press pad 3 (also referred to simply as a pad or a stripper) that presses down on the amorphous metal sheet 1 placed on the die 2 from above; and a punch 4 that descends from above the amorphous metal sheet 1 placed on the die 2 into a punch hole 2a in the die 2 to punch out portions of the amorphous metal sheet 1 that are not required for the product. As shown in FIG. 1 , the amorphous metal sheet 1 is cut between the outer periphery of the tip of the punch 4 and the inner periphery of the upper end of the die 2. As shown in FIG. 2 , the punch 4 is generally cylindrical. The tip surface (lower end surface) 4a of the punch 4 is formed into an inclined surface that forms a shear angle (inclination angle) θ with a plane perpendicular to the direction in which the punch 4 moves (the downward and upward directions: see the two-dot chain lines in FIGS. 1 and 2 ) (see FIG. 3 ). The shear angle is the angle between the tip surface of the punch 4 and a plane (hereinafter simply referred to as the transverse plane) perpendicular to the direction in which the punch 4 moves. The tip surface 4a of the punch 4 is formed as a plane that is uniformly inclined at the shear angle θ, i.e., an inclined surface that is inclined in one direction relative to the transverse plane. The angle θ is the angle formed by the line segment connecting the most forward (lower end) point 4a1 of the tip surface 4a to the most rearward (upper end) point 4a2, and the transverse plane. The shear amount is often used as an index equivalent to the shear angle θ. The shear amount S is the distance between point 4a1 and point 4a2 in the direction in which the punch 4 moves.

[0011] When the punch 4 is lowered by the press, point 4a1 comes into contact with the amorphous metal sheet 1, and cutting of the amorphous metal sheet 1 begins between the punch 4 and the upper inner peripheral edge of the die 2. From point 4a1, the amorphous metal sheet 1 is then cut sequentially at two locations along the outer peripheral edge of the tip of the punch 4, and finally, the cutting ends at point 4a2. That is, when cutting of the amorphous metal sheet 1 begins, only one location is cut, and thereafter, only two locations are cut, and when cutting of the amorphous metal sheet 1 ends, only one location is cut. In this embodiment, in which hole punching is performed by cutting in this manner, the impact (reaction force of the shear load) applied to the punch 4 during the hole punching process can be significantly reduced compared to conventional hole punching in which the entire circumference of the hole is cut simultaneously by the punch and die.

[0012] 4 is a graph showing the relationship between the punch stroke and the shear load applied to the punch during the punching of amorphous metal foil in this embodiment and in a conventional embodiment. It can be seen that in the case of a conventional punch with no inclination of the tip end face (shear angle θ = 0), a large shear load is applied suddenly during a short punch stroke. In contrast, in the case of the punch with an inclination of the tip end face (shear angle θ > 0) of this embodiment, a small shear load is applied gradually during a long punch stroke. Thus, in this embodiment, no large impact force is applied to the punch 4 or the press machine that drives the punch 4, which prevents distortion or damage to various parts of the press machine and the generation of large processing noise and vibration.

[0013] [Shear Angle] When the shear angle θ is large, i.e., when the shear amount S is large, the maximum shear load decreases. When the shear amount S is equal to the thickness T of the amorphous metal sheet 1 (S = T), the shear load is approximately 1 / 2. When the shear amount S is equal to twice the thickness T of the amorphous metal sheet 1 (S = 2T), the shear load is approximately 1 / 3. However, as shown in Figure 5, when the shear amount S is greater than a certain value, cracks C occur in the amorphous metal sheet 1. When the punch 4 cuts the amorphous metal sheet 1, the previously cut portion is pressed downward by the tip surface 4a of the punch 4. This downward pressed portion pulls the uncut portion downward (see Figure 1). This tensile force causes stress concentration at the portion cut by the punch 4 (the boundary between the previously cut portion and the uncut portion), which causes cracks C to occur.

[0014] As the shear amount S increases, the length by which the downwardly pressed portion pulls the uncut portion downward increases, and the tensile force also increases. The shear amount S at which cracks C occur was confirmed through the following experiment. <Experiment> Circular punching was performed on an amorphous metal sheet. The amorphous metal sheet used was an Fe-based amorphous foil with a thickness of 0.026 mm and a Vickers hardness of 900 HV. The punch used for punching was cylindrical, with its tip formed into an inclined surface that was inclined at a predetermined angle relative to a plane perpendicular to the direction of punch movement. Multiple punches with different diameters R and shear amounts S were used. Three types of punches with diameters R of 10 mm, 30 mm, and 60 mm were used, and for each of these three types of punches, five types of shear amounts S were used: 0.03 mm, 0.04 mm, 0.05 mm, 0.06 mm, and 0.07 mm. A total of 15 types of punches were prepared. Then, it was investigated whether or not cracks C occurred as a result of punching using all 15 types of punches. As a result of the experiment, as shown in the table of Figure 6, for all punches with three types of diameter R, cracks C did not occur when the shear amount S was 0.03 mm, 0.04 mm, or 0.05 mm, but cracks occurred when the shear amount S was 0.06 mm or 0.07 mm. (In the table, ◯ indicates that cracks C did not occur, and × indicates that cracks C occurred.)

[0015] The experimental results showed that, regardless of the punch diameter R, cracks C did not occur when the shear amount S was 0.03 mm, 0.04 mm, or 0.05 mm, which was less than 0.052 mm, twice the thickness of the amorphous metal sheet (0.026 mm), but cracks C occurred when the shear amount S was 0.06 mm or 0.07 mm, which was greater than 0.052 mm. In other words, it was found that when punching an amorphous metal sheet, cracks C are less likely to occur in the amorphous metal sheet if the shear amount S is less than twice the thickness T of the amorphous metal sheet.

[0016] When punching an amorphous metal sheet, the condition for preventing cracks C from occurring in the amorphous metal sheet is that S≦2T is satisfied. From this condition, the condition for the shear angle θ is determined. If the maximum length of the tip surface 4a of the punch 4 in the inclined direction in the cross section is L (since the punch 4 is cylindrical, L is the diameter R of the circle that is the cross section), this length L, the shear angle θ, and the shear amount S have a relationship of tan θ=S / L (see Figure 3). By rearranging this equation, S=Ltanθ, and the above-mentioned S≦2T, we obtain Ltanθ≦2T. Therefore, if the shear angle θ satisfies tanθ≦2T / L, cracks C are unlikely to occur.

[0017] As shown in Figure 7, when punching the amorphous metal sheet 1, the punched piece P punched by the punch 4 is warped. This is because, as described above, when punching with the punch 4 having an inclined tip surface, the previously cut portion is pressed downward by the tip surface 4a of the punch 4, and this pressed portion is bent downward, causing warping at the punched portion of the amorphous metal sheet 1. Because amorphous metal foil has high hardness, this warping remains even after punching. Because it takes time and cost to treat the remaining warping and flatten it, it is not preferable to turn the punched piece P into a product, and it is preferable to process the portion other than the punched piece P into a product. In other words, when punching the amorphous metal sheet 1, it is preferable to use a punching process that turns the punched portion into a product, rather than a punching process that turns the portion other than the punched portion into a product.

[0018] [Specific Example] Figure 8 shows a specific example using the punching process on the amorphous metal sheet 1 of the embodiment. The shape shown in Figure 8(f) is the desired product shape. In this specific example, as described above, it is preferable to use punching to turn the parts other than the punched parts into a product, so a process of punching out the unnecessary parts is adopted. As shown in Figure 8(f), if there are multiple areas to be punched, punching them all at once can cause a large impact and, depending on the shape of the object to be punched, may not be able to cut cleanly. Therefore, it is preferable to perform the process through multiple punching processes. In this specific example, the product shape is punched in four steps.

[0019] Step (1): As shown in FIG. 8( a), a large circular hole is punched out in the center. The punch used for punching is a punch with an inclined tip surface 4a, similar to the punch 4 in the embodiment. Step (2): As shown in FIG. 8( b), six small circular holes are punched out around the large central hole. Six punches with inclined tip surfaces 4a, similar to the punch 4 in the embodiment, are used for punching, and six holes are punched out simultaneously. Note that the six holes are punched out in a single step, but these may be punched out in multiple steps. Step (3): As shown in FIG. 8( c), six rectangular holes are punched out connecting the large central hole and the six small holes surrounding it. The punch used for punching is a punch with a rectangular cross section perpendicular to the direction of punch movement, and six punches with inclined tip surfaces along one of the diagonals of the rectangle are used to punch out six holes simultaneously. Although the six holes are punched in one step, they may be punched in multiple steps.

[0020] Step (4): As shown in Figure 8(d), the outer periphery of the part to be made into the product is punched out into a circular shape. The entire part to be made into the product can be punched out into a circular shape using a cylindrical punch. However, in this case, as described above, the punched part is used for the product, which results in warping of the product. Therefore, in this example, a cylindrical punch is used to punch out the outer periphery of the part to be made into the product, and the inner part of the circumference that is not punched out is used for the product. This punching process results in a product without warping. Figure 8(e) shows the remaining amorphous metal sheet 1 that is not used for the product, and Figure 8(f) shows the part that has been machined into the product shape as described above. The punch used is a cylindrical punch, but its tip surface is shaped so that the entire cylinder forms an inclined surface. The tip surface of the punch is a wide circular surface when viewed from the direction of punch movement. On the tip surface of the punch, the most forward (lowest) point on the outer periphery and the most forward (lowest) point on the inner periphery are arranged at one location on the circumference so that they are aligned in the radial direction of the cylinder, and on the radially opposite side of these points, the most rearward (upper) point on the outer periphery and the most rearward (upper) point on the inner periphery are arranged so that they are aligned in the radial direction of the cylinder.

[0021] When the punch is lowered by the press, the leading edge of the punch on the outer periphery comes into contact with the amorphous metal sheet 1, and cutting of the amorphous metal sheet 1 on the outer periphery begins between the punch and the inner periphery of the die. The amorphous metal sheet 1 is then cut sequentially at two locations on the outer periphery of the punch. Next, the leading edge of the punch on the inner periphery comes into contact with the amorphous metal sheet 1, and cutting of the amorphous metal sheet 1 on the inner periphery begins between the punch and the inner periphery of the die. The amorphous metal sheet 1 is then cut sequentially at two locations on the inner periphery of the punch. Finally, cutting of the amorphous metal sheet 1 on the inner periphery is completed at the rearmost point on the inner periphery of the punch, and then cutting of the amorphous metal sheet 1 on the inner periphery is completed at the rearmost point on the inner periphery of the punch. That is, when cutting of the amorphous metal sheet 1 starts, only one place is cut, and thereafter, only two to four places are cut, and when cutting of the amorphous metal sheet 1 is finished, only one place is cut.

[0022] When punching the amorphous metal sheet 1, the amorphous metal sheet 1 is sandwiched between the die 2 and the press pad 3, but it is preferable to sandwich at least the entire portion that will become the product between the die 2 and the press pad 3 rather than just the periphery of the punched area between the die 2 and the press pad 3. By sandwiching the entire portion that will become the product between the die 2 and the press pad 3, it is possible to prevent deformation or damage to the portion that will become the product.

[0023] Although the embodiments and specific examples of the present invention have been described in detail with reference to the drawings, the present invention is not limited to these embodiments and specific examples, and even if there are design changes and the like within the scope of the gist of the present invention, they are included in the present invention.

[0024] 1 amorphous metal sheet 2 die 2a punch hole 3 pressing pad 4 punch 4a tip surface 4a1 tip point 4a2 rear end point C crack L maximum length of tip surface 4a in the inclined direction in the cross section P punched piece R diameter of punch 4 S amount of shear T thickness of amorphous metal sheet 1 θ shear angle

Claims

1. A method for punching amorphous metal foil into a predetermined shape using a press, comprising the steps of placing the amorphous metal foil on a die and punching out a portion of the amorphous metal foil placed on the die with a punch, wherein the tip surface of the punch is an inclined surface that is inclined in one direction with respect to a plane perpendicular to the direction of movement of the punch.

2. A method for punching amorphous metal foil according to claim 1, characterized in that the following relationship is satisfied: tan θ≦2T / L, where θ is the inclination angle of the tip surface of the punch relative to a plane perpendicular to the moving direction of the punch, L is the length of the tip surface of the punch in the inclined direction in the plane perpendicular to the moving direction of the punch, and T is the thickness of the amorphous metal foil.

3. A method for punching amorphous metal foil according to claim 1 or 2, characterized in that the thickness of the amorphous metal foil is 0.01 mm or more and 0.1 mm or less.

4. A method for punching amorphous metal foil according to claim 1 or 2, characterized in that the punching process is a punching process for cutting out unnecessary portions from the amorphous metal foil.

5. A punch for punching amorphous metal foil, which is used to punch amorphous metal foil into a predetermined shape using a press, characterized in that the tip surface of the punch is an inclined surface that is inclined in one direction with respect to a plane perpendicular to the moving direction of the punch.

6. A punch for punching amorphous metal foil according to claim 5, characterized in that the following relationship is satisfied: tan θ≦2T / L, where θ is the inclination angle of the tip surface of the punch relative to a plane perpendicular to the moving direction of the punch, L is the length of the tip surface of the punch in the inclined direction on the plane perpendicular to the moving direction of the punch, and T is the thickness of the amorphous metal foil.

7. A press machine equipped with the punch for punching amorphous metal foil according to claim 5 or 6.

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