JP6111138B2 - Flat die for worm rolling and manufacturing method thereof - Google Patents

Description

  The present invention relates to a flat die for rolling, and more particularly to a flat die for worm rolling for rolling a thread of a worm.

  As a technique for manufacturing a worm of a worm gear, a method of rolling a worm thread (teeth) using a worm rolling flat die having a large number of machining teeth is known (see Patent Document 1). In addition, with respect to such a rolling die, the surface layer portion of the rolling molding surface provided with the processing teeth is hardened by nitriding, and an oxide film is provided on the surface thereof to improve the retention performance of the lubricant, thereby improving the wear resistance. A technique for improving heat resistance and seizure resistance is known (see Patent Document 2). By providing the oxide film, the workability (worm material) is plastically deformed and the rolling processability of flowing along the machining teeth is improved. For example, the top of the worm screw thread is formed along the tooth bottom surface of the machining teeth. Top roll rolling to form is also possible.

JP-A-7-185713 JP 2010-5654 A

  However, the rolling die provided with the oxide film in this way is easy to slip due to the oxide film containing the lubricant when the processing teeth bite into the workpiece, so that the biting property is deteriorated and the rolling processing accuracy is impaired. It is. In order to prevent this, it is necessary to increase the rolling pressure that presses the rolling die against the workpiece. However, since a large load is applied to the processing teeth of the rolling die, it is caused by the load and rubbing friction during the rolling process. Peeling and abrasion of the oxide film are accelerated, and the expected durability cannot be obtained.

  On the other hand, although not yet known, it is conceivable to remove the oxide film on the front end side portion of the chamfered portion by polishing or mask it during the oxidation treatment, but both are troublesome and time consuming. This is disadvantageous in terms of cost.

  The present invention has been made against the background of the above circumstances. The object of the present invention is to use a flat die for warm rolling in which an oxide film is provided on the rolling molding surface while suppressing rolling pressure. It is to improve the sticking property so that excellent rolling processing accuracy and durability can be obtained.

In order to achieve such an object, the first invention includes a rolling molding surface that rolls a thread of a worm with a large number of processing teeth, and an oxide film is provided on the rolling molding surface. In the manufacturing method of a flat die for worm rolling, a shot peening process is performed on a biting start portion of the biting portion of the rolling molding surface where the rolling process is started, and the tip of the processed tooth The oxide film provided on the surface is removed.

2nd invention is the manufacturing method of the flat die | dye for worm rolling of 1st invention, The said shot peening process is in the range from 30 to 50% of the biting part from the front end of the rolling direction in the said biting part. It is characterized by being given.

According to a third aspect of the present invention, in the method for manufacturing a flat die for worm rolling according to the first or second aspect of the present invention, the bottom surface and flank (side surface of the processed tooth) of the processed tooth of the portion subjected to the shot peening treatment The oxide film remains, and the oxide film on the tooth bottom surface has a film thickness ratio of 0.8 or more with respect to the portion not subjected to the shot peening treatment.

According to a fourth aspect of the present invention, there is provided a method for producing a flat die for worm rolling according to any one of the first to third aspects of the present invention, wherein a tooth tip surface of the processed tooth from which the oxide film has been removed by the shot peening treatment is set to a surface diameter of 0.00. A large number of recesses are provided at a depth of 01 to 0.1 mm.

The fifth invention is a method for producing a flat die for worm rolling according to any one of the first invention to the fourth invention, wherein the shot peening treatment is performed by using amorphous particles having a particle diameter in the range of 80 to 200 μm as a. It is characterized by being carried out by injecting perpendicularly to the rolling molding surface at an injection pressure of 2 to 6 MPa.

In such a manufacturing method of a flat die for worm rolling, shot peening treatment is performed on the biting start portion where rolling processing is started out of the biting portion of the rolling molded surface, and the tooth tip surface of the processed tooth Since the oxide film is removed, the processing teeth can easily bite into the workpiece at the start of the rolling process, and the biting property can be improved while suppressing the rolling pressure. Thereby, the slip of the workpiece is suppressed, and the oxide film is left as it is except for the portion where the start of biting occurs, and the seizure resistance and the rolling processability by the oxide film can be maintained, so that excellent rolling process accuracy can be obtained. Moreover, durability of a tool improves because rolling pressure can be reduced.

  On the other hand, since the oxide film is removed by the shot peening process, the oxide film can be easily and inexpensively removed as compared with the case where it is removed by polishing or masked during the oxidation process. In addition, the pressure angle of the worm screw thread is generally steep within a range of about 14 ° to 25 °, and the flank of the processing teeth of the rolling die is relatively steep according to the screw thread. The shot (particle) projection angle with respect to the flank is reduced, and the oxide film removal performance is lowered. Thereby, it is possible to leave the oxide film of the flank while removing the oxide film on the tooth tip surface by the shot peening process, and it is possible to appropriately ensure the seizure resistance and the rolling processability by the oxide film.

  In the second invention, shot peening treatment is applied to the range of 30 to 50% from the front end in the rolling direction of the biting portion of the rolling molded surface, and the oxide film on the tooth tip surface of the processed tooth in that range is removed. Therefore, the effects of the first invention can be obtained appropriately. That is, in general, the flat die is configured to start biting within a range of 30 to 50% from the front end of the biting portion regardless of the dimensional error or assembly error of each portion. While the oxide film on the tooth tip surface is surely removed to improve the biting property, the oxide film of the other part is left and the seizure resistance and the rolling workability can be appropriately ensured.

  In the third invention, the oxide film remains on the bottom surface and the flank of the processed tooth in the portion subjected to the shot peening treatment, and the oxide film on the bottom surface is a film formed with the portion not subjected to the shot peening treatment. Since the thickness ratio is 0.8 or more, the oxide film appropriately secures seizure resistance and rolling processability. At the front end side portion of the chamfered part, the workpiece does not reach the bottom of the processed tooth, but the oxide film with a predetermined film thickness remains on the flank, so that seizure resistance and rolling workability are properly achieved. It can be secured. In other words, shots bounced off by flank and the like collide with the tooth bottom surface at a relatively low speed, and shots are likely to collect and stay on the tooth bottom portion, so that the oxide film on the tooth bottom surface is the most difficult to remove. An oxide film remains with a larger film thickness on the tooth bottom side. For this reason, by leaving an oxide film at a thickness ratio of 0.8 or more on the tooth bottom, it is possible to leave an oxide film with a film thickness that can ensure predetermined seizure resistance and rolling processability on the flank. is there.

  In the fourth aspect of the invention, since the tip of the processed tooth from which the oxide film has been removed by the shot peening process is provided with a large number of recesses having a depth of 0.01 to 0.1 mm, the workpiece bites into the recesses. As a result, slippage between the processing teeth and the workpiece is more appropriately suppressed, and the thread of the worm can be rolled with higher accuracy.

In the fifth aspect of the invention , the shot peening treatment for the biting portion is performed by injecting the amorphous particles having a particle diameter in the range of 80 to 200 μm perpendicularly to the rolling molding surface at an injection pressure of 0.2 to 6 MPa. Therefore, it is possible to appropriately remove the oxide film on the tooth tip surface of the processed tooth in the biting portion . In addition, since the amorphous particles are hard and difficult to chip, even when shot peening is performed repeatedly using the particles, the change in particle diameter is suppressed, and the removal performance of the oxide film is maintained substantially constant over a long period of time. As a result, stable die quality can be obtained, including the fact that an oxide film having a predetermined thickness is left on the flank and a predetermined recess is provided on the tooth tip surface.

It is a schematic front view explaining the flat die | dye for worm rolling manufactured according to the manufacturing method of this invention. It is a figure explaining an example of the rolling processing method using the flat die of FIG. It is sectional drawing of the processing tooth in the finishing part of the flat die of FIG. 1, and is an expanded sectional view of the III-III arrow part in FIG. 1. It is sectional drawing of the process tooth in the front-end side part of the biting part of the flat die of FIG. 1, and is an expanded sectional view of the IV-IV arrow part in FIG. 1, and also the partial enlarged view which expanded further the tooth tip part FIG. FIGS. 5A and 5B are diagrams for explaining a process for removing an oxide film on a front end side portion of a bite portion by shot peening when manufacturing the flat die of FIG. 1, both of which are cross-sectional views corresponding to FIG. 4. It is a figure explaining the result of having carried out the rolling process of the thread of a worm using this invention product and the conventional product, and investigated the durability. FIG. 2 is a perspective view showing an example of a worm that is rolled by the flat die of FIG. 1.

The flat die for worm rolling manufactured in accordance with the method of the present invention is formed by rolling a worm on its outer peripheral surface by, for example, pressing and rolling a gear material between a pair of fixed and moving dies. The pair of flat dies arranged parallel to each other on both sides of the gear material supported rotatably about the axis can be moved linearly between the pair of flat dies. It is also possible to roll the worm by rotating it while pinching the gear material. The present invention is preferably applied to a flat die for rolling a cylindrical worm having a cylindrical outer shape, but can also be applied to a flat die for rolling a drum-shaped worm having an outer shape. In addition, the cross-sectional shape of the thread of the worm can take various forms. For example, the tooth tip (the top of the thread) or the bottom (the bottom of the thread groove) may be a straight line or a curved line such as an arc. The cross-sectional shape is appropriately determined according to the cross-sectional shape of this screw thread (directly, the cross-sectional shape of the thread groove portion).

  In general, tool steels such as SKD (alloy tool steel) and SKH (high-speed tool steel) defined in JIS are suitably used as the tool base of the flat die for worm rolling. As the oxidation treatment for forming the oxide film, for example, a steam oxidation treatment is preferably used, but other oxidation treatment methods may be employed. Further, it is desirable to provide a hardened layer by nitriding or the like before forming the oxide film. When a nitride layer is provided as the hardened layer, various nitriding methods such as ion nitriding, salt bath nitriding, and gas nitriding are possible. These hardened layers and oxide films are desirably provided over the entire roll-formed surface including the tip surface, flank, and bottom surface of the processed teeth.

  The rolling forming surface provided with a large number of machined teeth consists of a finished part provided with machined teeth in a plane parallel to a reference plane (such as the bottom of a flat die) parallel to the rolling direction, and a front end from the finished part. It has a chamfered portion where the tooth tip gradually lowers toward the side. The chamfered portion may be one in which the processed teeth having the same cross-sectional shape as the finished portion are generally lowered, but may be one in which only the tooth tip side of the processed teeth is cut obliquely. It is desirable to provide a relief portion that becomes lower at a larger inclination angle than the chamfered portion on the rear end side of the finished portion, that is, on the side opposite to the chamfered portion in the rolling direction.

  And the shot peening process is performed to the biting start part which touches a workpiece | work first among the said biting parts, and the oxide film of the tooth-tip surface of a process tooth is removed. Although it is desirable to completely remove the oxide film on the tooth tip surface, a part of the oxide film may remain. Since the start portion of biting may vary due to dimensional errors in each part or assembly errors for the rolling processing machine, the shot peening processing area should be included to ensure that the biting start portion is included regardless of these errors. It is desirable to set. If shot peening is applied in the range from the front end in the rolling direction to 30 to 50% of the biting portion as in the second invention, the oxide film including the biting start portion is usually removed regardless of the above error. can do. If the removal range of the oxide film is less than 30%, the effect of improving the corrosion resistance may not be obtained properly. On the other hand, if it exceeds 50%, the seizure resistance and the rolling processability by the oxide film may be reduced. There is a possibility that the rolling processing accuracy is impaired due to the inhibition. However, depending on the flat die, there is a possibility that the biting start portion will be in a position exceeding the range up to the above 50%. For example, when carrying out the first invention, shot peening is performed in the range exceeding 50% of the biting portion. A treatment may be performed to remove the oxide film.

  In the third invention, the film thickness of the oxide film on the tooth bottom surface has a film thickness ratio of 0.8 or more with respect to the film thickness of the portion not subjected to the shot peening treatment. Shot peening may be performed until the thickness ratio is less than 0.8. What is necessary is just to compare this film thickness by each average film thickness.

  In the fourth invention, many dents having a depth of 0.01 to 0.1 mm are provided on the tip surface of the processed tooth by the shot peening process. However, there may be a dent shallower or deeper than this. Absent. It is desirable that 80% or more of the many recesses have a depth in the range of 0.01 to 0.1 mm. The shape of the dent is determined according to the shape of the shot. For example, in the case of a spherical shot, a spherical (cross-sectional arc) dent is provided.

  In the fifth invention, amorphous particles having a particle diameter in the range of 80 to 200 μm are injected at an injection pressure of 0.2 to 6 MPa, and shot peening is performed using shots of materials other than amorphous particles such as cemented carbide and iron. Processing can also be performed. The particle diameter and the injection pressure can be appropriately changed according to the material and shape of the shot. As amorphous particles, various amorphous shots such as alloy particles described in Japanese Patent No. 4317930 can be used.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic front view for explaining a worm rolling flat die 10 (hereinafter simply referred to as a flat die 10) manufactured according to the manufacturing method of the present invention. As shown in FIG. 2, a pair of flat dies 10 are arranged in parallel with each other on both sides of a columnar workpiece (worm material) 14 rotatably supported around a shaft center by a pair of centers 12, and are vertically moved. By being moved relative to each other in a symmetrical manner, the workpiece 14 is rotated around the axis while being clamped from both sides, and a thread 52 of a worm 50 as shown in FIG. 7 is rolled. The worm 50 is an example of a multi-row cylindrical worm. An arrow F in FIGS. 1 and 2 represents a rolling direction that is a moving direction when rolling. 1 and 2 are not accurate, and particularly in FIG. 2, the diameter of the workpiece 14 is shown larger than that of the flat die 10.

  The flat die 10 is made of tool steel such as SKD, and includes a rolling forming surface 22 provided with a number of machining teeth 20 for rolling the thread 52 of the worm 50. 3 and 4 are enlarged cross-sectional views of the machined tooth 20, FIG. 3 is a cross-sectional view of the machined tooth 20 taken along the line III-III in FIG. 1, that is, the finish portion 32, and FIG. It is sectional drawing of the processing tooth | gear 20 in the arrow view part, ie, the biting front part 34f. The processing teeth 20 are projecting ridges corresponding to the thread grooves of the worm 50, and are provided so as to be inclined from the rolling direction F at an inclination angle corresponding to the lead angle of the thread 52 of the worm 50. A thread 52 of the target worm 50 is rolled by being plastically deformed (metal flow) so that the workpiece 14 enters the tooth gap portion of the processing tooth 20 and being raised. In this embodiment, the tooth tip surface 24 of the machining tooth 20 bites into the outer peripheral surface of the workpiece 14, whereby the metal flow of the pushed workpiece 14 flows along the flank 26 of the machining tooth 20 and reaches the tooth bottom surface 28. The top roll rolling is performed in which the crest of the screw thread 52 is formed along the root surface 28. The inclination angle of the flank 26 of the machining tooth 20 is determined according to the pressure angle of the thread 52 of the worm 50. In this embodiment, the pressure angle is 20 °, and the inclination angle of the flank 26 is also about 20 °.

  Returning to FIG. 1, the rolling forming surface 22 is formed by a finishing portion 32 in which the processing teeth 20 are provided in a plane parallel to the bottom surface 30 which is a reference plane parallel to the rolling direction F, and the rolling portion 32 is rolled from the finishing portion 32. A chamfered portion 34 that linearly inclines toward the bottom surface 30 side toward the front end 38 in the production direction F is provided. Further, on the rear end side of the finishing portion 32, that is, on the side opposite to the biting portion 34, a relief portion 36 that is inclined toward the bottom surface 30 side at a larger inclination angle than the biting portion 34 is provided. As is apparent from FIGS. 3 and 4, the biting portion 34 has the processing teeth 20 having the same cross-sectional shape as the finishing portion 32, and the processing teeth 20 include the flank 26 and the tooth bottom surface 28. Overall it is low.

  A nitrided layer 40 is provided as a hardened layer by ion nitriding on the rolled molding surface 22, and an oxide film 42 is formed on the nitrided layer 40 by steam oxidation. These nitride layer 40 and oxide film 42 are provided on the entire surface of the rolling molding surface 22 including the tooth tip surface 24, the flank 26, and the tooth bottom surface 28 of the processed tooth 20, but the front portion of the bite in FIG. In 34f, the shot peening process shown in FIG. 5 is performed thereafter, whereby the oxide film 42 on the tooth tip surface 24 is removed. The chamfered front portion 34f includes a chamfer start portion that first contacts the workpiece 14 and starts the rolling process within a range from the front end 38 to 30 to 50% of the chamfered portion 34 in the rolling direction F. It is determined as appropriate in consideration of errors in each part. Thus, by removing the oxide film 42 on the tooth tip surface 24 of the processed tooth 20 at the biting start portion, slippage between the processed tooth 20 and the workpiece 14 is suppressed, and the rolling process is appropriately started. As a result, the rolling processing accuracy is improved. If the range where the oxide film 42 is removed is less than 30%, there is a possibility that the biting start portion is removed and the effect of improving the biting property may not be properly obtained. There is a possibility that the seizure resistance and the rolling processability are hindered and the rolling accuracy is impaired.

The shot peening treatment is performed on the rolling molding surface 22 of a spherical metal shot (amorphous particles in this embodiment) 44 having a particle diameter in the range of 80 to 200 μm with an injection pressure of 0.2 to 6 MPa. This is done by jetting vertically. This shot peening process can completely remove at least the oxide film 42 on the tooth tip surface 24 in the front part 34f of the bite, and the film thickness of the oxide film 42 in the part not subjected to the shot peening process on the tooth bottom surface 28. On the other hand, the particle diameter, the injection pressure, the processing time, etc. are determined so that the oxide film 42 remains at a film thickness ratio of 0.8 or more. The shots 44 projected on the rolling molding surface 22 are automatically collected and repeatedly used for shot peening.

  As shown in FIG. 5 (b), the shot 44 bounced off by the flank 26 and the like collides with the tooth bottom surface 28 at a relatively low speed, and the shot 44 easily collects and stays at the tooth bottom portion. The oxide film 42 on the bottom surface 28 is most difficult to remove. Therefore, as shown in FIG. 5C, the oxide film 42 remains on the tooth bottom surface 28 with the largest film thickness, and the oxide film 42 remains on the flank 26 with a film thickness larger toward the tooth bottom side. For this reason, by leaving the oxide film 42 on the tooth bottom surface 28 at a film thickness ratio of 0.8 or more, the oxide film 42 having a film thickness capable of ensuring predetermined seizure resistance and rolling workability is left on the flank 26. be able to. In the chamfered front portion 34f, the metal flow due to plastic deformation of the workpiece 14 does not reach the bottom portion of the machined tooth 20, but the oxide film 42 having a predetermined thickness remains on the flank 26, so that seizure resistance is maintained. In addition, the rolling processability can be appropriately secured.

  In addition, when the shot peening process is performed in this manner, the oxide film 42 on the tooth tip surface 24 of the processed tooth 20 in the chamfered front portion 34f is completely removed, and a partial enlarged view shown in FIG. As can be seen from the above, a large number of recesses 46 are formed in the tooth tip surface 24 by shot peening. The depth of the recesses 46 is about 0.01 to 0.1 mm, that is, 80% or more of the many recesses 46 has a depth within the range of 0.01 to 0.1 mm. As a result, the slippage of the workpiece 14 at the start of the rolling process is more reliably prevented.

  As described above, in the flat die 10 of this embodiment, the biting front portion including the biting start portion where the rolling process is started, of the rolling molding surface 22 provided with the nitride layer 40 and the oxide film 42. Since the shot peening process is applied to 34f and the oxide film 42 on the tooth tip surface 24 of the machined tooth 20 is removed, the machined tooth 20 is likely to bite into the workpiece 14 at the start of the rolling process, thereby suppressing the rolling pressure. However, the biting property can be improved. As a result, the slippage of the workpiece 14 is suppressed, and the oxide film 42 remains as it is except for the front portion 34f, and the seizure resistance and the rolling processability by the oxide film 42 are maintained. Rolling processing accuracy can be obtained. Moreover, durability of a tool improves because rolling pressure can be reduced.

  On the other hand, since the oxide film 42 has been removed by the shot peening process, the oxide film 42 can be removed more easily and at a lower cost than when it is removed by polishing or masked during the oxidation process. Further, the flank 26 of the processing tooth 20 has a relatively steep slope corresponding to the pressure angle of the thread 52 of the worm 50. In this embodiment, the inclination angle is about 20 °. The projection angle of 44 becomes smaller and the removal performance of the oxide film 42 becomes lower. For this reason, it is possible to leave the oxide film 42 of the flank 26 while removing the oxide film 42 of the tooth tip surface 24 by shot peening treatment, and appropriately ensure seizure resistance and rolling workability by the oxide film 42. it can.

  Further, the front portion 34f with biting to which the shot peening process is performed is in a range of 30 to 50% from the front end 38 of the biting portion 34, and the oxide film 42 on the tooth tip surface 24 of the processing tooth 20 of that portion. Therefore, the biting start portion 34 is included in the biting front portion 34 regardless of the dimensional error or assembly error of each portion. As a result, the oxide film 42 on the tooth tip surface 24 of the processed tooth 20 at the start portion of the bite is reliably removed to improve the bite property, and the other portion of the oxide film 42 is left and seizure resistance is maintained. In addition, the rolling processability can be appropriately secured.

  In addition, the oxide film 42 remains on the bottom surface 28 and the flank 26 of the processed tooth 20 of the front portion 34f subjected to the shot peening process, and the oxide film 42 on the bottom surface 28 is subjected to the shot peening process. Since the film thickness ratio with respect to the unapplied portion has a film thickness of 0.8 or more, the oxide film 42 ensures adequate seizure resistance and rollability. In the chamfered front portion 34f, the metal flow of the workpiece 14 does not reach the bottom portion of the processed tooth 20, but the oxide film 42 having a predetermined film thickness remains on the flank 26, thereby preventing seizure resistance and rolling. Processability can be secured appropriately.

  Further, since the tip surface 24 of the processed tooth 20 from which the oxide film 42 has been removed by the shot peening process is provided with a large number of recesses 46 having a depth of 0.01 to 0.1 mm, As the workpiece 14 bites in, the slip between the processing teeth 20 and the workpiece 14 is more appropriately suppressed, and the thread 52 of the worm 50 can be rolled with higher accuracy.

Further, in this embodiment, amorphous particles having a particle diameter in the range of 80 to 200 μm are used as the shot 44 when performing the shot peening process, and the rolling molding surface 22 is applied at an injection pressure of 0.2 to 6 MPa. Since it is injected substantially perpendicularly, the oxide film 42 on the tooth tip surface 24 of the processing tooth 20 can be appropriately removed. In addition, since the amorphous particles have high hardness and are not easily chipped, even when the shot 44 is collected and repeatedly used for shot peening treatment, the change in particle diameter is suppressed, and the removal performance of the oxide film 42 is maintained for a long period of time. Therefore, stable die quality including obtaining a predetermined thickness of the oxide film 42 on the flank 26 and providing a predetermined recess 46 on the tooth tip surface 24 can be obtained.

Here, the product of the present invention (flat die 10) from which the oxide film 42 of the front portion 34f of the bite is removed by the shot peening process, and such a shot peening process is not performed, and the roll forming including the front side portion 34f of the bite is performed. When a durability test was performed under the following processing conditions using a conventional product in which the oxide film 42 was provided over the entire surface 22, the result shown in FIG. 6 was obtained. “Φ” of the worm specification is called, “Z” is the number of teeth of the worm wheel meshing with the worm 50, “m” is a module, and “PA” is a pressure angle. In the size of the flat die 10, “W” is a width, “T” is a height, and “L” is a total length. “S25C” of the workpiece 14 is a symbol of the type of carbon steel for machine structure defined in JIS, and “HRB” is a hardness symbol of Rockwell hardness defined in JIS. Further, the durability life determination was made based on whether or not the thread 52 of the rolled worm 50 exceeded the dimensional tolerance.
(Processing conditions)
Warm specifications: φ13.4 × Z25 × m0.5 × PA20 °
Flat die 10 size: W25mm x T40mm x L400mm
Chamfer 34 length: 165mm
Length of chamfered front portion 34f: 63 mm (38%)
Work 14: S25C (80HRB)

  As is apparent from the test results of FIG. 6, according to the product of the present invention, durability about 1.5 times that of the conventional product was obtained. In addition to the tool life, when the thread pitch accuracy of the rolled worm 50 was examined, the conventional product was about ± 10%, while the product of the present invention was about ± 8%. Accuracy has also improved.

  As mentioned above, although the Example of this invention was described in detail based on drawing, this is an embodiment to the last, and this invention is implemented in the aspect which added various change and improvement based on the knowledge of those skilled in the art. Can do.

  10: Flat die for worm rolling 20: Processing teeth 22: Rolling molding surface 24: Tip surface 26: Frank 28: Tooth bottom 34: Chamfered portion 34f: Chamfered front portion (Chamfered start portion) 38: Front end 42: oxide film 44: shot (amorphous particles) 46: dent 50: worm 52: screw thread F: rolling direction

Claims (5)

In a method for producing a flat die for worm rolling, which has a rolling molding surface that rolls a thread of a worm with a large number of processing teeth, and an oxide film is provided on the rolling molding surface.
A shot peening process is performed on a biting start portion where the rolling process is started in a biting portion of the rolling molding surface, and the oxide film provided on the tooth tip surface of the processed tooth is removed. A method for producing a flat die for worm rolling, characterized by comprising : 2. The worm rolling flat according to claim 1, wherein the shot peening treatment is performed in a range of 30 to 50% of the biting portion from a front end of the biting portion in a rolling direction. Dies manufacturing method. The oxide film remains on the bottom surface and the flank of the processed tooth of the portion subjected to the shot peening treatment, and the oxide film on the bottom surface of the portion with the portion not subjected to the shot peening treatment The method for producing a flat die for worm rolling according to claim 1 or 2, wherein the film thickness ratio is 0.8 or more . The dent surface of the processed tooth from which the oxide film has been removed by the shot peening treatment is provided with a number of recesses having a depth of 0.01 to 0.1 mm. The manufacturing method of the flat die | dye for worm rolling of any one of these . Before SL shot peening, claims, characterized in that is carried out by injecting perpendicular to the rolling shaping surface of amorphous particles having a particle size in the range of 80~200μm in injection pressure of 0.2~6MPa Item 5. The method for producing a flat die for worm rolling according to any one of Items 1 to 4 .

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