TW202412966A - Rolling dies - Google Patents

Abstract

The present invention provides a rolling die which, in rolling processing of a hollow member, can suppress elongation deformation of a material to be rolled in the circumferential direction and the axial direction as much as possible without increasing the size of the rolling die and without using a core rod having a special structure during rolling processing, and can obtain a product having a desired tooth profile. Provided is a rolling die in which a plurality of grooves (6) inclined at a predetermined inclination angle (alpha) with respect to the rolling direction in plan view are provided on each machining tooth (5) from the starting end side of a nip section (2) to a predetermined position in the rolling direction of the nip section (2), and a plurality of divided machining teeth (5a) are formed by the grooves (6). Each of the breaking teeth (5a) is disposed in the rolling direction so as to have a phase difference in the width direction of the die body (1).

Description

Roller mold

The present invention relates to a roller mold.

Traditionally, rolling processing is widely used in the manufacture of metal splines, serrations, gears, screws, lead screws, and worms. The rolling die with rolling teeth (processing teeth) is used to clamp the cylindrical rolled material, and while applying pressure, the outer peripheral surface of the rolled material is plastically deformed to form the desired tooth shape. Compared with cutting, rolling has the advantages of good mass production and suitable for mass production; improving the hardness of the rolled product surface by work hardening and improving the strength; improving the processing roughness of the rolled product surface by the burnishing effect between the processing teeth of the rolling die and the rolled material. In addition, bolt grooves and teeth are widely used in automotive parts such as drive shafts and steering shafts. In recent years, with the demand for lightweight vehicles, the above-mentioned bolt grooves and other products (rolled products) are not limited to solid products. There is also a high demand for hollow products with "holes with a circular cross-section along the roughly cylindrical center axis". However, when a hollow material is used as the rolled material and the outer surface of the hollow material is rolled, the rolled material stretches and deforms in the circumferential and axial directions, and a product with the desired tooth shape cannot be obtained. In addition, when the rolling load is too large, the rolled material may be cut. In this way, in order to prevent the "rolled material (hollow material) from stretching and deforming in the circumferential and axial directions" as much as possible, a method of rolling is adopted in which a rod-shaped core (also called a core rod, a core shaft, etc.) is inserted into the "hole along the slightly cylindrical center axis". However, the following problem still exists: it is difficult to obtain a product with the desired tooth shape by simply using a core. In addition, a rolling flat die or a rolling under-round die (a rolling die having a shape of "a part of the outer circumference of a substantially cylindrical shape being cut off") having a general introduction portion formed therein, wherein as the rolling processing at the introduction portion is carried out (towards the terminal side of the rolling direction), the processing teeth are The more the pressing amount (processing amount) of the rolled material increases, for example, in the flat rolling die, the processing teeth of the lead-in part are set so that the front edge line of the processing teeth (the virtual line connecting the front edges of the processing teeth) is closer to the rolled material from the starting end side of the rolling direction to the end side of the rolling direction, thus forming an inclination. Although the method tries to prevent the rolled material (hollow material) from stretching and deforming in the circumferential and axial directions by "relaxing the inclination of the leading edge of the processing tooth of the lead-in part and slowly applying the rolling load to the rolled material", the problem of "difficulty in obtaining a product with the desired tooth shape" still cannot be solved. In addition, the length of the lead-in part must be extended, which results in the problem of increasing the size of the rolling die. Therefore, in the case of manufacturing the above-mentioned hollow products, the following manufacturing method is usually adopted: after performing roller rolling processing on a substantially cylindrical solid material to "form the desired tooth shape such as bolt grooves", a circular cross-section hole processing is performed along the substantially cylindrical center axis. In this method, there is a problem of increased manufacturing cost due to the increase in the hole processing step. In view of this, to date, a roller rolling processing method for hollow materials such as Patent Documents 1 and 2 has been proposed. [Prior Art] [Patent Document] [Patent Document 1] Japanese Patent Publication No. 2014-054644 [Patent Document 2] Japanese Patent Publication No. 2002-143970

[Problem to be solved by the invention] In the above-mentioned patent document 1, a method for rolling processing of a hollow material is disclosed, wherein a hard ball group formed by a plurality of hard balls is accommodated in a through hole of the hollow material having a through hole "connected to two end openings", a jig is inserted from the two end openings, and the hard ball group is pressurized by the two jigs while positioning the hollow material, and the tooth-shaped processing surface of the rolling die is pressed against the outer peripheral surface of the hollow material to roll the outer peripheral surface of the hollow material, and after rolling, the hard ball group is taken out from the through hole to manufacture a hollow rolled product. However, this method does not have a rod-shaped object with a circular cross-section as a core (so-called round rod), but is a method using a hard ball group formed by a plurality of hard balls. Since it requires the steps of "accommodating the hard ball group formed by a plurality of hard balls in the through hole of the hollow material", "positioning the hollow material while pressurizing the hard ball group", and "removing the hard ball group from the through hole after rolling", there is a problem of "processing time is too time-consuming", and the advantage (advantage) of "rolling processing with good mass productivity and most suitable for mass production" cannot be utilized. In addition, the above-mentioned patent document 2 discloses a method for manufacturing a hollow gear, wherein an inner diameter spindle having concave and convex portions on the outer circumferential surface, "each concave portion and each convex portion extending in parallel to each other in the axial direction and continuously arranged in the circumferential direction", is inserted into the central axial hole of a cylindrical workpiece, and while the workpiece and the inner diameter spindle are rotated together, the tooth processing surface of the rolling die is pressed against the outer circumferential surface of the workpiece, and the tooth shape is roll-formed on the outer circumferential surface. Since the roll-forming is performed while the convex portions arranged on the outer circumferential surface of the inner diameter spindle are pressed against the inner circumferential surface of the workpiece, the convex portions can limit "the flow of material in the circumferential direction of the workpiece" and the expansion of the circumference of the workpiece extending toward the inner circumferential surface can be suppressed. However, since this method is to press the convex parts provided on the outer peripheral surface of the inner diameter core shaft (core) to the inner peripheral surface of the workpiece while rolling and forming, not only the inner peripheral surface of the workpiece is deformed and cannot meet the size specifications of the inner diameter of the workpiece, but also it is very time-consuming to remove the workpiece from the inner diameter core shaft (core), and sometimes it is even impossible to remove it. The present invention is developed in view of the above-mentioned current situation, and its purpose is to provide a rolling die that can be used in the rolling processing of hollow materials without enlarging the rolling die and without using a core of a special structure during rolling processing, and can maximally suppress the elongation and deformation of the rolled material in the circumferential direction and axial direction, and obtain a product with a desired tooth shape. [Means for Solving the Problem] The gist of the present invention is explained with reference to the drawings. A rolling die has an introduction portion 2, a finishing portion 3 and an introduction portion 4, which are respectively provided with processing teeth 5 from the starting end side of the rolling direction of the die body 1 to the terminal side of the rolling direction, and the processing teeth 5 promote plastic deformation of the outer peripheral surface of the rolled material W to roll out the desired tooth shape. The rolling die is characterized in that: from the starting end side of the introduction portion 2 to the terminal side of the rolling direction, the finishing portion 3 and the introduction portion 4 are provided with processing teeth 5. From the specific position of the introduction part 2 in the rolling direction, each processing tooth 5 is provided with: a plurality of grooves 6 inclined at a specific tilt angle α to the rolling direction in a top view, and a plurality of split processing teeth 5a are formed by the grooves 6, and each split processing tooth 5a is arranged to have a phase difference in the width direction of the mold body 1 in the rolling direction. In addition, in the rolling mold described in claim 1, the split processing tooth 5a is arranged to have a phase difference that can process the entire rolling width of the rolled material W in the split processing tooth area 7 where the split processing tooth 5a is arranged. In addition, in the roller mold described in claim 1, the groove 6 is provided at a position from the starting end position of the introduction portion 2 to 60% to 95% of the length L2 of the introduction portion 2. In addition, in the roller mold described in claim 2, the groove 6 is provided at a position from the starting end position of the introduction portion 2 to 60% to 95% of the length L2 of the introduction portion 2. In addition, in the roller mold described in claim 1, the groove 6 is provided at a position from a specific distance from the starting end of the introduction portion 2 to 60% to 95% of the length L2 of the introduction portion 2. In addition, in the roller die described in claim 2, the groove 6 is provided at a position at a specific distance from the starting end of the introduction portion 2 to a position of 60% to 95% of the length L2 of the introduction portion 2. In addition, in the roller die described in claim 1, the tooth width W1 of the split processing tooth 5a is less than 3.3 mm, and the groove 6 is provided at equal intervals in the direction of the tooth intersection of the split processing tooth 5a. In addition, in the roller die described in claim 2, the tooth width W1 of the split processing tooth 5a is less than 3.3 mm, and the groove 6 is provided at equal intervals in the direction of the tooth intersection of the split processing tooth 5a. In addition, in the roller die described in claim 3, the tooth width W1 of the split processing tooth 5a is less than 3.3 mm, and the grooves 6 are arranged at equal intervals in the direction of the tooth intersection of the split processing tooth 5a. In addition, in the roller die described in claim 4, the tooth width W1 of the split processing tooth 5a is less than 3.3 mm, and the grooves 6 are arranged at equal intervals in the direction of the tooth intersection of the split processing tooth 5a. In addition, in the roller die described in claim 5, the tooth width W1 of the split processing tooth 5a is less than 3.3 mm, and the grooves 6 are arranged at equal intervals in the direction of the tooth intersection of the split processing tooth 5a. In addition, in the roller mold described in claim 6, the tooth width W1 of the aforementioned split processing tooth 5a is less than 3.3 mm, and the aforementioned groove 6 is arranged at equal intervals in the direction of the tooth intersection line of the aforementioned split processing tooth 5a. In addition, in the roller mold described in any one of claims 1 to 12, the aforementioned tilt angle α is 0.35°~7.10°. In addition, in the roller mold described in any one of claims 1 to 12, the aforementioned groove 6 is a straight line in a top view. In addition, in the roller mold described in claim 13, the aforementioned groove 6 is a straight line in a top view. In addition, in the rolling die described in any one of claim 1 to claim 12, a decreasing portion 7b is provided in a specific range on the rolling direction terminal side of the aforementioned segmentation processing tooth area 7 having the aforementioned segmentation processing tooth 5a, and the decreasing portion 7b is configured such that the groove depth D of the aforementioned groove 6 gradually becomes shallower toward the rolling direction terminal, and the groove width W2 of the aforementioned groove 6 gradually becomes narrower. In addition, in the rolling die described in claim 13, a decreasing portion 7b is provided in a specific range on the rolling direction terminal side of the aforementioned segmentation processing tooth area 7 where the aforementioned segmentation processing tooth 5a is provided, and the decreasing portion 7b is configured such that the groove depth D of the aforementioned groove 6 gradually becomes shallower toward the rolling direction terminal, and the groove width W2 of the aforementioned groove 6 gradually becomes narrower. In addition, in the rolling die described in claim 14, a decreasing portion 7b is provided in a specific range on the rolling direction terminal side of the aforementioned segmentation processing tooth area 7 where the aforementioned segmentation processing tooth 5a is provided, and the decreasing portion 7b is configured such that the groove depth D of the aforementioned groove 6 gradually becomes shallower toward the rolling direction terminal, and the groove width W2 of the aforementioned groove 6 gradually becomes narrower. In addition, in the rolling die described in claim 15, a decreasing portion 7b is provided in a specific range on the rolling direction terminal side of the aforementioned segmentation processing tooth area 7 where the aforementioned segmentation processing tooth 5a is provided, and the decreasing portion 7b is configured such that the groove depth D of the aforementioned groove 6 gradually becomes shallower toward the rolling direction terminal, and the groove width W2 of the aforementioned groove 6 gradually becomes narrower. [Effect of the invention] The present invention, based on the structure as described above, can be used in the rolling process of hollow materials without increasing the size of the rolling die and without using a core of a special structure during the rolling process. It can maximally suppress the elongation and deformation of the rolled material in the circumferential and axial directions, and obtain a rolling die with a desired tooth shape.

The present invention is shown in the drawings and the embodiments of the present invention that are considered suitable are briefly described. In the present invention, from the starting end side of the introduction part 2 to the specific position of the introduction part 2 in the rolling direction, each processing tooth 5 is provided with a plurality of grooves 6 that are "inclined at a specific inclination angle α to the rolling direction in a top view". The processing tooth 5 is divided by the grooves 6 to form a plurality of divided processing teeth 5a. Since each divided processing tooth 5a has a phase difference in the width direction of the mold body 1 in the rolling direction (the divided processing tooth 5a adjacent to the rolling direction does not present a phase difference along the rolling direction), the processing tooth 5 is divided by the grooves 6 to form a plurality of divided processing teeth 5a. Therefore, in the segmented processing tooth area 7 of the introduction portion 2, the rolled material W is intermittently processed, and the processing load is concentrated on the "tooth leading edge of the segmented processing tooth 5a whose pressing area is smaller than the processing tooth 5". Even when the rolled material W is a hollow material with a thin material thickness, the elongation and deformation of the rolled material W in the circumferential direction and the axial direction can be suppressed to the maximum extent. That is, in the conventional rolling die, as shown in FIG. 16, since the entire front edge of the processing tooth 25 extending in the direction of the tooth intersection line of the die body 21 is pressed into the tooth groove of the rolled material W, when the rolled material W is a hollow material with a thin material thickness, the material does not rise (bulge) toward the "tooth groove of the die for processing solid material" well, thereby causing radial failure when a core bone is not used, and even when a core bone is used, The material W to be rolled is deformed in the axial direction and the circumferential direction, and cannot be plastically processed into a specific tooth shape. For example, as shown in Figures 14 and 15, the present invention has the split processing teeth 5a pressing the material W to be rolled. As the rolling process proceeds, the split processing teeth 5a move in the direction of the tooth intersection line in sequence and perform intermittent processing. In addition, the area of the material W to be rolled is reduced, and the processing load is concentrated on the tooth front edge of each split processing tooth 5a, improving the "bulge of the material of the rolled material W" and forming the desired shape. In this way, even if the material W to be rolled is a hollow material with a thin material thickness, the rolling die can be suppressed from stretching and deforming in the circumferential direction and the axial direction. [Example] The specific embodiment of the present invention is described with reference to the drawings. The present embodiment is related to a rolling die having an introduction portion 2, a finishing portion 3 and an outlet portion 4, which are respectively provided with processing teeth 5 from the rolling direction starting end side of the die body 1 toward the rolling direction terminal side, and the processing teeth 5 promote the plastic deformation of the outer peripheral surface of the rolled material W to roll out the desired tooth shape. Specifically, the present embodiment is an example of applying the rolling die of the present invention to a rolling flat die for rolling bolt grooves, tooth patterns and gears. The following is a detailed description of the structure of each part of the present embodiment. In this embodiment, the mold body 1 is rectangular in a top view as shown in FIG. 1 , and the bottom surface 8 forms a "flat surface serving as a reference surface". In addition, a large number of processing teeth 5 for "forming a tooth shape for the rolled material W" are provided on the top surface located on the opposite side of the bottom surface 8. The tooth front edge lines of the processing teeth 5 (the virtual lines connecting the tooth front edges of the processing teeth 5) are shown as solid lines in the explanatory front view of FIG. 1 (the figure on the lower side of FIG. 1 ). In addition, the mold body 1 of this embodiment is shot blasted in a specific range from the rolling direction starting end side of the mold top surface provided with the processing teeth 5 toward the rolling direction terminal side for the purpose of preventing the sliding of the rolled material W (preventing the rolled material W from being offset from the position of the processing teeth 5) (in this embodiment, shot blasting is performed on a range of about 2/3 of the length (full length) of the introduction part 2 indicated by the figure number L2 in the figure (the range indicated by the figure number SB in the figure)). The figure number L1 in the figure represents the sum of the ranges (lengths) of the introduction part 2, the finishing part 3 and the lead-out part 4 in the rolling direction. In addition, this embodiment is a rolling flat die for processing a general bolt groove (a bolt groove having a tooth shape parallel to the axial direction of the rolled material W), and in the die body 1, the processing teeth 5 of the introduction part 2, the finishing part 3 and the lead-out part 4 are formed into a mountain shape (slightly trapezoidal shape) in a front view angle, and constitute straight processing teeth "extending straightly toward the width direction of the die body 1, more specifically, toward the direction perpendicular to the rolling direction", and are arranged in parallel at specific intervals toward the rolling direction. By defining the extending setting direction of the processing teeth 5 as a direction inclined to the "direction perpendicular to the rolling direction", it can be applied to a rolling die for processing a helical bolt groove (helical spline), a helical gear (helical gear), etc. Specifically, the processing teeth 5 of the introduction part 2 are configured such that the tooth depth gradually increases from the starting end side in the rolling direction toward the terminal side in the rolling direction, and the outer periphery of the rolled material W is gradually pressed into the rolled material W, and the tooth shape is raised. In addition, the processing teeth 5 of the finishing part 3 are configured such that a certain (constant) tooth depth (the tooth depth substantially the same as that of the processing teeth 5 at the terminal end of the introduction part 2) is set, and the tooth shape formed in the introduction part 2 is finished to the product size. In addition, the processing teeth 5 of the lead-out part 4 are configured such that an "inclined surface inclined downward toward the terminal side in the rolling direction" is set, and the position of the front end surface gradually becomes lower toward the terminal side in the rolling direction. In addition, the introduction portion 2 of the present embodiment, as shown in FIG1, constitutes a segmented processing tooth area portion 7 from the starting end position to a specific position in the rolling direction, and the segmented processing tooth area portion 7 is provided with: a plurality of segmented processing teeth 5a formed by segmenting each processing tooth 5 in the width direction of the mold body 1 by a plurality of grooves 6. The figure number X in the figure represents the rolling direction range (length) of the aforementioned segmented processing tooth area portion 7. In the segmented processing tooth area portion 7, as shown in FIG2, the segmented processing teeth 5a are arranged in a straight line in the width direction of the mold body 1, and in the rolling direction, they are arranged to have a phase difference in the width direction of the mold body 1. Specifically, the segmentation processing teeth 5a in the segmentation processing tooth area 7 are configured to have a phase difference that can process "the entire rolling width of the rolled material W or the substantially entire rolling width" in the segmentation processing tooth area 7. The rolling width referred to here refers to the range of the axial direction of the tooth shape formed by rolling processing on the rolled material W. In addition, the segmentation processing tooth area 7 of the present embodiment is set at a position from the starting end position of the introduction part 2 to 60% to 95% of the length L2 of the introduction part 2. By setting the segmentation processing tooth region 7, i.e., the segmentation processing tooth 5a, from the starting end of the introduction part 2, the range of the segmentation processing tooth region 7 can be set wide in the introduction part 2 of a predetermined length, so that the rolling processing performed by the segmentation processing tooth 5a can be performed in a larger amount, and the effect of the present invention, i.e., the effect of suppressing the elongation and deformation of the rolled material W in the circumferential direction and the axial direction, can be better exerted. In addition, the segmentation processing tooth region 7 may not be a structure starting from the starting end of the introduction part 2, but may be a structure starting from "a position separated from the starting end of the introduction part 2 by an appropriate distance" as shown in FIG. 23. In this case, the position where the segmentation processing tooth region 7 is provided (the position where the segmentation processing tooth region 7 starts, i.e., the starting position of the groove 6) is preferably set to a position separated by "a distance of 0.5 to 2 rotations of the rolled material W". In addition, the reason for defining the range of the split processing tooth 5a as "the position of 60% to 95% of the length L2 of the introduction portion 2" is that: when the split processing tooth 5a is only located at a position less than half of the length of the introduction portion 2, the expected effect cannot be exerted. If it is set to extend over the entire length of the introduction portion 2, that is, when it is set to the boundary position with the finishing portion 3, even after the processing tooth 5 of the finishing portion 3 is rolled, the tooth intersection line formed on the tooth shape of the rolled material W cannot be aligned, and there is a concern that scratches (caused by the grooves of the grooves 6) may remain on the tooth surface after rolling. Therefore, the upper limit position of the range where the split processing teeth 5a are provided can be set to "slightly move forward (slightly close to the starting end side in the rolling direction) compared to the boundary position with the finishing part 3", and the best position is "the position to 95% of the length L2 of the introduction part 2". In addition, the groove 6 (groove 6 that divides the processing teeth 5) that forms the split processing teeth 5a is formed by grinding using a grindstone: as shown in Figure 3, the groove width becomes wider from the bottom side to the top. The formation of the groove 6 is not limited to the above-mentioned processing, and for example, it can also be formed by laser processing. In addition, when the groove width W2 of the groove 6 is "too narrow relative to the tooth width W1 of the split processing tooth 5a described later", since it becomes a shape close to the known product (a product without the groove 6 and without the split processing tooth 5a), it is impossible to obtain a sufficient deformation suppression effect for the rolled material W with a thin material thickness. In addition, when the groove width W2 is "too wide relative to the tooth width W1", the processing load of the finished part 3 becomes large due to the generation of the unprocessed part, which further causes the rolled material W to deform. Therefore, the groove width W2 of the groove 6 needs to be set according to the tooth width W1 of the split processing tooth 5a. Based on this point, the groove width W2 of the groove 6 can be appropriately set within a range that does not damage the effect of the present embodiment. The groove width is preferably equal to or narrower than the tooth width W1 of the splitting processing tooth 5a. Specifically, it is best to set the ratio of the tooth width W1 of the splitting processing tooth 5a/the groove width W2 of the groove 6 to be 0.9~1.8. The specification that the ratio of the tooth width W1 of the split processing tooth 5a/the groove width W2 of the groove 6 is 0.9 (the specification of Experimental Example 2 described later) becomes the specification of "the groove width W2 is slightly wider than the tooth width W1". In this case, although a slight unprocessed portion remains in the split processing tooth area portion 7 of the introduction portion 2, since almost the entire area of the roller width is processed, there is no situation of "excessive processing load of the finishing portion 3". Therefore, as described above, it is included in the optimal range, and is the specification included in "the groove width equal to the tooth width W1 of the split processing tooth 5a". In addition, in the present embodiment, the groove width W2 of the groove 6, as shown in Figure 3, means "the groove width in the width direction of the mold body 1 at the upper edge of the groove 6 (the widest part of the groove width)". In addition, in the present embodiment, the tooth width W1 of the splitting processing tooth 5a, as shown in Figure 3, means "the tooth width in the width direction of the mold body 1 at the front end surface of the splitting processing tooth 5a". In addition, the groove 6 of the present embodiment is provided along the inclination of the processing tooth 5 of the introduction portion 2 (the inclination of the front edge of the processing tooth 5) from the starting end side in the rolling direction toward the rear end side in the rolling direction, and the groove depth D of the groove 6 based on the front edge of the processing tooth 5 is set to a constant (constant) depth. The groove depth D of the groove 6 can be appropriately set within a range that does not impair the effects of the present embodiment, and it does not matter if it is set to a constant (constant) depth based on the front edge of the processing tooth 5. In addition, although in the present embodiment, the groove depth D of the groove 6 is set to a depth greater than the tooth depth of the processing tooth 5, so as to completely divide the processing tooth 5, it can also be set to a depth shallower than the tooth depth of the processing tooth 5 as shown in FIG. 11 as long as it is a specific depth that can exert the effect of the present embodiment. For example, the groove depth D of the groove 6 can be set corresponding to the processability of the rolled material W. When the rolled material W is a "material that is easily raised by rolling (a material with high ductility)", it is sufficient to set the groove depth D of the groove 6 to be deeper (for example, set it to be greater than the tooth depth of the processing tooth 5). When it is a "material that is not easy to rise (a material with high work hardening property)", in order to prevent the loss during rolling caused by the reduction in strength of the split processing tooth 5a, it is sufficient to set the groove depth D of the groove 6 to be shallower (shallower than the tooth depth of the processing tooth 5, for example, set it to a depth of 50% of the tooth depth of the processing tooth 5). In addition, the grooves 6 of this embodiment are arranged at equal intervals in the direction of the tooth intersection of the segmentation processing teeth 5a in order to make the tooth width W1 of the segmentation processing teeth 5a less than 3.3 mm (once the tooth width W1 of the segmentation processing teeth 5a is set to a value (wide value) larger than the above value, the thin rolled material W will not be able to obtain a sufficient deformation suppression effect). As mentioned above, this embodiment is a roll flat die for processing a general bolt groove (a bolt groove formed parallel to the axial direction of the rolled material W), so the tooth intersection direction is consistent with the width direction of the die body 1. Although the narrower the tooth width W1 of the split processing tooth 5a, the better the deformation suppression effect of the rolled material W can be obtained, on the contrary, it is easy to produce a gap, which leads to the problem of "shortened tool life". Therefore, the setting of the tooth width W1 of the split processing tooth 5a must consider the balance between "the deformation suppression effect of the rolled material W" and "the tool life". Specifically, the tooth front edge width of the first tooth of the mold in the rolling direction is defined as the threshold value. If the tooth width W1 is narrower than the threshold value, it is very easy to produce a gap. Therefore, the tooth width W1 is preferably set to: the tooth front edge width of the first tooth of the mold in the rolling direction is greater than. Based on this point, the grooves 6 of this embodiment are arranged at equal intervals in the direction of the tooth intersection of the split processing teeth 5a in order to make the tooth width W1 of the split processing teeth 5a of the complete shape (the state divided by two grooves 6) be greater than 0.5 mm and less than 3.3 mm. In addition, the grooves 6 of this embodiment are arranged relative to the roll direction: inclined toward the "width direction of the mold body 1", that is, the "tooth intersection direction of the processing teeth 5". Specifically, in the top view angle (tooth depth direction viewing angle), it is inclined at a specific inclination angle α relative to the roll direction. In addition, each groove 6 is arranged in the roll direction to be a straight line (linear and continuous) in the top view angle as shown in Figure 2. By providing the groove 6 in the above manner, the segmentation processing teeth 5a can be easily arranged in the rolling direction in a state with a phase difference in the width direction of the mold body 1. The groove 6 is not limited to being "provided to be a straight line in a top view as in the present embodiment", and can also be provided in a straight line (linear and discontinuous) along a straight line in a top view as shown in another example of the present embodiment shown in FIG. 11(b). Specifically, the groove 6 of the present embodiment is inclined at an angle (inclination angle α) of 0.35° to 7.10° relative to the rolling direction in a top view. In the present embodiment, the "deepest pressing amount (maximum processing amount) of the splitting processing tooth 5a to press the rolled material in the tooth depth direction" is defined as within 0.14 mm, and by setting the groove 6 at the aforementioned angle, in the splitting processing tooth area 7, During the period when the rolled material W forms 0.5 to 2 rotations, the entire rolling width of the rolled material W or substantially the entire rolling width is processed to form an "unprocessed portion" (if the tilt angle α becomes larger, an axial load will be applied to the rolled material W during the rolling period, increasing the concern that the rolled material W will bend. Therefore, the tilt angle α is preferably set not to exceed the aforementioned range). The reason why the maximum processing amount of the split processing tooth 5a must be set to within 0.14mm is based on the results of various experiments including Experimental Examples 1 to 3 (this embodiment: the maximum processing amount of the split processing tooth 5a is 0.14mm). When the maximum processing amount exceeds 0.14mm, the processing load on the rolled material will become too large, causing the rolled material W to stretch and deform in the circumferential direction and the axial direction. For example, in the case of a bolt groove processing mold with "module 0.3, number of bolt groove teeth 66, and lead-in processing amount 0.055mm/rev", if the groove 6 is set in order to process the entire width of the roller or approximately the entire width of the roller during the period in which the rolled material W forms two rotations, the maximum processing amount of the divided processing tooth 5a (the processing amount of the second rotation) is 0.1375mm and is within 0.14mm, so it becomes a structure that can obtain the effect of the present invention. In contrast, in the case of a bolt groove processing mold with "module 1.0, number of bolt groove teeth 27, and lead-in processing amount 0.14mm/rev", if the groove 6 is set in order to process the entire width of the roller or approximately the entire width of the roller while the rolled material W forms two rotations, the maximum processing amount of the split processing teeth 5 (the processing amount of the second rotation) will become 0.35mm, which exceeds 0.14mm, thereby causing the rolled material W to stretch and deform in the circumferential and axial directions, and it is impossible to obtain a good result. In this case, in order to prevent the maximum machining amount from exceeding 0.14 mm, the groove 6 must be set so that "the entire width of the roller or substantially the entire width of the roller is machined every 0.5 rotations." Specifically, in the case of "bolt groove with tooth front edge circular diameter φ21, module 0.3, and number of teeth 66", when the total length L of the mold body 1 is 410 mm, the length L2 of the introduction portion 2 is 289 mm, and the pitch P of the groove 6 is defined as 0.782 mm, and when the entire roller width or approximately the entire roller width is processed during two rotations of the rolled material W, the tilt angle α is 0.35° (MIN). When the pitch P of the groove 6 is defined as 6.967 mm, and when the entire roller width or approximately the entire roller width is processed during one rotation of the rolled material W, the tilt angle α becomes 5.88° (MAX). Furthermore, in the case of "bolt groove with tooth front edge circular diameter φ17.4, module 0.47, and number of teeth 36", when the total length L of the mold body 1 is 410 mm, L2 of the introduction portion 2 is 304 mm, and the pitch P of the groove 6 is defined as 1.347 mm, and when the entire roller width or approximately the entire roller width is processed during two rotations of the rolled material W, the tilt angle α is 0.73° (MIN), and when the pitch P of the groove 6 is defined as 6.967 mm, and when the entire roller width or approximately the entire roller width is processed during one rotation of the rolled material W, the tilt angle α becomes 7.10° (MAX). In addition, in the case of "tooth front edge circular diameter φ27.5, module 1.0, number of teeth 27", the tilt angle α becomes 1.79°~4.13° (please refer to Experimental Examples 1~4 described later). In addition, a decreasing portion 7b is provided at the end side of the roller direction of the segmented processing tooth area portion 7 of this embodiment. Specifically, the decreasing portion 7b is set in the range of 6 to 12 processing teeth 5 at the end of the divided processing tooth area portion 7, and the groove 6 set in each processing tooth 5 of the decreasing portion 7b is set to a shallower groove depth and a narrower groove width than "the groove 6 of the divided processing area portion 7a which is set on the starting end side closer to the starting end side of the roller direction than the decreasing portion 7b in the divided processing tooth area portion 7". Not only that, the groove 6 set in "the processing tooth 5 closer to the end of the decreasing portion 7b" is set to a shallower groove depth and a narrower groove width. In addition, the groove depth of the groove 6 at the decreasing portion 7b can also become shallower in a curved manner from "the boundary between the starting end side dividing processing tooth area 7a and the decreasing portion 7b" toward the end of the decreasing portion 7b. For example, it can also become shallower slowly and linearly along the slope of the decreasing angle g set as follows (please refer to Figure 4). The decreasing angle g = arctan (the groove depth D of the groove 6 at the boundary between the starting end side segmented processing tooth area 7a and the decreasing portion 7b/the length of the decreasing portion 7b in the rolling direction) By providing the decreasing portion 7b, the shape change of the processing tooth 5 caused by the presence of the groove 6 in the "starting end side segmented processing tooth area 7a" and "in the introduction portion 2, closer to the end side of the rolling direction than the segmented processing tooth area 7" tends to be stable, thereby suppressing the rapid change of the processing load and the elongation deformation of the rolled material. The lead-in portion 2 of this embodiment, as shown in FIG. 1, has a certain (constant) inclination of the tooth front edge line, that is, the processing amount of the lead-in portion 2 (the processing amount per rotation of the rolled material W) is set to be certain (constant). The lead-in portion 2 can also be constructed as follows: a specific range measured at the starting end of the lead-in portion 2 is defined as the first lead-in layer, and the remaining lead-in portion 2 is defined as the second lead-in layer, the inclination of the tooth front edge line of the first lead-in layer is increased, and the inclination of the tooth front edge line of the second lead-in layer is reduced, the processing amount in the first lead-in layer is increased, and the processing amount in the second lead-in layer is reduced. In addition, although the present embodiment, as previously described, applies the roll-rolling die of the present invention to the roll-rolling flat die shown in FIG12, the roll-rolling die of the present invention can also be applied to the roll-rolling under-rounding die shown in FIG13. The roll-rolling under-rounding die has a rotation direction in the rolling direction, and the roll-rolling teeth formed on its outer circumference are sequentially and continuously provided from the starting end side in the rolling direction: an introduction portion 2, whose distance from the rotation axis of the roll-rolling under-rounding die to the tooth front edge of the processing tooth 5 is different; a finishing portion 3 and a guide portion 4. In the case of a roll-rolling under-rounding die, the groove 6 is set in a spiral shape at a lead angle (also called a lead angle) α around the rotation axis of the roll-rolling under-rounding die, and the lead angle α is equivalent to the tilt angle α of the roll-rolling flat die (see Figure 13 (b)). In this way, by setting the groove 6 in a spiral shape around the rotation axis of the roll-rolling under-rounding die, the groove 6 is tilted at a specific tilt angle α relative to the roll direction in the top view of the introduction part 2 of the roll-rolling under-rounding die where the groove 6 is formed, and is set to be a straight line in the roll direction in the top view (slightly curved and almost straight line state). In other words, as shown in FIG. 13( b), the groove 6 is inclined at a specific tilt angle α relative to the rolling direction, similar to the flat rolling mold, in the unfolded state where the "outer peripheral surface of the roll-rolling under-rounding mold" has been unfolded into a plane, and is arranged to form a straight line in the rolling direction when viewed from above. Therefore, in the roll-rolling under-rounding mold, by arranging the groove 6 in a spiral shape around the rotation axis of the roll-rolling under-rounding mold, the same effect as the "effect applied to the flat rolling mold described below" can be achieved. Since the roller under-round mold is slightly cylindrical, the groove 6 located at the end side of the left and right direction (roller direction) of the visible range appears to be slightly curved when viewed from above. In this embodiment, this state of appearing to be slightly curved is also included in "appearing to be a straight line in a top view angle". Since the present embodiment is constructed as described above, the split processing tooth area portion 7 formed in the introduction portion 2 performs processing intermittently while the "position where the split processing tooth 5a presses the rolled material W" moves in the width direction of the mold body 1. Not only that, the area of the rolled material W pressed in becomes smaller than that in the case where the "rolled material W is pressed in by the processing tooth 5". By concentrating the processing load on the leading edge of each split processing tooth 5a, the split processing tooth 5a is more likely to be introduced (bite) into the rolled material W. Even in the case where the "rolled material W is a hollow material with a thin material thickness", the elongation deformation in the circumferential direction and the axial direction can be suppressed. In the rolling process of the bolt groove of the hollow material, the greater the ratio of the tooth depth of the bolt groove to the material thickness of the rolled material W, the greater the elongation deformation in the circumferential direction and the axial direction, making it difficult to form the desired tooth shape. In addition, the greater the ratio of the inner diameter of the rolled material W (the diameter of the hollow part of the rolled material W) to the outer diameter (the diameter of the rolled material W), that is, the thinner the material thickness of the rolled material W, the greater the elongation deformation in the circumferential direction and the axial direction, making it difficult to form the desired tooth shape. Specifically, the applicant's achievements so far, when assuming a bolt groove with a modulus of 0.3 to 1.1, are limited to the case where the ratio of the bolt groove tooth depth to the material thickness of the rolled material W is less than 17% and the inner diameter of the rolled material W is ( In the case where the ratio of the depth of the bolt groove to the material thickness of the rolled material W is less than 20% and the ratio of the inner diameter of the rolled material W (the diameter of the hollow part of the rolled material W) to the outer diameter (the diameter of the rolled material W) is less than 47%, even if the core is used, it is only in the case where the ratio of the depth of the bolt groove to the material thickness of the rolled material W is less than 20% and the ratio of the inner diameter of the rolled material W (the diameter of the hollow part of the rolled material W) to the outer diameter (the diameter of the rolled material W) is less than 47%. However, by adopting the present embodiment, as long as the conditions that "the ratio of the tooth depth of the bolt groove to the material thickness of the rolled material W is less than 20%, and the ratio of the inner diameter of the rolled material W (the diameter of the hollow part of the rolled material W) to the outer diameter (the diameter of the rolled material W) is less than 55%" are met, it can be well processed without using a core bone. In addition, by adopting the core bone, an object that meets the conditions that "the ratio of the tooth depth of the bolt groove to the material thickness of the rolled material W is less than 30%, and the ratio of the inner diameter of the rolled material W (the diameter of the hollow part of the rolled material W) to the outer diameter (the diameter of the rolled material W) is less than 70%" can be well processed. The following is an experiment (evaluation experiment) to support the effect of the present embodiment described above. <Experiment 1> As shown in Tables 1 and 2, a conventional general rolling flat die (hereinafter referred to as "conventional example 1" and "conventional example 2") was used; a total of 6 rolling flat dies of Experimental Examples 1 to 4, which had different structures such as the tooth width of the split processing tooth 5a in the present embodiment, were used to perform bolt groove rolling processing using a general core bone on the rolled material W of the hollow material, and an evaluation was performed on whether the rolled material W had elongation deformation in the circumferential direction and the axial direction. For the symbols recorded in Table 1, L is the length of the mold body 1, L2 is the length of the introduction part 2, X is the rolling direction range (length) of the segmented processing tooth area part 7, and X/L2 is the ratio of the range X of the segmented processing tooth area part 7 (the length of the rolling direction range of the segmented processing tooth area part 7) to the length L2 of the introduction part 2 (the introduction part length L2) (please refer to Figure 1). In addition, for the symbols recorded in Table 2, W1 is the tooth width of the split processing tooth 5a, W2 is the groove width of the groove 6, P is the pitch of the groove 6, α is the inclination angle of the groove 6, β is the groove angle of the groove 6, D is the groove depth of the groove 6, W3 is the tooth front edge width of the first tooth of the split processing tooth area part 7 in the introduction part 2 in the rolling direction, W1/W3 is the tooth width ratio of the split processing tooth 5a, DP is the bolt groove pitch of the mold (the pitch of the bolt groove processing tooth in the rolling direction), and W1/W2 is the ratio of the tooth width of the split processing tooth 5a to the groove width of the groove 6 (please refer to Figures 2 and 3). Specifically, for hollow materials W with different material thicknesses (material thickness 4mm~8mm), bolt groove rolling processing was performed using a core and the following conditions, and the pin diameter, tooth root circle diameter, tooth shape error, tooth intersection error, pitch cumulative error and tooth groove deflection were measured. Based on the measurement results, whether the rolled material W produced elongation deformation in the circumferential and axial directions was evaluated. <Processing conditions> ‧Bolt groove specifications: tooth front edge diameter φ27.5×Z27×m1.0×PA37.5° Tooth depth: 1.2mm The above Z is the number of bolt groove teeth, m is the module, and PA is the symbol indicating the pressure angle. ‧Material of rolled material: carbon steel (S45C) ‧Material diameter: 26.46mm ‧Processing amount: 0.14mm/rev for traditional example 1 and experimental examples 1~3 0.09mm/rev for traditional example 2 and experimental example 4 ‧Tooth depth h of the first tooth of the guide part 2: 0.6964mm for traditional example 1 and experimental examples 1~3 0.6464mm for traditional example 2 and experimental example 4 ‧Material of rolling die: die steel (SKD11) ‧Distance in the rolling direction traveled by the rolled material per rotation: 83.1mm (=the pitch of the processing teeth of the bolt groove in the rolling direction DP3.0777mm×Z27) ‧Processing conditions: In the center of the roller width, the center value of the over-pin diameter specification is the target <Core used> ‧Material: Carbon steel (quenched) ‧Core size and inner diameter: Please refer to Table 3 below In addition, further explaining Experimental Examples 1 to 4, the number of grooves of the rolled material W is based on the first tooth of the lower mold (the first groove). In Experimental Examples 1 to 3, when the length L2 of the lead-in portion of the mold is set to 449 mm and the number of teeth of the lead-in portion 2 is designed to be 146 teeth, as shown in FIG. 6, the first tooth, the 28th tooth, the 55th tooth, the 82nd tooth, and the 109th tooth of the lower mold are The processing teeth 5 of the 136th tooth become the teeth for processing the first groove of the rolled material W. In addition, the upper mold processes the same groove as the "groove processed by the first tooth of the lower mold" by rotating the rolled material W half a circle, so the processing teeth 5 of the 14th tooth, the 41st tooth, the 68th tooth, the 95th tooth and the 122nd tooth become the teeth for processing the first groove of the rolled material W. In Experimental Example 4, when the length L2 of the lead-in portion of the mold is set to 754 mm and the number of teeth of the lead-in portion 2 is designed to be 245 teeth, as shown in FIG6 , the processing teeth 5 of the 1st, 28th, 55th, 82nd, 109th, 136th, 163rd, 190th, 217th and 244th teeth of the lower mold become the processing teeth 5 for processing the rolled material. In addition, the upper die processes the same groove as the "groove processed by the first tooth of the lower die" by rotating the rolled material W half a circle, so the processing teeth 5 of the 14th tooth, the 41st tooth, the 68th tooth, the 95th tooth, the 122nd tooth, the 149th tooth, the 176th tooth, the 203rd tooth and the 230th tooth become the teeth used to process the first groove of the rolled material W. In addition to the above description, in Experimental Examples 1 to 4, in order to process the entire width of the roll or the approximate entire width of the roll in each half-turn rotation (0.5 rotation) of the rolled material W, the phase of the groove 6 (the offset of the mold body 1 in the width direction) is set. The specifications of each measurement item are shown in Table 4. In addition, the evaluation results are shown in Table 5. In the evaluation results, all items of the over-pin diameter, tooth root circle diameter, tooth shape error, tooth intersection error, pitch cumulative error and tooth groove deflection as evaluation items are marked as "○" if they meet the specifications shown in Table 4, and "×" if even one of the items does not meet the specifications. Those that have not been evaluated are marked as "-". As shown in Table 5, in Conventional Example 1, although a good processed shape with suppressed elongation deformation in the circumferential and axial directions can be obtained for rolled materials W with material thicknesses of 8 mm, 7 mm, and 6 mm, elongation deformation in the circumferential and axial directions is confirmed for rolled materials W with a material thickness of less than 5 mm. In contrast, in Experimental Examples 1 to 4 (the present embodiment), it can be confirmed in all molds that even when facing a rolled material W with a material thickness of 5 mm, a good processing shape in which the elongation deformation in the circumferential and axial directions is suppressed can be obtained. In addition, although in Traditional Example 2 in which the introduction portion length L2 is set longer than "Traditional Example 1 and Experimental Examples 1 to 3", it is confirmed that elongation deformation in the circumferential and axial directions occurs when facing a rolled material W with a material thickness of 4 mm, in Experimental Example 4 (the present embodiment) in which the introduction portion length L2 is set to the same length as that of Traditional Example 2, it can be confirmed that a good processing shape in which the elongation deformation in the circumferential and axial directions is suppressed can be obtained even when facing a rolled material W with a material thickness of 4 mm. In addition, Table 6 and FIG. 7 to FIG. 10 show the detailed results of bolt groove rolling processing on the rolled material W with a material thickness of 5 mm in Conventional Example 1 and Experimental Examples 1 to 4. As shown in Table 6, in the conventional example 1, due to the elongation deformation in the circumferential direction and the axial direction, the three items of the pin diameter, the pitch cumulative error and the tooth groove deflection did not meet the specifications. In contrast, in the present embodiment (experimental examples 1 to 4), all items met the specifications, and a good processing shape with suppressed elongation deformation in the circumferential direction and the axial direction was obtained. Based on the mold specifications of the experimental example 1, the groove depth D of the groove 6 was changed to a shallower depth and set to 0.10 mm, and the bolt groove rolling processing and evaluation were carried out under the same conditions as the above experiment. As in the case where the groove depth D of the groove 6 is 0.95 mm (Experimental Example 1), all evaluation items meet the specifications, and a good processing shape with suppressed elongation deformation in the circumferential direction and the axial direction is obtained. In the bolt groove rolling process of Experimental Example 1, in the segmented processing tooth area 7 of the introduction part 2, the segmented processing tooth 5a contacts the same tooth groove on the rolled material W and at different positions in the rolling width direction (axial direction of the rolled material W) every 0.5 rotation of the rolled material W. This is because: since the processing amount is 0.14 mm/rev, as long as the groove depth D is set to a depth of 0.07 mm (0.14 mm×0.5) or more, the groove 6 will not contact the rolled material W during the rolling process. <Experiment 2> In Experiment 2, conventional Example 1 and Experimental Examples 1 to 4 used in Experiment 1 were used to perform bolt groove rolling processing on hollow materials W with different material thicknesses (material thickness 6mm to 8mm) without using a core. The pin diameter, tooth root circle diameter, tooth shape error, tooth intersection error, pitch cumulative error and tooth groove deflection were measured. Based on the measurement results, whether the rolled material W produced elongation deformation in the circumferential direction and axial direction was evaluated. The evaluation results are shown in Table 7. In the evaluation results, as in Experiment 1, all the items of the evaluation items, namely, the over-screw diameter, tooth root circle diameter, tooth shape error, tooth intersection error, pitch cumulative error, and tooth groove deflection, which meet the specifications shown in Table 4 are marked as "○", and even if one of the items does not meet the specifications, it is marked as "×". As shown in Table 7, in conventional example 1, once the material thickness is not more than 7 mm, it is impossible to obtain a "good processing shape in which the elongation deformation in the circumferential direction and the axial direction is suppressed", but in experimental examples 1 to 4 (the present embodiment), the following excellent results can be confirmed: even when facing a rolled material W with a material thickness of 6 mm and without using a core, a good processing shape in which the elongation deformation in the circumferential direction and the axial direction is suppressed can be obtained. <Experiment 3> In Experiment 3, rolling processing was performed under processing conditions such as "bolt groove specifications and material of rolled material" that are different from those in Experiment 1, and whether the rolled material W produces elongation deformation in the circumferential direction and the axial direction was evaluated. Specifically, as shown in Tables 8 and 9, in this embodiment, the flat rolling dies of Experimental Examples 5 to 8, which have different specifications from the flat rolling dies of Experimental Examples 1 to 4, were used to perform bolt groove rolling processing on the rolled material W of the hollow material without using a core, and the pin diameter, tooth root circle diameter, tooth shape error, tooth intersection error, pitch cumulative error and The tooth groove deflection is measured, and based on the measurement results, whether the rolled material W produces elongation deformation in the circumferential direction and the axial direction is evaluated (Experimental Examples 7 and 8 are evaluations of whether the rolled material W produces elongation deformation in the circumferential direction and the axial direction when the tooth width W1 of the split processing tooth 5a is set to the minimum width (Experimental Example 7) and the maximum width (Experimental Example 8). The symbols recorded in Tables 8 and 9 are the same as those in Experiment 1, so their descriptions are omitted. <Processing conditions> ‧Bolt groove specifications: Tooth front edge diameter φ17.4×Z36×m0.47×PA45° Tooth depth: 0.512mm The above Z is the number of teeth in the bolt groove, m is the module, and PA is the symbol indicating the pressure angle. ‧Material of rolled material: carbon steel (S43C) ‧Material diameter: 16.91mm ‧Processing amount: 0.05mm/rev for Experimental Examples 5, 7, and 8; 0.031mm/rev for Experimental Example 6 ‧Tooth depth h of the first tooth of the guide part 2: 0.289mm ‧Material of the rolling die: die steel (SKD11) ‧Distance in the rolling direction traveled by the rolled material per rotation: 53.0mm ‧Processing conditions: In the center of the rolling width, with the center value of the over-pin diameter specification as the target ‧No core bone is used (the two ends of the rolled material W are held at the correct center) In Experiment 3, two types of hollow rolled materials W with different material thicknesses (material thickness 4.2 mm and 3.5 mm) were used to evaluate whether elongation deformation in the circumferential and axial directions occurred. The specifications of each measurement item are shown in Table 10. In addition, the evaluation results are shown in Table 11. In addition, the measurement results of each measurement item of Experimental Examples 5 and 6 are shown in Figures 17 to 22. In the evaluation results, all items of the over-thread diameter, tooth root circle diameter, tooth shape error, tooth intersection error, pitch cumulative error and tooth groove deflection as evaluation items are marked as "○" if they meet the specifications shown in Table 10, and "×" if even one of the items does not meet the specifications. As shown in Table 11, in all of Experimental Examples 5 to 8, it was confirmed that a good processing shape in which the elongation deformation in the circumferential direction and the axial direction was suppressed was obtained regardless of the material thickness. In addition, as shown in Figures 17 to 22, Experimental Example 6 obtained a good result overall compared to Experimental Example 5. This is considered to be due to the fact that the deformation suppression effect was improved by setting the pitch P of the groove 6 to half and reducing the tooth width W1 of the split processing tooth 5a to half. <Experiment 4> In Experiment 4, for a bolt groove with different specifications from Experiment 3 (tooth front edge circular diameter φ21×Z66×m0.3×PA30°), the material diameter of the rolled material W was defined as 20.42mm (material: carbon steel (S45C)), and the rolled material W of the hollow material was rolled without using a core bar, and an evaluation was conducted to determine whether the rolled material W would produce elongation deformation in the circumferential and axial directions. Specifically, as shown in Table 12, the "over-pin diameter, tooth root diameter and gauge evaluation" were measured when the tooth width W1 of the split processing tooth 5a was set to the minimum width (Experimental Example 9) and the maximum width (Experimental Example 10), and then the rolled material W was evaluated based on the measurement results to see whether elongation deformation in the circumferential direction and the axial direction occurred. The setting conditions of each mold body 1 of Experimental Examples 9 and 10 are shown in Table 13. In addition, since the symbols recorded in Tables 12 and 13 are the same as those in Experiment 1, their description is omitted. The specifications of each measurement item are shown in Table 14. In addition, the evaluation results are shown in Table 15. In the evaluation results, all the evaluation items that meet the specifications are marked as "○", and even if one of the items does not meet the specifications, it is marked as "×". As shown in Table 15, in Experiment 9 in which the tooth width W1 of the split processing tooth 5a was set to the minimum width of 0.503 mm, and in Experiment 10 in which the tooth width W1 was set to the maximum width of 3.3 mm, the results of each evaluation item meeting the specifications were obtained regardless of the material thickness. <Experiment 5> In Experiment 5, the rolled material W was rolled without using a core using dies with different positions of the split processing tooth area 7, and whether the rolled material W produced elongation deformation in the circumferential direction and the axial direction was evaluated. Specifically, as shown in Table 16, for the case where the split processing tooth area portion 7 is set from the starting end of the introduction portion 2 (Experimental Example 11) and the case where the split processing tooth area portion 7 is set from the position "from the starting end of the introduction portion 2, separated by two rotation amounts of the rolled material W" (Experimental Example 12), the "over-pin diameter, tooth root circle diameter, tooth shape error, tooth intersection error, pitch cumulative error and tooth groove deflection" are measured, and then based on the measurement results, it is evaluated whether the rolled material W produces circumferential and axial elongation deformation. In Experiment 5, the bolt groove specification is a bolt groove with a tooth front edge circular diameter of φ18×Z22×m0.8×PA40°, and the material diameter of the rolled material W is defined as 16.89 mm (material: carbon steel (S45C)). In addition, the setting conditions of each mold body 1 of Experimental Examples 11 and 12 are shown in Table 17. In addition, since the symbols recorded in Tables 16 and 17 are the same as those in Experiment 1, their description is omitted. The evaluation results are shown in Table 18. In the evaluation results, all evaluation items that meet the specifications are marked as "○", and even if one item does not meet the specifications, it is marked as "×". As shown in Table 18, even when the segmented processing tooth area 7 is set from the position of "the distance of two rotations of the rolled material W separated by the starting end of the introduction part 2", the results of each evaluation item meeting the specifications are obtained for each material thickness. In this embodiment, in the above-mentioned experiments 1 to 5, hollow materials are used as the rolled material W and the good effect of the present invention is confirmed. Even in the case of rolling processing using solid materials as the rolled material W, the elongation and deformation of the rolled material W in the circumferential direction and the axial direction can be suppressed to the maximum extent, and a good product with the desired tooth shape can be obtained. In addition, the present invention is not limited to this embodiment, and the specific structure of each component can be appropriately designed to obtain.

1: Mold body 2: Lead-in section 3: Finishing section 4: Lead-out section 5: Processing teeth 5a: Split processing teeth 6: Groove 7: Split processing tooth area 7b: Descending section D: Groove depth L2: Lead-in section length W: Rolled material W1: Split processing tooth width W2: Groove width α: Groove inclination angle

[Figure 1] is an explanatory top view and an explanatory front view showing the present embodiment. [Figure 2] is an explanatory top view showing the segmentation processing tooth area of the introduction part of the present embodiment. [Figure 3] is an explanatory side view showing the groove and segmentation processing tooth of the present embodiment. [Figure 4] is an explanatory front view and an explanatory side view showing the introduction part of the present embodiment. [Figure 5] is an explanatory top view showing the descending part of the introduction part of the present embodiment. [Figure 6] is an explanatory diagram showing the "processing tooth (segmentation processing tooth) used to process the first groove of the rolled material" in the present embodiment. [Figure 7] is a graph showing the "measurement results of the over pin diameter (OPD)" in Experiment 1. [Figure 8] is a graph showing the "measurement results of tooth root circle diameter" in Experiment 1. [Figure 9] is a graph showing the "measurement results of cumulative pitch error" in Experiment 1. [Figure 10] is a graph showing the "measurement results of tooth groove deflection" in Experiment 1. [Figure 11] is a diagram showing the grooves and split teeth of other examples (types with shallow groove depth) of this embodiment, where (a) is an explanatory side view and (b) is an explanatory top view. [Figure 12] is a schematic explanatory diagram of roller rolling processing using this embodiment (roller rolling flat dies). [Figure 13] is a diagram of rolling processing of another example (applied to the case of rolling incremental dies) using this embodiment, wherein (a) is a schematic diagram and (b) is a top view of the important parts. [Figure 14] is an explanatory diagram showing the processing state of the first groove of the rolled material in the case of this embodiment. [Figure 15] is an explanatory diagram showing the processing state of the first groove of the rolled material in the case of this embodiment. [Figure 16] is an explanatory diagram showing the processing state of the first groove of the rolled material in the case of the conventional example. [Figure 17] is a graph showing the "measurement results of the over-screw diameter" in Experiment 3. [Figure 18] is a graph showing the "measurement results of tooth root circle diameter" in Experiment 3. [Figure 19] is a graph showing the "measurement results of tooth shape error" in Experiment 3. [Figure 20] is a graph showing the "measurement results of tooth intersection error" in Experiment 3. [Figure 21] is a graph showing the "measurement results of pitch accumulation error" in Experiment 3. [Figure 22] is a graph showing the "measurement results of tooth groove deflection" in Experiment 3. [Figure 23] is an explanatory top view showing another example of this embodiment (a type of splitting the processing tooth area and setting it at a predetermined distance from the starting end of the introduction part).

1: Mold body

2: Introduction section

3: Finishing Department

4: Export section

5: Processing teeth

5a: Split processing teeth

6: Groove

7: Split and process the tooth area

7a: Starting end side splitting processing area

7b: Regressive part

8: Bottom

L: The total length of the mold body

L1: Range (length) of each roller direction of the introduction part, finishing part and output part

L2: Length of the insertion part

SB: Range of shot peening treatment

X: Roller direction range (length) of the split processing tooth area

Claims (19)

A rolling die has an introduction part, a finishing part and an introduction part respectively provided with processing teeth from the rolling direction starting end side of the die body toward the rolling direction terminal side, and the processing teeth cause the outer peripheral surface of the rolled material to be plastically deformed to roll the desired tooth shape. Its characteristics are: From the starting end side of the aforementioned introduction part to a specific position in the rolling direction of the introduction part, each of the aforementioned processing teeth is provided with: a plurality of grooves inclined at a specific inclination angle relative to the rolling direction in a top view, and a plurality of split processing teeth are formed by the grooves, and each of the split processing teeth is arranged to have a phase difference in the width direction of the aforementioned die body in the rolling direction. The roller mold as recited in claim 1, wherein the split processing teeth are arranged to have a phase difference that can process the entire roller width of the rolled material in the split processing tooth area where the split processing teeth are arranged. The roller mold as recited in claim 1, wherein the groove is located at a position from the starting end of the introduction portion to a position 60% to 95% of the length of the introduction portion. The roller mold as described in claim 2, wherein the groove is located at a position from the starting end of the introduction portion to a position 60% to 95% of the length of the introduction portion. The roller mold as recited in claim 1, wherein the groove is disposed at a position which is a specific distance from the starting end of the introduction portion and ends at a position which is 60% to 95% of the length of the introduction portion. The roller mold as recited in claim 2, wherein the groove is disposed at a position which is a specific distance from the starting end of the introduction portion and ends at a position which is 60% to 95% of the length of the introduction portion. The roller die as recited in claim 1, wherein the tooth width of the aforementioned split processing teeth is less than 3.3 mm, and the aforementioned grooves are arranged at equal intervals in the direction of the tooth intersection line of the aforementioned split processing teeth. The roller die as recited in claim 2, wherein the tooth width of the aforementioned split processing teeth is less than 3.3 mm, and the aforementioned grooves are arranged at equal intervals in the direction of the tooth intersection line of the aforementioned split processing teeth. The roller die as recited in claim 3, wherein the tooth width of the aforementioned split processing teeth is less than 3.3 mm, and the aforementioned grooves are arranged at equal intervals in the direction of the tooth intersection line of the aforementioned split processing teeth. The roller die as recited in claim 4, wherein the tooth width of the aforementioned split processing teeth is less than 3.3 mm, and the aforementioned grooves are arranged at equal intervals in the direction of the tooth intersection line of the aforementioned split processing teeth. The roller die as recited in claim 5, wherein the tooth width of the aforementioned split processing teeth is less than 3.3 mm, and the aforementioned grooves are arranged at equal intervals in the direction of the tooth intersection line of the aforementioned split processing teeth. The roller die as recited in claim 6, wherein the tooth width of the aforementioned split processing teeth is less than 3.3 mm, and the aforementioned grooves are arranged at equal intervals in the direction of the tooth intersection line of the aforementioned split processing teeth. A roller mold as described in any one of claim 1 to claim 12, wherein the aforementioned inclination angle is 0.35°~7.10°. A roller mold as recited in any one of claim 1 to claim 12, wherein the groove is configured to be a straight line in a top view. As described in claim 13, the aforementioned groove is configured to be a straight line in a top view. A roller mold as described in any one of claim 1 to claim 12, wherein a decreasing portion is provided in a specific range on the terminal side of the roller direction of the aforementioned split processing tooth area where the aforementioned split processing teeth are provided, and the decreasing portion is configured: toward the terminal end in the roller direction, the groove depth of the aforementioned groove gradually becomes shallower, and the groove width of the aforementioned groove gradually becomes narrower. As described in claim 13, a rolling die is provided with a decreasing portion in a specific range on the terminal side of the rolling direction of the aforementioned segmentation processing tooth area where the aforementioned segmentation processing teeth are provided, and the decreasing portion is configured such that: toward the terminal end in the rolling direction, the groove depth of the aforementioned groove gradually becomes shallower, and the groove width of the aforementioned groove gradually becomes narrower. As described in claim 14, a rolling die is provided with a decreasing portion in a specific range on the terminal side of the rolling direction of the aforementioned split processing tooth area where the aforementioned split processing teeth are provided, and the decreasing portion is configured such that: toward the terminal end in the rolling direction, the groove depth of the aforementioned groove gradually becomes shallower, and the groove width of the aforementioned groove gradually becomes narrower. As described in claim 15, a rolling die is provided with a decreasing portion in a specific range on the terminal side of the rolling direction of the aforementioned split processing tooth area where the aforementioned split processing teeth are provided, and the decreasing portion is configured such that: toward the terminal end in the rolling direction, the groove depth of the aforementioned groove gradually becomes shallower, and the groove width of the aforementioned groove gradually becomes narrower.

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