JP4875588B2 - Round bar material forging method - Google Patents

Description

  The present invention relates to a forging method in which a cross-sectional shape is finished from a rod-shaped material having a polygonal shape or the like to a round bar having a circular cross-sectional shape using a mold having a round groove.

  As a forging method for forging a rod-shaped material with a cross-sectional shape from a polygonal shape into a round rod material, the rod-shaped material is fed in the axial direction when opening a mold having a pair of open and closed round grooves, and around the axis There is known a spiral forging method in which forging is performed by rotating for a predetermined angle and repeating forging to reduce the material by closing the mold (see, for example, Patent Documents 1 to 3). In Patent Document 1, FIGS. 5 (a) to 5 (c) are finished from the rod-shaped material into a round bar material by spiral forging using round groove molds 11, 11 that open and close by driving a press (not shown). It shows the process. FIG. 5A shows a state after forging in the first pass (closed operation). The material 12 forged by the closed operation of the round groove molds 11 and 11 is the round groove molds 11 and 11. The groove bottom portion 11a is filled, and a part of the groove bottom portion 11a is bitten between the relief portions 11b and 11b of the round groove molds 11 and 11, and the biting portion 12a is generated. After the forging of the first pass is completed, the material 12 is fed in the axial direction, and the material 12 is rotated about the axis by an angle θ, so that the material 12 is bitten out as shown in FIG. The part 12a is rotated to the groove bottom part 11a side of the round groove anvil 11. In the second pass forging performed by the closing operation of the round groove mold 11, as shown in FIG. 5C, the biting portion 12a is squeezed by the groove bottom portion 11a, so that the biting portion 12a is the groove bottom portion. Although it flows along 11a and disappears, in the vicinity of the portion where the biting portion is formed, a recess 12c is generated and a new biting portion 12b is generated. As described above, the dent 12c generated by the second pass forging remains until the end of the subsequent spiral forging, and there is a problem that the roundness of the round bar is deteriorated. For this reason, in Patent Document 1, in order to reduce the depth of the recess 12c as much as possible, the rotation angle θ around the axis of the material at the time of each opening operation of the round groove mold 11 is determined based on the actual measurement data. A hot forging method of over 45 degrees and 75 degrees or less is disclosed.

On the other hand, in Patent Document 2, a manipulator that holds a workpiece is always covered when a round bar is manufactured by repeatedly reducing the workpiece with an anvil from a direction perpendicular to the axis and moving the workpiece in the axial direction. A spiral forging method is disclosed in which the workpiece is advanced in the direction away from the workpiece pressure lower portion and the workpiece is rotated about its axis. Moreover, in patent document 3, by the same spiral forging method, the curvature radius of the round groove bottom part of an anvil is made smaller than the finishing cross-sectional radius of a workpiece so that the difference may be less than 8 mm, or A method of forging using an anvil that contacts on four sides is disclosed.
Japanese Patent Laid-Open No. 2002-102987 JP 2004-283855 A Japanese Patent Laid-Open No. 2005-7402

However, as disclosed in Patent Document 1, in spiral forging, when forging is performed in small increments by limiting the rotation angle θ to an acute angle range (θ <75 degrees) in all passes, generally the finished surface texture is Although it becomes good, the forging time until finishing to a round bar becomes long, and the production efficiency decreases. Moreover, although the amount of movement per one pass of the material (work material) and the size of the previous shape also affect the surface texture, Patent Document 1 describes the amount of movement and the shape and dimensions of the forged material. Nothing is listed.
Further, in Patent Document 2, only the manipulator moving direction for suppressing the bending of the workpiece is specified, and the amount of movement and rotation of the workpiece affecting the surface accuracy and productivity in spiral forging. Nothing is stated about the angle. Furthermore, Patent Document 3 defines an anvil shape from the viewpoint of suppressing the bending of the workpiece and ensuring the roundness (surface accuracy), but the amount of movement of the workpiece that also affects the productivity There is nothing written about the rotation angle.

  Accordingly, an object of the present invention is to provide a rotational angle of a material to be forged in spiral forging in which a cross-sectional shape is forged from a rod-shaped material having a polygonal shape into a round bar having a circular cross-section using a die having a round groove. It is to provide a forging method capable of efficiently producing a round bar with good surface accuracy in consideration of both the amount of movement and the amount of movement.

  In order to solve the above problems, the present invention employs the following configuration.

  A forging method for a round bar according to claim 1 is a pair of round groove molds in which a workpiece is moved in its axial direction, rotated by an angle θ around its axis, and the length in the indented longitudinal direction is W. Forging method in which rolling by rolling is performed sequentially from one end of the work piece to the other end in the axial direction, and the axial movement from one end to the other end is performed once to finish the round bar while applying rotation and reduction The radius R of the round groove portion of the round groove mold is larger than ½ of the finished diameter D of the round bar, and the central angle θG is larger than 75 ° and smaller than 180 °. The depth H is smaller than ½ of the finishing diameter D, the mold wall surfaces on both sides of the round groove are formed in a flat or curved shape, and the rotation angle θ around the axis is larger than 75 °. The center angle is equal to or less than θG and the workpiece is subjected to one pressure reduction in a round groove mold. Characterized by the movement amount A of the axial direction and W × θ / 180 or less

  FIG. 1A shows the cross-sectional shape of the round groove mold 1. At the groove bottoms of the dies 1, 1, a circular arc part 2 having a radius R and having a central angle θG (75 ° <θ <180 °), that is, a radius R, is planar (metal mold). Relief portions 3 and 3 having a linear shape in the mold cross-sectional shape are formed. The radius R of the round groove portion 2 is H × 2 ≦ D ≦ R × 2 (the depth H of the round groove portion 2 = R−Sf / 2, Sf: the round groove portion 2 is covered by the diameter D of the finished round bar. It is designed to fill the gaps between the flange portions 1f and 1f of the upper and lower molds 1 and 1 when they are brought into contact with the workpiece 4 and reduced. Then, the upper and lower molds 1 and 1 are moved up and down (closed and opened), and the workpiece 4 made of steel such as carbon steel or low alloy steel is reduced, that is, forged. The gap Sf corresponds to the gap S when the mold is closed, and when the movement in the axial direction is repeated a plurality of times, the gap Sf is a gap under the final movement. FIG. 1B is a round groove mold 1a similar to the round groove mold 1 shown in FIG. 1A, but the relief portions 3a and 3a are curved (curved in the cross section of the mold). It differs in that it is formed.

  FIG. 2A shows the relationship between the number of feeds Nt / the number of rotations Nr and the deviation in diameter (difference between the maximum diameter and the minimum diameter in the same cross section), that is, the surface accuracy in the spiral forging, as a workpiece (raw material). Using an octagonal material, the ratio of the cross-sectional area S1 to the cross-sectional area S2 of the finished round bar (Φ300 mm), that is, the cross-sectional area increase ratio S1 / S2 is changed by three levels, the rotation angle θ is constant at 90 °, and gold This shows the result of an actual machine forging experiment in which the center angle θG of the die is 150 ° and the length of the lower part of the same pressure is W = 300 mm, and the amount of movement in the axial direction per reduction is changed. Here, the number of times of feeding Nt is the number of times the upper and lower molds 1 and 1 are squeezed down while the workpiece 4 moves in the axial direction over the indented length W of the mold, that is, Nt = W / (per one reduction) The number of rotations Nr is the number of rotations required for the workpiece 4 to rotate 360 °, that is, Nr = 360 / rotation angle θ.

  FIG. 1 shows that the larger the ratio Nt / Nr, the smaller the deviation in diameter, that is, the surface accuracy improves. As can be seen from the tendency shown in FIG. 2 (a), in general, the smaller the number of rotations Nr, that is, the larger the rotation angle θ, the smaller the deviation in diameter and the surface accuracy (dimensional accuracy) is improved. The rotation angle θ> 75 °, which is not disclosed in the prior art documents such as Patent Document 1, is set as the technical range on the lower limit side of the rotation angle of the present invention. In addition, since the forging can be efficiently performed by reducing the pressure so that the pressing surface against the workpiece does not overlap with one pressing (mold closing operation), the angle of the round groove of the round groove mold, that is, the central angle The lower limit of θG is set to θG> 75 ° corresponding to the rotation angle θ. On the other hand, when the central angle θG of the round groove portion is 180 °, the relief portions cannot be formed on both sides of the round groove portion, and the above-described workpiece biting occurs. Therefore, since the upper limit of the central angle θG of the round groove portion needs to be smaller than 180 °, θG <180 ° is set as the technical range on the upper limit side of the present invention. The upper limit of the rotation angle θ is smaller than the central angle θG because the shape of the material (workpiece) is formed by the arc portion of the mold 1, that is, the circular groove portion 2. The lines of pitch = 1 and pitch = 2 in FIG. 2B are in the length direction of the round groove mold 1 (1a) for each rotation of the angle θ by contact with the round groove mold 1 (1a). The trajectory connecting the contact points in the circumferential direction with the workpiece 4 at the end portion is shown. When the pitch = 1, 2, the feed number Nt / rotation number Nr corresponds to 1, 2, respectively.

  Further, when the relief portions 3 and 3 on both sides of the round groove portion 2 are formed in a flat (straight) shape, the contour of the work material after the reduction becomes good, so that the round bar material that can be forged with one die The dimension (diameter) range can be increased. On the other hand, when the relief portions 3a and 3a are formed in a curved surface shape (curved shape in the mold cross-sectional shape), the metal flow of the work material from the mold circular groove portion 2 to the relief portions 3a and 3a on both sides accompanying the reduction. Since the surface becomes smooth, the surface properties are good. Furthermore, by setting the amount of movement per pressure to W × θ / 180 or less, it is possible to make contact with the round groove portion of the round groove mold over the entire circumferential surface of the workpiece, so that the dimensional accuracy of the finished round bar Will improve.

  In the round bar forging method according to claim 2, the cross-sectional shape perpendicular to the axial direction of the workpiece is a polygon, and the ratio S1 / S2 of the cross-sectional area S1 to the cross-sectional area S2 of the round bar is , 1.05 to 1.25.

  By making the cross-sectional shape of the workpiece (raw material) polygonal (hexagonal or more), the metal flow at the time of forging becomes good and molding into a round bar becomes easy. If the cross-sectional area ratio is smaller than 1.05, the rolling allowance (cross-sectional reduction amount) in the round groove mold is reduced, so that the movement amount per one reduction is reduced, that is, in the round groove mold. Even if the number of rotations of the workpiece is increased, the dimensional accuracy of the finished round bar will be changed. Further, in spiral forging in which a longitudinal reduction from one end to the other end of the workpiece is performed once to finish a round bar, if the cross-sectional area ratio is greater than 1.25, the reduction margin (cross-sectional reduction amount) ) Becomes too large, and the amount of cross-sectional reduction is insufficient with a normal movement amount or pitch, and if the amount of reduction is increased to compensate for this, surface wrinkles are generated by biting out of the mold.

  A forging method of a round bar according to claim 3 is the forging which is sequentially performed in the process of moving the workpiece in the axial direction from one end to the other end, and the workpiece is axially handled by a handling device. It is characterized by forging while pulling.

  As described above, the forging is performed by pulling the workpiece in the axial direction by the handling device, thereby suppressing the bending of the workpiece.

  The method for forging a round bar according to claim 4 is to move the workpiece in the axial direction, rotate the workpiece around the axis by an angle θ, and perform rolling down by a pair of round groove molds having an indented length W. In the forging method, which is sequentially performed in the axial direction from one end of the workpiece to the other end, and the round movement is repeated a plurality of times from the one end to the other end in the axial direction with rotation and rolling down to finish the round bar. The radius R of the round groove portion of the groove mold is larger than ½ of the finishing diameter D of the round bar, and the central angle θG is larger than 75 ° and smaller than 180 °. The mold wall surface is formed in a planar shape or a curved shape, the rotation angle θ around the axis is greater than 75 ° and less than or equal to the center angle θG, and at least the final forging in the plurality of axial movements In the axial direction per pressure reduction Characterized in that the amount A and W × θ / 180 or less.

  The central angle θG of the round groove portion of the round groove mold and the rotation angle θ of the workpiece were determined in the same manner as in the case of performing the axial movement once. When the longitudinal reduction is performed a plurality of times, the amount of movement per reduction in the final round that has a large influence on the surface accuracy (dimensional accuracy and surface properties) of the finished round bar is set to W × θ / 180 or less. Since the entire circumferential surface of the workpiece can be brought into contact with the round groove portion of the round groove mold, the dimensional accuracy of the finished round bar is improved. Further, as shown in FIG. 1B, when the relief part of the round groove mold is formed in a curved shape, the covering from the mold round groove part 2 to the relief parts 3a and 3a on both sides is caused by the reduction. Since the metal flow of the processed material becomes smooth, the surface properties are good.

  In the forging method of a round bar according to claim 5, the forging is sequentially performed in the process of moving the workpiece in the axial direction from one end to the other end, and a plurality of axial movements from the one end to the other end are performed. When it is repeated, at least the final movement in the axial direction is characterized in that the workpiece is forged while being pulled in the axial direction by a handling device.

  In this way, by forging in the final axial movement, forging while pulling the workpiece in the axial direction by the handling device, the occurrence of bending of the workpiece (finished round bar) is suppressed. Furthermore, in the odd-numbered movement from the first axial movement, the workpiece is forged while being pushed in the axial direction by the handling device, and in the even-numbered movement, the workpiece is axially moved by the handling device. When forging while pulling, the workpiece is always moved in the axial direction from the one end to the other end with the rolling and rotation of the round groove mold, so extra handling is performed. The forging efficiency is improved.

  In the method of forging a round bar according to claim 6, in the movement in the axial direction that is repeated a plurality of times, the movement amount A per reduction is set to W × θ / 180 or less, and the amount of movement Af per pressure in the round groove mold in the final axial movement is W × θ / 180 / n (= A / n, where n is a real number of 1 or more) or less. It is characterized by that.

  If the range of the movement amount A is determined in this way, in the forging in the movement in each axial direction from the movement in the first axial direction to the movement in the final axial direction, within the range of the movement amount, The workpiece A can determine a movement amount A that can be reduced by bringing the entire circumferential surface of the workpiece into contact with the round groove portion of the round groove mold. In addition, by reducing the amount of final movement, which has a greater influence on the dimensional accuracy of the finished round bar material, than the amount of movement in the previous stage, the reduction in forging efficiency, that is, productivity, is suppressed. However, it is possible to improve the surface accuracy of the round bar. Note that the real number n is a surface so that at least a non-pressing lower surface that does not contact with the round groove mold is not formed between the streaks 6, 6 on the outer peripheral surface of the workpiece in FIG. In order to make the state even better, it can be determined according to the magnitude of the rotation angle θ so that the pressed surface due to contact with the round groove mold covers the entire outer peripheral surface of the workpiece.

  In the method of forging a round bar according to claim 7, in the axial movement repeated a plurality of times, from forging in the first axial movement to forging in the final axial movement, The amount of movement A per pressure is alternately set to W × θ / 180 or less or W × θ / 180 / n (n: a real number of 1 or more) or less.

  As described above, the surface accuracy of the round bar can also be improved while suppressing the decrease in productivity by making the movement amount alternately As / n. As described above, n can be determined in accordance with the magnitude of the rotation angle θ so that the pressed surface due to contact with the round groove mold covers the entire outer peripheral surface of the workpiece.

  In the method for forging a round bar according to claim 8, in the axial movement that is repeated a plurality of times, the number of rounds around the axis of the workpiece in the forging in the odd number of movements counted from the first axial movement. The rotation direction and the rotation direction of the workpiece in forging in the even-numbered movement are opposite directions.

  In this way, by reversing the rotation direction of the workpiece for each movement in the axial direction, the deviation of the metal flow in the workpiece cross section is corrected, and the mechanical properties of the finished round bar, etc. Variations in quality can be reduced.

  In the method of forging a round bar according to claim 9, in the axial movement that is repeated a plurality of times, the round bar material around the axis of the workpiece in the forging in the number of movements from the first axial movement to the middle. The rotation direction is opposite to the rotation direction of the workpiece in forging in the number of movements from the middle number of movements to the last number of movements.

  Even in this case, the deviation of the metal flow in the cross section of the workpiece can be corrected, and variations in quality such as mechanical properties of the finished round bar can be reduced. Here, the intermediate means that the number of times of (Nev / 2) is performed when the movement in the axial direction is an even number of times (Nev), and ((Nod + 1) / 2) when the number of times of the movement in the axial direction is an odd number (Nod). The number of times or ((Nod-1) / 2) times.

  In the method for forging a round bar according to claim 10, the cross-sectional shape perpendicular to the axial direction of the workpiece is a polygon, and the cross-sectional area ratio S1 / the cross-sectional area ratio S1 / the cross-sectional area S1 of the round bar. S2 is in the range of 1.05-1.30.

  By setting the cross-sectional shape of the workpiece (raw material) to, for example, a hexagonal or more polygonal shape, the metal flow at the time of forging becomes good, and molding into a round bar becomes easy. If the cross-sectional area ratio is smaller than 1.05, the rolling allowance (cross-sectional reduction amount) in the round groove mold is reduced, so that the movement amount per one reduction is reduced, that is, in the round groove mold. Even if the number of rotations of the workpiece is increased, the dimensional accuracy of the finished round bar will be changed. In addition, in the case of performing a plurality of longitudinal reductions, if the cross-sectional area ratio is greater than 1.3, the reduction allowance (cross-sectional reduction amount) becomes too large, and the cross-section is reduced with a normal movement amount or pitch. The amount of reduction is insufficient, and if the amount of reduction is increased to compensate for this, surface flaws occur and forging becomes impossible.

  The round bar forging method according to an eleventh aspect is characterized in that the polygon is an octagon.

  By making the cross-sectional shape of the workpiece (raw material) octagonal, the workpiece is formed from the raw steel ingot with the appropriate number of passes (rolling), and the metal flow during forging is improved with the round groove mold. Therefore, it becomes easy to form a round bar. In particular, considering the productivity in spiral forging, a regular octagon or a shape close to a regular octagon is desirable.

  In the present invention, a spiral forging is performed by forging a workpiece with rotation and axial movement using a round groove mold with an indentation length of W, and finishing the workpiece into a round bar by forging in one axial movement. In this method, the center angle θG of the round groove portion of the round groove mold is defined as described above, the rotation angle θ of the workpiece is set to be larger than 75 °, and the axial movement amount A per one reduction is expressed as W. Since forging was performed by controlling both the rotation angle θ and the movement amount A at a value of × θ / 180 or less, the mold circle was formed over the entire circumferential direction of the workpiece with a small number of revolutions in the round groove mold. It can be made to contact a groove part, and it can improve both forging efficiency and the dimensional accuracy of a round bar.

  Also, a spiral forging method in which a work piece is forged with rotation and axial movement using a round groove mold with an indentation length of W, and finished into a round bar by forging in repeated axial movements. As in the case of forging in one axial movement, the central angle θG of the round groove is specified, and the rotation angle θ of the workpiece is made larger than 75 °, greatly affecting the dimensional accuracy of the round bar. In at least the final axial movement, the rotational angle A is set to W × θ / 180 or less, preferably W × θ / 180 / n (n is a real number of 1 or more). Since the forging is performed by controlling both θ and the movement amount A, it is possible to bring the die round groove portion into contact with the entire circumferential surface of the work piece with a small number of revolutions in the round groove die. Can improve both efficiency and dimensional accuracy of round bars. wear. Further, when the reduction in the axial movement is performed once and the movement in the axial direction is repeated a plurality of times, at least the reduction in the axial movement of the last time, the workpiece is moved by the handling device. By forging while pulling in the axial direction, bending of the finished round bar can be suppressed. Further, the rotation direction around the axis of the workpiece in the odd-numbered movement from the first axial movement and the rotation direction of the workpiece in the even-numbered movement are opposite to each other. By reversing the rotation direction of the work piece for each movement in the axial direction, the deviation of the metal flow in the cross section of the work piece is corrected, and the mechanical properties of the finished round bar vary. Can be reduced.

  Embodiments of the present invention will be described below with reference to FIGS. 3 and 4 and Tables 1 and 2.

  FIG. 3 schematically shows a forging state of a workpiece by the forging method of the embodiment. A workpiece 4 made of a steel material such as carbon steel or low alloy steel having a polygonal cross-sectional shape, for example, a regular octagon or a regular octagon, is axially moved by a manipulator 5 serving as a handling device. The upper and lower molds 1 and 1a having the indentation length W having the cross-sectional shape shown in FIGS. The workpiece 4 is gripped by the arm portions 5a and 5a of the manipulator 5 every time the molds 1 and 1a are pressed down (closed operation), and a predetermined angle θ (75 ° <θ) around the axis. ≦ θG) is rotated clockwise or counterclockwise. For each rotation, the workpiece 4 is fed in the axial direction (longitudinal direction), for example, in the direction of being pulled by the manipulator 5, and the forging operation of “rotation-axial movement” is performed. 4 is repeated from one end 4a to the other end 4b, and the forging in one axial movement from the one end 4a to the other end 4b of the workpiece 1 is completed. When the axial movement is performed a plurality of times, as shown in FIG. 3, for example, after the forging in the movement in the pulling direction from one end 4 a to the other end 4 b is completed, the workpiece 4 is moved to the other end. Forging is performed in the movement in the axial direction, which is sent in the pushing direction from 4b to one end 4a. In this way, the workpiece 4 is alternately sent in the pulling direction and the pressing direction, and the axial movement with rotation and reduction is repeated a plurality of times. At that time, from the viewpoint of suppressing the bending of the workpiece 4, it is desirable to perform the reduction while pulling the workpiece 4 in the pulling direction, that is, in the axial direction. In addition, from the viewpoint of correcting the deviation of the metal flow in the cross section of the workpiece and reducing the quality variation such as the mechanical properties of the finished round bar, the rotation direction around the axis of the workpiece 4 is illustrated. As shown in FIG. 3, it is desirable that the direction of rotation in the clockwise direction C <b> 1 or the counterclockwise direction C <b> 2 is reversed in each axial movement as viewed from the manipulator 5 side. From the same point of view, in the forging in a plurality of axial movements, in the rotational direction in the number of movements from the first axial movement to the middle, and in the number of movements from the middle number of movements to the final number The direction of rotation can be reversed. Note that the shape of the material (workpiece 4) is not necessarily limited to an octagon, and for example, a material having a hexagonal shape or a 32-gonal shape can also be used.

  A round groove mold (θG = 90 °, R = 190 mm, S = 40 mm, H = shown in FIG. 1) from a carbon steel material having a regular octagonal cross section and a length of 10 m, and an indentation length W of 300 mm. 170mm), with a rotation angle θ equal to θG and 90 °, forging in one axial movement, in spiral forging to finish a round bar with a target dimension of Φ340mm, product round bar with material cross-sectional area S1 By changing the increasing rate S1 / S2 and the moving amount A with respect to the cross-sectional area S2 of the material (Φ340 mm), the forging temperature (temperature of the workpiece 4) is set to 700 ° C., and the deformation analysis means (three-dimensional deformation analysis software) Table 1 shows the results of calculating the surface accuracy (deviation diameter difference) and forging time of the bar. At that time, the surface accuracy (deviation difference) and the forging time obtained under the forging conditions of 50 mm corresponding to the material area increase rate S1 / S2 of 1.20 and the movement amount A of n = 3 are determined for pass / fail. The reference value was used. The moving direction of the workpiece in the axial direction is the “pulling direction” shown in FIG. The forging temperature is desirably 300 ° C. or higher. When forging under light pressure at a temperature lower than 300 ° C., defects occur.

From Table 1, since the material area increase rate S1 / S2 is outside the range of the appropriate area increase rate at 1.04 and 1.3, the surface accuracy is lower than the reference example (No. 5, No. 6). In addition, when the moving amount is 200 mm exceeding W × θ / 180, the forging time is shortened compared with the reference example, but the surface accuracy is greatly reduced (No. 7). This is because when the amount of movement per pressure exceeds W × θ / 180, the spiral-shaped streak interval Lw (see FIG. 4) becomes rough, and the pressed surface by the round groove mold does not overlap. This is because the polygonal shape of the material remains on a part of the surface of the processed material and the surface accuracy is deteriorated. On the other hand, when the area increase rate S1 / S2 is 1.10, 1.09 and the rotation angle θ is 90 ° within the appropriate range, the surface accuracy is better than the reference example of No. 1 (No. 2, No. 3, No. 4). Comparing the data of No.2, No.3, and No.4, when the rotation angle θ is the same and the material area increase rate S1 / S2 is almost the same, the movement amount is reduced to W × θ / 180 or less. Accordingly, as schematically shown in FIG. 4, the interval Lw between the spiral streaks 6 formed by contact with the round groove mold 1 is narrowed, that is, the round groove metal is formed on the surface of the workpiece 4. By overlapping the pressing surface 7 by the mold 1 many times, the surface accuracy (deviation diameter difference) and surface properties are improved. As described above, the streak 6 is not a contact mark continuously formed on the outer peripheral surface of the workpiece 4 due to contact with the round groove mold 1, but a round groove mold every rotation of the angle θ. 1 corresponds to a trajectory connecting contact points in the circumferential direction with the workpiece 4 at the end in the length direction. When the forging temperature is 250 ° C. and lower than 300 ° C., the area increase rate, the moving amount, and the rotation angle θ are within the technical scope of the present invention, and even if the surface accuracy is good, A defect occurred (Reference Example No. 8).

  Thus, using the round groove mold having the shape shown in FIG. 1, the rotation angle θ is larger than 90 ° and 75 °, and the material area increase rate S1 / S2 is in the range of 1.05 to 1.25. The surface accuracy of the round bar can be improved by reducing the movement amount to W × θ / 180 or less. Even if the mold relief portion 3a is formed in a curved shape as shown in FIG. 1B, it is possible to improve the surface accuracy as described above.

  A round groove mold (R = 150 mm, S = 50 mm, shown in FIGS. 1 (a) and (b) having a regular octagonal cross-sectional shape and a carbon steel material having a length of 10 m and an indentation length W of 300 mm. In spiral forging, in which the rotation angle θ is 90 ° in the same manner as in Example 1 using 2 passes (twice in the longitudinal direction), and the target dimension is finished into a round bar with a diameter of 350 mm. By changing the increase rate S1 / S2, the moving amount A and the rotation direction of the material cross-sectional area S1 with respect to the cross-sectional area S2 of the product round bar (Φ350mm), the deformation analysis means (three-dimensional deformation analysis software) Table 2 shows the results of calculating the surface accuracy (deviation in diameter) and forging time. At that time, the material area increase rate S1 / S2 is 15%, the moving amount A and the rotational direction are both 150 mm and forward direction (clockwise direction) corresponding to W / 2 in both the first pass and the second pass. The surface accuracy (deviation diameter difference) and forging time obtained under the conditions were used as reference values for the pass / fail judgment. Note that the movement amount A (mm) / order "order" indicates that the feed direction is the forward direction, that is, the movement direction in the axial movement of the workpiece 4 is the "pull direction" shown in FIG. .

  From Table 2, when the material area increase rate S1 / S2 is 1.03, the surface accuracy is lower than that of the reference example (No. 2), and when S1 / S2 is 1.35, the surface accuracy is lower than that of the reference example. Forging time also increases (No. 3). On the other hand, when the area increase rate S1 / S2 becomes 1.05, the surface accuracy recovers to the same level as the reference example (No. 4), and even if S1 / S2 is 1.30, the surface accuracy is the same as the reference example. (No.5) In the examples of No.4 and No.5, the rotation direction (1 pass / 2 pass) is different from the reference example of No.1, but this difference in the rotation direction affects the metal flow in the cross section. It does not affect the surface accuracy itself. If the mold relief part is formed in a curve (curved surface), the surface accuracy is improved over the reference example (No. 6). By reducing the amount of movement in the final axial direction, that is, the final pass (second pass), the surface accuracy is improved over the reference example (No. 7 to No. 9, No. 11). Even if the moving amount is reduced, the forging time is shortened (No. 8, No. 9) by increasing the moving amount on the first stage (first pass). Further, the surface accuracy is improved when the movement amount A on the front side (first pass) is 150 mm and satisfies W × θ / 180 or less (No. 7, No. 11). Furthermore, by reversing the feed direction, that is, the axial direction of movement in the first pass and the second pass, the workpiece is always moved with a reduction by the round groove mold, so that the surface accuracy is lowered. In addition, the forging time is greatly shortened (than the reference example) (No. 10). The movement amount A = 150 mm on the rear stage (second pass) corresponds to n = 1.0 (Examples No. 4, No. 5, No. 10), and the movement amount A = 100 mm is n. = 1.5 (Examples No. 7, No. 8), and the movement amount A = 50 mm corresponds to n = 3 (Examples No. 9, No. 11).

  As described above, the surface angle of the round bar can be improved by increasing the rotation angle θ to 90 ° and greater than 75 ° to reduce the amount of movement in at least the final axial movement. Moreover, the fall of surface accuracy can be prevented by keeping raw material area increase rate S1 / S2 in the range of 1.05-1.30. Furthermore, by alternately moving the workpiece in the axial direction in the opposite direction, the forging time is significantly shortened, and the surface accuracy is improved by forming the relief portion of the round groove mold in a curved surface.

(A) It is explanatory drawing which shows the cross-sectional shape (relief part: planar shape) of the round groove metal mold | die used with the forging method of embodiment. (B) It is explanatory drawing which shows the cross-sectional shape (relief part: curved surface shape) of the round groove metal mold | die used with the forging method of embodiment. (A) It is explanatory drawing which shows the relationship between (the number of feeds / number of rotations) and the surface accuracy in the round groove metal mold | die of a workpiece. (B) It is explanatory drawing which shows typically the locus | trajectory of the contact point of the said (number of times of feeding / number of rotations) and the metal mold | die edge part on the surface of a workpiece. It is explanatory drawing which shows typically the forge situation by the forge method of embodiment. It is explanatory drawing which shows typically that the pressing surface by a round groove metal mold | die is formed in a spiral shape on the surface of a workpiece. (A)-(c) It is explanatory drawing which shows the spiral forging method of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a: Round groove metal mold 1f: Mold flange part 2: Round groove part 3, 3a: Relief part 4: Work material 4a, 4b: Work material edge part 5: Manipulator 5a: Arm part 6: Muscle 7: Pressed surface

Claims (11)

  The workpiece is moved in the axial direction, rotated about the axis by an angle θ, and the reduction by the pair of round groove dies having a length in the longitudinal direction of the indented portion is reduced from one end to the other end of the workpiece. In the forging method in which a round bar is finished while applying rotation and reduction by performing the axial movement from one end to the other end in a time, and then performing the axial movement from one end to the other. R is larger than 1/2 of the finished diameter D of the round bar, its central angle θG is larger than 75 ° and smaller than 180 °, and the depth H of the round groove is 1 / of the finished diameter D. Is smaller than 2, the mold wall surfaces on both sides of the round groove portion are formed in a flat or curved shape, the rotation angle θ around the axis is greater than 75 ° and less than or equal to the center angle θG, and the workpiece The amount of movement A in the axial direction per one pressure in a round groove mold is W × θ / 18 A forging method of a round bar material characterized by being 0 or less.   The cross-sectional shape perpendicular to the axial direction of the workpiece is a polygon, and the ratio S1 / S2 of the cross-sectional area S1 to the cross-sectional area S2 of the round bar is in the range of 1.05 to 1.25. The method for forging a round bar according to claim 1.   2. The forging which is sequentially performed in the process of moving the workpiece in the axial direction from one end to the other end, forging the workpiece while pulling the workpiece in the axial direction by a handling device. Or the forging method of the round bar material of 2.   The workpiece is moved in its axial direction, rotated around the axis by an angle θ, and the reduction by a pair of round groove molds with a rolling-down length of W is applied in the axial direction from one end of the workpiece to the other. In the forging method in which the round groove material of the round groove mold has a radius R, the radius R of the round groove mold is the same as the above. It is larger than 1/2 of the finished diameter D of the round bar, its central angle θG is larger than 75 ° and smaller than 180 °, and the mold wall surfaces on both sides of this round groove are formed in a flat or curved shape. , The rotation angle θ around the axis is greater than 75 ° and less than or equal to the central angle θG, and the forging in the plurality of axial movements is at least axial movement per one reduction in the final movement. The amount A should be W × θ / 180 or less. Forging method of round bar material which is characterized in.   When the forging is sequentially performed in the process of moving the workpiece from one end to the other end in the axial direction, and the axial movement from the one end to the other end is repeated a plurality of times, at least the final axial direction 5. The method of forging a round bar according to claim 4, wherein the workpiece is forged while pulling the workpiece in the axial direction by a handling device.   In the movement in the axial direction repeated a plurality of times, the movement amount A per reduction is set to W × θ / 180 or less in the movement before the final movement in the axial direction, and in the final movement in the axial direction. 6. The movement amount Af per pressure in the round groove mold is set to W × θ / 180 / n (= A / n, where n is a real number of 1 or more) or less. 6. Forging round bar material.   In the axial movement that is repeated a plurality of times, the amount of movement A per reduction in each movement is alternately expressed as W × θ from the forging in the first axial movement to the forging in the final axial movement. 6. The method for forging a round bar material according to claim 4, wherein the forging method is set to any one of / 180 or less or W × θ / 180 / n (n: a real number of 1 or more).   In the axial movement repeated a plurality of times, the rotational direction around the axis of the workpiece in the forging in the odd number of movements counted from the first axial movement and the forging in the even number of movements. The method for forging a round bar according to any one of claims 4 to 7, wherein the direction of rotation of the workpiece is opposite. In the axial movement which is repeated a plurality of times, the rotational direction of the axis around the workpiece in the forging in the number of movements to the middle from the movement of the first axis direction, the last round from the mobile number of the middle The forging method of a round bar according to any one of claims 4 to 7, wherein the direction of rotation of the workpiece in the forging in the number of movements up to is reverse.   The cross-sectional shape perpendicular to the axial direction of the workpiece is a polygon, and the ratio S1 / S2 of the cross-sectional area S1 to the cross-sectional area S2 of the round bar is in the range of 1.05 to 1.30. The method for forging a round bar material according to any one of claims 4 to 9, wherein:   The round bar forging method according to claim 1, wherein the polygon is an octagon.

Images