JP3700811B2 - Cold forging method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cold forging method suitable for forming, for example, thin precision parts by forging.
[0002]
[Prior art]
Conventionally, there has been known a method of forming a workpiece by forging to obtain a precision part. However, according to the conventional forging method, a highly accurate one cannot be obtained. For example, when manufacturing a precision part (ring body) having a ring shape as shown in FIG. 20, the accuracy of the outer diameter A and the inner diameter B is not so high. For this reason, after precision forging such a precision part work as shown in FIG. 21, after cold forging in step S1, the stress is removed and spheroidized in step S2. In step S3, cutting is required. After the cutting and quenching and tempering hardening processes in step S4, finish polishing is performed in step S5 to obtain precision parts suitable for bearings, for example. As an example, when obtaining a highly accurate error between the outer diameter A and the inner diameter B, that is, a fluctuation of 0.03 or less, since the accuracy is low, an extra cutting process in step S3 is required.
[0003]
[Problems to be solved by the invention]
Conventionally, in the manufacturing method of a ring body by the forging process described in FIG. 21 above, for example, a work containing about 1% carbon such as bearing steel (SUJ material as an example) as a material has poor forgeability, and even after cold forging. In the rough finishing cutting process, there is a lot of machining allowance for the inner diameter B, and the efficiency and productivity of the yield surface are deteriorated. In particular, as described above, when obtaining a high-accuracy one having a runout of 0.03 or less, an extra step is required, resulting in poor productivity .
[0004]
The present invention has been made to solve the above-mentioned problem, and can eliminate the cutting process by rough finishing, and can improve the yield and efficiency of precision parts having a bottomed hole or a through hole in the center. A cold forging method is provided .
[0005]
[Means for Solving the Problems]
According to the first aspect of the present invention, there is provided a cold forging method in which a forging process is performed a plurality of times by a mold for concavely concentrating both surfaces of a workpiece, and the workpiece is used as a different mold for each forging process. Are formed in a column having a tip portion that is recessed in a conical shape, and a line segment in which the conical surface of the tip portion is orthogonal to the central axis of the column body and a ridge line of the conical surface of the tip portion of the column body The mold that determines the size of the clearance angle, which is the angle between the mold and the mold used in the subsequent forging process, has a larger clearance angle than the mold used in the previous forging process. It is characterized by.
In the invention of claim 2, the conical surface of the tip of the mold is formed by a plurality of peripheral surfaces provided extending in the direction along the central axis and having different angles with the central axis, The surface is formed into a surface that reduces the clearance angle as it approaches the tip of the tip.
In the invention of claim 3, in the subsequent forging process, a die made of a column having a diameter slightly smaller than the diameter of the hole formed in the workpiece in the previous forging process was used .
In the invention of claim 4, a preliminary hole having a shallow depth is formed in the previous forging process, and then a deep hole is formed by applying forging pressure to the preliminary hole in the subsequent forging process .
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
First, an outline of a cold forging method according to an embodiment of the present invention will be described with reference to FIGS.
[0007]
In the cold forging method of the present embodiment, first, in the first forging step, as shown in FIG. 1, the overall length is relatively longer than the outer diameter, for example, for a workpiece 1 made of a metal material containing about 1% of carbon. By applying forging pressure from both sides and performing upsetting, a work 1 having a disc shape is obtained as shown in FIG.
In FIG. 1, the workpiece 1 having a long overall length is used to improve shear cutting performance. In the first forging step shown in FIG. 2, tapers 1 a and 1 b are formed on the outer peripheral edges of both surfaces of the work 1.
[0008]
In the second forging step, as shown in FIG. 3, a concavity-depressed recess 1j is formed on one side of the workpiece 1, and an outer peripheral taper surface 1n, a flat surface 1t, an inner peripheral taper surface 1f on the opposite surface. And the recessed part 1w which consists of conical depressions is formed. The angle of the concave portion 1w on the front end side 1w1 is about ½ smaller than that on the rear end side 1w2. The outer and inner tapered surfaces 1n and 1f preferably have an inclination angle of about 40 to 50 degrees.
The concave portion 1j made of a conical depression is useful for positioning the center position when forging in the next step, and the concave portion 1w made of a conical depression is useful for guiding a punch in the next step. is there. That is, since it is sharp in the center direction, the workpiece 1 can be accurately positioned at the center of the mold when pressure is applied by the mold.
[0009]
In the third forging step, after the workpiece 1 is inverted, forging is performed to provide a preliminary hole 1q with a step 1h on one side as shown in FIG. The preliminary hole 1q functions as a hole for guiding a hole insertion pin for smoothly performing hole insertion with a hole insertion pin in the next process. The description of the opposite surface is the same as in the second forging step.
[0010]
In the fourth forging step, after the workpiece 1 is reversed, the workpiece 1 is forged so that the hole insertion pins 24 are inserted into the side where the preliminary hole 1q is formed as shown in FIG. The hole 1q is formed so as to allow the excess portion to escape in the direction indicated by the arrow. A preliminary hole 1r is formed on the opposite surface by punching.
In this way, a semi-finished product in which the thin portion 1m is formed inside the cylindrical body 1y can be obtained.
[0011]
In the fifth forging step, after the workpiece 1 is reversed, the thin portion 1m is displaced by a certain distance along the central axis within the cylindrical body 1y, and half-cutting is performed. The thin portion 1m is broken in a state where it is connected to the cylindrical body 1y in the section m.
[0012]
In the sixth forging step, as will be described later with reference to FIG. 19, the half-thinned thin portion 1m is punched in the same direction as the half-punching direction. At the time of this punching, the inner surface of the hole of the cylindrical body 1y is simultaneously shaved and smoothed.
The above is the outline of the first embodiment.
[0013]
7 to 18 are process diagrams showing the details of one embodiment of the cold forging method according to the present invention, and show the details when forging using a mold. In the present invention, first, the cylindrical workpiece 1 described with reference to FIG. 1 is placed on both sides (left side) with a knockout pin 21 as one mold and a punch 31 as the other mold of a forging apparatus as shown in FIG. , Right or top, bottom), forging pressure is applied to obtain a disk-shaped workpiece 1 (see FIG. 2). In this case, the knockout pin 21 is usually used to push up and take out the molded workpiece 1 from below, and is positioned in the through hole 41a of the die 41 so as to be movable up and down. And the shape of the recessed part 4a of the die | dye 41 has a bottom face shape suitable for shape | molding the taper 1a on the outer peripheral side of both surfaces of the workpiece | work 1. FIG. A die 41 b is also provided on the upper side, and the shape of the lower surface 41 c of the die 41 b is also set to a shape suitable for forming the tapered surface 1 b on the workpiece 1.
[0014]
As shown in FIG. 7, a forging pressure is applied to the cylindrical workpiece 1 from the upper side in the first forging step, and the workpiece 1 having the tapered surfaces 1 a and 1 b on the outer circumferences of both surfaces is next. Is supplied to the forging apparatus shown in FIG. In the second forging step shown in FIG. 8, forging pressure is applied to both surfaces of the work 1 by the knockout pins 22 and the punch 32. At this time, the outer diameter of the work 1 is the inner surface of the recess 42a provided in the die 42. Further, both sides are formed by the punch 32 and the knockout pin 22 shown in FIG. 9 (see FIG. 3). In this case, each of the punch 32 and the knockout pin 22 is a mold formed in a column having a tip portion that allows the both sides of the work 1 to be recessed in a conical shape. Knockout pin 22, conical surface of the tip, a plurality of different circumferential surface 22a of the angle between the provided by the central axis 22d extends in a direction along the central axis 22d of the knock-out pin 22, 22b, by 22c It is formed. The plurality of peripheral surfaces 22a, 22b, and 22c are formed on a surface that reduces the clearance angle as it approaches the tip of the tip. Relief angle is a plurality of peripheral surfaces 22a, 22b, 22c the angle between the tip against the segment 22e perpendicular to the center axis 22d of the knock-out pin 22. Strictly speaking, it is an angle formed by a line segment 22e perpendicular to the central axis 22d of the knockout pin 22 and each ridgeline of each of the peripheral surfaces 22a, 22b, and 22c that is a conical surface at the tip of the knockout pin 22. is there. That is, a plurality of peripheral surfaces 22a, 22b, and 22c that form a conical surface at the tip of the knockout pin 22 are formed between a line segment 22e that is orthogonal to the center axis 22d of the column of the knockout pin 22 and the tip of the column. The clearance angle α, which is an angle formed by the ridgelines of the plurality of peripheral surfaces 22a, 22b, and 22c forming the conical surface, is determined. The plurality of peripheral surfaces 22a, 22b, and 22c at the tip of the knockout pin 22 are formed on a surface that reduces the clearance angle as it approaches the tip. Specifically, the relief angle α2 is an angle between the line segment 22e perpendicular to the ridge line and the center axis 22d of the peripheral surface 22b of the knock-out pin 22 has been set to, for example 5-7 degrees, knockout pins 22 The clearance angle α1, which is the angle formed by the ridge line of the peripheral surface 22c closest to the distal end and the line segment 22e orthogonal to the central axis 22d, is set to about ½ of the clearance angle α2. Therefore, the front end side 1w1 of the recess 1w shown in FIG. 3 is formed by the peripheral surface 22c, and the rear end side 1w2 is formed by the peripheral surface 22b. In addition, the tips of the knockout pin 22 and the punch 32 are sharp and prevent the deflection of the front, rear, left, and right of the workpiece 1 by entering the center of the upper and lower surfaces of the workpiece 1. By performing forging by the forging apparatus based on FIG. 8, a workpiece having the conical recess 1j described in FIG. 3, the tapered surfaces 1n and 1f, the flat surface 1t, and the conical recess 1w is obtained. In FIG. 3, the outer peripheral tapered surface 1 n is formed by the die 42, and the inner peripheral tapered surface 1 f is formed by the peripheral surface 22 a of the pin 22. The work 1 is set in an inverted manner in a forging apparatus shown in FIG. 10 and forged.
[0015]
10 and 11, the knockout pin 23 has a tip-like conical surface formed by a plurality of peripheral surfaces 23a, 23b, and 23c, and the plurality of peripheral surfaces 23a, 23b, and 23c are formed at the tip of the tip portion. It becomes a surface that makes the clearance angle smaller as it gets closer. The clearance angle α3, which is the angle between the peripheral surface 23c at the tip of the knockout pin 23 and the line segment 22e, is 3 to 5 degrees, for example , and the clearance angle α4, which is the angle between the peripheral surface 23b and the line segment 22e, is 2 It is set to about twice . The same applies to the punch 33 . That is, the conical surface of the tip is formed by a plurality of peripheral surfaces 33a, 33b, and 33c, and the plurality of peripheral surfaces 33a, 33b, and 33c are surfaces that reduce the clearance angle as they approach the tip of the tip. Made. Specifically, the clearance angle α6 that is an angle formed by the peripheral surface 33b and the line segment 22e is 7 to 9 degrees, and the clearance angle α5 that is an angle formed by the peripheral surface 33c and the line segment 22e is 1/9 or less. It is set to about 2 smaller. Also in this case, the clearance angle formed by each peripheral surface is set larger than the clearance angle formed by the peripheral surface of the tip portion of the knockout pin 22 used in FIG. Note that a rising wall surface 33d parallel to the central axis 22d is provided between the peripheral surface 33a and the peripheral surface 33b, and the rising wall surface 33d is inserted into the hole of the workpiece 1 so as to be inserted into the hole. A preliminary hole (guide hole) 1q with a step 1h shown in FIG. In addition, since the center of the knockout pin 22 is inserted into the center of the recess 1j formed in advance in the second forging process, the workpiece 1 can be centered reliably, and the front, rear, left and right directions of the workpiece 1 can be performed. It becomes possible to perform forging while preventing the vibration more reliably. The workpiece 1 formed by such a forging apparatus is inverted and set in the forging apparatus 6 shown in FIG. 12, and forging is performed at the next stage.
[0016]
In the forging apparatus shown in FIG. 12, the workpiece 1 is forged by applying pressure from both sides of the workpiece 1 in the through-forming hole 44a provided in the die 44 with the punching pin 24 and the punch 34. The center side of 1 is further thinned. That is, the preliminary hole 1q in the third forging step is punched with the punch pin 24 (see FIG. 5).
[0017]
In this case, as shown in FIG. 13, the hole insertion pin 24 has an outer diameter φb smaller by several tens of μm than the outer diameter φa on the tip side of the punch 33, and can form a clearance described later. Further, the tip portion is composed of the peripheral surface 24c and the peripheral surface 24b, and the clearance angle α8 formed by the peripheral surface 24b is, for example, 9 to 11 degrees, and the clearance angle α7 formed by the peripheral surface 24c is about ½ of that. Each of the peripheral surfaces 24b and 24c is set to be gradually smaller than the clearance angle formed by the peripheral surfaces 23b and 23c of the tip portion of the knockout pin 23 used in FIG. . Further, the shape of the front end side of the punch 34 is substantially the same as the shape of the front end side of the punch 33 used in FIG. 10, but the clearance angle α10 formed by the peripheral surface 34b is 8-10. The clearance angle α9 formed by the peripheral surface 34c is set to about ½ thereof, and is set so that the clearance angle is larger than that of the punch 33 shown in FIG.
[0018]
Thus the relief angle of the circumferential surface of the distal end portion of the knock-out pin or punch forms used in the later step in the present embodiment, from the relief angle of the circumferential surface of the distal end portion of the knock-out pin or punch forms used in the previous step Is gradually increased, the air or oil reservoir 1g can be released in the direction of the clearance L between the molding surface 1S of the workpiece 1 and the die 20 such as a knockout pin or punch as shown in FIG. . In other words, the molding surface 1S is a molding surface molded in the previous process, but the clearance angle formed by the peripheral surface (conical surface) 20h of the tip portion of the knockout pin or punch die 20 used in the subsequent process is determined in the previous process. By making it larger than the clearance angle formed by the used knockout pin or the peripheral surface of the tip of the punch, the conical surface 20h of the die 20 in the subsequent process is formed more than the clearance angle formed by the molding surface 1S molded in the previous process. Since the clearance angle to be increased becomes larger , a clearance route for the air reservoir 1g can be secured between them, and the workpiece 1 is not shaken and the forging accuracy can be improved. As for the clearance L, deformation of the workpiece can be suppressed if the load applied at the time of drilling is basically managed so as not to exceed the load applied at the time of upsetting in the first forging process. The diameter φb of the hole insertion pin 24 is slightly smaller than the diameter φa of the preliminary hole 1q formed in the previous step (actually, the diameter of the preliminary hole is slightly reduced by the spring back), and a clearance of several tens of μm is provided. Since it has, air and oil are escaped from this clearance L.
[0019]
Further, the tip portions of the pins and punches in any process are formed by a plurality of circumferential surfaces having conical surfaces extending in the direction along the central axis and having different angles with the central axis. The multiple peripheral surfaces are formed in a surface that reduces the clearance angle as it approaches the tip of the tip, so even if the workpiece has a small diameter , the workpiece can be relatively easily moved from the center side to the peripheral direction. Can be forged.
[0020]
In the fourth forging process shown in FIGS. 12 and 13, the thin portion 1 m generated on the center side of the work 1 is formed at a position shifted on one side of the work 1. Then, it is inverted and set in the forging apparatus shown in FIG. 15 to perform half-forging (fifth forging step). That is, pressure is applied to the thin portion 1m of the workpiece 1 by the tip 25c of the half punch pin 25 in the central axis direction. In this case, the thin portion 1m is displaced in the upward direction in the figure by the tip 25c side of the half punch pin 25 (see FIG. 6), but this displacement is regulated by the lower end surface 35c of the punch 35 located in the upper part. The thin portion 1m is only displaced by a certain distance.
[0021]
In addition, the front end surface of the front end 25c of the half punch pin 25 is flat, and the lower end surface 35c of the punch 35 is also flat so that the thin portion 1m can be easily displaced. The workpiece 1 in which the thin portion 1m is displaced is translated (not reversed), and the thin portion 1m is moved in the same direction as the misalignment direction during half-punching by the forging apparatus shown in FIG. The thin portion 1m is separated from the workpiece 1 by applying pressure based on the above.
[0022]
In this case, as shown in FIG. 18, the punching pin 26 is formed with a shaving portion 26a formed of a ring-shaped protrusion on the outer peripheral side, and the shaving portion 26a is formed in a square shape and protrudes in the outer peripheral direction. The part is applied to the inner surface of the work 1.
[0023]
The hole punching pin 26 and the half punching pin 25 and the punch 35 shown in FIG. 16 have air vent holes 25f, 35f, and 26f penetrating upward and downward at the center thereof. It is possible to release the air on the upper and lower surfaces of the thin portion 1m of the workpiece via the.
[0024]
When the fifth forging process, which is the above-mentioned half-punching process, and the sixth forging process, which is a hole-punching process, are described in detail with reference to FIG. The position is shifted in one direction (see FIG. 6). In this case, the inner diameter φ2 on the opposite side is smaller than the inner diameter φ1 of the cylindrical body 1y of the workpiece 1 in the half punching direction by about several μm.
[0025]
In the hole punching process, for example, when the forging pressure is applied to the thin wall portion 1m using the hole punching pin 26t whose outer diameter φ4 is substantially equal to the inner diameter φ2 on the inlet side of the workpiece 1, the connection of the thin wall portion 1m is performed. It is considered that the connection trace ma generated in the portion m can be excised at once. However, in practice, the inner surface 1j on the exit side of the workpiece 1 may be cut off from the connection portion m as a starting point, and the burr B may occur.
[0026]
Therefore, in the present embodiment, the outer diameter φ3 on the tip end side of the hole punching pin 26 is made smaller by several tens of μm than the inner diameter φ2 of the workpiece 1, and the small diameter hole punching pin 26 is used. The shaving portion 26a is provided on the outer periphery of the rear portion, and the tip outer diameter φ5 of the shaving portion 26a is made to be larger by several μm than the inner diameter of the inner diameter φ2 on the inlet side of the work 1.
By doing so, it is assumed that the thin portion 1m is punched with the hole punching pin 26 while pressing the outer diameter of the work 1 on the punch 36 side. At the time of punching, ironing is performed on the entire inner surface of the work 1 by the shaving portion 26a and smoothed.
[0027]
According to this method, since the outer diameter φ3 on the front end side that presses the thin portion 1m of the punching pin 26 is smaller than the inner diameter φ2 on the inlet side, the inner surface 1j on the outlet side of the workpiece 1 is cut off to generate the burrs B. In addition, since the connection trace ma composed of stepped portions generated in the connection portion m is smoothed by the shaving portion 26a, a highly accurate part can be obtained, and in a later process, FIG. The cutting by step S3 shown is not required.
According to the actual trial result, it was confirmed that the vibration of the ring body having the outer diameter: the inner diameter = 1.4: 1 is suppressed to 0.03 or less.
[0028]
According to the present invention, since a precision part can be manufactured with high accuracy, the conventional heat treatment process (step S2) and cutting (step S3) can be omitted as shown in the step of FIG. 20, and the manufacturing process can be shortened.
[0029]
In the present invention, when forming a ring body, the first through sixth forging processes are passed through. However, in the case of manufacturing a precision product in which the center is thinned without the need for punching, The last half punching and hole punching steps may be omitted.
[0030]
As described above, according to the present invention, the angle of the tapered surface at the tip is increased as the forging process proceeds, so that the air pool and the forming hydraulic pressure can be released to the outside, and the influence of these formations Can be reliably transferred to a mold-shaped workpiece. In addition, since the tip shape has a two-stage configuration, the center of the mold with respect to the center of the workpiece can easily pick up the core, which is effective as a measure for preventing displacement. Moreover, since the air vent holes 25a, 35a, and 26a are provided, it is possible to reduce the load on the mold in the forging process.
[0031]
【The invention's effect】
As described above, according to the invention of claim 1, the forging process is performed a plurality of times by a mold that dents both sides of the workpiece in a conical shape, and the mold used in the subsequent forging process is used in the previous forging process. Because a die with a larger clearance angle than the used die was used, the cutting process by rough finishing can be omitted, and the yield and efficiency of precision parts with a bottomed hole or through hole in the center can be improved. In addition to being good, air and hydraulic pressure can be released, the load on the mold can be reduced, and a highly accurate product can be obtained.
[0032]
According to invention of Claim 2, the conical surface of the front-end | tip part of a metal mold | die is extended by the direction along a center axis | shaft, and is formed by the several surrounding surface from which an angle with a center axis differs, Since the peripheral surface of the surface is formed with a surface that reduces the clearance angle as it approaches the tip of the tip, it can be depressed by forging pressure on the upper and lower surfaces of the workpiece without difficulty and before and after the workpiece. , Left and right shake can be suppressed.
[0033]
According to the invention of claim 3, since the forging is performed using a mold having a diameter slightly smaller than the hole diameter of the previous process, a clearance is provided on the outer periphery of the mold, and air and hydraulic pressure are improved through the clearance. Can escape to the outside.
[0034]
According to the invention of claim 4, since the deep hole is formed after the preliminary hole is formed, unlike the case where the deep hole is formed at once, the high-precision hole is smoothly formed. Can be formed.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an outline of an embodiment of the present invention.
FIG. 2 is a first process diagram showing an outline of an embodiment of the present invention;
FIG. 3 is a second process diagram illustrating the outline of the embodiment of the invention.
FIG. 4 is a third process diagram illustrating the outline of the embodiment of the invention.
FIG. 5 is a fourth process diagram illustrating an outline of an embodiment of the present invention;
FIG. 6 is a fifth process diagram showing an outline of one embodiment of the present invention;
FIG. 7 is a first process diagram showing one embodiment of the present invention.
FIG. 8 is a second process diagram showing an embodiment of the present invention.
FIG. 9 is a side view showing a knockout pin used in a second step showing an embodiment of the present invention.
FIG. 10 is a third process diagram showing one embodiment of the present invention.
FIG. 11 is a side view showing details of a knockout pin and a punch used in a third step showing an embodiment of the present invention.
FIG. 12 is a fourth process diagram showing one embodiment of the present invention.
FIG. 13 is a side view showing details of a knockout pin and a punch used in a fourth step showing an embodiment of the present invention.
FIG. 14 is a cross-sectional view for explaining an embodiment of the present invention.
FIG. 15 is a diagram showing a fifth step showing an embodiment of the present invention.
FIG. 16 is a side view showing details of the knockout pin and the punch used in the fifth step showing the embodiment of the present invention.
FIG. 17 is a diagram showing a sixth step showing one embodiment of the present invention.
FIG. 18 is a side view showing details of the knockout pin used in the sixth step showing the embodiment of the present invention;
FIG. 19 is a diagram for explaining the operation of the embodiment of the invention.
FIG. 20 is a cross-sectional view showing a workpiece manufactured by a process showing a conventional example and an embodiment of the present invention.
FIG. 21 is a view showing a conventional process and a work forming process of the present invention.
[Explanation of symbols]
1 Workpiece, 21, 22, 23 Knockout pin, 24 Hole insertion pin, 25 Half punch pin, 26 Hole punch pin, 31, 32, 33, 34, 35, 36 Punch

Claims (4)

A cold forging method for performing forging process using a mold recessing both surfaces of a work conically multiple times as different molds are used for each forging step, tip recessing both surfaces of a work in a conical shape The clearance angle is a large angle formed by a line segment in which the conical surface of the tip is perpendicular to the central axis of the column and the ridge line of the conical surface of the tip of the column. A cold forging method characterized in that a mold having a larger clearance angle than that of a mold used in the previous forging process is used as a mold used in a subsequent forging process . The conical surface at the tip of the mold is formed by a plurality of peripheral surfaces extending in the direction along the central axis and having different angles with the central axis, and the plurality of peripheral surfaces are formed at the tip of the front end. The cold forging method according to claim 1, wherein the cold forging method is formed on a surface that reduces a clearance angle as it gets closer . Cold forging method according to claim 1 in the forging process, characterized in that had use in front of the forging process mold consisting column body of slightly smaller diameter than the diameter of the hole formed in the workpiece after. The deep hole is formed by applying forging pressure to the preliminary hole in the subsequent forging process after forming the preliminary hole having a shallow depth in the previous forging process. Cold forging method.

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