JP2005066684A - Method for producing forged member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production method by which a forged member having holes for lightening on a flange part can be produced with high precision without greatly changing the existing process. <P>SOLUTION: In a punch-out process in a hot-forging, a portion to be finally punched out in the forged member is made to be under half-punched state and thereafter, a half-punched core part is pressed and returned back to the shape of the original intermediate member. Then, after applying a prescribed machining and a prescribed heat-treatment, the half-punched core part is punched out to form the desired forged member. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a forged member. More specifically, the present invention relates to a method for manufacturing a forged member having a hole in a flange portion.

  As a method for manufacturing a hot forged member, for example, the following method has been proposed for a hub flange for a clutch used in an automobile or the like (see Patent Document 1).

  (1) Material cutting step → (2) Heating step → (3) Crushing step (hot forging) → (4) Blocker step (hot forging) → (5) Finisher step (hot forging) → ( 6) Punching process (hot punching) → (7) Heat treatment process → (8) Shot blasting process → (9) Lubricating treatment process → (10) Ironing process (cold ironing) → (11) Turning process. And by having a cold ironing process, especially an intermediate | middle square hole and a center spline hole can be finished with high precision, and it is supposed that the load concerning a manufacturing apparatus can be made small.

  However, in the method for manufacturing a forged member described above, since the hole is formed in the flange portion in the punching step (6), the shape of the hole portion is changed in the heat treatment step (7), and an accurate shape cannot be obtained. Therefore, the ironing step (10) is required. Further, in the turning process of (11), since the member is hardened by the heat treatment, the processing load is large, the productivity is reduced and the manufacturing cost is increased. There is a problem.

In particular, when a flange such as a helical gear used in a drive system unit is provided with a hole for weight reduction in a large forged member, a highly accurate one is required for the tooth surface and the end surface. The shape accuracy of the hole itself does not matter so much. It has been desired to develop a method for easily forming a hole in a flange portion without reducing the accuracy of a machined part.
JP 11-270580 A

  The present invention has been made in view of the above-described requirements, and provides a manufacturing method capable of manufacturing a forged member having a hole for weight reduction in a flange portion with high accuracy without greatly changing an existing process. For the purpose.

  The method for manufacturing a forged member according to the present invention is a method for manufacturing a forged member in which a predetermined hole is formed by hot punching in an intermediate member stamped by hot forging. A half punching process for shearing, a pressing back process for pressing the half punched core part into a half punching hole formed in the half punching process, and an intermediate member including the half punched core part pushed back. A machining step for machining into a predetermined shape, a heat treatment step for heat-treating the machined intermediate member, and a drawing-out step for drawing off a half-punch core portion of the heat-treated intermediate member. Features.

  The manufacturing method of the present invention includes the above steps, so that even if heat treatment such as carburizing is performed on the intermediate member after machining, the core portion is pressed into the hole portion of the flange portion. A forged member can be manufactured with the same high accuracy as that processed without a hole without deformation due to distortion.

  Further, the core portion pushed back into the half punch hole can be removed with a low load after the heat treatment. Therefore, regardless of the shape of the hole (the shape of the core), even if it is irregularly shaped, it can be pulled out with a simple actuator that moves up and down using an inexpensive and simple punching pin such as a cylindrical shape. It can be implemented with low equipment costs and a small manufacturing cost.

  Moreover, in the manufacturing method of the forge member of this invention, it can also be set as the process of performing a half punching process and a pushing-back process simultaneously. Furthermore, it is also preferable to perform the integrated half-returning step and the punching step for other portions at the same time. Thus, by integrating each process, the number of processes can be reduced and manufacturing cost can be reduced. Further, the existing hot forging process can be carried out without greatly changing.

  In the method for producing a forged member according to the present invention, a target value of a drop load in the drop step is set, and the half punching condition of the half punching step and the push back condition of the push back step are set so as to satisfy the target value. It is desirable to adjust.

  The target value of the pull-out load is the range in which the core part does not fall off due to the load during machining or the expansion / contraction of heat treatment, and the high-precision part machined in the drop-out process does not cause distortion such as deformation. Therefore, stable production and quality can be ensured by satisfying this target value.

The method for producing a forged member of the present invention is based on an intermediate member stamped by hot forging,
A half punching process in which the intermediate member is sheared with a punching amount equal to or less than the thickness of the intermediate member; A machining step for machining an intermediate member including a half-punched core portion into a predetermined shape, a heat treatment step for heat-treating the intermediate member including a half-punch core portion machined into a predetermined shape, and a heat-treated intermediate And a drawing-out step of drawing off the half-drawn core portion of the member.

  The manufacturing method of the forged member of this invention is demonstrated using the schematic process drawing of FIG.

  First, a material suitable for a forged member is cut into a predetermined size with a billet shear or a saw, and this material is heated to a temperature suitable for hot forging, for example, 1200 ° C. (a). In addition, this heating temperature can be determined according to the material of a raw material.

  After heating, the material is formed into a stamped first intermediate member W1 through a plurality of hot forging processes, that is, a scale-off process (b), a wasteland process (c), and a finishing process (d).

  Next, a hole P2 is formed by hot punching at a predetermined position of the shaft hole P1 and the flange portion of the center of the first intermediate member W1. At this time, the hole P2 in the flange portion is in a so-called half-extracted state in which the press stroke is stopped with an extraction amount less than the thickness of the flange portion (e). The central shaft hole P1 may be completely removed.

  The core part Q of the hole P2 in the half-punched flange part is pushed back to the original position (that is, inside the hole P2) in the next push-back step (f) to form the second intermediate member W2. This push-back process can also be performed by a trimming press process simultaneously with deburring of the first intermediate member.

  The inner surface of the shaft hole P1 of the obtained second intermediate member W2 is subjected to predetermined machining such as cutting or gear cutting on the outer periphery of the flange (g), followed by heat treatment such as carburizing and quenching ( h).

  And the forged member which has a desired hole in a flange part can be obtained by pulling out the half punching core part Q of the flange part remaining on the heat-treated second intermediate member W2 with a simple press or the like (i). .

  Here, a normal hot forging method can be employed from the material cutting / heating step (a) for forming the first intermediate member W1 to the finishing step (d) of the hot forging step.

  An example of the half punching die for carrying out the half punching step (e) of FIG. 1 is shown in FIG. The mold shown in FIG. 2 schematically shows a cross section of a mold that simultaneously forms the shaft hole of the intermediate member, P1, and the half punch hole P2. The upper die 1 is provided with a punch 3 for punching the shaft hole P1 and a punch 2 for forming the half punch hole P2, and the half punch hole P2 is opposed to the punch 2 via an intermediate member W1. A punching die 4 is arranged so as to do this. The punch 2 is set to be shorter than the punch 3, and at the same time as punching the shaft hole P1 by adjusting the press stroke, the punch 2 is sheared to a predetermined depth without removing the core Q, and the half punch hole P2 is formed. Can be formed.

  FIG. 3 shows an example of a return punch in a push-back process in which the half-punched core portion Q is pushed back into the half punch hole P2. Although the cylindrical return punch 5 is illustrated in FIG. 3, the punch 5 is not particularly limited as long as it has a shape capable of pushing back the punching core portion Q into the half punching hole P2. For example, it may be a protrusion type or a pin type.

  It is also desirable to use a process-intensive mold that enables the half-drawing step and the push-back step in one step (hereinafter referred to as half-drawing back). An example is shown in FIG. 4 has a biasing means 7 such as a spring for pressing the punch 2 in the punching direction after forming the half punching hole P2, and the punching die 4 is punched into the hollow portion. A return punch 5 provided with a biasing means 8 such as a spring for pushing the core portion Q back into the punch hole P2 is movably fitted along the axis. When the intermediate member W1 is punched with the mold having such a structure, the half punching hole P2 is first formed by the punch 2 provided in the upper mold. At this time, since the urging means 8 is compressed and the urging force is increased, the return punch 5 is urged as the upper die is raised, and the punching core portion Q is sandwiched between the punch 2 and the return punch 5 so as to be half-cut. It is pushed back into the hole P2.

  As described above, it is also preferable to consolidate a punching process of another part (for example, a shaft hole) of the intermediate member into the half pulling back process consolidated into one process. FIG. 5 shows an example of a mold in which the punching of the shaft hole P1 and the half punching back process of the half punching hole P2 are integrated into one process. The punch 3 for forming the shaft hole P1 is added to the upper mold in the mold shown in FIG.

  As described above, since the processes can be integrated only by remodeling a part of the mold, it is possible to carry out the predetermined half pull-out without increasing the total number of processes for hot forging.

  Machining such as gear cutting on the outer periphery of the flange and carburizing treatment for the second intermediate member W2 that has been half-removed can be performed in the same manner as a normal intermediate member that does not have a hole in the flange portion. Yes, there are no restrictions.

  Since the half punching process is performed in the hot forging process, the periphery of the hole P2 after half punching is rapidly cooled by a punch, and the periphery of the pulling back part is further cooled by pushing the punching core part Q back into the hole P2. Is done. Therefore, when the second intermediate member W2 is cooled, the pulled-out core portion Q is lightly press-fitted into the punch hole P2 due to the shrinkage balance of the entire intermediate member. Therefore, there is no fear that the core portion Q will drop off in the subsequent machining process or heat treatment process. Further, when machining or heat treatment is performed on the intermediate member having a hole, the intermediate member may be distorted due to the presence of the hole. However, in the second intermediate member W2 that has been half-removed, it is the same as the hole P2. Since there is a stuffing of material, it is considered that the load due to machining and the expansion / contraction due to heat treatment are almost the same as those of the intermediate member without holes.

  By the way, in a heat treatment for a long time at a high temperature such as carburizing treatment, depending on the material, a diffusion phenomenon of material components may occur during the heat treatment, and the core portion Q may be reattached to the inner peripheral portion of the punch hole P2. . However, since the second intermediate member W2 is half-cut hot, an oxide scale is generated on the inner surface of the punch hole P2 and the cross-section of the punch core portion Q. And since this oxide scale can inhibit the diffusion phenomenon of the material component during the heat treatment and prevent strong reattachment, it is possible to keep the pull-out load for pulling the core-out portion Q low.

  Thus, the core part Q remaining on the second intermediate member W2 after the heat treatment can be removed with a low load. For example, by using a pull-out jig 10 in which a cylindrical punch pin 9 as shown in FIG. 6 is fixed, it is easy to press the core portion Q with a simple actuator that can move up and down simply. Can be removed. In this case, for example, even if the shape (hole shape) of the extraction core portion is an irregular shape as shown by P in FIG. 7, it is possible to use an extraction pin having a simple cross-sectional shape such as a circle or a square. it can.

  The pull-out load for pulling out the core portion Q includes various amounts such as the amount by which the first intermediate member W1 is half-extracted, the clearance at the time of half-extraction, the temperature at the time of pushing back the core portion Q and the amount of return. The target load can be adjusted by adjusting the factor to an appropriate value.

  An example of the relationship between various factors and the drop-off load in these half-drawing steps is qualitatively shown in FIG. (A) is a relationship with the half punching amount (depth of the punching hole P2). As the half punching amount increases, the dropout load decreases. Moreover, (b) is a relationship with the return amount of the extraction core part Q in the pushing back process. In this case, the removal load hardly changes until the extraction core portion Q coins with the inner surface of the extraction hole P2. However, it tends to increase as coining occurs.

  Therefore, if the relationship between the above-mentioned factors and the drop-off load is converted into data, the pull-out core part Q will not drop off due to the load during machining or the expansion / contraction of heat treatment, and the machine can be used in the drop-off process. Appropriate values of various factors in the redrawing process can be obtained in accordance with the target load for pulling out that does not cause distortion such as deformation in the processed high-accuracy part.

  FIG. 9 shows a flowchart for controlling the drop load. First, a drop stress α that can maintain the machining accuracy of the member in the drop step is obtained. Next, a stress β at which the core part does not fall off in the machining process and a stress γ at which the core part does not fall off in the heat treatment process are obtained. Here, the stress β and the stress γ must be smaller than the stress α. From these values, the stress β is compared with the stress γ, and the larger value is extracted to determine the target load F to be removed.

  When the target load F is determined, the appropriate value of each factor is determined from the relationship between each factor in the withdrawal process and the withdrawal load F, such as the half withdrawal amount and pushback amount obtained in advance as illustrated in FIG. Can be sought. Perform stamping with appropriate values of each factor obtained to verify whether there is any contradiction, and if there is a conflict, repeat until the target load F is within the allowable range and verify each factor with correction. To do. Needless to say, the obtained conditions are finally determined in consideration of equipment restrictions and manufacturing costs.

As described above, in the method for producing a forged member of the present invention, the portion of the forged member that is finally desired to be removed is brought into a half-removed state, and then the half-removed core portion is pressed to obtain substantially the original first intermediate member W1. Return to shape. And after carrying out a predetermined machining and performing a predetermined heat treatment, the half-punched core part is pulled out to obtain a desired forged member. Therefore, the method for manufacturing a forged member of the present invention has the following advantages.
1) Even if heat treatment is performed after machining, a forged member having substantially the same dimensional accuracy as when there is no hole in the flange can be obtained. For example, as shown in FIG. 10B, when the hole P is punched into the flange portion by hot forging or the like and then subjected to machining or heat treatment, the portion where the hole P is formed contracts and the entire flange is contracted. The shape may be deformed. However, when half extraction is performed as shown in (a) and the hole portion P has a core portion, a member having substantially the same shape as a member having no hole in the flange portion can be obtained.
2) The present invention can incorporate the half-draw back process into the existing hot forging process with a slight complication of the mold structure. Also, the process of removing the core part can be performed by an inexpensive simple press or the like. Therefore, the method of the present invention can be carried out with low equipment cost and a slight increase in manufacturing cost without greatly changing the existing process.
3) It is possible to form a hole that is lighter to the limit while ensuring the accuracy of other high-precision parts of the forged member, and it is possible to reduce the weight of the forged member and to suppress noise generation. it can.
4) In the heat-cooled composite tooth profile forging member 20 having the tooth profile surface 22 on the cylindrical section 21 shown in FIG. 11, the core section Q is pulled out by pulling back the core section Q as shown in (a). It is possible to prevent dimensional changes due to drawing expansion and contraction (arrows in (b) figure). In addition, the core part Q pulled back can be simultaneously removed by cold coining or the like. As a result, high-precision cold coining is possible.
5) By adjusting the amount of withdrawal after half-punching, the core in the withdrawal core is raised and dent deformation is formed, so that the phase in the machining process and the withdrawal step of the core Can make decisions easier.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used for manufacturing a hot forged member of a helical gear used for a transmission gear used in a transmission such as an automobile. In particular, it is effective in reducing the weight of a forged member having a large flange portion.

It is explanatory drawing which shows the manufacturing process of the forge member of this invention. It is a cross-sectional schematic diagram explaining the process which consolidated the half punching process and the centering process. It is explanatory drawing which shows an example of a withdrawal process. It is a cross-sectional schematic diagram explaining the process which consolidated the half extraction process and the extraction process. It is a cross-sectional schematic diagram explaining the process which consolidated the half punching process, the drawing back process, and the centering process. It is a perspective view which shows an example of the extraction pin in the extraction process. It is a schematic diagram which illustrates the hole shape of a flange part. It is a conceptual diagram which illustrates the relationship between the various factors in a half withdrawal process, and a withdrawal load. It is a flowchart which controls a drop-off load. It is a conceptual diagram which illustrates the shape of the forge member after heat processing. (A) Heat treatment after half pull back. (B): Heat treatment after drilling. It is a partial process figure of the heat-cooling compound tooth profile forging member which has a tooth profile surface in a cylindrical part. (A) When the core is half-removed. (B) When the core is punched out.

Explanation of symbols

2: Half punching punch 3: Punching punch 4: Half punching die 5: Return punch 9: Punching pin 10: Removal jig 20: Heat-cooled composite tooth profile forging member 21: Cylindrical portion 22: Tooth profile P1: Shaft hole P2 : Half punch hole Q: Pull core

Claims (4)

In the method for manufacturing a forged member in which a predetermined hole is formed by hot punching for an intermediate member stamped by hot forging,
A half punching process in which shearing is performed with a punching amount equal to or less than the thickness of the intermediate member;
A pushing-back step of pressing the half-punched core portion half-pressed and pushing it back into the half-punching hole formed in the half-punching step;
A machining step of machining the intermediate member including the pushed back core portion into a predetermined shape;
A heat treatment step for heat-treating the machined intermediate member;
A forging member, comprising: a step of removing the half core portion of the intermediate member that has been heat-treated.   The method for producing a forged member according to claim 1, wherein the half punching step and the pulling back step are performed simultaneously.   The method for producing a forged member according to claim 2, wherein a punching process for another part is simultaneously performed.   The target value of the drop-off load in the drop-out process is set, and the half-drawing condition in the half-drawing process and the push-back condition in the push-back process are adjusted so as to satisfy the target value. The manufacturing method of the forge member as described in any one of.

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