JP4265480B2 - Manufacturing method of forged parts and forged parts - Google Patents

Description

  The present invention relates to a forged part manufacturing method and a forged part, and more particularly to a forged part manufacturing method and a forged part having a hole that causes stress concentration.

  Various strength parts used for automobiles and the like are manufactured by hot forging. One of them is a clutch hub flange disclosed in Patent Document 1 below. The manufacturing method of the hub flange for a clutch composed of this hot forged member is as follows: (1) material cutting step, (2) heating step, (3) crushing step (hot forging), (4) blocker step (heat (5) Finisher process (hot forging), (6) Punching process (hot punching), (7) Heat treatment process, (8) Shot blasting process, (9) Lubrication process, (10) Ironing A process (cold ironing) and (11) a cutting process.

  Here, in the “punching process (hot punching)”, a long hole is formed in the flange part from the viewpoint of weight reduction, etc., but in the subsequent “heat treatment process”, the hole part is deformed and the dimensional accuracy deteriorates. It is possible.

  On the other hand, it is conceivable to carry out the “punching process (hot punching)” after the “heat treatment process”, however, since sufficient heat treatment does not enter the periphery of the hole such as a long hole formed in the flange part. It is conceivable that the strength in the region becomes insufficient. In particular, in the case of a long hole or the like, stress concentrates on the semicircular region provided at both ends, and therefore the strength of the semicircular region needs to be sufficient.

Further, after the “heat treatment step”, a “punching step” using a laser can be considered. However, there is a possibility that the heat treatment effect may be reduced by the heat of the laser.
JP 11-270580 A

  The problems to be solved by the present invention are a decrease in the dimensional accuracy of the forged part and a lack of strength in the stress concentration part when a hole that causes stress concentration in the forged part is provided. Accordingly, an object of the present invention is to provide a method for producing a forged part and a forged part capable of improving the strength of a stress concentration site without causing a reduction in dimensional accuracy.

In the method for manufacturing a forged part based on the present invention, the intermediate member stamped by hot forging is subjected to a heat treatment, and then a forged part manufacturing method including a step of forming a predetermined long hole portion. there are, relative to the intermediate member, the position corresponding to both end portions of the upper Symbol predetermined length hole, the prepared hole forming step of forming a small pilot hole than the predetermined length hole, the heat treatment process It is prepared before the heat treatment process.

  In another embodiment of the invention, the pilot hole is formed by machining or punching.

In another form of the invention, between the prepared hole forming step and the heat treatment step, the region corresponding to the elongated hole portion is subjected to shearing so as to include the prepared hole, and the above described hole is removed from the punched hole. A half-punching step for forming a punched core portion extruded with a drawing amount equal to or less than the thickness of the intermediate member; and a push-back step for pressing the punched core portion and pushing it back into the punched hole after the half-punching step. have. Moreover, in the said long hole part formation process, the said long hole part is formed by dropping the said core part from the said intermediate member with respect to the intermediate member to which the said heat processing was performed.

  Moreover, in the other form of the said invention, it has a machining process for machining the said intermediate member in a predetermined shape after the said pushing-back process and before the said heat treatment process.

According to another aspect of the invention, in the long hole portion forming step, the long hole portion is formed by cutting or laser processing the intermediate member subjected to the heat treatment.

A forged component based on the present invention is a forged component manufactured by the above-described method for manufacturing a forged component, and the forged component has a surface hardness of a peripheral portion of a predetermined long hole portion in another region. It contains a part larger than the surface hardness.

Moreover, in the other form of the said invention, it has a boundary line in the connection part of the said other site | part and the site | part which has a surface hardness larger than the surface hardness of the said other site | part.

According to the method for manufacturing a forged part based on the present invention, after forming a pilot hole smaller than the predetermined long hole portion at a position corresponding to both ends of the predetermined long hole portion, the heat treatment is performed. It is possible to improve the strength of the stress concentration portion ( region where the pilot hole is formed) in the peripheral portion of the predetermined long hole portion. After that, by forming a predetermined elongated hole portion so as to include this pilot hole, since the hole processing is performed after the heat treatment, it is possible to avoid a decrease in the dimensional accuracy of the elongated hole portion due to the heat treatment. It becomes possible. As a result, it becomes easy to form a long hole for the purpose of weight reduction, and it becomes possible to reduce the weight of the forged part.

  Moreover, a pilot hole can be accurately formed by forming the pilot hole by machining. Further, by forming the prepared hole by punching, an increase in the manufacturing cost of the forged product can be suppressed. Moreover, since the pilot hole forming process can be employed simultaneously with other hole forming processes provided in the forged product, the productivity of the forged product can be improved.

  In addition, a half punching process for forming a core part extruded from the punched hole with a thickness less than the thickness of the intermediate member, and a push-back process for pressing the core part and pushing it back to the punched hole are performed. Then, by applying a heat treatment step and removing the core part from the intermediate member, the heat-strain is caused because the core part is pressed into the hole of the intermediate part during heat treatment. The deformation of the punched hole can be prevented. As a result, it becomes possible to produce a forged part having the same dimensional accuracy as when no hole is provided.

  Moreover, the core part press-fitted into the hole can be easily removed after the heat treatment. As a result, even if the hole has an irregular shape regardless of the shape of the hole (extracting core portion), the extracting core portion should be formed using a simple shape extracting pin such as a cylindrical shape without using the irregular shape extracting pin. Can be removed. Thereby, it becomes possible to suppress the cost increase of the manufacturing equipment required for manufacture of a forge part.

  In addition, since the core part is press-fitted into the punched hole, it can be pulled out with a low load when cutting the hole part. It can be dropped.

  In the forged part based on the present invention, the surface hardness at the stress concentration site is higher than in other regions. As a result, a forged part having excellent strength characteristics can be obtained.

  Hereinafter, a method for producing a forged part and embodiments of the forged part based on the present invention will be described with reference to the drawings. In the embodiment described below, a case where the present invention is applied to a gear will be described as an example of a forged part.

(Embodiment 1)
First, with reference to FIGS. 1-5, the manufacturing method and forged component (gear) of the forged component (gear) in Embodiment 1 are demonstrated. 1 is a plan view of an intermediate part for forming a forged part (gear) according to the present embodiment, and FIG. 2 is a plan view of the forged part (gear) according to the present embodiment.

  In the present embodiment, in the process of manufacturing a gear which is a forged part, first, (1) cutting process of material, (2) heating process, (3) crushing process (hot forging), (4) blocker process ( A stamped intermediate member 100A as shown in FIG. 1 is prepared by hot forging) and (5) finisher process (hot forging). Thereafter, the pilot hole 10 is formed at a predetermined position of the intermediate part 100A by machining or punching.

  As a position for forming the pilot hole 10, in the present embodiment, a long hole portion 102 is formed in the intermediate part 100 </ b> A in a subsequent process (two-dot chain line in FIG. 1), but the final molding is performed. It is formed in the region of both end portions corresponding to the stress concentration portion of the elongated hole portion 102 of the gear 100. The size of the pilot hole 10 is set to an opening diameter equal to or smaller than the diameter of the semicircular region formed at the end of the long hole portion 102. In addition, although the state in which the bolt hole 103 and the shaft hole 104 are formed is illustrated in the intermediate part in FIG. 1, the molding process of the elongated hole portion 102 is performed simultaneously with the molding process of the elongated hole portion 102 described later. It is also possible to mold by a subsequent process.

  Next, referring to FIG. 2, after forming the prepared hole 10, the intermediate member 100 </ b> A is subjected to heat treatment, and then the elongated hole portion 102 is formed so as to include the prepared hole 10. Thereafter, the gear 100 is completed by applying a predetermined process to the intermediate member.

  As described above, in the present embodiment, the pilot hole 10 is provided in a region corresponding to the stress concentration portion of the elongated hole portion 102 of the gear 100 that is finally molded with respect to the intermediate member 100A stamped by hot forging. A pilot hole forming step for forming (total of six locations), a heat treatment step for subjecting the intermediate member 100A formed with the pilot hole 10 to a heat treatment, and a pilot hole for the intermediate member 100A subjected to the heat treatment. 10 and a hole forming step for forming the arc-shaped long hole 102 so as to include 10.

  Hereinafter, the characteristics of this manufacturing process will be described with reference to FIGS. 3 to 5 are first to third process cross-sectional views illustrating a method for manufacturing a forged component (gear) according to the present embodiment according to the III-III cross section in FIG.

  Referring to FIG. 3, machining by a drill or punching using a punch or the like is performed on both end regions of intermediate part 100 </ b> A corresponding to stress concentration portions of elongated hole portion 102 of gear 100. Thus, the pilot hole 10 is formed. When the pilot hole 10 is formed by machining, the pilot hole 10 can be formed on the intermediate part 100A with high positional accuracy and dimensional accuracy. Further, when the pilot hole 10 is formed by punching, the pilot hole 10 can be formed by the same process as other punching holes, so that an increase in manufacturing cost of the gear 100 can be suppressed.

  Next, referring to FIG. 4, carburizing and quenching 20 is applied to the surface of intermediate part 100 </ b> A as a heat treatment to cure the exposed surface layer. At this time, since the surface of the pilot hole 10 is also exposed, the surface is hardened by carburizing and quenching.

  Next, referring to FIG. 5, the long hole portion 102 is formed in the intermediate member 100 </ b> A so as to include the prepared hole 10. In the formation of the elongated hole portion 102, it is possible to form by machining using a drill or the like, punching using a punch or the like, as in the case of forming the pilot hole 10, and as other processing methods, Laser machining and wire cutting can also be used.

  Here, the surface hardness and shape of the elongated hole portion 102 of the gear 100 formed by the manufacturing method described above will be described with reference to FIGS. 6 and 7. 6 is a plan view showing the shape of the long hole portion 102, and FIG. 7 is a partially enlarged plan view of a region surrounded by VII in FIG.

  With reference to FIG. 6, by adopting the above manufacturing method, in the elongated hole portion 102, the surface hardness is approximately equal in the semicircular region 102 </ b> A at both ends corresponding to the region where the pilot hole 10 is formed in advance. Whereas it is about 700 Hv, in the connection region 102B that connects the semicircular region 102A at both ends, the surface hardness is 300Hv or less, and the hardness of the semicircular region 102A that is a stress concentration site can be improved. Yes. In addition, referring to FIG. 7, a boundary line 102C may be formed at the boundary between the semicircular region 102A and the connection region 102B. Further, the intersection angle of the tangent line at the boundary line 102C between the semicircular region 102A and the connection region 102B is about 150 ° or more.

(Action / Effect)
As described above, according to the gear manufacturing method in this embodiment, the pilot hole 10 is formed in advance in the region corresponding to the stress concentration portion of the elongated hole portion 102 of the gear 100, and then the heat treatment is performed. The strength of the region corresponding to the stress concentration portion of the hole 102 can be improved. In addition, by forming the long hole portion 102 so as to include the pilot hole 10, the long hole processing is performed after the heat treatment processing, and therefore it is possible to avoid a decrease in dimensional accuracy of the long hole portion due to the heat treatment. It becomes possible. As a result, it is easy to form the elongated hole portion 102 for the purpose of reducing the weight of the gear 100, and the gear 100 can be reduced in weight.

(Embodiment 2)
Next, with reference to FIGS. 8 to 14, a method for manufacturing a forged part (gear) and a forged part (gear) in the second embodiment will be described. 8 to 12 are first to fifth process cross-sectional views showing a method for manufacturing a forged part (gear) in the present embodiment, and are cross-sectional views taken along the line III-III in FIG. is there. FIGS. 13 and 14 are schematic views showing the structure of a die and a punch for realizing the manufacturing method in the present embodiment.

  When compared with the manufacturing method in the first embodiment described above, the manufacturing method in the present embodiment is characterized by the formation of the elongated hole portion 102. Therefore, in the following description, only the characteristic part of this Embodiment is demonstrated and the overlapping description is not repeated.

  Referring to FIG. 8, machining by a drill or punching using a punch or the like is performed on both end regions of intermediate part 100 </ b> A, which are regions corresponding to stress concentration portions of elongated hole 102 of gear 100. Thus, the pilot hole 10 is formed.

  Next, referring to FIG. 9, the region corresponding to the long hole portion 102 is subjected to shearing so as to include the pilot hole 10, and the amount of extraction less than the wall thickness dimension (t) of the intermediate member 100A from the through hole 102D. To extrude (in the direction of arrow F1) to form the core part 30 (half punching process). Then, referring to FIG. 10, after the half punching process, the core part 30 is pressed upward (in the direction of arrow F <b> 2) to push the core part 30 back into the hole 102 </ b> D (push-back process).

  Next, referring to FIG. 11, carburizing and quenching 20 is applied to the surface of intermediate part 100A as a heat treatment to cure the exposed surface layer. At this time, since the surface of the pilot hole 10 is also exposed, the surface is hardened by carburizing and quenching. Further, during this heat treatment, since the core part 30 is press-fitted into the hole 102D of the intermediate part 100A, deformation of the hole 102D due to thermal strain can be prevented.

  Next, with reference to FIG. 12, the long hole portion 102 is formed so as to include the pilot hole 10 in the intermediate member 100A. In the formation of the elongated hole portion 102, it is possible to form by machining using a drill or the like, punching using a punch or the like, as in the case of forming the pilot hole 10, and as other processing methods, Laser machining and wire cutting can also be used.

  Here, since the core 30 is press-fitted into the hole 102D, when the long hole 102 is cut, it can be removed with a low load, and when laser processing is performed. , It is possible to drop out due to low output.

  In addition, what is shown to FIG. 13 and FIG. 14 can be used as a structure of the die | dye and punch used for the said half extraction process and the said pushing back process. FIG. 13 is a diagram showing the structure of the punch 200 and the punching die 210 used in the half punching process. The punch 200 is provided with a half punching punch 201 for punching the punching core portion 30 and a core punching punch 202 for completely punching the shaft hole punching core portion 104A. A die 210 is disposed. By processing the punch 200 in a state where the intermediate member 100A is placed on the die 210, the shaft hole core 104A is punched, and at the same time, the core 30 is thickened from the hole 102D to the thickness of the intermediate member 100A. Extruded with a drawing amount less than the dimension (t).

  FIG. 14 shows a return punch 300 used in the push-back process. When the return punch 300 is raised in a state where the intermediate member 100A is fixed, the punching core 30 is pressed by the punch 300, and the punching core 30 is removed. It will be pushed back into the hole 102D.

  Here, the surface hardness of the long hole portion 102 of the gear 100 formed by the manufacturing method described above will be described with reference to FIGS. 15 to 17. 15 is a schematic perspective view showing the shape of the long hole portion 102, FIG. 16 is a view showing a carbon concentration distribution corresponding to the view A in FIG. 15, and FIG. It is a figure which shows carbon concentration distribution corresponding to B view.

  Referring to FIG. 16, by adopting the above manufacturing method, in the long hole portion 102, the semicircular region 102 </ b> A at both ends corresponding to the region where the pilot hole 10 has been formed in advance is near the cross-sectional surface. The maximum value of the carbon concentration increases by about 0.4% or more (absolute value of about 0.6% or more) from the carbon concentration of the intermediate member 100A itself, which is the base material, and the surface hardness is high. On the other hand, referring to FIG. 17, in connection region 102B, the maximum value of the carbon concentration in the vicinity of the cross-sectional surface is less than about 0.4% (about the absolute value of the carbon concentration of intermediate member 100A as the base material). (Less than 0.6%) and the hardness is lower than that of the semicircular region 102A.

(Action / Effect)
As described above, the same effects as those of the first embodiment can also be obtained by the gear manufacturing method according to this embodiment. In addition, by adopting a half punching process and a pushing back process, it is possible to manufacture a gear having the same dimensional accuracy as in the case where no long hole is provided.

In each of the above embodiments, the case where the present invention is applied to the elongated hole portion 102 having an arc shape has been described. However, the elongated hole portion may be a straight shape, an S shape, or the like. Not .

  Moreover, although the case where a gear is used as an example of a forged part is described, the gear is not limited, and the present invention can be applied to various forged parts having an equivalent function.

  Accordingly, the above-described embodiment disclosed herein is illustrative in all respects and does not serve as a basis for limited interpretation. Therefore, the technical scope of the present invention is not interpreted only by the above-described embodiments, but is defined based on the description of the claims. Further, all modifications within the meaning and scope equivalent to the scope of the claims are included.

FIG. 3 is a plan view of an intermediate part for forming a forged part (gear) in the first embodiment. FIG. 3 is a plan view of a forged part (gear) in the first embodiment. FIG. 6 is a first process cross-sectional view illustrating the method for manufacturing the forged component (gear) in the first embodiment. FIG. 6 is a second process cross-sectional view illustrating the method for manufacturing the forged component (gear) in the first embodiment. FIG. 10 is a third process cross-sectional view illustrating the method for manufacturing the forged component (gear) in the first embodiment. FIG. 3 is a plan view showing the shape of a long hole portion of the forged component (gear) in the first embodiment. FIG. 7 is a partially enlarged plan view of a region surrounded by IIV in FIG. 6. FIG. 10 is a first process cross-sectional view illustrating the method for manufacturing the forged component (gear) in the second embodiment. FIG. 10 is a second process cross-sectional view illustrating the method for manufacturing the forged component (gear) in the second embodiment. FIG. 10 is a third process cross-sectional view illustrating the method for manufacturing the forged component (gear) in the second embodiment. It is a 4th process sectional view showing a manufacturing method of a forge part (gear) in Embodiment 2. FIG. 10 is a fifth process cross-sectional view illustrating the method for manufacturing the forged component (gear) in the second embodiment. FIG. 10 is a first schematic diagram showing a structure of a die and a punch for realizing the manufacturing method in the second embodiment. FIG. 10 is a second schematic diagram illustrating a punch structure for realizing the manufacturing method according to the second embodiment. FIG. 6 is a schematic perspective view showing the shape of a long hole portion of a forged component (gear) in a second embodiment. It is a figure which shows the carbon concentration distribution corresponding to A view in FIG. It is a figure which shows carbon concentration distribution corresponding to the B view in FIG.

Explanation of symbols

  10 pilot hole, 30 core, 100 gear, 100A intermediate member, 102 long hole, 102A semicircular region, 102B connection region, 102C boundary line, 102D punch hole, 103 bolt hole, 104 shaft hole, 104A shaft hole Core punch, 200 punch, 201 half punch, 202 core punch, 210 punch die, 300 return punch.

Claims (9)

A method for producing a forged part including a step of forming a predetermined long hole portion after performing a heat treatment on an intermediate member stamped by hot forging,
Relative to the intermediate member, the position corresponding to both end portions of the front Symbol predetermined length hole, the prepared hole forming step of forming a small pilot hole than the predetermined long hole portion, a heat treatment step of performing the heat treatment process A method for producing forged parts in preparation for   The forged product manufacturing method according to claim 1, wherein the pilot hole is formed by machining.   The forged product manufacturing method according to claim 1, wherein the pilot hole is formed by punching. Between the pilot hole forming step and the heat treatment step,
A half punching process for forming a core part extruded from the punched hole with a punching amount equal to or less than the thickness of the intermediate member by subjecting the region corresponding to the long hole part to shear processing so as to include the pilot hole;
After the half punching process, the pressing core part is pressed and pushed back into the punching hole, and
In the elongated hole forming step,
For the intermediate member subjected to the heat treatment, the elongated hole portion is formed by removing the punched core portion from the intermediate member.
A method for producing a forged part according to claim 2. After the push-back process and before the heat treatment process,
A machining step for machining the intermediate member into a predetermined shape;
The method for manufacturing a forged part according to claim 4. The forged part manufacturing method according to any one of claims 1 to 5, wherein the long hole portion forming step includes a step of forming the long hole portion by cutting the intermediate member subjected to the heat treatment. The forged part manufacturing method according to any one of claims 1 to 5, wherein the long hole portion forming step includes a step of forming the long hole portion by laser processing on the intermediate member subjected to the heat treatment. . A forged part produced by the method for producing a forged part according to claim 1,
The forged parts, the surface hardness of the peripheral portion of the predetermined length bore comprises a greater portion than the surface hardness of the other portions, forged parts. The forged component according to claim 8, wherein the forged part has a boundary line at a connecting portion between the other portion and a portion having a surface hardness larger than the surface hardness of the other portion .

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