JP2013063444A - Forging die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a forging die capable of preventing a ceramics second inner die from cracking and breaking and usable for a long time.SOLUTION: The forging die 1a includes: a cylindrical outer die 2; and a cylindrical inner die 3 fitted to the inner side of the outer die 2 and having one end side serving as an introduction part 31 of a treated material 35 and an inner peripheral face 32 serving as a molding part 6 for molding the treated material 35. The inner die 3 includes a metallic first inner die 3a and the ceramics second inner die 3b located on one end side relative to the first inner die 3a. An end face on one end side of the first inner die 3a includes a first recess 4 located at a portion separated from an inner peripheral face 32a and a first abutment face 10 brought into contact with the second inner die 3b on the inner peripheral face 32 side from the first recess 4, and opposes to an end face of the second inner die 3b at a portion corresponding to the first recess 4 via an air gap. Thus, this prevents the ceramics second inner die 3b from cracking and breaking, so as to use the forging die 1a for a long time.

Description

  The present invention relates to a forging die.

  Conventionally, as a metal processing method, there is a forging method in which a workpiece introduced into a molding part of a lower mold is pressed using an upper mold. A forging die as a lower die used in such a forging method is, for example, disclosed in Patent Document 1, which is fitted into a cylindrical outer die and a cylindrical outer die, and a workpiece is molded. A cylindrical inner mold, and the inner mold includes a ceramic upper inner mold and a metal lower inner mold arranged on the workpiece introduction side. There has been proposed a structure in which the lower end surface and the upper end surface of the lower inner mold are in close contact with each other without a gap.

JP-A-10-128486

  However, in the forging die proposed in Patent Document 1, the entire lower end surface of the upper inner die is in close contact with the upper end surface of the lower inner die, and when the workpiece is forged, Since there is no escape space for deformation of the mold, there is a problem that a large repulsive force is generated at the interface between the upper inner mold and the lower inner mold, and the lower end surface of the ceramic upper inner mold is cracked or broken.

  The present invention has been devised to solve the above problems, and in a forging die having a metal die and a ceramic die as an inner die, the ceramic die is cracked or damaged. An object of the present invention is to provide a forging die that hardly occurs and can be used over a long period of time.

  The forging die of the present invention is a cylindrical outer die, fitted inside the outer die, one end side is an introduction portion for the workpiece, and an inner peripheral surface is a molding for molding the workpiece. A cylindrical inner mold, and the inner mold has a first inner mold made of metal and a second inner mold made of ceramics positioned on the one end side with respect to the first inner mold. The end surface on the one end side of the first inner mold has a first recess at a portion spaced from the inner peripheral surface, and the second inner mold is closer to the inner peripheral surface than the first recess. And a first contact surface that is in contact with the first recess and is opposed to the end surface of the second inner mold through a gap at a portion corresponding to the first recess.

  According to the forging die of the present invention, at the time of forging, the gap between the first inner die and the second inner die due to the first recess serves as a refuge for deformation of the first inner die, and the first inner die and the second inner die. Since the repulsive force generated at the interface with the mold is easily relieved, the ceramic second inner mold is hardly cracked or damaged, and can be a forged mold that can be used for a long time.

(A) is a schematic longitudinal cross-sectional view which shows an example of the forging die of this embodiment, (b) is a schematic cross-sectional view in the A-A 'line of (a). It is a schematic diagram which shows the forging method using the forging die of this embodiment, (a) is a schematic longitudinal cross-sectional view of the state which introduce | transduced the workpiece into the forging die, (b) presses the introduced workpiece It is a schematic longitudinal cross-sectional view of the state which is pressing and forging with the type | mold. (A) (b) is a schematic cross-sectional view which shows the other example of the dent in the end surface of the one end side of a 1st inner type | mold. (A) is a schematic longitudinal cross-sectional view which shows the other example of the forging die of this embodiment, (b) is a schematic cross-sectional view in the B-B 'line of (a). (A) is a schematic longitudinal cross-sectional view which shows the further another example of the forging die of this embodiment, (b) is a schematic cross-sectional view in the C-C 'line of (a). (A) is a schematic cross-sectional view which shows the further another example of the forging die of this embodiment, (b) is a schematic longitudinal cross-sectional view in the D-D 'line | wire of (a).

  Hereinafter, an example of the forging die of this embodiment will be described.

  In FIG. 1, (a) is a schematic longitudinal cross-sectional view which shows an example of the forging die of this embodiment, (b) is a schematic cross-sectional view in the A-A 'line of (a).

  The forging die 1a is fitted into a cylindrical outer die 2 and an inner side of the outer die 2, one end side is used as a workpiece introduction portion 31, and an inner peripheral surface 32 is used for molding the workpiece. A cylindrical inner mold 3 is provided as a molding part 6. The one end side of the inner mold 3 is the upper end side of the inner mold 3 in FIGS. 1 (a), 2, 4 (a), 5 (a), and 6 (a). The inner peripheral surface 32 of the inner mold 3 is composed of an inner peripheral surface 32b of the second inner mold 3b and an inner peripheral surface 32a of the first inner mold 3a. In other words, the inner mold 3 is formed with a cylindrical cavity penetrating in the vertical direction, and the cavity located in the introduction part 31 is more than the cavity on the lower end surface side of the first inner mold 3a and the second inner mold 3b. Widened.

  Furthermore, the inner mold 3 has a metal first inner mold 3a and a ceramic second inner mold 3b positioned on one end side with respect to the first inner mold 3a, and one end side of the first inner mold 3a. The end face (upper end face) has a first dent 4 at a portion spaced from the inner peripheral face 32a. As shown in FIG. 1B, the first recess 4 is formed concentrically with the circular cavity forming the inner peripheral surface 32a on the upper end surface of the first inner mold 3a. Further, the end surface on the one end side of the first inner mold 3 a has a first contact surface 10 in contact with the second inner mold 3 b on the inner peripheral surface 32 a side with respect to the first recess 4, and corresponds to the first recess 4. The part is opposed to the lower end surface of the second inner mold 3b through a gap.

  As shown in FIG. 1B, in the forging die 1a, the first recess 4 is provided in an annular shape. In other words, in the first inner die 3a, the portion having the contact surface 10 is annularly formed. It protrudes toward the lower end surface of the 1 inner mold 3b. Hereinafter, this portion is referred to as a first convex portion 5.

2A and 2B are schematic views showing a forging method using the forging die 1a. FIG. 2A is a schematic longitudinal sectional view showing a state in which the workpiece 35 is introduced into the forging die 1a, and FIG. It is a schematic longitudinal cross-sectional view which shows the state which presses the material 35 with the press die 9, and is forging.

  In the forging method using the forging die 1a of this embodiment, as shown in FIG. 2 (a), first, a work material 35 made of metal, for example, is introduced into the introduction portion 31 of the forging die 1a. As shown in (b), the workpiece 35 is molded into a desired shape by hitting the workpiece 35 with the pressing die 9 and applying pressure using the pressing die 9. The workpiece 35 made of metal introduced into the introduction part 31 may be heated by appropriately setting the temperature in accordance with the type of metal, the dimensional accuracy of the finish, and the like, and the viscosity may be adjusted.

In the forging die 1a of the present embodiment, during forging, the gap between the first inner die 3a and the second inner die 3b due to the first recess 4 serves as a refuge for deformation of the first inner die 3a, and the first inner die 3a Since the repulsive force generated at the interface between 3a and the second inner mold 3b is easily relieved, the ceramic second inner mold 3b is not easily cracked or damaged, and can be used for a long time. In addition, since the first convex portion 5 of the first inner mold 3a is deformed, stress applied to the second inner mold 3b during forging can be more efficiently dispersed, so that the second inner mold 3b made of ceramics The cracks and breakage that occur can be further suppressed, and the forging die 1a can be used over a longer period.

  Moreover, in FIG. 1, although the cylindrical shape where the outer diameter of the 1st metal mold | die 3a and the 2nd metal mold | die 3b is the same was demonstrated, the 1st metal mold | die 3a and the 2nd metal | mold 2 to the extent which does not deviate from the range of this invention. The size of the mold 3b may be appropriately changed according to the application, and may be a rectangular tube shape instead of a cylindrical shape. Furthermore, the first mold 3a and the second mold 3b may be formed with a square columnar cavity instead of a columnar cavity.

  The first convex portion 5 deformed by use can be reused by polishing, or can be removed by grinding or the like, for example, to newly provide the first concave portion 4 or newly to the first convex portion. 5 can be easily reused by producing a metal member having the same shape as 5 and joining it to the first inner mold 3a by welding or the like.

Here, the first recess 4 has a depth d from the upper end surface of the first convex portion 5, in other words, a depth d from the lower end surface of the second inner mold 3b, which is the height of the second inner mold 3b. It is preferable to form such that H is 0.5% to 5% and the width w is 50% to 90% of the maximum wall width W of the second inner mold 3b. The width w is represented by the distance between the outer peripheral surface of the first convex portion 5 and the outer peripheral surface of the first inner mold 3a. The maximum wall width W is represented by the longest distance among the distances from the inner peripheral surface 32b of the second inner mold 3b to the outer peripheral surface of the second inner mold 3b.

  If the size of the first dent 4 is within the above range, the repulsive force generated at the interface between the first inner mold 3a and the second inner mold 3b can be more efficiently relaxed during forging. The second inner mold 3b is less prone to cracking and breakage and can be used for a longer period of time.

  FIGS. 3A and 3B are schematic cross-sectional views showing another example of the first dent 4 on the end face on the one end side of the first inner mold 3a.

  FIG. 3A shows a plurality of first dents 4 on the end surface of the first inner mold 3a on one end side so as to surround the first convex portion in a portion spaced from the inner peripheral surface 32. In FIG. Four are formed. In addition, in the end surface on the one end side of the first inner mold 3a, a first convex portion 5 ′ protruding toward the lower end surface of the second inner mold 3b is formed between the adjacent first dents 4, and this The height of the first convex portion 5 ′ is the same as the height of the first convex portion 5.

  Further, in FIG. 3B, as in FIG. 3A, four first dents 4 are formed on the end face on the one end side of the first inner mold 3a at a position separated from the inner peripheral surface 32a. The width of the first convex portion 5 ′ between the adjacent first dents 4 increases toward the outer peripheral surface. The first dent 4 may be three or less and five or more.

  As shown in FIGS. 3 (a) and 3 (b), when a plurality of first dents 4 are formed on the end face on one end side of the first inner mold 3a at a position separated from the inner peripheral surface 32, the first inner mold 3a. The first convex portion 5 'of 3a and the second inner mold 3b come into contact with each other, and by increasing the contact area between the first inner mold 3a and the second inner mold 3b, the unit area of the contact surface is increased. Since this stress can be reduced, the stress applied to the second inner mold 3b can be efficiently dispersed by the first inner mold 3a during forging, and the second inner mold 3b made of ceramic is cracked. It is difficult to cause damage and can be used for a longer period of time, and the deformation amount of the first convex portion 5 can be reduced.

In addition, a plurality of first dents 4 are formed in a portion spaced from the inner peripheral surface 32a on the end face on the one end side of the first inner mold 3a, and the first convex part 5 ′ between the adjacent first dents 4 is formed. Since the width of the first convex portion 5 ′ becomes wider as it approaches the outer mold 2, the second inner mold 3b can be supported more stably. In the forging, the stress applied to the second inner mold 3b can be more efficiently dispersed in the first inner mold 3a, and the ceramic second inner mold 3b is not easily cracked or damaged, and can be used for a longer period of time. .

  4A is a schematic longitudinal sectional view showing another example of the forging die according to the present embodiment, and FIG. 4B is a schematic transverse sectional view taken along line B-B ′ of FIG.

  The forging die 1b shown in FIG. 4 has an end surface 14 on the other end side of the first inner die 3a as the first contact surface 10 of the first inner die 3a moves from the inner peripheral surface 32 of the inner die 3 toward the outer peripheral surface. It is inclined toward.

  When the forging die 1b has such a structure, since the contact area between the first inner die 3a and the second inner die 3b can be increased, the stress applied to the second inner die 3b during forging is The first convex portion 5 can be efficiently dispersed. As a result, cracks and breakage occurring in the ceramic second inner mold 3b can be further suppressed, and the forging mold 1b can be used for a longer period of time.

  If the angle formed between the inclined surface 10 of the first inner mold 3a and the plane perpendicular to the axis L of the first inner mold 3a is θ, θ is 15 ° to 60 °. The stress applied to the mold 3b can be efficiently dispersed.

  The first abutment surface 10 of the first inner mold 3a has a larger contact area between the first inner mold 3a and the second inner mold 3b than the inner peripheral surface 32b of the first inner mold 3b. Although it may be inclined toward the end surface on the one end side of the second inner die 3b as it goes toward the outer peripheral surface side, stress is generated in the outer peripheral direction of the first inner die 3a and the second inner die 3b during forging. Since it is easy, the direction of the forging die 1b described above can more efficiently disperse the stress applied to the second inner die 3b during forging.

  5A is a schematic longitudinal sectional view showing still another example of the forging die according to the present embodiment, and FIG. 5B is a schematic transverse sectional view taken along line C-C ′ of FIG.

  In the forging die 1c shown in FIG. 5, the outer die 2 has a protruding portion 7 that protrudes toward the second inner die 3b side on one end side from the first contact surface 10 of the first inner die 3a. The second inner mold 3 b is fixed by the portion 7 and the first contact surface 10. Further, the protruding portion 7 is formed in an annular shape at an end portion on one end side (upper end side) of the outer mold 2. In addition, as shown in FIG.5 (b), although the contact surface with the 2nd inner mold | type 3b of the protrusion part 7 is a plane, it may be a curved surface.

  When the forging die 1c has such a structure, the second inner die 3b is firmly fixed to the outer die 2 by the protruding portion 7 of the outer die 2 and the contact surface 10 of the first inner die 3a. Therefore, even if a stress repeatedly occurs in the second inner mold 3b, the contact surface of the second inner mold 3b with the outer mold 2 is not easily worn. Thereby, the crack and breakage which arise in the ceramic 2nd inner type | mold 3b can further be suppressed, and the forging die 1c can be used over a longer period.

  Moreover, the protrusion part 7 has the inclined surface 17 which inclines toward the end surface of the one end side (upper end side) of the outer mold | type 2 as it goes inside from the internal peripheral surface of the outer mold | type 2, in other words, inclined surface 17 is preferably formed so as to face the abutting surface 10, and when the protruding portion 7 has the inclined surface 17, the inclined surface 17 of the protruding portion 7 of the outer mold 2 and the first inner mold 3 a Since the second inner mold 3b is more firmly fixed to the outer mold 2 with the contact surface 10, even if a repeated stress is generated in the second inner mold 3b, the second inner mold 3b is in contact with the outer mold 2. The contact surface is less likely to be worn. In addition, a part of the workpiece is less likely to enter the gap between the first inner mold 3a and the second inner mold 3b, and burrs are less likely to occur in the processed product.

  If the angle between the inclined surface 17 of the outer mold 2 and the surface perpendicular to the axis L of the first inner mold 3a is θ ′, the inclination of the outer mold 2 is particularly suitable if θ ′ is 15 ° to 60 °. The second inner mold 3b is more firmly fixed by the surface 17 and the inclined surface 10 of the first inner mold, and the contact surface of the second inner mold 3b with the outer mold 2 is not easily worn. The angles θ and θ ′ may have different values as long as they are within the above range.

  6A is a schematic longitudinal sectional view showing still another example of the forging die of the present embodiment, and FIG. 6B is a schematic transverse sectional view taken along line D-D ′ of FIG.

  In the forging die 1d shown in FIG. 6, with respect to the forging die 1a shown in FIG. 1, the end surface on one end side of the first inner die 3a is spaced from the first recess 4 to the outer peripheral surface side of the first inner die 3a. Further, a concentric second dent 4 'is provided at the portion. Moreover, it has 2nd contact surface 10 'which contact | connects the 2nd inner mold | type 3b between 1st dent 4 and 2nd dent 4', and the site | part corresponding to 2nd dent 4 'is through a space | gap. It faces the end surface of the second inner mold 3b. In other words, an annular first convex portion 5 is formed continuously on the inner peripheral surface 32, and an annular first recess 4 is formed on the outer peripheral side of the first convex portion 5. An annular second convex portion 8 is formed so as to surround, and an annular second recess 4 ′ is formed so as to surround the second convex portion 8.

  With such a structure, the area of the contact surfaces (first contact surface 10 and second contact surface 10 ′) between the first inner mold 3a and the second inner mold 3b can be increased. Since the stress applied per unit area of the contact surface can be reduced, the stress applied to the second inner mold 3b can be efficiently dispersed by the first inner mold 3a, and the second inner mold 3b made of ceramics. In addition, cracks and breakage are less likely to occur, and it can be used for a longer period of time, and the amount of deformation of the first convex portion 5 can be reduced.

  The second recess 4 ′ may be connected to the first recess 4 so as to separate the second convex portion 8 into a plurality of parts. In this case, when the plurality of second convex portions 8 are arranged at symmetrical positions with respect to the first convex portion 5, the stress applied to the second inner mold 3b during the forging can be made more uniform. Since it becomes easy to disperse | distribute, the crack and breakage which arise in the ceramic 2nd inner mold | type 3b can further be suppressed, and the forging die 1d can be used over a long period of time.

Here, the first recess 4 and the second recess 4 ′ have a depth d of 0.5% or more and 5% or less of the height H of the second inner mold 3b, respectively, and the widths of the first recess 4 and the second recess 4 ′. The sum of w and w 'is the second inner mold 3
It is preferably formed so as to be 50% or more and 90% or less of the maximum wall width W of b. The width w ′ is represented by the distance between the outer peripheral surface of the second convex portion 8 and the outer peripheral surface of the first inner mold 3a.

  In the forging dies 1a to 1d of the present embodiment, the first inner mold 3a and the second inner mold 3b are such that the surface area of the inner peripheral surface 32b of the second inner mold 3b is the same as that of the inner peripheral surface 32a of the first inner mold 3a. It is preferable to form it so as to be larger than the surface area. In other words, the thickness in the vertical direction of the second inner mold 3b is preferably larger than the thickness of the first inner mold 3a.

  With such a structure, the contact area between the workpiece and the second inner mold 3b made of ceramics, which is more excellent in wear resistance than metal, can be increased, and deterioration due to wear of the forging mold can be reduced. Can be used for a long time.

Moreover, as ceramics used for the second inner mold 3b of the forging dies 1a to 1d, oxide ceramics such as alumina (Al ₂ O ₃ ) and zirconia (ZrO ₂ ), silicon nitride (Si ₃ N ₄ ), carbonized Non-oxide ceramics such as silicon (SiC) can be used. In particular, silicon nitride (Si ₃ N ₄ ) having high hardness and excellent wear resistance is preferably used.

Further, as the metal used for the outer mold 2 and the first inner mold 3a, die steel (SKD, SK)
T) is preferably used, and in particular, when a metal having an oxide film formed by heat treatment or the like is used as the first inner mold 3a, it is possible to suppress the occurrence of rust on the surface of the first inner mold 3a. preferable.

  Next, an example of a method for manufacturing the forging dies 1a to 1d of the present embodiment will be described.

  First, the metal outer mold 2 and the first inner mold 3a are manufactured. From the die steel ingot, a metal lump that is the base of the outer die 2 and the first inner die 3a is cut out and processed using a metal processing machine such as a universal grinder to obtain a predetermined inner diameter, outer diameter, and height. The outer mold 2 having the first and the first inner mold 3a are manufactured. In particular, the inner peripheral surface of the outer mold 2 and the outer peripheral surface of the first inner mold 3a have, for example, 0.1 to 0.5% interference allowance at room temperature so that the first inner mold 3a can be inserted into the outer mold 2. Provide and finish processing such as buffing.

  In addition, what is necessary is just to form the inclination of the 1st dent 4, the 2nd dent 4 ', the 1st convex-shaped part 5, the inclination of the outer mold | type 2, etc. using metal processing machines, such as a universal grinder.

  Next, a manufacturing method in the case where the second inner mold 3b is formed using a silicon nitride sintered body as a ceramic will be described.

A commercially available silicon nitride primary material having an average particle size of 0.5 to 10 μm, a predetermined amount of sintering aid, a binder,
After mixing with a solvent to form a slurry, a secondary raw material is obtained by spray granulation using a spray dryer (spray dryer). And a cylindrical molded object is shape | molded by the isostatic press molding method (rubber press) using this secondary raw material. After that, the molded body is cut so as to have a predetermined shape, fired in a reducing atmosphere furnace at a temperature of 1800 to 2100 ° C., ground as necessary, and the contact surface with the outer mold 2 is formed. By polishing, a second inner mold 3b made of a silicon nitride-based sintered body whose inner peripheral surface is the molded portion 6 can be obtained.

Further, it is preferable to process the outer peripheral surface of the second inner mold 3b and the inner peripheral surface of the outer mold 2 so as to provide, for example, 0.5 to 1% interference. If the interference margin is within this range, when the metal outer mold 2 is thermally expanded by heating during forging, the second inner mold 3b is unlikely to loosen and a large stress is applied to the second inner mold 3b during press-fitting. Even if it is applied, a crack or breakage hardly occurs in a part of the second inner mold 3b.

  Then, the forged dies 1a to 1d can be obtained by fitting the first inner die 3a and the second inner die 3b to the produced outer die 2.

  Examples of the present invention will be described below.

  A forging die 1a shown in FIG. 1 was produced. First, from the die steel ingot, metal ingots to be the outer mold 2 and the second inner mold 3b were cut out.

Next, the cut metal lump was processed using a universal grinder to produce a cylindrical outer mold 2 having an outer diameter of 200 mm, an inner diameter of 150 mm, and a height of 200 mm. Similarly, a cylindrical first inner mold 3a is produced by using the cut metal lump so that the outer diameter is 150 mm, the height is 100 mm, and the diameter of the molded part 6 is 30 mm. An end face on one side of the mold 3a is ground to form an annular first recess 4 having a depth d of 1 mm so as to form an annular first convex portion 5 having an outer diameter of φ50 mm, an inner diameter of φ30 mm, and a height of 1 mm. did. In addition, the interference margin of the outer diameter of the first inner mold 3a was set to 0.3%.

Next, in order to manufacture the second inner mold 3b, a silicon nitride primary raw material powder having a purity of 87% is prepared, and 13.5% by mass of a sintering aid is added to 100% by mass of the silicon nitride primary raw material powder. 1% by weight of binder
Then, 0.3% by mass of a dispersant and 100% by mass of a solvent were added to form a slurry, which was then granulated with a spray granulator (spray dryer) to produce a secondary raw material powder. And the cylindrical molded object was shape | molded by the isostatic press molding method using this secondary raw material powder. After that, this molded body was cut and fired at a maximum temperature of 1900 ° in a reducing atmosphere furnace, and the obtained sintered body was ground and the height H was 100 mm and the outer diameter was φ150 mm. When the end surface on the introduction side is the upper surface, the inner diameter of the molding portion 6 on the upper surface side is φ80 mm, the inner diameter of the molding portion 6 on the lower surface side is φ30 mm, and between the molding portion 6 on the upper surface side and the molding portion 6 on the lower surface side. A second inner mold 3b having an inclination with an inclination angle of 60 ° was produced. The outer diameter of the second inner mold 3b is 0.5%.

  Thereafter, the forged die 1a was obtained by fitting the first inner die 3a and the second inner die 3b to the produced outer die 2, respectively.

  Further, as a comparative example, a conventional forging die was obtained by the same manufacturing method as described above except that the first recess 4 was not provided in the first inner die 3a.

  Next, two types of forging dies, a forging die 1a and a forging die of a comparative example in which the first indentation 4 is not provided in the metal first inner die 3a, are respectively attached to the same forging device, and the workpiece is attached. A test was conducted to form a shaft by applying pressure. The test was carried out continuously for 30 days (20 hours a day), and it was confirmed that the inner mold of each forging mold was not loose, cracked or broken.

  As a result, the forging die of the comparative example in which the first dent 4 was not provided was damaged by continuous molding for 10 days, and the test had to be interrupted halfway. When tracing the crack of the damaged forging die, it was found that the crack generated in a part of the contact portion between the second inner die 3b and the first inner die 3a was the source of the fracture.

  On the other hand, the forging die 1a provided with the first dent 4 was not cracked or damaged even during 30 days of continuous molding, and a forged product could be obtained stably. Moreover, when the forged die 1a after the test is cleaved from the center by grinding, and the state of the contact portion between the first inner die 3a and the second inner die 3b is confirmed, the first convex portion 5 of the first inner die 3a Although the edge was slightly deformed, no cracks were observed, indicating that it could be used for a longer period of time.

  Next, the forging die 1b shown in FIG. 4 was manufactured. First, the outer mold 2 was manufactured by the same manufacturing method as in Example 1.

  For the first inner mold 3a, the upper surface of the first convex portion 5 that becomes the first contact surface 10 with the second inner mold 32b when the end surface on the introduction side of the workpiece is the upper surface is universally ground. Example 1 except that the inclined surface is inclined at an angle (θ) of 30 ° toward the end surface 14 on the other end side of the first inner mold 3a as it goes from the inner peripheral surface 32a toward the outer peripheral surface side by machining with a board. The same method was used.

  Further, the second inner mold 3b has an end surface on the other end side of the first inner mold 3a as the surface corresponding to the first contact surface 10 of the first convex portion 5 moves from the inner peripheral surface 32a toward the outer peripheral surface. It was manufactured by the same method as in Example 1 except that the inclined surface was inclined at an angle of 30 ° toward 14.

  Then, the forged die 1b was obtained by fitting the first inner die 3a and the second inner die 3b to the produced outer die 2, respectively.

Next, the forging die 1b was attached to the same forging device as in Example 1, and the test was performed to pressurize the workpiece and mold the automobile part that becomes a part of the axle. When the test was conducted for 30 days in the same manner as in Example 1, a forged product could be stably obtained without causing breakage. Moreover, when the forged die 1a after the test was cleaved from the center by grinding and the state of the contact portion between the second inner die 3b and the first inner die 3a was confirmed, the first convex portion 5 was The deformation was smaller than that of the forging die 1a. Therefore, the stress applied to the second inner mold 3b can be efficiently dispersed by the first inner mold 3a, the second inner mold 3b is not easily cracked or damaged, and the amount of deformation of the first convex portion 5 is reduced. It was found that it can be made smaller and can be used for a longer period of time.

  Next, the forging die 1c shown in FIG. 5 was manufactured. First, the outer mold 2 is manufactured by the same manufacturing method as in Example 1 except that the annular protrusion 7 having the inclined surface 17 is formed by a universal grinder at the end portion on the one end side of the outer mold 2. did. In the outer mold 2, the inner diameter of the portion provided with the protrusion 7 was φ144 mm, and the inclination angle (θ ′) of the inclined surface 17 was 60 °.

  The first inner mold 3a is cut by cutting so that the surface of the first convex portion 5 that becomes the first contact surface 10 with the second inner mold 3b is inclined parallel to the inclined surface 17 of the outer mold 2. It was produced by the same production method as in Example 2 except that it was machined.

  In addition, the second inner mold 3b is formed at the portion corresponding to the inclined surface 17 of the outer mold 2 with an inclined surface that is inclined parallel to the inclined surface 17 by cutting, and the first abutment of the first convex portion 5 A surface corresponding to the surface 10 was produced by the same manufacturing method as in Example 1 except that the surface corresponding to the inclined surface 17 of the outer mold 2 was inclined.

  Then, the forged die 1c was obtained by fitting the first inner die 3a and the second inner die 3b to the produced outer die 2, respectively.

  Next, the forging die 1c was attached to the same forging device as in Example 1, the workpiece was pressurized, and a test for molding an automobile part that became a part of the axle was performed. The test was carried out continuously for 60 days (20 hours a day), and the inner mold of each forging die was checked for cracks and breaks on the day, and the day on which cracks and breaks occurred was recorded.

  For comparison, the same test was performed on the forging dies 1a and 1b.

  As a result, the forging die 1a was 43 days, the forging die 1b was 53 days, and the first inner die 3a was not cracked or damaged. The forging die 1c did not crack or break for 60 days. Further, in the second inner mold 3b of the forged molds 1a, 1b, and 1c after the test, when the contact surface of the outer mold 2 with the second inner mold 3b was confirmed, the second inner mold 3b of the forged mold 1c was It was found that the wear was small compared to the second inner mold 3b of the forging dies 1a, 1b. The degree of wear was confirmed by comparing the length of the outer periphery of the second inner mold 3b before the test with the length of the outer periphery of the second inner mold 3b after the test.

  Therefore, since the second inner mold 3b is firmly fixed by the inclined surface 17 and the first contact surface 10 of the first inner mold 3a, the contact surface of the outer mold 2 with the second inner mold 3b. It was found that the forging die 1c can be used for a longer period of time because cracks and breakage occurring in the ceramic second inner die 3b can be further suppressed.

  Next, a forging die 1d shown in FIG. 6 was manufactured. First, a first convex portion 5 similar to that of the first embodiment and an annular second convex portion 8 having a height of 1 mm and a width of 5 mm are formed at a position 25 mm away from the first convex portion 5. Thus, the 1st inner mold 3a was manufactured with the manufacturing method similar to Example 1 except providing the 1st dent 4 and the 2nd dent 4 '.

  Further, the outer mold 2 and the second inner mold 3b were manufactured by the same manufacturing method as in Example 1.

  Then, the first inner mold 3a and the second inner mold 3b were fitted to the outer mold 2 to obtain a forging mold 1d.

  Next, the forging die 1d was attached to the same forging device as in Example 1, and the test was performed to pressurize the workpiece and mold an automobile part that becomes a part of the axle. The test was conducted for 45 days.

  As a result, the forging die 1d was not damaged, and a forged product could be obtained stably. Moreover, when the forged die 1a after the test was cleaved from the center by grinding, and the state of the contact surface between the first inner die 3a and the second inner die 3b was confirmed, the first convex portion 5 of the forged die 1d was It was found that the deformation was small compared to the first convex part 5 of the forging die 1a of Example 1, and it could be used for a longer period.

1a, 1b, 1c, 1d: Forging die 2: Outer die 3a: First inner die 3b: Second inner die 4: First depression 4 ′: Second depression 5: First convex portion 6: Molding portion 7: Protruding part 8: Second convex part 9: Pressing type
10: First contact surface
10 ': Second contact surface
17: Inclined outer surface
31: Introduction
32: Inner peripheral surface
32a: Inner peripheral surface of the first inner mold
32b: Inner peripheral surface of the second inner mold
35: Work material

Claims (4)

  A cylindrical outer mold, a cylindrical shape that is fitted inside the outer mold, one end side is an introduction part of the workpiece, and an inner peripheral surface is a molding part for molding the workpiece An inner mold, the inner mold having a first inner mold made of metal and a second inner mold made of ceramics positioned on the one end side with respect to the first inner mold, and the first inner mold The end surface of the one end side has a first recess at a part spaced from the inner peripheral surface, and the first contact surface is in contact with the second inner mold on the inner peripheral surface side of the first recess. And a forging die that is opposed to the end surface of the second inner die through a gap at a portion corresponding to the first recess.   The first contact surface of the first inner mold is inclined toward the end surface on the other end side of the first inner mold as it goes from the inner peripheral surface of the first inner mold to the outer peripheral surface side. The forging die according to claim 1, wherein   The outer mold has a projecting portion projecting toward the second inner mold side on the one end side from the first abutting surface of the first inner mold, and the projecting portion and the first abutting surface. The forging die according to claim 2, wherein the second inner die is fixed. The end surface on the one end side of the first inner mold has a second recess at a portion spaced from the first recess toward the outer peripheral surface side of the first inner mold, and the first recess and the second recess. And a second abutting surface in contact with the second inner mold, and is opposed to the end surface of the second inner mold through a gap at a portion corresponding to the second recess. The forging die according to any one of claims 1 to 3.

Images