JP6165694B2 - Hot forging machine - Google Patents

Description

  The present invention relates to a hot forging device that forges a large hollow forged product using a mold, and more particularly to a technique for releasing a hollow forged product from a mold.

In general, titanium alloys such as nickel alloys, aluminum alloys, and Ti-6Al-4V have excellent mechanical properties and heat resistance, so they are used in engine parts for transportation equipment such as aircraft and vehicles, and structural members such as chassis. It has been.
A mold was used as a method for forging a large hollow forged product (hollow shaft forged product) used for the structural member described above using a workpiece (such as a titanium alloy) having such excellent mechanical properties. A hot forging method (for example, a drilling hot forging method) is used. The hot forging method for drilling is a method in which a heated solid work material is placed in a lower mold that has been formed in advance to simulate a product shape, and the work material is kept in a high temperature state while being convex. In this method, a punch (an upper die having a protrusion at the center of the pressure surface) is pushed in, and a dent (hole) is formed while being deformed so as to be stretched into a shape along the convex punch.

If the hot forging method described above is used, a metal flow that conforms to the product shape can be obtained during deformation during hot forging. Therefore, it is more tenacious than other processing methods and has excellent mechanical properties such as impact fracture resistance. A forged product (molded product) can be obtained.
However, when the upper mold is pushed into the lower mold in order to produce a molded product, the molded product may come into close contact with the protrusions of the upper mold. Under this circumstance, when the upper mold is pulled upward, that is, when the molded product is released from the upper mold, there arises a problem that the molded product rises together with the upper mold. If such a problem occurs, it becomes difficult to release the molded product from the upper mold.

For example, Patent Documents 1 and 2 disclose techniques for solving this problem.
In Patent Document 1, in a mold apparatus that performs forging by a pair of molds that can move relative to each other in a closing direction, at least one of the molds has a knockout ring that has an extruded surface that is continuous in the circumferential direction of the annular end surface of the forged product. A forging die apparatus provided with a knockout pin for driving the knockout ring in a direction protruding from the inner surface of the die behind the knockout ring, and provided with a biasing means for returning the knockout ring to a predetermined position. Is disclosed.

  Patent Document 2 discloses a die forging method in which a forging material is plastically flowed by being pressed in a forging die to be molded into a predetermined shape, and a back pressure is applied by applying a die spin to one end surface of the forging material. A forging step in which a forging step is performed in which a punch is driven into the forging material or a mold is pressed against the forging material while the die spins are provided on the same axis, and the plurality of die spins are formed during the forging step. A die forging method in which the relative position changes is disclosed.

JP-A-8-243678 JP 2001-137996 A

In recent years, large hollow forgings used in large transport equipment such as aircraft have been required to have high mechanical properties, and forging with complicated deformation that imparts high strain to improve the mechanical properties. It is often manufactured through the process.
A hollow forged product manufactured by such a complicated forging process often comes into close contact with the mold and is often very difficult to release.

Specifically, in a hot forging method for drilling in which a hole or a dent is formed by pushing an upper die having a protrusion, a dent (hole) in a hollow forged product formed after forging is formed by the upper metal It strongly adheres to the protrusions of the mold, making it difficult to release the hollow forged product and the protrusions.
For example, the reason why the work material strongly adheres to the protrusion of the upper mold during hot forging is, for example, “The heated work material is thermally contracted due to a temperature drop, and the protrusion of the upper mold is `` I will hold you like tightening '', `` The tip of the protrusion of the upper mold will rise in temperature and thermally expand, and the protrusion will hold the work piece '' or `` Lubricant It causes cutting and the work piece and the protrusion of the upper mold adhere to each other or sticks by friction ”or“ adhesive strength when sticky lubricants such as glass are used. ”

Therefore, it is conceivable to employ the mold release technique disclosed in Patent Documents 1 and 2.
However, the forging die apparatus disclosed in Patent Document 1 has a complicated knockout structure composed of a plurality of members, as can be seen from FIG. It seems to be difficult to employ it in a forging device for manufacturing the steel. In addition, when hot forging a large hollow forged product used in an aircraft or the like using the technique of Patent Document 1, a very large knockout force is required when releasing the hollow forged product from the upper die. Become. Therefore, since it is necessary to manufacture an upper mold that can withstand a very large knockout force, it is considered that the manufacturing cost is high.

  Further, in Patent Document 2, the punch at the center of the upper mold is movable up and down, the molded product is held at the outer edge of the upper mold, and the molded product is removed from the upper mold by pulling the center punch upward. A technique capable of releasing a mold is disclosed. However, when hot forging large hollow forgings used in aircraft, etc. using this technology, the center punch is pulled while pressing the tightly forged hollow forging against the lower mold side with the outer edge of the upper mold. When removing, an extremely large force is required for the upper die and the punch. Therefore, since it is necessary to manufacture an upper mold that can withstand a very large force, it is conceivable that the structure is complicated and the manufacturing cost is high.

That is, the techniques of Patent Documents 1 and 2 are considered to be unsuitable techniques when hot forging large hollow forged products having high mechanical properties.
Therefore, in view of the above-mentioned problems, the present invention uses a press ascending force to make a protrusion even when a hollow forged product is in close contact with the protrusion of the upper die and it becomes difficult to release after hot forging. An object of the present invention is to provide a hot forging device that can reliably and easily be released without damaging a hollow forged product.

In order to solve the above-described problems, the present invention takes the following technical means.
The hot forging device according to the present invention includes a bottomed cylindrical recess that is open at the top, and a lower mold in which a workpiece to be heated is inserted into the recess, and a lower surface from the pressed surface. In a hot forging apparatus having an upper mold that is formed with a projecting projection portion and is pressed from above the workpiece inserted into the lower mold, the upper surface of the lower mold is A locking groove having an open top is formed, and the locking groove is for inserting a long locking body so as to cut out the upper side of the peripheral edge of the recess. And at least one of the locking grooves, the side wall forming the locking groove and having a side wall close to the recess being inclined toward the inside of the locking groove. The end is penetrated with respect to the outer peripheral surface of the said lower metal mold | die.

Preferably, the inclined surface of the locking groove has an inclination angle of 3 ° to 30 °.
Preferably, the side surface of the locking body facing the inclined surface of the locking groove may have the same inclination angle as the inclined surface of the locking groove.
Preferably, the locking groove is provided at a position facing each other so as to sandwich the concave portion.

Preferably, the locking body and a long fitting body formed separately from the locking body are inserted into the locking groove together.
Preferably, the side wall that forms the locking groove, the side wall close to the recess, is located inside the peripheral edge of the recess when the lower mold is viewed from the side.
Preferably, a lower part of the lower mold is provided with a knockout mechanism.

  According to the hot forging device according to the present invention, after hot forging, even if the hollow forged product is in close contact with the protrusion of the upper mold and it becomes difficult to release, the protrusion using the press ascending force. Therefore, the mold can be reliably and easily released without damaging the hollow forged product.

It is a figure which shows the hot forging apparatus of this invention. It is the side view and sectional drawing of the hot forging apparatus of this invention. It is AA sectional drawing of FIG. It is an expanded sectional view of the locking groove formed in the lower mold. It is a figure which shows the procedure which manufactures a hollow forging product using the hot forging apparatus of this invention (processed material charging process). It is a figure which shows the procedure which manufactures a hollow forging product using the hot forging apparatus of this invention (upper die reduction process). It is a figure which shows the procedure which manufactures a hollow forging product using the hot forging apparatus of this invention (locking body insertion process). It is a figure which shows the procedure which manufactures a hollow forging product using the hot forging apparatus of this invention (fitting body insertion process). It is a figure which shows the procedure which manufactures a hollow forging product using the hot forging apparatus of this invention (upper mold release process). It is a figure which shows the procedure which manufactures a hollow forging product using the hot forging apparatus of this invention (lower metal mold release process). It is a top view which shows the modification of the locking groove formed in the lower metal mold | die.

[First Embodiment]
Hereinafter, the hot forging device of the first embodiment will be described in detail with reference to the drawings.
The hollow forged product 41 (sometimes simply referred to as a forged product) forged by the hot forging device 1 of the first embodiment is an engine member of a transport device such as an aircraft or a vehicle, or a structural member such as a chassis. It is manufactured in the hollow forging process of the previous process which manufactures the large sized hollow shaft forged product used for.

Further, in the hollow forging in the first embodiment, the material is deformed to the front side (lower side) along the reduction direction with respect to the reduction direction of the upper mold 2 having the convex protrusions 3, and the recess 42 ( It is also called forging hot forging because it is forging in which a hole portion is formed.
As shown in FIGS. 1 to 3, the hot forging device 1 of the first embodiment inserts a heated workpiece 40 into a mold, and the workpiece 40 along the shape of the mold. By deforming in a hot state, a forged product having a desired shape is formed. Specifically, this hot forging device 1 has a mold for forming a forged product, and this mold can be divided into two parts, upper and lower, and the workpiece 40 is The lower mold 6 is inserted and placed, and the upper mold 2 is used to squeeze the workpiece 40 placed on the lower mold 6 from above.

  The upper mold 2 is disposed above the lower mold 6, and is approached and separated from above the workpiece 40 placed in the lower mold 6, and the upper mold 2 is lowered. By doing so, it is possible to reduce the work material 40 so as to be crushed from above. A projection 3 (punch) for reducing the workpiece 40 is formed at the center of the upper mold 2. The punch 3 in this embodiment is elongate vertically, for example, and its axial length is higher than the height of the workpiece 40.

Although the punch 3 in the present embodiment is elongated in the vertical direction, it may have a large diameter or may be lower than the height of the workpiece 40. That is, the length of the punch 3 varies depending on the shape of the hollow forged product 41 to be hot forged.
The punch 3 has a convex shape facing downward, an indented portion 4 that is depressed from the center of the upper surface of the workpiece 40, and an extruded portion 5 that is connected to the upper portion of the indented portion 4 and has a taper or straight shape. Have

As shown in FIG. 2, the indented portion 4 of the punch 3 in the present embodiment has, for example, a flat surface at the center of the vertical axis, and a peripheral edge of the flat surface is R (fillet). The extrusion part 5 is made into the shape expanded so that it might spread as it goes to the upper part.
Note that the shape of the punch 3 in this embodiment (the shape of the pen tip in a side view) is an example, and any shape may be used as long as the shape projects downward. The shape of the punch 3 is, for example, a rectangular shape in a side view in which the tip of the indenter 4 is a flat surface facing in the horizontal direction, a tapered shape with a sharp center at the tip of the indenter 4, or the indenter 4 The tip may be a hemispherical shape expanded from the diameter of the extruded portion 5.

The lower mold 6 includes a bottomed cylindrical concave portion 7 whose upper side is open, and a heated workpiece 40 is inserted into the concave portion 7 and placed thereon.
Specifically, as shown in FIGS. 2 and 3, the inner diameter of the lower mold 6 is slightly larger than the outer diameter of the workpiece 40 and the height thereof is the center of the lower die 6 at the upper side. A bottomed cylindrical recess 7 higher than the height of the material 40 is formed, and a columnar workpiece 40 can be inserted into the recess 7 from the upper side to the lower side.

  A knockout mechanism is provided at the lower part of the lower mold 6. The knockout mechanism includes a knockout bar that discharges the hollow forged product 41 that has been forged, and a cylinder mechanism (not shown) that moves the knockout bar 9 in the vertical direction. The knockout bar 9 is disposed so as to be movable in the vertical direction at a position corresponding to the concave portion 7 of the lower mold 6. The knockout bar 9 is moved upward by a cylinder mechanism to form a hollow forged product 41 (work to be processed after forging). The hollow forged product 41 can be peeled off from the lower die 6 by pushing up the material 40). Further, a mold support mechanism (not shown) is provided below the lower mold 6 so that the lower mold 6 can be supported on the floor surface or the like by the mold support mechanism.

Next, the upper surface of the lower mold 6 which is a feature of the present invention will be described with reference to the drawings.
A locking groove 30 is formed on the upper surface of the lower mold 6. A long locking body 33 and a long fitting formed separately from the locking body 33 are formed in the locking groove 30. The combined unit 35 is inserted together.
The locking groove 30 (hereinafter referred to as a dovetail groove) is formed such that the upper side is open and the upper side of the peripheral edge 8 of the recess 7 is cut away. The cross section of the dovetail groove 30 is a substantially rectangular space.

The dovetail groove 30 is provided at a facing position so as to sandwich the recess 7 in a plan view so as to reliably hook the upper surface of the hollow forged product 41 when the upper mold 2 is released. That is, two dovetail grooves 30 are formed on the upper surface of the lower mold 6 and are symmetric about the vertical axis of the lower mold 6.
Specifically, the dovetail 30 of the first embodiment has both ends penetrating the outer peripheral surface of the lower mold 6, and the midway portion penetrates so as to cut out the upper side of the peripheral edge portion 8 of the recess 7. . That is, the dovetail groove 30 is formed such that the midway portion overlaps the upper side of the peripheral edge portion 8 of the concave portion 7, in other words, the midway portion of the dovetail groove 30 and the upper side of the peripheral edge portion 8 of the concave portion 7 overlap each other. The dovetail 30 has a bottom 31 connected to the upper side of the peripheral edge 8 of the recess 7 and is formed in a step shape in a sectional view. That is, the dovetail 30 is formed so as to communicate with the recess 7.

  The dovetail groove 30 has a width in which a locking body 33 and a fitting body 35 to be described later can be inserted, and the bottom 31 is wider than the opening width on the upper side. The width of the dovetail groove 30 is a width dimension obtained by combining the width of the locking body 33 and the width of the fitting body 35, that is, a width in which the locking body 33 and the fitting body 35 are inserted with a slight gap. . It is desirable that the width of the dovetail groove 30 is, for example, about 1 to 2% wider than the total width of the locking body 33 and the fitting body 35.

2 to 4, the gap between the dovetail groove 30, the locking body 33, and the fitting body 35 is shown large so that the dovetail groove 30, a locking body 33 and a fitting body 35 described later can be easily explained. Yes.
Further, the bottom 31 of the dovetail groove 30 is positioned higher than the upper surface of the hollow forged product 41 after forging.
In addition, the cross-sectional shape and length of the dovetail 30 are exemplary, and are not particularly limited as long as the hollow forged product 41 can be reliably released from the punch 3 without being damaged.

As shown in FIGS. 2 and 4, among the side walls forming the dovetail groove 30, the side wall 32 on the side close to the recess 7 is an inclined surface that falls down toward the inside of the dovetail groove 30. . That is, the inclined surface 32 of the dovetail 30 is formed so that the upper side faces the radially outer side of the recess 7 in a side view of the lower mold 6.
Further, the inclined surface 32 (the side wall 32 on the side close to the recess 7) is located on the inner side of the peripheral edge 8 of the recess 7 when the lower mold 6 is viewed from the side. That is, the inclined surface 32 is formed so as to be positioned above the upper outer edge portion 43 of the hollow forged product 41 placed in the recess 7.

  Further, the inclined surface 32 of the dovetail groove 30 is a predetermined distance from the vertical axis of the recess 7 (X in FIG. 2). For example, in FIG. 2, when the radius of the recess 7 of the lower mold 6 is 250 mm (diameter 500 mm), the distance X between the vertical axis of the recess 7 of the lower mold 6 and the inclined surface 32 of the dovetail 30 is 150 mm. It is desirable to be about ~ 240 mm. On the other hand, it is desirable that the width and height of the cotter pin 33 and the fitting pin 35 be about 30 mm to 100 mm.

The inclined surface 32 has an inclination angle θ of 3 ° or more and 30 ° or less with respect to the axial center of the concave portion 7 facing the up-down direction. By setting the angle θ of the inclined surface 32 within the above-described range, when the upper die 2 is pulled upward, the upper outer edge portion 43 of the hollow forged product 41 is securely hooked, and the hollow forged product 41 is removed from the punch 3. Can be released.
In addition, the distance of the inclined surface 32 and the width and height of the cotter pin 33 and the fitting pin 35 are exemplary, and the hollow forged product 41 can be reliably released from the punch 3 without damage. If there is, it does not specifically limit.

The locking body 33 (hereinafter referred to as a cotter pin) of the first embodiment is a long member made of, for example, a steel material, and is inserted into the above-described dovetail 30.
The cotter pin 33 has a width that allows the lower bottom to be wider than the width of the upper bottom and allows the fitting body 35 described later to be inserted together.
Further, the height of the cotter pin 33 is set such that there is no significant difference with respect to the height of the dovetail groove 30. It is desirable that the height of the cotter pin 33 is set to a difference within a range of about ± 30% with respect to the height of the dovetail groove 30. For example, when the height of the cotter pin 33 is 50 mm, the height of the dovetail 30 is preferably about 40 mm to 70 mm.

Further, the length of the cotter pin 33 is longer than the length of the dovetail groove 30. For example, as shown in FIG. 3, the length of the cotter pin 33 may be about 1.5 times the length of the dovetail groove 30.
The cross-sectional shape and length of the cotter pin 33 are exemplary, and are not particularly limited as long as the hollow forged product 41 can be reliably released from the punch 3 without damage.

A side surface of the dovetail groove 30 facing the inclined surface 32, that is, a side surface of the cotter pin 33 near the recess 7 has the same inclination angle as the inclined surface 32 of the dovetail groove 30. That is, the angle θ of the inclined surface 34 of the cotter pin 33 is 3 ° or more and 30 ° or less.
By setting the inclined surface 34 of the cotter pin 33 and the inclined surface 32 of the dovetail groove 30 to the same inclination angle θ, the inclined surface of the cotter pin 33 when the cotter pin 33 is inserted into the dovetail groove 30 as shown by the dotted line in FIG. 34 and the inclined surface 32 of the dovetail groove 30 face each other so as to overlap each other, and the inclined surface 34 of the cotter pin 33 is hidden behind the upper surface of the lower mold 6 in the AA cross-sectional view of FIG.

In such a situation, when the inclined surface 34 of the cotter pin 33 releases the hollow forged product 41 from the upper mold 2 as shown by a one-dot chain line in FIG. 32 is fully engaged, i.e., is in sufficient surface contact.
Therefore, when the upper die 2 is pulled upward in a situation where the hollow forged product 41 is stuck to the punch 3 of the upper die 2, the upper outer edge 43 of the hollow forged product 41 is caught by the cotter pin 33, and the press Due to the ascending force (force to pull up the upper mold 2), the hollow forged product 41 in close contact with the upper mold 2 is peeled off.

The fitting body 35 (hereinafter referred to as a fitting pin) of the first embodiment is inserted next to the cotter pin 33 and is a long member.
As shown in FIG. 4, when the fitting pin 35 is inserted into the dovetail groove 30 together with the cotter pin 33, the fitting pin 35 comes into contact with the upper outer edge portion 43 (shoulder portion) of the hollow forged product 41 (worked material 40 after forging). The positional relationship is such that it does not. The fitting pin 35 is manufactured with substantially the same shape (height and length, etc.) and material as the cotter pin 33 described above.

  For example, the height of the fitting pin 35 is set so as not to be greatly different from the height of the dovetail groove 30 and is within a range of about ± 30% with respect to the height of the dovetail groove 30. It is desirable to make a difference. For example, the fitting pin 35 may have the same height as the cotter pin 33 (50 mm). In addition, the length of the fitting pin 35 may be substantially the same as the length of the cotter pin 33, or may be longer or shorter than the length of the cotter pin 33 in consideration of easy attachment / detachment of the fitting pin 35.

  On the other hand, the difference between the fitting pin 35 and the cotter pin 33 is that the inclined surface 34 is not provided, that is, the width of the upper base and the width of the lower base of the fitting pin 35 are the same. That is, the fitting pin 35 is a bar having a substantially square cross section. The fitting pin 35 of the present embodiment has a substantially square cross section, but any cross-sectional shape (for example, any shape) can be used as long as the cotter pin 33 functions to keep the cotter pin 33 from moving in the horizontal direction (lateral direction). It may be a rod having a circular cross section.

This fitting pin 35 ensures that the cotter pin 33 can be removed even if the cotter pin 33 is bent for some reason when releasing the hollow forged product 41.
For example, when the hollow forged product 41 is released from the punch 3, the force for pulling up the upper die 2 becomes strong, and the raised hollow forged product 41 bent (damages) the cotter pin 33. In this case, the fitting pin 35 inserted next to the cotter pin 33 is first taken out. As a result, the dovetail groove 30 on the side far from the recess 7 becomes empty, and the bent cotter pin 33 can be moved and taken out to the empty space.

The cotter pin 33 and the fitting pin 35 shown in FIG. 2 and FIG. 4 are inserted with a slight clearance with respect to the dovetail groove 30, but are loosely fitted, that is, the cotter pin 33. In addition, the fitting pin 35 may be slidably contacted with the inner wall surface of the dovetail groove 30.
Next, a method for manufacturing the hollow forged product 41 using the hot forging device 1 described above, that is, a drilling hot forging method will be described with reference to the drawings.

As shown in FIG. 5A to FIG. 5F, the drilling hot forging method according to the first embodiment performs drilling hot forging on the workpiece 40 after the hot upset forging process (not shown) in the previous process. This is a method for manufacturing a hollow forged product 41 having a U-shaped cross-sectional view, in which a hollow recess 42 (hole) is formed.
The hot forging method for drilling using the hot forging device 1 of the present invention includes a workpiece 40 charging step for charging the workpiece 40 into the recess 7 of the lower die 6, and the charged workpiece 40, an upper die pressing step for lowering the punch 3 of the upper die 2, a locking member insertion step for inserting the cotter pin 33 into the dovetail groove 30 of the lower die 6, and a fitting pin for the dovetail 30 35, a fitting body inserting step for inserting 35, an upper die releasing step for releasing the hollow forged product 41 from the upper die 2, and a lower die releasing step for releasing the hollow forged product 41 from the lower die 6. And have.

In FIG. 5A, the workpiece 40 after the upset forging process is loaded and placed in the recess 7 of the lower mold 6 (workpiece loading step). The workpiece 40 after the upset forging process is forged several times after being forged several times, and the outer diameter is substantially the same as the inner diameter of the recess 7 of the lower mold 6. The workpiece 40 after upset forging is inserted so as to fit into the recess 7.
Next, in FIG. 5B, the upper mold 2 disposed above the lower mold 6 is lowered, and the punch 3 is pressed against the workpiece 40 to be pressed down (upper mold pressing step). Due to the reduction of the punch 3, a recess 42 (hole) is formed in the center portion of the workpiece 40 in the vertical direction. That is, the hollow forged product 41 is manufactured.

At this time, the height of the hollow forged product 41 is slightly higher than the height of the workpiece 40 before the punch 3 is reduced. Further, in the upper die reduction process, a high strain is imparted to the hollow forged product 41.
Subsequently, in FIG. 5C, the cotter pin 33 is inserted into the dovetail groove 30 in a state where the punch 3 is pressed down on the workpiece 40 (a state where the hollow forged product 41 is manufactured) (engagement body insertion step). ). At this time, the cotter pin 33 is inserted so that the inclined surface 34 of the cotter pin 33 and the inclined surface 32 of the dovetail groove 30 face each other. By doing in this way, the part by the side of the inclined surface 34 of the cotter pin 33 will be located above the upper outer edge part 43 of the hollow forged product 41.

  In FIG. 5D, the fitting pin 35 is inserted in the dovetail groove 30 in the situation where the hollow forged product 41 is manufactured (fitting body insertion step). At this time, the fitting pin 35 is inserted next to the cotter pin 33 so that the inclined surface 34 of the cotter pin 33 inserted in the dovetail groove 30 and the inclined surface 32 of the dovetail groove 30 are not separated. By doing in this way, as for the fitting pin 35, the inclined surface 34 of the cotter pin 33 and the inclined surface 32 of the dovetail groove 30 will face reliably.

  In FIG. 5E, the upper die 2 is pulled upward (upper die releasing step) under the situation where the cotter pin 33 and the fitting pin 35 are inserted into the dovetail groove 30 (under the situation shown in FIG. 5D). At this time, the hollow forged product 41 (worked material 40 after forging) attached to the punch 3 rises together with the upper mold 2. Then, the upper outer edge 43 of the hollow forged product 41 comes to be caught by the cotter pin 33. Then, the hollow forged product 41 caught on the cotter pin 33 is released so as to be peeled off from the punch 3 of the upper mold 2 and remains in the recess 7. Thereafter, only the upper mold 2 is pulled upward.

Thus, the cotter pin 33 inserted in the dovetail 30 on the side close to the recess 7 can reliably release the hollow forged product 41 from the upper mold 2 without damaging it.
In FIG. 5F, the fitting pin 35 is taken out from the dovetail groove 30 of the lower mold 6, and then the cotter pin 33 is taken out from the dovetail groove 30. And the knockout stick | rod 9 with which the lower part of the recessed part 7 was moved is moved upwards, and it molds so that the hollow forged product 41 may be extruded from the lower mold 6 (lower mold release process).

In the lower mold releasing step, even when the cotter pin 33 is bent in the upper mold releasing step, the dovetail groove 30 on the far side from the concave portion 7 is removed after removing the fitting pin 35 on the radially outer side of the concave portion 7. The bent cotter pin 33 can be taken out by removing the cotter pin 33 by shifting it to the outside.
After that, the hollow forged product 41 that has finished drilling hot forging is sent to the drilling process, and the central portion facing the axial direction of the hollow forged product 41 is punched (penetrated) by punching forging, shearing, etc. The low strain portion remaining in the hollow forged product 41 is removed. Note that the lower portion of the hollow forged product 41 having a U-shaped cross-sectional view may be penetrated by machining or the like.

As described above, according to the hot forging device 1 in which the dovetail groove 30 is formed on the upper surface of the lower die 6 and the cotter pin 33 and the fitting pin 35 are inserted into the dovetail groove 30, Even after the forging, even if the hollow forged product 41 is in close contact with the punch 3 of the upper mold 2 and it becomes difficult to release, the hollow forged product 41 is damaged from the punch 3 by using the force to pull up the upper mold 2. It can be reliably and easily released without any problems.
[Second Embodiment]
Next, a second embodiment (modified example) of the hot forging device 1 according to the present invention will be described with reference to FIG.

As shown in FIG. 6, the second embodiment of the hot forging device 1 is substantially the same as the configuration of the hot forging device 1 described above.
That is, the configuration of the second embodiment of the hot forging device 1 includes an upper mold 2 having a punch 3 in the center and a lower mold 6 having a recess 7 in which a workpiece 40 is inserted. Is the same.
Further, the second embodiment has a dovetail groove 30 formed on the upper side of the peripheral edge 8 of the recess 7 of the lower mold 6, and a cotter pin 33 and a fitting pin 35 inserted into the dovetail groove 30. The same is true. Moreover, the point that the dovetail groove | channel 30 is provided in the position which faces so that the recessed part 7 may be pinched | interposed is also the same. In the second embodiment, the cross-sectional shape of the dovetail groove 30 and the cross-sectional shapes of the cotter pin 33 and the fitting pin 35 are the same.

On the other hand, in the second embodiment, the length of the dovetail groove 30 is different from the length of the dovetail groove 30 of the hot forging device 1 of the first embodiment.
Specifically, in the dovetail groove 30 of the second embodiment, only one end penetrates the outer peripheral surface of the lower mold 6 and the other end does not penetrate the outer peripheral surface of the lower mold 6. Only the upper part of the peripheral edge 8 of the recess 7 is cut away. That is, the dovetail 30 of the present modification is formed so that the other end overlaps with a part of the recess 7, in other words, the other end overlaps with a part of the upper side of the peripheral edge 8 of the recess 7.

Therefore, the other end of the dovetail groove 30 in the second embodiment is terminated halfway without passing through the peripheral edge 8 of the recess 7.
As shown in FIG. 6, the dovetail groove 30 of the second embodiment is, for example, in plan view, for example, the other end is up to the vertical axis of the recess 7, that is, about 1 / of the length of the dovetail groove 30 of the first embodiment. 2. In addition, the lengths of the cotter pin 33 and the fitting pin 35 of the second embodiment are longer than the length of the dovetail groove 30 so as to correspond to the dovetail groove 30.

  As described above, the hot forging device 1 according to the second embodiment has the dovetail groove 30 whose other end is terminated above the peripheral edge 8 of the recess 7, and one of the cotter pins 33 inserted into the dovetail groove 30. It is a feature that the portion is configured to be caught by the upper outer edge portion 43 of the hollow forged product 41. According to this configuration, when releasing the hollow forged product 41 (the workpiece 40 after forging), the cotter pin 33 protruding from the notched portion always catches a part of the upper surface of the hollow forged product 41. The hollow forged product 41 in close contact with the upper mold 2 can be reliably released.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. In the embodiment disclosed herein, matters that are not explicitly disclosed, such as operating conditions and operating conditions, various parameters, dimensions, weights, volumes, and the like of the constituents, depart from the scope normally practiced by those skilled in the art. Instead, values that can be easily assumed by those skilled in the art are employed.

For example, in the above-described embodiment, the case where two dovetail grooves 30 are formed in the lower mold 6 has been described as an example. However, as long as the cotter pin 33 can be disposed on the upper outer edge portion 43 of the workpiece 40. Only one may be formed.
Further, although the cotter pin 33 has been described as a long bar, it may be a long plate. Although the number of the fitting pins 35 is one each, a plurality of the fitting pins 35 may be provided.

The length of the dovetail 30 of the second embodiment is such that a part of the cotter pin 33 inserted into the dovetail 30 overlaps with the upper outer edge 43 of the hollow forged product 41 in the recess 7 in plan view. If there is, it does not specifically limit.
In the above-described embodiment, the hot forging device used in the hollow forging process (drilling hot forging) has been described. However, the technology of the present invention is applicable to any hot forging device having a convex upper die. (A configuration in which the upper outer edge 43 (shoulder) of the hollow forged product 41 (the workpiece 40 after forging) is pressed by the cotter pin 33) is applicable. For example, a hot forging device used in an upsetting forging process or a hollow shaft forging process can be used.

1 Hot Forging Device 2 Upper Die 3 Projection (Punch)
4 Indentation part 5 Extrusion part 6 Lower mold 7 Recess 8 Peripheral part 9 Knockout stick 30 Locking groove (ant groove)
31 Bottom 32 Inclined surface (side wall near the recess)
33 Locking body (cotter pin)
34 inclined surface 35 fitting body (fitting pin)
40 Work material 41 Hollow forged product 42 Recessed part (hole part)
43 Upper outer edge

Claims (7)

A bottom mold having a bottomed cylindrical recess that is open at the top, and a lower mold in which the heated work material is inserted into the recess, and a convex protrusion that protrudes downward from the pressed surface are formed. And in a hot forging device comprising an upper die for reducing the work material charged in the lower die from above,
On the upper surface of the lower mold, a locking groove whose upper side is open is formed,
The locking groove is a side wall in which a long locking body is inserted, is formed so as to cut out the upper side of the peripheral edge of the recess, and forms the locking groove. The side wall close to the recess is an inclined surface that is falling toward the inside of the locking groove,
The hot forging device, wherein at least one end of the locking groove penetrates the outer peripheral surface of the lower mold.   The hot forging device according to claim 1, wherein the inclined surface of the locking groove has an inclination angle of 3 ° to 30 °.   The hot forging device according to claim 2, wherein a side surface of the locking body facing the inclined surface of the locking groove has the same inclination angle as the inclined surface of the locking groove.   The hot forging device according to any one of claims 1 to 3, wherein the locking groove is provided at a position facing each other so as to sandwich the concave portion.   The locking groove and a long fitting body formed separately from the locking body are inserted in the locking groove together. Hot forging device according to crab.   The side wall forming the locking groove, the side wall close to the recess is located inside the peripheral edge of the recess when the lower mold is viewed from the side. The hot forging apparatus in any one of 1-5.   The hot forging device according to any one of claims 1 to 6, wherein a knockout mechanism is provided at a lower portion of the lower die.