JP5373378B2 - Forging method - Google Patents

Abstract

The present invention is to provide a forging method capable of transferring a workpiece with a high degree of positional accuracy. The present invention is directed to a forging method in which a workpiece (W) disposed at a workpiece introducing section (50) is sandwiched and held from both sides of the workpiece with a pair of claws (42) provided to a pair of feed bars (41) arranged on both sides of a transferring line by closing the feed bars (41), and transferred to a workpiece processing section by opening the feed bars (41) after moving the feed bars (41) forward to the workpiece processing section with the workpiece (W) sandwiched and held, and the workpiece (W) transferred to the workpiece processing section is forged. In the method, the workpiece (W) is previously provided with an engaging portion (85) and the claw (42) is previously provided with an engaging portion receiving portion (45) so that the workpiece (W) is positioned by engaging the engaging portion (85) with the engaging portion receiving portion (45) at the time of sandwiching and holding the workpiece (W) with the claws (42).

Description

  The present invention relates to, for example, a forging method and related technology for forging a workpiece to be transferred.

  A multi-stage forging apparatus that forms a workpiece by a plurality of continuous forging processes is well known.

  A conventional multistage forging apparatus performs, for example, a primary molding die for performing primary molding on a workpiece and secondary molding for a primary molded workpiece, as shown in Patent Documents 1 and 2 below, for example. And a transfer device for transferring the workpiece from the primary molding die to the secondary molding die.

Usually, the transfer device includes a pair of feed bars arranged in parallel on both sides of the transport line, and a pair of claws provided to face each other inside the pair of feed bars. Then, by closing the pair of feed bars, for example, the workpiece (primary molded product) formed in the primary molding die is clamped (chucked) by the pair of claws, and in this state, the feed bar moves to the transport line. The workpiece is arranged at a position corresponding to the secondary molding die. Thereafter, the pair of feed bars are opened and the workpiece chuck is released, so that the workpiece is set in the secondary molding die.
Japanese Utility Model Publication No. 63-281737 JP 2007-130680 A

  In the multi-stage forging apparatus that performs forging a plurality of times as described above, it is possible to obtain a secondary molded product having a complicated shape such as an engine piston material, but processing to a complicated shape by secondary molding. Therefore, the primary molded product by the primary molding has a shape having a volume balance that is calculated in advance so that no defects are generated in the secondary molding. For this reason, when the primary molded product is set in the secondary molding die, if the position of the primary molded product is shifted, the secondary molding cannot be performed with accuracy, and a lack of detail or a lack of meat. There is a problem that defects such as entanglement (molding defects) occur.

This invention has been made in view of the above problems, and when transferring a work from an upstream work processing unit such as a primary molding die to a downstream work processing unit such as a secondary molding die, It is an object of the present invention to provide a forging method and related technology capable of preventing the position of a workpiece from shifting and performing forging with high accuracy.

  In order to achieve the above object, the present invention comprises the following arrangement.

[1] By closing the pair of feed bars arranged on both sides of the transfer line, the pair of claws provided on the pair of feed bars sandwich the workpiece installed in the workpiece carry-in portion from both sides, In the sandwiched state, the pair of feed bars are moved forward along the transfer line and then opened to transfer the workpiece to the workpiece processing unit, while forging the workpiece transferred to the workpiece processing unit. A forging method to be performed,
While providing an engaging portion on the workpiece, an engaged portion is provided on the claw,
A forging method comprising positioning the workpiece by engaging the engaging portion with the engaged portion when the workpiece is sandwiched between the pair of claws.

  [2] One of the engaging portion and the engaged portion is configured by a positioning convex portion, and the remaining one is configured by a positioning concave portion that is positioned by fitting the positioning convex portion. The forging method according to item 1 above.

[3] A work discharge section is provided on the downstream side along the conveyance line of the work processing section, and a plurality of the pair of claws are provided on the pair of feed bars.
By closing the pair of feed bars, the workpieces of the workpiece loading unit and the workpiece processing unit are respectively clamped by the corresponding pairs of claws, and the pair of feed bars are advanced and opened in the clamped state. 3. The forging method according to item 1 or 2, wherein the workpieces sandwiched between the pairs of claws are transferred to the workpiece processing unit and the workpiece discharge unit, respectively.

[4] The work processing unit includes a plurality of work processing units arranged along a transfer line,
By closing the pair of feed bars, the workpiece loading unit and the workpieces of the plurality of cake processing units are respectively clamped by the corresponding pairs of claws, and the pair of feed bars are advanced in the sandwiched state. The forging method according to the preceding item 3, wherein the workpieces sandwiched between the claws of each set are transferred to the plurality of workpiece processing units and the workpiece discharge unit, respectively, by opening from the above.

[5] The work processing unit includes a first work processing unit and a second work processing unit disposed on the downstream side of the first work processing unit,
The first workpiece processing unit is configured as a primary molding unit that performs primary molding by die forging on a workpiece to obtain a primary molded product,
5. The forging method according to item 3 or 4 above, wherein the second workpiece processing unit is configured as a secondary molding unit that performs secondary molding by die forging on the primary molded product to obtain a secondary molded product.

  [6] The forging method according to item 5, wherein the engaging portion of the workpiece is formed by the primary forming.

[7] The engaging portion formed in the primary molded product as the workpiece is constituted by a positioning convex portion,
7. The forging method according to 5 or 6 above, wherein the volume balance of the secondary molded product is achieved by pushing in at least a part of the positioning convex portion after the primary molding to increase the thickness.

  [8] The forging method as recited in the aforementioned Item 7, wherein the positioning projection is pushed by the secondary forming.

[9] The engaging portion formed in the primary molded product as the workpiece is constituted by a positioning convex portion,
7. The forging method as described in 5 or 6 above, wherein the positioning convex portion is removed after the primary molding to achieve a volume balance of the secondary molded product.

  [10] Any one of [5] to [9], wherein a piston material in which a pair of skirt portions and a pair of pin boss portions are integrally formed on one surface side of the land portion is produced as a secondary molded product. Forging method.

  [11] The forging method according to the above item 10, wherein the engaging portion is formed on an outer peripheral surface of a planned skirt portion corresponding to the skirt portion in the primary molded product.

  [12] The forging method according to item 2, wherein guide portions for guiding the convex portion to the positioning concave portion are provided on both sides of the positioning convex portion.

[13] The forging method according to any one of items 1 to 12, wherein a workpiece made of aluminum or an aluminum alloy is used.

[14] When the pair of feed bars arranged on both sides of the transfer line is closed, the workpiece installed in the workpiece loading section is clamped from both sides by the pair of claws provided on the pair of feed bars. In the sandwiched state, the workpiece is transferred to the workpiece processing unit by opening the pair of feed bars after moving forward along the conveying line, while the workpiece transferred to the workpiece processing unit, A forging device in which forging is performed,
An engaging part is provided on the workpiece, and an engaged part is provided on the claw,
A forging apparatus characterized in that, when a workpiece is sandwiched between the pair of claws, the workpiece is positioned by engaging the engaging portion with the engaged portion.

[15] A workpiece discharge unit is provided on the downstream side along the transfer line of the workpiece processing unit,
The work processing unit includes a first work processing unit and a second work processing unit arranged on the downstream side of the first work processing unit,
When the pair of feed bars are closed, the workpiece loading unit and the workpieces of the first and second workpiece processing units are respectively clamped by the corresponding sets of claws, and the pair of feed bars are advanced in the clamped state. By opening it, the workpieces sandwiched between the claws of each set are configured to be transferred to the first and second workpiece processing units and the workpiece discharge unit, respectively.
A primary molding die for performing primary molding on the workpiece to obtain a primary molded product is provided in the first workpiece processing unit,
Wherein the second work section, forging apparatus as recited in claim 14 secondary molding die for obtaining a secondary molded article by performing a secondary molding with respect to the primary molded product is provided.

[16] By closing the pair of feed bars disposed on both sides of the transfer line, the pair of claws provided on the pair of feed bars sandwich the workpiece installed in the workpiece carry-in portion from both sides, A workpiece transfer method in which the workpiece is transferred to the workpiece processing unit by opening the pair of feed bars along the conveyance line after being opened in a sandwiched state,
While providing an engaging portion on the workpiece, an engaged portion is provided on the claw,
A workpiece transfer method, wherein the workpiece is positioned by engaging the engaging portion with the engaged portion when the workpiece is clamped by the pair of claws.

[17] When the pair of feed bars disposed on both sides of the transfer line is closed, the workpiece installed in the workpiece carry-in portion is clamped from both sides by the pair of claws provided on the pair of feed bars. The workpiece transfer device in which the workpiece is transferred to the workpiece processing unit by opening the pair of feed bars after moving forward along the conveying line in the sandwiched state,
An engaging part is provided on the workpiece, and an engaged part is provided on the claw,
A workpiece transfer device, wherein the workpiece is positioned by engaging the engaging portion with the engaged portion when the workpiece is sandwiched between the pair of claws.

  According to the forging method of the invention [1], when the work is sandwiched between the pair of claws, the engaging part provided on the work is engaged with the engaged part provided on the claw to position the work. Therefore, the position shift of the workpiece can be prevented and forging can be performed with high accuracy.

  According to the forging method of the invention [2], the workpiece can be positioned reliably.

  According to the forging method of the invention [3], a plurality of workpieces can be transferred sequentially in parallel, and the production efficiency can be improved.

  According to the forging method of the invention [4], the workpiece can be processed with respect to the workpiece by a plurality of workpiece processing units.

  According to the forging method of the invention [5], a workpiece can be formed in two stages of primary forming and secondary forming, and a forged product having a complicated shape can be obtained.

  According to the forging method of the invention [6], since the engaging portion is formed on the workpiece by primary forming, the productivity is improved as compared with the case where the step of forming the engaging portion is performed separately. be able to.

  According to the forging method of the invention [7], the volume balance in the forged product can be easily adjusted.

  According to the forging method of the invention [8], productivity can be further improved as compared with the case where the engaging protrusion is pushed separately.

  According to the forging method of the invention [9], the volume balance in the forged product can be easily adjusted.

  According to the forging method of the invention [10], a piston material can be manufactured as a forged product.

  According to the forging method of the invention [11], the primary molded product as a workpiece can be transferred in a stable state while reliably positioning.

  According to the forging method of the invention [12], the positioning convex portion can be reliably fitted by the positioning concave portion, so that the workpiece can be positioned more reliably.

  According to the forging method of the invention [13], a forged product made of aluminum can be obtained.

  According to the forging device of the invention [14], similarly to the above, when the workpiece is sandwiched between the pair of claws, the engaging portion provided on the workpiece is engaged with the engaged portion provided on the nail, Since the workpiece is positioned, the displacement of the workpiece can be prevented, and forging can be performed with high positional accuracy.

  According to the forging device of the invention [15], a forged product having a complicated shape can be obtained in the same manner as described above.

  According to the workpiece transfer method of the invention [16], similarly to the above, when the workpiece is sandwiched between the pair of claws, the engagement portion provided on the workpiece is engaged with the engaged portion provided on the claw. Since the workpiece is positioned, the displacement of the workpiece can be prevented and the workpiece can be transferred with high positional accuracy.

  According to the workpiece transfer device of the invention [17], when the workpiece is clamped by the pair of claws, the engagement portion provided on the workpiece is engaged with the engaged portion provided on the claw, as described above. Since the workpiece is positioned, the displacement of the workpiece can be prevented and the workpiece can be transferred with high positional accuracy.

  FIG. 1 is a schematic plan view showing a multistage forging apparatus to which a forging method according to an embodiment of the present invention is applied, and FIG. 2 is a side view. As shown in both figures, this forging device can perform two types of die forging, primary forming and secondary forming, on the workpiece (W) sequentially transferred by the transfer device (4). ing.

The forging device, over from upstream to downstream along the conveying line (FIG left) (right), word over click loading unit (50), primary and secondary molding section (51) (52) and the workpiece The discharge part (53) is sequentially provided in this order.

In the present embodiment, the forging apparatus, the members constituting the molds 1 and 2 and the like, the workpiece W, etc., which will be described in detail below, are on the left side from the right side (work discharge side, downstream side) in FIGS. The front is the case where the workpiece is seen (upstream side).

  In this embodiment, the workpiece carry-in part (50) is comprised by the downstream end part of workpiece carrying-in means, such as a carrying-in conveyor (56). Then, the work (W) is carried into the inside from the outside of the apparatus by the carry-in conveyor (56), is conveyed to the conveyor end, that is, the work carry-in part (50), and waits.

  The primary molding part (51) constitutes a first work processing part, and the secondary molding part (52) constitutes a second work processing part. The primary molding part (51) and the secondary molding part (52) are provided with a primary molding die (1) and a secondary molding die (2), respectively. In the primary molding section (51), primary molding such as rough molding is performed on the workpiece (W) by the primary molding die (1), and the workpiece (W) is formed in the secondary molding section (52). ), Secondary molding such as main molding (finish molding) is performed by the secondary molding die (2).

  The workpiece discharge part (53) is comprised by the upstream edge part of workpiece | work carrying-out means, such as a carrying-out conveyor (57). And the workpiece | work (W) arrange | positioned at a conveyor edge part, ie, a workpiece | work discharge | emission part (53), is carried out to the apparatus exterior by the discharge | emission conveyor (57).

Further, the forging apparatus is provided with a transfer device (4), and the transfer device (4) moves the workpiece (W) from the workpiece carry-in portion (50) to the primary molding portion (51) and the secondary molding portion. (52) and the workpiece discharge section (53) can be sequentially transferred.

  In the present embodiment, the workpiece (W) before the primary molding is referred to as a forging material (W0), and the workpiece (W) after the primary molding and before the secondary molding is referred to as a primary molded product (W1). The workpiece (W) after the secondary molding is referred to as a secondary molded product (W2), a forged product (W2), or a piston material (W2). The forging material (W0), the primary molded product (W1), and the secondary molded product (W2) are collectively referred to as a workpiece (W).

  As shown in FIG. 4, the piston material (W2) as a secondary molded product manufactured by the forging device of the present embodiment includes a circular land portion (91), and one surface side of the land portion (91) ( A pair of skirt portions (92) and (92), a pair of pin boss portions (93) and (93), and a sidewall portion (94) are integrally provided on the lower surface side.

  The pair of skirt portions (92) and (92) are provided at the left and right end portions of the outer peripheral edge portion on the one surface side of the land portion (91) so as to protrude to the lower surface side.

  The pair of pin boss portions (93) and (93) are provided on both the front and rear sides of the intermediate portion on the one surface side of the land portion (91) so as to protrude to the lower surface side.

  The sidewall portions (94) are provided on the left and right sides of the pair of front and rear pin boss portions (93) and (93), respectively, and the left and right sides of the front pin boss portion (93) and the pair of skirt portions (92) and (92). Projects to the lower surface side in such a manner that the front end portion is connected and the left and right sides of the rear pin boss portion (93) are connected to the rear end portions of the pair of skirt portions (92) and (92). It is provided to do.

  As shown in FIGS. 5 and 6, the primary molded product (W1) of the present embodiment includes a thick disc-shaped main body portion (81), and is provided on one surface side (lower surface side) of the main body portion (81). A pair of planned skirt portions (82) (82) and a pair of planned pin boss portions (83) (83) are provided integrally.

  The pair of planned skirt portions (82) and (82) are provided on both left and right end portions of the outer peripheral edge portion on one surface side of the main body portion (81) so as to bulge to the lower surface side, and by secondary molding, The skirt portions (92) and (92) are formed.

  The pair of planned pin boss portions (83) and (83) are provided on both front and rear sides of the intermediate portion on one surface side of the land portion (91) so as to protrude to the lower surface side, and the pin boss portions (93 are formed by secondary molding. ) (93).

  Furthermore, the positioning convex part (85) which comprises an engaging part protrudes to one side (outer diameter direction) in the one side part of the outer peripheral surface in the main-body part (81) of a primary molded product (W1). Are integrally formed.

  The upper portion of the positioning convex portion (85) is formed in a trapezoidal shape corresponding to the inner peripheral shape of the claw (42) in the feed bar (41) described later. Inclined surfaces are provided on both side portions of the portion (85), and the both side portions are configured as both side guide portions (86) (86). Further, an inclined surface is provided on the lower side portion of the positioning convex portion (85), and the lower side portion is configured as a lower guide portion (87).

  As shown in FIG. 7, the forging material (W0) of the present embodiment has a short cylindrical shape (disk shape). As the forging material (W0), for example, a continuous cast bar of aluminum (including an aluminum alloy) or a continuous extruded bar cut into a volume corresponding to a predetermined weight by a saw cutting process can be used.

  Specific composition components of the forging material (W0) are Si: 5 to 18% by mass, Cu: 2 to 5% by mass, Mg: 0.3 to 1.0% by mass, Fe: 0.1 to 0.8% Preferred examples include aluminum alloys containing mass%, Ni: 0.1 to 3 mass%, Mn: 0.1 to 0.5 mass%, and Cr: 0.1 to 0.5 mass%.

  As shown in FIGS. 1 and 2, the transfer device (4) of the present embodiment includes a pair of feed bars (41) and (41) that are arranged on both sides of the conveyance line.

  The pair of feed bars (41) (41) both extend along the transport line (front-rear direction) and are arranged in parallel. The pair of feed bars (41) and (41) can be opened / closed by a driving means (not shown) so as to move in the direction of contact / separation (left / right direction) with each other, and can move in the front / rear direction in synchronization. Further, the pair of feed bars (41) and (41) can move in the vertical direction in synchronization.

  Inside the pair of feed bars (41) and (41), a plurality of pairs (three sets) of a pair of claws (42) and (42) arranged to face each other are provided at predetermined intervals along the front-rear direction. . Each claw (42) is fixed to the feed bar (41) via a claw holder (43).

  Each pair of claws (42) and (42) has a workpiece carry-in part (50) and a molding part (51) in a state in which the pair of feed bars (41) and (41) are retracted (a state moved to the left side in FIG. 1). In the state where the pair of feed bars (41) and (41) are moved forward (the state moved to the right side in FIG. 1), the forming portions (51) and (52) and the workpiece discharge are respectively disposed. It arrange | positions corresponding to a part (53), respectively. When the pair of feed bars (41) and (41) are closed in the retracted state, the workpieces (W) installed in the workpiece carry-in section (50) and the molding sections (51) and (52) The claws (42) and (42) are held (chucked). Further, when the pair of feed bars (41) and (41) are moved up and moved forward (moved to the right side in FIG. 1) in the clamped state, three sets of claws (42) and (42) are formed into the molded portion (51). (52) and the work discharge unit (53). Further, in this state, when the pair of feed bars (41) (41) are opened after being lowered, the gripping by the respective claws (42) is released, and the workpieces (W) are formed into the molding parts (51) (52). ) And the work discharge unit (53). Thereby, each workpiece | work (W) installed in the workpiece | work carrying-in part (50) and the shaping | molding part (51) (52) is transferred to a shaping | molding part (51) (52) and a workpiece discharge part (53). It will be. After the transfer, the pair of feed bars (41) (41) moves backward to the left in FIG. 1 by retreating and stands by in an open state (initial state).

  Thus, the workpieces (W) are sequentially transferred in parallel, so that the workpieces (W) sequentially supplied to the workpiece carry-in unit (50) are converted into the primary molding unit (51), the secondary molding unit (52), and The workpieces are sequentially transferred to the work discharge unit (53) and discharged sequentially.

Here, as shown in FIGS. 1 and 3 in this embodiment, each claw (42) of the transfer device (4) has a V-groove-shaped or U-groove-shaped positioning recess (45) in the middle portion in plan view. the has its positioning recess (45) of the inner peripheral shape is formed in a trapezoidal shape corresponding to the outer peripheral shape of the positioning protrusion (85) in the above-mentioned primary-molded article (W1) Yes. The inner surfaces on both sides of the trapezoidal positioning recess (45) are formed so as to be inclined corresponding to the both side guide portions (86) (86) of the positioning projection (85), and the both side guide portions (46) ( 46).

  When the primary molded product (W1) is sandwiched between the corresponding pair of claws (42) and (42), as will be described in detail later, it is placed in the positioning recess (45) of the one claw (42). The positioning convex part (85) of the primary molded product (W1) is fitted, so that the primary molded product (W1) is positioned.

  In the present embodiment, the positioning recess (45) of the claw (42) is configured as the engaged portion.

  Furthermore, in this embodiment, the shape of the positioning convex part (85) of the primary molded product (W1) is formed so as to correspond to the shape of the positioning concave part (45) of the claw (42). ) Is used as a positioning recess (45).

  As shown in FIG. 2, in the forging device of the present embodiment, the primary molding die (1) is disposed in the primary molding part (51) and the secondary molding part (52) is secondary molded. A mold (2) is arranged.

  As shown in FIGS. 2 and 8, the primary molding die (1) includes a lower die (11) and a punch (16) as an upper die.

  The lower mold (11) is open upward and has a molding hole (12) for molding the primary molded product (W1). The inner peripheral surface of the molding hole (12) is formed corresponding to the outer peripheral surface shape excluding the upper end surface of the primary molded product (W1). That is, the inner surface of the molding hole (12) has a concave portion (mold portion) for forming the main body portion (81), the skirt planned portion (82), and the pin boss planned portion (83) in the primary molded product (W1). Each is provided.

  Further, on the inner peripheral side surface of the molding hole (12), a female groove portion (13) for positioning convex portion for forming the positioning convex portion (85) is formed on the outer surface shape of the positioning convex portion (85). Correspondingly formed.

  The lower mold (11) having this configuration is assembled to the lower plate (10) via the lower mold holder (14).

  The lower side portion of the punch (16) is formed in a shape that can be inserted into the molding hole (12) of the lower mold (11) in a compatible state. On the outer peripheral side surface of the punch (16), there is formed a convex-shaped male part for positioning convex part (17) corresponding to the female part for positioning convex part (13) of the lower mold (11). Has been.

  The punch (16) having this configuration is assembled to the upper plate (20) via a punch holder (18).

  The upper plate (20) is configured to be moved up and down by an elevating drive means (not shown), and the punch (18) is moved up and down by the upper plate (20) to form a molding hole ( 12) It is designed to be driven in. Further, at the time of driving, the male part (17) for positioning convex part of the punch (18) is driven into the female concave part (13) of the lower mold (11).

  A knockout pin (not shown) is accommodated at the bottom of the molding hole (12) in the lower mold (11) so as to protrude upward from the bottom surface of the molding hole (12). As will be described later, the primary molded product (W1) molded in the molding hole (12) of the lower mold (11) is pushed up by the knockout pin, and the primary molded product (W1) is A predetermined amount protrudes upward from the molding hole (12) of the mold (11).

  As shown in FIGS. 9 and 10, the secondary molding die (2) includes a lower die (21) and a punch (26) as an upper die.

  The lower mold (21) has a molding hole (22) for opening upward and molding the secondary molded product (W2). The inner peripheral surface of the molding hole (22) is formed corresponding to the outer peripheral surface shape excluding the upper end surface of the secondary molded product (W2). That is, the inner surface of the molding hole (22) has recesses for forming the land portion (91), the skirt portion (92), the pin boss portion (93), and the sidewall portion (94) in the secondary molded product (W2). Each is provided.

  Further, on the inner peripheral side surface of the forming hole (12), a female concave portion (23) for positioning convex portion having a concave groove shape is formed corresponding to the positioning convex portion (85).

  The lower mold (21) having this configuration is assembled to the lower plate (10) via the lower mold holder (24).

  The lower side portion of the punch (26) is formed in a shape that can be inserted into the molding hole (22) of the lower mold (21) in a conforming state. On the outer peripheral side surface of the punch (26), a male part (27) for positioning convex part having a convex shape is formed corresponding to the female part (23) for positioning convex part of the lower die (21). Has been.

  The punch (26) having this configuration is assembled to the upper plate (20) via a punch holder (28).

When the upper plate (20) is lowered, the secondary molding punch (26) is lowered in synchronization with the primary molding punch (16) and the molding hole ( 22) of the secondary molding die (2) is obtained. ). Further, at the time of driving, the male part (27) for positioning convex part of the secondary molding punch (26) is driven into the female part (23) of the lower mold (21).

  In the secondary molding die (2), a knockout pin (not shown) is provided at the bottom of the molding hole (22) in the lower die (21), as in the primary molding die (1). Can be protruded, and after the molding, the secondary molded product (W2) is pushed up by the knockout pin, and the secondary molded product (W2) is located above the molding hole (22) of the lower mold (21). A fixed amount protrudes.

  In the multistage forging device of the present embodiment, the conditions (forging conditions) when performing forging are as follows. That is, the temperature of the workpiece (W) is 380 to 540 ° C., the upper die (punch) temperature in the primary molding die (1) and the secondary molding die (2) is 100 to 250 ° C., and the lower die temperature is 150. Set to ~ 370 ° C. In this embodiment, since primary molding and secondary molding are performed continuously, the workpiece temperature should be set higher in the primary molding. That is, the workpiece temperature in the primary molding is set to −30 to −60 ° C. with respect to the solidus temperature of the workpiece (W), and the primary molding is performed in the secondary molding by heat removal from the mold. It is good to set so that it may become -20--60 degreeC with respect to the workpiece | work temperature of eyes. More preferably, the work temperature of the secondary molding is set so as not to be 370 ° C. or lower.

  Moreover, as a lubricant for the workpiece (W), a graphite-based lubricant is used, and is applied by dipping or bonding. Further, as a lubricant for the mold, an aqueous graphite lubricant or a combination of an oily graphite lubricant and an aqueous graphite lubricant is used. Furthermore, the mold is lubricated both during the primary molding and during the secondary molding.

  Next, a forging operation in the forging device of the present embodiment will be described. In this apparatus, primary molding and secondary molding are performed in parallel at the same time, and a plurality of workpieces (W) are transferred in parallel at the same time. In order to facilitate the above, various operations sequentially performed on one forging material (W0) will be described in time series.

  First, the pair of feed bars (41) (41) is in an open state at the retracted position. In this initial state, the forging material (W0) is carried in from the outside of the apparatus by the carry-in conveyor (56), and the workpiece standby unit (50). At this time, the forging material (W0) is arranged such that its axis is oriented in the vertical direction (vertical direction).

  Subsequently, the pair of feed bars (41) and (41) are closed, and the upper portion of the forging material (W0) of the work carry-in portion (50) is the nail (42 on the left side in FIG. 1). ) (42).

  Thereafter, the pair of feed bars (41) and (41) move up and then move forward, and the forging material (W0) sandwiched between the first set of claws (42) and (42) is formed in the primary molding portion (51). It arrange | positions corresponding to the shaping | molding hole (12) of a lower metal mold | die (11).

Subsequently, the pair of feed bars (41) (41) descends. At this time, as described above, the forging material (W0) is sandwiched between the pair of claws (42) and (42), and the lower side portion protrudes downward. Therefore, when the feed bar is lowered, the lower part of the forging material (W0) sandwiched between the pair of claws (42) and (42) is inserted into the upper part of the molding hole (12) of the lower mold (11). .

  Then, in the inserted state, the pair of feed bars (41) (41) is opened, the clamping to the forging material (W0) is released, and the forging material (W0) becomes a molding hole ( 12). Here, in the present embodiment, since the lower side portion of the forging material (W0) is inserted into the forming hole (12), the clamping to the forging material (W0) is released. W0) is reliably and accurately accommodated in the molding hole (12). For this reason, for example, it is possible to reliably prevent the occurrence of poor installation, for example, when the forging material (W0) is displaced during insertion or inserted in a posture different from the normal posture. Therefore, the mold forming described later can be performed smoothly with high accuracy.

  Here, in this embodiment, it is preferable that the upper portion of the forged material (W0) is sandwiched between the pair of claws (42) and (42). That is, when the lower part of the forged material (W0) is sandwiched between the pair of claws (42) and (42), when the feed bar (41) (41) is lowered, the pair of claws (42) When (42) interferes with the lower mold (11), the lower side portion of the forging material (W0) cannot be placed in the state inserted into the forming hole (12), and the feed bar (41) ( When 41) is opened, it may be difficult to put the forging material (W0) into the forming hole (12) with high positional accuracy. Therefore, in this embodiment, when the feed bar (41) (41) is lowered by holding the upper portion of the forging material (W0) by the pair of claws (42) (42), the forging is performed. The lower side of the material (W0) can be securely inserted into the molding hole (12), and when the feed bar (41) (41) is opened, the forging material (W0) is reliably molded. It can be put into the hole (12).

  Subsequently, the upper plate (20) is lowered and the punch (16) is driven into the molding hole (12) of the lower mold (11), and the forging material (W0) is placed in each recess of the molding hole (12). It is press-fitted and molded into a primary molded product (W1).

  As described above, the primary molded product (W1) includes one side of the outer peripheral surface of the main body (81) in addition to the main body (81), the planned skirt (82) and the planned pin boss (83). The part is provided with a positioning convex part (85) protruding in the outer diameter direction.

  8 indicates the state of the punch (16) at the lowermost position when the punch (16) is driven.

  After the driving of the punch (16) is completed, after the upper plate (20) and the punch (16) are raised, the primary molded product (W1) is pushed up by the knockout pin and the primary molded product (W1) ) Is disposed so as to protrude upward from the molding hole (12).

  On the other hand, during this molding, the pair of feed bars (41) (41) are retracted and returned to the initial state, and when the primary molded product (W1) is pushed upward by the knockout pin as described above, The feed bar (41) (41) is closed, and the upper part of the primary molded product (W1) of the primary molded part (51) is the second set (second from the left in FIG. 1) of the claws (42 ) (42).

  At this time, the positioning convex part (85) formed in the primary molded product (W1) is engaged (fitted) in an appropriate state in the positioning concave part (45) of the one side claw (42), The primary molded product (W1) is positioned relative to the transfer device (4).

  Here, even when the position of the primary molded product (W1) is slightly shifted when the primary molded product (W1) is held between the claws (42) and (42), the positional shift is corrected. That is, as shown in FIG. 3, if the position of the primary molded product (W1) is shifted when being pinched by the claws (42) (42), the positioning convex portion (85) of the primary molded product (W1). ) Is guided by abutting on both side guide portions (46) and (46) of the positioning recess (45), or the opening edge of the positioning recess (45) is positioned by the positioning projection (85). By being brought into contact with and guided by the guide portions (86) and (86), the position of the primary molded product (W1) is corrected while finely moving. Thus, when the positional deviation of the primary molded product (W1) is absorbed and the positioning is accurately performed, the positioning convex portion (85) is adapted to the positioning concave portion (45). In this way, the primary molded product (W1) is sandwiched between the pair of claws (42) and (42) of the transfer device (4) in a state of being accurately positioned.

  Subsequently, the pair of feed bars (41) and (41) are moved up and then moved forward, and the primary molded product (W1) sandwiched between the second pair of claws (42) and (42) becomes the secondary molded portion. It arrange | positions corresponding to the shaping | molding hole (22) of the lower metal mold | die (21) in (52).

  Thereafter, as shown in FIG. 11, the pair of feed bars (41) and (41) are lowered, and the lower part of the primary molded product (W1) sandwiched between the claws (42) and (42) is the lower mold. It is inserted into the upper part of the molding hole (22) of (21). Furthermore, the lower part of the positioning convex part (85) in the primary molded product (W1) is inserted into the upper part of the female part for positioning convex part (23) in the molding hole (22).

  In this state, the pair of feed bars (41) (41) is opened, the nipping to the primary molded product (W1) is released, and the primary molded product (W1) molds the positioning convex portion (85). It is inserted into the molding hole (22) while being inserted into the female mold part (23) for positioning projection of the hole (22).

  At this time, in this embodiment, since the primary molded product (W1) is introduced in a state where a part (lower side portion) is inserted into the molding hole (22), the primary molded product (W1) is In the molding hole (22), it is reliably accommodated with high positional accuracy. Furthermore, the primary molded product (W1) has a molding hole (22) in a state where a part (lower side portion) of the positioning convex portion (85) is inserted into the positioning convex female portion (23). In particular, the positioning of the primary molded product (W1) in the direction around the axis (circumferential direction) can be performed accurately, so that the primary molded product (W1) is more accurately positioned in the lower mold ( 21) is set in the molding hole (22).

  Here, in the present embodiment, similarly to the above, when the pair of feed bars (41) (41) is lowered, the lower side portion of the primary molded product (W1) is inserted into the molding hole (22). The upper part of the primary molded product (W1) is sandwiched between the pair of claws (42) (42) so that they can be arranged in a state.

  In the present embodiment, even if the primary molded product (W1) is slightly displaced, the positioning convex portion (85) when the primary molded product (W1) is put into the molding hole (22). The lower guide portion (87) provided on the lower side portion of the lower die (21) comes into contact with the opening edge of the positioning projection male portion (23) and is guided, thereby being primary. The molded product (W1) is reliably accommodated in the molding hole (22) of the lower mold (21).

  Thereafter, the upper plate (20) is lowered and the punch (26) is driven into the molding hole (22) of the lower mold (21), so that the primary molded product (W1) is in each recess of the molding hole (22). To be molded into a secondary molded product (W2). By this molding, the main body portion (81) is molded into the land portion (91), the planned skirt portion (82) is molded into the skirt portion (92), and the planned pin boss portion (83) is molded into the pin boss portion (93). . Further, the positioning convex part (85) is clamped by the positioning convex female part (23) of the lower mold (21) and the positioning convex male part (27) of the punch (26), It is compressed in the axial direction and formed into a positioning projection mark (95) having a short axial direction.

  9 indicates the state of the punch (26) at the lowest end position when the punch (26) is driven.

  After the driving of the punch (26) is completed, the upper plate (20) and the punch (26) are raised, and then the secondary molded product (W2) is pushed up by the knockout pin, and the secondary molded product (W2). ) Is disposed so as to protrude upward from the forming hole (22).

  On the other hand, during this molding, the pair of feed bars (41) (41) are retracted and returned to the initial state, and when the secondary molded product (W2) is pushed upward by the knockout pin as described above, The feed bar (41) (41) is closed, and the upper part of the secondary molded product (W2) of the secondary molded part (52) is the nail (42) of the third set (right end part in FIG. 1). It is clamped from both sides by (42).

  At this time, similarly to the primary molded product (W1), the positioning projection mark (95) is engaged (fitted) in an appropriate state within the positioning recess (45) of the claw (42) on one side. Thus, the positioning of the secondary molded product (W2) is accurately achieved.

  Subsequently, the pair of feed bars (41) and (41) move up after being moved up, and the secondary molded product (W2) sandwiched between the third claws (42) and (42) is moved to the workpiece discharge section (53). It is arranged corresponding to.

  Thereafter, the pair of feed bars (41) (41) are lowered and then opened to release the clamping to the secondary molded product (W2), and the secondary molded product (W2) is moved to the work discharge section (53). Placed on top.

  The secondary molded product (W2) placed on the workpiece discharge section (53) is discharged to a predetermined location by the discharge conveyor (57). Thus, a series of forging processes is completed for the workpiece (W).

  As described above, in the multistage forging device of the present embodiment, primary forming and secondary forming are performed in parallel. That is, each work (W) placed on the work carry-in part (50) and the forming part (51) (52) is made up of three pairs of claws (42) (42) in the pair of feed bars (41) (41). They are sandwiched at the same time and transferred to the forming sections (51) and (52) and the workpiece discharge section (53), respectively. Subsequently, primary molding and secondary molding are simultaneously performed on the workpieces (W) of the molding sections (51) and (52), while the workpieces are carried in (50) by the carry-in conveyor (56) during the molding. The workpiece (forging material) is carried into the workpiece, and the workpiece (secondary molded product W2) arranged in the workpiece discharge section (53) is discharged by the carry-out conveyor (57). As described above, the transfer operation and the forming operation of the workpiece (W) by the pair of feed bars (41) and (41) are alternately and repeatedly performed, whereby primary forming and secondary forming are performed on the plurality of workpieces (W). Molding is sequentially performed in parallel, and secondary molded products (forged products) are sequentially discharged.

  In addition, the forged product (W2) manufactured in this way is formed as a forged product with a final shape by performing cutting treatment or the like as necessary to remove burrs, positioning protrusion marks (95), and the like. It is what is done.

  As described above, according to the forging method in the forging device of the present embodiment, the positioning projection (85) is formed on the workpiece (W) by the primary molding, and is made to correspond to the projection (85). Since the positioning recess (45) is formed in the claw (42), when the primary molded product (W1) is clamped by the claw (42) (42), the concave and convex portions (45) (85) are engaged. Thus, the primary molded product (W1) can be positioned, and the primary molded product (W1) can be accurately transferred to the secondary molding die (2). Therefore, in the secondary molding die (2), the primary molded product (W1) can be molded in a regular posture without positional deviation, and a high-quality secondary molded product (W2) can be reliably obtained. it can.

  Furthermore, in this embodiment, since the positioning convex part (85) is formed on the workpiece (W) at the time of the primary molding, it is not necessary to separately provide a process for forming the positioning convex part, and an increase in the number of processes can be prevented. High productivity can be maintained.

  Further, in the forging device of the present embodiment, since the transfer device (4) is used, it is possible to convey in a constant cycle time and in a short time, and therefore, temperature control which is an important condition in forging. For example, the mold temperature and workpiece temperature can be easily and stably managed as described above, and excellent machining performance can be realized more reliably, which is effective in the forging technique.

  Furthermore, the forging apparatus of this embodiment can reduce a conveyance mistake and can implement | achieve the stable forging operation by using a transfer apparatus (4). For this reason, for example, fluctuations in the mold temperature due to operation stop due to a conveyance mistake can be suppressed, and the above temperature management can be performed more easily and stably, which is more effective in the forging technology. is there.

Here, as shown in FIG. 4, the piston material (W2) manufactured by the forging device of the present embodiment has a center (93x) of the pin boss portion (93) at the thrust side (one side) with respect to the piston center (W2x). Is offset by a predetermined amount (Δx). For this reason, the piston material (W2) is formed in a volume balance such that the thrust side volume is slightly increased.

  Under such circumstances, it is necessary to adjust the volume balance at the stage of the secondary molded product (W2) as the final finished molded product in the forging process, particularly the closed forging process as in the present embodiment. is there.

  Therefore, in the present embodiment, a positioning convex portion (85) is formed at a position corresponding to the thrust side (one side skirt portion) of the primary molded product (W1) by primary molding, and positioning is performed at the time of secondary molding. It is possible to accurately adjust the volume balance by pushing the convex portion (85) and increasing the thrust side volume. In this volume balance adjustment method, adjustment is made by the amount of pressing of the convex portion (85) at the time of secondary molding, so that the primary molded product (W1) in the primary molding before the secondary molding has a large volume balance. It can be manufactured without consideration, volume balance can be easily adjusted, and productivity can be further improved.

  In addition, when pushing in the positioning convex part (85) at the time of secondary molding, in the above embodiment, only a part of the positioning convex part (85) is pushed in to increase the thickness, but in the present invention, positioning is performed. The pushing amount of the convex portion (85) is not particularly limited, and may be set freely as necessary. For example, the entire positioning convex portion (85) may be pushed in to increase the thickness.

  On the other hand, in the primary molded product (W1), the positioning projection (85) is formed on the opposite side to the thrust side (on the skirt on the opposite side of the thrust), and the positioning projection after the secondary molding. It is also possible to cut the part (85) to adjust the volume balance. As described above, when the volume on the thrust side is relatively increased by the removal of the convex portion (85) after the secondary molding, the volume balance of the primary molded product (W1) during the primary molding is It can be set evenly on the anti-thrust side, and the volume balance during primary molding can be easily adjusted.

  Thus, in this embodiment, since the positioning convex part (85) is formed in the skirt part (thrust side or anti-thrust side), the forged product (W2) is formed by pushing or cutting the convex part (85). ) Volume balance can be easily adjusted. However, in the present invention, the positioning convex portion (85) is not necessarily formed in the skirt portion, and may be formed in another portion.

  In the case where at least a part of the positioning convex portion (85) is not pushed in at the time of secondary molding and the trace (95) is left in the subsequent cutting process, The projection mark (95) can be used for positioning in the cutting process, and the cutting operation can be performed smoothly.

  FIG. 12 is a view showing the claw (42) of the feed bar (41) in the multistage forging device which is a modification of the present invention. As shown in the figure, this apparatus is provided with a work carry-in part, a primary forming part, a secondary forming part, and a work discharge part as in the above-described embodiment, and moves the work between them by a transfer device. . The transfer device includes a pair of feed bars (41) and (41). A pair of claws (42) and (42) facing each other are provided along the transport line on the pair of feed bars (41) and (41). A plurality of sets are provided at predetermined intervals.

  The pair of claws (42) (42) is constituted by a flat plate member having a rectangular shape in plan view. The opposing surfaces (tip surfaces) of the pair of claws (42) and (42) are formed by flat surfaces (vertical surfaces), and are configured as positioning portions (engaged portions).

  On the other hand, in the workpiece (W) processed by this forging apparatus, the workpiece material has a cylindrical shape (disk shape) as in the above embodiment.

  Further, as shown in FIGS. 13 and 14, the primary molded product (W1) protrudes to one side on both sides of the circular main body portion (81) and one surface side (upper surface side) of the main body portion (81). And a pair of pin boss planned portions (83) and (83) formed integrally with each other.

  The pair of pin boss planned portions (83) and (83) are formed into pin boss portions by secondary molding, and have a rectangular parallelepiped shape. The outer side surfaces of the pin boss planned portions (83) and (83) are constituted by vertical surfaces and are configured as positioning portions (engaging portions).

  In this forging apparatus, a pin boss portion, a skirt portion, and a sidewall portion are formed on the upper surface side of the workpiece (W). That is, as shown in FIG. 15, the primary molding die (1) of this forging apparatus is a pin boss plan for molding the pin boss planned portions (83) (83) on the punch (16) as the upper die. The part formation recessed part (161) (161) is formed. Further, as shown in FIG. 16, in the secondary molding die (2), pin boss portion forming recesses (261) and (261) for forming the pin boss portion are formed in the punch (26) as the upper die. ing.

  In this modification, since the other configuration is the same as that of the above-described embodiment, the same or corresponding parts are denoted by the same or corresponding reference numerals, and redundant description is omitted.

  In this forging apparatus, after the molding with the primary molding die (2), the pair of feed bars (41) (41) is closed. As a result, as shown in FIG. 12, the tip surfaces of the pair of claws (42) (42) come into contact with the outer surfaces on both sides of the pin boss planned portions (83) (83) in the primary molded product (W1). The next molded product (W1) is sandwiched between the pair of claws (42) and (42). At this time, the tip surfaces of the pair of claws (42) and (42) are constituted by vertical flat surfaces, and the pin boss planned portion (83) of the primary molded product (W1) on which the tip surfaces are abutted and supported. Since the outer surface of (83) is also constituted by a vertical surface, positioning of the primary molded product (W1) with respect to the transfer device is achieved by surface contact with each other. That is, when the position of the primary molded product (W1) is shifted when sandwiched between the claws (42) and (42), the outer peripheral edge of the front end surface of the claws (42) and (42) becomes the pin boss planned portion (83). ) By being brought into contact with and guided by the outer surface of (83), the position of the primary molded product (W1) is corrected while finely moving. Thus, when the positional deviation of the primary molded product (W1) is absorbed and the positioning is accurately performed, the tip surfaces of the claws (42) and (42) are the outer surfaces of the pin boss planned portions (83) and (83). In surface contact. Thus, the primary molded product (W1) is sandwiched between the pair of claws (42) and (42) of the transfer device in a state of being accurately positioned.

  Thereafter, similarly to the above, by the movement of the pair of feed bars (41) and (41), the primary molded product (W1) sandwiched between the pair of claws (42) and (42) moves to the secondary molded portion, Therefore, the pair of feed bars (41) (41) is opened, and the primary molded product (W1) is put into the molding hole (12) in the lower mold (21) of the secondary molding die (2). .

  Thereafter, in the same manner as described above, secondary molding is performed, and the transfer device transfers and discharges the workpiece to the workpiece discharge section.

  Also in the multistage forging device of this modification, similar effects can be obtained as described above.

  Furthermore, in this modified example, it is not necessary to form a special molded portion for positioning in the primary molded product (W1), and the primary molded product (W1) having a simple shape is adopted. Can be easily implemented.

  In the above embodiment, the convex portion (85) is formed on the workpiece (W) side for positioning, and the concave portion (45) is formed on the claw (42) side so that the concave and convex portions are engaged. However, the present invention is not limited to this, and in the present invention, positioning may be achieved by forming a concave portion for positioning on the workpiece side and forming a convex portion on the claw side and engaging the concave and convex portions.

  Furthermore, in the above-described embodiment, the workpiece is formed by the two forming portions of the primary forming portion and the secondary forming portion. However, in the present invention, the forming portion is not limited to two, and the forming portion is There may be one or three or more. Further, when a plurality of forming portions are provided, it is not necessary to perform die forging in all the forming portions, and a molding other than forging, for example, a burr removal process by press working or the like may be employed.

  The forging method of the present invention can be applied to a forging technique in which forging is performed on a workpiece to be transferred.

It is a top view which shows the forge processing apparatus which can apply the forge processing method which is embodiment of this invention. It is a side view which shows the forge processing apparatus of embodiment. It is a top view which expands and shows the 2nd set of nail | claw part in the apparatus of FIG. It is a front view which shows the piston raw material manufactured with the forge processing apparatus of embodiment. It is a perspective view which shows the primary molded product manufactured by the forge processing apparatus of embodiment. It is a figure which shows the primary molded product manufactured with the forge processing apparatus of embodiment, Comprising: The figure (a) is a top view, The figure (b) is front sectional drawing, The figure (c) is side sectional drawing. is there. It is a perspective view which shows the forge raw material employ | adopted as the forge processing apparatus of embodiment. It is front sectional drawing which shows the metal mold | die for primary molding in the forge processing apparatus of embodiment. It is front sectional drawing which shows the metal mold | die for secondary forming in the forge processing apparatus of embodiment. It is a figure which shows the lower metal mold | die for the secondary shaping | molding die in embodiment, Comprising: The figure (a) is a top view, The figure (b) is front sectional drawing, The figure (c) is side sectional drawing. . It is front sectional drawing which expands partially and shows the state immediately before throwing a primary molded product into the shaping | molding hole of a metal mold | die for secondary shaping | molding in the forge processing apparatus of embodiment. It is a figure which expands and shows the nail | claw periphery in the forge processing apparatus which can apply the forging method which is a modification of this invention, Comprising: The figure (a) is a top view, The figure (b) is a front view. It is a perspective view which shows the primary molded product manufactured with the forge processing apparatus of a modification. It is a figure which shows the primary molded product manufactured with the forge processing apparatus of a modification, Comprising: The figure (a) is a top view, The figure (b) is side sectional drawing, The figure (c) is front sectional drawing. is there. It is front sectional drawing which shows the primary shaping | molding die in the forge processing apparatus of a modification. It is front sectional drawing which shows the secondary shaping die in the forge processing apparatus of a modification.

DESCRIPTION OF SYMBOLS 1 ... Primary molding die 2 ... Secondary molding die 4 ... Transfer apparatus 41 ... Feed bar 42 ... Claw 45 ... Positioning recessed part (engaged part)
50 ... Work carry-in part 51 ... Primary forming part (1st work process part)
52 ... Secondary forming section (second work processing section)
54 ... Work discharging part 82 ... Skirt scheduled part 85 ... Positioning convex part (engaging part)
86 ... Guide part 91 ... Land part 92 ... Skirt part 93 ... Pin boss part W ... Work W0 ... Work material W1 ... Primary molded product W2 ... Secondary molded product (piston material, forged product)

Claims (9)

By closing the pair of feed bars arranged on both sides of the transfer line, the pair of claws provided on the pair of feed bars clamps the workpiece installed in the workpiece carry-in section from both sides, and in the clamping state The workpiece is transferred to the workpiece processing unit by opening the pair of feed bars after being advanced along the conveying line, and forging is performed on the workpiece transferred to the workpiece processing unit. Forging method,
While providing an engaging portion on the workpiece, an engaged portion is provided on the claw,
While the workpiece is clamped by the pair of claws, the workpiece is positioned by engaging the engaging portion with the engaged portion ,
A work discharge unit is provided on the downstream side along the conveyance line of the work processing unit, and a plurality of the pair of claws are provided on the pair of feed bars.
By closing the pair of feed bars, the workpieces of the workpiece loading unit and the workpiece processing unit are respectively clamped by the corresponding pairs of claws, and the pair of feed bars are advanced and opened in the clamped state. Thus, the work sandwiched between each pair of claws is transferred to the work processing unit and the work discharge unit,
The work processing unit includes a first work processing unit and a second work processing unit arranged on the downstream side of the first work processing unit,
The first workpiece processing unit is configured as a primary molding unit that performs primary molding by die forging on a workpiece to obtain a primary molded product,
The second workpiece processing unit is configured as a secondary molding unit that performs secondary molding by die forging on the primary molded product to obtain a secondary molded product,
The engaging portion formed in the primary molded product as a workpiece is constituted by a positioning convex portion,
A forging method characterized in that, after the primary molding, at least a part of the positioning convex portion is pushed in to increase the thickness, thereby achieving a volume balance of the secondary molded product . The pre-Symbol engaged portions, forging method according to claim 1 which is to constitute the positioning recess to achieve positioning fitted to the positioning projection. The work processing unit has a plurality of work processing units arranged along a conveyance line,
By closing the pair of feed bars, the workpiece loading unit and the workpieces of the plurality of cake processing units are respectively clamped by the corresponding pairs of claws, and the pair of feed bars are advanced in the sandwiched state. The forging method according to claim 1 or 2 , wherein the workpieces sandwiched between each pair of claws are transferred to the plurality of workpiece processing units and the workpiece discharge unit, respectively, by opening from the top. The forging method according to any one of claims 1 to 3 , wherein the engaging portion of the workpiece is formed by the primary forming. The forging method according to any one of claims 1 to 4, wherein the positioning projection is pushed by the secondary forming. The forging according to any one of claims 1 to 5 , wherein a piston material in which a pair of skirt portions and a pair of pin boss portions are integrally formed on one surface side of the land portion is produced as a secondary molded product. Processing method. The forging method according to claim 6 , wherein the engaging portion is formed on an outer peripheral surface of a planned skirt portion corresponding to the skirt portion in the primary molded product.   The forging method according to claim 2, wherein guide portions for guiding the convex portion to the positioning concave portion are provided on both sides of the positioning convex portion. The forging method according to any one of claims 1 to 8, wherein a workpiece made of aluminum or an aluminum alloy is used.

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