阅读说明：本技术 精密锻造法、精密锻造装置及精密锻造件 (Precision forging method, precision forging apparatus, and precision forged article ) 是由 王志刚 于 2020-04-22 设计创作，主要内容包括：精密锻造法具有：以金属材料(10)的周壁(14)的顶端面与止动部(24)对置、并且金属材料(10)的底部(12)与冲头(30)对置的方式,将金属材料(10)配置于冲模(20)的冲模孔(22)内。另外,精密锻造法具有：使在加工端面(31)的缘部具有切削刃(32)的冲头(30)在冲模孔(22)内移动,据此利用切削刃(32)切入壁部(14)的厚度方向的一部分,并且使该切入部分引起剪切变形。(The precision forging method comprises: the metal material (10) is disposed in a die hole (22) of a die (20) such that the tip end surface of a peripheral wall (14) of the metal material (10) faces a stopper (24) and the bottom (12) of the metal material (10) faces a punch (30). The precision forging method further includes: a punch (30) having a cutting edge (32) at the edge of a machined end surface (31) is moved within a punch hole (22), whereby a part of a wall portion (14) in the thickness direction is cut by the cutting edge (32), and the cut part is caused to shear-deform.)

1. A precision forging method comprising: a method of precision forging a metal material (10) having a wall portion (14, 60, 114) extending in a moving direction of a punch (30) and a pre-machining projecting wall (12A, 17A, 64A, 112A, 120A) extending from the wall portion (14, 60, 114) in a crossing direction crossing the moving direction, the method comprising the steps of disposing the metal material (10) in a die hole (22) of a die (20), and forging the metal material (10) by the movement of the punch (30), the precision forging method comprising:

a step 1 of disposing the punch (30) having a machined end surface (31) and a cutting edge (32) formed at an edge of the machined end surface in the punch hole (22) so as to face a part of the wall portion (14, 60, 114) of the metal material (10) in the thickness direction and the pre-machining projecting wall (12A, 17A, 64A, 112A, 120A); and

and a2 nd step of moving the punch (30) within a height range of the wall portion (14, 60, 114) while holding the metal material (10) in a moving direction of the punch (30) and holding the length of the protrusion wall before machining in the intersecting direction, thereby causing the cutting portion to cut a part of the wall portion (14, 60, 114) in the thickness direction by the cutting edge (32) on a moving path of the punch (30) and causing shear deformation of the cutting portion so as to move the cutting portion in the protrusion wall before machining.

2. The precision forging method according to claim 1,

the step 1 comprises the following steps:

disposing the metallic material (10) having the wall portion (14, 60, 114) with a fitting region at least partially in surface contact with an inner surface of the die hole (22) and having the pre-machining projecting wall (12A, 17A, 64A, 112A, 120A) on an opposite side of the fitting region in the die hole (22); and

the cutting edge (32) of the punch (30) is disposed apart from the inner surface of the die hole (22) by at least less than the thickness of the wall portion,

the 2 nd step comprises: the metal material is cut into by the cutting edge (32) in such a way that the mating region of the wall section (14, 60, 114) remains.

3. The precision forging method according to claim 1,

the step 1 comprises the following steps:

disposing the metallic material (10) in the die hole (22) in such a manner that the wall portion (14, 60, 114) is spaced apart from the inner surface of the die hole (22) and the pre-machining projecting wall (17A) is in at least partial surface-to-surface contact with the inner surface of the die hole (22); and the cutting edge (32) is formed at a position more inward than the surface contact side.

4. The precision forging method according to any one of claim 1 to claim 3,

the punch (30) is a1 st punch,

the step 1 comprises the following steps: a2 nd punch (40) is disposed on the side opposite to the 1 st punch with the pre-processing projecting wall (12A, 17A, 64A, 112A, 120A) therebetween,

the step 2 comprises the following steps: the 2 nd punch (40) is moved following the movement of the 1 st punch (30) in the moving direction.

5. The precision forging method according to any one of claim 2 to claim 4,

the wall portion is a peripheral wall portion,

the cutting amount of the punch relative to the peripheral wall is t₀The length of the punch in the crossing direction is 2t greater than the inner diameter of the peripheral wall₀mm，

Thickness t of the protrusion wall before machining_c0T is not less than 0.1mm_c0≤20mm，

R is a radius of curvature of a junction line (B) between the peripheral wall and the pre-processing projecting wall and on the opposite side of the pre-processing projecting wall from the punch_cpWhen r is_cp/t_c0The case of < 2.0 is true,

the metal material is represented by t₀/t_c0Processed so as to satisfy the following inequality (1),

t₀/t_c0≥0.052r_cp/t_c0+0.23......(1)。

6. the precision forging method according to any one of claim 2 to claim 4,

the wall portion is a peripheral wall portion,

the cutting amount of the punch relative to the peripheral wall is t₀The length of the punch in the crossing direction is 2t greater than the inner diameter of the peripheral wall₀mm，

Thickness t of the protrusion wall before machining_c0T is not less than 0.1mm_c0≤20mm，

R is a radius of curvature at a junction line (B) between the peripheral wall and the pre-working projecting wall and on the opposite side of the pre-working projecting wall from the punch with the pre-working projecting wall therebetween_cpWhen r is_cp/t_c0The establishment of more than or equal to 2.0,

the metal material is represented by t₀/t_c0Is processed so as to satisfy the following inequality (2),

t₀/t_c0≥3.0r_cp/t_c0-5.7......(2)。

7. the precision forging method according to any one of claim 1 to claim 6,

the 2 nd step comprises: a stopper portion (24) is brought into abutment with a tip end face of the wall portion (14, 60, 114) so that the metal material (10) is held in a moving direction of the punch (30).

8. A precision forging apparatus for forging a metal material (10), comprising:

a die (20) having a die hole (22) configured to dispose the metal material (10); and

a punch (30) configured to move within the die hole (22) to forge the metal material (10),

the metal material (10) has: a wall portion (14, 60, 114) extending along a moving direction of the punch (30); and a pre-processing projecting wall (12A, 17A, 64A, 112A, 120A) extending from the wall portion (14, 60, 114) in a crossing direction crossing the moving direction,

the punch (30) is disposed so as to face a part of the wall portion (14, 60, 114) in the thickness direction and the pre-machining projecting wall (12A, 17A, 64A, 112A, 120A) when the metal material (10) is disposed in the punch hole (22),

the punch (30) has a machined end surface and a cutting edge (32) formed at the edge of the machined end surface,

the cutting edge (32) is configured to: when the punch (30) moves within the height range of the wall portion (14, 60, 114), a part of the wall portion (14, 60, 114) in the thickness direction is cut in the moving path of the punch (30), and the cut-in part is caused to undergo shear deformation.

9. The precision forging apparatus according to claim 8,

the stop device is further provided with a stop part (24), wherein the stop part (24) is configured to: when the punch (30) moves, the metal material (10) is held in the moving direction of the punch (30) by abutting against the tip end surface of the wall portion (14, 60, 114).

10. A precision forging comprising:

a wall part extending in the 1 st direction;

a processed projecting wall extending from the wall portion in a2 nd direction intersecting the 1 st direction, the processed projecting wall having a1 st surface and a2 nd surface opposite to the 1 st surface, the 1 st surface being located on a side where a joining line (a) between the wall portion and the processed projecting wall is located; and

a forging flow line (W) extending from the joining line (A) to the joining line (B) of the 2 nd face.

11. The precision forging of claim 10,

the wall portion is a circumferential wall extending in a circumferential manner,

the processed protruding wall is an inward flange or a bottom formed on the inner surface of the peripheral wall or an outward flange formed on the outer surface of the peripheral wall.

12. The precision forging of claim 10,

the wall portion has a flat plate shape, or is bent or curved in a cross-sectional view perpendicular to the 1 st direction.

Technical Field

The present disclosure relates to a precision forging method, a precision forging apparatus, and a precision forged article.

Background

Precision forging, which is cold forging, is widely used for manufacturing precision parts for small parts used in automobiles, electric and electronic devices, and the like, because it enables high-precision parts to be manufactured at low cost (see patent documents 1 and 2). Precision forging is a method of forming a workpiece by a combination of upsetting and pressing, which is a basic construction method, and requires a large tool pressure to press the workpiece into an unfilled portion of a die at the final stage of the forming process.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 4-55034

Patent document 2: japanese laid-open patent publication No. 61-255740

Non-patent document

Non-patent document 1: wang Zhi (Zhi Gang Wang), Dong Zheng (Wen Zheng Dong), Gouguekang (Hiroyasu Yatou), "method for Forming peripheral フランジ of force ツプ of board footwear による り (A new Forming method of thin on a draught cup by plate)", proceeding manufacturing method 15(2018), 955 minus 960, [ online ], "17 th metalworking country (17th International Conference on Metal Forming)", metalworking 2018, 16-199 Yue rich , Japan (Metal Forming 2018, 16-19 Sepber, Toyohashi, Japan) [ and 24 d.24 g.2 years ], インタ - ネツト < https: // www.sciencedirect.com/journal/procedia-manufacturing/vol/15/suppl/C? page 2>

Disclosure of Invention

Problems to be solved by the invention

In the prior art, even if the processing conditions such as material flow and lubrication of the workpiece are optimized, the minimum tool pressure needs to be 3 times or more the tensile strength of the workpiece. Therefore, the precision forging of a high-strength material or a large-sized member cannot be performed due to the restriction of the pressure resistance limit of the tool material.

In fig. 6 of non-patent document 1, the outward flange of the drawn cup is formed by a forming process. In this example, a part of the outer peripheral side of the peripheral wall of the drawn cup is shaved by a punch, and the shaved metal portion is formed to have an outward flange. However, the outward flange is deformed so as to extend without being restricted in a free space in a radial direction with respect to the axial center of the cup during the forming. Therefore, there is a risk of material cracking at the peripheral wall portion opposite to the tip end of the tip of the punch. Fig. 23 is a cut cross section of a connecting portion between the outward flange and the peripheral wall of the cup when the drawn cup subjected to the shaving process is cut in the axial direction. Fig. 24 is an enlarged cross section of a portion surrounded by a square frame in fig. 23. As shown in the two figures, it was confirmed that material cracks occurred at the joint portion of the outward flange and the peripheral wall.

The purpose of the present disclosure is to provide a precision forging method, a precision forging device, and a precision forged part, which can avoid excessive tool pressure during precision forging and which do not risk cracking.

Means for solving the problems

The precision forging method comprises the following steps: a metal material is arranged in a die hole of a die, and the metal material is forged by moving a punch, and the metal material has a wall portion extending in a moving direction of the punch and a pre-processing projecting wall extending from the wall portion in a direction intersecting the moving direction.

The precision forging method comprises the following steps: the punch having a machined end surface and a cutting edge formed at an edge of the machined end surface is disposed in the punch hole so as to face the pre-machining projecting wall and a portion of the wall portion of the metal material in the thickness direction.

The precision forging method further comprises the step 2: the method includes the steps of moving the punch within a height range of the wall portion while holding the metal material in a moving direction of the punch and holding a length of the pre-machining protruding wall in the intersecting direction, thereby causing the cutting portion to cut a portion of the wall portion in a thickness direction by the cutting edge on a moving path of the punch and causing shear deformation of the cutting portion so that the cutting portion moves in a direction of the pre-machining protruding wall.

In addition, the method may further include: disposing the metallic material having the wall portion with a fitting region at least partially in surface contact with an inner surface of the die hole and the pre-machining projecting wall on an opposite side of the fitting region in the die hole; and the cutting edge of the punch is disposed apart from the inner surface of the die hole by at least a thickness smaller than the wall portion. The 2 nd step may also include: the cutting edge is used to cut into the metal material in such a manner that the engagement area of the wall portion remains displaced.

In addition, the step 1 may further include: disposing the metallic material in the die hole such that the wall portion is spaced apart from the inner surface of the die hole and the pre-machining projecting wall is in at least partial surface contact with the inner surface of the die hole; and the cutting edge is formed at a position inside the surface contact side.

In the precision forging method, the punch may be a1 st punch, and the 1 st step may include: a2 nd punch is disposed on the opposite side of the 1 st punch with the pre-processing projecting wall therebetween. In addition, the 2 nd step may also include: and moving the 2 nd punch following the 1 st punch in the moving direction.

In the precision forging method, the wall may be a peripheral wall, and the cutting amount of the punch relative to the peripheral wall may be t₀The length of the punch in the crossing direction is 2t greater than the inner diameter of the peripheral wall₀mm. Thickness t of the protrusion wall before machining_c0Can also satisfy t is less than or equal to 0.1mm_c0Less than or equal to 20 mm. R may be a radius of curvature of a joining line between the peripheral wall and the pre-working projecting wall and on a side opposite to the punch with the pre-working projecting wall interposed therebetween_cpWhen r is_cp/t_c0< 2.0 is true. Further, the metal material may be represented by t₀/t_c0Processed so as to satisfy the following inequality (1).

t₀/t_c0≥0.052r_cp/t_c0+0.23......(1)

In the precision forging method, the wall may be a peripheral wall, and the punch may be opposed to the peripheral wallThe cutting amount in the peripheral wall is t₀The length of the punch in the crossing direction is 2t greater than the inner diameter of the peripheral wall₀mm. Thickness t of the protrusion wall before machining_c0Can also satisfy t is less than or equal to 0.1mm_c0Less than or equal to 20 mm. R may be a radius of curvature of a joining line between the peripheral wall and the pre-working projecting wall and on a side opposite to the punch with the pre-working projecting wall interposed therebetween_cpWhen r is_cp/t_c0More than or equal to 2.0. Further, the metal material may be represented by t₀/t_c0Processed so as to satisfy the following inequality (2).

t₀/t_c0≥3.0r_cp/t_c0-5.7......(2)

In the precision forging method, the 2 nd step may include: a stopper portion is brought into abutment with a tip end surface of the wall portion so that the metal material is held in a moving direction of the punch.

The precision forging apparatus of the present disclosure is a precision forging apparatus for forging a metal material, and includes: a die having a die hole configured to dispose the metal material; and a punch configured to move in the die hole to forge the metal material. The metal material has: a wall portion extending along a moving direction of the punch; and a pre-processing projecting wall extending from the wall portion in a direction intersecting the moving direction. The punch is disposed to face the portion of the wall portion in the thickness direction and the pre-processing protruding wall when the metal material is disposed in the die hole. The punch has a machined end surface and a cutting edge formed at an edge of the machined end surface. The cutting edge is configured to: when the punch moves within the height range of the wall portion, a part of the wall portion in the thickness direction is cut in the moving path of the punch, and the cut-in portion is caused to undergo shear deformation.

Further, the precision forging apparatus may further include a stopper configured to: the punch abuts against a tip end surface of the wall portion when the punch moves, and the metal material is held in a moving direction of the punch.

The precision forging of this disclosure has: a wall part extending in the 1 st direction; and a processed projecting wall extending from the wall portion in a2 nd direction intersecting the 1 st direction. The processed projecting wall has a1 st surface and a2 nd surface opposite to the 1 st surface, and the 1 st surface is located on a side where a joining line (a) between the wall portion and the processed projecting wall is located. The precision forging further has a forging flow line (W) extending from the joining line (A) to the 2 nd face joining line (B).

In the precision forged part, the wall portion may be a peripheral wall extending in a surrounding manner, and the processed projecting wall may be an inward flange or a bottom portion formed on an inner surface of the peripheral wall or an outward flange formed on an outer surface of the peripheral wall.

In the precision forged part, the wall portion may have a flat plate shape or may be bent or bent in a cross-sectional view perpendicular to the 1 st direction.

Effects of the invention

According to the present disclosure, excessive tool pressure in precision forging can be avoided, and the risk of cracking is eliminated.

Drawings

Fig. 1(a) to (c) are explanatory views showing steps of the precision forging method according to embodiment 1.

FIG. 2(a) is a schematic view of cutting forging, and (b) is a schematic view showing a shear velocity V_sAnd an explanatory diagram of the relationship between the punch speed V and the radial speed Vc in the vicinity of the chip shearing region.

Fig. 3(a) is a sectional view of a main part of the metal material before the cutting forging, and (b) is a sectional view of a main part of the metal material after the cutting forging.

Fig. 4(a) is a sectional view of the punch near the corner at the start of the cutting forging, (b) is an enlarged sectional view of (a), (c) is a sectional view of the punch near the corner at a stage later than (a), (d) is an enlarged sectional view of (c), (e) is a sectional view of the punch near the corner at a stage later than (c), and (f) is an enlarged sectional view of (e).

Fig. 5 is a characteristic diagram of p/C with respect to the stroke of the punch.

Fig. 6 is an enlarged cross-sectional view of (a) a portion near the peripheral edge portion of the inner surface of the bottom portion at the start of the cutting forging (near the corner of the reverse punch), (b) a portion near the peripheral edge portion of the inner surface of the bottom portion at a later stage than (a) (near the corner of the reverse punch), where sink marks are generated, (c) a portion near the peripheral edge portion of the inner surface of the bottom portion at a later stage than (b) (near the corner of the reverse punch), where sink marks are generated, and (d) a portion near the corner of the inner surface of the bottom portion at a later stage than (c) (near the corner of the reverse punch).

Fig. 7 is a characteristic diagram showing a region where sink marks are generated and a region where sink marks are not generated.

Fig. 8 is a sectional view of (a) a steel plate of the metal material 10, (b) the metal material 10 after the drawing step, (c) the metal material 10 after ironing, and (d) the metal material 10 after precision forging.

Fig. 9(a) is a photograph of a cross section of the forging showing the forging flow line, and (b) is a photograph of a cross section of the forging showing the forging flow line by a line.

FIG. 10 is a photograph showing a cross-section of the forged material of FIG. 9(a) in which Vickers hardness is given to the cross-sectional portion.

Fig. 11(a) is a perspective view of the metal material of embodiment 2 before machining, (b) is a longitudinal sectional view of the metal material before machining, (c) is a perspective view of the precision forged part after machining, and (d) is a longitudinal sectional view of the precision forged part after machining.

Fig. 12(a) and (b) are explanatory views showing steps of the precision forging method according to embodiment 2.

Fig. 13(a) is a perspective view of the metal material of embodiment 3 before machining, (b) is a longitudinal sectional view of the metal material before machining, (c) is a perspective view of the precision forged part after machining, and (d) is a longitudinal sectional view of the precision forged part after machining.

Fig. 14(a) and (b) are explanatory views showing steps of the precision forging method according to embodiment 3.

Fig. 15(a) is a perspective view of the metal material of embodiment 4 before machining, (b) is a longitudinal sectional view of the metal material before machining, (c) is a perspective view of the precision forged part after machining, and (d) is a longitudinal sectional view of the precision forged part after machining.

Fig. 16(a) and (b) are explanatory views showing steps of the precision forging method according to embodiment 4.

Fig. 17(a) is a perspective view of the metal material of embodiment 5 before machining, (b) is a longitudinal sectional view of the metal material before machining, (c) is a perspective view of the precision forged part after machining, and (d) is a longitudinal sectional view of the precision forged part after machining.

Fig. 18(a) is a perspective view of the metal material of embodiment 6 before machining, (b) is a longitudinal sectional view of the metal material before machining, (c) is a perspective view of the precision forged part after machining, and (d) is a longitudinal sectional view of the precision forged part after machining.

Fig. 19(a) is a perspective view of the metal material of embodiment 7 before machining, and (b) is a perspective view of the precision forged part after machining.

Fig. 20(a) and (b) are explanatory views showing steps of the precision forging method according to embodiment 7.

Fig. 21(a) is a perspective view of a metal material before machining according to embodiment 8, (b) is a perspective view of a precision forged product after machining according to embodiment 8, and (c) is a perspective view of a precision forged product after machining according to embodiment 9.

Fig. 22(a) and (b) are explanatory views showing steps of the precision forging method according to embodiment 8.

Fig. 23 is a cut cross section of a connecting portion between the outward flange and the peripheral wall of the cup when the drawn cup is cut in the axial direction after the shaving process of non-patent document 1.

Fig. 24 is an enlarged cross section of a portion surrounded by a square frame in fig. 23.

Detailed Description

A precision forging method, a precision forging apparatus, and a precision forged product according to embodiment 1 will be described with reference to fig. 1 and 2. First, the metal material 10 used in the present embodiment will be described.

< metallic Material 10>

As shown in fig. 1(a), the metal material 10 is not limited as long as it can be used in the plastic working method. Examples of the steel sheet used in the plastic working method include cold rolled high tensile steel sheets (SPFC, SPFCY, SPFH, sphy), cold rolled steel sheets (SPCC, SPCCT, SPCD, SPCE, SPCEN), SPP, and the like. Examples of stainless steel used in the plastic working method include SUS201, SUS304, SUS316, SUS321, SUS440, and SUS 450. Examples of the aluminum alloy wrought material used in the plastic working method include a3003, a3004, a5005, a2014, a2017, and a 2024. Further, as the metal material used in the plastic working method, alloy steel: SCr (chromium steel) material, SCM (chromium molybdenum steel) material, SNCM (nickel chromium molybdenum steel) material, and the like.

As shown in fig. 1(a), the shape of the metal material 10 used in the later-described step 1 has: a peripheral wall 14 which is a wall portion extending in a surrounding manner; and a bottom portion 12A integrally connected to the peripheral wall 14 at one end side of the peripheral wall 14, and having an opening at the other end. The method of forming the shape is not limited. For example, the metal sheet may be formed by drawing or cutting. The peripheral wall 14 extends in the 1 st direction as the axial direction thereof. The bottom portion 12A is extended in a direction intersecting with the axial direction (in detail, a direction perpendicular thereto), that is, in a radial direction from the peripheral wall 14, and is formed in a flat plate shape. The bottom portion is denoted by reference numeral "12A" before precision forging, i.e., before machining, and is denoted by reference numeral "12B" during and after precision forging. The bottom 12A corresponds to a projecting wall before processing. The bottom 12B corresponds to a protruding wall after machining.

The cross-sectional shape of the space 16 surrounded by the peripheral wall 14 may be circular, elliptical, gear-shaped, or square, but may be other shapes, and is not limited thereto.

< precision forging apparatus >

Next, the precision forging apparatus 50 used in the present embodiment will be described.

As shown in fig. 1(a) to 1(c) and 2(a), the precision forging apparatus 50 includes a die 20, a punch 30, a stopper 24, and a counter punch 40. In fig. 1(a) to 1(c), 2(a), and 4(a) to 4(f), for convenience of description, the punch 30, the counter punch 40, the stopper 24, and the die 20 are shown upside down so that the punch 30 is moved upward from below in the drawing during forging. That is, in the actual precision forging apparatus 50, the punch 30 is disposed above. The reverse punch 40 is disposed below and driven to allow the punch 30 to move downward from above during forging. The back pressure is applied to the counter punch 40 by an unillustrated air cylinder or the like. In other embodiments described below in embodiment 2, the punch 30, the counter punch 40, the die 20, and the like are also shown upside down so that the punch 30 is moved upward from below in the drawing during forging.

A die hole 22 is formed in the die 20. The cross-sectional shape of the punch hole 22 is circular in the present embodiment, but is not limited as long as it conforms to the outer shape of the peripheral wall 14. The stopper 24 is fixed to the inner circumferential surface of the punch hole 22 so as to be horizontal. The outer peripheral shape of the stopper portion 24 is preferably the same as the cross-sectional shape of the die hole 22 so as to follow the cross-sectional shape of the die hole 22. Therefore, in the present embodiment, the stopper portion 24 is formed in a circular ring shape in accordance with the outer shape of the metal material 10.

In order to follow the cross-sectional shape of the die hole 22 as described above, the stopper 24 is formed in a non-circular ring shape when the cross-sectional shape of the die hole 22 is a shape other than a circle. For example, when the cross-sectional shape of the die hole 22 is a polygonal shape such as a triangle, a quadrangle, a pentagon, or an oval, the outer shape of the stopper 24 may be conformed to those shapes.

Since the stopper 24 abuts the entire end surface of the peripheral wall 14 of the metal material 10, the thickness in the radial direction is the same as the thickness in the radial direction of the peripheral wall 14. The stopper 24 may be a locking stepped portion formed integrally with the die 20.

As shown in fig. 1(a) to 1(c) and 2(a), the machined end surface 31 of the punch 30 is formed flat, and a circular cutting edge 32 is formed over the entire periphery of the edge of the machined end surface in a plan view. The cutting edges 32 are disposed radially opposite to and apart from the inner circumferential surface of the punch hole 22. That is, the cutting edge 32 is disposed apart from the inner peripheral surface of the punch hole 22 with a gap S therebetween. The cutting edge 32 is formed so as to move continuous chips generated when cutting the bottom portion 12A (12B) of the metal material 10 toward the center portion (axial center) of the punch 30.

The punch 30 is formed to have a diameter smaller than the inner diameter of the die hole 22, and the punch 30 is disposed coaxially with the axial center of the die hole 22. When the punch 30 moves in the die hole 22, the peripheral edge of the bottom portion 12A (12B) of the metal material 10, which will be described later, that is, the portion located radially outward of the cutting edge 32 can remain in the gap S between the punch 30 and the inner peripheral surface of the die hole 22 as it is.

The counter punch 40 facing the punch 30 is disposed so as to enter a space surrounded by the peripheral wall 14 and the bottom portion 12A (12B) of the metal material 10 and to abut against the inner bottom surface of the bottom portion 12A (12B). Further, back pressure is applied to the counter punch 40 by an unillustrated air cylinder or the like, and the inner bottom surface of the bottom portion 12A (12B) is constantly pressed. The punch 30 corresponds to the 1 st punch, and the reverse punch 40 corresponds to the 2 nd punch. Further, the reverse punch 40 is not required and may not be present.

Next, the precision forging method according to the present embodiment will be described. Precision forging is sometimes referred to as cutting forging in this specification.

< precision forging method >

Next, the precision forging method will be described with reference to fig. 1(a) to 1(c), 2(a), 3(b), 4(a) to 4(f), 5, 6(a) to 6(d), and 7.

(1 st step)

As shown in fig. 1(a), in step 1, the metal material 10 having the bottom portion 12A and the peripheral wall 14 is placed in the die hole 22 of the die 20 of the precision forging apparatus 50, and the tip end surface of the peripheral wall 14 is brought into contact with the stopper 24. In this state, the peripheral wall 14 extends along the moving direction of the punch 30 inside the die hole 22, and the bottom portion 12A extends in a direction intersecting the moving direction. Here, the moving direction of the punch 30 coincides with the axial center direction of the peripheral wall 14. The outer peripheral surface of the peripheral wall 14 is in surface contact with the inner peripheral surface of the die hole 22. The area of surface contact of the outer peripheral surface of the peripheral wall 14 corresponds to the fitting area. In the present embodiment, the entire outer peripheral surface of the peripheral wall 14 is set as the fitting region and is brought into surface contact with the inner peripheral surface of the die hole 22, but the fitting region is not limited to the entire outer peripheral surface of the peripheral wall 14. Only a part of the outer peripheral surface of the peripheral wall 14 in the axial direction may be in surface contact with the inner peripheral surface of the die hole 22, and this part may be used as the fitting region. The bottom 12A extends from the peripheral wall 14 in a direction opposite the mating area of the peripheral wall 14. The radial direction of the peripheral wall 14 coincides with the thickness direction of the peripheral wall 14. The punch 30 is disposed in the die hole 22 so as to face the axial direction of the peripheral wall 14 with respect to a part of the peripheral wall 14 in the thickness direction and the bottom portion 12A. A part of the peripheral wall 14 facing the punch 30 in the thickness direction is a region of the peripheral wall 14 located on the inner peripheral side of the outer peripheral edge of the cutting edge 32. In the present embodiment, the punch 30 is opposed to a part of the peripheral wall 14 in the thickness direction, but the punch 30 may be opposed to the entire peripheral wall 14 in the thickness direction depending on the position where the cutting edge 32 is provided.

(step 2)

In the 2 nd step, the punch 30 is moved toward the bottom portion 12A, and pressed by the cutting edge 32 while cutting the bottom portion 12A (see fig. 1(b), 1(c), and 4(a) to 4 (f)). At this time, the metal material 10 is held by the stopper 24 in the moving direction of the punch 30. The amount of movement of the punch 30 from the position where the punch 30 first contacts the bottom 12A is within a range of not less than the thickness of the bottom 12A and less than the height h (see fig. 1 a) of the peripheral wall 14.

When the punch 30 presses the bottom portion 12A and cuts a portion of the peripheral wall 14 in the thickness direction with the cutting edge 32, a joining line a of the bottom portion 12A (12B) with which the cutting edge 32 touches is formed as shown in fig. 2 (a). The joining line a is formed continuously with the joining portion of the remaining portion of the peripheral wall 14 and the bottom portion 12A (12B) which is not cut by the cutting edge 32, as shown in fig. 2 (a). In the present embodiment, the joining line a is formed in the circumferential direction of the peripheral wall 14. Shear deformation is caused by the cutting edge 32 between the joining line a and the peripheral edge portion of the inner surface of the bottom portion 12A (12B). The peripheral edge portion of the inner surface of the bottom portion 12A (12B) is also a joining line B between the bottom portion 12B and the peripheral wall 14. The joining line B of the present embodiment is formed continuously in the circumferential direction with the bottom portion 12A (12B) interposed therebetween at the corner on the opposite side to the punch 30. The material (chips) sheared by the cutting edge 32 flows into the bottom portion 12A (12B) (also referred to as a node) between the punch 30 and the counter punch 40, and a forging flow line W is formed between the joining line a and the joining line B in fig. 2A. Hereinafter, the portion after cutting and forging corresponding to the joining line a is referred to as a peripheral edge portion a of the bottom portion 12B.

The inner bottom surface of the bottom portion 12B located on the side where the joining line B is located corresponds to the 2 nd surface, and the outer bottom surface of the bottom portion 12B located on the side opposite to the inner bottom surface corresponds to the 1 st surface. The forging flow line W extends from the joining line a of the 1 st face (outer bottom face) to the 2 nd face (inner bottom face).

The bottom portions 12A and 12B are bound by the die 20 so as not to change in size in a direction intersecting the moving direction of the punch 30 as shown in fig. 1(a) to 1 (c). Therefore, as the machining of the punch 30 progresses, the material (chips) moves while being compressed toward the joint, and the thickness of the joint increases.

The flow of the metal material 10 at this time will be described in detail later.

Back pressure F given to the counter punch 40_bSufficiently smaller than the pressing force F of the punch 30, i.e., F_b< F. When the thickness of the segment increases as described above, the reverse punch 40 is retracted against a biasing force (back pressure) applied from an unillustrated air cylinder or the like.

As shown in fig. 1(c) and 2(a), when the punch 30 moves while pressing the bottom portion 12A (12B), a portion of the peripheral wall 14 located radially outward of the cutting edge 32, that is, an engagement region in surface contact with the inner peripheral surface of the die hole 22 remains intact, and is located at a position where the gap S between the die 20 and the punch 30 is partially filled. The fitting region of the peripheral wall 14 is formed in a cylindrical shape. As a result, a precision forged product having peripheral walls on both surfaces of the bottom portion 12B, that is, a precision forged product having an H-shaped longitudinal section can be obtained.

Here, the pressing force p per unit area of the punch 30 required for the machining is estimated based on the energy U required for the machining as follows.

(2 k: deformation resistance of metallic Material, t_c: the thickness of the segments is such that,shear angle, d: diameter of the punch 30, μ: coefficient of friction)

In addition to this, the present invention is,expressed by the following equation.

< derivation of equation (3) >

The derivation of the above formula (3) will be described below.

As shown in fig. 2(a), the length of the punch 30 extending radially outward from the inner peripheral surface of the peripheral wall 14 is t₀When the cutting ratio r is

Furthermore, t₀The difference between the radius of the inner peripheral surface of the peripheral wall 14 and the radius of the punch 30 is the amount of cutting of the punch 30 in the radial direction of the peripheral wall 14.

The speed V of the chip (chip) of the shearing zone moving radially of the punch 30, according to the retention of the mass of the material being sheared_cIs that

Further, V is the speed of the punch 30. Shear rate V_sWhen vector decomposition is performed as shown in FIG. 2(b), thenAll the energy U input by the punch 30 during machining is U ═ F · V.

F is the pressing force of the punch 30. Energy E at shearing required for shearing a region_sCan be estimated by the following formula.

E_s＝π·d(t₀ ²+t_c ²)^1/2V_s·k......(7)

k is the shear resistance (deformation resistance) of the metal material. d is the diameter of the punch 30. Here, the energy E required for compressing the chips in the radial direction_cThe calculation can be as follows.

E_c＝2π·d·t_c·k·V_c......(8)

Energy E dissipated due to friction between the chip and the punch 30_fCan be calculated by the following equation.

E_f＝μ·F·V_c......(9)

μ is the coefficient of friction between the chip and the punch 30. When the back pressure (force application) of the reverse punch 40 is F_bTaking the energy of the back pressure as E_bWhen the temperature of the water is higher than the set temperature,

E_b＝F_b·V......(10)。

because U is E_s+E_c+E_f+E_b......(11)

Therefore, the pressing force F of the punch 30 is expressed by the following equation.

Here, because F_b< F, so that F is_bWhen the average pressing force p (per unit area) of the punch 30 is set to a negligibly small value, the average pressing force p is expressed by equation (3).

In addition, in a general sense,is in the range of 0.1 to 1.0, mu is in the range of 0.1 to 0.3, so that p/2k is 3t_c/d～12t_c/d。

Because of t_cSince the ratio/d is in the range of 0.01 to 0.1, p/2k is less than 1, and is considerably smaller than that in the case of conventional cold forging.

< flow of Metal Material 10>

Here, the flow of the metal material 10 generated by the cutting forging of the 2 nd step was confirmed by a simulation experiment. The simulation experiment software used was the commercial finite element analysis code DEFORM 2D. The conditions of the simulation experiment are shown in table 1.

[ Table 1]

Simulation of the conditions of the experiment

Parameter(s)	Unit of	Value of
			Flow stress of work	MPa	σ＝Cεn
Coefficient of plasticity, C, of work	MPa	501
			Work Cure index, n		0.24
Inner diameter of work piece, dw	mm	60
			Thickness of peripheral wall of work piece, tw	mm	2
Thickness of the bottom of the work, tc0	mm	2
			Radius of corner R of work piece Rc	mm	0.1-3.5
Diameter of the punch, d	mm	60-64
			Radius of the punch shoulder, rp	mm	0.1
Speed of the punch, V	mm/s	10
			Diameter of reverse punch, dcp	mm	60
Reverse punch shoulder radius, rcp	mm	0.1-3.5
			Back pressure of the reverse punch, pb/C		0.005-0.05
Coefficient of friction with die, mud		0.1
			Coefficient of friction with the counter punch, mucp		0.1
Coefficient of friction with the punch, mup		0.1-0.5

Fig. 3(a) is a sectional view of the metal material 10 before the cutting forging. As shown in the drawing, points a1 to a3 are indicated at a plurality of points on the upper surface (inner surface) of the bottom portion 12A, points a4 to a6 are indicated at a plurality of points on the inner peripheral surface of the peripheral wall 14, points b1 to b4 are indicated at a plurality of points on the lower surface (outer surface) of the bottom portion 12A, and points c1 to c4 are indicated at points on the movement locus of the cutting edge 32 of the punch 30.

Fig. 3(b) is a cross-sectional view of the metal material 10 after completion of the cutting and forging of the punch 30, which is obtained by a simulation experiment. As shown in the figure, the points a 1-a 3 and the points B1-B4 of the bottom portion 12B move toward the radial center of the bottom portion 12B. Further, a plurality of points a 4-a 6 on the inner peripheral surface of the peripheral wall 14 move on the upper surface of the bottom portion 12B.

All of points c1 to c4 located on the movement trajectory of the cutting edge 32 shown in fig. 3(a) move on the lower surface of the bottom portion 12B. From this, it is understood that work hardening by the cutting forging contributes to product strength such as pressure resistance of the bottom portion 12B.

Fig. 5 is a characteristic diagram of p (pressure)/C with respect to the stroke of the punch 30 in the example of the simulation experiment.

In fig. 5, points Q1 to Q3 correspond to the stages shown in fig. 4(b), 4(d), and 4(f), respectively. Fig. 4(a) is a sectional view of the vicinity of the corner of the punch at the initial stage of the cutting forging, and fig. 4(b) is an enlarged sectional view of fig. 4 (a). Fig. 4(c) is a cross-sectional view of the punch at a later stage than fig. 4(a) near the corner, and fig. 4(d) is an enlarged cross-sectional view of fig. 4 (c). Fig. 4(e) is a cross-sectional view of the punch at a later stage than fig. 4(c) near the corner, and fig. 4(f) is an enlarged cross-sectional view of fig. 4 (e). In fig. 4(B), 4(d) and 4(f), the region between the bottom portion 12A (12B) and the peripheral wall 14 and the region connecting the peripheral edge portions A, B of the upper and lower surfaces of the bottom portion 12B are regions where shear stress concentrates in the cutting forging. The region where the stress is concentrated is indicated by hatching oriented in a direction different from hatching at the other portions of the bottom portion 12A (12B) and the peripheral wall 14. In addition, similarly to fig. 6(b) to 6(d) described later, the region where the stress is concentrated is indicated by hatching oriented differently from other portions.

As shown in fig. 4(a) to 4(f), the punch 30 moves by a distance equal to or greater than the thickness of the bottom portion 12A after coming into contact with the bottom portion 12A. The bottom portion 12B is moved in the same direction as the punch 30 by the movement of the punch 30 and the shear deformation between the punch 30 and the counter punch 40 accompanying the movement. It can be confirmed that: the bottom 12B remains almost flat and does not swell locally under the conditions of the simulation experiment. It can be confirmed that: in the vicinity of the upper surface (inner surface) of the bottom portion 12B and the corner of the counter punch 40, a slightly recessed concave portion having a gentle concavity is formed. That is, it can be confirmed that the thickness of the bottom portion 12B is slightly thinned in the vicinity of the corner of the reverse punch 40. In addition, it was confirmed that: the concave portion having a gentle concavity formed on the upper surface of the bottom portion 12B is enlarged toward the radial center side of the bottom portion 12B as the stroke of the punch 30 is increased.

As shown in fig. 5, when the stroke (moving amount) of the punch 30 increases from the point Q1, the pressing force of the punch 30 rapidly increases. The pressure of the punch 30 gradually increases from the point Q2 at which the edge portion (cutting edge 32) of the punch 30 reaches the shear region. Also, in the shear region including the point Q3, the pressure of the punch 30 is stabilized.

Although not shown, it was confirmed that the shape of the observed product hardly changed in a simulation experiment in which the magnitude of the back pressure of the reverse punch 40 was changed a plurality of times.

< recesses and sink marks having gentle concavities >

In the simulation experiment, a case where a concave portion having a gentle concave surface is generated as described above and a case where a concave portion having a sharp shape (hereinafter referred to as sink mark) is generated were observed. It is considered that the concave portion and the sink mark having a gentle concave surface are related to the radius of curvature on the joining line B of the inner surface of the bottom portion 12A opposed to the corner of the counter punch 40. Hereinafter, the radius of curvature at the joining line B of the inner surface of the bottom portion 12A may be referred to as a shoulder radius. If the shoulder radius is large, the metal material becomes insufficient at the joining line B of the inner surface of the bottom portion 12A at the initial stage of the cutting process.

When the concave portion having a gentle concave surface is generated, as shown in fig. 4(b), stress concentrates on the point a in the initial stage of shear deformation. As shown in fig. 4(d) and 4(f), the following are observed: the concave portion having a gentle concave surface becomes large as the shear deformation proceeds.

On the other hand, examples of simulation experiments in which sink marks occur are shown in fig. 6(a) to 6 (d). FIG. 6(a) shows the shoulder radius r of the junction line B of the inner surface of the bottom portion 12A_cp2mm, and the moving amount of the punch 30 is 0. No stress appears in the state before the cutting process shown in fig. 6 (a). Fig. 6(B) to 6(d) show that when the movement amounts of the punch 30 are changed to 1mm, 3mm, and 6mm from the state of fig. 6(a), a sharp sink mark is generated in the vicinity of the joining line B of the inner surface of the bottom portion 12B, and the size of the sink mark increases as the movement amount increases. In the example of fig. 6(d), the sink mark grows to a length of approximately 30% of the thickness of the bottom portion 12B.

Here, the boundary region in the case where the concave portion having the gentle concave surface is generated and the boundary region in the case where the sink mark is generated are searched for by the simulation experiment. As an example of the simulation experiment, SPCC and t are used for the metal material 10₀1mm, and is set tot_c(＝t_c0) 1mm, 2mm, 4mm, and d 62 mm. I.e., the amount of bisection of the insertion t₀And the thickness t of the bottom 12A_c0The simulation experiment was performed for a plurality of combinations of (2) to (3) to obtain a plurality of simulation experiment results H1 to H5, J1 to J9, and L1 to L5 (see fig. 7).

p_b/C

The flow stress σ is set to 501 ∈^0.24MPa, back pressure p of the reverse punch 40_bset/C to 0.005 and set the coefficient of friction between the reverse punch 40 and the metal material to μ_pIs set to mu_p＝0.1。t_c0Is the thickness t of the bottom portion 12A of the metal material 10 before the cutting forging_c0。

The results of the simulation experiment are shown in the characteristic diagram of fig. 7. In FIG. 7, the vertical axis is t₀/t_c0The horizontal axis is r_cp/t_c0. As shown in the figure, by basing on (r)_cp，t₀/t_c0) The results of the multiple simulation experiments H1 to H5, J1 to J9, and L1 to L6 were subjected to regression analysis to determine t which was classified into the case where sink marks were generated and the case where concave portions N having gentle concavities were generated without generating sink marks₀/t_c0The line of (2). The right side of inequalities (1), (2), (13) to (16) described later is a formula representing the line.

H1-H5 are t_c0Results of simulation experiments in the case of 1mm, J1 to J9 represent t_c0Results of simulation experiments in the case of 2mm, L1 to L6 are t_c0Simulation test results in case of 4 mm. Further, the diameter of the punch 30 is 2t larger than the inner diameter of the peripheral wall 14₀mm。

<Thickness t of bottom 12A_c0＝1mm、r_cp/t_c0<2.0 case>

t₀/t_c0≥0.052r_cp/t_c0+0.23......(1)

Thus, the thickness t at the bottom 12A_c0Is 1mm, and r_cp/t_c0In the case of < 2.0, it is preferable to set the condition so as to satisfy inequality (1) in order to prevent sink marks.

<Thickness t of bottom 12A_c0＝1mm、r_cp/t_c0Case of ≧ 2.0>

t₀/t_c0≥3.0r_cp/t_c0-5.7......(2)

Thus, at t_c0Is 1mm, and r_cp/t_c0In the case of ≧ 2.0, the condition is preferably set so as to satisfy inequality (2) in order to prevent sink marks.

<Thickness t of bottom 12A_c0＝2mm、r_cp/t_c0<1.5 cases>

t₀/t_c0≥0.106r_cp/t_c0+0.23......(13)

Thus, at t_c0Is 2mm, and r_cp/t_c0If < 1.5, the condition is preferably set to satisfy inequality (13) in order to prevent sink marks.

<Thickness t of bottom 12A_c0＝2mm、r_cp/t_c0Case of ≧ 1.5>

t₀/t_c0≥2.1r_cp/t_c0-2.8......(14)

Thus, at t_c02mm and r_cp/t_c0In the case of ≧ 1.5, the condition is preferably set so as to satisfy the inequality (14).

<Thickness t of bottom 12A_c0＝4mm、r_cp/t_c0<1.5 cases>

t₀/t_c0≥0.067r_cp/t_c0+0.23......(15)

Thus, at t_c0Is 4mm, and r_cp/t_c0<In the case of 1.5, it is preferable to set the condition so as to satisfy inequality (15) in order to prevent sink marks.

<Thickness t of bottom 12A_c0＝4mm、r_cp/t_c0Case of ≧ 1.5>

t₀/t_c0≥0.66r_cp/t_c0-0.64......(16)

Thus, at t_c0Is 4mm, and r_cp/t_c0In the case of ≧ 1.5, the condition is preferably set so as to satisfy the inequality (16) in order to prevent sink marks.

In addition, even if sink marks occur, there may be cases where there is no problem with sink marks, and therefore the numerical values and inequalities (1), (2), (13) to (16) are not limited thereto.

The description will be made based on the results of a simulation experiment in which the thickness of the bottom portion 12A is set to 1mm, 2mm, or 4 mm. However, for example, in the case where the thickness available on the market is 0.1mm, even the "thickness t of the bottom portion 12A" is_c0＝0.1mm、r_cp/t_c0If the condition is set to satisfy inequality (1) < 2.0 ", a concave portion having a gentle concave surface without sink marks can be reliably obtained.

In addition, even at "the thickness t of the bottom portion 12A_c0＝0.1mm、r_cp/t_c0In the case of ≧ 2.0 ", if the condition is set so as to satisfy inequality (2), a concave portion having a gentle concave surface without generating sink marks can be reliably obtained.

Also in the case of an extremely thick bottom, for example, in the case of "thickness t of bottom 12A_c0＝20mm、r_cp/t_c0If the condition is set to satisfy inequality (1) in the case of < 2.0 ″, a concave portion having a gentle concave surface without sink marks can be obtained.

In addition, even the "thickness t of the bottom portion 12A_c0＝20mm、r_cp/t_c0In the case of ≧ 2.0 ", by setting the condition so as to satisfy inequality (2), a concave portion having a gentle concave surface without generating sink marks can be obtained.

The present embodiment has the following features.

(1) The precision forging method of the present embodiment includes: a metal material having a wall portion 14 extending in the moving direction of the punch and a bottom portion 12A (projecting wall before machining) extending from the wall portion 14 in the direction intersecting the moving direction is disposed in a die hole 22 of a die 20, and the metal material 10 is forged by the movement of the punch 30.

In step 1, a punch 30 having a machined end surface 31 and a cutting edge 32 formed at an edge of the machined end surface 31 is disposed in the die hole 22 so as to face a part of the wall portion 14 of the metal material 10 in the thickness direction and the bottom portion 12A (projecting wall before machining).

In the 2 nd step, the punch 30 is moved within the height range of the wall portion 14 while holding the metal material 10 in the moving direction of the punch 30 and holding the length of the bottom portion 12A (projecting wall before machining) in the intersecting direction, whereby a part of the wall portion 14 in the thickness direction is cut by the cutting edge on the moving path of the punch 30 and the cut portion is shear-deformed so as to move in the direction of the bottom portion 12A (projecting wall before machining). When the punch 30 faces the entire thickness direction of the peripheral wall 14, the punch 30 cuts the entire thickness direction of the peripheral wall 14 with a cutting edge on the moving path, and the cut portion moves in the direction of the bottom portion 12A (projecting wall before machining) to cause shear deformation in the cut portion.

As a result, according to the present embodiment, it is possible to perform precision forging with a small tool pressure, unlike the conventional one. That is, excessive tool pressure in precision forging can be avoided. Further, since the chip generating mechanism in the cutting process is applied to the forging process, chips can be generated as a part of the product without being separated from the metal material. Further, since an excessive tool pressure is not required, it can be applied to precision forging of a hollow member made of a high-strength material having a large size and a complicated cross-sectional shape.

In the 2 nd step, since the dimension of the bottom portion 12A (projecting wall before machining) in the intersecting direction is maintained, the risk of material cracking can be eliminated at the cut portion of the peripheral wall opposite to the cutting edge of the punch. The precision forging method according to the present embodiment may be referred to as a cutting forging method as a new concept, and may be referred to as a third basic construction method in addition to two basic construction methods of upsetting and extruding.

(2) In the precision forging method according to the present embodiment, in step 1, the metal material 10 having the wall portion 14 having the fitting region at least partially in surface contact with the inner surface of the die hole 22 and the bottom portion 12A (projecting wall before machining) located on the opposite side of the fitting region is disposed in the die hole 22, and the cutting edge 32 of the punch 30 is disposed apart from the inner surface of the die hole 22 by at least a thickness smaller than the wall portion 14. In step 2, the cutting edge 32 cuts into the metal material 10 so that the fitting region of the wall portion 14 remains. As a result, when the fitting region remains, the remaining portion of the peripheral wall 14 can be formed in a tubular shape. Further, unlike the present embodiment, when the entire engagement region is moved in the direction of the bottom (pre-machining projecting wall) by a punch omitting the cutting edge 32, the portion is deformed to form a non-cylindrical shape.

(3) In the precision forging method according to the present embodiment, when the punch 30 is the 1 st punch, the reverse punch 40 as the 2 nd punch is disposed on the opposite side of the punch 30 as the 1 st punch with the bottom portion 12A interposed therebetween. In step 2, the reverse punch 40 moves following the movement of the punch 30 in the moving direction.

As a result, the chips of the sheared and removed material are moved toward the node (bottom) by the reverse punch to which a certain back pressure is applied, and compressed, and a solidified portion can be formed at the bottom.

(4) In the precision forging method of the present embodiment, the cutting depth is t₀At this time, the radial length of the punch 30 is 2t greater than the inner diameter of the peripheral wall 14₀mm. Radius at shoulder r_cpAnd the thickness t of the bottom 12A (projecting wall before machining)_c0Satisfy r_cp/t_c0In the case of < 2.0, t is₀/t_c0The metal material 10 is processed so as to satisfy the following inequality (1).

t₀/t_c0≥0.052r_cp/t_c0+0.23......(1)

In addition, at shoulder radius r_cpAnd the thickness t of the bottom 12A (projecting wall before machining)_c0Satisfy r_cpWhen/tc 0 is not less than 2.0, t is₀/t_c0The metal material 10 is processed so as to satisfy the following inequality (2).

t₀/t_c0≥3.0r_cp/t_c0-5.7......(2)

As a result, when the inequality (1) or the inequality (2) is satisfied, a precision forged product having no sink mark can be obtained.

(5) In the precision forging method according to the present embodiment, in the 2 nd step, the stopper 24 abuts on the distal end surface of the peripheral wall 14, and the metal material 10 (specifically, the peripheral wall 14 as the wall portion) is held in the moving direction of the punch 30. As a result, in step 2, the cutting process can be efficiently performed.

(6) The precision forging apparatus includes a die 20 and a punch 30. The metal material 10 is disposed in the die hole 22, and the metal material 10 has a peripheral wall 14 extending along the moving direction of the punch 30 and a bottom portion 12A extending from the peripheral wall 14 in a direction intersecting the moving direction. The metal material 10 is manufactured by the movement of the punch 30. The punch 30 is disposed to face a part of the peripheral wall 14 in the thickness direction and the bottom portion 12A when the metal material 10 is disposed in the punch hole 22. The punch 30 has a machined end surface and a cutting edge 32 formed at an edge of the machined end surface. When the punch 30 moves within the height range of the peripheral wall 14, the cutting edge 32 cuts a portion of the peripheral wall 14 in the thickness direction on the moving path of the punch 30, and causes shear deformation of the cut portion.

As a result, unlike the conventional art, a precision forging apparatus can be obtained which can perform precision forging with a small tool pressure, that is, which can avoid an excessive tool pressure in precision forging.

Further, since the chip generation mechanism in the cutting process is applied to the forging process, a precision forging apparatus can be obtained in which chips can be generated as a part of a product without being separated from a metal material. Further, according to the precision forging apparatus, since an excessive tool pressure is not required, it is possible to perform precision forging of a hollow member made of a high-strength material having a large size and a complicated cross-sectional shape.

(7) The precision forging apparatus of the present embodiment includes the stopper 24, and when the punch 30 moves within the height range of the peripheral wall 14, the stopper 24 abuts against the distal end surface of the peripheral wall 14 so as to hold the metal material 10 in the moving direction of the punch 30. As a result, a precision forging apparatus capable of efficiently performing cutting can be obtained.

(8) The precision forged part of the present embodiment includes: a peripheral wall 14 extending in a1 st direction as an axial direction; and a bottom portion 12B extending from the peripheral wall 14 in a2 nd direction which is a radial direction intersecting the 1 st direction. The bottom portion 12B has: a1 st surface located on a side where a joining line a between the peripheral wall 14 and the bottom 12B is located; and a2 nd surface on the opposite side of the 1 st surface. The precision forging has a forging flow line extending from the joining line a to the joining line B of the 2 nd face. As a result, the precision forged product can be produced by a precision forging apparatus which does not require excessive tool pressure. That is, the precision forged material of the present embodiment can be obtained with a small tool pressure. That is, the precision forged material according to the present embodiment can avoid excessive tool pressure in precision forging. Further, chips generated during the cutting process can be generated as a part of the precision forged material without being separated. Further, since the precision forged material does not require an excessive tool pressure, it can be formed into a hollow member made of a high-strength material having a large size and a complicated cross-sectional shape.

(9) The precision forging of the present embodiment has a peripheral wall 14 extending in a surrounding manner as a wall portion, and has a bottom portion 12B formed on an inner surface of the peripheral wall 14. As a result, the above-described operational effect (8) can be achieved as a precision forged part having a peripheral wall and a bottom portion.

(examples)

Next, an embodiment will be described with reference to fig. 8(a) to 8(d), 9(a), 9(b), and 10. The conditions of the examples are shown in Table 2.

[ Table 2]

Conditions of the examples

Here, the flow stress σ of the metal material 10 is set to 501 ∈^0.24MPa. The initial flow stress of the metal material 10 was 193MPa, and the plastic modulus of the metal material 10 was 501 MPa. The metal material 10 is formed by a process of forming a thin filmA round plate having a diameter of 100mm was cut from 1.93mm cold rolled steel. All tools used in this manufacturing method were formed of high-speed tool steel (SKH51(═ HRC 63)). In addition, the forging tool is coated with TiAlN to prevent scratches. Further, G-3764 (prepared from Japanese working oil, viscosity at 40 ℃ C.: 550X 10)^-6m²As lubricating oil. The forging process was performed by a 1100KN servo press. The load of the punch 30 during forging is measured by a strain gauge provided on the rear plate of the punch 30. Further, the back pressure of the reverse punch 40 is given by a cylinder.

As shown in the drawing conditions of table 2, a metal material 10 (see fig. 8(a)) of a steel sheet (thickness 1.93mm) made of SPCC was subjected to drawing, and as shown in fig. 8(b), a cup-shaped metal material 10 having a peripheral wall 14 formed on the peripheral edges of a bottom portion 12 and a bottom portion 12 was obtained. In this drawing, the diameter of a punch (not shown), the diameter of a die (not shown), and the radius of a die shoulder were 60mm, 64.2mm, and 12mm, respectively.

By this drawing, the radius of curvature (punch shoulder radius) at the joining line B (see fig. 8B) of the inner surface of the bottom portion 12 was set to 10 mm.

Then, further ironing is performed to form a forging material cup shown in fig. 8 (c). The diameters of a punch (not shown) and a die (not shown) used for the ironing are 60mm and 63.66mm, respectively. By this ironing, the radius of curvature (punch shoulder radius) at the joining line B of the inner surface of the bottom portion 12 was set to 0.1 mm.

Next, the cutting amount t to the forging material cup is set by using a precision forging apparatus 50 (see fig. 1(a) and the like)₀Cutting forging was performed with the speed V of the punch 30 set to 5.8mm/s, respectively at 1.0mm and 2.0 mm. The die 20 used for the cutting forging is the same as the die used for the ironing, and the cutting depth t is the same as the cutting depth t₀In the case of 1.0mm, a punch 30 having a diameter of 62mm and a die 20 having a diameter of 63.66mm were used. In addition, the reverse punch 40 uses a reverse punch having a diameter of 60 mm. The back pressure of the counter punch 40 was 0.05. The punch 30 moves within a range of not less than the thickness of the bottom portion 12 and not more than the height of the peripheral wall 14.

In the conventional shearing (punching) process, the punch moves by more than the thickness of the plate material from the state of being in contact with the plate material, but the bottom portion pressed by the punch breaks. In contrast, in the present embodiment, the bottom portion does not break, but moves within the height range of the peripheral wall in accordance with the movement of the punch.

In the conventional half blanking process, the punch is moved from a state of being in contact with the plate material by a movement amount not exceeding the thickness of the plate material. In contrast, in the present embodiment, the bottom portion moves within the height range of the peripheral wall in accordance with the movement of the punch.

By this cutting and forging, the radius of curvature of the inner and outer surfaces of the peripheral edge portion of the bottom portion 12 was set to 0.1 mm. By this cutting forging, the material constituting the bottom portion 12 can be freely moved without being damaged. As a result of measuring the load of the punch 30 with the strain gauge, the pressing force p/C of the punch 30 required for the machining is about 0.3 times the plastic coefficient of the metal material 10.

The photographs of the sections of the bottom portion 12 and the peripheral wall 14, which were obtained by cutting the precision forged material formed as described above in the height direction, are shown in fig. 9(a) and 9 (b).

The lower line appears in fig. 9 (a): this line is clearly shown by a broken line in fig. 9(b), and indicates a forging flow line W of a portion subjected to shear deformation by the cutting forging. The forging flow line W is peculiar to the cutting forging method, and the elimination of the forging flow line W requires heat treatment of a precision forging, which requires large cost. Further, when fig. 23 and 24 of the conventional example and fig. 9(a) and 9(b) of the present example are compared, it can be confirmed that the forging flow line W is not present in the conventional example.

Fig. 10 shows the results of measuring the vickers hardness at a plurality of points in the shear region (the region of the bottom portion 12 on the left side of the forging flow line W in fig. 9 (b)) in which shear deformation occurs and the region around the shear region in the cross section of the precision forged material formed as described above. The values represent vickers hardness. As shown in fig. 10, the vickers hardness of the shear region is about 2 times higher than that of the portion near the outer surface of the peripheral wall 14 of the precision forged material, and the shear region is harder than the peripheral region.

(embodiment 2)

Next, a precision forging apparatus and a precision forged material according to embodiment 2 will be described with reference to fig. 11(a) to 11(d), and fig. 12(a) and 12 (b). In the following embodiments including the present embodiment, the same reference numerals are given to the same or equivalent parts as those of embodiment 1 in the drawings.

As shown in fig. 11(a) and 11(b), the metal material 10 before processing in the present embodiment includes a cylindrical peripheral wall 14 and a bottom portion 12A integrally connected to a lower portion of the peripheral wall 14, as in embodiment 1. However, the bottom portion 12 of embodiment 1 is formed in a flat plate shape extending in a direction intersecting the axial direction, i.e., in a radial direction, but the bottom portion 12A of the present embodiment is different in that its outer surface is a concave surface which is a part of a spherical surface and its inner surface is a convex surface which is a part of a spherical surface.

As shown by the two-dot chain line in fig. 11(b), the bottom portion 12A may be formed such that the outer surface is a convex surface that is a part of a spherical surface and the inner surface is a concave surface that is a part of a spherical surface.

Alternatively, although not shown, both the inner and outer surfaces of the bottom portion 12A may be concave surfaces that are a part of a spherical surface, or may be convex surfaces that are a part of a spherical surface. That is, the planar shape and the sectional shape of the bottom surface 12A are not limited.

The precision forging apparatus 50 used in the present embodiment will be explained.

As shown in fig. 12(a) and 12(b), the precision forging apparatus 500 includes a die 20, a punch 30, a stopper 24, and a counter punch 40, as in embodiment 1, and the die 20 includes a die hole 22.

In embodiment 1, the machined end surface 31 of the punch 30 is formed flat. In contrast, in the present embodiment, as shown in fig. 12(a) and 12(b), the machining end surface 31 of the punch 30 is formed to be convex so as to follow the outer surface of the bottom portion 12A of the metal material 10. That is, as shown in fig. 12(a), the machined end surface 31 is a convex surface which is a part of a spherical surface so as to follow the concave surface of the outer surface of the bottom portion 12A.

As shown in fig. 12(a) and 12(b), a cutting edge 32 is formed on the entire periphery of the edge of the machined end surface 31 of the punch 30. The cutting edge 32 is formed to move continuous chips generated when cutting the bottom portion 12A (12B) of the metal material 10 toward the center portion (axial center) of the punch 30, as in embodiment 1. The other structures are the same as those of embodiment 1.

Since the precision forging method in embodiment 2 is the same as embodiment 1, step 1 is illustrated in fig. 12(a), and step 2 is illustrated in fig. 12(b) instead of the detailed description.

Fig. 11(c) is a perspective view of the precision forged product after machining, and fig. 11(d) is a longitudinal sectional view of the precision forged product after machining. In fig. 11(d), the bottom portion 12B indicated by the two-dot chain line is a bottom portion 12B of a precision forged product obtained by machining the metal material 10 before machining having the bottom portion 12A indicated by the two-dot chain line in fig. 11 (B). Although not shown in the drawings, the machining end surface 31 of the punch 30 is formed on the concave surface so as to follow the outer surface of the bottom portion 12A of the metal material 10.

The same effects as those described in (1) to (8) of embodiment 1 can be obtained in this embodiment as well.

(embodiment 3)

Next, a precision forging apparatus and a precision forged material according to embodiment 3 will be described with reference to fig. 13(a) to 13(d), and fig. 14(a) and 14 (b).

As shown in fig. 13(a) and 13(b), the metal material 10 before machining according to the present embodiment includes, in the same manner as in embodiment 1: a cylindrical peripheral wall 14; a top wall 15 integrally connected to the peripheral wall 14 so as to close an opening at one end of the peripheral wall 14; and an outward flange 17A integrally connected to the outer peripheral surface of the other end of the peripheral wall 14 and extending radially outward. The peripheral wall 14 extends in the 1 st direction as the axial direction thereof. The flange 17A is extended in a direction intersecting the axial direction, i.e., in a radial direction, and is formed in a flat plate shape.

The top wall 15 is formed in a flat plate shape extending in a direction intersecting the axial direction, i.e., in a radial direction, but is not limited to the flat plate shape, and may have an outer surface which is a concave surface as a part of a spherical surface and an inner surface which is a convex surface as a part of the spherical surface. Conversely, the top wall 15 may have an outer surface that is a convex surface that is a part of a spherical surface and an inner surface that is a concave surface that is a part of a spherical surface. Alternatively, although not shown, both the inner and outer surfaces of the top wall 15 may be concave surfaces that are part of a spherical surface, or convex surfaces that are part of a spherical surface. That is, the planar shape and the sectional shape of the top wall 15 are not limited.

The precision forging apparatus 50 used in the present embodiment will be explained.

As shown in fig. 14(a) and 14(b), the precision forging apparatus 50 includes a die 20, a punch 30, a stopper 24, an ejector 25, and a reverse punch 40, and the die 20 has a die hole 22. The cross-sectional shape of the die hole 22 is formed in a circular shape, but is not limited thereto, and may be formed in other shapes. The cross-sectional shape of the die hole 22 may be formed in a shape conforming to the outer shape of the flange 17A or in a shape not conforming thereto. When the inner surface of the die hole 22 is not uniform, the flange 17A may have a shape at least partially in surface contact with the inner surface. In the present embodiment, the flange 17A is formed in a shape conforming to the inner surface of the die hole 22 as a whole.

As shown in fig. 14(a) and 14(b), the punch 30 is formed in a cylindrical shape. The punch 30 has the same outer diameter as the inner diameter of the die hole 22, and a cutting edge 32 is formed at an end edge on the inner peripheral side of the punch 30. The cutting edge 32 is formed so as to move continuous chips generated when cutting the peripheral wall 14 of the metal material 10 radially outward.

The cutting edge 32 of the punch 30 has an inner diameter longer than the inner diameter of the peripheral wall 14 and shorter than the outer diameter of the peripheral wall 14, and the cutting edge 32 of the punch 30 is disposed coaxially with the axis of the die hole 22. That is, the cutting edge 32 is formed at a position inside the side (outer peripheral surface) of the flange 17A in contact with the inner surface of the die hole 22. Thus, the punch 30 is disposed to face the flange 17A and a part of the peripheral wall 14 in the thickness direction. The cutting edge 32 is disposed so as to be able to cause shear deformation in a portion of the peripheral wall 14 in the thickness direction, that is, in an outer peripheral region of the peripheral wall 14 that is located radially outward of the inner peripheral edge of the cutting edge 32.

The stopper 24 is disposed coaxially with the axial center of the punch hole 22, and as shown in fig. 14(a), the stopper 24 is formed in a circular shape so that the cross section thereof matches the outer shape of the top wall 15 of the metal material 10. The stopper 24 is disposed so as to abut against the outer surface of the top wall 15 when shear deformation occurs in an outer peripheral region of the peripheral wall 14 located radially outward of the cutting edge 32. The stopper 24 may hold the metal material 10 during the cutting of the metal material 10. Therefore, the stopper 24 does not have to conform to the outer shape of the top wall 15, and may be longer or shorter than the top wall 15 in the radial direction, or may have a non-circular cross-sectional shape.

The ejector 25 has a main body portion 25a having a circular cross section and a fitting portion 25b having a circular cross section and smaller in diameter than the main body portion 25 a. The fitting portion 25b has the same diameter as the diameter of the internal space of the peripheral wall 14, and is detachably fitted into the peripheral wall 14. In the case where the peripheral wall 14 of the metal material 10 is not cylindrical but has a non-circular cross section, the cross-sectional shape of the fitting portion 25b may be formed to be a cross-sectional shape that matches the cross-sectional shape of the inner peripheral surface of the peripheral wall 14.

A locking stepped portion 25c is formed between the main body portion 25a and the fitting portion 25 b. The locking stepped portion 25c locks the end surface of the peripheral wall 14 when the fitting portion 25b is fitted into the peripheral wall 14. The outer diameter of the main body portion 25a may be set to be close to the cutting edge 32. When the punch 30 moves in the die hole 22, the inner peripheral side region of the peripheral wall 14 in contact with the locking stepped portion 25c can remain as it is.

The reverse punch 40 opposed to the punch 30 is formed in a cylindrical shape, and is disposed so as to enter a space surrounded by the peripheral wall 14 of the metal material 10 and the inner peripheral surface of the die hole 22 and to abut against the flange 17A. Further, back pressure is applied to the counter punch 40 by an air cylinder or the like, not shown, so that the counter punch 40 always presses the flange 17A. The punch 30 corresponds to the 1 st punch, and the reverse punch 40 corresponds to the 2 nd punch. Further, the reverse punch 40 is not required and may not be present.

Next, the precision forging method according to the present embodiment will be described.

(1 st step)

As shown in fig. 14(a), in step 1, the metal material 10 having the flange 17A and the peripheral wall 14 is placed in the die hole 22 of the die 20 of the precision forging apparatus 50, and the outer surface of the top wall 15 is brought into contact with the stopper 24. In this state, the peripheral wall 14 is disposed so as to extend along the punch moving direction of the punch hole 22, and the flange 17A is disposed so as to extend in a direction intersecting the punch moving direction. Here, the punch moving direction coincides with the axial center direction of the peripheral wall 14. The outer peripheral surface of the flange 17A is in surface contact with the inner peripheral surface of the die hole 22.

The punch 30 is disposed in the punch hole 22 so as to face a portion of the peripheral wall 14 in the thickness direction and the flange 17A. A portion of the peripheral wall 14 facing the punch 30 in the thickness direction is an outer peripheral side region of the peripheral wall 14 located radially outward of the inner peripheral edge of the cutting edge 32.

(step 2)

In step 2, the punch 30 is moved toward the flange 17A and pressed while cutting the peripheral wall 14 with the cutting edge 32. Here, the metal material 10 is held by the stopper 24 in the moving direction of the punch 30. The amount of movement of the punch 30 after the punch 30 first comes into contact with the flange 17A is not less than the thickness of the flange 17A and less than the height h of the peripheral wall 14 (see fig. 14 a).

Here, when the punch 30 presses the flange 17A to cut a part of the peripheral wall 14 in the thickness direction with the cutting edge 32, shear deformation is caused by the cutting edge 32 between a joining line a of the flange 17A (17B) which is touched by the cutting edge 32 formed on the machined end surface of the punch 30 and a joining line B between the flange 17A (17B) and the outer peripheral surface of the peripheral wall 14. Note that the flange before cutting is denoted by reference numeral "17A", and the flange during or after cutting is denoted by reference numeral "17B". The flange 17A corresponds to a projecting wall before machining. The flange 17B corresponds to a machined projecting wall.

The material (chips) sheared by the cutting edge 32 flows into the flange 17A (also referred to as a node) between the punch 30 and the counter punch 40, and in fig. 14a, a forging flow line W is formed between the joining line a and the joining line B.

Fig. 14(B) is a view in which the cutting process is finished at a position where the flange 17B and the outer surface of the top wall 15 are flush with each other. As shown in fig. 14(B), the forging flow line W extends from the portion denoted by reference numeral "B" to the portion denoted by reference numeral "a". In fig. 14(B), the part marked with the reference numeral "B" is a part that becomes the joining line B before the flange 17B becomes flush with the outer surface of the top wall 15. Here, the joining line B remains as a trace even in a state where the flange 17B is flush with the outer surface of the ceiling wall 15. The surface of the flange 17B on the side where the joining line a is located corresponds to the 1 st surface, and the surface of the flange 17B on the side opposite to the 1 st surface corresponds to the 2 nd surface.

The flanges 17A and 17B are bound by the die 20 so as not to change in size in a direction intersecting the moving direction of the punch 30 as shown in fig. 14(a) and 14 (B). Therefore, as the machining of the punch 30 progresses, the material (chips) moves while being compressed toward the joint, and the thickness of the joint increases.

Further, the back pressure F given to the reverse punch 40_bAs in embodiment 1, the pressing force F is sufficiently smaller than the pressing force F of the punch 30, i.e., F_b< F. When the thickness of the segment increases as described above, the reverse punch 40 is retracted against a biasing force (back pressure) applied from an unillustrated air cylinder or the like.

As shown in fig. 14(B), when the punch 30 moves while pressing the flange 17B, a portion of the peripheral wall 14 located radially inward of the cutting edge 32, that is, an engagement region in surface contact with the outer peripheral surface of the fitting portion 25B of the ejector 25 remains as it is.

After the cutting process of the punch 30 is completed, the stopper 24 and the reverse punch 40 are separated from the die 20, and the ejector 25 is moved toward the stopper 24, whereby the metal material 10 is released from the die 20.

As a result, as shown in fig. 13(c) and 13(d), in the metal material 10 after the cutting process, that is, the precision forged material, the flange 17A before the process located at one end of the peripheral wall 14 moves to the other end of the peripheral wall 14 and becomes the flange 17B. As shown in fig. 13(B) and 13(d), the thickness of the flange 17B after processing is thicker than that of the flange 17A before processingThe thickness is increased and the thickness K after processing of the peripheral wall 14₁Thickness K before machining₀And (5) thinning.

Embodiment 3 has the same operational effects as those of (1), (3), (5) to (7) of embodiment 2, and has the following features.

(10) The precision forged part of the present embodiment includes: a peripheral wall 14 extending in a1 st direction as an axial direction; and a flange 17B extending from the peripheral wall 14 in the 2 nd direction, which is a radial direction intersecting the 1 st direction. The flange 17B has: a1 st surface located on a side where a joining line a between the peripheral wall 14 and the flange 17B is located; and a2 nd surface on the opposite side of the 1 st surface. The precision forged part has a forged part streamline W extending from the joining line A to the joining line B of the 2 nd surface. As a result, when manufacturing the precision forged product, it is possible to manufacture the precision forged product by using a precision forging apparatus that does not require excessive tool pressure. That is, the precision forged material of the present embodiment can be obtained with a small tool pressure. That is, the precision forged material according to the present embodiment can avoid excessive tool pressure in precision forging. Further, chips generated during the cutting process are not separated and are generated as a part of the precision forged material. Further, since the precision forged material does not require an excessive tool pressure, it can be formed into a hollow member made of a high-strength material having a large size and a complicated cross-sectional shape.

(11) The precision forged part of the present embodiment has a peripheral wall 14 extending in a surrounding manner as a wall portion, and has an outward flange 17B formed on an outer surface of the peripheral wall 14. As a result, the above-described operational effect (10) can be achieved as a precision forged part having a peripheral wall and a flange.

(embodiment 4)

Next, a precision forging apparatus and a precision forged material according to embodiment 4 will be described with reference to fig. 15(a) to 15(d), and fig. 16(a) and 16 (b). This embodiment is partially different from embodiment 3, and therefore, a different configuration will be mainly described.

As shown in fig. 15(a) and 15(b), the metal material 10 before processing according to the present embodiment has a double-layer cylindrical shape by including an inner cylinder 60 and an outer cylinder 62 which are coaxially arranged. One end of the inner cylinder 60 and one end of the outer cylinder 62 are integrally connected by a bottom portion 64A. An annular groove 63 is formed between the inner cylinder 60 and the outer cylinder 62. The inner cylinder 60 corresponds to a peripheral wall and a wall portion, is formed in a cylindrical shape, and extends in the 1 st direction as an axial direction thereof. As shown in fig. 16(a), the outer cylinder 62 is formed in a cylindrical shape, and has the same outer diameter as the inner diameter of the punch hole 22 of the die 20 of the precision forging apparatus.

The bottom portion 64A is extended in a direction intersecting the axial direction, i.e., a radial direction, and is formed in a flat plate shape.

The bottom portion 64A is formed in a flat plate shape extending in a direction intersecting the axial direction, i.e., in a radial direction, but is not limited to the flat plate shape. The cross-sectional shapes of the inner cylinder 60 and the outer cylinder 62 are circular, but are not limited to circular, and may be other shapes.

The precision forging apparatus 50 used in the present embodiment will be explained.

As shown in fig. 16(a) and 16(b), the precision forging apparatus 50 includes a die 20, a punch 30, a stopper 24, and a counter punch 40, and the die 20 has a die hole 22. The cross-sectional shape of the punch hole 22 is formed in a circular shape, but is not limited as long as it conforms to at least a part of the outer shape of the outer cylinder 62.

As shown in fig. 16(a) and 16(b), the punch 30 is formed in a cylindrical shape. The punch 30 has the same outer diameter as the inner diameter of the die hole 22, and a cutting edge 32 is formed at an end edge on the inner peripheral side of the punch 30. The cutting edge 32 is formed so as to move continuous chips generated when cutting the peripheral wall 60 of the metal material 10 radially outward.

The cutting edge 32 of the punch 30 has an inner diameter longer than that of the inner cylinder 60 and shorter than the outer diameter of the inner cylinder 60, and the cutting edge 32 of the punch 30 is disposed coaxially with the axis of the die hole 22. Thus, the punch 30 is disposed to face a part of the inner tube 60 in the thickness direction and the bottom portion 64A. The cutting edge 32 is disposed so that a part of the inner tube 60 in the thickness direction, that is, an outer peripheral region of the inner tube 60 located radially outward of the inner peripheral edge of the cutting edge 32 can be shear-deformed. Further, the thickness direction of the inner cylinder 60 coincides with the radial direction.

The stopper 24 is disposed coaxially with the axial center of the punch hole 22 and fixed by a fixing member not shown. As shown in fig. 16(a), the stopper 24 has a tip end portion fitted into the inner tube 60 of the metal material 10 and a stepped portion 24a abutting on an end face of the inner tube 60.

The reverse punch 40 opposed to the punch 30 is formed in a cylindrical shape. The reverse punch 40 is disposed so as to be fitted into the groove 63 between the inner cylinder 60 and the outer cylinder 62 of the metal material 10 and to abut against the bottom portion 64A. Further, back pressure is applied to the counter punch 40 by an unillustrated air cylinder or the like, and the counter punch 40 constantly presses the bottom portion 64A. The punch 30 corresponds to the 1 st punch, and the reverse punch 40 corresponds to the 2 nd punch. Further, the reverse punch 40 may be absent.

Next, the precision forging method according to the present embodiment will be described.

(1 st step)

As shown in fig. 16(a), in step 1, the metal material 10 is placed in the die hole 22 of the die 20 of the precision forging apparatus 50, and the inner cylinder 60 is fitted to the stopper 24 so that the end face of the inner cylinder 60 contacts the stepped portion 24 a. In this state, the inner cylinder 60 is disposed so as to extend along the punch moving direction of the punch hole 22, and the bottom portion 64A is disposed so as to extend in a direction intersecting the punch moving direction. Here, the punch moving direction coincides with the axial direction of the inner cylinder 60. The outer peripheral surface of the bottom portion 64A, that is, the outer peripheral surface of the outer cylinder 62, is in surface contact with the inner peripheral surface of the die hole 22.

The punch 30 is disposed in the punch hole 22 so as to face a part of the inner cylinder 60 in the thickness direction and the bottom portion 64A. A part of the inner cylinder 60 facing the punch 30 in the thickness direction is an outer peripheral region of the inner cylinder 60 located radially outward of the inner peripheral edge of the cutting edge 32.

(step 2)

In step 2, the punch 30 is moved toward the bottom portion 64A and pressed while cutting the inner tube 60 with the cutting edge 32. Here, the metal material 10 is held by the stopper 24 in the moving direction of the punch 30. The amount of movement of the punch 30 after the punch 30 first comes into contact with the bottom portion 64A is within a range of not less than the thickness of the bottom portion 64A and less than the height of the inner cylinder 60.

Here, when the punch 30 presses the bottom portion 64A to cut a part of the inner tube 60 in the thickness direction by the cutting edge 32, shear deformation is caused by the cutting edge 32 between a joining line a of the bottom portion 64A (64B) which is abutted by the cutting edge 32 formed on the machined end surface of the punch 30 and a joining line B between the bottom portion 64A (64B) and the outer peripheral surface of the inner tube 60. The bottom portion before cutting is denoted by reference numeral "64A", and the flange during or after cutting is denoted by reference numeral "64B". The bottom 64A corresponds to the projecting wall before machining. The bottom 64B corresponds to a machined projecting wall.

The material (chips) sheared by the cutting edge 32 flows into a bottom portion 64A (also referred to as a node) between the punch 30 and the counter punch 40, and a forging flow line W is formed between the joining line a and the joining line B in fig. 16 a.

The surface of the bottom portion 64A (64B) located on the side where the joining line B is located corresponds to the 1 st surface, and the surface of the bottom portion 64A (64B) located on the side opposite to the 1 st surface corresponds to the 2 nd surface. Fig. 16(b) is a view showing that the cutting process is completed. As shown in fig. 16(B), the forging flow line W extends from the portion of the 1 st face denoted by reference numeral "B" to the portion of the 2 nd face denoted by reference numeral "a".

The bottom portions 64A and 64B are bound by the die 20 so as not to change in size in a direction intersecting the moving direction of the punch 30 as shown in fig. 16(a) and 16 (B). Therefore, as the punch 30 is machined, the material (chips) moves while being compressed toward the joint, thereby increasing the thickness of the joint.

Further, the back pressure F given to the reverse punch 40_bAs in embodiment 1, the pressing force F is sufficiently smaller than the pressing force F of the punch 30, i.e., F_b< F. When the thickness of the segment increases as described above, the reverse punch 40 is retracted against a biasing force (back pressure) applied from an unillustrated air cylinder or the like.

As shown in fig. 16(B), when the punch 30 moves while pressing the bottom portion 64B, the portion of the inner cylinder 60 located radially inward of the cutting edge 32 remains as it is.

As a result, as shown in fig. 15(c) and 15(d), in the cut metal material 10, that is, the precision forged material, the one end of the inner cylinder 60 is positionedThe pre-processed bottom portion 64A moves toward the other end of the inner cylinder 60 and becomes a bottom portion 64B. As shown in fig. 15(B) and 15(d), the thickness of the bottom part 64B after machining is thicker than the thickness of the bottom part 64A before machining, and the thickness K after machining of the cutting target portion of the inner tube 60₁Thickness K before machining₀And (5) thinning.

Embodiment 4 has the same operational effects as embodiment 3.

(embodiment 5)

Next, embodiment 5 will be described with reference to fig. 17(a) to 17 (d).

As shown in fig. 17(a) and 17(b), the metal material 10 before processing in the present embodiment includes a cylindrical peripheral wall 14 and a bottom portion 12A integrally connected to a lower portion of the peripheral wall 14, as in embodiment 1.

The precision forging apparatus 50 used in the present embodiment is different in the shape of the cutting edge 32 from the precision forging apparatus 50 described in embodiment 1. In embodiment 1, the machined end surface 31 of the punch 30 is formed flat, and a circular cutting edge 32 is formed around the entire periphery of the edge of the machined end surface 31 when the punch 30 is viewed in plan. In contrast, in the present embodiment, the machined end surface 31 of the punch 30 is formed in a flat shape, and cutting edges 32 including recesses and protrusions alternately arranged in the circumferential direction are formed on the entire periphery of the edge portion of the machined end surface 31 in a plan view of the punch 30. The configuration is the same as that of embodiment 1 except for the configuration of the cutting edge 32 of the punch 30 of the precision forging apparatus 50. The cutting edge 32 is not limited to the shape in which the concave portions and the convex portions are alternately arranged, and may have another shape.

Since the precision forging method in embodiment 5 is the same as embodiment 1, step 1 is illustrated in fig. 1(a), and step 2 is illustrated in fig. 1(b) and 1(c) instead of the detailed description.

Fig. 17(c) is a perspective view of the precision forged product after machining, and fig. 17(d) is a longitudinal sectional view of the precision forged product after machining. As shown in fig. 17(c) and 17(d), on the inner peripheral surface of the peripheral wall 14 of the metal material 10 on the machined end side, convex portions 14a and concave portions 14 are alternately arranged in the circumferential direction by the cutting edge 32 of the punch 30. Further, as shown in fig. 17(d), a forging flow line W is formed between the joining line a and the joining line B.

As shown in fig. 17(B) and 17(d), the thickness of the bottom 12B after machining is thicker than the thickness of the bottom 12A before machining, and the thickness K after machining of the cutting target portion of the peripheral wall 14₁Thickness K before machining₀And (5) thinning.

(embodiment 6)

Next, embodiment 6 will be described with reference to fig. 18(a) to 18 (d).

As shown in fig. 18(a) and 18(b), the metal material 10 before processing in the present embodiment includes a cylindrical peripheral wall 14 and a bottom portion 12A integrally connected to a lower portion of the peripheral wall 14, as in embodiment 1.

In embodiment 1, the bottom portion 12A is formed in a flat plate shape as a whole, but in the present embodiment, a central region of the bottom portion 12A bulges in a direction in which the peripheral wall 14 extends, and a bulging portion 19 is formed as a cylindrical body having a top wall when viewed from fig. 18 (b). The bulging portion 19 is formed in a circular cross section and is disposed coaxially with the peripheral wall 14. A circular annular groove 19a is formed between the bulging portion 19 and the peripheral wall 14.

The precision forging apparatus 50 used in the present embodiment is not shown, but is configured similarly to the precision forging apparatus 50 described in embodiment 1, and therefore, the description thereof is omitted.

The precision forging method according to embodiment 6 is the same as that according to embodiment 1, and therefore, the description thereof is omitted. Fig. 18(c) is a perspective view of the precision forged product after machining, and fig. 18(d) is a longitudinal sectional view of the precision forged product after machining.

As a result of the cutting forging using the above-described precision forging apparatus, as shown in fig. 18(c) and 18(d), in the metal material 10 after the cutting, that is, the precision forged material, the pre-machined bottom portion 12A located at one end of the peripheral wall 14 moves toward the other end of the peripheral wall 14 and becomes the bottom portion 12B. As shown in fig. 18(B) and 18(d), the thickness of the bottom 12B after machining is thicker than the thickness of the bottom 12A before machining, and the thickness K after machining of the cutting target portion of the peripheral wall 14₁Thickness K before machining₀And (5) thinning.

Embodiment 6 has the same operational effects as embodiment 1.

(7 th embodiment)

Next, a precision forging apparatus and a precision forged material according to embodiment 7 will be described with reference to fig. 19(a), 19(b), 20(a), and 20 (b).

As shown in fig. 19(a), the metal material 10 before machining has a square plate-shaped wall portion 114 and a square plate-shaped before-machining projecting wall 112A integrally connected to a lower portion of the wall portion 114, and has an L-shaped cross section. That is, the pre-processing projecting wall 112A extends from the wall portion 114 in the orthogonal direction, which is the direction intersecting the height direction of the wall portion 114. The wall portion 114 corresponds to a flat plate-like wall portion. The height direction corresponds to the 1 st direction. The direction orthogonal to the direction intersecting the height direction corresponds to the 2 nd direction. In the following description, the projecting wall before machining is denoted by reference numeral "112A", and the projecting wall during or after machining is denoted by reference numeral "112B".

The precision forging apparatus 50 used in the present embodiment will be explained.

As shown in fig. 20(a) and 20(b), the precision forging apparatus 50 includes a die 20, a punch 30, a stopper 24, and a counter punch 40, and the die 20 has a die hole 22.

The punch hole 22 is formed in a rectangular, i.e., square cross section so that the projecting wall 112A can be fitted before machining. The punch hole 22 has two inner surfaces 22a, 22b facing each other corresponding to the long sides of the rectangular cross section. The 1 st inner surface 22a is in sliding contact with one side surface of the punch 32 and the counter punch 40, and the 2 nd inner surface 22b is separated from the other side surface of the punch 32 and the counter punch 40.

The stopper 24 is formed in a prism shape and fixed to the die 20 so as to abut against the wall portion 114. The stopper 24 may be a locking stepped portion formed integrally with the die 20.

As shown in fig. 20(a) and 20(b), the punch 30 is formed in a plate shape. The machined end surface of the punch 30 is formed flat, and a cutting edge 32 is formed at the edge of the machined end surface facing the 2 nd inner surface 22b of the die hole 22. In fig. 20(a), the cutting edge 32 extends in a direction perpendicular to the paper surface. The No. 2 inner surface 22b is disposed apart from the punch hole 22 with a gap S therebetween. The cutting edge 32 is formed so as to move a continuous chip generated when cutting the wall portion 114 of the metal material 10 toward the inner surface 22 a.

When the punch 30 moves in the die hole 22, a portion of the metal material 10 located closer to the inner surface 22b than the cutting edge 32 can remain as it is in the gap S between the punch 30 and the 2 nd inner surface 22 b.

The counter punch 40 facing the punch 30 is disposed so as to abut against a space surrounded by the wall portion 114 of the metal material 10, the pre-machining protruding wall 112A, the 1 st inner surface 22A, and the like. The back pressure is applied to the counter punch 40 by an air cylinder or the like, not shown, and the counter punch 40 always presses the protruding wall 112A. Further, the reverse punch 40 may be absent.

Next, the precision forging method according to the present embodiment will be described.

(1 st step)

As shown in fig. 20(a), in step 1, the metallic material 10 having the pre-processing projecting wall 112A and the wall portion 114 is disposed in the die hole 22 of the die 20, and the wall portion 114 is brought into contact with the stopper portion 24. In this state, the wall portion 114 is disposed so as to be along the punch moving direction of the punch hole 22, and the pre-machining projecting wall 112A is disposed so as to extend in a direction intersecting the punch moving direction. Here, the punch moving direction coincides with the height direction of the wall portion 114. In addition, the end surface of the protrusion wall 112A before machining is in surface contact with the 1 st inner surface 22A of the die hole 22.

The punch 30 is disposed in the punch hole 22 so as to face the projecting wall 112A and a part of the wall portion 114 in the thickness direction before machining.

(step 2)

In step 2, the punch 30 is moved toward the pre-machining projection wall 112A and pressed by the cutting edge 32 while cutting the wall portion 114. Here, the metal material 10 is held by the stopper 24 in the moving direction of the punch 30. The amount of movement of the punch 30 after the punch 30 first comes into contact with the protrusion wall 112A before machining is within a range of less than the height of the wall portion 114.

Here, when the punch 30 presses the pre-processing projecting wall 112A (112B) and cuts a part of the wall portion 114 in the thickness direction by the cutting edge 32, shear deformation is caused by the cutting edge 32 between a joining line a of the projecting wall 112A (112B) with which the cutting edge 32 of the punch 30 touches and a joining line B between the projecting wall 112A (112B) and the wall portion 114. In fig. 20(a), the cutting edge 32 extends in a direction perpendicular to the paper surface, and therefore the join line A, B of the present embodiment is a straight line.

The material (chips) sheared by the cutting edge 32 flows into a projecting wall 112A (112B) (also referred to as a node) between the punch 30 and the counter punch 40, and a forging flow line W is formed between the joining line a and the joining line B in fig. 20B. The surface of the projecting wall 112A (112B) on the side where the joining line B is located corresponds to the 1 st surface, and the surface of the projecting wall 112A (112B) on the side opposite to the 1 st surface corresponds to the 2 nd surface. As shown in FIG. 20(B), the forging flow line W extends from the portion of the 1 st face indicated by reference numeral "B" to the portion of the 2 nd face indicated by reference numeral "A".

The pre-processing projecting wall 112A (post-processing projecting wall 112B) is bound by the die 20 so as not to change in size in a direction intersecting the moving direction of the punch 30 as shown in fig. 20(a) and 20 (B). Therefore, as the punch 30 is machined, the material (chips) moves while being compressed toward the joint, thereby increasing the thickness of the joint.

Further, the back pressure F given to the reverse punch 40_bAs in embodiment 1, the pressing force F is sufficiently smaller than the pressing force F of the punch 30, i.e., F_b< F. When the thickness of the segment increases as described above, the reverse punch 40 is retracted against a biasing force (back pressure) applied from an unillustrated air cylinder or the like.

As a result, as shown in fig. 20(a) and 20(B), in the metal material 10 after the cutting process, that is, the precision forged material, the pre-processing projecting wall 112A located at one end of the wall portion 114 moves toward the other end of the portion 114 to become the projecting wall 112B.

As shown in fig. 19(a) and 19(B), the thickness of the projection wall 112B after processing is thicker than the thickness of the projection wall 112A before processing.

In embodiment 7, the wall portion 114 is formed in a flat plate shape, but may be formed in a bent shape in a cross-sectional view perpendicular to the 1 st direction. In this case, the cutting edge 32 of the punch 30 is preferably formed in a shape conforming to the bending of the wall portion 114.

(embodiment 8)

Next, a precision forging apparatus and a precision forged material according to embodiment 8 will be described with reference to fig. 21(a), 21(b), 22(a), and 22 (b).

As shown in fig. 21(a), the metal material 10 before processing according to the present embodiment includes: a semi-circular wall portion 114; and a semicircular flange 120A integrally connected to the outer peripheral surface of the proximal end of the wall portion 114 and extending in the radial direction. That is, the flange 120A projects in a radial direction intersecting the height direction of the wall portion 114 with respect to the wall portion 114. The flange 120A corresponds to an outward flange. The wall portion 114 corresponds to a curved wall portion. The wall portion 114 is formed in a semicircular shape in a transverse cross section, but is not limited to the semicircular shape, and may be formed in another circular arc shape such as a C-shape or a shape in which the radius of curvature changes in the circumferential direction. In the present embodiment, the height direction of the wall portion 114 corresponds to the 1 st direction. The radiation direction corresponds to the 2 nd direction.

The precision forging apparatus 50 used in the present embodiment will be explained.

As shown in fig. 22(a) and 22(b), the precision forging apparatus 50 includes a die 20, a punch 30, a stopper 24, and a reverse punch 40, and the die 20 has a die hole 22.

The punch hole 22 is formed by a1 st inner surface 22a which is a flat surface and a2 nd inner surface 22b which is a concave curved surface, and has a semicircular cross section into which the flange 120A can be fitted. The punch 30 and the cutting edge 32 are formed in a semicircular shape, have the same outer radius of curvature as the 2 nd inner surface 22b, and are in slidable contact with the 2 nd inner surface 22 b. The radial length of the machined end face of the punch 30 is longer than the amount of protrusion of the flange 120A from the wall portion 114 and shorter than the total value of the amount of protrusion of the flange 120A and the thickness of the wall portion 114 in the radial direction. A cutting edge 32 is formed integrally with an inner edge of the machined end surface of the punch 30.

The reverse punch 40 is formed in a semicircular ring shape, has the same outer radius of curvature as the 2 nd inner surface 22b, and is in slidable contact with the 2 nd inner surface 22 b. The inside of the reverse punch 40 has the same radius of curvature as the outer surface of the wall portion 114 with which it is in sliding ground contact. An end surface of the reverse punch 40 facing the punch 30 is formed as a flat surface and abuts against the flange 120A.

The radial width of the counter punch 40 is the same as the amount of protrusion of the flange 120A from the wall portion 114.

The punch 30 is disposed apart from the 1 st inner surface 22a, and forms a gap S between the cutting edge 32 and the 1 st inner surface 22 a. The stop 24 is fixed relative to the die 20. The stopper 24 has a side surface 24d as a flat surface and a side surface 24e as a convex curved surface, and is formed in a semicircular shape in cross section. The stopper 24 has a body portion 24h and a tip portion 24 g. The radius of the side surface 24e of the tip portion 24g is smaller than the radius of the side surface 24e of the body portion 24h, and a locking stepped portion 24f is formed between the body portion 24h and the tip portion 24 g.

As shown in fig. 22(a) and 22(b), the locking stepped portion 24f abuts against the distal end surface of the wall portion 114. The side surface 24e of the body portion 24h of the stopper portion 24 is in slidable contact with the counter punch 40. In addition, the side surface 24e of the tip end portion 24g of the stopper portion 24 is in surface contact with the inner surface of the wall portion 114. The side surface 24d of the stopper 24 is entirely in surface contact with the 1 st inner surface 22 a.

In the precision forging method and the effect of the present embodiment, the description of the precision forging method described in embodiment 7 is omitted as long as "flange 120A" is replaced with another term "before machining of projecting wall 112A", flange 120B "is replaced with another term" after machining of projecting wall 112B ", fig. 22" is replaced with another term "fig. 20", fig. 21 "is replaced with another term" fig. 19 ", 112A" is replaced with another term "120A", and "120B" is replaced with another term "112B". The flange 120A corresponds to a projecting wall before machining. Since the cutting edge 32 of the punch 30 of the present embodiment is semicircular, the joining line A, B is semicircular.

In the above description, the flange 120B after machining may be located closer to the base end than the center portion of the wall portion 114 in the height direction of the wall portion 114, or may be located at the upper end portion of the wall portion 114 in the height direction as shown in fig. 21 (c).

In embodiment 8 in which the outward flange is provided, the inward flange may be provided instead of the outward flange.

Description of the reference numerals

10: a metal material; 12A, 12B: a bottom; 14: a peripheral wall; 16: a space; 20: punching a die; 22: punching a die hole; 24: a stopper portion; 30: a punch; 32: a cutting edge; 40: a reverse punch; 50: a precision forging device; A. b: a bonding wire; w: and (4) streamline of the forging piece.