JP7612325B2 - Upsetting device, upsetting method, and upsetting product - Google Patents

Description

The present invention relates to an upsetting device for annular materials, an upsetting method, and an upsetting product.

Conventionally, many annular rotating parts such as bearings, rollers, and gear parts are manufactured by cutting round bar material. For example, a technology has been disclosed in which a steel pipe is cut to a specified width to manufacture a cut ring, the cut ring is subjected to a specified machining process, and then forged to manufacture a bearing race (see Patent Document 1). However, this type of cutting has a low yield rate and a significantly low productivity tact time because the parts are manufactured by cutting out the material.
For this reason, there is an increasing need to press an annular material to produce a shape close to the final shape, and then perform only the finishing by cutting.For example, a technology has been disclosed in which a cylindrical material is compressed in the axial direction and its central part is protruded outward to form a bent part (see Patent Document 2).

JP 2007-130673 A Japanese Unexamined Patent Publication No. 63-26230

However, when the technology of Patent Document 2 is used to increase the thickness of a thin bearing steel pipe by simply upsetting, the pipe takes on a barrel shape curved in the center.
An object of the present invention is to provide an upsetting apparatus, an upsetting method, and an upsetting product that are capable of reducing the degree of curvature that results in a barrel shape.

The first aspect of the present invention provides an upsetting device that includes a first die having a first pressing surface, a second die having a second pressing surface opposed to the first pressing surface, and a drive unit that can drive the first die and the second die in a direction to move relatively closer to or farther apart, and that sandwiches and presses an annular material between the first pressing surface and the second pressing surface from both sides in a direction along an axis, and at least one of the first pressing surface and the second pressing surface is a side surface of a cone with a vertex at a point on the device axis that coincides with the axis of the annular material when the annular material is pressed.

The pressing surface may be a side surface of a cone, and in a cross section passing through the device axis and parallel to the device axis, the inclination angle θ of the inner angle between the device axis and the side surface of the cone may be 75° or more.

The pressing surface may be a side surface of a cone, and in a cross section passing through the device axis and parallel to the device axis, the inclination angle θ on the inner angle between the device axis and the side surface of the cone may be 83° or more and 89° or less.

The pressing surface is a side surface of a cone, and when a friction coefficient between the pressing surface and the annular material is μ in a cross section passing through the device axis and parallel to the device axis, the inclination angle θ of the inner angle between the device axis and the side surface of the cone is:
θ may be 90°−tan ⁻¹ μ.

The pressing surface may be the side surface of a cone, and in a cross section passing through the device axis and parallel to the device axis, the inclination angle θ of the inner angle between the device axis and the side surface of the cone may be 60° or more.

The pressing surface may be a side surface of a cone, and in a cross section passing through the device axis and parallel to the device axis, the inclination angle θ on the inner angle between the device axis and the side surface of the cone may be 76° or more and 88° or less.

The pressing surface may be a side surface of a cone, and when a friction coefficient between the pressing surface and the annular material is μ in a cross section passing through the device axis and parallel to the device axis, an inclination angle θ on the inner angle between the device axis and the side surface of the cone may be θ = 90° - 2 × tan ^-1 μ.

At least one of the first pressing surface and the second pressing surface may be provided with a positioning protrusion that is inserted into the central through hole of the annular material.

The second aspect of the present invention provides an upsetting method comprising: an arrangement step of arranging an annular material between a first die having a first pressing surface and a second die having a second pressing surface opposed to the first pressing surface; and an upsetting step of sandwiching and pressing the annular material between the first pressing surface and the second pressing surface from both ends in the direction along the axis by driving the first die and the second die in a direction relatively approaching each other, in which at least one of the first pressing surface and the second pressing surface is the side surface of a cone with a vertex at a point on the device axis that is aligned with the axis of the annular material when the annular material is pressed.

The upsetting process may be a free upsetting process in which the outer and inner surfaces of the annular material are not constrained.

The pressing surface is a side surface of a cone, and when a friction coefficient between the pressing surface and the annular material in a cross section passing through the device axis and parallel to the device axis is μ, an inclination angle θ on the inner angle between the device axis and the side surface of the cone may be θ = 90° - tan ^-1 μ.

The pressing surface is a side surface of a cone, and when a friction coefficient between the pressing surface and the annular material in a cross section passing through the device axis and parallel to the device axis is μ, an inclination angle θ on the inner angle between the device axis and the side surface of the cone may be θ = 90° - 2 × tan ^-1 μ.

The positioning step may include a positioning step of positioning the annular material by inserting a positioning protrusion, centered on the device axis and provided on at least one of the first pressing surface and the second pressing surface, into a central through hole of the annular material.

The third aspect of the present invention provides a swaged product that is annular, has a central inner diameter portion on the inner diameter side at the center in the axial direction, a central outer diameter portion on the outer diameter side at the center, a one-end inner diameter portion on the inner diameter side at one end in the axial direction, and an other-end inner diameter portion on the inner diameter side at the other end in the axial direction, and is harder.

The central inner diameter portion may be at least 5% harder than the central outer diameter portion.

The present invention provides an upsetting device, an upsetting method, and an upsetting product that can reduce the degree of curvature that results in a barrel shape.

1 is a schematic cross-sectional view of an upsetting apparatus 1 according to an embodiment. 1A to 1C are diagrams illustrating an upsetting method according to an embodiment. 1A to 1C are diagrams illustrating an upsetting method according to a first comparative example. 1A to 1C are diagrams illustrating the forces acting on an annular material 100 when an upsetting apparatus 1A of a first comparative embodiment is used. 1 is a diagram illustrating the relationship between the friction coefficient μ and the angle φ when an object of weight W is placed on an inclined surface. 1 is a diagram illustrating the relationship between the friction coefficient and the friction angle when a force F is applied to an inclined surface to compress a member. FIG. 11 is a table showing the shapes of upset-machined products 200, 200A when φ is classified into different cases. 13 is a result of an FEM analysis comparing the amount of radial material displacement of an upset processed product with and without an inclination of the pressing surface of a die. 1 is a diagram showing equivalent strains of an upset-processed product 200 in the embodiment and an upset-processed product 200A in a first comparative embodiment. FIG. 13 is a graph showing the FEM analysis results and actual measurements of the inner diameter and outer dimensions of the upper and lower surfaces of the upset processed products 200, 200A when the die angle is changed from 90° to 83°. 13 is a graph showing the inner diameter difference and the outer diameter difference near the upper surface and near the center line M for upset-processed products 200 and 200A processed by changing the inclination angle θ of the pressing surface. FIG. 12 is a diagram for explaining values indicated on the vertical axis in FIG. 11 . The results show the Vickers hardness measurements at different positions. This is a diagram comparing grain flows in products processed using different processing methods.

(Upsetting equipment)
1 is a schematic cross-section of an upsetting apparatus 1 according to an embodiment of the present invention. In the embodiment, the upsetting apparatus 1 is an apparatus for compressing an annular material 100 in the direction of an axis A0 to expand the diameter and increase the thickness. Note that, although the annular material 100 is upset in the embodiment, the present invention is not limited thereto, and may be an apparatus for upsetting, for example, an angular annular material or an elliptical annular material. In addition, although the upsetting apparatus 1 upsets the annular material 100 from the top and bottom directions, the present invention is not limited thereto, and may be an apparatus for upsetting, for example, from the side directions.

The upsetting device 1 comprises a lower die 2 (first die), an upper die 3 (second die) that is substantially the same shape as the lower die 2 and is disposed above the lower die 2, centered on the same device axis A1 as the lower die 2, a guide section 4 that guides the relative movement of the upper die 3 and the lower die 2 in the vertical direction, and a drive section 5 that drives the upper die 3 and the lower die 2 relative to each other in the vertical direction. The lower die 2 and the upper die 3 are collectively referred to as the die 10.

(Lower die 2)
The lower die 2 is generally cylindrical, and has a lower die pressing surface 21 (first pressing surface) on its upper surface. The lower die pressing surface 21 is part of the side surface of a cone that has a vertex at a point on the device axis A1 and widens in diameter downward. A lower die positioning protrusion 22 that protrudes upward in a cylindrical shape is provided on the upper surface within a range of a predetermined diameter centered on the device axis A1. The outer diameter of the lower die positioning protrusion 22 is generally equal to the inner diameter of the through hole 101 of the annular material 100.
As shown in FIG. 1, in a cross section passing through the device axis A1, the inclination angle (lower mold inclination angle) θ1 on the inner angle side of the lower mold pressing surface 21 relative to the device axis A1 is less than 90°, and in this embodiment, the lower mold inclination angle θ1 is 87°.
In the embodiment, the lower die pressing surface 21 is the side surface of a cone, but is not limited to this and may be the side surface of another pyramid, for example a pyramid, depending on the shape of the annular material to be processed.

(Upper mold 3)
The upper mold 3 is the same shape as the lower mold 2 but upside down. That is, it is substantially cylindrical, and has an upper mold pressing surface 31 (second pressing surface) on its lower surface, which faces the lower mold pressing surface 21. The upper mold pressing surface 31 is a part of the side surface of a cone that has a vertex at a point on the device axis A1 and whose diameter increases as it extends upward. On the lower surface, within a range of a predetermined diameter centered on the device axis A1, an upper mold positioning protrusion 32 that protrudes downward in a cylindrical shape is provided. The outer diameter of the upper mold positioning protrusion 32 is substantially equal to the inner diameter of the through hole 101 of the annular material 100.
As shown in Figure 1, in a vertical cross section passing through the device axis A1, the inclination angle θ2 (upper mold inclination angle) of the upper mold pressing surface 31 on the inner angle side relative to the device axis A1 is less than 90°, and in this embodiment, the upper mold inclination angle θ2 is 87°.
In addition, like the lower die pressing surface 21, the upper die pressing surface 31 in the embodiment is the side surface of a cone, but is not limited to this and may be a pyramid or the like depending on the shape of the annular material to be processed.

(Guide part 4)
The guide part 4 is a cylindrical member of a predetermined thickness that is arranged on the outer periphery of the lower mold 2 and the upper mold 3. The inner diameter of a through hole 41 of the guide part 4 is approximately the same as the outer diameter of the upper mold 3 and the lower mold 2. The guide part 4 and the lower mold 2 are placed on a pedestal 6.
The lower mold 2 and the upper mold 3 are arranged with a certain distance between them in the device axis A1 direction and centered on the device axis A1 inside the through hole 41 of the guide part 4, with the upper mold pressing surface 31 and the lower mold pressing surface 21 facing each other. When the lower mold 2 and the upper mold 3 move relatively to each other in the device axis A1 direction, they are guided straight by the through hole 41 of the guide part 4.

(Drive unit 5)
In this embodiment, the drive unit 5 drives the upper mold 3 in the direction of the device axis A1 in a direction approaching and moving away from the lower mold 2. However, the present invention is not limited to this, and any drive unit may be used as long as it drives the upper mold 3 and the lower mold 2 relatively to each other in the direction of the device axis A1.
The upsetting device of the embodiment is a free upsetting device that does not constrain the outer periphery of the annular material 100 during upsetting.

(Embodiment of upsetting method)
FIG. 2 is a diagram for explaining the upsetting method of the embodiment.
2A is a perspective view of the annular material 100 before processing. The annular material 100 is a rotating body centered on an axis line A0. Note that, in the embodiment, the workpiece processed by the upsetting device 1 is the annular material 100, but is not limited thereto and may be, for example, a rectangular annular material or an elliptical annular material.

2(b) is a diagram illustrating the positioning step of the upsetting method. The lower side of the through hole 101 of the annular material 100 is inserted into the outer side of the lower die positioning protrusion 22 of the lower die 2. As a result, the annular material 100 is positioned and arranged in the center of the lower die pressing surface 21.
Then, the drive unit 5 is driven to lower the upper die pressing surface 31, and the upper die positioning protrusion 32 of the upper die 3 is inserted into the through hole 101 of the annular material 100. As a result, the upper die positioning protrusion 32 of the upper die 3 is inserted above the through hole 101 of the annular material 100. The axis A0 of the annular material 100 coincides with the device axis A1 of the upsetting device 1, and the annular material 100 is held in the center of the upsetting device 1.

Figure 2(c) is a diagram explaining the upsetting process of the upsetting processing method. The upper die 3 is further lowered by driving the driving unit 5, and the annular material 100 is compressed in the direction of the axis A0 (machine axis A1) with a predetermined pressure force, expanding the diameter and increasing the thickness of the annular material 100 in the direction perpendicular to the axis A0 direction.

2(d) and (e) are diagrams showing an upset-processed product 200, which is the state after processing of the annular material 100, where (d) is a cross-sectional view passing through and parallel to the axis A0, and (e) is a perspective view.
The upset product 200 is compressed in the direction of the axis A0 from the state of the annular raw material 100, and is thickened in the direction perpendicular to the direction of the axis A0. In the embodiment shown in Fig. 2, the outer surface 200a and the inner surface 200b of the upset product 200 are linear extending vertically in the cross section shown in the figure, i.e., they are not curved. In addition, the upper surface 200u and the lower surface 200d of the upset product 200 are in the form of conical side surfaces (inner surfaces) corresponding to the upper die pressing surface 31 and the lower die pressing surface 21.

In the embodiment of the upset product 200 shown in FIG. 2, the outer surface 200a and the inner surface 200b are linear and extend vertically in the cross section shown. However, the scope of the present invention does not necessarily require a completely linear shape, and it is sufficient if the amount of outward protrusion is smaller than the first comparative embodiment described below, and also includes cases where the product protrudes inward.

(Comparative upsetting method)
FIG. 3 is a diagram for explaining the upsetting method of the first comparative embodiment.
3A is a perspective view of the annular material 100 before processing. The annular material 100 is the same as that of the embodiment.

3B is a diagram for explaining the positioning step of the upsetting method of the first comparative embodiment. The upsetting apparatus 1A of the first comparative embodiment differs from the upsetting apparatus 1 of the embodiment in the shape of the lower die pressing surface 21A and the upper die pressing surface 31A. The lower die pressing surface 21A and the upper die pressing surface 31A of the first comparative embodiment are not the side surfaces of a cone, but are flat surfaces extending in a direction perpendicular to the device axis A1 (horizontal direction).
In the positioning step, similarly to the embodiment, the lower side of the through hole 101 of the annular material 100 is inserted into the outer side of the lower die positioning protrusion 22A of the lower die 2A. This positions and disposes the annular material 100 at the center of the lower die pressing surface 21A.
Then, the drive unit is driven to lower the upper die pressing surface 31A and insert the upper die positioning protrusion 32A of the upper die 3A into the through hole 101 of the annular material 100. As a result, the upper die positioning protrusion 32A of the upper die 3A is inserted above the through hole 101 of the annular material 100. The axis A0 of the annular material 100 coincides with the device axis A1 of the upsetting apparatus 1A, and the annular material 100 is held in the center of the upsetting apparatus 1A.

Figure 3(c) is a diagram explaining the upsetting process of the upsetting processing method in the comparative embodiment. The upper die 3A is further lowered by driving the driving unit 5. This compresses the annular material 100 in the direction of the axis A0 (device axis A1), and the annular material 100 is expanded in diameter and thickened in the direction perpendicular to the axis A0.

3(d) and (e) are diagrams showing the upset processed product 200A after processing in the comparative embodiment, (d) being a cross-sectional view passing through the axis A0 and parallel to the axis A0, and (e) being a perspective view. The upset processed product 200A of the first comparative embodiment is compressed in the direction of the axis A0 from the state of the annular raw material 100 as in the embodiment, and is thickened in the direction perpendicular to the axis A0. The upset processed product 200A of the first comparative embodiment differs from the upset processed product 200 of the embodiment in that the central portions of the outer surface 200Aa and the inner surface 200Ab are curved and expanded outward, forming a so-called barrel shape.

(Reason why the first comparative embodiment has a barrel shape)
The reason why the first comparative embodiment has such a barrel shape will be described.
When a load F acts on an object and it moves a distance s, it is most stable for the object to move in such a way that the work W = F x s is minimized. In other words, when F is constant, it is most stable for the object to move in such a way that s is minimized.
Even when the annular material 100 is set between the upper mold 3 and the lower mold 2 having flat pressing surfaces as in the first comparative example, the movement in which the movement distance s is small is considered to be the most stable movement.

As an example, when a circular ring-shaped material 100 having an outer diameter (radius) of 6 mm, an inner diameter (radius) of 5 mm, and a height of 10 mm is set at a constant volume and a compression rate of 50%, the following occurs.
(1) If the inner diameter does not change, the outer diameter (radius) increases from 6 mm to (√47) mm ≈ 6.86 mm. In other words, the movement distance s of the outer diameter portion from the axis A0 is 0.86 mm.
(2) When the outer diameter does not change, the inner diameter (radius) decreases from 5 mm to (√14) mm ≈ 3.74 mm. In other words, the movement distance s of the outer diameter portion from the axis A0 is 1.26 mm.
Therefore, in free upsetting without constraint, a change in the outer diameter dimension results in less work W than a change in the inner diameter dimension, and is therefore considered to be more stable.
Therefore, when the annular material 100 is upset in the first comparative example of upsetting, it is considered that, from the standpoint of stability, it is more likely that the material will move to the outer diameter side and expand in diameter than the material will move to the inner diameter side and reduce in diameter.

Figure 4 is a diagram explaining the forces acting on the annular material 100 when using the upsetting processing device 1A of the first comparative embodiment. When the material of the annular material 100 tries to move toward the outer diameter, a friction force fi = μ × F (μ is the friction coefficient) acts between the upper die pressing surface 31A and the upper surface of the annular material 100, and between the lower die pressing surface 21A and the lower surface of the annular material 100, in the opposite direction to the direction r in which the material tries to move, i.e., toward the inner diameter.

On the other hand, the influence of the friction force fi is small near the center line M in the axial direction A0 of the annular material 100. For this reason, the amount of radial displacement of the material differs between the vicinity of the upper and lower surfaces of the annular material 100 and the vicinity of the center line M. In other words, the amount of radial deformation is large near the center line M and small near the upper and lower surfaces. As a result, the upset product 200A is thought to have a barrel shape as shown in Figures 3(c), (d), and (e).

(Reason for reducing the protrusion amount in the embodiment)
Next, the reason why the outward protrusion amount is smaller in the embodiment than in the comparative example will be described.
(1) Relationship between friction coefficient μ and friction angle φ An object of weight W is placed on an inclined plane, and the inclination is gradually increased until the angle of inclination reaches angle φ, at which point the object begins to slide.
Figure 5 is a diagram explaining the relationship between the friction coefficient μ and angle φ when an object of weight W is placed on an inclined surface. As shown in the figure, when the inclination of the inclined surface is angle φ, the weight W is resolved into a direct pressure R perpendicular to the inclined surface and a force P parallel to the inclined surface. In this case, the static friction force f (f = μ x R) of the object is balanced with the force P trying to slide the object, so
f = μ × R = P
Therefore, the friction coefficient μ is
μ=P/R=(Wsinφ)/(Wcosφ)=tanφ
It becomes.

(2) Application to upsetting This relational expression μ=tanφ is applied to the upsetting of the present application (free upsetting where the side surface is not constrained). Figure 6 is a diagram for explaining the relationship between the friction coefficient and the friction angle when a force F is applied to the inclined surface to compress the member. The following explanation will be given using the upper die pressing surface 31 and the top surface side of the annular material 100 as examples.
F: Load R: Component of load F in a direction perpendicular to the upper die pressing surface 31 of the upper die 3 (direct pressure force)
P: component of load F in a direction parallel to the upper die pressing surface 31 of the upper die 3; fp: static friction force acting in the opposite direction with the same magnitude as the force P; φ: inclination φ of the upper die pressing surface 31 relative to the horizontal plane
μ: friction coefficient between the upper die 3 and the upper surface of the annular material 100, and fmax: maximum friction force.

So then,
P=F×sinφ, R=F×cosφ,
fmax=μ×R,
fp = P (until fmax < P)
It becomes.

When an object is slid as shown in Figure 5, the object is stationary when P ≦ μ × R. However, in the case of upsetting as shown in Figure 6, when P ≦ μ × R, the material moves in the outer diameter direction, which is a smaller moving distance. Therefore, a friction force fi acting in the opposite direction to the direction in which the material moves, i.e., toward the inner diameter, also exists at the same time. However, friction does not occur beyond the maximum friction force fmax, so the sum of the static friction forces fp and fi is equal to fmax.
In the upsetting process of the present invention, under the condition P≦μ×R, the object can move in two directions: toward the inner diameter due to a force P parallel to the inclined surface, and toward the outer diameter due to free upsetting.
The maximum frictional force fmax is calculated by the product of the force (direct pressure force) R perpendicular to the slope and the friction coefficient μ. However, since this force acts in the opposite direction to the object moving on the slope, there exists a frictional force fp that acts in the opposite direction to the force P parallel to the slope, and a frictional force fi that acts in the opposite direction to the movement toward the outer diameter due to free upsetting, and the relationship between these is fmax = fp + fi.

That is,
When P≦μ×R,
Since fmax=fp+fi and fp=P,
fi=fmax-fp=μ×R-P=(μ×F×cosφ)-(F×sinφ)=(μ×F)×(cosφ-sinφ/μ)
It becomes.

7 is a table showing the shapes of the upset processed products 200 (embodiment) and 200A (first comparative embodiment) when classified according to φ. The size of the arrow indicates the magnitude of the friction force or the amount of displacement.
(1) When φ=0 (first comparative example)
fi = μ×F, fp = 0, and the friction force f is f = μ×F and acts in the inward direction.
Therefore, in the first comparative form, as described above, the amount of deformation is small near the upper and lower surfaces that abut against the pressing surface, and the amount of radial deformation is large near the center line M, and as a result, the upset processed product 200A becomes barrel-shaped as shown in Figures 3(c), (d), and (e).

(2) When cosφ>sinφ/μ (embodiment)
Since fp and P cancel each other out, the apparent friction force f is equal to fi.
As a result, f satisfies 0<f<μ×F in the inner diameter direction.
In this case, φ is μ>sinφ/cosφ=tanφ, and can be determined by φ<tan ⁻¹ μ.
In this embodiment, the apparent frictional force is smaller than that of the first comparative embodiment, and therefore the difference between the amount of deformation near the upper and lower surfaces that are in contact with the pressing surface and the amount of radial deformation near the center line M is smaller than in the first comparative embodiment.

(3) When cosφ=sinφ/μ (embodiment)
Since fi = 0 and fp = fmax = P, fp is balanced and canceled out by P, so the apparent friction force f is f = 0.
In this case, φ is μ=sinφ/cosφ=tanφ, so it can be determined as φ=tan ⁻¹ μ.
Therefore, cosφ=sinφ/μ is the most preferable range in the embodiment, and there is no difference between the amount of deformation near the upper and lower surfaces in contact with the pressing surface and the amount of radial deformation near the center line M. Therefore, if the inclination φ of the upper mold pressing surface 31 with respect to the horizontal plane is set to φ=tan ^-1 μ (μ is a friction coefficient), the friction force f generated at the boundary surface between the mold and the annular material 100 can be made to appear zero, and the amount of radial displacement of the material near the center line M and the mold boundary surface becomes equal. Therefore, the outer surface 200a and the inner surface 200b of the upset product 200 can be made linear, extending vertically in the cross section shown in Figures 2(d) and (e).

(Verification results)
Fig. 8 shows the results of a finite element method (FEM) analysis comparing the amount of material displacement in the radial direction of an upset product with and without the inclination of the pressing surface of the die. Fig. 8(d) on the far right side of the figure shows the positions of the material displacement shown in Figs. 8(a), (b), and (c).
The friction coefficient μ between steel types and die materials when using general lubricants is 0.03 to 0.12, with a maximum of 0.25. In this FEM analysis, however, a frequently used friction coefficient μ of 0.05 was applied.

The various conditions are as follows:
Analysis method: FEM
Circular ring material Steel type: SUJ2
Inner diameter: 14.2 mm
Outer diameter: 28.4 mm
Height: 50.5mm
Friction coefficient μ: 0.05
Compression force: (a) 724 kN, (b) 811 kN, (c) 838 kN
Compression ratio: 50%

Figure 8 (c) shows an upset product 200I produced when an annular material 100 is upset using an upset processing device with upper and lower die pressing surfaces that extend parallel to each other in the horizontal direction under ideal processing conditions without friction. The upset product 200I produced under ideal processing conditions has the same radial material displacement near the center line M as near the upper and lower surfaces.

Figure 8 (a) shows a first comparative form of an upsetting processed product 200A obtained when an annular material 100 is upset using an upsetting processing apparatus 1A having an upper die pressing surface 31A and a lower die pressing surface 21A extending parallel to each other and horizontally under realistic processing conditions in which friction is present.
In the first comparative example, a frictional force (μ×F) acts in the inward direction near the upper and lower surfaces, so the amount of displacement of the material is small. Also, in the vicinity of the center line M, the effect of the frictional force is small, so the amount of displacement is large.

Fig. 8(b) shows the present embodiment. In this embodiment, realistic friction exists, but the upsetting product 200 is obtained when the annular material 100 is upset by an upsetting device 1 having an upper die pressing surface 31 and a lower die pressing surface 21, which are inclined surfaces with φ=tan ^-1 μ (μ is the friction coefficient), with respect to the annular material 100. According to the embodiment, it can be seen that the difference in the amount of material displacement between the vicinity of the center line M and the vicinity of the upper and lower surfaces is small, and is close to the ideal state of Fig. 8(c) where there is no friction.

(Regarding the inclination angle θ)
As described above, in the embodiment, the upper mold inclination angle θ2 and the lower mold inclination angle θ1 are 87°. The effect of this will be described. Note that the following description is common to the upper mold inclination angle θ2 and the lower mold inclination angle θ1, so it will be commonly described as the inclination angle θ.
As shown in FIG. 6, the relationship between the angle φ and the inclination angle θ of the die 10 is θ=90°-φ=90°-tan ⁻¹ μ.
In addition, this relation is
Since tan θ=1/tan φ=1/μ,
It can also be expressed as θ=tan ⁻¹ (1/μ).
In other words, if μ is known, the inclination angle θ can be calculated. Note that in the method of estimating the friction coefficient μ through experiments, the accuracy of μ includes an error of about ±0.02, so the inclination angle includes the θ calculated here up to ±1.5°.

(Relationship between μ and inclination angle θ)
In the embodiment, if μ=0.05, the inclination angle θ at which the apparent frictional force f becomes f=0 is given by:
θ=tan ^-1 (1/μ)
= tan ^-1 (1/0.05)
= 87°, the amount of radial displacement of the annular material 100 becomes equal near the center line M and at the die boundary surface, and the formed upset product 200 does not become barrel-shaped.
In addition, since μ has an error, the inclination angle θ is within the range of 85.5°≦θ≦88.5° (85.5° or more and 88.5° or less).

(Preferable range to avoid bending)
The friction coefficient μ varies depending on the metal material used as the die in the upsetting apparatus 1, the material of the annular raw material, the lubricating oil, etc. Generally, the maximum friction coefficient μmax is about 0.25, so θ=tan ⁻¹ (1/μ), and therefore θ=75° (rounded down to the nearest whole number).
Among these, the range that is usually used is 0.03≦μ≦0.12. In this case, 83°≦θ≦89° (83° or more and 89° or less).

Figure 9(a) shows the results of an analysis of the equivalent strain of the upset product 200A in the first comparative embodiment with μ = 0.05 and an inclination angle θ = 90°, and Figure 9(b) shows the results of an analysis of the equivalent strain of the upset product 200 in the embodiment with μ = 0.05 and an inclination angle θ = 87°.

The analysis method and various conditions are as follows.
Analysis method: FEM
Circular ring material Steel type: SUJ2
Inner diameter: 14.2 mm
Outer diameter: 28.4 mm
Height: 50.5mm
Compression force: (a) 724 kN, (b) 811 kN
Compression ratio: 50%

The dotted line in the figure indicates the target shape of the upset product 200. As shown in the figure, in the embodiment, the equivalent strain was approximately uniform, while in the first comparative embodiment, the equivalent strain value varied greatly. Furthermore, the upset product 200 in the embodiment was closer to the ideal shape.

Figure 10 is a graph showing the FEM analysis results of the inner diameter dimensions and outer dimensions on the upper and lower surfaces of the upset processed products 200, 200A when the die angle is changed from 90° to 83°, as well as the actual measured values when the die angle is 90°, 88°, 87°, 86°, and 84°.
A method for estimating the friction coefficient μ is described in the revised edition of Science of Plastic Processing (1st edition, March 14, 2014).
The method involves ring compression, in which a ring-shaped test piece is compressed between parallel tools. When friction is low, the ring inner diameter expands, and when friction is high, the ring inner diameter decreases. This change in the ring inner diameter is determined by comparing the calculated results with the change in the ring inner diameter obtained experimentally. The friction coefficient was determined to be μ = 0.05 when confirmed with the experimental product.

The analysis method and various conditions are as follows.
The following circular materials were used:
Steel type: SUJ2
Inner diameter: 14.2 mm
Outer diameter: 28.4 mm
Height: 50.5mm
In addition, upsetting was carried out under the following conditions.
Press equipment: 4000kN mechanical press (hydraulic unit, manufactured by Rikenki Co., Ltd.)
Press motion: crank Press speed: 10 spm
Mold material: SKD11
Lubricating oil: G-3456 (manufactured by Nippon Kogyo Oil Co., Ltd.)
Compression force: die angle 90° 748kN, 88° 801kN, 87° 834kN, 86° 773kN, 84° 657kN
Compression ratio: 50%
Analysis method: FEM
Circular ring material Steel type: SUJ2
Inner diameter: 14.2 mm
Outer diameter: 28.4 mm
Height: 50.5mm
Compression force: die angle 90° 724kN, 88° 788kN, 87° 811kN, 86° 765kN, 84° 664kN, 83° 629kN
Compression ratio: 50%

As shown in the figure, the actual measured values of the outer dimension A and inner diameter dimension a of the upset processed products 200, 200A are approximately consistent with the results of the FEM analysis based on the mechanism described in Figure 7, demonstrating the high reliability of the mechanism described in Figure 7.

(Change in shape due to change in θ)
Fig. 11 is a graph based on the results of FEM analysis showing the inner diameter difference and the outer diameter difference near the upper surface and near the center line M of upset-processed products 200, 200A processed by changing the inclination angle θ of the pressing surface of the upsetting device 1 when the friction coefficient μ is 0.05. Fig. 12 is a diagram explaining the values indicated by the vertical axis in Fig. 11. As shown in Fig. 12, the outer diameter of the upper part of the upset-processed product 200 of the embodiment is A, the inner diameter of the upper part is a, the outer diameter of the central part is B, and the inner diameter of the central part is b.

The difference b-a between the inner diameter b at the center and the inner diameter a at the top is defined as the inner diameter difference. If b-a is a positive value, it indicates that the diameter at the center of the through hole of the upset product 200 is larger than the diameter at the top. If b-a is a negative value, it indicates that the diameter at the center of the through hole of the upset product 200 is smaller than the diameter at the top.

The difference B-A between the outer diameter B of the upper part and the outer diameter A of the upper part is taken as the outer diameter difference. If B-A is a positive value, it indicates that the diameter of the central part of the outer diameter of the upset processed product 200 is larger than the diameter of the upper part. In other words, it is barrel-shaped. If B-A is a negative value, it indicates that the diameter of the central part of the outer diameter of the upset processed product 200 is smaller than the diameter of the upper part. In other words, it is a shape with a recessed center.

As shown in FIG. 11, when the inclination angle θ of the mold is changed from 90° to 83°, the values of the inner diameter difference and the outer diameter difference change. Note that the inclination angle of the mold of 90° is the case of the first comparative embodiment. Also, as shown in FIG. 11, when the mold angle is changed, the inner diameter difference and the outer diameter difference become approximately equal values. In other words, the amount of protrusion on the outer diameter side and the amount of narrowing on the inner diameter side are considered to be approximately equal, and the protruding portion of the outer diameter portion becomes the concave portion of the inner diameter portion.

In the case of the embodiment, when μ=0.05, the inclination angle θ is about 87° (=90°−tan ⁻¹ μ). At this time, the difference between the inner diameter and the outer diameter becomes approximately zero, as shown in FIG.
In addition, in the experimental estimation method of the friction coefficient μ, the accuracy of μ includes an error of about ±0.02, so the inclination angle is considered to include 85.5°≦θ≦88.5° (85.5° or more and 88.5° or less) (= tan ⁻¹ (1/μ) ±1.5°), where the θ calculated here is ±1.5°.

(Inner protrusion shape)
When the inclination angle θ is smaller than 87° (when the inclination with respect to the horizontal becomes large), the value of the inner diameter difference and the outer diameter difference becomes negative. When the inclination angle θ is 90°-2×tan ^-1 μ, it is possible to manufacture an upset-processed product that has an inward protrusion by the same amount as the upset-processed product 200A that has an outward protrusion in the first comparative embodiment. Note that in the method of estimating the friction coefficient μ through experiments, the accuracy of μ includes an error of about ±0.02, so the inclination angle includes the θ calculated here up to ±3.0°.
That is, the inclination angle θ for producing an upset-processed product with the same inward protrusion as when pressed with a flat pressing surface is:
Generally, θ=60° when the friction coefficient μmax=0.25 is the maximum, and within this, the range that is usually used is 0.03≦μ≦0.12. In this case, 76°≦θ≦88° (76° or more and 88° or less).

In this way, by changing the inclination angle θ, the radial position of the center of the axial line A0 direction of the upset product can be changed relative to the upper and lower parts. In other words, by changing the inclination angle θ, it is possible to manufacture upset products of any shape, such as a barrel shape with an outward protrusion, a cylindrical shape with no curved sides, or a constricted shape with an inward protrusion.

(hardness)
Figure 13 shows the results of measuring Vickers hardness at different positions on (a) annular material 100 before processing, (b) an upsetting product 200 processed by the upsetting processing apparatus 1 of the first comparative embodiment, and (c) an upsetting product 200 processed by the upsetting processing apparatus 1 of the embodiment.
The following circular materials were used:
Steel type: SUJ2
Inner diameter: 14.2 mm
Outer diameter: 28.4 mm
Height: 50.5mm
In addition, upsetting was carried out under the following conditions.
Press equipment: 4000kN mechanical press (hydraulic unit, manufactured by Rikenki Co., Ltd.)
Press motion: crank Press speed: 10 spm
Mold material: SKD11
Lubricating oil: G-3456 (manufactured by Nippon Kogyo Oil Co., Ltd.)
Compressive force: (b) 748 kN, (c) 834 kN
Compression ratio: 50%
The Vickers hardness was measured at 15 points in total, 1, 2, 3, 4, and 5 from the top in the longitudinal direction and 3 points A, B, and C from the outer diameter side in the radial direction. The unit is HV, and the test load is 9.8 N.

When an object is plastically deformed, as the degree of deformation increases, obstacles (grain boundaries, precipitates, other dislocations) gradually accumulate and cause the density to increase, resulting in work hardening, which increases the strength of the material. In other words, the more a material is deformed, the harder it becomes.

As described above, when a load is applied by the mold 10 near the upper surface of the annular material 100 close to the upper die 3 and near the lower surface of the annular material 100 close to the lower die 2, the material moves toward the outer diameter side, which is a smaller moving distance, in the first comparative embodiment with θ = 90° and the embodiment with θ = 87°. Therefore, the degree of deformation is greater on the outer diameter side than on the inner diameter side.

As a result, the hardness of the upper portion (side fixed point 1) and the lower portion (side fixed point 5) of the annular material 100 is in the order of outer diameter portion (measurement point A) > central portion (measurement point B) > inner diameter portion (measurement point C). This is the same in the first comparative embodiment and the embodiment.

On the other hand, since the central portion (measurement point 3) is located in the center between the upper mold 3 and the lower mold 2, the deformation is dominated by compression by the upper mold 3 and the lower mold 2, and as the compression rate of the material increases, the degree of deformation increases and the material becomes harder.
That is, in the first comparative embodiment, the upper die 3 and the lower die 2 are horizontal, so the compression rates of the outer diameter portion and the inner diameter portion are the same, there is no difference in the degree of deformation, and the hardness at the measurement points A, B, and C is approximately equal.
However, in the embodiment, the pressing surfaces of the upper mold 3 and the lower mold 2 are inclined, so that the compression ratio of the inner diameter portion is high and the compression ratio of the outer diameter portion is low. Therefore, there is a difference in the degree of deformation, and the outer diameter portion (measurement point A) < the central portion (measurement point B) < the inner diameter portion (measurement point C).

As described above, the upset product 200 of the embodiment has the hardest central portion of the inner diameter portion (side fixed point C), and the softest upper and lower portions of the inner diameter portion. This makes it easier to perform H-shape processing by sandwiching the upper and lower portions of the softest inner diameter portion between dies and pressing them in, and then punching out the pressed surface, making it easier to perform finish punching processing than the upset product 200 as an intermediate product according to the first comparative embodiment.

FIG. 14 is a diagram comparing grain flows in products processed using different processing methods.
1A is a diagram showing grain flows of an upset-processed product 200 according to an embodiment, FIG. 1B is a diagram showing grain flows of an upset-processed product 200 according to a first comparative embodiment, and FIG. 1C is a diagram showing grain flows of an upset-processed product 200 according to a second comparative embodiment.
The second comparative example is an upset-processed product 200B in which the outer diameter side of the annular material 100 is constrained by an outer wall and processed into a rectangular shape.

In an upset product 200A according to a first comparative embodiment shown in FIG. 14(b), the grain flows in the vicinity of a center line M in the longitudinal direction of the annular raw material 100 are perpendicular to the axis A0, i.e., horizontal.
However, the grain flows in the vicinity of the upper surface pressed by upper die pressing surface 31 are not parallel to upper die pressing surface 31. Similarly, the grain flows in the vicinity of the lower surface pressed by lower die pressing surface 21 are not parallel to lower die pressing surface 21.

In the upset product 200B according to the second comparative embodiment shown in FIG. 14(c), the grain flow lines near the longitudinal center line M of the annular material 100 are not perpendicular to the axis A0, i.e., they are not horizontal. The grain flow lines near the upper surface pressed by the upper die pressing surface 31 are not parallel to the upper die pressing surface 31. Moreover, the grain flow lines near the lower surface pressed by the lower die pressing surface 21 are not parallel to the lower die pressing surface 21.

However, in the upset product 200 according to the embodiment shown in FIG. 14( a ), the grain flow lines in the vicinity of the center line M in the longitudinal direction of the annular raw material 100 are perpendicular to the axis A 0 , that is, horizontal.
As one moves above center line M, the grain flow line gradually inclines, and the grain flow line in the vicinity of the upper surface pressed by upper die pressing surface 31 is approximately parallel to upper die pressing surface 31 , i.e., has the same inclination as upper die pressing surface 31 .
The grain flow lines gradually incline downward from center line M, and the grain flow lines in the vicinity of the lower surface pressed by lower die pressing surface 21 are approximately parallel to lower die pressing surface 21 , i.e., have the same inclination as lower die pressing surface 21 .
In comparison with the first and second comparative examples, the intervals between the grain flows are generally uniform, indicating that forging has been performed without unevenness.

As described above, according to this embodiment, the annular material is gradually pressed from the inner diameter against the pressing surface, which is the side surface of a cone having an inclination angle of less than 90°. This allows the cross-sectional shape of the inner and outer diameter surfaces to be linearly thickened.
In addition, since the diameter can be expanded without bending or buckling in the center after processing, it is possible to increase the thickness of thin bearing steel pipes.
The load of the press can be reduced to about 1/2.5 compared to when the side surface of the annular material 100 is flattened by restraining the side surface.

θ: Inclination angle θ1: Lower mold inclination angle θ2: Upper mold inclination angle θ2: Inclination angle μ: Friction coefficient A0: Axis line A1: Equipment axis line 1: Upsetting equipment 10: Mold 2: Lower mold (first mold)
21: Lower pressing surface (first pressing surface)
22: Lower die positioning protrusion 3: Upper die (second die)
31: Upper pressing surface (second pressing surface)
32: Upper die positioning protrusion 41: Through hole 5: Drive part 100: Ring-shaped material (ring-shaped material)
101: Through hole 200: Upset processed product 200a: Outside surface 200b: Inside surface

Claims (15)

A first mold having a first pressing surface;
a second mold having a second pressing surface opposed to the first pressing surface;
a drive unit capable of driving the first mold and the second mold in a direction to move relatively closer to or away from each other,
An upsetting processing device that sandwiches and presses an annular material between the first pressing surface and the second pressing surface from both sides in a direction along an axis,
An upsetting processing apparatus, wherein the first pressing surface and the second pressing surface are sides of a cone having a vertex at a point on an apparatus axis that coincides with the axis of the annular material when the annular material is pressed. the first pressing surface and the second pressing surface are side surfaces of a cone,
In a cross section passing through the device axis and parallel to the device axis, the inclination angle θ of the inner angle between the device axis and the side surface of the cone is 75° or more.
2. The upsetting apparatus according to claim 1. the first pressing surface and the second pressing surface are side surfaces of a cone,
In a cross section passing through the device axis and parallel to the device axis, the inclination angle θ of the inner angle between the device axis and the side surface of the cone is 83° or more and 89° or less.
3. An upsetting apparatus according to claim 1 or 2. the first pressing surface and the second pressing surface are side surfaces of a cone,
In a cross section passing through the device axis and parallel to the device axis, when the friction coefficient between the annular material and each of the first pressing surface and the second pressing surface is μ, the inclination angle θ of the inner angle between the device axis and the side surface of the cone is:
θ=90°−tan ⁻ 1μ,
The upsetting apparatus according to any one of claims 1 to 3. the first pressing surface and the second pressing surface are side surfaces of a cone,
In a cross section passing through the device axis and parallel to the device axis, the inclination angle θ of the inner angle between the device axis and the side surface of the cone is 60° or more.
2. The upsetting apparatus according to claim 1. the first pressing surface and the second pressing surface are side surfaces of a cone,
In a cross section passing through the device axis and parallel to the device axis, the inclination angle θ of the inner angle between the device axis and the side surface of the cone is 76° or more and 88° or less.
6. An upsetting apparatus according to claim 1 or 5. the first pressing surface and the second pressing surface are side surfaces of a cone,
In a cross section passing through the device axis and parallel to the device axis, when the friction coefficient between the annular material and each of the first pressing surface and the second pressing surface is μ, the inclination angle θ of the inner angle between the device axis and the side surface of the cone is:
θ=90°−2×tan−1μ.
7. An upsetting apparatus according to claim 1, 5 or 6. At least one of the first pressing surface and the second pressing surface is provided with a positioning protrusion to be inserted into a central through hole of the annular material.
An upsetting apparatus according to any one of claims 1 to 7. a positioning step of positioning an annular material between a first die having a first pressing surface and a second die having a second pressing surface opposite to the first pressing surface;
a swaging process in which the annular blank is sandwiched and pressed between the first pressing surface and the second pressing surface from both ends in a direction along the axis by driving the first die and the second die in a direction in which they approach each other relatively,
A method for upsetting, wherein the first pressing surface and the second pressing surface are sides of a cone having a vertex at a point on an apparatus axis that is aligned with the axis of the annular material when the annular material is pressed. The upsetting step includes:
A free upsetting process in which the outer peripheral surface and the inner peripheral surface of the annular blank are not constrained.
The upsetting method according to claim 9. the first pressing surface and the second pressing surface are side surfaces of a cone,
In a cross section passing through the device axis and parallel to the device axis, when the friction coefficient between the annular material and each of the first pressing surface and the second pressing surface is μ, the inclination angle θ on the inner angle side between the device axis and the side surface of the cone is θ = 90 ° - tan - 1 μ.
The upsetting method according to claim 9 or 10. the first pressing surface and the second pressing surface are side surfaces of a cone,
In a cross section passing through the device axis and parallel to the device axis, when the friction coefficient between the annular material and each of the first pressing surface and the second pressing surface is μ, the inclination angle θ on the inner angle side between the device axis and the side surface of the cone is θ = 90 ° - 2 × tan -1 μ.
The upsetting method according to claim 9 or 10. The placing step includes:
A positioning step of positioning the annular material by inserting a positioning protrusion, which is provided on at least one of the first pressing surface and the second pressing surface and is centered on the device axis, into a central through hole of the annular material.
The upsetting method according to any one of claims 9 to 12. It is cyclic,
The central inner diameter portion on the inner diameter side at the center in the axial direction is
A central outer diameter portion on an outer diameter side at the center;
an inner diameter portion on an inner diameter side at one end side of the axial direction;
an inner diameter portion on the other end side of the inner diameter side at the other end side in the axial direction,
Upset processed product. The central inner diameter portion is at least 5% harder than the central outer diameter portion.
15. The upset product according to claim 14.

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