JPH04333502A - Method for reducing rod-shaped sintered material - Google Patents

Abstract

PURPOSE:To obtain a rod-shaped sintered material excellent in tensile strength and elongation by reducing. CONSTITUTION:One end of a rod-shaped sintered material 9 is inserted into the tapered hole 1a of a die 1, the other end is abutted on a presser member 7, at least one reinforcing member 10 is mounted on the sintered material 9 to prevent its buckling, and a liq. lubricant 25 is applied on the sintered material 9. Under these conditions, the die 1 or the member 7 is moved, and hence the sintered body 9 is passed through the hole 1a from its one end and strain- hardened by reducing. The dimensional precision is improved since the material is continuously worked, the density of the powder formed material is increased because a large hydrostatic pressure is exerted in the sintered material, and a forging crack is effectively prevented at its center. Furthermore, since the material is passed through the tapered hole and strain-hardened, the density and strength are increased, excellent tensile strength and elongation are obtained, and buckling is obviated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a punching method for obtaining a rod-shaped sintered material having excellent tensile strength and elongation properties.

0002

BACKGROUND OF THE INVENTION Conventionally, a penetrating body for injection into a protective object has been manufactured by reducing the diameter of a rod-shaped sintered material. To reduce the diameter of this rod-shaped sintered material, which is a powder compact, it is common to use a swaging process using two or four dies or a push-cut tap. Therefore, this processing method has a tensile strength of T. S. When applying to high-strength materials of around 100Kgf/mm2, the processing load is large, so
A large-scale dedicated machine is required, and even if a large-scale dedicated machine is used, there is a technical problem in that a high density increase cannot be achieved. In addition, since it is a discontinuous and intermittent processing method, significant improvement in dimensional accuracy cannot be expected and the product is likely to be bent.

Furthermore, in such a processing method, compressive force does not act on the entire cross section, but radial tensile force acts on the center. Therefore, in the case of materials with low ductility and difficult to process, the radius will not be applied during processing. So-called fir cracks that extend in the direction tend to occur in the center. This is because a sintered body obtained by sintering powder has high strength and is brittle, and therefore easily cracks during processing.

0004

[Means for Solving the Problems] The present invention has been made in view of such conventional technical problems, and is composed of a die having a tapered hole portion whose diameter gradually decreases;
The powder is sintered so that the diameter is larger than the small diameter end of the tapered hole, and a long rod-shaped sintered material is used for the die.
Insert one end of the rod-shaped sintered material into the tapered hole of the die,
With the other end in contact with the pressing member and with liquid lubricant applied to the outer peripheral surface of the rod-shaped sintered material, the die or the pressing member is moved in the direction of the center axis of the rod-shaped sintered material. A method for punching a rod-shaped sintered material, in which the rod-shaped sintered material is gradually punched out from a tapered hole portion of a die to strain-harden the rod-shaped sintered material by punching, the rod-shaped sintered material having at least one piece that suppresses buckling. This is a method for punching a rod-shaped sintered material into which a reinforcing member is fitted. A guide member that guides the movement of the outer peripheral surface of the reinforcing member can be fixed to the pressing member,
Further, a fixture capable of fixing the reinforcing member to an arbitrary location on the guide member can be provided.

[0005]

[Operation] A rod-shaped sintered material whose outer peripheral surface is coated with liquid lubricant is inserted through the reinforcing member and set between the pressing member and the tapered hole of the die. Next, the die or the pressing member is moved in the direction of the central axis of the rod-shaped sintered material to press fit the rod-shaped sintered material into the tapered hole of the die, reduce the cross-sectional area, and gradually push it out from the small diameter end. Since the rod-shaped sintered material that has passed through the die is thus swaged, the mechanical properties (eg, tensile strength, elongation, impact value, etc.) of the rod-shaped sintered material can be improved.

[0006] When passing through the die, the rod-shaped sintered material with an incompressible liquid lubricant around it moves and is reduced in diameter without being subjected to large frictional forces, thereby reducing the diameter of the rod-shaped sintered material by punching. A strain-hardened product is obtained. Furthermore,
The liquid lubricant applied to the outer circumferential surface of the rod-shaped sintered material is interposed between it and the tapered hole of the die, reducing frictional force and preventing surface roughening and seizure that can easily occur with high-strength materials. . In this type of punching of a rod-shaped sintered material, the reinforcing member fitted onto the rod-shaped sintered material suppresses buckling of the rod-shaped sintered material that is subjected to compressive force in the central axis direction between the die and the pressing member. It functions as follows.

[0007] In this way, the rod-shaped sintered material extruded from the tapered hole is compressed by a large hydrostatic pressure by also receiving the compressive force from the die in the direction of the central axis.
Since it passes through the tapered hole and undergoes strain hardening due to punching, high density and high strength can be obtained satisfactorily. That is, the density of the rod-shaped sintered material having pores can be extremely well increased using the powder molded material, and the formation of cracks in the center of the rod-shaped sintered material made of a difficult-to-process material can be effectively prevented.

Furthermore, the liquid lubricant interposed on the outer periphery of the rod-shaped sintered material makes the frictional force between the rod-shaped sintered material and the die extremely small. The variation in internal strain distribution is small, and the non-uniformity in the mechanical properties of the product is significantly reduced. In addition, if a guide member that guides the outer circumferential surface of the reinforcing member is fixed to the pressing member, the guide member restricts the movement of the reinforcing member in a direction that intersects with the central axis direction. buckling can be suppressed even better. Furthermore, if a fixture capable of fixing the reinforcing member to any location on the guide member is provided, the reinforcing member can be fixed at a position suitable for suppressing buckling of the rod-shaped sintered material. Note that the rod-shaped sintered material can be processed not only at room temperature, but also in a warm state by heating up to about 500°C.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 7 show a punching device used in one embodiment of the punching method. In the figure, reference numeral 1 indicates a die, which has a tapered hole portion 1a having a diameter gradually reduced and having a small diameter end portion 1b. The die 1 is placed on a cylindrical support member 2 with its central axis aligned, and is fixed by screwing a nut member 3 fixed to the bottom surface onto the upper end of the support member 2. The support member 2 is vertically erected with its lower end fixed to the lower base 4 via the fixing member 5.

On the other hand, an upper base plate 6 is placed opposite the lower base plate 4. A flange member 8 for fixing a bush 7, which is a pressing member, is fixed to the lower surface of the upper base plate 6 by bolts (not shown). Deploy. The rod-shaped sintered material 9 is a powder molded material obtained by sintering metal powder, and has a tensile strength of T. S. 100Kg
f/mm2 high strength material (for example, W-Ni-
It is made of Fe sintered alloy). The rod-shaped sintered material 9 is a rod-shaped body having a slightly larger diameter (specifically, about 20 to 30% larger in cross-sectional area) than the small-diameter end 1b of the tapered hole 1a of the die 1. It is sufficiently long.

Further, a reinforcing member 10 is fitted onto the outer peripheral surface of the rod-shaped sintered material 9. In this embodiment, the reinforcing members 10 are provided with a pair of identical prismatic reinforcing members 10, as shown in FIGS.
3, each reinforcing member element 10a is divided into two parts,
10b has a through hole 10c extending in the direction of the central axis in the assembled state, and an annular notch 10d for weight reduction is provided in the middle part of the outer peripheral surface. Furthermore, bolts 11 are implanted in the outer surfaces of each reinforcing member element 10a, 10b.

Further, the flange member 8 is provided with guide members 12, 1 for guiding the outer peripheral surfaces of the pair of reinforcing members 10.
3 are fixed to face the outer edge of the flange member 8. The guide members 12 and 13 are substantially plate-shaped, and have slit portions 12a and 13 extending in the central axis direction as shown in FIG.
a are formed to face each other. Each reinforcing member 10 is assembled by movably receiving a rod-shaped sintered material 9 in a through hole 10c, and bolts 11 are inserted into each slit portion 12a, 13a.
are inserted, and the guide members 12 and 13 are fixed to the flange member 8 with bolts (not shown). Then, the rod-shaped sintered material 9
In order to satisfactorily suppress the buckling of
are screwed and fixed to the guide members 12 and 13. These bolts 11 and nuts 14 constitute a fixture capable of fixing the reinforcing member 10 to any location in the central axis direction of the guide members 12 and 13.

The pressing drive means 15 for lowering the upper base 6 will be explained with reference to FIG. 5. The pressing drive means 15 is
The main component is a double-acting cylinder device 16 having a cylinder 16a fixed to the center of the upper surface of the upper base plate 6. The cylinder 16a is slidably fitted into the piston 16b.
The upper chamber 16c and the lower chamber 16d are divided by the upper chamber 16c and the lower chamber 16d. 1
A piston rod 6e is inserted through the rod cover in a liquid-tight manner, and its protruding upper end is connected to the lower surface of the support base 18. This support base 18 is fixed to the lower base 4 via pillars 17. A hydraulic pump 22 is connected to the cylinder 16a via a switching valve 19 having positions a, b, and c, a variable flow rate control valve 20, and a relief valve 21.
is connected. Each 23 is a reservoir for storing working fluid, and 24 is a pressure gauge.

Next, a method for punching a rod-shaped sintered material using the punching apparatus having the above structure will be explained. A liquid lubricant 2 is applied to the outer peripheral surface of the rod-shaped sintered material 9 as shown in FIG.
5 was applied in advance to form a thin film. liquid lubricant 2
5 is a highly viscous sol-like molybdenum disulfide or the like.

Initially, the guide members 12, 13 and the reinforcing member 10 are removed. Also, the switching valve 19 is set to the a position, and the hydraulic pump 22 supplies the working fluid to the upper chamber 16.
c, the lower chamber 16d is drained, and the upper base plate 6 is driven upward. By this operation, the space between the upper and lower base plates 6 and 4 is sufficiently expanded, so that the rod-shaped sintered material 9 is placed between the bush 7 of the upper base plate 6 and the tapered hole portion 1a of the die 1. Next, the reinforcing member 10 is assembled so that the rod-shaped sintered material 9 is received in the through hole 10c, and each slit portion 12a,
13a and insert the bolt 11 into the guide members 12, 13.
is fixed to the flange member 8 with bolts. Reinforcement member 10
is at an appropriate position in the direction of the central axis of the rod-shaped sintered material 9, and screw the nuts 14 onto each bolt 11 to attach the guide members 12, 13.
Fixed and set. The reinforcing member 10 is installed at a position where buckling of the rod-shaped sintered material 9 is likely to occur.

When the setting is completed, the switching valve 19 is set to the position b, and after draining both chambers 16c and 16d, the switching valve 19 is set to the position c, and the working fluid from the hydraulic pump 22 is sent to the lower chamber 16d. The upper base plate 6 is driven downward. As a result, the rod-shaped sintered material 9 whose upper end is supported in contact with the bush 7 is press-fitted into the tapered hole 1a of the die 1, and is gradually pushed out from the small diameter end 1b while reducing its cross-sectional area. The rod-shaped sintered material 9 that has passed through the die 1 in this manner is subjected to diameter reduction processing, and has mechanical properties (such as tensile strength, elongation,
impact value, etc.) is improved.

During punching of the rod-shaped sintered material 9, compressive force is applied to the rod-shaped sintered material 9 in the vertical direction, that is, in the direction of the central axis. shows a tendency to bend and buckle. However, the bending deformation of the intermediate portion of the rod-shaped sintered material 9 is caused by the reinforcing member 1
0, and passes through the tapered hole 1a of the die 1 without buckling. Movement of the reinforcing member 10 in a direction intersecting the central axis direction is suppressed by the guide members 12 and 13.

When the upper base plate 6 and the reinforcing member 10 come to interfere with each other as shown in FIG. 7 as the upper base plate 6 descends, the switching valve 19 is set to position b and the punching process is interrupted. Then, the bolts 11 and nuts 14 are unscrewed, the guide members 12 and 13 are removed, and the reinforcing member elements 10a and 10b which form each of the two halves of one reinforcing member 10 are removed, and the punching process is continued. When the punching process is performed in this way and the upper base plate 6 approaches the die 1 with all the reinforcing members 10 removed, a rod-shaped member (not shown) having a smaller diameter than the small-diameter end 1b of the tapered hole 1a is inserted. It is interposed between the bush 7 and the upper end surface of the rod-shaped sintered material 9, and punching is performed so that the entire rod-shaped sintered material 9 passes through the tapered hole portion 1a. The rod-shaped sintered material 9 that has been punched out is taken out from the lower end of the support member 2 and processed into a penetrating body or the like to be injected into a protective object.

When passing through the die 1, the rod-shaped sintered material 9 has a thin film of incompressible liquid lubricant 25 interposed around it.
The diameter is reduced by moving without receiving much frictional force,
This results in a product that is well strain hardened by punching. Furthermore, since the liquid lubricant 25 applied to the outer peripheral surface of the rod-shaped sintered material 9 is interposed between the rod-shaped sintered material 9 and the tapered hole 1a of the die 1, the rod-shaped sintered material 9 located in the tapered hole 1a of the die 1 is particularly is compressed by a compressive force in the direction of the central axis from the upper base plate 6 side, and is compressed under hydrostatic pressure by receiving compressive force from the outer periphery, thereby promoting high density and high strength.

In this way, the rod-shaped sintered material 9 extruded from the small diameter end 1b is not only subjected to compressive force in the central axis direction from the upper base plate 6, but also compressed by a large hydrostatic pressure, and is tapered. Since it passes through the hole 1a and undergoes strain hardening by punching, high density and high strength can be obtained satisfactorily. In other words, the density of the rod-shaped sintered material 9 having pores is extremely well increased by being a powder molded material, and the formation of cracks in the center of the rod-shaped sintered material 9 made of a difficult-to-process material is well prevented. . Specifically, the large pores in the rod-shaped sintered material 9, which is a sintered body, are compressed and collapsed, the sizes of the mixed pores become uniform, and the porosity can be reduced to 0.5% or less, Mechanical properties can be improved.

Furthermore, the liquid lubricant 25 interposed in a thin film on the outer periphery of the rod-shaped sintered material 9 makes the frictional force between the rod-shaped sintered material 9 and the die 1 extremely small. It is possible to prevent surface roughness and seizure that tend to occur with high-strength materials, and to reduce fluctuations in the strain distribution inside the bar-shaped sintered material 9 during processing, thereby significantly reducing non-uniformity in the mechanical properties of the product.

By the way, the rod-shaped sintered material 9 can be processed not only at room temperature, but also in a warm state by heating up to about 500°C. As described above, since the buckling of the rod-shaped sintered material 9 is well suppressed, the lower base plate 4 is driven upward while the die 1 in FIG. Even if it is pushed into the hole 1a and punched out, substantially the same effect can be obtained.

Furthermore, the guide members 12 and 13 can be formed into rectangular tube shapes to increase their rigidity. However, in that case, the bolts 11 of the reinforcing member 10 are made removable, and the bolts 11 are removed from the reinforcing member 10 and the guide members 12,
13 is sufficiently lowered toward the supporting member 2 side, the reinforcing member 10 divided into two parts is exposed, and the reinforcing member 10 is attached and detached.

[0024]

[Effect of the invention] As understood from the above explanation,
According to the method for punching a rod-shaped sintered material according to the present invention,
The following effects can be obtained. (1) Since the punching process is performed virtually continuously,
A good improvement in dimensional accuracy is achieved. (2) Since not only a pressing force in the central axis direction but also a large hydrostatic pressure acts inside the rod-shaped sintered material, the density of the powder compact can be favorably increased. In addition, compressive force also acts in the central axis direction, and no axial tensile stress is generated in the center, so
It is effective in preventing fir cracks in the center of low-ductile and difficult-to-process materials that extend in the radial direction during processing. Furthermore, since the material passes through the tapered hole and undergoes strain hardening by punching, high density and high strength can be obtained satisfactorily. As a result, a rod-shaped sintered material having both good tensile strength and elongation properties can be obtained.

(3) The liquid lubricant is interposed in the form of a thin film between the rod-shaped sintered material and the die wall, and the friction between them is significantly reduced, so that the strain distribution generated inside the rod-shaped sintered material during processing is reduced. Smaller variations reduce non-uniformity in the mechanical properties of the product. (4) The large pores in the rod-shaped sintered material, which is a sintered body, are greatly compressed and collapsed by hydrostatic pressure, making it possible to uniform the size of the mixed pores and to reduce the porosity favorably.
As a result, mechanical properties are improved. (5) At least one reinforcing member is fitted around the rod-shaped sintered material to suppress buckling, so that the long rod-shaped sintered material can be punched without bending.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a punching device used in one embodiment of the present invention.

FIG. 2 is a diagram showing a reinforcing member as well.

FIG. 3 is a sectional view taken along the line III--III in FIG. 2.

FIG. 4 is a diagram showing a guide member according to one embodiment of the present invention.

FIG. 5 is a sectional view similarly showing the pressing drive means.

FIG. 6 is a cross-sectional view showing a rod-shaped sintered material.

[Fig. 7] Similarly, an action explanatory diagram.

[Explanation of symbols]

1: Dice, 1a: Tapered hole, 1b: Small diameter end, 2:
Supporting member, 4: Lower base, 6: Upper base, 7: Button (pressing member), 9: Rod-shaped sintered material, 10: Reinforcement member, 10a,
10b: reinforcing member element, 10c: through hole, 10d: annular notch, 11: bolt (fixing tool), 12, 13: guide member, 12a, 13a: slit section, 14: nut (fixing tool), 15: Pressing drive means, 16: Cylinder device, 1
6a: cylinder, 16b: piston, 17: strut, 18
: Support base, 19: Switching valve, 22: Hydraulic pump, 2
5: Liquid lubricant.

Claims (3)

[Claims] Claim 1: A die having a tapered hole whose diameter gradually decreases, and a long rod-shaped die made by sintering powder so that the diameter is larger than the small diameter end of the tapered hole. Using sintered material, one end of the rod-shaped sintered material is inserted into the tapered hole of the die, the other end is brought into contact with the pressing member, and a liquid lubricant is applied to the outer peripheral surface of the rod-shaped sintered material. move the die or pressing member in the direction of the central axis of the rod-shaped sintered material,
A method for punching a rod-shaped sintered material by gradually punching out the rod-shaped sintered material from a tapered hole of a die, strain hardening the rod-shaped sintered material by punching, and suppressing buckling of the rod-shaped sintered material. A method for punching a rod-shaped sintered material, the method comprising fitting at least one reinforcing member to the outside of the rod-shaped sintered material. 2. The method for punching a rod-shaped sintered material according to claim 1, wherein a guide member for slidingly guiding the outer circumferential surface of the reinforcing member is fixed to the pressing member. 3. The method for punching a rod-shaped sintered material according to claim 2, further comprising a fixture capable of fixing the reinforcing member to an arbitrary location on the guide member.