JPH0723485B2 - Sintered material processing method - Google Patents

Description

The present invention relates to a method for processing a sintered material obtained by sintering powder.

[Conventional technology and its problems]

Conventionally, for reducing the diameter of a round bar material which is a sintered material, a swaging process using two or four dies or a stamping tap is generally used. Then, this processing method is YS10
When applied to a high-strength material of about 0 kgf / mm ² , the processing load is large, so a large-scale special machine is required, and there is a technical problem that a high density increase cannot be obtained even when using a large-scale special machine. is there. In addition, since it is an intermittent processing method, it is not possible to expect a significant improvement in dimensional accuracy, and bending is likely to occur. Furthermore, in such a processing method, the compressive force does not act on the whole, and the tensile stress in the radial direction acts on the central portion, so that hydrostatic pressure cannot be obtained in the case of a material with low ductility and difficult to process. In addition to this, so-called fir cracks extending in the radial direction are likely to occur in the central portion during processing. This is because the sintered body obtained by sintering powder has high strength and is brittle,
This is also due to the fact that cracks are likely to occur during processing.

[Means for Solving the Problems]

The present invention has been made in view of such a conventional technical problem, and the configuration thereof is such that an opening, a large-diameter cylindrical portion, a taper portion that gradually reduces in diameter, and the other end open sequentially from one end. Using a die that forms a small-diameter cylindrical portion, insert a round bar material that has a smaller diameter than the large-diameter cylindrical section and sinters powder into the large-diameter cylindrical section of the die, A liquid-tight plunger is slidably inserted into the large-diameter cylindrical portion with a lubricating liquid interposed around the periphery, and a pressing force from one end side is applied to the plunger to move the round bar material into a die. This is a processing method of a sintered material in which a taper portion and a small-diameter tubular portion are sequentially passed and strain hardening is performed by extrusion.

[Action]

This method for processing a sintered material can be carried out with a relatively small pressing force, and the die is placed on the bed of an ordinary pressing device for use.

First, a round bar material having a diameter smaller than that of the large-diameter cylindrical portion is inserted into the large-diameter cylindrical portion of the die, and the lubricating liquid is interposed in a thin film shape.

The round bar material is made of a sintered material obtained by sintering metal powder, and a high strength material can be used. The thin-film lubricating liquid is formed around the round bar material, that is, between the outer circumference and the plunger.

A plunger integral with the ram of the press machine is fitted in a liquid-tight and slidable manner into this large-diameter cylindrical portion.

Then, the ram of the pressing device is lowered, and a pressing force is applied to one end of the round bar material through the plunger and the thin film of the lubricating liquid. As a result, the round bar material in which a non-compressible lubricating liquid is interleaved in the form of a thin film descends with almost no frictional force, the diameter is reduced by the tapered part of the die, and the other end is die-cut. Is gradually extruded through the opening of the small-diameter tubular portion, thereby obtaining a strain-hardened product by extrusion.

At that time, by interposing a lubricating liquid between the plunger and one end surface of the round bar material, the round bar material located in the large-diameter cylindrical portion and the tapered portion can apply the pressing force from the ram of the pressing device from the plunger. The hydrostatic pressure of the lubricating liquid is received from the outer periphery while being received in the axial direction, and is compressed to promote high density and high strength.

Further, due to the lubricating liquid interposed in the form of a thin film, the frictional force between the round bar material and the die wall becomes extremely small, and the fluctuation of the strain distribution inside the round bar material during processing becomes small.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 to 3 show one embodiment. Reference numeral 1 in the figure
Shows a container, and a large-diameter hole portion 1b and a small-diameter hole portion 1c, which are connected to each other via the step surface 1a, are formed inside with their central axes aligned. The cylindrical die 2 is press-fitted and fitted into the large-diameter hole portion 1b of the container 1 by shrink fit, and the die 2
The other end surface of is locked to the step surface 1a. As shown in FIG. 2, the die 2 is provided with a cavity 2a penetrating in the central axis direction. The cavity 2a has an opening 2b having a circular cross section, a large-diameter cylindrical portion 2c, a tapered portion 2d having a gradually decreasing diameter, and a small-diameter cylindrical portion 2e having an opening at the other end, which are sequentially formed from one end. However,
The small-diameter hole portion 1c of the container 1 has a larger diameter than the small-diameter cylindrical portion 2e.
It does not block the ends.

The container 1 containing the die 2 in this manner is placed on the bed 3 of the pressing device with a pair of block-shaped spacers 4 interposed therebetween.

Next, the lubricating liquid 5 is filled around the round bar material 6 in a thin film form, and the round bar material 6 is inserted into the cavity 2a of the die 2 as shown in FIG. The round bar material 6 is a sintered material obtained by sintering metal powder, and is usually formed of a high-strength material (for example, a W-Ni-Fe sintered alloy) of about YS 100 kgf / mm ² . . That is, the round bar material 6 has a diameter slightly smaller than that of the large-diameter cylindrical portion 2c of the die 2 to form a thin film layer of the lubricating liquid 5 on the outer peripheral portion thereof, and the lubricating liquid is formed between it and the plunger 7 described later. 5 layers are formed. The lubricating liquid 5 is a highly viscous sol oil or the like.

As a method of filling the lubricating liquid 5 into a thin film between the large-diameter cylindrical portion 2c of the die 2 and the round bar material 6 as described above, the die 2
The lubricating liquid 5 is poured into the large-diameter cylindrical portion 2c in a state where the small-diameter cylindrical portion 2e is closed, and then the round bar material 6 is inserted into the hollow portion 2a, and as shown in FIG. The other end peripheral edge may be brought into liquid tight contact with the tapered portion 2d to release the closed state of the small diameter cylindrical portion 2e.

Plunger 7 which is integral with a ram (not shown) of the press device is fluid-tightly and slidably inserted into this large-diameter cylindrical portion 2c. Specifically, the plunger 7 includes a seal ring 7a having pressure resistance, and the plunger 7 is fitted into the large-diameter cylindrical portion 2c via the seal ring 7a to maintain liquid tightness.

Then, the ram of the pressing device is lowered, and a pressing force is applied to one end of the round bar material 6 through the plunger 7 and the thin film of the lubricating liquid 5. As a result, the round bar material 6 with the incompressible lubricating liquid 5 intervening in the form of a thin film descends with almost no frictional force, and is reduced in diameter by the tapered portion 2d of the die 2, The end portion is gradually extruded from the opening of the small-diameter cylindrical portion 2e of the die 2, whereby the end portion is strain-hardened by the extrusion process and a product is obtained between the pair of spacers 4.

At that time, by interposing the lubricating liquid 5 between the plunger 7 and one end surface of the round bar material 6, the round bar material 6 located in the large-diameter tubular portion 2c and the tapered portion 2d of the cavity 2a is pressed. Lower pressure from the ram of the device is received from the plunger 7 in the axial direction, and hydrostatic pressure action of the lubricating liquid 5 is received from the outer periphery to be compressed, so that high density and high strength are promoted.

In this way, the round bar material 6 extruded from the small diameter tubular portion 2e
Is compressed not only by the pressure from the ram of the press machine but also by the hydrostatic action of the lubricating liquid 5, and it is strain-hardened by extrusion through the tapered portion 2d. And high strength can be satisfactorily obtained.
That is, when the round bar material 6 passes through the large-diameter cylindrical portion 2c and the taper portion 2d, it receives a pressing force in the axial direction from the plunger 7 and a large hydrostatic pressure action of the lubricating liquid 5, so that the pores are made of the sintered material. The density increase of the round bar material 6 having the above can be obtained extremely well, and it is possible to favorably prevent fir cracks from occurring in the central portion of the round bar material 6 made of a difficult-to-process material. Specifically, the large pores in the round rod material 6 which is a sintered body are largely compressed and crushed, the sizes of the mixed pores are made uniform, and the porosity can be reduced to 0.5% or less. (For example, tensile strength, elongation, impact value, etc.) are improved.

Further, since the lubricating liquid 5 intervening in a thin film on the outer periphery of the round bar material 6 makes the frictional force between the round bar material 6 and the wall of the cavity 2a of the die 2 extremely small, during processing The variation in the strain distribution inside the round bar material 6 is small, and the non-uniformity in the mechanical properties of the product is significantly reduced.

〔The invention's effect〕

As can be understood from the above description, according to the present invention, the following effects can be obtained.

． It is possible to use a general-purpose press device and does not require a large-scale dedicated machine, so that it is easy to implement.
In addition, since it is a continuous processing method, dimensional accuracy can be improved satisfactorily and bending is less likely to occur.

． Not only the pressing force from the plunger but also a large hydrostatic pressure acts on the inside of the round bar material, so the density increase of the sintered material is satisfactorily obtained, and the compressive force also acts in the radial direction, and the radial direction is applied to the center. Since it does not generate tensile stress, it is effective in preventing fir cracks in the central portion of the material having low ductility and difficult to process, which is caused by extending in the radial direction during processing.

Further, since it passes through the tapered portion and undergoes strain hardening by extrusion processing, high density and high strength can be satisfactorily obtained.

． The lubricating liquid intervenes in a thin film between the round bar material and the die wall, and significantly reduces the friction between them, so the variation in the strain distribution generated inside the round bar material during processing is small, and the mechanical properties of the product Non-uniformity is reduced.

． Large pores in the sintered rod material are largely compressed and crushed by the hydrostatic effect, and the mixed pores are made uniform, and the porosity can be reduced to 0.5% or less. Mechanical properties are improved.

[Brief description of drawings]

1 to 3 show one embodiment of the present invention, FIG. 1 is a sectional view showing an apparatus for processing a sintered material, FIG. 2 is a sectional view showing a die,
FIG. 3 is an operation explanatory view. 1: Container, 1a: Step, 1b: Large diameter hole, 1c: Small diameter hole, 2: Die,
2a: Hollow part, 2b: Opening, 2c: Large diameter cylindrical part, 2d: Tapered part, 2e: Small diameter cylindrical part, 3: Bed of press machine, 4: Spacer, 5: Lubricating liquid, 6: Round bar material , 7: Plunger, 7a: Seal ring.

Claims (1)

[Claims] 1. A die having an opening, a large-diameter cylindrical portion, a taper portion having a gradually decreasing diameter, and a small-diameter cylindrical portion having the other end opened sequentially from one end, wherein the large-diameter cylindrical portion of the die is used. With a diameter smaller than that of the large-diameter cylindrical portion, a powder-sintered round bar material is inserted, and a lubricating liquid is interposed around the round bar material,
A liquid-tight plunger is slidably inserted into the large-diameter tubular portion,
A method for processing a sintered material, characterized in that a pressing force from one end side is applied to the plunger to sequentially pass the round bar material through a taper portion and a small-diameter tubular portion of a die, and strain hardening is performed by extrusion. .