JPH02149604A - Manufacture of compression molding of powder - Google Patents

Abstract

PURPOSE:To simplify production process without deteriorating material quality and to manufacture a compression molding having high density by packing metal powder into a metallic vessel, giving vibration, evacuating after increasing the packing density, sealing and compression-forming. CONSTITUTION:The metal powder (about 5 - 500mu particle diameter) or mixed powder 3 of the metal and ceramics (about 1 - 100mu particle diameter) is packed in a metallic vessel 1 consisting of a metal pipe 2 (about 1.0 - 10.0mm thickness) and a bottom cover 2a (about 0.3 - 5.0mm thickness) and having good plastic workability. This vessel 1 is laid on center part at upper end of a vibrating device 4 (about 3 - 100Hz vibration frequency) to give the vibration and the packing density is made to about 60 - 80% and the upper cover 5 (about 1 - 5mm thickness) arranging a gas exhaust pipe 6 is connected. Successively, the pressure in the vessel 1 is reduced to about 10<-5> - 10<-1>Torr and after sealing the gas exhaust pipe 6, the hot compression-molding is executed at about 1,000 - 10,000kgf/cm<2> compressed pressure to attain close to 100% density. By this method, the cold compression molding process is omitted and the compression forming of the powder is obtd. at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing a pressed IIM compact by powder metallurgy.

(Prior art) Powder metallurgy is originally a method in which metal powder is placed in a mold, compression molded, and then sintered at a temperature below the melting temperature. Because of its residual properties and poor toughness, its use was limited to materials that are difficult to process, such as cemented carbide and tungsten wire, or materials that are difficult to manufacture without using powder metallurgy, such as high-melting point materials.

However, in recent years, a method has been developed in which after cold-compressing a powder of metal, it is placed in a metal container, evacuated, sealed, and hot-processed together with the metal container. It has come to be known as true density sintered alloy and is being used in various fields.

The above method using a metal container is particularly effective for alloys that are easily oxidized, such as aluminum alloys.

That is, in alloys that are easily oxidized such as aluminum alloys, since an oxide film is generally present on the powder surface, metal atoms and gas diffusion are difficult to occur at the contact portions between the powders. Therefore, the above-mentioned method of vacuum processing, destroying the oxide film on the powder surface, and sintering is particularly effective. L4
Composite materials in which fine particles such as C3 are dispersed have excellent wear resistance and heat resistance, and are being developed as parts for automobiles and the like.

(Problems to be Solved by the Invention) In the method for manufacturing a true density sintered alloy described above, the powder is cold compression molded and then evacuated, and the air in the gaps between the powder and the gas adsorbed on the powder surface are removed. It is necessary to remove moisture etc. At this time, if cold compression molding is performed to a high density ratio, gas bubbles tend to become isolated between powder particles, and when a product in this state is hot molded, it appears as if the voids have been compressed and disappeared. However, when heat treatment such as solution treatment is subsequently performed, the gas expands and coagulates, causing defects such as blisters and cracks. Therefore, in cold compression molding, the density ratio is relatively low so that the internal air can be easily discharged, but as a result, cracks may occur when the cold-open molded product is taken out of the mold or inserted into a metal container. Cold-open molding must be performed to prevent the product from collapsing or collapsing.

Therefore, the cold compression molding step and the subsequent step of inserting the cold-opened compact into a metal container have had various difficulties.

Therefore, in order to avoid such difficulties, it is most desirable if the cold compression molding step can be omitted. However, when the powder is packed in a metal container, the packing density of the powder is 40~
50%, and when this is hot-opened, the amount of deformation during compression processing becomes large, causing the problem that the metal container buckles and gets rolled up into the powder part, deteriorating the yield of the healthy part.

The present invention was made in view of these problems, and aims to omit the cold forming step in the true density powder molding metallurgical material manufacturing process, increase the packing density of the powder, and simplify the manufacturing process and reduce costs.

(Means for Solving the Problems) The present invention involves filling a metal container with metal powder or a mixed powder of metal and ceramics, increasing the packing density of the powder by applying vibration during or after the filling, and then The present invention provides a method for producing a compression molded product of powder, which comprises evacuating the inside of a metal container, sealing the container, and compression molding the container to 100% density.

First, in the method of the present invention, filling of the powder can be carried out using the metal containers shown in FIGS. 1 and 2 above. 4 is a vibration device which will be described later. Further, 2a is a bottom cover welded to the lower end opening of the metal pipe 2. The metal container l is made of materials such as An, Cu, Fe, Ni, and P.
Among metals such as B, Sn, and alloys thereof, any metal having good plastic workability can be preferably used. The metal pipe 2 preferably has a thickness of 1.0 to 10.0 mm, and the bottom cover 2a preferably has a thickness of 0.3 to 5.0 mm. Within this range, it will fully function as a metal container. The shape (cross-sectional shape) of the metal container used in the present invention is not particularly limited.

The powder to which the method of the present invention is applied may be any powder made of metals such as Cu, Fe, Co, W, Mo, etc., as well as alloys thereof, in addition to An, and the manufacturing methods thereof include gas atomization, centrifugal atomization, It may be manufactured by any method such as a rotating cup method or a rotating electrode method. The particle size of the powder is not particularly limited, but is preferably 5 to 500 ILm.

In addition, as ceramic powder, 5iC1WC, BC
Carbide systems such as Si3N4, AmonN, BN, TiN, etc., A410, ZrOz,
An oxide system such as M g OIS 102, BeO, or the above-mentioned composite compound is applied. The shape of the ceramic powder is not limited to granules, but may be any shape such as long fibers or short fibers. Whiskers or the like may also be used. The particle size of the powder is preferably 1 to 1100p. Further, the mixing ratio of the metal powder in the ceramic powder is preferably up to about 50% by volume; within this range, a compression molded body can be produced without causing any problems.

In the present invention, vibration is applied to the powder when or after filling the metal container with the powder, and this can be done using the vibration device 4. The vibrating device 4 has a cylindrical portion formed at the center of the upper end, into which the lower part of the metal container 1 is inserted and installed, so that it can vibrate back and forth and up and down. The frequency of vibration is desirably one that generates vibrations of 3 to 100 Hz, particularly one that generates vibrations of 5 to 30 Hz. Regarding the strength of vibration applied to the powder, the stronger the vibration, the shorter the time it takes for the powder to increase its packing density, which is advantageous.If it is too strong, the powder will scatter, so apply the strongest vibration without causing the powder to scatter. Or ideal.

In addition, when using a mixture of metal powder and ceramic powder, if the difference in specific gravity between the metal powder and ceramic powder is large, the ceramic powder may separate or become unevenly distributed when strong vibrations are applied for a long time. Therefore, it is necessary to consider the difference in specific gravity, the time to apply vibration, etc. for each powder used.

In the present invention, this vibration increases the packing density of the powder, preferably in the range of 60 to 80%.If the packing density is within this range, the metal container will buckle significantly during subsequent compression molding, significantly reducing the yield. Compression molded bodies can be produced without deterioration.

As described above, the metal container 1 filled with the powder 3 that has been subjected to vibrations is evacuated, or this evacuation method is 1. For example, as shown in FIG. The upper lid 5 is connected by welding, etc., and an exhaust pipe 6 is provided on the upper lid 5, and a vacuum exhaust device (not shown) is connected to this.
This can be done by reducing the pressure to 1 O'Torr. After the exhaust pipe 6 is evacuated, it is sealed by being crimped by hitting it with a hammer or the like. Note that the material used for the upper lid 5 is one that has good weldability to the metal container. There is no particular limit to the thickness of the plate, but it is 1 to 5 m.
m is preferred.

After evacuation, the sealed metal container 1 is then subjected to hot compression molding using a conventional method such as a hydraulic press or hot isostatic pressing to densify it to 100% density to obtain a compression molded body. The compression pressure at this time is 1000 to 100
00 K g f / cm' is preferred.

In addition, in the method of the present invention, as shown in FIG. 3, an air exhaust hole 7 is provided in the bottom cover 2a of the metal pipe 2, and an air-permeable tape 8 is attached to the hole 7 to close it. is more preferable, and by providing an air exhaust hole, the strength of the vibration applied to the powder during vibration can be weakened and the vibration time can be shortened. This air exhaust hole 7 is closed by welding after applying vibration to increase the packing density. Note that the tape 8 is provided to prevent powder from being released from the air exhaust hole 7.

FIG. 4 shows the other side of the metal container used in the present invention, in which a weight 9 is placed on the upper end of the powder to apply pressure when the metal container 1 is filled with powder. In this way, the strength of the vibration applied to the powder can be weakened,
Vibration time can be shortened and packing density can be increased.

(Example) The present invention will be explained in more detail below based on Examples.

Pure aluminum was used for the metal vibrator 2, which was carried out using the apparatus shown in FIGS. 1 and 2, and pure aluminum was also used for the bottom cover 2a.

The dimensions of this metal vibrator 2 with one end closed are 200 mm in outer diameter.
, the wall thickness is 5 mm, the height is 700 mm, and the thickness of the bottom cover 2a is 3 m.
It is m. Powder 3 used in the experiment is a 7091A1 alloy powder with a particle size of 1105p or less and this AI grain powder of 15μ.
2 of mixed powder to which 10% by volume of SiC powder of m or less is added
It is a kind.

The above mixed powder 3 is filled into the metal vibrator 2 made of pure aluminum in an amount that will have a height of 300 mm when the true density is made, and this is set in the vibrating device 4 to vibrate at 12.5 Hz for 3
to increase packing density. As shown in FIG. 2, the top lid 5 was welded to the opening of the metal vibrator 2, and a vacuum exhaust device ( (not shown) by 400
``The inside of the metal pipe is heated to 1O-2 Torr while heating to C.
It was evacuated and sealed. Ten such molded bodies were produced, and these were hot-formed and pressed at 400°C to form a billet.

For comparison, 10 billets filled with powder were vacuum evacuated and hot-formed under the same conditions as described above without vibration and were produced. Furthermore, a cold compact of the mixed powder was produced by a conventional method. In other words, the above mixed powder was directly filled into a mold with an inner diameter of 200 mm, and the relative density was 85%.
This was cold compression molded to give the following properties, taken out from the mold, inserted into the same pure aluminum metal vibrator as above, heated to 400°C, evacuated to vacuum, and sealed.

Ten pieces of this molded body were produced, and these were hot-formed and pressed at 400°C to form a billet.

After cold-opening the A1 alloy powder under the above conditions,
It was processed into a billet by hot compression molding.

After cutting these billets until the outer pipe was completely removed, the diameter of the healthy billet portion was measured to determine the yield. Next, it was extruded to a diameter of 70 mm at a temperature of 420°C. This extruded material was solution-treated at 488°C for 1 hour, then cooled with water, and then subjected to T6 aging treatment at 120°C for 24 hours, and the presence or absence of blisters on the surface of the extruded material was observed.
The strength of the extruded material was measured. Table 1 shows the yield of the healthy part of the billet, the presence or absence of blistering S after solution treatment, and the tensile test results during T6 treatment.

As is clear from Table 1, the billet formed without applying vibration has buckled aluminum pipes and the diameter of the healthy part of the billet is small, whereas the diameter of the billet of the present invention is equivalent to that of the conventional method. It shows the yield. In addition, although the method of the present invention does not involve cold compression molding using a press, it does not cause blisters due to solution treatment and has the same strength as powder metallurgy materials manufactured by conventional methods. It can be seen that there was no adverse effect due to the change and simplification of the .

(Effects of the Invention) According to the present invention, it is possible to omit the cold compression molding process in the conventional manufacturing process of true density sintered materials without deteriorating the material quality, resulting in a significant reduction in manufacturing costs. It has a great effect.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are a schematic cross-sectional view and a perspective view of one embodiment of an apparatus used for manufacturing a compression molded article of the present invention. FIGS. 3 and 4 are an explanatory perspective view and a sectional view of the other side of the metal container used in the present invention. l...metal container, 2...metal vibrator, 2a...
Bottom cover, 3... Powder, 4... Vibration device, 5... Top cover, 6... Exhaust pipe, 7... Air exhaust hole, 8... Breathable tape, 9... Weight . to

Claims (1)

[Claims] A metal container is filled with metal powder or a mixed powder of metal and ceramics, vibration is applied during or after the filling to increase the packing density of the powder, and the inside of the metal container is evacuated and sealed. 1. A method for producing a compression molded powder body, characterized by compression molding the powder to a density of 1.5%.