JPH06279805A - Production of ceramic powder or metallic powder sintered compact - Google Patents

Abstract

PURPOSE:To easily obtain a small-sized sintered compact by injection molding a kneaded body which contains ceramic powder or metallic powder inspecific ratios and is composed of the balance an org. binder, then compressing the molded. article while degreasing and sintering the molded article. CONSTITUTION:The kneaded body composed of 5 to 40vol.% and the balance the org. binder is injection molded to form the molded article 32. This molded article 32 is installed in a degreasing furnace 31 where the molded article is degreased by heating. The atmosphere pressure in the degreasing furnace body 31 is increased by a compressor 42 to compress the molded article 32. A pressure reducing valve 44 is opened after the completion of the compression and after the molded article 32 is cooled, the molded article is sintered in a sintering furnace. The formation of the cavity of the molds to be used for the injection molding to a relatively large size is possible. Since the flow property of the kneaded body is improved at the time of the injection molding, the molding is relatively easy. The molded article shrinks largely and, therefore, the sintered compact of a small size is easily obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a sintered body formed by sintering ceramic powder or metal powder.

[0002]

2. Description of the Related Art Conventionally, various methods such as die molding, hydrostatic molding, hot press molding, tape molding, extrusion molding and cast molding have been carried out as a method for producing powder metallurgy and ceramics. Among them, ceramic powder injection molding and metal powder injection molding have recently attracted attention as a method for relatively easily manufacturing a complicated shape.

As a method for producing these, for example, Japanese Patent Laid-Open No.
7-198202 and JP-A-62-37302.
The invention described in the publication is disclosed. These methods are
A kneaded body obtained by kneading a ceramic powder or a metal powder, an organic binder and a molding aid generally called is injection-molded, and the molded body is degreased and then sintered to obtain a product.

[0004]

However, the above-mentioned prior art has the following drawbacks. That is, although the linear shrinkage ratio of the sintered body with respect to the injection molded body is 10 to 20%, which is larger than that of plastic, as the final sintered body becomes smaller, the cavity of the molding die used during injection molding also becomes smaller. It becomes small. For example, in order to obtain a gear having an outer diameter of 0.1 mm, it is necessary to machine a cavity of 0.125 mm. Therefore, the smaller and finer the final sintered body is, the smaller and finer the cavity of the molding die becomes, and the more difficult the molding becomes.

The mechanical strength of the injection-molded article obtained in the injection-molding step is responsible for the binding of the organic binder in the injection-molding material. If the injection-molded body itself becomes minute, the amount of the binder material that holds the structure will naturally be extremely small, and it will be difficult to maintain the shape of the injection-molded body itself.

Further, a flow characteristic of the kneaded body is a factor that greatly influences the injection moldability. The kneaded body is usually composed of ceramic powder or metal powder of 50 to 80 vol% and the balance of organic binder of 20 to 50 vol% as described in the above-mentioned prior art patent publication. The thermal conductivity is 3 to 25 times larger,
Therefore, cooling and solidification in the cavity during injection molding are extremely fast.

The smaller the cavity, the more exponentially increases its surface area with respect to its volume. Cooling and solidification in the cavity during injection molding is performed from the cavity surface. Therefore, the smaller the cavity is, the more this tendency is increased, and in some cases, the compound is cooled and solidified before being filled in the cavity, so that the green body itself cannot be obtained.

Therefore, the present invention was developed in view of the above-mentioned drawbacks of the prior art, and provides a method for producing a ceramic powder or a metal powder sintered body from which a minute sintered body can be easily obtained. The purpose is to

[0009]

According to the present invention, there is provided an injection molding step of injection molding a kneaded body having a ceramic powder or a metal powder in an amount of 5 to 40 vol% and the remainder being an organic binder, and degreasing the injection molded body. A degreasing step for sintering, and a sintering step for sintering the degreased molded body, the steps of the injection molding step and the degreasing step, during the degreasing step, between the degreasing step and the sintering step, and the sintering step. In the manufacturing method, the molded body is compressed at at least one of the inside.

[0010]

In the present invention, since a large amount of the organic binder is mixed in the kneaded body of the ceramic powder or the metal powder, which is a molding material, and the organic binder, the fluidity at the time of injection molding is very good and it is a fine cavity. However, it can be sufficiently filled. Regarding sintering, when the sintering mechanism is solid phase sintering, for example, in the case of metal powder such as stainless steel and carbon steel, the degreasing step, the degreasing step and the sintering are performed between the injection molding step and the degreasing step. Since there is a compression step at least at one point between the step and the sintering step, the powder particles come into contact with each other, grain boundary growth occurs from the contact point, and it becomes possible to sinter.

Further, the one whose sintering mechanism is liquid phase sintering, such as alumina (Al ₂ O ₃ ) and zirconia (ZrO)
_{In the case} of ceramic powders such as ₂ ) or metal powders that are sintered by the liquid phase sintering method, since there is also a compression step, the liquid phase generated during sintering can agglomerate the liquid. That is, it becomes possible to sinter.

[0012]

Embodiment 1 FIGS. 1 to 5 show this embodiment, FIG. 1 is a partial sectional view of an injection mold, FIG. 2 is a perspective view of a molded body, and FIG. 3 is a schematic configuration diagram of a degreasing furnace. FIG. 4 is a graph showing the temperature and atmospheric pressure conditions in the degreasing furnace in the degreasing step, FIG.
3 is a flowchart showing a manufacturing process.

FIG. 1 shows an injection molding die. The fixed die 1 has a fixed plate 4 fixed to a fixed side mounting plate 3 and a sprue bush 6 having a sprue 5 penetrating the fixed side mounting plate 3 and the fixed plate 4. And a locate ring 7 which is attached to the fixed side attachment plate 3 so as to communicate with the sprue bush 6 and which fixes the fixed die to a platen of an injection molding machine (not shown).

On the other hand, the movable mold 2 includes a movable plate 10 mounted on a movable side mounting plate 9 via a spacer block 8, a protruding plate 11 provided on the movable plate 10 so as to be movable left and right, and an injection molded body. In order to project, the projecting plate 11 is provided with a projecting rod 12 provided on the projecting plate 11 and a projecting rod 14 provided on the projecting plate 11 so as to correspond to the runner.

Further, a fitting portion 15 is formed on the movable plate 10, and a movable insert 16 is attached to the fitting portion 15. The movable insert 16 is formed in the shape of an injection molded body, and the fixed mold 1 and the movable mold 2 are brought into close contact with each other, whereby a cavity 17 formed in the movable insert 16 is formed.
Is configured. The cavity 17 has a long side of 3.8 mm, a short side of 2.1 mm, and a height of 3.4 mm.

FIG. 3 shows a degreasing furnace. A degreasing furnace main body 31 is provided with an installation table 33 for installing an injection molded body 32 injection-molded in an injection molding process, and an exhaust port 34 and an intake port 35. And a pressure increasing port 40 and a pressure reducing port 43. A binder trap 36 is connected to the next stage of the exhaust port 34, and a heater 37 is connected to the next stage of the binder trap 36. An air blower 39 having a fan 38 is connected to the front of the intake port 35, and the air blower 39 is connected to the heater 37. In addition, a valve 41 is provided next to the pressure increasing port 40.
The compressor 42 is connected via. further,
A pressure reducing valve 44 is connected to the next stage of the pressure reducing port 43.

FIG. 5 is a flowchart showing the manufacturing process, which will be specifically described below with reference to the same drawing. Average particle size 10
μm stainless steel (SUS316L) powder 15.5v
ol%, polystyrene 8 as an organic binder
3.0 vol%, paraffin wax 0.8 vol% and stearic acid 0.7 vol% are charged into a kneader (not shown) and kneaded, and then put into a granulator (not shown) to form pellets. Then, after that, it is put into an injection molding machine (not shown).

At this time, the injection molding machine has a fixed mold 1 and a movable mold 2.
A cavity 17 is formed by closely adhering to each other, and the kneaded body in the molten state is injected to obtain an injection molded body 32. Then, the fixed mold 1 and the movable mold 2 are opened, and the protruding plate 11 is moved forward to move the protruding rods 12 and 14 forward so that the injection molded body 32 is projected. Then, the injection molded body 32 is set on the installation table 33 in the degreasing furnace main body 31, the heater 37 is energized to heat at a temperature rising rate of 10 ° C./H, and the fan 38 is rotated to rotate the degreasing furnace. Intake port 35 in main body 31 → degreasing furnace main body 31 → exhaust port 34 →
Binder trap 36 → Heater 37 → Blower 39 →
A flow of an atmosphere that circulates in the order of the intake port 35 is generated.

After the temperature inside the degreasing furnace main body 31 reaches 350 ° C., the temperature inside the degreasing furnace main body 31 is maintained at this temperature for 10 hours and then allowed to cool. At this time, the atmospheric pressure in the degasser furnace body 31 was 1 kgf / c until 38 hours after the start of temperature increase.
After maintaining m ² , the valve 41 is opened and the compressor 42
The atmospheric pressure in the degreasing furnace main body 31 is set to 3.5 kg / hour.
The pressure is increased at f / cm ² , and when the pressure reaches 8 kgf / cm ² , the injection molded body 32 is compressed by holding for 7 hours.

Thereafter, the compressor 42 is stopped, the valve 41 is closed, the decompression valve 44 is opened, the atmospheric pressure in the degreasing furnace main body 31 is reduced to 1 kgf / cm ² through the decompression port 43, and after the decompression is completed, the decompression valve 44 To close. The injection-molded body 32 after completion of cooling is transferred to a sintering furnace (not shown) for sintering, and as a final sintered body, a small structure having a long side of 2.0 mm, a short side of 1.1 mm and a height of 1.8 mm. Got the body

In this embodiment, since the kneaded body has a large ratio of metal powder to the organic binder, the fluidity thereof is slightly inferior to that of ordinary plastic, in this case polystyrene, and injection molding is performed. Molding is possible without problems. Moreover, since the molding is compressed by increasing the atmospheric pressure while heating the injection molding in the degreasing step, the metal powders come into contact with each other. Therefore, in the sintering after degreasing, grain boundary growth occurs from the contact point between the metal powders, so that the sintering becomes possible, the compact compacts greatly, and the final compact sintered compact can be obtained.

According to this embodiment, the cavity for obtaining the injection-molded body is approximately 1.
Because it can be made 9 times larger, its formation is extremely easy,
A compact sintered body can be easily obtained. That is, since the cavity of the molding die can be formed to be relatively large and the kneaded body has good fluidity, an injection molded body can be easily obtained. In addition, since the injection molded body is compressed during the subsequent degreasing, a large contracted compact sintered body can be easily obtained.

In the present embodiment, the compression is performed in the latter half of the degreasing step, but the invention is not limited to this. For example, the compression may be performed from the start of the degreasing step. Although the heating degreasing method is used as the degreasing method, an extraction degreasing method may be used instead. Also in this case, a predetermined effect can be obtained by compressing the injection molded body at an appropriate portion during the degreasing process. Furthermore, it is possible to combine these methods and use the first half of the degreasing as the extraction degreasing method and the latter half as the heating degreasing method to compress at an appropriate portion thereof.

Further, in this embodiment, metal powder (SU
S316L) is used, but instead of this, ceramics such as alumina (Al ₂ O ₃ ) and zirconia (Zr
O ₂ ) and SiO ₂ can likewise be sintered.

Further, in this embodiment, the compression of the injection molded body is performed in the degreasing step, but the injection molded body may be compressed before the degreasing of the injection molded body after the injection molding. Further, the injection molded body may be compressed after the degreasing is completed, that is, before the sintering step after the degreasing step. In this case, the same degree of shrinkage as that in the degreasing step is obtained, and the degreasing is performed by using a compression chamber that performs compression on the injection molded body as one step and that is different from the defurnace furnace. The furnace and compression chamber can be replaced with existing ones. Further, the degreasing method and the powder to be sintered may be any of the above methods and powders.

[0026]

[Embodiment 2] FIGS. 6 and 7 show the present embodiment, FIG. 6 is a schematic configuration diagram of a sintering furnace, and FIG. 7 is a graph showing temperature and atmospheric pressure conditions in the sintering furnace in the sintering process. is there. In this embodiment, the configurations and operations common to those in the first embodiment will be omitted. The sintering furnace 51 is provided with a gas introduction port 53 and an exhaust port 54, a heater terminal 56 penetrates the ceiling of the sintering furnace 51, and a heater 55 is connected to the lower portion to fix it in the sintering furnace interior 52. Has been done. An installation stand 57 for installing the degreased body 58 is installed in the sintering furnace 52.

A gas introduction valve 59 is connected to the front stage of the gas introduction port 53, and a compressor 60 and a gas source valve 61 are connected to the front stage.
Further, an Ar gas cylinder (not shown) is connected to the front stage. In addition, a gas bypass valve 62 that bypasses the gas source valve 61 and the compressor 60 is provided,
The gas introduction valve 59 and the Ar gas cylinder can be directly connected to each other. Further, the next stage of the exhaust port 54 is branched into an exhaust valve 63 and a leak valve 64, and a vacuum pump (not shown) is connected to the next stage of the exhaust valve 63.

This embodiment will be specifically described below. Metal powder (SUS304) 11.8vol with an average particle size of 8 μm
%, Polyethylene 87.3 vol%, and stearic alcohol 0.9 vol% are kneaded to obtain an injection-molded article by the injection molding die used in Example 1 above. Then, the injection molded body was transferred to a degreasing furnace and heated at 8.5 ° C./H to 325
When the temperature reaches ℃, it is held for 12 hours and then left to cool. At this time, the atmospheric pressure in the degreasing furnace main body is kept constant at 1 kgf / cm ² .

Then, the degreased body is placed in the sintering furnace 5 of the sintering furnace 51.
It is transferred to the installation table 57 installed in 2. Heater 55
Is energized to heat the inside 52 of the sintering furnace at 100 ° C./H. At this time, both the gas introduction valve 59 and the gas source valve 61 are opened, and the atmosphere in the sintering furnace 52 is set to A by the compressor 60.
The pressure is increased at 1 kgf / cm ² per hour with r gas. The degreased body contains metal powder, and has a certain degree of airtightness even though it is a porous body in order to maintain its structure. Therefore, the degreased body is compressed by the increase of the atmospheric pressure in the sintering furnace 52.

After that, the atmosphere in the sintering furnace 52 was 10 kgf.
/ Cm ² is maintained for 2 hours, then the compressor 60 is stopped to close both the gas introduction valve 59 and the gas source valve 61, and the exhaust valve 63 is opened to burn with a vacuum pump (not shown). 52 atmosphere pressure in the furnace is 10 ^-4
Reduce the pressure to Torr. On the other hand, the temperature in the sintering furnace 52 is 130
When the temperature reached 0 ° C., it was held for 2 hours and then allowed to cool to obtain a small-sized structure having a long side of 1.8 mm, a short side of 0.8 mm and a height of 1.6 mm as a final sintered body.

In this example, since the kneaded body had a large proportion of metal powder in the organic binder, its fluidity was slightly inferior to that of ordinary plastic, polyethylene in this case, and injection molding was performed. Molding is possible without problems. Moreover, since the molding is compressed by increasing the atmospheric pressure while heating the injection molding in the sintering step, the metal powders come into contact with each other. Therefore, since grain boundary growth occurs from the contact point between the metal powders, it becomes possible to sinter, the compact compacts greatly, and the final compact sintered compact can be obtained.

According to this embodiment, the cavity for obtaining the injection-molded body is approximately 2.
Since it can be made three times as large, its formation becomes extremely easy, and an injection-molded body was also very easily obtained. Further, since the injection-molded body was greatly shrunk by subsequent sintering, a compact sintered body could be easily obtained. Further, since the injection molded body is compressed during sintering, it is effective in preventing deformation during sintering.

In this embodiment, the compression is performed in the latter half of the sintering process, but the present invention is not limited to this. For example, the compression may be performed from the start of the sintering process. Although metal powder (SUS316L) is used in this embodiment, ceramics such as alumina (Al ₂ O ₃ ),
Zirconia (ZrO ₂ ) and SiO ₂ can be similarly sintered.

In this embodiment, the compression of the injection-molded body was performed during the sintering step, but the compression of the injection-molded body may be performed before the sintering of the molded body after the degreasing step. In this case, a shrinkage rate similar to that in the sintering process is obtained, and the compression of the injection molded body is performed as one process by using a compression chamber that is different from the sintering furnace. Existing furnaces and compression chambers can be used.

Further, in each of the embodiments, the compression process was carried out at only one place, but it is possible to perform the compression process at any place between the injection molding process and the completion of the sintering process and at any place between the processes. The effect of can be obtained.

Further, in the present invention, the ratio of the ceramic powder or the metal powder to the organic binder is 5 to 4.
It was set to 0 vol%, but when it exceeds 40 vol%, the linear shrinkage ratio of the sintered body to the injection molded body is at most 1
It is 0 to 20%, and the cavity of the injection molding die for obtaining the small sintered body cannot be made so large, so that its formation is very difficult.

When the above-mentioned split pressure is less than 5 vol%, the sinterability is extremely deteriorated even if the injection-molded body is compressed somewhere from the injection molding process to the sintering process. That is, in the case of solid phase sintering, it becomes difficult for powders to come into contact with each other and the sinterability deteriorates. Also, in the case of liquid phase sintering, the liquid phase generated at the time of sintering cannot agglomerate the powder and cannot be sintered.

Further, the compression in the present invention can be carried out irrespective of the temperature, for example, the compression may be carried out at room temperature.

[0039]

As described above, according to the method for producing a ceramic powder or a metal powder sintered body according to the present invention, the cavities of the molding dies used for injection molding are compared when a small sized sintered body is obtained. The cavities themselves can be easily formed. In addition, injection molding can be easily performed because the fluidity of the kneaded body is extremely improved. Furthermore, since the injection-molded body shrinks greatly, a compact sintered body can be easily obtained.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing a first embodiment.

FIG. 2 is a perspective view showing a first embodiment.

FIG. 3 is a schematic configuration diagram showing a first embodiment.

FIG. 4 is a graph showing Example 1.

FIG. 5 is a flowchart showing a first embodiment.

FIG. 6 is a schematic configuration diagram showing a second embodiment.

FIG. 7 is a graph showing Example 2.

[Explanation of symbols]

 1 Fixed type 2 Movable type 3 Fixed side mounting plate 4 Fixed plate 9 Movable side mounting plate 10 Movable plate 16 Movable insert 17 Cavity 31 Degreasing furnace main body 32 Injection molded body 36 Binder trap 37 Heating heater 39 Blower section 42 Compressor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenji Haga 2-43-2 Hatagaya, Shibuya-ku, Tokyo Inside Olympus Optical Co., Ltd.

Claims (1)

[Claims] 1. Ceramic powder or metal powder is 5-4.
0 vol%, the injection molding step of injection molding a kneaded body composed of the balance of the organic binder, a degreasing step of degreasing the injection-molded molded body, and a sintering step of sintering the degreased molded body, Between the injection molding process and the degreasing process,
A method for producing a sintered body, comprising compressing the molded body during the degreasing step, between the degreasing step and the sintering step, and at at least one of the sintering steps.