JPH02166201A - Manufacture of high density sintered body - Google Patents

Abstract

PURPOSE:To manufacture a sintered body having high density and high dimmensional accuracy by packing powder for sintering having different average particle diameters into a forming mold, exciting and sintering the obtd. high density powder packed body. CONSTITUTION:The large diameter powder having <=200mu the average particle diameter A and the small diameter having 0.5-20mu the average particle diameter C are mixed under condition of >=10 A/C so that blending ratio of the small diameter powder becomes 10-40wt.%. Successively, the mixed powder 5 is charged into a mold body 2 in the forming mold 1, and binder is impregnated under pressurizing to the powder packed body 5, and this is vibrated with an exciting machine 4 for the prescribed time to make the high density powder formed body, and after executing de-binder treatment, this is sintered. By this method, the sintered body having high density and high dimensional accuracy is manufactured at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing a sintered body by molding a sintering powder such as metal or ceramics and then firing it.

(Prior art) By molding sintering powder made of metal powder, ceramic powder, etc. to produce a molded body, and performing various post-processing on the sintered body obtained by firing the molded body. , machine parts and molds are manufactured.

As a method for producing the above-mentioned molded body, there is a compression molding method using a die press shown in FIG. In this method, a pressing mold 20 formed by a bottom plate 22, a mold 21, and a punch 23 is filled with sintering powder 24, and a compressor is used to compress the punch into
A very high pressure of 7000 kgf/afl is applied to solidify the powder by binding it with a binder or plastically deforming the powder for some raw materials to obtain a powder compact, and then the compact is fired. Aya on the method of manufacturing sintered bodies.

(Problems to be Solved by the Invention) In order to omit or minimize post-processing of the sintered compact obtained by the method described above, it is necessary to mold the sintered compact into the final product shape or as close to the final product shape as possible. It is desirable to keep it. Therefore, the powder compact before sintering is molded into a shape that is almost the same as the final product shape, and the sintering shrinkage rate during firing of the compact is isotropic, and the shrinkage rate is made as small as possible. Therefore, it is required to make the density distribution of the powder compact (hereinafter, density refers to relative density, and refers to the powder volume ratio to the total volume) distribution as high as possible. .

However, in the case of the above-mentioned mold press molding, Pascal's principle does not hold true for powder as it does for fluids, so uneven pressure distribution occurs, and furthermore, due to friction between the powder and the mold wall, powder molding Since the density of the body is locally non-uniform, the sintering shrinkage rate becomes anisotropic, causing deformation of the sintered body and dimensional errors. Furthermore, in order to increase the density of the powder compact, a very high pressure of 1000 to 7000 kgf/c+fl is required, which increases the manufacturing cost.

The present invention has been made in view of the above-mentioned problems, and by forming a powder filling body with a high density and uniform density distribution and firing the filling body, a sintered compact with high density and high dimensional accuracy is obtained. The purpose is to provide a way to obtain

(Means for Solving the Problems) The present invention, which has been made to achieve the above object, involves filling a mold with sintering powders having different average particle diameters, and vibrating the mold to obtain a high-density powder-filled body. After that, the powder-filled body is fired to obtain a sintered body. In order to obtain a high-density powder-filled body, the sintering powder is a large-diameter powder with an average particle diameter of 200 μm or less and a powder with an average particle diameter of 0.5 to 207 μm.
A mixed powder with a small-diameter powder of % 10 to 40%, or the average particle diameter is 200 μm
The following large diameter powders and medium diameter powders of 20-60μ and 0.
A mixed powder with a small-diameter powder of 5 to 20 μM, where A/B is 3 when the average particle diameter of the large-diameter powder is A, the average particle diameter of the medium-diameter powder is B, and the average particle diameter of the small-diameter powder is C. or more and B
/C is 3 or more, and the blending ratio in the mixed powder is % by weight
Large diameter powder: 60-90%, medium diameter powder: 5-30%,
It is preferable that small diameter powder = 5 to 30%. In addition, when firing a powder-filled body, the powder-filled body is pre-sintered while it is housed in a mold, or the powder-filled body is pre-sintered while it is housed in a mold, and the pre-sintered powder is It is preferable to sinter the filled body, and further, the powder filled body is impregnated with a binder under pressure in a mold and solidified, or the powder filled body is degassed in a mold and then suction impregnated with Pine Gu and solidified. By firing the solidified powder-filled body, a sintered body with high density and high dimensional accuracy can be obtained.

(Function) A sintering powder composed of mixed powders with different average particle diameters (hereinafter, average particle diameter refers to the particle diameter when the cumulative weight under the sieve of the powder is 50%) is placed in a mold. After filling, the mold is vibrated vertically, horizontally, or by a combination thereof for a certain period of time without applying pressure. Due to this vibration, the individual powder particles move while changing their positions with respect to each other, and medium- or small-diameter particles fill the gaps between large-diameter particles and form a close-packed structure, making it possible to obtain a high-density powder-filled body. Can be done.

At the same time, since no pressure is applied to the powder in the mold, uneven pressure transmission and friction with the mold wall are less likely to occur, and powder bridging can be prevented, making it easier to fill the powder in the mold. The non-uniformity of the density distribution of the body can be reduced to 1710 or less when compacting with a conventional mold press.

In order to obtain a powder packed body with high density and uniform density distribution, in the case of a mixed powder consisting of two types of large diameter particles (average particle diameter: A) and small diameter particles (average particle diameter: C), A/C
If the ratio of small diameter particles in the mixed powder is 10 to 40% by weight, the density of the powder packed body formed from both should be 75% or more. Can be done.

Furthermore, large diameter particles (average particle diameter: A), medium diameter particles (
In the case of a mixed powder consisting of three types of average particle diameter, B) and small diameter particles (average particle diameter: C), A/B is 3 or more and B/C is 3 or more, and the composition of each powder in the mixed powder is The ratio is 60 to 90% by weight for large particles, and 5 to 90% for medium particles.
30%, small-diameter particles: By setting it in the range of 5 to 30%, a powder packed body having a density of 75% or more can be obtained.

In addition, when taking sinterability into account, the average particle size of each powder is
For both metals and ceramics, large diameter particles are 2007/m or more F, medium diameter particles are 20 to 60 μm, and small diameter particles are 0.5 to 20 μm.
It is desirable to set it to m.

When firing the powder-filled body described above, a mold made of a highly refractory material can be used, and the mold can be fired together with the powder-filled body housed therein.

According to the above firing method, there is no need to add a binder, and therefore, a dehindering step is not necessary, and the process can be shortened. Furthermore, it is possible to eliminate the cause of cracks in the molded body due to gas generation during binder removal.

In the above-mentioned firing, it is also possible to perform temporary sintering at a low temperature to form a powder compact, and then fire only this compact. in this case,
In addition to the above-mentioned advantages, a sintered body can be manufactured at low cost without requiring a mold made of an expensive highly refractory material.

On the other hand, 20kgf/c+f was added to the powder filling body in the mold.
The binder is impregnated under pressure at a low pressure of less than 1 liter. Alternatively, a powder compact can be obtained by sucking and deaerating the air between the powder particles constituting the powder filling body, and then sucking and impregnating the binder and solidifying the binder.

According to the above method, since there is no binder present at the contact point of the powder particles, a dehindering step is required, but a decrease in density of the powder compact due to the step [2] can be prevented. Therefore, a powder compact can be obtained without impairing the high density and uniform density distribution during formation of the powder-filled body. By firing the molded body after removing the binder, a sintered body with high density and uniform density distribution can be obtained. Also, molds made of expensive highly refractory materials are not required.

(Example) Hereinafter, a method for manufacturing a high-density sintered body of the present invention will be described.

First, the sintering powder used in the present invention will be explained.

The material of the powder for sintering is pulverization method, water atomization method,
Gas Atomize Method 1 Various metal powders, ceramic powders, or powders in which ceramic powder is added to metal powders, etc., produced by the carbonyl method etc. can be used.

By filling a mold with a mixed powder made of the above-mentioned materials and having different average particle diameters and then shaking the mold, a high-density powder filling can be obtained as described above. In the case of a mixed powder consisting of two types of powder with different particle sizes, the average particle size of the large particle powder should be increased by 20
0.07 zm or less, and the average particle diameter C of the small diameter particle powder is 0.07 zm or less.
It is best to set it to 5 to 20 μm, and furthermore, the A/C should be set to 10 or more.
It is preferable that the blending ratio of the small diameter particle powder in the -1 mixed powder is 10 to 40% by weight. In addition, in the case of a mixed powder consisting of three types of powders with different particle sizes, the average particle size A of the large particle powder should be 200 μm or less, the average particle size B of the medium particle powder should be 20 to 60 μm, and the small particle size The average particle diameter C of the particle powder is preferably 0.5 to 2071 m, and A/B
is 3 or more and B/C is 3 or more, and the blending ratio of each powder in the mixed powder is, in weight%, large diameter particles: 60 to 90%, medium diameter particles: 5 to 30%, small diameter particles = 5 to 30%. It is better to

Incidentally, as the powder for sintering, the particle size distribution shown in Fig. 1 is used.
Large particle a with an average particle diameter of 140 μm and average particle diameter 4 μm
As a result of measuring the density while tapping using a mixed powder (compounding ratio of small diameter particles 20% by weight) from small diameter particles C, as shown in Fig. 2, it was observed that the density improved as the number of tapping increased, The density was approximately 80% after 100 tappings. Furthermore, various mixed powders were prepared using the two types of powders by changing the blending ratio of both powders, and after tamping the mixed powders 300 times, the density was measured. The results are shown in FIG. In the figure, the maximum density was 83%. Moreover, when the blending ratio of small-diameter particles is 10 to 40% by weight, a density of 75% or more is obtained. Further, when the density of a mixed powder obtained by adding medium-sized particles with an average particle size of 40 μm to the above two types of powder was measured, it was 82%. The blending ratio of each powder in the mixed powder at this time is large diameter particles: medium diameter particles: small diameter particles: 70:10:
20 and 60:20:20.

Next, a method for manufacturing a powder filling body of sintering powder will be described.

The fourth session shows the apparatus for producing a powder-filled body according to this embodiment, and a predetermined shape is transferred to the powder-filled body on the bottom of the mold body 2, which is open at the top and forms a container for sintering powder. A mold 1, which has been formed by attaching a template 3 for the purpose of the vibration, is placed on the excitation plate [4].

In order to obtain a powder-filled body using the manufacturing apparatus described above, the sintering powder 5 described above may be charged into the mold 1 and vibrated by the vibrator 4 for a certain period of time. In this case, the vibration conditions such as vibration amplitude, vibration frequency, and vibration time are such that the powder particles move due to vibration, form a close-packed optical fiber structure, and the powder filling has the highest density. Select as appropriate depending on the type and blending ratio. By the above operation, a uniform and high-density powder filling body can be easily obtained in the mold 1.

Next, a method for manufacturing a powder compact and a sintered body from the powder-filled body will be explained.

When the mold 1 is made of a highly refractory material that can withstand the sintering temperature of the sintering powder, the powder-filled body molded as described above is stored in the mold 1 and fired together with the mold 1. A sintered body can be obtained directly. As the above-mentioned highly refractory material, heat-resistant metal materials such as stainless steel and Inconel, highly refractory ceramic materials such as alumina and silica, or graphite can be used.

Furthermore, if the powder-filled body formed as described above is temporarily sintered at a low temperature while being housed in the mold 1 to form a uniform and high-density powder compact, only the compact is fired. It is also possible to obtain a uniform, high-density sintered body from the above-mentioned expensive and highly refractory materials without the need for molds.

Alternatively, a powder-filled body formed in the mold as described above may be impregnated with a binder and solidified to obtain a uniform and high-density powder compact. A high-density sintered body can be obtained by firing the molded body after debinding treatment. As the above binder, in addition to acrylic resins, paraffin resins, cellulose acetate resins, etc., thermosetting resins such as phenolic resins can be used as appropriate. The above-mentioned binder can be used alone, or appropriately dissolved or diluted in a solvent such as water or an organic solvent.

There are two methods for impregnating the powder filling in the mold with the binder: pressurizing the binder with a low pressure of 20 kgf/cnt or less, and sucking and deaerating the air in the powder filling with a degassing device. There is a method of suction impregnation. FIG. 5 shows the procedure for sucking and impregnating a powder-filled body with a binder.
After forming a uniform, high-density powder filling body 5a, a lid 11 is provided at the upper opening of the mold 1a, and a deaerator is attached to the lower part. The mold 1a is provided with a deaeration hole 6 which communicates with a deaerator, and the air inside the mold 1a is degassed by a vacuum pump 7. On the other hand, the lid 11 is provided with a binder supply hole 10, and after degassing, the binder 9 is supplied under pressure into the mold Ia via the supply pump 8, and the powder filler 5a is impregnated with the binder.

In the figure, 12 is a binder feed valve, and 13 is a deaeration valve.

In addition, when air passes through the powder layer during vacuum degassing, particles on the top surface of the powder packed body 5a may be scattered, or the powder packing may crack due to the high air passage resistance due to the high powder filling rate. There is a possibility that this may occur. For this reason, it is desirable that the vacuum degassing is performed from the bottom of the powder packing, and that a perforated plate 14 is placed on the top of the packing during degassing to apply a pressure of 1 atmosphere or less.

Incidentally, Japanese Unexamined Patent Publication No. 10405/1988 discloses a slurry deliquification method. In this method, a slurry composed of ceramic powder, a binder, and water or an organic solvent is injected into a mold that has a porous material on at least a portion of the inner surface of the mold and is pressurized. This is a method of squeezing out the material into the desired shape. In this method, a powder compact can be produced using a slurry made of ceramic powder, metal powder, or a mixed powder thereof that satisfies the average particle size range, average particle size ratio, and blending ratio of the present invention as a raw material slurry. Conceivable.

However, even with slurry, it is not possible to obtain a completely uniform pressure distribution as seen with general fluids, and Pascal's principle does not hold true. That is, since the pressure distribution within the mold filled with the slurry is non-uniform, the density of the powder-filled body becomes partially non-uniform. Furthermore, as the deliquification progresses, the slurry approaches the behavior of only powder, and the powder itself may cause bridging, resulting in localized non-uniform density areas. Incidentally, the non-uniformity of the density distribution of the powder packed body produced by the slurry deliquification method using the mixed powder satisfying the conditions of the present invention was about twice that of the present invention.

In addition, in the slurry deliquid method, the molding pressure is 100,100 O/c.
Since the pressure is low, below +fl, the density of the powder compact is 50
~60% is the limit. In contrast, in the present invention, a density of 75% or more can be easily obtained without applying pressure.

Furthermore, in order to obtain a high-density sintered body from the above-mentioned low-density powder compact, it is necessary to change the firing conditions (increasing the sintering temperature, increasing the firing time, etc., which increases the cost). However, there are drawbacks such as large shrinkage during sintering and poor dimensional stability of the sintered body.

Specific examples will be described below.

<Example 1> (1) A template is attached to a mold having a deaeration hole, and a large-diameter iron powder with an average particle diameter of 140 μm and an average particle diameter of 4 μm are placed inside the template.
A mixed powder containing small-diameter iron powder such that the blending ratio of small-diameter iron powder was 20% by weight was charged.

(2) Next, the mold was mounted on a vibrator and vibrated in the vertical direction at an amplitude of 15+mn and a frequency of IHz for 5 minutes to obtain a powder-filled body.

(3) The mold was removed from the vibrator, a perforated plate was placed on the top surface of the powder-filled body, and the air between the powder particles was degassed under vacuum according to the procedure shown in FIG.

(4) Pour 5 kg of binder solution from the binder supply hole.
A pressure of f/ca was applied to add and impregnate the powder filler in an amount of 4% by weight. The binder used at this time was an acrylic resin binder (manufactured by Mitsui Toatsu Chemical Co., Ltd., trade name: Hind Ceram NΔ320) diluted with water to adjust the volume ratio to 60%.

(5) The powder-filled body was held at 130° C. for 1 hour to remove moisture and solidify to obtain a powder compact. At this time, the density of the molded body is 78%, and while the density non-uniformity of each part of the molded body is approximately 10% in conventional mold press molding, in this example, the density is within 0.5%. I was able to suppress it.

(6) The powder compact obtained above was held at 450°C for 1 hour to remove the binder, and then fired at 1300"C for 1 hour to obtain a sintered body. The contraction was isodirectional, with almost no difference observed depending on direction or location.

In addition, the amount of linear shrinkage of the sintered body is about 17% in conventional die press molding, but in this example, it is about 2.
5%, and a significant improvement in dimensional stability was recognized.

<Example 2> (1) Using a mullite container as a mold, large-diameter iron powder with an average particle diameter of 140 μm and small-diameter iron powder with an average particle diameter of 4 μm were placed in the mold, and the mixing ratio of the small-diameter iron powder was 20% by weight. % mixed powder was charged.

(2) The mold was mounted on a vibration device and vibrated vertically at an amplitude of 15 mm and a frequency of IHz for 3 minutes to obtain a powder-filled body.

(3) With the powder filling body stored in the mold 13
A sintered body was obtained by firing at 00°C for 1 hour. The sintered body is
As in Example 1, the shrinkage during firing was uniform and showed almost no difference depending on the location, and a sintered body with high density and high dimensional stability was obtained.

(Effects of the Invention) According to the present invention, a mold is filled with a mixed powder consisting of sintering powders having different average particle diameters, and the powder is moved by vibration, and finally a close-packed optical fiber is formed. Due to the formation of the structure, dense powder packings can be obtained very easily. In addition, since the powder is not pressurized, uneven distribution of pressure inside the powder packing body due to pressurization and friction with the mold wall are less likely to occur, and bridging of the powder can be prevented, so the powder filling inside the mold is less likely to occur. It is possible to achieve uniform density distribution in the body. Therefore, a uniform and high-density powder-filled body can be obtained very easily, and by firing the packed body, a high-density and highly dimensionally accurate sintered body can be easily manufactured.

When the mixed powder is composed of two types of powders with different particle sizes, the average particle size A of the large-diameter powder is set to 200.
μm or less, and the average particle diameter C of the small diameter powder is 0.5 to 20
When expressed as μm, by setting the A/C to 10 or more and setting the blending ratio of small-diameter powder in the mixed powder to 10 to 40% by weight, a powder packed body with a high density of 75% or more can be easily obtained. be able to.

Furthermore, when the mixed powder is composed of three types of powders with different particle sizes, the average particle size A of the large-diameter powder is set to 200.
71 m or less, and the average particle size B of the medium-sized powder is 20 to 60.
μl, and the average particle size C of small particles is 0.5 to 20 μl.
m, A/B is 3 or more and B/C is 3 or more, and the blending ratio of each powder in the mixed powder is large diameter powder + 60 to 90% by weight, medium diameter powder: 5 to 30%. , small-diameter powder: By setting the content to 5 to 30%, a high-density powder packed body with a density of 75% or more can be easily obtained.

If the powder-filled body described above is formed in a mold made of a highly refractory material, a sintered body can be obtained by firing the mold together, so there is no need to add a binder.
There is no need for a binder removal process, and the cause of cracks in the molded body due to gas generation during binder removal can be eliminated.

Therefore, the manufacturing process can be shortened, and defects associated with binder removal do not occur.

Alternatively, the powder-filled body can be pre-sintered at a low temperature to form a powder compact, and the compact can be fired at a high temperature to obtain a sintered body. In this case, in addition to the above-mentioned advantages, a mold made of an expensive highly refractory material is not required, so a high-density sintered body can be manufactured at a lower cost.

On the other hand, the powder filling body in the mold is impregnated with a binder under pressure. Alternatively, a powder compact can be obtained by deaerating the air in the powder filling body and then sucking and impregnating the powder with a binder and solidifying it. In this case, since the binder is not present at the contact points of the powder particles constituting the powder-filled body, although a binder removal process is necessary, it is possible to prevent the density of the powder compact from decreasing due to this process. Therefore, a powder compact can be obtained without impairing the uniform and high density during the formation of the powder-filled body. By firing the molded body after removing the binder, a sintered body with high density and extremely high dimensional accuracy can be obtained. In this case, only the powder compact solidified with the binder is fired, so there is no need for any heat-resistant molds such as molds made from the aforementioned expensive highly refractory materials or molds for temporary sintering. Sintered bodies can be manufactured at low cost.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the particle size distribution of two types of powders with different average particle diameters according to this example, and Fig. 2 is a graph showing the relationship between the number of tappings and the relative density of a mixed powder consisting of the powders in Fig. 1. , FIG. 3 is a graph showing the relationship between the proportion of small-diameter powder and the relative density in the mixed powder made of the powders shown in FIG. 1, and FIG. FIG. 6 is an explanatory diagram showing the method of suctioning and adding the binder according to the present example, and FIG. 6 is an explanatory diagram showing conventional mold press molding. Patent applicant: Kobe Steel, Ltd. (Ni11) h \f (%) Needle with imr

Claims (7)

[Claims] (1) A mold is filled with sintering powders having different average particle diameters, and the powder is vibrated to obtain a high-density powder-filled body, and then the powder-filled body is fired to obtain a sintered body. A method for manufacturing a high-density sintered body. (2) The sintering powder is a mixed powder of a large-diameter powder with an average particle diameter of 200 μm or less and a small-diameter powder with an average particle diameter of 0.5 to 20 μm, where the average particle diameter of the large-diameter powder is A, and the average particle diameter of the small-diameter powder is 2. The manufacturing method according to claim 1, wherein A/C is 10 or more when the particle size is C, and the blending ratio of the small diameter powder in the mixed powder is 10 to 40% by weight. (3) Powder for sintering includes large-diameter powder with an average particle diameter of 200 μm or less, medium-diameter powder with an average particle diameter of 20 to 60 μm, and powder with an average particle diameter of 0.5 to 20 μm.
A mixed powder with a small-diameter powder of μm, where the average particle diameter of the large-diameter powder is A, the average particle diameter of the medium-diameter powder is B, and the average particle diameter of the small-diameter powder is C, and A/B is 3 or more. B/C is 3
In the above, the blending ratio in the mixed powder is as follows: large-diameter powder: 60-90%, medium-diameter powder: 5-30%, small-diameter powder:
The manufacturing method according to claim 1, wherein the content is 5 to 30%. (4) The manufacturing method according to claim (1), wherein when firing the powder-filled body, the powder-filled body is fired while being housed in a mold. (5) The manufacturing method according to claim (1), wherein when firing the powder-filled body, the powder-filled body is pre-sintered while being housed in a mold, and the pre-sintered powder-filled body is fired. . (6) The manufacturing method according to claim (1), wherein the powder-filled body is impregnated with a binder under pressure in a mold and solidified, and the solidified powder-filled body is fired. (7) The manufacturing method according to claim (1), wherein the powder-filled body is degassed in a mold, and then the binder is suction-impregnated and solidified, and the solidified powder-filled body is fired.