JP2001098302A - Metal powder injection molding method and medical treatment implement composed of metallic sintered body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the defect of the appearance in a sintered body at the time of cooling in a sintering stage and to secure the original components in the surface of the sintered body. SOLUTION: In a metal powder injection molding method having a molding stage in which a compound composed of a kneaded material of metal powder and an organic binder is subjected to injection molding to form into a molded body, a degreasing stage in which the molded body is degreased in a state of being set on a sintering jig composed of ceramics to form into a degreased body and a sintering stage in which the degreased body is sintered in a sintering furnace and is cooled to form into a metallic sintered body, at the time of the cooling in the sintering stage, inert gas is regularly fed into the sintering furnace, and moreover, the gas is exhausted from the inside of the sintering furnace to control the pressure in the sintering furnace to 1 to 200 Torr. The adhesion of the ceramics components onto the surface of the sintered body, the furnace wall of the sintering furnace and the surface of a setter can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal powder injection molding method for injection-molding a compound comprising a kneaded product of a metal powder and an organic binder to obtain a sintered body through a degreasing and sintering step. The present invention relates to a medical treatment tool made of a sintered metal body.

[0002]

2. Description of the Related Art As a method for mass-producing high-density metal parts having a complicated small shape, a metal powder injection molding method (Metal I.P.
njection Molding (hereinafter, MIM))
Is used. This MIM is obtained by kneading and pulverizing a metal powder and an organic binder, or supplying a pulverized product as a compound to an injection molding machine, heating and kneading in a heating cylinder, and then performing injection molding to form a molded product (green). Body). Then, the green body is placed on a sintering jig (setter) made of ceramics, and the green body is degreased to remove the organic binder component, thereby obtaining a degreased body (brown body). Further, the brown body is transferred to a sintering furnace while being set on a setter and sintered, and then the sintering furnace is cooled to obtain a metal sintered body.

In such a conventional method, when cooling in the above-described sintering step, sintering is performed within a certain temperature range within a cooling range from a maximum sintering temperature to a normal temperature at which a sintered body can be taken out. An inert gas was sealed in the furnace.

[0004]

Generally, in sintering under a high vacuum, a part of the ceramic component of the setter is volatilized.
Ceramic components of the setter are scattered in the sintering furnace. In this state, if an inert gas is sealed in the sintering furnace within a certain temperature range and cooled as in the past, the ceramic components that have been scattered solidify with the cooling in the sintering furnace and solidify. The ceramic component adheres to the surface of the sintered body and the furnace wall. This adhesion results in poor appearance of the sintered body.
Further, due to the adhesion to the surface of the sintered body, the surface of the sintered body is made of a material different from the original component. In addition, the ceramic components that have been scattered under a high-temperature vacuum adhere to the furnace wall and setter of the sintering furnace during cooling when the inert gas is filled, causing contamination of the furnace and the setter. I have.

On the other hand, in the case of a medical treatment tool in which a metal component made of a metal sintered body is inserted immediately into the body, if the surface of the metal sintered body contains nonstandard components, it may be used. It cannot be done.

The present invention has been made in consideration of such conventional problems, and when cooling in the sintering process, the surface of the sintered body, the furnace wall of the sintering furnace, and the surface of the setter are also cooled. A metal powder injection molding method capable of preventing the adhesion of ceramic components, eliminating appearance defects of the sintered body, and securing the original components on the surface of the sintered body, and a medical treatment tool comprising the metal sintered body The purpose is to provide.

[0007]

According to a first aspect of the present invention, there is provided a metal powder injection molding method, wherein a compound comprising a kneaded mixture of a metal powder and an organic binder is injection-molded into a molded product. A forming step, a degreasing step in which the formed body is degreased by being placed on a sintering jig made of ceramics to form a degreased body, and the degreased body is sintered in a sintering furnace and cooled to form a metal sintering body. In a metal powder injection molding method having a sintering step of forming a consolidated body, when cooling in the sintering step, an inert gas is always supplied into the sintering furnace and exhausted from the sintering furnace. The pressure in the sintering furnace to 1 Torr or more 2
It is characterized by being not more than 00 Torr.

In the present invention, during the cooling in the sintering step, the supply and exhaust of the inert gas into the sintering furnace are always performed. As a result, the ceramic component of the setter that has volatilized during high-temperature sintering under vacuum is exhausted together with the inert gas, thereby preventing the ceramic component from adhering to the sintered body, furnace wall, and the setter due to solidification during cooling. Can be.

A second aspect of the present invention is the invention according to the first aspect, wherein the cooling in the sintering step is performed by cooling from a maximum sintering temperature to a temperature not lower than room temperature.

According to the present invention, the ceramics volatilized from the setter are cooled from the maximum sintering temperature to an abnormal temperature, and the above-mentioned inert gas is constantly supplied and sucked and the pressure in the sintering furnace is adjusted during the cooling. Can be more reliably prevented from adhering to the sintered body and the furnace wall.

According to a third aspect of the present invention, a medical treatment tool is obtained by the metal powder injection molding method according to the first or second aspect.

[0012] This medical treatment tool has good surface quality with no adhesion of ceramics to the surface of the metal sintered body and no alteration of the surface component of the sintered body.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing specific embodiments, an outline of a metal powder injection molding method according to the present invention will be described. In the present invention, the pressure in the sintering furnace is set to 1 Torr or more and 200 Ton while supplying and exhausting inert gas.
rr or less. At a pressure of 1 Torr or less, since the vacuum is high, the number of molecules in the sintering furnace is small and the cooling time is very long. In addition, when cooling is performed in a vacuum at a high temperature, the components of the sintered body evaporate from the surface of the sintered body, deteriorating the surface state of the sintered body, and the components of the sintered body itself also volatilize due to volatilization. Degrades from the material.

On the other hand, if the furnace pressure is 200 Torr or more, the furnace pressure is too high, so that when the ceramic component volatilized from the setter is exhausted by the inert gas,
It adheres to the surface of the sintered body and the furnace wall. Therefore, by supplying and exhausting the inert gas at a furnace pressure of 1 Torr or more and 200 Torr or less during cooling as in the present invention, it is possible to prevent the ceramic component from adhering to the sintered body, the furnace wall, and the setter. This makes it possible to prevent poor appearance of the sintered body,
Moreover, the quality of the original sintered body surface can be secured, and furthermore,
A good metal sintered body can be obtained by preventing contamination of the sintering furnace.

In the present invention, the furnace pressure during cooling is 1 To
Although it is rr or more and 200 Torr or less, the range of 50 Torr or more and 150 Torr or less is preferable, and more preferably 80 Torr or more and 120 Torr or less in order to more reliably prevent the ceramic component from adhering to the sintered body and the furnace wall.
The range below Torr is good.

The inert gas used in the present invention only needs to be inert under a high-temperature vacuum, and may be argon, nitrogen or helium, and is not limited thereto.

(Embodiment 1) The compound used in this embodiment is a metal powder of SUS316L and an organic binder for the metal powder, such as paraffin wax, acrylic, polystyrene, stearic acid, EVA,
A mixture obtained by kneading a total of 11 parts by weight of dibutyl phthalate was used. In this embodiment, a forceps 1 as a medical treatment tool shown in FIGS. 1 and 2 is manufactured. The forceps are
It has a cup-shaped blade portion 2 at the tip, and an attachment portion 3 for mounting to the endoscope main body is continuously provided on the blade portion 2. As a setter for performing degreasing and sintering, a ceramic made of alumina having a purity of 99.6% and a porosity of 0% was used.

In the molding step, injection molding was performed with the cylinder temperature of the injection molding machine set at a maximum of 160 ° C. After the obtained green body is set on a setter, it is transferred to a degreasing step. The degreasing step is performed in an air atmosphere, and is heated and degreased at a maximum temperature of 350 ° C. In the sintering process after degreasing, the furnace pressure is set to 1 × 10 ⁻⁵ Torr under vacuum.
Heated to a temperature of 300 ° C./h up to
From 0 ° C. to 1350 ° C., argon gas was supplied into the furnace and evacuated, and the furnace pressure was set to 5 Torr and the temperature was increased by 30 ° C.
Heating was performed at 0 ° C./h, and sintering was performed at a maximum sintering temperature of 1350 ° C. for 2 hours. After that, cooling is performed. In a cooling temperature range from 1350 ° C. to 30 ° C. (a temperature equal to or higher than normal temperature) during the cooling, an air supply valve is adjusted to constantly supply argon gas into the furnace, and a vacuum pump is used. By performing evacuation, the furnace pressure was adjusted to 100 Torr and cooling was performed, thereby obtaining a metal sintered body.

In this embodiment, in the cooling temperature range from 1350 ° C. to 30 ° C. during cooling in the sintering step,
Argon gas was supplied and exhausted, and cooling was performed by adjusting the furnace pressure to 100 Torr, so that the alumina component volatilized from the setter at the time of temperature increase and at the maximum temperature was cooled outside the sintering furnace before solidifying. It was possible to discharge to.

Table 1 shows the results of measurement of the surface roughness of the sintered body obtained according to this embodiment and analysis of the components of the surface. Comparative Example 1 in Table 1 uses the same molded product and setter under the same conditions up to the maximum sintering temperature. From 1350 ° C. during sintering cooling to 30 ° C., at a furnace pressure of 600 Torr with argon gas. It is the surface roughness and the component analysis of the surface of the sintered compact which enclosed and cooled.

[0021]

[Table 1]

From Table 1, it can be seen that the surface roughness of the first embodiment was as good as 6.0 s, whereas the surface roughness of Comparative Example 1 was 10 s.
The surface roughness was deteriorated due to the adhesion of 8s and the alumina component. According to the result of the surface analysis, according to the first embodiment, the alumina component is 28.2%, which is much higher in Comparative Example 1 than in the alumina component of 0.1%.

In this embodiment, it is possible to prevent alumina from adhering to the sintered body, prevent appearance defects that impair the surface roughness of the sintered body, and secure the quality of the surface of the sintered body, which is the original material. Can be. It is also possible to prevent sintering furnace and setter contamination. Further, even if the metal sintered body obtained in this embodiment is used for a metal part such as a medical treatment tool that directly enters the body, and high quality is required for surface roughness and surface components, Required quality can be secured.

(Embodiment 2) In Embodiment 2, the same compounds and parts as those used in Embodiment 1 were used. The molding conditions and the degreasing conditions were the same as in the first embodiment. The setter used in this embodiment is made of ceramics having a zirconia purity of 95%, calcia of 5%, and a porosity of 5%.

In the sintering step of this embodiment, the pressure is set to 1000 ° C. under a high vacuum with a furnace pressure of 5 × 10 ⁻⁵ Torr.
It is heated at a temperature rising gradient of 00 ° C./h.
Supply and exhaust argon gas into the furnace up to 0 ° C,
Heating was performed at a furnace pressure of 5 Torr and a temperature rising gradient of 300 ° C./h, and sintering was performed at a maximum sintering temperature of 1350 ° C. for 2 hours. Thereafter, cooling is performed.
In the cooling temperature range from 50 ° C. to 30 ° C., while adjusting the air supply valve to constantly supply argon gas into the furnace,
By evacuating with a vacuum pump, 80 Torr
Cooling was performed by adjusting the furnace pressure to r, thereby obtaining a metal sintered body.

As described above, when cooling, 1350 ° C. to 30
By supplying and exhausting argon gas at a cooling temperature range of up to 80 ° C. and cooling at a furnace pressure of 80 Torr, before volatilization of components volatilized from the zirconia setter at the time of temperature increase and at the maximum temperature, the solidification occurs. It was possible to discharge it outside the sintering furnace.

Table 1 shows the results of surface roughness and surface component analysis of the sintered body obtained according to this embodiment. Comparative Example 2 in Table 1 uses the same molded article and setter under the same conditions up to the maximum sintering temperature. From 1350 ° C. during sintering cooling to 30 ° C., using an argon gas at a furnace pressure of 600 Torr. It is the surface roughness and the component analysis of the surface of the sintered compact which enclosed and cooled.

According to Table 1, the surface roughness was 5.8 s in the second embodiment, which was as good as 5.8 s.
The surface roughness was deteriorated by the adhesion of 2s and the zirconia component. Further, as a result of the surface analysis, the zirconia component was detected as 0.1% in the second embodiment, whereas the zirconia component was detected as 2.1% in the comparative example 2.

According to such an embodiment, it is possible to prevent zirconia from adhering to the sintered body, to prevent poor appearance of the sintered body, and to secure the original quality of the surface of the sintered body. It is possible to prevent contamination of the sintering furnace and the setter.

(Embodiment 3) The compounds and component shapes used in this embodiment are the same as those used in Embodiments 1 and 2. The molding conditions and the degreasing conditions were the same as in the first embodiment. The setter used in this embodiment has an alumina purity of 99.6% and a porosity of 11
% Of ceramics.

In the sintering step of this embodiment, the pressure is set to 1000 ° C. under a high vacuum at a furnace pressure of 5 × 10 ⁻⁵ Torr.
It is heated at a temperature rising gradient of 00 ° C./h.
Supply and exhaust argon gas into the furnace up to 0 ° C,
Heating was performed at a furnace pressure of 5 Torr and a temperature rising gradient of 300 ° C./h, and sintering was performed at a maximum sintering temperature of 1350 ° C. for 2 hours. Thereafter, cooling is performed.
In the cooling temperature range from 50 ° C. to 30 ° C., while adjusting the air supply valve to constantly supply argon gas into the furnace,
By evacuating with a vacuum pump, 50 Torr
Cooling was performed by adjusting the furnace pressure to r, thereby obtaining a metal sintered body.

As described above, when cooling, 1350 ° C. to 30
By supplying and exhausting helium gas in the cooling temperature range up to 50 ° C., and cooling at a furnace pressure of 50 Torr, before volatilization of components volatilized from the alumina setter at the time of temperature increase and at the highest temperature, solidification occurs. It was possible to discharge it outside the sintering furnace.

Table 1 shows the results of surface roughness and surface component analysis of the sintered body obtained by this embodiment. Comparative Example 3 in Table 1 uses the same molded product and setter under the same conditions up to the maximum sintering temperature, from 1350 ° C. during sintering cooling to 30 ° C., using a helium gas at a furnace pressure of 400 Torr. It is the surface roughness and the component analysis of the surface of the sintered compact which enclosed and cooled.

From Table 1, it can be seen that the surface roughness was 6.8 s in the third embodiment, which was as good as 6.8 s.
The surface roughness was deteriorated due to the adhesion of 2s and the alumina component. As a result of the surface analysis, the alumina component was very small at 0.2% in the third embodiment, whereas the alumina component was detected as large as 32% in the comparative example 3.

According to such an embodiment, similarly to the first and second embodiments, it is possible to prevent the adhesion to the sintered body, prevent the appearance of the sintered body from being defective, and furthermore, prevent the surface of the original sintered body from being deteriorated. The quality was able to be secured. In addition, contamination of the sintering furnace and the setter can be prevented.

As is apparent from the above description, the present invention includes the following inventions.

(1) Degreasing and sintering are performed in a state in which a compound obtained by kneading a metal powder and an organic binder is used as a material and a molded body obtained by injection molding is placed on a sintering jig made of ceramics. In the metal powder injection molding method to obtain a sintered metal body, the supply and exhaust of the inert gas into the sintering furnace are performed in the cooling temperature range from the maximum sintering temperature at the time of cooling in the sintering step to a normal temperature or higher. A metal powder injection molding method, which is always performed, and cooling is performed at a furnace pressure of 1 Torr to 200 Torr to obtain a sintered metal body.

According to the present invention, since the ceramics volatilized from the sintering jig can be prevented from adhering to the sintered body, the furnace wall and the setter, the appearance of the sintered body can be prevented from being poor, and the surface of the original sintered body can be prevented. Quality can be ensured, and further, contamination of the sintering furnace can be prevented, and a good metal sintered body can be obtained.

(2) A medical treatment tool comprising a metal sintered body obtained by the method according to the above (1).

In this medical treatment tool, since the ceramics do not adhere to the surface of the metal sintered body, good surface quality can be obtained even when used as a medical jig inserted directly into the body, for example.

[0041]

According to the first aspect of the present invention, when cooling, 1T
Since the inert gas is supplied and exhausted at a furnace pressure of not less than orr and not more than 200 Torr, it is possible to prevent the ceramic component from adhering to the sintered body, the furnace wall and the setter, and thereby prevent the appearance of the sintered body from being defective. In addition, the quality of the original sintered body surface can be secured, and furthermore, contamination of the sintering furnace is prevented,
A good metal sintered body can be obtained.

According to the second aspect of the invention, it is possible to more reliably prevent the ceramics volatilized from the setter from adhering to the sintered body and the furnace wall.

According to the third aspect of the present invention, since there is no attachment of ceramics to the surface of the metal sintered body and no deterioration of the surface component of the sintered body, it is used, for example, as a medical jig directly inserted into the body. However, it is possible to obtain good results.

[Brief description of the drawings]

FIG. 1 is a partially broken side view showing forceps of a medical treatment tool manufactured according to Embodiments 1 to 3.

FIG. 2 is a partially broken plan view of FIG.

[Explanation of symbols]

 1 forceps

Continued on the front page (72) Inventor Takuya Kodama 2-43-2 Hatagaya, Shibuya-ku, Tokyo F-term in Olympus Optical Co., Ltd. 4K018 AA33 CA30 DA28 DA32 DA33 KA70

Claims (3)

[Claims] 1. A molding step of injection molding a compound comprising a kneaded product of a metal powder and an organic binder to form a molded body, and degreasing the molded body in a state of being placed on a sintering jig made of ceramics. In a metal powder injection molding method, comprising: a degreasing step of forming a degreased body; and a sintering step of sintering the degreased body in a sintering furnace and cooling to form a metal sintered body. A metal powder injection molding method, wherein an inert gas is constantly supplied into the sintering furnace, and the pressure in the sintering furnace is reduced to 1 Torr or more and 200 Torr or less while exhausting the gas from the sintering furnace. . 2. The metal powder injection molding method according to claim 1, wherein cooling is performed from a maximum sintering temperature to a temperature equal to or higher than a normal temperature when cooling in the sintering step. 3. A medical treatment tool comprising a metal sintered body obtained by the metal powder injection molding method according to claim 1.