JPH0551688A - Production of high density sintered compact of stainless steel - Google Patents

Abstract

PURPOSE:To prevent the occurrence of change in shape by gravity, etc., before sintering and to obtain a high density sintered compact having superior dimensional accuracy by adding specific amounts of Fe-V powder of specific grain size to a stainless steel powder of specific grain size and subjecting the resulting powder mixture to compacting and to sintering. CONSTITUTION:An Fe-V powder of 1-10mu average grain size is added to a water atomized stainless steel powder of 5-20mu average grain size so that V content in a sintered compact becomes 0.10-2.0wt.%, and the resulting powder mixture is compacted and sintered. By the above procedure, the green compact before sintering can be prevented from getting brittle and the occurrence of deformation by gravity, etc., before sintering can be prevented. As to the average grain size of the stainless steel powder to be used, manufacturing costs are increased when it is below 5mu, and, on the other hand, sintering characteristics become insufficient when it exceeds 2mu. Manufacturing costs are increased when the average grain size of the Fe-V powder is below 1mu, and, when it exceeds 10mu, the deformation preventing effect is reduced. Corrosion resistance is deteriorated when the above-mentioned content of the Fe-V powder exceeds 2.0, and, on the other hand, deformation is increased because the amount of pulverized powder acting as sintering auxiliary is decreased when it is below 0.1%.

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 high density stainless steel sintered body by powder metallurgy.

[0002]

2. Description of the Related Art The powder metallurgy method is characterized in that it is possible to easily mass-produce a member which is difficult to manufacture by a melt casting method.
In conventional powder metallurgy, powder with a particle size of 60 to 100 μm was used for compression molding, but the sintered density ratio of the sintered body is 90% at most.
However, the mechanical properties and magnetic properties are inferior to those of the melt-cast material. On the other hand, recent technological advances in powder metallurgy have facilitated the use of fine powders. If fine powder having an average particle size of 20 μm or less is used, the sinterability is improved, and it is possible to obtain a sintered density of 90% or more, further 95% or more. In this case, there are methods such as compression molding, injection molding, slip casting, etc. as the molding method, and each of the raw material fine powder is granulated with good mold filling property, compounding treatment capable of injection molding with thermoplastic resin, slurry Chemical treatment,
It enables industrial molding.

When molding and sintering such fine powder to produce a high-density sintered body, it is difficult to keep the shape of the sintered body sound. With the conventional powder metallurgy, the metal powder particles are brought into close contact with each other in compression molding, and a molded product having a certain strength can be obtained. When the molded body is sintered, the sintering is always started while maintaining the strength about the initial strength of the molded body, so that the shape is not easily lost. However, in the case of fine powder, the strength of the molded body is maintained by using the binder as an auxiliary agent at the time of molding, but since the binder is removed at a considerably low temperature prior to the progress of sintering, sintering starts at a high temperature. Pass through the stage until it becomes brittle molded body strength. At that time, there is a problem that unfavorable deformation occurs due to the self-weight of the molded body and the dimensions of the finally obtained sintered body are largely changed.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned situation, the present invention proposes a method for increasing the strength of a compact after the binder is removed and before the sintering is started, the compact becomes brittle. It is for doing.

[0005]

When water atomized stainless steel powder is sintered, the surface of the stainless steel powder is Cr,
Since it is covered with a non-reducing oxide such as Mn or Si, the sintering does not proceed after the binder is removed, and the compact during the sintering process becomes particularly fragile. Therefore, the present inventors have conducted intensive studies on a method of preventing weakening at this stage and increasing the strength of a molded body, and mixing Fe-V powder with stainless steel powder,
It was discovered that if compacted and sintered, the sintering proceeds at low temperature and acts as an adhesive agent for the particles of stainless steel powder, at which point the strength of the compact can be improved and deformation due to its own weight, etc. can be prevented. Based on this finding, the present invention has been completed. According to the present invention, Fe-V powder having an average particle size of 1 to 10 μm is added to water atomized stainless steel powder having an average particle size of 5 to 20 μm so that the V content is 0.10 to 2.0% by weight in the final sintered body. A method for producing a high-density stainless steel sintered body, which comprises molding and sintering.

[0006]

According to the present invention, by adding 1 to 10 μm Fe-V powder to stainless steel powder having an average particle size of 5 to 20 μm and compacting and sintering, the compact becomes fragile before sintering. As a result, the deformation of the shape before sintering due to its own weight can be suppressed. The average particle size of the stainless steel powder used is 5 μm
The smaller the size, the higher the manufacturing cost, while the average particle size is 20.
If the average particle size exceeds 5 μm, the sinterability is insufficient, so the average particle size is 5
The range is up to 20 μm. The average particle size of the added Fe-V powder is
If it is less than 1 μm, the manufacturing cost is high, while if the average particle size exceeds 10 μm, the effect of suppressing deformation is reduced. Therefore, the average particle size is set to 1 to 10 μm.

Further, the amount of the Fe-V powder mixed is set so that the V content of the final sintered body is 0.1% or more and 2.0% or less because the corrosion resistance is deteriorated when it exceeds 2.0%. On the other hand, if it is less than 0.1%, the amount of fine powder that serves as a sintering aid is small, resulting in large deformation. The Fe-V powder may be water atomized powder or ground powder. The appropriate amount of V in Fe-V powder is 20 to 80%. Furthermore, the amounts of Cr, Ni, Mo, etc. should be set to the target values in the finally obtained sintered body.
Adjust the amounts of i and Mo in advance.

[0008]

【Example】

(Example 1) Average particle size 3, 5.1, 10.2, 17.0, 23.6 μm
High-pressure water atomized SUS 304 stainless steel powder and Fe-V crushed powder having an average particle size of 4.7 μm were prepared. The Fe-V crushed powder was prepared by crushing Fe-50 wt% V alloy with an attritor. To 100 parts by weight of various stainless steel powders, 1.41 parts of Fe-V ground powder was added and mixed. 2.0% by weight of camphor was added to each mixture, and the length was 35 mm at a molding pressure of 2 t / cm ² .
A rectangular parallelepiped with a width of 10 mm and a height of 5 mm was molded. Spacing between compacts 25
placed so as to extend over the alumina angle bars standing in mm, the temperature was raised at a rate of vacuum 10 ⁰ C / min, held for 2 hours at 1250 ° C..
After cooling, the density of the sintered body was measured by the Archimedes method. As the amount of deformation, the distance at which the center of the sintered body sank downward due to its own weight was measured. Table 1 shows the measurement results. When Fe-V powder was added, the deformation due to its own weight was clearly suppressed.

(Example 2) High-pressure water atomized stainless steel powder having an average particle size of 10.2 μm and an average particle size of 2.5, 7.3 and 1
2.4 μm Fe-V powder (V content: 50% by weight) was added to 100 parts by weight of stainless steel powder, and 1.41 parts by weight of Fe-V powder was added and mixed. These mixtures were molded and sintered in the same manner as in Example 1, and the amount of deformation was measured. The results are shown in Table 2. From Table 2, only the examples of the present invention have the deformation suppressing effect.

[0010]

As described above, according to the present invention, a dimensional accuracy is high and a high density stainless steel sintered body can be manufactured, and therefore, it is highly useful as a technique for manufacturing a complex shaped part.

[Table 1]

[Table 2]

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[Procedure amendment]

[Submission date] September 24, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Detailed explanation of the invention

[Correction method] Change

[Correction content]

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 high density stainless steel sintered body by powder metallurgy.

[0002]

2. Description of the Related Art The powder metallurgy method is characterized in that it is possible to easily mass-produce a member which is difficult to manufacture by a melt casting method.
In the conventional powder metallurgy, powder having a particle diameter of 60 to 100 μm was used for compression molding, but the sintered density ratio of the sintered body is at most about 90%, which is higher than mechanical properties and melting characteristics. Magnetic properties are inferior. On the other hand, recent technological advances in powder metallurgy have facilitated the use of fine powders. Average particle size 20μ
Use of fine powder of m or less improves sinterability, and 90%
As described above, a sintered density of 95% or more can be obtained. In this case, there are methods such as compression molding, injection molding, slip casting, etc. as the molding method, and each of the raw material fine powder is granulated with good mold filling property, compounding treatment capable of injection molding with thermoplastic resin, slurry Chemical treatment is applied to enable industrial molding.

When molding and sintering such fine powder to produce a high-density sintered body, it is difficult to keep the shape of the sintered body sound. With the conventional powder metallurgy, the metal powder particles are brought into close contact with each other in compression molding, and a molded product having a certain strength can be obtained. When the molded body is sintered, the sintering is always started while maintaining the strength about the initial strength of the molded body, so that the shape is not easily lost. However, in the case of fine powder, the strength of the molded body is maintained by using the binder as an auxiliary agent at the time of molding, but since the binder is removed at a considerably low temperature prior to the progress of sintering, sintering starts at a high temperature. Pass through the stage until it becomes brittle molded body strength. At that time, there is a problem that unfavorable deformation occurs due to the self-weight of the molded body and the dimensions of the finally obtained sintered body are largely changed.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned situation, the present invention proposes a method for increasing the strength of a compact after the binder is removed and before the sintering is started, the compact becomes brittle. It is for doing.

[0005]

When water atomized stainless steel powder is sintered, the surface of the stainless steel powder is Cr,
Since it is covered with a non-reducing oxide such as Mn or Si, the sintering does not proceed after the binder is removed, and the compact during the sintering process becomes particularly fragile. Therefore, as a result of intensive studies on the method of preventing the brittleness at this stage and increasing the strength of the molded body, the present inventors mixed the Fe-V powder with the stainless steel powder, molded and sintered it, and fired it at a low temperature. It was discovered that the bonding progresses and it acts as an adhesive agent for the particles of the stainless steel powder, at which point the strength of the molded body can be improved and deformation due to its own weight or the like can be prevented beforehand, and based on this finding, the present invention Came to make. The present invention relates to water atomized stainless steel powder having an average particle size of 5 to 20 μm and Fe-having an average particle size of 1 to 10 μm.
A method for producing a high-density stainless steel sintered body, characterized in that V powder is added to the final sintered body so that the V content is 0.10 to 2.0% by weight, and the mixture is molded and sintered. ..

[0006]

According to the present invention, by adding 1 to 10 µm Fe-V powder to stainless steel powder having an average particle diameter of 5 to 20 µm and performing sintering, the molded body becomes brittle before sintering. As a result, the deformation of the shape before sintering due to its own weight can be suppressed. If the average particle size of the stainless steel powder to be used is less than 5 μm, the manufacturing cost will increase, while if the average particle size exceeds 20 μm, the sinterability will be insufficient, so the average particle size will be in the range of 5 to 20 μm. Fe-V to be added
If the average particle size of the powder is less than 1 μm, the manufacturing cost is high, while if the average particle size exceeds 10 μm, the effect of suppressing deformation is reduced. Therefore, the average particle size is set to 1 to 10 μm.

Further, the V content of the final sintered body is set to 0.1% or more and 2.0% or less because the amount of the Fe-V powder to be mixed is set to more than 2.0% because the corrosion resistance deteriorates. This is because.
On the other hand, if it is less than 0.1%, the amount of fine powder that serves as a sintering aid is small, so that the deformation is large. The Fe-V powder may be water atomized powder or pulverized powder. The amount of V in the Fe-V powder is suitably 20 to 80%. Further Cr, N
The amounts of i, Mo, etc. are also adjusted so that the amounts of Cr, Ni, Mo of the stainless steel powder are adjusted to the target values in the finally obtained sintered body.

[0008]

Examples (Example 1) Average particle size 3, 5.1, 10.2, 17.
High-pressure water atomized SUS304 stainless steel powder of 0,23.6 μm and Fe-V crushed powder having an average particle diameter of 4.7 μm were prepared. Fe-V ground powder is Fe-50 wt% V
It was made by crushing the alloy with an attritor. To 100 parts by weight of various stainless steel powders, 1.41 parts of Fe-V ground powder was added and mixed. 2.0% by weight of camphor was added to each mixture, and the length was 3 at a molding pressure of ² t / cm ^2.
A rectangular parallelepiped having a size of 5 mm, a width of 10 mm and a height of 5 mm was molded.
The molded body is placed so as to straddle an alumina square bar standing at an interval of 25 mm, and the temperature is raised in vacuum at a rate of 10 ° C./min,
It was kept at 1250 ° C for 2 hours. After cooling, the density of the sintered body was measured by the Archimedes method. As the amount of deformation, the distance at which the center of the sintered body was sunk downward due to its own weight was measured. Table 1 shows the measurement results. When the Fe-V powder is added, the deformation due to its own weight is clearly suppressed.

[0009]

[ Table 1 ]

[0010] (Example 2) high-pressure water atomizing stainless steel powder having an average particle diameter 10.2μm and average particle diameter 2.5,
Fe-V powder of 7.3 and 12.4 μm (V content: 50
Wt%) to 100 parts by weight of stainless steel powder, Fe
1.41 parts by weight of -V powder was added and mixed. These mixtures were molded and sintered in the same manner as in Example 1, and the amount of deformation was measured. The results are shown in Table 2. From Table 2, only the examples of the present invention have the deformation suppressing effect.

[ 0011 ]

[ Table 2 ]

[ 0012 ]

As described above, according to the present invention, a dimensional accuracy is high and a high density stainless steel sintered body can be manufactured, and therefore, it is highly useful as a technique for manufacturing a complex shaped part.

Claims (1)

[Claims] 1. A Fe-V powder having an average particle size of 1 to 10 μm is added to water atomized stainless steel powder having an average particle size of 5 to 20 μm so that the V content of the sintered body is 0.10 to 2.0% by weight. , A method for producing a high-density stainless steel sintered body characterized by forming and sintering.