JPH11315302A - Powder metallurgy powder and mixed powder for powder metallurgy - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To increase the molding density of an obtained sintered body, impart sufficient strength, and improve dimensional accuracy. SOLUTION: This is a substantially spherical powder for powder metallurgy, and the primary particle powder serving as the basis of the powder for powder metallurgy has an average particle diameter of 20%.
It is a non-spherical shape having a diameter of about 200 μm, and is bonded by such a bonding force that the powder for powder metallurgy is disintegrated into the primary particle powder by a compression force during compression molding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a powder for powder metallurgy formed by combining non-spherical primary particle powders.

[0002]

2. Description of the Related Art Powder metallurgy is a method for producing various metal parts by compressing and sintering a metal powder. Specifically, first, the raw material powder is inserted into a product-shaped mold by a powder feeder moving back and forth, and protrudes from the mold by a bottom surface of the powder feeder provided to slide on the upper surface of the mold. The raw material powder can be filled in the mold by scraping the raw material powder. Next, it is pressurized and compressed to obtain a molded body having a predetermined density. This is heated and sintered to produce a sintered body.

[0003] Examples of iron-based metal powders used in powder metallurgy include iron powders and reduced powders obtained mainly by atomization. An additive element powder for improving the strength, a mold lubricant powder for preventing seizure and the like are mixed with this, and used as a raw material powder. This iron-based powder
It is non-spherical in order to ensure the strength of the compact after compression molding, and is designed so that the powders are easily entangled with each other.

[0004] However, when the powder is made non-spherical, when the iron-based powder is inserted into a mold, the friction between the powders causes a decrease in the fluidity and a decrease in the packing density. For this reason, the packing density of the raw material powder inserted into the mold tends to be unevenly distributed. Furthermore, when the raw material powder protruding from the mold is scraped, the raw material powder near the surface of the mold moves in the traveling direction of the powder feeder, and is pressed against the wall surface of the mold on the traveling direction side of the powder feeder. Tend to increase the packing density of the raw material powder. In particular, when manufacturing a component having a complicated shape or manufacturing a component having a large diameter or height, the packing density tends to be uneven. The non-uniformity of the packing density causes a reduction in dimensional accuracy of the sintered body after sintering. For this reason, a post-process such as sizing and machining of dimension correction of the sintered body is required.

On the other hand, there is known a method in which fine particles having a weight average diameter of 1 to 18 μm are granulated using an organic binder and supplied to a powder metallurgy method (Japanese Patent Application Laid-Open No. Hei 4-214801). Reference).

[0006] In this method, since the fine particles are inserted into the mold using the granules, the frictional resistance between the powders can be reduced, and the packing density of the granules in the mold can be made uniform. Becomes possible. In addition, since the particles are bound by the organic binder, the granules are easily broken into fine particles during compression molding.
For this reason, the voids generated between the granules can be closed.

[0007]

However, in the above-mentioned method, an organic binder needs to be used in a large amount of 6 to 34% by volume of the granulated material in order to granulate the fine particles. For this reason, the molding density of the product obtained after sintering does not increase, the strength of the sintered body is not sufficient, and cracks may occur.
In addition, since a large amount of the organic binder is contained, shrinkage during sintering is large and dimensional accuracy may be deteriorated. Furthermore, since microparticles are used, there is a problem that shrinkage during sintering is large and dimensional accuracy of the obtained sintered body is deteriorated. For this reason, post-processes such as sizing and machining of the obtained sintered body are required.

Accordingly, the present invention aims to increase the molding density of the obtained sintered body, provide sufficient strength, and improve dimensional accuracy.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a powder for powder metallurgy having a substantially spherical shape.
The secondary particle powder has a non-spherical shape with an average particle diameter of 20 to 200 μm, and is used in which the powder for powder metallurgy is bonded by a compressive force at the time of compression molding to a degree that the powder for powder metallurgy is crushed into the primary particle powder. This solves the above problem.

The primary particle powder has an average particle diameter of 20 to
Since the powder of 200 μm is used, it is possible to prevent the dimensional accuracy of the sintered body from being deteriorated due to the fineness of the raw material powder. In addition, since powder metallurgy is performed using powder for powder metallurgy in which primary particle powders are bonded with an appropriate bonding force, the packing density in the mold can be made uniform, and the powders can be formed during compression molding. By crushing, the voids generated between the powders can be closed, and the molding density and dimensional accuracy are high,
It is possible to obtain a strong sintered body.

[0011]

Embodiments of the present invention will be described below. The powder for powder metallurgy according to the present invention refers to a raw material powder used for obtaining a sintered body by powder metallurgy.
A secondary particle powder obtained by binding secondary particle powder with an appropriate bonding force. Hereinafter, the powder for powder metallurgy according to the present invention,
It is referred to as “secondary particle powder”. The method of obtaining a sintered body by this powder metallurgy method is, specifically, a compression molding step of inserting a raw material powder into a product-shaped mold and compressing under a predetermined pressure.
And a sintering step of heating and sintering the obtained molded body to produce a sintered body.

The above-mentioned primary particle powder includes a metal powder having an average particle diameter of 20 to 200 μm and a non-metal powder.

[0013] Examples of the metal powder include an iron-based powder and a non-ferrous metal powder. The iron-based powder includes pure iron powder, iron-based alloy powder such as carbon steel, iron-based partially sintered powder, and the like. Further, examples of the non-ferrous metal powder include metals such as copper, nickel, manganese, chromium, and aluminum, and powders of various alloys not containing iron. Further, the non-metallic powder refers to a powder other than metal, such as graphite powder.

The primary particle powder used in the present invention includes one or a mixture of the above metal powders. In addition, a mixture obtained by adding one or more kinds of non-ferrous metal powder to this can also be used.

As the metal powder used as the primary particle powder, metal powder or reduced powder obtained by an atomizing method can be used, as long as the strength of the compact obtained in the compression molding step can be maintained. Among them, metal powder obtained by the atomizing method is more preferable, and as the iron-based powder, atomized iron powder is more preferable.

The average particle size of the primary particle powder is 20 to 20.
0 μm is preferable, and 50 to 120 μm is preferable. 200μ
If it exceeds m, coarse pores are generated in the sintered body obtained by the above sintering step, and the strength may be reduced. When the thickness is less than 20 μm, in the compression molding step,
The primary particle powder easily enters the clearance between the molds, and may cause seizure.

The shape of the primary particle powder is preferably non-spherical, such as having a convex portion, a concave portion and the like. This is because, when the primary particle powder is compression-molded, the primary particle powder is easily entangled with each other and has a predetermined bonding force, so that the strength of the compact and the sintered body can be secured. is there.

Indicators indicating such a non-spherical state include the ratio of apparent density to tap density, circularity, needle ratio, specific surface area, and the like.

The apparent density (hereinafter abbreviated as “AD”) refers to the density including the space existing between particles when a particle to be measured is gently placed in a container having a fixed volume. JIS Z 2504-1960 describes the measurement method. In addition, the tap density (hereinafter, “TD”)
Abbreviated. )) Refers to the density in a state where the particles to be measured are placed while applying vibration to a container having a fixed volume and the space existing between the particles is reduced as much as possible.
08-1992 describes the measuring method. As for the ratio of AD and TD of the primary particle powder, AD / TD is preferably less than 83%, and more preferably 78 to 82%. When it is 83% or more, the shape of the primary particle powder becomes nearly spherical, the entanglement between the secondary particle powder and the primary particle powder constituting the compact is reduced, and the strength of the sintered body is reduced. The handleability of the molded article also decreases.

The circularity refers to the deviation of an arbitrary projected image of a particle from a perfect circle. When the area of the projected image is A and its peripheral length is L, it is expressed by the following equation. Can be. Circularity = 4π × A / L ^{2 Since} this circularity varies depending on the projection direction, a plurality of circularities are measured, and the average value is used. The average circularity of the primary particle powder is preferably less than 0.7, and 0.6 or more.
Less than 7 is preferred. When the average circularity is 0.7 or more,
The shape of the primary particle powder becomes nearly spherical, the entanglement between the secondary particle powder and the primary particle powder constituting the compact decreases, and the strength of the sintered body decreases.

The acicular ratio indicates the fineness of a particle. When the maximum diameter of an arbitrary projected image of a particle is D and the diameter diagonal to this maximum diameter is d, the following formula is used. Can be represented. Needle ratio = D / d Since this needle ratio varies depending on the particles, a plurality of needle ratios are measured, and the average value is used. The average acicular ratio of the primary particle powder is preferably 1.45 or more and 1.45 to 1.8.
Is preferred. When the average acicular ratio is less than 1.45, the shape of the primary particle powder becomes close to a sphere, the entanglement between the secondary particle powder and the primary particle powder constituting the molded body decreases, and the sintering occurs. Body strength is reduced.

The specific surface area refers to the surface area of the particles per fixed volume, and the specific surface area of the primary particle powder is 300 mm
² / mm ³ or more is good, and 300 to 3000 mm ² / mm
³ is preferred. When the specific surface area is less than 300 mm ² / mm ³ , it indicates that the shape of the primary particle powder is close to spherical, and the entanglement between the secondary particle powder and the primary particle powder constituting the molded body is reduced. The strength of the sintered body decreases.

The secondary particle powder is a powder obtained by binding the primary particle powder with a bonding force that is sufficient to break the primary particle powder into the primary particle powder by a compressive force during compression molding. The average particle diameter of the secondary particle powder is preferably from 40 to 500 μm, and more preferably from 70 to 180 μm. If it exceeds 500 μm, the compressibility at the time of the above-mentioned compression molding is deteriorated, and coarse pores are formed after sintering, and the strength may be deteriorated. 40 μm
If smaller, the primary particle powder does not constitute the secondary particle powder, the non-spherical state is maintained, the fluidity deteriorates, and the packing density in the mold in the compression molding step is reduced. descend.

In the method of combining the primary particle powder into the secondary particle powder, the bonding force of the produced secondary particle powder is crushed into the primary particle powder by the compression force at the time of compression molding in powder metallurgy. The method is not particularly limited as long as the method is performed, and various methods can be used. For example, stirring granulation,
Examples thereof include a fluidized-bed granulation method, a spray-drying method, and a combination thereof. Further, a mechanical granulation method using a ball mill, a vibration mill, or the like can also be used. Furthermore, a so-called metal diffusion bonding method of performing temporary sintering at a temperature lower than the sintering temperature in the sintering step and crushing the same may be used. Furthermore, granulation can also be performed with an organic binder. Among the above,
When a granulation method using an organic binder is used, the bonding force between the primary particle powders in the obtained secondary particle powder is broken into the primary particle powder by the compression force at the time of compression molding. It is more preferable because the strength of the molded article obtained in the above-mentioned compression molding step is increased. Examples of the organic binder include a polyvinyl alcohol type and an acrylic type.

The amount of the organic binder used is preferably 1.5% by weight or less based on the secondary particle powder, and is preferably 0.05 to 0.1% by weight.
4% by weight is preferred. If the content exceeds 1.5% by weight, the compressibility during compression molding is reduced due to the volume occupied by the organic binder, and the strength of the obtained molded body is reduced. Further, the organic binder may be 0% by weight. In this case, instead of the method using the organic binder, another method described above is employed. Among these, it is preferable to use a so-called mechanical bonding method in which the primary particle powders are bonded to each other by pressing, among the above-mentioned bonding methods by metal diffusion bonding and the above-mentioned mechanical granulation methods. .
In these methods, the bonding force between the primary particle powders in the obtained secondary particle powder has a bonding force suitable for pulverizing the primary particle powder into the primary particle powder by the compression force at the time of compression molding. As a result, the strength of the molded article obtained in the compression molding step is increased. When an organic binder is used, a mold lubricant used at the time of compression molding can be omitted or reduced.

The above-mentioned secondary particle powder preferably has a substantially spherical shape, that is, a shape close to a spherical shape. This is because the fluidity of the secondary particle powder is improved, so that the secondary particle powder can be uniformly inserted into the mold during compression molding, and a uniform molded body can be obtained. It is because it can increase.

Indices indicating such a nearly spherical shape include AD / TD, powder fluidity, circularity, and needle ratio.

AD / TD of the secondary particle powder is 83% to 1%.
00% is good, and 84-90% is preferable. AD / TD
Is an index representing the frictional force between particles, and a higher value indicates better fluidity. If it is less than 83%, the fluidity is reduced, the packing density at the time of compression molding is likely to be uneven, and the strength of the sintered body is reduced.

The powder flowability is an index indicating the flowability of the secondary particle powder, and can be measured by the method described in JIS Z2502-1958. However, since the apparent density of each particle is different and the volume at 50 g is different for each particle, it is converted to the time required for a volume of 1 cm ³ to flow.
The powder flowability is preferably less than 1.65 sec / cm ³ ,
~ 1.6 sec / cm ³ is preferred. If it is 1.65 seconds / cm ³ or more, the packing density tends to be uneven during compression molding.

The average circularity of the secondary particle powder is preferably 0.7 or more, more preferably 0.75 to 1. Average circularity is 0.7
If it is less than the above, the frictional force between the particles increases, and the fluidity of the secondary particle powder is remarkably reduced.

The average acicular ratio of the secondary particle powder is preferably less than 1.45, more preferably from 1 to 1.4. Average needle ratio is 1.4
When it is 5 or more, the secondary particle powder becomes elongated and becomes difficult to rotate at the time of flowing, so that the flowability decreases.

As an index indicating the strength of the secondary particle powder, a Rutler value can be used. This Rattler value indicates the strength of the molded body, and is expressed by JPMA P11-1.
992 describes the measurement method. When a secondary particle powder or a mixture of the secondary particle powder and the primary particle powder is molded to form a molded body having a density of 6.9 to 7.1 g / cm ³ ,
What is necessary is that the Rattler value of this compact is 1% or less.
Preferably it is 0.6%. If it exceeds 1%, cracking or chipping tends to occur during handling.

In addition, the above secondary particle powder has a
The molding density when molded in a mold at 0 to 800 MPa is 3% by using the primary particle powder as a raw material of the secondary particle powder.
The molding density of 9 when the mold is molded at 00 to 800 MPa
The content is preferably 7% or more, and more preferably 98 to 101%. If it is less than 97%, the secondary particle powder is difficult to be crushed during compression molding, so that the voids between the secondary particle powders remain in the obtained molded body without being crushed, and the obtained molded body or sintered body This is because this causes a decrease in strength.

The powder used in the powder metallurgy method is not limited to the above-mentioned secondary particle powder alone, and is a mixed powder for powder metallurgy obtained by mixing the above-mentioned primary particle powder with the above-mentioned secondary particle powder. You may. At this time, the secondary particle powder accounts for 20% by weight or more, preferably 50% by weight of the entire powder mixture for powder metallurgy.
８０80%, and the remainder is preferably the primary particle powder. By including the secondary particle powder in an amount of 20% by weight or more, it is possible to obtain economically favorable particles having good fluidity. If the content of the secondary particle powder is less than 20% by weight, the remarkable effect of adding the secondary particle powder cannot be obtained.

[0035]

EXAMPLES [Primary Particle Powder] Pure iron powder having an average particle diameter of 75 μm (hereinafter referred to as “1.
Next particle powder ". ) And an average particle diameter of 30μ
m pure iron powder (hereinafter abbreviated as “primary particle powder”).
Was manufactured. In addition, pure iron powder having an average particle diameter of 74 μm (hereinafter abbreviated as “primary particle powder”) was produced according to a usual reduction method. AD of each of these primary particle powders
Table 1 shows / TD, average circularity, and average needle ratio. Here, AD is T in accordance with JIS Z2504-1960.
D was measured according to JPMA P08-1992. The average circularity was calculated by taking a photograph of the appearance of the projected image of the particles with an optical microscope, determining the circularity of each of the 50 particles, and averaging them. The circularity is
The area A and the perimeter L of the projected image were measured and determined using the following equation. Circularity = 4π × A / L ^{2 The} average acicular ratio is obtained by averaging the acicular ratios of 50 particles in the appearance photograph of the projected image of the particles in the same manner as in the case of the circularity. Was calculated. The needle ratio is
The maximum diameter D of the above projected image and the diameter d diagonal to the maximum diameter were measured and determined using the following equation. Needle ratio = D / d

[0036]

[Table 1]

[Examples 1 to 5, Comparative Examples 2 to 3] The above primary particle powder was fluidized and stirred in a fluidized bed, and a 5% by weight aqueous solution of polyvinyl alcohol (hereinafter abbreviated as “PVA”) was added thereto. Was sprayed. When the amount of PVA became 0.3% by weight of the total amount of the primary particle powder and PVA, the spraying was stopped and dried. The obtained combined product was crushed by a crusher, and particles having an average particle size shown in Table 2 were fractionated to obtain secondary particle powder. AD / TD of each secondary particle powder,
The average circularity, average needle ratio, flowability and density variation were measured. Table 2 shows the results. In addition, AD / TD, the average circularity, and the average needle ratio were measured by the above-mentioned methods. The fluidity was measured according to JIS Z 2502-1958, and was converted to the time during which a volume of 1 cm ³ flows.

The above density variation was measured as follows. After blending 0.8% by weight of a wax-based lubricant with each of the secondary particle powders, a ring-shaped material (outer diameter 35 mm, inner diameter 25 mm, thickness 10 mm) having a molding density of 6.8 g / cm ³ was compression-molded at 1130 ° C. For 1 hour under a nitrogen atmosphere,
Ten sintered bodies were obtained. The ring-shaped object was equally divided into four parts by two planes passing through the central axis of the ring-shaped object, and the density of each divided piece was measured. The average of the difference between the maximum value and the minimum value of the density of each divided piece of the obtained sintered body was defined as the density variation. In addition, pores in the surface layer of the sintered body were observed, and it was also observed whether or not coarse pores existed. Table 2 also shows the results.

[Comparative Example 1] The fluidity, the density variation and the presence or absence of coarse pores of the primary particle powder were measured without preparing the secondary particle powder by combining the primary particle powder. Observed. Table 2 shows the results.

[0040]

[Table 2]

Results In Examples 1 to 5, the AD / TD was 85% or more and the average circularity was 0.65 or more. There was almost no variation in density. Comparative Examples 1 and 2 had an AD / TD of 83.
%, And the fluidity did not improve. Comparative Example 3
Since the average particle diameter of the powder exceeded 500 μm, coarse pores of 200 μm or more were observed on the surface of the sintered body.

[Examples 6 to 11, Comparative Example 5] Secondary particles having the average particle diameter described in Example 6 in Table 3 were obtained by combining the primary particle powders in the same manner as described in Example 1. A powder was obtained. Either the primary particle powder or the primary particle powder is added to the secondary particle powder in an amount shown in Table 3 to obtain a mixed powder, and AD / TD, average circularity, average acicular ratio, fluidity and The density variation was measured by the above method. Table 3 shows the results.

[Comparative Example 4] The fluidity and the density variation of the primary particle powder itself were measured without producing the secondary particle powder by bonding the primary particle powder. Table 3 shows the results.

[0044]

[Table 3]

As a result, in Examples 6 to 11, the mold was filled with the powder uniformly, and there was almost no variation in the density in the sintered body. In Comparative Examples 4 and 5, AD / TD was less than 83%, and the fluidity was not improved.

Example 12 A primary particle powder mixture was prepared by mixing 2% by weight of copper powder having an average particle diameter of 30 μm and 0.8% by weight of a wax-based mold lubricant with the above primary particle powder. . This primary particle powder mixture was combined in the same manner as described in Example 1 to obtain a secondary particle powder having an average particle diameter of 105 μm. The AD / TD, the average circularity, the average needle ratio, the fluidity and the density variation were measured by the above-described methods. Table 4 shows the results. Further, the obtained ring-shaped sintered body was equally divided into four parts as described in Example 1, and the copper content of each divided piece was measured. The average of the difference between the maximum value and the minimum value of the copper content of each obtained divided piece, that is, the copper segregation was calculated, and the variation in the copper content was examined. Table 4 also shows the results.

[Comparative Example 6] The fluidity, density variation and copper content segregation of the primary particle powder mixture itself were measured without producing the secondary particles by bonding the primary particle powder mixture of Example 12. did. Table 4 shows the results.

[0048]

[Table 4]

As a result, by using the secondary particle powder, the density variation was almost eliminated and the distribution of copper could be made substantially uniform.

[Examples 13 to 18] The primary particle powders were combined by the following method to form secondary particle powders. -Bonding method: A 3% PVA aqueous solution was sprayed while stirring the primary particle powder in the fluidized bed. When the amount of PVA reached 0.8% by weight of the total amount of the primary particle powder and PVA, the spraying was stopped and dried. The obtained combined matter was crushed by a crusher, and the particles having an average particle diameter shown in Table 5 were obtained.
Secondary particle powder was obtained.

Bonding method: Except that the amount of sprayed PVA was set to 1% by weight of the total amount of the primary particle powder and PVA, the bonding method having the average particle diameter shown in Table 5 was performed in the same manner as in the bonding method described above. Secondary particle powder was obtained.

Bonding method: except that the sprayed PVA amount was 1.2% by weight of the total amount of the primary particle powder and PVA.
In the same manner as in the above bonding method, secondary particle powder having the average particle diameter shown in Table 5 was obtained.

Bonding method: except that the sprayed PVA amount was 1.5% by weight of the total amount of the primary particle powder and PVA.
In the same manner as in the above bonding method, secondary particle powder having the average particle diameter shown in Table 5 was obtained.

Bonding method: primary particle powder is heated to 900 ° C. in a heating furnace to sinter the particles, and after cooling,
The powder was crushed by a crusher to obtain a secondary particle powder having an average particle diameter shown in Table 5.

Bonding method: A flake-like molded body is produced by sandwiching the primary particle powder in a roller and compressing the flake-shaped molded body.
Secondary particle powder was obtained.

The secondary particle powder obtained by each of the above bonding methods was molded in a tablet die having an area of 1 cm ² by applying the pressure shown in Table 5. For comparison, the particles used in Comparative Example 1, ie, the primary particle powder, were similarly molded. These molding densities and the ratio to the molding density when the primary particle powder was molded were measured.
Further, the Rattler value was measured. Table 5 shows the results. The Rattler value is expressed in JPMA P11-1992.
The measurement was performed according to the method described in “1.

[0057]

[Table 5]

As a result , all of Examples 13 to 18 show good compressibility, and also have a good Rutler value, which is considered to be excellent in handling in mass production.

[0059]

As described above, the powder for powder metallurgy according to the present invention is a powder obtained by bonding primary particle powders with a predetermined bonding force, so that the fluidity is improved as compared with a case where the primary particle powder is used as it is. Further, this secondary particle powder is liable to be crushed when pressurized. For this reason, a compact having a higher packing density can be obtained by compression molding. Therefore, the sintered body obtained after sintering has a uniform density and a high strength.

In addition, since the primary particle powder having a predetermined average particle diameter, which is usually supplied to the compression molding as it is, is combined by a predetermined method into a secondary particle powder, it is not necessary to use a granulated powder unless it is originally granulated. The dimensional accuracy after sintering is improved as compared with the case of fine particles that cannot be obtained. For this reason, a product can be obtained without performing post-processes such as sizing and mechanical processing for dimension correction of the sintered body.

Claims (16)

[Claims] 1. A powder for powder metallurgy having a substantially spherical shape, wherein the primary particle powder serving as a basis of the powder for powder metallurgy is a non-spherical powder having an average particle diameter of 20 to 200 μm, and is formed by a compressive force during compression molding. A powder for powder metallurgy having an average particle diameter of 40 to 500 µm, wherein the powder for powder metallurgy is bonded to the primary particle powder by a bonding force enough to be crushed. 2. An apparent density of 83 to 100 of tap density.
%. The powder for powder metallurgy according to claim 1, wherein 3. The powder for powder metallurgy according to claim 1, wherein the powder fluidity is less than 1.65 sec / cm ³ . 4. The powder for powder metallurgy according to claim 1, wherein the average circularity is formed to 0.7 or more. 5. The powder for powder metallurgy according to claim 1, wherein the average needle ratio is less than 1.45. 6. The method according to claim 1, wherein the primary particles are bound by an organic binder of 1.5% by weight or less.
5. The powder for powder metallurgy according to any one of 5. 7. The powder for powder metallurgy according to claim 1, wherein the primary particle powders are connected to each other by metal diffusion bonding. 8. The powder for powder metallurgy according to claim 1, wherein the primary particle powders are connected to each other by mechanical bonding. 9. The powder for powder metallurgy according to claim 1, wherein the apparent density of the primary particle powder is less than 83% of the tap density of the primary particle powder. 10. An average circularity of the primary particle powder is 0.1.
The powder for powder metallurgy according to any one of claims 1 to 8, which is less than 7. 11. An average acicular ratio of the primary particle powder is 1.
The powder for powder metallurgy according to any one of claims 1 to 8, which has a particle size of 45 or more. 12. The primary particle powder is composed of one or more kinds of metal powders, or a mixture of one or more kinds of metal powders and one or more kinds of non-metallic powders. Item 10. The powder for powder metallurgy according to any one of Items 1 to 8. 13. The specific surface area of the primary particle powder is 300.
Powder metallurgical powder according to claim 1 is mm ² / mm ³ or more. 14. The molding density when compression-molded at 300 to 800 MPa is 300 to 800.
The powder for powder metallurgy according to any one of claims 1 to 13, which has a molding density of 97% or more when compression-molded at MPa. 15. A molded product having a density of 6.9 to 7.1 g / cm ³ obtained by compression molding has a Rattler value of 1
% Or less. 16. A powder mixture for powder metallurgy comprising the powder metallurgy powder according to claim 1 in an amount of 20% by weight or more, and the balance being the primary particle powder.