JP5439926B2 - Iron-based mixed powder for powder metallurgy - Google Patents

Description

  The present invention relates to an iron-based mixed powder suitable for use in powder metallurgy technology.

  The iron-based mixed powder used in the powder metallurgy technique is manufactured by mixing iron powder, which is a basic component, with metal powder containing an alloy component (hereinafter referred to as alloy powder) and a lubricant. At that time, graphite powder, copper powder, iron phosphide powder or the like is generally used as the alloy powder, and zinc stearate, lithium stearate or the like is used as the lubricant. Further, a machinability improving powder (for example, MnS) may be added as necessary.

  In applying such iron-based mixed powder to powder metallurgy technology, the iron-based mixed powder is filled in a mold and pressure-molded and manufactured (hereinafter referred to as a green compact) is removed from the mold. And sinter. However, since iron powder, alloy powder, lubricant, machinability improving powder, etc. have different characteristics (ie, particle size, shape, specific gravity, etc.), the iron-based mixed powder obtained by mixing is transported. In addition, there has been a problem that alloy powder, lubricant, machinability improving powder and the like are segregated in the iron-based mixed powder during charging into the hopper and discharging from the hopper.

  When a green compact is produced from segregated iron-based mixed powder, a uniform distribution of characteristics (ie, component and density) cannot be obtained within a single green compact, and the characteristics vary among multiple green compacts. Occurs. Therefore, a sintered body obtained by sintering such a green compact is inevitably reduced in size and strength, and the yield of the sintered body is reduced.

Therefore, various techniques for preventing segregation of iron powder, alloy powder, lubricant, machinability improving powder and the like in the iron-based mixed powder have been studied.
For example, Patent Documents 1 to 3 disclose a technique in which an alloy powder is attached in advance to the surface of iron powder.
Patent Document 4 proposes a technique for improving the outflow of segregation preventing powder by adding a free lubricant.

Furthermore, Patent Document 5 discloses a technique for producing an iron-based mixed powder using iron powder having a predetermined particle size distribution. This technique prevents variations in the characteristics of the green compact by improving the filling properties when filling the iron-based powder into the mold, and thus prevents the yield of the sintered body from being lowered.
However, it is generally known that when the fluidity of the iron-based mixed powder and the filling property into the mold are enhanced, the pressing force (hereinafter referred to as the unloading power) when the green compact is taken out from the mold is increased. In other words, when iron-based mixed powder with improved fluidity and filling properties is used, the output is increased, resulting in a decrease in productivity due to the long time required to take out the green compact and a decrease in yield due to the occurrence of defects in the green compact. Is often invited.

  In order to reduce the punching power of the green compact, it is effective to use a soft and extensible lubricant at the temperature at which the iron-based mixed powder is pressure-molded. The reason is that the lubricant exudes from the iron-based mixed powder by pressure molding and adheres to the mold surface, reducing the frictional force between the mold and the green compact. However, since such a lubricant has stretchability, it easily adheres to the particles of iron powder and alloy powder, and inhibits the fluidity and filling properties of the iron-based mixed powder.

Therefore, it has been difficult to achieve both improvement in fluidity and filling property of the iron-based mixed powder and reduction in the extraction force of the green compact.
In order to solve this problem, a two-layered lubricant having a lubricant for reducing the unloading power as a core and a lubricant for improving the fluidity has been studied. However, such lubricants are expensive to manufacture. In addition, since the particle size of the lubricant increases and it becomes difficult to be crushed during pressure molding, the lubricant particles remain in the green compact and burn or vaporize by sintering to form cavities. The cavities generated in this way are defects in the sintered body, leading to a decrease in the yield of the sintered body.

Japanese Unexamined Patent Publication No. 1-219101 JP-A-2-217403 Japanese Patent Laid-Open No. 3-165502 Japanese Unexamined Patent Publication No. 5-148505 JP 2002-280103 A

  The present invention has been developed in view of the above-mentioned present situation, and is capable of improving the fluidity of the iron-based mixed powder and reducing the punching force of the green compact by an inexpensive means, and improving the productivity of the molding process and the sintering process. An object of the present invention is to provide an iron-based mixed powder for powder metallurgy that can achieve an improvement and an improvement in the yield of a green compact and a sintered body.

That is, the gist configuration of the present invention is as follows.
1. An iron-based powder for powder metallurgy in which porous particles containing a lubricant are mixed with iron-based powder, the porous particles being
Chemical formula: MOxHy (where x> 0, y> 0)
Where M: metal element or metalloid element
O: Oxygen
H: composition represented by hydrogen (except for _{MgO · Al 2 O 3 · xSiO} 2 · yH 2 O) powder metallurgical iron-based mixed powder characterized by comprising a.

2. The porous particles further contain phosphorus, and have the following chemical formula: MOxHyPz (where x> 0, y> 0, z> 0)
Where M: metal element or metalloid element
O: Oxygen
H: Hydrogen
P: The iron-based mixed powder for powder metallurgy according to 1 above, which has a composition represented by phosphorus.

3. 3. The iron-based mixed powder for powder metallurgy according to 1 or 2 above, wherein the amount of the porous particles based on the entire iron-based mixed powder is 0.001 to 10% by mass.

4). 4. The iron-based mixed powder for powder metallurgy according to any one of 1 to 3 above, wherein the porous particles are aggregates of primary fine particles having a particle size of 0.001 to 10 μm.

5. The iron-based mixed powder for powder metallurgy according to any one of the above 1 to 4, wherein the porous particles have a connected channel structure.

6). 6. The iron-based mixed powder for powder metallurgy according to any one of 1 to 5 above, wherein the porous particles have a particle size of 1 to 100 μm.

7). The iron-based mixed powder for powder metallurgy according to any one of 1 to 6 above, wherein the ratio of the lubricant is 10 to 400 parts by mass with respect to 100 parts by mass of the porous particles.

8). 8. The lubricant according to any one of 1 to 7 above, wherein the lubricant is one or more selected from metal soap, bisamide, fatty acid amide, fatty acid, liquid lubricant, and thermoplastic resin. Iron-based mixed powder for powder metallurgy.

9. 9. The iron-based powder for powder metallurgy according to any one of 1 to 8 above, wherein the iron-based powder is obtained by attaching an alloy powder to the surface of the iron powder via an organic binder.

Ten. 10. The iron-based powder for powder metallurgy according to any one of 1 to 9 above, wherein the iron-based powder for powder metallurgy contains a free lubricant.

  According to the present invention, it is possible to achieve both improvement in the fluidity and filling property of the iron-based mixed powder for powder metallurgy and reduction in the output power of the green compact by inexpensive means. As a result, it is possible to improve the productivity and yield of the green compact and the sintered body, and to manufacture a sintered product having a large and complicated shape.

It is the schematic diagram which illustrated the porous particle according to this invention.

Hereinafter, the present invention will be specifically described.
The iron-based mixed powder for powder metallurgy of the present invention basically comprises porous particles containing iron-based powder and a lubricant, and further contains an alloy powder, a cutting ability improving powder, and a free lubricant as required. It is a mixture.
First, the porous particles used in the present invention will be described.
The porous particles have voids in the particles, and the production method is not particularly limited, but those having a structure as shown in FIGS. 1 (a) and 1 (b) are preferable.
FIG. 1 (a) is a porous particle 1 made of an aggregate of fine powder (hereinafter referred to as primary fine particles) having a particle size of 0.001 to 10 μm. In the figure, reference numeral 2 denotes primary fine particles, and 3 denotes a lubricant.
FIG. 1 (b) shows a porous particle 1 having a connected channel structure (including a sponge shape). In the figure, reference numeral 4 indicates the channel structure, and a lubricant 3 is contained therein.

Here, the porous particles (hereinafter referred to as porous particles A) shown in FIG.
The porous particles A are
Chemical formula: MOxHy (where x> 0, y> 0)
Here, a composition represented by M: metal element or metalloid element, O: oxygen, H: hydrogen (hereinafter referred to as composition MOH), or chemical formula: MOxHyPz (where x> 0, y> 0, z> 0) )
Here, it is obtained by granulating primary fine particles having a composition represented by M: metal element or metalloid element, O: oxygen, H: hydrogen, P: phosphorus (hereinafter referred to as composition MOHP), It is an aggregate of primary fine particles. In general, O and H in the chemical formula are contained as hydroxyl groups or crystal water.

  Here, when the particle size of the primary fine particles is less than 0.001 μm, the voids between the particles of the primary fine particles become minute, so that a sufficient amount of lubricant cannot be retained, and the effect of reducing the unplugging power cannot be obtained. Moreover, clogging occurs during storage and transportation, which not only hinders operation, but extremely fine primary fine particles cause an increase in manufacturing cost. On the other hand, if it exceeds 10 μm, the voids between the primary fine particles are enlarged, so that the lubricant easily flows out, and a sufficient amount of lubricant cannot be retained, and the effect of reducing the unplugging power cannot be obtained. Therefore, the particle diameter of the primary fine particles is preferably in the range of 0.001 to 10 μm. More preferably, it is the range of 0.01-1.0 micrometer.

  Further, when the particle size of the porous particles, which are aggregates of primary fine particles, is less than 1 μm, the porous particles containing the lubricant are interspersed between the iron-based mixed powders when the iron-based mixed powder for powder metallurgy is pressed. Segregated to become difficult to be crushed and the contained lubricant is difficult to be released, so the effect of reducing the unplugging power cannot be obtained. On the other hand, when the thickness exceeds 100 μm, the porous particles remain in the green compact as they are, resulting in defects in the sintered body obtained by sintering the green compact, causing a reduction in the strength of the sintered body. . Therefore, the particle size of the porous particles is preferably in the range of 1 to 100 μm. In order to further reduce the above disadvantages, the thickness is more preferably in the range of 1 to 40 μm, still more preferably in the range of 10 to 25 μm.

When the porous particles are produced by granulating the MOH particles or MOHP particles, a porous particle containing the lubricant can be obtained by granulating by adding a lubricant to the MOH particles or the MOHP particles. it can.
Such lubricants are not particularly limited, but include metal soaps (eg, zinc stearate, manganese stearate, lithium stearate, etc.), bisamides (eg, ethylene bisstearic acid amides), fatty acid amides including monoamides ( For example, stearic acid monoamide, erucic acid amide, etc.), fatty acid (eg, oleic acid, stearic acid, etc.), liquid lubricant (eg, phosphate ester, polyol ester, mineral oil, polyglycol, etc.), thermoplastic resin (eg, polyamide, polyethylene, Polyacetal, etc.) are particularly preferred because they have the effect of reducing the green compact output.
However, lubricants that are liquid at room temperature, such as fatty acids and liquid lubricants, cause liquid cross-linking between MOH particles or between MOHP particles, and the particles adhere to each other and agglomerate, which may reduce fluidity. . In addition, wax-based lubricants such as fatty acid amides are solid at room temperature, but because of their high adhesiveness, particles adhere to each other and aggregate, which may reduce fluidity. Accordingly, it is necessary to appropriately select the lubricant added when granulating in consideration of these characteristics. In that case, you may use individually, respectively, and may use 2 or more types together.

  Further, a lubricant may be impregnated into porous particles produced by granulating MOH particles or MOHP particles. In this case, as the lubricant, metal soap (for example, zinc stearate, manganese stearate, lithium stearate, etc.), bisamide (for example, ethylene bis stearamide, etc.), fatty acid amide containing monoamide (for example, stearic acid monoamide, erucic acid) Amide etc.), fatty acids (eg oleic acid, stearic acid etc.), liquid lubricants (eg phosphate esters, polyol esters, mineral oil, polyglycol etc.), thermoplastic resins (eg polyamide, polyethylene, polyacetal etc.) This is preferable because it has the effect of reducing the body output.

  In particular, fatty acids and liquid lubricants are preferred because they are easily impregnated into porous particles. The lubricants impregnated into the porous particles may be used alone or in combination of two or more in consideration of these characteristics.

  Here, if the addition amount (total) of the lubricant is less than 10 parts by mass with respect to 100 parts by mass of MOH particles or MOHP particles, the effect of reducing the green compact output is not obtained. On the other hand, when the amount exceeds 400 parts by mass, the MOH particles, the MOHP particles, or the porous particles aggregate, so that the fluidity may be lowered. Therefore, the amount of lubricant added when granulating MOH particles or MOHP particles, or the amount of lubricant impregnated into the porous particles obtained by granulation is the same as when adding or impregnating the lubricant alone or in combination. In any case, it is preferable that the porous particles are within a range of 10 to 400 parts by mass with respect to 100 parts by mass of the porous particles.

  As the powder of composition MOH, powders of iron hydroxide, aluminum hydroxide and the like can be used. On the other hand, powder such as hydroxyapatite can be used as the powder of composition MOHP. Moreover, the powder containing multiple types of M like lithium iron phosphate can also be utilized. These powders may be used alone or in combination of two or more.

Next, the porous particles (hereinafter referred to as porous particles B) shown in FIG.
In the porous particle B having such a structure, silica gel or the like can be used as the porous particle having the composition MOH, and hydroxyapatite porous particles or the like can be used as the porous particle having the composition MOHP. In addition, bacterial (tubular) iron oxide particles derived from bacteria can be used. Furthermore, particles containing a plurality of types of M, such as Florite R (petal-like calcium silicate, manufactured by Tokuyama), can also be used. These porous particles may be used alone or in combination of two or more.

  Like the porous particles A, these porous particles B are impregnated with a lubricant. The lubricant used and the impregnation technique are the same as in the case of the porous particles A.

  In either case of the porous particles A and the porous particles B, the MOH particles and the MOHP particles may coexist and may contain unavoidable impurities (N, C, etc.) mixed in the manufacturing process. Good.

  The blending amount of the porous particles containing the lubricant described above with respect to the entire iron-based mixed powder is preferably about 0.001 to 10% by mass. This is because if the amount of the porous particles is less than 0.001% by mass, the addition effect is poor. On the other hand, if the amount exceeds 10% by mass, not only the fluidity of the iron-based mixed powder but also the powder molded product and sintered This is because the characteristics of the product may deteriorate. In order to further reduce these adverse effects, the blending amount of the porous particles is more preferably in the range of 0.1 to 1% by mass.

Next, the iron-based powder used in the present invention will be described.
In the present invention, as iron-based powder, pure iron powder such as atomized iron powder and reduced iron powder, or partially diffused alloyed steel powder and fully alloyed steel powder, and further partially diffused alloy components in fully alloyed steel powder. The hybrid steel powder etc. which were made to be illustrated are illustrated.

Examples of the alloy powder include graphite powder, metal powder such as Cu, Mo, and Ni, boron powder, and cuprous oxide powder. The strength of the sintered body can be increased by mixing these alloy powders with the iron-based powder. Examples of the machinability improving powder include MnS powder. These alloy powders or machinability improving powders may be used alone or in combination of two kinds.
The blending amount of the above-mentioned alloy powder and machinability improving powder is preferably about 0.1 to 10% by mass in the iron-based mixed powder. This is because the strength of the obtained sintered body is advantageously improved by blending the alloy powder in an amount of 0.1% by mass or more, while the dimensional accuracy of the sintered body is lowered when the amount exceeds 10% by mass.

  In particular, in the present invention, the iron-based powder is preferably one in which an alloy powder or a machinability improving powder is attached to the surface of the iron powder via an organic binder (hereinafter referred to as alloy component-coated iron powder). By attaching the alloy powder or the machinability improving powder to the surface of the iron powder, segregation of the alloy powder or the machinability improving powder can be prevented. The characteristics of the iron powder to be used are not limited, and are appropriately selected according to the specifications required for the sintered product obtained by sintering the green compact.

  The organic binder is preferably a fatty acid amide or a metal soap. These organic binders may be used alone or in combination of two or more. When the amount of the organic binder added to the entire iron-based mixed powder is less than 0.05% by mass, the alloy powder and the machinability improving powder cannot be uniformly and sufficiently adhered to the surface of the iron powder. On the other hand, if it exceeds 0.6% by mass, the iron powder adheres and agglomerates, which may reduce the fluidity. Therefore, the amount of organic binder added is preferably in the range of 0.05 to 0.6% by mass.

  Further, in the present invention, a free lubricant may be added in order to improve the fluidity of the iron-based mixed powder for powder metallurgy. This free lubricant is added separately from the lubricant to be encapsulated in the porous particles, and the amount added is preferably 1% by mass or less as a percentage of the total iron-based mixed powder for powder metallurgy. The types of free lubricants include metal soaps (eg, zinc stearate, manganese stearate, lithium stearate, etc.), bisamides (eg, ethylene bisstearic acid amide), fatty acid amides including monoamides (eg, stearic acid monoamide, erucic acid amide) Etc.), fatty acids (for example, oleic acid, stearic acid, etc.), and thermoplastic resins (for example, polyamide, polyethylene, polyacetal, etc.) are preferred because they have the effect of reducing the output of the green compact.

Particularly preferably, the porous particles obtained as described above, the alloy component-coated iron powder, the free lubricant, and the like are mixed to obtain an iron-based mixed powder for powder metallurgy. As the mixing apparatus, conventionally known stirring blade type mixers (for example, Henschel mixer) and container rotation type mixers (for example, V type mixer, double cone mixer, etc.) can be used.
The iron-based mixed powder for powder metallurgy thus obtained has excellent fluidity and filling properties, and can reduce the output of the green compact. Moreover, an iron-based mixed powder for powder metallurgy can be produced using an inexpensive material.

As iron-based powder, pure iron powder (atomized iron powder having an average particle size of about 80 μm) and alloy component-coated iron powder in which alloy powder is attached to the surface of this pure iron powder via an organic binder Prepared the kind. Two types of alloy powders were used: copper powder (average particle size: 25 μm): 2 mass% and graphite powder (average particle size: 5 μm): 0.8 mass%. As organic binders, stearic acid monoamide: 0.05 mass% and ethylenebisstearic acid amide: 0.05 mass% were used. In addition, all of these addition ratios are ratios which occupy for the whole iron-based powder.
Further, the MOH particles or MOHP particles as shown in Table 1 were added and impregnated with a lubricant to produce porous particles containing the lubricant as shown in FIG. 1 (a). Further, hydroxyapatite particles (MOHP particles) were impregnated with a lubricant to obtain porous particles having a structure as shown in FIG.

  The average particle diameter of the raw material particles (average particle diameter of the primary fine particles), the average particle diameter of the porous particles, the type and amount of impregnation of the lubricant, and the blending amount of the porous particles containing the lubricant with respect to the entire iron-based powder are: As shown in Table 1. The average particle size of the particles was measured by photographing the particles with a scanning electron microscope.

The above iron-based powder (alloy component exterior iron powder), porous particles enclosing a lubricant, and free lubricant shown in Table 2 were mixed at various ratios to obtain an iron-based mixed powder for powder metallurgy. .
Table 2 shows the results of measurement of the fluidity of the obtained iron-based mixed powder for powder metallurgy. The fluidity of the mixed powder is evaluated according to JIS Z 2502. If this fluidity is 30 sec / 50 g or less, the fluidity can be said to be good.

Next, each iron-based mixed powder obtained was filled in a mold and pressure-formed at a pressure of 980 MPa at room temperature to obtain a cylindrical compact (outer diameter: 11 mm, height: 11 mm). . At that time, Table 2 shows the measurement results of the extraction force when the green compact is extracted from the mold and the green density of the obtained green compact. In addition, if the extraction power is 20 MPa or less, it can be said that the extraction performance is excellent. Further, if the green density is 7.3 Mg / m ³ or more, the compressibility is good.

As shown in Table 2, the inventive examples 1 to 9 all had a fluidity of 30 sec / 50 g or less and good fluidity. In addition, the output power was 20 MPa or less, and the output performance was excellent. Furthermore, the green density was at least 7.32 Mg / m ³ , and a high green density could be obtained.

  In accordance with the present invention, by mixing an appropriate amount of porous particles containing a lubricant in the iron-based powder, not only the fluidity and compressibility of the iron-based mixed powder is improved, but also the output of the green compact is greatly increased. As a result, it greatly contributes to improvement of productivity and reduction of manufacturing cost.

DESCRIPTION OF SYMBOLS 1 Porous particle 2 Primary particle 3 Lubricant 4 Connected channel structure

Claims (10)

An iron-based powder for powder metallurgy in which porous particles containing a lubricant are mixed with iron-based powder, the porous particles being
Chemical formula: MOxHy (where x> 0, y> 0)
Here, M: metal element or a metalloid element, O: oxygen, H: powder characterized by comprising a composition represented by hydrogen (except for _{MgO · Al 2 O 3 · xSiO} 2 · yH 2 O) Iron-based mixed powder for metallurgy. The porous particles further contain phosphorus, and have the following chemical formula: MOxHyPz (where x> 0, y> 0, z> 0)
The iron-based mixed powder for powder metallurgy according to claim 1, wherein the composition is represented by M: metal element or metalloid element, O: oxygen, H: hydrogen, P: phosphorus.   The iron-based mixed powder for powder metallurgy according to claim 1 or 2, wherein a blending amount of the porous particles with respect to the entire iron-based mixed powder is 0.001 to 10% by mass.   The iron-based mixed powder for powder metallurgy according to any one of claims 1 to 3, wherein the porous particle is an aggregate of primary fine particles having a particle size of 0.001 to 10 µm.   The iron-based mixed powder for powder metallurgy according to claim 1, wherein the porous particles have a connected channel structure.   The iron-based mixed powder for powder metallurgy according to claim 1, wherein the porous particles have a particle size of 1 to 100 μm.   The iron-based mixed powder for powder metallurgy according to any one of claims 1 to 6, wherein a ratio of the lubricant is 10 to 400 parts by mass with respect to 100 parts by mass of the porous particles.   8. The lubricant according to claim 1, wherein the lubricant is one or more selected from metal soap, bisamide, fatty acid amide, fatty acid, liquid lubricant, and thermoplastic resin. Iron-based mixed powder for powder metallurgy.   The iron-based powder for powder metallurgy according to any one of claims 1 to 8, wherein the iron-based powder is obtained by attaching an alloy powder to an iron powder surface via an organic binder.   The iron-base powder for powder metallurgy according to any one of claims 1 to 9, wherein the iron-base powder for powder metallurgy contains a free lubricant.

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