JP5544928B2 - Granulated powder and method for producing granulated powder - Google Patents

Description

  The present invention relates to a granulated powder and a method for producing the granulated powder.

As a method for molding metal powder, a compression molding method is known in which a mixture of metal powder and an organic binder is filled in a predetermined mold and compressed to obtain a molded body having a predetermined shape. The obtained molded body becomes a sintered metal body through a degreasing process for removing the organic binder and a firing process for sintering the metal powder. Such a technique is an example of a powder metallurgy technique, and since it can manufacture a large amount of a metal sintered body having a complicated shape depending on the shape of a mold, it has been widely used in many industrial fields in recent years.
In the compression molding method, first, it is necessary to fill the mold with metal powder as much as possible. This is because if there is a gap in the mold, the gap remains as a void in the molded body, and finally the denseness of the metal sintered body is impaired.

  However, a fine powder having an average particle size of 10 μm or less may be used as the metal powder. Such a fine powder has low fluidity, and therefore has poor filling properties in the mold. For this reason, improving the fluidity is performed by granulating a mixture of the metal powder and the organic binder into larger particles. When the mixture is granulated, a plurality of particles in the metal powder are bound together by an organic binder, resulting in a larger granulated powder. Since the granulated powder has higher fluidity than the metal powder, the granulated powder has excellent filling properties in the mold and enables the production of a dense molded body and a sintered body.

For example, Patent Document 1 discloses a method in which a granulated powder of metal powder is compression-molded, and the obtained molded body is fired at a high temperature of 1200 ° C. or higher to obtain a sintered body.
However, a firing furnace that can be used at a temperature of 1200 ° C. or higher is expensive and has a high running cost because it requires a special heat-resistant structure.
On the other hand, when the firing temperature is lowered, the density of the sintered body is lowered, and problems such as inferior mechanical properties appear.

JP 2005-154847 A

  An object of the present invention is to produce a granulated powder that can be satisfactorily sintered even when fired at a relatively low temperature and can produce a high-density sintered body, and a granulated powder that can easily produce such a granulated powder. It is to provide a method.

The above object is achieved by the present invention described below.
The granulated powder of the present invention is a granulated powder formed by binding a plurality of metal particles with an organic binder,
The organic binder, which comprises a polyvinyl alcohol or a derivative thereof, a polyhydric alcohol, which is composed of one at least of glycols and glycerin, and organic amine or a derivative thereof, and
The polyhydric alcohol is added in an amount of 0.005 to 2 parts by weight based on 1 part by weight of the polyvinyl alcohol or derivative thereof,
In the organic binder, the total content of the polyvinyl alcohol or derivative thereof and the polyhydric alcohol is 14.5% by weight or more,
The apparent density of the granulated powder is 20% to 50% of the true density of the metal particles.
Thereby, a granulated powder that can be satisfactorily sintered even when fired at a relatively low temperature and can produce a high-density sintered body is obtained.

In the granulated powder of the present invention, the polyhydric alcohol is preferably glycerin.
Glycerin has a relatively small molecular weight among polyhydric alcohols and a large ratio of hydroxyl groups, so it easily enters between the molecules of polyvinyl alcohol and contains many sites that contribute to hydrogen bonding. Contributes to densification of granulated powder. In addition, glycerin has an appropriate viscosity, and can further improve the binding property of the metal powder during granulation and the shape retention of the molded body.

In the granulated powder of the present invention, the amount of the polyhydric alcohol added is preferably 0.01 parts by weight or more and 0.2 parts by weight or less with respect to 100 parts by weight of the metal particles.
As a result, the granulated powder can be particularly densified, a high-density sintered body can be obtained, and stress at the time of compression molding can be accumulated in the molded body and released with deformation after molding. Occurrence can be prevented.

In the granulated powder of the present invention, the apparent density of the granulated powder is preferably 25.6% to 50% of the true density of the metal particles .

In the granulated powder of the present invention, the organic amine is preferably at least one of alkylamine, cycloalkylamine, alkanolamine and derivatives thereof.
Thereby, further densification of the granulated powder is promoted.
In the granulated powder of the present invention, the amount of the organic amine added is preferably 0.001 to 5 parts by weight with respect to 100 parts by weight of the metal particles.
Thereby, further densification of the granulated powder and further improvement of weather resistance are promoted.
In the granulated powder of the present invention, the content of the organic binder in the granulated powder is preferably 0.1 wt% or more and 5.53 wt% or less.
Thereby, the disintegration at the time of shaping | molding and the shape retention property of a subsequent molded object can be improved. As a result, a sintered body excellent in density and dimensional accuracy can be obtained.

Method for producing a granulated powder of the present invention, supply and polyvinyl alcohol or a derivative thereof, a polyhydric alcohol, which is composed of one at least of glycols and glycerin, and organic amine or a derivative thereof, a solution of an organic binder containing a However, by rolling and / or flowing the metal powder, the metal powder is granulated to obtain a granulated powder,
In the granulated powder, the addition amount of the polyhydric alcohol is 0.005 parts by weight or more and 2 parts by weight or less with respect to 1 part by weight of the polyvinyl alcohol or a derivative thereof.
In the granulated powder, the total content of the polyvinyl alcohol or derivative thereof and the polyhydric alcohol in the organic binder is 14.5% by weight or more,
The apparent density of the granulated powder is 20% to 50% of the true density of the particles of the metal powder .
Thereby, it is possible to easily produce a granulated powder that can be satisfactorily sintered even when fired at a relatively low temperature and can produce a high-density sintered body.
In the granulated powder manufacturing method of the present invention, the organic binder solution is preferably supplied by spraying.
Thereby, since a binder solution is supplied to granulated powder uniformly without excess and deficiency, the shape and size of granulated powder can be made uniform. As a result, a granulated powder having a uniform particle size distribution is obtained.

It is a schematic diagram which shows the structure of the rolling granulation apparatus used in the manufacturing method of the granulated powder of this invention. It is a graph which shows distribution of the molded object obtained in each Example when a horizontal axis | shaft is the addition amount of glycerol and a vertical axis | shaft is a shaping | molding density.

Hereinafter, the granulated powder and the method for producing the granulated powder of the present invention will be described in detail based on preferred embodiments based on the accompanying drawings.
The granulated powder of the present invention contains a metal powder and an organic binder, and is formed by binding a plurality of metal particles in the metal powder with an organic binder.
Moreover, the organic binder used for this invention contains polyvinyl alcohol or its derivative (s), and a polyhydric alcohol . And the granulated powder of this invention has the characteristics that the apparent density is 20 to 50% of the true density of metal powder (metal material which comprises metal powder).
Such a granulated powder sinters well even when fired at a relatively low temperature, and can produce a high-density sintered body. For this reason, it has the advantage that the baking furnace which does not have a special heat-resistant structure, and which does not require a running cost can be used.

Hereinafter, the granulated powder of the present invention will be described in detail.
(Metal powder)
Although it does not specifically limit as metal powder, For example, Mg, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Pd, Ag, In, Sn, Sn, Ta, W, or these alloys are mentioned.

Among these, powders of various Fe-based alloys such as stainless steel, die steel, high speed tool steel, low carbon steel, Fe—Ni alloy, Fe—Ni—Co alloy are preferably used as the metal powder. Since such an Fe-based alloy has excellent mechanical properties, a sintered body obtained using this Fe-based alloy powder has excellent mechanical properties and can be used for a wide range of applications.
Examples of the stainless steel include SUS304, SUS316, SUS317, SUS329, SUS410, SUS430, SUS440, and SUS630.

The average particle size of the metal powder is preferably 1 to 30 μm, more preferably 3 to 20 μm, and still more preferably 3 to 10 μm. A metal powder having such a particle size can finally produce a sufficiently dense sintered body while avoiding a decrease in compressibility during molding.
In addition, when an average particle diameter is less than the said lower limit, metal powder tends to aggregate and there exists a possibility that the compressibility at the time of shaping | molding may fall remarkably. On the other hand, when the average particle diameter exceeds the upper limit, the gap between the powder particles becomes too large, and the final sintered body may not be sufficiently densified.

Moreover, the tap density of the metal powder used in the present invention, for example, in the case of Fe-based alloy powder is preferably at 3.5 g / cm ³ or more, more preferably 3.8 g / cm ³ or more. When the metal powder has such a large tap density, the filling property between the particles is particularly high when the granulated powder is obtained. For this reason, a particularly dense sintered body can be finally obtained.
The specific surface area of the metal powder used in the present invention is not particularly limited, but is preferably 0.15 m ² / g or more, more preferably 0.2 m ² / g or more, and 0.3 m ^2. / G or more is more preferable. If the metal powder has a large specific surface area as described above, the surface activity (surface energy) is increased, and therefore, it can be easily sintered even when less energy is applied. Therefore, when the compact is sintered, it can be sintered in a shorter time. As a result, the sintered compact can be densified even when firing at a low temperature.

Such a metal powder may be produced by any method, for example, an atomizing method (water atomizing method, gas atomizing method, high-speed rotating water atomizing method, etc.), reduction method, carbonyl method, pulverization method, etc. What was manufactured by the method can be used.
Among these, it is preferable to use what was manufactured by the atomizing method for metal powder. According to the atomizing method, a metal powder having an extremely small average particle diameter as described above can be efficiently produced. Moreover, there can be obtained a metal powder having a small particle size variation and a uniform particle size. Therefore, by using such a metal powder, the formation of pores in the sintered body can be surely prevented, and the density can be improved.
In addition, since the metal powder produced by the atomizing method has a spherical shape that is relatively close to a true sphere, the metal powder has excellent dispersibility and fluidity with respect to the binder. For this reason, when the granulated powder is filled into a mold and molded, the filling property can be improved, and a denser sintered body can be finally obtained.

(Organic binder)
In this invention, as above-mentioned as an organic binder, polyvinyl alcohol (PVA) or its derivative (s), and a polyhydric alcohol are included.
Here, with the conventional granulated powder, a high apparent density could not be realized. This is probably because the distance between the particles of the metal powder could not be shortened sufficiently. In particular, when the particle size of the metal powder is small, the metal powder becomes bulky, and the above tendency is more remarkable.

On the other hand, when the above organic binder is used, when the metal powder and the organic binder are mixed and granulated to produce a granulated powder, the assemblability of the metal powder is improved and the granulated powder having a high apparent density. Is obtained.
In such a densified granulated powder, the distance between the metal particles is sufficiently small, and therefore, sintering is started at a lower temperature and in a shorter time during degreasing and firing. Therefore, it is possible to use a firing furnace that does not have a special heat-resistant structure, is relatively inexpensive, and does not require running costs, and a high-density sintered body can be efficiently manufactured.

The reason why the granulated powder of the present invention has the above effects is as follows.
First, polyvinyl alcohol or a derivative thereof and polyhydric alcohol are uniformly mixed regardless of the mixing ratio of the two. This is because the hydroxyl groups of both molecules are attracted by hydrogen bonds, and the intermolecular distance is narrowed. In particular, it is considered that polyhydric alcohol molecules penetrate between polyvinyl alcohol molecules and contribute to shortening the intermolecular distance of polyvinyl alcohol. In addition, the above organic binder decomposes rapidly at a relatively low temperature, and is therefore unlikely to be a hindrance to sintering. For this reason, it is thought that the molded object formed by shape | molding the granulated powder of this invention will sinter at lower temperature and for a shorter time.

  Moreover, it is thought that the molecule | numerator of these organic binders attracts also to the particle | grains of metal powder by a hydrogen bond. This is because a hydroxyl bond is exposed on the particle surface of the metal powder, and a hydrogen bond is generated between the hydroxyl group and the hydroxyl group of the organic binder molecule. As a result, the distance between the metal powder particles is shortened, and it is considered that the granulated powder is densified, and the sintered body is further densified.

For the reasons as described above, the granulated powder of the present invention becomes dense and its apparent density increases. Specifically, the apparent density [g / cm ³ ] of the granulated powder of the present invention is 20% to 50% of the true density [g / cm ³ ] of the metal powder. Such a granulated powder sinters well even when fired at a relatively low temperature, and can produce a high-density sintered body. For this reason, it has the advantage that the baking furnace which does not have a special heat-resistant structure, and which does not require a running cost can be used.

In addition, it is possible to reduce the amount of plasticizer and lubricant used to increase the sintered density, or to stop the use itself. For this reason, the fall of the sintered density by addition of these is prevented, the further improvement of a sintered density can be aimed at, and cost reduction can also be achieved.
In addition, if the apparent density of the granulated powder is densified to the above range, the shrinkage rate during sintering is reduced accordingly. As a result, the dimension of the sintered body is difficult to deviate from the target value, and the dimensional accuracy of the sintered body can be increased. That is, according to the present invention, a sintered body with high dimensional accuracy can be obtained.

As polyvinyl alcohol or a derivative thereof, those having a weight average molecular weight of about 2000 to 200000 are preferably used, and those having a weight average molecular weight of about 5000 to 150,000 are more preferably used. Polyvinyl alcohol having such a weight average molecular weight is optimal as an organic binder in terms of viscosity and thermal decomposability. That is, the polyvinyl alcohol is highly compatible with the binding property of the metal powder at the time of granulation, the disintegration property at the time of molding, and the shape retention of the molded product thereafter. As a result, a sintered body excellent in density and dimensional accuracy can be obtained by using the granulated powder of the present invention.
In addition, the derivative | guide_body of polyvinyl alcohol means what substituted the hydrogen atom couple | bonded with the carbon atom with various functional groups, and an alkyl group, a silyl group, an acrylate group etc. are mentioned as a functional group, for example. .

On the other hand, examples of the polyhydric alcohol include ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, pentanediol, hexanediol, heptanediol, diethylene glycol, and glycols such as dipropylene glycol, glycerin, and the like. 1 type or 2 types or more can be used in combination.
Of these, glycerin is preferred as the polyhydric alcohol used in the present invention. Glycerin is a polyhydric alcohol having a relatively low molecular weight and a high hydroxyl group abundance ratio. For this reason, in addition to easily entering between the molecules of polyvinyl alcohol, the number of sites contributing to the hydrogen bond described above increases, and the granulated powder is further densified. In addition, glycerin has an appropriate viscosity, and can further improve the binding property of the metal powder during granulation and the shape retention of the molded body.

Such a polyhydric alcohol is preferably added in a proportion of 0.01 parts by weight or more and 0.2 parts by weight or less, based on 100 parts by weight of the metal powder, and 0.01 parts by weight or more and 0.1 parts by weight or less. It is more preferable to add at the following ratio. By adding the polyhydric alcohol in such an addition amount, the granulated powder can be particularly densified.
In addition, when the addition amount of a polyhydric alcohol is less than the said lower limit, there exists a possibility that the density of granulated powder and by extension, the density of a sintered compact may fall. On the other hand, when the amount of polyhydric alcohol added exceeds the upper limit, the density of the granulated powder also decreases, and stress during compression molding is accumulated in the molded body, and the residual stress is released with deformation after molding. Phenomenon, so-called springback, increases. For this reason, there exists a possibility that the dimensional accuracy of a sintered compact may fall or a crack etc. may generate | occur | produce.

Further, the polyhydric alcohol with respect to 1 part by weight of polyvinyl alcohol or its derivative is preferably added in an amount of less than 2 parts by weight or more 0.005 parts by weight, less than 1 part by weight 0.01 part by weight More preferably, it is 0.02 part by weight or more and 0.5 part by weight or less. Thereby, the densification of the granulated powder by shortening the intermolecular distance of the polyvinyl alcohol by polyhydric alcohol and sufficient disintegration at the time of shaping | molding of the granulated powder can be made compatible more highly.

  The organic binder preferably contains an organic amine or a derivative thereof in addition to the above components. By including organic amines or derivatives thereof, the fluidity and weather resistance of the metal powder can be enhanced. These organic amines contain an amino group in each molecule, but the amino group spontaneously adsorbs on the particle surface of the metal powder, so that friction between particles can be reduced. As a result, the fluidity of the metal powder is improved and the distance between particles is reduced, thereby contributing to densification of the granulated powder. In addition, the organic amines adsorbed on the particle surface reduce the chance of contact between the particle and the outside air, thereby protecting the particle from oxygen, moisture, etc., and improving the weather resistance of the particle.

In addition, it is thought that adsorption | suction to the particle | grain surface of an amino group is based on the interaction of the lone electron pair which the amino group which is a polar group has, and the adsorption site on the particle | grain surface of a metal powder.
Examples of such organic amines include alkylamines, cycloalkylamines, alkanolamines, allylamines, arylamines, alkoxyamines, and derivatives thereof, among which alkylamines are particularly preferred. , Cycloalkylamines, alkanolamines and derivatives thereof are preferably used. These amines contribute to further densification of the granulated powder.

Examples of alkylamines include n-hexylamine, n-heptylamine, n-octylamine (normal octylamine), monoalkylamines such as 2-ethylhexylamine, dialkylamines such as diisobutylamine, diisopropyl And trialkylamines such as ethylamine.
Examples of cycloalkylamines include cyclohexylamine and dicyclohexylamine.

Examples of the alkanolamines include monoethanolamine, diethanolamine, triethanolamine, monopropanolamine, dipropanolamine, tripropanolamine, N, N-dimethylethanolamine, N, N-diethylethanolamine, N- Examples include aminoethylethanolamine, N-methylethanolamine, N-methyldiethanolamine.
Further, the derivatives of these organic amines are not particularly limited, but preferably organic amine nitrites, organic amine carboxylates, organic amine chromates, organic amine acetates and the like. Can be used.

Such organic amines are preferably added in a proportion of 0.001 part by weight or more and 5 parts by weight or less with respect to 100 parts by weight of the metal powder, and in a proportion of 0.005 part by weight or more and 1 part by weight or less. More preferably, it is added. By adding organic amines in such an addition amount, the granulated powder can be further densified and further improved in weather resistance.
By the way, as the organic binder, in addition to the above components, for example, polyvinylpyrrolidone (PVP), stearic acid, ethylene bisstearamide, ethylene vinyl copolymer, paraffin, wax, sodium alginate, agar, gum arabic, resin And may contain sucrose.

Moreover, additives, such as a phthalate ester (Example: DOP, DEP, DBP), adipic acid ester, trimellitic acid ester, sebacic acid ester, may be added to the organic binder as needed.
In addition to the above components, antioxidants, degreasing accelerators, surfactants, and the like may be added as additives.
However, the total content of the polyvinyl alcohol or derivative thereof and the polyhydric alcohol in the organic binder is preferably 80% by weight or more, and more preferably 90% by weight or more. By setting the content within the above range, a sufficiently high-density granulated powder can be obtained.

(Granulated powder)
The granulated powder of the present invention contains the above metal powder and an organic binder. The content of the organic binder in the granulated powder is preferably 0.1% by weight or more and 20% by weight or less. It is more preferably 3% by weight or more and 3% by weight or less, and further preferably 0.5% by weight or more and 2.5% by weight or less. When the content of the organic binder is within the above range, the binding property between the particles of the metal powder and sufficient densification of the granulated powder can be achieved. Moreover, by using such granulated powder, the disintegration property at the time of shaping | molding and the shape retention property of a subsequent molded object can be improved. As a result, a sintered body excellent in density and dimensional accuracy can be obtained.

  Here, as described above, the apparent density of the granulated powder of the present invention is 20% to 50% of the true density of the metal powder. The apparent density of the granulated powder is the ratio between the mass and the volume of the granulated powder in the natural filling state, and can be measured by the apparent density test method for metal powder defined in JIS Z 2504. On the other hand, the true density of the metal powder is the true density of the metal material constituting the metal powder.

  By using the organic binder as described above, the granulated powder is densified, and a granulated powder in which the ratio of the apparent density to the true density of the metal powder is within the above range is obtained. Such a granulated powder can form a molded body having a high molding density when it is molded, and can further form a sintered body having a high sintering density. Moreover, since the shrinkage rate at the time of sintering can be suppressed, the dimensional accuracy of the sintered body can be increased.

The apparent density of the granulated powder of the present invention is within the above range with respect to the true density of the metal powder, but is preferably 25% or more and 45% or less, more preferably 30% or more and 40% or less. .
When the apparent density is less than the lower limit, the granulated powder is not sufficiently densified, and the sinterability at low temperatures is significantly reduced. On the other hand, when the apparent density exceeds the upper limit, the granulated powder becomes excessively dense, and an appropriate disintegration property at the time of molding cannot be obtained.
In addition, each particle shape of the granulated powder of the present invention has a great influence on fluidity and filling properties. From this viewpoint, it is preferable that each particle shape of the granulated powder is a shape close to a true sphere.

(Production method of granulated powder)
Next, an embodiment of a method for producing a granulated powder of the present invention will be described.
Hereinafter, prior to the description of the method for producing the granulated powder, the granulator used in this production method will be described.
FIG. 1 is a schematic diagram showing the configuration of a rolling granulator used in the method for producing granulated powder of the present invention. In addition, Fig.1 (a) is a longitudinal cross-sectional view of a rolling granulation apparatus, FIG.1 (b) is the sectional view on the AA line of Fig.1 (a).

The rolling granulator 1 includes a processing container 10 for performing granulation, a blade 20 and a cross screw 30 disposed in the processing container 10, and a spray nozzle 40.
As shown in FIG. 1A, the processing container 10 has a bottom part 11 and a side wall part 12 erected from the bottom part 11, and the side wall part 12 has an inner diameter and an outer diameter from the upper side to the lower side. It has a gradually increasing weight shape (for example, a truncated cone shape). Since the processing container 10 (side wall portion 12) has such a shape, the powder blown up on the outer peripheral side of the processing container 10 by the blade 20 in the processing container 10 falls to the center side of the processing container 10. An air current can be formed. As a result, the powder can be processed without unevenness, and a granulated powder having a sharp particle size distribution can be efficiently produced.

Further, the processing container 10 has an opening on the upper side, and a lid portion 13 is mounted so as to close the opening.
The blade 20 includes a base 23 and three rotary blades 21, 21, 21 having one end fixed to the base 23 and provided radially at substantially equal intervals.
A through hole 110 is provided at the center of the bottom 11 of the processing container 10, and the rotation drive shaft 22 is inserted through the through hole 110.

The upper end of the rotational drive shaft 22 is fixed to the base 23, and the lower end is connected to a rotational drive source (not shown). Then, the rotational drive shaft 22 is rotationally driven in the forward and reverse directions by the rotational drive source, whereby the blade 20 rotates.
Further, the rotary blades 21, 21, and 21 are respectively fixed to be inclined with respect to the rotary drive shaft 22 so that the front side in the rotation direction of the blade 20 is a downward slope. Thereby, with rotation of the blade 20, the powder can be effectively jumped up and the airflow as described above can be formed.

A through hole 130 is provided in the side wall portion 12 of the processing container 10, and the rotation drive shaft 31 is inserted into the through hole 130.
One end of the rotation drive shaft 31 is fixed to the cross screw 30 and the other end is connected to a rotation drive source (not shown). Then, the rotational screw 31 is rotated in the forward and reverse directions by the rotational driving source, whereby the cross screw 30 is rotated.

The spray nozzle 40 is provided through the lid portion 13 attached to the processing container 10, and the supply port is located in the processing container 10. Thereby, it is comprised so that a solvent can be sprayed in the processing container 10. FIG. By spraying the solvent from the spray nozzle 40, a downward air flow is generated in the vicinity of the spray nozzle 40.
Here, the operation of the rolling granulator 1 as described above, that is, a method for producing a granulated powder using the rolling granulator 1 will be described. The granulated powder production method using the rolling granulator 1 is an example of the granulated powder production method of the present invention, and it goes without saying that the granulated powder production method of the present invention is not limited thereto. .

Next, the manufacturing method of granulated powder is demonstrated.
The method for producing a granulated powder according to the present embodiment granulates a metal powder by rolling and / or flowing the metal powder while supplying an organic binder solution (binder solution).
First, metal powder is put into the processing container 10 of the rolling granulation apparatus 1 as described above. Then, the metal powder is rolled and / or fluidized by stirring with the blade 20.

  At the same time, the binder solution is sprayed from the spray nozzle 40. The binder solution in the mist state wets the metal powder and binds the particles of the metal powder. As a result, the metal powder is granulated, and the granulated powder 80 is obtained. The granulated powder 80 gradually moves (rolls) to the outer peripheral side (side wall portion 12 side) of the processing container 10 as the blade 20 rotates, and is spun up by the rotary blade 21. The granulated powder 80 that has been bounced down descends on the center side of the processing vessel 10 and is rolled by the blade 20 again. When such a series of processes is repeated, shaping is performed and a granulated powder 80 close to a true sphere is formed. As a result, a dense granulated powder having a short interparticle distance can be obtained.

Further, in the process of granulation, when the particles being granulated come into contact with the rotating cross screw 30, particles having a large particle diameter (particles having a high degree of granulation) are crushed. Thereby, excessive granulation is suppressed and the particle size distribution of the granulated powder is controlled to a narrow width.
The binder solution may be supplied by any method, for example, by putting it in the processing container 10 in advance, but it is preferable to spray from above as shown in FIG. Thereby, since the binder solution is uniformly and sufficiently supplied to the granulated powder 80 bounced up by the blade 20, the shape and size of the granulated powder 80 can be made uniform. In particular, when the granulated powder 80 floats in the air, the entire surface of the particles of the granulated powder 80 is wetted evenly by contacting with the binder solution, so that the homogenization becomes more remarkable. As a result, a granulated powder 80 having a uniform particle size distribution is obtained.

  Examples of the solvent used for the binder solution include inorganic solvents such as water, carbon disulfide, and carbon tetrachloride, methyl ethyl ketone (MEK), acetone, diethyl ketone, methyl isobutyl ketone (MIBK), methyl isopropyl ketone (MIPK), Ketone solvents such as cyclohexanone, 3-heptanone, 4-heptanone, methanol, ethanol, n-propanol, isopropanol, n-butanol, i-butanol, t-butanol, 3-methyl-1-butanol, 1-pentanol, Alcohol solvents such as 2-pentanol, n-hexanol, cyclohexanol, 1-heptanol, 1-octanol, 2-octanol, 2-methoxyethanol, allyl alcohol, furfuryl alcohol, phenol, diethyl ether, di Ethers such as propyl ether, diisopropyl ether, dibutyl ether, 1,2-dimethoxyethane (DME), 1,4-dioxane, tetrahydrofuran (THF), tetrahydropyran (THP), anisole, diethylene glycol dimethyl ether (diglyme), 2-methoxyethanol Solvents, cellosolve solvents such as methyl cellosolve, ethyl cellosolve, phenyl cellosolve, aliphatic hydrocarbon solvents such as hexane, pentane, heptane, cyclohexane, methylcyclohexane, octane, didecane, methylcyclohexene, isoprene, toluene, xylene, benzene , Aromatic hydrocarbon solvents such as ethylbenzene and naphthalene, pyridine, pyrazine, furan, pyrrole, thiophene, 2-methylpyridine, 3-methylpi Aromatic heterocyclic compound solvents such as gin, 4-methylpyridine, furfuryl alcohol, amide solvents such as N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMA), dichloromethane, chloroform, 1 Halogenated solvents such as, 2-dichloroethane, trichloroethylene, chlorobenzene, acetylacetone, ethyl acetate, methyl acetate, isopropyl acetate, isobutyl acetate, isopentyl acetate, ethyl chloroacetate, butyl chloroacetate, isobutyl chloroacetate, ethyl formate, isobutyl formate, Ester solvents such as ethyl acrylate, methyl methacrylate and ethyl benzoate, amine solvents such as trimethylamine, hexylamine, triethylamine and aniline, nitrile solvents such as acrylonitrile and acetonitrile Nitro solvents such as nitromethane and nitroethane, organic solvents such as aldehyde solvents such as acetaldehyde, propionaldehyde, butyraldehyde, pentanal, and acrylic aldehyde, and the like. One or more selected from these are mixed. Things can be used.

  Here, the number of rotations of the blade 20 per unit time (hereinafter simply referred to as “the number of rotations”) is not particularly limited as long as the rolling of the granulated powder 80 can be ensured to the minimum, but for example, 50 rpm or more and 500 rpm or less. Is preferably about 100 rpm or more and 300 rpm or less. When the rotational speed of the blade 20 is within the above range, the granulated powder 80 can be efficiently rolled and granulated efficiently. Moreover, since a moderate compaction state is obtained, it can be set as the granulated powder with a higher apparent density. As a result, it is possible to obtain a granulated powder 80 that is denser and has a particularly narrow particle size distribution width.

  On the other hand, when the rotation speed of the blade 20 is less than the lower limit, rolling and jumping up of the granulated powder 80 becomes insufficient, which may cause uneven granulation. Moreover, there is a possibility that the compaction will be insufficient, resulting in a granulated powder 80 with a low apparent density, and a granulated powder 80 that is not spherical and has an irregular shape and poor fluidity. On the other hand, when the rotation speed of the blade 20 exceeds the upper limit, the granulated particles are crushed by the blade 20 and there is a possibility that the amount of powder that does not progress is increased.

Moreover, the rotation speed per unit time of the cross screw 30 at the time of granulation is not specifically limited, For example, it is preferable that it is about 50 rpm or more and 3500 rpm or less, and it is more preferable that it is about 100 rpm or more and 3000 rpm or less. Thereby, particle | grains with a big particle diameter can be crushed and particle diameter can be equalize | homogenized, preventing excessive crushing.
The supply rate of the binder solution is not particularly limited, but is preferably, for example, from 20 g / min to 1000 g / min, more preferably from 30 g / min to 800 g / min, and more preferably from 50 g / min to 600 g. More preferably, it is less than / min. When the supply rate of the binder solution is a value within the above range, the particle size distribution of the obtained granulated powder is made sharper while the bonding (granulation) of the metal powder by the binder solution proceeds without unevenness. it can.

On the other hand, when the supply rate of the binder solution is less than the lower limit value, there is a possibility of causing uneven granulation. On the other hand, if the supply rate of the binder solution exceeds the upper limit, granulation may proceed excessively. As a result, the obtained granulated powder may have a wide particle size distribution.
Further, the concentration of the organic binder in the binder solution is preferably 0.5% by weight to 20% by weight, more preferably 1% by weight to 15% by weight, and more preferably 2% by weight to 10% by weight. More preferably, it is as follows.

The granulation treatment time (stirring time) is not particularly limited, but is preferably 1 minute to 90 minutes, more preferably 2 minutes to 85 minutes, and more preferably 3 minutes to 80 minutes. More preferably. Thereby, the residual of ungranulated granulated powder can be suppressed and the particle size distribution of the obtained granulated powder can be made sufficiently sharp.
On the other hand, when the granulation treatment time is less than the lower limit, a relatively large amount of small particle size powder (such as ungranulated metal powder) may remain. On the other hand, when the granulation treatment time exceeds the upper limit, a solvent is directly applied to a powder having a relatively large particle size (a lump of powder that does not roll or flow), which may cause uneven granulation. There is.

  Moreover, you may make it spray (supply) the solvent which can melt | dissolve an organic binder with respect to granulated powder as needed. Thereby, further uniformization of the shape and size of the granulated powder is achieved.

A granulated powder is obtained as described above.
In addition, although the technique common to the rolling granulation method, the fluidized bed granulation method, or the rolling fluidized granulation method which is one of the granulation methods has been described above, the granulation method is not limited thereto. Alternatively, a spray drying (spray drying) method or the like can be used.
Further, the use of the granulated powder of the present invention is not particularly limited. For example, the production of a molded body containing the granulated powder, particularly the sintering obtained by sintering the molded body containing the granulated powder. It can use suitably for manufacture of a body.

(Method for producing sintered body)
Hereinafter, an example of the manufacturing method of a sintered compact is demonstrated.
<Molding>
First, using the granulated powder of the present invention as described above, it is molded by a press molding machine to produce a molded body having a desired shape and size. The granulated powder of the present invention itself is dense and has a high filling property. For this reason, a high-density molded body can be produced, and finally a sintered body having a high density and a small shrinkage rate can be obtained.
It should be noted that the shape and size of the molded body to be manufactured is determined in consideration of the shrinkage due to subsequent degreasing and sintering. The molding method is not limited to press molding, and may be compression molding, injection molding, or the like.

<Degreasing treatment>
A degreasing treatment (debinding treatment) is performed on the molded body obtained in the molding step described above to obtain a degreased body. The degreasing treatment is not particularly limited, but a non-oxidizing atmosphere, for example, in a vacuum or a reduced pressure state (for example, 1 × 10 ⁻¹ Torr or more and 1 × 10 ⁻⁶ Torr or less), or nitrogen gas, argon gas, hydrogen gas, The heat treatment is performed in a gas such as ammonia decomposition gas. In this case, the conditions for the heat treatment are slightly different depending on the decomposition start temperature of the organic binder, but are preferably about 100 ° C. to 750 ° C. and about 0.5 hours to 40 hours, more preferably 150 ° C. to 700 ° C. The following is about 1 hour to 24 hours.

Further, degreasing by such heat treatment may be performed in a plurality of steps (stages) for various purposes (for example, for shortening the degreasing time). In this case, for example, a method in which the first half is degreased at a low temperature and the second half at a high temperature, a method in which low temperature and high temperature are repeated, and the like can be mentioned.
Note that the organic binder may not be completely removed by the degreasing treatment, and for example, a part of the organic binder may remain at the time of completion of the degreasing treatment.

<Baking>
The degreased body obtained in the degreasing process described above is fired and sintered in a sintering furnace to obtain a desired sintered body. By this firing, the metal powder constituting the granulated powder diffuses and grows, and as a whole, a dense sintered body having a high density and a low porosity can be obtained.
The firing temperature during firing varies slightly depending on the composition of the granulated powder. For example, when an Fe-based alloy powder is used, it is preferably 900 ° C. or more and less than 1200 ° C., and is 1000 ° C. or more and 1180 ° C. or less. Is more preferable. When the firing temperature is within the above range, a sintered body can be efficiently produced using a firing furnace that does not have a special heat-resistant structure, is relatively inexpensive, and does not require running costs. When the firing temperature is less than the lower limit, the sintering of the metal powder does not proceed sufficiently, and the porosity of the finally obtained sintered body increases and sufficient mechanical strength cannot be obtained. There is a fear. On the other hand, if the firing temperature exceeds the upper limit, it is necessary to use a firing furnace having a special heat-resistant structure, and the ease of firing is reduced.

The maximum temperature holding time during firing is preferably about 0.5 hours to 8 hours, and more preferably about 0.75 hours to 5 hours.
The firing atmosphere is not particularly limited, but is preferably a reduced pressure (vacuum) or non-oxidizing atmosphere. Thereby, characteristic deterioration due to metal oxidation can be prevented. A preferable firing atmosphere is a reduced pressure (vacuum) of 1 Torr or less (more preferably 1 × 10 ⁻² Torr or more and 1 × 10 ⁻⁶ Torr or less), or an inert gas such as nitrogen gas or argon gas of 1 Torr or more and 760 Torr or less. An atmosphere or a hydrogen gas atmosphere of 1 to 760 Torr is preferable.

Note that the firing atmosphere may change during firing. For example, first, the pressure is reduced to 1 × 10 ⁻² Torr or more and 1 × 10 ⁻⁶ Torr or less (vacuum), and can be switched to the inert gas as described above.
Moreover, you may perform baking by two steps or more. For example, primary firing and secondary firing with different firing conditions may be performed, and the firing temperature of the secondary firing may be higher than the firing temperature of the primary firing.
Note that the sintered body obtained as described above may be used for any purpose, and examples of its use include various machine parts.

  The relative density of the sintered body obtained as described above varies depending on the application and the like, but is expected to be, for example, more than 93%, preferably 94% or more. Such a sintered body is particularly excellent in mechanical properties. In addition, by using the granulated powder of the present invention, a sintered body having excellent mechanical properties can be efficiently produced even when firing at a low temperature.

As mentioned above, although this invention was demonstrated based on suitable embodiment, this invention is not limited to these.
For example, in the manufacturing method of granulated powder, arbitrary processes can be added as needed.
Moreover, the apparatus used for the manufacturing method of the granulated powder of this invention is not limited to the thing of embodiment mentioned above. For example, in the above-described embodiment, the description has been given by using the rolling granulator. However, the fluidized bed granulating apparatus that performs granulation by the fluid action, the rolling fluid granulator that performs granulation by the rolling fluid action, the spray You may make it use the spray-drying apparatus etc. to dry.

1. Production of granulated powder (Example 1)
<1> First, 2% Ni—Fe alloy powder (manufactured by Epson Atmix Co., Ltd., true density 7.827 g / cm ³ ) having an average particle diameter of 6 μm produced by a water atomization method was prepared as a raw material powder. The composition of 2% Ni—Fe is as follows: C: 0.4 to 0.6 mass%, Si: 0.35 mass% or less, Mn: 0.8 mass% or less, P: 0.03 mass% or less, S: 0.045% by mass or less, Ni: 1.5 to 2.5% by mass, Cr: 0.2% by mass or less, Fe: remainder.

<2> On the other hand, polyvinyl alcohol (manufactured by Kuraray Co., Ltd., RS-1717), glycerin (manufactured by Wako Pure Chemical Industries, Ltd.) and an alkylamine derivative (acetate salt) were prepared as organic binders. Moreover, ion-exchange water was prepared as a solvent. The amount of solvent added was 50 g per 1 g of organic binder. Moreover, the saponification degree of polyvinyl alcohol was 93, and the polymerization degree was 1700.
Next, a binder solution was prepared by mixing polyvinyl alcohol, glycerin and organic amines in ion exchange water and cooling to room temperature. In addition, the addition amount of polyvinyl alcohol, glycerin, and an alkylamine derivative was 0.8 weight part, 0.01 weight part, and 0.1 weight part with respect to 100 weight part of metal powders.

<3> Next, the raw material powder was put into a processing container of a tumbling granulator (manufactured by POWREC, VG-25). Then, the raw material powder was rolled under the following conditions while spraying the binder solution from the spray nozzle of the rolling granulator. This obtained the granulated powder with an average particle diameter of 75 micrometers.
<Rolling conditions>
・ Blade rotation speed: 200rpm
・ Cross screw speed: 2500rpm
-Binder solution supply rate: 200 g / min-Granulation time: 90 minutes

(Examples 2-9)
A granulated powder was obtained in the same manner as in Example 1 except that the amount of glycerin added was as shown in Table 1.
(Examples 10 to 15)
A granulated powder was obtained in the same manner as in Example 3 except that the amount of organic amine added was as shown in Table 1.

(Examples 16 to 21)
A granulated powder was obtained in the same manner as in Example 3 except that the addition amount of polyvinyl alcohol was as shown in Table 2.
(Example 22)
A granulated powder was obtained in the same manner as in Example 3 except that the addition of organic amines was omitted.

(Examples 23 to 26)
A granulated powder was obtained in the same manner as in Example 1 except that the composition and addition amount of the polyhydric alcohol or the composition and addition amount of the organic amines were as shown in Table 2, respectively.
(Examples 27 and 28)
Granulated powder was obtained in the same manner as in Example 22 and Example 3, except that the composition of the metal powder was changed to SUS-316L (true density: 7.98 g / cm ³ ).

(Comparative Examples 1-3)
Granulated powders were obtained in the same manner as in Example 1 except that the organic binder was composed only of polyvinyl alcohol (the addition of glycerin and alkylamine derivatives was omitted) and the addition amount was as shown in Table 2.
(Comparative Example 4)
A granulated powder was obtained in the same manner as in Comparative Example 1 except that polyvinylpyrrolidone was used instead of polyvinyl alcohol.

(Comparative Example 5)
A granulated powder was obtained in the same manner as in Comparative Example 4 except that glycerin and an alkylamine derivative were further added to the organic binder.
(Comparative Example 6)
A granulated powder was obtained in the same manner as in Example 28 except that the organic binder was composed only of polyvinyl alcohol (the addition of glycerin and alkylamine derivatives was omitted).

2. 2. Evaluation of Granulated Powder 2.1 Evaluation of Apparent Density The apparent density of the granulated powder obtained in each Example and each Comparative Example was measured. And the ratio with respect to the true density of each metal powder was computed.
2.2 Evaluation of molding density The granulated powder obtained in each Example and each Comparative Example was molded under the molding conditions shown below.
<Molding conditions>
Molding method: Press molding method Molding shape: 20 mm square cube shape Molding pressure: 600 MPa (6 t / cm ² )
Next, the size and weight of the obtained molded body were measured and calculated from the measured values.

2.3 Evaluation of Sintering Density Subsequently, the obtained molded body was degreased under the degreasing conditions shown below.
<Degreasing conditions>
・ Degreasing temperature: 600 ° C
Degreasing time: 1 hour Degreasing atmosphere: hydrogen gas atmosphere Next, the obtained degreased body was fired under the firing conditions shown below. This obtained the sintered compact.

<Baking conditions>
・ Baking temperature: 1150 ° C
-Firing time: 3 hours-Firing atmosphere: reduced pressure Ar atmosphere-Atmospheric pressure: 1.3 kPa (10 Torr)
Next, the density of the obtained sintered body was measured by a method according to the Archimedes method (specified in JIS Z 2501). Further, the relative density of the sintered body was calculated from the measured sintered density and the true density of the metal powder.

2.4 Evaluation of dimensional accuracy Next, the width dimension of the obtained sintered body was measured with a micrometer. The measured values were evaluated based on the following evaluation criteria based on “normal tolerance of width” defined in JIS B 0411 (normal tolerance of sintered metal product).
In addition, the width | variety of a sintered compact is a dimension of the direction orthogonal to the compression direction at the time of press molding.

<Evaluation criteria>
A: Grade is fine (tolerance ± 0.1 mm or less)
○: Grade is intermediate (tolerance ± 0.1 mm or more ± 0.2 mm or less)
Δ: Grade is normal (tolerance: more than ± 0.2mm ± 0.5mm or less)
X: Not acceptable The results of evaluations 2.1 to 2.4 are shown in Tables 1 and 2 above.

As is clear from Tables 1 and 2, it was confirmed that the compacts and sintered bodies obtained in each Example had a high density. In particular, the use of glycerin as a polyhydric alcohol, optimizing the content of the polyhydric alcohol, the like, it has been found that can specifically enhance the molding density and the sintering density.
FIG. 2 is a graph showing the distribution of the molded bodies obtained in Examples 1 to 9, where the horizontal axis represents the amount of glycerin added and the vertical axis represents the molding density.
Also from FIG. 2, it is recognized that the molding density can be particularly increased when the amount of polyhydric alcohol added is 0.01 parts by weight or more and 0.2 parts by weight or less with respect to 100 parts by weight of the metal powder.
Moreover, it was recognized that the sintered compact obtained in each Example was excellent in dimensional accuracy.

On the other hand, for the granulated powder obtained in Comparative Example 1, the sintered temperature was changed from 1150 ° C. to 1250 ° C. to obtain a sintered body. The sintered body obtained had a sintered density of 7.41 g / cm ³ and was equivalent to the sintered density of the sintered body obtained using the granulated powder obtained in Example 1. . From this, according to the present invention, it has been clarified that even if sintering is performed at a relatively low temperature by using a versatile and inexpensive firing furnace, it can be satisfactorily sintered.

  DESCRIPTION OF SYMBOLS 1 ... Rolling granulator 10 ... Processing container 11 ... Bottom part 110 ... Through hole 12 ... Side wall part 13 ... Cover part 130 ... Through hole 20 ... Blade 21 ... Rotary blade 22 ... Rotation Drive shaft 23 …… Base 30 …… Cross screw 31 …… Rotation drive shaft 40 …… Spray nozzle 80 …… Granulated powder

Claims (9)

A granulated powder formed by binding a plurality of metal particles with an organic binder,
The organic binder, which comprises a polyvinyl alcohol or a derivative thereof, a polyhydric alcohol, which is composed of one at least of glycols and glycerin, and organic amine or a derivative thereof, and
The polyhydric alcohol is added in an amount of 0.005 to 2 parts by weight based on 1 part by weight of the polyvinyl alcohol or derivative thereof,
In the organic binder, the total content of the polyvinyl alcohol or derivative thereof and the polyhydric alcohol is 14.5% by weight or more,
The apparent density of the granulated powder is 20% or more and 50% or less of the true density of the metal particles. The granulated powder according to claim 1, wherein the polyhydric alcohol is glycerin. The granulated powder according to claim 1 or 2, wherein the polyhydric alcohol is added in an amount of 0.01 parts by weight to 0.2 parts by weight with respect to 100 parts by weight of the metal particles. The apparent density of the granulated powder is granulated powder according to any one of claims 1 to 3 is 50% or less 25.6% or more of the true density of the metal particles. The granulated powder according to any one of claims 1 to 4 , wherein the organic amine is at least one of alkylamine, cycloalkylamine, alkanolamine and derivatives thereof. The amount of the organic amine, the relative metal particles 100 parts by weight of granulated powder according to any one of claims 1 to 5 or less than 5 parts by weight 0.001 part by weight. The content of the organic binder, granulated powder according to any one of claims 1 to 6 is 5.53 wt% or less 0.1% or more by weight of the granulated powder. Polyvinyl alcohol or a derivative thereof, a polyhydric alcohol, which is composed of one at least of glycols and glycerin, and organic amines or derivatives thereof, while supplying a solution of an organic binder comprising a rolling metal powders and / or By allowing the metal powder to granulate and obtain a granulated powder by flowing ,
In the granulated powder, the addition amount of the polyhydric alcohol is 0.005 parts by weight or more and 2 parts by weight or less with respect to 1 part by weight of the polyvinyl alcohol or a derivative thereof.
In the granulated powder, the total content of the polyvinyl alcohol or derivative thereof and the polyhydric alcohol in the organic binder is 14.5% by weight or more,
The apparent density of the granulated powder is 20% or more and 50% or less of the true density of the particles of the metal powder .   The method for producing a granulated powder according to claim 8, wherein the solution of the organic binder is supplied by spraying.

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