JP2744469B2 - Powder manufacturing method by multi-stage grinding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to metals, nonmetals, and compounds thereof (hereinafter, referred to as “metals”).
In particular, the present invention relates to a pulverization method for pulverizing a material having much plastic deformation into fine powder to obtain a powder having good fluidity (that is, spherical particles).

[Prior Art and Problems to be Solved by the Invention] Conventional pulverization techniques include the following. That is,
In the pulverization method using compressive shearing force, when used to pulverize metals, non-metals and these compounds, the material to be pulverized has ductility and malleability. The product produced by the shearing force will have a flat shape, albeit fine particles. For this reason, when the fluidity as a powder or the injection molding is performed, the fluidity when mixed with a resin is poor, and the powder cannot be used.

On the other hand, when the impact crushing method is used, impact energy is absorbed by plastic deformation based on ductility and malleability of the material to be crushed, and the material to be crushed cannot be finely crushed. Therefore, it is difficult to obtain fine particles.

When crushing a combination of a material having spreadability and a brittle material by a conventional impact crushing method, spheroidization is generally performed after the brittle material is attached to the surface of the spreadable material,
The composition ratio depends on the surface area of the spreadable material. For this reason, the composition ratio of the brittle material to the extensible material is limited to several mol%.

In the present invention, in view of the above circumstances, in particular, when crushing an object to be crushed with a large plastic deformation having ductility and malleability, crushing this by a physical method, and producing a spherical powder with fine particles. The purpose is to provide.

Accordingly, an object of the present invention is to provide a pulverizing method for pulverizing a substance having a large plastic deformation into a spherical or almost spherical fine particle by performing a multi-stage pulverizing process in combination. Further, the present invention provides a method for producing a mechanical alloy by mixing and grinding a material to be ground containing a ductile metal material, that is, producing a mechanically produced alloy by mechanically mixing and grinding a ductile metal material. The aim is to provide a way to. Another object of the present invention is to pulverize a metal, a nonmetal, a compound thereof and a mixture thereof into a fine powder and mix the mixture in a controlled composition ratio to obtain a powder having good fluidity and not causing component separation. I do.

[Means for Solving the Problems] In order to solve the above-mentioned technical problems, the present invention provides a method for producing powder by pulverizing metals and nonmetals and their compounds (hereinafter referred to as “objects to be pulverized”) into ultrafine particles. In the method, a pulverizing treatment by a pressure shearing force (hereinafter referred to as a pressure pulverizing treatment)
A multi-stage pulverization process by combining a powder with an impact force of the powder itself and a pulverization process by the impact force of the powder and a rotating body (hereinafter referred to as an impact pulverization process). Things. In that case, it is preferable to use the pressure pulverization treatment in the first stage and then use the impact pulverization treatment in the second stage. In addition, at least one
It is preferable to perform the pressure pulverization before the final stage by using more than one impact pulverization. The impact crushing process is performed in the subsequent stage, the pressure crushing process is performed in the preceding stage, and the flat fine particle powder produced in the preceding pressure crushing process is subjected to a spherical or spherical shape in the subsequent impact crushing process. It is preferable to use a fine particle powder having a shape close to that of the fine particles. In the pressure crushing process in the first stage, the particularly large plastic deformation among the crushed materials is crushed to a diameter of 15 μm or less, and the flat particles out of the resulting particles are subjected to impact crushing in the second stage. In the treatment, it is preferable to make the particles spherical. Further, when performing the subsequent impact pulverization treatment, it is preferable to add a small amount of resin and a surfactant to the material to be pulverized to form a spherical shape. In order to prevent oxidation of the object to be crushed, it is preferable to carry out the crushing treatment in an atmosphere of an inert gas, a nitrogen gas or a gas containing little oxygen in the above-mentioned pressure crushing treatment and impact crushing treatment. It is preferable that the pressure pulverization is performed by a roller mill or a ball mill, and the impact pulverization is performed by a jet mill or a rotary impact pulverization.

The pulverization method to be used in the first stage according to the present invention is a pressure pulverization method, which is a pulverization method using a pressure shear force. Also, the impact treatment method that should be used in the later stage is
This is a processing method of pulverizing by the impact force of the powder itself and the impact force of the powder and the rotating body. In the pulverization method of the present invention, the two are combined to perform a multi-stage pulverization treatment.

In the conventional pulverization method, in the case of a material having a large plastic deformation such as a metal, it is not only impossible to produce fine particles by the impact pulverization process alone, but also, in some cases, a plurality of particles are mutually bonded. Often, coalescence into one particle also occurs.

In the pulverization method of the present invention, in order to prevent such coalescence of particles, a surfactant and a polymer are also effective, but before that, in the pulverization method of the present invention, after the impact pulverization apparatus, a classifier is used. Using, classify the combined particles,
This is prevented by grinding again.

The present invention is suitable for producing powder of extremely fine and spherical particles. In order to produce fine particles, it is necessary to increase the number of times that the object to be circulated circulates between the pulverizing zone and the classification zone, thereby increasing the opportunity for the object to obtain pulverizing energy.

When the crushed material is circulated in this way, the circulated crushed material increases, and not only the burden on the classifier increases,
The particle size distribution of the material to be pulverized is widened, and as a result, in the product, the coarse powder is likely to be mixed into the fine powder, and the fine powder is more likely to be mixed into the coarse powder, which may deteriorate the product quality.

In addition, regardless of the pulverization treatment of the present invention, if classification is not performed in the former stage, large particles and fine particles are mixed in a rotary pulverizer and an impact is applied, and the particles are united rapidly. The rate increases, grinding and coalescing zones occur, increasing the burden on the overall system, increasing energy consumption and deteriorating product quality.

On the other hand, according to the pulverization method of the present invention, by separating the classifier according to the pulverizer, each load can be reduced, and good quality can be ensured. Thus, a method and an apparatus for producing a powder having excellent particle characteristics such as particle distribution and particle shape can be provided.

Further, in the pulverization method of the present invention, aggregation of particles generated by a single-stage classifier can be solved together with shape control using a rotary pulverizer.

In order to explain the multi-stage pulverization method according to the present invention, as the compression pulverization processing, a roller mill processing is used, and as the impact pulverization processing, a rotary impact pulverizer is used. It is not limited.

Furthermore, the ultrafine particles obtained by the present invention are spherical particles, and therefore, a fluid having high fluidity can be obtained.

FIG. 8 and FIG. 9 are electron micrographs showing the particle structure of powder obtained when a nickel-based metal is crushed by a conventional roller mill alone with a roller mill. Figure 8 shows 2000
FIG. 9 is an electron micrograph at × 6000 and FIG. 9 is an electron micrograph at × 6000. That is, in the conventional grinding with a roller mill alone, the particles obtained are flat, cannot be obtained as spherical or nearly spherical particles, and a powder having good fluidity has not been obtained.

On the other hand, FIGS. 10 and 11 are electron micrographs showing the particle structure of a finished nickel-based metal powder product obtained by the multistage pulverization method according to the present invention. FIG. 10 is a 2000 × electron micrograph, and FIG. 11 is a 6000 × electron micrograph. That is, as compared with the particles shown in FIGS. 8 and 9, the powder pulverized by the multistage pulverization method of the present invention was found to have spherical or nearly spherical particles.

As described above, the fine particle powder produced by the present invention has excellent powder characteristics, high fluidity, and extremely excellent handling.

The pulverized fine particle product obtained by the present invention can be used, for example, as a raw material for a sintered body. Further, it is effective for manufacturing a mechanical alloy.

Next, the pulverization treatment method according to the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

[Example 1] Pulverization is performed by a roller mill and a rotary impact pulverizer shown in Fig. 1 or Fig. 2, then classified by a classification device, and fine particles are collected by a dust collection device. That is, FIG. 1 shows a vertical mill, and FIG. 2 shows a horizontal mill partially.

1 and 2, 1 is a roller mill table driving device, that is, a motor and a reduction gear, 2 is a table, 3 is a gas introduction slit, 4 is a roller, 5 is a casing, and 6 is a casing. , An inner casing, 7 is a chute to be pulverized, 8 is a pulverized substance, that is, a new feed, 9 is a coarse powder return damper, 10 is a rotary impactor in a rotary impact pulverizer, 11 Is the liner, 12
Reference numeral denotes a striking plate driving device, 13 is a mixed gas outlet conduit, 14 is a rotary blade in the single-stage classifier, 15 is a casing, 16 is a rotary blade driving device, and 17 is a mixed gas inlet conduit.

In the apparatus shown in FIG. 1 or FIG. 2, the object to be crushed 8 is dropped onto the crushing table 2 through the input chute 7,
The centrifugal force based on the rotation of the table 2 guides the roller between the table end face 3 and the roller 4 near the end of the table, where a shearing force and a compressive force are applied and crushed.

Next, the pulverized raw material is introduced into a rotary striking plate 10 that performs impact pulverization together with the gas 20 guided from the gas inlet. Here, the object to be pulverized in the gas is subjected to an impact by the rotary impact plate 10 and the liner 11 while passing through the gap between them, and the shape of the pulverized particles is changed. This impact crusher
The material to be ground that has passed through 10 and 11 is classified into coarse powder and fine powder by the rotating blades of the classification device 14. The classified coarse powder passes through a return space 21 and is further subjected to a pulverizing process together with a newly charged object (ie, a new feed) 8.

On the other hand, the sufficiently pulverized fine powder is guided from the space 17 to the dust collecting device above and becomes a product.

In a material having a large plastic deformation such as a metal, it is not only impossible to produce fine particles by the impact pulverization process alone, but also, in some cases, a plurality of particles may be separated from each other by one.
Surfactants and polymers are effective in preventing coalescence into two particles. However, in the pulverization method of the present invention, the combined particles are classified by using a classifier after the impact pulverizer, and are pulverized again to prevent this.

This multi-stage pulverization method is performed by a combination of pulverization processes shown in a flow sheet of FIG.

[Example 2] In the same manner as in Example 1, a powder is obtained by a roller mill, then a classification device, and then a rotary impact device or a classification device, and a method of collecting fine particles by a dust collector method. And performed by the apparatus shown in FIG.

In the apparatus shown in FIG. 3, reference numerals are the same as those in FIGS. 1 and 2, and 18 is a rotating blade in a two-stage classifying apparatus, 19 is a casing, 20 is a rotating blade drive, 21 Is a mixed gas inlet conduit, and 22 is a coarse powder return chute.

Also in the apparatus shown in FIG. 3, the object to be ground (new feed) 8 is ground between the roller 4 and the table 2 in FIG. 3, as shown in FIG. 1 and FIG. It is led to the machine and classified by the rotating blades 14, and the classified coarse powder falls into the lower part, and between the roller 4 and the table 2,
The objects to be crushed 8 are both crushed again.

On the other hand, the fine powder in the gas that has exited the classifier 14 is directly guided to the rotary impact pulverizer through the conduit 17, and passes through the gap between the rotary hitting plate 10 and the liner 11, and the particles are generated by the impact force. The pulverized material having a spherical shape is supplied to a mixed gas outlet conduit.
It is led to the second-stage classifier 18 through 13 and the mixed gas conduit 21. Here, the fine particles classified by the rotating blades 18 are used as products. On the other hand, the classified coarse particles are passed through the coarse powder return chutes 19 and 22,
Returned to 4, 2.

This multi-stage pulverization method is performed by a combination of pulverization processes shown in a flow sheet of FIG.

Example 3 This will be described with reference to a flow sheet of FIG.

The object to be crushed is crushed in the order of a roller mill, a classifier, a rotary crusher, and a dust collector.

That is, a dust collector is provided immediately after the rotary impact crusher from the method of Embodiment 2, and the second-stage classifier is omitted. In this treatment method, the product particle size distribution does not satisfy the strict requirements, but in this pulverization method,
The apparatus can be simplified and an economical grinding method can be obtained.

[Example 4] As shown in the flow sheet of Fig. 7, pulverization is performed by a roller mill-> classification device-> impact grinding device-> classification device (return coarse powder-> impact grinding device).

In this pulverization processing method, the configuration of the apparatus is the same as in Example 2. In this pulverization processing method, the configuration of the apparatus is the same as that of the second embodiment. This is an advantageous pulverizing treatment method.

Tables 1 and 2 show that the nickel-based metal was produced by the pulverization treatment method according to the present invention, the water atomization method, and the pulverization method using only a roller mill to produce fine particle powder. Shows the results of comparison by critical powder volume ratio and average particle size (μm) of the pulverized particles,
That is, the results are shown by the evaluation of the critical powder volume ratio of the obtained powder and the result of evaluation by the average particle size (μm).

In Table 1, the production method or pulverization method is shown by a water atomization pulverization method, a roller mill single pulverization method, and a multi-stage pulverization method according to the present invention. The “critical powder volume ratio” is an index for determining the possibility of injection molding when performing powder injection molding.
It means the amount of powder that can be contained in a mixture that can be injection-molded under a certain condition when a mixture of a resin or the like and a metal powder is prepared. As this value is larger, the amount of resin can be reduced, and therefore, when decomposing and removing the resin in the degreasing step, the molded body can be degreased in a short time without causing defects, and the shrinkage during sintering is small. This is also advantageous in controlling the dimensions of the product.

The measuring method of “critical powder volume ratio” is based on ASTN-D-281-3.
The oil absorption test method of 1 was carried out by improving the evaluation method of ceramic injection molding. That is, in this critical particle volume concentration method (CPVC), a mixture of oleic acid and ceramic powder is mixed with a roller-type blade mixer, and the mixing ratio of ceramic and oleic acid is changed to measure a change in torque. This measured value shows the maximum torque at a certain oleic acid value, and this value shows the maximum amount of powder when the mixture of the ceramic powder and oleic acid shows flow characteristics. It has been confirmed from empirical experiments that the value measured with oleic acid is related to the amount of binder when performing injection molding.

Judging from these measurement results, the powder produced by the pulverization treatment of the present invention is far superior to the powder pulverized by the roller mill alone, and the powder produced by the “water atomization” method shown in FIG. From an electron micrograph showing the particle structure of the powder, it is clear that the spherical particle powder obtained according to the present invention exhibits good characteristics as a spherical particle.

Further, as shown in Table 2, the powder produced by the water atomizing method has a large average particle size, and is apparently separated from the resin during kneading and is unsuitable for injection molding.

[Effects of the Invention] The following remarkable technical effects were obtained by the pulverizing method of the present invention.

First, it is possible to obtain a powder that is significantly better than a powder that has been pulverized by a conventional roller mill alone.

Second, it is possible to obtain a spherical particle powder having better characteristics than spherical particles produced by water atomization.

Third, an economical pulverization method that can provide an ultrafine powder capable of reducing the production cost can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a roller mill used in the pulverizing method of the present invention. FIG. 2 is a schematic sectional view of the modified roller mill of FIG. FIG. 3 is a schematic sectional view showing another combination of the roller mills. FIG. 4 is a flow sheet of the pulverizing method according to the present invention. FIG. 5 is a flow sheet according to another embodiment of the present invention. 6 and 7 are flow sheets according to another embodiment of the present invention. FIG. 8 and FIG. 9 are electron micrographs showing the particle structure of powder obtained by grinding a nickel-based metal with a roller mill alone. FIG. 10 and FIG. 11 are electron micrographs showing the particle structure of the metal powder crushed by the crushing method of the present invention. FIG. 12 is an electron micrograph showing the particle structure of a spherical powder produced by a conventional water atomizing method.

Claims (9)

(57) [Claims] Claims: 1. A powder production method for pulverizing metal, non-metal, and a compound thereof (hereinafter, referred to as an object to be pulverized) into ultrafine particles, comprising: A powder production method by a multi-stage pulverization process, wherein a multi-stage pulverization process is performed by combining an impact force of the body itself and a pulverization process with a powder and an impact force of a rotating body (hereinafter referred to as an impact pulverization process). 2. The method for producing a powder according to claim 1, wherein
The method for producing a powder according to claim 1, wherein a pressure pulverization treatment is used in a first stage, and then an impact pulverization treatment is used in a second stage. 3. The powder production method according to claim 1, wherein at least one or more impact crushing processes are used in the final stage, and the pressure crushing process is performed before the final stage. 4. The impact crushing process is performed in a subsequent stage, the pressure crushing process is performed in a preceding stage, and the flat fine particle powder produced in the pressure crushing process in the preceding stage is subjected to an impact crushing process in a subsequent stage. 4. The powder production method according to claim 1, wherein the powder is formed into a spherical or nearly spherical fine particle powder. 5. In the pressure crushing process in the first stage, among the crushed materials, those having particularly large plastic deformation are crushed to a diameter of 15 μm or less, and flat particles out of the resulting particles are replaced in the second stage. The method for producing a powder according to any one of claims 1, 2, 3, and 4, wherein the powder is formed into a spherical shape by impact crushing. 6. When the object to be ground is a mixture of a ductile metal material and a brittle material or a mixture of materials having different ductile metal materials, the mixture is further mixed and further pulverized to a particle size of 15 microns or less. The powder production method according to claim 1, 2, 3, 4, or 5, wherein the mixed flat particles produced at that time are sphericalized by using a subsequent impact pulverization treatment. 7. The method according to claim 1, wherein a small amount of a resin and a surfactant are added to the material to be pulverized in the subsequent impact pulverization treatment to form a spherical shape. Alternatively, the powder production method according to 6. 8. In order to prevent oxidation of the material to be crushed, an inert gas,
The pulverization process is performed in an atmosphere of a nitrogen gas or a gas containing less oxygen, wherein the pulverization process is performed.
8. The method for producing a powder according to 6 or 7. 9. The method according to claim 1, wherein the pressure crushing is performed by a roller mill or a ball mill, and the impact crushing is performed by a jet mill or a rotary impact crush.
The powder production method according to 2, 3, 4, 5, 6, 7, or 8.