WO2009153865A1 - Micropowder producing apparatus and process - Google Patents

Abstract

A powder producing apparatus comprising a housing (or chamber) (1), a rod raw material storage unit (3) provided in the housing, a support unit (5) for seizing the rod raw material, inserting it into a below disposed crucible (6) and holding the same while being heated and melted, heating means (7) for melting the rod raw material in the crucible, means (8) for heating the interior of the crucible from thereinside, a rotator (9) for rotating the crucible around the central axis thereof so as to cause the rod raw material having been melted and dropped in the crucible to rise along the wall of the crucible and to scatter in atomized form from a crucible opening by centrifugal force, and a product container (11) for collecting a product resulting from atomized form scattering and cooling in the housing.

Description

Fine powder production apparatus and production method

The present invention relates to metals, alloys and metal oxides used for powder metallurgy spherical powders, magnetic materials, thermal spraying spherical metal powders, conductive paste metal powders, solder balls, and regenerators for magnetic refrigerators, The present invention relates to a spherical fine particle production apparatus applicable to a wide range of inorganic and organic substances used in foods, pharmaceuticals, chemical industries, and the like, and a production method using the centrifugal spray method.

The centrifugal spraying method and atomizing method (Japanese Patent Laid-Open No. 2006-2176, Japanese Patent Laid-Open No. 10-85583) adopted as a conventional fine powder production method have a very wide particle size distribution of the produced powder, and the fine powder As a centrifugal spraying method using a rotating crucible for the purpose of manufacturing, for example, “a fine powder forming method using a rotating crucible and its apparatus (Japanese Patent Laid-Open No. 2007-332406)” has been proposed.

However, in Japanese Patent Application Laid-Open No. 2007-332406, the raw material is melted in a melting furnace and then poured into a rotating crucible through a tundish for the purpose of holding the molten metal. Therefore, a melting furnace or a tundish as a container for holding the molten metal for a long time in some form is required. For these melting furnaces and tundishes, metals and ceramics are selected in consideration of the reactivity with the target raw materials, but titanium and some rare metals are extremely reactive and can hold these metals without contamination. Or it is difficult to select a container.

On the other hand, for active metals such as titanium and aluminum, the atomization technology by melting and holding molten metal using levitation without using a ceramic crucible for the purpose of melting at a certain level or lower is well known ( Leviatomize process). However, the Leviatomize process is a method of melting so that the molten metal does not contact the crucible by the interaction between the induction coil and the current induced in the molten metal by high-frequency induction, and the molten metal held in space vigorously fluctuates. Therefore, although there is no hindrance to the spraying method that does not require stable quasi-static pouring, it cannot be adopted in the spraying method that requires a quiet pouring flow with respect to the rotating crucible as in the present invention.

The present invention is a technique devised to solve these problems, and the molten material can be manufactured almost completely in a non-contact manner with the refractory, and the poured molten metal is placed in a rotating crucible. Because it is sprayed in an extremely short time of contact, contamination from the crucible is very slight even for active metals.
JP 2006-2176 A Japanese Patent Laid-Open No. 10-85583 JP 2007-332406 A

Spherical powders for powder metallurgy, magnetic materials, spherical metal powders for thermal spraying, metal powders for conductive pastes, solder balls, and metals, alloys and metal oxides used in regenerator materials for magnetic refrigerators, foods, pharmaceuticals, The present invention provides a spherical fine particle production apparatus that can be applied to a wide range of inorganic and organic substances used in the chemical industry, etc., and a production method using the centrifugal spray method.

The housing (1), the rod raw material storage device (3) provided in the housing, and the rod raw material are gripped and loaded into the crucible (6) disposed below and held while being heated and melted. A supporting device (5), a heating means (7) for melting the rod raw material in the crucible, a means (8) for heating the inside of the crucible from the inside, and rotating the crucible around its central axis, The rod raw material dissolved and dripped in is lifted along the crucible wall and sprayed in a spray form from the crucible opening by centrifugal force, and sprayed in the spray form to be cooled and trapped in the housing. A product container (11) to be collected is provided.

In addition, the powder production method is such that the rod raw material is gripped by the support device (5) provided in the housing (1), charged into the crucible (6) disposed below, heated and melted, and the rod raw material is obtained. The crucible is melted in the crucible, the inside of the crucible is heated from the inside, the crucible is rotated around its central axis, the rod raw material melted and dropped in the crucible is raised along the crucible wall, and the crucible is opened from the opening at the upper end of the crucible. The powder manufacturing method is characterized in that the rod raw material melted by centrifugal force due to rotation is scattered in a spray form, the sprayed powder is cooled and collected in a product container (11) in the housing. .

According to the present invention, since the molten metal droplets scattered from the opening end of the upper end surface of the crucible have a uniform velocity distribution, it is possible to produce a powder composed of fine particles having a narrow particle size distribution width and uniform particle size. It is. Furthermore, since the melted melt can be additionally melted as a raw material melt, powder can be continuously produced, and high productivity is ensured.

Next, the effects of the present invention will be described with respect to specific applications.
BGA (Ball Grid Array) and CSP (Chip Size Package), which are solder ball microminiature LSI components, are used in mobile phones, digital home appliances, etc., but solder balls are used as contact materials. The current ball size is 50-100 μm, but it is desirable to reduce it to 5-10 μm in the future in response to LSI miniaturization. The fine particles according to the method of the present invention have high size uniformity and roundness, Snxz-Ag system, Sn-Ag-Cu system, Sn-Ag-Cu-Bi system, Sn-Bi system, Sn-Cu system and , Sn-Zn and other lead-free solder can be manufactured.
In recent years, surface coating technology using “high-speed particle collision technology” that collides particles, which have been accelerated to sound velocity levels represented by cold spray, with a member has attracted attention. Ti, Co, chromium-nickel alloys and super- Hard alloy powder is used as a surface coating technology for aircraft engine parts. For this purpose, fine powders of about 20 μm or less are preferred, and it is essential that the particles used be nearly spherical in order to prevent a decrease in the scattering speed during particle transportation by the carrier gas, fluidity, and deformation mechanism during particle collision. Furthermore, there is a great demand for uniform particle size in terms of efficiency. The particles according to the present invention are used as these particles.
For MIM (metal injection molding material)
Titatan alloys are generally used as aircraft materials, chemical equipment materials, etc., but titanium is difficult to process, and powder metallurgy has attracted attention. The conventional press-molding powder metallurgy method is used, but a metal powder injection molding method (Metal Injection Molding: hereinafter referred to as MIM) has been developed, in which the raw material powder is wrapped in a binder. The compact has a high density, a small surface roughness, and a spherical and dense fine powder with a high packing density is desirable in order to improve the density of the compact after sintering. Furthermore, the spherical fine powder is more fluid. It's easy to do. The production of the powder according to the present invention can provide a powder suitable for such use.

It is a figure which shows the whole structure of this invention. High-frequency induction coil for heating the rotating crucible in the housing (or chamber) in the conceptual diagram of the whole powder processing equipment showing the room for storing the rod-shaped spare raw material and the drive and supply mechanism in the upper part The conceptual diagram of the apparatus which melt | dissolves the rod-shaped raw material using this is shown. The conceptual diagram around a crucible showing a manufacturing apparatus for manufacturing a fine powder by melting a rod raw material with a high frequency induction heating coil and heating a rotating crucible inner wall is shown. It is a figure which shows the structure of the resistance heater with a bottom part. The conceptual diagram around a crucible when a high-frequency induction heating coil is installed as a double-winding coil for heating a rotating crucible and melting a rod raw material is shown. These are the conceptual diagrams which show the structure of the crucible periphery at the time of employ | adopting the heating method of the rod-shaped raw material and spraying rotation crucible by a halogen lamp or a xenon lamp heating system. It is a photograph which shows an example of the shape of the copper fine powder manufactured by this invention.

Explanation of symbols

1 Housing (or chamber)
2 Rod raw material 21 Raw material follow-up device 22 Gate valve 23 Pouring droplet 24 Liquid film 3 Raw material storage device 4 Rod raw material supply mechanism 5 Rod raw material support device 6 Crucible 61 Heat insulating material 62 Heat-resistant steel container 63 Fin for cooling 7 Rod raw material melting Coil 8 Crucible heater 81 Heating light source 82 Condensing mirror 83 Heated light beer 9 Crucible rotating device 10 Spattered powder 11 Product container

Embodiment of the Invention

The above apparatus is a technique combining a local melting technique using a high frequency and a centrifugal spraying method using a rotating crucible using an active metal or the like as a raw material.
As shown in FIG. 1, in the present invention, the raw material is not melted in advance, but is supplied as a rod raw material, sequentially melted by a high frequency coil, and scattered by a rotating crucible to obtain a powder.
In order to stably transfer the poured raw material to the opening of the crucible rotated by centrifugal force, it is necessary to keep the temperature of the rotating crucible at or above the melting temperature of the molten metal, and preferably the outer periphery is a refractory metal. Heat can be efficiently heated on the inner surface of a rotating crucible that is reinforced with strength. The shape of the crucible is relatively cylindrical, has a certain depth (H), and the opening diameter (D) has a D / H of about 10 to 0.5 (FIG. 2). This is because spraying becomes difficult when D exceeds 10, and uniform spraying cannot be performed when D is less than 0.5.

The molten metal poured in the vicinity of the crucible rotation center flows through the crucible inner surface with a liquid film of 1 mm or less, for example, by the centrifugal force of the crucible rotation, along the side surface from the bottom of the crucible. It is desirable to insert (Fig. 2).
In addition to the cylindrical heater (Figs. 3 (A) and 3 (B)), the rotating crucible is heated from the inner surface by inserting a high-frequency induction coil into the crucible together with a susceptor such as carbon (Fig. 4) As a method capable of heating from a remote place, laser irradiation or a halogen lamp method using a condensing mirror (FIG. 5) can also be applied. The shape of the crucible may be any shape that allows uniform spraying from a uniform opening,
For this purpose, the side wall is cylindrical, and the side wall may be within ± 15 degrees about the vertical. If this range is exceeded, smooth and uniform spraying becomes difficult.

When high-frequency induction heating of the rod material, it is desirable to control the induction coil for melting the raw material rod and the induction coil for rotating crucible heating independently using two high-frequency power sources. Both may be heated (dissolved) with a double coil. When two high-frequency power supplies are used, it may be impossible to control them when the generated frequencies are close to each other. However, in order to smoothly and continuously dissolve from the end of the rod-shaped material, the target material The frequency of several tens of kilohertz to several megahertz is generally required, but the crucible heating uses a susceptor having conductivity such as carbon and the frequency of several kilohertz. And mutual interference between the two high-frequency power sources can be avoided.

On the other hand, various heating means can be considered as the means of sequential melting from the end of the rod-shaped raw material to be supplied, and the high frequency induction heating generally adopted in the FZ (floating zone) method of silicon single crystal is the most. Although convenient, it is also possible to melt and pour the material rod using plasma melting, current melting with a resistance heating heater or lamp heating melting.

In general, when high-frequency induction melting of rod-shaped metal is performed from the end, it naturally falls after reaching the melting temperature of the metal and at a predetermined temperature determined by the local melt's own weight, viscosity, surface tension, etc. And then poured. Therefore, in order to control the pouring speed, stable melting and pouring from the rod end is performed by applying a high frequency induction power balanced with the descending speed of the raw material rod.
The susceptor installed inside the inductor for melting the raw material does not need to be installed when the rod-shaped raw material is a conductor. If the susceptor is not installed, power can be concentrated on the rod end and the end can be turned on. This is advantageous for stable dissolution from the part.

In addition to the electrical resistance of the raw material and the diameter and descending speed of the raw material rod, the melting behavior of the raw material rod changes depending on the number of turns of the high frequency coil, the shape of the high frequency coil, the applied power, and the frequency of the applied high frequency. It is important to select these conditions so that a continuous and stable flow is formed from the raw material edge for the falling pouring flow.

Using a pure titanium round rod with a diameter of 80 mm as a raw material, applying a high frequency of 1 MHz to a 1-turn inductor, and by induction melting, a high-speed rotating crucible mainly composed of CaO housed in a stainless steel outer crucible through a heat insulating material The molten metal was supplied. The CaO crucible was heated by inserting a high-density carbon heater into the crucible.

The carbon heater used was a cylindrical heater with slits in the vertical direction as shown in FIG. The cylindrical heater is a cylindrical heater with a bottom, avoiding the pouring part near the center of the bottom so that the bottom of the crucible can also be heated (Fig. 3 (B)).

The pouring flow that melted and dropped was controlled by changing the descending speed of the raw material rod and the high frequency power for melting the raw material.
Stable and continuous melting with a power supply of 36 kW for a raw material rod that is rotating at 5 cm per minute (approximately 1.1 kg per minute) while rotating at a rotation speed of 15 times per minute except at the beginning of melting. Was made. The rotating crucible built in the heat-resistant steel crucible through the heat insulating material was kept at about 1700 ° C while giving 35,000 revolutions per minute. The amount of dissolution can be controlled by measuring the weight of the rod material.

A high-speed rotation mainly composed of MgO with a diameter of 200mm that is housed in a stainless steel outer crucible through heat insulation by applying a high frequency of 500kHz to a 3-turn induction coil using a pure copper round bar with a diameter of 80mm as a raw material. The molten metal was supplied to the crucible. The MgO crucible was heated by inserting a carbon carbon heater with high density into the crucible.
The carbon heater used was a cylindrical heater with a bottom and a slit in the vertical direction as shown in FIG. Continuous melting at a descent rate of 5 cm / min (approximately 2.1 kg / min) except at the beginning of melting while controlling the pouring flow of melting and falling by changing the descent speed of the raw material rod and the high frequency power for melting the raw material And hot water. The rotating crucible was maintained at about 1150 ° C while applying 35,000 revolutions per minute.

Using a SUS316L round bar with a diameter of 80mm as a raw material, a high-speed rotation mainly composed of MgO with a diameter of 200mm that is housed in an outer crucible made of stainless steel through heat insulation by applying a high frequency of 1MHz to a one-turn inductor and induction melting The molten metal was supplied to the crucible. The MgO crucible was heated by inserting a high-density carbon heater into the crucible.
The carbon heater used was a cylindrical heater with a bottom and a slit in the vertical direction shown in FIG. 3 (FIGS. 3A and 3B), as in Example 1 and Example 2. The lowering speed of the raw material rod was continuously melted at a rate of 5 cm / min (approximately 2.0 kg / min) except for the initial stage of melting and hot water was supplied. The rotating crucible was maintained at about 1570 ° C while applying 35,000 revolutions per minute.

Comparative Example 1
After melting 50 kg of pure titanium with a crucible containing CaO as the main component, the inner surface that comes into contact with the molten metal is poured out into a tundish made of ceramics containing CaO as the main component, and installed at the bottom. The nozzle was poured into a rotating crucible containing CaO as a main component at a predetermined speed.
The material and rotation speed of the rotating crucible, the hot water supply speed to the rotating crucible, etc. were carried out under conditions as close to Example 1 as possible, and compared with the powder produced in Example 1.

In addition, before the amount of remaining molten metal in the first melt completely disappeared, the melting was started for the second time while shutting off from the atmosphere using the raw material charging mechanism, and about 100 kg of powder was continuously processed.
The produced powder had a large degree of contamination as a whole compared with Example 1, and oxidation oxidation was particularly remarkable at the end of the pulverization treatment. This is presumed to be the result of about 1 hour having elapsed from dissolution to powdering treatment. The particle size distribution of the produced powder was similar to Example 1.

Comparative Example 2: Using TD In the same manner as in Comparative Example 1, 50 kg of pure copper was dissolved twice and poured into a rotating crucible sequentially through a tundish. Since molten pure copper is less active than molten titanium, general materials mainly composed of MgO were selected for melting crucibles, tundish, and rotating crucibles.
The particle size distribution of the produced powder was almost the same as that of Example 2, but the oxygen content was considerably larger than that of the powder obtained in Example 2.
Table 1 summarizes the main test conditions and the characteristics of the produced powder for the three examples of the present invention and Comparative Examples 1 and 2. The particle size is smaller than that of the conventional method, the shape is spherical, and the particle size distribution width is small.

図６に製造された微粉末形状の写真の１例を示すが、きわめて真円に近く、また、直径の分布は均一であることが示されている。
発明の効果

FIG. 6 shows an example of a photograph of the fine powder shape produced, which is very close to a perfect circle and shows that the diameter distribution is uniform.
The invention's effect

Copper powder for conductive paste:
The powder to be used for the conductive pace is required to have a spherical shape and a fine size from the viewpoint of uniform coatability and fluidity, and the powder size is several microns in diameter. The powder by can be desirably utilized.

Thermal spray material:
In addition to being able to obtain multi-layer coatings without heat effects, and directly coating materials and materials that are impossible with conventional technology, it is highly productive as a component manufacturing device, and the device cost is low. , Surface coating technology using “high-speed particle impact technology” has attracted attention, and Ti, Co, chromium-Nickel alloy, cemented carbide powder, etc. are used for aircraft engine parts for the purpose of improving heat resistance and oxidation resistance, It is used as a surface coating technology for generator turbine blades and boiler tubes.
For these, fine powders of about 20 μm or less are preferable, and it is essential that the particles used are nearly spherical in order to prevent the scattering speed from being reduced during carrier transport by the carrier gas, and for the fluidity and deformation mechanism during particle collision. Furthermore, the demand for uniform particle size from the viewpoint of efficiency is strong, and it has been found that the powder produced by the present invention is desirable.

For MIM (metal injection molding material):
Titatan alloys are generally used as aircraft materials and chemical equipment materials because they have the advantages of light weight and high strength, and have excellent corrosion resistance. However, titanium is difficult to process, and aircraft. In the case of a product with a complicated shape such as a member, the low product yield is very expensive, and in order to solve such problems, the raw material powder is wrapped with a binder as a powder metallurgy method. There is a metal powder injection molding method (Metal Injection Molding: hereinafter referred to as MIM), and its use is rapidly expanding in recent years.
Compressive formability of MIM raw powder is not required. Rather, in order to improve the density after sintering, spherical and dense fine powder with higher packing density is desirable, and spherical fine powder is more likely to flow. From the viewpoint of reducing product defects, spherical fine powder is indispensable. The fine powder produced according to the present invention can be used as a material for such a method.

Industrial application fields

Although the effects of the present invention have been described with respect to the production of fine metal powder, the present invention can be widely used as a fine powder production apparatus for plastics, medicines, foodstuffs and the like.

Claims (14)

A housing (1);
A rod material storage device (3) provided in the housing;
A support device (5) for holding the rod raw material, charging the crucible (6) disposed below, and holding the rod raw material while heating and melting;
Heating means (7) for melting the rod material in the crucible, and means (8) for heating the inside of the crucible from the inside;
A rotating device (9) for rotating the crucible around its central axis, raising the rod raw material dissolved and dripped in the crucible along the crucible wall, and spraying it in a spray form from the crucible opening by centrifugal force;
A product container (11) that scatters and cools in the form of a spray and collects in the housing;
A powder manufacturing apparatus composed of When the rod raw material is added from the raw material adding device (21) via the gate valve (22), the rod raw material is supplied to the raw material storage device (3) in the housing, and is sequentially supplied to the rod support device (5). The powder manufacturing apparatus according to claim 1. The powder production apparatus according to claim 1, wherein the raw material rod support device is connected to a raw material rod supply mechanism (4) for supplying the rod while rotating the rod for uniform melting. The powder manufacturing apparatus according to claim 1, wherein the heating and melting means of the raw material rod is a coil to which high-frequency power is supplied. The powder manufacturing apparatus according to claim 1, wherein the means for heating the crucible from the inside is a graphite heating body or nichrome wire heating body that is resistance-heated by electric power. 6. The powder production apparatus according to claim 5, wherein a heat insulating material is lined on the inside of the graphite resistance heating body or the nichrome wire heating body, and the crucible on the outside thereof is heated. The heating means (7) for melting the rod material in the crucible and the means (71) for heating the inside of the crucible from the inside are both high-frequency coils, and both are coils arranged in the susceptor (72). Powder manufacturing equipment. 2. The powder production apparatus according to claim 1, wherein the rod raw material and the inner surface of the crucible are heated by a combination of a reflector and a halogen lamp or a xenon lamp. The powder manufacturing apparatus according to claim 1, wherein the crucible is a ceramic or a refractory metal crucible. The powder manufacturing apparatus according to claim 1, wherein the crucible is cylindrical and the ratio (D / H) of the upper diameter (D) to the depth (H) is 10 to 0.5. 2. The powder production apparatus according to claim 1, wherein the taper of the crucible wall is ± 15 degrees with respect to the vertical line. The powder manufacturing apparatus of Claim 1 provided with the control apparatus which measures the descent | fall speed of the said raw material rod or the weight change of a raw material rod, and controls the hot water supply speed | rate. The said crucible is a powder manufacturing apparatus of Claim 1 which provided the heat insulating material in the outer side, and was further equipped with the container of the heat resistant steel and the fin for cooling. The rod raw material is gripped by the support device (5) provided in the housing (1), charged into the crucible (6) disposed below, heated and melted,
The rod raw material is dissolved in a crucible,
The inside of the crucible is heated from the inside, the crucible is rotated around its central axis, and the rod raw material dissolved and dropped in the crucible is raised along the crucible wall,
The rod material melted by the centrifugal force generated by the crucible rotation from the opening at the top of the crucible is sprayed and sprayed.
A method for producing a powder, wherein the sprayed powder is cooled and collected in a product container (11) in the housing.

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