JP2000008103A - Drying of metal powder and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To swiftly and perfectly execute the drying of metal powder by substituting water adhered to the surface of the metal powder by a volatile solvent and thereafter removing the volatile solvent by heating. SOLUTION: Metal powder is charged into a cooling water tank 46. This metal powder is transferred into vessels 49 by a transferring means 50. A volatile solvent is stored in the plural vessels 49, and the vessels 49 are arranged in low order of the solvent concn. The metal powder is transferred into the vessel 49 high in the solvent concn. in order, and water adhered to the metal powder is substituted by the solvent. The diluted solvent is fed to a distilling column 52 by a circulating means 51, is concentrated and is fed to the vessel 49 highest in the concn. by a circulating pump 53. The metal powder is conveyed to a heating means 48 by a conveyer 50A. The heating means 48 removes the volatile solvent adhered to the metal powder by heating and vibration. The dry metal powder falls into a tray 56 and is stored therein.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for drying a metal powder (wet powder) obtained by a water atomizing method or a wet powder such as a metal powder after surface treatment such as chemical treatment and plating. It concerns the device.

[0002]

2. Description of the Related Art A rapidly solidified metal powder has a fine crystal grain and can contain an alloy element in a supersaturated state. For example, an extruded material or a sintered material formed by rapidly solidified metal powder of aluminum or an alloy thereof is It has excellent material properties that are not provided by ingots, and is attracting attention as a material for machine parts and the like.

As a preferred method for producing the above-mentioned rapidly solidified metal powder, Japanese Patent Publication No. 7-103407 and Japanese Patent No. 2719074 are used.
Atomization method disclosed in U.S. Pat.
787,935, 4,869,469 and the like, and a gas atomizing method. Metal powder obtained by the water atomization method or metal powder that has been subjected to surface treatment such as fluorine treatment or plating is a wet powder having a liquid (water) adhered to its surface. To dry.

Heretofore, as disclosed in Japanese Patent Publication No. 7-103407 and the like, methods and apparatuses such as hot air stream drying, fluidized bed drying, and heat transfer drying have been adopted as the drying method and apparatus. .

[0005]

The drying method using an air stream requires large-scale equipment such as a heater and a blower for generating hot air, which involves problems of equipment cost and noise, and has a problem of oxidizing the surface of the metal powder. It is not economical because a large amount of inert gas for prevention is used. Also,
In the case of metal powder or the like, there is a problem that kinetic energy of the powder given by the air flow causes wear of the equipment, and this wear powder is mixed.

Further, the indirect method of drying by heat transfer requires a high-temperature heat source to dry a large amount of powder.
When the heat source is at a high temperature (for example, when the temperature exceeds about 500 ° C.), there is a concern that the metal powder may be transformed due to overheating at a portion in contact with the heat transfer surface. In fact, it is difficult to obtain desirable conditions for drying a large amount of powder quickly, because of the contradictory characteristics that it takes time and accelerates oxidation of the powder surface.

SUMMARY OF THE INVENTION In view of the foregoing, the present invention replaces a liquid (water) adhering to the surface of a metal powder with a volatile solvent (eg, ethyl alcohol) to dry the metal powder quickly and completely. In addition, an object of the present invention is to provide a drying method and an apparatus that are less likely to cause abrasion of equipment and the like.

[0008]

The present invention employs the following technical means to achieve the above object. That is, the method for drying metal powder of the present invention according to claim 1 is characterized in that after the surface adhering liquid (water) of the metal powder is replaced with a volatile solvent, the volatile solvent is removed (evaporated) by heating. It is assumed that.

According to a second aspect of the present invention, there is provided the method for drying a metal powder according to the first aspect, wherein the replacement solution of the volatile solvent diluted by the replacement with the surface adhering liquid (water) is mixed with water. It is characterized in that it is separated and concentrated from water by distillation concentration or membrane separation by utilizing a vaporization temperature difference, and is recycled and reused. Further, in the method for drying metal powder of the present invention according to claim 3, in claim 1 or 2, the volatile solvent or the replacement solution is transferred from a higher concentration to a lower concentration, while the metal powder is The concentration is transferred from low to high.

According to a fourth aspect of the present invention, there is provided the method for drying a metal powder according to the first to third aspects, wherein the metal powder is vibrated when the volatile solvent is removed (evaporated) by heating. Is what you do. Furthermore, the metal powder drying apparatus of the present invention according to claim 5 is a replacement means for immersing or exposing the metal powder in a volatile solvent to replace the liquid (water) adhering to the surface of the powder with the volatile solvent; Heating means for heating the metal powder via the means to remove (evaporate) the volatile solvent.

According to a sixth aspect of the present invention, in the metal powder drying apparatus according to the fifth aspect, the replacement means includes a plurality of volatile solvents containing volatile solvents in order of decreasing concentration to increasing concentration. And a transfer means for transferring the metal powder to the container having the low concentration to the high concentration. Further, the metal powder drying apparatus of the present invention according to claim 7 is characterized in that, in claim 5 or 6, the heating means is provided with a vibration applying means for vibrating the metal powder. .

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method and the apparatus of the present invention will be described below with reference to the drawings. FIG. 1 shows the overall configuration of a metal powder production facility, in which molten metal sent from a continuous pouring device 1 passes through a pulverizing device 2, a continuous dewatering machine 3, and a drying device 4 according to the present invention to produce product metal. Powdered.

The continuous pouring apparatus 1 has a main body container 6 made of a fire-resistant heat insulating material. The container 6 is provided with a metal molten metal supply port 8 which can be sealed by a lid 7 and is inactive. A pressure medium supply pipe 9 for gas or the like and a discharge pipe 10 for the molten metal in the container are provided, and a recess 12 having an induction heating coil 11 is provided at the bottom. The temperature of the molten metal 13 in the container 6 is controlled by the coil 11 and the pressure medium supply pipe 9 is controlled.
The gas is pressure-fed to the pulverizing device 2 through the discharge pipe 10 by an inert gas such as an argon gas injected from the gas supply line. Discharge pipe 10
Is kept warm by a suitable heat keeping means such as formation of a heat insulating layer or an induction heater.

The powdering device 2 includes a cylinder 21 for forming a swirling cooling liquid layer, an injection crucible 22 for injecting and supplying a molten metal to the cooling liquid layer, and a cooling liquid for the cylinder 21. Means such as a pump 26 for supply.
The cylindrical body 21 is cylindrical as shown in FIG.
At its upper end, a lid 24 having an opening 23 of an appropriate size is formed at the center thereof. The lid 24 is provided on the outer peripheral side of the upper end for jetting and supplying the coolant from the tangential direction along the peripheral surface of the cylinder. A coolant ejection hole 25 is provided, and is connected to a discharge port of a pump 26 by piping. A ring 27 for adjusting the thickness of the coolant layer is attached to the inner peripheral surface of the intermediate portion of the cylindrical body 21 by bolts 28 so as to be detachable and replaceable. A cylindrical net 29 for draining liquid is connected to the lower end of the cylindrical body 21, and a funnel 30 is attached to the lower end thereof.

The coolant ejected from the coolant ejection holes 25 along the inner peripheral surface of the cylindrical body 21 flows down while rotating along the inner peripheral surface of the cylindrical body 21 and has a constant inner diameter due to the centrifugal force of the swirling flow. Of the cooling liquid layer 31 is formed. The cooling liquid that has flowed over the layer thickness adjusting ring 27 flows down due to centrifugal force.
It is further discharged and flows into the funnel 30. Net 29
The discharged coolant is collected in the tank 33 from the bottom of the cover 32 provided on the outer periphery of the net 29. The coolant in the tank 33 is circulated and supplied to the cylinder 21 by the pump 26. The tank 33 is provided with a supply coolant supply pipe (not shown), and a cooler may be appropriately provided in the tank or in the middle of the circulation path. Water is generally used as the cooling liquid.

An injection crucible 22 serving as a molten metal supply means is provided above the lid 24, a heating coil 36 is wound around the outer periphery thereof, and a nozzle hole 37 is opened at the bottom thereof. ing. The molten metal is pressure-fed from the continuous pouring device 1 to the injection crucible 22. The continuous dewatering machine 3 includes a rotating drum 41 whose diameter is increased upward, a peripheral wall of an intermediate portion of the drum 41 is formed of a screen plate having a large number of pores, and an inner peripheral surface is provided with powder after dehydration. A large number of convex ribs 24 for sending out to the outside are formed. A cooling liquid collecting cover 43 is provided on the outer peripheral surface side of the rotating drum 41, and the drained cooling liquid is collected in the tank 33 from the bottom thereof. Further, a metal powder collecting cover 44 is provided above the rotating drum 41, and a discharge chute 45 is additionally provided.

The drying device 4 according to the present invention comprises the dewatering machine 3
A cooling water tank 46 for temporarily storing the powder from the discharge chute 45, and a replacement means 47 for replacing the liquid (water) adhering to the surface of the powder with a volatile solvent such as ethyl alcohol. And heating means 48 for heating the metal powder that has passed through to remove (evaporate) the volatile solvent.

More specifically, referring to FIGS. 1 and 3, the replacement means 47 includes a plurality of containers 49 containing a volatile solvent, the containers 49 having a low concentration of the volatile solvent. In the figure, three units are arranged in series from the highest to the lowest, and a magnetic separation illustrated by an endless magnetic separation belt is provided between the cooling water tank 46 and the container 49 and the adjacent container 49 and between the final container 49 and the heating means 48. Transfer means 50 by the device
Here, the structure is such that the metal powder is transferred to a container 49 having a low to high concentration of the volatile solvent into the container 49, thereby replacing the water content of the powder with the volatile solvent.

The container 49 has a weir 49A and a stirrer 49B exemplified by a propeller for stirring the solvent in the container 49, and is further diluted by replacing the powder with water adhering thereto. The replacement solution of the volatile solvent is provided with a circulating means 51 for recycling and concentrating by distillation utilizing a difference in vaporization temperature with water, or separating and concentrating with water by membrane separation, and circulating and reusing the same. A distilling body 52 having an outlet 52A for separated water and a circulation pump 53 are provided, and the volatile solvent or the replacement solution is transferred from a higher concentration to a lower concentration.

A conveyor 50A is disposed between the replacement means 47 and the heating means 48, and the metal powder in which almost all of the wet powder surface (water) is replaced by a volatile solvent layer is heated via the conveyor 50A. It can be transported to the means 48.
The heating means 48 includes a heating element 5 such as resistance heating or high-frequency heating.
In the example shown in the drawing, a heating plate 55 having a plurality of plates 4 is provided. A plurality of the plates 55 are arranged in the up-down direction. 56.

That is, in the first embodiment of the present invention illustrated in FIG. 1 and FIG. 3, the wet powder in the water tank 46 is collected by the transfer means 50 and put into the first-stage container 49, By immersing in the volatile solvent contained in 49, moisture (adhering liquid) wet on the surface of the wet powder dissolves in the solvent and repeats this (in the example shown, it is shown three times). As a result, the wet powder surface is almost replaced by the volatile solvent layer.

By activating the agitator 49B in the container 49, the concentration of the solvent in the container 49 becomes uniform, and the volatile solvent and / or the replacement liquid thereof are changed from the higher concentration to the lower concentration. The solvent can be replenished to a minimum by transferring to the water and recycling it by utilizing the difference in vaporization temperature with water and the difference in the size of molecules.

The wet powder that has been sequentially transferred from the lower concentration to the higher concentration and replaced by the volatile solvent layer is transferred to the heating means 48 in a state of being mixed with the volatile solvent, and the heating removes the solvent layer (evaporation). ). By vibrating (oscillating) up and down or back and forth or left and right during this heating, the powder surface receives heat conduction uniformly and is quickly heated by the heat conduction between particles and the solvent is evaporated,
The dried powder is collected in the tray 56.

The dried powder is a clean powder having no residual cooling water. When such a metal powder is also used for molding, the wettability with a binder is good, and a state without a surface oxide film can be obtained by storing the dried powder in an inert gas. It is possible to obtain a molded article free from deterioration such as magnetic properties. FIG. 4 shows a second embodiment of the present invention, in which a pouring apparatus 1 and a pulverizing apparatus 2 are used.
1st Embodiment (refer FIG. 1) about the liquid removal machine 3
Therefore, the common parts are indicated by common symbols, and the drying device 4
Are different.

That is, in the first embodiment, the powder obtained by water atomization is obtained by immersing the powder in a volatile solvent and replacing the adhered water with the solvent.
In the second embodiment shown in FIG.
7 are arranged in series in the longitudinal direction (three in the figure), and the wet powder flowing naturally (falling under its own weight) in the cylindrical body 57 via a nozzle 57A provided in the cylindrical body 57 with respect to wet powder. The solvent is replaced by exposing the solvent by ejecting the volatile solvent, and the diluting solvent is recovered from the outlet 57B (may be recycled).
The heating means 48 is provided with a heating plate 48A in the conveyor so that the replacement solvent is evaporated.

In the second embodiment, the nozzle 57A
Can be sprayed as an aerosol (atomization). In this case, the concentration of the solvent may be gradually increased from the upper stage to the lower stage, or may be the same, and the conveyor constituting the heating means 48 may vibrate it. It may be the one that causes it. Although the embodiment of the present invention is as described above,
The following design changes are free.

As a device before the drying device 4 (pre-process), means other than those shown in the drawing can be adopted, and a rotary drum method may be used as long as metal powder is obtained by a water atomizing method. The transfer means 50 is not limited to a magnetic separation conveyor (one that conveys by magnetic force), but may be a bucket conveyor or other conveyance means. Further, the heating means 48 may be a hot air heating system other than the heater.

The method and apparatus of the present invention can be applied to a metal melt spinning method, in particular, an extrusion method, a tiller method, etc., and can be applied to a metal powder (wet powder) that has been subjected to surface treatment such as plating. Applicable. Further, the dewatering machine 3 may be omitted, and the wet powder may be directly supplied from the pulverizing device 2 to the replacing means 4.

[0029]

According to the present invention, a clean powder having no residual moisture can be obtained, so that the characteristics of the metal do not deteriorate.
In addition, when this metal powder is used for molding, the wettability with a binder is good, and a state without a surface oxide film can be obtained by storing the dried powder in an inert gas. It is possible to obtain a molded body without deterioration in characteristics and the like.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an entire facility showing a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a powdering device, which is a main part of FIG.

FIG. 3 is a configuration diagram of a drying device, which is a main part of FIG.

FIG. 4 is a configuration diagram of an entire facility showing a second embodiment of the present invention.

[Explanation of symbols]

 4 Drying Device 47 Replacement Means 48 Heating Means 49 Container 50 Transfer Means

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Yamamoto 1-1-1, Hama, Amagasaki-shi, Hyogo Prefecture Inside Kubota Research & Development Laboratory Co., Ltd. (72) Inventor Hideo Koshimoto 1-1-1, Hama, Amagasaki-shi, Hyogo Stock (72) Inventor Isamu Otsuka 1-1-1, Hama, Amagasaki-shi, Hyogo Co., Ltd. Inside Kubota Technology Development Laboratory (72) Inventor, Yoshimasa Okuno 1-1-1, Hama, Amagasaki-shi, Hyogo Co., Ltd. Inside the Kubota Technology Development Laboratory (72) Inventor Tohru Kawai 1-1-1, Hama, Amagasaki-shi, Hyogo Prefecture Inside the Kubota Technology Research Laboratory (72) Michio Yamaguchi 1-1-1, Hama, Amagasaki-shi, Hyogo Prefecture Kubota Technology Co., Ltd. Inside the Development Laboratory (72) Inventor Maya Sue 1-1-1, Hama, Amagasaki City, Hyogo Pref. Research house F-term (reference) 3L113 AA01 AA07 AB05 AC08 AC13 AC19 AC21 AC28 AC35 AC45 AC46 AC48 AC49 AC58 AC63 AC64 AC75 AC79 AC86 BA02 CA12 DA06 DA10 DA18 DA24 4K017 AA02 FA29 4K018 BC09

Claims (7)

[Claims] 1. A method for drying metal powder, comprising: replacing a liquid (water) adhering to the surface of a metal powder with a volatile solvent; and removing (evaporating) the volatile solvent by heating. 2. A replacement solution of a volatile solvent, which is diluted by replacement with the surface adhering liquid (water), is separated and concentrated from water by distillation concentration or membrane separation using a vaporization temperature difference with water and circulated. The method for drying metal powder according to claim 1, wherein the metal powder is reused. 3. The method according to claim 2, wherein the volatile solvent or the displacement solution is transferred from a higher concentration to a lower concentration, while the metal powder is transferred from the lower concentration to a higher concentration. 3. The method for drying a metal powder according to 1 or 2. 4. Removal of volatile solvents by heating (evaporation)
The method for drying metal powder according to any one of claims 1 to 3, wherein the metal powder is vibrated. 5. A replacement means for immersing or exposing a metal powder in a volatile solvent to replace a liquid (water) adhering to the surface of the powder with a volatile solvent, and heating the metal powder passing through the replacement means to form a volatile solvent. A heating unit for removing (evaporating) the solvent; and a drying device for the metal powder. 6. The replacement means comprises: a plurality of containers containing volatile solvents in order of low to high concentration; and transfer means for transferring metal powder to the low to high concentration containers. The apparatus for drying metal powder according to claim 5, comprising: 7. The metal powder drying apparatus according to claim 5, wherein the heating means is provided with a vibration applying means for vibrating the metal powder.