JPH062018A - Method and apparatus for producing flaky particle from molten metal - Google Patents

Abstract

(57) [Summary] [Objective] It is an object to provide a method and apparatus for producing rapidly solidified flaky particles by combining centrifugal atomization with cooling of a metal substrate. [Structure] The flow of molten metal is centrifugally separated into droplets by a rotating disk. The molten droplets solidify as flaky particles as soon as they impinge on the annular plane of the cooled rotating concave disk. The coagulated flaky particles are sequentially separated from the annular surface by centrifugal force and collected in the chamber.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method and apparatus for directly producing rapidly solidified flaky particles from a melt. In particular, the present invention solidifies the liquid droplets as flaky particles at a high cooling rate by pouring a stream of molten metal into a rotating member to separate the molten metal into droplets and then impinging the liquid droplets onto a cooled rotating metal substrate. Method and device capable of performing. The solidified flaky particles are separated from the rotating metal substrate by centrifugal force and collected in the chamber.

[0002]

BACKGROUND OF THE INVENTION Since Dr. Duwez invented the splat cooling process in 1960, rapid solidification technology has become a newly developed field in metallurgy and promotes the mechanical and physical properties of different alloys. It's a new road. Rapid solidification techniques have the advantages of refining the microstructure, expanding the solidification limit, producing a uniform concentration distribution and forming an amorphous phase. Such features provide greater freedom in alloy design and achieve better mechanical and physical properties than previous conventional processes.

The purpose of rapid solidification powder metallurgy is to solidify molten metal at high cooling rates (10 ² k / s and above) to form granular, flaky or strip metal particles. The metal particles are compacted, sintered and hot worked to produce the final product. According to related studies, the quality of rapidly solidified powder has a great influence on the mechanical properties of alloy products. Therefore, the process of producing rapidly solidified powders is a very crucial step in the overall process.

Many methods have been developed to produce rapidly solidified powders. In essence, in order to achieve the highest cooling rates, each method requires that at least one diameter of the powder product be as small as possible to transfer heat to the cooling medium as quickly as possible. For example, air atomization methods use air atomization and air cooling. Powdered product becomes spherical with a cooling rate of at approximately 10 ^2-3 k / sec. Since mechanical energy is mainly used to accelerate the molten metal, the energy used for atomization is very low, only around 2% to 4%.

Another example is the American Aluminum Company (ALCO) which uses air atomization and metal substrate cooling.
It is the Alcoa spray method developed in A). Molten metal is atomized by air and then sprayed onto the surface of a rapidly rotating, water-cooled roller. The metal strips on the rollers are stripped off with a brush and collected in a collector. The cooling rate is up to about 10 ⁵ k / sec. The pieces are disc-shaped, but often not flat, but overlapping. Similarly, the momentum transfer efficiency of air atomization used in this method is low.

Rapid Solidification Rate (RSR) technology, developed by Pratt & Whiteney Company, US Pat. Nos. 4,078,873 and 4,343,750, show the use of centrifugal atomization and helium cooling. Molten metal flows through a funnel onto a disk rotating at high speed (approximately 24000 rpm). Centrifugal force causes radial acceleration, which causes the droplets to atomize after leaving the disc. The droplets are rapidly cooled by circulating in a helium environment, forming a spherical powder and solidifying. The atomization efficiency of RSR is relatively high. However, the cooling rate of RSR is about 10 ⁵ k / sec. RSR is expensive because it uses helium cooling.

[0007]

SUMMARY OF THE INVENTION The main object of the present invention is to provide a method for producing rapidly solidified flaky metal powder. Another object of the present invention is to provide a method for producing a rapidly solidified flake metal powder having a relatively high atomization efficiency.

Another object of the present invention is to provide a method for producing a rapidly solidified flaky metal powder having a relatively high cooling rate. Another object of the present invention is to provide a method for producing rapidly solidified flake metal powder at a relatively low cost. A final object of the invention is to provide an apparatus for producing this rapidly solidified flaky metal powder.

The present invention features a combined centrifugal atomization and metal substrate cooling process. In other words, the present invention uses a high speed centrifugal atomization disk to improve atomization efficiency and a rotating metal substrate to improve cooling rate. The metal substrate is coaxially placed under the atomizing disc, 1000 rpm to 3000
Spin at speeds in the rpm range. Its shape is dish-shaped. The upper surface of the metal substrate is concave, and the edge portion of the metal substrate has an angle of about 10 ° to 30 ° with respect to the horizontal plane so as to cover the flight path of the molten metal splash. The metallic substance is made of a material having a high thermal conductivity such as copper, and is cooled by jetting water on the bottom surface. Therefore, when the molten metal droplets collide with the cooling substrate, they spread to form a thin, long film, while the latent heat of the molten metal droplet can be transferred to the cooling substrate to achieve the highest cooling rate.

[0010]

The manufacturing method according to the invention comprises the following steps: (1) providing a rotating dish-shaped metal substrate having a concave upper surface; (2) directing the molten metal onto the inclined surface of the cooling substrate. The liquid droplets are separated outward as liquid droplets, and the liquid droplets are solidified into metal particles. The metal particles are caused to leave the cooling substrate by centrifugal force, and (3) the solidified metal particles are collected. The apparatus for producing the rapidly solidified powder according to the present invention is:
(A) a means for melting the metal; (b) a first rotating disk for separating the molten metal; (c) a second rotating disk having a concave upper surface surrounding the first rotating disk for splat cooling; (D) means for guiding molten metal onto the first rotating disk; (e) means for collecting the solidified powder.

[0011]

Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. However, although the preferred embodiments of the invention are illustrated, the detailed description and specific examples disclosed herein are illustrative only, and the invention is susceptible to various modifications and changes without departing from the scope and spirit of the claims. Can be easily achieved by those skilled in the art.

The present invention is more fully understood from the following detailed description and drawings, which are exemplary only and not limiting. Referring to FIGS. 1 and 2, by resistance heating or induction heating or an arc, the raw alloy material is optionally melted in a melting furnace 1 in a vacuum or protective environment. The power supply 2 supplies the energy required for melting. The melting furnace 1 has a supporting means 4
Supported by. The supporting means 4 is provided with a rotating means 30. The melting furnace 1 can be tilted by rotating means 30 for pouring the melt and the funnel crucible 6. The melt flows through conduit 7 onto atomizing disc 9, where it is atomized by centrifugal force. The funnel-shaped crucible 6 is supported by the support means 4. The atomizing disc 9 is a motor 8 which is a conduction motor or an air motor with a rotation speed in the range of 3000 rpm to 20000 rpm depending on the type of alloy and the powder of the desired size.
Driven by. The motor 8 is fixed on the pedestal 5. The atomizing disc 9 can be either plate-shaped or cap-shaped and its diameter can range from 7 cm to 20 cm. The funnel-shaped crucible 6 and the motor 8 are separated from the collection chamber 20 by a heat-resistant cap-shaped tube 13. Splat cooling rotating substrate 14
Is below the atomizing disc 9. The atomized metal particles collide with the splat cooling substrate 14 and the particles are splat cooling substrate 1.
When it spreads to the inclined surface of No. 4, it is instantly cooled. The splat cooling substrate 14 is disk-shaped and is tapered at an angle in the range of 10 ° to 30 °. If the angle is very small, the splat effect is reduced. If the angle is very large, the flaky powder escapes very little from the splat cooling substrate 14 and then deposits on the splat cooling substrate 14. The splat cooling substrate 14 is cooled by cooling water sprayed from the lower circular pipe 15. 5 splat cooling disks
It is driven by the conduction motor 18 at speeds in the range of 00 rpm to 3000 rpm. The electric motor 18 is arranged in the housing 17. A flange 16 is mounted on the shaft of the electric motor 18, which protects the bearing of the motor 18 from water damage. The cooling water prevents water from contaminating the alloy powder.
Isolated by 9. The cooling water exits from the outlet 21. In addition, the cap 3 of the collecting chamber 20 has a circular gas pipe 11 to prevent powder from accumulating at the corners and to reduce the size of the collecting chamber 20.
Is provided. The splat cooled alloy powder spills into the collection chamber 20 due to centrifugal force. The gas is ejected from a gas tube 11 which deflects the powder, so that the powder falls fast. The larger powder falls into the first collector 23. The smaller powder is sucked into the cyclone separator 22 and collected in the second collector 25.

The splat cooling substrate 14 is made of a material having a high heat transfer coefficient such as copper. The atomizing disc 9 and the splat cooling substrate 14 can move vertically along their central axes to adjust the position where the molten droplets impinge on the splat cooling disc 14 to improve the cooling rate. Under normal conditions the atomizing disc 9 is a splat cooling disc 1
4 to about 1 to 8 cm higher.

Several experimental examples will be described below to show the effect of the present invention. Experiment 1 Pure aluminum was melted in a melting furnace at 750 ° C.
Pour into funnel crucible at 0 g / min. The melt is 1500
It flows onto an atomizing disc rotating at 0 rpm and then the droplets are splat cooled on a splat cooling substrate rotating at 2000 rpm. The powder is flaky. The piece size is −
It is distributed in the range of 14 mesh to 4325 mesh.
The thickness of the flakes is in the range of 5 μm to 30 μm. The feature size of the microstructure features is 1 μm or less. Cooling rate is 10
Higher than ⁶ k / sec.

Experiment 2 Al-12% Si alloy was melted at 780 ° C. and 1200
Pour into funnel crucible at g / min. 15 atomizing disks
Rotate at 000 rpm. 200 splat cooling boards
Rotate at 0 rpm. A flaky Al-12% Si alloy powder is obtained. The flaky dimensions are distributed in the range of -14 mesh to +325 mesh. The microstructure of the powder is finer than that of the conventional powder, as shown in FIG. The cooling rate is higher than 10 ⁶ k / sec.

Experiment 3 The Fe-20% B alloy is melted in a quartz crucible under a protective environment at approximately 1350 ° C. and poured into a funnel crucible under pressure. The atomizing disc rotates at 20000 rpm. The splat cooling substrate rotates at 2000 rpm. Flake shaped Fe-20
B alloy powder is obtained. The flaky structure is amorphous.

While the present invention has been described by way of example and having described several preferred embodiments, it should be understood that the invention is not limited to the disclosed embodiments. On the contrary, the intention is to cover various modifications and similar arrangements included within the spirit and scope of the invention, which scope should be construed broadly to include all such modifications and similar constructions. .

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the entire apparatus of the present invention.

FIG. 2 is a partially enlarged schematic view showing the relationship between an atomizing disk and a cooling substrate.

FIG. 3 is a graph showing the size distribution of a metal powder produced by the method according to the present invention.

FIG. 4 is a photomicrograph of rapidly solidified aluminum flake particles produced by the method of the present invention.

FIG. 5 is a micrograph of a rapidly solidified Al-12Si alloy piece made by the method of the present invention.

[Explanation of symbols]

 1 Melting Furnace 2 Power Supply 3 Cap 4 Support Means 5 Stand 6 Funnel Crucible 7 Conduit 8, 18 Motor 9 Atomization Disc 11 Gas Pipe 13 Tube 14 Rotating Substrate 16 Flange 17 Housing 19 Cylindrical Case 20 Collection Chamber 21 Outlet 22 Cyclone Separator 23,25 Collector 30 Rotating means

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[Procedure amendment]

[Submission date] June 15, 1992

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 4

[Correction method] Change

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[Figure 4]

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 5

[Correction method] Change

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[Figure 5]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Xu Guangyuan No. 101, Guangfu Road, Hsinchu City, Taiwan No. 101, Guangfu Road, Tsinghua University (72) No. 101, Guangfu Road, Hsinchu City, Taiwan Qinghua University Materials Science Engineering Laboratory

Claims (15)

[Claims] 1. A molten metal is prepared; (b) The molten metal is poured into a first rotating disc; (c) The molten metal is separated into separate molten droplets from the outer periphery of the first rotating disc. (D) impinging the molten droplets on the annular plane of a second rotating concave disc surrounding the first rotating disc; (e) converting the molten droplets into a liquid film on the annular plane; (f) ) Coagulating the liquid film on the annular plane as flaky particles; (g) allowing the flaky particles to leave the annular plane by centrifugal force; (h) comprising the steps of collecting the flaky particles A method for producing flaky particles from molten metal. 2. The annular plane is inclined from the outer periphery of the first rotating disk into the passage of the molten droplet at an angle of 10 ° to 30 ° at which the molten droplet can spread on the annular plane. A method for producing flaky particles. 3. The method for producing flaky particles according to claim 1, wherein the second rotating disk is made of a material having high thermal conductivity. 4. The method for producing flaky particles according to claim 1, further comprising providing means for cooling the second rotating disk from the bottom surface. 5. The method for producing flaky particles according to claim 1, wherein the first rotating disk and the second rotating disk are arranged coaxially. 6. The cooling substrate is 500 rpm to 3000.
The method for producing flaky particles according to claim 1, which rotates at a speed in the range of rpm. 7. The rotating means comprises 3000 rpm to 200 rpm.
The method for producing flaky particles according to claim 4, which is rotated at a speed in the range of 00 rpm. 8. (a) a means for melting the metal; (b) a first rotating disk for separating the molten metal; (c) a second having a concave upper surface surrounding the first rotating disk for splat cooling. An apparatus for producing metal powder from molten metal, comprising: (d) means for guiding molten metal onto the first rotating disk; and (e) means for collecting the solidified powder. 9. The apparatus for producing metal powder according to claim 8, wherein the cooling disk is made of a material having high thermal conductivity. 10. An edge of the cooling disk is approximately 10 with a horizontal plane.
The apparatus for producing metal powder according to claim 8, wherein the apparatus has an angle of 30 ° to 30 °. 11. The apparatus for producing metal powder according to claim 8, further comprising cooling means for cooling the second rotating disk. 12. The second rotating disk is 500 rpm
The apparatus for producing metal powder according to claim 8, wherein the apparatus rotates at a speed in the range of ˜3000 rpm. 13. The first rotating disk is 3000 rp
The apparatus for producing metal powder according to claim 8, which rotates at a speed in the range of m to 20,000 rpm. 14. The apparatus for producing metal powder according to claim 8, wherein the guiding means is a funnel-shaped crucible. 15. The apparatus for producing metal powder according to claim 8, wherein said collecting means is a chamber associated with a cyclone separator.