US3761548A - Method of producing metal particles - Google Patents

Method of producing metal particles Download PDF

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Publication number
US3761548A
US3761548A US00086837A US3761548DA US3761548A US 3761548 A US3761548 A US 3761548A US 00086837 A US00086837 A US 00086837A US 3761548D A US3761548D A US 3761548DA US 3761548 A US3761548 A US 3761548A
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Prior art keywords
melt
cylinder
hollow
pellet
perforations
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US00086837A
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English (en)
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H Winter
W Schuster
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/06—Making metallic powder or suspensions thereof using physical processes starting from liquid material
    • B22F9/08—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying
    • B22F9/10—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying using centrifugal force

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  • ABSTRACT A method of producing metal particles and especially smooth-surfaced round orelongated metal particles having a low surface-volume ratio whereby a rotating cylinder with perforated parts has a riser reaching into a bath of the liquid and is rotated at a speed such that molten metal cast from the perforations of the cylinder is replaced by a rising current of the molten metal.
  • Our present invention relates to a method of producing metal particles; more particularly the invention relates to a system for producing metal particles with improved topography and physical properties and to the production of metal particles from metals which have not hitherto been used for such purposes.
  • One of the known systems for producing metal granules with a limited specific surface area has made use of a centrifugal basket or crucible into which the molten metal is filled from above.
  • the crucible may be provided with openings through which streams of the molten metal are ejected by centrifugal force as the crucible is rotated rapidly.
  • the technique exploits the principle that a free falling stream of liquid is broken up by the surface tension into droplets. The problems with this method, however, were manifold.
  • the characteristics of the granular product were dependent upon the level of the melt within the crucible or centrifugal vessel and it was difficult to control this level or maintain the level sufficiently constant to produce consistently large quantities of metal granules of a uniform character.
  • the melt in the rotating crucible has the tendency to freeze and to clog the openings or borings, since the required amount of heat is delivered to the crucible with the incoming melt, any interruptions or unregularities in the flow of the melt lead to the interruption of the production. lPerhaps of greater importance is the fact that with higher melting metals and alloys the crucibles were required to be of ceramic and were relatively brittle, but had to be rotated at high speed.
  • Another object of this invention is to provide an improved method of producing metal particles of the character described, which will obviate the aforementioned disadvantages.
  • the molten metal discharged through the perforations draws a continuous stream of metal from the supply bath into which the free lower end of the dip tube is immersed.
  • an inert gas into the head of the cylinder at a small pressure above ambient to avoid reactions of the melt I with the surrounding atmosphere inside the perforations.
  • the apparatus used to carry it out comprises a hollow lower cylinder intended to extend below the surface of the melt as contained in a receptacle which may be upwardly open or may have a free surface which may vary.
  • a perforated hollow upper cylinder having its free upper end sealed by a plug, cap or cover.
  • the apparatus carrying out the method is rotatable about the axis of the coaxial cylin ders to draw metal from the melt into the cylinder and eject it from the hollow upper cylinder radially and/or tangentially by centrifugal force.
  • d ranges between 3 and 15 cm while the perforation diameter lies between 0.3 and 2.5 mm. More specifically, we prefer an arrangement in which d, is between 5 and cm and, better still, below 7.5 cm while the diameter of the perforations lies between 0.8 and 1.8 mm, preferably less than 1.2 mm and, even better, less than 0.6 mm.
  • the cylinder may, according to the invention, comprise a perforated sheet, sieve, net or screen or may be formed from a solid cylinder through which the perforations are drilled.
  • a perforated sheet, sieve, net or screen or may be formed from a solid cylinder through which the perforations are drilled.
  • the inner surface of the hollow upper cylinder or hollow lower cylinder, or both, may be roughened or provided with fins to promote rotative entrainment of the molten metal with the cylinders and the latter may be driven by a shaft fixed to the cover of the cylinders.
  • the shaft may be hollow to permit the inert gas to be introduced as described earlier.
  • any gas which is nonreactive with the melt include the rare gases, nitrogen, hydrogen, other reducing atmospheres (e.g., carbon monoxide), etc.
  • the vessel receiving the bath may be connected with a reservoir adapted to feed additional molten metal to the vessel substantially at the rate at which the melt is discharged by the rotating cylinder or drum. Furthermore, we may provide means for pressurizing the melt and driving it upwardly through the hollow lower cylinder to augment the upward inducement of the melt resulting from the pump effect of the rotating upper cylinder.
  • the hollow lower cylinder and the hollow upper cylinder may be composed of or lined with iron, cast iron, steel, refractory metals and alloys, graphite or a ceramic material such as alumina, magnesia or zirconia to which may be added particles of metal selected, for example, from the group which consists of chromium, molybdenum and tungsten.
  • the preferred rotational speed of the cylinder is 600 to 9,000 rpm when d, ranges between 3 and 15cm and when the diameter of the perforations is between 0.3 and 2.5mm. Within this range, the sub-range of 1,500 to 6,000 rpm provides most effective results, especially when d, is held between 5 and 10cm and the perforations have a diameter of 0.8 to 1.8mm. Also, when the speed of rotation is greater than 7,000 rpm, d should be less than 7.5cm and the perforation diameter less than 1.2mm.
  • the melt into which the hollow lower cylinder extends is covered with a floating layer of a material protecting against atmospheric contamination, e.g., fused salt, and the region surrounding the cylinder may be placed under reduced pressure or vacuum.
  • a floating layer of a material protecting against atmospheric contamination e.g., fused salt
  • the region surrounding the cylinder may be placed under reduced pressure or vacuum.
  • an inert gas atmosphere (as defined) in the space surrounding the upper cylinder and we may direct jets of inert gas at the cylinder wall from which the droplets are discharged to protect the rapidly solidifying droplets of the melt.
  • the present method is best carried out with molten magnesium alloy, lead, lead alloys, tin, tin alloys, zinc, zinc alloys, alkali metals, alkali metal alloys, aluminum, aluminum alloys, copper and copper alloys.
  • FIG. 1 is an axial cross-sectional view through an apparatus embodying the present invention
  • FIG. 2 is a vertical section illustrating one mode of supplying molten metal to the system.
  • FIGS. 3 and 4 are vertical sections diagrammatically illustrating other embodiments of the instant invention.
  • the rotating pellet sprayer 23 as shown in FIG. 1, consists of three main parts, namely, a hollow, perforated upper cylinder 0 as the upper part, a conical middle part b, and an elongated hollow lower cylinder c, reaching below the surface of the melt l0, connecting the interior of the upper cylinder a with the surrounding melt.
  • This pellet sprayer 23 can be rotated by a shaft 1 connected to a motor (not shown) at its upper end and to a cover 3 of the hollow cylinder a at the lower end of shaft 1.
  • pellet sprayer 23 reaching with its hollow lower cylinder c below the melt 10, is always heated up by the heat of the melt even if at a standstill, so that the tendency of the melt to solidify and clog the perforations 6 is minimized.
  • pellet sprayer 23 empties each melt-containing vessel as far as the hollow lower cylinder c reaches down into the melt. Therefore small differences in the level of the melt have nearly no influence on the performance of the device.
  • the wall thickness of the perforations hollow upper cylinder a with its perforations 6 should be limited, to avoid disintegration of melt in the passages 8 forming the perforations due to the difference of centrifugal forcesin the parts near the axis of rotation and the parts at a greater distance from it.
  • the wall thickness of the perforations hollow upper cylinder a with its perforations 6 should be limited, to avoid disintegration of melt in the passages 8 forming the perforations due to the difference of centrifugal forcesin the parts near the axis of rotation and the parts at a greater distance from it.
  • a perforated hollow upper cylinder consisting of a net or sieve made of a heatand corrosion-resistant material, such as niobium alloys for copper melts, stainless steels for aluminum melts, or nickel for lead melts.
  • the ratio ti /d where d is the inner diameter and 11 the outer diameter of the perforated hollow upper cylinder a should be greater than 0.33, preferably greater than 0.66.
  • the inner diameter d of the hollow lower cylinder c should be smaller than (1,, preferably between 0.5 d and 0.211,.
  • the size of the pellet sprayer 23 should be related to the rotational speed and to the diameter of the passages 8, if output and size distribution for a given size of the resulting product are to be optimal.
  • the inner diameter d, of the perforated upper cylinder a should be more than 3 cm and less than cm, preferably between 5 and 10 cm, while the number of revolutions per minute should be more than 600 and less than 9,000 rpm.
  • the diameter of the passages 8 or perforations 6 should be between 0.3 and 2.5 mm, preferably 0.8 to 1.8 mm.
  • the inner diameter d, of the hollow upper cylinder 21 should be below 7.5 cm, preferably less than S cm.
  • the speed of rotation should be more than 7,000 rpm, preferably between 9,000 and 10,000 rpm.
  • the diameter of the passages 8 should be less than 1.2 mm, preferably less than 0.6 mm.
  • An upward direction of the passages 8 is of advantage, as the particles should travel as long a way as possible, for instance to assure solidification, in free flight.
  • the even and continuous flow of the melt can be improved further if the feeding vessel 21 for the pellet sprayer 23 is connected with a large melting vessel 2, so that the fluctuation in the level of the melt in the feeding vessel 21 is kept small (HO. 2).
  • Another method can be applied if a continuous production is not necessary and only the contents of a rather large feeding vessel has to be emptied.
  • the melt can be forced into the pellet sprayer 23.
  • the gas pressure can be lowered; in H6. 3 the level of the melt 33 in a fixed cylinder 34 put into the feeding vessel can be lifted by gas pressure so that the pellet sprayer 23 can stay in continuous production.
  • a regulation system for instance coupled with an electrical contact in the upper part of fixed cylinder 34, can vary the gas pressure in order to keep the level of melt inside the fixed cylinder 34 nearly constant.
  • the cylinder 34 is not absolutely necessary. It can be replaced by an appropriately sized hollow lower cylinder c of the pellet sprayer 23.
  • the melt of such a reactive metal is covered with salt mixtures well known in the art.
  • the hollow lower cylinder 0 reaches through the salt cover floating on the surface of the melt and sucks the melt in below the surface.
  • the melt contacts the surrounding atmosphere only when it leaves the perforations 6 in form of a liquid, disintegrating into droplets which solidify so fast that, below a certain diameter of about 0.7mm, the granules do not burn while on their flight through the air.
  • Granulated lead particles made by the above method have a shining surface and can be used for the fabrication of leaded steels.
  • the pellet sprayer should preferably be of iron, case iron, or steel. If the melt is of aluminum or an aluminum alloy, it may be of iron, cast iron, steel, graphite, or a ceramic material. In the case of copper or a copper alloy, the pellet sprayer should be of graphite or a ceramic material. If the melt is of iron or steel, the pellet sprayer should be of ceramic material such as AI O MgO, or ZrO preferably with metallic additions such as Cr, Mo, and W.
  • the diameter of the pellet sprayer shown in FIG. I can be much reduced compared with an open rotating crucible of the same production capacity. So the danger of breaking for the pellet sprayer is much reduced compared with an open rotating crucible. This feature is even more pronounced because the closed construction of the pellet sprayer is more rigid and the pellet sprayer suspended on its axis 1 runs in a very stable position nearly without vibration and even better stability with increasing rotations per minute. Furthermore the hollow lower cylinder c submerged under the melt proves to be an additional vibration-damping element.
  • Pellet sprayers with a small diameter and a surprising production rate can be made while increasing the speed of rotation up to the limit the material used can endure.
  • pellet sprayers of a diameter d of about 3.5cm and a hollow perforated upper cylinder a made of perforated sheet or net commercial production of 3 tons of lead powder per hour is feasible, if the speed of rotation is raised to 18,000 rpm.
  • the melt ejected from the hollow perforated upper cylinder a should not be allowed to come into contact with the air. This can be achieved by surrounding the whole apparatus with an inert atmosphere, or by directing jets of inert gas at the hollow perforated upper cylinder 11.
  • the pellet sprayer 23 can be situated in a compartment held at a reduced pressure or in a vacuum; if the feeding vessel is closed from this compartment and is at atmospheric pressure, flow of the melt through the pellet sprayer will be enhanced.
  • EXAMPLE II The device illustrated in FIG. 1, supplied with molten metal using the arrangement illustrated in FIG. 4 by the application of gas pressure at least sufficient to maintain a uniform flow into the cylinder, was used to produce aluminum granules.
  • the cylinder was composed of graphite and had an internal diameter a of 6.4cm, an external diameter d of 8cm and a hollow lower cylinder with an internal diameter d of 2.2cm.
  • the perfo rations had a diameter of 1.2mm and the system was rotated at 3,500 r.p.m. to produce 1.4 tons per hour of the granules with a diameter of about 0.5mm.
  • the same system was used with equivalent results to granulate molten copper.
  • the enveloping gas at 1 atmosphere absolute was argon.
  • EXAMPLE III Using the dimensions of the sprayer of Example II, but an upper cylinder and hollow lower cylinder consisting of fired ceramic composed in equal parts by weight of ZrO and molybdenum powder, about 5 tons per hour of cast iron granules were obtained.
  • said cylinders consisting essentially of at least one substance selected from the group which consists of iron, nickel, cobalt, steel, refractory metals, graphite and ceramic, provided that said cylinders are composed of iron or steel when the molten metal is magnesium, lead, tin or an alkali metal or alloy thereof, said cylinders are composed of iron, steel, graphite or ceramic when the molten metal is aluminum or an alloy thereof, the cylinders are composed of graphite or ceramic when the molten metal is copper or an alloy thereof, and the cylinders are composed of ceramic when the molten metal is iron or an alloy thereof;

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  • Manufacture Of Metal Powder And Suspensions Thereof (AREA)
  • Manufacture And Refinement Of Metals (AREA)
US00086837A 1969-11-04 1970-11-04 Method of producing metal particles Expired - Lifetime US3761548A (en)

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CA (1) CA928030A (fr)
DE (1) DE2049458C3 (fr)
GB (1) GB1225596A (fr)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4127158A (en) * 1973-10-15 1978-11-28 Toyo Kohan Co., Ltd. Process for preparing hollow metallic bodies
US5332198A (en) * 1992-03-05 1994-07-26 National Science Council Method for producing rapidly-solidified flake-like metal powder and apparatus for producing the same
US6168307B1 (en) 1998-07-08 2001-01-02 Norsk Hydro Asa Rotor for the treatment of liquid
US20010022755A1 (en) * 1999-12-20 2001-09-20 Holtzapple Mark T. Mixer system and method
WO2015034425A1 (fr) * 2013-09-05 2015-03-12 Uvån Holding Ab Granulation de matériau fondu
WO2015152814A1 (fr) * 2014-04-03 2015-10-08 Uvån Holding Ab Granulation de ferrochrome fondu

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2294588A (en) * 1938-11-15 1942-09-01 Pazsiczky Gedeon Von Method of and apparatus for producing glass fibers
US3442988A (en) * 1966-04-04 1969-05-06 Reynolds Metals Co Method for preparing metal particles
US3466352A (en) * 1967-12-18 1969-09-09 Corbett Ass Inc Process for producing fibers
US3532775A (en) * 1969-04-10 1970-10-06 Aluminum Co Of America Method for producing aluminum particles

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2294588A (en) * 1938-11-15 1942-09-01 Pazsiczky Gedeon Von Method of and apparatus for producing glass fibers
US3442988A (en) * 1966-04-04 1969-05-06 Reynolds Metals Co Method for preparing metal particles
US3466352A (en) * 1967-12-18 1969-09-09 Corbett Ass Inc Process for producing fibers
US3532775A (en) * 1969-04-10 1970-10-06 Aluminum Co Of America Method for producing aluminum particles

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4127158A (en) * 1973-10-15 1978-11-28 Toyo Kohan Co., Ltd. Process for preparing hollow metallic bodies
US5332198A (en) * 1992-03-05 1994-07-26 National Science Council Method for producing rapidly-solidified flake-like metal powder and apparatus for producing the same
US6168307B1 (en) 1998-07-08 2001-01-02 Norsk Hydro Asa Rotor for the treatment of liquid
US20010022755A1 (en) * 1999-12-20 2001-09-20 Holtzapple Mark T. Mixer system and method
WO2015034425A1 (fr) * 2013-09-05 2015-03-12 Uvån Holding Ab Granulation de matériau fondu
EP3041629A4 (fr) * 2013-09-05 2016-10-05 Uvån Holding Ab Granulation de matériau fondu
EA031421B1 (ru) * 2013-09-05 2018-12-28 Увон Холдинг Аб Гранулирование расплавленного материала
US10618112B2 (en) 2013-09-05 2020-04-14 Uvan Holding Ab Granulation of molten material
WO2015152814A1 (fr) * 2014-04-03 2015-10-08 Uvån Holding Ab Granulation de ferrochrome fondu
CN106102969A (zh) * 2014-04-03 2016-11-09 尤万控股股份公司 熔融铬铁的造粒
CN106102969B (zh) * 2014-04-03 2018-09-18 尤万控股股份公司 熔融铬铁的造粒
RU2682356C2 (ru) * 2014-04-03 2019-03-19 Увон Холдинг Аб Гранулирование расплавленного феррохрома

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Publication number Publication date
CA928030A (en) 1973-06-12
DE2049458A1 (de) 1971-05-19
DE2049458C3 (de) 1975-09-11
GB1225596A (fr) 1971-03-17
DE2049458B2 (de) 1975-01-30

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