US2676359A

US2676359A - Atomizing magnesium and its alloys

Info

Publication number: US2676359A
Application number: US161972A
Authority: US
Inventors: Douglas S Chisholm
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1950-05-15
Filing date: 1950-05-15
Publication date: 1954-04-27
Anticipated expiration: 1971-04-27

Description

April 27, 1954 D. s. CHISHOLM 2,675,359

ATOMIZING MAGNESIUM AND ms ALLOYS Filed May 15, 1950 INVEN TOR. Doug/05 5 Ch/s/w/m A TTORNE Y5 Patented Apr. 1954 UNITED sTA Es v PATENT OFFICE ,ac'zasso y.

as. M Application May 15, 1950, Serial N0. 161,972

The invention relates to a method of atomizing magnesium and its alloys.

In my copending application Serial No. 159,370, filed May 1, 1950, there is disclosed a method of atomizing magnesium and its alloys which inyolves the impingement of a cool hydrocarbon gas (methane, ethane, propane, butane) againstathin stream of the molten metal. The cool Bas breaks up the molten metal into fine spherical droplets which solidify into smooth spheres with an invisible protective coating. The coated particles thus obtained are unique in that, among other unusual properties they possess, they do not become united into a compact even under the application of compressive pressures as high as 100,000 pounds per square inch,.and they are diillcult to ignite with the flame of a match.

The present invention concerns a modification of the foregoing method of atomizing magnesium and its alloys and is based upon the discovery that by mixing with the hydrocarbon gas used to atomize the molten metal a sufllcient quantity of a fog-forming liquid to at least saturate the atomizing gas with the vapor of the liquid and entrain some of the liquid in the atomizing gas as a fog, the solid atomized particles of metal obtained are jagged rather-than smooth, are capable of being compacted under pressure, and readily ignite with the flame of a match. The invention then consists of the method hereinafter fully described and particularly pointed out-in the claims, reference being had to the accompanying drawing.

In the said drawing. Fig. 1 is a photograph at a magnification of 7 diameters of a sample of atomized magnesium alloy made by atomizing with dry hydrocarbon gas, the sample, being a Claims. (CI- 18-47.

spread thinly on a flat white background. Fig. 2

is a similar photograph of a thinly spread sample of the same magnesium-base alloy atomized according to the method of the invention using water saturated natural gas containing entrained liquid water as a fog.

In carrying out the invention, the magnesium or magnesium-base alloy to be atomized is brought to the molten state and heated preferably not more than about 100 to 250 Fahrenheit degrees above the melting point. The molten metal is allowed to fall in a thin stream and a jet of hydrocarbon gas of the paraflln series at least saturated with fog-forming liquid is impinged against it. The size of the metal stream does not appear to be critical. Where very. high rates of production are not required, a stream of diameter 2 velocity of the hydrocarbon gas doe not appear to be sharply critical and satisfactory atomizing can be had withgas pressures at the jet as low as 15 pounds per square inch and as high as pounds per square inch or more. The diameter of the gas jet is preferably greater than that of the stream of metal.

The hydrocarbon gases which may be used contain from 1 to 4 carbon atoms, e. g. methane, ethane, propane, and butane. Mixtures of these gases may be used. They may be saturated with the fog-forming liquid in any convenient manner as by introducing the liquid into the gas as it flows to the jet. The amount of fog-forming liquid beyond that needed to saturate the atomizing gas is not sharply critical. An excess, beyond saturating amounts, of about 0.05 gram per cubic foot of the ga measured at atmospheric pressur is sufllcient. although larger amounts giay be used. For example, at F. about 0.5 gram of water per cubic foot of the gas before compressing to jet pressure is sufilcient to produce about 2 per cent by weight more water in the gas than is needed for saturation and produces a fog as the compressed gas issues from the jet. No harm appears to result from the use of a considerable quantity of the fog-forming liquid, 1. e. far more than is needed to saturate the gas with the vapor of the liquid. An excess, over saturating amounts, of up to about 5 grams per cubic foot is tolerable. Over-saturating the atomizing gas withthe fogforming liquid to produce a fog therein is readily accomplished byv spraying the fog-forming liquid into'the gas stream on its way to the atomizingv jet so-that a or fog is formed in the gas jet stream before it strikes the molten metal to be atomized. I,

While water is the preferred fog-forming liquid, other liquids may be used having; a boiling point betweenabout 50 C. and C. Examples of liquids boiling within the aforesaid range are octane, isobutyl alcohol, ethyl alcohol. methanol. propyl alcohol, toluene, benzene, xylene, and light distillate. These liquids are generally neutral, 1. e. neither acid nor alkaline and do not actively attack the magnesium. ey add to the cooling eiIect of the atomizing g by abstracting heat from the molten metal as the liquid particles of the fog evaporate.

Referring to Fig. 2, as an example of the product of the invention, it will be seen that the atomized particles are characterized by jaggedness of shape, the surface is rough and is comprised of many sharp points and sharp edges.

of 0.08 to 0.25 inch is generally satisfactory. The 55 These particles resulted from aomizing a mag- 3 nesium-base alloy having a nominal composition 01' 3 per cent of aluminum, 1 per cent or zinc,

0.5 per cent of manganese, the balance being magnesium. In the atomizing operation, the alloywas melted and heated to 1300 1". A Jet oi wet natural gas having a diameter of 0.25 inch was impinged upon stalling stream of the heated alloy having a diameter of 0.1 inch at the point of application the gas jet. The atomizing gas, before the addition 0! the water, contained by volume per cent N3, 80 per cent CH4. 8 per cent Calls, and 2 per cent Cal-Is. To this atomizing gas was added about 0.5 gram of liquid water per cubic foot or .the atomizing gas at room temperature which was then compressed to pounds per square inch and impinged by means or a Jet against the falling molten metal stream.

For comparison, the same alloy atomized in the same manner with the same hydrocarbon gas before the addition of water produced smooth spherical particles, as shown in Fig. 1.

y The jagged particles obtained according to the invention, unlike those obtained with dry natural gas atomization, are compactable, noniree flowing, and can be ignited with the flame oia match. They are more suitable for pyrotechnical purposes than the rounded particles.

I claim:

l. The method of convertinga molten mass 4 consisting of magnesium or alloy thereof into solid particles having a Jagged form which consists in letting fall the molten mass in a thin stream and directing a Jet consisting of parailln hydrocarbon gas against the fallin stream with suillcient velocity to break up the stream into particles, the hydrocarbon gas being selected from the group consisting of methane, ethane, propane, and butane and containing an entrained neutral liquid as a fog in amount between about 0.05 and 5 grams per cubic foot of thegas beyond that required for saturation at atmospheric pressure, said entrained neutral liquid having a boilin; point between and C.

2. The method according to claim 1 in which the entrained neutral liquid is water.

References Cited in the ills of this patent UNITED s'ra'rns PATENTS Number Name Date 1,351,865 Nicol Sept. 7, 1020 2,371,105 Lepsoe Mar. 6, 1045 2,436,520 Mahoney et ai. Feb. 24, 1948 OTHER REFERENCES .Ber. No. 268,381, Kaui'mann (A. P. 0.) published July 13, 1943. a

Claims

1. THE METHOD OF CONVERTING A MOLTEN MASS CONSISTING OF MAGNESIUM OF ALLOY THEREOF INTO SOLID PARTICLES HAVING A JAGGED FORM WHICH CONSISTS IN LETTING FALL THE MOLTEN MASS IN A THIN STREAM AND DIRECTING A JET CONSISTING OF PARAFFIN HYDROCARBON GAS AGAINST THE FALLING STREAM WITH SUFFICIENT VELOCITY TO BREAK UP THE STREAM INTO PARTICLES, THE HYDROCARBON GAS BEING SELECTED FROM THE GROUP CONSISTING OF METHANE, ETHANE, PROPANE, AND BUTANE AND CONTAINING AN ENTRAINED NEUTRAL LIQUID AS A FOG IN AMOUNT BETWEEN ABOUT 0.05 AND 5 GRAMS PER CUBIC FOOT OF THE GAS BEYOND THAT REQUIRED FOR SATURATION AT A ATMOSPHERIC PRESSURE, SAID ENTRAINED NEUTRAL LIQUID HAVING A BOILING POING BETWEEN 50* AND 175* C.