US 2284551 A
Description (OCR text may contain errors)
May 26, 1942. P. P. ALEXANDER PACKING OF POWDERED METALS Filed Aug. 3, 1940' 1 .92am? flieasazader,
fliiornqy Patented May 26, 1942 UNITED STATES PATENT OFFICE 2,284,551 raoxmo or rownnm'sn METALS Peter P. Alexander, Marblehead, Mass.
' Application August a, 1940, Serial No. 350,788
My invention relates to the packing of powdered metals and more especially to a method of packing powdered metals for shipment such that the metals may reach the consumer incondition for immediate use and without requiring processing to overcome conditions incident to the transportation oi the same.
It is well known that metals in the form of finely divided powders are subject to oxidation when exposed to the air which oxidation in many cases is so rapid as to take the form of combustion with accompanying high temperatures. This rapid oxidation of the powdered metals is produced especially ii. they are shaken violently or friction between the grains induced in other manner. Thus very fine powders of ireshly reduced iron or cobalt, when heated even slightly above room temperature and violently shaken in air, catch fire and burn until they are transformed into the corresponding oxides. If finely powdered metals are packed in ordinary containers the temperatures and handling to which they are subjected during shipment is often such that spontaneous combustion will result. This condition, with respect to fine powders of freshly reduced iron or cobalt, can usually be prevented by letting the powdered metals stand undisturbed in an atmosphere of carbon dioxide or even air, after reduction and before packing, until the individual grains become covered with thin protective layers of oxide whereupon they may be packed and handled during transportation without danger of combustion.
The situation is more diiilcult in the case of such metals as titanium, zirconium, thorium and uranium. Very fine powders of these metals, when in perfectly dry state, are not only subject to spontaneous combustion due to either elevation of temperature or friction of the particles if they are shaken in air but the problem of transportation thereof is also complicated by the fact that a few metals, titanium for example,
unite with nitrogen forming nitrides Just as readily as they unite with oxygen to form oxides. In other words they burn in pure nitrogen just as readily as they do in oxygen or in air. Spontaneous combustion of certain finely divided metals, zirconium, for example, may be avoided during shipment by adding thereto water in amounts neighboring 20%, the water transforming the whole mass into a more or less clay-like of view or the consumer who, on receiving this material must dry it first in air and then in a vacuum oven before he can use the powdered material in various practical applications. Furthermore, the drying of fine powdered zirconium is an extremely dimcult operation and sometimesfif not conducted properly, leads to the sudden combustion of the metal. Moreover, the fine powdered metals if left wet for long periods of time are subject to hydration which spoils the quality thereoi for most of the purposes for which there is a commercial demand.
As the principal object of the present invention I contemplate a method of packing of powdered metals such as zirconium, titanium, etc., wherein not only is the danger of spontaneous or other combustion eliminated but in which the powdered metals reach the consumer in condition for immediate use without the necessity of drying or other processing.
In a more specific aspect the invention relates to a method of transportation of finely divided metals in dry condition wherein the particles are protected by a surrounding envelope from contact with oxygen, nitrogen or other gas which may induce their combustion or otherwise cause their deterioration and wherein the particles, including the surfaces thereof, remain in pure unchanged state so that they may be ready for immediate use when they reach the hands of the consumer.
The invention has to do particularly with the packing and transportation of finely powdered zirconium, titanium, thorium and uranium and in the practice of the same the particles of these metals are surrounded with an inert envelope which, while not wetting or changing the composition of the metals, on the surface .or otherwise, nevertheless prevents them from coming into contact with oxygen, nitrogen or other gas which will induce combustion or otherwise contaminate the particles. Specifically the inert envelope takes the form or a monatomic gas I such as argon, the powdered metals together substance. However, while eliminating thedan -ifl conium is extremely undesirable from the point with the enveloping argon being sealed in a container against contact with the surrounding atmosphere.
The several figures of the drawing are diagrammatic illustrations of the way in which the powdered metals may be handled during the packing thereof, Fig. 1 being an elevational view partly in section showing the powdered metal being introduced into a container and Figs. 2 and 3 being elevational views partly in section, showihg two methods for replacing the air or other gas in the container with argon or other monatomic gas.
The container for the powdered metals may be of any suitable material and in the form indicated by the reference numeral I0, in the drawing, is provided with a neck II on which a sealing cap l2 may be received. It is important that the powdered metals be introduced into the container under conditions which will not promote their combustion, for example, if they were poured into the container through the air there is a. great likelihood that combustion would result. The procedure may of course be varied, but in any event the processing of the metals prior to packaging may be controlled so that at the time they are ready for packaging they are insulated against movement in an atmosphere containing any gas which would promote their combustion or contamination. Thus the metals may be placed in a funneled container 68, such as that shown in Fig. 1, the metals in the container it. being surrounded with argon or other inert monatomic gas. The funnel container it in the form shown is provided at its lower end with a valve or cut-oil it and is threaded or otherwise provided with means for attachmerit to the container it. Also connected to the lower end of the container i3 below the cut-ofi Mic a valved connection 55 leading to a vacuum pump (not shown). Air is withdrawn from the container ill and when a sumcient degree of vacuum has been efiected the valved connector it is closed and the cut-ofi it opened to permit the powdered metal to pass into the container, argon or other monatomic gas being permitted to enter the container ill at the same time as the powdered metals. When the desired amount of powdered metal has been introduced into the container and the pressure of the argon contained therein reaches that of the external atmosphere, the cut-off may be closed and the container in unthreaded or otherwise disconnected from the funneled container it. At this time there will be no danger of combustion of the powdered metals, as there will be no rapid influx of the atmosphere due to the fact that the container is under atmospheric pressure.
After the powdered metal has been introduced into the container II) it will be apparent that some, if not all, of the argon or other monatomic 888 will escape from the container and will be replaced with the surrounding atmosphere. In order that the atmosphere may be removed prior to the time the container is shipped and in order to insure that the container is filled with a monatomic gas, the sealing cap l2 may be threaded loosely on the container and the latter introduced into a collapsible rubber bag, such as that indicated at It in Fig. 2, the bag 16 having a, neck H to which is connected branches i8 and I9, branch I8 leading to a vacuum pump and branch I9 leading to a source of supply of argon or other monatomic gas. A valve 20 is provided in the neck I'I'below the branches IB and I9 and the latter are also provided with valves, as at 2| and 22. After introduction of the container II] in the bag IS the valves 20 and 2| are opened and the valve 22 closed, the vacuum pump being operated to withdraw air from the interior of the bag 3, the latter collapsing into contact with the walls of the container III, the upper end of e the bag however being of heavy enough construction so that it will not completely collapse due to the reduction of pressure. Not only is the air withdrawn from the interior of the bag I6 but due to the loose condition of the cap I2 on the container III the air in the container will pass into the bag and outwardly through the neck thereof. When a suflicient degree of vacuum has been reached within the bag [6 and thus the container I0, the valve 2! is closed and the operation of the vacuum pump discontinued, the valve 22 being opened to permit the argon to flow into the .bag I8 and thus into the container Hi. When the pressure within the bag l6 reaches that of the atmosphere, the cap I2 isthreaded into tight engagement with the neck ll of the container in sealing the latter against the escape of the argon, whereupon the flow of argon through the branch l9 into the bag may be discontinued by closing the valve 22 and the sealed container I!) removed therefrom.
In the form shown in Fig. 3 of the drawing, a special type of cap is provided for the container ill, the cap in this instance having a tubular stem 23 provided with a valve 24, the upper end of the stem being threaded as at 25 for connection by a T-connector (not shown herein) to a. vacuum pump and toe. source of argon or other monatomic gas. The procedure is much the same as in that form shown in Fig. 2, except that in this instance the cap is threaded into tight engagement with the upper end of the neck, the
gas in the container it being withdrawn thereafter and replaced with argon, whereupon the valve 24 is closed and the threaded end 25 of the stem 23 unscrewed from the Y-connection whereupon a cap is threaded on the stem 23 to further seal the same.
It will be apparent to those skilled in the art that the container after sealing may be subjected to any amount of rough handling without danger of the frictional movement of the metal grains, one on another, causing any combustion of the same as the surrounding envelope of inert gas is incapable of supporting such combustion, nor will any change in temperature have an adverse eflect on the metals. The materials thus may reach the consumer in a dry condition ready for use without further processmg.
The presence of the monatomic gas in the container at atmospheric pressure not only prevents combustion or other change in the powdered metals during shipment, but also brings about a condition such that the container may be opened and the contents thereof withdrawn without danger. If all the air was withdrawn and the inside of the container maintained in gas-exhausted condition, the prevention of the combustion of the powdered metals upon the opening of the container would be diflicult. It will be apparent that upon the breaking of the seal the external air would rush into the container. There would be an immediate adsorption of great quantities of gas by the particles of metal and this, together with the mechanical disturbance of the particles, would result in their immediate and complete combustion. When the container is filled with argon or other monatomic gas at atmospheric pressure, the container may be opened without entailing any rush of the atmosphere thereinto so that the rapid adsorption of the air and distiglrtbance of the particles of metal will not res Of course if it is desired the metals may be insulated against contact with the atmosphere during the further processing of the same, but if frictional movement of the particles is avoided by so handling them that they are not poured through the atmosphere, or subjected to unreasonable temperatures, they may be handled during their use without danger of combustion.
It will also be apparent to those skilled in the art that other inert gases such as helium, neon, krypton ad xenon may be used in place of argon and furthermore while the method of packing described above is particularly useful in connection with finely powdered titanium, zirconium, thorium and uranium it will be understood that it is not limited in its utility to these particular metals but has wider applicability. Thus while I have described the invention with great particularity it will be understood that the same is not limited to the precise details described but is capable of modification and variation within the spirit of the invention and the scope of the appended claims.
What I claim is:
1. The combination of a, gas-tight container, a finely pulverulent metal selected from the group consisting of titanium, zirconium, thorium and uranium in said container, the free space in said container being filled with a monatomic gas selected from the group consisting of argon, helium, neon and xenon.
2. A method of preserving a finely divided metal selected from the group consisting of titanium, zirconium, thorium and uranium, which comprises placing said finely divided metal into a pressure-tight receptacle and filling all the free space in said receptacle with an inert monatomic gas selected from the group consisting of argon, helium, neon and xenon, and sealing the container While so filled.
3. A method of preserving a finely divided metal selected from the group consisting of titanium, zirconium, thorium and uranium, which comprises placing said finely divided metal into a pressure-tight receptacle, pulling a vacuum in said receptacle, and filling all the free space in said receptacle with an inert monatomic gas selected from the group consisting of argon, he-
7 lium. neon and xenon, and sealing the container while so filled.
PETER P. ALEXANDER.