US2250687A - Manufacture of alloys - Google Patents

Description

Patented July 29, 1941 MANUFACTURE OF ALLOYS Helmut von Zeppelin, Bitteri'eld, Germany, as-

signor, by mesne assignments, to Walther H. Duisberg, New York, N. Y.

No Drawing.

Application February 18, 1939, Se-

rial No. 257,199. In Germany March 2, 1938 8 Claims. (Cl. 75-122) This invention relates to improvements in the manufacture of alloys.

While alloys are generally made simply by melting together the constituents, it is sometimes useful to combine the formation of the alloy with the reduction of one or more of the metallic constituents from its compounds such as oxides, this being particularly the case, when the preparation of the metallic constituent in itself is cumbersome, or when such constituent is but difilcultly alloyable because of its high melting point, or for other reasons. In cases of the latter kind, either a mixture of the reducible compound and the reducing agent is added to the molten base metal or vice versa, the reducible compound alone is introduced into the molten base metal containing a suitable reducing agent in the form of an alloy. When the base metal happens to be capable of acting in itself as the reducing agent, then of course the reducible compound is simply introduced into the base metal.

This procedure has proved useful in a great many cases; in some cases, however, when the reducible compound is of an easily volatilizable nature, then the losses occurring, particularly when the base metal is a metal having a high melting point, e. g. iron, nickel, copper, are very considerable. Moreover, when the reducible compound is introduced into a melt consisting of the base metal and the reducing agent, the re ducing action of the latter is substantially diminished by' its dilution with the base metal which has no such reducing action. Thus the reduction is only completed after an extended I period of time and this, in turn, results in a still more considerable volatilization of the reducible compound. A further disadvantage of the known processes consists in that in the high temperature range frequently employed, the reaction'takes place rather vigorously, and thus frequently causes the reacting mixture which is in contact with the crucible material (e. g. iron or graphite) to attack the latter; thus, constituents of the crucible material, particularly carbon, are taken up by the alloy under formation. In this manner the alloy not only becomes contaminated, but frequently the formation of compounds such as carbides also has a retarding effect upon the formation of the alloy itself.

It is an object of the present invention to substantially suppress or even completely avoid the volatiliza-tion of reducible alloy compounds when used in processes of the aforesaid kind. A

further object of the invention is to avoid attack of the crucible material used for carrying out such process, thereby also avoiding the formation of compounds such as carbides with its undesirable consequences. A further object of the invention is to enable the formation of the alloy to proceed under particularly favorable circumstances and in the shortest possible time.

According to the invention a mixture of the reducible compound and the reducing agent is placed in a vessel consisting of another metal-- which metal is preferably the base metal of the alloy to be formed-and this vessel is progressively heated from without. In this manner, as soon as the temperature of reaction is attained by heating, the mixture is caused to react. On further heating, the vessel itself is caused to melt, this being also promoted by the heat of reaction which serves to heat the vessel. In this manner, the metal formed by reduction is brought into intimate contact With the melting metal constituting the vessel immediately after such first-named metal has been formed by reduction, and the formation of the desired alloy thus takes place under particularly favorable circumstances.

The vessel to be used according to the invention may be of cylindrical shape, e. g. in the form of a capsule; the heating thereof is ad-' vantageously effected by disposing the vessel containing the reaction mixture within a crucible and embedded in a saline mixture which, on melting of the materials contained in the crucible, serves as a flux. The crucible itself is preferably heated from without, this resulting first in a melting of the flux, and thereupon, progressively, in the initiation of the reaction, and the melting of the capsule. The particular usefulness of the present process may be attributed to the fact that in causing the reaction to take place in a more or less confined space, viz. the vessel, and at the lowest possible'temperature, volatilization of the reducible compound is kept at a minimum. Even if the reaction be not entirely completed before the melting of the vessel, then, on further raising the temperature for the purpose of melting the vessel, volatilization of the remainder of the reducible compound cannot take place to any appreciable extent, since the compounds already formed in the reaction act as diluents and sub stantially counteract such volatilization.

Formation of the alloy is thus completed within a relatively short time, generally in less than about 5 minutes. 01' course it is also possible .to first prepare a saline melt alone and then to insert the vessel containing the reaction mixture into such saline melt. Equally it is not necessary that the whole of the base metal required for the formation of the alloy be represented by the material forming the vessel, it being possible to employ any further quantities of base metal required for this purpose in the form of ingots or other suitable shape. Nor is it necessary that the vessel consist of the base metal at all, it being equally possible to employ other metallic in gredients of the alloy for this purpose or even an ingredient which, after formation of the alloy, can be removed therefrom by subsequent volatilization. Finally the salt melt preferably employed can be put to repeated use, each batch of alloy, as and when formed, being tapped from the crucible and a further vessel containing the reaction mixture being introduced into the saline flux, which is then of course permanently kept at the required temperature.

The application of the invention will hereinafter be illustrated by a number of examples. The invention however is not limited thereto but may be suitably employed for producing alloys containing metals by the reduction of any of their easily volatilizable compounds, particularly alloys containing metals of the fifth and sixth groups of the periodic system, and also alloys containing cerium, particularly of low-melting light metals such as aluminium and magnesium, in which reduction of the oxides of alloying components frequently meets with some difliculty.

Example I 325 grms. of a reaction mixture consisting of 2400 P. B. W. of beryllium chloride (11.2 B.). 150 P. B. W. of sodium chloride and 735 P. B. W. of fine magnesium granules are pressed into a cylindrical capsule of copper sheet weighing 228 grms. The capsule is then gradually introduced into a melt of sodium chloride which has been heated to 1050" C. in a graphite crucible. That part of the capsule which first comes into contact with the hot melt conveys the heat into the interior, thus causing the contents of the capsule to react already when the temperature in the interior attains between 400 and 700 C. The reaction, which is further promoted by the heat of the reaction itself, rapidly spreads through the whole of the reaction mixture which latter becomes substantially fused. When the reaction is completed, the copper sheet forming the capsule also begins to melt and immediately takes up the beryllium formed in the course of the reaction while forming an alloy'therewith. The

7 performance of the reaction together with the subsequent formation of an alloy takes place within about two minutes. When the contents of the crucible have come to rest, they are quickly stirred whereupon the molten alloy formed is separated from the saline melt by decanting or tapping. 249.5 grms. of a copper beryllium alloy containing 9.7% of beryllium and 90.3% of copper are obtained in this manner. Thus it is seen that 91% of the beryllium introduced as beryllium chloride, and 98.8% of the copper forming the capsule have been recovered in the form of an alloy. The saline melt can be immediately employed for the preparation of a fresh batch of alloy.

Example II An intimate mixture of 38 P. B. W. of zirconium chloride (ZrCh), 9 P. B. W. of sodium chloride, 9 P. B. W. of magnesium chloride and P. B. W.

of metallic magnesium is Dressed into a cylindrical capsule of pure magnesium, the weight of such capsule in relation to the quantity of zirconium chloride employed being such that it suffices for the formation of a magnesium base alloy containing about 1% of zirconium: The capsule which is provided with a loosely fitting cover is inserted into a saline melt heated to about 850 C. The reaction between the magnesium and the zirconium chloride contained in the reaction mixture proceeds without perceptible volatilization of zirconium chloride from the capsule; after about two minutes the capsule itself melts while enveloping the reacted mixture and subsequently forms an alloy with the metallic zirconium. In order to ensure uniform composition of the alloy, the whole is then briefly stirred, and finally the molten alloy is cast by decanting or tapping.

Iclaim:

1. A process of producing alloys of a base metal with another metal formed by reduction of an easily volatilizable compound of said other metal which comprises disposing said volatilizable compound together with a reducing agent in a metal lic container the metal of which is adapted to alloy with the metal obtained from the volatilizable compound, the container having a melting point above the temperature necessary to cause the reaction of the embedded reduction mixture, and supplying heat to said container so that the reduction of the volatilizable compound takes place first without any appreciable melting of the container and thereafter, at further supply of heat, the container itself melts down and now alloys with the metal obtained from the volatilizable compound.

2. A process of producing alloys of a base metal with another metal formed by reduction of an easily volatilizable compound of said other metal, which comprises disposing said volatilizable compound together with a reducing agent in a metallic container the metal of which is adapted to alloy with the metal obtained from the volatilizable compound having a melting point at or above the temperature necessary to cause reaction of said substances and introducing said container into a molten saline flux heated to tem peratures adapted to cause melting of said container.

3. A process of producing alloys of a base metal with another metal formed by reduction of an easily volatilizable compound of said other metal, which comprises disposing said volatilizable compound together with a reducing agent in a container consisting of the base metal of the alloy to be formed and having a melting point at or .above the temperature necessary to cause reaction of said substances and inserting said container into a molten saline fiux heated to temperatures adapted to cause melting of said container.

4. A process of producing a heavy metal beryllium alloy which comprises disposing a mixture of a beryllium halide and a light metal adapted to reduce said beryllium halide, in reactive proportions in a container made from such heavy metal and gradually supplying heat to said container until said container is molten.

5. A process of producing a heavy metal beryllium alloy which comprises disposing a mixture of beryllium chloride and magnesium, in reactive proportions in a container made from such heavy metal and gradually supplying heat to said container until said container is molten.

6. A process of producing a magnesium zirconium alloy which comprises disposing a mixture of heavy metal and introducing said container into l0 a molten saline flux heated to temperatures adapted to cause melting of said container.

8. A process of producing a magnesium zirconium alloy which comprises disposing a mixture of a zirconiumhalide and magnesium in a magnesium container and introducing said container into a molten saline flux heated to temperatures adapted to cause melting of said container.

HELMUT VON ZEPPELIN.