US2041493A - Pulverulent alloy - Google Patents

Description

UNITED STATES PATENT OFFICE PULYERULENT ALLOY Leo Schlecht and Albert Helnzel, Ludwigshafenon-the-Rhine, Germany, minors to I. G. Farbenindustrie Aktiengesellschaft, Frankforton-the-Main, Germany No Drawing. Application January 19,1934, lsg-al' No. 707.339. In Germany Jan 24 17 Claims. (01. 75-122) The present invention relates to a process of der; it is often preferable to use other comproducing pulverulent alloys of metals capable pounds, for example nitrates which on heating of forming metal carbonyls. yield the substances hindering the fritting to-'v Pulverulent alloys, as for example of iron with gether". When working in a non-reducing atnickel, cobalt, chromium, molybdenum or tungmosphere the substances hindering the fritting sten, have hitherto usually been obtained by metogether may be prepared from the metals to chanical comminution of compact alloys. This be alloyed by slightly oxidizing the metal powder method of working is lengthy and costly because itself precedent to the heat treatment giving as a rule such alloys are very tough, especially rise to the desired alloy formation.

when they contain no carbon and oxygen. More- The addition substances are preferably mixed 10 over, the particles of powder readily become conas intimately as possible with the mixture of taminated with undesirable foreign substances; the pulverulent metals derived from carbonyls. their shape, also, is not uniform. A very intimate mixing is obtained for example We have now found that pulverulent alloys of by grinding the dry or wet mixture in a ball mill l5 metals forming carbonyls are obtained in an esor by making into a paste and triturating the pecially advantageous manner by thermally demetal powder with a solution or suspension of composing a mixture of the carbonyls of the dethe addition materials, as for example with a sired alloy constituents, coating the particles of i n of m n sium or aluminium nitrate. the resulting metal powder with a substance Small amounts of additional substances, as for hindering the fritting together thereof and then example less than 1 per cent, are usually sum- 20 heating the coated powder in a no oxidizing, cient to prevent the agglomeration ofthe pari. e. an inert or reducing atmosphere so that alloy ticles.

formation takes place by diffusion within the If it is desired to remove the additional subparticles of the metal powder without smelting. stances from the metal powder after the heat- The thermal decomposition of the carbonyl ing, substances are chosen which are capable of 25 mixture, which is employed for example in the subsequent removal by dissolution, as for exform of a mixture of two or more liquid or solid ample with dilute acids, by frothing or by magmetal carbonyls, or a solution thereof, for exnetic separation in conjunction with wind-siftample a solution of one or more solid metal caring.

bonyls in one or more liquid metal carbonyls, and Temperatures above 500 C. are suitable for 30 atomized or vaporized into the decomposition the heating of the metal powders with the addichamber, is preferably carried out at temperation substances for the purpose of forming altures below 450 C. in order to avoid too strong loys; at temperatures below 500 0., the formaa deposition of carbon. To produce the most tion of alloys usually takes place incompletely uniform distribution possible of the carbonyl and very slowly. It is preferable to work be- 35 mixture, other gases, as for example carbon tween 900 and 1000 C. The duration of heatmonoxide, carbon dioxide, nitrogen or ammonia, ing may be shorter the higher the temperature may also be introduced into the decomposition employed, and the smaller the size of the particles chamber, or the metal carbonyls may be atomized of the metal powder. It is especially advantageby means of such gases. In particular, decompoous to carry out the heating of the metal powders 40 sition in the hot free space of a heated vessel in a current of hydrogen because in this way the has proved advantageous because globular pardiffusion within the particles of the metal powticles of uniform size are thus obtained throughder is accelerated by the simultaneous volatilizeout. The vessel may be heated either externally, tion of the carbon usually present.

or by introducing hot inert gases into the vessel, The resulting alloy powders are distinguished 45 if desired in counter-current to the metal carby their purity and the globular shape of the bonyls introduced. single particles. The pulverulent alloys, espe- As coating substances hindering fritting tocially powders of alloys of nickel-iron containing gether as previously mentioned, refractory subpreferably between 40 and 80 per cent of nickel,

stances, as for example oxides of alkaline earth or nickel-iron-cobalt, in particular such as con- 50 metals, of magnesium, aluminium, beryllium and tain between 25 and 50 per cent of iron, between zinc and ceramic substances, silica, titanic acid 30 and 60 per cent of nickel and between 15 and other diflicultly fusible or diflicultly reducible and 30 per cent of cobalt, or alloys of the latter compounds, are used. It is not necessary to kind containing up to-10 per cent of molybadd these compounds as such to the metal powdenum or tungsten to increase the electric re- 55 sistance, have very good magnetic properties and consequently may be employed with special advantage for electromagnetic purposes, as for example ior the preparation of mass cores for Pupin coils or in the radio industry. When preparing alloys intended for electromagnetic purposes, the hydrogen treatment for decarbonizing the powder is preferably carried on until the carbon content of the powder has fallen to 0.04 per cent or less.

Sometimes it may happen that the mass obtained in the manner described slightly coheres. In such cases merely a slight mechanical treatment, for example by shaking or if desired grinding for a short time will produce the pulverulent alloy aimed at.

The following example will further illustrate the nature of this invention but the invention is not restricted to this example. The parts are by weight.

Example 20 parts of a nickel-iron powder, consisting of 41.8 per cent of nickel, 1.4 per cent of carbon and the remainder iron, which has been obtained by the thermal decomposition of a mixture of nickel carbonyl and iron carbonyl in the hot free space of a heated vessel, are made into a paste with a solution of 1.2 parts of aluminium nitrate in 4 parts of water. The resulting mass is heated for 12 hours at 1000 C. in a stream of hydrogen. The aluminium nitrate is thus converted into aluminium oxide and the carbon content of the powder is lowered to 0.04 per cent. The frothy, easily friable mass obtained after the heating may be readily converted into anextremely finely divided powder with globular single particles by grinding in a ball mill. The ground product is heated again for about half an hour at 800 C. and then worked up into mass cores for Pupin coils in the usual manner.

What we claim is:--

i. A process for producing pulverulent alloys of metals capable of forming metal carbonyls which comprises heating a mixture of at least two metal carbonyls at a temperature up to about 450 C. to decompose the carbonyls, coating the metal particles of the resulting powder with a substance hindering the fritting together and then heating the coated powder in a non-oxidizing atmosphere at a temperature sufliciently high to effect alloying by diffusion within the particles of the metal powder without smelting.

2. A process for producing pulverulent alloys of metals capable of forming metal carbonyls which comprises heating a mixture of at least two metal carbonyls at a temperature up to about 450 C. to decompose the carbonyls, coating the resulting powder with up to l per cent by weight of a substance hindering the fritting together and then heating thecoated powder in a nonoxidizing atmosphere at a temperature sufiiciently high to efiect alloying by diffusion within the particles of the metal powder without smeltns.

3. A process for producing pulverulent alloys of metals capable of forming metal carbonyls which comprises heating a mixture of at least two metal carbonyls at a temperature up to about 450 C. to decompose the carbonyls, coating the resulting powder with a substance hindering the fritting together and then heating the coated powder in a non-oxidizing atmosphere at a temperature above 500 C. to effect alloying by diffusion within the particles of the metal powder without smelting.

4. A process for producing pulverulent alloys of metals capable of forming metal carbonyls which comprises heating a mixture of at least two metal carbonyls at a temperature up to about 450 C. to decompose the carbonyls, coating the resulting powder with a substance hindering the fritting together and then heating the coated powder in a non-oxidizing atmosphere at a temperature between about 900 C. and about 1000 C. to eifect alloying by diffusion within the particles of the metal powder without smelting.

5. A process for producing pulverulent alloys of metals capable of forming metal carbonyls which comprises heating a mixture of at least two metal carbonyls at a temperature up to about 450 C. to decompose the carbonyls, coating the resulting powder with a substance hindering the fritting together" and then heating the coated powder in a reducing atmosphere at a temperature above 500 C. to effect alloying by diffusion within the particles of the metal powder without smelting.

6. A process for producing pulverulent alloys of metals capable of forming metal carbonyls which comprises heating a mixture of at least two metal carbonyls at a. temperature up to about 450 C. to decompose the carbonyls, coating the resulting powder with a substance hindering the fritting together and then heating the coated powder in a hydrogen atmosphere at a temperature above 500 C. to effect alloying by diffusion within the particles of the metal powder without smelting and thus producing an alloy with a carbon content of at the most 0.04 per cent.

7. A process for producing pulverulent alloys of metals capable of forming metal carbonyls which comprises heating a mixture of at least two metal carbonyls at a temperature up to about 450 C. to decompose the carbonyls, coating the resulting powder with a refractory substance selected from the group consisting of the oxides of the alkaline earth metals, magnesium and aluminium and then heating the coated powder in a non-oxidizing atmosphere at a temperature willciently high to effect alloying by diffusion within the particles of the metal powder without smelting.

8. A process for producing pulverulent alloys of metals capable of forming metal carbonyls which comprises heating a mixture of at least two metal carbonyls at a temperature up to about 450 C. to decompose the carbonyls, mixing the resulting powder with up to 1 per cent by weight of a refractory substance selected from the group consisting of the oxides of alkaline earth metals, magnesium and aluminium and then heating the resulting mixture in a hydrogen atmosphere at a temperature between about 900 and about 1000 C. to efiect alloying by diffusion within the particles of the metal powder without smelting and thus producing an alby with a carbon content of at the most 0.04 per cent.

9. A process for producing pulverulent alloys of metals capable of forming metal carbonyls which comprises heating a mixture of at least two metal carbonyls at a temperature up to about 450 C. to decompose the carbonyls, coating the resulting powder with at least one substance which on heating yields a substance hindering the fritting together and then heating the coated powder in a non-oxidizing atmosphere at atemperature sumciently high to effect alloying by diii'usion within the particles of the metal powder without smelting.

10. A process for producing pulverulent alloys 01' metals capable of forming metal carbonyls which comprises heating a mixture oi at least two metal carbonyls at a temperature up to about 450 C. to decompose the carbonyls, coating the resulting powder with at least one substance which on heating yields a substance hindering the fritting together" and then heating the coated powder in a non-oxidizing atmosphere at a temperature above 500 C. to eiTect alloying by diffusion within the particles of the metal powder without smelting.

11. A process for producing pulverulent alloys of metals capable 01' forming metal carbonyls which comprises heating a mixture of at least two metal carbonyls at a temperature up to about 450C. to decompose the carbonyls, coating the resulting powder with at least one substance which on heating yields a substance hindering the fritting together and thenheating the coated powder in a reducing atmosphere at a temperature above 500 C. to effect alloying by diii'usion within the particles of the metal powder without smelting.

12.v A process for producing pulverulent alloys of metals capable of forming metal carbonyls which comprises heating a mixture of at least two metal carbonyls at a temperature up to about 450 C. to decompose the carbonyls, coating the resulting powder with at least one substance which on heating yields a substance hindering the fritting together" and then heating the coated powder in a hydrogen atmosphere at a temperature between about 900 and about 1000 C. to eiiect alloying by diflusion within the particles of the metal powder without smelting and thus producing an alloy with a carbon content of at the most 0.04 per cent.

13. A process for producing pulverulent alloys of metals capable of forming metal carbonyls which comprises heating a mixture of 'at least two metal carbonyls at a temperature up to about 450 C. to decompose the carbonyls, slight- 1y oxidizing the particles or the resulting metal powder and then heating the powder in an inert atmosphere at a temperature sumciently high to effect alloying by diflusion within the particles oi the metal powder without smelting.

14. A process for producing pulverulent alloys of metals capable of forming metal carbonyls 5 which comprises heating a mixture of at least two metal carbonyls at a temperature up to about450 C. to decompose the carbonyls, slightly oxidizing the particles 01' the resulting metal powder and then heating the powder in an inert atmosphere at a temperature above 500 C. to effect alloying by diffusion within the particles of the metal powder without smelting.

15. A process for producing pulverulent alloys of metals capable of forming metal carbonyls which comprises heating a mixture of-at least two metal carbonyls at a temperature up to about 450 C. to decompose the carbonyls, slightly oxidizing the particles of the resulting metal powder and then heating the powder in an inert atmosphere at a temperature between about 900 and about 1000 C. to eil'ect alloying by dii'- fusion'within the particles of the metal powder without smelting.

16. A process for producing pulverulent alloys of metals capable of forming metal carbonyls which comprises heating a mixture of at least two metal carbonyls at a temperature up to about 450 C. to decompose the carbonyls, slightly oxidizing the particles 01' the resulting metal powder and then heating the powder in a nitrogen atmosphere at a temperature suiliciently' high to efl'ect alloying by diilusion within the particles of the metal powder without smelting.

1'7. A process for producing pulverulent alloys of metals capable of forming metal carbonyls which comprises heating a mixture of at least two metal carbonyls at a temperature up to about 450 C. to decompose the carbonyls, slightly oxidizing the particles of the resulting metal 43 powder and then heating the powder in a nitrogen atmosphere at a temperature between about 900 and 1000 C. to eii'ect alloying by diflusion within the particles of the metal powder without smelting. 45-

LEO SCHLECHT. ALBERT