US2536362A

US2536362A - Treatment of molten metals

Info

Publication number: US2536362A
Application number: US133954A
Authority: US
Inventors: Clyde T Gallinger; William R Huey
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1949-12-19
Filing date: 1949-12-19
Publication date: 1951-01-02
Anticipated expiration: 1968-01-02

Description

Patented Jan. 2, l9l

2,536,362 (UNIT D STATES? PATENT OFFICE 2,536,362 7 v TREATMENT OF MOLTEN METALS Clyde T. Gallinger, Wilmington, on, and William R. Huey, swarthmore, Pa, assigno'rs toE. I. dii Pont de Nemours' & Company, Wilmington, DeL, a corporation of Delaware No Drawing.

invention relates to the treatment or niolt'en heavy metals with alkali metals and more particularly to a new and improvedmethod for adding a, low boiling alkali metal such as sodium to a melt of a heavy metal such as copper, iron or steel.

It has been known for many years that the addition of an alkali metal to heavy metalss'ch as steel, iron or copper has considerable utility in removing oxides and other impurities from the molten metal. Because of its cheapness and availability in large quantities, sodium is the preferred alkali metal for this purpose. However, despite the many proposals: that have been made for accomplishing such addition of sodium to heavy metal melts, heretofore this has been practiced commercially only to a verylimited extent. The addition of sodium in the solid or liquid state is fraught with considerable hazard because of its boiling point (880 C.), which isseveral hundred degrees below the melting point of iron or steel. The addition of liquid or solid bath or by introducinginto the molten bathcapsules of iron or lead filled with sodium. Such methods usually cause violent and hazardous disturban-ces in the molten bath. It has been found that sodium can safely be added to steel by pass-'- ing a gaseous mixture of sodium vapor and nitrogen into the molten metal, but thismethod re quires additional and rather costly equipment and so far has not gone into commercial use.

An object of the present invention is an improved, relatively non-hazardous method for the addition of the low boiling alkali metals into molten heavy metal baths having temperatures around 1000 C. and higher. A further object is an improved method for treating molten ferrous metals such as steel and'oast iron with sodium. Another object is to treat a molten metal at a temperature above 1 000 C. by adding thereto another metal whose boiling pointlies below the temperatilreoi the molten metal. Still other objects will be apparent from the following description of the invention.

In accordance with the present invention the above objects may be attained by introducing into a molten heavy metal having a temperature above about 1000" C. a dispersion of finely divided sodium (or other alkali metal boiling below 1000 C.) inaa carbonaceous liquid. Such dispersions may be made by agitating a carbonaceous liquid such as kerosene or other petroleum hydrocarbon or the like with the alkali metal at Application December 19, 1949, I Serial No. 133,954

8 Claims. (CL-"7 5 5 8) alkalime'ta'l enters the melt without causing any harmful or hazardous agitation of the molten 1 bath.

By way of illustration, the invention is particularly welladapted for the addition of sodium to baths of molten cast iron or steel. This may be conveniently done by pouring a stream of the molten metal, for example, from a furnace or a cupola,' in to adadle orother suitable container and simultaneously pouring in a stream ofsodium dispersiom, preferably so that the two streams intermingle within the ladle. As an example of this mode of operation, one thousand pounds of molten cast iron was poured into a crucible while a stream of a sodium dispersion in kerosene was introduced simultaneously, close to the stream of inflowing molten iron. The sodium dispersion contained 42% by weight of sodium and was forced in a conventional manner by;

means of nitrogen pressure from a container through a small tube ending in an orifice diameter. The tube was arranged to direct the streamof sodium against the stream of molten iron flowinginto the crucible. In this way 242- grams of sodium were added in a period of about 39 seconds. Flames of burning kerosene appeared above the cruciblebut there was no violent or; hazardous disturbance of the molten metal.

In previous tests, sodium was, added to a crucible or ladle while molten cast iron or molten steel, was poured therein, by throwing in small pieces of sodium or iron capsules filled with sodium or ironor, steel outof the crucible or ladle, constitutin an unusually hazardous operation.

The present invention is not restricted to the above mode of operation but any suitable means. for contacting the sodium dispersions with thev It is generally. preferred to pour a stream of the. sodium disper-,. sion against, or in proximity to, a, stream of. moltenmetal entering a container such as a ladle. or crucible, .so that the down-flowing stream of. metal will carry the dispersion, or sodium released from it, beneath the surface of the molten.

molten metal may be utilized.

dispersionjrom' an orifice placed close to, or.-

beneath, the surface of the molten bath. Also, if desired, the sodium dispersion may be merely poured onto the surface of the molten metal. In such operation, of course, the surface of the melt must be free of slag or other covering layer which would prevent contact of the dispersion with the molten metal. It is generally preferable, however, to introduce a stream of the sodium dispersion simultaneously with a stream of molten metal entering a container such as a crucible, ladle or mold.

While it is preferred to employ sodium in the practice of this invention, the present description applies equally to the other alkali metals which have atmospheric boiling points below 1000 C., i. e., potassium, cesium and rubidium. Herein, the term low boiling alkali metals is employed to designate sodium and the other alkali metals which boil at temperatures below 1000" C. at atmospheric pressure. If desired, mixtures or alloys of the low boiling metals with each other or with other substances may be used, particularly mixtures or alloys containing at least 50 molar percent of low boiling alkali metal.

The various known dispersions of sodium or other low boiling alkali metals in carbonaceous materials may be utilized in practicing the invention. Thus, the sodium may be dispersed in a low boiling hydrocarbon such as kerosene, in light or heavy hydrocarbon oils or in other carbonaceous materials such as parafiin waxes, aromatic hydrocarbons, asphalts, pitch and the like. Such dispersions can conveniently be prepared by stirring such carbonaceous substances at temperatures at which both they and the sodium are in liquid state until the sodium is dispersed into particles of a diameter not greater than about 1 or 2 millimeters. Preferably, I prefer to disperse the sodium in a light hydrocarbon such as kerosene with the addition of a dispersing agent such as a fatty acid so as to produce a stable dispersion of sodium particles averaging not greater than around 100 microns diameter. Methods for preparing particularly suitable dispersions are described in the U. S. patents to V. L. Hansley, Nos. 2,394,608; 2,487,333; and 2,487,- 334. Such stable dispersions may be shipped and stored for long periods of time and may be readily introduced through a pipe or tube by flow induced by gravity or by pressure of nitrogen gas on a container filledwith the dispersion. The

carbonaceous dispersant should be substantially chemically inert to the alkali metal and preferably will be volatile or will have or form volatile components at the temperatures encountered in use, so that vapor thereof will burn when the dispersion is added to the metal melt.

The invention is not restricted to the addition of sodium or other low boiling alkali metal to steel but may be used for the addition of those alkali metals or alloys thereof to any molten metal, the temperature of which is about 1100 C. or higher, for example, melts of iron, cast iron, all grades of steel, copper, nickel, silver and various alloys, e. g., brass, various bronzes, Monel and Nichrome. The invention also is suitable for alkali metal treatment of the various ferroalloys such as ferro-chrome, ferro-vanadium, ferro-nickel, ferro-manganese and the like. The dispersion further may be employed to incorporate alkali metal into melts of low melting metals, such as lead, tin and the like, particularly when the melts are at temperatures of such as 1000 C. and higher.

The present invention further may be utilized to add to a molten metal at a temperature of about 1000 C. or higher, a proportionately small amount of any treating metal whose atmospheric boiling point is below the temperature of the melt. In such operations, the high temperature 5 of the molten metal causes rapid vaporization of the treating metal as added, resulting in hazardous disturbance of the melt. By adding the treating metal in the form of a dispersion in a carbonaceous material in accordance with the present invention, such additions may be made with little or no disturbance of the melt.

We claim:

1. In a process for treating a molten metal at a temperature not lower than about 1000 C., by adding thereto a treating metal, whose atmospheric boiling point is below the temperature of said molten metal, the step comprising adding to said molten metal a .dispersion of said treating metal in acarbonaceous substance.

molten metal, the temperature of which exceeds 1000 C., a dispersion in a liquid hydrocarbon of a metal boiling below the temperature of said molten metal.

3. The process which comprises adding to a molten metal having a melting point above about 1000 C., a dispersion of a low boiling alkali metal in a carbonaceous substance.

4. The process which comprises adding to a molten metal having a melting point above about 1000 C., a dispersion of a low boiling alkali metal in a liquid hydrocarbon.

5. The process which comprises flowing a stream of a molten metal having a melting point above about 1000 C. into a container and simultaneously flowing into said container a stream of a dispersion of an alkali metal in a carbonaceous liquid.

6. The process which comprises flowing a stream of a molten ferrous metal into a container and simultaneously flowing into said container a stream of a dispersion of sodium in a carbonaceous liquid.

'7. The process which comprises flowing a a stream of a molten steel into a container and simultaneously flowing into said container a stream of a dispersion of sodium in a liquid hydrocarbon.

8. The process which comprises flowing a w stream of a molten cast iron into a container and simultaneously flowing into said container a stream of a dispersion of sodium in a liquid hydrocarbon.

CLYDE T. GALLINGER.

55 WILLIAM R. HUEY.

REFERENCES CITED The following references are of record in the file of this patent:

Great Britain Dec. 17, 1930 2. The process which comprises adding to a-

Claims

2. THE PROCESS WHICH COMPRISES ADDING TO A MOLTEN METAL, THE TEMPERATURE OF WHICH EXCEEDS 1000* C., A DISPERSION IN A LIQUID HYDROCARBON OF A METAL BOILING BELOW THE TEMPERATURE OF SAID MOLTEN METAL.