US2085802A - Treatment of metals - Google Patents

Description

Patented July 6, 1937 2,085,802 TREATMENT OF METALS Charles Hardy, Pelham Manor, N. Y., assignor, by mesne-assignments, to Charles Hardy, Inc., New York, N. Y., a corporation of New York No Drawing. Application August 22, 1935,

Serial No. 37,331

' 7 Claims. (01. 7558) UNITED STATES PATENT OFFICE This invention is concerned with the intro duction of alkali or alkaline-earth metals into molten baths of metal to purify or alloy with the metal of the bath, and contemplates a novel method whereby this may be accomplished. The invention also contemplates a novel method of preparing alkali or alkaline-earth metals for introduction into molten metal baths as well as a means for preserving these metals during storage, prior to their use in metallurgical operations. The invention further contemplates the provision of a new article of manufacture in which alkali or alkaline-earth metals are preserved in a convenient form for use in metallurgy and allied arts.

It has been proposed heretofore to employ alkali and alkaline-earth metals in the purification of base metals. Thus it has been proposed to add calcium in lump form to molten baths of base metal such as iron, the efiect of the lump calcium thus added being to remove impurities such as orwgen, silicon and phosphorus from the bath combined with the calcium in a slag. It has also been proposed to agglomerate finely divided alkali and alkaline-earth -metals with finely divided alloy metals and to introduce the agglomerate into molten metal baths to purify or alloy with the base metal of the bath. While these proposals for employing calcium and other alkaline earth or alkali metals offer great advantages, the rapidly expanding use of calcium and other alkali and alkaline-earth metals has made it desirable to produce these metals in a more convenient form which; may be stored for long periods without danger of undue oxidation.

The alkali metals such as sodium and potassium and the alkaline-earth metals such as barium, strontium, calcium and magnesium are oxidized very readily. Storage of these metals, therefore, presents a serious problem. Thus, lump calcium even in relatively tight containers, tends to oxidize; and this oxidation represents a potential loss when it is sought to utilize the properties of calcium for removing impurities in metal baths. The agglomeration of finely divided alkali or alkaline-earth metals with other finely divided metals to form a briquette does not always prevent the aforementioned undesirable oxidation. In such briquettes the tendency for rapid oxidation of the alkali and alkaline-earth metals may persist and infact may be aggravated by the presence of metals which are less electro-positive than the alkali and alkaline-earth metals. The alkali metals such as caesium, rubidium, potassium, sodium, and lithium, and the alkalineearth metals such as barium, strontium, calcium and magnesium stand at the head of the electro-motive force series of metals. In other words, the alkali and alkaline-earth metals will replace any other metals present in a compound, and are, of course, preferentially oxidized (if at all) when coupled with other metals. Furthermore, the galvanic effect caused by difference in potential between particles of alkali or alkalinel0 earth metals and other metals may tend to accelerate the oxidation of the alkali or alkalineearth metals.

Unless extremely high pressures are used, (and often this is not commercially feasible) it is dif- 15 ficult to obtain-an agglomerate of finely divided -metals which is not porous. Porosity, by increasing the exposed surface of alkali or alkalineearth metals per unit of volume, also tends to increase oxidation.

In view of the fact that alkali and alkalineearth metals are seldom employed in metallurgical operations immediately after their production, and because it is necessary to have an adequate supply on hand, the alkali or alkalineearth metals should be prepared in such a form that they will keep for indefinite periods without substantial deterioration.

As a result of my investigations, I have developed a method whereby alkali and alkalineearth metals may be placed in a form for convenient metallurgical use and, moreover, may be stored for indefinite periods. I have also developed a method whereby alkali or alkaline- .earth metals may be added to, molten baths of metal with the assurance that a maximum utilization of the metals may be obtained. As previously indicated, my invention also contemplates the provision of a new article of manufacture for the storage and subsequent utilization of the alkali 40 and. alkaline-earth metals in metallurgy.

In accordance with my invention I prepare elongated pieces of cores of alkali or alkalineearth metals, preferably by extrusion, and sheathe these elongated pieces in metal or other mathrough a molten bath of another metal under practice of my invention, I heat calcium to this temperature range in the absence of oxygen and preferably in an inert or reducing atmosphere. The calcium is then extruded and sheathed with a coating of another metal without giving the calcium an opportunity to oxidize substantially. Preferably, the sheath comprises metal corresponding to the base metal bath in which it is.

proposed to employ the calcium. In another preferred modification of my invention, the sheath comprises alloy metals which are to be added to the bath of base metal. If it is, proposed to utilize the calcium in the purification. of copper, for example, the freshly extruded calcium may be introduced immediately into a tightly fitting copper tube. In the application of my invention to steel metallurgy, it is convenient to extrude the calcium into a tightly fitting tube of ,a chromiumiron alloy, of a vanadium-iron alloy, or of other suitable iron or steel alloys. If the dimensions of the core and the sheath are properly chosen, the sheathed calcium may be rolled into coils, from which appropriate lengths may be cut from time to time as the uses of the material dictate.

In another aspect of my invention, I contemplate the extrusion of calcium and other alkali or alkaline-earth metals into metal sheaths, thereafter cutting the sheathed material into con- -venient lengths and crimping the ends so as to completely enclose the core and form a convenient cartridge.

Calcium is often introduced into lead alloys used in the manufacture of cable sheathings, storage battery grids, bearings, and related materials. In accordance with my invention, I extrude calcium into a rod or wire at a temperature between 420 C. and 460 C. in a non-oxidizing atmosphere, cool the rod under non-oxidizing conditions, and draw it immediately through a bath of molten lead maintained at such a temperature that the lead congeals on the surface of the calcium rod to form a thin and substantially uniform sheathing. The sheathed calcium is then in a convenient form for storage and may be utilized at any time in the preparation of a lead alloy.

Assume that it is desired to make a lead alloy containing a certain percentage of calcium. A known weight of lead is melted, and into the resulting molten bath is introduced a predetermined length of the lead-sheathed calcium rod, either in cartridge form or as: cut from the end of a longer piece which may be conveniently kept in the form of a coil. The calcium thus introduced together with the lead sheath are melted and the calcium alloys immediately with the lead upon slight agitation.

The following specific example illustrates the preparation of calcium and other alkali or alkaline-earth metals for use in deoxidizing copper:

A supply of calcium is placed in a container from which air is excluded, heated with an oxyacetylene flame of reducing nature to a temperametal or combinations ture between 420 C. and 460 C., and extruded through an extrusion press into a wire approximately one-quarter of an inch in diameter. The calcium wire is thrust promptly into a copper tube having a thin wall and an internal diameter of approximately one-quarter inch. The op- .eration is facilitated by heating the copper tube slightly so as to expand it. Upon cooling, the copper tube shrinks so as to envelop the calcium core tightly. The operation should be conducted in the absence of oxygen or with suflicient promptness that the calcium is not oxidized appreciably. Otherwise, the calcium wire not only oxidizes but becomes fissured.

In another modified practice of my invention the alkali metal, the alkaline-earth metal or combination thereof is extruded into a tube of a slag-forming constituent such as silica, or alumina.

When calcium or other alkali or alkaline-earth metal is to be introduced into molten baths of iron or steel, it is convenient to insert the sheathed calcium rod or cartridge. into an aperture in the end of a heavy iron or steel rod or pipe of sufficient length that the pipe can be inserted into a ladle or furnace and the end containing the calcium pushed down to the bottom thereof. In this way, the calcium core and the metal sheath may be held below the surface of the molten bath until the reaction or the solution of alloy constituents is complete. The natural buoyant effect of the molten bath is thus counteracted and a complete utilizationof the materials introduced is assured.

In the event that it is desired to introduce a long length of sheathed calcium into a metal bath the sheathed calcium can be unrolled and gradually thrust into the bath until a predetermined length has been consumed. In this way, the unconsumed portion of the coated calcium serves as a handle whichpermits the material to be thrust deeply into the bath.

When short pieces of sheathed rods or crimped cartridges are employed, these may be propelled into the bath with an air-gun or other device to a depth such that reaction or solution will occur before the rod or cartridge is buoyed to the surface.

When the cross-section of the coated calcium rod or wire is substantially uniform it is an easy matter to calibrate the length in terms of the weight of calcium contained. It is easy to determine, for example, how many pounds of calcium is contained in a running foot of the rod. This is of advantage in metallurgical operations in that a given charge of calcium, or other alkali or alkaline-earth metal, may be determined by simple linear measurement, the necessity for weighing the charge being eliminated.

It will be understood that the invention is not limited to the specific examples given. Any alkali or alkaline-earth metal may be employed as the core and any other metal employed as the sheath providing that the metallic ingredients of the sheath are not deleterious to the molten bath into which the alkali oralkaline-earth metal is introduced. Other modifications of my invention will undoubtedly occur to the man skilled in the art without, however, departing from. my inventive concepts.

I claim:

1. An elongated metal object having a solid continuous core of relatively small and of substantially uniform cross-section composed of an extruded metal selected from the group-consist- 75 ing of the alkali and alkaline-earth metals, said core being enveloped by a thin continuous tightly fitting sheath of substantially uniform cross-section composed of a' dissimilar metal which is more resistant to oxidation than the core, said sheath being crimped at the ends to seal the extruded metal from the atmosphere.

2. An elongated flexible coiled metal object having a solid core of uniform and relatively small cross-section composed of a metal selected from the group consistirg of the alkali and alkalineearth metals and a tightly fitting open-ended substantially imperforated sheath of substantially uniform cross-section composed of a dissimilar metal that is more resistant to oxidation than the alkali or the alkaline-earth metals fitted tightly around the core.

. 3. An elongated coiled metal object which comprises a calcium metalcore of relatively small and substantially uniform cross-section and a tightly fitting protective sheath of substantially uniform cross-section composed of a dissimilar metal which is more resistant to oxidation than calcium.

4. A method of introducing metals selected I from the group consisting of the alkali and alkaline earth metals into a molten bath of base metal which comprises forming an elongated subtube, introducing the piece into the molten bath;

and melting it therein.

5. Method according to claim 4 in which the core of alkali or alkaline earth metal is introduced into a heated tube having an internal diameter approximating the external diameter of the core and the tube is thereafter allowed to cool so'that it shrinks tightly about the'core.

6. Method according to claim 4 in which the core of alkali or alkaline earth metal is extruded into the tube in a non-oxidizing atmosphere.

'7. A long wire of relatively small and uniform cross-section having a core of metal selected from v the group consisting of the alkali and alkaline earth metals surrounded by a tightly fitting continuous sheathof a less easily oxidizable metal.

CHARLES HARDY.