US2116891A - Process for the production of solder and terne metals - Google Patents

Description

till

atentedl May 10, 1938 arisen class F a rnonnorron or SQLDER AND 'ihhlillt METALS dirt ilanah, Philadelphia, Fa,

Application done to, 1193?,

Serial No. %541 8 Claims.

materials lrom non-ierrous scraps and lay-prodncts consisting principally of lead and tin. and also containing antimony, as Well as some amounts of arsenic, zinc, copper, etc.

another object is to utilize scrap metals, such as loahhitts, hard metals or anti-friction metals, tor the production oi solder metal.

.iinother ohiect is to utilize scrap metals oi the foregoing character in the production of terne metals.

Another ohlect oi the invention is to reduce the antimony, slnc, arsenic, etc, content oi the aforesaid non-ferrous metallic scraps.

holder metals are alloys oi lead and tin and, commercially, contain from to 50% of tin.

, ilrnall amounts oi antimony are also present. in

colder metals permissible tolerances of antimony range from 0.1% to 1%. However, the heat soltier metals are those in which the antimony does not eaceed il.2d%.

Terrie metals are alloys oi lead and tin, in which the tin content does not exceed 25%, and should not contain more than @2570 oi antimony.

The basic materials, from which the solder and terne metals are produced according to the present invention, are heterogeneous mixtures oi various non ierrous scraps, residues and lay-prodncts which are not readily converted by inertpensive methods into commercially marketable products.

have discovered that heterogeneous mixtures various non-ferrous metallic scraps of the iorcgoing character may he molten and that it is possible, at comparatively low temperatures, to eliminate therefrom antimony, arsenic, copper, zinc, etc. In carrying out the invention it is advisable so to commingle the various scraps, depending upon their lead and tin contents, as to obtain a final alloy which will have the desired proportions of tin and lead. The elimination therefrom of antimony, copper, zinc, and arsenic will leave an alloy of lead and tin having the particularly required characteristics. The antimony is removed from the molten alloy by means oi an alkali metal, such as metallic sodium. This operation also results in the removal of the (@711. ill-63) arsenic. The zinc is removed in the coarse of the operation by means of a caustic alhali, such as sodium hydroxid, the use of which is herelmalter described. Copper, if it be present in errcessive quantities, is removed prior to the opera tion for removal of the antimony, arsenic and zinc, and that step will he hereinafter described.

the process is carried out by melting the all-- love or. metals to be treated in a ltettlc and main taining the temperature at not more than dd F. to 150 F. alcove the melting point. v

The molten metal contained in the nettle is then covered with a layer of caustic alltali, such as haired sodinrn hydroxid. This haired material. iorms an effective sealing layer. it may he shoveled on to the surface of the molten metal and thereby distributed evenly over the surface.

Metallic sodium; comes in the trade normally in the form; of ingots, Weighing about twelve pounds each. coated with heavy mineral oil lay immersion thereof in the oil. it. heavy mineral oil oi the de sired characteristics is either a motor lubricating oil, or a heavy fuel oil.

The oil coated ingot of sodium is then inserted 25 into a crutch and the crotch then lowered into the molten rnetal. By means of this arrangemeat the sodinrn' is completely innn'ersed with in the molten alloy and, as it melts, it is ahle chemically to react with the antimony oi the molten metal. at the temperature at which the molten alloy is maintained, the oil, which coats: the pig oi sodium, is rapidly volatiliaed; This causes considerable ebullition and the bubbles hie-air through the surlace. The vapor oi the volatilized mineral oil produces a protective gas oils layer over the suriace on the kettle. It pro dates a considerable smoke pail and sometimes hreairs into home. The coating of the sodi with the mineral oil prevents the inetalirorn lg niting spontaneously. Since the reaction of the sodium with the molte metal or alloy is errothermic, from this point on no external heat is applied to the kettle containing the molten metal.

The sodium and antimony unite to form definite intermetallic compounds. Ii arsenic be present in the raw materials, the sodium-antimony compound will also include the analogous sodium-arsenic compound which is formed at the same time. They have a lower specific grav 50 ity than the molten metal or alloy from which they separate and rise to the surface. However, a small amount thereof is retained in solution by the molten metal.

These inter-metallic compounds are crystal- The ingots oi the sodium are line, and the crystaiswill interstitially occlude considerable amounts of tin and lead. On com ing into contact with caustic soda, the sodium intermetallic compounds with antimony and arsenic dissolve therein, and consequently the greater part of the tin and lead carried by the compounds is released and falls back into the molten metal. Inasmuch as these sodium compounds spontaneously ignite at the temperature of operation, the caustic soda layer also serves as an ignition preventive. The protective gas layer resulting from the volatilization of the mineral oil also plays an important role in suppressing the spontaneous ignition.

The intermetallic compound of sodium and antimony, in combination with the layer of sodium hydroxid, at the temperature of operation, forms a skim or layer of pasty or mushy consistency. From time to time this mushy material is removed from the surface of the melt by means of a perforated skimmer.

The quantity of sodium required in the operation is predetermined from an analysis of the material to be treated, and the operation is continued until the calculated amount of sodium has been consumed.

At this point it may be convenient to withdraw a small quantity of the molten material from the kettle and analyze it for its antimony content. If it be found that the antimony content does not exceed the limit of acceptable tolerance by more than 0.15% to 0.20%, caustic soda is then stirred into the metal, preferably by a mechanical mixer, to dissolve that portion of the sodium-antimony, arsenic compounds which were retained in solution by the molten metal.

However, if the antimony content does exceed the limit of tolerance by more than the above amounts, additional metallic sodium is required to complete the treatment.

It is necessary at all times to maintain a layer of flaked sodium hydroxid on the surface to combine with the intermetallic compound. This may be accomplished by adding the flaked sodium hydroxid in accordance with the requirements of the operation.

The bulk of the excess sodium remaining within the molten alloy or metal may be removed by means of steam. This operation is carried out by the introduction of water into the melt through appropriate tubes. The water is vaporized at the temperature of the molten metal and furnishes the steam which reacts with the sodium, forming hydrogen and sodium oxid. The sodium oxid rises to the surface of the molten metal or alloy. A fine spray of water is played on the surface, thereby converting the sodium oxid to sodium hydroxid, which further serves to combine with more of the sodium-antimony compound.

The last traces of excess sodium, however, are removed by means of sulphur. Either flower or stick sulphur is stirred into the metal. This also serves to remove the remainder of the copper contained in the molten metal or alloy. The metal resulting from the manipulation described is a commercial solder metal.

The material, which was skimmed from the surface of the molten metal and which consists predominantly of sodium hydroxid and the sodium-antimony intermetallic compound, is mixed with a quantity of silica, such as sand and coal, or coke breeze (rice), and the mixture is fused at about 1000 F. to 1200 F.

The sodium contained in the sodium-antimony arsenic compounds and the caustic soda react to form a slag consisting of sodium hydroxid, sodium carbonate and sodium silicate. The antimony and arsenic, if present, together with some tin and lead resulting from this fusion, is free from sodium and can be utilized for the production of antimony alloys, such as anti-friction metals or type-metals.

Copper is soluble only to a limited extent in alloys of lead and tin. Pure tin in the solid state will dissolve 2.5% of copper. Pure lead in the solid state will dissolve 0.06% of copper. In alloys of these metals the copper retained in solid solution ranges between the foregoing percentages. Thus, if alloys of lead and tin contain greater quantities of copper than the solubility limits of the copper at or slightly above the melting point, i. e., from 50 F. to-150 F. above the melting point, the excess copper separates out from the mother metal and rises to the surface in the form of mush compounds. These mush compounds contain the copper in form of copper-tin and copper-antimony compounds, together with quantities of the mother metal.

Upon' introduction of the sodium into the molten metal to form the sodium-antimonycompound, there results a further separation of the copper from the molten lead and tin alloy. In order to avoid copper contaminationof the antimony subsequently tobe recovered, it is necessary to reduce the copper content of the original melt to a point where the copper will, at all temperatures, remain completely soluble in the tin and lead alloys.

This is accomplished by a preliminary reduction of the copper content of the molten scraps or other metals to be converted into solder or Zinc also forms intermetallic compounds with copper and antimony, and excessive quantities of zinc will rise to the surface with the mushy compounds. That portion of the zinc which is, nevertheless, retained in solution is removed during the course of the processing with the alkali metal and the caustic soda.

The advantage of the foregoing process lies in the fact that it is carried out at comparatively low temperatures. When carried out at high temperatures, considerable quantities of sodium and caustic soda are lost. Furthermore, at high temperatures the fumes of these substances are irritating. Theycause great discomfort to the workmen engaged in the operation, as well as other persons throughout the plant.

A specific example of the operation of this process is summarized as follows: In the operation of'the process computations of the amounts of soda and sodium hydroxids to be used are based upon the quantity of antimony present in the mixture from which the solder or terne metals are to be produced. The arsenic and zinc are computed as antimony. The metallic sodium used is equal to one-half of the antimony and the from non-ferrous metallic scraps and wastes,

such as babbitts, white metals and the like, which comprises the decopperization thereof to a point where the copper will not separate out from the metal or alloy upon treatment for removal of antimony, arsenic and zinc by means of alkali metals and caustic alkali, and removing antimony, arsenic and zinc by means of an alkali metal and caustic alkali.

2. Process of producing solder or terne metals from non-ferrous metallic scraps and wastes, such as babbitts, white metals and the like, which comprises melting the same and heating to a temperature not exceeding 50 to 150 F. above the point where the entire material becomes molten, decopperizing said melt to a point where the copper will not separate out from the metal or alloy upon treatment for removal of antimony, arsenic and zinc by means of metallic sodium and caustic soda, and removing antimony, arsenic and zinc by means of metallic sodium and caustic soda.

3. Process of producing solder or terne metals from mixtures of non-ferrous metallic scraps and wastes, such as babbitts, white metals and the like, which comprises melting the same and heating to a temperature not exceeding 50 to 150 F. above the point where the entire material becomes molten, decopperizing said melt to a point where the copper will not separate out from the metal or alloy upon the addition of metallic sodium and caustic soda, removing antimony, arsenic and zinc by means of metallic sodium and caustic soda, and removing the unconsumed metallic sodium from the melt by means of steam.

4. In the process for the production of solder br terne metals from mixtures of non-ferrous metallic scraps and wastes, such as babbitts, white metals, and the like, which comprises melting same and heating to a temperature not exceeding 50 to 150 F. above the point where the entire material becomes molten, decopperizing same to a point where copper will not separate out from the metal or alloy upon the addition of Na and NaOH, the step for the removal of antimony,

arsenic and zinc, which comprises covering the surface of the molten metal or alloy with a layer of flaked or granular caustic soda to form an effective cover, coating the metallic sodium with a heavy oil, such as a heavy mineral oil, and introducing said coated metallic sodium under the surface of the molten metal to form compounds of sodium with antimony, arsenic and zinc, and removing the commingled compounds of sodium and caustic soda from the molten metal. 1

5. Process for the recovery of antimony from the sodium-antimony caustic soda skim formed in removing said metal from babbitts, white metals and the like, by means of metallic sodium and caustic soda, which comprises the fusion of same with silica, such as sand, and carbon, such as coal, or coke, and separating the slag thus formed from the antimony regulus.

6. Process of producing solder or terne metals from non-ferrous metallic scraps and wastes, such as babbitts, white metals and the like, which comprises melting the same and heating to a temperature not exceeding 50 to 150 F. above the point where the entire material becomes molten, decopperizing said melt to a point where the copper will not separate out from the metal or alloy upon treatment for removal of antimony, arsenic and zinc by means of alkali metal and caustic alkali, and removing antimony, arsenic and zinc by means of alkali metal and caustic alkali.

'7. Process of producing solder or terne metals from mixtures of non-ferrous metallic scraps and wastes, such as babbitts, white metals and the like, which comprises melting the same and heating to a temperature not exceeding 50 to 150 F. above the point where the entire material becomes molten, decopperizing said melt' to a point where the copper will not separate out from the metal or alloy upon the addition of metallic sodium and caustic soda, removing antimony, arsenic and zinc by means of metallic sodium and caustic soda, and removing the major portion of the unconsumed metallic sodium from the melt by means of steam.

8. Processor producing solder or terne metals from mixtures of non-ferrous metallic scraps and wastes, such as babbitts, white metals and the like, which comprises melting the same and heating to a temperaturelnot exceeding 50 to 150 F. above the point where the entire material becomes molten, decopperizing said melt to a point where the copper will not separate out from the metal or alloy upon the addition of metallic sodium and caustic soda, removing antimony, ar-

senic and zinc by means of metallic sodium and caustic soda, and removing the major portion of the unconsumed metallic sodium from the melt by means of steam and removing the last traces of the sodium from the melt by means of sulphur.

ALBERT HANAK.