US1669580A - Process for extracting tin mixture from lead and tin alloys - Google Patents

Description

MayI 15, 192s. 1,669,580

' M. SPEICHERT PROCESS FOR EXTRACTING TIN MIXTURE FROM LEAD AND TIN ALLOYS Filed Sept. 18. 1926 2 Sheets- Sheet 1 May 'S/OL'CherZ" May 159 192s. 1,669,580

M. SPEICHERT PROCESS FOR EXTRACTING TIN MIXTURE FROM LEAD AND TIN ALLOYS Filed Sept. 18. 1926 2 Sheets-$11691 2 Patented May 1928,

l UNITED psr-Atras mix srnrcnnnr, or BEBLIN-TEMPELHOF, GERMANY.

Pnocnss For. nx'rnacrINe TIN mix'runn :rnom Laan ann TIN nous.

Application filed September 18, 1926, Serial No. 136,299, and in Germany @ctober 11,`1924.

This invention relates to a process 'for extracting tin mixture from lead and -'tin ,alloys containing antimony and copper or one of these metals with. or without small t3 amounts of other metals, 1 or for preparing bearing metals or the like free trom lead or having" only a small proportion theri.

Liuation or segregation was hitherto resorte to as a means ci extracting compol@ nents from alloys or extracting alloys of dissimilar composition therefrom by melting the easily liqueed components out of the solid remaining residue of theinitial material. This method of proceeding however l@ has only a limited number of applications because the composition of the products thus obtained is not always as expected, chiey for the reason that the temperature cannot` be regulated' with sulicient accuracy, the 'consequence being that the melted-out metal is not uniform in composition. v

Furthermore, the old liquation process must be carried through several stages or steps inorder to secure an alloy of fairly accurate composition. h

The rocess of my invention overcomes these dlculties encountered in the liquation process by the substitution therefor of a single stage or step which correspondsl to and yet is essentially different from the last step of the liquation'process, and by which an alloy of accurate composition can be obtained. v

I have found that it is possible to extract 85 individual components or alloys of dissimilar 4but quite definite composition from metal alloys above referred to by first melting the wholeof the;- alloy and thereafterl slowly allowing it to cool. Certain componentsof 40 the alloys crystallize individually or as .a

mixture while other components remain 'luidv and may be removed in thatA state from the melting furnace. For allowing the fluid portion to be drawn off the molten metal bath should have a certain depth to enable the solid and liquid portion to separate from each other well. This renders it possible to separate individual components or alloys of deiinite composition (more particularly eutectic mixtures having a definite melting point) by suitably regulating the temperature and selecting the composition of .the charge. I

Taking as an example an alloy of tin, an-

timony, lead and copper, as available. inr

scrap from bearing metal, melting the said alloy as just outlined and allowin it to cool slowly, antimony and copper. reac the solid state while tin and lead with a practically negligible percentage oi antimony and cope per remain duid. The li uid nflixture forms the so-called tin mixture suitableas a main component of solder.

ils another example, the initial material may be made up by mixing scrap of dissimilar composition so that tin and lead in the molten material are in proportion of their eutectic mixture. lin this case there is a practically complete separation of the eutectic mixturefof tin and lead with the exceedingly small percentage of antimony and copper, on the one hand, and oi copper and antimony, on the other hand. The formation and removal of the eutectic mixture are of course not prevented byan excess of tin or lead,v but the amount oimetal in excess is lost as it solidiies with the antimony and the copper. f

The above method 'of proceeding is likewise suitable for makingbearing metals or the like free from lead or having only a small proportionthereof. To this end the charge must have' an ample proportion of copper and a large excess of tin. Lead may thus be completely extracted by removing the mixture which contains the whole (or substantially the whole) of the lead and which remains fluid when ,the molten material cools down, leaving behind an alloy of tin,

may of course contain the minpnquantities of other metals above referred' to.

charge composed of 44% tin, 32% lead, 20% antimony and 4% copper is melted and allowed to cool to 182 C. The mixture of 55 and 3.5 parts off4 antimony, remains Huid and is drawn olf while the remaining antimony and copper are left behind in the solid state.

parts of tin and 41.4 parts of lead, with an lallowable proportion Aof 0.1 part of copper Ewample Z, for making bearing metal poor n Zeadf-A charge composed of 70% tin, 13% lead, 12% antimony and,5% copperis melted and allowed to cool to 182 C. Out of 100 parts of the charge 30 parts of tin mixture are obtained in the form of a fluid mixture (55 parts ofl tin and 41.4 parts of lead, with the allowable proportion of 0.1% copper and 3.5% antimony) and parts of solid bearing metal are obtained, containing 76% tin, and 16% antimony, 7% copper and 1% lead.

The process can be carried out in a similar manner, if the starting material, besides lead and tin, contains instead of both antimony and copper, only one of these metals.

Example 3 A charge composed of 46% tin, 34% lead and 20% antimony is melted and allowed to cool to 182 C. The mixture of 55 parts'of tin and 41.4 parts of lead with the allowable proportion of 3.5 parts of anti- .mony remains fluid and is drawn off, while the main quantity of antimony is left behind in the solid state.

The process just described can be carried out in reverberatory furnaces differing from the ordinary types of such furnaces only in that the dimensions, especially as regards depth of hearth, must be large enough to allow the molten material to cool so slowly that the crystallizing components separate from those which remain fluid; in other words, the material f must not solidify throughout.

The process may be carried out for exam# le in a cylindrical furnace rotatable about its longitudinal axis, as commonly used for melting copper.

A furnace of this nature is illustrated in Figure 1 in cross-section.

This furnace comprises a casing 1 'with a lining 2 of refractory material. The end faces of thev furnace have a heat-resisting Wall '3 extending vertically alongtwo-thirds of the said faces. A gas burner (not shown) is above the said wall at one end of the'furnace, the products of combustion escaping.

at. the other end. The material to be melted is introduced through a charging hole 4, whereafter 'heat is applied until all the charge is melted. IThe supply of heat is now discontinued and'the furnace is allowed to cool slowly. It cools Von all sides so that a crystallized outer layer 5 is formed while the centre or core 6 remains. fluid. A pyrom-- eter shows when thc cooling reaches the desired point and a tap tube 7 (suitably extended into the interior of the furnace)` is opened so that the said fluid centre o r corel flows out bv gravity since air is allowed to4 pass through the. porous crystalline outer layer.' The furnace is mounted. on rollersr8 so that it may be tilted by means of a suitmoving the fluid material.

The furnace shown in cross-section in'Figure 2 has proved particularly suitable for carrying out the present process. i This furnace, preferably rectangular or circular in cross-section, comprises a hearth made of fire-resisting material 9 and considerably deeper than in the usual reverberdischarged through a chimney 12.

. able gear for the purpose ofcompletely re-kantimony and co i small amounts o 'and which may contain smal The charge is allowed to cool after it has been melted. In this case it-cools from the surface, so that the crystallized components form an upper layer 13 while those that remain fluid are at 14 in the lower portion of the hearth. They can thus be drawn intoa receptacle 16 through a tap hole 15. As shown in the drawings, the floor of the hole.

What I claim is y 1. A process-for extracting, from lead and tin alloys containing antimony and copper and which may contain small amounts of other metals, an alloy known as tin mixture and being a eutectic mixture containing from 54.5 to 55% of tin, not more than 3.6% of antimony, not more than 0.2% of copper, the remainder bein lead, said process consisting in meltin immediately heart-l1 hassurfaces inclined towards the tap as a whole, without any revious treatment such vas liquation, the sald starting allo slight percentage of antimony and co per remains fluid, y. and ,drawing of said uid mixture. i

2. A process for extracting, from lead and tin alloys containing antimony and copper' amounts of other metals. an alloy known as tin mixture and being a eutectic mixture containing from 54.5 to 55% of tin, not more than 3.6% of antimony, not more than 0.2% of v copper, the remainder being lead, said process consisting inv selecting said starting alloys so that the lead and tin are in the proportions of the said eutect-ic mixture, melting said alloys, cooling the molten material until onlyamixture of lead andvtn with only a slight percentage of antmon and copper remains fluid, Aand drawing o said fluid mixture.

3. The process for extracting tin mix-` ture from lead and, tin allo s containing per and whic may contain other metals, in which al- 10U cooling the molten material until only t e said mixture of lead and tin with only a' loys the proportion of tin is such that practically all the lead is combined with tin to form therewith a eutectic mixture, there being enough tin left to form with the other metals including copper and antimony an alloy having the required composition for use as a bearing metal, which process consists in melt-ing said alloys, coolin the molten material until only a mixture o lead and tin with a practically negligible per- 10 centage of antimony and copper remains fluid, and separating the fluid tin mixture from the solid portion forming the bearing metal.

In testimony whereof I have aiiixed my 15 signature.

MAX SPEICHERT.

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