- Email: [email protected]
Solders for aluminum
232
2Votcs aT/*/ 0b~zJJze/lts.
[J. F. I.,
SOLDERS FOR ALITMINUM. The one great drawback to the application of aluminum for a large number of uses i~l the arts for which its lightness, color, resistance to oxidation and the ease with which it can be rolled, drawn into wire, pressed and spun up into various shapes, etc., is the difficulty of soldering joints. While some approximations have been made to a durable solder, among which that of Kichards' should be named, it is nevertheless true t h a t an entirely satisfactory solution of the problem has yet to be fom~d. The difficulties encountered arc threefold : t'J ) The high h e a t conductivity of alunfinum, which abstracts heat rapidly from t h e joint a n d (2) galvanic action between the aluminum and the metals of tile solder by which tile aluminum, the more eleqtro-positive metal, is corroded and the joint destroyed. it is comparatively easy to make an apparently perfect soldered joint of aluminmu with varions mixtures of zinc and tin, for the reason that when freshly made, the adherence is all t h a t could be desired. The effects of the galvanic corrosion may nlake themselves apparent after the work has been exposed to atmospheric influences for some months. The rapid heat eoncluctivity of the metal can be practically obviated by applying artificial heat to the joint while the solder is being applied. It has been proposed to use aluminum in considerahle proportio~Js in the solder to avoid the effects of galvanic action, but while this artifice might accomplish tile desired result, t h e joints cannot be made with the soldering iron, because of the high heat required to melt the alloy. A perfect solder for alumimml is still to be found. W. CONCERNING CALCIUM CARI~IDE. In a recent article on the analysis and purification of acetylene, Rossel and Landriset quote figures which show t h a t the ~roportion of hydrogen by volume in commercial acetylene usually ranges from 0'2 to 0"3 per cent., and does not exceed the latter limit even when the carbide is made in the presence of an excess of lime, says the London E%drical ]~e~,iea,. Using an alternating current in the furnace, part of the lime excess volatilizes and part melts without deconlposition, yielding a carbide of specially fine crystalline appearance ; only the small residue is dissociated to metallic calcium, and, accordi n g to the present authors, only that part of the residue which happens to be in the middle of the finishished lumps of carbide remains as metal, and generates hydrogen when it conies in contact with water. H y d r o g e n ill acetylene is objectionable since, b u r n i n g as it does with a non-Inminous flame, it reduces the illuminating power of the crude gas. It is known t h a t a considerable quantity of h y d r o g e n may exist in acetylene when the gas has been generated in a faulty apparatus which encourages overheating, and t h e quantity may easily reach a figure that seriously affects the reading of the photometer. This hydrogen is due to various decompositions occurring in t h e process of evolution, and it can be totally avoided by proper construction of the generating plant. The hydrogen arising from the metallic calcium of the carbide is naturally unavoidable ; but Rossel and Landriset clearly show that its amount is too small to be in the least degree sensible to the consumer. Indeed, it is difficult to understand how any appreciable a m o u n t of metallic Calcium can appear in a material made in an alternating furnace, where true electrolysis is theoretically excluded.
2Votcs aT/*/ 0b~zJJze/lts.
[J. F. I.,
SOLDERS FOR ALITMINUM. The one great drawback to the application of aluminum for a large number of uses i~l the arts for which its lightness, color, resistance to oxidation and the ease with which it can be rolled, drawn into wire, pressed and spun up into various shapes, etc., is the difficulty of soldering joints. While some approximations have been made to a durable solder, among which that of Kichards' should be named, it is nevertheless true t h a t an entirely satisfactory solution of the problem has yet to be fom~d. The difficulties encountered arc threefold : t'J ) The high h e a t conductivity of alunfinum, which abstracts heat rapidly from t h e joint a n d (2) galvanic action between the aluminum and the metals of tile solder by which tile aluminum, the more eleqtro-positive metal, is corroded and the joint destroyed. it is comparatively easy to make an apparently perfect soldered joint of aluminmu with varions mixtures of zinc and tin, for the reason that when freshly made, the adherence is all t h a t could be desired. The effects of the galvanic corrosion may nlake themselves apparent after the work has been exposed to atmospheric influences for some months. The rapid heat eoncluctivity of the metal can be practically obviated by applying artificial heat to the joint while the solder is being applied. It has been proposed to use aluminum in considerahle proportio~Js in the solder to avoid the effects of galvanic action, but while this artifice might accomplish tile desired result, t h e joints cannot be made with the soldering iron, because of the high heat required to melt the alloy. A perfect solder for alumimml is still to be found. W. CONCERNING CALCIUM CARI~IDE. In a recent article on the analysis and purification of acetylene, Rossel and Landriset quote figures which show t h a t the ~roportion of hydrogen by volume in commercial acetylene usually ranges from 0'2 to 0"3 per cent., and does not exceed the latter limit even when the carbide is made in the presence of an excess of lime, says the London E%drical ]~e~,iea,. Using an alternating current in the furnace, part of the lime excess volatilizes and part melts without deconlposition, yielding a carbide of specially fine crystalline appearance ; only the small residue is dissociated to metallic calcium, and, accordi n g to the present authors, only that part of the residue which happens to be in the middle of the finishished lumps of carbide remains as metal, and generates hydrogen when it conies in contact with water. H y d r o g e n ill acetylene is objectionable since, b u r n i n g as it does with a non-Inminous flame, it reduces the illuminating power of the crude gas. It is known t h a t a considerable quantity of h y d r o g e n may exist in acetylene when the gas has been generated in a faulty apparatus which encourages overheating, and t h e quantity may easily reach a figure that seriously affects the reading of the photometer. This hydrogen is due to various decompositions occurring in t h e process of evolution, and it can be totally avoided by proper construction of the generating plant. The hydrogen arising from the metallic calcium of the carbide is naturally unavoidable ; but Rossel and Landriset clearly show that its amount is too small to be in the least degree sensible to the consumer. Indeed, it is difficult to understand how any appreciable a m o u n t of metallic Calcium can appear in a material made in an alternating furnace, where true electrolysis is theoretically excluded.