alloys, soft defined in 1909 yearalloys, soft - Alloys, Soft;
alloys, soft -
Soft AlloyThis alloy will adhere so firmly to metallic, glass, and porcelain surfaces, that it can be used as a solder, and is invaluable when the articles to be soldered are of such a nature that they cannot bear a high degree of temperature. It consists of finely pulverised copper or copper-dust, and is obtained by precipitating copper from the sulphate by means of metallic zinc: 20, 30, or 36 parts of this copper-dust, according to the hardness desired, are placed in a cast-iron or porcelain-lined mortar, and well mixed with some sulphuric acid having a specific gravity of 1185. Add to the paste thus formed 70 parts (by weight) of mercury, constantly stirring. When thoroughly mixed, the amalgam must be carefully rinsed in warm water to remove the acid, then laid aside to cool. In 10 or 12 hours it will be hard enough to scratch tin. When it is to be used, it should be heated to a temperature of 707° F. (375° C.), when it becomes as soft as wax by kneading it in an iron mortar. In this ductile state it can be spread upon any surface, to which, as it cools and hardens, it adheres very tenaciously.
For Small ArticlesThis alloy melts at a lower degree of temperature than the one just described, and is very hard without being brittle. It consists of 6 parts bismuth, 3 zinc, and 13 lead. The 3 metals, after having been well melted and stirred together, should be poured into another melting-pot, and melted again. This alloy cools with remarkably clear cut edges, and if the articles made of it are dipped in dilute nitric acid, then rinsed in clear water, and polished with a woollen rag, the raised parts of the surface will have a fine polish, while the sunken parts will have a dark grey, antique appearance, which forms a pretty contrast. The proportions of the different metals, dividing the alloy into 100 parts, are: 27.27 bismuth, 59.09 lead, 13.64 zinc.
For Small CastingsContains 6 parts bismuth, 3 tin, 13 lead. This alloy should be melted, run into bars, and laid aside till wanted, when it should be remelted. An alloy of 3 parts bismuth, 1 tin, 1 lead, for small castings, is harder, and yet it is not brittle. It can be finished with a contrasting surface of bright polish and dark grey, if it is washed in nitric acid, well diluted, rinsed, and polished with a woollen rag as described in the alloy for small articles given above.
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