alloys fluxes

Значение термина alloys fluxes в knolik

alloys fluxes - Alloys Fluxes
alloys fluxes - The best flux for alloys of copper and tin is rosin. It should be added when the metals are almost melted. Another good flux is sal-ammoniac. In using this flux the copper is usually melted first and the flux added. When it is in the mushy state, after the flux has been put in, the zinc and tin are added. A good flux for old brass is common rosin-soap. It should be added in small lumps, and stirred down into the metal when in the molten state. In forming alloys of different metals, the molten metals should always be kept under a covering of black glass or pulverised charcoal, to prevent oxidation.

Black flux, as it is commonly called, is composed of 7 parts crude tartar, 6 of saltpetre, 2 of common bottle-glass, and by some a small amount of calcined borax is added. These ingredients are first finely pounded and mixed, and then gradually heated in an iron pot or ladle so as to burn them together. Care should be taken not to overheat the mixture, and as soon as it is thoroughly melted and mixed together it should be removed from the fire and allowed to cool. After it has cooled, it is finely pulverised and sifted, and is then ready for use. It has a great affinity for moisture and should be protected against it by being placed in glass bottles and the bottles corked up until wanted for use. This is the most powerful flux that can be made. It is but little employed in forming or fluxing alloys, but principally by as sayers in assaying different kinds of metallic ores. In these assays the quantity of black flux used varies according to the quality of the ores, but the amount is generally about equal proportions of ore and flux. The ore is first roasted, and then finely broken up and mixed with the flux, and the whole is then rapidly heated in a crucible. If the flux does not make the slag sufficiently fluid to allow the metal to settle, a small amount of calcined borax is added, which makes the slag more liquid, and permits the metal to pass to the bottom of the crucible. The crucible is then removed from the fire, and the mixture is either poured from it or allowed to cool in it. After it has cooled, the slag is knocked off with a hammer, and a button of metal is obtained. When using this flux, the clay crucible, without either coal or graphite (plumbago), is preferred, for the flux is very hard on a crucible that contains either of these substances. Black flux is used by some foundry-men in melting the fine scrap-sweepings from the floor, and dross and refuse from the crucible. By melting these in a crucible with black flux, they obtain considerable amounts of metal from them that would otherwise be lost. (E. Kirk.)

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