Patent Fluxes
In addition to the limestone, fluorspar, and other fluxes, used in the cupola, blast-furnaces, puddling-furnace, smelting and refining, steel, and copper and brass works, there are numerous other compounds, etc., which are protected by letters-patent, by the use of which it is claimed that steel can be welded to steel or iron, with the best results; preventing the metal from burning by flowing easily, and enveloping it so as to exclude the air. For cupola-melting it is claimed they will save fuel, improve iron, make clean cupolas, and other improvements too numerous to mention. Mr. Kirk, author of "Founding of Metals," is the inventor of a flux for the cupola, and in presenting his compound says as follows: "It will make hard iron soft, will reduce the percentage of iron lost in melting, will cleanse iron of impurities, will flux the cupola, and make a brittle slag. In introducing this compound as a cupola-flux, we introduce an entirely different theory of fluxing from that used in a blast-furnace, or that formerly used in the cupola, for we propose to flux the iron entirely with the gases generated by the compound, and not with the slag formed by it. The chemicals which we use in the compound are very rich in carbon, and when distributed over the fuel and heated by it they generate a very strong carbonic gas in the cupola, and this gas is absorbed by the iron from the time it begins to heat until it is drawn out of the cupola; so that we have a great deal more time to operate upon it than any of the mineral fluxes do, yet we do not have time enough to change an iron from one extreme to the other, and can only improve it to a certain extent at one melting; but by continued re-melting with the compound we can change the hardest of iron to the softest. If any founder doubts this theory of fluxing and improving iron by the gases, he has only to throw sufficient brimstone into his cupola on the fuel to form a sulphuric gas in the cupola, and he will find his iron to be as hard as glass; and if iron can be hardened by one gas, it can be softened by another." See FLUX; CUPOLA; SLAG.