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METHODS FOR MELTING TO TEST CAST IRON. 365
slag-hole as at E, Fig. 69, and the use of flux, a " heat " can be prolonged to run several hours. If lime was used for a flux, about four pounds to every one hundred of iron charged should cause the slag to run freely. We are only entering into these details in order to illustrate the fact that the cupolas can be used for heavier "heats" than test bars would necessitate.*
In melting with a crucible in the cupola, Fig. 69, use a size like No. 18 Dixon's brass. In preparing the cupola for melting with crucibles, put in a sand bottom within two inches of the level of the tuyeres. Have a bed of coke, when well burnt up, ten inches high, and on this set the crucible charged with its burden of iron to be melted. Fill all around between the crucible and the cupola lining with small coke, level with the top of pot. Cover the pot over with a clay cover, which can be formed in a core box and rodded the same as one would a dry sand core to prevent its cracking, or the bottom of an old crucible can be used. The smaller the iron is broken the more quickly it will melt, and hence the easier will it be on the pot and more economical in fuel. After the pot is covered, the cover D is placed on to close the furnace. The blast is now put on the same as if iron were being melted direct in a cupola. The pressure should, for crucible work, range from two to three ounces; for cupola work, four to eight ounces can be used, and such
* Should any desire plans, with complete specifications, for constructing small, permanent cupolas, ranging from twelve inches to eighteen inches diameter, strictly for melting light "heats" without crucible arrangements, we would refer them to "Moulder's Text-Book," page 265, and in the same work, page 248, will be found a cheap temporary arrangement for melting from fifty to one hundred pounds of iron, Ferrochrom.