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Full text of "Metallurgy Of Cast Iron"

PROPERTIES   OF   ORES   USED   IN   MAKING   CAST   IRON.     29
centrates as existed in the crude ores, and hence, separators to eliminate sulphur from this class of ore have proved a failure.
High sulphur ores are sometimes subjected to a process called "roasting" or " calcination" which generally drives off a greater part of the sulphur.
Varieties of iron ores are very numerous. In order to classify them they are chiefly placed under one or the other of the following heads: hematites, magnetites, and carbonates. Of the first there are two kinds, known as the brown and red hematites. There is more red hematite used than all the other ores combined. Red hematite is generally quite free from sulphur, and it is found in almost every shape in which ore is found and exists in large quantities. Messaba ore, a soft ore now largely used to make both Bessemer and foundry iron, is a red hematite which, it was thought, a few years ago, by experts, to be unsuited for the blast furnace on account of its being such a dusty, fine soil material.
Magnetic ore is the next variety generally recognized in the order of classification. This ore is found in veins and is generally classed with the hard and refractory ores. It is generally a dense black material, which must be crushed or broken to suit the varying conditions of smelting. In Canada and New Zealand magnetic ore is found in the form of coarse gravel or sand, which, as a rule, furnacemen prefer not to use if it can be avoided. Magnetic ores are often discovered by the attraction they exert upon the compass needle. They are often very free of phosphorus and sulphur, but if they are too high in phosphorus and sulphur they will not be used as long as sufficient ore of suit-             {f H \esent in the ore.    Both these manganese metals are               jf|V