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82 METALLURGY OF CAST IRON.
in blast a few minutes before the one going out of blast is shut off.
The sectional views of iron and brick hot blast stoves shown in Figs. 14 and 15, respectively, are of stoves in use within a 4'stone's throw" of the author's foundry. The brick stoves shown are of the most modern type, recently built, and are said to be giving excellent satisfaction. Before these stoves were built, iron ones were used by the same furnace. The four stoves are said to have cost $40,000, and by their adoption the owners were enabled to produce pig iron 30 cents per ton cheaper than when the iron stoves were used, owing to the brick stoves causing the furnace to use less fuel and give a larger yield of iron, also cheaper cost of repairs than those required in iron stoves. It may seem a small saving for the investment of $40, ooo. When pig iron was selling for from $30 to $50 per ton and the furnaceman had a margin of profit of from $15 to $30, no one thought of investing $40,000 just to save 30 cents per ton on iron made. When $10 to $14 per ton is about all a furnaceman can get for his iron, as is now often the case, a saving of 30 cents per ton is quite an item, especially so if it will permit one furnaceman underselling another and leave a few cents profit on his sales.
There are several different types of brick hot blast stoves now in use, and it now seems as if it will be but a few years before iron stoves will be almost wholly abandoned, mainly because the brick stove can make iron more cheaply than the iron stove. A large number of furnaces are still using iron stoves, but as soon as they are worn out, or competition gets too keen, they will no doubt be largely replaced by the brick stoves.ding " or "slips" from the use of fine ores, etc. It may also beency :|,