Page:The American Cyclopædia (1879) Volume II.djvu/763

 BLOOMARY 743 erected in Connecticut for the treatment of the metal thus produced, but were abandoned on account of an act of parliament forbidding the manufacture of steel in the British colonies. In the districts where it was first worked, in- cluding northern New Jersey and the adja- cent parts of New York and Pennsylvania, the bloomary process has fallen into disuse since wood has become scarce, and extensive work- ings of coal in the vicinity, with great facilities for transportation, have rendered it more pro- fitable to treat the ores in the blast furnace than in the bloomary fire. In northern New York, on the contrary, the use of the bloom- ary process has continued to extend within the past few years, and in 1868 the production of iron by this method in that region was esti- mated at nearly 40,000 tons, a large portion of which is consumed at Pittsburgh for the manufacture of steel by cementation, for which it is much prized. Two establishments in the vicinity of Keeseville had in that year respec- tively 18 and 21 bloomary fires, and the whole number in activity in Essex and Cimton counties in 1867 was said to be 186. It is only in moun- tainous regions, abounding in rich iron ores and wood suitable for charcoal, and still inacces- sible to railways, that this process can hold its ground. Its advantages are, that the outlay and floating capital required are inconsiderable, and the consumption of charcoal comparatively small. The direct mode of reduction can only be applied to rich ores, which to yield good results in the German or Catalan bloomary should contain not much less than 50 per cent, of iron, while much richer ores are to be pre- ferred. Two tons, and of the richest and purest ores H ton, will under careful manage- ment yield one ton of blooms. The bloomary hearths used in northern New York vary in area from 27x30 to 28x32 inches, and in depth from 20 to 25 inches above the tuyere, and from 8 to 14 inches below. The sides are of heavy cast-iron plates, and the bottom, though often of beaten earth or cinders, is in the best constructed hearths also of iron, made hollow and kept cool by a current of water circu- lating through it. The side plates slope gently inward in descending, and rest on ledges in the bottom plate. A water box is let into the tuyere plate. The tuyere, which is inclined downward, has its opening in the form of a segment of a circle. In some localities these dimensions differ from those given ; and the bloomaries lately erected at Moisie in the lower St. Lawrence, for the treatment of the mag- netic iron sands, measure 32 x 30 inches, and have the tuyere nearly horizontal. The blast employed in the American bloomaries has a pressure of 1| to If lb., and is heated to 550 or 600 F., by passing through inverted siphon tubes of cast iron placed in a chamber above the furnace. By the use of the hot blast the production of the furnaces is much increased, and a considerable saving of charcoal is effect- ed without any deterioration in the quality of 1 the metal. The working of these furnaces is conducted as follows : The fire being kept ac- tive and the furnace heaped with coal, the coarsely pulverized ore is scattered at short in- tervals upon the top of the burning fuel, and in its passage downward is reduced to the metal- lic state, but reaches the bottom without being melted and there accumulates, the grains ag- glomerating into an irregular mass or loup, while the earthy matters form a liquid slag or cinder which lies around and above it, and is drawn off from time to time through an open- ing in the front plate. At the end of two or three hours, or when a sufficiently large loup is formed, this is lifted by means of a bar from the bottom, brought before the tuyere for a few minutes to give it a greater heat, and then carried to the hammer, where it is wrought into a bloom ; the bloomary fire itself being generally used for reheating. This opera- tion being concluded, the addition of ore to the fire is resumed, and the production of iron is kept up with but little interruption. A skilled workman will with a large-sized bloomary fur- nace bring out a loup of 300 Ibs. every three hours, thus making the produce of a day of 24 hours 2,400 Ibs. of rough blooms. The con- sumption of charcoal is from 250 to 300 bushels, (weighing 16 or 18 Ibs. to the bushel) for each ton of 2,000 Ibs. of blooms produced. In addi- tion to the cost of the ore and coal, which varies somewhat with the locality, the estimate of a competent iron master in northern New York in 1868 gave for wages $9, and for general ex- penses $3 50, for each ton of blooms produced. Several plans have been introduced having for their object the reduction of rich iron ores at low temperatures in close chambers by carbonic oxide, and the spongy metallic iron thus ob- tained was in many cases transferred at once to a hearth and converted into blooms. Such was the case in the methods of Clay, of Chenot, and of Renton. In the manufacture of blooms from cast iron by the Walloon method, now to a great extent superseded by puddling, the iron, generally purified by a first fusion in what is called a running-out fire, is brought in small portions at a time before the tuyere on a char- coal fire similar to the German bloomary fire just described, and known as a sinking fire. It there melts down and is at the same time de- carbonized, the product accumulating in the bottom of the furnace in a loup, which is treat- ed in the manner already described and yields a bloom of malleable iron. The iron thus ob- tained is superior in quality to that produced by puddling, and for the finer kinds of metal the process is still practised in some parts of the United States, and to a considerable extent in Sweden, where a modification of the bloomary known as the Lancashire hearth is employed. The loss in this process of conversion is con- siderable, and the consumption of charcoal in the production of the pig iron and its subse- quent conversion in the bloomary fire is about equal to that required in the direct process.