Page:The American Cyclopædia (1879) Volume V.djvu/658

 654 DAMASCUS BLADES beenthe first to suspect the real nature of the Indian process. By producing the steel with a considerable excess of carbon, and by a suita- ble method of cooling, he found that two dis- tinct compounds of the metal with carbon were formed, one of which may be steel, and the other of a quality approaching cast iron. Left to cool slowly, these tend to separate from their confused mixture, and to crystallize, each quality by itself; the slower the cooling the more complete is this separation, and the coarser the bands of stripes or lines in the hammered steel. The steel was prepared by M. Breant by melting soft iron with -^ its weight of lampblack ; a much more ready way of making steel than by the cementation pro- cess. With this he made excellent blades, and also from filings of gray cast iron mixed with an equal quantity of the same oxidized, the materials being carefully stirred during their fusion. The more oxidized the iron the better the effect, a large proportion of carbon causing the steel to work badly under the hammer. Gen. Anosoff, however, who repeated these experiments, was not satisfied with the results, the steel appearing to him to have neither the true lines of the Damascus nor its excellent qualities. The Indian method of carbonizing the iron, which they obtain direct from the ore, getting only about 15 per cent, of metal from the magnetic oxide they employ, is to place it in crucibles made of clay, intermixed with straw, adding about 10 per cent, of dry wood in small bits, and cover it in the crucible with two or three green leaves; only a little more than a pound of iron is the charge of each cru- cible. They exercise a choice in the wood and leaves, selecting of the former the cassia auricu- lata, and of the latter the asclepias gigantea or the convolvulus laurifolius. The crucibles are then closely covered with moistened clay, rammed to exclude the air, and 20 or more of them placed together in a small blast furnace, and, with charcoal for fuel, kept at as high a temperature as possible for about 2-J- hours. On removing them from the fire and cooling, they are broken, and the steel obtained in the form of a melted lump. If this is covered with irregular protuberances, the quality is bad ; but if the surface is smooth, and covered with striae radiating from the centre, the operation has succeeded, and the steel is excellent. Four or five of these lumps are commonly rejected. The best are remelted, and then, on account of their brittleness, they are exposed to a red heat for some hours in a small wind furnace, by which a portion of the carbon is removed, and the steel is softened, so that it can be easily drawn out under the hammer. This Indian steel, in the opinion of Mr. Stodart, is far supe- rior for cutlery to the best English cast steel. One of the best samples selected by Gen. Ano- soff, and analyzed by M. Ilimoff, gave the fol- lowing result : iron, 98; carboD, 1-31 ; sulphur, O'OH ; silicium, 0'5 ; aluminum, 0-055 ; copper, 0-3; silver, traces. The researches of Gen. Anosoff were made with great minuteness, and their results present many curious and in- teresting particulars. The information he ac- quired upon the subject led to the establish- ment of works at Zlatust in the Ural moun- tains, where the manufacture of Damascus steel is carried on by a process of his own in- vention. The quality of the steel he found to be indicated by the appearance of the lines upon the surface, by the color of the ground, and by that of the light reflected from its face. The scoriae detached from the metal in forging receive from it the impression of its lines, and when examined by the aid of a microscope they serve better to denote its character than the metal itself; but much experience is required to distinguish correctly the effects of the great variety of lines. Straight lines nearly parallel indicate a bad quality of steel. As they short- en and curve, the quality improves. It is still better when the short lines are broken up, and the spaces between them are dotted over with isolated points, particularly if they become like the meshes of a net, and are connected by ser- pentine lines running in different directions. The most perfect quality of steel is indicated by the threads or lines forming little points or knots, and being arranged in groups of the same pattern over the whole surface of the steel. Figures coarsely and strongly marked are much to be preferred to fine delineations. The sco- riae also indicate the depth of the color of the steel ; those of deep color and vitreous are the best. When the cool surface of the melted steel in the crucible is not uniform and displays no colored reflections, the quality is bad. The more brilliant the lustre and the more decided the reflection, the better it is, especially if this has a golden yellow tint. It may also have a bluish or reddish color. The peculiarities of the lines (whether properly coarse, or whether too fine) appear to Gen. Anosoff to depend upon the proportion of carbon and the intimacy of its combination with the iron. The color of the wa- tered lines and that of the ground depend upon the purity of the iron and tlie carbon ; a ground of deep shade and brilliant lustre, with undula- tions of white, indicates purity of materials. The reflection which the surface of the steel gives is the best indication of the condition in which the carbon exists in it. In the yellow-colored only is the combination of carbon and iron complete. When the reflection is red, the car- bon is mixed with some strange substance; and when there is no reflection, the carbon is apparently unaltered from its original condi- tion, and the steel, if largely charged with it, is brittle. Gen. Anosoff produced steel hav- ing the qualities of Damascus by four different methods. That which was the most practica- ble consisted in melting the iron in crucibles with graphite. A charge of 11 Ibs. of iron, or a smaller one for a very hard steel, is intro- duced into the crucible with ^ as much graph- ite, and J% part of scales of iron, together with a certain quantity of some flux, as dolomite.