WROUGHT Bum The iron made by the an dents, and, indeed, by all peoples up to 1350, when east iron was first produced in the German blast-furnaces, was wrought iron, and it was produced from the ore in a single operation. To-day wrought iron is nearly always obtained by treating pig or cast iron made in the blast-furnace, and the process is said to be 'in direct.' as compared with the 'direct' process of the ancients. The direct process is still em ployed by all savage races who make iron, and is also in use where the character of the ore. the fuel, or other conditions make the adoption of the blast-furnace impracticable. A few forms of the direct process will be described here. The ancients employed small hearths, the fuel used being charcoal and the necessary draught being obtained either by means of rude bellows or by arranging the hearth at the top of a gully or channel in such a manner as to take advantage of the prevailing wind. Such hearths are now used in Africa and some parts of India by the natives. A modification of the hearth process once extensively used in Southern Europe, but now extinct, was the Catalan process, the name being derived from the Province of Catalonia, in Spain. where the process was probably first em ployed. This process is chiefly notable because of the form of water blower used, which was calkd a tromp". Sec BLowING MacutNEs.
A more important hearth process was the _4 mericon btoomery process. much resembling the Catalan proeess, hut showing an advance in the use of more modern blowing machines with hot blast, and in the provision of means for cool ing the furrmee walls by water. The three proe esses described were hearth processes. A more common form of the direct process eonsists in the use of blast-furnaces. These furnaces are insignificant in size. ns compared with modern east-iron blast-furnaces; the smaller ones are from -IV, to li feet in height, while the largest seldom exceed 10 feet in height. These furnaces arc extensively used by the natives of India, who produce au excellent quality of iron in them. The two modern forms of the direct proc
ess are the retort process and the reverberatory furnace process. in the retort process, of which there are several forms, the ore, reduced to a tine division, is placed in the heating chamber with charcoal or other earbonaccous matter, and is heated either by the external tire or by means of gaseous fuel. the prodhiets of combination of NI hid' are made to pass through the charge. In the reverberatory-furnace process line ore anal coke are reduced in n reverberatory furnace by miscous fuel. In all of these processes thus far mentioned the direct product of the furnace is a spongy mass of metallic iron and slag, which has to be squeezed or hammered to remove the bulk of the cinder.
The preceding brief review of the direct proc ess of producing wrought iron may be summed up by saying that nt present there is no direct process known which is capable of competing for n lengthened period and on a broad scale with the indirect process. The manufacture of wrought iron from cast iron by this process is accomplished by purification. This further puri fication is always carried out by means of oxi dation. though the details of the process vary according to whether the necessary oxygen is sup plied chiefly from the atmosphere or from other materials added for the purpose, and also as to whether the iron to be purified is heated in a separate furnace or chamber from that in which the fuel is burned, or in direct contact with the fuel. The furnaces used may be divid ed into two classes—(I ) hearths and (2) rever beratory furnaces. In hearths the fuel is burned in direct contact with the iron, and the chief source of oxygen is the atmosphere; in the rever beratory furnace the oxygen is obtained from t,pecial 'oxidizing materials added for the pur pose, rind the fuel is burned in a chamber sepa rate from, but communicating with. the cham ber in which the charge is placed. With this outline of the methods of producing wrought iron from cast iron, attention will lie turned to the process which is chiefly employed.