360 



METALLURGY. (PROCESSES.) 



facturing furnaces, effect a considerable economy of 

 fuel, prevent the production of coal gas (carbonic 

 oxide), burn profitably the smaller sizes of anthra- 

 cite coals, and effect a great saving through the less 

 frequent necessity of cleaning boiler-furnace fires. 



A plant for welding iron, as for trolley rails, by 

 electricity, operated in Buffalo, N. Y., consists of 

 five cars. One of them, termed the sand-blast 

 car, goes ahead and prepares the rail joint for 

 the welding apparatus. Following this come 

 three cars, the first of which is the welder car, 

 next the car containing a rotary transformer, 

 and then the motor and booster car. The coupling 

 of this train is adjusted so that the welder car 

 can move ahead or back several inches without 

 any change of position of the cars following. It 

 can thus change its position along the joint that 

 is being made without disturbing the other two 

 cars. The welding of joints can be made on either 

 old or new track and on paved or unpaved streets, 

 hut where old track is welded the pavement has 

 to be removed for a few inches in front of the 

 rail joint. On new track the weld may be made 

 before the pavement is laid or replaced. When 

 a joint is to be welded a bar of steel 1 inch by 3 

 inches, and 8 inches long, on which are 3 bosses, 

 is placed at each side of the rail web and the 

 jaws of the welding machine are allowed to grip 

 it. A pressure of about 1,400 pounds is applied 

 by means of a hydraulic jack connected to the 

 upper end of the welding machine. As soon as 

 this pressure is applied the electric current is 

 turned on. Instantly the metal between the 

 welder jaws begins to heat. It grows brighter 

 and brighter until a welding temperature is 

 reached, when the current is immediately cut off, 

 while the pressure on the weld is increased to about 

 35 tons. Artificial means of cooling are at once 

 applied to the weld, in order that the process may 

 be hastened while the pressure is on. The com- 

 paratively cold portions of the bars about the boss 

 prevent the more plastic metal from spreading, and 

 the heavy pressure so confines it as to give no 

 opportunity for coarse crystallization while cool- 

 ing. The center weld is made first, and the ends 

 of the bar are next similarly treated, so that three 

 welds are made at one joint. As the welding bars 

 cool they exert a most powerful influence to bring 

 the ends of the rail together and make a perfectly 

 tight joint. A car with emery wheels operated 

 by a motor follows and dresses any rough parts 

 of the joint. 



Among the characteristic disadvantages attend- 

 ing the use of blast-furnace gases as compared 

 with other gases, M. Enrique Disdier, of Bilbao, 

 enumerates variable composition, low ratio of com- 

 bustible to noncombustible gases, admixture of 

 large quantities of dust, acid, and metallic vapors, 

 and high percentage of moisture. The economy 

 that would ensue upon the direct application of 

 these gases to the production of power by the 

 gas engine was of great importance. The produc- 

 tion of a ton of pig iron involved the consump- 

 tion of a ton of coal, and one horse power per 

 hour might be obtained by the consumption of 

 4 cubic metres (1,414 cubic feet) of gas. Assum- 

 ing these data, then it would be found that a 

 blast furnace was able by means of its waste gas 

 to generate nearly 2,100 horse power for every 

 hundred tons of pig iron produced daily after 

 making nil due provision for heating and blasting. 

 While the blast furnace has thus far been con- 

 sidered on its own merits as a source of power, 

 its almost indispensable associate, the coke oven, 

 can not be neglected as a gas generator, and there- 

 tore a power producer. With its gases the ob- 

 jection of variable composition does not obtain; 



further, these gases are rich in combustible con- 

 stituents, carry little or no dust, are absolutely 

 free from metallic vapors, and their moisture is 

 low. All existing coke ovens may be divided into 

 two main groups those in which by-products, 

 chiefly tar and ammonia, are recovered, and those 

 which burn their gases without recovery of any 

 of the by-products. For driving gas engines 

 coke-oven gases possess many advantages over 

 the blast-furnace gases. They give 30 per cent, 

 more power with the same size of engine, and 

 the gas mains and distributing pipes can be made 

 very much smaller, so that the plant is rendered 

 much cheaper. Various opinions were expressed 

 in the discussion of this paper in the Iron and 

 Steel Institute concerning the practicability of 

 using the blast-furnace gases, the dust they carry, 

 contrary to the author's assertion, being specified 

 as the most formidable difficulty in the way. 



A difference in method between reverberatory 

 and hearth smelting of lead is marked by Capt. C. 

 C. Longridge in that in reverberatory smelting the 

 two operations of roasting and reaction of which 

 the process consists are repeated one after the 

 other, while in hearth smelting the same operations 

 are performed simultaneously. In the reverbera- 

 tory furnace the lead is reduced from the ore by 

 the interaction of unaltered galena (sulphide) with 

 sulphate and oxide ; in the hearth furnace an addi- 

 tional reduction of lead oxide by carbon takes 

 place. The reverberatory process is performed 

 without a blast; in the hearth process the blast is 

 used, and the ore and fuel do not rest upon a 

 solid bed, but on a bath of molten lead; the 

 charge is never fused, but at intervals the blast 

 is stopped, a part of the charge is removed, the 

 poor slag is separated from it, and after cooling 

 and admixture of lime to stiffen it the charge 

 portion is returned to the furnace. Both processes 

 have their advantages and disadvantages. The 

 hearth process has the advantages that the con- 

 sumption of fuel is less and that the furnace 

 can be sorted and stopped without much loss, 

 or serious risk to the structure. Its disadvan- 

 tages are that power is required for the blast, 

 the fumes are more injurious to the workmen. 

 ore of purer quality and higher grade is required, 

 and on account of the blast ore in fine powder 

 can not be treated without previous agglomera- 

 tion. It is therefore chiefly suitable for inter- 

 mittent work with small quantities of high-grade 

 nonargentiferous ores. Both products and tbo 

 treatment of them are the same as in reverberatory 

 smelting. There is, however, an intermediate 

 product consisting of ore, slag, and fuel, termed 

 " brouse," which is washed and remelted with sub- 

 sequent charges. Rome of the advantages of the 

 reverberatory process are that raw ores can be 

 smelted by it without preliminary or independent 

 calcination, raw fuel can be used, the Insses of 

 silver and lead by volatilization are small, and the 

 slag losses are strictly moderate. " Unbrickc'il 

 fines " can be smelted by it without excessive loss 

 in flue dust, extraction is easy, and the plant is 

 cheaply erected. Its defects are that as intimate 

 contact of metallic particles is necessary, only rich 

 sulphides or mixtures of sulphides nnd carbonate-* 

 containing, say, 68 or 70 per cent, of lead, are 

 suitable for reverberatory smelting. For the same 

 reason the hre must be fairly pure. Blendes, iron 

 pyrites, chalcopyrites. calc-spar, barytes, silica. 

 lime, magnesia, etc., must not therefore be present 

 in any considerable proportions. Other defects 

 comprise slowness of operation, heavy fuel con- 

 sumption, the amount of skilled labor required. 

 and the richness of the slags, which necessitate- 

 their retrcatment. 



