April ii, 191 8] 



NATURE 



105 



MODERN METHODS OF WELDING. 



THE union of two pieces of metal by fire fusion 

 and hammeringf is an old-established art in 

 connection with iron, and is rendered easy by the 

 fact that the change from liquid to solid is not 



rupt in the case of this metal, which exists in 



■)asty condition over a considerable range of 

 M in{>erature. Since the invention of the oxy- 

 Indrogen blowpipe by Hare in 

 1801, steady progress has been 

 made with the welding of iron 

 and other metals by methods in- 

 volving flame heating, the earliest 

 >iiccesses in this direction being 

 achieved with platinum and lead. 

 During the ISst ten years flame 

 \\elding has made rapid strides, 

 mainly owing to the use of acetyl- 

 ( lie as the combustible gas, and 



now firmly established as an 



ryday process in all large 

 ;;ii;ineering workshops. The high 

 temperature procurable by the 

 use of electricity has led to the 

 ilevelopment of electric welding, 

 w hich is now employed for a large 

 \ariety of operations, and may 

 be expected to extend still more 

 as electric power grows cheaper. 

 In addition to the foregoing, a 

 further method of welding is pro- 

 \ ided by*.the use of "thermit" 

 jiiixture, which has proved Suc- 

 re ssful for many classes of work. 

 During the present time of stress 

 all the methods named are being 

 used to the utmost, and are 

 jilaving an invaluable part in the 

 j)ioduction of munitions of war. 



The gases used for flame weld- 



I ing may be either hydrogen, coal- 



I sjas, water-gas, or acetylene, 



'ich are burnt In blowpipes of 



table construction in air or 



wAVgen, according to the tem- 



j perature needed. Hydrogen is 



more expensive than the other 



ses named, and is used only in 



ses in which the work might 

 damaged by impurities such 



sulphur and phosphorus, one 



both of these being liable to 

 present in the alternative 



-es. Coal-gas has long been 



d for the autogenous soldering of lead, but has 



1 been applied to any great extent to the welding 



iron, owing to its varying composition and the 



sence of impurities. Water-gas, which has 

 advantage of being the cheapest of all gases 



table for welding, is now extensively employed 

 pipe welding, particularly in America and 



rmany, the parts to be joined being brought 



a welding heat by blowpipes, and then ham- 

 XO. 2528, VOL. lOl] 



IIB 



mered with a pneumatic hammer, or pressed to- 

 gether by rollers. Fig. i, from a paper published 

 by Capt. Caldwell, R.E., in the Transactions of 

 the Institution of Engineers and Shipbuilders »n 

 Scotland for February last, shows a pipe welded 

 in this manner and used in a hydro-electric in- 

 stallation in California. Water-gas is used in this 

 connection as a substitute for a fire, and the tem- 

 perature attained need not be so high as that 



Large pipe welded by water-g.-is method. From Transactions of the Institution of Engineers 

 and Shipbuilders in Scotland. 



required for fusion welding, in which joining is 

 effected without hammering. 



The oxy-acetylene flame is most generally used 

 for fusion welding, owing to its high temperature, 

 which, at the hottest part, approaches 3000° C, 

 a further advantage being that a zone of unburnt 

 hydrogen exists round the working-tip of the 

 flame, which prevents oxidation of the work. In 

 fastening two surfaces by fusion welding, the 



