ELECTRIC WELDING DEVELOPMENT." 



Bv Emhu Thomson. 



The art of weld in o- iron is prol^ably as old as the earliest produc- 

 tion of that metal by man. In fact, the reduction of iron in the 

 primitive forges demanded the union by welding of the reduced par- 

 ticles, for no true fusion could have resulted, the percentage of car- 

 bon present being too low. Until the closing years of the last cen- 

 tury iron Avas the only weldable metal, if we excej^t gold and plati- 

 num — too expensive for connnon application. 



The fact that nearly pure iron, so difficult to melt, becomes quite 

 plastic at high temperatures, while the oxide, or black scale, melts 

 long before the metal itself becomes fluid, thus providing a liquid 

 flux which is squeezed out during the process of union, accounts for 

 the unique position which iron held until recent years. l^Hien, how- 

 ever, the heating effects of electric current energy, so perfectly under 

 control, were applied to weld metals, a metal or alloy which would 

 not weld became the exception instead of the rule, as l)efore. ]Much 

 of the former work of the smithy fire is now accomplished by the 

 electric welding transformer, and although many metals are easily 

 manipulated by the electric process, iron, of course, still occupies, as 

 ever, the principal place. 



The electric weld is becoming a more and more important factor 

 in nian}^ industries. During recent years the extension of its appli- 

 cation has been steady, and each year has Avitnessed its entrance into 

 new fields. Sometimes, indeed, new manufactures, or new ways of 

 obtaining results, have been based upon its use. The electric welds 

 under consideration are the results of that operation of uniting two 

 pieces of metal by what is known as the '' Thomson process,'' first 

 brought out by the writer and rendered available in connnercial 

 practice a considerable number of years ago. The rai)idity, flexi- 

 bility, cleanliness, neatness, accuracy, and economy of the electric 

 process has Avon for it such an inq)ortant standing in the arts that 

 many future extensions in its application are assured. 



The uniformity of the work, the control of the operation, the ex- 

 treme localization of the heat to the particular j^ni'ts to l)e united, 

 and the fact that the process is not limited to ii"on and steel, but can 



a Reprinted, by permission, from Cassier's Magazine, New York, June. 1004. 



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