204 THE APPLICATION OF ELECTRIC WELDING ' 



5. Kind of current, i. e., alternating or direct. 



6. Amperage and voltage. 



7. Skill of the operator. 



8. Method of preparing and building up the joint. 



1 . In regard to the first, it may be said that good welds have been produced by 

 either, but the covered electrodes have been found to produce, in general, a more 

 ductile weld, a very desirable quality in ship construction. 



^ There are two distinct types of covered electrodes known as the gaseous flux and 

 the liquid flux. The former, developed by Kjellberg, is covered with a fireproof 

 sleeve of non-conducting material which projects sufficiently far into the arc to pro- 

 tect the heated end of the electrode metal from oxidation by the atmosphere, guiding 

 the molten metal direct into the arc and reducing heat losses. 



In the liquid flux process the covering melts with the electrode, forming a molten 

 flux over the end of the electrode and over the added metal, thus protecting both 

 from oxidation from the air. This flux by reducing chilling, in a measure, serves an 

 annealing function, but its chief value seems to be the protection from oxidation 

 with the accompanying brittleness and porosity caused by the reaction of the oxygen 

 on the carbon and iron of the molten metal. The solidified flux is chipped and 

 brushed ofif before building up the next layer. 



There are a large number of different makes of liquid flux covered electrodes 

 on the market, but it is not proposed here to go into their respective merits or draw- 

 backs. Careful investigation and experimental work are being carried out by the 

 Welding Committee with most of the known makes, and the results will be published 

 in due course. 



2. The chemical composition of the electrode is to-day considered to be a most 

 important variable, and after an exhaustive series of tests the Welding Committee 

 has drawn up the following tentative specification for electrodes intended to be used 

 in welding mild steel of shipbuilding quality: — 



Chemical Composition. — Carbon, not over 0.18 per cent; manganese, not over 

 0.55 per cent; phosphorus, not over 0.05 per cent; sulphur, not over 0.05 per cent; 

 silicon, not over 0.08 per cent. 



Sizes: — 



Allowable tolerance .006 plus or minus. 



Material. — The material from which the wire is manufactured shall be made by 

 any approved process. Material made by puddling process not allowed. 



Physical Properties. — Wire to be of uniform homogeneous structure, free from 

 segregation, oxides, pipes, seams, etc., as proven by micro-photographs. This wire 

 may or may not be covered, 



