TO SHIP CONSTRUCTION. 229 



the last year, and perhaps more noticeably during the last six months, has led us to have a more 

 definite and positive knowledge of the conditions essential to sound welding than has been 

 heretofore available. 



We have been heartily encouraged by the Emergency Fleet Corporation in making these 

 researches, and we believe that we already have a rich return for the outlay and that still 

 further lessons of the greatest value will be learned by us in the very near future. 



Even the briefest outline of the extensive and important work which we have in hand 

 would occupy too much time. Consequently, I have concluded to deal chiefly with a single sub- 

 ject, namely, with the results of a series of tests of double- Vee welds of half-inch ship plate 

 of the following composition: — Carbon, 0.25; manganese, 0.46; silicon, 0.034; sulphur, 0.03; 

 phosphorus, 0.04. 



Welds of the dimensions shown on the chart (8 inches long, 45-degree, double- Vee welds) 

 were made at a dozen different places in the presence of Messrs. Wirt ajid Jones of our com- 

 mittee. At each place the operator employed whatever conditions were considered most suita- 

 ble. All sorts and sizes of electrodes, including bare and covered types, were used. While 

 in the majority of cases direct current was employed, alternating current welding is also well 

 represented by quite a number of welds made at different places. Some alternating current 

 welds were made with 60 cycles and some with 25 cycles. If Mr. Cox's paper had been read 

 a fortnight later, we could have contributed the results of some 30 per cent more such 

 welds, the tests of which have not yet been completed. It is, however, reasonably certain 

 that the results from these remaining samples could not materially alter • the conclusions. I 

 wish to make the most careful reservations O'f entire right to amend our conclusions in any 

 way when we have had time to further check and digest our work. In fact, the material which 

 I am now placing before you has been arranged in so short a space of time that it has been 

 impracticable for me to submit it to the Welding Research Sub-Committee for any revision 

 or endorsement of the statements which I shall make. Consequently, and with much concern 

 at the responsibility, I must put them forward as merely my own opinions. 



One remarkable observation relates to the utter absence of any agreement amongst weld- 

 ing specialists as to the preferable electrode material and as to the conditions as regards sys- 

 tem of supply and the conditions as regards current and voltage for obtaining the best results. 



My first step was to divide the results into two groups, namely, welds made with bare elec- 

 trodes and welds made with covered electrodes, with a view to comparing their mechanical 

 characteristics as regards bending strength, torsion strength, tensile strength and per cent 

 elongation at fracture. This attempt led me nowhere; any difference in the average results 

 were too small to be admitted to possess significance. 



This was also the case when I attempted to contrast D. C. and A. C. welds. I found no 

 notable difference in the mechanical characteristics. 



But, on studying the influence of the current employed in making the weld, there at once 

 became apparent a very great improvement in all the mechanical characteristics A^ith increas- 

 ing current. The four diagrams in the upper row of the chart (Plate 158) speak for 

 themselves. 



Black squares ■ relate to A. C. welds made with coated electrodes. 

 White squares □ relate to D. C. welds made with coated electrodes. 

 Black circles # relate to A. C. welds made with bare electrodes. 

 White circles O relate to D. C. welds made with bare electrodes. 



