162 NOTES ON CHAIN CABLES. 



strength of the weld, the forces acting in a direct manner to part the welded sur- 

 faces. With a weld on the end the stresses over the weld are resisted by the strength 

 of the weld, assisted by the form of the link, so that fracture along the weld can 

 only take place by parting the weld and deforming the link at this point. The 

 strength of form of the link at this point is nearly equal to the proof stress to which 

 the chain is subjected. 



The effect of working and heating the link in the vicinity of the weld is to make 

 it dense and hard at this point, decreasing its ductility. With a side-welded link 

 this will result in the side opposite the weld stretching more readily than the welded 

 side, thus bringing heavier stresses on the welded side, resulting in non-uniform de- 

 formation and earlier breaks. With the end weld the change in structure of the 

 welded portion does not upset the balance of stresses nor result in such non-uni- 

 form deformation, as the welded end is not required to act in exactly the same man- 

 ner as the opposite end. The effect should be greater and more uniform strength. 



This advantage of the end weld would be overcome to a certain extent by heat 

 treatment, designed to remove internal stresses and re-establish the original struc- 

 ture of the iron and make it again uniform. 



Aside from the preceding it is largely a question of where the weld can be 

 most easily and surely made. 



A good weld depends on: 



(i) Properly formed scarf. 



(2) Proper heat. 



(3) Proper working. 



As regards the scarf, the two methods are equal, in that the scarf is as easily 

 formed in one case as in the other. 



The side-welded link is more difficult to heat, as may be readily imagined, since 

 it is harder to insert the side of the link than the end of the link in the fire, and 

 the adjoining link interferes more seriously in the case of the side weld. 



The side weld is somewhat more easily worked than the end weld, owing to the 

 straight form of the link at the point where the weld is made. This advantage is 

 somewhat overcome by the fact that the side weld requires two operations. The 

 weld is made on one side of the link over one-half the breadth of the scarf, the link 

 re-heated, turned and welded on the other side. The end weld is made with one 

 operation and one heat. This difference is due to the difference in ease of heating 

 and in the form of the tools necessary to make the weld. It would appear that 

 this double working introduces greater possibility of dirt being enclosed at the weld 

 and of the centers not being welded. 



The advantages of the end weld become more marked when the weld is made 

 in dies, as the end may be more easily inserted in dies than the side, and the ad- 

 joining link being slipped down to the end of the link opposite the weld does not 

 interfere with the action of the dies. So it is that all machine-welded chain is 

 welded on the end. 



The English practice is to weld heavy chain on the side by hand, on the grounds 



