Some Fundamental Problems in 

 Percussive Welding 



By ERIC EDEN SUMNER 



(Manuscript received February 5, 1954) 



The basic processes of percussive welding are presented. Large variations 

 in arc duration residt from the spread in initiation separation, magnetic 

 bridging effects, and the amplifying effect of evaporation. Higher voltages 

 are shown to decrease the relative spread of initiation separation. An analysis 

 of bridging suggests minimizing the ratio of current to separation. A welding 

 circuit offering independence from arc-duration variations is developed. 

 The use of a capacitative transmission line, or approximations thereto, 

 has residted in greatly improved process control. 



IXTRODUCTION 



Early work in percussive welding goes back to late in the nineteenth 

 century. Both applications and accounts in literature are relatively 

 rare. However, this type of welding should have considerable applic- 

 ability in \'iew of some rather outstanchng advantages: 



1. The fact that the arc potential is approximately 15 volts permits 

 the addition of considerable energy Avithin a very short time and, rela- 

 tive to resistance welding, small currents for shorter times are possible. 

 This allows the welding electrodes to be placed well away from the weld 

 zone Anthout overheating of adjacent areas. Effects of deflection due 

 to the high electrode clamping forces can be minimized. 



2. The compatibility problem between the materials and geometries 

 of the parts to be welded are eased relative to the slower butt welding 

 method. 



3. The welds produced in a controlled process are quite strong and 

 can well approach the intrinsic strength of the parts to be welded. 



4. The percussive welding process is very fast. Use in high speed 

 automatic production is advantageous. 



The problem treated in this paper arose dining a very short study 

 program at Bell Telephone Laboratories, Inc. in connection with a new 



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