DEVELOPMENT OF TECHNIQUES FOR WELDING V-CR-TI ALLOYS

Welding vanadium alloys is complicated by interstitial impurity introd uction and redistribution at elevated temperatures. Gas tungsten are ( GTA) welding, which will probably be required for the fabrication of l arge tokamak structures, must be done in a glove box environment. Weld s were evaluated by Charpy testing. GTA welds could be made with a duc tile to brittle transition temperature (DBTT) of 50 degrees C with a p ost-weld heat treatment (PWHT) or by using a heated Ti getter system o n the glove box to reduce interstitial contamination. Titanium-O,N,C p recipitates in the fusion zone were found to transform to a more oxyge n-rich phase during a PWHT of 950 degrees C/2 h. Hydrogen was found to promote cleavage cracking following welding in cases where the atmosp here was contaminated. Grain size and microstructure also affected wel d embrittlement. (C) 1998 Published by Elsevier Science B.V. All right s reserved.