DEVELOPMENT OF EQUIPMENT FOR AUTOMATIC NARROW-GAP WELDING FOR SHIPYARD USE.

The design of the automatic Narrow-Gap welder was finalized and construction begun. A thermocouple and infrared temperature sensing systems were evaluated and the infrared system selected on the basis of accuracy and ability to measure temperature without direct contact with the heated plate. Twin-wire procedures were developed for flat-position welding with the consumable-insert fiber-glass-tape weld backup. The resulting weld has excellent contour and leaves little reinforcement to be ground off. Narrow-Gap welds in HY-140 steel using Linde X-150 wire were made using both the standard 80 percent argon-20 percent CO2 shielding-gas mixture and a special shielding-gas mixture of 60 percent helium-38 percent argon-2 percent oxygen. All of the welds contained either shrinkage voids or porosity. It is believed that the X-150 wire available was unsatisfactory for Narrow-Gap welding. Attempts to introduce artificial lack-of-fusion defects into Narrow-Gap welds in the flat position indicated that in this position the process is insensitive to large variations in voltage, current, and travel speed. Author