A technique for the fusion welding of uranium has been under development and several methods of fusion welding have been investigated. The inert gas, shield arc method has proven to be the most satisfactory of the processes thus far examined. Uranium properly weld by this method was free from porosity, cracks, and oxide inclusions. Certain precautions and some special techniques were required to make good welds.

The annealing or heat treatment of uranium in any medium other than a good vacuum or purified helium atmosphere, will lower the room temperature properties of ultimate strength, hardness and elongation. In general, the elongation of vacuum annealed uranium exceeds considerably the elongation of air or salt annealed uranium. Any annealing medium which permits contact of the uranium metal with atmospheric gases tends to produce low elongation and ductility and a lowering of the ultimate strength. The above is true for uranium in any solid form, whether it is rolled sheet, cast bars or plates, rolled rod, or extruded shapes. Annealing in the molten salt bath (65% potassium carbonate and 35% lithium carbonate), which is used by Los Alamos and other laboratories concerned with the fabrication of uranium, produces the lowest elongation or ductility and ultimate strength when compared to similar properties of metal annealed in the other media examined. Mass spectrometer analyses of the dissolved gases present in high ductility and low ductility uranium indicate that dissolved hydrogen is probably the chief cause of low physical properties.