... follows: R05200, unalloyed tantalum, electron-beam furnace or vacuum-arc melt, or both, R05400, unalloyed tantalum, powder-metallurgy consolidation, ... % tantalum 2.5 % tungsten, electron-beam furnace or vacuum-arc melt, or both, R05240 tantalum alloy, 60 % tantalum 40 % ... columbium, electron-beam furnace or vacuum-arc melt, or both.Permissible variations in diameter for wires Diameter, ...