Fused double-walled carbon nanotube (DWNT) fibers were made with a strength of a 700 GPa Young's modulus. This strength was seen in prior experiments, in 2010 and 2011, where electron beams welded DWNTs in microscopic bundles together and the fused bundles had 700 GPa tensile strength. There is now an effort to scale up production of ultrahigh strength material using high temperatures (1700-2300 C) and about 800 atmospheres of pressure instead of an expensive and time-consuming process using high-voltage e-beams. The electron dose available from commercial e-beam facilitaties is so low that processing macroscopic DWNT materials would take months instead of half an hour or less. The same thermal treatment process will enable manufacturing wires that have the highest conductivity of all carbon nanotube wires.