Abstract: An explosion welding method for metal tube liners in which a metal tube of smaller outside diameter is positioned coaxially within a metal tube of larger inside diameter with one or more shims inserted at opposed tube ends to form a uniform annular gap. The tubes are vertically positioned on a flat surface, and the smaller tube is filled with explosive material detonated from its top surface. The detonation initiates a uniform explosive front traveling down the smaller tube expanding the internal surface of the smaller tube with sufficient velocity to weld the tubes. A vacuum may be formed within the annular gap and/or gas(es) introduced therein to prevent build-up of excessive heat at the explosive front.