to the preferred embodiment of the present invention where referring to fig3 the face 12 of first work piece 1 is positioned in upper fixed chuck 101 relative to the coil 301 as it would appear preparatory to and during heating so that a controlled gap is obtained sufficiently large to ensure electrical isolation but close enough to obtain satisfactory inductive field coupling between the coil and the first work piece 1 to heat its face 12 similarly the position of second work piece 2 in lower moving chuck 102 and the position of forge piston 205 are adjusted to obtain a similar gap between the end face 13 of work piece 2 and coil 301 where the position of forge piston 205 is further arranged to have sufficient stroke to bring the end faces 12 and 13 of work pieces 1 and 2 into contact with the coil 301 retracted rotary piston 206 is typically set in a fully retracted position prior to welding following positioning of the work pieces with the coil extended shielding gas is introduced into the enclosed space sufficient to substantially purge oxygen from the environment in contact with the work piece end faces 12 and 13 until they.