Patent ID: 7399264

Claim:
A process of producing high pressure tubing from austenitic stainless steel, the process comprising the steps of: causing a continuous austenitic stainless steel strip to pass through pre-weld rolls to produce a continuous tubular shape having opposing edges separated by a longitudinal gap therebetween, the pre-weld rolls being enclosed in a forming housing; maintaining the gap with a seam guide inserted into the gap; while directing a liquid-free gas mixture of an inert gas and a gaseous fluxing agent at the gap and into an interior of the tubular shape, causing the continuous tubular shape to pass through a high frequency induction coil that generates eddy currents in the opposing edges of the tubular shape to cause heating of the opposing edges while surfaces of the tubular shape subjected to heating by the induction coil are flooded with the liquid-free gas mixture, the induction coil operating at a frequency of about 400 to about 1100 KHz and being enclosed in a weld housing so that the weld and forming housings are thermally insulated from each other; applying pressure to the tubular shape with weld rolls to force the opposing edges together to form a continuous tubing having a continuous butt weld joint, the weld rolls being mounted on weld roll shafts and enclosed with the induction coil in the weld housing; and quenching the butt weld joint with an inert gas without the assistance of liquid; wherein the gaseous fluxing agent consists essentially of trimethylborate, acetone, and methanol.