Prodn. of thick-walled metal high-pressure pipes with smooth interiors - by alternating cold deformation and thermal treatment stages plus application of ductile non-ferrous metal or alloy to pipe interior

摘要

Thick-walled, metal, high-pressure pipes with relatively smooth interiors and D/s 2.4-4.0 are mfd. from welded or seamless unfinished piping by a process involving alternate cold deformation and thermal treatment until the required dimensions are achieved, final cold deformation being pref. stretching with an internal instrument, this being followed by a final thermal treatment. A ductile non-ferrous metal or metal alloy with a m.pt. lower than the pipe material is applied to the interior pipe surface immediately prior to final thermal treatment. Heat evolved during said treatment causes the metal to fuse with the pipe. Finally, the pipe interior undergoes smoothing. ADVANTAGE - A simple, economic process resulting in pipes able to withstand a pulsating, inner pressure in excess of 1000-1500 bar. In an example, a plain carbon steel (St30Al/St30Si) unfinished pipe, dimensions 42.4 x 5.6 mm, undergoes the following process steps: cold drawing then annealing at 900-940 deg.C in a protective gas atmos.; three separate cold drawing stages (giving pipe dimensions 15.2 x 2.70 mm) then annealing under the previously quoted conditions; cold drawing (11.25 x 2.47 mm) then annealing; cold drawing (8.2 x 215 mm) then annealing; cold drawing (5.95 x 2.05 mm); application of copper solder wire then heating at 990 deg.C in a protective gas atmos; smoothing (expanding) of interior surface, giving final dimensions of 6.0 x 2.0 mm.