GB1380345A - Method of welding metals under water - Google Patents

Abstract

1380345 Welding by fusion DIRECTOR OF NATIONAL RESEARCH INSTITUTE FOR METALS 8 March 1972 [21 Aug 1971] 10857/72 Heading B3R In plasma arc, MIG or TIG welding under water, the plasma column or shielding gas issuing from the torch is surrounded by a layer of fluid to cover to stabilize the arc and prevent rapid water cooling of the workpiece. The surrounding layer of fluid may comprise a viscous liquid having viscosity of at least 10 centipoises or may comprise a gas. A viscous liquid may be water glass, millet jelly, aniline, glycerol and may contain arc stabilizers such as calcium carbonate, potassium silicate, titanium oxide, or the finely divided particles of a gasgenerating substance, e.g. starch or cellulose. A surrounding gas may be argon, carbon dioxide or an oxygen/carbon dioxide mixture. Plasma gas may be argon or helium, and MIG or TIG shielding gas may be argon. As shown a plasma torch comprises a tungsten or thorium containing cathode 4 connected to starter and main power supply 10, 11, and a copper anode nozzle 5 connected to the starter supply 10. The workpiece 12 is connected to the main supply 11. Plasma gas is fed through an inlet 15, the resulting plasma column issuing from the anode nozzle opening 6. The latter is surrounded by an annular slit 7 through which viscous liquid, fed through an inlet 9 and pooled at 8, issues to surround the plasma column. The slit 7 inclination to the torch axis is - 10 to + 30 degrees. Filler metal 17 may or may not be fed to the weld zone. The plasma gas flow rate should be high (at least 8 litres per minute) during non-transferred arc starting and reduced (to 2-10 litres per minute) for transferred arc operation. The description discloses examples of butt and fillet lap welding and the use of copper or alumina backing plates. In a two pass butt weld using a plasma arc surrounded by a gas layer, a filler wire is introduced for the second pass.