Underwater hyperbaric dry welding of high strength steel arctic oil and gas pipelines

Abstract

Abstract The paper describes the results of research about orbital hyperbaric FCA-welding of API X70 steel pipes with the use of gas-shielded flux cored wires with the flux of TiO2-CaF2 system with the higher content of fluorides in the flux core. As a result of the research, the dependences of the welding current, arc voltage, metallurgical features and mechanical properties depending the pressure in the hyperbaric chamber are determined. The use of gas-shielded flux cored wires of TiO2-CaF2 system within the gas pressure 0,1–0,6 MPa, for the orbital welding of API X70 steel provides the favourable microstructure of welded joint and mechanical properties of welds according to the Class A per ANSI/AWS D3.6M:2010.