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

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.