This paper presents results from a recently completed program that evaluated numerous commercially available flux-cored arc welding and submerged arc welding consumables designed for use with structural steels having nominal yield strengths of 70 to 80 ksi (483 to 552 MPa). The program characterized tensile and toughness properties of test welds as a function of welding process and parameters. The paper provides guidance on the optimum welding conditions that will help maintain minimum weld metal strength and toughness properties for high-strength steels used in critical offshore structures.
As the oil and gas industry continues to develop reservoirs in deep water, the growing complexity and desire for weight limitations in deep water installations is driving the need for use of higher-strength plate steel (>65 ksi (450 MPa) yield strength (YS)). Steel manufacturers are able to produce quality base materials with appropriate strength and toughness levels to meet the current need. However, structural fabricators that have traditionally built this type of infrastructure have not had much experience in working with steels in this strength level. These fabricators often work with materials not exceeding 50 or 60 ksi (345 or 414 MPa) in YS and some have, consequently, expressed concern about taking on fabrication projects requiring higher-strength materials.
The concerns fabricators have identified include:
Availability of suitable welding consumables.
Increased potential for hydrogen cracking.
Reduced welding productivity.
Lack of experience with high-strength steel (HSS) materials and suitably matched welding consumables.
Without adequate guidance offered to the industry, expanded use of high-strength steels (HSS) could be constrained due to these perceived technology gaps in welding of these materials. As a consequence, the design and weight saving advantages that HSS offers for deep water installations may not be fully realized without prudent guidance on optimized welding parameters.
To aid in addressing some of these issues, a program was funded by the Oil & Gas Strategic Technology Committee, coordinated by EWI, to characterize typical mechanical and metallurgical properties that can be achieved using commercially available submerged arc welding (SAW) and flux-cored arc welding (FCAW) consumables having nominal yield strengths of 70 and 80 ksi (483 and552 MPa). The results of this program will aid in establishing weld procedure specification requirements for HSS.
