Weldability Pre-qualification of Steels for Deepwater Service
The weldability of steels for deepwater applications must be determined long before welding procedures are qualified. The weldments of deepwater equipment such as steel catenary risers (SCRs) are subjected to currents that result in high cyclic stresses. It is imperative that steels selected for this service have high CTOD fracture toughness values after welding to ensure good weldability. These CTOD values are used to determine the defect acceptance criteria that are used for inspection of the weldments. The base metal and weld metal properties are easily obtained, but because the weld joint design changes the position of the HAZs, the CTOD value for the HAZ is usually a combination of the base, weld consumable, and HAZ. The value obtained from such a test is suspect, and may give an overly optimistic value if the weld metal and /or base metal have high CTOD values. This presentation covers the various strategies for determining the true weldability long before construction commences, using API RP 2Z Type tests for pre-qualification of base materials.
