Abstract
The ultrasonic inspection of thick-walled welded joint with austenitic weld metal has proven to be a challenge due to its anisotropic microstructure that can promote ultrasonic waves attenuation. This work aimed to optimize the phased array ultrasonic inspection of the thick-walled joint of a 9% Ni steel pipe welded with Ni-based superalloy 625. The development was carried out by CIVA numeric simulation to preview the beam behavior during the inspection of GTAW (Gas Tungsten Arc Welding)/SMAW (Shielded Metal Arc Welding) joint with anisotropic weld metal. To validate the simulation results, experimental tests were performed with a phased array transducer using longitudinal waves on a calibration block withdrawn from the joint. The configuration of low frequency (2.25 MHz), 16 active elements and a scanning angle of 48° ensured the inspection of the entire joint and the computational simulation proved to be essential for the success of the inspection.
Highlights
Cryogenic 9% Ni steel has been used almost exclusively in the storage and transport of liquefied gases in the form of sheets of small and medium thicknesses
The results showed that with the proper combination of phased array ultrasonic parameters, it is possible to inspect the HAZ (Heat Affected Zone) and the whole weld metal of thick-walled 9% Ni welded joints, providing security for this new application in the Brazilian pre-salt industry
The adopted filler metals were Ni-based superalloy 625 (ERNiCrMo-3/AWS A5.14 and ENiCrMo-3/AWS A5.11 for gas tungsten arc welded (GTAW) and shielded metal arc welded (SMAW), respectively)
Summary
Cryogenic 9% Ni steel has been used almost exclusively in the storage and transport of liquefied gases in the form of sheets of small and medium thicknesses. Hirsekorn [10] compared the effect of ultrasonic longitudinal and transversal waves in austenitic weld metals and concluded that the sonic speed and the beam deflection are different according to the scanning incidence angle. Sound pressure, when the phased array technique is used, relies on the number of active elements, focal distance, propagation angle, ultrasonic speed and transducer frequency. The results showed that with the proper combination of phased array ultrasonic parameters, it is possible to inspect the HAZ (Heat Affected Zone) and the whole weld metal of thick-walled 9% Ni welded joints, providing security for this new application in the Brazilian pre-salt industry
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