RAMESH KUMAR BUDDU ET.AL 1 STUDIES OF ULTRASONIC AND PHASED ARRAY INSPECTION TECHNIQUES NDT ON HIGH THICK SS 316L WELDED JOINT MOCK-UPS OF FUSION REACTOR COMPONENTS FABRICATION APPLICATIONS RAMESH KUMAR BUDDU, KEDAR BHOPE, MAYUR MEHTA, S S KHIRWADKAR Institute for Plasma Research, Bhat, Gandhinagar-382428, India. Email: [email protected]Abstract Fusion reactor components manufacturing are mainly deals with Austenitic stainless steels with different type welding techniques and kind of joints. Thick steel like 40 mm & 60 mm plates are used mainly in the fabrication of vacuum vessel, first wall divertor and others. Based on the requirements, different weld joining techniques like Tungsten Inert Gas (TIG) welding, Narrow Groove TIG (NG-TIG) welding, Electron Beam Welding (EBW) are employed for fabrication of subsystems in fusion reactors. To qualify the weld joints quality, Ultrasonic and Phased Array examinations have shown advantage over the conventional non-destructive tests for the welds inspection. These techniques provide the versatile inspection and identification of the weld defects of the complex geometries and ease of access and providing quickly the needful tests. Weld mock-up coupons have been fabricated with different welding procedures (TIG, EB, and NG-TIG) and joint preparations such as butt and Narrow groove, T-weld joints of 40 mm and 60 mm thick plates of SS316L. The non- destructive testing (NDT) studies have been carried out with conventional ultrasonic examinations (A-scan technique), Phased Array examination techniques on the different weld SS316L plate mock-ups. Calibrations have been carried out with known size defect and reference methods of V1 & V2 blocks both with ultrasonic inspection and Phased Array ultrasonic technique. Phased array examination has shown superiority over the conventional ultrasonic technique by revealing the minor size defects with volumetric inspection. However, the detected weld defects are well within the acceptable limits. The experimental methodology and results will be presented in the paper. 1. INTRODUCTION Austenitic stainless steel is the key structural steel material used for various components fabrication in fusion reactors and advanced reactor systems. SS 316L steels are used for the major components like vacuum vessel, first wall plasma facing diverters, cryostats and other sub systems[1-2]. The fabrication of these structural components is carried by different joining techniques like TIG welding (TIG), laser beam welding (LBW) and hybrid laser-TIG welding and electron beam welding (EBW) for development [3-5]. However, due to the complexity involved in welding process choices and procedures, the joints are having weld defects like porosity, undercuts, blow holes, slags inclusion, incomplete penetration, lack of side wall fusion and excess penetration during the joining process. Hence, weld quality inspection and qualification of these fabricated components is a challenging task in terms of accessibility of complex shapes and sizes of the fabricated components [6-7]. In case of thick section steel welds inspection, the techniques like X-ray radiography and ultrasonic scan tests are prominent for the evaluation of the weld defects throughout the weld depth. Liquid penetrant tests are useful for the detection of surface cracks, voids or discontinuities, but they pose limitation if the vacuum compatibility which is needed as the chemicals used have outgassing effects. Ultrasonic examination has proved to be the dominant tool for inspection of the welded structures defects inspection as by using angle probe it can detect the defects in wide range with proper calibration implementation [8-9]. However, the limitation arises when the weld zone large grain structures cause the attenuation at the edges and sound waves get scattered [10]. This further cause the interpretation of the signals which are difficult to resolve due to poor signal to noise ratio to interpret the defect nature. This technique equally poses the higher degree of anisotropy, higher attenuation and dispersion features for the stainless steel and welded materials of higher thickness. This limits the ultrasonic inspection process for accurate identification of weld defects details. Phased array ultrasonic inspection technique has the capabilities of beam steering, sectorial scanning and focussing at the depths of welds [11]. This additionally provides for multiple angle beam steering process across the sample with single sensor having wide range. This technique provides volumetric defects analysis with different beam angle probe and detects in single position. Full penetration weld examination can be carried out with this technique. This paper reports the weld quality evaluation of 40 mm and 60 mm thick SS316L plates fabricated by multipass TIG (Tungsten Inert Gas) welding. T-type weld joints are examined by view of typical welds in vacuum sectors have many types thicker plates like ribs and shells require to be inspected volumetrically. EBW (Electron beam welding) joints are essential in keys and inboard side vacuum vessel shells with very low weld distortion ,hence this kind of EB weld coupons are fabricated to establish the weld inspection tests. Also the efforts are made to establish the ultrasonic examinations and phased array ultrasonic examinations on weld coupons of 40 mm and 60 mm SS316L plates.
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STUDIES OF ULTRASONIC AND PHASED ARRAY INSPECTION ... · Phased Array examination techniques on the different weld SS316L plate mock-ups. Calibrations have been carried out with known
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RAMESH KUMAR BUDDU ET.AL
1
STUDIES OF ULTRASONIC AND PHASED ARRAY INSPECTION TECHNIQUES
NDT ON HIGH THICK SS 316L WELDED JOINT MOCK-UPS OF FUSION
REACTOR COMPONENTS FABRICATION APPLICATIONS
RAMESH KUMAR BUDDU, KEDAR BHOPE, MAYUR MEHTA, S S KHIRWADKAR
Institute for Plasma Research, Bhat, Gandhinagar-382428, India.