環(huán)形磁場(chǎng)磁體外殼上的焊接技術(shù)外文文獻(xiàn)

Contents lists available at ScienceDirect Fusion Engineering and Design journal homepage Welding technologies applied on casings for JT 60SA toroidal fi eld magnet Paolo Rossia Antonio Cucchiaroa Gian Mario Pollia Mariantonietta Gabrieleb Guido Cipolloneb Massimiliano Tacconellib Valerio Tomarchioc aENEA Department of Fusion and Technology for Nuclear Safety and Security Via Enrico Fermi 45 00044 Frascati Rome Italy bWalter Tosto Via Erasmo Piaggio 66100 Chieti Italy cFusion for Energy JT 60SA European Home Team Boltzmannstrasse 2 D 85748 Garching Germany A R T I C L E I N F O Keywords JT 60SA tokamak Toroidal fi eld coil Welding technology A B S T R A C T In the framework of the Broader Approach program ENEA supplied the Toroidal Field TF coil casings for JT 60SA tokamak ENEA commissioned the manufacture of the full set of eighteen casings for the integration of the TF coils plus two additional spare casings to the company Walter Tosto Chieti Italy The casing is segmented in one outboard straight leg an outboard curved leg and three inboard covers The preliminary design of the casing components has been prepared under the coordination of Fusion for Energy The detail design has been fi nalized involving industrial partners responsible for the subsequent integration of the coils Contract started in 2012 with the design and fabrication of mock ups representative of the most important cross sections of the casing complete with the relative welding chamfers and cooling channels Walter Tosto completed the manufacturing drawings of the casing components the qualifi cation of the welding processes and the defi nition of all the manufacturing procedures in 2013 Casing production activities started in 2014 and the full procurement of the eighteen casings plus two additional spare casings was completed within August 2017 This paper provides an overview of the welding technologies applied for the casing procurement such as the selection process qualifi cation activities welding operations fi nal checks and considerations 1 Introduction The construction in Japan of the large superconducting tokamak JT 60SA started in the framework of the Broader Approach BA program between European Union and Japan to contribute to an early realiza tion of fusion energy and aimed to develop operational scenarios re levant for ITER and DEMO JT 60SA is a large tokamak with a fully superconducting magnet system including 18 Toroidal Field TF D shaped coils 6 Equilibrium Field EF coils and one Central Solenoid CS with four modules 1 The voluntary contribution to the JT 60SA project from ENEA the Italian Agency for New Technologies Energy and Sustainable Economic Development included the design manufacture and test of 9 super conducting TF coils winding pack 18 stainless steel TF coil casings to enclosure the winding packs part of the CS and PF Power Supply and Switching Network Units In 2012 ENEA awarded a contract to the company Walter Tosto Chieti Italy for the supply of the full set of eighteen TF coil casings plus two additional spare ones The design of the casing components has been prepared under the coordination of Fusion for Energy and then fi nalized by ENEA and Walter Tosto involving the industrial partners responsibleforthesubsequentintegrationofthecoils ASG Superconductors ASG Genoa Italy selected by ENEA for the Italian coils and General Electric GE Belfort France selected by CEA for the French coils 2 Casing production activities started in 2014 and the full procurement of the eighteen casings plus two additional spare casings was completed within August 2017 3 The authors have already described the main technical and man agement aspects of the casing production 3 6 hence the present paper would show an overview of the welding technologies applied for the casing procurement such as the selection process qualifi cation ac tivities welding operations fi nal checks and considerations 2 Casing material and composition Each TF coil casing is 7 5m high and 4 5m wide and is produced by assembling and welding materials from rolled plates and from forgings made of stainless steel FM316LNL as defi ned by JSME code 7 with https doi org 10 1016 j fusengdes 2019 01 121 Received 8 October 2018 Received in revised form 23 January 2019 Accepted 24 January 2019 Corresponding author E mail address paolo rossi enea it P Rossi Fusion Engineering and Design 146 2019 946 949 Available online 01 February 2019 0920 3796 2019 Elsevier B V All rights reserved T Nitrogen content in the range of 0 08 0 11 and Cobalt content less than 500 ppm The straight leg is composed of a straight part and two elbows The straight part is made from two side wings welded to a central base Each elbow is made up of two half elbows machined from one forged block and welded to the central band made from plates including one small forged piece Electron Beam welding EBW is used to join the wings to the base and to weld the half elbows to the central band then the straight part is welded to the elbows by GTAW Gas Tungsten Arc Welding Two cooling pipes are also welded onto the inner surfaces of the wings of the straight leg The curved leg is composed by two wings EB welded to a central base and then a vertical port and external sup ports are welded by GTAW SMAW Shielded Metal Arc Welding processes Other four smaller components of the curved leg are pro cured as loose chamfered plates The casing composition is shown in Fig 1 Two diff erent sets of mock ups were also part of the supply They were representative of the straight leg and the curved leg cross sections complete with the relative welding chamfers and cooling channels and were used to qualify the welding processes and to validate the casing manufacturing processes 3 Welding processes EBW has been selected for the longer welds of the lateral wings of the straight leg and curved leg in order to reduce the following dis tortions and deformations All the casing internal channel welds composition of curved leg wings and base and welding of the elbows to the straight leg were done by GTAW manual welding narrow gap technique External supports of the curved legs were welded by SMAW and GTAW SMAW Extra thicknesses and extra lengths were foreseen on all the com ponents in order to recover possible shrinkages deformations distor tions after welding and machining operations Walter Tosto performed qualifi cation using diff erent welding tech nologies EBW GTAW GTAW SMAW issue of preliminary welding procedure specifi cation pWPS chamfer details welding consumables welding parameters etc execution of welding mock ups execution of nondestructive tests VT PT UT RT micro and macrographic tests execution of destructive tests mechanical tests tensile bend impact and hardness tests then elaboration of the process qualifi cation record PQR and preparation of the fi nal WPS The welding qualifi cation activities were collected in a specifi c Welding Book Three complete sets of jigs have been realized for the assembly and welding operations of the elbows the straight parts the curved legs and fi nally the welding of the external supports to curved legs as shown in Fig 2 A dedicated rotating jig see Fig 3 was realized for the GTAW transversal welding of the elbows to the straight part in PA ISO 1G ASME position preparing the joint by a double U shaped chamfer using 2 4 mm diameter fi ller rod with a typical current of 110 190A 3 1 Electron beam welding EBW is a special fusion welding process based on a narrow electron beam that is able to concentrate welding energy in a small portion of the joint accomplishing the great advantage of a very limited thermal distortion It is necessary that the whole EBW process took place in vacuum conditions in order mainly to improve electron acceleration in the beam to prevent energy dispersion or absorption due to the pre sence of gases and to avoid welding pool contamination Due to the large dimensions of the casing components qualifi cation and production of EB welding activities were performed in a large chamberfacilityshowninFig 4 volume700m3 dimensions 7m 7m 15m in Pro Beam Burg Germany In this chamber a robot arm mounted on a gantry on the sidewall carries out the move ment of the EB generator There are several video systems to follow the activities in the chamber including one camera at the EB generator that shows the weld pool during welding The position information and all movements are processed with an integrated control system and an online electron optical view follows the weld bath hole movement during the welding operation So it was possible to join each of the two wings both for the curved leg and straight leg to the central base plate in one only vacuum cycle and in 2 welding runs that in case of the curved leg was 9 5 m long and 75mm thick and for the straight leg was 4 5 m long and 45mm tick A minor length 2m but again a high thickness of 62mm were the di mensions of the elbow welds The EBW typical cycle consisted of ma chine set up then casing component handling and mounting on the machine movable table pumping welding and venting operations The overall duration of one leg EBW cycle was about 12 15hours each time Fig 1 Segmentation of the casing components Fig 2 Welding of the external supports to the curved leg Fig 3 GTAW transversal welding of elbows to the straight leg Fig 4 Electron beam welding of the curved leg P Rossi et al Fusion Engineering and Design 146 2019 946 949 947 Electrical key parameters used for casing EB welds were within the following ranges 80 120 kV acceleration voltage 180 360 mA beam current 22 29kW beam power Vacuum level in the chamber was 10 3mbar and the welding speed varied from 120 to 350mm min No fi ller material and no chamfer preparation was required but the se parate parts needed to be faced with a typical gap of 0 2 mm anyway lower than 0 5mm and a maximum step value of 2mm Backing strips and beam stopper were also tack welded on the casing components in order to obtain a complete penetration of the beam and consequently of the weld 3 2 He cooling pipe weld on the straight legs The two cooling channels foreseen on the straight leg internal sur face were required to comply with a strong thermal transmission then theoretically a continuous welding for over 4 5 m would be the best solution But the risk of blowing through the tube also due to the un comfortable position of the welder suggested a GTAW step welding sequence on both sides of the cooling channels with a pitch of 100mm a gap of 5mm and throat depth of 3mm see Fig 5 NDT leak and pressure test confi rmed that 100 of the step welds were satisfactory 4 Final checks 100 volumetric checks of all the welds were foreseen Non de structive examination of large part of welds of coil casings components was performed using Radiographic Testing RT Non destructive ND tests were completed with conventional ultrasonic test UT visual checks VT and dye penetrant test PT all based on ASME Code re quirements Where the geometry of component made the RT inspection not feasible due to limited access at back side or lack of minimum distance to place the source UT was selected to inspect the weld volume taking advantage of Phased Array PA UT technology Phased array is an advanced ultrasonic technique The probe is made up of several crystals diff erently than conventional UT and by exciting them with appro priate parameters is possible to steer and shape the beam inside the material concentrating energy where the inspected geometry requires The behavior of the beam can be predicted using advanced software showing the component inspected and where the beam goes inside it Scan plan settings can be optimized in a simulation by changing the shape of the beam and the position of the probe All inspections per formed by PA UT are encoded fi xing the starting point of scanning it is possible to have the real position and amplitude of each indication found This capability off ers the possibility to have a report similar to a RT fi lm Moreover all inspection data and reports are recorded dis played and can be analyzed Some trials have been performed to validate the reliability of this inspection method for the casing components using a one to one mock up with artifi cial defects machined inside Thanks to this method it has been possible to inspect in an eff ective and quick way the long EB welds that joined curved and straight leg to the lateral wings In Fig 6 it is shown a typical scanning fi le with an indication of the defect found in an EB weld of a straight leg during repair actions Usually it was not possible to precisely measure the real dimensions of the scanned in dication after defect repair since almost all indications were removed during repairing grinding activities Additional test consisted in further UT of the EB welded joints plus PT after fi nal machining and a further overall penetrant testing before delivery the fi nished components to eventually detect and repair even any minor superfi cial defect After all the main criticalities resulting from the welding activities were repairs of EB weld defects and control of deformation after welding and machining The learning process after the realization of the initial fi rst com ponents helped to control the deformations and shrinkages induced on the legs and in particular on the curved one after main welding and machining processes While the indications or defects found after EB welds on the straight part of the straight leg on the curved leg and on the elbows probably due to the high thickness required additional welding repair actions grinding welding NDT increasing the pro duction duration with consequent problems on activities synchroniza tion Worth noting are the total number of welds performed and checked 1240 the total length of EB welds with high thicknesses 45 mm 62mm 75mm 700m and the total length of TIG step welding of the cooling pipes 400 m 5 Conclusions In 2012 ENEA commissioned the company Walter Tosto the fabri cation of the casings for JT 60SA TF magnet Manufacturing was pre ceded by an intense design activity and supported by the realization of representative full scale mock ups used to validate the selected pro cesses Welding was deeply involved during manufacturing activities A careful qualifi cation program was studied and performed on diff erent welding technologies EBW GTAW SMAW in order to optimize the casing component composition in terms of quality and schedule results Production of full set of 18 casings plus 2 additional ones was completed in 2017 after about 5 years All the TF coils have been progressively integrated inserting the superconducting winding packs into the steel casings 8 9 tested in cryogenic conditions at full current 10 delivered in Japan and fi nally installed in JT 60SA tokamak within June 2018 11 Disclaimer The views and opinions expressed herein are the sole responsibility of the authors and do not necessarily refl ect those of Fusion for Energy and the European Commission Fig 5 He cooling channel welding Fig 6 UT phased array technique Comparison between scanning fi le and defect indication found during grinding process P Rossi et al Fusion Engineering and Design 146 2019 946 949 948 Acknowledgments The authors would like to thank the Pro beam Electron beam welding group Burg Germany for their contribution during welding qualifi cation and