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The key technology research of electron beam welding in CFETR vacuum vessel collar
Fusion Engineering and Design 139 (2019) 14–18
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
The key technology research of electron beam welding in CFETR vacuum vessel collar
T
Zhihong Liua,b, , Jiefeng Wua,b, Xiaosong Fanb, Qiuyue Xiongb, Jianguo Maa,b ⁎
a b
Key Laboratory of Special Welding Technology of Anhui Province, Huainan, China Institute of Plasma Physics, Chinese Academy of Science, Hefei, China
ARTICLE INFO
ABSTRACT
Keywords: CFETR VV Electron beam welding VV collar Welding deformation Residual stress
Chinese Fusion Engineering Testing Reactor(CFETR) is a fully superconducting magnet Tokamak, and the key components of CFETR have been studied. As one of the pre-research projects, 1/8 full-scale vacuum vessel(VV) aims to grasp the key technology of molding, welding, non-destructive testing and measurement in the aspect of building a large-scale vacuum vessel, and accumulate experience for the formal construction of CFETR. The project has been officially launched by Institute of Plasma Physics Chinese Academy of Sciences(ASIPP) in 2015. In the manufacturing process of 1/8 full-scale VV, the electron beam welding is adopted at the VV collar in order to reduce welding deformation. As a large-scale electron beam welding (EBW) system set up in ASIPP, the research work of electron beam welding technology has been carried out, with periodical achievements obtained. This paper will introduce the key technology and research progress of the electron beam welding for the VV collar in detail.
1. Introduction Chinese Fusion Engineering Testing Reactor (CFETR) is a superconducting magnet Tokamak, with a scale equal to ITER [1,2]. At present, the research and development on key components of the CFETR has already begun. The 1/8 full scale vacuum vessel(VV) has been officially launched by Institute of plasma Physics Chinese Academy of Science(ASIPP) in 2015. In the manufacturing process of 1/ 8 full scale VV, the electron beam welding(EBW) is adopted at the VV collar in order to reduce welding deformation, and a large-scale electron beam welding system has been set up by ASIPP in 2017. Along with the process of 1/8 V V collar parts have been finished, the EBW tooling is in manufacturing. In view of the deformation and residual stress distribution in the process of VV collar welding, simulation analysis and experimental study have been carried out, with periodical achievements obtained. In this paper, the development of EBW technology for VV collar will be introduced in detail. 2. The design of 1/8 full size VV collar According to the current design [3] of the CFETR, 1/8 full size VV is
⁎
double-shell construction. The thickness of inner and outer shell is 180–380 mm and the wall thickness of single-layer shell is 50 mm. The VV has 3 ports, upper port, equatorial port and lower port. Each port is composed of port collar and its extension.1/8 full size VV is as shown in Fig. 1. Because the size of VV port, port collar and its extension will be manufactured in the factory respectively, and then assemble at the assembly site of the VV section. The extension of VV port has a relatively regular geometric construction, it’s easy to manufacture by hot press molding [4]. The collar between the VV and the extension has a very complex three-dimensional structure, which is difficult to molding directly. Therefore, the collar will be divided into several small parts for bending using thick stainless steel forgings, After milling, they are welded into a whole port collar. At last, the VV shell, port collar and its extension will be welded into an integrated VV section. The collar of outer shell of VV upper can be divided into part A and part B according to its structure, and each part is composed of some subsections. The diagram of subsections is shown in Figs. 2 and 3 shows port collar after processing. The thickness of single layer shell of VV is 50 mm and the throughthickness direction of VV has no processing allowance after assembling
Corresponding author at: Key Laboratory of Special Welding Technology of Anhui Province, Huainan, China. E-mail address: [email protected] (Z. Liu).
https://doi.org/10.1016/j.fusengdes.2018.12.059 Received 10 October 2018; Received in revised form 10 December 2018; Accepted 18 December 2018 0920-3796/ © 2018 Elsevier B.V. All rights reserved.
Fusion Engineering and Design 139 (2019) 14–18
Z. Liu et al.
Fig. 4. The vacuum EBW equipment.
Fig. 1. 1/8 full size VV.
Fig. 5. The diagram of part A and part B subsections of upper port collar. Fig. 2. The diagram of subsections.
Table 2 The parameter of electron beam welding.
Fig. 3. Port collar after processing. Table 1 The parameter of EBW system. Component
Specification/Type
Electron beam gun High voltage source Vacuum vessel
G600KM HCV-150 kV/60kW 7200 × 3550 × 2600 mm
Parameter
Specification
Working distance(mm) Accelerating voltage(kV) Beam current(mA) Focusing lens current(mA) Focus setting Surface travel speed(mm/s)
306 150 97 2507 Lower focus 5
large size and thick wall of the collar in the VV, it is proposed to adopt the EBW to weld the port collar. Automatic narrow gap tungsten argon arc welding(NG-TIG)is used between the port collar and the extension. 3. The design of EBW scheme of outer collar for upper port In terms of the present design, the structure and size of the upper, equatorial and lower port collar of the VV are different, and the size of outer collar of the upper port is the maximum, 4320 × 2322 × 1212 mm, the size of inner collar of the equatorial port is the minimum, 2300 × 975 × 339 mm. Therefore, the EBW equipment is selected
and welding. Therefore, it is necessary to reduce the welding deformation as much as possible during the welding process. Based on the analysis of the existing welding methods and the characteristics of the
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Fusion Engineering and Design 139 (2019) 14–18
Z. Liu et al.
Fig. 6. The Diagram of welding tooling of part A and part B. Table 3 The welding sequence of outer collar of the upper port. Component
Scheme
A
Scheme Scheme Scheme Scheme
B
The sequence of welding 1 2 1 2
(1 + 2)+(3 + 4+5 + 6) (1+(3 + 4+5))+(2 + 6) (7 + 10)+(8 + 11)+(9 + 12) (7 + 8+9)+(10 + 11 + 12)
according to the size of outer collar of upper port. ASIPP set up a set of electron beam welding system whose volume is 66 m3 in 2017 in order to carry out related EBW. This system can meet welding requirements of all ports of CFETR VV. The parameter of EBW system is shown in Table 1.The vacuum EBW equipment is shown in Fig. 4 According to the current design, the outer collar of the upper port is divided into part A and part B. Part A is composed of 6 subsections, and part B is composed of 6 subsections. As shown in Fig. 5. In the port collar welding process, there are usually two ways to control the welding deformation. The first is optimizing the parameter of welding, and the second is optimizing the sequence of welding. The welding parameters have been determined by a large number of welding experiments. The parameter of EBW is shown in Table 2. Due to the different structure and size of VV ports of CFETR, the unique welding scheme will be adopted to every port collar. There are 2 aspects needed to consider as to designing welding scheme. One is designing and optimizing welding tooling to reducing weight but keep sufficient intensity, and welding tooling can provide appropriate operating space to perform EBW. The other is optimizing welding technology in order to reduce deformation during welding and reduce
Fig. 7. The results of welding deformation and stress of part A.
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Fusion Engineering and Design 139 (2019) 14–18
Z. Liu et al.
residual stress after welding. Through the previous analysis and the results of process pre-study, the tooling of outer collar of upper port is as shown in Fig. 6. Due to the limited range of motion of the electron gun in the EBW system, the majority of movements are realized by moving or rotating working table during welding. Through analysis and welding experiments, there are two welding schemes for electron beam welding of collars, the welding sequence is shown in Table 3. In the welding process of port collar, welding sequence will affect welding deformation and residual stress. In order to minimize welding deformation and residual stress, the finite element simulation of welding process will provide theoretical basis for the selection of welding sequence. In order to decrease calculation and shorten the calculation time, the finite element analysis of welding process will be carried out by combining the thermo-elastic-plastic method with the inherent strain method. Firstly, the SYSWELD software is used to extract the plastic strain as the input of the inherent strain analysis through the thermoelastic-plastic method, and then the ANSYS software is used to analyze the inherent strain of the port collar. The welding process of SYSWLED is analyzed by three-dimensional non-linear thermal entity element. The heat source model is double ellipsoid + cone composite heat source. The heat radiation loss is calculated by Stephen-Boltzmann equation. The absorptivity is set to 0.8 according to experience. Because the collar is welded by vacuum electron beam welding, the convection loss is set to 0 W/m2. The ANSYS inherent strain analysis uses linear solid element SOLID185 and hexahedron mesh in the weld zone. By the parameter obtained through welding test, the welding process is simulated and analyzed in different welding sequence. The results of welding deformation and stress distribution are shown in Figs. 7 and 8. From the Fig. 7, the part A of upper port collar is welded according to scheme 1, the maximum deformation is 2.2 mm locating at the welding between No.4 and No.5 subsections of collars. The maximum stress of the part A is 73.9 MPa after welding. If welding according to scheme 2, the maximum deformation is 3.96 mm locating at the welding between No.2 and No.6 subsections of collars. The maximum stress of part A is 83.2 MPa after welding. Because the welding deformation and residual stress of scheme 1 is much less than scheme 2, scheme 1 is the preferred choice. From the Fig. 8, the part B of upper port collar is welded according to scheme 1, the maximum deformation is 2.1 mm locating at the welding between No.10 and No.11subsections of collars. The maximum stress of part B is 153.9 MPa after welding. If welding according to scheme 2, the maximum deformation is 3.9 mm locating at the welding between No.7 and No.10 subsections of collars. The maximum stress of B is 170 MPa after welding. Because the welding deformation and residual stress of scheme 1 is much less than scheme 2, scheme 1 is the preferred choice. The part A and part B will be welded into an integrated upper port collar through electron beam welding. The result of welding deformation and residual distribution is as shown in Fig. 9. The overall deformation of the upper port is 3.88 mm and the maximum stress is 183.5 MPa, which meet design requirements. 4. Conclusion The electron beam welding scheme of the CFETR port collar has been determined through the simulation analysis and welding experiments conducted in the early stage. The next step is to further optimize the welding process by welding full-scale mock-up. The welding of 1/8 full size of the port collar of VV will be completed by the end of 2019.
Fig. 8. The results of welding deformation and stress of part B.
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Fusion Engineering and Design 139 (2019) 14–18
Z. Liu et al.
Fig. 9. The results of welding deformation and stress of upper port collar.
Acknowledgments
References
This work is carried out by Institute of Plasma Physics China Academy of Sciences and Key Laboratory of Special Welding Technology of Anhui Province. It’s supported by China National Magnetic Confinement Fusion Science Program (Grant No.:2015GB107000).
[1] Y. Wan, Mission of CFETR, ITER Training Forum & Second Workshop on MFE Development Strategy (2012). [2] ITER DDD 1.5 Vacuum Vessel, DDD-IDM-22FPWQ, G15DDD 04 01-06-25 R0.1. [3] Y.T. Song, S.T. Wu, et al., Concept design of CFETR tokamak machine, IEEE Trans. Plasma Sci. IEEE Nucl. Plasma Sci. Soc. 42 (2014) 503–509. [4] Ma Jianguo, et al., R&D of Full-Scale Partial Vacuum Vessel Mockup for Future Fusion Engineering Test Reactor in China, J Fusion Energy 34 (2015) 666–670.
18
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
The key technology research of electron beam welding in CFETR vacuum vessel collar
T
Zhihong Liua,b, , Jiefeng Wua,b, Xiaosong Fanb, Qiuyue Xiongb, Jianguo Maa,b ⁎
a b
Key Laboratory of Special Welding Technology of Anhui Province, Huainan, China Institute of Plasma Physics, Chinese Academy of Science, Hefei, China
ARTICLE INFO
ABSTRACT
Keywords: CFETR VV Electron beam welding VV collar Welding deformation Residual stress
Chinese Fusion Engineering Testing Reactor(CFETR) is a fully superconducting magnet Tokamak, and the key components of CFETR have been studied. As one of the pre-research projects, 1/8 full-scale vacuum vessel(VV) aims to grasp the key technology of molding, welding, non-destructive testing and measurement in the aspect of building a large-scale vacuum vessel, and accumulate experience for the formal construction of CFETR. The project has been officially launched by Institute of Plasma Physics Chinese Academy of Sciences(ASIPP) in 2015. In the manufacturing process of 1/8 full-scale VV, the electron beam welding is adopted at the VV collar in order to reduce welding deformation. As a large-scale electron beam welding (EBW) system set up in ASIPP, the research work of electron beam welding technology has been carried out, with periodical achievements obtained. This paper will introduce the key technology and research progress of the electron beam welding for the VV collar in detail.
1. Introduction Chinese Fusion Engineering Testing Reactor (CFETR) is a superconducting magnet Tokamak, with a scale equal to ITER [1,2]. At present, the research and development on key components of the CFETR has already begun. The 1/8 full scale vacuum vessel(VV) has been officially launched by Institute of plasma Physics Chinese Academy of Science(ASIPP) in 2015. In the manufacturing process of 1/ 8 full scale VV, the electron beam welding(EBW) is adopted at the VV collar in order to reduce welding deformation, and a large-scale electron beam welding system has been set up by ASIPP in 2017. Along with the process of 1/8 V V collar parts have been finished, the EBW tooling is in manufacturing. In view of the deformation and residual stress distribution in the process of VV collar welding, simulation analysis and experimental study have been carried out, with periodical achievements obtained. In this paper, the development of EBW technology for VV collar will be introduced in detail. 2. The design of 1/8 full size VV collar According to the current design [3] of the CFETR, 1/8 full size VV is
⁎
double-shell construction. The thickness of inner and outer shell is 180–380 mm and the wall thickness of single-layer shell is 50 mm. The VV has 3 ports, upper port, equatorial port and lower port. Each port is composed of port collar and its extension.1/8 full size VV is as shown in Fig. 1. Because the size of VV port, port collar and its extension will be manufactured in the factory respectively, and then assemble at the assembly site of the VV section. The extension of VV port has a relatively regular geometric construction, it’s easy to manufacture by hot press molding [4]. The collar between the VV and the extension has a very complex three-dimensional structure, which is difficult to molding directly. Therefore, the collar will be divided into several small parts for bending using thick stainless steel forgings, After milling, they are welded into a whole port collar. At last, the VV shell, port collar and its extension will be welded into an integrated VV section. The collar of outer shell of VV upper can be divided into part A and part B according to its structure, and each part is composed of some subsections. The diagram of subsections is shown in Figs. 2 and 3 shows port collar after processing. The thickness of single layer shell of VV is 50 mm and the throughthickness direction of VV has no processing allowance after assembling
Corresponding author at: Key Laboratory of Special Welding Technology of Anhui Province, Huainan, China. E-mail address: [email protected] (Z. Liu).
https://doi.org/10.1016/j.fusengdes.2018.12.059 Received 10 October 2018; Received in revised form 10 December 2018; Accepted 18 December 2018 0920-3796/ © 2018 Elsevier B.V. All rights reserved.
Fusion Engineering and Design 139 (2019) 14–18
Z. Liu et al.
Fig. 4. The vacuum EBW equipment.
Fig. 1. 1/8 full size VV.
Fig. 5. The diagram of part A and part B subsections of upper port collar. Fig. 2. The diagram of subsections.
Table 2 The parameter of electron beam welding.
Fig. 3. Port collar after processing. Table 1 The parameter of EBW system. Component
Specification/Type
Electron beam gun High voltage source Vacuum vessel
G600KM HCV-150 kV/60kW 7200 × 3550 × 2600 mm
Parameter
Specification
Working distance(mm) Accelerating voltage(kV) Beam current(mA) Focusing lens current(mA) Focus setting Surface travel speed(mm/s)
306 150 97 2507 Lower focus 5
large size and thick wall of the collar in the VV, it is proposed to adopt the EBW to weld the port collar. Automatic narrow gap tungsten argon arc welding(NG-TIG)is used between the port collar and the extension. 3. The design of EBW scheme of outer collar for upper port In terms of the present design, the structure and size of the upper, equatorial and lower port collar of the VV are different, and the size of outer collar of the upper port is the maximum, 4320 × 2322 × 1212 mm, the size of inner collar of the equatorial port is the minimum, 2300 × 975 × 339 mm. Therefore, the EBW equipment is selected
and welding. Therefore, it is necessary to reduce the welding deformation as much as possible during the welding process. Based on the analysis of the existing welding methods and the characteristics of the
15
Fusion Engineering and Design 139 (2019) 14–18
Z. Liu et al.
Fig. 6. The Diagram of welding tooling of part A and part B. Table 3 The welding sequence of outer collar of the upper port. Component
Scheme
A
Scheme Scheme Scheme Scheme
B
The sequence of welding 1 2 1 2
(1 + 2)+(3 + 4+5 + 6) (1+(3 + 4+5))+(2 + 6) (7 + 10)+(8 + 11)+(9 + 12) (7 + 8+9)+(10 + 11 + 12)
according to the size of outer collar of upper port. ASIPP set up a set of electron beam welding system whose volume is 66 m3 in 2017 in order to carry out related EBW. This system can meet welding requirements of all ports of CFETR VV. The parameter of EBW system is shown in Table 1.The vacuum EBW equipment is shown in Fig. 4 According to the current design, the outer collar of the upper port is divided into part A and part B. Part A is composed of 6 subsections, and part B is composed of 6 subsections. As shown in Fig. 5. In the port collar welding process, there are usually two ways to control the welding deformation. The first is optimizing the parameter of welding, and the second is optimizing the sequence of welding. The welding parameters have been determined by a large number of welding experiments. The parameter of EBW is shown in Table 2. Due to the different structure and size of VV ports of CFETR, the unique welding scheme will be adopted to every port collar. There are 2 aspects needed to consider as to designing welding scheme. One is designing and optimizing welding tooling to reducing weight but keep sufficient intensity, and welding tooling can provide appropriate operating space to perform EBW. The other is optimizing welding technology in order to reduce deformation during welding and reduce
Fig. 7. The results of welding deformation and stress of part A.
16
Fusion Engineering and Design 139 (2019) 14–18
Z. Liu et al.
residual stress after welding. Through the previous analysis and the results of process pre-study, the tooling of outer collar of upper port is as shown in Fig. 6. Due to the limited range of motion of the electron gun in the EBW system, the majority of movements are realized by moving or rotating working table during welding. Through analysis and welding experiments, there are two welding schemes for electron beam welding of collars, the welding sequence is shown in Table 3. In the welding process of port collar, welding sequence will affect welding deformation and residual stress. In order to minimize welding deformation and residual stress, the finite element simulation of welding process will provide theoretical basis for the selection of welding sequence. In order to decrease calculation and shorten the calculation time, the finite element analysis of welding process will be carried out by combining the thermo-elastic-plastic method with the inherent strain method. Firstly, the SYSWELD software is used to extract the plastic strain as the input of the inherent strain analysis through the thermoelastic-plastic method, and then the ANSYS software is used to analyze the inherent strain of the port collar. The welding process of SYSWLED is analyzed by three-dimensional non-linear thermal entity element. The heat source model is double ellipsoid + cone composite heat source. The heat radiation loss is calculated by Stephen-Boltzmann equation. The absorptivity is set to 0.8 according to experience. Because the collar is welded by vacuum electron beam welding, the convection loss is set to 0 W/m2. The ANSYS inherent strain analysis uses linear solid element SOLID185 and hexahedron mesh in the weld zone. By the parameter obtained through welding test, the welding process is simulated and analyzed in different welding sequence. The results of welding deformation and stress distribution are shown in Figs. 7 and 8. From the Fig. 7, the part A of upper port collar is welded according to scheme 1, the maximum deformation is 2.2 mm locating at the welding between No.4 and No.5 subsections of collars. The maximum stress of the part A is 73.9 MPa after welding. If welding according to scheme 2, the maximum deformation is 3.96 mm locating at the welding between No.2 and No.6 subsections of collars. The maximum stress of part A is 83.2 MPa after welding. Because the welding deformation and residual stress of scheme 1 is much less than scheme 2, scheme 1 is the preferred choice. From the Fig. 8, the part B of upper port collar is welded according to scheme 1, the maximum deformation is 2.1 mm locating at the welding between No.10 and No.11subsections of collars. The maximum stress of part B is 153.9 MPa after welding. If welding according to scheme 2, the maximum deformation is 3.9 mm locating at the welding between No.7 and No.10 subsections of collars. The maximum stress of B is 170 MPa after welding. Because the welding deformation and residual stress of scheme 1 is much less than scheme 2, scheme 1 is the preferred choice. The part A and part B will be welded into an integrated upper port collar through electron beam welding. The result of welding deformation and residual distribution is as shown in Fig. 9. The overall deformation of the upper port is 3.88 mm and the maximum stress is 183.5 MPa, which meet design requirements. 4. Conclusion The electron beam welding scheme of the CFETR port collar has been determined through the simulation analysis and welding experiments conducted in the early stage. The next step is to further optimize the welding process by welding full-scale mock-up. The welding of 1/8 full size of the port collar of VV will be completed by the end of 2019.
Fig. 8. The results of welding deformation and stress of part B.
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Fusion Engineering and Design 139 (2019) 14–18
Z. Liu et al.
Fig. 9. The results of welding deformation and stress of upper port collar.
Acknowledgments
References
This work is carried out by Institute of Plasma Physics China Academy of Sciences and Key Laboratory of Special Welding Technology of Anhui Province. It’s supported by China National Magnetic Confinement Fusion Science Program (Grant No.:2015GB107000).
[1] Y. Wan, Mission of CFETR, ITER Training Forum & Second Workshop on MFE Development Strategy (2012). [2] ITER DDD 1.5 Vacuum Vessel, DDD-IDM-22FPWQ, G15DDD 04 01-06-25 R0.1. [3] Y.T. Song, S.T. Wu, et al., Concept design of CFETR tokamak machine, IEEE Trans. Plasma Sci. IEEE Nucl. Plasma Sci. Soc. 42 (2014) 503–509. [4] Ma Jianguo, et al., R&D of Full-Scale Partial Vacuum Vessel Mockup for Future Fusion Engineering Test Reactor in China, J Fusion Energy 34 (2015) 666–670.
18