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Kabushiki Kaisha Kobe Seiko Sho and Kobe Special Tube Co. | Date: 2013-01-16

Disclosed are: a welding method capable of increasing the welding speed up to approximately 20m/min., yet capable of producing good bead configurations and preventing welding defects such as blowholes; and a method of producing a welded member using the welding method. Specifically disclosed is a laser/arc hybrid welding method for butt-welding flat plates of stainless steel, titanium, or titanium alloy, or butt-welding both ends of a strip-shaped plate of stainless steel, titanium, or titanium alloy which has been formed into a tubular shape, wherein in the butt welding, the laser beam irradiation and the arc discharge trace the same welding line in such a manner that laser welding is followed by TIG arc welding.


Takahashi Y.,Japan Atomic Energy Agency | Isono T.,Japan Atomic Energy Agency | Hamada K.,Japan Atomic Energy Agency | Nunoya Y.,Japan Atomic Energy Agency | And 16 more authors.
IEEE Transactions on Applied Superconductivity | Year: 2012

Japan Atomic Energy Agency (JAEA) was the first to start the mass production of the TF conductors (jacketing) in March 2010 among the 6 parties who are procuring TF conductors in the ITER project. A 760-m Cu dummy conductor was successfully fabricated prior to the manufacture of the actual Nb 3Snconductors. Suitable manufacturing techniques for the long TF conductors were established during fabrication of the dummy conductor. This paper summarizes the technical developments including a high-level quality assurance, leading to the first successful mass production of ITER TF conductor. Approximately 63 Nb 3Sntons of strands were manufactured by the two suppliers by August 2011. This amount corresponds to approximately 60% of the total contribution from Japan. Five sDP conductors (415 m) and six rDP conductors (760 m) to be used in the TF coils were completed as of February 2011. This amount corresponds to approximately 25% of the total contribution (rDP: 24, sDP: 9) from Japan. JAEA is manufacturing one conductor per month under a contract with two Japanese companies for strands, one company for cabling and one company for jacketing. This progress is a significant step in the construction of the ITER machine. © 2011 IEEE.


Hamada K.,Japan Atomic Energy Agency | Kawano K.,Japan Atomic Energy Agency | Saito T.,Japan Atomic Energy Agency | Iguchi M.,Japan Atomic Energy Agency | And 3 more authors.
AIP Conference Proceedings | Year: 2012

Twenty-five percent of the total toroidal field (TF) coil conductors at the ITER are supplied by the Japan Atomic Energy Agency (JAEA). The jacket section of a TF conductor is made of modified 316LN. The JAEA tested three types of tensile specimens (Japanese-Industrial-Standards-type and ASTM-type) cut from the jacket at 4.2 K. The ASTM-type specimen had a longer and wider reduced section than did the JIS-type specimen. The results of the test showed that the EL of the as-received (AR) jacket was independent of the specimen shape. However, after cold working and aging, the EL of the specimens deteriorated because of sensitization, and the EL distribution in these specimens was larger than that in the case of the AR specimens. It could be inferred that the shape of a test specimen having low ductility is the key determinant of the specimen's susceptibility to fracture. © 2012 American Institute of Physics.


Takahashi Y.,Japan Atomic Energy Agency | Nabara Y.,Japan Atomic Energy Agency | Hemmi T.,Japan Atomic Energy Agency | Nunoya Y.,Japan Atomic Energy Agency | And 16 more authors.
IEEE Transactions on Applied Superconductivity | Year: 2013

In March 2010, the Japan Atomic Energy Agency (JAEA) was the first to start the mass production of toroidal field (TF) conductors among the six parties who were procuring TF conductors in the International Thermonuclear Experimental Reactor project. The height and width of the TF coils are 14 m and 9 m, respectively. The conductor is a cable-in-conduit conductor with an operating current of 68 kA. A circular multistage superconducting cable is inserted into a circular stainless steel jacket with a thickness of 2 mm. A total of 900 Nb3Sn strands and 522 copper strands are cabled around the central spiral and then wrapped with stainless steel tape whose thickness is 0.1 mm. The superconducting cables are inserted into the jacket assembled using the automatic butt Tungsten Inert Gas welding technique. Cable insertion is one of the key technologies in the jacketing process because the gap between the inner surface of the jacket and the outer diameter of the superconducting cable is only 2 mm in diameter. It was observed that the cabling pitch of the destructive sample is longer than the original pitch at cabling. JAEA carried out the tensile tests of the cable and the measurement of the cable rotation during the insertion to investigate the cause of the elongation. The cause of elongation was clarified, and the results are described in this paper. © 2002-2011 IEEE.


Takahashi Y.,Japan Atomic Energy Agency | Suwa T.,Japan Atomic Energy Agency | Nabara Y.,Japan Atomic Energy Agency | Ozeki H.,Japan Atomic Energy Agency | And 13 more authors.
IEEE Transactions on Applied Superconductivity | Year: 2015

The Japan Atomic Energy Agency is responsible for procuring all amounts of central solenoid (CS) conductors for International Thermonuclear Experimental Reactor, including CS jacket sections. The conductor is cable-in-conduit conductor with a central spiral. A total of 576 Nb3Sn strands and 288 copper strands are cabled around the central spiral and then wrapped with stainless steel tape whose thickness is 0.08 mm. The maximum operating current is 40 kA at magnetic field of 13 T. CS jacket section is circular in square type tube made of JK2LB, which is high manganese stainless steel with boron added. Unit length of jacket sections is 7 m, and 6400 sections will be manufactured and inspected. Outer/inner dimension and weight are 51.3/35.3 mm and around 100 kg, respectively. Since the CS conductor suffers 60 000 cycles of high electromagnetic force in the lifetime, severe requirements were specified for jacket sections in terms of not only high mechanical performance at 4 K but also of the size of initial defects in the jacket section. The minimum allowable defect size is estimated to be 2 mm2 × 0.2 mm by linear elastic fracture mechanics. Eddy current test (ECT) and phased array ultrasonic test (PAUT) were developed for non-destructive examination. The defects on inner and outer surfaces can be detected by ECT. The defects inside the jacket section can be detected by PAUT. These technologies and the inspected results of more than 700 jacket sections are reported in this paper. © 2014 IEEE.


Kawamori M.,Kobe Steel | Kinugasa J.,Kobe Steel | Yonenaga Y.,Kobe Steel | Fukuta Y.,Kobe Steel | And 5 more authors.
Zairyo to Kankyo/ Corrosion Engineering | Year: 2015

To improve the corrosion resistance of the duplex stainless steels, great efforts have been made to clarify the pitting initiation in order to suppress the pitting corrosion which is one of the most hazardous forms of the stainless steels' failure. In general, manganese sulfide( MnS) is known to act as the pitting initiation in environments containing chloride ions. Thus, the inclusion control is essential for the development of duplex stainless steels with high corrosion resistance. In this study, the effects of the inclusion control by Ta addition on the pitting corrosion resistance of the duplex stainless steels were investigated. The Ta-bearing duplex stainless steels exhibited the remarkably high pitting corrosion resistance compared to that of the duplex stainless steels without Ta. The Ta-bearing duplex stainless steel contains no MnS inclusion but( Ta, Mn)-oxysulfide. This indicates that sulfur is stabilized as( Ta, Mn) -oxysulfide instead of MnS which is the typical pitting initiation. Ta addition to the super duplex stainless steel improved the pitting corrosion resistance because MnS, which acts as a pitting initiation, was modified to the electrochemically-stable Ta-containing inclusions.


Nishizawa N.,Kobe Special Tube Co. | Nagao M.,Kobe Special Tube Co. | Kawamori M.,Kobe Steel | Yonenaga Y.,Kobe Steel | And 2 more authors.
Zairyo to Kankyo/ Corrosion Engineering | Year: 2015

Duplex stainless steel has high corrosion resistance and high strength. However, pitting corrosion occurs in duplex stainless steel in the solution containing high concentrated chloride ion. Pitting corrosion is caused by dissolution of inclusion, such as manganese sulfide( MnS). In previous study, the pitting corrosion resistance of the super duplex stainless steels including 20 ppmS could improve by Ta addition in the steels. In this study, we investigated the effect of addition of Ta on pitting corrosion behavior in standard duplex stainless steels including 10 ppm S. In conclusion, we observed that pitting corrosion resistance of standard duplex stainless steels could improve by addition over 0.06 mass% addition of Ta.


Kawamori M.,Kobe Steel | Kinugasa J.,Kobe Steel | Yonenaga Y.,Kobe Steel | Fukuta Y.,Kobe Steel | And 5 more authors.
Zairyo to Kankyo/ Corrosion Engineering | Year: 2015

The inclusion control is essential for the development of duplex stainless steels with high local corrosion resistance. In this study, the effect of the inclusion control by Ta addition on the crevice corrosion resistance of the super duplex stainless steels was investigated. The Ta-bearing super duplex stainless steels exhibited the higher crevice corrosion resistance compared to the super duplex stainless steels without Ta. In the super duplex stainless steels without Ta, the dissolution of MnS was observed after the crevice corrosion test, indicating that MnS acts as the initiation of the crevice corrosion. In the Ta-bearing super duplex stainless steels, part of MnS was modified to the (Ta, Mn)-oxysulfide which did not dissolve after the same crevice corrosion test as was conducted for the base alloy without Ta. This demonstrates that (Ta, Mn)-oxysulfide is electrochemically-stable. Thus, Ta addition to the super duplex stainless steel improved the crevice corrosion resistance because of a decrease of MnS which was modified to the electrochemically-stable Ta-containing inclusions.


Disclosed are: a welding method capable of increasing the welding speed up to approximately 20 m/min., yet capable of producing good bead configurations and preventing welding defects such as blowholes; and a method of producing a welded member using the welding method. Specifically disclosed is a laser/arc hybrid welding method for butt-welding flat plates of stainless steel, titanium, or titanium alloy, or butt-welding both ends of a strip-shaped plate of stainless steel, titanium, or titanium alloy which has been formed into a tubular shape, wherein in the butt welding, the laser beam irradiation and the arc discharge trace the same welding line in such a manner that laser welding is followed by TIG arc welding.

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