QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY
Online ISSN : 2434-8252
Print ISSN : 0288-4771
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  • Toshifumi YUJI, Shinichi TASHIRO, Titinan METHONG, Hiroyuki KINOSHITA, Kentaro YASUI, Toshio BOUNO,
    Noritsugu
    KAMATA
    , Le Huy PHAN, Manabu TANAKA
    QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY
    2017 Volume 35 Issue 2 47s-50s
    Published: 2017
    Released on J-STAGE: February 01, 2018
    JOURNAL FREE ACCESS
    The cleaning action with AC Tungsten Inert Gas (TIG) welding is attributed to the removal process of oxide film caused by cathode spots. In this study, a double shielding gas torch, which used the internal shielding gas of helium and the external shielding gas of helium or helium with 5.0 % oxygen, was employed to investigate influence of admixture of oxygen into the shielding gas on the cathode spot behavior in AC TIG welding. The cathode spots were photographed by a high-speed video camera and their distribution and velocity are discussed. Consequently, it was found that when the oxygen was mixed into the shielding gas, the number of cathode spots seemed to increase. Furthermore, the average velocity of cathode spots was considerably decreased to approximately 50 m/s near the center of the weld pool compared with 100m/s in case of pure helium shielding gas.
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  • Kazumasa NISHIO, Mitsuaki KATOH, Tomiko YAMAGUCHI, Tatsuya TOKUNAGA, Atsuo MATSUMOTO
    QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY
    2003 Volume 21 Issue 4 553-559
    Published: 2003
    Released on J-STAGE: November 16, 2004
    JOURNAL FREE ACCESS
    The lap welding of titanium sheet and mild steel sheet was performed with Cu-base filler foil as an insert metal using a seam welding method. The weldability was investigated in comparison with seam welds without the use of the insert metal. Without the insert metal, the seam welds were easily peeled off at the weld interface between the titanium and the mild steel. On the other hand, with the insert metal, the sound welds were produced at all welding conditions applied in this study. Therefore, it was concluded that the formation of intermetallic compounds, such as FeTi and Fe2Ti, were suppressed by using the insert metal. The result of the tensile shear test showed that the fractures occurred at the weld interface between the titanium and the mild steel, and the values of maximum tensile shear strength were approximately 100 to 120 MPa independent of the welding conditions. The XRD and EDX analyses on the fractured surfaces after performing the tensile shear test revealed that a very small amount of the insert metal remained at the weld interface between the titanium and the mild steel and also CuTi, Cu2Ti and β-Ti were formed at the interface. Consequently, the very small amount of the insert metal that remained at the weld interface between the titanium and the mild steel prevented the formation of brittle intermetallic compounds such as FeTi and Fe2Ti.
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  • Tadayuki OTANI, Susumu TSUKAMOTO, Goro ARAKANE, Akio OHMORI
    QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY
    2003 Volume 21 Issue 2 267-273
    Published: 2003
    Released on J-STAGE: August 31, 2004
    JOURNAL FREE ACCESS
    HAZ characteristics of laser welded ultra-fine grained steels were investigated using a 20 kW CO2 laser facility. A narrow softening region was clearly observed in HAZ welded at low welding speed of less than 0.017 m/s. The softening was caused by coarsening of ferrite grains which were heated above Ac1. On the other hand, HAZ softening was suppressed at higher welding speeds of more than 0.033 m/s due to the formation of tiny dispersed MA constituents and reducing grain coarsening. The prior austenite grain size was also examined at various welding speeds. The result indicate that the prior austenite grain size decreased with increasing the welding speed and with decreasing the initial ferrite grain size.
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  • Tadao NAKAGOMI, Yuri SUZUKI, Hirofumi KANEKO, Shintaro KANAZAKI
    QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY
    2018 Volume 36 Issue 4 293-301
    Published: 2018
    Released on J-STAGE: January 22, 2019
    JOURNAL FREE ACCESS
    The purpose of this paper is to examine the yield load, yield angle, maximum load, and fracture angle of the front fillet weld joint, following experiments and analytical studies. According to the research of the past, it is known that the strength of front fillet weld joint is higher than the strength of side fillet weld joint. However, the detailed stress state of front fillet weld joint has not been investigated. The yield load, yield angle, maximum load, and fracture angle were investigated by loading test using specimen which was cut by electric discharge machining in order to match the material characteristic of the front fillet weld joint part and the plate elements. In this paper, the mechanical performance of shape of front fillet weld joint was clarified through loading test. Then, detailed stress state and strain state of fillet weld joint are investigated by 3D analytical studies as it could not be grasped by loading test.
    As a result of the studies, loading test indicates that the yield load is 1.16 and 1.17 times, the maximum load is 1.83 times and 1.84 times design formula of front fillet weld joint, yield surface is 27°, fracture surface is 21° and 15°. Then, in the 3D analytical study, the yield load is 1.27 times and the maximum load is 1.97 times.
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  • Tomotaka HAYASHI, Kazuki MATSUBAYASHI, Seiji KATAYAMA, Nobuyuki ABE, Akira MATSUNAWA, Akira OHMORI
    QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY
    2002 Volume 20 Issue 2 228-236
    Published: 2002
    Released on J-STAGE: March 28, 2003
    JOURNAL FREE ACCESS
    Porosity is easily formed in a keyhole-type of deeply penetrated laser weld beads. In this study, therefore, high power CO2 laser welding utilizing a single spot or a tandem twin-spot beam was performed on thick plates of Type 304 steel with the objectives of investigating feasibility of porosity prevention and establishing the optimum conditions in tandem twin-spot beam welding. Porosity formation tendency was first investigated in a partial penetration weld made with a single-spot CO2 laser beam at low speed. Consequently, it was confirmed that many pores were present near the bottom parts of the weld beads produced without and with assist gas at a power exceeding 10 and 15 kW, respectively. On the other hand, it was revealed that the number of pores was drastically reduced by twin-spot laser beam welding. Especially, some weld beads produced at 30 kW indicated the best grade of the inspection test result according to JIS Z3106. Subsequently, the reason for the reduced porosity was investigated by using the microfocused X-ray transmission in-situ observation system with a high speed video camera. During high-power laser welding of Type 304 with the single-spot beam, it was confirmed that the keyhole fluctuated up and down and consequently a lot of bubbles were generated from the keyhole tip near the bottom part of the molten pool, leading to the formation of porosity. On the other hand, when an enlarged keyhole was produced by a twin-spot beam, few bubbles were generated from the keyhole tip. Moreover, even if the bubbles were formed, most of them did not move away from the formation location and were soon absorbed in the keyhole. This is interpreted by considering that no strong melt flow was induced near the bottom part of the molten pool just behind the tip of the widened keyhole. Consequently, the difference of porosity formation between single-spot and twin-spot laser beam welding is attributed to the differences of their bubble formation mechanisms, liquid flow near the bottom part of the molten pool, and the bubble disappearance via the keyhole.
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  • Masahiro FUKUMOTO, Hajime NAKAMURA, Motohiro YAMADA, Toshiaki YASUI, Koyata TAKAHASHI
    QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY
    2005 Volume 23 Issue 4 608-612
    Published: 2005
    Released on J-STAGE: June 06, 2006
    JOURNAL FREE ACCESS
    Aluminum nitride (AlN) is one of the attractive ceramics in respect of its excellent properties. It was possible to fabricate Al/AlN composite coatings onto carbon steel substrate by reactive RF plasma spray process. However, most of the coatings peeled off due to the difference of thermal expansion coefficient between AlN and carbon steel. It might be possible to prevent peeling of AlN coatings with formation of Al layer between substrate and AlN coating. To fabricate these coatings, it was necessary to control the nitriding reaction. Thus, nitriding process of aluminum powder in the reactive RF plasma spray process was investigated. Then the coatings were fabricated with changing nitrogen flow rate in the plasma gas. Although it was difficult to fabricate functionally graded AlN coating, it was possible to prevent the peeling off of the coatings with formation of Al layer between carbon steel substrate and AlN layer on the surface of the coatings.
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