JOURNAL OF THE JAPAN WELDING SOCIETY
Online ISSN : 1883-7204
Print ISSN : 0021-4787
ISSN-L : 0021-4787
Volume 44, Issue 1
Displaying 1-7 of 7 articles from this issue
  • Masao Mizuno
    1975 Volume 44 Issue 1 Pages 8-21
    Published: January 25, 1975
    Released on J-STAGE: August 05, 2011
    JOURNAL FREE ACCESS
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  • Tohru Tomoto, Akira Sakaguchi, Kohzo Horimoto
    1975 Volume 44 Issue 1 Pages 22-35
    Published: January 25, 1975
    Released on J-STAGE: August 05, 2011
    JOURNAL FREE ACCESS
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  • Kazuyuki Minoda, Toshio Irisawa
    1975 Volume 44 Issue 1 Pages 35-47
    Published: January 25, 1975
    Released on J-STAGE: August 05, 2011
    JOURNAL FREE ACCESS
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  • Bead Formation in Welding With the Use of Back-up Bars
    Kuichi Tsuchiya, Koji Kishimoto, Tsunebumi Matsunaga, Eiichi Nakano
    1975 Volume 44 Issue 1 Pages 48-57
    Published: January 25, 1975
    Released on J-STAGE: August 05, 2011
    JOURNAL FREE ACCESS
    In this report, the application of back-up bars is studied for experiment to prevent drop of molten metal in order to obtain a sound root bead in the plasma arc welding of thick plate.
    As a result, it is found possible to overcome a series of arcing, blow holes and poor appearance of the underbead produced when a normal back-up bar is used, by improvements such as gas shielding, edge preparation of root gap in I groove joint and setting of two back-up bars. Thus, sound root beads were obtained.
    The results of the experiments are summarized as follows:
    1) Although the plasma arc is considered more rigid than normal open arc, its column somewhat changes its shape during welding due to magnetic force, depending on the distance from edge of the test piece. The arc is faced forward up to 10cm from weld-start edge, then it changes to the opposite direction. Sound bead can be obtained when the arc is faced backward.
    2) It is confirmed that the optimum value of the flow rate of argon shielding gas is 50l/min, that of the hole diameter of the shielding gas passage in nozzle cover is 15-20 mm and that of the root gap of I groovej oint is 5-8mm.
    3) It is also found that the optimum value of the gap between two back-up bars is 1.0-2.0mm and that of the clearance between the back-up bars and the base metal is 0.5-2.0mm to produce sound beads.
    4) Although the bead is affected by various welding factors, such as welding current I, plasma gas flow rate Qp, welding speed ν, arc constricting wall length of nozzle l1 and arc length la, in general a good bead obtained in this experiment has shown inherent characteristics in its cross section which has near-hyperbolic fusion lines.
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  • Kin-ichi Nagai, Haruhiko Fujita, Mitsumasa Iwata, Kensaku Takenaka
    1975 Volume 44 Issue 1 Pages 58-65
    Published: January 25, 1975
    Released on J-STAGE: August 05, 2011
    JOURNAL FREE ACCESS
    Using a mild steel which is quench-aged, that is, overaged at 200, 100, 50 and 30°C, after the solution treatment for 30 minutes at 680°C and quenching into iced water, reversed bending fatigue tests of plain and notched specimens were carried out, and precipitated particles due to quench aging were observed by transmission electron microscope.
    The results obtained are summarized as follows:
    (1) The fatigue strength of mild steel is more increased by the quench aging at 30 or 50°C than by annealing or quenching.
    (2) The increment of fatigue strength in various notched specimens due to thequench aging is more conspicuous than that in a plain specimen.
    (3) Precipitated particles in ferrite matrix become fine and distributed densely, as the aging temperature is decreased. As the dislocation motion is disturbed by such particles, the stress concentration due to the dislocation pile-up decreases and then the fatigue limit of quench-aged steel is increased in proportion to the reciprocal of square root of mean free distance between particles.
    (4) The quench aging is effective on decreasing the propagation rate of fatigue crack.
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  • Effect of Solidification Rate on the Tougness of as-solidified Steel
    Isao Masumoto, Isamu Karasuno, Hironori Ozaki
    1975 Volume 44 Issue 1 Pages 66-76
    Published: January 25, 1975
    Released on J-STAGE: August 05, 2011
    JOURNAL FREE ACCESS
    Previous reports showed that the toughness of as-solidified steel was significantly influenced by the injurious sulfur-segregation through the Fe-Ni-C ternary peritectic reaction. This peritectic reaction may be affected by the solidification rate.
    Then, in this study the influences of solidication rates on solidification structures, sulfur-segregation and toughness were investigated using as-solidified steel through and not through the Fe-C and Fe-Ni peritectic reaction. The solidification rates were changed by three kinds of molds, corresponding to manual arc welding or TIG welding, submerged arc welding and electroslag welding.
    The results obtained are as follows;
    1) In the cases of 0.3 mm/sec and 1.4 mm/sec solidification rate, the toughness of as-solidified steel deteriorates abruptly and the solidification grain boundary is etched remarkably at about 0.1 % of carbon content and 2.5 % of nickel content.
    These critical contents decrease with an increasing solidification rate.
    2) Micro-segregation of sulfur on solidification grain boundary and deterioration of stoughness increase with a decreasing solidification rate.
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  • Shigeo Hasebe, Yoshiaki Kawaguchi, Kazushige Arimochi
    1975 Volume 44 Issue 1 Pages 77-84
    Published: January 25, 1975
    Released on J-STAGE: August 05, 2011
    JOURNAL FREE ACCESS
    In order to secure the safety of welded structures against brittle failure, a proposal on quality assessment of weld bond of structural steel plate is presented. This proposal is based on a general equation correlating the brittle fracture initiation characteristics under the reisdual stress of welded joints with Charpy impact characteristics, which is obtained as follows.
    1) Bending COD test is available as a small size Kc Test. Good coincidence is found between the results of COD Test and Deep Notch Test, when the critical COD is translated to Kc value.
    2) Ty-evaluation is proposed from the results of Cross Weld Notch Test. Ty is the safe-side estimation of the brittle fracture initiation temperature in the residual stress field of welded joints, which can simply be obtained from Bending COD Test or Deep Notch Test on weld bond using the equation Kcy√πC.
    3) From the results of COD Test and Deep Notch Test, an equation correlating the brittle fracture initiation temperature Ty with Charpy transition temperature vTs is introduced as follows.
    Ty = 234+1.5vTs+12√t-65lnσy0/F(σy0, C)
    Fy0, C) = 324+65lnσy0/273 + ln 3000/σy0√πC
    where, Ty ; safe-side estimation of britlte fracture initiatilon temperature in the residual stress field of welded joints (°K),
    vTs : Charpy 50% cyrstallinity transition temperature (°K),
    t : plate thickness (mm),
    σy0 : yield strength of material under room temperature (kg/mm2),
    C : half crack length in infinite plate (mm).
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