JOURNAL OF THE JAPAN WELDING SOCIETY
Online ISSN : 1883-7204
Print ISSN : 0021-4787
ISSN-L : 0021-4787
Volume 48 , Issue 12
Showing 1-12 articles out of 12 articles from the selected issue
  • Isao Masumoto
    1979 Volume 48 Issue 12 Pages 1020-1021
    Published: December 05, 1979
    Released: August 05, 2011
    JOURNALS FREE ACCESS
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  • Shuji Nakata, Takio Okuda, Masahiro Ogawa
    1979 Volume 48 Issue 12 Pages 1022-1027
    Published: December 05, 1979
    Released: August 05, 2011
    JOURNALS FREE ACCESS
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  • Nobutaka Yurioka, Takashi Yatake, Ryuichi Kataoka, Shigeru Ohshita
    1979 Volume 48 Issue 12 Pages 1028-1033
    Published: December 05, 1979
    Released: August 05, 2011
    JOURNALS FREE ACCESS
    The initiation and propagation of root cracks in steel weldments have been investigated by H-slit restraint cracking tests. The experimental variables examined in the tests are chemical compositions in steel in terms of PCM (0.20 to 0.27), diffusible hydrogen in weld metal in terms of HJIS (0.4 to 30ml/100gr), tensile restraint in terms of RF (300 to 3, 500 kgf/mm⋅mm), ambient temperature (0, 20 and 30°C) and groove shape (V, y and _??_).
    It has been found that a root cracking tendency in root-pass welds may be given by the following parameter PHM:
    PHM=PCM+0.075log HJIS+0.15log (0.017 Kt⋅σw)
    where, Kt⋅σw is a local stress at the weld root, Kt and σw being a notch stress concentration factor and an average stress of the weld metal, respectively. σw has been given by a function of plate thickness and RF.
    Accoustic emission measurements have revealed that an incubation time for root cracking becomes shorter and that a velocity in crack propagation becomes higher as the PHM value increases. With a decrease in an ambient temperature, a root cracking susceptibility has increased while a crack velocity decreasing unlike the case of increasing PHM.
    The preheating temperature necessary for preventing root cracking in root-pass welds can be obtained by looking into t100, the cooling time from the welding completion to 100°C, longer than (t100)cr given as:
    (t100)cr=10.5×104(PHM-0.276)2
    A relationship between t100 measured at test plates and pheheating temperatures has been prepared for various plate thicknesses and heat-inputs.
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  • Masayoshi Kureishi
    1979 Volume 48 Issue 12 Pages 1033-1040
    Published: December 05, 1979
    Released: August 05, 2011
    JOURNALS FREE ACCESS
    The temperature rise at a point P(x, y) on a thin plate heated by a moving pulsed point heat sourse is expressed by the following equation,
    θ= qav/4πλ (T1+T2)⋅evw/2k⋅{1/T1+1/k⋅T2 Σm-1n=0 n2Sn1(γ)+ 1/k⋅t1+T2 Σmn=1 n2'Sn1'(γ) }
    x2Sx1= ∫x2x1 e-ζ- γ/ζ /ζ ⋅dζ, γ=α⋅δ δ= 4ka+v2/4k
    n1=δ(t-nTc-T1), n2=δ(t-nTc) α= y2+w2/4k
    n1'=δ(t-nTc), n2'=δ(t-nTc+T2), ω=vt-x
    where.
    qav: average heat quantity(= q1⋅T1+q2⋅T2/T1+T2 )
    κ: =q1/q2
    Tc: period(=T1+T2)
    v: velocity of heat sourse
    t: time after commence of heating
    λ: heat conductivity
    α: coefficient of cooling
    k: thermal diffusivity
    (q1, q2; heat quantity at pulse time T1, interpulse time T2, resnectively)
    This equation was applied to thermal analysis of the pulsed TIG welding, and various temperature curves were obtained for various shapes of pulsed current. This equation was used for determination of experimental welding conditions for the pulsed TIG welding, and this process and result are also reported.
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  • Yukio Mori, Isao Masumoto
    1979 Volume 48 Issue 12 Pages 1041-1047
    Published: December 05, 1979
    Released: August 05, 2011
    JOURNALS FREE ACCESS
    There is often a crack at the center of the welding bead which was welded at a high deposition rate or with a deep penetration method, that is, submerged arc welding or CO2 arc welding method etc..
    When the groove angle is small or welding conditions are inadequate, cracks are found in the first bead of I, V and K etc. shaped grooves. It has been well known that this crack has a close connection with the so called "pear-shaped bead."
    In this report, the relations among the welding conditions, groove angles and the shape of bead were studied. The values of the factors of bead shape were decided by the welding conditions and groove angles.
    The values of P/W and Wm/W became the larger, the pear shaped bead more formed, where P: depth of bead, W: width of bead surface and Wm: max. width in bead.
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  • Isao Masumoto, Hirohito Hira
    1979 Volume 48 Issue 12 Pages 1048-1053
    Published: December 05, 1979
    Released: August 05, 2011
    JOURNALS FREE ACCESS
    During friction welding, joint interface should be heavy worked at high temperature. So, controlled hot torsion test wars carried out to study the deformation resistance and induced microstructures during this high temperature heavy-working. And these results were compared with friction torque and microstructures of friction welded joint.
    Main results were as follows;
    (1) Deformation resistance during high temperature heavy-working and induced microstructure depend on strain rate and temperature.
    (2) The power relation between steady state torque or austenite grain size and Zener-Hollomon parameter was obtained.
    (3) Austenite grain size of weld interface can be estimated from the friction torque by using the result of hot torsion test.
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  • Hiroshi Ikawa, Yoshikuni Nakao, Kazutoshi Nishimoto, Mitsuo Terashima
    1979 Volume 48 Issue 12 Pages 1054-1059
    Published: December 05, 1979
    Released: August 05, 2011
    JOURNALS FREE ACCESS
    The factors which influence the toughness in the weld metal of high purity 30Cr-2Mo steel were investigated. On the basis of the results, the mechanism of the deterioration in the toughness of the weld metal was discussed. The results obtained in this study are as follows:
    (1) The remarkable deterioration in the toughness is occurral in the TIG weld metal when the shielding for the welds is insufficient.
    (2) Grain size and 475°C embrittlement do not significantly influence the toughness of the weld metal in as-welded condition.
    (3) The main cause of the deterioration in the toughness of the weld metal is picking-up of nitrogen during welding.
    (4) When picking-up of nitrogen is slight and nitrogen in the weld metal is less than about 100 ppm, no nitride precipitates. In this case, interstitial nitrogen atoms cause the embrittlement due to forming Cottrell atomosphere or distorting the lattice. However, when picking-up of nitrogen is heavier and the content of nitrogen in the weld metal grows up more than about 100 ppm, disc-like Cr2N precipitates on (100) plane in the matrix. Consequently, in addition to the cause mentioned above, the precipitation hardening by Cr2N and the lowering the energy for the cleavage fracture due to the fact that disc-like Cr2N precipitates on (100) plane cause the embrittlement of the weld metal.
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  • Masahide Kamakura, Masatoshi Nihei, Etsuo Sasaki, Masao Kanao, Michio ...
    1979 Volume 48 Issue 12 Pages 1060-1064
    Published: December 05, 1979
    Released: August 05, 2011
    JOURNALS FREE ACCESS
    In the previous report, presented were test results on the effect of size and frequency on fatigue properties of SM50B butt welded joints, and it was concluded that the thickness of specimen had remarkable effect on the fatigue strength, and that the effect was mainly caused by the difference of stress concentration due to shape of reinforcement for each thickness. On the other hand, other factors scarcely had significant effect on the fatigue strength.
    The present paper presents test results on the effect of specimen size including the effect of thickness of rib for the case of non-load carrying fillet welded joints. As a result of the test, same conclusions as that of the butt welded joints were obtained for the non-load carrying fillet welded joints.
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  • Hiroya Taguchi, Mitsuaki Haneda, Shoji Imanaga, Itsuhiko Sejima
    1979 Volume 48 Issue 12 Pages 1065-1069
    Published: December 05, 1979
    Released: August 05, 2011
    JOURNALS FREE ACCESS
    The authors have developed a new plasma welding process with the filler wire heated by the arc from the wire (named "arc wire").
    A new plasma welding process with "arc-wire" addition is described.
    This paper deals with the characteristics of the current through the filler wire and observation of the metal transfer by the high-speed camera.
    The results obtained are as follows;
    1) In plasma arc welding with "arc-wire" addition, the deposition rate increases until it nearly equals that of the CO2-arc welding.
    2) When the constant votlage characteristics is used for the "arc-wire" power supply, Iw is regulated to an adequate current value automatically by the self adjusting action.
    3) From high-speed films of the metal transfer it has been clarified that the molten filler wire transfers to the molten pool with streaming transfer just like the water flow and the liquid metal is constricted into several little droplets between the tip of the wire and the molten pool.
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  • Takehiko Watanabe, Isao Okane, Masahiro Kitajima
    1979 Volume 48 Issue 12 Pages 1070-1077
    Published: December 05, 1979
    Released: August 05, 2011
    JOURNALS FREE ACCESS
    It seems very likely that cold cracking due to hydrogen can be nucleated from either liquated grain boundaries and/or liquated segregation bands in weld heat-affected zone. It has been in need to make much study on the formation of partially-melted regions in HAZ of steel weldment.
    In this study, the effect of alloying elements and carbon content on partially melting in HAZ of several steels made in a laboratory was examined using a high temperature microscope.
    Preferential grain-boundary liquation, which occurred at the lower temperature than the solidus, was observed at synthetic HAZ of steels with carbon contents above 0.1 wt%, and was the most remarkable at about 0.14 wt% carbon content.
    It was known that there was a close correlation between the liquation phenomenon of grain boundary and the segregation tendency of alloying elements (Ni, Cr and Mo) at the bands associated with worked cast ingot.
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  • Atsushi Hasui, Yasuo Suga
    1979 Volume 48 Issue 12 Pages 1077-1083
    Published: December 05, 1979
    Released: August 05, 2011
    JOURNALS FREE ACCESS
    Thermal cycles of underwater welds in gravity arc welding were measured. The effect of welding parameters on cooling process, cooling rate at the bond line were investigated. Moreover, experimental formulas and nomographs were proposed to estimate cooling rate of underwater welds.
    Main results are summarized as follows:
    (1) Underwater welds are cooled rapidly owing mainly to the heat transfer from surface of weld to the sorrounding water. So the cooling rate of underwater weld is much higher than that of open air weld.
    (2) Welding parameters which have a considarable effect on cooling rate of underwater welds are weld heat input, water temperature, water pressure, thickness of base metal, welding position (slope of base metal) and location of weld bead.
    (3) Cooling rate (R) and cooling times (S500, S300) of underwater welds may be estimated by means of the following experimental formulas.
    R=6:25×105K (0.56sin2/3θ+1) Q-0.95t1/6
    S500=455R-1.09
    S300=780R-1.09
    And nomographs to estimate cooling rate and cooling times of underwater welds are made.
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  • Yoshihiko Mukai, Masato Murata
    1979 Volume 48 Issue 12 Pages 1084-1089
    Published: December 05, 1979
    Released: August 05, 2011
    JOURNALS FREE ACCESS
    Crack propagation features of Stress Corrosion Cracking (SCC) in 42 % MgCl2 solution (143°C) were investigated on welded joints of type 304 stainless steel. Sensitivity of SCC was highest in coarse-grained region of welded joint. This would be caused by the fact that slip ocurred more easily and yield strength was lower in material with coarse grains. In sensitized region by weld thermal cycle, sensitivity for SCC was lower than that of base metal and their fracture surfaces were characterized by transgranular fracture in both of them. The lowest sensitivity was gained in weld metal. This would be caused by so called keying effect of δ phase on SCC, as the weld metal had duplex phases (δ+γ).
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