JOURNAL OF THE JAPAN WELDING SOCIETY
Online ISSN : 1883-7204
Print ISSN : 0021-4787
ISSN-L : 0021-4787
Volume 46, Issue 10
Displaying 1-8 of 8 articles from this issue
  • Application of grain growth equation to the selection of welding conditions
    Hiroshi Ikawa, Hiroaki Oshige
    1977 Volume 46 Issue 10 Pages 713-720
    Published: October 05, 1977
    Released on J-STAGE: August 05, 2011
    JOURNAL FREE ACCESS
    In this report, it was confirmed that the results obtained in previous report could be applied to the selection of welding conditions in order to improve the toughness in weld-heat affected zone (HAZ) of hieh tensile steels.
    Main results obtained are as follows.
    (1) Toughness of high tensile steels with various microstructures can be improved by refinement of prior austenite grain.
    (2) Austenite grain size in HAZ of electron beam welding can be calculated using Eq. (1) derived in previous report.
    (3) In electron beam welding of 100 kg/mm2 grade high tensile steel, it was calrified that toughness' in HAZ could be improved considerably if heat input per penetration depth was controlled under 2.6 KJ/cm2, using Eq. (1).
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  • Detection of penetration depth by capturing charged porticles from molten metal
    Hirosada Irie, Tatsuya Hashimoto, Michio Inagaki
    1977 Volume 46 Issue 10 Pages 721-727
    Published: October 05, 1977
    Released on J-STAGE: August 05, 2011
    JOURNAL FREE ACCESS
    It can be supposed that there are many particles emitted from molten metal during electron beam welding and that amount of these particles depends largely upon the state of molten metal. In order to detect the penetration depth or state of fusion zone, we tried to capture those particles, especially electrons using copper electrodes, named probes, disposed near molten metal and negatively biased with respect to specimen. Comparison between probe current and penetration depth or state of spouting vapor was carried out. Results obtained are summerized as follows;
    1) Energy of most electrons captured by probe is very small, less than 1 eV.
    2) Probe current consists of a DC component and AC components of various frequencies.
    3) The DC component relates closely to macroscopic penetration depth.
    4) Probe current also relates closely to vapor spouting from molten metal, so that probe current represents macroscopic state of fusion zone.
    5) An AC component of frequency range between 50 and 100 Hz. corresponds to ripple line or solidification line of fusion zone of metal and displays movement of molten metal.
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  • Effect of Water Pressure on Chemical Composition and Strength of Weld Metal
    Yoshiaki Arata, Masanobu Hamasaki, Jitsuo Sakakibara
    1977 Volume 46 Issue 10 Pages 728-734
    Published: October 05, 1977
    Released on J-STAGE: August 05, 2011
    JOURNAL FREE ACCESS
    The effect of water pressure on chemical compositions and non-diffusible hydrogen content in weld metal was studied by use of high water. pressure simulator. The water curtain type MIG arc welding method was applied to the butt welding of mild steel under high pressure levels corresponding to water depth of 50 m and 90 m. The results obtained are as follows.
    1) In case the pure argon was used as a shielding gas, silicon, manganese and carbon content in weld metal were not affected with water depth. On the other hand, when oxygen was added to argon, these elements decreased with increasing of oxygen content and arc length under the constant water pressure and also decreased with increasing of water pressure under the constant oxygen content and the constant arc length.
    2) Non-diffusible hydrogen content in weld metal was not affected so much with increasing of water pressure and was in the range of 2.2-3.5 cc/100 g, which was very low level compared with the other wet welding method.
    3) Effect of root gap was dissimilar in plate thickness. For the single pass butt welding of 6 mm thick plate, the appropriate gap was 0 mm or 2-3 mm.
    4) The hardness in welds was not affected with water pressure. The hardness in weld metal decreased with increasing of oxygen content which affected the increase of molten metal and decrease of deoxidizes elements.
    5) Single pass and multi-pass butt welds, welded in down hand position under high water pressure, included no defect and passed not only in tensile test but also in 180°bending test.
    6) Good results were obtained in Charpy V-notch impact test of deposited metal welded. under water depth of 50 m. Oxygen addition to shielding gas was available for increasing the impact value.
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  • Proper Heat Input Control Methods Relevant to Characteristics of Power Sources with Different No-Load Voltages
    Shuji Nakata, Masahiro Nishikawa, Takanori Suematsu, Takeyoshi Kaneda
    1977 Volume 46 Issue 10 Pages 735-741
    Published: October 05, 1977
    Released on J-STAGE: August 05, 2011
    JOURNAL FREE ACCESS
    Based on the previous work, the regions of welding conditions were roughly decided by the electrode force and the, weld current in the power sources of drooping characteristics with different no-load voltages such as 3.3V and 6.3V. The region of the suitable welding condition was estimated by taking account of the indentation and the tensile shear strength.
    The indentation was found to be seriously affected by the initial splash during collapse of projection in the case of using the power source with no-load voltage of 6.3V and by the splash in the latter half weld time after collapse of projection in the case of using the power source with that of 3.3V. Especially the expulsive initial splash was responsible for the deformation of nugget shape, unstablity of tensile shear strength with a large amount of scatter and unstable failure of welds in the tear or the shear fracture at the rate about 50%. The tensile shear strength tended toward saturation immediately after the occurrence of the splash in the latter half weld time.
    In order to suppress these splashes and overcome these faults of the weld, the up slope electrode force was adaptively introduced in the power source with no-load voltage of 3.3V and the up slope control in the weld current at the initial weld time was remarkably adaptable in the power source with no-load voltage of 6.3V.
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  • Hideo Kinoshita, Toshifumi Kubohori
    1977 Volume 46 Issue 10 Pages 741-748
    Published: October 05, 1977
    Released on J-STAGE: August 05, 2011
    JOURNAL FREE ACCESS
    This study is carried out to clarify the relation between stress concentration and fatigue strength, and between initiation and propagation of crack and fatigue strength.
    For this purpose, double-Vee butt joints with incomplete penetration are used. As non-destructive inspection, ultrasonic inspection and X-ray inspection are used and compared with the characteristics.
    The results obtained are summarized as follows.
    (1) By the bend fatigue test of specimen with incomplete penetration, it is found that the fatigue strength decreases rapidly as the size of incomplete penetration is increased.
    (2) The failure do not occur lower than a certain value of initial range in stress intensity factor ΔKi dependent upon size of incomplete penetration in this experiment.
    (3) By the ultrasonic inspection, the range in fatigue strength is estimated by the maximum echo height.
    (4) By the ultrasonic inspection, fatigue crack initiation is identified up to about 30% in total fatigue life. On the other hand, by the X-ray inspection, the total fatigue life is divided into three regions. In 1st region, incomplete penetration is undetectable, in 2nd region, incomplete penetration is detectable and in 3rd region, initiation and propagation of crack is identified.
    (5) The relation between the crack propagation rate da/dN and the range in stress intensity factor ΔK is given by the following expression da/dN=5.48×10-14(ΔK)5.7.
    (6) By the bend fatigue test of specimen with incomplete penetration, stress concentration factor a and fatigue notch factor β is rapidly increased as the size of incomplete penetration is increased.
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  • Voltage across electrodes and current flow area of plate surface
    Tashio Yamamoto, Takio Okuda
    1977 Volume 46 Issue 10 Pages 748-753
    Published: October 05, 1977
    Released on J-STAGE: August 05, 2011
    JOURNAL FREE ACCESS
    Voltage across electrodes and current flow area of the contact part between a electrode and a plate are measured to elucidate the current distribution in the plate. The results obtained are as follows.
    (1) Voltage across electrodes increases with increased welding current. The increment of the voltage becomes large as welding speed increases.
    (2) Resistance across electrodes Re decreases with increased welding current and electrode force. Re at the current value corresponding to commencement of nugget formation is almost same in any welding speed but Re at the same nugget penetration increases as welding speed increases.
    (3) Both length between start to center of electrodes and it to end of the current flow area are smarller than that of contact area between the electrode and the plate.
    (4) The current flow length Ls of the contact part between the electrode and the plate increases with increased welding current and electrode force. The increment of Ls at same welding speed decreases as plate thickness decreases:
    (5) Average current density δs of the contact part between the electrode and the plate is nearly same regardless of welding curernt for plate thickness above 1.2 mm but of δs, 0.5 mm in thickness increases slightly as welding current increases. δs increases with increased welding speed.
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  • Effect of Grain Refining on Hot Cracking of Welds
    Kazuyuki Minoda, Toshio Irisawa, Hideyuki Nagaoka
    1977 Volume 46 Issue 10 Pages 754-761
    Published: October 05, 1977
    Released on J-STAGE: August 05, 2011
    JOURNAL FREE ACCESS
    The effect of grain refinement on hot cracking susceptibility of 5083/5183 weldments was examined using y-type cracking test and slit-type cracking test. Furthermore, the effective preventive methods of micro-cracks in multi-pass welding were also investigated. Test results obtained are summarized as follows:
    1. Hot cracking susceptibility of 5083/5183 weldments was markedly reduced by addition of grain refiner Ti, B. In this case, it was more effective to add Ti, B to base plate rather than to electrode wire.
    2. Both y-type cracking test for thicker plate and slit-type cracking test for thin plate might be applicable to the assessement of hot. cracking susceptibility of Al alloys.
    3. In multi-pass welding, some micro-cracks were observed in the heat affected weld metal, especially in the region heated twice or three times by subsequent welding, or in the weld metal along the weaving line. Tohse micro-cracks are also prevented successfully by addition of grain refiner and control of welding conditions.
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  • Masanori Matsuoka, Yutaka Kasamatsu
    1977 Volume 46 Issue 10 Pages 761-768
    Published: October 05, 1977
    Released on J-STAGE: August 05, 2011
    JOURNAL FREE ACCESS
    The relationship between the fracture appearance transition temperature υTrs in the V-notch Charpy test and the brittle fracture initiation temperature in the COD test has been investigated. The obtained results can be summarized as follows:-
    (1) The relationship can be expressed by the equation,
    [Tδ]^σ=σ_c=c = (0.006121δy+0.4704)νTrs+8.26√t+0.608δy[{1n(c/40)(2σ/δy)2}+{c(2σ/δy)2-40}/100]-90.2(°K)
    where [Tδ]^σ=σ_c=c is the critical temperature at which the brittle fracture is initiated in an infinite plate with a crack of a length 2C and application of an uniform stress σ, δy is the nominal yield strength and t is the thickness of steel plates.
    (2) For preventing brittle fracture in welded structures made with HT60 or HT80, the required value of νTrs for the welds should be lowered with an increase in the strength and the thickness of steel plates, the design stress and the length of the crack in the welds. And the maximum acceptable crack length should be decreased with an increase in the strength and the thickness of steel plates, the design stress and νTrs.
    (3) The maximum acceptable crack length, for preventing brittle fracture in welds of HT60 or HT80 welded with the same heat input of 40-50 kj/cm, increases with the plate thickness up to the thickness of 40 mm and decreases with the plate thickness in a range of more than 40 mm.
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