JOURNAL OF THE JAPAN WELDING SOCIETY
Online ISSN : 1883-7204
Print ISSN : 0021-4787
ISSN-L : 0021-4787
Volume 51, Issue 8
Displaying 1-16 of 16 articles from this issue
  • Yukio Ueda, Keiji Fukuda, You Chul Kim, Ryoichi Koki
    1982 Volume 51 Issue 8 Pages 636-643
    Published: August 05, 1982
    Released on J-STAGE: August 05, 2011
    JOURNAL FREE ACCESS
    The mechanism of the cold weld cracking may be simply stated from the mechanical aspect that the cold crack initiates when the stress and strain induced at a point reach the critical values. In this respect, the stress and strain are the important information to prevent initiation of cold cracking from the dynamical point of view. In connection to this, a series of researches is carried out on this kind of problems. A slit weld in a rectangular plate is chosen as the basic research model because of its two dimensional restraint state in which the constraint of thermal expansion and shrinkage varies along the weld line.
    In this paper, experiments are conducted in order to investigate the validity of the already proposed analytical calculation method for the inherent shrinkage which is the direct factor of producing restraint stresses and strains in the perpendicular direction to the weld line and for thus produced restraint stresses and strains. From the result, the characteristics of the restraint stress and strain produced in the weld metal are clarified. At the same time, the restraint strain which can be estimated by a simple calculation is proposed as a more general dynamical measure for initiation of cold cracking. In addition, the restraint intensities under three loading conditions are investigated of their significance as a dynamical factor in case of estimating the restraint stress and strain.
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  • Yukio Ueda, Keiji Fukuda, You Chul Kim
    1982 Volume 51 Issue 8 Pages 644-650
    Published: August 05, 1982
    Released on J-STAGE: August 05, 2011
    JOURNAL FREE ACCESS
    Welded structures are inevitably accompanied by deformation and residual stresses produced by construction, which sometimes cause initiation of various types of weld cracking. In order to avoid the weld cracking, the y-Groove cracking test specimen has been widely used as the cold cracking sensitivity specimen to determine appropriate materials and welding conditions.
    In this paper, the dynamical characteristics of the y-Groove cracking test specimen of arbitrary thickness are clarified by discussing the restraint stresses and strains produced in this specimen for general cases of welding where the size of the specimen changes and heat input varies. The results are as follows:
    (1) For evaluation of restraint stresses and strains produced perpendicular to the weld line in the weld metal of a y-Groove cracking test specimen, the analytical calculation method which was already presented for comparatively thin plates is extended for thicker plates. Then, the restraint stresses and strains under the influence of the ratio of plate thickness to throat thickness can be analytically calculated without conducting three dimensional elastic-plastic analysis.
    (2) The magnitude of restraint stresses and strains produced in a slit weld specimen vary with the amount of heat input, that is, they are dependent on the ratio of l/hcr. Judging the severity of the dynamical condition of the specimen from the magnitude of restraint stresses and strains, the infinite plate is the severest. The infinite plate may be replaced by a finite plate of which size ratio is (B/l≥4.0, L/l≥3.7). Then, the size ratio of the y-Groove cracking test specimen is not necessarily the severest.
    (3) Among the slit weld specimens with the same size ratio as the y-Groove cracking test specimen, the actual size of the y-Groove cracking test specimen achieves the severest dynamical condition for the specific heat input Q=17000J/cm.
    (4) When the thickness of the y-Groove cracking test specimen increases, the restraint strain (the sum of the elastic and plastic components) produced in the weld metal of the first pass also increases. However, the increasing tendency saturates at the plate thickness of approximately h=50 mm. From this fact, the necessary plate thickness for the specimen is 50 mm to determine the welding condition for the first pass of very thick plates.
    (5) For the slit specimen (B/l=1.875, L/l=2.5), the plastic restraint strains increase with an increase of the effective average restraint intensity (Rp)η, and their increasing tendencies are very similar (in Fig. 6). Therefore, (Rp)η may be used as a simple dynamical measure to compare the severity of the dynamical condition in place of the restraint strain.
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  • Correlation between Notch Toughness and Reprecipitation of AIN on Cooling Stage of Welding Thermal Cycle
    Itaru Watanabe, Motoaki Suzuki, Toshifumi Kojima, Syoji Tsuchida
    1982 Volume 51 Issue 8 Pages 650-657
    Published: August 05, 1982
    Released on J-STAGE: August 05, 2011
    JOURNAL FREE ACCESS
    Previous paper demonstrated that the C-Mn steels for low temperature service with high Al-low Nmicro Ti could ensure a high weld-HAZ toughness even in high heat input welding. It was assumed that such superior weld-HAZ toughness is attributed to a significant reduction of free-N resulted from reprecipitation of AlN on cooling stage after welding.
    To verify the mechanisms which governs correlation between the weld-HAZ toughness and N, Al and Ti contents of steel, the morphologies of N in weld-HAZ were determined by careful phase analysis including hydrogen carrier reduction analysis, iodin methanol alkali fusion analysis and acid decomposition analysis. Results obtained were as follows:
    (1) Free-N which is produced by dissociation of nitrides on heating will be caught by Al and.reprecipitates as AlN on cooling stage of welding thermal cycles.
    (2) These phenomena will be accelarated by increase in sol. Al content.
    (4) Repriecipitation of AlN occures at the temperature range from 850°C to 600°C on the cooling stage of welding thermal cycles.
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  • Study on Notch Toughness of Weld Metal in Large Current MIG Arc Welding
    Itaru Watanabe, Toshifumi Kojima, Motoaki Suzuki
    1982 Volume 51 Issue 8 Pages 657-665
    Published: August 05, 1982
    Released on J-STAGE: August 05, 2011
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    In previous papers, the authors demonstrated that the addition of Ti and B are extremely effective to improve the notch toughness of weld metal and verified the inherent and complex effects of Ti, B and oxygen on the refinement of microstructure.
    This paper deals with the notch toughness of weld metal produced by the multipass large current MIG arc welding. Attention was focused on the effects of alloying elements such as Ti, B, oxygen, nitrogen and post weld heat treatments on the notch toughness of weld metal. The results obtained were as follows:
    (1) Ti-B weld metal consisting predominantly of acicular ferrite structures gives the optimum toughness at Ti content of 0.02%. The oxygen content ranging from 300 to 500 ppm has little influence on its toughness.
    (2) Nitrogen deteriorates the notch toughness of Si-Mn-Mo weld metal significantly, whereas Ti-B weld metal shows highly tolerance to it.
    (3) The deleterious effect of stress relieved heat treatment on the notch toughness of Ti-B weld metal is due to temper embrittlement phenomenon which occurs during the cooling stage after heat treatment.
    (4) The toughness of quenched and tempered weld metal made by Si-Mn-Ni-Cr containing consumable wires gives good correlation with tensile strength and oxygen content, and the transition temperatures of Charpy impact test are lowered by decreasing oxygen content within the tensile strength range of 60-65 kg/mm2.
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  • Kunihiko Satoh, Mitsuru Tamura, Takashi Ohmae, Yukio Manabe, Kosaburo ...
    1982 Volume 51 Issue 8 Pages 665-672
    Published: August 05, 1982
    Released on J-STAGE: August 05, 2011
    JOURNAL FREE ACCESS
    A retarded cooling method was conceived to improve the quality of the welded joints obtained with the "locally drying underwater welding method", and underwater welding test using this retarded cooling method was carried out. The test results are summarized as follows:
    1) From the heat conduction analysis of the instantaneous plane heat source and the base metal around which was cooled with water, it was clarified that when the ideal insulation material of 100 mm wide and 300 mm long at maximum was applied around the groove to be welded, the welds obtained with the above underwater welding method were cooled to 300°C at nearly the same rate as that on land.
    2) In the test, the insulation material of l mm thick and 100 mm wide was firmly applied on either side of the groove to be welded on both of the top and bottom surface, and also the shielding material which traveled with the welding torch was provided. When underwater welding was made using these insulators, the validity of the above heat conduction model was almost proved. Further the welded beads produced by this method had a hardness similar to those made on land.
    3) Significant improvements were observed in the mechanical properties, such as elongation, reduction of area tensile strength, bending ductility, and Charpy absorved energy of the joints welded by the locally drying underwater welding system using this retarded cooling method, as compared with those of the welds obtained by the same system not using the retarded cooling method. The values obtained by the test were quite near to those of air welds.
    4) In the three-point bending COD test, the temperature at, which stable slow crack occurred in the weld produced by this method prior to brittle fracture was 30°C lower than that in the weld obtained by the previous method, namely; -130°C--110°C. These values are little different from thosee of air welds.
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  • Weld Joint Strength of Mullite Ceramics
    Hiroshi Maruo, Isamu Miyamoto, Yohihiko Inoue, Yoshiaki Arata
    1982 Volume 51 Issue 8 Pages 672-679
    Published: August 05, 1982
    Released on J-STAGE: August 05, 2011
    JOURNAL FREE ACCESS
    Mechanical strength of laser-welded mullite ceramics with 48wt% and 59wt% Al2O3 has been estimated by a three-point bending test. Resistances to thermal shock and thermal cycle have also been discussed. Results obtained are summerized as follows:
    (1) In 48 wt% Al2O3, strength of weld joint decreases with increasing number of blowhole which tends to appear adjacent to the fusion boundary due to high viscosity of the molten material. Alumina filler, which decreases the viscosity of the molten material, can enhance the joint efficiency up to 100%.
    (2) In 59 wt% Al2O3, 100% of joint efficiency is obtainable in root bend test. However, the joint efficiency in face bending is not as high as 50% due to the weld defect in the bead surface. Filler material increases the joint efficiency by forming reinforcement.
    (3) Resistances to thermal shock and thermal cycle of weld joint are as high as those of the base materials.
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  • Kunihiko Satoh, Masao Toyoda, Kazuhiro Nohara, Shunichi Takeda, Michis ...
    1982 Volume 51 Issue 8 Pages 679-686
    Published: August 05, 1982
    Released on J-STAGE: August 05, 2011
    JOURNAL FREE ACCESS
    Electron beam welded joints of structural steels have occasionally remarkable mechanical heterogeneity because the electron beam welding is a high energy density welding process. Fracture toughness evaluation is considerably affected by the local mechanical heterogeneity, in paticular the use of V-notch charpy test brings a difficult problem such as missing of fracture path from the net section. In the present paper, Charpy impact tests have been carried out of the electron beam welded joints of HT80 steel. The elastoplastic calculations based on FEM analysis have been conducted for considering the significance of absorbed energy of Charpy test, and Charpy tests of specimen with both-side deep groove also have been done in order to clarify how to use Charpy impact tests for evaluating fracture transition behaviors of electron beam welds.
    The absorbed energy of the V-notch Charpy specimen of electron beam welds is not necessarily a proper measure due to the existence of locally mechanical heterogeneity. In the Charpy test of specimen with both-side deep groove, fracture propagates straightly along net section and the transition temperature obtained in that test is useful index to evaluate the fracture transition behavior of electron beam welds. By using the evaluation method proposed in the present paper, the fracture toughness of weld metal of electron beam welded joint depends upon the heat input of electron beam welding, that is the width of weld metal. The weld metal of welded joint with lower heat input occasionally has a sufficient toughness as same as the base metal, although hardness of weld metal is considerably higher than that of base metal.
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  • Takeshi Nishi, Haruo Fujita, Sumichika Haseba, Masahiro Ohara
    1982 Volume 51 Issue 8 Pages 686-692
    Published: August 05, 1982
    Released on J-STAGE: August 05, 2011
    JOURNAL FREE ACCESS
    Undercutting restricts the upper limit of welding speed in submerged arc welding. However, the process of undercutting has been incompletely known because of the difficulty in process observation. Accordingly, a X-ray observing apparatus and a decantation techniuqe were applied to quantitative investigation of the process of undercutting. This investigation aimed to understand dominant controlling factors for the occurrence of undercutting.
    The results were as follows;
    (1) Two variables mainly affect the occurrence of undercutting One is a displacement of molten metal (Xm) and the other is a solidification point along a toe of weld pool (Xs). When the molten metal is displaced more than the solidification point (Xm>Xs), the undercutting occurs.
    (2) A distribution of arc heat source mainly influences the solidification point. The distribution in crossing to welding direction gives the worst influence.
    (3) It seems that the dynamic component of arc pressure gives motivating force for molten metal to displace, and that the static component affects little.
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  • Friction Welding of Stud to Plate
    Hirohito Hira, Fumiyoshi Kanatani, Takao Uemura, Atsushi Shiomi, Kazuo ...
    1982 Volume 51 Issue 8 Pages 693-700
    Published: August 05, 1982
    Released on J-STAGE: August 05, 2011
    JOURNAL FREE ACCESS
    In the previous report, difference between brake type and inertia type friction welding was discussed, then effect of various parameters on burn-off behaviours and macrostructures of the same diameter bar friction welds was studied. Deceleration condition of rotation was shown very effective parameter.
    In this report, friction welding parameters and joint design for the welding of stud to plate joint was considered.
    Experimental results were as follows;
    1) Friction welding of stud to plate joint was relatively difficult than welding of same diameter bar joint, because some characteristic defects caused by the shape effect was appeared. So, the parameters of higher pressure and longer deceleration time should be used for the stud to plate joint than those for same diameter bar joint.
    2) When same welding condition was used for both stud to plate and same diameter bar joint, the former showed rather convex shape heat affected zone.
    3) Heat affected zone of stud to plate joint became narrower and concave shape with increase of pres-sure and deceleration time similarly the case of same diameter bar joint.
    4) Movement of friction surface from the plate face to stud was occurred when low pressure was used for stud to plate joint. And moved zone was difficult to be removed only by using high upsetting pressure.
    5) Protrusion should be prepared when frictoin pressure was restricted to the low level.
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  • Kenji Ohshima, Minoru Abe, Takefumi Kubota
    1982 Volume 51 Issue 8 Pages 700-707
    Published: August 05, 1982
    Released on J-STAGE: August 05, 2011
    JOURNAL FREE ACCESS
    A computer controlled system is proposed for improving the stability of the pulsed arc in a constant wire feed rate system. The pulsed current transfer is achieved by pulsing the current between the globular and spray transfer current ranges. In the pulse durations the current conduction occurs over the whole metal drop surface through the plasma, and promotes the magnetic force field conducive to the spray transfer. When the pulse durations are long, a few droplets may successively be detached from the electrode. Drops should be ejected one by one from the electrode tip at a regular frequency synchronizing with the frequency of current pulses, in order to improve the stability of the pulsed current transfer with a sufficiently short arc. For this purpose, the saw tooth current is used in the pulse peak current range.
    The voltage drop at the electrode extension is dependent upon Ohm's law and will be greater with long electrode extensions. Hence, even if the voltage at the point of current pickup is kept constant, the arc voltage or arc length varies with a variation in the current and electrode extension. A sampled-data control system computes the arc length in process of the arc welding by using the current and voltage at the point of current pickup, and determines the current magnitude on each cycle of pulsating current to keep the arc length constant.
    The behavior of the arc welding system is described by difference equations. The stability of the arc is discussed by studying the solution in the transient state.
    Experiments are also carried out in the sampled-data control system which contains transistors and integrated circuits, and the metal transfer and arc phenomena are observed by means of the high speed motion pictures. The validity of the theoretical results is confirmed by the experimental investigations.
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  • 1982 Volume 51 Issue 8 Pages 708-721
    Published: August 05, 1982
    Released on J-STAGE: August 05, 2011
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  • 1982 Volume 51 Issue 8 Pages 711
    Published: 1982
    Released on J-STAGE: August 05, 2011
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  • 1982 Volume 51 Issue 8 Pages 714
    Published: 1982
    Released on J-STAGE: August 05, 2011
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  • 1982 Volume 51 Issue 8 Pages 715
    Published: 1982
    Released on J-STAGE: August 05, 2011
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  • 1982 Volume 51 Issue 8 Pages 716
    Published: 1982
    Released on J-STAGE: August 05, 2011
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  • 1982 Volume 51 Issue 8 Pages 719
    Published: 1982
    Released on J-STAGE: August 05, 2011
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