JOURNAL OF THE JAPAN WELDING SOCIETY
Online ISSN : 1883-7204
Print ISSN : 0021-4787
ISSN-L : 0021-4787
Volume 52 , Issue 2
Showing 1-21 articles out of 21 articles from the selected issue
  • Kunihiko Satoh, Masao Toyoda, Kazuhiro Nohara, Yoshikazu Suita, Masabu ...
    1983 Volume 52 Issue 2 Pages 83-90
    Published: February 05, 1983
    Released: August 05, 2011
    JOURNALS FREE ACCESS
    To estimate the residual stresses and deformations due to circumferential welds of a pipe, this paper suggests the trapezoid-inherent strain model in which stresses and deformations are obtained to apply the Green function introduced by Shirakawa. The stresses and deformations calculated from the analytical model agree well with those measured in the experimental circumferential welds. Accordingly, the parameters determining the properties of the residual stresses and deformations could be derived analytically by means of the model. The parameters made experimentally proof of much suitability, are (Tav)θ.βθ{=(Q/cρhl)⋅βθ} and, βθ(=l/√ah). Where Q, c and pare net heat input per unit weld length, specific heat and density, and a, h and 1 are the mean radius, thickness and length of a, cylindrical shell respectively. The length I being sufficiently larger than a and h, the residual stresses and deformations are determined by the single parameter (Tav)θ⋅βθ.
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  • Yukio Ueda, Keiji Nakacho, Tsubasa Shimizu, Katsumi Ohkubo
    1983 Volume 52 Issue 2 Pages 90-97
    Published: February 05, 1983
    Released: August 05, 2011
    JOURNALS FREE ACCESS
    Many pipes of stainless steel such as SUS 304 are used for various facilities including nuclear energy plants. In some specific conditions, stress corrosion cracking may occur on the inner surface of these pipes in the weld zone. In order to mechanically prevent the stress corrosion cracking from occurring, welding residual stresses on this surface should be converted into compressive ones. In the previous report, the authors showed effectiveness of the heat-sink welding (water cooling) to accomplish this end by conducting theoretical analysis and an experiment on residual stresses in the 4B pipe of SUS 304 by the conventional welding and the heat-sink welding at a certain standard heat-input condition.
    In this research, different pipe sizes and varied heat-input are applied. The welding residual stresses by the conventional welding and the heat-sink welding are obtained by the theoretical analysis and their production mechanisms are clarified. Hence the influence of the above changes of conditions on effectiveness of the heat-sink welding is investigated. The main results are summarized as follow.
    (1) In case of thin pipes such as 2B and 4B pipes, it is important to minimize heat-input per one pass (especially for latter half passes) in order to improve the effectiveness of the heat-sink welding. The effectiveness can be predicted either by theoretical analysis of the temperature distribution history with consideration of the characteristic of heat transfer under spray-watering or by experimental measurement.
    (2) In case of 24B pipes, thick pipes, it is desirable to minimize heat-input for the first half passes, by which the heat-sink welding becomes more effective. In addition, no matter whether the conventional welding or the heat-sink welding, it is important to prevent angular distorsion which produces tensile axial stresses on the inner surface of the pipe in the weld zone. Possible measures to meet these requirements are to apply restraining jigs, to minimize the section area of the groove (ex. application of the narrow gap arc welding), and to change continuous welding to skip one.
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  • Kazuyoshi Matsuoka, Tamotsu Naoi
    1983 Volume 52 Issue 2 Pages 97-103
    Published: February 05, 1983
    Released: August 05, 2011
    JOURNALS FREE ACCESS
    The circumferential weld is one of the most popular methods of fabrication of tubular structures and pipings. Due to the weld, residual stresses (hoop and axial) on the inside of the pipe are highly tensile. The tensile residual stress is one of the factors of intergranular stress cororsion cracking of pipings. Several methods which produce compressive residual stresses along the inner surface of the welded pipe have been investigated. They are the methods using thermal elasto-plastic process; induction heating for stress improvement, backlay welding, heat sink welding, and so on. On the other hand, it may be possible to improve the residual stresses due to the circumferential weld of pipes, using some mechanical process; for example, internal pressure, explosion along the inside surface of the weldment.
    This paper deals with the stress release effect of internal pressure on the residual stresses due to the circumferential welds of pipes. In the first part, the analytical procedure is presented. The initial residual stress distribution is described as the sum of the "inherent stress" due to weld shrinkage and the 'stress induced by the "inherent stress". The incremental formula is presented for calculating the state of stresses under internal pressure. In the second part, the analytical results are compared with experimental results. The analytical results show good agreement with the experimental results. The final part of the paper deals with the assessments of stress release effect of internal pressure on the residual stresses due to the circumferential welds of pipes. The assessments are as follows.
    1) The influence of welding conditions, dimensions and. yield stress of pipes on.the effect of internal pressure.
    2) Especially, the influence of heat-input; the less the heat-input of the last layer of the circumferential weld is, the more effectively the residual stresses are improved by means of internal pressure.
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  • Yukio Ueda, Keiji Fukuda, You Chul Kim
    1983 Volume 52 Issue 2 Pages 104-109
    Published: February 05, 1983
    Released: August 05, 2011
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    In this paper, a series of elastic analysis was conducted on the restraint intensity of a rectangular plate with a slit, changing only the plate thickness (keeping the throat thickness constant) and the distance from the center of plate thickness to that of throat thickness. Two -types of loading conditions were used for the above analysis, which were (1) application of uniformly distributed loads along the slit and (2) imposition of uniform displacement, instead.
    The main results are as follows.
    1) If the ratio of the plate thickness to the throat thickness, h/hw is approximately smaller than 3.5, it may be considered that the plate thickness is entirely effective regardless of the type of groove. On the other hand, if the ratio is greater than the above (for thicker plate thickness), the restraint intensity is not in a simple proportion to its plate thickness, and converges to a certain limit. An expression of the correction factor r/ for the effectiveness of plate thickness is proposed.
    2) If the first weld is laid deviated from the center of the plate thickness, the out-of-plane bending deformation is produced according to the magnitude of the eccentricity and the effective restraint intensity at the center of the plate thickness decreases. However, within the range of eccentricity e=h'/(h/2)= 2h'/h<0.4 (h' is the distance from the center of plate thickness to that of throat thickness), the influence of the eccentricity can be neglected. An expression of the correction factor η' for the effect of eccentricity is formulated.
    3) If the one side angle of the practical groove is within 45 degrees, the influence of the groove form can be disregarded.
    4) As very accurate correction factors η and η' were obtained, the effective restraint intensity in a slit weld joint of a finite rectangular thick plate can be calculated simply by multiplying these correction factors to the two dimensional restraint intensity on which the thickness of the base plate is entirely effective. Consequently, the effective restraint intensity can be obtained simply without performing three dimensional elastic analysis which requires a huge amount of computing time.
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  • Yukio Ueda, Keiji Fukuda
    1983 Volume 52 Issue 2 Pages 110-117
    Published: February 05, 1983
    Released: August 05, 2011
    JOURNALS FREE ACCESS
    The authors developed the measuring theory of three dimensional residual stresses induced in a long welded joint based on the theory of inherent strain, and two methods, Ly method and Lz method, were presented. Although these methods enable us to obtain very accurate residual stress distributions, they require so many measurements and machinery cutting. In many practical cases, the distribution at a specific point is sufficient for special purposes.
    To this end, in this paper, the authors developed an approximate measuring method of three dimensional residual stresses along the thickness direction at a specific point, based on the Ly method.
    According to this method which is named nLy method, the object is cut into a specimen with the specified aspect ratio. As the result, the cross section of the new specimen is in the state of plane deformation and effective longitudinal inherent strains can be measured in a simple way. Then, three dimensional residual stresses can be estimated by two dimensional stress analysis in stead of three dimensional one, using the finite element method.
    Furthermore, a simple estimation method which is named simple .L, method is proposed, admitting inclusion of estimation errors by simplification. By this method, three dimensional residual stresses can be estimated only by performing simple manual calculation.
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  • Mutsuo Nakanishi, Yi-ichi Komizo, Ichiro Seta
    1983 Volume 52 Issue 2 Pages 117-124
    Published: February 05, 1983
    Released: August 05, 2011
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    For low temperature service at -45°C-60°C, steel plates with little Ni content are used generally. The base metals of these plates have good toughness, because of various thermal or thermo-mechanical treatment. But the heat-affected zones of weldments in these plates have poor toughness frequently, because of disappearing of these treatment's effects by welding thermal cycles.
    In this paper, ultra low S-Ca treatment is combined with already well known TiN dispersing treatment. This new treatment is developed more effective to keep good toughness of welded HAZ than only TiN dispersing treatment. This treatment is dispersing not only TiN particles but also Ca (O, S) particles. So, for example, vTrs is improved about 10°C-20°C from one of the only TiN dispersing treatment on Charpy test.
    In this case, it is better to control Ti/N ratio near by 2. Ca (O, S) particles dispersed in steel are existing very stable at high temperature which TiN particles already are unstable at. So, Ca (O, S) particles take an important part of improving HAZ toughness.
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  • Mutsuo Nakanishi, Norio Katsumoto, Yuichi Komizo, Masaaki Tanaka
    1983 Volume 52 Issue 2 Pages 125-131
    Published: February 05, 1983
    Released: August 05, 2011
    JOURNALS FREE ACCESS
    Many investigations on low carbon weld metals have revealed that weld metal composed of fine acicular ferrite has sufficient toughness and the addition of Ti or T1-B into weld metals effectively forms the acicular ferrite microstructures. However, the majority of these investigations were concerned in the approximate strength range of 50-70 kg/mm2 and not in the range over 70 kg/mm2.
    The toughness of baimtic and/or ferntic weld metal of high strength steel was investigated in this report.
    The specimens of weld metal were prepared by DC-GMA welding process and the effects of the oxygen content and silicon content on the toughness of weld metal were investigated
    The oxygen levels affected the microstructure change of high strength steel weld metal as had been found in 50-70 kg/mm2. And decreasing silicon content in weld metal was remarkably effective in producing the fine microstructure and imrpoving charpy impact properties of high strength steel weld metal
    The test results could be explained in terms of decreasing martensite-austenite (M-A) constituent with decreasing silicon content.
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  • Koreaki Tamaki, Jippei Suzuki, Yoshimoto Nakaseko
    1983 Volume 52 Issue 2 Pages 132-140
    Published: February 05, 1983
    Released: August 05, 2011
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    This study devoted to the influences of chromium and molybdenum on the reheat cracking sensitivity of Cr-Mo steels from view points of their carbide phases. X-ray analyses, electron microscopic observations and hardness measurements were carried out on the synthetic 12 Cr-Mo steels in order to clarify the carbide reactions and the change of hardness accompanied by carbide precipitation during tempering at 500 to 700°C for, 1 to 100 hours. The results are summarized as follows. 1) Molybdenum carbide M2C precipitates in such the Cr-Mo steels of relatively lower chromium content and of higher carcking sensitivity. Precipitation of M2C causes the secondary hardening and the delay of softening both at 550°C which were revealed by the measurement at room temperature and at high temperature, respectively. Such temperature corresponds to that of crack initiation. Therefore, M2C prevents the softening of grain interior and promotes to cause cracking along the grain boundary (prior-austenite grain boundary). 2) Chromium carbide M7C3 precipitates in such the Cr-Mo steels of higher chromium content and of lower cracking sensitivity. Precipitation of M7C3 also causes the secondary hardening, but the hardening temperature is about 500°C and is lower than that of crack initiation. 3) It has been informed that carbide would precipitate along the grain boundary and cause the brittleness. But such the precipitation along the grain boundary was recognized in this study not only in the steels of higher cracking sensitivity but also in those of lower cracking sensitivity. Therefore it is concluded that grain boundary precipitation of carbide does not cause the grain boundary brittleness.
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  • Yoshio Araki, Hitoaki Sano, Masaru Kominami, Hiroki Oikawa
    1983 Volume 52 Issue 2 Pages 140-147
    Published: February 05, 1983
    Released: August 05, 2011
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    Fundamental studies on the prevention of welding cracks of heat resistaing superalloys and ultra high strength steels were made and as a result, developed an economical method of obtaining heat resisting .weld metal with low cracking sensitivity by using fully austenitic Cr-NiMn filler metal containing a certain amount of additional elements and Ar-base mixed shielding gases. These methods are already adopted for welding of heat resisting superalloys, hear resisting steels and low alloy high strength steels, obtaining good results.
    The superior properties of the weld obtained by this method are, described in this paper, which are summarized as follows:
    (1) High cracking resistance is obtained by eliminating the effects of deleterious impurities such as CrS and NiS.
    (2) High heat resistance is obtained by the prevention of -phase formation and the uniform deposition of stable carbide M23C6 in the austenitic matrix of weld metal.
    (3) Good impact properties is obtained at high and low temperatures and also in the case high temperature isheld for a long time.
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  • Kazushige Arimochi, Mutsuo Nakanishi, Susumu Satoh, Fumiyoshi Minami, ...
    1983 Volume 52 Issue 2 Pages 148-154
    Published: February 05, 1983
    Released: August 05, 2011
    JOURNALS FREE ACCESS
    The mechanical heterogeneity in welds influences, remarkably the results of fracture toughness tests, But such an influence has not yet been clarified sufficiently.
    In the present paper, as the first step to establish the rational method to evaluate the fracture toughness of welds with mechanical heterogeneity, the 3 point bending COD test on 9%Ni steel welded joint made of austenitic electrode was investigated. FEM analysis and experiments on deformation behavior of bending specimen with notch located at heat affected zone made clear that the mechanical heterogeneity in welds causes the unsymmetrical spread of plastic deformed region from notch tip, resulting in the unsymmetrical crack opening behavior, that is, the opening displacement of the soft weld metal side of crack becomes larger comparative to that of base metal side with the increase of bending stress, and this behavior is expressed accurately by using the two different rotational factors which are not same to that in case of homogeneous material.
    These results imply that the ordinarily adopted 3 point bending COD test method is not adequate as the fracture toughness testing method for the 9%Ni steel welded joint.
    Instead of ordinary one, the new method taking into account the effect of mechanical heterogeneity on the crack opening behavior was proposed as follows:
    δ= [r1 (W-a)/{a+r1 (W-a)+z}⋅ a/(l+a)+r2 (W-a)/ {a+r2 (W-a)+z}⋅1/(l+a)] Vg
    where r1=0.6, r2=0.1 a=V1/V2 Vg: crack mouth opening displacement a: crack length W: specimen width Z: distance of clip gage location from test piece surface
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  • Kunihiko Satoh, Masao Toyoda, Fumiyoshi Minami, Susumu Satoh, Mutsuo N ...
    1983 Volume 52 Issue 2 Pages 154-161
    Published: February 05, 1983
    Released: August 05, 2011
    JOURNALS FREE ACCESS
    Fracture performance of welds is influenced by mechanical and/or metallurgical heterogeneity caused inevitably in the welded joint. In the present paper, consideration has been carried out of plastic deformations and crack opening behaviors of cracked welds with mechanical heterogeneity, in particular, in strength. Finite element analyses based on elasto-plastic theory have been conducted for overmatched and undermatched weld joints with crack existing along fusion line under tension or bending.
    A considerably unsymmetrical plastic behavior is observed in the notched welds with heterogeneity in strength. Accordingly, the plastic behavior results in unsymmetriccal crack opening. As the degree of unsymmetrical opening is affected, by the strength ratio of weld metal to base metal, the total opening displacement calculated from global COD does not necessarily control deformation of each material in the vicinity of crack tip. The local COD defined in the present paper may become an appreciate measure of deformation of crack tip as same in homogeneous material, exclusive of the part of which strength level is corisiderably higher than that of other part.
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  • Itaru Watanabe, Motoaki Suzuki, Toshifumi Kojima
    1983 Volume 52 Issue 2 Pages 161-169
    Published: February 05, 1983
    Released: August 05, 2011
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    The available data on the brittle fracture initiation properties, of 9% Ni steel weldments bear out their satisfactorily high toughness at low temperatures, but have a'little ambiguity that arises in connection with the pop-in fractures and the tendency of HAZ cracks to deviate, into the lower, strength ductile weld metal which are observed when conducting fracture toughness tests on 9% Ni steel. weldments at low temperatures. However, no basic concept by which to assess. the significance of such fracture. behavior has been established yet.
    With this fact in mind, and investigation was undertaken in order to arrive at a more precise interpretation of the correlation between a such fracture behavior and structural intergity of 9% Ni steel LNG storage tanks. Three-point bending COD tests using coil-spring loading equipment and wide plate tests were performed on 9% Ni steel weldments made using the austenitic Ni-based and matching ferritic fillers. In these tests the pop-in behavior was also observed to some extent at -196°C, and the tendency for elimination of pop-ins by precipitating complete failure was predominantly observed at the same level off stress intensity in COD terms. It was nevertheless shown that 9% Ni steel weld-HAZs had no doubt satisfactory toughness at the LNG temperature(-162°C).
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  • Masatoshi Kojima, Koreaki Tamaki, Tsutomu Furuta
    1983 Volume 52 Issue 2 Pages 169-177
    Published: February 05, 1983
    Released: August 05, 2011
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    Aluminum specimens consisted of the couple of tubes and single, concave or convex tapered cores, were welded by electromagnetic welding. Equipment with capacitor of 1, 000 μF was used under the charged voltage of 4.5 kV. Variations of welded areas with tapered angles of cores (α), and the wavy patterns at the interfaces of welded areas were examined. From these results, variations of impact angle distributions in each joint, and the acceptable areas of impact angle for each position were also obtained. The results could be summerized as follows:
    (1) Position, width and numbers of welded area varied systematically with α.
    (2) 7.5° for convex tapered core joint, 12.5° for single tapered core joint and 17.5° for concave tapered core joint were the optimum tapered angles of cores. Maximum total welded lengthes were about 10 mm for both single and concave tapered core joints, and 8 mm for convex tapered core joint.
    (3) Wavy patterns, whose wave length became longer as the distance from the beginning of welded area increased, were observed at the interfaces of welded areas.
    (4) Both factors of the impact angle distribution in each joint andt he acceptable area of impact angle for each position affected the result of electromagnetic welding. Welded area was the position whose impact angle distribution was contained within the acceptable area of impact angle.
    (5) Impact angle distribution for each joint depends upon the tapered angle of core, but the acceptable area of impact angle depends little upon the tapered angle of core.
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  • Itaru Watanabe, Motoaki Suzuki, Toshifumi Kojima, Osamu Hirano
    1983 Volume 52 Issue 2 Pages 177-185
    Published: February 05, 1983
    Released: August 05, 2011
    JOURNALS FREE ACCESS
    This paper describes the arc physics which forms the basis of large current MIG arc welding with particular reference to plasma gas flow-induced dynamic pressure and the droplet transfer mode. Dynamic pressure was measured and compared with theoretical values. The transfer characteristics of droplets was examined with high speed camera and oscillograph. The effects of the shielding gas composition and the chemical composition of wire on the transfer characteristics were determined. A phenomenon peculiar to large current MIG arc welding was revealed as follows.
    (1) The dynamic pressure induced by plasma gas flow is reduced by large diameter wire.
    (2) The transition from streaming to globular transfer was found to be continuous with respect to welding current and arc voltage.
    (3) This transition occurred even when the arc voltage was increased at the constant current.
    (4) These tendency was particularly pronounced when the CO2 content of shielding gas and Si content of wire were relatively high.
    A study was undertaken to clarify the mechanism of arc voltage dependency on droplet transfer mode. The vapourization of oxides from the surface of molten metal on the electrode tip should be considered a factor which governs the droplet transfer.
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  • Itaru Watanabe, Motoaki Suzuki, Toshifumi Kojima, Osamu Hirano
    1983 Volume 52 Issue 2 Pages 185-192
    Published: February 05, 1983
    Released: August 05, 2011
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    This investigation was carried out to clarify the mechanism of the magnetic arc blow occurred in UOE pipe longitudinal inside seam welding by large current MIG arc welding process, and to establish the preventions against this phenomenon.
    The magnetic flux density around the arc was measured with aid of simulated model. The results obtained are summarized as follows.
    (1) The magnetic flux density around the arc in inside welding of pipes showed asymmetrical distribution.
    (2) Welding arc is blown toward the lower density side i.e. molten pool.
    (3) The asymmetrical disribution of magnetic flux density is caused by the earth current and welding current through the boom inserted to the pipe.
    (4) The prevention against the arc blow is established on the basis of the results obtained.
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  • 1983 Volume 52 Issue 2 Pages 193-202
    Published: February 05, 1983
    Released: August 05, 2011
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  • 1983 Volume 52 Issue 2 Pages 193a
    Published: 1983
    Released: August 05, 2011
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  • 1983 Volume 52 Issue 2 Pages 194
    Published: 1983
    Released: August 05, 2011
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  • 1983 Volume 52 Issue 2 Pages 199
    Published: 1983
    Released: August 05, 2011
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  • 1983 Volume 52 Issue 2 Pages 200
    Published: 1983
    Released: August 05, 2011
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  • 1983 Volume 52 Issue 2 Pages 204-240
    Published: February 05, 1983
    Released: August 05, 2011
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