Online ISSN : 1883-7204
Print ISSN : 0021-4787
ISSN-L : 0021-4787
Volume 48 , Issue 5
Showing 1-15 articles out of 15 articles from the selected issue
  • Toshiro Kikuchi, Iwao Onishi
    1979 Volume 48 Issue 5 Pages 259-265
    Published: May 05, 1979
    Released: August 05, 2011
    The present authors have referred to the grain size and matrix structure as the metallurgical factors having effects on the sensitivity to reheat cracking, and studied the effects of these factors on the reheat cracking.
    The results of the study obtained are summarized as follows:
    1) The effect of the peak temperature during the synthetic thermal cycle on the sensitivity to reheat cracking is large. The higher the peak temperature rises, the larger the sensitivity to reheat cracking becomes. It has become evident that in this instance, because the difference in the matrix hardness and 0.2% proof stress is negligibly small due to the difference in the peak temperatures, the effect of the grain size is noticeably great.
    2) Although the effect of the matrix structure on the sensitivity to reheat cracking does not manifest itself prominently as much as the grain size would do. As the matrix structure becomes softer, the sensitivity to reheat cracking decrease.
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  • Shizuo Mukae, Mitsuaki Kato, Kazumasa Nishio
    1979 Volume 48 Issue 5 Pages 266-271
    Published: May 05, 1979
    Released: August 05, 2011
    The suppression effects of the fine precipitate dispersions of micro-alloy elements, such as Ti and Nb, to the grain growth in carbon steel weld zone have been investigated using both methods of the isothermal heating experiment and the metallographic observations of TIG welds. The results obtained are as follows.
    1) Austenite grain diameter, Dx(T, t), in steel, which contains X% of micro-alloy element, isothermally heated at T°C for t sec is expressed by following equation
    Dx(T, t)=Dx=0(T, t)exp(-mX)
    where Dx=0(T, t) is austenite grain diameter of steel without micro-element. Designating exp(-mX) by P, parameter P would express quantitatively suppression effect of microalloy elements to austenite grain growth. Additions of Zr and Ti make P value considerably small comparing with Nb addition.
    2) Time exponent, n, in isothermal grain growth, D=ktn, becomes remarkably small value as increasing Ti and Zr contents; at Ti 0.08 % and Zr 0.05 %, n value would be less than 0.1 and comes to show very weak temperature dependence. Also, addition of small amount of Ti or Zr considerably increases the activation energy for austenite grain growth.
    3) Both sizes of celluler substructure and maximum grain in HAZ rapidly decrease as adding of Ti or Zr; linear relationship exists between both sizes.
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  • Junichi Kinugawa, Sadao Fukushima, Takeshi Fukushima
    1979 Volume 48 Issue 5 Pages 272-278
    Published: May 05, 1979
    Released: August 05, 2011
    Transformation behavior of heat-affected zone during underwater wet welding was investigated by comparing with that of welding in air.
    Welding was carried out at a depth of 20 cm in fresh water by using a plasma arc as a source of heat and 19 mm thick plates of steel (JIS-SM41A and SM50B) as base metals, while synthetic heat-affected zone tests were conducted.
    The attention was focussed on coarse-grained regions near the center of bond.
    The results are summarized as follows:
    1) For both of SM41A and SM50B, Fs temperature during cooling of underwater wet welding is lower by about 20°C and Ms temperature is higher within the limit of some 25°C than those of welding in air.
    2) In order to equalize the amount of Martensite in an underwater wet weld with that in air, it is required for both of SM41A and SM50B that cooling time from A3 to 500°C during underwater wet welding is longer within the limit of some 50 % than that during welding in air.
    3) In case an underwater wet weld and a weld in air contain the same amount of Martensite, no significant difference in their hardness is found for SM41A and SM50B.
    4) In the same case as above, however, cooling of underwater wet welding makes 50 % shear transition temperature of SM50B higher by about 10°C than that of welding in air.
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  • Kunihiko Satoh, Masao Toyoda, Yoshiharu Mutoh, Toshihiko Tanaka, Shuji ...
    1979 Volume 48 Issue 5 Pages 278-283
    Published: May 05, 1979
    Released: August 05, 2011
    It is well known that fracture initiation behaviors is influenced by Hot Straining during weld thermal cycle. In the present report, attention is forcussed to the influence of embrittlement due to weld thermal strain on processes of fracture. The processes of fracture of notched materials, KD32 and HT80 steel, subjected to hot-straining or strain-aging are made observation. Hot straining and strain aging influence not only on initiation and propagation behaviors of ductile fracture. In the materials subjected to hot straining and strain aging, initiation and propagation of ductile crack occur in the range of smaller deformation than in the virgin materials. The mutual relation between the increase in Ti-temperature or the decrease of width of stretched zone and the increase in harolness of notched-material subjected to straining can be observed.
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  • Akira Sakaguchi, Masao Mizuno, Yoichi Tomii
    1979 Volume 48 Issue 5 Pages 284-290
    Published: May 05, 1979
    Released: August 05, 2011
    In this report, the tendency of blow hole formation was investigated for MIG welds of aluminum alloy A5083P-O, in case of which the surface treatments adopted for base metal were changed. The adopted treatments were three kinds, machining, wire brushing, and chemical treatment, and welds were produced in horizontal position, using mainly V-groove bead on plate test pieces.
    Furthermore, the effect of intervals after treatment was also investigated.
    The results obtained are summarized as following.
    (1) Chemical treatment surface forms more blow holes than machining and wire brushing surface.
    (2) Several days interval after chemical treatment increases the number of blow holes, but even about 30 days interval after machining does not affect.
    (3) Butt welds form more and large blow holes than V-groove bead on plate in case of same surface treatment.
    (4) At chemical treatment, temperature, concentration, dipping time of NaOH solution were changed, keeping HNO3 conditions constant. The heavier conditions (temp. was higher, conc. was stronger, time was longer), the more blow holes wer formed. Especially, in case of omission of dipping in HNO3 solution, blow holes increase markedly.
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  • Yoshiaki Arata, Fukuhisa Matsuda, Yutaka Shibata, Yoshihisa Ono, Mitsu ...
    1979 Volume 48 Issue 5 Pages 290-297
    Published: May 05, 1979
    Released: August 05, 2011
    In this investigation the various notch-fracture toughness values were studied and evaluated for the electron beam (EB)-weld metals of structural high strength steels (HT50 and 80) by means of deep notch, crack opening displacement (COD) and Charpy impact tests, and furthermore the mutual relations between them were discussed.
    The remarkable conclusions are as follows.
    (1) The notch-fracture toughness of EB-weld metals showed lower value than that for base metal in general, and it tended to be lowered with an increase of weld heat input regardless of the difference in the method of notch toughness test.
    (2) The peculiar phenomenons that the fracture path of test specimen differs at a specific testing temperature were commonly observed in all notch toughness tests adopted in this investigation, especially in the narrow-fused and hardenable EB-weld metal of 10 KJ/cm weld heat input. In general such specific temperature was called “Fracture path transition temperature, TF” in this report.
    (3) The toughness values of EB-weld metal were distinctly affected by the difference in fracture path of specimen in Charpy impact test, however they have no relation with such “fracture path transition” in deep notch and COD tests.
    (4) The fracture toughness for the EB-weld metal of HT80 steel is in general superior to that for HT50 weld metal from the results for three types of toughness test adopted. Especially it showed higher value than the toughness for conventional arc weld metal in deep notch and COD tests.
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  • Kunihiko Satoh, Toshio Terasaki
    1979 Volume 48 Issue 5 Pages 298-303
    Published: May 05, 1979
    Released: August 05, 2011
    Concerning root crack belonging to hydrogen induced cold cracking, many researches have been done from mechanical and metallurgical points of view. Concept of restraint intensity is proposed to indicate quantitatively the conditions for prevention of root crack in Japan. Restraint intensity is related with average net stress and strain in weld metal, but it is not related with local stress and strain at the root of weld. According to researches in fracture mechanics field, crack initiation is considered to be a function of local stress or strain at a point where cracking is expected. Local stress at the root of weld will be one of useful informations for studying on root crack.
    In this report, effect of joint geometry on local stress or stress concentration factor at the root of weld is studied by use of finite element method based on two dimensional elasto-plastic theory. The conclusions obtained in this report are summarized as follows:
    1. Stress concentration factor at the root in the first-pass welding is changed considerably with groove type. It is increased with the decreased of root angle and with the increase of plate thickness and throat depth. (See Table 3)
    2. Conventinal equation for determining stress concentration factor as a function of thickness, throat depth and root angle is given. (See equation (1), Table 4, Figs. 6, 7)
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  • Yoshiaki Arata, Hiroshi Maruo, Katsunori Inoue, Masami Futamata, Tetsu ...
    1979 Volume 48 Issue 5 Pages 304-309
    Published: May 05, 1979
    Released: August 05, 2011
    In this paper we describe an experimental study of evaluation by hearing acuity, undesired sound and some characteristics of welding arc sound.
    The results obtained are summerized as follows:
    1) We can discern the arc voltage difference by hearing of variable welding arc sound within proper arc voltage.
    2) NRN of welding arc sound is 78 in CO2 arc welding and 85 in MIG arc welding of 400A. Then, it is often necessary to protect the organ of hearing from undesired sound of high current welding and impulse welding.
    3) Welding arc sound is constituted from wide-band random signal and sine signal of ripple frequency of power source. Intensity of the sine signal emphasized in a Globular and Spray transfer region with increaseing arc voltage.
    4) Welding arc sound is remarkably affected by change of droplet transfer and it has the stability in wide region with proper arc voltage. But sound pressure level is the smallest when the arc voltage is larger than proper one.
    5) The 707Hz-2245Hz bandwidth is an important frequency region of welding arc sound and in this bandwidth we can get some informations of arc voltage, gas shielding and electrode extension.
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  • Kotoji Ando, Nobukazu Ogura, Masaki Koshiro
    1979 Volume 48 Issue 5 Pages 309-314
    Published: May 05, 1979
    Released: August 05, 2011
    A new test method has been proposed to evaluate bond's fracture toughness (δc) easily. Three points bend (BNP) specimens were extracted from welded test blocks with notch of poor penetration.
    The tip of the notch in BNP specimen was located on a fusion line in modified-Vee joint. Three points bend tests have been made on weldments of three kinds of structural steels, and fracture toughness of bond has been measured over a wide temperature range using BNP test specimens. Results can be summarrized as follows;
    1. To estimate the bond's toughness exactly, notch tip must be laid in the coarse grained HAZ zone, but it is wearisome to machine such notch.
    2. The notch tip of the BNP specimen is precisely on fusion line, and it is easy to prepare BNP specimen.
    3. Bond's toughness of BNP specimen largely depends on angular distortion of joint.
    4. Temperature dependenceiof bond's toughness can be easily estimated with safety, by using BNP specimen welded under high bending constraint to prevent the occurence of angular distortion during welding.
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  • Ikuo Okamoto, Akira Omori, Masaaki Kawamura
    1979 Volume 48 Issue 5 Pages 315-319
    Published: May 05, 1979
    Released: August 05, 2011
    A lead wire set on a zinc spraying coated film was joined by a paralled gap resistance welding method. In this joining, the wire penetrates into the film, depending on welding heat input under constant electrode force. On the other hand, the peel strength of the joint increases as the penetration depth increases, but the deeper penetration may effect on the insulation of a plastic capacitor due to welding heat. Then, a something controlling method of the penetration depth is to be considerable to perform a sound lead wire joint.
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  • Hiroshi Tamura, Young Sik Kim, Noboru Kato
    1979 Volume 48 Issue 5 Pages 319-325
    Published: May 05, 1979
    Released: August 05, 2011
    The through-the-thickness and in-plane strain behaviours at the crack tip for HT80 and SM41 steels were observed continuously on various specimen geometries, using optical interference method. The relationship between the elastic-plastic strain distribution, or the elastic to plastic zone size ratio and specimen geometry was investigated. In addition, the characteristics of the transition behaviours from plane strain to plane stress condition were clarified on two steels.
    Main results obtained are as follows.
    (1) Under the same loading condition, the larger the specimen thickness is, the larger the elastic zone size on specimen surface and the elastic to plastic zone size ratio become.
    (2) Under the same loading condition, the plastic zone size in plane of SM41 steel of which the transition boundary of elastic-plastic deformation is clear, is larger than that of HT80 steel, while the throughthe-thickness strain is the about same on two steels.
    (3) The transition from plane strain to plane stress condition in SM41 steel, takes place after the hinge type plastic flow achieved the general yield. However, the transition of that in HT80 steel takes place when the plastic zone size is about a quarter of specimen thickness.
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  • Jun Matsumoto, Ikuro Hashimoto, Akio Honda, Tetsuro Morita
    1979 Volume 48 Issue 5 Pages 325-332
    Published: May 05, 1979
    Released: August 05, 2011
    Fatigue strength of butt joints welded with weaving has been investigated for SM58 steel by the fatigue test under pulsating tension. The specimens are classified into 6 groups by the weaving angle ranging from 0 to 45 degrees, and the amount of transverse shift of welding torch is ±2 mm. Zero degree of weaving angle means the straight weld line. When the weaving angle is changed, the geometrical shape at the toe of weld is consequently transformed. The fatigue strength is influenced by both the weaving of bead and the geometrical shape at the toe of weld. It was found that the fatigue strength increases as the weaving angle of torch increases.
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  • Shigetsugu Asakura, Hiroshi Wachi
    1979 Volume 48 Issue 5 Pages 332-337
    Published: May 05, 1979
    Released: August 05, 2011
    Slit type weld cracking test was performed to investigate the effect of preheating temperature on the cracking of the weld heat affected zone (HAZ) in 13Cr-Ni and 13Cr-Ni-Mo cast steels. The obtained results are as follows.
    (1) Cracking starting temperature of HAZ was decreased with the increased in preheating temperature. When the preheating temperature was increased from room temperature (RT) towerds 250-350°C, cold cracking starting temperature decreased from 115-160°C to RT or lower.
    (2) Maximum hardness of HAZ were almost no variations even when preheating temperature was increased, but width of harding area of HAZ increased in respons to increasing of the preheating temperature.
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  • Yoshihiko Mukai, Masato Murata, Hisafumi Fukushima
    1979 Volume 48 Issue 5 Pages 338-343
    Published: May 05, 1979
    Released: August 05, 2011
    To study the applicability of fracture mechanics to stress corrosion cracking of SUS 304 stainless steel in 42% MgCl2 solution (143°C), three different types of tests i.e, K increasing, constant and decreasing type have been performed. It was made clear that crack propagation rate, da/dt was well characterized by K value in almost the same way in spite of the difference of testing types. Namely, the corelation curve between da/dt and K value could be divided roughly into two regions, regions I and II. In region I, da/dt was approximately proportional to the square of K value and in region II, after discontenious dropping of da/dt, da/dt increased again with K increasing. In addition, it was confirmed from the result of K decreasing type test that threshold stress intensity factor for stress corrosion cracking, Krsaa was nealy equal to 10 kg mm-3/2 in this combination of environment and material. From the observation of crack appearance, it was made clear that crack grew along single path in region I but it branched almost into two cracks in region II, so that the dropping of da/dt in region II would be caused by decreasing of K value with crack branching.
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  • Isao Masumoto, Tohru Akaishi, Koichi Yoneda, Kazuo Matsuda
    1979 Volume 48 Issue 5 Pages 344-349
    Published: May 05, 1979
    Released: August 05, 2011
    In the previous report, it was deduced that fatigue strength improvement of welded joint by spot heating below A1 point and rapid cooling is mainly due to the quench aging effect, using notched plate specimens.
    This conclusion of the previous report was confirmed in this study, using butt and fillet welded joint of SS41 and SM50B steel.
    Results obtained were as follows:
    1) Fatigue strength of butt, Tee fillet and cruciform fillet welded joints were remarkably improved by center spot heating or side spot heating. Therefore, it is deduced that quench again effect is significant cause to improve the fatigue strength of welded joint by such heat treatment. This result was the same as the previous conclusion.
    2) There was no remarkable difference between the effect of spot heat treatment on fatigue strength of SS41 steel and SM50B steel welded joint.
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