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Volume 38, Issue 9
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The meturagical aspects of the weld metal and the welding defectsAkira Uchida1969 Volume 38 Issue 9 Pages 955-969
Published: September 25, 1969
Released on J-STAGE: August 05, 2011
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Yasuhiro Nishio, Takashi Ohmae, Yasuhiro Fukaya1969 Volume 38 Issue 9 Pages 970-979
Published: September 25, 1969
Released on J-STAGE: August 05, 2011
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Hiroshi Ikawa1969 Volume 38 Issue 9 Pages 979-990
Published: September 25, 1969
Released on J-STAGE: August 05, 2011
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Shigeo Shin1969 Volume 38 Issue 9 Pages 991-1005
Published: September 25, 1969
Released on J-STAGE: August 05, 2011
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Kazuo Ikeda, Hiroshi Maenaka1969 Volume 38 Issue 9 Pages 1006-1012
Published: September 25, 1969
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSRecently, employment of 9% Ni steels for low temperature structures such as liquid oxygen storage tank has been increasing. The most important problem for those structures is the brittle fracture characteristics of materials.
9% Ni steel has been welded with 70% Ni electrode such as Incoweld A. However, the electrode is very expensive, and reduction of nickel content has been strongly demanded.
In this paper, the brittle fracture initiation characteristics of 9% Ni steel plates quenched and tempered (QT) and doubly normalized and tempered (NNT) was investigated by the deep notch test.
In addition, the brittle fracture initiation characteristics of bond and weld metal deposited with 70, 50, 40, 35, 20 and 12% Ni electrodes was investigated.
It can be concluded that 9% Ni steel is excellent in brittle fracture initiation characteristics and can be applied safely to the liquid nitrogen storage tank, and all kinds of electrode tested provide similar quality of bond and weld metal. Weld metals with a notch never fracture in a brittle manner even at -196°C.View full abstractDownload PDF (3307K) -
Deoxidation reactions in arc weldingEiichi Tsunetomi, Hiroyuki Katayama1969 Volume 38 Issue 9 Pages 1013-1020
Published: September 25, 1969
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSIn our previous papers, deoxidation reactions in arc melting were reported. According to those results, the following became clear: (1) Deoxidation reaction in arc melting can be treated as a reaction at some mean temperature. (2) The reaction is recognized as a first order reaction. (3) The reaction rate is proportional to the current and inversely proportional to the volume in the molten pool.
In this paper, the Si and Si-Mn deoxidation reactions in arc welding were studied on the basis of the previous results. Weldings, using a mother plate (with or without an oxidizing surface) which contained Si, Mn and a wire in which oxygen was contained, were performed under certain pressures of Argon. This prevents the absorption of oxygen from the atmosphere into the molten pool. From those experiments, the relation between the oxygen content and the welding condition as well as the content of Si, Mn was investigated and analysed using the reaction equation proposed. This equation was obtained under the assumption that the pool was in a state of complete mixing and also by the application of the rate equation reported in our previous paper, as follows:
([%0]i-[%0])/([%0]-[%0]e)=ko⋅I/Sf
where [%0] is oxygen content in pool; [%0]i is initial oxygen content; [%0]e is apparent equilibrium oxygen content in pool; I is current; S is nugget area; f is welding speed; ko is rate constant.
The experimental results show that the oxygen content does not change perceptibly, even though the welding speed or the current may change where the initial oxygen content and the content of Si, Mn are constant. On the other hand, the values of I/Sf are almost constant within the limits of this experiment. Therefore, it is understood that the above results are mainly caused by the right side of the equation being constant. Furthermore, the relation between the value or k0 calculated by the equation and the contents of Si, Mn, shows the same tendency as the one related to arc melting. Therefore, the equation proposed does not contradict the previous result in arc melting.
From the above, quantitative treatment of deoxidation reactions in arc welding may be possible by applying this equation.View full abstractDownload PDF (545K) -
Harumasa Nakamura, Michio Inagaki1969 Volume 38 Issue 9 Pages 1021-1034
Published: September 25, 1969
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSA delayed failure test was done with notched specimens of synthetic heat-affected zone of highstrength steel. The test method was a so-called "charge and stress method, in which the specimen was subjected, at first, to a weld thermal cycle, charged with hydrogen electrolytically and then loaded in sustained manner. The main conclusions obtained in the study are as follows:
(1) Root crack susceptibility of the heat-affected zone in the first layer weld of a low-alloy high-strength steel can be examined in the delayed failure test of the synthetic heat-affected zone of steel.
(2) A new criterion was proposed for comparison of susceptibilities to hydrogen embrittlement of the synthetic heat-affected zones of steels. The ratio of a critical stress in the delayed failure test (σt) to a normal notch strength (σt) of synthetic specimens of a steel was plotted against a diffusible hydrogen content of the specimen in a graph with logarithmic graduation. The value of the ratio at a specific hydrogen content (e.g. 1.0 cc/100 gr) was adopted as the criterion.
(3) A critical stress increased with an increase of cooling time in a weld thermal cycle except for a 9% Ni steel. The stress also increased with decreases in diffusible hydrogen content and notch sharpness.
(4) Susceptibility to hydrogen embrittlement of a low-carbon martensite was affected by other alloying elements even if the carbon content and the hardness were not changed.
(5) Susceptibility to hydrogen embrittlement of a low-carbon martensite was increased by rapid quenching and also by repeated quenching.
(6) A bainitic structure which was isothermally transformed just above the M, temperature had a high susceptibility to hydrogen embrittlement. The susceptibility was nearly equal to that of an autotempered martensite.
(7) There was a relation between the new criterion in the delayed failure test and the critical restraining stress for root cracking in the heat-affected zone in the weld of the same steel in the TRC (Tensile Restraint Cracking) test.View full abstractDownload PDF (2380K) -
Characteristics of Carbon Arc at Low Pressure Hydrogen AtmosphereK. Nishiguchi, A. Matsunawa, T. Kitada1969 Volume 38 Issue 9 Pages 1035-1042
Published: September 25, 1969
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSSystematic research has been made on arc phenomena at low pressure atmosphere to clarify the electrode mechanism. Distinguished features of low pressure arc were found in cathode and anode phenomena, which appear eminently in the arc characteristics and appearance. For example, pure graphite cathode, which used to behave as a typical thermionic cathode (hot cathode), exhibits so called cold cathode under the condition of low pressure and small current. This cold cathode is characterized by random movement of a constricted cathode spot and strong vapour jet from the spot area.
This paper discusses the result of the systematic analysis on arc characteristics and their relation to transition of the cathode mode. The experiment was done under the condition of 10-150 Torr of pure Hydrogen atmosphere and 10-120 A of arc current. The electrode material was pure graphite rods (99.99%) of 6 mmφ.
Conclusions obtained are as follows:
(1) Transition of the cathode mode from the hot cathode to the cold cathode is mainly governed by arc current I, ambient gas pressure p and ionization p4tential Vi of the gas in the cathode fall region. Arc voltage suddenly falls by a few volts when the hot cathode changes to the cold one, though the average electric field of arc column Ep increases abruptly because of the shrinkage of column. This fact suggests that, in the cold cathode mode, Carbon rather than Hydrogen is ionized in the cathode fall region, and consequently the cathode drop Vσ reduces.
(2) Sum of the anode and cathode drops, (VA+VC), increases gradually in the range of the hot cathode with the decrease of ambient gas pressure and arc current. This value of (VA+VC) suddenly falls by 3-4 volts under the critical condition of ambient gas pressure and arc current when the cathode mode changes to the cold cathode. This abrupt change of (VA+VC) is due to the decrease of the cathode drop VC.
(3) In the range of the cold cathode, (VA +VC) decreases with the reduction of ambient gas pressure, while (VA+VC) remains almost constant against arc current.
(4) Variation of the cathode drop VC in both cathode. modes is explained qualitatively by Slepian's ionization mechanism in the cathode fall region.View full abstractDownload PDF (3418K) -
Relation among applied stress, diffusivity of hydrogen and delayed fracture of SteelIwao Onishi, Yoneo Kikuta, Takao Araki, Kanetake Nakatani, Toshihide F ...1969 Volume 38 Issue 9 Pages 1043-1050
Published: September 25, 1969
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSHydrogen embrittlement of steel has been treated as one of the phenomena of the delayed fracture. In this case, the applied stress and the behavior of hydrogen in steel have a great importance.
In the previous studies, the behavior of hydrogen in steel has been examined by the experiments of hydrogen permeability through the steel membrane and hydrogen occuludability in steel at room temperature. On the other hand, authors have investigated the relation between the applied stress and the fracture time of hydrogenated steel.
In the present paper, an effect of, the behavior of hydrogen on the phenomena of the delayed fracture was examined by using Constant Load Rupture testing. The tensile specimens were hydrogenated by cathodic method under constant load. The relation among the applied stress, the diffusion distance and the fracture time was examined.
The results obtained are as follows;
The square of hydrogen diffusion distance and the fracture time of specimen are linearly a related. Therefore, diffusion of hydrogen in steel is thought to depend upon Fick's law, as aturhors described previ-ously, and the diffusion coefficient of hydrogen in HT-80 steel is in the order of 10-6-10-7 Cm2/sec in this experimental condition.
Moreover, in the case of C.L.R. testing, if the specimens are applied with a stress, varying the diffusion distance of hydrogen, the concentration of hydrogen in the fracture part of specimens would be always constant and the difference of fracture time would depend upon the time when hydrogen is segregated to the same concentration through various distances of diffusion.View full abstractDownload PDF (527K) -
Iwao Onishi, Ikuo Okamoto, Takeshi Ariga, Mituru Arii1969 Volume 38 Issue 9 Pages 1051-1056
Published: September 25, 1969
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSThe corrosion currents of zinc and Al-Sn alloy due to contact with dissimilar metals, such as aluminum or tin, were measured in 3% NaCl aqueous solution at 25°C. In those cells, furthermore, the effects of the ratio of electrode areas on the corrosion current were investigated. Based on the results of these measurements, an analysis for the corrosion current density of each alloy, which was shown in the previous report, was made to explore the structural factors of that. The results obtained from this methodical analysis are summarized as follows
(1) The corrosion current densities of Zn-Al alloy and Zn-Sn alloy could be approximately expressed as the sum of the corrosion current density of zinc only that acts as anode on the alloy constituents added to the corrosion current density of zinc in contact with another metal contained in each alloy.
(2) As the corrosion behaviour of Al-Sn alloy, the galvanic cell of which anode component was the aluminum of binary eutectic and cathode components were both the tin of eutectic and the aluminum of primary crystal on the alloy system was considered to be formed. The calculated current density of such anode was about 3.6 mA/cm2.
(3) On the corrosion of tin-soldered joint in aluminum, the joint failure life introduced with an electrolytically calculating method by using the above mentioned value was coincident with the phenomena observed in our experiments. It was presumed, therefore, that the interfacial failure of such joint occurred along the aluminum of eutectic included in the interfacial layer that forms at between base metal and solder.View full abstractDownload PDF (1760K)
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