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Volume 47, Issue 10
Displaying 1-7 of 7 articles from this issue
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Consideration on the Mechanism of Post-Weld Heat Treatment CrackingHiroshi Ikawa, Yoshikuni Nakao, Koji Kagawa1978 Volume 47 Issue 10 Pages 679-685
Published: October 05, 1978
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSFrom the results obtained in this study, the mechanism of post-weld heat treatment (PWHT) cracking in Ni-base heat resistant alloys is as follows. Namely, when the welded joint which contains high residual stress is heated to the solution treatment temperature, fine r' particles precipitate in the matrices of coarse grains adjacent to the weld interface and as the result, flow stress in coarse grain region increases.
The increase of flow stress in matrix results in concentrating stress at the triple point of grain boundary. If the stress concentrated at the triple point of grain boundary exceeds the cohesive strength of grain boundary which is decreased by the segregation of S to the grain boundary, PWHT cracking occurs at coarse grain boundary.View full abstractDownload PDF (3039K) -
Eijiro Sugihara, Katsuyuki Amanuma1978 Volume 47 Issue 10 Pages 685-690
Published: October 05, 1978
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSDeveloped was a new remote control device of control-cableless type for AC arc welding machine. Important features of the new device were that a reference voltage of servomechanism for locating the movable iron core of welding machine at a desired position was selected among a number of ones prescribed on potentiometers before start of welding works and so welding current was regulated in a stepwise manner according to a control signal which was generated at the control box on the welding site and fed to welding machine through welding cable. Therefore, it is unnecessary to use a iroublesome control cable to transmit a reference voltage to welding machine.
Compensation of the settings of welding current for variation in input voltage and performance of the newly developed device operated simultaneously with usual voltage reducing device were discussed. Satisfactory operation of the device was recognized with error of less than ±2% in spite of fairly strong noise from universal motor of control use. Using this device, even a less experienced welder could regulate welding current correctly and rapidly with the simple operation of control box. It is hoped that successful application of the new device will serve to enhance labor-saving, efficiency of welding works, and assurance of weld quality.View full abstractDownload PDF (1418K) -
In the Case of CO2 Non Gas Shielded Semi-Automatic Arc WeldingTakanori Nishida, Sakae Miyamoto, Hiroshi Mikami1978 Volume 47 Issue 10 Pages 691-697
Published: October 05, 1978
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSIn a previous paper, it was clarified that the welding fume produced during arc welding with coated electrode can be converted to the value measured by the filter paper method by multiplying the correction factor 2 measured with the digital dust indicator irrespective of the electrode or the weldment.
In this report, similar experiments were performed in other cases. The results obtained are as follows.
(1) The value of fume density which is produced during semi-automatic carbon-dioxide and non-gas shielded arc welding was obtained by the filter paper method and the indication of digital dust indicator.
There is a proportional relationship similar to that of arc welding with coated electrode and not influenced by the weldment.
(2) It is possible to obtain the same accurate value of welding fume density as that obtained by the filter paper method by multiplying the correction factor 5 to the corresponding value measured with digital dust indicator in semi-automatic carbon-dioxide arc welding and the correction factor 3 in case of semi-automatic non-gas shielded arc welding.
(3) Welding fume is mainly composed of Fe, and Mn, and the collected welding fume in the actual welding site was quantitatively analyzed, obtaining some representative oxides, that is, 49.2% Fe2O3 and 7.2% MnO.
(4) Based on these experimental results, it is possible to easily assess a working environment if the fume density in the actual welding sit is measured, and the measured value is compared with the permissible fume density prescribed by the Welding Engineering Standard (WES 9004-1976) ofJapan.View full abstractDownload PDF (3628K) -
On Joint PerformanceKunihiko Satoh, Masao Toyoda, Kazuaki Ukita, Ryuji Shimoda, Akihiro Na ...1978 Volume 47 Issue 10 Pages 697-704
Published: October 05, 1978
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSIn this report, joint performance tests of HT80 heavy plates for penstock with lower strength weld metal are carried out to investigate load-carrying capacity, joint ductility, brittle fracture initiation and fatigue behavior.
Test results obtained are summarized as follows:
(1) According'to the tension tests of transverse welded wide plate specimens free from appreciable weld flaws, joint strength σu and percent elongation εu in a large gauge length are given by the conventional formulas,
σu ≥ {0.87σWu+0.29σBu σBu when 0.7<σWu/σBu<0.82
when 0.82 ≤ σWu/σBu
εu ≥ 11(σWu/σBu)-6(%) when 0.7<σWu/σBu<1
in which σWu, σBu are tensile strength obtained by coupon test of weld metal and base plate respectively. The σu-value of the specimen welded with the JIS D 5816 type electrode is found to clear 80 kg/mm2 or the nominal tensile strength level of the base plate.
(2) As the results of fluctuating tensile fatigue test of butt welded specimen with reinforcement, fatigue crack is not suspected to initiate during service life of the penstock under planning even when the undermatching electrode is applied to circumferential weld connections. It is also found by the tension test of welded wide plate specimens with a surface notch at a weld fusion line that there is no difference in fracture strength at the temperatures ranging 0°C through-20°C between welded specimens made with the AWS E 11016 type and the JIS D 5816 type electrodes.View full abstractDownload PDF (511K) -
Fatigue Strength Improvement of Semi-Circular Notched Plane SpecimenIsao Masumoto, Tohru Akaishi, Handl Hedwig1978 Volume 47 Issue 10 Pages 704-708
Published: October 05, 1978
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSIt is well known that spot heating and following rapid cooling increase the fatigue strength of welded joint. And the reason has been attributed to the residual stress change from tension to compression at the location of fatigue crack initiation.
However, there are many different reports' about the effect of residual stress on the fatigue strength of welded joint. And their conclusions does not always coincide.
Therefore, it is a little problem to consider that the change of residual stress distribution should increase fatigue strength of welded joint.
On the other hand, it has been previously reported that the reasons of fatigue strength improvement by hot galvanizing and rapid cooling was mainly aging effect.
In this report, the effect of residual stress change and aging effect by spot heating up to about 580°C and rapid cooling on fatigue strength are investigated, using SS41 steel plate and in vacuum melted 0.003 % and 0.27 % carbon steel.
Results obtained are as follows:
1) The fatigue strength of SS41 steel plate is almost equally increased, in spite of different residual. stress distribution by center spot heating, notch root spot heating and furnace heating followed by rapid cooling.
2) While fatigue strength of 0.003 % carbon steel plate do not increase by center spot heating and rapid cooling, fatigue strength of 0.27% carbon steel plate increases by the same heat treatment.
These experimental results make deduce that one of the main reason of the fatigue strength improvement of welded joint by spot heating and rapid cooling is aging effect of over saturated carbon in a-ferrite.View full abstractDownload PDF (388K) -
Significances of Welding Condition for Weld FormationToshio Yamamoto, Takio Okuda1978 Volume 47 Issue 10 Pages 709-715
Published: October 05, 1978
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSSignificances of welding current, speed and electrode force are considered introducing basic parameters for weld formation. These are summarized as follows.
(1) The type of weld formation can be devided into two types according to welding speed.
(2) In high speed seam welding, the nugget enlarges both by the increases of current density δs, δi and by the increase of heating time Ts Ti.
(3) The weldable current range ΔIa decreases with increased welding speed because decrements of δs and δs against the increase of current enlarge and the contacting time Ts decreases.
(4) The welding current to form the nugget increases with increased electrode force because the areas of current path As Ai increase and the coefficient of heat conduction h increases.
(5) The weldable current range ΔIa at the same welding speed increases with increased electrode force because the contact lengths between electrodes and plates Ls increase resulting in the increase of the cooling time Ts.View full abstractDownload PDF (548K) -
Yoshiaki Arata, Shinichi Murakami, Hisakatsu Nishihara, Toshiaki Moric ...1978 Volume 47 Issue 10 Pages 715-720
Published: October 05, 1978
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSHK-40 (0.4C-25Cr-20Ni) centrifugal cast steel pipes have been used for reforming and cracking tubes in the reaction furnace for the petro-chemical industry.
The authors have studied the application of the plasma arc welding to the cirucmferential joint of those pipes and developed the proper programming as to the start of weld, formation of back bead, crater treatment etc. and previously reported about it.
This programming, however, has been effective only as to one pass welding for thin wall pipes. After that the authors developed the proper programming as to multi-pass welding for thick wall pipes.
The quality and adaptability of this new programming and the properties of joint obtained by it are reported.View full abstractDownload PDF (2991K)
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