Now the theory is generally accepted about the fatigue behavior of a notched specimen that a fatigue crack is initiated when the stress value at a point apart ε0 from the root of the notch equals the fatigue strength of the material. In this paper, the value of ε0 is investigated about a welded joint having incomplete penetration. Then, experiments were made on butt welded specimens with on incomplete penetration perpendicular to load direction. It was found that the value of ε0 was constant (about 0.2mm) regardless of root gaps.
Die Zerlegung des Lichtbogens beim elektrischen Schweissen in zwei Bestandteile, nämlich, einen vom Überzugsmaterialder Elektrode herruhrenden Teil and anderen vom Kernmetalldrahte herrührenden Teil, vollzieht sich durch die Vereinigung der Versuchswerte aus drei Messungen: die Messung der maximalen Lichtbogenlänge zwischen eine Stahlplatte and eine senkrecht zu dieser Platte gerichteten Überzugelektrode, die Messung der maximalen Lichtbogenlänge zwischen den entgegengesetzten Enden von zwei Überzugelektroden der gleichen Sorte wie im ersten Falle and die Messung der maximalen Lichtbogenlänge zwischen ein Ende einer Überzugelektrode der gleichen Sorte wie in den beiden obigen Fälle and ein Ende einer überzugloser Elektrode. Durch die Ergebnisse der Anwendung des Verfahrens auf verschiedenen Überzugelektroden wurde die Verständlichkeit der Theorie des Zerlegungsverfahrens gut bewiesen. Dadurch auch wurde die Zusammensetzung des Schweisslichtbogens unter veränderlicher Stärke des elektrischen Stroms mit konstanter Spannung abgeklärt.
Ni-Mc-Cr Alloy (Hastelloy C) is attracting attention in recent years, as a corrosion resistant material available for use in chemical plants and equipments. It has been necessary for us to establish techniques for production and fabrication of this alloy. We carried out experimental researches concerned with weldability, workability and heat treatment of this alloy. The results obtained are summarized as follows; 1. As decrease of alongation in hot-shortness range from 500°C is not heavy, it is expected that the welding crack sensitivity will not be an important problem on this alloy. 2. The precipitation takes place in temperature range from 600°C to 1150°C, and it becomes most pronounced at 800°C and 900°C. 3. Work-hardening properties of this alloy are clarified, and the allowable limit of cold working ratio is estimated 20% in mother metals and 10% in weld metals. 4. By using inert gas shielded-tungsten arc welding process, sound welds from anycracks or porosities can be obtained without difficulty. However, to prevent precipitation and grain growth, it must be noted, that the weldments have to be cooled as fast as posible. 5. In case of an overlay welding on mild steel plates, effects of dilution extend to the third layer. 6. This alloy should be solution heat-treated by holding at temperature from 1200°C to 1250°C, and then cooled rapidly in water or air.
A physico-chemical study has been made on the chemical reactions between slags and metals in welding processes using two series of electrodes containing 10% Fe-Al and 5% Fe-Mn, or 15% Fe-Al and 5% Fe-Mn in the coatings as deoxidizers, and the following results were obtained. (1) Equilibrium index K'Mn decreases with increasing basicities of slags BL and Fe-Al contents in the coatings. The relations between K'Mn and BL are represented by the following equations; log K'Mn(10Al, Mn Deoxidation)=-0.047BL+0.167 log K'Mn(15Al, Mn Deoxidation)=-0.047BL-0.013 (2) K'Al increases with increasing BL and Fe-Al contents. The relations between K'Al and BL are represented by the following equations; log K'Al(10Al, Mn Deoxidation)=+0.074BL+3.175 log K'Al(15Al, Mn Deoxidation)=+0.074BL+3.517 (3) K'SiO2 decreases with increasing BL, and increases with increasing Fe-Al contents. The relations between K'SiO2 and BL are represented by the following equations; log K'SiO2(10Al, Mn Deoxidation)=-0.408BL-0.757 log K'SiO2(15Al, Mn Deoxidation)=-0.408BL-0.585 (4) K'TiO2 decreases with increasing BL, and increases with increasing Fe-Al contents. The relations between K'TiO2 and BL are represented by the following equations; log K'TiO2(10Al, Mn Deoxidation)=-0.204BL-1.807 log K'TiO2(15Al, Mn Deoxidation)=-0.204BL-1.574 (5) The activity coefficients yMmOn of various oxides in weld slags are represented by the following equations, where yMmOn→1, when BL→O; log y MnO=+0.047BL log y Al2O3=-0.074BL log y SiO2=-0.408BL log y TiO2=-0.204BL
Mechanical properties were investigated of welded joints of commercial pure titanium sheets of 1 and 2 mm thickness, which were welded by TIG in a controlled atmosphere welding chamber filled with either pure or impure argon mixed with an impurity gas of air, nitrogen, oxygen or hydrogen. Moreover, comparison of mechanical properties of TIG welds in pure argon welding atmosphere (760 mmHg) with electron-beam welds in high vacuum was done. The conclusions are as follows: (1) Quantity of N2 and O2 gases in weld metal increased proportionally with an increase of air partial pressure in argon welding atmosphere. (2) Air gas more than 103 to 1.4×103 ppm(vol.) in pure argon atmosphere increased the hardness, and embrittled the mechanical properties of weld metal. (3) Among the three elementary gases of N2, O2 and H2, N2 gas had the most detrimental effect on weld metal. However, H2 did not change the hardness and tensile strength, although it embrittled the weld metal when it exceeded 104 ppm. (4) Embrittleness at room temperature in mechanical properties, especially in reduction of area and elongation, of contaminated weld metal which was welded in impure argon was not observed at temperatures over about 300°C. (5) Estimation of other mechanical properties and quantity of gases in weld metal is possible by measuring only the hardness in the weld metal (shown in Fig. 24). (6) The weld metal welded in pure argon was the most hardened and strongest zone in a welded joint, and therefore tensile fracture of a welded joint occurred in base metal. (7) Rupture at 1000 hr. of weld and base metal at 400°C were about 9.5 kg/mm2. (8) Impact strength of the electron-beam weld of a 6 mm thick plate was about 30% greater than the TIG weld obtained in a pure argon atmosphere (760 mmHg).