The authors investigated the effect of welding on the low temperature brittleness of ship steel. Manual and submerged welds were used and the various Charpy impact specimens selected along a line perpendicular to welding beads were tested over a range of temperatures at which the mode of fracture changed from shear to cleavage. The distributions of transition temperatures located off the line of the weld were determined and compared with their metallurgical structures, hardness and temperature distributions. Generally, the fusion zone of a weld showed more extensive notch toughness than others especially at lower temperatures. The test results showed that the brittle zone does not exactly coincide with the heat-affected zone, but was farther located from the weld than the latter. Though the cause is not clarified, it is assumed to be the result of aging phenomena due to thermal cycles. Further inquiry is continued on this point.
"Activation energy" may be observed as a procedure of testing weld metals to guess from the numerical magnitude of that energy whether the weld metal is stable or unstable with regard to the atomic arrangement. This procedure will also help in deciding proper uses of several types of electrodes according to their characteristics. "Activation energy" observation should be carried out to the same extent as various other mechanical tests, especially in the case of a weld metal in which high temperature was used.
The mechanical properties resulting from the deoxidation with ilmenite or iron-sand system flux in wich Mn and Si have been included, were studied. The results follow: 1) Of the components of the mixture, ilmenite gives the best result at 30%. It works with a good result even at 50%. 2) Iron-sand gives a better result when mixed with ilmenite. The mixing ratio was set at iron-sand/ ilmenite=20/30, both together making 50 against the total fllux, as 100. A very good result was obtained from, this ratio. When efficiency in deoxidizing mild steel arc welds is aimed at, the general tendency of some of the factors that affect the ouality of mild steel arc welds are: i) That there exists a close relationship between the amounts of C and Mn in mild steel arc welds. An increase of Mn is naturally accompanied by an increase of C. ii) That the quantity of Mn remaining in mild steel arc welds after the Mn has been consumed in deoxidation affects the mechanical properties of mild steel arc welds. The best result is obtained when It stays within the range between 0.35-0.45%.
A new measureing system for welding heat is established. The system is consisted or an automatic welding head, a remote controller, a parallel rotating table and metallic calorimeters. Experimental results of ordinal covered electrodes used manual welding in a. c. arc welding are shown in fig. 5, 6, 7 and appendix.
By experiments on the test specimens of 7 kinds of butt welded joints connected by lateral, frontal and oblique (45°) fillets respectively or combinatively which have equal throat sectional areas, the author measured the deformation resulting from tensile static load, strength of the joint and inclination of the breaking surface of fillet. From these measured results, the author made comparative studies in regard to the following items. Strength of the joint, the max. shearing stress in fillet at the elastic and ultimate loads, inclination of the breaking surface of fillet, deformations of the joint and apparent modulus of elasticity of the joint.