The effect of phosphorus on crack-sensitivity of austenitic Cr-Ni stainless steel weld metal is investigated with the segmented-circular groove test process. The test results indicate that the effect depends on ferrite content in weld metal and phosphorus is allowable up to 0.05%, 0.10%, 0.13%, 0.15% each 3%, 7%, 9%, 12% ferrite level calculated in accordance with schaeflier's data.
A bar of an ordinary coated electrodes or a pair of them touching lengthwise to each other is laid parallel to the surface of steel plate at a suitable distance therefrom. When the electric arc is struck between the electrode tip and the surface of plate, it continues in existence of itself until the electrode is cosumed and thus the welding is done automatically. Using such a simple method of automatic welding, scme foundamental studies were done and the following results were obtained. (1) The distance between the core wire of electrode and the surface of steel plate for sucessful welding should be taken greater as the diameter of electrode increases. It should be also taken greater as the electric current applied is low. (2) The welding speed becomes greater as the intensity of current increases. To obtain the same welding speed for different sizes of electrodes the electric current should be cotrolled almost in the same proportion as the sectional area of the electrode wires. (3) The depth of penetration becomes greater as the electric current increases. Relating the arc voltage, the penetration becomes also greater as the voltage increases for a certain range of its intensity. Above this range of voltage the penetration becomes less owing to the marked spattering. (4) As the electric current increases, the breadth of bead becomes greater, while the height becomes less. (5) The rate of deposition of weld metal is far greater in the case of a pair electrodes as compared to that in the case of a single electrode. Regarding the rate of spattering the reverse is the case. (6) In the Vee butt welding the bevelling angle must be taken a little greater than in ordinary practise such as 100-120°. In the straight butt welding the gap between the plate edges must be taken greater as the electric current applied is lower to obtain perfect welding.
This paper reports the investigation of weldable high tensile structural steels, having 60-70kg/mm2 tensile strength, with a satisfactory notch toughness and weldability. The main conclusions are obtai-ned as follows; (1) In the present results upon the effects of alloying elements for Mn-V type steel, comparatively satisfying results are obtained for Modifyed Vanity Type Steel, contain about 0.5% Ni. (2) Concerning the range of chemical composition of commercial steel, it is difficult to satisfy both the high tensile strength and lower Maximum Hardness of Heat-Affected zone. (3) High Tensile, High Notch-Tough Steel, ("2H" Steel) obtained after special heattreatment has a tensile strength over 60kg/mm2 and higher yield ratio of 85% and excellent notch-toughness and weIdability as shown in table 4. Therefore this "2H" Steel is the most practical steel for use welding construction.
In this report the structural interpretations are given for the torsional creep charactors, especially the transition phenomenon of the increasing creep rate with the augument of prestrain, of prestrained mild steels to various extent in torsion at room temperature. They are as follows : 1. The innergranular recrystalization in addition to the recrystalization at grain boundary was observed more easily on the prestrained steels above the transition range. Where the innergranular recrystalization was observed as the hypertrophies of slip band and deformation or kink band at 450°and 530°C and as the hypertrophies and the recrystalized grains developed from them at 600°C. 2. Below the transition range, at 450°C and lower shear stresses, the ordinary boundary-recrysta-lization was replaced with uniformly wide grain boundary. 3. Cells were, also, observed more easily on the prestrained steels above the transition range. However, as they were not so prominent as shown in the 4th Report, the transition phenomenon can be mainly interpreted from the point of view of innergranular recrystatization. 4. The abrupt increase in the number of X-ray diffraction spot was seen above the transition range at 600°C at which the recrystalized grains developed from the hypertrophies were observed. But, in other cases, the spots were not seen and the tendency to reproduction of extinguished striation or, at least, the arrest of the extinguishment as shown in the 4th Report was not seen because of the in-distinctness of the cell structure. 5. As the curvature of the disturbed crystal lattice by coldworking is much large above the transition point, the number of the potential nucleus of recrystalization is much large and the time needed for the activation of potential nucleus in the subsequent heating is much small. 6. Above the transition range, the crystal lattice around the nuclei is enough straind to grow much numerous nuclei more easily. And the tendencies of this growing and that nuclei mentioned above interprete the numerous and comparatively prominont recrystalization above the transition range.
The authors improved the Sato's type apparatus for quenching test so as to suit for cooling test from very high heating temperatures. And they used this with an oscillograph for recording of cooling curves of many specimens which were cooled in various rates immediately after rapid heating. Moreover, they performed microscopic examinations and hardness tests on the specimens above mentioned. Judging from these experimental results, they constructed the continuous cooling transformation diagrams of the high tensile steel "Wel-ten 55" (a product of the Yawata Iron Works, its tensile strength 55kg/mm2), in cases of rapid heating maximum temperatures 900° and 1300°C. The diagram in case of the maximum temperature 1300°C differs extremely from that in case of the maximum temperature 900°C. The each transformation field, in which ferrite, pearlite or intermediate structure appears, in case of the maximum heating temperature 1300°C, exists in the range which is in the longer cooling time and lower temperature side in comparison with the corresponding field in case of the maximum heating temperature 900°C. This means the following facts. In case of the maximum heating temperature 1300°C, the grain sizes of specimens after cooling is larger than those in case of 900°C. Accordingly, it is more difficult to transform in case of rapid cooling from A3 transformation point to 500°C, becomes smaller, the area of ferrite decreases and the one of martensite increases remarkably in the cooled specimen and the hardness becomes higher. And this tendency of hardness-increase is stronger in case of cooling from 1300°C than in case of 900°C.
The hot cracking tendency of a weld bead is obviously one of the most important features throoughly to known in practice. As a result, this topic has been pondered by a good many investigators. A fairly large number of substantially different tests resulted, unfortunately, none of the test methods known at present actually meets satisfactory requirements. Recently, however, FISCO test was reported by H. M. Schnadt has yielded excellent results, therefore, it is now expected to develop electrodes and check the manufacture in progress. This report is results of the fundamental test carried out with various electrodes, operators and welding conditions for the appreciation of this new test method. It was confirmed experimentally that the FISCO test possesses the following good number of advantages. (1) The results can easily be determined and expressed. (2) It is accurate and readily reproducible, and its results are independant of the operator. (3) It is highly sensitive and has a good severing power. (4) Its rigour may be varied at wish and continuously between 0 and a very elevated maximum value. (5) It suits all sorts of electrodes. (6) Any chamfer shape may be used. (7) It requires very little steel and every plate may be used several times. (8) It can be welded with all position. Thanks to these advantages, it allows hot crack sensitivity of electrodes to be determined easily, accurately and faithfully and is, as a result, actually well suited for the developement and selection of electrodes.
We measure deformations of thin disks when heat sources move around center holes shown in Fig. 1, in the cases of a=50mm; b=100, 150 and 200mm; t, time required for heat source to go round, =120, 180 and 240 sec. Points where deformations are measured are shown in Fig. 2. The shape of disk surface after heat supply is characterized by curves, for example, shown in Fig. 3. Defining deformation-quantity I, II, III, IV, we discuss deformations of these thin disks in various cases. Moreover, we treat time variations of these deformations.