すみ肉溶接部の剥離性破壊におよぼす鋼材および溶接の影響

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It is well known that rolled steels have different mechanical properties by the testing directions. Ductility in the direction of plate thickness is especially inferior to the one in the rolling surface. The anisotropy in mechanical properties of rolled steels will have to be taken into consideration on the design and construction of welded structures in which the plate is subjected to tensile load in its thickness direction through fillet-weld joint. One example of the failures produced by the effect of the poor ductility in the thickness direction of rolled steels is pull-out type fracture in fillet-weld joints. It has been often experienced at the joints of through bracket and transverse bulkhead in oil tankers. The pull-out type fracture will be affected by 1) the anisotropy of steels used, 2) difference in toughness between weld metal and mother plate and 3) stress distribution in fillet welds. In this paper effect of the factor 1) and 2) is investigated. A new testing method, unsymmetrical double notch Charpy impact test of which specimen is shown in Fig. 1,is introduced to evaluate quantitatively the toughness of steel for pull-out type fracture. In this test, crack initiated from the center notch of the specimen will pass through the other notch when eccentricity ι of the notches is small, but it will not pass after the magnitude of ι exceeds a certain limit. The critical value of ι is denoted by ι_<CR>. The magnitude of ι_<CR> for steels tested is shown in Fig. 4 and Table 2. It has a close corelation to the anisotropy of the steels as shown in Fig. 6,and the double notch Charpy impact test seems to be very effective to evaluate the anisotropy of the steels. In order to know the effect of the difference in toughness between weld metal and mother plate, U-notch Charpy impact tests as shown in Fig. 8 were conducted for some combinations of steels and electrodes. Area percentage of pull-out type fracture was adopted as a criterion. (see Fig. 9) Relation between the area percentage and ι_<CR> obtained by double notch Charpy tests is shown in Figs. 11(a)-(d). Steels welded by low hydrogen type electrode show greater area percentage of pull-out type fracture. Steels having greater anisotropy seems to have the tendency to cause much pull-out type fracture. The specimens which have greater area of pull-out type fracture showed lower energy absorption. (see Fig. 12). The area percentage of pull-out type fracture in the specimen seems to show no sensitive difference in the range of temperature between 50℃ and 150℃. (see Fig. 13)
社団法人溶接学会の論文
1960-11-25

すみ肉溶接部の剥離性破壊におよぼす鋼材および溶接の影響

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