高張力鋼熱サイクル再現部の疲労特性について(第 2 報) : 切欠材について

概要

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There are many factors lowering the fatigue strength of welded joints, for example, undercutting, geometrical effect of reinforcement, residual stresses, microstructural change in weld heat affected zone, etc. Among those many factors, we tried to study the fatigue strength of weld heat affeeted zone of various kinds of high tensile strength steels, including ultimate strengths from 60Kg/(mm)^2 to 80Kg/(mm)^2. In order to reproduce the microstructures of various portions in weld heat affected zone, test pieces were subjected to thermal cycles by the synthetic thermal cycle aparatus, with the peak heating temperatures of these thermal cycles set at 640,740,850 1000 and 1350℃; then machined to V-grooved specimens. Amsler's high frequency vibrophore fatigue testing machine was used. Fatigue limits of all notched specimens as well as those of smooth specimens subjected to weld thermal cycles are nearly equal to or higher than that of each base metal and are proportional to static tensile strengths of various portions in weld heat affected zone. These results mean that the reduction of fatigue limits of butt weld joints of high tensile strength steels including ultimate strengths from 60Kg/(mm)^2 to 80Kg/(mm)^2 is not due to the micro-structural change in weld heat affected zone. Difference in fatigue behavior between different steels, is explained by the previous lath structure of low carbon martensite.
社団法人溶接学会の論文
1968-09-25