マンガンシリコン系高張力鋼のオーストリアビード曲げ試験

抄録

The bead-bend ductility of high-tensile manganese-silicon steels was investigated by Austrian test, Kommerell type longitudinal bead-bend test. Twelve steel plates of 20mm thickness were tested. As the basic criteria for evaluating steels, (a) the transition temperature at which the maximum bend angle reached at 90 degrees, (b) the maximum bend angle a-id (c) the bend angle at first crack at room temperature were used.
The conclusions may be summarized as follows ;
(1) Bead-bend ductility of test steels were remarkably inferior to that of the current mild ship steels. Therefore, in order to secure a satisfactory service performance of high tensile steels for welded structure, weldability test such as a bead bend ductility test is indispensable.
(2) The maximum bend angle and the bend angle at first crack were closely related to the maximum hardnesses of heat-affected zone, and the both values decreased considerably as the maximum hardness etceeded about 350 VHN.
(3) It was shown that normalizing before welding had not a pronounced effect on bead-bend ductility of test steels, but post-heating above 300°C improved the ductility significantly.