Hajime Nakamura1, Yoshikazu Kuriyama1 and Yasuhisa Yamazaki1
1Ishikawajima-Harima Heavy Industries Co., Ltd., Tokyo
In the preceding paper, the authors reported that a remarkable brittle zone exists in HAZ (Heat-Affected-Zone) of HT-100 steel welded joints. The results of brittle fracture tests showed that brittle cracks always run over the parts of 0.5 to 1.0 mm apart from the fusion line heated to 1150°∼1350°C during welding. Therefore it is important to make clear why HAZ of HT-100 steel shows such a brittle behavior.
Chemical analysis showed that no remarkable changes in composition were observed across HAZ, and this was also confirmed by an X-ray-microanalyser. The increase of free nitrogen as a result of decomposition of AlN in the steel was though to be not harmful to the embrittlement of HAZ. After various investigations the authors concluded that the embrittlement of HAZ was mainly dependent on the microstructure change due to heating above Ac3 and rapid cooling during welding.
Please do not copy without permission.