Fractographic Investigation on Root Crack in the TRC Test of HY-130 Steel : Studies on Fractography of Welded Zone (II)

概要

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The clue of the weld cracking of HY-130 has been explored by observing the fracture surface of the root crack of HY-130, HY-90 and HY-110 undergone the TRC test with a scanning electron microscope. Main conclusions obtained are as follows: (1) The whole of the fracture surface consists of three or four characteristic fracture regions. (2) The distribution of the each characteristic fracture region depends on the kind of the base metal, the applied stress in the TRC test, the preheating temperature and the welding procedure. (3) The root crack of HY-130 with SMA welding predominantly propagates through the weld metal and contains a large quantity of intergranular fracture region in the lowest applied stress. Therefore the major problem of the weld cracking of HY-130 exists in the weld metal. (4) The root crack of HY-130 with SMA welding mainly consists of hydrogen-induced crack, though there are few micro solidification cracks. (5) Dimple fracture region is formed by an unstable crack propagation and a linear fracture mechanics can be approximately applied to the fracture.
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