| Abstract |
| Experimental flux cored wire with micro-addition of rare earth metal was manufactured and used to make 3-point bend CTOD specimens to assess the fracture toughness of the weld metal. The weld metal showed much higher CTOD value, 2.58 mm at 40 ℃, than the weld metal that contained no rare earth metal. Microstructural observations and fractography of the CTOD specimens indicated that the excellent fracture toughness of the weld metal is due to the microstructural modification of rare earth metal. Continuous cooling transformation diagrams showed that micro-addition of rare earth metal delayed the phase transformation of the weld metal during cooling, resulting in a larger amount of tough microstructure (acicular ferrite) instead of brittle microstructure(grain boundary ferrite). Nano-SIMS analysis showed that the reason for the delay of the phase transformation of the weld metal was the segregation of rare earth metal on the grain boundaries of austenite. |
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| Key Words |
| alloys, welding, toughness, SIMS, rare earth metal |
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