The 2.25Cr-1Mo-0.25V steel, which has excellent thermal mechanical properties under high pressure and temperature, is widely applied in the pressure equipment. Previous researches show that crack generated in the Heat Affected Zone (HAZ) is one of the main failure mechanisms for the high pressure equipment. Consequently, this work aims at investigating the fracture behavior of HAZ by fracture toughness test. A set of specimens was manufactured with the welding current of 580 A, then, specimens were tempered at 705 °C for 32 h. Along with the fracture toughness test, the fracture properties (e.g. crack initiation, propagation and fracture) of specimens were monitored by acoustic emission (AE). Comparing the AE amplitude of each specimen, the crack initiation point was verified by the first peak of AE result, and the analysis of deformation work at the initiation crack point has also been carried out to investigate fracture properties and the fracture toughness of HAZ of the 2.25Cr-1Mo-0.25V steel. Then the relationship between deformation work and crack length has been studied, and the fracture toughness of HAZ could be obtained. Analyzing the fracture characteristics of experiment process and fracture toughness of HAZ has a significant guidance for the further applications of 2.25Cr-1Mo-0.25V steel.

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