Experimental study on the Z-direction fracture toughness of steel structural thick plate and its HAZ

Several adverse factors will make largely negative effect on the Z-direction properties of the steel structure thick plate, such as the center segregation induced by plate thickness increase, residual stress yielded by the hot influence of weld, connection restrain, and low temperature- related brittle properties. Fracture toughness has been an important fracture-related index for evaluating the Z-direction properties. In order to investigate the Z-direction fracture toughness of steel thick plate, both the X-direction and Z-direction specimens were sampled from base metal, considering the different plate thickness, weld size;then, fracture toughness(critical values of CTOD)of Q345B steel thick plate at different temperature were determined by the three point bending(TPB)tests. The variation law of CTOD values versus temperature was also fitted by the Boltzmann functions, and an electron microscope was employed to analyze the fractured face of the TPB specimens. Experimental results show that with the increase of plate thickness and weld size, CTOD values decrease;as the temperature decreases, the CTOD values fall down, and the Z-direction fracture toughness is inferior to the X-direction fracture toughness. This paper also provide the experimental data and technical reference of Z-direction fracture toughness of steel structure thickness plate. ©, 2014, Tianjin University. All right reserved.