Within industry developing rapidly, buildings become higher and larger, and offshore structures like drilling platforms increase continuously, which means the steel thick plate is used more and more widely. Thickness increase leads to the amount of weld increase, which means more heat-affect makes the performance of weld and the adjacent steel material deteriorate, and the sensitivity of weld defects is also relatively more significant. These factors cause the weld toughness performance of steel thick plate to get worse, especially in the low-temperature environment. Therefore, it is very necessary to study the impact toughness of weld of steel thick plate. This paper does an experimental study on the impact toughness of butt weld of 150mm thick plate at low temperature, including weld metal and heat-affect zone. The results show that the impact toughness of them reduces with the temperature reducing, and that of heat-affect zone also reduces with the position changing from the surface to the center along the thickness direction, variation of which is the same as steel thick plate itself, but value relatively decreases. The paper also gives a regression analysis with Boltzmann equation, obtaining the ductile-brittle transition temperature of weld metal and heat affected zone under different conditions and its variation. Test conclusions indicate that butt weld of thick plate of steel structure has clear brittle features, which must be paid sufficient attention to.
Thick plate of steel structure is used more and more widely, including ultra-high and large-span construction. In China, most of steel thick plate were imported in early time, and the codes did not make the relevant provisions about it, therefore, various kinds of cracks with obvious characteristics of low stress brittle fracture appeared in a large number of elements during the welding and service, which gradually attracted industrial community's attention.