Abstract: Aiming at the crack defects of Q345R hot-rolled steel plate welding ring (transverse) welding seam (hereinafter referred to as girth welding) in the reactor-settler of FCCU, this paper analyzes the cracks on the base metal of the steel plate and welding joint from such aspects as the metallographic structure of the base metal and the weld, the impacts of the steel plate rolling process on the end edge stress and "weld brittle resistance" caused by secondary processing. Through adopting welding process optimization measures, the welding quality of the product is guaranteed.

Key words: Q345R, hot-rolled steel plate, girth welding, crack; welding brittleness resistance, welding technology