Microstructure and Characteristics of Hi-strength/Hi-toughness Welded Joint of Pipe for Crane Jib Service

Described here in the paper is a tungsten-containing high-strength/high-toughness BG890QL steel pipe. And the welded joint of the said pipe is compared with that of the tungsten-free Q890L steel pipe in terms of metallographic structure, fatigue behavior, tensile property and impact toughness, etc.The results reveal the following facts.Although mechanical properties of the two kinds of steel pipes are similar, the fatigue behavior of the BG890QL pipe is much better;the welded joint areas of both pipes have the same zones, i.e., the weld zone, the coarse grain zone, the fine grain zone and the tempering-softening zone;addition of W element changes the phase transformation behavior during the welding process, which makes the grains of weld and heat affected zone finer, and thus the overall mechanical properties of the weld and heat affected zone are improved.