Experimental Research on Mechanical Properties of Welded Joints of Q500qD High-Strength Cold-Rolled Circular Steel Tubes

In order to solve the problem of insufficient research on the engineering application of Q500 high-strength steel tubes， this paper conducted the material performance test and welding process research， the results showed that： after cold processing of Q500qD steel plates， the yield strength and tensile strength increased to 585-591 MPa and 700-715 MPa， respectively， the yield ratio increased to 0.82-0.84， while the ductility decreased. The impact energy （219-233 J at -20 ℃） met the requirements of High Strength Low Alloy Structural Steels （GB/T 1591-2018）， indicating good toughness after cold working. When T624T1-1C1A-N3M1 welding wires were used for the same steel butt welding， the tensile strength of the weld met the standard requirements， and the fracture occurred in the weld， which verified the validity of the yield strength matching principle. The tensile strength and impact power of Q500qD and Q355B dissimilar steel welded joints met the requirements of Code for Welding of Steel Structures （GB/T 50661-2011）. The research showed that the yield ratio of high-strength steel increased with the increase of the grade. It is suggested that the steel plate used in building structure should be preferred in the project， the welding parameters should be optimized （the same steel should be matched according to yield， and the dissimilar steel should be strengthened according to tensile strength） to ensure the safety and reliability of the structure.