Research on toughening mechanism of weld metal with metal powder flux-cored wire for 960 MPa high strength steel

Metal powder flux-cored wire for 960MPa high strength steel was developed, which adding Mn、Ni、Mo and Cr as main alloy system, and adding Ti, B, Nb and Al as microalloying system. Mechanical properties of welded joint which was welded by gas metal arc welding was tested by tensile testing and low temperature impact testing. The mechanism of adding alloy element into wire powder was analyzed by microstructure observation, scanning electron microscope testing, energy dispersive spectrometer analysis and transmission electron microscope testing. The results show that the average tensile strength of welded joint is 952.24 MPa, and the low temperature impact energy at -20 ℃ is 70 J. The low temperature impact energy of weld metal will improve by self-developed flux cored wire, and the strength of welded joint still keep higher. The main alloying elements adding into wire powder can improve strength by solid solution strengthening and dispersion strengthening. Microalloying elements can improve low temperature impact toughness of weld metal by refining grain, blocking generate proeutectoid ferrite, and increasing nuclear opportunity of acicular ferrtie in the grain.