Effects of Titanium and Zirconium Elements on Microstructure and Mechanical Properties of Deposited Metal of Self-shield Flux Cored Wires

On the basis of Mn-Ni-Mo-Cr system self-developed self-shielded flux cored wire, a new-typed welding wire was developed through adding elements titanium and zirconium with mass fraction 0.09% and 0.045% respectively into flux cored wire. Welding test was carried out on Q235 steel by using flux cored wires with/without micro-alloy elements, and then the effects of micro-alloy elements titanium and zirconium on microstructure and mechanical properties of the deposited metal were studied. And, the effects mechanism of micro-alloy elements titanium and zirconium on deposited metal was discussed. The results show that after adding titanium and zirconium elements, microstructure of the deposited metal was smaller, acicular ferrite was more, but its hardness changed little, and its tensile strength and elongation increased by respectively 7% and 13% compared to the deposited metal of welding wire without micro-alloy elements; Meanwhile, the impact toughness of the deposited metal at -20 ℃ increased by 1.42 times. The micro-alloy titanium element in the flux cored wire will be beneficial to remove oxygen and remove nitrogen and promote the nucleation and growth of acicular ferrite, as well as the micro-alloying zirconium element will be beneficial to remove oxygen and refine microstructure.