Effect of Ti content on microstructure and mechanical properties of 960 MPa high strength steel weld metal

LIU Zishen; CAO Rui; JIAO Shishun; YANG Fei; ZHU Yuting; ZHANG Kejing; LIU Chuntao

doi:10.16579/j.issn.1001.9669.2025.09.017

Abstract：In order to improve the comprehensive mechanical properties of 960 MPa high strength steel weld metal,the optimum content of Ti element in 960 MPa high strength steel weld metal was revealed.Firstly,four kinds of weld metals with different Ti contents(0.01%-0.08%)were designed and welded.The effects of Ti content on the microstructure and mechanical properties of welds were systematically studied by scanning electron microscopy,energy dispersive spectroscopy,tensile and impact tests.The effect of Ti content on the initiation energy and propagation energy was evaluated by fracture observation and fracture morphology.The results show that when the Ti content is less than 0.06%,the microstructure of the weld metal changes from granular bainite to granular bainite+acicular ferrite.With the increase of Ti content,the content of acicular ferrite increases significantly.When the Ti content reaches 0.06%,the tensile strength reaches 939 MPa,the elongation reaches 23.5%,the elongation increases by 27%compared with Ti0.01,and the impact absorption energy at-40℃reaches 104 J;when the Ti content increases to 0.08%,the formation of coarse lath bainite and the precipitation of TiN lead to a sharp decrease in plasticity and toughness,the elongation decreases to 18.2%,and the impact energy at-40℃is only 25 J.Ti promotes the nucleation of acicular ferrite and improves the comprehensive mechanical properties by forming TiO2 inclusions.However,excessive Ti will induce the precipitation of brittle phase and the formation of coarse lath bainite,which significantly deteriorates the plasticity and toughness.