稀土Ce在大热输入焊缝金属中的作用

研究了稀土Ce对大热输入焊缝金属中夹杂物尺寸大小和分布,焊缝金属的显微组织和力学性能的影响,探讨了稀土Ce的氧硫化物诱导针状铁素体的形核机理。结果表明,稀土Ce能细化焊缝金属的夹杂物,使焊缝金属中直径小于2.0μm的非金属夹杂物达90%以上。稀土Ce在大热输入焊缝金属中以Ce2O2S、Ce3S4和CeS的形式存在,形成中心为Al2O3、TiO、MnO和SiO2,表面为Ce2O2S、Ce2S3或CeS的非金属夹杂物,位于夹杂物表面的Ce2O2S、Ce3S4和CeS诱导针状铁素体形核,增加焊缝金属中针状铁素体的含量,抑制先共析铁素体的生成,细化焊缝金属晶粒,提高焊缝金属的韧性。稀土Ce的氧硫化物诱导针状铁素体形核的机理是Ce2O2S、Ce3S4和CeS与针状铁素体的错配度小。

Role of rare earth Ce in large heat input weld metals

The effects of the rare earth Ce on the size distribution of non-metal inclusions,microscopic structure and mechanical properties of large heat input weld metals were studied.The mechanism that inclusions of the rare earth Ce induce the formation of acicular ferrites was discussed.The results show that the rare earth Ce can refine inclusions in weld metals,making the percentage of the inclusions with mean diameters of less 2.0 μm above 90%.The rare earth Ce in weld metals exists in the forms of Ce2O2S,Ce3S4and CeS after deoxidization and desulphurization reactions.The center of the inclusions is Al2O3,TiO,MnO and SiO2,and the surface is Ce2O2S,Ce3S4and CeS.Ce2O2S,Ce3S4and CeS on the inclusion surface induce the formation nucleation of acicular ferrites,increase the amount of acicular ferrites,refine the weld metal grains,restrain the growth of proeutectoid ferrites,and improve the notch toughness values of the weld metals.The mechanism that Ce2O2S,Ce3S4and CeS induce the formation nucleation of acicular ferrites is that Ce oxide sulphide particles exhibit good lattice coherency with acicular ferrites with little lattice mismatch.