Mo对690MPa低合金高强钢熔敷金属力学性能的影响

Effect of Mo on mechanical properties of deposited metal for 690 MPa high strength low alloy steel

焊接效率是海洋平台及船体建造的关键,不预热焊接能够显著提高焊接施工效率、降低建造成本。文中采用焊条电弧焊在不预热条件下制备了2种Mo含量不同690 MPa低合金高强钢熔敷金属,对其组织和性能之间的关系进行了分析。研究发现,Mo元素对熔敷金属微观组织、相变过程、塑性及强韧性具有显著影响。在成分体系0.02%~0.03%C,4.4%~4.5%(Mn+Cr+Ni),0.23%~0.61%Mo条件下,通过Mo元素调控获得细化、良好塑性、高强韧性熔敷金属组织。细小、良好塑性组织在冲击过程中能够抑制裂纹萌生和扩展,显著提高了熔敷金属的低温冲击韧性。然而,组织细化与塑性提高对于韧性改善机制存在显著差异,组织细化提高了晶界密度进而阻碍裂纹扩展,塑性良好的组织抑制了裂纹萌生并阻碍其扩展。在0.03%C,4.4%(Mn+Cr+Ni),0.23%Mo成分体系及不预热焊接条件下,获得了抗拉强度742 MPa,-50℃冲击吸收能量82~114 J(平均值103 J)的熔敷金属。

Welding efficiency is the key to ocean platform and hull construction.Welding efficiency can be increased and the cost of construction can be reduced by no preheating welding.Two kinds of deposited metal of 690 MPa high strength low alloy steel with different Mo content were prepared by shielded metal arc welding(SMAW)without preheating.The relationship between microstructure and mechanical properties was analyzed.The results showed that Mo content had obvious effect on microstructure,phase transformation,plasticity and strength-toughness properties.With the chemical composition system of 0.02%~0.03%C,4.4%~4.5%(Mn+Cr+Ni),0.23%~0.61%Mo,refined microstructure with good plasticity,high strength and toughness was obtained by controlling Mo content.Fine microstructure with good plasticity restrained the initiation and extension of crack,which obviously increased the impact toughness of the deposited metal.However,the mechanism of improvement on the toughness by microstructure refinement was obviously different from that of increased plasticity.The density of grain boundary was increased by the refined microstructure,which hindered the extension of crack.Microstructure with good plasticity restrained the initiation of crack and hinder its extension.The deposited metal with tensile strength of 742 MPa,-50℃impact absorbed energy of 82~114J(average value was 103 J)was obtained with the chemical component of 0.03%C,4.4%(Mn+Cr+Ni),0.23%Mo without preheating before welding.