焊丝成分对超高强装甲钢焊接接头组织与性能的影响

Effects of Welding Wire Composition on the Microstructures and Mechanical Properties of Ultra-high Strength Armored Steel Welded Joints

利用气体保护电弧焊工艺完成了4.5 mm和9.0 mm超高强装甲钢的焊接,研究了焊丝(MG70S-6和ER307Si焊丝)成分对接头组织与性能的影响,通过光学显微镜(OM)、扫描电子显微镜(SEM)、能谱分析(EDS)、X射线衍射(XRD)等表征方法对焊接接头各区域进行微观组织和物相结构的分析,并测试了接头的硬度分布、拉伸性能和冲击韧性。结果表明,焊接接头成形质量良好,无明显未熔合、气孔、裂纹等缺陷,焊缝区组织为片状马氏体、针状铁素体和少量粒状贝氏体,完全淬火区组织为马氏体和贝氏体,不完全淬火区组织为马氏体和铁素体,回火区析出网状渗碳体。焊接接头的热影响区软化现象较为明显,接头难以达到与母材等强,断裂主要发生在焊缝区,呈现出脆性断裂特征。采用ER307Si焊丝焊接的9.0 mm装甲钢接头的焊缝室温冲击功达到94 J,完全满足使用要求。

4.5 mm and 9.0 mm thick ultra-high strength armored steels were welded successfully by robotic gas-shielded arc welding technique,and the effects of welding wire(MG70S-6,ER307Si)composition on the microstructures and mechanical properties of welded joints were investigated.The microstructures and phase structures of welded joints were analyzed by optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive analysis(EDS)and X-ray diffraction(XRD),and the hardness,tensile properties and impact toughness of welded joints were also examined.The results showed that the welded joints were well formed without visible defects such as lack of fusion,pores or cracks.The microstructures of weld metals were composed of flaky martensite,acicular ferrite and a small amount of granular bainite,and the microstructures of the fully quenched zone were martensite and bainite.The incomplete quenched zone was composed of mixed microstructure of martensite and ferrite,and reticular cementite was precipitated in the tempering zone.The softening phenomenon of the heat-affected zone of the welded joint was relatively obvious,and the joint strengths were all lower than those of base metals,and the fracture mainly occurred in the weld zone,reflecting the characteristics of brittle fracture.The room temperature impact energy of the 9.0 mm armored steel joint welded with ER307Si reached 94 J,which could meet the application requirements.