自保护药芯焊丝焊缝组织及性能研究

采用E71T8-Ni1J自保护药芯焊丝进行X70管线钢管半自动焊接，通过光谱分析、金相、扫描电镜、力学性能等试验手段，研究了X70管线钢管自保护药芯焊丝焊缝不同焊层及层间热影响区的组织特征和力学性能。试验结果表明，根焊组织主要由细小的等轴晶、板条马氏体和少量粒状贝氏体组成：填充焊层中可以观察到明显的奥氏体晶界，组织主要由准多边形铁素体、粒状贝氏体和M／A组元组成：层间热影响区组织由少量准多边形铁素体、粒状贝氏体、M／A组元以及沿奥氏体晶界连续分布的“项链状”M／A组成。焊缝的抗拉强度为720～750MPa，-20℃夏比冲击功为78～128．5J。层间热影响区组织中沿晶界分布的“项链状”M，A、晶内粒状贝氏体板条间形成的平行排列的条状M／A组元以及焊缝中粗大不均匀的组织会降低焊缝的韧性。

Research on Weld Microstructure and Properties of Self-shielded Flux Cored Wire

Adopting E71TS-NilJ self-shielded flux cored wire to conduct semi-automatic welding for X70 line pipe,the weld microstructure characteristics and mechanical properties of different welding layer and interlayer HAZ of self-shielded flux cored wire were investigated by spectrum analysis, metallographic microscope, scanning electron microscopy （SEM） and mechanical properties test. The experimental results showed that the mierostructure of root welding mainly consists of fine equiaxed grains, a small amount of granular bainite（GB） and lath martensite; obvious austenite grain boundaries can be observed on filling welding layer, and the microstructure is mainly composed of quasi-polygonal ferrite, granular bainite and M/A constituents; the heat affected zone（HAZ） microstructure of the welding layer is composed of quasi-polygonal ferrite, granular bainite, M/A constituents and the chain-like M/A constituents distributing continuously along the austensite boundaries. The tensile strength of the weld metal is between 720 MPa and 750 MPa, and charpy impact energy is 78-128.5 J at -20℃. The chain-like M/A distributing along the grain boundaries, the parallel arrangement of strip M/A between transgranular granular bainite lath in the weld layer HAZ, and rough and uneven weld metal mierostructure will reduce the toughness of weld metal.