Influence of the Flux Coating with Different Cu/Al Ratios on X80 Pipeline Steel Welding Seam

Abstract

In this study, X80 pipeline steel was welded by self-made welding electrode with different Cu/Al ratios in flux coating. The microstructure and mechanical properties of X80 steel welding seam were investigated by optical microscope, energy-dispersive spectroscopy, scanning electron microscope, X-ray diffraction. The hardness, tensile and impact tests were carried out. The electrochemical corrosion and uniform corrosion properties of welding seam were also studied in sulfide environment. The experimental results reveal that alloying agent such as Cu and Al can transform to the welding seam very well. Furthermore, the microstructure and properties of welding seam can be improved effectively with a suitable Cu/Al content ratio. By reducing the Cu/Al content ratio, the mechanical properties and corrosion resistance properties increase initially and then decrease. When the Cu/Al ratio is maintained at 6:2 in the flux coating, the welding seam has more acicular ferrite, resulting in the best mechanical properties and corrosion resistance. Moreover, the addition of Cu and Al elements does not result in a serious deterioration of the resistance to HIC.