The structure of weld metal, made by flux-cored flux-cored wire with the addition of 0.3% of zirconium oxide at the beginning of scaly morphology, was investigated. The structure of the seam represents needle ferrite. This can be said that the dissociation of zirconium oxide in an electric arc is not an obstacle to the modifying effect that manifests itself both in the course of the interaction of zirconium with oxygen and in the surface activity of zirconium in a crystallizing melt based on iron. Zirconium oxide, thus, is a modifier of both the first and second kind for the crystallizing weld metal. Excess oxygen, presumably, forms seam pores with a diameter of less than 1 m, which, however, does not significantly affect the mechanical properties of the welded seam. The bottom line: the obtained data will be used in the development of electrode materials for the welding of tubular steels.