Concrete filled steel tube and steel tube conversion joint suitable for large power transmission tower

The invention belongs to the technical field of power transmission tower construction, and particularly relates to a concrete filled steel tube and steel tube conversion joint suitable for a large power transmission tower. The device comprises a lower-layer steel pipe concrete and an upper-layer steel pipe which are coaxially assembled; the structure is characterized in that a sleeve-shaped grouting pipe is axially arranged on the top end face of the lower-layer concrete-filled steel tube and protrudes towards the interior of a pipe cavity of the upper-layer concrete-filled steel tube, so that the grouting pipe and the lower-layer concrete-filled steel tube are combined to form a two-section type stepped sleeve structure with mutually communicated sleeve cavities; a flange face is arranged on a shaft shoulder of the two-section type stepped sleeve structure, so that flange fit is formed between the flange face and a pipe opening in the bottom end of the upper-layer steel pipe. The device has the advantages of