Steel tube

The utility model provides a steel tube. The steel tube is provided with a circular cross section, a circular through hole running through the whole steel tube is formed in the center of the steel tube along the direction of the longitudinal axis of the steel tube, the diameters of the circular through hole along the direction of the longitudinal axis of the steel tube are the same, the wall thickness of the steel tube periodically changes along the direction of the longitudinal axis of the steel tube, and the minimum wall thickness of the steel tube is 80%-50% of the maximum wall thickness of the steel tube, and the distance between adjacent positions of the minimum wall thickness and the maximum wall thickness is 400-800mm. Due to the fact that the diameters of the circular through hole in the center of the steel tube are the same, the influence is little for processing, and the only thing that gets changed is that the rolled wall thickness periodically changes, so that the contact area between the steel tube and a tube joint is increased, and the frictional force between the steel tube and the tube joint can be increased. Since the surface of the steel tube is rough and uneven, the tube joint can be clamped at the part with the minimum wall thickness and is unlikely to slide, so that the safety of connection is greatly strengthened.