Square and round pipe

The utility model discloses a square and round tube which comprises an inner tube, an outer tube is fixedly connected to the outer wall of the inner tube, round tubes are arranged at the four corners of the inner wall of the outer tube, and the outer portions of the round tubes are attached to the outer wall of the inner tube. The square and round pipe relates to the technical field of pipes, through the combined design of the inner pipe and the outer pipe, the inner pipe can be protected by the outer pipe, external pressure and collision are prevented, the outer pipe is used for supporting the inner pipe, so that the corners of the inner pipe are prevented from being directly damaged by external force, and the flat positions of the four sides of the outer pipe are extruded; the bending-resistant and torsional strength is guaranteed, meanwhile, the problem that corners of the square pipe are prone to damage is solved, the compression resistance, smashing resistance and other capacities of the corners are grea