Positioning tool used for welding of cylinder barrel and provided with two-way air cylinder

The positioning tool comprises a workbench, the inner wall of the workbench is fixedly connected with a limiting ring, the top face of the limiting ring is in lap joint with a cylinder barrel body, and the cylinder barrel body is in sliding connection with the inner wall of the workbench. A first electric push rod is started to push a fixing frame, a two-way air cylinder and a plurality of push plates to enter a cylinder barrel body, the two-way air cylinder is started to push the push plates to be in lap joint with the inner wall of the cylinder barrel body, a rotating mechanism is started to drive the push plates and the cylinder barrel body to rotate, and a welding workpiece is clamped in a clamp; the moving assembly is started to drive the positioning mechanism and the welding workpiece to move up and down, the positioning mechanism is started to push the welding workpiece to make contact with the cylinder barrel body, welding work can be started, the purpose of automatically positioning the welding workp