Welding plug and usage method thereof

The invention discloses a welding plug and a usage method thereof and belongs to the technical field of oil and gas pipeline maintenance, first-aid repair and reconstruction. The welding plug is used for plugging a penetrating hole, with the diameter of 20 mm or below, of an oil and gas pipeline and comprises a seal cap (1) and a plugging head (2). The seal cap (1) comprises a connecting section (11) and a seal section (12). The seal section (12) is a hollow cylinder with one opened end and the other closed end. One end of the connecting section (11) is connected with the outer side of the closed end of the seal section (12), and a threaded hole is formed in the other end of the connecting section (11). One end of the plugging head (2) is a cylinder, the other end of the plugging head (2) is a cone, and the cylinder end of the plugging head (2) is connected with the inner side of the closed end of the seal section (12) and is in clearance fit with the inner side. The outer surface of the opened end of the sea