Continuous machining method for friction plunger in underwater welding process

The invention discloses a continuous machining method for a friction plunger in the underwater welding process. The method includes the following steps that first, the pre-drilling process is executed on the surface of a base material to be repaired; second, a welding plunger is mounted in a drill hole, a welding plunger hole is filled, and a friction plunger welded joint is formed; third, the redundant length part of the welding plunger is cut; fourth, the surface of the base material is polished; fifth, a cylindrical drill bit used for pre-drilling is mounted, the distribution position of the next friction plunger welded joint is selected, the first step, the second step, the third step and the fourth step are executed again until a plurality of friction plunger welded joints are overlapped with one another to form a friction stitch welding seam, and accordingly an entire crack in the surface of the base material can be repaired. By the adoption of the method, continuous underwater machining including the four main processes of drilling, welding, cutting and polishing can be achieved only by a spindle head, friction plunger welding is applied to practical engineering of surface crack defect repairs, the welding quality of underwater steel structures is greatly improved, the welding seam quality is improved, and therefore technical support is provided for repairing ocean platforms and submarine pipelines.