Stirring head used for welding narrow-step water channel cover plate and welding technology for narrow-step water channel cover plate

The invention discloses a stirring head used for welding a narrow-step water channel cover plate and a welding technology for the narrow-step water channel cover plate. The invention aims to provide the stirring head for the narrow-step water channel cover plate structure and the corresponding welding technology, and friction stirring welding for the water channel cover plate structure in which the ratio of the step width to the welding depth is not larger than 0.5 is realized, so that the weight of a product is reduced, and the structure space is saved. The stirring head for welding the narrow-step water channel cover plate comprises a shaft holder and a stirring needle; the stirring needle comprises a needle body and needle tip, wherein the needle body is circular truncated cone-shaped, and the needle tip is cylinder-shaped; the upper part of the needle body is coaxially fixed to the shaft shoulder, and the lower part of the needle body is coaxially fixed to the needle tip; and the surface of the needle body and the bottom surface of the shaft shoulder are separately provided with threads, and the surface of the needle tip is smoothly polished.