Thick plate narrow gap welding method based on gnawing assistance

The invention discloses a thick plate narrow gap welding method based on gnawing assistance. The thick plate narrow gap welding method comprises the following steps that S1, two to-be-welded base materials are butted and clamped on a heating table, an assembly gap is reserved between to-be-welded surfaces of the two to-be-welded base materials, and brazing filler metal with a semi-solid characteristic is preset in the assembly gap; and S2, the center of the end of a stirring needle is adjusted to be placed at the center line of the assembly gap, the stirring needle is in a taper step shape ora taper thread shape or a taper step thread shape, the diameter of the end of the stirring needle is larger than the width of the assembly gap, the welding temperature is adjusted to enable the brazing filler metal to be in a semi-solid state, the solid fraction of the semi-solid brazing filler metal is 10%-60%, the welding process parameters are set, the stirring needle is pressed to the target depth and then moves in th