Ironing plate for friction stir welding apparatus and friction stir welding apparatus including the same, and friction stir welding method

An ironing plate for a friction stir welding apparatus, the ironing plate mounted to the friction stir welding apparatus, the friction stir welding apparatus welding two metallic plates through friction stirring while utilizing frictional heat generated by rotating a rotating tool,

• wherein the ironing plate is mounted to the friction stir welding apparatus in such a manner as to surround an outer peripheral portion of the rotating tool and does not rotate together with the rotating tool,
• wherein an inside diameter of a portion of the ironing plate in which the rotating tool is inserted is larger than the rotating tool, and, when the ironing plate is disposed in such a manner as to surround the outer peripheral portion of the rotating tool, a material inflow passage into which a surplus material generated due to the welding of the two metallic plates flows is formed between the ironing plate and the rotating tool,
• wherein a surface of the ironing plate facing the two metallic plates has a first inclined surface inclined relative to a plane orthogonal to a rotation axis of the rotating tool, and
• wherein the first inclined surface is provided on a backward facing side with respect to a progressing direction of the welding of the two metallic plates by the friction stir welding apparatus, the first inclined surface extending from an outer peripheral portion of the ironing plate to at least the material inflow passage formed between the ironing plate and the rotating tool.