Method for manufacturing heat exchanger plate and method for friction stir welding

A method for manufacturing a heat exchanger plate, comprising:

• a lid groove closing process to insert a lid plate into a lid groove formed at a periphery of a concave groove opening to a surface of a base member;
• a primary joining process to perform friction stirring while relatively moving a rotary tool equipped with a stirring pin along a butting portion of a side wall of the lid groove and a side surface of the lid plate;
• and
• a deburring process to remove burrs generated by friction stirring using the rotary tool after finishing the primary joining process,
• wherein the stirring pin has a tapered shape so as to have a smaller diameter in a hanging down direction and has a continuous spiral groove formed on an outer peripheral surface, the spiral groove is configured to rotate in a counter-clockwise direction as it goes downward when the rotary tool is used for rotating in the clockwise direction, and the spiral groove is configured to rotate in the clockwise direction as it goes downward when the rotary tool is used for rotating in the counter-clockwise direction, and
• wherein, in the primary joining process, the stirring pin which is rotating is inserted into the butting portion until a front end of the stirring pin reaches a bottom surface of the lid groove, and the friction stirring is performed to the butting portion and the bottom surface of the lid groove with a base part of the stirring pin being exposed in a state of only the stirring pin being in contact with the base member and the lid plate while plastically fluidized material does not flow into the concave groove.