| 摘要 |
PROBLEM TO BE SOLVED: To provide a cavity forming method hardly crushing a cavity, and hardly causing a surface defect, when forming the cavity on the inside of a metallic member by frictional agitation.SOLUTION: A cavity forming rotary tool 1A is used when forming a cavity of presenting a cross-sectional substantially rectangular shape on the inside of an aluminum alloy member by frictional agitation, and comprises a shoulder part 2 and an agitation pin 3 suspended from this shoulder part 2, and a spiral groove is carved on an outer peripheral surface of the agitation pin 3. The tip of the agitation pin 3 presents a flat surface with the axial direction of the agitation pin 3 as a normal line, and a value of dividing an outer diameter of the shoulder part 2 by an outer diameter of the tip of the agitation pin 3, is set so as to become 1.4 to 3.1. An angle of the spiral groove 3a to a reference surface with the axial direction of the agitation pin 3 as a normal line, is also set in 20 degrees to 40 degrees.SELECTED DRAWING: Figure 3 |
