| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a void forming method by which when forming a void inside a metal member by friction stirring, the void is resistant to collapse and surface defects are hardly formed.SOLUTION: In a void forming method for forming a void inside a metal member Z, a rotary tool 1 for forming the void has a shoulder part 2 and a stirring pin 3. A helical groove 3a is engraved in the outer peripheral surface of the stirring pin 3, and the helical groove 3a is formed to be clockwise. A value obtained by dividing the outer diameter of the shoulder part 2 by the outer diameter of the tip of the stirring pin 3 is set to be 1.4 or more and 2.2 or less. The angle of the helical groove 3a is set to be 20 degrees or more and 40 degrees or less. When relatively moving the rotary tool 1 for forming the void, a distance between the surface Za of the metal member Z and the bottom surface 2a of the shoulder part 2 is set to be 0-3.0 mm, and the rotary tool 1 for forming the void is rotated clockwise.</p> |
