| 摘要 |
PROBLEM TO BE SOLVED: To prevent occurrence of tunnel-like hollow failure due to shortage of plasticized solid phase metal volume for filling the clearance, serious flash- like failures and the like due to excess metal, even if a clearance exists between butt faces by using a simple clamp jig. SOLUTION: In this jointing method, a formula: 0.80C<=A+B<=1.3, preferably 0.80C<=A+B<=1.0C will be satisfied, where a center vertical sectional area in a spacing 5 surrounded with a flat plane FS contacting with a bottom end face edge (shoulder of a rotation tool) 3S of a rotary axis 3 of a rotation tool RT, a bottom face 3bs with a concave face of the rotary axis 3, and an outer peripheral face 4os of an agitating pin 4 is A (mm2), a vertical sectional area of an upper undercut 7 of a jointing part 6 is B (mm2), and a vertical sectional area of a clearance 2 between the butt faces is C (mm2). Furthermore, the rotation tool RT is formed in a manner that an angleθformed with the flat plane FS and the bottom face 3bs of the concave face of the rotary axis 3 becomes 5-20 degrees.
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