STRUCTURE REFORMING METHOD OF CASTING

PROBLEM TO BE SOLVED: To provide a structure reforming method which surely prevents the surface of a casting and a casting defect from being communicated with each other. SOLUTION: A rotary tool 20 having a base part 31, and a projecting part 32 extending by inclining from a front end 31a in an axial line direction of the base part 31 in a direction approaching a rear end 31b in the axial line direction as the projecting part protrudes in the radial direction of the base part 31 and progresses in one R1 of the peripheral direction around the rotary axis L1 is used to conduct friction stirring by rotating the rotary tool 20 in the one R1 of the peripheral direction. Thereby a fluid 38 with a softened part plastically flowing is formed in a prepared hole 36. The fluid 38 moves in the rotating direction R1 and also in the axial line direction Z1 and thereby the fluid 38 is made easier to stir and the amount of the fluid 38 plastically flowing can be increased. As a result, the fluid 38 can increase the solidified reforming layer 39 and can increase the amount of dissipation of the casting defects, and the inner peripheral surface of the prepared hole of the casting 19 is more surely prevented from being communicated with the casting defect. COPYRIGHT: (C)2008,JPO&INPIT