Patent ID: 7523851
Filing Date: 2009-04-28
Classification: B23K

Abstract:
1. A frictional spot joining method of metal members, in which a work comprising a first metal member and a second metal member that lap over is provided, a melting point of the second metal member being higher than that of the first metal member, and a rotational tool is pushed against the work from a side of the first metal member and the first metal member is softened and made in a plastic flow state by a frictional heat generated through a rotational and pressing operation of the rotational tool, the frictional spot joining method comprising: a step of providing the rotational tool that comprises a shoulder portion to face the work and a pin portion that is located on a rotational axis of the rotational tool and projects toward the work from the shoulder portion; a first step of pushing the rotational tool under rotation with a first pressing force until the first metal member is softened by the rotational tool whose pin portion or both pin portion and shoulder portion come into the first metal member; a second step of pushing the rotational tool under rotation with a second pressing force that is greater than the first pressing force until a tip of the pin portion of the rotational tool reaches a specified point that is at a distance from a joining face of the first and second metal members; and a third step of maintaining the pressing force of the rotational tool under rotation at a third pressing force that is smaller than the second pressing force until a specified period of time elapses after the tip of the pin portion has reached said specified point that is at the distance from the joining face; wherein said first pressing force is 1.47 kN or more and 3.43 kN or less, said second pressing force is 1.74 kN or more and 5.88 kN or less, and said third pressing force is 0.49 kN or more and 1.47 kN or less.