Friction stir welding tool with shoulders having different areas; methods using such tool; product welded with such tool

Abstract

The present application relates to a friction stir welding tool () for joining two adjacent work pieces (), which work pieces comprise portions () to be welded and having a narrow space there between on one side, said tool having an axis of rotation, and comprising a first shoulder (), a second shoulder (), and a pin () arranged so as to connect the first and second shoulders, wherein said first shoulder has a first contact surface for friction heat generation to the work pieces to be joined during welding, said first contact surface having a first contact area, and said second shoulder has a second contact surface for friction heat generation to an opposite surface () of the same portions of the work pieces to be joined, said second contact surface having a second contact area, the first and second areas having different sizes, where the first area is a larger sized area than the second area. The application also relates to a method of joining work pieces, a product comprising joined pieces, and the use of such friction stir welding tool.