JOINT STRUCTURE

A joint structure includes a first metallic material (1) having a first projection (8); a second metallic material (3) similar in type to the first metallic material (1) and weldable to the first metallic material (1), the second metallic material (3) having a first penetrating part (11) larger in diameter or width than the first projection (8), the first projection (8) being positioned in the first penetrating part (11); and a different type of material (2) different in type from the first metallic material (1) and the second metallic material (3) and difficult to be welded to the first metallic material (1) and the second metallic material (3), the different type of material (2) having a second penetrating part (12) larger in diameter or width than the first projection (8), the rim of the second penetrating part (12) being spaced radially or widthwise from the first projection (8) by a first gap (6). The first projection (8) is positioned in the second penetrating part (12) with the first gap (6) between the first projection (8) and the second penetrating part (12). The first projection (8) is further positioned in the first penetrating part (11). Hence, the different type of material (2) is sandwiched between the first metallic material (1) and the second metallic material (3). The outer edge of the first projection (8) is welded to the inner edge of the first penetrating part (11) so that the first metallic material (1) and the second metallic material (3) are melted and joined together to compress and fix the different type of material (2) between the first metallic material (1) and the second metallic material (3), thereby fixing the first metallic material (1), the second metallic material (3), and the different type of material (2) together. A discharge opening (14) is provided in at least one of the first metallic material (1) and the second metallic material (3).