Joint structure

A joint structure comprising:

• a first metallic material having a first projection;
• a second metallic material similar in type to the first metallic material and weldable to the first metallic material;
• and
• a different type of material different in type from the first metallic material and the second metallic material, the different type of material having a first penetrating part and sandwiched between the first metallic material and the second metallic material, the different type of material being difficult to be welded to the first metallic material and the second metallic material,
• wherein
• the first projection is smaller in diameter or width than the first penetrating part and is spaced radially or widthwise from a rim of the first penetrating part by a first gap,
• the first projection is positioned in the first penetrating part and is spaced from the second metallic material by a second gap in a thickness direction of the first penetrating part, the second gap having a size of a predetermined percentage of a thickness of the first projection of the first metallic material to which arc in arc welding is applied, and
• the first metallic material and the second metallic material are melted and joined together inside the first penetrating part to compress and fix the different type of material, so that the different type of material, the first metallic material, and the second metallic material are fixed together.