Flange joining structure and seal body used therein

A flange joining structure comprising:

• a first member including a first annular flange portion;
• a second member including a second annular flange portion;
• and
• a seal body disposed between the first annular flange portion of the first member and the second annular flange portion of the second member, wherein
• a bolt is inserted through a through hole of a plurality of through holes in each of the first annular flange portion, the second annular flange portion, and the seal body,
• a nut is screwed onto a male screw portion of the bolt so that the first annular flange portion and the second annular flange portion are joined to each other,
• the seal body includes:
• an annular base portion formed of a metallic plate;
• and
• an elastic sealing unit integrally formed on the annular base portion,
• the plurality of the through holes are provided on the annular base portion at an interval along a circumference direction,
• the elastic sealing unit is provided to entirely cover the annular base portion, a first protrusion that is formed of a hard material, protrudes in a direction perpendicular to a plane extension direction of the annular base portion and comes into contact with the annular base portion is provided on one surface side of the annular base portion of the seal body,
• a second protrusion that is formed of a hard material, protrudes in the direction perpendicular to the plane extension direction of the annular base portion and comes into contact with the annular base portion is provided on another surface side,
• the first protrusion and the second protrusion are covered with the elastic sealing unit, and
• the elastic sealing unit of the seal body provides sealing between the first annular flange portion of the first member and the second annular flange portion of the second member.