Multiple-Winding Pipe Forming Device and Multiple-Winding Pipe Forming Method

A multiple-winding pipe forming device for forming a wound pipe, the multiple-winding pipe forming device comprising:

• a plurality of pairs of forming rollers arranged along a feeding direction of a metal sheet that is an object of forming, each pair of forming rollers opposing one another so as to sandwich the metal sheet, and the plurality of pairs of forming rollers curling the metal sheet and winding the metal sheet into a roll shape;
• and
• a mandrel fabricated of metal, the mandrel including:
• a shaft that extends in the feeding direction and is disposed inside the metal sheet wound in the roll shape, one end side of the shaft being retained, which one end side is disposed upstream in the feeding direction, and
• a working portion provided at an opposite end side of the shaft from a side thereof at which the one end side is disposed, the working portion including a taper portion that increases in diameter from upstream to downstream in the feeding direction,
• wherein the taper portion of the working portion is disposed at a position at which the metal sheet wound in the roll shape is sandwiched by, of the plurality of pairs of forming rollers, a pair of the forming rollers that is disposed at a downstream side in the feeding direction.