Apparatus for producing branch structure in metal pipe, and method for producing branch structure in metal pipe

An apparatus for producing a branch structure in a metal pipe, the apparatus comprising:

• a die having a spherical shape, and having a central axis, and moreover having a first diameter and a second diameter, which is shorter than the first diameter, extending in a direction perpendicular to a direction in which the central axis extends;
• and
• a connecting member that can be connected to the die;
• the die having a front curved surface portion, a largest diameter portion and a rear curved surface portion provided in this order along the direction in which the central axis extends;
• wherein at a time when the die having been inserted into the metal pipe is to be removed to outside of a metal pipe by the connecting member connected to the die, first flanging is performed by the front curved surface portion on a pilot hole that is formed at a branch portion formation position in the metal pipe and that runs radially through a body of the metal pipe, and the connecting member causes the removed die to rotate by a predetermined angle about the central axis and inserting the die to the first flanged pilot hole, whereupon second flanging is performed on the first flanged pilot hole, from outside the metal pipe by the rotated rear curved surface portion.