Manufacture of pipe stubs in walls of very great thickness

A process of fabrication of a pipe stub from a wall of very great thickness constituting a portion of a chamber under pressure, said process comprising machining an aperture in the wall along an axis corresponding to the axis of the pipe stub to be obtained, the aperture having a diameter of the order of the thickness of the wall and being formed with rounded edges at the internal and external surfaces of the wall, placing the wall on a tubular anvil provided with a central conduit coaxial with the aperture and whose diameter corresponds substantially to the exterior diameter of the pipe stub to be obtained, the anvil being formed with an upper rounded surface whose diameter progressively increases up to a rounded bearing face whose shape corresponds to that of the wall at the juncture with said pipe stub, heating the wall at least in the region surrounding the aperture to a temperature greater than the transformation point A1 but less than the forging temperature, and deforming the wall by introducing a punch with force into the aperture, the punch having a first centering tip of diameter slightly less that of the aperture followed by a conical surface merging with said tip and widening in a direction away from the point and which is rounded in convex form and connects successively to a cylindrical portion whose diameter is substantially equal to the interior diameter of the pipe stub to be obtained, the introduction of the punch first centering the tip in the aperture and then progressively deforming the wall to form the pipe by progressive enlargement of the aperture by progressive penetration of the conical surface of the punch with concurrent diminution of the thickness of the sheet to form a deformed portion coming to be applied against the rounded surface of the anvil.