Abstract: An object is to prolong the life of a ring tool, and improve the productivity of a welded pipe. A ring tool unit is held in a downstream-side end portion of a mandrel to be inserted into a welded pipe currently being manufactured from the upstream side of a welding position, and is used as a cutting tool for continuously cutting a bead produced on the inner surface of the welded pipe, wherein the ring tool unit is formed by fitting a ring tool having a ring-like blade in a sleeve having a circular hole for holding the outer circumference of the ring tool.

Abstract: An object is to prolong the life of a ring tool, and improve the productivity of a welded pipe. A ring tool unit is held in a downstream-side end portion of a mandrel to be inserted into a welded pipe currently being manufactured from the upstream side of a welding position, and is used as a cutting tool for continuously cutting a bead produced on the inner surface of the welded pipe, wherein the ring tool unit is formed by fitting a ring tool having a ring-like blade in a sleeve having a circular hole for holding the outer circumference of the ring tool.

Abstract: In a solar cell including a photoelectric conversion layer 14 disposed on a flexible substrate 11 and constituted by a laminated layer of non-single crystalline silicon thin films, the flexible substrate 11 has a coefficient of linear thermal expansion of is 2.0 ppm to 10.0 ppm. By this, the coefficient of linear thermal expansion of the flexible substrate 11 and that of the photoelectric conversion layer 14 become close to each other, so that warp and deformation during manufacturing steps and after the steps are decreased. Further, since stress applied to the photoelectric conversion layer 14 is also lessened, the photoelectric conversion efficiency can be increased.