JPS5570428A - Expanding method for steel pipe - Google Patents

Abstract

PURPOSE: To surely prevent the defective deformation, by applying the primary expansion to the pipe material to be expanded at a rate of expansion smaller than the specified rate of expansion over the whole length, and next, by applying the second expansion with the die whose position is adjusted so as to correct the defective deformation generated in the primary expansion.

CONSTITUTION: At expanding the welded steel pipe 1, especially the one manufactured by the UOE pipe forming method, the primary expansion is first applied with the first expander 2 over the whole length at the rate of expansion about 0.3W 0.7% in general, and about 0.5% ordinarly. Next, the bend and roundness of the pipe material 1' subjected to the primary expansion are tested, and if they are normal, the ordinary expansion is applied by the second expander 2' over the whole length, finishing into the product size. If the anomalous defective deformation is found out, the second expansion is carried out suitably controlling the expansion work in order to correct the defective deformation and to finish into the product size. The rate of expansion at the second expansion is suitable to be about 0.4W 0.7%.

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