JPS56136230A - Roll forming method for manufacturing electric welded tube - Google Patents

Abstract

PURPOSE: To eliminate the roofing phenomenon in the latter process, and to smooth the surface of weld zone after the forming process, by applying the backward bending process to the middle zone of the strip and the inward bending process to lateral both edges of the strip in the early stage of the forming process, and next, by applying the flattening process to the backward bent middle zone and the inward bending process to the inward bent lateral both edges.

CONSTITUTION: No.1 roll works as follows; the middle zone C of the strip is backward bent in the direction inverse to the pipe forming direction, and the lateral edge B is inward bent in order to straighten the deformation of the edge B caused by the slitting process. No.2 roll flattens the middle zone C; and No.3 roll bends the flat zone near the lateral edge B. After these preliminary processes, No.4 roll, that is a side roll, bends the bottom zone of the pipe. Next, No.5 roll corrects the R of the bottom zone of the pipe; No.6 roll applies the bending process to the bottom zone of the pipe, and also, prevents the rolling phenomenon of the pipe. No.7 roll presses and bends the bottom zone of the pipe, and No.8 roll forms the pipe into a vertical elliptical shape. According to the present processes, a thick-walled pipe in a small diameter is formed in a good shape, and the surface of the weld zone after finishing the forming process is obtained in good condition, so that the internal beads can be smoothly cut off.

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