JPS5750219A - Manufacture of square metallic blanc pipe by roll forming - Google Patents

Abstract

PURPOSE: To prevent occurrence of lap of welding edge by preliminarily forming each side of a square metallic blanc pipe that is to be introduced to welding rolls that has desired circular arc convex outward by corner bending rolls and fin pass rolls.

CONSTITUTION: In the first process, a metallic strip 1 is sent to an upper corner bending roll 3 through a pinch roll. The upper corner bending roll consists of an upper roll 4a and a lower roll 4b. In the second process, the upper side corner is bent leaving the length that constitutes the upper side of the square metallic pipe and, at the same time, a circular arc shape is added to the metallic strip 1. In the third process, the metallic strip 1 in which left and right side corners are formed to circular arc form is passed between upper and lower rolls 6a, 6b of a lower side corner bending roll 6 to bend lower side corners at inner side of left and right upper side corners. In the fourth process, it is led to a fii pass roll 9 and the upper, left and right, and lower sides are formed by compression to desired form, and each side is preliminarily formed to shape that has circular arc convex outward.

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