JPS55144332A - Bending process of metal pipe - Google Patents

Abstract

PURPOSE: To prevent occurrence of reduction of thickness and flattening phenomenon of metal pipe on the outside of bending, by cooling the band region of a proper width at the both sides in the circumferential direction spaced at an appropriate distance from the outermost side position of the bending part of metal pipe when heating.

CONSTITUTION: A metal pipe 1 is passed between guide rolls 2, 2 and 3, 3, and is locally heated in ring form by means of high frequency inductor 4. While buckling and holding the bend end part of the part 1 with a clamp 6, the pipe 1 after heating is cooled in the specified parts as described below, and a bending moment is given to the pipe by rotary guide of an arm 5 to bend while continuously deforming plastically. That is, vicinities A, A of parts spaced by distance (a) from the vertical axis at the bending outside T of the pipe 1 when heating are cooled. Therefore, the length of A-A on the outside T becomes tension region, while the length of A-A in the bending inside C becomes compressive region. The tensile strength of cooled band regions A, A is set extremely larger than in the other regions. As a result of this, reduction of the thickness on the outside T may be prevented, and also flattening may be also avoided because component of force in the vector direction may work in band regions A, A.

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