METHOD OF PRODUCING POLYGONAL PIPE OF LOW-DUCTILE STEEL Russian patent published in 2017 - IPC B21C37/15 

FIELD: technological processes.

SUBSTANCE: method includes introduction into the circular pipe shell of the wedge segments with the working surfaces formed by two active faces located at an angle to each other, distributing the section of the pipe shell by radially exposing of the working surfaces of the wedge segments to the inner surface of the pipe shell, removing the dispensing force, moving the expander head along the axis of the pipe shell and the distribution of the subsequent section of the pipe shell. Step-by-step distribution of the pipe shell is carried out in two transitions: on the preliminary transition, the distribution is carried out to the outer perimeter equal to 0.4-0.5 of the final value of the external perimeter of the finished pipe, and with a radius of rounding between the inner faces equal to 1.9-2.1 of the radius of rounding between the inner faces of the finished pipe, in this case, at the first step of the distribution, a preliminary transition is made at the lead-in section of the shell, then the dispensing force is removed and a second distribution step is carried out, at which the final transfer of the distribution at the lead-in section of the shell obtained in the first step of distribution, to the size and shape of the finished pipe with simultaneous formation of the preliminary transfer of the distribution on the subsequent section of the pipe shell.

EFFECT: elimination of the probability of discontinuity on the edges of a polygonal pipe during its distribution.

2 cl, 5 dwg