JPS55103203A - Continuous rolling method for pipe - Google Patents

Abstract

PURPOSE: To improve the dimensional accuracy of the finished pipe, at carrying out titled rolling work with the caliber train of approximately ellipse type formed by the roll couples, by constituting the mandrel, to be inserted into the pipe, of a double construction with a specified ratio between the inner diameter of outer shell and outer diameter of inner core.

CONSTITUTION: The mandrel is constituted of the outer shell M₁ directly participating in the rolling work, and the inner core M₂ placed in the outer shell so as to restrict the deformation of the outer shell M₁. The ratio between the inner diameter D of outer shell and the outer diameter (d) of inner core in specified by 1.01≤ D/d≤1.10. This lower limit is required for inserting the inner core into the outer shell, and the upper limit is restricted by the roundness of the mandrel after the rolling work. Then the seamless metallic pipe P is rolled by the reducing rolls 1, 1', under the following conditions. The shape of calibers, size in the rolling direction, and the rolling reduction given by the bottom of caliber, are gradually made respectively true roundness, smaller, and smaller, with advance toward the stand on the exit side; and besides, the total rolling reductions are made almost equal between the odd- and even-number stands. Additionally, the lubricant oil is injected to the gap between the outer shell and inner core so as to jet out against the contact plane between the outer shell and the inner wall of the pipe, on purpose to prevent the damage of the mandrel.

COPYRIGHT: (C)1980,JPO&Japio