PROCEDURE OF EXTENSION ROLLING AT MILL FOR ROLLING SEAMLESS TUBES ON MANDREL Russian patent published in 2009 - IPC B21B17/04 

FIELD: metallurgy.

SUBSTANCE: invention refers to forming of metals, particularly to rolling seamless steel tubes on mandrel. Ratio of external length of circumference of a hollow billet to finished circumference length corresponding to perimeter of billet tube at the exit from the finishing mill is at least 1.1, while contents of Cr in the billet tube is less, than 10%. Also 1.06 ≤ of ratio of roll-pass curve in the 1^st mill to finished length of circumference ≤ 1.12, 1.05 ≤ ratio of length of roll-pass curve in the 2^nd mill to finished length of circumference ≤ 1.10, and length of roll-pass curve in the 1^st mill > length of roll-pass curve in the 2^nd mill.

EFFECT: preventing both overfilling and under-filling of roll-passes applying one combination of calibrated rolls.

2 cl, 1 ex, 6 dwg