SEAMLESS TUBE PRODUCING METHOD Russian patent published in 2007 - IPC B21B17/00 

FIELD: rolled stock production, namely manufacture of seamless tube by rolling with elongation and sizing.

SUBSTANCE: rolling with elongation is realized in mandrel mill having rolling stands. Each rolling stand includes sizing rolls for changing wall thickness of in circumference direction of initial tube. Position and number of changes of wall thickness are determined preliminarily according to changes of wall thickness formed in circumference direction of seamless steel tube during sizing process and then initial tube is subjected to sizing. Wall thickness changes are lowered thickness portions and they are arranged in circumference direction of initial tube by angle 45° relative to reduction direction in last rolling stand providing rolling with elongation. Inter-roll gap of mandrel mill is set less than gap between rolls whose roll grooved pass is in the form of circle. Mandrel rod with outer diameter less than outer diameter of mandrel rod by means of which wall thickness of tube achieves desired value at outlet side of mandrel mill when roll grooved pass is in the form of circle.

EFFECT: possibility for preventing local changes of wall thickness in circumference direction.

6 cl, 3 tbl, 2 ex