METHOD FOR HOT ROLLING OF SEAMLESS THIN-WALL TUBES Russian patent published in 1999 - IPC

FIELD: rolled tube production, possibly rolling tubes between ridged rolls in aggregates with three-roll expanding mill. SUBSTANCE: method for hot rolling seamless thin-wall tubes comprises steps of piercing billet to sleeve in piercing mill, subsequently rolling sleeve in expanding mill between ridged rolls; at piercing thinning rear end of sleeve at side of inner diameter and drawing rolls apart at expanding said end. Sum of value of thinning wall of sleeve end at piercing and value of drawing apart each ridged roll in expanding mill should be equal to 1.1-1.3 of ridge height. EFFECT: lowered out-off-roundness of tube along its whole length, prevention of formation of trihedral portion on rear end of tube, simplified process of guiding mandrel to sleeve in expanding mill.