METHOD FOR FORMING SEAMLESS TUBE Russian patent published in 2007 - IPC B21B19/04 

FIELD: manufacture of tubes while controlling rotary forging procedure.

SUBSTANCE: method comprises steps of rolling and piercing by means of pair of cone-type rolls while mounting mandrel along rolling line in condition when one of given mathematical expressions corresponds to such parameters as relation of roll diameter in restricted portion to roll inlet diameter, revolution number of blank during period from blank to roll engagement till motion of blank to nose part of mandrel, reduction degree. Selection of concrete mathematical expression depends upon predetermined range of relation of said diameters of rolls. Strict satisfaction of offered conditions of rolling process eliminates incorrect blank and rolls engagement.

EFFECT: prevention of flaw occurring on inner surface of rolled material caused by changing for the worse of blank workability at hot state of blank.

3 dwg, 5 tbl, 2 ex