METHOD OF MANUFACTURING SOLID-DRAWN HOT-ROLLED PIPES Russian patent published in 2008 - IPC B21B17/04 

FIELD: technological processes.

SUBSTANCE: invention pertains to treatment of metals using pressure, particularly to pipe rolling. The method involves rolling cylinder-pipe in two longitudinal rolling tandem figures with stretching in each figure in rolls with multifaceted calibres on short immoveable cone-cylindrical mandrels. Rolling is done in mandrels with equal height of calibres for both figures. The elongation ratio in the first figure is 1.2-1.9, and in the second is 1.0-1.07. The mandrels have equal external diameters or the external diameter of the mandrel of the second figure is 1 mm more than the external diameter of the first figure. The invention allows for reducing or completely eliminates defects on the inner surface in form of longitudinal rolled marks and lowers transverse variation in wall thickness.

EFFECT: reduction or elimination of defects on the inner surface of the pipe and lowering transverse variation in thickness.