SCREW PIERCING METHOD IN A FOUR-ROLL MILL Russian patent published in 2021 - IPC B21B19/04 

FIELD: screw piercing.

SUBSTANCE: invention relates to screw piercing in a four-roll mill, carried out by four driven rolls deployed at feed and rolling angles, two of which are cup-shaped, and the other two are different from cup-shaped. The workpiece is gripped by rotating rolls, squeezed in diameter in the input cone of the deformation zone, piercing of the workpiece with a mandrel at the piercing section and rolling of the pierced sleeve in the outlet cone of the deformation zone. The workpiece is gripped by the rolls with a deformation zone ovalization coefficient equal to 1.0. Compression in the input cone of the rolls is carried out with an increase in the ovalization coefficient to a value of 1.07 - 1.12 in the section of the deformation zone in front of the mandrel nose. The piercing is carried out with a decrease in the ovalization coefficient to a value of 1.05 - 1.09 in the section of the pinching of the rolls. When rolling in the outlet cone, the ovalization coefficient is gradually reduced to 1.0, and in the section of metal separation from the rolls, the roll diameters are equal.

EFFECT: elaboration of the structure of the workpiece is ensured, the conditions for piercing are improved, and the accuracy of the geometric dimensions of the workpiece is increased.

1 cl, 3 dwg, 1 ex