METHOD OF SCREW PIERCING IN FOUR-ROLL MILL Russian patent published in 2024 - IPC B21B19/04 

FIELD: various technological processes.

SUBSTANCE: invention relates to screw piercing in four-roll mill. Piercing is performed by four driven rolls turned through feed and rolling angles. Two rolls have mushroom shape, and the other two are cup-shaped. Workpiece is gripped by rotating rolls, its diameter is reduced in the inlet cone of the deformation centre, the workpiece is pierced on the mandrel and the pierced sleeve is rolled in the outlet cone of the deformation centre. Gripping of workpiece by rolls, filling of deformation centre with metal and steady process of piercing is carried out at constant rotation frequency of cup-shaped and mushroom-shaped rolls providing equal peripheral speed of rolls in outlet section of deformation centre. End of piercing process is performed at peripheral speed of cup-shaped rolls equal to 0.1–0.3 of peripheral speed at steady-state rolling process.

EFFECT: ruled out crushing and rupture of rear ends of rolled sleeves.

1 cl, 2 dwg, 1 ex