SCREW ROLLING MILL MANDREL FOR PIERCING WORKPIECES MADE OF ALLOYED, HIGH-CHROMIUM AND STAINLESS GRADES OF STEEL Russian patent published in 2023 - IPC B21B25/00 

FIELD: production of pipes.

SUBSTANCE: invention is related to screw rolling for piercing blanks in the production of seamless pipes. The mandrel of a screw rolling mill for piercing blanks contains front, rolling, calibrating and cylindrical sections. The outer surface of the mandrel is made profiled in form of elevations and recesses alternating in the longitudinal section at a given length. The recesses are located from the end of the mandrel at a distance of no more than 0.5 of the diameter of the nose section of the mandrel at a length not less than the sum of the lengths of the nose and rolled sections of the mandrel. The width of the first recess from the end of the mandrel does not exceed 0.65 steps of applying the recesses. In this case, the pitch and depth of the recesses are determined by mathematical dependencies, and the angle between the side of the recess and the axis of the mandrel is no more than 130°.

EFFECT: durability of the mandrels is increased and the quality of the inner surface of the rolled pipes is improved.

22 cl, 8 dwg, 2 tbl