METHOD OF HELICAL PIERCING OF CAST BILLET Russian patent published in 2013 - IPC B21B19/04 

FIELD: process engineering.

SUBSTANCE: invention is intended for increasing tool life and quality of inner surface of rolled tube from cast and continuously cast billet at rotary piercer. Proposed comprises feeding the billet to forming rolls with conical entrance, throat and conical exit developed through angle of feed and rolling-off, billet grip by rolls, helical piercing at mandrel-free section of roll conical entrance and billet piercing by mandrel at mandrel section of roll conical entrance. Note here that piercing is performed with reduction to throat at different degree of deformation. Uniform metal pressure distribution at tool is ensured by accentuated increase in reduction at mandrel-free section of the roll conical entrance spaced from roll front end for 0.3-0.6 on conical entrance length and decrease in reduction at mandrel section of roll conical entrance spaced from mandrel nose from 0.1-0.4 of mandrel length.

EFFECT: accentuated increase in reduction by 2,04-15,0 percent.

2 dwg, 1 tbl