METHOD OF MAKING WELL CASING SIZED TO 244,5×7,9, 244,5×9 AND 244,5×10 mm AT PIPE ROLLING UNIT WITH PILGER MILLS Russian patent published in 2014 - IPC B21B21/00 

FIELD: process engineering.

SUBSTANCE: invention relates to pipe rolling. Continuously-cast 430 mm-dia billets are heated to plasticity temperature. Said billets are pierced at piercing mill on 250 mm-dia mandrel with drawing µ=1.56. Produced sleeves are rolled at Pilger mill to pipe sections at fixed sleeves feed to strain zone at steady-state rolling conditions m_st. Pipe sections are cut to equal lengths, heated, gaged and straightened. Preliminary acceptance is carried our, thread is cut, couplings are screwed on, hydraulic tests are carried out and pipes are accepted. Continuously-cast biller length is defined by relationships $$L_b=\frac{L_p}{{\mu }_{\Sigma }},$$ $${\mu }_{\Sigma }={\mu }_p{\mu }_{rol}=\frac{R^2{}_{b}K}{(D_P-S_{rat})S_{rat}},$$ where L_p=36000 is design length of rolled pipe, mm; µ_Σ=µ_pµ_rol is total factor of drawing the billet to commercial; R_b is billet radius, mm; K=0.965 is factor allowing for waste of metal at heating in continuous furnace; D_p=244.5 is rated pipe OD, mm; S_rat is design wall depth at pipe rolling at Pilger mills equal to 8.25, 9.25 and 10.35 mm.

EFFECT: higher reliability of screwed pipe joints.

3 cl, 1 tbl