PRODUCTION OF SEAMLESS HOT-WORKED MACHINED 610×36,53×3000-3450 mm FROM 15X5M-GRADE STEEL FOR REFINERY COMMUNICATIONS WITH STRINGENT REQUIREMENTS TO GEOMETRICAL SIZES Russian patent published in 2015 - IPC B21B21/00 

FIELD: process engineering.

SUBSTANCE: invention relates to metallurgy. Forged pieces sized to 650×1630±50 mm are turned to billets to bore central holes therein. Blanks are heated to ductility temperature and pierced at screw rolling stand to sleeves-blanks. Rate of forming of the ends of sleeves-blanks at exit of rolls for the length of 0.50-0.75 of strain source length is decreased by 30-40%. Blanks are heated to ductility temperature and pierced at screw rolling stand to sleeves-blanks. Rolling rate V_roll.out. of lengthwise sleeves-blanks rear ends at roll outlet by length equal to 0.75-1.0 of deformation source is decreased and its magnitude is defined by expression: $$V_{roll.out.}=\frac{{\mu }_p}{{\mu }_r}{V}_{roll.est.},$$ where µ_p is drawing at piercing to sleeve-blanks, µ_r is drawing at rolling of sleeves-blanks to rerolled stock, V_roll.est. is roll rpm at established rolling. Rerolled sleeves-blanks are heat treated, bored and turned to commercial pipes.

EFFECT: higher mechanical properties and precision of pipe sizes.

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