| 摘要 |
FIELD: rolled tube production, possibly in tube rolling plants with pilger mills. SUBSTANCE: method for making seamless hot rolled conversion elongated tube-blanks of hard-to-form kinds of steels and alloys comprises steps of turning, drilling, boring ingots after their electroslag refining and forged blanks or piercing them in press for further turning or boring to sleeve-blanks; heating them until ductility temperature; rolling sleeve-blanks in pilger mill between rolls (having on polishing zone grooved pass with tangential outlets or oval-shaped grooved pass) with use of mandrel whose mean diameter is less than inner diameter of sleeve-blanks; rolling sleeve-blanks to conversion hot rolled tube-blanks in pilger mill between grooved rolls at difference between inner diameter of sleeve-blanks and mean diameter of mandrels Dsl.in.- Dm.m. = 10 - 20 mm while providing elongation factor mu equal to 6.0 or less, where mu - elongation factor in pilger mill; D sl. in. - inner diameter of sleeve-blank, mm; Dm.m. - mean diameter of mandrel, mm. It is possible to roll in pilger mill between rolls with round grooved pass having angle alpha = 25 - 30 degrees of cross outlet in polishing zone, where alpha - angle of cross outlet of rolls of pilger mill in polishing zone, degrees; or between rolls with oval-shaped grooved pass at relation B/H = 1.1 - 1.15, where B - width of roll groove in polishing zone, mm; H - height of roll grooved pass. Invention lowers possibility of occurring inner flaws of tube-blanks such as scabs, provides elimination of mandrels jamming at rolling ingot-sleeves with less difference between their inner diameter and mean diameter of mandrels that is with larger wall thickness. EFFECT: lowered difference thickness of tubes due to using mandrels with less conicity degree, lowered metal consumption at ingot - tubular blank conversion, reduced loads of rolls and drive unit of pilger mill. 2 cl, 1 tbl
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