FIELD: rolled tube production, namely process for straightening end curvature of cold rolled large- and mean-diameter tubes.
SUBSTANCE: method comprises steps of rolling tubes on cone mandrel in cold rolling mill while front end of cone mandrel is spaced from outer guide by distance 850 - 900 mm and inner diameter of guide exceeds outer diameter of tube by 30 - 40 mm. Then tube is straightened in six-roll straightening machine. End curvature of tube is straightened by means of detachable cylindrical inserts mounted onto mandrel stem with possibility of rotation and translation motion relative to stem. Said inserts are fixed at end side of stem by means of washer and fastening screw. Length of cylindrical inserts is determined according to expression Lin = K x Dt, where Dt - outer diameter of tubes, mm; K = (1.5 - 3.0), coefficient having large values for rolling tubes with smaller diameters. Diameter of cylindrical inserts is determined according to expression Din = Din. t - Δ, where Din.t - inner diameter of tubes, mm; Δ = (0.5 - 1.0) - gap between inner diameter of tube and outer diameter of insert whose large values correspond to tubes with larger wall thickness, mm. Front end of insert is rounded by radius whose value is determined according to expression R = Ro - R fr , where Ro - radius of cylindrical insert, mm; R fr - radius of front end of mandrel, mm. Detachable cylindrical inserts are made of cast iron with spherical graphite; lubricant layer is applied onto said inserts before rolling each tube.
EFFECT: lowered factor of metal consumption, lowered (or completely eliminated) quantity of curvature scrap of tube end.
7 cl, 1 dwg, 1 tbl, 1 ex
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