METHOD AND MILL FOR MANUFACTURING LONGITUDINALLY WELDED TUBES Russian patent published in 2015 - IPC B21C37/08 

FIELD: metallurgy.

SUBSTANCE: shaping of a band in rolls with open passes is performed till a bending angle of 180°, moulding of a tube workpiece in a drawing die - by folding the band edges into a tube workpiece till the scheduled angle; moulding is performed in the rolls with cold passes with a split washer; final moulding in the rolls with closed passes without any split washer with the same diameter for its calibration into the tube prior to welding. The mill includes a frame, a housing with vertical rolls, lower and upper moulding drive rolls with open passes and closed passes with a split washer, edger rolls alternating with them, the drawing die, a drive and a welding device. The drawing die is fixed with hold-down planks in the housing mounted on the frame after the last rolls with open passes and made in the form of a sleeve with a pass with a conical surface, which is located inside it, with a diameter reducing from the inlet side to the outlet side. The pass is located so that a cross section in the form of an ellipse is formed in a plane perpendicular to the frame axis. After the rolls with closed passes with the split washer there installed are rolls for calibration of the tube workpiece into a tube before the welding device.

EFFECT: excluding twisting of workpiece edges.

2 cl, 8 dwg