ES319041A1 - Production of seamless tubes - Google Patents

Abstract

In a pilger rolling mill for producing seamless tubes, the hollow metal body to be rolled is pressed on to the mandrel prior to the insertion of the body between the rolls, and automatic means are provided for withdrawing the mandrel and body out of the rolls during the pointing operation, and for returning the mandrel and body to the rolls just before the impact points of the rolls face each other, the automatic means being arranged to be controlled in synchronism with the rotary movement of the roller. A hot bloom 1, Fig. 10, coming from a piercing mill rolls on to the table of a press 2, where a previously lubricated mandrel 3 is inserted by a device 4, is compressed by dies 9 of the press on to the mandrel, the bloom and mandrel are lifted by a crane 13 and dropped into a mandrel holder 14 and a stripper ring 15, rams 22 feed the mandrel carriage 21, mandrel 3, and bloom 1, towards pilger rolls 34, where the bloom is first pointed, and then rolled into a tube 44. Rams 22 now withdraw carriage 21 until the mandrel lies over a table 47, the mandrel is released, table 47 moves the mandrel sideways, which is then transported backwards by a means 48 to a cooling grid, and then plunged into a trough 49. The forward end of the bloom may be pressed on to the mandrel by dies (5), Fig. 2 (not shown), or the rear end may be pressed by dies (9), Fig. 8 (not shown). In a modification, four die rolls (10), Fig. 11 (not shown), compress the forward end of the bloom, or bloom 1 may be rolled completely by four rolls. In a still further modification, three roller stands 12 are provided, Fig. 13. Coolant passes through a duct 17 in the mandrel, Fig. 9, and returns to an outlet 19 through an annular passage 18. The mandrel holder 14 is mounted on a splined bar 20 which passes through a rotating device 31 and is connected to a fluid piston 32 of carriage 21, Figs. 3 and 4. Liquid under pressure, which may also be the coolant, passes through a central bore in piston 32 and bar 20, through oblique bores 24, Fig. 9, into a chamber 25, and actuates a pin 26 which projects into the bore of the mandrel and locks the latter. A control box 35 supplies air to either side of piston 32, and a dash pot brake 36 is provided for stopping the feed at the correct position. In a modification, piston 36 is actuated during the pointing period by gas pressure creased by the ignition of an explosive mixture. On retraction, the bloom and mandrel are rotated through 90 degrees by device 31 or the angle may be varied if a hexagonal tube is being rolled. Rolls 34 are driven through gear 38, Fig. 10, connected to a motor 39, and a rotating disc 40 having apertures which permit light to actuate photo-cells 43, control valve control box 35, and rotating device 31, synchronously with rolls 34. A roller 34a is provided for determining the axial position of the bloom during pointing.