The invention relates to rolling and can be used in rolling sectional and sheet steels, non-ferrous and non-metal materials.

Known in the art is a stand comprising a housing, rolls, a roll drive means and a screwdown mechanism in the form of a screw (A.N.Tselikov "Machines and Aggregates of Metallurgical Plants", vol. 3, Moscow, METALLURGIYA Publishers, 1981).

A disadvantage of the screwdown mechanism of a conventional stand is a low speed and accuracy of adjusting a clearance between rolls. For instance, the travel speed of housing screws in the QUARTO stands of hot rolling finishing mill group 2000 is from 0.5 to Imm/s. (P.I. Poloukhin "Rolling", Moscow, METALLURGIYA Publishers, 1982). A low accuracy of rolling is also explained by an appreciable amount of springing of said stand screwdown mechanism elements.

Also known is a hydraulic screwdown replacing housing screws or working in combination therewith. (Firm SMS-Demag, the Third Congress of Rolling Mill Operators, Lipetsk, 19-22 October, 1999. The report by Pelking "The Latest Technologies in Cold Rolling"; the technological instruction TI 105-PHL-16-96, OAO Severstal, "Rolling of Strips on Five-stand Cold-Rolled Sheet Production Mill 1700", 1996).

The travel speed of rods of hydraulic screwdowns (HS), according to these sources, is 2.5 mm/s. Accuracy of adjustment is limited by the springing of elements of a hydraulic screwdown and a degree of elastic deformation of oil accounting for about 0.5 to 1%.

Known is a stand (Patent RF 2138346, published 27.09.99. Bulletin No 27) which is provided with two permanent magnet means located at the periphery of contact, with respect to each other, with like poles, of which one is situated close to a press roll and the other―close to a stand housing, both magnet means being provided with field coils for magnetizing, demagnetizing, reversing the sense of magnetization and neutralizing the magnetic fields and also with hydraulic cylinders for lifting and lowering repulsion magnet means.

A disadvantage of the conventional screwdown mechanism is the impossibility to use it in updating the existing stands equipped with housing screws with an electromechanical drive means and hydraulic screwdowns which directly impact upon the rolls via chucks.

An object of the invention is to update a screwdown, increase the travel speed of rolls and consequent precision of rolling.

Said object is achieved owing to the fact that the screwdown mechanism of a stand comprising a hydraulic cylinder disposed between a stand housing and a chuck of a support roll is made up of a rod implemented from a permanent magnet, such as a barium oxide magnet, encompassed by an electromagnetic coil, at least two coils mounted in the chucks of support (press) rolls, which are disposed installed with respect to each other, and, along with this, one of them is connected with a d.c. source and the other - with a capacitor bank. The electromagnetic coil embracing the rod-magnet provides for regulating a rolling force within a tolerance zone by a thickness of strip, the electromagnetic coil connected with the d.c. source and mounted in the roll chuck provides the attraction or repulsion of the chuck from a hydraulic cylinder piston, and the coil connected with a capacitor bank contributes to delicately adjusting a clearance between rolls (i.e. a thickness of strip) owing to issuing thereinto large quantity narrow current pulses of a corresponding sign.

A concept of invention is explained in Fig. I showing a general diagram of a screwdown mechanism.

The screwdown mechanism comprises a spherical bearing I supported by a frame 2 of a stand, a rod 3 composed of a permanent magnet means (for example, the barium oxide one), a body 4 of a hydraulic cylinder, a coil 5 connected to a d.c. source 6, a hydraulic system 7, a chuck 8, a coil 9 and a coil 10 both mounted in the chuck 8, a capacitor bank 11, a charging device 12, a control unit 13. Said frame 2, bearing I, body 4, chuck 8 are made of non-magnetic materials.

The screwdown mechanism is operated in the following manner.

The coarse adjustment of a clearance between rolls is carried out by feeding oil under pressure from a hydraulic system 7 for a rod 3, said coarse adjustment providing, at the time of rolling, a rolling force P_h. With variations of a thickness of strip within thickness tolerance limits its adjustment is performed by supplying into coils 5 and 9, the continuous currents of a corresponding sign, which permits obtaining a rolling force P=P_h+P_em or P=P_h - P_em. With a polarity N-N, a chuck 8 is repulsed from the rod 3 with a force P_em and then P=P_h+P_em, thus reducing a thickness of strip; with a polarity N-S, the chuck 8 is attracted to the rod 3 with a force P_em and then P=P_h-P_em, thus increasing the strip thickness.

In the event of an abrupt (unexpected) change, during rolling, in a thickness of strip, a discharge current pulse is sent to a coil 10 from a capacitor bank 11 of a corresponding sign and a clearance between rolls is changed in a stand in a very short time span (1≈10⁵ A, τ≈10^-5s).

It is hence only logical to see that the invention allows one to use on the existing mills, in addition to hydraulic screwdowns (HS), an electromagnetic screwdown to carry out a more accurate rolling of strips.