RU2141880C1 - Rolling stand - Google Patents

Abstract

FIELD: rolled stock production, possibly in shops for cold and hot rolling of ferrous and non-ferrous metals and alloys and also for rolling non-metallic materials. SUBSTANCE: rolling stand includes frame, rolls, roll drive unit, magnetic circuits, electric current source. Rolling stand is provided at least with two autonomous electromagnetic systems arranged symmetrically relative to rolling plane. Each system includes magnetic circuit with driving coil, two movable magnetic circuit-cores turned one to another by their different poles and pressure rolling roll placed between them. Pressure rolling roll is mounted in holder of magnetic material with possibility of vertical motion together with holder relative to poles and normally relative to rolling plane and with possibility of transmitting electromagnetic effort onto rolled strip and(or) rolling roll. Holder is mounted on shock absorbers. Pressure roll is mounted on stationary cooled shaft connected with separate electric current source. EFFECT: enlarged constructional and manufacturing possibilities of rolling stand, enhanced quality of rolled strip. 2 dwg

Description

 The invention relates to rolling production and can be used in the shops for hot and cold rolling of ferrous and non-ferrous metals and alloys, as well as for rolling non-metallic materials.

 Known rolling mill containing a frame, rolls, drive rolls, (A. N. Tselikov "Machines and assemblies of metallurgical plants", t. 3, M. Metallurgy, 1981).

 The disadvantages of the known stands are the inevitable deflection of the rolls during rolling, the elastic deformation of the elements of the stand (bed, rolls, pressure screws, bearings, pillows) arising from the rolling force.

 When the rolling force changes due to fluctuations in the mechanical properties of the rolled metal, strip thickness, tension, and other random factors, the elastic deformations of the stands (i.e., the rigidity of the stands) change, which leads to a change in the preset gap.

 When rolling thin sheets, the change in the roll gap and the roll deflection are, as a rule, commensurate not only with tolerances on the final product, but also with its thickness. A change in the stand setting caused by elastic deformations, in adverse cases, can lead to strip breaks and thickness variations both in width and in length. The change in the deflection of the rolls, due to the factors noted above, leads to a decrease in the accuracy of rolling, increases the undulation of the strips, which reduces the surface quality of the finished product.

 To reduce the deflection of the work rolls, support rolls of a larger diameter are used, complex roll anti-bending systems are installed, which reduces their durability.

 Multi-roll stands are complex in design, have a lower coefficient of performance compared to two-roll stands.

 Known closest to the proposed rolling mill containing a bed, rolls, roll drive, electric current source, magnetic circuit (A.S. N 737032, M. C. B 21 B 1/02, publ. 1980).

 The disadvantage of the stand is that it transfers the rolling force to the elements of the stand and, as a result, the occurrence of elastic deformations of the bed, rolls, pillows, which leads to fluctuations in the roll gap and profile sizes of the rolled strip, which reduces the quality of the finished product. To obtain large rolling forces, large currents are required, which can lead to overheating of the rolls, a change in the roll profile, i.e. to reduce product quality.

 The purpose of the invention is improving the design, expanding the technological capabilities of the rolling stand, improving the quality of finished products.

 This goal is achieved in that the rolling stand containing the bed, rolls, roll drive, magnetic circuits, an electric current source is equipped with at least two autonomous electromagnetic (magnetic) systems located symmetrically relative to the rolling plane, each of which consists of a magnetic circuit equipped with a coil excitation, located inside the tank with a cooler, of two movable magnetic cores-cores facing each other with opposite poles and a push between them a rolling roll mounted in a cage of magnetic material with the ability to move together with the cage relative to the poles, perpendicular to the plane of rolling and transmitting electromagnetic (magnetic) force to the rolled strip and / or work roll, the cage being mounted on shock absorbers, and the pressure roll mounted on a stationary cooled a shaft connected to an electric current source.

The proposed stand is characterized in that it uses the known effect of the interaction of a conductor with electric current with an external magnetic / electromagnetic field to create a rolling force P _a , for which the rolling stand is equipped with a source of magnetic field and direct electric current, and communication means. The force acting on a current conductor placed in an external magnetic field is:
_{P a = B • I • L} (H), ( 1)
where B is the magnetic induction of an external magnetic field, T _l ;
I is the current in the conductor (roll), A;
L is the length of the active part of the conductor, m

где I_y - ток в катушке возбуждения, А;
W - число витков катушки;
μ_δ = 4π•10^-7 Гн/м; магнитная проницаемость воздуха;
δ - воздушный зазор, м;
m - число воздушных зазоров, с учетом выражений (1) и (2) сила, действующая на один валок, будет равна:

Активное давление валка на металл с учетом того, что длина дуги контакта валка с металлом равна:

где R - радиус валка;
Δh - абсолютное обжатие,
определяется по формуле:

где b_n - ширина полосы, м.Induction in the air gap "δ" is determined by the expression:

where I _y is the current in the excitation coil, A;
W is the number of turns of the coil;
μ _δ = 4π • 10 ^-7 GN / m; magnetic permeability of air;
δ is the air gap, m;
m is the number of air gaps, taking into account expressions (1) and (2), the force acting on one roll will be equal to:

Active pressure of the roll on the metal, taking into account the fact that the length of the arc of contact between the roll and the metal is

where R is the radius of the roll;
Δh is the absolute compression,
determined by the formula:

where b _n is the bandwidth, m

 As follows from the analysis of formula (3), the rolling force does not depend on the distance “a” between the rolls, therefore, the cage can be designed like DUO, Quarto, Sexto for both hot and cold rolling.

In addition, to increase the current in the rolls, to ensure safety, the roll barrels are isolated from the current-carrying rod, which is cooled, for example, with liquid nitrogen, which reduces its electrical resistance, i.e., increases the current (and therefore the drawing force P _a without increasing the power of the current source).

 The invention is illustrated by drawings, where in FIG. 1 schematically shows a general view of the Quarto rolling mill, FIG. 2 is a sectional view of this stand AA.

The rolling stand (Fig. 1, Fig. 2) consists of a frame 1 made of non-magnetic material, magnetic cores 2, excitation coils 3, refrigerators 4, DC sources - 5, moving poles - 6, pressure rolls - 7, work rolls - 8, holder - 9 made of magnetic material, clearance mechanisms δ - 10, roll cooling systems - 11, current conductors - 12, current collectors - 13, slip rings - 14, current-carrying shafts - 15, on which rollers - 7 are mounted, equipped with sliding bearings - 16, shock absorbers - 17, compensating the weight of the rolls and centering the roll and relative to the rolling plane. Work rolls - 8, pressure rolls - 7 are installed in pairs in holders - 9, made of magnetic material. Between the inner surface of the cage - 9 and the surface of the roll - 7 there is a technological gap "C" (0.1 mm each) for supplying coolant, and gaps "δ" are provided between the outer surfaces of the magnetic cores 6 and the clips. Using mechanisms - 10, the gap "δ" can be changed from 0 to several millimeters, tilt the surface of the pole 6 in the horizontal plane by an angle "α" in both directions, thereby changing the magnetic induction of the roll barrels - 7, and therefore the rolling force P _a and the pressure of the work rolls is 8 per metal across the width of the strip.

 Rolling mill works as follows.

The cooling system 11 of the coils 3 and the pressure rolls 7 is turned on. The DC source 5 is turned on, the current I _y is supplied to the coils 3, and the currents I of different directions are supplied to the rollers 7. In this case, the electromagnetic forces P _a act in different directions from the rolling plane and the rolls 7 are moved away together with the clips 9 from each other. Since the rolls 8 are mounted in the same clips 9, they will also separate from each other, forming a gap sufficient to capture the strip. The roll drives 8 are turned on (roll drives not shown). At the moment of capture band switches current direction I in one of the roll and its value is brought to the value required to generate the rolling force P _a. In this case, the electromagnetic forces P _a act towards the rolling plane, moving the pressure rolls 7 towards each other, and the rolls 7 transfer these forces to the rolls 8, which in turn press on the metal from two opposite sides, deforming it. Pressure "q _b " is transmitted from the side of the rolls 8 to the metal evenly. Since the forces P _a acting on the rolls 7 and 8 are equal in magnitude and directed towards them, they are fully compensated, their resultant is zero, therefore, the rolling force is not transmitted to the roll supports, bearings, bed, etc., therefore, their elastic no deformation.

 To adjust the thickness of the strip along the width, the gap "δ" along the roll barrel 7 is changed in the manner described above, thereby changing the amount of strip stretching across the width. In this way, the ribbing and crescent shape of the strip can also be eliminated. Reducing bending moments in the rolls will positively affect the flatness of the strip.

 The use of the proposed stand allows you to improve the quality of the rental by preventing defects such as warping, grooves, crescent, transverse and longitudinal thickness variations associated with insufficient rigidity of the stand. Reducing bending moments in the rolls significantly increases their durability.

 The management of the rolling process is simplified due to the absence of push mechanisms, devices for anti-bending of the rolls and their axial movement in the proposed stand.

 The profile of the strip and its thickness are controlled by changing the current in the coils of electromagnets, i.e. direct impact on an adjustable electrical quantity, and not on inert systems, which include hydraulic and electromechanical devices in existing rolling stands.

 The use of the proposed stand allows the rolling of tin in Quarto stands instead of twenty roll stands, and can significantly increase the efficiency of the rolling stands by reducing the work required by the drive rolls to overcome the elastic deformations of the rolling stand elements.

Claims (1)

 A rolling stand containing a bed, rolls, roll drive, magnetic cores, an electric current source connected to the deformation zone by means of switching, characterized in that it is equipped with at least two autonomous electromagnetic systems located symmetrically relative to the rolling plane, each of which consists of a magnetic circuit equipped with an excitation coil, fed from an individual source of electric current, located inside the tank with a cooler, two movable magnetic circuits-heart of the plates facing each other with opposite strips, and a pressure rolling roll enclosed between them, mounted in a cage of magnetic material with the possibility of vertical movement together with the cage relative to the poles perpendicular to the rolling plane and transmitting electromagnetic force to the rolled strip and / or work roll, and the cage mounted on shock absorbers, and the pressure roll is mounted on a fixed cooled shaft connected to an individual source of electric current.

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