RU2466808C1 - Casting-rolling plant for sheet cold rolling from aluminium and its alloys - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: proposed plant comprises casting machine, rolling stands with roller drives, withdrawal rollers with drives mounted after last stand, guillotine-shears and two driven reels. Note here that drives of last and penultimate stands. Withdrawal rollers and reels are electrically interconnected to maintain invariable roller rpm-to-breakdown feed speed ratio after reaching preset rolling moment. Note also that reels are mounted to allow plane-parallel vertical displacement of their drums. Note that withdrawal roller working surfaces are gummed.

EFFECT: higher quality of strip with corrugation not exceeding 0,1 mm per running metre.

6 cl, 1 dwg

Description

The invention relates to the field of metallurgy and can be used in the production of directly from the melt of cold rolled strips of aluminum and its alloys on casting and rolling units.

Known foundry unit for the production of hot rolled strips of aluminum and its alloys on hot rolling mills from slabs (see, for example, Erhard Hermann. Continuous casting. Metallurgizdat. Moscow. 1961. S.143-145).

The disadvantages of the known casting and rolling unit:

- discreteness of the process, causing instability of the properties of the tape along its length;

- the presence of restrictions on the weight of the roll (or riot).

A known casting and rolling unit for the production of tapes of aluminum and its alloys, including continuous casting of a billet from a melt, rolling the billet into a finished tape and winding it into a riot (see, for example, V. A. Chebotareva and V. A. Samsonov. Liteyno rolling mill for the production of wire rod, sheets and ribbons of non-ferrous metals. "Heavy engineering". No. 5. 2007. Pages 20-27).

Advantages of the well-known foundry-rolling unit:

- the continuity of the process, ensuring the stability of the properties of the tape along its length;

- the possibility of obtaining riots of tape with almost unlimited mass, determined only by the technical capabilities of the casting and rolling unit.

A disadvantage of the known casting and rolling unit is the appearance of a roll curvature of the tape during its winding onto the winder drum, which leads to non-flatness of the tape.

The technical result of the invention is to improve the quality of products by obtaining them with ultra-high flatness (with a warp not higher than 0.1 mm per linear meter) when rolling a cold-rolled strip, provided that it is horizontal when leaving the rolls of the last rolling stand.

This technical result is achieved by using a casting and rolling unit for the production of cold-rolled sheet products from aluminum and its alloys, including a casting machine and rolling stands with drives, with pulling rollers and guillotine shears installed behind the last stand, after which two winders are placed; the drive of the last and penultimate stand, as well as the pulling rollers are made with a rigid electrical connection between each other according to the speed of movement of the processed roll; between the last and penultimate stands there is a collector for supplying technological coolant to the tackle, installed only above the tackle; guillotine shears are volatile; the working surfaces of the pulling rollers are gummed with rubber from hard varieties; roll temperature meters (pyrometers) are installed at least at the exit of the last rolling stand and at the entrance to the last rolling stand, and coilers are installed with the possibility of plane-parallel movement of their drums in the vertical direction.

The proposed technical solution allows you to get cards with ultra-high flatness due to the following features of this design:

- due to the very accurate maintenance of the ratio of the rotation frequencies of the rolls of the last and second to last, as well as the ratio of the rotation frequencies of the rolls of the last stand and pulling rollers, the front and rear specific tension of the roll in the last stand can be raised to (2/3) from the yield strength of the tape, which is significantly more than conventional rolling;

- due to the almost complete elimination of the warping of the tape when it leaves the rolls of the penultimate stand (where preparation of high-quality tackle for the last stand is being prepared), and then at the exit from the rolls of the last stand;

- due to which, as a result, the flatness indices of the hot-rolled strip turn out to be one or two orders of magnitude higher than during ordinary rolling of the strip.

The proposed technical solution is shown in the figure, which shows a diagram of a casting and rolling unit, where:

- figure 1 shows a view of the casting and rolling unit from the side.

A casting machine 2 is installed behind capacity 1 for liquid aluminum, followed by rolling stands with drives: the penultimate 3 and the last 4; behind the last stand, pulling rollers 5 with a drive and flying guillotine shears 6 are installed (drives of rolling stands and pulling rollers are not conventionally shown in the figure).

After scissors 6 there are two winders: 7 and 8.

All the machines of the casting and rolling unit are interconnected by a continuously machined roll in the form of a cast billet 9 between the casting machine 2 and the penultimate stand 3, the rolling 10 and between the rolling stands 3 and 4 and the finished tape 11, between the last stand 4 and winders 7 or 8 .

Along the line of the casting and rolling unit, meters of rolling temperature were installed: pyrometer 12 - at the exit of the casting machine 2, pyrometer 13 - at the exit of the penultimate stand 3 and pyrometer 14 - at the entrance to the last stand 4; It should be noted that only two pyrometers are involved in the control system of the casting and rolling unit: 13 and 14.

To supply technological coolant to the tackle 10, a collector 15 is mounted above it; there is no similar collector below so as not to disrupt the normal operation of the pyrometers 13 and 14.

The casting and rolling unit operates as follows.

Liquid aluminum from the tank 1 enters the zone of the rotating rolls of the casting machine 2. The temperature of the cast billet 9 emerging from it is measured with a pyrometer 13. Passing through the rolls of the rolling stand 3, the billet 9 changes its thickness to h _o , turning into a tackle 10 for the subsequent rolling stand 4 ; the temperature of the roll 10 in the interval between stands 3 and 4 is measured with pyrometers 13 and 14.

Having passed stand 4, the rolling 10 turns into a finished tape 11 of thickness h _k , which is wound into a riot on the drum of the winder 7.

After winding a riot full in mass, they include flying guillotine shears 6, which are made volatile (this is indicated by two horizontal counter-directed arrows 16).

Moving at a speed equal to the speed of movement of the tape 11, flying guillotine shears 6 cut it; the rear end of the tape formed in this case is wound up in a riot on the drum of the winder 7, and the formed, in turn, front end of the tape 11 is tucked onto the drum of the winder 8 (this is exactly the moment shown in the figure).

An ultra-flat cold-rolled strip 11 emerges from the last rolling stand 4. In order to avoid the formation of roll curvature on it when winding the reel 7 or 8 onto the drum, the thickness of the finished strip 11 should not exceed (h _k ) _max ; otherwise, tensile stresses (in the upper fibers) and compressions (in the lower ones) that exceed the yield strength of the tape will occur in the outer fibers of the cross section of the tape. As a result, plastic deformation of the metal appears, which will lead to the winding of the rolled tape 11 into a roll.

The maximum permissible thickness of the finished tape indicated above is calculated by the empirical formula:

where D _B and σ _s1 are the diameter of the reel drum (7 and 8) in mm and the yield strength in kgf / mm ^{2 of the} tape 11, caged in the last stand 4.

Ultimately, the sequence of technological operations in the production of cold-rolled sheet products from aluminum and its alloys is as follows.

In the rolls of the casting machine 2 from the tank 1 serves liquid aluminum. Formed in the machine 2 cast billet 9, having passed rolling stands 3 and 4, turns into a tackle 10 and then into a finished tape 11.

Rolling in the last stand 4 is carried out with the application of longitudinal tension to the roll: rear T _about (to roll 10) and front T ₁ (to the finished tape 11); moreover, when rolling the front end of the tape 11, the rear tension T _o created in front of the rolls of the last stand 4 is maintained equal to zero.

This is necessary in order to be able to measure the initial values of the rolling force P _about and the moment of rolling M _about in the last stand 4, necessary for further technological calculations; while for the front tension support its working value T ₁ ; the value of T ₁ consists of two components: the increment of tension on the winder T _m and tension (T ₁ -T _m ), which is developed by pulling rollers 5; the specified tension is 70 ... 80% of the total front tension T ₁ , i.e. its largest part, and therefore the tension (T ₁ -T _m ) is called the main front tension.

The rear T _about and the front T ₁ tension calculated respectively according to the formulas:

where: σ _so and σ _s1 are the yield strength of the roll in kgf / mm ² , respectively, at the inlet and outlet of the rolls of the last stand 4;

h ₀ and h _to - the thickness of the rolled 10 and tape 11 in mm, respectively;

c - roll width in mm.

And if the set value of the front tension T _{1 is} adjusted according to the current of the electric motors in the drives of the pulling rollers 5 and winders 7 or 8, then the value of the back tension T _{0 is} adjusted as follows.

At the end of rolling the front end of the tape 11, at which the back tension T _{0 was} maintained equal to zero, the rotation speed of the rolls of the last stand 4 is gradually raised until the total rolling moment on the rolls of this stand increases from the initial value M ₀ to the working value M ₁ ; the latter is calculated by the formula:

where M ₀ and P ₀ are the initial values of the force and rolling moment in kgf, respectively, and kgf mm, measured during rolling of the front end of the tape 11 in the last stand 4 without rear tension;

σ _so - yield strength of the roll in kgf / mm ² at the exit from the rolls of the penultimate stand 3, calculated in accordance with the readings of the pyrometer 13;

D is the diameter in mm of the roll barrel in the last stand 4.

An increase in the rolling moment from M ₀ , measured in fact, to M ₁ , calculated by the formula (4), indicates that the rear tension has risen from zero to a value of T ₀ calculated by the formula (2); those. back tension is determined indirectly. This method turned out to be more accurate than direct measurement, since the thickness of the tackle h ₀ before the last stand 4 can reach 10 mm or more. With such a large thickness, the plastic component during the bending of the tape 11 on a tensorolic (not shown conventionally in Fig. 1), which measures the force of the rear tension, can reach 70 ... 80% of the measured force. Therefore, the measurement error will not be measured as a percentage, but in times.

The surface of the pulling rollers 5 is gummed with hard grades of rubber. Therefore, despite a sufficiently large absolute force N of pressing them against the tape 11 (it reaches 3000 kgf or more), the surface of the finished tape is not damaged for two reasons: firstly, due to the elastic flattening of the rubber “shirt”, a sufficiently large area of the mutual the contact of the rollers 5 and the tape 11; secondly, the relatively high coefficient of friction between the rubber and the metal of the tape allows you to limit the relative pressure of the rollers against the tape by their double ratio.

Particular attention is paid to the fact that the tape 11, which comes out of the rolls of the last stand 4, is strictly horizontal (or rather, it should be perpendicular to the vertical axis "O-O" connecting the centers of the rolls of stand 4 (see figure 1). Otherwise, the roll curvature will be replaced by the longitudinal curvature of the tape 11, which will be formed due to the asymmetry of the deformation zone of the tape in the rolls of the stand 4.

To maintain the indicated symmetry of the deformation zone at any given rolling moment, the horizontalness of the tape 11 exiting the rolls is supported as follows: for each revolution of the reel 7 or 8, it is lowered in plane-parallel mode exactly by an amount equal to the thickness of the wound tape.

For this reason, the winders 7 and 8 are installed with the possibility of plane-parallel movement of their drums in the vertical direction, i.e. arrows 17 and 18.

In order to simplify the design of the casting and rolling unit, the tape 11 in the interval between the last stand 4 and the pulling rollers 5, the tape 11 is not subjected to cooling. Instead, the condition was set that the cooling system in the interval between stands 3 and 4 should guarantee cooling of the tackle so that it enters the rolls of stand 4 with a temperature of 20 ... 40 ° C. To this end, the collector 15 is configured to control the flow rate of the process coolant.

But the main feature of the proposed casting and rolling unit is that in the spaces between stands 3 and 4, as well as between stand 4 and rollers 5, it operates in the correct stretching machine mode. As you know, the plastic tensile strain of the tape in machines of this type can reach 1.6 ... 1.8%. Therefore, upon reaching a predetermined value of the rolling moment M ₁ in stand 4 (and therefore a predetermined rear tension T ₀ ), both ratios of rotation frequencies: rolls of stands 3 and 4, as well as rolls of stand 4 and rollers 5 are kept constant constant with accuracy no worse less than ± (0.16 ... 0.18)% for each of both ratios. This requirement stems from the fact that the accuracy of maintaining the ratio of rotational speeds should be at least an order of magnitude less than the maximum possible plastic deformation, i.e. (1.6 ... 1.8)%: 10 = (0.16 ... 0.18)%.

For this purpose, the drive stands 3 and 4, as well as the pulling rollers 5 are made with a rigid electrical connection between each other according to the speed of the moving processed roll.

Thus, through the use of the proposed technical solution, the quality of the product is improved by obtaining it with ultra-high flatness (with a warp of not higher than 0.1 mm per linear meter), i.e. by one or two orders of magnitude than with conventional rolling of the tape under conditions of preparation in the penultimate stand of high-quality tackle for the last stand.

Claims (6)

1. A casting and rolling unit for the production of cold rolled sheets of aluminum and its alloys, comprising a casting machine and rolling stands with roll drives, pulling rollers, guillotine shears and two winders with drives installed after the last stand, with drives of the last and penultimate stand, pulling rollers and winders are electrically connected to each other to maintain a constant speed of the moving processed roll after reaching the specified value of the rolling moment, the winders are mounted with the possibility of a plane allelic drums move them in the vertical direction, and the working surfaces of the pinch rollers gummed. 2. The casting and rolling unit according to claim 1, characterized in that between the last and penultimate rolling stands there is a collector for supplying technological coolant to the tackle. 3. The casting and rolling unit according to claim 2, characterized in that the collector is mounted above the rolling stock. 4. The casting and rolling unit according to claim 1, characterized in that the guillotine shears are volatile. 5. The casting and rolling unit according to claim 1, characterized in that the working surfaces of the pulling rollers are gummed with rubber from hard grades. 6. The casting and rolling unit according to claim 1, characterized in that at the exit from the penultimate rolling stand, as well as at the entrance to the last rolling stand, meters of rolling temperature are installed.

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