RU2466807C1 - Casting-rollersersing plant for sheet hot rollersersing 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, pressure rollers and sheet stacker. Note here that withdrawal roller drives roller drives of last and penultimate stands are electrically interconnected to maintain invariable roller rpm-to-breakdown feed speed ratio for continuous sheet stacking. Note also that withdrawal roller working surfaces are gummed.

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

10 cl, 2 dwg, 1 tbl

Description

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

A well-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. Moscow: Metallurgizdat, 1961. Pages 144-145).

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 well-known foundry unit for the production of hot-rolled tapes of aluminum and its alloys, including continuous casting of a billet from a melt, hot rolling of a billet into a finished tape and its winding into a riot (see, for example, V. A. Chebotarev and V. A. Samsonov. Liteyno Rolling units 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.

The disadvantage of this method is the occurrence of a roll curvature of the tape in the process of winding it on the reel drum, which leads to non-flatness of the tape.

The technical result of the invention is to improve the quality of products by obtaining its ultra-high flatness (with a warp of not higher than 0.1 mm per linear meter) when rolling a hot-rolled strip, followed by its division into cards or sheets.

This technical result is achieved by using a casting and rolling unit for the production of hot-rolled sheet products from aluminum and its alloys, including a casting machine and rolling stands with drives, pulling rollers with a drive, pinch rollers and a cassette device for stacking sheets in packs, the drive of the last two rolling stands and pulling rollers are made with electrical communication with each other according to the speed of movement of the processed roll; between the last stand and the pulling rollers there is a collector mounted above the roll, the pulling rollers mounted with the possibility of longitudinal movement along the axis of the casting and rolling unit, and the rollers themselves are gummed with heat-resistant hard rubber; the guillotine shears are volatile, and the cassette device is made up of two independent cassettes, rigidly interconnected, with the longitudinal axis passing through both cassettes being perpendicular to the axis of the casting and rolling unit, both cassettes have the freedom of joint movement along their longitudinal axis, and along pyrometers are installed on the axis of the unit: at the entrance to the last stand and pulling rollers, as well as at the exit from the penultimate and last stand.

The proposed technical solution allows to obtain 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 penultimate stands, 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 of the yield strength of the tape, which is much more than with 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 the cutting of a hot-rolled tape, which is in a straight-line state, on separate cards (without winding it in riots), this eliminates the appearance of roll curvature;

- 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 essence of the proposed technical solution is clear from the following drawings, which depict a diagram of a casting and rolling unit, where: Fig. 1 shows a side view of the casting and rolling unit, and Fig. 2 shows a cross section along the cassette device of the casting and rolling unit (" AA "in figure 1).

Capacity 1 for liquid aluminum is installed in front of the casting machine 2 with a drive, which is not conventionally shown in Fig. 1. Behind the machine 2, a first hot-rolling mill stand 3 is installed, and then a second hot-rolling mill stand 4 with drives, which are not conventionally shown in FIG. hereinafter referred to as the penultimate 3 and last 4 rolling stands, since there can be not two rolling stands, but three and even more.

At the exit from the last stand 4, successively installed: pulling rollers 5 with a drive (not shown conventionally in figure 1), guillotine shears 6, pinch rollers 7 and cassette device 8 for stacking sheets in bundles.

Along the entire line of the casting and rolling unit, up to scissors 6, there is a continuously machined roll: a continuously cast billet 9, a tackle 10 and a finished tape 11.

In the spaces between the casting machine 2 and stand 3, between stands 3 and 4, and also between stand 4 and pulling rollers 5, temperature meters (pyrometers) 12, 13, 14, 15 and 16 are installed, and in the gap between stand 4 and rollers 5, an additional collector 17 is installed.

The molten aluminum from the tank 1 is fed to a casting machine 2, on the rolls of which a continuously cast billet 9 is formed. After the crystallization process is completed, the billet 9 in the form of a solid enters the penultimate stand 3, where a tack 10 is formed from the billet 9, having a thickness h _o . The latter in the hot state enters the last stand 4, from which it comes out in the form of a finished tape 11 having a thickness h _k , under tension T ₁ , which is created by the pulling rollers 5.

The finished tape 11, having a rectilinear shape in the longitudinal direction, enters the guillotine shears 6, in which the tape 11 is divided into separate sheets (cards) 18. Separated from the continuously rolled tape 11, they are fed into the cassette device 8 with pinch rollers 7 where they are stacked in a pack.

At the beginning of the casting-rolling process, i.e. at the front end of the roll, the rear tension T ₀ in the last stand 4 is maintained close to zero. This is necessary in order to be able to experimentally fix the initial values of the rolling force P ₀ and torque M ₀ on the rolls of the last stand 4, while the front tension is given the working value T ₁ from the very beginning.

Then, the rotation speed of the rolls of the last stand is increased at a constant speed of rotation of the rolls of the penultimate stand 3 until the back tension increases from zero to a value of T ₀ = 0.67 σ _so (in · h ₀ ), where σ _so and h ₀ are the yield strength the roll and its thickness at the exit of the rolls of the stand 3; in - the width of the roll.

The value of T _{0 is} determined indirectly, by increasing the torque on the roll of the last stand 4; the increase in the speed of rotation of the rolls of this stand is stopped when the moment reaches the value of M ₁ , which is determined on the formula below (7).

The front tension T _{1 is} created by the drive of the pulling rollers 5 due to their pressing against the tape 11 with a force N equal to twice the tension T ₁ .

The proposed casting and rolling unit for the production of sheets with ultra-high flatness is based on the process of straightening the tackle 10 with a tensile force T ₀ , which is developed in the area between stands 3 and 4. In order to avoid tearing off the tack, the force T _{0 is} controlled not by its value, but by the value of plastic deformation rolled, which is supported with high accuracy. To this end, the ratio of the frequency of rotation of the rolls of stands 3 and 4, as well as stand 4 and pulling rollers 5 is kept constant with high accuracy. A similar pattern occurs in the area between stand 4 and rollers 5.

Coolant is supplied to the rolled strip 11 from the collector 17. The primary removal of this liquid from the surface of the finished tape is carried out by squeezing it by the pulling rollers 5, and the second by natural evaporation of the liquid followed by drying of the tape due to the internal heat contained in the tape 11, t .e. without additional supply of heat from the outside.

For this purpose, the temperature of the tape at the exit of the rollers 5 is maintained in the range of 120 ... 130 ° C. At a higher temperature, the rubber decomposes on the surface of the gummed rollers 5. At a lower temperature, the heat supply in the tape 11 will not be sufficient for the natural evaporation and drying of the tape 11 after it leaves the rollers 5.

And since the rolling speed in the stand 4 and the thickness h _{to the} finished tape 11 varies from order to order, the duration of cooling of the tape should also change. For this purpose, change the length of the section "S", limited from the rear side by the rolls of the stand 4, and from the front by the rollers 5; it is along the length of the indicated section that coolant is supplied to the tape 11.

To change the length "S", the pulling rollers 5 are moved along the casting and rolling unit in the longitudinal direction.

In the following numerical example of the principle of operation of the proposed unit, the tackle 10 before the last stand 4, the tackle has a thickness h ₀ = 4 mm, and the finished tape 11 and individual sheets 18 have a thickness h _k = 2 mm; the diameter of the rolls of rolling stands 3 and 4 is equal to D = 300 mm (see figure 1). The tension of the tape 11 at the exit of this stand is equal to T ₀ = 1333 kgf and T ₁ = 950 kgf, respectively; rolling forces in stand 4: at T ₀ = 0 we have P = 60,000 kgf, and at T ₀ = 1333 kgf we have P ₀ = 56,500 kgf, respectively, and the torques on the rolls of stand 4 are M ₀ = 860000 kgf · mm and M ₁ = 970000 kgf · mm; N is the pressure force of the rollers 5 to the tape 11 is N = 2800 kgf.

Roll temperature t _p :

Under pyrometer No. 12 13 fourteen fifteen 16 t _p , ° C t ₂ = 500 t ₃ = 400 t ₃ = 350 t ₄ = 300 t ₅ = 125

The average length of the irrigation section of the belt 11 is S = 2.5 m. The rolling speed in stand 4 is V ₄ = 0.067 m / s. The width of the tape 11 is equal to = 200 mm

Obtaining the required front tension T _{1 is} provided by creating the appropriate torque on the drive necks of the pulling rollers and does not cause any problems. And to obtain the required rear tension T _{0 it is} necessary to operate with the moment of rolling M ₁ in the last stand.

For this, as indicated at the beginning, the force P ₀ and the rolling moment M ₀ , which occur at the front end of the tape when rolling in the last stand without back tension, are measured. Then find the experimental values:

- average specific pressure in the deformation zone without back tension:

where F _p = (in · l) is the contact area of the roll with the rolled tape;

l is the length of the capture arc;

- the coefficient of the shoulder application of the rolling force

The average specific pressure in the deformation zone with rear tension:

Steady-state rolling moment:

M ₁ = 2 (P ₀ / F _p -σ _s0 / 2) · F _p · lM ₀ / (2P ₀ l) + 0,67σ _s0 (b ₀ ) (D / 2)

Finally we get the working formula:

; F₀=вh₀ Where

; F ₀ = Bh ₀

To ensure the principle of operation of the casting and rolling unit described above, the following conditions must be met.

When switching to the stationary rolling process, in order to avoid breaks in the roll between the penultimate and last stands, as well as between the last stand and the pulling rollers, the ratios of the rotation frequency of the rolls and the pulling rollers are kept constant with an error of not less than ± (0.16 ... 0.18% ) Such a hard range is determined based on the practice of correct stretching machines, when the plastic elongation of the ruling tape by 1.6 ... 1.8% still does not lead to tape breaks, and the accuracy of maintaining this value should be an order of magnitude higher, i.e. the above ± (0.16 ... 0.18)%.

For this purpose, the drives of the last two rolling stands 3 and 4 and the pulling rollers 5 are made with electrical communication with each other according to the speed of movement of the processed roll.

The pulling rollers 5 have work surfaces gummed with heat-resistant rubber of hard grades.

, а полную ширину этой площадки этой площадки имеет равной 2в_сп=22 мм.To obtain a front tension force equal to T ₁ = 0.67 · 3.5 (3 · 200) = 1400 kgf, the clamping force of the rollers 5 to the belt 11 should be N = 2 · 1400 = 2800 kgf. Then for 1 mm of the width of the tape in = 200 mm there is a linear force of 14 kgf / mm. When the diameter of the roller D _p = 500 mm, lined with a jacket made of heat-resistant rubber, the elastic flattening of this shirt will be δ = 0.5 mm. Half the width of the flattening pad is

, and the full width of this site of this site is 2c _sp = 22 mm.

Then the average contact pressure is P _con = 14/22 = 0.64 kgf / mm ² or 64 kgf / cm ² , which is quite acceptable for hard grades of rubber.

Checking the stock by friction. Coefficient of friction of rubber on aluminum f = 0.35; the friction force on both pulling rollers T _Tr = 2Nf = 2 · 2800 · 0.35 = 1960 kgf or about 2000 kgf, and only T ₁ = 1400 kgf is needed; those. the required supply is T _Tr / T ₁ = 2000/1400 = 1.43 or 43%, which is quite enough.

Located between the last stand 4 and the pulling rollers 5, the collector 17 has the following features:

a) it is installed only on top of the roll 10; this is done in order to ensure favorable conditions for the operation of the pyrometers 15 and 16 installed under the peal 10 (at the exit of the last stand 4 and in front of the pulling rollers 5);

b) in order to simplify the supply system for the roll of process coolant, the collector 17 is made without controlling the flow of this fluid; the latter entails additional design requirements for the pulling rollers.

Therefore, the pulling rollers 5 have freedom of longitudinal movement along the axis of the casting and rolling unit. This is done so that in the absence of a coolant flow controller, the cooling intensity of the rolled strip 11 is controlled by the length (and therefore the area) of contact of the coolant with the tape 11.

When choosing the heat transfer coefficient for heat transfer from the tape 11 to the coolant, we can assume that for a liquid on a steam cushion it is equal to α = 100 kcal / (m ² · h · deg) - see the book AMLitvin. Theoretical foundations of heat engineering. Moscow-Leningrad: "Energy". 1964 p. 236 ... 238.

The heat flux density during heat transfer from the tape to the liquid is determined as q = α (t _liquid. -T _walls ). When t _fluid. = 60 ° С and _wall t = 210 ° С (average) we have q = 100 (210-60) = 15000 kcal / (m ² · h). At a speed of V = 4 m / min, the belt 11 passes in an hour the path L = 4 · 60 = 240 meters; the mass of the tape 11 of this length G _hour = 0.003 · 0.2 · 240 · 2.7 = 0.39 tons = 390 kg With such a mass and the required temperature difference Δt = 175 ° C, the amount of heat to be removed will be Q = G _hour · Δt · C _p = 390 · 175 · 0.11 = 7500 kcal, where C _p = 0.11 is the specific heat of aluminum .

As a result, the necessary contact area of the tape 11 with the coolant: F _c = Q / q = 7500/15000 = 0.5 m ² . Such a contact area can be provided on the length of the tape 11, equal to S = F _c / in = 0.5 / 0.2 = 2.5 m; it is at such a distance from the rolls of the stand 4 that the pulling rollers 5 should be located, working, in this case, as squeezing rollers; and for the operational adjustment of the temperature of the tape for each degree of temperature, the rollers 5 must be moved approximately 15 mm.

Guillotine shears 6 are made volatile. This is necessary in order to ensure the cutting of a continuous moving belt 11. For this purpose, the scissors 6 move synchronously with the moving belt 11, and after the next cut with an increased speed, they return to their original position.

The cassette device 8 is made double and consists of two independent cassettes, rigidly interconnected. This allows, without interrupting the continuous movement of the rolled strip 11, to change packs in which the cut sheets 18 are stacked.

For this purpose, the longitudinal axis passing through both cassettes 8 is located perpendicular to the axis of the casting and rolling unit, and the cassettes have the freedom of joint movement along their longitudinal axis.

This technical solution allows you to quickly remove from the axis of the casting and rolling unit a cassette filled with sheets, replacing it with an empty cassette from which the previous stack of sheets has already been removed. In this case, the movement of the cartridge from the central position to the extreme (left or right) should occur during the passage of the next sheet through the pulling rollers 5.

Roll temperature meters (pyrometers) are installed at least at the entrance to the last stand 4 and pulling rollers 5, as well as at the exit from the penultimate 3 and last 4 rolling stands; we are talking about pyrometers 13, 14, 15 and 16. In fact, there may be more pyrometers (for example, pyrometer 12 at the exit of the casting machine 2), but it is these four pyrometers that are necessary devices for the normal conduct of the process.

Thus, through the use of the proposed method, 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 (10)

1. A casting and rolling unit for the production of packaged hot rolled sheets of aluminum and its alloys, comprising a casting machine, rolling stands with roll drives, pulling rolls with a drive installed after the last rolling stand, guillotine shears, pinch rollers and a cassette stacker sheets in a pack, while the drives of the pulling rollers and the drives of the rolls of the last and penultimate rolling stands are electrically connected to each other to maintain a constant ratio of the rotational speeds of the said rolls velocity of roll processed for continuity of stacking sheets in a pack, wherein the working surfaces of the pinch rollers gummed. 2. The casting and rolling unit according to claim 1, characterized in that between the last stand and the pulling rollers there is a manifold for supplying the process 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 pulling rollers are mounted with the possibility of longitudinal movement along the axis of the casting and rolling unit. 5. The casting and rolling unit according to claim 1, characterized in that the guillotine shears are made volatile. 6. The casting and rolling unit according to claim 1, characterized in that the cassette device is made double and consists of two independent cassettes, rigidly interconnected. 7. The casting and rolling unit according to claim 6, characterized in that the longitudinal axis passing through both cassettes is perpendicular to the axis of the casting and rolling unit. 8. The casting and rolling unit according to claim 7, characterized in that both cassettes are mounted with the possibility of joint movement along their longitudinal axis. 9. The casting and rolling unit according to claim 1, characterized in that at least at the entrance to the last stand and to the pulling rollers, as well as at the exit from the penultimate and last stand, the gauges of rolling temperature — pyrometers — are installed. 10. The casting and rolling unit according to claim 1, characterized in that the working surfaces of the pulling rollers are gummed with heat-resistant hard rubber.

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