RU2368456C2 - Method of continuous casting and rolling of metals - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method includes pouring of different metals or alloys into different tanks, in which there are submerged rollers, and receiving after rolling of compound bimetal sheet. Into area of connection of two sheets, over meniscus of liquid metal it is supplied inert gas.

EFFECT: hardening of connection of layers in bimetal sheet.

9 dwg, 1 ex

Description

The invention relates to metallurgy, and more particularly to methods of continuous casting - rolling of metals in a combined process in order to obtain mainly metal sheets directly from its liquid phase.

A known method of continuous casting with a mold in the form of a cooled roll, see Germany patent No. 2419373, MKI B22D 11/01, 1977. The roll is made with a rim immersed in molten liquid metal, and crystallization occurs on this surface.

However, the dimensional accuracy of the obtained ingot is very low, which makes it difficult to obtain high-quality metal.

There is also known a method X. Christophenes casting metal with feeding it into rotating rolls, see US patent No. 4811781, MKI B22D 11/06 (NKI 104-480) from 1988. In this method, molten metal is fed into the rotating rolls through a special mouthpiece. Due to the difficult operating conditions, the mouthpiece has to be made by molding from SiO ₂ boron powders and aluminosilicate fibers, followed by sintering at high temperatures.

The cost of such mouthpieces is very high, and the reliability in the production of thin sheets is low. When casting and rolling sheets with a thickness of 5-6 mm and smaller holes, they often “freeze”, it is very difficult to maintain the metal level and process stops and accidents often occur.

There is also known a method according to Japanese patent No. 1-57954, MKI B22D 11/00, which provides for the immersion of the rolls in a bath with liquid metal and crystallization of metal on them. However, crystallization also occurs on the end surfaces of the roll barrels, due to which it is not possible to obtain a sheet of rectangular section.

The closest analogue of this method is the method according to Japan patent 1-224147 (A) (Appl. No. 63-50851), MKI B22D 11/06. According to the patent, a container with liquid metal is placed under the metal receiver and liquid metal is supplied from it to the metal receiver. Two rotating rolls are immersed in this metal, on which crystallization of the metal takes place. The resulting two tapes are combined and subjected to joint rolling in a second pair of rolls.

This method provides the advantage that the complex problem of feeding liquid metal into a narrow roll gap and controlling the level of liquid metal in said gap is eliminated.

However, the reliability of the process remains low, since when two rolls are immersed in a liquid metal, the crystallization of the metal occurs not only on cylindrical barrels, but also on their end surfaces. Therefore, we get not a sheet of rectangular section, but a profile in the form close to the channel, and after connecting two profiles - a section close to the I-beam. To avoid large losses of metal, it is necessary to use plates of refractory material pressed against the rolls at the ends. Under conditions of high temperatures and friction, the resistance of these plates is low, they often fail and the reliability of the casting-rolling process is low.

A device designed to implement the method is illustrated by the drawings according to figures 1-9.

Figure 1 shows a diagram of the device and the implementation of the continuous casting and rolling method, and figure 2 is a diagram of the connection of two crystallization fronts formed from the surfaces of both rolls.

Figure 3 shows one of the rolls with a metal section hardened on its surface. Figures 4 and 5 show sections B-B and A-A along the cross section of the roll and the hardened metal section.

In Fig.6 shows a diagram of the unit, designed to implement the method, and Fig.7 - the location of two sections of hardened metal on the rolls and the boundary of the liquid phase. Fig. 8 shows a metal detector mounted on support rollers, and Fig. 9 shows a metal detector made of two different containers into which various metals or alloys are poured, and then crystallization of various metals (alloys) takes place on each roll. The following notation is used here: 1 and 2 — rolls that play the role of both crystallizers and tools that carry out plastic deformation of hardened metal.

On the conical sections of the roll barrels (and along the edges of the cylindrical sections) there are rings 3, 4 of refractory materials with low thermal conductivity. The rolls are partially immersed in liquid metal 5 located in the metal receiver 6.

On the rolls during their rotation, metal sections 7, 8 harden, which, after their joining and rolling, form a sheet 9.

The roll 1 consists of an axis 10 and a band 11, between which along the longitudinal grooves 12 there passes water (cooler) entering through the hole 13 along the axis of the roll, and then through the radial holes 14. The cooler is discharged through the radial holes 15 and channel 16. Through nozzles 17, an inert gas is supplied to the junction zone of two hardened metal sections.

The rolls are installed in the bearing bearings 18, and through the spindles 19 and gearbox 20 they are driven into rotation by the engine 21.

Through pipes 22 and 23, water is supplied and discharged through axial holes in the rolls.

The metal receiver is mounted to rotate on the rollers 24. Through the gears 25 and 26, as well as the gearbox 27, the rotation is carried out by the engine 28.

When casting a bimetallic ingot into a metal receiver, consisting of two containers 29 and 30, separated by a wall 31, two liquid metals or alloys 32 and 33 are located, and therefore the bimetallic ingot consists of metals 34 and 35.

Here is the operational description of the method. The first operation consists in preparing the metal receiver, drying its lining, and heating it to cast steel to at least 1200 ° C.

The second operation consists in pouring liquid metal from the furnace into the metal receiver. Next, we implement the third operation, bring the rolls 1 and 2 into rotation and immerse them in liquid metal, Figs. 1, 2.

On each of the water-cooled rolls 1, 2 there are cylindrical sections of roll barrels and conical sections. Bandages 3 and 4 of refractory material are put on the edges of the barrels. The rolls are immersed in the molten metal 5 located in the metal receiver 6, so that the meniscus plane of the molten metal 5 intersects the conical sections of the barrel and is located below the end surfaces of the roll barrels.

The angles of the conical surfaces (horizontal) should be equal to 20-35 ° C, which provides the possibility of rolling the profile and at the same time the ability to easily adjust the level of liquid metal.

It is a sign that the end surfaces “C”, FIGS. 1, 2, are above the level of the meniscus ensures that no metal crystallization occurs on the end surfaces. Such crystallization would impede the implementation of the process.

Since the end surfaces of the rolls “C” are not in contact with the molten metal 5, no mechanical seals are needed.

The crystallization scheme is visible in figure 2, and it is symmetrical about the x axis, and the crystallization front is perpendicular to the y axis. The cross section of the ingot in figure 2 is shaded, and the connection of the crystallization fronts of two sections of the solid phase 7 and 8 occurs on the x axis. A completely hardened ingot 9 moves upward from the rolls. Annular bandages 3 and 4 of refractory material with low thermal conductivity prevent crystallization at the sites of contact of these bandages with liquid metal. If there were no bandages made of a material with low thermal conductivity, and the rolls on the entire surface were made of cooled metal, then the cross-sectional shape of the sheet 9 would be as dashed as shown in Fig. 2. In this case, the side trim after rolling would be much higher.

Therefore, the distinguishing features of this operation are the immersion of the rolls in the molten metal so that the plane of the meniscus of the melt intersects only the conical sections of the rolls (but not the end surfaces of the barrel), ensure the formation of the ingot only from the surfaces of the barrel rolls (sections of solid phase 7 and 8).

The rolls consist of axes 10 and bandages 11 (Figs. 3, 4, 5), and along the longitudinal grooves 12 a cooler moves - water entering through hole 13, radial holes 14. Water is discharged through radial holes 15 and axial 16. Through nozzles 17 during the implementation of this operation, an inert gas, for example argon, is supplied to prevent oxidation of the metal.

The rollers rotate in the bearing bearings 18, and their drive through the spindles 19 and the gearbox 20 is carried out by electric motors 21, Fig.6. The drive can be individual (for each roll - a separate engine) or general: with one electric motor 21 and gear cage, providing torque transmission to both rolls.

The position of the meniscus level can be characterized by the angle α ₁ , and the position of the end of the crystallization zone by the angle α ₂ , see Fig. 7.

If α ₂ ≥ α ₁ , then over the entire arc from α ₁ to α _{2 there} is a contact of the surface of the roll with liquid metal.

When the radius of the roll R and its angular velocity ω, the solidification time during the joint movement of the roll with the bandage 11 (Fig.7) and the section of solid metal 7 will be equal to:

where v is the peripheral speed of the rolls v = ωR. During this time, the thickness of the crust will be δ (τ).

To determine δ (τ) we take the formula:

,

,

where x ₀ and k are the values for a given metal or alloy, see Brovman M.Ya., Tsarev A.V. "On the issue of crystallization of steel ingots." // Metals. 1997. No4. S.44-48.

(45°). Тогда по формуле (1):Let it be necessary to obtain steel sheets with a thickness of h = 1.5 mm, R = 0.5 m, v = 60 m / min = 1 m / s,

(45 °). Then by the formula (1):

According to the formula (2) at k = 0.8 * 10 ^-5 m ² / s; x ₀ = 6 * 10 ^-3 m

The double thickness (the same layer crystallizes on the second roll) has an approximate thickness h ₀ ≈ 2 × 10 ^-3 , and after crystallization is completed and a single sheet 9 is formed, its plastic deformation occurs. The degree of deformation will be:

This degree of deformation will ensure the study of the cast structure, the reduction of porosity and the production of high quality sheets. Performance will be

here ρ is the density of the metal, b is the sheet width, taken equal to b = 1.5 m. Hourly productivity G = 60.75 t / h, and with the number of working hours in a year of 7000, annual productivity will be G≈425 thousand tons.

One pair of rolls with a diameter of 1 meter will provide metal mini-plant with a capacity of 425 thousand tons.

Six similar streams can ensure the release of a sheet in the amount of 2.5 million tons per year.

If, during the movement of the sections of the crust of the ingot 7 and 8, the meniscus level is reached, the metal “leaves” the liquid phase, and the combination of these two sections and their joint plastic deformation by rolling starts above the meniscus level. In view of this, an important feature of the method is that inert gas, for example argon, is supplied to the junction of two sheets above the meniscus by means of a nozzle 17, FIG. 3.

This prevents the oxidation of internal surfaces, provides high continuity and quality of sheet metal.

In the process of implementing the third operation, in which crystallization of the metal and its plastic deformation of rolling occurs, it is necessary to adjust the level of liquid metal 5 in the metal receiver 6 (to keep it constant). You can do this by continuous casting of metal, as shown in Fig.7.

But it is possible, especially with a smelting mass of not more than 50 tons, to pour all the smelting into the metal receiver 6, and then adjust the level by turning the metal receiver relative to a certain axis O parallel to the axes of the work rolls, as shown in Fig. 8.

The thickness of the lining is not constant, corresponding to a constant value of Ro, but changes so that when turning counterclockwise, Fig. 8, the boundary of the lining changes, and this leads to an increase in the melt level 5 (the position of the boundary of the lining EF after rotation in Fig. 8 shows dotted line).

The implementation of the method with pouring all the heat from the furnace into the metal receiver and subsequent casting of the metal by turning the metal receiver eliminates the use of casting ladles. For steel, this means the ability to reduce the overheating of liquid metal by 80-100 ° C and get savings on every ton of steel.

those. E = 60.8 ÷ 76 MJ / t, where C = 760 J / kg × deg - heat capacity, Δt - steel overheating temperature.

Reducing overheating will reduce the melting time of the metal and wear of the furnace lining (i.e., increase its durability).

When casting bimetallic ingots, each of the rolls 1 and 2 is immersed in different containers 32 and 33, into which various metals or alloys are filled.

The metal detector can be made with a common base 30 and with a partition 31 dividing the metal detector into various containers. After hardening and rolling, we obtain a sheet consisting of two metals or alloys, indicated in Fig. 9 by positions 34 and 35.

The method provides a tight connection of different alloys, metals immediately after solidification and their joint plastic deformation, which allows you to reliably obtain a bimetallic sheet of high quality.

Above the rolls 1, 2 can be located additional pairs of rolls in the stands of the duo or quarto for further rolling of the sheet and subsequent cutting, dressing or reeling into rolls.

The last fourth operation is the end of the process of metal crystallization on the rolls and its rolling when the meniscus level of the melt is lowered and the residual metal and slag are drained through the holes in the bottom of the metal receiver into the provided tank (it should also function as an emergency tank during casting).

We give a specific example of the implementation of the method.

и радиусы обоих валков R=0,5 м. Валки выполнены со стальными осями и бандажами из бронзы.We take the angles α ₁ and α ₂ equal to

and the radii of both rolls R = 0.5 m. The rolls are made with steel axles and bronze bandages.

. Согласно формуле (1) время контакта поверхностей валков с жидким металлом составит:Let the casting speed be equal to v = 0.8 m / s = 48 m / min, and the angular velocity of the rolls

. According to the formula (1), the contact time of the surfaces of the rolls with liquid metal is:

The bimetallic sheet is casted, and carbon steel 33 is poured into the container 29, Fig. 9, and 1X18H9T steel, indicated by 32, into the container 30. The tanks are separated by a partition 31. For carbon steel according to the formula (2) with k = 0.8 × 10 ^-5 m ² / s, x ₀ = 6 × 10 ^-3 m we get:

For stainless steel with k = 0.6 × 10 ^-5 m ² / s, x ₀ = 6 × 10 ^-3 m we get:

; а степень деформации:The total thickness will be 2.3 × 10 ^-3 m, and when it is compressed to a thickness h = 1.5 × 10 ^-3 m, the drawing coefficient will be

; and the degree of deformation:

Such a high degree of deformation will ensure the study of the cast structure, elimination of porosity in the central zone of the ingot and tight connection of sheets 34 and 35. The area of their connection is blown with argon from nozzle 17 to reduce metal oxidation.

With a sheet width of b = 2 meters, the productivity will be:

or 64.8 t / h. With the number of working hours per year equal to 7000, an annual output of 453 thousand tons of bimetal will be provided (with one stream).

The method of continuous casting and rolling of metals provides increased process reliability and the following advantages.

1. The complex problem of feeding liquid metal into rolls is solved with a small roll gap (1-5 mm). No need to use nozzles, funnels for the distribution of liquid metal across the width of the sheet.

2. The difficult problem of controlling the level of metal in a roll mold for casting sheets with a thickness of 1-6 mm disappears. There is no need to use systems with radioactive isotopes. The level of liquid metal in a metal receiver measuring several meters is easy to adjust.

3. The length of the casting - rolling zone is increased, which makes it possible to increase the casting speed and productivity.

4. The complex problem associated with the manufacture and operation of end plates from refractory material is being solved (now it is their durability that limits the operating time of combined roller units). When using this method, there is no need to use these end plates.

5. The possibility of breaking through the ingot crust under the mold is eliminated, and the reliability of the unit increases.

6. It is possible to exclude the casting ladle from the technological cycle by pouring liquid metal from the furnace directly into the metal receiver, and then turning the metal receiver to adjust the liquid metal level in it. For steel, this means reducing its heating by 80-100 ° C and saving up to 70 MJ of energy per ton of steel ingot.

7. The method provides the possibility of obtaining a bimetallic ingot from two melts of various metals or alloys with their joint plastic deformation.

Claims (1)

A method of continuous casting and rolling of metals to obtain, after rolling, a composite bimetallic sheet, comprising pouring various metals or alloys into different containers and immersing rolls into them, characterized in that an inert gas is fed into the junction zone of two sheets crystallized on the rolls above the meniscus of the liquid metal.

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