RU2374032C2 - Ingot-forming equipment - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to continuous metal casting. Ingot-forming equipment of machinery for metal continuous casting contains external casing and copper bushing installed open separated by partitions for vertical channels with undependable supplying and withdrawal of cooling medium. Between external casing and copper bushing it is installed internal casing. On external and internal sides of copper bushing there are coated heat-insulating coatings, thickness of which is strictly increasing to bottom part of ingot-forming equipment. On internal side of copper bushing contacting to melt there are applied antiwear coatings of variable thickness. Internal casing is connected to external casing and copper bushing by rods from materials with different thermal conduction with heat-insulating wave-like coating of variable thickness at sections located in channels of cooling medium withdrawal. In rods there are implemented holes for hollow bushes. Between external and internal casings there are installed bearing sleeves centred by rods.

EFFECT: elimination of walls caving in of ingot-forming equipment, it is excluded boiling of cooling medium, it is reduced wear rate of ingot-forming equipment walls.

6 cl, 4 dwg

Description

The invention relates to metallurgy, in particular to continuous casting of metals, and can be used in the smelting of alloys, including high alloy, requiring controlled control of the intensity of heat removal from the crystallizing ingot, as well as for alloys with a wide range of temperatures of the beginning and end of crystallization.

Crystallizers of continuous metal casting machines are designed to remove heat from the melt and the initial formation of the outer layer - the crust of continuously cast billets.

Crystallizers for the continuous casting of steel are known, containing wall plates made of copper or its alloys and having wear-resistant and heat-resistant coatings on the working surfaces. In this case, the working surface of the wall plates is made with a regular microrelief, the ridges of which are oriented perpendicular to the direction of movement of the ingot. In fact, the working (cooling) area of the walls is 1.2-1.5 times larger than the nominal. The distance between the ridges of the microrelief is 0.3-2.0 mm, and the depth of the depressions increases with increasing distance from the meniscus of the metal in the mold from 20 to 200 microns. The microrelief on the surface of the copper wall of the mold is protected from wear by coating with a variable thickness.

The design of the mold allows to increase the cooling efficiency of the ingot due to the formation of a separating lubricating layer between the wearing surfaces of the plate-ingot, as well as to reduce friction losses (RF Patent No. 2141884 IPC B22D 11/04, published on November 27, 1999).

As a disadvantage of the mold, it should be noted that an increase in the surface area of its walls due to corrugation does not increase the actual contact area of the sleeve with the melt, since the metal does not flow into the recesses.

A known mold for continuous casting of metals, providing high quality cast bar, allowing to optimize heat removal from the bar, which is partially in the molten state. The mold is made with repeatedly repeating conical shaped cavity, open from two opposite sides. Moreover, the surface of the cavity from the side in contact with the cooler is made with at least one zone of material with a high coefficient of thermal conductivity. Cavities containing cavities with a triangular, trapezoidal or circular cross-section are located transverse to the casting direction. The distance between the middle of the recesses is 1-10 microns, that is, part of the surface of the cavity on the cooling side is made rough. The depressions themselves on the surface of the cavity, on the cooling side by cooling media, have various shapes and / or depths and are preferably located in the zone of greatest heat transfer (RF Patent No. 2171730 IPC B22D 11/04, published on 05.27.1998).

The disadvantage of a multicone mold is that the roughness turbulates only the coolant flows to a small extent and is not very significant, since the flow without turbulence is turbulized. In addition, the recesses create stagnant zones of the coolant and lead to its boiling, as well as the formation of scale, which reduces heat dissipation.

A known mold of continuous casting machines comprising a case with copper working walls, in which longitudinal channels are made for passing a cooling medium with a cross-sectional shape in the form of a trapezoid, with the large base of the trapezoid facing the working surface of the wall and directed parallel to it, and the width ratio the large base of the trapezoid to its height is 0.3 ÷ 3.0 and, in addition, longitudinal ribs are made on the surface of the channels. The use of a mold with such cooling channels provides a significant reduction in the maximum temperature of its working surface due to an increase in the heat sink intensity, a decrease in the level of temperature stresses that can lead to warping of the walls, and also due to a decrease in the scale deposition rate and an improvement in the cooling of the washed channel wall (RF Patent No. 2120347 IPC B22D 11/057, publ. 10/20/1998).

The disadvantage of this mold is that there is a frequency of changes in the intensity of heat removal along the perimeter of the mold and an increase in resistance to the flow of the cooler, as well as the formation of stagnant zones in the corners of the trapezoid, which leads to a distortion of the mold wall shape.

A device is known for intensifying cooling of a crystallizer of continuous casting of steel and alloys, which makes it possible to increase the productivity and durability of the mold by increasing the intensity of heat removal from the working walls of the mold. Cylindrical cooling channels are made in the working walls of the mold with elements inserted into them, which can rotate along their longitudinal axis when the coolant moves. Elements are made in the form of strips of rectangular shape, the thickness of which is correlated with the diameter of the circular opening of the channel. The bands are twisted along the longitudinal axis of the channels for a given number of revolutions necessary for maximum use of the cooling ability of the medium (RF Patent No. 2203150 IPC B22D 11/04, published on April 27, 2003).

The disadvantage of this mold is that an increase in the intensity of heat removal is achieved by reducing the volume of fluid circulating in the channel. For this reason, its temperature rises and can exceed the boiling point of the cooler, and again the problem of scale formation arises.

The closest analogue of the present invention is a mold containing a cooled sleeve for forming a narrow and wide faces of the workpiece, which is fastened to the body by means of bushings and bolts. Vertical and horizontal dividing partitions are attached to the bushings. In the case opposite each chamber formed by dividing partitions, windows with nozzles for supplying cooler from the collector are made. Along the perimeter of the liner there are vertical and horizontal ribs to relieve stress from the fasteners. The gap between the sleeve and the housing is regulated by the height of the bushings and ribs and is 0.04-0.10 fraction of the perimeter of the cavity. The design of the mold provides controlled cooling along its height and perimeter (USSR Author's Certificate No. 980936 IPC B22D 11/04, publ. 15.12. 1992 - prototype).

Along with the advantages of the mold in question, it has a number of disadvantages.

The separation of the mold with the help of both vertical and horizontal partitions does not allow a gradual change in the rates of heat removal along the height and perimeter of the mold. The necessary variations are made stepwise, which leads not only to sharp local temperature drops in the walls of the mold, but also to changes in the dimensions of its cavity and, as a result, to uncontrolled changes in the sizes of the continuously cast ingot and the appearance of internal stresses in the surface layers of the metal. The lack of the possibility of periodic and controlled changes in the rate of heat removal from the cooled surfaces to relieve accumulated stresses. The formation of scale in areas of intense heat removal from the surface of the mold. The outer mold housing was not used to accelerate heat removal. The formation of horizontal and longitudinal cracks of both the outer and inner layers of the metal in the continuously cast ingot remains possible. The likelihood of freezing of the continuously cast ingot in the areas of the mold with an increased temperature of its surface increases.

The tasks to which the invention is directed include expanding the assortment of continuously cast steels, in particular alloys with a wide range of crystallization temperatures (medium carbon, carbon, alloyed, including graphitized), reducing the pulling forces, stabilizing the size of continuously cast ingots, and reducing the probability of the formation of external and internal cracks and the probability of metal breakthroughs after the continuously cast ingot leaves the mold, as well as in the dispersion of the structures ingot ry.

The technical result of the invention is to eliminate the deflection of the walls of the mold, to exclude boiling of the cooling medium on the surfaces of the heat sink, to reduce the rate of wear of the walls of the mold and increase its service life.

The technical result is achieved by the fact that in the mold containing the casing and the copper sleeve installed with a gap separated by partitions into vertical channels with independent supply and removal of the cooling medium, according to the invention, an internal casing is additionally installed between the casing and the casing, while both casing and the casing are connected among themselves rods made of materials with different thermal conductivity, on the parts of which are located in the channels that divert the cooling medium, heat-insulating shaped coatings of variable thickness, the rods contain openings for accommodating hollow bushes in them, made with the possibility of movement along the axis of the rods, support bushes are installed between the outer and inner cases, centered by the rods, the sleeve is made with heat-insulating coatings, the thickness of which increases monotonically to the bottom of the mold as from the external and internal sides of the sleeve, and on the external side of the sleeve in contact with the melt, wear-resistant coatings of variable thickness are additionally applied us.

The copper base of the sleeve is made with a monotonous decrease in its thickness along the height of the mold. The ends of the rods are connected directly to the copper base of the sleeve. Differential thermocouples are placed in hollow bushings. At the outer ends of the rods are waveguides connected to an ultrasonic generator. Parts of the rods located in the outer casing are sealed.

The essence of the invention lies in the fact that the decrease in the intensity of the heat flux from the continuously cast ingot due to insulation is compensated by the increase in the actual contact surface of the cooling medium with the mold. Reducing the density of heat fluxes is achieved by applying insulation to the cooled surfaces of the rods and the surface of the liner in contact with the melt. Compensation for the decrease in the specific heat sink rate is carried out by increasing the total heat sink surface, which consists of non-heat-insulated sections of the inner mold body and heat-insulated rods attached to more heated sections of the liner.

The invention is illustrated by drawings, in which Fig. 1 schematically shows a vertical section of a mold, in Fig. 2 shows a horizontal section, in Fig. 3 is a diagram of a coating on a wall of a sleeve, in Fig. 4 is a diagram of an installation of rods in a mold.

The mold contains two cases - the outer 1 and the inner 2, a copper sleeve 3 (Figs. 1 and 2), heat-insulating metal, ceramic-metal or ceramic coatings 5 and 6 (Figs. 3 and 4) of variable thickness, increasing on its surface, on both sides from the top of the mold along the entire length of the sleeve. On the side of the sleeve in contact with the cooling medium, additionally 4 coatings are applied periodically (wave-like) of variable thickness and length (Fig. 3), consisting of layers of textolite, faolite or other materials with a thermal conductivity not exceeding 2 watts / mK. On the heat-insulating coating 6 is applied protective wear-resistant coating layers, for example, of titanium carbide 7 and titanium nitride 8 (figure 3). Both cases 1, 2 and sleeve 3 are interconnected by rods 9 made of copper, bronze or brass, cooled by a medium supplied and discharged through vertical channels 10 and 11, respectively. Parts of the rods 9 located in the outlet channels 11 are covered with wave-like heat-insulating coatings 12 of variable thickness. Vertical partitions 13 and 14, forming channels 10 and 11, separate the rods from each other and are located between the outer 1 and inner 2 cases, and also between the case 2 and the sleeve 3. The ends 15 of the rods 9 are connected directly to the copper component 16 of the sleeve 3. Support 4, the steel sleeves 17 shown in FIG. 4, centered by the rods 9, fix the gap between the outer case 1 and the inner case 2. Hollow sleeves 18 (FIG. 4) are located in the holes of the rods 9, in which the sheathed thermocouples are placed 19. The rods 9, coming out of the outer corp the whisker 1, through a waveguide 20 connected to an ultrasonic generator 21. Sealing the outer casing of the mold is carried out by a stopper 22 with a rubber or teflon seal 23.

The proposed mold (see figure 1) works as follows. First, the cooling medium enters the external channels 10, between the housing 1 and 2, which removes heat from the walls of the inner case 2. Next, the cooling medium enters the gap with the channels 11 located between the wall of the inner case 2 and the sleeve 3, where it is heated from the surfaces of the coated sleeve 4 and 5 from the rods 9, insulated with a layer 12, and from the inner case 2. As the cooling medium moves from the lower sections of the mold, the cooling medium heats up to a temperature of no higher than 100 ° C, i.e. not in boiling mode due to the large The reasons for the heat transfer surface, as well as due to restrictions on heat removal from the sleeve 3, covered with layers 4-7, and leaves the mold through the channels 11. The magnitude of the water flow through each of the channels is set in accordance with the temperature reached by the height of the mold by the position of the hollow bushings 17. An increase in the intensity of heat removal by the rods 9 from the copper base 16 of the sleeve is achieved by connecting the ends of the 15 rods to portions of the sleeve with an elevated temperature. The temperature control of the rods 9 is achieved by moving the hollow bushings 17 along the axis of the rods 9, after measuring the temperature with thermocouples 19 and changing the water flow through the channels 10 and 11. The deflection of the housing 2 relative to the housing 1 is eliminated by the installation of the supporting sleeves 16. In addition, an increase in heat transfer is achieved by supply ultrasonic energy to the ends of the rods 9 emerging from the outer casing 1 through the waveguide 20 from the generator 21

The proposed design of the mold allows you to adjust the surface temperature of the ingots and the thickness of the hardened layer. This is done by varying the flow rate of the coolers, choosing the values of thermal conductivity and the thickness of the insulating layers, which allows you to fix the specified size and shape of the continuously cast ingot. Due to this, the resulting thermal stresses in the hardened shell of the continuously cast ingot are removed and the formation of longitudinal and transverse cracks is prevented; it becomes possible to increase the rate of metal casting due to an increase in the average heat removal rate and the structure of crystallized steel is improved.

The achieved advantages of the new mold design are as follows:

- wall deflections are reduced by installing copper, bronze or brass rods of a given size in the gap between the mold sleeve and the inner case, limiting its displacements during heating;

- the shape of the continuously cast ingot is preserved by increasing the heat exchange surfaces with the cooling medium by the rods and the second mold body;

- it becomes possible to periodically change the intensity of the heat sink along the height of the mold and reduce the likelihood of breakthroughs of the hardened shell of the ingot;

- independent regulation of the flow of the cooling medium in each of the supply channels of the mold excludes its boiling;

- increases the service life of the sleeve due to the application of wear-resistant coatings;

- the use of energy of ultrasonic vibrations expands the possibilities of additional regulation of the intensity of heat removal;

- stabilization of the size of the “crust” formed in the mold expands the possibilities of subsequent control of the ingot structure by pulsed continuous crystallization (INCO) both in the mold and in the secondary cooling zone [RF patent No. 2101129, priority date 26.09.1996].

Claims (6)

1. The mold of a continuous metal casting machine, comprising an outer casing and a copper sleeve installed with a gap separated by partitions into vertical channels with independent inlet and outlet of a cooling medium, characterized in that it further comprises an inner casing installed between the outer casing and the copper sleeve and connected with them by means of rods made of material with different thermal conductivity, with holes for accommodating hollow bushings in them, made with the possibility of moving along the axis of the rod, with supporting sleeves centered between the rods installed between the outer and inner cases, the rods are made with a heat-insulating wave-like coating of variable thickness deposited on sections located in the channels of the cooling medium, the copper sleeve is made with heat-insulating coatings on the outside and inside, the thickness of which monotonously increases to the bottom of the mold, and on the inner side of the copper sleeve in contact with the melt, wear-resistant coatings are additionally applied belt thickness. 2. The mold according to claim 1, characterized in that the copper sleeve is made with a monotonous decrease in thickness along the height of the mold. 3. The mold according to claim 1, characterized in that the rods are connected with their ends directly to the copper sleeve. 4. The mold according to claim 1, characterized in that it is equipped with differential thermocouples placed in hollow bushings. 5. The mold according to claim 1 or 3, characterized in that it is equipped with an ultrasonic generator with waveguides connected to the outer ends of the rods. 6. The mold according to claim 1 or 3, characterized in that the rods located on the site in the outer casing are sealed.

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