JPH0250822B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The object of the invention is a horizontal continuous casting apparatus for metals or alloys, in particular steel.

In horizontal continuous casting, the molten metal leaving the molten metal vessel reaches a horizontal continuous casting mold made of a thermally conductive metal and usually cooled with a cooling medium, where it begins to solidify from its surface as it is formed into a slab. . The solid slab solidified shell formed in this process is
The thickness increases while passing through the mold. However, this solidified shell is still relatively thin in normally cast metals or alloys after leaving the mold, so the drawn slab is still not stable for operations such as e.g. drawing from the mold. It's not enough. One or more recoolers are therefore provided downstream of the mold in the direction of movement of the slab, in which an increase in the thickness of the solidified shell which increases the strength of the slab takes place, so that the center The still molten slab can be captured by a slab withdrawal device, for example a pinch roll, without fear of damage and can be subsequently manipulated as desired.

In order to stabilize the strength of the slab after forming as quickly as possible, it has been found that ensuring uniform cooling around the perimeter of the slab in the mold is an important factor.

From the continuous casting of billets and blooms, it is known to increase the heat dissipation in the longitudinal direction of the slab by tapering the entire surface of the mold cavity, thus promoting the growth of the solidified shell. It is also described how to determine the taper of the mold, taking into account shrinkage, to improve heat dissipation and to achieve the effect of growing a solidified shell while reducing mold friction. Any mold dimensions that are initially optimally set may change during operation due to wear and/or distortion, e.g., a predetermined taper may be lost, or
Alternatively, a reverse taper may occur. Such unfavorable mold dimensions can lead to damage, such as cracking or breakage, of the cast slab.

Furthermore, it is known to take into account the differences in the carbon content of the steel and therefore with respect to heat dissipation and mold friction when modifying the taper of the mold.

In order to avoid damage to the mold due to wear and/or strain, it is common practice in practice to check the mold dimensions with a gauge when the equipment is shut down, but this requires expensive measurements.

European Patent Application No. 26487 describes a method for monitoring the condition of a mold during mold operation,
This method makes it possible to detect undesirable changes in mold dimensions and thus prevent the aforementioned slab damage, such as cracking or breakage.

In this method, the respective actual value of the cooling capacity of the mold is determined and compared with a setpoint value defined in relation to the carbon content of the steel to be molded and the residence time in the mold, and the actual value and this setpoint are compared. If the deviation between the values is too large, a detrimental change in the mold dimensions is confirmed. The necessary measures are then taken to ensure the desired quality of the slab. Although this known method allows early detection of slab damage caused by unfavorable mold dimensions, it does not take into account the modification or readjustment of the mold dimensions during operation.

European Patent Application No. 26390 describes a method for setting the displacement rate of the short sides of a plate mold in continuous casting of steel, in which the spacing of the short sides is varied to change the size during continuous casting operations. It's getting old. This displacement rate must be kept as low as possible in order to minimize the length of the transition point of the slab, i.e. the length of the slab section and the material loss between the already cast size and the new size to be cast. However, this may cause cross-sectional expansion and breakage of the slab.

In this method, the amount of heat extracted by the cooling medium at the short side of the mold during displacement is measured, and the amount of heat extracted is measured at such a rate that the amount of heat extracted does not fall below a predetermined value.
The short side is displaced. Setting the position of two sides other than the short side of the mold is not considered in both of these methods.

From German Patent Application No. 2415224, a method is known for controlling the cooling capacity of only the short walls of a plate mold in continuous casting, these short walls being clamped between the long walls. , before the start of casting, the casting cavity between the short walls is provided with a taper that becomes narrower in the direction of slab movement and is adapted to the steel quality and slab width. Before the start of casting, this taper is further set to a target value corresponding to a predetermined casting speed and/or casting temperature, and during the casting operation, if there is a deviation in the casting speed and/or casting temperature,
The taper is varied to a predetermined target value corresponding to these changing casting parameters.

All the known methods mentioned so far adapt the dimensions of the mold to the dimensional changes in the slab that occur or are expected due to changes in the casting parameters, quality of the metal or alloy, or due to desired cross-sectional changes in the slab. However, only the position of the short side wall of the plate mold is changed.

These methods do not take into account the other sides of the slab, nor do they take into account dimensional changes that occur in the slab due to subsequent cooling after leaving the forming mold, vibration processes that occur during that process, phase changes, etc. However, it is these processes that are important for the strength of the manufactured slab and the homogeneity and quality of the slab.

The known methods already mentioned therefore do not concern the condition of the slab or its treatment after leaving the mold. However, during the subsequent cooling in the recooler after leaving the forming mold, changes in the cross-section of the slab, usually a reduction in cross-section, occur, and these cross-sectional changes are quite non-uniform due to the phase changes that occur at different temperatures. , so that, despite cooling, for example, the dimensions remain unchanged in the middle.

In addition to molds that can adapt to changes in the cross-sectional dimensions of the slab in one direction, recooling devices for vertical and circular continuous casters have also become known, which spray a cooling medium (usually water) directly onto the slab. As a result, the slab is cooled.

For example, Austrian Patent No. 303987 describes such a device, in which the amount of cooling water sprayed onto the slab is controlled based on the surface temperature of the slab before it enters the recooler and after it leaves the recooler. is detected by a detector, and the detected data is processed in a central computer that controls the cooling water supply setting device.

A similar device is described in DE 193 2 884 A1, which provides for the control of various movements of an arc series device. Here, too, the amount of cooling water sprayed onto the slab is regulated by a recooling device which likewise operates according to the direct cooling principle. In the apparatus according to this published application, the control of the mold cooling capacity by controlling the amount of cooling medium flowing through the mold further includes a temperature detector and a flow rate detector for detecting the amount of heat extracted by the cooling medium. It is done using

In the last two recooling devices, the cooling medium is sprayed directly onto the slab, so even if the dimensional change of the slab due to cooling does not cause a problem, the direct contact between the cooling medium and the slab does not generate steam. This results in significant drawbacks such as non-uniform cooling and, in some cases, reactions between the metal and the cooling medium.

The object here is to provide a device which makes it possible, without direct contact with a cooling medium, to treat the slab, which, during its subsequent cooling leaving the mold, is brought into different individual conditions depending on the quality of its material. The present invention begins with.

In particular, it is an object of the present invention to achieve uniform cooling over the circumference of the slab and the formation of a solidified shell of uniform thickness over the circumference, thus achieving an optimal optimization of the produced slab depending on the alloy to be cast. The aim is to ensure stability and strength, so that damage or breakage is completely avoided during handling of the slab, especially during withdrawal, and a high material quality is obtained.

In order to solve this problem, a molten metal container, a horizontal mold connected to the molten metal container and cooled, and at least one recirculating mold installed after the mold and passed through a cooling medium to cool the slab coming out of the mold. According to the present invention, in a horizontal continuous casting apparatus having a cooler, a temperature detector for detecting the temperature of a cooling medium passed through the recooler, and a device for drawing out slabs, the recooler It is composed of a plurality of cooling elements that surround the slab to be processed and are divided along the periphery and have cooling surfaces that can be displaced in the radial direction relative to the center of the slab and that can come into contact with the slab. A radially displacing setting device is associated, and a control device is provided for controlling these setting devices, so that the radial position of the cooling element is set by the setting device in response to the output signal of the temperature sensor.

By means of the device according to the invention, the amount of heat released from the slab to the recooler can be individually set to a desired value on the main surface of the slab to be drawn and preferably in various parts in the longitudinal direction, and individual cooling can be carried out. The cooling capacity of the components can be matched to each other and to the requirements, finish and condition of the material being cast in each case.
It is therefore possible to carry out individually controlled cooling of the entire circumference and length of the slab, the result of which is, for example, uniform over the circumference of the slab and even and continuous in the direction of movement of the slab. This is manifested in the thickness of the solidified shell that increases. A slab with such a solidified shell that is uniform or uniformly thick can on the one hand be manipulated without danger, and on the other hand the finished slab obtained as a product is distinguished by a high reproducible homogeneity and quality. There is.

By individually controlling the pressing force of the individual cooling elements on the slab and/or by individually controlling the amount of cooling medium flowing through each cooling element, dimensional deviations in the slab may be eliminated. For example, even if the slab is slightly distorted or deflected after leaving the mold,
Uniform cooling over the circumference and thus the formation of a uniform solidified shell increasing in thickness uniformly in the longitudinal direction is ensured.

Controlling the pressing force of the individual cooling surfaces or cooling elements of the recooler in order to achieve uniform heat dissipation over the circumference of the slab can be carried out in practice, for example, as follows. That is, a temperature detector, such as a thermocouple, is provided at the coolant inlet and outlet of each cooling element, and a flow rate detector is preferably provided at the inlet and outlet of each cooling element. Measurement data obtained by these detectors of each cooling element, in particular data about the amount of cooling medium flowing through the cooling element per unit time and the temperature difference between the inlet and the outlet of the respective cooling element. are supplied to a central control unit, and from these data the control unit calculates the amount of heat extracted by the individual cooling elements, e.g. and compared with the stored target output data of the individual cooling elements of the recooling device. With the deviation data obtained from the comparison, the pressing force of the individual cooling elements on the slab and/or the amount of cooling medium flowing through these elements per unit time can be varied and adjusted in advance according to the metal or alloy to be cast. To obtain a stored desired value of cooling capacity.

In a preferred embodiment of the device according to the invention, the amount of heat extracted from each cooling element by the cooling medium is
Each is compared with target values set separately if possible, and if the actual value deviates from the predetermined target value,
By displacing the individual cooling elements by means of a setting device, the pressing force of these cooling elements acting on the respective slab surface and/or the flow rate of the cooling medium through the individual cooling elements reach the target value. will be changed up to.

In the device according to the invention, the control device is preferably formed by a computer or a microprocessor with data and program storage. The controller is easily integrated into existing large data processing and conversion equipment.

When withdrawing the slab with vibration, each cooling element undergoes a specific cooling program for each step, which adjusts the pressing force or the flow rate of the cooling medium as a function of time according to predetermined characteristics. Control. The use of microprocessors is likewise advantageous for such minute steps.

Preferably, the setting device for changing the position of the cooling element or the mechanism for adjusting the flow rate of the cooling medium is provided with a digitally controllable DC motor that operates stepwise. This direct current motor allows a particularly precise setting of the setting device. Other setting devices for adjusting the pressing force of the cooling element on the slab surface include, for example, a hydraulic operating element, an induction coil, and the like.

If it is considered to adjust and match the cooling capacity of the individual cooling elements with respect to the flow rate of the cooling medium, the setting device may be a flow regulator such as a valve, spool, etc. installed at the inlet or outlet of the cooling element. connected to the mechanism. Push force and cooling medium velocity can likewise be used in combination with each other to adjust and harmonize the cooling capacity of the individual cooling elements of each recooler. This has the advantage that if one of both devices fails, the healthy device can continue operating without interruption.

According to a special embodiment, the cooling elements of the recooler that are arranged above the axial horizontal plane with respect to the slab operate with a higher pressing force and/or a higher cooling medium flow rate than the cooling elements that are below this horizontal plane. It's becoming possible.

This measure yields the following advantages. That is, on the bottom surface of each slab, the pressing force against the wall surface of the cooling element is larger than the pressing force on the side surface or the top surface due to the weight of the slab. As a result, the thermal center of the slab, and therefore the molten core, is shifted from the center of the slab toward the top surface.
The thickness of the solidified shell on the upper surface of the slab is therefore smaller than on its lower surface. In order to increase the pressing force of the cooling element acting on the upper surface of the slab according to the invention, a relatively large amount of heat is dissipated there. As a result, the heat center is moved towards the lower surface of the slab and towards the geometrical center of the slab, so that a solidified shell of the desired thickness that is uniform over the entire circumference is obtained.

With the device according to the invention, especially when applying the variant embodiments described above, thermal stresses in the solidified shell of the slab are avoided, thereby improving the quality of the product.

The individual cooling elements of the recooling device, which is formed by one or more recoolers, are adapted to the taper of the slab to be cooled by a setting device so that they gradually approach the slab axis in the direction of slab movement. is set to However, if the taper of the slab changes during cooling due to the changing shrinkage properties of the cast metal within a certain temperature interval, these cooling elements can likewise be set to this new changing taper. It is composed of In order to take into account the taper, it is advantageous to configure the cooling surface of the cooling element, which slides into contact with the surface of the slab, to be narrower in the direction of movement of the slab.

Advantageously, the recooling device is divided into two to four recoolers, each recooler having a number of cooling elements and cooling surfaces equal to the number of individual surfaces forming the outer circumference of the slab. be. By dividing the recooling device into a plurality of recoolers, it is possible to precisely align the cooling elements to the slab, which, as already mentioned above, changes dimensions depending on the respective shrinkage state.

In order to obtain a homogeneous solidified shell, the cooling element or its cooling surface downstream in the direction of billet withdrawal,
The dimension perpendicular to the slab axis is reduced as much as possible so that each surface of the slab's outer periphery contacts only the center area or the area near the center, and the ridge of the slab and each individual surface of the slab's outer periphery An embodiment is preferred in which the cooling element or its cooling surface does not come into contact with the area close to the edge of the surface.

Therefore, in the device according to the invention, it is not necessarily necessary to cool the entire circumference of the slab, and therefore the individual circumferential surfaces of the square columnar slab, over its entire width by cooling elements. During the subsequent advancement of the slab, even immediately after leaving the mold, only the center and areas around the individual surfaces to be cooled on the periphery of the slab are affected by the pressing force and/or by the cooling medium flow. It is advantageous to control the cooling by means of individual cooling elements so that the edges or edge regions of the slab, which in any case are mostly naturally cooled, are not forcedly cooled by the cooling elements of the recooling device.

The device according to the invention will be explained in detail with reference to the drawings.

In the conventional stationary continuous casting apparatus shown in FIGS. 1 and 2, the molten metal vessel 1 or the molten metal distributor, which is made of a refractory material and contains the molten metal 2 to be cast, is made of a thermally conductive metal. A continuous casting mold 4 with a molding surface 4a follows. The mold 4 is connected to a fixedly configured recooler 5, the cooling surface 6 of which is also made of a thermally conductive metal, the cooling surface 6 of the slab 3 moving through the recooler 5. Sliding contact.

The cooling medium passed through the stationary recooler 5 and the mold 4 flows from the inlet 8 to the outlet 9 along the path shown in chain lines in the figure, and removes heat from the slab passing through the mold 4 and the recooler 5. remove. In the casting process, the molten metal 2 reaches the cavity of the mold 4 from the molten metal container 1 where it is cooled, where it begins to solidify from the outside while forming the slab 3. The solidified shell 3a surrounding the molten core 3b of the slab 3 is still thin and unstable in the mold 4, and when the slab passes through the recooler 5 where the slab surface contacts the cooling surface 6, the progress of the slab is Gain thickness and strength continuously in the direction. After the slab leaves the recooler, the slab 3 is solidified to such an extent that it can be withdrawn and manipulated without fear of damage.
During the cooling process and solidification process in the recooler 5, the entire slab 3 shrinks, so that the slab 3 gradually becomes thinner in the advancing direction.

The permanently formed cooling surface 6 of the recooler 5 is
Since it is normally tapered in the direction of movement of the slab, contact with the similarly tapered slab surface is maintained along the cooling surface 6 due to shrinkage, and therefore as much as possible. Continuously over the entire length of the recooler 5, effective cooling of the slab is ensured. Of course, once a fixed recooler has a defined taper, it does not change and is therefore not optimally matched to the different shrinkage conditions of different metals or alloys of varying composition. If the taper is large, the slab will not move in the recooler.

It should be briefly noted here that the slab 3 is continuously or vibrably pulled out of the mold and recooler by means of a drawing device (not shown), for example pinch rolls, and then, for example, by cutting the slab.
Further desired operations such as storage etc. are performed.

FIG. 3 schematically shows an apparatus constructed according to the invention, the individual parts being provided with the same reference numerals as used in FIGS. 1 and 2, and the apparatus relating to the casting process itself also shown in FIG. and operates in the same manner as the device shown in FIG.

In the illustrated embodiment, the individual cooling elements 5a-5
After the cooling medium passes through the forming mold 4 through c.
It is passed in the same direction as the slab movement. It should be emphasized here that the cooling medium can also be guided differently through the cooling elements 5a to 5c, and that each cooling element can optionally also have its own cooling medium circuit; Advantageously, in a device with individually controllable cooling elements according to the invention,
In this device, in addition to the control of the pressing force or only the control of cooling of the slab, the amount of cooling medium flowing through each cooling element per unit time is determined in order to achieve uniform cooling over the circumference of the slab. This is done by changes in

The cooling elements 5a to 5c are connected via springs 10 to a setting plate 11 which can be set by means of a setting device 12 to vary its position, in particular its distance from the recooler axis or the slab axis. Due to the force of the spring 10, the cooling elements 5a to 5c or their cooling surfaces are
In order to obtain movement toward the surface of the slab 3 passing through,
It is pressed parallel to the respective slab surface, not parallel to the slab axis, to achieve uniform cooling thereof. The setting device 12 advantageously includes a digitally controllable step-operated DC motor.

At the inlets 8a, 8b, 8c of the cooling medium, as well as at the outlets 9a, 9b, 9c, a temperature detector 13 or 14, for example a thermocouple, is integrated, and in addition, for example, the cooling medium (usually water) is connected to a recooler. At the exit point, a detector 15 is provided which measures the amount of cooling medium passing through the cooling elements 5a-5c. The detector is 1
The characteristic quantities detected by 3, 14, and 15 are supplied to a control device computer 16, which processes these characteristic quantities into data regarding heat radiation, and the data thus obtained is stored in a storage device 17. Compare with the characteristic values corresponding to each metal to be cast.

If there is a deviation, the computer 16 respectively gives a suitable instruction, for example in the form of a pulse, to the setting device 12, for example its electric motor, which causes the setting plate 11 to be
Therefore, the positions of the cooling elements 5a to 5c are changed, and the information supplied from the detectors 13 to 15 is transmitted to the computer 16.
The calculated data is made to match the stored desired heat radiation value of each cooling element.

The device according to the invention shown in FIGS. 4 and 5 corresponds in general to the device shown in FIG. Corresponding parts are therefore given the same reference numerals. Here, the recooler includes two cooling elements 5a,
5b. Cooling surfaces 6a, 6 are provided around the outer peripheral surface of the slab 3 to cool it.
Cooling elements 5a and 5b that are in sliding contact with the slab 3 at b
are provided in a common peripheral tube 7 that surrounds them, and a pressure spring 10 is passed through an opening 7a of this tube 7 to press the individual cooling elements 5a, 5b against the surface of the slab 3 or individual surfaces. ing. Although not shown in these figures, the inlets 8a, 8 have the above-mentioned detectors.
The cooling medium is passed through the cooling elements 5a, 5b through the cooling elements 5a, 5b and the outlet ports 9a, 9b.

The device shown here includes a device for setting the pressing force of each cooling element, for example, a setting plate 11 and a setting device 1.
2 is provided outside the outer circumferential tube 7, so it is not affected by temperature rise.

It can be seen from FIG. 4 that the cooling elements 5a, 5b are arranged closer to each other in the direction of slab movement than the outer circumferential tube 7, and are therefore adapted to the taper caused by the shrinkage of the slab 3. The precise setting of the pressing force takes place by loading and unloading the spring 10 by means of a setting plate 11 whose position is variable by means of a setting device 12, controlled by the amount of heat extracted.

6 to 10 show a continuous casting apparatus similar to the apparatus according to FIGS. 4 and 5, in which the recooler 5 is divided into three cooling elements 5a to 5c. The reference numbers in FIGS. 6-10 correspond to those in FIGS. 4 and 5. Cooling elements 5a to 5 are provided therein in the direction of slab movement.
c or the cooling surfaces 6a to 6c in contact with the slab 3,
It is shown that its dimensions are gradually reduced perpendicular to the direction of slab movement and away from the ridge of the slab. In this way, the edges of the slab 3 are not forcedly cooled, so that excessive cooling, which would lead to an undesirable thickening of the solidified shell in the area of the edges and thus to inhomogeneities, such as cracks, is avoided.

[Brief explanation of drawings]

Figure 1 is a vertical cross-sectional view of a conventional fixed continuous casting device.
Figure 2 is a sectional view taken along the - plane of Figure 1;
The figure is a longitudinal sectional view of the continuous casting apparatus of the present invention having a cooling element whose pressing force can be set and whose position can be changed.
The figure is a longitudinal cross-sectional view of a continuous casting apparatus of the present invention having a recooler with two cooling elements, FIG. 5 is a cross-sectional view on the - plane of FIG. FIG. 7 is a schematic plan view of the cooling surface after removing the outer tube shown in FIG. 6, and FIGS. 8, 9, and 10 are respectively XII-XII plane of Figure 6,
FIG. 1... Molten metal container, 2... Molten metal, 3... Slab, 4... Mold, 5... Recooler, 5a to 5c...
...Cooling element, 6a-6c...Cooling surface, 8a-8c
...Cooling medium inlet, 9a-9c...Cooling medium outlet, 12...Setting device, 13-15...Detector, 16, 17...Control device.

Claims (1)

[Claims] 1. A molten metal container, a horizontal mold connected to the molten metal container and cooled, and at least one recirculating mold provided after the mold and cooled by passing a cooling medium through the mold. In a horizontal continuous casting apparatus that has a cooler, a temperature detector that detects the temperature of the cooling medium passed through the recooler, and a device for drawing out the slab, the recooler 5 removes the slab 3 to be cooled. a cooling surface 6 that surrounds and is divided along the periphery, is displaceable in the radial direction with respect to the center of the slab 3, and is capable of contacting the slab 3;
A plurality of cooling elements 5 with a or 6b or 6c
a, 5b, or 5c, each cooling element is attached with a setting device 12 for displacing it in the radial direction, and control devices 16, 17 are provided to control these setting devices 12, and temperature detectors 13, 1
4. A horizontal continuous casting apparatus, characterized in that the setting device 12 sets the radial position of the cooling element 5a, 5b, or 5c according to the output signal of the horizontal continuous casting apparatus. 2. Device according to claim 1, characterized in that the control devices 16, 17 are formed by a computer or a microprocessor 16 with a storage device 17 for data and programs. 3. Device according to claim 1, characterized in that the setting device 12 comprises a digitally controlled DC motor operating stepwise. 4 Cooling elements 5a, 5b, 5c of the recooler 5 provided above the horizontal plane passing through the axis of the slab 3
2. The device according to claim 1, wherein the device is operable with a higher pressing force or a higher cooling medium flow rate than the cooling elements below this horizontal plane. 5 Cooling element 5 in sliding contact with the surface of slab 3
2. The device according to claim 1, wherein the cooling surfaces 6a, 6b, 6c of the cooling surfaces 6a, 5b, 5c are configured to become narrower in the direction in which the slab is pulled out. 6. The cooling elements 5a, 5b, 5c or their cooling surfaces 6a, 6b, 6c reduce the dimension perpendicular to the slab axis in the direction of slab withdrawal, so that the ridges of the individual surfaces on the outer periphery of the slab 3 are reduced. In the range close to , there are cooling elements 5a,
Device according to claim 1, characterized in that 5b, 5c or their cooling surfaces 6a, 6b, 6c do not touch. 7. Device according to claim 1, characterized in that the control device 16, 17 controls the amount of cooling medium passing through the recooler 5.