JP4232491B2 - Continuous casting mold - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a continuous casting mold, and more particularly to a continuous casting mold in which the cooling strength can be changed between a mold upper part and a mold lower part in a casting slab casting direction.
[0002]
[Prior art]
The purpose of the continuous casting mold is to cool the poured molten steel to form a solidified shell at the site where it comes into contact with the mold, and to form a solidified shell on the surface of the slab that can withstand drawing down the mold. . For this purpose, the continuous casting mold uses copper or copper alloy with excellent thermal conductivity as the material, and adopts a water-cooled structural mold that forcibly cools the opposite side of the contact surface with the molten steel. .
[0003]
In recent years, the slab drawing speed in continuous casting operations has been increased mainly for the purpose of improving productivity, thereby shortening the residence time in the mold. From the viewpoint of stable operation in high-speed casting, the mold outlet section In order to obtain a solidified shell having a predetermined thickness, cooling in the mold is further strengthened.
[0004]
By the way, the solidified shell in the mold is constantly subjected to thermal stress as the temperature of the solidified shell itself decreases, and when the cooling in the mold is strengthened, nonuniform solidification occurs in the width direction of the mold. In addition, since the thermal stress itself increases, cracks and cracks along the casting direction tend to occur in the solidified shell. In particular, in the so-called medium carbon steel, which has a strong cracking sensitivity and a peritectic reaction with a carbon concentration of 0.08 to 0.2 mass%, longitudinal cracks are generated on the surface of the slab, which impairs the maintenance of the slab. Not only that, but the vertical cracks may even extend to the breakout just below the mold. In addition, the initial solidification rate increases with the strengthening of the mold cooling, and it becomes easy to trap the mold powder and Ar gas bubbles in the solidified shell at the molten steel surface in the mold, which also deteriorates the quality of the slab. It is a cause.
[0005]
For this reason, a method has been proposed to maintain a high quality slab surface as a slow cooling on the molten steel surface in the mold (hereinafter referred to as “meniscus”), while ensuring a sufficient solidified shell thickness as a strong cooling at the bottom of the mold. Has been.
[0006]
For example, Patent Document 1 proposes a method of adding a slowly cooled mold powder into a mold without changing the cooling ability of the mold itself. According to this method, since the mold powder having a low thermal conductivity and a high melting point flows between the solidified shell and the mold, heat transfer to the mold at the meniscus portion is suppressed and the cooling is performed slowly. It is possible to produce a slab excellent in surface quality without reducing the speed.
[0007]
Further, in Patent Document 2 and Patent Document 3, it is assumed that slow cooling to the extent that the properties of the mold powder are changed is not sufficient, and cooling is performed on the upper side of the mold including the meniscus position and on the downstream side in the casting direction. Proposing a continuous casting mold that can adjust the cooling strength on the upper and lower sides of the mold by dividing the slit, which is the water flow path, and adjusting the cooling water amount independently for each of the divided upper and lower slits. Has been. According to Patent Document 2 and Patent Document 3, it is possible to independently select an arbitrary cooling strength between the upper part and the lower part of the mold, and it is possible to cast a slab with less surface flaws.
[0008]
[Patent Document 1]
JP-A-5-277680 [0009]
[Patent Document 2]
JP-A-7-51804 [0010]
[Patent Document 3]
Japanese Patent Laid-Open No. 7-124711
[Problems to be solved by the invention]
However, Patent Document 2 and Patent Document 3 have the following problems. That is, since the slit is divided into an upper part and a lower part, the cooling capacity of the divided part that becomes the boundary is insufficient, the mold copper plate temperature rises in the divided part, and the deformation of the mold copper sheet due to thermal expansion occurs. It will cause a decrease in the service life. Moreover, in patent document 3, the space | interval of adjacent slits must be widened, and the cooling capability of the whole casting_mold | template falls. Furthermore, two sets of piping for water supply and drainage are required, which not only increases the equipment cost, but also complicates the piping and makes maintenance inspection difficult.
[0012]
The present invention has been made in view of the above circumstances, and the object of the present invention is to prevent the meniscus portion from being slowly cooled without degrading the cooling ability even at the boundary position between the meniscus portion and the lower side thereof. It is possible to provide a continuous casting mold in which the cooling strength can be changed between the portion and the lower side thereof, and the equipment cost is relatively low.
[0013]
[Means for Solving the Problems]
The continuous casting mold according to the first invention for solving the above problems is provided in a copper mold, with respect to a flow path of cooling water for cooling the copper mold, a single water supply unit, A continuous casting mold having at least two drainage portions separated in the casting direction, wherein the water supply portion is installed downstream in the casting direction, and the drainage portion is upstream of the water supply portion in the casting direction. It is characterized by being installed on the side.
[0014]
The continuous casting mold according to the second invention is characterized in that, in the first invention, the drainage portion is provided at two locations.
[0015]
The continuous casting mold according to the third invention is characterized in that, in the second invention, the interval between the two drainage portions is 100 mm or more away in the casting direction.
[0016]
In the continuous casting mold according to the fourth invention, in the second or third invention, a flow rate adjusting means for adjusting the amount of cooling water discharged from the drainage portion is installed in the drainage portion on the downstream side in the casting direction. It is characterized by being.
[0018]
In the continuous casting mold according to the present invention, the cooling water drainage portions for cooling the copper mold are installed at two or more locations in the casting direction, so the cooling water supplied from the downstream side in the casting direction into the cooling water flow path is The amount of cooling water discharged from each of these drainage portions and passing through the cooling water flow path decreases toward the upstream side in the casting direction. Therefore, the cooling capacity is weakened on the upstream side in the casting direction, that is, on the meniscus side, and can be slowly cooled. it can. And since a cooling water flow path is continuing from the upper part of a casting_mold | template to the lower part, a cooling capability changes continuously according to the amount of cooling water which passes a cooling water flow path, and is like the boundary area of patent document 2 and patent document 3 A region where the cooling capacity is insufficient is not formed. Furthermore, when two drainage sections are provided, one water supply section is sufficient, so compared to the case where two sets of water supply / drainage pipes are installed independently, the facility cost can be reduced accordingly. it can.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings. 1-3 is a figure which shows an example of embodiment of this invention, Comprising: FIG. 1 is the schematic which shows the water supply / drainage structure of the casting mold for continuous casting which concerns on invention, FIG. 2 is the continuous which concerns on this invention FIG. 3 is a perspective view of a casting mold, and FIG. 3 is a cross-sectional view of a portion of the mold long-side copper plate shown in FIG.
[0020]
As shown in these figures, the long copper plate 2 constituting the mold 1 for a slab continuous casting machine has a large number of cooling water flow paths on the surface opposite to the surface in direct contact with the molten steel. The slits 3 are provided side by side in the width direction of the long mold copper plate 2 from the top to the bottom of the long mold copper plate 2. And the water box 4 for plugging the opening of the slit 3 and making each slit 3 into an independent cooling water flow path is provided on the surface of the long copper plate 2 on which the slit 3 is installed, by bolts and screws (not shown). For example, the mold long side copper plate 2 is attached in close contact. The water box 4 is provided with water supply holes 6 communicating with all the slits 3 in the width direction of the mold long side copper plate 2 on the lower side thereof, and all of the width direction of the mold long side copper plate 2 in the upper side thereof. A drain hole 11 and a drain hole 15 communicating with the slit 3 are provided. In this case, the slit 3 is linear, and the cross-sectional area thereof is substantially the same between the upper part and the lower part of the long-side copper plate 2, and there is no reason to define the interval between adjacent slits 3 in particular. , Can be any interval optimal for operating conditions.
[0021]
The water supply hole 6 communicates with a water distribution pipe 7 installed on the back surface of the water box 4 over the entire width direction of the mold long side copper plate 2, and the water distribution pipe 7 communicates with a water supply pipe 8 provided with a flow control valve 9. is doing. That is, the water supply hole 5, the water distribution pipe 7, the water supply pipe 8, and the flow rate control valve 9 constitute a water supply unit 5 for cooling water to the slit 3. In the water supply section 5 having this configuration, the cooling water for cooling the long copper plate 2 is sent to the water distribution pipe 7 through the water supply pipe 8 while the supply flow rate is controlled by the flow rate control valve 9. 7 is distributed in the width direction of the mold long-side copper plate 2 and supplied into the slits 3 through the water supply holes 6.
[0022]
On the other hand, the drain hole 11 communicates with the water collecting pipe 12 installed on the back surface of the water box 4 over the entire width direction of the long copper plate 2, and the water collecting pipe 12 communicates with the drain pipe 13. That is, the drainage hole 11, the water collection pipe 12, and the drainage pipe 13 constitute a first drainage unit 10 for cooling water from the slit 3. In the first drainage unit 10 having this configuration, the cooling water discharged from the slits 3 in the width direction of the long copper plate 2 through the drainage holes 11 is collected by the water collecting pipe 12, and the collected cooling water is It is discharged out of the system through the drain pipe 13.
[0023]
The drain hole 15 communicates with a water collecting pipe 16 installed on the back surface of the water box 4 over the entire width direction of the long copper plate 2 of the mold, and the water collecting pipe 16 has a drain pipe 17 provided with a flow control valve 18. Communicated with. That is, the drainage hole 15, the water collection pipe 16, the drainage pipe 17, and the flow rate control valve 18 constitute a second drainage unit 14 for the cooling water from the slit 3. The opening degree of the flow rate adjusting valve 18 is controlled by an opening degree controller 19. In the second drainage section 14 having this configuration, the cooling water discharged from the slits 3 in the width direction of the long copper plate 2 through the drainage holes 15 is collected by the water collecting pipe 16, and the collected cooling water is Then, it is discharged out of the system through the drain pipe 17 while the flow rate discharged by the opening controller 19 is controlled.
[0024]
The drain hole 15 shown in FIG. 1 has a straight tube shape and is installed in a direction perpendicular to the slit 3. In order to make it easier for the cooling water flowing in the slit 3 to flow out from the drain hole 15, The contact surface of the hole 15 with the slit 3 is made into an arc shape (R is attached), the inner diameter of the drain hole 15 is tapered so that the slit 3 side is larger and the water collecting pipe 16 side is smaller, or the drain hole 15 is You may take measures, such as installing diagonally along the direction of the flow of the slit 3.
[0025]
As shown in FIG. 3, a temperature measuring element 20 for detecting the temperature in the vicinity of the meniscus of the long-side copper plate 2 is disposed on the long-side copper plate 2 at a substantially intermediate position between the drain holes 11 and 15. The value detected by the temperature measuring element 20 is input to an opening controller 19 that controls the opening of the flow rate control valve 18. A thermocouple or the like may be used as the temperature measuring element 20.
[0026]
FIG. 1 is a diagram of a mold long side copper plate 2 constituting a mold 1 for a slab continuous casting machine, but a mold short side copper plate 21 constituting the mold 1 is also provided with one water supply section and two pieces according to the above. A drainage section can be installed. FIG. 2 is a perspective view of the mold 1 according to the present invention configured by combining the mold long-side copper plate 2 and the mold short-side copper plate 21 having such a cooling water supply / drainage structure. In FIG. The water supply / drainage structure of the mold long side copper plate 2 and the water supply / drainage structure of the mold short side copper plate 21 are omitted. Reference numeral 22 in FIG. 2 denotes a water box for the mold short side copper plate 21. In the slab continuous casting machine, the contact area between the mold short-side copper plate 21 and the molten steel poured into the mold 1 is significantly smaller than the contact area between the mold long-side copper plate 2 and the slab surface quality is improved. Since there is little influence, it is not necessary to install two drainage parts in the mold short side copper plate 21. FIG. 1 shows a mold 1 for a vertical bending slab continuous casting machine. In the case of a curved continuous casting machine, the mold also has a shape along a curved radius.
[0027]
The cooling capacity of the mold 1 depends on the flow rate of the cooling water flowing through the slit 3 that is the flow path of the cooling water, the temperature of the cooling water, and the flow rate of the cooling water. That is, the greater the flow rate, the lower the coolant temperature, and the faster the coolant flow rate, the higher the cooling capacity. In the mold 1 according to the present invention having the above-described configuration, the cooling water in the slit 3 can be discharged from the second drainage portion 14, so that the amount of cooling water in the slit 3 above the second drainage portion 14 is less. can do. Therefore, on the upper side of the second drainage section 14, the flow rate of the cooling water passing through the slit 3 is reduced, and the flow rate is reduced as the flow rate is reduced, so that the mold cooling ability is lowered.
[0028]
Since the rate of decrease in cooling capacity on the upper side of the second drainage portion 14 depends on the flow rate of the cooling water discharged from the second drainage portion 14, the opening degree of the flow rate adjustment valve 18 is adjusted to adjust the second By arbitrarily setting the flow rate of the cooling water discharged from the drainage part 14, the cooling capacity on the upper side of the second drainage part 14 can be arbitrarily adjusted. In the mold 1 according to the present invention, cooling water is introduced from the lower side of the mold 1, and the temperature of the cooling water gradually rises while rising in the slit 3. The upper part has a smaller cooling capacity. Moreover, if the 2nd drainage part 14 is closed, a mold cooling capability will become the same as a conventional mold.
[0029]
In this case, a target value is set for the temperature at which the cooling capacity is lowered, that is, the mold temperature in the vicinity of the meniscus in the mold, and the detected value is set to the target value using the opening controller 19 based on the detected value by the temperature measuring element 20. By adjusting the opening degree of the flow rate control valve 18 so as to match, the cooling capacity on the upper side of the second drainage portion 14 is substantially constant even if there is a change in casting conditions such as a change in the slab drawing speed. Can be.
[0030]
When the continuous casting operation is performed using the mold 1 according to the present invention, the meniscus position in the mold 1 is cast at least above the second drainage portion 14. When the meniscus position is on the lower side of the second drainage part 14, the cooling ability lowering effect on the upper part of the mold of the mold 1 according to the present invention cannot be applied to the meniscus part. In order to slowly cool the meniscus position with the meniscus position always above the second drainage part 14, the distance L in the casting direction between the drainage hole 11 and the drainage hole 15 shown in FIG. preferable.
[0031]
In FIG. 1, there are two cooling water drainage portions from the slit 3, but a third drainage portion and further a fourth drainage portion are installed below the second drainage portion 14. Also good. However, in order to adjust the flow rate of the cooling water discharged from the added drainage unit, it is necessary to install a flow rate control valve in the added drainage unit, as in the second drainage unit 14. In the above description, the flow path of the cooling water has a slit shape, but a through hole is provided in a copper mold, and even in a mold having the through hole as a cooling water flow path, a bypass hole is provided in the middle of the through hole. The present invention can be applied.
[0032]
By casting the molten steel using the mold 1 according to the present invention, the cooling of the meniscus portion in the mold is slowly cooled, and vertical cracks formed in the initial solidification stage among the slab surface defects, as well as mold powder, Capture and entrapment of non-metallic inclusions, which are deoxidation products, and inert gas bubbles in the solidified shell are greatly reduced, and it is possible to stably obtain a slab having good surface properties. In addition, the cooling capacity of the mold 1 gradually decreases between the upper and lower portions of the mold 1 with the second drainage section 14 as a boundary, and the cooling capacity does not become insufficient in the boundary region. Therefore, a mold life equivalent to that of a conventional mold can be achieved. Furthermore, since the predetermined purpose is achieved only by installing at least two drainage sections, only one drainage section is added to the conventional mold, and the equipment cost is kept relatively low. be able to.
[0033]
The present invention is not limited to the above description and can be variously modified. For example, in the above description, it is a mold for a slab continuous casting machine, but it can be applied to a mold for a bloom continuous casting machine and a mold for a billet continuous casting machine in accordance with the above description. The cooling water supply / drainage structure is not limited to the above, and any structure may be used. In short, as long as at least two drainage portions are provided apart from each other in the casting direction with respect to the cooling water flow path to which cooling water is supplied from the lower side of the mold, any other structure may be used. .
[0034]
【The invention's effect】
According to the continuous casting mold according to the present invention, the cooling of the meniscus portion in the mold is slowly cooled, and vertical cracks and mold powder and deoxidation products formed in the initial solidification stage among the slab surface defects. In addition to significantly reducing the trapping and entrainment of certain non-metallic inclusions and inert gas bubbles in the solidified shell, it is possible not only to stably obtain slabs with good surface properties, but also to slowly cool parts. In the boundary area between the normal cooling section and the normal cooling section, the mold cooling capacity gradually decreases and the mold cooling capacity does not become insufficient. Therefore, it is possible to achieve the same mold life as the conventional mold, which is industrially beneficial. The effect is brought about.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of an embodiment of the present invention, and is a schematic diagram showing a water supply / drainage structure of a continuous casting mold according to the invention.
FIG. 2 is a diagram showing an example of an embodiment of the present invention, and is a perspective view of a continuous casting mold according to the present invention.
FIG. 3 is a cross-sectional view of a part of the mold long side copper plate shown in FIG. 1;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Mold 2 Mold long side copper plate 3 Slit 4 Water box 5 Water supply part 6 Water supply hole 7 Water supply pipe 8 Water supply pipe 9 Flow control valve 10 First drainage part 11 Drainage hole 12 Catchment pipe 13 Drainage pipe 14 Second drainage part 15 Drainage Hole 16 Drain pipe 17 Drain pipe 18 Flow control valve 19 Opening controller 20 Temperature measuring element 21 Mold short side copper plate 22 Water box

Claims (4)

  For continuous casting provided with a water supply part and at least two drainage parts apart in the casting direction with respect to the flow path of the cooling water for cooling the copper mold provided in the copper mold A casting mold for continuous casting, wherein the water supply part is installed downstream in the casting direction, and the drainage part is installed upstream in the casting direction with respect to the water supply part.   The continuous casting mold according to claim 1, wherein the drainage portion is provided at two locations.   The continuous casting mold according to claim 2, wherein the interval between the two drainage portions is 100 mm or more away in the casting direction.   The continuous casting apparatus according to claim 2 or 3, wherein a flow rate adjusting means for adjusting the amount of cooling water discharged from the drainage portion is installed in the drainage portion on the downstream side in the casting direction. template.

Images