JP4882406B2 - Cooling grid equipment for continuous casting machine and method for producing continuous cast slab - Google Patents

Description

  The present invention relates to a cooling grid facility for supporting and cooling a slab installed immediately below a mold of a continuous casting machine, and a slab manufacturing method using the continuous casting machine in which the cooling grid facility is installed. Is.

  In continuous casting of steel, molten steel poured from a ladle into a tundish is poured into a water-cooled mold through an immersion nozzle installed at the bottom of the tundish, and then the solidified shell formed by the mold is used. The cast slab as the outer shell is continuously drawn below the mold while being cooled, and a continuous cast slab is manufactured. In this case, first, in the mold, the molten steel is cooled by contacting the mold to form a solidified shell. Thereafter, the slab that has passed through the mold is pulled out in the casting direction by a pinch roll while being supported by a slab support / guide device including a guide roll, a cooling grid, a cooling plate, and the like. By being supported by the slab support / guide device, swelling of the slab in the thickness direction (referred to as “bulging”) is prevented. This slab support / guide device includes a spray nozzle such as a water spray nozzle or an air mist spray nozzle (hereinafter simply referred to as “spray nozzle” means both a water spray nozzle and an air mist spray nozzle). The slab is pulled out while being cooled by the cooling water sprayed from the spray nozzle, and eventually solidification to the center is completed. Then, it cut | disconnects to predetermined length with the slab cutting machine installed in the machine end of the continuous casting machine, and a continuous casting slab is manufactured.

  By the way, in recent years, in order to reduce the manufacturing cost, improvement in productivity has been demanded more than ever before, and in the continuous casting process, the speed of the manufacturing line, that is, the casting speed has been increased. In order to realize this high casting speed, it is necessary to solve various problems. In particular, a technique for more efficiently cooling and supporting the slab directly under the mold is required. Under high-speed casting, the thickness of the solidified shell immediately below the mold becomes thin, and this solidified shell breaks and breakout occurs, or the solidified shell does not break. Due to the pressure, bulging occurs, and the molten steel surface in the mold fluctuates up and down, and mold powder is caught in the solidified shell, resulting in problems such as quality defects. That is, there is a need for a method for efficiently cooling a slab directly under the mold while supporting a slab having a thin solidified shell thickness so that bulging does not occur.

  Conventionally, methods for supporting a slab directly under a mold are roughly classified into three types: a roll method, a cooling plate method, and a cooling grid method (see, for example, Non-Patent Document 1).

  In the roll method, a spray nozzle is installed in a gap between adjacent rolls in the casting direction, and the slab is supported by the roll while cooling the slab with cooling water sprayed from the spray nozzle. In this case, from the standpoint of cooling the slab, it is desirable to increase the roll diameter to increase the roll interval and widen the area of the slab that is water-cooled. Since it spreads, there is a problem that it becomes easy to bulge. Moreover, since the roll and the slab are in line contact, there is also a basic problem that the slab support area is small compared to the other two methods of supporting by the surface.

  In the cooling plate method, the entire width of the slab is supported by a single plate, and this plate has a water cooling structure in which a flow path for cooling water is formed. In addition to indirectly cooling the piece, it also has a function of directly cooling the slab by ejecting water from the surface of the plate toward the slab. Thus, in the cooling plate method, the entire width direction of the slab is supported by one large plate, which is a very effective method for preventing bulging of the slab, but the area for directly cooling the slab is small. Since it is small, there exists a problem that the cooling efficiency of slab is bad. Also, when a breakout occurs, there is no escape point for the steam generated after the water sprayed from the plate surface cools the slab, so there is a high risk of a steam explosion, which is also safe for operation. There is also a problem. Furthermore, since the plate is large and has an integral structure, it is also a big problem that processing and repair are difficult (see, for example, Patent Document 1).

The cooling grid method is composed of a wear plate for directly contacting and supporting the slab, a back frame for supporting the wear plate, and a water spray nozzle installed in the gap between the wear plates. A large number of arranged wear plates support the slab, and the slab is directly cooled by cooling water sprayed from a large number of water spray nozzles to secure a slab support area and at the same time, It is equipment that has both of securing the area of direct cooling (see, for example, Patent Document 2 and Patent Document 3).
JP-A-57-25268 Japanese Patent Laid-Open No. 2002-120054 Japanese Utility Model Publication No. 6-23647 Miyoshi et al., Iron and Steel, Vol.60 (1974) No.7.p.860-867

  However, a careful examination of conventional cooling grid type equipment revealed that the conventional cooling grid equipment has the following problems.

  That is, in the conventional cooling grid equipment, the slab is cooled mainly by the cooling water sprayed from the water spray nozzle installed in the gap between the adjacent wear plates. The cooling water is not directly applied to the contact part between the plate and the slab, and the cooling capacity of this part is weak, and the cooling capacity of the entire cooling grid equipment is insufficient at the time of high speed casting that is currently required. . This is because the wear plate itself is not a water cooling structure, but is cooled by spray water sprayed from a water spray nozzle installed in the gap of the wear plate, and the contact portion between the slab and the wear plate is indirectly by the wear plate. This is because it becomes cooling.

  The present invention has been made in view of the above circumstances, and the object of the present invention is to ensure a sufficient support area of the slab when the slab support just below the mold is carried out by the cooling grid method, and at the same time, It is to provide a cooling grid facility for a continuous casting machine with improved cooling capacity, and to provide a method for producing a continuous cast slab using a continuous casting machine equipped with this cooling grid facility.

  The present inventors have intensively studied and studied in order to solve the above problems. The results of the examination and research are explained below.

  One way to increase the cooling capacity of the cooling grid equipment is to reduce the area ratio of the wear plate in the total area of the cooling grid equipment and to increase the area ratio directly cooled by the spray water sprayed. It is done. However, the area ratio of the wear plate in the total area of the cooling grid equipment is about 20% to 60%. From the viewpoint of stably supporting the slab, this area ratio can be greatly reduced from the current level. Have difficulty. Therefore, in the present invention, as a means for increasing the cooling capacity of the cooling grid equipment, it has been studied to further improve the cooling capacity of the portion directly cooled by the spray.

  The cooling grid equipment used directly under the mold of the actual operation, that is, an experimental device that simulates the structure combining the wear plate and the water spray nozzle is manufactured, and the water spray used in the actual operation in this experimental device. The nozzle was changed to another type of nozzle, and an experiment was conducted to cool the heated steel material using this nozzle, and the cooling capacity under each condition was compared and evaluated.

  As a result, it was found that the nozzle shown in FIG. 1 (hereinafter referred to as “cooling water supply nozzle”) that forms a shower-like water flow group is excellent in cooling capacity. 1A and 1B are schematic views showing an example of a cooling water supply nozzle employed in the present invention, where FIG. 1A is a front view and FIG. 1B is a side sectional view. However, FIG. 1B is a cross-sectional view taken along the line X-X ′ of FIG.

  As shown in FIG. 1, the cooling water supply nozzle 15 includes a box-shaped nozzle head 16 and a cooling water supply pipe 18 having a rectifying hole 19, and a plurality of nozzle holes 17 are formed on the front surface of the nozzle head 16. The cooling water is ejected from these nozzle holes 17 like a shower. The cooling water supply pipe 18 is formed of a closed end pipe having a tip end penetratingly connected into the box portion of the nozzle head 16 and having a plurality of rectifying holes 19 on the side surface portion. This structure is provided with a rectifying function and a header function for cooling water to be uniformly ejected from a plurality of nozzle holes 17 provided on the front surface of the nozzle head 16. The water spray nozzle used in actual operation for the cooling water supply nozzle 15 is generally called a full cone type water spray nozzle, and sprays the cooling water in a conical shape.

  The steel material for cooling was heated for about 1 hour in an electric furnace maintained at 1200 ° C., and then the steel material was taken out and fixed to an experimental apparatus to start cooling. During cooling, the temperature change of the steel material was measured with a thermocouple embedded in the steel material. And this temperature measurement value was read with the personal computer, and the heat transfer coefficient in the steel material surface was calculated in combination with the numerical calculation (details of the experimental method will be described later in Example 1).

As a result, the heat transfer coefficient is significantly improved when the cooling water supply nozzle 15 that forms the shower-like water flow group is used, compared with the case where the conventional water spray nozzle is used. It was found that the cooling capacity of the slab can be enhanced. In this case, it was found that the number density of the shower-like water flow group was preferably 0.08 / cm ² or more. This is because if the number density of the shower-like water flow group is less than 0.08 / cm ² , the number of parts cooled by the water flow decreases and the cooling capacity decreases. Here, the number density of the shower-like water flow group is a value obtained by dividing the number of shower-like cooling water flows ejected from one cooling water supply nozzle 15 by the area of the wear plate gap, “Wear plate gap area = (gap length of wear plates adjacent in the slab width direction) × (gap length of wear plates adjacent in the casting direction)”.

Moreover, it turned out that it is suitable for the discharge flow velocity of the cooling water ejected from the nozzle hole 17 of the cooling water supply nozzle 15 to be 2.0 m / second or more. This is because when the cooling water discharge flow rate is less than 2.0 m / sec, the cooling capacity is lowered because the water flow hangs down until reaching the slab. Furthermore, it has been found that it is preferable that the water density of the cooling water ejected from the cooling water supply nozzle 15 to the gap between the wear plates is in the range of 1000 liters / minute · m ² to 6000 liters / minute · m ² . If the water density is less than 1000 liters / minute · m ² , the cooling capacity does not increase because the amount of water itself is small. On the other hand, if the water density exceeds 6000 liters / minute · m ² , This is because the stagnation of the cooling water is difficult to reach the cast slab. Here, the water density of the cooling water is a value obtained by dividing the flow rate per minute of the cooling water ejected from one cooling water supply nozzle 15 by the area of the wear plate gap. The area of the wear plate gap is as described above.

  Moreover, in this cooling water supply nozzle 15, it turned out that a cooling capability improves by arrange | positioning the nozzle hole which injects a water flow toward the boundary part of a slab and a wear plate in the nozzle head 16. FIG. Here, an additional nozzle hole for injecting a water flow toward the boundary between the slab and the wear plate is displayed as a cooling water supply nozzle 15 </ b> A and is distinguished from the cooling water supply nozzle 15.

  Specifically, as shown in FIG. 2, the outer periphery of the nozzle head 16 of the cooling water supply nozzle 15A is inclined toward a plurality of inclined nozzle holes 26, that is, the boundary between the slab and the wear plate. An inclined nozzle hole 26 is additionally arranged, and a water flow is made to collide with the outer peripheral portion in the wear plate gap region and the side surface of the wear plate, and these portions are cooled simultaneously. Here, FIG. 2 is a schematic view showing another example of the cooling water supply nozzle employed in the present invention, (A) is a front view, (B) is a side sectional view, and the cooling water supply nozzle 15A is Structures other than the additional arrangement of the inclined nozzle holes 26 are the same as those of the cooling water supply nozzle 15 shown in FIG. 1, and the same portions are denoted by the same reference numerals. 2B is a cross-sectional view taken along the line X-X ′ of FIG.

The optimal water density of the cooling water ejected from the cooling water supply nozzle 15A to the gap between the wear plates becomes larger than the water density of the cooling water supply nozzle 15 by additionally arranging the inclined nozzle holes 26, and is 2000 liters / minute. It has been found that it is preferable to use m ² or more and 8000 liters / minute · m ² or less. If the water density is less than 2000 liters / minute · m ² , the cooling capacity does not increase because the amount of water itself is small. On the other hand, if the water density exceeds 8000 liters / minute · m ² , cooling water enters the gap between the wear plates. This is because the stagnation of the coolant and the newly supplied cooling water hardly reach the slab.

  Furthermore, in order to improve cooling capacity, it turned out that it is suitable to give a cooling function also to the wear plate itself. Specifically, a plurality of grooves are provided on the side of the wear plate that comes into contact with the slab, and an injection hole for injecting cooling water toward the inside of the groove is provided in the groove portion. It is to use a type of wear plate that cools the slab with the cooling water to be sprayed.

The present invention has been made on the basis of the above examination results, and the cooling grid equipment for a continuous casting machine according to the first invention is a cooling grid equipment for a continuous casting machine installed immediately below the mold of the continuous casting machine. A cooling water supply nozzle comprising a box-shaped nozzle head and a cooling water supply pipe having a rectifying hole in a gap between wear plates that contact the slab and support the slab , wherein the nozzle A plurality of nozzle holes are provided on the front surface of the head, and a cooling water supply nozzle is provided to cool the slab by ejecting a shower-like stream of water from these nozzle holes toward the slab. It is a feature.

In the cooling grid equipment for a continuous casting machine according to the second invention, in the first invention, the wear plate is provided with a groove on the surface in contact with the slab, and is cooled toward the inside of the groove. The present invention is characterized in that an ejection hole for ejecting the medium is provided.

The cooling grid equipment for a continuous casting machine according to a third aspect is the slab according to the first aspect , wherein the cooling water supply nozzle is further disposed on the outer periphery of the nozzle hole so as to be inclined to the nozzle head. And a wear plate outer edge, and a nozzle hole with an inclination for ejecting a shower-like water flow toward the boundary portion.

Method for producing a fourth continuous casting slab according to the invention is a continuous casting machine used with a continuous casting machine cooling grid installation according to the first invention, ejecting a shower-like water flow group from the cooling water supply nozzle Then, the slab is cast while being cooled.

Fifth method for fabricating continuous casting slab according to the invention is a continuous casting machine used with a continuous casting machine cooling grid installation according to the second invention, ejecting a shower-like water flow group from the cooling water supply nozzle In addition, it is characterized in that the casting is cast while cooling the slab by injecting cooling water from the ejection holes provided in the wear plate.

A method for producing a continuous cast slab according to a sixth aspect of the invention uses a continuous caster equipped with the cooling grid equipment for a continuous caster according to the third aspect of the invention, and ejects a shower-like stream of water from a cooling water supply nozzle. Then, the slab is cast while being cooled.

  According to the cooling grid equipment for a continuous casting machine according to the present invention having the above-described configuration, the slab can be reliably supported, and at the same time, the cooling of the slab can be improved, even under high-speed casting conditions. It is possible to stably cast a high-quality slab without causing operational trouble, and an industrially beneficial effect is brought about.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 3 is a view showing an embodiment of the present invention, and is a schematic view of a continuous casting machine equipped with a cooling grid facility according to the present invention. FIG. 4 is an enlarged perspective view of the cooling grid facility in FIG. .

  As shown in FIG. 3, the continuous casting machine 1 is provided with a mold 5 for cooling and solidifying the molten steel 10 to form the outer shell shape of the slab 11. A tundish 2 for relaying and supplying molten steel 10 supplied from a ladle (not shown) to the mold 5 is installed. A sliding nozzle 3 for adjusting the flow rate of the molten steel 10 injected from the tundish 2 into the mold 5 is installed at the bottom of the tundish 2, and the molten steel 10 is injected into the mold 5 at the lower surface of the sliding nozzle 3. An immersion nozzle 4 made of a refractory material is installed.

  On the other hand, below the mold 5, a cooling grid facility 6 is installed immediately below the mold 5, and below the cooling grid facility 6, a plurality of opposed slab support rolls 7 are installed. The cooling grid equipment 6 and the slab support roll 7 are slab support / guide devices for guiding the slab 11 pulled out from the mold 5 while guiding the slab 11 downward. A pinch roll (not shown) for pulling out is included. A spray nozzle (not shown) such as a water spray nozzle or an air mist spray nozzle is disposed in the gap between the slab support rolls 7 adjacent in the casting direction, and the slab is cooled by cooling water sprayed from these spray nozzles. 11 is cooled while being pulled out.

  A plurality of transport rolls 8 for transporting the cast slab 11 is installed on the downstream side of the slab support roll 7. Above the transport roll 8, the cast slab 11 to be cast is provided. A slab cutting machine 9 for cutting a slab 11a having a predetermined length is disposed.

  As shown in FIG. 4, the cooling grid facility 6 is adjacent to a large number of wear plates 14 arranged in a staggered manner for supporting the slab 11 and a back frame (not shown) that supports the wear plates 14. The cooling water supply nozzle 15 or the cooling water supply nozzle 15 </ b> A installed in the gap of the wear plate 14 is configured. In FIG. 4, the cooling grid equipment 6 is shown only in a part in the width direction of the slab 11, but the cooling grid equipment 6 is installed over the entire width of the slab 11.

  The cooling water supply nozzle 15 for ejecting the shower-like water flow group has the same structure as the cooling water supply nozzle 15 shown in FIG. 1 described above, and the cooling water supply nozzle 15A is the cooling water supply shown in FIG. 2 described above. It has the same structure as the nozzle 15A. Hereinafter, the cooling water supply nozzle 15 will be described with reference to FIG. 1, and the cooling water supply nozzle 15A will be described with reference to FIG. First, the cooling water supply nozzle 15 will be described.

  As shown in FIG. 1, the cooling water supply nozzle 15 includes a box-shaped nozzle head 16 and a cooling water supply pipe 18 having a rectifying hole 19. A plurality of nozzle holes 17 are provided on the front surface of the nozzle head 16, and cooling water is ejected from these nozzle holes 17 in a shower shape. The cooling water supply pipe 18 is a closed end pipe having a tip connected through the box portion of the nozzle head 16 and having a plurality of rectifying holes 19 on the side surface thereof. The structure of the cooling water supply pipe 18 has a rectifying function and a header function for uniformly ejecting cooling water from a plurality of nozzle holes 17 provided on the front surface of the nozzle head 16.

The diameter and the number of holes of the nozzle hole 17 are basically determined according to the flow rate of the cooling water to be supplied. From the viewpoint of preventing the nozzle hole 17 from being clogged with foreign matters suspended in the cooling water, The diameter is preferably 3 mm or more. However, if the diameter of the nozzle hole 17 is made too large while the flow rate of the cooling water remains constant, the cooling flow rate of the cooling water from the nozzle hole 17 decreases, so that the water flow droops before reaching the slab 11. As a result, the cooling capacity decreases. Accordingly, it is desirable that the diameter and the number of the holes of the nozzle holes 17 are assured as possible in the range where the water flow injected from each nozzle hole 17 does not stay after colliding with the slab 11. Specifically, the number of nozzle holes 17 is determined so as to form a shower-like water flow group of 0.08 lines / cm ² or more with respect to the area of the gap of the wear plate 14, and these are arranged in a staggered manner. Then, it is good to adjust the cooling water flow rate.

  Next, the cooling water supply nozzle 15A will be described. As shown in FIG. 2, not only in the gap region of the wear plate 14 but also the outer peripheral portion in the gap region of the wear plate 14 and the side surface of the wear plate 14, the water flow is collided to simultaneously cool these portions. Like the cooling water supply nozzle 15, the cooling water supply nozzle 15 </ b> A that can be configured includes a box-shaped nozzle head 16 and a cooling water supply pipe 18 having a rectifying hole 19. On the front surface of the nozzle head 16, a plurality of nozzle holes 17 and a plurality of nozzle holes 17 are arranged on the outer periphery of the nozzle hole 17 and inclined to the nozzle head 16 toward the boundary between the slab 11 and the wear plate 14. The inclined nozzle hole 26 is provided toward the surface of the slab 11 from the nozzle hole 17 and at the boundary between the slab 11 and the outer edge of the wear plate 14 from the inclined nozzle hole 26. Cooling water spouts out like a shower. The cooling water supply pipe 18 is a closed end pipe having a tip connected through the box portion of the nozzle head 16 and having a plurality of rectifying holes 19 on the side surface thereof. The structure of the cooling water supply pipe 18 has a rectifying function and a header function for uniformly ejecting cooling water from the plurality of nozzle holes 17 and the inclined nozzle holes 26 provided on the front surface of the nozzle head 16. Is.

The diameter and the number of holes of the nozzle hole 17 and the inclined nozzle hole 26 are basically determined according to the flow rate of the cooling water to be supplied. However, the nozzle hole 17 and the inclined nozzle hole due to foreign matters suspended in the cooling water. From the viewpoint of preventing clogging of 26, the diameter is desirably 3 mm or more. However, if the diameter of the nozzle hole 17 and the inclined nozzle hole 26 is excessively increased while the flow rate of the cooling water remains constant, the discharge speed of the cooling water from the nozzle hole 17 and the inclined nozzle hole 26 decreases. The water flow hangs down until it reaches the slab 11, and the cooling capacity decreases. Accordingly, the diameter and the number of holes of the nozzle hole 17 and the inclined nozzle hole 26 are within the range where the water flow injected from each nozzle hole 17 and the inclined nozzle hole 26 does not stay after colliding with the slab 11. It is desirable to ensure the maximum. Specifically, the number of nozzle holes 17 and the inclined nozzle holes 26 is determined so as to form a shower-like water flow group of 0.08 lines / cm ² or more with respect to the area of the gap of the wear plate 14, The cooling water flow rate should be adjusted. The nozzle holes 17 are staggered, and the inclined nozzle holes 26 are staggered with respect to the nozzle holes 17 on the outer periphery of the nozzle head 16.

  The wear plate 14 shown in FIG. 4 is a rectangular type, but may be a lattice type as shown in Non-Patent Document 1. In short, if the structure is such that the support area of the slab 11 by the wear plate 14 is 20 to 60% and other parts can be cooled by the cooling water supply nozzle 15 or the cooling water supply nozzle 15A, the wear plate 14 Any shape may be used. Further, the installation length of the cooling grid facility 6 in the casting direction is not particularly limited, and may be any number as long as at least the wear plates 14 are arranged in a staggered manner in the casting direction. However, since the cooling grid equipment 6 is originally a device that supports the slab 11 directly under the mold, a length of 3 m or more is not required.

  The wear plate 14 is usually made of cast steel or cast iron and has a flat plate shape with a flat contact surface with the slab 11, and is cooled by cooling water sprayed from the cooling water supply nozzle 15 or the cooling water supply nozzle 15A. The slab 11 in a portion that comes into contact with the wear plate 14 is not cooled directly by the cooling water, but is indirectly cooled through the wear plate 14. In order to further enhance the cooling ability in the cooling grid facility 6, it is preferable to use a wear plate 14 provided with a cooling function. Specifically, it is preferable to use a wear plate 14 having the shape shown in FIG.

  As shown in FIG. 5, the wear plate 14 provided with a cooling function is provided with a groove 20 on the contact surface with the slab 11, and injects cooling water as a cooling medium toward the inside of the groove 20. An ejection hole 21 is provided in each groove 20. The inside of the wear plate 14 is a cooling water flow path 22, and the cooling water supplied to the flow path 22 via the introduction pipe 23 is jetted from each ejection hole 21. Therefore, since the cooling water passes through the flow path 22 provided inside the wear plate 14, the wear plate 14 is also cooled by the cooling water passing through the flow path 22. That is, the wear plate 14 provided with the cooling function is a wear plate 14 intended to improve cooling by the cooling water sprayed from the ejection holes 21 and to improve cooling by the wear plate 14 having a water cooling structure. On the other hand, the conventional wear plate having no cooling function is flat without the groove 20 on the surface in contact with the slab 11, and also has a structure in which water is cooled from the inside without the ejection hole 21. Absent. 5A and 5B are diagrams showing an example of the shape of the wear plate provided with a cooling function, where FIG. 5A is a front view and FIG. 5B is a side sectional view. Moreover, in FIG. 5, although the groove | channel 20 is installed in the horizontal direction with respect to the wear plate 14, it may be a vertical direction or an oblique direction. Further, the groove 20 does not have to be a straight line and may be a curved line. In short, any shape may be used as long as water vapor escapes through the groove 20.

  The diameter of the ejection hole 21 is determined from the flow rate of the cooling water ejected from the ejection hole 21. If the diameter of the cooling water is excessively large while the flow rate of the cooling water is kept constant, the collision pressure hitting the slab 11 of the cooling water is lowered, a vapor film is generated, and the cooling capacity is reduced. However, if the diameter of the ejection hole 21 is too small in order to ensure the flow rate, clogging may occur and cooling may become impossible. Therefore, from the viewpoint of preventing clogging, the diameter is desirably 3 mm or more. Moreover, what is necessary is just to determine the number of the ejection holes 21 according to the flow volume of a cooling water. Moreover, when installing the several ejection hole 21 in the same groove | channel 20, it is desirable to determine the space | interval with the adjacent ejection hole 21 so that the cooling water injected from each ejection hole 21 may not stay. In the case where the diameter of the ejection hole 21 is 3 mm, it is preferably separated by about 30 mm.

  The average heat transfer coefficient is improved by injecting the cooling water from the ejection holes 21 using the wear plate 14, and the heat transfer coefficient at the position cooled by the cooling water supply nozzle 15 and the position in contact with the wear plate 14. The difference between the heat transfer coefficient and the heat transfer coefficient becomes small, and uniform cooling becomes possible.

In this case, the density of the amount of water ejected from the ejection holes 21 is preferably in the range of 200 liters / minute · m ² or more and 8000 liters / minute · m ² or less. If it is less than 200 liters / minute · m ² , cooling by the wear plate 14 does not improve, while if the water density exceeds 8000 liters / minute · m ² , new water directly contacts the slab surface. The heat transfer coefficient is not improved because there is no loss. Note that the density of the amount of cooling water ejected from the ejection holes 21 is the total amount of cooling water ejected from all the ejection holes 21 installed in one wear plate 14 per minute. It is a value obtained by dividing by the area of the contact surface (including the groove area) with the piece 11.

  Using the continuous casting machine 1 having such a configuration, the molten steel 10 staying in the tundish 2 is injected into the mold 5 through the immersion nozzle 4 while adjusting the flow rate by the sliding nozzle 3. The molten steel 10 injected into the mold 5 is cooled in contact with the mold 5 to form a solidified shell 12. While maintaining the molten steel surface position in the mold 5 at a substantially constant position, the slab 11 having the surface as the solidified shell 12 and the inside as the unsolidified phase 13 is continuously drawn below the mold 5 to continuously cast the molten steel 10. carry out. The slab 11 from which the mold 5 has been drawn is cooled while being supported by the cooling grid equipment 6 and the slab support roll 7, and eventually solidifies completely to the inside. The cast slab 11 is cut by a slab cutting machine 9 to produce a slab 11a having a predetermined length.

At that time, the discharge flow rate in the nozzle hole 17 of the cooling water supply nozzle 15 is 2 m / sec or more, and the water density of the cooling water in the wear plate gap is 1000 liters / minute · m ² or more and 6000 liters / minute · m ² or less. It is desirable to adjust the amount of cooling water ejected from the cooling water supply nozzle 15 so as to be in the range. In the case of the cooling water supply nozzle 15A, the discharge flow rate in the nozzle hole 17 and the inclined nozzle hole 26 of the cooling water supply nozzle 15A is 2 m / second or more, and the water density of the cooling water in the wear plate gap is 2000 liters / second. It is desirable to adjust the amount of cooling water ejected from the cooling water supply nozzle 15A so as to be in the range of min · m ^{2 to} 8000 liters / min · m ² . In addition, the spray amount of the cooling water from the spray nozzle installed in the gap between the slab support rolls 7 is not particularly specified, and an optimal range is appropriately set according to the steel type to be cast and the casting speed. .

  By cooling the slab 11 using the cooling grid equipment 6 having the above-described configuration, the slab 11 can be cooled efficiently while being stably supported. Is possible. Moreover, when the wear plate 14 shown in FIG. 5 is used, since the nonuniformity of cooling in the cooling grid equipment 6 can be improved, the surface crack of the slab 11 caused by the nonuniform cooling can be prevented. Is also possible.

  An experimental device that simulates the cooling grid equipment used directly under the mold in actual operation, that is, a structure directly under the mold that combines a wear plate and a water spray nozzle, is manufactured. The steel material heated was cooled using the nozzle and the cooling water supply nozzle which cools a slab by ejecting a shower-like stream of water, and the cooling capacity was compared and evaluated.

  The cooling water supply nozzle 15 shown in FIG. 1 and the cooling water supply nozzle 15 </ b> A shown in FIG. 2 were prepared as the cooling water supply nozzle that ejects a shower-like water flow group and cools the slab. That is, it is composed of a box-shaped nozzle head 16 and a cooling water supply pipe 18 having a rectifying hole 19, and a plurality of nozzle holes 17 are provided on the front surface of the nozzle head 16. The cooling water supply nozzle 15 is capable of jetting cooling water, and a cooling water supply pipe 18 having a box-shaped nozzle head 16 and a rectifying hole 19. The hole 17 and the inclined nozzle hole 26 are provided, and the cooling water supply nozzle 15 </ b> A is capable of ejecting the cooling water from the nozzle hole 17 and the inclined nozzle hole 26 in a shower shape. In both the cooling water supply nozzle 15 and the cooling water supply nozzle 15A, the outer dimensions of the nozzle head portion are a height of 89 mm, a width of 89 mm, and a depth of 95 mm. The nozzle holes 17 arranged in a staggered manner are provided in front of the nozzle head of the cooling water supply nozzle 15, and the nozzle holes 17 and the nozzle holes 26 arranged in a staggered manner are provided in front of the nozzle head of the cooling water supply nozzle 15A, respectively. . On the other hand, the conventional water spray nozzle is a full cone type water spray nozzle that sprays water conically from one nozzle hole. The wear plate used was a wear plate on a normal flat plate.

  As a method for laboratory evaluation of the cooling capacity, a method is generally used in which water is sprayed on the heated steel material to cool it, and the heat transfer coefficient is obtained from the temperature history of the steel material. A hole was provided on the side opposite to the surface to be cooled, a thermocouple was embedded therein, and the temperature history was measured with the thermocouple.

  In the experiment, as shown in FIG. 6, an apparatus having a configuration in which six cooling water supply nozzles 15 or six cooling water supply nozzles 15 </ b> A and six wear plates 14 were combined was used. For comparison, an apparatus provided with a full cone type water spray nozzle instead of the cooling water supply nozzles 15 and 15A was also used. As shown in FIG. 7, the heated steel material 24 is brought into contact with the wear plate 14 to cool the steel material 24 by injecting cooling water from the cooling water supply nozzle 15, the cooling water supply nozzle 15A and the water spray nozzle. did. In any case, the distance from the steel surface to the nozzle front surface was 80 mm. FIG. 6 is a schematic diagram of an experimental apparatus for comparing and evaluating the cooling capacity of the cooling water supply nozzle, and FIG. 7 is a side sectional view showing an evaluation test method for the cooling capacity of the cooling water supply nozzle. 7 shows the case where the cooling water supply nozzle 15 is used.

  As the steel material 24 to be heated, a steel material made of carbon steel having a width of 400 mm, a height of 600 mm, a thickness of 20 mm, and a carbon concentration of 0.2% by mass is used. Eleven holes 8 mm deep and 18 mm deep were made, and a K-type sheathed thermocouple 25 having a diameter of 1.6 mm was embedded therein. As shown in FIG. 6, the thermocouple 25 was embedded at 11 positions directly below the cooling water supply nozzle 15 to which the cooling water is directly applied. In the experiment, the steel material 24 was heated in an electric furnace maintained at 1200 ° C. for about 1 hour, the uniformly heated steel material 24 was taken out and fixed to the experimental apparatus, and cooling was started. During the cooling of the steel material 24, eleven temperature measurement values by the thermocouple 25 were taken into a personal computer every 0.1 second. After the experiment, calculate the heat transfer coefficient (local heat transfer coefficient) at the position of each thermocouple by combining the measured temperature history and numerical calculation, and calculate the area average value of the obtained local heat transfer coefficient for the cooling nozzle. The cooling capacity was evaluated.

  The test was conducted at the following six levels.

  Level 1: A conventional full cone type water spray nozzle was used, and the amount of cooling water per water spray nozzle was 25 liters / minute. Hereinafter, level 1 is referred to as “conventional example 1”.

  Level 2: The test was performed by using the cooling water supply nozzle 15 for ejecting a shower-like water flow group, and the cooling water amount per cooling water supply nozzle being 25 liters / minute, which is the same as in the conventional example 1. The diameter of the nozzle hole 17 of the cooling water supply nozzle 15 is 3.0 mm, the number of nozzle holes 17 installed per cooling water supply nozzle is 13, and these nozzle holes 17 are arranged in the height direction and the width direction. The nozzle heads 16 are staggered at a pitch of 30 mm. In this case, the discharge flow rate of the cooling water ejected from the nozzle hole 17 is 4.5 m / sec. Hereinafter, Level 2 is referred to as “Example 1 of the present invention”.

  Level 3: A cooling water supply nozzle 15 that ejects a shower-like water flow group is used, and the amount of cooling water per cooling water supply nozzle is 25 liters / minute, which is the same as in Conventional Example 1 and Invention Example 1, and tested. went. The diameter of the nozzle hole 17 of the cooling water supply nozzle 15 was 4.8 mm, and the nozzle holes 17 were installed at a total of five locations in the center and four corners of the nozzle head 16 for one cooling water supply nozzle. The intervals in the height direction and the width direction of the nozzle holes 17 installed at the four corners were set to 48 mm. In this case, the discharge flow rate of the cooling water ejected from the nozzle hole 17 is 4.6 m / sec, which is substantially equal to that of the first example of the present invention. Hereinafter, Level 3 is referred to as “Example 2 of the present invention”.

  Level 4: A test was conducted using a conventional full cone type water spray nozzle and a cooling water amount per water spray nozzle of 48 liters / minute. Hereinafter, level 4 is referred to as “conventional example 2”.

  Level 5: The test was performed by using the cooling water supply nozzle 15 for ejecting a shower-like water flow group, and the cooling water amount per one cooling water supply nozzle was 48 liters / minute, which was the same as in the conventional example 2. The cooling water supply nozzle 15 used was the same as that of Example 1 of the present invention. In this case, the discharge speed of the cooling water ejected from the nozzle hole 17 is 8.8 m / sec. Hereinafter, Level 5 is referred to as “Example 3 of the present invention”.

  Level 6: Cooling water supply using the cooling water supply nozzle 15A in which the inclined nozzle hole 26 is arranged and the shower-like water flow can collide with the outer peripheral portion in the wear plate gap region and the side surface of the wear plate. The test was performed with the cooling water amount per nozzle being 48 liters / minute, which is the same as in Conventional Example 2 and Invention Example 3. The diameter of the nozzle hole 17 of the cooling water supply nozzle 15A was 3.0 mm, the number of nozzle holes 17 installed per cooling water supply nozzle was 13, and the nozzle holes 17 were arranged in the same manner as Example 3 of the present invention. A total of twelve inclined nozzle holes 26 are arranged on the outer periphery of the nozzle head 16 of the cooling water supply nozzle 15A. The diameter of the inclined nozzle hole 26 is 3.0 mm, which is the same as that of the nozzle hole 17. In this case, the discharge flow rate of the cooling water ejected from the nozzle hole 17 and the inclined nozzle hole 26 is 4.6 m / sec. Hereinafter, Level 6 is referred to as “Example 4 of the present invention”.

  Table 1 shows the average heat transfer coefficient of the wear plate gap when the surface temperature of the steel material 24 is 850 ° C., measured at these six levels. Here, the average heat transfer coefficient is obtained by calculating the local heat transfer coefficient at the thermocouple installation position shown in FIG. 6 and taking the area average value with respect to the wear plate gap.

As shown in Table 1, the average heat transfer coefficient of the wear plate gap in Conventional Example 1 was 2156 kcal / m ² · hr · K. On the other hand, in Example 1 of the present invention, the average heat transfer coefficient of the wear plate gap was 2753 kcal / m ² · hr · K, and the cooling efficiency was improved by about 28% compared to the conventional example. Further, in the present invention example 2, the average value of the heat transfer coefficient is 2235 kcal / m ² · hr · K, and the cooling water flow rate and the cooling water discharge flow rate are substantially the same as those of the present invention example 1, The cooling capacity was only about 4% higher than the conventional example. From this, it was found that it is important to secure the number of water streams per unit cooling area to a certain degree or more in order to enhance the cooling ability even when forming a shower-like water stream group. In this regard, from the test results obtained by variously changing the number of nozzle holes and the nozzle diameter of the cooling water supply nozzle 15, a shower-like water flow group of 0.08 / cm ² or more with respect to the area of the wear plate gap was formed. It has been found that it is preferable to cool the slab.

Moreover, from the test result which changed the flow volume of the cooling water using the cooling water supply nozzle 15 used in the present invention example 1, the discharge flow rate of the cooling water ejected from the nozzle hole 17 is 2.0 m / second or more, The cooling water supplied per cooling water supply nozzle is optimally in the range of 1000 liters / minute · m ² or more and 6000 liters / minute · m ² or less with respect to the wear plate gap area. It turns out that. When the cooling water discharge flow rate is less than 2.0 m / sec, the cooling capacity decreases because the water flow hangs down until reaching the slab. In addition, if the water density is less than 1000 liters / minute · m ² , the cooling capacity does not increase because the amount of water itself is small, and if it exceeds 6000 liters / minute · m ² , the cooling water stays in the gap between the wear plates. This is because the supplied cooling water is difficult to reach the slab.

In addition, the average heat transfer coefficient of the wear plate gap in Conventional Example 2 in which the water density was increased was 2847 kcal / m ² · hr · K. On the other hand, in Example 3 of the present invention, the average heat transfer coefficient of the wear plate gap was 3559 kcal / m ² · hr · K, and the cooling efficiency was improved by about 25% compared to Conventional Example 2. Further, in Example 4 of the present invention, the average heat transfer coefficient is 4609 kcal / m ² · hr · K, and the cooling capacity is 62 as compared with Conventional Example 2 although the cooling water flow rate is almost the same as that of Example 3 of the present invention. % Also improved. Therefore, even in the case of forming a shower-like water flow group, in order to increase the cooling capacity, the shower-like water flow is also caused to collide with the outer peripheral portion in the wear plate gap region and the wear plate side surface, so that these regions are It was found that it is important to increase the cooling capacity of the.

Moreover, from the test result which changed the flow volume of the cooling water using the cooling water supply nozzle 15A used in the present invention example 4, the discharge speed of the cooling water ejected from the nozzle hole 17 and the inclined nozzle hole 26 is 2.0 m. The cooling water supplied per cooling water supply nozzle is 2000 liters / minute · m ² or more and 8000 liters / minute · m ² or less with respect to the area of the wear plate gap. It turns out that it is optimal. When the cooling water discharge speed is less than 2.0 m / sec, the cooling capacity is lowered because the water flow hangs down until reaching the slab. In addition, if the water density is less than 2000 liters / minute · m ² , the cooling capacity does not increase because the amount of water itself is small, and if it exceeds 8000 liters / minute · m ² , cooling water stays in the gap between the wear plates, and newly This is because the supplied cooling water is difficult to reach the slab.

It is the schematic which shows one example of the cooling water supply nozzle employ | adopted by this invention, (A) is a front view, (B) is side sectional drawing. It is the schematic which shows the other example of the cooling water supply nozzle employ | adopted by this invention, (A) is a front view, (B) is side sectional drawing. It is the schematic of the continuous casting machine provided with the cooling grid installation which concerns on this invention. It is an expansion perspective view of the cooling grid installation in FIG. It is a figure which shows an example of the shape of the wear plate which provided the cooling function, (A) is a front view, (B) is side sectional drawing. It is the schematic of the experimental apparatus for comparing and evaluating the cooling capacity of the cooling water supply nozzle employ | adopted by this invention. It is side surface sectional drawing which shows the evaluation test method of the cooling capacity of the cooling water supply nozzle employ | adopted by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Continuous casting machine 2 Tundish 3 Sliding nozzle 4 Immersion nozzle 5 Mold 6 Cooling grid equipment 7 Casting piece support roll 8 Conveyance roll 9 Cast piece cutting machine 10 Molten steel 11 Cast piece 12 Solidified shell 13 Unsolidified phase 14 Wear plate 15 Cooling water Supply nozzle 16 Nozzle head 17 Nozzle hole 18 Cooling water supply pipe 19 Rectification hole 20 Groove 21 Ejection hole 22 Flow path 23 Introduction pipe 24 Steel material 25 Thermocouple 26 Inclined nozzle hole

Claims (6)

This is a cooling grid facility for a continuous casting machine installed immediately below the mold of the continuous casting machine, and has a box-shaped nozzle head and a cooling hole having a flow straightening hole in the gap of a wear plate that contacts the slab and supports the slab. A cooling water supply nozzle comprising a water supply pipe, and a plurality of nozzle holes are provided on the front surface of the nozzle head, and a shower-like water flow group is directed from these nozzle holes toward the slab. A cooling grid facility for a continuous casting machine, wherein a cooling water supply nozzle is provided to cool the slab by jetting. The wear plate is characterized in that a groove is provided on the surface on the side in contact with the slab, and an ejection hole for injecting a cooling medium toward the inside of the groove is provided. The cooling grid equipment for a continuous casting machine according to claim 1 . The cooling water supply nozzle is further disposed at an outer periphery of the nozzle hole so as to incline the nozzle head, and an inclination angle for ejecting a shower-like water flow toward the boundary between the slab and the outer edge of the wear plate. The cooling grid equipment for a continuous casting machine according to claim 1, further comprising an attached nozzle hole. A continuous casting machine provided with the cooling grid equipment for a continuous casting machine according to claim 1 is used for casting while cooling a slab by ejecting a shower-like stream of water from a cooling water supply nozzle. A method for producing cast slabs. A continuous casting machine comprising the cooling grid equipment for a continuous casting machine according to claim 2 is used to eject a shower-like stream of water from a cooling water supply nozzle and to inject cooling water from an ejection hole provided in a wear plate. And producing a continuous cast slab characterized by casting the slab while cooling it. A continuous casting machine provided with the cooling grid equipment for a continuous casting machine according to claim 3 is used for casting while cooling a slab by ejecting a shower-like stream of water from a cooling water supply nozzle. A method for producing cast slabs.

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