Nozzle arrangement method for secondary cooling of continuously cast billets

Abstract

This invention provides a nozzle arrangement method for secondary cooling of continuously cast billets, comprising: dividing the secondary cooling area of ​​the continuously cast billet into a spray zone for spraying and covering the billet body, an air-cooling zone to avoid spraying and cooling the corners of the billet, and a splashing zone located between the spray zone and the air-cooling zone; arranging nozzles at corresponding positions in the secondary cooling area according to the positions and areas of the spray zone, splashing zone, and air-cooling zone, so that the spray range of the nozzles covers the spray zone, and simultaneously forms the splashing zone and the air-cooling zone. This invention solves the problem in the prior art where adjusting the secondary cooling process alone cannot solve the problem of corner cracks under existing nozzle arrangements.

Description

Technical Field

[0001] This invention relates to the field of continuous casting processing technology, and more specifically, to a nozzle arrangement method for secondary cooling of continuously cast billets. Background Technology

[0002] Reduction technology is an effective technique for improving segregation, porosity, and shrinkage cavities in continuously cast billets, and its research and application have developed rapidly in recent years. Reduction technology includes light reduction, a combination of light and heavy reduction, and heavy reduction. Light reduction involves progressive reduction using multiple rollers, typically requiring 3-6 rollers, with a total reduction of approximately 8-16 mm, depending on the billet cross-section, steel grade, and solidification process. The combination of light and heavy reduction essentially builds upon light reduction by applying one or two larger reductions to subsequent rollers or rollers near the solidification end, such as a single roller reduction of 5-10 mm. Heavy reduction, compared to the previous two methods, specifically refers to achieving a large reduction using 1-2 pairs of rollers, such as a single roller reduction of 30 mm. Furthermore, the reduction location is relatively wide from a process perspective, starting from the center with a solidity of 0.3 and extending to a certain area after solidification.

[0003] As described above, the pressing technique improves the internal quality of the cast billet by deforming it through the pressing action of rollers. The pressing amount of a single roller ranges from less than 1 mm to more than 20 mm. However, pressing also has a negative effect, leading to corner cracks. These cracks manifest as micro-transverse or longitudinal cracks. They can occur simultaneously with oscillation marks or outside the oscillation mark area. Cracks generally occur within 15 mm of the corner, present both under pressing and without pressing, and some are even located directly at the corner tip. Comparison reveals that without pressing, corner cracks are absent or minimal, while they are highly likely to exist after pressing. Therefore, it can be confirmed that these are cracks caused by pressing, specifically surface corner cracks resulting from pressing.

[0004] Currently, regarding this type of corner cracking, practical experience shows that while it doesn't affect the quality of rolled bars and wire rods, it certainly poses a potential risk. Furthermore, rolling larger bars, if the rolling ratio is insufficient, will inevitably lead to problems. The current approach mainly involves adjusting the water flow in the two cooling zones after the secondary cooling stage to try and increase the overall billet temperature, thereby minimizing corner cracking. However, in practice, this hasn't been very effective. Process tracking reveals that even after reducing the water flow after the secondary cooling stage, the corner temperature remains low when corner cracks occur, the corner appears black, and in most cases, the cracks are more likely to occur on the inner arc side. This demonstrates that simply adjusting the secondary cooling process with the existing nozzle arrangement is insufficient to improve corner cracking. Summary of the Invention

[0005] In view of the above problems, the purpose of this invention is to provide a nozzle arrangement method for secondary cooling of continuously cast billets, so as to solve the problem of corner cracks that cannot be solved by simply adjusting the secondary cooling process under the existing nozzle arrangement.

[0006] This invention provides a nozzle arrangement method for secondary cooling of continuously cast billets, characterized by comprising the following steps:

[0007] S1. In the secondary cooling zone of the continuously cast billet, a spray zone is divided to cover the billet body with spray, an air cooling zone is divided to avoid spray cooling the corners of the continuously cast billet, and a sputtering zone is located between the spray zone and the air cooling zone.

[0008] S2. Based on the position and area of ​​the spray zone, the sputtering zone and the air-cooling zone, nozzles are arranged at the corresponding positions in the secondary cooling zone so that the spray range of the nozzles covers the spray zone, thereby forming the sputtering zone and the air-cooling zone.

[0009] Furthermore, a preferred embodiment is that, in step S1, the secondary cooling region is divided into a spray zone, an air-cooling zone, and a sputtering zone corresponding to the inner arc surface of the continuously cast billet.

[0010] Furthermore, a preferred embodiment is that, in step S1, the secondary cooling region is divided into a spray zone, an air-cooling zone, and a sputtering zone, which correspond to the two sides of the continuously cast billet, respectively.

[0011] Furthermore, in a preferred embodiment, the area of ​​the sputtering zone corresponding to both sides of the continuous casting billet is one-third of the area of ​​the sputtering zone corresponding to the inner arc surface of the continuous casting billet.

[0012] Furthermore, a preferred embodiment is that, in step S1, a spray zone and an air-cooling zone corresponding to the outer arc surface of the continuously cast billet are divided in the secondary cooling zone.

[0013] Furthermore, a preferred embodiment is that the adjacent boundaries of the sputtering area and the air-cooling area overlap by 5 to 10 mm.

[0014] Furthermore, in a preferred embodiment, the factors considered when arranging the nozzles in step S2 include: water pressure, air pressure, the arrangement height of the nozzles, the type of nozzles, the surface temperature of the continuously cast billet, the arc surface where the nozzles are located, and the angle of the continuously cast billet.

[0015] Furthermore, a preferred approach is to consider the heat transfer effect of the sputtering zone in the selection, design, and arrangement of the nozzle, and to use the sputtering zone as the coverage area of ​​the nozzle.

[0016] Furthermore, a preferred embodiment is that the nozzle is an aerosol nozzle with a narrow angle of 30°, the narrow angle covering the width direction of the cast billet.

[0017] As can be seen from the above technical solution, the nozzle arrangement method for secondary cooling of continuously cast billets provided by the present invention first divides the secondary cooling area of ​​the continuously cast billet into a spray zone for spraying and covering the billet body, an air-cooling zone to avoid spraying and cooling the corners of the billet, and a splashing zone located between the spray zone and the air-cooling zone. Then, according to the position and area of ​​the spray zone, splashing zone, and air-cooling zone, nozzles are arranged at the corresponding positions in the secondary cooling area so that the spray range of the nozzles covers the spray zone, and the cooling water in the spray zone forms a flowing water mold in the splashing zone. The splashing zone is considered as an extension of the nozzle coverage area, thereby ensuring that the air-cooling zone is absolutely air-cooled, thereby increasing the corner temperature of the continuously cast billet when it reaches the pressing position, thereby improving the structural toughness of the corner area of ​​the billet, and thus avoiding corner cracks caused by pressing. The nozzle arrangement method for secondary cooling of continuously cast billets provided by the present invention is the most economical way to solve the corner cracks caused by pressing, requiring only optimization of the nozzle arrangement design without involving the modification of other equipment.

[0018] To achieve the foregoing and related objectives, one or more aspects of the invention include the features that will be described in detail below. The following description and accompanying drawings illustrate certain exemplary aspects of the invention. However, these aspects indicate only a few of the various ways in which the principles of the invention can be used. Furthermore, the invention is intended to encompass all such aspects and their equivalents. Attached Figure Description

[0019] Other objects and results of the invention will become more apparent and readily understood with reference to the following description taken in conjunction with the accompanying drawings. In the drawings:

[0020] Figure 1 This is a flowchart of a nozzle arrangement method for secondary cooling of continuously cast billets according to an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the area division in the secondary cooling region according to an embodiment of the present invention.

[0022] In the attached diagram, 1-continuous casting billet, 2-spraying zone, 3-air cooling zone, 4-splashing zone, 5-nozzle.

[0023] In the accompanying drawings, the same reference numerals indicate similar or corresponding features or functions. Detailed Implementation

[0024] In the following description, numerous specific details are set forth for illustrative purposes and to provide a thorough understanding of one or more embodiments. However, it will be apparent that these embodiments may also be implemented without these specific details.

[0025] In view of the aforementioned prior art, which cannot solve the problem of corner cracks by simply adjusting the secondary cooling process under the existing nozzle arrangement, a nozzle arrangement method for secondary cooling of continuously cast billets is proposed.

[0026] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0027] To illustrate the nozzle arrangement method for secondary cooling of continuously cast billets provided by this invention Figure 1 A flow chart of a nozzle arrangement method for secondary cooling of a continuously cast billet according to an embodiment of the present invention is shown; Figure 2 The division of the secondary cooling region according to an embodiment of the present invention is shown.

[0028] like Figure 1 Combination Figure 2 As shown in the figure, the nozzle arrangement method for secondary cooling of continuously cast billets provided by the present invention is characterized by comprising the following steps:

[0029] S1. In the secondary cooling zone of the continuously cast billet, a spray zone 2 is divided to spray and cover the billet body of the continuously cast billet 1, an air cooling zone 3 is divided to avoid spraying and cooling the corners of the continuously cast billet 1, and a splashing zone 4 is located between the spray zone 2 and the air cooling zone 3.

[0030] S2. Based on the location and area of ​​the spray zone 2, the splash zone 4 and the air-cooling zone 3, nozzles 5 are arranged at the corresponding positions in the secondary cooling zone so that the spray range of the nozzles 5 covers the spray zone 2, and the cooling water in the spray zone 2 forms a flowing water pattern in the splash zone 4, but does not flow into the air-cooling zone 3.

[0031] Before the continuously cast billet enters the secondary cooling zone, it can be simulated using three-dimensional software to divide the area into spray zone 2, air cooling zone 3, and splash zone 4. Alternatively, it can be divided experimentally by making multiple adjustments to divide the area into spray zone 2, air cooling zone 3, and splash zone 4. As long as the above areas can be divided before the continuously cast billet undergoes secondary cooling spraying, there are no special limitations here. Those skilled in the art can complete the division of the above areas according to the actual situation.

[0032] In the technical solution of this invention, the concept of a "splash zone" is established based on the coverage of the spray area of ​​nozzle 5, such as... Figure 2As shown, the sputtering zone 4 is a layer of flowing water mold formed by the cooling water of the nozzle 5 spraying area. There is still a certain heat exchange capacity in the sputtering zone 5. It should be regarded as an extension of the cooling of the nozzle 5 spraying area, which will bring about the cooling effect of the billet temperature. Therefore, it is carefully considered in this invention to effectively avoid the occurrence of corner cracks.

[0033] By first dividing the secondary cooling zone of the continuously cast billet into a spray zone 2 (covering the billet body), an air-cooling zone 3 (avoiding spray cooling of the corners of the billet), and a splashing zone 4 (located between the spray zone 2 and the air-cooling zone 3), and then arranging nozzles 5 at corresponding positions in the secondary cooling zone according to the positions and areas of the spray zone 2, splashing zone 4, and air-cooling zone 3, the spray range of the nozzles 5 covers the spray zone 2, and the cooling water in the spray zone 2 forms a flowing water pattern in the splashing zone 4. The splashing zone 4 is considered as an extension of the coverage area of ​​the nozzles 5, thereby ensuring that the air-cooling zone 3 is absolutely air-cooled, thus increasing the corner temperature of the continuously cast billet when it reaches the pressing position, thereby improving the structural toughness of the corner area of ​​the billet and avoiding corner cracks caused by pressing. The nozzle arrangement method for secondary cooling of continuously cast billets provided by this invention is the most economical way to solve the corner cracks caused by pressing, requiring only optimized design of the nozzle arrangement without involving modifications to other equipment.

[0034] As a preferred embodiment of the present invention, in step S1, a spray zone 2, an air-cooling zone 3, and a sputtering zone 4 corresponding to the inner arc surface of the continuous casting billet 1 are divided in the secondary cooling zone.

[0035] For the inner arc surface of continuously cast billet 1 ( Figure 2 The nozzle 5 corresponding to the upper part of the image (in the image) will be more prominent and larger in area because water tends to accumulate in the inner arc surface of the splash zone 4, forming a significant heat exchange area. Therefore, for the inner arc surface of the continuously cast billet 1, it is necessary to divide the area into a corresponding spray zone 2, an air-cooling zone 3, and a splash zone 4.

[0036] As a preferred embodiment of the present invention, in step S1, the secondary cooling area is divided into a spray zone, an air cooling zone, and a sputtering zone, which correspond to the two sides of the continuous casting billet 1, respectively.

[0037] Both sides of the continuous casting billet 1, i.e. the side arc surface of the continuous casting billet 1, will also generate a certain amount of water retention when the nozzle 5 sprays, but it will be smaller than the inner arc surface. Therefore, for both sides of the continuous casting billet 1, it is necessary to separate the corresponding spraying zone 2, air cooling zone 3 and splashing zone 4 respectively.

[0038] As a preferred embodiment of the present invention, the area of ​​the sputtering zone corresponding to both sides of the continuous casting billet 1 is one-third of the area of ​​the sputtering zone 4 corresponding to the inner arc surface of the continuous casting billet 1.

[0039] The nozzle selection, design, and arrangement take into account the influence of the sputtering zone 4 on different arc surfaces. The inner arc surface considers the sputtering zone 4, while the outer arc surface ignores the sputtering zone 4. The two sides are considered as one-third of the area of ​​the sputtering zone 4 on the inner arc surface 4. This scheme is based on the results obtained from multiple actual tests.

[0040] As a preferred embodiment of the present invention, in step S1, a spray zone 2 and an air-cooling zone 3 corresponding to the outer arc surface of the continuous casting billet 1 are divided in the secondary cooling zone.

[0041] Outer arc surface of continuous casting billet 1 ( Figure 2 The splash zone 4 (below) can be ignored because the water hitting the continuously cast billet 1 will immediately fall off due to gravity and will not form a storage zone. Regarding the angle of the continuously cast billet, for example, if the nozzle 5 is located in the horizontal section of the continuous casting, the water flow in the splash zone 4 will be poor. In addition, due to the influence of Leidenfrost temperature, the heat exchange effect will decrease. However, if the nozzle is located in the arc section of the continuous casting, the water stored in the splash zone 4 will flow quickly towards the billet pulling direction under the action of gravity, resulting in a better heat exchange effect.

[0042] As a preferred embodiment of the present invention, the adjacent boundaries of the sputtering region 4 and the air-cooling region 3 overlap by 5 to 10 mm.

[0043] The heat transfer coefficient in the sputtering zone 4 is not uniform. The heat transfer effect of the sputtering zone is worse the further away from the spraying area. Given the requirements of the air-cooled zone 3 without water spraying, the heat transfer effect of the section of the sputtering zone 4 far away from the spraying zone 2 is considered. Therefore, the sputtering zone 4 can overlap with the adjacent boundary of the air-cooled zone 3 by 5 to 10 mm, which ensures that the corner area is not cooled and the continuous casting billet 1 far away from the corner area is cooled.

[0044] As a preferred embodiment of the present invention, in step S2, the factors considered when arranging the nozzle 5 include: water pressure, air pressure, arrangement height of the nozzle 5, type of nozzle 5, surface temperature of the continuous casting billet 1, arc surface where the nozzle 5 is located, and angle of the continuous casting billet 1.

[0045] Based on the concept of the sputtering zone 4, the arrangement of nozzles 5 must consider the heat transfer effect of the sputtering zone 4. If the sputtering zone 4 is not considered, and it is assumed that there is no heat transfer in areas not reached by nozzles 5, the corner temperature will be too low. For example, if the spray area of ​​nozzle 5 is 15mm away from the corner, it is assumed that the corner is not cooled. However, due to the presence of the sputtering zone 4, assuming the sputtering zone 4 is 15mm wide, the corner is effectively cooled throughout. Furthermore, the inner arc surface is more prone to forming a sputtering zone, leading to excessively low corner temperatures on the inner arc surface of the cast billet. Therefore, the heat transfer effect of the sputtering zone 4 must be considered in the selection, design, and arrangement of nozzles 5, treating the sputtering zone 4 as part of the coverage area of ​​nozzle 5. This ensures that the air-cooled zone 3 is absolutely air-cooled, effectively improving the corner temperature.

[0046] As a preferred embodiment of the present invention, the heat exchange effect of the sputtering zone 4 should be considered in the selection, design and arrangement of the nozzle 5, and the sputtering zone 4 should be used as the coverage area of ​​the nozzle 5.

[0047] Furthermore, a preferred embodiment is that nozzle 5 is an aerosol nozzle with a narrow angle of 30°, covering the width direction of the cast billet. The type of nozzle 5 and the narrow angle can be adjusted accordingly based on actual conditions.

[0048] To better illustrate the nozzle arrangement method for secondary cooling of continuously cast billets provided by this invention, the following example is provided:

[0049] Taking the continuous casting production of small square billets in a certain factory as an example, the cross-section is 160X160mm, the machine is a full arc type with an arc radius of 10m, the secondary cooling is divided into 5 zones, the 5 zones range from 6.9m to 10.22m, the nozzle is an aerosol nozzle, the model is HPZ2.6-65QZ2, the narrow angle is 30°, and the narrow angle covers the width direction of the billet.

[0050] To increase the temperature in the corner region of the cast billet, the nozzle arrangement in zone 5 was redesigned. Under normal operating air and water pressure, the spray zone width of this nozzle on the horizontal cast billet surface is approximately 12 mm. To increase the temperature of the cast billet within 15 mm of the corner where pressure cracks occur, water is not sprayed into the cast billet region within 15 mm of the corner. This is based on the nozzle arrangement method for secondary cooling of continuously cast billets provided by the present invention.

[0051] For the inner arc surface of the continuously cast billet, considering the 12mm splashing zone on both sides of the nozzle, the nozzle arrangement height is 200mm, and the nozzle spraying area length is 107mm.

[0052] For the outer arc surface of the continuously cast billet, without considering the splashing zone, the nozzle arrangement height is 130mm and the nozzle spraying area length is 131mm;

[0053] For both sides of the continuously cast billet, the area of ​​the sputtering zone is designed to be one-third of the area of ​​the sputtering zone corresponding to the inner arc surface, the nozzle arrangement height is 235mm, and the nozzle spraying area length is 126mm.

[0054] It should be noted that this embodiment is merely a detailed description of the nozzle arrangement method for secondary cooling of continuously cast billets provided by the present invention in practical applications, and does not limit the technical solution provided by the present invention.

[0055] As can be seen from the above specific embodiments, the nozzle arrangement method for secondary cooling of continuously cast billets provided by the present invention first divides the secondary cooling area of ​​the continuously cast billet into a spray zone that sprays and covers the billet body, an air-cooling zone that avoids spraying and cooling the corners of the billet, and a splashing zone located between the spray zone and the air-cooling zone. Then, according to the position and area of ​​the spray zone, splashing zone, and air-cooling zone, nozzles are arranged at the corresponding positions in the secondary cooling area so that the spray range of the nozzles covers the spray zone, and the cooling water in the spray zone forms a flowing water pattern in the splashing zone. The splashing zone is considered as an extension of the nozzle coverage area, thereby ensuring that the air-cooling zone is absolutely air-cooled, thereby increasing the corner temperature of the continuously cast billet when it reaches the pressing position, thereby improving the structural toughness of the corner area of ​​the billet, and thus avoiding corner cracks caused by pressing. The nozzle arrangement method for secondary cooling of continuously cast billets provided by the present invention is the most economical way to solve the corner cracks caused by pressing, requiring only optimized design of the nozzle arrangement without involving modifications to other equipment.

[0056] The nozzle arrangement method for secondary cooling of continuously cast billets according to the present invention has been described above by way of example with reference to the accompanying drawings. However, those skilled in the art should understand that various modifications can be made to the nozzle arrangement method for secondary cooling of continuously cast billets according to the present invention without departing from the scope of the invention. Therefore, the scope of protection of the present invention should be determined by the contents of the appended claims.

Claims

1. A nozzle arrangement method for secondary cooling of continuously cast billets, characterized in that, Includes the following steps: S1. In the secondary cooling zone of the continuously cast billet, a spray zone is divided to cover the billet body with spray, an air cooling zone is divided to avoid spray cooling the corners of the continuously cast billet, and a sputtering zone is located between the spray zone and the air cooling zone. S2. Based on the position and area of ​​the spray zone, the sputtering zone and the air-cooling zone, nozzles are arranged at the corresponding positions in the secondary cooling zone so that the spray range of the nozzles covers the spray zone, thereby forming the sputtering zone and the air-cooling zone.

2. The nozzle arrangement method for secondary cooling of continuously cast billets according to claim 1, characterized in that, In step S1, In the secondary cooling zone, a spray zone, an air cooling zone, and a sputtering zone are defined, corresponding to the inner arc surface of the continuously cast billet.

3. The nozzle arrangement method for secondary cooling of continuously cast billets according to claim 2, characterized in that, In step S1, In the secondary cooling zone, a spray zone, an air cooling zone, and a sputtering zone are respectively divided to correspond to the two sides of the continuously cast billet.

4. The nozzle arrangement method for secondary cooling of continuously cast billets according to claim 3, characterized in that, The area of ​​the sputtering zone corresponding to both sides of the continuous casting billet is one-third of the area of ​​the sputtering zone corresponding to the inner arc surface of the continuous casting billet.

5. The nozzle arrangement method for secondary cooling of continuously cast billets according to claim 1, characterized in that, In step S1, In the secondary cooling zone, a spray zone and an air cooling zone are divided to correspond to the outer arc surface of the continuously cast billet.

6. The nozzle arrangement method for secondary cooling of continuously cast billets according to claim 1, characterized in that, The sputtering zone overlaps with the adjacent boundary of the air-cooling zone by 5 to 10 mm.

7. The nozzle arrangement method for secondary cooling of continuously cast billets according to claim 1, characterized in that, In step S2, Factors considered when arranging the nozzles include: water pressure, air pressure, nozzle arrangement height, nozzle type, surface temperature of the continuously cast billet, the arc surface where the nozzle is located, and the angle of the continuously cast billet.

8. The nozzle arrangement method for secondary cooling of continuously cast billets according to any one of claims 1 to 7, characterized in that, The heat transfer effect of the sputtering zone should be considered in the selection, design and arrangement of the nozzle, and the sputtering zone should be used as the coverage area of ​​the nozzle.

9. The nozzle arrangement method for secondary cooling of continuously cast billets according to any one of claims 1 to 7, characterized in that, The nozzle is an aerosol nozzle with a narrow angle of 30°, which covers the width direction of the cast billet.

Images