A method for controlling the narrow face profile and corner transverse crack of a narrow face concave continuous casting billet

Abstract

The present application provides a kind of narrow face concave continuous casting billet narrow face morphology and corner transverse crack control method, method includes: the width of the straight-arc structure convex arc surface mould narrow face copper plate plane area is 50mm;Arc area convex height is 11mm, arc area and plane area adopt R60 circular arc tangent smooth transition.Narrow face foot roller is configured as straight arc structure, the width of two sides flat area is 20mm, foot roller arc surface and the shape of mould arc surface is same.The narrow face concave continuous casting billet narrow face morphology and corner transverse crack control method provided by the present application is combined with the actual production of narrow face concave billet, and the method for optimizing and improving the narrow face morphology of narrow face concave billet and reducing corner transverse crack is proposed through theoretical analysis and related test, to solve the new problems in the application of new technology in the field, to eliminate the black line defects of wide and thick plate rolling, and to improve the physical quality of billet.

Description

Technical Field

[0001] This invention relates to the field of steelmaking continuous casting, specifically to a method for controlling the narrow-face morphology and corner transverse cracks of a narrow-face concave continuous casting billet. Background Technology

[0002] To address the frequent problem of straight-line cracks (also known as edge straight cracks / black lines) at the edges of heavy plates during rolling, a technology using a narrow-faced copper plate with a straight-arc structure and convex arc surface in the continuous casting machine for heavy plates was adopted. This narrow-faced copper plate has a 30mm wide flat edge and an arc surface in the middle, with a smooth transition between the arc and flat areas. The foot rolls are convex arc surface foot rolls, producing a right-angled, narrow-faced, concave continuous casting billet. Furthermore, to mitigate transverse corner cracks in the billet, a new technology for ultra-fine grain refinement in the corners of the billet using secondary cooling was employed (related patent: CN 114682747). A new type of slab continuous casting machine (slab continuous casting machine) features a new ultra-strong cooling equipment for the narrow-faced foot rolls. This new equipment retains the original four pairs of narrow-faced foot rolls with one nozzle below each roll, adding one nozzle on each side to spray water towards the corner of the slab. Water is supplied to these nozzles via a dedicated water supply circuit, with the water supply volume varying with the casting speed. This achieves strong cooling of the slab's narrow-faced corner structure, promoting grain refinement and the dispersed precipitation of carbonitrides in microalloyed steels, thus controlling transverse corner cracks. After applying these two technologies, the straight-line cracks at the edges of thick plates are significantly improved, and transverse corner cracks in the slab are also alleviated to some extent.

[0003] Based on the application of the above two technologies to produce narrow-faced concave continuous casting billets, under the condition that other process equipment parameters remain unchanged, the actual produced billet narrow-faced morphology does not achieve the right-angled concave billet morphology. The narrow face of the billet is still a fully concave structure, and the corners of the billet are still relatively sharp. In addition, corner transverse crack defects still occasionally occur in the production of niobium-containing microalloyed steel.

[0004] Therefore, it can be seen that although the grain size of the narrow face and corners of the billet is refined through the strong cooling of the foot rolls in the existing technology, the sharp corners result in rapid heat dissipation and transfer. Under the cooling effect of the secondary cooling water, the temperature of the billet corners is too low, and transverse cracks at the corners still occasionally occur when producing niobium-containing microalloyed steel. Summary of the Invention

[0005] This invention provides a method for controlling the narrow face morphology and corner transverse cracks of a narrow-face concave continuous casting billet. It solves the quality problems that occur in the practical application of the narrow-face copper plate technology of the straight-arc structure convex crystallizer and the new technology of ultra-fine grains at the corner of the billet in the secondary cooling process. The method is optimized based on the actual on-site process and equipment.

[0006] The methods include:

[0007] The narrow copper plate plane area of ​​the crystallizer with a straight-arc structure and convex arc surface is 50mm wide.

[0008] The arc-shaped area is configured with a protrusion height of 11mm, and the arc-shaped area and the flat area are smoothly transitioned by an R60 circular arc.

[0009] It should be further noted that in the method, the narrow-faced foot roller is configured as a straight arc structure, with a width of 20mm for the straight areas on both sides, and the arc surface of the foot roller has the same shape as the arc surface of the crystallizer.

[0010] It should be further noted that the method also controls the zero-stage cooling;

[0011] The production width of the continuous casting machine for thick plates is 1500mm, 1800mm, 2000mm, 2200mm, and 2400mm.

[0012] It should be further explained that there are 256 nozzles on the inner and outer arcs of the zero-segment spray system, which are controlled in three zones. The nozzles in each row are staggered. The first zone controls the three rows of nozzles on the upper part of the inner and outer arcs, with 8, 7, and 8 nozzles in each row, respectively.

[0013] The second zone controls the middle position of the inner and outer arcs with 6 rows of nozzles, with each row containing 7, 8, 7, 8, 7, 8 nozzles respectively;

[0014] The lower part of the third zone control is equipped with 8 rows of nozzles, with each row containing 7, 8, 7, 8, 7, 8, 7, 8, 7 respectively.

[0015] It should be further noted that when the width of the billet is 1500mm, after the edge nozzles in the second zone are blocked, the number of nozzles in the middle zone is distributed as follows: 3, 4, 3, 4, 3, 4; after the edge nozzles in the third zone are blocked, the number of nozzles in the middle zone is distributed as follows: 3, 4, 3, 4, 3, 4, 3, 4.

[0016] When the width of the billet is 1800mm, after the edge nozzles in the second zone are blocked, the number of nozzles in the middle zone is distributed as follows: 5, 4, 5, 4, 5, 4; after the edge nozzles in the third zone are blocked, the number of nozzles in the middle zone is distributed as follows: 5, 4, 5, 4, 5, 4, 5, 4.

[0017] When the width of the billet is 2000mm, after the edge nozzles in the second zone are blocked, the number of nozzles in the middle zone is distributed as follows: 5, 6, 5, 6, 5, 6; after the edge nozzles in the third zone are blocked, the number of nozzles in the middle zone is distributed as follows: 5, 6, 5, 6, 5, 6, 5, 6.

[0018] When the width of the billet is 2200mm, after the side nozzles in the second zone are blocked, the number of nozzles in the middle zone is distributed as follows: 7, 6, 7, 6, 7, 6; after the side nozzles in the third zone are blocked, the number of nozzles in the middle zone is distributed as follows: 7, 6, 7, 6, 7, 6, 7, 6.

[0019] It should be further noted that the method also includes a control method based on the secondary cooling water shear ratio:

[0020] Among them, the wide and thick plate continuous casting machine has a total of 8 fan-shaped sections, arc sections and straightening sections, with a total of 512 secondary cooling nozzles, which are controlled in four zones. The number of inner and outer arc nozzles in the arc section and straightening section is the same. Each fan-shaped section has 7 rows of nozzles, and there are 4 nozzles between every two rollers. Along the direction of the billet, the middle two rows of nozzles form one branch, and the two rows of nozzles on both sides form one branch, realizing independent control of secondary cooling water spray in the width direction.

[0021] The method involves controlling the temperature at the corner of the billet in the straightening section above 950℃, and setting the secondary cooling water cutting ratio for each width separately; by measuring the straightening temperature, the temperature is gradually adjusted to form the preset cutting water ratio.

[0022] It should be further noted that the method also includes a secondary cooling water volume control method: cooling control is performed on the inner and outer arc spray water of the wide-face foot roller in the first secondary cooling zone and the inner and outer arc spray water of the three rows of nozzles on the upper part of the zero section in the second zone.

[0023] The total water volume of the inner and outer arcs in the second cooling zone is as follows: for the 200mm cross-section, the pulling speed is controlled at 250-350 l / min within the range of 1.0-1.4m / min; for the 250mm cross-section, the pulling speed is controlled at 200-300 l / min within the range of 0.8-1.2m / min.

[0024] The total water volume for the inner and outer arcs of the second cooling zone is as follows: for the 200mm cross-section, the pulling speed is controlled at 400-600 l / min within the range of 1.0-1.4 m / min; for the 250mm cross-section, the pulling speed is controlled at 300-450 l / min within the range of 0.8-1.2 m / min.

[0025] Slightly reduce the water spray volume in other areas of the secondary cooling system, and control the water content per ton of steel in the secondary cooling system within the range of 0.5-0.7 l / kg.

[0026] As can be seen from the above technical solutions, the present invention has the following advantages:

[0027] The present invention provides a method for controlling the narrow face morphology and corner transverse cracks of narrow face concave continuous casting billets. Combining the actual production of narrow face concave billets, the method proposes an optimization and improvement method for the narrow face morphology of narrow face concave casting billets and the reduction of corner transverse cracks through theoretical analysis and related experiments. This solves new problems that arise in the field application of new technologies and improves the quality of the casting billets while eliminating the black line defect in the rolling of thick plates.

[0028] This invention analyzes and studies the problems of narrow face morphology and transverse cracks in niobium-containing steel corners that occur in the production of narrow face concave continuous casting billets based on existing technologies. It proposes improved schemes for narrow face copper plates and narrow face foot rolls in the crystallizer. Based on different billet widths, it designs schemes for zero-segment nozzle blocking, secondary cooling water width cutting ratio control optimization, secondary cooling water volume control optimization, and equipment precision adjustment control requirements. These measures effectively ensure the billet quality of narrow face concave billets and effectively reduce the rollout process error rate. Attached Figure Description

[0029] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 A schematic diagram of an improved scheme for a narrow-face copper plate for a 200mm thick crystallizer;

[0031] Figure 2 A schematic diagram of an improved scheme for a narrow-faced foot roller in a 250mm thick crystallizer;

[0032] Figure 3 A schematic diagram of an improved narrow-face foot roller design for a 200mm thick crystallizer;

[0033] Figure 4 A schematic diagram of an improved scheme for a narrow-faced foot roller in a 250mm thick crystallizer;

[0034] Figure 5 This is a schematic diagram of the nozzle blocking scheme for different billet widths in the zero section. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] The method for controlling the narrow-face morphology and corner transverse cracks of narrow-face concave continuous casting billets involved in this invention mainly addresses the problem that narrow-face concave continuous casting billets produced using straight-arc structure convex arc surface crystallizers and narrow-face copper plate technology with ultra-fine corner grains in secondary cooling technology still exhibit a completely concave structure in their narrow-face morphology, resulting in relatively sharp corners. Simultaneously, the method of this invention also solves the problem that due to the sharp corners, heat dissipation and heat transfer are rapid, leading to excessively low corner temperatures under the cooling effect of secondary cooling water, occasionally resulting in corner transverse cracks when producing niobium-containing microalloyed steels.

[0037] This invention addresses the problems of improving billet morphology and preventing transverse cracks by improving and optimizing the narrow copper plate structure of the crystallizer, the foot roller structure, the control of nozzle blockage at the zero section of the fan-shaped segment, the arc section of the fan-shaped segment, the control of secondary cooling water cutting in the straightening section, the control of equipment precision, and the control of nitrogen content in the steel. It also solves new problems that arise in the field application of new technologies, and improves the quality of billets while eliminating black line defects in the rolling of thick plates.

[0038] In the embodiments of the present invention, the narrow copper plate edge of the straight-arc convex arc surface crystallizer has a width of 30mm and is flat. The arc surface protrudes 11mm. The arc surface and the flat surface are smoothly transitioned by an R60 circular arc. It is believed that the transition part between the arc surface and the flat surface is cooled by the copper plates on both sides of the arc surface and the straight surface in the crystallizer, and the cooling effect is good. Due to the good cooling effect in the transition area, the billet shell shrinks and detaches from the crystallizer. Under the influence of the temperature of the liquid steel, the internal billet shell gradually melts, causing the billet shell to become thinner. Under the static pressure of the molten steel, it re-contacts the copper plate of the crystallizer. This process is repeated. Overall, when exiting the crystallizer, the thickness of the billet shell in the transition area is less than that in other parts of the narrow surface. Because the billet shell is thinner here, after exiting the crystallizer, this transition area and the flat area are subjected to the pressure and tension of the convex foot roller. This part of the billet shell will continue to be concave inward, resulting in a full arc structure on the narrow surface of the billet, with relatively sharp corners. To address this issue, the width of the narrow-face copper plate edge of the convex crystallizer was widened, increasing the width of the flat area from 30mm to 50mm. This ensures that even with some inward deformation in the transition area, a portion of the flat area remains at the corner of the billet, preventing sharp corners. The improved narrow-face copper plate design for the crystallizer is attached. Figure 1 and attached Figure 2 As shown.

[0039] In the embodiments of the present invention, the improvement of the narrow-faced foot roller is based on the fact that the narrow-faced foot roller is a fully convex arc surface, and the length of the narrow-faced foot roller is about 50mm smaller than the width of the narrow-faced copper plate. Based on the change in the shape of the narrow-faced copper plate in this invention, the narrow-faced foot roller needs to be correspondingly changed to a straight arc structure, with a 20mm wide flat area on both sides. The arc surface of the foot roller has the same shape as the arc surface of the crystallizer. The improved scheme for the narrow-faced foot roller of the crystallizer is attached. Figure 3 and attached Figure 4 As shown.

[0040] Regarding the zero-segment cooling control of this invention, the wide and thick plate continuous casting machine mainly produces widths of 1500mm, 1800mm, 2000mm, 2200mm, and 2400mm. There are a total of 256 existing zero-segment spray nozzles on the inner and outer arcs, controlled in three zones. The nozzles in each row are staggered. Zone 1 controls the upper three rows of nozzles on the inner and outer arcs, with a nozzle distribution of 8+7+8. Zone 2 controls the middle six rows of nozzles on the inner and outer arcs, with a nozzle distribution of 7+8+7+8+7+8. Zone 3 controls the lower eight rows of nozzles, with a nozzle distribution of 7+8+7+8+7+8+7+8+7. In this embodiment, the "+" can be understood as a separator.

[0041] In this embodiment, to adapt to the application of the new technology for ultra-fine grain refinement in the corners of the billet and to ensure the strong cooling effect of the billet, the nozzles and water flow rate in the first zone remain unchanged. In the second and third zones, to prevent overcooling at the corners, when changing the width of the casting machine, a special tool is designed to clog some of the edge nozzles. The clogging rules are as follows:

[0042]

[0043] A diagram illustrating the nozzle clogging rules is attached. Figure 5 As shown.

[0044] Secondary cooling water slitting ratio control:

[0045] The continuous casting machine for thick plates has eight fan-shaped sections, including arc-shaped, straightening, and three other sections, with a total of 512 secondary cooling nozzles. These are controlled in four zones. The number of nozzles on the inner and outer arc sections of the arc and straightening sections is the same. Each fan-shaped section has seven rows of nozzles, with four nozzles between every two rollers. Along the billet direction, the middle two rows of nozzles form one branch, and the two rows on each side form another branch, thus achieving independent control of the secondary cooling water spray in the width direction. Currently, the secondary cooling water volume ratio (water volume in the middle two rows / water volume on both sides) for each zone does not change with the billet width and remains at 1.40. This ratio cannot adapt to maintaining a constant cooling intensity at the corners of the billet when the width changes. Specifically, when producing narrow sections (e.g., 1500mm wide), the corner cooling is too strong, resulting in excessively low corner temperatures and transverse cracks during straightening. Conversely, when producing wide sections (e.g., 2400mm wide), the corner cooling is too weak, leading to uneven distribution of secondary cooling water in the width direction and causing internal quality problems in the billet. To solve this problem and ensure that the temperature of the billet corner in the straightening section is controlled above 950℃, the secondary cooling water cutting ratio for each width was optimized separately. Through practical measurement and gradual adjustment of the straightening temperature, the following cutting water ratio was formed.

[0046] Secondary cooling water section ratio (middle / both sides) 1.52 1.40 1.25 1.15 1.1

[0047] In one exemplary embodiment, a secondary cooling water volume control method is also involved. Here, to ensure the application effect of the new technology for ultra-fine grains at the corner of the billet, strong cooling is implemented in the first secondary cooling zone (controlling the water spraying inside and outside the wide-face foot roller) and the second zone (controlling the water spraying inside and outside the three rows of nozzles on the upper part of the zero section). The total water volume of the inner and outer arcs in the first secondary cooling zone is controlled at 250-350 l / min for a 200mm section drawing speed within the range of 1.0-1.4m / min, and at 200-300 l / min for a 250mm section drawing speed within the range of 0.8-1.2m / min. The total water volume of the inner and outer arcs in the second secondary cooling zone is controlled at 400-600 l / min for a 200mm section drawing speed within the range of 1.0-1.4m / min, and at 300-450 l / min for a 250mm section drawing speed within the range of 0.8-1.2m / min. Slightly reduce the amount of water sprayed in other areas of the secondary cooling system, and control the water content per ton of steel in the secondary cooling system within the range of 0.5-0.7 l / kg.

[0048] This invention also relates to a method for controlling the precision of equipment: the arc deviation of each roller in the fan-shaped section must not exceed 0.2mm. In actual production, a problem of unilateral corner cracks occurred. The arc deviation and roller gap were found to meet the standards. Analysis showed that the fan-shaped section as a whole was not level in the width direction. Therefore, it is necessary to correct the levelness of the rollers in the fan-shaped section to ensure that the levelness of the rollers in the fan-shaped section is within the range of 0.05mm / m.

[0049] Based on the above control methods, through analysis and research on the problems of narrow face morphology and transverse cracks in niobium-containing steel corners in the production of narrow face concave continuous casting billets using existing technologies, an improved scheme for the narrow face copper plate and narrow face foot roll of the crystallizer is proposed. According to different billet widths, a zero-segment nozzle blocking scheme, a secondary cooling water width cutting ratio control optimization scheme, a secondary cooling water volume control optimization scheme, and equipment precision adjustment control requirements are designed to effectively ensure the billet quality of narrow face concave billets and effectively reduce the rolling process reversal rate.

[0050] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0051] Furthermore, as a refinement and extension of the specific implementation of the above embodiments, in order to fully explain the specific implementation process in this embodiment, the specific implementation method of controlling the narrow face morphology and corner transverse cracks of the narrow face concave continuous casting billet is described.

[0052] Taking a steel plant's 200mm thick wide and heavy plate continuous casting machine as an example, it mainly produces widths of 1500mm, 1800mm, 2000mm, 2200mm, and 2400mm.

[0053] In this embodiment, the narrow-face copper plate is improved as follows: Currently, the narrow-face copper plate of the straight-arc convex arc-shaped crystallizer has a 30mm width of flat surface at its edge, with an 11mm protrusion in the arc area. The arc area and the flat area are smoothly transitioned by a 60mm radius arc. The improvement to the narrow-face copper plate is to widen the flat area of ​​the narrow-face copper plate edge, increasing it from 30mm to 50mm. This way, even if some concave deformation occurs in the transition area, a portion of the flat area can still be retained at the corner of the billet, preventing sharp corner morphology from occurring.

[0054] Improvement of the narrow-face foot roller: Currently, the narrow-face foot roller has a fully convex arc surface, and its length is approximately 50mm shorter than the width of the narrow-face copper plate. Based on the change in the shape of the narrow-face copper plate, the narrow-face foot roller needs to be modified to a straight arc structure, with a 20mm wide flat area on both sides. The arc surface of the foot roller should have the same shape as the arc surface of the crystallizer. The improvement plan for the narrow-face foot roller of the crystallizer is attached. Figure 3 .

[0055] This embodiment also controls the zero-segment cooling: To adapt to the application of the new technology of ultra-fine grain secondary cooling at the corners of the billet and to ensure the strong cooling effect of the billet, the nozzles and water flow rate in the first zone remain unchanged. In the second and third zones, to prevent overcooling at the corners, when changing widths for different production widths, a special tool is designed to clog some of the edge nozzles, and the clogging rules are established as follows:

[0056]

[0057] A diagram illustrating the nozzle clogging rules is attached. Figure 5 .

[0058] The secondary cooling water sag ratio control method in this embodiment is as follows:

[0059] Currently, the secondary cooling water ratio for each section (water volume in the middle two columns / water volume on both sides) remains constant at 1.40 regardless of the billet width. This ratio cannot maintain a constant cooling intensity at the billet corners when the width varies. To address this issue and ensure that the billet corner temperature is controlled above 950℃ in the straightening section, the secondary cooling water ratio for each width was optimized separately. Through practical measurement and gradual adjustment based on the straightening temperature, the following water ratio was achieved.

[0060] Secondary cooling water section ratio (middle / both sides) 1.52 1.40 1.25 1.15 1.1

[0061] Secondary Cooling Water Control: To ensure the effectiveness of the new secondary cooling technology for ultra-fine grains at the corners of the billet, intensive cooling is implemented in Zone 1 (controlling the water spraying inside and outside the wide-face foot rollers) and Zone 2 (controlling the water spraying inside and outside the three rows of nozzles on the upper part of the zero section). The total water volume for the inner and outer arcs in Zone 1 is controlled at 250-350 L / min for a 200mm cross-section drawing speed within the range of 1.0-1.4 m / min; the total water volume for the inner and outer arcs in Zone 2 is controlled at 400-600 L / min for a 200mm cross-section drawing speed within the range of 1.0-1.4 m / min. The water spray volume is slightly reduced in other secondary cooling areas, and the water volume per ton of steel in the secondary cooling is controlled within the range of 0.5-0.7 L / kg.

[0062] Equipment precision control: The arc deviation of each roller in the sector segment must not exceed 0.2mm. In actual production, a problem of unilateral corner cracking occurred. The arc deviation and roller gap were found to meet the standards. Analysis showed that the sector segment as a whole was not level in the width direction. Therefore, it is necessary to correct the levelness of the rollers in the sector segment to ensure that the levelness of the rollers in the sector segment is within 0.05mm / m. Specific Implementation Example 2:

[0064] Taking a steel plant's 250mm thick wide and thick plate continuous casting machine as an example, it mainly produces widths of 1500mm, 1800mm, 2000mm, 2200mm, and 2400mm.

[0065] The improvement to the narrow-face copper plate in this embodiment is as follows: Currently, the narrow-face copper plate of the convex arc-shaped crystallizer has a 30mm width of flat surface at the edge, with an 11mm protrusion height in the arc area. The arc area and the flat area are smoothly transitioned by a 60mm radius arc. The improvement measure is to widen the flat area of ​​the narrow-face copper plate edge of the convex crystallizer, increasing the width of the flat area from 30mm to 50mm. This way, even if some concave deformation occurs in the transition area, a portion of the flat area can still be retained at the corner of the billet, preventing sharp corner morphology. The improved scheme for the narrow-face copper plate of the crystallizer is attached. Figure 2 .

[0066] The improvement method for the narrow-faced foot roller is as follows: Currently, the narrow-faced foot roller has a fully convex arc surface, and its length is about 50mm smaller than the width of the narrow-faced copper plate. To change the shape of the narrow-faced copper plate, the narrow-faced foot roller needs to be modified to a straight arc structure, with a 20mm wide flat area on both sides. The arc surface of the foot roller should have the same shape as the arc surface of the crystallizer. The improvement scheme for the narrow-faced foot roller of the crystallizer is attached. Figure 4 .

[0067] The zero-segment cooling control method is as follows: To adapt to the application of the new technology of ultra-fine grain secondary cooling at the corners of the billet and to ensure the strong cooling effect of the billet, the nozzles and water flow rate in the first zone remain unchanged. In the second and third zones, to prevent overcooling at the corners, when changing widths for different production widths, a special tool is designed to clog some of the edge nozzles. The clogging rules are as follows:

[0068]

[0069] A diagram illustrating the nozzle clogging rules is attached. Figure 5 .

[0070] The method for controlling the shear ratio of the secondary cooling water is as follows:

[0071] Currently, the secondary cooling water ratio for each section (water volume in the middle two columns / water volume on both sides) remains constant at 1.40 regardless of the billet width. This ratio cannot maintain a constant cooling intensity at the billet corners when the width varies. To address this issue and ensure that the billet corner temperature is controlled above 950℃ in the straightening section, the secondary cooling water ratio for each width was optimized separately. Through practical measurement and gradual adjustment based on the straightening temperature, the following water ratio was achieved.

[0072] Secondary cooling water section ratio (middle / both sides) 1.52 1.40 1.25 1.15 1.1

[0073] The secondary cooling water volume control method is as follows: To ensure the application effect of the new technology for ultra-fine grains in the corners of the billet, strong cooling is implemented in the first secondary cooling zone (controlling the water spraying inside and outside the wide-face foot rollers) and the second secondary cooling zone (controlling the water spraying inside and outside the three rows of nozzles on the upper part of the zero section). The total water volume of the inner and outer arcs in the first secondary cooling zone is controlled at 200-300 L / min for a 250mm cross-section with a drawing speed of 0.8-1.2m / min; the total water volume of the inner and outer arcs in the second secondary cooling zone is controlled at 300-450 L / min for a 250mm cross-section with a drawing speed of 0.8-1.2m / min. The water spray volume in other areas of the secondary cooling zone is slightly reduced, and the water volume per ton of steel in the secondary cooling zone is controlled within the range of 0.5-0.7 L / kg.

[0074] The equipment precision control method is as follows: the arc deviation of each roller in the sector segment must not exceed 0.2mm. In actual production, a problem of unilateral corner cracking occurred. The arc deviation and roller gap were found to meet the standards. Analysis showed that the sector segment as a whole was not level in the width direction. Therefore, it is necessary to correct the levelness of the rollers in the sector segment to ensure that the levelness of the rollers in the sector segment is within the range of 0.05mm / m.

[0075] The control methods described above can be implemented in electronic hardware, computer software, or a combination of both, by combining the units and algorithm steps of the various examples disclosed in this document. To clearly illustrate the interchangeability of hardware and software, the components and steps of each example have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0076] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a full understanding of embodiments of the invention. However, those skilled in the art will recognize that the technical solutions of the invention can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of the invention.

[0077] The method for controlling the narrow-face morphology and corner transverse cracks of narrow-face concave continuous casting billets provided by this invention comprises the unit and algorithm steps of various examples described in conjunction with the embodiments disclosed herein. These steps can be implemented using electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of each example have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0078] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for controlling the narrow-face morphology and corner transverse cracks of a narrow-face concave continuous casting billet, characterized in that the method... include: The narrow copper plate plane area of ​​the crystallizer with a straight-arc structure and convex arc surface is 50mm wide. The arc-shaped area protrudes 11mm, and the arc-shaped area and the flat area are smoothly transitioned by an R60 circular arc. In this method, the narrow-faced foot roller is configured as a straight arc structure with a width of 20mm for the straight areas on both sides, and the arc surface of the foot roller has the same shape as the arc surface of the crystallizer. The method also includes a secondary cooling water volume control method: cooling control of the inner and outer arc spray water of the wide-face foot roller in the first secondary cooling zone and the inner and outer arc spray water of the three rows of nozzles on the upper part of the zero section in the second secondary cooling zone; The total water volume of the inner and outer arcs in the second cooling zone is as follows: for the 200mm cross-section, the pulling speed is controlled at 250-350 l / min within the range of 1.0-1.4m / min; for the 250mm cross-section, the pulling speed is controlled at 200-300 l / min within the range of 0.8-1.2m / min. The total water flow rate for the inner and outer arcs of the second cooling zone is as follows: for the 200mm cross-section, the pulling speed is controlled at 400-600 l / min within the range of 1.0-1.4 m / min; for the 250mm cross-section, the pulling speed is controlled at 300-450 l / min within the range of 0.8-1.2 m / min. Slightly reduce the water spray volume in other areas of the secondary cooling system, and control the water content per ton of steel in the secondary cooling system within the range of 0.5-0.7 l / kg; The method also includes: The zero-segment spray system has 256 nozzles on the inner and outer arcs, which are controlled in three zones. The nozzles in each row are staggered. Zone 1 controls the three rows of nozzles on the upper part of the inner and outer arcs, with 8, 7, and 8 nozzles in each row, respectively. The second zone controls the middle position of the inner and outer arcs with 6 rows of nozzles, with each row containing 7, 8, 7, 8, 7, 8 nozzles respectively; The lower part of the third zone control is equipped with 8 rows of nozzles, with the number of nozzles in each row being 7, 8, 7, 8, 7, 8, 7, 8, 7 respectively; The method also includes a control method based on the secondary cooling water shear ratio: Among them, the wide and thick plate continuous casting machine has a total of 8 fan-shaped sections, arc sections and straightening sections, with a total of 512 secondary cooling nozzles, which are controlled in four zones. The number of inner and outer arc nozzles in the arc section and straightening section is the same. Each fan-shaped section has 7 rows of nozzles, and there are 4 nozzles between every two rollers. Along the direction of the billet, the middle two rows of nozzles form one branch, and the two rows of nozzles on both sides form one branch, realizing independent control of secondary cooling water spray in the width direction. The method involves controlling the temperature at the corner of the billet in the straightening section above 950℃, and setting the secondary cooling water cutting ratio for each width separately; by measuring the straightening temperature, the temperature is gradually adjusted to form the preset cutting water ratio.

2. The method for controlling the narrow-face morphology and corner transverse cracks of a narrow-face concave continuous casting billet according to claim 1, characterized in that, The method also controls the zero-stage cooling; The production width of the continuous casting machine for thick plates is 1500mm, 1800mm, 2000mm, 2200mm, and 2400mm.

3. The method for controlling the narrow-face morphology and corner transverse cracks of a narrow-face concave continuous casting billet according to claim 2, characterized in that, When the width of the billet is 1500mm, after the side nozzles in the second zone are blocked, the number of nozzles in the middle zone is distributed as follows: 3, 4, 3, 4, 3, 4; after the side nozzles in the third zone are blocked, the number of nozzles in the middle zone is distributed as follows: 3, 4, 3, 4, 3, 4, 3, 4.

4. The method for controlling the narrow-face morphology and corner transverse cracks of a narrow-face concave continuous casting billet according to claim 2, characterized in that, When the width of the billet is 1800mm, after the edge nozzles in the second zone are blocked, the number of nozzles in the middle zone is distributed as follows: 5, 4, 5, 4, 5, 4; after the edge nozzles in the third zone are blocked, the number of nozzles in the middle zone is distributed as follows: 5, 4, 5, 4, 5, 4, 5, 4.

5. The method for controlling the narrow-face morphology and corner transverse cracks of a narrow-face concave continuous casting billet according to claim 2, characterized in that, When the width of the billet is 2000mm, after the edge nozzles in the second zone are blocked, the number of nozzles in the middle zone is distributed as follows: 5, 6, 5, 6, 5, 6; after the edge nozzles in the third zone are blocked, the number of nozzles in the middle zone is distributed as follows: 5, 6, 5, 6, 5, 6, 5, 6.

6. The method for controlling the narrow-face morphology and corner transverse cracks of a narrow-face concave continuous casting billet according to claim 2, characterized in that, When the width of the billet is 2200mm, after the side nozzles in the second zone are blocked, the number of nozzles in the middle zone is distributed as follows: 7, 6, 7, 6, 7, 6; after the side nozzles in the third zone are blocked, the number of nozzles in the middle zone is distributed as follows: 7, 6, 7, 6, 7, 6, 7, 6.

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