A method and device for tail blank capping of a wide and heavy plate

Abstract

The present application belongs to the technical field of continuous casting process, and particularly relates to a method and device for sealing the top of a wide and thick plate tail blank, the method comprising the following steps: after the tundish casting is completed, the casting machine pulling speed is reduced to 0.2 m / min; after the pulling speed is reduced to 0.2 m / min, a spring is pushed into the crystallizer; after the spring is pushed in, the intermediate control sector opening degree is notified to exit the light pressing down control; after the sector opening degree exits the light pressing down control, the casting machine slowly increases the pulling speed to the target speed after maintaining the set time at 0.2 m / min. The present application is safer to operate and realizes non-stop operation in the whole process, which can reduce the damage of the sector; and the spring is used for cooling, which has a better cooling effect than the combination of the cooling steel square block and the cooling metal particles, and can effectively avoid the occurrence of the blasting accident and the injury event caused by the poor sealing of the top; meanwhile, the sector opening degree exits the light pressing down in the sealing process of the present application, which can greatly improve the success rate of the sealing.

Description

Technical Field

[0001] This invention belongs to the field of continuous casting technology, and specifically relates to a method and apparatus for sealing the tail billet of a thick plate. Background Technology

[0002] Tail-end sealing refers to the process of adjusting the billet pulling speed based on the drop in molten steel level in the tundish near the end of continuous casting. This ensures the top surface of the billet's tail end solidifies completely before it exits the crystallizer, preventing molten steel from flowing out and causing injury or equipment damage. Poor sealing occurs when the surface shell thickness is insufficient to withstand the internal pressure of the molten steel, creating a weak point. This allows cooling water to enter and vaporize upon contact with the molten steel, generating a large amount of steam that cannot be expelled, leading to a blowout and equipment damage.

[0003] The capping method generally involves increasing the surface cooling of the tail billet to form a sufficiently thick shell on its surface within a short time, resisting the internal pressure of the molten steel and smoothly pulling the billet out of the fan-shaped section. The capping methods currently mainly used in existing technology include the following steps:

[0004] 1. After the tundish casting is completed (stopper closed), reduce the casting machine speed to 0.3 m / min;

[0005] 2. When the billet is 200-300mm from the top of the crystallizer, stop the straightening machine (straightening speed 0m / min) and stir the liquid surface in the crystallizer with an oxygen tube to form a "pit" (shrinkage depth 50-100mm). After stopping the machine for 1-2 minutes, start the straightening machine (straightening speed 0.3m / min).

[0006] 3. When the tail billet is pulled to about 500-600mm from the top, stop the straightening machine (pulling speed 0m / min) and observe the shrinkage of the tail billet. Under normal circumstances, use the cooling water pipe to pump water into the crystallizer. After pumping water for 1-2 minutes and waiting for the water to dry, restart the straightening machine (pulling speed 0.3m / min).

[0007] 4. When the tail billet is 100-200mm away from the crystallizer outlet, stop the straightening machine (stretching speed 0m / min), and notify the central control operator to fully open the cooling water regulating valve in Zone 1. After the machine is stopped for 90-200 seconds (controlled according to the cross-sectional size), slowly increase the stretching speed to above 1.0m / min.

[0008] The above method involves multiple shutdowns during the capping process, which exacerbates damage to the sector section; it also stirs the liquid level in the crystallizer and injects water into the crystallizer during the capping process, which may cause blasting accidents and injuries due to poor capping.

[0009] To address the aforementioned issues, Chinese patent CN110681838A proposes a high-speed, non-stop, waterless capping method for thick plate continuous casting machines. First, based on the measured tonnage and actual liquid level in the tundish, the tundish casting speed is reduced by acceleration (0.30-0.45 m / min). Then, while maintaining the casting speed, the liquid level is determined, and the stopper is closed. Next, a layer of cooling steel blocks is added to the surface of the unsolidified molten steel in the crystallizer, and a layer of cooling metal particles is added into the crystallizer. When the tail billet reaches the bottom of the crystallizer, the acceleration is increased to the target casting speed. However, this patent uses a casting speed between 0.30-0.45 m / min, which poses significant safety hazards during operation, and the capping effect is poor. Furthermore, the patent uses a combination of cooling steel blocks and cooling metal particles for cooling during capping, which is ineffective and can easily cause molten steel to be squeezed out at higher casting speeds during capping, leading to blowouts.

[0010] To address the aforementioned problems, this invention proposes a capping method that can avoid blasting accidents and injuries caused by improper capping during the capping process, reduce damage to the sector section, and improve the success rate of capping. Summary of the Invention

[0011] To address the above problems, this invention proposes a method for capping the tail of a thick slab, the capping method comprising the following steps:

[0012] After the intermediate ladle casting is completed, reduce the casting machine speed to 0.2 m / min;

[0013] After the pulling speed is reduced to 0.2 m / min, a spring is pushed into the crystallizer;

[0014] After the spring is pushed in, it notifies the central control sector opening to disengage from the light pressure control.

[0015] After the opening of the sector section is removed from the light pressure control, the casting machine maintains a casting speed of 0.2 m / min for a set time before slowly increasing the casting speed to the target speed.

[0016] Furthermore, the process of reducing the casting speed to 0.2 m / min is as follows:

[0017] Reduce the casting speed to 0.2 m / min within 6 minutes at an acceleration of 0.15 m / min.

[0018] Furthermore, the number of springs is 10-20.

[0019] Furthermore, the set time is 5-7 minutes.

[0020] Furthermore, the process of the casting machine slowly increasing its drawing speed to the target speed is as follows:

[0021] Increase the casting machine speed to the target speed within 5-7 minutes by accelerating at 0.15 m / min.

[0022] Furthermore, the target speed is 1.0 m / min - 1.2 m / min.

[0023] On the other hand, the present invention proposes a capping device for a thick slab tail billet, the capping device comprising:

[0024] The speed reduction unit is used to control the casting machine to reduce the casting speed to 0.2m / min after the tundish casting is completed;

[0025] The spring-pushing unit is used to push the spring into the crystallizer after the pulling speed drops to 0.2 m / min;

[0026] The control unit is exited to notify the central control sector opening degree to exit the light pressure control after the spring is pushed in.

[0027] The speed-up unit is used to control the casting machine to slowly increase the casting speed to the target speed after the opening of the sector section is out of light pressure control, maintaining the casting speed at 0.2m / min for a set time.

[0028] Furthermore, the number of springs pushed into the crystallizer in the spring pushing unit is 10-20.

[0029] Furthermore, the set time in the acceleration unit is 5-7 minutes.

[0030] Furthermore, the target speed in the acceleration unit is 1.0 m / min to 1.2 m / min.

[0031] The beneficial effects of this invention are:

[0032] This invention reduces the casting machine speed to 0.2 m / min during the capping process, making operation safer and allowing for continuous operation without shutting down the machine, thus reducing damage to the sector section. After the speed is reduced to 0.2 m / min, springs are pushed into the crystallizer for cooling, which is more effective than cooling steel blocks and metal particles together, and effectively prevents blasting accidents and injuries caused by poor capping. Furthermore, this invention uses a continuous casting machine with a light reduction function, controlling the opening degree of the sector section during capping to exit the light reduction phase, which greatly improves the success rate of capping.

[0033] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention will be realized and obtained from the description, claims, and drawings. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 A flowchart of the method for sealing the tail billet of a thick plate in an embodiment of the present invention is shown. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, 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.

[0037] This invention proposes a method for capping the tail of a thick slab to address the problems of multiple machine stops during capping in existing capping technologies, which exacerbate damage to the fan-shaped section; and the risks of blasting accidents and injuries due to improper capping caused by agitating the liquid level in the crystallizer and injecting water into it. This invention is used on casting machines with a light-pressure function for large slabs. The light pressure applied after the spring pushes the slab into the crystallizer helps to increase the distance between the molten steel and the end of the tail slab, making it less prone to leakage.

[0038] The flowchart of the method for capping the tail billet of the thick plate proposed in this invention is as follows: Figure 1 As shown, the specific steps include:

[0039] After the tundish casting is completed, reduce the casting machine speed to 0.2 m / min;

[0040] Specifically, a slow descent with an acceleration of 0.15m per minute should be used, while a rapid descent with an acceleration of 6m per minute should not be used, as rapid descent will result in poor capping.

[0041] After the casting speed is reduced to 0.2 m / min, 10-20 springs are pushed into the crystallizer. The springs will absorb heat when they enter the molten steel, which will accelerate the solidification of the molten steel on the upper surface of the billet. In addition, the use of spring cooling can effectively avoid the occurrence of blasting accidents and injuries caused by poor sealing.

[0042] After the spring pushes into the crystallizer, it notifies the central control fan-shaped section opening to exit the light pressure control; after maintaining a pulling speed of 0.2 m / min for 5 to 7 minutes, the pulling speed is slowly increased to 1.0 m / min-1.2 m / min with an acceleration of 0.15 m / min.

[0043] Because several sector segments are reduced by 3-5mm before capping, the molten steel will flow into the reduced sector segments when the light reduction is removed during capping. The large shrinkage space of the tail billet makes it difficult for the molten steel to flow out during capping, causing poor capping. This invention uses a continuous casting machine with light reduction function. During the capping process, the opening of the sector segments is removed from the light reduction, which can greatly improve the success rate of capping.

[0044] The following example uses a steel plant to cap a medium carbon low alloy steel continuous casting slab of Amm*(B1—B2)mm. The capping method of the present invention is used to cap the slab, with a specific specification of 230mm*(1300-1930)mm.

[0045] Example 1

[0046] A steel plant used the method of this invention to cap 230mm*(1300-1930)mm medium carbon low alloy steel continuous casting slabs. The specific steps are as follows:

[0047] After the casting is completed in the tundish, the casting speed is reduced to 0.2 m / min with an acceleration of 0.15 m / min;

[0048] After the pulling speed is reduced to 0.2 m / min, 10 springs are pushed into the crystallizer;

[0049] After the spring is pushed in, it notifies the central control sector opening to disengage from the light pressure control.

[0050] After maintaining a pulling speed of 0.2 m / min for 5 minutes, slowly increase the pulling speed to 1.0 m / min with an acceleration of 0.15 m / min.

[0051] Example 2

[0052] A steel plant used the method of this invention to cap 230mm*(1300-1930)mm medium carbon low alloy steel continuous casting slabs. The specific steps are as follows:

[0053] After the tundish casting is completed, reduce the casting machine speed to 0.2 m / min;

[0054] After the pulling speed is reduced to 0.2 m / min, 10 springs are pushed into the crystallizer;

[0055] After the spring is pushed in, it notifies the central control sector opening to disengage from the light pressure control.

[0056] After maintaining a pulling speed of 0.2 m / min for 6 minutes, slowly increase the pulling speed to 1.0 m / min with an acceleration of 0.15 m / min.

[0057] Example 3

[0058] A steel plant used the method of this invention to cap 230mm*(1300-1930)mm medium carbon low alloy steel continuous casting slabs. The specific steps are as follows:

[0059] After the tundish casting is completed, reduce the casting machine speed to 0.2 m / min;

[0060] After the pulling speed is reduced to 0.2 m / min, 10 springs are pushed into the crystallizer;

[0061] After the spring is pushed in, it notifies the central control sector opening to disengage from the light pressure control.

[0062] After maintaining a pulling speed of 0.2 m / min for 7 minutes, slowly increase the pulling speed to 1.0 m / min with an acceleration of 0.15 m / min.

[0063] Example 4

[0064] A steel plant used the method of this invention to cap 230mm*(1300-1930)mm medium carbon low alloy steel continuous casting slabs. The specific steps are as follows:

[0065] After the tundish casting is completed, reduce the casting machine speed to 0.2 m / min;

[0066] After the pulling speed is reduced to 0.2 m / min, 15 springs are pushed into the crystallizer;

[0067] After the spring is pushed in, it notifies the central control sector opening to disengage from the light pressure control.

[0068] After maintaining a pulling speed of 0.2 m / min for 7 minutes, slowly increase the pulling speed to 1.0 m / min with an acceleration of 0.15 m / min.

[0069] Example 5

[0070] A steel plant used the method of this invention to cap 230mm*(1300-2000)mm medium carbon low alloy steel continuous casting slabs. The specific steps are as follows:

[0071] After the tundish casting is completed, reduce the casting machine speed to 0.2 m / min;

[0072] After the pulling speed is reduced to 0.2 m / min, 16 springs are pushed into the crystallizer;

[0073] After the spring is pushed in, it notifies the central control sector opening to disengage from the light pressure control.

[0074] After maintaining a pulling speed of 0.2 m / min for 7 minutes, slowly increase the pulling speed to 1.0 m / min with an acceleration of 0.15 m / min.

[0075] Example 6

[0076] A steel plant used the method of this invention to cap 230mm*(1300-2030)mm medium carbon low alloy steel continuous casting slabs. The specific steps are as follows:

[0077] After the tundish casting is completed, reduce the casting machine speed to 0.2 m / min;

[0078] After the pulling speed is reduced to 0.2 m / min, 20 springs are pushed into the crystallizer;

[0079] After the spring is pushed in, it notifies the central control sector opening to disengage from the light pressure control.

[0080] After maintaining a pulling speed of 0.2 m / min for 7 minutes, slowly increase the pulling speed to 1.2 m / min with an acceleration of 0.15 m / min.

[0081] Test Example 1

[0082] The tail billets cast according to the methods in Examples 1-6 (the methods proposed in this invention) all showed good low-magnification quality. There were no intermediate cracks or shrinkage cavities at 600mm from the tail. No surface quality defects were found on the surface of the continuously cast billets. No surface quality defects were found on the surface of the rolled steel plates. The steel plates passed the flaw detection test. After the final casting and sealing, the opening degree and arc connection of the sector section were measured, and the control accuracy was good.

[0083] Comparative Example 1

[0084] A steel plant used the method of this invention to cap 230mm*(1300-1930)mm medium carbon low alloy steel continuous casting slabs. The specific steps are as follows:

[0085] After the tundish casting is completed, the casting machine speed is reduced to 0.2 m / min with an acceleration of 0.30 m / min;

[0086] After the pulling speed is reduced to 0.2 m / min, 10 springs are pushed into the crystallizer;

[0087] After the spring is pushed in, it notifies the central control sector opening to disengage from the light pressure control.

[0088] After maintaining a pulling speed of 0.20 m / min for 5 minutes, slowly increase the pulling speed to 1.0 m / min with an acceleration of 0.30 m / min.

[0089] Comparative Example 2

[0090] A steel plant used the method of this invention to cap 230mm*(1300-1930)mm medium carbon low alloy steel continuous casting slabs. The specific steps are as follows:

[0091] After the tundish casting is completed, the casting machine speed is reduced to 0.2 m / min with an acceleration of 0.30 m / min;

[0092] After the pulling speed is reduced to 0.2 m / min, 10 springs are pushed into the crystallizer;

[0093] After the spring is pushed in, the opening of the sector segment does not retract under light pressure control;

[0094] After maintaining a pulling speed of 0.20 m / min for 5 minutes, slowly increase the pulling speed to 1.0 m / min with an acceleration of 0.15 m / min.

[0095] Comparative Example 3

[0096] A steel mill capped a 230mm*(1300-2030)mm medium-carbon low-alloy steel continuous casting slab using the method proposed in patent publication number CN110681838A.

[0097] After the tundish casting is completed, reduce the casting machine speed to 0.45 m / min;

[0098] After the casting speed is reduced to 0.45 m / min, the stopper is closed to stop casting. Then, a layer of cooling steel blocks with a size of 40 mm * 40 mm * 40 mm is first placed on the surface of the molten steel in the crystallizer. Then, a layer of cooling iron filings or nail tips with a thickness of 6 mm is placed in the crystallizer, and 20 springs are pushed into the crystallizer. When the tail billet reaches the bottom of the crystallizer, the speed is increased uniformly by 0.05 m / min every 20 seconds. When the casting speed reaches 0.7 m / min, the speed is increased uniformly by 0.1 m / min every 20 seconds to the target casting speed of 1.35 m / min.

[0099] Application Example 1

[0100] After two years of operation using the capping methods in Examples 1-6, no capping failures occurred. When operating using the method in Comparative Example 1, there were an average of 2-4 capping failures per year. When operating using the methods in Comparative Examples 2 and 3 (i.e., the methods previously used by a certain steel plant), there were an average of 4-5 capping failures per year.

[0101] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for capping the tail of a thick slab, characterized in that, The capping method includes the following steps: After the intermediate ladle casting is completed, reduce the casting machine speed to 0.2 m / min; After the pulling speed is reduced to 0.2 m / min, a spring is pushed into the crystallizer; After the spring is pushed in, it notifies the central control sector opening to disengage from the light pressure control. After the opening of the sector section is removed from the light pressure control, the casting machine maintains a casting speed of 0.2 m / min for a set time before slowly increasing the casting speed to the target speed.

2. The method for capping the tail of a thick plate according to claim 1, characterized in that, The process of reducing the casting speed of the casting machine to 0.2 m / min is as follows: Reduce the casting speed to 0.2 m / min within 6 minutes at an acceleration of 0.15 m / min.

3. The method for capping the tail of a thick plate according to claim 1, characterized in that, The number of springs is 10-20.

4. The method for capping the tail of a thick plate according to claim 1, characterized in that, The set time is 5-7 minutes.

5. The method for capping the tail of a thick plate according to claim 1, characterized in that, The process of slowly increasing the speed to the target speed is as follows: Increase the casting machine speed to the target speed within 5-7 minutes by accelerating at 0.15 m / min.

6. The method for capping the tail of a thick plate according to claim 4 or 5, characterized in that, The target speed is 1.0 m / min - 1.2 m / min.

7. A device for sealing the tail of a thick slab, characterized in that, The capping device includes: The speed reduction unit is used to control the casting machine speed to be reduced to 0.2m / min after the tundish casting is completed; The spring-pushing unit is used to push the spring into the crystallizer after the pulling speed drops to 0.2 m / min; The control unit is exited to notify the central control sector opening degree to exit the light pressure control after the spring is pushed in. The speed-up unit is used to control the casting machine to maintain a casting speed of 0.2 m / min for a set time after the opening of the sector section is out of light pressure control, and then slowly increase the casting speed to the target speed.

8. The thick slab tail billet capping device according to claim 7, characterized in that, The number of springs pushed into the crystallizer in the spring pushing unit is 10-20.

9. A thick slab tail billet capping device according to claim 7, characterized in that, The set time for the spring push-in unit is 5-7 minutes.

10. A thick slab tail-end sealing device according to claim 7, characterized in that, The target speed in the acceleration unit is 1.0 m / min to 1.2 m / min.

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