A method for increasing the casting time of thin strip continuous casting

Abstract

This invention belongs to the field of steel production technology and relates to a method for improving the casting time of thin strip continuous casting. The method includes baking the side sealing plate and core nozzle to be installed, simultaneously raising the ladle, tundish, and transition ladle systems during the replacement process, and guiding the flow channel through a slide rail (guide rail) below the distributed outlet holes of the transition ladle to guide the molten steel flow. At this time, the replacement of the side sealing plate and core nozzle, etc., is completed without closing the ladle (large ladle) slide plate and tundish slide plate. After replacement, the ladle, tundish, and transition ladle systems are restored to their normal casting positions for continuous casting. By guiding the molten steel flow from the transition ladle before replacing the molten side sealing plate and core nozzle, the method solves the problems of low production efficiency and high cost associated with replacing side sealing plates and core nozzles during casting stoppages, improves production continuity, and reduces production costs.

Description

Technical Field

[0001] This invention belongs to the field of steel production and relates to a method for improving the casting time of thin strip continuous casting. Background Technology

[0002] Thin strip continuous casting technology is a new type of thin strip steel production process. Compared with traditional continuous casting and hot rolling processes, it has advantages such as shorter production process, fewer steps, lower energy consumption, and environmental friendliness. The thin strip continuous casting process involves distributing molten steel through a core nozzle to a molten pool consisting of a pair of counter-rotating casting rolls and a pair of side sealing plates via an intermediate ladle and transition ladle. The molten steel is directly cooled and solidified into a strip on the surface of the casting rolls. After twin-roll casting and rolling, thin strip steel of 1.5~2.5mm is directly produced. Then, it is rolled into thin strip steel products of the target thickness through a single-pass rolling mill.

[0003] However, this technology currently faces certain bottlenecks: a limited number of consecutive casting heats and short continuous casting time. The core nozzle and side sealing plate are two core components of the thin strip continuous casting process, with the service life of the side sealing plate being a key factor restricting continuous casting. Abnormal cracking and bridging of the core nozzle can cause casting stoppages, affecting the number of consecutive casting heats and the casting time. The currently used thickness and material of the side sealing plate limit the average number of consecutive casting heats in thin strip continuous casting to 4-6 heats, with a casting time of 6-8 hours, after which the side sealing plate needs to be replaced. Both replacing the side sealing plate and the core nozzle require production to be halted, restricting production continuity and limiting the number of consecutive casting heats and the casting time.

[0004] Currently, most patents related to side sealing plates focus on material development or designing devices to ensure uniform wear and extend their service life. In the current thin strip continuous casting process, the middle portion of the side sealing plate is in contact with molten steel and subjected to erosion, while its edges are in contact with the casting roll end face and are worn down. The wear rate is typically greater than the erosion rate. Under the thrust, the un-eroded middle portion of the side sealing plate enters the molten pool. Excessive un-eroded refractory material entering the molten pool severely affects thin strip forming and edge quality, ultimately forcing production to halt.

[0005] Specifically, each casting cycle involves a maximum of 4 to 6 heats, with a casting time of 6 to 8 hours. The unit must be stopped and restarted for the casting process, which is time-consuming and labor-intensive. On the other hand, each restart requires the replacement of consumable parts such as the tundish, transition ladle, core nozzle, side sealing plate, and long nozzle, which not only affects the continuity of production but also results in the underutilization of the refractory materials in the tundish and transition ladle. This greatly increases the production cost per ton of steel for this technology.

[0006] Chinese patent document 201810586451.6 discloses a continuous replacement device and method for side sealing plates in thin strip continuous casting. It uses a rotator with a rotation function and a push rod with a vertical movement function to replace the side sealing plates online, improving production continuity. However, when the above equipment and method replaces the side sealing plates, the molten pool contains molten steel, and the steel-facing surfaces of the two side sealing plates to be replaced and used for replacement are not on the same vertical plane, which poses a risk of molten pool instability, molten steel spillage, and steel leakage. At the same time, because the side sealing plates are not baked, there is a risk of the side sealing plates breaking due to thermal shock. Replacing the side sealing plates when the molten pool contains molten steel can easily cause greater accident risks to the core equipment of the twin roll casting machine. Chinese patent document 202110600210.4 discloses a method for improving the casting time of thin strip continuous casting and its side sealing device. By improving the shape and installation method of the side sealing plate, the casting time of thin strip continuous casting is improved. In the above method, when the displacement of the side sealing plate is L≥(1 / 10~1 / 2)d (where d is the thickness of the side sealing plate in mm, and L is in mm), the side sealing plate is first moved outward along the axial direction of the crystallizing roller, so that the end face of the crystallizing roller is disengaged from the groove on the surface of the side sealing plate. Then the side sealing plate is moved upward or downward until the groove on the side sealing plate is completely removed. In the above method, when the side sealing plate is separated from the crystallizing roll end face, the molten steel in the pool is very likely to enter the gap between the side sealing plate and the crystallizing roll end face and the groove on the surface of the side sealing plate due to static pressure. Under the cooling of the crystallizing roll, cold steel is formed, which affects the normal wear and sealing effect of the side sealing plate and causes problems such as molten steel spillage and leakage in the pool. Similarly, since the side sealing plate is not baked, there is also a risk of the side sealing plate breaking due to thermal shock. Replacing the side sealing plate when the pool contains molten steel can easily cause greater accident risks to the core equipment of the twin-roll casting machine.

[0007] In other words, existing mature technologies and methods for replacing side sealing plates after smelting has stopped, or technologies and methods for replacing side sealing plates online that are still under research, either affect the continuity of production and require the replacement of consumables such as tundishes, transition tundishes, core nozzles, side sealing plates, and long nozzles, resulting in high production costs, or the risk of production instability or even steel leakage causing major accidents during the online replacement of side sealing plates. Both have problems that need to be improved. Summary of the Invention

[0008] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a method for improving the casting time of thin strip continuous casting.

[0009] The method of this invention adds a movable molten steel diversion channel between the transition ladle and the twin-roll molten pool. When the side sealing plate and core nozzle need to be replaced, the molten steel diversion channel is opened below the transition ladle's flow nozzle to catch the molten steel flowing from the transition ladle and divert it to the emergency ladle, creating space and time for replacing the core nozzle and side sealing plate. After the core nozzle and side sealing plate are replaced, the molten steel diversion channel can be moved away, and molten steel continues to flow through the transition ladle's flow nozzle to the core nozzle, from which it is distributed to various directions of the molten pool, forming a stable molten pool for continued casting. This increases the number of consecutive castings and casting time in thin strip continuous casting, and makes full use of the single tundish and transition ladle, significantly reducing overall production costs.

[0010] According to one aspect of the present invention, a method for increasing the casting time in thin strip continuous casting is provided, the method comprising the following steps:

[0011] (1) Bake the core gate to be put into production. The baking time is controlled at 10~120min and the baking temperature is controlled at 800~1200℃. Bake the side sealing plate to be put into production. The baking time is controlled at 3~60min and the baking temperature is controlled at 800~1200℃.

[0012] (2) Before replacing the side sealing plate and the core nozzle, control the pulling speed to 10~35m / min, adjust the liquid level of the tundish to 400~600mm, and control the opening degree of the ladle slide plate and the tundish slide plate;

[0013] (3) Before replacing the side sealing plate and the core nozzle, the casting system consisting of the ladle, tundish and transition ladle is raised simultaneously, with the raising speed controlled at 3~15mm / s and the raising height controlled at 200~400mm.

[0014] (4) The molten steel is guided into the distributed outlet hole of the transition ladle by the guide rail. The feeding speed of the molten steel is controlled to be 0.5~3m / min.

[0015] (5) Replace the baked side seals and core nozzles, replacing 1-2 side seals and 1-2 core nozzles;

[0016] (6) Remove the diversion channel, wherein the removal speed of the diversion channel is controlled at 0.5~3m / min;

[0017] (7) Restore the casting system consisting of the ladle, tundish and transition ladle to the normal casting position for normal casting, and increase the casting speed to 40~80m / min.

[0018] According to the method for improving the casting time of thin strip continuous casting of the present invention, preferably, the composition of the molten steel is carbon steel, weathering steel or stainless steel.

[0019] According to the method for increasing the casting time of thin strip continuous casting of the present invention, preferably, the removal of the guide groove is divided into a first stage and a second stage, wherein the removal speed of the first stage is less than the removal speed of the second stage.

[0020] According to the method for improving the casting time of thin strip continuous casting of the present invention, preferably, the core nozzle to be launched is baked, the baking time is controlled to be 30~90min, and the baking temperature is controlled to be 800~1200℃.

[0021] According to the method for improving the casting time of thin strip continuous casting of the present invention, preferably, the side sealing plate to be put into the line is baked, the baking time is controlled to be 5~30 min, and the baking temperature is controlled to be 800~1200℃.

[0022] According to the method for increasing the casting time of thin strip continuous casting of the present invention, preferably, before replacing the side sealing plate and the core nozzle, the casting speed is controlled to be reduced to 20~30m / min, and the liquid level in the tundish is adjusted to 400~500mm.

[0023] According to the method for increasing the casting time of thin strip continuous casting of the present invention, preferably, the casting system consisting of ladle, tundish and transition ladle is raised synchronously, wherein the raising speed is controlled at 5~10mm / s and the raising height is controlled at 250~400mm.

[0024] According to the method for improving the casting time of thin strip continuous casting of the present invention, preferably, the molten steel is guided into the distributed outlet holes of the transition ladle by the guide rail, wherein the feeding speed of the molten steel guide is controlled to be 1~2m / min.

[0025] According to the method for increasing the casting time of thin strip continuous casting of the present invention, preferably, after the molten steel flowing out of the transition ladle is diverted, the baked side sealing plate and core nozzle are replaced, wherein two side sealing plates are replaced and two core nozzles are replaced.

[0026] According to the method for increasing the casting time of thin strip continuous casting of the present invention, preferably, when removing the guide groove, the removal speed of the guide groove is controlled to be 0.5~2m / min.

[0027] According to the method for increasing the casting time of thin strip continuous casting of the present invention, preferably, in step (7), the casting speed is increased to 50~70m / min.

[0028] According to the method for improving the casting time of thin strip continuous casting of the present invention, preferably, the thickness of the cast strip is controlled at 1.5~2.5mm.

[0029] According to the method for improving the casting time of thin strip continuous casting of the present invention, preferably, the thickness of the cast strip is controlled at 1.7~2.2mm.

[0030] In the method for improving the casting time of thin strip continuous casting according to the present invention, preferably, the guide rail is a slide rail.

[0031] The beneficial effects of the present invention: Compared with the prior art, the technical advantages and beneficial effects of the present invention include at least the following:

[0032] 1. The device and method of the present invention can avoid the production stoppage caused by having to close the intermediate tundish slide when replacing side sealing plates or core gates and other accessories.

[0033] 2. The device and method of the present invention can replace accessories such as side sealing plates and core nozzles without interrupting the flow of the transition ladle, and can even handle other abnormalities in the casting and rolling area, thereby increasing the number of consecutive casting furnaces and the continuous casting time.

[0034] 3. The device and method of the present invention have high reliability and are easy to operate and implement. Compared with existing online replacement methods for side sealing plates, the device and method of the present invention have a higher safety factor.

[0035] 4. The apparatus and method of the present invention significantly save time and costs associated with stopping production to replace intermediate packages, transition packages and accessories, make full use of the refractory life, and effectively reduce the overall production cost. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention.

[0037] Figure 1 A schematic diagram of a method and apparatus for thin strip continuous casting;

[0038] Figure 2 This is a schematic diagram of the transition package according to the present invention;

[0039] Figure 3 and Figure 4 This is a schematic diagram of the method and apparatus for improving the casting time of thin strip continuous casting according to Embodiments 1-2 of the present invention. Detailed Implementation

[0040] 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. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0041] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0042] The following are embodiments of the present invention. The described embodiments are only a part of the embodiments of the present invention. All other embodiments that can be obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0043] See now Figures 1-4 The diagram shows the following components: 1. Ladle, 2. Ladle (large ladle) slide plate, 3. Long nozzle, 4. Tundish, 5. Tundish slide plate, 6. Tundish nozzle, 7. Transition ladle, 8. Casting roll, 9. Side sealing plate, 10. Core nozzle, 11. Molten pool, 12. Strip steel, 13. Rolling mill, 14. Drainage channel, 15. Slide rail (guide rail).

[0044] like Figure 2 As shown, the transition package 7 of this embodiment of the invention is provided with a transition package inlet 16 and a distributed liquid outlet 17 in sequence.

[0045] See Figure 1 In practical implementation, the existing technology typically includes the following steps in the casting and stopping process:

[0046] S1. Casting process: The qualified molten steel produced by the primary refining furnace and the refining furnace is placed in the ladle 1. The ladle 1 containing molten steel is lifted by the overhead crane to the continuous casting rotary table. The tundish car is started to move the tundish 4 to the casting position. The rotary table is rotated to move the ladle 1 containing molten steel to the top of the impact zone of the tundish 4. The long nozzle 3 is installed and connected to the steel outlet of the ladle 1 and placed in the impact zone of the tundish 4. After the previous and next processes are completed, the ladle slide plate 2 is opened to complete the casting operation.

[0047] S2. Establish the working liquid level in the tundish: After pouring begins, the tundish slide plate 5 is closed, and the molten steel in the ladle 1 continuously fills the tundish 4 to establish the working liquid level in the tundish, for example, 700~800mm.

[0048] S3. Steel Liquid Flow: After the working level of the steel liquid in the tundish 4 is established, the tundish slide plate 5 is opened, and the steel liquid enters the transition ladle inlet 16 through the tundish nozzle 6, and is distributed through the distributed outlet holes 17. See [link / reference needed]. Figure 2 .

[0049] S4. Establishing the molten pool level: The molten steel in the transition ladle 7 is distributed through the distributed outlet holes 17 to the molten pool 11 formed by a pair of counter-rotating casting rolls 8 and a pair of side sealing plates 9. The stable molten pool level is controlled and established by controlling the casting speed and matching the opening degree of the tundish slide plate 5.

[0050] S5. Casting and Rolling: After a stable molten pool level is established, the molten steel in the molten pool 11 comes into rotational contact with the surface of the casting roll 8 and cools and solidifies on the surface of the casting roll 8 to form a metal billet shell. This shell is brought together in the gap between the two casting rolls 8 to form a strip steel 12 with a thickness of 1.5~2.5mm. The strip steel 12 is rolled into the target product through a rolling mill 13.

[0051] S6. Ladle Changing and Continuous Pouring: After 60-120 minutes of pouring, the molten steel in ladle 1 is exhausted and ladle changing is required. Close ladle slide plate 2, remove long nozzle 3, rotate the rotary table to complete the ladle rotation, rotate back to long nozzle 3, install and connect long nozzle 3, open ladle slide plate 2, and complete the ladle changing and continuous pouring operation.

[0052] S7. Stop Casting: Under current technical conditions, if steps S1~S6 are repeated for 4~6 heats, and casting continues for 6~8 hours, the side sealing plates must be replaced due to wear, forcing the production line to stop casting. The stop casting operation includes closing the ladle slide plate 2, continuing to pour molten steel into the tundish 4, closing the tundish slide plate 5 when the tundish liquid level drops to 200~300mm, continuing to pour for 1~2 minutes, and completing the stop casting operation after the molten steel in the transition ladle 7 and the molten pool 11 has been poured.

[0053] After the above steps are completed, prepare for the new pouring cycle. At this time, all components including the tundish 4, transition tundish 7, side sealing plate 9, core nozzle 10, and accessories need to be replaced. In particular, the service life of the tundish 4, transition tundish 7, and long nozzle 3 has not been fully utilized.

[0054] The reason why it is necessary to replace the tundish 4, transition ladle 7, side sealing plate 9, core nozzle 10, and all accessories before starting a new casting cycle is that during the stop casting process in step S7, cold steel and casting residue remain at the bottom of the tundish 4. Simultaneously, during the stop casting process in step S7, the distributed liquid outlet 17 in the transition ladle 7 is prone to cold steel buildup due to its small diameter. The cold steel and casting residue remaining at the bottom of the tundish 4, along with the cold steel in the transition ladle 7, clog the tundish nozzle 6 and the distributed liquid outlet 17. These operational and technical defects mean that existing technology typically allows for a maximum of 4-6 consecutive castings, and after 6-8 hours of continuous casting, the tundish 4, transition ladle 7, side sealing plate 9, core nozzle 10, and their accessories must be replaced.

[0055] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following is combined with... Figure 3 , Figure 4 The following is a detailed description of the specific embodiments and effects of the present invention, including Examples 1 and 2.

[0056] Example 1 is the same as steps S1-S6 in the previous comparative example. The difference between Example 1 and the previous comparative example is that the side sealing plate needs to be replaced after 5 consecutive heats. At this time, the S7 stop-pouring operation is not performed. When there are 20 tons left in the ladle after the 5th heat, the casting speed is reduced from 55m / min to 25m / min. The hydraulic system drives the synchronous lifting of ladle 1 to transition ladle 7. See [link to relevant documentation]. Figure 3 and Figure 4 The diversion channel 14 is fed into the distributed outlet hole 17 of the transition ladle 7 via the slide rail (guide rail) 15. At this time, with the ladle (bulk ladle) slide plate 2 and the tundish slide plate 5 not closed, the side sealing plate 9 and the core nozzle 10 are replaced (after the fourth heat is completed, the side sealing plate 9 and the core nozzle 10 to be put into operation are baked). After replacement, simulate casting for 10 seconds, open the diversion channel 14, and execute steps S3~S5 to complete the replacement of the side sealing plate 9 and the core nozzle 10. Then repeat step S6 to complete 10 heats of continuous casting. After continuous casting for 14 hours, execute step S7 to complete the stop casting operation and check the refractory lining of the tundish.

[0057] Example 2 is the same as steps S1-S6 in the previous comparative example. The difference between Example 2 and the previous comparative example is that during the third heat of continuous casting, the side sealing plate was poorly worn, the edge of strip 12 was damaged, and molten steel spilled from the molten pool 11. It was necessary to replace the side sealing plate 9 (the side sealing plate 9 to be put into service and the core nozzle 10 were heated with high heat). At this time, the S7 stop casting operation was not performed. When the ladle had 30 tons remaining, the casting speed was reduced from 60m / min to 25m / min, and the hydraulic system was driven to synchronously lift the ladle 1 to the transition ladle 7. See [link to relevant documentation]. Figure 3 and Figure 4 The diversion channel 14 is sent to the bottom of the distributed liquid outlet 17 of the transition ladle 7 by the slide rail (guide rail) 15. At this time, the side sealing plate 9 and the core nozzle 10 are replaced while the ladle (large ladle) slide plate 2 and the tundish slide plate 5 are not closed. After replacement, simulate casting for 10 seconds, open the diversion channel 14, and execute steps S3~S5 to complete the replacement of the side sealing plate 9 and the core nozzle 10. Then repeat step S6 to complete the continuous casting of 8 heats. After continuous casting for 11.2 hours, execute step S7 to complete the stop casting operation.

[0058] The following conclusions can be drawn from the above examples:

[0059] Compared with the prior art, the present invention improves production continuity by using the diversion channel 14 to divert water and then replacing the side sealing plate 9 and core sprue 10, thereby avoiding the situation where the original components of the tundish 4 and transition package 7 become unusable after the flow is interrupted and the side sealing plate 9 and core sprue 10 are replaced. This avoids and eliminates the need for pouring stoppages caused by abnormal situations, thereby increasing the utilization space of the refractory material of the entire tundish 4 and transition package 7, improving production continuity, reducing production costs, and allowing the operation of the diversion channel to be completed mechanically without requiring close-range operation by personnel, thus improving the safety of the production process.

[0060] The above description is merely a specific embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for improving the casting time of thin strip continuous casting, characterized in that, The method includes the following steps: (1) Bake the core gate to be put into production. The baking time is controlled at 10~120min and the baking temperature is controlled at 800~1200℃. Bake the side sealing plate to be put into production. The baking time is controlled at 3~60min and the baking temperature is controlled at 800~1200℃. (2) Before replacing the side sealing plate and the core nozzle, control the pulling speed to 10~35m / min, adjust the liquid level of the tundish to 400~600mm, and control the opening degree of the ladle slide plate and the tundish slide plate; (3) Before replacing the side sealing plate and the core nozzle, the casting system consisting of the ladle, tundish and transition ladle is raised simultaneously, with the raising speed controlled at 3~15mm / s and the raising height controlled at 200~400mm. (4) The molten steel is guided into the distributed outlet hole of the transition ladle by the guide rail. The feeding speed of the molten steel is controlled to be 0.5~3m / min. (5) Replace the baked side seals and core nozzles, replacing 1-2 side seals and 1-2 core nozzles; (6) Remove the diversion channel, wherein the removal speed of the diversion channel is controlled at 0.5~3m / min; (7) Restore the casting system consisting of the ladle, tundish and transition ladle to the normal casting position for normal casting, and increase the casting speed to 40~80m / min.

2. The method for increasing the casting time of thin strip continuous casting according to claim 1, characterized in that: The molten steel is composed of carbon steel, weathering steel, or stainless steel.

3. The method for increasing the casting time of thin strip continuous casting according to claim 1, characterized in that: The removal of the drainage channel is divided into a first stage and a second stage. The removal speed in the first stage is less than that in the second stage.

4. The method for increasing the casting time of thin strip continuous casting according to claim 1, characterized in that: Bake the core sprue before it goes online. The baking time should be controlled at 30-90 minutes and the baking temperature at 800-1200℃.

5. The method for increasing the casting time of thin strip continuous casting according to claim 1, characterized in that: Bake the side sealing plates to be put into production. The baking time should be controlled at 5~30 minutes and the baking temperature at 800~1200℃.

6. The method for increasing the casting time of thin strip continuous casting according to claim 1, characterized in that: Before replacing the side sealing plate and core nozzle, control the pulling speed to reduce to 20~30m / min and adjust the tundish liquid level to 400~500mm.

7. The method for increasing the casting time of thin strip continuous casting according to claim 1, characterized in that: The casting system consists of a ladle, tundish, and transition ladle that are raised synchronously, with the raising speed controlled at 5~10mm / s and the raising height controlled at 250~400mm.

8. The method for increasing the casting time of thin strip continuous casting according to claim 1, characterized in that: The molten steel is guided into the distributed outlet holes of the transition ladle by the guide rail, and the feeding speed of the molten steel is controlled at 1~2m / min.

9. The method for increasing the casting time of thin strip continuous casting according to claim 1, characterized in that: After the molten steel flowing out of the transition ladle is diverted, the baked side sealing plates and core nozzles are replaced, including replacing 2 side sealing plates and 2 core nozzles.

10. The method for increasing the casting time of thin strip continuous casting according to claim 1, characterized in that: When removing the diversion channel, the removal speed of the diversion channel should be controlled at 0.5~2m / min.

11. The method for increasing the casting time of thin strip continuous casting according to any one of claims 1 to 10, characterized in that: In step (7), the pulling speed is increased to 50~70m / min.

12. The method for increasing the casting time of thin strip continuous casting according to any one of claims 1 to 10, characterized in that: The thickness of the cast strip is controlled between 1.5 and 2.5 mm.

13. The method for increasing the casting time of thin strip continuous casting according to claim 12, characterized in that: The thickness of the cast strip is controlled between 1.7 and 2.2 mm.

14. The method for increasing the casting time of thin strip continuous casting according to claim 1 or 8, characterized in that: The guide rail is a slide rail.

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