An efficient production method for thin-gauge strip steel

Abstract

This invention belongs to the field of steel production technology and relates to an efficient production method for thin-gauge strip steel. The method involves simultaneously raising the tundish and transition ladle before changing the work rolls, and guiding the molten steel through a guide rail or slide rail below the distributed outlet holes of the transition ladle. This allows for the replacement of work rolls with surface quality issues even when the ladle and tundish slide plates are not closed. After replacement, the tundish and transition ladle systems are restored to their normal casting positions for continuous casting, enabling the rolling production of thin-gauge (≤0.8mm) strip steel in a shorter time. This invention solves the problems of low production efficiency and high cost caused by traditional work roll changing methods, significantly improves production continuity, increases the single-cast yield and production efficiency of thin-gauge strip steel, and reduces the overall production cost of thin-gauge strip casting and rolling.

Description

Technical Field

[0001] This invention belongs to the field of steel production technology and relates to an efficient production method for thin-gauge strip steel. More specifically, this invention proposes an efficient production method for thin-gauge strip steel using twin-roll casting and rolling based on online work roll changing technology. Background Technology

[0002] Twin-roll casting and rolling technology for producing strip steel is a cutting-edge metallurgical technology with the greatest development potential in the steel industry today. Compared with traditional continuous casting and hot rolling processes, twin-roll casting and rolling has advantages such as shorter production process, fewer steps, lower energy consumption, and environmental friendliness.

[0003] Currently, the commercially viable twin-roll casting process involves distributing molten steel through a core nozzle into a molten pool consisting of a pair of counter-rotating casting rolls and a pair of side sealing plates. After twin-roll casting, a strip of 1.5–2.5 mm is directly produced, which is then rolled into the target thickness using a single-pass mill. The twin-roll casting process can produce carbon steel, weathering steel, silicon steel, and other products. The production line uses only one single-pass mill, and the thinnest rolled thickness currently is approximately 0.6 mm.

[0004] In actual production, thin-gauge (≤0.8mm) strip steel is highly susceptible to quality problems such as indentation and excessive roughness. These problems are mainly caused by factors related to the rolling mill rolls. The work rolls operate under high temperatures, severely impacting their lifespan. When indented or excessively rough rolls appear, continuing to produce thin-gauge strips will result in all subsequent thin-gauge strips exhibiting indentation or excessive roughness, leading to substandard products. Therefore, when such problems arise, the only solution is to revert to producing thicker strips, significantly impacting the yield of thin-gauge strips per casting cycle. Alternatively, these problems may lead to a casting stoppage, replacement of the work rolls, and restarting production. However, frequent casting stoppages, restarts, or reverts to producing thicker strips severely restrict the production efficiency and yield of thin-gauge (≤0.8mm) strips per casting cycle, affecting the casting cost and product competitiveness per casting cycle.

[0005] Specifically, replacing the work rolls requires replacing consumable parts such as the tundish, transition ladle, core nozzle, side sealing plate, and long nozzle each time casting resumes. This not only disrupts production continuity but also results in underutilization of the refractory materials in the tundish and transition ladle, significantly increasing the production cost per casting cycle. Furthermore, stopping and starting casting is time-consuming and labor-intensive, severely impacting production efficiency. To maintain production continuity, if work rolls that cannot meet the surface quality requirements for thin-gauge rolling continue to be used, the current only solution is to produce thicker strip steel to avoid indentations or excessive roughness in coils. This severely restricts the yield of thin-gauge (≤0.8mm) strip steel per casting cycle, affecting the competitiveness of twin-roll thin strip technology and products.

[0006] Chinese patent document 201910130257.1 discloses a rolling method for improving the surface quality of strip in twin-roll continuous casting. This method involves installing two rolling mills on a twin-roll continuous casting production line. When surface problems occur on one mill, the other mill is used instead. The problematic mill's rolls are replaced online, improving production continuity and product surface quality. This method involves adding rolling mills and rolling passes to the existing production line design and is currently still in the theoretical research stage. This method increases the production line length, and replacing work rolls while strip is passing through at high speed on the production line poses a significant safety risk.

[0007] In other words, existing mature technologies and methods for replacing work rolls after a casting stop, or technologies and methods for replacing work rolls online that are still under research, have two main drawbacks: First, the stopping and starting of casting operations affect the continuity of production, and at the same time, it is necessary to replace consumable parts such as tundishes, transition tundishes, core nozzles, side sealing plates, and long nozzles, resulting in high production costs. Second, the online work roll replacement process currently under research is extremely prone to causing production instability or even major accidents.

[0008] Therefore, there is an urgent need for a new method or device to solve the above problems, so as to produce thin strip steel (≤0.8mm) efficiently and at low cost, improve the output rate and production efficiency of single casting of thin strip steel, and enhance the competitiveness of twin-roll thin strip casting and rolling technology and related products. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide an efficient production method and apparatus for thin-gauge strip steel using a twin-roll thin strip continuous casting machine based on online work roll replacement. This invention overcomes the limitations of existing twin-roll continuous casting methods where, when surface defects such as indentations or excessive roughness occur in the strip steel, the only solutions are to "return to thicker" production or to replace the work roll by stopping casting.

[0010] The main method of this invention is to add a movable molten steel diversion channel between the transition ladle and the molten pool. When the hot rolling work roll needs to be replaced in a single pass, the molten steel diversion channel is opened below the flow port of the transition ladle to catch the molten steel flowing from the transition ladle and divert it to the emergency ladle. The hot rolling work roll is replaced online while maintaining continuous flow in the tundish and transition ladle. After the work roll replacement is completed, the molten steel diversion channel is opened, and the molten steel continues to flow through the flow port of the transition ladle to the core nozzle, and then distributed to various directions of the molten pool from the core nozzle to form a stable molten pool for continued casting. This allows for the rapid rolling of thin-gauge (≤0.8mm) strip steel, thereby improving production continuity, making full use of consumable parts such as single tundishes and transition ladles, and reducing production costs.

[0011] Meanwhile, the method of the present invention utilizes the good surface quality of the newly replaced hot rolling work rolls to produce thin-gauge (≤0.8mm) strip steel, thereby improving the yield and production efficiency of thin-gauge (≤0.8mm) strip steel in a single casting.

[0012] According to one aspect of the present invention, a highly efficient method for producing thin-gauge strip steel is proposed, the method comprising the following steps:

[0013] (1) When indentations appear on the hot rolled strip of twin roll casting, it is determined that the hot rolled work roll in the mill needs to be replaced, and the pulling speed is reduced to 20~35m / min, and the liquid level in the tundish is controlled to 400~600mm;

[0014] (2) Before replacing the hot rolling work roll, the intermediate tundish and transition tundish of the twin-roll casting system are raised synchronously, wherein the raising speed of the intermediate tundish and the transition tundish is controlled at 5~10mm / s and the raising height is controlled at 250~400mm.

[0015] (3) The guide rail is used to guide the flow channel into the distributed outlet hole of the transition ladle to guide the molten steel, wherein the advancing speed of the flow channel is controlled to be 1~2m / min;

[0016] (4) After the molten steel in the transition ladle is diverted, the hot rolling work roll that needs to be replaced in the mill is pushed out, and the spare work roll for replacement is pushed into the mill.

[0017] (5) Remove the drainage channel. The first removal time period is the first 15 seconds before the drainage channel is removed, and the second removal time period is from 15 seconds until the removal is completed. The first removal time period is carried out at a speed of 0.5~1m / min, and the second removal time period is carried out at a speed of 1~3m / min.

[0018] (6) Restore the intermediate tundish and the transition tundish of the casting system to normal casting, increase the casting speed to 40~80m / min, and control the intermediate tundish to the normal working liquid level of 700~800mm.

[0019] According to the efficient production method of thin strip steel of the present invention, preferably, in step (1), after determining that the hot rolling work roll in the rolling mill needs to be replaced, the pulling speed is reduced to 20~25m / min.

[0020] According to the efficient production method of thin strip steel of the present invention, preferably, in step (1), after determining that the hot rolling work roll in the rolling mill needs to be replaced, the liquid level in the tundish is controlled to be 400~500mm.

[0021] According to the efficient production method of thin strip steel of the present invention, preferably, in step (2), the intermediate ladle and the transition ladle of the twin-roll casting system are raised synchronously, and the raising speed of the intermediate ladle and the transition ladle is controlled to be 8~10mm / s.

[0022] According to the efficient production method of thin strip steel of the present invention, preferably, in step (2), the intermediate ladle and the transition ladle of the twin-roll casting system are raised simultaneously, and the raising height of the intermediate ladle and the transition ladle is controlled to be 350~400mm.

[0023] According to the efficient production method of thin strip steel of the present invention, preferably, in step (5), the second withdrawal time period is carried out at a speed of 2~3m / min.

[0024] According to the efficient production method of thin strip steel of the present invention, preferably, in step (6), the drawing speed is increased to 60~80m / min.

[0025] According to the efficient production method of thin-gauge strip steel of the present invention, preferably, the thickness of the thin-gauge strip steel is ≤0.8mm.

[0026] According to the efficient production method of thin-gauge strip steel of the present invention, preferably, the thickness of the thin-gauge strip steel is 0.6~0.8mm.

[0027] According to the efficient production method of thin-gauge strip steel of the present invention, preferably, the molten steel composition of the thin-gauge strip steel is carbon steel, weathering steel or stainless steel.

[0028] In the efficient production method of thin-gauge strip steel according to the present invention, preferably, the guide rail is a slide rail.

[0029] The beneficial effects of this invention are:

[0030] 1. The device and method of the present invention can avoid the production stoppage caused by the need to close the tundish slide when changing hot rolling work rolls and accessories.

[0031] 2. The device and method of the present invention can replace the work rolls and accessories without interrupting the flow of the transition ladle, and can even handle other abnormalities in the casting and rolling area, significantly improving production continuity.

[0032] 3. The device and method described in this invention are simple and reliable, and easy to operate and implement. Compared with existing online work roller replacement methods developed or under research, the method of this invention is safer.

[0033] 4. The apparatus and method of the present invention save time and cost by stopping production to replace intermediate packages, transition packages and accessories, and make full use of the refractory material that was not originally ineffective, which is equivalent to extending the service life of the refractory material and reducing production costs.

[0034] 5. With the apparatus and method of the present invention, more qualified thin-gauge (≤0.8mm) strip steel can be rolled in a single casting, thereby improving the output rate and production efficiency of thin-gauge strip steel. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required in the description of the embodiments or the prior art are briefly introduced below. Obviously, the drawings described below are merely some embodiments recorded in the present invention, and not limitations thereof. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0036] Figure 1 This is a schematic diagram of an efficient production method and apparatus for producing thin strip steel using twin-roll casting and rolling based on online work roll replacement, according to an embodiment of the present invention.

[0037] Figure 2 This is a schematic diagram of the transition ladle of the casting system according to an embodiment of the present invention.

[0038] Figure 3 This is a diagram illustrating the surface quality of the strip steel according to an embodiment of the present invention.

[0039] Figure 4 This is a diagram illustrating the surface quality of the strip steel as shown in the comparative example. 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] Now for reference Figure 1 and Figure 2This invention illustrates an efficient production method and apparatus for producing thin-gauge strip steel using twin-roll casting and rolling based on online work roll replacement, according to an embodiment of the present invention. Figure 1 and Figure 2 The following components or structures are shown: 1. Ladle (large ladle) slide plate 2. Long nozzle 3. Tundish 4. Tundish slide plate 5. Tundish nozzle 6. Transition ladle 7. Casting roll 8. Side sealing plate 9. Core nozzle 10. Molten pool 11. Strip 12. Rolling mill 13. Work roll 14. Drainage channel 15. Slide rail (guide rail) 16.

[0044] like Figure 2 As shown, the transition package 7 of this embodiment of the invention is provided with a transition package inlet 17 and a distributed liquid outlet 18 in sequence.

[0045] See Figure 1 In the specific implementation of this invention, the existing normal casting and rolling and offline replacement of work rolls under normal circumstances are described as follows.

[0046] S1. Normal casting and rolling process: The qualified molten steel produced by the primary refining furnace and the refining furnace is placed in the ladle 1. The molten steel enters the transition ladle 7 through the long nozzle 3, the tundish 4, and the tundish nozzle 6, and is distributed through the distributed liquid outlet holes 18.

[0047] The molten steel flows through distributed outlet holes 18 into the molten pool 11 formed by a pair of counter-rotating casting rolls 8 and a pair of side sealing plates 9. A stable molten pool level is established by controlling the casting speed and the opening degree of the matching tundish slide plate 5.

[0048] After a stable molten pool level is established, the molten steel in the molten pool 11 comes into rotating 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 then 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 then rolled into the target product through one pass of the rolling mill 13.

[0049] S2. Stop Casting: Under existing technology, when the rolled product fails to reach the target thickness or acceptable surface quality, and the work rolls need to be replaced, the production line is forced to stop casting. The stop casting operation steps include 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 executing the twin-roll casting machine shutdown procedure after the molten steel in the transition ladle 7 and the molten pool 11 has been poured to complete the stop casting operation.

[0050] S3. Replace the work roll: After the above steps are completed, prepare for the new casting. At this time, the work roll 14 on the production line needs to be pushed out of the rolling mill 13, and the new work roll 14 needs to be hoisted and pushed into the rolling mill to complete the work roll replacement operation.

[0051] In addition, when preparing for a new casting cycle, all components, including the tundish 4, transition tundish 7, side sealing plate 9, core nozzle 10, and accessories, were replaced. However, the service life of these components was not fully utilized.

[0052] To further illustrate the technical means and effects of the present invention in achieving the intended purpose, the specific embodiments and effects of the present invention will be described in detail below with reference to the accompanying drawings, examples and comparative examples.

[0053] Example

[0054] (1) The qualified carbon steel molten steel after being smelted in the primary smelting furnace and the refining furnace is cast into a strip by a pair of counter-rotating casting rolls. After casting 60 tons of molten steel is poured, it is gradually cast into a 1.75mm thick strip with the casting speed controlled at 62~63m / min.

[0055] (2) The 1.75mm thick cast strip is hot rolled into a 0.8mm thick strip in one pass. After that, the rolling mill maintains a rolling force of ≥6.5MN and continuously casts 120 tons.

[0056] (3) When the working rolls work under high load for a long time in a high-temperature environment, the surface quality of the working rolls deteriorates, and indentations appear on the strip. The working rolls need to be replaced or production needs to be stopped.

[0057] (4) Perform the online work roll replacement operation, reduce the pulling speed to 23±0.5m / min, lift the intermediate tundish and transition tundish, advance the diversion trough, clear the roller conveyor, create time and space for online work roll replacement, push out and push in the work roll to be replaced, and complete the online work roll replacement. In this embodiment of the invention, the diversion trough is externally made of steel, 1.5~2.0m long, 0.3~0.4m wide, and 0.2~0.25m high, and is lined with refractory material, laid on a slope of 5~15°.

[0058] (5) Remove the diversion trough. For the first 15 seconds after startup, withdraw at a speed of 0.5 m / min. Afterward, withdraw at a speed of 1~2 m / min. Then, lower the intermediate ladle and transition ladle to the casting position and resume normal casting. After casting 25 tons of molten steel, gradually roll it into a 0.8 mm strip.

[0059] (6) Continue rolling 150 tons of thin-gauge (≤0.8mm) steel, casting 480 tons of molten steel in the entire process, producing 270 tons of indentation-free thin-gauge (≤0.8mm) strip steel with good surface quality. See [link / reference]. Figure 3 The surface of the thin strip steel shown.

[0060] Comparative Example

[0061] (1) The qualified carbon steel molten steel after being smelted in the primary smelting furnace and the refining furnace is cast into a strip by a pair of counter-rotating casting rolls. After casting, 55 tons of molten steel are poured and then gradually cast into a 1.76mm thick strip at a casting speed of 61~62m / min.

[0062] (2) The 1.76mm thick strip is hot rolled into a 0.8mm thick strip in one pass. After that, the rolling mill maintains a rolling force of ≥6.5MN and continuously casts 100 tons.

[0063] (3) After the second batch of mixed casting, indentations appeared on the strip and the surface quality of the work roll deteriorated, so casting had to be stopped and the work roll replaced.

[0064] (4) Maintain production continuity and continue casting 20 tons of 0.8mm specification, and return to production of non-order products.

[0065] (5) A total of 360 tons of molten steel were cast in the entire process, producing 130 tons of thin-gauge (≤0.8mm) strip steel, of which 35 tons were steel coils with indentation problems. For surface quality, please refer to [reference needed]. Figure 4 As shown, the indentation is clearly visible.

[0066] Based on the descriptions of the examples and comparative examples, the following conclusions can be drawn:

[0067] Compared with the prior art, the present invention adopts the method of diverting the flow through the diversion channel 15 and replacing the work roll 14 online, which makes the output rate of qualified thin strip (≤0.8mm) higher, and at the same time improves the production continuity and the steel throughput per casting. This avoids the situation in the past where the original parts such as the tundish 4 and transition ladle 7 could not continue to be used after the casting stopped and the work roll was replaced. This increases the utilization space of the refractory material of the entire tundish 4 and transition ladle 7, improves the production continuity, reduces the production cost, and improves the output rate of thin strip (≤0.8mm) per casting and the overall production efficiency.

[0068] The above description is only a specific embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made 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 the efficient production of thin gauge strip steel, characterised in that, The method comprises the following steps: (1) when the hot rolling strip of the double roll casting appears indentation, it is judged that the hot rolling work roll in the rolling mill needs to be replaced, the pulling speed is reduced to 20-35 m / min, and the intermediate package liquid level is controlled to 400-600 mm; (2) before replacing the hot rolling work roll, the intermediate package and the transition package of the double roll casting casting system are synchronously lifted up, wherein the lifting speed of the intermediate package and the transition package is controlled to 5-10 mm / s, and the lifting height is controlled to 250-400 mm; (3) the flow guide groove is sent into the distributed liquid outlet hole below the transition package of the guide rail for steel liquid flow guide, wherein the advancing speed of the flow guide groove is controlled to 1-2 m / min; (4) after the steel liquid in the transition package is guided, the hot rolling work roll that needs to be replaced in the rolling mill is pushed out, and the standby work roll for replacement is pushed into the rolling mill; (5) the flow guide groove is removed, the first removal time period is the first 15 s of removing the flow guide groove, and the second removal time period is after 15 s until the removal is completed, wherein the first removal time period is carried out at a speed of 0.5-1 m / min, and the second removal time period is carried out at a speed of 1-3 m / min; (6) the intermediate package and the transition package of the casting system are restored for normal casting, the pulling speed is increased to 40-80 m / min, and the intermediate package is controlled to the normal working liquid level of 700-800 mm.

2. The high-efficiency production method of thin-gauge strip steel according to claim 1, characterized in that: in step (1), after it is judged that the hot rolling work roll in the rolling mill needs to be replaced, the pulling speed is reduced to 20-25 m / min.

3. The high-efficiency production method of thin-gauge strip steel according to claim 1, characterized in that: in step (1), after it is judged that the hot rolling work roll in the rolling mill needs to be replaced, the intermediate package liquid level is controlled to 400-500 mm.

4. The high-efficiency production method of thin-gauge strip steel according to claim 1, characterized in that: in step (2), the intermediate package and the transition package of the double roll casting casting system are synchronously lifted up, and the lifting speed of the intermediate package and the transition package is controlled to 8-10 mm / s.

5. The high-efficiency production method of thin-gauge strip steel according to claim 1, characterized in that: in step (2), the intermediate package and the transition package of the double roll casting casting system are synchronously lifted up, and the lifting height of the intermediate package and the transition package is controlled to 350-400 mm.

6. The high-efficiency production method of thin-gauge strip steel according to claim 1, characterized in that: in step (5), the second removal time period is carried out at a speed of 2-3 m / min.

7. The high-efficiency production method of thin-gauge strip steel according to claim 1, characterized in that: in step (6), the pulling speed is increased to 60-80 m / min.

8. The high-efficiency production method of thin-gauge strip steel according to any one of claims 1-7, characterized in that: the thickness of the thin-gauge strip steel is ≤0.8 mm.

9. The high-efficiency production method of thin-gauge strip steel according to claim 8, characterized in that: the thickness of the thin-gauge strip steel is 0.6-0.8 mm.

10. The method of efficiently producing a thin gauge strip steel according to any one of claims 1 to 7, wherein: the molten steel composition is a carbon steel, weathering steel, or stainless steel composition. the guide is a slide rail.

11. A method of efficient production of thin gauge strip steel as claimed in claim 1, wherein: ​

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