A slab superior carbon steel tundish quick change process

Abstract

The application discloses a slab excellent carbon steel tundish quick change process and belongs to the technical field of metallurgy. The slab excellent carbon steel tundish quick change process comprises the following steps: baking a new tundish, improving the outgoing molten steel temperature of the former and the latter furnace period before and after the quick change tundish, and adjusting the fan-shaped segment roll gap and the tension and straightening roll pressure to pour the last furnace molten steel; after the last furnace molten steel is poured, the casting blank pulling speed is adjusted, the old tundish stopper blind plate is pushed when the pouring stop weight is reached, the casting blank speed is reduced, the new tundish is replaced, and the tundish change is completed. By using the process technology, the slab caster realizes the excellent carbon steel tundish quick change, has the characteristics of simple operation and high tundish quick change success rate, and is suitable for use in the slab production excellent carbon steel tundish quick change.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and more specifically, to a quick-change process for tundishes used in the production of high-carbon steel slabs. Background Technology

[0002] In current metallurgical enterprises, increasing the capacity of slab continuous casting machines mainly relies on implementing ladle-changing production. The quick ladle change technology in continuous casting is a method to reduce the number of casting machine downtimes and production preparations, increase slab capacity, and improve casting machine operating rates. Plain carbon steel refers to steel with a carbon content of 0.08% to 0.45%, while high-carbon steel has a carbon content of 0.45% to 0.75%, making it a type of steel with a higher carbon content. Due to the high-temperature and solidification characteristics of high-carbon steel, during continuous casting, the molten steel experiences a larger solidification shrinkage rate in the crystallizer, resulting in lower strength and plasticity. It is highly susceptible to cracking during cooling, and even in air-cooled conditions, temperature stress can cause the cast billet to fracture. Currently, without a suitable method for controlling the quick tundish change process, when producing high-carbon steel on a slab continuous casting machine, without adopting the quick tundish change operation, only about 15 heats can be produced per casting cycle. After stopping casting, the interval for re-sending the dummy ingot for production preparation is at least 1 hour, which greatly affects the efficiency and output of slab continuous casting. At the same time, it generates a large amount of head and tail billets and cut-off waste, affecting the continuous casting yield.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects of the prior art and provide a quick-change process for tundishes of high-carbon steel slabs.

[0005] The technical problem solved by this invention is achieved by the following technical solution.

[0006] This invention provides a quick-change process for tundishes used in high-carbon steel slabs, comprising the following steps: baking the new tundish and increasing the temperature of molten steel leaving the station before and after the quick-change tundish, and adjusting the roller gap of the fan-shaped section and the pressure of the straightening rollers for the final heat of molten steel pouring; after the final heat of molten steel is poured, adjusting the billet casting speed, and when the stop casting weight is reached, pushing the blind plate with the old tundish clamping bar, and simultaneously reducing the casting speed to replace the new tundish, thus completing the ladle receiving process.

[0007] The present invention has the following beneficial effects:

[0008] This invention provides a quick-change process for tundishes used in high-carbon steel slab production, comprising the following steps: baking the new tundish and increasing the temperature of the molten steel exiting the station before and after the quick-change tundish; adjusting the pressure of the fan-shaped roll gap and the leveling rolls for the final heat of molten steel pour; after the final heat of molten steel is poured, adjusting the billet casting speed until the stop casting weight is reached, then pushing the blind plate with the old tundish clamping bar, simultaneously reducing the casting speed to replace the new tundish, thus completing the ladle connection. This reduces the ladle connection time and prevents the billet shell in the crystallizer from shrinking too quickly during the connection process, which could cause the billet shell to break off the immersion nozzle. This invention employs a continuous casting speed method, where the old tundish clamping bar pushes the blind plate while the casting speed is reduced to replace the new tundish. Using this method, quick-change of tundishes for high-carbon steel slab production can be achieved. Attached Figure Description

[0009] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0010] Figure 1 Flowchart for quick ladle changeover of high-carbon steel slab;

[0011] Figure 2 The speed curves for quick-change between old and new intermediate packages are shown. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0013] The following is a detailed description of a quick-change process for tundishes of high-carbon steel slabs provided by an embodiment of the present invention.

[0014] To address the current limitation of slab casting machines in not being able to quickly change tundishes for high-carbon steel, this invention provides a tundish quick-change process for slab casting of high-carbon steel. Using this process, slab casting machines can achieve quick tundish changes for high-carbon steel, featuring simple operation and a high success rate. It is suitable for use in tundish quick-change processes for high-carbon steel production in slabs. (See flowchart for slab casting high-carbon steel tundish quick-change process). Figure 1 This includes the following steps:

[0015] Quick intermediate package replacement operation steps:

[0016] Preparations before quick replacement:

[0017] Baking of intermediate buns and immersion gates: Baking time for spare intermediate buns is 4-5 hours, baking temperature of intermediate buns is 1050-1150℃, baking time of immersion gates is 50-90 minutes, and baking temperature of intermediate buns is 1000-1100℃.

[0018] Steel temperature control: The temperature of molten steel leaving the station before and after the quick tundish change is controlled at the upper limit of the first casting heat + 5℃ (1550-1560℃). The ladle category is controlled according to A and B categories (to prevent the ladle temperature from being too low during the ladle receiving process, resulting in the risk of cold steel getting stuck and poor ladle joints, the temperature of the furnace before and after the quick tundish change is increased. The temperature of molten steel leaving the station before and after the quick tundish change is controlled at the upper limit of the first casting heat + 5℃ (1550-1560℃). The ladle category is controlled according to A and B categories).

[0019] Preparation and inspection of tools before changing bags: Prepare the tools and equipment used for changing bags: splash guards, slag removers, wooden strips, etc.; check whether the standby intermediate bag baking machine is lifting and lowering normally, and whether the standby intermediate bag lifting and moving normally; remove debris from the intermediate bag car track to ensure smooth operation of the intermediate bag car.

[0020] Sector-shaped roll gap control and straightening roll pressure: For the final ladle pouring, the dynamic soft pressure control (L2) is switched to static roll gap control (L1), and the straightening roll pressure is increased from 4.5 MPa to 6 MPa. After the pouring speed drops to 0.5 m / min, the 12-segment roll gap is raised by 20 mm. After the ladle is finished, the pouring speed is gradually increased back to 0.5 m / min, and the 12-segment roll gap is restored. Old operating method: Dynamic soft pressure (L2) is used throughout, with a straightening roll pressure of 4.5 MPa. After the final ladle pouring, the ladle sliding nozzle is closed, and the turret fork arm is raised to its highest position. After the new ladle of molten steel is placed, the turret is rotated back to the pouring position, while the fork arm remains at its highest position. Under the old operating method, dynamic soft pressure (L2) is used throughout, with a straightening roll pressure of 4.5 MPa. During the quick ladle change process, the wicking shrinkage is at segments 8-9 for a 270 mm thick ladle and at segments 7-8 for a 220 mm thick ladle. Because the molten core of the billet is long and the ladle deceleration time is short, the shrinkage is insufficient (it does not shrink to the straightening section). The billet has a slight bulge at the end of solidification, which leads to high resistance when pulling the billet and failure to pull it to the ladle. This is especially true at the 12th section, where the 12th section rollers can easily jam the billet. By improving the operation and adopting the solution provided in the embodiment of this invention, the molten core shrinks to the 7th-8th section during the quick ladle change process for a 270mm thick billet and to the 6th-7th section for a 220mm thick billet. At the same time, after raising the gap between the 12th section rollers by 20mm, the billet passes through each sector smoothly.

[0021] Quick exchange between old and new intermediate packages:

[0022] With 14-17 tons of molten steel remaining in the tundish, end the standby tundish baking process. Approximately 3 minutes before shutting off the old tundish, switch the crystallizer level control to manual and rotate the crystallizer level sensor to the rear position. Simultaneously, inspect the standby tundish, shut off the nozzle baking gas and tundish baking device, push the blind flange with the clamping bar, immediately lift the old tundish and move it above the slag pan. Clean the slag strips around the crystallizer billet shell, and perform black slag operation in the crystallizer, controlling the slag layer thickness to 60-70 mm. At the same time, move the new tundish, which is currently in the slag pan position, to the pouring position.

[0023] New Tundish Casting: Move the new tundish, which is currently in the slag pan position, to the casting position and align the tundish nozzle. Simultaneously, lower the tundish and start casting in the ladle. Lower the immersion nozzle above the molten steel surface in the crystallizer. Make minor adjustments to the tundish nozzle for alignment. When the ladle has cast approximately 4-5 tons of molten steel, jog the tundish down to the side hole of the immersion nozzle below the molten steel surface in the crystallizer to begin casting. Press the first bar to start casting the large steel flow. During the ladle receiving process, use a wooden stick to jog the molten steel surface in the crystallizer near the tundish nozzle to observe for any condensed steel or billet shells that do not detach from the mold. Remove any large slag skin around the crystallizer to prevent incompletely solidified molten steel from catching the slag skin and causing joint leakage.

[0024] The speed control curve for receiving the package during the quick changeover process between the old and new intermediate packages is shown below. Figure 2 The specific pulling speed control is as follows:

[0025] After the molten steel is poured from the ladle, begin reducing the casting speed manually to 0.20 m / min (in increments of 0.02 m / min every 15-20 seconds). Maintain the speed at 0.2 m / min for 1-2 minutes, until the liquid core is collected to within 8 segments. Push the blind plate with the old ladle's stopper bar, and simultaneously adjust the casting speed to 0.03 m / min to replace the old ladle. After the new ladle's stopper bar is pressed open to begin pouring, manually increase the casting speed to 0.2 m / min and maintain it for 2 minutes, then increase it to 0.3 m / min. Once the billet exits the crystallizer at the interface, gradually increase the casting speed to the target speed. For a billet thickness of 220 mm, the ladle receiving time should be ≤110 seconds; for a billet thickness of 270 mm, ≤150 seconds. The old operation was as follows: After pouring molten steel from the ladle, the casting speed was reduced. Within 2 minutes, the speed was manually reduced to 0.80 m / min and maintained at 0.80 m / min for at least 3 minutes. When the weight for stopping pouring was reached, the old ladle clamping bar pushed the blind plate, and at the same time, the "stop" button of the straightening machine was pressed. The casting speed automatically returned to zero. At this time, the molten steel level in the crystallizer was at or slightly below the meniscus. In the old operation, after the ladle stopper was opened to start pouring, the casting speed was manually increased to 0.5 m / min and maintained for 1 minute. After the billet exited the crystallizer at the interface, the casting speed was gradually increased to the target casting speed. Because the casting speed was increased, the molten core of the billet was extended. The short deceleration time at the ladle resulted in insufficient shrinkage (not shrinking to the straightening section). At the end of solidification, the billet had a slight bulge, resulting in high resistance and difficulty in casting. By improving the operation, the solution provided in the embodiments of the present invention can reduce the receiving time, prevent the billet shell inside the crystallizer from shrinking too quickly during the receiving process, and prevent the billet shell from breaking off at the immersion nozzle. By adopting a continuous pulling speed method, the pulling speed is reduced to 0.03m / min for quick tundish replacement, thereby improving the success rate of quick tundish replacement.

[0026] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0027] Example 1

[0028] A quick-change process for tundish in high-carbon steel slabs is described in the flowchart below. Figure 1 Quick intermediate package replacement operation steps:

[0029] Preparations before quick replacement:

[0030] Baking of intermediate buns and immersion gates: Baking time for spare intermediate buns is 4-5 hours, baking temperature of intermediate buns is 1050-1150℃, baking time of immersion gates is 50-90 minutes, and baking temperature of intermediate buns is 1000-1100℃.

[0031] Steel temperature control: The temperature of molten steel leaving the station before and after quick tundish change is controlled at the upper limit of the first casting furnace + 5℃ (1550-1560℃), and the ladle category is controlled according to A and B category ladles.

[0032] Preparation and inspection of tools before changing bags: Prepare the tools and equipment used for changing bags: splash guards, slag removers, wooden strips, etc.; check whether the standby intermediate bag baking machine is lifting and lowering normally, and whether the standby intermediate bag lifting and moving normally; remove debris from the intermediate bag car track to ensure smooth operation of the intermediate bag car.

[0033] Sector-shaped roll gap control and tension roller pressure: For the last ladle pouring, the dynamic soft pressure control (L2) was switched to static roll gap control (L1), and the tension roller pressure was increased from 4.5 MPa to 6 MPa. After the pouring speed was reduced to 0.5 m / min, the 12-segment roll gap was raised by 20 mm. After the ladle was finished, the pouring speed was increased to 0.5 m / min and the 12-segment roll gap was gradually restored.

[0034] Quick exchange between old and new intermediate packages:

[0035] With 14-17 tons of molten steel remaining in the tundish, end the standby tundish baking process. Approximately 3 minutes before shutting off the molten steel in the old tundish, switch the crystallizer level control to manual and rotate the crystallizer level sensor to the rear position. Simultaneously, inspect the new tundish, shut off the baking gas at the new nozzle and the new tundish baking device, and immediately lift and move the old tundish above the slag pan after the old tundish's baffle plate is pushed back. Clean the slag strips around the crystallizer billet shell, and perform black slag operation in the crystallizer, controlling the slag layer thickness to 60-70 mm. At the same time, move the new tundish, which is currently in the slag pan position, to the pouring position.

[0036] New Tundish Casting: Move the new tundish, which is currently in the slag pan position, to the casting position and align the tundish nozzle. Simultaneously, lower the new tundish and start casting in the ladle. Lower the submerged entry nozzle above the molten steel surface in the crystallizer. Make minor adjustments to the tundish nozzle for alignment. When the ladle has cast approximately 4.3 tons of molten steel, jog the tundish down to the side hole of the submerged entry nozzle below the molten steel surface in the crystallizer to begin casting. Press the first bar to start casting with a large flow of steel. During the ladle receiving process, use a wooden stick to jog the molten steel surface in the crystallizer near the tundish nozzle to observe for any condensed steel or billet shells that do not detach from the mold. Remove any large slag skin around the crystallizer to prevent incompletely solidified molten steel from catching the slag skin and causing leakage at the joint.

[0037] The packing speed control during the quick changeover process between old and new intermediate packs is as follows:

[0038] After the molten steel is poured from the ladle, begin reducing the casting speed manually to 0.20 m / min (in increments of 0.02 m / min every 15-20 seconds). Maintain the speed at 0.2 m / min for 1-2 minutes, until the liquid core is collected to within 8 segments. Push the blind plate with the old tundish clamping bar, and simultaneously adjust the casting speed to 0.03 m / min to replace the tundish. After the tundish stopper bar is opened and casting begins, manually increase the casting speed to 0.2 m / min and maintain it for 2 minutes, then increase it to 0.3 m / min. Once the slab exits the crystallizer at the casting interface, gradually increase the casting speed to the target speed. For a slab thickness of 220 mm, the ladle receiving time should be ≤110 seconds; for a slab thickness of 270 mm, ≤150 seconds.

[0039] Example 2

[0040] Preparations before quick replacement:

[0041] Baking of intermediate buns and immersion gates: Baking time for spare intermediate buns is 4 hours, baking temperature of intermediate buns is 1060℃, baking time of immersion gates is 55 minutes, and baking temperature of intermediate buns is 1015℃.

[0042] Steel temperature control: Before the tundish is changed, the ladle is a Class B ladle with a steel outlet temperature of 1550℃; the ladle of the receiving ladle is a Class A ladle with a steel outlet temperature of 1560℃.

[0043] Preparation and inspection of tools before changing bags: Prepare the tools and equipment used for changing bags: splash guards, slag removers, wooden strips, etc.; check whether the standby intermediate bag baking machine is lifting and lowering normally, and whether the standby intermediate bag lifting and moving normally; remove debris from the intermediate bag car track to ensure smooth operation of the intermediate bag car.

[0044] Sector-shaped roll gap control and tension roller pressure: For the last ladle pouring, the dynamic soft pressure control (L2) was switched to static roll gap control (L1), and the tension roller pressure was increased from 4.5 MPa to 6 MPa. After the pouring speed was reduced to 0.5 m / min, the 12-segment roll gap was raised by 20 mm. After the ladle was finished, the pouring speed was increased to 0.5 m / min and the 12-segment roll gap was gradually restored.

[0045] Quick exchange between old and new intermediate packages:

[0046] With 17 tons of molten steel remaining in the tundish, the standby tundish baking process is completed. Approximately 3 minutes before shutting off the molten steel in the old tundish, the crystallizer level control is switched to manual control, and the crystallizer level sensor is rotated to the rear position. Simultaneously, the new tundish is inspected, and the baking gas at the new nozzle and the new tundish baking device are shut off. After the old tundish's baffle plate is pushed back, the old tundish is immediately lifted and moved above the slag pan. The slag strips around the crystallizer billet shell are cleaned, and the black slag operation in the crystallizer is performed, controlling the slag layer thickness to 66 mm. At the same time, the new tundish, which is currently in the slag pan position, is moved to the pouring position.

[0047] New Tundish Casting: Move the new tundish, which is currently in the slag pan position, to the casting position and align the tundish nozzle. Simultaneously, lower the new tundish and start casting in the ladle. Lower the submerged entry nozzle above the molten steel surface in the crystallizer. Make minor adjustments to the tundish nozzle for alignment. When the ladle has cast approximately 4.9 tons of molten steel, jog the tundish down to the side hole of the submerged entry nozzle below the molten steel surface in the crystallizer to begin casting. Press the first bar to start casting with a large flow of steel. During the ladle receiving process, use a wooden stick to jog the molten steel surface in the crystallizer near the tundish nozzle to observe for any condensed steel or billet shells that do not detach from the mold. Remove any large slag skin around the crystallizer to prevent incompletely solidified molten steel from catching the slag skin and causing leakage at the joint.

[0048] The packing speed control during the quick changeover process between old and new intermediate packs is as follows:

[0049] After the molten steel is poured from the ladle, the casting speed is reduced manually to 0.20 m / min (in increments of 0.02 m / min every 15-20 seconds). The speed is maintained at 0.2 m / min for 1-2 minutes until the liquid core is collected to within 8 segments. The old tundish retainer pushes the blind plate, and the casting speed is adjusted to 0.03 m / min to replace the tundish. After the tundish plug is opened and casting begins, the casting speed is manually increased to 0.2 m / min and maintained for 2 minutes, then increased to 0.3 m / min. Once the slab exits the crystallizer at the interface, the casting speed is gradually increased to the target speed. The ladle receiving time is 65 seconds for a 220 mm slab thickness and 120 seconds for a 270 mm slab thickness.

[0050] Example 3

[0051] Preparations before quick replacement:

[0052] Baking of intermediate buns and immersion gates: Baking time for spare intermediate buns is 4.2 hours, baking temperature of intermediate buns is 1085℃, baking time of immersion gates is 70 minutes, and baking temperature of intermediate buns is 1050℃.

[0053] Steel temperature control: Before the tundish is changed, the ladle is a Class A ladle with a steel outlet temperature of 1560℃; the ladle of the next ladle is a Class B ladle with a steel outlet temperature of 1558℃.

[0054] Preparation and inspection of tools before changing bags: Prepare the tools and equipment used for changing bags: splash guards, slag removers, wooden strips, etc.; check whether the standby intermediate bag baking machine is lifting and lowering normally, and whether the standby intermediate bag lifting and moving normally; remove debris from the intermediate bag car track to ensure smooth operation of the intermediate bag car.

[0055] Sector-shaped roll gap control and tension roller pressure: For the last ladle pouring, the dynamic soft pressure control (L2) was switched to static roll gap control (L1), and the tension roller pressure was increased from 4.5 MPa to 6 MPa. After the pouring speed was reduced to 0.5 m / min, the 12-segment roll gap was raised by 20 mm. After the ladle was finished, the pouring speed was increased to 0.5 m / min and the 12-segment roll gap was gradually restored.

[0056] Quick exchange between old and new intermediate packages:

[0057] With 15 tons of molten steel remaining in the tundish, the standby tundish baking process is completed. Approximately 3 minutes before shutting off the old tundish, the crystallizer level control is switched to manual control, and the crystallizer level sensor is rotated to the rear position. Simultaneously, the new tundish is inspected, and the baking gas at the new nozzle and the new tundish baking device are shut off. After the old tundish's baffle plate is pushed back, the old tundish is immediately lifted and moved above the slag pan. The slag strips around the crystallizer billet shell are cleaned, and the black slag operation in the crystallizer is performed, controlling the slag layer thickness to 61 mm. At the same time, the new tundish, which is currently in the slag pan position, is moved to the pouring position.

[0058] New Tundish Casting: Move the new tundish, which is currently in the slag pan position, to the casting position and align the tundish nozzle. Simultaneously, lower the new tundish and start casting in the ladle. Lower the submerged entry nozzle above the molten steel surface in the crystallizer. Make minor adjustments to the tundish nozzle for alignment. When the ladle has cast approximately 4.5 tons of molten steel, jog the tundish down to the side hole of the submerged entry nozzle below the molten steel surface in the crystallizer to begin casting. The first bar is used to force open the large flow of steel for casting. During the ladle receiving process, use a wooden stick to jog the molten steel surface in the crystallizer near the tundish nozzle to observe for any condensed steel or billet shells that do not detach from the mold. Remove any large slag skin around the crystallizer to prevent incompletely solidified molten steel from catching the slag skin and causing joint leakage.

[0059] The packing speed control during the quick changeover process between old and new intermediate packs is as follows:

[0060] After the molten steel is poured from the ladle, the casting speed is reduced manually to 0.20 m / min (in increments of 0.02 m / min every 15-20 seconds). The speed is maintained at 0.2 m / min for 1-2 minutes until the liquid core is collected to within 8 segments. The old tundish retainer pushes the blind plate, and the casting speed is adjusted to 0.03 m / min to replace the tundish. After the tundish plug is opened and casting begins, the casting speed is manually increased to 0.2 m / min and maintained for 2 minutes, then increased to 0.3 m / min. Once the slab exits the crystallizer at the interface, the casting speed is gradually increased to the target speed. The ladle receiving time is 100 seconds for a 220 mm slab thickness and 130 seconds for a 270 mm slab thickness.

[0061] Example 4

[0062] Preparations before quick replacement:

[0063] Baking of intermediate buns and immersion gates: Baking time for spare intermediate buns is 4.5 hours, baking temperature of intermediate buns is 1123℃, baking time of immersion gates is 80 minutes, and baking temperature of intermediate buns is 1092℃.

[0064] Steel temperature control: Before the tundish is changed, the ladle is a Class A ladle with a steel outlet temperature of 1555℃; the ladle of the next ladle is a Class B ladle with a steel outlet temperature of 1553℃.

[0065] Preparation and inspection of tools before changing bags: Prepare the tools and equipment used for changing bags: splash guards, slag removers, wooden strips, etc.; check whether the standby intermediate bag baking machine is lifting and lowering normally, and whether the standby intermediate bag lifting and moving normally; remove debris from the intermediate bag car track to ensure smooth operation of the intermediate bag car.

[0066] Sector-shaped roll gap control and tension roller pressure: For the last ladle pouring, the dynamic soft pressure control (L2) was switched to static roll gap control (L1), and the tension roller pressure was increased from 4.5 MPa to 6 MPa. After the pouring speed was reduced to 0.5 m / min, the 12-segment roll gap was raised by 20 mm. After the ladle was finished, the pouring speed was increased to 0.5 m / min and the 12-segment roll gap was gradually restored.

[0067] Quick exchange between old and new intermediate packages:

[0068] With 14.3 tons of molten steel remaining in the tundish, the standby tundish baking process is completed. Approximately 3 minutes before shutting off the molten steel in the old tundish, the crystallizer level control is switched to manual control and the crystallizer level sensor is rotated to the rear position. Simultaneously, the new tundish is inspected, and the baking gas at the new nozzle and the new tundish baking device are shut off. After the old tundish's baffle plate is pushed back, the old tundish is immediately lifted and moved above the slag pan. The slag bars around the crystallizer billet shell are cleaned, and the black slag operation in the crystallizer is performed, controlling the slag layer thickness to 68 mm. At the same time, the new tundish, which is currently in the slag pan position, is moved to the pouring position.

[0069] New Tundish Casting: Move the new tundish, which is currently in the slag pan position, to the casting position and align the tundish nozzle. Simultaneously, lower the new tundish and start casting in the ladle. Lower the submerged entry nozzle above the molten steel surface in the crystallizer. Make minor adjustments to the tundish nozzle and align it. When the ladle has cast approximately 5 tons of molten steel, jog the tundish down to the submerged entry nozzle side hole below the molten steel surface in the crystallizer to begin casting. Press the first bar to start casting the large steel flow. During the ladle receiving process, use a wooden stick to jog the molten steel surface in the crystallizer near the tundish nozzle to observe for any condensed steel or billet shells that do not detach from the mold. Remove any large slag skin around the crystallizer to prevent incompletely solidified molten steel from catching the slag skin and causing joint leakage.

[0070] The packing speed control during the quick changeover process between old and new intermediate packs is as follows:

[0071] After the molten steel is poured from the ladle, the casting speed is reduced manually to 0.20 m / min (in increments of 0.02 m / min every 15-20 seconds). The speed is maintained at 0.2 m / min for 1-2 minutes until the liquid core is collected to within 8 segments. The old tundish retainer pushes the blind plate, and the casting speed is adjusted to 0.03 m / min to replace the tundish. After the tundish plug is opened and casting begins, the casting speed is manually increased to 0.2 m / min and maintained for 2 minutes, then increased to 0.3 m / min. Once the slab exits the crystallizer at the interface, the casting speed is gradually increased to the target speed. The ladle receiving time is 105 seconds for a 220 mm thick slab and 136 seconds for a 270 mm thick slab.

[0072] Example 5

[0073] Preparations before quick replacement:

[0074] Baking of intermediate buns and immersion gates: Baking time for spare intermediate buns is 4.8 hours, baking temperature of intermediate buns is 1130℃, baking time of immersion gates is 85 minutes, and baking temperature of intermediate buns is 1095℃.

[0075] Steel temperature control: Before the tundish is changed, the ladle is a Class B ladle with a steel outlet temperature of 1554℃; the ladle of the receiving ladle is a Class A ladle with a steel outlet temperature of 1558℃.

[0076] Preparation and inspection of tools before changing bags: Prepare the tools and equipment used for changing bags: splash guards, slag removers, wooden strips, etc.; check whether the standby intermediate bag baking machine is lifting and lowering normally, and whether the standby intermediate bag lifting and moving normally; remove debris from the intermediate bag car track to ensure smooth operation of the intermediate bag car.

[0077] Sector-shaped roll gap control and tension roller pressure: For the last ladle pouring, the dynamic soft pressure control (L2) was switched to static roll gap control (L1), and the tension roller pressure was increased from 4.5 MPa to 6 MPa. After the pouring speed was reduced to 0.5 m / min, the 12-segment roll gap was raised by 20 mm. After the ladle was finished, the pouring speed was increased to 0.5 m / min and the 12-segment roll gap was gradually restored.

[0078] Quick exchange between old and new intermediate packages:

[0079] With 16.3t of molten steel remaining in the tundish, the standby tundish baking process is completed. Approximately 3 minutes before shutting off the molten steel in the old tundish, the crystallizer level control is switched to manual control and the crystallizer level sensor is rotated to the rear position. Simultaneously, the new tundish is inspected, and the baking gas at the new nozzle and the baking device for the new tundish are shut off. After the blind plate is pushed back by the old tundish clamping bar, the old tundish is immediately lifted and moved above the slag pan. The slag strips around the crystallizer billet shell are cleaned, and the black slag operation in the crystallizer is carried out, controlling the slag layer thickness to 64mm. At the same time, the new tundish, which is in the slag pan position, is moved to the pouring position.

[0080] New Tundish Casting: Move the new tundish, which is currently in the slag pan position, to the casting position and align the tundish nozzle. Simultaneously, lower the new tundish and start casting in the ladle. Lower the submerged entry nozzle above the molten steel surface in the crystallizer. Make minor adjustments to the tundish nozzle and align it. When the ladle has cast approximately 4 tons of molten steel, jog the tundish down to the submerged entry nozzle side hole below the molten steel surface in the crystallizer to begin casting. Press the first bar to start casting the large steel flow. During the ladle receiving process, use a wooden stick to jog the molten steel surface in the crystallizer near the tundish nozzle to observe for any condensed steel or billet shells that do not detach from the mold. Remove any large slag skin around the crystallizer to prevent incompletely solidified molten steel from catching the slag skin and causing joint leakage.

[0081] The packing speed control during the quick changeover process between old and new intermediate packs is as follows:

[0082] After the molten steel is poured from the ladle, begin reducing the casting speed manually to 0.20 m / min (in increments of 0.02 m / min every 15-20 seconds). Maintain the speed at 0.2 m / min for 1-2 minutes, until the liquid core is collected to within 8 segments. Push the blind plate with the old tundish clamping bar, and simultaneously adjust the casting speed to 0.03 m / min to replace the tundish. After the tundish stopper bar is opened and casting begins, manually increase the casting speed to 0.2 m / min and maintain it for 2 minutes, then increase it to 0.3 m / min. Once the slab exits the crystallizer at the casting interface, gradually increase the casting speed to the target speed. For a slab thickness of 220 mm, the ladle receiving time should be ≤110 seconds; for a slab thickness of 270 mm, ≤150 seconds.

[0083] Comparative Example 1

[0084] Similar to the steps in Example 1, the only difference is that the old operation method resulted in the failure of the quick change of the middle package.

[0085] Preparations before quick replacement:

[0086] Baking of intermediate buns and immersion gates: Baking time for spare intermediate buns is 6 hours, baking temperature of intermediate buns is 1210℃, baking time of immersion gates is 180 minutes, and baking temperature of intermediate buns is 1200℃.

[0087] Steel temperature control: The temperature of molten steel leaving the station before and after quick tundish change is controlled at the upper limit of the continuous casting standard.

[0088] Sector roll gap control and tension roller pressure: The sector roll gap is controlled by dynamic soft pressure L2, and the tension roller pressure is 4.5 MPa.

[0089] Quick exchange between old and new intermediate packages:

[0090] After shutting off the molten steel from the old tundish, end the baking of the standby tundish and simultaneously inspect the new tundish. Immediately lift the old tundish and move it above the slag pan. Clean the slag bars around the crystallizer billet shell, and handle the black slag operation in the crystallizer, controlling the slag layer thickness to 60-70mm. At the same time, move the new tundish, which is currently in the slag pan position, to the pouring position.

[0091] New Tundish Casting: Move the new tundish, which is in the slag pan position, to the casting position and center the tundish nozzle. Simultaneously, lower the new tundish and start casting the main ladle. Lower the submerged entry nozzle above the molten steel surface in the crystallizer. Make minor adjustments to the tundish nozzle and center it. After the main ladle has cast about 4-5 tons of molten steel, jog the tundish down to the submerged entry nozzle side hole below the molten steel surface in the crystallizer to start casting.

[0092] The packing speed control during the quick changeover process between old and new intermediate packs is as follows:

[0093] After the molten steel is poured from the ladle, begin reducing the casting speed. Within 2 minutes, manually reduce the speed to 0.80 m / min and maintain this speed for at least 3 minutes. When the desired weight for stopping pouring is reached, push the blind plate with the ladle clamping bar and simultaneously press the "stop" button on the straightening machine. The casting speed will automatically return to zero. At this point, the molten steel level in the crystallizer should be at or slightly below the meniscus. After the ladle stopper is opened to allow pouring, manually increase the casting speed to 0.5 m / min and maintain this speed for 1 minute. Once the billet exits the crystallizer at the interface, gradually increase the casting speed to the target speed.

[0094] Comparative Example 2

[0095] Similar to the steps in Example 1, the only difference is that the roll gap of the fan-shaped section of the last batch of ladle is controlled by dynamic soft pressing L2, and the pressure of the straightening roller is 4.5 MPa. If the roll gap of the fan-shaped section is pressed too much and the pressure of the straightening roller is too low, it is easy to cause a large resistance to the billet during the ladle receiving process, resulting in a decrease in the success rate of the quick change of the tundish.

[0096] Comparative Example 3

[0097] Similar to the steps in Example 1, the only difference is that the baking temperature of the new intermediate ladle is 1210℃, the baking time of the intermediate ladle is long, and when the baking temperature is ≥1200℃, it causes oxidation and melting of the stopper rod, melting, deformation and loosening of the stopper rod core and cross arm, melting and deformation of the ladle cover steel structure and refractory material falling off, collapse of the working layer and adhesion of the stopper rod head to the upper nozzle cup, etc., which leads to a decrease in the success rate of quick change of the intermediate ladle.

[0098] Comparative Example 4

[0099] Similar to the steps in Example 1, the only difference is that the immersion time for the sprue baking is 180 minutes, and the sprue is baked to 1168°C. If the baking time and temperature are too high, the aluminum-carbon or zirconium-carbon sprue will oxidize and decarburize, and its strength and lifespan will be reduced, affecting the overall lifespan of the tundish.

[0100] The above information shows that: increasing the furnace temperature before and after quick ladle changes can effectively prevent risks such as low ladle temperature during ladle receiving, cold steel jamming during casting, and poor ladle joint marks; increasing the straightening roller pressure from 4.5 MPa to 6 MPa and lowering the drawing speed to 0.5 m / min while raising the 12-section roller gap by 20 mm can effectively reduce the billet resistance during ladle receiving; and adopting a continuous drawing speed method with a drawing speed reduced to 0.03 m / min for quick ladle changes can effectively reduce ladle receiving time and prevent the billet shell in the crystallizer from shrinking too quickly during the ladle receiving process, causing the billet shell to break off at the immersion nozzle.

[0101] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A quick-change process for tundishes used in the production of high-carbon steel slabs, characterized in that, Includes the following steps: The new tundish is baked, and the temperature of the molten steel exiting the station is increased before and after the quick tundish change. The pressure of the fan-shaped section roll gap and the leveling rolls is adjusted for the final heat of molten steel pouring. Three minutes before shutting off the molten steel in the old tundish, the crystallizer level control is switched to manual control and the crystallizer level sensor is rotated to the rear position. At the same time, the new tundish is inspected, and the baking gas and baking device at the new tundish nozzle are shut off. After the blind plate is pushed back by the old tundish clamping bar, the old tundish is immediately lifted and moved above the slag pan. The slag bars around the crystallizer billet shell are cleaned. During the black slag operation in the crystallizer, the slag layer thickness is controlled to be 60-70mm. Simultaneously, the new tundish, currently in the slag pan position, is moved to the pouring position, and the new tundish nozzle is aligned. While lowering the new tundish, the main ladle begins pouring, lowering the immersion nozzle of the new tundish above the molten steel surface in the crystallizer. Fine-tune and align the new tundish nozzle. When the main ladle pours to 4-5 tons of molten steel in the new tundish, the new tundish is jogged down until the immersion nozzle side hole is below the molten steel surface in the crystallizer, and pouring begins. The first bar is used to force open the large steel flow for pouring. Among these steps: The sector segment includes 1 to 12 segments. Adjusting the sector segment roll gap and tension roller pressure for the final heat of molten steel pouring includes the following steps: When pouring the final heat of molten steel, the sector segment roll gap control mode is changed from dynamic soft pressure L2 control mode to static roll gap L1 control mode. The tension roller pressure is increased from 4.5MPa to 6MPa. After the tensioning speed is reduced to 0.5m / min, the 12-segment roll gap is raised by 20mm. After the ladle is received, the tensioning speed is increased to 0.5m / min and the 12-segment roll gap is gradually restored.

2. The tundish quick-change process for high-carbon steel slabs according to claim 1, characterized in that, During the ladle receiving process, use a wooden stick to jog the liquid level in the crystallizer near the tundish nozzle to observe whether there is any condensation of cold steel or billet shell that does not detach from the mold. Pick out any large slag skin around the crystallizer to prevent the incompletely solidified molten steel from capturing the slag skin and causing steel leakage at the joint.

3. The tundish quick-change process for high-carbon steel slabs according to claim 1, characterized in that, The ladle casting speed control is as follows: After the last heat of molten steel is poured, start to reduce the casting speed manually to 0.20 m / min, in increments of 0.02 m / min every 15-20 seconds. Maintain the casting speed at 0.2 m / min for 1-2 minutes, and control the liquid core contraction within 8 stages. Push the blind plate with the old tundish jamming bar, and at the same time adjust the casting speed to 0.03 m / min to replace the new tundish. After the new tundish opens the stopper bar and starts casting, manually increase the casting speed to 0.2 m / min and maintain it for 2 minutes, then increase the casting speed to 0.3 m / min. After the billet exits the crystallizer at the interface, gradually increase the casting speed to the target casting speed.

4. The tundish quick-change process for high-carbon steel slabs according to claim 1, characterized in that, The ladle receiving time is controlled as follows: for a billet thickness of 220mm, the ladle receiving time is ≤ 110s; for a billet thickness of 270mm, the ladle receiving time is ≤ 150s.

5. The tundish quick-change process for high-carbon steel slabs according to claim 1, characterized in that, The wick shrinkage during the packing process is controlled as follows: for a 270mm thick pack, the wick shrinkage is controlled at 7-8 segments; for a 220mm thick pack, the wick shrinkage is controlled at 6-7 segments.

6. The tundish quick-change process for high-carbon steel slabs according to claim 1, characterized in that, Baking the new intermediate loaf includes controlling the baking temperature of the new intermediate loaf at 1050-1150℃ for 4-5 hours, and the baking temperature of the immersion nozzle at 1000-1100℃ for 50-90 minutes.

7. The tundish quick-change process for high-carbon steel slabs according to claim 6, characterized in that, Also includes: The new tundish is baked until 14-17 tons of molten steel remain in the old tundish, at which point the baking process is complete.

8. The quick-change process for tundishes of high-carbon steel slabs according to claim 1, characterized in that, The temperature of molten steel leaving the station before and after the quick tundish change includes: the temperature of molten steel leaving the station before and after the quick tundish change is controlled at the upper limit of the first casting furnace plus 5℃.

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