A method for rapid hot standby of a tundish

Abstract

The present invention discloses a method for rapid hot standby of a tundish. The method is as follows: Predict the required duration of process technology and equipment maintenance. Before hot standby, increase the ladle charging temperature by 5°C for the last furnace and perform tundish slag discharging, control the tundish slag thickness within 40 mm, and conduct inspection of the slag line on the tundish wall during the hot standby process, requiring the tundish wall erosion to be <20 mm and the flow stabilizer to be >200 mm; After the ladle pouring is completed, measure the molten steel level height in the tundish. When the liquid level height reaches 150 - 250 mm, stop pouring the tundish, quickly move the tundish car to the baking position for high-fire baking, and quickly perform the operation of sealing the dummy bar after the continuous casting billet is pulled out; The method for rapid hot standby of the tundish of the present invention can determine the shutdown and flow-blocking timing according to the liquid level height of the tundish, and can accurately judge the remaining molten steel in the tundish by using the molten steel measuring device, avoiding the difficulty in starting casting caused by slag entrainment; When the continuous caster shuts down, only the tail billet is discharged and the dummy bar is sealed, and the controlled duration is about 40 minutes, which can ensure the rapid resumption of production of the continuous casting and the entire steelmaking system.

Description

Technical Field

[0001] The invention specifically relates to a method for rapid hot standby of a tundish, and belongs to the technical field of hot standby equipment for a tundish. Background Art

[0002] During the continuous casting production process, the production was interrupted due to fluctuations in equipment and technology, and the continuous casting and pouring work within the planned production could not be met; re-baking the ladle affected the continuous casting machine's operating time by more than 3 hours; in order to reduce the continuous casting machine's downtime, improve the continuous casting operation rate, increase the utilization rate of refractory materials and reduce the cost of refractory materials, according to process adjustments and equipment maintenance time, the tundish poured online by continuous casting was used for hot standby after shutdown; the hot standby of the continuous casting tundish is to control the temperature and liquid level of the molten steel in the tundish before the continuous casting machine stops pouring, and to bake the tundish with a high fire after the flow is blocked to improve the hot standby Hot standby temperature, the operator sends the ingot to restart the machine according to the scheduled downtime; the continuous casting machine can shorten the abnormal downtime and improve the continuous casting operation rate; through the online hot standby technology of the tundish, the downtime of the continuous casting machine under the conditions of process adjustment and emergency equipment maintenance is effectively reduced, the operation rate of the continuous casting machine is improved and the cost of refractory materials is reduced; the hot standby technology of the continuous casting dry material tundish in the existing technology is affected by the downtime, baking temperature and reserved molten steel factors, resulting in a lower success rate of pouring after hot standby, and it is easy to cause startup failure accidents such as unsuccessful drainage, water nozzle dispersion and high-temperature steel leakage. Summary of the invention

[0003] To solve the above problems, the present invention proposes a method for rapid hot standby of the tundish. The continuous casting machine is shut down only for the time of discharging the tail billet and sealing the ingot, and the control time is about 40 minutes, which can ensure that the continuous casting and the entire steelmaking system can quickly resume production.

[0004] The method for rapid hot standby of tundish in the present invention can perform hot standby of dry-material tundish in hot state when dealing with sudden process and equipment problems, solve the time limit for restarting casting after continuous casting shutdown, improve the success rate and operation rate of starting casting, and effectively reduce the refractory cost; it can effectively balance and stabilize the entire steelmaking, gas, and rolling systems, and avoid continuous furnace shutdown and machine shutdown caused by the long baking time of tundish during restart of continuous casting, thus preventing the chain production impact on the iron, steel, rolling, and driving systems; the method is as follows: Predict the required duration for process and equipment maintenance. Before hot standby, increase the ladle charging temperature by 5°C for the last furnace of the heat treatment and perform slag removal from the tundish, control the tundish slag thickness within 40 mm, check the slag line on the tundish wall during the hot standby process, and require the tundish wall erosion to be < 20 mm and the flow stabilizer to be > 200 mm; after the ladle casting is completed, measure the molten steel level height in the tundish. When the liquid level height reaches 150 - 250 mm, stop casting the tundish and add 5 - 6 bags of covering agent to cover the molten steel, quickly move the tundish car to the baking position for high-fire baking, and quickly perform the sealing and dummy bar insertion operation after the cast billet is pulled out; when starting up, according to the ladle charging temperature of 1620 - 1630°C, quickly perform the tundish nozzle drainage operation after the ladle starts casting. Ensure that the cold steel in the upper nozzle is cleaned up after the liquid level in the tundish exceeds 400 mm, and perform the normal tundish flow opening operation, and adjust the secondary cooling water distribution coefficient according to 1.2.

[0005] Further, the method is specifically as follows:

[0006] 2.1. When other processes require short-time shutdown for treatment, the continuous caster immediately performs tundish slag removal to ensure that the tundish slag thickness is not higher than 40 mm. The tundish retains no more than 250 mm of molten steel, and ensure that no slag flows through the tundish nozzle. Check the slag line on the tundish wall during the hot standby process, and require the tundish wall erosion to be < 20 mm and the flow stabilizer to be > 200 mm. Plug the flow of all strands with blind blocks and then replace the nozzles with φ15 for standby. Clean up the swing troughs of each strand. If there are problems with the troughs, repair and bake them in time to ensure they can be used for starting casting.

[0007] 2.2. After the tundish stops casting, quickly move the tundish car to the baking position of the baking furnace for intelligent high-fire baking to ensure that the tundish temperature is not lower than 1100°C; observe the working layer of the tundish in time to prevent the collapse of the working layer of the tundish. Pay attention to draining the water in the baking furnace pipeline in winter.

[0008] 2.3. The intermediate shutdown time is controlled within 1.5 hours according to the duration of the affected process for treatment; for the starting casting heat treatment, use a hot standby ladle, and according to the interval time of tundish shutdown, the ladle charging temperature is 1620 - 1630°C.

[0009] 2.4. After ladle charging, quickly raise the liquid level to more than 400 mm by opening the lower nozzle of the ladle. During the process, it is not allowed to control the ladle nozzle, and the full flow must be opened;

[0010] 2.5. After the tundish is started with a large ladle, the tundish begins to drain. First, concentrate on draining for one casting cycle to ensure the molten steel circulation in the tundish after successful single-strand drainage. During the drainage process, it is required that two people cooperate and drain continuously to ensure the start of casting after the molten steel forms a stream. If the drainage is successful more than 3 times, the φ15 nozzle needs to be replaced before starting the casting.

[0011] 2.6. After the tundish casting is successful, adjust the secondary cooling water coefficient according to the tundish molten steel temperature. When the temperature exceeds 1560 °C, adjust it according to 1.2 to ensure that the specific water volume is greater than 1.4 L / Kg to avoid high-temperature breakout accidents.

[0012] 2.7. During subsequent production, appropriately reduce the number of continuous casting heats according to the tundish slag line condition, and the total casting time shall not exceed 40 hours.

[0013] Compared with the prior art, the method for rapid hot standby of the tundish of the present invention has the following advantages:

[0014] 1. Determine the shutdown and flow-blocking timing according to the liquid level height of the tundish. The molten steel measuring device can accurately judge the remaining molten steel in the tundish to avoid difficulty in starting casting caused by slag entrainment.

[0015] 2. Determine the charging temperature of 1620 - 1630 °C according to the remaining molten steel in the tundish. Make full use of the starting casting molten steel temperature to heat up and pre-melt the molten steel at the bottom of the tundish, which can ensure the success rate of rapid drainage; after the large ladle starts casting, the tundish conducts rapid nozzle drainage to ensure the rapid circulation of the molten steel flow field in the tundish and improve the starting casting success rate.

[0016] 3. For the rapid hot standby of the dry-material tundish, when the continuous caster stops, only the tail billet is discharged and the ingot is sealed and led. The controlled duration is about 40 minutes, which can ensure the rapid resumption of production of the continuous casting and the entire steelmaking system; compared with the existing dry-material tundish baking and temperature increase for 3 hours, the steel plant can shorten the shutdown time by more than 2 hours when dealing with abnormal problems in the processing procedure, and the stop and start efficiency is increased by 67%. Specific embodiments

[0017] Example 1:

[0018] The method for rapid hot standby of tundish in the present invention can perform hot standby of dry material tundish in hot state when sudden process and equipment problems occur, solve the time limit for restarting casting after continuous casting shutdown, improve the success rate and operation rate of starting casting, and effectively reduce the refractory cost; it can effectively balance and stabilize the entire steelmaking, gas, and rolling systems, and avoid continuous furnace shutdown and machine shutdown caused by the long baking time of tundish during the restart of continuous casting, thus avoiding the chain production impact on the iron, steel, rolling, and drive systems. The method is as follows: Predict the required duration for process and equipment maintenance. Before hot standby, increase the ladle charging temperature by 5°C for the last furnace of the current heat and perform slag tapping from the tundish. Control the tundish slag thickness within 40 mm. During the hot standby process, check the slag line on the tundish wall, with the requirement that the tundish wall erosion is < 20 mm and the flow stabilizer is > 200 mm. After the ladle casting is completed, measure the molten steel level height in the tundish. When the liquid level height reaches 150 - 250 mm, stop casting the tundish and add 5 - 6 bags of covering agent to cover the molten steel. Quickly move the tundish car to the baking position for high-intensity baking. After the cast strand billet is pulled out, quickly perform the sealing and dummy bar insertion operation. When starting up, according to the ladle charging temperature of 1620 - 1630°C, quickly perform the tundish nozzle drainage operation after the ladle starts casting. Ensure that after the molten steel level in the tundish exceeds 400 mm, the cold steel in the upper nozzle is cleaned up, and then perform the normal tundish casting operation. Adjust the secondary cooling water distribution coefficient according to 1.2.

[0019] The specific method is as follows:

[0020] 2.1. When short-term shutdown for treatment is required in other processes, the continuous casting machine immediately performs slag tapping from the tundish to ensure that the tundish slag thickness is not higher than 40 mm. The molten steel remaining in the tundish does not exceed 250 mm, and ensure that no slag flows through the tundish nozzle. During the hot standby process, check the slag line on the tundish wall, with the requirement that the tundish wall erosion is < 20 mm and the flow stabilizer is > 200 mm. Block the flow of all strands with blind blocks and then replace the nozzle with a diameter of φ15 for standby. Clean each pouring launder, and if there are problems with the launder, repair and bake it in time to ensure its use during starting casting.

[0021] 2.2. After the tundish stops casting, quickly move the tundish car to the baking position of the baking furnace for intelligent high-intensity baking to ensure that the tundish temperature is not lower than 1100°C; observe the working layer of the tundish in time to prevent the collapse of the working layer of the tundish. Pay attention to draining water from the baking furnace pipeline in winter.

[0022] 2.3. The intermediate stop casting time is controlled within 1.5 hours according to the duration of the affected process for treatment; for the starting casting heat, use a hot standby ladle, and according to the interval time of tundish stop casting, the ladle charging temperature is 1620 - 1630°C.

[0023] 2.4. After ladle charging, quickly raise the liquid level to above 400 mm by opening the lower nozzle of the ladle. During the process, it is not allowed to control the ladle nozzle, and the full flow must be opened.

[0024] 2.5. After the tundish starts to drain when the large ladle is initially tapped, conduct the tundish drainage for one casting cycle first to ensure the molten steel circulation in the tundish after successful single-strand drainage. During the drainage process, two people are required to cooperate and continuously drain to ensure the start of casting after the molten steel forms a stream. For those with more than 3 successful drainages, the φ15 nozzle needs to be replaced before starting casting.

[0025] 2.6. After successful tundish casting, adjust the secondary cooling coefficient according to the tundish molten steel temperature. When the temperature exceeds 1560°C, adjust it according to 1.2 to ensure that the specific water volume is greater than 1.4 L / Kg and avoid high-temperature breakout accidents.

[0026] 2.7. During subsequent production, appropriately reduce the number of continuous casting heats according to the tundish slag line situation, and the total casting time shall not exceed 40 hours.

[0027] The method for rapid hot standby of the tundish of the present invention has the following advantages:

[0028] 1. Determine the shutdown and flow-blocking timing according to the liquid level height of the tundish. The molten steel measurement device can accurately judge the remaining molten steel in the tundish and avoid difficulties in starting casting caused by slag inclusion.

[0029] 2. Determine the charging temperature at 1620 - 1630°C according to the remaining molten steel in the tundish. Make full use of the starting casting molten steel temperature to heat up and pre-melt the molten steel at the bottom of the tundish, which can ensure the success rate of rapid drainage; after the large ladle starts casting, the tundish conducts rapid nozzle drainage to ensure the rapid circulation of the molten steel flow field in the tundish and improve the starting casting success rate.

[0030] 3. For the rapid hot standby of the dry-material tundish, when the continuous caster stops, only the tail billet is discharged and the ingot is sealed and led, and the controlled duration is about 40 minutes, which can ensure the rapid resumption of production of the continuous casting and the entire steelmaking system; compared with the existing dry-material tundish baking and temperature raising for 3 hours, the steel plant can shorten the shutdown time by more than 2 hours when dealing with abnormal problems in the processing procedure, and the stop and start efficiency is increased by 67%.

[0031] 4. In terms of cost control, calculated according to 20 heats of casting with each tundish after hot standby, 150 tons of molten steel per heat, and a contract price of 6.64 yuan per ton of steel, the cost reduction for one tundish is: 20 heats * 150 tons / heat * 6.64 yuan / ton of steel = 19,920 yuan, reducing the cost of a single tundish in abnormal situations by more than 25%.

[0032] The above embodiments are only the preferred embodiments of the present invention. Therefore, any equivalent changes or modifications made according to the structures, features, and principles described in the scope of the present invention patent application are included in the scope of the present invention patent application.

Claims

1. A method for rapid hot standby of a tundish, characterized in that: The method is as follows: Predict the required duration of process technology and equipment maintenance. Before hot standby, increase the ladle charging temperature by 5°C for the last furnace and carry out tundish slag removal. Control the tundish slag thickness within 40 mm. Conduct inspection of the tundish wall slag line during the hot standby process, requiring the tundish wall erosion to be <20 mm and the flow stabilizer to be >200 mm. After the ladle casting is completed, measure the molten steel level in the tundish. When the liquid level reaches 150 - 250 mm, stop pouring the tundish and add 5 - 6 bags of covering flux to cover the molten steel. Quickly move the tundish car to the baking position for high-intensity baking. After the continuous casting billet is pulled out, quickly conduct the sealing and dummy bar operation. When starting up, according to the ladle charging temperature at 1620 - 1630°C, quickly conduct the tundish nozzle drainage operation after the ladle starts pouring. Ensure that the cold steel in the upper nozzle is cleaned up after the liquid level in the tundish exceeds 400 mm, and conduct the normal tundish flow opening operation. Adjust the secondary cooling water distribution coefficient according to 1.

2. The specific method is as follows: 2.

1. When other processes require short-term shutdown for treatment, the continuous caster immediately conducts tundish slag removal, with the tundish slag thickness not exceeding 40 mm; the tundish retains no more than 250 mm of molten steel to prevent slag from flowing out of the tundish nozzle. Conduct inspection of the tundish wall slag line during the hot standby process, with the tundish wall erosion <20 mm and the flow stabilizer >200 mm; block the flow of all strands with blind blocks and then replace the nozzles with φ15 for standby, and clean up the swing troughs of each strand. 2.

2. After the tundish stops pouring, quickly move the tundish car to the baking position of the baking furnace for intelligent high-intensity baking to keep the tundish temperature not lower than 1100°C; observe the working layer of the tundish to prevent the collapse of the working layer of the tundish. 2.

3. The intermediate pouring stop time is controlled within 1.5 hours according to the duration of the affected process. For the starting pouring heat, use a hot standby ladle, and according to the tundish pouring stop interval, the ladle charging temperature is 1620 - 1630°C. 2.

4. After ladle charging, quickly open the ladle bottom nozzle to raise the liquid level above 400 mm. 2.

5. After the ladle starts pouring, the tundish starts to drain. First, concentrate on draining one strand to ensure the molten steel circulation in the tundish after successful single-strand drainage; during the drainage process, require two people to cooperate and continuously drain to ensure pouring after the molten steel forms a stream; if the drainage is successful more than 3 times, replace the nozzle with φ15 before pouring. 2.

6. After the tundish pouring is successful, adjust the secondary cooling water coefficient according to the tundish molten steel temperature. When the temperature exceeds 1560°C, adjust it according to 1.2 to ensure that the specific water consumption is greater than 1.4 L / Kg.