A quick-change method for continuous casting tundish suitable for high-speed casting process

Abstract

The present invention discloses a method for quick-changing a continuous casting tundish suitable for a high-speed casting process. The method for quick-changing a continuous casting tundish optimizes the tundish quick-changing process and effectively controls the process of stopping casting of an upper tundish and starting casting of a lower tundish by reasonably setting quick-changing parameters. The method can shorten the quick-changing time of the continuous casting tundish under the high-speed casting process, meet the quick-changing requirements of the tundish under the high-speed casting process, improve the success rate of quick-changing of the continuous casting tundish, and improve the operating rate of the continuous casting machine; at the same time, it can reduce the overall energy efficiency of production and alleviate the labor intensity and safety risks of workers.

Description

Technical Field

[0001] The present invention relates to the technical field of continuous casting, in particular to a quick-changing method for a continuous casting tundish suitable for a high-speed casting process. Background Art

[0002] With the development of continuous casting technology, the demand for extreme efficiency and improved overall competitiveness in production is increasing. The service life of refractory materials restricts the continuous casting time, which in turn affects the efficiency of the continuous casting machine. Currently, the life of the tundish for producing special steel is generally around 12 casts. Therefore, to ensure continuous casting of molten steel, online tundish replacement is necessary. Quick tundish change not only improves the efficiency of the continuous casting machine, but also reduces overall energy consumption.

[0003] The quick change of tundish means that when different steel grades are mixed, the casting of the last tundish of the previous steel grade is stopped when the casting reaches a certain tonnage, and the tundish car is driven to the baking position. When the molten steel in the crystallizer reaches the target height, the pre-prepared quick connector is placed, and then the spare tundish car is driven to the casting position. After all these are prepared, the large ladle starts pouring. After casting reaches the target tonnage, the stopper rod is opened, and the tundish starts to cast the first batch of molten steel of the next steel grade, realizing the quick change process of the tundish.

[0004] Currently, quick change of tundish is achieved under medium and low drawing speed (0-1.0m / min) process conditions. Most of the existing quick change methods of tundish cannot meet the quick change requirements of tundish under high drawing speed (maximum 2.6m / min) process, which affects the overall energy efficiency of production.

[0005] For example, patent CN108284210A discloses a method for improving the success rate of quick-change continuous casting tundishes. After the standby tundish begins pouring, the emergence time is controlled at 80-120 seconds. When the molten steel in the crystallizer reaches 115-125 mm from the bottom of the submerged nozzle, the continuous casting machine's casting speed is started. After starting, the casting speed is 0.3 m / min. The 0.3 m / min casting speed is maintained for 1 minute, and then the casting speed is increased to the normal value of 0.9 m / min. The time from stopping casting with the working tundish to starting pouring with the standby tundish and starting the casting speed in the crystallizer is controlled at 4-5 minutes. This method starts with a casting speed of 0.3 m / min after quickly changing the tundish, and then increases it to the normal value of 0.9 m / min. Both the starting casting speed and the normal casting speed are low and cannot meet the production requirements of high-speed casting processes.

[0006] For example, patent CN112247133A discloses a quick-change connector for a tundish, a method of using the connector, and a process for stopping casting, changing casting, and resuming casting. The starting drawing speed during billet drawing is 0.13-0.16 m / min. When the molten steel level in the crystallizer is 195-205 mm away from the water gap of the crystallizer, the drawing speed increases gradually from 1.3-1.6 m / min to 0.28-0.33 m / min within 14-17 seconds; when the molten steel level in the crystallizer reaches 145-155 mm away from the water gap of the crystallizer, the drawing speed increases gradually from 0.8-1.2 m / min to 0.33-0.36 m / min within 9-12 seconds. Similarly, the starting drawing speed and the normal drawing speed after the quick-change tundish of this method are both low, which cannot meet the production requirements of the high-speed drawing process. Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the present invention provides a continuous casting ladle quick-change method suitable for high-speed casting process, which can shorten the continuous casting ladle quick-change time under high-speed casting process and improve the continuous casting machine operation rate.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0009] The method for quickly changing a continuous casting tundish suitable for a high-speed casting process comprises the following steps:

[0010] S1: When the tonnage of the tundish in the previous furnace is left with a certain amount of tonnage, the tundish quick change program is started, and the spare tundish is moved to the waiting position in advance;

[0011] S2. Reduce the casting speed from the target casting speed to 0.5-0.7m / min, close the stopper rod, and stop casting the upper tundish;

[0012] S3. Measure the distance L between the tail of the ingot in the mold and the upper edge of the mold copper tube when casting is stopped. When L meets the technical requirements, return the casting speed to 0 m / min and adjust the secondary cooling water volume to 40-80% of normal casting to reduce the cooling rate of the ingot. When the casting speed returns to 0 m / min, the tundish car must be raised synchronously to prevent the waiting time from causing steel dripping from the nozzle and forming a steel shell at the tail of the ingot, which may affect the placement of the quick-change connector.

[0013] S4. Open the spare tundish to the casting position and adjust the position of the submerged nozzle to ensure that the nozzle is aligned with the crystallizer; start pouring in the large ladle. When the molten steel tonnage in the spare tundish reaches 20-25t, open the stopper and start pouring in the tundish;

[0014] S5. The interval between closing the stopper rod and stopping casting in the furnace before the quick change and opening the stopper rod in the furnace after the quick change should be 6 to 10 minutes. If it exceeds 10 minutes, the casting of that flow is prohibited. Otherwise, the tundish temperature will be low or the billet will be excessively cooled, causing the billet to stagnate and the quick change will fail.

[0015] S6. The first rod to open the stopper must be a medium-large flow, especially when the superheat of the molten steel is low, which is conducive to the melting of the billet tail and the formation of a stable connection; the emergence time is 10-12s, and the liquid level rises to S=0mm. When the liquid level rises to S=50-60mm, the straightening machine starts, and the starting time is t1=12-15s; the starting speed of the first stage after quick change is 0.5-0.7m / min, and the holding time is t2=15-20s. The starting speed of the second stage is 0.9-1.0m / min, and the holding time is t4=25-30s. The process time of the pulling speed rising to 1m / min is t3=20-25s; finally, the pulling speed rises from 1m / min to the target speed for stable casting, and the quick change is successful.

[0016] Further:

[0017] In the step S1, when the remaining tonnage of the tundish in the previous furnace is 11-13 tons, the tundish quick change program is started.

[0018] In the step S2, the maximum value of the target pulling speed is 2.6 m / min.

[0019] In the step S3, for steels with C≥0.45%, L is 500-550 mm, and for steels with C<0.45%, L is 550-600 mm.

[0020] Before the step S4, and before the previous furnace stops casting, the operation of adding protective slag to the crystallizer is reduced.

[0021] Before the step S4, the tundish car of the previous furnace is driven out to the baking position to process the slag strips generated in the crystallizer during the casting process of the previous furnace, especially to remove the agglomerated slag, and then the quick-change connector can be installed.

[0022] Before the step S6, the inner cavity of the crystallizer should be oiled before quick change, especially the inner and outer arc positions, to increase the lubrication effect and reduce the resistance to casting.

[0023] In step S6, the starting liquid level is 25% to 30% of the liquid level detection range.

[0024] In the step S6, the baking time of the nozzle in the next furnace is selected to be 60 to 90 minutes, which cannot be too long to prevent the refractory material from falling off due to excessive temperature, resulting in the nozzle being blocked and unable to be quickly replaced and poured.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] The method for quick-changing the continuous casting tundish suitable for the high-casting speed process is reasonably designed. By reasonably setting the quick-changing parameters, optimizing the tundish quick-changing process, and properly controlling the upper tundish stop pouring and the lower tundish start pouring process, the quick-changing time of the continuous casting tundish can be shortened under the high-casting speed production process, thereby meeting the tundish quick-changing requirements under the high-casting speed production process and improving the operating rate of the continuous casting machine. At the same time, it can reduce the overall energy efficiency of production and alleviate the labor intensity and safety risks of workers. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The following is a brief description of the contents and symbols in the drawings of this specification:

[0028] Figure 1 Schematic diagram of the distance between the tail of the ingot in the crystallizer and the upper edge of the copper tube of the crystallizer according to the present invention.

[0029] Figure 2 Schematic diagram of the liquid level detected in the crystallizer of the present invention.

[0030] Figure 3 Schematic diagram of the quick-change starting pulling speed and time distribution of the present invention. DETAILED DESCRIPTION

[0031] The specific implementation of the present invention will be further explained in detail below through description of embodiments with reference to the accompanying drawings.

[0032] like Figures 1 to 3 As shown, the continuous casting tundish quick-change method suitable for high-speed casting process includes the following steps:

[0033] When the tonnage of the tundish in the previous furnace is 12 tons remaining, the tundish quick change program is started and the spare tundish is moved to the waiting position in advance.

[0034] The casting speed was reduced from the target casting speed (maximum 2.6 m / min) to 0.6 m / min, the stopper rod was closed, and the casting of the upper furnace ladle was stopped.

[0035] Measure the distance (L) between the tail of the ingot in the mold and the upper edge of the mold copper tube when casting is stopped. When L meets the technical requirements, return the casting speed to 0 m / min and adjust the secondary cooling water volume to 40-80% of normal casting to reduce the cooling rate of the ingot. When the casting speed returns to 0 m / min, the tundish car should be raised simultaneously to prevent excessive waiting time, which may cause steel dripping from the nozzle and the formation of a steel shell at the end of the ingot, which may affect the placement of the quick-change connector.

[0036] For steel grades with C ≥ 0.45%, L is 500-550 mm; for steel grades with C < 0.45%, L is 550-600 mm.

[0037] Furthermore, before the previous furnace tundish stops casting, the addition of mold slag to the crystallizer can be appropriately reduced. The previous furnace tundish car is driven out to the baking position to handle the slag strips generated in the crystallizer during the previous furnace casting process, especially to remove the agglomerated slag, and then the quick-change connector can be installed.

[0038] Move the spare tundish to the casting position and adjust the submerged nozzle position to ensure it is aligned with the mold. Start pouring from the main ladle. When the molten steel tonnage in the spare tundish reaches 20-25t, remove the stopper and start pouring from the tundish.

[0039] The interval between closing the stopper rod and stopping casting in the furnace before quick change and opening the stopper rod in the furnace after quick change is 6 to 10 minutes. If it exceeds 10 minutes, pouring is prohibited for that flow, otherwise it will cause low temperature in the tundish or excessive cooling of the billet, resulting in billet stagnation and failure of quick change.

[0040] Before quick change, the inner cavity of the crystallizer should be oiled, especially the inner and outer arcs, to increase the lubrication effect and reduce the resistance to casting.

[0041] The first rod to open the stopper must be medium to large flow, especially when the superheat of the molten steel is low, which is conducive to the melting of the billet tail and the formation of a stable connection. The emergence time is 10 to 12 seconds, and the liquid level rises to S = 0mm. When the liquid level rises to S = 50 to 60mm (the starting liquid level is 25% to 30% of the liquid level detection range), the straightening machine starts, and the starting time is t1 = 12 to 15 seconds. The starting speed of the first stage after quick change is 0.6m / min, and the holding time is t2 = 15 to 20 seconds. The starting speed of the second stage is 1.0m / min, and the holding time is t4 = 25 to 30 seconds. The process time t3 of the pulling speed from 0.6m / min to 1m / min is 20 to 25 seconds. Finally, the pulling speed is increased from 1m / min to the target speed of 2.6m / min for stable casting, and the quick change is successful.

[0042] The baking time of the nozzle of the next furnace should be selected between 60 and 90 minutes. It should not be too long to prevent the refractory material from falling off due to excessive temperature, which will cause the nozzle to be blocked and unable to be quickly replaced and poured.

[0043] The continuous casting tundish quick-change method of the present invention optimizes the tundish quick-change process by reasonably setting the quick-change parameters, and effectively controls the process of stopping casting of the upper tundish and starting casting of the lower tundish. It can shorten the continuous casting tundish quick-change time under the high-speed production process, meet the tundish quick-change requirements under the high-speed production process, and improve the operation rate of the continuous casting machine. At the same time, it can reduce the overall energy efficiency of production and alleviate the labor intensity and safety risks of workers.

[0044] The specific embodiments of the present invention are:

[0045] The specific implementation method is now developed with the goal of producing steel grades with C ≥ 0.45% and a casting speed of 2.6 m / min. A method for improving the success rate of quick-change of continuous casting tundishes includes the following steps:

[0046] Step 1: When the tonnage of the tundish in the previous furnace is 12 tons, start the tundish quick change program, bake the nozzle of the spare tundish to 90 minutes in advance, the target temperature is 800℃, and then move to the waiting position to wait;

[0047] Step 2: Reduce the casting speed from the target casting speed of 2.6m / min to 0.6m / min, close the stopper rod, and stop casting in the upper furnace ladle;

[0048] Step 3: When the distance L between the tail of the ingot in the mold and the upper edge of the mold copper tube is 600 mm, the casting speed is returned to 0 m / min and the secondary cooling water volume is adjusted to 50% of that of normal casting to reduce the cooling rate of the ingot. When the casting speed returns to 0 m / min, the tundish car is simultaneously raised to prevent excessive waiting time, which may cause steel dripping from the nozzle and the formation of a steel shell at the end of the ingot, which may affect the placement of the quick-change connector.

[0049] Step 4: Before the previous tundish stops casting, appropriately reduce the amount of protective slag added to the crystallizer;

[0050] Step 5: The tundish car of the previous furnace is driven to the baking position, the slag strips generated in the crystallizer during the casting process of the upper furnace are processed, the agglomerated slag is removed, and then the quick-change connector is installed;

[0051] Step 6: Open the spare tundish to the casting position, adjust the position of the submerged nozzle to ensure that the nozzle is aligned with the crystallizer; start pouring from the large ladle. When the molten steel tonnage in the spare tundish reaches 25t, open the stopper and start pouring from the tundish.

[0052] Step 7: The interval from closing the stopper rod and stopping pouring in the furnace before quick change to opening the stopper rod in the furnace after quick change should be controlled at 8 minutes;

[0053] Step 8: Before quick change, the inner cavity of the crystallizer should be oiled, focusing on the inner and outer arc positions;

[0054] Step 9: The first rod of the stopper rod is opened to supply medium and large flow, and the emergence time is 12s. The liquid level rises to S = 0mm. When the liquid level rises to S = 60mm, the straightening machine starts, and the starting time is t1 = 15s. After the quick change, the starting speed of the first stage is 0.6m / min, and the holding time is t2 = 20s. The starting speed of the second stage is 1.0m / min, and the holding time is t4 = 30s. The process time of increasing the pulling speed from 0.6m / min to 1m / min is t3 = 25s. Finally, the pulling speed is increased from 1m / min to the target speed of 2.6m / min, and stable casting is achieved. The quick change is successful.

[0055] The method of the present invention has been verified and stably used in actual production. The success rate of quick replacement of the tundish under the high-casting speed production process has been greatly improved, basically reaching 100%, thereby improving the continuous casting production efficiency, reducing the overall energy consumption, and alleviating the labor intensity and safety risks of on-site operators.

[0056] The present invention is described above by way of example in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the scope of protection of the present invention.

Claims

1. A method for quick-changing a continuous casting tundish suitable for a high-speed casting process, characterized by: The continuous casting tundish quick-change method comprises the following steps: S1. When the remaining tonnage of the tundish in the previous furnace is 11-13 tons, the tundish quick change program is started and the spare tundish is moved to the waiting position in advance; S2. Reduce the casting speed from the target casting speed to 0.5-0.7m / min, close the stopper rod, and stop casting the upper tundish; S3. Measure the distance L between the tail of the ingot in the mold and the upper edge of the mold copper tube when casting is stopped. When L meets the technical requirements, return the casting speed to 0 m / min and adjust the secondary cooling water volume to 40-80% of normal casting to reduce the cooling rate of the ingot. When the casting speed returns to 0 m / min, the tundish car must be raised synchronously to prevent steel dripping from the nozzle and the formation of a steel shell at the tail of the ingot due to long waiting time, which affects the placement of the quick-change connector. S4. Open the spare tundish to the casting position and adjust the position of the submerged nozzle to ensure that the nozzle is aligned with the crystallizer; start pouring in the large ladle. When the molten steel tonnage in the spare tundish reaches 20-25t, open the stopper and start pouring in the tundish; S5. The interval between closing the stopper rod and stopping casting in the furnace before quick change and opening the stopper rod in the furnace after quick change should be 6 to 10 minutes. If it exceeds 10 minutes, casting of that flow is prohibited. Otherwise, the tundish temperature will be low or the billet will be excessively cooled, causing billet stagnation and failure of quick change. S6. The first rod to open the stopper must be medium and large flow. When the superheat of the molten steel is low, it is conducive to the melting of the billet tail and the formation of a stable connection; the emergence time is 10~12s, and the liquid level rises to S=0mm. When the liquid level rises to S=50~60mm, the straightening machine starts, and the starting time is t1=12~15s; the starting speed of the first stage after quick change is 0.5-0.7m / min, and the holding time is t2=15~20s. The starting speed of the second stage is 0.9-1.0m / min, and the holding time is t4=25~30s. The process time of the pulling speed increasing to 1m / min is t3=20~25s; finally, the pulling speed increases from 1m / min to the target speed for stable casting, and the quick change is successful.

2. The method for quick-changing a continuous casting tundish suitable for a high-speed casting process according to claim 1, characterized in that: In the step S1, when the remaining tonnage of the tundish in the previous furnace is 11 tons, the tundish quick change program is started.

3. The method for quick-changing a continuous casting tundish suitable for a high-speed casting process according to claim 1, characterized in that: In the step S2, the maximum value of the target pulling speed is 2.6 m / min.

4. The method for quick-changing a continuous casting tundish suitable for a high-speed casting process according to claim 1, characterized in that: In the step S3, for steels with C≥0.45%, L is 500-550 mm, and for steels with C<0.45%, L is 550-600 mm.

5. The method for quick-changing a continuous casting tundish suitable for a high-speed casting process according to claim 1, characterized in that: Before the step S4, and before the previous furnace stops casting, the operation of adding protective slag to the crystallizer is reduced.

6. The method for quick-changing a continuous casting tundish suitable for a high-speed casting process according to claim 1, characterized in that: Before the step S4, the tundish car of the previous furnace is driven out to the baking position to process the slag strips generated in the crystallizer during the casting process of the previous furnace. The agglomerated slag must be removed before the quick-change connector can be installed.

7. The method for quick-changing a continuous casting tundish suitable for a high-speed casting process according to claim 1, characterized in that: Before the step S6, the inner cavity of the crystallizer should be oiled before quick change to increase the lubrication effect and reduce the resistance to casting.

8. The method for quick-changing a continuous casting tundish suitable for a high-speed casting process according to claim 1, characterized in that: In step S6, the starting liquid level is 25% to 30% of the liquid level detection range.

9. The method for quick-changing a continuous casting tundish suitable for a high-speed casting process according to claim 1, characterized in that: In the step S6, the baking time of the nozzle in the next furnace is selected to be 60~90min, which cannot be too long to prevent the refractory material from falling off due to excessive temperature, resulting in the nozzle being blocked and unable to be quickly replaced and poured.

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