A method for reducing superheat of molten steel in continuous casting tundish
By adopting a regenerative tundish and a ventilated tundish cover plate in the continuous casting tundish, combined with the batch addition and periodic replenishment of the covering agent, the problem of inaccurate control of molten steel superheat in the tundish was solved, thereby improving the quality of the cast billet and increasing production efficiency.
Patent Information
- Application Number
- CN202211242215.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-10-11
- Publication Date
- 2025-10-28
- Estimated Expiration
- 2042-10-11
AI Technical Summary
In the continuous casting process, it is difficult to precisely control the superheat of molten steel in the tundish, resulting in large temperature fluctuations in the molten steel, which affects the quality of the cast billet and production efficiency. Moreover, existing cooling measures are either costly or inefficient.
By adopting a heat-storing tundish and a ventilated tundish cover plate, combined with the batch addition and regular replenishment of the covering agent, the baking time and the timing of molten steel flow are optimized to ensure temperature uniformity and reduce the temperature drop of molten steel.
It effectively reduced the superheat of molten steel in the tundish, improved the quality of the billet and the casting speed, reduced tundish erosion, and enhanced production efficiency and the stability of the continuous casting process.
Smart Images
Figure BDA0003885201070000051 
Figure BDA0003885201070000061
Abstract
Description
Technical Field
[0001] This invention relates to the field of continuous casting production in steel plants, and in particular to a method for reducing the superheat of molten steel in the tundish during continuous casting. This method can reduce the temperature drop of molten steel in the tundish at the start of continuous casting and during the pouring process, reduce the corrosion of the tundish by molten steel, and can also increase the casting speed of the billet to a certain extent, thereby improving the quality of the billet. Background Technology
[0002] Solidification of metals is an exothermic process. The degree of superheat indicates how much the molten metal exceeds its melting point temperature. The greater the superheat, the more heat needs to be released for solidification, and the longer the solidification time required for the same heat transfer. Therefore, the degree of superheat affects the solidification behavior of molten metal materials. For example, when the superheat is too high, the solidification time of the billet with the same cross-section is long, element segregation is large, and the central segregation level is high; the billet shell is thinner, making it prone to surface cracks or inducing cavitation; the surface dendrites are coarse, increasing the tendency to form central cracks in the secondary cooling zone. Reducing the superheat can promote the transformation of columnar crystals to equiaxed crystals, increase the equiaxed crystal ratio, and thus benefit the homogenization of the billet structure; however, if the superheat is too low, the molten steel viscosity is high, the fluidity is poor, which is not conducive to the flotation of inclusions, and it is easy to cause the nozzle to be blocked or even frozen during continuous casting, resulting in defects such as porosity and shrinkage cavities in the continuously cast billet. Therefore, the superheat of molten steel directly affects the continuous casting process parameters, the surface quality of the billet, the shell thickness, the dendrite spacing, and the internal quality of the billet. The superheat of molten steel has a significant impact on the quality of continuously cast billets, thus requiring precise control of the superheat in the tundish. To reduce process temperature loss and fluctuations and keep the superheat of molten steel within a suitable range, common measures include covering the ladle and tundish with insulating agents; ladle baking and tundish baking; covering the ladle or tundish; scrap cooling; plasma heating of the tundish; and electromagnetic induction heating of the tundish. When the ladle or tundish temperature is too high, methods such as prolonged cooling, adding scrap to the molten steel, or introducing inert gas are often used to reduce the superheat. However, prolonged cooling affects production continuity and reduces efficiency; if the scrap has not undergone surface treatment or baking, it increases the risk of excessive oxide inclusions and hydrogen embrittlement in the steel; introducing inert gas can achieve a cooling effect but increases costs.
[0003] The primary function of the tundish in continuous casting is to receive molten steel from the ladle, playing a crucial role in transitioning from intermittent to continuous production in steelmaking. In actual production, it has been found that the overall superheat of the molten steel is relatively high due to factors such as the quality of tundish baking, the effectiveness of the protective slag, and the overall insulation effect of the tundish. Higher superheat increases refractory material consumption throughout the steelmaking process, increases the quantity and size of inclusions in the molten steel, and also leads to a decrease in continuous casting speed, reducing production efficiency. However, lower superheat increases the risk of low initial casting rate and "frozen eyes" during casting. Therefore, to ensure smooth casting of molten steel, the superheat of the first heat of molten steel in the tundish is generally controlled at 35-45℃, and the superheat of the molten steel in subsequent heats is generally controlled at 25-35℃. Summary of the Invention
[0004] The purpose of this invention is to address the shortcomings of the prior art by providing a method for reducing the superheat of molten steel in the continuous casting tundish, solving the problem of superheat of molten steel during the start-up and pouring processes of continuous casting, and laying the foundation for achieving stable mass production of low-cost, high-quality steel billets.
[0005] To solve the above problems, the technical solution adopted by the present invention is as follows:
[0006] A method for reducing the superheat of molten steel in a continuous casting tundish, the method comprising the following steps:
[0007] 1) The intermediate bread adopts a heat storage intermediate bread, and during the baking process, the intermediate bread cover is ventilated throughout the process, and the water outlet of the intermediate bread is connected to a forced ventilation pipe;
[0008] 2) After the intermediate bread oven is turned off, cover the baking holes on the ventilated intermediate bread cover with a cover plate lined with heat insulation cotton;
[0009] 3) Based on the specific circumstances of the tundish car start-up time, the ladle rotation time, and the ladle long nozzle preparation time, ensure that the tundish car arrival time, the ladle transfer to the pouring position time, and the ladle long nozzle are all consistent with the online time.
[0010] 4) Before hanging the long spout of the large ladle, remove the cover plate of the large ladle pouring port of the ventilated intermediate ladle;
[0011] 5) After hanging the long nozzle of the ladle, the ladle begins to be poured. When the molten steel flows out from the guide hole of the tundish retaining wall, open the drying hole cover plates on both sides of the ventilated tundish and add the tundish covering agent into the tundish through the drying hole cover plates on both sides of the ventilated tundish.
[0012] 6) When the molten steel has submerged the bottom opening of the long nozzle of the ladle, add the tundish covering agent through the pouring port of the ventilated tundish.
[0013] 7) After the tundish is successfully started to pour, add the tundish covering agent to the tundish through the drying holes on both sides of the ventilated tundish.
[0014] 8) After the intermediate ladle has been stabilized and poured, regularly observe the consumption of the covering agent in the intermediate ladle and replenish it in a timely manner to ensure that the surface of the covering agent does not turn red.
[0015] 9) When changing packages, the transfer of the large package and the preparation of the long sprue of the large package should be carried out simultaneously to ensure that the large package is in place and the long sprue is ready for operation.
[0016] Preferably, in step 5), the tundish covering agent is added to the tundish at a rate of 1-3 kg / ton of steel.
[0017] More preferably, in step 5), the tundish covering agent is added to the tundish at a rate of 2 kg / ton of steel.
[0018] Preferably, in step 6), 0.5-1 kg / ton of steel is added as tundish covering agent from the pouring port of the ventilated tundish.
[0019] More preferably, in step 6), 0.8 kg / ton of steel is added as tundish covering agent from the pouring port of the ventilated tundish.
[0020] Preferably, in step 7), the tundish is simultaneously added with a covering agent at a dosage of 3-5 kg / ton of steel tundish.
[0021] More preferably, in step 7), the tundish is simultaneously added with a covering agent at a dosage of 4 kg / ton of steel.
[0022] Preferably, in step 8), the amount of intermediate ladle covering agent added each time is 0.5-0.8 kg / ton of steel.
[0023] More preferably, in step 8), the amount of intermediate ladle covering agent added each time is 0.6 kg / ton of steel.
[0024] In this invention, the center segregation and center porosity of the obtained continuous casting billet are both 0.5.
[0025] According to a preferred embodiment of the present invention, a method for reducing the superheat of molten steel in a continuous casting tundish includes the following steps:
[0026] 1) A heat-storage intermediate loaf is used, and the loaf cover is ventilated throughout the baking process, with the drain outlet connected to a forced ventilation pipe. Additionally, in the later stages of baking, the baking progress inside the intermediate loaf is confirmed by visual inspection and temperature measurement using a handheld infrared thermometer.
[0027] 2) After the intermediate bread oven is turned off, cover the baking holes on the ventilated intermediate bread cover with a cover plate lined with heat insulation cotton to improve the insulation effect of the intermediate bread.
[0028] 3) Based on the specific circumstances of the intermediate ladle car start-up time, the ladle turn-around time, and the ladle long nozzle preparation time, ensure that the intermediate ladle car arrival time, the ladle transfer to the pouring position time, and the ladle long nozzle are ready for online pouring are consistent, thereby reducing the ladle waiting time.
[0029] 4) Before the operator hangs the long nozzle of the large ladle, remove the cover plate of the pouring port of the large ladle in the ventilation intermediate ladle.
[0030] 5) After the operator hangs the long nozzle of the ladle, the ladle begins to be poured. When the molten steel flows out from the guide hole of the tundish retaining wall, the drying hole cover plates on both sides of the ventilated tundish are opened, and tundish covering agent is added at the same time according to the dosage of 1-3 kg / ton of steel.
[0031] 6) When the molten steel has submerged the long nozzle of the ladle, add the tundish covering agent through the pouring port of the ventilated tundish.
[0032] 7) After the tundish is successfully started to pour, add tundish covering agent at a rate of 3-5 kg / ton of steel through the drying holes on both sides of the ventilated tundish.
[0033] 8) After the intermediate ladle has been stably poured, regularly observe the consumption of the covering agent in the intermediate ladle and replenish it in time to ensure that the surface of the covering agent does not turn red.
[0034] 9) The subcontracting of the main package and the preparation of the main package's long sprue are carried out simultaneously to ensure that the main package is in place and the long sprue is ready for operation.
[0035] This invention employs measures such as a regenerative tundish, reducing waiting time at each stage, and establishing a system for adding protective slag in batches at different locations. The key benefit is solving the problems of high pouring temperature of the first furnace of molten steel and large temperature fluctuations in the molten steel during continuous casting. It can reduce the temperature drop of molten steel in the tundish at the beginning of continuous casting and during pouring, reduce the corrosion of the tundish by molten steel, and to a certain extent increase the casting speed of the billet, improve the quality of the billet, and enhance the overall quality of the billet.
[0036] The beneficial effects of adopting the above technical solution are as follows:
[0037] (1) The heat storage tundish + baking tundish uses a ventilated tundish cover plate throughout the process, which can not only reduce the gas consumption of the tundish baking tundish, but also improve the uniformity of the temperature field inside the tundish, improve the temperature uniformity of the tundish refractory material, enhance the baking effect of the tundish, and increase the tundish sequential opening rate.
[0038] (2) By timely covering the drying holes and reasonably scheduling the time to reduce the waiting time, the temperature drop inside the tundish can be reduced, thus ensuring successful pouring.
[0039] (3) After the molten steel flows out of the guide hole of the retaining wall, a small amount of covering agent is added to the tundish drying hole. This not only improves the heat preservation effect of the molten steel, but also reduces the cooling effect of the covering agent on the molten steel.
[0040] (4) After the molten steel has passed the long nozzle of the ladle, a covering agent is added to the impact zone to reduce the exposure time of the molten steel and reduce the temperature drop of the molten steel.
[0041] (5) During the pouring process, regularly check the consumption of the covering agent and add it in time to stabilize the temperature of the molten steel and reduce the temperature drop.
[0042] (6) The subcontracting of the tundish and the preparation of the long nozzle of the tundish are carried out at the same time to ensure that the tundish is in place and the long nozzle is ready for online operation. This can reduce the fluctuation of the molten steel level in the tundish and reduce the degree of fluctuation of the molten steel temperature. Detailed Implementation
[0043] The present invention will now be described in further detail with reference to specific embodiments.
[0044] A method for reducing the superheat of molten steel in a continuous casting tundish includes the following steps:
[0045] (1) A heat-storage intermediate bread is used, and the intermediate bread cover is ventilated throughout the baking process. The drain outlet of the intermediate bread is connected to a forced ventilation pipe. At the same time, in the later stage of the intermediate bread baking, the baking condition inside the intermediate bread is confirmed by manual visual inspection and handheld infrared thermometer.
[0046] (2) After the intermediate bread oven is turned off, cover the baking holes on the ventilated intermediate bread cover with a cover plate lined with heat insulation cotton to improve the insulation effect of the intermediate bread.
[0047] (3) Based on the specific circumstances of the intermediate ladle car start time, the ladle turn time, and the ladle long nozzle preparation time, ensure that the intermediate ladle car arrival time, the ladle transfer to the pouring position time, and the ladle long nozzle are ready for online pouring are consistent, thereby reducing the ladle waiting time.
[0048] 4) Before the operator hangs the long nozzle of the large ladle, remove the cover plate of the pouring port of the large ladle in the ventilation intermediate ladle.
[0049] 5) After the operator hangs the long nozzle of the ladle, the ladle begins to be poured. When the molten steel flows out from the guide hole of the tundish retaining wall, the drying hole cover plates on both sides of the ventilated tundish are opened, and the tundish covering agent is added at the same time.
[0050] 6) When the molten steel has submerged the bottom opening of the long nozzle of the ladle, add the tundish covering agent through the pouring port of the ventilated tundish.
[0051] 7) After the tundish is successfully started to pour, add the tundish covering agent at the same time through the drying holes on both sides of the ventilated tundish.
[0052] 8) After the intermediate ladle has been stably poured, regularly observe the consumption of the covering agent in the intermediate ladle and replenish it in time to ensure that the surface of the covering agent does not turn red.
[0053] 9) When changing packages, the transfer of the large package and the preparation of the long sprue of the large package should be carried out simultaneously to ensure that the large package is in place and the long sprue is ready for operation.
[0054] Example 1:
[0055] In this example, the waiting time for the first ladle heat is 2 minutes. After the operator hangs the long nozzle on the ladle, the ladle pouring begins. When the molten steel flows out from the guide hole in the tundish retaining wall, the drying hole covers on both sides of the ventilated tundish are opened, and 1 kg of tundish covering agent is added to the tundish on each side simultaneously. When the molten steel has submerged the long nozzle, 0.5 kg of tundish covering agent is added through the ladle pouring port of the ventilated tundish. After successful pouring in the tundish, 3 kg of tundish covering agent is added to the tundish on each side through the drying holes on both sides of the ventilated tundish. After normal pouring, 0.5 kg of tundish covering agent is added periodically per ton of steel to ensure the liquid surface does not turn red. The superheat of the first continuous casting and the superheat of the molten steel in the subsequent continuous casting heats are shown in Table 1.
[0056] Table 1. Superheat of the first continuous casting and the superheat of the molten steel in the continuous casting batches in different embodiments and comparative examples.
[0057]
[0058]
[0059] Example 2:
[0060] In this example, the waiting time for the first ladle heat is 3 minutes. After the operator hangs the long nozzle on the ladle, the ladle pouring begins. When the molten steel flows out from the guide hole in the tundish retaining wall, the drying hole covers on both sides of the ventilated tundish are opened, and 2 kg of tundish covering agent is added to the tundish on each side simultaneously. When the molten steel has submerged the long nozzle, 1 kg of tundish covering agent is added through the ladle pouring port of the ventilated tundish. After successful pouring in the tundish, 4 kg of tundish covering agent is added to the tundish on each side through the drying holes on both sides of the ventilated tundish. After normal pouring, 0.6 kg of tundish covering agent is added periodically per ton of steel to ensure the liquid surface does not turn red. The superheat of the first continuous casting and the superheat of the molten steel in the subsequent continuous casting heats are shown in Table 1.
[0061] Example 3:
[0062] In this example, the waiting time for the first ladle heat is 1 minute. After the operator hangs the long nozzle on the ladle, the ladle pouring begins. When the molten steel flows out from the guide hole in the tundish retaining wall, the drying hole covers on both sides of the ventilated tundish are opened, and 3 kg of tundish covering agent is added to the tundish on each side simultaneously. When the molten steel has submerged the long nozzle, 1 kg of tundish covering agent is added through the ladle pouring port of the ventilated tundish. After successful pouring in the tundish, 5 kg of tundish covering agent is added to the tundish on each side through the drying holes on both sides of the ventilated tundish. After normal pouring, 0.7 kg of tundish covering agent is added periodically per ton of steel to ensure the liquid surface does not turn red. The superheat of the first continuous casting and the superheat of the molten steel in the subsequent continuous casting heats are shown in Table 1.
[0063] Comparative Example 1:
[0064] In this example, the waiting time for the first ladle heat is 5 minutes. After the operator hangs the long nozzle on the ladle, the ladle pouring begins. The drying hole covers on both sides of the ventilated tundish are opened, and 5 kg of tundish covering agent is added to each side simultaneously. After successful pouring in the tundish, 0.4 kg of tundish covering agent is added periodically per ton of steel to ensure the liquid surface does not turn red. The superheat of the first continuous casting and the superheat of the molten steel in subsequent heats are shown in Table 1.
[0065] Comparative Example 2:
[0066] In this example, the waiting time for the first ladle heat is 3 minutes. After the operator hangs the long nozzle on the ladle, the ladle pouring begins. The drying hole covers on both sides of the ventilated tundish are opened, and 8 kg of tundish covering agent is added to each side simultaneously. After successful pouring in the tundish, 0.5 kg of tundish covering agent is added periodically per ton of steel to ensure the liquid surface does not turn red. The superheat of the first continuous casting and the superheat of the molten steel in subsequent heats are shown in Table 1.
[0067] Comparing the data in Table 1, it can be seen that the average superheat of the first heat in the embodiment was reduced by 14.5℃, the superheat of the continuous casting heats was reduced by 4.5℃, and the proportion of continuous casting heats with superheat within 15-25℃ was 60.0%, indicating that the method described in this invention can effectively reduce the superheat of each heat in continuous casting and can increase the proportion of heats with low superheat; the average continuous casting time was increased by 8.7h, indicating that low superheat helps to reduce the corrosion of molten steel on the refractory material in the tundish; the center segregation and center porosity of the billet were both reduced by 0.5 grades, indicating that the method helps to improve the internal quality of the billet; the average casting speed was increased by 0.08m / min, indicating that the method can improve the continuous casting production efficiency while ensuring the quality of the billet, and has a good effect on improving the capacity of the continuous casting process.
[0068] The upper and lower limits of the process parameters (such as temperature, time, etc.) and the range values of the present invention can all achieve the method, and examples are not listed here.
[0069] All aspects not described in detail in this invention can be covered using conventional technical knowledge in the field.
[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.
Claims
1. A method for reducing the superheat of molten steel in a continuous casting tundish, the method comprising the following steps: 1) The intermediate bread adopts a heat storage intermediate bread, and during the baking process, the intermediate bread cover is ventilated throughout the process, and the water outlet of the intermediate bread is connected to a forced ventilation pipe; 2) After the intermediate bread oven is turned off, cover the baking holes on the ventilated intermediate bread cover with a cover plate lined with heat insulation cotton; 3) Based on the specific circumstances of the tundish car start-up time, the ladle rotation time, and the ladle long nozzle preparation time, ensure that the tundish car arrival time, the ladle transfer to the pouring position time, and the ladle long nozzle are all consistent with the online time. 4) Before hanging the long spout of the large ladle, remove the cover plate of the large ladle pouring port of the ventilated intermediate ladle; 5) After hanging the long nozzle of the ladle, the ladle begins to be poured. When the molten steel flows out from the guide hole of the tundish retaining wall, open the drying hole cover plates on both sides of the ventilated tundish and add the tundish covering agent into the tundish through the drying hole on both sides of the ventilated tundish at a rate of 1-3 kg / ton of steel on each side. 6) When the molten steel has submerged the bottom opening of the ladle's long nozzle, add 0.5-1 kg / ton of tundish covering agent through the ladle pouring port of the ventilated tundish; 7) After the tundish is successfully started to pour, add the tundish covering agent to the tundish through the drying holes on both sides of the ventilated tundish at a rate of 3-5 kg / ton of steel per side. 8) After the tundish is stabilized, regularly observe the consumption of the covering agent in the tundish and replenish it in a timely manner to ensure that the surface of the covering agent does not turn red; the amount of covering agent added to the tundish each time is 0.5-0.8 kg / ton of steel; 9) When changing packages, the transfer of the large package and the preparation of the long sprue of the large package should be carried out simultaneously to ensure that the large package is in place and the long sprue is ready for operation.
2. The method for reducing the superheat of molten steel in a continuous casting tundish according to claim 1, characterized in that, In step 5), the tundish covering agent is added to the tundish at a rate of 2 kg / ton of steel per side.
3. The method for reducing the superheat of molten steel in a continuous casting tundish according to claim 1, characterized in that, In step 6), add 0.8 kg / ton of tundish covering agent from the pouring port of the ventilated tundish.
4. The method for reducing the superheat of molten steel in a continuous casting tundish according to claim 1, characterized in that, In step 7), the tundish is simultaneously filled with 4 kg of covering agent per ton of steel.
5. A method for reducing the superheat of molten steel in a continuous casting tundish according to claim 1, characterized in that, In step 8), the amount of tundish covering agent added each time is 0.6 kg / ton of steel.
6. The method for reducing the superheat of molten steel in a continuous casting tundish according to claim 1, characterized in that, The center segregation and center porosity of the obtained continuous casting billet are both 0.5.