Production method for refining and slagging continuous casting tundish slag

Abstract

The invention discloses a production method for refining and slagging tundish slag in continuous casting. According to a covering agent added in the continuous casting tundish in the casting starting and casting process, tundish slag is formed after the surface of molten steel in the tundish is melted, before tundish casting is finished, the tundish slag in the tundish completely overflows into a slag basin, and the tundish slag in the slag basin is transferred to a refining area through a crown block. And slag is not added during steel tapping during refining and smelting of steel types of the same slag system, and tundish slag is adopted for slagging and smelting. By adopting the method, the continuous casting tundish slag can be completely recovered, the pollution of tundish slag discharge to the environment is reduced, and the smelting cost is reduced; and during tundish slag smelting, slagging and deoxidation are fast, and the cleanliness of molten steel is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of iron and steel metallurgy, and relates to a production method for refining and slagging slag in a continuous casting tundish. Background Art

[0002] As my country's steel production gradually increases, the problem of overproduction is becoming increasingly serious, posing multiple challenges to major steel companies. First, raw material price fluctuations directly impact steel production costs. Second, tightening environmental protection policies are putting pressure on steel companies to reduce emissions. Furthermore, overcapacity in the steel industry is leading to fierce market competition and price pressure. Therefore, in the steel production process, reducing production costs and promoting green transformation are bound to dominate the fierce competition.

[0003] In the steelmaking process, recycling metallurgical slag is an important means of reducing costs and minimizing environmental pollution. For example, the recycling technology for ladle slag is relatively mature. A common practice is to directly dump the hot ladle slag left after the previous heat of molten steel into the next heat of molten steel for reuse. This method is simple to operate and has been widely adopted within the industry.

[0004] However, effective recycling of slag produced in the tundish (or tundish) during continuous steel casting (continuous casting) is rarely reported. This is primarily due to two major technical bottlenecks: first, the relatively small amount of tundish slag and its low heat capacity make it prone to heat loss and difficult to maintain. Second, the complex recycling process requires specialized equipment and processes, resulting in high costs and significant challenges.

[0005] The continuous casting tundish covering agent is a key material for stable production and ingot quality during the continuous casting process. Its composition includes limestone, fluorite, and silicates, and it exhibits low melting points, good fluidity, and low oxidizability. It also isolates the air during the production process to prevent oxidation of the molten steel, insulates the molten steel to prevent splashing during pouring, and absorbs inclusions within the tundish. In traditional production processes, the tundish slag produced during the pouring process (whether overflowed or residual after pouring) is typically collected in an open overflow trough. Due to the open and large size of the trough, the tundish slag cools rapidly and adheres to the trough walls, ultimately requiring disposal as waste or storage in the open air. This disposal method not only results in a significant waste of valuable resources but also poses a potential pollution risk to the surrounding environment.

[0006] In fact, the tundish slag, produced after melting the high-temperature molten steel in the tundish, exhibits excellent properties such as a low melting point, good fluidity, and low oxidizability. Its chemical composition is highly similar to the slag-forming agent components required for subsequent steel refining. This indicates that the tundish slag itself has extremely high recycling value, but existing technologies have failed to effectively explore and utilize this value, resulting in a technological gap and waste of resources. Therefore, developing a method for efficiently and cost-effectively recycling high-temperature tundish slag for direct use in refining and slag-forming has become a pressing technical challenge for the steel industry. Summary of the Invention

[0007] In view of the above analysis, the present invention provides a method for hot recovery of continuous casting tundish slag and direct use in subsequent refining and slag making of the same slag-based steel. A slag basin with a heat-insulating function is used to collect the high-temperature tundish slag at the end of the pouring process and quickly transfer it to a refining furnace, where its residual heat and existing chemical composition are used to replace the traditional cold slag-making material. The present invention recycles the continuous casting tundish slag and directly uses it for slag making of the same slag-based steel. This production method effectively solves the problems of material waste and environmental pollution caused by the existing practice of selling or separately processing the tundish slag. At the same time, the tundish slag is used for refining, slag making, and smelting, achieving the goals of rapid slag making and deoxidation, effectively improving production efficiency and reducing production costs.

[0008] The present invention provides a production method for refining and slagging continuous casting tundish slag, a specific process and equipment, which realizes hot and efficient recovery of tundish slag. The specific steps are as follows: (1) After the ladle reaches the continuous casting turret, the baked tundish is transferred from the baking position to the pouring position via the tundish car. The molten steel after the first furnace of refining and smelting is lifted in the ladle by the overhead crane to the continuous casting turret to wait for pouring. The tundish has been baked in advance, and the baking end temperature is greater than 1100℃. The baked tundish can effectively reduce the temperature drop of the molten steel from the ladle to the tundish, preventing the molten steel from cooling and solidifying at the bottom of the tundish.

[0009] (2) The molten steel in the ladle enters the tundish through the ladle shroud. A covering agent is added to the surface of the molten steel in the tundish to cover it. The covering agent melts on the surface of the molten steel to form tundish slag. The ladle shroud is a refractory material connecting the ladle and the tundish. After the molten steel enters the tundish, a covering agent is added through the baking hole above the tundish cover to cover it. This prevents the molten steel from being oxidized, keeps the molten steel warm, and absorbs inclusions in the molten steel. The composition of this covering agent is similar to the target slag composition of the slag surface at the end of refining this steel grade. That is, after the covering agent melts, a slag with a specific alkalinity or acidity is formed.

[0010] (3) After the addition of the covering agent in the tundish is completed, the submerged nozzle in the tundish is opened, and the molten steel enters the crystallizer through the submerged nozzle to cool and solidify into a steel billet. After the pouring of the molten steel in the ladle is completed, the next ladle of molten steel is replaced to continue pouring.

[0011] The tundish submerged nozzle is the refractory material connecting the tundish and the mold. The tundish's service life is determined by the production volume of the steel grade or its maximum lifespan. Therefore, after the first ladle of molten steel is poured, it is necessary to continue pouring the next batch of refined and smelted molten steel using a rotary table.

[0012] (4) Before the last furnace is finished, all the molten tundish slag covering the surface of the molten steel in the tundish will overflow and flow into the slag basin with heat preservation function. Before the last furnace is finished, the tundish is filled with molten steel by opening the long water nozzle of the large ladle, and all the tundish slag floating on the surface of the molten steel will overflow. Before the slag overflows, the top cover of the slag basin is opened, the locking pin at the bottom of the slag basin is closed, and a layer of light blanket is laid on the bottom steel plate to prevent the tundish slag from sticking to the bottom steel plate and to insulate the tundish slag. After all the tundish slag has overflowed into the slag basin, the temperature of the tundish slag is between 600 and 800 °C, and the top cover of the slag basin is closed.

[0013] (5) The tundish slag in the slag basin is transferred to the refining area by an overhead crane. When the converter smelts the steel of the same slag system as the tundish slag, no slag is added or the addition of conventional slag (such as lime and slagging agent) is greatly reduced. When the molten steel reaches the refining station after tapping, the locking pin at the bottom of the slag basin is opened and the high-temperature tundish slag in the slag basin is added to the surface of the molten steel.

[0014] (6) The molten steel is electrified, heated, and the slag surface is deoxidized and the composition is adjusted. After the temperature and composition are adjusted, the molten steel is transferred to the continuous casting for pouring.

[0015] Furthermore, the timing for adding covering agent into the tundish is when the weight of the molten steel in the tundish reaches 1 / 2 of the total loading weight. The total amount of covering agent added for the first furnace is 7~8kg / T, where T is the weight (ton) of the tundish filled with molten steel. During the continuous pouring process, 20~30kg of covering agent is added for each furnace when the tundish is changed.

[0016] Furthermore, before the pouring ends at the last furnace, that is, when the remaining amount of molten steel in the ladle is less than 10t, the opening of the long shroud of the large ladle is opened to the maximum, the molten steel in the tundish is controlled to the highest position, and the tundish slag on the surface of the molten steel overflows into the slag basin.

[0017] Furthermore, the steel grade with the same slag system as the tundish slag smelted in the converter is the steel grade with the same deoxidation method during tapping, which is silicon deoxidation or aluminum deoxidation.

[0018] Furthermore, the maximum allowable time range from the start of slag overflow to the addition of slag to the refining furnace is 15 to 40 minutes. (The normal time from continuous casting to refining is 15 to 40 minutes, which is relatively short, so the entire process from the end of slag overflow to the addition of slag to the refining furnace can also be controlled within this range.)

[0019] Furthermore, the slag basin is a trapezoidal structure, the four sides of the slag basin and the top cover are made of corundum castable material, and the bottom is an openable iron plate; before the tundish slag is loaded, a 5cm thick ceramic fiber lightweight blanket is spread on the bottom iron plate, and the composition of the lightweight blanket is 40-50% Al2O3 content, 45-55% SiO2 content, fiber fineness 4-6um, thermal conductivity coefficient less than 0.19, and volume density 125-130kg / m 3 .

[0020] Compared with the existing production process, the present invention has the following beneficial effects.

[0021] (1) The present invention uses a special slag basin with corundum castable around and on the top surface and steel plate at the bottom. The basin has good thermal insulation conditions around and on the top. A layer of ceramic fiber lightweight blanket is spread on the bottom above the steel plate, which can not only effectively prevent the tundish slag from sticking to the bottom steel plate, but also effectively prevent the tundish slag from losing heat. The slag is discharged in a centralized manner to ensure the temperature of the tundish slag. All the tundish slag is recycled and reused, reducing the slag consumption during the converter tapping process. This fundamentally solves the problems of tundish slag resource waste and environmental pollution in the existing technology, and meets the requirements of green and sustainable development of the steel industry.

[0022] (2) Directly utilizing the tundish slag replaces some of the expensive cold refining slag materials (such as lime, fluorite, etc.), significantly reducing the raw material procurement costs of the refining process. At the same time, by utilizing the residual heat carried by the tundish slag itself, the energy consumption in the refining process is reduced, resulting in significant overall economic benefits. The hot tundish slag used in the present invention has the characteristics of low melting point and good fluidity. After being put into the refining furnace, it does not need to undergo a long melting process and can quickly form a uniform liquid slag layer, effectively shortening the refining and smelting time, and improving the production rhythm and equipment utilization rate.

[0023] Furthermore, the covering agent completely melts within the tundish and spreads evenly across the molten steel surface. This slag has a low melting point, melts quickly and evenly, and exhibits extremely low oxidizing properties. Furthermore, after the final pour is completely overflowed, it is quickly transferred to the refining process for slag formation and smelting. This ensures a consistently high slag temperature, allowing for rapid melting and adsorption of inclusions in the steel. This eliminates the need for the traditional process of adding slag, which absorbs heat from the steel, causing low molten steel temperatures, and also creates the problem of slow melting. Using tundish slag for smelting significantly shortens refining time.

[0024] In summary, the present invention can realize the recycling of tundish slag, reduce environmental pollution and material waste; at the same time, by utilizing the characteristics of low melting point, good uniformity and low oxidizability of tundish slag, the production efficiency can be greatly improved and the quality of molten steel can be improved in the circulating slagging process. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 : A schematic front view cross-sectional view of the slag basin used in the present invention after the tundish slag is loaded.

[0026] Figure 2 : A schematic top view of the slag basin used in the present invention after the tundish slag is loaded.

[0027] Figure 3 : The schematic diagram of the slag basin used in the present invention.

[0028] In the figure: 1. Tundish slag, 2. Top cover of slag basin castable, 3. Side wall of slag basin castable, 4. Ceramic fiber lightweight blanket at the bottom of slag basin, 5. Steel plate at the bottom of slag basin, 6. Four hooks of slag basin, 7. Locking pin of steel plate at the bottom of slag basin, 8. Movable pin of steel plate at the bottom of slag basin, 9. Movable pin of top cover of slag basin castable. DETAILED DESCRIPTION

[0029] The present invention is further illustrated below by taking the production examples of cold heading steel ML08Al (implementing standard GB / T6478-2015) and carbon structural steel 70 and 60 (implementing standard GB / T 4354-2008) with a steel packing amount between 120 and 140 tons as an example.

[0030] Among them, the slag composition control requirements for cold heading steel ML08Al after refining are CaO: 45~65%, SiO2: 2.5~7.5%, MnO: ≤1.0%, MgO: ≤10%, S: ≤1.5%, Al2O3: 25~45%, FeO: ≤1.0%; the slag composition control requirements for carbon structural steel 70 after refining are CaO: 35~55%, SiO2: 20~40%, MnO: ≤3.0%, MgO: ≤15%, S: ≤1.0%, Al2O3: 5~15%, FeO: ≤3.0%.

[0031] Example 1: (1) The weight of the first furnace of ML08Al molten steel is 135 tons. After slag making and deoxidation, and the composition and temperature are adjusted, the ladle filled with ML08Al is hoisted onto the continuous casting turntable. The baking of the tundish that is being baked is stopped, and the tundish is transferred from the baking position to the pouring position by the tundish car. When the tundish reaches the pouring position, the internal temperature is measured to be 1150℃.

[0032] (2) Put the large ladle shroud on the ladle outlet, open the large ladle shroud, and the molten steel in the ladle flows into the tundish from the large ladle shroud. The weight of the tundish filled with molten steel is 40 tons. When the weight of the molten steel in the tundish reaches 20 tons, start adding 300 kg of covering agent into the tundish. The covering agent composition is CaO: 51%, SiO2: 3.2%, MnO: 0.4%, MgO: 2.2%, S: 0.1%, Al2O3: 42.9%, FeO: 0.2%. The covering agent is added before the weight of the molten steel in the tundish reaches 30 tons. The covering agent melts on the surface of the molten steel to form tundish slag.

[0033] (3) After the addition of the covering agent to the tundish is completed, the submerged nozzle in the tundish is opened, and the molten steel enters the crystallizer through the submerged nozzle to cool and solidify into billets. When there are 15 tons of molten steel left in the first furnace ML08Al ladle, the second furnace ML08Al molten steel weighing 130 tons arrives at the preparation position of the continuous casting turntable. The molten steel in the first furnace ML08Al ladle is completely poured, the large ladle long nozzle is closed and removed, and the second furnace ML08Al ladle at the preparation position is transferred from the preparation position to the pouring position, the large ladle long nozzle is installed and opened, and the second furnace ML08Al molten steel enters the tundish through the large ladle long nozzle, and 20kg of covering agent is added around the large ladle long nozzle.

[0034] (3) After the pouring of the second furnace of ML08Al is completed, continue pouring the third furnace, and continue pouring until the 20th furnace reaches the service life of the ladle. It is necessary to replace the ladle and start pouring again.

[0035] (4) The 20th heat is the last heat of ML08Al. When there are 9 tons of remaining in the last heat, the shroud is opened to the maximum, the bottom of the slag basin is covered with a layer of ceramic fiber lightweight blanket 4, and the steel plate locking pin 7 at the bottom of the slag basin is closed. The slag basin is placed at the slag overflow outlet of the tundish, the top cover 2 of the slag basin is opened, and the molten tundish slag covering the surface of the molten steel in the tundish is completely overflowed and flows into the slag basin. The weight of the tundish slag 1 in the slag basin is 650 kg, and the top cover 2 of the slag basin is closed.

[0036] (5) The four hooks 6 of the slag basin are hung by the overhead crane, and the slag basin and the tundish slag 1 are transferred to the refining area by the overhead crane. The converter smelting is restarted to produce the first furnace of ML08Al. No slag is added when the first furnace of ML08Al is tapped. After tapping, when the molten steel reaches the refining station, the slag basin and the tundish slag 1 are lifted above the molten steel by the overhead crane, the locking pin 7 of the steel plate at the bottom of the slag basin is opened, and 650kg of the tundish 1 in the slag basin is added to the surface of the molten steel. At this time, the temperature of the tundish slag 1 is 620℃.

[0037] (6) After adding tundish slag to the first furnace of ML08Al, the molten steel temperature was measured at 1535°C. The power was turned on, the temperature was raised, the slag surface was deoxidized, and the composition was adjusted. After the composition was adjusted, the molten steel temperature was measured at 1605°C, and the molten steel was transferred to the continuous casting for pouring. The power consumption of this furnace was 62 kWh / t, and the total heating time was 35 minutes.

[0038] Example 2: (1) The weight of the first batch of molten steel is 128 tons. After slag making and deoxidation, and the composition and temperature are adjusted, the ladle filled with 70 tons reaches the continuous casting turntable, and the baking of the tundish is stopped. The tundish is transferred from the baking position to the pouring position by the tundish car. When the tundish reaches the pouring position, the internal temperature is measured to be 1165℃.

[0039] (2) The ladle shroud is mounted on the ladle outlet, and the ladle shroud is opened. The molten steel in the ladle flows into the tundish from the ladle shroud. The weight of the tundish filled with molten steel is 46 tons. When the weight of the molten steel in the tundish reaches 23 tons, 350 kg of covering agent is added to the tundish. The covering agent composition is CaO: 52%, SiO2: 37.9%, MnO: 0.4%, MgO: 2.8%, S: 0.5%, Al2O3: 5.8%, FeO: 0.6%. The covering agent is added before the weight of the molten steel in the tundish reaches 33 tons. The covering agent melts on the surface of the molten steel and becomes tundish slag.

[0040] (3) After the addition of the covering agent in the tundish is completed, the submerged nozzle in the tundish is opened, and the molten steel enters the crystallizer through the submerged nozzle to cool and solidify into billets. When there are 15 tons of molten steel left in the 70-gallon ladle of the first furnace, the 70-gallon molten steel of the second furnace weighing 135 tons arrives at the preparation position of the continuous casting turntable. The molten steel in the 70-gallon ladle of the first furnace is completely poured, and the large ladle long nozzle is closed and removed. The 70-gallon ladle of the second furnace at the preparation position is transferred from the preparation position to the pouring position, and the large ladle long nozzle is installed and opened. The molten steel of the second furnace enters the tundish through the large ladle long nozzle, and 25 kg of covering agent is added around the large ladle long nozzle.

[0041] (3) After the pouring of the second furnace 70 is completed, continue pouring the third furnace, and continue pouring until the 25th furnace reaches the service life of the ladle. It is necessary to replace the ladle and start pouring again.

[0042] (4) The 25th heat is the last heat of the 70 heats. When there are 8 tons left in the last heat, the ladle shroud is opened to the maximum, the bottom of the slag basin is covered with a layer of ceramic fiber lightweight blanket 4, and the steel plate locking pin 7 at the bottom of the slag basin is closed. The slag basin is placed at the tundish overflow outlet, the top cover 2 of the slag basin is opened, and the molten tundish slag covering the surface of the molten steel in the tundish is completely overflowed and flows into the slag basin. The weight of the tundish slag 1 in the slag basin is 750 kg, and the top cover 2 of the slag basin is closed.

[0043] (5) The four hooks 6 of the slag basin are hung by the overhead crane, and the slag basin and the tundish slag 1 are transferred to the refining area by the overhead crane. The converter smelting is restarted to produce the first furnace 60. No slag is added when the first furnace 60 is tapped. After tapping, when the molten steel reaches the refining station, the slag basin and the tundish slag 1 are lifted above the molten steel by the overhead crane, the locking pin 7 of the steel plate at the bottom of the slag basin is opened, and the 750kg tundish 1 in the slag basin is added to the surface of the molten steel. At this time, the temperature of the tundish slag 1 is 650℃.

[0044] (6) After adding the tundish slag to furnace 1, the temperature of the molten steel was measured at 1510°C. The power was turned on, the temperature was raised, the slag surface was deoxidized, and the composition was adjusted. After the composition was adjusted, the temperature of the molten steel was measured at 1570°C, and the molten steel was transferred to the continuous casting for pouring. The power consumption of this furnace was 60 kWh / t, and the total heating time was 33 minutes.

[0045] Comparative Example 1: Comparative Example 1 differs from Example 1 in that no slag basin is used to recover the tundish slag. That is, during the continuous pouring process in steps (3) and (4), the tundish slag in the tundish normally overflows into the slag trough. In step (5), 500 kg of lime and 300 kg of slag are added to slag formation when tapping the first furnace of ML08Al. Other operations are the same as in Example 1.

[0046] After the first ML08Al furnace arrived at the refining station, the molten steel temperature was measured at 1530°C. Power was then applied, the temperature was raised, slag surface deoxidation was performed, and composition adjustment was performed. Once the composition was in place, the molten steel temperature was measured at 1602°C, and the steel was transferred to the continuous casting station for pouring. The furnace consumed 68 kWh / t of electricity, and the total heating time was 42 minutes.

[0047] Comparative Example 2: Compared with Example 2, Comparative Example 2 differs in that no slag basin is used to recover the tundish slag. That is, during the continuous pouring process in steps (3) and (4), the tundish slag in the tundish normally overflows into the slag trough. In step (5), 550 kg of lime and 300 kg of slag are added to slag formation when the first furnace 60 is tapped.

[0048] After furnace 60 arrived at the refining station, the molten steel temperature was measured at 1512°C. Power was then applied, the temperature was raised, slag surface deoxidation was performed, and composition adjustment was performed. Once the composition was adjusted, the molten steel temperature was measured at 1575°C, and the steel was transferred to the continuous casting station for pouring. The furnace consumed 69 kWh / t of electricity, and the total heating time was 44 minutes.

[0049] Comparative Example 3: Comparative Example 3 differs from Example 2 in that, in step (4), the 25th heat is the last heat of 70. When the last heat has 8 tons remaining, the ladle shroud is opened to the maximum, and a common open slag trough is used to load the tundish slag. The weight of the tundish slag in the slag trough is 740 kg. In step (5), no slag is added when the first heat 60 is tapped. After tapping, when the molten steel reaches the refining station, the tundish slag is moved to the top of the molten steel by a crane and poured into the top of the molten steel by a cutting and oblique method. At this time, the tundish slag adheres to the bottom of the slag trough. The actual amount of tundish slag on the surface of the molten steel is 260 kg. At this time, the temperature of the tundish slag is 350°C.

[0050] After furnace 60 arrived at the refining station, the molten steel temperature was measured at 1507°C. Power was then applied, the temperature was raised, slag surface deoxidation was performed, and composition adjustment was performed. During the refining process, 400kg of lime and 200kg of slagging agent were added. After the composition adjustment was complete, the molten steel temperature was measured at 1574°C, and the steel was transferred to the continuous casting station for pouring. The furnace consumed 66kWh / t of electricity, and the total heating time was 42 minutes.

[0051] Table 1 compares the refining process of Examples 1-2 and Comparative Examples 1-3. Compared with Example 1, in smelting the same steel grade, Comparative Example 1 needs to add slag, which causes the refining heating rate to be 0.29°C / min lower and the refining power consumption to increase by 6kwh / t; Compared with Example 2, Comparative Example 2 needs to add slag, which causes the refining heating rate to be 0.38°C / min lower and the refining power consumption to increase by 9kwh / t; Compared with Example 2, Comparative Example 3 needs to add slag, which causes the refining heating rate to be 0.22°C / min lower and the refining power consumption to increase by 6kwh / t.

[0052] Table 1 Implementation Add slag Refining temperature / ℃ Refining heating time / min Refining heating rate / ℃ / min Refining power consumption / kwh / t Example 1 0 70 35 2.00 62 Example 2 0 60 33 1.81 60 Comparative Example 1 500kg lime + 300kg slagging agent 72 42 1.71 68 Comparative Example 2 550kg lime + 300kg slagging agent 63 44 1.43 69 Comparative Example 3 400kg lime + 200kg slagging agent 67 42 1.59 66 The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A production method for refining and slagging slag in a continuous casting tundish, characterized by: The tundish slag formed after the steel liquid surface in the continuous casting tundish is recovered and directly used for refining and slag smelting of the same slag series steel, including the following steps: (1) Before the end of the last furnace of the continuous casting process, the molten slag on the surface of the molten steel in the tundish is overflowed and collected in a slag basin with heat preservation function; (2) transporting the slag basin containing the high-temperature tundish slag to a refining station; (3) When refining the next batch of molten steel with the same slag system as the tundish slag, no conventional slag is added or the addition of the conventional slag is reduced after the converter is tapped, and the high-temperature tundish slag in the slag basin is added to the surface of the molten steel in the refining furnace as the initial slag-making material; (4) The molten steel after adding the tundish slag is subjected to subsequent refining treatment.

2. The method according to claim 1, wherein: The slag overflow operation in step (1) is specifically as follows: when the remaining amount of molten steel in the last ladle is less than 10t, the opening degree of the long shroud of the large ladle is increased to raise the molten steel level in the tundish to the slag overflow port, thereby causing the tundish slag to overflow.

3. The method according to claim 1, wherein: The slag basin with thermal insulation function is a trapezoidal structure, whose side walls and top cover are made of refractory castables, and the bottom is an openable steel plate structure, the opening and closing of which is controlled by a locking pin; before collecting the tundish slag, a layer of ceramic fiber lightweight blanket is laid on the bottom steel plate of the slag basin.

4. The method according to claim 1, wherein: In step (2) and step (3), the time from the completion of collecting the tundish slag to its addition to the surface of the molten steel in the refining furnace is controlled to be 10 to 40 minutes.

5. The method according to claim 1, wherein: The same slag steel grade refers to the same deoxidation method, and the chemical composition of the target refined slag matches the chemical composition of the recovered tundish slag.

6. The method according to claim 1, wherein: The tundish slag comes from the covering agent added in the tundish. The total amount of the covering agent added is 7-8 kg / T, where T is the weight (tons) of the tundish filled with molten steel. During the continuous pouring process, 20-30 kg of covering agent is added for each furnace ladle change.

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