A method for reducing the entrapment of slag in tundish during the exchange of ladle

Abstract

The application discloses a method for reducing slag entrapment in a tundish during ladle change, and solves the technical problem of slag entrapment in the prior art. The method comprises the following steps: stopping pouring and lifting a first ladle; placing a second ladle above the tundish and gradually lowering the second ladle, while blowing air to a long nozzle of the second ladle until the long nozzle of the second ladle is inserted into the tundish below the liquid level by 280-320 mm; the long nozzle of the second ladle is connected with a slag skimmer, and the slag skimmer comprises a connecting section and a skimming section which are connected with each other, the connecting section is connected to the long nozzle, and the outer diameter of the skimming section decreases from top to bottom; opening a slide plate of the second ladle, so that the molten steel in the second ladle flows into the tundish through the long nozzle, and the ladle change is completed; and the air blowing amount in the case that the insertion depth H of the long nozzle is not greater than 150 mm is greater than the air blowing amount in the case that the insertion depth H of the long nozzle is greater than 150 mm, so as to reduce the slag entrapment. The method provided by the application can reduce the slag entrapment amount of the molten steel, improve the cleanliness of the molten steel, and reduce the cracking rate of finished products.

Description

Technical Field

[0001] This application belongs to the field of continuous casting technology, specifically relating to a method for reducing slag entrainment in the ladle during the ladle exchange process. Background Technology

[0002] During the steel casting process, the process of exchanging ladles disturbs the flow field of molten steel in the tundish. When the previous ladle is stopped, the liquid level in the tundish drops, and the ladle, along with its long nozzle, is lifted out of the tundish. After the ladle turret is repositioned, the new ladle descends, and the long nozzle of the new ladle is reinserted into the molten steel in the tundish.

[0003] During the insertion of the new long nozzle into the tundish, slag can be trapped in the molten steel. This slag can then enter the crystallizer during continuous casting and be captured by the solidified billet shell. It is also prone to cracking during the stamping deformation process after rolling. Summary of the Invention

[0004] To address the technical problem of slag entrapment during ladle exchange, this application provides a method for reducing slag entrapment during ladle exchange.

[0005] This application provides a method for reducing slag entrainment in ladles during ladle exchange, comprising:

[0006] The first ladle stopped pouring and rose;

[0007] The second ladle is placed above the intermediate ladle and gradually lowered while air is blown into the long nozzle of the second ladle until the long nozzle of the second ladle is inserted 280mm to 320mm below the liquid surface in the intermediate ladle; the long nozzle of the second ladle is connected to a skimmer, which includes a connecting section and a skimming section connected to the long nozzle, and the outer diameter of the skimming section decreases from top to bottom;

[0008] Open the slide plate of the second ladle to allow molten steel to flow into the intermediate ladle through the long nozzle of the second ladle, thus completing the ladle exchange;

[0009] Wherein, the air blowing volume is greater when the insertion depth H of the long water nozzle is not greater than 150 mm than when the insertion depth H of the long water nozzle is greater than 150 mm, so as to reduce slag entrainment.

[0010] In some embodiments, the insertion depth H of the long nozzle and the air volume N of the long nozzle are related as follows:

[0011] When H≤150mm, N is 110L / min~200L / min;

[0012] When H > 150 mm, N is 80 L / min ~ 110 L / min.

[0013] In some implementations, when 150mm < H < 300mm, N is 95L / min to 110L / min;

[0014] When H≥300mm, N is 80L / min~100L / min.

[0015] In some embodiments, the wall thickness of the skimming section decreases sequentially from top to bottom.

[0016] In some embodiments, the skimmer is a steel skimmer, the upper wall thickness of the skimmer section is 0.8mm to 1.5mm, and the lower wall thickness of the skimmer section is 0.2mm to 0.5mm.

[0017] In some embodiments, the connecting section includes a plurality of spring clips, which are arranged sequentially at intervals along the circumference of the skimming section and located outside the long nozzle.

[0018] In some embodiments, the inner diameter of the middle portion of the connecting segment is smaller than the inner diameters of both ends.

[0019] In some embodiments, the inner diameter of the upper end of the connecting section is α(D+60)mm, the inner diameter of the middle section is α(D-10)mm, and the inner diameter of the lower end is α(D+30)mm, where D is the original inner diameter of the long nozzle, and the value of α ranges from 0.9 to 1.

[0020] In some implementations, throughout the entire casting cycle, α from the first furnace to the set furnace is greater than α from the set furnace to the last furnace, where the set furnace is greater than 1 and less than the last furnace.

[0021] In some implementations, α is related to the number of furnaces in the entire casting process as follows:

[0022] From the first furnace to the designated furnace number: the value of α ranges from 0.95 to 1;

[0023] From the first furnace to the last furnace, the value of α ranges from 0.9 to 0.95.

[0024] According to the method for reducing slag entrainment in the tundish during ladle exchange provided in this application embodiment, while employing a skimmer, the air flow rate during the long nozzle descent process is controlled. The air flow rate is large in the early stage of descent, resulting in significant flow field disturbance, which promotes the melting of the skimmer and the separation of the skimmer from the adhered tundish slag, thus breaking up the tundish slag. The air flow rate is small in the later stage, resulting in a more stable flow field, promoting the floating of small tundish slag particles, reducing the amount of slag in the molten steel, improving product cleanliness, and reducing the stamping cracking rate. Attached Figure Description

[0025] Figure 1 A schematic diagram of the structure for injecting molten steel into the tundish from the ladle is shown.

[0026] Figure 2 A schematic diagram of the skimmer is shown.

[0027] Figure 3 A schematic diagram of the robotic arm is shown.

[0028] Explanation of reference numerals in the attached figures:

[0029] 10-Skimmer, 11-Connecting section, 12-Skimmer section, 20-Mechanical arm, 21-Handle, 22-Support ring, 30-Ladle, 40-Long nozzle, 50-Intermediate ladle. Detailed Implementation

[0030] To enable those skilled in the art to more clearly understand this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0031] This application provides a method for reducing slag in the ladle during the ladle exchange process, which can reduce the amount of slag in the molten steel, improve the cleanliness of the molten steel, and improve the surface quality of the steel coil.

[0032] Please see Figure 1 In the continuous casting process of changing the ladle 30, the new ladle 30 needs to move downwards, carrying the long nozzle 40 and the skimmer 10 into the molten steel in the tundish 50. The skimmer 10 gradually melts into the molten steel after entering the molten steel. Since the new ladle 30 does not have the long nozzle 40 installed at its lower end, the skimmer 10 needs to be installed at the lower end of the long nozzle 40 of the new ladle 30 via the robotic arm 20 before it descends. The ladle 30 descends, carrying the long nozzle 40 downwards into the molten steel in the tundish 50, thus achieving the skimming effect. Therefore, before introducing the method for reducing slag entrapment in the tundish 50 during the ladle 30 exchange process, the skimmer 10 and robotic arm 20 involved in the method provided in this application will be introduced first:

[0033] Please see Figure 2 The skimmer 10 includes a connecting section 11 and a skimmer section 12 connected together. The lower end of the skimmer section 12 is provided with a through hole, which allows gas to be discharged from the through hole when the long nozzle 40 is blown. The connecting section 11 is connected to the long nozzle 40. The outer diameter of the skimmer section 12 decreases from top to bottom. Therefore, the tip of the skimmer section 12 is first inserted into the slag layer of the tundish 50 and the molten steel in sequence, thereby guiding the long nozzle 40 into the molten steel, reducing the amount of slag adhering to the long nozzle 40, and thus reducing slag entrapment.

[0034] The robotic arm 20 serves as a connection device between the skimmer 10 and the long nozzle 40. In some embodiments, please refer to [reference needed]. Figure 3 The robotic arm 20 includes a handle 21 and a support ring 22 into which the skimming section 12 of the skimmer 10 is inserted. The handle 21 is connected to the support ring 22. The skimming section 12 is conical, with its lower end inserted into the support ring 22, the middle part of the skimming section 12 contacting the support ring 22, and the upper end located above the support ring 22. By manually operating the handle 21, the connecting section 11 is fitted over the long nozzle 40, thus connecting the skimmer 10 to the long nozzle 40.

[0035] Having clarified the structure of the skimmer 10 and the robotic arm 20, the method for reducing slag entrapment in the inter-ladle 50 during the exchange of the ladle 30, as provided in this application, will be described in detail below.

[0036] Methods to reduce slag entrainment in the tundish during the 30-ton ladle exchange process include:

[0037] Step 1: Stop pouring the first ladle and raise it;

[0038] Step 2: Place the second ladle above the tundish 50 and gradually lower it while blowing air into the long nozzle 40 of the second ladle until the long nozzle 40 of the second ladle is inserted 280mm~320mm below the liquid level inside the tundish 50; the long nozzle 40 of the second ladle is connected to a skimmer 10.

[0039] Step 3: Open the slide plate of the second ladle to allow molten steel to flow into the intermediate ladle 50 through the long nozzle 40 of the second ladle, thus completing the exchange of ladle 30.

[0040] Ladle 30 is a container for holding clean molten steel. Generally, after refining in processes such as LF refining or RH refining, ladle 30 will obtain clean molten steel with the required composition and temperature. Ladle 30, carrying the clean molten steel, is transferred from the refining process to the ladle 30 rotary table. The ladle 30 rotary table has two stations, and the ladle 30s at the two stations are used for casting alternately.

[0041] In step 1, after the molten steel in the previous ladle 30 is poured out, the first ladle rises, along with its long nozzle 40, which is then manually removed. The ladle 30 is then rotated on a turntable, causing the first ladle to move away. The second ladle rotates to a position above the tundish 50, and the removed long nozzle 40 and skimmer 10 are sequentially connected to the bottom of the second ladle. The second ladle then descends with the long nozzle 40 and skimmer 10, allowing the long nozzle 40 to insert into the molten steel in the tundish 50. Because the outer diameter of the skimming section 12 of the skimmer 10 decreases from top to bottom, the tip of the skimmer 10 first inserts into the slag layer on the surface of the molten steel in the tundish 50. As the skimmer 10 continues to be inserted, some of the slag from the tundish 50 adheres to the surface of the skimmer 10, while some moves away from the skimmer 10 as it moves across the liquid surface, preventing a large amount of slag from entering the long nozzle 40. After the skimmer 10 enters the molten steel in the tundish 50, its tip melts first. Due to the slag from the tundish 50 adhering to it, the body of the skimmer 10 first forms a net-like structure in a very short time, and then slowly melts completely into molten steel. The slag from the tundish 50 it carries also gradually changes from large particles to small particles and floats to the top of the slag.

[0042] Before the slide gate of the second ladle is opened, argon gas is blown into the long nozzle 40. The argon gas moves downward from the upper end of the long nozzle 40 and exits through the through hole at the lower end of the skimming section 12. This removes air from the long nozzle 40 and prevents secondary oxidation when the molten steel in the second ladle flows out of the long nozzle 40. The insertion depth of the long nozzle 40 refers to the distance from the lower end of the long nozzle 40 to the surface of the molten steel in the tundish 50. Since the air blowing volume is greater when the insertion depth H of the long nozzle 40 is not greater than 150 mm than when the insertion depth H of the long nozzle 40 is greater than 150 mm, the air blowing volume decreases as the insertion depth of the long nozzle 40 increases.

[0043] In the early stage when the slag skimmer 10 enters the molten steel, its shallow depth makes it less prone to slag entanglement. Even if slag entanglement occurs, there is sufficient time for it to float and be removed. Furthermore, the slag skimmer 10 is relatively large in size, carrying a significant amount of tundish slag. Its overall mass and size are substantial, and large-volume air blowing can promote the melting of the slag skimmer 10 while also facilitating the separation of the tundish slag from the slag skimmer 10. In the later stage when the slag skimmer 10 enters the molten steel, its depth increases. As the slag skimmer 10 melts, its size decreases, and its through-hole gradually enlarges. The tundish slag is gradually broken down into small particles, and small-volume air blowing causes minimal disturbance to these small particles, making slag entanglement less likely.

[0044] This application controls the amount of air blown at different times during the insertion depth of the long nozzle 40, which not only avoids secondary oxidation of molten steel, but also improves the slag skimming effect of the skimmer 10 and reduces the risk of slag entanglement.

[0045] In some embodiments, the air volume decreases sequentially when the insertion depth H of the long nozzle 40 is not greater than 150 mm, when the insertion depth H of the long nozzle 40 is 150 mm < H < 300 mm, and when the insertion depth H of the long nozzle 40 is ≥ 300 mm. Combined with the state changes of the skimmer 10 during the melting process, this promotes the melting of the skimmer 10 and the separation of the skimmer 10 from the slag in the tundish 50 in the early stage, and promotes the floating of small particles of slag in the tundish 50 in the later stage, thereby ensuring the cleanliness of the molten steel and improving the surface quality of the steel coil.

[0046] Regarding the relationship between the insertion depth H of the long nozzle 40 and the air volume N of the long nozzle 40, in some embodiments:

[0047] When H≤150mm, N is 110L / min~200L / min, for example 120 L / min, 125 L / min, 130L / min, 140 L / min, 150 L / min, 160 L / min, 170 L / min, 180 L / min or 190 L / min, etc.

[0048] When H > 150 mm, N is 80 L / min to 110 L / min, for example, 85 L / min, 90 L / min, 95 L / min, 100 L / min, 105 L / min or 108 L / min, etc.

[0049] When the insertion depth is no more than 150 mm, an air blowing rate greater than 200 L / min may cause violent disturbance to the molten steel to some extent. After the slag from the tundish 50 is entrained in the molten steel, it is difficult to float due to the influence of the steel flow field. If the air blowing rate is less than 110 L / min, it may affect the separation effect between the slag skimmer 10 and the slag from the tundish 50 in the early stage. In the later stage, more small particles of slag from the tundish 50 will remain in the tundish 50. Some of the small particles of slag from the tundish 50 may not have time to float and will enter the billet, affecting the surface quality of the steel coil.

[0050] When the insertion depth is greater than 150 mm, an air blowing rate of less than 80 L / min is, to some extent, detrimental to the flotation of small particles of 50 slag in the tundish, affecting the surface quality of the steel coil. An air blowing rate greater than 110 L / min may, to some extent, cause severe disturbance to the molten steel flow, which is also detrimental to the flotation of small particles of 50 slag in the tundish, affecting the surface quality of the steel coil.

[0051] For insertion depths greater than 150 mm, more specifically, in some embodiments:

[0052] When 150mm < H < 300mm, N is 95L / min ~ 110L / min;

[0053] When H≥300mm, N is 80L / min~100L / min.

[0054] The skimmer 10 is a hollow tubular structure. The through-hole at its lower end serves as an outlet for the blown-in gas. The gas exiting through the through-hole moves upwards, causing the tundish slag to float to the surface. In some embodiments, the wall thickness of the skimmer 10 decreases from top to bottom, meaning the upper wall is thicker and the lower wall is thinner. This facilitates melting at the bottom of the skimmer 10 before melting at the top, achieving both skimming and accelerating the bottom-up melting process. This promotes the separation of the skimmer 10 from the tundish slag and reduces the amount of tundish slag entering the molten steel. In other embodiments, the wall thickness of the skimmer 10 is the same at all positions, also achieving bottom-up melting.

[0055] In some embodiments, the skimmer 10 is a steel skimmer, which does not contaminate the molten steel after melting. In other embodiments, the skimmer 10 may also be an alloy skimmer, the material of which may be the same as the type of alloy to be added to the molten steel.

[0056] In some embodiments, the wall thickness of the upper end of the skimming section 12 can be 0.8mm to 1.5mm, such as 0.9mm, 1mm, 1.2mm, 1.3mm or 1.4mm, and the wall thickness of the lower end of the skimming section 12 can be 0.2mm to 0.5mm, such as 0.3mm or 0.4mm, so that it can melt quickly and also achieve the skimming function.

[0057] In some embodiments, the connecting section 11 includes a plurality of spring plates, such as 5, 6, or 8, which are arranged sequentially at intervals along the circumference of the skimming section 12 and located outside the long nozzle 40. The skimming device 10 is connected to the long nozzle 40 by the plurality of spring plates abutting against the outer periphery of the long nozzle 40. The spring plates can be spring sheets, such as steel spring sheets or other alloy spring sheets; this application does not impose any limitations.

[0058] In some embodiments, the inner diameter of the middle part of the connecting section 11 is smaller than the inner diameters of both ends. The upper end has a large diameter, which can guide the connecting section 11 to fit over the long water inlet 40. The middle part has a small inner diameter, which can achieve tight clamping between the connecting section 11 and the long water inlet 40. The lower end has a large diameter, which can achieve transition with the skimming section 12.

[0059] In some embodiments, the inner diameter of the upper end of the connecting section 11 is α(D+60)mm, the inner diameter of the middle part is α(D-10)mm, and the inner diameter of the lower end is α(D+30)mm, where D is the original inner diameter of the long nozzle 40, and the value of α ranges from 0.9 to 1.

[0060] In some embodiments, throughout the entire casting process, α from the first furnace to the set furnace is greater than α from the set furnace to the last furnace, where the set furnace is greater than 1 and less than the last furnace.

[0061] The long nozzle 40 is made of refractory material. As the casting process progresses, the lower end of the long nozzle 40 will wear down, and its outer diameter will become smaller. Therefore, in the entire casting process, the diameter of α is larger in the earlier furnaces and the upper diameter of the connecting section 11 is larger, while the diameter of α is smaller in the later furnaces and the upper diameter of the connecting section 11 is smaller. This matches the size change of the long nozzle 40, resulting in higher connection stability.

[0062] In some embodiments, the relationship between α and the furnace number in the entire casting process is as follows:

[0063] From the first furnace to the designated furnace number: the value of α ranges from 0.95 to 1;

[0064] From the first furnace to the last furnace, the value of α ranges from 0.9 to 0.95.

[0065] Example 1

[0066] The steel used in this casting is ultra-low carbon steel. A total of 7 heats were cast in this batch, and the original outer diameter of the long nozzle 40 was 230mm.

[0067] The α coefficient of the first three skimmers 10 is 0.98. Therefore, the upper diameter of the connecting section 11 of the skimmer 10 is 284 mm, the middle diameter is 216 mm, and the lower diameter is 255 mm.

[0068] The α coefficient of the skimmer 10 in the last 4 furnaces is 0.92. Therefore, the upper diameter of the connecting section 11 of the skimmer 10 is 267 mm, the middle diameter is 202 mm, and the lower diameter is 239 mm.

[0069] During the insertion of molten steel into the tundish, argon gas is blown in through the long nozzle 40. The argon gas volume and immersion depth are controlled as follows: when the insertion depth of the long nozzle 40 is 0~150mm, the blowing volume is controlled at 120L / min; when the insertion depth of the long nozzle 40 is 150~300mm, the blowing volume is controlled at 100L / min; when the insertion depth of the long nozzle 40 is ≥300mm, the blowing volume is controlled at 90L / min.

[0070] The solution implemented in this example can effectively reduce the slag entrapment during the changeover process and reduce the defect rate caused by stamping cracks at the client end by 55%.

[0071] Example 2

[0072] The steel used in this casting is low-carbon steel. A total of 10 heats were cast in this batch, and the original outer diameter of the long nozzle 40 is 220mm.

[0073] The α coefficient of the first 5 furnace skimmers 10 is 0.97. Therefore, the upper diameter of the connecting section 11 of the skimmer 10 is 272 mm, the middle diameter is 204 mm, and the lower diameter is 243 mm.

[0074] The α coefficient of the skimmer 10 in the last 5 furnaces is 0.93. Therefore, the upper diameter of the connecting section 11 of the skimmer 10 is 260mm, the middle diameter is 195mm, and the lower diameter is 233mm.

[0075] During the insertion of molten steel into the tundish (50mm), the air volume and immersion depth of the long nozzle (40) are controlled as follows: For insertion depths of 0-150mm, the air volume is controlled at 150L / min; for insertion depths of 150-300mm, the air volume is controlled at 108L / min; and for insertion depths ≥300mm, the air volume is controlled at 90L / min. Using this invention effectively reduces slag entrapment into the tundish (50mm) during ladle changes, and reduces the defect rate caused by stamping cracks at the client end by 49%.

[0076] Example 3

[0077] The steel used in this casting is ultra-low carbon steel. A total of 6 heats were cast in this batch, and the original outer diameter of the long nozzle 40 was 230mm.

[0078] The α coefficient of the first three skimmers 10 is 0.96, and the β coefficient of the robotic arm 20 is 0.73. Therefore, the upper diameter of the connecting section 11 of the skimmer 10 is 278 mm, the middle diameter is 211 mm, and the lower diameter is 250 mm.

[0079] The α coefficient of the skimmer 10 in the last three furnaces is 0.91, and the β coefficient of the robotic arm 20 is 0.67. Therefore, the upper diameter of the connecting section 11 of the skimmer 10 is 264 mm, the middle diameter is 200 mm, and the lower diameter is 237 mm.

[0080] During the insertion of molten steel into the tundish (50mm), the air volume and immersion depth of the long nozzle (40) are controlled as follows: For insertion depths of 0-150mm, the air volume is controlled at 170L / min; for insertion depths of 150-300mm, the air volume is controlled at 98L / min; and for insertion depths ≥300mm, the air volume is controlled at 85L / min. Using this invention effectively reduces slag entrapment into the tundish (50mm) during ladle changes, and reduces the defect rate caused by stamping cracks at the client end by 44%.

[0081] The method provided by this invention has at least the following advantages:

[0082] (1) A new slag skimmer 10 was added during the ladle change process. Due to the addition of the conical slag skimmer 10, when the long nozzle 40 is inserted into the molten steel, the head of the slag skimmer 10 contacts the molten steel and skims off the slag from the tundish 50, gradually melting it. Once the long nozzle 40 is inserted deeply, the slag skimmer 10 completely melts, and the slide gate is opened to begin pouring. Therefore, the slag skimmer 10 solves the problem of slag entrapment in the tundish 50 during the ladle change process from the source.

[0083] (2) The argon gas volume of the long nozzle 40 is controlled in stages. Due to the use of the skimmer 10, the disturbed area of ​​the liquid surface of the tundish 50 increases. Therefore, the gas volume is adjusted in stages according to different insertion depths of the long nozzle 40. When the insertion depth of the long nozzle 40 is shallow, the disturbed area of ​​the liquid surface of the tundish 50 increases, and more steel slag is attached to the lower part of the skimmer 10. The gas volume of the long nozzle 40 is large, which promotes the separation of the skimmer 10 from the slag of the tundish 50 and accelerates the melting of the skimmer 10. When the insertion depth of the long nozzle 40 is deeper, the gas volume of the long nozzle 40 decreases, which not only accelerates the melting of the skimmer 10, but also reduces the disturbance to the molten steel and promotes the floating of the slag of the tundish 50. As the insertion depth of the long nozzle 40 is further increased, a smaller gas volume is used for blowing. The flow field is stable and the flow velocity is low. The slag of the tundish 50 adsorbed on the skimmer 10 is called small particle slag as the skimmer 10 is completely dissolved. It floats faster in a relatively calm flow field.

[0084] (3) Adjust the size of the connecting section 11 according to the changes in the long nozzle 40 with each casting cycle. In the first to intermediate casting cycles, since the long nozzle 40 is less eroded, the size of the skimmer 10 needs to be designed to be larger, which will help it to grip the long nozzle 40 more easily while ensuring gripping strength. In the intermediate to final casting cycles, since the long nozzle 40 has been eroded, the setting coefficient of the connecting section 11 of the skimmer 10 needs to be reduced to better grip the long nozzle 40. The present invention has a simple structure and is easy to use. After adopting the technology of the present invention, the slag entanglement of the tundish 50 can be effectively reduced, and the stamping cracking rate caused by the slag entanglement of the tundish 50 is reduced by 40-80%.

[0085] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0086] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", and "counterclockwise" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0087] In this application, unless otherwise expressly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0088] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0089] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for reducing slag entrainment in ladles during ladle exchange, characterized in that, include: The first ladle stopped pouring and rose; The second ladle is placed above the intermediate ladle and gradually lowered while air is blown into its long nozzle until it is inserted 280mm-320mm below the liquid surface in the intermediate ladle. The long nozzle of the second ladle is connected to a skimmer, which includes a connecting section and a skimmer section. The connecting section is attached to the long nozzle, and the outer diameter of the skimmer section decreases from top to bottom. The skimmer is a hollow tubular structure with a through-hole at the lower end serving as a discharge outlet. The inner diameter of the connecting section is α(D+60)mm at the upper end, α(D-10)mm in the middle, and α(D+30)mm at the lower end. D is the original inner diameter of the long nozzle, and α ranges from 0.9 to 1. Open the slide plate of the second ladle to allow the molten steel in the second ladle to flow into the intermediate ladle through the long nozzle, thus completing the ladle exchange; Wherein, the air blowing volume when the insertion depth H of the long water nozzle is not greater than 150 mm is greater than the air blowing volume when the insertion depth H of the long water nozzle is greater than 150 mm, so as to reduce slag entrainment. The insertion depth H of the long nozzle and the air volume N of the long nozzle are related as follows: When H≤150mm, N is 110L / min~200L / min; When H > 150 mm, N is 80 L / min ~ 110 L / min; Throughout the entire casting cycle, the α value from the first heat to the designated heat is greater than the α value from the designated heat to the last heat; the designated heat is greater than 1 and less than the last heat; the relationship between α and the heats in the entire casting cycle is as follows: From the first furnace to the designated furnace number, the value of α ranges from 0.95 to 1; From the first furnace to the last furnace, the value of α ranges from 0.9 to 0.

95.

2. The method for reducing slag entrainment in the ladle during the steel ladle exchange process according to claim 1, characterized in that, When 150mm < H < 300mm, N is 95L / min ~ 110L / min; When H≥300mm, N is 80L / min~100L / min.

3. The method for reducing slag entrainment in the ladle during the steel ladle exchange process according to any one of claims 1-2, characterized in that, From top to bottom, the wall thickness of the skimming section decreases sequentially.

4. The method for reducing slag entrainment in the ladle during the steel ladle exchange process according to claim 3, characterized in that, The skimmer is a steel skimmer, with the upper wall thickness of the skimming section being 0.8mm to 1.5mm and the lower wall thickness of the skimming section being 0.2mm to 0.5mm.

5. The method for reducing slag entrainment in the ladle during the steel ladle exchange process according to any one of claims 1-2, characterized in that, The connecting section includes multiple spring pieces, which are arranged sequentially at intervals along the circumference of the skimming section and located outside the long water inlet.

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