Method for reducing tundish slag entrapment in steel ladle exchange process

Abstract

The invention discloses a method for reducing slag entrapment of a tundish in the steel ladle exchange process. The technical problem of slag entrapment in the steel ladle exchange process in the prior art is solved. The method comprises the steps that a first steel ladle stops pouring and ascends; the second steel ladle is placed above the tundish and gradually descends, and meanwhile air is blown to a long nozzle of the second steel ladle till the long nozzle of the second steel ladle is inserted into the position, below 280 mm-320 mm, of the liquid level in the tundish; the long nozzle of the second steel ladle is connected with a skimmer, the 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 is sequentially reduced from top to bottom; the sliding plate of the second steel ladle is opened, so that molten steel in the second steel ladle flows into the tundish through the long nozzle, and steel ladle exchange is completed; the air blowing amount under the condition that the insertion depth H of the long nozzle is not greater than 150mm is greater than that under the condition that the insertion depth H of the long nozzle is greater than 150mm, so that slag entrapment is reduced. According to the method, the slag entrapment amount of the molten steel can be reduced, the cleanliness of the molten steel is improved, and the stamping cracking rate of finished products is reduced.

Description

Technical Field

[0001] The present application belongs to the technical field of continuous casting, and in particular relates to a method for reducing slag rolling in the intermediate ladle during the ladle exchange process. Background Art

[0002] During the steel casting process, the ladle exchange process disturbs the flow field of the molten steel in the tundish. The previous ladle stops pouring, and the tundish liquid level drops. The ladle with the long shroud is lifted out of the tundish liquid level. After the ladle turret exchanges positions, the new ladle descends, and the long shroud with the new ladle is inserted into the molten steel in the tundish again.

[0003] In the process of inserting the new long shroud into the tundish, slag will form in the molten steel, which will be captured by the solidified shell when entering the crystallizer during the continuous casting process and will easily crack during the stamping deformation process after rolling. Summary of the invention

[0004] In order to solve the current technical problem of slag rolling in the process of exchanging ladles, the present application provides a method for reducing slag rolling in the intermediate ladle during the process of exchanging ladles.

[0005] The present application provides a method for reducing slag rolling in the intermediate ladle during ladle exchange, comprising:

[0006] The first ladle stops pouring and rises;

[0007] The second ladle is placed above the tundish and gradually lowered, while blowing air to the shroud of the second ladle until the shroud of the second ladle is inserted to below the liquid level in the tundish by 280 mm to 320 mm; the shroud of the second ladle is connected to a skimmer, the skimmer comprises a connecting section and a skimmer section connected to each other, the connecting section is connected to the shroud, and the outer diameter of the skimmer section decreases from top to bottom;

[0008] Opening the slide plate of the second ladle to allow the molten steel to flow into the tundish through the long shroud of the second ladle, thereby completing the ladle exchange;

[0009] Wherein, when the insertion depth H of the long shroud is not greater than 150 mm, the blowing amount is greater than the blowing amount when the insertion depth H of the long shroud is greater than 150 mm, so as to reduce slag entanglement.

[0010] In some embodiments, the shroud insertion depth H and the air blowing volume N of the shroud meet the following relationship:

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

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

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

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

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

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

[0017] In some embodiments, the connecting section includes a plurality of spring pieces, which are sequentially spaced apart along the circumference of the slag skimming section and are located outside the long shroud.

[0018] In some embodiments, the inner diameter of the middle portion of the connecting segment is smaller than the inner diameters of the two 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 part is α(D-10) mm, and the inner diameter of the lower end is α(D+30) mm, wherein D is the original inner diameter of the long water nozzle, and the value range of α is 0.9 to 1.

[0020] In some embodiments, in the entire casting process, α from the first heat to the set heat is greater than α from the set heat to the last heat, and the set heat is greater than 1 and less than the heat of the last heat.

[0021] In some embodiments, the relationship between α and the heat in the entire casting is:

[0022] From the first furnace to the set furnace: the value range of α is 0.95 to 1;

[0023] Set the furnace to the last furnace, and the value range of α is 0.9~0.95.

[0024] According to the method for reducing tundish slag during ladle exchange provided by the embodiment of the present application, while using a slag skimmer, the blowing flow rate during the descent of the long shroud is controlled, the blowing volume is large in the early stage of descent, the flow field disturbance is large, the melting of the slag skimmer is promoted, and the separation of the slag skimmer from the adhered tundish slag is promoted, and the tundish slag is broken. The blowing volume is small in the later stage, which makes the flow field more stable, promotes the floating of small particles of tundish slag, reduces the amount of slag in the molten steel, improves the cleanliness of the product, and reduces the stamping cracking rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The schematic diagram shows the structure of the ladle injecting molten steel into the tundish.

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

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

[0028] Description of reference numerals:

[0029] 10-slag skimmer, 11-connecting section, 12-slag skimmer section, 20-mechanical arm, 21-handle, 22-support ring, 30-ladle, 40-long shroud, 50-tundish. DETAILED DESCRIPTION

[0030] In order to make the technical personnel in the technical field to which the present application belongs to understand the present application more clearly, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

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

[0032] See also Figure 1 During the continuous casting process of changing the ladle 30, the new ladle 30 needs to move downward, and move with the long water nozzle 40 and the slag skimmer 10 into the molten steel in the tundish 50. The slag skimmer 10 enters the molten steel and gradually melts into molten steel. The new ladle 30 does not have a long water nozzle 40 installed at the lower end. Therefore, before the new ladle 30 descends, the slag skimmer 10 needs to be installed at the lower end of the long water nozzle 40 of the new ladle 30 through the robotic arm 20. The ladle 30 descends, and moves downward with the long water nozzle 40 into the molten steel in the tundish 50 to achieve the slag skimming effect. Therefore, before introducing the method of reducing the slag rolling of the tundish 50 during the exchange of the ladle 30, the slag skimmer 10 and the robotic arm 20 involved in the method provided in the present application are first introduced:

[0033] See also Figure 2 The slag skimmer 10 includes a connecting section 11 and a slag skimmer section 12 connected to each other. A through hole is provided at the lower end of the slag skimmer section 12, so that when the long water nozzle 40 is blown, the gas is discharged from the through hole. The connecting section 11 is connected to the long water nozzle 40. The outer diameter of the slag skimmer section 12 decreases from top to bottom. Therefore, the tip of the slag skimmer section 12 is first inserted into the slag layer of the tundish 50 and the molten steel in turn, thereby guiding the long water nozzle 40 to be inserted into the molten steel, reducing the amount of slag sticking to the long water nozzle 40, and thus reducing slag rolling.

[0034] The mechanical arm 20 is used as a connection tool for the skimmer 10 and the long shroud 40. In some embodiments, refer to Figure 3 The mechanical arm 20 includes a handle 21 and a support ring 22 for inserting the skimmer section 12 of the skimmer 10, and the handle 21 is connected to the support ring 22. The skimmer section 12 is conical, and its lower end is inserted into the support ring 22, the middle of the skimmer section 12 contacts the support ring 22, and the upper end is located above the support ring 22. By manually operating the handle 21, the connecting section 11 is sleeved outside the long shroud 40, so that the skimmer 10 is connected to the long shroud 40.

[0035] After understanding the existing structures of the slag skimmer 10 and the robot arm 20 , the method for reducing slag rolling in the intermediate ladle 50 during the exchange of the ladle 30 provided by the present application will be described in detail below.

[0036] Methods for reducing slag roll-up in the intermediate ladle 50 during the ladle 30 exchange process include:

[0037] Step 1: The first ladle stops pouring and rises;

[0038] Step 2: Place the second ladle above the tundish 50, gradually lower it, and blow air to the long shroud 40 of the second ladle until the long shroud 40 of the second ladle is inserted to 280mm to 320mm below the liquid level in the tundish 50; the long shroud 40 of the second ladle is connected to the skimmer 10,

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

[0040] The ladle 30 is a container for holding clean molten steel. Generally speaking, after the LF refining process or the RH refining process, the ladle 30 will obtain clean molten steel with composition and temperature that meet the requirements. The ladle 30 is transferred from the refining process with the clean molten steel to the ladle 30 turntable. The ladle 30 turntable has two workstations, and the ladles 30 on the two workstations are cast alternately.

[0041] In step 1, the molten steel in the previous ladle 30 is poured out, and the first ladle rises with the shroud 40 of the first ladle, and then the shroud 40 is manually removed. Then, the first ladle is rotated by rotating the ladle 30 turntable, and the second ladle is rotated to the top of the tundish 50, and then the removed shroud 40 and the skimmer 10 are connected to the bottom of the second ladle in sequence, and then the second ladle descends with the shroud 40 and the skimmer 10, so that the shroud 40 is inserted into the molten steel in the tundish 50. Since the outer diameter of the skimming section 12 of the skimmer 10 decreases from top to bottom, the tip of the skimmer 10 is first inserted into the slag layer on the surface of the molten steel in the tundish 50. As the skimmer 10 is continuously inserted, part of the slag in the tundish 50 will adhere to the surface of the skimmer 10, and part will gradually move away from the skimmer 10 on the liquid surface, so as to prevent a large amount of slag in the tundish 50 from entering the shroud 40. After the skimmer 10 enters the molten steel in the tundish 50, the tip melts first. Due to the slag of the tundish 50 attached to the body of the skimmer 10, the body first forms a network in a very short time, and then slowly and completely melts into molten steel. The slag of the tundish 50 carried by it also gradually changes from large particles to small particles and floats into the slag.

[0042] Before the slide plate of the second ladle is opened, argon is blown into the shroud 40, and the argon moves downward from the upper end of the shroud 40 and is discharged from the through hole at the lower end of the slag skimming section 12, so that the air in the shroud 40 can be discharged to avoid secondary oxidation when the molten steel in the second ladle flows out from the shroud 40. The insertion depth of the shroud 40 refers to the distance between the lower end of the shroud 40 and the molten steel surface in the tundish 50. Since the blowing amount when the insertion depth H of the shroud 40 is not greater than 150 mm is greater than the blowing amount when the insertion depth H of the shroud 40 is greater than 150 mm, that is, as the insertion depth of the shroud 40 is deeper, the blowing amount is smaller.

[0043] In the early stage of the slag skimmer 10 entering the molten steel, the depth is shallow and slag is not easy to be entangled. Even if slag is entangled, there is enough time for it to float up and be removed; and the size of the slag skimmer 10 is relatively large, and it carries more slag in the ladle 50, and the overall mass and size are relatively large. Large air volume blowing can promote the melting of the slag skimmer 10, and at the same time, it can also promote the separation of the slag in the ladle 50 and the slag skimmer 10; in the later stage of the slag skimmer 10 entering the molten steel, the depth is deep, and as the slag skimmer 10 melts, its size will also become smaller, the through hole will gradually become larger, and the slag in the ladle 50 will also be gradually broken into small particles. The small amount of air blowing has little disturbance on the small particles of the ladle 50 slag, and slag is not easy to be entangled.

[0044] The present application controls the blowing volume at different periods of the insertion depth of the long shroud 40, thereby avoiding secondary oxidation of molten steel, improving the slag skimming effect of the slag skimmer 10, and reducing the risk of slag rolling.

[0045] In some embodiments, the blowing volume when the long water nozzle 40 is inserted to a depth H of no more than 150 mm, the blowing volume when the long water nozzle 40 is inserted to a depth of 150 mm<H<300 mm, and the blowing volume when the long water nozzle 40 is inserted to a depth of H≥300 mm are successively reduced, which is combined with the state change during the melting process of the skimmer 10 to promote 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 to promote 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 shroud 40 and the blowing volume N of the shroud 40, in some embodiments:

[0047] When H≤150mm, N is 110L / min-200L / min, such as 120L / min, 125L / min, 130L / min, 140L / min, 150L / min, 160L / min, 170L / min, 180L / min or 190L / min, etc.;

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

[0049] When the insertion depth is not higher than 150mm, the blowing volume is greater than 200L / min, which may cause severe disturbance of the molten steel to a certain extent. The slag in the tundish 50 is drawn into the molten steel and is affected by the steel flow field and is difficult to float up. When the blowing volume is less than 110L / min, it may affect the separation effect of the slag skimmer 10 and the slag in the tundish 50 in the early stage to a certain extent. In the later stage, more small particles of slag in the tundish 50 will remain in the tundish 50, and some of the small particles of slag in the tundish 50 may not have time to float up and enter the ingot, affecting the surface quality of the steel coil.

[0050] When the insertion depth is higher than 150mm, the blowing volume is less than 80L / min, which is not conducive to the floating of small particles of 50 slag in the tundish to a certain extent, affecting the surface quality of the steel coil. When the blowing volume is greater than 110L / min, the molten steel flow may be violently disturbed to a certain extent, which is not conducive to the floating of small particles of 50 slag in the tundish, affecting the surface quality of the steel coil.

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

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

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

[0054] The skimmer 10 is a hollow tubular structure. The through hole at the lower end can be used as an outlet for blowing gas. The gas discharged from the through hole moves upward, which can drive the tundish slag to float. In some embodiments, the wall thickness of the skimmer 10 decreases from top to bottom, that is, the wall thickness of the upper end of the skimmer 10 is thick, and the wall thickness of the lower end is thin, so that the lower part of the skimmer 10 melts first and the upper part melts later, which not only realizes the skimming function, but also accelerates the melting of the skimmer 10 from bottom to top, promotes the separation of the skimmer 10 from the tundish 50 slag, and reduces the tundish 50 slag entering the molten steel. In other embodiments, the wall thickness of the skimmer 10 is the same at each position, which can also achieve melting from bottom to top.

[0055] In some embodiments, the skimmer 10 is a steel skimmer, which does not pollute the molten steel after melting. In other embodiments, the skimmer 10 can also be an alloy skimmer, and the material of the alloy skimmer can be the same as the type of alloy required 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~1.5mm, for example 0.9mm, 1mm, 1.2mm, 1.3mm or 1.4mm, etc., and the wall thickness of the lower end of the skimming section 12 can be 0.2mm~0.5mm, for example 0.3mm, or 0.4mm, etc., which can melt quickly and realize the skimming function.

[0057] In some embodiments, the connecting section 11 includes a plurality of spring pieces, such as 5, 6 or 8, which are sequentially arranged at intervals along the circumference of the skimmer section 12 and are located outside the long shroud 40. The connection between the skimmer 10 and the long shroud 40 is achieved by abutting the outer circumference of the long shroud 40 with the plurality of spring pieces. The spring piece may be a spring piece, such as a steel spring piece or other alloy spring pieces, which is not limited in the present application.

[0058] In some embodiments, the inner diameter of the middle part of the connecting section 11 is smaller than the inner diameters of the two ends. The diameter of the upper end is large, which can guide the connecting section 11 to be sleeved outside the long water outlet 40. The inner diameter of the middle part is small, which can achieve tight clamping between the connecting section 11 and the long water outlet 40. The diameter of the lower end is large, 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, wherein D is the original inner diameter of the long water nozzle 40, and the value range of α is 0.9 to 1.

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

[0061] The long water nozzle 40 is made of refractory material. As the casting process proceeds, the lower end of the long water nozzle 40 will be worn and its outer diameter will become smaller. Therefore, in the entire casting process, the α of the front furnace is relatively large, and the upper end diameter of the connecting section 11 is large, while the α of the rear furnace is relatively small, and the upper end diameter of the connecting section 11 is small, which matches the size change of the long water nozzle 40 and has higher connection stability.

[0062] In some embodiments, the relationship between α and the heat in the entire casting is:

[0063] From the first furnace to the set furnace: the value range of α is 0.95 to 1;

[0064] Set the furnace to the last furnace, and the value range of α is 0.9~0.95.

[0065] Example 1

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

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

[0068] The α coefficient of the skimmer 10 for the rear 4 furnaces is 0.92, so 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 process of inserting the molten steel into the tundish 50, argon is blown into the shroud 40, and the argon gas volume and immersion depth are controlled as follows: when the insertion depth of the shroud 40 is 0-150mm, the blowing volume is controlled at 120L / min; when the insertion depth of the shroud 40 is 150-300mm, the blowing volume is controlled at 100L / min; when the insertion depth of the shroud 40 is ≥300mm, the blowing volume is controlled at 90L / min.

[0070] After adopting the solution of the embodiment, the slag involvement of the intermediate package 50 during the package change process can be effectively reduced, and the defect rate caused by stamping cracking at the client end is reduced by 55%.

[0071] Example 2

[0072] The casting steel type is low carbon steel. A total of 10 furnaces are cast in this casting. The original outer diameter of the long nozzle 40 is 220mm.

[0073] The α coefficient of the first five furnace skimmers 10 is 0.97, so 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 for the rear 5 furnaces is 0.93, so the diameter of the upper end of the connecting section 11 of the skimmer 10 is 260 mm, the diameter of the middle part is 195 mm, and the diameter of the lower end is 233 mm.

[0075] During the process of inserting the tundish 50 steel liquid, the air volume and immersion depth of the shroud 40 are controlled as follows: the shroud 40 insertion depth is 0-150mm, the air blowing volume is controlled at 150L / min, the shroud 40 insertion depth is 150-300mm, the air blowing volume is controlled at 108L / min, the shroud 40 insertion depth is ≥300mm, and the air blowing volume is controlled at 90L / min. The technology of the present invention can effectively reduce the slag involvement of the tundish 50 during the shroud change process, and the defect rate caused by stamping cracking of the client is reduced by 49%.

[0076] Example 3

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

[0078] The α coefficient of the skimmer 10 of the first three furnaces is 0.96, and the β coefficient of the mechanical 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 slag skimmer 10 of the rear 5 furnaces is 0.91, and the β coefficient of the mechanical arm 20 is 0.67. Therefore, the upper end diameter of the connecting section 11 of the slag skimmer 10 is 264 mm, the middle diameter is 200 mm, and the lower end diameter is 237 mm.

[0080] During the process of inserting the tundish 50 steel liquid, the air volume and immersion depth of the shroud 40 are controlled as follows: the shroud 40 insertion depth is 0-150mm, the blowing volume is controlled at 170L / min, the shroud 40 insertion depth is 150-300mm, the blowing volume is controlled at 98L / min, the shroud 40 insertion depth is ≥300mm, and the blowing volume is controlled at 85L / min. The technology of the present invention can effectively reduce the slag involvement of the tundish 50 during the shroud change process, and the defect rate caused by stamping cracking of the client is reduced by 44%.

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

[0082] (1) A new slag skimmer 10 is added during the ladle changing process. During the ladle changing process, due to the addition of the conical slag skimmer 10, when the long shroud 40 is inserted into the molten steel, the head of the slag skimmer 10 contacts the molten steel and skims off the slag in the tundish 50, which gradually melts. When the long shroud 40 is inserted deeper, the slag skimmer 10 is completely melted, and the slide plate is opened to start pouring. Therefore, the slag skimmer 10 solves the problem of slag rolling in the tundish 50 during the ladle changing process from the source.

[0083] (2) Control the blowing volume of argon gas of the long shroud 40 in stages. Due to the use of the slag skimmer 10, the disturbed area of ​​the liquid surface of the tundish 50 increases. Therefore, the blowing volume is adjusted in stages according to the different insertion depths of the long shroud 40. When the insertion depth of the long shroud 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 slag skimmer 10. The blowing volume of the long shroud 40 is large, which promotes the separation of the slag skimmer 10 from the slag of the tundish 50 and accelerates the melting of the slag skimmer 10. When the insertion depth of the long shroud 40 is deep, the blowing volume of the long shroud 40 becomes smaller, which not only accelerates the melting of the slag skimmer 10, but also reduces the disturbance to the molten steel and promotes the floating of the slag of the tundish 50. In the process of further deepening the insertion depth of the long shroud 40, a smaller amount of gas is used for blowing, the flow field is stable and the flow rate is small. The slag of the tundish 50 adsorbed on the slag skimmer 10 is called small particle slag as the slag skimmer 10 is completely dissolved, and it floats faster in a relatively calm flow field.

[0084] (3) The size of the connecting section 11 is adjusted according to the change of the shroud 40 with the casting. In this casting, the shroud 40 is lightly corroded from the first furnace to the middle furnace, so the size of the skimmer 10 needs to be designed to be larger, which is conducive to the skimmer 10 to grasp the shroud 40 more conveniently while ensuring the grip. In this casting, the shroud 40 has been corroded from the middle furnace to the last furnace, so the setting coefficient of the connecting section 11 of the skimmer 10 needs to be reduced to better grasp the shroud 40. The present invention has a simple structure and is easy to use. After adopting the technology of the present invention, the slag rolling of the tundish 50 can be effectively reduced, and the stamping cracking rate caused by the slag rolling of the tundish 50 is reduced by 40-80%.

[0085] In the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0086] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise" and "counterclockwise" indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0087] In this application, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0088] In addition, the descriptions of "first", "second", etc. in this application are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

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

Claims

1. A method for reducing slag in the intermediate ladle during ladle exchange, characterized in that: include: The first ladle stops pouring and rises; The second ladle is placed above the tundish and gradually lowered, while blowing air to the shroud of the second ladle until the shroud of the second ladle is inserted to below the liquid level in the tundish by 280 mm to 320 mm; the shroud of the second ladle is connected to a skimmer, the skimmer comprises a connecting section and a skimmer section connected to each other, the connecting section is connected to the shroud, and the outer diameter of the skimmer section decreases from top to bottom; Opening the slide plate of the second ladle to allow the molten steel in the second ladle to flow into the tundish through the long shroud, thus completing the ladle exchange; The air blowing amount when the insertion depth H of the long shroud is not greater than 150 mm is greater than the air blowing amount when the insertion depth H of the long shroud is greater than 150 mm, so as to reduce slag entanglement.

2. The method for reducing slag entrainment in the ladle during ladle exchange according to claim 1, characterized in that: The insertion depth H of the shroud and the blowing volume N of the shroud meet the following relationship: When H≤150mm, N is 110L / min~200L / min; When H>150mm, N is 80L / min~110L / min.

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

4. The method for reducing slag inclusion in the intermediate ladle during ladle exchange according to any one of claims 1 to 3, characterized in that: From top to bottom, the wall thickness of the slag skimming section decreases successively.

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

6. The method for reducing slag inclusion in the intermediate ladle during ladle exchange according to any one of claims 1 to 3, characterized in that: The connecting section comprises a plurality of spring pieces, which are sequentially arranged at intervals along the circumference of the slag skimming section and are located outside the long shroud.

7. The method for reducing slag entrainment in the ladle during ladle exchange according to claim 6, characterized in that: The inner diameter of the middle portion of the connecting section is smaller than the inner diameters of the two ends.

8. The method for reducing slag entrainment in the ladle during ladle exchange according to claim 7, characterized in that: The inner diameter of the upper end of the connecting section 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, wherein D is the original inner diameter of the long nozzle, and the value range of α is 0.9-1.

9. The method for reducing slag entrainment in the ladle during ladle exchange according to claim 8, characterized in that: In 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, and the set furnace is greater than 1 and less than the last furnace.

10. The method for reducing slag entrainment in the ladle during ladle exchange according to claim 9, characterized in that: The relationship between α and the number of heats in the entire casting process is: From the first furnace to the set furnace: the value range of α is 0.95 to 1; Set the furnace to the last furnace, and the value range of α is 0.9~0.95.

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