Control method for improving tank turning cleanliness of thick top slag

Abstract

The invention discloses a control method for improving the tank turning cleanliness of thick top slag, and belongs to the technical field of steel smelting. The control method disclosed by the invention mainly comprises the following steps: reducing the moving-out temperature at the last stage of LF furnace smelting in a refining process and reducing the addition amount of thick slag material lime of thick top slag to reduce the viscosity of the thick top slag so as to enable the thick top slag to reach a state suitable for tank turning, and increasing the addition amount of a thermal insulation material in a semicircular side area of a tank turning opening of a molten steel tank before loading and casting, the top slag skull probability in the tank turning opening area is reduced, in the tank turning process, the tank turning speed, the tank turning angle and the waiting time of the maximum tank turning angle are increased according to the thick slag characteristic, top slag can be smoothly turned out, after tank turning, the tank body with serious slag accumulation on the side of the tank turning opening is cleaned, and smoothness of a tank turning channel is guaranteed. The method successfully solves the problem of low tank turning cleaning rate of the thick top slag in the prior art, reduces the tapping temperature drop of the converter, improves the production efficiency and reduces the production cost.

Description

Technical Field

[0001] The invention belongs to the technical field of steel smelting, and in particular relates to a control method for improving the cleanliness of viscous top slag tank turning. Background Art

[0002] In the steelmaking process, top slag is an important part of the secondary refining process, and its composition, properties and state directly affect the secondary refining effect of steel. Among them, in order to meet the technical requirements of certain process paths, thick top slag is a common type of top slag, but due to its high viscosity, it is easy to produce slag hanging, agglomeration, and large-area slag bottom during the tank turning process, resulting in low cleanliness during tank turning, which seriously affects steelmaking efficiency, production costs and product quality.

[0003] The invention patent with the publication number CN110468257A discloses a ladle top slag modification method suitable for low-carbon and ultra-low-carbon steel, which includes: 1. During the converter steel tapping process, the ladle does not blow argon, and does not add any deoxidizer or slag-making material; 2. After the steel tapping is completed, a strong deoxidizing ferroalloy with a specific gravity between the top slag and the molten steel is added to the ladle, and the amount of the strong deoxidizing ferroalloy added is determined according to the actual amount of molten steel in the ladle; 3. After the strong deoxidizing ferroalloy is added, lime flux is added to the ladle, and the amount of lime added is determined according to the actual amount of molten steel in the ladle; 4. When the RH cycle breaks through the vacuum chamber, before the molten steel just drops out of the vacuum chamber, a strong deoxidizing alloy is added to the molten steel in the vacuum chamber, and the amount of the strong deoxidizing alloy added is determined according to the actual amount of molten steel; 5. The operation method of RH decarburization, deoxidation and alloying is the same as the current conventional method of the steel plant. The application of the present invention can significantly change the oxidation of the ladle top slag, and the cleanliness index of the molten steel is improved to varying degrees, and the modification process does not pollute the on-site environment, which can meet environmental protection requirements. However, the prior art only involves methods for modifying ladle top slag, but does not involve methods for effectively controlling the cleanliness of thick top slag during ladle turning. Researching and developing a control method for improving the cleanliness of thick top slag during ladle turning is an urgent problem to be solved in the steelmaking industry. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a control method for improving the cleanliness of thick top slag tank turning, so as to solve the problem of low cleanliness of thick top slag tank turning in the prior art, thereby reducing the temperature drop of steel tapping from the converter, increasing the service life of the molten steel tank, reducing the inclusion content in the molten steel, improving production efficiency and reducing production costs.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a control method for improving the cleanliness of a viscous top slag tank turning process, comprising the following steps:

[0007] (1) The removal temperature at the end of LF furnace smelting in the refining process is reduced and the amount of lime added to the thick slag is reduced to reduce the viscosity of the thick top slag to make it reach a state suitable for tank turning. During the thick slag process at the end of LF furnace smelting, the amount of lime added to the thick slag is controlled to be 4-5.5 kg / ton of steel, corresponding to the molten steel removal temperature of 1565-1570°C;

[0008] (2) Before pouring on the machine, add insulation to the top slag surface of the molten steel tank. The insulation covering thickness of the semicircular side area of ​​the molten steel tank opening is ≥30mm. It should be spread in a fan-shaped manner from the center of the molten steel tank opening to the tank wall of the molten steel tank opening to ensure that the insulation covering the contact area between the tank wall and the top slag is fully covered with a covering thickness of ≥40mm, so as to avoid the top slag solidification crust caused by the rapid temperature drop of the top slag near the tank wall and the welding with the molten steel tank wall to block the slag turning channel;

[0009] (3) Before turning over the tank, the steel ladle is shaken at an angle of 30° to 60°, so that the viscous top slag is evenly distributed in the steel ladle during the subsequent turning over process, thereby improving the cleanliness of the tank; after the shaking is completed, the tank turning procedure is carried out, and the turning speed and angle are controlled. The turning speed is controlled to be 4.5° / s to 5.5° / s, and the turning angle is controlled to be between 165° and 175°. The waiting time at the maximum angle is ≥30 seconds, so that the top slag can be separated from the tank body as soon as possible, avoiding the problems of slag hanging on the tank wall, slag accumulation at the tank mouth, and agglomeration;

[0010] (4) After the tank is turned over, when the longest lateral slag growth on the side of the tank opening is ≥ 10% of the diameter of the tank opening, compulsory cleaning is carried out to remove obstacles at the slag turning channel and improve the cleanliness of the tank turning.

[0011] Based on the above technical scheme, further, the composition control range of the thick top slag after thickening in step (1) is as follows: CaO: 45%~55%, SiO2: 15%~22%, Al2O3≤10%, MgO≤15%, FeO≤1%, Fe2O3≤0.2%, MnO≤0.5%, TiO2≤1%, and the basicity R is controlled between 3.3 and 3.8.

[0012] Based on the above technical solution, further, in step (2), the amount of insulation added on the semicircular side of the tank mouth is 0.8 to 1.2 kg / ton of steel, and the amount of insulation added on the other semicircular side of the tank mouth is 0.3 to 0.7 kg / ton of steel.

[0013] Based on the above technical solution, further, the heat-insulating agent in step (2) includes carbonized rice husks and a composite heat-insulating agent mainly composed of carbon materials.

[0014] Based on the above technical solution, further, in step (4), cleaning is performed when the longest lateral slag growth on the steel ladle opening side reaches 10 to 20% of the steel ladle opening diameter.

[0015] Based on the above technical scheme, further, the chemical composition and weight percentage of the molten steel in the molten steel tank are as follows: C: 0.72%~0.78%, Si: 0.50%~0.70%, Mn: 0.75%~1.05%, P≤0.025%, S≤0.025%, Cr≤0.15%, V: 0.040%~0.080%, Alt: ≤0.008%, and the balance is Fe and unavoidable impurities.

[0016] Based on the above technical scheme, further, before thickening the slag, the composition control range is as follows: CaO: 40%~50%, SiO2: 28%~35%, Al2O3: 5%~15%, MgO≤15%, FeO≤1%, Fe2O3≤0.2%, MnO≤0.5%, TiO2≤1%, and the basicity R is controlled between 1.8 and 2.3.

[0017] Based on the above technical solution, further, the amount of lime as a slagging agent added before thickening the slag is 2 to 4 kg / ton of steel, and the amount of bauxite as a slagging agent added is 0.5 to 1.5 kg / ton of steel.

[0018] The beneficial effects of the present invention compared with the prior art are as follows:

[0019] The control method of the present invention mainly includes lowering the removal temperature at the end of smelting of the LF furnace in the refining process and reducing the amount of lime added to the thick slag material of the thick top slag to reduce the viscosity of the thick top slag to make it reach a state suitable for tank turning. Before casting on the machine, the amount of insulation material added to the semicircular side area of ​​the steel ladle tank turning mouth is increased to reduce the probability of top slag solidification in the tank turning mouth area, so as to achieve the purpose of smoothly turning out the top slag; in the tank turning process, the tank turning speed, tank turning angle and waiting time for the maximum tank turning angle are increased according to the characteristics of the thick slag, so that the top slag can be turned out smoothly, avoiding the problems of slag hanging and slag accumulation on the tank turning mouth side; after turning the tank, the tank body with serious slag accumulation on the tank turning mouth side is cleaned to ensure the smoothness of the tank turning channel. The present invention successfully solves the problem of low cleanliness of the thick top slag in the prior art, thereby reducing the temperature drop of the converter steel tapping, improving the service life of the steel ladle, reducing the inclusion content in the molten steel, improving production efficiency and reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention, the drawings related to the embodiments are briefly introduced below.

[0021] Figure 1 The present invention is a flow chart of a control method for improving the cleanliness of a viscous top slag tank turning process.

[0022] Figure 2 This is a diagram of the cleaning effect in Example 1.

[0023] Figure 3 This is the cleaning effect diagram in Comparative Example 1. DETAILED DESCRIPTION

[0024] The present invention is described in detail below with reference to the embodiments, but the embodiments of the present invention are not limited thereto. Obviously, the embodiments described below are only partial embodiments of the present invention. For those skilled in the art, other similar embodiments obtained without creative labor all fall within the protection scope of the present invention.

[0025] Example 1

[0026] This embodiment provides a control method for improving the cleanliness of the viscous top slag tank during the smelting process of heavy rail steel U75V, such as Figure 1 As shown in Table 1, the chemical composition and weight percentage of heavy rail steel U75V are shown in Table 1.

[0027] Table 1 Chemical composition and weight percentage of heavy rail steel U75V

[0028]

[0029] The following steps are involved:

[0030] Step 1, adjusting the amount of lime added and the removal temperature of the thick slag at the end of the first refining;

[0031] Before thickening the slag, the amount of lime added as a slagging agent is 3kg / ton steel, and the amount of bauxite added as a slagging agent is 1kg / ton steel. The composition control range is shown in Table 2.

[0032] Table 2 Ingredient Control Range

[0033] CaO <![CDATA[SiO2]]> <![CDATA[Al2O3]]> MgO FeO <![CDATA[Fe2O3]]> MnO <![CDATA[TiO2]]> Alkalinity R 40～50％ 28～35％ 5-15％ ≤15％ ≤1％ ≤0.2％ ≤0.5％ ≤1％ 1.8-2.3

[0034] During the thick slag process at the end of the first refining (LF furnace), the target temperature of the tundish is 1500±5℃, and the amount of lime added to the thick slag is controlled to be 4Kg / ton of steel (reduced to 57% of the amount added in the original process). In order to ensure the stability of the temperature drop during the subsequent process, the composition control range of this type of thick top slag is clarified. The composition control range of the thick top slag is shown in Table 3;

[0035] Table 3 Composition control range of thick top slag after thickening

[0036] CaO <![CDATA[SiO2]]> <![CDATA[Al2O3]]> MgO FeO <![CDATA[Fe2O3]]> MnO <![CDATA[TiO2]]> Alkalinity R 45％ 15～22％ ≤10％ ≤15％ ≤1％ ≤0.2％ ≤0.5％ ≤1％ 3.3

[0037] The molten steel removal temperature of the first refining furnace (LF furnace) is set to 1565°C (15°C lower than the original process). The purpose of the composition of the thickened slag and the control range of the removal temperature of the LF furnace for smelting heavy rail steel specified in the present invention is not only to reduce the amount of thickened slag added while ensuring the viscosity of the top slag, to ensure the thickened slag effect of easy separation of the steel-slag interface of the thick top slag in the subsequent refining process (VD furnace) and the temperature drop stability of the process treatment; but also to make the state of the thick top slag before molten steel casting more inclined to the state of the top slag after the overall temperature drop after the molten steel tank is cast on the machine; thereby reducing the probability of a sudden increase in the viscosity of the top slag and poor fluidity caused by the temperature drop of the top slag after the casting is completed, and reducing the probability of premature hardening and coagulation of the thick top slag, and on the basis of the control method involved in the combined step 2, the target temperature of the casting tundish of the heavy rail steel can be stably controlled at 1500±5°C to meet the process requirements of the heavy rail steel;

[0038] Step 2: Before casting on the machine, add the top slag surface insulation agent to perform regional targeted control;

[0039] Before casting on the machine, the amount of insulation (carbonized rice husk) added to the semicircular side of the steel tank mouth is increased to twice the original amount (the insulation on the semicircular side of the steel tank mouth is increased to 1kg / ton of steel), and the insulation coverage thickness in this area must be ≥30mm as a whole, and it must be spread in a fan shape from the center of the steel tank mouth to the tank wall of the tank mouth. Focus on ensuring that the contact area between the tank wall and the top slag is fully covered with insulation, and the coverage thickness must be ≥40mm, in order to avoid the top slag solidification crust caused by the rapid temperature drop of the top slag near the tank wall and the welding with the steel tank wall to block the slag turning channel.

[0040] Step 3: Control the can turning speed and can turning angle;

[0041] During the tank turning process, in view of the characteristics of the thick top slag, a shaking process is added on the basis of the original normal tank turning, and the shaking angle is controlled at 30°, in order to make the thick top slag evenly distributed in the molten steel tank during the subsequent tank turning process, thereby improving the cleanliness of the tank turning; after the shaking is completed, the tank turning procedure is carried out, and the tank turning speed and angle are required to be controlled. The tank turning speed is controlled at 4.5° / second, and the tank turning angle is increased to 175°. The waiting time at the maximum angle is required to be ≥30 seconds, so that the top slag can be separated from the tank body as soon as possible to avoid the problems of slag hanging on the tank wall, slag accumulation at the tank mouth, and agglomeration. Specifically, according to the nature of the top slag and the size of the tank body, appropriate parameters such as the tank turning speed and the tank turning angle can be set to achieve the improvement of the cleanliness of the tank turning.

[0042] Step 4: Prepare the ladle and clean the slag at the ladle opening

[0043] After turning over the tank, the mouth of the molten steel tank shall be cleaned. For the slag edge on one side of the tank opening, if the longest lateral slag growth is greater than 10% of the diameter of the molten steel tank mouth, it shall be compulsory to clean it. (When the molten steel loading is 100 tons and the tank mouth diameter is 4 meters, when the longest part of the slag along the lateral growth tending to the center of the tank body diameter is greater than 400mm from the outer wall of the tank, it shall be cleaned) to remove the obstacles of the slag turning channel and improve the cleanliness of the tank turning.

[0044] Example 2

[0045] This embodiment provides a control method for improving the cleanliness of the viscous top slag tank during the smelting process of heavy rail steel U75V, such as Figure 1 As shown, the chemical composition and weight percentage of heavy rail steel U75V are shown in Table 1, which includes the following steps:

[0046] Step 1, adjusting the amount of lime added and the removal temperature of the thick slag at the end of the first refining;

[0047] Before thickening the slag, the amount of lime added as a slagging agent is 3kg / ton steel, and the amount of bauxite added as a slagging agent is 1kg / ton steel. The composition control range is shown in Table 2.

[0048] During the thick slag process at the end of the first refining (LF furnace), the target temperature of the tundish is 1500±5℃, and the amount of lime added to the thick slag is controlled to be 5kg / ton steel (reduced to 71% of the amount added in the original process). In order to ensure the stability of the temperature drop during the subsequent process, the composition control range of this type of thick top slag is clarified. The composition control range of the thick top slag is shown in Table 4;

[0049] Table 4 Composition control range of thick top slag after thickening

[0050] CaO <![CDATA[SiO2]]> <![CDATA[Al2O3]]> MgO FeO <![CDATA[Fe2O3]]> MnO <![CDATA[TiO2]]> Alkalinity R 52％ 15～22％ ≤10％ ≤15％ ≤1％ ≤0.2％ ≤0.5％ ≤1％ 3.6

[0051] The molten steel removal temperature of the first refining furnace (LF furnace) is set to 1568°C (12°C lower than the original process). The purpose of the composition of the thickened slag and the control range of the removal temperature of the LF furnace for smelting heavy rail steel specified in the present invention is not only to reduce the amount of thickened slag added while ensuring the viscosity of the top slag, to ensure the thickened slag effect of easy separation of the steel-slag interface of the thick top slag in the subsequent refining process and the temperature drop stability of the process treatment; but also to make the state of the thick top slag before molten steel casting more inclined to the state of the top slag after the overall temperature drop after the molten steel tank is cast on the machine; thereby reducing the probability of a sudden increase in the viscosity of the top slag and poor fluidity caused by the temperature drop of the top slag after the casting is completed, and reducing the probability of premature hardening and coagulation of the thick top slag, and on the basis of the control method involved in the combined step 2, the target temperature of the casting tundish of the heavy rail steel can be stably controlled at 1500±5°C to meet the process requirements of the heavy rail steel;

[0052] Step 2: Before casting on the machine, add the top slag surface insulation agent to perform regional targeted control;

[0053] Before casting on the machine, the amount of insulation (carbonized rice husk) added to the semicircular side of the steel tank mouth is increased to twice the original amount (the insulation on the semicircular side of the steel tank mouth is increased to 1kg / ton of steel), and the insulation coverage thickness in this area must be ≥30mm as a whole, and it must be spread in a fan shape from the center of the steel tank mouth to the tank wall of the tank mouth. Focus on ensuring that the contact area between the tank wall and the top slag is fully covered with insulation, and the coverage thickness must be ≥40mm, in order to avoid the top slag solidification crust caused by the rapid temperature drop of the top slag near the tank wall and the welding with the steel tank wall to block the slag turning channel.

[0054] Step 3: Control the can turning speed and can turning angle;

[0055] During the tank turning process, in view of the characteristics of the thick top slag, a shaking process is added on the basis of the original normal tank turning, and the shaking angle is controlled at 45°, in order to make the thick top slag evenly distributed in the molten steel tank during the subsequent tank turning process, thereby improving the cleanliness of the tank turning; after the shaking is completed, the tank turning procedure is carried out, and the tank turning speed and angle are required to be controlled. The tank turning speed is controlled at 4° / second, and the tank turning angle is increased to 170°. The waiting time at the maximum angle is required to be ≥30 seconds, so that the top slag can be separated from the tank body as soon as possible to avoid the problems of slag hanging on the tank wall, slag accumulation at the tank mouth, and agglomeration. Specifically, according to the nature of the top slag and the size of the tank body, appropriate parameters such as the tank turning speed and the tank turning angle can be set to achieve the improvement of the cleanliness of the tank turning.

[0056] Step 4: Prepare the ladle and clean the slag at the ladle opening

[0057] After turning over the tank, the mouth of the molten steel tank is cleaned. For the slag edge on one side of the tank opening, if the longest lateral slag growth is greater than 15% of the diameter of the molten steel tank mouth, it is necessary to carry out compulsory cleaning (when the molten steel loading is 100 tons and the tank mouth diameter is 4 meters, when the longest point of the slag along the lateral growth tending to the center of the tank body diameter is greater than 600mm from the outer wall of the tank, it is necessary to clean it) to remove obstacles at the slag turning channel and improve the cleanliness of the tank turning.

[0058] Example 3

[0059] This embodiment provides a control method for improving the cleanliness of the viscous top slag tank during the smelting process of heavy rail steel U75V, such as Figure 1 As shown, the chemical composition and weight percentage of heavy rail steel U75V are shown in Table 1, which includes the following steps:

[0060] Step 1, adjusting the amount of lime added and the removal temperature of the thick slag at the end of the first refining;

[0061] Before thickening the slag, the amount of lime added as a slagging agent is 3kg / ton steel, and the amount of bauxite added as a slagging agent is 1kg / ton steel. The composition control range is shown in Table 2.

[0062] During the thick slag process at the end of the first refining (LF furnace), the target temperature of the tundish is 1500±5℃, and the amount of lime added to the thick slag is controlled to be 5.5kg / ton steel (reduced to 78% of the original process addition amount on average). In order to ensure the stability of the temperature drop during the subsequent process, the composition control range of this type of thick top slag is clarified. The composition control range of the thick top slag is shown in Table 5.

[0063] Table 5 Composition control range of thick top slag after thickening

[0064] CaO <![CDATA[SiO2]]> <![CDATA[Al2O3]]> MgO FeO <![CDATA[Fe2O3]]> MnO <![CDATA[TiO2]]> Alkalinity R 55％ 15～22％ ≤10％ ≤15％ ≤1％ ≤0.2％ ≤0.5％ ≤1％ 3.8

[0065] The molten steel removal temperature of the first refining furnace (LF furnace) is set to 1570°C (10°C lower than the original process). The purpose of the composition of the thickened slag and the control range of the removal temperature of the LF furnace for smelting heavy rail steel specified in the present invention is not only to reduce the amount of thickened slag added while ensuring the viscosity of the top slag, to ensure the thickened slag effect of easy separation of the steel-slag interface of the thick top slag in the subsequent refining process and the temperature drop stability of the process treatment; but also to make the state of the thick top slag before molten steel casting more inclined to the state of the top slag after the overall temperature drop after the molten steel tank is cast on the machine; thereby reducing the probability of a sudden increase in the viscosity of the top slag and poor fluidity caused by the temperature drop of the top slag after the casting is completed, and reducing the probability of premature hardening and coagulation of the thick top slag, and on the basis of the control method involved in the combined step 2, the target temperature of the casting tundish of the heavy rail steel can be stably controlled at 1500±5°C to meet the process requirements of the heavy rail steel;

[0066] Step 2: Before casting on the machine, add the top slag surface insulation agent to perform regional targeted control;

[0067] Before casting on the machine, the amount of insulation (carbonized rice husk) added to the semicircular side of the steel tank mouth is increased to twice the original amount (the insulation on the semicircular side of the steel tank mouth is increased to 1kg / ton of steel), and the insulation coverage thickness in this area must be ≥30mm as a whole, and it must be spread in a fan shape from the center of the steel tank mouth to the tank wall of the tank mouth. Focus on ensuring that the contact area between the tank wall and the top slag is fully covered with insulation, and the coverage thickness must be ≥40mm, in order to avoid the top slag solidification crust caused by the rapid temperature drop of the top slag near the tank wall and the welding with the steel tank wall to block the slag turning channel.

[0068] Step 3: Control the can turning speed and can turning angle;

[0069] During the tank turning process, in view of the characteristics of the thick top slag, a shaking process is added on the basis of the original normal tank turning, and the shaking angle is controlled at 60°, in order to make the thick top slag evenly distributed in the molten steel tank during the subsequent tank turning process, thereby improving the cleanliness of the tank turning; after the shaking is completed, the tank turning procedure is carried out, and the tank turning speed and angle are required to be controlled. The tank turning speed is controlled at 5.5° / second, and the tank turning angle is increased to 165°. The waiting time at the maximum angle is required to be ≥30 seconds, so that the top slag can be separated from the tank body as soon as possible, avoiding the problems of slag hanging on the tank wall, slag accumulation at the tank mouth, and agglomeration. Specifically, according to the nature of the top slag and the size of the tank body, appropriate parameters such as the tank turning speed and the tank turning angle can be set to achieve the improvement of the cleanliness of the tank turning.

[0070] Step 4: Prepare the ladle and clean the slag at the ladle opening

[0071] After turning over the tank, the mouth of the molten steel tank is cleaned. For the slag edge on one side of the tank opening, if the longest lateral slag growth is greater than 20% of the diameter of the molten steel tank mouth, it is necessary to carry out compulsory cleaning (when the molten steel loading is 100 tons and the tank mouth diameter is 4 meters, when the longest point of the slag along the lateral growth tending to the center of the tank body diameter is greater than 800mm from the outer wall of the tank, it is necessary to clean it) to remove obstacles at the slag turning channel and improve the cleanliness of the tank turning.

[0072] Comparative Example 1

[0073] This comparative example provides a method for turning over the viscous top slag during the smelting process of heavy rail steel U75V. The chemical composition and weight percentage of the heavy rail steel U75V are shown in Table 1, and the method comprises the following steps:

[0074] Step 1: During the thick slag process at the end of the first refining (LF furnace), the target temperature of the tundish is 1500±5℃, the amount of lime added as a slag-making agent before thickening is 3kg / ton of steel, and the amount of bauxite added as a slag-reducing agent is 1kg / ton of steel. The composition control range is shown in Table 2. The amount of lime added to the thick slag is 7kg / ton of steel, and the temperature of the LF furnace out is 1580℃.

[0075] Step 2: Add a heat preservation agent (carbonized rice husk) before casting to cover the top slag surface. The amount added is 0.5 / ton of steel.

[0076] Step 3, can turning program, control the can turning speed and can turning angle, the can turning speed is controlled to 5° / second, and the can turning angle is 155°;

[0077] Step 4: After turning over the tank, for the accumulated slag edge on one side of the tank opening, the process requirement is that when the growth degree of the slag edge at the molten steel tank opening affects the operation of the subsequent process: such as blocking the LF furnace unloading port, etc., the slag edge of the tank opening should be cleaned.

[0078] Table 6 Statistics of cleanliness rate of Example 1 and Comparative Example 1

[0079]

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A control method for improving the cleanliness of viscous top slag tank turning, characterized in that: The steps include: (1) The removal temperature at the end of LF furnace smelting in the refining process is reduced and the amount of lime added to the thick slag is reduced to reduce the viscosity of the thick top slag to make it reach a state suitable for tank turning. During the thick slag process at the end of LF furnace smelting, the amount of lime added to the thick slag is controlled to be 4-5.5 kg / ton of steel, corresponding to the molten steel removal temperature of 1565-1570°C; (2) Add insulation to the top slag surface of the molten steel tank before casting. The insulation thickness of the semicircular side area of ​​the molten steel tank opening is ≥30mm, ensuring that the insulation in the contact area between the tank wall and the top slag is fully covered and the coverage thickness is ≥40mm; (3) Before turning over the tank, add a shaking process for the molten steel tank, and control the shaking angle at 30° to 60°. After the shaking is completed, the tank turning procedure is carried out, and the tank turning speed and angle are controlled. The tank turning speed is controlled to 4.5° / s to 5.5° / s, and the tank turning angle is controlled between 165° and 175°. The waiting time at the maximum angle is ≥30 seconds; (4) After the tank is turned over, when the longest lateral slag growth on the side of the tank opening is ≥ 10% of the diameter of the tank opening, compulsory cleaning is carried out to improve the cleanliness of the tank turning.

2. The control method according to claim 1, characterized in that: The composition control range of the thick top slag after thickening in step (1) is as follows: CaO: 45% to 55%, SiO2: 15% to 22%, Al2O3≤10%, MgO≤15%, FeO≤1%, Fe2O3≤0.2%, MnO≤0.5%, TiO2≤1%, and the basicity R is controlled between 3.3 and 3.

8.

3. The control method according to claim 1, characterized in that: In step (2), the amount of heat-insulating agent added to the semicircular side of the tank opening is 0.8-1.2 kg / ton of steel, and the amount of heat-insulating agent added to the other semicircular side of the tank opening is 0.3-0.7 kg / ton of steel.

4. The control method according to claim 1, characterized in that: The heat-insulating agent in step (2) includes carbonized rice husk and a composite heat-insulating agent mainly composed of carbon materials.

5. The control method according to claim 1, characterized in that: In step (4), cleaning is performed when the longest lateral slag growth on the side of the steel ladle opening reaches 10 to 20% of the diameter of the steel ladle opening.

6. The control method according to claim 1, characterized in that: Before thickening the slag, the composition control range is as follows: CaO: 40%~50%, SiO2: 28%~35%, Al2O3: 5%~15%, MgO≤15%, FeO≤1%, Fe2O3≤0.2%, MnO≤0.5%, TiO2≤1%, and the basicity R is controlled between 1.8 and 2.

3.

7. The control method according to claim 6, characterized in that: Before thickening the slag, the amount of lime added as a slagging agent is 2 to 4 kg / ton of steel, and the amount of bauxite added as a slagging agent is 0.5 to 1.5 kg / ton of steel.

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