Method for environmental modification of if steel top slag

Abstract

The application discloses an IF steel top slag environment-friendly modification method and belongs to the technical field of converter, refining, continuous casting and ladle logistics. The IF steel top slag environment-friendly modification method solves the problems of non-environmental protection and cost increase in the prior art. The IF steel top slag environment-friendly modification method adopts the ladle casting residual slag of a converter LF-RH continuous casting process path, weighs the reducing slag at the end of continuous casting, and then pours the reducing slag into a ladle at the end of hot repair masonry. The ladle is used to receive converter IF steel molten steel. The reducing property of the reducing slag is used to reduce the oxidizing property of the top slag. In addition, corresponding small lime is added according to the weight of the reducing slag during the converter tapping process. The reducing property of the ladle casting residual slag is utilized. The reducing property of the IF steel top slag is modified by using the reducing property of the reducing slag at the end of continuous casting. The oxidizing property of the top slag can be reduced. The heat of the reducing slag is used to reduce the discharge of the slag and steel. In addition, the traditional modifier is not used. The hot reducing slag at the end of continuous casting is used. A large amount of smoke dust generated in the process of modifying the top slag is avoided. Therefore, the purpose of IF steel green environmental protection and low-cost modification is achieved.

Description

Technical Field

[0001] This invention relates to the fields of converter, refining, continuous casting, and ladle logistics technology, specifically a method for environmentally friendly modification of top slag in IF steel. Background Technology

[0002] During the converter tapping process, highly oxidizing slag inside the converter is inevitably carried into the ladle by the molten steel. The main harm of top slag to molten steel occurs from the end of refining to continuous casting. Top slag will transfer oxygen into the molten steel, causing secondary oxidation. Because the molten steel in this process does not have good kinetic stirring conditions, the secondary oxidized inclusions are not easy to float to the surface, directly deteriorating the quality of the cast billet.

[0003] Chinese patent CN103374642B discloses a deoxidizing modifier for ladle top slag. The main components of this modifier, by mass percentage, are: Al: 30-50%, CaO: 50-30%, Al₂O₃: 5.0-8.0%, SiO₂: ≤3.0%, S+P≤0.07%, C: 0.7-1.4%, CaF₂: 3.0-8.0%, and H₂O≤0.2%. This patented modifier is a reducing modifier, which can solve the oxidation problem of ladle top slag during low-carbon steel production, providing a guarantee for vacuum desulfurization and purified production of pipeline steel. However, the patent has a problem: the modifier has a particle size of 10-30 mm, and the Al particle size is less than 1 mm. When added to the surface of the ladle top slag after tapping from the converter, the top slag and the modifier react rapidly, quickly generating a large amount of flue gas, polluting the air, and seriously affecting the occupational health of workers.

[0004] Chinese patent CN109252010A discloses a smelting method for controlling the oxidizability of top slag in IF steel. This method includes four main processes: converter smelting (LD), LF furnace refining, RH refining, and continuous casting (CC). The patented method achieves more stable oxidizability of the top slag and oxygen content in the steel at the end of RH refining. The patent relates to LF furnace refining: after the molten steel arrives at the station, a heating operation is performed for 8–12 minutes to raise the temperature by 10–20°C. Then, 1.0–1.5 kg of carbon powder per ton of molten steel is added to the slag surface. At the end of LF furnace refining, the oxygen content [O] in the steel is 300–500 ppm, the molten steel temperature is 1670–1690°C, and the oxidizability of the top slag (wT.Fe) is 6–8%. However, the patent has a problem: the method involves refining the steel in the LF furnace after tapping, adding a refining step to the IF production process, resulting in a longer production cycle, greater heat loss, and a significant increase in production costs.

[0005] Therefore, since the existing requirements are not met, we propose an environmentally friendly method for upgrading IF steel top slag. Summary of the Invention

[0006] The purpose of this invention is to provide an environmentally friendly method for upgrading IF steel top slag. By recycling the reducing slag from the converter LF-RH continuous casting process, the oxidizing properties of IF steel top slag are reduced, thereby achieving the goal of green, environmentally friendly, and low-cost upgrading of IF steel and solving the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for environmentally friendly upgrading of IF steel top slag, comprising the following steps:

[0008] Step 1: Using the LF-RH continuous casting process, the weight of the ladle ai and the slag residue after the continuous casting is △G1. The slag residue is added to the empty ladle aj that is to receive the molten steel. The empty ladle aj is weighed and the weight of the empty ladle ai is △G2.

[0009] Step 2: Based on the weight of the slag residue, add small lime and aluminum granules to the steel stream during the converter tapping process;

[0010] Step 3: When the steel ladle AJ is being hot-repaired on the tilting platform, the permeable bricks, inlet and outlet water outlets, and sliding plate equipment are repaired in sequence. After the repair is completed, the sliding plate is closed, and drainage sand is added to the water outlet channel as required.

[0011] Step 4: The slag residue from the ladle after continuous casting is added to the ladle to be held by the molten steel for hot repair.

[0012] Step 5: Use the reducing slag from the LF-RH continuous casting process in the converter to modify the top slag of the next heat of IF steel.

[0013] Furthermore, in step one, the steel ladles are numbered respectively, specifically including a1, a2, a3...ai, aj...an.

[0014] Furthermore, the weight of the casting residue is expressed by the following formula:

[0015] △G=△G1-△G2,

[0016] During the converter tapping process, a certain amount of lime and aluminum granules are added based on the weight of the residual slag calculated according to the above formula.

[0017] Furthermore, the amount of lime added is:

[0018] △G≤1t, the amount of lime added is 1±0.3kg / t;

[0019] 1<△G≤2t, the amount of lime added is 1.5±0.3kg / t;

[0020] 2<△G≤3t, the amount of lime added is 2.5±0.3kg / t;

[0021] 4<△G≤5t, the amount of lime added is 3±0.3kg / t;

[0022] △G>5t, the amount of lime added is 3.5±0.3kg / t.

[0023] Furthermore, the aluminum granules need to be added according to the oxygen content at the converter endpoint, and the amount of aluminum granules added is:

[0024] [O] < 350 ppm, aluminum granules added amount 50 ± 20 kg;

[0025] 350ppm≤[O]<450ppm, aluminum granules added amount is 70±20kg;

[0026] 450ppm≤[O]<550ppm, aluminum particle addition amount is 90±20kg;

[0027] [O]≥550ppm, aluminum granules added amount is 110±20kg.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] 1. This invention adopts the converter LF-RH continuous casting process. After the molten steel is cast, there will be residual liquid reducing slag in the ladle. The reducing slag after the continuous casting is finished is weighed and added to the ladle after hot repair and lining. This ladle is used to receive IF steel from the converter. The top slag can be modified and the reducing slag in the converter LF-RH continuous casting process can be utilized. The reducing slag after casting can be used to modify the top slag of IF steel, which not only reduces the oxidation of the top slag, but also uses its heat to reduce the discharge of slag steel.

[0030] 2. This invention does not use traditional modifiers. The hot reducing slag ensures the modification effect while significantly reducing the cost. At the same time, it avoids the generation of a large amount of smoke and dust during the top slag modification process, thereby achieving the goal of green, environmentally friendly and low-cost modification of IF steel. Attached Figure Description

[0031] Figure 1 This is a flowchart of the environmentally friendly upgrading method for IF steel top slag of the present invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] To address the technical problems arising from the rapid chemical reaction between existing modifiers and top slag, which generates large amounts of flue gas, pollutes the air, seriously affects the occupational health of workers, and results in long production cycles, significant heat loss, and substantial increases in production costs, please refer to [the relevant documentation / reference]. Figure 1 This embodiment provides the following technical solution:

[0034] A method for environmentally friendly upgrading of IF steel top slag includes the following steps:

[0035] Step 1: Using the LF-RH continuous casting process, the weight of the ladle ai and the slag residue after the continuous casting is △G1. The slag residue is added to the empty ladle aj that is to receive the molten steel. The empty ladle aj is weighed and the weight of the empty ladle ai is △G2.

[0036] The steel ladles are numbered separately, specifically a1, a2, a3...ai, aj...an;

[0037] The weight of residual slag is expressed by the following formula:

[0038] △G=△G1-△G2,

[0039] During the converter tapping process, a certain amount of lime and aluminum granules are added based on the weight of the residual slag calculated by the above formula.

[0040] Step 2: Based on the weight of the slag residue, add small lime and aluminum granules to the steel stream during the converter tapping process;

[0041] Step 3: When the steel ladle AJ is being hot-repaired on the tilting platform, the permeable bricks, inlet and outlet water outlets, and sliding plate equipment are repaired in sequence. After the repair is completed, the sliding plate is closed, and drainage sand is added to the water outlet channel as required.

[0042] Step 4: The slag residue from the ladle after continuous casting is added to the ladle to be held by the molten steel for hot repair.

[0043] Step 5: Use the reducing slag from the LF-RH continuous casting process in the converter to modify the top slag of the next heat of IF steel.

[0044] Specifically, in the LF-RH continuous casting process of a converter, 1-5 tons of liquid reducing slag remain in the ladle after the molten steel is poured. This reducing slag is weighed and then added to the ladle after hot repair and lining as described in step three. This ladle is used to receive IF steel from the converter. The reducing properties of the slag are used to reduce the oxidizing properties of the top slag. During the tapping process in the converter, a small amount of lime is added according to the weight of the reducing slag. This invention utilizes the reducing slag as a resource. This invention utilizes the reducing slag remaining after casting to modify the top slag of IF steel. This not only reduces the oxidizability of the top slag, achieving a TFe ≤ 8% for the top slag, but also uses its heat to reduce the discharge of slag steel. Furthermore, this invention does not use traditional modifiers. By using hot reducing slag remaining, it significantly reduces costs while ensuring the modification effect. At the same time, it avoids generating a large amount of smoke and dust during the top slag modification process, thus achieving low-cost, pollution-free top slag modification, providing protection for enterprise environmental improvement and employee occupational health.

[0045] The specific requirements for adding small limestone are shown in Table 1:

[0046] Table 1. Amount of lime added during the steel tapping process.

[0047]

[0048] As shown in Table 1, during the converter tapping process, a corresponding amount of lime is added according to the weight of the reducing slag. The specific amounts of lime added are as follows: for ΔG≤1t, the amount of lime added is 1±0.3kg / t; for 1<ΔG≤2t, the amount of lime added is 1.5±0.3kg / t; for 2<ΔG≤3t, the amount of lime added is 2.5±0.3kg / t; for 4<ΔG≤5t, the amount of lime added is 3±0.3kg / t; and for ΔG>5t, the amount of lime added is 3.5±0.3kg / t.

[0049] The specific requirements for adding small limestone are shown in Table 2:

[0050] Table 2 Correspondence between aluminum granule addition during steel tapping and final oxygen content

[0051]

[0052] As shown in Table 2, during the converter tapping process, aluminum particles are added according to the weight of the reducing slag and the oxygen content at the converter endpoint. The amounts of oxygen and aluminum particles added at the converter endpoint are shown in Table 2. Specifically, for [O] < 350 ppm, the amount of aluminum particles added is 50 ± 20 kg; for 350 ppm ≤ [O] < 450 ppm, the amount of aluminum particles added is 70 ± 20 kg; for 450 ppm ≤ [O] < 550 ppm, the amount of aluminum particles added is 90 ± 20 kg; and for [O] ≥ 550 ppm, the amount of aluminum particles added is 110 ± 20 kg.

[0053] It should be noted that if the oxygen content at the converter endpoint is not determined, aluminum particles should be added at a rate of 350 ≤ [O] < 450 ppm; for furnaces where the oxygen content is not measured during make-up blowing, aluminum particles should be added at a rate of 450 ≤ [O] < 550 ppm.

[0054] The present invention will be further described below with reference to specific embodiments.

[0055] Real-time Example 1

[0056] This embodiment describes an environmentally friendly method for upgrading the top slag of IF steel, taking a 300T converter, refining, continuous casting, and ladle production process as an example.

[0057] The steel type is DC06. The specific composition requirements for DC06 steel RH blast furnace steel are shown in Table 3.

[0058] Table 3. Composition Requirements for DC06 Steel RH Breakthrough Molten Steel

[0059]

[0060] In this embodiment, the amount of molten steel is 315 tons; after the converter blowing process is completed, the molten steel is subjected to oxygen determination, [O] 终点 =384ppm; the specific composition requirements for M280VK molten steel in the BOF-LF-CC process are shown in Table 4:

[0061]

[0062] Table 4. Composition Requirements for M280VK Steel LF Molten Steel

[0063] As shown above, after continuous casting of M280VK steel, the residual slag is 2.57t. According to Table 1, 2kg / t of lime should be added during tapping, and 649kg of lime should actually be added. According to Table 2, aluminum particles should be added to the top slag surface of the ladle after tapping based on the oxygen value. 70±20kg of aluminum particles should be added during tapping, and 84kg of aluminum particles should actually be added. The RH carbon requirement for this steel grade is 0.0012%, and the oxygen content after decarburization is 217ppm. The composition of the top slag after RH cavitation is shown in Table 5.

[0064] Table 5 RH top ash composition

[0065]

[0066] Example 2

[0067] This embodiment describes an environmentally friendly method for upgrading the top slag of IF steel, taking a 300T converter, refining, continuous casting, and ladle production process as an example.

[0068] The steel type is 170P. The composition requirements for the molten steel in the ladle of 170P steel are detailed in Table 6.

[0069] Table 6. Composition Requirements for Ladle Steel in 170P Steel

[0070]

[0071]

[0072] In this embodiment, the amount of molten steel is 311 tons; after the converter blowing process is completed, the molten steel is subjected to oxygen determination, [O] 终点 =356ppm; the specific composition requirements for SPHC-P molten steel in the BOF-LF-CC process are shown in Table 7:

[0073] Table 7. Composition Requirements for SPHC-P Steel LF Molten Steel

[0074]

[0075] As shown above, the weight of the residual slag after continuous casting of SPHC-P steel is 4.18t. According to Table 1, 2kg / t of lime was added during tapping, and 908kg of lime was actually added. According to Table 2, aluminum particles were added to the top slag surface of the ladle after tapping, based on the oxygen value. 70±20kg of aluminum particles were added during tapping, and 75kg of aluminum particles were actually added. The RH carbon requirement for this steel grade is 0.045%, and the oxygen content after decarburization is 172ppm. The composition of the top slag after RH cavitation is shown in Table 8.

[0076] Table 8 RH Top Ash Composition

[0077] Element CaO <![CDATA[SiO2]]> MnO MgO <![CDATA[P2O5]]> <![CDATA[Al2O3]]> S TFe content / % 38.71 5.60 2.22 6.6 0.58 30.77 0.058 6.35

[0078] Example 3

[0079] This embodiment describes an environmentally friendly method for upgrading the top slag of IF steel, taking a 300T converter, refining, continuous casting, and ladle production process as an example.

[0080] The steel grade is DC04. The specific requirements for the composition of molten steel in the ladle for DC04 steel are shown in Table 9.

[0081] Table 9 Requirements for the Composition of Molten Steel in the Ladle of DC04 Steel

[0082]

[0083] In this embodiment, the amount of molten steel is 291.57 tons; after the converter blowing process is completed, the molten steel is subjected to oxygen determination, [O] 终点 =452ppm; the composition requirements for 780DP molten steel in the BOF-LF-RH-CC process are detailed in Table 10:

[0084] Table 10. Composition Requirements for Molten Steel in Ladle of 780DP Steel

[0085]

[0086] As shown above, the weight of the residual slag after continuous casting of SPHC-P steel is 5.9t. According to Table 1, 3.5kg / t of lime should be added during tapping, and 1050kg of lime should actually be added. According to Table 2, aluminum particles should be added to the top slag surface of the ladle after tapping based on the oxygen value. 90±20kg of aluminum particles should be added during tapping, and 102kg of aluminum particles should actually be added. The RH carbon requirement for this steel grade is 0.0020%, and the oxygen content after decarburization is 262ppm. The composition of the top slag after RH cavitation is shown in Table 11.

[0087] Table 11 RH Top Ash Composition

[0088] Element CaO <![CDATA[SiO2]]> MnO MgO <![CDATA[P2O5]]> <![CDATA[Al2O3]]> S TFe content / % 38.80 3.80 3.629 4.77 0.67 38.51 0.024 7.48

[0089] Example 4

[0090] This embodiment describes an environmentally friendly method for upgrading the top slag of IF steel, taking a 300T converter, refining, continuous casting, and ladle production process as an example.

[0091] The steel type is H260YD. The specific requirements for the composition of molten steel in the ladle of H260YD steel are shown in Table 12.

[0092] Table 12 H260YD Steel Ladle Steel Composition Requirements

[0093]

[0094] In this embodiment, the amount of molten steel is 331.5 tons; after the converter blowing is completed, the oxygen content of the molten steel is determined, and no additional blowing is performed during the process. The endpoint [O] was not measured; the composition requirements of 65Mn molten steel for the BOF-LF-CC process are detailed in Table 13.

[0095] Table 13. Composition Requirements for Molten Steel in Ladle of 65Mn Steel

[0096]

[0097] As shown above, the weight of the residual slag after continuous casting of 65Mn steel is 1.5t. According to Table 1, 1.5kg / t of lime should be added during tapping, and 450kg of lime should actually be added. According to Table 2, aluminum particles should be added to the top slag surface of the ladle after tapping based on the oxygen value. 70±20kg of aluminum particles should be added during tapping, and 83kg of aluminum particles should actually be added. The RH carbon requirement for this steel grade is 0.0020%, and the oxygen content after decarburization is 231ppm. The composition of the top slag after RH cavitation is shown in Table 14.

[0098] Table 14 RH Top Ash Composition

[0099] Element CaO <![CDATA[SiO2]]> MnO MgO <![CDATA[P2O5]]> <![CDATA[Al2O3]]> S TFe content / % 44.50 7.66 3.37 6.46 1.22 20.7 0.030 6.41

[0100] Working Principle: The environmentally friendly modification method for IF steel top slag of this invention adopts the ladle casting residue from the converter LF-RH continuous casting process. After the molten steel is cast, liquid reducing slag remains in the ladle. By weighing the reducing slag after continuous casting and adding it to the ladle after hot repair and lining, this ladle can be used to receive IF steel from the converter. The reducing property of the reducing slag is used to reduce the oxidation property in the top slag. Secondly, during the tapping process of the converter, a corresponding amount of lime is added according to the weight of the reducing slag. The reducing casting residue after casting is used to modify the IF steel top slag, which can achieve the purpose of green, environmentally friendly, and low-cost modification of IF steel. It does not use traditional modifiers, which reduces costs while ensuring the modification effect. At the same time, it avoids the generation of a large amount of smoke and dust during the top slag modification process, thus achieving low-cost and pollution-free top slag modification.

[0101] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0102] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for environmentally friendly modification of IF steel top slag, characterized in that: Includes the following steps: Step 1: Using the LF-RH continuous casting process, the weight of the ladle ai and the slag residue after the continuous casting is △G1. The slag residue is added to the empty ladle aj that is to receive the molten steel. The empty ladle aj is weighed and the weight of the empty ladle ai is △G2. Step 2: Based on the weight of the slag residue, add small lime and aluminum granules to the steel stream during the converter tapping process; Step 3: When the steel ladle AJ is being hot-repaired on the tilting platform, the permeable bricks, inlet and outlet water outlets, and sliding plate equipment are repaired in sequence. After the repair is completed, the sliding plate is closed, and drainage sand is added to the water outlet channel as required. Step 4: The slag residue from the ladle after continuous casting is added to the ladle to be held by the molten steel for hot repair. Step 5: Use the reducing slag from the LF-RH continuous casting process in the converter to modify the top slag of the next heat of IF steel. In step one, the steel ladles are numbered respectively, specifically including a1, a2, a3...ai, aj...an; The weight of the casting residue is expressed by the following formula: △G = △G1 - △G2, During the converter tapping process, a certain amount of lime and aluminum granules are added based on the weight of the residual slag calculated by the above formula. The amount of lime added is: △G≤1t, the amount of lime added is 1±0.3kg / t; 1<△G≤2t, the amount of lime added is 1.5±0.3kg / t; 2<△G≤3t, the amount of lime added is 2.5±0.3kg / t; 4<△G≤5t, the amount of lime added is 3±0.3kg / t; If △G>5t, the amount of lime added is 3.5±0.3kg / t; The aluminum granules need to be added according to the oxygen content at the converter endpoint, and the amount of aluminum granules added is: [O] < 350 ppm, aluminum granules added amount 50 ± 20 kg; 350ppm≤[O]<450ppm, aluminum granules added amount is 70±20kg; 450ppm≤[O]<550ppm, aluminum particle addition amount is 90±20kg; [O]≥550ppm, aluminum granules added amount is 110±20kg.

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