LF furnace smelting method suitable for RH process path steel grade steel ladle casting residue recovery

Abstract

The invention discloses an LF furnace smelting method suitable for RH process path steel grade steel ladle casting residue recovery, and belongs to the technical field of ferrous metallurgy. The method comprises the following steps: calculating slag weight according to a formula; slag FeO is determined according to steel types C and Als, and the first-time aluminum adding amount of the LF furnace is calculated; heating for the first time, and determining the forced stirring time after heating according to the desulfurization rate; sampling after an aluminum supplementing system is executed according to the furnace slag color; and adjusting components, temperature and calcium treatment, and discharging the molten steel. According to the method, the steel ladle casting residue of the RH process path steel grade is poured into an empty steel ladle before tapping, and an adaptive LF deoxidation system and an operation method are designed, so that safe and efficient recycling of the steel ladle casting residue of the RH process path steel grade is realized, the casting residue is effectively recycled, the metal yield is increased, and the production cost is reduced. And the smelting period of the LF furnace can be shortened, the desulfurization effect is improved, the nitrogen content of outbound molten steel of the LF furnace is reduced, the production cost is reduced while the quality of the molten steel and the production efficiency are improved, and multiple production requirements of a steel plant are met.

Description

Technical Field

[0001] This invention relates to the field of iron and steel metallurgy technology, and more specifically, to an LF furnace smelting method for recovering ladle residues of steel grades applicable to the RH process route. Background Technology

[0002] The common steelmaking process in China is either converter-LF-continuous casting or converter-RH-continuous casting. The converter is a primary refining furnace, while LF and RH are secondary refining furnaces. The LF furnace has functions such as heating, alloying, and desulfurization by creating reducing slag, while the RH furnace has functions such as deep decarburization, deoxidation, and alloying. Continuous casting involves pouring molten steel from a ladle into a continuous casting billet. The molten steel in the ladle is topped with slag, the properties of which are related to the steel grade and the smelting process.

[0003] When the smelting process route is converter-LF-continuous casting, the LF furnace requires desulfurization, so the slag must have strong reducing properties (the slag FeO+MnO content is generally less than 1%). When the smelting process route is converter-RH-continuous casting, especially when this process is used to produce ultra-low carbon steel grades such as automotive steel sheets and non-oriented silicon steel, the slag must have strong oxidizing properties (the slag FeO+MnO content is generally greater than 5%).

[0004] Recovering ladle residue from continuous casting is a common steelmaking technique. Because molten steel and slag mix together during the later stages of casting, making precise separation difficult, ladle residue consists of both molten steel and slag. Recovering the molten steel from the residue is highly profitable, making it a primary goal for steel mills. However, the slag in the residue may not have any recovery value.

[0005] When the slag is reducing, returning this portion of the casting residue to the ladle in the "converter-LF-continuous casting" process not only recovers the molten steel from the casting residue, but the slag can also be used as slag-forming material, resulting in good metallurgical effects. However, when the slag is oxidizing, returning this portion of the casting residue to the ladle in the "converter-LF-continuous casting" process requires the addition of deoxidizers during LF smelting to remove oxygen from the slag in the casting residue. This leads to adverse consequences such as prolonged LF smelting time and reduced desulfurization effect.

[0006] Chinese Patent (Authorization Announcement No.: CN113102712B) discloses "A Method for Recycling Ladle Residue Applicable to Ultra-Low Carbon Steel". This method uses a ladle filled with molten iron to repeatedly recycle ladle residue. After deoxidation, the recycled residue and molten iron in the ladle are added to the converter. The characteristic of this method is that it can recycle ladle residue containing oxidizing slag of ultra-low carbon steel. Chinese Patent (Publication No.: CN112899433A) discloses "A Method for Recycling Ladle Residue Steel and Residue Slag". The idea is: (1) Pre-fill the ladle with bottom molten iron; (2) Fill the ladle with residue steel and residue slag and stir evenly; (3) Fill the ladle with the remaining molten iron, then remove the residue slag with a slag remover, and then add it to the converter for smelting. The shortcomings of the above two patents are that the recycling logistics are relatively complicated, requiring multiple uses of the ladle, and the recycling efficiency is relatively low.

[0007] Chinese patent (authorization announcement number: CN111349743B) discloses "An energy-saving and emission-reduction method for recycling hot casting slag." Through a comprehensive review and summary of the feasibility analysis, process design, advantages and disadvantages analysis of recycling process points, formulation of process standards, formulation of process operations, and analysis of post-recycling effects, a practical and feasible method for recycling hot casting slag has been developed. Recycling casting slag improves the steel recovery rate, reduces auxiliary material consumption, promotes rapid slag formation during refining, shortens refining time, and improves refining efficiency. However, as indicated in the specification

[0003] (after the steel casting is completed, the slag in the steel ladle, i.e., casting slag, has good fluidity, and the slag undergoes modification treatment during steel refining, resulting in high CaO content, high alkalinity, and strong reducing properties. Most ladle casting slag has strong refining capabilities, while retaining a certain amount of molten steel. It also has high sensible heat; therefore, ladle casting slag has excellent comprehensive utilization value.), the hot casting slag mentioned in this technology is reducing slag. In addition, the process for recovering casting residues in the refining furnace (LF) mentions adjusting the amount of quicklime added according to the steel grade and the sulfur content of the incoming steel.

[0008] Chinese patent (publication number: CN120575007A) discloses a "method for recovering hot ladle casting residue." The technical approach involves two methods: direct recovery of hot ladle casting residue to the ladle and recovery of hot ladle casting residue to the ladle after transfer in a heating transfer tank. The advantage is that this technology, by setting up a heating transfer tank, can regulate the pace of hot ladle casting residue recovery and increase the recovery rate. The disadvantage is that it requires a heating transfer tank, resulting in a significant investment, making it impractical for most steel mills.

[0009] The scientific paper "Experiment on the Use of Hot LF Casting Residue Slag for Steel Desulfurization" (Journal of Liaoning University of Science and Technology, Vol. 35, No. 6, December 2012) mentions the use of hot casting residue slag for steel desulfurization in the LF process. However, the casting residue slag is the reducing slag produced by the LF furnace process. In addition, the paper also mentions that Tangshan Iron and Steel, Taiyuan Iron and Steel, Anyang Iron and Steel and other domestic companies have achieved the recycling of hot LF steel slag, realizing the comprehensive utilization of energy and resources.

[0010] The scientific paper "Feasibility Analysis of Hot Casting Slag Recycling" (Baosteel Technology, No. 5, 2016) analyzes the recycling pathways for casting slag, pointing out that from the perspective of the steelmaking process, hot casting slag recycling can be done by returning it to the ladle, converter, or refining furnace, and must be considered comprehensively based on specific circumstances. Returning casting slag to the refining furnace is a more ideal choice. Casting slag is mostly basic reducing slag, generally with high basicity and low oxidizing power. From an energy-saving perspective, for smelting the same steel grade, returning casting slag to the refining furnace is more suitable. However, the paper does not mention the smelting process in the refining furnace after the casting slag is returned.

[0011] The publicly available information above shows that the existing methods for recycling ladle casting residue have limitations, mainly as follows: 1) When ladle casting residue is returned to the converter for utilization, the recycling efficiency is low; 2) Although the method of returning ladle casting residue to the refining furnace is mentioned, the slag in the ladle casting residue is mostly strongly reducing slag, and there is no mention of how to recover strongly oxidizing slag or how the LF process should be adjusted after recovery. Summary of the Invention

[0012] 1. The technical problem that the invention aims to solve

[0013] To address the shortcomings and deficiencies of existing technologies, this invention provides an LF furnace smelting method for recovering ladle residue from steel grades in the RH process path. This method involves pouring the ladle residue (molten steel + ladle slag) from steel grades in the RH process path into an empty ladle before tapping, and designing a suitable LF deoxidation system and operating method to achieve safe and efficient recovery and utilization of ladle residue from steel grades in the RH process path. This not only effectively recovers the residue and improves the metal yield, but also shortens the LF furnace smelting cycle, improves the desulfurization effect, and reduces the nitrogen content of the molten steel exiting the LF furnace. It improves the quality of molten steel, increases production efficiency, and reduces production costs, thus meeting the multiple production needs of steel plants.

[0014] 2. Technical Solution

[0015] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0016] The present invention relates to an LF furnace smelting method for recovering ladle slag in steel grades using the RH process path. The RH process path refers to the smelting process path of the steel grade as converter → RH → continuous casting; the slag at the RH outlet has a TFe content of ≥3%, with the remainder being CaO, SiO2, MnO, and Al2O3. The method includes the following steps:

[0017] S1: Primary steelmaking in the LF process route of converter smelting;

[0018] S2: Before tapping steel from the converter, the ladle prepared to receive molten steel from the converter is placed on the ladle car track and weighed to obtain WB1; the ladle casting residue containing RH process route steel grades is directly turned over to the empty ladle by a crane and then weighed to obtain WB2.

[0019] W 炉渣重量 = (WB2-WB1) / 4;

[0020] S3: Classify FeO in slag based on the C and Als of the specific steel grade in the RH process path:

[0021]

[0022] S4: Converter tapping. During the tapping process, the amount of slag fed into the converter is controlled to avoid excessive slag feeding; deoxidation is carried out during the tapping process.

[0023] S5: After tapping the steel, take steel sample 1 at the back of the furnace to test the composition, and then hoist the ladle into the LF furnace for smelting;

[0024] S6: After the molten steel enters the LF furnace, the bottom of the ladle is blown with argon and strongly stirred for 1-2 minutes. Aluminum particles are added for strong deoxidation. The amount of aluminum particles = the amount of aluminum consumed to remove oxygen from the slag residue in the casting + the amount of aluminum consumed for alloying. After adding the aluminum particles, the stirring is strong for 1-2 minutes, then switched to medium stirring, and then heating is started. During the heating process, lime is added according to the slag-reducing effect.

[0025] The calculation method for aluminum consumption in removing oxygen from slag residue during casting is as follows:

[0026] 2Al + 3FeO = Al₂O₃ + 3Fe;

[0027] From this chemical equation, we can see that M Al =54*W 炉渣重量 *1000*slag FeO / (3*72);

[0028] Method for calculating aluminum consumption in alloying:

[0029] Aluminum consumption for alloying = molten steel consumption * (LF outgoing target Als + Als lost during LF smelting - Als after furnace).

[0030] S7: During the heating period, heating will be stopped when the predicted molten steel temperature reaches the target temperature at the LF outlet +20℃; after heating is stopped, the bottom blowing argon flow rate will be increased to strongly stir and desulfurize the molten steel, and the strong stirring time will be determined according to the desulfurization rate;

[0031] S8: After the strong stirring is completed, take a slag sample and observe the slag color: if the slag is white, take steel sample 2; if the slag is black, add 0.5 kg / t of aluminum granules to the steel and stir strongly for 5 minutes, then take steel sample 2; if the slag is gray, add 0.2 kg / t of aluminum granules to the steel and stir strongly for 3 minutes, then take steel sample 2. Measure the temperature after taking steel sample 2.

[0032] S9: Adjust the temperature based on the temperature measurement results, adjust the composition based on the analysis results of steel sample 2, and perform calcium treatment according to the steel grade process; take steel sample 3 for temperature measurement before the molten steel leaves the station.

[0033] Furthermore, in S9, the adjustment of composition, temperature, and calcium treatment process follows the conventional operating standards of LF furnaces in the metallurgical industry.

[0034] Furthermore, in S7, the strong stirring time is as follows:

[0035]

[0036] Desulfurization rate = (S content after furnace - target S content of LF furnace for steel grade) / S content after furnace.

[0037] Furthermore, in S4, the amount of slag discharged from the converter during the tapping process is controlled to be no more than 2 kg / ton of steel.

[0038] Furthermore, in S4, the addition of deoxidizer ensures that the Al content of the molten steel after furnace casting is between 0.010% and 0.040% under the condition that the same steel grade is not recast.

[0039] 3. Beneficial effects

[0040] Compared with the prior art, the technical solution provided by this invention has the following advantages:

[0041] This invention provides an LF furnace smelting method for recovering ladle residue for steel grades in the RH process. This method involves pouring the ladle residue (molten steel + ladle slag) of RH process steel grades into an empty ladle before tapping, and designing a suitable LF deoxidation system and operating method. This achieves safe and efficient recovery and utilization of ladle residue for RH process steel grades. It not only effectively recovers residue and improves metal yield, but also shortens the LF furnace smelting cycle, improves desulfurization effect, and reduces the nitrogen content of molten steel exiting the LF furnace. This improves steel quality and production efficiency while reducing production costs, thus meeting the multiple production needs of steel plants. Attached Figure Description

[0042] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0043] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0044] Example 1

[0045] from Figure 1 As can be seen, the LF furnace smelting method for recovering casting residue from steel ladles in the RH process path of this embodiment is for continuously cast ultra-low carbon automotive steel, grade: DC06 (chemical composition standard as follows), whose casting residue is to be turned over to the ladle of steel grades in the LF process path.

[0046]

[0047] The ultra-low carbon automotive steel sheet has C≤0.0030%, ALs:0.015-0.070%, and its slag FeO is at the 7% level;

[0048]

[0049] The primary steel produced by the converter smelting LF process route, furnace number S1, steel grade MBTRG00105, has the following LF outlet composition standard as shown in the table below.

[0050] Before tapping steel from the S1 furnace, the ladle prepared to receive the molten steel from the S1 furnace is placed on the ladle car track and weighed to obtain 304 tons of WB1; the casting residue of the ultra-low carbon automotive sheet steel ladle is directly poured into the empty ladle by a crane and then weighed to obtain 314 tons, WB0 = (314-304) / 4 = 2.5 tons.

[0051] S1 furnace tapping: During the tapping process, the amount of slag fed into the converter is controlled. The slag thickness in the ladle is measured to be 70mm, and the amount of slag fed into the ladle is no more than 2kg / ton of steel. During the tapping process, 2.4kg / t of steel aluminum granules are added to the molten steel for deoxidation.

[0052] After tapping the steel, a steel sample 1 was taken from the furnace to test its composition. The sample contained 0.020% Al and 0.026% sulfur. The steel ladle was then hoisted into the LF furnace for smelting.

[0053] After the molten steel enters the LF furnace, the bottom of the ladle is blown with argon and strongly stirred for 1.5 minutes. 271 kg of aluminum granules are added for strong deoxidation. After the aluminum granules are added, the stirring is strong for 2 minutes, then switched to medium stirring. Then the temperature of steel sample 1 is measured. After the temperature is measured, heating begins. During the heating process, lime is added according to the slag-reducing effect.

[0054] The calculation process for aluminum granules is as follows:

[0055] Aluminum particle weight = Aluminum consumption for removing oxygen from slag residue + Aluminum consumption for alloying. Where, aluminum consumption for removing oxygen from slag residue = 54 * 2.5 * 1000 * 8% / (3 * 72 * 50%) = 100 kg; aluminum consumption for alloying = molten steel weight * (LF outlet target Als + Als lost during LF smelting - Als after furnace) = 310 * 1000 * (0.035% + 0.040% - 0.020%) = 171 kg; aluminum particle weight = 100 + 171 = 271 kg.

[0056] Heating is stopped when the predicted molten steel temperature reaches the LF outlet target temperature +20℃. After heating is stopped, the bottom-blown argon flow rate is increased to strongly stir and desulfurize the molten steel. The stirring time is determined based on the desulfurization rate. Desulfurization rate = (S content after furnace - LF furnace target S content for steel grade) / S content after furnace = (0.020% - 0.006%) / 0.020% = 70%. Based on the desulfurization rate of this furnace, the strong stirring time is set to ≥7 minutes.

[0057] After 7 minutes of vigorous stirring, take a slag sample and observe the slag color. If the slag is white, take steel sample 2 and temperature measurement steel sample 2.

[0058] Adjust the temperature based on the results of temperature measurement of steel sample 2, adjust the composition based on the analysis results of steel sample 2, and perform calcium treatment according to the steel grade process. Before the molten steel leaves the station, take steel sample 3 and temperature measurement of steel sample 3 (the composition, temperature, and calcium treatment process are the same as the routine LF operation in the metallurgical industry).

[0059]

[0060]

[0061] Example 2:

[0062] This embodiment describes an LF furnace smelting method for recovering casting residue from RH process path steel grades in ladles. Specifically, it addresses the continuous casting of RH process path steel grade MBRYT23524, with the casting residue intended to be transferred to the LF process path steel grade ladle. The chemical composition standard for MBRYT23524 is shown in the table below.

[0063]

[0064] Based on its composition, its slag FeO is at the 5% level;

[0065] The primary steel produced by the converter LF process is furnace number S2, steel grade MBTLA34006, and its LF outlet composition standard is as follows:

[0066]

[0067] Before tapping steel from the S2 furnace, the ladle prepared to receive the molten steel from the S2 furnace is placed on the ladle car track and weighed to obtain 307 tons of WB1; the casting residue of the ultra-low carbon automotive sheet steel ladle is directly poured into the empty ladle by a crane and then weighed to obtain 321 tons, WB0 = (321-307) / 4 = 3.5 tons.

[0068] S2 furnace tapping: During the tapping process, the amount of slag fed into the converter is controlled. The slag thickness in the ladle is measured to be 80mm, and the amount of slag fed into the ladle is no more than 2kg / ton of steel. During the tapping process, 2.5kg / t of steel aluminum granules are added to the molten steel for deoxidation.

[0069] After tapping, a steel sample 1 was taken from the furnace to test its composition, which showed that Als was 0.029% and sulfur content was 0.031%. Then, the ladle was hoisted into the LF furnace for smelting.

[0070] After the molten steel enters the LF furnace, the bottom of the ladle is blown with argon and strongly stirred for 1.8 minutes. 226 kg of aluminum granules are added for strong deoxidation. After the aluminum granules are added, the stirring is strong for 1.5 minutes, then switched to medium stirring. Then the temperature of steel sample 1 is measured. After the temperature is measured, heating begins. During the heating process, lime is added according to the slag-reducing effect.

[0071] The calculation process for aluminum granules is as follows:

[0072] Aluminum particle weight = Aluminum consumption for removing oxygen from slag residue + Aluminum consumption for alloying. Where, aluminum consumption for removing oxygen from slag residue = 54 * 3.5 * 1000 * 5% / (3 * 72 * 50%) = 88 kg; aluminum consumption for alloying = molten steel volume * (LF outlet target Als + Als lost during LF smelting - Als after furnace) = 298 * 1000 * (0.035% + 0.040% - 0.029%) = 138 kg. Aluminum particle weight = 88 + 138 = 226 kg;

[0073] Heating is stopped when the predicted molten steel temperature reaches the target LF outlet temperature +20℃. After heating is stopped, the bottom-blown argon flow rate is increased to strongly stir and desulfurize the molten steel. The stirring time is determined based on the desulfurization rate. Desulfurization rate = (S content after furnace - target S content in LF furnace for steel grade) / S content after furnace = (0.031% - 0.004%) / 0.031% = 87%. Based on the desulfurization rate, the strong stirring time is set to ≥10 minutes.

[0074] After 10 minutes of vigorous stirring, take a slag sample and observe the slag color. If the slag is white, take steel sample 2 and temperature measurement steel sample 2.

[0075] Adjust the temperature based on the results of temperature measurement of steel sample 2, adjust the composition based on the analysis results of steel sample 2, and perform calcium treatment according to the steel grade process. Before the molten steel leaves the station, take steel sample 3 and temperature measurement of steel sample 3 (the composition, temperature, and calcium treatment process are the same as the routine LF operation in the metallurgical industry).

[0076]

[0077]

[0078] Comparative Example 1:

[0079] The primary steel produced by the converter smelting LF process route, furnace number D1, steel grade MBTRG00105, has the following LF outlet composition standard as shown in the table below.

[0080]

[0081] When tapping steel from furnace D1, the slag thickness in the ladle was measured to be 200 mm at the end of tapping, and the slag discharge rate was 3.5 kg / ton of steel. During the tapping process, 2.4 kg / t of steel aluminum granules were added to deoxidize the molten steel.

[0082] After tapping, a steel sample 1 is taken from the furnace to test the composition, which shows that Als is 0.003% and sulfur content is 0.025%. Then the ladle is hoisted into the LF furnace for smelting.

[0083] After the molten steel enters the LF furnace, the bottom of the ladle is blown with argon and strongly stirred for 1.5 minutes. 222 kg of aluminum granules are added for strong deoxidation. After the aluminum granules are added, the stirring is strong and then switched to medium stirring. Then steel sample 1 is tested and heating is started. During the heating process, lime is added according to the slag-reducing effect.

[0084] The calculation process for aluminum granules is as follows:

[0085] Aluminum granule quantity = Aluminum consumption for alloying, Aluminum consumption for alloying = Molten steel quantity * (LF outlet target Als + Als lost during LF smelting - Als after furnace) = 309 * 1000 * (0.035% + 0.040% - 0.003%) = 222 kg. Aluminum granule quantity = 222 kg;

[0086] Heating was stopped when the predicted steel temperature reached 1600℃. After stopping heating, the bottom-blowing argon flow rate was increased to vigorously stir the steel for 5 minutes for desulfurization. After 5 minutes of vigorous stirring, a slag sample was taken and the slag color was observed. The slag was black. Based on experience, 100 kg of aluminum granules was added, and the steel was vigorously stirred for 6 minutes. The slag sample was taken again and the slag color was observed. The slag was white. Two steel samples were taken and two temperature-measuring steel samples were taken.

[0087] Adjust the temperature based on the results of temperature measurement of steel sample 2, adjust the composition based on the analysis results of steel sample 2, and perform calcium treatment according to the steel grade process. Before the molten steel leaves the station, take steel sample 3 and temperature measurement of steel sample 3 (the composition, temperature, and calcium treatment process are the same as the routine LF operation in the metallurgical industry).

[0088]

[0089]

[0090] Comparative Example 2:

[0091] The primary steel produced by the converter LF process route, furnace number D2, steel grade MBTLA34006, has the following LF outlet composition standard as shown in the table below;

[0092]

[0093] D2 furnace tapping: control the amount of slag added to the converter during tapping, measure the slag thickness in the ladle to be 75mm, and add 1.5kg / t of steel-aluminum granules to deoxidize the molten steel during tapping.

[0094] After tapping, a steel sample 1 was taken from the furnace to test its composition, which showed that Als was 0.007% and sulfur content was 0.029%. Then, the ladle was hoisted into the LF furnace for smelting.

[0095] After the molten steel enters the LF furnace, the bottom of the ladle is blown with argon and strongly stirred for 1.4 minutes. 207 kg of aluminum granules are added for strong deoxidation. After the aluminum granules are added, the stirring is strong for 1.5 minutes, then switched to medium stirring. Then the temperature of steel sample 1 is measured. After the temperature is measured, heating begins. During the heating process, lime is added according to the slag-reducing effect.

[0096] The calculation process for aluminum granules is as follows:

[0097] Aluminum granule quantity = Aluminum consumption for alloying, Aluminum consumption for alloying = Molten steel quantity * (LF outlet target Als + Als lost during LF smelting - Als after furnace) = 301 * 1000 * (0.035% + 0.040% - 0.007%) = 207 kg. Aluminum granule quantity = 207 kg;

[0098] Heating was stopped when the predicted molten steel temperature reached the LF outlet target temperature +20℃. After stopping heating, the bottom-blowing argon flow rate was increased to strongly stir the molten steel for 4 minutes for desulfurization. After 4 minutes of strong stirring, a slag sample was taken and the slag color was observed. The slag was black. Based on experience, 120 kg of aluminum granules was added, and strong stirring was carried out for 3 minutes. The slag sample was taken again and the slag color was observed. The slag was gray. Based on experience, 90 kg of aluminum granules was added, and strong stirring was carried out for 3 minutes. The slag sample was taken again and the slag color was observed. The slag was white. Two steel samples and two temperature-measuring steel samples were taken.

[0099] Adjust the temperature based on the results of temperature measurement of steel sample 2, adjust the composition based on the analysis results of steel sample 2, and perform calcium treatment according to the steel grade process. Before the molten steel leaves the station, take steel sample 3 and temperature measurement of steel sample 3 (the composition, temperature, and calcium treatment process are the same as the routine LF operation in the metallurgical industry).

[0100]

[0101]

[0102] The principles of this technology are as follows: 1) The slag in the RH process has a high oxidizing property. If the casting residue is returned to the ladle containing molten steel, the oxygen in the slag will react with the carbon in the molten steel to generate carbon monoxide gas. Due to the small free space in the molten steel, the slag is likely to overflow from the ladle opening, posing a safety hazard. 2) The casting residue is a mixture of slag and molten steel. Determining the weight of the slag turned into the empty ladle is a prerequisite for determining the amount of deoxidized aluminum particles. Therefore, through industrial experiments and the density difference between molten steel and slag, it was determined that the weight of the slag turned into the empty ladle is 1 / 4 of the total amount of the recovered casting residue. In addition, the relationship between the FeO content in the slag and the steel grade was obtained through research, thereby quickly obtaining the FeO content in the recovered casting residue slag. 3) The LF deoxidation and slag-forming system is improved, resulting in efficient deoxidation and slag-forming, high desulfurization rate, and shortened smelting time.

[0103] This invention enables the safe and efficient recycling of ladle residue for steel grades produced in the RH process. Applying this technology to LF smelting not only effectively recovers the residue from RH process steel grades and improves metal yield, but also shortens the LF furnace smelting cycle by 7.5 minutes and reduces the nitrogen content of the molten steel exiting the LF furnace by 8.5 ppm.

[0104] This invention achieves safe and efficient recycling of ladle residue (molten steel + ladle slag) for steel grades in the RH process by pouring it into an empty ladle before tapping, and by designing a reasonable LF deoxidation system and operating method.

[0105] This invention provides an LF furnace smelting method for recovering ladle residue of steel grades in the RH process. This method not only achieves efficient and safe recovery of ladle residue for steel grades in the RH process, but also reduces LF smelting time, improves desulfurization efficiency, and lowers nitrogen content in molten steel, among other benefits, while simultaneously improving quality, increasing production efficiency, and reducing production costs.

[0106] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. An LF furnace smelting method applicable to the recovery of ladle casting residue for steel grades in the RH process path, characterized in that: The RH process path refers to the following: the smelting process path for the steel grade is converter → RH → continuous casting; the slag at the RH outlet has a TFe content of ≥3%, with the remainder being CaO, SiO2, MnO, and Al2O3; the method includes the following steps: S1: Primary steelmaking in the LF process route of converter smelting; S2: Before tapping steel from the converter, the ladle prepared to receive molten steel from the converter is placed on the ladle car track and weighed to obtain WB1; the ladle casting residue containing RH process route steel grades is directly turned over to the empty ladle by a crane and then weighed to obtain WB2. W 炉渣重量 =(WB2-WB1) / 4; S3: Classify FeO in slag based on the C and Als of the specific steel grade in the RH process path: S4: Converter tapping. During the tapping process, the amount of slag fed into the converter is controlled to avoid excessive slag feeding; deoxidation is carried out during the tapping process. S5: After tapping the steel, take steel sample 1 at the back of the furnace to test the composition, and then hoist the ladle into the LF furnace for smelting; S6: After the molten steel enters the LF furnace, the bottom of the ladle is blown with argon and strongly stirred for 1-2 minutes. Aluminum particles are added for strong deoxidation. The amount of aluminum particles = the amount of aluminum consumed to remove oxygen from the slag residue in the casting + the amount of aluminum consumed for alloying. After adding the aluminum particles, the stirring is strong for 1-2 minutes, then switched to medium stirring, and then heating is started. During the heating process, lime is added according to the slag-reducing effect. The calculation method for aluminum consumption in removing oxygen from slag residue during casting is as follows: 2Al + 3FeO = Al₂O₃ + 3Fe; From this chemical equation, we can see that M Al =54*W 炉渣重量 *1000*slag FeO / (3*72); Method for calculating aluminum consumption in alloying: Aluminum consumption for alloying = molten steel consumption * (LF outgoing target Als + Als lost during LF smelting - Als after furnace). S7: During the heating period, heating will be stopped when the predicted molten steel temperature reaches the target temperature at the LF outlet +20℃; after heating is stopped, the bottom blowing argon flow rate will be increased to strongly stir and desulfurize the molten steel, and the strong stirring time will be determined according to the desulfurization rate; S8: After the strong stirring is completed, take a slag sample and observe the slag color: if the slag is white, take steel sample 2; if the slag is black, add 0.5 kg / t of aluminum granules to the steel and stir strongly for 5 minutes, then take steel sample 2; if the slag is gray, add 0.2 kg / t of aluminum granules to the steel and stir strongly for 3 minutes, then take steel sample 2. Measure the temperature after taking steel sample 2. S9: Adjust the temperature based on the temperature measurement results, adjust the composition based on the analysis results of steel sample 2, and perform calcium treatment according to the steel grade process; take steel sample 3 for temperature measurement before the molten steel leaves the station.

2. The LF furnace smelting method for recovering ladle residue of steel grades applicable to the RH process path according to claim 1, characterized in that: In S9, the adjustment of composition, temperature, and calcium treatment process follows the conventional operating standards of LF furnaces in the metallurgical industry.

3. The LF furnace smelting method for recovering ladle residue of steel grades applicable to the RH process path according to claim 1, characterized in that: In S7, the strong stirring time is as follows: Desulfurization rate = (S content after furnace - target S content of LF furnace for steel grade) / S content after furnace.

4. The LF furnace smelting method for recovering ladle residue of steel grades applicable to the RH process path according to claim 1, characterized in that: In S4, the amount of slag discharged from the converter during the steel tapping process is controlled to be no more than 2 kg / ton of steel.

5. The LF furnace smelting method for recovering ladle residue of steel grades applicable to the RH process path according to claim 1, characterized in that: In S4, the addition of deoxidizer is such that, under the condition that the steel grade is not recast, the Al content of the molten steel after furnace is between 0.010% and 0.040%.

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