Method capable of effectively avoiding calcium carbide in LF refining process
By using argon gas during the LF refining process to blow the bottom of the ladle and selective arc slag, and adding an appropriate amount of lime, slag agent and carbon enhancer to the molten steel, the problem of the decrease in the slag CaO content in aluminum calming steel is solved, the production of calcium carbide is avoided, and the purity and production efficiency of the molten steel are improved.
Patent Information
- Application Number
- CN202411863278.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-17
- Publication Date
- 2025-04-11
AI Technical Summary
During the LF refining process of aluminum calming steel, the CaO content in the slag decreases due to the use of carbon-containing carbon enhancers, resulting in an increase in the melting point of the slag and a decrease in adsorption and inclusion capacity, and problems such as ladle overflow, slag plate bonding, and increase in casting residues occur.
After the molten steel reaches the LF refining furnace, use a larger flow of argon gas to blow the bottom of the ladle to judge the activity of the slag surface, and select directly or long arc slag to the molten steel and add lime, slag agent and carbon enhancer to the molten steel to improve the slag melting condition and prevent the carbon enhancer from staying in the slag.
It effectively avoids the production of calcium carbide during LF refining, improves the purity of molten steel, reduces the risk of ladle overflow and slag plate bonding, and improves production efficiency and product quality.
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of steel smelting, and in particular to a method for effectively preventing calcium carbide from occurring in an LF refining process. Background Art
[0002] Refining involves degassing, deoxidizing, desulfurizing, removing inclusions, fine-tuning alloy composition, and precisely controlling temperature in a refining unit to improve steel quality and meet the specific requirements of different steel grades. Refining processes primarily include LF refining, RH refining, and CAS refining. LF refining is suitable for steels with low oxygen and sulfur content; RH refining is suitable for low-carbon and ultra-low-carbon steels, as well as steels with strict gas content control requirements; and CAS refining is suitable for steels with relatively loose sulfur or oxygen content requirements. Killed steel refers to completely deoxidized steel, meaning that the oxygen content does not exceed 0.01% by mass (typically between 0.002% and 0.003%). Due to its low oxygen content, killed steel exhibits uniform texture, fine structure, low impurities, minimal segregation, excellent impact toughness and weldability, and low cold brittleness and aging sensitivity. It is widely used in the chemical, marine, bridge, and construction industries. According to different element control methods, killed steel can be divided into niobium killed steel, vanadium titanium killed steel, aluminum killed steel and slag killed steel. Aluminum killed steel has good corrosion resistance and is currently the most widely used killed steel.
[0003] During the production of aluminum-killed steel, aluminum deoxidizers are typically added to the molten steel during tapping to deoxidize and alloy it. However, excessive use of aluminum deoxidizers can lead to the formation of numerous non-metallic oxide inclusions in the steel, degrading its quality. Adding a recarburizer to the molten steel tapped from the converter can increase its carbon content, reduce the amount of dissolved oxygen in the steel, and minimize the formation of inclusions, ultimately improving its purity while lowering production costs. Without the use of CaC2, when the molten steel from the converter reaches the LF refining furnace, the added recarburizer cannot be stirred into the molten steel under the condition of low steel temperature or compacted slag. At this time, the electrodes are energized to melt the slag and heat it. The CaO in the slag reacts with the carbon-containing recarburizer under the high-temperature arc to produce CaC2 and release CO. Since the FeO content in aluminum-killed steel is relatively low (generally below 0.7%), CaC2 cannot be reduced to CaO by reacting with sufficient FeO under the high-temperature environment of molten steel smelting, which significantly reduces the CaO content in the slag. The melting point of the slag easily deviates from the low melting point region of the CaO-Al2O3-SiO2 ternary slag phase diagram, resulting in an increase in the slag melting point and a decrease in the ability to adsorb inclusions. This leads to serious ladle slag overflow, compacted slag after refining, increased casting residue after pouring, and the inability to remove or clean the ladle slag during tumbling, which affects production safety and costs. At the same time, surface defects and internal defects of the steel plate caused by inclusions increase significantly. Summary of the Invention
[0004] In view of the problem that the CaO content in the slag of the aluminum-deoxidized killed steel in the prior art decreases due to the use of a carbon-containing recarburizer during the LF refining process, the present invention provides a method that can effectively avoid the occurrence of calcium carbide in the LF refining process. First, a large flow of argon gas is used for ladle bottom blowing to judge the activity of the slag surface. Then, according to the activity of the slag surface, direct or long-arc slagging is selected to add auxiliary materials such as lime, slagging agent and recarburizer to the molten steel, thereby improving the slag melting condition of the molten steel, preventing the recarburizer from being retained in the slag and reacting with the slag to consume CaO, and improving the purity of the molten steel.
[0005] The technical solutions of the present invention are as follows: A method for effectively avoiding the occurrence of calcium carbide in an LF refining process comprises the following steps: Step 1: After the molten steel reaches the LF refining furnace, start the first argon blowing from the bottom of the ladle for stirring. The flow rate of the first argon blowing from the bottom of the ladle is 70-90Nm 3 / h; Step 2: When the slag surface shows signs of hardening and / or unmelted large lumps, first power on the long arc to melt the slag. After the slag is melted, turn off the power, add lime, slag dissolving agent and recarburizer, then start the secondary ladle bottom blowing argon to stir, and after the slag is completely melted, take steel sample 1 for testing. When the slag surface does not show signs of hardening and large lumps and has good fluidity, first take steel sample 1 for testing, then add lime, slag dissolving agent and recarburizer, start the secondary ladle bottom blowing argon to stir, and make the slag completely melted. The flow rate of the secondary ladle bottom blowing argon is 30-70Nm 3 / h; Step 3: Based on the composition test results of steel sample 1, adjust the composition of the molten steel in the ladle to the target value for the finished product, measure the molten steel temperature and take steel sample 2 for composition test, and adjust the temperature of the molten steel to the target temperature for LF refining outlet according to the temperature measurement results; Step 4: Compare the composition test results of steel sample 2 with the target value of the finished product and calibrate the composition of the molten steel; Step 5: Soft-blow the molten steel whose composition meets the target value of finished product and whose temperature meets the target temperature of LF refining station. During the soft-blowing process, keep the slag surface of the molten steel slightly moving and without bright rings; Step 6: After the soft blowing is completed, the gas is stopped, the molten steel is discharged from the station and hoisted to the continuous casting process.
[0006] Furthermore, in step one, the molten steel is double-blown converter aluminum-deoxidized killed steel. Aluminum-deoxidized killed steel refers to all steel types that are aluminum-deoxidized during the converter tapping process, including low-carbon and alloy steel, medium-carbon and alloy steel, high-carbon and alloy steel, etc.
[0007] Furthermore, in step 1, the stirring time of the first argon blowing from the ladle bottom is 2-4 minutes, preferably 3 minutes. The flow rate of the argon blowing from the ladle bottom can be set according to the ventilation effect of the ladle bottom blowing.
[0008] Furthermore, in step 2, the stirring time of the secondary ladle bottom blowing argon is 2-5 minutes.
[0009] Furthermore, in step 2, the amount of lime used is 600-800 kg, the amount of slagging agent used is 300-350 kg, and the amount of recarburizer used is 50-400 kg. The amounts of lime, slagging agent, and recarburizer used can be adjusted within the above ranges according to the requirements of the converter endpoint, sulfur content, and carbon content of the molten steel.
[0010] Furthermore, the slagging agent includes the following components in mass percentage: Al2O3 68%, CaO 25%, Al 6%, and the rest are residual elements such as S, P, and N; the recarburizer is graphite carbon powder.
[0011] Furthermore, in step 2, short arc heating is used to heat the slag after it is completely melted. Short arc heating can quickly heat the molten steel, which is beneficial to improving production efficiency and increasing the fluidity of the slag. The target temperature of short arc heating needs to be set according to the liquidus temperature of different steel grades, the comprehensive temperature drop of the ladle, the superheat, etc.
[0012] Furthermore, in step three, if the temperature of the molten steel in the ladle is lower than the LF refining outlet target temperature, the temperature of the molten steel is raised to the LF refining outlet target temperature by short arc electric heating. The heating rate can be regulated by selecting different heating gears. Under normal circumstances, 4 gears of electric heating are used. If the molten steel temperature is too low, that is, the LF refining outlet target temperature - process temperature drop - molten steel liquidus temperature is less than 15°C, a high gear that improves the heating efficiency is required. Under good slag removal conditions, the gear of electric heating has no effect on the fluidity of the slag, but the on-site noise will be very high at a high gear, affecting the occupational health of employees.
[0013] Furthermore, in step 5, the flow rate of soft blowing is 5-12Nm 3 / h, the soft blowing time is 6-10min, and the soft blowing flow rate can be determined according to the ventilation effect of the ladle bottom blowing.
[0014] Furthermore, in step five, 150-250 m of calcium wire is first fed into the molten steel to control the Ca content of the molten steel to 0.015 wt%-0.020 wt%, and then soft blowing and killing are performed.
[0015] The beneficial effects of the present invention are: The present invention provides a method for effectively avoiding the occurrence of calcium carbide in the LF refining process. After the molten steel reaches the LF refining furnace, argon is first blown from the bottom of the ladle at a large flow rate for stirring. The activity of the slag surface is judged based on the fluctuation of the slag surface and the bubbling of argon on the slag surface. When there are conditions such as large-area hardening on the slag surface and poor melting that affect the activity of the slag surface, long arc slag melting is first used to promote slag melting. After the slag is melted, the power is turned off, lime, slag reducing agent and recarburizer are added, and argon is blown from the bottom of the ladle for the second time to promote the recarburizer to separate from the slag and enter the molten steel, effectively preventing the recarburizer from reacting with CaO in the slag to generate CaC2 due to being retained in the slag. When the slag surface activity is good, the recarburizer will not be retained in the slag. The present invention only promotes the recarburizer to separate from the slag and enter the molten steel through the second ladle bottom blowing of argon, thereby preventing the recarburizer from reacting with CaO in the slag while saving production costs.
[0016] In summary, the present invention adopts different methods to treat molten steel according to the difference in the activity of the slag surface, thereby avoiding the recarburizer from being retained in the slag and preventing the C in the recarburizer and CaO in the slag from reacting as follows under the action of the high-temperature electric arc: C+CaO→CaC2+CO↑, thereby improving the slag melting condition of the molten steel, avoiding the recarburizer from consuming CaO, improving the purity of the molten steel, improving the slag foaming phenomenon, and preventing the occurrence of unsafe phenomena such as ladle slag overflow during the LF refining process. DETAILED DESCRIPTION
[0017] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work should fall within the scope of protection of the present invention.
[0018] Example 1 This example uses a combined-blowing converter (BOF)-LF refining-continuous casting process to produce ship plate steel A. During the combined-blowing converter process, the converter charging ratio was 81%, the tapping volume was 245 tons, the steel grade's liquidus temperature was 1515°C, the required pouring superheat was 15-30°C, and the casting cycle was 35 minutes. The converter temperature after tapping was measured at 1635°C. After tapping, 5 tons of rebar offcuts were added to the ladle at the back of the furnace.
[0019] The LF refining process adopts a method that can effectively avoid the occurrence of calcium carbide during the LF refining process, including the following steps: Step 1: After the molten steel reaches the LF refining furnace, open the bottom of the ladle to blow argon for stirring. The argon flow rate is 80Nm 3 / h, after stirring for 3 minutes, the argon gas was turned off. The molten steel was aluminum-deoxidized killed steel from a double-blown converter.
[0020] Step 2: Observe that there are large pieces of unmelted slag on the slag surface in the ladle and the ladle bottom blowing has good air permeability. Start the heating system and close the switch, use the 5-speed long arc heating to melt the slag, cut off the power and open the switch after 5 minutes, observe that the large pieces of unmelted slag on the slag surface have melted, and the slag fluidity is good. As needed, add 260kg of graphite carbon powder, 600kg of lime, and 300kg of slag dissolving agent, then start the secondary ladle bottom blowing argon and continue stirring for 3 minutes. The flow rate of the secondary ladle bottom blowing argon is 40Nm 3 / h. After the slag was completely melted, steel sample 1 was taken for composition analysis. Simultaneously, the molten steel temperature was measured at 1536°C. The heating system was switched on and the molten steel temperature was raised using short-arc heating at level 4 for 10 minutes. No ladle overflow occurred during this process, indicating that no CaC2 was generated during the treatment process. Slag samples were then taken for composition analysis. The main components of the slag sample are shown in Table 1. The remaining components are unavoidable impurities (not shown in Table 1). The slag dissolving agent contained the following components by mass percentage: Al2O3 68%, CaO 25%, Al 6%, and the remainder being residual elements such as S, P, and N.
[0021] Table 1 Analysis results of main components of slag sample of Example 1 (wt%)
[0022] Step 3: During the process of heating with 4-speed short arc, check the composition test results of steel sample 1. After heating for 10 minutes, stop the power supply, calculate and add the corresponding medium carbon ferromanganese, Al, etc. according to the composition test results of steel sample 1 to make alloy fine-tuning, and adjust the composition of the molten steel in the ladle to the target value of the finished product. After the alloy is added, start blowing argon at the bottom of the ladle for the third stirring. The argon flow rate is 35Nm 3 / h, the third stirring time is 3min. After the third stirring is completed, take steel sample 2 for chemical analysis, and determine the temperature of the molten steel to be 1576℃, which meets the target temperature of LF refining of A ship plate steel. After taking steel sample 2, immediately send the sample, and adjust the argon flow rate to 7Nm 3 / h, waiting for the composition test results of steel sample 2. After 5 minutes, the composition test results of steel sample 2 are transmitted to the composition information system.
[0023] Step 4: Compare the composition test results of steel sample 2 with the finished product composition of ship plate steel A. The composition of steel sample 2 meets the steel grade requirements.
[0024] Step 5: Soft blow the molten steel at a flow rate of 5Nm 3 / h, the soft blowing time is 6 minutes, and during the soft blowing process, the slag surface of the molten steel is kept slightly moving and without bright circles.
[0025] Step 6: After the soft blowing is completed, stop the gas, and the molten steel will be discharged from the station and hoisted to the continuous casting machine.
[0026] Example 2 This example uses a combined-blowing converter (BOF)-LF refining-continuous casting process to produce SPHC low-carbon appliance steel. During the combined-blowing converter process, the converter charging ratio is 85%, the tapping volume is 245 tons, the steel liquidus temperature is 1529°C, the casting superheat requirement is 15-30°C, and the casting cycle is 33 minutes. The temperature measured after tapping is 1647°C.
[0027] The LF refining process adopts a method that can effectively avoid the occurrence of calcium carbide during the LF refining process, including the following steps: Step 1: After the molten steel reaches the LF refining furnace, open the bottom of the ladle to blow argon for stirring. The argon flow rate is 85Nm 3 / h, after stirring for 3 minutes, the argon gas was turned off. The molten steel was aluminum-deoxidized killed steel from a double-blown converter.
[0028] Step 2: Observe that there are large pieces of unmelted slag on the slag surface in the ladle and the ladle bottom blowing has good air permeability. Start the heating system and close the switch, use the 5-speed long arc heating to melt the slag, cut off the power and open the switch after 5 minutes, observe that the large pieces of unmelted slag on the slag surface have melted, and the slag fluidity is good. As needed, add 58kg of graphite carbon powder, 600kg of lime, and 350kg of slag dissolving agent, then start the secondary ladle bottom blowing argon and continue stirring for 3 minutes. The flow rate of the secondary ladle bottom blowing argon is 35Nm 3 / h. After the slag was completely melted, steel sample 1 was taken for composition analysis. Simultaneously, the molten steel temperature was measured at 1536°C. The heating system was switched on and the molten steel temperature was raised using 4-speed short-arc heating for 12 minutes. No ladle overflow occurred during this process, indicating that no CaC2 was generated during the treatment. Slag samples were then taken for composition analysis. The main components of the slag sample are shown in Table 2, with the remaining components being unavoidable impurities (not shown in Table 2). The slag-removing agent contained the following components by mass percentage: Al2O3 68%, CaO 25%, Al 6%, and the remainder being residual elements such as S, P, and N.
[0029] Table 2 Analysis results of main components of slag sample of Example 2 (wt%)
[0030] Step 3: During the process of heating with 4-speed short arc, check the composition test results of steel sample 1. After heating for 12 minutes, stop the power supply, calculate and add the corresponding medium carbon ferromanganese, Al, etc. according to the composition test results of steel sample 1 to make alloy fine-tuning, and adjust the composition of the molten steel in the ladle to the target value of the finished product. After the alloy is added, start blowing argon at the bottom of the ladle for the third stirring. The argon flow rate is 30Nm 3 / h, the third stirring time is 3min. After the third stirring is completed, take steel sample 2 for chemical analysis, and determine the temperature of the molten steel to be 1585℃, which meets the target temperature of LF refining for low carbon steel. After taking steel sample 2, immediately send the sample and adjust the argon flow rate to 6Nm 3 / h, waiting for the composition test results of steel sample 2. After 5 minutes, the composition test results of steel sample 2 are transmitted to the composition information system.
[0031] Step 4: Compare the composition test results of steel sample 2 with the composition of SPHC low carbon steel. The composition of steel sample 2 meets the steel grade requirements.
[0032] Step 5: Soft blow the molten steel at a flow rate of 6Nm 3 / h, the soft blowing time is 8min, and during the soft blowing process, the slag surface of the molten steel is kept slightly moving and without bright circles.
[0033] Step 6: After the soft blowing is completed, the gas is stopped and the molten steel is discharged from the station and hoisted to the continuous casting machine. Example 3 This example uses a combined-blowing converter (BOF)-LF refining-continuous casting process to produce SPHC low-carbon appliance steel. During the combined-blowing converter process, the converter charging ratio is 85%, the tapping volume is 245 tons, the steel liquidus temperature is 1529°C, the casting superheat requirement is 15-30°C, and the casting cycle is 33 minutes. The temperature measured after tapping is 1643°C.
[0034] The LF refining process adopts a method that can effectively avoid the occurrence of calcium carbide during the LF refining process, including the following steps: Step 1: After the molten steel reaches the LF refining furnace, open the bottom of the ladle to blow argon for stirring. The argon flow rate is 85Nm 3 / h, after stirring for 3 minutes, the argon gas was turned off. The molten steel was aluminum-deoxidized killed steel from a double-blown converter.
[0035] Step 2: Observe that there are no large pieces of unmelted slag on the slag surface in the ladle, the slag has good fluidity, and the ladle bottom blowing has good air permeability. Take steel sample 1 for sample testing. According to the test results of the sample composition after the converter is tapped, feed 200m of Al wire first after arriving at the station, add 0.040wt% of molten steel Als according to the target, and measure the molten steel temperature at 1546℃. After adding 60kg of graphite carbon powder, 600kg of lime, and 330kg of slag dissolving agent, start the secondary ladle bottom blowing of argon and continue stirring for 3min. The flow rate of the secondary ladle bottom blowing argon is 35Nm 3 / h. After stirring for 3 minutes, two steel samples were taken for composition analysis. Simultaneously, the heating system was switched on and the molten steel temperature was raised using 4-speed short-arc heating for 12 minutes. No ladle overflow occurred during this process, indicating that no CaC2 was generated during the treatment. Slag samples were then taken for composition analysis. The results of the main components of the slag samples are shown in Table 3. The slag dissolving agent contained the following components by mass percentage: Al2O3 68%, CaO 25%, Al 6%, with the remainder being residual elements such as S, P, and N.
[0036] Table 3 Analysis results of main components of slag sample of Example 3 (wt%)
[0037] Step 3: During the 4-speed heating process, check the test results of steel sample 2. After heating for 12 minutes, open the switch and stop the power supply. The molten steel temperature is 1595℃. According to the test results of steel sample 2, add 170kg of medium carbon ferromanganese and 35kg of Al particles to make alloy fine-tuning. Start the third argon blowing from the bottom of the ladle and continue stirring for 3 minutes. The flow rate of the third argon blowing from the bottom of the ladle is 35Nm 3 / h, take 3 samples for testing, and measure the temperature of molten steel at 1588℃. At the same time, adjust the argon flow rate to 8Nm 3 / h, waiting for the composition test results of sample 2. 5 minutes later, the composition test results of steel sample 3 are transmitted to the composition information system.
[0038] Step 4: Compare the composition test results of steel sample 3 with the composition of SPHC low carbon steel. The composition of steel sample 3 meets the steel grade requirements.
[0039] Step 5: Soft blow the molten steel at a flow rate of 6Nm 3 / h, the soft blowing time is 7min, and during the soft blowing process, the slag surface of the molten steel is kept slightly moving and without bright circles.
[0040] Step 6: After the soft blowing is completed, stop the gas, and the molten steel will be discharged from the station and hoisted to the continuous casting machine.
[0041] Comparative Example 1 This example uses a combined-blowing converter (BOF)-LF refining-continuous casting process to produce SPHC low-carbon appliance steel. During the combined-blowing converter process, the converter charging ratio is 85%, the tapping volume is 245 tons, the steel liquidus temperature is 1529°C, the casting superheat requirement is 15-30°C, and the casting cycle is 33 minutes. The temperature measured after tapping is 1643°C.
[0042] The LF refining process includes the following steps: Step 1: After the molten steel reaches the LF refining furnace, open the ladle bottom blowing argon gas for the first stirring. The flow rate of the ladle bottom blowing argon gas is 85Nm 3 / h, after stirring for 3 minutes, the argon gas was turned off. The molten steel was aluminum-deoxidized killed steel from a double-blown converter.
[0043] Step 2: Observe the ladle's slag surface for large chunks of unmelted slag, indicating poor slag fluidity and average ladle bottom-blowing permeability. Based on the compositional analysis results from the previous process, upon arrival, 200 m of Al wire was fed, and the molten steel Als was added to the target 0.040%. Steel sample 1 was then collected for composition analysis. The molten steel temperature was measured at 1550°C. After adding 600 kg of lime, 330 kg of slag disintegrator, and 60 kg of graphite powder, the heating system was closed and the molten steel temperature was raised using 5-speed long-arc heating for 12 minutes. Three minutes after power was applied, the slag in the ladle began to foam and overflowed the ladle's top opening, indicating that the CaO and graphite powder coexisting in the slag, under the influence of the high temperature, reacted to form CaO + 3C = CaC2 + CO. The power was immediately disconnected and the slag sample 1 was collected for composition analysis. The results of the main components of slag sample 1 are shown in Table 4. The slagging agent includes the following components in mass percentage: Al2O3 68%, CaO 25%, Al 6%, and the rest are residual elements such as S, P, and N.
[0044] Step 3: At this time, the heating system is closed, and the 5-speed short arc slag is used. After 3 minutes, the power supply is stopped, and the argon gas is turned on for the second stirring. The flow rate of the argon gas at the bottom of the ladle is 90Nm 3 / h, and observe the melting of the slag under strong stirring. After stirring for 5 minutes, the large pieces of slag have melted, the fluidity has improved significantly, and the argon blowing effect at the bottom of the ladle is good.
[0045] Step 4: Steel Sample 1 was taken for composition analysis. The molten steel temperature was measured at 1532°C. The heating system was switched on and the molten steel temperature was raised using short-arc heating at level 4 for 15 minutes. No ladle overflow occurred during this process, indicating that the slag was completely melted and no CaC₂ was produced. Slag Sample 2 was then taken for composition analysis. The main components of Slag Sample 2 are shown in Table 4. The remaining components are unavoidable impurities (not shown in Table 4). The slag dissolving agent contained the following components by mass percentage: Al₂O₃ 68%, CaO 25%, Al 6%, and the remainder was residual elements such as S, P, and N.
[0046] Table 4 Analysis results of main components of slag sample 1-2 of comparative example 1 (wt%)
[0047] Step 3: During the 4-speed heating process, check the composition test results of steel sample 1. After heating for 15 minutes, turn off the switch and stop the power. According to the composition test results of steel sample 1, calculate and add the corresponding medium carbon ferromanganese, Al, etc. to make alloy fine-tuning. Adjust the composition of the molten steel in the ladle to the target value of the finished product. After the alloy is added, start the argon blowing at the bottom of the ladle for the third stirring. The flow rate of the argon blowing at the bottom of the ladle is 30Nm 3 / h, the third stirring time is 3min. After stirring, take steel sample 2 for testing, and measure the temperature of molten steel to be 1586℃, which is in line with the target temperature of LF refining for low carbon steel. After taking steel sample 2, immediately send the sample and adjust the argon flow rate to 8Nm 3 / h, waiting for the composition test results of steel sample 2. After 5 minutes, the composition test results of steel sample 2 are transmitted to the composition information system.
[0048] Step 4: Compare the composition test results of steel sample 2 with the composition of SPHC low carbon steel. The composition of steel sample 2 meets the steel grade requirements.
[0049] Step 5: Soft blow the molten steel at a flow rate of 6Nm 3 / h, the soft blowing time is 8min, and during the soft blowing process, the slag surface of the molten steel is kept slightly moving and without bright circles.
[0050] Step 6: After the soft blowing is completed, stop the gas, and the molten steel will be discharged from the station and hoisted to the continuous casting machine.
[0051] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and substance of the present invention, persons of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and such modifications or substitutions shall be within the scope of the present invention. Any changes or substitutions that can be readily conceived by persons skilled in the art within the technical scope disclosed in the present invention shall be within the scope of protection of the present invention.
Claims
1. A method for effectively avoiding the occurrence of calcium carbide in the LF refining process, characterized in that: The steps include: Step 1: After the molten steel reaches the LF refining furnace, start the first ladle bottom blowing argon for stirring. The flow rate of the first ladle bottom blowing argon is 70-90Nm 3 / h; Step 2: When the slag surface shows signs of hardening and / or large unmelted lumps, first turn on the power to perform long arc slagging. After the slag is melted, turn off the power, add lime, slagging agent and carburizer, then start blowing argon from the bottom of the secondary ladle for stirring. After the slag is completely melted, take steel sample 1 for testing. When the slag surface does not show signs of hardening and large lumps, first take steel sample 1 for testing, then add lime, slagging agent and carburizer, start blowing argon from the bottom of the secondary ladle for stirring, so that the slag is completely melted. The flow rate of the secondary ladle bottom blowing argon is 30-70Nm 3 / h; Step 3: According to the test results of steel sample 1, adjust the composition of the molten steel in the ladle to the target value of the finished product, measure the temperature of the molten steel and take steel sample 2 for testing the composition, and adjust the temperature of the molten steel to the target temperature of LF refining station according to the temperature measurement results; Step 4: Compare the composition test results of steel sample 2 with the target value of the finished product and calibrate the composition of the molten steel; Step 5: Soft blowing is performed on the molten steel whose composition meets the target value of the finished product and whose temperature meets the target temperature of LF refining station; Step 6: After the soft blowing is completed, the gas is stopped, the molten steel leaves the station and is hoisted to the continuous casting process.
2. A method for effectively avoiding the occurrence of calcium carbide in the LF refining process as claimed in claim 1, characterized in that: In step 1, the molten steel is double-blown converter aluminum deoxidation killed steel.
3. A method for effectively avoiding the occurrence of calcium carbide in the LF refining process as claimed in claim 1, characterized in that: In step 1, the stirring time of the first ladle bottom blowing argon is 2-4 minutes.
4. A method for effectively avoiding the occurrence of calcium carbide in the LF refining process as claimed in claim 1, characterized in that: In step 2, the stirring time of the secondary ladle bottom blowing argon is 2-5 minutes.
5. A method for effectively avoiding the occurrence of calcium carbide in the LF refining process as claimed in claim 1, characterized in that: In step 2, the amount of lime used is 600-800kg, the amount of slagging agent used is 300-350kg, and the amount of carbon increaser used is 50-400kg.
6. A method for effectively avoiding the occurrence of calcium carbide in the LF refining process as claimed in claim 5, characterized in that: The slag-forming agent includes the following components in mass percentage: Al2O3 68%, CaO 25%, Al 6%, and the rest are residual elements such as S, P, and N; the recarburizer is graphite carbon powder.
7. A method for effectively avoiding the occurrence of calcium carbide in the LF refining process as claimed in claim 1, characterized in that: In step 2, short arc heating is used to increase the temperature after the slag is completely melted.
8. A method for effectively avoiding the occurrence of calcium carbide in the LF refining process as claimed in claim 1, characterized in that: In step three, the temperature of the molten steel is raised to the LF refining outlet target temperature by short arc heating.
9. A method for effectively avoiding the occurrence of calcium carbide in the LF refining process as claimed in claim 1, characterized in that: In step 5, the flow rate of soft blowing is 5-12Nm 3 / h, soft blowing time is 6-10min.
10. A method for effectively avoiding the occurrence of calcium carbide in the LF refining process as claimed in claim 1, characterized in that: In step five, 150-250 m of calcium wire is first fed into the molten steel, followed by soft blowing and calming.