Method for refining furnace smelting submerged arc addition

Abstract

This invention relates to the field of auxiliary materials application technology in iron and steel metallurgy, and discloses a method for adding submerged arc refining agent in refining furnaces. Addressing the problems of combustion and explosion hazards, poor stability of foamed slag, and low deoxidation efficiency in existing calcium carbide slag-making processes, this invention employs a calcium carbide-free composite refining agent, using a three-stage progressive addition strategy to achieve deep deoxidation and stable submerged arc refining: the first stage adds 50%–70% of the total amount before or within 30 seconds after power-on to establish high reduction potential; the second stage adds 15%–25% 4–6 minutes after power-on to maintain the emulsified state of the slag layer; and the third stage adds the remaining amount 8–12 minutes after power-on to achieve deep purification. This invention also includes a dynamic adjustment mechanism based on slag fluidity, foaming height, and color. Using this method, the oxygen content of the molten steel before tapping can be controlled below 15 ppm, the submerged arc rate can be maintained above 90%, the risk of calcium carbide combustion and explosion can be eliminated, and it is suitable for LF refining of ordinary carbon steel and low alloy steel.

Description

Technical Field

[0001] This invention relates to the field of auxiliary materials for iron and steel metallurgy, and in particular to a method for adding submerged arc agents in refining furnaces. Background Technology

[0002] In modern steelmaking processes, the LF (Ladle Furnace) refining furnace, as a crucial link between primary refining and continuous casting, undertakes multiple core tasks, including deoxidation, desulfurization, inclusion removal, temperature increase, and composition fine-tuning. Among these, the quality of the slag-forming process directly determines the purity of the molten steel and production efficiency. For a long time, in the LF refining slag-forming process, to create a strong reducing atmosphere and form good foamed slag for submerged arc heating, the industry has widely used calcium carbide (CaC2) as the main deoxidizer and foaming agent. This is based on the fact that the reaction of calcium carbide with oxides in steel slag produces a large amount of CO gas, which not only effectively reduces the FeO content in the slag but also achieves slag layer foaming through gas escape, thereby encapsulating the electrodes, improving thermal efficiency, and preventing nitrogen absorption by the molten steel.

[0003] However, despite the maturity of calcium carbide slag-forming technology, its technical defects in practical applications have become a bottleneck restricting the improvement of refining levels. First, calcium carbide readily absorbs moisture and hydrolyzes to produce acetylene (C2H2), posing a significant risk of combustion and explosion in the high-temperature and high-spark furnace environment. Second, the decomposition and reaction processes of calcium carbide are often extremely violent and difficult to control precisely. This "explosive" reaction characteristic, while causing rapid foaming in the initial stages, results in extremely rapid foam decay, leading to "defoaming" of the slag layer in the later stages of refining, resulting in red slag or even open arc operation. This not only significantly reduces the thermal efficiency of the electric arc but also exacerbates the erosion of refractory materials. More critically, existing methods for adding non-calcium carbide-based submerged arc agents mostly follow the "one-time addition" or simple "empirical batch" model for calcium carbide, lacking a scientific segmentation strategy based on refining reaction kinetics. This crude method of addition ignores the different requirements for slag redox potential (Eh) and viscosity in the early, middle, and late stages of refining. This often leads to obstructed flotation channels for deoxidation products or stagnation of slag-steel interface reactions, making it difficult to achieve the production requirements of high-quality steel with ultra-low oxygen (e.g., Total Oxygen ≤ 15ppm). Therefore, developing an intrinsically safe, non-calcium carbide-based submerged arc agent addition method that can precisely control slag layer properties throughout the refining process is of paramount industrial value for improving the metallurgical quality of special steels and high-quality structural steels. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for adding submerged arc agent in refining furnaces. This method achieves deep deoxidation and stable submerged arc under calcium carbide-free conditions through a three-stage progressive addition strategy based on reaction kinetics, combined with a dynamic slag condition feedback mechanism.

[0005] According to a first aspect of the present invention, a method for adding submerged arc flux in a refining furnace is provided. This method is applied to the smelting process of an LF refining furnace, and its core lies in strictly dividing the addition process of the submerged arc flux into three progressive stages with different functional orientations. Specifically, the first stage addition step is set after the molten steel enters the furnace and before power heating, or within 30 seconds after the start of power heating, adding a first portion of the submerged arc flux into the refining furnace, and the amount of this portion added is strictly limited to 50% to 70% of the total amount of submerged arc flux added. The thermodynamic basis for setting this high initial addition ratio is that: in the early stage of refining, the content of unstable oxides such as FeO and MnO in the slag is the highest, requiring the use of a high concentration of reducing agent to establish a huge chemical potential gradient to provide a strong mass transfer driving force, thereby rapidly converting the oxidized slag into reduced slag in a very short time before power supply; at the same time, the addition of 50%-70% can ensure that sufficient CO bubbles are generated at the moment of arc ignition, rapidly forming a "submerged arc layer" and avoiding heat radiation loss and nitrogen absorption by the molten steel in the early stage of arc ignition.

[0006] Subsequently, the method of the present invention performs a second-stage addition step, namely, adding a second portion of the submerged arc agent into the refining furnace 4 to 6 minutes after the start of electric heating, with the addition amount controlled at 15% to 25% of the total amount. The reason for choosing the 4 to 6 minute time window is that after the initial violent reaction, a large amount of reducing agent in the slag has been consumed, and as the temperature of the molten steel rises, the viscosity of the slag changes, and the foam stability begins to decrease. At this time, the addition of 15%-25% of the submerged arc agent aims to compensate for the reducing agent consumed by the reaction, utilize the newly generated microbubbles to "activate" the slag layer, maintain the emulsified state of the slag-steel interface, and provide continuous kinetic conditions for the capture of inclusions.

[0007] Furthermore, the method of this invention performs a third-stage addition step, namely, adding a third portion of the submerged arc agent into the refining furnace 8 to 12 minutes after the start of electric heating. The amount added is the remainder of the total submerged arc agent added (usually 5% to 35%). This stage belongs to the "deep deoxidation and slag stabilization" period. At this time, the temperature of the molten steel is close to the target value. The main purpose of adding the last portion of the submerged arc agent is no longer to generate gas vigorously, but to precisely fine-tune the basicity and reducing properties of the slag, prevent the "re-drying" or "phosphorus return" phenomenon in the later stage of refining, and ensure that the dissolved oxygen in the molten steel can be further extracted and reduced by the highly reducing slag system before tapping.

[0008] In one specific embodiment of the present invention, the timing control of the above three stages is further refined and optimized. Specifically, the first stage is completed after the molten steel enters the station but before the power heating begins; the second stage is carried out 5 minutes after the power heating begins; and the third stage is carried out 10 minutes after the power heating begins. This precise anchoring of time points is based on the typical reaction cycle of LF refining summarized from numerous industrial tests, which can maximize the matching of the coupling relationship between the slag melting rate and the molten steel temperature rise rate.

[0009] Furthermore, to ensure optimal metallurgical results, this invention limits the total amount of submerged arc agent added to 0.5 kg / t steel to 0.8 kg / t steel, and modifies the slag system established on the basis of the basic slag-forming material (such as lime). Preferably, the addition amounts of the first, second, and third parts of the submerged arc agent are 0.36 kg / t steel, 0.12 kg / t steel, and 0.12 kg / t steel, respectively (i.e., an optimized combination of 60%:20%:20% or a similar ratio). This formulation constitutes an optimal "inverted triangle" addition model, avoiding both insufficient initial reduction leading to delayed deoxidation and excessive addition later, which could result in increased carbon or silicon content. Simultaneously, this invention explicitly limits the submerged arc agent to a composite refining agent that does not contain calcium carbide, typically containing at least a deoxidizing element selected from carbon, silicon, and aluminum. Excluding calcium carbide not only fundamentally eliminates the risk of acetylene combustion and explosion but also avoids the problem of deteriorated slag fluidity caused by excessive CaO solid phase from calcium carbide decomposition.

[0010] Furthermore, another key technical feature of this invention is the introduction of a dynamic adjustment step based on slag condition. Specifically, before the second and third stages of addition, the slag condition is monitored in real time and adjusted accordingly. Regarding slag fluidity, if a crust or static state is observed on the slag surface, it indicates that the high-melting-point silicate network structure in the slag system is too dense or that excessive solid phase precipitation has occurred. In this case, the amount of submerged arc flux added in that stage needs to be increased by 10% to 20%, and 0.3-0.5 kg / t of fluorite should be added in conjunction. Fluorite (CaF2) is used as a flux, and its F... - Ions can effectively break the Si-O-Si bonds in the silicate network structure, thereby significantly reducing the viscosity of the slag and restoring its fluidity. Combined with the thermal effect generated by the increased submerged arc agent, the crust can be melted and formed quickly.

[0011] Regarding the foaming height of the slag, if the foaming height is less than 50mm or an open arc appears, it indicates insufficient gas source or excessive surface tension in the slag. The amount of submerged arc agent needs to be increased, or it needs to be added in the next stage earlier to supplement the gas generation source. Conversely, if the foaming height is greater than 200mm or there is an overflow tendency, the amount added needs to be reduced or the addition delayed to prevent a "major slag overturning" accident. Regarding the slag color, if it is yellow or red, it directly indicates that the FeO content in the slag is too high (>2%), indicating strong oxidizing properties. 10%-20% of submerged arc agent must be added to enhance the reduction reaction. If the slag is whitish, it indicates excessive reducing properties or excessive basicity. The amount added can be appropriately reduced to save costs and prevent the molten steel from returning to silicon.

[0012] The core reaction mechanism of this invention is as follows: 1. Initial strong reduction (thermodynamically driven): Utilizing a high concentration (50-70%) of reducing agent to establish a large chemical potential gradient ( It provides a powerful reaction driving force, instantly transforming highly oxidizing slag into reducing slag.

[0013] 2. Mid-term steady-state emulsification (kinetic maintenance): By supplementing the foaming source, the slag-gas-metal three-phase emulsion state is maintained, increasing the mass transfer area. ), increase the deoxygenation rate constant ( ).

[0014] 3. Post-treatment deep purification (interfacial adsorption): Trace amounts are added to fine-tune the viscosity, utilizing the highly reducing slag for... The chemical adsorption of inclusions achieves ultimate deoxygenation.

[0015] The method for adding submerged arc flux in refining furnaces provided by this invention has significant advantages over existing technologies: First, this invention significantly improves deoxidation efficiency and steel purity through a three-stage progressive addition strategy. Unlike traditional methods where a single addition leads to a rapid decline in reducing capacity over time, this invention utilizes a high dose of 60% submerged arc agent in the early refining stage to establish an extremely high reducing potential, rapidly removing most of the iron oxide from the slag. Subsequently, through batch replenishment in the middle and later stages, the slag-steel interface is consistently maintained in a state of high reducing activity. This stepwise control mechanism ensures that the slag layer's distribution coefficient to oxygen in the molten steel remains at an optimal level, thereby stably controlling the oxygen content of the molten steel before tapping to below 15 ppm, a reduction of more than 40% compared to traditional processes, and significantly reducing residual oxide inclusions.

[0016] Secondly, this invention achieves stable control of the slag layer foaming state throughout the entire process through a scientific material distribution and dynamic adjustment mechanism, significantly improving energy utilization efficiency. This method avoids the phenomenon of "rapid collapse after explosive foaming" common in traditional calcium carbide processes. By supplementing the foaming source at critical points of 5 and 10 minutes after power supply, the uniformity of the foam slag height (arc submersion rate ≥90%) is maintained throughout the refining cycle. The stable foam slag not only effectively shields against arc radiation, significantly improving arc heat utilization efficiency, reducing power consumption, and shortening power supply time, but also significantly reduces the loss of refractory materials caused by thermal shock and arc erosion.

[0017] Finally, this invention establishes a multi-dimensional dynamic feedback adjustment system based on slag conditions (flowability, height, color), endowing the process with extremely strong adaptability and robustness. This mechanism breaks the rigid operating mode, allowing operators to intervene in real time according to the specific physicochemical state of each heat of steel (such as fluctuations in slag quantity and temperature differences). In particular, through the synergistic effect of fluoride ion depolymerization silicate network and the thermal effect of reducing agent, it effectively solves the common slag formation difficulties and crusting problems in the refining process, ensuring the consistency of quality between different heats, while completely eliminating the use of calcium carbide, achieving inherent safety and greening of the LF refining process. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of the three-stage addition method of the submerged arc agent in the refining furnace according to the present invention; Figure 2 This is a schematic diagram showing the proportion of arc-submerging agent added at each stage of the present invention. Detailed Implementation

[0019] The method for adding submerged arc flux in refining furnaces proposed in this invention is as follows: Figure 1 , Figure 2 As shown, this invention aims to address issues such as low deoxidation efficiency, poor stability of foamy slag, and safety hazards associated with calcium carbide operations during LF refining. The submerged arc agent used in this embodiment is a non-calcium carbide composite refining agent, whose main chemical components (by weight percentage) are: Al 10-15%, C 10-15%, Si 5-10%, CaO 25-35%, Al2O3 10-18%, with the balance being MgO and unavoidable impurities (of which the MgO content is not less than 7%). This composition design aims to rapidly reduce the oxygen potential in the slag by utilizing the strong reducing properties of Al / Si, and to generate micro-CO bubble sources by utilizing the reaction of C with oxides in the slag. Combined with the CaO / Al2O3 matrix, the slag basicity (R) is adjusted to the range of 2.0-3.5 to construct a suitable liquid phase region.

[0020] This embodiment specifies that all examples and comparative examples adopt the standard LF slag-forming system. Specifically, during the steel tapping process and the initial stage of slag entry, active lime (CaO≥90%) is added at a ratio of 6.0-8.0 kg / t steel to ensure that the slag binary basicity (CaO / SiO2) reaches the desulfurization benchmark of 3.0-4.0. The "arc-submerging agent" described in this invention is added on top of this basic slag system as a modifier and reducing agent.

[0021] Test methods and evaluation criteria To objectively evaluate the effects of each embodiment and comparative example, the following standard methods were used for testing: 1. Total Oxygen Content (TO): According to GB / T11261-2006 "Determination of Oxygen Content in Steel - Pulse Heating Inert Gas Melting-Infrared Absorption Method", after soft blowing before tapping, online measurement was performed using a constant oxygen probe and matching instruments. Samples were taken and verified using a LECO oxygen and nitrogen analyzer, and the average value was taken. Unit: ppm.

[0022] 2. Arc submersion rate: The entire refining and power supply process is recorded by a camera on the furnace cover.

[0023] Calculation formula: .

[0024] Judgment criteria: If the arc light is not directly exposed on the slag surface, it is considered "fully submerged arc".

[0025] 3. Desulfurization rate ( ): The desulfurization rate indirectly reflects the reducibility (low FeO content in the slag) and fluidity (good kinetic conditions) of the slag.

[0026] 4. Refining power consumption: Records the power consumption of the entire LF refining process, converted to kWh / t steel.

[0027] 5. Slag fluidity score: The sensory score is given by senior steelmaking workers through slag hook testing (1-5 points, with 5 points being the best fluidity and 1 point being severe crusting).

[0028] All the following examples were conducted on a 120-ton LF refining furnace at a steel plant, using Q355B steel. The average temperature of the molten steel entering the furnace was 1560±10℃, the average oxygen content was 550±30ppm, and the sulfur content was 0.035%. The basic lime addition was uniformly 700kg / furnace (approximately 5.8kg / t). The total baseline addition of the submerged arc flux was set at 0.6kg / t steel.

[0029] Example 1 (Optimal Example) Strictly follow the preferred formulation of this invention: First stage (before power transmission): Add 0.36 kg / t (60%).

[0030] Second stage (power supply 5 min): Add 0.12 kg / t (20%).

[0031] Third stage (power supply 10 min): Add the remaining amount of 0.12 kg / t (20%).

[0032] The process conditions were good, and dynamic adjustment was not triggered.

[0033] Example 2 (High Initial Investment Ratio) Test the upper limit of the first stage: First stage (30s after power supply): Add 0.42kg / t (70%).

[0034] Second stage (power supply 4 min): Add 0.09 kg / t (15%).

[0035] Third stage (power supply 8 min): Add the remaining amount of 0.09 kg / t (15%).

[0036] Example 3 (Low Initial Investment Ratio) Test the lower limit of the first stage: First stage (before power transmission): Add 0.30 kg / t (50%).

[0037] Second stage (6 minutes of power supply): Add 0.15 kg / t (25%).

[0038] Third stage (power supply 12 min): Add the remaining amount of 0.15 kg / t (25%).

[0039] Example 4 (Large-scale test) For furnaces with high oxygen content at the inlet (650 ppm), the total addition amount will be increased to 0.8 kg / t. Phase 1 (60%): 0.48 kg / t.

[0040] Second stage (20%): 0.16 kg / t.

[0041] Third stage (20%): 0.16 kg / t.

[0042] Example 5 (Dynamic Adjustment - Poor Flowability) Simulate an abnormal slag condition scenario. Before executing the second stage, partial crusting was observed on the slag surface (flowability score 2 points).

[0043] Trigger adjustment: Increase the amount added in the second stage by 20% (to 0.144 kg / t), and add an additional 0.4 kg / t of fluorite.

[0044] The third stage involves resuming normal addition (0.12 kg / t).

[0045] Example 6 (Dynamic Adjustment - Insufficient Foaming) Simulate a scenario of insufficient foaming. Eight minutes after power is supplied (before the third stage), exposed electric arcs were observed, and the foaming height was <50mm.

[0046] Trigger adjustment: The third stage is initiated 8 minutes after power is supplied, and the amount added is increased to 0.15 kg / t (25%).

[0047] Comparative Example 1 A non-calcium carbide-based arc-submerging agent is used, but the method is as follows: 100% (0.6 kg / t) is added all at once after entering the station. No subsequent additions are made.

[0048] Comparative Example 2 The solution was added in three equal parts: 33% (before powering on) - 33% (5 min) - 34% (10 min). The "inverted triangle" gradient was not observed.

[0049] Comparative Example 3 Calcium carbide is used for deoxidation and slag formation. 0.4 kg / t of calcium carbide is added at the start of the process, and an additional 0.2 kg / t is added during the refining process.

[0050] Comparative Example 4 is divided into only two segments: 50% (before power supply) - 50% (10 minutes after power supply). The intermediate steady-state maintenance stage is missing.

[0051] Table 1 Performance Test Results Based on the above experimental data, the following profound mechanistic conclusions can be drawn: 1. Thermodynamic necessity of the "inverted triangle" gradient (Comparative Example 1 and Comparative Example 2): The total oxygen content of Example 1 (60 / 20 / 20) (11.5 ppm) was significantly lower than that of Comparative Example 2 (equal distribution method, 19.8 ppm). This confirms the crucial role of the high concentration addition in the first stage of this invention. According to the principle of chemical kinetics (law of mass action), the deoxidation reaction rate is directly proportional to the product of reactant concentrations. In the early stage of refining, the oxygen activity of the molten steel is high. At this time, adding more than 60% of the submerged arc agent can instantly establish an extremely high reduction driving force at the slag-steel interface, allowing the deoxidation reaction to reach a quasi-equilibrium state within minutes. However, Comparative Example 2, due to insufficient initial addition (only 33%), resulted in incomplete initial deoxidation, with a large amount of FeO remaining in the slag. This not only corroded the furnace lining but also hindered the distribution ratio of sulfur (…). )promote.

[0052] 2. Dynamic stability achieved through multi-stage addition (comparative Example 1 with Comparative Examples 1 and 4): Although Comparative Example 1 (one-time addition) showed rapid initial deoxidation, the arc-submerging rate plummeted to 65% and power consumption soared to 52.0 kWh / t in the later stages of power transmission (after 15 minutes). This is because the foaming component (C) in the arc-submerging agent is consumed only once; as refining progresses, the gas source dries up, and the slag layer "dead." Example 1, through pulsed replenishment in the second and third stages, effectively superimposed a new reaction source on the reaction kinetic curve, maintaining the continuous generation and escape of microbubbles in the slag layer. This continuous "micro-stirring" effect significantly reduced the thickness of the liquid boundary layer (…). This enhances mass transfer during the deep deoxygenation phase. Data from Comparative Example 4 (two-stage) show that the absence of the intermediate second stage results in a "debubbling window" in the 5-10 minute interval, demonstrating the indivisibility of the three stages.

[0053] 3. Engineering robustness of the dynamic adjustment mechanism (Examples 5 and 6): Example 5 simulated the harsh "cold slag / crust" conditions. Without intervention, such furnace runs typically result in a significant decrease in inclusion removal rates. However, through the dynamic adjustment mechanism of this invention (increasing the arc-submerging agent + introducing fluorite), the inclusion removal rate is significantly reduced by utilizing the properties of fluorite... Ion-pair silicon-oxygen tetrahedral network structure ( The depolymerization effect of the compound, combined with the high alkalinity of the base slag, successfully controlled the total oxygen content at 13.5 ppm. This proves that the present invention is not merely a fixed formulation, but a process control system with adaptive capabilities.

[0054] 4. Advantages of non-calcium carbide processes (Comparative Example 1 and Comparative Example 3): Although Comparative Example 3 (calcium carbide process) also achieved a certain deoxidation effect (18.0 ppm), its arc-submerging rate fluctuated greatly (82%), and the final oxygen content was higher than that of this invention. This is because the acetylene bubbles generated by the calcium carbide reaction are large in size and escape quickly, resulting in foam slag that "comes and goes quickly," unlike the fine and uniform bubbles generated by the composite arc-submerging agent (C / Si / Al synergy) in this invention. More importantly, no acetylene gas was detected throughout the entire process of the examples, eliminating safety hazards and aligning with the development direction of green metallurgy.

[0055] In summary, this invention achieves efficient, stable, and safe refining slag formation by precisely controlling the spatiotemporal distribution of chemical potential gradient and reaction kinetics. Its technical effects are unpredictable and unattainable by existing conventional methods.

[0056] It should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of refining furnace smelting submerged electrodes, characterized in that, The method is applied to the LF refining furnace smelting process and includes the following three progressive addition steps: The first stage of adding the agent involves adding the first part of the submerged arc agent into the refining furnace after the molten steel enters the station and before the power is supplied for heating, or within 30 seconds after the power is supplied for heating. The amount of the first part of the submerged arc agent added is 50% to 70% of the total amount of submerged arc agent added. The second stage of the addition process: During the period of 4 to 6 minutes after the start of power supply and heating, the second part of the submerged arc agent is added into the refining furnace. The amount of the second part of the submerged arc agent added is 15% to 25% of the total amount of submerged arc agent added. The third stage of the process involves adding the third part of the submerged arc agent into the refining furnace 8 to 12 minutes after the start of power-on heating. The amount of the third part of the submerged arc agent added is the remainder of the total amount of submerged arc agent added; Wherein, the sum of the masses of the first part, the second part, and the third part of the submerged arc agent is equal to the total amount of submerged arc agent added; The arc-submerging agent is a composite refining agent that does not contain calcium carbide.

2. The method of refining furnace smelting of submerged electrodes according to claim 1, characterized in that, The timing control of the first, second, and third stage addition steps is as follows: the first stage addition step is completed after the molten steel enters the station and before the power heating is started; the second stage addition step is performed 5 minutes after the power heating starts; and the third stage addition step is performed 10 minutes after the power heating starts.

3. The method for adding submerged arc agent in refining furnace smelting according to claim 1, characterized in that, The total amount of the submerged arc agent added is 0.5-0.8 kg / t steel; the amount of the first part of the submerged arc agent added is 0.36 kg / t steel; the amount of the second part of the submerged arc agent added is 0.12 kg / t steel; and the amount of the third part of the submerged arc agent added is 0.12 kg / t steel.

4. The method for adding submerged arc agent in refining furnace smelting according to claim 1, characterized in that, The submerged arc agent contains at least one deoxidizing element selected from carbon, silicon, and aluminum; the method does not add calcium carbide as a deoxidizing agent or foaming agent throughout the entire process.

5. The method for adding submerged arc agent in refining furnace smelting according to claim 1, characterized in that, The method further includes a dynamic adjustment step of detecting the slag condition and adjusting the amount of submerged arc agent added based on the detection results before performing the second-stage addition step and / or the third-stage addition step.

6. The method for adding submerged arc agent in refining furnace smelting according to claim 5, characterized in that, The dynamic adjustment steps include adjusting the slag fluidity: observing the slag surface, when the slag surface shows a crust or a static state, it is determined that the slag fluidity is poor. At this time, the amount of submerged arc agent added at this stage is increased by 10% to 20% based on the original set value, and an additional 0.3 kg / t steel to 0.5 kg / t steel of fluorite is added to the refining furnace; when the slag surface shows a flowing state and there is no crust, it is determined that the slag fluidity is good, and at this time, the submerged arc agent is added according to the original set value.

7. The method for adding submerged arc agent in refining furnace smelting according to claim 5, characterized in that, The dynamic adjustment step includes adjusting the foaming height of the slag: when the foaming height of the slag is less than 50mm or an open arc appears, the amount of arc-submerging agent added in the current stage is increased based on the original set value, or the execution time of the next stage addition step is advanced by 1 to 2 minutes. When the foaming height of the slag exceeds 200mm or there is a tendency to overflow, the amount of submerged arc agent added in this stage should be reduced from the original set value, or the execution time of the next stage addition step should be postponed.

8. The method for adding submerged arc agent in refining furnace smelting according to claim 5, characterized in that, The dynamic adjustment step includes adjusting the slag color: when the slag is yellow or red, it is determined that the slag has strong oxidizing properties, and the amount of submerged arc agent added in this stage is increased by 10% to 20% based on the original set value; when the slag is whitish, it is determined that the slag has excessive reducing properties, and the amount of submerged arc agent added in this stage is reduced by 10% to 20% based on the original set value.

9. The method for adding submerged arc agent in refining furnace smelting according to any one of claims 1 to 8, characterized in that, The steel smelted in the refining furnace is Q235 series plain carbon steel or Q355 series low alloy steel, and the initial oxygen content of the molten steel when it enters the station is 400ppm to 650ppm.

10. The method for adding submerged arc agent in refining furnace smelting according to any one of claims 1 to 8, characterized in that, The oxygen content of the molten steel before tapping is controlled to be no higher than 15 ppm by the method described above, and the arc burial rate of the electrodes is maintained above 90% during the electric heating process.

Images