A method for dephosphorization of nickel-iron melt outside the furnace

Abstract

The application discloses a nickel-iron molten steel off-furnace dephosphorization refining method, relates to the field of nickel-iron alloy smelting, and uses a nickel-iron ladle for existing iron tapping and receiving as an in-situ refining reactor, adopts CaO-Fe2O3-CaF2 ternary oxidizing refining slag, and realizes off-furnace dephosphorization by combining with argon bottom blowing and grading stirring, and comprises the following steps: iron tapping preparation, iron tapping synchronous premixing, strong stirring dephosphorization refining and static layering and slagging. Fe2O3 is used as a solid oxygen source, the characteristics of slow decomposition and oxygen supply of the nickel-iron temperature interval are combined, the selective oxidation of phosphorus elements is combined with the difference in oxidation free energy of phosphorus and nickel, the problem of excessive oxidation of nickel caused by direct oxygen blowing is avoided, the refining temperature interval and the reaction length are accurately controlled, the oxidation reaction of nickel is inhibited, the oxidation loss rate of nickel metal is controlled at a low level, the metal loss cost of the dephosphorization process is reduced, the cost of mixed burning of high-phosphorus laterite ore is low, and the raw material procurement range is widened.

Description

Technical Field

[0001] This invention relates to the field of nickel-iron alloy smelting, and particularly to an external dephosphorization refining method for molten nickel-iron. Background Technology

[0002] Phosphorus is a harmful impurity in stainless steel production. The entire RKEF process is conducted in a strong reducing atmosphere, and almost 100% of the phosphorus in the raw ore is reduced into the molten nickel-iron. As nickel-iron is the core raw material for stainless steel and special alloy steel, phosphorus will reduce the low-temperature toughness, weldability and corrosion resistance of the steel. Currently, the main technical approaches for dephosphorization of nickel-iron are divided into two categories: in-furnace dephosphorization and out-of-furnace dephosphorization. In-furnace dephosphorization requires the oxidation and fixation of phosphorus in an oxidizing atmosphere. However, the RKEF submerged arc furnace is a strong reducing smelting environment throughout the process, with extremely low oxygen potential inside the furnace, which does not meet the thermodynamic conditions for the dephosphorization reaction and cannot achieve effective dephosphorization inside the furnace. If the atmosphere inside the furnace is forcibly adjusted to an oxidizing state, it will lead to a large amount of oxidation of the main metals such as nickel and iron, resulting in serious metal loss. Traditionally, the only option is to purchase high-priced low-phosphorus ore.

[0003] Existing external dephosphorization technologies mostly directly borrow from steelmaking dephosphorization processes, using oxygen to be directly blown into molten iron. Although this can provide a high oxygen potential, the oxidation selectivity of nickel and phosphorus is poor, and the oxygen blowing process will cause a large amount of nickel to be oxidized and burned off, resulting in a high nickel metal loss rate. Static slag washing or simple mechanical stirring slag-based dephosphorization methods have limited slag-metal contact area, poor reaction kinetics, generally low dephosphorization rates, and dephosphorization depths that are difficult to meet the requirements of high-end products. Furthermore, most existing dephosphorization solutions require the addition of dedicated dephosphorization furnaces and reaction tanks as independent reactors, necessitating modifications to existing production and logistics routes, making direct application on existing RKEF production lines difficult.

[0004] Therefore, we propose an external dephosphorization refining method for molten nickel to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide an external dephosphorization refining method for molten nickel-iron to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: an external dephosphorization refining method for molten nickel-iron, using molten nickel-iron produced by an RKEF submerged arc furnace as the treatment object, using an existing nickel-iron ladle for tapping as an in-situ refining reactor, employing a CaO-Fe2O3-CaF2 ternary oxidizing refining slag, and combining bottom-blown argon gas with staged stirring to achieve external dephosphorization, specifically including the following steps: Preparations before tapping S1: Modify the nickel-iron ladle, install permeable bricks at the bottom of the ladle and connect it to the high-pressure argon gas pipeline, and equip it with quantitative slag feeding equipment and slag removal equipment; prepare synthetic refining slag and prepare it quantitatively, and preheat the nickel-iron ladle; S2 Iron Tapping Synchronous Premixing: After the molten iron is tapped from the electric arc furnace and the surface of the molten iron is above the top of the permeable brick, the synthetic refining slag is simultaneously fed into the nickel-iron ladle along with the iron flow. At the same time, bottom blowing argon gas is turned on for weak stirring. The slag material is initially melted and uniformly mixed by utilizing the impact kinetic energy of the iron flow and the stirring effect of the gas. S3 Strong Stirring Refining Dephosphorization: After the iron tapping and slag feeding are synchronized, the bottom blowing argon gas is switched to strong stirring mode to form a large number of diffused bubbles in the nickel-iron ladle. The drag force of the bubbles drives the nickel-iron liquid to roll throughout the entire area, so that the liquid refining slag is deeply rolled into the interior of the molten iron to form a slag-gold emulsion layer, and the dephosphorization refining reaction is carried out within the preset temperature range. S4 Settling and Slag Removal: After refining, the argon supply is stopped, and the slag and iron are allowed to settle and separate by gravity. After passing the test, the phosphorus-rich slag on the surface is removed to obtain dephosphorized nickel-iron molten iron, which is then sent to the casting process.

[0007] Preferably, based on the final synthetic refining slag in step S1, The slag basicity CaO / SiO2 is 2.5~4.0, forming a high-alkalinity environment. Under the high-alkalinity environment, phosphorus in the nickel-iron molten iron is oxidized to P2O5. The high-alkalinity slag fixes it into stable CaO·P2O5 calcium phosphate, inhibiting the remelting of phosphorus into the molten iron after dephosphorization. By adding Fe2O3 as a solid oxygen source and utilizing the difference in oxidation free energy between phosphorus and nickel, oxygen is continuously supplied at the slag-gold interface to selectively oxidize phosphorus in molten iron, thus ensuring the dephosphorization oxygen potential while keeping nickel oxidation loss at a low level. Adding CaF2 as a flux lowers the melting point of the slag system, ensuring that the slag has good fluidity at the tapping temperature of nickel-iron.

[0008] Preferably, the preferred ratio of the synthetic refining slag described in step S1 is as follows: the slag basicity CaO / SiO2 is 3.0~3.5; the Fe2O3 consumption is 20~25kg / t; the CaF2 consumption is 6~8kg / t; Fe2O3 decomposes at around 1450℃ to selectively oxidize active phosphorus elements, thereby controlling the reduction of nickel oxidation loss rate.

[0009] Preferably, the bottom-blown argon gas employs a two-stage stirring mode: The premixing stage of molten iron adopts a weak stirring mode, which promotes the melting and mixing of slag materials while suppressing secondary oxidation and temperature drop of molten iron caused by atmospheric entrainment. After tapping the iron, switch to strong stirring mode to increase the slag-metal contact surface area and accelerate the dephosphorization reaction rate.

[0010] Preferably, the ternary synthesis refining slag is pre-processed into granules or compressed into pellets to improve the melting rate; the slag feeding process is matched with the iron tapping rate in real time, and the slag is evenly thrown into the nickel-iron ladle with the iron flow to avoid the slag from forming a crust and floating, which would affect the subsequent refining effect.

[0011] Preferably, the composition ratio and total amount of refining slag, as well as the stirring intensity and refining time of bottom-blown argon, are dynamically adjusted according to the different grades of initial phosphorus content in molten nickel, so as to reduce nickel oxidation loss and process operating costs while meeting the dephosphorization index. Strategy for dynamically adjusting process parameters based on the initial phosphorus content of molten nickel: When the initial phosphorus content is >0.08%, the working conditions for high-phosphorus ore are as follows: Fe2O3 consumption is 28-30 kg / t, alkalinity is 3.8-4.0, strong stirring time is extended to 12-15 min, and stirring intensity is 35-40 L / min·t. When the initial phosphorus content is 0.06% to 0.08%, under the condition of medium phosphate ore: the optimized parameters are implemented, the Fe2O3 consumption is 22 to 25 kg / t, the alkalinity is 3.0 to 3.8, the stirring intensity is 30 to 35 L / min·t, and the time is 10 min. By reducing the slag amount and stirring intensity, nickel loss and operating costs are further reduced. When the initial phosphorus content is <0.06%, for low-phosphate ore conditions: reduce Fe2O3 to 12-15 kg / t, alkalinity to 2.5-3.0, cancel strong stirring and use only weak stirring mode, with stirring intensity of 10-20 L / min. t, time 10min, further reducing nickel loss and operating costs.

[0012] Preferably, before tapping iron, the erosion thickness of the nickel-iron ladle reactor lining and the integrity of the permeable bricks at the bottom of the nickel-iron ladle are checked to confirm that the residual thickness of the lining is greater than the set threshold thickness; the gas supply pipeline is confirmed to be unobstructed and airtight by introducing argon gas for a test blow, so as to avoid the safety hazards of permeable brick blockage and iron leakage during the refining process.

[0013] Preferably, based on the strong stirring mode described in step S3, the gas supply pressure is stabilized at 0.4~0.8MPa, and the gas supply intensity is continuously and steplessly adjusted by using PID closed-loop regulating valve opening to avoid molten iron splashing and overflowing from the ladle edge.

[0014] Preferably, based on the sampling and testing before slag removal in step S4, the phosphorus and nickel content of the nickel-iron molten metal is tested: If the indicators are not up to standard, add oxygen source Fe2O3 and repeat step S3. After refining, turn off the argon gas and let it stand for 1-2 minutes to allow the slag and iron to separate fully and settle by gravity. Then test the phosphorus and nickel content of the nickel-iron molten metal again until the indicators are up to standard. Based on the results, adjust the ratio of synthetic slag to nickel-iron molten metal. Once the indicators meet the requirements, start the mechanical slag remover and gradually remove the surface layer of phosphorus-rich dephosphorization slag along the wall.

[0015] Preferably, based on feedback adjustment of the ratio of synthetic slag to molten nickel-iron, an adaptive incremental correction model based on the residual phosphorus content of the first round of refining is adopted, specifically including the following operational logic: Dephosphorization deviation determination: The phosphorus content of the nickel-iron molten metal after the first strong stirring refining was sampled and tested. Combined with the initial phosphorus content predicted by the electric arc furnace, the actual dephosphorization rate was calculated. in, This represents the actual phosphorus removal rate. This represents the initial phosphorus content. The phosphorus content of the nickel-iron molten metal after the first strong stirring refining; The endpoint phosphorus content is set to ≤0.030% according to product requirements. The difference from the target value is subject to tiered correction. The specific tiered feedback correction steps are as follows: Primary under-dephosphorization, 0.030% < ≤0.050%: This is considered a slight lack of kinetics. The initial Fe2O3 addition for the next heat of molten iron of the same tonnage should be 10% to 15% higher than the baseline value. The CaO addition should be adjusted proportionally to the basicity of 3.5, while the CaF2 addition should remain unchanged. Secondary severe under-dephosphorization, >0.050%: This indicates a severe deficiency in thermodynamic oxygen potential or a large deviation in the initial phosphorus forecast. The initial Fe2O3 addition for the next batch should be 25%–30% higher than the baseline value, and the upper limit of alkalinity should be forcibly raised to 4.0. Excessive oxygen warning: If phosphorus is qualified but nickel loss exceeds the standard after Fe2O3 is added and refining, the initial Fe2O3 addition for the next batch will be reduced by 10% in the opposite direction, and the dephosphorization rate will be compensated by increasing the stirring intensity to 40L / min·t.

[0016] The technical effects and advantages of this invention are as follows: 1. A thermodynamic system with high alkalinity and high oxygen potential is constructed by using CaO-Fe2O3-CaF2 ternary refining slag. Combined with the slag-gold emulsion layer formed by strong bottom blowing argon stirring, the specific surface area of ​​the slag-gold reaction is increased, and the dephosphorization reaction kinetics are optimized. Under suitable operating conditions, a high dephosphorization rate is achieved, reducing the phosphorus content of medium-high phosphorus nickel molten iron to below the standard of high-end raw materials, effectively solving the problem that the RKEF process cannot efficiently dephosphorize.

[0017] 2. Using Fe2O3 as a solid oxygen source, leveraging its slow decomposition and oxygen supply characteristics within the nickel-iron temperature range, and combining the difference in oxidation free energy between phosphorus and nickel, selective oxidation of phosphorus is achieved, avoiding the problem of excessive nickel oxidation caused by direct oxygen blowing. By precisely controlling the refining temperature range and reaction time, the oxidation reaction of nickel is suppressed, keeping the nickel metal oxidation loss rate at a low level, reducing the metal loss cost of the dephosphorization process, and enabling the blending of inexpensive high-phosphorus laterite ore, thus broadening the range of raw material procurement and producing low-phosphorus nickel-iron products.

[0018] 3. The existing ferronickel ladle in the production process can be used as an in-situ refining reactor. The modification can be completed simply by adding permeable bricks to the bottom of the ladle and installing supporting gas supply and feeding equipment. There is no need to add a special dephosphorization reactor or change the existing production and logistics layout. The modification can be completed within the equipment maintenance cycle without affecting normal production order, reducing the modification cost of technology implementation and adapting to the upgrade needs of existing RKEF production lines.

[0019] 4. The slag premixing is completed simultaneously during the iron tapping process. After the iron tapping is completed, the refining, dephosphorization and slag removal processes are completed directly within the iron tapping interval. The refining time can be compressed to the range of the single furnace iron tapping interval, matching the single furnace iron tapping interval cycle of the submerged arc furnace. The dephosphorization process is embedded in the existing production process without the need for additional process waiting time, and does not affect the original production capacity, thus realizing the connection between the dephosphorization process and the main production process.

[0020] 5. Based on the different grades of initial phosphorus content in molten nickel and iron, dynamically adjust the basicity of refining slag, oxygen source consumption, stirring intensity, and refining time; reduce slag quantity and stirring intensity for low-phosphorus raw materials, and optimize dephosphorization conditions for high-phosphorus raw materials. Under the premise of ensuring that dephosphorization indicators meet the standards, reduce slag consumption, gas consumption, and metal loss, and achieve operating cost under different raw material conditions.

[0021] 6. Before tapping, the erosion status of the lining, the integrity of the permeable bricks, and the air tightness of the air passage are checked to avoid safety and quality risks such as iron leakage and permeable brick blockage from the source. Combined with the static stratification and deep slag removal control after refining, the problems of phosphorus return and excessive iron loss can be effectively avoided, ensuring the quality stability of the final low phosphorus nickel-iron product. Attached Figure Description

[0022] Figure 1 This is an overall flowchart of the present invention; Figure 2 This is a flowchart illustrating the preparation process before tapping iron according to the present invention. Figure 3 This is a flowchart illustrating the dynamic proportioning and synchronous feeding process of refining slag in this invention. Figure 4 This is a flowchart of the bottom-blown argon gas control process of the present invention; Figure 5 This is a flowchart of the refining and dephosphorization process of the present invention; Figure 6 This is a structural diagram of the nickel-iron dephosphorization device of the present invention; Figure 7 This is a comparison chart of P content before and after refining in this invention.

[0023] In the picture: 1. Nickel-iron ladle; 2. Permeable brick; 3. Slag remover. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] This invention provides, for example Figures 1-7 The method for dephosphorizing and refining molten nickel-iron in an external furnace, as shown, involves tapping iron from an RKEF submerged arc furnace, using nickel-iron ladle 1 as a reactor, and employing CaO-Fe2O3-CaF2 to synthesize an oxidizing refining slag. Strong stirring is achieved using bottom-blown argon gas, and slag premixing is completed simultaneously during tapping. After tapping, strong stirring refining and dephosphorization are performed. The specific steps include: Preparations before tapping S1: Modify the nickel-iron ladle 1, install permeable bricks 2 at the bottom of the ladle and connect it to the high-pressure argon gas pipeline, and equip it with quantitative slag feeding equipment and slag removal equipment; prepare synthetic refining slag and prepare it quantitatively, and preheat the nickel-iron ladle 1. S2 Iron Tapping Synchronous Premixing: After the molten iron is tapped from the electric arc furnace and the surface of the molten iron is above the top surface of the permeable brick 2, the synthetic refining slag is simultaneously fed into the nickel-iron ladle 1 along with the iron flow. At the same time, bottom blowing argon gas is turned on for weak stirring. The slag material is initially melted and uniformly mixed by utilizing the impact kinetic energy of the iron flow and the stirring effect of the gas. S3 Strong Stirring Refining and Dephosphorization: After the iron tapping and slag feeding are completed simultaneously, the bottom blowing argon gas is switched to strong stirring mode, and a large number of diffused bubbles are formed in the nickel-iron ladle 1. The drag force of the bubbles drives the nickel-iron liquid to roll throughout the entire area, so that the liquid refining slag is deeply rolled into the interior of the molten iron to form a slag-gold emulsion layer, and the dephosphorization refining reaction is carried out within the preset temperature range. S4 Settling and Slag Removal: After refining, the argon supply is stopped, and the slag and iron are allowed to settle and separate by gravity. After passing the test, the phosphorus-rich slag on the surface is removed to obtain dephosphorized nickel-iron molten iron, which is then sent to the casting process.

[0026] Step S1: Preparations before tapping iron Instead of in-furnace dephosphorization, the existing nickel-iron ladle 1 used for iron tapping is directly used as an in-situ refining reactor. A porous, diffused, permeable brick 2 is installed by drilling holes at the bottom of the nickel-iron ladle 1 reactor. A high-pressure argon gas pipeline is connected to the bottom of the reactor, and a pressure reducing valve is installed to stabilize the working pressure. A flow meter and a solenoid valve are connected in series on the high-pressure argon gas pipeline to regulate the argon gas flow. The original hydraulic tilting mechanism is retained, and a slag feeding chute with weighing function and a mechanical slag remover 3 are provided. Before tapping the iron, check the erosion thickness of the lining of the nickel-iron ladle 1 reactor and the integrity of the bottom permeable brick 2 of the nickel-iron ladle 1. Confirm that the residual thickness of the lining is greater than the set threshold thickness, preferably the set threshold thickness is 60% greater than the original design thickness. Confirm that the gas supply pipeline is unobstructed and the airtightness is qualified by introducing argon gas into the high-pressure argon gas pipeline and performing a test blow, so as to avoid micro-blockage of the vent holes. It is preferable to introduce 0.6MPa argon gas for 30 seconds to test the airflow and observe the uniformity of the return air bubble distribution in each area of ​​the package opening; By verifying the equipment status in advance, safety and quality accidents such as blockage of the permeable brick 2 and iron leakage during the refining process can be avoided, thus ensuring the stable operation of the process.

[0027] During tapping, based on the predicted tapping amount of the electric arc furnace, synthesize refining slag according to the proportion, determine the total amount to be added based on the predicted tapping amount, confirm that the silo is well stocked, and preferably pre-crush and screen the synthetic slag into 5-20mm granules or press it into Φ20mm pellets to improve the melting rate.

[0028] Based on the amount of iron to be tapped, determine the amount of iron to be tapped that needs to be processed and the corresponding amount of synthetic refining slag, and ensure that they are mixed in proportion. The weighed synthetic slag is loaded into the slag feeding chute silo for automatic feeding. The preferred automatic feeding rate is 25 kg / t × the current furnace tapping tonnage. The empty nickel-iron ladle 1 is preheated by gas baking to 800~900℃, preferably 850℃, so that there is no water accumulation and no slag on the bottom of the ladle, to prevent the heat released during dephosphorization from being absorbed by the ladle wall and causing slag crusting. Specifically disclosed is the synthesis of refining slag according to the specified ratio, using CaO-Fe2O3-CaF2 to synthesize oxidizing refining slag. The composition and dosage of the oxidizing refining slag meet the following requirements: The final synthesis of the refining slag system with an alkalinity of CaO / SiO2 controlled at 2.5~4.0, preferably 3.0~3.5; A high-alkalinity environment is created, which reduces the activity of P2O5 generated after phosphorus is oxidized in molten nickel-iron. The high-alkalinity slag fixes it into stable CaO·P2O5 calcium phosphate, preventing phosphorus from melting back into the molten iron after dephosphorization and ensuring the depth of dephosphorization.

[0029] The Fe2O3 consumption is 10-30 kg / t of nickel-iron molten iron, preferably 20-25 kg / t; Fe2O3, acting as a solid oxygen source, provides continuous and gentle oxygen supply at the slag-metal interface, oxidizing P in the molten iron to P2O5. Compared to directly blowing oxygen into the molten iron, which would drastically oxidize Ni, Fe2O3 slowly decomposes and supplies oxygen at around 1450℃. By utilizing the difference in oxidation free energy between P and Ni, it achieves selective oxidation of P, which has higher activity. This controls Ni burn-off from the source. The solid oxygen source of Fe2O3 provides more uniform oxygen supply, reducing excessive oxidation of nickel and keeping nickel oxidation loss low while ensuring the dephosphorization oxygen potential. The CaF2 consumption is 5-10 kg / t of nickel-iron molten iron, preferably 6-8 kg / t; CaF2, as a flux, can lower the melting point of the slag system to below 1300℃. The tapping temperature of ferronickel is about 1350~1450℃. CaO has a high melting point, and adding CaF2 can lower the melting point of the slag system, so that the ferronickel can maintain good fluidity at the tapping temperature, making it easier for the slag to be entrained into the molten iron, ensuring full contact between the slag and the metal interface, and avoiding the reaction stagnation caused by the slag becoming sticky at low temperatures. The natural temperature of the ferronickel after tapping is just right in the thermodynamic window, and no additional heating or cooling is required. Step S2: Synchronous premixing during iron tapping Iron is tapped from the RKEF submerged arc furnace. The molten nickel-iron is poured into the preheated nickel-iron ladle 1. After the molten iron surface is 200-300mm above the top surface of the permeable brick 2, the automatic slag feeding is started. The CaO-Fe2O3-CaF2 ternary synthetic slag is evenly added into the iron flow, so that the slag is thrown into the nickel-iron ladle 1 with the iron flow. The slag particles are initially dispersed by the kinetic energy of the falling molten nickel-iron. Then, the argon flow rate is controlled by the flow meter and solenoid valve, and the bottom blowing argon gas in the high-pressure argon gas pipeline is turned on. The preferred mode is bottom-blowing argon with weak stirring, with a gas supply rate of 10–20 L / min. The molten nickel-iron is kept under a gas pressure of 0.2~0.4MPa to form diffuse bubbles in the nickel-iron ladle 1, which in turn cause the mixture of molten iron and slag to tumble. This step utilizes the combined effects of the molten iron flow and gentle stirring to promote the melting and initial mixing of the slag. Compared to adding slag all at once after tapping, this step accelerates the melting and mixing speed by having the slag mix in proportion with the molten nickel-iron, and also avoids the slag from forming a crust and floating, thus preventing it from affecting subsequent strong stirring refining. By activating the bottom-blown argon weak stirring mode, the mixing effect is ensured, while atmospheric entrainment is suppressed to reduce secondary oxidation, reduce the temperature drop of molten iron, and avoid affecting the subsequent casting effect.

[0030] Using Fe2O3 as a solid oxygen source avoids excessive nickel oxidation caused by direct oxygen blowing. Fe2O3 slowly decomposes at the slag-gold interface, transferring active oxygen to the molten iron. The reaction is as follows: Or under conditions where molten iron coexists: In the formula: Fe2O3 and FeO represent the components in the slag phase; O represents the active oxygen dissolved in the nickel-iron liquid; After phosphorus in the molten iron is oxidized by active oxygen, it is immediately captured by CaO in the high-basicity slag to form stable calcium phosphate. Combined with the oxygen-donating form of FeO, the core dephosphorization reaction is as follows: The reaction exhibits ΔG < 0 in the temperature range of 1450–1520 °C, simultaneously satisfying the three thermodynamic conditions required for exothermic dephosphorization reactions: low temperature, high oxygen potential, and high alkalinity, thus constructing a complete dephosphorization reaction system. The temperature window is lower than that for dephosphorization in steelmaking, which is suitable for low temperatures; oxygen is supplied by Fe2O3 to achieve high oxygen potential; high basicity is provided by CaO, which oxidizes phosphorus to P2O5 and fixes it in high basicity slag. Step S3: Strong stirring refining and dephosphorization After the RKEF submerged arc furnace finishes tapping iron, and ensures that the CaO-Fe2O3-CaF2 ternary synthesis slag is simultaneously fed into the iron stream, the process is completed through the prior proportional feeding design to ensure that the tapping iron and the CaO-Fe2O3-CaF2 ternary synthesis slag are fed in sync. At this point, switch from the weak stirring mode to the strong stirring mode using bottom-blown argon gas, increasing the gas supply intensity to 25–40 L / min. The preferred flow rate for molten nickel-iron is 30–35 L / min. The gas supply pressure is kept stable at 0.4~0.8MPa. Instantaneous overpressure is strictly prohibited to prevent molten iron from splashing and overflowing the ladle edge. This is to achieve the formation of a large number of diffused bubbles in the nickel-iron ladle 1. The high specific gravity nickel-iron liquid is rolled all over the area by the drag force of the bubbles, and the liquid refining slag is rolled into the interior to form an emulsion layer. During the intense stirring process, the refining slag and molten nickel-iron are fully mixed to form a slag-gold emulsion layer. The specific surface area of ​​the slag-gold is increased compared to static slag washing. Phosphorus in the molten iron is continuously oxidized and generates stable calcium phosphate, which enters the slag phase. The slag phase is the slag that is relatively separated from the molten metal in the molten state. P in the metal phase is oxidized under the oxygen potential provided by Fe2O3 to generate P2O5. P2O5 migrates to the interface between the slag phase and the metal phase and is captured by CaO in the high basicity slag phase to form 3CaO·P2O5 locked in the slag phase. Finally, the entire slag phase is removed by skimming, and the phosphorus leaves the molten nickel-iron along with the slag. The refining process controls the molten iron temperature at 1480~1520℃ and the refining time at 5~15min, preferably 8~12min; This step involves introducing high-pressure argon gas through the porous permeable brick 2 at the bottom of the nickel-iron ladle 1 and the high-pressure argon gas pipeline network. Combined with the bottom dam design, it eliminates the dead zone of stirring. By forming a large number of diffused bubbles in the nickel-iron ladle 1, the drag force of the bubbles drives the high-density nickel-iron liquid to roll all over the area, deeply entraining the liquid refining slag into the interior of the molten iron to form a three-dimensional emulsion reaction layer. The reaction interface area is larger than that of static slag washing, and the dephosphorization reaction rate is increased. This allows the refining time to be compressed into the iron-making interval of a single furnace, which is perfectly matched with the iron-making rate of the electric arc furnace and does not occupy the production cycle. By controlling the temperature of the nickel-iron molten metal at 1480℃~1520℃, the slag fluidity and reaction kinetic rate are ensured by keeping the temperature above 1480℃; the risk of phosphorus reversion caused by calcium phosphate decomposition when the temperature exceeds 1550℃ is avoided, while NiO formation is suppressed and nickel oxidation loss is reduced.

[0031] Step S4: Settling and Layering, and Skimming Off the Residue After refining, turn off the argon gas and let it stand for 1-2 minutes to allow the slag and iron to separate fully and settle by gravity, reducing the iron beads entrained during the slag removal process. Sampling and testing of phosphorus and nickel content in ferronickel was performed. If the indicators were not up to standard, Fe2O3 oxygen source was added, and the refining process was repeated. Argon gas was introduced again for strong stirring to form an emulsion layer. Step S3 was repeated for strong stirring refining and dephosphorization. After refining, the argon gas was turned off, and the mixture was allowed to stand for 1-2 minutes to allow the slag and iron to separate fully and settle by gravity. The phosphorus and nickel content in ferronickel was tested again until the indicators were up to standard. Based on the results, the ratio of synthetic slag to ferronickel was adjusted. Once the indicators are qualified, start the mechanical slag remover 3 to gradually remove the surface phosphorus-rich dephosphorization slag along the ladle wall. Control the thickness of the residual slag in the ladle after slag removal to be <10mm. The slag removal should be ≥95% thorough to avoid phosphorus reversion caused by the residual slag. After the slag removal is completed, measure the temperature. The temperature of the molten iron is usually maintained above 1420℃. The temperature drop is offset by the heat released from dephosphorization. If the temperature drop is too large, a carbonized rice husk heat-insulating covering agent can be added. The nickel-iron molten iron is directly sent to the subsequent casting process.

[0032] The feedback adjustment of the ratio of synthetic slag to molten nickel in step S4 adopts an adaptive incremental correction model based on the residual phosphorus content of the first round of refining, specifically including the following operational logic: Dephosphorization deviation determination: The phosphorus content of the nickel-iron molten metal after the first strong stirring refining was sampled and tested. Combined with the initial phosphorus content predicted by the electric arc furnace, the actual dephosphorization rate was calculated. in, This represents the actual phosphorus removal rate. This represents the initial phosphorus content. The phosphorus content of the nickel-iron molten metal after the first strong stirring refining; The endpoint phosphorus content is set to ≤0.030% according to product requirements. The difference from the target value is subject to tiered correction. The specific tiered feedback correction steps are as follows: Primary under-dephosphorization, 0.030% < ≤0.050%: This is considered a slight lack of kinetics. The initial Fe2O3 addition for the next heat of molten iron of the same tonnage should be 10% to 15% higher than the baseline value. The CaO addition should be adjusted proportionally to the basicity of 3.5, while the CaF2 addition should remain unchanged. Secondary severe under-dephosphorization, >0.050%: This indicates a severe deficiency in thermodynamic oxygen potential or a large deviation in the initial phosphorus forecast. The initial Fe2O3 addition for the next batch should be 25%–30% higher than the baseline value, and the upper limit of alkalinity should be forcibly raised to 4.0. Excessive oxygen warning: If phosphorus is qualified but nickel loss exceeds the standard after Fe2O3 is added and refining, the initial Fe2O3 addition for the next batch will be reduced by 10% in the opposite direction. The dephosphorization rate will be compensated by increasing the stirring intensity to 40L / min·t instead of simply adding oxygen.

[0033] Proportional linkage update mechanism: The PLC control system records the actual compliance data after this correction and automatically updates the recommended slag mix ratio database for this batch of laterite nickel ore. For example: The original setting for Fe2O3 consumption in nickel ore was 22 kg / t; in a certain batch, due to fluctuations in the phosphorus content of the ore, the initial endpoint phosphorus was 0.048%, triggering a first-level correction; the next batch will automatically change the same ore batching to 25 kg / t Fe2O3, and correspondingly adjust the amount of CaO accordingly.

[0034] If the final phosphorus level does not decrease after adding Fe2O3, it is determined that the problem is not related to oxygen potential but rather to phosphorus return caused by slag residue. The system will automatically issue an instruction: cancel the increase in slag amount for the next heat, instead increase the slag removal waiting time and trigger the deep scraping mode of the mechanical slag remover 3. The scraper will rotate one circle along the wall, and at the same time mark the nickel-iron ladle 1 to check the permeable brick 2 to prevent blockage.

[0035] This step reduces iron loss by allowing the slag to settle and separate into layers, and prevents phosphorus reversion by thoroughly removing the slag, thus ensuring the stable quality of the final low-phosphorus nickel-iron product.

[0036] Specifically disclosed is the parameter dynamic adjustment based on the initial phosphorus content: Initial phosphorus content > 0.08%, high phosphorus ore working conditions: Fe2O3 consumption is 28-30 kg / t, alkalinity is 3.8-4.0, strong stirring time is extended to 12-15 min, and stirring intensity is 35-40 L / min·t; Initial phosphorus content 0.06%~0.08%, medium phosphate ore operating conditions: Execute the optimized parameters, Fe2O3 consumption is 22~25kg / t, alkalinity is 3.0~3.8, stirring intensity is 30~35L / min·t, time is 10min. By reducing the slag amount and stirring intensity, nickel loss and operating costs are further reduced. Initial phosphorus content <0.06%, low-phosphate ore conditions: reduce Fe2O3 to 12-15 kg / t, alkalinity to 2.5-3.0, cancel strong stirring and use only weak stirring mode, stirring intensity to 10-20 L / min. t, time 10min, further reducing nickel loss and operating costs.

[0037] Specifically, the experimental variables and test plan design: 1. Orthogonal test of basicity and oxidation potential of refining slag: The designed slag basicity is: original slag, 2.5, 3.5; The oxygen supply capacity of Fe2O3 is: 0, 10 kg / t, and 25 kg / t; The design slag alkalinity and Fe2O3 oxygen supply were cross-combined to test the decrease in nickel-iron-phosphorus content and the phosphorus distribution ratio Lp. 2. Test on the effect of bottom-blown argon stirring intensity on kinetics: The bottom-blown argon intensity was set to: 0, 15 L / min·t weak stirring mode, and 35 L / min·t strong stirring mode, and the degree of slag-gold mixing and dephosphorization reaction rate were detected.

[0038] 3. Monitoring of effective metal Ni burn-off rate: Under different refining conditions, the Ni content in the slag and molten iron was analyzed to assess the impact of dephosphorization operation on the oxidation loss of nickel metal; No control: Verify whether spontaneous dephosphorization capability can be achieved by natural cooling alone under the strong reduction characteristics of the entire RKEF process, and confirm the existence of process bottlenecks; Specific implementation parameters: Following the existing technical process of the factory, the molten nickel-iron flows directly into an ordinary steel ladle without any modification after being discharged from the electric arc furnace. No synthetic refining slag is added, no bottom blowing pipeline is opened, and no slag removal and settling process is performed. After tapping, the iron is allowed to cool down naturally and then cast. Test results: It can be seen that the phosphorus content in the molten iron remained unchanged throughout the process, proving that the strong reducing atmosphere in the RKEF furnace meant that 100% of the phosphorus could not be removed by natural cooling after entering the iron, and low-phosphorus ore was required. Weakly oxidizing slag group: Specific implementation parameters: Pretreatment: Select a 10t capacity nickel-iron ladle 1, with porous permeable bricks 2 embedded in the bottom of the ladle, and preheat the nickel-iron ladle 1 to 850℃ before tapping the iron; Synthetic slag preparation: Add active lime and quartz sand to adjust the slag system basicity to CaO / SiO2=2.5 per ton of nickel-iron liquid, and simultaneously mix in Fe2O3, adjusting the oxygen supply of Fe2O3 to 10kg / t; CaF2 was added to the nickel-iron ladle 1 to lower the melting point of the nickel-iron liquid and increase its fluidity. Process control: When tapping iron from the electric arc furnace, the iron stream rushes into the nickel-iron ladle 1, and bottom blowing argon gas is turned on simultaneously. The bottom blowing argon gas intensity is set to 15L (min·t) in weak stirring mode. After stirring for 8 minutes, the gas is turned off, and the ladle is left to stand for 3 minutes. After mechanical slag removal, the ladle is directly cast. Test results: Strong oxidizing slag group: Specific implementation parameters: Pretreatment: Select a 10t capacity nickel-iron ladle 1, with porous permeable bricks 2 embedded in the bottom of the ladle, and preheat the nickel-iron ladle 1 to 850℃ before tapping the iron; Synthetic slag preparation: Add active lime and quartz sand per ton of nickel-iron liquid to adjust the slag basicity to CaO / SiO2=3.5, and simultaneously mix in Fe2O3, adjusting the oxygen supply of Fe2O3 to 25kg / t; CaF2 was added to the nickel-iron ladle 1 to lower the melting point of the nickel-iron liquid and increase its fluidity. Process control: When tapping iron from the electric arc furnace, the iron stream rushes into the nickel-iron ladle 1, and bottom blowing argon gas is turned on simultaneously. The bottom blowing argon gas intensity is set to 35L / (min·t) strong stirring mode. After stirring continuously for 10 minutes, the gas is turned off, and the ladle is left to stand for 3 minutes. After mechanical slag removal, the ladle is directly cast. Test results: Based on the ladle refining test and chemical analysis of nickel-iron ladle 1, the following conclusions were drawn: 1. Dephosphorization thermodynamic and kinetic equilibrium verification: The strong oxidation stirring group creates a local high oxygen potential by increasing the iron oxide in the refining slag. At the same time, the bottom blowing argon gas provides excellent kinetic stirring conditions, which makes phosphorus rapidly oxidized to P2O5 and firmly fixed by the high basicity slag.

[0039] 2. Breakthrough progress in dephosphorization indicators: By adopting a scheme of alkalinity of 3.5, Fe2O3 25kg / t and strong stirring, the phosphorus content at the end of nickel-iron production was reduced from 0.080% to 0.025%, and the dephosphorization rate reached 68.7%, breaking the process bottleneck that RKEF could not dephosphorize.

[0040] 3. Loss control and overall benefits: While achieving efficient dephosphorization, the effective metal Ni oxidation loss rate is controlled within an acceptable range of 1.2% by optimizing the refining time, making the blending of high-phosphorus, low-priced ores economically feasible.

[0041] A dedicated dephosphorization device based on an out-of-furnace dephosphorization refining method for molten nickel includes a nickel-iron ladle body, a bottom-blowing gas supply system, a quantitative slag addition system, and a slag removal system. Nickel-iron ladle 1 body: The outer shell of the ladle is made of steel, and the inner lining is made of high-alumina magnesium refractory. The slag line area is thickened with a 50mm anti-corrosion layer, which improves the resistance to alkaline slag erosion compared to ordinary ladle linings. At least one porous dispersion permeable brick 2 is symmetrically installed at the bottom of the ladle. It is preferred that the permeable brick 2 is installed at 1 / 2 of the radius of the bottom of the ladle and is arranged at a 15° angle to the ladle wall to avoid direct blowing to the ladle wall and to generate circulation without dead corners. The material of the permeable brick 2 is preferably corundum spinel, with an operating temperature ≥1700℃ and a pressure resistance ≥1.0MPa.

[0042] By directly modifying the existing nickel-iron ladle 1, there is no need to add a new dedicated reactor. The modification only involves the bottom permeable brick 2 and the optimization of the ladle lining. It can be completed during the equipment maintenance period without affecting the normal production order.

[0043] Bottom-blown air supply system: Includes a high-pressure argon gas pipeline network, pressure reducing valve, electromagnetic flow regulating valve, digital flow meter and quick connector, check valve and explosion-proof plate added to the pipeline, and permeable brick 2 connected to the argon gas pipeline network through quick connector; The system has two preset parameters: weak agitation and strong agitation. It integrates a PLC controller to realize automatic switching of iron output in conjunction with the setting, which can be switched with one button. The flow control accuracy is ±1L / min, the pressure adjustment range is 0.2~1.0MPa, and it is equipped with a blockage audible and visual alarm module.

[0044] The system's gas supply parameters are precise and controllable, enabling stable implementation of a staged stirring mode that combines weak stirring for pre-melting and strong stirring for emulsification, thus ensuring stable reproduction of kinetic conditions.

[0045] Furthermore, the system can abandon the fixed gear switching logic and has a built-in dynamic mapping algorithm for iron output, liquid level, and gas supply intensity: The PLC collects the cumulative iron output and molten iron liquid level height fed back by the weighing sensor of nickel-iron ladle 1 in real time, and automatically calculates and outputs the optimal bottom blowing flow rate setting value at the current moment in combination with the preset initial phosphorus content level. During the iron output and filling stage, it automatically matches the 10~20L / min·t weak stirring range to maintain slag pre-melting. After the iron output end signal is triggered, it seamlessly switches to the 25~40L / min·t strong stirring range. During the strong stirring process, according to the airflow fluctuations fed back by the flow meter in real time, the valve opening is finely adjusted by PID closed loop to achieve continuous stepless adjustment of gas supply intensity with control accuracy of ±1L / min and pressure adaptive stability at 0.2~1.0MPa. The system is equipped with a 2-stage blockage diagnosis model for permeable bricks: when the deviation between the set flow rate and the actual feedback flow rate is greater than 5% or the back pressure rises abnormally, an audible and visual alarm is immediately triggered and the system automatically switches to the backflushing and unblocking program to ensure a stable flow field.

[0046] Quantitative slag addition system: Located above the iron tapping station, it includes a closed weighing hopper and a variable frequency screw feeder. The hopper volume matches the daily iron tapping volume, and the feeding accuracy error is ≤±2%. It is equipped with a radar level gauge to monitor the material level in real time. It automatically matches the slag feeding acceleration rate and total amount according to the real-time iron tapping volume of the submerged arc furnace, so as to realize the simultaneous completion of iron tapping and slag feeding.

[0047] This system avoids the unevenness of manual slag addition, ensuring a precise slag-to-iron ratio and stable dephosphorization effect.

[0048] Slag removal system: The hydraulic cantilever slag remover 3 is used. The slag removal head is adapted to the diameter of the nickel-iron ladle 1. The slag removal stroke covers the entire ladle surface, quickly and thoroughly removing phosphorus-rich slag. The slag remover 3 is equipped with a special phosphorus-rich slag receiving bucket on the side. The slag bucket is lined with an alkali-resistant coating to prevent P2O5 dust from polluting the environment and reduce phosphorus return and iron loss.

[0049] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. 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 for dephosphorizing and refining molten nickel-iron outside the ladle, using molten nickel-iron produced by an RKEF submerged arc furnace as the target material, characterized in that, Using the existing nickel-iron ladle (1) for ferroalloy tapping as an in-situ refining reactor, and employing CaO-Fe2O3-CaF2 ternary oxidizing refining slag, combined with bottom-blown argon gas staged stirring, external dephosphorization is achieved, specifically including the following steps: Preparations before tapping S1: Modify the nickel-iron ladle (1), install permeable bricks (2) at the bottom of the ladle and connect it to the high-pressure argon gas pipeline, and provide a quantitative slag feeding device and a slag removal device; prepare synthetic refining slag and prepare it quantitatively, and preheat the nickel-iron ladle (1); S2 Iron Tapping Synchronous Premixing: After the molten iron taps out of the electric arc furnace and the surface of the molten iron is above the top surface of the permeable brick (2), the synthetic refining slag is simultaneously fed into the nickel-iron ladle (1) along with the iron flow. At the same time, the bottom blowing argon gas is turned on for weak stirring. The slag material is initially melted and uniformly mixed by utilizing the impact kinetic energy of the iron flow and the stirring effect of the gas. S3 Strong Stirring Refining Dephosphorization: After the iron tapping and slag feeding are completed simultaneously, the bottom blowing argon gas is switched to strong stirring mode, and a large number of diffused bubbles are formed in the nickel-iron ladle (1). The drag force of the bubbles drives the nickel-iron liquid to roll over the whole area, so that the liquid refining slag is deeply rolled into the iron liquid to form a slag-gold emulsion layer, and the dephosphorization refining reaction is carried out within the preset temperature range. S4 Settling and Slag Removal: After refining, the argon supply is stopped, and the slag and iron are allowed to settle and separate by gravity. After passing the test, the phosphorus-rich slag on the surface is removed to obtain dephosphorized nickel-iron molten iron, which is then sent to the casting process.

2. The method for dephosphorizing and refining molten nickel-iron outside the furnace according to claim 1, characterized in that, Based on the final synthesized refining slag in step S1 The slag basicity CaO / SiO2 is 2.5~4.0, forming a high-alkalinity environment. Under the high-alkalinity environment, phosphorus in the nickel-iron molten iron is oxidized to P2O5. The high-alkalinity slag fixes it into stable CaO·P2O5 calcium phosphate, inhibiting the remelting of phosphorus into the molten iron after dephosphorization. By adding Fe2O3 as a solid oxygen source and utilizing the difference in oxidation free energy between phosphorus and nickel, oxygen is continuously supplied at the slag-gold interface to selectively oxidize phosphorus in molten iron, thus ensuring the dephosphorization oxygen potential while keeping nickel oxidation loss at a low level. Adding CaF2 as a flux lowers the melting point of the slag system, ensuring that the slag has good fluidity at the tapping temperature of nickel-iron.

3. The method for out-of-furnace dephosphorization refining of molten nickel-iron according to claim 2, characterized in that, The preferred ratio of the synthetic refining slag described in step S1 is as follows: the slag basicity CaO / SiO2 is 3.0~3.5; the Fe2O3 consumption is 20~25kg / t; the CaF2 consumption is 6~8kg / t; Fe2O3 decomposes at around 1450℃ to selectively oxidize active phosphorus elements, thereby controlling the reduction of nickel oxidation loss rate.

4. The method for out-of-furnace dephosphorization refining of molten nickel-iron according to claim 1, characterized in that, Bottom-blown argon gas is produced using a two-stage stirring mode: The premixing stage of molten iron adopts a weak stirring mode, which promotes the melting and mixing of slag materials while suppressing secondary oxidation and temperature drop of molten iron caused by atmospheric entrainment. After tapping the iron, switch to strong stirring mode to increase the slag-metal contact surface area and accelerate the dephosphorization reaction rate.

5. The method for dephosphorizing and refining molten nickel-iron outside the ladle according to claim 1, characterized in that, The ternary synthesis refining slag is pre-processed into granules or pressed into pellets to improve the melting rate; the slag feeding process is matched with the iron tapping rate in real time, and the slag is evenly thrown into the nickel-iron ladle with the iron flow (1) to avoid the slag from forming a crust and floating, which would affect the subsequent refining effect.

6. The method for dephosphorizing and refining molten nickel-iron outside the ladle according to claim 1, characterized in that, Based on the different grades of initial phosphorus content in molten nickel, the composition ratio of refining slag, total addition amount, stirring intensity of bottom-blown argon, and refining time are dynamically adjusted to reduce nickel oxidation loss and process operating costs while meeting dephosphorization targets. Strategy for dynamically adjusting process parameters based on the initial phosphorus content of molten nickel: When the initial phosphorus content is >0.08%, the working conditions for high-phosphorus ore are as follows: Fe2O3 consumption is 28-30 kg / t, alkalinity is 3.8-4.0, strong stirring time is extended to 12-15 min, and stirring intensity is 35-40 L / min·t. When the initial phosphorus content is 0.06% to 0.08%, under the condition of medium phosphate ore: the optimized parameters are implemented, the Fe2O3 consumption is 22 to 25 kg / t, the alkalinity is 3.0 to 3.8, the stirring intensity is 30 to 35 L / min·t, and the time is 10 min. By reducing the slag amount and stirring intensity, nickel loss and operating costs are further reduced. When the initial phosphorus content is <0.06%, for low-phosphate ore conditions: reduce Fe2O3 to 12-15 kg / t, alkalinity to 2.5-3.0, cancel strong stirring and use only weak stirring mode, with stirring intensity of 10-20 L / min. t, time 10min, further reducing nickel loss and operating costs.

7. The method for dephosphorizing and refining molten nickel-iron outside the ladle according to claim 1, characterized in that, Before tapping iron, check the erosion thickness of the reactor lining of the nickel-iron ladle (1) and the integrity of the permeable brick (2) at the bottom of the nickel-iron ladle (1) to confirm that the residual thickness of the lining is greater than the set threshold thickness; confirm that the gas supply pipeline is unobstructed and the airtightness is qualified by introducing argon gas for test blowing, so as to avoid the safety hazards of blockage of permeable brick (2) and iron leakage during the refining process.

8. The method for dephosphorizing and refining molten nickel-iron outside the ladle according to claim 1, characterized in that, Based on the strong stirring mode described in step S3, the gas supply pressure is stabilized at 0.4~0.8MPa, and the gas supply intensity is continuously and steplessly adjusted by using PID closed-loop regulating valve opening to avoid molten iron splashing and overflowing from the ladle edge.

9. The method for dephosphorizing and refining molten nickel-iron outside the ladle according to claim 1, characterized in that, Based on the sampling and testing before slag removal in step S4, the phosphorus and nickel content of the nickel-iron molten iron was tested: If the indicators are not up to standard, add oxygen source Fe2O3 and repeat step S3. After refining, turn off the argon gas and let it stand for 1-2 minutes to allow the slag and iron to separate fully and settle by gravity. Then test the phosphorus and nickel content of the nickel-iron molten metal again until the indicators are up to standard. Based on the results, adjust the ratio of synthetic slag to nickel-iron molten metal. Once the indicators are qualified, start the mechanical slag remover (3) and gradually remove the surface phosphorus-rich dephosphorization slag along the wall.

10. The method for dephosphorizing and refining molten nickel-iron furnace according to claim 9, characterized in that, Based on feedback adjustment of the ratio of synthetic slag to molten nickel-iron, an adaptive incremental correction model based on the residual phosphorus content of the first round of refining is adopted, which specifically includes the following operational logic: Dephosphorization deviation determination: The phosphorus content of the nickel-iron molten metal after the first strong stirring refining was sampled and tested. Combined with the initial phosphorus content predicted by the electric arc furnace, the actual dephosphorization rate was calculated. in, This represents the actual phosphorus removal rate. This represents the initial phosphorus content. The phosphorus content of the nickel-iron molten metal after the first strong stirring refining; The endpoint phosphorus content is set to ≤0.030% according to product requirements. The difference from the target value is subject to tiered correction. The specific tiered feedback correction steps are as follows: Primary under-dephosphorization, 0.030% < ≤0.050%: This is considered a slight lack of kinetics. The initial Fe2O3 addition for the next heat of molten iron of the same tonnage should be 10% to 15% higher than the baseline value. The CaO addition should be adjusted proportionally to the basicity of 3.5, while the CaF2 addition should remain unchanged. Secondary severe under-dephosphorization, >0.050%: This indicates a severe deficiency in thermodynamic oxygen potential or a large deviation in the initial phosphorus forecast. The initial Fe2O3 addition for the next batch should be 25%–30% higher than the baseline value, and the upper limit of alkalinity should be forcibly raised to 4.

0. Excessive oxygen warning: If phosphorus is qualified but nickel loss exceeds the standard after Fe2O3 is added and refining, the initial Fe2O3 addition for the next batch will be reduced by 10% in the opposite direction, and the dephosphorization rate will be compensated by increasing the stirring intensity to 40L / min·t.

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