Low-nitrogen chromium iron hot charging refining method based on residual amount control

Abstract

The application provides a low-nitrogen chromium iron hot charging refining method based on reduction residual control, and relates to the technical field of ferroalloy smelting. The method comprises the following steps: drying and preheating chromium ore and lime, and adding part of the chromium ore and the lime into a refining electric furnace to form an initial slag; hot charging liquid low-carbon silicon chromium alloy discharged from an ore smelting furnace in batches, and adding the remaining chromium ore and lime between adjacent two pouring processes to perform silicon hot reduction. After all the furnace charges are added, sampling is performed on the reduction slag, the over-limit amount of Cr2O3 and FeO relative to the corresponding preset value is determined to determine the mass of the liquid low-carbon silicon chromium alloy in the current round of supplement, sampling is performed again after the supplement, and the two oxides are required to reach the end point until the two oxides reach the end point requirement. After the reduction is completed, the power supply is reduced to homogenize the alloy liquid, the alloy liquid is discharged into a ladle together with the reduction slag, and the alloy liquid is transported and poured with a low drop difference under the coverage of the slag layer. The application can match the supplement amount of the reducing agent with the remaining reduction load in the furnace well, and improve the accuracy of the reduction end point judgment and control.

Description

Technical Field

[0001] This application relates to the field of ferroalloy smelting technology, and in particular to a hot-charge refining method for low-nitrogen ferrochrome based on reduction balance control. Background Technology

[0002] Ferrochrome is an important ferroalloy raw material for smelting stainless steel, heat-resistant steel, and other chromium-containing alloy steels. Medium-carbon ferrochrome, low-carbon ferrochrome, and micro-carbon ferrochrome are typically produced using a silicothermic reduction method. This method utilizes silicon in a silicon-chromium alloy to reduce chromium and iron oxides in chromite, allowing the reduced chromium and iron to enter the molten alloy. The resulting silica reacts with slag-forming materials such as lime to form slag. As downstream smelting processes increasingly demand higher nitrogen content and compositional stability in ferrochrome, actual production is gradually adopting the method of directly charging liquid silicon-chromium alloy into refining electric furnaces. This utilizes the sensible heat inherent in the silicon-chromium alloy, shortening the melting and heating process of the furnace charge, and providing a technological basis for the production of low-nitrogen medium-carbon, low-carbon, and micro-carbon ferrochrome.

[0003] In existing hot-charge refining processes, the amounts of silicon-chromium alloy and lime are typically determined first based on the planned amount of chromium ore, the chemical composition of the raw materials, and the requirements of the target product. Then, the chromium ore, lime, and liquid silicon-chromium alloy are added to the refining electric furnace in batches or alternately, allowing the liquid silicon-chromium alloy to undergo a silicothermic reduction reaction with the chromium ore. In the later stages of smelting, operators generally assess the reduction progress based on the predetermined batching amount, reaction time, furnace temperature, and slag appearance, and decide whether to continue adding silicon-chromium alloy based on production experience. Once the reduction reaction is deemed to have reached the required level, the iron is tapped, transferred, and cast. This method utilizes the sensible heat of the liquid silicon-chromium alloy to complete ferrochrome refining, but the subsequent addition of silicon-chromium alloy still largely depends on the pre-batching results and manual experience.

[0004] However, the actual composition of the chromium ore used in different furnace runs, the amount of slag in the furnace, the reaction temperature, and the actual utilization rate of silicon can all fluctuate. Even with the same initial batching system, the amount of chromium and iron oxides that have not yet been reduced in the slag during the later stages of smelting may differ. Determining the amount of silicon-chromium alloy to be added solely based on the predetermined batching amount, reaction time, or slag appearance makes it difficult to match the added reducing agent with the actual remaining reduction load in the furnace: insufficient addition will result in incomplete reduction of chromium and iron oxides in the slag; excessive addition will increase silicon-chromium alloy consumption and affect alloy composition control. Therefore, how to determine the amount of silicon-chromium alloy to be added based on the actual remaining reduction load in the furnace during the later stages of smelting to improve the accuracy of reduction endpoint control is a key technical problem that needs to be solved in existing low-nitrogen ferrochrome hot-charge refining processes. Summary of the Invention

[0005] This application provides a hot-charge refining method for low-nitrogen ferrochrome based on reduction balance control, which solves the problem that the amount of silicon-chromium alloy added during the hot-charge refining process of low-nitrogen ferrochrome is difficult to match with the actual remaining reduction load in the furnace, resulting in insufficient accuracy in controlling the reduction endpoint.

[0006] This application provides a method for hot-charge refining of low-nitrogen ferrochrome based on reduction balance control, comprising the following steps:

[0007] S1, chromite and lime are dried and preheated, and a portion of them are added to a refining electric furnace and energized to melt them, forming the initial slag;

[0008] S2, the liquid low-carbon silicon-chromium alloy from the submerged arc furnace is placed in a silicon-chromium alloy bag, and the liquid low-carbon silicon-chromium alloy is poured into the refining electric furnace in batches from the silicon-chromium alloy bag. Between two consecutive pours, the remaining chromium ore and lime are added to allow the liquid low-carbon silicon-chromium alloy to undergo a silicothermic reduction reaction with the chromium ore to obtain ferrochrome alloy liquid and reduction slag.

[0009] S3. After adding chromite and lime, take a sample of the reduction slag and add liquid low-carbon silicon-chromium alloy according to the content of Cr2O3 and FeO in the reduction slag. After adding, continue the reaction and take a sample again. When the mass fraction of Cr2O3 in the reduction slag is not greater than the first preset value and the mass fraction of FeO is not greater than the second preset value, the reduction ends.

[0010] S4, reduce the power supply of the refining electric furnace and homogenize the ferrochrome alloy liquid. Discharge the homogenized ferrochrome alloy liquid along with the reducing slag into the molten iron ladle, so that the reducing slag forms a covering slag layer on the surface of the ferrochrome alloy liquid. Under the cover of the covering slag layer, the transfer and casting are completed within a preset time to obtain low-nitrogen, medium-low-carbon ferrochrome.

[0011] In one optional embodiment, in step S1, the chromite and lime are dried to a moisture content of no more than 0.20% by mass, and then preheated to 300-600°C; the particle size of the chromite is 10-60 mm, and the particle size of the lime is 10-50 mm.

[0012] In one optional implementation, in step S1, the chromite and lime added to form the initial slag account for 20% to 40% of the corresponding planned total addition amount, respectively. After being energized and melted to the surface of the furnace charge to form a continuous slag layer, step S2 is implemented.

[0013] In one optional embodiment, in step S2, the liquid low-carbon silicon-chromium alloy has a Cr mass fraction of 27% to 35%, a Si mass fraction of 38% to 50%, a C mass fraction of no more than 0.10%, and a heat-applied temperature of 1400 to 1600°C.

[0014] In one optional embodiment, in step S2, the liquid low-carbon silicon-chromium alloy used for the silicothermic reduction reaction is divided into an initial pour and subsequent pours, wherein the initial pour accounts for 40% to 60% of the total liquid low-carbon silicon-chromium alloy used for the silicothermic reduction reaction; the subsequent pours are divided into 2 or 3 batches and poured sequentially, and the remaining chromium ore and lime are divided into batches of the same number as the subsequent pours; after the initial pour of the liquid low-carbon silicon-chromium alloy is completed and between the pours of two adjacent batches of subsequent pours, a batch of chromium ore and a batch of lime are added respectively.

[0015] In one optional embodiment, in step S2, the reaction temperature inside the refining furnace is controlled at 1650–1800°C.

[0016] The total amount of lime added is determined to make the binary basicity of the reducing slag 1.5 to 1.9, where the binary basicity is the mass ratio of CaO to SiO2 in the reducing slag.

[0017] In an optional implementation, in step S3, the mass fractions of Cr2O3 and FeO in the reduction residue obtained from the i-th sampling are denoted as w, respectively. Cr,i and w Fe,i Let the first preset value and the second preset value be denoted as w respectively. Cr,0 and w Fe,0 When w Cr,i >w Cr,0 When the amount of chromium oxide exceeds the limit by Δw Cr,i =w Cr,i -w Cr,0 Otherwise, take Δw Cr,i =0; when w Fe,i >w Fe,0 When the amount of iron oxide exceeds the limit by Δw Fe,i =w Fe,i -w Fe,0 Otherwise, take Δw Fe,i =0; The replenishment mass of liquid low-carbon silicon-chromium alloy in this round is determined according to the following formula:

[0018] ;

[0019] In the formula, m i The mass of liquid low-carbon silicon-chromium alloy added in this round is expressed in kg; m z,0 The reference mass of the reduction slag in this furnace, determined before step S3, is expressed in kg; w SiThe mass fraction of Si in the liquid low-carbon silicon-chromium alloy to be added is expressed as a decimal; k is the reduction correction coefficient, ranging from 1.05 to 1.20; the reference mass of the reduction slag in this furnace is the product of the total mass of chromium ore added in this furnace and the preset slag production coefficient, which is the average ratio of the mass of reduction slag discharged from the furnace to the total mass of chromium ore added in historical furnaces corresponding to the chromium ore grade, lime addition system and smelting conditions of this furnace.

[0020] In one optional implementation, in step S3, after each round of adding liquid low-carbon silicon-chromium alloy corresponding to the mass added in this round, the reaction continues for 3 to 8 minutes, and then the reduction residue is sampled.

[0021] If the mass fraction of either Cr2O3 or FeO obtained from this sampling is still greater than the corresponding preset value, the mass to be added in the next round will be determined and added based on the sampling results.

[0022] In one optional embodiment, the first preset value is preset within the range of 1.5% to 3.0%, and the second preset value is preset within the range of 0.5% to 1.5%. In step S4, after the reduction ends, the power supply of the refining electric furnace is reduced to 30% to 60% of the power supply during the silicothermic reduction reaction stage in step S2, and maintained at the reduced power supply for 3 to 8 minutes to homogenize the ferrochrome alloy liquid, and then the iron is tapped.

[0023] In one optional embodiment, in step S4, the tapping temperature is 1650–1750°C. The ferrochrome alloy liquid and reducing slag flow into the ladle through the tapping port and tapping trough of the refining electric furnace, so that the reducing slag entering the ladle floats on the surface of the ferrochrome alloy liquid and covers the exposed surface of the ferrochrome alloy liquid. The time from the start of tapping from the refining electric furnace to the completion of casting does not exceed 20 minutes, specifically controlled to be 8–20 minutes. During casting, the vertical distance between the ladle nozzle and the upper edge of the mold is not greater than 300 mm, and the depth of the ferrochrome alloy liquid in the mold is 100–250 mm.

[0024] Compared with the prior art, this application has at least the following beneficial effects:

[0025] 1. This application provides a method for hot-charging refining of low-nitrogen ferrochrome based on reduction balance control. First, chromium ore and lime are dried and preheated, with a portion of them pre-added to the refining electric furnace to form initial slag. This allows the subsequently added liquid low-carbon silicon-chromium alloy to directly enter the already formed liquid slag phase and participate in the reaction, avoiding the concentrated addition of liquid alloy and solid charge before a stable slag has formed in the furnace. Subsequently, liquid low-carbon silicon-chromium alloy is poured into the refining electric furnace in batches from a silicon-chromium alloy ladle, with the remaining chromium ore and lime added between adjacent pours. This allows the reducing agent and the material to be reduced to contact and react in stages according to the smelting process. Through the above-mentioned initial slag formation and batch alternating charging method, the abrupt change in the furnace reaction state caused by the concentrated addition of liquid silicon-chromium alloy and solid charge can be reduced. This allows chromium and iron oxides in the chromium ore to gradually participate in silicothermic reduction in the furnace, which is beneficial to improving the uniformity of the reaction process and the composition of the reduction slag. This provides a more reliable material basis for judging the actual remaining reduction load in the furnace by sampling the reduction slag in the later stages of smelting.

[0026] 2. After the addition of chromite and lime, this application no longer determines whether to add silicon-chromium alloy solely based on the predetermined batching amount, smelting time, or slag appearance. Instead, it samples the reduction slag and adds liquid low-carbon silicon-chromium alloy according to the actual content of Cr2O3 and FeO in the slag. The residual Cr2O3 and FeO in the reduction slag correspond to chromium oxides and iron oxides that have not yet been reduced, respectively, and their content reflects the remaining reduction load formed in the current furnace under the existing raw material composition, reaction conditions, and actual silicon utilization. Therefore, using the detection results of these two substances as the basis for adding liquid low-carbon silicon-chromium alloy ensures that the addition operation is based on the actual reduction state of the current furnace, rather than mechanically applying the initial calculation results or relying on manual experience. After addition, the reaction continues and sampling is repeated. Reduction ends only when the mass fraction of Cr2O3 in the reduction slag is not greater than the first preset value and the mass fraction of FeO is not greater than the second preset value. This ensures that the two main oxides to be reduced are subject to endpoint constraints, avoiding the situation where the low content of one oxide masks the fact that the other oxide is still too high. This reduces the risk of insufficient reduction due to inadequate silicon-chromium alloy addition and the risk of ineffective consumption of reducing agent due to excessive addition, thereby improving the accuracy of reduction endpoint judgment and control.

[0027] 3. After the reduction endpoint is met, this application reduces the power supply of the refining electric furnace and homogenizes the ferrochrome alloy liquid, thus transitioning the smelting process from the reduction reaction stage to the post-endpoint stabilization stage. Reducing the power supply avoids maintaining a strong high-temperature reaction state after the reduction endpoint has been reached. Homogenization helps reduce the composition and temperature differences within the ferrochrome alloy liquid caused by the previous batch feeding and localized reactions, making the alloy liquid state more stable before tapping. Subsequently, the homogenized ferrochrome alloy liquid, along with the reducing slag, is discharged into the ladle. Utilizing the characteristic of the reducing slag floating on the surface of the ferrochrome alloy liquid, a covering slag layer is formed. Under the cover of this slag layer, transfer and casting are completed within a preset time. This reduces the surface area and duration of the high-temperature ferrochrome alloy liquid directly exposed to air after tapping, reducing the chance of nitrogen absorption during transfer and casting. Therefore, this application, while improving the accuracy of reduction endpoint control, also maintains the alloy liquid state through post-endpoint homogenization, covering, and time-limited transfer and casting, which is beneficial for stably obtaining low-nitrogen, low-carbon ferrochrome. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 A flowchart of a low-nitrogen ferrochrome hot-charge refining method based on reduction margin control, provided as an embodiment of this application. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are also within the scope of protection of this application.

[0031] like Figure 1 As shown in the figure, this application provides a method for hot-charging refining of low-nitrogen ferrochrome based on reduction balance control, specifically including the following steps:

[0032] S1, chromite and lime are dried and preheated, and a portion of them are added to a refining electric furnace and energized to melt them, forming the initial slag;

[0033] S2, the liquid low-carbon silicon-chromium alloy from the submerged arc furnace is placed in a silicon-chromium alloy bag, and the liquid low-carbon silicon-chromium alloy is poured into the refining electric furnace in batches from the silicon-chromium alloy bag. Between two consecutive pours, the remaining chromium ore and lime are added to allow the liquid low-carbon silicon-chromium alloy to undergo a silicothermic reduction reaction with the chromium ore to obtain ferrochrome alloy liquid and reduction slag.

[0034] S3. After adding chromite and lime, take a sample of the reduction slag and add liquid low-carbon silicon-chromium alloy according to the content of Cr2O3 and FeO in the reduction slag. After adding, continue the reaction and take a sample again. When the mass fraction of Cr2O3 in the reduction slag is not greater than the first preset value and the mass fraction of FeO is not greater than the second preset value, the reduction ends.

[0035] S4, reduce the power supply of the refining electric furnace and homogenize the ferrochrome alloy liquid. The homogenized ferrochrome alloy liquid, together with the reducing slag, is discharged into the molten iron ladle, so that the reducing slag forms a covering slag layer on the surface of the ferrochrome alloy liquid. Under the cover of the covering slag layer, the transfer and casting are completed within a preset time to obtain low nitrogen, medium and low carbon ferrochrome.

[0036] The term "low-nitrogen ferrochrome" as used in this application includes low-nitrogen medium-carbon ferrochrome, low-nitrogen low-carbon ferrochrome, and low-nitrogen micro-carbon ferrochrome obtained by refining chromium ore through silicothermic reduction using liquid low-carbon silicon-chromium alloy. Specific products will be tested for composition according to the intended production grade; the reduction balance control method in this application is not limited to a single ferrochrome grade.

[0037] This application can be implemented on existing ferroalloy production lines. The main equipment used includes an electric arc furnace for producing liquid low-carbon silicon-chromium alloy, a silicon-chromium alloy ladle for holding and transferring the liquid low-carbon silicon-chromium alloy, a refining electric furnace for silicothermic reduction, a tapping trough connected to the tapping spout of the refining electric furnace, a ladle for receiving molten ferrochrome alloy and reducing slag, and a casting mold. Raw material drying and preheating, furnace temperature measurement, slag sampling, and composition analysis can all be performed using existing equipment and conventional operations on the production line.

[0038] Before use, both the silicon-chromium alloy ladle and the molten iron ladle should be cleaned and baked to ensure there is no standing water or obvious dampness inside. Liquid low-carbon silicon-chromium alloy enters the ladle after exiting the submerged arc furnace; its temperature can be measured using a conventional temperature measuring device after exiting the furnace or before being poured into the refining electric furnace. During transportation, the ladle can be covered and insulated according to existing production line procedures, but sealed pipelines are not required.

[0039] Chromium ore and lime were sampled and analyzed separately before being added to the refining electric furnace. The analysis of chromium ore included at least Cr₂O₃, iron oxides, SiO₂, MgO, and Al₂O₃; the analysis of lime included at least available CaO and SiO₂; and the analysis of liquid low-carbon silicon-chromium alloy included at least Cr, Si, and C. The moisture content of the raw materials was determined by weighing the difference in mass before and after drying, and the particle size of the raw materials was determined by sieving.

[0040] Sampling of the reducing slag is preferably carried out after the reaction in the furnace has slowed significantly. The same type of sampling spoon is used for each sampling, taking samples from a representative slag layer location within the refining electric furnace, avoiding slag adhering to the furnace wall and localized areas near the taphole, and minimizing the contamination of alloy droplets. After the slag sample cools, visible metal particles are removed, and the sample is crushed, ground, and mixed thoroughly. The mass fractions of Cr2O3 and FeO are then determined using existing chemical or instrumental analysis methods available on the production line. The sampling location, sample preparation method, and analytical method remain consistent for each sampling session.

[0041] The low-nitrogen ferrochrome hot-charge refining method based on reduction margin control provided in this embodiment involves drying and preheating chromite and lime separately in steps S1 and S2. A portion of these materials is then added to a refining electric furnace and energized for melting until a continuous and fluid initial slag is formed within the furnace. After the initial slag is formed, the liquid low-carbon silicon-chromium alloy from the submerged arc furnace is loaded into a silicon-chromium alloy ladle, which is then poured into the refining electric furnace in batches. After each batch of liquid low-carbon silicon-chromium alloy is poured, a batch of remaining chromite and lime is added once the reaction in the furnace has stabilized, before the next batch of liquid low-carbon silicon-chromium alloy is poured. The initial slag provides a liquid reaction medium for the subsequently added liquid low-carbon silicon-chromium alloy, chromite, and lime, allowing chromium and iron oxides in the chromite to gradually enter the slag and contact with silicon. The batch pouring and intermittent feeding also reduce temperature and reaction intensity fluctuations caused by the concentrated addition of large amounts of liquid alloy and solid charge. Therefore, the materials inside the furnace can melt and react in stages as the smelting process progresses, the silicothermic reduction process is relatively stable, and it is also convenient to evaluate the reduction process of this furnace based on the actual composition of the reduction slag after all the chromium ore and lime have been added.

[0042] In this embodiment, after the addition of chromite and lime, the melting and reaction within the furnace are maintained to ensure that the newly added charge fully enters the molten slag and participates in the silicothermic reduction. The reduction slag is then sampled, ideally from a region of good slag fluidity within the furnace, avoiding surface crusting and minimizing metal entrainment. After cooling, crushing, and grinding, the slag sample is analyzed for the mass fractions of Cr2O3 and FeO. Cr2O3 and FeO reflect the remaining unreduced chromium oxides and iron oxides in the reduction slag, respectively. Therefore, this embodiment determines whether to add liquid low-carbon silicon-chromium alloy based on the detection results of these two components. If the detection results exceed the corresponding preset values, it indicates that there is still a corresponding residual reduction load in the furnace, requiring the addition of liquid low-carbon silicon-chromium alloy and continued reaction. After addition, sampling and testing are repeated until the mass fraction of Cr2O3 is no greater than the first preset value and the mass fraction of FeO is no greater than the second preset value, at which point the reduction process ends. With this approach, the replenishment of silicon-chromium alloy no longer depends solely on the initial batching results, reaction time, or operational experience, but is linked to the actual remaining levels of the two main oxides in the reduction slag of the current furnace. Ending the reduction only after both indicators are met reduces the likelihood of premature furnace shutdown due to a single indicator being met. It also helps reduce the possibility of insufficient reduction caused by inadequate replenishment and excessive silicon-chromium alloy consumption due to excessive replenishment, thus improving the accuracy of the reduction endpoint determination.

[0043] Furthermore, in this embodiment, after the reduction endpoint is reached, the power supply of the refining electric furnace is reduced, and homogenization is performed while the ferrochrome alloy liquid and reducing slag remain molten and flowable. During this stage, no chromite or liquid low-carbon silicon-chromium alloy is added; the main method is to utilize the self-flow of the molten pool and continuous heating at a lower power to reduce temperature and compositional differences caused by earlier batch feeding and localized reactions, thus stabilizing the state of the ferrochrome alloy liquid before tapping. After homogenization, the ferrochrome alloy liquid, along with the reducing slag, is discharged into a pre-dried ladle. Due to the density difference between the reducing slag and the ferrochrome alloy liquid, the reducing slag floats to the surface of the ferrochrome alloy liquid after entering the ladle, covering its exposed surface. The preset time can be determined before production based on the distance from the refining electric furnace to the casting position, the ladle transfer method, and the casting cycle. After tapping, the transfer and casting are completed within this time, reducing the prolonged residence of the ladle at high temperatures. Power reduction and homogenization help maintain the stability of the molten alloy state before tapping; the covering of reducing slag and the control of transfer and casting time can reduce the area and duration of direct contact between the high-temperature ferrochrome alloy liquid and air, reduce the possibility of continued nitrogen absorption during transfer and casting, and thus help obtain low-nitrogen, low-carbon ferrochrome.

[0044] As an optional solution in this embodiment, in step S1, chromite and lime are dried to a moisture content of no more than 0.20% by mass, and then preheated to 300-600°C; the particle size of chromite is 10-60 mm, and the particle size of lime is 10-50 mm.

[0045] Before step S1 in the above embodiment, the chromium ore and lime are crushed and screened separately to control the particle size of the chromium ore to 10-60 mm and the particle size of the lime to 10-50 mm. Materials larger than the upper limit obtained from screening can be returned to the crushing process, while finer materials smaller than the lower limit can be collected separately and not directly mixed into the materials used in this furnace. After particle size adjustment, the chromium ore and lime are respectively sent to conventional drying equipment for drying, and samples are taken in batches at the discharge end of the drying equipment to determine the moisture content. The moisture content can be determined by weighing the change in mass before and after drying, with the percentage of the mass reduction of the sample before and after drying relative to the mass of the sample before drying as the moisture content. When the moisture content of both chromium ore and lime is not greater than 0.20%, they are then sent to preheating equipment to be heated to 300-600°C. The raw material temperature can be measured at the discharge end of the preheating equipment using a thermocouple or infrared thermometer, and the raw materials are promptly sent to the refining furnace after discharge to reduce temperature drop and re-moisture absorption during transportation and waiting. For continuous preheating, multiple temperature measurement points can be taken at intervals at the discharge end; for batch preheating, the temperature can be measured at different locations in the same batch of material, and the determination that the batch of material has completed preheating is based on the fact that all measurement points are within the above temperature range.

[0046] Furthermore, this embodiment controls the moisture content of chromite and lime to no more than 0.20%, which reduces local splashing and charge agitation caused by rapid vaporization of moisture after the water-containing charge enters the high-temperature refining electric furnace. It also reduces the heat consumed by moisture evaporation. Preheating the two raw materials to 300–600°C reduces the temperature difference between the solid charge and the high-temperature melt in the furnace, allowing the chromite and lime added to the refining electric furnace to heat up quickly and participate in melting, slagging, and reduction reactions, thus helping to reduce furnace temperature fluctuations during the charging stage. The particle size range is coordinated with the above drying and preheating treatments: if the particle size of chromite and lime is too small, more dust is easily generated during screening, transfer, and charging, and may be carried out with the furnace gas; if the particle size is too large, the time required for internal heating and melting is longer. Controlling the chromite to 10–60 mm and the lime to 10–50 mm facilitates heat transfer to the interior of the particles during drying and preheating, and also promotes gradual melting of the raw materials after they are added to the furnace. Therefore, the process of forming the initial slag in step S1 can be relatively stable, and the raw materials with a relatively consistent state can be provided for the subsequent silothermic reduction of liquid low-carbon silicon-chromium alloy and chromium ore.

[0047] As an optional solution in this embodiment, in step S1, the chromite and lime added to form the initial slag account for 20% to 40% of the corresponding planned total addition amount. After being energized and melted to the surface of the furnace charge to form a continuous slag layer, step S2 is implemented.

[0048] In this embodiment, before smelting begins, the planned total amount of chromium ore and lime to be added to the furnace is determined. 20%–40% of each of the planned total amounts is weighed out to form the initial slag, with the remainder reserved for subsequent additions. Here, the proportions of chromium ore and lime are calculated based on their respective planned total amounts, not their combined mass. The weighed chromium ore and lime are added to the refining electric furnace, which is then powered on for melting. During melting, the surface state of the furnace charge can be observed through the furnace opening. When the liquid slag gradually melts from a locally dispersed state and becomes a unified whole, forming a continuously distributed slag layer in the main area of ​​the furnace charge surface, without large areas of isolated slag or clearly exposed dry material, it can be determined that the initial slag has formed. After reaching this state, liquid low-carbon silicon-chromium alloy is poured into the refining electric furnace in batches. Using the above determination method provides a clear on-site basis for the start time of step S2, avoiding the reliance solely on the power-on time as the criterion for determining whether the initial slag formation has been completed.

[0049] The chromite and lime used to form the initial slag each account for 20% to 40% of the planned total addition. This allows for the initial establishment of a certain amount of liquid slag phase within the refining electric furnace, while reserving a significant amount of chromite and lime for subsequent batch additions. If the initial addition ratio is too low, the amount of liquid slag phase formed in the furnace will be insufficient, resulting in a limited amount of slag medium that can contact and react with the chromite when the subsequent liquid low-carbon silicon-chromium alloy enters the furnace. Conversely, if the initial addition ratio is too high, a large amount of solid charge will be concentrated in step S1 for melting, prolonging the initial slag formation process and reducing the amount of chromite and lime available for subsequent alternating charging. By limiting the initial addition ratio of the two raw materials within the aforementioned range and using the formation of a continuous slag layer on the charge surface as a condition for transitioning to step S2, a suitable relationship can be maintained between the initial slag quantity and the requirements for subsequent batch charging. Therefore, after the liquid low-carbon silicon-chromium alloy enters the furnace, it can first come into contact with the continuous slag layer, and the remaining chromite and lime can be added in batches during the subsequent pouring process, which helps to reduce the fluctuation of the material state in the early stage of the reaction and allows the subsequent silothermic reduction process to proceed more smoothly.

[0050] As an optional solution in this embodiment, in step S2, the mass fraction of Cr in the liquid low-carbon silicon-chromium alloy is 27% to 35%, the mass fraction of Si is 38% to 50%, the mass fraction of C is not greater than 0.10%, and the hot-fitting temperature is 1400 to 1600°C.

[0051] In the above embodiments, the liquid low-carbon silicon-chromium alloy used is directly loaded into the silicon-chromium alloy ladle after exiting the submerged arc furnace. Before or after the alloy exits the furnace, representative samples can be obtained according to the existing sampling system at the production site, and the mass fractions of Cr, Si, and C can be tested. Only when the test results meet the following conditions—Cr 27%–35%, Si 38%–50%, and C not exceeding 0.10%—can the liquid low-carbon silicon-chromium alloy be used for hot charging refining in this furnace. Sampling should avoid slag and ladle wall adhering substances. Samples should be prepared and analyzed after cooling. For the same ladle of alloy, the composition record from the submerged arc furnace can be used for verification. When alloy liquids from different ladles are used together, the mass and composition of each ladle should be recorded separately, and a weighted calculation should be performed according to the mass of each ladle to determine whether the Cr, Si, and C of the mixed liquid low-carbon silicon-chromium alloy are within the above ranges. This provides a clear basis for the composition of the reducing agent entering the refining electric furnace and facilitates subsequent replenishment operations based on the actual content of Cr2O3 and FeO in the reducing slag.

[0052] After molten low-carbon silicon-chromium alloy is loaded into the silicon-chromium alloy ladle, unnecessary dwell time should be minimized, and the hot-charging temperature should be measured before pouring into the refining electric furnace. The temperature can be measured at a representative location inside the ladle using an immersion thermometer after the alloy liquid has been loaded and surface slag removed; alternatively, a calibrated thermometer suitable for high-temperature molten metal can be used. The temperature measurement location should avoid the ladle wall, bottom, and surface slag. Hot charging should commence when the measured temperature is between 1400 and 1600°C. During transfer, silicon-chromium alloy ladles with lids or insulating linings can be used, and the timing of furnace discharge, transfer, and refining electric furnace receiving should be carefully coordinated to ensure the alloy liquid remains flowable during pouring. If the waiting time after temperature measurement is long, the temperature should be measured again before pouring to avoid directly using the furnace discharge temperature as the actual hot-charging temperature.

[0053] The aforementioned composition range and hot charging temperature together limit the reduction capacity, carbon introduction amount, and thermal state of the liquid low-carbon silicon-chromium alloy when it enters the refining electric furnace. Si is the main reducing component in the silicothermic reduction reaction. Controlling its mass fraction at 38%–50% ensures that the effective reducing component per unit mass of alloy is within a relatively concentrated range, reducing significant changes in the actual reduction capacity corresponding to the same added mass due to excessive fluctuations in silicon content. A Cr mass fraction of 27%–35% ensures that the alloy introduces chromium into the molten metal while providing silicon, which is compatible with the composition of low-nitrogen ferrochrome products. A C mass fraction of no more than 0.10% reduces the carbon introduced by the reducing agent itself, which is more advantageous for controlling the carbon content of medium-carbon, low-carbon, and micro-carbon ferrochrome. Hot charging the liquid low-carbon silicon-chromium alloy at 1400–1600℃ utilizes its sensible heat and reduces localized solidification or molten pool temperature drop caused by excessively low temperatures after the alloy is added. Therefore, the alloy composition and hot charging state are relatively stable, and the correspondence between the added mass and the actual reduction effect is easier to control when subsequent batches are poured and replenished according to the composition of the reducing slag.

[0054] As an optional solution in this embodiment, in step S2, the liquid low-carbon silicon-chromium alloy used for the silicothermic reduction reaction is divided into an initial pour and subsequent pours. The initial pour accounts for 40% to 60% of the total liquid low-carbon silicon-chromium alloy used for the silicothermic reduction reaction. The subsequent pours are divided into 2 or 3 batches and poured sequentially. The remaining chromium ore and lime are divided into the same number of batches as the subsequent pours. After the initial pour of the liquid low-carbon silicon-chromium alloy is completed and between the pours of two adjacent batches of subsequent pours, a batch of chromium ore and a batch of lime are added respectively.

[0055] Before implementing step S2 in this embodiment, the planned total amount of liquid low-carbon silicon-chromium alloy used for the main silicothermic reduction reaction in this furnace is first determined. This planned total amount refers to the mass of liquid low-carbon silicon-chromium alloy poured in batches during step S2, excluding any subsequent additions based on the sampling results of the reduction slag. The first batch of pours is determined to be 40%–60% of the planned total amount, with the remaining portion used as subsequent pours, which are then divided into 2 or 3 batches. The mass of each batch of liquid low-carbon silicon-chromium alloy can be determined using the weighing device of the silicon-chromium alloy ladle, or calculated based on the change in ladle mass before and after pouring. Simultaneously, the chromium ore and lime that have not yet been added to the refining electric furnace after the initial slag formation are designated as remaining chromium ore and remaining lime, respectively, and then divided into corresponding 2 or 3 batches according to the number of subsequent pours. Each batch of material is typically allocated according to the planned mass; when minor adjustments are needed during production, the sum of the masses of each batch should still equal the remaining planned total amount of the corresponding material, ensuring a clear mass basis for the entire batch feeding process.

[0056] Furthermore, to ensure a clear implementation method for the mass distribution of subsequent batches of materials, when the subsequent pouring volume is divided into two batches, the two batches of liquid low-carbon silicon-chromium alloy can be divided equally in a 1:1 mass ratio; the remaining chromium ore and lime after the initial slag formation are also divided equally in a 1:1 mass ratio into two batches. When the subsequent pouring volume is divided into three batches, the three batches of liquid low-carbon silicon-chromium alloy can be divided equally in a 1:1:1 mass ratio, and the remaining chromium ore and lime are also divided equally in three batches. The above mass ratios refer to the mass distribution ratio between batches within the same material, and do not represent the mass ratio of the three materials: liquid low-carbon silicon-chromium alloy, chromium ore, and lime.

[0057] During the actual charging process, the first batch of liquid low-carbon silicon-chromium alloy is poured into the refining electric furnace, where the initial slag has already formed. After the first batch is poured, the first batch of chromium ore and lime is added, followed by the next batch of liquid low-carbon silicon-chromium alloy. If the subsequent batches are poured in two batches, the second batch of chromium ore and lime is added between the two batches of liquid low-carbon silicon-chromium alloy. If the subsequent batches are poured in three batches, the second and third batches of chromium ore and lime are added sequentially between adjacent batches of liquid low-carbon silicon-chromium alloy. Before each batch is started, the agitation and splashing of the material inside the furnace can be observed. Once the violent reaction caused by the previous batch has subsided, and the newly added chromium ore and lime have entered the slag and are no longer significantly accumulating on the slag surface, the next batch of liquid low-carbon silicon-chromium alloy is poured.

[0058] The initial pour volume is controlled at 40%–60% of the planned total, providing a certain amount of liquid reducing agent to the furnace after the initial slag formation, while reserving a considerable portion of liquid low-carbon silicon-chromium alloy for subsequent batch additions. This approach initiates the silicothermic reduction of chromium and iron oxides in the chromium ore without concentrating the planned liquid low-carbon silicon-chromium alloy into the furnace during the initial main charging phase. Subsequent pour volumes use the same batch numbers as the remaining chromium ore and lime, proceeding in the order of "adding one batch of chromium ore and lime, then pouring the next batch of liquid low-carbon silicon-chromium alloy." This ensures that each batch of solid charge comes into timely contact with the subsequently added liquid reducing agent after entering the slag, reducing the possibility of excessive reducing agent in localized areas or concentrated accumulation of oxides to be reduced. Alternating batch additions also minimize the furnace temperature drop and sudden changes in reaction intensity caused by adding a large amount of solid charge at once, allowing the melting, slag formation, and silicothermic reduction of the charge to proceed gradually with the charging process. Therefore, the reaction state and composition of the reducing slag in the furnace are usually more uniform at the end of step S2, which also makes it easier to judge the remaining reduction load and implement supplementary control based on the sampling results of the reducing slag.

[0059] As an optional solution in this embodiment, in step S2, the reaction temperature in the refining electric furnace is controlled at 1650-1800°C.

[0060] The total amount of lime added is determined to make the binary basicity of the reducing slag 1.5 to 1.9, where binary basicity is the mass ratio of CaO to SiO2 in the reducing slag.

[0061] In this embodiment, during the silicothermic reduction process in step S2, the reaction temperature inside the refining electric furnace is controlled between 1650 and 1800°C. The reaction temperature can be measured using an insertion thermocouple or a non-contact temperature measuring device suitable for high-temperature melt temperature measurement. The temperature measurement location should be selected in an area that reflects the temperature of the molten pool inside the furnace and is less affected by the electric arc and furnace wall. Measurements should be taken after the start of batch pouring of liquid low-carbon silicon-chromium alloy, after each stage of material addition, and before sampling the reduction slag. If the measured temperature is below 1650°C, the addition of furnace charge can be temporarily suspended and the power supply increased to allow the material inside the furnace to continue heating and melting. If the measured temperature is close to or above 1800°C, the power supply can be reduced, and material addition can continue after the reaction inside the furnace has stabilized. The total amount of lime added is determined before the start of smelting in this furnace. Specifically, based on the chemical analysis results of chromium ore, lime, and other materials fed into the furnace, the amount of CaO and SiO2 introduced can be calculated. Combined with the planned addition of chromium ore and liquid low-carbon silicon-chromium alloy for this furnace, the total amount of SiO2 entering the reducing slag during the silothermic reduction process can be estimated. Then, a target binary basicity within the range of 1.5 to 1.9 is selected. The required CaO mass is calculated back-calculated based on the ratio of CaO mass to SiO2 mass in the reducing slag. Finally, the total amount of lime added is calculated based on the effective CaO content in the lime. For production using the same batch or similar raw materials continuously, the calculated value can be modified for production purposes based on the final slag analysis results of previous stable furnace runs. After the furnace run is completed, the binary basicity is verified using the reducing slag test results.

[0062] Maintaining the reaction temperature between 1650 and 1800℃ ensures good flowability of the reducing slag within the furnace and allows the added chromite and lime to gradually melt and dissolve into the slag phase. After the chromium and iron oxides in the chromite enter the liquid slag phase, they come into sufficient contact with the silicon in the liquid low-carbon silicon-chromium alloy, enabling the silaneothermic reduction reaction to proceed continuously. If the temperature is too low, the slag fluidity decreases, the melting rate of solid materials slows down, and the reaction time is easily prolonged; if the temperature is too high, unnecessary heat loss increases, and the high-temperature load on the furnace lining is aggravated. Therefore, the above temperature range takes into account the melting of materials, slag flow, and the operating conditions of the refining electric furnace, helping to reduce temperature fluctuations during the smelting process.

[0063] Furthermore, in this embodiment, the binary basicity of the reduction slag is expressed as the mass ratio of CaO to SiO2. After silicon reduces chromium and iron oxides in chromite ore, SiO2 is generated. Adding lime allows CaO to enter the slag phase and form slag with SiO2. When the binary basicity is controlled between 1.5 and 1.9, the slag phase has a CaO content compatible with the generated SiO2, which reduces the relative activity of SiO2 in the slag phase, making it easier for the silothermic reduction reaction to continue towards the formation of chromium and iron. Simultaneously, this range avoids slag with high SiO2 content and poor fluidity due to insufficient lime addition, and also reduces the increase in unmelted lime and melting burden caused by excessive lime addition. The reaction temperature control and binary basicity control work together; the former provides the temperature conditions for lime dissolution into the slag and slag flow, while the latter adjusts the composition of the reduction slag. This allows the reducing slag to remain in a relatively uniform molten state within the furnace, reducing the impact of locally sticky slag or unmelted lime on the reaction and sampling, and providing more stable process conditions for subsequent judgment of the reduction process based on the Cr2O3 and FeO content in the reducing slag.

[0064] As an optional solution in this embodiment, in step S3, the mass fractions of Cr2O3 and FeO in the reduction residue obtained from the i-th sampling are respectively denoted as w. Cr,i and w Fe,i Let the first preset value and the second preset value be denoted as w respectively. Cr,0 and w Fe,0 When w Cr,i >w Cr,0 When the amount of chromium oxide exceeds the limit by Δw Cr,i =w Cr,i -w Cr,0 Otherwise, take Δw Cr,i =0; when w Fe,i >w Fe,0 When the amount of iron oxide exceeds the limit by Δw Fe,i =w Fe,i -w Fe,0 Otherwise, take Δw Fe,i =0; The replenishment mass of liquid low-carbon silicon-chromium alloy in this round is determined according to the following formula:

[0065] ;

[0066] In the formula, m i The mass of liquid low-carbon silicon-chromium alloy added in this round is expressed in kg; m z,0 The reference mass of the reduction slag in this furnace, determined before step S3, is expressed in kg; w SiThe mass fraction of Si in the liquid low-carbon silicon-chromium alloy to be added is expressed as a decimal; k is the reduction correction coefficient, ranging from 1.05 to 1.20; the reference mass of the reduction slag in this furnace is the product of the total mass of chromium ore added in this furnace and the preset slag production coefficient. The preset slag production coefficient is the average ratio of the mass of reduction slag discharged from the furnace to the total mass of chromium ore added in historical furnaces corresponding to the chromium ore grade, lime addition system and smelting conditions of this furnace.

[0067] In this embodiment, after all the chromium ore and lime have been added and the reaction continues, the reducing slag is subjected to the first... Secondary sampling. Sampling locations should be chosen in areas where the molten slag flow within the furnace is relatively stable and reflects the composition of the main slag phases, avoiding areas with surface crusts, unmelted material accumulation, and areas with obvious entrainment of molten metal. After cooling, crushing, and grinding, the mass fractions of Cr2O3 and FeO in the obtained slag samples are determined, and the results are recorded as follows: and The first and second preset values ​​were determined before this round of sampling calculations, and are denoted as follows: and All the above mass fractions are substituted into decimal form during calculation. For example, a mass fraction of 2.0% corresponds to a value of 0.020. In the second sampling This indicates the sampling and replenishment rounds. The first sampling is recorded as round 1, and the number increases sequentially when sampling is performed again after replenishment and continued reaction.

[0068] When calculating the replenishment mass for this round, first determine the excess amount of each of the two oxides relative to their respective preset values. At that time, take Otherwise take The FeO excess limit is determined in the same manner: when At that time, take Otherwise take By using this method of separately taking the difference and setting non-exceeding limits to zero, the oxides that have already reached the preset value will no longer generate negative silicon requirements, nor will they offset the reduction requirements corresponding to another oxide that is still exceeding the limit. Therefore, subsequent calculations focus on the actual remaining portion of the reduction residue that exceeds the endpoint requirement, rather than offsetting the deviations of the two oxides.

[0069] After obtaining two over-limit quantities, the replenishment mass of liquid low-carbon silicon-chromium alloy for this round is determined according to the following formula:

[0070] ;

[0071] In the formula, This indicates the amount of Cr2O3 that still needs to be reduced relative to the first preset value. This represents the remaining FeO mass that needs to be reduced relative to the second preset value. The coefficient 0.277 originates from the theoretical silicon consumption when Cr2O3 is reduced by silicon; that is, based on the reaction relationship, the mass of silicon required for the complete reduction of a unit mass of Cr2O3 is approximately 0.277 times its mass. The coefficient 0.196 corresponds to the theoretical silicon consumption when a unit mass of FeO is reduced by silicon. Adding these two values ​​yields the theoretical silicon requirement corresponding to the remaining reduction load in this round, which is then divided by the mass fraction of Si in the liquid low-carbon silicon-chromium alloy to be added. This can be converted into the mass of liquid low-carbon silicon-chromium alloy. Since not all silicon in the furnace is used for the reduction of the two oxides mentioned above, and there are deviations in actual production due to sampling analysis, slag quantity estimation, and reaction utilization, a reduction correction factor in the range of 1.05 to 1.20 is applied. The mass replenished in this round was obtained. .

[0072] Standard mass of reducing slag in this furnace Before step S3 begins, a unified quality benchmark is determined and used for calculations in each round. First, stable furnaces with complete weighing records are selected from historical furnaces corresponding to the chromium ore grade, lime addition regime, and smelting conditions of this furnace. The ratio of the mass of reduction slag discharged from the furnace to the total mass of chromium ore added in each historical furnace is calculated. Then, the average of these ratios is taken as the preset slag production coefficient. Multiplying the total mass of chromium ore added in this furnace by this preset slag production coefficient yields the final product. The reference mass of the reduction slag here is an estimated reference mass used in the supplementary calculation, and does not represent the reference mass of the first slag. Real-time measured mass of the reducing slag in the furnace during the second sampling. Reduction correction factor. The replenishment amount can be pre-selected within the range of 1.05 to 1.20 based on the replenishment results of historical furnaces under the same production conditions. When the raw materials and smelting conditions remain stable, the value verified in production can be used. If there are significant changes in the batch of raw materials or smelting conditions, the value should be re-verified. By converting the excess mass fraction of oxides into excess mass using the reduction slag baseline mass, and then determining the replenishment amount based on theoretical silicon consumption, silicon content, and correction coefficients, the residual reduction degree reflected by the slag sample composition can be converted into an executable replenishment mass of liquid low-carbon silicon-chromium alloy. This establishes a correspondence between the replenishment operation and the actual reduction state of the current furnace, and reduces the deviation caused by simply relying on fixed empirical replenishment amounts.

[0073] As an optional solution in this embodiment, in step S3, after each round of adding liquid low-carbon silicon-chromium alloy corresponding to the mass added in this round, the reaction continues for 3 to 8 minutes, and then the reduction residue is sampled.

[0074] If the mass fraction of either Cr2O3 or FeO obtained from this sampling is still greater than the corresponding preset value, the mass to be added in the next round will be determined and added based on the sampling results.

[0075] In the above embodiments, after determining the replenishment mass of liquid low-carbon silicon-chromium alloy in this round based on the sampling results of the reduction slag in the current round, the corresponding mass of liquid low-carbon silicon-chromium alloy is added to the refining electric furnace. The reaction time is calculated from the end of this round of replenishment, and the reaction continues for 3-8 minutes while the material in the furnace remains molten and undergoes silicothermic reduction, before the next reduction slag sampling. This reaction time is used to disperse the newly added liquid low-carbon silicon-chromium alloy in the molten pool and to allow the silicon to continue reacting with the chromium and iron oxides in the reduction slag that have not yet been reduced. The sampling location, sampling method, and sample processing method after the reaction should be consistent with the previous round to reduce analytical deviations caused by changes in sampling conditions between different rounds. After obtaining the slag sample, the mass fractions of Cr2O3 and FeO are measured and compared with the first and second preset values. If both mass fractions are not greater than their corresponding preset values, no further replenishment will be performed. If either of them is still greater than its corresponding preset value, the current test result will be used as the new calculation basis to redetermine the replenishment mass of liquid low-carbon silicon-chromium alloy for the next round. The mass already replenished in the previous round will not be counted again in the next round; the replenishment amount in the next round will only correspond to the remaining reduction balance reflected in this sampling. The above process of "replenishment, reaction, sampling, testing, and recalculation" will be carried out sequentially until both indicators simultaneously meet the endpoint requirements.

[0076] A 3-8 minute reaction time is allowed after each addition to reduce judgment bias caused by immediate sampling before the newly added liquid low-carbon silicon-chromium alloy has fully participated in the reaction. This allows subsequent slag samples to better reflect the reduction state after this addition. If any indicator still exceeds the limit in the retest results, the mass of the next addition is recalculated. The new test results can then be used to correct deviations in the previous calculations, sampling analysis, and actual silicon utilization. As additions and retests are performed round by round, the amount of liquid low-carbon silicon-chromium alloy added is adjusted according to the remaining reduction load, rather than being added continuously at once according to the initial calculation results. This reduces the possibility of single calculation deviations being carried over to the entire addition process and also reduces the risk of over-addition caused by operating with a large addition amount near the reduction endpoint. This helps ensure that Cr2O3 and FeO reach their corresponding preset values ​​before ending the reduction, improving the matching degree between the reduction endpoint control and the actual reaction state of the current furnace.

[0077] As an optional solution in this embodiment, the first preset value is preset in the range of 1.5% to 3.0%, and the second preset value is preset in the range of 0.5% to 1.5%. In step S4, after the reduction ends, the power supply of the refining electric furnace is reduced to 30% to 60% of the power supply of the silicon thermal reduction reaction stage in step S2, and maintained at the reduced power supply for 3 to 8 minutes to homogenize the ferrochrome alloy liquid, and then the iron is tapped.

[0078] In this embodiment, before the start of smelting in this furnace, a first preset value and a second preset value are determined. The first preset value is used to determine whether the Cr2O3 in the reducing slag has reached the reduction endpoint requirement, and its specific value is preset within the range of 1.5% to 3.0%. The second preset value is used to determine whether the FeO in the reducing slag has reached the reduction endpoint requirement, and its specific value is preset within the range of 0.5% to 1.5%. Both preset values ​​are expressed as mass fractions and remain unchanged during each round of sampling, calculation, and replenishment in the same furnace. In actual use, production records or verification furnaces under the same raw material conditions and smelting system can be combined to select a specific value within the above range that can balance the degree of reduction and the amount of liquid low-carbon silicon-chromium alloy, and the selected value is recorded in the furnace smelting record. When the value is close to the lower limit of the range, the requirements for the residual of the corresponding oxides in the final slag are stricter; when the value is close to the upper limit of the range, the endpoint determination is relatively lenient. Therefore, the settings should not be changed arbitrarily during the smelting process to avoid changes in the calculation basis of the replenishment amount in each round.

[0079] The silicothermic reduction stage ends when the mass fractions of Cr2O3 and FeO in the reducing slag are not greater than the corresponding preset values. Subsequently, the power supply used during the stable silicothermic reduction reaction in step S2 is used as the reference power. This reference power can be directly read from the active power setpoint or stable operating power record in the refining electric furnace control system. After the reduction ends, the power supply is reduced to 30%–60% of the reference power by adjusting the power supply level, electrode current, or corresponding power control parameters of the refining electric furnace, and maintained at this power for 3–8 minutes. During this period, no chromite, lime, or liquid low-carbon silicon-chromium alloy is added, and the ferrochrome alloy liquid and reducing slag in the furnace remain molten and flowable. Operators can perform routine monitoring based on the melt flow state and temperature measurement results; when a significant downward trend in temperature appears, the specific values ​​can be adjusted within the above power ratio and holding time range, but the high power state of the silicothermic reduction reaction stage will not be restored.

[0080] The first and second preset values ​​set clear endpoint boundaries for Cr2O3 and FeO in the reduction slag, respectively, providing a detectable and repeatable basis for judging the end of reduction and reducing the bias caused by judging the endpoint solely based on reaction time or slag appearance. Reducing the power supply after meeting both endpoint requirements allows the refining electric furnace to smoothly transition from the reduction reaction state to the homogenization state before tapping, reducing unnecessary heating caused by maintaining high power after reaching the endpoint. Maintaining the reduced power for 3–8 minutes allows time for the temperature and composition differences within the ferrochrome alloy liquid to gradually decrease while maintaining melt fluidity; too short a holding time makes it difficult to fully realize the homogenization effect, while too long a holding time increases the residence time and heat consumption before tapping. Therefore, the endpoint preset value and the power reduction homogenization are interconnected, providing clear operational boundaries between the end point of reduction and the pre-tapping treatment, which helps stabilize the state of the ferrochrome alloy liquid before tapping.

[0081] As an optional solution in this embodiment, in step S4, the tapping temperature is 1650-1750℃. The ferrochrome alloy liquid and reducing slag flow into the ladle through the tapping port and tapping trough of the refining electric furnace, so that the reducing slag entering the ladle floats on the surface of the ferrochrome alloy liquid and covers the exposed liquid surface of the ferrochrome alloy liquid. The time from the start of tapping in the refining electric furnace to the completion of casting does not exceed 20 minutes, specifically controlled to be 8-20 minutes. During casting, the vertical distance between the ladle nozzle and the upper edge of the mold is not greater than 300mm, and the depth of the ferrochrome alloy liquid in the mold is 100-250mm.

[0082] In this embodiment, after homogenization of the ferrochrome alloy melt, the molten pool temperature is measured before the tapping of the refining electric furnace, and tapping begins when the temperature reaches 1650–1750°C. The temperature can be measured using an insertion-type thermometer suitable for high-temperature molten metals, with the measurement location chosen to reflect the overall temperature of the ferrochrome alloy melt while avoiding slag crusting; alternatively, the temperature can be remeasured during the initial tapping stage based on the stable flow of the alloy melt. If the measured temperature is below the above range, power can be supplied to raise the temperature and the measurement repeated; if the temperature is above the above range, the power supply can be appropriately reduced while maintaining the fluidity of the melt, and tapping can resume after the temperature drops. Before tapping, the tapping port and tapping trough of the refining electric furnace are cleaned to ensure a continuous flow of ferrochrome alloy melt and reducing slag into the ladle. During tapping, the reducing slag is not completely skimmed off beforehand; instead, it is allowed to enter the ladle along with the ferrochrome alloy melt. Upon entering the ladle, the reducing slag floats due to the density difference with the ferrochrome alloy melt and spreads on the surface. On-site, the coverage status can be judged by observing whether there are still continuous exposed bright metal surfaces on the liquid surface. When a local metal surface is exposed, the tapping rhythm and the position of the ladle can be adjusted to allow the reducing slag flowing in to continue to spread and cover the exposed liquid surface. The control condition is not to use the slag layer reaching a fixed thickness.

[0083] Timing begins when the refining electric furnace starts tapping iron. The starting point of timing is the first continuous flow of molten ferrochrome alloy or a mixture of molten ferrochrome alloy and reducing slag from the taphole. The ending point is when the last batch of molten ferrochrome alloy in the ladle completes filling the mold. The tapping, ladle transfer, and casting processes should be pre-connected to minimize waiting time after tapping, keeping the entire process within 8–20 minutes. During casting, the ladle's lifting height and tilting angle are adjusted according to the ladle spout position, ensuring the vertical distance between the spout outlet and the upper edge of the mold is no more than 300 mm. This distance can be verified before casting using a ruler or on-site positioning marks and adjusted as the spout position changes during pouring. The depth of the molten ferrochrome alloy in the mold is controlled by both the effective cavity depth of the mold and the single pouring volume. The corresponding filling mass can be pre-determined based on the mold size and controlled within 100–250 mm during casting by adjusting the liquid level or using a quantitative pouring method. The depth of the ferrochrome alloy melt here is the vertical height of the molten metal from the bottom of the mold to the surface of the molten metal, excluding the thickness of the slag layer covering the surface of the molten metal.

[0084] Controlling the tapping temperature at 1650–1750℃ ensures the necessary fluidity of the ferrochrome alloy molten metal and reducing slag during the tapping trough, ladle, and casting process. This facilitates the timely floating and spreading of the reducing slag after it enters the ladle. Covering the exposed surface of the ferrochrome alloy molten metal with reducing slag reduces the area of ​​direct contact between the high-temperature molten metal and the surrounding air. Furthermore, limiting the time from tapping to casting completion to 8–20 minutes and controlling the casting drop to within 300 mm reduces prolonged residence of the high-temperature ferrochrome alloy molten metal and the surface agitation and splashing caused by large drop impacts. Maintaining a molten metal layer of 100–250 mm within the mold prevents the alloy from forming an excessively thin, widely spreading layer, and also facilitates maintaining a continuous and stable casting process. These conditions work together during the high-temperature stage after tapping, primarily reducing the time, area, and degree of disturbance of the ferrochrome alloy molten metal during transfer and casting, thereby reducing the possibility of further nitrogen absorption and contributing to the stability of low-nitrogen ferrochrome product quality.

[0085] To further illustrate the specific implementation process of the method of this application under different combinations of process parameters, three embodiments are listed below. Each embodiment follows the aforementioned steps: raw material pretreatment, initial slag formation, batch hot charging of liquid low-carbon silicon-chromium alloy, slag sampling and replenishment control, power reduction homogenization, and slag-bearing transfer and casting. The slag sampling analysis values ​​and the replenishment mass obtained based on them, as shown in the embodiments, are used to illustrate the calculation and cyclic control process of the reduction margin; in actual production, calculations should be performed based on the actual raw material composition of the corresponding furnace, the slag analysis results, the slag reference mass, and the actual mass fraction of Si in the liquid low-carbon silicon-chromium alloy to be replenished.

[0086] For the nitrogen content of low-nitrogen ferrochrome, a representative sample can be selected from the ferrochrome products obtained from the same furnace after casting and cooling for testing. During sample preparation, the surface oxide layer and visible inclusions that may affect the analytical results are removed. Then, the mass fraction of N is determined using existing ferroalloy nitrogen content analysis methods, such as the inert gas melting-thermal conductivity method or an equivalent analysis method calibrated on-site. The obtained N content is compared with the nitrogen content requirements of the corresponding grades of low-nitrogen medium-carbon ferrochrome, low-nitrogen low-carbon ferrochrome, or low-nitrogen micro-carbon ferrochrome to be produced. If the requirements of the corresponding grade are met, the product from that furnace is deemed to have met the corresponding low-nitrogen ferrochrome requirements.

[0087] It should be noted that the low-nitrogen control in this embodiment does not rely on setting up a dedicated denitrification reaction during the refining process, but mainly on reducing the opportunity for high-temperature ferrochrome alloy liquid to continue absorbing nitrogen during the later stages of refining, tapping, transfer, and casting. The liquid low-carbon silicon-chromium alloy is directly charged hot after exiting the submerged arc furnace, reducing the additional high-temperature treatment required for remelting and reheating the cold silicon-chromium alloy. After reaching the reduction endpoint, the power supply is reduced and homogenization is performed. Subsequently, the ferrochrome alloy liquid, along with the reducing slag, is discharged into the ladle, allowing the floating reducing slag to cover the exposed surface of the ferrochrome alloy liquid. Transfer and casting are completed within a preset time. This reduces the area and duration of direct contact between the high-temperature ferrochrome alloy liquid and air, thereby reducing the possibility of subsequent nitrogen absorption. Therefore, the process measures described in this embodiment provide the corresponding process conditions for obtaining low-nitrogen ferrochrome. Whether the final product meets the corresponding low-nitrogen grade is still subject to the actual nitrogen content test results.

[0088] Example 1

[0089] This embodiment illustrates the implementation method when the subsequent pouring volume is divided into two batches. The planned total mass of chromite added is 10,000 kg. The chromite and lime are dried to a moisture content of no more than 0.20% by mass and preheated to 450°C; the particle size of the chromite is 10–60 mm, and the particle size of the lime is 10–50 mm. 30% of the planned total mass of chromite and lime is added to the refining electric furnace and energized for melting until a continuous slag layer forms on the main surface area of ​​the furnace charge. The total amount of lime added is determined to achieve a binary basicity of 1.7 in the reducing slag.

[0090] In this embodiment, the liquid low-carbon silicon-chromium alloy used has a Cr mass fraction of 31%, a Si mass fraction of 44%, and a C mass fraction of 0.06%, with a hot charging temperature of 1500℃. The planned total amount of liquid low-carbon silicon-chromium alloy used for the main silicon thermal reduction reaction is determined according to the furnace batching calculation, with the first batch accounting for 50%, and the remaining 50% divided into two batches as subsequent batches. The remaining chromium ore and lime after the initial slag formation are also divided into two batches. In this embodiment, the two batches of liquid low-carbon silicon-chromium alloy in the subsequent batches are divided into equal mass ratios of 1:1; the two batches of remaining chromium ore after the initial slag formation are divided into equal mass ratios of 1:1, and the two batches of remaining lime are also divided into equal mass ratios of 1:1. Specifically, the liquid low-carbon silicon-chromium alloy is added in the following order: first batch of liquid low-carbon silicon-chromium alloy, first batch of remaining chromium ore and lime, first batch of subsequent liquid low-carbon silicon-chromium alloy, second batch of remaining chromium ore and lime, and second batch of subsequent liquid low-carbon silicon-chromium alloy. The silicon thermal reduction reaction temperature is controlled at 1720~1760℃.

[0091] The historical slag production coefficient corresponding to the chromium ore grade, lime addition system, and smelting conditions of this furnace is preset to 1.50. Therefore, the baseline mass of the reduction slag in this furnace is 10000 × 1.50 = 15000 kg. The first preset value is set to 2.0%, the second preset value is set to 1.0%, and the reduction correction coefficient k is taken as 1.10. The mass fraction of Cr2O3 in the reduction slag measured in the first sampling was 4.8%, the mass fraction of FeO was 2.2%, and the corresponding excess of chromium oxide was 0.048 - 0.020 = 0.028, and the excess of iron oxide was 0.022 - 0.010 = 0.012. Substituting the above values, the baseline mass of the reduction slag in this furnace, and the Si mass fraction of 0.44 into the aforementioned calculation formula, the mass of liquid low-carbon silicon-chromium alloy added in the first round is approximately 379 kg.

[0092] After the first round of addition, the reaction continued for 5 minutes, and the reduction residue was sampled again. The second sample showed a Cr₂O₃ mass fraction of 2.3% and an FeO mass fraction of 1.1%, with corresponding excesses of 0.003 g of chromium oxide and 0.001 g of iron oxide. Based on this, the calculated mass of the second round of addition was approximately 39 kg. After the second round of addition, the reaction continued for 5 minutes, and another sample was taken. The reduction was terminated when the Cr₂O₃ mass fraction was no greater than 2.0% and the FeO mass fraction was no greater than 1.0% in the third sample.

[0093] After reduction, the power supply of the refining electric furnace is reduced to 45% of the power supply during the silicothermic reduction reaction stage, and maintained for 5 minutes to homogenize the ferrochrome alloy liquid. Tapping begins at a tapping temperature of 1680–1720℃, allowing the ferrochrome alloy liquid and reducing slag to enter the ladle together, with the floating reducing slag covering the exposed surface of the ferrochrome alloy liquid. The time from tapping to casting completion is controlled at 15 minutes. During casting, the vertical distance between the ladle spout and the upper edge of the mold should not exceed 300 mm, and the depth of the ferrochrome alloy liquid in the mold should be controlled at 180 mm.

[0094] Example 2

[0095] This embodiment illustrates the implementation method when the subsequent pouring volume is divided into 3 batches. The planned total mass of chromite added is 8000 kg. The chromite and lime are dried to a moisture content of no more than 0.20% by mass and preheated to 350°C; the particle size of the chromite is 10–60 mm, and the particle size of the lime is 10–50 mm. The chromite and lime used to form the initial slag each account for 20% of the corresponding planned total addition, and are energized and melted onto the surface of the furnace charge to form a continuous slag layer. The total amount of lime added is determined to achieve a binary basicity of 1.5 in the reducing slag.

[0096] In this embodiment, the liquid low-carbon silicon-chromium alloy used has a Cr mass fraction of 29%, a Si mass fraction of 46%, and a C mass fraction of 0.08%, with a hot-charging temperature of 1450℃. The initial pour accounts for 40% of the planned total amount of liquid low-carbon silicon-chromium alloy used in the main silicothermic reduction reaction, with the remaining pours divided into three batches. The remaining chromium ore and lime are also divided into three batches, and are added in the following order: the first batch of chromium ore and lime is added after the first batch of liquid low-carbon silicon-chromium alloy is poured; subsequently, the second and third batches of chromium ore and lime are added sequentially between adjacent batches of liquid low-carbon silicon-chromium alloy. The silicothermic reduction reaction temperature is controlled at 1650–1720℃.

[0097] The preset slag production coefficient for the corresponding historical furnace is 1.42, and the baseline mass of the reduction slag in this furnace is 8000 × 1.42 = 11360 kg. The first preset value is set at 2.5%, the second preset value is set at 1.2%, and the reduction correction coefficient k is taken as 1.08. A sampling test in a certain round showed that the mass fraction of Cr2O3 in the reduction slag was 4.1%, and the mass fraction of FeO was 1.8%, exceeding the corresponding preset values ​​by 0.016 and 0.006 respectively. Based on the mass fraction of Si in the liquid low-carbon silicon-chromium alloy to be added (0.46%), the mass to be added in this round is approximately 150 kg. After addition, the reaction continues for 3–6 minutes, and the new sampling results are used to determine whether to continue adding; if any indicator still exceeds the corresponding preset value, the mass to be added in the next round is recalculated until the mass fractions of Cr2O3 and FeO both reach the corresponding endpoint requirements.

[0098] After reaching the reduction endpoint, the power supply of the refining electric furnace is reduced to 30% of the power supply during the silicothermic reduction reaction stage, and maintained for 3 minutes for homogenization. At a tapping temperature of 1650–1690℃, the molten ferrochrome alloy and reducing slag flow together into the ladle, with the reducing slag covering the exposed surface of the molten ferrochrome alloy. The time from the start of tapping to the completion of casting is controlled to be 8–14 minutes. During casting, the vertical distance between the ladle spout and the upper edge of the mold should not exceed 300 mm, and the depth of the molten ferrochrome alloy in the mold should be controlled to be 100–160 mm.

[0099] Example 3

[0100] This embodiment employs a relatively high raw material preheating temperature and a relatively low final slag preset value. The planned total mass of chromite added is 9600 kg. The chromite and lime are dried to a moisture content of no more than 0.20% and preheated to 600°C; the chromite particle size is 10–60 mm, and the lime particle size is 10–50 mm. The chromite and lime used to form the initial slag each account for 40% of the corresponding planned total addition, and are energized and melted onto the surface of the furnace charge to form a continuous slag layer. The total amount of lime added is determined to achieve a binary basicity of 1.9 in the reducing slag.

[0101] In this embodiment, the liquid low-carbon silicon-chromium alloy has a Cr mass fraction of 35%, a Si mass fraction of 42%, and a C mass fraction of 0.05%, and the hot charging temperature is 1600℃. The initial pour accounts for 60% of the planned total amount of liquid low-carbon silicon-chromium alloy used in the main silothermic reduction reaction. The remaining subsequent pours are divided into two batches, and the remaining chromite and lime are also divided into two batches accordingly, and are added in the same alternating feeding sequence as in Example 1. The silothermic reduction reaction temperature is controlled at 1750–1800℃.

[0102] The preset slag production coefficient for the corresponding historical furnace is 1.40, and the baseline mass of the reduction slag in this furnace is 9600 × 1.40 = 13440 kg. The first preset value is set to 1.5%, the second preset value is set to 0.5%, and the reduction correction coefficient k is taken as 1.15. A sampling test in a certain round showed that the mass fraction of Cr2O3 in the reduction slag was 3.5%, and the mass fraction of FeO was 1.3%, with excesses of 0.020 and 0.008 respectively relative to the corresponding preset values. Based on the mass fraction of Si in the liquid low-carbon silicon-chromium alloy to be added (0.42%), the mass to be added in this round is approximately 262 kg. After addition, the reaction continues for 8 minutes, and the mass to be added in the next round is recalculated based on the new sampling results until the mass fractions of both oxides are no greater than the corresponding preset values.

[0103] After reaching the reduction endpoint, the power supply of the refining electric furnace is reduced to 60% of the power supply during the silicothermic reduction reaction stage, and maintained for 8 minutes to homogenize the ferrochrome alloy liquid. At a tapping temperature of 1720–1750℃, the ferrochrome alloy liquid and reducing slag are introduced into the ladle together, and the molten ferrochrome alloy liquid is transferred and cast while the reducing slag covers the exposed surface of the molten ferrochrome alloy liquid. The time from the start of tapping to the completion of casting is controlled at 16–20 minutes, the vertical distance between the ladle nozzle and the upper edge of the mold is controlled at 200–300 mm, and the depth of the ferrochrome alloy liquid in the mold is controlled at 200–250 mm.

[0104] The three embodiments described above illustrate the implementation process under different raw material preheating temperatures, initial slag proportions, batching methods for liquid low-carbon silicon-chromium alloy, preset final slag values, and homogenization casting conditions. The specific replenishment mass in each embodiment is determined by the analysis value of the reducing slag in the current batch, the baseline mass of the reducing slag in this furnace, the actual mass fraction of Si in the liquid low-carbon silicon-chromium alloy to be replenished, and the reduction correction coefficient. This amount is not intended to be a fixed replenishment quantity directly applied to other batches. In actual production, specific values ​​can be selected within the aforementioned parameter range, taking into account raw material conditions and the operating status of the refining electric furnace. Replenishment and retesting should be completed round by round based on the sampling results.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for hot-charging refining of low-nitrogen ferrochrome based on reduction balance control, characterized in that, Includes the following steps: S1, chromite and lime are dried and preheated, and a portion of them are added to a refining electric furnace and energized to melt them, forming the initial slag; S2, the liquid low-carbon silicon-chromium alloy from the submerged arc furnace is placed in a silicon-chromium alloy bag, and the liquid low-carbon silicon-chromium alloy is poured into the refining electric furnace in batches from the silicon-chromium alloy bag. Between two consecutive pours, the remaining chromium ore and lime are added to allow the liquid low-carbon silicon-chromium alloy to undergo a silicothermic reduction reaction with the chromium ore to obtain ferrochrome alloy liquid and reduction slag. S3. After adding chromite and lime, take a sample of the reduction slag and add liquid low-carbon silicon-chromium alloy according to the content of Cr2O3 and FeO in the reduction slag. After adding, continue the reaction and take a sample again. When the mass fraction of Cr2O3 in the reduction slag is not greater than the first preset value and the mass fraction of FeO is not greater than the second preset value, the reduction ends. S4, reduce the power supply of the refining electric furnace and homogenize the ferrochrome alloy liquid. Discharge the homogenized ferrochrome alloy liquid along with the reducing slag into the molten iron ladle, so that the reducing slag forms a covering slag layer on the surface of the ferrochrome alloy liquid. Under the cover of the covering slag layer, the transfer and casting are completed within a preset time to obtain low-nitrogen, medium-low-carbon ferrochrome.

2. The low-nitrogen ferrochrome hot-charging refining method based on reduction balance control according to claim 1, characterized in that, In step S1, the chromite and lime are dried to a moisture content of no more than 0.20% by mass, and then preheated to 300-600°C; the particle size of the chromite is 10-60 mm, and the particle size of the lime is 10-50 mm.

3. The low-nitrogen ferrochrome hot-charging refining method based on reduction balance control according to claim 1, characterized in that, In step S1, the chromite and lime added to form the initial slag account for 20% to 40% of the corresponding planned total addition amount. After being energized and melted to the surface of the furnace charge to form a continuous slag layer, step S2 is implemented.

4. The low-nitrogen ferrochrome hot-charging refining method based on reduction balance control according to claim 1, characterized in that, In step S2, the liquid low-carbon silicon-chromium alloy contains 27%–35% Cr, 38%–50% Si, and no more than 0.10% C by mass, and the hot-fitting temperature is 1400–1600℃.

5. The low-nitrogen ferrochrome hot-charging refining method based on reduction balance control according to claim 1, characterized in that, In step S2, the liquid low-carbon silicon-chromium alloy used for the silicothermic reduction reaction is divided into an initial pour and subsequent pours. The initial pour accounts for 40% to 60% of the total liquid low-carbon silicon-chromium alloy used for the silicothermic reduction reaction. The subsequent pours are divided into 2 or 3 batches and poured sequentially. The remaining chromium ore and lime are divided into batches of the same number as the subsequent pours. After the initial pour of the liquid low-carbon silicon-chromium alloy is completed and between the pours of two adjacent batches of subsequent pours, a batch of chromium ore and a batch of lime are added respectively.

6. The low-nitrogen ferrochrome hot-charging refining method based on reduction balance control according to claim 1, characterized in that, In step S2, the reaction temperature inside the refining electric furnace is controlled at 1650–1800°C; The total amount of lime added is determined to make the binary basicity of the reducing slag 1.5 to 1.9, where the binary basicity is the mass ratio of CaO to SiO2 in the reducing slag.

7. The low-nitrogen ferrochrome hot-charging refining method based on reduction balance control according to claim 1, characterized in that, In step S3, the mass fractions of Cr2O3 and FeO in the reduction residue obtained from the i-th sampling are denoted as w, respectively. Cr,i and w Fe,i Let the first preset value and the second preset value be denoted as w respectively. Cr,0 and w Fe,0 When w Cr,i >w Cr,0 When the amount of chromium oxide exceeds the limit by Δw Cr,i =w Cr,i -w Cr,0 Otherwise, take Δw Cr,i =0; when w Fe,i >w Fe,0 When the amount of iron oxide exceeds the limit by Δw Fe,i =w Fe,i -w Fe,0 Otherwise, take Δw Fe,i =0; The replenishment mass of liquid low-carbon silicon-chromium alloy in this round is determined according to the following formula: ； In the formula, m i The mass of liquid low-carbon silicon-chromium alloy added in this round is expressed in kg; m z,0 The reference mass of the reduction slag in this furnace, determined before step S3, is expressed in kg; w Si The mass fraction of Si in the liquid low-carbon silicon-chromium alloy to be added is expressed as a decimal; k is the reduction correction coefficient, ranging from 1.05 to 1.20; the reference mass of the reduction slag in this furnace is the product of the total mass of chromium ore added in this furnace and the preset slag production coefficient, which is the average ratio of the mass of reduction slag discharged from the furnace to the total mass of chromium ore added in historical furnaces corresponding to the chromium ore grade, lime addition system and smelting conditions of this furnace.

8. The low-nitrogen ferrochrome hot-charging refining method based on reduction balance control according to claim 7, characterized in that, In step S3, after each round of replenishment of liquid low-carbon silicon-chromium alloy corresponding to the mass of the current round, the reaction continues for 3 to 8 minutes, and then the reduction residue is sampled. If the mass fraction of either Cr2O3 or FeO obtained from this sampling is still greater than the corresponding preset value, the mass to be added in the next round will be determined and added based on the sampling results.

9. The low-nitrogen ferrochrome hot-charging refining method based on reduction balance control according to claim 7 or 8, characterized in that, The first preset value is preset within the range of 1.5% to 3.0%, and the second preset value is preset within the range of 0.5% to 1.5%. In step S4, after the reduction ends, the power supply of the refining electric furnace is reduced to 30% to 60% of the power supply of the silicon thermal reduction reaction stage in step S2, and maintained at the reduced power supply for 3 to 8 minutes to homogenize the ferrochrome alloy liquid, and then the iron is tapped.

10. The low-nitrogen ferrochrome hot-charging refining method based on reduction balance control according to any one of claims 1-8, characterized in that, In step S4, the tapping temperature is 1650-1750℃. The ferrochrome alloy liquid and reducing slag flow into the ladle through the tapping port and tapping trough of the refining electric furnace, so that the reducing slag entering the ladle floats on the surface of the ferrochrome alloy liquid and covers the exposed surface of the ferrochrome alloy liquid. The time from the start of tapping in the refining electric furnace to the completion of casting does not exceed 20 minutes, specifically controlled to be 8-20 minutes. During casting, the vertical distance between the ladle nozzle and the upper edge of the mold is not greater than 300mm, and the depth of the ferrochrome alloy liquid in the mold is 100-250mm.

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