Low-carbon silicon-chromium alloy and production method thereof

Abstract

The invention provides a low-carbon silicon-chromium alloy and a production method thereof.The method includes the steps that silica, coke and high-carbon ferrochrome are crushed and then mixed, and a mixed raw material is obtained; putting the mixed raw material into an electric furnace, supplying power, and smelting to obtain molten iron; the molten iron is injected into a steel ladle for ladle-to-ladle operation, and after ladle-to-ladle operation is finished, the molten iron is left to stand until a slag layer is solidified; and casting the molten iron on the lower layer of the steel ladle to obtain the low-carbon silicon-chromium alloy. According to the method, the ladle-to-ladle operation which is the out-of-furnace decarburization process is set, quality improvement and carbon reduction can be carried out on the molten iron under the condition that normal work of the electric furnace is not affected, and the effects of guaranteeing the production efficiency and improving the product quality are achieved at the same time. And the ladle-to-ladle operation is set, so that the carbon content in the silicon-chromium alloy can be effectively reduced, the silicon-chromium alloy with the low carbon content is obtained, and an effective guarantee is provided for downstream production of low-carbon refined ferrochromium from a raw material end.

Description

Technical Field

[0001] This application relates to silicon-chromium alloy smelting technology, and more particularly to a low-carbon silicon-chromium alloy and its production method. Background Technology

[0002] Ferrosilicon chromium is a chromium-silicon-iron alloy produced by the reduction of chromium ore and silicon ore. It contains elements such as carbon and is mainly used in the metallurgical field as a desulfurizing agent, reducing agent, and refractory material. In the machinery manufacturing and aerospace industries, it can be used to process high-strength parts and high-temperature alloy components. It is also an intermediate product in the production of low-carbon and micro-carbon ferrochrome and is one of the main chromium-based ferroalloy products. The quality of silicon-chromium alloy is closely related to the quality of refined ferrochrome; to produce low-carbon, high-quality refined ferrochrome, a corresponding low-carbon silicon-chromium alloy is necessary.

[0003] Therefore, reducing the carbon content in silicon-chromium alloys is key to improving the quality and efficiency of refined ferrochrome. Summary of the Invention

[0004] This application provides a low-carbon silicon-chromium alloy and its production method, which provides a raw material guarantee for downstream industries to improve the quality and efficiency of refined ferrochrome.

[0005] In a first aspect, this application provides a method for producing a low-carbon silicon-chromium alloy, comprising the following steps: Silica, coke, and high-carbon ferrochrome are crushed separately and then mixed to obtain a mixed raw material; The mixed raw materials are fed into an electric furnace and powered on for smelting to obtain molten iron; The molten iron is poured into the ladle and then poured into the ladle. After the pouring is completed, the molten iron is left to stand until the slag layer solidifies. The molten iron in the lower layer of the ladle is poured to obtain a low-carbon silicon-chromium alloy.

[0006] The low-carbon silicon-chromium alloy and its production method disclosed in this application have the following beneficial effects: 1) The method of this application first uses coke to reduce silica to obtain active silicon, and then uses the generated silicon liquid to react with carbides in high carbon ferrochrome melt to generate low carbon silicon-chromium alloy and remove carbon. The subsequent pouring operation strengthens the renewal of the slag-metal reaction interface through physical stirring, promotes the mass transfer and transfer of dissolved impurities to the slag phase, and is beneficial to the production of high-quality silicon-chromium alloy.

[0007] 2) The method of this application incorporates an external decarburization process called ladle-turning, which can improve the quality and reduce the carbon content of molten iron without affecting the normal operation of the electric furnace, thus ensuring both production efficiency and product quality. Furthermore, the ladle-turning operation effectively reduces the carbon content in the silicon-chromium alloy, resulting in a low-carbon silicon-chromium alloy, providing a reliable raw material source for downstream production of low-carbon refined ferrochrome.

[0008] Optionally, the smelting process includes: Take 0.3 to 0.4 times the amount of mixed raw materials and put them into the bottom of the electric furnace. Smelt them into liquid for 1 to 1.2 hours. Then put the remaining mixed raw materials into the electric furnace and continue smelting for 2.8 to 3 hours to obtain molten iron. The power supply voltage is 275~282V, the current is 8200~8500A, and it is AC power supply.

[0009] Optionally, the packet reloading operation includes: Pour the molten iron into the ladle, let it stand for 3-4 minutes, and then pour the ladle over the ladle 3-5 times. After each pour, let it stand for 3-4 minutes. Control the pouring of each ladle of molten iron to be completed within 5-8 minutes.

[0010] Optionally, a gas blowing operation is also included in the settling stage after the unloading is completed, including: A mixture of carbon dioxide and oxygen is sprayed downwards from the top of the ladle at a pressure of 1.0~1.2 MPa. Simultaneously, carbon dioxide gas is blown into the molten iron from the side of the ladle at a pressure of 1.2~1.4MPa for 10~15min.

[0011] Optionally, the volume ratio of carbon dioxide to oxygen in the mixture of carbon dioxide and oxygen is 1:(2~4).

[0012] Optionally, the weight ratio of silica, coke and high-carbon ferrochrome in the mixed raw materials is 3~3.2:(1.6~1.7):(1.05~1.1).

[0013] Optionally, the particle size of the crushed silica is 10~40mm; The crushed particle size of coke is 5~20mm; The crushing particle size of high-carbon ferrochrome is 30~50mm.

[0014] Optionally, the silica content in the silica is ≥97%; The coke contains ≥82% fixed carbon, ≤14% ash, and ≤8% moisture. High-carbon ferrochrome contains >65% chromium and ≤10% carbon.

[0015] Optionally, the ladle is cylindrical with an inner diameter of 1.4±0.1m and an inner height of 1.7±0.1m.

[0016] Secondly, this application provides a low-carbon silicon-chromium alloy, prepared by any of the methods described in the first aspect.

[0017] The beneficial effects of the low-carbon silicon-chromium alloy provided in this application are as mentioned in the first aspect above, and will not be repeated here. Detailed Implementation

[0018] 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.

[0019] In a first aspect, this application provides a method for producing low-carbon silicon chromium alloy, comprising the following steps: Silica, coke, and high-carbon ferrochrome are crushed separately and then mixed to obtain a mixed raw material; The mixed raw materials are fed into an electric furnace and powered on for smelting to obtain molten iron; The molten iron is poured into the ladle and then poured into the ladle. After the pouring is completed, the molten iron is left to stand until the slag layer solidifies. The molten iron in the lower layer of the ladle is poured to obtain a low-carbon silicon-chromium alloy.

[0020] In this application, silica (the main source of SiO2), coke (a reducing agent and carbon source), and high-carbon ferrochrome (the initial carrier of chromium and carbon) are crushed separately and then mixed. The crushing process increases the contact area between reactants and shortens the diffusion distance of reactant molecules or atoms between the solid and liquid phases, thereby significantly improving the kinetic rate of multiphase chemical reactions (mainly reduction reactions) in subsequent high-temperature smelting. Uniform mixing avoids incomplete or over-reaction in certain areas, ensuring a uniform final alloy composition.

[0021] The mixed raw materials are fed into an electric furnace and smelted for 3-4 hours. During the smelting process, a high-temperature (usually exceeding 1600°C), reducing chemical environment is created in the submerged arc furnace under the action of electric arc and resistance heat. In this environment, a series of complex metallurgical physicochemical processes occur: carbon in the coke undergoes a carbothermic reduction reaction with silicon dioxide in silica (main reaction: SiO2 + 2C → Si + 2CO↑), generating elemental silicon and releasing carbon monoxide gas; at the same time, high-carbon ferrochrome partially melts, and the chromium and carbon in it dissolve in the generated ferrosilicon melt. More importantly, the silicon dissolved in the melt undergoes a decarburization reaction of "silicon reducing carbon" with the carbon carried by the high-carbon ferrochrome itself, as well as carbon that may be absorbed from the coke (e.g., Cr7C3 + 7Si → 7CrSi + 3C, or carbides react with silicon to generate silicon carbide and enter the slag phase, or carbon is replaced by silicon and removed in the form of carbon monoxide). Smelting by electric current for 3-4 hours can provide sufficient energy for the above-mentioned endothermic reduction reaction and diffusion-controlled decarburization reaction, ensuring that the reaction is close to equilibrium, the chromium element is reduced and alloyed to the maximum extent, and the excess carbon is deeply removed by silicon.

[0022] During the pouring process, the molten iron is transferred from one container to another, a crucial physical refining process. The vigorous agitation caused by the gravity-induced drop and turbulence breaks down and disperses the initial slag phase or high-melting-point intermediate phase within the electric furnace. This increases the slag-metal interface, promoting mass transfer of impurities (such as phosphorus and sulfur) or fine non-metallic inclusions dissolved in the molten metal into the slag phase. Simultaneously, the turbulence provides a "cleaning" effect, ensuring thorough contact between the molten metal droplets and the slag phase, enhancing impurity oxidation or slag-forming reactions. Furthermore, the agitation promotes temperature and composition homogenization within the molten pool. The subsequent settling process utilizes the density difference between the slag phase (primarily composed of silicates formed from SiO2, CaO, and Al2O3) and the molten iron (silicon-chromium alloy melt) to achieve slag-metal separation in a static state. Once the slag layer solidifies, a solid slag shell is formed, facilitating the subsequent separation of the pure molten iron from the solid slag.

[0023] Finally, the molten iron from the lower layer of the ladle is poured into the mold. Choosing the lower layer is to avoid the solidified slag layer above and any small amount of inclusions that may be suspended on top, ensuring that only pure alloy melt is poured into the mold. This process, through steps of crushing and mixing, high-temperature reduction and decarburization smelting, ladle refining and slag-metal separation, and finally, pouring the pure lower layer of molten iron, achieves the transformation from raw materials to low-carbon silicon-chromium alloy products.

[0024] The low-carbon silicon-chromium alloy and its production method disclosed in this application have the following beneficial effects: 1) The method of this application first uses coke to reduce silica to obtain active silicon, and then uses the generated silicon liquid to react with carbides in high carbon ferrochrome melt to generate low carbon silicon-chromium alloy and remove carbon. The subsequent pouring operation strengthens the renewal of the slag-metal reaction interface through physical stirring, promotes the mass transfer and transfer of dissolved impurities to the slag phase, and is beneficial to the production of high-quality silicon-chromium alloy.

[0025] 2) The method of this application incorporates an external decarburization process called ladle-turning, which can improve the quality and reduce the carbon content of molten iron without affecting the normal operation of the electric furnace, thus ensuring both production efficiency and product quality. Furthermore, the ladle-turning operation effectively reduces the carbon content in the silicon-chromium alloy, resulting in a low-carbon silicon-chromium alloy.

[0026] Optionally, the smelting process includes: Take 0.3 to 0.4 times the amount of mixed raw materials and put them into the bottom of the electric furnace. Smelt them into liquid for 1 to 1.2 hours. Then put the remaining mixed raw materials into the electric furnace and continue smelting for 2.8 to 3 hours to obtain molten iron. The power supply voltage is 275~282V, the current is 8200~8500A, and it is AC power supply.

[0027] In this application, the purpose of laying a portion of the mixed raw materials at the bottom is to pre-form a conductive and heat-storing molten pool foundation at the furnace bottom. Under the electric arc heating, the coke rapidly heats up and generates heat, while the silica softens, melts, and undergoes an initial reduction reaction with the coke. After approximately 1 hour of smelting, this portion of the raw materials transforms into a liquid layer primarily composed of ferrosilicon melt and some nascent ferrochrome melt, providing a high-temperature liquid medium for the subsequent addition of the remaining furnace charge. The remaining charge, once poured in, can be rapidly heated, submerged, and dissolved, avoiding the drastic temperature fluctuations and "splashing" caused by directly adding cold material, thus making the smelting process more stable. Furthermore, the presence of the liquid molten pool enhances the mass transfer process and accelerates the exchange of matter between the solid furnace charge and the reacted products.

[0028] Secondly, after a stable liquid molten pool is formed, the remaining majority of the mixed raw materials are added, and smelting continues for 2.8 to 3 hours. This stage is the main reaction period and the deep decarburization period. The addition of a large amount of furnace charge causes a dramatic increase in the volume of the molten pool and the reaction interface. The system operates under AC power parameters of 275-282V voltage and 8200-8500A. The higher secondary voltage facilitates the formation of a longer electric arc, increases the temperature in the arc zone, enhances radiative heat transfer to the molten pool, and expands the high-temperature reaction zone. The strong current ensures the total input power, meeting the needs of melting a large amount of furnace charge and the significant heat absorption required for the reduction reaction. Compared to DC power, AC power supply has a periodic change in current direction, which, under the action of electromagnetic force, produces a periodic stirring effect on the molten pool (electromagnetic stirring). Although this stirring is not as strong as mechanical stirring, it helps to promote the homogenization of composition and temperature within the molten pool, accelerates the diffusion of reactants and products, and makes the decarburization reaction more thorough.

[0029] Optionally, the packet reloading operation includes: Pour the molten iron into the ladle, let it stand for 3-4 minutes, and then pour the ladle over the ladle 3-5 times. After each pour, let it stand for 3-4 minutes. Control the pouring of each ladle of molten iron to be completed within 5-8 minutes.

[0030] In this application, after the high-temperature molten iron is poured into the ladle, it is first allowed to stand for 3-4 minutes. The purpose of standing is to allow the gas entrained during the pouring process to have time to escape initially, and at the same time, to allow some large non-metallic inclusions or nascent slag droplets with large density differences to begin to float under the action of gravity, forming a preliminary slag-metal stratification interface, providing a relatively clear starting state for the subsequent ladle pouring operation.

[0031] Then, the molten iron is repeatedly poured from one ladle into another empty ladle, 3-5 times. This pouring utilizes the intense gravity and impact to create vigorous turbulence and shear force. This mechanical agitation significantly increases the contact area and renewal rate between the slag and molten metal phases, breaking down the localized diffusion boundary layers that might form during settling. This allows harmful impurities dissolved in the metal (such as sulfur and phosphorus) or trace amounts of high-carbon phases to migrate to the slag-metal interface and enter the slag phase through chemical reactions (such as absorption by alkaline oxides in the slag) or physical adsorption. Secondly, the "slag-rolling" and "washing" effects of the turbulence allow the molten metal to pass through the slag layer in the form of fine droplets, or disperses the slag phase in the molten metal as fine particles, achieving forced slag-metal mixing and reaction, thus accelerating the refining process. Simultaneously, the agitation promotes temperature homogenization of the entire melt within the ladle, preventing premature precipitation of high-carbon or impurity phases due to localized supercooling. In addition, the process of pouring the ladle increases the contact between the molten iron and the air, which causes the carbon in the molten iron to react with the oxygen in the air to generate gas, which is then released, thus reducing carbon content.

[0032] After each inversion, the vessel is allowed to stand for 3-4 minutes to create conditions for the next forced stirring to separate the slag and gold. After one inversion and stirring, a large number of fine inclusions are generated or exposed, requiring a period of settling time for these fine particles to float, aggregate, and grow, eventually separating from the molten metal. This repeated "stirring-setting" cycle is essentially a step-by-step, multi-stage slag-gold separation and refining process. Each stirring promotes the reaction and the formation / exposure of inclusions, while each settling completes partial separation. After multiple cycles, the impurity removal efficiency is far higher than that of a single long settling.

[0033] Each ladle of molten iron should be poured within 5-8 minutes. Too short a time may result in insufficient agitation; too long a time will increase the exposure and circulation time of the molten iron in the air, leading to excessive temperature drop and poor fluidity. This not only affects the pouring operation itself, but may also cause high-melting-point phases to precipitate in the molten metal, affecting the subsequent casting quality and alloy properties.

[0034] Optionally, a gas blowing operation is also included in the settling stage after the unloading is completed, including: A mixture of carbon dioxide and oxygen is sprayed downwards from the top of the ladle at a pressure of 1.0~1.2 MPa. Simultaneously, carbon dioxide gas is blown into the molten iron from the side of the ladle at a pressure of 1.2~1.4MPa for 10~15min.

[0035] In this application, a mixture of carbon dioxide (CO2) and oxygen (O2) is blown downwards from the top of the ladle (pressure 1.0-1.2 MPa). The main area of ​​action of the top blowing is the slag layer and the surface of the molten iron in the upper part of the ladle. The principle is twofold: First, the kinetic energy of the blown gas is used to stir the slag layer, even partially penetrating it, renewing the slag-metal interface, preventing slag crusting, and maintaining the slag's activity and reactivity. Second, the blown oxygen and carbon dioxide act as oxidizing gases, reacting with elements on the surface of the molten iron or at the slag-iron interface. Oxygen can directly oxidize elements such as silicon and chromium in the molten iron (e.g., Si + O2 → SiO2; 2Cr + 3 / 2O2 → Cr2O3), and the resulting oxides enter the slag phase. Carbon dioxide, being a weak oxidant, reacts with elements such as carbon and silicon in the molten iron in an endothermic reaction (e.g., CO2 + C → 2CO; 2CO2 + Si → SiO2 + 2CO). This gentle oxidation helps to further decarburize deeply, while avoiding the drastic temperature rise and element loss that can occur with pure oxygen. The combination of oxidant and diluent in the top-blown mixed gas allows for more precise control of the intensity and temperature of the oxidation reaction.

[0036] Simultaneously, pure carbon dioxide gas at a higher pressure (1.2-1.4 MPa) is blown into the ladle from the side. Side blowing is typically achieved using an immersion lance or permeable bricks, aiming to deliver the gas directly into the depths of the molten iron. The high-pressure CO2 gas floats to the surface of the high-temperature molten iron in the form of numerous tiny bubbles. These bubbles act as moving "microreactors" and "flotation carriers," performing the following functions: First, the CO2 in the bubbles reacts with carbon atoms in the molten iron at the gas-liquid interface (C + CO2 → 2CO), generating CO gas that flows into the bubbles, causing them to grow. This process directly removes dissolved carbon from the molten iron. Second, the rising bubbles strongly agitate the melt, promoting uniformity of composition and temperature, and accelerating the mass transfer of dissolved impurities to the bubble surface or slag phase. Furthermore, during the flotation process, the bubble surface can adsorb tiny non-metallic inclusions suspended in the molten iron (such as Al2O3, SiO2 particles, or carbide particles), carrying them to the slag layer and significantly purifying the molten iron. The continuous blowing time of 10-15 minutes provides ample time for these physicochemical reactions to occur. The side-blowing of pure CO2 avoids the introduction of strong oxidants into the depths of the molten iron, thus preventing the excessive oxidation and loss of valuable elements such as chromium.

[0037] Optionally, the volume ratio of carbon dioxide to oxygen in the mixture of carbon dioxide and oxygen is 1:(2~4).

[0038] In this application, carbon dioxide (CO2) exhibits a relatively mild oxidation effect on elements such as carbon and silicon in molten iron at high temperatures, and the reaction is endothermic. Oxygen (O2), on the other hand, is a strong oxidizing agent, with a vigorous oxidation reaction and a large amount of heat release. When an O2 / CO2 ratio of 1:2 to 1:4 is used, it means that the mixed gas has a moderately strong oxidizing property. Its working principle is as follows: 1) Sufficient oxygen content ensures the necessary oxidative refining intensity, which can effectively oxidize and remove residual silicon in the molten iron (generating SiO2 which enters the slag, further reducing the alloy silicon content or adjusting the slag composition) and other easily oxidizable impurities that may exist. At the same time, the large amount of heat released by the oxidation reaction can compensate for the temperature drop of the molten iron during the blowing process, the ladle pouring process, and the settling process, maintaining good fluidity of the molten iron, which is crucial for subsequent casting. 2) The mixed carbon dioxide gas plays multiple regulatory roles. First, it dilutes the oxygen concentration, preventing the formation of excessively strong oxidation zones below the lance or in localized areas during pure oxygen blowing. This reduces the risk of chromium being over-oxidized to Cr2O3 and lost (Cr2O3 entering the slag leads to a decrease in chromium recovery). Second, the endothermic reaction involving CO2 buffers the temperature rise caused by O2 oxidation, preventing excessively high local temperatures from exacerbating the erosion of the ladle refractory materials and also helping to control the final smelting temperature within an ideal range. Finally, CO2 itself also participates in the decarburization reaction, serving as an additional carbon removal method. This ratio range represents an optimized balance between achieving sufficient oxidative refining (primarily O2), moderate decarburization and temperature control (the role of CO2), and the recovery rate of key elements (chromium).

[0039] Optionally, the weight ratio of silica, coke and high-carbon ferrochrome in the mixed raw materials is 3~3.2:(1.6~1.7):(1.05~1.1).

[0040] In this application, silica (SiO2) is the source of silicon and also the main acidic oxide in slag formation. The proportion of silica must first ensure sufficient silicon is provided to reduce the carbon in high-carbon ferrochrome (generating CO or SiC) and ultimately form the target silicon-chromium alloy (mainly CrSi, CrSi2, etc.). Too little silica will lead to incomplete decarburization and excessive carbon content in the alloy; too much silica will result in excessively high silicon content in the alloy, potentially deviating from the target grade, and will also generate excessive slag, increasing energy consumption and chromium loss.

[0041] Secondly, coke serves as both a reducing agent and a carbon source. Its proportion requires precise calculation. On one hand, it must provide sufficient carbon atoms to reduce silicon dioxide in silica (SiO2 + 2C → Si + 2CO↑), the main reaction that releases silicon. Insufficient carbon leads to incomplete reduction, low iron yield, and high residual SiO2 in the slag. On the other hand, coke is also one of the initial carbon introducers (another source is high-carbon ferrochrome). In the subsequent silicon decarburization reaction, metallic silicon is needed to remove carbon; therefore, the initial total carbon content (from coke and high-carbon ferrochrome) must match the target decarburization depth. This proportion of coke, under the premise of sufficient silica reduction, works synergistically with the carbon introduced by high-carbon ferrochrome to effectively remove the total carbon to a low carbon level from the silicon ultimately present in the alloy.

[0042] Finally, high-carbon ferrochrome is the main source of chromium and the initial carrier of high carbon. Its dosage directly determines the chromium content and total yield of the final alloy. In the proportioning, it is related to the amount of silica and coke. Sufficient silica and coke are needed to process (reduce and decarburize) the high-carbon ferrochrome. The combined effect of these three factors determines the composition of the slag formed after smelting (such as the activity of SiO2, Cr2O3, CaO, etc.), which in turn affects the slag's melting point, viscosity, and reactivity. In this application, the slag basicity is generally adjusted to between 0.68 and 0.72. Quicklime (calcium oxide content > 80%) can be used to adjust the basicity, and fluorite can be added to adjust the slag's fluidity.

[0043] Optionally, the particle size of the crushed silica is 10~40mm; The crushed particle size of coke is 5~20mm; The crushing particle size of high-carbon ferrochrome is 30~50mm.

[0044] In this application, the silica particle size is controlled between 10-40 mm. Silica, as the main slag-forming material and silicon-providing raw material, needs to undergo a process from solid-state heating, softening, melting, to reduction by carbon. If the particle size is too large (e.g., >40 mm), the ratio of its heated surface area to its volume is small, resulting in a long internal heat conduction path and a slow melting rate. It may not be able to completely melt and react within a given smelting cycle, causing "raw material" residue, reducing production efficiency, and potentially leading to uneven slag composition due to unreacted SiO2 in certain areas. If the particle size is too fine (e.g., <10 mm), although the specific surface area is large and the reaction rate is fast, it will severely deteriorate the permeability of the furnace bed. In submerged arc furnace smelting, a large amount of CO gas generated in the lower reaction needs to escape through the upper bed. Excessively fine particles will block the gas channels, leading to increased furnace pressure, potentially causing safety accidents such as furnace blowouts and sparking, while also causing uneven furnace gas distribution and affecting heat exchange efficiency.

[0045] The coke particle size is controlled between 5-20 mm. Coke serves as a reducing agent, a conductor, and a loose framework. A smaller particle size (5-20 mm) is beneficial for: 1) increasing the contact points with silica particles, accelerating the initial stage of the solid-solid reaction; 2) more uniform distribution in the furnace charge, forming a continuous conductive network, ensuring uniform charge resistance and stable current distribution, avoiding "arc instability" or "electrode lifting" caused by current concentration; and 3) allowing finer coke particles to participate in the reaction more quickly, replenishing the reducing agent promptly. However, excessively fine particles are easily carried away by furnace gas, increasing consumption and affecting permeability. This range ensures that the coke can effectively perform its reducing and conductive functions.

[0046] The particle size of high-carbon ferrochrome should be controlled between 30-50 mm. As a metallic material, the main purpose of crushing high-carbon ferrochrome is not to participate in solid-phase reactions, but rather to: 1) facilitate uniform mixing with silica and coke, avoiding segregation during feeding; and 2) control its melting rate. Crushing it to a suitable size (30-50 mm) allows it to be heated and melted at a reasonable rate after falling into the formed molten pool. If the particle size is too large, melting will be too slow, and unmelted lumps may remain in the later stages of smelting, affecting compositional uniformity and decarburization. If the particle size is too small, it may melt too quickly and prematurely, releasing the high-carbon ferrochrome molten material before the silica has been fully reduced to sufficient silicon liquid, which is detrimental to the subsequent silicothermic decarburization reaction and may lead to incomplete decarburization.

[0047] Optionally, the silica content in the silica is ≥97%; The coke contains ≥82% fixed carbon, ≤14% ash, and ≤8% moisture. High-carbon ferrochrome contains >65% chromium and ≤10% carbon.

[0048] This application specifies that the silica content (SiO2) in the silica must be ≥97%, implying a high requirement for silica grade. High-purity SiO2 minimizes the introduction of impurities such as aluminum, calcium, and iron oxides. These impurities (such as Al2O3, CaO, and Fe2O3) can enter the slag, altering its composition, melting point, viscosity, and chemical properties. For example, excessive Al2O3 can cause the slag to become sticky, making slag-metal separation difficult; fluctuations in the content of CaO and Fe2O3 can affect slag basicity, thereby influencing the reducing activity of SiO2 and the loss form of chromium in the slag. Using high-grade silica makes the slag composition more controllable and closer to the design value, which is beneficial for stable operation and improved chromium recovery.

[0049] The specifications stipulate that coke should contain ≥82% fixed carbon, ≤14% ash, and ≤8% moisture. High fixed carbon content ensures the effectiveness of coke as a reducing agent and calorific value, providing more reducing carbon and calorific value per unit weight. Since ash mainly consists of inert substances such as SiO2, Al2O3, and CaO, which do not participate in beneficial reduction reactions and ultimately all enter the slag, increasing slag volume, low ash content is required. Excessive slag volume means more heat is consumed in melting the slag, higher chromium content is lost as physical inclusions in the slag, and potentially worse slag-metal separation. Moisture content (≤8%) is controlled to prevent hydrogen production from water decomposition at high temperatures or to avoid furnace charge splashing, which could compromise safety, and also to prevent moisture evaporation from consuming additional heat.

[0050] The standard specifies that high-carbon ferrochrome must contain >65% chromium and ≤10% carbon. The high chromium content ensures the effectiveness of the raw materials, reduces the introduction of non-target elements such as iron, results in a more concentrated final alloy composition, and simplifies subsequent composition adjustments. Specifying an upper limit for carbon content (≤10%) allows for more accurate calculation of the total carbon load and the required amount of decarburized silicon during process design. Excessive fluctuations in the carbon content of the raw materials will prevent the stable production of low-carbon products using a fixed batching ratio, potentially leading to excessive carbon content or wasted silicon. This standard provides stable input parameters for batching calculations.

[0051] Optionally, the ladle is cylindrical with an inner diameter of 1.4±0.1m and an inner height of 1.7±0.1m.

[0052] The cylindrical structure is designed to create a simple and regular internal space. This facilitates the formation of a stable and clear slag-metal interface when the molten iron is allowed to settle, making it easier to assess the separation process. During the pouring process, the molten iron can be poured out smoothly, reducing residue and wall adhesion.

[0053] The dimensions (inner diameter approximately 1.4m, inner height approximately 1.7m) were primarily determined by the height-to-width ratio (H / D≈1.2). This ratio has several advantages: First, for a given volume of molten iron (e.g., approximately 2.6m³), a relatively high liquid column depth allows for greater distances that small inclusions need to travel to float to the surface during settling. More importantly, a deeper molten pool creates a stronger vertical circulation after pouring or during air blowing, enhancing the mixing effect. Second, from a heat dissipation perspective, the ratio of the ladle's heat dissipation area (side area + top area) to its volume needs to be appropriate. This specific surface area ensures that the temperature drop of the molten iron remains within a controllable range during the necessary settling and blowing time (a few minutes). This prevents the molten iron from becoming too viscous due to excessive heat dissipation, which could affect casting, or from requiring additional cooling due to slow heat dissipation, which could extend the processing cycle. Secondly, the dimensions are matched to the typical volume of molten iron in a single ladle (determined by the electric furnace capacity), ensuring an appropriate filling height within the ladle (neither too full to prevent overflow, nor too shallow to result in excessive heat dissipation and poor agitation). Fourthly, from an operational safety and ergonomic perspective, this ladle size facilitates lifting, positioning, and tipping. The inner diameter and height tolerances (±0.1m) are set within the allowable fluctuation range of the manufacturing process, ensuring operational consistency between different ladles.

[0054] Secondly, this application provides a low-carbon silicon-chromium alloy prepared by any of the methods described above.

[0055] The beneficial effects of the low-carbon silicon-chromium alloy provided in this application are as mentioned in the first aspect above, and will not be repeated here. Specific Implementation

[0056] Take the silicon-chromium alloy with smelting grade FeCr30Si40-C as an example. Example 1

[0057] A low-carbon silicon-chromium alloy is produced by the following method: S101. Silica, coke, and high-carbon ferrochrome are crushed and mixed separately to obtain a mixed raw material. The weight ratio of silica, coke, and high-carbon ferrochrome in the mixed raw material is 3:1.6:1.05.

[0058] S102. Take 0.3 times the amount of mixed raw materials and put them into the bottom of the electric furnace. Smelt them into liquid by powering on for 1 hour. Then put the remaining mixed raw materials into the electric furnace and continue to smelt for 3 hours to obtain molten iron. The power supply voltage is 275V and the current is 8500A. The power supply is AC.

[0059] S103. Pour molten iron into a ladle, let it stand for 3-4 minutes, then pour the ladle three times, letting it stand for 3-4 minutes after each pour. Control the pouring of each ladle of molten iron to be completed within 5-8 minutes. After pouring, spray a mixture of carbon dioxide and oxygen from the top of the ladle downwards at a pressure of 1.0 MPa. The volume ratio of carbon dioxide to oxygen in the mixture is 1:2. At the same time, blow carbon dioxide gas into the molten iron from the side of the ladle at a pressure of 1.2 MPa for 15 minutes. Then let the molten iron stand until the slag layer solidifies.

[0060] S104. Cast the molten iron from the lower layer of the ladle to obtain a low-carbon silicon-chromium alloy.

[0061] The measured silicon content was 31.05%; chromium content was 49.17%; and carbon content was 0.023%. Example 2

[0062] A low-carbon silicon-chromium alloy is produced by the following method: S201. Silica, coke, and high-carbon ferrochrome are crushed and mixed separately to obtain a mixed raw material. The weight ratio of silica, coke, and high-carbon ferrochrome in the mixed raw material is 3.2:1.7:1.1.

[0063] S202. Take 0.4 times the amount of mixed raw materials and put them into the bottom of the electric furnace. Smelt them into liquid for 1.2 hours. Then put the remaining mixed raw materials into the electric furnace and continue to smelt for 2.8 hours to obtain molten iron. The power supply voltage is 282V and the current is 8200A. The power supply is AC.

[0064] S203. Pour molten iron into a ladle, let it stand for 3-4 minutes, then pour the ladle five times, letting it stand for 3-4 minutes after each pour. Control the pouring of each ladle of molten iron to be completed within 5-8 minutes. After the pouring is finished, spray a mixture of carbon dioxide and oxygen from the top of the ladle downwards at a pressure of 1.2 MPa (the volume ratio of carbon dioxide to oxygen in the mixture is 1:4). At the same time, blow carbon dioxide gas into the molten iron from the side of the ladle at a pressure of 1.4 MPa for 10 minutes. Then let the molten iron stand until the slag layer solidifies.

[0065] S204. Cast the molten iron from the lower layer of the ladle to obtain a low-carbon silicon-chromium alloy.

[0066] The measured silicon content was 30.91%; chromium content was 49.56%; and carbon content was 0.025%. Example 3

[0067] A low-carbon silicon-chromium alloy is produced by the following method: S301. Silica, coke, and high-carbon ferrochrome are crushed and mixed separately to obtain a mixed raw material. The weight ratio of silica, coke, and high-carbon ferrochrome in the mixed raw material is 3.1:1.65:1.07.

[0068] S302. Take 0.35 times the amount of mixed raw materials and put them into the bottom of the electric furnace. Smelt them into liquid by powering on for 1 hour. Then put the remaining mixed raw materials into the electric furnace and continue to smelt for 3 hours to obtain molten iron. The power supply voltage is 280V and the current is 8300A, AC power supply.

[0069] S303. Pour molten iron into a ladle and let it stand for 3-4 minutes. Then, pour the ladle four times, letting it stand for 3-4 minutes after each pour. Control the pouring of each ladle of molten iron to be completed within 5-8 minutes. After pouring, spray a mixture of carbon dioxide and oxygen from the top of the ladle downwards at a pressure of 1.2 MPa. The volume ratio of carbon dioxide to oxygen in the mixture is 1:(2-4). At the same time, blow carbon dioxide gas into the molten iron from the side of the ladle at a pressure of 1.3 MPa for 12 minutes. Then let the molten iron stand until the slag layer solidifies.

[0070] S304. The lower layer of molten iron in the ladle is cast to obtain a low-carbon silicon-chromium alloy.

[0071] The measured silicon content was 31.23%; chromium content was 50.09%; and carbon content was 0.017%. Example 4

[0072] The remaining operations are the same as in Example 3, except that no blowing is performed after the bag is turned over.

[0073] The measured silicon content was 30.21%; chromium content was 50.12%; and carbon content was 0.041%.

[0074] The silicon-chromium alloys from Examples 1 to 4 were tested according to GB / T 4009-2008 Silicon-Chromium Alloys. The contents of silicon, chromium, and carbon were statistically analyzed, and the results are summarized in Table 1. Table 1

[0075] As can be seen from the results in Table 1, the silicon-chromium alloy prepared by the method of this application has a carbon content of ≤0.025%. However, a comparison of the results of Example 3 and Example 4 shows that the silicon-chromium alloy produced without the blowing process has a higher carbon content, at 0.041%.

[0076] 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 producing a low carbon silicon-chromium alloy, characterized by, Includes the following steps: Silica, coke, and high-carbon ferrochrome are crushed separately and then mixed to obtain a mixed raw material; The mixed raw materials are fed into an electric furnace and powered on for smelting to obtain molten iron; The molten iron is poured into the ladle and then poured into the ladle. After the pouring is completed, the molten iron is left to stand until the slag layer solidifies. The molten iron in the lower layer of the ladle is poured to obtain a low-carbon silicon-chromium alloy.

2. The method of producing a low carbon silicon-chromium alloy according to claim 1, characterized by, The smelting process includes: Take 0.3 to 0.4 times the amount of mixed raw materials and put them into the bottom of the electric furnace. Smelt them into liquid for 1 to 1.2 hours. Then put the remaining mixed raw materials into the electric furnace and continue smelting for 2.8 to 3 hours to obtain molten iron. The power supply voltage is 275~282V, the current is 8200~8500A, and it is AC power supply.

3. The method of producing a low carbon silicon-chromium alloy according to claim 1, characterized by, The package restorage operation includes: Pour the molten iron into the ladle, let it stand for 3-4 minutes, and then pour the ladle over the ladle 3-5 times. After each pour, let it stand for 3-4 minutes. Control the pouring of each ladle of molten iron to be completed within 5-8 minutes.

4. The method for producing low-carbon silicon-chromium alloy according to claim 1, characterized in that, After the bale is poured, a gas blowing operation is also included in the settling stage, including: A mixture of carbon dioxide and oxygen is sprayed downwards from the top of the ladle at a pressure of 1.0~1.2 MPa. Simultaneously, carbon dioxide gas is blown into the molten iron from the side of the ladle at a pressure of 1.2~1.4MPa for 10~15min.

5. The method for producing low-carbon silicon-chromium alloy according to claim 4, characterized in that, The volume ratio of carbon dioxide to oxygen in the mixture of carbon dioxide and oxygen is 1:(2~4).

6. The method for producing low-carbon silicon-chromium alloy according to claim 1, characterized in that, By weight, the weight ratio of silica, coke and high-carbon ferrochrome in the mixed raw materials is 3~3.2∶(1.6~1.7)∶(1.05~1.1).

7. The method for producing low-carbon silicon-chromium alloy according to claim 1, characterized in that, The crushed particle size of the silica is 10~40mm; The crushed coke has a particle size of 5~20mm; The crushing particle size of high-carbon ferrochrome is 30~50mm.

8. The method for producing low-carbon silicon-chromium alloy according to claim 1, characterized in that, The silica contains ≥97% silicon dioxide; The coke contains ≥82% fixed carbon, ≤14% ash, and ≤8% moisture. High-carbon ferrochrome contains >65% chromium and ≤10% carbon.

9. The method for producing low-carbon silicon-chromium alloy according to any one of claims 1 to 8, characterized in that, The steel ladle is cylindrical with an inner diameter of 1.4±0.1m and an inner height of 1.7±0.1m.

10. A low-carbon silicon-chromium alloy, characterized in that, It is prepared by the method described in any one of claims 1 to 9 above.

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