Method for forming graphite electrode protective layer and method for smelting special ferroalloy with low carbon content

Abstract

The present invention discloses a method for forming a protective layer on a graphite electrode, comprising: uniformly spraying a liquid binder on the surface of a graphite electrode at room temperature to impart adhesiveness to the surface of the graphite electrode; placing an aluminothermic furnace below the graphite electrode with the adhesiveness after the spraying; and fumigating the graphite electrode with flue gas generated by a thermite reaction in the aluminothermic furnace; and cooling the graphite electrode after the fumigation to form a protective layer on the surface of the graphite electrode. The present invention also discloses a method for smelting a low-carbon specialty ferroalloy using graphite electrodes formed with a protective layer. By fumigating the graphite electrode with flue gas generated by the aluminothermic furnace to impart a protective layer on the surface of the graphite electrode, the present invention controls the consumption of the graphite electrode. When such graphite electrodes are used for smelting specialty ferroalloys, the graphite electrode consumes more slowly and is less likely to fall off, thereby controlling the problem of excessive carbon content in the smelted specialty ferroalloy caused by falling graphite electrode material.

Description

Technical Field

[0001] The present invention belongs to the field of metallurgy, and in particular relates to a method for forming a graphite electrode protective layer and a method for smelting a special iron alloy with a low carbon content by using the graphite electrode formed with the protective layer. Background Art

[0002] Ferrovanadium smelting is a metallurgical process that uses the electrothermic method for high-temperature reduction, utilizing arc heat and resistance heat from the charge to melt the material and maintain a liquid molten pool. The electric heating process utilizes graphite electrodes, whose raw materials are primarily a mixture of petroleum coke and coal tar pitch. These electrodes have advantages such as low thermal expansion coefficient, light weight, strong corrosion resistance, ease of processing, and excellent thermal shock resistance. They are widely used in processes such as electric furnace steelmaking and molten steel refining. However, compared to steelmaking, the ferrovanadium smelting process involves higher temperatures (1800-2100°C) and longer smelting times (90-180 minutes). The electrodes are constantly exposed to high temperatures, resulting in high graphite electrode consumption, which can easily cause them to fall off and break into the slag, causing the carbon content of the ferrovanadium alloy to exceed the specified limit.

[0003] For example, according to the national standard for FeV80 alloy, the carbon content of Grade A FeV80 alloy must be controlled to no more than 0.15%, while that of Grades B and C must be controlled to no more than 0.3%. Both the national standard and downstream steel users place high demands on the carbon content of FeV80 alloy. Graphite electrodes are crucial components for electrical heating. They must ensure stable operation and prevent significant carburization of the FeV80 alloy, placing high demands on the actual smelting process. Conventional impregnation methods typically immerse the electrodes in a chemical agent, allowing the electrode surface to react chemically with the agent to improve their resistance to high-temperature oxidation. The antioxidants used for electrode impregnation include SiO2, ZrO2, and P2O5, making them suitable for arc furnace electrodes in steelmaking. However, in aluminothermic reduction smelting systems, the reaction between the impregnated antioxidants and the aluminum metal introduces new impurities, which not only affects the effectiveness of the oxidant but also has a certain impact on the FeV80 alloy product. The main source of carbon content in FeV80 alloy products is the graphite electrode. Therefore, the key to obtaining FeV80 alloy with low carbon content lies in controlling the quality and usage status of the graphite electrode. Using reasonable methods to create a suitable electrode protective layer is the key to reducing the carburization of FeV80 alloy caused by graphite electrode damage.

[0004] The following briefly describes the relevant prior art:

[0005] Patent CN91103258.4 discloses a method for forming an alloyed protective coating on the surface of a graphite electrode. The method uses oxides such as Na2O, B2O3, SiO2, and Al2O3, as solvents, and other salts, and oxides such as TiO2, Cr2O3, NiO, and V2O5 as solutes. The solvent concentration is 70-99.5%, the solute concentration is 0.5-30%, and the melting point is 600-1200°C. A high-temperature melt is controlled at 800-1500°C, and the graphite electrode is immersed in the melt. A reducing agent (which can be solid, liquid, or gaseous) is added to reduce the solute oxides and form a metal carbide alloy coating on the graphite electrode surface. This alloy carbide is firmly bonded to the graphite electrode substrate, is dense, and has good conductivity. However, this method is an impregnation method for protecting graphite electrodes, and the protective layer production method is relatively complex and the process is lengthy.

[0006] Patent CN200510047757.7 discloses a protective coating for reducing graphite electrode consumption and a production method, wherein the coating comprises (by weight): B2O3: 5-8%, MoSi2: 8-15%, TiO2: 5-10%, Cr2O3: 3-10%, Al2O3: 3-10%, and sulfonated silicone resin: 40-65%. The production method is to pre-melt and sinter the powder pellets, then crush and screen them, separating the -180 to +300 mesh powder as group A filler and the -300 mesh powder as group B filler; the A and B groups of fillers are mixed in a ratio of 7:3 to form a coating solid filler; by adding a trace amount of molybdenum silicide with a thermal expansion coefficient similar to that of the graphite material, the coating can maintain a thermal expansion coefficient similar to that of the graphite electrode in all temperature ranges of heating, and the particle size composition of the solid components of the coating can be controlled to quickly form a stable and continuous coating with a gradient structure, avoiding peeling or flaking of the coating, thereby improving the strength of the coating and achieving an effective protective effect. However, this method belongs to the coating method for protecting graphite electrodes, and the production method is relatively complicated and the process is long.

[0007] Patent CN201110031966.8 discloses a method for improving the oxidation resistance of graphite electrodes using flame spraying. This method utilizes flame spraying technology to spray a three-layer composite coating onto the surface of the graphite electrode. The main components, from the inside out, are silicon, aluminum borate, and metallic aluminum. Under the high-temperature operating environment of the graphite electrode, the inner layer reacts and tightly bonds with the graphite matrix, the middle layer provides thermal insulation, and the outermost layer not only passivates the surface but also melts and penetrates into the pores of the electrode, effectively isolating the graphite matrix from oxygen and improving the bonding strength between the coating and the matrix. Practice has shown that surface treatment of graphite electrodes using this method can significantly improve the electrode's oxidation resistance, reducing electrode consumption per ton of steel by more than 18% compared to untreated graphite electrodes. However, this method involves flame spraying to protect graphite electrodes, and the production method is relatively complex and the process is lengthy.

[0008] Patent CN201710276386.2 discloses a graphite electrode protection method, which includes the following steps: first, heating the graphite electrode to a surface temperature of 1500°C or above, and then using high-pressure nitrogen to spray a mixed powder of SiO2 and TiO2 onto the surface of the hot graphite electrode, and forming a dense carbide or nitride coating on the surface of the graphite electrode through a reduction reaction and a nitridation reaction. The beneficial effect of the present invention is that: using high-pressure nitrogen to spray a mixed powder of SiO2 and TiO2 onto the surface of the hot graphite electrode, a dense carbide or nitride coating is formed on the surface of the graphite electrode through a reduction reaction and a nitridation reaction, which plays the role of isolating the graphite electrode body, thereby slowing down the oxidation consumption rate of the graphite electrode. The protective coating is densely bonded to the surface of the graphite electrode, is not easy to fall off, and does not affect its conductivity, thereby extending the service life of the graphite electrode and reducing the production cost of the electric furnace. However, this method has a large powder loss, and the use of high-pressure nitrogen makes it difficult to operate stably.

[0009] Patent CN201711269095.7 discloses an electrode for electric arc furnace steelmaking and a spraying method thereof, belonging to the technical field of metallurgical production equipment accessory repair and maintenance process technology, and provides an electrode for electric arc furnace steelmaking and a spraying method thereof with a longer service life and significantly reduced oxidation efficiency during use. The electrode includes a graphite electrode body, and the electrode also includes a high-temperature protective layer, and the high-temperature protective layer is coated on the surface of the graphite electrode body. The spraying method uses compressed air as the power to spray a slurry of refractory material online onto the graphite electrode body to obtain the electrode. However, this method belongs to the slurry spraying method for protecting graphite electrodes, and the manufacturing process is relatively complicated.

[0010] Patent CN201710293274.8 discloses a method for controlling the carbon content of FeV80 alloy. The method includes the following steps: mixing raw materials such as V2O5, aluminum granules, iron granules, and lime, adding them to a furnace for smelting in batches, and slag removal after each batch. Slag removal is performed until all raw materials have been smelted in the furnace. The mixed slag in the furnace is poured into an ingot mold, cooled, and crushed. A decarburizer is added during the smelting and tapping process. However, this method involves controlling the smelting process and requires the addition of an additional decarburizer, making the process relatively complex.

[0011] In view of this, it can be seen that there is still room for improvement in the control of the consumption state of graphite electrodes and the control of the carbon content of special ferroalloys in the existing technology. Summary of the Invention

[0012] In response to the problem that the graphite electrodes used in the current electric aluminothermic smelting of special ferroalloys are consumed in large quantities, resulting in the carbon content of the special ferroalloys easily exceeding the standard, the present invention provides a method for forming a graphite electrode protective layer and a method for smelting a low-carbon special ferroalloy using a graphite electrode with a protective layer. The consumption state of the graphite electrode is controlled by forming a protective layer on the surface of the graphite electrode. When the graphite electrode with the protective layer formed on the surface is used to smelt the special ferroalloy, the consumption rate of the graphite electrode is slowed down and it is not easy to fall off. Therefore, the problem of excessive carbon content in the smelted special ferroalloy caused by the falling graphite electrode material can be controlled.

[0013] In order to achieve the above object, the present invention adopts the following technical solutions:

[0014] According to one aspect of the present invention, a method for forming a protective layer on a graphite electrode is provided, comprising the following steps: uniformly spraying a liquid binder on the surface of a graphite electrode at room temperature to make the surface of the graphite electrode sticky; placing an aluminothermic furnace under the graphite electrode with a sticky surface after spraying, and fumigating the graphite electrode with smoke generated by a thermite reaction in the aluminothermic furnace; and cooling the graphite electrode after the fumigation is completed to form a protective layer on the surface of the graphite electrode.

[0015] According to one embodiment of the present invention, the liquid binder sprayed on the surface of the graphite electrode comprises the following components: a solution, an inorganic binder, and an organic binder. The contents of these components, by mass percentage, are: 90-95% solution (preferably an aqueous solution, more preferably a supernatant from vanadium precipitation), 2-4% inorganic binder (preferably calcium hydroxide), and 3-8% organic binder (preferably sodium carboxymethyl cellulose).

[0016] According to one embodiment of the present invention, the method for forming a graphite electrode protective layer further includes: before spraying the liquid adhesive on the surface of the graphite electrode, inspecting the graphite electrode and knocking out joints of the graphite electrode that are prone to loosening or falling off.

[0017] According to one embodiment of the present invention, 1 to 5 thermite furnaces are placed in succession below the sprayed graphite electrode having a sticky surface.

[0018] According to one embodiment of the present invention, the fumigation time of the graphite electrode is 30 minutes to 150 minutes.

[0019] According to one embodiment of the present invention, the graphite electrode is cooled by natural cooling, and is naturally cooled to room temperature in the air.

[0020] According to another aspect of the present invention, a method for smelting a special ferroalloy with a low carbon content is provided, the method comprising: before smelting, forming a protective layer on a graphite electrode using the above-mentioned method for forming a graphite electrode protective layer; and during the smelting process, using the graphite electrode with the protective layer formed thereon.

[0021] According to one embodiment of the present invention, the smelting method can be used for smelting vanadium-ferroalloy, molybdenum-ferroalloy, titanium-ferroalloy, niobium-ferroalloy and tungsten-ferroalloy by electro-aluminothermic method.

[0022] According to one embodiment of the present invention, when the smelting method is used to smelt vanadium-ferroalloy by the electric aluminothermic process, vanadium-aluminum alloy scrap with a carbon content of less than 0.01% and vanadium flake with a carbon content of less than 0.01% are selected as vanadium-containing raw materials.

[0023] By adopting the above technical solution, the present invention has the following beneficial effects:

[0024] The present invention controls the consumption of graphite electrodes by spraying a liquid binder on the surface of the graphite electrode and fumigating the graphite electrode with flue gas generated by the thermite reaction in an aluminothermic reduction furnace to form a protective layer on the graphite electrode surface. The graphite electrode protective layer obtained by the flue gas fumigation method of the present invention is tightly bonded to the surface of the graphite electrode, is not easily detached, and does not affect its conductivity. This can extend the service life of the graphite electrode and reduce the production cost of the electric furnace.

[0025] When the present invention uses a graphite electrode with a protective layer to smelt special ferroalloys, the consumption rate of the graphite electrode is slowed down and it is not easy to fall off or break into the slag. As a result, the problem of excessive carbon content in the smelted special ferroalloy caused by the fallen graphite electrode material can be controlled, and a special ferroalloy product with a lower carbon content can be obtained.

[0026] The present invention utilizes the flue gas generated by the thermite reaction in the thermite reduction furnace as a resource, turning smelting dust into treasure, and forms a protective layer through graphite electrode surface pretreatment-online fumigation. It has good industrial collaborative development, mutual complementary demonstration effect and environmental protection effect of efficient utilization of secondary resources of dust and innovative recycling.

[0027] Compared to the prior art described in the aforementioned documents, the present invention significantly differs in terms of the method for obtaining the graphite electrode surface protective layer and its intended use. Compared to the processes described in the aforementioned documents, the present invention utilizes source control, eliminating the need for adding specialized decarburizing agents during the smelting process. This simplifies the smelting process and offers advantages such as a shorter process, higher efficiency, energy conservation, environmental protection, and enhanced operability. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A process flow chart of the method for forming a graphite electrode protective layer provided by the present invention;

[0029] Figure 2 This is a photo of the graphite electrode before fumigation;

[0030] Figure 3 This is a photo of the graphite electrode after fumigation;

[0031] Figure 4 A process flow chart of the smelting method of the low-carbon special ferroalloy provided by the present invention;

[0032] Figure 5 This is a technical roadmap for the preparation method of the low-carbon content FeV80 alloy provided by the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] As required, specific embodiments of the present invention are disclosed in this specification; however, it should be understood that the disclosed embodiments are merely illustrative of the invention, which may be implemented in various alternative forms. In the following description, various operating parameters and components are described in connection with various contemplated embodiments. These specific parameters and components are provided herein as examples only and are not intended to be limiting.

[0035] like Figure 1 As shown, the first aspect of the present invention provides a method 10 for forming a graphite electrode protective layer, the method 10 comprising the following steps:

[0036] S11: Pretreatment of the graphite electrode surface: Specifically, a liquid adhesive is evenly sprayed on the surface of the graphite electrode at room temperature to make the surface of the graphite electrode sticky.

[0037] S12: Fumigating the graphite electrode with flue gas. Specifically, an aluminothermic furnace is placed under the graphite electrode with a sticky surface after spraying, and the graphite electrode is fumigated with flue gas generated by the thermite reaction in the aluminothermic furnace.

[0038] S13: Cooling the graphite electrode. Specifically, after the fumigation is completed, the graphite electrode is cooled to form a protective layer on the surface of the graphite electrode.

[0039] The present invention pre-treats the graphite electrode so that the surface of the graphite electrode becomes sticky. Then, when the graphite electrode is fumigated with the flue gas generated by the thermite reaction, a portion of the flue gas generated by the thermite reaction is physically adsorbed on the surface of the graphite electrode due to the stickiness of the electrode surface, while the other portion chemically reacts with the carbon in the graphite electrode to form carbides. For at least these two reasons, a dense protective layer is formed on the surface of the graphite electrode through the two-step operation of graphite electrode pre-treatment and fumigation with flue gas, which serves to isolate the graphite electrode body and thus control the consumption state of the graphite electrode. The graphite electrode protective layer obtained by the graphite electrode protective layer formation method of the present invention is densely bonded to the surface of the graphite electrode, is not easy to fall off, and does not affect its conductivity. It can extend the service life of the graphite electrode and reduce the production cost of the electric furnace.

[0040] In the present invention, in step S11, the graphite electrode surface is pretreated at room temperature, the purpose of which is to make the graphite electrode surface have the property of adhering particles, which helps the particles in the flue gas in the subsequent flue gas fumigation process to better adhere to the graphite electrode surface.

[0041] The "aluminothermic furnace" mentioned above can be any smelting furnace used for performing aluminothermic reduction reactions, and the present invention is not limited thereto. "Aluminothermic furnace" is sometimes also referred to as "aluminothermic reduction furnace," and the two are used interchangeably herein. The aluminothermic reaction performed in the aluminothermic furnace can be any reaction that utilizes the reducing properties of aluminum to produce a high-melting-point metal, and the present invention is not limited thereto. The flue gas generated by the aluminothermic reaction in the aluminothermic furnace contains a large amount of Al2O3 particles, which are easily adsorbed on the surface of the graphite electrode during the fumigation process.

[0042] In some embodiments of the present invention, the liquid binder sprayed on the graphite electrode surface is formulated from the following components: a solution, an inorganic binder, and an organic binder. By mass percentage, the following components are present: solution (preferably an aqueous solution, more preferably a vanadium precipitation supernatant): 90-95%, inorganic binder (preferably calcium hydroxide): 2-4%, and organic binder (preferably sodium carboxymethyl cellulose): 3-8%. The graphite electrode surface inherently has poor adhesion and is not easily adsorbed. Spraying the liquid binder is intended to improve the adhesion of the graphite electrode surface. The inorganic binder, organic binder, and solution are combined to form a neutral or alkaline solution with a high viscosity. The inorganic and organic binders enhance the adhesion through the combined action and synergistic adhesion of the inorganic and organic binders. Adsorption occurs primarily through electrostatic adsorption, hydrogen bonding, and chemical adsorption. The "vanadium precipitation supernatant" referred to herein refers to the supernatant remaining after purification and enrichment of vanadium. Generally, its composition is: a V ion concentration of 0.5-1.5 g / L in the solution. The advantages of using the liquid binder of the above components to spray the graphite electrode are: the raw materials are cheap and easy to obtain, the adhesion is strong, and it does not affect the quality of the alloy product. In other embodiments of the present invention, the liquid binder sprayed on the surface of the graphite electrode may have other components different from the specific components described above, as long as it can make the surface of the graphite electrode sticky so that the flue gas generated by the subsequent thermite reaction can be adsorbed on the surface of the graphite electrode. Although preferred examples of solutions, inorganic binders and organic binders are given above, it should be understood by those skilled in the art that the specific compositions of the solutions, inorganic binders and organic binders are not limited thereto, and solutions, inorganic binders and organic binders of other compositions known in the art can be used.

[0043] In some embodiments of the present invention, prior to step S11 "graphite electrode surface pretreatment," the graphite electrode protective layer forming method 10 may additionally include a "graphite electrode inspection" step. Specifically, the graphite electrode is inspected and joints that are prone to loosening or falling are removed. This step helps ensure the quality of the graphite electrode itself, facilitates the subsequent formation of the protective layer, and can enhance the robustness of the subsequently formed protective layer, thereby improving the performance of the graphite electrode.

[0044] In some embodiments of the present invention, in step S12, one to five thermites are placed continuously beneath the sprayed, sticky graphite electrode. The term "continuous placement" here means that after the thermite reaction in one thermite placed beneath the graphite electrode is complete, another thermite, about to react, is moved beneath the graphite electrode, and so on. This allows the same graphite electrode to be continuously fumigated using the fumes generated by the thermite reactions in one to five thermites. This continuous fumigation ensures that physical adsorption and chemical reactions occur sufficiently on the graphite electrode surface, thereby forming a dense protective layer. While taking into account production output requirements, placing one to five thermites continuously beneath the graphite electrode can be achieved by either keeping the graphite electrode stationary and moving the thermite, or by keeping the thermite stationary and moving the graphite electrode.

[0045] In some embodiments of the present invention, in step S12, the graphite electrode is fumigated for 30 to 150 minutes. This fumigation time ensures sufficient physical adsorption and chemical reactions on the graphite electrode surface, thereby forming a dense protective layer. A fumigation time that is too short will not be conducive to the formation of a dense protective layer, and the graphite electrode surface may remain exposed, or the protective layer may be partially insufficient and easily damaged. A fumigation time that is too long may, on the one hand, result in an excessively thick protective layer, poor adhesion, and easy detachment, and, on the other hand, be cost-ineffective.

[0046] In some embodiments of the present invention, in step S13, the graphite electrode is cooled to room temperature for curing. The graphite electrode can be cooled naturally. Compared to cooling methods such as air cooling or water cooling, natural cooling has the following advantages: the graphite electrode is also heated by the high-temperature flue gas during the fumigation process. Natural cooling allows the protective layer on the surface of the graphite electrode to slowly cool to room temperature through convection with the air, preventing thermal stress caused by rapid cooling and heating, which can lead to spalling.

[0047] Figure 2 and 3 The graphite electrode is shown in the following photos before and after fumigation. It can be seen that before fumigation, the surface of the graphite electrode is relatively smooth; after fumigation, the surface of the graphite electrode is relatively rough, and a protective layer has obviously formed.

[0048] Based on the above description, it can be seen that the method for forming a graphite electrode protective layer provided in the first aspect of the present invention sprays a liquid binder on the surface of the graphite electrode and uses the flue gas generated by the thermite reaction in an aluminothermic reduction furnace to fumigate the graphite electrode, thereby obtaining a dense protective layer on the surface of the graphite electrode, thereby controlling the consumption of the graphite electrode during use. The graphite electrode protective layer obtained by the flue gas fumigation method of the present invention is densely bonded to the surface of the graphite electrode, is not easily detached, and does not affect its conductivity, thereby extending the service life of the graphite electrode and reducing the production cost of the electric furnace.

[0049] like Figure 4 As shown, the second aspect of the present invention provides a smelting method 20 for a special ferroalloy with a low carbon content, and the smelting method 20 for a special ferroalloy with a low carbon content comprises the following steps:

[0050] S21: Before smelting, forming a protective layer on the graphite electrode to be used using the graphite electrode protective layer forming method described above;

[0051] S22: During the smelting process, a graphite electrode having a protective layer is used for smelting.

[0052] In some embodiments of the present invention, the smelting method 20 for producing a low-carbon specialty ferroalloy can be used to smelt specialty ferroalloys such as vanadium-ferroalloys, molybdenum-ferroalloys, titanium-ferroalloys, niobium-ferroalloys, and tungsten-ferroalloys using the electrothermal process. Those skilled in the art will appreciate that the smelting method 20 described herein is not limited to a specific smelting process and can be employed as long as graphite electrodes are used in the smelting process and the carbon content of the resulting alloy product needs to be controlled.

[0053] In some embodiments of the present invention, the smelting method 20 for a low-carbon specialty ferroalloy can be used to smelt FeV80 alloy using the electrothermic process. When using the electrothermic process to smelt FeV80 alloy, vanadium-aluminum alloy scrap with a carbon content of less than 0.01% and vanadium flakes with a carbon content of less than 0.01% can be used as vanadium-containing raw materials. Using such low-carbon, vanadium-containing raw materials helps further reduce the carbon content in the resulting FeV80 alloy.

[0054] The second aspect of the present invention provides a method for smelting a special ferroalloy with a low carbon content. Since a graphite electrode with a protective layer is used during the smelting process, the consumption rate of the graphite electrode is slowed down and it is not easy to fall off or break into the slag. As a result, the problem of excessive carbon content in the smelted special ferroalloy caused by the detached graphite electrode material can be controlled, and a special ferroalloy product with a low carbon content can be obtained.

[0055] like Figure 5As shown, the third aspect of the present invention provides a method 30 for preparing a FeV80 alloy with a low carbon content, and the method 30 for preparing a FeV80 alloy with a low carbon content comprises the following steps:

[0056] S31: Inspection and surface pretreatment of graphite electrodes, i.e., first knocking out the joints of the graphite electrodes that are prone to loosening or falling off, and then evenly spraying a liquid binder on the surface of the room-temperature graphite electrodes used in ferrovanadium smelting. The binder is composed of the following components by mass percentage: vanadium precipitation supernatant: 90-95%, calcium hydroxide: 2-4%, sodium carboxymethyl cellulose: 3-8%, to obtain a graphite electrode with a sticky surface after spraying;

[0057] S32: placing 1 to 5 thermites in succession below the sprayed graphite electrode, wherein the thermites contain a mixture of oxides and metallic aluminum, which reacts spontaneously after ignition and produces smoke containing Al2O3, wherein the oxide in the mixture is V2O5, igniting the materials in the thermites, causing a thermite reaction, and producing a large amount of smoke containing Al2O3 particles, which begins to fumigate the sprayed graphite electrode, and the fumigation time is 30 minutes to 150 minutes;

[0058] S33: After cooling and curing the graphite electrode for 30 minutes to 150 minutes, a graphite electrode with a protective layer on the surface is obtained;

[0059] S34: Without affecting the normal smelting of vanadium-aluminum alloy, conventional FeV80 alloy electro-aluminothermic smelting is carried out using a graphite electrode with a protective layer on the surface. After the smelting is completed, the low-carbon FeV80 alloy is obtained by standing, dismantling the furnace, and cooling.

[0060] In some embodiments of the present invention, in step S32, the aluminothermic furnace used is a vanadium-aluminum alloy smelting aluminothermic furnace. The aluminothermic furnace is equipped with materials according to vanadium-aluminum alloy production requirements, and the flue gas generated during the vanadium-aluminum alloy smelting process is used to fumigate the graphite electrodes for the ferrovanadium furnace. This resource-resourced utilization of the smoke generated during the vanadium-aluminum alloy smelting process transforms the smelting smoke into valuable resources. By pre-treating the graphite electrode surface and then fumigating the graphite electrodes for the ferrovanadium furnace online, a protective layer is formed. This has the environmental benefits of promoting the coordinated development of the vanadium-aluminum and ferrovanadium industries, achieving a mutually complementary demonstration effect, and efficiently utilizing the smoke dust as a secondary resource for innovative recycling.

[0061] In some embodiments of the present invention, in step S34, when smelting the FeV80 alloy, vanadium-aluminum scrap alloy with a carbon content of less than 0.01% and vanadium flakes with a carbon content of less than 0.01% are selected as vanadium-containing raw materials. Using vanadium-aluminum scrap alloy with an extremely low carbon content as raw materials helps further reduce the carbon content in the smelted FeV80 alloy.

[0062] A third aspect of the present invention provides a method for preparing a low-carbon FeV80 alloy. By fumigating a graphite electrode with flue gas from an aluminothermic reduction furnace to create a surface protective layer, the method controls the consumption of the graphite electrode. This controls the carbon content of the alloy at the source, resulting in a low-carbon FeV80 alloy product with a qualified composition. The carbon content of the FeV80 alloy is stably controlled at 0.05% to 0.09%, improving product quality and achieving a smelting yield of 96.52% to 97.23%.

[0063] The present invention will be described in detail below through specific examples.

[0064] Example 1

[0065] First, the joints of the graphite electrode that are prone to loosening and falling are knocked out, and then a liquid binder is sprayed on the surface of the room-temperature graphite electrode used in ferrovanadium smelting. The composition of the binder is vanadium precipitation supernatant: calcium hydroxide: sodium carboxymethyl cellulose in a ratio of 95:2:3, so as to obtain a graphite electrode with a sticky surface after spraying; then 5 thermite furnaces are placed continuously under the sprayed graphite electrode, and the materials in the thermite furnaces are prepared according to the production requirements of vanadium-aluminum alloy. The thermite furnaces are filled with a mixture of oxides and metallic aluminum, which can react spontaneously after ignition. The oxide in the mixture is V2O5; ignition The material in the aluminothermic furnace undergoes a thermite reaction, generating a large amount of flue gas containing Al2O3 particles, which begins to fumigate the sprayed graphite electrode. The flue gas fumigation time is 150 minutes. After the graphite electrode is naturally cooled and cured to room temperature, a graphite electrode with a protective layer on the surface is obtained. The graphite electrode with a protective layer on the surface is used for conventional FeV80 alloy electrothermic smelting. Vanadium-aluminum alloy scrap with a carbon content of 0.005% and vanadium flake with a carbon content of 0.006% are selected as vanadium-containing raw materials. After the smelting is completed, the FeV80 alloy with a carbon content of 0.05% is obtained after standing, dismantling the furnace, and cooling.

[0066] Example 2

[0067] First, the joints of the graphite electrode that are prone to loosening and falling are knocked out, and then a liquid binder is sprayed on the surface of the room-temperature graphite electrode used in ferrovanadium smelting. The composition of the binder is vanadium precipitation supernatant: calcium hydroxide: sodium carboxymethyl cellulose in a ratio of 90:4:6, so that a graphite electrode with a sticky surface after spraying is obtained; then three thermite furnaces are placed continuously under the sprayed graphite electrode, and the materials in the thermite furnaces are prepared according to the production requirements of vanadium-aluminum alloy. The thermite furnaces are filled with a mixture of oxides and metallic aluminum, which can react spontaneously after ignition. The oxide in the mixture is V2O5; ignition The material in the aluminothermic furnace undergoes a thermite reaction, generating a large amount of flue gas containing Al2O3 particles, which begins to fumigate the sprayed graphite electrode. The flue gas fumigation time is 120 minutes. After the graphite electrode is naturally cooled and cured to room temperature, a graphite electrode with a protective layer on the surface is obtained. The graphite electrode with a protective layer on the surface is used for conventional FeV80 alloy electrothermic smelting. Vanadium-aluminum alloy scrap with a carbon content of 0.004% and vanadium flake with a carbon content of 0.005% are selected as vanadium-containing raw materials. After the smelting is completed, the FeV80 alloy with a carbon content of 0.09% is obtained after standing, dismantling the furnace, and cooling.

[0068] Example 3

[0069] First, the joints of the graphite electrode that are easy to loosen and fall off are knocked out, and then a liquid binder is sprayed on the surface of the room-temperature graphite electrode used in ferrovanadium smelting. The composition of the binder is vanadium precipitation supernatant: calcium hydroxide: sodium carboxymethyl cellulose in a ratio of 90:4:6, so as to obtain a graphite electrode with a sticky surface after spraying; then two thermite furnaces are placed continuously under the sprayed graphite electrode, and the materials in the thermite furnaces are prepared according to the production requirements of vanadium-aluminum alloy. The thermite furnaces are filled with a mixture of oxides and metallic aluminum, which can react spontaneously after ignition, and the oxide in the mixture is V2O5; The material in the aluminothermic furnace is burned, and a thermite reaction occurs, generating a large amount of flue gas containing Al2O3 particles, which begins to fumigate the sprayed graphite electrode. The flue gas fumigation time is 30 minutes. After the graphite electrode is naturally cooled and cured to room temperature, a graphite electrode with a protective layer on the surface is obtained. The graphite electrode with a protective layer on the surface is used for conventional FeV80 alloy electrothermic smelting. Vanadium-aluminum alloy scrap with a carbon content of 0.002% and vanadium flake with a carbon content of 0.002% are selected as vanadium-containing raw materials. After the smelting is completed, the FeV80 alloy with a carbon content of 0.07% is obtained after standing, dismantling the furnace, and cooling.

[0070] Example 4

[0071] First, the joints of the graphite electrode that are easy to loosen and fall off are knocked out, and then a liquid binder is sprayed on the surface of the room-temperature graphite electrode used in ferrovanadium smelting. The composition of the binder is vanadium precipitation supernatant: calcium hydroxide: sodium carboxymethyl cellulose in a ratio of 90:2:8, so as to obtain a graphite electrode with a sticky surface after spraying; then, an aluminothermic furnace is continuously placed under the sprayed graphite electrode, and the materials in the aluminothermic furnace are prepared according to the production requirements of vanadium-aluminum alloy. The aluminothermic furnace is filled with a mixture of oxides and metallic aluminum, which can react spontaneously after ignition. The oxide in the mixture is V2O5; ignition The material in the aluminothermic furnace undergoes a thermite reaction, generating a large amount of flue gas containing Al2O3 particles, which begins to fumigate the sprayed graphite electrode. The flue gas fumigation time is 150 minutes. After the graphite electrode is naturally cooled and cured to room temperature, a graphite electrode with a protective layer on the surface is obtained. The graphite electrode with a protective layer on the surface is used for conventional FeV80 alloy electrothermic smelting. Vanadium-aluminum alloy scrap with a carbon content of 0.005% and vanadium flake with a carbon content of 0.002% are selected as vanadium-containing raw materials. After the smelting is completed, the FeV80 alloy with a carbon content of 0.05% is obtained after standing, dismantling the furnace, and cooling.

[0072] Comparative Example 1

[0073] Conventional FeV80 alloy electro-aluminothermic smelting was carried out using untreated graphite electrodes. Vanadium-aluminum alloy scraps with a carbon content of 0.002% and vanadium flakes with a carbon content of 0.006% were selected as vanadium-containing raw materials. After the smelting was completed, the FeV80 alloy with a carbon content of 0.21% was obtained after standing, dismantling the furnace, and cooling.

[0074] Comparative Example 2

[0075] Conventional FeV80 alloy electro-aluminothermic smelting was carried out using untreated graphite electrodes. Vanadium-aluminum alloy scraps with a carbon content of 0.005% and vanadium flakes with a carbon content of 0.003% were selected as vanadium-containing raw materials. After the smelting was completed, the FeV80 alloy with a carbon content of 0.18% was obtained after standing, dismantling the furnace, and cooling.

[0076] Comparative Example 3

[0077] Conventional FeV80 alloy electro-aluminothermic smelting was carried out using untreated graphite electrodes. Vanadium-aluminum alloy scraps with a carbon content of 0.004% and vanadium flakes with a carbon content of 0.002% were selected as vanadium-containing raw materials. After the smelting was completed, the FeV80 alloy with a carbon content of 0.16% was obtained after standing, dismantling the furnace, and cooling.

[0078] The experimental results of the above Examples 1-4 and Comparative Examples 1-3 can confirm that when the graphite electrodes treated by the method described in the present invention are used for FeV80 alloy smelting, the carbon content of the smelted FeV80 alloy is significantly reduced compared to that when the untreated graphite electrodes are used for FeV80 alloy smelting.

Claims

1. A method for forming a graphite electrode protective layer, characterized in that: The following steps are involved: Evenly spraying a liquid binder on the surface of a graphite electrode at room temperature to make the surface of the graphite electrode sticky, wherein the liquid binder is prepared from a solution, an inorganic binder, and an organic binder, and the inorganic binder is calcium hydroxide; An aluminothermic furnace is placed under the sprayed graphite electrode with a sticky surface, and the graphite electrode is fumigated with smoke generated by a thermite reaction in the aluminothermic furnace. The aluminothermic furnace contains a mixture containing oxides and metallic aluminum, which spontaneously undergoes a thermite reaction after ignition and produces smoke containing Al2O3 particles. During the fumigation process, the Al2O3 particles are easily adsorbed on the surface of the graphite electrode and chemically react with the graphite electrode. The fumigation time is 30 minutes to 150 minutes. After the fumigation is completed, the graphite electrode is cooled to form a protective layer on the surface of the graphite electrode.

2. The method for forming a graphite electrode protective layer according to claim 1, wherein: in: The composition of the liquid binder is as follows by mass percentage: solution: 90-95%, inorganic binder: 2-4%, organic binder: 3-8%; The solution used in the liquid binder is an aqueous solution or a supernatant of vanadium precipitation; The organic binder used in the liquid binder is sodium carboxymethyl cellulose.

3. The method for forming a graphite electrode protective layer according to claim 1, wherein: The method for forming a graphite electrode protective layer further includes: before spraying the liquid adhesive on the surface of the graphite electrode, inspecting the graphite electrode and knocking out joints of the graphite electrode that are prone to loosening or falling off.

4. The method for forming a graphite electrode protective layer according to claim 1, wherein: One to five aluminum thermites are placed in succession under the sprayed graphite electrode having a sticky surface.

5. The method for forming a graphite electrode protective layer according to claim 1, wherein: The graphite electrode is cooled by natural cooling.

6. A method for smelting a low-carbon special ferroalloy, the method comprising: Before smelting, a protective layer is formed on the graphite electrode using the graphite electrode protective layer forming method described in any one of claims 1 to 5; In the smelting process of special ferroalloys, graphite electrodes with a protective layer are used.

7. The smelting method of the low-carbon special ferroalloy according to claim 6, characterized in that: The smelting method is used for smelting vanadium-ferroalloy, molybdenum-ferroalloy, titanium-ferroalloy, niobium-ferroalloy and tungsten-ferroalloy by electro-aluminothermic method.

8. The smelting method of the low-carbon special ferroalloy according to claim 7, characterized in that: When the smelting method is used to smelt vanadium-ferroalloy by the electric aluminothermic process, vanadium-aluminum alloy scraps with a carbon content of less than 0.01% and vanadium flakes with a carbon content of less than 0.01% are selected as vanadium-containing raw materials.

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