Electrode paste for an electric arc furnace and method for preparing the same

Abstract

The present application relates to the technical field of electrode paste, and particularly relates to an electrode paste for an electric arc furnace and a preparation method thereof, which comprises three-grade particle size graded anthracite aggregate modified by high-temperature electric calcination and KH-550 silane coupling agent, modified silicon carbide whisker and boron-doped graphite-like carbon nitride composite filler, medium-temperature pitch-polyborosiloxane binder mediated by maleic anhydride, and graphite powder-borax functional additive. The preparation process adopts step-by-step mixing and two-stage sintering process, a covalent bond interface bridging structure is constructed by a coupling agent, a composite dispersant is used to regulate the multi-dimensional network distribution of the filler, and the process is synergistically used to improve the compactness of the blank and the interface bonding force. The interface of each component of the electrode paste is firmly combined, a ceramic protective phase can be formed at high temperature, excellent electrical conductivity and mechanical strength are combined, and the service life of the electrode paste for the electric arc furnace is prolonged.

Description

Technical Field

[0001] This application relates to the field of electrode paste technology, specifically to an electrode paste for submerged arc furnaces and its preparation method. Background Technology

[0002] Submerged arc furnaces are core equipment in the metallurgical industry for smelting ferroalloys, calcium carbide, and other products. Electrode paste, as a key raw material for the self-baking electrodes of submerged arc furnaces, directly determines the working stability and service life of the electrodes, thus affecting the production efficiency of the submerged arc furnace. Existing electrode pastes for submerged arc furnaces mainly consist of solid aggregates, binders, and a small amount of additives. The solid aggregates are mostly natural anthracite, and the binder is primarily a single medium-temperature pitch. The components mainly rely on physical adsorption for bonding, resulting in weak interfacial adhesion. This defect leads to problems such as filler agglomeration, binder softening and loss, and interface cracking between aggregates and binders under the high-temperature working environment of submerged arc furnaces. This, in turn, causes a significant decrease in high-temperature compressive strength and insufficient thermal shock resistance, ultimately leading to electrode breakage, excessive oxidation loss, and a shortened service life. To improve performance, existing technologies have attempted to introduce fillers and functional additives, but because the interfacial compatibility between fillers and aggregates and binders has not been resolved, not only is a synergistic reinforcement effect not achieved, but the uneven dispersion of fillers may further deteriorate the conductivity and structural stability of the electrode paste. At the same time, traditional binders have low carbonization rates and are difficult to form stable cross-linked networks to lock together the components at high temperatures, thus failing to fundamentally improve the high-temperature stability of the electrode paste.

[0003] Therefore, how to solve the problem of poor high-temperature stability and short service life caused by weak interfacial bonding of components in existing electric arc furnace electrode paste has become a technical bottleneck that the industry urgently needs to overcome. Summary of the Invention

[0004] To address the aforementioned issues, this application provides an electrode paste for submerged arc furnaces and its preparation method. The method involves modifying KH-550 by high-temperature electric calcination of three-grade anthracite, modifying KH-560 by acid washing of silicon carbide whiskers, and combining it with boron-doped graphene-like carbon nitride to prepare a modified composite filler. A compatible binder is prepared by blending maleic anhydride-mediated medium-temperature pitch with polyborosiloxane. Combined with a two-stage sintering process, the method strengthens the interfacial bonding of the multi-components and constructs a stable composite system, thereby improving the high-temperature stability of the electrode paste and extending its service life.

[0005] To achieve the above objectives, this application adopts the following technical solution:

[0006] In a first aspect, this application provides an electrode paste for a submerged arc furnace, comprising solid aggregate, modified composite filler, binder, and functional additives; the solid aggregate is obtained by high-temperature electric calcination of three-grade anthracite coal and modification with KH-550 silane coupling agent ethanol solution; the modified composite filler is obtained by treating modified silicon carbide whiskers and boron-doped graphene nitride with a composite dispersant; the modified silicon carbide whiskers are obtained by first acid washing of silicon carbide whiskers and then modification with KH-560 coupling agent ethanol solution, and the boron-doped graphene nitride is obtained by reacting urea and boric acid precursors; the binder is obtained by blending medium-temperature asphalt with polyborosiloxane; the functional additives include graphite powder and borax.

[0007] Preferably, the three-stage anthracite comprises a first anthracite, a second anthracite, and a third anthracite; the first anthracite has a particle size of 3-5 mm, the second anthracite has a particle size of 1-2 mm, and the third anthracite has a particle size of 0.1-0.5 mm; the mass ratio of the first anthracite, the second anthracite, and the third anthracite is (2-4):(3-5):(2-4); the mass ratio of the three-stage anthracite to the KH-550 silane coupling agent ethanol solution is 1:(4-6); and the mass fraction of the KH-550 silane coupling agent ethanol solution is 1wt%-3wt%.

[0008] This application adopts a three-stage particle size distribution design. By stacking anthracite with different particle sizes, the densification effect is improved, the porosity of the system is reduced, and the interparticle interface contact is strengthened. The KH-550 silane coupling agent modification forms a Si-OC covalent bond bridging structure with the hydroxyl groups generated by its hydrolysis and the hydroxyl groups on the surface of the anthracite. At the same time, the terminal amino groups are grafted to form active sites, which improves the interfacial compatibility between the solid aggregate and the subsequent binder and filler, and avoids the loose bonding between the aggregate and other components.

[0009] Preferably, the mass ratio of the modified silicon carbide whiskers, boron-doped graphene carbon nitride, and composite dispersant is 1:(1-3):(0.02-0.08); the composite dispersant is polyethylene glycol 400 and sodium dodecylbenzenesulfonate; the mass ratio of polyethylene glycol 400 and sodium dodecylbenzenesulfonate is (1-3):1; the acid used for pickling is hydrochloric acid solution; the mass fraction of the hydrochloric acid solution is 5wt%-8wt%; the mass fraction of the KH-560 coupling agent ethanol solution is 2wt%-4wt%; the mass ratio of the silicon carbide whiskers, hydrochloric acid solution, and KH-560 coupling agent ethanol solution is 1:(3-5):(3-5); and the mass ratio of urea and boric acid precursor is (8-12):1.

[0010] In this application, hydrochloric acid pickling removes the oxide layer and impurities from the surface of silicon carbide whiskers, exposing active hydroxyl sites and laying the foundation for subsequent coupling agent modification. The KH-560 coupling agent forms covalent bonds with the hydroxyl groups on the surface of silicon carbide whiskers through epoxy groups, and simultaneously interacts with the active functional groups of boron-doped graphene-like carbon nitride and the binder, enhancing the interfacial bonding force between the one-dimensional whiskers and other components. The composite dispersant, through the steric hindrance effect of polyethylene glycol 400 and the electrostatic repulsion effect of sodium dodecylbenzenesulfonate, synergistically inhibits the aggregation of modified silicon carbide whiskers and boron-doped graphene-like carbon nitride, ensuring uniform dispersion and the construction of a multidimensional network structure. Urea and boric acid, as precursors, achieve boron atom doping through a thermal polycondensation reaction. Boron atoms replace some carbon atoms in the carbon-nitrogen framework to form active sites, both disrupting the intrinsic insulation of carbon nitride to construct conductive channels and enhancing antioxidant properties by adsorbing oxygen free radicals through empty orbitals.

[0011] Preferably, the mass ratio of the medium-temperature asphalt to polyborosiloxane is (6-8):(2-4); the mass ratio of the graphite powder to borax is (4-6):3; and the mass ratio of the solid aggregate, modified composite filler, binder and functional additive is (3-5):1:(0.6-1.2):(0.2-0.5).

[0012] In this application, a synergistic bonding system is constructed by blending medium-temperature asphalt and polyborosiloxane. The medium-temperature asphalt provides excellent adhesion to ensure tight bonding between components, while the high-bond-energy Si-O and BO bonds in the polyborosiloxane enhance the high-temperature stability of the system. The two work synergistically to balance bonding strength and high-temperature resistance. Graphite powder can fill the gaps between components and form a continuous conductive interface with the carbon matrix, further optimizing the conductivity of the electrode paste. Borax can act as a mineralizer to promote the graphitization process of anthracite and graphite powder, optimizing the interface structure. At the same time, the B2O3 generated by decomposition at high temperature can form a dense oxide layer, inhibiting high-temperature oxidation and ablation of the carbon matrix.

[0013] Secondly, this application provides a method for preparing electrode paste for submerged arc furnaces, comprising the following steps:

[0014] Step 1. Take three-stage particle size distribution anthracite and place it in a high-temperature electric calcining furnace for high-temperature electric calcination treatment. Calcinate under an inert gas protective atmosphere and cool to room temperature to obtain calcined anthracite. Then add the calcined anthracite to a KH-550 silane coupling agent ethanol solution, stir to react, filter, and dry the filter residue to obtain solid aggregate.

[0015] Step 2. The silicon carbide whiskers are acid-washed and stirred, filtered, washed, and dried. Then, KH-560 coupling agent ethanol solution is added, stirred, filtered, and dried to obtain modified silicon carbide whiskers. Urea and boric acid are mixed and ground evenly, placed in a tube furnace under nitrogen protection, heated and kept at the temperature, cooled, ground, and sieved to obtain boron-doped graphene-like carbon nitride. The modified silicon carbide whiskers, boron-doped graphene-like carbon nitride, and composite dispersant are mixed, deionized water is added, ultrasonically dispersed, and spray-dried to obtain modified composite filler.

[0016] Step 3. Mix maleic anhydride and medium-temperature asphalt in a melting kettle and stir to melt, to obtain an asphalt premix; add polyborosiloxane to the asphalt premix and simultaneously shear and stir at high speed to obtain a binder;

[0017] Step 4. Add solid aggregate and modified composite filler to a high-speed mixer, add binder, heat and stir to mix, then add functional additives and continue stirring to obtain a paste; transfer the paste into a mold, press and shape to obtain an electrode paste blank;

[0018] Step 5. Place the electrode paste blank in a sintering furnace, and perform a first heating and sintering under a nitrogen atmosphere, followed by a second heating and sintering; then cool naturally to room temperature under nitrogen protection to obtain the electrode paste for submerged arc furnace.

[0019] Preferably, in step 1, the high-temperature electric calcination treatment is carried out at a temperature of 1800-2000℃ for 4-6 hours; the stirring reaction is carried out at a temperature of 60-80℃ for 2-3 hours.

[0020] In this application, high-temperature electric calcination can remove volatile matter, moisture and impurities from anthracite, improve its graphitization degree, optimize particle surface activity, and provide sufficient active sites for subsequent coupling agent modification.

[0021] Preferably, in step 2, the temperature for the acid washing and stirring reaction is 80-90℃ and the time is 2-3h; the temperature for the stirring reaction in the KH-560 coupling agent ethanol solution is 70-80℃ and the time is 2-4h; the temperature for heating in the tube furnace is 550-600℃ and the time for holding the reaction is 3-4h; the mesh size for sieving is 100-300 mesh; the power for ultrasonic dispersion is 300-500W and the time is 30-40min; the mass ratio of the composite dispersant to deionized water is 1:(2-3); and the inlet air temperature for spray drying is 150-160℃ and the outlet air temperature is 80-90℃.

[0022] Preferably, in step 3, the mass ratio of maleic anhydride to medium-temperature asphalt is 1:(8-12); the stirring and melting temperature is 160-180℃ and the time is 30-50 min; the high-speed shearing speed is 2000-3000 r / min and the time is 1-1.5 h.

[0023] In this application, the stirring and melting process, through temperature and time control, ensures that maleic anhydride and medium-temperature asphalt fully melt and react, allowing the unsaturated double bonds of maleic anhydride to form an addition reaction with the aromatic rings in the asphalt, successfully introducing polar carboxyl groups. These carboxyl groups can undergo esterification with the Si-OH groups of polyborosiloxanes, building an interfacial bridge between the asphalt and polyborosiloxanes and solving the problem of poor compatibility when directly blended. High-speed shearing, through speed and time control, further promotes the uniform mixing of medium-temperature asphalt and polyborosiloxanes, avoiding phase separation caused by uneven local concentrations, forming a uniform and stable blended bonding system, and providing a guarantee for stable interfacial bonding with aggregates and fillers in the subsequent process.

[0024] Preferably, in step 4, the temperature for adding the mixture to the high-speed mixer for heating and stirring is 150-160℃, and the time is 1-1.5h; the time for continuing stirring and mixing is 30-50min; and the pressure for pressing and molding is 10-15MPa, and the time is 30-50min.

[0025] In this application, heating and stirring keep the binder in a molten state, fully wetting the surface of solid aggregates and modified composite fillers, promoting interfacial wetting between components, and improving mixing uniformity; at the same time, temperature control can prevent the binder from degrading due to excessively high temperature, or from having insufficient fluidity due to excessively low temperature, which would affect the wetting effect.

[0026] Preferably, in step 5, the first heating rate is 2-3℃ / min, the temperature is 200-250℃, and the sintering time is 2-3h; the second heating rate is 3-5℃ / min, the temperature is 1000-1200℃, and the sintering time is 4-6h.

[0027] Compared with the prior art, the beneficial effects of this application are as follows:

[0028] This application provides an electrode paste for submerged arc furnaces and its preparation method. First, anthracite with a three-stage particle size distribution undergoes high-temperature electric calcination to remove volatiles and impurities. Then, it is modified with an ethanol solution of KH-550 silane coupling agent. The ethoxy groups in the modified paste hydrolyze to generate hydroxyl groups, which then undergo a condensation reaction with the hydroxyl groups on the surface of the anthracite, constructing a Si-OC covalent bond interfacial bridging structure. Simultaneously, amino groups at the molecular ends are grafted to form active sites, improving the interfacial compatibility between the solid aggregate and the subsequent binder. Silicon carbide whiskers are then acid-washed with hydrochloric acid to remove the surface oxide layer and expose the active hydroxyl groups. They are then modified with an ethanol solution of KH-560 coupling agent, whose epoxy groups interact with the silicon carbide... The hydroxyl groups on the surface of silicon whiskers are covalently bonded and can interact with the active functional groups of other components to enhance the interfacial bonding force. Boron-doped graphene-like carbon nitride is generated by the thermal condensation reaction of urea and boric acid precursor. Boron atoms replace some carbon atoms in the carbon-nitrogen framework to form doping active sites, which not only destroys the intrinsic insulation to build conductive channels, but also enhances the antioxidant properties by adsorbing oxygen free radicals through the empty orbitals of boron atoms. Under the action of composite dispersant, the two inhibit agglomeration through the steric hindrance effect of polyethylene glycol 400 and the electrostatic repulsion effect of sodium dodecylbenzenesulfonate, forming a multidimensional network structure. In the binder system, when maleic anhydride is mixed and melted with medium-temperature asphalt, polar carboxyl groups are introduced. These carboxyl groups undergo esterification with the Si-OH of polyborosiloxane, building an interfacial bridge between the asphalt and polyborosiloxane, thus solving the problem of poor compatibility between the two. At the same time, the high bond energy Si-O and BO bonds contained in polyborosiloxane can form a Si-BO ceramic phase at high temperatures to encapsulate the carbon matrix, improving its high-temperature stability. In the functional additives, graphite powder fills the gaps between the components to build additional continuous conductive channels. Borax decomposes at high temperatures to generate B2O3, which acts as a mineralizer to promote the graphitization process of anthracite and graphite powder, and can also react with oxygen to form a dense oxide layer to inhibit the ablation of the carbon matrix. The stepwise mixing process ensures uniform dispersion of each component through orderly control of room temperature dry mixing and heating with binder. Gradient pressure molding achieves uniform density of the green body through the synergistic effect of pre-pressure degassing and main pressure densification. The two-stage sintering process first removes moisture and low-molecular-weight volatiles by debinding at low temperature, then controls the carbonization of the binder and the fusion process of the interfaces of each component by high-temperature sintering. Finally, inert gas is used for slow cooling to release residual stress and prevent cracking. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of a process for preparing electrode paste for a submerged arc furnace. Detailed Implementation

[0030] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the application will be further described in detail below with reference to embodiments. However, this should not be construed as limiting the scope of this application to the following examples. All other embodiments obtained by those skilled in the art without creative effort without departing from the above-described methodological spirit of this application are within the scope of protection of this application.

[0031] In this application, the terminology used is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0032] The singular forms “for,” “or,” “a,” “any,” and “the” used in this application are intended to include the plural forms unless the context clearly indicates otherwise.

[0033] The following will describe in detail, with reference to different embodiments, an electrode paste for a submerged arc furnace and its preparation method thereof provided in this application.

[0034] Example 1

[0035] like Figure 1 As shown, this embodiment provides an electrode paste for a submerged arc furnace and its preparation method, the preparation method including the following steps:

[0036] Step 1. Take three-stage anthracite, which includes first anthracite, second anthracite, and third anthracite; the particle size of the first anthracite is 3 mm, the particle size of the second anthracite is 1 mm, and the particle size of the third anthracite is 0.1 mm; the mass ratio of the first anthracite, second anthracite, and third anthracite is 2:3:2; place the three-stage anthracite in a high-temperature electric calcining furnace for high-temperature electric calcination treatment, calcining at 1800℃ under an inert gas protective atmosphere for 4 hours, and cooling to room temperature to obtain calcined anthracite; then add the calcined anthracite to a 1 wt% KH-550 silane coupling agent ethanol solution, wherein the mass ratio of the three-stage anthracite to the KH-550 silane coupling agent ethanol solution is 1:4, stir and react at 60℃ for 2 hours, filter, and dry the filter residue to obtain surface-modified solid aggregate;

[0037] Step 2. Add silicon carbide whiskers to a 5 wt% hydrochloric acid solution for acid washing, stir and react at 80°C for 2 hours, filter, wash and dry, then add a 2 wt% KH-560 coupling agent ethanol solution. The mass ratio of silicon carbide whiskers, hydrochloric acid solution and KH-560 coupling agent ethanol solution is 1:3:3. Stir and react at 70°C for 2 hours, filter and dry to obtain modified silicon carbide whiskers. Mix urea and boric acid at a mass ratio of 8:1 and grind evenly. Place in a tube furnace under nitrogen protection, heat to 550°C and hold for 3 hours. h, after cooling, grind through a 100-mesh sieve to obtain boron-doped graphene-like carbon nitride; mix the modified silicon carbide whiskers, boron-doped graphene-like carbon nitride, and composite dispersant at a mass ratio of 1:1:0.02, wherein the composite dispersant is a mixture of polyethylene glycol 400 and sodium dodecylbenzene sulfonate at a mass ratio of 1:1, then add deionized water and ultrasonically disperse at 300W power for 30min, wherein the mass ratio of composite dispersant to deionized water is 1:2; obtain the modified composite filler by spray drying, wherein the spray drying inlet air temperature is 150℃ and the outlet air temperature is 80℃;

[0038] Step 3. Mix maleic anhydride and medium-temperature asphalt at a mass ratio of 1:8, place in a 160℃ melting kettle and stir to melt for 30 minutes to obtain an asphalt premix; keep the temperature at 160℃, slowly add polyborosiloxane to the asphalt premix, the mass ratio of medium-temperature asphalt to polyborosiloxane is 6:2, and at the same time, shear and stir at 2000r / min for 1 hour to obtain a binder;

[0039] Step 4. Add solid aggregate and modified composite filler to a high-speed mixer, add binder, heat to 150℃ and stir for 1 hour, then add functional additive and continue stirring for 30 minutes to obtain a paste. The functional additive is graphite powder and borax mixed in a mass ratio of 4:3. The mass ratio of solid aggregate, modified composite filler, binder and functional additive is 3:1:0.6:0.2. Transfer the paste into a mold and press it under 10MPa pressure for 30 minutes to obtain an electrode paste blank.

[0040] Step 5. Place the electrode paste blank in a sintering furnace and sinter it for 2 hours at 200°C for the first time under a nitrogen atmosphere by heating at 2°C / min; then sinter it for 4 hours at 1000°C for the second time by heating at 3°C / min; and then cool it naturally to room temperature under nitrogen protection to obtain the electrode paste for the submerged arc furnace.

[0041] Example 2

[0042] like Figure 1 As shown, this embodiment provides an electrode paste for a submerged arc furnace and its preparation method, the preparation method including the following steps:

[0043] Step 1. Take three-stage anthracite, which includes first anthracite, second anthracite, and third anthracite; the particle size of the first anthracite is 4 mm, the particle size of the second anthracite is 1.5 mm, and the particle size of the third anthracite is 0.3 mm; the mass ratio of the first anthracite, second anthracite, and third anthracite is 3:4:3; place the three-stage anthracite in a high-temperature electric calcining furnace for high-temperature electric calcination treatment, calcining at 1900℃ for 5 hours under an inert gas protective atmosphere, and cooling to room temperature to obtain calcined anthracite; then add the calcined anthracite to a 2wt% KH-550 silane coupling agent ethanol solution, wherein the mass ratio of the three-stage anthracite to the KH-550 silane coupling agent ethanol solution is 1:5, stir and react at 70℃ for 2.5 hours, filter, and dry the filter residue to obtain surface-modified solid aggregate;

[0044] Step 2. Add silicon carbide whiskers to a 6 wt% hydrochloric acid solution for acid washing, stir at 85°C for 2.5 h, filter, wash, and dry. Then add a 3 wt% KH-560 coupling agent ethanol solution. The mass ratio of silicon carbide whiskers, hydrochloric acid solution, and KH-560 coupling agent ethanol solution is 1:4:4. Stir at 75°C for 3 h, filter, and dry to obtain modified silicon carbide whiskers. Mix urea and boric acid at a mass ratio of 10:1, grind evenly, place in a tube furnace under nitrogen protection, heat to 580°C, and hold for 3 hours. After cooling for 0.5 hours, the mixture is ground through a 200-mesh sieve to obtain boron-doped graphene-like carbon nitride. The modified silicon carbide whiskers, boron-doped graphene-like carbon nitride, and a composite dispersant are mixed at a mass ratio of 1:2:0.06. The composite dispersant is a mixture of polyethylene glycol 400 and sodium dodecylbenzene sulfonate at a mass ratio of 2:1. Deionized water is then added and the mixture is ultrasonically dispersed at 400W for 35 minutes, where the mass ratio of the composite dispersant to deionized water is 1:2.5. The modified composite filler is obtained by spray drying, with an inlet air temperature of 155℃ and an outlet air temperature of 85℃.

[0045] Step 3. Mix maleic anhydride and medium-temperature asphalt at a mass ratio of 1:10, place in a 170℃ melting kettle and stir to melt for 40 minutes to obtain an asphalt premix; keep the temperature at 170℃, slowly add polyborosiloxane to the asphalt premix, the mass ratio of medium-temperature asphalt to polyborosiloxane is 7:3, and at the same time, shear and stir at a high speed of 2500r / min for 1.2h to obtain a binder;

[0046] Step 4. Add solid aggregate and modified composite filler to a high-speed mixer, add binder, heat to 155℃ and stir for 1.2 hours, then add functional additive and continue stirring for 40 minutes to obtain a paste. The functional additive is graphite powder and borax mixed in a mass ratio of 5:3. The mass ratio of solid aggregate, modified composite filler, binder and functional additive is 4:1:1:0.3. Transfer the paste into a mold and press it under 12MPa pressure for 40 minutes to obtain an electrode paste blank.

[0047] Step 5. Place the electrode paste blank in a sintering furnace and sinter it for 2.5 hours at 220°C for the first time under a nitrogen atmosphere by heating at 2.5°C / min; then sinter it for 5 hours at 1100°C for the second time by heating at 4°C / min; and then cool it naturally to room temperature under nitrogen protection to obtain the electrode paste for submerged arc furnace.

[0048] Example 3

[0049] like Figure 1 As shown, this embodiment provides an electrode paste for a submerged arc furnace and its preparation method, the preparation method including the following steps:

[0050] Step 1. Take three-stage anthracite, which includes first anthracite, second anthracite, and third anthracite; the particle size of the first anthracite is 5 mm, the particle size of the second anthracite is 2 mm, and the particle size of the third anthracite is 0.5 mm; the mass ratio of the first anthracite, second anthracite, and third anthracite is 4:5:4; place the three-stage anthracite in a high-temperature electric calcining furnace for high-temperature electric calcination treatment, calcining at 2000℃ under an inert gas protective atmosphere for 6 hours, and cooling to room temperature to obtain calcined anthracite; then add the calcined anthracite to a 3wt% KH-550 silane coupling agent ethanol solution, wherein the mass ratio of the three-stage anthracite to the KH-550 silane coupling agent ethanol solution is 1:6, stir and react at 80℃ for 3 hours, filter, and dry the filter residue to obtain surface-modified solid aggregate;

[0051] Step 2. Add silicon carbide whiskers to an 8 wt% hydrochloric acid solution for acid washing, stir at 90°C for 3 hours, filter, wash, and dry. Then add a 4 wt% KH-560 coupling agent ethanol solution. The mass ratio of silicon carbide whiskers, hydrochloric acid solution, and KH-560 coupling agent ethanol solution is 1:5:5. Stir at 80°C for 4 hours, filter, and dry to obtain modified silicon carbide whiskers. Mix urea and boric acid at a mass ratio of 12:1, grind evenly, place in a tube furnace under nitrogen protection, heat to 600°C, and maintain the temperature for reaction. After 4 hours of cooling, the mixture is ground through a 300-mesh sieve to obtain boron-doped graphene-like carbon nitride. The modified silicon carbide whiskers, boron-doped graphene-like carbon nitride, and a composite dispersant are mixed at a mass ratio of 1:3:0.08. The composite dispersant is a mixture of polyethylene glycol 400 and sodium dodecylbenzene sulfonate at a mass ratio of 3:1. Deionized water is then added and the mixture is ultrasonically dispersed at 500W for 40 minutes, with the mass ratio of the composite dispersant to deionized water being 1:3. The modified composite filler is obtained by spray drying, with an inlet air temperature of 160℃ and an outlet air temperature of 90℃.

[0052] Step 3. Mix maleic anhydride and medium-temperature asphalt at a mass ratio of 1:12, place in a 180°C melting kettle and stir for 50 minutes to obtain an asphalt premix; maintain the temperature at 180°C, slowly add polyborosiloxane to the asphalt premix, the mass ratio of medium-temperature asphalt to polyborosiloxane is 8:4, and simultaneously shear and stir at 3000 r / min for 1.5 hours to obtain a binder;

[0053] Step 4. Add solid aggregate and modified composite filler to a high-speed mixer, add binder, heat to 160℃ and stir for 1.5 hours, then add functional additive and continue stirring for 50 minutes to obtain a paste. The functional additive is graphite powder and borax mixed in a mass ratio of 6:3. The mass ratio of solid aggregate, modified composite filler, binder and functional additive is 5:1:1.2:0.5. Transfer the paste into a mold and press it under 15MPa pressure for 50 minutes to obtain an electrode paste blank.

[0054] Step 5. Place the electrode paste blank in a sintering furnace and sinter it for 3 hours at 250°C with a first heating rate of 3°C / min under a nitrogen atmosphere; then sinter it for 6 hours at 1200°C with a second heating rate of 5°C / min; and finally cool it naturally to room temperature under nitrogen protection to obtain the electrode paste for submerged arc furnace.

[0055] Comparative Example 1

[0056] An electrode paste for a submerged arc furnace and its preparation method are disclosed. The difference between this method and Example 3 is that the three-stage particle size distribution anthracite is not modified with KH-550 silane coupling agent after calcination in step 1.

[0057] Comparative Example 2

[0058] An electrode paste for a submerged arc furnace and its preparation method are disclosed, which differ from Example 3 in that the silicon carbide crystals are not acid-washed in step 2.

[0059] Comparative Example 3

[0060] An electrode paste for a submerged arc furnace and its preparation method are disclosed, which differ from Example 3 in that in step 2, boron-doped graphene-like carbon nitride is replaced with ordinary graphene-like carbon nitride without boron doping.

[0061] Comparative Example 4

[0062] An electrode paste for a submerged arc furnace and its preparation method are disclosed, which differ from Example 3 in that polyborosiloxane and maleic anhydride are not added in step 3.

[0063] Performance testing:

[0064] 1. Resistivity at room temperature (μΩ·m): The resistivity of the electrode paste sample with a diameter of 50mm×50mm was tested at three points at the center and edge using the four-probe method, and the average value was taken as the final result.

[0065] 2. Compressive strength at room temperature (MPa): Place the Φ50mm×50mm electrode paste sample on a universal testing machine and test the compressive strength at a loading rate of 1mm / min.

[0066] 3. High-temperature thermal shock stability (cycles): Heat the Φ50mm×50mm electrode paste sample to 1000℃ and hold for 1 hour, then quickly immerse it in 20℃ water to cool it. Repeat this cycle until the sample shows visible cracks. Record the number of cycles, which is the number of thermal shock stability cycles.

[0067] 4. High-temperature antioxidant weight loss rate (%): After weighing the initial mass of the electrode paste sample, place it in a muffle furnace with an air atmosphere at 1000℃ for 2 hours. After cooling, weigh the remaining mass and calculate the percentage of the difference between the initial mass and the remaining mass relative to the initial mass. This percentage is the antioxidant weight loss rate.

[0068] 5. Bulk density (g / cm³): The Archimedes displacement method was used to measure the mass of the electrode paste sample in air and the mass immersed in deionized water using an electronic balance. The bulk density of the sample was calculated by combining the density of water, and thus the density was obtained.

[0069] The performance test data analysis is as follows:

[0070] Table 1. Performance test data of electrode pastes for submerged arc furnaces prepared in Examples 1-3 and Comparative Examples 1-4

[0071] Group Resistivity at room temperature (μΩ·m) Compressive strength at room temperature (MPa) High-temperature thermal shock stability (times) High-temperature antioxidant weight loss rate (%) <![CDATA[Apparent density (g / cm 3 )]]> Example 1 48.2 35.6 15 7.8 1.65 Example 2 41.5 40.3 20 6.2 1.73 Example 3 36.8 45.1 24 5.1 1.81 Comparative Example 1 68.5 28.7 11 16.3 1.48 Comparative Example 2 52.3 32.4 14 12.5 1.57 Comparative Example 3 89.6 39.2 17 27.8 1.70 Comparative Example 4 69.3 20.5 5 29.4 1.45

[0072] As shown in Table 1, through the synergistic technical solutions of solid aggregate, modified silicon carbide whiskers, boron-doped graphene-carbon nitride composite filler, polyborosiloxane, and medium-temperature asphalt binder, as well as the gradient optimization of process parameters, Examples 1-3 showed a significant increasing trend in various core properties. Among them, Example 3 performed best, with a room temperature resistivity as low as 36.8 μΩ·m, a room temperature compressive strength as high as 45.1 MPa, a high temperature thermal shock stability of 24 cycles, a high temperature oxidation weight loss rate of only 5.1%, and a bulk density increased to 1.81 g / cm³, demonstrating excellent electrical conductivity, mechanical strength, high temperature stability, and structural compactness. The outstanding performance stems from the synergistic effect of various innovative links: high-temperature electric calcination improves the graphitization degree of anthracite, and KH-550 modification constructs Si-OC covalent bonds to strengthen the interfacial bonding; acid washing removes silicon carbide whisker impurities, KH-560 modification improves its compatibility with the matrix, and boron-doped graphene-like carbon nitride constructs a "one-dimensional enhancement-two-dimensional conductivity" multi-dimensional network; maleic anhydride introduces polar carboxyl groups to build interfacial bridges, solves the compatibility problem between polyborosiloxane and medium-temperature pitch, and high bond energy Si-O / BO bonds improve high-temperature stability; gradient optimization of process parameters further promotes uniform dispersion and interfacial fusion of various components.

[0073] Compared with Example 3, Comparative Example 1 lacked the KH-550 silane coupling agent modification step after calcination of anthracite with three-stage particle size distribution. As a result, it was impossible to construct the Si-OC covalent bond interface bridging structure. The surface activity of the solid aggregate was low, and the interfacial bonding force with the binder and composite filler was greatly weakened. The internal porosity of the system increased, resulting in a room temperature resistivity of 68.5 μΩ·m, a room temperature compressive strength of 28.7 MPa, a high temperature thermal shock stability of only 11 cycles, a high temperature oxidation weight loss rate of 16.3%, and a volume density of 1.48 g / cm³. This fully demonstrates the key role of KH-550 modification in strengthening interfacial bonding and improving the system's density and overall performance.

[0074] Compared to Example 3, Comparative Example 2 lacked the acid washing step for silicon carbide whiskers. This resulted in residual oxide layers and impurities on the surface of the whiskers, insufficient active sites, and an inability to fully react with the KH-560 coupling agent. Furthermore, it struggled to form a stable bond with boron-doped graphene-like carbon nitride and the matrix, easily leading to localized agglomeration and interface defects. Consequently, its room temperature resistivity increased to 52.3 μΩ·m, its room temperature compressive strength decreased to 32.4 MPa, its high-temperature thermal shock stability was 14 cycles, its high-temperature oxidation weight loss rate was 12.5%, and its bulk density was 1.57 g / cm³. 3 This highlights the necessity of acid pickling for enhancing the activity of silicon carbide whiskers and optimizing interfacial bonding.

[0075] Compared with Example 3, in Comparative Example 3, boron-doped graphene-like carbon nitride was replaced with undoped ordinary graphene-like carbon nitride. The active sites introduced by boron atom doping were missing. This not only failed to destroy the intrinsic insulation of carbon nitride to build an effective conductive channel, but also lost the antioxidant function of adsorbing oxygen free radicals in the empty orbitals of boron atoms. As a result, its room temperature resistivity soared to 89.6 μΩ·m, and its high temperature antioxidant weight loss rate surged to 27.8%. Although the room temperature compressive strength (39.2 MPa) and volume density decreased relatively mildly due to the retention of other modification steps, the core properties of conductivity and antioxidant properties were greatly reduced, which fully demonstrates the indispensability of boron doping modification.

[0076] Compared with Example 3, Comparative Example 4 lacked the addition of polyborosiloxane and maleic anhydride, and only used a single medium-temperature asphalt as a binder. It could not solve the compatibility problem by building an interfacial bridge with maleic anhydride, nor did it have the high-temperature stability improvement brought by the high bond energy Si-O / BO bonds of polyborosiloxane. This resulted in extremely poor interfacial wettability between the binder and solid aggregates and composite fillers, which was easily degraded and peeled off at high temperatures. Its room temperature compressive strength dropped sharply to 20.5 MPa, its high-temperature thermal shock stability was only 5 times, its high-temperature oxidation weight loss rate was as high as 29.4%, its room temperature resistivity was 69.3 μΩ·m, and its bulk density was 1.45 g / cm³. All properties collapsed, which confirmed the decisive supporting role of maleic anhydride-mediated polyborosiloxane / medium-temperature asphalt compatible binder in the performance of the system.

[0077] In summary, Examples 1-3, through the synergistic effect of solid aggregate modification and strengthening, multi-dimensional synergy of composite fillers, construction of compatible binders, and precise control of process parameters, solved the problem of weak interfacial bonding among existing electrode paste components, achieving simultaneous improvement in conductivity, mechanical strength, high-temperature stability, and structural density. In contrast, each comparative example, lacking key innovative elements, exhibited specific performance defects, further demonstrating the necessity and synergistic value of the innovations in this application. The electrode paste for submerged arc furnaces prepared by this method can stably adapt to the high-temperature, high-current, and strong mechanical impact operating conditions of submerged arc furnaces, providing a reliable technical solution for the preparation of high-performance electrode pastes.

[0078] Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this application. Various changes and modifications can be made to this application without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of this application as claimed. The scope of protection of this application is defined by the equivalents of the appended claims.

Claims

1. An electrode paste for a submerged arc furnace, characterized in that, The product comprises solid aggregate, modified composite filler, binder, and functional additives. The solid aggregate is obtained by high-temperature electric calcination of three-grade anthracite coal followed by modification with KH-550 silane coupling agent ethanol solution. The modified composite filler is obtained by treating modified silicon carbide whiskers and boron-doped graphene-like carbon nitride with a composite dispersant. The modified silicon carbide whiskers are obtained by first acid washing of silicon carbide whiskers and then modification with KH-560 coupling agent ethanol solution. The boron-doped graphene-like carbon nitride uses urea and boric acid precursors. The reaction yields the binder, which is obtained by blending medium-temperature asphalt with polyborosiloxane. The functional additives include graphite powder and borax. The mass ratio of the solid aggregate, modified composite filler, binder, and functional additives is (3-5):1:(0.6-1.2):(0.2-0.5). The binder is prepared by mixing maleic anhydride and medium-temperature asphalt in a melting kettle and stirring to obtain an asphalt premix. Polyborosiloxane is added to the asphalt premix, and the mixture is simultaneously sheared and stirred at high speed to obtain the binder.

2. The electrode paste for a submerged arc furnace according to claim 1, characterized in that, The three-stage anthracite comprises first anthracite, second anthracite, and third anthracite; the first anthracite has a particle size of 3-5 mm, the second anthracite has a particle size of 1-2 mm, and the third anthracite has a particle size of 0.1-0.5 mm; the mass ratio of the first, second, and third anthracite is (2-4):(3-5):(2-4); the mass ratio of the three-stage anthracite to the KH-550 silane coupling agent ethanol solution is 1:(4-6); and the mass fraction of the KH-550 silane coupling agent ethanol solution is 1wt%-3wt%.

3. The electrode paste for a submerged arc furnace according to claim 1, characterized in that, The mass ratio of the modified silicon carbide whiskers, boron-doped graphene-like carbon nitride, and composite dispersant is 1:(1-3):(0.02-0.08); the composite dispersant is polyethylene glycol 400 and sodium dodecylbenzenesulfonate; the mass ratio of polyethylene glycol 400 and sodium dodecylbenzenesulfonate is (1-3):1; the acid used for pickling is hydrochloric acid solution; the mass fraction of the hydrochloric acid solution is 5wt%-8wt%; the mass fraction of the KH-560 coupling agent ethanol solution is 2wt%-4wt%; the mass ratio of the silicon carbide whiskers, hydrochloric acid solution, and KH-560 coupling agent ethanol solution is 1:(3-5):(3-5); the mass ratio of the urea and boric acid precursor is (8-12):

1.

4. The electrode paste for a submerged arc furnace according to claim 1, characterized in that, The mass ratio of the medium-temperature asphalt to polyborosiloxane is (6-8):(2-4); the mass ratio of the graphite powder to borax is (4-6):

3.

5. A method for preparing electrode paste for a submerged arc furnace according to any one of claims 1-4, characterized in that, Includes the following steps: Step 1. Take three-stage particle size distribution anthracite and place it in a high-temperature electric calcining furnace for high-temperature electric calcination treatment. Calcinate under an inert gas protective atmosphere and cool to room temperature to obtain calcined anthracite. Then add the calcined anthracite to a KH-550 silane coupling agent ethanol solution, stir to react, filter, and dry the filter residue to obtain solid aggregate. Step 2. The silicon carbide whiskers are acid-washed and stirred, filtered, washed and dried, then added to KH-560 coupling agent ethanol solution, stirred and reacted, filtered and dried to obtain modified silicon carbide whiskers. Urea and boric acid were mixed and ground evenly, and placed in a tube furnace under nitrogen protection. After heating and holding for reaction, the mixture was cooled, ground and sieved to obtain boron-doped graphene-like carbon nitride. The modified silicon carbide whiskers, boron-doped graphene-like carbon nitride and composite dispersant were mixed, and deionized water was added for ultrasonic dispersion. After spray drying, the modified composite filler was obtained. Step 3. Mix maleic anhydride and medium-temperature asphalt in a melting kettle and stir to melt, to obtain an asphalt premix; add polyborosiloxane to the asphalt premix and simultaneously shear and stir at high speed to obtain a binder; Step 4. Add solid aggregate and modified composite filler to a high-speed mixer, add binder, heat and stir to mix, then add functional additives and continue stirring to obtain a paste; transfer the paste into a mold, press and shape to obtain an electrode paste blank; Step 5. Place the electrode paste blank in a sintering furnace, sinter it for the first time under a nitrogen atmosphere, and then sinter it for the second time under a nitrogen atmosphere. Then, cool it naturally to room temperature under nitrogen protection to obtain the electrode paste for electric arc furnace.

6. The method for preparing electrode paste for a submerged arc furnace according to claim 5, characterized in that, In step 1, the high-temperature electric calcination treatment is carried out at a temperature of 1800-2000℃ for 4-6 hours; the stirring reaction is carried out at a temperature of 60-80℃ for 2-3 hours.

7. The method for preparing electrode paste for a submerged arc furnace according to claim 5, characterized in that, In step 2, the temperature for the acid washing and stirring reaction is 80-90℃ and the time is 2-3h; the temperature for the stirring reaction in the KH-560 coupling agent ethanol solution is 70-80℃ and the time is 2-4h; the temperature for heating in the tube furnace is 550-600℃ and the time for holding the reaction is 3-4h; the mesh size for sieving is 100-300 mesh; the power for ultrasonic dispersion is 300-500W and the time is 30-40min; the mass ratio of the composite dispersant to deionized water is 1:(2-3); and the inlet air temperature for spray drying is 150-160℃ and the outlet air temperature is 80-90℃.

8. The method for preparing electrode paste for a submerged arc furnace according to claim 5, characterized in that, In step 3, the stirring and melting temperature is 160-180℃ and the time is 30-50 min; the high-speed shearing speed is 2000-3000 r / min and the time is 1-1.5 h.

9. The method for preparing electrode paste for a submerged arc furnace according to claim 5, characterized in that, In step 4, the temperature of the mixture added to the high-speed mixer for heating and stirring is 150-160℃, and the time is 1-1.5h; the stirring and mixing time is 30-50min; the pressure for pressing and molding is 10-15MPa, and the time is 30-50min.

10. The method for preparing electrode paste for a submerged arc furnace according to claim 5, characterized in that, In step 5, the first heating rate is 2-3℃ / min, the temperature is 200-250℃, and the sintering time is 2-3h; the second heating rate is 3-5℃ / min, the temperature is 1000-1200℃, and the sintering time is 4-6h.

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