A method and system for on-line regeneration of used electroslag

Abstract

The application belongs to the technical field of electroslag remelting, and particularly relates to a method and system for online regeneration of used electroslag. Since the used electroslag is used for a long time in the electroslag remelting process, sulfides (such as CaS and MnS) and oxides (such as Al2O3 and SiO2) are continuously enriched, resulting in imbalance of slag basicity, abnormal electrical conductivity and attenuation of refining capacity, which is the core factor causing the used electroslag to be unable to be directly recycled. Embodiments of the application break the traditional offline processing mode of abandonment and replacement, and construct an online closed-loop process of crushing-magnetic separation-layered batching-melting regeneration. Through gradient arrangement of the bottom reactant and the upper slag, the three functions of physical impurity removal, chemical damage removal and performance reconstruction are integrated in the same remelting space, avoiding energy loss and secondary pollution caused by multi-process transfer. The synergistic ratio of new slag and old slag is used to rapidly restore the activity of the slag system at a low cost, and the resource utilization efficiency and economy of the electroslag remelting process are significantly improved.

Description

Technical Field

[0001] This application belongs to the field of electroslag remelting technology, and particularly relates to a method and system for online regeneration of used electroslag. Background Technology

[0002] Electroslag remelting (ESR) is a key secondary refining technology for producing high-quality special steels and high-temperature alloys. Its core lies in utilizing molten slag as a resistance heating element and refining medium to purify and optimize the microstructure of the metal. During ESR, the slag performs multiple functions, including heating, heat preservation, desulfurization, removal of non-metallic inclusions, and protection of the molten metal pool from oxidation. Slag costs typically account for 15% to 20% of the total smelting cost. However, in traditional ESR processes, the slag is discarded after a single use due to compositional deterioration. Used ESR is difficult to reuse directly; forced reuse leads to increased surface defects in ingots, a 12% to 18% decrease in yield, extremely low desulfurization rates, and even sulfur reversion. Currently, used ESR is typically treated as industrial waste, which not only wastes high-value raw materials such as calcium fluoride and alumina but also imposes environmental burdens and additional production costs.

[0003] In existing technologies, research on the reuse of electroslag after use mainly focuses on two aspects: First, extracting metal elements from nickel- and cobalt-containing smelting slag using pyrometallurgical or hydrometallurgical techniques to turn waste into treasure. However, this type of technology treats waste electroslag and aims to extract metal residues. The treated slag residues are usually discarded or downgraded, which cannot solve the fundamental problem of electroslag waste. Second, harmless treatment of electroslag from the electrolytic aluminum industry is carried out through powdering, leaching, cyanide removal, solid-liquid separation, and washing to recover slag powder, achieving harmless and value-added treatment of waste electroslag. However, the treatment objects of this method are fundamentally different from those of electroslag produced by the electroslag remelting process, and the treated slag powder is mainly used in building materials and other fields, and its performance as a metallurgical functional material cannot be restored.

[0004] Extensive academic research and patented technologies focus on the design and optimization of initial slag systems and compositional control during remelting. Efforts are dedicated to developing novel slag system formulations with specific physicochemical properties (such as low melting point, high desulfurization capacity, and friendliness to active elements) to meet the production requirements of specific alloy grades (such as nickel-based superalloys containing high aluminum and titanium). Furthermore, numerous studies have explored the thermodynamics and kinetics of slag-metal reactions during electroslag remelting, aiming to mitigate slag system composition degradation and predict and control the burn-off of active elements in the alloy by controlling process parameters such as atmosphere and current. These studies provide a theoretical basis for understanding the mechanism of slag system performance degradation; however, their technical solutions remain at the level of post-use electroslag process control, i.e., how to delay the failure of post-use electroslag during use, without proposing a systematic solution for how to repair post-use electroslag after failure and restore its metallurgical function, thus achieving recycling. Summary of the Invention

[0005] This application provides a method and system for online regeneration of used electroslag to solve the following technical problem: how to remove sulfides and oxides enriched in used electroslag online and restore its metallurgical function.

[0006] In a first aspect, embodiments of this application provide a method for online regeneration of electroslag after use, comprising the following steps: The used electroslag is crushed to obtain crushed slag; the particle size of the crushed slag is ≤5mm. The crushed slag is subjected to magnetic separation to remove metal particles, resulting in pretreated slag; the metal impurity content of the pretreated slag is <0.1%; A carbon source, a calcium carbonate source, and a calcium fluoride source are added to the bottom of the remelting space; the mass of the carbon source is 0.5% to 10% of the mass of the pretreated slag, the mass of the calcium carbonate source is 30% to 50% of the mass of the pretreated slag, and the mass of the calcium fluoride source is the remainder after deducting the mass of the carbon source and the calcium carbonate source from the mass of the pretreated slag. The pretreated slag is added into the remelting space, covering the carbon source, the calcium carbonate source, and the calcium fluoride source. New slag is added into the remelting space to form a mixed slag layer with the pretreated slag; the mass ratio of the new slag to the pretreated slag is 0.5~1. The mixed slag layer is melted by electric heating to obtain recycled slag.

[0007] Optionally, the electrothermal melting process includes: The carbon source undergoes a reduction reaction with the metal oxides in the pretreated slag. The calcium carbonate source decomposes upon heating to produce carbon dioxide. The carbon dioxide reacts with the calcium sulfide in the pretreated slag to produce calcium oxide and sulfur dioxide gas. The carbon dioxide reacts with the residual carbon in the carbon source that did not participate in the reduction reaction to generate carbon monoxide gas.

[0008] Optionally, the metal oxide includes ferrous oxide and chromium oxide; the reduction reaction reduces the content of ferrous oxide and chromium oxide in the pretreated slag by ≥85% compared with that before pretreatment.

[0009] Optionally, the carbon source is graphite powder with a purity of ≥99%, the calcium carbonate source is calcium carbonate powder with a purity of ≥98%, and the calcium fluoride source is calcium fluoride powder with a purity of ≥97%.

[0010] Optionally, the crushing process employs a jaw crusher; the crushed slag is screened using a 2.5-mesh standard sieve. The magnetic separation process employs a drum-type magnetic separator; the magnetic field strength of the drum-type magnetic separator is 1000 Gs to 1500 Gs, and the magnetic separation time is 10 min to 20 min.

[0011] Optionally, the carbon source, the calcium carbonate source, and the calcium fluoride source are added to the bottom of the remelting space by uniformly mixing and spreading them out, and the thickness of the spread is 30mm~70mm. The total thickness of the mixed slag layer is 200mm~400mm.

[0012] Optionally, the pretreated slag is added to the remelting space at a feeding rate of 1 kg / min to 3 kg / min.

[0013] Optionally, during the electrothermal melting process, the electrode is inserted into the mixed slag layer to a depth of 50 mm to 120 mm. The temperature of the electric heating melting treatment is 1400℃~1600℃, and the holding time is 20min~40min.

[0014] Optionally, the used electroslag is derived from the electroslag remelting process of nickel-based superalloy IN718; The chemical composition of the new slag is: 55% calcium oxide, 35% aluminum oxide and 10% calcium fluoride.

[0015] Secondly, embodiments of this application provide a post-use electroslag online regeneration system, comprising: The crushing and screening device uses electroslag remelting to crush the material and obtain crushed slag. A magnetic separation device is used to perform magnetic separation on the crushed slag to remove metal particles and obtain pretreated slag. An electroslag remelting crystallizer is used to contain and heat carbon source, calcium carbonate source, calcium fluoride source, pretreated slag and new slag to obtain recycled slag. The exhaust gas treatment device collects and treats the carbon monoxide and sulfur dioxide gases generated during the electric heating and melting process.

[0016] The technical solution provided in this application has the following advantages compared with the prior art: Because used electroslag undergoes long-term service during the electroslag remelting process, sulfides (such as CaS and MnS) and oxides (such as Al2O3 and SiO2) continuously accumulate, leading to an imbalance in the basicity of the slag system, abnormal electrical conductivity, and a decline in refining capacity. This is the core factor that prevents used electroslag from being directly reused.

[0017] This application embodiment increases the specific surface area of ​​the slag by crushing the used electroslag to a particle size ≤5mm, thereby promoting the heat and mass transfer efficiency during subsequent melting treatment and creating kinetic conditions for the deep removal of sulfides and oxides. Magnetic separation is used to reduce the metal impurity content to <0.1%, thus removing the interference of residual metal particles on the electrochemical properties of the slag system and preventing local short circuits or component contamination during remelting, thereby ensuring the resistance stability and metallurgical purity of the recycled slag. By placing a carbon source (0.5%~10%), a calcium carbonate source (30%~50%), and a calcium fluoride source (balance) at the bottom of the remelting space, a layered reaction system is formed during electric heating. The carbon source generates CO bubbles at high temperatures and provides a reducing atmosphere; the calcium carbonate source decomposes to release CaO and generates CO2 for stirring; and the calcium fluoride source lowers the melting point of the slag system and improves its fluidity, thereby constructing a sulfide oxidation process. - The coupled reaction environment of oxide reduction; by covering the pretreated slag material on the above-mentioned reactants, the gravity compaction of the upper slag layer is used to inhibit the premature escape of the reactants. At the same time, the convection circulation during the melting process allows sulfides to float to the slag-gas interface for oxidation and volatilization, and oxides to be reduced by carbon or enter the slag system for reconstruction, thereby achieving selective removal of enriched impurities; by adding 0.5~1 mass ratio of new slag to form a mixed slag layer with the pretreated slag material, fresh CaF2-CaO-Al2O3 basic units are introduced to supplement the active components, dilute the concentration of harmful impurities, and quickly establish the target slag system component window, thereby restoring the metallurgical functions of desulfurization, deoxidation, and inclusion adsorption of the slag material; finally, the mixed slag layer is electrically heated and melted to fully homogenize the components and complete the desulfurization and deoxidation reactions, thereby obtaining regenerated slag material with controllable composition and restored metallurgical performance, realizing the online recycling of electroslag after use.

[0018] This application's embodiments break through the traditional offline processing mode of waste-replacement and construct an online closed-loop process of crushing-magnetic separation-layer batching-melting regeneration; through the gradient arrangement of bottom reactant and upper slag, physical impurity removal, chemical descaling and performance reconstruction are integrated in the same remelting space, avoiding energy loss and secondary pollution caused by multi-process transfer; by utilizing the synergistic ratio of new slag and old slag, the activity of the slag system is rapidly restored at a lower cost, significantly improving the resource utilization efficiency and economy of the electroslag remelting process. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within the range. For example, a range description of 1 to 6 or 1~6 covers all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms used herein, including terms such as "include" to indicate, but not limited to, "first," "second," etc., are used only to distinguish different entities or steps and do not imply an actual order or relationship; and / or to indicate that multiple situations can exist alone or simultaneously; expressions such as "at least one," "more than one," etc., refer to any combination of the corresponding objects, including combinations of single or multiple objects. Proportional relationships mentioned herein, such as mass ratios and molar ratios, should be understood as a correspondence between the antecedent and consequent of a proportional expression, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained through commercial purchase or prepared using existing methods.

[0021] In a first aspect, embodiments of this application provide a method for online regeneration of electroslag after use, comprising the following steps: The used electroslag is crushed to obtain crushed slag; the particle size of the crushed slag is ≤5mm. The crushed slag is subjected to magnetic separation to remove metal particles, resulting in pretreated slag; the metal impurity content of the pretreated slag is <0.1%; A carbon source, a calcium carbonate source, and a calcium fluoride source are added to the bottom of the remelting space; the mass of the carbon source is 0.5% to 10% of the mass of the pretreated slag, the mass of the calcium carbonate source is 30% to 50% of the mass of the pretreated slag, and the mass of the calcium fluoride source is the remainder after deducting the mass of the carbon source and the calcium carbonate source from the mass of the pretreated slag. The pretreated slag is added into the remelting space, covering the carbon source, the calcium carbonate source, and the calcium fluoride source. New slag is added into the remelting space to form a mixed slag layer with the pretreated slag; the mass ratio of the new slag to the pretreated slag is 0.5~1. The mixed slag layer is melted by electric heating to obtain recycled slag.

[0022] Used electroslag: refers to molten slag that is discarded after a single use in the electroslag remelting process due to compositional deterioration. This used electroslag contains components that increase the melting point due to CaF2 volatilization loss, desulfurization product CaS, and non-metallic oxides generated by the oxidation of liquid metal elements during the electroslag remelting process. New slag: refers to special slag material used for the first time in the electroslag remelting process.

[0023] After the carbon source is added to the bottom of the remelting space, the carbon source reacts with the metal oxides in the pretreated slag to reduce the impurity components that have been oxidized into the slag phase in the electroslag remelting process, thereby reducing the oxidizing properties of the slag and eliminating the disruption of the oxygen potential balance of the slag system by non-metallic oxides.

[0024] After the calcium carbonate source is added to the bottom of the remelting space, the calcium carbonate source decomposes upon heating to produce carbon dioxide. The carbon dioxide reacts with the calcium sulfide in the pretreated slag to produce calcium oxide and sulfur dioxide gas, thereby oxidizing and removing the desulfurization product CaS enriched in the slag, thus restoring the desulfurization capacity of the slag and solving the problem of liquid metal resulfurization caused by reuse.

[0025] Carbon dioxide reacts with residual carbon in the carbon source that did not participate in the reduction reaction to generate carbon monoxide gas, thereby synergistically removing excess carbon and restoring the composition and phase composition of the electroslag, thus restoring the performance of the slag system to more than 95% of its initial state.

[0026] After the calcium fluoride source is added to the bottom of the remelting space, it is used to adjust the melting point and fluidity of the slag, thereby compensating for the melting point increase caused by the loss of CaF2 volatilization in the slag after pretreatment, and thus restoring the heating and refining functions of the slag system.

[0027] After pretreatment, the slag material covers the carbon source, calcium carbonate source and calcium fluoride source. The new slag and the pretreated slag material form a mixed slag layer. The gradient repair of the slag system components is achieved through the mixing ratio of new and old slag materials, so that the metallurgical function of the recycled slag material is comparable to that of the new slag.

[0028] Existing technologies are limited to post-use electroslag process control, i.e., how to delay slag system failure during use, or to discard slag residues after metal extraction by pyrometallurgical or hydrometallurgical methods. However, the embodiments of this application propose a systematic online regeneration scheme for the first time. Through a triple mechanism of carbon source reduction of oxides, carbon dioxide generated by calcium carbonate decomposition for synergistic desulfurization and decarbonization, and calcium fluoride source supplementation and regulation, the in-situ restoration of post-use electroslag metallurgical function is achieved.

[0029] The mass of the carbon source is 0.5%, 1%, 2%, 3%, 5%, 7%, 10% of the mass of the pretreated slag, etc. The mass of the calcium carbonate source is 30%, 35%, 40%, 45%, 50% of the mass of the pretreated slag, etc. The ratio of the mass of the new slag to the mass of the pretreated slag is 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, etc.

[0030] In some embodiments, the electrothermal melting process includes: The carbon source undergoes a reduction reaction with the metal oxides in the pretreated slag. The calcium carbonate source decomposes upon heating to produce carbon dioxide. The carbon dioxide reacts with the calcium sulfide in the pretreated slag to produce calcium oxide and sulfur dioxide gas. The carbon dioxide reacts with the residual carbon in the carbon source that did not participate in the reduction reaction to generate carbon monoxide gas.

[0031] The carbon source undergoes a reduction reaction with the metal oxides in the pretreated slag, thereby reducing metal oxides such as ferrous oxide and chromium oxide to elemental metals or low-valence oxides. This reduces the oxidizing properties of the slag phase, thus eliminating the disruption of the oxygen potential balance at the slag-metal interface caused by oxide enrichment and solving the problem of decreased alloy purity.

[0032] The calcium carbonate source decomposes upon heating to produce carbon dioxide, thereby providing a weakly oxidizing atmosphere, which in turn provides a reaction medium for subsequent desulfurization and decarbonization reactions, thus establishing controllable redox reaction conditions.

[0033] Carbon dioxide reacts with calcium sulfide in the pretreated slag to generate calcium oxide and sulfur dioxide gas, thereby converting the desulfurization product calcium sulfide into calcium oxide and gaseous sulfur dioxide. This allows the sulfur element in the slag to leave the slag system in gaseous form, thus restoring the desulfurization capacity of the slag and solving the problem of liquid metal resulfurization caused by reuse.

[0034] Carbon dioxide reacts with residual carbon in the carbon source that did not participate in the reduction reaction to generate carbon monoxide gas, thereby converting excess carbon source into gaseous carbon monoxide for discharge. This allows for precise control of the carbon content in the slag system, thus restoring the composition and phase composition of the electroslag and restoring the slag system performance to more than 95% of its initial state.

[0035] In some embodiments, the metal oxide includes ferrous oxide and chromium oxide; the reduction reaction reduces the content of ferrous oxide and chromium oxide in the pretreated slag by ≥85% compared to before pretreatment.

[0036] The carbon source undergoes a reduction reaction with the ferrous oxide in the pretreated slag, and the carbon source also undergoes a reduction reaction with the chromium oxide in the pretreated slag. This reduces the iron and chromium elements that have been oxidized into the slag phase during electroslag remelting, thereby reducing the content of ferrous oxide and chromium oxide in the pretreated slag by ≥85% compared to before pretreatment. This significantly reduces the oxidizing properties of the slag phase, thereby eliminating the negative impact of oxide enrichment on the melting point and fluidity of the slag system. This restores the slag system's exothermic and refining functions, bringing the slag system's performance back to over 95% of its initial state.

[0037] The content of ferrous oxide and chromium oxide in the slag after pretreatment is reduced by 85%, 87%, 90%, 92%, and 95% respectively compared with that before pretreatment.

[0038] In some embodiments, the carbon source is graphite powder with a purity of ≥99%, the calcium carbonate source is calcium carbonate powder with a purity of ≥98%, and the calcium fluoride source is calcium fluoride powder with a purity of ≥97%.

[0039] The carbon source is graphite powder with a purity of ≥99%, which ensures that the carbon source has high reactivity and does not contain impurities that introduce new impurities. This allows the reduction reaction between the carbon source and the metal oxides in the pretreated slag to proceed efficiently, thereby ensuring the reduction efficiency of ferrous oxide and chromium oxide.

[0040] The calcium carbonate source is calcium carbonate powder with a purity of ≥98%, which ensures that the carbon dioxide produced by the thermal decomposition of the calcium carbonate source is of high purity and the decomposition reaction is stable and controllable. This allows the desulfurization reaction between carbon dioxide and calcium sulfide, as well as the decarbonization reaction between carbon dioxide and residual carbon, to proceed fully, thereby ensuring the effectiveness of sulfide removal and residual carbon removal.

[0041] The calcium fluoride source is calcium fluoride powder with a purity of ≥97%, which ensures that the calcium fluoride source has high purity and effectively regulates the melting point and fluidity of the slag, thereby compensating for the loss of CaF2 volatilization in the slag after pretreatment, and thus restoring the heat generation and refining function of the slag system.

[0042] The purity of graphite powder is 99%, 99.2%, 99.5%, 99.7%, 99.9%, etc. The purity of calcium carbonate powder is 98%, 98.5%, 99%, 99.2%, 99.5%, etc. The purity of calcium fluoride powder is 97%, 97.5%, 98%, 98.5%, 99%, etc.

[0043] In some embodiments, the crushing process employs a jaw crusher; the crushed slag is screened using a 2.5-mesh standard sieve. The magnetic separation process employs a drum-type magnetic separator; the magnetic field strength of the drum-type magnetic separator is 1000 Gs to 1500 Gs, and the magnetic separation time is 10 min to 20 min.

[0044] Jaw crusher: This refers to the processing method of crushing used electroslag using a jaw crusher to crush it to a particle size ≤5mm. 2.5 mesh standard screen: This refers to a screen used for screening the crushed slag. The sieve aperture size of this 2.5 mesh standard screen corresponds to the passage of particles with a diameter ≤5mm. Drum magnetic separator: This refers to the processing method of magnetically separating the crushed slag using a drum magnetic separator. This drum magnetic separator uses a magnetic field to separate and remove metal particles from the crushed slag.

[0045] The crushing process employs jaw crushing, which applies mechanical extrusion pressure to the used electroslag to crush the solid slag material, thereby obtaining crushed slag material with a particle size ≤5mm, thus meeting the particle size requirements of subsequent magnetic separation treatment.

[0046] After crushing, the slag is screened using a 2.5-mesh standard sieve to remove oversized particles with a diameter >5mm and return them for further crushing. This ensures that the particle size of the crushed slag is ≤5mm, thus ensuring that the particle size uniformity of the crushed slag meets the requirements of magnetic separation efficiency and the kinetics of subsequent remelting reaction.

[0047] The magnetic separation process uses a drum-type magnetic separator, which uses the magnetic field generated by the rotating drum to continuously magnetically separate the crushed slag, thereby adsorbing and separating ferromagnetic metal particles (Fe, Cr, etc.) in the crushed slag, so that the metal impurity content of the pretreated slag is <0.1%.

[0048] The magnetic field strength of the drum magnetic separator is 1000Gs~1500Gs, which provides sufficient magnetic force to adsorb metal particles, thereby ensuring the effective separation of metal particles from slag.

[0049] The magnetic separation time of the drum magnetic separator is 10min~20min, which ensures that the slag after crushing has sufficient residence time in the magnetic field, so that the metal particles are fully adsorbed and removed, thus ensuring that the metal impurity content of the slag after pretreatment is <0.1%, thereby avoiding the metal impurities from entering the remelting space and affecting the metallurgical purity of the recycled slag, so that the slag system performance is restored to more than 95% of the initial state.

[0050] The magnetic field strength of the drum magnetic separator is 1000 Gs, 1100 Gs, 1200 Gs, 1300 Gs, 1400 Gs, 1500 Gs, etc. The magnetic separation time of the drum magnetic separator is 10 min, 12 min, 15 min, 18 min, 20 min, etc.

[0051] In some embodiments, the carbon source, the calcium carbonate source, and the calcium fluoride source are added to the bottom of the remelting space by uniformly mixing and spreading them out, and the thickness of the spread is 30mm~70mm. The total thickness of the mixed slag layer is 200mm~400mm.

[0052] Uniformly mixed and then spread out: This refers to the feeding method in which the carbon source, calcium carbonate source and calcium fluoride source are mixed evenly and then spread out in a flat manner before being added to the bottom of the remelting space.

[0053] The carbon source, calcium carbonate source, and calcium fluoride source are added to the bottom of the remelting space by uniformly mixing and spreading them out. This results in a uniformly composed bottom layer of materials at the bottom of the remelting space, ensuring that the contact interfaces between the reactants and the pretreated slag are evenly distributed after the slag is covered. This allows the reduction reaction of the carbon source with the metal oxide, the desulfurization reaction of the carbon dioxide produced by the decomposition of the calcium carbonate source with the calcium sulfide, and the decarbonization reaction of the carbon dioxide with the residual carbon to occur uniformly at the bottom of the slag layer. This avoids fluctuations in the slag composition caused by uneven local reactions, thereby restoring the slag performance to more than 95% of its initial state.

[0054] The thickness of the layer is 30mm~70mm, which controls the thickness of the bottom reactant layer within a reasonable range. This ensures that heat can be evenly transferred to the bottom material during the electric heating process and that the calcium carbonate source is fully decomposed. This allows the carbon dioxide generation rate and amount to meet the requirements of the desulfurization and decarbonization reactions, while avoiding incomplete decomposition due to an excessively thick bottom material or insufficient reactants due to an excessively thin bottom material.

[0055] The total thickness of the mixed slag layer is 200mm~400mm, thereby controlling the total thickness of the mixed material layer formed by the pretreated slag and the new slag within a reasonable range. This ensures the resistance heating efficiency and the uniformity of the slag layer temperature distribution after the electrode is inserted into the mixed slag layer, so that the electrothermal melting treatment can be carried out efficiently at a temperature of 1400℃~1600℃, thereby fully restoring the metallurgical function of the recycled slag.

[0056] The thickness of the flat layer is 30mm, 40mm, 50mm, 60mm, 70mm, etc. The total thickness of the mixed slag layer is 200mm, 250mm, 300mm, 350mm, 400mm, etc.

[0057] In some embodiments, the pretreated slag is added to the remelting space at a feeding rate of 1 kg / min to 3 kg / min.

[0058] The pretreated slag is added to the remelting space at a feeding rate of 1 kg / min to 3 kg / min. This controls the rate at which the pretreated slag enters the remelting space within a reasonable range, thus avoiding the accumulation and uneven distribution of the pretreated slag in the remelting space due to excessive feeding speed, or the low production efficiency due to excessive feeding speed. This ensures that the pretreated slag forms a uniform covering layer on top of the carbon source, calcium carbonate source, and calcium fluoride source, thereby ensuring a smooth contact interface between the pretreated slag and the underlying reactants and consistent reaction conditions. This allows the reduction reaction of the carbon source with metal oxides, the desulfurization reaction of carbon dioxide with calcium sulfide, and the decarbonization reaction of carbon dioxide with residual carbon to proceed uniformly, thereby restoring the slag system performance to more than 95% of its initial state.

[0059] Feeding speeds are: 1 kg / min, 1.5 kg / min, 2 kg / min, 2.5 kg / min, 3 kg / min, etc.

[0060] In some embodiments, during the electrothermal melting process, the electrode is inserted into the mixed slag layer to a depth of 50 mm to 120 mm. The temperature of the electric heating melting treatment is 1400℃~1600℃, and the holding time is 20min~40min.

[0061] During the electrothermal melting process, the electrode is inserted into the mixed slag layer to a depth of 50mm~120mm, thereby controlling the immersion depth of the electrode in the mixed slag layer within a reasonable range. This ensures the resistance heating efficiency and uniform current distribution between the electrode and the mixed slag layer, allowing the mixed slag layer to be uniformly heated to 1400℃~1600℃ under energized conditions.

[0062] The temperature of the electric heating melting treatment is 1400℃~1600℃, so that the mixed slag layer reaches the temperature condition for complete melting of the slag material. This allows the reduction reaction of carbon source and metal oxide, the reaction of calcium carbonate source decomposing to produce carbon dioxide, the desulfurization reaction of carbon dioxide and calcium sulfide, and the decarbonization reaction of carbon dioxide and residual carbon to be carried out efficiently in the high-temperature molten state, thereby fully removing sulfides and oxides in the slag system.

[0063] The heat preservation time is 20min~40min, which ensures sufficient time for chemical reaction in the high temperature molten state, thereby allowing the calcium carbonate source to decompose fully, the calcium sulfide to oxidize fully, and the residual carbon to react fully, so that the slag system composition and phase composition are fully restored, and the slag system performance is restored to more than 95% of the initial state.

[0064] The electrode insertion depth into the mixed slag layer is 50mm, 70mm, 80mm, 100mm, 120mm, etc. The electrothermal melting temperatures are 1400℃, 1450℃, 1500℃, 1550℃, 1600℃, etc. The holding times are 20min, 25min, 30min, 35min, 40min, etc.

[0065] In some embodiments, the used electroslag is derived from the electroslag remelting process of nickel-based superalloy IN718; The chemical composition of the new slag is: 55% calcium oxide, 35% aluminum oxide and 10% calcium fluoride.

[0066] IN718, a nickel-based superalloy, refers to a precipitation-hardening nickel-based superalloy containing elements such as nickel, chromium, iron, niobium, and molybdenum. This nickel-based superalloy IN718 is smelted using CaF2-Al2O3-CaO slag in the electroslag remelting process.

[0067] The electroslag used is derived from the electroslag remelting process of nickel-based superalloy IN718, thereby clarifying the source of the pretreated slag material and the initial slag system composition characteristics. Then, targeted repair is carried out on the deterioration mechanism of CaF2 volatilization, calcium sulfide enrichment, ferrous oxide and chromium oxide accumulation generated during the electroslag remelting process of this specific alloy system.

[0068] The chemical composition of the new slag is 55% calcium oxide, 35% aluminum oxide and 10% calcium fluoride. This determines the alkalinity and composition ratio of the new slag, so that when the new slag and the pretreated slag form a mixed slag layer, the slag system components can be gradually repaired and the performance can be complemented. This allows the chemical composition and metallurgical function of the recycled slag to be restored to a state comparable to that of the new slag, and the slag system performance to be restored to more than 95% of its initial state.

[0069] Secondly, embodiments of this application provide a post-use electroslag online regeneration system, comprising: The crushing and screening device uses electroslag remelting to crush the material and obtain crushed slag. A magnetic separation device is used to perform magnetic separation on the crushed slag to remove metal particles and obtain pretreated slag. An electroslag remelting crystallizer is used to contain and heat carbon source, calcium carbonate source, calcium fluoride source, pretreated slag and new slag to obtain recycled slag. The exhaust gas treatment device collects and treats the carbon monoxide and sulfur dioxide gases generated during the electric heating and melting process.

[0070] Crushing and screening device: refers to mechanical equipment used to crush used electroslag and obtain crushed slag material. This device includes a jaw crusher and a 2.5-mesh standard screen. Magnetic separation device: refers to mechanical equipment used to magnetically separate the crushed slag material and remove metal particles to obtain pretreated slag material. This magnetic separation device is a drum-type magnetic separator. Electroslag remelting crystallizer: refers to container equipment used to hold carbon source, calcium carbonate source, calcium fluoride source, pretreated slag material, and new slag, and to perform electrothermal melting to obtain recycled slag material. The electroslag remelting crystallizer forms a remelting space inside. Tail gas treatment device: refers to environmental protection equipment used to collect and treat carbon monoxide and sulfur dioxide gases generated during the electrothermal melting process.

[0071] The crushing and screening device crushes the used electroslag and obtains crushed slag, thereby mechanically reducing the particle size of the solid used electroslag, so that the particle size of the crushed slag is ≤5mm and meets the particle size requirements of subsequent magnetic separation.

[0072] The magnetic separator treats the crushed slag with magnetic separation and removes metal particles to obtain pretreated slag. The magnetic field separates the ferromagnetic metal particles in the crushed slag, thereby ensuring that the metal impurity content of the pretreated slag is less than 0.1%, thus ensuring the purity of the raw materials entering the electroslag remelting crystallizer.

[0073] The electroslag remelting crystallizer contains carbon source, calcium carbonate source, calcium fluoride source, pretreated slag and new slag, and heats and melts them to obtain recycled slag. In this way, a chemical reaction environment is created in the remelting space where carbon source reduces metal oxides and carbon dioxide generated by the decomposition of calcium carbonate source removes calcium sulfide and residual carbon. This allows sulfides and oxides in the slag system to be removed online and the performance of the slag system to be restored to more than 95% of its initial state.

[0074] The exhaust gas treatment device collects and treats the carbon monoxide and sulfur dioxide gases generated during the electric heating and melting process, thereby discharging the gaseous reaction products from the remelting space and treating them in an environmentally friendly manner. This prevents the accumulation of carbon monoxide and sulfur dioxide in the remelting space from affecting the reaction balance or causing safety hazards, thus ensuring that the online regeneration process meets the environmental protection requirements of industrial production.

[0075] This application embodiment constructs for the first time a complete system architecture for online regeneration of used electroslag. Through the series configuration of crushing and screening device, magnetic separation device, electroslag remelting crystallizer, and tail gas treatment device, the entire closed-loop treatment of used electroslag from pretreatment to online regeneration and tail gas treatment is realized, thereby solving the problems of resource waste and environmental pollution caused by the treatment of used electroslag as industrial waste in the prior art.

[0076] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to industry standards. If there is no corresponding industry standard, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0077] Example 1 Target audience: Electroslag remelting for nickel-based superalloy IN718 smelting Initial slag system: CaF2 70% + Al2O3 15% + CaO 15% The used electroslag is crushed to obtain crushed slag; the particle size of the crushed slag is ≤5mm.

[0078] The crushed slag is subjected to magnetic separation to remove metal particles, resulting in pretreated slag; the metal impurity content of the pretreated slag is 0.08%.

[0079] A carbon source, a calcium carbonate source, and a calcium fluoride source are added to the bottom of the remelting space. The mass of the carbon source is 3% of the mass of the pretreated slag, the mass of the calcium carbonate source is 30% of the mass of the pretreated slag, and the mass of the calcium fluoride source is the remainder after deducting the mass of the carbon source and the calcium carbonate source from the mass of the pretreated slag. The carbon source is graphite powder with a purity ≥99%, the calcium carbonate source is calcium carbonate powder with a purity ≥98%, and the calcium fluoride source is calcium fluoride powder with a purity ≥97%. The carbon source, the calcium carbonate source, and the calcium fluoride source are added to the bottom of the remelting space by uniformly mixing and then spreading them out, with a thickness of 50 mm.

[0080] The pretreated slag is added into the remelting space, covering the carbon source, the calcium carbonate source, and the calcium fluoride source; the pretreated slag is added into the remelting space at a feeding rate of 2 kg / min.

[0081] New slag is added to the remelting space to form a mixed slag layer with the pretreated slag material; the mass ratio of the new slag to the pretreated slag material is 1.0; the chemical composition of the new slag is: 55% calcium oxide, 35% aluminum oxide and 10% calcium fluoride; the total thickness of the mixed slag layer is 300 mm.

[0082] The mixed slag layer is subjected to electric heating and melting treatment to obtain recycled slag material; during the electric heating and melting treatment, the electrode is inserted into the mixed slag layer to a depth of 80 mm; the temperature of the electric heating and melting treatment is 1500℃, and the holding time is 30 min.

[0083] Results data: The desulfurization rate reached 98% of that of new slag; the content of ferrous oxide and chromium oxide in the slag was reduced by 85% compared with that before pretreatment; the content of metallic impurities was 0.08%; there were no slag grooves on the surface of the ingot; the grain size of the ingot was consistent with that of the new slag electroslag ingot; and the amount of new slag used was reduced by 50%.

[0084] Example 2 Target audience: Electroslag remelting for nickel-based superalloy IN718 smelting Initial slag system: CaF2 70% + Al2O3 15% + CaO 15% The used electroslag is crushed to obtain crushed slag; the particle size of the crushed slag is ≤5mm.

[0085] The crushed slag is subjected to magnetic separation to remove metal particles, resulting in pretreated slag; the metal impurity content of the pretreated slag is 0.06%.

[0086] A carbon source, a calcium carbonate source, and a calcium fluoride source are added to the bottom of the remelting space. The mass of the carbon source is 0.5% of the mass of the pretreated slag, the mass of the calcium carbonate source is 50% of the mass of the pretreated slag, and the mass of the calcium fluoride source is the remainder after deducting the mass of the carbon source and the calcium carbonate source from the mass of the pretreated slag. The carbon source is graphite powder with a purity ≥99%, the calcium carbonate source is calcium carbonate powder with a purity ≥98%, and the calcium fluoride source is calcium fluoride powder with a purity ≥97%. The carbon source, the calcium carbonate source, and the calcium fluoride source are added to the bottom of the remelting space by uniformly mixing and then spreading them out, with a layer thickness of 30 mm.

[0087] The pretreated slag is added into the remelting space, covering the carbon source, the calcium carbonate source, and the calcium fluoride source; the pretreated slag is added into the remelting space at a feeding rate of 1 kg / min.

[0088] New slag is added to the remelting space to form a mixed slag layer with the pretreated slag material; the mass ratio of the new slag to the pretreated slag material is 0.5; the chemical composition of the new slag is: 55% calcium oxide, 35% aluminum oxide and 10% calcium fluoride; the total thickness of the mixed slag layer is 200 mm.

[0089] The mixed slag layer is subjected to electric heating and melting treatment to obtain recycled slag material; during the electric heating and melting treatment, the electrode is inserted into the mixed slag layer to a depth of 50 mm; the temperature of the electric heating and melting treatment is 1400℃, and the holding time is 20 min.

[0090] Results data: The desulfurization rate reached 95% of that of new slag; the content of ferrous oxide and chromium oxide in the slag was reduced by 87% compared with that before pretreatment; the content of metallic impurities was 0.06%; and there were no slag grooves on the surface of the ingot.

[0091] Example 3 Target audience: Electroslag remelting for nickel-based superalloy IN718 smelting Initial slag system: CaF2 70% + Al2O3 15% + CaO 15% The used electroslag is crushed to obtain crushed slag; the particle size of the crushed slag is ≤5mm.

[0092] The crushed slag is subjected to magnetic separation to remove metal particles, resulting in pretreated slag; the metal impurity content of the pretreated slag is 0.07%.

[0093] A carbon source, a calcium carbonate source, and a calcium fluoride source are added to the bottom of the remelting space. The mass of the carbon source is 10% of the mass of the pretreated slag, the mass of the calcium carbonate source is 40% of the mass of the pretreated slag, and the mass of the calcium fluoride source is the remainder after deducting the mass of the carbon source and the calcium carbonate source from the mass of the pretreated slag. The carbon source is graphite powder with a purity ≥99%, the calcium carbonate source is calcium carbonate powder with a purity ≥98%, and the calcium fluoride source is calcium fluoride powder with a purity ≥97%. The carbon source, the calcium carbonate source, and the calcium fluoride source are added to the bottom of the remelting space by uniformly mixing and then spreading them out, with a thickness of 70 mm.

[0094] The pretreated slag is added into the remelting space, covering the carbon source, the calcium carbonate source, and the calcium fluoride source; the pretreated slag is added into the remelting space at a feeding rate of 3 kg / min.

[0095] New slag is added to the remelting space to form a mixed slag layer with the pretreated slag material; the mass ratio of the new slag to the pretreated slag material is 0.8; the chemical composition of the new slag is: 55% calcium oxide, 35% aluminum oxide and 10% calcium fluoride; the total thickness of the mixed slag layer is 400 mm.

[0096] The mixed slag layer is subjected to electric heating and melting treatment to obtain recycled slag material; during the electric heating and melting treatment, the electrode is inserted into the mixed slag layer to a depth of 120 mm; the temperature of the electric heating and melting treatment is 1600℃, and the holding time is 40 min.

[0097] Results data: The desulfurization rate reached 96% of that of new slag; the content of ferrous oxide and chromium oxide in the slag was reduced by 90% compared with that before pretreatment; the content of metallic impurities was 0.07%; and there were no slag grooves on the surface of the ingot.

[0098] Example 4 Target audience: Electroslag remelting for nickel-based superalloy IN718 smelting Initial slag system: CaF2 70% + Al2O3 15% + CaO 15% The used electroslag is crushed to obtain crushed slag; the particle size of the crushed slag is ≤5mm.

[0099] The crushed slag is subjected to magnetic separation to remove metal particles, resulting in pretreated slag; the metal impurity content of the pretreated slag is 0.05%.

[0100] A carbon source, a calcium carbonate source, and a calcium fluoride source are added to the bottom of the remelting space. The mass of the carbon source is 5% of the mass of the pretreated slag, the mass of the calcium carbonate source is 35% of the mass of the pretreated slag, and the mass of the calcium fluoride source is the remainder after deducting the mass of the carbon source and the calcium carbonate source from the mass of the pretreated slag. The carbon source is graphite powder with a purity ≥99%, the calcium carbonate source is calcium carbonate powder with a purity ≥98%, and the calcium fluoride source is calcium fluoride powder with a purity ≥97%. The carbon source, the calcium carbonate source, and the calcium fluoride source are added to the bottom of the remelting space by uniformly mixing and then spreading them out, with a thickness of 40 mm.

[0101] The pretreated slag is added into the remelting space, covering the carbon source, the calcium carbonate source, and the calcium fluoride source; the pretreated slag is added into the remelting space at a feeding rate of 1.5 kg / min.

[0102] New slag is added to the remelting space to form a mixed slag layer with the pretreated slag material; the mass ratio of the new slag to the pretreated slag material is 0.6; the chemical composition of the new slag is: 55% calcium oxide, 35% aluminum oxide and 10% calcium fluoride; the total thickness of the mixed slag layer is 250 mm.

[0103] The mixed slag layer is subjected to electric heating and melting treatment to obtain recycled slag material; during the electric heating and melting treatment, the electrode is inserted into the mixed slag layer to a depth of 70 mm; the temperature of the electric heating and melting treatment is 1450℃, and the holding time is 25 min.

[0104] Results data: The desulfurization rate reached 97% of that of new slag; the content of ferrous oxide and chromium oxide in the slag was reduced by 88% compared with that before pretreatment; the content of metallic impurities was 0.05%; and there were no slag grooves on the surface of the ingot.

[0105] Example 5 Target audience: Electroslag remelting for nickel-based superalloy IN718 smelting Initial slag system: CaF2 70% + Al2O3 15% + CaO 15% The used electroslag is crushed to obtain crushed slag; the particle size of the crushed slag is ≤5mm.

[0106] The crushed slag is subjected to magnetic separation to remove metal particles, resulting in pretreated slag; the metal impurity content of the pretreated slag is 0.09%.

[0107] A carbon source, a calcium carbonate source, and a calcium fluoride source are added to the bottom of the remelting space. The mass of the carbon source is 7% of the mass of the pretreated slag, the mass of the calcium carbonate source is 45% of the mass of the pretreated slag, and the mass of the calcium fluoride source is the remainder after deducting the mass of the carbon source and the calcium carbonate source from the mass of the pretreated slag. The carbon source is graphite powder with a purity ≥99%, the calcium carbonate source is calcium carbonate powder with a purity ≥98%, and the calcium fluoride source is calcium fluoride powder with a purity ≥97%. The carbon source, the calcium carbonate source, and the calcium fluoride source are added to the bottom of the remelting space by uniformly mixing and then spreading them out, with a thickness of 60 mm.

[0108] The pretreated slag is added into the remelting space, covering the carbon source, the calcium carbonate source, and the calcium fluoride source; the pretreated slag is added into the remelting space at a feeding rate of 2.5 kg / min.

[0109] New slag is added to the remelting space to form a mixed slag layer with the pretreated slag material; the mass ratio of the new slag to the pretreated slag material is 0.9; the chemical composition of the new slag is: 55% calcium oxide, 35% aluminum oxide and 10% calcium fluoride; the total thickness of the mixed slag layer is 350 mm.

[0110] The mixed slag layer is subjected to electric heating and melting treatment to obtain recycled slag material; during the electric heating and melting treatment, the electrode is inserted into the mixed slag layer to a depth of 100 mm; the temperature of the electric heating and melting treatment is 1550℃, and the holding time is 35 min.

[0111] Results data: The desulfurization rate reached 96% of that of new slag; the content of ferrous oxide and chromium oxide in the slag was reduced by 89% compared with that before pretreatment; the content of metallic impurities was 0.09%; and there were no slag grooves on the surface of the ingot.

[0112] Comparative Example 1 Target audience: Electroslag remelting for nickel-based superalloy IN718 smelting The used electroslag is crushed to obtain crushed slag; the particle size of the crushed slag is ≤5mm.

[0113] The crushed slag is subjected to magnetic separation to remove metal particles, resulting in pretreated slag; the metal impurity content of the pretreated slag is <0.1%.

[0114] The pretreated slag is completely recycled. The electroslag remelting equipment is started, the electrode is inserted into the pretreated slag to a depth of 80 mm, the temperature is raised to 1500 °C and held for 30 min.

[0115] Results data: Slag grooves appeared on the surface of the ingot, and the desulfurization rate was 20%.

[0116] Comparative Example 2 Target audience: Electroslag remelting for nickel-based superalloy IN718 smelting The used electroslag is crushed to obtain crushed slag; the particle size of the crushed slag is ≤5mm.

[0117] The crushed slag is subjected to magnetic separation to remove metal particles, resulting in pretreated slag; the metal impurity content of the pretreated slag is 0.08%.

[0118] A carbon source is added to the bottom of the remelting space; the mass of the carbon source is 3% of the mass of the pretreated slag; the carbon source is graphite powder with a purity of ≥99%.

[0119] The pretreated slag is added into the remelting space, covering the carbon source.

[0120] Fresh slag is added to the remelting space to form a mixed slag layer with the pretreated slag; the mass ratio of the fresh slag to the pretreated slag is 1.0; the chemical composition of the fresh slag is: 55% calcium oxide, 35% aluminum oxide and 10% calcium fluoride.

[0121] The mixed slag layer is subjected to electric heating to melt it; the temperature of the electric heating melting treatment is 1500℃, and the holding time is 30min.

[0122] Results data: Slight slag grooves appeared on the surface of the ingot, the desulfurization rate reached 60% of the desulfurization rate of new slag, and the content of ferrous oxide and chromium oxide in the slag was reduced by 82% compared with that before pretreatment.

[0123] Comparative Example 3 Target audience: Electroslag remelting for nickel-based superalloy IN718 smelting The used electroslag is crushed to obtain crushed slag; the particle size of the crushed slag is ≤5mm.

[0124] The crushed slag is subjected to magnetic separation to remove metal particles, resulting in pretreated slag; the metal impurity content of the pretreated slag is 0.07%.

[0125] Calcium carbonate source and calcium fluoride source are added to the bottom of the remelting space; the mass of the calcium carbonate source is 30% of the mass of the pretreated slag, and the mass of the calcium fluoride source is the remainder after deducting the mass of the calcium carbonate source from the mass of the pretreated slag; the calcium carbonate source is calcium carbonate powder with a purity ≥ 98%, and the calcium fluoride source is calcium fluoride powder with a purity ≥ 97%.

[0126] The pretreated slag is added into the remelting space, covering the calcium carbonate source and the calcium fluoride source.

[0127] Fresh slag is added to the remelting space to form a mixed slag layer with the pretreated slag; the mass ratio of the fresh slag to the pretreated slag is 1.0; the chemical composition of the fresh slag is: 55% calcium oxide, 35% aluminum oxide and 10% calcium fluoride.

[0128] The mixed slag layer is subjected to electric heating to melt it; the temperature of the electric heating melting treatment is 1500℃, and the holding time is 30min.

[0129] Results data: Slag grooves appeared on the surface of the ingot, the desulfurization rate reached 45% of the desulfurization rate of new slag, and the content of ferrous oxide and chromium oxide in the slag was reduced by 15% compared with that before pretreatment.

[0130] Comparative Example 4 Target audience: Electroslag remelting for nickel-based superalloy IN718 smelting The used electroslag is crushed to obtain crushed slag; the particle size of the crushed slag is ≤5mm.

[0131] The crushed slag is subjected to magnetic separation to remove metal particles, resulting in pretreated slag; the metal impurity content of the pretreated slag is 0.06%.

[0132] A carbon source, a calcium carbonate source, and a calcium fluoride source are added to the bottom of the remelting space. The mass of the carbon source is 15% of the mass of the pretreated slag, the mass of the calcium carbonate source is 30% of the mass of the pretreated slag, and the mass of the calcium fluoride source is the remainder after deducting the mass of the carbon source and the mass of the calcium carbonate source from the mass of the pretreated slag. The carbon source is graphite powder with a purity ≥ 99%, the calcium carbonate source is calcium carbonate powder with a purity ≥ 98%, and the calcium fluoride source is calcium fluoride powder with a purity ≥ 97%.

[0133] The pretreated slag is added into the remelting space, covering the carbon source, the calcium carbonate source, and the calcium fluoride source.

[0134] Fresh slag is added to the remelting space to form a mixed slag layer with the pretreated slag; the mass ratio of the fresh slag to the pretreated slag is 1.0; the chemical composition of the fresh slag is: 55% calcium oxide, 35% aluminum oxide and 10% calcium fluoride.

[0135] The mixed slag layer is subjected to electric heating to melt it; the temperature of the electric heating melting treatment is 1500℃, and the holding time is 30min.

[0136] Results data: Carbon inclusion defects appeared on the surface of the ingot, the desulfurization rate reached 70% of the desulfurization rate of new slag, and the residual carbon content in the slag exceeded the standard.

[0137] Comparative Example 5 Target audience: Electroslag remelting for nickel-based superalloy IN718 smelting The used electroslag is crushed to obtain crushed slag; the particle size of the crushed slag is ≤5mm.

[0138] The crushed slag is subjected to magnetic separation to remove metal particles, resulting in pretreated slag; the metal impurity content of the pretreated slag is 0.08%.

[0139] A carbon source, a calcium carbonate source, and a calcium fluoride source are added to the bottom of the remelting space. The mass of the carbon source is 3% of the mass of the pretreated slag, the mass of the calcium carbonate source is 20% of the mass of the pretreated slag, and the mass of the calcium fluoride source is the remainder after deducting the mass of the carbon source and the mass of the calcium carbonate source from the mass of the pretreated slag. The carbon source is graphite powder with a purity ≥ 99%, the calcium carbonate source is calcium carbonate powder with a purity ≥ 98%, and the calcium fluoride source is calcium fluoride powder with a purity ≥ 97%.

[0140] The pretreated slag is added into the remelting space, covering the carbon source, the calcium carbonate source, and the calcium fluoride source.

[0141] Fresh slag is added to the remelting space to form a mixed slag layer with the pretreated slag; the mass ratio of the fresh slag to the pretreated slag is 1.0; the chemical composition of the fresh slag is: 55% calcium oxide, 35% aluminum oxide and 10% calcium fluoride.

[0142] The mixed slag layer is subjected to electric heating to melt it; the temperature of the electric heating melting treatment is 1500℃, and the holding time is 30min.

[0143] Results data: Slight slag grooves appeared on the surface of the ingot, the desulfurization rate reached 75% of the desulfurization rate of new slag, and the removal rate of calcium sulfide in the slag was insufficient.

[0144] Experimental methods for evaluating results: 1. Desulfurization rate determination method The desulfurization rate was determined using a sulfur content analysis method. The sulfur content of the alloy liquid obtained from the electroslag remelting process with virgin slag was measured as a baseline value, and the sulfur content of the alloy liquid obtained in each example and comparative example was measured as the measured value. The desulfurization rate was calculated using the formula: Desulfurization rate = (Initial sulfur content - Final sulfur content) / Initial sulfur content × 100%. The desulfurization rate of the examples is expressed as a percentage relative to the desulfurization rate of virgin slag.

[0145] 2. Methods for determining the content of ferrous oxide and chromium oxide The contents of ferrous oxide and chromium oxide in the slag were determined by X-ray fluorescence spectrometry (XRF). The contents of ferrous oxide and chromium oxide in the pretreated slag were measured as initial values, and the contents of ferrous oxide and chromium oxide in the slag after electrothermal melting were measured as final values. The reduction rate of ferrous oxide and chromium oxide content was calculated using the formula: Reduction rate = (Initial content - Final content) / Initial content × 100%.

[0146] 3. Methods for determining the content of metallic impurities The content of metal elements such as iron and chromium in the slag was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) and converted into the percentage of metal impurities.

[0147] 4. Ingot Surface Quality Inspection Methods The surface of the ingot obtained by electroslag remelting was inspected using a combination of visual inspection and penetrant testing methods. The presence and severity of surface defects such as slag grooves, cracks, and inclusions were recorded.

[0148] 5. Ingot Grain Size Testing Method Metallographic microscopy was used to observe the specimens, which were prepared according to the standard metallographic sample preparation procedure. After etching, the grain morphology and size of the ingots were observed and compared with the grain size of the new slag electroslag ingots for evaluation.

[0149] 6. Calculation method for the reduction rate of new slag usage The reduction rate of new slag usage = (new slag usage in conventional processes - new slag usage in this process) / new slag usage in conventional processes × 100%.

[0150] 7. Method for determining residual carbon content The residual carbon content in the slag was determined using a high-frequency infrared carbon-sulfur analyzer, and compared with the standard allowable value to determine whether it exceeded the standard.

[0151] 8. Evaluation method for calcium sulfide removal The presence of calcium sulfide phase in the slag was qualitatively detected by X-ray diffraction (XRD) analysis, and the removal rate of calcium sulfide was calculated by combining the sulfur element mass balance.

[0152] As shown by the above performance data, the technological advancements of this application's technical solution include: 1. Significant improvement in desulfurization efficiency The desulfurization rates of Examples 1 to 5 all reached over 95% of the desulfurization rate of virgin slag, specifically 95% to 98%, while the desulfurization rate of Comparative Example 1 was only 20%, and the desulfurization rates of Comparative Examples 2 to 5 were 60%, 45%, 70%, and 75% of the desulfurization rate of virgin slag, respectively. The technical solution of this application, through the synergistic effect of carbon source reducing metal oxides and carbon dioxide generated from the decomposition of calcium carbonate source to remove calcium sulfide, improves the desulfurization efficiency by 375% to 490% compared to directly reusing post-use electroslag, and by 58% to 118% compared to some technical solutions that only add carbon source or only add calcium carbonate source, thereby solving the key problem of liquid metal resulfurization caused by the reuse of post-use electroslag.

[0153] 2. Significantly improved oxide removal efficiency The reduction rates of ferrous oxide and chromium oxide content in Examples 1 to 5 all reached over 85%, specifically 85% to 90%, while the reduction rate of ferrous oxide and chromium oxide content in Comparative Example 3 was only 15%. The technical solution of this application, through the synergistic ratio of carbon source, calcium carbonate source, and calcium fluoride source, improves the oxide removal efficiency by 467% to 500% compared to technical solutions that only add calcium carbonate and calcium fluoride sources without adding carbon sources, thereby effectively eliminating the disruption of the oxygen potential balance of the slag system by non-metallic oxides.

[0154] 3. Comprehensive improvement in ingot surface quality The ingots of Examples 1 to 5 showed no slag grooves on their surfaces, while the ingots of Comparative Examples 1 and 3 showed slag grooves. The ingots of Comparative Examples 2 and 5 showed slight slag grooves, and the ingot of Comparative Example 4 showed carbon inclusion defects. The technical solution of this application completely eliminates surface defects of the ingots through the optimization and synergistic reaction of the carbon source, calcium carbonate source, and calcium fluoride source, thereby achieving a surface quality comparable to that of virgin slag electroslag ingots.

[0155] 4. Stable control of metal impurity content The metal impurity content in Examples 1 to 5 was consistently between 0.05% and 0.09%, and all were below 0.1%, indicating that the technical solution of this application, through the control of process parameters of crushing and magnetic separation, can stably remove metal particles from the used electroslag, thereby ensuring the metallurgical purity of the recycled slag.

[0156] 5. Significant reduction in the amount of new slag used The reduction rate of new slag usage in Example 1 reached 50%, indicating that the technical solution of this application achieves efficient recycling of used electroslag through online regeneration and reuse, thereby significantly reducing the production cost of the electroslag remelting process.

[0157] 6. Full recovery of slag system performance The grain size of the ingot in Example 1 is consistent with that of the new slag electroslag ingot, indicating that the technical solution of this application restores the slag system performance to more than 95% of its initial state through a triple mechanism of carbon source reduction of oxides, carbon dioxide removal of calcium sulfide and residual carbon, and calcium fluoride source adjustment of melting point and fluidity, thereby achieving in-situ restoration of the electroslag metallurgical function after use.

[0158] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for online regeneration of electroslag after use, characterized in that, Includes the following steps: The used electroslag is crushed to obtain crushed slag; the particle size of the crushed slag is ≤5mm. The crushed slag is subjected to magnetic separation to remove metal particles, resulting in pretreated slag; the metal impurity content of the pretreated slag is <0.1%; A carbon source, a calcium carbonate source, and a calcium fluoride source are added to the bottom of the remelting space; the mass of the carbon source is 0.5% to 10% of the mass of the pretreated slag, the mass of the calcium carbonate source is 30% to 50% of the mass of the pretreated slag, and the mass of the calcium fluoride source is the remainder after deducting the mass of the carbon source and the calcium carbonate source from the mass of the pretreated slag. The pretreated slag is added into the remelting space, covering the carbon source, the calcium carbonate source, and the calcium fluoride source. New slag is added into the remelting space to form a mixed slag layer with the pretreated slag; the mass ratio of the new slag to the pretreated slag is 0.5~1. The mixed slag layer is melted by electric heating to obtain recycled slag.

2. The method for online regeneration of electroslag after use according to claim 1, characterized in that, The electrothermal melting process includes: The carbon source undergoes a reduction reaction with the metal oxides in the pretreated slag. The calcium carbonate source decomposes upon heating to produce carbon dioxide. The carbon dioxide reacts with the calcium sulfide in the pretreated slag to produce calcium oxide and sulfur dioxide gas. The carbon dioxide reacts with the residual carbon in the carbon source that did not participate in the reduction reaction to generate carbon monoxide gas.

3. The method for online regeneration of electroslag after use according to claim 2, characterized in that, The metal oxides include ferrous oxide and chromium oxide; the reduction reaction reduces the content of ferrous oxide and chromium oxide in the pretreated slag by ≥85% compared with that before pretreatment.

4. The method for online regeneration of electroslag after use according to claim 1, characterized in that, The carbon source is graphite powder with a purity of ≥99%, the calcium carbonate source is calcium carbonate powder with a purity of ≥98%, and the calcium fluoride source is calcium fluoride powder with a purity of ≥97%.

5. The method for online regeneration of electroslag after use according to claim 1, characterized in that, The crushing process employs a jaw crusher; the crushed slag is screened using a 2.5-mesh standard sieve. The magnetic separation process employs a drum-type magnetic separator; the magnetic field strength of the drum-type magnetic separator is 1000 Gs to 1500 Gs, and the magnetic separation time is 10 min to 20 min.

6. The method for online regeneration of electroslag after use according to claim 1, characterized in that, The carbon source, the calcium carbonate source, and the calcium fluoride source are added to the bottom of the remelting space by uniformly mixing and spreading them out, and the thickness of the spread is 30mm~70mm. The total thickness of the mixed slag layer is 200mm~400mm.

7. The method for online regeneration of electroslag after use according to claim 1, characterized in that, The pretreated slag is added into the remelting space at a feeding rate of 1 kg / min to 3 kg / min.

8. The method for online regeneration of electroslag after use according to claim 1, characterized in that, During the electrothermal melting process, the electrode is inserted into the mixed slag layer to a depth of 50mm~120mm. The temperature of the electric heating melting treatment is 1400℃~1600℃, and the holding time is 20min~40min.

9. The method for online regeneration of electroslag after use according to claim 1, characterized in that, The electroslag used is derived from the electroslag remelting process of nickel-based superalloy IN718. The chemical composition of the new slag is: 55% calcium oxide, 35% aluminum oxide and 10% calcium fluoride.

10. A post-use electroslag online regeneration system, characterized in that, include: The crushing and screening device uses electroslag remelting to crush the material and obtain crushed slag. A magnetic separation device is used to perform magnetic separation on the crushed slag to remove metal particles and obtain pretreated slag. An electroslag remelting crystallizer is used to contain and heat carbon source, calcium carbonate source, calcium fluoride source, pretreated slag and new slag to obtain recycled slag. The exhaust gas treatment device collects and treats the carbon monoxide and sulfur dioxide gases generated during the electric heating and melting process.