Method for preparing monel alloy by deep desulfurization of copper-nickel intermediate alloy

Abstract

The application discloses a method for preparing monel alloy through deep desulfurization of copper-nickel intermediate alloy, which uses high-sulfur copper-nickel intermediate alloy reduced from smelting solid waste as raw material, melts through a non-vacuum induction furnace, refines through an AOD furnace, compounding remelting through a vacuum induction furnace, deep impurity removal through an electroslag furnace and casting to obtain the monel alloy. The AOD furnace adopts a three-time circulating slagging-desulfurization-discharging process, and is matched with a silicon-calcium block, lime and fluorite composite slag system and bottom-side blowing composite argon stirring, so that the alkalinity, slag layer thickness and deoxidization condition are accurately controlled to realize deep desulfurization. Subsequently, the vacuum impurity removal and electroslag remelting are further used for purifying and optimizing the organization. The prepared monel alloy has S less than or equal to 0.005%, low impurity content, solves the problems of incomplete desulfurization and high cost in the traditional process, and realizes solid waste resource utilization and low-cost and efficient preparation.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal metallurgical refining technology, and specifically relates to a method for deep desulfurization of copper-nickel master alloys to prepare Monel alloys. Background Technology

[0002] Monel alloys, as high-performance copper-nickel based alloys, possess excellent corrosion resistance, high-temperature resistance, and mechanical properties, and are widely used in high-end fields such as aerospace, marine engineering, and chemical equipment. Traditional Monel alloy production often uses high-purity electrolytic copper and electrolytic nickel as raw materials, resulting in high costs and significant resource consumption. However, copper-nickel smelting solid waste generated by the metallurgical industry contains a certain amount of copper and nickel resources. If this waste can be reduced and purified into copper-nickel master alloys and used in Monel alloy production, it will not only reduce raw material costs but also achieve solid waste resource utilization, aligning with the trend of green metallurgy development.

[0003] However, the sulfur content in copper-nickel master alloys obtained from the reduction of smelting solid waste is high (0.5%-0.8%), far exceeding the sulfur requirements of Monel alloys (typically ≤0.005%). Sulfur easily forms low-melting-point sulfides (such as Ni3S2 and Cu2S) in the alloy, leading to deterioration of the alloy's hot working properties, hot brittleness, and seriously affecting product quality. Existing desulfurization processes mostly employ single-batch slag-forming desulfurization or vacuum desulfurization, which suffer from low desulfurization efficiency, long processing time, and low copper-nickel yield, making it difficult to meet the needs of industrial production. Therefore, developing a highly efficient deep desulfurization process for copper-nickel master alloys is of great significance for promoting the resource utilization of smelting solid waste and the low-cost preparation of Monel alloys.

[0004] Currently, the purification of copper-nickel master alloys mainly employs electrolysis technology. High-purity electrolytic copper and nickel are obtained through electrolytic separation. While this achieves metal purification, the process suffers from drawbacks such as long process time, high energy consumption, high production costs, and low efficiency. Furthermore, the electrolytic products need to be remelted to prepare the copper-nickel alloy, adding to the production steps. To address these issues, the industry has attempted to use traditional furnace slag-forming desulfurization processes to treat copper-nickel master alloys. However, these processes suffer from incomplete desulfurization, poor slag-metal separation, low metal yield, and high auxiliary material consumption, making it difficult to reduce the sulfur content to below 0.005% for industrial applications. Simultaneously, the slag thickness in traditional desulfurization processes often fails to meet the mass transfer efficiency requirements for sulfur, resulting in unreasonable design, low alkalinity control precision, and poor desulfurization reaction kinetics. This leads to low desulfurization efficiency and long reaction times, failing to meet the demands of continuous industrial production. Summary of the Invention

[0005] One object of the present invention is to provide a method for preparing Monel alloy by deep desulfurization of copper-nickel master alloy, comprising the following steps: S1. The copper-nickel master alloy is melted into a copper-nickel alloy liquid using a non-vacuum induction furnace, wherein the sulfur content in the copper-nickel master alloy is 0.5%-0.8%; S2. Pour the molten copper-nickel alloy liquid into the AOD furnace, heat it and introduce argon gas; S3 and AOD furnaces are used for slag formation, desulfurization and slag discharge to complete desulfurization; S4. The desulfurized alloy liquid is fed into a vacuum induction furnace for remelting and recombining. After casting and cooling, a Monel alloy electrode rod is obtained. S5. Place the Monel alloy electrode rod in an electroslag furnace for melting and deep impurity removal to obtain the standard Monel alloy product.

[0006] Preferably, in S3, the slag formation, desulfurization, and slag discharge are repeated three times in a single cycle, with each operation including: First, add 4-5 kg / t of calcium silicate blocks, 20-25 kg / t of lime, and 10-12 kg / t of fluorite, and control the slag basicity CaO / SiO2 = 3.5-4.0; Secondly, the AOD furnace is started with bottom-blowing and side-blowing combined argon gas stirring, with a total argon gas flow rate of 0.8-1.2 Nm³. 3 Stir at a speed of 1 / min for 20 minutes; Next, after stirring, completely drain the residue.

[0007] The next operation should be carried out within 5-10 minutes after the slag is discharged.

[0008] The same mass of silicon-calcium blocks is added each time, which can quickly and deeply desulfurize the sulfur, and the reaction endpoint is easy to control during the desulfurization process.

[0009] The selected slag-forming agent contains effective elements such as CaO, which have a high bonding strength with S, forming a sulfur-containing refractory slag for removal.

[0010] Preferably, in step S1, a copper slag-forming agent is added to the bottom of a non-vacuum induction furnace, followed by the addition of a copper-nickel master alloy ingot. The mass ratio of the copper slag-forming agent to the copper-nickel master alloy is 1:1000. The furnace is heated to 1250-1350℃ and kept at a constant temperature for 80-100 minutes to form a copper-nickel alloy liquid.

[0011] Preferably, in step S5, the slag system is CaF2-Al2O3-CaO (mass ratio 60:20:20), the furnace temperature is 1600-1650℃, and the remelting rate is 2-3 kg / min.

[0012] Preferably, during each desulfurization process, the slag layer thickness inside the AOD furnace is controlled at 80-120 mm to ensure that the mass transfer path of sulfur is ≤5 mm.

[0013] Preferably, the ratio of lime to fluorite is 2:1 to 2.5:1. Under this ratio, the slag-forming white slag system fully adsorbs various impurities in the melt, and the temperature is controlled at 1350℃.

[0014] Preferably, in step S3, the alloy liquid is heated to 1650±10℃, and the flow rate of stirring argon gas is 0.3-0.5 Nm. 3 / min.

[0015] Preferably, aluminum particles are added at the same time as the calcium silicate blocks, with 0.3-0.8 kg / t of aluminum particles. The aluminum particles act as a deoxidizer, and react with the alloy liquid to achieve deep deoxidation, so that [O] in the alloy liquid is <20 ppm.

[0016] Preferably, in step S4, the casting temperature is 1580-1600℃, the mold preheating temperature is 300-400℃, the casting speed is 0.8-1.2t / min, and the Monel alloy electrode rod is obtained after cooling.

[0017] Preferably, the prepared Monel alloy has the following chemical composition by mass percentage: Cu 66%-69%, Ni 29%-32%, S≤0.005%, C≤0.02%, Fe≤0.5%, Si≤0.1%, with the balance being unavoidable impurity elements.

[0018] The present invention has the following beneficial effects: This invention uses high-sulfur copper-nickel master alloy reduced from smelting solid waste as raw material to prepare Monel alloy, replacing traditional high-purity electrolytic copper-nickel, significantly reducing raw material costs and realizing the resource utilization of solid waste, which is in line with the development trend of green metallurgy. It adopts a three-cycle slag-desulfurization-slag discharge process in an AOD furnace, combined with precise slag system ratio, alkalinity control and bottom-side blowing combined argon gas stirring, which can efficiently reduce the sulfur content from 0.5%~0.8% to ≤0.005%, and the desulfurization is thorough and stable. Simultaneously, it is combined with deep deoxidation and vacuum induction furnace and electroslag furnace combined remelting process to achieve deoxidation, degassing and deep impurity removal of alloy liquid, with oxygen content below 20ppm, significantly reducing the number of inclusions, and the ingot structure is dense and uniform without porosity and shrinkage defects. The final Monel alloy has a precise and controllable composition and low content of harmful impurities.

[0019] This invention addresses the problems of low mass transfer efficiency and long reaction cycle in traditional desulfurization processes. By precisely controlling the slag layer thickness to 80-120mm, the mass transfer path of sulfur is shortened to less than 5mm, reducing the time for the desulfurization reaction to reach equilibrium and shortening the total desulfurization time. Compared with traditional multi-furnace repeated desulfurization processes, production efficiency is improved.

[0020] The deoxidation-desulfurization synergistic mechanism of stepwise equal addition of silicon-calcium blocks in this invention continuously maintains an ultra-low oxygen environment in the alloy liquid by adding silicon-calcium blocks and aluminum granules in three batches in equal amounts, preventing the problems of local over-addition, high burn-off rate, and low effective utilization rate caused by one-time addition of deoxidizer; at the same time, by using a precise ratio of lime to fluorite of 2:1 to 2.5:1, the melting point of the slag system is reduced to 1350℃, which has good fluidity and sulfur capacity at the desulfurization temperature. The amount of fluorite used is reduced, the consumption of lime auxiliary materials is reduced, the input of slag-forming auxiliary materials is reduced, and the production cost is reduced.

[0021] Meanwhile, the three-batch gradient slag replacement process achieves near full utilization of the sulfur capacity of the slag system, with the sulfur saturation of each batch of discharged slag exceeding 90%, resulting in a reduction in the amount of desulfurization slag generated compared to traditional slag-making processes. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] This invention discloses a method for preparing Monel alloy through deep desulfurization of copper-nickel master alloy, specifically including the following steps: S1. The copper-nickel master alloy is melted into a copper-nickel alloy liquid using a non-vacuum induction furnace, wherein the sulfur content in the copper-nickel master alloy is 0.5%-0.8%; S2. Pour the molten copper-nickel alloy liquid into the AOD furnace, heat it and introduce argon gas; S3 and AOD furnaces are used for slag formation, desulfurization and slag discharge to complete desulfurization; S4. The desulfurized alloy liquid is fed into a vacuum induction furnace for remelting and recombining. After casting and cooling, a Monel alloy electrode rod is obtained.

[0024] S5. Place the Monel alloy electrode rod in an electroslag furnace for melting and deep impurity removal to obtain the standard Monel alloy product.

[0025] In this invention, a copper-nickel master alloy obtained by reduction and purification of copper-nickel smelting solid waste is used as raw material. The mass percentage of the components of the copper-nickel master alloy is Cu 65%-68%, Ni 28%-30%, and S 0.5%-0.8%.

[0026] In S1, a copper slag-forming agent is added to the bottom of a non-vacuum induction furnace, with the ratio of the copper slag-forming agent to the copper-nickel master alloy being 1:1000.

[0027] The copper-nickel intermediate alloy ingot is placed in a non-vacuum induction furnace and heated to 1250-1350℃ for 80-100 minutes to form a copper-nickel alloy liquid.

[0028] The copper-nickel alloy liquid is then heated to 1480-1500℃, transferred through an intermediate ladle, and sent into the AOD furnace.

[0029] In S2, argon gas is introduced into the AOD furnace to raise the temperature of the alloy liquid to 1650±10℃ and maintain it until the desulfurization is completed.

[0030] In S3, three consecutive slag-making, desulfurization, and slag discharge processes are carried out in the AOD furnace. After each slag discharge, the sulfur content in the molten alloy liquid is tested until the standard of S≤0.005% is obtained, thus completing the S3 desulfurization.

[0031] The single-stage slag formation, desulfurization, and slag discharge methods are as follows: First, add calcium silicate blocks, lime, and fluorite simultaneously, and control the slag basicity CaO / SiO2 = 3.5-4.0; Secondly, argon gas is simultaneously blown from the bottom and side inside the AOD furnace to stir the material for 20 minutes, and the FeO content in the slag is controlled to be ≤0.5% during the stirring process. Next, after stirring, the slag is discharged.

[0032] Among them, the slag-forming agent composed of calcium silicate blocks, lime and fluorite has a high bonding strength between effective elements such as CaO and S, forming a sulfur-containing refractory slag for removal.

[0033] Aluminum granules are added at the same time as the calcium silicate blocks, at a rate of 0.3-0.8 kg / t. The aluminum granules act as a deoxidizer, and the aluminum metal combines with oxygen to achieve deep deoxidation, so that the [O] in the alloy liquid is less than 20 ppm.

[0034] The amount of calcium silicate blocks added each time is 4-5 kg / t. The composition of the calcium silicate blocks is (wt%) Ca 30%-35% and Si 60%-65%, with a particle size of 10-30 mm. The mass of calcium silicate blocks added each time is the same, which can achieve rapid and deep desulfurization, and the reaction endpoint is easy to control during desulfurization.

[0035] The amount of lime added each time is 20-25 kg / t. The amount of fluorite added each time is 10-12 kg / t. The ratio of lime to fluorite is 2:1-2.5:1. Under this ratio, the melting point of the slag-forming system is 1350℃, which can fully adsorb impurities in the solution.

[0036] The total argon flow rate for each bottom and side blow is 0.8-1.2 Nm³. 3 / min, stirring time 20min.

[0037] Within 5-10 minutes after slag removal, allow the alloy liquid to settle and become uniform before proceeding to the next operation.

[0038] The thickness of the slag layer in the AOD furnace formed by a single slag making and desulfurization process is 80-120mm, which helps to ensure that the mass transfer path of sulfur is ≤5mm and improves the desulfurization efficiency.

[0039] In S4, the vacuum degree in the vacuum induction furnace is controlled to be ≤10Pa, the casting temperature is controlled at 1580-1600℃, the mold preheating temperature is 300-400℃, the casting speed is 0.8-1.2t / min, and after cooling, Monel alloy electrode rods are obtained.

[0040] In S5, the Monel alloy electrode rod prepared in S4 is sent to an electroslag furnace for melting and deep impurity removal. The temperature inside the electroslag furnace is controlled at 1600-1650℃, and the remelting rate is 2-3 kg / min.

[0041] The slag system used in the electroslag furnace is CaF2-Al2O3-CaO (mass ratio 60:20:20).

[0042] The chemical composition of the prepared Monel alloy by mass percentage is: Cu 66%-69%, Ni 29%-32%, S≤0.005%, C≤0.02%, Fe≤0.5%, Si≤0.1%, with the balance being unavoidable impurity elements, and the content of each individual impurity element ≤0.05%, and the total impurity content ≤0.5%.

[0043] In this invention, the AOD furnace (argon-oxygen decarbonization furnace) achieves decarbonization through argon blowing, and completes deep desulfurization and preliminary deoxygenation during the reduction period.

[0044] Preliminary deoxidation mechanism: After decarburization, the oxygen content in the alloy liquid reaches several hundred ppm. Adding deoxidizers such as metallic aluminum, by means of precise control of the reaction between the metallic aluminum in the deoxidizer and the oxygen element in the alloy liquid, can reduce the oxygen content in the alloy liquid to 50~80 ppm or even lower, thus completing the preliminary deoxidation.

[0045] Deep desulfurization mechanism: During the reduction period, a high-basicity CaO-based slag is created. After deoxidation, the low oxygen potential of the alloy liquid creates a thermodynamic basis for desulfurization. The intense stirring of the side-blown argon gas greatly increases the steel-slag contact area and interface renewal rate. The generated CaS stably enters the slag phase, reducing sulfur to below 0.005% and achieving deep desulfurization.

[0046] In this invention, the vacuum induction furnace (VIM) melts materials under high vacuum conditions through electromagnetic induction heating, achieving vacuum deoxidation and denitrification without inclusions, and simultaneously removing low-melting-point harmful impurities.

[0047] Deep deoxidation mechanism: The deoxidation capacity of carbon under vacuum is far greater than that under normal pressure. The reaction involves the combination of oxygen and carbon elements in the impurities with carbon elements in the reducing agent. The generated CO gas is continuously pumped away by the vacuum pump, and the reaction equilibrium continues to advance in the positive direction, achieving efficient deoxidation without solid deoxidation products. The oxygen content can be reduced to below 20 ppm. In the later stage of refining, aluminum, silicon and other precipitating deoxidizers can be added for further deep deoxidation. The deoxidation products are removed by floating under electromagnetic stirring.

[0048] Denitrification mechanism: Nitrogen dissolved in the alloy liquid exists in a free form. Under vacuum, it combines to form nitrogen molecules, and the partial pressure of N2 in the gas phase is greatly reduced, which promotes the continuous denitrification reaction. At the same time, the CO bubbles generated by the carbon-oxygen reaction form a "gas washing" effect, adsorbing nitrogen atoms and escaping with the bubbles, further enhancing the denitrification effect. The nitrogen content can be reduced to below 10 ppm, and efficient dehydrogenation and volatilization removal of low-melting-point harmful impurities such as Pb, Bi, and Sn can be achieved simultaneously.

[0049] In this invention, the electroslag remelting furnace (ESR) achieves drop-by-drop remelting of consumable electrodes through slag resistance heating, and achieves deep impurity removal through slag washing and refining, interfacial adsorption and chemical reaction, while simultaneously optimizing the solidification structure of the ingot.

[0050] Non-metallic inclusions deep removal: When the molten metal droplets formed by electrode melting pass through the high-temperature slag layer, they achieve an ultra-large contact area with the slag (up to 300m²). 2 The slag can fully wet and adsorb non-metallic inclusions such as Al2O3 and silicates based on the principle of interfacial tension balance. At the same time, the high viscosity slag can mechanically filter and capture large-sized inclusions, reducing the number of inclusions by more than 50%, and refining the size of the remaining inclusions, which are then dispersed.

[0051] Deep removal of residual impurities: The high-alkalinity slag reacts with the residual sulfur in the alloy liquid, and the generated CaS stably enters the slag phase, achieving a desulfurization rate of 60%~80%, which can reduce sulfur to below 0.005%; the slag covers the metal molten pool throughout the process, isolating it from the atmosphere to avoid secondary oxidation, and the water-cooled crystallizer eliminates refractory material contamination, achieving the final deep purification.

[0052] Microstructure optimization: Achieves bottom-up directional solidification, eliminates defects such as ingot porosity and shrinkage cavities, and significantly improves ingot density and microstructure uniformity. Example 1

[0053] The copper-nickel master alloy processed in this embodiment is obtained by reduction and purification of copper-nickel smelting solid waste. Its composition is: Cu 66.5%, Ni 29.2%, S 0.62%, with the remainder being unavoidable impurities. The processing scale is 15t.

[0054] The above copper-nickel master alloy was deeply desulfurized to prepare Monel alloy: Step 1: Non-vacuum induction furnace melting. Add 15kg of copper slag-forming agent to the bottom of a 15-ton non-vacuum induction furnace, followed by 15t of copper-nickel intermediate alloy ingot. Heat to 1300℃ and melt at a constant temperature for 90 minutes to completely melt the alloy ingot and form a copper-nickel alloy liquid. Step 2, alloy liquid transfer: The alloy liquid is discharged to the intermediate ladle, and the temperature of the alloy liquid is controlled at 1495℃. Then it is poured into the 10-ton AOD furnace at a uniform speed. Step 3: Heating the AOD furnace: Introduce argon gas into the AOD furnace (flow rate 0.4 Nm³). 3 ( / min) protection, heat to 1652℃ and maintain; Step 4, three batches of desulfurization: First batch: Add 5 kg / t of calcium silicate blocks (20 mm particle size), 0.3 kg / t of aluminum granules, 22 kg / t of lime, and 11 kg / t of fluorite. The slag basicity is CaO / SiO2 = 3.8. Start the composite argon gas stirring (flow rate 1.0 Nm). 3 ( / min) 20min, slag FeO content 0.45%, after slag discharge, alloy liquid S content decreased to 0.09%; Second batch: Within 5 minutes after slag discharge, add 4.5 kg / t of calcium silicate blocks, 0.3 kg / t of aluminum granules, 23 kg / t of lime, and 10.5 kg / t of fluorite. The slag basicity CaO / SiO2=3.7. Stir for 20 minutes. The slag FeO content is 0.42%. After slag discharge, the S content of the alloy liquid drops to 0.016%. Third batch: Within 5 minutes after slag discharge, add 4.8 kg / t of calcium silicate blocks, 0.3 kg / t of aluminum granules, 24 kg / t of lime, and 11.2 kg / t of fluorite. The slag basicity CaO / SiO2=3.9. Stir for 20 minutes. The slag FeO content is 0.40%. After slag discharge, the S content of the alloy liquid drops to 0.0025%. Step 5, Remelting: The desulfurized alloy liquid is sent to a vacuum induction furnace for remelting to adjust the alloy composition. It is then cast under vacuum conditions ≤10Pa and casting temperature of 1580℃. The mold preheating temperature is 350℃ and the casting speed is 1.0t / min. After cooling, the Monel alloy electrode rod is obtained.

[0055] Step Six: Deep Impurity Removal in Electroslag Furnace The Monel alloy electrode rods after being remelted in a vacuum induction furnace were transferred to an electroslag furnace for deep impurity removal. The slag system was CaF2-Al2O3-CaO (mass ratio 60:20:20), the temperature was controlled at 1620℃, and the remelting speed was 2kg / min to obtain the final standard product. Example 2

[0056] The copper-nickel master alloy processed in this embodiment is obtained by reduction and purification of copper-nickel smelting solid waste: Cu 65.2%, Ni 28.5%, S 0.55%, and the processing scale is 10t.

[0057] The above copper-nickel master alloy was deeply desulfurized to prepare Monel alloy: Step 1: Non-vacuum induction furnace melting: Add 10kg of copper slag-forming agent to the bottom of a 10-ton non-vacuum induction furnace, add 10t of copper-nickel intermediate alloy ingot, heat to 1250℃, and melt at a constant temperature for 100min. Step 2, alloy liquid transfer: Control the temperature of the tundish at 1480℃ and pour the alloy liquid into an 8-ton AOD furnace; Step 3: Heating the AOD furnace: Introduce argon gas (flow rate 0.3 Nm³). 3 ( / min), raise the temperature to 1645℃ and maintain it; Step 4, three batches of desulfurization: First batch: Add 4 kg / t of calcium silicate blocks, 0.4 kg / t of aluminum granules, 20 kg / t of lime, and 10 kg / t of fluorite; slag basicity 3.5; argon blowing flow rate 0.8 Nm. 3 Stir for 20 minutes at a constant speed ( / min), and after removing the slag, S = 0.085%. Second batch: Add 4 kg / t of calcium silicate blocks, 0.4 kg / t of aluminum granules, 20 kg / t of lime, and 10 kg / t of fluorite. The slag basicity is 3.5. Stir for 20 minutes. After slag discharge, the S=0.015%. Third batch: Add 4 kg / t of calcium silicate blocks, 0.4 kg / t of aluminum granules, 20 kg / t of lime, and 10 kg / t of fluorite. The slag basicity is 3.5. Stir for 20 minutes. After slag discharge, S=0.0028%. Step 5, Remelting: The desulfurized alloy liquid is sent to a vacuum induction furnace for remelting to adjust the alloy composition. It is then cast under vacuum conditions ≤10Pa and casting temperature of 1590℃. The mold preheating temperature is 300℃ and the casting speed is 1.0t / min. After cooling, the Monel alloy electrode rod is obtained.

[0058] Step Six: Deep Impurity Removal in Electroslag Furnace The Monel alloy electrode rods after being remelted in a vacuum induction furnace were transferred to an electroslag furnace for deep impurity removal. The slag system was CaF2-Al2O3-CaO (mass ratio 60:20:20), the temperature was controlled at 1600℃, and the remelting speed was 2kg / min to obtain the final standard product. Example 3

[0059] The copper-nickel master alloy processed in this embodiment is obtained by reduction and purification of copper-nickel smelting solid waste: Cu 67.8%, Ni 29.8%, S 0.78%, with a processing scale of 20t.

[0060] Step 1: Non-vacuum induction furnace melting: Add 20kg of copper slag-forming agent to the bottom of a 20-ton non-vacuum induction furnace, add 20t of copper-nickel master alloy ingot, heat to 1350℃, and melt at a constant temperature for 80 minutes. Step 2, alloy liquid transfer: Control the temperature of the tundish at 1500℃ and pour the alloy liquid into a 15-ton AOD furnace; Step 3: Heating the AOD furnace: Introduce argon gas (flow rate 0.5 Nm³). 3( / min), raise the temperature to 1658℃ and maintain it; Step 4, three batches of desulfurization: First batch: Add 5 kg / t of calcium silicate blocks, 0.5 kg / t of aluminum granules, 25 kg / t of lime, and 12 kg / t of fluorite; slag basicity 4.0; argon blowing flow rate 1.2 Nm. 3 Stirring for 20 minutes at a constant speed ( / min), after removing the slag, S = 0.092%; Second batch: Add 5 kg / t of calcium silicate blocks, 0.5 kg / t of aluminum granules, 25 kg / t of lime, and 12 kg / t of fluorite. The slag basicity is 4.0. Stir for 20 minutes. After slag discharge, the S=0.018%. Third batch: Add 5 kg / t of calcium silicate blocks, 0.5 kg / t of aluminum granules, 25 kg / t of lime, and 12 kg / t of fluorite. The slag basicity is 4.0. Stir for 20 minutes. After slag discharge, the S=0.0022%. Step 5, Remelting: The desulfurized alloy liquid is sent to a vacuum induction furnace for remelting to adjust the alloy composition. It is then cast under vacuum conditions ≤10Pa and casting temperature of 1600℃. The mold preheating temperature is 400℃ and the casting speed is 1.20t / min. After cooling, the Monel alloy electrode rod is obtained.

[0061] Step Six: Deep Impurity Removal in Electroslag Furnace The Monel alloy electrode rods, after being remelted in a vacuum induction furnace, were transferred to an electroslag furnace for deep impurity removal. The slag system was CaF2-Al2O3-CaO (mass ratio 60:20:20), the temperature was controlled at 1650℃, and the remelting rate was 3kg / min, thus obtaining the final standard product.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing Monel alloy through deep desulfurization of copper-nickel master alloy, characterized in that, Includes the following steps: S1. The copper-nickel master alloy is melted into a copper-nickel alloy liquid using a non-vacuum induction furnace, wherein the sulfur content in the copper-nickel master alloy is 0.5%-0.8%; S2. Pour the molten copper-nickel alloy liquid into the AOD furnace, heat it and introduce argon gas; S3 and AOD furnaces are used for slag formation, desulfurization and slag discharge to complete desulfurization; S4. The desulfurized alloy liquid is fed into a vacuum induction furnace for remelting and recombining. After casting and cooling, a Monel alloy electrode rod is obtained. S5. Place the Monel alloy electrode rod in an electroslag furnace for melting and deep impurity removal to obtain a standard Monel alloy product. In S3, the slag formation, desulfurization, and slag discharge are repeated three times in a single cycle. Each operation includes: First, add 4-5 kg / t of calcium silicate blocks, 20-25 kg / t of lime, and 10-12 kg / t of fluorite, and control the slag basicity CaO / SiO2 = 3.5-4.0; Secondly, the bottom-blowing and side-blowing combined argon gas stirring is started in the AOD furnace, with a total argon gas flow rate of 0.8-1.2 Nm³ / min, and stirring is carried out for 20 minutes; Next, after stirring, completely drain the residue; During each desulfurization process, the slag layer thickness inside the AOD furnace is controlled at 80-120mm to ensure that the mass transfer path of sulfur is ≤5mm. The ratio of lime to fluorite is 2:1 to 2.5:

1.

2. The method for preparing Monel alloy by deep desulfurization of copper-nickel master alloy as described in claim 1, characterized in that, In step S1, a copper slag-forming agent is added to the bottom of a non-vacuum induction furnace, followed by the addition of a copper-nickel master alloy ingot. The mass ratio of the copper slag-forming agent to the copper-nickel master alloy is 1:1000. The furnace is heated to 1250-1350℃ and kept at a constant temperature for 80-100 minutes to form a copper-nickel alloy liquid.

3. The method for preparing Monel alloy by deep desulfurization of copper-nickel master alloy as described in claim 1, characterized in that, In S5, the slag system is CaF2-Al2O3-CaO with a mass ratio of 60:20:20, the furnace temperature is 1600-1650℃, and the remelting rate is 2-3 kg / min.

4. The method for preparing Monel alloy by deep desulfurization of copper-nickel master alloy as described in claim 1, characterized in that, In step S3, the alloy liquid is heated to 1650±10℃, and the flow rate of stirring argon gas is 0.3-0.5 Nm³ / min.

5. The method for preparing Monel alloy by deep desulfurization of copper-nickel master alloy as described in claim 1, characterized in that, Aluminum particles are added at the same time as the silicon-calcium block. The aluminum particles react with the alloy liquid to achieve deep deoxidation, so that the [O] in the alloy liquid is less than 20 ppm.

6. The method for preparing Monel alloy by deep desulfurization of copper-nickel master alloy as described in claim 1, characterized in that, In step S4, the casting temperature is 1580-1600℃, the mold preheating temperature is 300-400℃, the casting speed is 0.8-1.2t / min, and after cooling, a Monel alloy electrode rod is obtained.

7. The method for preparing Monel alloy by deep desulfurization of copper-nickel master alloy as described in claim 1, characterized in that, The chemical composition of the prepared Monel alloy is as follows (mass percentage): Cu 66%-69%, Ni 29%-32%, S≤0.005%, C≤0.02%, Fe≤0.5%, Si≤0.1%, with the balance being unavoidable impurity elements.