Method for synergistically separating impurity elements of scrap brass melt through electric pulse and refining agent

Abstract

The invention discloses a method for synergistically separating impurity elements of brass melt through electric pulse and a refining agent, which comprises the following steps: dividing the refining agent into two parts, heating a scrap brass material to obtain a melt, adding a first part of the refining agent into the melt, then applying electric pulse into the melt for treatment for a period of time, then adding a second part of the refining agent, and then treating for a period of time; and stopping heating, continuously applying the electric pulse to the solidification stage of the melt for a period of time, and turning off the pulse power supply. According to the method, the pulse current is applied to the scrap brass melt, the refining flux is supplemented, the electric pulse parameters and the refining agent formula are optimized, and the step-by-step synergistic treatment process is combined, so that the content of impurity elements such as Bi and Fe is effectively reduced, meanwhile, the energy consumption and the production cost are reduced, and the quality of the regenerated brass alloy is improved. The method adopts an electric pulse and refining flux synergistic treatment process, has the characteristics of low energy consumption, good impurity removal effect, flexible and controllable parameters, simple process and the like, and can be applied to purification of various alloy melts.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal recycling and metallurgy technology, and specifically relates to a method for the synergistic separation of impurity elements in molten brass using electrical pulses and refining agents. Background Technology

[0002] As an important raw material in scrap copper, the recycling and reuse of scrap brass plays a crucial role in the green and sustainable development of the recycled copper processing industry, mainly in reducing the cost of using primary copper, reducing energy consumption, and reducing carbon dioxide emissions. Scrap brass raw materials have high impurity content and complex composition, often including impurity elements such as Pb, Bi, Sn, Al, Fe, and Ni. The residue of these impurity elements significantly reduces the mechanical and processing properties of brass alloys. Bi and Fe are two common impurity elements in scrap brass. When the Bi content is too high, the Bi phase is distributed in a network-like film at the interface between the α and β phases, severely affecting the hot working properties of the alloy. Fe has low solid solubility in Cu; an appropriate amount of Fe can improve the overall mechanical properties of recycled brass, but excessive Fe will significantly reduce its corrosion resistance. Furthermore, Fe impurities are inevitably introduced during the sorting, screening, smelting, and casting processes of scrap brass.

[0003] Traditional flux refining methods mainly include oxidative refining, sulfide refining, and composite separation. The core of oxidative refining is based on the different affinities of various metals with oxygen, oxidizing impurities in the crude metal into oxides insoluble in the main metal, which then float to the surface of the melt through slag formation. Sulfide refining is similar, mainly relying on sulfiding agents to form slag and remove impurity elements. The principle of composite separation is to add another type of alloying element that can react with impurity elements in the melt, forming intermetallic compounds. These compounds then agglomerate and form slag under the adsorption of the flux, ultimately removing the impurity elements. Composite separation is particularly effective at removing Pb and Bi. However, these refining methods suffer from problems such as cumbersome procedures, high energy consumption, significant metal loss, and environmental pollution. In particular, the large-scale use of fluorine-containing fluxes can cause secondary pollution and damage to human health and the ecological environment. Therefore, to meet the sustainable development needs of the recycled copper industry, and given the many shortcomings of existing traditional processes, it is urgent to explore a separation and recycling method that is effective in removing impurities, low in cost, and environmentally friendly.

[0004] Electrical pulse technology has been widely studied as a novel, efficient, low-energy, and environmentally friendly heat treatment process. It plays a crucial role in accelerating alloy recrystallization, promoting precipitation phase transformation, increasing element diffusion rates, refining solidification structures, and migrating and separating impurities and inclusions. It has been proven that electrical pulses can effectively remove small-sized non-metallic inclusions from molten steel and significantly affect their morphology, size, and distribution. Patent (CN113755892A) reports a method for removing multi-element impurities from scrap copper using pulsed current. Applying pulsed current to molten scrap copper effectively removes impurities such as Pb, Sn, Fe, and Al, further improving the purity of recycled copper alloys. In summary, pulsed current melt purification technology overcomes the shortcomings of traditional oxidation refining methods that utilize differences in metal activity, and features high efficiency, low energy consumption, short process, and environmental friendliness. The separation of impurity elements in molten metal can be achieved by applying pulsed current. Pulsed current melt treatment can promote impurity separation through electromigration and electrical free energy, but it is affected by process parameters such as pulse current intensity, pulse frequency, pulse width, and electrode insertion method. Furthermore, pulsed current is more effective for removing elements with significant solubility variations. Overall, compared to composite separation methods, pulsed current melt treatment has a lower impurity removal efficiency, and even after pulsed current treatment, a large number of impurity elements still remain in certain areas of the ingot, indicating that most have not been removed from the melt. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for the synergistic separation of impurity elements from molten brass using electrical pulses and refining agents. This invention applies a pulsed current to molten scrap brass, supplemented by a refining flux. By optimizing the electrical pulse parameters and refining flux formulation, and combining a step-by-step synergistic treatment process, the content of impurity elements such as Bi and Fe is effectively reduced, achieving highly efficient separation of impurity elements from molten scrap brass. Simultaneously, energy consumption and production costs are reduced, and the quality of recycled brass alloys is improved. The synergistic treatment process of electrical pulses and refining flux in this invention features low energy consumption, good impurity removal effect, flexible and controllable parameters, and simple process, and can be applied to the purification of various alloy melts.

[0006] To achieve the above objectives, the following technical solution is adopted: This invention discloses a method for synergistically separating impurity elements from molten brass using electric pulses and refining agents. The refining agent is divided into two parts. Waste brass material is heated to obtain a melt. The first part of the refining agent is added to the melt. Then, an electric pulse is applied to the melt for a period of time. The second part of the refining agent is added. After another period of treatment, heating is stopped. The electric pulse is then applied to the solidification stage of the melt for a period of time. Finally, the pulse power supply is turned off to obtain the final product. The mass ratio of the first part of the refining agent to the second part of the refining agent is 1 to 3:1.

[0007] The present invention employs an electric pulse and a refining agent to synergistically separate impurity elements from molten brass. Under the action of the electric pulse, based on the difference in effective charge between impurity atoms and the matrix, impurity atoms in the melt migrate directionally towards the cathode or anode due to electromigration. Furthermore, when a certain current density distribution difference exists within the melt, impurity atoms can also migrate and diffuse directionally towards the surface or bottom of the melt under the driving force of the current density gradient. During this migration and diffusion process, impurity elements interact with the refining agent to form a low-density slag phase (such as Fe2B, FeB, CaBi, etc.). The slag phase rises to the melt surface due to the accelerated melt convection induced by the electric pulse, and is ultimately removed by skimming. On the other hand, the refining agent can ionize into charged ions in the molten state. Under the action of the electric field, molten salt ions move in the direction opposite to their charge, effectively adsorbing impurity atoms and slag phases during this movement, thereby enriching and distributing them at both the cathode and anode ends, achieving purification of the molten brass.

[0008] Experiments have shown that continuing to apply pulsed current during the cooling and solidification process can further improve the impurity removal rate. This is because, as the temperature decreases during cooling and solidification, the solubility of impurity elements Bi / Fe in the Cu matrix decreases, causing them to precipitate as single-element phases. The application of pulsed current creates a current density gradient driving force, which accelerates the decrease in the solubility of impurity elements. Under the influence of the electric field, the precipitated impurity atoms easily migrate directionally to the bottom region and eventually form large-sized impurity phases, thus separating them.

[0009] In this invention, the refining agent is divided into two parts. The first part is added first, and the added refining agent covers the surface of the melt to form a liquid film, which prevents the oxidation and burning of beneficial elements and can also react with impurity elements in the initial stage. After a period of electrical pulse treatment, the second part is added, which can make the refining agent more evenly dispersed, the reaction less violent and controllable, reduce element segregation, promote uniform distribution of components, ensure that impurities are in full contact with the refining agent, and improve the impurity removal efficiency. At the same time, adding the refining agent in batches can keep the slag with suitable fluidity, which is convenient for slag removal. And by controlling the amount of refining agent added in the two batches within the range of this invention, the impurity removal effect is optimal.

[0010] In a preferred embodiment, the scrap brass material is first crushed and placed in a graphite crucible. Then, one end of two graphite electrode rods connected to a pulse power supply is inserted into the graphite crucible to a depth of 1 / 4 to 1 / 2 of the total height of the melt.

[0011] Experiments have shown that the insertion depth of the graphite electrode has a significant impact on the impurity separation behavior of brass melt. Controlling the insertion depth of the graphite electrode rod within the range of this invention yields good results. When the graphite electrode insertion depth is shallow, the current density distribution within the melt varies considerably, with a higher current density near the graphite electrode rod and a lower current density at the bottom, resulting in a current density distribution difference. According to the theory of electric free energy, to stabilize the system's electric free energy, the migration of impurity atoms from high current density regions to low current density regions is a process of reducing the system's electric free energy, conforming to the principle of minimum energy. Therefore, under the action of pulsed current, a large number of impurity atoms migrate to the bottom region and accumulate, forming large-sized Bi-rich phase particles or petal-shaped Fe-rich phases. When the graphite electrode rod is inserted to a greater depth, close to the bottom of the melt, the melt current density tends to be uniformly distributed, with no obvious current density gradient difference within the melt. At this point, the electromigration effect of the current dominates, and the effective electromigration charge number of metal atoms determines the migration direction of the metal atoms. When the effective charge number is positive, the migration direction of metal atoms is consistent with the direction of the electric field, i.e., they move from the anode to the cathode. When the effective charge number is negative, the migration direction of metal atoms is consistent with the direction of the electron wind, i.e., they migrate from the cathode to the anode. Therefore, a large amount of impurity phase enrichment can be observed on either the anode or cathode side. In summary, the insertion depth of the graphite electrode rod affects the migration direction of impurity atoms. By optimizing the insertion depth of the graphite electrode rod, the direction of directional migration of impurity atoms can be controlled, thereby achieving localized purification of the melt.

[0012] In this invention, graphite rods are used as electrodes. One end of two graphite electrode rods is inserted into the melt, and the other end is connected with a copper wire, which is then connected to a pulse power supply device.

[0013] In a preferred embodiment, the refining agent, by mass percentage, has the following composition: Na2B4O7 30%~50%, Na2CO3 10%~20%, NaCl 5%~10%, NaF 5%~10%, and Cu-21.8Ca alloy 10%~30%.

[0014] The refining agent provided by this invention, Na2B4O7 and NaCl, synergistically and uniformly cover the surface of the brass melt to form a liquid film, reducing the contact between the melt and air and lowering the degree of oxidation. In addition, Na2B4O7 can also be used to separate Fe impurities from the copper melt, while NaCl can dissolve or adsorb certain impurities in the melt, helping to remove some suspended solid impurity particles. Na2CO3 can promote the reduction reaction of certain impurities (such as some metal oxides), transforming the impurities into more easily removed forms, and can also adjust the melt viscosity, affecting the existence form and behavior of impurities in the melt, thereby facilitating subsequent purification operations, and Cu-21. In the 8Ca alloy, Ca reacts with Pb and Bi elements in the brass melt to form Ca-Bi and Ca-Pb compounds with low density and high melting point. The added NaF can react with Ca-Bi and Ca-Pb compounds, and the resulting substances can act as binders to aggregate fine impurity particles, forming composite compounds with lower density and larger size, which are more likely to float to the surface of the melt and then be removed by slag removal, thus achieving efficient removal of impurities Pb and Bi. In addition, Ca may act as a heterogeneous nucleation core, increasing the number of nuclei, inhibiting grain growth, and refining the grains of brass, thereby improving the mechanical and processing properties of brass. Meanwhile, Ca has high reactivity and can play a deoxidizing role. Ca can also improve the uniformity of the structure. Through the interaction with other elements, it promotes the uniform distribution of alloying elements in the melt, reduces component segregation, and improves the uniformity of the brass structure. NaF can also lower the melting point of NaCl and improve the covering performance. Through the synergistic effect of the above components, the refining agent of the present invention has a better impurity removal effect on waste brass. Moreover, the above-mentioned refining agent formula of the present invention has an excellent synergistic effect with electric pulse.

[0015] In a preferred embodiment, the total amount of the refining agent is 0.5% to 2% of the mass of the scrap brass.

[0016] In this invention, with the assistance of electrical pulses, the amount of refining agent can be significantly reduced. Optimal results are achieved by controlling the total amount of refining agent added within the aforementioned range. If the amount of refining agent added is too small, it cannot effectively remove impurities and inclusions from the molten scrap copper. Its adsorption and removal capacity for inclusions is limited, preventing inclusions or compounds from fully floating to the surface for removal. Residual inclusions will still cause casting defects, reducing the quality of copper ingots. When the amount of refining agent added is too large, some components may remain in the matrix, introducing new impurities and increasing the impurity content. Residual refining agent may adversely affect subsequent alloy processing, such as causing surface cracks during rolling and stretching. Furthermore, it increases raw material costs and environmental pollution risks. Excessive refining agent can also carry away some molten copper during slag removal, exacerbating copper loss.

[0017] In actual operation, the preparation process of the refining agent is as follows: each component is prepared according to the design ratio, ball-milled and mixed, heated in an oven (e.g., 150℃) for 1-2 hours to remove moisture, and then wrapped and compacted with copper foil.

[0018] The preferred method is to heat the scrap brass material to 1000℃~1100℃ and hold it for 2~10 minutes to obtain a melt.

[0019] In a preferred embodiment, a first portion of refining agent is added to the melt, and then an electric pulse treatment is applied to the melt at 1000~1100℃ for 5~15 minutes. Then, a second portion of refining agent is added, and the electric pulse treatment is continued for another 5~15 minutes before heating is stopped.

[0020] By controlling the processing time after adding the refining agent twice within the range of this invention, the burn-off of easily oxidized substances can be avoided, while ensuring that the refining agent and impurities react fully. At the same time, the pulsed current has a significant effect on the agglomeration and flotation of the slag phase in the melt and the migration and enrichment of impurity atoms, thereby obtaining a high-purity alloy.

[0021] The preferred method is to continue applying electrical pulse treatment to the solidification stage of the melt for 10-30 minutes, and then turn off the pulse power supply.

[0022] The best performance of the final alloy is achieved when the duration of pulsed current application during the solidification stage is controlled within the range of this invention. If the processing time is too short, impurity atoms in the melt cannot migrate and diffuse sufficiently. If the processing time is too long, the melt may overheat, the cooling rate may decrease, and the grains may coarsen.

[0023] In a preferred embodiment, the waveform of the pulse power supply used for the electrical pulse processing is a rectangular wave, and the voltage of the pulse power supply is 0~12V.

[0024] Experiments have shown that square-wave pulsed current exhibits abrupt changes. At the same pulse current peak value and pulse width, the induced electromagnetic field intensity generated within the molten metal is greater than that of triangular and sine waves. This results in a stronger electromagnetic force exerted by the square-wave pulsed current on the melt, more effectively promoting the migration of inclusions. The strong electromagnetic force can also intensify the flow within the melt, leading to a better refinement effect on the melt.

[0025] In a preferred embodiment, the pulse frequency of the electric pulse melt treatment is 20~1000Hz, and the pulse current is 50~250A.

[0026] Optimal treatment results are achieved when the pulse current is controlled within the aforementioned range. If the pulse current is too low, the electromigration effect of the melt is insufficient to induce the migration and enrichment of impurity atoms, thus failing to achieve a good purification effect. Furthermore, due to the low current intensity, a longer treatment time is required to achieve the desired effect, leading to a prolonged production cycle and low production efficiency. When the pulse current is too high, excessive Joule heating is generated due to the thermal effect, causing the melt temperature to become too high, resulting in irregular movement of impurity atoms within the melt. In addition, excessive current can also cause violent electromagnetic stirring, leading to violent fluctuations in the liquid surface, which in turn causes the melt to absorb air and create inclusions, affecting the quality of the ingot.

[0027] The preferred method is to turn off the pulse power supply and cool the furnace to room temperature to obtain the purified brass alloy.

[0028] The synergistic processing technology of electrical pulse and refining flux of the present invention has the following beneficial effects: (1) Compared with the traditional flux refining method, the combined processing of electric pulse and refining flux reduces the amount of refining flux used to a certain extent, reduces energy consumption, and achieves green and low-carbon production; compared with single electric pulse melt processing, the combined processing can further improve the impurity removal efficiency and achieve efficient separation of impurity elements. (2) This synergistic treatment process not only utilizes the electromigration effect and the theory of electric free energy to promote the migration of impurity atoms, but also significantly improves the chemical adsorption effect of the refining agent, thereby reducing the content of impurity elements such as Bi and Fe by 40% to 80%, effectively purifying the brass melt. (3) The pulse current parameters are flexible and controllable. The electrical pulse parameters (such as current intensity, frequency, waveform and electrode insertion method) and the type and content of refining flux can be changed and optimized, and then applied to the purification of various alloy melts. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of an electric pulse melt processing device. Detailed Implementation

[0030] The technical solution of the present invention will be better understood below with reference to specific embodiments. The following description of the embodiments is to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without creative effort. Therefore, the present invention is not limited to the following embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention.

[0031] This invention reports a method for the synergistic separation of impurity elements in brass using electrical pulses and refining flux. A pulsed current is applied to molten scrap brass, supplemented by a refining flux. By optimizing the electrical pulse parameters and the refining flux formulation, combined with a step-by-step synergistic treatment process, the content of impurity elements such as Bi and Fe is effectively reduced. This achieves efficient separation of impurity elements from molten scrap brass, reducing energy consumption and cost, and improving the quality of recycled brass alloys. The synergistic treatment process of electrical pulses and refining flux features low energy consumption, good impurity removal effect, flexible and controllable parameters, and simple process, and can be applied to the purification of various alloy melts.

[0032] The specific steps of the synergistic treatment method of electrical pulse and refining agent are as follows: (1) After crushing the brass raw material, place it in a graphite crucible. Using graphite rods as electrodes, insert one end of two graphite electrode rods into the melt, and connect the other end with a copper wire. The copper wire is connected to a pulse power supply device. The graphite electrode rods are inserted to about half the height of the molten metal. (2) Heat the scrap brass material to 1000℃ and hold for 2 minutes to ensure complete melting of the brass alloy. Then add half the required amount of refining flux. The refining flux consists of 40%~60% Na2B4O7, 20%~30% Na2CO3, 10%~20% NaCl, 5%~10% NaF, and 10%~30% Cu-21.8Ca alloy. The amount of refining flux added is 0.5%~2% of the mass of the molten brass. (3) Turn on the pulse power supply, adjust the electric pulse parameters to the target parameters, and after being treated with an electric pulse of 1000~1100℃ for 5~15 minutes, add the remaining refining flux, continue to keep warm for 5~15 minutes, and then turn off the high frequency induction heating power supply. (4) Continue to apply electric pulse treatment to the solidification stage of the melt for 10~30 minutes, then turn off the pulse power supply until the alloy cools down to room temperature with the furnace, and then take samples for testing and analysis.

[0033] Example 1

[0034] (1) Cut and crush the brass raw material, weigh about 1000g of waste and place it in a graphite crucible. Using graphite rods as electrodes, insert one end of the two graphite rods into the melt, and connect the other end to a copper wire led out from a pulse power supply device. Calculate the height of the melt in advance, and insert the graphite electrode rods to about half the height of the molten metal; (2) Heat the scrap brass material to 1000℃ and hold for 2 minutes to ensure complete melting of the brass alloy. Then add half the required amount of refining flux. Refining flux composition: Na₂B₄O₇ 50%, Na₂CO₃ 20%, NaCl 10%, NaF 10%, Cu-21.8Ca 10%. The amount of alloy refining flux added accounts for 0.5% of the mass of the molten brass. (3) Turn on the pulse power supply and set the pulse current parameters: pulse current 50A, pulse frequency 650Hz. After being treated with 1000℃ electric pulse for 5 minutes, add the remaining refined flux, continue to hold for 5 minutes, and then turn off the high-frequency induction heating power supply; (4) Continue to apply electrical pulses during the solidification stage of the melt. After 20 minutes of treatment, turn off the pulse power supply until the alloy cools down to room temperature with the furnace. Then, cut a longitudinal section between the two graphite electrode rods and take a sample for chemical composition testing. The contents of Bi and Fe impurities in the ingot were measured to be 1.21 wt.% and 0.87 wt.% respectively using inductively coupled plasma atomic emission spectrometry. After synergistic treatment, the contents of Bi and Fe impurities were reduced to 0.38 wt.% and 0.35 wt.% respectively, with impurity removal rates of 68.5% and 59.8% respectively, as shown in Table 1.

[0035]

[0036] Comparative Example 1: All other conditions were the same as in Example 1, except that no refining flux was added. Repeating the above steps, under the action of a single pulsed current, the contents of Bi and Fe elements, impurities in brass, decreased from the initial 1.2 wt.% and 0.87 wt.% to 0.51 wt.% and 0.42 wt.%, respectively. The impurity removal rates were 57.5% and 51.7%, respectively.

[0037] As can be seen, in Example 1, the removal rates of impurities Bi and Fe were increased by 19.1% and 15.7%, respectively, through the synergistic treatment technology of pulsed current and flux refining.

[0038] Example 2

[0039] (1) Cut and crush the brass raw material, weigh about 1000g of waste and place it in a graphite crucible. Using graphite rods as electrodes, insert one end of the two graphite rods into the melt, and connect the other end to a copper wire led out from a pulse power supply device. Calculate the height of the melt in advance, and insert the graphite electrode rods to about half the height of the molten metal; (2) Heat the scrap brass material to 1000℃ and hold for 2 minutes to ensure complete melting of the brass alloy. Then add half the required amount of refining flux. Refining flux composition: Na₂B₄O₇ 30%, Na₂CO₃ 20%, NaCl 10%, NaF 10%, Cu-21.8Ca 30%. The amount of alloy refining flux added is 1% of the mass of the molten brass. (3) Turn on the pulse power supply and set the pulse current parameters: pulse current 100A, pulse frequency 1000Hz. After being treated with an electric pulse at 1050℃ for 10 minutes, add the remaining refined flux, continue to hold for 10 minutes, and then turn off the high-frequency induction heating power supply; (4) Continue to apply electrical pulses during the solidification stage of the melt. After 10 minutes of treatment, turn off the pulse power supply until the alloy cools down to room temperature with the furnace. Then, cut a longitudinal section between the two graphite electrode rods and take a sample for chemical composition testing. The contents of Bi and Fe impurities in the ingot were measured to be 1.32 wt.% and 0.68 wt.% respectively using inductively coupled plasma atomic emission spectrometry. After synergistic treatment, the contents of Bi and Fe impurities were reduced to 0.4 wt.% and 0.27 wt.% respectively, with impurity removal rates of 69.7% and 60.3% respectively, as shown in Table 2.

[0040]

[0041] Comparative Example 2: All other conditions were the same as in Example 2, except that no refining flux was added. Repeating the above steps, under the action of a single pulsed current, the contents of Bi and Fe elements in the brass impurities decreased from the initial 1.32 wt.% and 0.68 wt.% to 0.59 wt.% and 0.32 wt.%, respectively. The impurity removal rates were 55.3% and 52.9%, respectively. It can be seen that Example 2, through the synergistic treatment technology of pulsed current and flux refining, improved the impurity removal rates of Bi and Fe elements by 26% and 14%, respectively.

[0042] Example 3

[0043] (1) Cut and crush the brass raw material, weigh about 1000g of waste and place it in a graphite crucible. Using graphite rods as electrodes, insert one end of the two graphite rods into the melt, and connect the other end to a copper wire led out from a pulse power supply device. Calculate the height of the melt in advance, and insert the graphite electrode rods to about half the height of the molten metal; (2) Heat the scrap brass material to 1000℃ and hold for 2 minutes to ensure complete melting of the brass alloy. Then add half the required amount of refining flux. Refining flux composition: Na₂B₄O₇ 40%, Na₂CO₃ 10%, NaCl 10%, NaF 10%, Cu-21.8Ca 30%. The amount of refining flux added is 2% of the mass of the molten brass. (3) Turn on the pulse power supply and set the pulse current parameters: pulse current 150A, pulse frequency 500Hz. After being treated with an electric pulse at 1100℃ for 15 minutes, add the remaining refined flux, continue to hold for 10 minutes, and then turn off the high-frequency induction heating power supply; (4) Continue to apply electrical pulses during the solidification stage of the melt. After 20 minutes of treatment, turn off the pulse power supply until the alloy cools down to room temperature with the furnace. Then, cut a longitudinal section area between the two graphite electrode rods and take a sample for chemical composition testing. The contents of Bi and Fe impurities in the ingot were measured to be 1.36 wt.% and 0.98 wt.% respectively using inductively coupled plasma atomic emission spectrometry. After synergistic treatment, the contents of Bi and Fe impurities were reduced to 0.32 wt.% and 0.37 wt.% respectively, with impurity removal rates of 76.5% and 62.2% respectively, as shown in Table 3.

[0044]

[0045] Comparative Example 3 All other conditions were the same as in Example 3, except that no refining flux was added. Repeating the above steps, under the action of a single pulsed current, the contents of Bi and Fe elements in the brass impurities decreased from the initial 1.36 wt.% and 0.98 wt.% to 0.55 wt.% and 0.47 wt.%, respectively. The impurity removal rates were 59.6% and 52.0%, respectively. It can be seen that in Example 3, through the synergistic treatment technology of pulsed current and flux refining, the impurity removal rates of Bi and Fe elements were increased by 28.3% and 19.6%, respectively.

[0046] Example 4

[0047] (1) Cut and crush the brass raw material, weigh about 1000g of waste and place it in a graphite crucible. Using graphite rods as electrodes, insert one end of the two graphite rods into the melt, and connect the other end to a copper wire led out from a pulse power supply device. Calculate the height of the melt in advance, and insert the graphite electrode rods to about half the height of the molten metal; (2) Heat the scrap brass material to 1000℃ and hold for 2 minutes to ensure complete melting of the brass alloy. Then add half the amount of refining flux. The refining flux composition is: Na2B4O7 45%, Na2CO3 10%, NaCl 5%, NaF 10%, Cu-21.8Ca 30%. The amount of refining flux added accounts for 1% of the mass of the brass melt. (3) Turn on the pulse power supply and set the pulse current parameters: pulse current 200A, pulse frequency 800Hz. After being treated with 1000℃ electric pulse for 15 minutes, add the remaining refining flux, continue to hold for 5 minutes, and then turn off the high-frequency induction heating power supply; (4) Continue to apply electrical pulses during the solidification stage of the melt. After 30 minutes of treatment, turn off the pulse power supply until the alloy cools down to room temperature with the furnace. Then, cut a longitudinal section between the two graphite electrode rods and take a sample for chemical composition testing. The contents of Bi and Fe impurities in the ingot were measured to be 1.43 wt.% and 0.79 wt.% respectively using inductively coupled plasma atomic emission spectrometry. After synergistic treatment, the contents of Bi and Fe impurities were reduced to 0.48 wt.% and 0.32 wt.% respectively, with impurity removal rates of 66.4% and 59.5% respectively, as shown in Table 4.

[0048]

[0049] Comparative Example 4 All other conditions were the same as in Example 4, except that no refining flux was added. Repeating the above steps, under the action of a single pulsed current, the contents of Bi and Fe elements in the brass impurities decreased from the initial 1.43 wt.% and 0.79 wt.% to 0.55 wt.% and 0.37 wt.%, respectively. The impurity removal rates were 61.5% and 53.2%, respectively. It can be seen that, compared with Example 4, the impurity removal rates of Bi and Fe elements were increased by 8% and 11.8%, respectively, using the pulsed current and flux refining synergistic treatment technology.

[0050] Example 5

[0051] (1) Cut and crush the brass raw material, weigh about 1000g of waste and place it in a graphite crucible. Using graphite rods as electrodes, insert one end of the two graphite rods into the melt, and connect the other end to a copper wire led out from a pulse power supply device. Calculate the height of the melt in advance, and insert the graphite electrode rods to about half the height of the molten metal; (2) Heat the scrap brass material to 1000℃ and hold for 2 minutes to ensure complete melting of the brass alloy. Then add half the amount of refining flux. The refining flux composition is: Na2B4O7 30%, Na2CO3 20%, NaCl 10%, NaF 10%, Cu-21.8Ca 30%. The amount of refining flux added accounts for 2% of the mass of the brass melt. (3) Turn on the pulse power supply and set the pulse current parameters: pulse current 250A, pulse frequency 900Hz. After being treated with 1080℃ electric pulse for 15 minutes, add the remaining refined flux, continue to hold for 10 minutes, and then turn off the high-frequency induction heating power supply; (4) Continue to apply electrical pulses during the solidification stage of the melt. After 15 minutes, turn off the pulse power supply until the alloy cools down to room temperature with the furnace. Then, cut a longitudinal section between the two graphite electrode rods and take a sample for chemical composition testing. The contents of Bi and Fe impurities in the ingot were measured to be 1.62 wt.% and 0.99 wt.% respectively using inductively coupled plasma atomic emission spectrometry. After synergistic treatment, the contents of Bi and Fe impurities were reduced to 0.57 wt.% and 0.39 wt.% respectively, with impurity removal rates of 64.8% and 60.6%, as shown in Table 5.

[0052]

[0053] Comparative Example 5 All other conditions were the same as in Example 5, except that no refining flux was added. Repeating the above steps, under the action of a single pulsed current, the contents of Bi and Fe elements in the brass impurities decreased from the initial 1.62 wt.% and 0.99 wt.% to 0.65 wt.% and 0.49 wt.%, respectively. The impurity removal rates were 59.8% and 50.5%, respectively. It can be seen that, compared with the pulsed current and flux refining synergistic treatment technology in Example 5, the impurity removal rates of Bi and Fe elements were increased by 8.4% and 20%, respectively.

[0054] Example 6

[0055] (1) Cut and crush the brass raw material, weigh about 1000g of waste and place it in a graphite crucible. Using graphite rods as electrodes, insert one end of the two graphite rods into the melt, and connect the other end to a copper wire led out from a pulse power supply device. Calculate the height of the melt in advance, and insert the graphite electrode rods to about half the height of the molten metal; (2) Heat the scrap brass material to 1000℃ and hold for 2 minutes to ensure complete melting of the brass alloy. Then add half the amount of refining flux. The refining flux composition is: Na2B4O7 40%, Na2CO3 20%, NaCl 10%, NaF 10%, Cu-21.8Ca 20%. The amount of refining flux added accounts for 1% of the mass of the brass melt. (3) Turn on the pulse power supply and set the pulse current parameters: pulse current 150A, pulse frequency 700Hz. After being treated with an electric pulse at 1020℃ for 10 minutes, add the remaining refining flux, continue to hold for 5 minutes, and then turn off the high-frequency induction heating power supply; (4) Continue to apply electrical pulses during the solidification stage of the melt. After 20 minutes of treatment, turn off the pulse power supply until the alloy cools down to room temperature with the furnace. Then, cut a longitudinal section between the two graphite electrode rods and take a sample for chemical composition testing. The contents of Bi and Fe impurities in the ingot were measured to be 1.17 wt.% and 0.83 wt.% respectively using inductively coupled plasma atomic emission spectrometry. After synergistic treatment, the contents of Bi and Fe impurities were reduced to 0.34 wt.% and 0.27 wt.% respectively, with impurity removal rates of 70.9% and 67.5% respectively, as shown in Table 6.

[0056]

[0057] Comparative Example 6 All other conditions were the same as in Example 6, except that no refining flux was added. Repeating the above steps, under the action of a single pulsed current, the content of Bi and Fe elements in brass impurities decreased from the initial 1.17 wt.% and 0.83 wt.% to 0.45 wt.% and 0.38 wt.%, respectively. The impurity removal rates were 61.5% and 54.2%, respectively. It can be seen that Example 6, through the synergistic treatment technology of pulsed current and flux refining, improved the impurity removal rates of Bi and Fe elements by 15.3% and 24.5%, respectively.

[0058] Comparative Example 7 Using the same refining agent composition as in Example 3, the brass melt was purified by adding only refining flux without pulsed current. The refining agent composition and corresponding addition amounts were: Na₂B₄O₇ 40%, Na₂CO₃ 10%, NaCl 10%, NaF 10%, and Cu-21.8Ca 30%. The amount of refining flux added accounted for 2% of the mass of the brass melt. The refining temperature was 1000℃, and the holding time was 10 min. After flux refining, the contents of impurities Bi and Fe decreased from 1.36 wt.% and 0.98 wt.% to 0.63 wt.% and 0.51 wt.%, respectively, with impurity removal rates of 53.7% and 48%, respectively.

[0059] Comparative Example 8 The steps and parameters used in Example 3 are the same, except that the electric pulse treatment time during the solidification stage is shortened.

[0060] The steps for the synergistic processing of electrical pulse and flux refining are as follows: (1) Cut and crush the brass raw material, weigh about 1000g of waste and place it in a graphite crucible. Using graphite rods as electrodes, insert one end of the two graphite rods into the melt, and connect the other end to a copper wire led out from a pulse power supply device. Calculate the height of the melt in advance, and insert the graphite electrode rods to about half the height of the molten metal; (2) Heat the scrap brass material to 1000℃ and hold for 2 minutes to ensure complete melting of the brass alloy. Then add half the amount of refining flux. The refining flux composition is: Na2B4O7 45%, Na2CO3 10%, NaCl 5%, NaF 10%, Cu-21.8Ca 30%. The amount of refining flux added accounts for 1% of the mass of the brass melt. (3) Turn on the pulse power supply and set the pulse current parameters: pulse current 150A, pulse frequency 500Hz. After being treated with an electric pulse at 1100℃ for 15 minutes, add the remaining refined flux, continue to hold for 10 minutes, and then turn off the high-frequency induction heating power supply; (4) Continue to apply electric pulses to the solidification stage of the melt. After processing for 5 minutes, turn off the pulse power supply until the alloy cools down to room temperature with the furnace. Then cut a longitudinal section area between the two graphite electrode rods and take a sample for chemical composition testing.

[0061] After synergistic treatment with pulsed current and flux refining, the contents of impurities Bi and Fe were reduced from 1.36 wt.% and 0.98 wt.% to 0.45 wt.% and 0.48 wt.%, respectively, with impurity removal rates of 67% and 51.0%, respectively.

[0062] Comparative Example 9 The steps and parameters used in Example 4 are the same, except that one component of the refining agent (Cu-21.8Ca alloy) is missing.

[0063] The steps for the synergistic processing of electrical pulse and flux refining are as follows: (1) Cut and crush the brass raw material, weigh about 1000g of waste and place it in a graphite crucible. Using graphite rods as electrodes, insert one end of the two graphite rods into the melt, and connect the other end to a copper wire led out from a pulse power supply device. Calculate the height of the melt in advance, and insert the graphite electrode rods to about half the height of the molten metal; (2) Heat the scrap brass material to 1000℃ and hold for 2 minutes to ensure complete melting of the brass alloy. Then add half the amount of refining flux. The refining flux composition is: Na2B4O7 45%, Na2CO3 20%, NaCl 15%, NaF 20%. The amount of refining flux added accounts for 1% of the mass of the brass melt. (3) Turn on the pulse power supply and set the pulse current parameters: pulse current 200A, pulse frequency 800Hz. After being treated with 1000℃ electric pulse for 15 minutes, add the remaining refining flux, continue to hold for 5 minutes, and then turn off the high-frequency induction heating power supply; (4) Continue to apply electric pulses to the solidification stage of the melt. After 30 minutes, turn off the pulse power supply until the alloy cools down to room temperature with the furnace. Then, cut a longitudinal section area between the two graphite electrode rods and take a sample for chemical composition testing.

[0064] After synergistic treatment with pulsed current and flux refining, the contents of impurities Bi and Fe elements decreased from 1.43 wt.% and 0.79 wt.% to 0.59 wt.% and 0.39 wt.%, respectively, with impurity removal rates of 58.7% and 50.6%, respectively.

[0065] Comparative Example 10 Similar to the steps and parameters used in Example 4, the refining agent was added in a single step instead of in two stages.

[0066] The steps for the synergistic processing of electrical pulse and flux refining are as follows: (1) Cut and crush the brass raw material, weigh about 1000g of waste and place it in a graphite crucible. Using graphite rods as electrodes, insert one end of the two graphite rods into the melt, and connect the other end to a copper wire led out from a pulse power supply device. Calculate the height of the melt in advance, and insert the graphite electrode rods to about half the height of the molten metal; (2) Heat the scrap brass material to 1000℃ and hold for 2 minutes to ensure complete melting of the brass alloy. Then add all the refining flux. The refining flux composition is: Na2B4O7 45%, Na2CO3 20%, NaCl 15%, NaF 20%. The amount of refining flux added accounts for 1% of the mass of the brass melt. (3) Turn on the pulse power supply and set the pulse current parameters: pulse current 200A, pulse frequency 800Hz. After being treated with a 1000℃ electric pulse for 15 minutes, turn off the high-frequency induction heating power supply; (4) Continue to apply electric pulses to the solidification stage of the melt. After 30 minutes, turn off the pulse power supply until the alloy cools down to room temperature with the furnace. Then, cut a longitudinal section area between the two graphite electrode rods and take a sample for chemical composition testing.

[0067] After synergistic treatment with pulsed current and flux refining, the contents of impurities Bi and Fe elements decreased from 1.43 wt.% and 0.79 wt.% to 0.53 wt.% and 0.40 wt.%, respectively, with impurity removal rates of 63% and 49.4%, respectively.

Claims

1. A method for synergistic separation of impurity elements from molten brass using electrical pulses and refining agents, characterized in that: Divide the refining agent into two parts, heat the scrap brass material to obtain a melt, add the first part of the refining agent to the melt, then apply an electric pulse to the melt for a period of time, then add the second part of the refining agent, and after another period of time, stop heating, continue to apply an electric pulse to the solidification stage of the melt for a period of time, and then turn off the pulse power supply to obtain the product. The mass ratio of the first part of the refining agent to the second part of the refining agent is 1 to 3:

1.

2. The method for synergistic separation of impurity elements in molten brass using electrical pulses and refining agents according to claim 1, characterized in that: First, crush the scrap brass material and place it in a graphite crucible. Then, insert one end of two graphite electrode rods connected to the pulse power supply into the graphite crucible. The depth of insertion of the graphite electrode rods is 1 / 4 to 1 / 2 of the total height of the melt.

3. The method for synergistic separation of impurity elements in molten brass using electrical pulses and refining agents according to claim 1, characterized in that: The refining agent, by mass percentage, has the following composition: Na2B4O7 30%~50%, Na2CO3 10%~20%, NaCl 5%~10%, NaF 5%~10%, and Cu-21.8Ca alloy 10%~30%.

4. The method for synergistic separation of impurity elements in molten brass using electrical pulses and refining agents according to claim 1, characterized in that: The total amount of the refining agent is 0.5% to 2% of the mass of the scrap brass.

5. The method for synergistic separation of impurity elements in molten brass using electrical pulses and refining agents according to claim 1, characterized in that: Heat the scrap brass material to 1000℃~1100℃ and hold for 2~10 minutes to obtain a melt.

6. The method for synergistic separation of impurity elements in molten brass using electrical pulses and refining agents according to claim 1, characterized in that: Add the first part of refining agent to the melt, then apply an electric pulse treatment to the melt at 1000~1100℃ for 5~15 minutes, then add the second part of refining agent, continue the electric pulse treatment for 5~15 minutes, and then stop heating.

7. The method for synergistic separation of impurity elements in molten brass using electrical pulses and refining agents according to claim 1, characterized in that: Continue to apply electrical pulse treatment to the solidification stage of the melt for 10-30 minutes, then turn off the pulse power supply.

8. The method for synergistic separation of impurity elements in molten brass using electrical pulses and refining agents according to claim 1, characterized in that: The waveform of the pulse power supply used for the electrical pulse processing is a rectangular wave, and the voltage of the pulse power supply is 0~12V.

9. The method for synergistic separation of impurity elements in molten brass using electrical pulses and refining agents according to claim 1, characterized in that: The pulse frequency of the electrical pulse processing is 20~1000Hz, and the pulse current is 50~250A.

10. The method for synergistic separation of impurity elements in molten brass using electrical pulses and refining agents according to claim 1, characterized in that: After turning off the pulse power supply, the brass alloy was obtained after cooling to room temperature in the furnace to obtain impurities.

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