A gradient current net blocking device, vacuum induction melting furnace and blocking method

Abstract

The present application relates to a kind of gradient current net blocking device, vacuum induction melting furnace and blocking method, gradient current net blocking device generates gradient current net in the case of being passed into pulse current, gradient current net blocking device is in vacuum induction melting furnace, for the inclusion in the vacuum alloy before casting is blocked, inclusion includes oxygen, nitrogen, sulfur, and the content of inclusion is reduced by blocking.The gradient current net is formed by pulse current in the chute, and the gradient current net forms resistance to the movement of inclusion in high-temperature alloy melt, thereby filtering and removing inclusion from high-temperature alloy melt;In addition, since the pulse current changes the free energy of high-temperature alloy melt system, the solid solubility of oxygen, nitrogen and sulfur in high-temperature alloy melt is reduced, the discharge of oxygen, nitrogen and sulfur gas components is promoted, and the solid solubility of oxygen, nitrogen and sulfur in high-temperature alloy melt is further reduced;Pulse current ensures that larger current gradient is constructed under low energy consumption, so that the method of the present application is green and energy-saving.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature alloy melt purification technology, and particularly relates to a gradient current grid blocking device, a vacuum induction melting furnace, and a blocking method. Background Technology

[0002] Nickel-based and other high-temperature alloys possess advantages such as high high-temperature strength, good oxidation resistance and heat corrosion resistance, and low fatigue crack propagation rate, making them widely used in the aerospace field and a preferred material for manufacturing key hot-end components such as turbine disks for advanced aero-engines. With the continuous improvement of engine thrust-to-weight ratio, higher requirements are placed on the performance of turbine disk materials, as well as the purity of high-temperature alloys. Impurity elements in nickel-based high-temperature alloys, especially oxygen, nitrogen, and sulfur, have a significant impact on their performance and service life. High oxygen, nitrogen, and sulfur content leading to porosity and inclusion defects is one of the causes of stress concentration and even fracture. Inclusions in nickel-based high-temperature alloys mainly include: ceramic inclusions, simple oxygen, nitrogen, and sulfide inclusions, and slag inclusions. ① Ceramic inclusions mainly contain complex composite oxide inclusions such as aluminum, calcium, silicon, oxygen, and sodium. These oxides form relatively large particle inclusions in the alloy, with Al2O3·SiO2 and MgO·Al2O3 as the main components, and also containing small amounts of calcium, sodium, and aluminum silicates. Because these inclusions are typically large in size in nickel-based superalloys, they are hard, brittle, and have poor deformability, significantly reducing the fatigue performance and impact resistance of the superalloys. ② Simple oxygen, nitrogen, and sulfide inclusions are mainly composed of simple compounds formed by non-metallic elements such as carbon, nitrogen, oxygen, and sulfur with metallic elements. These inclusions in the alloy mainly consist of simple metallic compounds such as oxides (Al₂O₃ and SiO₂), sulfides (FeS, MnS), and nitrides (NbN, TiN). These inclusions are small in size, usually rhomboid in shape, hard and brittle, and easily cause fatigue failure due to excessive stress concentration. ③ Slag inclusions are mainly composed of metallic elements such as titanium, tantalum, niobium, oxygen, aluminum, calcium, and chromium. These metallic elements will combine with sulfur and oxygen during the alloy smelting process to form complex sulfides or sulfur oxides, such as (Mn, Ni)S and Y2OS. They vary in size and have irregular shapes in the alloy, which can easily cause segregation in the alloy, leading to cracks inside the alloy, reducing the fatigue life of the alloy, and thus affecting the application performance of the alloy.

[0003] Existing technology 1, a method for preparing high-purity nickel-based superalloys using magnetic field-enhanced electron beam refining and casting, involves coupling a magnetic field to the superalloy melt during electron beam refining and melting, thereby controlling inclusion movement and achieving melt purification. This method utilizes the Lorentz force generated by the magnetic field to electromagnetically stir the melt for purification, which is a conventional electromagnetic purification technique. However, this Lorentz force causes the melt itself to move, and the fluid flow field can lead to the re-entry of inclusions, resulting in insufficient impurity removal.

[0004] The prior art (Technology 2) describes a method and apparatus for purifying molten metal using electromagnetic vortex driving force. This method applies an electromagnetic composite field to the high-temperature alloy melt as it flows through a trough, generating a vortex driving force to remove inclusions through directional movement. However, this electromagnetic composite field requires the coupling of direct current and a gradient magnetic field to create the vortex suction force and control the directional movement of inclusions. This necessitates complex modifications to the high-temperature alloy trough and requires a large current to meet the inclusion removal requirements, both of which increase smelting costs and energy consumption.

[0005] Existing traditional processes such as vacuum induction melting, vacuum melting + electroslag remelting, Ca treatment, and ceramic filtration can no longer meet the requirements of the aerospace industry for high-temperature alloys with higher purity. Therefore, it is urgent to study a low-pollution, low-emission, and low-cost high-efficiency industrial high-temperature alloy melting and impurity removal technology. Summary of the Invention

[0006] In order to overcome the problems existing in the current technology, the present invention provides a gradient current grid blocking device, a vacuum induction melting furnace and a blocking method to solve the above-mentioned problems existing in the prior art.

[0007] A gradient current grid blocking device, the device comprising: a chute, a power supply, and electrodes.

[0008] The chute includes a high-temperature alloy melt pool, a first-stage slag baffle plate, and a second-stage slag baffle plate. The high-temperature alloy melt pool is located at one end of the chute and is used to contain the high-temperature alloy melt.

[0009] The first-stage slag baffle and the second-stage slag baffle are arranged side by side at the other end of the chute to block inclusions in the high-temperature alloy melt.

[0010] The two electrodes are respectively fixed to the front side of the first-stage slag baffle, between the first-stage slag baffle and the second-stage slag baffle, or to the rear side of the second-stage slag baffle, for generating current in the high-temperature alloy melt;

[0011] The power source is connected to the two electrodes to provide pulsed current.

[0012] As described above and in any possible implementation, a further implementation is provided in which the power supply is a pulse generator, and the pulse current parameters generated are: frequency 1Hz~10000Hz, pulse width 1μs~200μs, and current density 1A / mm². 2 ~1000A / mm 2 .

[0013] In addition to the aspects and any possible implementations described above, a further implementation is provided, which further includes a wire through which the power source connects the two electrodes, the wire being a copper wire wrapped with ceramic insulating fiber.

[0014] In addition to the aspects and any possible implementations described above, a further implementation is provided in which the electrode is made of pure nickel and is in the shape of a strip, a rod, or other shapes.

[0015] The present invention also provides a vacuum induction melting furnace, including the gradient current grid blocking device, wherein the gradient current grid blocking device is fixed inside the vacuum induction melting furnace.

[0016] In addition to the aspects described above and any possible implementations, a further implementation is provided in which the vacuum induction melting furnace further includes a ceramic filter screen disposed between the second-stage slag baffle plate of the gradient current grid blocking device and the other end of the chute.

[0017] The present invention also provides a method for blocking inclusions in high-temperature alloys, wherein the method is implemented using the vacuum induction melting furnace described in the present invention.

[0018] In addition to the aspects and any possible implementations described above, a further implementation is provided, the method comprising the following steps:

[0019] S1. Add the high-temperature alloy raw material to the vacuum induction melting furnace, and start the vacuum induction melting furnace to melt the high-temperature alloy;

[0020] S2. Set the pulse current parameters, turn on the power supply of the gradient current network blocking device, and apply the pulse current generated by the power supply to the two electrodes. The two electrodes form a gradient current network at a fixed position.

[0021] S3. The gradient current grid blocks the movement of inclusions in the molten high-temperature alloy in S1, and retains the inclusions in the chute. After the high-temperature alloy with the inclusions removed is further filtered by the ceramic filter and two slag baffles, it is cast to form the master alloy.

[0022] S4. Prepare at least three samples from at least three different samples of the master alloy, and measure the oxygen, nitrogen and sulfur content in at least the three samples.

[0023] In addition to the aspects described above and any possible implementation, a further implementation is provided in which the pulse current parameters in S2 are set to a frequency of 2000Hz, a current of 200A, and a pulse width of 10μs, 30μs, or 60μs.

[0024] In addition to the aspects and any possible implementations described above, a further implementation is provided, which further includes S5. After grinding and polishing at least three samples, inclusion analysis is performed, and inclusions with a size greater than 0.5 μm per square millimeter in each sample are counted, and the average value of the counts of at least three samples is taken to measure the content of inclusions.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention has the following advantages over the prior art:

[0027] The gradient current grid blocking device of this invention generates a gradient current grid when a pulsed current is applied. This device, used in a vacuum induction melting furnace, blocks inclusions in the vacuum alloy before casting. These inclusions include oxygen, nitrogen, and sulfur. Blocking reduces the inclusion content, thereby reducing the oxygen, nitrogen, and sulfur content in the high-temperature alloy. The gradient current grid is formed by the pulsed current within the chute. This grid resists the movement of inclusions in the high-temperature alloy melt, thus filtering them out. Furthermore, the pulsed current alters the free energy of the high-temperature alloy melt system, reducing the solid solubility of oxygen, nitrogen, and sulfur, promoting the expulsion of these gaseous components, and further reducing the dissolved oxygen, nitrogen, and sulfur content in the melt. Moreover, the pulsed current ensures a larger current gradient with low energy consumption, making the blocking method of this invention green and energy-efficient. In addition, this invention does not require complex structural modifications to existing high-temperature alloy chutes; simply applying two electrodes at appropriate locations achieves excellent high-temperature alloy purification. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the device structure of the present invention;

[0029] Figure 2 A schematic diagram of the process of this invention. Detailed Implementation

[0030] To better understand the technical solution of this invention, the content of this invention includes, but is not limited to, the specific embodiments described below. Similar technologies and methods should be considered within the scope of protection of this invention. To make the technical problems to be solved, the technical solutions, and advantages of this invention clearer, a detailed description will be provided below in conjunction with the accompanying drawings and specific embodiments.

[0031] It should be understood that the embodiments described in this invention are merely some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0032] like Figure 1 As shown, this invention provides a gradient current grid blocking device for high-temperature alloy smelting. The chute includes a high-temperature alloy melt pool, a first-stage slag-blocking plate, and a second-stage slag-blocking plate. The high-temperature alloy melt pool is located at one end of the chute to accommodate the high-temperature alloy melt. The first-stage and second-stage slag-blocking plates are arranged side-by-side at the other end of the chute to block inclusions in the high-temperature alloy melt. Both slag-blocking plates are used to block slag on the upper side of the high-temperature alloy melt, which is formed by the accumulation of a large number of inclusions. The chute is the carrier in the high-temperature alloy casting process. During the casting process, the high-temperature alloy melt first enters the chute. Because the density of the slag formed by inclusions in the high-temperature alloy is lower than that of the high-temperature alloy melt, the slag floats on top of the high-temperature alloy melt and is blocked by the two-stage slag-blocking plates. The clean high-temperature alloy melt flows through the holes on the lower side of the slag-blocking plates and then enters the casting mold for casting.

[0033] The two electrodes can be fixed to the front side of the first-stage slag-blocking plate, between the first-stage and second-stage slag-blocking plates, or to the rear side of the second-stage slag-blocking plate, respectively. Current flows from the positive electrode to the negative electrode, thereby forming a certain current distribution in the high-temperature alloy melt.

[0034] The power source is connected to the two electrodes via the wires. The power source generates a pulse current, which flows through the wires and electrodes into the high-temperature alloy melt.

[0035] When the high-temperature alloy melt enters the chute, the pulsed current flows through the two electrodes placed in the chute and forms a certain gradient current distribution in the high-temperature alloy melt. This gradient current hinders the movement of inclusions, thereby achieving the removal of inclusions from the high-temperature alloy melt.

[0036] The power source is a pulse generator, the wire material is copper wire wrapped with ceramic heat-insulating fiber, and there are two electrodes made of pure nickel in the form of strips, rods, or other shapes and sizes.

[0037] A pulse generator is used as the power source, and electrodes of various shapes made of pure nickel are installed on the high-temperature alloy melt casting chute. The specific installation positions can be in front of, behind, or below the first-stage slag baffle, or behind the second-stage slag baffle. Different electrode positions result in different current distributions, leading to varying filtration effects on inclusions. In this invention, installing the electrodes in front of, behind, or below the slag baffle creates a gradient current network, thereby filtering inclusions in the high-temperature alloy melt. The two electrodes are connected to the positive and negative terminals of the pulse power source, respectively. When the electrodes apply current to the high-temperature alloy melt, a specific current distribution is formed within the melt in the chute. The current distribution characteristics in the high-temperature alloy melt are determined by the shape of the melt, its resistance, and the positions of the two electrodes. The current distribution characteristics can be simulated using Maxwell's equations. In this invention, the unevenly distributed current formed by the electrodes creates a gradient current network that hinders the movement of inclusions.

[0038] Preferably, the present invention also provides a vacuum induction melting furnace, including the gradient current grid blocking device of the present invention. The gradient current grid blocking device is fixed inside the vacuum induction melting furnace. The vacuum induction melting furnace is an existing high-temperature alloy melting device, which includes a casting process, that is, pouring the high-temperature alloy melt into a chute, and then pouring the high-temperature alloy melt into a mold for casting. In the present invention, two electrodes are applied at corresponding positions of the two baffles of the chute. After the electrodes are energized, a current gradient grid is formed in the chute. That is, the high-temperature alloy chute, power supply, electrodes and wires constitute the gradient current grid blocking device of the present invention. The current gradient grid can filter inclusions and greatly improve the cleanliness of the cast high-temperature alloy.

[0039] The vacuum induction melting furnace also includes a ceramic filter screen, which is disposed between the second-stage slag baffle plate of the gradient current grid blocking device and the end of the chute, for further filtering out inclusions in the high-temperature alloy.

[0040] In the vacuum induction melting and casting process of high-temperature alloys, pulsed currents are applied at multiple locations in the casting chute. The pulsed current parameters are controlled as follows: frequency 1Hz~10000Hz, pulse width 1μs~200μs, and current density 1A / mm². 2 ~1000A / mm 2 .

[0041] Harmful inclusions exist in high-temperature alloy melts, including oxides, nitrogen oxides, and sulfides. High-temperature alloys also contain dissolved oxygen, nitrogen, and sulfur elements, which can form the aforementioned inclusions during solidification. Therefore, it is necessary to smelt high-temperature alloys to remove these inclusions and harmful elements such as oxygen, nitrogen, and sulfur. This invention provides a method for removing inclusions and reducing the oxygen, nitrogen, and sulfur content in high-temperature alloys, achieved using a vacuum induction furnace with an applied gradient current grid blocking device, specifically including the following steps:

[0042] S1. Add the high-temperature alloy raw material to the vacuum induction melting furnace, and start the vacuum induction melting furnace to melt the high-temperature alloy. The high-temperature alloy raw material can be raw material, high-temperature alloy waste, production return material, etc. Since the waste has a higher content of inclusions, the method of the present invention can remove them more effectively.

[0043] S2. Set the pulse current parameters, turn on the power supply of the gradient current grid blocking device, and the pulse current generated by the power supply is applied to the high-temperature alloy melt through two electrodes. The unevenly distributed current is formed between the two electrodes, thus forming a gradient current grid. This gradient current grid can hinder the movement of inclusions and filter them out from the high-temperature alloy melt. In this step, the pulse current parameters are set to a frequency of 2000Hz, a current of 200A, and a pulse width of 10μs, 30μs, or 60μs.

[0044] S3. The gradient current network blocks the movement of inclusions in the molten high-temperature alloy in S1, trapping the inclusions in the chute. After further filtration by the ceramic filter, the high-temperature alloy with inclusions removed is cast to form the master alloy. In the chute, due to the different density distribution of the current network, a gradient current network is formed at the chute opening, which hinders the movement of inclusions in the high-temperature alloy melt. At the same time, due to the change in the free energy of the alloy system by the pulse current, the solid solubility of oxygen, nitrogen, and sulfur in the high-temperature alloy melt is reduced, promoting the discharge of dissolved oxygen, nitrogen, sulfur, and other gaseous components, reducing the dissolved oxygen, nitrogen, and sulfur content in the high-temperature alloy, thereby significantly reducing the total oxygen, nitrogen, and sulfur content in the high-temperature alloy melt and improving the cleanliness of the cast high-temperature alloy.

[0045] S4. Take at least three samples from at least three different parts of the master alloy and measure the oxygen, nitrogen and sulfur content in the at least three samples to obtain the total oxygen, nitrogen and sulfur content of the master alloy, so as to verify the purity of the cast master alloy.

[0046] S5. After polishing at least three samples, perform inclusion analysis. Count the inclusions larger than 0.5 μm per square millimeter in each sample, and take the average of the counts from at least three samples to measure the inclusion content in order to determine the purity of the casting master alloy.

[0047] In this invention, the first-stage slag-blocking plate is a primary slag-blocking plate, and the second-stage slag-blocking plate is a secondary slag-blocking plate.

[0048] Example 1:

[0049] This embodiment applies a gradient current grid to the vacuum induction melting and casting process of IN738LC high-temperature alloy to block the movement of inclusions and improve the cleanliness of the material. The specific steps are as follows:

[0050] Step 1: Use pure nickel to make a strip electrode, then install the electrode on the lower side of the first-stage slag baffle of the chute, and then send the chute into the vacuum casting chamber of the 1500kg vacuum induction melting furnace.

[0051] Step 2: Using IN738LC high-temperature alloy recycled material as raw material, IN718 is a type of high-temperature alloy. IN718 recycled material is scrap of IN718, which may have a slightly higher inclusion content. The recycled material is added to a 1500kg vacuum induction melting furnace. After the high-temperature alloy melts in the 1500kg vacuum induction melting furnace, casting is performed. Before casting begins, a pulsed current is activated, with the following parameters set: frequency 2000Hz, current 200A, pulse width 60μs. The pulsed current forms a gradient current network to impede the movement of inclusions in the high-temperature alloy. The pulsed current generated by the power supply is applied to the high-temperature alloy melt through two electrodes, forming a certain current distribution in the high-temperature alloy melt in the chute. The current distribution characteristics in the melt are determined by the shape of the high-temperature alloy melt, the resistance of the high-temperature alloy melt, and the positions of the two electrodes. The current distribution characteristics can be simulated and calculated using existing Maxwell's equations and other existing algorithms. The unevenly distributed current forms a gradient current network, which hinders the movement of inclusions, preventing them from flowing through the holes on the underside of the baffle plate and thus retaining them in the chute. This filters out inclusions from the high-temperature alloy melt, allowing the pure high-temperature alloy melt to flow through the gradient current network, while the inclusions are blocked and retained in the chute. Simultaneously, the pulsed current's influence on the free energy of the high-temperature alloy melt system reduces the solid solubility of oxygen, nitrogen, and sulfur in the melt, promoting the expulsion of these gaseous components and further reducing the total oxygen, nitrogen, and sulfur content of the high-temperature alloy melt.

[0052] Step 3: Using wire cutting, three cubes (6mm × 6mm × 6mm) were taken from the top, bottom, and middle sections of the cast master alloy rod. The sulfur content of the materials from these three different locations was measured using glow discharge mass spectrometry, and the nitrogen and oxygen content was tested using a nitrogen, hydrogen, and oxygen analyzer. The removal efficiency of this method for harmful elements such as oxygen, nitrogen, and sulfur can be determined by analyzing the oxygen, nitrogen, and sulfur content of the master alloy. After polishing, the samples from the three locations were subjected to automated inclusion analysis using a field emission scanning electron microscope (FET), counting inclusions larger than 0.5μm per square millimeter. The oxygen, nitrogen, sulfur, and inclusion contents were averaged across the three locations. The filtration effect of this method on inclusions can be determined by analyzing the oxygen, nitrogen, and sulfur content of the master alloy.

[0053] Example 2:

[0054] Step 1: Use pure nickel to make a strip electrode, then install the electrode on the lower side of the first-stage slag baffle of the chute, and then send the chute into the vacuum casting chamber of the 1500kg vacuum induction melting furnace.

[0055] Step 2: IN738LC high-temperature alloy recycled material is added to a 1500kg vacuum induction melting furnace. After the high-temperature alloy melts in the furnace, it is cast. Before casting begins, a pulsed current is activated, with the following parameters set: frequency 2000Hz, current 200A, pulse width 30μs. The pulsed current forms a gradient current network to block the movement of inclusions in the high-temperature alloy. The pulsed current generated by the power supply is applied to the high-temperature alloy melt through two electrodes, forming a certain current distribution in the melt within the chute. The current distribution characteristics in the melt are determined by the shape of the melt, its resistance, and the positions of the electrodes. The current distribution characteristics can be simulated using Maxwell's equations. The unevenly distributed current forms a gradient current network, which hinders the movement of inclusions, preventing them from flowing through the holes under the baffle plate and thus retaining them in the chute, thereby filtering them out of the high-temperature alloy melt. The process involves allowing pure high-temperature alloy melt to flow through a gradient current grid, while inclusions are blocked and retained in the chute by the grid. Simultaneously, the pulsed current's effect on the free energy of the high-temperature alloy melt system reduces the solid solubility of oxygen, nitrogen, and sulfur in the melt, promoting the removal of these gaseous components and further decreasing the total oxygen, nitrogen, and sulfur content of the high-temperature alloy melt.

[0056] Step 3: Using wire cutting, three cubes (6mm × 6mm × 6mm) were taken from the top, bottom, and middle sections of the cast master alloy rod. The sulfur content of the materials from these three different locations was measured using glow discharge mass spectrometry, and the nitrogen and oxygen content was tested using a nitrogen, hydrogen, and oxygen analyzer. The removal efficiency of this method for harmful elements such as oxygen, nitrogen, and sulfur can be determined by analyzing the oxygen, nitrogen, and sulfur content of the master alloy. After polishing the samples from the three locations, automatic inclusion analysis was performed using a field emission scanning electron microscope. Inclusions larger than 0.5μm per square millimeter were counted. The oxygen, nitrogen, sulfur, and inclusion contents were averaged across the three locations. The filtration effect of this method on inclusions can be determined by analyzing the oxygen, nitrogen, and sulfur content of the master alloy.

[0057] Example 3:

[0058] Step 1: Use pure nickel to make a strip electrode, then install the electrode on the lower side of the first-stage slag baffle of the chute, and then send the chute into the vacuum casting chamber of the 1500kg vacuum induction melting furnace.

[0059] Step 2: IN738LC high-temperature alloy recycled material is added to a 1500kg vacuum induction melting furnace. After the high-temperature alloy melts in the furnace, it is cast. Before casting begins, a pulsed current is activated, with the following parameters set: frequency 2000Hz, current 200A, pulse width 10μs. The pulsed current forms a gradient current network to block the movement of inclusions in the high-temperature alloy. The pulsed current generated by the power supply is applied to the high-temperature alloy melt through two electrodes, forming a certain current distribution in the melt within the chute. The current distribution characteristics in the melt are determined by the shape of the melt, its resistance, and the positions of the electrodes. The current distribution characteristics can be simulated using Maxwell's equations. The unevenly distributed current forms a gradient current network, which hinders the movement of inclusions, preventing them from flowing through the holes under the baffle plate and thus retaining them in the chute, thereby filtering them out of the high-temperature alloy melt. The process involves allowing pure high-temperature alloy melt to flow through a gradient current grid, while inclusions are blocked and retained in the chute by the grid. Simultaneously, the pulsed current's effect on the free energy of the high-temperature alloy melt system reduces the solid solubility of oxygen, nitrogen, and sulfur in the melt, promoting the removal of these gaseous components and further decreasing the total oxygen, nitrogen, and sulfur content of the high-temperature alloy melt.

[0060] Step 3: Using wire cutting, three cubes with dimensions of 6mm × 6mm × 6mm were taken from the top, bottom, and middle sections of the cast master alloy rod. The sulfur content of the materials from these three different locations was measured using glow discharge mass spectrometry, and the nitrogen and oxygen content was tested using a nitrogen, hydrogen, and oxygen analyzer. The removal effect of this method on harmful elements such as oxygen, nitrogen, and sulfur can be determined by the oxygen, nitrogen, and sulfur content of the master alloy. After grinding and polishing, the samples from the three locations were subjected to automatic inclusion analysis using a field emission scanning electron microscope. Inclusions larger than 0.5μm per square millimeter were counted. The oxygen, nitrogen, sulfur, and inclusion contents were taken as the average content of the three locations. The filtration effect of this method on inclusions can be determined by the oxygen, nitrogen, and sulfur content of the master alloy. Example 4:

[0061] Step 1: Use pure nickel to make a strip electrode, then install the electrode on the lower side of the secondary slag baffle of the chute, and then send the chute into the vacuum casting chamber of the 1500kg vacuum induction melting furnace.

[0062] Step 2: IN738LC high-temperature alloy recycled material is added to a 1500kg vacuum induction melting furnace. After the high-temperature alloy melts in the furnace, it is cast. Before casting begins, a pulsed current is activated, with the following parameters set: frequency 1000Hz, current 200A, pulse width 60μs. The pulsed current forms a gradient current network to block the movement of inclusions in the high-temperature alloy. The pulsed current generated by the power supply is applied to the high-temperature alloy melt through two electrodes, forming a certain current distribution in the melt within the chute. The current distribution characteristics in the melt are determined by the shape of the melt, its resistance, and the positions of the electrodes. The current distribution characteristics can be simulated using Maxwell's equations. The unevenly distributed current forms a gradient current network, which hinders the movement of inclusions, preventing them from flowing through the holes under the baffle plate and thus retaining them in the chute, thereby filtering them out of the high-temperature alloy melt. Pure high-temperature alloy melt flows through a gradient current grid, while inclusions are blocked and retained in the chute by the grid. Simultaneously, the pulsed current affects the free energy of the high-temperature alloy melt system, reducing the solid solubility of oxygen, nitrogen, and sulfur in the melt, promoting the expulsion of gaseous components such as oxygen, nitrogen, and sulfur, and further reducing the total oxygen, nitrogen, and sulfur content of the high-temperature alloy melt.

[0063] Step 3: Using wire cutting, three cubes (6mm × 6mm × 6mm) were taken from the top, bottom, and middle sections of the cast master alloy rod. The sulfur content of the materials from these three different locations was measured using glow discharge mass spectrometry, and the nitrogen and oxygen content was tested using a nitrogen, hydrogen, and oxygen analyzer. The removal efficiency of this method for harmful elements such as oxygen, nitrogen, and sulfur can be determined by analyzing the oxygen, nitrogen, and sulfur content of the master alloy. After polishing, the samples from the three locations were subjected to automated inclusion analysis using a field emission scanning electron microscope (FET), counting inclusions larger than 0.5μm per square millimeter. The oxygen, nitrogen, sulfur, and inclusion contents were averaged across the three locations. The filtration effect of this method on inclusions can be determined by analyzing the oxygen, nitrogen, and sulfur content of the master alloy.

[0064] Example 5:

[0065] Step 1: Use pure nickel to make a strip electrode, then install the electrode in front of the secondary slag baffle of the chute, and then send the chute into the vacuum casting chamber of the 1500kg vacuum induction melting furnace.

[0066] Step 2: IN738LC high-temperature alloy recycled material is added to a 1500kg vacuum induction melting furnace. After the high-temperature alloy melts in the furnace, it is cast. Before casting begins, a pulsed current is activated, with the following parameters set: frequency 2000Hz, current 200A, pulse width 60μs. The pulsed current forms a gradient current network to block the movement of inclusions in the high-temperature alloy. The pulsed current generated by the power supply is applied to the high-temperature alloy melt through two electrodes, forming a certain current distribution in the melt within the chute. The current distribution characteristics in the melt are determined by the shape of the melt, its resistance, and the positions of the electrodes. The current distribution characteristics can be simulated using Maxwell's equations. The unevenly distributed current forms a gradient current network, which hinders the movement of inclusions, preventing them from flowing through the holes under the baffle plate and thus retaining them in the chute, thereby filtering them out of the high-temperature alloy melt. Pure high-temperature alloy melt flows through a gradient current grid, while inclusions are blocked and retained in the chute by the grid. Simultaneously, the pulsed current affects the free energy of the high-temperature alloy melt system, reducing the solid solubility of oxygen, nitrogen, and sulfur in the melt, promoting the expulsion of gaseous components such as oxygen, nitrogen, and sulfur, and further reducing the total oxygen, nitrogen, and sulfur content of the high-temperature alloy melt.

[0067] Step 3: Using wire cutting, three cubes (6mm × 6mm × 6mm) were taken from the top, bottom, and middle sections of the cast master alloy rod. The sulfur content of the materials from these three different locations was measured using glow discharge mass spectrometry, and the nitrogen and oxygen content was tested using a nitrogen, hydrogen, and oxygen analyzer. The removal efficiency of this method for harmful elements such as oxygen, nitrogen, and sulfur can be determined by analyzing the oxygen, nitrogen, and sulfur content of the master alloy. After polishing, the samples from the three locations were subjected to automated inclusion analysis using a field emission scanning electron microscope (FET), counting inclusions larger than 0.5μm per square millimeter. The oxygen, nitrogen, sulfur, and inclusion contents were averaged across the three locations. The filtration effect of this method on inclusions can be determined by analyzing the oxygen, nitrogen, and sulfur content of the master alloy.

[0068] Example 6:

[0069] Step 1: Use pure nickel to make a strip electrode, then install the electrode on the back side of the secondary slag baffle of the chute, and then send the chute into the vacuum casting chamber of the 1500kg vacuum induction melting furnace.

[0070] Step 2: IN738LC high-temperature alloy recycled material is added to a 1500kg vacuum induction melting furnace. After the high-temperature alloy melts in the furnace, it is cast. Before casting begins, a pulsed current is activated, with the following parameters set: frequency 2000Hz, current 200A, pulse width 60μs. The pulsed current forms a gradient current network to block the movement of inclusions in the high-temperature alloy. The pulsed current generated by the power supply is applied to the high-temperature alloy melt through two electrodes, forming a certain current distribution in the melt within the chute. The current distribution characteristics in the melt are determined by the shape of the melt, its resistance, and the positions of the electrodes. The current distribution characteristics can be simulated using Maxwell's equations. The unevenly distributed current forms a gradient current network, which hinders the movement of inclusions, preventing them from flowing through the holes under the baffle plate and thus retaining them in the chute, thereby filtering them out of the high-temperature alloy melt. Pure high-temperature alloy melt flows through a gradient current grid, while inclusions are blocked and retained in the chute by the grid. Simultaneously, the pulsed current affects the free energy of the high-temperature alloy melt system, reducing the solid solubility of oxygen, nitrogen, and sulfur in the melt, promoting the expulsion of gaseous components such as oxygen, nitrogen, and sulfur, and further reducing the total oxygen, nitrogen, and sulfur content of the high-temperature alloy melt.

[0071] Step 3: Using wire cutting, three cubes (6mm × 6mm × 6mm) were taken from the top, bottom, and middle sections of the cast master alloy rod. The sulfur content of the materials from these three different locations was measured using glow discharge mass spectrometry, and the nitrogen and oxygen content was tested using a nitrogen, hydrogen, and oxygen analyzer. The removal efficiency of this method for harmful elements such as oxygen, nitrogen, and sulfur can be determined by analyzing the oxygen, nitrogen, and sulfur content of the master alloy. After polishing, the samples from the three locations were subjected to automated inclusion analysis using a field emission scanning electron microscope (FET), counting inclusions larger than 0.5μm per square millimeter. The oxygen, nitrogen, sulfur, and inclusion contents were averaged across the three locations. The filtration effect of this method on inclusions can be determined by analyzing the oxygen, nitrogen, and sulfur content of the master alloy.

[0072] Example 7 (Reference Group):

[0073] Step 1: Use pure nickel to make a strip electrode, then install the electrode on the lower side of the secondary slag baffle of the chute, and then send the chute into the vacuum casting chamber of the 1500kg vacuum induction melting furnace.

[0074] Step 2: IN738LC high-temperature alloy recycled material is added to a 1500kg vacuum induction melting furnace. After the high-temperature alloy melts in the furnace, it is cast. Before casting begins, a pulsed current is activated, with the following parameters set: frequency 0Hz, current 0A, pulse width 0μs. The pulsed current forms a gradient current network to impede the movement of inclusions in the high-temperature alloy. The pulsed current generated by the power supply is applied to the high-temperature alloy melt through two electrodes, forming a certain current distribution in the melt within the chute. The current distribution characteristics in the melt are determined by the shape of the melt, its resistance, and the positions of the electrodes. The current distribution characteristics can be simulated using Maxwell's equations. The non-uniformly distributed current forms a gradient current network, which hinders the movement of inclusions, preventing them from flowing through the holes under the baffle plate and thus retaining them in the chute, thereby filtering them out of the high-temperature alloy melt. Pure high-temperature alloy melt flows through a gradient current grid, while inclusions are blocked and retained in the chute by the grid. Simultaneously, the pulsed current affects the free energy of the high-temperature alloy melt system, reducing the solid solubility of oxygen, nitrogen, and sulfur in the melt, promoting the expulsion of gaseous components such as oxygen, nitrogen, and sulfur, and further reducing the total oxygen, nitrogen, and sulfur content of the high-temperature alloy melt.

[0075] Step 3: Using wire cutting, three cubes (6mm × 6mm × 6mm) were taken from the top, bottom, and middle sections of the cast master alloy rod. The sulfur content of the materials from these three different locations was measured using glow discharge mass spectrometry, and the nitrogen and oxygen content was tested using a nitrogen, hydrogen, and oxygen analyzer. The removal efficiency of this method for harmful elements such as oxygen, nitrogen, and sulfur can be determined by analyzing the oxygen, nitrogen, and sulfur content of the master alloy. After polishing, the samples from the three locations were subjected to automated inclusion analysis using a field emission scanning electron microscope (FET), counting inclusions larger than 0.5μm per square millimeter. The oxygen, nitrogen, sulfur, and inclusion contents were averaged across the three locations. The filtration effect of this method on inclusions can be determined by analyzing the oxygen, nitrogen, and sulfur content of the master alloy.

[0076] As shown in Table 1, compared to Example 7, the gradient current mesh treatment in Example 1 significantly reduced the content of oxygen, nitrogen, sulfur, and inclusions in the master alloy. This indicates that the gradient current mesh treatment method proposed in this patent has a significant effect on the removal of oxygen, nitrogen, sulfur, and inclusions from high-temperature alloys. Example 1 used the following pulse current parameters: frequency 2000Hz, current 200A, and pulse width 60μs, achieving the best removal effect of oxygen, nitrogen, sulfur, and inclusions. In Examples 2 and 3, compared to Example 1, reducing the pulse width significantly reduced the removal effect of oxygen, nitrogen, sulfur, and inclusions. In Example 4, compared to Example 1, reducing the pulse frequency slightly reduced the removal effect of oxygen, nitrogen, sulfur, and inclusions. In Example 5, compared to Example 1, changing the electrode application site from the bottom to the front significantly reduced the removal effect of oxygen, nitrogen, sulfur, and inclusions. In Example 6, compared to Example 1, changing the electrode application site from the bottom to the rear significantly reduced the removal effect of oxygen, nitrogen, sulfur, and inclusions. The above results demonstrate that gradient current meshes are highly effective in removing inclusions and harmful elements such as oxygen, nitrogen, and sulfur from high-temperature alloys. The pulse current parameters have a decisive influence on the removal of inclusions and harmful elements such as oxygen, nitrogen, and sulfur. Under the same operational description, mounting the electrode below the slag baffle plate yields even better results.

[0077] Table 1. Inclusions and elemental analysis of the master alloy rods obtained in the examples.

[0078]

[0079] The above description is merely a specific embodiment of the present invention for IN738LC high-temperature alloy, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art who, within the technical scope disclosed in the present invention, makes equivalent substitutions for similar materials or equipment or adjusts relevant technical parameters according to the technical solution and inventive concept of the present invention should be covered within the scope of protection of the present invention.

[0080] The foregoing description illustrates and describes several preferred embodiments of the present invention. However, as previously stated, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the inventive concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A gradient current grid blocking device, characterized in that, The device includes: a chute, a power source, and electrodes. The chute includes a high-temperature alloy melt pool, a first-stage slag baffle plate, and a second-stage slag baffle plate. The high-temperature alloy melt pool is located at one end of the chute and is used to contain the high-temperature alloy melt. The first-stage slag baffle and the second-stage slag baffle are arranged side by side at the other end of the chute to block inclusions in the high-temperature alloy melt. The two electrodes are respectively fixed to the front side of the first-stage slag baffle, between the first-stage slag baffle and the second-stage slag baffle, or to the rear side of the second-stage slag baffle, for generating current in the high-temperature alloy melt; The power source is connected to the two electrodes to provide pulsed current.

2. The gradient current grid blocking device according to claim 1, characterized in that, The power supply is a pulse generator, and the pulse current parameters generated are: frequency 1Hz~10000Hz, pulse width 1μs~200μs, and current density 1A / mm². 2 ~1000A / mm 2 .

3. The gradient current grid blocking device according to claim 1, characterized in that, It also includes a wire, through which the power source connects the two electrodes, the wire being a copper wire wrapped with ceramic insulating fiber.

4. The gradient current grid blocking device according to claim 1, characterized in that, The electrode is made of pure nickel and is in the shape of a strip, a rod, or other shapes.

5. A vacuum induction melting furnace, characterized in that, The gradient current grid blocking device according to any one of claims 1-4 is fixed inside the vacuum induction melting furnace.

6. The vacuum induction melting furnace according to claim 5, characterized in that, The vacuum induction melting furnace also includes a ceramic filter screen, which is disposed between the second-stage slag baffle plate of the gradient current grid blocking device and the other end of the chute.

7. A method for blocking inclusions in high-temperature alloys, characterized in that, The method is implemented using the vacuum induction melting furnace described in any one of claims 5-6.

8. The method for blocking inclusions in high-temperature alloys according to claim 7, characterized in that, The method consists of the following steps: S1. Add the high-temperature alloy raw material to the vacuum induction melting furnace, and start the vacuum induction melting furnace to melt the high-temperature alloy; S2. Set the pulse current parameters, turn on the power supply of the gradient current network blocking device, and apply the pulse current generated by the power supply to the two electrodes, forming a gradient current network at the two electrodes in a fixed position; S3. The gradient current grid blocks the movement of inclusions in the molten high-temperature alloy in S1, and retains the inclusions in the chute. After the high-temperature alloy with the inclusions removed is further filtered by two slag baffles and a ceramic filter, it is cast to form a master alloy. S4. Prepare at least three samples from at least three different samples of the master alloy, and measure the oxygen, nitrogen and sulfur content in at least the three samples.

9. The method according to claim 8, characterized in that, In S2, the pulse current parameters are set to a frequency of 2000Hz, a current of 200A, and a pulse width of 10μs, 30μs, or 60μs.

10. The method according to claim 8, characterized in that, It also includes S5. After grinding and polishing at least three samples, inclusion analysis is performed. In each sample, inclusions with a size greater than 0.5 μm in a square millimeter range are counted, and the average value of the counts of at least three samples is taken to measure the content of inclusions.

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