Rheological die casting preparation method for aluminum electrolytic metal ceramic anode

Abstract

The present invention provides a rheological die casting preparation method for an aluminum electrolytic metal ceramic anode, comprising: mixing metal ceramic powder and an organic binder to obtain a material agglomerate, molding the material agglomerate to obtain an anode shell material, fixing a T-shaped electric connection guide rod containing a soldering lug to the center of a mold, preheating the mold, and preheating the anode shell material, then injecting the anode shell material into a cavity of the mold via a flow channel, cooling and demolding the mold to obtain a metal ceramic anode blank containing the T-shaped electric connection guide rod, degreasing and sintering the metal ceramic anode blank containing the electric connection guide rod to obtain the aluminum electrolytic metal ceramic anode. According to the present invention, integrated near net shape forming of the special-shaped metal ceramic anode shell and the electric connection guide rod is realized by means of the rheological die casting preparation method, and the bottom of the T-shaped guide rod is tightly connected to the inner wall of the metal ceramic, solving the problems that aluminum electrolytic metal ceramic of a complex structure is difficult to form, and the electric connection guide rod is prone to falling off.

Description

A method for preparing anode for aluminum electrolysis metal ceramics by rheocasting Technical Field

[0001] The invention belongs to the technical field of powder metallurgy and powder engineering, and relates to an inert anode for aluminum electrolysis, and in particular to a rheo-compression molding method for preparing a metal ceramic anode for aluminum electrolysis. Background Art

[0002] Carbon-free aluminum electrolysis technology is a new aluminum production technology that replaces traditional carbon anodes with inert anodes. It reduces carbon consumption and eliminates greenhouse gas and toxic gas emissions during the electrolysis process, and is currently a key area of ​​focus for the international aluminum industry. NiFe2O4-based cermets, with their excellent electrical conductivity, thermal shock resistance, and corrosion resistance, are an important type of inert anode material. Currently, the manufacture of complex-shaped cermet inert anodes faces challenges such as forming difficulties, low sintering density, and difficulty connecting to metal electrical connection rods, severely hindering the industrial application of metal inert anodes. Technical issues

[0003] At present, the shape of metal ceramic inert anodes is mostly deep cup-shaped, and the internal structure is relatively simple, which cannot provide sufficiently strong electrical connections, such as patent US2020 / 0063279; anodes with complex shapes, such as US2020 / 0115812A1 metal anode, are difficult to apply to metal ceramic material systems due to processing difficulties; patent CN113172222A discloses a complex anode with a T-shaped structure, which is manufactured by a gel injection molding process, and can achieve rapid net forming of metal ceramic inert anodes, but the material system applicable to this method and the size of the anode obtained are still limited; patent CN113337849A discloses a 3D printing preparation method for metal ceramic inert anodes, but the manufacturing process is long and does not consider the electrical connection problem of special-shaped structures; patents EP2853621B1 and US7316577B2 use intermediate fillers and co-firing to complete the electrical connection of conductive rods, but can only complete the connection of vertical rods, and the bonding strength and conductivity after electrical connection are limited. Technical Solutions

[0004] In order to solve the above-mentioned technical problems existing in the background technology, the purpose of the present invention is to provide a method for preparing aluminum electrolytic metal ceramic anodes by rheo-injection molding. The method provided by the present invention can realize the one-time near-net forming of the special-shaped metal ceramic anode shell and the electrical connection of the T-shaped guide rod. The process is rapid and the forming precision is high. At the same time, the high-densification sintering of the anode shell and the electrical connection of the guide rod are completed simultaneously through one-step sintering, without the need for separate processing and welding processes. It is suitable for mass production of aluminum electrolytic metal ceramic inert anodes with complex geometric shapes, high performance and high precision.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a rheo-injection preparation method for an aluminum electrolysis metal ceramic anode. The method comprises the following steps: mixing metal ceramic powder with an organic binder to obtain a material mass, molding the material mass to obtain an anode shell material, fixing a T-shaped electrical connection guide rod containing a welding piece at the center of a mold, preheating the mold to a temperature 10-50° C. higher than the softening point of the anode shell material, and simultaneously preheating the anode shell material to a temperature 10-50° C. higher than the softening point of the anode shell material; then, at a pressure of 20-200 MPa, preferably 20-50 MPa, injecting the anode shell material into the cavity of the mold through a flow channel, maintaining the pressure for 1-60 minutes, stopping mold heating, and demolding the mold after cooling to obtain a metal ceramic anode blank containing the T-shaped electrical connection guide rod; and degreasing and sintering the metal ceramic anode blank containing the T-shaped electrical connection guide rod to obtain the aluminum electrolysis metal ceramic anode.

[0007] The present invention is the first to provide a rheo-injection preparation method for an aluminum electrolytic metal ceramic anode. The rheo-injection material (anode shell material) is preheated to a temperature higher than the material softening point, so that the rheo-injection material exhibits shear-thinning and easy-flowing characteristics. Then, under a certain pressure, the rheo-injection material is injected through a flow channel into a mold containing a T-shaped electrical connection guide rod containing a welding piece and preheated to a temperature 10-50°C higher than the material softening point. After cooling, solidification and demolding, a green body with high surface quality, complex external structure and high green body density uniformity is obtained. Then, through degreasing and sintering, a highly uniform and dense aluminum electrolytic metal ceramic anode is obtained, realizing a one-time near-net forming of the electrical connection between the special-shaped structure metal ceramic anode shell and the T-shaped guide rod.

[0008] In a preferred embodiment, the metal ceramic powder is composed of metal powder and ceramic powder, and the ceramic powder is composed of ceramic raw material powder and ceramic sintering aid powder. The metal powder is composed of the following composition by mass percentage: Ni 10~60%, M1 5~30%, and the balance is Fe, and the M1 is selected from at least one of Cu, Co, Cr, Mn, Al, Ag, Zn, Ti, Sn, W, Mo, Zr, and Nb; the ceramic raw material powder is selected from at least one of chromium ferrite, manganese ferrite, iron ferrite, cobalt ferrite, nickel ferrite, nickel ferrite, copper ferrite, and zinc ferrite, and the ceramic sintering aid powder is selected from at least one of nickel oxide, vanadium oxide, barium oxide, scandium oxide, yttrium oxide, copper oxide, lanthanum oxide, and cerium oxide. The mass fraction of the ceramic sintering aid powder in the ceramic powder is 0~20%.

[0009] Furthermore, the average particle size of the metal powder and the ceramic powder is 0.05-1 μm, and the volume ratio of the metal powder to the ceramic powder is 1:1-8.

[0010] In a preferred embodiment, the mass fraction of the organic binder in the material mass is 30-50%.

[0011] In a preferred embodiment, the organic binder is composed of the following by volume percentage: 65-90 vol% of filling binder, 5-35 vol% of backbone binder, and 1-8 vol% of additives.

[0012] Further preferably, the organic binder comprises, by volume percentage, 70-80 vol% filler binder, 12-27 vol% backbone binder, and 1.5-5 vol% additives. Using this preferred organic binder formulation, the anode casing material obtained after rheo-compression sintering has optimal product performance.

[0013] More preferably, the filling binder is selected from at least one of paraffin wax, carnauba wax, microcrystalline wax, beeswax, polyethylene wax, polyoxymethylene, and polyethylene glycol.

[0014] The backbone binder is selected from at least one of polypropylene, polyethylene, polystyrene, polymethyl methacrylate, and ethylene-vinyl acetate copolymer.

[0015] The additive is selected from at least one of stearic acid, zinc stearate, glycerol, castor oil, peanut oil, dibutyl phthalate, dioctyl phthalate, β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 4[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester, 4,4'-methylenebis(2,6-di-tert-butylphenol), and 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate.

[0016] In a preferred embodiment, the mixing process is as follows: first, the metal ceramic powder is placed in a mixer for preheating and dehydration; then, a backbone binder is added and the first mixing is performed above the melting point of the backbone binder; then, a filling binder and an additive are added and the second mixing is performed above the combined melting point of the filling binder and the additive.

[0017] Further preferably, the preheating and dehydration temperature is 80-150° C., preferably 100-120° C., the preheating and dehydration time is 15-120 min, preferably 30-60 min, and the rotor speed during preheating and dehydration is 1-30 r / min, preferably 5-10 r / min.

[0018] Further preferably, the first mixing time is 15 to 120 min, preferably 20 to 60 min, and the rotor speed of the first mixing is 1 to 30 r / min, preferably 5 to 15 r / min.

[0019] Further preferably, the second mixing time is 30 to 120 min, preferably 45 to 60 min, and the rotor speed of the second mixing is 20 to 60 r / min, preferably 30 to 45 r / min.

[0020] The raw material powder and the organic binder can be fully mixed by the above mixing method.

[0021] In a preferred embodiment, the anode casing material is in the form of powder, particles, or blocks, and the blocks are selected from at least one of discs containing circular holes, squares, and honeycomb-shaped blocks.

[0022] The inventors found that the anode shell materials with the above three morphologies all have good filling effects. When the block is a honeycomb coal-like block, a heating rod can be inserted into the pores of the honeycomb coal-like block to achieve rapid and uniform heating of large volume materials. The material preheating process time is ≤30min, which can prevent the loss of binder in the material due to too long time and reduce the process stability of rheo-injection molding.

[0023] Further preferably, when the anode casing material is powder, the particle size of the anode casing material is 10-500 μm, preferably 50-200 μm.

[0024] Further preferably, when the anode shell material is particles, the particle size is 2 to 8 mm, preferably 3 to 5 mm.

[0025] When the anode shell material is powder, it is crushed by a crusher. When the anode shell material is particles, it is granulated by a screw granulator. When the anode shell material is block, it is pressed into shape by block tableting.

[0026] In a preferred embodiment, when the anode shell material is 10-50°C above the softening point, the shear rate is 100s -1 When the anode shell material is used, the viscosity is 200-1000 Pa·S, preferably 50-400 Pa·S.

[0027] The anode casing material of the present invention has high density uniformity in various parts of the green body after forming, and the density difference value of each part is ≤1.5 wt%, and in a preferred embodiment is ≤0.8 wt%. The material also has good thermal stability. Under the condition of being 10-50°C higher than the softening point of the binder and being kept warm for 60 minutes, the mass loss of the material is ≤1.0 wt%, and in a preferred embodiment is ≤0.6 wt%.

[0028] When the viscosity of the anode casing material is too high (>1000Pa) at 10~50℃ above the softening point, its fluidity is poor, which will reduce the density uniformity of the formed green body. The density difference between different parts is >1.5 wt%. The green body is prone to deformation after sintering and has poor dimensional stability. When the viscosity of the anode casing material is too low (<20Pa), its fluidity is too high, and the binder content in the formed green body is too high, which will reduce the forming pressure of the formed green body. Pores are likely to remain in the formed green body. In addition, it is difficult to remove the binder from the green body after sintering, and large-sized green bodies are prone to cracking during the sintering process.

[0029] In the present invention, a welding piece is provided at the bottom of the electrical connection guide rod, which can promote the rapid integrated connection between the T-shaped electrical connection guide rod and the anode shell. In actual operation, the welding piece can be first welded to the bottom of the T-shaped electrical connection guide rod by soldering, or the welding piece can be simply placed at the bottom of the T-shaped electrical connection guide rod. The subsequent welding piece can be sintered to complete the connection of the two parts by utilizing the melting and solidification process.

[0030] Further preferably, the welding piece has a diameter of 120-180 mm and a thickness of 1-5 mm.

[0031] In a preferred embodiment, the welding sheet is a Cu-Ni-M2 alloy, and its composition is as follows, by mass percentage: Ni 20-40%, M2 10-60%, and the balance is Cu, and the M2 is selected from at least one of Ti, Cr, V, Nb, Pd, Sn, Co, Ag, and Ag.

[0032] The inventors discovered that the aforementioned composition and dimensions provide excellent wettability between the solder guide rod and the anode casing surface, facilitating a rapid and stable connection at sintering temperatures. When the soldering point is too high (Ni > 40%), the solder fails to melt during sintering. A lack of M2 reduces the solder's wettability and bonding ability. When the soldering thickness is too small (<1mm), the weld strength decreases. When the soldering thickness is too thick (>5mm), the gap between the guide rod and the casing increases.

[0033] In a preferred embodiment, the T-shaped electrical connecting rod is a Ni-Cu-M3 alloy having the following composition by mass: 60-80% Ni, 20-40% Cu, and the balance M3, where M3 is selected from at least one of Fe, V, W, Cr, Mo, Zr, Hf, Nb, Ta, and Re. The T-shaped electrical connecting rod with this composition has a melting point (>1400°C) to prevent softening and deformation during sintering.

[0034] In a preferred solution, the mold is preheated to a temperature 120-180° C. higher than the softening point of the anode casing material, and the anode casing material is simultaneously preheated to a temperature 120-180° C. higher than the softening point of the anode casing material.

[0035] In a preferred embodiment, when the rheo-compression injection material is preheated, a pressure of 5 to 200 MPa, preferably 30 to 100 MPa, is applied to the rheo-compression injection material.

[0036] After obtaining the rheological injection material, the rheological injection material is preheated to a temperature 10~50℃ higher than the softening point of the material. In actual operation, if the material is in the form of powder or particles, the material can be directly placed in an oven or in the heating bin of an injection machine for preheating. The preheating temperature is ≥ the mixing temperature of the material. It is further preferred to place the material in the heating bin of an injection machine for preheating, and apply a pressure of 5~200MPa to the material, preferably 30~100MPa, to accelerate the uniform heating of the material powder or particles; if the material is in the form of a block, the material is placed in a specific heating device or in the heating bin of an injection machine. It is further preferred to use a specific heating device, and the heating method is oil heating, microwave heating, etc., so that the block material quickly reaches the preheating temperature.

[0037] In a preferred embodiment, the degreasing process is to first place the metal ceramic anode body in an organic solvent and perform solvent degreasing at 20-60°C, preferably 30-50°C, or first perform catalytic degreasing of the metal ceramic anode body in an environment of nitric acid vapor or oxalic acid vapor at 100-140°C, and then perform thermal degreasing.

[0038] The degreasing method of the present invention adopts a two-step process. The first step of degreasing adopts solvent degreasing and / or catalytic degreasing to form interconnected pores; the second step of degreasing adopts thermal degreasing to remove the remaining binder by thermal decomposition; after the degreasing is completed, the green body is finally subjected to high-temperature sintering and densification to obtain a large-scale complex powder metallurgy product. The solvent degreasing is to place the green body in a solvent corresponding to the polymer filling component A and slowly dissolve and remove it at low temperature; the removal temperature is 20~60℃, preferably 30~50℃; the catalytic degreasing is for when the polymer filling component A is a polyformaldehyde binder, the green body is placed in a nitric acid or oxalic acid type catalytic degreasing furnace, nitric acid or oxalic acid vapor is introduced, and the polyformaldehyde is quickly removed at a temperature of 100~140℃.

[0039] In a preferred embodiment, the sintering is carried out under a protective atmosphere, the sintering temperature is 1200-1350° C., the sintering time is 4-8 hours, and the heating rate is 2-8° C. / min.

[0040] Further preferably, the protective atmosphere is a nitrogen atmosphere. Beneficial effects

[0041] Compared with the prior art, the present invention has the following advantages:

[0042] (1) The present invention provides a rheo-injection method for preparing an aluminum electrolytic metal ceramic anode and an electrical connection. The rheo-injection method realizes the integrated near-net forming of a special-shaped metal ceramic anode and an electrical connection guide rod, thereby solving the problems of complex forming process and loose electrical connection of aluminum electrolytic metal ceramics with complex structures.

[0043] (2) The present invention provides a rheo-injection manufacturing method for aluminum electrolytic metal ceramic anodes and electrical connections, which uses a POM-based feeding system to achieve low-pressure forming of the blank. The extruded feed has a high solid phase content and good fluidity. The resulting blank has high strength and good density, and has better applicability for large-scale rapid preparation of complex-shaped blanks.

[0044] (3) The present invention provides a rheo-injection method for preparing an aluminum electrolytic metal ceramic anode and an electrical connection. Through the wetting behavior of the brazing material after high-temperature melting during the sintering process and the weight of the metal guide rod, the bottom of the guide rod and the inner wall of the metal ceramic are tightly connected while completing the densification of the metal ceramic shell. At the same time, the T-shaped guide rod can suspend anode shells of larger size and higher specific gravity, solving the problem that the electrical connection guide rod is easy to fall off during operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] FIG1 is a process flow chart of the present invention.

[0046] FIG2 is a schematic diagram of the mold structure of the present invention.

[0047] FIG3 is a schematic diagram of the anode structure of the present invention, wherein 1 is the anode shell; 2 is the electrical connection guide rod; and 3 is the connecting welding piece. Modes for Carrying Out the Invention

[0048] The following describes the preferred embodiments of the present invention in detail with reference to the accompanying drawings to make the advantages and features of the present invention more easily understood by those skilled in the art, thereby making a clearer and more precise definition of the scope of protection of the present invention. The embodiments of the present invention include:

[0049] Example 1

[0050] Step S1, placing metal ceramic powder raw materials (1.5 kg Ni powder with an average particle size of 0.2 μm, 1.2 kg Cu ​​powder with an average particle size of 0.2 μm, 0.3 kg Fe powder with an average particle size of 0.2 μm, 1.5 kg Ni powder with an average particle size of 0.2 μm, 6.3 kg NiFe2O4 powder with an average particle size of 1.5 μm, 0.7 kg NiO powder with an average particle size of 1.5 μm) into a mixer for preheating and dehydration, with a drying temperature of 120°C, a preheating time of 45 minutes, and a rotor speed of 5 r / min; then adding 5 .3kg of organic binder was mixed twice, and the addition order was as follows by volume percentage: 13vol% of high-density polyethylene and 4vol% of ethylene-vinyl acetate copolymer were added, the mixing temperature was 190℃, the mixing time was 30min, and the rotor speed was 10r / min; 80vol% of ordinary paraffin and 3vol% of stearic acid were added, the mixing temperature was 160℃, the mixing time was 60min, and the rotor speed was 45r / min; the mixed materials were placed in a crusher to obtain granular materials with an average particle size of 3-4mm;

[0051] Step S2: Place the above materials into a heating chamber of an injection molding machine for preheating, and apply a pressure of 50 MPa to the materials at a preheating temperature of 160°C;

[0052] Step S3: brazing a 3 mm thick, 150 mm diameter Cu-20Ni-15Ti welding sheet to the bottom of a Ni-30Cu-10Cr guide rod, and placing them together as a core rod in a mold and fixing their positions; after the material is fully preheated and softened, the material is directly injection molded through the runner into the T-shaped mold cavity to complete the densification of the green body; wherein the injection mold temperature is 160°C and the injection pressure is 30 MPa; then, after cooling until the green body solidifies, the green body can be demolded and removed;

[0053] Step S4: first, the green body is placed in n-heptane solvent and subjected to solvent degreasing at 40° C. for 48 hours; then, the green body is subjected to thermal degreasing at a degreasing temperature of 600° C. for 2 hours;

[0054] Step S5, placing the metal ceramic blank with the inner core described in step S4 in an atmosphere sintering furnace, with a sintering atmosphere of nitrogen, a sintering temperature of 1250°C, a sintering time of 4 hours, and a heating rate of 5°C / min.

[0055] The metal-ceramic integrated anode obtained in this example has a high aspect ratio and a complex bottom curved surface. The external dimensional accuracy is less than ±2.0mm / 100mm, the porosity of the shell after sintering is less than 5%, and the shear strength at the connection interface is 128MPa.

[0056] Example 2

[0057] Step S1: prepare metal ceramic powder raw materials (0.9 kg Fe powder with an average particle size of 0.2 μm, 1 kg Ni powder with an average particle size of 0.2 μm, 0.1 kg Co powder with an average particle size of 0.1 μm, 0.1 kg Mn powder with an average particle size of 0.1 μm, 1.5 kg Ni powder with an average particle size of 0.2 μm, 1.2 kg NiFe2O4 powder with an average particle size of 1.5 ... 0.1 kg of MnFe2O4 powder with an average particle size of 1.5 μm and 0.1 kg of CoO powder with an average particle size of 1.5 μm were placed in a mixer and preheated and dehydrated at a drying temperature of 150°C, a preheating time of 30 minutes, and a rotor speed of 5 r / min. 3.6 kg of an organic binder was then added and mixed twice. The addition order, calculated by volume percentage, was as follows: 18.5 vol% of polypropylene was added at a mixing temperature of 200°C, a mixing time of 60 minutes, and a rotor speed of 5 r / min; 80 vol% of polyoxymethylene, 1 vol% of stearic acid, and 0.5 vol% of dioctyl phthalate were added at a mixing temperature of 180°C, a mixing time of 45 minutes, and a rotor speed of 40 r / min. The mixed materials were placed in a crusher to obtain granular materials with an average particle size of 3 to 4 mm.

[0058] Step S2: Place the above materials into a heating chamber of an injection molding machine for preheating, and apply a pressure of 50 MPa to the materials at a preheating temperature of 160°C;

[0059] Step S3: brazing a 3 mm thick, 150 mm diameter Cu-20Ni-15Ti welding sheet to the bottom of a Ni-30Cu-10Cr guide rod, and placing them together as a core rod in a mold and fixing their positions; after the material is fully preheated and softened, the material is directly injection molded through the runner into the T-shaped mold cavity to complete the densification of the green body; wherein the injection mold temperature is 160°C and the injection pressure is 90 MPa; then, after cooling until the green body solidifies, the green body can be demolded and removed;

[0060] Step S4: first, the green body is placed in an oxalic acid catalytic degreasing furnace and catalytically degreased at 120° C. for 24 hours; then, the cemented carbide green body is thermally degreased at a degreasing temperature of 500° C. for 2 hours;

[0061] Step S5, placing the metal ceramic blank with the inner core described in step S4 in an atmosphere sintering furnace, with a sintering atmosphere of nitrogen, a sintering temperature of 1200° C., a sintering time of 4 hours, and a heating rate of 8° C. / min.

[0062] The metal-ceramic integrated anode obtained in this example has a high aspect ratio and a complex bottom curved surface. The external dimensional accuracy is less than ±2.0mm / 100mm, the porosity of the shell after sintering is less than 3%, and the shear strength at the connection interface is 151MPa.

[0063] Example 3

[0064] Step S1: placing metal ceramic powder raw materials (1.4 kg of Cu powder with an average particle size of 0.2 μm, 0.4 kg of Cu powder with an average particle size of 0.2 μm, 0.1 kg of Fe powder with an average particle size of 0.2 μm, 1.5 kg of Ni powder with an average particle size of 0.2 μm, 2.7 kg of NiFe2O4 powder with an average particle size of 1.5 μm, and 0.1 kg of BaO powder with an average particle size of 1.5 μm) into a mixer and preheating and dehydrating the mixture. The drying temperature is 150° C., the preheating time is 30 minutes, and the rotor speed is 5 rpm. Then, 3.7 kg of organic binder was added and mixed twice. The order of addition by volume percentage was as follows: 18.5 vol% of polypropylene was added, the mixing temperature was 200 ° C, the mixing time was 60 min, and the rotor speed was 5 r / min; 80 vol% of polyoxymethylene, 1 vol% of stearic acid and 0.5 vol% of dioctyl phthalate were added, the mixing temperature was 180 ° C, the mixing time was 45 min, and the rotor speed was 40 r / min; the mixed materials were placed in a crusher to obtain granular materials with an average particle size of 3~4 mm.

[0065] Step S2: Place the above materials into a heating chamber of an injection molding machine for preheating, and apply a pressure of 50 MPa to the materials at a preheating temperature of 160°C;

[0066] Step S3: brazing a 3 mm thick, 150 mm diameter Cu-20Ni-15Ti welding sheet to the bottom of a Ni-30Cu-10Cr guide rod, and placing them together as a core rod in a mold and fixing their positions; after the material is fully preheated and softened, the material is directly injection molded through the runner into the T-shaped mold cavity to complete the densification of the green body; wherein the injection mold temperature is 160°C and the injection pressure is 60 MPa; then, after cooling until the green body solidifies, the green body can be demolded and removed;

[0067] In step S4, the blank is first placed in an oxalic acid catalytic degreasing furnace and catalytically degreased at 120°C for 24 hours; then the cemented carbide blank is thermally degreased at a degreasing temperature of 500°C for 2 hours; in step S5, the metal ceramic blank with an inner core described in step S4 is placed in an atmosphere sintering furnace with a sintering atmosphere of nitrogen, a sintering temperature of 1280°C, a sintering time of 4 hours, and a heating rate of 3°C / min.

[0068] The metal-ceramic integrated anode obtained in this example has a high aspect ratio and a complex bottom curved surface. The external dimensional accuracy is less than ±2.0mm / 100mm, the porosity of the shell after sintering is less than 7%, and the shear strength at the connection interface is 107MPa.

[0069] Comparative Example 1

[0070] Other conditions were the same as those in Example 1, except that the organic binder content in step S1 was reduced to 25%. As a result, the material could not be discharged from the pores due to the low fluidity and viscosity of the material mass, resulting in the inability to proceed with the injection molding process.

[0071] Comparative Example 2

[0072] Other conditions were the same as those in Example 1, except that the injection pressure in step S2 was increased to 220 MPa. As a result, the feed was too high, causing the unevenly heated material to block the channel, making continuous discharge and continuous extrusion impossible.

[0073] Comparative Example 3

[0074] Other conditions were the same as those in Example 1, except that the thickness of the solder sheet in step S3 was increased to 8 mm. As a result, during the sintering process, the volume of the solder sheet changed too much after melting, causing the T-shaped guide rod to sink severely and tilt uncontrollably, seriously reducing the dimensional accuracy.

[0075] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention's description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A rheo-injection method for preparing a metal ceramic anode for aluminum electrolysis, characterized in that: The metal ceramic powder is kneaded with an organic binder to obtain a material mass, and the material mass is molded to obtain an anode shell material. A T-shaped electrical connection guide rod containing a welding sheet is fixed at the center of a mold, and the mold is preheated to a temperature 10-50°C higher than the softening point of the anode shell material. At the same time, the anode shell material is preheated to a temperature 10-50°C higher than the softening point of the anode shell material. Then, at a pressure of 20-200 MPa, the anode shell material is injected into the cavity of the mold through a flow channel, and the pressure is maintained for 1-60 minutes. The mold heating is stopped, and the mold is cooled and demolded to obtain a metal ceramic anode blank containing a T-shaped electrical connection guide rod. The metal ceramic anode blank containing electrical connections is degreased and sintered to obtain an aluminum electrolysis metal ceramic anode.

2. The rheo-injection method for preparing a metal ceramic anode for aluminum electrolysis according to claim 1, characterized in that: The metal ceramic powder is composed of metal powder and ceramic powder, and the ceramic powder is composed of ceramic raw material powder and ceramic sintering aid powder. The metal powder is composed of the following by mass percentage: Ni 10-60%, M1 5-30%, and the balance is Fe, and the M1 is selected from at least one of Cu, Co, Cr, Mn, Al, Ag, Zn, Ti, Sn, W, Mo, Zr, and Nb; the ceramic raw material powder is selected from at least one of chromium ferrite, manganese ferrite, iron ferrite, cobalt ferrite, nickel ferrite, nickel ferrite, copper ferrite, and zinc ferrite, and the ceramic sintering aid powder is selected from at least one of nickel oxide, vanadium oxide, barium oxide, scandium oxide, yttrium oxide, copper oxide, lanthanum oxide, and cerium oxide, and the mass fraction of the ceramic sintering aid powder in the ceramic powder is 0-20%; The average particle size of the metal powder and the ceramic powder is 0.05-1 μm, and the volume ratio of the metal powder to the ceramic powder is 1:1-8.

3. The rheo-injection method for preparing a metal ceramic anode for aluminum electrolysis according to claim 1, characterized in that: In the material mass, the mass fraction of the organic binder is 30-50%. The organic binder is composed of the following by volume percentage: 65-90 vol% of filling binder, 5-35 vol% of backbone binder, and 1-8 vol% of additives; The filling binder is selected from at least one of paraffin wax, carnauba wax, microcrystalline wax, beeswax, polyethylene wax, polyoxymethylene, and polyethylene glycol. The backbone binder is selected from at least one of polypropylene, polyethylene, polystyrene, polymethyl methacrylate, and ethylene-vinyl acetate copolymer. The additive is selected from at least one of stearic acid, zinc stearate, glycerol, castor oil, peanut oil, dibutyl phthalate, dioctyl phthalate, β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 4[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester, 4,4'-methylenebis(2,6-di-tert-butylphenol), and 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate.

4. The rheo-injection method for preparing a metal ceramic anode for aluminum electrolysis according to claim 1, characterized in that: The mixing process is as follows: firstly, the metal ceramic powder and the organic binder are placed in a mixer, preheated and dehydrated, then the backbone binder is added, and the first mixing is performed above the melting point of the backbone binder, and then the filling binder and the additive are added, and the second mixing is performed above the blending melting point of the filling binder and the additive; The preheating and dehydration temperature is 80-150°C, the preheating and dehydration time is 15-120 minutes, and the rotor speed during preheating and dehydration is 1-30 r / min. The first mixing time is 15-120 min, and the rotor speed of the first mixing is 1-30 r / min; The second mixing time is 30-120 min, and the rotor speed of the second mixing is 20-60 r / min.

5. The rheo-injection method for preparing a metal ceramic anode for aluminum electrolysis according to claim 1, characterized in that: The anode shell material has a morphology of powder, particles, and blocks, and the blocks are selected from at least one of a disc with round holes, a square, and a honeycomb briquette-shaped block; When the anode shell material is powder, the particle size of the anode shell material is 10-500 μm. When the powder metallurgy anode shell material is particles, the particle size is 2-8 mm.

6. The rheo-injection method for preparing a metal ceramic anode for aluminum electrolysis according to claim 1, characterized in that: When the anode shell material is 10-50°C above the softening point, the shear rate is 100S -1 When the viscosity of the anode shell material is 200~1000Pa·S.

7. The rheo-injection method for preparing a metal ceramic anode for aluminum electrolysis according to claim 1, characterized in that: The welding piece has a diameter of 120-180 mm and a thickness of 1-5 mm; The welding sheet is a Cu-Ni-M2 alloy, and its composition is as follows by mass percentage: Ni 20-40%, M2 10-60%, and the balance is Cu, and the M2 is selected from at least one of Ti, Cr, V, Nb, Pd, Sn, Co, Ag, and Ag; The T-shaped electrical connecting rod is a Ni-Cu-M3 alloy, and its composition is as follows by mass percentage: Ni 60-80%, Cu 20-40%, and the remainder is M3, and the M3 is selected from at least one of Fe, V, W, Cr, Mo, Zr, Hf, Nb, Ta, and Re.

8. The rheo-injection method for preparing a metal ceramic anode for aluminum electrolysis according to claim 1, characterized in that: When the rheo-injection material is preheated, 5-200 MPa is applied to the rheo-injection material.

9. The rheo-injection method for preparing a metal ceramic anode for aluminum electrolysis according to claim 1, characterized in that: The degreasing process is to first place the metal ceramic anode blank in an organic solvent at 20-60°C for solvent degreasing, or first place the metal ceramic anode blank in a nitric acid vapor or oxalic acid vapor environment at 100-140°C for catalytic degreasing, and then perform thermal degreasing.

10. The rheo-injection method for preparing a metal ceramic anode for aluminum electrolysis according to claim 1, characterized in that: The sintering is carried out under a protective atmosphere, the sintering temperature is 1200-1350° C., the sintering time is 4-8 hours, and the heating rate is 2-8° C. / min; the protective atmosphere is a nitrogen atmosphere.

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