Preparation method of refining agent for smelting aluminum alloy profile

Abstract

The invention relates to the field of refining agent preparation, and discloses a preparation method of a refining agent for smelting an aluminum alloy profile, and the refining agent for smelting comprises magnesium carbonate, potassium carbonate, magnesium fluoride, aluminum fluoride, an additive, potassium fluosilicate and potassium fluoroaluminate. The preparation method comprises the following steps: mixing the components, drying and dehydrating, molding by a press, crushing and granulating, and performing multi-stage screening to obtain the refining agent for smelting. The additive is formed by mixing calcium nitride and modified silicon nitride according to the mass ratio of 1: (1-2); the modified silicon nitride is prepared by grafting silicon tetrachloride with cerium chloride, magnesium chloride and n-propylamine, generating silicon nitride in situ in a pyrolysis process, carrying out spark plasma sintering to obtain silicon nitride ceramic, and coating the surface of the silicon nitride ceramic with aluminum powder by taking sodium water glass as an adhesive. And impurities and oxide layers in the aluminum alloy can be effectively removed, and the quality and purity of the aluminum alloy are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of refining agent preparation, and in particular relates to a method for preparing a refining agent for smelting aluminum alloy profiles. Background Art

[0002] Aluminum alloy is a kind of nonferrous metal structural material widely used in industry, and has been widely used in aviation, aerospace, automobile, machinery manufacturing, shipbuilding and chemical industries. Aluminum alloy has low density, but relatively high strength, close to or exceeding high-quality steel, good plasticity, can be processed into various profiles, has excellent electrical conductivity, thermal conductivity and corrosion resistance, and can be processed into aluminum alloy profiles of various shapes and specifications.

[0003] Aluminum and its aluminum alloys are easy to oxidize and absorb gas during the smelting and casting process, which makes it very easy to form gas and inclusions in the aluminum liquid, causing a series of defects such as pores, shrinkage holes, shrinkage, cracks, insufficient casting and leakage in the castings, which greatly reduces the strength, plasticity, fatigue resistance, corrosion resistance and other properties of the material, and even causes the castings to be scrapped, which greatly limits the application of aluminum alloys. Therefore, it is of great significance to improve the purity of aluminum alloys.

[0004] The existing purification methods for aluminum and aluminum alloy melts include filtration purification, non-adsorption purification and adsorption purification. Among them, filtration purification has a small processing capacity, requires regular replacement of the filter medium, and has a high operating cost; non-adsorption purification mainly includes vacuum purification, ultrasonic purification and electromagnetic purification, but the equipment investment is large and the operating cost is high; adsorption purification mainly includes gas refining and refining agent purification. Among them, the refining agent purification method has been widely used in actual production due to its advantages such as easy operation, low price and good purification effect.

[0005] The commonly used aluminum and aluminum alloy refining agents are mostly binary or ternary chloride systems, which are mainly composed of magnesium chloride, potassium chloride, sodium chloride, barium chloride and other material components. This type of refining agent has a certain ability to remove slag inclusions and active hydrogen in aluminum liquid, but the chlorine content in this type of refining agent is relatively high. Under high temperature conditions, chloride salts and metallic aluminum are prone to strong redox reactions to generate chlorine gas, which will cause serious environmental pollution after diffusion. In addition, this type of chloride molten salt has a serious erosion on the lining of the refining furnace, which is one of the important reasons for the spalling of the lining. In addition, the use of sodium salts such as sodium chloride, sodium fluoroaluminate, sodium sulfate, and sodium fluoride contained in the existing refining agents will introduce sodium into the aluminum alloy, thereby causing the "sodium embrittlement" phenomenon. Summary of the invention

[0006] In order to solve the deficiencies mentioned in the above background technology, the purpose of the present invention is to provide a method for preparing a refining agent for smelting aluminum alloy profiles. The prepared refining agent for smelting is sodium-free and chlorine-free, is more environmentally friendly to use, can effectively remove impurities and oxide layers in aluminum alloys, and improve the quality and purity of aluminum alloys.

[0007] The purpose of the present invention can be achieved through the following technical solutions: A method for preparing a refining agent for smelting aluminum alloy profiles, wherein the refining agent for smelting comprises the following components in parts by weight: 25-32 parts of magnesium carbonate, 20-30 parts of potassium carbonate, 5-8 parts of magnesium fluoride, 5-10 parts of aluminum fluoride, 5-10 parts of additives, 4-8 parts of potassium fluorosilicate, and 3-7 parts of potassium fluoroaluminate; The preparation method comprises the following steps: S1, putting parts by weight of magnesium carbonate, potassium carbonate, magnesium fluoride, aluminum fluoride, additives, potassium fluorosilicate and potassium fluoroaluminate into a blender and mixing and stirring to obtain a mixture; S2, drying and dehydrating the mixture; S3, forming the dried and dehydrated mixture by a press, crushing and granulating, and multi-stage screening to prepare a refining agent for smelting; The additive is a mixture of calcium nitride and modified silicon nitride in a mass ratio of 1:1-2; the modified silicon nitride is prepared by grafting silicon tetrachloride with cerium chloride, magnesium chloride and n-propylamine and in-situ generating silicon nitride during pyrolysis, then sintering through discharge plasma to obtain silicon nitride ceramic powder, and using sodium water glass as a binder to coat aluminum powder on the surface of the silicon nitride ceramic powder.

[0008] Preferably, the drying and dehydration conditions in step S2 are set as: vacuum degree 0.4-0.6 MPa, temperature 100-120° C., and time 2-4 h.

[0009] Preferably, the method for preparing the modified silicon nitride comprises the following steps: (1) Silicon tetrachloride, cerium chloride and magnesium chloride are dissolved in pyridine, stirred and mixed thoroughly, and n-propylamine is added. The mixture is reacted at 110-125°C in a nitrogen atmosphere for 40-48 hours, and then transferred to a tube furnace for heat treatment, and finally cooled to room temperature to prepare silicon nitride powder. (2) grinding and crushing the silicon nitride powder, placing it in a graphite mold, performing spark plasma sintering, and then grinding and crushing it to prepare silicon nitride ceramic powder; (3) Aluminum powder, sodium water glass and silicon nitride ceramic powder are mixed thoroughly and then filled into a mold. The powder is pressed into shape by a powder tablet press at a pressure of 10-15 MPa, and then crushed and sieved to prepare modified silicon nitride.

[0010] Preferably, the heat treatment step in the tubular furnace in step (1) is as follows: heating to 350-420°C at 8-12°C / min in a nitrogen atmosphere for reaction for 3-5h, and then heating to 900-1050°C at 6-12°C / min for pyrolysis for 4-5h.

[0011] Preferably, in step (1), the addition ratio of silicon tetrachloride, cerium chloride, magnesium chloride, pyridine and n-propylamine is 10-12 g: 0.15-0.35 g: 0.12-0.25 g: 17-25 mL: 5-12 mL.

[0012] Preferably, the sintering temperature of the spark plasma sintering in step (2) is 1400-1550° C., the sintering pressure is 35-50 MPa, and the holding time is 20-30 min.

[0013] Preferably, in step (3), the addition ratio of aluminum powder, sodium water glass and silicon nitride ceramic powder is 7-9 g: 1.5-2 mL: 5-7 g.

[0014] Preferably, the particle size of the smelting refining agent is 60-100 mesh.

[0015] Beneficial effects of the present invention: The smelting refining agent prepared by the present invention contains no sodium and no chlorine, does not generate toxic chloride gas during use, does not contain nitrate, sulfate and hexachloroethane, reduces the emission of irritating and unpleasant gases, and is more environmentally friendly to use. The carbonate contained in the refining agent decomposes or reacts with aluminum to generate carbon dioxide gas, while releasing a large amount of heat, thereby enhancing the flow and dispersion of the refining agent and improving the diffusion conditions of inclusions. The added fluoride reduces the interfacial tension between the flux and the aluminum liquid, increases the wetting angle between the inclusion and the aluminum liquid, thereby reducing the adhesion work of the aluminum liquid to the inclusion. At the same time, the fluoride in the flux can corrode the metal body on the aluminum oxide-aluminum interface, so that the oxide film falls off and melts into the melt. In addition, the present invention uses cerium chloride, magnesium chloride and n-propylamine to graft silicon tetrachloride and Silicon nitride is generated in situ during the pyrolysis process, and then high-purity silicon nitride ceramic powder is prepared by discharge plasma sintering. Sodium water glass is used as a binder, and aluminum powder is coated on the surface of the silicon nitride ceramic powder to prepare an additive, which improves the mechanical properties, durability and processing properties of the aluminum alloy and improves the refining effect. The additive and calcium nitride are added to the matrix, and the nitrogen generated by the reaction of nitride and oxide impurities can effectively adsorb aluminum oxide impurities and take away hydrogen in the melt, and has a refining, metamorphic and modifying effect on the aluminum alloy, which can improve the mechanical properties of the aluminum alloy. The introduced calcium and silicon elements can make aluminum oxide into spheroidized composite inclusions mCaO·nAl2O3 or Ca-Si-Al system inclusions, which promotes the aggregation, floating and removal of inclusions. The smelting refining agent prepared by the present invention can effectively remove impurities and oxide layers in aluminum alloys, and improve the quality and purity of aluminum alloys. DETAILED DESCRIPTION

[0016] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] Example 1 A method for preparing modified silicon nitride comprises the following steps: (1) 11.2 g of silicon tetrachloride, 0.28 g of cerium chloride and 0.17 g of magnesium chloride were dissolved in 20 mL of pyridine, stirred and mixed thoroughly, 10 mL of n-propylamine was added, and the mixture was reacted at 120 °C in a nitrogen atmosphere for 45 h, then moved to a tube furnace, heated to 400 °C at 10 °C / min in a nitrogen atmosphere for 5 h, then heated to 1000 °C at 8 °C / min for pyrolysis for 4 h, and finally cooled to room temperature to prepare silicon nitride powder; (2) grinding and crushing the silicon nitride powder, placing it in a graphite mold, and performing spark plasma sintering at a sintering temperature of 1450° C., a sintering pressure of 38 MPa, and a holding time of 30 min, and then grinding and crushing it to prepare silicon nitride ceramic powder; (3) Take 9 g of aluminum powder, 2 mL of sodium water glass and 7 g of silicon nitride ceramic powder, mix them thoroughly, then fill them into a mold, use a powder tablet press to press and form them at a pressure of 14 MPa, and then crush and sieve them to prepare modified silicon nitride.

[0018] Example 2 A refining agent for smelting aluminum alloy profiles comprises the following components in parts by weight: 25 parts of magnesium carbonate, 22 parts of potassium carbonate, 5 parts of magnesium fluoride, 5 parts of aluminum fluoride, 5 parts of additives, 5 parts of potassium fluorosilicate, and 3 parts of potassium fluoroaluminate, wherein the additive is a mixture of calcium nitride and modified silicon nitride in a mass ratio of 1:1.

[0019] The method for preparing the above-mentioned refining agent for smelting the aluminum alloy profile comprises the following steps: S1, putting parts by weight of magnesium carbonate, potassium carbonate, magnesium fluoride, aluminum fluoride, additives, potassium fluorosilicate and potassium fluoroaluminate into a blender and mixing and stirring to obtain a mixture; S2, drying and dehydrating the mixture, the vacuum degree of drying and dehydration is set to 0.5MPa, the temperature is 115°C, and the time is 3h; S3, forming the dried and dehydrated mixture through a press, crushing and granulating it, and screening it in multiple stages to prepare a refining agent for smelting.

[0020] Embodiment 3 A refining agent for smelting aluminum alloy profiles comprises the following components in parts by weight: 27 parts of magnesium carbonate, 25 parts of potassium carbonate, 6 parts of magnesium fluoride, 7 parts of aluminum fluoride, 8 parts of additives, 7 parts of potassium fluorosilicate, and 5 parts of potassium fluoroaluminate, wherein the additive is a mixture of calcium nitride and modified silicon nitride in a mass ratio of 1:1.5.

[0021] The preparation method of the refining agent for smelting the above-mentioned aluminum alloy profile is the same as that in Example 2.

[0022] Example 4 A refining agent for smelting aluminum alloy profiles comprises the following components in parts by weight: 32 parts of magnesium carbonate, 28 parts of potassium carbonate, 8 parts of magnesium fluoride, 8 parts of aluminum fluoride, 10 parts of additives, 8 parts of potassium fluorosilicate, and 7 parts of potassium fluoroaluminate, wherein the additive is a mixture of calcium nitride and modified silicon nitride in a mass ratio of 1:2.

[0023] The preparation method of the refining agent for smelting the above-mentioned aluminum alloy profile is the same as that in Example 2.

[0024] Comparative Example 1 A refining agent for smelting aluminum alloy profiles comprises the following components in parts by weight: 25 parts of magnesium carbonate, 22 parts of potassium carbonate, 5 parts of magnesium fluoride, 5 parts of aluminum fluoride, 5 parts of potassium fluorosilicate, and 5 parts of potassium fluoroaluminate.

[0025] The preparation method of the refining agent for smelting the above-mentioned aluminum alloy profile is the same as that in Example 2.

[0026] Comparative Example 2 A commercially available refining agent is composed of the following components in percentage by mass: 42% sodium chloride, 42% potassium chloride, 3% sodium fluoride, 2% sodium sulfate, 4% sodium carbonate, and 7% sodium hexafluoroaluminate.

[0027] Performance Testing An A356 aluminum alloy ingot (Si 6.67%, Mg 0.376%, Ti 0.137%, Cu 0.031%, Zn 0.016%, Fe 0.025%, Al balance) was placed in a graphite crucible, heated to 730°C at a rate of 20°C / min in a resistance furnace for smelting for 30 minutes, then heated to 750°C and added with the refining agent prepared in Example 2-4 and Comparative Example 1-2 in an amount of 2%. After standing for 30 minutes, the slag was removed and cast using a metal mold. The ingot size was 200 mm×100 mm×20 mm, and the performance test was performed: (1) Pour the refining agents prepared in Examples 2-5 and Comparative Examples 1-2 into an alumina crucible, place the crucible in a resistance furnace and heat it to 750°C, take 5g of A356 aluminum alloy ingot and put it into the crucible, stir it repeatedly for 20 minutes, take out the crucible, air cool it, dissolve the solidified flux with hot water after cooling, pick out the aluminum blocks, filter out the precipitate, use an analytical balance to weigh the mass m0 and m1 of the aluminum alloy before and after the flux washing, measure 3 and take the average value, and calculate the mass fraction of inclusions: W = (m0-m1) / m0×100%. The data results are shown in Table 1.

[0028] (2) A metallographic sample was cut from the ingot and polished. The morphology of inclusions was observed using an optical microscope with a field magnification of 100 times. Thirty fields of view were randomly selected to measure the area fraction of inclusions and the average value was taken. The hydrogen content was measured online using an ELH-IV hydrogen meter with an accuracy of 0.01 mL per 100 g of aluminum liquid. According to GB / T 228.1-2010, a tensile test was performed using a universal testing machine at a tensile speed of 2 mm / min. The data results are shown in Table 1.

[0029] Table 1 Test results of sample performance

[0030] It can be seen from the data in Table 1 that the refining agent prepared by Examples 2-4 of the present invention has a better purification effect than Comparative Examples 1-2, and after purification by the refining agent, the tensile strength and elongation measured in Examples 2-4 are both improved compared with Comparative Examples 1-2. Among them, Comparative Example 1 does not contain additive components, and its measured inclusion content is increased compared with Example 2-4, and its tensile strength and elongation are reduced compared with Example 2-4, indicating that the addition of additive components can improve the purification effect of the refining agent and the mechanical properties of the aluminum alloy. Comparative Example 2 uses a commercially available chlorine-containing and sodium-containing refining agent, and its measured purification effect is slightly lower than that of Example 2-4, and its mechanical properties are worse than those of Example 2-4.

[0031] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0032] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for preparing a refining agent for smelting aluminum alloy profiles, characterized in that: The smelting refining agent comprises the following components by weight: 25-32 parts of magnesium carbonate, 20-30 parts of potassium carbonate, 5-8 parts of magnesium fluoride, 5-10 parts of aluminum fluoride, 5-10 parts of additives, 4-8 parts of potassium fluorosilicate, and 3-7 parts of potassium fluoroaluminate; The preparation method comprises the following steps: S1, putting parts by weight of magnesium carbonate, potassium carbonate, magnesium fluoride, aluminum fluoride, additives, potassium fluorosilicate and potassium fluoroaluminate into a blender and mixing and stirring to obtain a mixture; S2, drying and dehydrating the mixture; S3, forming the dried and dehydrated mixture by a press, crushing and granulating, and multi-stage screening to prepare a refining agent for smelting; The additive is a mixture of calcium nitride and modified silicon nitride in a mass ratio of 1:1-2; the modified silicon nitride is prepared by grafting silicon tetrachloride with cerium chloride, magnesium chloride and n-propylamine and in-situ generating silicon nitride during pyrolysis, then sintering through discharge plasma to obtain silicon nitride ceramic powder, and using sodium water glass as a binder to coat aluminum powder on the surface of the silicon nitride ceramic powder.

2. The method for preparing a refining agent for smelting aluminum alloy profiles according to claim 1, characterized in that: The drying and dehydration conditions in step S2 are set as follows: vacuum degree 0.4-0.6 MPa, temperature 100-120° C., and time 2-4 h.

3. The method for preparing a refining agent for smelting aluminum alloy profiles according to claim 1, characterized in that: The preparation method of the modified silicon nitride comprises the following steps: (1) Silicon tetrachloride, cerium chloride and magnesium chloride are dissolved in pyridine, stirred and mixed thoroughly, and n-propylamine is added. The mixture is reacted at 110-125°C in a nitrogen atmosphere for 40-48 hours, and then transferred to a tube furnace for heat treatment, and finally cooled to room temperature to prepare silicon nitride powder. (2) grinding and crushing the silicon nitride powder, placing it in a graphite mold, performing spark plasma sintering, and then grinding and crushing it to prepare silicon nitride ceramic powder; (3) Aluminum powder, sodium water glass and silicon nitride ceramic powder are mixed thoroughly and then filled into a mold. The powder is pressed into shape by a powder tablet press at a pressure of 10-15 MPa, and then crushed and sieved to prepare modified silicon nitride.

4. The method for preparing a refining agent for smelting aluminum alloy profiles according to claim 3, characterized in that: The heat treatment step in the tubular furnace in step (1) is as follows: heating to 350-420°C at 8-12°C / min in a nitrogen atmosphere for reaction for 3-5h, and then heating to 900-1050°C at 6-12°C / min for pyrolysis for 4-5h.

5. The method for preparing a refining agent for smelting aluminum alloy profiles according to claim 3, characterized in that: In the step (1), the addition ratio of silicon tetrachloride, cerium chloride, magnesium chloride, pyridine and n-propylamine is 10-12 g: 0.15-0.35 g: 0.12-0.25 g: 17-25 mL: 5-12 mL.

6. The method for preparing a refining agent for smelting aluminum alloy profiles according to claim 3, characterized in that: The sintering temperature of the spark plasma sintering in the step (2) is 1400-1550° C., the sintering pressure is 35-50 MPa, and the holding time is 20-30 min.

7. The method for preparing a refining agent for smelting aluminum alloy profiles according to claim 3, characterized in that: In the step (3), the addition ratio of aluminum powder, sodium water glass and silicon nitride ceramic powder is 7-9 g: 1.5-2 mL: 5-7 g.

8. The method for preparing a refining agent for smelting aluminum alloy profiles according to claim 1, characterized in that: The particle size of the smelting refining agent is 60-100 meshes.

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