A method for improving the yield of master alloy and reducing gas phase impurities

Abstract

The present invention relates to the field of master alloy smelting and discloses a method for improving master alloy yield and reducing gaseous impurities. MgO, CaO, Al2O3, cryolite (Na3AlF6), KCl, and MgCl2 are ground into powder, added with an adhesive, and mixed to form pellets to produce a shielding agent, which is then dried. An ignition agent is prepared using potassium permanganate, aluminum powder, and potassium chlorate in a specific ratio. An oxide, a reducing agent, and a slag-forming agent are uniformly mixed in a specific ratio to prepare a reactant. After the materials are distributed, a reaction is triggered by lower electrical ignition, and the reactant is fully cooled to produce the desired master alloy. The shielding agent isolates the reaction process from air, preventing gaseous impurities from participating in the reaction. This method transforms the conventional off-furnace aluminothermic reduction process into a nearly pure vacuum self-propagating reaction, reducing alloy splashing and achieving an increased alloy yield and a reduced gaseous impurity content.

Description

Technical Field

[0001] The invention relates to the field of master alloy smelting, and in particular to a method for improving the yield of master alloy and reducing gas phase impurities. Background Art

[0002] Currently, the majority of master alloys for titanium alloys are prepared using an off-furnace method (aluminothermic reduction), which involves a reduction reaction between oxides and aluminum in an atmospheric atmosphere to produce the master alloy. However, this traditional off-furnace method, conducted in an open atmosphere, suffers from two drawbacks: low yield and high levels of gaseous impurities. Specifically, the aluminothermic reduction method is an instantaneous exothermic reaction, and the reactants have a relatively low bulk density. Consequently, the intense heat generated in a short period of time can cause significant splashing of the raw materials, resulting in raw material loss and reduced alloy yield. Furthermore, the entire reaction is exposed to the atmosphere, which inevitably introduces impurity gaseous elements into the alloy, causing a high impurity content and reduced quality in the master alloy.

[0003] Prior art, such as patents CN 118563104 A and CN 119433320 A, disclose methods for increasing the yield of master alloys. However, these methods are only applicable to vacuum aluminothermic processes, and no methods for increasing the yield of master alloys produced outside the furnace have been reported. Limited reports exist on methods for reducing the gaseous impurity content in master alloys. For example, patent CN 202310933568 proposes a method for preparing a low-oxygen vanadium aluminum alloy. This method uses a V65Al finished product to cover the reaction raw materials during the aluminothermic reaction, thereby isolating the infiltration of gaseous impurities during the cooling phase. While this method is simple and easy to operate, it requires sacrificing the surface V65Al alloy to maintain the low-oxygen properties of the internal alloy, resulting in reduced material utilization and significant waste, making it impractical for practical production. Patents CN 118064751 A and CN 118516574 A each disclose a method for preparing a low-impurity master alloy. However, both methods are based on the vacuum aluminothermic process, requiring high equipment investment and unsuitable for small and medium-sized enterprises. Patent CN202311667681 discloses a device and method for preparing low-oxygen vanadium aluminum alloy, but the device is too complex in structure and has a high single production cost, making it unsuitable for industrial-scale production.

[0004] In summary, developing a method suitable for the off-furnace method that can significantly improve the primary yield of the master alloy and significantly reduce the content of gas-phase impurities in the alloy is an urgent problem to be solved in the master alloy industry. Summary of the Invention

[0005] In view of this, based on the above problems, the purpose of the present invention is to provide a method for improving the yield of intermediate alloys and reducing gas-phase impurities, effectively solving the common industry problems of low yield and high gas-phase impurities in the existing off-furnace intermediate alloys, and meeting the low-cost, large-scale production needs of small and micro enterprises.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for improving the yield of master alloy and reducing gas-phase impurities comprises the following steps:

[0008] (1) MgO, CaO, Al2O3, cryolite (Na3AlF6), KCl, and MgCl2 are ground into powder, added with an adhesive, mixed and pelletized to prepare a shielding agent, and the obtained shielding agent is dried;

[0009] (2) Prepare an ignition agent using potassium permanganate, aluminum powder, and potassium chlorate in a certain proportion;

[0010] (3) uniformly mixing the oxide, the reducing agent and the slag-forming agent in a certain ratio to prepare the reactant;

[0011] (4) Place the reactants, ignition agent, and shielding agent in the reactor in a certain order;

[0012] (5) After the material is laid, the reaction is triggered by electric ignition from the bottom. After sufficient cooling, the material is taken out of the furnace to obtain the prepared alloy.

[0013] Optionally, the main components of the shielding agent, in percentage by mass, include: Al2O3 25-37%, Na3AlF6 12-15%, CaO 9-16%, MgO 5-10%, KCl 9-18%, and MgCl2 13-28%.

[0014] The shielding agent configured according to the above composition and ratio has the following benefits: First, the components in the shielding agent only include salts such as KCl and alkaline oxides such as CaO. Under the high temperature conditions during the reaction process, they mainly combine with alumina to form a composite slag system, which floats on the top layer; and the reducing agent in the reaction raw material is aluminum, while the CaO and MgO oxides in the shielding agent do not have the conditions to react with Al because their formation enthalpy is lower than that of Al2O3; the impurities mainly restricted by downstream titanium alloy companies are elements such as W, Mo, Ta, Nb, Si, and Co, and there are no restrictions on elements such as K and Na, so these elements are not considered to be impurities; second, the density range of the shielding agent is 2.80-3.15g / cm 3 , its density is much lower than that of thermite reaction slag, which ensures that the shielding agent is at the top of the reaction system throughout the reaction process and will not sink into the slag liquid, let alone the alloy liquid, thus ensuring the effectiveness of isolating the reactants from the air; thirdly, the shielding agent is alkaline as a whole and can adapt to all refractory materials that can be used in thermite reaction (magnesia bricks, corundum bricks, graphite, magnesia-chrome bricks, etc.), with minimal corrosion to the refractory materials, thus ensuring the long life of the reaction refractory materials.

[0015] Optionally, the adhesive is bisphenol A epoxy resin, and the amount of the adhesive added is 5-9% of the total mass of the shielding agent.

[0016] It should be noted that bisphenol A epoxy resin is a non-water-soluble adhesive, which has good fluidity. Its combustion products are gases such as CO and CO2. The combustion products are all volatilized in the form of gas, and there are no solid products after combustion. Therefore, using it as an adhesive will not produce impurities that affect the quality of the alloy produced after the thermite reaction. In addition, the curing conditions are simple, the epoxy resin removal conditions are easy to achieve, and the equipment conditions are not demanding.

[0017] Optionally, in step (1), the shielding agent obtained by mixing and pelletizing has a spherical diameter ranging from 1 to 3 mm.

[0018] The particle size range is controlled within 1-3mm to achieve a comprehensive balance between the overall fluidity of the shielding agent and its airtightness after accumulation. If the particle size is too large, the gaps between the particles will be too large, and the airtightness of the underlying thermite reaction materials cannot be guaranteed. If the particle size is too small, the fluidity between the particles will deteriorate, and the shielding agent layer will not be able to follow the volume changes of the reactants before and after the reaction. In the later stages of the reaction, the shielding agent layer will bridge, allowing air to enter between the shielding agent layer and the slag + alloy liquid mixture, failing to isolate the air. This will lead to excessively high oxygen and nitrogen content in the alloy impurities, reducing the alloy quality.

[0019] Optionally, the pelletizing conditions of the shielding agent are: pelletizing in a pelletizer at 45-65° C. for 1-3 hours, then drying in the shade for 24 hours, calcining in a high-temperature furnace at 600-780° C. for 2-4 hours, and cooling in the furnace.

[0020] The purpose of this operation is to completely burn out the adhesive within the temperature range of 600-780℃ while ensuring that the shielding agent is in a stable spherical granular form, so as to prevent the adhesive from being heated and burned during the thermite reaction and the smoke and other gases generated from it from endangering the health of the operators.

[0021] Optionally, in step (2), the mass ratio of aluminum powder, potassium permanganate and potassium chlorate is 1:(1.5-2.6):(0.5-1.3), and the purity is greater than 99.99%.

[0022] Conventional ignition agents are prepared by mixing aluminum powder and potassium permanganate in a mass ratio of 1:(3.5-4.5). The present invention partially replaces potassium permanganate with potassium chlorate as the ignition agent. On the one hand, since potassium chlorate is less expensive than potassium permanganate, the cost of the ignition agent can be reduced. On the other hand, the heat released by the reaction of potassium chlorate with aluminum is lower than that of potassium permanganate. This can reduce the problem of splashing of starting materials caused by the sudden large amount of heat released by the ignition agent during the ignition process, thereby improving the alloy yield.

[0023] Optionally, the purity of the oxide and the reduced product in step (3) is higher than 97%, and the particle size is 5-100 μm. Whether to add a slag-forming agent is determined based on the liquid flow state after the reaction and the intensity of the reaction. The slag-forming agent is a mixture of one or more of calcium fluoride and calcium oxide.

[0024] It should be noted that limiting the purity and particle size of the oxides and the reduced products is conducive to the smooth and efficient occurrence of the reaction.

[0025] Optionally, in the process of laying the material in step (4), the shielding agent is placed on the upper layer of the reactant, and the ignition agent is placed at the lower corner of the reactant (the ignition agent is placed at any one of the four corners of the bottom of the molten pool); the mass ratio of the reactant to the shielding agent is 1:(0.3-0.45), and the mass of the ignition agent is 0.02-0.05% of the mass of the reactant.

[0026] It should be noted that the conventional off-furnace method for preparing alloys all uses top ignition. This is mainly because the reaction raw materials of the conventional off-furnace method are located at the top layer, and directly throwing the ignition agent can directly contact the reaction raw materials, so top ignition is the most convenient. However, the present invention has a layer of shielding agent on the upper layer of the reactants, so it does not have the conditions for top ignition and can only use the bottom ignition method.

[0027] In the present invention, the material of the reactor furnace is not limited and can be any one of graphite, magnesia brick, corundum brick, pure copper, etc.

[0028] Optionally, in step (5), a hole is left on the outer wall of the furnace body at the corner where the ignition agent is placed, for the ignition lead to pass through, and the end of the ignition lead is connected to a heating wire, and the heating wire is in full contact with the ignition agent. When the ignition lead is energized, the end heating wire releases heat, ignites the ignition agent, and then triggers the reactants to undergo a self-propagating reaction.

[0029] Furthermore, the ignition lead in step (5) is made of high-purity aluminum wire with a purity greater than 99.9%; the heating wire is made of iron-chromium-aluminum alloy wire, which is less polluting to the reaction product alloy than other heating wires such as molybdenum wire and tungsten wire.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) High alloy yield. By placing a layer of shielding agent on top of the reaction raw materials, the reactants are isolated from the air, preventing oxygen from participating in the reaction process. This transforms the ordinary aluminothermic reduction process outside the furnace into a nearly pure vacuum self-propagating reaction, weakening the intensity of the reaction and minimizing splashing, thereby achieving an increase in alloy yield.

[0032] (2) Low gas phase impurity content. Under the action of the shielding agent, the reactants and products do not come into contact with harmful impurity gases throughout the process, thereby avoiding the incorporation of impurity gas elements into the alloy and reducing the gas phase impurity content.

[0033] (3) Simple operation, low cost, and easy to scale up production. The main difference between the method of the present invention and the conventional off-furnace method is the use of a shielding agent and the change in the ignition method. These two changes do not involve the introduction of new equipment or major equipment modifications. In addition, the shielding agent components are basically composed of low-cost conventional salts and alkali metal oxides, so the production cost is low. The production operation mode is changed from top ignition to bottom ignition, and the process is electrically controlled, which makes the operation more convenient and more suitable for enterprises to achieve large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0035] Figure 1 This is a schematic diagram of the material distribution method and the distribution positions of the ignition agent and ignition wire of the present invention. DETAILED DESCRIPTION

[0036] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0037] The term "embodiment" is used herein specifically to describe any embodiment as "exemplary," and should not be construed as superior or preferable to other embodiments. Performance indicators in the embodiments of this application were tested using conventional testing methods in the art, unless otherwise specified. It should be understood that the terms used in this application are intended solely to describe specific implementations and are not intended to limit the disclosure herein.

[0038] Unless otherwise specified, the technical and scientific terms used herein have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs; other experimental methods and technical means not specifically specified in this application refer to experimental methods and technical means commonly used by ordinary technicians in this field.

[0039] In the description of the present invention, it should be understood that the terms "middle", "upper", "lower", "ascend", "descend", "vertical", "surface", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0040] In order to better illustrate the content of this application, numerous specific details are provided in the specific examples below. It should be understood by those skilled in the art that this application can be implemented without certain specific details. In the examples, some methods, means, instruments, equipment, etc. well known to those skilled in the art are not described in detail in order to highlight the main purpose of this application.

[0041] Under the premise of no conflict, the technical features disclosed in the embodiments of this application can be combined arbitrarily, and the resulting technical solutions belong to the contents disclosed in the embodiments of this application.

[0042] The invention discloses a method for improving the yield of master alloy and reducing gas phase impurities.

[0043] For a better understanding of the present invention, the present invention is further specifically described below through the following examples, but it should not be understood as limiting the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above invention content are also considered to fall within the scope of protection of the present invention.

[0044] Example 1

[0045] The present invention provides a method for improving the yield of master alloy and reducing gas-phase impurities, which specifically comprises the following steps:

[0046] (1) 18.36 kg MgO, 18.36 kg CaO, 45.9 kg Al2O3, 27.54 kg cryolite (Na3AlF6), 31.2 kg KCl and 42.2 kg MgCl2 were ground into powder, added with 16.5 kg bisphenol A epoxy resin adhesive and placed in a granulator for mixing and pelletizing. The granulation conditions were as follows: pelletizing in a granulator at 65 °C for 3 h, then drying in the shade for 24 h, then calcining in a high-temperature furnace at 720 °C for 2 h, and then cooling in the furnace;

[0047] (2) Take 98.7g of potassium permanganate, 65g of aluminum powder and 40.3g of potassium chlorate and mix them evenly to prepare an ignition agent;

[0048] (3) Weigh 189.1 kg of vanadium pentoxide, 146.5 kg of aluminum powder, and 31.5 kg of calcium fluoride as reaction raw materials, dry them in a drying kiln at 120°C for 6 h, and then put them into a V-type mixer for thorough mixing;

[0049] (4) Pile the prepared ignition agent in the corner of the molten pool, and then evenly place the reaction materials on the top of the ignition agent. Pay attention to compacting while placing the reaction materials. After the reaction materials are placed, let the shielding agent fall naturally to the upper layer of the reactants. Be sure not to compact it in this step. Keep the shielding agent loose so that it can change with the volume of the reactants as the reaction proceeds.

[0050] (5) Fix the iron-chromium-aluminum heating wire (the heating wire needs to be wound into a spiral) at the ends of the positive and negative ignition leads, and then insert the connected leads into the holes in the furnace body on the side of the ignition agent. Wait until the heating wire fully contacts the ignition agent and stops, then turn on the ignition switch to energize the leads. At this time, the heating wire releases a large amount of heat to ignite the ignition agent, and then trigger the reaction;

[0051] (6) After 38 seconds, the material reaction is completed and the material is taken out of the furnace after cooling for 24 hours to obtain the prepared V65Al intermediate alloy.

[0052] Example 2-Example 4

[0053] The difference between Example 2 to Example 4 and Example 1 lies in the shielding agent formula. The specific formula differences are shown in Table 1.

[0054] Table 1 Differences between Example 2-Example 4 and Example 1

[0055]

[0056] Example 5

[0057] The difference between Example 5 and Example 1 lies in the different grades of the prepared master alloys. The specific grades and amounts of the reaction raw materials are shown in Table 2.

[0058] Table 2: Master alloy grades and raw material amounts prepared in Example 5

[0059]

[0060] The alloy yield and gas-phase impurity content of the master alloys of Examples 1 to 5 prepared by the method of the present invention were statistically analyzed, and the statistical results are shown in Table 3.

[0061] Table 3 Results of the yield of master alloys and gas phase impurity content of Examples 1 to 5

[0062]

[0063] It can be seen that the impurity O content of the intermediate alloys prepared by the method of the present invention in the examples is less than 0.02%, and the N content is less than 0.015%, both of which are maintained at a relatively low content level. The yield of various alloys is more than 94.6%, which proves the obvious effect of the method of the present invention in improving the yield and reducing the content of gas-phase impurities.

[0064] Comparative Example 1

[0065] The difference between Comparative Example 1 and Example 1 is that the alloy is prepared using a conventional off-furnace method. The specific difference between the two is that only reactants are piled in the molten pool, no shielding agent and ignition agent are required, and the ignition method is top ignition. The implementation steps are as follows:

[0066] The weighed raw materials are dried and mixed evenly, and then placed into the built molten pool. After all the raw materials are loaded, the upper surface of the raw materials is compacted and flattened, and then the furnace cover is installed and pushed into the combustion room. Then, the ignited magnesium rod is thrown into the reaction raw materials in the furnace body as an ignition material to trigger the reaction. The furnace is cooled for 12 hours and then taken out of the furnace to obtain the prepared alloy.

[0067] The yield and gas phase impurity content of the V65Al master alloy prepared in Comparative Example 1 were statistically analyzed, and the results are shown in Table 4.

[0068] Table 4 Results of the yield of master alloy and gas phase impurity content in Comparative Example 1

[0069]

[0070] It can be seen that, both the gaseous impurity content in alloy yield and alloy becomes worse than that in Example 1, this is mainly because in reaction process, reaction mass loses the air-isolating effect of shielding agent, reactant is fully in contact with air, after reaction is triggered, the oxygen in the air plays a suitable combustion-supporting effect to reaction, reaction heat is amplified, and under huge outflow heat, a considerable part of raw materials is splashed to the outside of reaction furnace body, forms loss, and alloy yield is reduced. Moreover, in reaction process, reactant contacts with the harmful gaseous impurities in the air all the time, especially in cooling stage, this part impurity gas is easier to enter in alloy, finally forms the phenomenon that gaseous impurities are high in alloy.

[0071] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for improving the yield of master alloy and reducing gas phase impurities, characterized in that: The following steps are involved: (1) MgO, CaO, Al2O3, cryolite Na3AlF6, KCl, and MgCl2 are ground into powder, added with adhesive, and mixed to form balls to prepare a shielding agent; (2) Prepare an ignition agent using potassium permanganate, aluminum powder, and potassium chlorate in a certain proportion; (3) uniformly mixing vanadium pentoxide, aluminum powder, and slag-forming agent in a certain ratio to prepare a reactant; (4) Place the reactants, ignition agent, and shielding agent in the reactor in a certain order; (5) After the material is laid, the reaction is triggered by electric ignition from the bottom. After sufficient cooling, the material is taken out of the furnace to obtain the prepared alloy.

2. The method for improving the yield of master alloy and reducing gas phase impurities according to claim 1, characterized in that: The main components of the shielding agent, in terms of mass percentage, include: Al2O3 25-37%, Na3AlF6 12-15%, CaO 9-16%, MgO 5-10%, KCl 9-18%, and MgCl2 13-28%.

3. The method for improving the yield of master alloy and reducing gas phase impurities according to claim 1, characterized in that: The adhesive is bisphenol A epoxy resin, and the amount of the adhesive added is 5-9% of the total mass of the shielding agent.

4. The method for improving the yield of master alloy and reducing gas phase impurities according to claim 1, characterized in that: In step (1), the shielding agent obtained by mixing and pelletizing has a spherical diameter ranging from 1 to 3 mm.

5. The method for improving the yield of master alloy and reducing gas phase impurities according to claim 1 or 4, characterized in that: The pelletizing conditions of the shielding agent are as follows: pelletizing in a pelletizer at 45-65° C. for 1-3 hours, then drying in the shade for 24 hours, calcining in a high-temperature furnace at 600-780° C. for 2-4 hours, and cooling in the furnace.

6. The method for improving the yield of master alloy and reducing gas phase impurities according to claim 1, characterized in that: In step (2), the mass ratio of aluminum powder, potassium permanganate and potassium chlorate is 1:(1.5-2.6):(0.5-1.3).

7. The method for improving the yield of master alloy and reducing gas phase impurities according to claim 1, characterized in that: In step (3), whether to add a slag-forming agent is determined based on the liquid flow state after the reaction and the intensity of the reaction. The slag-forming agent is a mixture of one or more of calcium fluoride and calcium oxide.

8. The method for improving the yield of master alloy and reducing gas phase impurities according to claim 1, characterized in that: In step (4), during the fabrication process, the shielding agent is placed on the upper layer of the reactant, and the ignition agent is placed at the lower corner of the reactant; the mass ratio of the reactant to the shielding agent is 1:(0.3-0.45), and the mass of the ignition agent is 0.02-0.05% of the mass of the reactant.

9. The method for improving the yield of master alloy and reducing gas phase impurities according to claim 1, characterized in that: In step (5), a hole for the ignition wire to pass through is left on the outer wall of the furnace body at the corner where the ignition agent is placed. The end of the ignition wire is connected to a heating wire, and the heating wire is in full contact with the ignition agent. When the ignition wire is energized, the heating wire at the end releases heat, ignites the ignition agent, and then triggers the reactants to undergo a self-propagating reaction.

10. The method for improving the yield of master alloy and reducing gas phase impurities according to claim 1, characterized in that: In step (5), the ignition lead is made of high-purity aluminum wire with a purity greater than 99.9%; the heating wire is made of iron-chromium-aluminum alloy wire.

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