Aluminum-magnesium alloy melt composite purifying agent and aluminum-magnesium alloy melt refining method

Abstract

The invention discloses an aluminum-magnesium alloy melt composite purifying agent and an aluminum-magnesium alloy melt refining method. The invention relates to the technical field of aluminum alloy smelting and purification, and aims to solve the problems that in the prior art, the inclusion form is special, the hydrogen content control difficulty is high, and a purifying agent is poor in universality. The aluminum-magnesium alloy melt composite purifying agent comprises the following components in percentage by mass: 36%-44% of titanium-boron-containing composite salt; the titanium-boron-containing composite salt comprises a mixture of potassium fluotitanate and potassium fluoborate; 26%-34% of a multi-element eutectic villiaumite; the multi-element eutectic villiaumite comprises sodium fluoride, aluminum fluoride and calcium fluoride; 20%-30% of a composite gas source generating agent; the composite gas source generating agent comprises potassium sulfate, sodium nitrate and ferric oxide; 4%-10% of a rheological and activating auxiliary agent; the rheological and activating auxiliary agent comprises lithium fluoride and sodium metasilicate; according to the method, deep dehydrogenation can be achieved, MgAl2O4 inclusions are removed, the yield of the magnesium element is high, and the method is green and environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy smelting and purification technology, and in particular to a composite purifying agent for aluminum-magnesium alloy melts and a refining method for aluminum-magnesium alloy melts. Background Technology

[0002] Aluminum-magnesium alloys are widely used in transportation, marine engineering, and packaging due to their excellent strength, corrosion resistance, and weldability. However, the physicochemical properties of magnesium present unique challenges to melt quality control. Oxide inclusions generated during smelting are primarily magnesium-aluminum spinel, which are often finely dispersed in microstructure. These inclusions have extremely high interfacial energy with the molten aluminum and poor wettability, making them difficult to separate from the melt using conventional flotation or adsorption mechanisms. These residual hard particles easily become microcrack initiations during subsequent rolling or stretching. Hydrogen solubility in liquid magnesium is significantly higher than in aluminum, increasing the sensitivity of the aluminum-magnesium melt to hydrogen. While traditional chloride salt dehydrogenation technology can reduce hydrogen content, it causes severe magnesium loss and is accompanied by toxic gas emissions, failing to meet green production requirements. Commercially available general-purpose aluminum alloy refining agents are mostly designed for Al-Si alloys or low-magnesium alloys; their composition systems lack sufficient wettability and capture ability for magnesium-aluminum spinel, making deep purification difficult. Therefore, developing a specialized formulation and process that can specifically address the above problems and achieve efficient, environmentally friendly, and low-loss purification is of great significance for improving the reliability and production efficiency of high-end aluminum-magnesium alloy products. Summary of the Invention

[0003] The purpose of this invention is to provide a composite purifying agent for aluminum-magnesium alloy melts and a refining method for aluminum-magnesium alloy melts, so as to solve the problems of special inclusion morphology, difficulty in controlling hydrogen content, and poor universality of purifying agents in the prior art.

[0004] In a first aspect, the present invention provides an aluminum-magnesium alloy melt composite purifying agent, comprising the following components in weight percentage: The titanium-boron composite salt contains 36%-44% titanium-boron composite salt; the titanium-boron composite salt contains a mixture of potassium fluorotitanate and potassium fluoroborate; The multi-component eutectic fluoride salt comprises 26%-34% sodium fluoride, aluminum fluoride, and calcium fluoride. The composite gas generator comprises 20%-30% potassium sulfate, sodium nitrate, and iron oxide. 4%-10% rheology and activation aids; the rheology and activation aids include lithium fluoride and sodium metasilicate.

[0005] Furthermore, in the titanium-boron composite salt, the mass ratio of potassium fluorotitanate to potassium fluoroborate is (7:3) to (8:2).

[0006] Furthermore, the multi-element eutectic fluoride salt, by mass fraction, comprises 42%-48% sodium fluoride, 38%-44% aluminum fluoride, and 10%-16% calcium fluoride.

[0007] Furthermore, in the composite gas generator, the mass ratio of potassium sulfate, sodium nitrate and iron oxide is (5-6):(3-4):1.

[0008] Furthermore, the physical morphology of the aluminum-magnesium alloy melt composite purifying agent is a particle size of 0.3mm-1.2mm and a bulk density of 1.2g / cm³. 3 -1.6g / cm 3 granules.

[0009] Secondly, the present invention provides a method for refining aluminum-magnesium alloy melts, using the aforementioned aluminum-magnesium alloy melt composite purifying agent, the method comprising the following steps: Step 1: Control the temperature of the aluminum-magnesium alloy melt at 722℃-732℃ and perform inert gas pretreatment; Step 2: The preheated aluminum-magnesium alloy melt composite purifying agent is transported to a high-speed rotary jetting device through an inert carrier gas and injected into the aluminum-magnesium alloy melt for dynamic refining. Step 3: After stopping the addition of the aluminum-magnesium alloy melt composite purifying agent, continue to purge the melt with inert gas in a rotating manner, and then let it stand. Step four: After the aluminum-magnesium alloy melt has been allowed to stand, it is subjected to multi-stage online filtration before casting.

[0010] Furthermore, in step two, the preheating temperature of the aluminum-magnesium alloy melt composite purifying agent is 280℃-320℃, and its dosage is 0.16%-0.24% of the total mass of the aluminum-magnesium alloy melt.

[0011] Furthermore, in step two, the rotational speed of the high-speed rotary jet blowing device is 350 rpm-550 rpm, and the dynamic refining time satisfies the following relationship with the magnesium content of the aluminum-magnesium alloy: T≈2×[Mg]+5; In the formula, T is the dynamic refining time in minutes; [Mg] is the magnesium content of the aluminum-magnesium alloy in wt%.

[0012] Furthermore, in step four, the multi-stage online filtration includes at least one stage of rigid porous media deep bed filtration and one stage of ceramic fiber filter plate filtration.

[0013] Furthermore, the aluminum-magnesium alloy is a 5XXX series aluminum alloy with a magnesium mass fraction between 2% and 6%.

[0014] The beneficial effects of this invention are as follows: This invention achieves multiple technological breakthroughs in the purification of high-magnesium-content aluminum alloy melts through an innovative composite purifying agent formulation and refining process. The titanium-boron composite salt component in the purifying agent can generate high surface energy active sites in situ within the melt, strongly adsorbing fine magnesium-aluminum spinel inclusions. Simultaneously, the multi-element eutectic fluoride salt component can chemically modify the inclusion surface. Under the synergistic effect of these two mechanisms, traditionally difficult-to-remove spinel inclusions are efficiently transformed into easily separable aggregates, significantly improving melt cleanliness. The composite gas generator releases oxidizing gases through stepwise thermal decomposition, creating a mild and continuous hydrogen removal environment. While efficiently reducing hydrogen content, it significantly reduces magnesium oxidation loss, solving the problems of high magnesium burn-off and environmental pollution caused by traditional chloride salt hydrogen removal technology. The process combining preheated purifying agent and high-speed rotary jetting enhances the dispersion and contact efficiency of the reactant in the melt, improves refining kinetic efficiency, and reduces the amount of purifying agent used. The entire process is chlorine-free, avoiding the emission of toxic gases and meeting the requirements of green production. Furthermore, by adjusting the processing time parameters, it can be flexibly adapted to aluminum-magnesium alloys with different magnesium contents, making it widely applicable in production and providing reliable technical support for the stable production of high-end aluminum-magnesium alloy products. Attached Figure Description

[0015] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0016] Figure 1 This is a flowchart of a process for refining aluminum-magnesium alloy melts. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. The technical solutions provided by various embodiments of this invention will be described in detail below with reference to the accompanying drawings.

[0018] This invention provides a composite purifying agent for aluminum-magnesium alloy melts, which is prepared by melt blending, cooling and pulverizing the following components in mass percentage: Titanium-boron composite salt (component I): 36%-44%, composed of potassium fluorotitanate and potassium fluoroborate in a mass ratio of (K2TiF6):(KBF4) of (7:3) to (8:2). This component undergoes thermal decomposition and participates in the reaction in the melt, aiming to generate high-density micron / submicron-sized titanium-boron compound (mainly TiB2) dispersed particles in situ. The crystal structure and surface properties of these particles enable them to strongly adsorb and anchor fine MgAl2O4 particles, promoting their heterogeneous aggregation and coarsening.

[0019] Multi-component eutectic fluoride salt (component II): 26%-34%, a sodium fluoride-aluminum fluoride-calcium fluoride system. Its preferred composition (mass fraction) is: NaF 42%-48%, AlF 338%-44%, CaF 210%-16%. This eutectic mixture has a low initial melting temperature (<700℃) and exhibits good fluidity at refining temperatures. Its function is to penetrate and chemically modify the surface state of MgAl2O4 inclusions, reducing their interfacial tension with molten aluminum, thereby significantly increasing the probability of inclusions being captured by flux or adhered by bubbles.

[0020] Composite gas generator (component III): 20%-30%, composed of potassium sulfate (K2SO4), sodium nitrate (NaNO3), and iron oxide (Fe2O3), with a mass ratio of (5-6):(3-4):1. This composite system undergoes a stepwise thermal decomposition at the melt temperature, continuously and controllably releasing oxidizing gaseous products (such as SO3, NO2, and O2) and newly formed solid particles. These active substances can efficiently react with dissolved hydrogen to generate water vapor, which is then carried away by rising bubbles, while simultaneously avoiding excessive oxidation and loss of magnesium due to excessive oxidation potential.

[0021] Rheology and activating agent (component IV): 4%-10%, including lithium fluoride (LiF) and sodium metasilicate (Na2SiO3), in a mass ratio of approximately (1:1) to (2:1). This component is used to regulate the overall melting characteristics, dispersibility in the melt, and reaction kinetics of the purifying agent, ensuring a stable and thorough purification process.

[0022] Preferably, the composite purifying agent is processed into dense particles with a particle size range of 0.3 mm to 1.2 mm and a bulk density of 1.26 g / cm³. 3 -1.6g / cm 3 .

[0023] Please see Figure 1 The present invention also provides a method for refining aluminum-magnesium alloy melts, using the above-mentioned aluminum-magnesium alloy melt composite purifying agent, the method comprising the following steps: Step 1: Control the temperature of the aluminum-magnesium alloy melt at 722℃-732℃ and perform inert gas pretreatment.

[0024] Specifically, the aluminum-magnesium alloy melt is heated to 722℃-732℃ and purged with an inert gas, such as argon, through a porous plug at the bottom of the molten pool at a low intensity, with a flow rate of 0.3 L / min·kg-0.8 L / min·kg, for 3-6 minutes, in order to initially homogenize the composition and remove some of the atmosphere.

[0025] Step 2: The preheated aluminum-magnesium alloy melt composite purifying agent is transported to a high-speed rotating jetting device via an inert carrier gas and injected into the aluminum-magnesium alloy melt for dynamic refining.

[0026] Specifically, aluminum-magnesium alloy melt composite purifying agent particles, accounting for 0.16%-0.24% of the total melt mass, are preheated to 280℃-320℃ under air-isolated conditions. The preheated aluminum-magnesium alloy melt composite purifying agent is then quantitatively and continuously fed through a dedicated Venturi feeder by a preheated inert carrier gas at 150℃-250℃ into a high-speed rotating jetting device at 350rpm-550rpm. This device injects the gas-solid mixture into the lower 1 / 3 to 1 / 2 depth region of the melt in the form of a high-speed jet.

[0027] The refining process is carried out under rotating jet spray conditions. The processing time (T, minutes) can be estimated and finely adjusted based on the magnesium content ([Mg], wt.%) in the alloy using the empirical formula T≈2×[Mg]+5. For example, in 5XXX series aluminum alloys with a magnesium mass fraction between 2% and 6%, for the 5052 alloy with [Mg]=2.5%, T≈10 minutes; for the 5356 alloy with [Mg]=5.0%, T≈15 minutes. During this process, the components of the aluminum-magnesium alloy melt composite purifier rapidly disperse, melt, and undergo the aforementioned physicochemical reactions in the intense melt turbulence field.

[0028] Step 3: After stopping the addition of the aluminum-magnesium alloy melt composite purifying agent, continue to purge the melt with inert gas in a rotating manner, and then let it stand.

[0029] Specifically, stop the supply of purifying agent and continue to purge the melt with pure inert gas through a rotating nozzle for 2.5 to 4 minutes to promote the flotation of reaction products and coarsened inclusions. Then let it stand for 5 to 10 minutes.

[0030] Step four: After the aluminum-magnesium alloy melt has been allowed to stand, it is subjected to multi-stage online filtration before casting.

[0031] Specifically, the settled melt is passed through a multi-stage online filtration unit. This unit preferably includes a rigid porous media filter bed and a high-mesh ceramic fiber filter plate. The filtered clean melt is then transferred to a holding furnace or directly cast. The rigid porous media filter bed is, for example, composed of fused alumina or silicon carbide particles.

[0032] The present invention will be further described below with reference to specific alloy grades, but the scope of protection of the present invention is not limited to the following embodiments.

[0033] Example 1: Purification of 5052 aluminum alloy (Al-2.5Mg-0.25Cr).

[0034] Raw materials and conditions: 500 kg of commercial 5052 alloy, melt temperature 728℃.

[0035] Purifying agent preparation: By mass percentage, component I (K2TiF6:KBF4=75:25) 40%, component II (NaF 45%, AlF3 40%, CaF2 15%) 30%, component III (K2SO4:NaNO3:Fe2O3=5.5:3.5:1) 24%, and component IV (LiF:Na2SiO3=1.5:1) 6%. After mixing and melting, the mixture is rapidly cooled and crushed, and particles of 0.3-1.0 mm are sieved.

[0036] Refining process: Pre-treatment with bottom-blown Ar (0.5 L / min·kg) at 728℃ for 4 minutes. 1.1 kg of purifying agent was preheated to 300℃, and the preheated Ar carrier gas was injected into the melt through a 450 rpm rotor for 10 minutes. After stopping the feed, pure Ar was purged for 3 minutes, and the melt was allowed to stand for 8 minutes. The melt was then passed sequentially through a 100 mm thick bed of corundum particles and a 40 ppi ceramic fiber filter plate.

[0037] Performance evaluation: Hydrogen content decreased from 0.30 mL / 100g Al to 0.06 mL / 100g Al (hydrogen analyzer). Melt cleanliness analysis (PoDFA method) showed a 92% decrease in the total inclusion area index. Magnesium recovery rate of ingot was 99.4% (spectral analysis). Subsequent rolled sheet surface quality was excellent, and anodizing showed no color difference.

[0038] Example 2: Purification of 5356 aluminum alloy (Al-5.0Mg-0.12Mn).

[0039] Raw materials and conditions: 500 kg of 5356 alloy, melt temperature 730℃.

[0040] Purifying agent and process adjustments: The purifying agent formula is the same as in Example 1, but the dosage is adjusted to 0.22% of the melt (i.e., 1.1 kg). The refining time is extended to 15 minutes, the rotor speed is increased to 500 rpm, and the settling time is extended to 10 minutes.

[0041] Effect evaluation: The hydrogen content decreased from 0.45 mL / 100g Al to 0.08 mL / 100g Al. Metallographic and SEM-EDS analyses showed that the typical MgAl2O4 spinel phase in the melt was essentially eliminated. The magnesium recovery rate was 98.8%. In automated welding applications, the prepared welding wire showed a significant reduction in weld porosity and stable weld mechanical properties.

[0042] Comparative example: The same 5356 melt was treated using the traditional method of pressing in 0.5% hexachloroethane (C2Cl6) blocks.

[0043] Results: Hydrogen content decreased to 0.18 mL / 100g Al, but the production site was filled with smoke. Magnesium recovery was only 93.5%. Macroscopically, the ingot showed many oxide film inclusions, which increased the breakage rate during subsequent wire drawing.

[0044] The embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention.

Claims

1. A composite purifying agent for aluminum-magnesium alloy melt, characterized in that, The components include the following components by mass percentage: The titanium-boron composite salt contains 36%-44% titanium-boron composite salt; the titanium-boron composite salt contains a mixture of potassium fluorotitanate and potassium fluoroborate; The multi-component eutectic fluoride salt comprises 26%-34% sodium fluoride, aluminum fluoride, and calcium fluoride. The composite gas generator comprises 20%-30% potassium sulfate, sodium nitrate, and iron oxide. 4%-10% rheology and activation aids; the rheology and activation aids include lithium fluoride and sodium metasilicate.

2. The aluminum-magnesium alloy melt composite purifying agent according to claim 1, characterized in that, In the titanium-boron composite salt, the mass ratio of potassium fluorotitanate to potassium fluoroborate is (7:3) to (8:2).

3. The aluminum-magnesium alloy melt composite purifying agent according to claim 1, characterized in that, The multi-element eutectic fluoride salt, by mass fraction, comprises 42%-48% sodium fluoride, 38%-44% aluminum fluoride, and 10%-16% calcium fluoride.

4. The aluminum-magnesium alloy melt composite purifying agent according to claim 1, characterized in that, In the composite gas generator, the mass ratio of potassium sulfate, sodium nitrate and iron oxide is (5-6):(3-4):

1.

5. The aluminum-magnesium alloy melt composite purifying agent according to claim 1, characterized in that, The physical morphology of the aluminum-magnesium alloy melt composite purifier is a particle size of 0.3mm-1.2mm and a bulk density of 1.2g / cm³. 3 -1.6g / cm 3 granules.

6. A method for refining aluminum-magnesium alloy melts, using the composite purifying agent for aluminum-magnesium alloy melts as described in any one of claims 1-5, characterized in that, The method includes the following steps: Step 1: Control the temperature of the aluminum-magnesium alloy melt at 722℃-732℃ and perform inert gas pretreatment; Step 2: The preheated aluminum-magnesium alloy melt composite purifying agent is transported to a high-speed rotary jetting device through an inert carrier gas and injected into the aluminum-magnesium alloy melt for dynamic refining. Step 3: After stopping the addition of the aluminum-magnesium alloy melt composite purifying agent, continue to purge the melt with inert gas in a rotating manner, and then let it stand. Step four: After the aluminum-magnesium alloy melt has been allowed to stand, it is subjected to multi-stage online filtration before casting.

7. The method for refining aluminum-magnesium alloy melt according to claim 6, characterized in that, In step two, the preheating temperature of the aluminum-magnesium alloy melt composite purifying agent is 280℃-320℃, and its dosage is 0.16%-0.24% of the total mass of the aluminum-magnesium alloy melt.

8. The method for refining aluminum-magnesium alloy melt according to claim 6, characterized in that, In step two, the rotation speed of the high-speed rotary jet blowing device is 350 rpm-550 rpm, and the dynamic refining time satisfies the following relationship with the magnesium content of the aluminum-magnesium alloy: T≈2×[Mg]+5; In the formula, T is the dynamic refining time in minutes; [Mg] is the magnesium content of the aluminum-magnesium alloy in wt%.

9. The method for refining aluminum-magnesium alloy melt according to claim 6, characterized in that, In step four, the multi-stage online filtration includes at least one stage of rigid porous media deep bed filtration and one stage of ceramic fiber filter plate filtration.

10. The method for refining aluminum-magnesium alloy melt according to claim 6, characterized in that, The aluminum-magnesium alloy is a 5XXX series aluminum alloy with a magnesium mass fraction between 2% and 6%.

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