Refined modifier, its preparation method, and production method of recycled aluminum alloy

Abstract

The present invention provides a refinement modifier for casting recycled aluminum alloy, which is characterized in that, by mass fraction, its chemical composition includes: Ti 2.5% - 6.5%, B 0.15 - 1.0%, C 0.15 - 0.8%, V 0.1 - 0.45%, Y 0.1 - 0.55%, and the balance is Al and other impurity elements; wherein, the total amount of the other impurity elements ≤ 0.15%, and among the other impurity elements, the content of a single impurity element ≤ 0.05%. The refinement modifier provided by the present invention has stable and efficient refinement effect, silicon modification effect and β-iron modification effect, with remarkable effects and worthy of popularization.

Description

Technical Field

[0001] The present invention belongs to the field of recycled aluminum alloy casting, and particularly relates to a refinement modifier and a preparation method thereof, a recycled aluminum alloy and a production method thereof. Background Art

[0002] Cast aluminum alloys have the advantages of high specific strength, corrosion resistance, simple production process and low cost, so they are widely used in the aerospace and automotive industries. However, the production process of electrolytic aluminum consumes a large amount of energy and produces a large amount of waste residue and waste gas. With the reduction of bauxite resources, the increasing demand for energy conservation, emission reduction and carbon emission reduction, it is urgent to develop recycled aluminum resources.

[0003] The recycled aluminum industry uses various waste aluminum materials to produce aluminum alloys. Compared with the industrial routes of bauxite, alumina, electrolytic aluminum and aluminum alloy, the energy consumption and greenhouse gas emissions are significantly reduced. Compared with the same amount of primary aluminum, the energy consumption for producing 1 ton of recycled aluminum is only 3%-5% of that of electrolytic aluminum, which can reduce the carbon dioxide emissions by 0.8 tons, save more than 10 tons of water, and at the same time reduce the treatment burden of solid waste, waste liquid and waste residue.

[0004] The graded recycling and utilization of recycled aluminum is the current development trend of the recycled aluminum industry. For example, in common technologies, refiners AlTiB and modifiers AlSr are mostly used in order to improve the performance of recycled aluminum alloys. Among them, the main functions of the refiner and the modifier include grain refinement and silicon modification.

[0005] Grain refinement can significantly improve the mechanical properties of recycled aluminum, such as tensile strength, yield strength and elongation. Fine grains effectively disperse the load and reduce stress concentration, thereby improving the overall strength of the material. At the same time, grain refinement helps to reduce defects and cracks in recycled aluminum, making the structure uniform and dense, so as to improve the corrosion resistance of recycled aluminum and extend the service life of the product.

[0006] And the silicon modification effect is also an important index of the modifier's function: in the hypereutectic aluminum-silicon alloy structure, there are primary silicon in large blocky polygons and eutectic silicon in lamellar shapes. The higher the silicon content, the more primary silicon, which seriously cuts the matrix and deteriorates the mechanical properties.

[0007] And silicon modification can significantly refine the eutectic silicon structure in recycled aluminum, making the eutectic silicon change from thick needle-like or plate-like to fine fibrous or dot-like. This structural transformation improves the fluidity of the alloy, reduces the tendency of hot cracking that may occur during the casting process, and thus improves the casting performance of the alloy. At the same time, silicon modification can also refine the eutectic silicon structure, and can also reduce the microshrinkage in the alloy, making the alloy structure more uniform and dense. The improvement of this structure helps to improve the mechanical properties such as tensile strength, yield strength and elongation of the alloy.

[0008] However, in the commonly used AlTiB grain refiner, its refining effect often deteriorates with the increase of holding time and is extremely unstable. In the AlSr modifier, due to the strong affinity between Sr element and hydrogen in the aluminum melt, it is easy to cause the aluminum alloy melt to absorb hydrogen, generate a large number of pores, and reduce the mechanical properties of the aluminum alloy material. At the same time, Sr element is relatively active, and it is easy to burn out during the addition process, affecting the product mechanical properties and increasing production costs.

[0009] In summary, in the production process of cast recycled aluminum, there is an urgent need for a refining and modifying agent that can efficiently and stably refine grains and modify silicon. Summary of the Invention

[0010] Aiming at solving the technical problems in the above-mentioned commonly used technologies, where the refining and modifying effects of the grain refiner and the modifier are unstable, thus affecting the quality of recycled aluminum alloy products, the present invention provides a refining and modifying agent for cast recycled aluminum alloy. In terms of mass fraction, its chemical composition includes: Ti 2.5% - 6.5%, B 0.15 - 1.0%, C 0.15 - 0.8%, V 0.1 - 0.45%, Y 0.1 - 0.55%, and the balance is Al and other impurity elements; among them, the total amount of the other impurity elements ≤ 0.15%, and among the other impurity elements, the content of a single impurity element ≤ 0.05%.

[0011] Further, in terms of mass fraction, its chemical composition includes: Ti 3.5% - 5.5%, B 0.6% - 0.8%, C 0.35% - 0.65%, V 0.25% - 0.35%, Y 0.25% - 0.4%, and the balance is Al and other impurity elements.

[0012] The present invention also provides a preparation method for the refining and modifying agent for cast recycled aluminum alloy, including the steps:

[0013] S1. At 800 - 870 °C, mix pure aluminum melt with K 2 TiF 6 , KBF 4 , separate the acid water leached from the melt to obtain a mixed melt;

[0014] S2. Keep warm, add graphite, vanadium, Al - Y master alloy and refining agent to the mixed melt, stir and then stand for 20 - 30 min, separate the scum precipitated from the melt to obtain the refining and modifying agent;

[0015] Among them, the elemental compositions of the pure aluminum melt, the K 2 TiF 6 , the KBF 4 , the graphite, the vanadium, and the Al - Y master alloy as a whole are the same as those of the refining and modifying agent;

[0016] In terms of mass fraction, the chemical composition of the refinement modifier includes: Ti 2.5% - 6.5%, B 0.15% - 1.0%, C 0.15% - 0.8%, V 0.1% - 0.45%, Y 0.1% - 0.55%, and the balance is Al and other impurity elements; among them, the total amount of the other impurity elements ≤ 0.15%, and among the other impurity elements, the content of a single impurity element ≤ 0.05%.

[0017] Further, the S2 includes: successively performing degassing treatment, crystallization treatment, and continuous casting and extrusion treatment on the melt after separating the floating slag to obtain the refinement modifier; among them, during the crystallization treatment process, the crystallization temperature is 730 - 750 °C, and the rotation speed is 8 - 15 r / min.

[0018] Further, pure aluminum is melted to obtain the pure aluminum melt;

[0019] Before the step S1, the pure aluminum, the K 2 TiF 6 , the KBF 4 , the graphite, the vanadium, and the Al - Y master alloy are subjected to drying treatment; among them, the temperature of the drying treatment is 240 - 260 °C, and the duration of the drying treatment is 45 - 60 min.

[0020] Further, the refining agent includes sodium chloride and / or potassium chloride, and the addition amount of the refining agent is 0.15% - 0.25% of the mass of the mixed melt.

[0021] The present invention provides a production method of recycled aluminum alloy, including steps:

[0022] After heating the recycled aluminum scrap to 750 - 780 °C, it is refined to obtain an aluminum - containing melt;

[0023] The refinement modifier prepared by the preparation method described in any one of the above is added to the aluminum - containing melt, and after stirring, it is left standing for 20 - 30 min to obtain a recycled aluminum melt; among them, the addition amount of the refinement modifier is 0.15% - 0.25% of the mass of the aluminum - containing melt;

[0024] The recycled aluminum melt is cast into a shape to obtain a recycled aluminum alloy.

[0025] Further, in the step of heating the recycled aluminum scrap to 750 - 780 °C and then refining to obtain an aluminum - containing melt, the refining includes:

[0026] A refining agent is added to the recycled aluminum scrap after heating, and it is refined for 20 - 30 minutes.

[0027] Further, in terms of mass fraction, the silicon content of the recycled aluminum scrap is 6.5% - 7.5%, and the silicon content of the recycled aluminum alloy is 6.5% - 7.5%.

[0028] Further, the recycled aluminum melt is cast into a shape to obtain a recycled aluminum alloy, which further includes: performing heat treatment on the casting obtained by casting the recycled aluminum melt to obtain a recycled aluminum component.

[0029] Compared with the prior art, the present invention has at least the following advantages:

[0030] The present invention provides a refining modifier for casting recycled aluminum alloy. In terms of mass fraction, the Ti content in the refining modifier is 2.5% - 6.5%, the B content is 0.15% - 1.0%, and the C content is 0.15% - 0.8%. By optimizing the ratio of titanium, boron, and carbon, various uniformly dispersed nucleation sites are formed in the aluminum melt under the convection of the aluminum melt by particles such as TiB 2 、TiBC、TiC、VB 2 : On the one hand, based on the interaction between multiple particles in the aluminum melt, particles such as TiB 2 、TiBC、TiC、VB 2 are relatively dispersed. Specifically, refer to Figure 1 、 Figure 2 ( Figure 1 is the SEM image of the refining modifier at 1500 times in an embodiment of the present invention, Figure 2 and this is the SEM image of the aluminum-titanium-boron refining agent at 2000 times in the common technology of the present invention). Intuitively, it can be seen that the particles in the present invention are evenly distributed and have clear boundaries, while in the common technology, the spacing of TiB 2 particles is small and they are adhered to each other with blurred boundaries, even forming large-scale agglomerations; on the other hand, 0.1% - 0.55% of yttrium element is additionally added to the refining modifier of the invention. The Y element can, on the basis of the relatively dispersed distribution of the aforementioned nucleation sites, increase the expansion coefficient of the nucleation sites in the aluminum melt and further improve the uniformity of the distribution of each particle.

[0031] The yttrium element can also make the TiB 2 particles relatively active to prevent grain aggregation and growth. For details, refer to Figure 1 、 Figure 2 . It can be seen that the agglomeration scale of TiB 2 in the refining modifier of the present invention is significantly reduced. It should be noted that another reason for the reduction of the TiB 2 agglomeration scale is the diversification of the refining particles. Based on the interaction between particles, the aggregation tendency of TiB 2 particles is also weakened, effectively avoiding the aggregation of TiB 2 particles.

[0032] Uniform and non-agglomerated refined particles form an efficient and stable refining effect, which does not decline with the prolongation of the holding time, thereby optimizing the mechanical properties of recycled aluminum alloy, avoiding the generation of quality defects, and making the structure uniform and fine with good corrosion resistance.

[0033] In the commonly used AlTiB refining agent, TiB 2 particles are prone to aggregation and often combine with oxide films or salt fluxes in the aluminum-containing melt to cause inclusions; at the same time, TiB 2 after long-term heat preservation, TiB 2 particles further precipitate and aggregate, resulting in a decline in the refining effect. Especially for aluminum-containing melts with a relatively high silicon content (such as a silicon content higher than 4%), large-sized and aggregated TiB 2 combines with silicon elements, producing a poisoning effect, making the grains significantly coarsened. Based on the dispersion effect brought by the diversification and homogenization of particles in the present invention, compared with the commonly used technology, the grains in the present invention are significantly refined and the refining effect is persistent; even in a high-silicon environment, the poisoning threat is very low... The above-mentioned effect differences further reflect the stable and reliable refining effect of the refining modifier in this application.

[0034] In the present invention, 0.1%-0.55% of yttrium element and 0.1%-0.45% of vanadium element are additionally added. The rare earth Y element can act together with the vanadium element to inhibit the growth of eutectic silicon, making the eutectic silicon in the form of short fibers, thereby realizing silicon modification.

[0035] Compared with the application of the modifier in the commonly used technology, based on the property differences between the yttrium element and the strontium element, the yttrium element is relatively stable and will not absorb hydrogen or burn out, ensuring the stable and safe production of recycled aluminum alloy products. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the structures shown in these drawings.

[0037] Figure 1 It is a 1500-fold SEM micrograph of the refining modifier for casting recycled aluminum alloy of the present invention;

[0038] Figure 2 It is a 2000-fold SEM micrograph of the AlTiB refining agent in the commonly used technology;

[0039] Figure 3 It is the TiB in the AlTiB refining agent in the commonly used technology in a high-silicon environment 2SEM micrograph of 3000 - fold particle aggregation;

[0040] Figure 4 Macrograin diagram of the recycled aluminum component using the grain refinement modifier for casting recycled aluminum alloy in Example 1 of the present invention;

[0041] Figure 5 Macrograin diagram of the recycled aluminum component using the traditional grain refinement modifier in Comparative Example 1;

[0042] Figure 6 Metallographic structure diagram of the recycled aluminum component using the grain refinement modifier for casting recycled aluminum alloy in Example 1;

[0043] Figure 7 Metallographic structure diagram of the recycled aluminum component using the traditional grain refinement modifier in Comparative Example 1;

[0044] Figure 8 Morphology diagram of Fe phase in the recycled aluminum component using the grain refinement modifier for casting recycled aluminum alloy in Example 1;

[0045] Figure 9 Morphology diagram of Fe phase in the recycled aluminum component using the traditional grain refinement modifier in Comparative Example 1; Detailed implementation mode

[0046] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0047] Moreover, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0048] When the embodiments give a numerical range, it should be understood that unless otherwise specified in the present invention, any value at both ends of each numerical range and any value between the two ends can be selected. Unless otherwise defined, all technical and scientific terms used in the present invention, based on the understanding of those of ordinary skill in the art of the prior art and the description of the present invention, can also use any methods, equipment, and materials similar or equivalent to the methods, equipment, and materials described in the embodiments of the present invention to implement the present invention.

[0049] The present invention provides a refinement modifier for casting recycled aluminum alloy. In terms of mass fraction, its chemical composition includes: Ti 2.5% - 6.5%, B 0.15% - 1.0%, C 0.15% - 0.8%, V 0.1% - 0.45%, Y 0.1% - 0.55%, and the balance is Al and other impurity elements; wherein, the total amount of the other impurity elements ≤ 0.15%, and among the other impurity elements, the content of a single impurity element ≤ 0.05%.

[0050] Among them, when the contents of titanium, boron, and carbon are lower than the lower limit of the range, it will lead to a small amount of refinement particles and insufficient refinement effect. When the contents of titanium and boron elements are higher than the upper limit, it will lead to the agglomeration of TiB 2 particles, and when the carbon element is too high, it will form Al 4 C 3 impurities; therefore, when the contents of the three elements fall within the above range, a variety of dispersed refinement particles can be formed, such as Figure 1 shown, where A is TiB 2 , B is TiBC, C is TiC, and D is VB 2 .

[0051] By optimizing the ratio of titanium, boron, and carbon, TiB 2 , TiBC, TiC, VB 2 and other particles can form a variety of uniformly dispersed nucleation sites in the aluminum melt under the convection of the aluminum melt: on the one hand, based on the interaction between the multi-component particles in the aluminum melt, TiB 2 , TiBC, TiC, VB 2 and other particles are relatively dispersed, specifically referring to Figure 1 , Figure 2 , where Figure 1 is the SEM image of the refinement modifier at XX times in an embodiment of the present invention, Figure 2 is the SEM image of the aluminum-titanium-boron refinement agent at XX times in the common technology of the present invention. It can be intuitively seen that the particles in the present invention are evenly distributed and have clear boundaries, while in the common technology, the spacing of TiB 2 particles is small and they are adhered to each other, even forming large-scale agglomeration; on the other hand, 0.1% - 0.55% of yttrium element is additionally added to the refinement modifier of the invention. The Y element can improve the expansion coefficient of the nucleation sites in the aluminum melt on the basis of the relatively dispersed distribution of the foregoing nucleation sites, and further improve the uniformity of the distribution of each particle.

[0052] The yttrium element can also make the TiB 2 particles relatively active to prevent grain aggregation and growth, as shown in detail in Figure 1 , Figure 2 . It can be seen that the agglomeration scale of TiB 2 in this embodiment is significantly reduced. It should be noted that TiB2 Another reason for the reduction in agglomeration size is the diversification of refined particles, which also weakens the TiB 2 The aggregation tendency of particles effectively avoids TiB 2 The aggregation of particles forms an efficient and stable refinement effect.

[0053] In the present invention, 0.1%-0.55% of yttrium and 0.1%-0.45% of vanadium are additionally added. Among them, the Y element can increase the expansion coefficient of the nucleation particles in the aluminum melt on the basis of the large amount and uniform distribution of the nucleation particles mentioned above, so that TiB 2 、TiBC、TiC、VB 2 The distribution of particles is more uniform while preventing the grains from agglomerating and growing, thereby synergistically optimizing the grain refinement effect. At the same time, the rare earth element Y can also work together with the vanadium element to inhibit the growth of eutectic silicon, making the eutectic silicon short-fibered, thereby achieving silicon metamorphism.

[0054] As the main development trend of grade-preserving recycling of recycled aluminum in the current recycled aluminum industry, the research on recycling and remelting technology of recycled aluminum alloys is of great significance and imperative. However, a large number of impurity elements will inevitably be introduced during the recycling and remelting process, among which Fe is the most common: Fe will form coarse needle-shaped β-Fe phase in the recycled aluminum alloy, which will have a serious splitting effect on the matrix, resulting in reduced plasticity of the material; at the same time, when the material is subjected to alternating loads, the β-Fe phase will become the source of fatigue cracks, greatly reducing the fatigue life of the material. In addition, the β-Fe phase will interfere with the flow of aluminum liquid between dendrites, resulting in micro-shrinkage... All of the above will significantly reduce the comprehensive mechanical properties of recycled aluminum alloy materials.

[0055] At present, there are two main measures to alleviate or reduce the harmful effects of iron: one is to try to reduce the amount of iron in the aluminum melt; the other is to improve the organizational morphology of the iron-rich phase in the aluminum alloy, that is, to inhibit the formation of needle-shaped β-Fe phase as much as possible, so as to generate Chinese character-shaped or fishbone-shaped α-Fe phase which is less harmful to the performance of the aluminum alloy.

[0056] The existing iron removal technologies for the former include gravity sedimentation, centrifugal separation, electromagnetic separation, and filtration. These methods can partially remove the iron-rich phase in the melt, but the efficiency and effect of physically reducing the iron content in the aluminum alloy are low, so they will not be elaborated here.

[0057] However, there are few studies on the existing technology for improving the microstructure of the iron-rich phase in aluminum alloys. Modifying the Fe-rich phase to control its morphology is an effective way to improve the performance of recycled aluminum alloys. Therefore, this application studies a refinement modifier. On the basis of the above-mentioned refinement effect, the yttrium and vanadium elements are used to coordinate and achieve constant and efficient β-Fe (Al 5 FeSi) phase to α-Fe (Al 8 Fe2 The transformation of the Si phase.

[0058] Specifically, the influence mechanism of rare earth element Y on the β-Fe phase is mainly to promote the nucleation of the iron-rich phase, refine the iron-rich phase, hinder the growth of the iron-rich phase, and at the same time make the β-Fe(Al 5 FeSi) phase transform from thick needle-like to fine fishbone-like α-Fe(Al 8 Fe 2 Si) phase, and the Al 15 (FeV) 3 Si 2 phase formed by the addition of ferrovanadium is added, comprehensively ensuring the transformation of the microstructure morphology of the iron-rich phase in the aluminum alloy and reducing the influence of the β-Fe phase on the elongation and fatigue properties of the aluminum alloy.

[0059] In some embodiments, by mass fraction, its chemical composition includes: Ti 3.5%-5.5%, B 0.6%-0.8%, C 0.35%-0.65%, V 0.25%-0.35%, Y 0.25%-0.4%, and the balance is Al and other impurity elements.

[0060] Specifically, by mass fraction, the chemical composition of the refinement modifier prepared by the present invention may include: Ti: 4.5%, B: 0.7%, C: 0.45%, V: 0.3%, Y: 0.35%, and the balance is Al and other impurity elements.

[0061] The present invention provides a preparation method of a refinement modifier for casting recycled aluminum alloy, including the steps:

[0062] S1. At 800-870 °C, mix pure aluminum melt with K 2 TiF 6 , KBF 4 , separate the acid water leached from the melt to obtain a mixed melt.

[0063] In some embodiments, before the step S1, the pure aluminum, the K 2 TiF 6 , the KBF 4 , the graphite, the vanadium, and the Al-Y master alloy are dried; wherein, the temperature of the drying treatment is 240-260 °C, and the duration of the drying treatment is 60 min.

[0064] Exemplarily, the required amount of pure aluminum, K 2 TiF 6 , KBF 4 , graphite, vanadium, and Al-Y master alloy can be weighed and placed in an incubator at 240-260 °C for drying for 60 min.

[0065] Exemplarily, the mass of pure aluminum can be 1000 Kg, and K 2 TiF 6 , KBF 4 , graphite, vanadium, and the mass of the Al-Y master alloy can be 138 - 335 Kg, 18 - 120 Kg, 1.5 - 8.5 Kg, 1 - 4.5 Kg, 5.5 - 28.5 Kg respectively

[0066] Graphite and vanadium can be in powder form to enhance their uniformity of dispersion and mass transfer ability in the melt, and the reaction efficiency is improved.

[0067] Melt industrial pure aluminum to obtain the pure aluminum melt.

[0068] Specifically, it may include the steps of: adding the weighed industrial pure aluminum into an induction furnace to melt, and heating up to 800 - 870 °C to form a pure aluminum melt.

[0069] In some specific embodiments, K 2 TiF 6 and KBF 4 mixed salts can be added to the pure aluminum melt, kept warm at a temperature of 800 - 870 °C, and stirred thoroughly for 25 - 35 min; until the acid water mainly composed of potassium fluoroaluminate is leached out in the melt, and after fishing out the acid water, a mixed melt is obtained.

[0070] S2. Keep warm, add graphite, vanadium, Al-Y master alloy and a refining agent to the mixed melt, stir and then let it stand for 20 - 30 min, separate the floating slag precipitated in the melt to obtain a grain refining and modification agent;

[0071] In terms of mass fraction, the chemical composition of the grain refining and modification agent includes: Ti 2.5% - 6.5%, B 0.15% - 1.0%, C 0.15% - 0.8%, V 0.1% - 0.45%, Y 0.1% - 0.55%, and the balance is Al and other impurity elements; among them, the total amount of the other impurity elements ≤ 0.15%, and for the other impurity elements, the content of a single impurity element ≤ 0.05%.

[0072] In some specific embodiments, the step S2 may include the steps of:

[0073] S21. At a temperature of 800 - 870 °C, graphite, vanadium and Al-Y master alloy can be added to the mixed melt, kept warm and stirred thoroughly for 25 - 35 min to completely melt the above components and uniformly disperse them in the mixed melt;

[0074] S22. After adding the refining agent, continue to stir thoroughly, let it stand for 20 minutes, and fish out the floating slag.

[0075] It should be noted that the static setting for 20 minutes still needs to be carried out under the heat preservation condition of 800 - 870 °C.

[0076] In some embodiments, the refining agent includes sodium chloride and / or potassium chloride, and the addition amount of the refining agent is 0.15% - 0.25% of the mass of the mixed melt.

[0077] The main components of the dross include a mixture of oxide inclusions, sodium chloride and / or potassium chloride.

[0078] S23. Perform degassing treatment, crystallization treatment, and continuous casting and extrusion treatment on the melt after separating the dross in sequence to obtain the refined modifier.

[0079] In some specific embodiments, a rotor degasser can be used to perform degassing treatment on the melt after separating the dross, and then the degassed melt is introduced into a launder and enters a crystallization wheel for crystallization treatment; finally, continuous casting and extrusion are carried out to obtain the wire rod of the refined modifier for recycled aluminum alloy.

[0080] Among them, the function of the degassing treatment is as follows: During the metal melting and casting process, the melt often absorbs a certain amount of gases, such as hydrogen, oxygen, etc. If these gases cannot be discharged in time during the solidification process, pores will be formed in the refined modifier, seriously affecting the mechanical properties and appearance quality of the casting. The degassing treatment can effectively remove these gases in the melt, thereby reducing the pore defects in the casting and improving the overall quality of the casting.

[0081] The crystallization treatment of the crystallization wheel can roll the melt into a formed shape.

[0082] Exemplarily, during the crystallization treatment, the crystallization temperature can be 730 - 750 °C, and the rotation speed can be 8 - 15 r / min; that is, the temperature of the crystallization wheel is controlled at 730 - 750 °C, and the rotation speed of the extrusion wheel is 8 - 15 r / min.

[0083] During the continuous casting and extrusion treatment, the refined modifier withstands the extrusion pressure of the extrusion wheel at high temperature, causing the coarse particles to break into small molecular particles, and at the same time improving the uniformity of the distribution of the refined particles and making the refining effect more stable and efficient.

[0084] The present invention also provides a production method for recycled aluminum alloy, including the steps:

[0085] S01. Heat the recycled aluminum scrap to 750 - 780 °C and then refine it to obtain an aluminum-containing melt.

[0086] Among them, the recycled aluminum scrap can include socially recycled aluminum, internally scrapped aluminum castings in the factory, and machined aluminum chips.

[0087] After the recycled aluminum scrap is heated to 750 - 780 °C, it can be melted into a melt.

[0088] Specifically, recycled aluminum scrap can be melted in a melting furnace at a temperature environment of 750 - 780 °C to form a melt. The refining agent in the aforementioned step S2 is added to the melt, and refined for 20 - 30 minutes. Then, slag is removed and skimmed, and then kept warm and static for 20 minutes to obtain an aluminum-containing melt.

[0089] Exemplarily, the addition amount of the refining agent is 0.15% - 0.25% of the mass of the melt to obtain an aluminum-containing melt.

[0090] Exemplarily, the refining agent includes sodium chloride and / or potassium chloride, and the addition amount of the refining agent is 0.15% - 0.25% of the mass of the melt.

[0091] It should be noted that the melt here is formed by melting recycled aluminum scrap.

[0092] S02. Add the refinement modifier prepared by any of the above preparation methods to the aluminum-containing melt, stir and then stand for 20 - 30 min to obtain a recycled aluminum melt; wherein, the addition amount of the refinement modifier is 0.15% - 0.25% of the mass of the aluminum-containing melt.

[0093] In some embodiments, the recycled aluminum melt can be degassed to optimize the appearance quality of the recycled aluminum alloy.

[0094] Exemplarily, argon degassing treatment can be adopted, and the time can be 15 min.

[0095] S03. The recycled aluminum melt is cast into a mold to obtain a recycled aluminum alloy.

[0096] In some embodiments, by mass fraction, the silicon content of the recycled aluminum scrap is 6.5% - 7.5%, and the silicon content of the recycled aluminum alloy is 6.5% - 7.5%.

[0097] Based on the foregoing, in the commonly used AlTiB refinement modifier, TiB 2 particles are prone to aggregation, as Figure 2 shown. As Figure 3 shown, limited by the silicon content of the aluminum-containing melt, for a melt environment with a silicon content higher than 4%, when the AlTiB refinement modifier is applied, TiB 2 will react with the Si element, resulting in a Si poisoning effect, causing the refinement function of the added refinement modifier to fail on a large scale; and the agglomerated TiB 2 reacts with silicon, resulting in obvious coarsening of the grains and forming quality defects.

[0098] However, in this application, the composition and ratio of the refinement modifier are redesigned, and a variety of uniform nucleation sites are formed in the refinement modifier (as Figure 1 shown, for example, TiB 2, TiBC, TiC, VB 2 The (such as particles) can be stably and efficiently applied to high-silicon environments with a silicon content as high as 6.5 - 7.5%, meeting the application requirements in the automotive industry, such as products like automotive aluminum alloy wheels, steering knuckles, and subframes, etc., with broad prospects.

[0099] Specifically, when the temperature of the recycled aluminum melt reaches 700 - 720 °C, it can be cast using a metal mold to obtain a recycled aluminum alloy.

[0100] In some embodiments, the recycled aluminum alloy obtained by casting the recycled aluminum melt further includes: subjecting the casting obtained by casting the recycled aluminum melt to heat treatment to obtain a recycled aluminum component.

[0101] It should be noted that the recycled aluminum alloy here includes amorphous materials in a broad sense, such as recycled aluminum alloy ingots; it also includes recycled aluminum components, such as recycled aluminum alloy fittings with specific structures. Usually, after casting using a mold, it also needs to undergo specific heat treatment processes to meet different performance requirements.

[0102] Exemplarily, the heat treatment can include T6 heat treatment.

[0103] T6 heat treatment is a commonly used metal hot working process, mainly applied to wrought aluminum alloys (different from cast aluminum alloys). This process includes two main steps: solution treatment and artificial aging. During the solution treatment process, high temperature enables alloying elements to dissolve fully, eliminating internal stress and locking structural defects, thereby improving the toughness of the material. And in the aging treatment stage, low-temperature precipitation can enhance the strength of the material. By precisely controlling the aging temperature and time, appropriate precipitate morphology and distribution can be produced, and thus ideal performance can be achieved.

[0104] The analysis methods for each dimension of the aforementioned recycled aluminum alloy and recycled aluminum component are as follows:

[0105] Take samples from the recycled aluminum alloy or the recycled aluminum component body for grain size detection.

[0106] Conduct metallographic structure analysis on the recycled aluminum component, observe and analyze the morphology of eutectic silicon to judge the modification effect.

[0107] Observe and analyze the morphology of the Fe phase to judge the effect of the refinement modifier on the morphology change of the Fe phase.

[0108] Take samples from the body to prepare material tensile property specimens, and conduct mechanical property tests through an electronic universal material testing machine to obtain the yield strength, tensile strength, and elongation.

[0109] Prepare a material fatigue performance specimen by sampling from the body, conduct material fatigue testing through an electro-hydraulic servo fatigue testing machine, and obtain the material fatigue limit strength. Among them, the material fatigue testing conditions are as follows: the test environment is room temperature, the loading direction is axial loading, the fatigue test stress ratio R is -1, the loading method is sinusoidal load, and the frequency is 30 - 100 Hz.

[0110] Compared with the prior art, the present invention has the following advantages:

[0111] (1) The present invention solves the problems of insufficient refinement of traditional refiners, easy burning loss and hydrogen absorption of modifiers, and an increase in acicular β-Fe phase in cast recycled aluminum alloys. For cast recycled aluminum alloys, the present invention can simultaneously achieve high-efficiency grain refinement, Si modification, improve the morphology of acicular β-Fe phase, and enhance the comprehensive mechanical properties of cast recycled aluminum alloys, especially elongation and fatigue performance;

[0112] (2) Compared with the common technology of adding a refiner, a modifier, and an alloy element for neutralizing Fe separately in three times or adding pure aluminum to reduce the Fe content, the present invention only needs to add a refining and modifying agent once, simplifies the process and operation, and the quality of the recycled aluminum melt is more stable;

[0113] (3) The refining and modifying agent of the present invention has stable and high refining effect, is not easy to decline, has low production cost, and at the same time has ultra-low carbon emissions, is environmentally friendly, and is suitable for large-scale application.

[0114] For the convenience of those skilled in the art to further understand the present invention, the following is an example:

[0115] Some nouns or names in the embodiments can be explained here.

[0116] Example 1

[0117] A refining and modifying agent for cast recycled aluminum alloy, the mass percentages of each component are: Ti: 4.5%, B: 0.7%, C: 0.45%, V: 0.3%, Y: 0.35%, and the balance is Al and unavoidable other impurity elements; the single content of other impurity elements ≤ 0.05%, and the total content ≤ 0.15%;

[0118] The preparation of the refining and modifying agent includes the following steps:

[0119] S1. Select industrial pure aluminum, K 2 TiF 6 、KBF 4 、graphite powder, V powder, Al-Y master alloy as raw materials, weigh the required raw materials and dry them in a constant temperature oven at 250 °C;

[0120] Add the weighed industrial pure aluminum into an induction furnace to melt, heat up to 850 °C, and add K 2 TiF6 and KBF 4 Mixing salts, heat insulating and fully stirring, fishing out acid water to obtain a mixed melt;

[0121] S21. Continuously add graphite powder, V powder and Al-Y master alloy, heat insulating and fully stirring to completely melt the above components and uniformly disperse them in the melt; wherein, pure aluminum, the above-mentioned K 2 TiF 6、 the above-mentioned KBF 4、 The masses of the above-mentioned graphite, vanadium, and Al-Y master alloy are 1000 Kg, 240 Kg, 85 Kg, 4.8 Kg, 3.2 Kg, and 18 Kg respectively;

[0122] S22. After adding a refining agent, continue to fully stir, stand for 20 minutes, and fish out the dross;

[0123] S23. Use a rotor degasser to degas the melt after fishing out the dross, then introduce the degassed melt into a launder and enter a crystallization wheel, control the temperature at 750 °C, and finally perform continuous casting and continuous extrusion. The rotation speed of the extrusion wheel is 10 r / min to obtain a refined modifier wire. The SEM diagram of the refined modifier wire is as Figure 1 shown.

[0124] Using the above-mentioned refined modifier to produce a cast recycled aluminum alloy includes the following steps:

[0125] S01. Melt recycled aluminum scraps (including socially recycled aluminum, scrapped aluminum castings inside the factory, and machined aluminum chips) in a melting furnace, control the temperature at 780 °C, add a refining agent for slag removal. The main components of the refining agent are NaCl and KCl, and the added amount is 0.2% of the melt mass. The refining time is 25 minutes. Skim the slag and stand for 20 minutes to obtain an aluminum-containing melt. The silicon content in the aluminum-containing melt is 6.5 - 7.5%;

[0126] S02. Add 0.2 wt% of the refined modifier to the aluminum-containing melt, fully stir, stand for 20 minutes, and then use a rotor degasser to degas. Argon is used for degassing, and the time is 15 minutes to obtain a recycled aluminum melt;

[0127] S03. When the temperature reaches 720 °C, use a metal mold for casting, and obtain a recycled aluminum component after T6 heat treatment.

[0128] Example 2

[0129] A refined modifier for a cast recycled aluminum alloy, with the mass percentages of each component being Ti: 3%, B: 0.3%, C: 0.25%, V: 0.2%, Y: 0.25%, and the balance being Al and unavoidable other impurity elements; the single content of other impurity elements ≤ 0.05%, and the total content ≤ 0.15%;

[0130] The preparation method of the refinement modifier comprises the following steps:

[0131] S1. Select industrial pure aluminum, K 2 TiF 6 、KBF 4 、graphite powder, V powder, and Al-Y master alloy as raw materials, weigh each required raw material and dry it in a constant-temperature oven at 250 °C;

[0132] Add the weighed industrial pure aluminum into an induction furnace to melt, raise the temperature to 850 °C, add the mixed salt of K 2 TiF 6 and KBF 4 , keep warm and stir thoroughly, fish out the acid water to obtain a mixed melt;

[0133] S21. Continuously add graphite powder, V powder, and Al-Y master alloy, keep warm and stir thoroughly to make all the above components melt and be evenly dispersed in the melt. Among them, the masses of pure aluminum, the K 2 TiF 6、 the KBF 4、 the graphite, the vanadium, and the Al-Y master alloy are 1000 Kg, 156 Kg, 36 Kg, 2.6 Kg, 2.1 Kg, and 13 Kg respectively;

[0134] S22. After adding the refining agent, continue to stir thoroughly, let it stand for 20 minutes, and fish out the dross;

[0135] S23. Use a rotor degasser to degas the melt after fishing out the dross, then introduce the degassed melt into a launder and into a crystallization wheel, control the temperature at 740 °C, and finally carry out continuous casting and continuous extrusion. The rotation speed of the extrusion wheel is 9 r / min to obtain a refinement modifier wire rod.

[0136] Using the refinement modifier to produce cast recycled aluminum alloy comprises the following steps:

[0137] S01. Melt the recycled aluminum waste (including socially recycled aluminum, scrapped aluminum castings inside the factory, and machined aluminum chips) in a melting furnace, control the temperature at 780 °C, add a refining agent for slag removal. The main components of the refining agent are NaCl and KCl, and the added amount is 0.2% of the mass of the aluminum melt. The refining time is 30 minutes, skim the slag, and let it stand for 20 minutes to obtain an aluminum-containing melt. The silicon content in the aluminum-containing melt is 6.5 - 7.5%;

[0138] S02. Add 0.2 wt% of the refinement modifier, stir thoroughly, let it stand for 20 minutes, and then use a rotor degasser to degas. Argon is used for degassing, and the time is 20 minutes to obtain a recycled aluminum melt;

[0139] S03. When the temperature reaches 715 °C, casting is carried out using a metal mold, and a recycled aluminum component is obtained after T6 heat treatment.

[0140] Example 3

[0141] A refinement modifier for casting recycled aluminum alloy, with the mass percentages of each component being: Ti: 6%, B: 0.9%, C: 0.7%, V: 0.45%, Y: 0.5%, and the balance being Al and inevitable other impurity elements; the individual content of other impurity elements ≤ 0.05%, and the total amount ≤ 0.15%;

[0142] The preparation of the refinement modifier includes the following steps:

[0143] S1. Select industrial pure aluminum, K 2 TiF 6 、KBF 4 、graphite powder, V powder, and Al-Y master alloy as raw materials, weigh each required raw material and dry it in a constant temperature oven at 250 °C;

[0144] Add the weighed industrial pure aluminum to an induction furnace and melt it, raise the temperature to 850 °C, add the mixed salts of K 2 TiF 6 and KBF 4 , keep warm and stir well, fish out the acid water to obtain a mixed melt;

[0145] S21. Continue to add graphite powder, V powder, and Al-Y master alloy, keep warm and stir well to melt all the above components and uniformly disperse them in the melt. Among them, the masses of pure aluminum, the K 2 TiF 6、 the KBF 4、 the graphite, the vanadium, and the Al-Y master alloy are 1000 Kg, 328 Kg, 113 Kg, 7.7 Kg, 4.9 Kg, and 27.5 Kg respectively;

[0146] S22. After adding the refining agent, continue to stir well, let it stand for 20 minutes, and fish out the floating slag;

[0147] S23. Use a rotor degasser to degas the melt after fishing out the floating slag, then introduce the degassed melt into a launder and into a crystallizing wheel, control the temperature at 745 °C, and finally carry out continuous casting and continuous extrusion, with the rotational speed of the extrusion wheel being 11 r / min to obtain the refinement modifier wire.

[0148] The production of casting recycled aluminum alloy using the refinement modifier includes the following steps:

[0149] S01. Melt the recycled aluminum waste (including socially recycled aluminum, scrapped aluminum castings within the factory, and machined aluminum chips) in a melting furnace at a temperature controlled at 780 °C. Add a refining agent for slag removal. The main components of the refining agent are NaCl and KCl, and the added amount is 0.2% of the mass of the aluminum melt. The refining time is 20 minutes. Skim the slag and let it stand for 20 minutes to obtain an aluminum-containing melt. The silicon content in the aluminum-containing melt is 6.5 - 7.5%;

[0150] S02. Add 0.2 wt% of the grain refinement modifier, stir well, let it stand for 20 minutes, and then use a rotor degasser for degassing. Argon is used for degassing, and the time is 10 minutes to obtain a recycled aluminum melt;

[0151] S03. When the temperature reaches 710 °C, use a metal mold for casting, and obtain a recycled aluminum component after T6 heat treatment.

[0152] Comparative Example 1

[0153] Specific steps for producing cast recycled aluminum alloy using traditional AlTiB grain refinement agent and AlSr modifier:

[0154] (1) Melt the recycled aluminum waste (including socially recycled aluminum, scrapped aluminum castings within the factory, and machined aluminum chips) in a melting furnace at a temperature controlled at 780 °C. Add a refining agent for slag removal. The main components of the refining agent are NaCl and KCl, and the added amount is 0.2% of the mass of the aluminum melt. The refining time is 25 minutes. Skim the slag and let it stand for 20 minutes to obtain an aluminum-containing melt. The silicon content in the aluminum-containing melt is 6.5 - 7.5%;

[0155] (2) Add 0.2 wt% of AlTiB grain refinement agent and 0.2 wt% AlSr modifier respectively, stir well, and let it stand for 20 minutes; among them, the SEM image of the AlTiB grain refinement agent is as Figure 2 shown, it can be seen that the boundaries between particles are blurred and TiB 2 forms large-scale agglomerations. The SEM image of the AlTiB grain refinement agent when melting in the aluminum-containing melt is as Figure 3 shown, it can be seen that the agglomeration of TiB 2 is even more serious.

[0156] (3) Use a rotor degasser for degassing. Argon is used for degassing, and the time is 15 minutes to obtain a recycled aluminum melt;

[0157] (4) When the temperature reaches 720 °C, use a metal mold for casting, and obtain a recycled aluminum component after T6 heat treatment.

[0158] Analysis Example 1

[0159] After obtaining the recycled aluminum components, samples were first taken from the bodies of Example 1 and Comparative Example 1 for grain size detection. According to GB / T 3246.2-2012, grain size statistics were carried out according to the mean intercept method. The average grain size of the recycled aluminum components prepared in Example 1 was 208 μm (see Figure 4 ), and the average grain size of the recycled aluminum components prepared in Comparative Example 1 was 583 μm (see Figure 5 ). It can be seen that the refinement effect of the refinement modifier provided by the present invention is significantly better than that of the AlTiB refinement agent.

[0160] Secondly, samples were taken from the bodies of Example 1 and Comparative Example 1 for metallographic structure analysis. The eutectic Si morphology of both was approximately spherical or short rod-shaped (see Figure 6 and Figure 7 ). The Si modification was good, indicating that the modification effect of the refinement modifier provided by the present invention is equivalent to that of the AlSr modifier.

[0161] In addition, the Fe phase was observed and analyzed. In Example 1, the α-Fe phase was mainly in the form of fine Chinese character-shaped or fishbone-shaped (see Figure 8 ), while in Comparative Example 1, a large number of thick needle-shaped β-Fe phases could be observed (see Figure 9 ).

[0162] Then, samples were taken from the bodies of Example 1, 2, 3 and Comparative Example 1 to prepare material tensile property specimens, and mechanical property tests were carried out by an electronic universal material testing machine. The tensile property detection was carried out according to the IS06892-1:2016 standard. At the same time, samples were taken to prepare material fatigue property specimens, and material fatigue tests were carried out by an electro-hydraulic servo fatigue testing machine. The material fatigue test conditions were as follows: the test environment was room temperature, the loading method was axial loading, the fatigue test stress ratio R was -1, the loading method was sinusoidal load, the frequency was 40 Hz, and 10 million cycles was the fatigue limit. The material fatigue property detection was carried out according to the GB / T 3075-2021 standard.

[0163] The average tensile properties of the recycled aluminum components prepared in Example 1, 2, 3 and Comparative Example 1 and the material fatigue limit strength obtained by the step method are shown in Table 1. It can be seen from the table that the elongation and material fatigue limit strength of the recycled aluminum components prepared using the refinement modifier of the present invention are significantly higher than those of the recycled aluminum components prepared using the traditional refinement modifier.

[0164]

[0165] In summary, the grain refinement modifier for casting recycled aluminum alloy provided by the present invention has a significantly better grain refinement effect than the AlTiB grain refinement agent, and its modification effect is equivalent to that of the AlSr modifier. It can significantly improve the morphology of the coarse needle-like β-Fe phase into a fine Chinese character-like or fishbone-like α-Fe phase, and ultimately greatly improve the comprehensive performance of recycled aluminum components, especially the elongation and the fatigue limit strength of the material.

[0166] In the above technical solution of the present invention, the above is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structural transformation made under the technical concept of the present invention by using the content of the specification and drawings of the present invention, or directly / indirectly applied to other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A refining modifier for casting recycled aluminum alloy, characterized in that: The chemical composition thereof includes, by mass fraction, Ti 2.5%-6.5%, B 0.15%-1.0%, C 0.15%-0.8%, V 0.1%-0.45%, Y 0.1%-0.55%, and the remainder is Al and other impurity elements; wherein the total amount of the other impurity elements is ≤0.15%, and the content of a single impurity element among the other impurity elements is ≤0.05%; the cast recycled aluminum alloy contains an iron phase, and the refining modifier causes the iron phase to exist mainly in the form of a Chinese character-shaped or fishbone-shaped α-Fe phase.

2. The refining and modifying agent for casting recycled aluminum alloy according to claim 1, characterized in that: Calculated by mass fraction, its chemical composition includes: Ti 3.5%-5.5%, B 0.6%-0.8%, C 0.35%-0.65%, V 0.25%-0.35%, Y 0.25%-0.4%, and the balance is Al and other impurity elements.

3. A method for preparing a refining modifier for casting recycled aluminum alloy, characterized in that: Includes steps: S1. Mixing pure aluminum melt with K2TiF6 and KBF4 at 800-870°C, separating the acid water leached from the melt, and obtaining a mixed melt; S2. Insulation, adding graphite, vanadium, Al-Y master alloy and refining agent to the mixed melt, stirring and standing for 20-30min, separating the slag precipitated from the melt, and obtaining a refined modifier; Wherein, the mass ratio of pure aluminum: the K2TiF6: the KBF4: the graphite: the vanadium: the Al-Y master alloy is 1000: (138-335): (18-120): (1.5-8.5): (1-4.5): (5.5-28.5); The chemical composition of the refining modifier includes, by mass fraction, Ti 2.5%-6.5%, B 0.15%-1.0%, C 0.15%-0.8%, V 0.1%-0.45%, Y 0.1%-0.55%, and the balance is Al and other impurity elements; wherein the total amount of the other impurity elements is ≤0.15%, and the content of a single impurity element among the other impurity elements is ≤0.05%; the cast recycled aluminum alloy contains an iron phase, and the refining modifier causes the iron phase to exist mainly in the form of a Chinese character-shaped or fishbone-shaped α-Fe phase.

4. The preparation method according to claim 3, characterized in that: The S2 comprises: sequentially performing degassing treatment, crystallization treatment and continuous casting and extrusion treatment on the melt after separation of slag to obtain the refined modifier; wherein, during the crystallization treatment, the crystallization temperature is 730-750° C. and the rotation speed is 8-15 r / min.

5. The preparation method according to claim 3, characterized in that: Melting pure aluminum to obtain the pure aluminum melt; Before step S1, the pure aluminum, the K2TiF6, the KBF4, the graphite, the vanadium, and the Al-Y master alloy are dried; wherein the drying temperature is 240-260° C., and the drying time is 45-60 min.

6. The preparation method according to claim 3, characterized in that: The refining agent includes sodium chloride and / or potassium chloride, and the added amount of the refining agent is 0.15%-0.25% of the mass of the mixed melt.

7. A method for producing a recycled aluminum alloy, characterized in that: Includes steps: The recycled aluminum waste is heated to 750-780°C and refined to obtain an aluminum-containing melt; Adding the refining modifier according to any one of claims 1 to 2 or the refining modifier prepared by the preparation method according to any one of claims 3 to 6 to the aluminum-containing melt, stirring and standing for 20 to 30 minutes to obtain a regenerated aluminum melt; wherein the amount of the refining modifier added is 0.15% to 0.25% of the mass of the aluminum-containing melt; The recycled aluminum melt is cast to obtain recycled aluminum alloy.

8. The production method according to claim 7, characterized in that: The recycled aluminum waste is heated to 750-780° C. and then refined to obtain an aluminum-containing melt. The refining includes: A refining agent is added to the heated recycled aluminum waste, and the refining is performed for 20 to 30 minutes.

9. The production method according to claim 7, characterized in that: In terms of mass fraction, the silicon content of the recycled aluminum waste is 6.5%-7.5%, and the silicon content of the recycled aluminum alloy is 6.5%-7.5%.

10. The production method according to claim 7, characterized in that: The recycled aluminum melt is casted to obtain the recycled aluminum alloy. Specifically, the casting obtained by casting the recycled aluminum melt is heat treated to obtain the recycled aluminum component.

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