Aluminum niobium boron refiner and method of making same

Abstract

The application provides an aluminum-niobium-boron refiner and a preparation method thereof, and relates to the technical field of alloys. The preparation method comprises the following steps: after an aluminum ingot is melted by heating to 1180-1220 DEG C, aluminum-niobium intermediate alloy is added for melting, a first part of aluminum-titanium intermediate alloy and a carbon source are added in sequence for stirring and dispersing, then aluminum-boron intermediate alloy is added for heat preservation and stirring to obtain a melt a containing composite core particles; after the melt a is cooled to 880-920 DEG C, a second part of aluminum-titanium intermediate alloy is added for heat preservation and stirring to obtain a melt b; the temperature is lowered to 780-800 DEG C, pure zinc ingot and pure magnesium ingot are added in sequence for heat preservation and stirring to obtain a melt c; the melt c is cooled to 740-760 DEG C, degassing refining is performed, slag is removed, the melt is placed, poured into a mold, and cooled to form the aluminum-niobium-boron refiner. The application can slow down the settlement of the refiner particles in the aluminum alloy melt to be refined, and improve the anti-Si poisoning capacity of the refiner in the aluminum alloy.

Description

Technical Field

[0001] This invention relates to the field of alloy technology, specifically to an aluminum-niobium-boron refining agent and its preparation method. Background Technology

[0002] During the casting process, aluminum alloys are prone to forming coarse columnar or dendritic structures, affecting the uniformity of the casting's microstructure, mechanical properties, and subsequent machinability. To obtain a fine, uniform equiaxed grain structure, grain refiners are typically added during the aluminum alloy smelting process to increase the number of nuclei and improve the casting's microstructure and overall properties. Currently, commonly used industrial grain refiners for aluminum alloys mainly include aluminum-titanium-boron (ATB) refiners. While ATB refiners have a certain refining effect in ordinary aluminum alloys, when used in high-silicon aluminum-silicon alloys such as A356, the Si in the melt easily reacts with the Ti in the refiner to form a Ti-Si phase, weakening the effective nucleation of TiB2 particles and leading to a decrease in the refining effect—a phenomenon known as Si poisoning.

[0003] To address the Si poisoning problem of aluminum-titanium-boron grain refiners in aluminum-silicon alloys, aluminum-niobium-boron grain refiners have been proposed in the prior art. For example, patent application CN111910092A discloses a method for preparing an aluminum-niobium-boron master alloy and the aluminum-niobium-boron master alloy itself. This master alloy is prepared using aluminum, niobium pentoxide, and boron, and is then used as a grain refiner in A356 aluminum alloy to improve the grain structure of the aluminum-silicon alloy. However, existing aluminum-niobium-boron grain refiners typically rely primarily on niobium boride particles for nucleation. Since niobium boride particles have a high density and a significant density difference with molten aluminum, they are prone to sedimentation and agglomeration during prolonged holding in molten aluminum, reducing the number of effective nucleated particles in the melt and leading to a decline in the grain refinement effect.

[0004] In addition, some aluminum-niobium-boron refining agents use fluorine-containing salt raw materials or refining agents in their preparation process. The preparation process may generate fluorine-containing gases or corrosive waste residues, increasing the pressure on environmental treatment and hindering large-scale industrial promotion.

[0005] In summary, there is a need to provide an aluminum-niobium-boron refining agent and its preparation method to solve the problems existing in the prior art. Summary of the Invention

[0006] In view of this, the present invention provides an aluminum-niobium-boron refining agent and its preparation method, which can slow down the sedimentation of refining agent particles in the aluminum alloy melt to be refined and improve the refining agent's resistance to Si poisoning in the aluminum alloy.

[0007] To achieve the above objectives, the present invention provides a method for preparing an aluminum-niobium-boron refining agent, comprising the following steps: S1. After heating the aluminum ingot to 1180~1220℃ to melt it, add aluminum-niobium master alloy to melt it, add the first part of aluminum-titanium master alloy and carbon source in sequence and stir and disperse it, then add aluminum-boron master alloy and keep it warm and stir to obtain melt a containing composite core particles. S2. After cooling melt a to 880~920℃, add the second part of aluminum-titanium master alloy and stir while keeping it warm to obtain melt b; cool to 780~800℃, add pure zinc ingot and pure magnesium ingot in sequence and stir while keeping it warm to obtain melt c; S3. Cool the melt c to 740~760℃, degas and refine, remove slag, let stand, pour into a mold, cool and shape to obtain aluminum niobium boron refining agent.

[0008] In step S1 of this invention, after heating the aluminum ingot to 1180~1220℃ and melting it, aluminum-niobium master alloy, a first part of aluminum-titanium master alloy, a carbon source, and aluminum-boron master alloy are added sequentially, followed by stirring and heat preservation treatment, so that Nb, Ti, C, and B can fully contact and react in the high-temperature aluminum melt. Among them, Ti and C have a strong affinity, which is conducive to the in-situ formation of titanium carbide particles in the aluminum melt; the subsequently introduced B can combine with Nb and Ti to form niobium-containing titanium boride particles, thereby obtaining melt a containing composite core particles. This composite core particle can use niobium-containing titanium boride as the main nucleation phase and titanium carbide as the auxiliary nucleation phase, increasing the effective nucleation site density in the melt and improving the nucleation ability.

[0009] Secondly, after forming melt a containing composite core particles, the present invention cools melt a to 880-920°C, then adds a second portion of aluminum-titanium master alloy and holds it at the same temperature with stirring to obtain melt b. This mid-temperature stage treatment replenishes the Ti content in the melt, which is beneficial for further forming an "aluminum-titanium transition layer" on the surface of the already formed composite core particles. The low-density "aluminum-titanium transition layer" can reduce the density difference between the composite core particles and the molten aluminum, slowing down the sedimentation and agglomeration of the composite core particles in the molten aluminum, thereby improving the suspension stability of the composite core particles in the melt. Next, melt b is further cooled to 780-800°C, and pure zinc ingots and pure magnesium ingots are added sequentially and held at the same temperature with stirring to obtain melt c. This low-temperature stage is beneficial for the enrichment of Mg and Zn components on the outside of the "aluminum-titanium transition layer" to form a magnesium / zinc composite outer layer, allowing the finer agent to disperse composite particles with a structure of "niobium titanium boride / titanium carbide core - aluminum-titanium transition layer - magnesium / zinc composite outer layer".

[0010] When the grain refiner of the present invention is applied to the treatment of aluminum-silicon alloys (such as A356 aluminum alloy), Mg in the magnesium / zinc composite outer layer can preferentially react with Si, reducing the adverse effects of Si on the internal niobium titanium boride / titanium carbide core, thereby improving the grain refiner's resistance to Si poisoning; at the same time, Zn and some Mg can form precipitates such as MgZn2, which pin the grain boundaries, inhibit the continued growth of grains, and improve the grain refiner's effect on the aluminum alloy.

[0011] The present invention does not use fluorine-containing materials such as KBF4 and Na2SiF6 in the preparation process, nor does it require the addition of rare earth elements. It only uses argon degassing and refining, thereby reducing the generation of fluorine-containing gases, corrosive waste residues and rare earth-related pollutants, and has the advantages of green production.

[0012] Optionally, the mass percentage of each element in the aluminum-niobium-boron refining agent is as follows: niobium 2%~3.5%, boron 0.25%~0.43%, titanium 0.8%~1.5%, magnesium 0.2%~0.5%, zinc 0.2%~0.5%, carbon 0.05%~0.15%, and the remainder is aluminum.

[0013] Optionally, in the aluminum-niobium-boron refining agent, the mass ratio of niobium to boron is (8~10):1, the mass ratio of titanium to boron is (2.5~4):1, and the sum of the mass percentages of magnesium and zinc is 0.4%~1%.

[0014] In this invention, by limiting the ratios of niobium to boron, titanium to boron, and the total amounts of magnesium and zinc, a good synergistic effect is maintained among the functional elements. On the one hand, this facilitates the formation of stable composite core particles by niobium, titanium, and boron, avoiding insufficient nucleation phases due to boron deficiency or adverse effects due to boron excess. On the other hand, it ensures that sufficient titanium can participate in the formation of composite core particles and the aluminum-titanium transition layer, and that sufficient magnesium and zinc can form a magnesium / zinc composite outer layer.

[0015] Optionally, the aluminum-titanium master alloy is an Al-10Ti master alloy, and the mass ratio of the first part of the aluminum-titanium master alloy to the second part of the aluminum-titanium master alloy is 3:7.

[0016] In this invention, the mass ratio of the first aluminum-titanium master alloy (Al-10Ti master alloy) and the second aluminum-titanium master alloy (Al-10Ti master alloy) is limited to 3:7. This allows some titanium to participate in the formation of the composite core particles of titanium carbide and niobium-containing titanium boride in step S1, with the remaining titanium supplementing the melt in step S2. This facilitates the formation of an aluminum-titanium transition layer on the outside of the composite core particles. This ensures that the composite core particles have a good nucleation basis and reduces the density difference between the composite core particles and the molten aluminum, slowing down particle settling and agglomeration, and improving its suspension stability.

[0017] In this invention, molten aluminum refers to aluminum or aluminum alloy melt in a molten state, including aluminum-based melt during the preparation of grain refiner, and aluminum alloy melt (such as A356 aluminum alloy melt) that has undergone grain refinement treatment using grain refiner.

[0018] Optionally, in step S1, after adding the aluminum-niobium master alloy, the mixture is electromagnetically stirred at a power of 10-20kW for 5-10 minutes, and after adding the first part of the aluminum-titanium master alloy, the mixture is electromagnetically stirred for another 3-5 minutes.

[0019] In this invention, electromagnetic stirring at 10-20 kW for 5-10 min after adding the aluminum-niobium master alloy promotes the full melting of the aluminum-niobium master alloy and ensures uniform dispersion of Nb in the molten aluminum. Continuing electromagnetic stirring for 3-5 min after adding the first portion of the aluminum-titanium master alloy facilitates full contact between Ti and components such as Nb and C, providing uniform melt conditions for the subsequent formation of composite core particles containing niobium titanium boride and titanium carbide, thereby improving the uniformity of composite core particle formation.

[0020] Optionally, in step S1, the carbon source is graphite powder; after adding the graphite powder, it is mechanically stirred at a speed of 300-500 rpm for 5-8 minutes; after adding the aluminum-boron master alloy, it is mechanically stirred at a speed of 300-500 rpm for 10-15 minutes.

[0021] In this invention, graphite powder is used as the carbon source, which has the advantages of wide availability of raw materials, low cost, and ease of industrial use. After adding graphite powder, mechanical stirring at a speed of 300-500 rpm for 5-8 minutes is beneficial to promote the dispersion of graphite powder, increase the contact opportunities between C and Ti, and thus promote the in-situ formation of titanium carbide.

[0022] Optionally, in step S2, after adding the second part of the aluminum-titanium master alloy, the mixture is mechanically stirred at a speed of 300-500 rpm for 15-20 minutes; after adding the pure zinc ingot, the mixture is mechanically stirred at a speed of 300-500 rpm for 2-3 minutes; and after adding the pure magnesium ingot, the mixture is mechanically stirred at a speed of 300-500 rpm for 10-15 minutes.

[0023] Optionally, in step S3, high-purity argon gas is introduced by rotary jetting for degassing and refining, with an argon gas pressure of 0.15~0.2MPa and a refining time of 10~15min.

[0024] In this invention, high-purity argon gas is introduced through a rotary jetting method for degassing and refining. The argon gas pressure and refining time are controlled within the above-mentioned range, which is conducive to the formation of uniform and fine bubbles in the melt, promoting the upward floating and discharge of hydrogen and inclusions in the melt, and improving the cleanliness of the material.

[0025] Optionally, in step S3, the cooling rate for cooling and shaping after pouring into the mold is 20~30K / s.

[0026] In this invention, the cooling and molding rate after pouring into the mold is controlled at 20~30K / s (>10K / s), which is beneficial to quickly fix the composite core particles, aluminum-titanium transition layer and magnesium / zinc composite outer layer already formed in the melt during the solidification process, reduce the excessive growth and segregation of each phase during the cooling process, and enable the composite particles to be more uniformly dispersed in the aluminum matrix, thereby improving the refining stability of the aluminum-niobium-boron refining agent during use.

[0027] The present invention also provides an aluminum-niobium-boron refining agent, which is prepared by the above-described method for preparing aluminum-niobium-boron refining agents.

[0028] The above-described technical solution of the present invention has at least the following beneficial effects: This invention improves the grain refiner's resistance to Si poisoning and its grain refinement effect on aluminum alloys by adding aluminum-niobium master alloy, a first part of aluminum-titanium master alloy, a carbon source and aluminum-boron master alloy, a second part of aluminum-titanium master alloy, pure zinc ingots and pure magnesium ingots at different temperature stages such as 1180~1220℃, 880~920℃ and 780~800℃ respectively.

[0029] The present invention does not use fluorine-containing materials such as KBF4 and Na2SiF6 in the preparation process, nor does it require the addition of rare earth elements. It only uses argon degassing and refining, thereby reducing the generation of fluorine-containing gases, corrosive waste residues and rare earth-related pollutants, and has the advantages of green production. Attached Figure Description

[0030] Figure 1 Micrograph of A356 alloy after adding the aluminum-niobium-boron refining agent prepared in Example 1 of this invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. The described embodiments are some embodiments of the present invention, and all other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0032] Example 1 In this embodiment, the mass percentages of each element in the aluminum-niobium-boron refining agent are as follows: Nb 3.0%, B 0.35%, Ti 1.2%, Mg 0.3%, Zn 0.3%, C 0.1%, and Al as the balance. Industrial pure aluminum ingots, Al-60Nb master alloy, Al-3B master alloy, Al-10Ti master alloy, pure magnesium ingots, pure zinc ingots, and graphite powder are prepared according to the above element mass percentages. The Al-10Ti master alloy is divided into two parts at a mass ratio of 3:7 for use in step S1 and the second part in step S2.

[0033] Step S1. Add industrial pure aluminum ingots to a medium-frequency electromagnetic induction furnace and heat to 1220℃. After the industrial pure aluminum ingots are completely melted, add Al-60Nb master alloy and electromagnetically stir for 10 minutes at a power of 20kW to fully melt the Al-60Nb master alloy. Add the first part of Al-10Ti master alloy to the melt and continue electromagnetic stirring for 5 minutes. Wrap the graphite powder with aluminum foil and press it into the depth of the melt with a bell jar. Start mechanical stirring and stir at a speed of 500rpm for 8 minutes. Then add Al-3B master alloy, keep it at 1220℃, and mechanically stir at a speed of 500rpm for 15 minutes to obtain melt a containing composite core particles.

[0034] Step S2. Cool melt a to 920°C, add the second part of Al-10Ti master alloy, and mechanically stir at 500 rpm for 20 min to obtain melt b; continue to cool melt b to 800°C, add pure zinc ingot, and mechanically stir at 500 rpm for 3 min to melt the pure zinc ingot; then use a bell jar to press the pure magnesium ingot deep into the melt, hold at 800°C, and mechanically stir at 500 rpm for 15 min to obtain melt c.

[0035] Step S3. Cool the melt c to 760℃, and use a rotary jet to introduce high-purity argon gas for degassing and refining. The argon gas pressure is 0.20MPa, and the refining time is 15min. After refining, remove the slag from the surface of the melt, let it stand for 5min, pour it into a mold, and cool it at a cooling rate of 30K / s to obtain the aluminum-niobium-boron refining agent.

[0036] Example 2 In this embodiment, the mass percentages of each element in the aluminum-niobium-boron refining agent are as follows: Nb 2.8%, B 0.30%, Ti 1.0%, Mg 0.25%, Zn 0.25%, C 0.08%, and Al as the balance. Industrial pure aluminum ingots, Al-60Nb master alloy, Al-3B master alloy, Al-10Ti master alloy, pure magnesium ingots, pure zinc ingots, and graphite powder are prepared according to the above element mass percentages. The Al-10Ti master alloy is divided into two parts at a mass ratio of 3:7 for use in step S1 and the second part in step S2.

[0037] Step S1. Add industrial pure aluminum ingots to a medium-frequency electromagnetic induction furnace and heat to 1200℃. After the industrial pure aluminum ingots are completely melted, add Al-60Nb master alloy and electromagnetically stir at 15kW for 8 minutes to fully melt the Al-60Nb master alloy. Add the first part of Al-10Ti master alloy to the melt and continue electromagnetic stirring for 4 minutes. Wrap the graphite powder in aluminum foil and press it into the depth of the melt with a bell jar. Start mechanical stirring and stir at 400rpm for 7 minutes. Then add Al-3B master alloy, keep at 1200℃, and mechanically stir at 350rpm for 12 minutes to obtain melt a containing composite core particles.

[0038] Step S2. Cool melt a to 900°C, add the second part of Al-10Ti master alloy, and mechanically stir at 450 rpm for 18 min to obtain melt b; continue to cool melt b to 790°C, add pure zinc ingot, and mechanically stir at 350 rpm for 2 min to melt the pure zinc ingot; then use a bell jar to press the pure magnesium ingot deep into the melt, hold at 790°C, and mechanically stir at 400 rpm for 12 min to obtain melt c.

[0039] Step S3. Cool the melt c to 750℃, and use a rotary jet to introduce high-purity argon gas for degassing and refining. The argon gas pressure is 0.18MPa, and the refining time is 13min. After refining, remove the slag from the surface of the melt, let it stand for 8min, pour it into a mold, and cool it at a cooling rate of 25K / s to obtain the aluminum-niobium-boron refining agent.

[0040] Example 3 In this embodiment, the mass percentages of each element in the aluminum-niobium-boron refining agent are as follows: Nb 3.2%, B 0.40%, Ti 1.3%, Mg 0.40%, Zn 0.40%, C 0.12%, and Al as the balance. Industrial pure aluminum ingots, Al-60Nb master alloy, Al-3B master alloy, Al-10Ti master alloy, pure magnesium ingots, pure zinc ingots, and graphite powder are prepared according to the above element mass percentages. The Al-10Ti master alloy is divided into two parts at a mass ratio of 3:7 for use in step S1 and the second part in step S2.

[0041] Step S1. Add industrial pure aluminum ingots to a medium-frequency electromagnetic induction furnace and heat to 1180℃. After the industrial pure aluminum ingots are completely melted, add Al-60Nb master alloy and electromagnetically stir for 5 minutes at a power of 10kW to fully melt the Al-60Nb master alloy. Add the first part of Al-10Ti master alloy to the melt and continue electromagnetic stirring for 3 minutes. Wrap the graphite powder with aluminum foil and press it into the depth of the melt with a bell jar. Start mechanical stirring and stir at a speed of 300rpm for 5 minutes. Then add Al-3B master alloy, keep it at 1180℃, and mechanically stir at a speed of 300rpm for 10 minutes to obtain melt a containing composite core particles.

[0042] Step S2. Cool melt a to 880°C, add the second part of Al-10Ti master alloy, and mechanically stir at 300 rpm for 15 min to obtain melt b; continue to cool melt b to 780°C, add pure zinc ingot, and mechanically stir at 300 rpm for 2 min to melt the pure zinc ingot; then use a bell jar to press the pure magnesium ingot deep into the melt, keep it at 780°C, and mechanically stir at 300 rpm for 10 min to obtain melt c.

[0043] Step S3. Cool the melt c to 740℃, and use a rotary jet to introduce high-purity argon gas for degassing and refining. The argon gas pressure is 0.15MPa, and the refining time is 10min. After refining, remove the slag from the surface of the melt, let it stand for 5min, pour it into a mold, and cool it at a cooling rate of 20K / s to obtain the aluminum-niobium-boron refining agent.

[0044] Example 4 In this embodiment, the mass percentages of each element in the aluminum-niobium-boron refining agent are as follows: Nb 2.0%, B 0.25%, Ti 0.8%, Mg 0.20%, Zn 0.20%, C 0.05%, and Al as the balance. Industrial pure aluminum ingots, Al-60Nb master alloy, Al-3B master alloy, Al-10Ti master alloy, pure magnesium ingots, pure zinc ingots, and graphite powder are prepared according to the above element mass percentages. The Al-10Ti master alloy is divided into two parts at a mass ratio of 3:7 for use in step S1 and the second part in step S2.

[0045] Step S1. Add industrial pure aluminum ingots to a medium-frequency electromagnetic induction furnace and heat to 1190℃. After the industrial pure aluminum ingots are completely melted, add Al-60Nb master alloy and electromagnetically stir for 8 minutes at a power of 15kW to fully melt the Al-60Nb master alloy. Add the first part of Al-10Ti master alloy to the melt and continue electromagnetic stirring for 3.5 minutes. Wrap the graphite powder with aluminum foil and press it into the depth of the melt with a bell jar. Start mechanical stirring and stir at a speed of 450rpm for 6 minutes. Then add Al-3B master alloy, keep it at 1190℃, and mechanically stir at a speed of 450rpm for 14 minutes to obtain melt a containing composite core particles.

[0046] Step S2. Cool melt a to 910°C, add the second part of Al-10Ti master alloy, and mechanically stir at 300 rpm for 18 min to obtain melt b; continue to cool melt b to 800°C, add pure zinc ingot, and mechanically stir at 400 rpm for 2 min to melt the pure zinc ingot; then use a bell jar to press the pure magnesium ingot deep into the melt, hold at 800°C, and mechanically stir at 450 rpm for 11 min to obtain melt c.

[0047] Step S3. Cool the melt c to 755℃, and use a rotary jet to introduce high-purity argon gas for degassing and refining. The argon gas pressure is 0.20MPa, and the refining time is 10min. After refining, remove the slag from the surface of the melt, let it stand for 6min, pour it into a mold, and cool it at a cooling rate of 22K / s to obtain the aluminum-niobium-boron refining agent.

[0048] Example 5 In this embodiment, the mass percentages of each element in the aluminum-niobium-boron refining agent are as follows: Nb 3.5%, B 0.43%, Ti 1.5%, Mg 0.50%, Zn 0.50%, C 0.15%, and Al as the balance. Industrial pure aluminum ingots, Al-60Nb master alloy, Al-3B master alloy, Al-10Ti master alloy, pure magnesium ingots, pure zinc ingots, and graphite powder are prepared according to the above element mass percentages. The Al-10Ti master alloy is divided into two parts at a mass ratio of 3:7 for use in step S1 and the second part for use in step S2.

[0049] Step S1. Add industrial pure aluminum ingots to a medium-frequency electromagnetic induction furnace and heat to 1210℃. After the industrial pure aluminum ingots are completely melted, add Al-60Nb master alloy and electromagnetically stir at 18kW for 7 minutes to fully melt the Al-60Nb master alloy. Add the first part of Al-10Ti master alloy to the melt and continue electromagnetic stirring for 5 minutes. Wrap the graphite powder in aluminum foil and press it into the depth of the melt with a bell jar. Start mechanical stirring and stir at 500rpm for 5 minutes. Then add Al-3B master alloy, keep at 1210℃, and mechanically stir at 500rpm for 10 minutes to obtain melt a containing composite core particles.

[0050] Step S2. Cool melt a to 890°C, add the second part of Al-10Ti master alloy, and mechanically stir at 500 rpm for 15 min to obtain melt b; continue to cool melt b to 790°C, add pure zinc ingot, and mechanically stir at 500 rpm for 2 min to melt the pure zinc ingot; then use a bell jar to press the pure magnesium ingot deep into the melt, hold at 790°C, and mechanically stir at 450 rpm for 10 min to obtain melt c.

[0051] Step S3. Cool the melt c to 750℃, and use a rotary jet to introduce high-purity argon gas for degassing and refining. The argon gas pressure is 0.16MPa, and the refining time is 15min. After refining, remove the slag from the surface of the melt, let it stand for 10min, pour it into a mold, and cool it at a cooling rate of 26K / s to obtain the aluminum-niobium-boron refining agent.

[0052] Example 6 In this embodiment, the mass percentages of each element in the aluminum-niobium-boron refining agent are as follows: Nb 2.5%, B 0.28%, Ti 1.1%, Mg 0.35%, Zn 0.25%, C 0.10%, and Al as the balance. Industrial pure aluminum ingots, Al-60Nb master alloy, Al-3B master alloy, Al-10Ti master alloy, pure magnesium ingots, pure zinc ingots, and graphite powder are prepared according to the above element mass percentages. The Al-10Ti master alloy is divided into two parts at a mass ratio of 3:7 for use in step S1 and the second part in step S2.

[0053] Step S1. Add industrial pure aluminum ingots to a medium-frequency electromagnetic induction furnace and heat to 1200℃. After the industrial pure aluminum ingots are completely melted, add Al-60Nb master alloy and electromagnetically stir for 10 minutes at a power of 15kW to fully melt the Al-60Nb master alloy. Add the first part of Al-10Ti master alloy to the melt and continue electromagnetic stirring for 5 minutes. Wrap the graphite powder with aluminum foil and press it into the depth of the melt with a bell jar. Start mechanical stirring and stir at a speed of 300rpm for 6 minutes. Then add Al-3B master alloy, keep it at 1200℃, and mechanically stir at a speed of 400rpm for 12 minutes to obtain melt a containing composite core particles.

[0054] Step S2. Cool melt a to 900°C, add the second part of Al-10Ti master alloy, and mechanically stir at 450 rpm for 18 min to obtain melt b; continue to cool melt b to 780°C, add pure zinc ingot, and mechanically stir at 300 rpm for 3 min to melt the pure zinc ingot; then use a bell jar to press the pure magnesium ingot deep into the melt, hold at 780°C, and mechanically stir at 300 rpm for 15 min to obtain melt c.

[0055] Step S3. Cool the melt c to 750℃, and use a rotary jet to introduce high-purity argon gas for degassing and refining. The argon gas pressure is 0.16MPa, and the refining time is 13min. After refining, remove the slag from the surface of the melt, let it stand for 8min, pour it into a mold, and cool it at a cooling rate of 30K / s to obtain the aluminum-niobium-boron refining agent.

[0056] The present invention also includes comparative examples and related experiments.

[0057] Comparative Example 1 The only difference from Example 1 is that Al-10Ti master alloy, graphite powder, pure zinc ingot and pure magnesium ingot were not added, and the corresponding processing steps were omitted. The remaining raw materials and preparation steps are the same as in Example 1, and the aluminum-niobium-boron refining agent is obtained.

[0058] Comparative Example 2 The only difference from Example 1 is that pure zinc ingots and pure magnesium ingots were not added; the other raw materials and preparation steps are the same as in Example 1, and the aluminum-niobium-boron refining agent is obtained.

[0059] Comparative Example 3 The only difference from Example 1 is that pure zinc ingots were not added; the other raw materials and preparation steps are the same as in Example 1, and the aluminum-niobium-boron refining agent is obtained.

[0060] Performance testing: Commercially available A356 aluminum alloy was selected as the reference alloy for the test. The A356 aluminum alloy was melted in a resistance furnace and heated to 730±5℃ until an A356 aluminum alloy melt was obtained. The aluminum-niobium-boron refining agents prepared in Examples 1-6 and Comparative Examples 1-3 were added to the A356 aluminum alloy melt at a rate of 0.5% of the melt's mass. The melt was stirred with a graphite rod for 60 seconds to ensure uniform dispersion. After stirring, the A356 aluminum alloy melt was held at this temperature for 60 minutes and then poured into a mold at 200℃. After cooling, the test sample was obtained.

[0061] Referring to the national standard GB / T 6394-2017 "Method for Determination of Average Grain Size of Metals", the average grain size of the test samples obtained from Examples 1-6 and Comparative Examples 1-3 was measured, and the test results are shown in Table 1.

[0062] Referring to the national standard GB / T 228.1-2021 "Metallic materials, tensile testing - Part 1: Test method at room temperature", the tensile strength, yield strength and elongation after fracture of the test samples obtained from Examples 1-6 and Comparative Examples 1-3 were tested. The test results are shown in Table 1.

[0063] Table 1

[0064] As shown in Table 1, compared to Comparative Examples 1-3, the A356 aluminum alloys treated in Examples 1-6 all exhibited smaller average grain sizes, while maintaining relatively high tensile strength, yield strength, and elongation after fracture. This indicates that the aluminum-niobium-boron grain refiner prepared in this invention can effectively refine the grains of A356 aluminum alloy and improve its mechanical properties, demonstrating good grain refinement effect and stability in use. Figure 1 As can be seen, after adding the aluminum-niobium-boron refining agent prepared in Example 1, the grain boundaries in the A356 alloy microstructure are relatively clear, and the grains are distributed in an irregular polygonal pattern, with no obvious areas of coarse grain concentration.

[0065] Compared to Example 1, Comparative Example 1, which did not contain Al-10Ti master alloy, graphite powder, pure zinc ingot, or pure magnesium ingot, showed a significantly larger average grain size. This indicates that the absence of the titanium carbide-assisted nucleation phase, the aluminum-titanium transition layer, and the magnesium / zinc composite outer layer resulted in insufficient effective nucleation sites for the grain refiner, decreased particle suspension stability and resistance to Si poisoning, leading to poor grain refinement.

[0066] Compared to Example 1, Comparative Example 2, which did not contain pure zinc or magnesium ingots, had a larger average grain size than Example 1. This indicates that without the magnesium / zinc composite outer layer, the grain refiner's inhibitory effect on grain growth is insufficient, making it difficult to maintain the grain refinement effect.

[0067] Compared to Example 1, Comparative Example 3, which did not add pure zinc ingots, still had a larger average grain size than Example 1. This indicates that although adding Mg alone can improve the resistance to Si poisoning to some extent, the lack of Zn participation results in insufficient magnesium / zinc synergy and a decrease in the grain refining effect of the refining agent.

[0068] The above are preferred embodiments of the present invention. Those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an aluminum-niobium-boron refining agent, characterized in that, The preparation steps include the following: S1. After heating the aluminum ingot to 1180~1220℃ to melt it, add aluminum-niobium master alloy to melt it, add the first part of aluminum-titanium master alloy and carbon source in sequence and stir and disperse it, then add aluminum-boron master alloy and keep it warm and stir to obtain melt a containing composite core particles. S2. After cooling melt a to 880~920℃, add the second part of aluminum-titanium master alloy and stir while keeping it warm to obtain melt b; cool to 780~800℃, add pure zinc ingot and pure magnesium ingot in sequence and stir while keeping it warm to obtain melt c; S3. Cool the melt c to 740~760℃, degas and refine, remove slag, let stand, pour into a mold, cool and shape to obtain aluminum niobium boron refining agent.

2. The method for preparing an aluminum-niobium-boron refining agent according to claim 1, characterized in that, The mass percentage of each element in the aluminum-niobium-boron refining agent is as follows: niobium 2%~3.5%, boron 0.25%~0.43%, titanium 0.8%~1.5%, magnesium 0.2%~0.5%, zinc 0.2%~0.5%, carbon 0.05%~0.15%, and the remainder is aluminum.

3. The method for preparing an aluminum-niobium-boron refining agent according to claim 2, characterized in that, In the aluminum-niobium-boron refining agent, the mass ratio of niobium to boron is (8~10):1, the mass ratio of titanium to boron is (2.5~4):1, and the sum of the mass percentages of magnesium and zinc is 0.4%~1%.

4. The method for preparing an aluminum-niobium-boron refining agent according to claim 1, characterized in that, The aluminum-titanium master alloy is an Al-10Ti master alloy, and the mass ratio of the first part of the aluminum-titanium master alloy to the second part of the aluminum-titanium master alloy is 3:

7.

5. The method for preparing an aluminum-niobium-boron refining agent according to claim 1, characterized in that, In step S1, after adding the aluminum-niobium master alloy, the mixture is electromagnetically stirred at a power of 10-20kW for 5-10 minutes. After adding the first part of the aluminum-titanium master alloy, the mixture is electromagnetically stirred for another 3-5 minutes.

6. The method for preparing an aluminum-niobium-boron refining agent according to claim 5, characterized in that, In step S1, the carbon source is graphite powder; after adding the graphite powder, the mixture is mechanically stirred at a speed of 300-500 rpm for 5-8 minutes; after adding the aluminum-boron master alloy, the mixture is mechanically stirred at a speed of 300-500 rpm for 10-15 minutes.

7. The method for preparing an aluminum-niobium-boron refining agent according to claim 1, characterized in that, In step S2, after adding the second part of the aluminum-titanium master alloy, the mixture is mechanically stirred at a speed of 300-500 rpm for 15-20 minutes; after adding the pure zinc ingot, the mixture is mechanically stirred at a speed of 300-500 rpm for 2-3 minutes; after adding the pure magnesium ingot, the mixture is mechanically stirred at a speed of 300-500 rpm for 10-15 minutes.

8. The method for preparing an aluminum-niobium-boron refining agent according to claim 1, characterized in that, In step S3, high-purity argon gas is introduced by rotary jetting for degassing and refining. The argon gas pressure is 0.15~0.2MPa and the refining time is 10~15min.

9. The method for preparing an aluminum-niobium-boron refining agent according to claim 8, characterized in that, In step S3, after the material is poured into the mold, the cooling rate for cooling and shaping is 20~30K / s.

10. An aluminum-niobium-boron refining agent, characterized in that, It is prepared by the method described in any one of claims 1 to 9 for the preparation of an aluminum-niobium-boron refining agent.

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