CN115627376B - Al-Nb-TiB for casting aluminum-silicon alloy 2 Preparation method of refiner - Google Patents

Abstract

The invention belongs to the technical field of manufacturing non-ferrous metals or alloys, and specifically discloses a method for preparing an Al-Nb- _TiB refiner for casting aluminum-silicon alloys, including first weighing Nb and Al, and melting and alloying them to obtain Al-Nb melt, followed by adding _TiB2 powder with a predetermined particle size distribution as the introduced nucleation particles, so that a Nb-rich modified transition layer is formed on the surface of _TiB2 particles and dispersed in the Al-Nb melt to obtain a homogeneous and stable Al-Nb- _TiB2 melt is poured into the metal mold subsequently, after cooling and solidifying, Al-Nb- _TiB2 refiner is obtained. This preparation method solves the problems of poor decay resistance and Si poisoning of the existing refiner, It has a significant refining effect on aluminum alloys, especially aluminum-silicon alloys, and has practical value for improving the alloy quality and performance of cast aluminum-silicon alloys.

Description

A kind of preparation method of Al-Nb-TiB2 refining agent for cast aluminum-silicon alloy

technical field

The invention belongs to the technical field of manufacturing nonferrous metals or alloys, in particular to the processing and preparation of aluminum alloys, and in particular to a method for preparing Al-Nb- _TiB2 refiners for casting aluminum-silicon alloys.

Background technique

As the most widely used cast aluminum alloy, Al-Si alloy accounts for about 80%-90% of the total cast aluminum alloy. At present, the production of aluminum alloy castings mainly adopts the addition of Al-Ti-B intermediate alloy ingots in the furnace. However, for aluminum-silicon alloys with a Si content greater than 3wt.%, the refined phase TiAl ₃ of Al-Ti-B, especially the TiAl ₃ on the surface of TiB ₂ particles, is eroded and damaged by Si atoms, resulting in poor refining effect, which is difficult to meet the industrial requirements. Production standards. The Al-Nb-B master alloy that has appeared in recent years, because the stability of NbAl ₃ formed by Nb and Al is higher than that of TiAl ₃ , it is not easy to be eroded by Si atoms in aluminum melt, and can be used in aluminum-silicon alloys with Si content less than 12wt.%. It plays a role in refinement and exhibits excellent resistance to Si poisoning. However, the second phase NbAl ₃ and NbB ₂ in the Al-Nb-B refiner has a large density and relative atomic mass, and is easy to agglomerate and settle in the aluminum melt, so the Al-Nb-B refiner has poor decay resistance. It needs to be stirred and cast immediately after melting, which seriously limits its industrial application.

At present, industrial production generally increases the amount of Al-Ti-B master alloy added from 0.2wt.% to more than 2wt.%. Although a better refining effect can be achieved, the refining cost is also increased accordingly. However, the emerging Al-Nb-B master alloy is difficult to put into large-scale industrial production because of its poor resistance to fading. Therefore, the development of a refined master alloy with strong resistance to Si poisoning and decay is of great importance to improve the quality of cast aluminum-silicon alloys and expand the application of cast aluminum-silicon alloys.

Contents of the invention

In order to solve the above-mentioned technical problems, the present invention provides a preparation method of Al-Nb- _TiB2 refiner for cast aluminum-silicon alloy, adopting the alloying of melting Al-Nb alloy first, and then adding _TiB2 powder with predetermined particle size distribution As the nucleation particles introduced, a Nb-rich modified transition layer is formed on the surface of the TiB ₂ particles and dispersed in the Al-Nb melt to obtain a uniform composition structure, which is conducive to the full refinement of the TiB ₂ and NbAl ₃ phases.

The complete technical scheme of the present invention comprises:

A kind of preparation method of Al-Nb- _TiB refiner for cast aluminum-silicon alloy, comprises the steps:

S1: Alloying of Al-Nb alloys

S1.1 Weighing raw materials: use 325 mesh Nb powder or high-purity Nb block as the niobium source, and weigh the niobium source and aluminum ingot according to the composition ratio of Nb:Al=(5~7):190 by mass;

S1.2 Alloying: Put the weighed niobium source and aluminum ingot into the crucible and heat it up to 900°C; after the aluminum ingot is completely melted into molten aluminum, keep it warm for 60 minutes, keep stirring during the heat preservation period, and the niobium source will melt into the aluminum Liquid, then add refining agent for refining to obtain Al-Nb melt;

S2: Introduction of _TiB nucleation particles

S2.1 Select TiB ₂ powder with a predetermined particle size distribution as the introduced nucleation particles, and the mass ratio of TiB ₂ to aluminum ingot is TiB ₂ : Al=(6~8):190;

S2.2 Introduce _TiB2 nucleation particles: preheat the weighed _TiB2 powder at 175°C for 30min, then add it into the Al-Nb melt at 900°C obtained in step S1.2, and keep stirring for 30~60min ; Form a Nb-rich modified transition layer on the surface of the _TiB2 particles and disperse it in the Al-Nb melt to obtain a homogeneous and stable Al-Nb- _TiB2 melt;

S3: Casting of Al-Nb-TiB ₂ alloy

After the Al-Nb-TiB ₂ melt is cooled to 800°C, the molten metal is poured into a metal mold, and the Al-Nb-TiB ₂ refiner is obtained after cooling and solidification.

Further, in step S1.1, the mass of the refining agent is 0.1% of the mass of the molten aluminum.

Further, in the step S2.1, the particle size of the TiB ₂ powder is: D ₅₀ =0.3-3.0um

Further, in the step S2.2, the TiB ₂ powder is wrapped with aluminum foil and then added to the Al-Nb melt.

Further, in the step S2.2, a graphite stirring rod is used to press the aluminum foil block wrapped with TiB ₂ powder to the middle and lower part of the Al-Nb melt, and wait for about 2 minutes until the aluminum foil is completely melted and the TiB ₂ powder is scattered.

Further, in the step S3, the metal mold is preheated at 175° C. for 1 hour.

Further, in the step S3, the metal mold is conical, the size is Φ50mm×80mm, and the material is H13 hot work mold steel.

Further, the Al-Nb-TiB ₂ refining agent for casting aluminum-silicon alloy obtained by the preparation method, the mass percentage of each element component of the refining agent is: Ti: 3-5%, Nb: 2.5- 3.5%, B: 0.5~1.5%, the balance is Al.

Further, the refiner contains the second phase TiB ₂ and NbAl ₃ .

Further, the mass fraction of TiB ₂ phase is 3-4%, the size is less than or equal to 3 μm, the mass fraction of NbAl ₃ phase is 5-7%, and the size is less than or equal to 10 μm, and the second phase TiB ₂ and NbAl ₃ are dispersedly distributed in the aluminum matrix middle.

Compared with the prior art, the present invention has the advantages of:

1. The Al-Nb- _TiB2 refining agent prepared by the present invention uses the _TiB2 phase as nucleation particles to ensure the efficient refining effect of the Al-Ti-B system on aluminum alloys, and Nb is introduced to modify the surface of _TiB2 . The problem of TiAl ₃ being damaged by Si element corrosion is avoided.

2. The Al-Nb-TiB ₂ refining agent prepared by the present invention can refine the α-Al in the aluminum-silicon alloy with a Si content of 7wt.% to 326.05 μm, which is better than the refining effect of Al-Ti-B by 549.06 μm.

3. After Al-Nb-TiB ₂ prepared by the present invention is added with Al-7Si, the refining effect of 450 μm or less can be maintained within the holding time of 10 minutes to 120 minutes, and the second phase of the Al-Nb-B refining agent is easy to settle. The thinning effect is greatly attenuated to 669.84 μm when kept warm for more than 30 minutes, and the Al-Nb-TiB ₂ prepared by the present invention has excellent decay resistance.

4. The preparation process in the present invention can realize the surface modification of TiB ₂ nucleation particles by Nb, and the obtained Al-Nb-TiB ₂ refiner has a unique second phase structure and uniform composition structure, which is beneficial to TiB ₂ and NbAl ₃ Phase to give full play to the refinement effect.

Description of drawings

Figure 1 is a photo of the metallographic structure of the Al-2.4Nb-4TiB ₂ refiner in Example 1 of the invention.

Fig. 2 is a comparison diagram of α-Al grain refinement of Al-2.4Nb-4TiB ₂ prepared in Example 1 of the invention versus Al-7Si alloy.

Fig. 3 is a comparison of the refining effect of Al-2.4Nb-4TiB ₂ on Al-7Si alloy under different refining times in Example 1 of the invention.

Fig. 4 is a comparison chart of α-Al grain refinement of Al-7Si alloy made by self-made Al-8Nb-1.7B in Comparative Example 1.

Fig. 5 is a comparison of the refining effect of Al-8Nb-1.7B on Al-7Si alloy under different refining times in Comparative Example 1.

FIG. 6 is a comparison chart of α-Al grain refinement of commercially available Al-5Ti-1B versus Al-7Si alloy in Comparative Example 2.

Figure 7 is a comparison of the refining effects of Al-2.4Nb-4TiB2, Al-8Nb-1.7B, and Al-5Ti-1B on Al-7Si alloys under different refining times in Example 1 and Comparative Examples 1 and 2.

Detailed ways

The technical solutions of the present invention will be further described in detail below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only for illustration and are not intended to limit this application.

The preparation method of a kind of Al-Nb- _TiB refiner alloy disclosed by the present invention comprises the following steps:

(1) Alloying of Al-Nb alloy

(1a) Weighing raw materials: use 325-mesh Nb powder or high-purity Nb block as the niobium source, and weigh the raw materials according to the following composition ratio: Nb is 25~35g, and aluminum ingot is 950g;

(1b) Alloying: Put the weighed metal raw material into a graphite crucible and put it into a crucible-type resistance melting furnace together with the crucible, and raise the temperature to 900°C; after the aluminum ingot is completely melted at 900°C, keep it warm for 60 minutes, during which time use The graphite stirring rod continuously stirs to accelerate the dissolution and uniform distribution of Nb. Add 0.1wt.% refining agent to refine the molten aluminum, and then skim off the scum on the surface of the molten aluminum to obtain an Al-Nb melt.

(2) Introduction of TiB ₂ nucleation particles

(2a) Weighing raw materials: Select TiB ₂ powder raw materials with suitable particle size distribution as the nucleation particles introduced as required, and weigh according to the following composition: TiB ₂ is 30~40g.

(2b) Introducing TiB ₂ nucleation particles: Wrap the weighed TiB ₂ powder with aluminum foil, preheat it at 175°C for 30min, and then add it into the Al-Nb melt kept at 900°C obtained in (1b). Graphite stirring rod presses the aluminum foil block wrapped with TiB ₂ powder to the middle and lower part of the melt, wait for about 2 minutes, until the aluminum foil is completely melted and the TiB ₂ powder is scattered, then use the graphite stirring rod to continue stirring for 30-60 minutes. TiB ₂ has poor wettability with aluminum melt. When TiB ₂ is directly added to pure aluminum melt, TiB ₂ sinks to the bottom and cannot be evenly dispersed in aluminum melt. Therefore, Al-Nb alloying needs to be completed first. TiB ₂ in Al-Nb alloy, due to the similar structure of NbAl ₃ and TiAl ₃ , a modified transition layer NbAl ₃ ^' is formed on the (0001) surface of TiB ₂ , and NbAl ₃ ^' can reduce the wetting of TiB ₂ and aluminum melt Angle, so that TiB ₂ particles are better dispersed in the Al-Nb melt, and a homogeneous and stable Al-Nb-TiB ₂ melt is obtained;

(3) Casting of Al-Nb-TiB2 refiner alloy

(3a) After the Al-Nb- _TiB2 melt is cooled to 800°C, pour the molten metal into a conical metal mold preheated at 175°C for 1h, and obtain the Al-Nb-TiB2 refiner alloy after cooling and solidification.

The Al-Nb-TiB _refiner alloy obtained by the preparation method of the present invention has the following element components and mass percentages: Ti: 3-5%, Nb: 2.5-3.5%, B: 0.5-1.5%, and the balance for Al. The alloy contains the second phase TiB ₂ and NbAl ₃ , in which the mass fraction of TiB ₂ phase is 3~4%, the size is below 3μm, the mass fraction of NbAl ₃ phase is 5~7%, the size is below 10μm, and all the second phases are uniformly dispersed in the aluminum matrix.

In order to further illustrate the effect of the preparation method of this embodiment, an unrefined aluminum-silicon alloy was prepared at the same time and refined using the refiner alloy obtained in this embodiment, including:

(4) Preparation of unrefined aluminum-silicon alloy

(4a) Put the weighed 650g aluminum ingot and 350g Al-20Si alloy into the crucible and put them into the resistance melting furnace together with the crucible, raise the temperature to 750°C, the composition of the aluminum alloy is: Al-7Si;

(4b) After the aluminum alloy is completely melted at 750°C, keep it warm for 30 minutes, add 0.1wt.% refining agent to refine the molten aluminum, and then skim off the scum on the surface of the molten aluminum; pour the molten metal into a cone that is preheated at 175°C for 1 hour In the shape metal mold, unrefined Al-7Si alloy is obtained;

(5) Refining of Al-7Si alloy by Al-Nb-TiB ₂ refiner

(5a) Put the weighed Al-7Si alloy into the crucible and put it into the resistance melting furnace together with the crucible, raise the temperature to 750°C, keep the temperature for 30min after the alloy is completely melted, add 0.1wt.% refining agent to the aluminum The liquid is refined, and then the scum on the surface of the aluminum liquid is skimmed; the Al-Nb- _TiB2 master alloy prepared in step (3a) is added in the aluminum melt, and the addition amount is 0.3 ~ 0.6wt.% of the Al-7Si alloy, and the Graphite stirring rod manually stirs the melt for 1~2min, and heats it at 750℃ for 1~120min;

Preferably, the addition amount of Al-Ti-Nb-B is 0.5wt.%, and the temperature is kept at 750°C for 10 min.

(5b) Pouring the molten metal into a conical metal mold preheated at 175° C. for 1 hour, cooling and solidifying to obtain a refined Al-7Si alloy of Al-Nb-TiB ₂ .

Preferably, the material of the hot work die steel mold used in step (5b) is: H13 hot work die steel, and the size of the tapered die is Φ50mm×80mm.

Aiming at the problems existing in the prior art, the preparation method disclosed in the present invention firstly solves the problem of poor decay resistance of the current Al-Nb-B master alloy. The second phase in Al-Nb-B alloy is NbAl ₃ , NbB ₂ , but ρ _(NbAl3) =4.52g/cm ³ , which is larger than ρ _(TiAl3) =3.357g/cm ³ ; ρ _(NbB2) =6.928g/cm 3 cm ³ , which is greater than ρ _(TiB2) =4.495g/cm ³ , so in the aluminum melt with ρ=2.7g/cm ³ , the sedimentation velocity of NbAl ₃ and NbB ₂ phases is far greater than that of TiAl ₃ and TiB ₂ phases, resulting in After the Al-Nb-B master alloy is added to the Al-Si melt, it needs to be cast immediately. However, casting Al-Si alloys often requires a long time of heat preservation. If the heat preservation time is too long, the NbAl ₃ and NbB ₂ phases in Al-Nb-B will settle rapidly, and their refining effect on Al-Si alloys will decline significantly.

Secondly, the invention solves the Si poisoning problem of the current Al-Ti-B refiner. When the Si content of the Al-Si alloy is greater than 3wt.%, Si atoms will erode and modify the TiAl ₃ layer on the surface of TiB ₂ in the Al-Ti-B alloy, which will increase the interface mismatch between α-Al and TiB ₂ , and the α- It is difficult for Al to nucleate heterogeneously on _TiB2 , resulting in the failure of Al-Ti-B refiner. The NbAl ₃ layer on the surface of NbB ₂ in Al-Nb-B is more stable than TiAl ₃ , and is not easily corroded by Si atoms. At the same time, the crystal structure of NbAl ₃ is the same as that of TiAl ₃ , and it can be segregated and modified on the surface of TiB ₂ like TiAl ₃ , forming a NbAl ₃ -TiB ₂ core-shell structure, enabling α-Al to nucleate heterogeneously on the NbAl ₃ layer on the surface of TiB ₂ , ensuring the refinement effect of the NbAl ₃ -TiB ₂ core-shell structure in Al-Si alloys, Overcome the Si poisoning problem of Al-Ti-B refiner.

For the above technical problems, the Al-Nb- _TiB refiner obtained by the preparation method of the present invention has a significant refinement effect on Al-7Si: _after adding Al-Nb-TiB, under the best refinement process (fine Addition amount of refining agent is 0.5wt.%, refinement temperature is 750°C, refinement time _is 10min), the grain size is refined to 326.05μm; It can maintain the refinement effect below 450μm, and has excellent resistance to fading. This technical scheme provides improved anti-recession of Al-Nb-B refiner, avoids the problem of Al-Ti-B refiner being poisoned by cast aluminum-silicon alloy Si at the same time, takes into account the advantages of the two types of refiners, and is helpful for improving casting The alloy quality and performance of aluminum-silicon alloy have practical value.

Example 1:

A kind of preparation technology of high-performance Al-Nb- _TiB refiner for cast aluminum-silicon alloy, comprises the following steps:

Step 1: Use 99% high-purity Nb blocks as the niobium source, and weigh the raw materials according to the following composition ratio: 24g of Nb, 950g of 99.9% aluminum ingots; put the weighed metal raw materials into a graphite crucible and carry Put them together into a crucible-type resistance melting furnace and raise the temperature to 900°C. After the aluminum ingot is completely melted at 900°C, keep it warm for 60 minutes. During this period, use a graphite stirring rod to continuously stir to accelerate the dissolution and uniform distribution of Nb. Add 0.1wt.% refining agent to refine the molten aluminum, and then skim off the scum on the surface of the molten aluminum to obtain an Al-Nb melt.

Step 2: Select TiB ₂ powder with a particle size distribution of D ₅₀ =2.97 μm as the source of nucleation particles to be introduced, and weigh it according to the following composition: TiB ₂ is 40g. Wrap the weighed TiB ₂ powder with aluminum foil, preheat it at 175°C for 30 minutes, then add it into the Al-Nb melt at 900°C obtained in Step 1, and immediately use a graphite stirring rod to wrap the TiB ₂ powder Press the aluminum foil agglomerate to the middle and lower part of the melt, wait for about 2 minutes, until the aluminum foil is completely melted, the TiB ₂ powder is scattered, and then use a graphite stirring rod to continue stirring for 30 minutes to obtain a homogeneous and stable Al-Nb-TiB ₂ melt;

Step 3: Cool the Al-Nb-TiB ₂ melt to 800°C, keep stirring with a graphite stirring rod during this period to avoid the precipitation of TiB ₂ and NbAl ₃ , and then pour the alloy liquid into a conical metal mold preheated at 175°C for 1h Inside, the Al-2.4Nb-4TiB ₂ alloy is obtained after cooling and solidification, and its metallographic structure is shown in Figure 1.

Step 4: Put 530g of pure aluminum ingot and 460g of Al-15Si alloy weighed into the crucible and put them into the resistance melting furnace together with the crucible, raise the temperature to 750°C, and control the composition of the aluminum alloy to be: Al-7Si; After the alloy is completely melted at 750°C, keep it warm for 30 minutes, add 0.1wt.% refining agent to refine the molten aluminum, and then skim off the scum on the surface of the molten aluminum; pour the molten metal into a conical metal mold preheated at 175°C for 1 hour , to obtain unrefined Al-7Si alloy;

Step 5: Put the weighed Al-7Si alloy into the crucible and put it into the resistance melting furnace together with the crucible, raise the temperature to 750°C, add the prepared Al-2.4Nb-4TiB ₂ master alloy into the aluminum melt, add The amount is 0.5wt.% of the Al-7Si alloy, and the melt is artificially stirred with a graphite stirring rod for 2 minutes, and kept at 750°C for 10, 30, 60, and 120 minutes respectively; the molten metal that reaches the corresponding holding time is poured to 175°C In the conical metal mold preheated for 1 hour, after cooling and solidification, Al-2.4Nb-4TiB ₂ refined Al-7Si alloys with refining times of 10, 30, 60 and 120 minutes were obtained. Cut the casting sample at a position 3cm away from the bottom of the sample, perform anodic coating treatment, and observe it with a polarizing microscope, as shown in Figure 2-3, Figure 2 shows Al-2.4Nb-4TiB ₂ vs. Alloy refinement effect, refinement time: (a) in Figure 2 is 10min; (b) in Figure 2 is 30min; (c) in Figure 2 is 60min; (d) in Figure 2 is 120min. Figure 3 shows the refinement effect of Al-2.4Nb-4TiB ₂ on Al-7Si alloy under different refinement times, which are 10min, 30min, 60min and 120min from left to right.

The aluminum grains were measured using the intercept method specified in the national standard GB/T 3246.1-2012. The refining effect was the best when the refining time was 10 minutes. The average size of α-Al grains in Al-7Si was 326.05 μm. The anti-fading property is good. Even if the refining time reaches 120min, the prepared Al-2.4Nb-4TiB ₂ still has a refining effect of 421.95μm on the α-Al grains in Al-7Si.

Comparative example 1: The refinement effect of self-made Al-8Nb-1.7B master alloy on Al-7Si, including the following steps:

Step 1: Use 99% high-purity Nb powder as the niobium source and 98% KBF ₄ as the boron source, and weigh the raw materials according to the following composition ratio: 960g of 99.9% pure aluminum ingot, 81g of high-purity Nb powder, and 203g of KBF ₄ . Place the weighed pure aluminum ingot in the crucible and put it into the crucible-type resistance melting furnace together with the crucible, and raise the temperature to 850°C; after the aluminum ingot is completely melted, keep it warm for 30 minutes, and add 0.1wt.% refining agent to the aluminum liquid Refining is carried out, and then the scum on the surface of the molten aluminum is skimmed off. Mix Nb powder and KBF ₄ raw material powder evenly with a mixer. After preheating at 175°C for 30 minutes, add them in two batches to the aluminum melt at 850°C. During this period, stir with a graphite stirring rod for 2 minutes every 15 minutes and keep it warm for 2 hours. Homogeneous and stable Al-Nb-B melt;

Step 2: Cool the Al-Nb-B melt to 750°C, keep stirring with a graphite stirring rod to avoid the precipitation of NbB ₂ and NbAl ₃ , and then pour the alloy liquid into a conical metal mold preheated at 175°C for 1 hour , to obtain Al-8Nb-1.7B alloy after cooling and solidification;

Step 3: Put the weighed Al-7Si alloy into the crucible and put it into the resistance melting furnace together with the crucible, raise the temperature to 750°C, add the self-made Al-8Nb-1.7B master alloy into the aluminum melt, and add the amount It is 0.5wt.% of the Al-7Si alloy, and the melt is artificially stirred with a graphite stirring rod for 2 minutes, and kept at 750°C for 10, 30, 60, and 120 minutes respectively; the molten metal that reaches the corresponding holding time is poured to 175°C for pre In a conical metal mold heated for 1 hour, Al-8Nb-1.7B refined Al-7Si alloys with refining times of 10, 30, 60 and 120 minutes were obtained after cooling and solidification. Cut the casting sample at the position 3cm from the bottom of the sample, carry out anodic coating treatment, and observe it with a polarizing microscope, as shown in Figure 4-5. Figure 4 shows the effect of Al-8Nb-1.7B on Al- The refinement effect of 7Si alloy, refinement time: (a) in Figure 4 is 10min; (b) in Figure 4 is 30min; (c) in Figure 4 is 60min; (d) in Figure 4 is 120min ; Figure 5 shows the refinement effect of Al-8Nb-1.7B on Al-7Si alloy under different refinement times, which are 10min, 30min, 60min and 120min from left to right. And use the intercept method specified in the national standard GB/T 3246.1-2012 to measure the aluminum grains, the refinement time is 10min, the refinement effect is the best, the average size of α-Al grains in Al-7Si is 335.56μm, However, the anti-fading property is not good, and the refining time reaches 30 minutes. The prepared Al-8Nb-1.7B has only a refining effect of 669.84 μm on the α-Al grains in Al-7Si. When the refining time is increased to 60 minutes, the prepared Al-8Nb-1.7B Al-8Nb-1.7B has basically no refining effect on Al-7Si, and the α-Al grain is close to 1000μm.

Comparative example 2: The refinement effect of commercially available Al-5Ti-1B master alloy on Al-7Si, including the following steps:

Step 1. Put the weighed Al-7Si in the crucible and put it into the crucible-type resistance melting furnace together with the crucible, and heat up to 750°C; after the aluminum ingot is completely melted, keep it warm for 30 minutes, and then add 0.1wt.% refining agent Refining the molten aluminum, then skimming off the scum on the surface of the molten aluminum; adding the commercially available Al-5Ti-1B master alloy to the Al-7Si melt, the addition amount is 0.5wt.% of Al-7Si, and using a graphite stirring rod Stir the melt and keep it warm at 750°C for 10 minutes;

Step 2. Pouring the aluminum melt into a conical metal mold preheated at 175°C for 1 hour, cooling and solidifying to obtain a refined Al-7Si sample of the Al-5Ti-1B master alloy. Cut the sample at a position 3cm away from the bottom of the sample, perform anodic coating treatment, observe with a polarizing microscope, as shown in Figure 6, and use the intercept method specified in the national standard GB/T 3246.1-2012 to analyze the aluminum grains. According to measurements, the commercially available Al-5Ti-1B master alloy has a limited refining effect on α-Al grains in Al-7Si when the refining time is 10 min, and the average size of α-Al grains is 549.06 μm.

As shown in Figure 7, the refinement of Al-2.4Nb-4TiB ₂ , Al-8Nb-1.7B, Al-5Ti-1B on Al-7Si alloy under different refinement times in Comparative Example 1 and Comparative Examples 1 and 2 effect, Al-2.4Nb-4TiB ₂ still has a refinement effect of about 400 μm on Al-7Si after 120 minutes of heat preservation, while Al-8Nb-1.7B basically loses the refinement effect after 60 minutes of heat preservation, and Al-2.4Nb-4TiB ₂ The anti-recession is far better than Al-8Nb-1.7B. Even if Al-5Ti-1B is held for 10 minutes, the refinement effect on Al-7Si is poor, which is far inferior to the grain size of 326.05 μm achieved by Al-2.4Nb-4TiB ₂ held for 10 minutes. Therefore, the Al-2.4Nb-4TiB ₂ prepared according to the present invention not only has a good refining effect on Al-7Si, but also has excellent decay resistance.

The above applications are only some embodiments of the present application. Those skilled in the art can make several modifications and improvements without departing from the inventive concept of the present application, and these all belong to the protection scope of the present application.

Claims (8)

1. Al-Nb-TiB for casting aluminum-silicon alloy ₂ The preparation method of the refiner is characterized by comprising the following steps:

step S1: alloying of an Al-Nb alloy comprising:

step S1.1 weighing raw materials: taking 325-mesh Nb powder or high-purity Nb blocks as a niobium source, wherein the mass ratio of Nb: al = (5~7): 190 of niobium source and aluminum ingot;

step S1.2 alloying: putting the weighed niobium source and aluminum ingot into a crucible, heating, and heating to 900 ℃; after the aluminum ingot is completely melted into aluminum liquid, preserving heat for 60min, continuously stirring during the heat preservation period, melting the niobium source in the aluminum liquid, and then adding a refining agent for refining to obtain an Al-Nb melt;

step S2: tiB ₂ The introduction of the nucleation particles comprises:

step S2.1 selection of TiB with a predetermined particle size distribution ₂ Powders as incorporated nucleation particles, tiB ₂ The mass ratio of the aluminum alloy to the aluminum ingot is TiB ₂ ：Al=（6~8）：190；

Step S2.2 introduction of TiB ₂ Nucleation particles: weighing TiB ₂ Preheating the powder at 175 deg.C for 30min, and adding into step S1.2 to obtainStirring the mixture in an Al-Nb melt with the temperature of 900 ℃ for 30 to 60min continuously; make TiB ₂ Forming a modified transition layer rich in Nb on the surface of the particles and dispersing the modified transition layer in the Al-Nb melt to obtain the homogeneous and stable Al-Nb-TiB ₂ Melting the materials;

and step S3: al-Nb-TiB ₂ Casting of alloys

Waiting for Al-Nb-TiB ₂ Cooling the melt to 800 ℃, pouring the molten metal into a metal mold, and cooling and solidifying to obtain Al-Nb-TiB ₂ A refiner; the refiner contains a second phase of TiB ₂ And NbAl ₃ ，TiB ₂ The phase mass fraction is 3~4%, the size is less than or equal to 3 mu m, nbAl ₃ The mass fraction of the phase is 5~7 percent, the size is less than or equal to 10 mu m, and the second phase TiB ₂ And NbAl ₃ Dispersed in the aluminum matrix.

2. Al-Nb-TiB for casting Al-Si alloy according to claim 1 ₂ The preparation method of the refiner is characterized in that in the step S1.1, the mass of the refiner is 0.1 percent of that of the molten aluminum.

3. The Al-Nb-TiB for casting Al-Si alloy according to claim 1 ₂ The preparation method of the refiner is characterized in that in the step S2.1, tiB ₂ The particle size of the powder was: d ₅₀ =0.3-3.0um。

4. Al-Nb-TiB for casting Al-Si alloy according to claim 1 ₂ A method for preparing a refiner, characterized in that in step S2.2, the TiB is ₂ The powder is wrapped by aluminum foil and then Al-Nb melt is added.

5. The Al-Nb-TiB for casting aluminum-silicon alloy according to claim 4 ₂ The preparation method of the refiner is characterized in that in the step S2.2, a graphite stirring rod is adopted to wrap TiB ₂ Pressing the powder aluminum foil block to the middle lower part of the Al-Nb melt, waiting for 2min until the aluminum foil is completely melted, and TiB ₂ The powder is scattered out.

6. Al-Nb-TiB for casting Al-Si alloy according to claim 1 ₂ The preparation method of the refiner is characterized in that in the step S3, the metal mold is preheated for 1 hour at 175 ℃.

7. Al-Nb-TiB for casting Al-Si alloy according to claim 6 ₂ The preparation method of the refiner is characterized in that in the step S3, the metal mold is conical, the size of the metal mold is phi 50mm multiplied by 80mm, and the material is H13 hot work mold steel.

8. Al-Nb-TiB for casting aluminum-silicon alloy obtained by the production method according to any one of claims 1 to 7 ₂ The refiner is characterized in that the refiner comprises the following element components in percentage by mass: ti:3~5%, nb:2.5 to 3.5%, B:0.5 to 1.5 percent, and the balance being Al.

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