A method for manufacturing an integrated die casting without correction and use thereof

Abstract

The application discloses a preparation method and application of a non-corrected integrated die casting. The alloy composition of the die casting is as follows: Si: 7.10-10.30 wt.%, Mn: 0.3-0.6 wt.%, Fe: 0.06-0.7 wt.%, Mg: 0.21-0.45 wt.%, Ti: 0.05-0.15 wt.%, Sr: 0.01-0.02 wt.%, Zr: 0.10-0.15 wt.%, V: <=0.02 wt.%, Cu: <=0.03 wt.%, Zn: <=0.02 wt.%, P: <=0.002 wt.%, and the balance is Al. The preparation method of the die casting comprises the following steps: smelting, adding of Al-4Ti-2B nanocrystalline seed alloy, die casting forming and cooling. The preparation method has low cost and short process, and the flatness of the die casting without correction can reach 0.1-0.3 mm / 300 mm. Compared with the die casting prepared by a conventional process, the flatness is improved by more than 90%, the die casting can meet the direct installation condition, the conventional correction link is removed, and the size stability and production efficiency of the large die casting are greatly improved.

Description

Technical Field

[0001] This invention relates to a method for preparing and using die-cast parts, and more particularly to a method for preparing and using Al-Si alloy die-cast parts. Background Technology

[0002] Currently, the development of highly integrated lightweight structural components has become a competitive hotspot in the automotive industry. Large-scale integrated high-pressure die casting technology possesses unique advantages such as short process, high efficiency, and high integration, making it the mainstream solution for achieving net-form fabrication of large-size, complex, thin-walled vehicle body structural components. Due to its excellent filling performance, load-bearing capacity, and low cost, hypoeutectic Al-Si alloys have become the preferred material for large, thin-walled die-cast structural components.

[0003] However, high-pressure die casting involves the rapid solidification and high-speed flow of a melt occurring simultaneously within a short period. Due to uneven thermal shrinkage during the forming process and the transmission of mold deformation, the cast parts often spring back, resulting in dimensional deviations from the design values. Therefore, currently, all integrated die-cast parts require a straightening process to ensure dimensional accuracy meets assembly requirements. Because die-cast parts are complex and large in size, the straightening operation is inefficient, making it difficult to meet the cost and efficiency demands of industrialization. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing an integrated die-cast part without straightening and its application, to solve the problem of dimensional deviation caused by springback of aluminum alloy die-cast parts, and the prepared casting has more stable dimensions after molding, and can meet assembly requirements without straightening.

[0005] The technical solution adopted in this invention is as follows:

[0006] A non-alignment integrated die-casting part, wherein the alloy composition of the die-casting part is: Si: 7.10-10.30 wt.%, Mn: 0.3-0.6 wt.%, Fe: 0.06-0.7 wt.%, Mg: 0.21-0.45 wt.%, Ti: 0.05-0.15 wt.%, Sr: 0.01-0.02 wt.%, Zr: 0.10-0.15 wt.%, V: ≤0.02 wt.%, Cu: ≤0.03 wt.%, Zn: ≤0.02 wt.%, P: ≤0.002 wt.%, with the balance being Al.

[0007] The preferred alloy composition of the die-casting is: Si: 7.10-9.0 wt.%, Mn: 0.3-0.55 wt.%, Fe: 0.09-0.5 wt.%, Mg: 0.21-0.35 wt.%, Ti: 0.05-0.12 wt.%, Sr: 0.01-0.02 wt.%, Zr: 0.10-0.15 wt.%, V: ≤0.02 wt.%, Cu: ≤0.03 wt.%, Zn: ≤0.02 wt.%, P: ≤0.002 wt.%, with the balance being Al.

[0008] The method for preparing the shape-free integrated die-cast part includes the following steps performed sequentially:

[0009] Step (1) Smelting: After the pure aluminum is melted, Al-Mn master alloy, Al-Si master alloy, Al-Ti master alloy and Al-Zr master alloy are added in sequence, and then the mixture is kept at a constant temperature.

[0010] Step (2) Refining: Add Al-4Ti-2B nanocrystalline seed alloy, Al-Sr master alloy and Al-Mg master alloy, and carry out rotary degassing and refining under the condition of passing inert gas. After refining, remove slag and keep warm.

[0011] Step (3) Die casting: Pour the alloy liquid into the mold, die cast, demold, and water cool to obtain an integrated die casting part that does not require straightening.

[0012] Preferably, in step (1), pure aluminum is melted at 750-800℃, and after adding intermediate alloy, it is kept at 750-800℃ for 0.5-2h; then cooled to 720-760℃ and kept at that temperature for another 0.5-2h.

[0013] In step (2), the refining temperature is 700-730℃, and the refining is carried out under the condition of rotating rotor and introducing inert gas; first, Al-4Ti-2B nanocrystalline seed alloy is added, and after 5-15 min, Al-Mg master alloy and Al-Sr master alloy are added and the melt is ultrasonically treated for 5-15 min; then the alloy liquid is kept at the temperature for 10-30 min.

[0014] In step (3), the mold temperature is maintained at 130-220℃; the pouring temperature is 680-720℃; the die casting parameters are: slow injection speed is 0.2-0.5m / s, fast injection speed is 1m / s-4m / s, and the holding pressure is 100~120MPa; the water cooling parameters are: after the casting is opened, it is placed in a water tank for cooling within 15-30s, and the cooling rate is controlled at 50-80℃ / s.

[0015] Preferably, the Mn content in the Al-Mn master alloy is 5%-30%;

[0016] And / or, the Si content in the Al-Si master alloy is 5%-30%;

[0017] And / or, the Ti content in the Al-Ti master alloy is 5%-30%;

[0018] And / or, the Mg content in the Al-Mg master alloy is 5%-30%;

[0019] And / or, the Sr content in the Al-Sr master alloy is 85%-95%;

[0020] And / or, the Zr content in the Al-Zr master alloy is 5%-30%.

[0021] More preferably, the content of Mn in Al-Mn is 10%; the content of Si in Al-Si is 10%; the content of Ti in Al-Ti is 10%; the content of Mg in Al-Mg is 10%; the content of Sr in Al-Sr is 90%; and the content of Zr in Al-Zr is 10%.

[0022] Preferably, the Al-4Ti-2B nanocrystalline seed alloy contains nanoparticles, and the average particle size of TiB2 particles in the nanoparticles is 100nm-600nm.

[0023] And / or, the Al-4Ti-2B nanocrystalline seed alloy is prepared according to the following method:

[0024] The uniformly mixed K2TiF6 powder and KBF4 powder were added to the molten aluminum from industrial pure aluminum and held at 730-800℃ for 30-60 min, followed by 30-60 min of rotary degassing. After standing, the slag was removed and the mixture was then cast to obtain Al-4Ti-2B nanocrystalline seed alloy. The mass ratio of K2TiF6 powder, KBF4 powder and industrial pure aluminum was (0.8-1.1):(1.4-2.0):(3.3-4.1).

[0025] Preferably, the inert gas is nitrogen and / or argon; the inert gas flow rate is 4-8 L / min.

[0026] The non-alignment integrated die-cast part is used in automotive body structural components.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] 1) This invention successfully refines the α-Al grains in Al-Si alloys by selecting appropriate TiB2 seed alloys, addition amounts, and addition processes, thereby improving the feeding ability of die-cast parts during the forming process, reducing the difference in shrinkage between dendrites, and lowering local internal stress. Therefore, introducing a certain amount of particles that can play a heterogeneous nucleation role into the solidification process under die-casting conditions is a promising method to optimize the flatness of die-cast parts by refining their grains. Industrially commonly used Al-Ti-B seed alloys, such as Al-3Ti-B and Al-5Ti-B, mostly have micron-sized particles, which are not effective under high-pressure casting conditions. Therefore, particles suitable for high-cooling-rate solidification conditions are needed. Since increasing the amount of B significantly increases the viscosity of the melt, thereby deteriorating the filling performance of the alloy during the die-casting process, the amount of particles added is crucial. Furthermore, in Al-Si alloys, Si atoms can damage the pseudo-crystalline layer on the surface of TiB2 particles, thus reducing the nucleation ability of the particles (Si poisoning). Therefore, the presence time of TiB2 particles in the melt cannot be too long. Simultaneously, TiB2 particles also interact with Sr in the melt. Therefore, traditional addition methods cannot fully utilize the particle's effect, and adopting an appropriate addition method is crucial for the actual nucleation effect. This patent application verifies through extensive experiments that, for the target aluminum alloy composition, the most significant refining effect is achieved by adding Al-4Ti-2B nanocrystalline seed alloy with TiB2 particle sizes of 100-600 nm during rotary degassing and refining.

[0029] 2) To address the issue that introduced TiB2 is prone to agglomeration, thus weakening its ability to regulate solidification behavior, this invention introduces ultrasonic assistance into the melt to achieve short-term dispersion of TiB2 particles. High-density nano-TiB2 seed alloys added to the melt quickly and uniformly diffuse within the melt under rotor stirring; however, TiB2 particles existing in clusters in the parent material are difficult to disperse. This is a significant factor limiting the actual effectiveness of TiB2 particles. The introduction of ultrasound can effectively disperse TiB2 clusters, thereby improving the utilization rate of TiB2. This patent application has been verified through extensive experiments: ultrasonic time of 5-20 minutes can effectively improve the efficiency of nano-TiB2 seed alloys, achieving a flatness of 0.1-0.3 mm in the uncorrected state of the die-cast parts.

[0030] 3) To address the problem of uneven internal shrinkage leading to excessive residual stress and deformation in die-cast parts after water cooling following demolding at high temperatures, this invention combines the control of solidification behavior during the die-casting process using TiB2 and the regulation of cooling rate after demolding to optimize the flatness of the casting. Extensive experimental verification of this patent application shows that controlling the time interval between gradual demolding and water cooling to an optimal 10-30 seconds effectively reduces residual stress in the casting, achieving a flatness of 0.1-0.3 mm for the die-cast part in its uncorrected state.

[0031] 4) The present invention performs refining under the condition of rotating rotor and introducing inert gas. When the rotary blowing has been carried out for 5-15 minutes, Al-Mg and Al-Sr intermediate alloys are added for refining. This order of addition can better ensure the impurity removal effect and avoid burn-off.

[0032] In summary, this invention optimizes the flatness of die-cast parts through synergistic control, resulting in die-cast parts that can be directly assembled without straightening. This significantly reduces the cost of large die-cast parts and improves production efficiency, making it suitable for large-scale industrial applications. Detailed Implementation

[0033] The present invention will be further described below with reference to embodiments and experimental data. Unless otherwise stated, all units used in this specification are international standard units, and all numerical values ​​and ranges appearing in the present invention should be understood to include systematic errors that are unavoidable in industrial production. Reagents or instruments used in the present invention, unless otherwise specified, are all commercially available conventional products.

[0034] In the following examples and comparative examples, the amount of relevant materials added during the preparation process is based on the composition of the prepared alloy.

[0035] Example 1

[0036] The alloy composition of the non-aligned aluminum alloy die-casting part prepared in this embodiment is as follows: Si: 7.80 wt.%, Mn: 0.50 wt.%, Fe: 0.35 wt.%, Mg: 0.31 wt.%, Ti: 0.11 wt.%, Sr: 0.02 wt.%, Zr: 0.12 wt.%, V: 0.005 wt.%, Cu: 0.01 wt.%, Zn: 0.005 wt.%, P: 0.001 wt.%, with the balance being Al.

[0037] The preparation steps for the non-alignment aluminum alloy die-casting part in this embodiment are as follows:

[0038] (1) Smelting: Pure aluminum ingots are melted at 800℃, and then Al-10Mn, Al-10Si, Al-10Ti and Al-10Zr are added in sequence. The mixture is kept at 800℃ for 1 hour to ensure uniform diffusion of elements. Then the temperature of the aluminum liquid is reduced to 720℃ and kept for 1.5 hours.

[0039] (2) Ultrasonic refining treatment: The refining temperature was 720℃. Refining was carried out under the condition of argon gas being introduced while the rotor was rotating. The gas flow rate was 6L / min and the rotation speed was 358r / min. First, Al-4Ti-2B nanocrystalline seed alloy was added. The particles contained in the Al-4Ti-2B nanocrystalline seed alloy were nanoparticles. The average particle size of TiB2 particles in the nanoparticles was 400 nm. After 5 min, Al-10Mg and Al-90Sr were added, and the melt was ultrasonically treated. The ultrasonic refining time was 15 min, and the total refining time was 20 min. After refining, the slag was removed, and then the alloy liquid was kept at a constant temperature for 15 min. Then, it was cooled to the pouring temperature of 710℃ in preparation for die casting.

[0040] (3) High pressure die casting: Heat the mold to keep the mold temperature at 200℃, pour the aluminum liquid into the barrel, the casting temperature is 710℃, the slow injection speed is 0.3m / s, the fast injection speed is 3m / s, increase the pressure to 100MPa, after the die casting is completed, take the casting out from the separated mold and water cool it. The time interval between demolding and water cooling is 15s, and the cooling rate is controlled at about 70℃ / s.

[0041] Example 2

[0042] The alloy composition of the non-aligned aluminum alloy die-casting part prepared in this embodiment is as follows: Si: 8.51 wt.%, Mn: 0.50 wt.%, Fe: 0.45 wt.%, Mg: 0.28 wt.%, Ti: 0.11 wt.%, Sr: 0.02 wt.%, Zr: 0.12 wt.%, V: 0.005 wt.%, Cu: 0.01 wt.%, Zn: 0.005 wt.%, P: 0.001 wt.%, with the balance being Al.

[0043] The preparation steps for the non-alignment aluminum alloy die-casting part in this embodiment are as follows:

[0044] (1) Smelting: Pure aluminum ingots are melted at 780℃, and then Al-10Mn, Al-10Si, Al-10Ti and Al-10Zr are added in sequence. The mixture is kept at 800℃ for 1 hour to ensure uniform diffusion of elements. Then the temperature of the aluminum liquid is reduced to 720℃ and kept for 1.5 hours.

[0045] (2) Ultrasonic refining treatment: The refining temperature was 720℃. Refining was carried out under the condition of argon gas being introduced while the rotor was rotating. The gas flow rate was 6L / min and the rotation speed was 358r / min. First, Al-4Ti-2B nanocrystalline seed alloy was added. The particles contained in the Al-4Ti-2B nanocrystalline seed alloy were nanoparticles. The average particle size of TiB2 particles in the nanoparticles was 400 nm. After 5 min, Al-10Mg and Al-90Sr were added, and the melt was ultrasonically treated. The ultrasonic refining time was 15 min, and the total refining time was 20 min. After refining, the slag was removed, and then the alloy liquid was kept at a constant temperature for 15 min. Then, it was cooled to the pouring temperature of 710℃ in preparation for die casting.

[0046] (3) High pressure die casting: Heat the mold to keep the mold temperature at 200℃, pour the aluminum liquid into the barrel, the casting temperature is 710℃, the slow injection speed is 0.3m / s, the fast injection speed is 3m / s, increase the pressure to 100MPa, after the die casting is completed, take the casting out from the separated mold and water cool it. The time interval between demolding and water cooling is 15s, and the cooling rate is controlled at about 70℃ / s.

[0047] Example 3

[0048] The alloy composition of the non-alignment aluminum alloy die-casting part prepared in this embodiment is as follows:

[0049] Si: 8.61 wt.%, Mn: 0.52 wt.%, Fe: 0.09 wt.%, Mg: 0.32 wt.%, Ti: 0.11 wt.%, Sr: 0.01 wt.%, Zr: 0.13 wt.%, V: 0.004wt.%, Cu: 0.015wt.%, Zn: 0.003wt.%, and the balance is Al.

[0050] The preparation steps for the non-alignment aluminum alloy die-casting part in this embodiment are as follows:

[0051] (1) Smelting: Pure aluminum ingots are melted at 750℃, and then Al-10Mn, Al-10Si, Al-10Ti and Al-10Zr are added in sequence. The mixture is kept at 800℃ for 1 hour to ensure uniform element diffusion. Then the temperature of the aluminum liquid is reduced to 720℃ and kept for 1.5 hours.

[0052] (2) Ultrasonic refining treatment: The refining temperature was 720℃. Refining was carried out under the condition of argon gas being introduced while the rotor was rotating. The gas flow rate was 6L / min and the rotation speed was 358r / min. First, Al-4Ti-2B nanocrystalline seed alloy was added. The particles contained in the Al-4Ti-2B nanocrystalline seed alloy were nanoparticles. The average particle size of TiB2 particles in the nanoparticles was 400 nm. After 5 min, Al-10Mg and Al-90Sr were added, and the melt was ultrasonically treated. The ultrasonic refining time was 15 min, and the total refining time was 20 min. After refining, the slag was removed, and then the alloy liquid was kept at a constant temperature for 15 min. Then, it was cooled to the pouring temperature of 710℃ in preparation for die casting.

[0053] (3) High pressure die casting: Heat the mold to keep the mold temperature at 200℃, pour the aluminum liquid into the barrel, the casting temperature is 710℃, the slow injection speed is 0.3m / s, the fast injection speed is 3m / s, increase the pressure to 100MPa, after the die casting is completed, take the casting out from the separated mold and water cool it. The time interval between demolding and water cooling is 15s, and the cooling rate is controlled at about 70℃ / s.

[0054] Comparative Example 1

[0055] The alloy composition of the non-aligned aluminum alloy die-casting part prepared in this comparative example is as follows: Si: 7.80 wt.%, Mn: 0.50 wt.%, Fe: 0.35 wt.%, Mg: 0.31 wt.%, Ti: 0.09 wt.%, Sr: 0.02 wt.%, Zr: 0.12 wt.%, V: 0.005 wt.%, Cu: 0.01 wt.%, Zn: 0.005 wt.%, P: 0.001 wt.%, with the balance being Al.

[0056] The preparation steps for this comparative example of a non-corrective aluminum alloy die-cast part are as follows:

[0057] (1) Smelting: Pure aluminum ingots are melted at 800℃, and then Al-10Mn, Al-10Si, Al-10Ti and Al-10Zr are added in sequence. The mixture is kept at 800℃ for 1 hour to ensure uniform diffusion of elements. Then the temperature of the aluminum liquid is reduced to 720℃ and kept for 1.5 hours.

[0058] (2) Ultrasonic refining: The refining temperature was 720℃. Refining was carried out under the condition of argon gas being introduced while the rotor was rotating. The gas flow rate was 6L / min and the rotation speed was 358r / min. After 5min, Al-10Mg and Al-90Sr were added, and the melt was ultrasonically treated. The ultrasonic refining time was 15min, and the total refining time was 20min. After refining, the slag was removed, and then the alloy liquid was kept at a constant temperature for 15min. Then it was cooled to the pouring temperature of 710℃ in preparation for die casting.

[0059] Note: No nanocrystalline seed alloy was added in this comparative example.

[0060] (3) High pressure die casting: Heat the mold to keep the mold temperature at 200℃, pour the aluminum liquid into the barrel, the slow injection speed is 0.3m / s, the fast injection speed is 3m / s, the pressure is 100MPa, after the die casting is completed, take the casting out from the separated mold and water cool it. The time interval between demolding and water cooling is 15s, and the cooling rate is controlled at about 70℃ / s.

[0061] Comparative Example 2

[0062] The alloy composition of the non-standardized aluminum alloy die-casting part prepared in this comparative example is as follows: Si: 7.90 wt.%, Mn: 0.51 wt.%, Fe: 0.13 wt.%, Mg: 0.29 wt.%, Ti: 0.12 wt.%, Sr: 0.02 wt.%, Zr: 0.13 wt.%, V: 0.002 wt.%, Cu: 0.01 wt.%, Zn: 0.005 wt.%, P: 0.001 wt.%, with the balance being Al.

[0063] The preparation steps for this comparative example of a non-corrective aluminum alloy die-cast part are as follows:

[0064] (1) Smelting: Pure aluminum ingots are melted at 800℃, and then Al-10Mn, Al-10Si, Al-10Ti and Al-10Zr are added in sequence. The mixture is kept at 800℃ for 1 hour to ensure uniform diffusion of elements. Then the temperature of the aluminum liquid is reduced to 720℃ and kept for 1.5 hours.

[0065] (2) Ultrasonic refining: The refining temperature was 720℃. Refining was carried out under the condition of argon gas being introduced while the rotor was rotating. The gas flow rate was 6L / min and the rotation speed was 358r / min. First, conventional Al-5Ti-B seed alloy was added. After 5 minutes, Al-10Mg and Al-90Sr were added, and the melt was ultrasonically treated. The ultrasonic refining time was 15 minutes, and the total refining time was 20 minutes. After refining, the slag was removed, and then the alloy liquid was kept at a constant temperature for 15 minutes. Then, it was cooled to the pouring temperature of 710℃ in preparation for die casting.

[0066] Note: In this comparative example, a conventional Al-5Ti-B seed alloy was added to replace the Al-4Ti-2B nanocrystalline seed alloy in Examples 1-3.

[0067] (3) High pressure die casting: Heat the mold to keep the mold temperature at 200℃, pour the aluminum liquid into the barrel, the slow injection speed is 0.3m / s, the fast injection speed is 3m / s, the pressure is 100MPa, after the die casting is completed, take the casting out from the separated mold and water cool it. The time interval between demolding and water cooling is 15s, and the cooling rate is controlled at about 70℃ / s.

[0068] Comparative Example 3

[0069] The alloy composition of the non-aligned aluminum alloy die-casting part prepared in this comparative example is as follows: Si: 7.90 wt.%, Mn: 0.52 wt.%, Fe: 0.21 wt.%, Mg: 0.26 wt.%, Ti: 0.11 wt.%, Sr: 0.017 wt.%, Zr: 0.11 wt.%, V: 0.006 wt.%, Cu: 0.02 wt.%, Zn: 0.004 wt.%, P: 0.001 wt.%, with the balance being Al.

[0070] The preparation steps for this comparative example of a non-corrective aluminum alloy die-cast part are as follows:

[0071] (1) Smelting: Pure aluminum ingots are melted at 800℃, and then Al-10Mn, Al-10Si, Al-10Ti and Al-10Zr are added in sequence. The mixture is kept at 800℃ for 1 hour to ensure uniform diffusion of elements. Then the temperature of the aluminum liquid is reduced to 720℃ and kept for 1.5 hours.

[0072] (2) Ultrasonic refining treatment: The refining temperature was 720℃. Refining was carried out under the condition of argon gas being introduced while the rotor was rotating. The gas flow rate was 6L / min and the rotation speed was 358r / min. First, Al-4Ti-2B nanocrystalline seed alloy was added. The particles contained in the Al-4Ti-2B nanocrystalline seed alloy were nanoparticles. The average particle size of TiB2 particles in the nanoparticles was 400 nm. After 5 min, Al-10Mg and Al-90Sr were added, and the melt was ultrasonically treated. The ultrasonic refining time was 15 min, and the total refining time was 20 min. After refining, the slag was removed, and then the alloy liquid was kept at a constant temperature for 15 min. Then, it was cooled to the pouring temperature of 710℃ in preparation for die casting.

[0073] (3) High pressure die casting: Heat the mold to keep the mold temperature at 200℃, pour the aluminum liquid into the barrel, the slow injection speed is 0.3m / s, the fast injection speed is 3m / s, the pressure is 100MPa, after the die casting is completed, take the casting out from the separated mold and water cool it. The time interval between demolding and water cooling is 5s, and the cooling rate is controlled at about 70℃ / s.

[0074] Note: The difference between this comparative example and Examples 1-3 is that the time interval between the casting being demolded and entering the water tank is 5 seconds, which is shorter than the 15 seconds in Examples 1-3.

[0075] Comparative Example 4

[0076] The alloy composition of the non-aligned aluminum alloy die-casting part prepared in this comparative example is as follows: Si: 8.3 wt.%, Mn: 0.51 wt.%, Fe: 0.43 wt.%, Mg: 0.24 wt.%, Ti: 0.11 wt.%, Sr: 0.018 wt.%, Zr: 0.14 wt.%, V: 0.004 wt.%, Cu: 0.017 wt.%, Zn: 0.004 wt.%, P: 0.001 wt.%, with the balance being Al.

[0077] The preparation steps for this comparative example of a non-corrective aluminum alloy die-cast part are as follows:

[0078] (1) Smelting: Pure aluminum ingots are melted at 800℃, and then Al-10Mn, Al-10Si, Al-10Ti and Al-10Zr are added in sequence. The mixture is kept at 800℃ for 1 hour to ensure uniform diffusion of elements. Then the temperature of the aluminum liquid is reduced to 720℃ and kept for 1.5 hours.

[0079] (2) Ultrasonic refining treatment: The refining temperature was 720℃. Refining was carried out under the condition of argon gas being introduced while the rotor was rotating. The gas flow rate was 6L / min and the rotation speed was 358r / min. At the same time, the melt was ultrasonically treated for 15min. When the rotary blowing was in progress for 5min, Al-10Mg and Al-90Sr were added. After refining, the slag was removed. Then the alloy liquid was allowed to stand for 15min and cooled to the pouring temperature in preparation for die casting. The pouring temperature was 710℃. Then Al-4Ti-2B nanocrystalline seed alloy was added to the melt. The particles contained in Al-4Ti-2B nanocrystalline seed alloy are nanoparticles. The average particle size of TiB2 particles in the nanoparticles is 400 nm. The mixture was mechanically stirred for 10s and then the melt was kept at 710℃.

[0080] Note: In this comparative example, the addition method is to add the mixture after rotary degassing and mechanically stir for 10 seconds.

[0081] (3) High pressure die casting: Heat the mold to keep the mold temperature at 200℃, pour the aluminum liquid into the barrel, the slow injection speed is 0.3m / s, the fast injection speed is 3m / s, the pressure is 100MPa, after the die casting is completed, take the casting out from the separated mold and water cool it. The time interval between demolding and water cooling is 15s, and the cooling rate is controlled at about 70℃ / s.

[0082] Comparative Example 5

[0083] The alloy composition of the non-standardized aluminum alloy die-casting part prepared in this comparative example is as follows: Si: 8.32 wt.%, Mn: 0.54 wt.%, Fe: 0.31 wt.%, Mg: 0.32 wt.%, Ti: 0.12 wt.%, Sr: 0.017 wt.%, Zr: 0.11 wt.%, V: 0.003 wt.%, Cu: 0.016 wt.%, Zn: 0.003 wt.%, P: 0.001 wt.%, with the balance being Al.

[0084] The preparation steps for this comparative example of a non-corrective aluminum alloy die-cast part are as follows:

[0085] (1) Smelting: Pure aluminum ingots are melted at 800℃, and then Al-10Mn, Al-10Si, Al-10Ti and Al-10Zr are added in sequence. The mixture is kept at 800℃ for 1 hour to ensure uniform diffusion of elements. Then the temperature of the aluminum liquid is reduced to 720℃ and kept for 1.5 hours.

[0086] (2) Ultrasonic refining treatment: The refining temperature was 720℃. Refining was carried out under the condition of argon gas being introduced while the rotor was rotating. The gas flow rate was 6L / min and the rotation speed was 358r / min. First, Al-4Ti-2B nanocrystalline seed alloy was added. The particles contained in the Al-4Ti-2B nanocrystalline seed alloy were nanoparticles. The average particle size of TiB2 particles in the nanoparticles was 400 nm. After 5 min, Al-10Mg and Al-10Sr were added, and the melt was ultrasonically treated. The ultrasonic refining time was 15 min, and the total refining time was 20 min. After refining, the slag was removed, and then the alloy liquid was kept at a constant temperature for 15 min. Then, it was cooled to the pouring temperature of 710℃ in preparation for die casting.

[0087] Note: The difference between this comparative example and Examples 1-3 is that Al-10Sr is used as the modifier instead of the Al-90Sr intermediate alloy in Examples 1-3.

[0088] (3) High pressure die casting: Heat the mold to keep the mold temperature at 200℃, pour the aluminum liquid into the barrel, the slow injection speed is 0.3m / s, the fast injection speed is 3m / s, the pressure is 100MPa, after the die casting is completed, take the casting out from the separated mold and water cool it. The time interval between demolding and water cooling is 15s, and the cooling rate is controlled at about 70℃ / s.

[0089] Flatness tests were conducted on the non-aligned aluminum alloy die castings prepared in Examples 1-2 and Comparative Examples 1-5, and the results are shown in Table 1.

[0090] This invention uses a coordinate measuring machine to measure the flatness of castings, and the standards followed are GB / T1182 and ISO1101. The specific operating procedure is as follows:

[0091] 1. Workpiece isothermal treatment (20±1℃, heat preservation ≥4h)

[0092] 2. Establish a reference coordinate system (3-2-1 positioning method)

[0093] 3. Collect point cloud data by grid (density ≥ 20 points / dm²)

[0094] 4. Fitting the reference plane using the least squares method.

[0095] Table 1

[0096] Case Flatness (mm / 300 mm) Example 1 0.15 Example 2 0.16 Example 3 0.14 Comparative Example 1 3.14 Comparative Example 2 2.95 Comparative Example 3 2.84 Comparative Example 4 3.12 Comparative Example 5 2.23

[0097] As can be seen from Table 1, the flatness of the die-cast parts prepared by Comparative Examples 1, 2, 3 and 4 is significantly higher than that of Examples 1-3. The flatness of all the comparative examples does not meet the conditions for direct assembly and requires subsequent straightening before assembly. However, the flatness of Examples 1-3 is ≤0.3 mm, which meets the conditions for direct assembly and does not require subsequent straightening treatment.

[0098] In Comparative Example 1, no nanocrystalline seed alloy was added, and the flatness of the die-cast parts prepared by this method was 2.1-4.7 mm. This indicates that the introduction of nano-TiB2 can significantly optimize the filling of the solid-liquid mixed phase and the grain feeding behavior during the die-casting process, reduce the residual strain in the casting, and thus optimize the flatness of the casting. Comparative Example 2, however, added the same amount of conventional Al-5Ti-B seed alloy, and the resulting casting flatness was 1.5-3.6 mm, significantly higher than that of Examples 1-3. Conventional Al-5Ti-B contains micron-sized TiB2 and Al3Ti particles, indicating that the optimization effect of this grain refiner on the filling behavior of the casting under die-casting conditions is not as good as that of the nano-TiB2 seed alloy used in Examples 1-3. The difference between Comparative Example 3 and Examples 1-3 is that the time interval from demolding to entering the water tank is 5 seconds, lower than the 15 seconds in Examples 1-3. However, the flatness of the castings prepared in Comparative Example 3 was 2.3-4.5 mm, still higher than that of Examples 1-3. This indicates that even when using nanocrystalline seed alloys to control the solidification structure of die castings, a suitable cooling method is still required to ensure the casting's flatness meets the requirements for direct assembly. Comparative Example 4 used the same nanocrystalline TiB2 seed alloy as Examples 1-3, but it was added after rotary degassing and mechanically stirred for 10 seconds. This suggests that adding TiB2 particles during rotary degassing facilitates particle dispersion and sufficient contact with the melt, thereby maximizing its heterogeneous nucleation ability and optimizing the flatness of the die casting.

[0099] The difference between Comparative Example 5 and Examples 1-3 is the use of Al-10Sr as a modifier. Since the Sr content of this intermediate alloy is 1 / 9 that of Al-90Sr, the amount added is significantly increased. This necessitates increased melting and stirring time, thus increasing the risk of gas entrapment and consequently deteriorating the melt quality. This indicates that using Al-90Sr can effectively improve production efficiency and melt quality, making it suitable for mass production in the die-casting industry.

[0100] The above case results demonstrate that the present invention can optimize the flatness of die castings by synergistically controlling the alloy composition, the type of intermediate alloy, the type and method of adding nano-TiB2 seed alloy, and the cooling method after demolding, thereby obtaining die castings that can be directly assembled without straightening.

[0101] The Al-4Ti-2B nanocrystalline seed alloy used in this invention is prepared as follows: A uniformly mixed mixture of K2TiF6 powder and KBF4 powder is added to molten aluminum made from industrial pure aluminum. The mixture is held at 730-800℃ for 30-60 minutes, followed by 30-60 minutes of rotary degassing. After standing for 30 minutes, slag is removed, and the mixture is then cast onto a disc casting machine to obtain the Al-4Ti-2B nanocrystalline seed alloy. The mass ratio of K2TiF6 powder, KBF4 powder, and industrial pure aluminum is 1:1.5:3.5.

Claims

1. A non-alignment integrated die-casting part, characterized in that... The alloy composition of the die-cast parts is: Si: 7.10-10.30 wt.%, Mn: 0.3-0.6 wt.%, Fe: 0.06-0.7 wt.%, Mg: 0.21-0.45 wt.%, Ti: 0.05-0.15wt.%, Sr: 0.01-0.02 wt.%, Zr: 0.10-0.15 wt.%, V: ≤0.02wt.%, Cu: ≤0.03wt.%, Zn: ≤0.02wt.%, P: ≤0.002wt.%, the balance is Al; The method for preparing the shape-free integrated die-cast part includes the following steps performed sequentially: Step (1) Smelting: After the pure aluminum is melted, Al-Mn master alloy, Al-Si master alloy, Al-Ti master alloy and Al-Zr master alloy are added in sequence, and then the mixture is kept at a constant temperature. The Sr content in Al-Sr master alloys is 85%-95%; Step (2) Refining: First, add Al-4Ti-2B nanocrystalline seed alloy, and after 5-15 min, add Al-Mg master alloy and Al-Sr master alloy. Under the condition of passing in inert gas, perform rotary degassing and refining. The refining temperature is 700-730℃. After refining, remove slag and keep warm. Step (3) Die casting: Pour the alloy liquid into the mold, die cast, demold, and water cool to obtain an integral die casting part that does not require straightening; In step (3), the mold temperature is maintained at 130-220℃; the pouring temperature is 680-720℃; the die casting parameters are: slow injection speed is 0.2-0.5m / s, fast injection speed is 1m / s-4m / s, and the holding pressure is 100~120MPa; the water cooling parameters are: after the casting is opened, it is placed in a water tank for cooling within 15-30s, and the cooling rate is controlled at 50-80℃ / s.

2. The non-alignment integrated die-casting part as described in claim 1, characterized in that... The alloy composition of the die-cast parts is: Si: 7.10-9.0 wt.%, Mn: 0.3-0.55 wt.%, Fe: 0.09-0.5 wt.%, Mg: 0.21-0.35 wt.%, Ti: 0.05-0.12wt.%, Sr: 0.01-0.02 wt.%, Zr: 0.10-0.15 wt.%, V: ≤0.02wt.%, Cu: ≤0.03wt.%, Zn: ≤0.02wt.%, P: ≤0.002wt.%, and the balance is Al.

3. The method for preparing the shape-free integrated die-cast part according to claim 1 or 2, characterized in that... This includes the following steps performed sequentially: Step (1) Smelting: After the pure aluminum is melted, Al-Mn master alloy, Al-Si master alloy, Al-Ti master alloy and Al-Zr master alloy are added in sequence, and then the mixture is kept at a constant temperature. Step (2) Refining: Add Al-4Ti-2B nanocrystalline seed alloy, Al-Sr master alloy and Al-Mg master alloy, and carry out rotary degassing and refining under the condition of passing inert gas. After refining, remove slag and keep warm. Step (3) Die casting: Pour the alloy liquid into the mold, die cast, demold, and water cool to obtain an integrated die casting part that does not require straightening.

4. The method for preparing the integral die-cast part without straightening as described in claim 3, characterized in that: In step (1), pure aluminum is melted at 750-800℃, and after adding intermediate alloy, it is kept at 750-800℃ for 0.5-2h; then cooled to 720-760℃ and kept at 750-800℃ for another 0.5-2h. In step (2), the refining temperature is 700-730℃, and the refining is carried out under the condition of rotating rotor and introducing inert gas; first, Al-4Ti-2B nanocrystalline seed alloy is added, and after 5-15 min, Al-Mg master alloy and Al-Sr master alloy are added and the melt is ultrasonically treated for 5-15 min; then the alloy liquid is kept at the temperature for 10-30 min. In step (3), the mold temperature is maintained at 130-220℃; the pouring temperature is 680-720℃; the die casting parameters are: slow injection speed is 0.2-0.5m / s, fast injection speed is 1m / s-4m / s, and the holding pressure is 100~120MPa; the water cooling parameters are: after the casting is opened, it is placed in a water tank for cooling within 15-30s, and the cooling rate is controlled at 50-80℃ / s.

5. The method for preparing an integrated die-cast part without straightening as described in claim 3 or 4, characterized in that: The Mn content in the Al-Mn master alloy is 5%-30%; And / or, the Si content in the Al-Si master alloy is 5%-30%; And / or, the Ti content in the Al-Ti master alloy is 5%-30%; And / or, the Mg content in the Al-Mg master alloy is 5%-30%; And / or, the Sr content in the Al-Sr master alloy is 85%-95%; And / or, the Zr content in the Al-Zr master alloy is 5%-30%.

6. The method for preparing an integrated die-cast part without straightening as described in claim 5, characterized in that: The Al-Mn contains 10% Mn; the Al-Si contains 10% Si; the Al-Ti contains 10% Ti; the Al-Mg contains 10% Mg; the Al-Sr contains 90% Sr; and the Al-Zr contains 10% Zr.

7. The method for preparing an integrated die-cast part without straightening as described in claim 3 or 4, characterized in that: The Al-4Ti-2B nanocrystalline seed alloy contains nanoparticles, and the average particle size of TiB2 particles in the nanoparticles is 100nm-600nm. And / or, the Al-4Ti-2B nanocrystalline seed alloy is prepared according to the following method: The uniformly mixed K2TiF6 powder and KBF4 powder were added to the molten aluminum from industrial pure aluminum and held at 730-800℃ for 30-60 min, followed by 30-60 min of rotary degassing. After standing, the slag was removed and the mixture was then cast to obtain Al-4Ti-2B nanocrystalline seed alloy. The mass ratio of K2TiF6 powder, KBF4 powder and industrial pure aluminum was (0.8-1.1):(1.4-2.0):(3.3-4.1).

8. The method for preparing the integral die-cast part without straightening according to claim 3 or 4, characterized in that: The inert gas is nitrogen and / or argon; the inert gas flow rate is 4-8 L / min.

9. The non-alignment integrated die-casting part according to claim 1 or 2 is applied to automotive body structural parts.

10. The die casting prepared by the method of any one of claims 3-8 is applied to automotive body structural parts.