Renewable high-pressure casting heat-treatment-free aluminum alloy as well as preparation method and application thereof

Abstract

The invention discloses a renewable high-pressure casting heat-treatment-free aluminum alloy and a preparation method and application thereof.The microstructure in an alloy body comprises an alpha-Al matrix, an Al-Si eutectic structure and a Fe-containing second phase, and the equivalent diameter of the alpha-Al matrix is smaller than or equal to 15 micrometers, the equivalent diameter of a pre-crystallization structure is smaller than or equal to 30 micrometers, and the equivalent diameter of the Al-Si eutectic structure is smaller than or equal to 30 micrometers. The area proportion of the pre-crystallization structure on an observation interface is smaller than or equal to 15%, the pre-crystallization structure comprises a primary alpha-Al phase and a primary Fe-rich phase, and the average equivalent diameter of the Fe-containing second phase is smaller than or equal to 10 micrometers. The preparation method has the following advantages that the cost is low, the mechanical property is excellent, the raw material source is wide, and the tolerance to impurity elements such as Fe content is high; a heat treatment process is not needed, and energy conservation and emission reduction are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy casting, and specifically relates to a renewable high-pressure casting heat-treatment-free aluminum alloy, a preparation method and an application thereof. Background Art

[0002] With the development of lightweight automobiles and the country's emphasis on and requirements for dual carbon goals, high vacuum die casting is currently mostly used for the production of large thin-walled structural parts such as car bodies, and heat treatment is usually required to meet the performance requirements of the car body. However, large thin-walled structural parts are easily deformed during heat treatment, causing casting failure, and heat treatment also leads to increased costs and increased carbon emissions. Therefore, the automotive aluminum alloy processing industry is currently actively developing heat-treatment-free alloys that meet performance requirements, especially heat-treatment-free toughened die-cast aluminum alloys will be the new favorite of the automotive industry.

[0003] The emergence of heat-treatment-free aluminum alloys has brought great advantages in cost and performance of body and chassis structural parts. Currently, the widely used and technologically mature heat-treatment-free alloys on the market mainly include the following:

[0004] In the 1990s, German aluminum company Rheinfelden GmbH developed the first high-ductility die-casting aluminum alloy, the Silafont-36 series aluminum alloy, which is the A365.0 alloy of the US standard. In addition, their company's Castasil-37 alloy is a high-toughness Al-Si alloy with a cast tensile strength of 250-300 MPa and an elongation of more than 12%. Without adding Mg elements for aging strengthening, the strength of the alloy is improved mainly by adding Mo, Zr and other elements to form fine dispersed phases containing Mo and Zr during the die-casting process. It has a great relationship with the wall thickness of the die-casting. The thinner the wall thickness, the faster the cooling rate, the smaller the grain size, and the higher the alloy strength of the final die-casting. This alloy is particularly suitable for the thin-walled, high-strength and high-toughness requirements of lightweight body parts.

[0005] Alcoa developed EZCAST TM Series C611 heat-treatment-free Al-Si die-casting aluminum alloy, etc., EZCAST TM The series of alloys were successfully developed by Alcoa in the 1990s and successfully applied to the structural parts of the all-aluminum body of Audi A8; C611 is a high-performance Al-Si die-casting aluminum alloy specially developed for lightweight thin-walled structural parts of automobiles. The silicon content of C611 alloy is equivalent to that of the most widely used cast aluminum alloy A356, and it has very good fluidity. It has been widely used by many die-casting manufacturers in Europe and the United States for the production of thin-walled structural parts (such as shock towers) for many years. At present, C611 alloy has been used in major domestic aluminum alloy body structural parts die-casting plants, and good results have been achieved.

[0006] Others include the die-cast aluminum alloys Aural-2 and Aural-3 developed by Alcan, which are also Al-Si-Mg-Mn alloys, with an upper limit of 0.2% Fe and 0.5% Mn. The ADC3SF alloy developed by Japan has an even lower Mn content of only 0.3-0.4%.

[0007] Chinese invention CN114438380A discloses a heat-treatment-free Al-Si aluminum alloy and a preparation method thereof, which obtains a uniform and dense microstructure by La+Ce addition combined with pressure casting, thereby achieving the effect of improving mechanical properties. However, rare earth elements are expensive, which increases production costs and cannot be industrially applied;

[0008] Chinese invention CN110079712A and Chinese invention CN113755722A both use relatively high purity electrolytic aluminum, industrial silicon and other additive materials, and strictly control the range of trace elements such as Ca, Na, P and other impurity elements, limit the content of impurity Fe, and limit the source of raw materials. They can only be prepared by casting raw materials such as pure aluminum and intermediate alloys. Compared with using recycled aluminum alloys as raw materials, the cost is high and the process is long.

[0009] Chinese invention CN114717455A and Chinese invention CN115003832A both add some trace elements to the alloy, such as 0-1.5wt.% Ni, 0.01-0.15wt.% Zr, 0.05-0.15wt.% V, 0.05-0.15wt.% Mo, etc. Excessive addition of alloying elements will damage the plasticity of the alloy and increase the production cost.

[0010] Therefore, in view of the above technical problems, it is necessary to provide a renewable high-pressure casting heat-treatment-free aluminum alloy, a preparation method and an application thereof.

[0011] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0012] The object of the present invention is to provide a renewable high pressure casting heat treatment-free aluminum alloy, a preparation method and an application thereof.

[0013] In order to achieve the above object, a technical solution provided by a specific embodiment of the present invention is as follows:

[0014] Aluminum alloy, the microstructure in the alloy body includes an α-Al matrix, an Al-Si eutectic structure and an Fe-containing second phase, and satisfies: the equivalent diameter of the α-Al matrix is ​​less than or equal to 15μm, the equivalent diameter of the pre-crystallization structure is less than or equal to 30μm, the area of ​​the pre-crystallization structure at the observation interface accounts for less than or equal to 15%, and the pre-crystallization structure includes a primary α-Al phase and a primary Fe-rich phase. Preferably, the tensile strength of the aluminum alloy is greater than or equal to 260MPa, the yield strength is greater than or equal to 140MPa, and the elongation is greater than or equal to 10%. In the high-pressure casting process, the pre-crystallization structure mainly includes a primary α-Al phase and a primary Fe-rich phase, among which the primary α-Al phase is the most important. The primary α-Al phase is usually larger in size and has a high degree of dendrite formation, while the primary Fe-rich phase usually forms a dendrite network structure together with the primary α-Al phase, and the content accounts for a very low proportion.

[0015] In one or more embodiments of the present invention, the size of the Al-Si eutectic structure is less than or equal to 10 μm, and the morphology of the eutectic Si particles is fibrous or spherical.

[0016] In one or more embodiments of the present invention, the Al-Si eutectic structure is a mixture of eutectic Si and Al, which is obtained by eutectic reaction when the temperature is reduced to the eutectic temperature. The content of Si in the eutectic structure is about 12.6wt%. The starting temperature of the eutectic reaction of the alloy is 577±1°C. For example, at about 576°C, a eutectic reaction will occur to form eutectic Al and Si phases. During the eutectic reaction, Al and Si in the remaining liquid phase will nucleate and grow, thereby forming a eutectic structure.

[0017] In one or more embodiments of the present invention, the Fe-containing second phase includes β-Al5FeSi, α-Al 15 (Fe,Mn,Cr)3Si2, π-Al9FeMg3Si5 phase.

[0018] In one or more embodiments of the present invention, the average equivalent diameter of the Fe-containing second phase is less than or equal to 10 μm, and the area proportion of the phase in the observed interface is less than or equal to 2.0%.

[0019] In one or more embodiments of the present invention, the morphology distribution of the Fe-containing second phase at the observation interface is block-shaped, Chinese character-shaped, or petal-shaped.

[0020] In one or more embodiments of the present invention, the aluminum alloy comprises: Si: 6.0-9.0wt.%, Mg: 0.05-0.3wt.%, Mn: 0.2-0.8wt.%, Cr: 0-0.3wt.%, Fe≤0.8wt.%, Sr: 0.015-0.03wt.%. The rest is Al and inevitable impurities. Preferably, the aluminum alloy comprises: Si: 6.5-8.5wt.%, Mg: 0.1-0.25wt.%, Mn: 0.3-0.6wt.%, Cr: 0.05-0.2wt.%, Fe≤0.5wt.%, Sr: 0.015-0.03wt.%. The rest is Al and inevitable impurities. Preferably, the aluminum alloy comprises: Si: 7.0-8.0 wt.%, Mg: 0.15-0.2 wt.%, Mn: 0.4-0.6 wt.%, Cr: 0.1-0.15 wt.%, Fe≤0.4 wt.%, Sr: 0.015-0.03 wt.%, and the balance is Al and unavoidable impurities.

[0021] In one or more embodiments of the present invention, the impurities are at least any one of the following: Cu≤0.50wt.%, Ni≤0.50wt.%, Zn≤1.5wt.%.

[0022] In one or more embodiments of the present invention, a method for preparing a renewable high pressure casting heat treatment-free aluminum alloy comprises the following steps:

[0023] S1: Pretreatment of scrap aluminum (pretreatment may include crushing and screening, magnetic separation, preheating and depainting, etc.);

[0024] S2: preparing and melting alloy raw materials, wherein the alloy raw materials include at least 30% of recycled aluminum alloy;

[0025] S3: refining and impurity removal;

[0026] S4: Deterioration and refinement

[0027] S5: Die casting.

[0028] Preferably, the preparation of the alloy raw material includes preheating and drying the alloy raw material. The preheating and drying temperature is 100-500° C. The alloy raw material is selected from pure metal, intermediate alloy or waste aluminum.

[0029] Preferably, the addition of scrap aluminum raw material is as follows: when recycled scrap aluminum is used as the raw material, the addition ratio of the scrap is 30% to 100%.

[0030] Preferably, the addition of scrap aluminum raw materials can be specifically done by adding purchased and sorted scrap aluminum materials into a smelting furnace after crushing, screening, magnetic separation, preheating and depainting. After the scrap aluminum materials are melted into molten aluminum, new materials such as intermediate alloys or pure aluminum ingots are added according to the actual measured composition, and the composition is adjusted to obtain the target aluminum alloy.

[0031] Preferably, the addition of new materials such as intermediate alloys or pure aluminum ingots is to first heat the pure Al ingot, Al-Si or quick-dissolving silicon to 720-760°C, and then add intermediate alloys such as Al-Mn, Al-Cr, Al-Fe after the raw materials are completely melted. After complete melting, stir evenly, then cool to 700-720°C, add pure Mg to melt, stir evenly, stir for 5-10 minutes, and then let stand for 5-10 minutes.

[0032] Preferably, the refining and impurity removal includes applying protective gas degassing to the alloy melt obtained by melting, and then adding refining agent, refiner, modifier, etc., and removing the surface scum after completion. Preferably, the applied protective gas is one or more of high-purity nitrogen and high-purity argon, the degassing temperature is 740-760°C, the degassing time is 10-30min, and the amount of refining agent added is 0.15-1.5wt.%. Preferably, the modifier is Al10Sr master alloy. Preferably, the refiner is Al-5Ti-B or TCB. Preferably, the amount of modifier added is 0.015-0.03wt.%. Preferably, the amount of refiner added is 0.15-0.3wt.%.

[0033] In one or more embodiments of the present invention, the renewable high pressure casting heat-free aluminum alloy is used in large integrated die casting. Preferably, the casting conditions in the integrated casting application are: the casting temperature is 680-710°C, and the mold temperature of the high pressure casting is 180-200°C.

[0034] In one or more embodiments of the present invention, the scrap aluminum used in the recycled aluminum alloy is selected from scrap aluminum alloy wheels, scrap engine hoods, scrap battery shells, steering knuckles, brake calipers, and packaging materials for beverages and foods. Preferably, the scrap aluminum grades used to recycle the recycled aluminum alloy are selected from 1xxx, 2xxx, 3xxx, 4xxx, 5xxx, 6xxx, 7xxx, 8xxx, etc. In addition, the recycled scrap aluminum may inevitably contain a small amount of impurities, such as Cu, Ni, Zn, etc.

[0035] Compared with the prior art, the renewable high-pressure casting heat-treatment-free aluminum alloy, preparation method and application of the present invention have the following advantages: low cost, the added elements are all common aluminum alloy intermediate elements, with few types, low content and low price; excellent mechanical properties, elongation in cast state ≥10%, yield strength ≥125MPa, and tensile strength ≥260MPa; wide source of raw materials, recycled aluminum can be directly used as raw material, the proportion of waste addition is high, and the tolerance for impurity elements such as Fe content is high; no heat treatment process is required, energy saving and emission reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 This is the Fe-rich phase morphology after Mn and Cr composite modification in one embodiment of the present invention.

[0038] Figure 2 is the microstructure diagram of the A1 alloy in Example 1;

[0039] Figure 3 is the microstructure diagram of the A2 alloy in Example 2;

[0040] Figure 4 This is the tensile fracture morphology of the B1 alloy in Comparative Example 1. DETAILED DESCRIPTION

[0041] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0042] In the following embodiments, the main alloy system of AlSiMgMnCr(Fe) is taken as an example to illustrate the scheme of the present invention. In this alloy:

[0043] Si element: A medium content of silicon can ensure that the alloy has sufficient fluidity and form a eutectic structure (secondary α-Al+Si) in the alloy to strengthen the alloy;

[0044] Mn element: refines grains, prevents mold sticking, and regulates iron phase. It plays different roles depending on the Fe content in the alloy: under low iron (≤0.2wt.%) conditions, it mainly plays a role in improving mold sticking; under high iron content (≥0.2wt.%), it mainly plays a role in regulating the iron phase;

[0045] Mg element: A small amount of Mg is added to increase the tensile strength and yield limit, and improve the machinability of the alloy;

[0046] Cr element: refines grains, regulates iron phase, and controls the dispersion and precipitation of primary phase;

[0047] Fe element: Recycled aluminum scrap can be used directly without additional Fe removal and reduction process, and the Fe tolerance is higher;

[0048] Sr element: Modifies Si to prevent deterioration of performance;

[0049] TCB / Al-Ti-B: grain refinement.

[0050] Embodiment 1:

[0051] The present embodiment discloses a high-pressure casting heat-treatment-free aluminum alloy A1, the components and weight percentages of which are: Si: 8.8wt.%, Mg: 0.18wt.%, Mn: 0.43wt.%, Cr: 0.08wt.%, Fe: 0.18%, and the rest are Al and unavoidable impurities. The preparation method of the high-pressure casting aluminum alloy based on the above components in the present embodiment includes the following steps: S1, batching: weigh the raw materials quantitatively according to the designed components, and fully dry them in a drying furnace at 300°C. S2, smelting: add pure Al and Al-Si alloy into the smelting furnace and melt them at 730°C; after the melting is completed, add Al-Fe, Al-Mn, Al-Cr and other intermediate alloys to continue smelting, and after it is completely melted, add pure Mg ingot through the pressure cover, and stir for 10 minutes to obtain a uniform melt. S3, refining: 740 ℃ into the aluminum alloy melt into high purity argon, while degassing add 0.15wt.% refining agent NK5048F2A, argon gas flow rate 0.1L / min, refining time 20min, after standing for 5min, 720 ℃ add 0.03% Sr modifier, after stirring and standing, add 0.3% TCB refiner, after stirring and standing, remove slag and impurities. S4, die casting: the refined aluminum alloy melt high pressure die casting to obtain the aluminum alloy, casting temperature 700 ℃, mold temperature 200 ℃.

[0052] The high-pressure casting heat-treatment-free aluminum alloy has a fracture elongation of 12.4% in the cast state, a yield strength of 133 MPa, and a tensile strength of 266 MPa.

[0053] Embodiment 2:

[0054] The present embodiment discloses a high-pressure casting heat-treatment-free aluminum alloy A2, the components and weight percentages of which are: Si: 7.7wt.%, Mg: 0.14wt.%, Mn: 0.65wt.%, Cr: 0.16wt.%, Fe: 0.49%, and the rest are Al and unavoidable impurities. The preparation method of the high-pressure casting aluminum alloy based on the above components in the present embodiment includes the following steps: S1, batching: weigh the raw materials quantitatively according to the designed components, and fully dry them in a drying furnace at 300°C. S2, smelting: add pure Al and Al-Si alloy into the smelting furnace and melt them at 730°C; after the melting is completed, add Al-Fe, Al-Mn, Al-Cr and other intermediate alloys to continue smelting, and after it is completely melted, add pure Mg ingot through the pressure cover, and stir for 10 minutes to obtain a uniform melt. S3, refining: 740 ℃ into the aluminum alloy melt into high purity argon, while degassing add 0.15wt.% refining agent NK5048F2A, argon gas flow rate 0.1L / min, refining time 20min, after standing for 5min, 720 ℃ add 0.02% Sr modifier, after stirring and standing, add 0.2% TCB refiner, after stirring and standing, remove slag and impurities. S4, die casting: the refined aluminum alloy melt high pressure die casting to obtain the aluminum alloy, casting temperature 690 ℃, mold temperature 200 ℃.

[0055] The high-pressure casting heat-treatment-free aluminum alloy has a fracture elongation of 10.2% in the cast state, a yield strength of 126 MPa, and a tensile strength of 260 MPa.

[0056] Embodiment 3:

[0057] The present embodiment discloses a high-pressure casting heat-treatment-free aluminum alloy A3, the components and weight percentages of which are: Si: 6.7wt.%, Mg: 0.26wt.%, Mn: 0.75wt.%, Cr: 0.1wt.%, Fe: 0.72%, and the rest are Al and unavoidable impurities. The preparation method of the high-pressure casting aluminum alloy based on the above components in the present embodiment includes the following steps: S1, batching: weigh the raw materials quantitatively according to the designed components, and fully dry them in a drying furnace at 300°C. S2, smelting: add pure Al and Al-Si alloy into the smelting furnace and melt them at 730°C; after the melting is completed, add Al-Fe, Al-Mn, Al-Cr and other intermediate alloys to continue smelting, and after it is completely melted, add pure Mg ingot through the pressure cover, and stir for 10 minutes to obtain a uniform melt. S3, refining: 740 ℃ into the aluminum alloy melt into high purity argon, while degassing add 0.15wt.% refining agent NK5048F2A, argon gas flow rate 0.1L / min, refining time 30min, after standing for 5min, 720 ℃ add 0.02% Sr modifier, after stirring and standing, add 0.25% TCB refiner, after stirring and standing, remove slag and impurities. S4, die casting: the refined aluminum alloy melt high pressure die casting to obtain the aluminum alloy, casting temperature 690 ℃, mold temperature 180 ℃.

[0058] The high pressure casting heat treatment-free aluminum alloy has a cast elongation of 10.3%, a yield strength of 142MPa, and a tensile strength of 264MPa. This is mainly due to the excessive Fe content in the alloy, which generates a large amount of brittle Fe-containing phases, greatly damaging the mechanical properties of the alloy.

[0059] Embodiment 4:

[0060] The present embodiment discloses a high-pressure casting heat-free aluminum alloy A4, in which 35wt.% of 4xxx and 5xxx mixed scrap aluminum is added, and the scrap aluminum is pre-crushed, screened, magnetically separated, and preheated and depainted before being added to the smelting furnace. After adding scrap aluminum to the raw materials, the composition of the alloy is adjusted to: Si: 7.0wt.%, Mg: 0.16wt.%, Mn: 0.42wt.%, Cr: 0.14wt.%, Fe: 0.27wt.%, and the rest is Al and unavoidable impurities, including impurities Cu: 0.22wt.%, Ni: 0.48wt.%, and Zn: 0.15wt.%. The preparation method of the high-pressure casting aluminum alloy based on the above composition in the present embodiment includes the following steps: S1, batching: quantitatively weigh the raw materials according to the designed composition, and fully dry them at 300°C in a drying furnace. S2. Melting: Add the pre-treated waste aluminum into the melting furnace and melt it at 730°C; after the melting is completed, add pure Al, Al-Si, Al-Fe, Al-Mn, Al-Cr and other intermediate alloys to continue melting, and add pure Mg ingots through the pressure cover after it is completely melted, and stir for 10 minutes to obtain a uniform melt. S3. Refining: Pass high-purity argon gas into the aluminum alloy melt at 740°C, add 0.2wt.% refining agent NK4847F5A while degassing, the argon gas flow rate is 0.1L / min, the refining time is 15min, and after standing for 5min, add 0.02% Sr modifier at 720°C, add 0.25% TCB refiner after stirring and standing, and remove slag and impurities after stirring and standing. S4. Die casting: The refined aluminum alloy melt is high-pressure die-cast to obtain the aluminum alloy, the casting temperature is 705°C, and the mold temperature is 180°C.

[0061] The high-pressure casting heat-treatment-free aluminum alloy has a fracture elongation of 11.2% in the cast state, a yield strength of 138 MPa, and a tensile strength of 267 MPa.

[0062] Embodiment 5:

[0063] The present embodiment discloses a high pressure casting heat-free aluminum alloy A5, in which 60wt.% of 2xxx, 3xxx and 6xxx mixed scrap aluminum is added, and the scrap aluminum is pre-crushed, screened, magnetically separated, and preheated and depainted before being added into the smelting furnace. After adding scrap aluminum to the raw materials, the composition of the alloy is adjusted to: Si: 7.2wt.%, Mg: 0.19wt.%, Mn: 0.41wt.%, Cr: 0.14wt.%, Fe: 0.35%, and the rest is Al and unavoidable impurities, including impurities Cu: 0.45wt.%, Ni: 0.13wt.%, and Zn: 0.26wt.%. The preparation method of the high pressure casting aluminum alloy based on the above composition in the present embodiment includes the following steps: S1, batching: quantitatively weigh the raw materials according to the designed composition, and fully dry them at 300℃ in a drying furnace. S2, smelting: add the pre-treated waste aluminum into the smelting furnace and melt it at 730℃; after the melting is completed, add pure Al, Al-Si, Al-Fe, Al-Mn, Al-Cr and other intermediate alloys to continue smelting, and add pure Mg ingots through the pressure cover after it is completely melted, and stir for 10 minutes to obtain a uniform melt. S3, refining: pass high-purity argon gas into the aluminum alloy melt at 740℃, add 0.15wt.% refining agent NK4847F5A while degassing, the argon gas flow rate is 0.1L / min, the refining time is 20min, and after standing for 5min, add 0.025% Sr modifier at 720℃, add 0.2% TCB refiner after stirring and standing, and remove slag and impurities after stirring and standing. S4, die casting: the refined aluminum alloy melt is high-pressure die-cast to obtain the aluminum alloy, the casting temperature is 695℃, and the mold temperature is 190℃.

[0064] The high-pressure casting heat-treatment-free aluminum alloy has a fracture elongation of 10.9% in the cast state, a yield strength of 131 MPa, and a tensile strength of 265 MPa.

[0065] Embodiment 6:

[0066] The present embodiment discloses a high pressure casting heat-free aluminum alloy A6, in which 75wt.% of 1xxx, 6xxx and 7xxx mixed scrap aluminum is added, and the scrap aluminum is pre-crushed, screened, magnetically separated, and preheated and depainted before being added into the smelting furnace. After adding scrap aluminum to the raw materials, the composition of the alloy is adjusted to: Si: 8.2wt.%, Mg: 0.21wt.%, Mn: 0.5wt.%, Cr: 0.15wt.%, Fe: 0.44%, and the rest is Al and unavoidable impurities, including impurities Cu: 0.16wt.%, Ni: 0.14wt.%, and Zn: 1.43wt.% introduced from the mixed scrap aluminum. The preparation method of the high pressure casting aluminum alloy based on the above composition in the present embodiment includes the following steps: S1, batching: quantitatively weigh the raw materials according to the designed composition, and fully dry them at 300℃ in a drying furnace. S2, smelting: add the pre-treated waste aluminum into the smelting furnace and melt it at 730℃; after the melting is completed, add pure Al, Al-Si, Al-Fe, Al-Mn, Al-Cr and other intermediate alloys to continue smelting, and add pure Mg ingots through the pressure cover after it is completely melted, and stir for 10 minutes to obtain a uniform melt. S3, refining: pass high-purity argon gas into the aluminum alloy melt at 740℃, add 0.15wt.% refining agent NK4847F5A while degassing, the argon gas flow rate is 0.1L / min, the refining time is 25min, and after standing for 5min, add 0.03% Sr modifier at 720℃, add 0.3% TCB refiner after stirring and standing, and remove slag and impurities after stirring and standing. S4, die casting: the refined aluminum alloy melt is high-pressure die-cast to obtain the aluminum alloy, the casting temperature is 705℃, and the mold temperature is 200℃.

[0067] The high-pressure casting heat-treatment-free aluminum alloy has a fracture elongation of 10.4% in the cast state, a yield strength of 127 MPa, and a tensile strength of 261 MPa.

[0068] Example 7

[0069] The difference between this embodiment and embodiment 1 is that the aluminum alloy comprises Si: 6.0wt.%, Mg: 0.05wt.%, Mn: 0.2wt.%, Fe: 0.8wt.%, and the rest is Al and unavoidable impurities. During smelting, Sr: 0.015wt.%, 0.02wt.% refining agent NK4847F5A, and 0.2wt.% TCB refiner are used.

[0070] Example 8

[0071] The difference between this embodiment and embodiment 1 is that the aluminum alloy comprises Si: 7.5wt.%, Mg: 0.15wt.%, Mn: 0.6wt.%, Cr: 0.1wt.%, Fe: 0.6wt.%, and the rest is Al and unavoidable impurities. During smelting, Sr: 0.02wt.%, 0.025wt.%, refining agent NK4847F5A, and 0.2wt.5% TCB refiner are used.

[0072] Example 9

[0073] The difference between this embodiment and embodiment 1 is that the aluminum alloy comprises Si: 9.0wt.%, Mg: 0.3wt.%, Mn: 0.8wt.%, Cr: 0.3wt.%, Fe: 0.7wt.%, and the rest is Al and unavoidable impurities. During smelting, Sr: 0.03wt.%, 0.03wt.% refining agent NK4847F5A, and 0.3wt.% TCB refiner.

[0074] Example 10

[0075] The only difference between this embodiment and embodiment 6 is that the impurities introduced by smelting scrap aluminum include Cu 0.50wt.%, Ni 0.50wt.%, and Zn 1.5wt.%.

[0076] Embodiment 11

[0077] The only difference between this embodiment and embodiment 6 is that the impurities introduced by smelting scrap aluminum include 0.50 wt.% Cu.

[0078] Example 12

[0079] The only difference between this embodiment and embodiment 6 is that the impurities introduced by smelting scrap aluminum include Ni 0.50wt.%, Zn 1.5wt.%.

[0080] Embodiment 13

[0081] The only difference between this embodiment and embodiment 6 is that the impurities introduced by smelting scrap aluminum include 0.50 wt.% Ni.

[0082] Embodiment 14

[0083] The difference between this embodiment and embodiment 6 is that the impurities introduced by smelting waste aluminum include Zn 1.5wt.%. Comparative Example 1:

[0084] The present embodiment discloses a high-pressure casting heat-free aluminum alloy B1, the components and weight percentages of which are: Si: 7.6wt.%, Mg: 0.12wt.%, Mn: 0.55wt.%, Cr: 0.18wt.%, Fe: 1.08wt.%, and the rest are Al and unavoidable impurities. The preparation method of the high-pressure casting aluminum alloy based on the above components in the present embodiment includes the following steps: S1, batching: weigh the raw materials quantitatively according to the designed components, and fully dry them in a drying furnace at 300°C. S2, smelting: add pure Al and Al-Si alloy into the smelting furnace and melt them at 730°C; after the melting is completed, add Al-Fe, Al-Mn, Al-Cr and other intermediate alloys to continue smelting, and after it is completely melted, add pure Mg ingot through the pressure cover, and stir for 10 minutes to obtain a uniform melt. S3, refining: 740 ℃ into the aluminum alloy melt into high purity argon, while degassing add 0.15wt.% refining agent NK5048F2A, argon gas flow rate 0.1L / min, refining time 20min, after standing for 5min, 720 ℃ add 0.025% Sr modifier, after stirring and standing, add 0.25% TCB refiner, after stirring and standing, remove slag and impurities. S4, die casting: the refined aluminum alloy melt high pressure die casting to obtain the aluminum alloy, casting temperature 695 ℃, mold temperature 185 ℃.

[0085] The high-pressure casting heat-treatment-free aluminum alloy has a fracture elongation of 3.9% in the cast state, a yield strength of 108 MPa, and a tensile strength of 201 MPa. Figure 4 This is the tensile fracture of B1 alloy. Analysis shows that the cracks mainly initiate from the Fe-containing phase. Due to the high Fe content in the alloy, a large amount of brittle Fe-containing phase is generated. The proportion of brittle phase increases sharply, which greatly harms the mechanical properties of the alloy and causes the elongation to decrease.

[0086] Comparative Example 2:

[0087] The present embodiment discloses a high-pressure casting heat-treatment-free aluminum alloy B2, the components and weight percentages of which are: Si: 7.1wt.%, Mg: 0.45wt.%, Mn: 0.48wt.%, Cr: 0.21wt.%, Fe: 0.66wt.%, and the rest are Al and unavoidable impurities. The preparation method of the high-pressure casting aluminum alloy based on the above components in the present embodiment includes the following steps: S1, batching: weigh the raw materials quantitatively according to the designed components, and fully dry them in a drying furnace at 300°C. S2, smelting: add pure Al and Al-Si alloy into the smelting furnace and melt them at 730°C; after the melting is completed, add Al-Fe, Al-Mn, Al-Cr and other intermediate alloys to continue smelting, and after it is completely melted, add pure Mg ingot through the pressure cover, and stir for 10 minutes to obtain a uniform melt. S3, refining: 740 ℃ into the aluminum alloy melt into high purity argon, while degassing add 0.15wt.% refining agent NK5048F2A, argon gas flow rate 0.1L / min, refining time 20min, after standing for 5min, 720 ℃ add 0.025% Sr modifier, after stirring and standing, add 0.25% TCB refiner, after stirring and standing, remove slag and impurities. S4, die casting: the refined aluminum alloy melt high pressure die casting to obtain the aluminum alloy, casting temperature 695 ℃, mold temperature 185 ℃.

[0088] The high pressure casting heat treatment-free aluminum alloy has a cast elongation of 5.2%, a yield strength of 156MPa, and a tensile strength of 244MPa. This is mainly due to the excessive Mg content in the alloy. Although the yield strength is significantly improved, the elongation of the material is seriously reduced.

[0089] Comparative Example 3:

[0090] The present embodiment discloses a high-pressure casting heat-treatment-free aluminum alloy B3, the components and weight percentages of which are: Si: 8.3wt.%, Mg: 0.25wt.%, Mn: 0.70wt.%, Cr: 0.38wt.%, Fe: 0.57wt.%, and the rest are Al and unavoidable impurities. The preparation method of the high-pressure casting aluminum alloy based on the above components in the present embodiment includes the following steps: S1, batching: weigh the raw materials quantitatively according to the designed components, and fully dry them in a drying furnace at 300°C. S2, smelting: add pure Al and Al-Si alloy into the smelting furnace and melt them at 730°C; after the melting is completed, add Al-Fe, Al-Mn, Al-Cr and other intermediate alloys to continue smelting, and after it is completely melted, add pure Mg ingot through the pressure cover, and stir for 10 minutes to obtain a uniform melt. S3, refining: 740 ℃ into the aluminum alloy melt into high purity argon, while degassing add 0.15wt.% refining agent NK5048F2A, argon gas flow rate 0.1L / min, refining time 20min, after standing for 5min, 720 ℃ add 0.025% Sr modifier, after stirring and standing, add 0.25% TCB refiner, after stirring and standing, remove slag and impurities. S4, die casting: the refined aluminum alloy melt high pressure die casting to obtain the aluminum alloy, casting temperature 695 ℃, mold temperature 185 ℃.

[0091] The high pressure casting heat treatment-free aluminum alloy has a cast elongation of 5.5%, a yield strength of 140MPa, and a tensile strength of 228MPa. This is mainly due to the excessive Cr content in the alloy, which generates a large amount of coarse primary Fe phase with a size greater than 50μm, resulting in local agglomeration of brittle phases and seriously reducing the elongation of the material.

[0092] The alloy embodiments of different compositions A1-A14 (corresponding to samples of Examples 1-14, respectively) and three comparative examples B1-B3 (corresponding to samples of Comparative Examples 1-3, respectively) were tested, and then compared with the C611 alloy which is currently more mature in application. The results show that the alloy composition within the protection scope of the present invention has better performance in strength and elongation than C611. The elongation El of the alloy within the protection scope of the present invention is ≥10%, σ 0.2 ≥125MPa,σ b ≥260MPa. Table 1 below is a table of components of the specific embodiment alloy and C611, and Table 2 below is a comparison of mechanical properties of the specific embodiment alloy, comparative alloy and C611.

[0093] Table 1: Specific Example Alloy and Comparative Example Composition Table (wt.%)

[0094]

[0095]

[0096] Table 2: Mechanical properties of specific example alloys and comparative examples

[0097]

[0098] By comparing Tables 1 and 2 above, it is found that alloying elements such as Fe, Mg, Cr, etc. will significantly affect the performance of the alloy after exceeding the upper limit of the solution of the present invention, as shown in the comparison between Comparative Examples B1, B2, B3 and other samples.

[0099] Including but not limited to the above embodiments, the refining agent can be commercially available and can meet the requirements, such as the main components of the refining agent include chlorides and fluorides of alkali metals and alkaline earth metals, and specific components include KCl, NaCl, NaF, CaF2, Na3AlF6, etc. These components can change the wettability of aluminum melt to oxides, make aluminum melt easy to separate from oxides, reduce the oxide content in the melt, and also change the state of the oxide film on the surface of the melt to improve the degassing effect.

[0100] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0101] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A renewable high-pressure casting heat-treatment-free aluminum alloy, the microstructure of which includes an α-Al matrix, an Al-Si eutectic structure and an Fe-containing second phase, and satisfies: the equivalent diameter of the α-Al matrix is ​​less than or equal to 15 μm, the equivalent diameter of the pre-crystallized structure is less than or equal to 30 μm, the area of ​​the pre-crystallized structure on the observation interface accounts for less than or equal to 15%, and the pre-crystallized structure includes a primary α-Al phase and a primary Fe-rich phase.

2. The renewable high pressure casting heat treatment-free aluminum alloy according to claim 1, characterized in that: The size of the Al-Si eutectic structure is less than or equal to 10 μm, and the morphology of the eutectic Si phase is fibrous or spherical.

3. The renewable high pressure casting heat treatment-free aluminum alloy according to claim 2, characterized in that: The Al-Si eutectic structure is a mechanical mixture of eutectic Si and Al, which is obtained through a eutectic reaction when the temperature is lowered to the eutectic temperature.

4. The renewable high pressure casting heat treatment-free aluminum alloy according to claim 1, characterized in that: The Fe-containing second phase includes β-Al5FeSi, α-Al 15 (Fe,Mn,Cr)3Si2, π-Al9FeMg3Si5 phase.

5. The renewable high pressure casting heat treatment-free aluminum alloy according to claim 4, characterized in that: The average equivalent diameter of the Fe-containing second phase is less than or equal to 10 μm, and the area proportion of the phase on the observed interface is less than or equal to 2.0%.

6. The renewable high pressure casting heat treatment-free aluminum alloy according to claim 5, characterized in that: The morphology distribution of the Fe-containing second phase at the observation interface is block-shaped, Chinese character-shaped, or petal-shaped.

7. The renewable high pressure casting heat treatment-free aluminum alloy according to any one of claims 1 to 6, characterized in that: The aluminum alloy comprises components of Si: 6.0-9.0wt.%, Mg: 0.05-0.3wt.%, Mn: 0.2-0.8wt.%, Cr: 0-0.3wt.%, Fe≤0.8wt.%, Sr: 0.015-0.03wt.%, and the rest are Al and unavoidable impurities.

8. The renewable high pressure casting heat treatment-free aluminum alloy according to claim 7, characterized in that: The impurities are at least any one of the following: Cu≤0.50wt.%, Ni≤0.50wt.%, Zn≤1.5wt.%.

9. The method for preparing a renewable high pressure casting heat treatment-free aluminum alloy according to any one of claims 1 to 8, comprising the following steps: S1: scrap aluminum pretreatment; S2: preparing and melting alloy raw materials, wherein the alloy raw materials include at least 30% of recycled aluminum alloy; S3: refining and impurity removal; S4: Deterioration and refinement S5: Die casting.

10. Use of the renewable high pressure casting heat-treatment-free aluminum alloy according to any one of claims 1 to 8 in large-scale integrated die casting.

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