Method for preparing die-casting aluminum alloy through coordinated regulation and control of component optimization and heat preservation process

Abstract

The invention discloses a method for preparing die-casting aluminum alloy through coordinated regulation and control of component optimization and a heat preservation process, and relates to the field of die-casting aluminum alloy materials and processes. The invention relates to a die-casting aluminum alloy sediment inhibition method through cooperative regulation and control of alloy component optimization and an aluminum water heat preservation process. According to the technology, the melt cleanliness is remarkably improved, the hydrogen content and non-metallic inclusions are reduced, the microscopic structure is refined, and generation of a coarse sedimentary phase is inhibited, so that the pore defect level of a casting is reduced, and the relative defect rate of sediments is reduced. The technological parameters of the method can be directly matched with an existing die-casting production line, and high industrial popularization performance is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of die-casting aluminum alloy materials and processes, and in particular to a method for preparing a die-casting aluminum alloy through composition optimization and heat preservation process coordination control. BACKGROUND

[0002] Die-casting aluminum alloys are widely used in the fields of automobiles, electronics, home appliances, etc. Their high production efficiency and excellent surface quality make them universally adopted in the industry. However, during the production process of die-casting aluminum parts, especially in the smelting-heat preservation-injection process, various deposits such as coarse intermetallic compounds, inclusions or oxides are often generated in the aluminum melt. These deposits not only affect the surface quality of the die-casting parts, but also cause mold blockage, injection system wear, increased scrap rate, and decreased production efficiency, among other problems.

[0003] Problems in the Prior Art

[0004] 1. Incomplete smelting and heat preservation process

[0005] Although there are many existing methods for smelting and heat preservation of aluminum alloys, most focus on temperature control stability, degassing, or improving uniformity, and lack overall design for deposit suppression. For example, patent CN114350986A discloses a smelting and heat preservation process for aluminum alloy, which emphasizes improving casting quality through optimization of temperature control and heat preservation structure, but does not specifically address systematic measures for suppression of intermetallic compounds or inclusions.

[0006] 2. Single mode of molten metal heat preservation and feeding

[0007] Patent CN114406241A proposes a method for molten metal heat preservation and feeding of a die-casting machine, mainly addressing how to effectively maintain the temperature of the molten metal and smoothly supply it, without deeply controlling the deposition risks caused by temperature gradients and uneven convection during the heat preservation process.

[0008] 3. Alloy composition or formula focusing on microscopic performance

[0009] For example, CN105112737A relates to a high-thermal-conductivity corrosion-resistant die-casting aluminum alloy and its preparation process, which focuses on enhancing the thermal conductivity and corrosion resistance of the product, and improves its microstructure through alloy design, but has limited discussion on suppression of deposition formation during the heat preservation stage.

[0010] Shortcomings in the development of existing technologies:

[0011] Separation of composition and process: current related technologies often only start from a single angle of composition or smelting process, lacking an overall method for controlling the generation of deposits from composition optimization and smelting-heat preservation-die casting.

[0012] Lack of specific practice parameters: although some patents mention temperature, time or equipment structure, they do not provide complete and operable parameter ranges and coordinated strategies, which are difficult to implement in actual production;

[0013] Lack of systematic verification: most documents focus on ideas or structural design, without complete test verification steps for microstructure, surface quality or defect rate.

[0014] Therefore, there is an urgent need for a deposition suppression technology scheme that comprehensively considers alloy composition optimization (including trace elements such as Mn, Zn, Ti, Sr, etc.) and melting-holding-injection process coordinated regulation, which can realize a systematic process from microstructure control, temperature control strategy, stirring / excitation frequency design to final injection matching, to ensure the surface quality of die castings, reduce deposits and improve production efficiency. SUMMARY

[0015] Based on the above technical status, a method for preparing die-casting aluminum alloy by optimizing composition and coordinating holding process is proposed. By optimizing the proportion of trace elements such as Mn, Zn, Ti, Sr, etc. in the alloy, and implementing temperature gradient control, refining degassing, stirring homogenization and other process measures during melting and holding stage, the formation of interfacial deposits during die casting process is effectively suppressed, thereby improving the surface quality of die castings and reducing the scrap rate.

[0016] The technical solution is as follows:

[0017] A method for preparing die-casting aluminum alloy by optimizing composition and coordinating holding process, comprising the following steps:

[0018] 1) Alloy composition by mass fraction:

[0019] Mn: 2.0-4.0 parts,

[0020] Zn: 0.1-2.0 parts,

[0021] Ti: 0.01-0.10 parts,

[0022] Sr: 0.005-0.10 parts,

[0023] Other elements: Mg: 0.2-1.0 parts; Si: 1.6-2.8 parts; Fe: ≤0.2 parts; Be: 0.009-0.05 parts; the rest is aluminum; the total of each component is 100 parts;

[0024] 2) Melting stage:

[0025] After uniformly mixing and stirring the above elements, heat melting is carried out, the melting time is 10-15 minutes, and uniform distribution is ensured;

[0026] 3) Refining degassing:

[0027] Inert gas is sprayed for 2-5 minutes, gas flow is 5-15 L / min;

[0028] 4) Holding stage:

[0029] Temperature is controlled at 650-700℃, holding time is 20-30 minutes;

[0030] Stirring or vibration is performed every 5-10 minutes, duration is 20-60 seconds;

[0031] 5) Deposit field treatment

[0032] The alloy is cooled to 180-240℃, 0.4-1.2 parts of supported additive is added, electromagnetic field is applied for 20-30 minutes, to promote the re-differentiation of the deposit and the directional distribution of the combined water;

[0033] 6) Cooling

[0034] Injection mold, natural cooling to room temperature, to obtain the surface treated die-cast aluminum alloy.

[0035] As preferred, the melting temperature is controlled at 740-760℃.

[0036] As preferred, the inert gas is selected from argon or nitrogen.

[0037] As preferred, the stirring in the holding stage is mechanical stirring, rotation speed is in the range of 50-200 r / min.

[0038] As preferred, the vibration in the holding stage is ultrasonic vibration, frequency is 20-40 kHz.

[0039] As preferred, the preparation method of the supported additive is:

[0040] 70-90 parts by mass of mullite powder is dispersed in 600-800 parts by mass of DMF, 5-7 parts by mass of 3-glycidyloxypropyltrimethoxysilane is added, reaction is performed at 70-80℃ for 80-100 minutes, to obtain the mullite carrier with surface epoxy modification;

[0041] The carrier is mixed with the polyester amide additive containing imide functional groups at a mass ratio of 12:1, stirring reaction is performed at 100-120℃ for 3 hours, chemical bonding loading is realized through the ring-opening reaction of the epoxy groups and the amino groups in the additive, and the supported additive is obtained after drying.

[0042] As preferred, the preparation method of the polyester amide additive containing imide functional groups is:

[0043] Add 40-60 parts of adipic acid, 30-50 parts of ethylenediamine, 3-6 parts of melamine polyphosphate into 80-120 parts of DMF, stir until completely dissolved; add 10-20 parts of maleic anhydride, and carry out acylation reaction at 60-80℃ for 1-2 hours to generate imide intermediate;

[0044] Add 3-6 parts of p-toluenesulfonic acid as catalyst, and continue to react at 100-120℃ for 3-4 hours to complete the polymerization reaction, and obtain polyester amide additive containing imide functional groups.

[0045] As preferred, the electromagnetic field strength in the sediment field treatment step is 0.2-0.4T.

[0046] Reaction mechanism

[0047] Additive synthesis mechanism: acylation reaction occurs between maleic anhydride and the amino group of diamine to form imide ring structure; polycondensation reaction occurs between the remaining amino group of diamine and diacid to form polyester amide main chain; esterification reaction occurs between the phosphate group of melamine polyphosphate and the carboxyl group of polyester amide to introduce melamine ring into the molecular chain and enhance the coordination ability with metal ions.

[0048] Loading mechanism: ring-opening reaction occurs between the epoxy group on the surface of mullite and the amino group in the additive to form stable C-N bond, ensuring that the additive does not fall off during high-temperature holding; the high-temperature resistance of mullite avoids decomposition of the additive at 620-660℃.

[0049] Synergistic regulation mechanism:

[0050] The imide functional group forms a hydrogen bond with the hydroxyl group (-OH) on the surface of die-cast aluminum alloy, and the melamine ring forms a coordination bond with Al 3+ , Mg 2+ in the deposit, promoting uniform redifferentiation of the deposit;

[0051] The phosphate group has strong polarity and can orientally adsorb and combine water, and under the polarization of the sediment field (electromagnetic field), it guides the combined water to uniformly distribute between the meshes, reducing the content fluctuation;

[0052] The micro-nano structure of the mullite carrier provides nucleation sites for redifferentiation of the deposit, avoiding agglomeration.

[0053] Technical effects:

[0054] 1. Significantly improve melt cleanliness and reduce pore tendency

[0055] By realizing immediate refining and degassing after melting, strictly controlling holding temperature and holding time, and intermittent stirring process, the hydrogen content and non-metallic inclusions in the melt can be effectively reduced.

[0056] 2. Inhibit the formation of sediment / coarse phase, optimize microstructure

[0057] The method combines the optimization of trace element components such as Mn, Ti, Sr, temperature control and stirring in the holding stage, and further combines the sediment field treatment, so that the area ratio of Al-Mn coarse sediment phase in the aluminum water is reduced. The grain size is improved, the structure is more detailed and uniform, and the segregation risk is inhibited.

[0058] 3. Water distribution is uniform, and sediment is re-differentiated

[0059] The water content fluctuation between the die-casting aluminum alloy zibo is reduced, and the uniformity is improved; the standard deviation of the re-differentiation particle size distribution of the sediment is reduced, the uniformity of the surface coverage is improved, and there is no obvious agglomeration phenomenon. DETAILED DESCRIPTION

[0060] The application will be further described below in conjunction with specific embodiments, but the embodiments do not limit the application in any form. Unless otherwise specified, the raw materials used in the embodiments of the application are conventional commercially available raw materials.

[0061] Example 1

[0062] 1) Alloy composition (by mass, total 100g)

[0063] Mn: 2.0g

[0064] Zn: 0.1g

[0065] Ti: 0.01g

[0066] Sr: 0.005g

[0067] Other elements: Mg: 0.2g; Si: 1.6g; Fe: 0.05g; Be: 0.009g; the rest is aluminum

[0068] 2) Melting stage

[0069] After uniformly mixing and stirring the above elements, heat melting is carried out, the melting temperature is controlled at 740℃, the melting time is 10 minutes, and the distribution is ensured to be uniform;

[0070] 3) Refining and degassing

[0071] Inert gas (argon) is used for cyclone blowing, the blowing time is 2 minutes, and the gas flow is 5L / min.

[0072] 4) Holding stage

[0073] The temperature is controlled at 650℃, and the holding time is 20 minutes;

[0074] Mechanical stirring is carried out every 10 minutes (rotation speed 50r / min), and the stirring duration is 20 seconds.

[0075] 5) Sediment field treatment

[0076] Cool the alloy to 180℃, add 0.4g of the supported additive, and treat under the action of a 0.2T electromagnetic field for 20 minutes to promote the redifferentiation of the sediment and the directional distribution of the bound water.

[0077] 6) Cooling

[0078] Inject the treated alloy into a mold and naturally cool to room temperature to obtain the surface-treated die-cast aluminum alloy.

[0079] Method for preparing the supported additive

[0080] Take 70g of mullite powder, disperse it in 600g of DMF, add 5g of 3-glycidyloxypropyltrimethoxysilane, and react at 70℃ for 80 minutes to obtain the mullite carrier with surface epoxy modification;

[0081] Mix the above carrier with the polyester amide additive containing imide functional groups at a mass ratio of 12:1, stir and react at 100℃ for 3 hours to achieve chemical bonding loading through the ring-opening reaction of the epoxy groups with the amino groups in the additive. After drying, the supported additive is obtained.

[0082] Method for preparing the polyester amide additive containing imide functional groups

[0083] Take 40g of adipic acid, 30g of ethylenediamine, and 3g of melamine polyphosphate, add them to 80g of DMF, and stir until completely dissolved; add 10g of maleic anhydride, and perform acylation reaction at 60℃ for 1 hour to generate an imide intermediate;

[0084] Add 3g of p-toluenesulfonic acid as a catalyst, and continue to react at 100℃ for 3 hours to complete the polymerization reaction, obtaining the polyester amide additive containing imide functional groups.

[0085] Example 2

[0086] 1) Alloy composition (by mass, total 100g)

[0087] Mn: 2.7g

[0088] Zn: 0.7g

[0089] Ti: 0.03g

[0090] Sr: 0.03g

[0091] Other elements: Mg: 0.4g; Si: 2.0g; Fe: 0.1g; Be: 0.02g; the rest is aluminum

[0092] 2) Melting stage

[0093] After the above elements are mixed and stirred uniformly, they are heated and melted. The melting temperature is controlled at 745°C, and the melting time is 12 minutes to ensure uniform distribution.

[0094] 3) Refining and degassing

[0095] Inert gas (argon) is used for cyclone injection. The injection time is 3 minutes, and the gas flow is 8 L / min.

[0096] 4) Holding stage

[0097] The temperature is controlled at 665°C, and the holding time is 23 minutes.

[0098] Ultrasonic excitation is performed every 9 minutes (frequency 25 kHz), and the excitation duration is 30 seconds.

[0099] 5) Sediment field treatment

[0100] The alloy is cooled to 200°C, 0.6g of supported additive is added, and treated under the action of a 0.25T electromagnetic field for 23 minutes to promote the redifferentiation of the sediment and the directional distribution of bound water.

[0101] 6) Cooling

[0102] The treated alloy is poured into a mold and naturally cooled to room temperature to obtain the surface-treated die-cast aluminum alloy.

[0103] Preparation method of supported additive

[0104] Take 75g of mullite powder, disperse it in 650g of DMF, add 5.5g of 3-glycidyloxypropyltrimethoxysilane, and react at 72°C for 85 minutes to obtain an epoxy-modified mullite carrier.

[0105] Mix the above carrier with a polyester amide additive containing imide functional groups in a mass ratio of 12:1, stir and react at 105°C for 3 hours to achieve chemical bonding and loading through ring-opening reaction of the epoxy group with the amino group in the additive. After drying, the supported additive is obtained.

[0106] Preparation method of polyester amide additive containing imide functional groups

[0107] Take 45g of adipic acid, 35g of ethylenediamine, and 4g of melamine polyphosphate, add to 90g of DMF, and stir until completely dissolved; add 13g of maleic anhydride, and perform acylation reaction at 65°C for 1.2 hours to generate an imide intermediate.

[0108] Add 4g of p-toluenesulfonic acid as catalyst, heat to 105°C and continue to react for 3.2 hours to complete the polymerization reaction, and obtain the polyester amide additive containing imide functional groups.

[0109] Example 3

[0110] 1) Alloy composition (by mass, total 100 g)

[0111] Mn: 3.3 g

[0112] Zn: 1.3 g

[0113] Ti: 0.07 g

[0114] Sr: 0.07 g

[0115] Other elements: Mg: 0.8 g; Si: 2.4 g; Fe: 0.15 g; Be: 0.035 g; the rest is aluminum

[0116] 2) Melting stage

[0117] After uniformly mixing the above elements, the temperature is raised for melting, the melting temperature is controlled at 755°C, the melting time is 14 minutes, and the distribution is ensured to be uniform;

[0118] 3) Refining and degassing

[0119] Inert gas (nitrogen) is used for cyclone injection, the injection time is 4 minutes, and the gas flow is 12 L / min.

[0120] 4) Holding stage

[0121] The temperature is controlled at 685°C, and the holding time is 27 minutes;

[0122] Mechanical stirring is performed every 7 minutes (rotation speed 150 r / min), and the stirring duration is 50 seconds.

[0123] 5) Sediment field treatment

[0124] The alloy is cooled to 220°C, 0.9 g of supported additive is added, and treated under the action of a 0.35T electromagnetic field for 27 minutes to promote the redifferentiation of the sediment and the directional distribution of combined water.

[0125] 6) Cooling

[0126] The treated alloy is injected into a mold and naturally cooled to room temperature to obtain a surface-treated die-cast aluminum alloy.

[0127] Preparation method of supported additive

[0128] 85 g of mullite powder is dispersed in 750 g of DMF, 6.5 g of 3-glycidyloxypropyltrimethoxysilane is added, and the reaction is carried out at 78°C for 95 minutes to obtain a mullite carrier with surface epoxy modification;

[0129] The above carrier is mixed with the polyester amide auxiliary containing imide functional groups at a mass ratio of 12:1, stirred and reacted at 115°C for 3 hours, chemically bonded and loaded through ring-opening reaction of the epoxy group and the amino group in the auxiliary, and dried to obtain the loaded auxiliary.

[0130] Method for preparing polyester amide auxiliary containing imide functional groups

[0131] 55 g of adipic acid, 45 g of ethylenediamine, and 5 g of melamine polyphosphate are added to 110 g of DMF and stirred until completely dissolved; 17 g of maleic anhydride is added, and acylation reaction is carried out at 75°C for 1.8 hours to generate an imide intermediate;

[0132] 5 g of p-toluenesulfonic acid is added as a catalyst, and the temperature is raised to 115°C for continued reaction for 3.8 hours to complete the polymerization reaction, and the polyester amide auxiliary containing imide functional groups is obtained.

[0133] Example 4

[0134] 1) Alloy composition (by mass, total 100 g)

[0135] Mn: 4.0 g

[0136] Zn: 2.0 g

[0137] Ti: 0.10 g

[0138] Sr: 0.10 g

[0139] Other elements: Mg: 1.0 g; Si: 2.8 g; Fe: 0.2 g; Be: 0.05 g; the rest is aluminum

[0140] 2) Melting stage

[0141] After the above elements are uniformly stirred, they are heated and melted, the melting temperature is controlled at 760°C, and the melting time is 15 minutes to ensure uniform distribution.

[0142] 3) Refining and degassing

[0143] Inert gas (nitrogen) is used for cyclone blowing, the blowing time is 5 minutes, and the gas flow is 15 L / min.

[0144] 4) Holding stage

[0145] The temperature is controlled at 700°C, and the holding time is 30 minutes;

[0146] Ultrasonic excitation is performed every 5 minutes (frequency 40 kHz), and the excitation duration is 60 seconds.

[0147] 5) Sediment field treatment

[0148] The alloy is cooled to 240℃, 1.2g of the supported additive is added, and the alloy is treated in an electromagnetic field of 0.4T for 30 minutes to promote the re-differentiation of the deposits and the directional distribution of the bound water.

[0149] 6) cooling

[0150] The treated alloy is injected into a mold and naturally cooled to room temperature to obtain the surface-treated die-cast aluminum alloy.

[0151] Method for preparing the supported additive

[0152] 90g of mullite powder is dispersed in 800g of DMF, 7g of 3-glycidyloxypropyltrimethoxysilane is added, and the mixture is reacted at 80℃ for 100 minutes to obtain the mullite carrier with surface epoxy modification;

[0153] The above carrier is mixed with the polyester amide additive containing imide functional groups at a mass ratio of 12:1, and the mixture is stirred and reacted at 120℃ for 3 hours to achieve chemical bonding loading through the ring-opening reaction of the epoxy groups with the amino groups in the additive. After drying, the supported additive is obtained.

[0154] Method for preparing the polyester amide additive containing imide functional groups

[0155] 60g of adipic acid, 50g of ethylenediamine, and 6g of melamine polyphosphate are added to 120g of DMF and stirred until completely dissolved; 20g of maleic anhydride is added, and the mixture is subjected to acylation reaction at 80℃ for 2 hours to generate an imide intermediate;

[0156] 6g of p-toluenesulfonic acid is added as a catalyst, and the mixture is heated to 120℃ and reacted for another 4 hours to complete the polymerization reaction, thereby obtaining the polyester amide additive containing imide functional groups.

[0157] Comparative Example 1

[0158] 1) Alloy composition (by mass, total 100g)

[0159] Mn: 2.0g

[0160] Zn: 0.1g

[0161] Ti: 0.01g

[0162] Sr: 0.005g

[0163] Other elements: Mg: 0.2g; Si: 1.6g; Fe: 0.05g; Be: 0.009g; the rest is aluminum

[0164] 2) Melting stage

[0165] The above elements are mixed and stirred uniformly, and then subjected to temperature rising smelting, with the smelting temperature controlled at 740°C and the smelting time being 10 minutes, to ensure uniform distribution.

[0166] 3) Refining and degassing

[0167] Inert gas (argon) is used for cyclone blowing, with the blowing time being 2 minutes and the gas flow being 5 L / min.

[0168] 4) Holding stage

[0169] The temperature is controlled at 650°C, and the holding time is 20 minutes.

[0170] Mechanical stirring is performed every 10 minutes (rotation speed 50 r / min), and the stirring duration is 20 seconds.

[0171] 5) Sediment field treatment

[0172] The alloy is cooled to 180°C, and subjected to treatment under the action of a 0.2T electromagnetic field for 20 minutes, to promote sediment re-differentiation and directional distribution of combined water.

[0173] 6) Cooling

[0174] The treated alloy is injected into a mold, and naturally cooled to room temperature, to obtain a surface treated die-cast aluminum alloy.

[0175] Comparative Example 2

[0176] 1) Alloy composition (by mass number, total 100 g)

[0177] Mn: 2.0 g

[0178] Zn: 0.1 g

[0179] Ti: 0.01 g

[0180] Sr: 0.005 g

[0181] Other elements: Mg: 0.2 g; Si: 1.6 g; Fe: 0.05 g; Be: 0.009 g; the rest is aluminum

[0182] 2) Smelting stage

[0183] The above elements are mixed and stirred uniformly, and then subjected to temperature rising smelting, with the smelting temperature controlled at 740°C and the smelting time being 10 minutes, to ensure uniform distribution.

[0184] 3) Refining and degassing

[0185] Inert gas (argon) is used for cyclone blowing, with the blowing time being 2 minutes and the gas flow being 5 L / min.

[0186] 4) Holding stage

[0187] Temperature control at 650℃, holding time 20 minutes;

[0188] Mechanical stirring (rotation speed 50r / min) was carried out every 10 minutes, and the stirring duration was 20 seconds.

[0189] 5) Sediment field treatment

[0190] The alloy was cooled to 180℃, 0.4g of the supported additive was added, and the alloy was treated under the action of a 0.2T electromagnetic field for 20 minutes to promote the re-differentiation of the sediment and the directional distribution of the combined water.

[0191] 6) Cooling

[0192] The treated alloy was injected into a mold and naturally cooled to room temperature to obtain the surface-treated die-cast aluminum alloy.

[0193] Method for preparing the supported additive

[0194] 70g of mullite powder was dispersed in 600g of DMF, 5g of 3-glycidyloxypropyltrimethoxysilane was added, and the mixture was reacted at 70℃ for 80 minutes to obtain the mullite carrier with surface epoxy modification;

[0195] The above carrier was mixed with the polyester amide additive containing imide functional groups at a mass ratio of 12:1, and the mixture was stirred and reacted at 100℃ for 3 hours to realize chemical bonding loading through the ring-opening reaction of the epoxy groups with the amino groups in the additive. After drying, the supported additive was obtained.

[0196] Method for preparing the polyester amide additive containing imide functional groups

[0197] 40g of adipic acid and 30g of ethylenediamine were added to 80g of DMF and stirred until completely dissolved; 10g of maleic anhydride was added, and an acylation reaction was carried out at 60℃ for 1 hour to generate an imide intermediate;

[0198] 3g of p-toluenesulfonic acid was added as a catalyst, and the temperature was raised to 100℃ for further reaction for 3 hours to complete the polymerization reaction, thereby obtaining the polyester amide additive containing imide functional groups.

[0199] Comparative Example 3

[0200] 1) Alloy composition (by mass, total 100g)

[0201] Mn: 2.0g

[0202] Zn: 0.1g

[0203] Ti: 0.01g

[0204] Sr: 0.005g

[0205] Other elements: Mg: 0.2g; Si: 1.6g; Fe: 0.05g; Be: 0.009g; the remainder is aluminum.

[0206] 2) Smelting stage

[0207] After mixing and stirring the above-mentioned elements evenly, the mixture is heated and melted. The melting temperature is controlled at 740℃ and the melting time is 10 minutes to ensure uniform distribution.

[0208] 3) Refining and degassing

[0209] The gas is swirled and purged using an inert gas (argon) for 2 minutes at a flow rate of 5 L / min.

[0210] 4) Insulation stage

[0211] The temperature is controlled at 650℃, and the heat preservation time is 20 minutes;

[0212] Mechanical stirring (50 rpm) is performed every 10 minutes for 20 seconds.

[0213] 5) Sediment field treatment

[0214] The alloy was cooled to 180°C, 0.4g of supported additive was added, and the mixture was treated under an electromagnetic field of 0.2T for 20 minutes to promote sediment redifferentiation and directional distribution of bound water.

[0215] 6) Cooling

[0216] The treated alloy is injected into a mold and allowed to cool naturally to room temperature to obtain a surface-treated die-cast aluminum alloy.

[0217] Preparation method of supported additives

[0218] Take 70g of mullite powder, disperse it in 600g of DMF, add 5g of 3-glycidyl etheroxypropyltrimethoxysilane, and react at 70℃ for 80 minutes to obtain a surface epoxy-modified mullite support.

[0219] The above-mentioned carrier was mixed with a polyester amide additive containing an imide functional group at a mass ratio of 12:1, and stirred at 100°C for 3 hours. Chemical bonding and loading were achieved through the ring-opening reaction of the epoxy group with the amino group in the additive. After drying, the supported additive was obtained.

[0220] Preparation method of polyesteramide additives containing imide functional groups

[0221] Take 40g adipic acid, 30g ethylenediamine, and 3g melamine polyphosphate, add them to 80g DMF, stir until completely dissolved, and carry out an acylation reaction at 60℃ for 1 hour to generate an imide intermediate.

[0222] Add 3g of p-toluenesulfonic acid as a catalyst, heat to 100℃ and continue the reaction for 3 hours to complete the polymerization reaction and obtain a polyesteramide auxiliary containing imide functional groups.

[0223] Test methods and results:

[0224] 1) Aluminum molten gas content / cleanliness: Reduced pressure test (RPT)

[0225] Objective: To evaluate the hydrogen content in the melt and the resulting porosity tendency; it can also serve as a process indicator of melt cleanliness.

[0226] Apparatus / Principle: A certain amount of molten aluminum is taken and solidified under reduced pressure of 80-100 mbar. The density or apparent pore volume fraction of the reduced-pressure sample and the atmospheric-pressure sample are measured, and the density index (DI) is calculated. The smaller the DI, the lower the tendency for porosity caused by hydrogen / inclusions.

[0227] 2) Qualitative and quantitative analysis of inclusions: PoDFA (Polyporous Ceramic Filter Method)

[0228] Objective: To conduct a qualitative and quantitative assessment of the composition and concentration of non-metallic inclusions in melts.

[0229] Apparatus / Principle: Under controlled conditions, a certain amount of molten aluminum is passed through a ceramic filter with a specific pore size to enrich inclusions. Subsequently, metallographic / SEM-EDS analysis is performed on the cross-section of the filter, and the area or volume fraction of inclusions per unit mass of metal is reported.

[0230] 3) Radiographic testing and porosity assessment (die castings)

[0231] Objective: To evaluate the defect level of internal porosity (porosity / shrinkage) in die castings.

[0232] Method: X-ray films were compared and rated according to ASTM E505 "Reference Films for Radiographic Inspection of Aluminum and Magnesium Die Castings", and the Class A (porosity) grade was recorded.

[0233] 4) Microstructure / grain size and sedimentary phase characterization

[0234] Sample preparation: Sampling, mounting, polishing, and etching were performed in accordance with the ASTM E3 metallographic specimen preparation guidelines.

[0235] Grain size: Grain size is evaluated according to ASTM E112 or equivalent standard, and the G value is reported.

[0236] Depositional / inclusion phases: Identification of Al-Mn phases (Al6Mn / Al) using optical microscopy + SEM / EDS 12 Mn), oxide inclusions, etc.

[0237] Table 1 Test Results

[0238]

[0239] Simultaneous improvement of RPT and PoDFA: In the example, with the combination of degassing, heat preservation zone and intermittent stirring, DI was significantly reduced, while PoDFA had the lowest inclusion area, indicating that the melt hydrogen and inclusion water were both superior.

[0240] X-ray porosity rating improvement: RPT / PoDFA improvement reduces the internal porosity of the corresponding casting, and the ASTM E505 rating is improved from A3-A4 to A2-A3.

[0241] Grain refinement and controlled deposition phase: The synergy of Ti, Sr and moderate Mn increases grain size (G↑) and decreases the area fraction of coarse Al-Mn phase; at the same time, the temperature window and stirring at the process end reduce deposition coarsening.

[0242] The applicant declares that the present invention is further illustrated by the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing die-cast aluminum alloys through synergistic control of composition optimization and heat preservation process, characterized in that, Includes the following steps: 1) Alloy composition by mass parts: Mn: 2.0-4.0 parts Zn: 0.1-2.0 parts Ti: 0.01-0.10 parts Sr: 0.005-0.10 parts Other elements: Mg: 0.2-1.0 parts; Si: 1.6-2.8 parts; Fe: ≤0.2 parts; Be: 0.009-0.05 parts; the remainder is aluminum; the total amount of all components is based on 100 parts. 2) Smelting stage: After mixing and stirring the above-mentioned elements evenly, heat and melt them for 10–15 minutes to ensure uniform distribution. 3) Refining and degassing: Use inert gas swirl jet to purge for 2-5 minutes at a gas flow rate of 5-15 L / min; 4) Insulation stage: The temperature should be controlled at 650-700℃, and the holding time should be 20-30 minutes; Stir or vibrate every 5-10 minutes for 20-60 seconds. 5) Sediment field treatment The alloy is cooled to 180-240℃, 0.4-1.2 parts of supported additives are added, and an electromagnetic field is applied for 20-30 minutes to promote the redifferentiation of deposits and the directional distribution of bound water. 6) Cooling The material is poured into a mold and allowed to cool naturally to room temperature to obtain a surface-treated die-cast aluminum alloy. The supported additive is prepared by reacting mullite powder, 3-glycidyl etheroxypropyltrimethoxysilane, and a polyesteramide additive containing an imide functional group. The polyester amide additive containing imide functional groups is prepared by reacting adipic acid, ethylenediamine, melamine polyphosphate, maleic anhydride, and p-toluenesulfonic acid.

2. The method for preparing die-cast aluminum alloys by synergistic control of composition optimization and heat preservation process according to claim 1, characterized in that: The temperature during the smelting stage is controlled at 740-760℃.

3. The method for preparing die-cast aluminum alloys by synergistic control of composition optimization and heat preservation process according to claim 1, characterized in that: The inert gas is selected from argon or nitrogen.

4. The method for preparing die-cast aluminum alloys by synergistic control of composition optimization and heat preservation process according to claim 1, characterized in that: The stirring during the heat preservation stage is mechanical stirring, with a speed range of 50-200 r / min.

5. The method for preparing die-cast aluminum alloys by synergistic control of composition optimization and heat preservation process according to claim 1, characterized in that: The vibration during the heat preservation stage is ultrasonic vibration with a frequency of 20-40kHz.

6. The method for preparing die-cast aluminum alloys by synergistic control of composition optimization and heat preservation process according to claim 1, characterized in that: The preparation method of the supported additive: According to the mass fraction, 70-90 parts by mass of mullite powder are dispersed in 600-800 parts by mass of DMF, and 5-7 parts by mass of 3-glycidyl etheroxypropyltrimethoxysilane are added. The mixture is reacted at 70-80℃ for 80-100 minutes to obtain a surface epoxy-modified mullite carrier. The carrier and the polyester amide additive containing imide functional groups were mixed at a mass ratio of 12:1 and stirred at 100-120℃ for 3 hours. Chemical bonding and loading were achieved through the ring-opening reaction of epoxy groups with amino groups in the additive. After drying, the supported additive was obtained.

7. The method for preparing die-cast aluminum alloys by synergistic control of composition optimization and heat preservation process according to claim 6, characterized in that: The preparation method of the polyesteramide auxiliary containing imide functional groups: Add 40-60 parts adipic acid, 30-50 parts ethylenediamine, and 3-6 parts melamine polyphosphate to 80-120 parts DMF and stir until completely dissolved; add 10-20 parts maleic anhydride and carry out an acylation reaction at 60-80℃ for 1-2 hours to generate an imide intermediate. Add 3-6 parts of p-toluenesulfonic acid as a catalyst, heat to 100-120℃ and continue the reaction for 3-4 hours to complete the polymerization reaction and obtain a polyesteramide auxiliary containing imide functional groups.

8. The method for preparing die-cast aluminum alloys by synergistic control of composition optimization and heat preservation process according to claim 1, characterized in that: The electromagnetic field strength in the sediment field treatment step is 0.2-0.4T.

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