A method for preparing die-casting aluminum alloy by synergistically controlling ingredient optimization and holding process

Abstract

The application discloses a method for preparing pressure casting aluminum alloy by optimizing components and cooperating with heat preservation process, and relates to the field of pressure casting aluminum alloy materials and processes. The method is a pressure casting aluminum alloy deposit inhibition method by optimizing alloy components and cooperating with aluminum water heat preservation process. The technology significantly improves the melt cleanliness, reduces the hydrogen content and non-metallic inclusions, refines the microstructure and inhibits the generation of coarse deposition phases, so that the air hole defect level of the castings is reduced, and the deposit related defect rate is reduced. The process parameters of the method can be directly adapted to the existing pressure casting production line, and the method has high industrial promotion.

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 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.

[0044] 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.

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

[0046] Reaction mechanism

[0047] Synthesis mechanism of additives: maleic anhydride undergoes acylation reaction with the amino group of diamine to form an imide ring structure; the diacid undergoes polycondensation reaction with the remaining amino group of diamine to form a polyesteramide backbone; the phosphate ester group of melamine polyphosphate undergoes esterification reaction with the carboxyl group of polyesteramide to introduce the melamine ring into the molecular chain and enhance its coordination ability with metal ions.

[0048] Loading mechanism: The epoxy groups on the surface of mullite undergo a ring-opening reaction with the amino groups in the additive to form stable CN bonds, ensuring that the additive does not fall off during high-temperature insulation; the high-temperature resistance of mullite prevents the additive from decomposing at 620-660℃.

[0049] Synergistic regulation mechanism:

[0050] The imide functional groups form hydrogen bonds with the hydroxyl groups (-OH) on the surface of the die-cast aluminum alloy, and the melamine rings bind with the Al in the deposits. 3+ Mg 2+ Formation of coordination bonds promotes uniform redifferentiation of sediments;

[0051] Phosphate groups have strong polarity and can directionally adsorb bound water. Under the polarization effect of the sediment field (electromagnetic field), they guide the bound water to be evenly distributed between the sesame seeds, reducing the content fluctuation.

[0052] The micro- and nano-structures of mullite carriers provide nucleation sites for sediment redifferentiation, preventing aggregation.

[0053] Technical effects:

[0054] 1. Significantly improves melt cleanliness and reduces porosity.

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

[0056] 2. Inhibit sediment / coarse phase formation and optimize microstructure.

[0057] This method combines optimization of trace element composition such as Mn, Ti, and Sr with temperature control and stirring during the heat preservation stage, along with sediment field treatment, to reduce the area ratio of coarse Al-Mn deposited phases in molten aluminum. This results in improved grain size, a finer and more uniform microstructure, and reduced risk of segregation.

[0058] 3. Uniform water distribution and sediment re-differentiation

[0059] The fluctuation of bound water content between the layers of the die-cast aluminum alloy decreased, and the uniformity was improved; the standard deviation of the redifferentiation particle size distribution of the sediment decreased, the uniformity of surface coverage improved, and there was no obvious agglomeration. Detailed Implementation

[0060] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[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 remainder is aluminum.

[0068] 2) Smelting stage

[0069] After mixing and stirring the above-mentioned elements evenly, heat and melt them. The melting temperature is controlled at 740℃ and the melting time is 10 minutes to ensure uniform distribution.

[0070] 3) Refining and degassing

[0071] The gas is swirled and purged using an inert gas (argon) for 2 minutes at a flow rate of 5 L / min.

[0072] 4) Insulation stage

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

[0074] Mechanical stirring (50 rpm) is performed every 10 minutes for 20 seconds.

[0075] 5) Sediment field treatment

[0076] 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.

[0077] 6) Cooling

[0078] 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.

[0079] Preparation method of supported additives

[0080] 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.

[0081] 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.

[0082] Preparation method of polyesteramide additives containing imide functional groups

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

[0084] 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.

[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 remainder is aluminum.

[0092] 2) Smelting stage

[0093] After mixing and stirring the above-mentioned elements evenly, the mixture is heated and melted. The melting temperature is controlled at 745℃ and the melting time is 12 minutes to ensure uniform distribution.

[0094] 3) Refining and degassing

[0095] Inert gas (argon) is used for swirling jetting for 3 minutes at a gas flow rate of 8 L / min.

[0096] 4) Insulation stage

[0097] The temperature was controlled at 665℃, and the heat preservation time was 23 minutes.

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

[0099] 5) Sediment field treatment

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

[0101] 6) Cooling

[0102] 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.

[0103] Preparation method of supported additives

[0104] Take 75g of mullite powder, disperse it in 650g of DMF, add 5.5g of 3-glycidyl etheroxypropyltrimethoxysilane, and react at 72℃ for 85 minutes to obtain a surface epoxy-modified mullite support.

[0105] 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 105°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.

[0106] Preparation method of polyesteramide additives containing imide functional groups

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

[0108] Add 4g of p-toluenesulfonic acid as a catalyst, heat to 105℃ and continue the reaction for 3.2 hours to complete the polymerization reaction and obtain a polyesteramide auxiliary containing imide functional groups.

[0109] Example 3

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

[0111] Mn: 3.3g

[0112] Zn: 1.3g

[0113] Ti: 0.07g

[0114] Sr: 0.07g

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

[0116] 2) Smelting stage

[0117] After mixing and stirring the above-mentioned elements evenly, the mixture is heated and melted. The melting temperature is controlled at 755℃ and the melting time is 14 minutes to ensure uniform distribution.

[0118] 3) Refining and degassing

[0119] Inert gas (nitrogen) is used for swirling purging for 4 minutes at a gas flow rate of 12 L / min.

[0120] 4) Insulation stage

[0121] The temperature was controlled at 685℃, and the heat preservation time was 27 minutes.

[0122] Mechanical stirring is performed every 7 minutes (150 rpm) for 50 seconds.

[0123] 5) Sediment field treatment

[0124] The alloy was cooled to 220°C, and 0.9g of supported additives were added. The mixture was then treated under an electromagnetic field of 0.35T for 27 minutes to promote sediment redifferentiation and directional distribution of bound water.

[0125] 6) Cooling

[0126] 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.

[0127] Preparation method of supported additives

[0128] Take 85g of mullite powder, disperse it in 750g of DMF, add 6.5g of 3-glycidyl etheroxypropyltrimethoxysilane, and react at 78℃ for 95 minutes to obtain a surface epoxy-modified mullite support.

[0129] 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 115°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.

[0130] Preparation method of polyesteramide additives containing imide functional groups

[0131] Take 55g adipic acid, 45g ethylenediamine, and 5g melamine polyphosphate, add them to 110g DMF, and stir until completely dissolved; add 17g maleic anhydride, and carry out an acylation reaction at 75℃ for 1.8 hours to generate an imide intermediate;

[0132] Add 5g of p-toluenesulfonic acid as a catalyst, heat to 115℃ and continue the reaction for 3.8 hours to complete the polymerization reaction and obtain a polyesteramide auxiliary containing imide functional groups.

[0133] Example 4

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

[0135] Mn: 4.0g

[0136] Zn: 2.0g

[0137] Ti: 0.10g

[0138] Sr: 0.10g

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

[0140] 2) Smelting stage

[0141] After mixing and stirring the above-mentioned elements evenly, heat and melt them at 760℃ for 15 minutes to ensure uniform distribution.

[0142] 3) Refining and degassing

[0143] Use inert gas (nitrogen) for swirling spraying for 5 minutes at a gas flow rate of 15 L / min.

[0144] 4) Insulation stage

[0145] The temperature is controlled at 700℃, and the heat preservation time is 30 minutes;

[0146] Ultrasonic excitation (frequency 40kHz) is performed every 5 minutes for 60 seconds.

[0147] 5) Sediment field treatment

[0148] The alloy was cooled to 240°C, 1.2g of supported additive was added, and the mixture was treated under an electromagnetic field of 0.4T for 30 minutes to promote sediment redifferentiation and directional distribution of bound water.

[0149] 6) Cooling

[0150] 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.

[0151] Preparation method of supported additives

[0152] Take 90g of mullite powder, disperse it in 800g of DMF, add 7g of 3-glycidyl etheroxypropyltrimethoxysilane, and react at 80℃ for 100 minutes to obtain a surface epoxy-modified mullite support.

[0153] 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 120°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.

[0154] Preparation method of polyesteramide additives containing imide functional groups

[0155] Take 60g of adipic acid, 50g of ethylenediamine, and 6g of melamine polyphosphate, add them to 120g of DMF, and stir until completely dissolved; add 20g of maleic anhydride, and carry out an acylation reaction at 80℃ for 2 hours to generate an imide intermediate;

[0156] Add 6g of p-toluenesulfonic acid as a catalyst, heat to 120℃ and continue the reaction for 4 hours to complete the polymerization reaction and obtain a polyesteramide auxiliary 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 remainder is aluminum.

[0164] 2) Smelting stage

[0165] After mixing and stirring the above-mentioned elements evenly, heat and melt them at 740℃ for 10 minutes to ensure uniform distribution.

[0166] 3) Refining and degassing

[0167] The gas is swirled and purged using an inert gas (argon) for 2 minutes at a flow rate of 5 L / min.

[0168] 4) Insulation stage

[0169] The temperature is controlled at 650℃, and the heat preservation time is 20 minutes;

[0170] Mechanical stirring (50 rpm) is performed every 10 minutes for 20 seconds.

[0171] 5) Sediment field treatment

[0172] The alloy was cooled to 180°C and treated under an electromagnetic field of 0.2T for 20 minutes to promote the redifferentiation of the deposits and the directional distribution of bound water.

[0173] 6) Cooling

[0174] 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.

[0175] Comparative Example 2

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

[0177] Mn: 2.0g

[0178] Zn: 0.1g

[0179] Ti: 0.01g

[0180] Sr: 0.005g

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

[0182] 2) Smelting stage

[0183] After mixing and stirring the above-mentioned elements evenly, heat and melt them. The melting temperature is controlled at 740℃ and the melting time is 10 minutes to ensure uniform distribution.

[0184] 3) Refining and degassing

[0185] The gas is swirled and purged using an inert gas (argon) for 2 minutes at a flow rate of 5 L / min.

[0186] 4) Insulation stage

[0187] The temperature is controlled at 650℃, and the heat preservation time is 20 minutes;

[0188] Mechanical stirring (50 rpm) is performed every 10 minutes for 20 seconds.

[0189] 5) Sediment field treatment

[0190] 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.

[0191] 6) Cooling

[0192] 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.

[0193] Preparation method of supported additives

[0194] 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.

[0195] 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.

[0196] Preparation method of polyesteramide additives containing imide functional groups

[0197] Take 40g of adipic acid and 30g of ethylenediamine, add them to 80g of DMF, and stir until completely dissolved; add 10g of maleic anhydride, and carry out an acylation reaction at 60℃ for 1 hour to generate an imide intermediate;

[0198] 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.

[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, heat and melt them. 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 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 and amino groups in the additive. After drying, the supported additive was obtained. 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.

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 20-40 kHz.

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 electromagnetic field strength in the sediment field treatment step is 0.2-0.4T.

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