A water-based PAG quenching medium containing temperature-sensitive polymer microgel, its preparation method and application

Abstract

This invention relates to a PAG water-based quenching medium containing thermosensitive polymer microgels, its preparation method, and its application, belonging to the field of heat treatment technology. The PAG water-based quenching medium, by weight percentage, comprises the following components: 2.0-5.0% PAG polymer, 0.5-2.5% polyether-modified polymethylsiloxane, 1.0-3.0% fatty amine polyoxyethylene ether, 0.2-1.0% triethanolamine, 0.2-0.8% benzotriazole, 0.05-1.0% thermosensitive crosslinked polymer microgels, 0.05-0.3% salicylic acid, with the balance being deionized water, and contains no inorganic layered silicate particles. The thermosensitive crosslinked polymer microgels have a volumetric phase transition temperature of 30-40°C, a hydrated particle size of 200-500 nm below this temperature, and a contracted particle size of 100-200 nm above this temperature. The quenching medium has a precipitate volume fraction of no more than 0.8% at high temperatures, an abrasion weight loss rate of no more than 0.02%, a particle size recovery rate of no less than 90% after cyclic temperature change, and a cooling rate of 74~78±3℃ / s at 300℃. It is suitable for quenching aluminum alloys.

Description

Technical Field

[0001] This invention relates to the field of heat treatment technology, and in particular to a PAG water-based quenching medium containing temperature-sensitive polymer microgels, its preparation method, and its application. Background Technology

[0002] Quenching media are key materials in metal heat treatment, especially in the solution quenching process of aluminum alloys. Their cooling characteristics directly affect the uniformity of the workpiece's microstructure, mechanical properties, and residual stress distribution. PAG (polyalkylene glycol) water-based quenching media, due to their combination of slow cooling properties similar to oil and cleanliness of water, have become one of the mainstream alternatives to quenching oil. Existing water-based quenching media, primarily composed of PAG polymers and compounded with various functional additives, have been reported. For example, Chinese invention patent application CN117778677A discloses a quenching medium for 7000 series aluminum alloys, which uses sodium-based bentonite as an inorganic suspending agent and auxiliary film-forming agent to adjust the high-temperature cooling characteristics of the quenching fluid. However, the aforementioned prior art all uses inorganic layered silicates (such as bentonite, montmorillonite, etc.) as suspending agents or film-forming aids. In actual use, these inorganic particles have the following objective defects: First, under long-term high-temperature environments of ≥60℃, the hydroxyl groups on the surface of bentonite particles undergo a removal reaction, and the van der Waals forces between the lamellae are enhanced, leading to irreversible agglomeration of particles and the formation of hard deposits, commonly known as "hard precipitates". These deposits not only cause a continuous decrease in the effective suspension concentration in the quenching fluid, resulting in a drift in cooling characteristics, but are also difficult to redisperse through conventional stirring or filtration methods, forcing the entire quenching fluid tank to be replaced. Second, the hard inorganic particles continuously scour the inner walls of the circulating pump impeller, valves, and pipelines, causing abrasive damage to the equipment, increasing maintenance costs, and shortening the equipment life.

[0003] Therefore, how to reduce or avoid inorganic particle sedimentation and erosion while maintaining cooling performance remains a technical problem to be solved in the field of PAG water-based quenching media. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a PAG water-based quenching medium containing temperature-sensitive polymer microgels, its preparation method, and its applications. This quenching medium can reduce or avoid inorganic particle sedimentation and abrasion defects while maintaining cooling properties.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a PAG water-based quenching medium containing thermosensitive polymer microgels, which comprises the following components by weight percentage: PAG polymer 2.0~5.0 wt%, polyether modified polymethylsiloxane 0.5~2.5 wt%, fatty amine polyoxyethylene ether 1.0~3.0 wt%, triethanolamine 0.2~1.0 wt%, benzotriazole 0.2~0.8 wt%, thermosensitive crosslinked polymer microgel 0.05~1.0 wt%, salicylic acid 0.05~0.3 wt%, balance deionized water; The quenching medium does not contain inorganic layered silicate particles; The thermosensitive cross-linked polymer microgel has a volume phase transition temperature (VPTT) of 30-40°C; the hydrated particle size of the thermosensitive cross-linked polymer microgel is 200-500 nm below the VPTT, and the contracted particle size is 100-200 nm above the VPTT.

[0006] As a preferred embodiment of the PAG water-based quenching medium of the present invention, the temperature-sensitive cross-linked polymer microgel is selected from any one or a combination of cross-linked poly(N-isopropylacrylamide) microgel, cross-linked poly(N,N-diethylacrylamide) microgel, and cross-linked poly(N-vinylcaprolactam) microgel; preferably, it is cross-linked poly(N-isopropylacrylamide) (PNIPAM) microgel.

[0007] As a preferred embodiment of the PAG water-based quenching medium of the present invention, when the temperature-sensitive cross-linked polymer microgel is cooled to a temperature below the volume phase transition temperature after being above the volume phase transition temperature, the recovery rate of its hydrated particle size is not less than 90%.

[0008] In a preferred embodiment of the PAG water-based quenching medium of the present invention, the mass ratio of the temperature-sensitive crosslinked polymer microgel to the PAG polymer is 1:5 to 1:50.

[0009] As a more preferred embodiment of the PAG water-based quenching medium containing temperature-sensitive polymer microgels described in this invention, the PAG polymer is a block copolymer or random copolymer of ethylene oxide and propylene oxide, wherein the molar ratio of ethylene oxide units to propylene oxide units is m / n=20~40, and the number average molecular weight is 20000~40000.

[0010] As a preferred embodiment of the PAG water-based quenching medium of the present invention, the polyether-modified polymethylsiloxane has a polyether grafting rate of not less than 50% and a number-average molecular weight of 5000~8000.

[0011] Secondly, the present invention provides a method for preparing the above-mentioned PAG water-based quenching medium containing temperature-sensitive polymer microgels, which includes the following steps: S1. Disperse the thermosensitive crosslinked polymer microgel in deionized water and stir until uniformly dispersed under conditions below its volume phase transition temperature to obtain a microgel pre-dispersion. S2. Add PAG polymer to deionized water at 60~70℃ and stir until completely dissolved to obtain PAG base liquid. Then cool the liquid to a temperature lower than the volume phase transition temperature of the thermosensitive crosslinked polymer microgel. S3. Under conditions below the volumetric phase transition temperature, polyether-modified polymethylsiloxane, fatty amine polyoxyethylene ether, triethanolamine, benzotriazole and salicylic acid are added sequentially to the PAG base liquid in step S2, and stirred until homogeneous. S4. Under conditions below the volumetric phase transition temperature, slowly add the microgel pre-dispersion obtained in step S1 to the mixture in step S3, replenish the remaining deionized water, and continue stirring until homogeneous to obtain the PAG water-based quenching medium. In a preferred embodiment of the preparation method described in this invention, the operating temperature of each step from S1 to S4 is not higher than the volume phase transition temperature of the thermosensitive crosslinked polymer microgel minus 5°C.

[0012] Thirdly, the present invention provides the application of the above-mentioned PAG water-based quenching medium containing temperature-sensitive polymer microgel or the PAG water-based quenching medium prepared by the above-mentioned preparation method in the quenching treatment of aluminum alloys.

[0013] In a preferred embodiment of the application described in this invention, the aluminum alloy is selected from 2-series aluminum alloys, 6-series aluminum alloys, or 7-series aluminum alloys; preferably, it is a 7-series aluminum alloy with a Cu content of not less than 1.0 wt%.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention discloses a PAG water-based quenching medium containing thermosensitive polymer microgel, its preparation method and application. The quenching medium is based on PAG polymer, compounded with polyether-modified polymethylsiloxane, fatty amine polyoxyethylene ether, triethanolamine, benzotriazole, thermosensitive crosslinked polymer microgel and salicylic acid, with the balance being deionized water, and does not contain inorganic layered silicate particles. First, after the quenching medium of the present invention is left to stand at 80°C for 168 hours, the volume fraction of the precipitate does not exceed 0.8%, and the precipitate is soft and flocculent, which can be dispersed by gentle shaking. This solves the problem of hard precipitation caused by particle agglomeration in existing inorganic bentonite-based quenching media during high-temperature cycling. Second, the quenching medium of the present invention has an abrasion weight loss rate of no more than 0.02% on 7050 aluminum alloy test pieces under cyclic shearing conditions, and the test piece surface is free of scratches, thus overcoming the abrasive damage to pipelines and pump bodies caused by inorganic particles. Furthermore, in the quenching medium of the present invention, the temperature-sensitive cross-linked polymer microgel exhibits a particle size recovery rate of no less than 90% after 5 cycles of temperature change, and a gel content of 96.3% in tetrahydrofuran (THF), demonstrating reversible swelling-shrinkage behavior; while linear PNIPAM exhibits a recovery rate of less than 50% and a gel content of 0% under the same conditions, completely dissolves in tetrahydrofuran (THF), and irreversibly flocculates after cycling; finally, the quenching medium of the present invention avoids hard precipitation and abrasion, while maintaining a stable cooling rate of 74~78±3℃ / s at 300℃, with a smooth cooling curve, which can meet the cooling requirements of aluminum alloy quenching.

[0015] In summary, the quenching medium provided by this invention has good high-temperature suspension stability, abrasion resistance and reversible recovery performance, and stable cooling performance, making it suitable for quenching treatment of aluminum alloys. Detailed Implementation

[0016] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments. The embodiments described below are some, but not all, embodiments of this invention. The embodiments of this invention are used to illustrate the invention, not to limit it. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. Unless otherwise specified, experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the manufacturer. The raw materials and reagents used are commercially available conventional products or products that conform to relevant national / industry standards and are all commercially available.

[0017] Source of raw materials In the following examples, the cross-linked poly(N-isopropylacrylamide) microgel used was prepared in the laboratory (preparation method is described in Preparation Example 1), and the other raw materials were commercially available industrial-grade products. In this application, unless otherwise specified, "%" represents the percentage of a component relative to the total mass of the quenching medium.

[0018] Preparation Example 1: Preparation of Thermosensitive Crosslinked PNIPAM Microgels 20.0 g of N-isopropylacrylamide (NIPAM) monomer, 0.6 g of N,N'-methylenebisacrylamide (BIS) crosslinking agent (3.0% of monomer mass), and 2.0 g of sodium dodecyl sulfate (SDS) emulsifier were dissolved in 800 mL of deionized water. After purging with nitrogen for 30 min to remove oxygen, the temperature was raised to 70 °C, and 0.15 g of ammonium persulfate (APS) initiator (0.75% of monomer mass) was added. Polymerization was carried out at a constant temperature for 5 hours under nitrogen protection. After the reaction was completed, the product was centrifuged and washed three times with deionized water at 10,000 rpm to remove free monomers and homopolymers. The product was then redispersed in deionized water to obtain a crosslinked PNIPAM microgel pre-emulsion with a solid content of approximately 5%.

[0019] The gel content of the cross-linked PNIPAM microgel prepared in this preparation example was determined by Soxhlet extraction (using tetrahydrofuran as solvent and reflux extraction for 24 hours). Under the same conditions, the gel content of linear poly(N-isopropylacrylamide) (linear PNIPAM) was 0% (completely dissolved). Dynamic light scattering analysis revealed that the average hydrated particle size of the microgel at 25°C was 350 nm, the average contracted particle size at 70°C was 150 nm, and the volumetric phase transition temperature was 35°C. These particle size variations indicate that the microgel contracts when heated above its volumetric phase transition temperature and recovers its swelling state when cooled below its volumetric phase transition temperature.

[0020] According to the particle size recovery rate determination method of this application (see Table 1 for details), the cross-linked PNIPAM microgels prepared in this example had a particle size recovery rate of 90% to 98% after 5 cycles of temperature change from 25℃ to 70℃ to 25℃.

[0021] Example 1 This embodiment provides a PAG water-based quenching medium containing temperature-sensitive polymer microgels, with the following components by weight percentage: PAG polymer (ethylene oxide / propylene oxide block copolymer, m / n=30, Mn=30000) 3.5% Polyether-modified polymethylsiloxane (grafting rate 60%, Mn=6500) 1.5%, fatty amine polyoxyethylene ether (octadecylamine polyoxyethylene (60) ether) 2.0%, Triethanolamine 0.6%, benzotriazole 0.5% Cross-linked PNIPAM microgels (VPTT=35℃, hydrated particle size 350nm, shrunken particle size 150nm) 0.3% Salicylic acid 0.15%; Deionized water: Balance.

[0022] In this embodiment, the hydration particle size recovery rate of the cross-linked PNIPAM microgel after recovering from above the volume phase transition temperature to below the volume phase transition temperature is not less than 90%.

[0023] This embodiment provides a method for preparing the above-mentioned PAG water-based quenching medium, the specific steps of which are as follows: S1: Take the cross-linked PNIPAM microgel pre-emulsion (calculated based on 0.3g of effective ingredient) prepared in Preparation Example 1, disperse it in 50g of deionized water, and stir it at 30℃ (at least 5℃ below VPTT=35℃) until it is uniformly dispersed to obtain the microgel pre-dispersion. S2: Add 3.5g of PAG polymer to 40g of deionized water, heat to 65℃, stir until completely dissolved to obtain PAG base liquid, and then cool to 30℃. S3: At 30°C, add 1.5g of polyether-modified polymethylsiloxane, 2.0g of fatty amine polyoxyethylene ether, 0.6g of triethanolamine, 0.5g of benzotriazole and 0.15g of salicylic acid sequentially to the PAG base liquid in step S2, and stir until homogeneous. S4: At 30°C, slowly add the microgel pre-dispersion obtained in step S1 to the mixture in step S3, add deionized water to make up to a total mass of 100g, and continue stirring for 30min until homogeneous to obtain the final product.

[0024] Example 2 The difference between this embodiment and Example 1 lies in the different components and their corresponding structural parameters, and their varying dosages. Specifically: The amount of PAG polymer used is 2.0 wt%, the molar ratio of ethylene oxide to propylene oxide is m / n=20, and the number average molecular weight is Mn=20000; The amount of polyether-modified polymethylsiloxane used is 0.5 wt%, the grafting rate is 50%, and the number average molecular weight is Mn=5000. The amount of fatty amine polyoxyethylene ether used is 1.0 wt%; the amount of triethanolamine used is 0.2 wt%. The dosage of benzotriazole is 0.2 wt%; The amount of cross-linked PNIPAM microgel used was 0.05wt%, its volume phase transition temperature was VPTT=32℃, its hydrated particle size was 250nm (below VPTT), and its contracted particle size was 120nm (above VPTT). The dosage of salicylic acid is 0.05 wt%. Deionized water: Balance.

[0025] In preparation steps S1-S4, the compounding temperature is adjusted to 27℃, while the PAG dissolution temperature remains at 65℃. The types of other components and preparation methods are the same as in Example 1.

[0026] The cross-linked PNIPAM microgel described in this embodiment recovers its hydrated particle size by no less than 90% when it recovers from a temperature above the volumetric phase transition temperature to a temperature below the volumetric phase transition temperature.

[0027] Example 3 The difference between this embodiment and Example 1 lies in the different components and their corresponding structural parameters, and their varying dosages. Specifically: The amount of PAG polymer used is 5.0 wt%, the molar ratio of ethylene oxide to propylene oxide is m / n=40, and the number average molecular weight is Mn=40000; The amount of polyether-modified polymethylsiloxane used is 2.5 wt%, the grafting rate is 70%, and the number average molecular weight is Mn=8000. The amount of fatty amine polyoxyethylene ether used is 3.0 wt%; the amount of triethanolamine used is 1.0 wt%. The dosage of benzotriazole was 0.8 wt%. The amount of cross-linked PNIPAM microgel used was 1.0 wt%, its volume phase transition temperature was VPTT=38℃, its hydrated particle size was 450 nm (below VPTT), and its contracted particle size was 180 nm (above VPTT). The dosage of salicylic acid is 0.3 wt%. Deionized water: Balance.

[0028] In preparation steps S1-S4, the compounding temperature is adjusted to 33℃, while the PAG dissolution temperature remains at 65℃. The types of other components and preparation methods are the same as in Example 1.

[0029] The cross-linked PNIPAM microgel described in this embodiment recovers its hydrated particle size by no less than 90% when it recovers from a temperature above the volumetric phase transition temperature to a temperature below the volumetric phase transition temperature.

[0030] Comparative Example 1 The difference between this comparative example and Example 1 is that the "crosslinked PNIPAM microgel 0.3% (VPTT=35℃, hydrated particle size 350nm, shrinkage particle size 150nm)" in Example 1 is replaced with an equal mass of sodium bentonite (commercially available industrial grade) 0.3%. All other components (PAG 3.5%, siloxane 1.5%, amine ether 2.0%, etc.) and preparation methods (including low-temperature 30℃ compounding) are exactly the same as in Example 1. This comparative example does not contain any thermosensitive cross-linked polymer microgels and contains inorganic layered silicate particles (bentonite).

[0031] Comparative Example 2 The difference between this comparative example and Example 1 is that the "crosslinked PNIPAM microgel 0.3%" in Example 1 is replaced with an equal mass of linear PNIPAM polymer (number average molecular weight Mn≈30000, linear polymer morphology) 0.3%, and the remaining components and preparation methods are the same as in Example 1. In this comparative example, a linear PNIPAM polymer replaced the microgel component in Example 1, containing no microgel particles, and the linear PNIPAM was in linear polymer form. Following the gel content determination method described in Preparation Example 1, Soxhlet extraction was performed for 24 hours using tetrahydrofuran as the solvent, and the gel content of the linear PNIPAM was 0% (completely dissolved).

[0032] Comparative Example 3 The difference between this comparative example and Example 1 is that the "crosslinked PNIPAM microgel 0.3%" in Example 1 is replaced with an equal mass of commercially available organic bentonite (dimethyl dioctadecylammonium modified montmorillonite, with an average particle size of about 1 μm). The remaining components and preparation methods are the same as in Example 1. This comparative example does not contain thermosensitive cross-linked polymer microgels.

[0033] Performance testing 1. Sample preparation and curing The quenching media prepared in the above embodiments and comparative examples are respectively numbered as Sample A (Example 1), Sample B (Example 2), Sample C (Example 3), Sample D (Comparative Example 1), Sample E (Comparative Example 2) and Sample F (Comparative Example 3).

[0034] 2. Testing Methods The performance test items, methods, and standards are shown in Table 1 below.

[0035] Table 1 Performance Test Items and Methods

[0036] 3. Test Results The above performance tests were performed on sample AF, and the test results are shown in the table below.

[0037] Table 2 Performance Test Results

[0038] Note: Gel content is an inherent parameter of microgels / polymers. Comparative Examples 1 and 3 do not contain the corresponding components and are therefore marked "not applicable". The gel content of linear PNIPAM in Comparative Example 2 is 0%. Particle size recovery rate is only applicable to samples containing microgel particles. It cannot be measured in Comparative Examples 1 and 3. The recovery rate of linear PNIPAM in Comparative Example 2 after temperature cycling is less than 50%.

[0039] 4. Test Result Analysis As can be seen from Table 2: Example 1 (Sample A) exhibits the best overall performance, fully meeting the long-term use requirements of industrial cyclic quenching: after high-temperature settling, the precipitate is loose and soft, easily dispersed by light shaking (<0.5%), the aluminum sheet shows no abrasion (weight loss ≤0.01%), the cooling rate at 300℃ is stable (75±2℃ / s), and the particle size recovery rate after 5 cycles of temperature change is ≥95%. Examples 2 (Sample B) and 3 (Sample C) also demonstrate excellent overall performance: the precipitate is soft and flocculent, easily dispersed by light shaking, the aluminum sheet weight loss rate is <0.02%, the particle size recovery rate is ≥90%, and the cooling rate at 300℃ is stable within the range of 74~78℃ / s, meeting the long-term use requirements of industrial cyclic quenching. It is evident that the technical solution of this invention has a wide range of applicable components and good adjustability.

[0040] In contrast, Comparative Example 1, with the same matrix formulation, showed severe hard precipitation (≥10%) and significant abrasion (weight loss of 0.32%) after replacing the microgel with bentonite; Comparative Example 2, using linear PNIPAM instead of microgel, had a particle size recovery rate of less than 50%; Comparative Example 3, using conventional organic modified bentonite, still had an abrasion rate (0.15%) that was 15 times that of Example 1.

[0041] This invention replaces inorganic bentonite with temperature-sensitive polymer microgel as the suspension / film-forming functional component of the quenching medium. By utilizing its reversible physical properties of "high-temperature shrinkage-low-temperature swelling", it solves the problems of high-temperature hard precipitation and pipeline erosion of inorganic bentonite while maintaining cooling performance.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A PAG water-based quenching medium containing a temperature-sensitive polymer microgel, characterized in that, By weight percentage, it consists of the following components: 2.0-5.0 wt% PAG polymer, 0.5-2.5 wt% polyether-modified polymethylsiloxane, 1.0-3.0 wt% fatty amine polyoxyethylene ether, 0.2-1.0 wt% triethanolamine, 0.2-0.8 wt% benzotriazole, 0.05-1.0 wt% thermosensitive crosslinked polymer microgel, 0.05-0.3 wt% salicylic acid, with the balance being deionized water; The quenching medium does not contain inorganic layered silicate particles; The thermosensitive cross-linked polymer microgel has a volume phase transition temperature of 30~40℃; the hydrated particle size of the thermosensitive cross-linked polymer microgel is 200~500nm below the volume phase transition temperature, and the contracted particle size is 100~200nm above the volume phase transition temperature.

2. The PAG water-based quenching medium as described in claim 1, characterized in that, The thermosensitive cross-linked polymer microgel is selected from any one or a combination of cross-linked poly(N-isopropylacrylamide) microgel, cross-linked poly(N,N-diethylacrylamide) microgel, and cross-linked poly(N-vinylcaprolactam) microgel; preferably, it is cross-linked poly(N-isopropylacrylamide) microgel.

3. The PAG water-based quenching medium as described in claim 1, characterized in that, When the thermosensitive cross-linked polymer microgel is cooled from above the volumetric phase transition temperature to below the volumetric phase transition temperature, the recovery rate of its hydrated particle size is not less than 90%.

4. The PAG water-based quenching medium as described in any one of claims 1 to 3, characterized in that, The mass ratio of the thermosensitive crosslinked polymer microgel to the PAG polymer is 1:5 to 1:

50.

5. The PAG water-based quenching medium as described in claim 1, characterized in that, The PAG polymer is a block copolymer or random copolymer of ethylene oxide and propylene oxide, wherein the molar ratio of ethylene oxide units to propylene oxide units is m / n=20~40, and the number average molecular weight is 20000~40000.

6. The PAG water-based quenching medium as described in claim 1, characterized in that, The polyether-modified polymethylsiloxane has a polyether grafting rate of not less than 50% and a number average molecular weight of 5000~8000.

7. A method for preparing a PAG water-based quenching medium containing thermosensitive polymer microgel as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1. The thermosensitive crosslinked polymer microgel is dispersed in deionized water and stirred until uniformly dispersed under conditions below its volume phase transition temperature to obtain a microgel pre-dispersion. S2. Add PAG polymer to deionized water at 60~70℃ and stir until completely dissolved to obtain PAG base liquid. Then cool the liquid to a temperature lower than the volume phase transition temperature of the thermosensitive crosslinked polymer microgel. S3. Under conditions below the volumetric phase transition temperature, polyether-modified polymethylsiloxane, fatty amine polyoxyethylene ether, triethanolamine, benzotriazole and salicylic acid are added sequentially to the PAG base liquid in step S2, and stirred until homogeneous. S4. Under conditions below the volumetric phase transition temperature, slowly add the microgel pre-dispersion obtained in step S1 to the mixture in step S3, replenish the remaining deionized water, and continue stirring until homogeneous to obtain the PAG water-based quenching medium.

8. The preparation method according to claim 7, characterized in that, In steps S1 to S4, the operating temperature of each step is no higher than the volume phase transition temperature of the thermosensitive crosslinked polymer microgel minus 5°C.

9. The application of the PAG water-based quenching medium as described in any one of claims 1 to 6 or the PAG water-based quenching medium prepared by the preparation method described in any one of claims 7 to 8 in the quenching treatment of aluminum alloys.

10. The application as described in claim 9, characterized in that, The aluminum alloy is selected from 2-series, 6-series, or 7-series aluminum alloys; preferably, it is a 7-series aluminum alloy with a Cu content of not less than 1.0 wt%.

Images