Quenching medium, its preparation method and application

Abstract

Disclosed is a quenching medium, which is composed of PAG polymer, polyether modified polymethylsiloxane, fatty amine polyoxyethylene ether, triethanolamine, benzotriazole, bentonite, salicylic acid, and the balance is water. In addition, the preparation method and application of the quenching medium are also disclosed. The quenching medium can improve the tensile strength and fracture toughness of 7000 series aluminum alloy after heat treatment. Compared with the prior art, the quenching medium can obtain equivalent or even better mechanical properties at a lower polymer concentration.

Description

Technical Field

[0001] This invention belongs to the field of metal heat treatment technology; it relates to a quenching medium, its preparation method, and its application. Background Technology

[0002] Heat treatment is a crucial technical step in the manufacturing of various mechanical products, and the quality of heat-treated workpieces directly affects their performance and lifespan. Quenching is a core step in heat treatment, involving heating the workpiece to a specified phase transformation temperature range, holding it at that temperature, and then rapidly cooling it with a coolant to achieve the required hardness and strength. The cooling performance of the quenching medium directly influences the phase transformation process and the resulting microstructure, thus directly impacting the workpiece's performance. Therefore, research in this area is of great importance to countries worldwide.

[0003] As is well known, commonly used quenching media include water and quenching oil. Due to the difference in cooling capacity between water and oil, many workpieces often deform and crack when quenched with water, while oil quenching fails to achieve the desired hardness or complete quenching. Therefore, in recent years, various countries have attached great importance to research and development in this field. The search for new quenching media, especially given the global energy crisis of the last century and the resulting rise in petroleum prices, has made finding alternatives to quenching oil a top priority.

[0004] Most water-soluble quenching media on the market are currently based on PAG and PVP. The use of these two polymers can reduce the cooling rate when using water alone. This prevents metal from cracking or becoming brittle due to sudden cooling. The vapor film formed on the hot workpiece surface reduces the cooling rate during forming. Quenching fluids containing different polymers will form different vapor films, exhibiting different quenching characteristics. PAG-based quenching media have been widely developed and applied both domestically and internationally. For example, UCON A and UCON E produced by Union Carbide, AQ251 and AQ364 produced by Hofton, and AQUATENSID produced by Derunbao are widely used in domestic and international markets.

[0005] Polyether / polyalkoxyl (PAG) quenching media containing PAG polymers have an inverse melting point of 63-85℃, during which time white flocculent substances will appear in the liquid. Maintaining a high concentration can form a stable vapor film (or product suspension film). Within the temperature range where martensite forms, the limiting quenching rate is 200-350℃.

[0006] Chinese invention application CN101660027A discloses a water-soluble polyether quenching medium for quenching metal materials. Its components and contents by weight percentage are: 1-30% water-soluble polyether, 0.1-1.0% rust inhibitor, 100-500ppm defoamer, 0.1-1.0% composite bactericide, 0.2-2% pH adjuster, and the balance being water. The water-soluble polyether is a condensation product of ethylene oxide and propylene oxide. Its characteristics include: readily available raw materials, simple production process, low price, good rust prevention, defoaming, and antibacterial properties, a wide cooling rate range (between oil and water), solving the problems of insufficient hardness in oil-quenched workpieces and cracking and deformation in water-quenched workpieces. It also reduces the risk of quenching ignition, improves production safety, and eliminates oil fume emissions, reducing environmental pollution.

[0007] Chinese invention application CN102140571A discloses an environmentally friendly water-soluble quenching medium. The components, by weight percentage, are: 0.5-20% water-soluble polyether with a molecular weight of 20,000-30,000; 0.5-30% water-soluble polyether with a molecular weight of 5,000-15,000; 0.5-1.5% rust inhibitor; 0.1-0.2% defoamer; 300-800 ppm bactericide; 200-500 ppm surfactant; 0.1-5% pH adjuster; and the remainder is water. This water-soluble quenching medium is suitable for the heat treatment of large castings and forgings. Furthermore, the average molecular weight of the polyether mixture can be adjusted as needed, and the heat resistance and viscosity of the water-soluble medium can be moderately adjusted. The quenching cooling rate can be adjusted by changing its concentration, thus expanding the application range of the quenching medium.

[0008] Chinese invention application CN112679723A discloses a two-terminated alkyl-terminated PAG polyether and its preparation method. This two-terminated alkyl-terminated PAG polyether is a novel type of PAG polyether obtained by alkyl-termining the terminal hydroxyl groups of a traditional PAG polyether. The two-terminated alkyl-terminated PAG polyether exhibits excellent viscosity-temperature properties, corrosion resistance, and lower pour point and foaming properties. At a consistent kinematic viscosity at 40°C, quenching fluids formulated with the two-terminated alkyl-terminated PAG polyether described herein exhibit superior quenching performance.

[0009] Among various aluminum alloys, the 7000 series aluminum alloys, which combine high strength and high toughness, are the most widely used. This series of alloys exhibits typical age-hardening characteristics and belongs to the Al-Zn-Mg aluminum alloy system.

[0010] In the heat treatment of 7000 series aluminum alloys, quenching is the most important and rigorous step. The purpose of quenching is to cool the solution-treated aluminum alloy to a relatively low temperature (generally room temperature) as quickly as possible, obtaining a supersaturated solid solution of solute atoms and vacancies, laying the foundation for age hardening. Generally, in the production of 7000 series aluminum alloys, the highest possible quenching cooling rate must be used to obtain the required mechanical properties and corrosion resistance. However, if the quenching cooling rate is too high, the residual stress level in the material will also be very large, causing warping or cracking of the aluminum alloy workpiece, while also resulting in poor dimensional stability.

[0011] Compared to the success and widespread adoption of PAG (polyacrylamide) quenching media in developed countries, China still lags significantly in the development and application of PAG quenching media in industry. For the heat treatment of 7000 series aluminum alloys, existing PAG quenching media still suffer from insufficient mechanical properties in the aluminum alloy workpieces. Strengthening research on water-soluble polymer quenching media and developing and producing stable organic polymer quenching agents that are environmentally friendly and aligned with sustainable development strategies is an inevitable trend. Summary of the Invention

[0012] To address the aforementioned deficiencies in existing technologies, the present invention aims to provide a quenching medium, its preparation method, and its application. Using the quenching medium described in this invention, the tensile strength and fracture toughness of 7000 series aluminum alloys after heat treatment are simultaneously improved. Compared to existing technologies, comparable or even better mechanical properties can be obtained at lower polymer concentrations.

[0013] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a quenching medium, wherein the composition of the quenching medium is as follows:

[0014]

[0015] According to the quenching medium of the present invention, the average molecular weight of the PAG polymer is Mw = 20,000-40,000.

[0016] According to the quenching medium of the present invention, the structural formula of the PAG polymer is:

[0017] HO-(CH2CH2O) m -[CH2CH(CH3)O] n -H; m / n = 30.

[0018] According to the quenching medium of the present invention, the average molecular weight of the polyether-modified polymethylsiloxane is Mw = 5,500-6,000.

[0019] According to the quenching medium of the present invention, the polyether-modified polymethylsiloxane has the following structural formula:

[0020]

[0021] x / y / p / q=46 / 2 / 16 / 4.

[0022] According to the quenching medium of the present invention, the fatty amine polyoxyethylene ether is selected from octadecylamine polyoxyethylene (60) ether.

[0023] According to the quenching medium of the present invention, the bentonite is selected from sodium-based bentonite.

[0024] On the other hand, the technical solution adopted by the present invention is as follows: a method for preparing a quenching medium according to the present invention, comprising: adding each component to water and mixing them evenly.

[0025] On another note, the technical solution adopted by the present invention is as follows: an application of the quenching medium according to the present invention for quenching treatment of aluminum alloys.

[0026] In the application described in this invention, the aluminum alloy is selected from 7000 series aluminum alloys.

[0027] The present invention has the following beneficial technical effects:

[0028] Using the quenching medium described in this invention, the tensile strength and fracture toughness of 7000 series aluminum alloys after heat treatment are simultaneously improved. Compared with existing technologies, comparable or even better mechanical properties can be obtained at lower polymer concentrations. Detailed Implementation

[0029] It must be noted that, unless the context clearly specifies otherwise, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the” can include one or more referents (i.e., two or more, including two).

[0030] Unless otherwise specified, numerical ranges in this invention are approximate and therefore may include values ​​outside of said range. The numerical range may be expressed in this invention as from “about” a particular value and / or to “about” another particular value. When such a range is expressed, another aspect includes from said one particular value and / or to another particular value. Similarly, when a value is expressed as an approximation using the antecedent “about,” it should be understood that said particular value forms another aspect. It should also be understood that each endpoint in a numerical range is significant in relation to and independent of another endpoint.

[0031] The reference to the weight parts of a specific element or component in the composition or article in the specification and the final claims refers to the weight relationship between that element or component and any other element or component in the composition or article, expressed in parts by weight.

[0032] In this invention, unless specifically indicated otherwise, or implied by the context or customary practice in the art, all solutions referred to herein are aqueous solutions; when the solute in the aqueous solution is a liquid, all fractions and percentages are by volume, and the volume percentage of a component is based on the total volume of the composition or product containing that component; when the solute in the aqueous solution is a solid, all fractions and percentages are by weight, and the weight percentage of a component is based on the total weight of the composition or product containing that component.

[0033] The terms “comprising,” “including,” “having,” and similar expressions used in this invention are not intended to exclude the presence of any optional components, steps, or procedures, whether or not any optional components, steps, or procedures are specifically disclosed. For the avoidance of any doubt, unless stated to the contrary, all methods claimed by using the term “comprising” may include one or more additional steps, equipment parts or components, and / or substances. In contrast, the term “consisting of” excludes any components, steps, or procedures not specifically described or enumerated. Unless otherwise stated, the term “or” refers to members listed individually and in any combination.

[0034] Furthermore, the contents of any patent or non-patent documents referenced in this invention are incorporated herein by full citation, especially regarding definitions disclosed in the relevant field (where there is no inconsistency with any definitions specifically provided herein) and common knowledge.

[0035] In this invention, unless otherwise specified, all parts are parts by weight, temperatures are expressed in °C or at ambient temperature, and pressures are at or near atmospheric pressure. Room temperature means 20-30 °C. Various variations and combinations of reaction conditions exist (e.g., component concentrations, desired solvents, solvent mixtures, temperature, pressure, and other reaction ranges) and conditions that can be used to optimize the purity and yield of the product obtained by the method. Only reasonable routine experiments are required to optimize such method conditions.

[0036] In this invention, the chemical composition of the aluminum alloy is as follows:

[0037] Al-6.7%Zn-2.6%Mg-2.6%Cu-0.06Ti%-0.13%Zr-0.5%Fe-0.12%Si.

[0038] The technical advantages of the present invention over the prior art are further illustrated below through embodiments and comparative examples.

[0039] Those skilled in the art will understand that the embodiments described are merely illustrative of the invention and should not be construed as limiting the invention.

[0040] Example 1

[0041] The formula for the quenching medium is as follows:

[0042] HO-(CH2CH2O) m -[CH2CH(CH3)O] n -H PAG polymer 3wt%;

[0043] The average molecular weight of the PAG polymer is Mw = 30,000; m / n = 30.

[0044]

[0045] 2 wt% polyether-modified polymethylsiloxane;

[0046] The average molecular weight of the polyether-modified polymethylsiloxane is Mw = 5,800.

[0047] x / y / p / q = 46 / 2 / 16 / 4;

[0048]

[0049]

[0050] Comparative Example 1

[0051] The formula for the quenching medium is as follows:

[0052] HO-(CH2CH2O) m -[CH2CH(CH3)O] n -H PAG polymer 5wt%;

[0053] The average molecular weight of the PAG polymer is Mw = 30,000; m / n = 30.

[0054]

[0055] Comparative Example 2

[0056] The formula for the quenching medium is as follows:

[0057]

[0058] 5 wt% polyether-modified polymethylsiloxane;

[0059] The average molecular weight of the polyether-modified polymethylsiloxane is Mw = 5,800.

[0060] x / y / p / q = 46 / 2 / 16 / 4;

[0061]

[0062]

[0063] Comparative Example 3

[0064] The formula for the quenching medium is as follows:

[0065] HO-(CH2CH2O) m -[CH2CH(CH3)O] n -H PAG polymer 4wt%;

[0066] The average molecular weight of the PAG polymer is Mw = 30,000; m / n = 30.

[0067]

[0068] Polyether-modified polymethylsiloxane 3wt%;

[0069] The average molecular weight of the polyether-modified polymethylsiloxane is Mw = 5,800.

[0070] x / y / p / q = 46 / 2 / 16 / 4;

[0071]

[0072] Performance testing

[0073] 20mm thick 7050 aluminum alloy sheet was used. Different quenching media were used to ensure the medium temperature was between 25-35℃. Solution treatment was performed by holding at 495±5℃ for 75 minutes; quenching was carried out in different media, followed by artificial aging at 120℃ for 48 hours. Tensile strength and fracture toughness tests were conducted according to national standards GB / T228.1-2021 and GB / T 4161-2007, respectively; the tensile speed was 2mm / min.

[0074] The results are shown in Table 1.

[0075] Table 1

[0076] Tensile strength / MPa <![CDATA[Fracture toughness / MPa·m 1 / 2 <!-- 6 -->]]> Example 1 608 41.6 Comparative Example 1 561 38.2 Comparative Example 2 553 37.4 Comparative Example 3 572 39.5

[0077] Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various modifications, substitutions, deletions, corrections or adjustments to the technical solutions of this invention, and these equivalent technical solutions also fall within the scope defined by the claims of this invention.

Claims

1. A quenching medium, characterized in that, The formula for the quenching medium is as follows: PAG polymer 3 wt%, PAG polymer molecular formula is HO- (CH2CH2O) m -[CH2CH(CH3)O] n -H; The average molecular weight of the PAG polymer is Mw=30,000; m / n=30. The structural formula of the polyether-modified polymethylsiloxane is: 2wt% polyether-modified polymethylsiloxane; The average molecular weight of the polyether-modified polymethylsiloxane is Mw=5,800; x / y / p / q=46 / 2 / 16 / 4. 2 wt% of octadecylamine polyoxyethylene (60) ether Triethanolamine 0.6 wt% Benzotriazole 0.5 wt%; Sodium-based bentonite 0.2 wt%; Salicylic acid 0.1 wt%; The remainder is water.

2. The method of claim 1, comprising: Add each component to the water and mix well.

3. The application of the quenching medium according to claim 1, used for quenching treatment of aluminum alloys.

4. In the application according to claim 3, the aluminum alloy is selected from 7000 series aluminum alloys.

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