Magnesium alloy cutting fluid and preparation method thereof

Abstract

The invention relates to the technical field of metal working fluids, in particular to a magnesium alloy cutting fluid and a preparation method thereof. The magnesium alloy cutting fluid is prepared from the following components in parts by mass: 6 to 10 parts of alcohol amine, 3 to 6 parts of organic phosphonic acid, 2 to 4 parts of ether carboxylic acid, 1 to 3 parts of waterborne polyether, 2 to 4 parts of phosphate, 1 to 3 parts of special amine, 0.5 to 2 parts of siloxane ketone, 0.5 to 2 parts of waterborne silicone oil, 0.5 to 2 parts of chelating agent, 1 to 3 parts of polyethylene polyamine, 0.1 to 0.5 part of waterborne graphene extreme pressure agent, 0 to 1.2 parts of auxiliary agent and 65 to 85 parts of water. By compounding various lubricants and extreme pressure agents such as alcohol amine, ether carboxylic acid, water-based polyether, phosphate, siloxane ketone, water-based silicone oil and a water-based graphene extreme pressure agent, an effective lubricating film is formed in the cutting process, friction is reduced, cutting force is reduced, formation of built-up edges is inhibited, and the service life of a cutter is prolonged.

Description

Technical Field

[0001] This invention relates to the field of metalworking fluid technology, specifically a magnesium alloy cutting fluid and its preparation method. Background Technology

[0002] AZ91D is one of the most widely used cast magnesium alloys, belonging to the Mg-Al-Zn alloy system. This alloy achieves strengthening through the synergistic effect of aluminum (Al), zinc (Zn), and manganese (Mn), thus striking a good balance between strength, lightweight, and corrosion resistance. As one of the lowest density metals among engineering structural materials, AZ91D magnesium alloy possesses excellent specific strength (e.g., 154 MPa·cm³ / g) and specific stiffness, holding an irreplaceable position in fields with urgent needs for lightweighting, such as automotive, 3C electronics, and aerospace.

[0003] The main advantages of AZ91D magnesium alloy include its lightweight, high specific strength, and good casting properties. It has a low density but good mechanical properties, with a tensile strength of approximately 230 MPa and a yield strength of approximately 160 MPa. Furthermore, this alloy possesses a certain degree of damping capability, absorbing vibrations and reducing noise, a characteristic that is particularly valuable in some precision equipment applications.

[0004] However, AZ91D magnesium alloy also has certain limitations. Although its corrosion resistance is better than that of pure magnesium, it is still not as good as that of aluminum alloys or steel, especially in humid or salt spray environments where it is prone to corrosion.

[0005] In the field of magnesium alloy machining, AZ91D, as a widely used high-strength cast magnesium alloy, places special demands on the performance of cutting fluids during its machining process. However, existing commercially available cutting fluid products have significant technical limitations when applied to the machining of AZ91D magnesium alloys.

[0006] The first manifestation is the lack of lubrication efficiency, that is, it is difficult to form a continuous and stable physical and chemical lubricating film under the high pressure interface of high-speed cutting, which leads to a sharp increase in cutting friction resistance and induces a serious built-up edge phenomenon, directly resulting in accelerated tool wear and shortened service life.

[0007] At the same time, due to their weak rust and corrosion resistance, such cutting fluids cannot effectively passivate the extremely high electrochemical activity of magnesium alloys, which makes it easy for magnesium hydroxide white spots or oxidation and blackening to form on the surface of the machined workpiece, seriously damaging the surface forming quality and yield.

[0008] An even more serious challenge lies in its prominent environmental safety risks. The release of volatile organic compounds (VOCs) from the product not only deteriorates the working environment, but also, in the high-temperature environment of the cutting zone, the highly active magnesium chips are very likely to undergo a violent oxidation reaction with the water-based medium and cause combustion. The instantaneous temperature can reach over 600°C, posing a significant fire and explosion hazard.

[0009] The aforementioned problems, such as lubrication failure, difficulty in controlling corrosion, and lack of safety barriers, overlap and produce synergistic negative effects, ultimately leading to low processing efficiency, frequent tool replacements, and soaring environmental governance costs during the production process. This poses a dual threat to the health and safety of operators and the economic benefits of the enterprise.

[0010] Therefore, developing an AZ91D magnesium alloy-specific cutting fluid that combines high-efficiency lubrication, strong corrosion protection, low volatility, and flame-retardant properties of magnesium chips is key to solving the current bottleneck in precision machining of magnesium alloys. Summary of the Invention

[0011] Regarding the aforementioned technical problems of AZ91D magnesium alloy cutting fluid in terms of lubrication performance, rust prevention, environmental safety, and material compatibility, the technical solution adopted by this invention to solve these problems is as follows: A magnesium alloy cutting fluid, by mass parts, comprises 6-10 parts of alkanolamine, 3-6 parts of organophosphonic acid, 2-4 parts of ether carboxylic acid, 1-3 parts of waterborne polyether, 2-4 parts of phosphate ester, 1-3 parts of special amine, 0.5-2 parts of siloxane ketone, 0.5-2 parts of waterborne silicone oil, 0.5-2 parts of chelating agent, 1-3 parts of polyethylene polyamine, 0.1-0.5 parts of waterborne graphene extreme pressure agent, 0-1.2 parts of additives, and 65-85 parts of water.

[0012] The magnesium alloy cutting fluid of this invention forms a composite lubricating film combining physical adsorption and chemical reaction through the compounding of water-based polyether, water-based graphene extreme pressure agent, and phosphate ester. Specifically, the water-based polyether provides hydrodynamic lubrication at the cutting interface; the water-based graphene extreme pressure agent acts as a nano-sized microsphere ball bearing, utilizing its layered structure to reduce the coefficient of friction under high pressure, and alleviates tool thermal wear caused by cutting heat accumulation by leveraging its high thermal conductivity; the phosphate ester undergoes a tribochemical reaction with the metal surface to generate a low-shear strength chemical film, reducing the adhesion tendency of chips to the tool, mitigating built-up edge formation, thereby improving workpiece surface quality and extending tool life.

[0013] To address the electrochemical activity of magnesium alloys, this invention employs a combination of alkanolamines, organophosphonic acids, a special amine (polyethylene polyamine), and a chelating agent. The alkanolamines, polyethylene polyamine, and the special amine work together to provide an alkaline reserve, stabilizing the system's pH value within the 8.0-9.5 range, thus forming a stable passivation film on the magnesium alloy surface and inhibiting hydrogen evolution. The organophosphonic acid and the chelating agent complex calcium and magnesium ions in the processing water, preventing their deposition in the cutting fluid. Simultaneously, they form a dense adsorption film on the magnesium alloy surface, blocking moisture and air penetration and inhibiting whitening or blackening after processing. Furthermore, the special amine and organophosphonic acid act as rust inhibitors, controlling the surface stability of the magnesium alloy through chemical adsorption rather than strong alkaline corrosion. Their multi-site chelating ability further eliminates the interference of hard water ions such as calcium and magnesium in the water on the stability of the cutting fluid, preventing solution stratification or filter clogging caused by the precipitation of metal soaps.

[0014] Among them, siloxane ketones and water-based silicone oil form a hydrophobic layer on the chip surface, which can reduce the contact area between magnesium chips and water, reduce the hydrogen release rate of the reaction, and, combined with the use of low-volatility base liquid, reduce the concentration of harmful vapors in the working environment and reduce the risk of combustion and explosion caused by hydrogen accumulation.

[0015] Furthermore, the ether carboxylic acid and siloxane components synergistically reduce the surface tension of the cutting fluid, improve its permeability and cleaning properties, and promote the discharge of chips with the fluid flow, preventing their accumulation inside the machine tool. Moreover, the chelating agent maintains the chemical stability of the cutting fluid under different water quality conditions, prevents the precipitation of effective components, and ensures continuous stability during the machining process.

[0016] Furthermore, the alkanolamine includes one or more of monoethanolamine, diethanolamine, and triethanolamine.

[0017] This invention uses alkanolamine compounds to provide an alkaline reserve for the system, which can stabilize the pH value of the cutting fluid in use within the range of 8.5-8.8, enabling the formation of a dense oxide film on the magnesium alloy surface and inhibiting further activation of the substrate. This invention, through the compounding of different types of alkanolamines, maintains rust-preventive properties while reducing skin irritation to operators.

[0018] Overall, alkanolamine compounds can neutralize acidic substances generated during cutting, maintain a relatively stable pH value in the cutting fluid, prevent the failure of rust-inhibiting components or the emergence of corrosion tendency due to excessively low pH, and reduce the exudation of components caused by pH fluctuations. Specifically, the hydroxyl and amino groups in alkanolamine molecules can form an adsorption layer on the metal surface, assisting phosphate esters and water-based polyethers in spreading at the tool-workpiece interface, thereby improving wettability, reducing local friction, and mitigating the risk of surface scratches on AZ91D magnesium alloys caused by uneven lubrication.

[0019] Specifically, diethanolamine and triethanolamine can weakly coordinate with magnesium ions, inhibiting the electrochemical corrosion reaction of magnesium to a certain extent. When used in combination with organophosphonic acids and chelating agents, they can improve the coverage and durability of the rust prevention system. The alkanolamines selected in this invention all have good water solubility and dispersibility, good compatibility with water, waterborne polyethers, siloxane ketones, and other components, and are not prone to causing stratification or gelation. This is beneficial for preparing uniform and stable cutting fluid concentrates or diluents, and facilitates mass production and on-site preparation.

[0020] Furthermore, the organophosphonic acid is one or more of hydroxyethylidene diphosphonic acid, aminotrimethylphosphonic acid, or 2-phosphonobutane-1,2,4-tricarboxylic acid.

[0021] Furthermore, as a preferred embodiment of the present invention and not a limitation thereof, the present invention selects organophosphonic acids such as hydroxyethylidene diphosphonic acid (HEDP), aminotrimethylphosphonic acid (ATMP), or 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA). The phosphonic acid groups in their molecular structure can coordinate with magnesium ions and react in situ with magnesium ions precipitated on the metal surface during the cutting process to form a chemically stable insoluble chelate protective film. This film has high density, can block the contact between the electrolyte solution and the magnesium substrate, inhibit the micro-battery reaction, and has a shielding effect on corrosive ions such as chloride ions, preventing pitting corrosion and intergranular corrosion of AZ91D magnesium alloy in humid environments.

[0022] Specifically, during magnesium alloy machining, the concentration of magnesium ions in the cutting fluid dynamically increases with the wear of the matrix. The organophosphonic acid component can chelate metal ions such as calcium, magnesium, and zinc in the circulating fluid, preventing them from combining with fatty acids or surfactants in the cutting fluid to form metal soap precipitates. This ensures that the cutting fluid does not precipitate or scale during long-term circulation, maintaining unobstructed cooling channels and filtration system efficiency. Compared to traditional inorganic phosphates, hydroxyethylidene diphosphonic acid and 2-phosphonobutane-1,2,4-tricarboxylic acid have superior thermal stability and are less prone to decomposition under high-temperature conditions in the cutting zone, ensuring machining continuity.

[0023] Furthermore, organophosphonates synergistically adsorb with phosphate esters and special amines on the metal surface, forming a gradient lubrication layer that provides boundary lubrication under both low-speed heavy-load and high-speed light-load conditions, reducing tool flank wear. This invention, by selecting organophosphonates, achieves corrosion inhibition at lower phosphorus contents, meeting industrial emission reduction technology requirements. It also exhibits good compatibility with aluminum alloy components or machine tool guide steel that may come into contact with these materials, preventing contact corrosion between dissimilar metals.

[0024] Furthermore, the ether carboxylic acid is one or more of sodium fatty alcohol polyoxyethylene ether carboxylate, ammonium fatty alcohol polyoxyethylene ether carboxylate, or magnesium fatty alcohol polyoxyethylene ether carboxylate.

[0025] This invention utilizes ether carboxylic acid compounds. The polyoxyethylene ether segments and carboxylate groups give them excellent solubility in hard water with high concentrations of calcium and magnesium ions. Especially in environments where magnesium ions continuously precipitate during processing, this effectively prevents metal soap from adhering to the machine tool and workpiece surfaces. Simultaneously, the ether carboxylic acid reduces the surface tension of the cutting fluid, allowing it to rapidly penetrate the cutting area and carrying away fine magnesium chips and oil stains from the processing zone, keeping the tool and workpiece surfaces clean and reducing secondary scratches caused by chip accumulation.

[0026] Specifically, the carboxylic acid groups of the ether carboxylic acid molecule can be directionally adsorbed on the surface of AZ91D magnesium alloy. Its long carbon segments form a flexible protective film at the metal interface, which plays an auxiliary lubricating role and alleviates the peeling force of the tool. This component has good compatibility with extreme pressure corrosion inhibitors such as organophosphonic acid and phosphate ester, which can promote the uniform distribution of each functional component on the metal surface. Through the steric hindrance effect between molecules, it enhances the compactness of the electrochemical shielding layer and inhibits the pitting corrosion risk of the magnesium matrix.

[0027] Furthermore, fatty alcohol polyoxyethylene ether carboxylate exhibits moderate foaming tendency and rapid defoaming speed under dynamic cutting environments, preventing cooling failure or pressure fluctuations due to foam overflow and ensuring the continuous operation of the high-pressure spraying process. Compared to strongly alkaline emulsifiers, ether carboxylate has a moderate pH value and low skin irritation, improving operator safety while protecting the magnesium alloy matrix from excessively rapid alkaline corrosion. In addition, ether carboxylate has a high biodegradability rate and contains no phenols or nitrogen-containing strong chelating components, aligning with the trend of green cutting fluid development and reducing the difficulty and environmental costs of subsequent wastewater treatment for enterprises.

[0028] Furthermore, the aqueous polyether includes synthetic fluorinated polyethers.

[0029] This invention utilizes synthetic fluorinated polyethers, which reduce the surface tension of the cutting fluid, allowing it to overcome the air gaps created by high machining temperatures and penetrate to the interface between the tool and the workpiece, ensuring real-time coverage of cooling and lubrication effects. In some embodiments, the extremely low surface tension of the synthetic fluorinated polyether, combined with the wetting properties of other surfactants, prevents the accumulation of fine magnesium alloy chips at the tool tip or in the workpiece grooves, improving chip removal efficiency and preventing surface scratches caused by secondary cutting.

[0030] Specifically, the synthetic fluorinated polyether has good thermal stability and is not easily carbonized or decomposed under high temperature conditions. The chemically inert isolation layer it provides can inhibit solid-phase welding between AZ91D magnesium alloy and tool material, and reduce adhesive wear of the tool.

[0031] Specifically, fluorinated polyethers have good leveling properties and can form a thin temporary protective film on the surface of magnesium alloys after processing, preventing environmental moisture from corroding the substrate. At the same time, they give the workpiece surface certain anti-fingerprint and easy-to-clean properties, simplifying subsequent cleaning processes.

[0032] This invention uses a modified waterborne polyether, specifically, the modified waterborne polyether is a synthetic fluorinated polyether C6F. 13 CH2CH2(OCH2CH2) n OH, which can reduce surface tension and improve lubricity. The preparation method of modified waterborne polyether includes the following steps: M1. Add the fluorinated alcohol initiator and catalyst to the reactor, heat, and dehydrate under vacuum. Specifically, add 364g of perfluorohexylethanol initiator and 2.0-3.5g of potassium hydroxide to the high-pressure reactor. Start stirring, heat to 100-110℃, and turn on the vacuum pump for dehydration under reduced pressure. Control the vacuum degree below -0.09MPa, and dehydrate for 1.0-1.5 hours to prevent moisture from initiating the formation of ethylene glycol impurities from ethylene oxide, ensuring the purity of the fluorinated polyether. Further, the perfluorohexylethanol is H,1H,2H,2H-perfluoro-1-octanol, with the molecular formula C6F. 13 CH2CH2OH.

[0033] M2. Under inert gas protection, ethylene oxide is introduced into the reactor, and the reaction temperature and pressure are controlled to carry out the polymerization reaction. The vacuum process is stopped, and the air inside the reactor is replaced three times with high-purity nitrogen to eliminate oxygen interference. The temperature is then increased to 120-135℃, and the pressure inside the reactor is maintained at 0.1-0.2 MPa. The required mass of ethylene oxide is calculated according to the set degree of polymerization. When n=10, 440g of ethylene oxide is added, and so on. Ethylene oxide is slowly introduced into the reactor using a metering pump, controlling the feeding rate to ensure the pressure inside the reactor does not exceed 0.4 MPa. After the feeding is complete, the reactor is stirred and kept at 130℃ for 2 hours to depressurize, until the pressure no longer decreases.

[0034] M3. By controlling the amount of ethylene oxide introduced, the degree of polymerization n of the polyether segment (OCH2CH2) is adjusted to obtain the target product C6F. 13 CH2CH2(OCH2CH2) n OH. Cool to 60-80℃, add an appropriate amount of glacial acetic acid or phosphoric acid to neutralize the residual KOH catalyst, and filter to remove the generated inorganic salt precipitate. Finally, remove a very small amount of light components by vacuum distillation to obtain a pale yellow to transparent liquid product: Synthetic fluorinated polyether C6F 13 CH2CH2(OCH2CH2) n OH, where n = 5 to 15.

[0035] Specifically, the preparation method of the modified aqueous polyether uses a monohydroxy fluorinated alcohol as an initiator, ensuring that the generated polyether has a unidirectional linear structure. Compared with polyhydroxy initiators, the product obtained by this invention has a narrower molecular weight distribution and exhibits better kinetic response speed when reducing surface tension.

[0036] Furthermore, C6F in the molecule 13 The segment has extremely strong hydrophobic and oleophobic properties, and can be oriented at the interface between the cutting fluid and air, and between the cutting fluid and metal. It can reduce the surface tension of the system with very low addition amount. The extremely low surface tension ensures that the cutting fluid can quickly penetrate into the nanoscale gaps where the tool contacts the magnesium alloy, carry away heat and provide extreme pressure protection.

[0037] In addition, the hydrophilicity provided by the polyether segments ensures the solubility of the product in water-based media, while the molecular film formed by the fluorocarbon segments on the surface of magnesium chips can effectively block water molecules, thereby synergistically inhibiting the hydrogen evolution reaction during the cutting process of magnesium alloys.

[0038] Furthermore, the phosphate ester includes one or more of potassium alkyl phosphate, sodium aryl phosphate, and sodium alkyl phosphate.

[0039] This invention utilizes phosphate ester salt components. Under the instantaneous high temperature in the cutting zone, phosphate ester groups can undergo a tribochemical reaction with the magnesium alloy surface, generating a phosphate chemical reaction film with low shear strength and high melting point. This film can withstand high loads and prevent direct dry friction at the metal interface. The spatial barrier provided by the alkyl or aryl long chains reduces cutting resistance and heat, mitigates tool flank wear, and ensures smooth machining under complex conditions.

[0040] Specifically, the anionic groups dissociated from phosphate salts in aqueous solution can be directionally adsorbed onto the anodic active sites on the surface of magnesium alloys, forming a dense molecular-level shielding layer. This shielding layer has good compatibility with the passivation film formed by organophosphonic acid and alkanolamine, synergistically improving the pitting corrosion resistance of magnesium alloys during temporary storage after processing and suppressing surface blackening caused by local potential differences.

[0041] This invention selects phosphate esters in the form of potassium or sodium salts, which gives them good solubility and dispersibility in water-based systems. They are less likely to generate excessive mechanical foam under high-speed circulating spray. At the same time, this component has a certain ability to resist interference from external oils, which can reduce the negative impact of external oils such as guide rail oil and hydraulic oil on the lubrication performance of the cutting fluid and extend the service life of the cutting fluid.

[0042] Furthermore, aryl phosphates offer better thermal stability, while alkyl phosphates focus on penetration lubrication. The combination of these two allows the cutting fluid to protect magnesium alloys while also providing corrosion inhibition protection for common machining center components such as aluminum, steel, and copper, reducing the risk of galvanic corrosion in multi-material environments. In addition, the long carbon chains of alkyl phosphate salts provide physical steric hindrance, while sodium and potassium salt forms enhance their stability in hard water, and the benzene ring structure of aryl phosphate salts improves film-forming stability at high temperatures in the cutting zone.

[0043] Furthermore, the special amine is one or more of benzyldimethylamine, morpholine, N,N-dimethylethanolamine, and imidazoline derivatives.

[0044] This invention uses benzyl dimethylamine and N,N-dimethylethanolamine to adjust and maintain the alkaline environment of the system. It has a moderate alkalinity, which can stabilize the pH value within the passivation range of magnesium alloy, inhibit the matrix activation caused by the accumulation of acidic substances. In addition, the stable alkaline environment can improve the stability of magnesium hydroxide passivation film, thereby reducing the hydrogen evolution reaction rate of water-based media on the surface of magnesium alloy.

[0045] Specifically, morpholine and imidazoline derivatives contain heteroatoms such as nitrogen and oxygen in their molecular structure, which can form coordination bonds with the magnesium alloy surface through lone pairs of electrons. Furthermore, the long carbon chains of imidazoline derivatives are oriented on the metal surface, which can construct a molecular adsorption film with hydrophobic properties. This film layer intertwines with the chemical films generated by organophosphonic acids and phosphate esters, filling the film defects at the microscopic level and enhancing the system's resistance to corrosion from salt spray and humid environments.

[0046] Specifically, the special amine components have a certain bio-inhibitory effect, which can reduce the amount of bactericide added, extend the service life of the cutting fluid, and prevent rancidity caused by microbial growth. Compared with traditional long-chain aliphatic amines, the special amines generate less static and dynamic foam in the circulation system, which is beneficial to maintaining pressure stability under high-pressure cutting conditions and avoiding the decrease in cooling efficiency caused by air entrainment.

[0047] In addition, morpholine and N,N-dimethylethanolamine have a certain degree of volatility, which can provide temporary vapor phase protection for magnesium alloy parts in the non-immersion area of ​​the machine tool cavity, reducing corrosion above the liquid surface. Furthermore, as a salt-forming neutralizing agent for acidic components such as organophosphonic acid and ether carboxylic acid, the amine salts generated have good water solubility and boundary lubrication properties, which helps to reduce the frictional power consumption between the tool and the workpiece.

[0048] Specifically, imidazoline derivatives can enhance the adsorption capacity of magnesium alloy surfaces and improve rust prevention performance. The preparation method of imidazoline derivatives includes the following steps: N1. Fatty acids react with diethylenetriamine under nitrogen protection. Specifically, 282g of oleic acid is added to a four-necked flask equipped with a stirrer, thermometer, water separator, and vacuum system. Under nitrogen protection, 113.5g of diethylenetriamine is slowly added dropwise. A slight excess of diethylenetriamine helps ensure complete reaction of the fatty acids and reduces the acid value in the final product.

[0049] The mixture of N2 and N1 is heated to initiate an amidation reaction. Stirring is started and the temperature is slowly increased to 140-160℃. One carboxyl group of the fatty acid undergoes a dehydration reaction with the terminal amino group of the diethylenetriamine to form an amide bond. This temperature is maintained for 2-3 hours. The water production is observed through a water separator. When the amount of distilled water is close to 90% of the theoretically calculated value (approximately 18g), the amidation stage is basically complete.

[0050] A mixture of N3 and N2 underwent a cyclization reaction under high temperature and reduced pressure. After the reaction was complete, the mixture was cooled to obtain the product. The temperature was then increased to 200-230℃, and the vacuum system was gradually opened to reduce the system pressure to below -0.08 MPa. The reaction was maintained under these high temperature and reduced pressure conditions for 3-4 hours. By forcibly removing the second water molecule, the ring closure of the amide intermediate to form an imidazoline ring was promoted. After the reaction was completed, the temperature was cooled to below 60℃ to obtain a brownish-yellow viscous liquid of oleic acid imidazoline.

[0051] Overall, in the preparation method of imidazoline derivatives, the conversion rate of intermediates was maximized and residual fatty acid soaps were reduced by using a two-stage stepped heating process and a subsequent reduced-pressure cyclization process. The high-purity imidazoline ring structure ensures that it can form more stable coordination bonds on the surface of AZ91D magnesium alloy through the lone pair electrons of nitrogen atoms, thereby enhancing the anti-erosion and anti-rust ability of the cutting fluid.

[0052] The oleic acid-based imidazoline prepared in this invention possesses a hydrophobic tail chain up to 17 carbon atoms. This tail chain forms a tightly packed layer on the metal surface, giving the cutting fluid excellent hydrophobic isolation properties, effectively preventing water-based media from penetrating into the magnesium alloy matrix and kinetically inhibiting the hydrogen evolution reaction. The primary amine retained at the end of the synthesized product gives it good water-soluble dispersion potential. In the cutting fluid system, this component not only acts as a powerful corrosion inhibitor but also provides boundary lubrication, synergistically reducing the coefficient of friction during cutting in conjunction with phosphate esters and graphene.

[0053] Further, the chelating agent is one or more of EDTA-4Na, DTPA-5Na, or HEDP sodium salt, and the polyethylene polyamine is one or more of tetraethylenepentamine, pentaethylenehexamine, or triethylenetetramine.

[0054] This invention employs a chelating agent combined with polyethylene polyamines. The chelating agent chelates calcium, magnesium, and aluminum ions precipitated from the processing water and the magnesium alloy matrix, preventing them from combining with ether carboxylic acid or phosphate ester components to form insoluble metal soaps. This avoids cutting fluid turbidity, stratification, or filter clogging caused by metal ion accumulation, ensuring the stability of the cutting fluid during recycling. The molecular chains of tetraethylenepentamine, pentaethylenehexamine, or triethylenetetramine contain multiple active amino groups, enabling multi-point anchoring and adsorption on the magnesium alloy surface. The adsorption film formed by their long-chain molecules at the metal interface is relatively dense, effectively shielding against the penetration of water molecules and corrosive media such as chloride ions. Furthermore, polyethylene polyamines have a neutralizing synergistic effect with acidic components such as organophosphonic acids. The resulting complex exhibits good hydrophobicity and chemical stability on the metal surface, inhibiting the formation of white spots on the magnesium alloy surface.

[0055] Overall, the timely chelation of free magnesium ions on the surface by chelating agents, combined with the coverage of active sites by polyethylene polyamines, can change the electrochemical characteristics of magnesium alloy surfaces, increase the hydrogen evolution overpotential, and synergize with the physical isolation effect of siloxane components to reduce the hydrogen release rate during processing and improve the operational safety in closed processing environments.

[0056] Based on the above settings, the use of high-purity polyethylene polyamine and stable sodium salt chelating agent can enhance the system's resistance to high cutting temperatures and microbial erosion, slow down the deterioration rate of the cutting fluid, and further, the strong chelating effect ensures that the cutting fluid residue on the workpiece surface is easily removed by subsequent water rinsing, avoiding the formation of hard and difficult-to-remove deposits of metal ion chelates on the workpiece surface, and improving the yield of subsequent coating or oxidation processes.

[0057] Furthermore, the adjuvants include biological stabilizers, antioxidants, and pH buffers.

[0058] This invention selects biological stabilizers, antioxidants, and pH buffers as additives. Among them, the biological stabilizers can inhibit the growth and metabolism of microorganisms in the cutting fluid, prevent the proliferation of bacteria and mold in the circulation system, avoid cutting fluid deterioration, odor, and pH fluctuations caused by microbial decomposition of organic components, reduce the need for frequent cutting fluid replacement, and lower operating costs and wastewater treatment pressure. Specifically, 0.05-0.1 parts of isothiazolinone derivatives are selected as the biological stabilizers to inhibit bacterial reproduction.

[0059] Furthermore, antioxidants, designed for the localized high-temperature environment during machining, can capture free radicals under the high-temperature impact of high-speed cutting, inhibiting the thermal oxidative degradation of organic lubricating components such as water-based polyethers and phosphate esters. This ensures that the lubricating film maintains its physicochemical properties after multiple machining cycles, preventing functional failure or abnormal viscosity caused by component oxidation. Specifically, 0.05-0.1 parts of butylated hydroxytoluene (BHT) is selected as the antioxidant, which can delay the oxidative decomposition of organophosphonic acids.

[0060] Furthermore, the pH buffer, together with the alkanolamine and special amines, forms a buffer solution. During processing, when acidic substances intrude, the system's alkalinity is maintained within a preset range through ion balance, preventing activation of the magnesium alloy matrix due to pH reduction. The stable pH environment ensures that film-forming components such as organophosphonic acids and polyethylene polyamines are in a good chemical state, guaranteeing the anti-corrosion effect on AZ91D magnesium alloy. Specifically, 0.5-1 part of AMP buffer is used to maintain pH stability. More specifically, the AMP buffer is aminomethylpropanol-2-amino-2-methyl-1-propanol.

[0061] Another object of the present invention is to provide a method for preparing a magnesium alloy cutting fluid, comprising the magnesium alloy cutting fluid as described above, including the following steps: S1. Add water to the mixing tank, heat to 40-50℃, add chelating agent and stir evenly. Stir for 8-12 minutes at a speed of 300-500 r / min. The lower speed is used to assist heat transfer and promote dissolution, while avoiding the introduction of excessive air due to excessive speed. S2. Add the alkanolamine, organophosphonic acid, special amine, and polyethylene polyamine in sequence, and stir until homogeneous. The stirring time is 12-18 minutes, and the stirring speed is 400-600 r / min. The medium stirring speed helps the heat to spread rapidly, ensures that the generated amine salt corrosion inhibitor molecules are evenly distributed, and prevents local overheating. S3. Add ether carboxylic acid, phosphate ester, and water-based polyether, stir evenly for 18-22 minutes at a speed of 800-1200 r / min; a higher speed can provide sufficient shear force to allow the ether carboxylic acid to fully emulsify the phosphate ester and other components into fine micelles. S4. Add siloxane ketone and water-based silicone oil, stir evenly for 8-12 minutes at a speed of 600-900 r / min; using a medium to high speed ensures that it is evenly coated by the emulsion system formed in the previous step, while avoiding the system foam from getting out of control due to extremely high speed. S5. Add the water-based graphene extreme pressure agent and additives, stir evenly for 3-8 minutes at a speed of 400-600 r / min; the low speed is to prevent excessive shear from damaging the modification layer on the graphene surface and to ensure that the additives are gently mixed in the system. S6. Cool to room temperature and adjust the pH value to 8.0-9.5 to obtain the magnesium alloy cutting fluid.

[0062] This invention provides a high-performance cutting fluid with lubricating properties, rust prevention, low irritating odor, and the ability to inhibit the oxidation reaction of magnesium chips. In preparation step S1, water is preheated to 40-50°C and a chelating agent is added. The heat-assisted dissolution solves the problem of slow dissolution and easy adhesion of the chelating agent in cold water, thereby reducing the surface tension of the water and accelerating the diffusion and dissolution of the chelating agent. By preferentially chelating metal ions in the mother liquor, it can prevent the subsequent addition of acidic or ionic components from forming insoluble precipitates with hard water metal ions, ensuring the clarity of the system.

[0063] In step S2, components such as alkanolamine and organophosphonic acid are added sequentially. The alkanolamine and organophosphonic acid undergo an acid-base neutralization reaction and release heat. By adding them sequentially and stirring continuously, the heat of reaction is dispersed to prevent local overheating and degradation of sensitive components. In addition, this sequence helps to generate amine salt structures with corrosion inhibition in situ in the system. This molecular-level dispersion has better interfacial adsorption activity than directly adding finished salts. At the same time, the generated amine salts are used to assist in the emulsification of subsequent oily components.

[0064] In steps S3 and S4, ether carboxylic acid, phosphate ester, and silicon components are introduced in stages. Ether carboxylic acid, as a surface-active component, preferentially establishes a micellar environment, providing a solubilization basis for the subsequently added phosphate ester, hydrophobic siloxane ketone, and waterborne silicone oil, ensuring the microemulsification effect of the hydrophobic components in the aqueous phase. In addition, this feeding sequence can prevent surfactants such as ether carboxylic acid from encapsulating silicone oil particles, causing the silicon components to aggregate, thereby ensuring that the cutting fluid can uniformly form a hydrophobic isolation layer on the magnesium chip surface during use.

[0065] Adding an aqueous graphene extreme pressure agent in step S5, placed as the last step, can reduce the damage of shear force to the graphene structure, thereby maintaining the integrity of its surface modification layer. In addition, adding it after the system viscosity has basically stabilized can also utilize the steric hindrance effect of the aforementioned polyether and surface active components to prevent secondary aggregation of graphene nanosheets, ensuring its uniform suspension in the circulating liquid and stable performance of extreme pressure.

[0066] In step S6, endpoint control is performed by adjusting the pH value to 8.0-9.5, placing it in the passivation zone of the magnesium alloy. This not only inhibits the hydrogen evolution reaction but also prevents excessive alkalinity from irritating the operator's skin. Furthermore, adjusting the pH value after cooling to room temperature eliminates the interference of temperature on electrode measurements, ensuring the standardization of product performance for each batch during mass production.

[0067] Furthermore, the kinematic viscosity of this cutting fluid at 20°C is 5-15 mm. 2 / s, when used, it needs to be diluted with deionized water at a mass ratio of 1:10 to 1:20. Due to the buffering effect of the alkanolamine and special amine, the pH of the diluted working solution is automatically stabilized in the range of 8.5–8.8, which inhibits the corrosion of magnesium alloy by forming a weakly alkaline environment and avoids saponification reaction.

[0068] The rust prevention performance of this cutting fluid meets the GB / T 6144-2010 standard: No rust on cast iron sheets for 24 hours, no rust on cast iron sheets for 48 hours, and no discoloration on copper sheets for 24 hours.

[0069] The beneficial effects of this invention are as follows: 1) This invention uses a combination of various lubricants and extreme pressure agents, such as alkanolamines, ether carboxylic acids, waterborne polyethers, phosphate esters, siloxane ketones, waterborne silicone oils, and waterborne graphene extreme pressure agents, to form an effective lubricating film during the cutting process, thereby reducing friction, lowering cutting forces, inhibiting the formation of built-up edge, and extending tool life.

[0070] 2) This invention utilizes the synergistic effect of components such as alkanolamines, organophosphonic acids, special amines, and polyethylenepolyamines to form a multi-layered rust-preventing protective layer, effectively preventing rust on workpieces and machine tools and avoiding defects such as blackening or white spots on the surface. By compounding various rust inhibitors and stabilizers, as well as water-based graphene extreme pressure agents, it effectively inhibits the oxidative combustion of magnesium chips, improving processing safety. The complexing effect of chelating agents prevents metal ion precipitation, improving the stability of the cutting fluid. This invention does not contain harmful substances such as nitrites, chlorine, and sulfur, has a low irritating odor, and is health-friendly for operators.

[0071] 3) This invention solves the problem of side reactions between components and improves stability by adding components in stages. This invention sets the order of addition, temperature conditions and final pH adjustment, which can give full play to the synergistic effect of each functional component in the preparation process, and obtain magnesium alloy cutting fluid with matching performance. This is beneficial to improve machining quality, extend tool life and reduce production and maintenance costs, while taking into account operational safety and environmental friendliness. Detailed Implementation

[0072] To enable those skilled in the art to better understand the technical solutions described in this invention, the following embodiments are provided for illustration. Unless otherwise specified, the raw materials, reagents, or devices used in the following embodiments can be obtained from conventional commercial channels or by existing known methods.

[0073] A magnesium alloy cutting fluid, by mass parts, comprises 6-10 parts of alkanolamine, 3-6 parts of organophosphonic acid, 2-4 parts of ether carboxylic acid, 1-3 parts of waterborne polyether, 2-4 parts of phosphate ester, 1-3 parts of special amine, 0.5-2 parts of siloxane ketone, 0.5-2 parts of waterborne silicone oil, 0.5-2 parts of chelating agent, 1-3 parts of polyethylene polyamine, 0.1-0.5 parts of waterborne graphene extreme pressure agent, 0-5 parts of additives, and 65-85 parts of water. The waterborne graphene extreme pressure agent can be Guangdong Youmatou waterborne extreme pressure lubricant.

[0074] The alkanolamine includes one or more of monoethanolamine, diethanolamine, and triethanolamine.

[0075] The organophosphonic acid is one or more of hydroxyethylidene diphosphonic acid, aminotrimethylphosphonic acid, or 2-phosphonobutane-1,2,4-tricarboxylic acid.

[0076] The ether carboxylic acid is one or more selected from sodium fatty alcohol polyoxyethylene ether carboxylate, ammonium fatty alcohol polyoxyethylene ether carboxylate, or magnesium fatty alcohol polyoxyethylene ether carboxylate. Specifically, sodium fatty alcohol polyoxyethylene ether carboxylate adopts C 12-14 Sodium fatty alcohol polyoxyethylene ether (3) carboxylate, ammonium fatty alcohol polyoxyethylene ether carboxylate is lauryl alcohol polyoxyethylene ether (3) carboxylate, and magnesium fatty alcohol polyoxyethylene ether carboxylate is coconut oil alcohol polyoxyethylene ether (5) carboxylate.

[0077] The aqueous polyether includes synthetic fluorinated polyether.

[0078] The waterborne polyether used is a modified waterborne polyether, which is a synthetic fluorinated polyether C6F. 13 CH2CH2(OCH2CH2) n The preparation method of OH-modified aqueous polyether includes the following steps: M1. Add 364g of perfluorohexylethanol initiator and 2.0-3.5g of potassium hydroxide to a high-pressure reactor. Start stirring, heat to 100-110℃, and turn on the vacuum pump for dehydration under reduced pressure, controlling the vacuum degree below -0.09MPa. The dehydration time is 1.0-1.5 hours. The perfluorohexylethanol is H,1H,2H,2H-perfluoro-1-octanol, with the molecular formula C6F. 13 CH2CH2OH.

[0079] M2. Replace the air inside the reactor three times with high-purity nitrogen, and continue heating to 120-135℃, maintaining the pressure inside the reactor at 0.1-0.2MPa. Slowly introduce ethylene oxide into the reactor using a metering pump, controlling the feeding rate to ensure the pressure inside the reactor does not exceed 0.4MPa. After the feeding is complete, continue stirring and maintaining the temperature at 130℃ for 2 hours to carry out the depressurization reaction, until the pressure no longer decreases.

[0080] M3. By controlling the amount of ethylene oxide introduced, the degree of polymerization n of the polyether segment (OCH2CH2) is adjusted to obtain the target product C6F. 13 CH2CH2(OCH2CH2) n OH. Cool to 60-80℃, add an appropriate amount of glacial acetic acid or phosphoric acid to neutralize the residual KOH catalyst, filter to remove the generated inorganic salt precipitate, and finally remove a very small amount of light components by vacuum distillation to obtain a pale yellow to transparent liquid product: Synthesis of fluorinated polyether C6F 13 CH2CH2(OCH2CH2) n OH, where n = 5 to 15.

[0081] The phosphate ester includes one or more of potassium alkyl phosphate, sodium aryl phosphate, and sodium alkyl phosphate. The potassium alkyl phosphate is potassium dodecyl phosphate, the sodium aryl phosphate is sodium phenolate polyoxyethylene ether phosphate, and the sodium alkyl phosphate is sodium octyl phosphate.

[0082] The special amine is one or more of benzyl dimethylamine, morpholine, N,N-dimethylethanolamine, and imidazoline derivatives.

[0083] The preparation method of imidazoline derivatives includes the following steps: N1. In a four-necked flask equipped with a stirrer, thermometer, water separator, and vacuum system, add 282g of oleic acid. Under nitrogen protection, slowly add 113.5g of diethylenetriamine dropwise.

[0084] The mixture of N2 and N1 is heated to carry out the amidation reaction; stirring is turned on and the temperature is slowly increased to 140-160℃, and this temperature is maintained for 2-3 hours. The water production is observed through the water separator. When the distillate water volume is close to 90% of the theoretical calculation value, the amidation stage is basically completed.

[0085] N3 is added, and the temperature is further increased to 200-230℃. The vacuum system is gradually turned on to reduce the system pressure to below -0.08MPa. The reaction is maintained under these high temperature and low pressure conditions for 3-4 hours. After the reaction is completed, the temperature is lowered to below 60℃ to obtain a brownish-yellow viscous liquid of oleic acid imidazoline.

[0086] The chelating agent is one or more of EDTA-4Na, DTPA-5Na, or HEDP sodium salt, and the polyethylene polyamine is one or more of tetraethylenepentamine, pentaethylenehexamine, or triethylenetetramine.

[0087] The adjuvants include biological stabilizers, antioxidants, and pH buffers.

[0088] The biological stabilizer used is 0.05-0.1 parts of isothiazolinone derivative, and MBS bactericide and preservative from Delan Chemical is selected.

[0089] The antioxidant used is 0.05-0.1 parts of butylated hydroxytoluene (BHT).

[0090] Use 0.5-1 part of AMP buffer to maintain pH stability. The AMP buffer used is AMP-95 aminomethylpropanol 2-amino-2-methyl-1-propanol from Hubei Maidehao.

[0091] A method for preparing magnesium alloy cutting fluid, comprising the magnesium alloy cutting fluid as described above, including the following steps: S1. Add water to the mixing tank, heat to 40-50℃, add chelating agent and stir evenly for 8-12 minutes at a speed of 300-500 r / min; S2. Add alcohol amine, organophosphonic acid, special amine and polyethylene polyamine in sequence, stir evenly, stir for 12-18 minutes, and rotate at 400-600 r / min; S3. Add ether carboxylic acid, phosphate ester, and water-based polyether, stir until homogeneous, stir for 18-22 minutes, and rotate at 800-1200 r / min. S4. Add siloxane ketone and water-based silicone oil, stir evenly for 8-12 minutes at a speed of 600-900 r / min; S5. Add water-based graphene extreme pressure agent and additives, stir evenly for 3-8 minutes at a speed of 400-600 r / min; S6. Cool to room temperature and adjust the pH value to 8.0-9.5 to obtain the magnesium alloy cutting fluid.

[0092] The kinematic viscosity of the cutting fluid at 20°C is 5-15 mm. 2 / s, when used, it needs to be diluted with deionized water at a mass ratio of 1:10 to 1:20, and the pH value after dilution should be between 8.5 and 8.8.

[0093] The rust prevention performance of this cutting fluid meets the GB / T 6144-2010 standard: No rust on cast iron sheets for 24 hours, no rust on cast iron sheets for 48 hours, and no discoloration on copper sheets for 24 hours.

[0094] Based on the above, the following are specific embodiments of the present invention: Example 1 A magnesium alloy cutting fluid, by mass parts, comprises 8 parts triethanolamine, 5 parts hydroxyethylidene diphosphonic acid, and C 12-14 3 parts of sodium carboxylate of fatty alcohol polyoxyethylene ether (3), 2 parts of synthetic fluorinated polyether, 3 parts of potassium dodecyl phosphate, 2 parts of benzyl dimethylamine, 1 part of siloxane ketone, 1 part of waterborne silicone oil, 1 part of EDTA-4Na, 2 parts of tetraethylenepentamine, 0.3 parts of waterborne graphene extreme pressure agent, and 73 parts of water.

[0095] A method for preparing magnesium alloy cutting fluid, comprising the magnesium alloy cutting fluid as described above, including the following steps: S1. Add water to the mixing vessel, heat to 45°C, add chelating agent and stir evenly for 10 minutes at a speed of 400 r / min; S2. Add alcohol amine, organophosphonic acid, special amine and polyethylene polyamine in sequence, stir evenly for 15 minutes, and rotate at 500 r / min. S3. Add ether carboxylic acid, phosphate ester, and water-based polyether, stir until homogeneous, stir for 20 minutes at a speed of 1000 r / min; S4. Add siloxane ketone and water-based silicone oil, stir evenly for 10 minutes at a speed of 800 r / min; S5. Add water-based graphene extreme pressure agent, stir evenly for 5 minutes at a speed of 500 r / min; S6. Cool to room temperature and adjust the pH value to 8.5 to obtain the magnesium alloy cutting fluid.

[0096] Example 2 A magnesium alloy cutting fluid, by mass parts, comprises 6 parts diethanolamine, 4 parts aminotrimethylphosphonic acid, 2.5 parts lauryl alcohol polyoxyethylene ether (3) carboxylic acid ammonium, 1.5 parts synthetic fluorinated polyether, 2.5 parts sodium phenolate polyoxyethylene ether phosphate, 1.5 parts morpholine, 1.5 parts siloxane ketone, 1.5 parts waterborne silicone oil, 1.5 parts DTPA-5Na, 2.5 parts pentaethylenehexamine, 0.4 parts waterborne graphene extreme pressure agent, and 74.6 parts water.

[0097] A method for preparing magnesium alloy cutting fluid, comprising the magnesium alloy cutting fluid as described above, including the following steps: S1. Add water to the mixing vessel, heat to 40°C, add chelating agent and stir evenly for 8 minutes at a speed of 300 r / min; S2. Add alcohol amine, organophosphonic acid, special amine and polyethylene polyamine in sequence, stir evenly, stir for 12 minutes, and rotate at 400 r / min; S3. Add ether carboxylic acid, phosphate ester, and water-based polyether, stir until homogeneous, stir for 18 minutes, and rotate at 800 r / min. S4. Add siloxane ketone and water-based silicone oil, stir evenly for 8 minutes at a speed of 600 r / min; S5. Add water-based graphene extreme pressure agent, stir evenly for 3 minutes at a speed of 400 r / min; S6. Cool to room temperature and adjust the pH value to 8.0 to obtain the magnesium alloy cutting fluid.

[0098] Example 3 A magnesium alloy cutting fluid, by mass, comprises 7 parts monoethanolamine, 4.5 parts 2-phosphobutane-1,2,4-tricarboxylic acid, 3.5 parts cocoyl alcohol polyoxyethylene ether (5) magnesium carboxylate, 2.5 parts synthetic fluorinated polyether, 3.5 parts sodium octyl phosphate, 2.5 parts N,N-dimethylethanolamine, 1 part siloxane ketone, 1 part waterborne silicone oil, 1 part sodium HEDP salt, 2 parts triethylenetetramine, 0.2 parts waterborne graphene extreme pressure agent, and 70.8 parts water.

[0099] A method for preparing magnesium alloy cutting fluid, comprising the magnesium alloy cutting fluid as described above, including the following steps: S1. Add water to the mixing vessel, heat to 50°C, add chelating agent and stir evenly for 12 minutes at a speed of 500 r / min; S2. Add alcohol amine, organophosphonic acid, special amine and polyethylene polyamine in sequence, stir evenly, stir for 18 minutes, and rotate at 600 r / min; S3. Add ether carboxylic acid, phosphate ester, and water-based polyether, stir until homogeneous, stir for 22 minutes, and rotate at 1200 r / min. S4. Add siloxane ketone and water-based silicone oil, stir evenly for 12 minutes at a speed of 900 r / min; S5. Add water-based graphene extreme pressure agent, stir evenly for 8 minutes at a speed of 600 r / min; S6. Cool to room temperature and adjust the pH value to 9.5 to obtain the magnesium alloy cutting fluid.

[0100] Example 4 A magnesium alloy cutting fluid, by mass parts, comprises 3 parts diethanolamine, 3 parts triethanolamine, 3 parts hydroxyethylidene diphosphonic acid, 3 parts 2-phosphobutane-1,2,4-tricarboxylic acid, 2 parts lauryl polyoxyethylene ether (3) carboxylic acid ammonium, 3 parts synthetic fluorinated polyether, 2 parts sodium phenolate polyoxyethylene ether phosphate, 3 parts oleic acid imidazoline, 0.5 parts siloxane ketone, 2 parts aqueous silicone oil, 1 part DTPA-5Na, 1 part HEDP sodium salt, 2 parts tetraethylenepentamine, 1 part pentaethylenehexamine, 0.5 parts aqueous graphene extreme pressure agent, 0.1 parts isothiazolinone derivative, 0.1 parts dibutylhydroxytoluene, 1 part AMP buffer, and 65 parts water.

[0101] A method for preparing magnesium alloy cutting fluid, comprising the magnesium alloy cutting fluid as described above, including the following steps: S1. Add water to the mixing vessel, heat to 40°C, add chelating agent and stir evenly for 9 minutes at a speed of 400 r / min; S2. Add alcohol amine, organophosphonic acid, special amine and polyethylene polyamine in sequence, stir evenly, stir for 16 minutes, and rotate at 500 r / min; S3. Add ether carboxylic acid, phosphate ester, and water-based polyether, stir until homogeneous, and stir for 21 minutes at a speed of 900 r / min. S4. Add siloxane ketone and water-based silicone oil, stir well, stir for 9 minutes, and rotate at 700 r / min. S5. Add water-based graphene extreme pressure agent and additives, stir evenly for 4 minutes at a speed of 500 r / min; S6. Cool to room temperature and adjust the pH value to 9.5 to obtain the magnesium alloy cutting fluid.

[0102] Example 5 A magnesium alloy cutting fluid, by mass parts, comprises 4 parts diethanolamine, 6 parts triethanolamine, 3 parts aminotrimethylphosphonic acid, and C 12-14 2 parts of sodium carboxylate of fatty alcohol polyoxyethylene ether (3), 2 parts of magnesium carboxylate of coconut oil alcohol polyoxyethylene ether (5), 1 part of synthetic fluorinated polyether, 2 parts of potassium salt of dodecyl phosphate, 2 parts of sodium salt of phenol polyoxyethylene ether phosphate, 0.5 parts of benzyl dimethylamine, 0.5 parts of oleic acid imidazoline, 2 parts of siloxane ketone, 0.5 parts of waterborne silicone oil, 0.5 parts of EDTA-4Na, 1 part of triethylenetetramine, 0.1 parts of waterborne graphene extreme pressure agent, 0-5 parts of additives, 0.05 parts of isothiazolinone derivative, 0.05 parts of dibutylhydroxytoluene, 0.5 parts of AMP buffer, and 85 parts of water.

[0103] A method for preparing magnesium alloy cutting fluid, comprising the magnesium alloy cutting fluid as described above, including the following steps: S1. Add water to the mixing vessel, heat to 48°C, add chelating agent and stir evenly for 10 minutes at a speed of 500 r / min; S2. Add alcohol amine, organophosphonic acid, special amine and polyethylene polyamine in sequence, stir evenly, stir for 16 minutes, and rotate at 600 r / min; S3. Add ether carboxylic acid, phosphate ester, and water-based polyether, stir until homogeneous, stir for 20 minutes, and rotate at 900 r / min. S4. Add siloxane ketone and water-based silicone oil, stir evenly for 9 minutes at a speed of 800 r / min; S5. Add water-based graphene extreme pressure agent and additives, stir evenly for 5 minutes at a speed of 500 r / min; S6. Cool to room temperature and adjust the pH value to 8.8 to obtain the magnesium alloy cutting fluid.

[0104] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the aqueous graphene extreme pressure agent in Comparative Example 1 is replaced with chlorinated paraffin, while the other components, dosages, preparation steps, and rotation speeds are the same as in Example 1.

[0105] Comparative Example 2 The difference between Comparative Example 2 and Example 2 is that Comparative Example 2 did not add siloxane ketones and water-based silicone oil, while the remaining components, amounts, preparation steps, and rotation speeds were the same as in Example 2.

[0106] Comparative Example 3 The difference between Comparative Example 3 and Example 3 is that Comparative Example 3 did not add coconut oil alcohol polyoxyethylene ether (5) magnesium carboxylate, while the remaining components, dosages, preparation steps, and rotation speeds were the same as in Example 3.

[0107] Comparative Example 4 The difference between Comparative Example 4 and Example 4 is that Comparative Example 4 did not add oleic acid imidazoline, while the remaining components, amounts, preparation steps, and rotation speed were the same as in Example 4.

[0108] Comparative Example 5 The difference between Comparative Example 5 and Example 5 is that in Comparative Example 5, aminotrimethylphosphonic acid was replaced with trisodium phosphate, while the remaining components, amounts, preparation steps, and rotation speed were the same as in Example 5.

[0109] Comparative Example 6 The difference between Comparative Example 6 and Example 4 is that in Comparative Example 6, the synthesized fluorinated polyether was replaced with fatty alcohol polyoxyethylene ether AEO-9, while the remaining components, amounts, preparation steps, and rotation speed were the same as in Example 4.

[0110] Comparative Example 7 The difference between Comparative Example 7 and Example 4 is that in Comparative Example 7, the materials from steps S2 and S3 are added simultaneously for mixing at a speed of 900 r / min. The remaining components, amounts, preparation steps, and speeds are the same as in Example 4.

[0111] Comparative Example 8 The difference between Comparative Example 8 and Example 4 is that the rotation speed in step S3 of Comparative Example 8 is adjusted to 300 r / min, while the remaining components, amounts, preparation steps, and rotation speed are the same as in Example 4.

[0112] Comparative Example 9 The difference between Comparative Example 9 and Example 5 is that the order of steps S3 and S4 is interchanged in Comparative Example 9, while the other components, amounts, and rotation speeds are the same as in Example 5.

[0113] Comparative Example 10 The difference between Comparative Example 10 and Example 5 is that in Comparative Example 10, all components were added to water at once and mixed at a total stirring time of 1 hour and a speed of 800 r / min. The remaining components and amounts were the same as in Example 5.

[0114] Comparative Example 11 Comparative Example 11 used commercially available Saint-Gobain general-purpose water-based cutting fluid.

[0115] Comparative Example Twelve Comparative Example 12 used commercially available Saint-Gobain general-purpose mineral oil-based cutting fluid.

[0116] 1. pH value after 5% dilution: 8.5-8.8; 2. Kinematic viscosity (20℃): 5-15 mm² / s; 3. Rust prevention performance: When installed according to GB / T 6144-2010 standard, Grade 1 cast iron sheets will not rust after 24 hours, cast iron sheets will not rust after 48 hours, and copper sheets will not discolor after 24 hours; 4. Lubrication performance (four-ball machine test): PB value (maximum non-seize load), PD value (sintering load); 5. Extreme pressure performance (Timken test): ≥35 psi; 6. Magnesium chip oxidation and combustion test: Magnesium chips were placed in cutting fluid and heated at 150°C for 1 hour. No combustion was observed. 7. Surface quality of magnesium alloy workpieces (observed after 48 hours): No defects, no blackening, no white spots; 8. Tool life (h); No surface damage; 9. Odor rating after 7 days of continuous use: Level 1 (slight odor, no discomfort), Level 2 (obvious odor, no discomfort), Level 3 (irritating odor, slight discomfort), Level 4 (strong odor, pungent or noticeably putrid odor). Performance tests were conducted on the above embodiments and comparative examples, and the results are summarized in Tables 1 and 2.

[0117] Table 1: Test results of comprehensive performance of magnesium alloy cutting fluids in Examples 1 to 5

[0118] Table 2: Test results of comprehensive performance of magnesium alloy cutting fluids in Comparative Examples 1 to 12

[0119] As shown in Tables 1 and 2, it can be seen from Examples 1 to 5 that the magnesium alloy cutting fluid of the present invention has stable pH value, rust prevention performance, lubrication performance, extreme pressure performance, processing safety, durability and environmental friendliness. It breaks through the significant technical limitations of existing commercially available cutting fluid products when applied to the processing of AZ91D magnesium alloy, and further meets application needs and user experience.

[0120] In Comparative Example 1, water-based graphene was replaced with chlorinated paraffin. Overall, the extreme pressure performance of Comparative Example 1 decreased. Compared to Example 1, localized white spots appeared on the workpiece surface in Comparative Example 1, and an irritating odor was generated during use. This indicates that chloride ions in chlorinated paraffin accelerate localized corrosion of magnesium alloys. The decrease in PB / PD value and Timken extreme pressure value in Comparative Example 1 indirectly proves that graphene provides a more stable friction-reducing effect in the extreme pressure region through a sheet-slip mechanism, while avoiding the formation of harmful byproducts.

[0121] Comparative Example 2, lacking both siloxane and water-based silicone oil, produced smoke during the magnesium chip oxidation combustion test, while the Example showed no combustion. This indicates that the component can form a hydrophobic coating on the magnesium chip surface, reducing direct contact between water and magnesium, effectively inhibiting the hydrogen evolution reaction, and ensuring operational safety.

[0122] In Comparative Example 3, without the addition of ether carboxylic acid, the cutting fluid viscosity increased, and the workpiece surface showed slight blackening accompanied by a putrid odor. This was due to insufficient wettability leading to poor removal of fine magnesium chips, which accumulated and oxidized in the machining area. Simultaneously, chip putrefaction exacerbated system deterioration, demonstrating the necessity of ether carboxylic acid in improving wetting and chip removal and maintaining system cleanliness in this invention.

[0123] After comparing the results of removing oleic acid-based imidazoline from the control group, the white spot coverage on the workpiece surface increased, but the overall rust prevention performance still met the standards. This indicates that imidazoline, through strong coordination adsorption between tertiary amine nitrogen and the magnesium surface, can fill the microscopic defects of the organophosphonic acid-polyethylene polyamine passivation film, improve the film density and resistance to chloride ion penetration, and play an auxiliary role in corrosion inhibition.

[0124] In Comparative Example 5, replacing organophosphonic acid with trisodium phosphate raised the pH of the system to above 9.8. The workpiece surface became noticeably blacker with increased white spots, and its rust-preventive performance decreased. This was because the inorganic phosphate was too alkaline, leading to a loose Mg(OH)₂ film that easily reacted with dissolved Mg. 2+ The formation of soluble complexes, which prevented the formation of an effective protective layer, validated the advantage of organophosphonic acids in constructing dense passivation films within a suitable pH range.

[0125] In Comparative Example 6, replacing the synthesized fluorinated polyether with ordinary polyether AEO-9 resulted in a decrease in both extreme pressure performance and tool life. Ordinary polyethers lack high-temperature stability and are prone to oxidation and breakage in the cutting zone. In contrast, the fluorinated polyether of this invention, with its high CF bond energy, can maintain the continuity of the lubricating film at high temperatures, thereby extending tool life.

[0126] Comparative Example 7 involved adding materials simultaneously in steps S2 and S3; Comparative Example 8 reduced the rotation speed of step S3 to 300 r / min; and Comparative Example 9 involved swapping the order of steps S3 and S4. All three resulted in increased system viscosity, decreased workpiece surface quality, or deteriorated safety performance. This indicates that stepwise material addition, appropriate rotation speed, and a reasonable feeding sequence are prerequisites for achieving uniform dispersion and functional synergy of the components. Inappropriate process parameters will damage emulsification stability and interfacial film quality.

[0127] Comparative Example 10, which used a single-feeding process, showed a comprehensive deterioration in all performance indicators, including rust prevention failure, shortened tool life, increased safety risks, and worsened odor. This demonstrates that the stepwise preparation process of this invention plays a decisive role in ensuring the uniformity of component dissolution, chemical compatibility, and long-term stability.

[0128] Comparative Example 11 is a general-purpose water-based liquid, which cannot effectively passivate the magnesium alloy interface. It showed safety hazards in the magnesium chip combustion test and could not prevent the oxidation and blackening problem unique to magnesium alloys.

[0129] Comparative Example 12 used a mineral oil-based cutting fluid, which had excellent lubrication performance, but the magnesium chips burned rapidly at 150°C, posing an uncontrollable safety risk. This indicates that the oil-based system has poor chemical compatibility with magnesium chips and cannot prevent the oxidation and blackening problem unique to magnesium alloys, making it unsuitable for magnesium alloy machining scenarios.

[0130] This invention utilizes a combination of various lubricants and extreme pressure agents, including alkanolamines, ether carboxylic acids, waterborne polyethers, phosphate esters, siloxane ketones, waterborne silicone oils, and waterborne graphene extreme pressure agents, to form an effective lubricating film during the cutting process. This reduces friction, lowers cutting forces, inhibits built-up edge formation, and extends tool life.

[0131] This invention utilizes the synergistic effect of components such as alkanolamines, organophosphonic acids, special amines, and polyethylenepolyamines to form a multi-layered rust-preventing protective layer, effectively preventing rust on workpieces and machine tools and avoiding defects such as blackening or white spots on the surface. By compounding various rust inhibitors and stabilizers, as well as water-based graphene extreme pressure agents, it effectively inhibits the oxidative combustion of magnesium chips, improving processing safety. The complexing effect of chelating agents prevents metal ion precipitation, improving the stability of the cutting fluid. This invention does not contain harmful substances such as nitrites, chlorine, and sulfur, has a low irritating odor, and is health-friendly for operators.

[0132] This invention addresses the issue of side reactions between components and improves stability through a phased addition process. By setting the order of addition, temperature conditions, and final pH adjustment, this invention can fully leverage the synergistic effect of each functional component during the preparation process, resulting in a magnesium alloy cutting fluid with matched performance. This is beneficial for improving machining quality, extending tool life, and reducing production and maintenance costs, while also ensuring operational safety and environmental friendliness.

[0133] The above examples are merely illustrative of the technical content of the present invention to facilitate easier understanding by the reader, but do not imply that the implementation of the present invention is limited to these examples. Any technical extensions or re-creations made based on the present invention are protected by the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A magnesium alloy cutting fluid, characterized in that: By mass, its components include 6-10 parts of alkanolamine, 3-6 parts of organophosphonic acid, 2-4 parts of ether carboxylic acid, 1-3 parts of waterborne polyether, 2-4 parts of phosphate ester, 1-3 parts of special amine, 0.5-2 parts of siloxane ketone, 0.5-2 parts of waterborne silicone oil, 0.5-2 parts of chelating agent, 1-3 parts of polyethylene polyamine, 0.1-0.5 parts of waterborne graphene extreme pressure agent, 0-1.2 parts of additives, and 65-85 parts of water.

2. The magnesium alloy cutting fluid according to claim 1, characterized in that: The alkanolamine includes one or more of monoethanolamine, diethanolamine, and triethanolamine.

3. The magnesium alloy cutting fluid according to claim 1, characterized in that: The organophosphonic acid is one or more of hydroxyethylidene diphosphonic acid, aminotrimethylphosphonic acid, or 2-phosphonobutane-1,2,4-tricarboxylic acid.

4. The magnesium alloy cutting fluid according to claim 1, characterized in that: The ether carboxylic acid is one or more of sodium fatty alcohol polyoxyethylene ether carboxylate, ammonium fatty alcohol polyoxyethylene ether carboxylate, or magnesium fatty alcohol polyoxyethylene ether carboxylate.

5. The magnesium alloy cutting fluid according to claim 1, characterized in that: The aqueous polyether includes synthetic fluorinated polyether.

6. The magnesium alloy cutting fluid according to claim 1, characterized in that: The phosphate ester includes one or more of potassium alkyl phosphate, sodium aryl phosphate, and sodium alkyl phosphate.

7. The magnesium alloy cutting fluid according to claim 1, characterized in that: The special amine is one or more of benzyl dimethylamine, morpholine, N,N-dimethylethanolamine, and imidazoline derivatives.

8. The magnesium alloy cutting fluid according to claim 1, characterized in that: The chelating agent is one or more of EDTA-4Na, DTPA-5Na, or HEDP sodium salt, and the polyethylene polyamine is one or more of tetraethylenepentamine, pentaethylenehexamine, or triethylenetetramine.

9. The magnesium alloy cutting fluid according to claim 1, characterized in that: The adjuvants include biological stabilizers, antioxidants, and pH buffers.

10. A method for preparing a magnesium alloy cutting fluid, comprising the magnesium alloy cutting fluid according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Add water to the mixing tank, heat to 40-50℃, add chelating agent and stir evenly; S2. Add alcohol amine, organophosphonic acid, special amine, and polyethylene polyamine in sequence, and stir until homogeneous; S3. Add ether carboxylic acid, phosphate ester, and water-based polyether, and stir until homogeneous; S4. Add siloxane and water-based silicone oil, and stir well; S5. Add water-based graphene extreme pressure agent and additives, and stir until homogeneous; S6. Cool to room temperature and adjust the pH value to 8.0-9.5 to obtain the magnesium alloy cutting fluid.

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