Multifunctional composite grinding fluid for cold working and preparation method of multifunctional composite grinding fluid

Abstract

The invention relates to the technical field of grinding fluid, in particular to multifunctional composite grinding fluid for cold working and a preparation method of the multifunctional composite grinding fluid. The grinding fluid is prepared from the following components in parts by weight: 49-55 parts of basic solvent; 44 to 52 parts of a lubricating system; 1.5 to 4.0 parts of a surface active and dispersing agent; 1.6 to 2.5 parts of an anti-rust and anti-corrosion system; 8-12 parts of a grinding and polishing system; 0.2 to 0.5 part of a rheological modifier; and 0.1 to 0.3 part of an antioxidant. Through the processes of step-by-step preparation, constant-temperature feeding, gradient ultrasonic dispersion, inert atmosphere protection, vacuum high-shear compounding, online performance monitoring and the like, the system is ensured to form a stable microemulsion phase and a uniform suspension phase, and the composite grinding fluid with good shear thinning characteristic, high dispersion stability and long service life is obtained. And when the device is applied to crystal precision machining, high-efficiency material removal and mirror surface polishing can be synchronously realized, the surface roughness is low, and the strict requirements of high-end automotive upholstery are met.

Description

Technical Field

[0001] This invention relates to the field of polishing fluid technology, and in particular to a multifunctional composite polishing fluid for cold working and its preparation method. Background Technology

[0002] As consumers' demands for aesthetics and quality in automotive interiors continue to rise, crystal decorative elements, due to their high transparency, excellent luster, and good wear resistance, have gradually become an important element in high-end automotive interior design. Currently, crystal materials are widely used in the decoration of small, precision components such as gear shift levers, door handles, center console buttons, and ambient lighting, significantly enhancing the overall sense of luxury and technology in the vehicle. The processing of these crystal products typically employs cold-working processes such as CNC precision carving, grinding, and polishing to achieve the shaping of complex curved surfaces and high-precision dimensions.

[0003] In the cold working process of crystal, polishing fluid, as a key auxiliary material, not only plays a role in cooling the tool and workpiece and reducing thermal deformation, but also needs to have excellent lubrication properties to reduce friction and wear, while providing effective grinding and polishing functions to improve processing efficiency and surface finish. However, existing commercially available cutting fluids or polishing fluids generally suffer from single functions and insufficient comprehensive performance: most products only focus on cooling or lubrication, making it difficult to meet the dual requirements of efficient grinding and mirror polishing; some imported composite processing fluids, although having better performance, are expensive and prone to foaming, poor dispersion stability, and long-term use can easily lead to sedimentation, deterioration, and other problems, affecting processing consistency and equipment lifespan.

[0004] Crystal is a brittle material that is prone to microcracks, requiring extremely high stress control and surface integrity during processing. Ordinary polishing fluids are insufficient to meet its high-precision, low-damage processing needs. Summary of the Invention

[0005] (a) Technical problems to be solved In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a multifunctional composite grinding fluid for cold processing of crystal products and its preparation method, which solves the technical problems of traditional processing fluids having single function, poor dispersion stability, easy foaming, insufficient anti-rust and antibacterial properties, and difficulty in achieving both high-efficiency grinding and mirror polishing.

[0006] (II) Technical Solution This application provides a multifunctional composite grinding fluid for cold processing of crystal products, which solves the technical problems of existing processing fluids having single function, poor comprehensive performance, and insufficient stability.

[0007] To achieve the above objectives, this application provides the following technical solution: In a first aspect, this application provides a multifunctional composite polishing slurry for cold working of crystal products, the polishing slurry comprising the following components in parts by weight: Base solvent: 49–55 parts; Lubrication system: 44-52 parts; Surfactants and dispersants: 1.5–4.0 parts; Rust and corrosion prevention system: 1.6–2.5 parts; Grinding and polishing system: 8-12 parts; Rheology modifier: 0.2–0.5 parts; Antioxidant: 0.1 to 0.3 parts.

[0008] In a further embodiment, the base solvent comprises: 48-52 parts deionized water and 1-2 parts ethylene glycol; The lubrication system comprises: 1-3 parts sorbitol, 3-5 parts triethanolamine, 35-37 parts glycerin, and 5-7 parts polyethylene glycol; The surfactant and dispersant comprises: 0.5-1.5 parts of fatty alcohol polyoxyethylene ether and 1-2.5 parts of sodium citrate; The rust and corrosion prevention system comprises: 0.7-1.0 parts of benzotriazole, 0.4-0.6 parts of sodium molybdate, 0.1-0.3 parts of isothiazolinone bactericide, and 0.4-0.6 parts of organosilicon defoamer; The grinding and polishing system comprises: 3-5 parts of diamond microcrystalline powder and 5-7 parts of cerium oxide polishing powder; The rheology modifier is 0.2-0.5 parts of xanthan gum; The antioxidant is 0.1 to 0.3 parts of ascorbyl palmitate.

[0009] The base solvent is primarily deionized water with ethylene glycol as a secondary solvent. This provides excellent thermal conductivity for effective cooling, and the addition of ethylene glycol enhances the system's antifreeze properties, lubricity, and compatibility with organic components, laying the foundation for subsequent microemulsion formation. The lubrication system consists of sorbitol, triethanolamine, glycerol, and polyethylene glycol. Glycerol acts as the primary lubricant, providing the base oil film strength. Triethanolamine combines lubrication and pH buffering functions, promoting film formation on metal surfaces and stabilizing the system. Sorbitol and polyethylene glycol synergistically enhance the viscoelasticity and boundary lubrication properties of the aqueous phase, maintaining the integrity of the lubricating film, especially under high shear conditions, effectively reducing frictional wear between the cutting tool and the crystal workpiece. The surfactant and dispersant, fatty alcohol polyoxyethylene ether (AEO-9), significantly reduces the liquid surface tension, improving wetting and penetration capabilities on the crystal surface. Sodium citrate, as an anionic dispersant, prevents agglomeration of grinding particles through charge repulsion. Both ensure the long-term stable dispersion of the grinding powder in the system. In the rust and corrosion prevention system, benzotriazole forms a dense adsorption film on the surface of copper machine tool parts, while sodium molybdate induces the formation of a passivating oxide film on the steel surface, achieving dual metal protection for the processing equipment. Isothiazolinone bactericides and silicone defoamers maintain the long-term stability of the liquid; the former inhibits spoilage caused by microbial growth, while the latter effectively controls foaming problems that may arise from the introduction of surfactants. The grinding and polishing system uses a blend of diamond microcrystalline powder and cerium oxide polishing powder to achieve integrated rough grinding and fine polishing: diamond microcrystalline powder has extremely high hardness, responsible for efficient material removal and surface smoothing; cerium oxide polishing powder achieves nanoscale surface finishing through chemimechanical action, obtaining a mirror-like gloss. Both work in a stable suspension environment constructed by xanthan gum, avoiding uneven processing caused by sedimentation. Xanthan gum, as a rheology modifier, gives the grinding fluid excellent shear-thinning properties. Its viscosity is high at static or low speeds, effectively suspending solid particles and preventing sedimentation; the viscosity decreases during high-speed processing, facilitating liquid flow and penetration into the processing area. Ascorbyl palmitate, as an antioxidant, protects easily oxidized components such as polyols and amines in the system, extending the service life of the grinding slurry. Together with bactericides and corrosion inhibitors, it maintains a long-term stable operating environment. It achieves highly efficient integration of cooling, lubrication, grinding, polishing, rust prevention, antibacterial properties, foam stabilization, and rheological control, making it particularly suitable for the high-precision, low-damage cold working requirements of brittle materials such as crystal.

[0010] Secondly, the present invention provides a method for preparing a multifunctional composite polishing fluid for cold processing of crystal products, characterized by comprising the following steps: Step 1: Add 38-40 parts of deionized water and 1-2 parts of ethylene glycol to a mixing tank and mix them, and control the temperature at 25±5℃; Step 2: Under constant temperature of 25±5℃, add 1-3 parts of sorbitol, 3-5 parts of triethanolamine, 35-37 parts of glycerol and 5-7 parts of polyethylene glycol in sequence. After the addition is completed, raise the temperature to 60±3℃, increase the stirring speed and stir at a constant temperature. Ensure the formation of a thermodynamically stable microemulsion phase by monitoring the viscosity. Step 3: After cooling to 45±3℃, add 0.5 to 1.5 parts of fatty alcohol polyoxyethylene ether and 1 to 2.5 parts of sodium citrate, stir continuously, and monitor the surface tension and pH value online. When the surface tension is ≤38 mN / m and the pH value is stable at 7.8 to 8.2, the system is considered stable. Step 4: Under an inert atmosphere and at 45±3℃, add 0.7-1.0 parts of benzotriazole, 0.4-0.6 parts of sodium molybdate, 0.1-0.3 parts of isothiazolinone bactericide and 0.4-0.6 parts of organosilicon defoamer in sequence, stir evenly and then test the conductivity. Step 5: Add 3-5 parts diamond microcrystalline powder, 5-7 parts cerium oxide polishing powder, 0.2-0.5 parts xanthan gum, and 10-12 parts deionized water to a separate dispersion tank. After swelling by low-speed stirring at 25±5℃, perform multi-stage ultrasonic treatment until the slurry D90≤2.0 μm to obtain a uniform suspension. Step 6: Inject the suspension obtained in Step 5 into the base liquid in Step 4 under vacuum conditions, while maintaining high shear stirring. After mixing is complete, continue shearing for 60 minutes. Step 7: Finally, add 0.1 to 0.3 parts of ascorbate palmitate, cool to 30°C, and homogenize and stir for 180 minutes. During this period, monitor the rheological properties to ensure viscosity stability, and obtain a multifunctional composite grinding fluid with shear thinning properties.

[0011] Mixing all raw materials at once can easily lead to problems such as uneven emulsification, particle agglomeration, and degradation of active ingredients, resulting in poor product stability and large performance fluctuations. Therefore, we adopted a phased, system-specific construction strategy. At room temperature, the base solvents, deionized water and ethylene glycol, are premixed to establish a stable initial liquid phase environment. Under isothermal conditions, lubricating components such as sorbitol, triethanolamine, glycerol, and polyethylene glycol are gradually added to avoid violent exothermic reactions or excessively high local concentrations. After the addition is complete, the temperature is slowly raised to 60°C, accompanied by high-speed stirring. Viscosity is monitored in real time to ensure the formation of a thermodynamically stable microemulsion phase, which is the foundation for achieving long-lasting lubrication and good dispersion. Subsequently, we cooled the temperature to 45℃ and added the surfactant fatty alcohol polyoxyethylene ether and the dispersant sodium citrate. This temperature window ensures sufficient activation of the surfactant without causing component decomposition. We specifically introduced an online monitoring mechanism: the dispersion base solution is considered complete only when the surface tension is ≤38 mN / m and the pH value is stable between 7.8 and 8.2. This ensures excellent wettability of the polishing slurry on the crystal surface and the electrochemical stability of the system. In the addition of rust- and corrosion-resistant components, we used an inert atmosphere to prevent easily oxidized corrosion inhibitors such as benzotriazole from failing at high temperatures. At the same time, we used conductivity detection to provide feedback on the ionic balance of the system. Instead of directly adding diamond microcrystalline powder and cerium oxide polishing powder to the main system, we pre-treated them with xanthan gum and some deionized water in a separate dispersion tank. First, the xanthan gum was swollen at a low speed, and then the particle agglomeration was broken up step by step through a three-stage gradient ultrasonic process until D90≤2.0μm, ensuring a highly uniform nanoscale suspension. The suspension was injected into the main base liquid under vacuum conditions, accompanied by high-shear stirring. The vacuum effectively eliminated air bubbles, while the high shear force promoted rapid and uniform fusion of the two phases. Shearing was then continued for 60 minutes to ensure structural stability. After the system cooled to 30°C, the temperature-sensitive antioxidant ascorbyl palmitate was added to prevent its high-temperature deactivation. Homogenization stirring was then performed for 180 minutes, during which the rheological curve was continuously monitored to ensure stability at a shear rate of 100 s⁻¹. -1 With viscosity fluctuations ≤ ±5%, a stable grinding fluid with excellent shear thinning properties is ultimately obtained. The entire process is the result of repeated experiments and optimizations. The temperature, rotation speed, feeding sequence, and monitoring parameters at each step have been carefully designed, truly realizing the transformation from experience-based formulation to process control and predictable results. This ensures that the product has excellent integrated cooling, lubrication, grinding, and polishing performance in practical applications, making it particularly suitable for high-precision cold processing of brittle materials such as crystals.

[0012] Without the introduction of an inert atmosphere in step 4, the rust prevention ability of the finished polishing slurry on the copper alloy parts of the machine tool will significantly decrease during long-term use, and problems such as darkening of color and viscosity fluctuations are likely to occur. Through systematic experimental verification, the process parameters of using nitrogen protection, controlling the flow rate at about 0.5 to 1.0 L / min, pre-blowing for 10 minutes, and continuing aeration until the end of step 4 were finally determined. These parameters effectively isolate oxygen without affecting the uniformity of the system due to excessive airflow. This seemingly small detail is one of the key control points to ensure the high performance, long life, and batch-to-batch consistency of the polishing slurry of this invention.

[0013] In a further embodiment, in step 1, the rotation speed is 250-350 rpm, and the stirring time is 5-10 minutes; the cooling water circulation is turned on, and the system temperature is precisely controlled at 25±5℃ and maintained for 10 minutes.

[0014] This operation lays the foundation for the stable construction of subsequent multiphase systems, improves the controllability of subsequent feeding and the repeatability of the reaction, and prevents poor microemulsion formation or abnormal viscosity due to fluctuations in initial conditions. This ensures the dispersion stability and long-term storage performance of the entire grinding fluid system and is an important process control point for achieving batch-to-batch consistency.

[0015] In a further embodiment, in step 2, each component is added at intervals of 3 to 5 minutes, and stirred for 5 minutes after addition; then the temperature is increased to 60±3℃ at a rate of 1.5 to 3℃ / min, while the stirring speed is increased to 550 to 650 rpm, and the mixture is stirred at a constant temperature for 40 to 60 minutes, until the apparent viscosity reaches 8.0±0.5 mPa·s and remains at that level for ≥30 minutes, so as to form a thermodynamically stable microemulsion phase.

[0016] Sorbitol, triethanolamine, glycerol, and polyethylene glycol are all highly polar organic compounds. Although soluble in water, rapid addition at once can easily lead to uneven micelle distribution, phase separation, or emulsification defects due to excessively high local concentrations, affecting the long-term stability of the system. By controlling the addition interval, each component is allowed to fully diffuse and initially swell in the system before the next is introduced, effectively avoiding competitive dissolution and abrupt changes in interfacial stress. After addition, slow heating helps to gradually enhance molecular thermal motion, promoting deep miscibility and self-assembly of the components in the aqueous phase, and avoiding water evaporation, local overheating, or microbubble formation caused by excessively rapid heating. Increasing the stirring speed to 550–650 rpm provides sufficient shear force to uniformly disperse high-viscosity components such as glycerol and polyethylene glycol, breaking the tendency of droplet aggregation and forming fine, uniform microemulsion droplets. Under these conditions, stirring is continued for 40–60 minutes, allowing the system to fully undergo the process of dissolution, diffusion, recombination, and equilibrium, ultimately forming a microemulsion structure with fine particle size, uniform distribution, and strong interfaces. The apparent viscosity was monitored in real time to ensure it reached 8.0 ± 0.5 mPa·s for at least 30 minutes, serving as a quantitative indicator of whether the microemulsion phase had truly reached thermodynamic stability. Stable viscosity indicates that the internal structure of the system is relatively stable, with no tendency for continuous aggregation or demulsification. This control strategy ensured the construction of the lubrication system and provided a stable and homogeneous continuous phase basis for the subsequent introduction of surfactants, rust inhibitors, and solid particles, thereby improving the overall dispersion stability, lubrication performance, and service life of the grinding fluid.

[0017] In a further embodiment, in step 3, the system from step 2 is cooled to 45±3℃ at a rate of 1-2℃ / min, and 0.5-1.5 parts of fatty alcohol polyoxyethylene ether and 1-2.5 parts of sodium citrate are added sequentially. The mixture is stirred at 550-650 rpm for 30 minutes. During this period, the surface tension is monitored online. When the surface tension is ≤38 mN / m and the pH value is stable at 7.8-8.2, the dispersion base liquid is considered to be constructed successfully.

[0018] If the temperature drops too quickly, the microemulsion droplets may aggregate or separate due to sudden thermal stress, destroying the stable structure formed earlier. A gentle cooling rate of 1–2 °C / min allows the system to maintain structural integrity as energy is gradually released, achieving a smooth transition from the high-temperature emulsified state to the mid-temperature functionalized state. Adding fatty alcohol polyoxyethylene ether (a nonionic surfactant) and sodium citrate (an anionic dispersant) at a suitable temperature of 45±3 °C ensures their full dissolution and activity while avoiding potential thermal degradation or increased foaming tendency of the surfactant at high temperatures. High-speed stirring ensures rapid and uniform dispersion of the two additives, preventing excessively high local concentrations that could lead to flocculation. The addition of fatty alcohol polyoxyethylene ether significantly reduces the surface tension of the liquid, improving the wetting and spreading ability of the polishing slurry on the surface of the crystal workpiece, which is beneficial for cooling and chip removal. Sodium citrate, through the negative charge generated by ionization, adsorbs onto the particle surface, enhancing the electrostatic repulsion between particles, preventing aggregation, and improving suspension stability. By monitoring the surface tension online to ensure it drops to ≤38 mN / m, the wettability can be assessed in real time. Maintaining a pH value within the weakly alkaline range of 7.8–8.2 ensures that amine components such as triethanolamine maintain good corrosion inhibition and film-forming capabilities while preventing strong alkalinity from corroding crystal materials or metal equipment. Only when both key parameters are simultaneously stable and meet the standards is the dispersion base solution considered complete, ensuring the system's interfacial properties, chemical stability, and functional consistency. This provides a high-quality continuous phase foundation for subsequent addition of rust-preventive components and introduction of solid particles.

[0019] In a further embodiment, in step 4, 0.7-1.0 parts of benzotriazole, 0.4-0.6 parts of sodium molybdate, 0.1-0.3 parts of isothiazolinone bactericide, and 0.4-0.6 parts of organosilicon defoamer are added sequentially at 45±3℃ under an inert atmosphere. After each additive is added, the mixture is stirred for 5 minutes at a stirring speed of 200-300 rpm for a total stirring time of not less than 30 minutes.

[0020] Adding the additives at a mild temperature of 45±3℃ ensures good dissolution and diffusion while preventing oxidation of benzotriazole or degradation of the active ingredients in the bactericide due to excessively high temperatures. Maintaining an inert atmosphere effectively isolates oxygen, preventing easily oxidized corrosion inhibitors such as benzotriazole from generating ineffective products under heating conditions, and ensuring their ability to form a dense adsorption film on the metal surface. Adding the additives sequentially, followed by continuous stirring for 5 minutes after each addition, helps achieve stepwise dispersion and reaction equilibrium, avoiding potential complexation interference or excessively high local concentrations caused by the simultaneous introduction of multiple functional additives. Using a medium-low stirring speed of 200–300 rpm is sufficient to promote uniform distribution of the additives while reducing shear heat generation and gas-liquid interface disturbance, lowering the risk of foam introduction, especially suitable for functional components sensitive to system equilibrium, such as defoamers and bactericides. Benzotriazole and sodium molybdate act as rust inhibitors; the former preferentially adsorbs onto the surface of copper alloy parts to form a protective film, while the latter induces the formation of a passivating oxide film on the steel surface, achieving dual metal protection for the processing equipment. Isothiazolinone bactericides inhibit microbial growth, preventing spoilage and deterioration of the grinding fluid during long-term use. Organosilicon defoamers control foaming problems that may arise from the presence of surfactants at the source, improving system operational stability. A total stirring time of at least 30 minutes ensures that all additives are fully dissolved, dispersed, and reach a dynamic equilibrium, laying a stable foundation for subsequent compounding with high-solids-content suspensions. In step 4, when the conductivity is less than 700 μS / cm, add 0.1–0.2 parts of sodium molybdate and stir for another 10 minutes; when the conductivity is greater than 800 μS / cm, add 1–2 parts of deionized water and stir for another 10 minutes.

[0021] In a further embodiment, in step 5, the d50 of the diamond microcrystalline powder is 0.6–1.0 μm, and the d50 of the cerium oxide polishing powder is 0.9–1.5 μm; the slurry is subjected to a three-stage ultrasonic dispersion treatment: The first stage involves ultrasonic treatment at 200 W power for 10 minutes to initially break up the soft agglomerates between the powders. The second stage involves increasing the ultrasonic power to 400 W for 15 minutes to further refine the particle aggregation state; The third stage involves high-intensity ultrasonic treatment at 500 W for 10 minutes to achieve nanoscale uniform dispersion.

[0022] If the test result meets the requirement of D90 ≤ 2.0μm, the dispersion is deemed qualified.

[0023] This step breaks down the agglomeration structure between powder particles, achieving nanoscale uniform dispersion and ensuring the suspension stability and processing consistency of solid particles in the final polishing slurry. Diamond microcrystalline powder and cerium oxide polishing powder are both high-density, high-surface-energy inorganic powders, which are prone to forming soft or even hard agglomerates in dry or initially wetted states. If directly added to the main system, they are difficult to disperse completely through conventional stirring, easily leading to sedimentation, scratching of the workpiece, or uneven polishing. Therefore, this invention employs a three-stage incremental power ultrasonic dispersion strategy from low to medium to high power. The first stage uses low-power ultrasound at 200 W for 10 minutes to generate a moderate cavitation effect, initially breaking down the loose aggregates between particles and avoiding particle breakage or equipment damage caused by direct high-power action. The second stage increases the power to medium-high at 400 W for 15 minutes to enhance cavitation intensity and microfluidic impact force, further breaking down secondary agglomerates and allowing particles to enter a more uniform suspension state. The third stage uses high-intensity ultrasound at 500 W for 10 minutes, using intense micro-turbulence, shock waves, and shear forces to completely destroy the remaining tightly aggregated structure, achieving a monodisperse or near-monodisperse state of particles in the liquid phase, fully utilizing their intrinsic grinding and polishing properties. This gradient ultrasound process improves dispersion efficiency and avoids problems such as local overheating, solvent vaporization, or xanthan gum molecular chain breakage caused by one-time high-intensity treatment. By setting D90≤2.0 μm as the criterion for qualified dispersion, it ensures that more than 90% of the particles are controlled within 2 micrometers in diameter, thus ensuring that the grinding slurry can efficiently cut without causing surface scratches due to the presence of large particles during use. This method significantly improves the dispersion uniformity and long-term stability of the solid functional phase, and is a key technical step to ensure that the polishing slurry achieves the integrated function of efficient polishing and mirror polishing.

[0024] In a further embodiment, in step 6, the obtained slurry is injected into the mixing tank at a flow rate of 0.5 L / min. During the injection process, the stirring speed is increased to 1200 rpm, and the vacuum system is turned on to apply a vacuum pressure of ~0.092 MPa. In step 7, 0.1 to 0.3 parts of ascorbate palmitate are added, heating is stopped, and the temperature is lowered to 30°C at a rate of ≤2°C / min. During the cooling process, stirring is carried out at 700 to 900 rpm. After the temperature drops to 30°C, the stirring speed is reduced to 400 rpm, and homogenization stirring continues for 180 minutes. During this period, the rheological curve is measured every 30 minutes to ensure that the temperature is within the range of 100 S / s. -1 Viscosity fluctuation ≤ ±5%.

[0025] The slurry contains a high concentration of diamond microcrystalline powder and cerium oxide polishing powder. If injected too quickly, excessively high local concentrations can lead to under-filling or agglomeration. However, slow addition at a low flow rate of 0.5 L / min allows the high-solids slurry to gradually and evenly enter the main base liquid, facilitating timely dispersion and mixing under high shear force and preventing particle aggregation. Increasing the stirring speed to 1200 rpm provides strong turbulence and shearing, significantly reducing droplet and particle size, promoting interfacial fusion between the microemulsion and solid suspension phases, and forming a dense, uniformly distributed composite system. The vacuum environment effectively eliminates air trapped during mixing, preventing bubbles from forming stable foams or micropore defects in the system. This not only improves liquid transparency and appearance quality but also avoids bubbles adhering to the workpiece surface, which could affect cooling and lubrication or cause machining marks. Vacuum degassing also reduces the long-term corrosion of subsequent antioxidants and metal corrosion inhibitors by dissolved oxygen, extending the service life of the polishing slurry. After proceeding to step 7, the thermosensitive ascorbyl palmitate is added at a low temperature below 30°C to maximize the protection of its antioxidant activity from high-temperature degradation. Subsequently, the temperature is lowered at a slow rate of ≤2°C / min, while maintaining a medium-high stirring speed of 700–900 rpm during the cooling process to ensure uniform temperature distribution and prevent phase separation or collapse of the xanthan gum network structure due to thermal stress. Once the system reaches 30°C, the stirring speed is adjusted to 400 rpm for a prolonged period of homogenization and stirring for 180 minutes. This maintains moderate disturbance to promote equilibrium of intermolecular interactions while avoiding excessive shear stress that could damage the already formed shear-thinned structure. Rheological curves are measured every 30 minutes during this period, with particular attention paid to the 100-second interval. -1 Whether the viscosity fluctuation under shear rate is controlled within ±5% is a parameter that directly reflects the rheological stability and batch-to-batch consistency of the system. Through this integrated process from vacuum shearing to gradient cooling to long-term homogenization to real-time monitoring, a multifunctional composite grinding fluid with stable structure, no foaming, good suspension properties, and excellent shear thinning characteristics is finally obtained, fundamentally ensuring its high efficiency, precision, and long-term reliability in crystal cold processing.

[0026] Thirdly, the aforementioned multifunctional composite polishing fluid is used in the cold processing of crystal products.

[0027] The isothiazolinone bactericide preferred in this application is ACTICIDE. ® CBM. The silicone defoamer is preferably at least one of BYK-A530 and Wacker 47d. The fatty alcohol polyoxyethylene ether is preferably AEO-9.

[0028] (III) Beneficial Effects This invention overcomes the problems of traditional processing fluids, such as single function, poor dispersibility, easy foaming, and short lifespan. Through stepwise microemulsion construction, inert atmosphere protection, three-stage gradient ultrasonic dispersion, vacuum high-shear composite, and online monitoring and feedback control based on key quality attributes, the long-term stability of the grinding fluid system is ensured. The resulting grinding fluid exhibits excellent shear-thinning characteristics, effectively suspending solid particles under static conditions to prevent sedimentation, and rapidly reducing viscosity under dynamic conditions to facilitate penetration and chip removal. Its surface tension is ≤38 mN / m, exhibiting excellent wetting and spreading properties and high cooling efficiency. The PB value on a four-ball mill is approximately 620 N, with a friction coefficient as low as 0.083, significantly reducing tool wear. Simultaneously, it possesses excellent metal protection capabilities, with a corrosion inhibition efficiency of >95% for copper sheets and achieving a "rust-free" rust prevention level for steel sheets. Furthermore, the synergistic effect of antioxidants and highly effective bactericides extends its service life. When applied to the processing of precision parts such as crystal buttons and gear shift levers, it can simultaneously achieve efficient material removal and mirror-level polishing, improve the average polishing rate, reduce surface roughness Ra, achieve a gloss level of over 900 GU at 60°, and achieve an apparent yield of ≥98%, free from scratches, haze, or micro-cracks, fully meeting the stringent requirements of high-end automotive interior parts for aesthetics, consistency, and reliability. Detailed Implementation

[0029] The embodiments of this application will be described in further detail below with reference to the examples. The detailed description of the following embodiments is used to illustrate the principles of this application, but should not be used to limit the scope of this application. This application can be implemented in many different forms and is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

[0030] These embodiments are provided to make the application thorough and complete, and to fully express the scope of the application to those skilled in the art. It should be noted that, unless otherwise specifically stated, the relative arrangement of components and steps, material composition, numerical expressions, and values ​​illustrated in these embodiments should be interpreted as merely exemplary and not as limiting.

[0031] It should be noted that, in the description of this application, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientation or positional relationship, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0032] Furthermore, the terms "first," "second," and similar terms used in this application do not indicate any order, quantity, or importance, but are merely used to distinguish different parts. "Vertical" is not strictly vertical, but within the permissible margin of error. "Parallel" is not strictly parallel, but within the permissible margin of error. Terms such as "including" or "contains" mean that the element preceding the word encompasses the element listed after it, and do not exclude the possibility of encompassing other elements as well.

[0033] It should also be noted that, in the description of this application, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this application depending on the specific circumstances. When a specific device is described as being located between a first device and a second device, an intermediary device may or may not be present between the specific device and the first or second device.

[0034] All terms used in this application have the same meaning as understood by one of ordinary skill in the art to which this application pertains, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant art, and not as idealized or highly formalized, unless expressly defined herein.

[0035] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0036] Example 1 Take 40.0 parts of deionized water and 2.0 parts of ethylene glycol and add them to a stirring tank. Start stirring, control the rotation speed at 350 rpm, and mix and stir for 10 minutes. Connect the cooling water circulation system, control the system temperature at 25°C, and maintain the constant temperature for 10 minutes to form a uniform basic solvent phase. Under the condition of constant temperature at 25°C, add 1.0 part of sorbitol, 5.0 parts of triethanolamine, 35.0 parts of glycerol, and 7.0 parts of polyethylene glycol in sequence. The feeding interval for each component is 5 minutes, and continue to stir for 5 minutes after feeding. After the feeding is completed, slowly raise the temperature to 60°C at a heating rate of 2.0°C / min, and at the same time increase the stirring speed to 650 rpm. Stir at a constant temperature for 50 minutes, and monitor the apparent viscosity in real time. When the viscosity reaches 8.0 mPa·s and remains stable for more than 30 minutes, it is determined that a thermodynamically stable microemulsion phase has been formed. Cool down to 45°C at a rate of 1.5°C / min, add 0.5 part of fatty alcohol polyoxyethylene ether (AEO-9) and 2.5 parts of sodium citrate in sequence, keep the stirring speed at 550 rpm, and continue to stir for 30 minutes. Monitor the surface tension and pH value online during this period. When the surface tension drops to 37.5 mN / m and the pH value is stable at 7.9, it is determined that the construction of the dispersion base liquid is completed. Under the nitrogen protection atmosphere, add 0.7 part of benzotriazole, 0.6 part of sodium molybdate, 0.1 part of isothiazolinone fungicide ACTICIDE® CBM, and 0.6 part of silicone defoamer BYK-A530 at 45°C at a flow rate of 0.8 L / min in sequence. Stir for 5 minutes after adding each auxiliary agent, control the stirring speed at 250 rpm, and the total stirring time reaches 35 minutes. After the stirring is completed, the measured conductivity is 720 μS / cm, which meets the requirements. Take another independent dispersion tank, add 10.0 parts of deionized water, and then put in 5.0 parts of diamond microcrystalline powder with d50 = 0.6 μm, 5.0 parts of cerium oxide polishing powder with d50 = 1.5 μm, and 0.5 part of xanthan gum. Stir at a low speed of 120 rpm for 25 minutes to fully swell the xanthan gum and form a uniform pre-dispersed slurry. Then perform a three-stage ultrasonic dispersion treatment: the first stage is 200 W ultrasonic for 10 minutes to initially break the soft agglomerates; the second stage is 400 W ultrasonic for 15 minutes to refine the particle aggregation state; the third stage is 500 W high-intensity ultrasonic for 10 minutes to achieve nano-level uniform dispersion. After testing with a laser particle size analyzer, the D90 of the slurry is 1.95 μm, which meets the requirement of ≤2.0 μm, and it is determined that the dispersion is qualified. Slowly inject the obtained suspension into the main stirring tank at a flow rate of 0.5 L / min. During the injection process, turn on the vacuum system, maintain the vacuum pressure at -0.095 MPa, and increase the stirring speed to 1200 rpm for high-shear mixing for 60 minutes to ensure complete fusion of the two phases.Finally, add 0.1 parts of ascorbate palmitate, stop heating, and cool down to 30°C at a rate of 1.8°C / min, while maintaining stirring at 700 rpm during the cooling process. After cooling is complete, adjust the speed to 400 rpm and continue homogenizing for 180 minutes, measuring the rheological curve every 30 minutes at a shear rate of 100 s. -1 The viscosity fluctuation was consistently controlled within ±4.2%. The final product was a light milky white, foam-free, multifunctional composite grinding fluid with significant shear-thinning properties.

[0037] Example 2 38.0 parts of deionized water and 1.0 part of ethylene glycol were added to a mixing tank, and the stirring speed was set to 250 rpm for 5 minutes. The system temperature was controlled at 25°C by circulating cooling water and maintained for 10 minutes to form an initial homogeneous environment. Under the constant temperature of 25°C, 3.0 parts of sorbitol, 3.0 parts of triethanolamine, 37.0 parts of glycerol, and 5.0 parts of polyethylene glycol were added sequentially, with a 3-minute interval between each addition, and stirring for 5 minutes after each addition. After the addition was complete, the temperature was increased to 60°C at a rate of 1.5°C / min, while the stirring speed was gradually increased to 550 rpm, and the mixture was stirred at the constant temperature for 60 minutes, while continuously monitoring the viscosity change. When the apparent viscosity of the system reached 8.0 mPa·s and remained stable for 35 minutes, the thermodynamically stable microemulsion phase was confirmed to have formed. Subsequently, the temperature was lowered to 45°C at a rate of 1.0°C / min. 1.5 parts of fatty alcohol polyoxyethylene ether (AEO-9) and 1.0 part of sodium citrate were added sequentially, maintaining a stirring speed of 650 rpm for 30 minutes, with surface tension and pH value monitored in real time. The dispersion base solution was considered complete when the surface tension dropped to 36.8 mN / m and the pH value stabilized at 8.1. Under a nitrogen protective atmosphere, at a flow rate of 1.0 L / min and 45°C, 1.0 part of benzotriazole, 0.4 parts of sodium molybdate, 0.3 parts of the isothiazolinone bactericide ACTICIDE® CBM, and 0.4 parts of the silicone defoamer Wacker 47d were added sequentially. After each additive was added, the mixture was stirred for 5 minutes at a stirring speed of 300 rpm for a total stirring time of 30 minutes. After stirring, the conductivity was measured to be 780 μS / cm, which is within a reasonable range. In a separate dispersion tank, 12.0 parts of deionized water were added, followed by 3.0 parts of diamond microcrystalline powder (d50=1.0 μm), 7.0 parts of cerium oxide polishing powder (d50=0.9 μm), and 0.2 parts of xanthan gum. After low-speed stirring to fully swell the xanthan gum, multi-stage ultrasonic dispersion was performed: the first stage was ultrasonication at 200 W for 10 minutes for initial deagglomeration; the second stage was ultrasonication at 400 W for 15 minutes for further refinement; and the third stage was ultrasonication at 500 W for 10 minutes to achieve highly uniform dispersion. The slurry D90 was measured to be 1.88 μm, meeting the standard of D90≤2.0 μm, indicating successful dispersion. This suspension was then injected into the main mixing tank at a flow rate of 0.5 L / min. During injection, the vacuum system was activated, maintaining a vacuum level below -0.092 MPa, while simultaneously maintaining high-shear stirring at 1200 rpm. After mixing, shearing continued for 60 minutes. Then, 0.3 parts of ascorbate palmitate were added, heating was stopped, and the temperature was slowly lowered to 30°C at a rate of 1.8°C / min, while maintaining stirring at 700 rpm during the cooling process. After cooling to the target temperature, the stirring speed was reduced to 400 rpm, and homogenization stirring was continued for 180 minutes. Rheological data were recorded every 30 minutes during this period, and the data was recorded at 100 s. -1The viscosity fluctuation at the shear rate was ±4.8%, indicating that the system has excellent rheological stability. A multifunctional composite grinding fluid with a transparent, slightly turbid consistency, good fluidity, and significant shear-thinning behavior was finally obtained. It cools rapidly, provides ample lubrication, produces no foam, does not spoil with long-term use, and can simultaneously perform efficient grinding and high-gloss mirror polishing. It is particularly suitable for automated processing of precision components such as crystal buttons and gear shift levers in automotive interiors.

[0038] To verify the interaction between the components and the process scheme, Comparative Example 1 and Comparative Example 16 were conducted in this application. Specific data from Examples 1 and 2, and Comparative Examples 1–16 (mainly data from the completion of grinding slurry preparation and cold processing) are shown in Tables 1 and 2 below.

[0039] Table 1: Detection data of Examples 1 and 2 and Comparative Examples 1 to 7.

[0040]

[0041] Table 2: Detection data for comparative examples 8-16.

[0042]

[0043] Comparative Example 1 This comparative example is the same as Example 1 under the same conditions, except that no inert atmosphere protection was used.

[0044] Electrochemical impedance spectroscopy (EIS) tests showed that the corrosion inhibition efficiency of the polishing slurry prepared in this comparative example on copper sheets was significantly lower than that in Example 1. After 10 simulated cycles, its rust prevention level on steel sheets decreased from "rust-free" in Example 1 to "slight pitting corrosion". At the same time, the RSD (relative standard deviation) of the rust prevention performance of the three batches of parallel experiments reached 12.5% ​​(not shown in Tables 1 and 2), which was higher than 4.3% in Example 1 (not shown in Tables 1 and 2), indicating poor system stability and reduced batch-to-batch consistency.

[0045] Comparative Example 2: This comparative example is the same as Example 1 in all other conditions, except that the amount of xanthan gum is set to 0 parts, while the other components and processes remain unchanged.

[0046] After the polishing slurry stood for 24 hours, the diamond microcrystalline powder and cerium oxide polishing powder showed significant sedimentation, with the sediment volume accounting for approximately 12%. Furthermore, the surface tension of the supernatant increased to 42.3 mN / m, indicating that the surfactant and dispersant lost their interfacial stabilizing effect due to particle aggregation. In actual processing, the surface roughness Ra value increased by 7 nm compared to Example 1, and the mirror uniformity significantly decreased. Xanthan gum not only provides viscosity support but also forms a viscoelastic network with glycerol and polyethylene glycol, synergistically maintaining particle dispersion stability with AEO-9 and sodium citrate. Its absence led to the collapse of the multiple complex stabilization mechanisms of the entire system.

[0047] Comparative Example 3 The comparative example was conducted under the same conditions as Example 1, except that the multi-stage ultrasonic treatment in step 5 was omitted, and instead, continuous ultrasonication at 300 W power was used for 25 minutes. The resulting slurry D90 was 2.8 μm, significantly higher than 2.0 μm, indicating severe particle agglomeration. The polishing slurry caused scratches on the crystal surface during use, resulting in poor mirror finish and easy nozzle clogging.

[0048] Comparative Example 4 This comparative example is identical to Example 1 in all other conditions, except that the amount of ethylene glycol is set to 0 parts, and deionized water is added to make up to 42 parts, while the rest remains unchanged. The lack of ethylene glycol leads to poor low-temperature fluidity of the system, resulting in abnormally high viscosity and pumping difficulties in a slightly cold environment (5°C); at the same time, the strength of the lubricating film decreases, and tool wear is aggravated.

[0049] Comparative Example 5 This comparative example is identical to Example 1 under the same conditions, except that fatty alcohol polyoxyethylene ether (AEO-9) is replaced with an equal amount of sodium dodecylbenzenesulfonate (LAS). Since LAS is a strong anionic surfactant, it exhibits charge repulsion and complexation tendencies with triethanolamine, leading to instability in the microemulsion phase. The system shows slight stratification, good wettability but produces excessive foam, affecting the cooling effect.

[0050] Comparative Example 6 This comparative example is identical to Example 1 in all other conditions, except that the vacuum system was not activated in step 6, and the mixing process was carried out at atmospheric pressure. The resulting polishing slurry contained a large number of microbubbles, appearing as a milky white foam. During use, these bubbles adhered to the workpiece surface, hindering cooling and lubrication, leading to localized overheating and ablation marks.

[0051] Comparative Example 7 This comparative example is identical to Example 1 under the same conditions, except that the diamond microcrystalline powder was replaced with coarse powder with d50=2.0μm, while the other conditions remained unchanged. Although the grinding efficiency was improved, the crystal surface showed fine scratches visible to the naked eye due to the excessive size of the hard particles, failing to meet the requirements for a high-gloss mirror finish.

[0052] Comparative Example 8 This comparative example is identical to Example 1 in all other conditions, except that in step 2, sorbitol, triethanolamine, glycerol, and polyethylene glycol are added all at once without any feeding intervals; the rest of the process remains the same. This results in excessively high local concentrations, causing glycerol and triethanolamine to form a gel prematurely, leading to uneven microemulsion formation, large viscosity fluctuations in the final product, and poor batch-to-batch consistency.

[0053] Comparative Example 9 This comparative example is identical to Example 1 under the same conditions, except that in step 6, the injection flow rate of the suspension was increased from 0.5 L / min to 2.0 L / min, while the other conditions remained unchanged. Due to the excessively fast feed rate, the high-solids content slurry failed to be sheared and dispersed in time, resulting in a "half-baked" phenomenon. Localized high-concentration particle zones existed in the system, leading to uneven grinding and a significant increase in the surface roughness Ra value of the workpiece.

[0054] Comparative Example 10 The comparative example was conducted under the same conditions as Example 1, except that the pH in step 3 was 6.5. The acidic environment caused the sodium molybdate to lose its corrosion-inhibiting ability, while the sodium citrate's dispersing effect weakened, resulting in decreased suspension stability and flocculation precipitation after 7 days. In contrast, no flocculation precipitation was observed in the example.

[0055] Comparative Example 11 This comparative example is identical to Example 1 in all other conditions, except that the cerium oxide polishing powder was reduced from 5.0 parts to 3.0 parts, while the diamond microcrystalline powder remained at 5.0 parts, and the rest remained unchanged. Due to the insufficient polishing components, although the polishing fluid possessed strong cutting ability, the subsequent mirror finishing effect was significantly weakened. After processing, the surface gloss of the crystal (60° angle gloss value) decreased from 920 GU in Example 1 to 713 GU, which could not meet the optical requirements of high-end decorative parts.

[0056] Comparative Example 12 This comparative example is identical to Example 1 under the same conditions, except that during the transition from step 6 to step 7, after heating was stopped, the temperature was rapidly reduced to 30°C at a rate of 5°C / min, instead of a slow reduction at a rate of ≤2°C / min. This rapid cooling caused localized rupture of the microemulsion structure due to thermal stress imbalance, resulting in uneven xanthan gum network formation, decreased suspension stability, slight water separation, and poor gloss.

[0057] Comparative Example 13 This comparative example is identical to Example 1 under the same conditions, except that the stirring speed was reduced from 1200 rpm to 800 rpm in step 6, while the other conditions remained unchanged. Insufficient shear force resulted in incomplete fusion between the high-solids content suspension and the main base liquid, leading to micro-enrichment at the two-phase interface, poor particle suspension stability, and the appearance of a visible sedimentation layer after 48 hours, whereas Examples 1 and 2 did not exhibit this phenomenon.

[0058] Comparative Example 14: This comparative example is identical to Example 1 in all other conditions, except that the isothiazolinone bactericide ACTICIDE® CBM was replaced with an equal amount of sodium benzoate. Sodium benzoate has a narrow antibacterial spectrum and low efficiency. After 20 days of storage under simulated high temperature and humidity conditions (40°C, RH 85%), a large amount of mold and bacteria were detected in the grinding slurry, the liquid became cloudy and smelly, and the rust-preventive components were destroyed by microbial metabolites, resulting in the loss of its anti-corrosion function.

[0059] Comparative Example 15 This comparative example is the same as Example 1 in all other conditions, except that the amount of fatty alcohol polyoxyethylene ether (AEO-9) used is 2.5 parts.

[0060] The surface tension of the system decreased to 32.1 mN / m, and the wettability was enhanced, but a large amount of stable foam was generated, accounting for 18% of the total volume, and lasting for more than 60 minutes. Online monitoring revealed that the coolant was severely entrained by bubbles during the spraying process, resulting in insufficient local cooling and microcracks on the workpiece surface. Excessive nonionic surfactant disrupted the HLB balance of the microemulsion phase, leading to an increased tendency for glycerol to separate from the aqueous phase. After 7 days of storage, trace amounts of oily substances precipitated at the bottom. Although excessive surfactant improved wettability, it caused uncontrolled foaming and system incompatibility, affecting cooling, lubrication, and storage stability. It was verified that 0.5–1.5 parts were the optimal range for balancing performance and stability.

[0061] Comparative Example 16 This comparative example is the same as Example 1 in all other conditions, except that the glycerol in the lubrication system is reduced from 35.0 parts to 30 parts. The rest of the formulation and process are exactly the same as in Example 1.

[0062] The strength of the lubricating film of the resulting polishing fluid decreased significantly. The PB value of the four-ball machine test showed that it decreased from 620 N in Example 1 to 512 N; the coefficient of friction increased from 0.083 to 0.112; the tool wear accelerated during the processing, and after 24 hours of continuous operation, the wear of the diamond grinding wheel increased by 28% compared with Example 1; at the same time, after the system was stored in a low humidity environment (RH 30%) for 48 hours, slight crystallization appeared on the surface and the fluidity deteriorated, while Examples 1 and 2 did not have this phenomenon.

[0063] Through stepwise preparation, isothermal feeding, gradient ultrasonic dispersion, inert atmosphere protection, vacuum high-shear compounding, and online performance monitoring, a stable microemulsion phase and a uniform suspension phase are formed in the system, resulting in a composite polishing slurry with good shear thinning characteristics, high dispersion stability, and long service life. When applied to precision crystal machining, it can simultaneously achieve efficient material removal and mirror-level polishing, resulting in low surface roughness and meeting the stringent requirements of high-end automotive interior parts.

[0064] The embodiments of this application have now been described in detail. To avoid obscuring the concept of this application, some details known in the art have not been described. Those skilled in the art can fully understand how to implement the technical solutions disclosed herein based on the above description.

[0065] While specific embodiments of this application have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of this application. Those skilled in the art should understand that modifications can be made to the above embodiments or equivalent substitutions can be made to some technical features without departing from the scope and spirit of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any manner.

Claims

1. A multifunctional composite grinding fluid for cold working, characterized in that, The grinding fluid comprises the following components in parts by weight: Base solvent: 49–55 parts; Lubrication system: 44-52 parts; Surfactants and dispersants: 1.5–4.0 parts; Rust and corrosion prevention system: 1.6–2.5 parts; Grinding and polishing system: 8-12 parts; Rheology modifier: 0.2–0.5 parts; Antioxidant: 0.1 to 0.3 parts.

2. The multifunctional composite grinding fluid according to claim 1, characterized in that, The base solvent comprises: 48-52 parts of deionized water and 1-2 parts of ethylene glycol; The lubrication system comprises: 1-3 parts sorbitol, 3-5 parts triethanolamine, 35-37 parts glycerin, and 5-7 parts polyethylene glycol; The surfactant and dispersant comprises: 0.5-1.5 parts of fatty alcohol polyoxyethylene ether and 1-2.5 parts of sodium citrate; The rust and corrosion prevention system comprises: 0.7-1.0 parts of benzotriazole, 0.4-0.6 parts of sodium molybdate, 0.1-0.3 parts of isothiazolinone bactericide, and 0.4-0.6 parts of organosilicon defoamer; The grinding and polishing system comprises: 3-5 parts of diamond microcrystalline powder and 5-7 parts of cerium oxide polishing powder; The rheology modifier is 0.2-0.5 parts of xanthan gum; The antioxidant is 0.1 to 0.3 parts of ascorbyl palmitate.

3. A method for preparing a multifunctional composite polishing fluid for cold processing of crystal products, characterized in that, Includes the following steps: Step 1: Add 38-40 parts of deionized water and 1-2 parts of ethylene glycol to a mixing tank and mix them, and control the temperature at 25±5℃; Step 2: Under constant temperature of 25±5℃, add 1-3 parts of sorbitol, 3-5 parts of triethanolamine, 35-37 parts of glycerol and 5-7 parts of polyethylene glycol in sequence. After the addition is completed, raise the temperature to 60±3℃, increase the stirring speed and stir at a constant temperature. Ensure the formation of a thermodynamically stable microemulsion phase by monitoring the viscosity. Step 3: After cooling to 45±3℃, add 0.5 to 1.5 parts of fatty alcohol polyoxyethylene ether and 1 to 2.5 parts of sodium citrate, stir continuously, and monitor the surface tension and pH value online. When the surface tension is ≤38 mN / m and the pH value is stable at 7.8 to 8.2, the system is considered stable. Step 4: Under an inert atmosphere and at 45±3℃, add 0.7-1.0 parts of benzotriazole, 0.4-0.6 parts of sodium molybdate, 0.1-0.3 parts of isothiazolinone bactericide and 0.4-0.6 parts of organosilicon defoamer in sequence, stir evenly and then test the conductivity. Step 5: Add 3-5 parts diamond microcrystalline powder, 5-7 parts cerium oxide polishing powder, 0.2-0.5 parts xanthan gum, and 10-12 parts deionized water to a separate dispersion tank. After swelling by low-speed stirring at 25±5℃, perform multi-stage ultrasonic treatment until the slurry D90≤2.0 μm to obtain a uniform suspension. Step 6: Inject the suspension obtained in step 5 into the base liquid obtained in step 4 under vacuum conditions, while maintaining high shear stirring. After mixing is complete, continue shearing for 60 minutes. Step 7: Finally, add 0.1 to 0.3 parts of ascorbate palmitate, cool to 30°C, and homogenize and stir for 180 minutes. During this period, monitor the rheological properties to ensure viscosity stability, and obtain a multifunctional composite grinding fluid with shear thinning properties.

4. The method for preparing the multifunctional composite grinding fluid according to claim 3, characterized in that, In step 1, the speed is 250-350 rpm, and the mixture is stirred for 5-10 minutes; then the cooling water circulation is turned on to precisely control the system temperature at 25±5℃ and maintain it for 10 minutes.

5. The method for preparing the multifunctional composite grinding fluid according to claim 3, characterized in that, In step 2, each component is added at intervals of 3 to 5 minutes, and stirred for 5 minutes after addition. Then, the temperature is increased to 60±3℃ at a rate of 1.5 to 3℃ / min, while the stirring speed is increased to 550 to 650 rpm. The mixture is stirred at a constant temperature for 40 to 60 minutes, and the apparent viscosity reaches 8.0±0.5 mPa·s and remains at that level for ≥30 minutes to form a thermodynamically stable microemulsion phase.

6. The method for preparing the multifunctional composite grinding fluid according to claim 3, characterized in that, In step 3, the system from step 2 is cooled to 45±3℃ at a rate of 1-2℃ / min, and 0.5-1.5 parts of fatty alcohol polyoxyethylene ether and 1-2.5 parts of sodium citrate are added sequentially. Stirring is maintained at 550-650 rpm for 30 minutes.

7. The method for preparing the multifunctional composite grinding fluid according to claim 3, characterized in that, In step 4, under an inert atmosphere at 45±3℃, add 0.7-1.0 parts of benzotriazole, 0.4-0.6 parts of sodium molybdate, 0.1-0.3 parts of isothiazolinone bactericide, and 0.4-0.6 parts of organosilicon defoamer in sequence. Stir for 5 minutes after each additive is added, stirring at 200-300 / min for a total stirring time of not less than 30 minutes.

8. The method for preparing the multifunctional composite grinding fluid according to claim 3, characterized in that, In step 5, the diamond microcrystalline powder has a d50 of 0.6–1.0 μm, and the cerium oxide polishing powder has a d50 of 0.9–1.5 μm; the slurry undergoes a three-stage ultrasonic dispersion treatment: The first stage involves ultrasonic treatment at 200 W power for 10 minutes to initially break up the soft agglomerates between the powders. The second stage involves increasing the ultrasonic power to 400 W for 15 minutes to further refine the particle aggregation state; The third stage involves high-intensity ultrasonic treatment at 500 W for 10 minutes to achieve nanoscale uniform dispersion.

9. The method for preparing the multifunctional composite grinding fluid according to claim 3, characterized in that, In step 6, the obtained slurry is injected into the mixing tank at a flow rate of 0.5 L / min. During the injection process, the stirring speed is increased to 1200 rpm, and the vacuum system is turned on to apply a vacuum pressure of ~0.092 MPa. 0.1 to 0.3 parts of ascorbate palmitate are added, heating is stopped, and the temperature is lowered to 30°C at a rate of ≤2°C / min. During the cooling process, stirring is carried out at 700 to 900 rpm. After the temperature drops to 30°C, the stirring speed is reduced to 400 rpm, and homogenization stirring continues for 180 minutes. During this period, the rheological curve is measured every 30 minutes to ensure that the temperature is within a shear rate of 100 S / min. -1 Viscosity fluctuation ≤ ±5%.

10. The use of a multifunctional composite polishing fluid as described in any one of claims 1 to 2 in the cold working of crystal products.

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