Low-foaming composite surfactant and its use in metal cutting

Abstract

The application relates to the technical field of surfactants, in particular to a low-foaming composite surfactant and application thereof in metal cutting, characterized in that the low-foaming composite surfactant is composed of 55-65% of nonionic surfactant, 4-12% of anionic surfactant, 10-20% of co-surfactant, 3-12% of functional additive and the balance of deionized water; the nonionic surfactant at least contains fatty alcohol polyoxyethylene ether and isomeric tridecanol polyoxyethylene ether; the anionic surfactant is selected from one or more of sodium alkyl benzene sulfonate, sodium fatty alcohol ether sulfate and alpha-olefin sulfonate; the co-surfactant at least contains alkyl glycoside; and the functional additive contains defoaming agent and antirust agent. The foam elimination efficiency is greatly improved through optimization of the nonionic surfactant combination and adoption of a special defoaming agent compounding scheme, and the generation and accumulation of foam in the cutting process are effectively inhibited.

Description

Technical Field

[0001] This invention relates to the field of surfactant technology, and more specifically to a low-foaming composite surfactant and its application in metal cutting. Background Technology

[0002] In metal cutting processes, surfactants, as the core functional component of cutting fluids, directly affect machining efficiency, workpiece quality, and tool life. With the manufacturing industry moving towards higher speeds and precision, higher demands are placed on the comprehensive performance of cutting fluids. They not only need to provide excellent lubrication, cooling, and rust prevention, but also address a series of problems caused by excessive foaming.

[0003] In existing technologies, surfactants for metal cutting mostly employ single-type or simple compound systems, which have many shortcomings that urgently need to be addressed. Single surfactants often struggle to balance low-foaming and lubricating properties. Under high-speed cutting conditions, they easily generate a large amount of foam, leading to poor cutting fluid circulation, uneven cooling and lubrication, and even foam overflow, affecting machining continuity and the workshop environment. While some compound systems attempt to improve the performance of individual surfactants, the synergy between components is insufficient, resulting in limited lubricating film formation capabilities. This exacerbates tool wear, and the workpiece surface roughness fails to meet the requirements of high-precision machining.

[0004] Meanwhile, existing systems have poor adaptability to different metal materials. When dealing with various processing objects such as carbon steel, alloy steel, and aluminum alloys with large differences in hardness, it is difficult to achieve ideal rust prevention and lubrication effects simultaneously. In addition, the defoamer in traditional systems has poor compatibility with other components, insufficient long-term defoaming ability, and lacks synergy between rust prevention and cooling functions. As a result, the workpiece is prone to corrosion after processing, especially under complex working conditions. These problems are more prominent and restrict the improvement of efficiency and quality assurance in metal cutting. Therefore, there is an urgent need to develop a low-foaming composite surfactant with excellent comprehensive performance. Summary of the Invention

[0005] The primary objective of this invention is to provide a low-foaming composite surfactant and its application in metal cutting.

[0006] A further objective of this invention is to provide a low-foaming composite surfactant, characterized in that, by mass percentage, it comprises 55%-65% nonionic surfactant, 4%-12% anionic surfactant, 10%-20% co-surfactant, 3%-12% functional additives, and the balance being deionized water.

[0007] The nonionic surfactant comprises at least fatty alcohol polyoxyethylene ether and isotridecyl alcohol polyoxyethylene ether;

[0008] The anionic surfactant is selected from one or more of sodium alkylbenzene sulfonate, sodium fatty alcohol ether sulfate, and α-olefin sulfonate;

[0009] The co-surfactant contains at least an alkyl glycoside; the functional additives contain defoamers and rust inhibitors.

[0010] Preferably, the nonionic surfactant further comprises polyoxyethylene polyoxypropylene block polyether, and the mass ratio of fatty alcohol polyoxyethylene ether, isotridecyl alcohol polyoxyethylene ether, and polyoxyethylene polyoxypropylene block polyether is 35-50:10-20:3-7.

[0011] Preferably, the anionic surfactant has a mass percentage of 6%-10% and contains at least one of sodium fatty alcohol ether sulfate or α-olefin sulfonate.

[0012] Preferably, the co-surfactant further comprises one or more of ethylene glycol monobutyl ether and diethylene glycol butyl ether, and the total mass ratio of alkyl glycoside to ethylene glycol monobutyl ether and diethylene glycol butyl ether is 1-3:1.

[0013] Preferably, the functional additive comprises 2%-5% defoamer and 2%-6% rust inhibitor; the defoamer is selected from silicone defoamers, or a compound of silicone defoamers and polyether defoamers; the rust inhibitor is selected from borate ester rust inhibitors, or a compound of borate ester rust inhibitors and petroleum sulfonate rust inhibitors.

[0014] Preferably, the functional additive further comprises 0.3%-1% of a chelating agent, wherein the chelating agent is disodium EDTA.

[0015] Preferably, the application of the low-foaming composite surfactant in metal cutting involves adding the composite surfactant to a base cutting fluid system at a mass fraction of 4%-6% to form a cutting fluid, and then using a wet cutting method to process the metal workpiece; the base cutting fluid system consists of mineral oil, extreme pressure agent, corrosion inhibitor and deionized water.

[0016] Preferably, the basic cutting fluid system contains, by mass percentage, 15%-25% mineral oil, 2%-4% extreme pressure agent, 0.5%-1.5% corrosion inhibitor, and the balance is deionized water.

[0017] Preferably, the metal workpiece is selected from one or more of carbon steel, alloy steel, and aluminum alloy.

[0018] Preferably, the cutting parameters are a cutting speed of 100-160 m / min, a feed rate of 0.15-0.22 mm / r, and a depth of cut of 2-3 mm.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. This invention significantly improves foam elimination efficiency and effectively suppresses foam generation and accumulation during cutting by optimizing the combination of nonionic surfactants and employing a specialized defoamer compounding scheme. It maintains a low-foaming state under different cutting speeds, avoiding foam overflow problems during high-speed cutting, ensuring the stable operation of the cutting fluid circulation system, and providing strong support for the continuity of the machining process.

[0021] 2. This invention, through the synergistic effect of multiple surfactants and precise control of component ratios, enhances the lubricating film formation capability of the cutting fluid at the tool-workpiece interface, effectively reducing the coefficient of friction during the cutting process. This not only reduces tool wear and extends tool life but also significantly reduces workpiece surface roughness, improves the dimensional accuracy and surface quality of the machined workpiece, and provides a reliable guarantee for high-precision machining.

[0022] 3. This invention optimizes the formulation of co-surfactants and utilizes the synergistic effect of rust inhibitors and chelating agents to enable composite surfactants to be suitable for machining various metal materials. Whether it's ordinary carbon steel, high-hardness alloy steel, or aluminum alloys and other metals with different properties, it can provide excellent lubrication, cooling, and rust prevention. This eliminates the need for frequent adjustments to the cutting fluid formulation for different materials, broadening its application scenarios and improving machining convenience.

[0023] 4. This invention, through the scientific formulation of functional additives, significantly improves rust prevention while ensuring excellent cooling effect and effective control of cutting temperature. The processed workpiece maintains a good surface condition even in complex environments, preventing rust formation. This not only ensures the subsequent performance of the workpiece but also reduces subsequent processing steps and lowers processing costs.

[0024] 5. The composite surfactant of this invention exhibits good compatibility among its components, maintaining stable performance under different addition ratios. It demonstrates strong process adaptability, meeting the needs of various cutting conditions. Its balanced overall performance provides an efficient and reliable solution for metal cutting, possessing significant practical application value and broad market prospects. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1:

[0027] Preparation of composite surfactants: Weigh each raw material according to the mass percentage. For nonionic surfactants, use 50% industrial grade fatty alcohol polyoxyethylene ether AEO-9 (purity ≥99%) and 10% industrial grade isomeric tridecyl alcohol polyoxyethylene ether 1309. For anionic surfactants, use 8% industrial grade sodium alkylbenzene sulfonate LAS. For co-surfactants, use 15% industrial grade alkyl glycoside APG (carbon chain length C8-C10, purity ≥98%). For functional additives, use 3% industrial grade silicone defoamer (viscosity 200±20mPa·s, purity ≥99.5%) and 2% industrial grade borate ester rust inhibitor. The remainder is made up to 100% with deionized water.

[0028] The preparation process is as follows: First, deionized water is injected into the reaction vessel, the temperature is raised to 45°C, the stirring speed is adjusted to 200 r / min, AEO-9 and 1309 are added in sequence, and the mixture is stirred at a constant temperature for 30 minutes until the raw materials are completely dissolved.

[0029] Then cool to 35°C, add LAS and APG, and stir continuously for 40 minutes while keeping the temperature stable;

[0030] Finally, add the silicone defoamer and borate ester rust inhibitor, stir at low speed for 20 minutes, and let it cool naturally to room temperature to obtain the low-foaming composite surfactant S1.

[0031] Metal cutting application: Add S1 at a mass fraction of 5% to the base cutting fluid system, which consists of 20% mineral oil, 3% extreme pressure agent, 1% corrosion inhibitor and 76% deionized water. After stirring evenly, the cutting fluid C1 is obtained.

[0032] 45# carbon steel (50mm×50mm×10mm, hardness HB200±10) was selected as the workpiece and wet cutting was used for turning. The cutting parameters were set as follows: cutting speed 120m / min, feed rate 0.2mm / r, depth of cut 2mm.

[0033] Example 2:

[0034] Based on the basic system of Example 1, the low foaming and lubricity properties were enhanced by optimizing the ratio of nonionic surfactants.

[0035] Preparation of composite surfactants: Weigh the raw materials according to the following mass percentages: 40% of industrial grade AEO-9 (purity ≥99%), 15% of industrial grade 1309, and 5% of industrial grade polyoxyethylene polyoxypropylene block polyether L61 (molecular weight 1000±50, purity ≥99%); 8% of industrial grade LAS; 15% of industrial grade APG (carbon chain length C8-C10, purity ≥98%); 3% of industrial grade silicone defoamer (viscosity 200±20mPa·s, purity ≥99.5%) and 2% of industrial grade borate ester rust inhibitor for functional additives; and make up the remainder to 100% with deionized water.

[0036] The preparation process follows the temperature and stirring parameters of Example 1, only adjusting the order of adding nonionic surfactants. AEO-9 and L61 are added first and stirred to dissolve, and then 1309 is added to ensure that the block polyether and fatty alcohol polyoxyethylene ether are fully compatible, thus preparing the composite surfactant S2.

[0037] Metal cutting application: Cutting fluid C2 was prepared using the same basic cutting fluid system and S2 addition ratio as in Example 1.

[0038] The workpiece being cut was still 45# carbon steel (50mm×50mm×10mm, hardness HB200±10). The cutting speed was adjusted to 150m / min to simulate a high-speed cutting scenario. The remaining cutting parameters were kept the same as in Example 1. The focus was on examining the foam control effect and lubrication performance under high-speed cutting conditions.

[0039] Example 3:

[0040] Based on the system of Example 2, ethylene glycol monobutyl ether and APG were combined as a co-surfactant to improve the system's dispersibility and synergistic rust-preventing effect. At the same time, AES was used to replace part of LAS, which reduced foaming and optimized lubrication performance.

[0041] Preparation of composite surfactants: Weigh the raw materials according to the following mass percentages: 40% industrial grade AEO-9 (purity ≥99%), 15% industrial grade 1309, and 5% industrial grade L61 (molecular weight 1000±50, purity ≥99%); 7% industrial grade sodium fatty alcohol ether sulfate (AES) as the anionic surfactant; 10% industrial grade APG (carbon chain length C8-C10, purity ≥98%) and 5% industrial grade ethylene glycol monobutyl ether as the co-surfactant; 2.5% industrial grade silicone defoamer (viscosity 200±20 mPa・s, purity ≥99.5%), 3% industrial grade borate ester rust inhibitor, and 0.5% analytical grade disodium EDTA (purity ≥99.8%). The remainder is made up to 100% with deionized water.

[0042] The preparation process is optimized as follows: Deionized water is heated to 50°C, and a nonionic surfactant is added and stirred for 35 minutes;

[0043] Cool to 30°C, add anionic surfactant and disodium EDTA, and stir for 30 minutes;

[0044] Add the co-surfactant and heat to 38°C, stirring for 25 minutes.

[0045] Finally, add defoamer and rust inhibitor, stir at low speed for 15 minutes, and cool to room temperature to obtain composite surfactant S3.

[0046] Metal cutting application: The preparation ratio of cutting fluid C3 is the same as in Example 1, but the workpiece is replaced with 20# alloy steel (size 50mm×50mm×10mm, hardness HB220±10).

[0047] The material has high hardness, which places more stringent requirements on lubrication and rust prevention. The cutting parameters were adjusted to a cutting speed of 130 m / min, a feed rate of 0.18 mm / r, and a depth of cut of 2.5 mm to examine the system's adaptability to cutting high-hardness metals.

[0048] Example 4:

[0049] Based on the system of Example 3, the range of raw material ratios is further expanded, and multi-component compounding is used to achieve cutting adaptation for a variety of metal materials.

[0050] Preparation of composite surfactants: Weigh the raw materials according to the following mass percentages: 35% industrial grade AEO-9 (purity ≥99%), 20% industrial grade 1309, and 5% industrial grade L61 (molecular weight 1000±50, purity ≥99%); 6% industrial grade α-olefin sulfonate AOS and 4% industrial grade AES; 8% industrial grade APG (carbon chain length C8-C10, purity ≥98%), 6% industrial grade ethylene glycol monobutyl ether, and 3% industrial grade diethylene glycol butyl ether; 2% industrial grade polyether defoamer and 2% industrial grade silicone defoamer (viscosity 200±20 mPa·s, purity ≥99.5%) (the combination of the two enhances the long-lasting defoaming ability); 4% industrial grade borate ester rust inhibitor, 1% industrial grade petroleum sulfonate rust inhibitor, and 0.8% analytical grade disodium EDTA (purity ≥99.8%); the remainder is made up to 100% with deionized water.

[0051] The preparation process adopts a stepwise heating-cooling cycle mode: first, the temperature is raised to 55℃ to dissolve the nonionic surfactant, then the temperature is lowered to 40℃ to add the anionic surfactant and chelating agent, the temperature is raised to 45℃ and stirred for 30 minutes, the temperature is lowered to 32℃ to add the co-surfactant and stirred for 40 minutes, and finally the defoamer and rust inhibitor are added and stirred at room temperature for 20 minutes to obtain the composite surfactant S4.

[0052] Metal cutting application: The addition ratio of S4 in the cutting fluid C4 was set to 4%-6%, covering a wide addition range. Cutting tests were conducted on three materials: 45# carbon steel (size 50mm×50mm×10mm, hardness HB200±10), 20# alloy steel (size 50mm×50mm×10mm, hardness HB220±10), and 6061 aluminum alloy (size 50mm×50mm×10mm, conforming to GB / T3190-2022 standard).

[0053] The cutting parameters were adjusted according to the different material properties, with the cutting speed ranging from 100 to 160 m / min, the feed rate ranging from 0.15 to 0.22 mm / r, and the depth of cut ranging from 2 to 3 mm. The overall performance of the system under different materials and additive ratios was comprehensively examined.

[0054] Comparative Example 1:

[0055] Using only industrial-grade AEO-9 (purity ≥99%) as the nonionic surfactant, and removing 1309 and L61 from Example 1, while keeping the remaining components and proportions the same as in Example 1, composite surfactant D1 and corresponding cutting fluid DC1 were prepared.

[0056] The cutting parameters and workpieces of Example 1 were used for testing to clarify the regulatory effect of block polyether on the low foaming and lubricity of the system.

[0057] Comparative Example 2:

[0058] Using a single industrial-grade LAS as the surfactant, the addition amount is 15%, without using a compound system. Only 10% industrial-grade APG (carbon chain length C8-C10, purity ≥98%) is added as the co-surfactant. The amount of defoamer is reduced to 1%. The remaining components and proportions are as described in Example 1. Composite surfactant D2 and corresponding cutting fluid DC2 are prepared.

[0059] The high-speed cutting parameters of Example 2 were used to test and compare the differences in foam control capabilities between the traditional system and the present invention.

[0060] Comparative Example 3:

[0061] Only industrial-grade APG (carbon chain length C8-C10, purity ≥98%) was retained as a co-surfactant, and ethylene glycol monobutyl ether in Example 3 was removed. The remaining components and proportions were the same as in Example 3, and composite surfactant D3 and corresponding cutting fluid DC3 were prepared.

[0062] The cutting parameters of the alloy steel in Example 3 were used to investigate the effects of the co-surfactant compound on the dispersibility and rust prevention of the system.

[0063] Comparative Example 4:

[0064] Only the industrial-grade borate ester rust inhibitor was retained, while the disodium EDTA and petroleum sulfonate in Example 4 were removed. The remaining components and proportions were the same as in Example 4, and the composite surfactant D4 and the corresponding cutting fluid DC4 were prepared.

[0065] The effects of chelating agents and compound rust inhibitors on the wide material compatibility of the system were analyzed using cutting tests on three materials in Example 4.

[0066] Performance testing and results analysis:

[0067] The basic information for the test is as follows:

[0068] Pretreatment of test workpieces: The surface of all test workpieces was ultrasonically cleaned with acetone for 15 min, dried and left to stand for 2 h to ensure that there was no rust or oil stains, and the initial roughness Ra=1.5±0.1μm.

[0069] Cutting fluid preparation process:

[0070] (1) At room temperature (25±2℃), add the surfactant component to deionized water and stir at 300r / min for 30min until completely dissolved;

[0071] (2) Heat to 50±3℃, add co-surfactant and defoamer, stir at 200r / min for 45min and keep at a constant temperature for 15min;

[0072] (3) Cool down to below 30℃, add rust inhibitor and chelating agent, stir for 20 minutes, and adjust the pH value to 8.5±0.5 (meeting the requirements of GB / T6144-2010 standard).

[0073] (4) After standing for 12 hours, filter with a 10μm filter screen to obtain the finished cutting fluid.

[0074] Test methods and standards:

[0075] (1) Foam performance: Refer to GB / T6144-2010, use Roche foam tester, temperature 25±2℃, cutting fluid concentration 4%-6%, record the initial and 5min residual foam height and calculate the elimination rate, repeat 3 times for each group and take the average value, with an error of ±2%.

[0076] (2) Lubrication performance:

[0077] PB value: According to GB / T3142-2005, it is tested using a four-ball friction and wear tester at 25±2℃ and 1450r / min. The minimum value of three tests is taken, with an error of ±10N.

[0078] Wear scar diameter: The wear scar of the steel ball was measured with a 40x microscope, and the average of 3 values ​​was taken, with an error of ±0.02mm.

[0079] (3) Cooling performance: A cutting test bench was used with a YT15 carbide turning tool. Cutting parameters were uniform. The highest temperature of the workpiece was recorded by a thermocouple sensor. The same material was repeated 3 times and the average value was taken. The accuracy was ±1℃.

[0080] (4) Surface roughness: The surface roughness was measured using an SJ-210 roughness tester. Five uniform test points were selected for each workpiece, and the average value was taken with an accuracy of ±0.001μm.

[0081] (5) Rust prevention and foam overflow:

[0082] Rust resistance: Refer to GB / T6144-2010, conduct 24h single-piece and 4h stacked-piece rust resistance tests in an environment of 35±2℃ and 95%±3% relative humidity;

[0083] Foam overflow: Simulate high-speed cutting at 200 m / min for 1 hour and observe the overflow phenomenon in the cutting fluid circulation system.

[0084] The test results are shown in Table 1 below:

[0085] Sample number Foam elimination rate (%, mean ± error) Residual foam height after 5 minutes (mm, average ± error) PB value (N, minimum value ± error) Wear scar diameter (mm, average value ± error) Maximum cutting temperature of the workpiece (°C, average value ± error) Surface roughness Ra value (μm, mean ± error) Foam overflow situation (high-speed cutting 1 hour) Corrosion status (single piece over 24 hours / stacked pieces over 4 hours) Example 1 (C1) 82±2 15±1 650±10 0.42±0.02 68±1 (45# carbon steel) 0.8±0.05 none None / None Example 2 (C2) 88±2 10±1 720±10 0.38±0.02 72±1 (45# carbon steel) 0.7±0.05 none None / None Example 3 (C3) 93±2 8±1 800±10 0.32±0.02 65±1 (20# alloy steel) 0.6±0.05 none None / None Example 4 (C4) ≥95±2 ≤5±1 750-820±10 ≤0.35±0.02 60±1 (6061 aluminum alloy); ≤72±1 (45# carbon steel / 20# alloy steel) ≤0.5±0.05 (6061 aluminum alloy); ≤0.7±0.05 (45# carbon steel / 20# alloy steel) none None / None Comparative Example 1 (DC1) 65±2 35±2 580±10 0.51±0.02 75±1 (45# carbon steel) 1.0±0.05 none None / None Comparative Example 2 (DC2) 58±2 50±2 550±10 0.55±0.02 78±1 (45# carbon steel) 1.1±0.05 Slight overflow None / None Comparative Example 3 (DC3) 70±2 25±2 600±10 0.45±0.02 76±1 (45# carbon steel) 0.9±0.05 none None / None Comparative Example 4 (DC4) 80±2 18±1 680±10 0.40±0.02 78±1 (45# carbon steel) 0.9±0.05 none Slight rust / None

[0086] Note: Example 4 covers an addition ratio of 4%-6% and three materials. The data are key performance range values. The test was repeated 3 times and the error met the requirements.

[0087] For samples without material specifications, 45# carbon steel was used as the test substrate;

[0088] Outliers were removed from the data using locally weighted linear regression to ensure its accuracy and validity.

[0089] The results are analyzed as follows:

[0090] (1) The foam elimination rate has been increased from 82% to ≥95%, and the residual foam height is ≤5mm. The core is the introduction of block polyether L61 and the compounding of organosilicon and polyether defoamer, which solves the industry pain point of insufficient foam suppression in traditional single surfactant system. It can still achieve long-term low foam under a wide addition ratio.

[0091] (2) The PB value was increased to 750-820N and the wear scar diameter was ≤0.35mm. This was due to the optimization of the nonionic surfactant ratio, the replacement of part of LAS with AES and the compounding of co-surfactants. The components synergistically enhanced the lubricating film formation ability, which was superior to single-component or simple compounding systems.

[0092] (3) The maximum cutting temperature of the workpiece is controlled at 60-72℃, the surface roughness Ra value is ≤0.7μm and there is no rust. Through the precise ratio of functional additives (EDTA disodium chelating agent, borate ester and petroleum sulfonate compound rust inhibitor), the synergistic optimization of cooling, rust prevention and surface quality is achieved. It can be adapted to a variety of metal materials such as 45# carbon steel, 20# alloy steel and 6061 aluminum alloy.

[0093] (4) Each comparative example lacks the key technical features of the present invention (block polyether compound, co-surfactant combination, defoamer compound, rust inhibitor-chelating agent synergistic system, etc.), and has one or more performance shortcomings, and cannot simultaneously meet the comprehensive requirements of metal cutting for low foaming, high lubrication, rust prevention and cooling.

[0094] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A low-foaming composite surfactant, characterized in that, By weight percentage, it consists of 55%-65% nonionic surfactant, 4%-12% anionic surfactant, 10%-20% co-surfactant, 3%-12% functional additives, and the balance deionized water. The anionic surfactant is selected from one or more of sodium alkylbenzene sulfonate, sodium fatty alcohol ether sulfate, and α-olefin sulfonate; The co-surfactant is an alkyl glycoside; the functional additives are defoamers and rust inhibitors. The nonionic surfactant is fatty alcohol polyoxyethylene ether, isotridecyl alcohol polyoxyethylene ether and polyoxyethylene polyoxypropylene block polyether, and the mass ratio of fatty alcohol polyoxyethylene ether, isotridecyl alcohol polyoxyethylene ether and polyoxyethylene polyoxypropylene block polyether is 35-50:10-20:3-7. The anionic surfactant has a mass percentage of 6%-10% and contains at least one of sodium fatty alcohol ether sulfate or α-olefin sulfonate; The co-surfactant further comprises one or more of ethylene glycol monobutyl ether and diethylene glycol butyl ether, and the total mass ratio of alkyl glycoside to ethylene glycol monobutyl ether and diethylene glycol butyl ether is 1-3:

1. The functional additive contains 2%-5% defoamer and 2%-6% rust inhibitor; the defoamer is selected from silicone defoamers, or a compound of silicone defoamers and polyether defoamers; the rust inhibitor is selected from borate ester rust inhibitors, or a compound of borate ester rust inhibitors and petroleum sulfonate rust inhibitors. The functional additive also contains 0.3%-1% chelating agent, wherein the chelating agent is disodium EDTA.

2. The application of the low-foaming composite surfactant according to claim 1 in metal cutting, characterized in that, The composite surfactant is added to the basic cutting fluid system at a mass fraction of 4%-6% to form a cutting fluid, and the metal workpiece is processed by wet cutting. The basic cutting fluid system consists of mineral oil, extreme pressure agent, corrosion inhibitor and deionized water.

3. The application according to claim 2, characterized in that, The basic cutting fluid system contains, by mass percentage, 15%-25% mineral oil, 2%-4% extreme pressure agent, 0.5%-1.5% corrosion inhibitor, and the balance is deionized water.

4. The application according to claim 2, characterized in that, The metal workpiece is selected from one or more of carbon steel, alloy steel, and aluminum alloy.

5. The application according to claim 2, characterized in that, The cutting parameters are: cutting speed 100-160m / min, feed rate 0.15-0.22mm / r, and depth of cut 2-3mm.