Environment-friendly metal cutting oil with high bearing capacity and high wear resistance

Abstract

The invention discloses environment-friendly metal cutting oil with high bearing capacity and high wear resistance, and belongs to the technical field of metal cutting fluid. The cutting fluid is composed of diisooctyl sebacate, a phosphate amine salt extreme pressure additive, a borate additive and a sulfurized extreme pressure additive, the sulfurized extreme pressure additive is sulfurized fatty acid ester and dialkyl pentasulfide (Rc2540), and the addition amount of the phosphate amine salt extreme pressure additive is 0.12-0.80% of the weight of base oil; the addition amount of the borate additive is 0.05-1.45% of the weight of the base oil, the addition amount of the sulfurized fatty acid ester is 0.10-0.85% of the weight of the base oil, and the addition amount of the dialkyl pentasulfide (Rc2540) is 0.20-0.85% of the weight of the base oil. The bearing capacity (Pb) of the cutting oil can reach more than 920N, and the diameter (Db) of a low-load long grinding scar can be less than 0.35 mm.

Description

Technical Field

[0001] The present invention relates to the technical field of metal cutting oils, and particularly relates to an environment-friendly metal cutting oil with high load-carrying and high anti-wear properties. Background Art

[0002] Cutting oils are widely used in modern metal cutting processes and have become an essential supporting material for machining. A research report by Frost and Sullivan on the current situation of the metal processing industry shows that enterprises with the ability to consume metal cutting oils (such as factories producing engines, etc.) have started to transfer their investment locations. For example, enterprises in North America have begun to establish their factories in China, India, and Mexico, while European manufacturers have started to transfer from Western Europe to Eastern Europe; the rise of replacing mineral oil with synthetic oil as the base oil provides a very good opportunity. In some developed regions such as the United States and Europe, vegetable cutting oils have begun to receive extensive attention worldwide. The rapid development of the metal processing industry has provided great opportunities for the widespread application of metal cutting oils. For example, the UNIST environment-friendly vegetable-based semi-dry cutting oil UNIST MISTOIL310 is mainly used in the processing of stainless steel. The French Scarland ZW vegetable cutting oil, as a non-mineral lubricating cutting oil, selects moderately refined vegetable oils and synthetic high-tech special additives and is formulated through exquisite processes. The advantages of the product are biodegradability and no environmental damage. In Japan, the usage rate of environment-friendly metal cutting oils has increased even more significantly. At the same time, most developed countries in the world are also actively conducting research and production on environment-friendly metal cutting oils.

[0003] Since the 1970s and 1980s, following the rapid growth of the world's industrial economy, the consumption of metalworking fluids in China has also increased day by day. From the mid-1990s to the early 21st century, the demand for water-based cutting fluids grew slowly, and the demand for cutting oils gradually recovered and increased rapidly. China also attaches importance to the research and application of environment-friendly cutting oils. In recent years, the demand for cutting oils in the Chinese market has increased year by year, but the research on domestic environment-friendly cutting oils is still lagging behind. Some excellent enterprises have developed many environment-friendly cutting oil additives, such as the T-323 extrusion anti-wear agent (amino thioester) of Jinzhou Herun Lubricant Additive Co., Ltd. Conducting research on green and environment-friendly cutting oils is not only an urgent topic in China but also the common goal pursued by many research institutions.

[0004] The base oils used in traditional cutting oils are mostly refined mineral oils, which have mature processes and low prices. However, they have poor biodegradability and can remain in water and soil for a long time, damaging the normal ecosystem. The synthetic ester molecule structure contains ester groups that are easy to adsorb on the metal surface, forming a firm lubricating film, having good anti-friction and anti-wear effects, and having good biodegradability. With the continuous improvement of the performance requirements and environmental hygiene requirements for cutting oils, synthetic esters are increasingly widely used as effective alternative components to mineral oils in cutting fluids.

[0005] Different types of synthetic esters have different applications in cutting oil products. Neopentyl polyol esters (NPE-3) have excellent properties. They refer to a class of synthetic esters in which the ester group ortho-position in the molecular structure is a quaternary carbon atom, mainly including neopentyl glycol esters, trimethylolpropane esters, and pentaerythritol esters. Among ester oils, polyol esters have the best performance and the best lubrication performance. The reason is that there is no hydrogen on the β-carbon atom in the neopentyl polyol ester molecular structure, and the bulky neopentyl group provides a good space shielding effect for the ester group, increasing the activation energy required for the thermal decomposition of neopentyl polyol to generate free radicals. This makes its thermal decomposition temperature usually about 50°C higher than that of dibasic acid esters, and at the same time makes its antioxidant performance better than that of general diesters; secondly, the lubricity of neopentyl polyol esters is better than that of diesters and mineral oils, far better than that of polyalphaolefins (PAO), and the mixed long- and short-chain esters have the smallest friction coefficient despite their low viscosity; thirdly, neopentyl polyol esters have good viscosity-temperature properties and evaporation properties. Due to the above advantages, neopentyl polyol esters have been widely used in the lubrication field. For example, jet engine lubricating oil, automobile engine lubricating oil, precision instrument oil, lubricating grease base oil for protecting machine parts, metal working fluids (such as cutting fluids), etc.

[0006] The additives in metal cutting oils also cause pollution to the environment in many aspects. For example, chlorinated paraffin is used as an extreme pressure anti-wear agent in cutting fluid components. Due to its carcinogenic risk and environmental pollution in post-treatment, it has been prohibited from use at present. Sodium nitrite and others are added as water-soluble rust inhibitors. They react with metals to form an insoluble dense oxide film on their surfaces, preventing the electrochemical corrosion process of metals. Most of these rust inhibitors are electrolytes, which are toxic, difficult to post-treat, and tend to be replaced. Molybdate rust inhibitors are non-toxic and pollution-free, but they are relatively expensive; organic phosphorus-containing rust inhibitors have a certain corrosive effect on copper and its alloys, and in addition, they will cause eutrophication of water bodies. Therefore, the development of low-phosphorus or phosphorus-free rust inhibitors is the main development trend. Adding anti-corrosion and bactericidal agents to metal cutting fluids can effectively kill and inhibit microorganisms. However, in recent years, due to the increasingly strict environmental protection regulations, common phenolic and formaldehyde-releasing bactericides have been restricted.

[0007] In view of the dual pressures faced by traditional cutting oils from increasingly demanding process requirements and increasingly stringent environmental protection regulations, it is imperative to improve and upgrade their technology. This not only requires continuous improvement of the processing performance of cutting fluids, but also should focus on the research, development and promotion of low-toxic and low-pollution environmentally friendly cutting fluid products. Summary of the Invention

[0008] Aiming at the above deficiencies existing in the prior art, the purpose of the present invention is to provide an environmentally friendly metal cutting oil with high load-carrying and high anti-wear properties. This cutting oil has excellent high load-carrying and high anti-wear properties at high and low temperatures, is non-toxic, and is suitable for various metal cutting oils.

[0009] To achieve the above purpose, the technical solution adopted by the present invention is as follows: An environmentally friendly metal cutting oil with high load-carrying and high anti-wear properties, which is composed of a base oil, a phosphate ester amine salt extreme pressure additive, a borate series additive and a sulfurized extreme pressure additive. The sulfurized extreme pressure additive is sulfurized fatty acid ester and dihydrocarbyl pentasulfide (Rc2540), wherein: the base oil is diisooctyl sebacate.

[0010] In this cutting oil, the addition amount of the phosphate ester amine salt extreme pressure additive is 0.12 - 0.80% of the weight of the base oil; the addition amount of the borate series additive is 0.05 - 1.60% of the weight of the base oil, the addition amount of the sulfurized fatty acid ester is 0.10 - 0.85% of the weight of the base oil, and the addition amount of the dihydrocarbyl pentasulfide (Rc2540) is 0.20 - 0.85% of the weight of the base oil.

[0011] Preferably, the weight ratio range of the addition of the sulfurized fatty acid ester to the dihydrocarbyl pentasulfide (Rc2540) is 0.23 - 5.

[0012] Preferably, the weight ratio of the addition of the phosphate ester amine salt extreme pressure additive to the borate series additive is greater than 0.2.

[0013] Further, the borate series additive is octadecaneoxy thionano calcium borate (T365).

[0014] Further, the phosphate ester amine salt extreme pressure additive is aliphatic phosphate ester amine salt (T6150). The aliphatic phosphate ester amine salt (T6150) is a mixture of a class of phosphate ester amine salts, and its structural general formula is as shown in formula (1): (1); In formula (1), R is a C1 - C4 aliphatic alkyl group, NH 2 R` is a C12 - C14 aliphatic alkyl primary amine.

[0015] Furthermore, the preferred formulation I of the cutting oil is as follows: the addition amounts of the phosphate ester amine salt extreme pressure additive, borate series additive, sulfurized fatty acid ester, and dihydrocarbyl pentasulfide (Rc2540) are 0.60 - 0.80%, 0.20 - 0.35%, 0.02 - 0.10%, and 0.65 - 0.78% of the weight of the base oil in sequence; alternatively, the addition amounts of the phosphate ester amine salt extreme pressure additive, borate series additive, sulfurized fatty acid ester, and dihydrocarbyl pentasulfide (Rc2540) are 0.25 - 0.42%, 1.2 - 1.65%, 0.50 - 0.75%, and 0.03 - 0.15% of the weight of the base oil in sequence. The load-carrying capacity (Pb) of the cutting oil of formulation I is greater than or equal to 920 N, and the low-load long-term wear scar diameter Db at a load F = 294 N and a loading time T = 60 min is less than 0.35 mm.

[0016] Furthermore, the preparation process of the environment-friendly cutting oil is as follows: add the phosphate ester amine salt extreme pressure additive, borate series additive, and sulfurized extreme pressure additive to the base oil in proportion, stir evenly, and then heat at 75 - 100 °C for 30 - 60 min to obtain the environment-friendly cutting oil.

[0017] The design mechanism and beneficial effects of the present invention are as follows: 1. The quality of the base oil directly affects the performance of the cutting oil, and the thermal stability of the cutting oil is closely related to its structure. The environment-friendly metal cutting fluid of the present invention uses diisooctyl sebacate as the base oil, which has many advantages, such as perfect low-temperature performance, strong solubility and cleanliness, appropriate lubricity and low volatility, low viscosity, good fluidity, etc. Most importantly, diisooctyl sebacate has very excellent biodegradability.

[0018] 2. The dosage of the additives in the cutting oil is small, and their content usually does not exceed 2% of the overall cutting oil. Even so, just relying on this small proportion of the additives determines the quality of a cutting oil product. The addition amount of the additives should be appropriate. Too little will affect the physical and chemical properties of the cutting oil, and too much will make the physical and chemical properties of the cutting oil unsatisfactory. By adding specific proportions of aliphatic phosphate ester amine salt (T6150), octadecaneoxy thionano calcium borate (T365), sulfurized fatty acid ester, and dihydrocarbyl pentasulfide (Rc2540) to the mixed base oil in the present invention, the compounded additives and the base oil act synergistically, improving the tribological properties and physical and chemical properties of the cutting oil.

[0019] 3. The environment-friendly metal cutting oil of the present invention has excellent anti-wear performance and environmental protection performance, and its load-carrying capacity at high and low temperatures is excellent. Description of the Drawings

[0020] Figure 1 shows the SEM photograph and energy spectrum of the wear scar on the steel ball in the four-ball test of sample D4 (F = 294 N, T = 60 min); among them: (a) and (b) are the SEM photographs of the wear scar magnified 500 times and 2000 times respectively; (c) is the total distribution spectrum diagram.

[0021] Figure 2 shows the typical positions and energy spectra in the wear scar of the steel ball in the four-ball test of sample D4; among them: (a) the typical positions on the SEM photograph of the wear scar; (b)-(d) are the energy spectra of spectrum 69, spectrum 70, and spectrum 71 respectively.

[0022] Figure 3 Photographs of guinea pig eyes 15 minutes after the start of the eye drop test (the upper picture is female, the middle picture is male, and the lower picture is young).

[0023] Figure 4 Photographs of guinea pig eyes 1 hour after the start of the eye drop test (the upper picture is female, the middle picture is male, and the lower picture is young).

[0024] Figure 5 Photographs of guinea pig eyes 24 hours after the start of the eye drop test (the upper picture is female, the middle picture is male, and the lower picture is young).

[0025] Figure 6 Photographs of guinea pig eyes 48 hours after the start of the eye drop test (the upper picture is female, the middle picture is male, and the lower picture is young).

[0026] Figure 7 Photographs of the back of guinea pigs on the 4th day of the smearing test (the upper picture is female, the middle picture is male, and the lower picture is young).

[0027] Figure 8 Photographs of the back of guinea pigs on the 8th day of the smearing test (the upper picture is female, the middle picture is male, and the lower picture is young).

[0028] Figure 9 Photographs of the back of guinea pigs on the 12th day of the smearing test (the upper picture is female, the middle picture is male, and the lower picture is young). Detailed implementation mode

[0029] To further understand the present invention, the present invention will be described below in conjunction with examples, but the examples are only for further elaborating the characteristics and advantages of the present invention, rather than limiting the claims of the present invention.

[0030] In the following examples and comparative examples, diisooctyl sebacate was purchased from Shandong Ruijie New Materials Co., Ltd., and the physical and chemical properties of diisooctyl sebacate are shown in Table 1.

[0031] The aliphatic phosphate ester amine salt (T6150) is a mixture of a class of phosphate ester amine salts, and its structural general formula is as shown in formula (1): (1); In formula (1), R is a C1-C4 aliphatic alkyl group, and NH 2 R` is a primary C12-C14 alkyl amine.

[0032] The preparation process of the fatty cluster phosphate ester amine salt (T6150) is as follows: Put a C1-C4 monohydric alcohol (such as isopropyl alcohol or n-butanol) into a reaction kettle, and add phosphorus pentoxide and / or white oil in batches under stirring at room temperature. After the feeding is completed, react at 60-80 °C to obtain a mixture of phosphate esters. Then add a primary C12-C14 alkyl amine (such as a tertiary alkyl primary amine) in batches. After the feeding is completed, react at 75-85 °C to generate a mixture of phosphate ester amine salts, which is the fatty cluster phosphate ester amine salt. Its synthesis route is as follows:

[0033] The physical and chemical properties of the fatty cluster phosphate ester amine salt T6150 are shown in Table 2.

[0034] Octadecaneoxy thionano calcium borate (T365) is purchased from Qingdao Mosel Lubricant Co., Ltd. The physical and chemical properties of T365 are shown in Table 3.

[0035] Sulfurized fatty acid ester: Purchased from Cangzhou Yida Boren Petrochemical Co., Ltd., model YD-3015; as a non-active sulfurized extreme pressure anti-wear agent with light color and low odor, it has good viscosity and adhesion. At the same time, it has the characteristics of thick oil film and good anti-wear performance. The physical and chemical properties of the sulfurized fatty acid ester are shown in Table 4.

[0036] Table 1 Physical and Chemical Properties of Diisooctyl Sebacate Table 2 Physical and Chemical Properties of Fatty Cluster Phosphate Ester Amine Salt T6150 Table 3 Physical and Chemical Properties of Octadecaneoxy Thionano Calcium Borate (T365) Table 4 Physical and Chemical Properties of Sulfurized Fatty Acid Ester (YD-3015) In the following examples and comparative examples, the environmentally friendly metal cutting oil is obtained by adding a phosphate ester amine salt extreme pressure additive, a borate-based additive, and a sulfurized extreme pressure additive to a diisooctyl sebacate base oil, stirring evenly, and heating at 85 °C for 50 min. Among them, the phosphate ester amine salt extreme pressure additive is a fatty cluster phosphate ester amine salt (T6150), the borate-based additive is octadecaneoxy thionano calcium borate (T365), and the sulfurized extreme pressure additive is a sulfurized fatty acid ester (YD-3015) and a dialkyl pentasulfide (Rc2540). The addition amounts of each additive are shown in Table 5. The proportion of each additive in Table 5 refers to the weight ratio of the addition amount to the base oil).

[0037] Table 5 Composition and Performance of Cutting Fluid with Diisooctyl Sebacate as Base Oil and T6150, T365, YD-3015, Rc2540 as Additives The cutting oils prepared in Examples 1-7, Examples 101-103 and Comparative Examples 1-3 were tested as follows: 1. Tribological performance test, and the test indexes were: the maximum non-seizure load Pb value and the low-load long-term wear test.

[0038] A four-ball friction and wear tester provided by Shenyang Great Wall Lubricating Oil Manufacturing Co., Ltd., and the manufacturer is Jinan Yihua Tribology Test Technology Co., Ltd. in Jinan, Shandong. The model of the four-ball tester is MRS-10P, the maximum test force is 10KN, the factory serial number is 1507, and the factory date is November 2015.

[0039] The test conditions for low-load long-term wear: load F = 294N, loading time T = 60min; The extreme pressure value Pb and the long-term wear value Db (F = 294N, T = 60min) of the cutting oil products tested in each example and comparative example are shown in Table 5.

[0040] It can be seen that when the addition amount of the additive in Sample D1, Sample D5, Sample D7, Sample D8 and Sample D9 does not meet the requirements or the additive ratio is inappropriate, the cutting fluid P B value is relatively low or the low-load long-term wear scar diameter (Db) value is relatively high.

[0041] After optimizing the mixing ratio of each component in the cutting oil, its load-carrying capacity (Pb) can reach more than 920N, and the long-term wear value Db (F = 294N, T = 60min) is less than 0.35mm, as shown in Examples 101, 102 and 103. The SEM photograph and energy spectrum diagram of the wear scar of the steel ball in the four-ball test of Sample D4 (Example 3) are shown in Figure 1. It can be very clearly seen from the SEM photographs of the wear scar in Figures 1(a)-(b) that there is corrosion on the wear scar surface, indicating that the elements in the additive in the cutting oil have a slight corrosion effect on the metal surface of the steel ball. This is because the fatty cluster phosphate ester amine salt T6150 has a corrosion effect on the wear scar of the steel ball; at the same time, it can also be seen that the size of the wear marks on the wear scar of the steel ball is small, the depth is shallow, and the wear marks are relatively evenly distributed, indicating that each additive added to diisooctyl sebacate plays a good anti-friction role. Figure 1(c) is the total energy spectrum diagram of the wear scar surface of the steel ball, and Figure 2 is the energy spectrum diagram of a typical position. It can be seen in the figure that elements such as P and S are present at each position on the wear scar surface of the steel ball, indicating that the additive plays a good anti-friction role during low-load long-term wear. (1) Preparation before the experiment

[0042] A total of three guinea pigs were used in this test, one female (242.5g), one male (251.4g), 2 months old; one young rat (210.2g). The selling unit is Liaoning Changsheng Biotechnology Co., Ltd., and the quality certificate number: 210726221101483537.

[0043] The sample oil selected was Sample D4 cutting oil.

[0044] The control oil sample was Borges Spanish Extra Virgin Olive Oil, an edible vegetable blended oil. The formulation was 88 wt% sunflower oil and 12 wt% extra virgin olive oil of special grade.

[0045] (2) Process and results of eye drop test Sample D4 cutting oil was dropped into the right eyes of guinea pigs, 3 - 5 ml each time, and the same amount of olive oil, 3 - 5 ml each time, was dropped into the left eyes of each guinea pig as a control.

[0046] The time intervals for eye drops were 3 min, 5 min, 10 min, 15 min, 30 min, 1 h, 2 h, 24 h, and 48 h. Photos were taken before each eye drop.

[0047] At 3 min after eye drops, the eyes of the guinea pigs that had received the sample oil and olive oil showed a narrowed state due to discomfort, and then gradually returned to normal.

[0048] From Figure 3 It can be seen that after 15 min from the start of the eye drop test, the eye state of the guinea pigs improved compared to the initial narrowed state, and the right eyes gradually widened.

[0049] Compared with the photos at 15 min, at Figure 4 1 h of the eye drop test, the improvement of the guinea pigs' eyes was not obvious, but it could be seen that the eyes were getting bigger and brighter.

[0050] At Figure 5 It can be seen that at 24 h of the eye drop test, there was no obvious difference in the eye state of the guinea pigs between the right eyes that received the sample oil and the left eyes that received the olive oil and the eye state of the guinea pigs under normal conditions.

[0051] After 48 h from the start of the eye drop test ( Figure 6 ), the right eyes of the guinea pigs that received the sample oil were bright and had completely returned to the normal state.

[0052] The above eye drop test was conducted on the cutting oils of other embodiments, and the test results were the same as those of Sample D4.

[0053] The above analysis of the test results shows that the cutting oil of the present invention has little impact on the eyes of guinea pigs and is non - toxic. (1) Preparation before the experiment

[0054] A total of 3 guinea pigs were used in this test. The selling unit was Liaoning Changsheng Biotechnology Co., Ltd., and the quality certificate number was: 210726221101483537. There was 1 adult female rat (286 g), 1 adult male rat (292 g), and 1 young rat (206 g).

[0055] Use sample D4 cutting oil as the sample oil.

[0056] The control oil sample is Borges Spanish extra-virgin olive oil, which is an edible vegetable blended oil. The formula is 88 wt% sunflower oil and 12 wt% extra-virgin olive oil of top grade.

[0057] (2) Smearing test process and result analysis Shave off part of the hair on the back of the guinea pigs for smearing the oil samples. Smear the sample oil on the right hind back of the guinea pigs, 2 - 3 ml each time. Smear olive oil on the left hind back of each guinea pig, also 2 - 3 ml each time as a control.

[0058] The smearing test lasts for fourteen days, ensuring to smear once a day. And take photos on the fourth day, the eighth day, the twelfth day, and two days after the end of the test. Figures 7-9 For the smearing photos (the photo order from top to bottom is female, male, and young mouse).

[0059] Figures 7-9 It can be very clearly seen the changes in the skin of the guinea pigs during the smearing test. From Figures 7-9 it can be known that during the whole smearing process, the skin of the guinea pigs always remained intact without any adverse phenomena. Thus, it can be known that sample D4 cutting oil, like olive oil, has no any bad influence on the skin of the guinea pigs.

[0060] During the whole smearing test process, the weights of the guinea pigs increased from 292 g for male, 286 g for female, and 206 g for young mouse to 408.6 g for male, 337.8 g for female, and 282.6 g for young mouse. The growth of each guinea pig was very good. Thus, it can be known that the smearing test has no any adverse influence on the growth of the guinea pigs.

[0061] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An environmentally friendly metal cutting oil with high load-bearing and high anti-wear properties, characterized by: The cutting oil is composed of base oil, phosphate amine salt extreme pressure additives, borate series additives and sulfurized extreme pressure additives. The sulfurized extreme pressure additives are sulfurized fatty acid esters and dialkyl pentasulfide Rc2540, wherein the base oil is diisooctyl sebacate.

2. The environmentally friendly metal cutting oil with high load-bearing and high anti-wear performance according to claim 1, characterized in that: The amount of the phosphate amine salt extreme pressure additive added is 0.12-0.80% of the base oil weight; the amount of the borate additive added is 0.05-1.60% of the base oil weight, the amount of the sulfurized fatty acid ester added is 0.10-0.85% of the base oil weight, and the amount of the dialkyl pentasulfide Rc2540 added is 0.20-0.85% of the base oil weight.

3. The environmentally friendly metal cutting fluid with high load-bearing and high wear resistance according to claim 2, characterized in that: The added weight ratio of the sulfided fatty acid ester to the dialkyl pentasulfide Rc2540 is in the range of 0.23-5.

4. The environmentally friendly metal cutting oil with high load-bearing and high anti-wear performance according to claim 3, characterized in that: The weight ratio of the phosphate amine salt extreme pressure additive to the borate additive is greater than 0.

2.

5. The environmentally friendly metal cutting oil with high load-bearing and high anti-wear performance according to claim 1, characterized in that: The borate additive is octadecyloxythio nano calcium borate T365.

6. The environmentally friendly metal cutting oil with high load-bearing and high anti-wear performance according to claim 1, characterized in that: The phosphate amine salt extreme pressure additive is a fatty cluster phosphate amine salt T6150. The fatty cluster phosphate amine salt T6150 is a mixture of phosphate amine salts, and its general structural formula is as follows: （1）； In formula (1), R is a C1-C4 aliphatic alkyl group, and NH2R' is a C12-C14 aliphatic alkyl primary amine.

7. The environmentally friendly metal cutting oil with high load-bearing and high anti-wear performance according to claim 1, characterized in that: The preferred formula I of the cutting oil is: the addition amounts of the phosphate amine salt extreme pressure additive, borate additive, sulfurized fatty acid ester and dialkyl pentasulfide Rc2540 are 0.60-0.80%, 0.20-0.35%, 0.02-0.10% and 0.65-0.78% of the base oil weight, respectively; or, the addition amounts of the phosphate amine salt extreme pressure additive, borate additive, sulfurized fatty acid ester and dialkyl pentasulfide Rc2540 are 0.25-0.42%, 1.2-1.65%, 0.50-0.75% and 0.03-0.15% of the base oil weight, respectively; the load-bearing capacity Pb ​​of the cutting oil of formula I is greater than or equal to 920N, and the low-load long wear spot diameter Db is less than 0.35mm at a load F=294N and a loading time T=60min.

8. The environmentally friendly metal cutting oil with high load-bearing and high anti-wear performance according to claim 1 or 7, characterized in that: The preparation process of the environmentally friendly cutting oil is as follows: adding phosphate amine salt extreme pressure additives, borate additives and sulfurized extreme pressure additives to the base oil in proportion, stirring evenly, and heating at 75-100° C. for 30-60 minutes to obtain the environmentally friendly cutting oil.

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