CN107164062B

CN107164062B - Metal working fluid and preparation method and application thereof

Info

Publication number: CN107164062B
Application number: CN201710541423.8A
Authority: CN
Inventors: 梅晖
Original assignee: Quaker Chemical China Co Ltd
Current assignee: Quaker Chemical China Co Ltd
Priority date: 2017-07-05
Filing date: 2017-07-05
Publication date: 2020-11-10
Anticipated expiration: 2037-07-05
Also published as: CN107164062A

Abstract

The invention provides a metal working fluid, which comprises the components of base oil, synthetic ester, organic acid, organic amine, a special lubricant, an auxiliary agent and water. The processing liquid has excellent lubricating property under low concentration, can better protect a newly-produced processing surface and the surface of a cutter and prevent the generation and abrasion of accumulated bits, has excellent antibacterial property and high biological stability under low concentration, does not use common extreme pressure lubricants such as chlorine, phosphorus, sulfur and the like to improve the lubrication, and has little harm to the environment and operators.

Description

Metal working fluid and preparation method and application thereof

Technical Field

The invention belongs to the field of metal processing, and relates to a metal processing liquid, and a preparation method and application thereof.

Background

Through the reform and the development for many years, the automobile industry in China is rapidly developed, and a relatively complete production layout is formed. The development and production technology of the engine serving as a key part of the automobile is mature day by day, and the engine has a considerable scale. The engine is the heart of the automobile, the structure is precise and complex, and the requirement on the processing precision is extremely high. The main body structure can be roughly divided into components such as a cylinder body, a cylinder cover, a crankshaft, a connecting rod, a piston, a camshaft and the like. The cylinder body and the cylinder cover are both of a box body structure with a plurality of holes and thin walls, wherein the machining difficulty is high, machining of conical surfaces of seat rings of an intake valve and an exhaust valve of the cylinder cover and guide pipe holes, machining of tappet holes, machining of camshaft holes and the like are carried out, and the machining precision directly influences the assembly precision and the working performance of the engine. The cutting fluid has a great influence on the processing quality of the workpiece. In recent years, with the introduction of foreign advanced equipment, higher requirements are put forward on cutting fluid while the production efficiency and the processing precision are greatly improved. In the process of machining engine parts, the boundary lubrication performance of the cutting fluid is an important index for improving the abrasion of a cutter and controlling the surface quality. The cutting fluid has excellent boundary lubricity and strong chemical adhesive force, can generate a pressure-bearing oil film between a workpiece and a cutter, reduces abrasive wear, absorbs cutting heat, enables chips to quickly separate from the front cutter surface of the cutter, and avoids chip accumulation and adhesive wear of a cutting edge.

In order to meet the requirement of machining precision, the cutting fluid used for machining the engine at present basically maintains high concentration of 8-10% or even higher concentration to ensure the required lubricating property. However, high concentration means more cutting fluid consumption, which not only increases the comprehensive use cost of the cutting fluid, but also increases the treatment capacity and difficulty of the waste fluid in the future. Some engine processing sites also try to reduce the use concentration of the cutting fluid, but the result is that the processing precision of parts is not required, the service life of a cutter is reduced, and even the cutter is broken. Meanwhile, the cutting fluid is easy to cause bacteria suddenly due to the reduction of the concentration, a large amount of additional bactericide is required to be added for maintenance, and the maintenance cost is increased.

Disclosure of Invention

In order to solve the technical problems in the prior art, the invention provides a metal working fluid which has excellent lubricating performance at low concentration, can better protect a newly-machined surface and a cutter surface and prevent the generation and abrasion of built-up edges, has excellent antibacterial performance and high biological stability at low concentration, does not use common extreme pressure lubricants such as chlorine, phosphorus, sulfur and the like to improve lubrication, and has little harm to the environment and operators.

In order to achieve the effect, the invention adopts the following technical scheme:

one of the purposes of the invention is to provide a metal working fluid, and the components of the metal working fluid comprise base oil, synthetic ester, organic acid, organic amine, special lubricant, auxiliary agent and water.

As a preferable technical scheme of the invention, the metal working fluid comprises the following components in percentage by mass:

wherein the base oil may be 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, or 45% by mass, the synthetic ester may be 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15% by mass, the organic acid may be 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, or 10% by mass, the organic amine may be 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15% by mass, the specific lubricant may be 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, or 5% by mass, the auxiliary agent may be 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, or 9% by mass, and the like, but not limited to the recited values, other values not listed in the above numerical ranges are also applicable.

As a preferred technical scheme of the invention, the base oil is isomeric hexadecane.

Preferably, the synthetic ester is 2-ethylhexyl benzoate and/or trimethylolpropane tricaprate.

As a preferred embodiment of the present invention, the organic acid comprises any one of dimerized ricinoleic acid, tall oil acid, isomerized stearic acid, lauric acid, gluconic acid or neodecanoic acid, or a combination of at least two of these, typical but non-limiting examples being: combinations of dimerized ricinoleic acid or tall oil acid, tall oil acid and isomerized stearic acid, isomerized stearic acid and lauric acid, lauric acid and gluconic acid, gluconic acid and neodecanoic acid, or dimerized ricinoleic acid, tall oil acid and isomerized stearic acid, and the like.

Preferably, the organic amine comprises any one of, or a combination of at least two of, diisopropanolamine, 2-amino-2-methylpropanol, 3-butoxypropylamine, N-diethylaniline, or hexamethylenetetramine, typical but non-limiting examples of which are: a combination of diisopropanolamine and 2-amino-2-methylpropanol, a combination of 2-amino-2-methylpropanol and 3-butoxypropylamine, a combination of 3-butoxypropylamine and N, N-diethylaniline, a combination of N, N-diethylaniline and hexamethylenetetramine, a combination of hexamethylenetetramine and diisopropanolamine, or a combination of diisopropanolamine, 2-amino-2-methylpropanol and 3-butoxypropylamine, and the like.

Preferably, the special lubricant is benzotriazole derivatives.

As a preferred technical scheme of the invention, the auxiliary agent comprises an emulsifier, a coupling agent, a bactericide and an antifoaming agent.

As a preferred embodiment of the present invention, the emulsifier comprises any one or a combination of at least two of alcohol ether carboxylic acid, fatty alcohol polyoxyethylene polyoxypropylene ether or polyisobutylene maleic anhydride, and typical but non-limiting examples of the combination are: a combination of alcohol ether carboxylic acid and fatty alcohol polyoxyethylene polyoxypropylene ether, a combination of fatty alcohol polyoxyethylene polyoxypropylene ether and polyisobutylene maleic anhydride, a combination of polyisobutylene maleic anhydride and alcohol ether carboxylic acid or a combination of alcohol ether carboxylic acid, fatty alcohol polyoxyethylene polyoxypropylene ether and polyisobutylene maleic anhydride, and the like.

Preferably, the emulsifier is present in an amount of 1-2% by weight, such as 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%, but not limited to the recited values, and other values not recited within the range of values are equally applicable.

Preferably, the coupling agent is triethylene glycol butyl ether.

Preferably, the coupling agent is present in an amount of 2 to 5% by weight, such as 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, but not limited to the recited values, and other values not recited within the range of values are equally applicable.

As a preferred technical scheme of the invention, the bactericide is a mixture of 2-butyl-1, 2-benzisothiazolin-3-one and 2-bromo-2-nitro-1, 3-propanediol.

Preferably, the amount of the bactericide is 1 to 2% by mass, such as 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%, but not limited to the listed values, and other values not listed in the range of the values are also applicable.

Preferably, the defoamer is dimethicone.

Preferably, the mass percent of the defoaming agent is 0.05-0.1%, such as 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%, but not limited to the recited values, and other values not recited in the range of the recited values are also applicable.

The invention selects the isoparaffin with low viscosity and the special synthetic ester, can more quickly enter a freshly generated processing surface with the help of the surfactant compared with the common mineral oil and the common synthetic ester, and simultaneously has excellent oil film strength. Meanwhile, benzotriazole derivatives are selected and can be strongly adsorbed on the metal surface, when the specified usage amount is reached, the prior isoparaffin and synthetic ester are matched, and the synergistic effect of the benzotriazole derivatives and the synthetic ester greatly improves the lubricating property of the metal working fluid, so that a newly-produced working surface and the surface of a cutter can be better protected, and the generation and the abrasion of built-up edges are prevented. In order to solve the problem of easy bacteria generation under the condition of low concentration, the invention selects two bactericides with high efficiency and good durability and is matched with organic amine with a special structure with the bacteriostasis function, so that the product of the invention can still keep good biological stability even under the condition of low concentration.

The second purpose of the invention is to provide a preparation method of the metal working fluid, which comprises the following steps:

(1) mixing base oil, synthetic ester, organic acid, organic amine and an emulsifier under stirring to obtain a first mixture;

(2) mixing the first mixture obtained in the step (1) with water, a special lubricant, a coupling agent and a bactericide under stirring to obtain a second mixture;

(3) and (3) mixing the second mixture obtained in the step (2) with a defoaming agent under stirring to obtain the metal working fluid.

In a preferred embodiment of the present invention, the stirring speed in the step (1) is 400 to 800rpm, such as 400rpm, 450rpm, 500rpm, 550rpm, 600rpm, 650rpm, 700rpm, 750rpm, or 800rpm, but is not limited to the above-mentioned values, and other values not listed in the above-mentioned range are also applicable.

Preferably, the stirring time in step (1) is 20-40 min, such as 20min, 22min, 25min, 28min, 30min, 32min, 35min, 38min or 40min, but not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, the stirring temperature in step (1) is 25 to 40 ℃, such as 25 ℃, 26 ℃, 28 ℃, 30 ℃, 32 ℃, 35 ℃, 38 ℃ or 40 ℃, but not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, the stirring speed of the stirring in step (2) is 400-800 rpm, such as 400rpm, 450rpm, 500rpm, 550rpm, 600rpm, 650rpm, 700rpm, 750rpm or 800rpm, but not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, the stirring time in step (2) is 20-40 min, such as 20min, 22min, 25min, 28min, 30min, 32min, 35min, 38min or 40min, but not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, the stirring temperature in step (2) is 25 to 40 ℃, such as 25 ℃, 26 ℃, 28 ℃, 30 ℃, 32 ℃, 35 ℃, 38 ℃ or 40 ℃, but not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, the stirring speed of the stirring in step (3) is 400-800 rpm, such as 400rpm, 450rpm, 500rpm, 550rpm, 600rpm, 650rpm, 700rpm, 750rpm or 800rpm, but not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, the stirring time in step (3) is 20-40 min, such as 20min, 22min, 25min, 28min, 30min, 32min, 35min, 38min or 40min, but not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, the stirring temperature in step (3) is 25 to 40 ℃, such as 25 ℃, 26 ℃, 28 ℃, 30 ℃, 32 ℃, 35 ℃, 38 ℃ or 40 ℃, but not limited to the recited values, and other values not recited in the range of the values are also applicable.

The invention also aims to provide the application of the metal processing liquid, and the metal processing liquid is used for processing automobile engine parts.

Compared with the prior art, the invention has at least the following beneficial effects:

(1) the invention provides a metal working fluid which has excellent lubricating property under the concentration of 4-5%, and the concentration of the conventional cutting fluid for engine processing in the prior art is required to be 8-10%, sometimes even higher;

(2) the present invention provides a metal working fluid having excellent antibacterial properties and biostability at low concentrations;

(3) the invention provides a metal working fluid which does not use common extreme pressure lubricants such as chlorine, phosphorus, sulfur and the like to improve lubrication and has little harm to the environment and operators;

(4) the invention provides a preparation method of metal working fluid, which is simple in process and suitable for industrial production.

Detailed Description

For the purpose of facilitating an understanding of the present invention, the present invention will now be described by way of examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

Example 1

A method of preparing a metalworking fluid, the method comprising the steps of:

(1) mixing 35g of isomeric hexadecane, 15g of benzoic acid-2-ethylhexyl ester, 5g of organic acid, 8g of organic amine and 2g of alcohol ether carboxylic acid at 30 ℃ under stirring at 600rpm for 30min to obtain a first mixture;

(2) mixing the first mixture obtained in the step (1) with 26.95g of water, 3g of benzotriazole derivative, 3g of triethylene glycol butyl ether and 2g of bactericide for 30min under stirring at 600rpm to obtain a second mixture;

(3) and (3) mixing the second mixture obtained in the step (2) with 0.05g of dimethyl silicone oil for 30min under the stirring of 600rpm to obtain the metal working fluid.

Wherein the organic acid is a mixture of ricinoleic acid, tall oil acid and isomeric stearic acid, and the organic amine is a mixture of diisopropanolamine, 2-amino-2-methylpropanol and 3-butoxypropylamine.

Example 2

A method of preparing a metalworking fluid, the method comprising the steps of:

(1) mixing 45g of isomeric hexadecane, 8g of trimethylolpropane tricaprate, 10g of organic acid, 15g of organic amine and 1g of fatty alcohol polyoxyethylene polyoxypropylene ether at 30 ℃ under the stirring of 600rpm for 30min to obtain a first mixture;

(2) mixing the first mixture obtained in the step (1) with 10.95g of water, 3g of benzotriazole derivative, 5g of triethylene glycol butyl ether and 2g of bactericide for 30min under stirring at 600rpm to obtain a second mixture;

Wherein the organic acid is a mixture of tall oil acid, isomeric stearic acid and lauric acid, and the organic amine is a combination of 2-amino-2-methylpropanol, 3-butoxypropylamine and N, N-diethylaniline.

Example 3

A method of preparing a metalworking fluid, the method comprising the steps of:

(1) mixing 40g of isomeric hexadecane, 10g of benzoic acid-2-ethylhexyl ester, 8g of organic acid, 12g of organic amine and 1.5g of polyisobutylene maleic anhydride at 30 ℃ for 30min with stirring at 600rpm to obtain a first mixture;

(2) mixing the first mixture obtained in the step (1) with 18.95g of water, 4g of benzotriazole derivative, 4g of triethylene glycol butyl ether and 2g of bactericide for 30min under the stirring of 600rpm to obtain a second mixture;

Wherein the organic acid is a mixture of lauric acid, gluconic acid and neodecanoic acid, and the organic amine is a mixture of 3-butoxypropylamine, N-diethylaniline and hexamethylenetetramine.

Example 4

A method of preparing a metalworking fluid, the method comprising the steps of:

(1) mixing 38g of isomeric hexadecane, 12g of trimethylolpropane tricaprate, 10g of organic acid, 10g of organic amine and 2g of polyisobutylene maleic anhydride at 45 ℃ under stirring at 400rpm for 40min to obtain a first mixture;

(2) mixing the first mixture obtained in the step (1) with 19.94g of water, 4g of benzotriazole derivative, 3g of triethylene glycol butyl ether and 1g of bactericide for 40min under the stirring of 400rpm to obtain a second mixture;

(3) and (3) mixing the second mixture obtained in the step (2) with 0.06g of dimethyl silicone oil for 40min under the stirring of 400rpm to obtain the metal working fluid.

Wherein the organic acid is a mixture of dimerized ricinoleic acid, lauric acid and neodecanoic acid, and the organic amine is a mixture of diisopropanolamine, 3-butoxypropylamine and N, N-diethylaniline.

Example 5

A method of preparing a metalworking fluid, the method comprising the steps of:

(1) mixing 42g of isomeric hexadecane, 13g of trimethylolpropane tricaprate, 8g of organic acid, 7g of organic amine and a mixture of 1.5g of polyisobutylene maleic anhydride and alcohol ether carboxylic acid at 20 ℃ for 20min under stirring at 800rpm to obtain a first mixture;

(2) mixing the first mixture obtained in the step (1) with 19.92g of water, 3.5g of benzotriazole derivative, 3.5g of triethylene glycol butyl ether and 1.5g of bactericide for 20min under the stirring of 800rpm to obtain a second mixture;

(3) and (3) mixing the second mixture obtained in the step (2) with 0.08g of dimethyl silicone oil for 20min under the stirring of 800rpm to obtain the metal working fluid.

Wherein the organic acid is a mixture of tall oil acid, isomeric stearic acid and gluconic acid, and the organic amine is a combination of diisopropanolamine, 3-butoxypropylamine, N-diethylaniline and hexamethylenetetramine.

Comparative example 1

A method of preparing a metal working fluid under the same conditions as in example 1 except that in step (1), mineral oil was used instead of iso-hexadecane.

Comparative example 2

A method for preparing a metal working fluid, which comprises the same steps as in example 1, except that isooctyl sebacate was used instead of 2-ethylhexyl benzoate in step (1).

Comparative example 3

A method for preparing a metal working fluid, which is the same as in example 1, except that the benzotriazole derivative is not added in the step (2).

Comparative example 4

A preparation method of a metal working fluid is the same as that of example 1 except that the amount of the benzotriazole derivative used in step (2) is 1g and the amount of water is 28.95 g.

Comparative example 5

A preparation method of a metal working fluid is the same as that of example 1 except that in the step (2), the dosage of the benzotriazole derivative is 10g, and the dosage of the water is 19.95 g.

Comparative example 6

A method for preparing a metal working fluid, which is the same as that of example 1 except that the bactericide added in step (2) is hydroxyethyl hexahydro-s-triazine.

Comparative example 7

A method of preparing a metal working fluid, which method is the same as in example 1 except that the organic amine used in step (1) is a mixture of p-methylaniline and p-ethylaniline.

The antibacterial agents used in examples 1-5 and comparative examples 1-7 were mixtures of 2-butyl-1, 2-benzisothiazolin-3-one and 2-bromo-2-nitro-1, 3-propanediol.

And (3) testing the lubricating property:

the tapping torque test System (TTT System G8) of Germany Microtap company is adopted to carry out tapping torque tests on examples 1-5, comparative examples 1-5 and traditional products, a simulation testing machine is used for directly carrying out tapping tests on a metal material test block provided with a reserved hole, and the tapping torque value or tapping efficiency is used for evaluating the processing performance of the cutting fluid. Compared with the traditional four-ball friction testing machine, the tapping torque testing machine adopts a mode of directly tapping to judge the cutting fluid, and is obviously closer to the cutting working condition of the testing machine than the four-ball friction testing machine. The tapping testing machine can adjust different rotating speeds and adjust the processing severity by adopting the extruding screw tap and the cutting screw tap respectively according to different materials, so that if the testing conditions can be carefully and effectively screened, the reliability of evaluating the processing performance of the cutting fluid by the tapping testing machine can be greatly improved.

Wherein, the tapping efficiency of the test product is (tapping torque value of the reference product/tapping torque value of the test product) × 100%.

Test parameters are as follows: the test adopts an extrusion screw tap, the rotating speed of a main shaft is 1200rpm, the material of a test plate is 6082Al, the concentration of the cutting fluid is 5%, and the concentration of a traditional product of the cutting fluid is 5%. The results are shown in Table 1.

TABLE 1

Remarking: the tapping efficiency values in the above tables are all referred to the traditional product

And (3) testing antibacterial performance:

reference is made to the standard practice of ASTM E2275-2003 for the evaluation of biocide and antimicrobial biocide properties in water-miscible metalworking fluids. The test is carried out under the condition of microbiological test, the test period is 8 weeks, a certain amount of strain is added into the metal working fluid periodically every week, then the bacteria number is detected periodically to confirm the antibacterial performance of the metal working fluid, if the bacteria number is continuously measured for two weeks>10⁵Then the determination is failure. According to the difference of microbes bred in the field processing liquid, antibacterial tests of bacteria and fungi are often separately performed. The antibacterial performance test was performed on example 1, comparative examples 6 and 7, and the conventional products according to the above procedure. The results are shown in tables 2 and 3. The concentrations of all samples in the test are3% and an initial pH of 9.5.

TABLE 2

TABLE 3

As can be seen from Table 1, the tapping torque values of examples 1-5 are less than 70, and as low as 64.5, while the tapping efficiency is greater than 170%, and as high as 182%, which proves that the metal working fluids of examples 1-5 have excellent lubricating properties at concentrations of 4-5%. Comparative example 1 substituting mineral oil for isomeric hexadecane resulted in a tapping torque value of 99.4 and a tapping efficiency of 118%; comparative example 2 the use of isooctyl sebacate instead of 2-ethylhexyl benzoate resulted in tapping torque values as high as 77.2, tapping efficiency of 152%, and a poorer lubricating effect than in example 1; comparative example 3 no benzotriazole derivative was added, resulting in a tapping torque value of 90.9 and a tapping efficiency of 129%; comparative example 4 the mass fraction of the amount of benzotriazole derivative was less than 3%, resulting in a tapping torque value of 84.7 and a tapping efficiency of 138%; comparative example 5 the mass fraction of the usage of benzotriazole derivatives is more than 5%, the tapping torque value is 66.0, the tapping efficiency is 178%, and the lubricating property of the machining fluid is not improved. While the tapping torque value of the conventional product was 117.2, the tapping efficiency was 100%, and the lubricating effect was inferior to that of examples 1 to 5.

As can be seen from tables 2 and 3, the invention of example 1 has good antibacterial performance and biological stability, while the comparison example 6 selects hydroxyethyl hexahydro-s-triazine as bactericide, and the comparison example 7 selects a mixture of p-methylaniline and p-ethylaniline as organic amine, which all result in the reduction of antibacterial performance and biological stability of the metal working fluid.

The applicant states that the present invention is illustrated by the above examples to show the detailed process equipment and process flow of the present invention, but the present invention is not limited to the above detailed process equipment and process flow, i.e. it does not mean that the present invention must rely on the above detailed process equipment and process flow to be implemented. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

Claims

1. The metal working fluid is characterized by comprising the following components in percentage by mass:

the base oil is isomeric hexadecyl alkane, and the synthetic ester is 2-ethylhexyl benzoate and/or trimethylolpropane tricaprate;

the special lubricant is benzotriazole derivatives.

2. The metal working fluid of claim 1 wherein the organic acid comprises any one of dimerized ricinoleic acid, tall oil acid, isomerized stearic acid, lauric acid, gluconic acid, or neodecanoic acid, or a combination of at least two thereof.

3. The metal working fluid of claim 1 wherein the organic amine comprises any one or a combination of at least two of diisopropanolamine, 2-amino-2-methylpropanol, 3-butoxypropylamine, N-diethylaniline or hexamethylenetetramine.

4. The metal working fluid of claim 1 wherein said adjuvants include emulsifiers, coupling agents, biocides, and defoamers.

5. The metal working fluid of claim 4 wherein the emulsifier comprises any one of, or a combination of at least two of, an alcohol ether carboxylic acid, a fatty alcohol polyoxyethylene polyoxypropylene ether, or a polyisobutylene maleic anhydride.

6. The metal working fluid according to claim 4, wherein the emulsifier is present in an amount of 1 to 2% by mass.

7. The metal working fluid of claim 4 wherein the coupling agent is triethylene glycol butyl ether.

8. The metal working fluid of claim 4, wherein the coupling agent is present in an amount of 2 to 5% by mass.

9. The metalworking fluid of claim 4 wherein the biocide is a mixture of 2-butyl-1, 2-benzisothiazolin-3-one and 2-bromo-2-nitro-1, 3 propanedioi.

10. The metal working fluid according to claim 4, wherein the bactericide is 1 to 2% by mass.

11. The metal working fluid of claim 4 wherein the anti-foaming agent is dimethicone.

12. The metal working fluid according to claim 4, wherein the defoaming agent is 0.05 to 0.1% by mass.

13. A method of preparing a metalworking fluid according to any of claims 1 to 12, comprising the steps of:

14. The method according to claim 13, wherein the stirring speed of the stirring in the step (1) is 400 to 800 rpm.

15. The preparation method according to claim 13, wherein the stirring time in the step (1) is 20 to 40 min.

16. The method according to claim 13, wherein the stirring temperature in the step (1) is 25 to 40 ℃.

17. The method according to claim 13, wherein the stirring speed of the stirring in the step (2) is 400 to 800 rpm.

18. The preparation method according to claim 13, wherein the stirring time in the step (2) is 20 to 40 min.

19. The method according to claim 13, wherein the stirring temperature in the step (2) is 25 to 40 ℃.

20. The method according to claim 13, wherein the stirring speed of the stirring in the step (3) is 400 to 800 rpm.

21. The method according to claim 13, wherein the stirring time in the step (3) is 20 to 40 min.

22. The method according to claim 13, wherein the stirring temperature in the step (3) is 25 to 40 ℃.

23. Use of a metal working fluid according to any one of claims 1 to 12 for the processing of automotive engine parts.