Extreme pressure tapping oil and preparation method thereof

Abstract

The invention relates to the technical field of metal processing oil, in particular to extreme pressure tapping oil and a preparation method thereof. The extreme pressure tapping oil comprises the following components in percentage by mass: 26%-33% of base oil, 13%-22% of an oiliness agent, 48%-57% of an extreme pressure anti-wear agent, 0.2%-0.5% of an antioxidant and 3%-5% of an anti-rust agent, the anti-wear reagent at extreme pressure comprises a chlorine-based anti-wear reagent at extreme pressure, a sulfur-based anti-wear reagent at extreme pressure and a phosphorus-based anti-wear reagent at extreme pressure; the content of the chlorine-based extreme pressure anti-wear agent in the extreme pressure tapping oil is not less than 35wt%; and the mass ratio of the chlorine-based anti-wear reagent at extreme pressure to the sum of the sulfur-based anti-wear reagent at extreme pressure and the phosphorus-based anti-wear reagent at extreme pressure is greater than 3: 1. According to the extreme pressure tapping oil disclosed by the invention, the chlorine-based extreme pressure anti-wear additive with an extremely high proportion is used as a core extreme pressure lubricating material, the phosphorus-based extreme pressure anti-wear additive and the non-active sulfur-based extreme pressure anti-wear additive with relatively low proportions are compounded, and excellent extreme pressure lubricating capacity is realized through the synergistic effect of multiple types of extreme pressure additives.

Description

Technical Field

[0001] This invention relates to the field of metalworking fluid technology, and in particular to an extreme pressure tapping fluid and its preparation method. Background Technology

[0002] Tapping oil is a metalworking fluid specifically designed for internal thread machining, possessing excellent extreme pressure lubrication, superior anti-sintering properties, and good adhesion. It effectively isolates direct metal-to-metal contact by forming a high-strength lubricating film between the tap and the workpiece, thereby significantly reducing cutting torque, inhibiting built-up edge formation, and making it suitable for tapping various difficult-to-machine materials. Furthermore, compared to water-based cutting fluids, tapping oil eliminates concerns about microbial growth, allows for longer oil change intervals, and provides stronger short-term rust protection for machine tools and workpieces. However, despite its outstanding performance, tapping oil generally faces a series of technical challenges in its application: 1. The lubricating film is difficult to continuously enter the cutting zone: As the tap goes deeper into the hole, especially when tapping deep holes or blind holes, it is difficult for the oil to break through the chip blockage and reach the cutting edge in time, which makes the cutting zone prone to "oil-deficient" or even "dry friction" state.

[0003] 2. Extremely High Contact Pressure and Extrusion Forming: The tapping process itself involves a significant amount of metal extrusion forming, especially when machining ductile materials (such as stainless steel and aluminum alloys), where the tap needs to extrude the metal into thread profiles. This extremely high contact pressure makes ordinary oil films very prone to rupture, leading to direct metal-to-metal contact. Current tapping oil sintering loads (four-ball PD value) are generally between 400-620 kgf, often resulting in tool breakage and thread breakage when tapping high-hardness materials. The extremely high contact pressure and instantaneous temperature associated with the tapping process make ordinary oil films very prone to rupture, leading to direct metal-to-metal contact, causing tool damage and poor workpiece quality.

[0004] 3. High frictional torque and demanding boundary lubrication: The tap's back face and the machined surface of the workpiece, as well as the tap's ribs and the thread flanks, are subjected to enormous normal pressure and sliding friction. If the oil film pressure is insufficient, the frictional torque will increase sharply, easily causing tap wear or even breakage.

[0005] 4. Severe work hardening tendency: When machining difficult-to-machine materials such as stainless steel, high-temperature alloys, and titanium alloys, intense plastic deformation causes the material surface to harden rapidly. This means that subsequent cutting edges need to cut through a layer of material with even higher hardness, further increasing the tool load and the requirements for the extreme pressure performance of the oil.

[0006] Therefore, when selecting tapping oil, if the material being processed is a difficult-to-machine material such as stainless steel, titanium alloy, or high-hardness alloy steel, or if it involves harsh working conditions such as deep holes or blind holes, ordinary tapping oil is often insufficient to meet the processing requirements. Special tapping oils with sufficiently strong extreme pressure performance must be selected for these special working conditions. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the purpose of this invention is to provide an extreme pressure tapping oil and its preparation method, which aims to improve the permeability and extreme pressure performance of the extreme pressure tapping oil.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of this invention provides an extreme pressure tapping oil, comprising the following components by mass percentage: 26%–33% base oil, 13%–22% oiliness agent, 48%–57% extreme pressure anti-wear agent, 0.2%–0.5% antioxidant, and 3%–5% rust inhibitor; wherein the extreme pressure anti-wear agent comprises chlorine-based extreme pressure anti-wear agent, sulfur-based extreme pressure anti-wear agent, and phosphorus-based extreme pressure anti-wear agent; the content of the chlorine-based extreme pressure anti-wear agent in the extreme pressure tapping oil is 35–40 wt%; and the mass ratio of the chlorine-based extreme pressure anti-wear agent to the sum of the sulfur-based and phosphorus-based extreme pressure anti-wear agents is greater than 3:1.

[0009] The extreme pressure tapping oil, wherein the base oil is selected from at least one of No. 68 white oil, 100N, 100SN, 150N, 150SN, 250N, and 250SN.

[0010] The extreme pressure tapping oil, wherein the oiliness agent is selected from at least one of trimethylolpropane oleate, pentaerythritol ester, isooctyl stearate, fatty acid methyl ester, isooctyl cocoate, and dioctyl terephthalate.

[0011] The extreme pressure tapping oil, wherein the chlorine-based extreme pressure anti-wear agent is chlorinated paraffin.

[0012] The extreme pressure tapping oil, wherein the sulfur-based extreme pressure anti-wear agent is selected from at least one of sulfurized lard and sulfurized fatty acid esters.

[0013] The extreme pressure tapping oil, wherein the phosphorus-based extreme pressure anti-wear agent is selected from at least one of tricresyl phosphate, isooctyl phosphate, acidic phosphate amine salt, oleo-based phosphite, oleoyl alcohol polyether phosphate, and oleoyl alcohol polyether phosphate.

[0014] The extreme pressure tapping oil, wherein the antioxidant is selected from at least one of 2,6-di-tert-butyl-p-cresol, N-phenyl-α-naphthylamine, and 4,4'-dioctyldiphenylamine.

[0015] The extreme pressure tapping oil, wherein the rust inhibitor is selected from carboxylate rust inhibitors.

[0016] The extreme pressure tapping oil, wherein the rust inhibitor is selected from at least one of zinc salt, magnesium salt, and calcium salt of naphthenic acid.

[0017] A second aspect of the present invention provides a method for preparing extreme pressure tapping oil, which is used to prepare the extreme pressure tapping oil as described above, comprising the following steps: S1. Mix the base oil and oiliness agent, and stir at room temperature until homogeneous and transparent; S2. Slowly add the extreme pressure anti-wear agent and stir at 55±5℃ until the solution is homogeneous; S3. Add antioxidants and rust inhibitors and stir until homogeneous to obtain a black, slightly transparent oil.

[0018] Beneficial Effects: This invention provides an extreme pressure tapping oil. This oil utilizes chlorine-based, sulfur-based, and phosphorus-based extreme pressure anti-wear agents, with a very high proportion (>35%) of chlorine-based extreme pressure anti-wear agent as the core extreme pressure lubricant, combined with a relatively low proportion of phosphorus-based and inactive sulfur-based extreme pressure anti-wear agents. Through the synergistic effect of these multiple types of extreme pressure agents, excellent anti-sintering and anti-wear properties are achieved. Its anti-sintering load can reach 1000 kgf, effectively protecting the tool and workpiece surfaces. Furthermore, considering the potential corrosion risk to equipment from high chlorine-based extreme pressure agents, an appropriate amount of rust inhibitor is added to the formula to ensure the oil has good rust prevention capabilities. Detailed Implementation

[0019] This invention provides an extreme pressure tapping oil and its preparation method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the following embodiments are provided to further illustrate the invention in detail. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0020] The first aspect of this invention provides an extreme pressure tapping oil, comprising, by weight percentage: 26%–33% base oil, 13%–22% oiliness agent, 48%–57% extreme pressure anti-wear agent, 0.2%–0.5% antioxidant, and 3%–5% rust inhibitor; the extreme pressure anti-wear agent includes chlorine-based, sulfur-based, and phosphorus-based extreme pressure anti-wear agents; the chlorine-based extreme pressure anti-wear agent is present in the extreme pressure tapping oil at a content of 35–40 wt%. The purpose of this formulation is to ensure that the oil can form a robust chemical lubrication film under instantaneous high temperature and pressure, while maintaining excellent permeability to reach even the smallest cutting areas. The extreme pressure anti-wear agent reacts chemically with the metal surface under high temperature and pressure to generate a low-shear-strength chemical reaction film, preventing direct contact between the tap and the workpiece (cold welding), which is crucial for resisting extremely high loads. Even under extremely difficult machining conditions (such as tapping large-size, deep blind holes), the lubrication effect of chlorine-containing extreme pressure agents remains irreplaceable. Therefore, the formulation uses a high proportion of chlorine-based extreme pressure anti-wear agents as the core extreme pressure lubricating material, combined with relatively low contents of phosphorus-based and inactive sulfur-based extreme pressure anti-wear agents. Excellent anti-sintering and anti-wear properties are achieved through the synergistic effect of multiple types of extreme pressure agents. Preferably, the mass ratio of chlorine-based extreme pressure anti-wear agent to the sum of sulfur-based and phosphorus-based extreme pressure anti-wear agents is not less than 3:1.

[0021] Preferably, the chlorine-based extreme pressure anti-wear agent is chlorinated paraffin. The ferric chloride film formed by chlorinated paraffin under high temperature and pressure has extremely low shear strength and a low coefficient of friction, which can effectively prevent sintering, seizing, and scratching of metal surfaces under high loads.

[0022] Preferably, the sulfur-based extreme pressure anti-wear agent is selected from at least one of sulfurized lard and sulfurized fatty acid esters.

[0023] Preferably, the phosphorus-based extreme pressure anti-wear agent is selected from at least one of tricresyl phosphate, isooctyl phosphate, acidic phosphate amine salt, oleyl phosphite, oleyl alcohol polyether phosphate, and oleyl alcohol polyether phosphate.

[0024] Preferably, the base oil is selected from at least one of No. 68 white oil, 100N, 100SN, 150N, 150SN, 250N, and 250SN. These base oils are characterized by good permeability and low viscosity, serving as a carrier to provide basic lubrication and cooling, and are responsible for delivering additives to the machining area. The high permeability and low viscosity of the base oil allow it to penetrate the dense metallographic structure of difficult-to-machine materials such as mold steel, quickly penetrating the tiny gaps between the tap and the workpiece to provide initial lubrication before the extreme pressure film is established.

[0025] Preferably, the oiling agent is selected from at least one of trimethylolpropane oleate, pentaerythritol oleate, isooctyl stearate, fatty acid methyl ester, isooctyl cocoate, and dioctyl terephthalate. The oiling agent is firmly adsorbed onto the metal surfaces of the tap and workpiece through its polar groups (such as carboxyl and hydroxyl groups) in its molecules, forming a dense physical lubricating film. This film provides physical adsorption lubrication under medium and low temperatures and medium loads, compensating for the lubrication gap before the extreme pressure agent is activated, synergistically reducing the coefficient of friction, and also aiding in dissolution.

[0026] Preferably, the antioxidant is selected from at least one of 2,6-di-tert-butyl-p-cresol, N-phenyl-α-naphthylamine, and 4,4'-dioctyldiphenylamine. Antioxidants are additives used in metal products, and their main function is to inhibit the reaction of base oil with oxygen under high temperature, high pressure, and metal catalysis, preventing the oil's acid value from increasing, viscosity from increasing, or the formation of gum deposits. Antioxidants interrupt chain oxidation reactions by capturing free radicals generated during oxidation or decomposing peroxides, thereby maintaining the chemical stability and service life of the oil. The selection of antioxidants directly affects the oil's ability to maintain performance during long-term storage or continuous heavy-load processing. By rationally selecting antioxidants, the antioxidant capacity of tapping oil can be significantly improved, oil change intervals extended, and lubrication failure or equipment corrosion problems caused by oil deterioration can be avoided.

[0027] Preferably, the rust inhibitor is selected from carboxylate-based rust inhibitors. Carboxylate-based rust inhibitors are oil-soluble rust inhibitors, known for their excellent rust-preventive properties and good oil solubility on various metals (such as steel, copper, and aluminum). Specifically, the rust inhibitor is selected from at least one of zinc, magnesium, and calcium salts of naphthenic acids. The carboxylate ions in the carboxylate rust inhibitor molecule can chemically adsorb or react with the metal surface (such as Fe and Cu) to form a strong adsorption film: the alkyl chains are arranged outwards, forming a dense hydrophobic barrier that effectively prevents the penetration of corrosive media such as H2O and O2. Among them, the adsorption film formed by zinc naphthenate is typically several nanometers thick and exhibits long-lasting rust prevention capabilities in medium and low temperature environments.

[0028] A second aspect of the present invention provides a method for preparing extreme pressure tapping oil, which is used to prepare the extreme pressure tapping oil as described above, comprising the following steps: S1. Mix the base oil and oiliness agent, and stir at room temperature until homogeneous and transparent; S2. Slowly add the extreme pressure anti-wear agent and stir at 55±5℃ until the solution is homogeneous; S3. Add antioxidants and rust inhibitors and stir until homogeneous to obtain a black, slightly transparent oil.

[0029] The present invention will be further illustrated by the following examples and comparative examples. The formulations of each example and comparative example are shown in Table 1 and Table 2.

[0030] Table 1

[0031] Table 2

[0032] The preparation methods of the tapping oil in the above embodiments and comparative examples are as follows: S1. Mix the base oil and oiliness agent, and stir at room temperature until homogeneous and transparent; S2. Slowly add the extreme pressure anti-wear agent and stir at 55±5℃ until the solution is homogeneous; S3. Add antioxidants and rust inhibitors and stir until homogeneous to obtain a black, slightly transparent oil.

[0033] The performance of the tapping oils in the above embodiments and comparative examples was tested.

[0034] Among them, kinematic viscosity (40℃, mm) 2 / s) Test according to GB / T 265, ASTM D445.

[0035] The corrosion grade of copper sheets shall be tested in accordance with GB / T 5096 and ASTM D130.

[0036] The test method for extreme pressure lubrication performance shall be in accordance with GB / T12583-1998. Test instrument model: Xiamen Tianji MS-10A.

[0037] The rust resistance test method shall be in accordance with SH / T 0081. Test instrument model: Q-LAB damp heat chamber.

[0038] The results are shown in Tables 3 and 4.

[0039] Table 3

[0040] The performance test results of Examples 1, 1, 2, and 3 are shown in Table 3. The test data show that Example 1 exhibits the best extreme pressure performance, with a sintering load (PD) value reaching 1000 kgf. In contrast, the PD value of Comparative Example 1 decreased by one level compared to Example 1. This is because the higher proportion of sulfurized fatty acid esters and chlorinated paraffins competed for adsorption on the limited active sites on the metal friction pair surface, producing an "antagonistic effect" and weakening the extreme pressure film formation. The extreme pressure performance of Comparative Example 2 declined more significantly than that of Example 1. This is mainly because the higher proportion of tricresyl phosphate not only competed for adsorption with chlorinated paraffins, but the reaction film formed by the phosphorus-based additives also focused on anti-wear protection, and its extreme pressure load-bearing capacity was far inferior to that of chlorine-based and sulfur-based reaction films. The PD value of Comparative Example 3 decreased by one level compared to Example 1, and the PB value also decreased significantly, indicating that the single chlorine-based extreme pressure film is insufficient in terms of anti-wear performance. This reflects that during the tapping process, when the temperature rises sharply, the strength of a single chloride film decreases or even begins to decompose. At this point, phosphorus-based additives are needed to replenish the film and reduce wear. Simultaneously, a small amount of sulfur-based additives are activated, and the resulting iron sulfide film (with a high melting point and strong load-bearing capacity) can promptly "fill the gap," thus forming a composite gradient lubricating film with a "chlorine film as the base and a sulfur film as the reinforcement." This multi-layered composite film structure is more robust and durable than a single lubricating film, which explains why Example 1 outperforms the comparative examples in both extreme pressure and anti-wear performance.

[0041] Table 4

[0042] Note: The damp heat result is the time when obvious rust spots begin to appear on the rust prevention test piece.

[0043] The damp heat test results in Table 4 show that, compared to Comparative Example 4 (which only showed obvious rust spots on the test piece after 72 hours), Examples 2, 5, and 6 containing zinc naphthenate had significantly longer rust prevention periods, while Comparative Example 4 (which did not contain zinc naphthenate) showed a significantly higher PD value than Comparative Example 4. This result indicates that zinc naphthenate plays a dual role in the formulation: firstly, as a rust inhibitor, it effectively suppresses the corrosion risk that extreme pressure anti-wear agents such as chlorinated paraffin may cause; secondly, it can form a boundary lubrication film on the metal surface during friction, reducing friction and wear. The mechanism of action of zinc naphthenate is as follows: under the action of frictional heat and pressure, zinc naphthenate forms a zinc-containing chemical reaction film (mainly zinc oxide) on the metal surface, which has a certain friction-reducing and anti-wear effect. By adding an appropriate amount of zinc naphthenate, the anti-wear gap between sulfur-based, chlorine-based, and phosphorus-based extreme pressure anti-wear agents can be filled, playing a synergistic lubricating role, thereby further improving the extreme pressure anti-wear performance of the system.

[0044] It is important to note that the amount of zinc naphthenate added needs to be carefully controlled. In Comparative Example 5, an excessive amount of zinc naphthenate was added, which led to competitive adsorption with other extreme pressure lubricants, resulting in an antagonistic effect. Therefore, compared with Example 2, its PB and PD values ​​were significantly reduced.

[0045] Comparative Example 6 used highly active sulfurized olefins to replace sulfurized lard. Although it still maintained good lubrication and extreme pressure performance, its copper corrosion test result was only 4c, indicating a serious risk of corrosion.

[0046] It is understood that those skilled in the art can make equivalent substitutions or modifications to the technical solution and inventive concept of the present invention, and all such substitutions or modifications should fall within the protection scope of the appended claims.

Claims

1. An extreme pressure tapping oil, characterized in that, By weight percentage, it comprises the following components: base oil 26%–33%, oiliness agent 13%–22%, extreme pressure anti-wear agent 48%–57%, antioxidant 0.2%–0.5%, and rust inhibitor 3%–5%; The extreme pressure anti-wear agent includes chlorine-based extreme pressure anti-wear agent, sulfur-based extreme pressure anti-wear agent and phosphorus-based extreme pressure anti-wear agent; The content of the chlorine-based extreme pressure anti-wear agent in the extreme pressure tapping oil is not less than 35 wt%; the mass ratio of the chlorine-based extreme pressure anti-wear agent to the sum of the sulfur-based and phosphorus-based extreme pressure anti-wear agents is greater than 3:

1.

2. The extreme pressure tapping oil according to claim 1, characterized in that, The base oil is selected from at least one of No. 68 white oil, 100N, 100SN, 150N, 150SN, 250N, and 250SN.

3. The extreme pressure tapping oil according to claim 1, characterized in that, The oiliness agent is selected from at least one of trimethylolpropane oleate, pentaerythritol ester, isooctyl stearate, fatty acid methyl ester, isooctyl cocoate, and dioctyl terephthalate.

4. The extreme pressure tapping oil according to claim 1, characterized in that, The chlorine-based extreme pressure anti-wear agent is chlorinated paraffin.

5. The extreme pressure tapping oil according to claim 1, characterized in that, The sulfur-based extreme pressure anti-wear agent is selected from at least one of sulfurized lard and sulfurized fatty acid esters.

6. The extreme pressure tapping oil according to claim 1, characterized in that, The phosphorus-based extreme pressure anti-wear agent is selected from at least one of tricresyl phosphate, isooctyl phosphate, acidic phosphate amine salt, oleo-based phosphite, oleoyl alcohol polyether phosphate, and oleoyl alcohol polyether phosphate.

7. The extreme pressure tapping oil according to claim 1, characterized in that, The antioxidant is selected from at least one of 2,6-di-tert-butyl-p-cresol, N-phenyl-α-naphthylamine, and 4,4'-dioctyldiphenylamine.

8. The extreme pressure tapping oil according to claim 1, characterized in that, The rust inhibitor is selected from carboxylate-based rust inhibitors.

9. The extreme pressure tapping oil according to claim 1, characterized in that, The rust inhibitor is selected from at least one of zinc salt, magnesium salt, and calcium salt of naphthenic acid.

10. A method for preparing extreme pressure tapping oil, used to prepare the extreme pressure tapping oil as described in any one of claims 1-9, comprising the following steps: S1. Mix the base oil and oiliness agent, and stir at room temperature until homogeneous and transparent; S2. Slowly add the extreme pressure anti-wear agent and stir at 55±5℃ until the solution is homogeneous; S3. Add antioxidants and rust inhibitors and stir until homogeneous to obtain a black, slightly transparent oil.

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