Special quenching oil for 05Cr15Ni5Cu4Nb precipitation-hardening stainless steel as well as preparation method and application of quenching oil

Abstract

The invention relates to the technical field of heat treatment quenching media, in particular to quenching oil special for 05Cr15Ni5Cu4Nb precipitation hardening stainless steel and a preparation method and application of the quenching oil. The special quenching oil for the 05Cr15Ni5Cu4Nb precipitation hardening stainless steel is prepared from the following components in percentage by mass: 88 to 95 percent of base oil combination, 1.5 to 5.0 percent of quick cooling agent, 2.0 to 3.5 percent of antioxidant and 1.0 to 4.0 percent of dispersing agent, the base oil composition is a mixture composed of refined hydrogenated mineral oil 150N and refined hydrogenated mineral oil 500N; the quick cooling agent is polyisobutene; the antioxidant is a combination of phenyl-alpha-naphthylamine and dialkyl dithiophosphate carbamate, or a combination of phenyl-alpha-naphthylamine and dilauryl thiodipropionate, and the antioxidant is a combination of phenyl-alpha-naphthylamine and dilauryl thiodipropionate. Through base oil compounding and rapid cooling agent dosage optimization, the step quenching effect of high-temperature rapid cooling and low-temperature slow cooling is achieved, martensite transformation of a 05Cr15Ni5Cu4Nb precipitation hardening stainless steel workpiece is stably completed near the Ms point, and a uniform and fine lath martensite structure is provided for subsequent aging strengthening.

Description

Technical Field

[0001] This invention relates to the field of heat treatment quenching media technology, specifically to a special quenching oil for 05Cr15Ni5Cu4Nb precipitation hardening stainless steel, its preparation method, and its application. Background Technology

[0002] Precipitation hardening stainless steel is a type of stainless steel that achieves high strength through heat treatment while maintaining excellent corrosion resistance and toughness. It combines the corrosion resistance of austenitic stainless steel with the heat-treatable strengthening properties of martensitic stainless steel, and is widely used in aerospace, chemical, medical, and high-end manufacturing fields.

[0003] The core characteristic of this type of steel is that after solution treatment (heating the material to a certain temperature to fully dissolve the alloying elements into the austenite, followed by rapid cooling (quenching) to obtain a supersaturated martensitic structure, which is the basis for subsequent hardening), a supersaturated structure is formed. Then, through aging treatment (usually holding at 480-620℃), elements such as copper, niobium, aluminum, and titanium precipitate as nanoscale intermetallic compounds or copper-rich phases, thereby significantly improving strength. Based on the different matrix structures, precipitation-hardening stainless steel can be divided into three categories: 1. Martensitic type: Martensite is formed directly after solution treatment, and then strengthened by aging to precipitate a copper-rich phase (ε-Cu). The process is simple and the strength is high, making it the most widely used type.

[0004] 2. Semi-austenitic type: The solid solution state is metastable austenite, which requires cold working or conditioning to induce martensitic transformation, followed by aging. It has excellent comprehensive properties and forming ability.

[0005] 3. Austenitic type: The matrix is ​​always austenitic, and it is strengthened by the precipitation of γ' phases such as Ni3(Al,Ti). It has excellent high-temperature strength and low-temperature toughness and is often used in aero-engine components.

[0006] 05Cr15Ni5Cu4Nb (15-5PH) is a high-performance martensitic precipitation hardening stainless steel improved from 17-4PH. It has good machinability in the solution state, and its strength is significantly improved after aging treatment. At the same time, it maintains excellent dimensional stability and fatigue resistance, making it particularly suitable for manufacturing high-stress, high-reliability precision parts.

[0007] This precipitation-hardening stainless steel has extremely high hardenability. For parts with simple shapes, uniform cross-sections, and small dimensions, even with slower cooling rates (such as air cooling), a uniform martensitic structure can be obtained on a larger cross-section, making it a feasible and economical process choice. However, air cooling has the following problems: ① The cooling rate is greatly affected by ambient temperature, workpiece size, and stacking method, with significant differences in cooling rates between different batches and even between different locations within the same batch; ② For parts with sharp corners, grooves, or abrupt changes in wall thickness, inconsistent cooling rates during air cooling can generate significant thermal stress, easily leading to quenching cracks at stress concentration points; ③ For workpieces with large cross-sections (such as φ200mm and above), air cooling may not guarantee 100% martensitic structure in the core, reducing overall strength.

[0008] To effectively avoid coarse core microstructure or the appearance of precipitates detrimental to performance due to insufficient cooling rate, the cooling rate of the core must be fast enough to obtain a uniform and fine lath martensite structure. For precision parts and complex-shaped components, ensuring uniform cooling and effective deformation control is crucial, making oil quenching particularly important. However, currently, there is very little publicly available information on dedicated quenching oils and their preparation processes for specific martensitic precipitation-hardening stainless steels like 05Cr15Ni5Cu4Nb. Existing quenching oils cannot fully meet the multiple requirements of high hardenability, controlled cooling rate near the Ms point, and smooth workpiece surface finish.

[0009] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0010] In view of the shortcomings of the prior art, the purpose of this invention is to provide a special quenching oil for 05Cr15Ni5Cu4Nb precipitation hardening stainless steel, its preparation method and application, aiming to solve the problem that existing quenching oils lack optimized design for the characteristics of 05Cr15Ni5Cu4Nb steel, and are difficult to balance high-temperature cooling rate, low-temperature cooling rate control, oxidation resistance and workpiece surface quality.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: A quenching oil specifically for 05Cr15Ni5Cu4Nb precipitation hardening stainless steel, comprising, by mass percentage: 88-95% base oil, 1.5-5.0% quick-cooling agent, 2.0-3.5% antioxidant, and 1.0-4% dispersant; wherein the base oil is a mixture of refined hydrogenated mineral oil 150N and refined hydrogenated mineral oil 500N; the quick-cooling agent is polyisobutylene; and the antioxidant is a combination of phenyl-α-naphthylamine and dialkyl dithiophosphate carbamate, or a combination of phenyl-α-naphthylamine and dilaurate thiodipropionate.

[0012] The quenching oil for 05Cr15Ni5Cu4Nb precipitation hardening stainless steel is wherein the dispersant is one of heptadecanylimidazoline succinate, alkyl salicylate calcium, or high-alkalinity synthetic calcium sulfonate.

[0013] The quenching oil specifically for 05Cr15Ni5Cu4Nb precipitation-hardening stainless steel, wherein the refined hydrogenated mineral oil 150N has a kinematic viscosity of 32.91 mmHg at 40°C. 2 The viscosity index is 144; the kinematic viscosity of the refined hydrogenated mineral oil 500N at 40°C is 88.96 mm² / s. 2 / s, viscosity index is 100.

[0014] The quenching oil specifically for 05Cr15Ni5Cu4Nb precipitation hardening stainless steel has a kinematic viscosity of 60-70 mmHg at 40°C. 2 The kinematic viscosity at 100℃ is 8.2-8.8 mm / s. 2 / s.

[0015] The quenching oil specifically for 05Cr15Ni5Cu4Nb precipitation hardening stainless steel has a moisture content of ≤300ppm.

[0016] A method for preparing a special quenching oil for 05Cr15Ni5Cu4Nb precipitation hardening stainless steel as described in this invention, comprising the following steps: Add the base oil mixture to the reactor, start stirring and heating, and raise the temperature to 60±5℃; While stirring, add the quick-cooling agent and antioxidant in sequence, and circulate and stir for 1.5-2.5 hours. Then add the dispersant and continue stirring for 0.5-1.5 hours. Heat the reactor to 100-110℃ and stir and circulate to remove water until the moisture content is ≤300ppm.

[0017] The present invention discloses the application of a special quenching oil for 05Cr15Ni5Cu4Nb precipitation hardening stainless steel in the heat treatment of 05Cr15Ni5Cu4Nb precipitation hardening stainless steel, wherein the application involves placing the 05Cr15Ni5Cu4Nb precipitation hardening stainless steel workpiece in the quenching oil at a temperature of 80-180°C after solution treatment for graded quenching.

[0018] In the aforementioned application, the staged quenching causes the workpiece to remain at a temperature near the Ms point in order to reduce the internal and external temperature difference during the martensitic transformation process and obtain a uniform lath martensitic structure with low internal stress.

[0019] In the aforementioned application, the quenching oil is used to ensure that the core of a 05Cr15Ni5Cu4Nb precipitation-hardening stainless steel workpiece with a cross-sectional dimension ≥ φ200mm obtains 100% martensitic structure.

[0020] Beneficial effects: This invention fully considers the phase transformation characteristics of 05Cr15Ni5Cu4Nb stainless steel (Ms point 202℃, M... f At 81℃, through base oil compounding and optimization of the amount of rapid cooling agent, a graded quenching effect of high-temperature rapid cooling and low-temperature slow cooling is achieved, enabling the workpiece to smoothly complete the martensitic transformation near the Ms point, providing a uniform and fine lath martensite structure for subsequent aging strengthening; the compounded antioxidant system of this invention produces a synergistic effect, with a rotating oxygen bomb time ≥285min, and oxidation stability nearly 3 times higher than that of a single component, effectively extending the service life of the oil; the compounded polymeric dispersant of this invention, through the dual synergistic effect of steric hindrance and charge repulsion, stably suspends contaminants, enabling the workpiece to achieve a gloss level of 1, meeting the requirements of precision parts. Attached Figure Description

[0021] Figure 1 This is a photograph of the quenching oil specifically for 05Cr15Ni5Cu4Nb precipitation hardening stainless steel prepared in Example 1 of this invention.

[0022] Figure 2 The image shows the results of the rotating oxygen bomb test on the quenching oil for 05Cr15Ni5Cu4Nb precipitation hardening stainless steel prepared in Example 1 of this invention.

[0023] Figure 3 The image shows the cooling performance of the special quenching oil for 05Cr15Ni5Cu4Nb precipitation hardening stainless steel prepared in Example 1 of this invention. Detailed Implementation

[0024] This invention provides a special quenching oil for 05Cr15Ni5Cu4Nb precipitation hardening stainless steel, its preparation method, and its application. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0025] The martensitic transformation of 05Cr15Ni5Cu4Nb has an initiation point Ms (202℃) and an end point M. f(81℃) The ideal quenching process is as follows: In the high-temperature region (above the Ms point), a sufficiently fast cooling rate is required to suppress proeutectoid phase transformations (such as pearlite and bainite transformations) and ensure that the supercooled austenite does not decompose. Below the Ms point, the martensitic transformation is completed instantaneously, and its volume expansion generates huge phase transformation stresses. If the temperature difference between the inside and outside of the workpiece is large at this time, the stress distribution will be uneven, which can easily lead to deformation and cracking.

[0026] To address the aforementioned problems, this invention provides a special quenching oil for 05Cr15Ni5Cu4Nb precipitation-hardening stainless steel, comprising, by mass percentage: 88-95% base oil, 1.5-5.0% quick-cooling agent, 2.0-3.5% antioxidant, and 1.0-4% dispersant; the base oil is a mixture of refined hydrogenated mineral oil 150N and refined hydrogenated mineral oil 500N; the quick-cooling agent is polyisobutylene; and the antioxidant is a combination of phenyl-α-naphthylamine and dialkyl dithiophosphate carbamate, or a combination of phenyl-α-naphthylamine and dilaurate thiodipropionate.

[0027] In this invention, the base oil accounts for approximately 85-98% of the quenching oil, and its quality directly affects the overall performance of the quenching oil. This invention selects refined hydrogenated mineral oils 150N and 500N for blending, based on the following synergistic considerations: the kinematic viscosity of the refined hydrogenated mineral oil 150N at 40°C is 32.91 mmHg. 2 With a viscosity index of 144, the low viscosity ensures good fluidity of the oil during the initial quenching stage, enabling it to quickly coat the workpiece and promote rapid rupture of the vapor film. The refined hydrogenated mineral oil 500N has a kinematic viscosity of 88.96 mm² at 40°C. 2 With a viscosity index of 100, its high viscosity helps form a stable oil film in the high-temperature zone (vapor film stage), delaying cooling and providing a good dissolving carrier for additives. When combined (150N to 500N in a mass ratio of 1:2-1:3), the kinematic viscosity at 40℃ can be precisely controlled to 60-70 mmHg by adjusting the ratio. 2 Within a viscosity range of / s, this range provides the oil with moderate wettability and fluidity in the high-temperature zone (vapor film stage), ensuring that the workpiece surface can be quickly covered by the oil, achieving cooling characteristics of moderate cooling rate in the high-temperature zone and gradual cooling rate in the low-temperature zone. More importantly, this viscosity combination provides an optimal dissolution and dispersion environment for subsequent additives (rapid cooling agents, antioxidants, dispersants), allowing each additive to fully exert its function and form a synergistic effect.

[0028] This invention selects polyisobutylene as a rapid cooling agent. Polyisobutylene is a high molecular weight compound with strong polarity. Its polar groups adsorb onto the workpiece surface at high temperatures, disrupting the stable vapor film and causing the oil to enter the boiling stage earlier. This significantly increases the characteristic temperature (HP value) and maximum cooling rate, allowing the workpiece to quickly pass through the most unstable region of austenite (approximately 800-400℃), avoiding non-martensitic transformation and ensuring a 100% martensitic structure in the core. This is the foundation for obtaining high hardness and high strength. The polyisobutylene exhibits good solubility and stability in 150N / 500N blended base oils and does not undergo phase separation. The polyisobutylene itself has a certain antioxidant capacity, and its combined action with blended antioxidants can further delay oil aging.

[0029] Furthermore, this invention controls the amount of polyisobutylene at 1.5-5.0%, which enables the quenching oil to obtain a sufficiently fast cooling rate (maximum cooling rate ≥78℃ / s) in the critical range of 800-400℃, ensuring that the nose region of the CCT curve is avoided. At the same time, the cooling rate in the 300℃ low-temperature region is controlled at 7-8℃ / s, avoiding excessive internal stress and crack risk caused by excessive cooling rate during the martensitic transformation process.

[0030] The antioxidant of this invention is a combination of phenyl-α-naphthylamine and dialkyl dithiophosphate carbamate, or a combination of phenyl-α-naphthylamine and dilaurate thiodipropionate. Phenyl-α-naphthylamine, as a chain-terminating antioxidant, can capture free radicals generated during oxidation and terminate the oxidation chain reaction; dialkyl dithiophosphate carbamate or dilaurate thiodipropionate, as a peroxide decomposer, can decompose peroxides generated during oxidation and prevent them from further initiating chain reactions. When combined, the chain terminator and the peroxide decomposer act on different stages of the oxidation reaction, forming a complete antioxidant barrier.

[0031] In some embodiments, the dispersant is one of heptadecanylimidazolinyl succinate, alkyl salicylate calcium, or high-base-value synthetic calcium sulfonate, but is not limited thereto.

[0032] Specifically, quenching oil inevitably introduces or generates solid contaminants during use, such as oxide scale detached from the workpiece surface, carbon deposits and sludge produced by oil oxidation, and dust falling from the air. If these tiny particles aggregate and settle in the oil, they will deposit on the workpiece surface, forming spots that are difficult to clean and severely affecting surface quality. In this embodiment, the dispersant, through the steric hindrance effect and charge repulsion, stably disperses and suspends the solid contaminants (carbon deposits, sludge, metal oxides, coke, etc.) generated during quenching in the oil, thereby preventing contaminants from settling on the workpiece surface and ensuring that the surface finish of the workpiece after quenching reaches Grade 1, meeting the requirements of precision parts. Furthermore, the dispersant forms a stable micelle structure in the 150N / 500N compound base oil, ensuring long-term dispersion; it also assists in the uniform distribution of the rapid cooling agent, avoiding excessively high local concentrations.

[0033] As an example, alkyl calcium salicylate, as a dispersant, has a molecular structure consisting of a polar head (lipophilic end) and a long nonpolar tail (oleophobic end). In oil, the polar head adsorbs onto the surface of solid contaminant particles, while the nonpolar tail extends into the oil. When multiple dispersant molecules adsorb onto the same particle, their long tails form a spatial barrier. When two adsorbed particles approach each other, this barrier generates a repulsive force, preventing the particles from colliding and agglomerating into larger particles. This mechanism is called steric stabilization. It allows solid contaminants to exist in a small, stable suspension in the oil, without settling to the workpiece surface or the bottom of the oil tank. Therefore, the workpiece surface treated with the quenching oil of this invention has an extremely high smoothness.

[0034] In some embodiments, a method for preparing a special quenching oil for 05Cr15Ni5Cu4Nb precipitation hardening stainless steel is also provided, which includes the following steps: S100. Add the base oil mixture to the reactor, start stirring and heating, and raise the temperature to 60±5℃. S200: While stirring, add the quick-cooling agent and antioxidant in sequence, and circulate and stir for 1.5-2.5 hours. Then add the dispersant and continue stirring for 0.5-1.5 hours. S300. Heat the reactor to 100-110℃ and stir and circulate to remove water until the moisture content is ≤300ppm.

[0035] In step S100, heating at 60±5℃ ensures the fluidity of the base oil while preventing the decomposition of heat-sensitive additives. In step S200, a quick-cooling agent and an antioxidant are added sequentially to ensure they are fully mixed with the base oil to form a stable antioxidant system. Then, a dispersant is added to prevent premature addition from affecting the dispersion effect of the quick-cooling agent and antioxidant. In step S300, water is removed by high-temperature stirring to ensure a moisture content ≤300ppm, guaranteeing product quality stability.

[0036] In some embodiments, the application of the special quenching oil for 05Cr15Ni5Cu4Nb precipitation hardening stainless steel as described in this invention in the heat treatment of 05Cr15Ni5Cu4Nb precipitation hardening stainless steel is also provided. The application involves placing the 05Cr15Ni5Cu4Nb precipitation hardening stainless steel workpiece in the quenching oil at a temperature of 80-180°C after solution treatment for graded quenching.

[0037] In this embodiment, the quenching oil is preheated to 80-180℃ before use, making it a graded quenching oil. When the workpiece temperature drops to around 200℃, the cooling rate automatically slows down due to the higher oil temperature. This allows the workpiece to undergo an isothermal or slow cooling process near the Ms point (202℃), reducing the temperature difference between the core and surface. As the temperature continues to drop into the M... f Below 81°C, the martensitic transformation occurs in a more uniform temperature field, resulting in a significant reduction in phase transformation stress. Therefore, while obtaining a fully martensitic structure, quenching stress and deformation are kept to a minimum.

[0038] In this invention, the staged quenching keeps the workpiece at a temperature near the Ms point to reduce the internal and external temperature difference during the martensitic transformation process and obtain a uniform lath martensitic structure with low internal stress; the quenching oil is used to ensure that the core of the 05Cr15Ni5Cu4Nb precipitation hardening stainless steel workpiece with a cross-sectional size ≥φ200mm obtains 100% martensitic structure.

[0039] The present invention will be further explained and illustrated below through specific embodiments: Raw materials of the present invention 150N: Guangdong Zhonghai Nanlian Energy Co., Ltd., kinematic viscosity at 40℃ is 32.91 mm. 2 / s, viscosity index is 144; 500N: Guangdong Zhonghai Nanlian Energy Co., Ltd., kinematic viscosity at 40℃ is 88.96 mmHg. 2 / s, viscosity index is 100; Polyisobutylene: Shandong Hongrui New Material Technology Co., Ltd.; Phenylacetyl-α-naphthylamine: Shanghai Demao Chemical Co., Ltd.; Dialkyl dithiophosphate carbamate: Hangzhou Shitian Chemical Co., Ltd.; Dilaurate thiodipropionic acid: Shandong Yousuo Chemical Technology Co., Ltd.; Heptadecanylimidazoline succinate: Beijing Benzene Ring Fine Chemical Products Co., Ltd.; Alkyl salicylate calcium: Jinzhou Shengda Chemical Co., Ltd.; High-alkali-value synthetic calcium sulfonate: Jingzhou Yinjie Chemical Co., Ltd.

[0040] Example 1 This embodiment provides a special quenching oil for 05Cr15Ni5Cu4Nb precipitation hardening stainless steel, the components of which, by mass percentage, are: Base oil composition: 92.5% (of which 150N: 29.7%, 500N: 62.8%); Rapid cooling agent: Polyisobutylene 3.0%; Antioxidant: 2.5% (phenyl-α-naphthylamine 1.0% + dialkyl dithiophosphate carbamate 1.5%); Dispersant: 2.0% alkyl salicylate calcium; Preparation process: Step 1: Add the base oil combination (150N and 500N) to the reactor, start stirring, and heat to 60°C; Step 2: While stirring, first add polyisobutylene and stir for 10 minutes. Then add the antioxidant and continue stirring for 2 hours. Next, add alkyl calcium salicylate and continue stirring for 1 hour. Step 3: Heat the reactor to 105℃, stir and circulate for 2 hours to remove water, take a sample to test the moisture content, the result is 118ppm, which meets the requirement of ≤300ppm, stop heating, and after cooling, the quenching oil product is obtained. Figure 1 As shown.

[0041] Example 2 This embodiment provides a special quenching oil for 05Cr15Ni5Cu4Nb precipitation hardening stainless steel, the components of which, by mass percentage, are: Base oil composition: 94% (of which 150N: 30%, 500N: 64%); Quick-cooling agent: 1.5% polyisobutylene; Antioxidant: 3.0% (phenyl-α-naphthylamine 1.5% + dilaurate thiodipropionate 1.5%); Dispersant: 1.5% high-alkalinity synthetic calcium sulfonate.

[0042] The preparation process is basically the same as in Example 1, except that in step 2, the cyclic stirring time is 2.5 hours, and after adding the dispersant, stirring continues for 1.5 hours; in step 3, the temperature is raised to 110°C and stirred for 2.5 hours.

[0043] Example 3 This embodiment provides a special quenching oil for 05Cr15Ni5Cu4Nb precipitation hardening stainless steel, the components of which, by mass percentage, are: Base oil composition: 89% (of which 150N: 28%, 500N: 61%); Rapid cooling agent: Polyisobutylene 5.0%; Antioxidant: 3.5% (phenyl-α-naphthylamine 2.0% + dialkyl dithiophosphate carbamate 1.5%); Dispersant: Heptadecanylimidazoline succinate 2.5%.

[0044] The preparation process is basically the same as in Example 1, except that in step 1 the temperature is raised to 65°C, in step 2 the cyclic stirring time is 1.5 hours, and after adding the dispersant, stirring is continued for 0.5 hours; in step 3 the temperature is raised to 100°C and stirred for 1.5 hours.

[0045] Comparative Example 1 (without rapid cooling agent) This comparative example provides a quenching oil that differs from Example 1 in that it does not contain the rapid cooling agent polyisobutylene, while the remaining components and processes are the same as in Example 1. Specifically, it consists of a base oil composition of 95.5%, an antioxidant of 2.5%, and a dispersant of 2.0%.

[0046] Comparative Example 2 (without antioxidants) This comparative example provides a quenching oil that differs from Example 1 in that it does not contain an antioxidant, while the remaining components and processes are the same as in Example 1. Specifically, it contains 95% base oil, 3.0% rapid cooling agent, and 2.0% dispersant.

[0047] Comparative Example 3 (without dispersant) This comparative example provides a quenching oil that differs from Example 1 in that it does not contain a dispersant, while the remaining components and processes are the same as in Example 1. Specifically, it contains 95% base oil, 3.0% rapid cooling agent, and 2.0% antioxidant.

[0048] Comparative Example 4 (Single 150N Base Oil) This comparative example provides a quenching oil, which differs from Example 1 in that the base oil is replaced with a single 150N mineral oil, while the remaining components and processes are the same as in Example 1.

[0049] Comparative Example 5 (the rapid cooling agent was replaced with sodium petroleum sulfonate) This comparative example provides a quenching oil, which differs from Example 1 in that the rapid cooling agent is replaced with sodium petroleum sulfonate, while the remaining components and processes are the same as in Example 1.

[0050] Comparative Example 6 (Single Antioxidant Component) This comparative example provides a quenching oil that differs from Example 1 in that the antioxidant is replaced with a single component (phenyl-α-naphthylamine), and dialkyl dithiophosphate carbamate is not added. The remaining components and processes are the same as in Example 1. Specifically: base oil composition 92.5%, rapid cooling agent 3.0%, antioxidant (phenyl-α-naphthylamine) 2.5%, dispersant 2.0%.

[0051] Comparative Example 7 (Excessive Refrigerant) This comparative example provides a quenching oil that differs from Example 1 in that the amount of the rapid cooling agent polyisobutylene added is increased to 8.0%, exceeding the 1.5-5.0% range specified in this invention. The remaining components and processes are the same as in Example 1. That is: base oil composition 87.5%, rapid cooling agent 8.0%, antioxidant 2.5%, and dispersant 2.0%.

[0052] Comparative Example 8 (Single 500N Base Oil) This comparative example provides a quenching oil that differs from Example 1 in that the base oil combination is replaced with a single 500N mineral oil, while the remaining components and processes are the same as in Example 1. Specifically: base oil (500N) 92.5%, rapid cooling agent 3.0%, antioxidant 2.5%, dispersant 2.0%.

[0053] Comparative Example 9 (Inappropriate Dispersant Type - Low Molecular Weight Succinimide) This comparative example provides a quenching oil that differs from Example 1 in that the dispersant is replaced with low molecular weight succinimide (molecular weight approximately 800, not the type selected in this invention), while the remaining components and processes are the same as in Example 1. Specifically: base oil composition 92.5%, rapid cooling agent 3.0%, antioxidant 2.5%, dispersant (low molecular weight succinimide) 2.0%.

[0054] The performance of the quenching oils prepared in the embodiments and comparative examples of the present invention was tested, and the results are shown in Tables 1-2. Figures 2-3 As shown, Table 1 shows the test results of the physicochemical properties of the quenching oils prepared in Examples 1-3 and Comparative Examples 1-9; Table 2 shows the test results of the cooling performance of the quenching oils prepared in Examples 1-3 and Comparative Examples 1-9. Figure 2 This is a diagram showing the results of the rotating oxygen bomb test on the quenching oil prepared in Example 1. Figure 3 The graph shows the cooling performance of the quenching oil prepared in Example 1 (test conditions: oil temperature 120℃, no stirring). The red line represents the cooling rate of the quenching oil at different temperatures, and the green line represents the temperature change of the quenching oil over time. The test methods include: (1) The cooling performance test method shall be carried out in accordance with Section 7 of JB / T7951 Test Method for Nickel Alloy Probes for Determining the Cooling Performance of Industrial Quenching Oil.

[0055] (2) The kinematic viscosity test method shall be carried out in accordance with Section 5 of the standard test method for determination of kinematic viscosity and calculation of dynamic viscosity of petroleum products in GB T265-1988.

[0056] (3) The open flash point test method shall be carried out in accordance with Section 5 of the standard test method for determination of kinematic viscosity and calculation of dynamic viscosity of petroleum products in GB T265-1988.

[0057] (4) The moisture test method shall be carried out in accordance with Section 8 of GB 11133-1989 Determination of Water Content in Liquid Petroleum Products (Karl Fischer Method).

[0058] (5) The rotating oxygen bomb test method shall be carried out in accordance with Section 9 of SH / T 0193-2008 Test Method for Rotating Oxygen Bomb of Lubricating Oil for Determination of Oxidation Stability.

[0059] (6) The brightness test method shall be carried out in accordance with Appendix A of SH / T 0564 Test Method for Heat Treatment Oil.

[0060] Table 1. Physicochemical property test results of Examples 1-3 and Comparative Examples 1-9

[0061] Table 2. Cooling performance test results of Examples 1-3 and Comparative Examples 1-9

[0062] from Figure 2 It can be seen that the quenching oil in Example 1 has excellent resistance to oxidation and aging, with an oxidation incubation period (OIT) time of nearly 300 minutes and a long service life.

[0063] from Figure 3 It can be seen that the quenching oil in Example 1 has moderate cooling performance, which can ensure that the steel maintains a certain cooling rate in the high-temperature range, avoid the formation of non-martensitic structure, and affect the subsequent age hardening strength; it has a low cooling rate in the low-temperature range, only 4.14℃ / s at 300℃, which greatly reduces the martensitic transformation rate, reduces the stress caused by the structural transformation, and thus effectively reduces the tendency of workpiece deformation and cracking.

[0064] By comparing the performance test results of Example 1 and Comparative Example 1 with Tables 1 and 2, it can be found that the maximum cooling rate of Comparative Example 1 is only 52.18℃ / s, and the time from 800℃ to 400℃ is as long as 9.5s, while the maximum cooling rate of Example 1 is 80.39℃ / s, and the time is only 5.8s. This comparison clearly shows that polyisobutylene rapid cooling agent can significantly improve the cooling rate in the high-temperature zone, enabling the quenching oil to have sufficient cooling capacity when passing through the "nose" region (approximately 800-400℃) of the CCT curve of 05Cr15Ni5Cu4Nb steel, thus avoiding the formation of non-martensitic structures such as pearlite and bainite. For workpieces with larger cross-sectional dimensions (such as φ200mm and above), this performance difference determines whether the core can obtain 100% martensitic structure.

[0065] Comparing the performance test results of Example 1 and Comparative Example 4, it can be found that although the maximum cooling rate of Comparative Example 4 is as high as 98.55℃ / s, its cooling rate at 300℃ is also as high as 12.5℃ / s, and the time from 800℃ to 400℃ is only 4.2s. This cooling characteristic of "too fast at high temperatures and too fast at low temperatures" is extremely unfavorable for 05Cr15Ni5Cu4Nb steel. The Ms point of this steel is about 202℃, and the martensitic transformation has a volume expansion effect. In the temperature range near the Ms point, if the cooling rate is too fast (as shown in Comparative Example 4), a huge temperature difference will be generated between the core and the surface of the workpiece, resulting in severe superposition of structural stress and thermal stress, which can easily lead to quenching cracks, especially for precision parts with sharp corners, grooves, or abrupt changes in wall thickness.

[0066] Comparing the performance test results of Example 1 and Comparative Example 8, it can be found that the maximum cooling rate of Comparative Example 8 is only 68.52℃ / s, and the time from 800℃ to 400℃ is extended to 7.2s, while the kinematic viscosity at 40℃ is as high as 88.96mm² / s. The excessively high viscosity and excessively low high-temperature cooling rate make it difficult to ensure that the core of the large cross-section workpiece obtains a fully martensitic structure. More importantly, the 300℃ cooling rate of Comparative Example 8 is only 5.8℃ / s. Although this is beneficial for reducing martensitic transformation stress, the excessively low low-temperature cooling rate will cause the workpiece to remain below the Ms point for too long, which may trigger a self-tempering effect of martensite, consuming some of the supersaturated solid solubility, thereby affecting the precipitation strengthening effect of the copper-rich phase (ε-Cu) in the subsequent aging treatment.

[0067] The above comparative data demonstrates that the present invention selects a blend of 150N and 500N, and by adjusting their ratio, precisely controls the kinematic viscosity at 40°C to be between 60-70 mmHg. 2 / s, in synergy with 3.0% polyisobutylene, achieves a graded quenching effect of rapid cooling at high temperatures and slow cooling at low temperatures. This synergistic effect cannot be achieved by a single base oil: 150N provides low viscosity to ensure initial fluidity, 500N provides high viscosity to regulate the low-temperature cooling rate, and polyisobutylene accelerates vapor film rupture to improve the high-temperature cooling rate; all three are indispensable.

[0068] Comparing the performance test results of Example 1 and Comparative Example 2, it can be found that the rotating oxygen bomb time of Comparative Example 2 is only 48 minutes, while that of Example 1 is 298 minutes. This indicates that, without antioxidants, quenching oil oxidizes rapidly at high temperatures, leading to increased viscosity, higher acid value, and the formation of large amounts of sludge and carbon deposits. This not only affects the stability of cooling performance but also contaminates the workpiece surface and shortens the service life of the oil.

[0069] Comparing the performance test results of Example 1 and Comparative Example 6, it can be found that the rotating bomb time of Comparative Example 6 is 112 min, which is better than Comparative Example 2 without antioxidant, but still much lower than 298 min of Example 1. This indicates that phenyl-α-naphthylamine, as a chain-terminating antioxidant, can capture free radicals, but cannot effectively decompose peroxides generated during oxidation. In contrast, the dialkyl dithiophosphate carbamate compounded in Example 1, as a peroxide decomposer, produces a significant synergistic effect with phenyl-α-naphthylamine: the chain terminator and the peroxide decomposer act on different stages of the oxidation reaction, forming a complete antioxidant barrier, thus improving oxidation stability by nearly 3 times. The comparative data above demonstrates that the compound antioxidant system (phenyl-α-naphthylamine + dialkyl dithiophosphate carbamate or dilaurate thiodipropionate) used in this invention produces a synergistic effect greater than the sum of its parts (1+1>2). For large-scale heat treatment production of 05Cr15Ni5Cu4Nb stainless steel, the quenching oil needs to maintain stable performance during long-term high-temperature service. Rapid oxidation of the oil can lead to a shift in cooling characteristics, thereby affecting the uniformity and reproducibility of the martensitic transformation. Therefore, the compound antioxidant system of this invention plays an irreplaceable role in ensuring consistent production quality.

[0070] Comparing the performance test results of Example 1 and Comparative Example 3, it can be found that the brightness of Comparative Example 3 is only level 3, while that of Example 1 is level 1. This indicates that without a dispersant, solid contaminants (carbon deposits, sludge, metal oxides, etc.) generated during the quenching process will accumulate and settle on the surface of the workpiece, forming stains that seriously affect the appearance and subsequent processing.

[0071] Comparing the performance test results of Example 1 and Comparative Example 3, it can be found that Comparative Example 9, using low molecular weight succinimide (molecular weight approximately 800) as a dispersant, only achieved a gloss level of 4, which is worse than Comparative Example 3 without a dispersant. This is because although low molecular weight succinimide has a certain dispersing ability, its low molecular weight makes it unable to form sufficient steric hindrance effect, making it difficult to effectively encapsulate and stably suspend solid contaminants. Furthermore, succinimide has a different chemical structure from the polymeric dispersants (such as calcium alkyl salicylate) selected in this invention, and its polar groups have poor compatibility with the base oil, making it prone to desorption at high temperatures, leading to dispersion failure. These contaminants may even aggregate more easily due to the improper introduction of the dispersant.

[0072] The comparative data above demonstrates that the polymeric dispersants selected in this invention (alkyl salicylate calcium, high-base-value synthetic calcium sulfonate, and heptadecanylimidazolinyl succinate, typically with molecular weights above 1000-2000) provide steric hindrance through their long-chain alkyl groups and charge repulsion through their polar groups, achieving a synergistic effect that ensures the long-term stable dispersion of solid contaminants. Simultaneously, the compatibility between the dispersant and the base oil is also crucial. In 150N / 500N blended base oils, the polymeric dispersant can form a stable micelle structure, achieving optimal dispersion. This synergistic effect between the base oil and the dispersant ensures that the workpiece surface finish reaches Grade 1, meeting the requirements of precision parts.

[0073] Comparing the performance test results of Example 1 and Comparative Example 7, it can be found that the maximum cooling rate of Comparative Example 7 (polyisobutylene addition of 8.0%) reached 92.45℃ / s, and the time from 800℃ to 400℃ was shortened to 4.3s. However, the cooling rate at 300℃ rose sharply to 11.8℃ / s. This cooling characteristic of excessively rapid high and low temperatures is extremely unfavorable for 05Cr15Ni5Cu4Nb steel. In the temperature range near the Ms point, excessively high low-temperature cooling rates can lead to excessive martensitic transformation stress, which can easily cause quenching cracks in precision parts. This invention controls the polyisobutylene content within the range of 1.5-5.0%, which is based on in-depth research on the martensitic transformation characteristics of this steel. This dosage range, in synergy with the base oil compounding system, achieves a graded quenching effect of rapid high-temperature cooling and slow low-temperature cooling. It is necessary to ensure a sufficient high-temperature cooling rate to avoid the nose region of the CCT curve, while controlling the low-temperature cooling rate within a reasonable range (7-8℃ / s at 300℃). Comparative Example 7 demonstrates that more rapid cooling agent is not necessarily better; there is an optimal threshold for this type of steel, and exceeding this threshold can introduce new problems.

[0074] Comparing the performance test results of Example 1 and Comparative Example 5, it can be found that in Comparative Example 5, using sodium petroleum sulfonate instead of polyisobutylene as the rapid cooling agent, the maximum cooling rate decreased to 62.37℃ / s, the time from 800℃ to 400℃ was extended to 7.8s, and the characteristic temperature was also significantly reduced. This indicates that although sodium petroleum sulfonate has certain surface activity, its ability to accelerate vapor film rupture is far inferior to that of polyisobutylene, and it cannot meet the high-temperature cooling rate requirements of 05Cr15Ni5Cu4Nb steel. The advantage of choosing polyisobutylene as the rapid cooling agent in this invention lies in its unique molecular structure: the polymer chain has strong polarity, which can quickly penetrate the vapor film and firmly adsorb onto the workpiece surface. This characteristic, combined with the 150N / 500N compound base oil, can significantly improve the high-temperature cooling rate while maintaining oil stability. Other types of rapid cooling agents cannot achieve the same effect, demonstrating the irreplaceable nature of polyisobutylene in this invention.

[0075] The above data generally demonstrates that each technical feature of this invention was not arbitrarily selected, but rather derived through experimental optimization based on a profound understanding of the physical and metallurgical properties of 05Cr15Ni5Cu4Nb precipitation-hardening stainless steel. There is a precise synergistic relationship between the components; a change in any variable will cause the overall performance to deviate from the optimal quenching requirements for this steel grade.

[0076] 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. A special quenching oil for 05Cr15Ni5Cu4Nb precipitation hardening stainless steel, characterized in that, By weight percentage, it consists of the following components: 88-95% base oil blend, 1.5-5.0% quick-cooling agent, 2.0-3.5% antioxidant, and 1.0-4.0% dispersant; the base oil blend is a mixture of refined hydrogenated mineral oil 150N and refined hydrogenated mineral oil 500N; the quick-cooling agent is polyisobutylene; the antioxidant is a combination of phenyl-α-naphthylamine and dialkyl dithiophosphate carbamate, or a combination of phenyl-α-naphthylamine and dilaurate thiodipropionate.

2. The quenching oil for 05Cr15Ni5Cu4Nb precipitation hardening stainless steel according to claim 1, characterized in that, The dispersant is one of heptadecanylimidazoline succinate, alkyl salicylate calcium, or high-base-value synthetic calcium sulfonate.

3. The quenching oil for 05Cr15Ni5Cu4Nb precipitation hardening stainless steel according to claim 1, characterized in that, The refined hydrogenated mineral oil 150N has a kinematic viscosity of 32.91 mm at 40°C. 2 The viscosity index is 144; the kinematic viscosity of the refined hydrogenated mineral oil 500N at 40°C is 88.96 mm² / s. 2 / s, viscosity index is 100.

4. The quenching oil for 05Cr15Ni5Cu4Nb precipitation hardening stainless steel according to claim 1, characterized in that, The kinematic viscosity of the quenching oil at 40℃ is 60-70 mm. 2 The kinematic viscosity at 100℃ is 8.2-8.8 mm / s. 2 / s.

5. The quenching oil for 05Cr15Ni5Cu4Nb precipitation hardening stainless steel according to claim 1, characterized in that, The moisture content of the quenching oil is ≤300ppm.

6. A method for preparing a special quenching oil for 05Cr15Ni5Cu4Nb precipitation hardening stainless steel according to any one of claims 1-5, characterized in that, Includes the following steps: Add the base oil mixture to the reactor, start stirring and heating, and raise the temperature to 60±5℃; While stirring, add the quick-cooling agent and antioxidant in sequence, and circulate and stir for 1.5-2.5 hours. Then add the dispersant and continue stirring for 0.5-1.5 hours. Heat the reactor to 100-110℃ and stir and circulate to remove water until the moisture content is ≤300ppm.

7. The application of a special quenching oil for 05Cr15Ni5Cu4Nb precipitation-hardening stainless steel according to any one of claims 1-5 in the heat treatment of 05Cr15Ni5Cu4Nb precipitation-hardening stainless steel, characterized in that, The application involves placing a 05Cr15Ni5Cu4Nb precipitation-hardening stainless steel workpiece, after solution treatment, into the quenching oil at a temperature of 80-180℃ for graded quenching.

8. The application according to claim 7, characterized in that, The staged quenching process keeps the workpiece at a temperature near the Ms point to reduce the internal and external temperature difference during the martensitic transformation process, thereby obtaining a uniform lath martensitic structure with low internal stress.

9. The application according to claim 7, characterized in that, The quenching oil is used to ensure that the core of 05Cr15Ni5Cu4Nb precipitation hardening stainless steel workpieces with a cross-sectional dimension ≥ φ200mm obtains 100% martensitic structure.

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