Electrolyte suitable for electrolytic grinding of 9Cr18Mo bearing steel and scheme determination method thereof

Abstract

The invention discloses an electrolyte suitable for electrolytic grinding of 9Cr18Mo bearing steel. The electrolyte comprises the following specific components in percentage by mass: 2 to 18 weight percent of sodium nitrate, 2 to 18 weight percent of sodium sulfate and 64 to 96 weight percent of deionized water. The electrolyte used in the invention is neutral, so that not only is the damage of acid-base corrosion to machine tool equipment avoided, but also the used chemical reagent is easy to purchase, low in price and simple and convenient to prepare; and the ion loss in the electrochemical machining process is very small, the electrolyte can be recycled, and the production cost is effectively reduced. The electrolyte provided by the invention can generate a uniform and compact passivation film on the surface of the 9Cr18Mo bearing steel. Compared with a base material, the passivation film has lower hardness and elasticity modulus, so that the passivation film can be removed by mechanical grinding more easily. And meanwhile, the passive film can remarkably reduce the uneven corrosion phenomenon on the surface of the workpiece, and the surface quality of the machined workpiece is greatly improved.

Description

Technical Field

[0001] The present invention relates to an electrolyte for electrolytic grinding of 9Cr18Mo bearing steel and a method for determining the scheme, belonging to the technical field of electrolytic machining of metal materials. Background Art

[0002] 9Cr18Mo is a high-carbon chromium martensitic stainless steel with high hardness, high wear resistance and good corrosion resistance, and is widely used in the fields of tools, medical surgical instruments, industrial cutting tools, precision parts and bearing manufacturing. During the working process of the bearing, its raceway surface is often in a complex working environment of high speed, high temperature and high load. Therefore, the processing quality of the raceway surface directly determines the overall performance and service life of the bearing. At present, the processing methods of the bearing raceway surface usually adopt traditional grinding wheel forming grinding and superfine lapping (such as oilstone grinding) processes. However, due to the high hardness and outstanding wear resistance of 9Cr18Mo bearing steel itself, traditional grinding processing methods often lead to low processing efficiency, and at the same time, problems such as grinding burns, surface cracks and surface hardening are likely to occur, seriously restricting the performance improvement of bearing products.

[0003] To solve the above problems, the electrolytic grinding technology came into being. Electrolytic grinding is a composite processing method that organically combines electrochemical machining and mechanical grinding, and shows significant advantages especially in the precision manufacturing field of difficult-to-grind materials. This technology generates a soft passivation film on the surface of the workpiece through electrochemical action, and then effectively removes this passivation film by mechanical grinding. This electrochemistry-mechanical synergistic effect not only significantly reduces the wear of the grinding wheel, but also improves the processing efficiency and the processing quality of the workpiece surface. For example, Sikorsky Aircraft Company in the United States successfully used electrolytic grinding technology to achieve the precision machining of complex gears, greatly improving the machining accuracy and economy; the electrolytic micro-finishing technology developed by Manfred G. Becker Company in Germany achieved high-precision and non-deformation fine machining; the electrolytic point grinding system developed by Tridex Technology Company was successfully applied to the manufacturing of precision needle tips of medical devices. These successful industrial cases fully reflect the significant advantages and broad application prospects of electrolytic grinding technology in overcoming high-hardness and difficult-to-machine materials.

[0004] However, the process effect of electrolytic grinding is affected by many factors, specifically including cathode structure design, electroprocessing parameters (voltage, current, interelectrode gap), workpiece material properties (such as conductivity, chemical stability and mechanical properties), mechanical grinding parameters (grinding wheel speed, grinding pressure), processing environment stability (machine tool vibration, temperature fluctuation) and the composition and ratio of the electrolyte. Among them, the electrolyte is one of the key links in the success or failure of the electrolytic grinding process. By optimizing the composition and ratio of the electrolyte, the processing accuracy and surface quality can be effectively improved, the production efficiency can be increased, and the processing cost can be reduced at the same time.

[0005] However, there is currently a lack of clear theoretical guidance for the preparation of electrolytic grinding electrolytes specifically for certain materials (such as 9Cr18Mo). In most cases, screening and optimization still rely on electrochemical experiments. This method has obvious limitations: First, most electrochemical polarization experiments are carried out in a static electrolyte environment, which is quite different from the dynamic flow condition of the electrolyte during the actual electrolytic grinding process, resulting in the experimental results being difficult to accurately reflect the actual processing situation. Second, some electrolytes (such as Na2SO4) are prone to crystallization due to temperature influence, further reducing the accuracy of the measurement data. In addition, some electrochemical experimental devices do not set strict constant temperature control conditions, causing fluctuations in the electrolyte concentration gradient and making the experimental data unable to accurately reflect the optimal electrolyte concentration range in real processing. Moreover, some existing studies directly use conventional electrolytes for processing experiments, ignoring the importance of optimizing the electrolyte for specific materials, so it is difficult to ensure the best processing effect.

[0006] For the electrolytic grinding of 9Cr18Mo bearing steel, special consideration needs to be given to the formation and stability of the surface passivation film brought about by the high strength and excellent corrosion resistance of the material itself. Traditional acidic or alkaline electrolytes are difficult to provide a stable corrosion and passivation balance environment, easily causing damage to the structure of the workpiece surface passivation film, thus reducing the processing accuracy and surface quality. In addition, acid-base electrolytes are corrosive to equipment, while neutral electrolytes can alleviate this problem to a certain extent.

[0007] Therefore, it is of great practical significance to develop a high-performance neutral electrolyte specifically for 9Cr18Mo bearing steel. Summary of the Invention

[0008] The purpose of the present invention is to provide an electrolyte suitable for electrolytic grinding of 9Cr18Mo bearing steel and a method for determining its formulation. The present invention can effectively solve the above problems and significantly improve the processing efficiency, surface quality of 9Cr18Mo bearing steel, and extend the service life of the grinding wheel. This achievement will not only further promote the application of 9Cr18Mo steel in the field of precision bearing manufacturing, but also provide important theoretical basis and practical guidance for the electrolytic grinding process of other difficult-to-grind materials, having wide popularization and application value.

[0009] The technical solution of the present invention: An electrolyte suitable for electrolytic grinding of 9Cr18Mo bearing steel, the specific composition and mass percentage content thereof are: sodium nitrate 2wt.% - 18wt.%, sodium sulfate 2wt.% - 18wt.%, deionized water 64wt.% - 96wt.%.

[0010] In the aforementioned electrolyte for electrolytic grinding of 9Cr18Mo bearing steel, the specific composition and mass percentage content are as follows: sodium nitrate 14.356 wt.%, sodium sulfate 7.841 wt.%, and deionized water 77.803 wt.%.

[0011] A method for determining the electrolyte solution for electrolytic grinding of 9Cr18Mo bearing steel

[0012] Step 1: First, determine the composite electrolyte components as sodium nitrate and sodium sulfate through electrochemical experiments;

[0013] Step 2: Then, systematically plan the electrolytic grinding experiments based on the uniform design method, and comprehensively investigate the influence of changes in the concentrations of sodium nitrate and sodium sulfate on the machining performance of 9Cr18Mo bearing steel. By analyzing the experimental data, a stepwise linear multiple regression model between the concentrations of the two electrolytes and the key process response indicators - material removal rate and surface roughness is constructed, thereby revealing the primary and secondary influence relationships of each factor on the machining performance;

[0014] Step 3: Use the WOA-GA intelligent optimization model constructed by integrating the whale optimization algorithm and the genetic algorithm to optimize the parameters of the above regression model, and finally obtain a set of electrolyte component ratios that can achieve the optimal process performance on the premise of considering both machining efficiency and surface quality.

[0015] In the aforementioned method for determining the electrolyte solution for electrolytic grinding of 9Cr18Mo bearing steel, the specific content of Step 1 is as follows: Select neutral electrolytes NaH2PO4·2H2O, Na2HPO4·12H2O, Na2SO4, NaNO3, NaClO3, Na2CO3, and NaCl. Eliminate the electrolytes with insignificant effects through linear sweep voltammetry experiments on the above electrolytes with a concentration of 10% each, and then combine the remaining electrolytes in pairs. Conduct linear sweep voltammetry experiments and potentiostatic experiments using the composite electrolyte to determine the best electrolyte combination.

[0016] In the aforementioned method for determining the electrolyte solution for electrolytic grinding of 9Cr18Mo bearing steel, the specific content of Step 2 and Step 3 is as follows: First, carry out electrolytic grinding experiments on 9Cr18Mo bearing steel according to the uniform design method, and collect the material removal rate y1 and surface roughness y2 as response indicators. Subsequently, use SPSS software to construct a multiple regression model between the concentrations of sodium nitrate and sodium sulfate and the material removal rate y1 and surface roughness y2, and use the WOA-GA intelligent optimization model constructed by integrating the whale optimization algorithm and the genetic algorithm to optimize the parameters of the established multiple regression model. Finally, obtain a set of electrolyte component ratios that can achieve the optimal process performance on the premise of considering both machining efficiency and surface quality.

[0017] In the above method for determining the electrolyte solution for electrolytic grinding of 9Cr18Mo bearing steel, the multiple regression model is as follows:

[0018]

[0019] In the formula, x1 represents the concentration of sodium nitrate, and x2 represents the concentration of sodium sulfate.

[0020] Advantages of the present invention: Compared with the prior art, the present invention has the following obvious advantages:

[0021] (1) Only basic electrochemical experiments (open circuit potential experiment, linear sweep voltammetry experiment, potentiostatic experiment) need to be carried out in this study to obtain the basic data for the selection of electrolyte solutions suitable for 9Cr18Mo bearing steel and other metal materials. On this basis, a mathematical regression model is constructed through the experimental data of electrolytic grinding, and an advanced intelligent hybrid algorithm is used for optimization, so as to realize the efficient and accurate optimization of the composition ratio of the electrolyte solution, and the results are more scientific and persuasive.

[0022] (2) The electrolyte solution used in the present invention is neutral, which not only avoids the damage to machine tools caused by acid-base corrosion, but also the chemical reagents used are easy to purchase, economical in price and simple to prepare; the ion loss during the electrochemical processing is negligible, and the electrolyte solution can be recycled and reused, effectively reducing the production cost.

[0023] (3) The electrolyte solution of the present invention can form a uniform and dense passivation film on the surface of 9Cr18Mo bearing steel. Compared with the substrate material, this passivation film has lower hardness and elastic modulus, so it is easier to be removed by mechanical grinding. At the same time, this passivation film can significantly reduce the uneven corrosion phenomenon on the surface of the workpiece, greatly improving the surface quality of the workpiece after processing. Description of the Drawings

[0024] Figure 1 is the linear sweep voltammetry curve of a single electrolyte;

[0025] Figure 2 is the electrochemical experiment effect diagram of the composite electrolyte solution. In the figure, a - linear sweep voltammetry experiment, b - potentiostatic experiment (1 - NaNO3 + Na2SO4; 2 - Na2SO4 + NaClO3; 3 - Na2SO4 + Na2CO3; 4 - NaNO3 + NaClO3; 5 - NaNO3 + Na2CO3; 6 - NaClO3 + Na2CO3);

[0026] Figure 3 is the open circuit potential of 9Cr18Mo bearing steel in sodium nitrate and sodium sulfate solutions respectively;

[0027] Figure 4Anodic polarization curve of 9Cr18Mo bearing steel in the electrolyte with optimized composition (14.356 wt.% sodium nitrate, 7.841 wt.% sodium sulfate, and 77.803 wt.% deionized water);

[0028] Figure 5 Microscopic morphology of the passive film after electrolytic corrosion of 9Cr18Mo bearing steel in the electrolyte with optimized composition;

[0029] Figure 6 Surface microscopic morphology of 9Cr18Mo bearing steel after electrolytic corrosion in the electrolyte with optimized composition;

[0030] Figure 7 Surface microscopic morphology of 9Cr18Mo bearing steel after electrochemical machining and mechanical grinding. Detailed implementation mode

[0031] The present invention will be further described below in conjunction with the drawings and embodiments, but it shall not be used as a basis for limiting the present invention.

[0032] Embodiment 1 of the present invention: An electrolyte suitable for electrolytic grinding of 9Cr18Mo bearing steel, characterized in that its specific composition and mass percentage content are: sodium nitrate 10 wt.%, sodium sulfate 10 wt.%, deionized water 80 wt.%.

[0033] Embodiment 2 of the present invention: An electrolyte suitable for electrolytic grinding of 9Cr18Mo bearing steel, characterized in that its specific composition and mass percentage content are: sodium nitrate 2 wt.%, sodium sulfate 8 wt.%, deionized water 90 wt.%.

[0034] Embodiment 3 of the present invention: An electrolyte suitable for electrolytic grinding of 9Cr18Mo bearing steel, characterized in that its specific composition and mass percentage content are: sodium nitrate 14 wt.%, sodium sulfate 16 wt.%, deionized water 70 wt.%.

[0035] Embodiment 4 of the present invention: An electrolyte suitable for electrolytic grinding of 9Cr18Mo bearing steel, characterized in that its specific composition and mass percentage content are: sodium nitrate 4 wt.%, sodium sulfate 14 wt.%, deionized water 82 wt.%.

[0036] Embodiment 5 of the present invention: An electrolyte suitable for electrolytic grinding of 9Cr18Mo bearing steel, characterized in that its specific composition and mass percentage content are: sodium nitrate 6 wt.%, sodium sulfate 4 wt.%, deionized water 90 wt.%.

[0037] Example 6 of the present invention: An electrolyte for electrolytic grinding of 9Cr18Mo bearing steel, characterized in that its specific composition and mass percentage content are: sodium nitrate 18 wt.%, sodium sulfate 12 wt.%, deionized water 70 wt.%.

[0038] Example 7 of the present invention: An electrolyte for electrolytic grinding of 9Cr18Mo bearing steel, characterized in that its specific composition and mass percentage content are: sodium nitrate 16 wt.%, sodium sulfate 6 wt.%, deionized water 78 wt.%.

[0039] Example 8 of the present invention: An electrolyte for electrolytic grinding of 9Cr18Mo bearing steel, characterized in that its specific composition and mass percentage content are: sodium nitrate 12 wt.%, sodium sulfate 2 wt.%, deionized water 86 wt.%.

[0040] Example 9 of the present invention: An electrolyte for electrolytic grinding of 9Cr18Mo bearing steel, characterized in that its specific composition and mass percentage content are: sodium nitrate 8 wt.%, sodium sulfate 18 wt.%, deionized water 74 wt.%.

[0041] Example 10 of the present invention: An electrolyte for electrolytic grinding of 9Cr18Mo bearing steel, the specific composition and mass percentage content are: sodium nitrate 14.356 wt.%, sodium sulfate 7.841 wt.%, deionized water 77.803 wt.%.

[0042] The method for determining the electrolyte solution for electrolytic grinding of 9Cr18Mo bearing steel in the above embodiments:

[0043] Step 1: First, determine the composite electrolyte composition as sodium nitrate and sodium sulfate through electrochemical experiments;

[0044] Step 2: Then, based on the uniform design method, systematically plan the electrolytic grinding experiment to reduce the number of experiments, improve the experimental efficiency, and comprehensively investigate the influence of the concentration changes of sodium nitrate and sodium sulfate on the machining performance of 9Cr18Mo bearing steel. By analyzing the experimental data, a stepwise linear multiple regression model between the concentrations of the two electrolytes and the key process response indicators - material removal rate (MRR) and surface roughness (Ra) was constructed, thereby revealing the primary and secondary influence relationships of each factor on the machining performance;

[0045] Step 3: To achieve the multi-objective optimization design of the electrolyte components, a WOA-GA intelligent optimization model constructed by integrating the whale optimization algorithm and the genetic algorithm is used to optimize the parameters of the above regression model. Finally, a set of electrolyte component ratios that can achieve the optimal process performance while taking into account the processing efficiency and surface quality are obtained. The optimized preferred formula is: sodium nitrate 14.356 wt.%, sodium sulfate 7.841 wt.%, deionized water 77.803 wt.%.

[0046] The specific content of Step 1 is as follows: Since acidic and alkaline electrolytes have strong corrosiveness to processing equipment (such as grinders), neutral electrolytes have become the first choice for electrolytic grinding of metal materials. Commonly used neutral electrolytes include Na2SO4, NaNO3, NaClO3, Na2CO3, and NaCl. Through linear sweep voltammetry experiments (as Figure 1 shown) on the above electrolytes with a concentration of 10% each, it is found that NaCl is not suitable for 9Cr18Mo bearing steel, and the black passivation film formed by it directly falls off. Since a single-component electrolyte is difficult to effectively form a passivation film, existing research has shown that composite electrolytes can efficiently form and stably maintain the passivation film on the surface due to the synergistic effect between components. On this basis, the selected electrolyte components are combined in pairs, and linear sweep voltammetry experiments and potentiostatic experiments are used to finally determine the composite electrolyte combination with the best performance. Further, the remaining 4 electrolytes are combined in pairs, and linear sweep voltammetry experiments (as Figure 1 shown) and potentiostatic experiments (as Figure 2 shown) are carried out using the composite electrolyte. The results show that the passivation films formed by Group a1 (NaNO3 + Na2SO4) and Group b1 (NaNO3 + Na2SO4) are the most dense and the darkest in color, with significant effects. Therefore, NaNO3 + Na2SO4 is finally determined as the best electrolyte combination for electrolytic grinding of 9Cr18Mo bearing steel.

[0047] According to relevant literature reports, the commonly used electrolyte concentrations in electrolytic grinding mainly focus on 10%, 15%, and 20%. Electrolytes with lower concentrations are not conducive to achieving a higher material removal rate, while higher concentrations may lead to an increase in the surface roughness of the workpiece. In addition, too high an electrolyte concentration may also cause the solution to become saturated, resulting in the phenomenon that the electrolyte cannot be completely dissolved. Based on this, the mixing ratio range of sodium nitrate and sodium sulfate is selected as 2 wt.% - 18 wt.%.

[0048] Step 2: In the linear sweep voltammetry experiment and potentiostatic electrochemical test of the composite electrolyte, although 10 wt.% NaNO3 and 10 wt.% Na2SO4 showed better effects than other electrolytes and could form a visible passivation film, it was still not sufficient to determine them as the optimal concentration combination. To further optimize the electrolyte formula, the uniform design method was introduced on this basis to carry out electrolytic grinding experiments, and combined with the genetic algorithm, the optimal electrolyte concentration ratio suitable for the electrolytic grinding of 9Cr18Mo bearing steel was systematically explored. Specifically, first, the electrolytic grinding experiment of 9Cr18Mo bearing steel was carried out according to the uniform design method (as shown in Table 1), and the material removal rate y1 (MRR) and surface roughness y2 (Ra) were collected as response indicators. The experimental data are shown in Table 1. Subsequently, the SPSS software was used to construct a multiple regression model between the concentration and the material removal rate and surface roughness (as shown in Equation (1)), and the WOA-GA intelligent optimization model constructed by the fusion of the whale optimization algorithm and the genetic algorithm was used to optimize the parameters of the established regression model. Finally, a set of electrolyte component ratios that can achieve the optimal process performance was obtained under the premise of considering both processing efficiency and surface quality.

[0049] Table 1 Experimental design and results of the electrolyte composition of 9Cr18Mo bearing steel

[0050]

[0051]

[0052] To verify the effect of the electrolyte component ratio with the optimal process performance determined by the above method, the following experiments were carried out:

[0053] Specific implementation steps of the experiment:

[0054] (1) Cut the 9Cr18Mo bearing steel into cube specimens with dimensions of 5 mm × 5 mm × 5 mm. Successively use sandpapers with different mesh numbers (400#, 800#, 1200#, 1500#, 2000#) to gradually polish the surface of the specimens to be bright with a metallographic polishing machine. After thoroughly cleaning with deionized water, spray 0.5 μm diamond spray polishing agent on the surface of the specimens and polish with a polishing cloth. Then use petroleum ether and absolute ethanol to degrease and ultrasonically clean the specimens. Finally, vacuum package them for standby.

[0055] (2) A three - electrode electrochemical test system was used to measure the open - circuit potential of the above - mentioned specimens in electrolytes with different components and contents. Specifically, the specimen processed in step one was used as the anode of the electrochemical experiment, a platinum sheet with a specification of 15 mm×15 mm was used as the auxiliary electrode, and a saturated KCl Ag / AgCl electrode was used as the reference electrode. The temperature of the electrolyte was strictly controlled within the range of 25±1℃ using an intelligent thermostat. The scanning time for each point in the experiment was set to 1 s, and the total measurement time was 7200 s. The experimental results of sodium nitrate and sodium sulfate are as Figure 3 shown. In the initial stage of the experiment, the open - circuit potential of the steel in both electrolytes showed a rapid decreasing trend, indicating that relatively intense electrochemical reactions occurred on the surface of the material in the initial stage (such as the dissolution of the passivation film on the material surface or the rapid activation of the metal matrix), suggesting that the steel has a high initial reaction sensitivity to both electrolyte environments. As time passed, the open - circuit potential tended to be stable, indicating that the surface of the material gradually reached a dynamic equilibrium state. In Na2SO4, the open - circuit potential stabilized at a relatively low level (about - 445 mV), indicating that the formation or stability of the passivation film on the steel surface is poor, and the material remains in a highly active state, which is not conducive to the formation of a dense protective film. In contrast, in the NaNO3 solution, the open - circuit potential stabilized at a higher level (about - 262 mV), indicating that the 9Cr18Mo bearing steel is more likely to form a relatively stable and dense oxide passivation film in this electrolyte environment, making the potential in a relatively positive range. This relatively high stable potential usually means that the surface has good electrochemical stability, which is conducive to achieving the desired surface passivation effect during the electrolytic grinding process. Therefore, from the perspective of the electrolytic grinding process, the NaNO3 electrolyte is more favorable for the formation of the surface passivation film of 9Cr18Mo bearing steel, helping to form a dense and stable passivation film, effectively improving the quality and corrosion resistance of the grinding surface; while the Na2SO4 environment may result in a poor surface passivation state, increasing the electrochemical corrosion sensitivity of the grinding surface.

[0056] (3) Using the electrolytes configured as above, anodic open - circuit potential, anodic polarization, and potentiostatic electrochemical experiments were carried out under a three - electrode system. Through the three - electrode system, linear sweep voltammetry was used to measure the polarization curves of the specimens in different electrolytes. The voltage sweep range was set from - 0.5 V to 3 V, and the sweep rate was 0.01 V / s. The measurement results of the preferred - component electrolyte are shown in Figure 4 . This linear sweep voltammogram clearly shows that in the environment of the Na2SO4 and NaNO3 composite electrolyte, the 9Cr18Mo bearing steel forms a highly stable passivation film in the range of - 0.5 V to 1.5 V (vs Ag / AgCl), the current density remains extremely low (about 01 mA / cm 2 ), the passivation zone is about 2.0 V wide, and the electrochemical performance is stable and reliable; the breakdown potential of the passivation film clearly occurs at about 2.0 V, and after breakdown, the current rapidly increases to several hundred mA / cm2 , with a very clear critical point. Therefore, this composite electrolyte can provide a clear and broad (recommended range of about 1.0V - 1.8V) processing potential window, meeting the precise control requirements of the electrolytic grinding process and the demand for high-quality surface machining. In summary, this electrolyte composite combination shows significantly better electrochemical performance than single electrolytes, has great practical application prospects, and is worthy of further process optimization and in-depth research.

[0057] (4) Through electrochemical corrosion experiments, observe the corrosion behavior of the specimens under different electrolyte components. Analyze the data of the open-circuit potential and polarization characteristics obtained from the electrochemical corrosion experiments, and analyze the microscopic morphology of the surface of the 9Cr18Mo bearing steel material specimens after electrolytic corrosion through microscopic observation. Set the power supply parameters as DC high-frequency 10V, power supply duty cycle 50%, frequency 10kHz, inter-electrode gap 0.8mm, and corrosion time 1min. The experiments show that in the electrolyte with optimized components, a relatively thick and uniform passivation film can be formed on the surface of 9Cr18Mo bearing steel, and the passivation effect is significant ( Figure 5 and Figure 6 ).

[0058] (5) After electrolytic grinding using the optimized electrolyte, a high surface accuracy and good microstructure are obtained on the 9Cr18Mo bearing surface, as Figure 7 shown.

Claims

1. An electrolyte suitable for electrolytic grinding of 9Cr18Mo bearing steel, characterized in that: Its specific composition and mass percentage content are as follows: sodium nitrate 2 wt.% - 18 wt.%, sodium sulfate 2 wt.% - 18 wt.%, deionized water 64 wt.% - 96 wt.%.

2. The electrolyte for electrolytic grinding of 9Cr18Mo bearing steel according to claim 1, characterized in that: The specific composition and mass percentage content are as follows: sodium nitrate 14.356 wt.%, sodium sulfate 7.841 wt.%, deionized water 77.803 wt.%.

3. A method for determining the electrolyte solution for electrolytic grinding of 9Cr18Mo bearing steel as described in any one of claims 1 - 2, characterized in that: Step 1: First, determine the composite electrolyte solution components as sodium nitrate and sodium sulfate through electrochemical experiments; Step 2: Then, based on the uniform design method, systematically plan the electrolytic grinding experiments, and comprehensively investigate the influence of the concentration changes of sodium nitrate and sodium sulfate on the machining performance of 9Cr18Mo bearing steel. By analyzing the experimental data, a stepwise linear multiple regression model between the concentrations of the two electrolytes and the key process response indicators - material removal rate and surface roughness is constructed, thereby revealing the primary and secondary influence relationships of each factor on the machining performance; Step 3: Use the WOA - GA intelligent optimization model constructed by integrating the whale optimization algorithm and the genetic algorithm to optimize the parameters of the above regression model, and finally obtain a set of electrolyte component ratios that can achieve the optimal process performance while taking into account machining efficiency and surface quality.

4. The method for determining the electrolyte solution for electrolytic grinding of 9Cr18Mo bearing steel according to claim 3, characterized in that: The specific content of Step 1 is as follows: Select neutral electrolyte solutions Na2SO4, NaNO3, NaClO3, Na2CO3, and NaCl. Eliminate the electrolyte solutions with insignificant effects through linear sweep voltammetry experiments on the above electrolyte solutions with a concentration of 10% each. Then, combine the remaining electrolyte solutions in pairs, and use the composite electrolyte solution for linear sweep voltammetry experiments and potentiostatic experiments to determine the best electrolyte solution combination.

5. The method for determining the electrolyte solution scheme for electrolytic grinding of 9Cr18Mo bearing steel according to claim 3, characterized in that: The specific content of Step 2 and Step 3 is as follows: First, carry out electrolytic grinding experiments on 9Cr18Mo bearing steel according to the uniform design method, and collect the material removal rate y1 and surface roughness y2 as response indicators. Subsequently, use SPSS software to construct a multiple regression model between the concentrations of sodium nitrate and sodium sulfate and the material removal rate y1 and surface roughness y2, and use the WOA - GA intelligent optimization model constructed by integrating the whale optimization algorithm and the genetic algorithm to optimize the parameters of the established multiple regression model, and finally obtain a set of electrolyte component ratios that can achieve the optimal process performance while taking into account machining efficiency and surface quality.

6. The method for determining the electrolyte solution for electrolytic grinding of 9Cr18Mo bearing steel according to claim 5, wherein: The multiple regression model is: In the formula, x1 represents the concentration of sodium nitrate, and x2 represents the concentration of sodium sulfate.

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