Discharge-electrochemical concurrent roughing method for metal matrix composites

Abstract

The application belongs to the technical field of composite machining, and discloses a rough machining method of metal matrix composite material by discharging and electrochemistry, which comprises the following steps: step one: obtaining a workpiece and a tool electrode, selecting machining power parameters and regulating resistance value based on the volume fraction of the workpiece reinforcing phase particles; step two: sequentially connecting the machining power, the regulating resistance and the workpiece, sequentially connecting the negative electrode of the machining power with the regulating resistance and the tool electrode, and connecting the positive electrode of the machining power with the workpiece; step three: opening the electrolyte to fill the electrolyte in the gap between the tool electrode and the workpiece, and opening the machining power and the regulating resistance; step four: moving the tool electrode along the preset feeding track relative to the workpiece; repeating steps three to four until the workpiece is machined. The technical scheme of the application realizes efficient machining by discharging and electrochemistry for metal matrix composite materials with different reinforcing phase volume fractions.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of composite machining, and particularly relates to a discharge-electrochemical combined rough machining method for metal matrix composite materials. BACKGROUND

[0002] Discharge-electrochemical combined machining is a non-contact machining technique based on electrochemical corrosion and discharge effect, and can be used for machining of insulating materials such as titanium alloy, high-temperature alloy or ceramic. The energy sources of electrolysis and discharge are both electric energy. Under the action of electrolysis, the workpiece material is dissolved into the electrolyte in the form of ions, so that the workpiece material is removed; under the action of discharge, the workpiece material is removed by the heat between the anode and the cathode.

[0003] At present, the research on the discharge-electrochemical combined machining method mainly focuses on two directions. One is the machining process mainly based on discharge effect, which utilizes the extremely high energy discharge generated during the machining process to quickly remove a large amount of workpiece material, thereby obtaining a high material removal rate. The other is the machining process mainly based on electrolysis effect, which utilizes the characteristics of high surface quality of electrolytic machining to obtain good surface quality.

[0004] The discharge-electrochemical combined machining method mainly based on discharge effect has a discharge current of hundreds of amperes and a discharge duration of several milliseconds during the machining process. The discharge belongs to arc discharge, and its energy is thousands of times that of spark discharge. Under the action of high-intensity discharge, a large amount of workpiece material is melted, vaporized and thrown out, thereby obtaining extremely high machining efficiency. However, due to the excessive discharge energy, on the one hand, it will cause serious electric shock, thereby reducing the machining efficiency. On the other hand, the excessive discharge energy will also cause the discharge pits on the workpiece surface to be too large, and the electrolysis effect is not sufficient to remove the surface defects, thereby reducing the machining precision and surface quality.

[0005] The discharge-electrochemical combined machining method mainly based on electrolysis effect has a strong electrolysis effect during the machining process, and the workpiece is continuously dissolved and removed under a high electrolysis current density. Therefore, it usually has high surface quality and machining precision. At this time, the discharge effect is weak, and the discharge effect plays an auxiliary role in the electrolysis effect, thereby promoting the breaking of the passivation film in the machining area. However, such machining process usually faces the problem of low machining efficiency, which limits the further application of the method.

[0006] For metal matrix composites, there is a large difference in the volume fraction of reinforcing phase particles. When processing low volume fraction metal matrix composites, due to the low content of high melting point reinforcing phase particles, high processing efficiency can be obtained when the discharge effect is weak; with the increase of the content of high melting point and non-conductive reinforcing phase, the discharge effect needs to be enhanced to obtain high material removal rate. Therefore, for metal matrix composites with different volume fractions, different processing processes with different discharge and electrolysis effects are needed to obtain good processing performance. However, the existing processing methods are to adjust the electrical and non-electrical parameters, and the process window is very narrow, which cannot realize the separate adjustment of the discharge and electrolysis effects, so there are problems such as poor process performance when processing metal matrix composites with different volume fractions.

[0007] Therefore, how to balance the electrolysis effect and the discharge effect is of great significance for the further promotion of the discharge-electrochemical composite machining method and the further application of metal matrix composites. SUMMARY

[0008] The purpose of the present application is to provide a metal matrix composite discharge-electrochemical rough machining method to solve the problems existing in the prior art.

[0009] To achieve the above purpose, the present application provides a metal matrix composite discharge-electrochemical rough machining method, comprising:

[0010] Step one: obtain a workpiece and a tool electrode, the workpiece is a metal matrix composite, obtain the volume fraction of the reinforcing phase particles of the workpiece, and select a machining power source and a regulating resistor based on the volume fraction of the reinforcing phase of the workpiece;

[0011] Step two: sequentially electrically connect the machining power source, the regulating resistor and the workpiece, and electrically connect the machining power source and the tool electrode;

[0012] Step three: fill the electrolyte in the gap between the tool electrode and the workpiece, generate an electrochemical reaction and produce a machining product;

[0013] Step four: move the tool electrode along a predetermined feed trajectory relative to the workpiece;

[0014] Repeat steps three to four until the workpiece is machined.

[0015] Optionally, the machining power source and the regulating resistor are selected based on the volume fraction of the reinforcing phase of the workpiece, specifically comprising:

[0016] Based on the volume fraction of the reinforcing phase particles of the workpiece, the voltage of the machining power source and the resistance value of the regulating resistor are set.

[0017] Optionally, the voltage of the machining power source and the resistance of the regulating resistor are set, and specifically include:

[0018] When the volume fraction of the workpiece is low, the voltage of the machining power source is 100-200V, and the resistance of the regulating resistor is 0.5-1.0Ω.

[0019] When the volume fraction of the workpiece is medium, the voltage of the machining power source is 40-100V, and the resistance of the regulating resistor is 0.1-0.5Ω.

[0020] When the volume fraction of the workpiece is high, the voltage of the machining power source is 40-80V, and the resistance of the regulating resistor is 0.05-0.1Ω.

[0021] Optionally, the machining power source adopts a direct current power source.

[0022] Optionally, in the process of moving the tool electrode along the preset feeding track relative to the workpiece, the tool electrode is also rotated around an axis in a preset rotation direction.

[0023] Optionally, the tool electrode is internally provided with a central hole, so that the electrolyte enters the machining gap between the tool electrode and the workpiece through the central hole of the tool electrode to generate an electrochemical reaction.

[0024] Optionally, the electrolyte adopts a neutral salt solution.

[0025] Optionally, the machining product includes insoluble machining products and detached silicon carbide particles.

[0026] The technical effect of the present application is:

[0027] 1. By connecting different regulating resistors in series in the machining circuit, the discharge current in the machining circuit can be controlled without significantly affecting the electrochemical dissolution. For low volume fraction metal matrix composites, increasing the resistance of the regulating resistor can obtain a weaker discharge effect and a stronger electrochemical dissolution effect; reducing the resistance of the regulating resistor can obtain a stronger discharge effect and a weaker electrochemical dissolution effect. For metal matrix composites with different volume fractions, different machining effects can be achieved by changing the resistance of the regulating resistor and the machining voltage. For metal matrix composites with different volume fractions, the machining process of the discharge effect and the electrochemical dissolution effect is realized.

[0028] 2. Under the action of the regulating resistor, there is no over-high energy discharge in the discharge-electrochemical composite machining process, the discharge current is effectively controlled, the tool electrode loss is reduced, the service life of the tool electrode is improved, the machining cost is reduced, and the machining efficiency is improved.

[0029] 3. Under the regulation of the resistance, the discharge current is controlled, the workpiece material removed by single discharge is less, the machining localization is improved, and the tool electrode loss is reduced due to the low energy discharge, so the electrolytic current is increased, and the discharge and electrochemistry are combined to realize the high-efficiency machining. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0031] The drawings constituting a part of the present application are used to provide further understanding of the present application, the illustrative embodiments of the present application and the description thereof are used to explain the present application, and do not constitute improper limitation on the present application. In the drawings:

[0032] Figure 1 A schematic diagram of the discharge-electrochemical rough machining method for the metal matrix composite in the embodiments of the present application;

[0033] Figure 2 A comparison diagram of machining currents when 0.1Ω is connected in series and when no regulation resistance is connected in series in the machining loop in the embodiments of the present application;

[0034] Figure 3 A comparison diagram of material removal rates when 0.1Ω is connected in series and when no regulation resistance is connected in series in the machining loop in the embodiments of the present application;

[0035] Figure 4 A comparison diagram of tool electrode losses when 0.1Ω is connected in series and when no regulation resistance is connected in series in the machining loop in the embodiments of the present application;

[0036] Label Name: 1, tool electrode feeding direction; 2, electrolyte; 3, insoluble product; 4, machining power supply; 5, regulation resistance; 6, workpiece; 7, detached silicon carbide particles; 8, tool electrode; 9, tool electrode rotation direction. DETAILED DESCRIPTION

[0037] Now, various exemplary embodiments of the present application will be described in detail, which should not be considered as a limitation on the present application, but should be understood as a more detailed description of some aspects, characteristics and embodiments of the present application.

[0038] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0039] Example 1

[0040] like Figure 1 - Figure 4 As shown, this embodiment provides a roughing method for metal matrix composites that combines discharge and electrochemical processes, including: obtaining a workpiece 6 and a tool electrode 8, wherein the workpiece 6 is a metal matrix composite, obtaining the volume fraction of the reinforcing phase particles of the workpiece 6, and selecting a processing power source 4 and a regulating resistor 5 based on the volume fraction of the reinforcing phase of the workpiece 6; step two: sequentially electrically connecting the processing power source 4, the regulating resistor 5, and the workpiece 6, and electrically connecting the processing power source 4 to the tool electrode 8; step three: filling the gap between the tool electrode 8 and the workpiece 6 with an electrolyte 2, causing an electrochemical reaction and generating processing products; step four: moving the tool electrode relative to the workpiece 6 along a preset feed trajectory; repeating steps three and four until the workpiece 6 is processed.

[0041] The method proposed in this embodiment connects a regulating resistor 5 in series between the tool electrode 8 or workpiece 6 and the machining power supply 4. By regulating the resistor 5, the current in the machining circuit is limited, thereby controlling the discharge effect in the discharge-electrochemical composite machining process. For high-volume-fraction metal matrix composites, a smaller resistance value of the regulating resistor 5 is used, resulting in a stronger discharge effect and a weaker electrochemical dissolution effect in the machining circuit. For low-volume-fraction metal matrix composites, a higher resistance value of the regulating resistor 5 is used, resulting in a weaker discharge effect and a stronger electrochemical dissolution effect in the machining circuit. Based on the characteristics of the workpiece material, by connecting different resistance values ​​of the regulating resistor 5 in series in the machining circuit, the discharge current and electrochemical dissolution current in the machining circuit can be controlled, realizing a roughing method that emphasizes both discharge and electrochemical processes for metal matrix composites.

[0042] This embodiment enables rough machining of metal matrix composites with different volume fractions. The connection relationship includes: the tool electrode 8 is connected to the negative terminal of the machining power supply 4, the workpiece 6 is connected to the positive terminal of the machining power supply 4, and the regulating resistor 5 is located between the tool electrode 8 or the workpiece 6 and the machining power supply 4. A high-conductivity electrolyte 2 is used as the working medium for the discharge-electrochemical composite machining, and the electrolyte 2 enters the machining area through the central hole of the tool electrode 8. The tool electrode 8 rotates around its axis and continuously feeds along the feed direction. Discharge occurs between the tool electrode feed direction 1 and the workpiece 6, while electrochemical reactions occur simultaneously or alternately in other areas. A large number of insoluble machining products and silicon carbide particles 7 passively detached due to electrochemical dissolution are generated in the machining area.

[0043] Implementation process: Install the tool electrode 8 and set the tool. Introduce electrolyte 2 into the tool electrode 8. Set the voltage of the machining power supply 4 and the resistance value of the regulating resistor 5 according to the reinforcing phase content of the workpiece 6. While the machining power supply 4 is running, the tool electrode 8 operates according to the predetermined program.

[0044] Wherein, the workpiece 6 is a metal matrix composite, and the resistance 5 has a resistance value of 0.05-1Ω.

[0045] The machining power source 4 used in the discharge electrolysis composite machining process is a direct current non-pulse power source or a direct current pulse power source.

[0046] The electrolyte 2 uses a neutral salt solution, and the solution solute of the neutral salt solution is sodium chloride or sodium nitrate, and the solvent of the neutral salt solution is water or ethylene glycol; the mass fraction of the solute of the neutral salt solution is greater than 5%.

[0047] If the workpiece 6 is a low-volume-fraction metal matrix composite, the resistance 5 is set to 0.5-1.0Ω, and the voltage of the machining power source 4 is set to 100-200V; if the workpiece 6 is a medium-volume-fraction metal matrix composite, the resistance 5 is set to 0.1-0.5Ω, and the voltage of the machining power source 4 is set to 40-100V; if the workpiece 6 is a high-volume-fraction metal matrix composite, the resistance 5 is set to 0.05-0.1Ω, and the voltage of the machining power source 4 is set to 40-80V. The discharge equivalent resistance is 0.05-0.3Ω, and the electrochemical dissolution equivalent resistance is 0.5-1Ω. In the electrochemical dissolution process, the voltage occupied by the resistance 5 is much smaller than the voltage occupied by the electrochemical dissolution equivalent resistance, that is, the existence of the resistance 5 has little effect on the electrochemical dissolution. In the discharge process, the discharge equivalent resistance is small, so a very high energy discharge will occur during the machining process, which will cause serious electrode wear and thus reduce the machining efficiency. Therefore, the discharge current is controlled by connecting the resistance 5 in series. Since the low-volume-fraction metal matrix composite contains only a small amount of reinforcing phase particles, it does not require high-energy arc discharge to achieve high machining efficiency. The low-volume-fraction metal matrix composite contains a large amount of metal matrix, so increasing the machining voltage can enhance the electrochemical dissolution effect and quickly remove the material. With the increase of the reinforcing phase content, it is necessary to increase the discharge current to quickly remove the high-melting-point reinforcing phase. Correspondingly, the metal matrix content decreases, and the electrolysis current needs to be reduced to prevent the strong electrochemical effect from deteriorating the machining effect. When machining high-volume-fraction metal matrix composites, strong discharge action is needed to remove the reinforcing phase, and weak electrolysis action is needed to remove the metal matrix.

[0048] The embodiment can control the discharge current in the machining circuit without significantly affecting the electrochemical dissolution by connecting different regulating resistors 5 in series in the machining circuit. For low volume fraction metal matrix composites, increasing the resistance of the regulating resistor 5 can obtain weaker discharge effect and stronger electrochemical dissolution effect; reducing the resistance of the regulating resistor 5 can obtain stronger discharge effect and weaker electrochemical dissolution effect. For metal matrix composites with different volume fractions, by changing the resistance of the regulating resistor 5 and the machining voltage, the machining process with both discharge effect and electrochemical dissolution effect can be realized.

[0049] In the embodiment, under the action of the regulating resistor 5, the discharge-electrochemical composite machining process will not produce excessively high energy discharge, the current of the discharge is effectively controlled, the tool electrode 8 loss is reduced, the service life of the tool electrode 8 is improved, the machining cost is reduced, and the machining efficiency is improved.

[0050] In the embodiment, under the action of the regulating resistor 5, the discharge current is controlled, the tool electrode 8 loss is reduced, the service life of the tool electrode 8 is improved, the machining cost is reduced, and the machining efficiency is improved.

[0051] Figure 1 The figure is a schematic diagram of a discharge-electrochemical composite rough machining method of metal matrix composites. The tool electrode 8 is connected to the negative electrode of the machining power supply 4, the workpiece 6 is connected to the positive electrode of the machining power supply 4, and the regulating resistor 5 is located between the tool electrode 8 or the workpiece 6 and the machining power supply 4. The regulating resistor 5 is used to limit the discharge current in the discharge process, and the presence of the regulating resistor 5 has little effect on the electrochemical dissolution process. The resistance of the regulating resistor 5 is determined according to the material of the workpiece 6. If the workpiece 6 is a low volume fraction metal matrix composite, the regulating resistor 5 is set to 0.5-1.0Ω, and the voltage of the machining power supply 4 is set to 100-200V; if the workpiece 6 is a medium volume fraction metal matrix composite, the regulating resistor 5 is set to 0.1-0.5Ω, and the voltage of the machining power supply 4 is set to 40-100V; if the workpiece 6 is a high volume fraction metal matrix composite, the regulating resistor 5 is set to 0.05-0.1Ω, and the voltage of the machining power supply 4 is set to 40-80V.

[0052] A high-conductivity electrolyte 2 is used as the working medium for discharge-electrochemical composite machining. The electrolyte 2 enters the machining area through the central hole of the tool electrode 8. The tool electrode 8 rotates around its axis and continuously feeds along the feed direction. Discharge occurs between the tool electrode feed direction 1 and the workpiece 6, and electrochemical reaction occurs simultaneously or alternately in other areas. A large amount of insoluble machining products and silicon carbide particles 7 passively shed due to electrochemical dissolution are produced in the machining area.

[0053] The specific example of the embodiment is that the material of the workpiece 6 used in the embodiment is 45vol% SiC P / Al, which belongs to the medium volume fraction metal matrix composite material, and the silicon carbide is uniformly distributed in the aluminum matrix in the form of particles. The regulating resistance 5 with a resistance of 0.1Ω is connected in series in the machining circuit before the experiment. The cerium-tungsten electrode with an outer diameter of 6mm and a center hole inner diameter of 3mm is used as the tool electrode 8 during the experiment. The 20wt% NaCl solution is used as the electrolyte 2, the temperature of the electrolyte 2 is 30℃, and the pressure is 0.6MPa. The machining voltage is set to 40V, and the feed rate is 60mm / min. Figure 2 The machining circuit current is compared before and after the regulating resistance 5 is connected in series in the machining circuit. It can be seen from Figure 2 that the discharge current in the machining circuit decreases from more than 1000A to about 220A after the regulating resistance 5 with a resistance of 0.1Ω is connected in series in the machining circuit, and the electrolysis current increases to about 26A. It can be seen from Figure 3 that the discharge effect is inhibited and the electrolysis effect is enhanced after the regulating resistance 5 with a resistance of 0.1Ω is connected in series in the machining circuit, while the total material removal rate remains stable. The material removal rate of the discharge effect decreases from 284.76mm 3 / min to 262.69mm 3 / min, and the material removal rate of the electrochemical dissolution effect increases from 60.03mm 3 / min to 82.75mm 3 / min. It can be seen from Figure 4 that the relative electrode loss rate decreases from 2.23% to 1.39% and the tool electrode 8 loss volume decreases from 3.44mm 3 to 1.83mm 3 after the regulating resistance 5 with a resistance of 0.1Ω is connected in series in the machining circuit, which benefits from the regulation of the discharge current.

[0054] Each embodiment in the specification is described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same and similar parts between each embodiment can be referred to each other.

[0055] The above is only the preferred specific implementation of the present application, but the protection scope of the present application is not limited to this. Any changes or replacements within the technical range disclosed in the present application can be easily thought by those skilled in the art, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A roughing method for metal matrix composite materials that combines discharge and electrochemical processes, characterized in that, include: Step 1: Obtain the workpiece (6) and the tool electrode (8). The workpiece (6) is a metal matrix composite material. Obtain the volume fraction of the reinforcing phase particles of the workpiece (6). Based on the volume fraction of the reinforcing phase particles of the workpiece (6), set the voltage of the processing power supply (4) and the resistance value of the regulating resistor (5). Step 2: Connect the processing power supply (4), the regulating resistor (5) and the workpiece (6) in sequence, and connect the processing power supply (4) to the tool electrode (8); Step 3: Fill the gap between the tool electrode (8) and the workpiece (6) with electrolyte (2) to generate an electrochemical reaction and produce processing products; Step 4: Move the tool electrode (8) relative to the workpiece (6) along a preset feed trajectory; Repeat steps three to four until the workpiece (6) is finished.

2. The roughing method for metal matrix composite materials emphasizing both discharge and electrochemical processes according to claim 1, characterized in that, The processing power supply (4) is a DC power supply.

3. The roughing method for metal matrix composite materials emphasizing both discharge and electrochemical processes according to claim 1, characterized in that, During the process of moving the tool electrode (8) relative to the workpiece (6) along a preset feed trajectory, the tool electrode (8) is also rotated about an axis along a preset rotation direction (9).

4. The roughing method for metal matrix composite materials emphasizing both discharge and electrochemical processes according to claim 1, characterized in that, The tool electrode (8) has a central hole inside, so that the electrolyte (2) enters the processing gap between the tool electrode (8) and the workpiece (6) through the central hole of the tool electrode (8) and undergoes an electrochemical reaction.

5. The roughing method for metal matrix composite materials emphasizing both discharge and electrochemical processes according to claim 1, characterized in that, The electrolyte (2) is a neutral salt solution.

6. The roughing method for metal matrix composite materials emphasizing both discharge and electrochemical processes according to claim 1, characterized in that, The processed products include insoluble processed products (3) and detached silicon carbide particles (7).

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