Magnetorheological polishing method for NiP modified reflector

Abstract

The invention discloses a magnetorheological polishing method for a NiP modified reflector, and the processing method comprises: preparing a NiP modified layer, and performing ultra-precision turning and magnetorheological polishing shaping processing on the NiP modified layer until the index requirements are met. In the magnetorheological polishing method for the NiP modified reflector of the invention, ultra-precision turning and magnetorheological polishing are used to process the NiP modified reflector blank workpiece, which can not only effectively eliminate the surface defects generated during the processing of the NiP modified reflector blank workpiece, but also be beneficial to improving the processing efficiency, and at the same time can improve the surface shape accuracy and surface quality of the processing, which is beneficial to processing the NiP modified reflector blank workpiece into a high-quality NiP modified reflector, and has the advantages of few processing defects, high processing quality, high processing efficiency, good repeatability, etc., which is of great significance for promoting the wide application of NiP modified reflectors in optical fields such as visible light bands and shorter wavelength bands.

Description

Technical Field

[0001] The invention belongs to the technical field of ultra-precision processing of optical elements and relates to a magnetorheological polishing processing method of a NiP modified reflecting mirror. Background Art

[0002] Reflectors made of materials such as aluminum, beryllium, beryllium aluminum alloy, and aluminum-based silicon carbide have the advantages of easy precision forming, high lightweight rate, and homogeneous optical and mechanical integration. They are increasingly widely used in the field of modern high-tech aerospace. However, materials such as aluminum, beryllium, beryllium aluminum alloy, and aluminum-based silicon carbide are sensitive to processing damage and are prone to scratches and pits during processing. The processing accuracy and surface quality are difficult to meet the application requirements of visible light and shorter wavelength optical systems, and can generally only meet the use requirements of infrared optical systems. The chemically plated NiP modified layer has excellent characteristics such as dense surface, low porosity, good corrosion resistance, good ductility, and good machinability. It is an ideal modified layer for reflectors and is often used for surface modification of reflectors to improve the processing performance of reflectors.

[0003] In order to make the blank workpiece of NiP modified reflector meet the application requirements of infrared optical system, it is necessary to use ultra-precision turning process for processing first. However, ultra-precision turning will leave periodic turning marks on the surface of NiP modified reflector, which will cause diffraction phenomenon and have an adverse effect on the imaging of optical system. Specifically, diffraction phenomenon is a manifestation of the wave nature of light. Periodic turning marks can be regarded as diffraction gratings that can act as dispersion elements. Diffraction phenomenon will reduce the reflectivity of the mirror surface and affect the performance of the reflector, which is extremely unfavorable to the improvement of the imaging quality of the optical system. In particular, in the existing conventional ultra-precision turning method, when the material properties of the NiP modified layer are poor or the ultra-precision turning process parameters are not properly selected, the surface of the processed mirror is prone to cracks, cavities, scratches, pits, peeling and other defects, which affect the processing quality. As a result, the surface roughness of the prepared NiP modified mirror is still high, and there are pits. At the same time, the existence of the above-mentioned shortcomings is not conducive to obtaining a higher quality NiP modified mirror through the polishing process, and it will increase the difficulty of the subsequent polishing process, making the processing efficiency of the polishing process very low. Therefore, for optical systems in applications such as visible light bands and shorter wavelength bands, it is also necessary to polish the NiP modified mirror that has completed ultra-precision turning to improve the surface accuracy and surface quality of the NiP modified mirror.

[0004] Magnetorheological finishing (MRF) is a process in which a magnetorheological polishing liquid ribbon moves on the workpiece surface at a specific motion trajectory and speed under the control of a computer. By controlling the residence time in each area, the amount of surface material removed can be accurately controlled to achieve the purpose of correcting the surface shape error and improving the surface quality. Magnetorheological polishing is based on the principle of chemical mechanical polishing. During processing, the workpiece material is removed by polishing abrasives under the combined influence of mechanical and chemical effects. It has application prospects in improving the surface shape accuracy and surface quality of NiP modified reflectors. However, in the existing magnetorheological polishing processing method of NiP modified reflectors, due to the incompatibility between the magnetorheological polishing liquid and the NiP modified layer, processing defects are prone to occur during polishing, and there are defects such as poor processing quality and low processing efficiency. It is difficult to effectively improve the surface shape accuracy and surface quality of the NiP modified reflector, and it is not conducive to promoting the wide application of NiP modified reflectors in applications such as the visible light band and shorter wavelength bands.

[0005] Therefore, obtaining a magnetorheological polishing method for a NiP modified reflector with high processing efficiency, good processing quality and good process repeatability is of great significance for higher quality NiP modified reflectors. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a magnetorheological polishing method for a NiP modified reflector with high processing efficiency, good processing quality and good process repeatability.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0008] A magnetorheological polishing method for a NiP modified reflector comprises the following steps:

[0009] Step S1, preparing a NiP modified layer on the surface of a reflector substrate to obtain a NiP modified reflector blank workpiece;

[0010] Step S2, performing ultra-precision turning on the NiP modified reflector blank workpiece to obtain a NiP modified reflector;

[0011] Step S3, performing wavefront interference detection on the NiP modified reflecting mirror to obtain the initial surface shape of the mirror surface of the NiP modified reflecting mirror;

[0012] Step S4, performing magnetorheological polishing and shaping processing on the NiP modified reflector using a magnetorheological polishing fluid according to the initial surface shape of the NiP modified reflector surface;

[0013] Step S5, performing wavefront interference detection and white light interference detection on the NiP modified reflector after magnetorheological polishing and shaping. If the index requirements are not met, jump to step S3, otherwise the processing is terminated, and the processing of the NiP modified reflector is completed.

[0014] The above magnetorheological polishing method is further improved, in step S4, the magnetorheological polishing liquid comprises the following raw material components in terms of volume percentage:

[0015] Magnetic material 30%~40%,

[0016] Polishing abrasive 5% to 10%,

[0017] Surfactant 1%~3%,

[0018] pH adjuster 0.5%~3%,

[0019] Rust inhibitor 0.5% to 1%, the rest is base carrier liquid;

[0020] The polishing abrasive grains are silicon carbide.

[0021] The magnetorheological polishing method is further improved in that the average particle size of the polishing abrasive particles is 85 nm to 115 nm.

[0022] The above magnetorheological polishing processing method is further improved in that the magnetic material is carbonyl iron powder.

[0023] The above magnetorheological polishing processing method is further improved, wherein the surfactant is at least one of glycerol, sodium dodecyl sulfate, sodium dodecyl sulfonate, and sodium dodecylbenzene sulfonate.

[0024] The above magnetorheological polishing processing method is further improved, wherein the pH regulator is at least one of potassium hydroxide, sodium hydroxide, sodium acetate, sodium carbonate, and sodium borate.

[0025] The above magnetorheological polishing processing method is further improved in that the rust inhibitor is sodium benzoate.

[0026] The above magnetorheological polishing processing method is further improved in that the base carrier liquid is deionized water.

[0027] The above magnetorheological polishing processing method is further improved in that the pH value of the magnetorheological polishing liquid is 9-10.

[0028] The above-mentioned magnetorheological polishing processing method is further improved. In step S4, the process parameters of the magnetorheological polishing and shaping processing are: the rotation speed of the polishing wheel is 150 rpm~210 rpm, the liquid flow rate of the magnetorheological polishing liquid is 80 mL / s~120 mL / s, the magnetorheological polishing liquid ribbon pressure depth is 0.2mm~0.4 mm, and the magnetic field current is 6.5 A~7.5 A.

[0029] The above magnetorheological polishing method is further improved, in step S1, preparing a NiP modified layer on the surface of the reflector substrate, comprising the following steps:

[0030] Step S1-1, preparing a NiP modified layer on the surface of the reflector substrate;

[0031] Step S1-2, inspect the NiP modified layer. If the NiP modified layer has quality defects, remove the NiP modified layer on the surface of the reflector substrate and jump to execute step S1-1 until the quality of the NiP modified layer meets the index requirements.

[0032] The above-mentioned magnetorheological polishing processing method is further improved. In step S1-1, a NiP modified layer is prepared on the surface of the reflector substrate by chemical nickel plating; the thickness of the NiP modified layer is 80 μm to 120 μm; the phosphorus content in the NiP modified layer is 9 wt % to 14 wt %; the material of the reflector substrate is light metal; the light metal includes at least one of aluminum alloy, beryllium, and aluminum-beryllium alloy.

[0033] The above-mentioned magnetorheological polishing processing method is further improved. In step S1-2, a microscope is used to detect the NiP modified layer, and the detection items include: whether the surface of the NiP modified layer has impurities, whether it is flat, whether it is uniform and dense, whether there are holes, whether there are gaps, and whether there are cracks; the quality of the NiP modified layer meets the index requirements, including meeting the following indicators: the surface of the NiP modified layer is free of impurities, flat and smooth, uniform and dense, without holes, without gaps, and without cracks.

[0034] The above-mentioned magnetorheological polishing processing method is further improved. After obtaining the NiP modified layer whose quality indicators meet the requirements in step S1-2, it also includes performing the following treatment on the NiP modified layer whose quality indicators meet the requirements: selecting a heat treatment method according to relevant standards and the type of reflector substrate, and heat treating the NiP modified layer to reduce hydrogen embrittlement and improve bonding strength.

[0035] The above-mentioned magnetorheological polishing processing method is further improved. In step S2, a diamond turning tool is used when ultra-precision turning the NiP modified layer; the rake angle of the diamond turning tool is 0°; the radius of the tip arc of the diamond turning tool is 0.5 mm to 2 mm; the blunt radius of the cutting edge of the diamond turning tool is 20 nm to 50 nm; the process parameters of the ultra-precision turning processing are: the machine tool spindle speed is 1200 rpm to 1600 rpm, the feed rate is 1 μm / r to 10 μm / r, and the cutting depth is 1 μm to 5 μm.

[0036] The above magnetorheological polishing method is further improved, and step S3 also includes: detecting whether the surface of the NiP modified reflector meets the ultra-precision turning index requirements, if not, jumping to executing step S2, otherwise jumping to executing step S4.

[0037] Compared with the prior art, the advantages of the present invention are:

[0038] (1) In view of the shortcomings of the existing magnetorheological polishing processing methods, such as many processing defects and poor processing quality, and the resulting processing accuracy and surface quality are difficult to meet the application requirements of visible light and shorter wavelength optical systems, the present invention creatively proposes a magnetorheological polishing processing method for a NiP modified reflector, firstly preparing a NiP modified layer on the surface of the reflector substrate to obtain a NiP modified reflector blank workpiece, and then performing ultra-precision turning on the NiP modified reflector blank workpiece, so that the surface of the NiP modified reflector blank workpiece becomes an optical reflective mirror surface, which can be used for interference measurement. Then, the initial surface shape of the NiP modified reflector is obtained through detection. On this basis, according to the initial surface shape data of the NiP modified reflector, the NiP modified reflector is subjected to magnetorheological polishing and shaping processing. The surface shape error of the NiP modified reflector is deterministically modified through magnetorheological polishing and shaping processing, and the mechanical and chemical actions during processing are controlled and balanced, thereby realizing ultra-precision processing of the NiP modified reflector and significantly improving the surface shape accuracy and surface quality of the NiP modified reflector, thereby meeting the application requirements of visible light and shorter wavelength optical systems. In the magnetorheological polishing processing method of the NiP modified reflector of the present invention, ultra-precision turning and magnetorheological polishing are used to process the NiP modified reflector blank workpiece, which can not only effectively eliminate the surface defects generated during the processing of the NiP modified reflector blank workpiece, which is beneficial to improving the processing efficiency, but also can improve the processing surface accuracy and surface quality, which is beneficial to processing the NiP modified reflector blank workpiece into a high-quality NiP modified reflector, and has the advantages of few processing defects, high processing quality, high processing efficiency, good repeatability, etc., which is of great significance for promoting the application and development of NiP modified reflectors in the field of optics.

[0039] (2) In the magnetorheological polishing processing method of the NiP modified reflector of the present invention, in order to solve the problems of the existing magnetorheological polishing liquid, such as easy agglomeration and poor compatibility with the NiP modified layer, and the resulting problems of easy processing defects, poor processing quality, low processing efficiency, etc., a magnetorheological polishing liquid is creatively provided, which comprises the following raw material components in terms of volume percentage: 30% to 40% of magnetic material, 5% to 10% of polishing abrasive particles, 1% to 3% of surfactant, 0.5% to 3% of pH adjuster, 0.5% to 1% of rust inhibitor, and the rest is base carrier liquid, wherein the polishing abrasive particles are silicon carbide. In the present invention, the addition of a surfactant can effectively improve the dispersibility of the magnetic material and prevent it from agglomerating. The addition of a rust inhibitor can also effectively prevent the magnetic material from rusting, thereby ensuring that it has stable magnetism and dispersibility. At the same time, the addition of a pH adjuster can also enhance the chemical corrosion of the magnetorheological polishing fluid on the NiP modified layer, thereby promoting the chemical reaction between the magnetorheological polishing fluid and the NiP modified layer to generate an easily removable oxide layer. Since the molecular bonding force between the components in the oxide layer is much smaller than the molecular bonding force between the components in the NiP modified layer, during the magnetorheological polishing process, the polishing abrasive in the magnetorheological polishing fluid can be made easier to remove. The surface material of the NiP modified reflector workpiece is removed, which is beneficial to improve the material removal efficiency of the NiP modified layer, so that the processing efficiency of magnetorheological polishing can be significantly improved. More importantly, with silicon carbide as the polishing abrasive, the mechanical grinding effect of the magnetorheological polishing fluid can be improved, and the oxide layer formed by chemical reaction on the surface of the NiP modified layer can be accurately removed under the cooperation of the magnetic substance, which is beneficial to improve the processing quality of the NiP modified layer. It can be seen that under the joint action of each component, not only can the defect of easy agglomeration of the polishing fluid be effectively improved, but also the chemical corrosion and mechanical grinding effect of the magnetorheological polishing fluid on the NiP modified layer are significantly enhanced. On this basis, in the present invention, by optimizing the amount of each component in the magnetorheological polishing fluid, the basic properties of the magnetorheological polishing fluid can be further improved, such as better anti-sedimentation performance, lower zero magnetic field viscosity, greater shear stress, and a magnetorheological polishing fluid with a relative balance of chemical corrosion and mechanical grinding and better adaptability with the NiP modified layer is obtained. In particular, when the amount of magnetic material is too small, it is difficult to form a magnetorheological effect, while too much magnetic material will easily aggravate agglomeration; when the amount of polishing abrasive is too small, the material removal efficiency is low, while too much will easily lead to over-processing and deterioration of surface quality; when the amount of surfactant is too small, the anti-sedimentation stability is poor and it is difficult to improve the agglomeration problem, while too much will significantly reduce the shear stress and make it difficult to achieve mechanical polishing; when the amount of rust inhibitor is too small, the magnetic particles will rust, while too much will also cause the magnetic particles to agglomerate.It can be seen that when the ratio of the magnetorheological polishing fluid is not good, the magnetorheological polishing fluid will have problems such as poor fluidity, agglomeration, sedimentation and rust, which will easily cause processing defects on the workpiece surface during magnetorheological polishing, which is not conducive to improving the surface quality of the processed workpiece, and may even make the processed workpiece unable to meet the use requirements. The more prominent problem is that it is easy to cause the magnetorheological polishing fluid circulation system on the processing machine tool to fail to work normally. In the present invention, by optimizing the raw material components of the magnetorheological polishing fluid and the amount of each component, the polishing performance of the magnetorheological polishing fluid can be significantly improved, and the magnetorheological polishing fluid has the advantages of good sedimentation performance, low zero magnetic field viscosity, large shear stress, relatively balanced chemical corrosion and mechanical grinding, good compatibility with the NiP modified layer, etc. As a new magnetorheological polishing fluid with excellent performance, the magnetorheological polishing fluid can be widely used in magnetorheological polishing and shaping processing of NiP modified layers, and can significantly improve the processing quality, processing efficiency and process repeatability of magnetorheological polishing, which is conducive to obtaining high-quality NiP modified reflectors without defects and small surface roughness, and has a promoting effect on realizing the wide application of NiP modified reflectors in applications such as visible light bands and shorter wavelength bands, and has high use value and good application prospects. It can be seen that in the present invention, by optimizing the raw material components and the amount of each component of the magnetorheological polishing fluid, the polishing performance of the magnetorheological polishing fluid can be significantly improved, and it is applied to the magnetorheological polishing and shaping processing of the NiP modified layer, which can significantly improve the processing quality, processing efficiency and process repeatability of the magnetorheological polishing, and is conducive to obtaining a higher quality NiP modified reflector with no defects and small surface roughness, wherein the processing efficiency can reach a peak removal efficiency of up to 5 μm / min and a volume removal efficiency of up to 0.2 mm. 3 / min; at the same time, by optimizing the process parameters of magnetorheological polishing, the surface accuracy and surface quality of the processing can be further improved, making the defects of the processed surface less.

[0040] (3) In the magnetorheological polishing processing method of the NiP modified reflector of the present invention, the magnetorheological polishing liquid used is optimized to have a pH value of 9-10. On the one hand, the chemical corrosion effect of the magnetorheological polishing liquid can be enhanced, and on the other hand, it can also effectively avoid the agglomeration and sedimentation of the magnetic particles due to rust. This is because when the pH value is too low, the carbonyl iron powder of the magnetic particles is easily oxidized and rusted, while when the pH value is too high, the polishing liquid is easily agglomerated and precipitated.

[0041] (4) In the magnetorheological polishing method of the NiP modified reflector of the present invention, the ultra-precision turning mechanism and process of the NiP modified reflector are studied and explored. By preparing a high-phosphorus content amorphous NiP modified layer that meets the processing requirements on the surface of the reflector substrate and optimizing the process parameters of the ultra-precision turning, the ultra-precision turning can be used to achieve high-quality, low-defect processing of the NiP modified layer, which is beneficial to improving the processing efficiency and processing quality of the NiP modified reflector, as well as improving the process repeatability, and can ensure that a high-quality reflector surface can be obtained after magnetorheological polishing. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0043] Figure 1 The figure is a flowchart of the magnetorheological polishing process of the NiP modified reflector in the embodiment of the present invention.

[0044] Figure 2 Result diagram of the surface error of the NiP modified layer after ultra-precision turning in an embodiment of the present invention.

[0045] Figure 3 Surface roughness diagram of the NiP modified layer after ultra-precision turning in an embodiment of the present invention.

[0046] Figure 4 Schematic diagram of the structure of the magnetorheological polishing device used in an embodiment of the present invention.

[0047] Figure 5 Schematic diagram of the removal principle of the magnetorheological polishing device used in an embodiment of the present invention.

[0048] Figure 6 The XPS Ni 2p of the NiP modified layer after magnetorheological polishing in the embodiment of the present invention is 3 / 2 picture.

[0049] Figure 7 XPS P 2p of the NiP modified layer after magnetorheological polishing in the embodiment of the present invention 3 / 2 picture.

[0050] Figure 8 This is a graph showing the surface error results of the NiP modified layer after magnetorheological polishing in an embodiment of the present invention.

[0051] Fig. 9 Surface roughness diagram of the NiP modified layer after magnetorheological polishing in an embodiment of the present invention.

[0052] Fig.10This is a physical picture of the finished NiP modified reflector prepared in an embodiment of the present invention.

[0053] Fig.11 This is a graph showing the surface roughness results of the NiP modified layer using a magnetorheological polishing fluid prepared with diamond as the polishing abrasive in an embodiment of the present invention.

[0054] Fig.12 This is a graph showing the surface roughness results of the NiP modified layer using the magnetorheological polishing fluid prepared with silicon carbide as the polishing abrasive in an embodiment of the present invention.

[0055] Fig.13 This is a graph showing the surface roughness results of the NiP modified layer using the magnetorheological polishing fluid prepared with silicon dioxide as the polishing abrasive in an embodiment of the present invention.

[0056] Fig.14 This is a graph showing the surface roughness results of the NiP modified layer using a magnetorheological polishing fluid prepared with aluminum oxide as the polishing abrasive in an embodiment of the present invention.

[0057] Fig.15 This is a graph showing the surface roughness results of the NiP modified layer using the magnetorheological polishing fluid prepared with cerium oxide as the polishing abrasive in an embodiment of the present invention.

[0058] Fig.16 This is a graph showing the sedimentation stability test results of a magnetorheological polishing fluid prepared using silicon carbide as the polishing abrasive in an embodiment of the present invention.

[0059] Fig.17 This is a graph showing the test results of zero magnetic field viscosity at different shear rates for a magnetorheological polishing fluid prepared using silicon carbide as polishing abrasive in an embodiment of the present invention.

[0060] Fig.18 This is a graph showing the shear yield test results of a magnetorheological polishing fluid prepared using silicon carbide as the polishing abrasive in an embodiment of the present invention at different magnetic field intensities. DETAILED DESCRIPTION

[0061] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments of the specification, but the protection scope of the present invention is not limited thereby. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0062] The "range" disclosed in the present invention can be defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can be inclusive or exclusive of the end values, and any end value can be included or excluded independently, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a specific parameter, it is understood that a range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are also listed, the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present invention, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, wherein a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations.

[0063] In the present invention, "plurality", "multiple" and the like, unless otherwise specified, refer to a number greater than or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0064] If not otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form a new technical solution.

[0065] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment or implementation of the present invention. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments. Reference to "implementations" herein has a similar understanding.

[0066] Those skilled in the art will appreciate that, in the methods of various embodiments or examples, the order in which each step is written does not mean a strict order of execution and does not constitute any limitation on the implementation process, and the detailed order of execution of each step should be determined by its function and possible internal logic. If there is no special explanation, all steps of the present invention can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0067] In the present invention, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0068] In the present invention, "optionally", "optional", and "optional" mean optional or dispensable, that is, any one of the two parallel solutions of "yes" or "no". If multiple "options" appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "option" is independent.

[0069] Aiming at the shortcomings of the existing magnetorheological polishing processing method, such as many processing defects and poor processing quality, and the resulting processing accuracy and surface quality are difficult to meet the application requirements of visible light and shorter wavelength optical systems, the present invention proposes a magnetorheological polishing processing method for NiP modified reflector, comprising the following steps:

[0070] Step S1, preparing a NiP modified layer on the surface of a reflector substrate to obtain a NiP modified reflector blank workpiece;

[0071] Step S2, performing ultra-precision turning on the NiP modified reflector blank workpiece to obtain a NiP modified reflector;

[0072] Step S3, performing wavefront interference detection on the NiP modified reflecting mirror to obtain the initial surface shape of the mirror surface of the NiP modified reflecting mirror;

[0073] Step S4, performing magnetorheological polishing and shaping processing on the NiP modified reflector using a magnetorheological polishing fluid according to the initial surface shape of the NiP modified reflector surface;

[0074] Step S5, performing wavefront interference detection and white light interference detection on the NiP modified reflector after magnetorheological polishing and shaping. If the index requirements are not met, jump to step S3, otherwise the processing is terminated, and the processing of the NiP modified reflector is completed.

[0075] In the magnetorheological polishing processing method of the NiP modified reflector in the above-mentioned embodiment, ultra-precision turning and magnetorheological polishing are used to process the NiP modified reflector blank workpiece, which can not only effectively eliminate the surface defects generated during the processing of the NiP modified reflector blank workpiece, but also help to improve the processing efficiency. At the same time, it can improve the processing surface accuracy and surface quality, which is conducive to processing the NiP modified reflector blank workpiece into a high-quality NiP modified reflector, which has the advantages of few processing defects, high processing quality, high processing efficiency, good repeatability, etc., and is of great significance for promoting the application and development of NiP modified reflectors in the field of optics.

[0076] Further improved, in the magnetorheological polishing processing method of the NiP modified reflector of the present invention, the magnetorheological polishing liquid used comprises the following raw material components according to volume percentage: 30% to 40% of magnetic substance, 5% to 10% of polishing abrasive, 1% to 3% of surfactant, 0.5% to 3% of pH adjuster, 0.5% to 1% of rust inhibitor, and the rest is base carrier liquid, wherein the polishing abrasive is silicon carbide.

[0077] It can be understood that the volume percentage refers to the volume fraction of the component in the magnetorheological polishing fluid.

[0078] In some embodiments, the volume percentage of the magnetic substance in the magnetorheological polishing fluid of the present invention is 30% to 40%. It can be understood that the volume fraction of the magnetic substance in the magnetorheological polishing fluid is 30 vol% to 40 vol%. As an example, the volume percentage of the magnetic substance in the magnetorheological polishing fluid may be 30%, 32%, 33%, 34%, 35%, 36%, 38%, 40%, or may be within the range of any two of the above point values ​​as end values. Optionally, the volume percentage of the magnetic substance in the magnetorheological polishing fluid is 32% to 38%.

[0079] In some embodiments, the volume percentage of polishing abrasive particles in the magnetorheological polishing fluid of the present invention is 5% to 10%. It can be understood that the volume fraction of polishing abrasive particles in the magnetorheological polishing fluid is 5 vol% to 10 vol%. As an example, the volume percentage of polishing abrasive particles in the magnetorheological polishing fluid may be 5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or any two of the above point values ​​as end values. Optionally, the volume percentage of polishing abrasive particles in the magnetorheological polishing fluid is 6% to 9%.

[0080] In some embodiments, the polishing abrasive grains used in the magnetorheological polishing fluid of the present invention are silicon carbide. Compared with conventional polishing abrasive grains (such as diamond, silicon dioxide, aluminum oxide, and cerium oxide), in the present invention, silicon carbide is used as a polishing abrasive grain for preparing the magnetorheological polishing fluid, which has better compatibility with the NiP modified layer, and is conducive to improving the processing quality and processing efficiency of magnetorheological polishing.

[0081] In some embodiments, the volume percentage of the surfactant in the magnetorheological polishing fluid of the present invention is 1% to 3%. It can be understood that the volume fraction of the surfactant in the magnetorheological polishing fluid is 1 vol% to 3 vol%. As an example, the volume percentage of the surfactant in the magnetorheological polishing fluid may be 1%, 1.1%, 1.2%, 1.4%, 1.5%, 1.8%, 2%, 2.4%, 2.5%, 2.7%, 2.9%, 3%, or any two of the above point values ​​as end values. Optionally, the volume percentage of the surfactant in the magnetorheological polishing fluid is 1.1% to 2.9%.

[0082] In some embodiments, the volume percentage of the pH adjuster in the magnetorheological polishing fluid of the present invention is 0.3% to 3%. It can be understood that the volume fraction of the pH adjuster in the magnetorheological polishing fluid is 0.3 vol% to 3 vol%. As an example, the volume percentage of the pH adjuster in the magnetorheological polishing fluid may be 0.3%, 0.4%, 0.5%, 0.8%, 1.0%, 1.2%, 1.4%, 1.5%, 1.8%, 2%, 2.4%, 2.5%, 2.7%, 2.9%, 3%, or any two of the above point values ​​as end values. Optionally, the volume percentage of the pH adjuster in the magnetorheological polishing fluid is 0.4% to 2.9%.

[0083] In some embodiments, the volume percentage of the rust inhibitor in the magnetorheological polishing fluid of the present invention is 0.5% to 1%. It can be understood that the volume fraction of the rust inhibitor in the magnetorheological polishing fluid is 0.5 vol% to 1 vol%. As an example, the volume percentage of the rust inhibitor in the magnetorheological polishing fluid may be 0.5%, 0.54%, 0.56%, 0.58%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.86%, 0.9%, 0.92%, 0.95%, 0.98%, 1%, or any two of the above point values ​​as end values. Optionally, the volume percentage of the rust inhibitor in the magnetorheological polishing fluid is 0.54% to 0.98%.

[0084] In the present invention, by optimizing the raw material components of the magnetorheological polishing fluid and the amount of each component, the polishing performance of the magnetorheological polishing fluid can be significantly improved, and the magnetorheological polishing fluid has the advantages of good sedimentation performance, low zero magnetic field viscosity, large shear stress, relatively balanced chemical corrosion and mechanical grinding, good compatibility with the NiP modified layer, etc. As a new magnetorheological polishing fluid with excellent performance, the magnetorheological polishing fluid can be widely used in magnetorheological polishing and shaping processing of NiP modified layers, and can significantly improve the processing quality, processing efficiency and process repeatability of magnetorheological polishing, which is conducive to obtaining high-quality NiP modified reflectors without defects and small surface roughness, and has a promoting effect on realizing the wide application of NiP modified reflectors in applications such as visible light bands and shorter wavelength bands, and has high use value and good application prospects.

[0085] Optionally, the average particle size of the polishing abrasive particles in the magnetorheological polishing fluid of the present invention is 85 nm to 115 nm.

[0086] Optionally, the magnetic substance in the magnetorheological polishing fluid of the present invention is carbonyl iron powder.

[0087] Optionally, the surfactant in the magnetorheological polishing liquid of the present invention is at least one of glycerol, sodium dodecyl sulfate, sodium dodecyl sulfonate, and sodium dodecylbenzene sulfonate.

[0088] Optionally, the pH regulator in the magnetorheological polishing liquid of the present invention is at least one of potassium hydroxide, sodium hydroxide, sodium acetate, sodium carbonate and sodium borate.

[0089] Optionally, the rust inhibitor in the magnetorheological polishing liquid of the present invention is sodium benzoate.

[0090] Optionally, the base carrier liquid in the magnetorheological polishing fluid of the present invention is deionized water.

[0091] Optionally, the pH value of the magnetorheological polishing fluid in the magnetorheological polishing fluid of the present invention is 9-10.

[0092] Further improved, in the magnetorheological polishing processing method of the NiP modified reflector of the present invention, the process parameters of the magnetorheological polishing and shaping processing are: the rotation speed of the polishing wheel is 150 rpm~210 rpm, the liquid flow rate of the magnetorheological polishing liquid is 80mL / s~120 mL / s, the magnetorheological polishing liquid ribbon pressure depth is 0.2mm~0.4mm, and the magnetic field current is 6.5A~7.5A.

[0093] Further improved, in the magnetorheological polishing method of the NiP modified reflector of the present invention, preparing a NiP modified layer on the surface of the reflector substrate comprises the following steps:

[0094] Step S1-1, preparing a NiP modified layer on the surface of the reflector substrate;

[0095] Step S1-2, inspect the NiP modified layer. If the NiP modified layer has quality defects, remove the NiP modified layer on the surface of the reflector substrate and jump to execute step S1-1 until the quality of the NiP modified layer meets the index requirements.

[0096] The above-mentioned magnetorheological polishing processing method is further improved. In step S1-1, a NiP modified layer is prepared on the surface of the reflector substrate by chemical nickel plating; the thickness of the NiP modified layer is 80 μm to 120 μm; the phosphorus content in the NiP modified layer is 9 wt % to 14 wt %; the material of the reflector substrate is light metal; the light metal includes at least one of aluminum alloy, beryllium, and aluminum-beryllium alloy.

[0097] The above-mentioned magnetorheological polishing processing method is further improved. In step S1-2, a microscope is used to detect the NiP modified layer, and the detection items include: whether the surface of the NiP modified layer has impurities, whether it is flat, whether it is uniform and dense, whether there are holes, whether there are gaps, and whether there are cracks; the quality of the NiP modified layer meets the index requirements, including meeting the following indicators: the surface of the NiP modified layer is free of impurities, flat and smooth, uniform and dense, without holes, without gaps, and without cracks.

[0098] The above-mentioned magnetorheological polishing processing method is further improved. After obtaining the NiP modified layer whose quality indicators meet the requirements in step S1-2, it also includes performing the following treatment on the NiP modified layer whose quality indicators meet the requirements: selecting a heat treatment method according to relevant standards and the type of reflector substrate, and heat treating the NiP modified layer to reduce hydrogen embrittlement and improve bonding strength.

[0099] The above-mentioned magnetorheological polishing processing method is further improved. In step S2, a diamond turning tool is used when ultra-precision turning the NiP modified layer; the rake angle of the diamond turning tool is 0°; the radius of the tip arc of the diamond turning tool is 0.5 mm to 2 mm; the blunt radius of the cutting edge of the diamond turning tool is 20 nm to 50 nm; the process parameters of the ultra-precision turning processing are: the machine tool spindle speed is 1200 rpm to 1600 rpm, the feed rate is 1 μm / r to 10 μm / r, and the cutting depth is 1 μm to 5 μm.

[0100] The above magnetorheological polishing method is further improved, and step S3 also includes: detecting whether the surface of the NiP modified reflector meets the ultra-precision turning index requirements, if not, jumping to executing step S2, otherwise jumping to executing step S4.

[0101] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0102] The workpiece to be processed in this embodiment is a NiP modified plane reflector with a diameter of 100 mm, and the substrate is 6061 aluminum alloy. The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, and the processing method used in the present invention is further explained.

[0103] like Figure 1 As shown, the magnetorheological polishing method of the NiP modified reflector of this embodiment comprises the following steps:

[0104] Step S1, preparing a NiP modified layer on the surface of a reflector substrate.

[0105] Step S2, inspect the NiP modified layer. If the NiP modified layer has quality defects, remove the NiP modified layer on the surface of the reflector substrate, and jump to step S1 until the quality of the NiP modified layer meets the index requirements and execute the next step.

[0106] Step S3, heat-treating the NiP modified layer, preparing the NiP modified layer on the surface of the reflector substrate, and obtaining a NiP modified reflector blank workpiece.

[0107] Step S4, performing ultra-precision turning on the NiP modified reflector blank workpiece, so that the reflection effect of the NiP modified layer on the surface of the reflector substrate meets the mirror reflection requirement, and obtaining the NiP modified reflector.

[0108] Step S5: Perform wavefront interference detection on the NiP modified reflecting mirror to obtain the initial surface shape of the mirror surface of the NiP modified reflecting mirror.

[0109] Step S6: According to the initial surface shape of the NiP modified reflector, magnetorheological polishing and shaping processing is performed on the NiP modified reflector using magnetorheological polishing fluid.

[0110] Step S7, performing wavefront interference detection and white light interference detection on the NiP modified reflector after magnetorheological polishing and shaping. If the index requirements are not met, jump to step S5, otherwise the processing is terminated, and the processing of the NiP modified reflector is completed.

[0111] In this embodiment, the material properties of the NiP modified layer directly affect the processing performance of ultra-precision turning. For example, during the chemical nickel plating process in step S1, if the plating process is not properly controlled, impurities are easily deposited on the surface of the NiP modified layer. At the same time, due to the small bonding force between the impurities and the NiP modified layer, when the NiP modified layer is subjected to ultra-precision turning, the impurities are driven by the turning tool to separate from the surface of the NiP modified layer, forming pit defects on the surface of the modified layer, or the turning tool drives the impurities to form scratches on the surface of the modified layer.

[0112] In view of the above problems, in steps S1 and S2 of the present embodiment, a NiP modified layer is prepared on the surface of the reflector substrate by chemical nickel plating. After the chemical nickel plating is completed, the NiP modified layer is inspected by a microscope. The inspection items include: whether the surface of the NiP modified layer has impurities, whether it is flat, whether it is uniform and dense, whether there are holes, whether there are gaps, and whether there are cracks. If the NiP modified layer has any of the above quality defects, the NiP modified layer on the surface of the reflector substrate is removed, and the process jumps to step S1, and the NiP modified layer is continued to be prepared on the surface of the reflector substrate by chemical nickel plating until the quality of the NiP modified layer meets the index requirements. Specifically, by observing under a strong light and using an ultra-depth of field microscope, it is ensured that the surface of the NiP modified layer is free of impurity deposition, flat and smooth, uniform and dense, and has no defects such as holes, gaps, and cracks. In this step, the quality of the NiP modified layer meets the index requirements, which can be determined according to actual conditions, such as impurity-free deposition means that there are no impurities on the surface of the NiP modified layer; generally speaking, chemical plating is an equal thickness deposition, so the preparation by chemical nickel plating can basically ensure that the NiP modified layer is flat and smooth; uniform density requires that the Ni element and the P element are randomly and uniformly distributed, because the NiP modified layer is an amorphous NiP modified layer, it is also easier to achieve; voids and cracks are usually easy to observe, they belong to very bad conditions, and they are scrapped when they appear, so once defects such as voids and cracks appear, the modified layer needs to be re-plated; holes are formed by hydrogen generated in chemical nickel plating, and their size and depth are required not to exceed the value of the cutting depth during ultra-precision turning.

[0113] In step S2 of this embodiment, the NiP modified layer plated on the 6061 aluminum alloy substrate meets the quality requirements, has a thickness of 100 μm, and a phosphorus content of 11 wt %, which is a high-phosphorus-content amorphous NiP modified layer.

[0114] In addition, during the chemical nickel plating process in step S1, not all chemical reaction products are beneficial to the formation of the NiP modified layer. For example, hydrogen will be generated during the chemical nickel plating, and hydrogen will form pores in the NiP modified layer, reducing the toughness and load capacity of the modified layer, affecting the bonding strength between the NiP modified layer and the reflector substrate, and further, when the NiP modified layer is subjected to ultra-precision turning, the NiP modified layer is prone to peeling and falling off.

[0115] In order to eliminate hydrogen embrittlement and enhance the bonding strength between the NiP modified layer and the substrate, it is also necessary to select a heat treatment method according to relevant standards and the type of reflector substrate, and heat treat the NiP modified layer whose quality meets the index requirements in step S1 to reduce hydrogen embrittlement and improve the bonding strength. Specifically: in step S3 of this embodiment, the NiP modified layer whose quality meets the index requirements plated on the 6061 aluminum alloy substrate is heat treated to reduce hydrogen embrittlement and improve the bonding strength. After testing by a tensile testing machine, the bonding strength between the substrate and the modified layer can reach 40 MPa after heat treatment to reduce hydrogen embrittlement and heat treatment to improve the bonding strength, which meets the requirements.

[0116] In step S4 of this embodiment, the NiP modified layer obtained after heat treatment in step S3 is subjected to ultra-precision turning, wherein a diamond turning tool is used when the modified layer is subjected to ultra-precision turning, wherein the rake angle of the diamond turning tool is 0°, the tool tip arc radius is 0.5 mm, the cutting edge blunt radius is 20 nm, and at the same time, the feed rate range is 10 μm / r, and the cutting depth is 5 μm; the machine tool spindle speed is 1500 rpm, so that the reflection effect of the NiP modified layer on the surface of the reflector substrate meets the mirror reflection requirements, and a NiP modified reflector is obtained.

[0117] Step S5 of this embodiment also includes the following steps: detecting whether the surface of the NiP modified reflector meets the ultra-precision turning index requirements, if not, jumping to step S4, otherwise jumping to step S6 to perform the next step of magnetorheological polishing.

[0118] In step S5 of this embodiment, a wavefront interferometer is used to perform wavefront interferometry on the NiP modified reflector after ultra-precision turning. The result is as follows: Figure 2 As shown in Figure 2, a white light interferometer was used to perform white light interferometry on the NiP modified reflector after ultra-precision turning. The results are shown in Figure 2. Figure 3 As shown. Figure 2 and Figure 3 It can be seen that the surface error RMS of the NiP modified reflector obtained after ultra-precision turning is 104.542 nm, and the surface roughness Ra is 2.025 nm.

[0119] In step S6 of this embodiment, a schematic diagram of a magnetorheological polishing device is used, as shown in FIG. Figure 4As shown, during magnetorheological polishing, the magnetorheological polishing fluid is output from the liquid storage tank through the output pump, and after stability control by the flowmeter and viscometer, the magnetorheological polishing fluid is delivered to the polishing wheel through the nozzle. Under the action of the gradient magnetic field, the magnetorheological polishing fluid can be converted into a solid within milliseconds to process the workpiece. After the processing is completed, the magnetorheological fluid is recovered to the liquid storage tank through the liquid recovery device and the recovery pump to complete the cycle. Since the yield stress of the magnetorheological fluid ribbon can be adjusted by controlling the magnitude of the magnetic field strength during magnetorheological polishing, this is conducive to the polishing abrasive particles in the magnetorheological polishing fluid to produce a micro-cutting effect on the workpiece surface, realizing micron-level or even nano-level material removal processing of the workpiece. At the same time, the magnetorheological polishing device is under the control of a computer system. The magnetorheological polishing liquid ribbon moves on the workpiece surface at a set trajectory and speed. At the same time, the computer system controls the residence time of the magnetorheological polishing liquid ribbon in each residence area, thereby achieving precise control of the amount of material removed and deterministic correction of the surface shape error of the workpiece surface. Therefore, the magnetorheological polishing workpiece can achieve very high surface shape accuracy and surface quality.

[0120] In step S6 of this embodiment, magnetorheological polishing and shaping processing is performed on the NiP modified reflector using magnetorheological polishing fluid according to the initial surface shape of the NiP modified reflector surface. The detailed steps include:

[0121] Step S6-1, magnetorheological polishing fluid is the medium between the machine tool and the workpiece during magnetorheological polishing processing, so it is necessary to prepare the magnetorheological polishing fluid first, wherein the magnetorheological polishing fluid used for processing NiP modified reflector has the following components: 35 vol% magnetic substance, 8 vol% polishing abrasive, 1.5 vol% surfactant, 1.5 vol% pH adjuster, 0.5 vol% rust inhibitor, and the rest is base carrier liquid.

[0122] Step S6-2, calculating the dwell time according to the initial surface shape after ultra-precision turning, selecting the processing path, generating the numerical control code, and performing magnetorheological polishing.

[0123] In step S6-1, the magnetic substance in the magnetorheological polishing liquid is carbonyl iron powder, the polishing abrasive is silicon carbide with an average particle size of 100 nm, the surfactant is propylene glycol, the pH adjuster is sodium carbonate, the pH value of the magnetorheological polishing liquid is 9.5, the rust inhibitor is sodium benzoate, and the base carrier liquid is deionized water.

[0124] In step S6-2, when magnetorheological polishing is used to process the NiP modified reflector, it is necessary to control the balance between mechanical removal and chemical reaction to obtain a high-quality, low-defect reflector surface. The chemical action is achieved by controlling the composition of the magnetorheological polishing fluid, while the mechanical action is controlled by the magnetorheological polishing process parameters of the machine tool. The magnetorheological polishing process parameters of the machine tool are: the speed of the polishing wheel is 180 rpm, the liquid flow rate of the magnetorheological fluid is 80 mL / s, the magnetorheological polishing fluid ribbon pressure depth is 0.3 mm, and the magnetic field current is 7.5 A. After testing, the sample was processed in only 16 minutes, with high processing efficiency.

[0125] In step S6 of this embodiment, the magnetorheological finishing technology (MRF) is to make the magnetorheological polishing liquid ribbon move on the workpiece surface with a specific motion trajectory and speed under the control of a computer. By controlling the residence time in each area, the amount of surface material removed can be accurately controlled to achieve the purpose of correcting the surface shape error and improving the surface quality. Magnetorheological polishing is based on the principle of chemical mechanical polishing. During processing, the workpiece material is removed by polishing abrasives under the combined influence of mechanical and chemical effects.

[0126] like Figure 5 As shown in the figure, the mechanical action is responsible for the workpiece material removal task. The pressure (P) applied to the workpiece surface during magnetorheological polishing is mainly composed of the pressure generated by the magnetic field and the fluid dynamic pressure:

[0127] (1).

[0128] In the above formula, P m is the magnetization pressure generated by the gradient magnetic field, P d It is the fluid dynamic pressure generated by the flow of polishing liquid.

[0129] (2).

[0130] In the above formula, φ is the volume ratio of carbonyl iron powder in magnetorheological polishing fluid, μ 0 is the vacuum permeability, μ f is the magnetic permeability of the magnetorheological fluid, μ p is the magnetic permeability of carbonyl iron powder in the polishing liquid, H is the magnetic field strength.

[0131] (3).

[0132] In the above formula, η 0 is the viscosity of magnetorheological polishing fluid;V is the tangential speed of the polishing wheel; h For along x Direction, height between workpiece and polishing wheel; R l is the radius of the polishing wheel.

[0133] Since the gap between the workpiece and the polishing wheel is much smaller than the polishing wheel radius, the surface speed of the polishing wheel can be used instead of the relative speed:

[0134] (4).

[0135] In the above formula, ω is the angular velocity of the polishing wheel, n is the polishing wheel speed.

[0136] The theoretical basis of material removal in magnetorheological polishing is the Preston equation, which can be used to obtain the material removal rate per unit time. for:

[0137] (5).

[0138] In the above formula, K is the Preston constant.

[0139] When the NiP modified reflector is processed by magnetorheological polishing, a chemical reaction will occur between the magnetorheological polishing fluid and the NiP modified layer on the reflector surface. The chemical state of the elements after the chemical reaction is analyzed by X-ray photoelectron spectroscopy (XPS). The results are as follows: Figure 6 and Figure 7 As shown. Figure 6 and 7 It can be seen that in Ni 2p 3 / 2 There are four obvious peaks in the fine spectrum, with binding energies around 852.1 eV, 852.8 eV, 854.1 eV, and 856.3 eV, respectively. These four peaks correspond to Ni-P 2p 3 / 2 , Ni 2p 3 / 2 、NiO 2p 3 / 2 and Ni2O32p 3 / 2 ; in P 2p 3 / 2 There are three obvious peaks in the fine spectrum, P 2p 3 / 2 The binding energies of these three peaks are around 129.6 eV, 130.2 eV, and 133.5 eV, respectively. These three peaks correspond to Ni-P 2p 3 / 2 、P 2p 3 / 2 and P2O32p 3 / 2 .

[0140] XPS analysis shows that in this embodiment, the magnetorheological polishing liquid and the NiP modified reflector undergo a chemical reaction to generate an easily removable oxide layer, and the molecular bonding force between the components in the oxide layer is much smaller than that between the components in the NiP modified layer. Therefore, the generation of the oxide layer can make it easier for the polishing abrasive in the polishing liquid to remove the surface material of the NiP modified reflector workpiece when the magnetorheological polishing is performed on the NiP modified reflector. Therefore, the chemical reaction is conducive to improving the material removal efficiency of the NiP modified layer and improving the surface quality of the NiP modified layer.

[0141] In step S7 of this embodiment, a wavefront interferometer is used to perform wavefront interferometry on the NiP modified reflector after magnetorheological polishing and shaping. The result is as follows: Figure 8 As shown in the figure, a white light interferometer was used to measure the NiP modified reflector after magnetorheological polishing. Fig. 9 As shown. Figure 8 and Fig. 9 It can be seen that the surface error RMS of the NiP modified reflector is 13.710 nm, and the surface roughness Ra is 0.530 nm. However, in the conventional magnetorheological polishing method, the surface roughness of the NiP modified reflector cannot reach the sub-nanometer precision range, and the surface error correction processing efficiency is low, and processing defects such as pits and scratches are prone to occur.

[0142] The NiP modified reflector product finally obtained in this embodiment is as follows: Fig.10 shown.

[0143] In step S7 of this embodiment, if the index requirement is not met, the process jumps to step S5, otherwise the processing ends, and the processing of the NiP modified reflector is completed.

[0144] In addition, according to the test, the magnetorheological polishing method used in the present invention can achieve a peak removal efficiency of up to 5 μm / min and a volume removal efficiency of up to 0.2 mm 3 / min, while the peak removal efficiency of conventional magnetorheological polishing method is less than 2μm / min and the volume removal efficiency is less than 0.05mm 3 / min.

[0145] In this embodiment, the influence of magnetorheological polishing fluids prepared with different polishing abrasives on the polishing effect is also investigated, as follows:

[0146] Five different magnetorheological polishing fluids were prepared. Except for the different polishing abrasives, other conditions were the same as the magnetorheological polishing fluid used in step S6. The NiP modified reflector was subjected to magnetorheological polishing and shaping processing using the magnetorheological polishing fluids prepared with different polishing abrasives. The processing parameters were the same as those in step S6. After processing, the surface morphology and surface roughness of the NiP modified reflector were measured. The results are shown in Figures 11-15.

[0147] Depend on Fig.11 It can be seen that when the magnetorheological polishing fluid prepared with diamond as the polishing abrasive is used to process the NiP modified reflector, many pits appear on the surface of the modified layer accompanied by a tailing phenomenon.

[0148] Depend on Fig.12 It can be seen that when the magnetorheological polishing fluid prepared with silicon carbide as the polishing abrasive is used to process the NiP modified reflector, the surface quality of the modified layer processed by silicon carbide abrasive is good, without defects such as pits and scratches, and the surface roughness value is small.

[0149] Depend on Fig.13 It can be seen that when the magnetorheological polishing fluid prepared with silicon dioxide as the polishing abrasive is used to process the NiP modified reflector, scratches appear on the surface of the NiP modified layer and the surface roughness value is also relatively large.

[0150] Depend on Fig.14 It can be seen that the magnetorheological polishing fluid prepared with aluminum oxide as the polishing abrasive is used to process NiP modified mirrors, which easily causes the surface roughness of the NiP modified layer to be poor. This is because the surface energy of nano-aluminum oxide is relatively high, which easily causes the abrasive to agglomerate, affecting the surface quality of the NiP modified metal mirror processing.

[0151] Depend on Fig.15 It can be seen that when the magnetorheological polishing fluid prepared with cerium oxide as the polishing abrasive is used to process the NiP modified metal reflector, the surface quality of the modified layer is poor. This may be because the chemical activity of cerium oxide is strong and the material removal efficiency is low, resulting in the chemical action being faster than the mechanical removal rate of the abrasive, resulting in excessive chemical corrosion on the surface of the NiP modified layer.

[0152] Depend on Figure 11-15 It can be seen from the results in that in the present invention, silicon carbide is used as the polishing abrasive to prepare the magnetorheological polishing liquid, which has better compatibility with the NiP modified layer, which is beneficial to improving the processing quality and efficiency of magnetorheological polishing.

[0153] In addition, the sedimentation stability, zero magnetic field viscosity and shear stress of the magnetorheological polishing fluid prepared with silicon carbide as polishing abrasive (i.e., the magnetorheological polishing fluid used in step S6) were also investigated. Figure 16-18 shown.

[0154] (1) Investigation of the sedimentation stability of magnetorheological polishing fluid

[0155] In magnetorheological polishing fluid, the density of the base carrier liquid is much lower than the density of the magnetic particles. The sedimentation problem of the magnetic particles caused by this has always been one of the thorny issues in the use of magnetorheological polishing fluid. Since the density of the base carrier liquid in the magnetorheological polishing fluid is much lower than the density of the magnetic particles, the sedimentation of the magnetic particles cannot be avoided. At the same time, if the magnetic particles agglomerate in the magnetorheological polishing fluid, the sedimentation problem of the polishing fluid will be further aggravated. Based on this, the sedimentation stability of the magnetorheological polishing fluid developed in this embodiment is analyzed, and the indicator for evaluating the sedimentation stability is the sedimentation rate. Specifically, the sedimentation rate of the magnetorheological polishing fluid is calculated using the measuring cylinder method. During the measurement, the prepared and fully stirred magnetorheological polishing fluid is first placed in a measuring cylinder, and the sedimentation height of the magnetic particles is recorded every 2 hours. Then, the sedimentation rate is calculated based on the sedimentation height result and combined with the following formula :

[0156] (6).

[0157] In the above formula, x is the height of the upper clear liquid after the magnetic particles are precipitated, and y is the height of the viscous part below the magnetic particles after the magnetic particles are precipitated.

[0158] Fig.16 This is a graph showing the sedimentation stability test results of a magnetorheological polishing fluid prepared using silicon carbide as the polishing abrasive in an embodiment of the present invention. Fig.16 In the figure, the black curve is the sedimentation curve drawn by the sedimentation rate test after the magnetorheological polishing liquid is prepared and stirred, and the red curve and blue curve are the sedimentation curves drawn by the test after being stirred again after standing for one week and two weeks respectively. Fig.16 It can be seen that the sedimentation rate of the magnetorheological polishing fluid after stirring is fast in the first 12 hours, and the sedimentation rate slows down and gradually stabilizes after 12 hours, and no longer continues to settle. The red curve and the blue curve show that the prepared magnetorheological polishing fluid can basically return to the initial dispersion state after being stirred after standing for a long time, indicating that the surfactant added to the polishing fluid has good anti-agglomeration and anti-sedimentation properties.

[0159] (2) Study on the zero magnetic field viscosity of magnetorheological polishing fluid

[0160] Zero magnetic field viscosity is one of the main indicators to measure the performance of magnetorheological polishing fluid. The zero magnetic field viscosity increases with the increase of magnetic particle content in the polishing fluid. The lower the zero magnetic field viscosity, the better the rheological properties of the polishing fluid. In actual processing, the lower the zero magnetic field viscosity of the magnetorheological polishing fluid, the more beneficial it is to the circulation of the polishing fluid.

[0161] The zero magnetic field viscosity of the magnetorheological polishing fluid was tested using the LC-LVT-1 rotational viscometer produced by a Shanghai company. The viscosity measurement range of the device is 6~6×106 mPa·s, and the rotor speed can be continuously variable from 0.1 to 200 rpm.

[0162] Fig.17 This is a graph showing the test results of zero magnetic field viscosity at different shear rates for a magnetorheological polishing fluid prepared using silicon carbide as polishing abrasive in an embodiment of the present invention.

[0163] from Fig.17 It can be seen that when the shear rate is low, the zero magnetic field viscosity of the polishing fluid decreases rapidly with the increase of the shear rate. As the shear rate increases, the viscosity of the magnetorheological polishing fluid decreases more and more slowly. When the shear rate is greater than 20 r / min, the viscosity of the magnetorheological polishing fluid tends to be stable. When the shear rate reaches 100 r / min, the zero magnetic field viscosity of the polishing fluid is 0.30 Pa·s, which meets the use requirements of the circulation system of the magnetorheological polishing equipment.

[0164] (3) Study on the shear stress of magnetorheological polishing fluid

[0165] In order to analyze the shear force characteristics of magnetorheological polishing fluid, the shear yield stress of magnetorheological polishing fluid prepared with silicon carbide as polishing abrasive was tested under different magnetic field intensities. The test results are as follows: Fig.18 shown.

[0166] Fig.18 This is a graph showing the shear yield test results of a magnetorheological polishing fluid prepared using silicon carbide as the polishing abrasive in an embodiment of the present invention at different magnetic field intensities.

[0167] from Fig.18 It can be seen that the shear yield stress of the magnetorheological polishing fluid increases with the increase of the magnetic field intensity, indicating that the magnetorheological polishing fluid has good rheological properties. When the magnetic field intensity is 200 mT, the shear yield stress test value of the magnetorheological polishing fluid is 17.6 kPa, indicating that the magnetorheological polishing fluid of the present invention has good rheological properties and can be applied in actual processing.

[0168] It can be seen from the above results that compared with conventional magnetorheological polishing fluid, in the present invention, by optimizing the raw material components and the amount of each component of the magnetorheological polishing fluid, the polishing performance of the magnetorheological polishing fluid can be significantly improved, and it has the advantages of good sedimentation performance, low zero magnetic field viscosity, large shear stress, relatively balanced chemical corrosion and mechanical grinding, and good compatibility with the NiP modified layer. As a new type of magnetorheological polishing fluid with excellent performance, it can be widely used in magnetorheological polishing and shaping processing of NiP modified layers, and can significantly improve the processing quality, processing efficiency and process repeatability of magnetorheological polishing, which is conducive to obtaining high-quality NiP modified reflectors without defects and small surface roughness, and has a promoting effect on the wide application of NiP modified reflectors in applications such as visible light bands and shorter wavelength bands. It has high use value and good application prospects. At the same time, compared with the conventional magnetorheological polishing processing method, in the magnetorheological polishing processing method of the NiP modified reflector of the present invention, ultra-precision turning and magnetorheological polishing are used to process the NiP modified reflector blank workpiece, which can not only effectively eliminate the surface defects generated during the processing of the NiP modified reflector blank workpiece, which is beneficial to improving the processing efficiency, but also can improve the processing surface accuracy and surface quality, which is beneficial to processing the NiP modified reflector blank workpiece into a high-quality NiP modified reflector, and has the advantages of few processing defects, high processing quality, high processing efficiency, good repeatability, etc., which is of great significance for promoting the application and development of NiP modified reflectors in the field of optics.

[0169] The above embodiments are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A magnetorheological polishing method for a NiP modified reflector, characterized in that: The following steps are involved: Step S1, preparing a NiP modified layer on the surface of a reflector substrate to obtain a NiP modified reflector blank workpiece; Step S2, performing ultra-precision turning on the NiP modified reflector blank workpiece to obtain a NiP modified reflector; Step S3, performing wavefront interference detection on the NiP modified reflecting mirror to obtain the initial surface shape of the mirror surface of the NiP modified reflecting mirror; Step S4: According to the initial surface shape of the NiP modified reflector, magnetorheological polishing and shaping processing is performed on the NiP modified reflector using a magnetorheological polishing fluid; the magnetorheological polishing fluid comprises the following raw material components in terms of volume percentage: Magnetic material 30%~40%, Polishing abrasive 5% to 10%, Surfactant 1%~3%, pH adjuster 0.5%~3%, Rust inhibitor 0.5% to 1%, the rest is base carrier liquid; The polishing abrasive particles are silicon carbide; Step S5, performing wavefront interference detection and white light interference detection on the NiP modified reflector after magnetorheological polishing and shaping. If the index requirements are not met, jump to step S3, otherwise the processing is terminated, and the processing of the NiP modified reflector is completed.

2. The magnetorheological polishing method according to claim 1, characterized in that: The average particle size of the polishing abrasive is 85 nm to 115 nm; the magnetic substance is carbonyl iron powder; the surfactant is at least one of propylene glycol, sodium dodecyl sulfate, sodium dodecyl sulfonate, and sodium dodecylbenzene sulfonate; the pH adjuster is at least one of potassium hydroxide, sodium hydroxide, sodium acetate, sodium carbonate, and sodium borate; the rust inhibitor is sodium benzoate; the base carrier liquid is deionized water; and the pH value of the magnetorheological polishing fluid is 9 to 10.

3. The magnetorheological polishing method according to claim 2, characterized in that: In step S4, the process parameters of the magnetorheological polishing and shaping processing are: the rotation speed of the polishing wheel is 150 rpm to 210 rpm, the liquid flow rate of the magnetorheological polishing liquid is 80 mL / s to 120 mL / s, the magnetorheological polishing liquid ribbon pressure depth is 0.2 mm to 0.4 mm, and the magnetic field current is 6.5 A to 7.5 A.

4. The magnetorheological polishing method according to any one of claims 1 to 3, characterized in that: In step S1, a NiP modified layer is prepared on the surface of the reflector substrate, comprising the following steps: Step S1-1, preparing a NiP modified layer on the surface of the reflector substrate; Step S1-2, inspect the NiP modified layer. If the NiP modified layer has quality defects, remove the NiP modified layer on the surface of the reflector substrate and jump to execute step S1-1 until the quality of the NiP modified layer meets the index requirements.

5. The magnetorheological polishing method according to claim 4, characterized in that: In step S1-1, a NiP modified layer is prepared on the surface of the reflector substrate by chemical nickel plating; the thickness of the NiP modified layer is 80 μm to 120 μm; the phosphorus content in the NiP modified layer is 9 wt % to 14 wt %; the material of the reflector substrate is light metal; the light metal includes at least one of aluminum alloy, beryllium, and aluminum-beryllium alloy.

6. The magnetorheological polishing method according to claim 4, characterized in that: In step S1-2, the NiP modified layer is inspected using a microscope, and the inspection items include: whether the surface of the NiP modified layer has impurities, whether it is flat, whether it is uniform and dense, whether it has holes, whether it has gaps, and whether it has cracks; the quality of the NiP modified layer meets the index requirements, including meeting the following indicators: the surface of the NiP modified layer is free of impurities, flat and smooth, uniform and dense, without holes, without gaps, and without cracks.

7. The magnetorheological polishing method according to claim 4, characterized in that: After obtaining the NiP modified layer with quality indicators that meet the requirements in step S1-2, the step also includes performing the following treatment on the NiP modified layer with quality indicators that meet the requirements: selecting a heat treatment method according to relevant standards and the type of reflector substrate, heat treating the NiP modified layer to reduce hydrogen embrittlement and improve bonding strength.

8. The magnetorheological polishing method according to any one of claims 1 to 3, characterized in that: In step S2, a diamond turning tool is used when ultra-precision turning the NiP modified layer; the rake angle of the diamond turning tool is 0°; the radius of the tip arc of the diamond turning tool is 0.5 mm to 2 mm; the blunt radius of the cutting edge of the diamond turning tool is 20 nm to 50 nm; the process parameters of the ultra-precision turning are: the machine tool spindle speed is 1200 rpm to 1600 rpm, the feed rate is 1 μm / r to 10 μm / r, and the cutting depth is 1 μm to 5 μm.

9. The magnetorheological polishing method according to any one of claims 1 to 3, characterized in that: Step S3 also includes: detecting whether the surface of the NiP modified reflector meets the ultra-precision turning index requirements, if not, jumping to executing step S2, otherwise jumping to executing step S4.

Images