WO2014161117A1

WO2014161117A1 - Oil film forming process and device using coupled magnetic nanoparticle jet stream and magnetic force workbench

Info

Publication number: WO2014161117A1
Application number: PCT/CN2013/001362
Authority: WO
Inventors: 李长河; 贾东洲; 王胜; 张强
Original assignee: 青岛理工大学
Priority date: 2013-04-02
Filing date: 2013-11-11
Publication date: 2014-10-09
Also published as: KR101730378B1; KR20150082179A

Abstract

Disclosed are an oil film forming process and device using a coupled magnetic nanoparticle jet stream and magnetic force workbench, comprising a magnetic force workbench (1), and a workpiece (2) attracted thereon by a magnetic force; a grinding wheel (4) provided at a workpiece (2) machining position, and a nozzle (8) mounted on a grinding wheel hood (3) at a position matching the workpiece (2), wherein the nozzle (8) is connected with a magnetic nanoparticle fluid feed device via a magnetic nanoparticle fluid delivery pipe (5), and connected to an air compressor via a compressed air delivery pipe (6); a magnetic nanoparticle fluid and compressed air are mixed and accelerated in the nozzle (8) to form a three-phase fluid mist spray, namely a mixed mist spray of compressed air, magnetic nanoparticles and grinding fluid base oil particles; and the three-phase fluid mist spray enters a grinding zone between the workpiece (2) and the grinding wheel (4), the magnetic force workbench is magnetically coupled with the three-phase fluid mist spray, and an oil film is formed on the surface of the workpiece (2). Magnetic nanoparticle fluid is delivered to the nozzle (8), forming a lubricating oil film on the surface of the workpiece on the magnetic workbench (1), thereby realizing maximum cooling and lubrication of the grinding and machining area.

Description

Magnetic nanoparticle jet and magnetic worktable coupling oil film forming process and device

The invention relates to a process and a device for forming an oil film coupled by a magnetic nanoparticle jet and a magnetic worktable.

Background technique

Micro-lubrication technology, also known as MQL (Minimal Quantity Lubrication) technology, is to mix and atomize a very small amount of lubricating fluid with a certain amount of compressed air, spray it into the grinding zone, and contact the grinding wheel with the grinding debris and the grinding wheel and the workpiece. The surface is effectively lubricated. This technology guarantees effective lubrication and cooling. Use minimal grinding fluid (approximately a few thousandths of the amount of conventional cast lubrication) to reduce cost and environmental pollution and damage to the human body. .

Nano-fluid micro-lubrication is based on the theory of enhanced heat transfer. It is known from the theory of enhanced heat transfer that the heat transfer capacity of solids is much greater than that of liquids and gases. The thermal conductivity of solid materials at ambient temperatures is orders of magnitude larger than that of fluid materials. The addition of solid particles to the micro-lubricating medium can significantly increase the thermal conductivity of the fluid medium, improve the ability of convective heat transfer, and greatly compensate for the lack of micro-lubrication cooling capacity. In addition, nanoparticles (referred to as ultra-fine micro-solid particles of size 1 ιοοTM) have special tribological properties such as anti-wear and anti-friction and high load-bearing capacity in lubrication and tribology. Nano-fluid micro-lubrication is the process of adding nano-scale solid particles into a micro-lubricating fluid medium to make nano-fluids, that is, nanoparticles, lubricants (oil, or oil-water mixture) are mixed with high-pressure gas and atomized and sprayed into the grinding zone as a jet.

The inventor conducted in-depth theoretical analysis and experimental verification of the micro-lubrication grinding supply system. The research results have applied for relevant patents, the invention patents applied by the inventor, nano-particle jet micro-lubricating grinding lubricant supply system.

(Patent No.: 201210153801. 2) discloses a nanoparticle jet micro-lubrication grinding lubricant supply system, which adds nano-scale solid particles into a degradable grinding fluid to make a lubricant for micro-lubrication grinding. The micro-feeding device converts the lubricant into a pulsed droplet having a fixed pressure, a variable pulse frequency, and a constant droplet diameter, and is sprayed into the grinding zone as a jet under the action of an air separation layer generated by the high-pressure gas. It has all the advantages of micro-lubrication technology, has stronger cooling performance and excellent tribological properties, effectively solves grinding burns, improves the surface quality of workpieces, and achieves low-carbon green with high efficiency, low consumption, environmental friendliness and resource conservation. Clean production is of great importance.

Invention patent: Nanoparticle jet micro-lubrication grinding surface roughness prediction method and device (patent number is

201210490401. 0) A method and apparatus for predicting the surface roughness of a grinding under the condition of minimal lubrication of a nanoparticle jet is disclosed. The utility model comprises a sensor lever, the left end of the sensor lever is provided with a stylus, the stylus is in contact with the surface of the grinding wheel, the right end of the sensor lever is connected with the inductive displacement sensor, and the fulcrum of the sensor lever is hinged with the measuring device body; the inductive displacement sensor and the alternating current The power connection is connected; the data output of the sensory displacement sensor is connected to the filter amplifier, the filter amplifier is connected to the calculator and the oscilloscope, and the calculator is also connected to the memory. It uses a matrix to characterize the shape of the wheel and then according to the grinding The surface forming mechanism of the workpiece is created, and the prediction model has high precision. It is not only easy to measure, but also has high equipment integration rate and high utilization rate. It also has high measurement accuracy and good reliability, and is more instructive for practice.

Invention patent: Nanoparticle jet micro-lubrication grinding 相 blue phase flow supply system (Patent No. 201110221543. 2) discloses a nano-particle jet micro-lubrication grinding three-phase flow supply system, which is characterized by: passing nano-fluid through liquid path The nozzle is delivered to the nozzle, and the high-pressure gas enters the nozzle through the gas path. The high-pressure gas and the nano-fluid are fully mixed and atomized in the nozzle mixing chamber, and accelerated into the vortex chamber after being accelerated by the acceleration chamber, and the vent hole of the compressed gas flow chamber enters, so that three The phase flow is further rotationally mixed and accelerated, and then the three-phase flow is injected into the grinding zone through the nozzle outlet in the form of atomized droplets.

However, in the disclosed technical solution, the viscosity of the nanofluid and the adhesion of the nanoparticle to the surface of the workpiece are changed under the coupling of the magnetic nanoparticle and the magnetic worktable, so that the nanoparticle participates in the enhanced heat transfer and the grinding wheel. / The workpiece interface forms a lubricating anti-friction film, J1 effectively reduces the drift of the nano-fluid droplets. Achieve low-carbon clean high-efficiency micro-lubrication grinding.

Although many scholars have carried out theoretical analysis and experimental research on nano-micro-lubrication, and have done a lot of demonstrations and experiments, they have not linked the magnetic nano-particle jet micro-lubrication with the grinding machine magnetic table, and no lubricant film has been established. The intrinsic relationship between the formation of magnetic nanoparticles and magnetic workbench, and the formation of oil film on the surface of magnetic nano-particles and magnetic table workpieces, and the inability to utilize the magnetic nanoparticle jets to lubricate the micro-grinding wheel/workpiece interface. Thermal advantages.

Summary of the invention

The object of the present invention is to solve the above problems, and to provide a magnetic nanoparticle jet and a magnetic worktable coupling oil film forming process and device, which utilizes the magnetic nanoparticle jet micro-lubrication in the field of grinding to be coupled with a magnetic worktable. The magnetic nanoparticle fluid is transported to the nozzle, and the magnetic nanoparticle fluid is sprayed to the grinding zone at a higher speed under the action of compressed air to form a lubricating oil film on the surface of the workpiece having the magnetic table, thereby maximizing the grinding processing region Cooling and lubrication.

To achieve the above object, the present invention adopts the following technical solutions:

A magnetic nanoparticle jet and a magnetic table coupled with an oil film forming device, comprising a magnetic working table, the workpiece is magnetically adsorbed thereon; the grinding wheel is disposed at a processing position of the workpiece, and the nozzle is mounted on the grinding wheel cover at a position matching the workpiece; The magnetic nano fluid delivery tube is connected to the magnetic nano fluid supply device, and is connected to the air compressor through the compressed air delivery tube; the magnetic nano fluid and the compressed air are mixed and accelerated in the nozzle to form a three-phase flow spray: compressed air, A mixed spray of magnetic nanoparticles and grinding fluid base oil particles; a three-phase flow spray enters a grinding zone between the workpiece and the grinding wheel, and the magnetic table is magnetically coupled with the three-phase flow spray to form an oil film on the surface of the workpiece.

The magnetic workbench is an electromagnetic workbench, which comprises a lower suction cup body and an upper cover plate; a heart is arranged in the suction cup body Body, the core is wound on the coil, and the coil is connected with the power control circuit; the cover plate is provided with a plurality of magnetism layers, and the cover plate is divided into a plurality of small blocks to form a distribution pattern between the N pole and the S pole, and the magnetic pole layer The majority of the magnetic lines of force are passed back through the workpiece to the suction cup body without being returned through the cover to form a complete magnetic circuit.

5nun。 The magnetic layer is made of a babbitt non-magnetic material, the width c is 2. 0-4. 5nun.

The total number of the N-pole block and the S-pole block is an odd number, each N-pole block, S-pole block is equal in width, and the N-end header width h, the N-pole block width 1 ₃ and the S-pole block width h ₂ exist. The following relationship, =丄^.

2

The power control circuit comprises a single-chip computer management unit, the single-chip computer management unit is connected with the optocoupler thyristor zero-crossing control AC switch unit, and the optocoupler thyristor zero-crossing control AC switch unit is connected with the rectification and filtering unit, and the rectification filter The unit is connected with the overload automatic protection unit, the overload automatic protection unit is connected with the arc-free voltage type switching control unit, and the arc-free voltage type switching control unit outputs the working voltage to the coil; the photoelectric coupling thyristor zero-crossing control AC switch unit and the communication The power transformer is connected, the AC power transformer is connected with the input end of the power frequency power supply; the single-chip computer management unit is also connected with the continuously adjustable voltage input control unit, the continuously adjustable voltage input control unit and the photoelectric coupling thyristor zero-crossing control AC switch unit Connection; The single-chip computer management unit is connected to the arc-free voltage type switching unit as a demagnetization circuit.

The distance d between the nozzle and the workpiece is 10-25 ctn, and the angle α between the nozzle and the workpiece is 15 ° -45 ° .

A film forming process of a magnetic nanoparticle jet and a magnetic table coupling oil film forming device, the steps of which are: Step 1: The magnetic working table adsorbs the workpiece on the surface thereof, and the grinding wheel is at a processing position above the workpiece; Step 2 At the beginning of the grinding, the nozzle sprays a three-phase flow formed by the magnetic nanofluid and the compressed air to a grinding zone between the workpiece and the grinding wheel;

Step 3: The magnetic field on the surface of the workpiece causes the magnetic nanoparticles to move along the magnetic lines of force, and the magnetic nanoparticles have an enhanced adsorption capacity on the surface of the workpiece; when the grinding wheel and the machined surface are rubbed, a tough physical adsorption oil film is formed;

Step 4: After the processing is completed, demagnetization of the magnetic table is performed.

The jet flow rate is 2. 5-5. 5 ml / min, and the compressed air pressure is 4. 0 - 10 bar.

The magnetic nano-fluid has a nanoparticle particle size of 100TM and a volume content of 1% to 30 vol%.

The invention has the following beneficial effects: it utilizes the magnetic field to adsorb the magnetic nanoparticles, and adsorbs the sprayed magnetic nano-fluid on the surface of the workpiece, thereby reducing the harm of the fine particles floating on the environment and the human body on the one hand, and strengthening on the other hand. The adsorption force of the nanoparticles on the surface of the workpiece makes it easier to form an oil film, which acts as a lubricant and heat sink. It has all the advantages of micro-lubrication technology. The surface of the workpiece coated with magnetic nanoparticles on the magnetic table has stronger cooling performance and excellent tribological characteristics, which effectively solves the grinding burn, improves the surface quality of the workpiece, and achieves high efficiency. Low-carbon, environmentally friendly, resource-saving, low-carbon green cleaner production is of paramount importance.

BRIEF DESCRIPTION OF THE DRAWINGS: Figure 1 is a perspective view of the final assembly of such an embodiment;

Figure 2 is a schematic diagram of the system of the liquid path and the gas path of this embodiment;

Figure 3 is a schematic view of the magnetic workbench deer through the embodiment;

Figure 4 is a structural view of a disk body of such an embodiment;

Figure 5 is a structural view of the cover of such an embodiment;

Figure 5a is a cross-sectional view taken along line Α-Λ of Figure 5;

Figure 5b is a cross-sectional view taken along line B-B of Figure 5;

Figure 5c is a cross-sectional view taken along line C-C of Figure 5;

Figure 5d is a cross-sectional view taken along line D-D of Figure 5;

Figure 6 is a block diagram showing the power control principle of the embodiment;

Figure 7 is a schematic view showing the relative position of the nozzle and the workpiece of the embodiment;

Figure 8 is a schematic view showing an oil film formed by general nanoparticle lubrication in this embodiment;

Figure 9 is a schematic view showing the oil film formed by the lubrication of magnetic nanoparticles under an external magnetic field in this embodiment:

Figure 10 is a graph showing the relationship between different lubrication conditions and friction coefficient in the experiment of this embodiment;

Figure 11 is a graph showing the relationship between different lubrication conditions and the diameter of the wear spot in the experiment of this embodiment;

Figure 12 is a graph showing the relationship between different lubrication conditions and the peak temperature of the grinding zone in the experiment of this embodiment;

Among them, 1-magnetic workbench, 2-workpiece, 3-wheel cover, 4-wheel, 5-magnetic nanofluidic tube, 6-compressed air delivery tube, 7-magnetic fixed suction cup, 8-nozzle, 9-cover , 10-sucker body, 11-heart, 12-coil, 13-magnet,

14-air compressor, 15-magnetic nanofluid storage tank, 16-filter I, 17-filter II, 18-hydraulic pump, 19-gas tank, 20-pressure gauge III, 21-pressure regulator II , 22-pressure regulator I, 23-throttle valve I, 24-throttle valve II, 25-turbine flowmeter I, 26-turbine flowmeter II, 27-pressure gauge II, 28-pressure gauge I, 29- Relief valve, 30-magnetic nano-fluid recovery tank, 31-N pole block, 32-S pole block, 33-N pole head plate, 34-N pole bar, 35-power frequency power input, 36- AC power transformer, 37 DC power supply, 38-working indicator light, 39-demagnetization switch, 40-single-chip computer management unit,

41-Opto-coupled thyristor zero-crossing control AC switch unit, 42-rectifier filter unit, 43-overload automatic protection unit. 44- No arc voltage polarity switching unit, 45-DC working voltage output terminal, 46-continuous Adjust the voltage input control unit.

detailed description:

The present invention will be described below with reference to the accompanying drawings:

As shown in the final assembly drawing of this embodiment of Fig. 1, this embodiment describes the process in the machining of the grinding machine. As can be seen from the figure, there is no fixture mounted on the magnetic table 1, and the workpiece 2 is fixed to the magnetic table 1 by electromagnetic attraction. The lubrication system uses a magnetic nanofluid micro-lubrication system, and the magnetic nanofluid and compressed air pass through the magnetic nanometer respectively. The fluid delivery tube 5 and the compressed air delivery tube 6 enter the nozzle 8 and are accelerated by mixing in the nozzle 8 to form a three-phase flow spray (compressed air, a mixed spray of solid magnetic nanoparticles and grinding liquid base oil particles). The three-phase flow spray injected in the nozzle 8 enters the ii §j zone between the workpiece 2 and the grinding wheel 4. The magnetic nanofluidic delivery tube 5 and the compressed air delivery tube 6 are fixed to the grinding wheel cover 3 by a magnetic fixing suction cup 7.

Figure 2 illustrates the liquid supply and air supply system of this embodiment. As can be seen from the figure, the gas routing air compressor 14, the filter I 16, the gas storage tank 19, the pressure regulating I 22, the throttling flow 23 and the turbine flow meter I 25 are connected in series and finally connected to the nozzle 8. The pressure gauge ΙΠ20 is used to monitor the pressure of the gas storage tank 19, and the pressure gauge 1 28 is used to monitor the gas outlet pressure to ensure the required air pressure. The liquid is composed of a main liquid circuit and a protection circuit, wherein the main liquid is routed to the magnetic nano fluid storage tank 15, the filter 11 17, the hydraulic pump 18, the pressure regulating valve 1121, the throttle valve II 24 and the turbine flow meter II 26 are sequentially connected. And finally connected to the nozzle 8. The pressure gauge Π 27 is used to monitor the liquid outlet pressure. The protection circuit consists of a relief valve 29 and a magnetic nanofluid recovery tank 30.

Figure 3 shows how the magnetic table works, based on the principle of electrical magnetic effects. The coil 12 is wound on a core body 11 which is laminated from a silicon steel sheet. When the coil 12 is energized, an electromagnetic iron with magnetic force is formed due to the principle of electromagnetic induction, and a magnetic pole distribution between the phases is formed on the surface of the cover plate 9. The magnetic flux passes through the core body 11 through the N-pole magnet block and the workpiece 2 on the cover plate 9, and is closed by the S-pole magnet block, the chuck body 10, and the core body 11 on the cover plate 9, and the workpiece 2 is sucked. The magnetic pole layer 13 is made of a babbitt non-magnetic material, and the width c is generally 2.0 - 4. 5mra. The magnetic insulating layer 13 divides the cover plate 9 into small pieces to form a distribution between the N pole and the S pole. form. The magneto-optical layer 13 allows most of the magnetic lines of force to pass back through the workpiece 2 to the chuck body 10 without going back through the cover plate 9 to form a complete magnetic circuit. When the current of the coil is increased, the strength of the magnetic field increases, and it can be seen that the magnetic lines of force are closed by the workpiece, so that the workpiece is magnetic.

4 is a structural view of the disk body of the embodiment. It can be seen from the figure that the table is a single-coil electromagnetic table, and the position of the coil can be seen therefrom, and the size of the center body 11 is d, X b, d, is the length of the heart, b, is the width of the heart; together with Figure 3, it can be known that after the coil is poured and dipped, it falls in the coil groove, the size of the coil groove is d ₂ X b ₂ , and d ₂ is the length of the groove , b ₂ is the slot width; the surrounding gap distance should have a gap of 3-8 cm as shown in a and b in Fig. 3, in order to water the asphalt, and there is also a slight gap between the coil 12 and the core 11. The size of the suction cup body is d _{: i} X b ₃ , which is the length of the suction cup body, and b ₃ is the width of the suction cup body. The size of the coil slot can be determined based on the number of turns of the coil being designed and the diameter of the wire. The internal thread distribution of the connection to the cover 9 is as shown.

Fig. 5 is a structural view of the cover plate of the embodiment. It can be seen that the N-pole block 31 and the S-pole block 32 are spaced apart from each other, and the middle portion is partitioned by the magnetism-extinguishing layer 13. Figure BB is a cross-sectional view of the N-pole block 31, Figure A-A is a cross-sectional view of the S-pole block 32, and DD is a cross-sectional view of the N-end tip plate 33, in which the full fill profile is a lead-plated process. It can be seen from the cross-sectional views that the N-pole block 31 is only connected to the chuck body 10, the S pole pole block 32 is only connected to the core body 11, and the middle is separated by the magnetism layer 13, and the N pole is The head plate 33, the N pole block 31, the S pole pole block 32, and the magnetism plate are sequentially connected to the N pole horizontal strip 34, so that the cover plate exhibits a magnetic pole distribution between the N pole and the S pole. The widths of the N pole block 31 and the S pole pole block 32 can be calculated according to the machine tool size when designing the machine tool, and the total number of the N pole pole block 31 and the S pole pole block 32 is 'odd, each N pole pole block 31, S pole pole The block 32 is equally wide, and the N-end header 33 has a width h, a N-pole block 31 width, and an S-pole block 32 width h ₂ . There is a relationship between h ₂ = h ₃ = _t . 6 is a block diagram of the power control principle of the embodiment, which is characterized in that it is managed by a single chip microcomputer, combined with photoelectric coupling, pulse width modulation, automatic control of the thyristor AC zero-crossing switch, and no arc spark voltage polarity switching.

The power control circuit includes a single-chip computer management unit 40. The single-chip computer management unit 40 is connected to the optocoupler thyristor zero-crossing control AC switch unit 41, and the optocoupler thyristor zero-crossing control AC switch unit 41 is connected to the rectification and filtering unit 42. The rectifying and filtering unit 42 is connected to the overload automatic protection unit 43, the overload automatic protection unit 43 is connected to the arcless voltage polarity switching unit 44, and the arcless voltage polarity switching unit 44 outputs the operating voltage to the coil; the optocoupler thyristor The zero-crossing control AC switch unit 41 is connected to the AC power transformer 36, and the AC power transformer 36 is connected to the power frequency power input terminal 35. The single-chip computer management unit 40 is also connected to the continuously adjustable voltage input control unit, and the continuously adjustable voltage input control is performed. The unit is connected to the optocoupler thyristor zero-crossing control AC switch unit 41; the single-chip computer management unit 40 is connected to the arc-free voltage polarity switching unit 44 as a demagnetization loop.

The circuit is provided with a continuously adjustable voltage input control unit module 46, which can continuously adjust the output DC voltage according to the mode of the single-chip computer management unit 40. It can be input in the external operation panel of the single-chip computer management unit 40. The required DC voltage value. The change of the DC voltage causes the current to change accordingly, which eventually causes the magnetic field strength of the magnetic table to change, thereby affecting the film formation and cooling characteristics of the magnetic nanojet. After the end of the processing, the power supply is stopped, and the demagnetization switch 39 is connected, and the DC electrode polarity converted by the rectifying and filtering unit 42 can be reversed by the arcless spark voltage polarity switching unit 44. Thereby, the workbench is reversely powered to achieve the purpose of demagnetization, as described in the specific process below.

The specific working process of this program is as follows - micro-lubrication is a lubrication technology that has been formed in recent years and is gradually recognized and used by people. The micro-lubrication grinding process is a cooling lubrication method in which compressed air is mixed with a trace amount of grinding fluid, atomized by an atomizing nozzle, and sprayed into a grinding zone. The micro-lubrication processing mode minimizes the use of grinding fluid, thereby effectively reducing the impact of the grinding fluid on the environment and human health. It is a pollution-free, environment-friendly green manufacturing technology. However, micro-lubrication is often accompanied by unsatisfactory surface quality and even burns. For this reason, some scholars have added nano-particles to the grinding fluid according to the theory of enhanced heat transfer. This has led to nano-minor lubrication, which has largely solved the above problems. However, in the grinding process, the energy consumed to remove the unit material volume is much larger than other cutting methods, and a large amount of heat is generated in the grinding zone. Excessively high grinding zone temperature will not only affect the quality of the machined surface and the service life of the grinding wheel, but also affect the performance of the lubricating fluid. ring.

When the temperature rises, the viscosity of the grinding fluid is reduced, which affects the forming ability of the grinding fluid on the machined surface and reduces the thickness and load bearing capacity of the lubricating oil film. Since the viscosity of the grinding fluid reduces the fluidity, when the grinding wheel comes into contact with the surface of the workpiece, the oil film is easily damaged. After the oil film is damaged, the grinding wheel will form a direct contact friction with the surface of the workpiece, so that the temperature of the grinding zone will rise sharply, which is very unfavorable for the grinding process, and will form a high temperature, the viscosity of the grinding fluid is lowered, and the temperature is further increased. Further reduce the vicious circle.

In order to solve the above problems of nano-micro-lubrication, the present invention proposes to add magnetic nano-particles (magnetic particles which can be magnetically guided by an external magnetic field) to a grinding fluid, form a micro-magnetic fluid, and interact with a magnetic workbench. Coupling, a technical method of forming an oil film with good lubrication and heat dissipation properties on the machined surface.

With the development of nanomaterials, there are many kinds of magnetic nanoparticles used in research, including Y-Fe ₂ 0 ₃ nanoparticles, Fe ₃ 0., nanoparticles, Fe ₃ N ₄ nanoparticles, Fe-Co nanoparticles, Ni-Fe nanoparticles, MnZnFe ₂ 0 ₄ nanoparticles, and the like.

The magnetic nanofluid (the mixed solution of the magnetic nanoparticles in a certain ratio with the grinding base liquid) flows through the liquid path into the nozzle 8, while the compressed gas flows through the gas path into the nozzle 8. The magnetic nanofluid and the compressed air are accelerated by mixing in the nozzle 8, and then ejected. According to the empirical nozzle 8 and the workpiece 2 distance d is 10-25cm, the nozzle angle α is set to 15 ° -45 °, the relative position of the nozzle 8 and the workpiece 2 is shown in Figure 7. The injection flow rate of the nozzle 5 is 2. 5-5. 5 ml/min, and the pressure of the compressed air is 4. 0_10 bar. The nanoparticles have a particle size of 100 nm and a volume content of 1% to 30 vol%.

It is known that the average suction force F of the magnetic table in this embodiment is 10 kg/cm ² , the minimum suction force is 7 kg/cm ² and the maximum suction force is 13 kg/cm ² , the number of turns of the coil is 2700 匝, and the diameter of the copper wire is 1. The film has a diameter of 1.67mm. The workbench material is quenched Q235 steel, and the magnetic insulation layer material is babbitt alloy. And the magnetic field strength of the table can be changed by the change of voltage, as follows.

According to Ohm's law of magnetic circuit:

The magnetic potential (amperes) is the product of the current I and the number of turns w, that is, H is the magnetic field (amperes / cm ² ), / is the length of the magnetic circuit. Formula 5

10 ⁸ , where Β is the magnetic induction (Gauss) and μ is the permeability (Heng/cm). Therefore, it can be seen that 5 = ^/ χ10 ⁸ , that is, the current I is proportional to the magnetic induction Β. It can be seen that changing the magnitude of the current in the magnetic circuit can change the magnitude of the magnetic induction, thereby ensuring the coupling of the required magnetic field strength with the magnetic nanoparticles.

According to Maxwell's law: _r , B ² lS

F

2〃 ₀

Where F is the electromagnetic attraction (Joules/cm), B is the magnetic induction (Weber/cm ² ), and S is the total surface area of the magnetic pole (cm ² ), μ. Air permeance coefficient (1. 25 X 10- ⁸ H / cm), Β kg when F is gravity gauss, S = l

B

Bring in and export E : V

5000 .

In summary, you can derive F : 丄 , from which you can see the relationship between current and table suction, with electricity

The 5000-flow increase table suction increases.

When considering the magnetic circuit air gap, use the modified public:

For the air gap length (cm), a is the dressing factor (about 3-5). Assume that the workpiece and table air gap is = _0.015 _cm , δ _Ύ =0. 015cm, then the total air gap length is = 2^+ ^ =0. 06cm take a=3 can be 'calculated

B = ^([ +S 0 ^( 0 = + l ^ 3 Ox. C=17175. 5640 Gauss, according to the conversion relationship, it is equal to

1717. 55,640 millitesla. This value is the average magnetic induction of the surface of the table. After the surface of the work surface is added to the surface of the workpiece, the magnetic induction of the surface of the workpiece is drastically reduced, and the material of the workpiece is diversified. The magnetic induction of the surface of the workpiece is not easy to calculate. Between millitesla. In summary, we can adjust the supply voltage to change the current, and then change the magnetic field strength of the workpiece surface to obtain the desired adsorption force to improve the lubrication and cooling performance.

When the nozzle sprays the three-phase flow and sprays it on the surface of the workpiece in the grinding zone, due to the presence of a magnetic field on the surface of the workpiece, the magnetic nanoparticles will move along the magnetic field line under the action of the magnetic field, and this movement will increase the flow resistance of the suspended particles, thereby performing For the increase in viscosity, non-Newtonian properties are presented. The cause of this increase in viscosity is the friction between the solid phase particles and the base liquid. Magnetic particles are subjected to magnetic moments and viscosity moments in an applied magnetic field. In the mortar, it is found that the increase of the applied magnetic field strength increases the viscosity of the magnetic lubricating film, and the viscosity of the magnetic lubricating film increases when the mass fraction of the magnetic nanoparticles is increased.

The increase in the viscosity of the grinding fluid will greatly affect the film forming ability, film formation, oil film thickness and oil film carrying capacity of the grinding fluid. At the same time, it will increase the adsorption capacity of nanoparticles on the surface of the workpiece, which will reduce the dispersion of nanoparticles and base oil particles due to the action of compressed air. In the traditional nanoparticle micro-lubrication, we found that when the nano-spray is sprayed on the surface of the workpiece, it will be blown away by the compressed gas to form a corrugated surface, the distribution is not uniform enough, and even some nanoparticles and base oil particles are blown out. The surface forms suspended particles in the surrounding air, which is very detrimental to the formation of the oil film, the environment and the health of the operator. However, under the action of the magnetic field on the surface of the workpiece, the magnetic nanoparticles will obviously enhance the adsorption capacity, which is beneficial to the uniform deposition of the nanoparticles, which greatly reduces the amount of scattering and improves the performance of the oil film.

In the general nano-slight lubrication, the distribution of the nanoparticles in the formed lubricating film is shown in Fig. 8. The oil film formed by the lubrication of the magnetic nanoparticles under the action of an external magnetic field is shown in Fig. 9. From the comparison of Fig. 9 and Fig. 8, it can be found that the oil film formed by the magnetic nanoparticle under the action of an external magnetic field is thicker than the general nano-fine lubricating oil film, and the magnetic nanoparticle is more easily enriched in the processing surface (when magnetic nanometer When the particle content is high, a magnetic flux can be formed on the surface of the workpiece. Therefore, the number of nanoparticles adsorbed on the processed surface is significantly larger than that of the nano-fine lubricant in the general nano-lubrication. Moreover, these magnetic nanoparticles are directly adsorbed on the surface of the workpiece, and the adsorption is very strong under the action of an external magnetic field. Therefore, when the grinding wheel and the machined surface are rubbed, the magnetic nano-particles under the action of an external magnetic field are more likely to produce a tough physical adsorption film, and the nano-particle content in the adsorption film is relatively high, so that the strength is higher. Cooling capacity.

Through the above analysis, we can find that the micro-lubrication of magnetic nanoparticles under the action of external magnetic field not only has all the advantages of micro-lubrication of general nano-particles, but also increases the thickness, hardness, and heat-dissipating ability of the oil film. In addition, under the action of an external magnetic field, the magnetic grinding fluid is fixed between the grinding wheel and the machined surface, and will not be seriously lost under the action of the tangential force, thus avoiding the loss of lubricating oil in the friction system. . At the same time, the dispersion of the magnetic spray is effectively controlled, which greatly reduces the content of suspended particles in the working environment, which is very beneficial to the health of the operator and the protection of the environment.

Moreover, since the magnetic nanoparticles have a very small particle size, they have no magnetic domain walls and have high saturation magnetization. The coercive force is zero and superparamagnetic. When there is an applied magnetic field during processing, the magnetism is immediately displayed, and the oil film is adsorbed on the surface of the workpiece, and after being ground by the grinding wheel, it will be adsorbed on the table and will not be scattered. However, when the finished table is demagnetized, its magnetic properties will disappear immediately, which is very beneficial for the cleaning of the workpiece and the working table.

Experimental verification and results analysis of this example - The surface grinding of 45 steel was carried out with the following parameters: grinding wheel speed 30 tn / _S , workpiece feed speed 0. 05 m / s, grinding depth 30 μ m, trace The lubrication nozzle flow rate is 2. 6 inl/min, and the compressed air pressure is 6 bar. In the experiment, a corundum grinding wheel was used, and the average grain size of the abrasive grains was 508 μm. The grinding fluid base oil used in the experiment was soybean oil (vegetable oil). The Mn content is 0. 50-0. The content of the carbon is 0. 42-0. 50%, the content of Si is 0. 17-0. 37%, Mn content 0. 50-0 25%。 The content of the content of 0. 25%.

Tested under four lubrication conditions, working condition 1 using a small amount of carbon nanotubes with a mass fraction of 3%, working condition 2 Minimal lubrication of MriZnFeA nanoparticles with a mass fraction of 3%, magnetic induction intensity of 12 mtesla on the surface of the workpiece, and micro-lubrication of MnZnFeA nanoparticles with a mass fraction of 6%. The magnetic induction intensity of the workpiece surface is 12 mtesla. Condition 4 uses a small amount of MnZnFe nanoparticles with a mass fraction of 6% for lubrication. The surface of the workpiece has a magnetic induction of 26 millitesla. The friction coefficient, the wear spot diameter and the peak temperature of the grinding zone were calculated under four different lubrication conditions.

As shown in Fig. 10, the friction coefficients under the four operating conditions are 0.41, 0.35, 0.229 and 0.24, respectively. As shown in Fig. 11, the diameters of the wear spots are 1. 25 ram, 0.85 mm, 0.71 and 0. 51⁄2 m, respectively. As shown in Figure 12, the peak temperatures in the grinding zone are 158 ° C, 139 ° C, 128 ° C and 117, respectively. C.

Through the comparison of the data of working condition 1 and working condition 2, it is found that the magnetic nano-particles under the action of external magnetic field as mentioned above are slightly lubricated, which shows better anti-wear and anti-wear and heat dissipation compared with the general nano-particle micro-lubrication. Characteristics. The reason is that magnetic nanoparticles can be adsorbed on the machined surface more quickly under the action of magnetic force, and are very strong and a large number, so that a relatively thick and tough lubricating film can be formed.

Comparing the data of working condition 2 and working condition 3, it is found that the magnetic nano-particles with larger mass fraction have better micro-lubrication effect when the magnetic induction intensity of the workpiece surface is the same. The reason is that a relatively large number of magnetic nanoparticles can be sufficiently adsorbed on the machined surface to form a thick and tough oil film. However, if the mass fraction continues to increase when it exceeds 18%, the surface quality of the processed surface decreases (generally less than 10%) because the excessive magnetic nanoparticles cause the particle spacing to be too small to agglomerate. After agglomeration, larger particles are formed, which acts as abrasive particles during the grinding process and destroys the machined surface.

Comparing the data of working condition 3 and working condition 4, it is found that when the mass fraction of magnetic nanoparticles is the same, the higher the magnetic induction intensity of the workpiece surface, the stronger the oil film formed and the better the heat dissipation. This indicates that the strengthening of the external magnetic field is advantageous for the magnetic nanoparticles to be more strongly adsorbed on the processing surface, thereby forming an oil film with excellent performance. However, as the magnetic field strength increases further (generally over 68 mT), the magnetic nanoparticles will hard agglomerate under the action of the magnetic field force, which will reduce the surface quality of the workpiece.

Claims

Claim

- ί. A magnetic rice particle jet and a magnetic table coupling oil film forming device, characterized in that it comprises a magnetic working table on which a workpiece is magnetically attracted; a grinding wheel is disposed at a processing position of the workpiece, and the nozzle is mounted on the grinding wheel cover a position to cooperate with the workpiece; the nozzle is connected to the magnetic nanofluid liquid supply device through the magnetic nano fluid delivery tube, and is connected to the air compressor through the compressed air delivery tube; the magnetic nano fluid and the compressed air are mixed and accelerated in the nozzle to form a three-phase flow Spray: a mixed spray of compressed air, magnetic nanoparticles and grinding fluid base oil particles; a three-phase flow spray into the grinding zone between the workpiece and the grinding wheel, the magnetic table is magnetically coupled to the three-phase flow spray, on the surface of the workpiece An oil film is formed.

2 . The magnetic nanoparticle jet and magnetic table coupled oil film forming apparatus according to claim 1 , wherein the magnetic working table is an electromagnetic working platform, and comprises a lower suction cup body and an upper cover plate; The body is provided with a heart body, the core is wound with a coil, and the coil is connected with the power control circuit; the cover plate is provided with a plurality of magnetic layers, and the cover plate is divided into a plurality of small blocks, and a distribution pattern between the drain and the S pole is formed. The magneto-optical layer causes most of the magnetic lines of force to pass back through the workpiece to the suction cup body without being returned through the cover to form a complete magnetic circuit.

0-4. The magnetic layer is made of a non-magnetic material of the babbitt alloy, the width c is 2. 0-4. 5tnm.

The apparatus for forming a magnetic nanoparticle jet and a magnetic table coupling oil film according to claim 2, wherein the total number of the N-pole block and the S-pole block is an odd number, and each of the N-pole block and the S-pole block has the same width. , and the N-end header width h, the N-pole width 13⁄4 and the S-pole width h ₂ have the following relationship, = = .

2

5 . The magnetic nanoparticle jet and magnetic table coupled oil film forming apparatus according to claim 2 , wherein the power control circuit comprises a single-chip computer management unit, the single-chip computer management unit and the optocoupled thyristor The zero-control AC switch unit is connected, the optocoupler thyristor zero-crossing control AC switch unit is connected with the rectification and filtering unit, the rectification and filtering unit is connected with the overload automatic protection unit, and the overload automatic protection unit is connected with the arc-free voltage polarity control unit, The arc voltage polarity switching control unit outputs the working voltage to the coil; the photoelectric coupling thyristor zero-crossing control AC switch unit is connected with the AC power transformer, and the AC power transformer is connected with the power frequency power input end; the single-chip computer management unit is also continuous with The voltage regulating input unit is connected, the continuously adjustable voltage input control unit is connected with the optocoupler thyristor zero-crossing control AC switch unit; the single-chip computer management unit is connected with the arc-free voltage polarity switching unit as a demagnetization loop.

6 . The magnetic nanoparticle jet and the magnetic table coupling oil film forming device according to claim 1 , wherein the distance d between the nozzle and the workpiece is 10-25 cm, and the angle α between the nozzle and the workpiece is 15° -45. ° .

A film forming process for a magnetic nanoparticle jet and a magnetic table coupled oil film forming apparatus according to any one of claims 1 to 6, wherein the steps are:

Step one, the magnetic workbench adsorbs the workpiece on the surface thereof, and the grinding wheel is in the processing position above the workpiece; Step two, at the beginning of the grinding, the nozzle sprays a three-phase flow formed by the magnetic nano-fluid and the compressed air to the grinding zone between the workpiece and the grinding wheel;

Step 3, the magnetic field on the surface of the workpiece causes the magnetic nanoparticles to move along the magnetic lines of force, and the magnetic nanoparticles have an enhanced adsorption capacity on the surface of the workpiece; when the grinding wheel and the machined surface are rubbed, a strong physical adsorption oil film is formed;

The film-forming process according to claim 7, wherein the nozzle injection flow rate is 2. 5-5. 5rnl/min, and the pressure of the compressed air is 4. 0-10 bar.

The film forming process according to claim 7, wherein the magnetic nanofluid has a particle diameter of 100 nm and a volume content of 1% to 30 vol%.