CN113070481B - Method for preparing metal powder by cavitation jet assisted arc micro-explosion and metal powder - Google Patents

Abstract

The invention relates to a method for preparing metal powder by cavitation jet assisted arc micro-explosion and the metal powder. The method comprises the steps of respectively connecting a flushing electrode and a workpiece with two poles of a power supply, adjusting the distance between the flushing electrode and the workpiece, and generating arc plasma in a discharge gap between the flushing electrode and the workpiece to enable a part of the workpiece to be molten; the liquid flushing electrode is provided with a variable-section flow passage, liquid flushing fluid is introduced from the variable-section flow passage, cavitation bubbles are generated in the process that the liquid flushing fluid flows through the variable-section flow passage, and the cavitation bubbles grow and collapse along with the flowing of the liquid flushing fluid to the workpiece; controlling the flow rate of the flushing fluid and the relative rotation speed of the flushing electrode and the workpiece, and under the impact force of the collapse of cavitation bubbles, enabling the arc plasma to deviate and break the arc to generate micro explosion, refining the melted workpiece in the explosion, condensing in the flushing fluid and collecting powder. Compared with the traditional electric arc micro-explosion powder making method, the method disclosed by the invention has the advantages that the cavitation jet technology is applied to the preparation of metal powder, the processing efficiency is improved, and the powder particle size is further refined.

Description

Method for preparing metal powder by cavitation jet assisted arc micro-explosion and metal powder

Technical Field

The invention relates to the field of preparation of metal powder, in particular to a method for preparing metal powder by cavitation jet auxiliary arc micro-explosion.

Background

Cavitation jet is a continuous jet that naturally produces cavitation bubbles in the jet. Currently, cavitation jets are used relatively widely in the cleaning field. The cavitation jet cleaning technology has the advantages of high efficiency, cleanness and safety, and has wide application in cleaning ships, power station boilers, heat exchangers, urban underground drainage pipelines and the like. The cavitation jet cleaning technology has the principle that: cavitation bubbles formed by cavitation can cause liquid to be discontinuous macroscopically, and when fluid containing the cavitation bubbles flows through a region with higher pressure, the cavitation bubbles collapse. In the cavitation process, cavitation bubbles are continuously generated, expanded and then rapidly collapsed, extremely high pressure and high-speed jet flow are generated in a local area in liquid flow, the cavitation bubbles collapse near a solid wall surface, and the wall surface can be repeatedly impacted by huge pressure, so that the removal of wall surface stains is initiated, and the cleaning is realized.

Patent 201911082177.X proposes a preparation method of novel spherical powder, which adopts an arc micro-explosion powder process technology to prepare spherical powder. Although the prepared spherical powder has low content of hollow powder and satellite powder, the powder preparation efficiency is higher, and the powder particle size is smaller. There is still a need to further explore the preparation method of powder with higher pulverizing efficiency and smaller particle size.

Disclosure of Invention

The invention provides a method for preparing metal powder by cavitation jet assisted arc micro-explosion by applying a cavitation jet technology to the preparation of metal powder. Compared with the traditional electric arc micro-explosion powder making method, the processing efficiency is improved, and the powder particle size is further refined.

The technical proposal is as follows:

a method for preparing metal powder by cavitation jet assisted arc micro-explosion comprises the following steps:

respectively connecting a flushing electrode and a workpiece with two poles of a power supply, adjusting the distance between the flushing electrode and the workpiece, and generating arc plasma in a discharge gap between the flushing electrode and the workpiece to enable a part of the workpiece to be molten;

the liquid flushing electrode is provided with a variable-section flow passage, liquid flushing fluid is introduced from the variable-section flow passage, cavitation bubbles are generated in the process of flowing through the variable-section flow passage, and the cavitation bubbles grow and collapse along with the flowing of the liquid flushing fluid to the workpiece;

controlling the flow speed of the flushing fluid and the relative rotation speed of the flushing electrode and the workpiece, enabling the arc plasma to deviate and break under the impact force of collapsing of the cavitation bubbles to generate micro explosion, refining the melted workpiece in the explosion, condensing in the flushing fluid and collecting powder.

In one embodiment, along the flow direction of the flushing fluid, the variable cross-section flow channel comprises an inlet section and a throat section which are connected in sequence; from the inlet section to the throat section, the size of the variable cross-section flow passage is narrowed, and the size of the variable cross-section flow passage satisfies: after the flushing fluid flows from the inlet section into the throat section, a first low-pressure area can be formed in the throat section, and the pressure of the first low-pressure area is smaller than the saturated vapor pressure of the flushing fluid.

In one embodiment, the radial cross-sectional area of the throat section is 0.2-0.8 times the radial cross-sectional area of the inlet section.

In one embodiment, the variable cross-section flow channel further comprises an outlet section downstream of and connected to the throat section, the variable cross-section flow channel widening in size from the throat section to the outlet section, and the variable cross-section flow channel having a size that satisfies: after the flushing fluid flows from the throat section into the outlet section, a second low pressure zone can be formed in the outlet section, and the pressure of the second low pressure zone is also smaller than the saturated vapor pressure of the flushing fluid.

In one embodiment, the radial cross-sectional area of the throat section is 0.2-0.8 times the radial cross-sectional area of the outlet section.

In one embodiment, the flushing fluid is a liquid medium.

In one embodiment, the method further comprises the step of introducing the flushing fluid from outside the flushing electrode in addition to introducing the flushing fluid from the variable cross-section flow channel.

In one embodiment, the workpiece is immersed in a fluid medium, which is a liquid medium.

In one embodiment, the power source is a pulsed power source.

In one embodiment, the rinse electrode is connected to an anode of a power source and the workpiece is connected to a cathode of the power source.

In one embodiment, the distance between the flushing electrode and the workpiece is 0.1mm-100mm;

when the flushing fluid is introduced, the flow speed of the flushing fluid is 20L/min-50L/min, and the pressure of the flushing fluid is 2Mpa-10Mpa;

the rotating speed of the flushing electrode relative to the workpiece is 100r/min-60000r/min.

The invention also provides the metal powder prepared by the method.

Compared with the prior art, the invention has the following beneficial effects:

the invention tries to apply cavitation jet technology to the preparation of metal powder by arc micro-explosion, cavitation bubbles are generated in a variable-section flow passage of a flushing fluid flowing through a flushing electrode, and grow and collapse along with the flowing of the flushing fluid to a workpiece. When cavitation bubbles exist in a discharge gap between a flushing electrode and a workpiece, arc plasma is easier to break through flushing fluid containing the cavitation bubbles to discharge, so that the powder preparation efficiency is improved, in addition, when cavitation bubbles collapse along with the increase of the pressure of surrounding fluid, instantaneous high energy is generated, the flowing of the flushing fluid is promoted, the phenomenon of unsmooth flushing is improved, the powerful impulsive force of a discharge gap is maintained, the effective flushing specific gravity of the flushing electrode is greatly improved, molten metal generated by processing in a powder preparation area can be efficiently flushed, powder is rapidly discharged, the accumulation of metal powder in the discharge gap is reduced, the electrode loss non-uniformity and the short circuit phenomenon caused by sustainable discharge of the accumulated powder are avoided, the better cooling effect is realized, the arc discharge processing efficiency is improved, meanwhile, the impact of shock waves and micro-jet impact are generated due to the collapse of the cavitation bubbles, the synergistic effect on a fluid arc breaking mechanism is further refined, and the particle size of the powder is further facilitated. In addition, when the traditional electric arc micro-explosion technology is used for preparing metal powder, because the discharge area is usually concentrated at the edge of the flushing electrode and is not the middle area for flowing out flushing fluid, the melting pits of the workpiece are also concentrated at the corresponding positions of the edge of the flushing electrode, the melting pits of the non-discharge area in the middle of the flushing electrode are fewer, the problem of uneven distribution of the melting pits occurs, the workpiece needs to be continuously moved on X, Y and Z axes, the powder preparation efficiency is reduced, and the cavitation jet assisted electric arc micro-explosion preparation method of the invention ensures that electric arcs can easily break through mixed gas-liquid media, ensures that the melting pits are uniformly distributed, reduces the frequency of moving the workpiece on X, Y and Z axes and improves the powder preparation efficiency.

Drawings

FIG. 1 is a schematic diagram of the operation of a liquid-filled electrode according to one embodiment;

FIG. 2 is a top view of a liquid-filled electrode according to one embodiment;

FIG. 3 is a schematic diagram of the operation of the liquid-filled electrode according to one embodiment;

FIG. 4 is a top view of a liquid-filled electrode according to one embodiment;

FIGS. 5 (a) - (d) are top views of the electrodes of different embodiments, respectively;

FIGS. 6 (a) - (b) are schematic illustrations of connection of the throat sections of the electrodes of different embodiments;

FIG. 7 is a schematic diagram of a structure of a liquid-filled electrode according to one embodiment;

FIG. 8 is a schematic diagram of the preparation of metal powder using cavitation jet assisted arc micro-blasting;

FIG. 9 is an SEM image of the powder prepared according to example 1;

fig. 10 is a schematic diagram of the operation of the flooded electrode of comparative example 1.

The reference numerals are explained as follows:

101: conductive material, 102: inlet section, 103: throat segment, 104: outlet section, 105: workpiece, 201: conductive material, 202: inlet section, 203: throat segment, 204: outlet section, 205: workpiece, 301: conductive material, 302: inlet section, 303: throat segment, 304: outlet section, 401: conductive material, 402: inlet section, 403: throat segment, 404: outlet section, 501: conductive material, 502: inlet section, 503: throat segment, 504: outlet section, 601: conductive material, 602: inlet section, 603: throat segment, 604: outlet section, 701: conductive material, 702: inlet section, 703: throat segment, 704: outlet section, 802: inlet section, 804: outlet section, 806: flow-blocking piece, 808: threads, 809: card slot, 902: inlet section, 904: outlet section, 906: flow-blocking piece, 907: snap ring, 1101: conductive material, 1102: inlet section, 1104: outlet section, 1105: workpiece, 110: a drain groove.

Detailed Description

The present invention will be described in further detail with reference to specific examples. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present invention.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.

In the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.

In the present invention, unless expressly stated or limited otherwise, a first feature "up" or "down" a second feature may be the first and second features in direct contact, or the first and second features in indirect contact via an intervening medium. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.

It will be understood that when an element is referred to as being "fixed" or "disposed" on another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," and the like are used herein for illustrative purposes only and are not meant to be the only embodiment.

It will be further understood that when interpreting the connection or positional relationship of elements, although not explicitly described, the connection and positional relationship are to be interpreted as including the range of errors that should be within an acceptable range of deviations from the particular values as determined by those skilled in the art. For example, "about," "approximately," or "substantially" may mean within one or more standard deviations, and is not limited herein.

Referring to fig. 1, a schematic diagram of the working condition of a liquid-flushing electrode according to an embodiment is shown, the liquid-flushing electrode is integrally formed by adopting a conductive material 101, and the conductive material 101 is graphite, so that the conductivity of the electrode can be effectively ensured, and the conductivity stability of the liquid-flushing electrode can be ensured. The outer periphery of the end of the flushing electrode at the outlet section 104 is provided with a chamfer, the flushing electrode is provided with a variable-section flow channel for the flushing fluid to flow, and the flushing fluid flows along the variable-section flow channel to the workpiece 105. Along the flowing direction of the flushing fluid, the variable cross-section flow channel comprises an inlet section 102, a throat section 103 and an outlet section 104 which are sequentially connected; fig. 2 shows a top view of the flushing electrode (chamfer not shown) of the present embodiment, the flushing electrode is cylindrical as a whole, the inlet section 102, the throat section 103 and the outlet section 104 are all circular, and the inlet section 102, the throat section 103 and the outlet section 104 are distributed along the central axis. In the specific example shown in fig. 1 and 2, the inlet section 102, the throat section 103 and the outlet section 104 are connected directly in this order.

From the inlet section 102 to the throat section 103, the size of the variable cross-section flow passage narrows, and the size of the variable cross-section flow passage satisfies: after flowing into the throat section 103 from the inlet section 102, the flushing fluid can form a first low pressure zone in the throat section 103, and the pressure of the first low pressure zone can be made to be less than the saturated vapor pressure of the flushing fluid.

In the above-mentioned special structure of the flushing electrode, after the flushing fluid flows into the throat section 103 from the inlet section 102, because the radial cross-sectional area of the throat section 103 is smaller than the radial cross-sectional area of the inlet section 102, the flow velocity of the flushing fluid is increased, the fluid flow velocity is increased, the pressure is reduced, a first low-pressure area is formed in the throat section 103, the radial cross-sectional areas of the throat section 103 and the inlet section 102 are controlled, the pressure of the first low-pressure area can be regulated, when the pressure of the first low-pressure area is smaller than the saturated vapor pressure of the flushing fluid at the temperature, cavitation bubbles (or referred to as gas core) mainly containing vapor can appear in the flushing fluid or on the liquid-solid interface, along with the flowing of the flushing fluid to the outlet section 104, the cavitation bubbles also flow to the outlet section 104 and continuously grow, when the cavitation bubbles are discharged from the outlet section 104, the cavitation bubbles collapse to generate instantaneous high energy to promote the flowing of the flushing fluid, the phenomenon of flushing fluid is improved, the powerful impulsion of the discharge gap is maintained, the effective flushing fluid specific gravity of the flushing electrode is greatly improved, the metal produced by high-efficiency flushing processing, the electric discharge machining efficiency is improved, and the electric arc machining efficiency is improved.

From the throat section 103 to the outlet section 104, the size of the variable-section flow passage becomes wider, and the size of the variable-section flow passage satisfies: after flowing from the throat section 103 into the outlet section 104, the second low pressure zone can be formed in the outlet section 104 and the pressure in the second low pressure zone can also be made less than the saturated vapor pressure of the flushing fluid.

After the flushing fluid flows into the outlet section 104 from the throat section 103, the radial cross-sectional area of the outlet section 104 is larger, the flow velocity of the flushing fluid flowing out of the center of the throat section 103 is large, the flow velocity of the flushing fluid flowing out of the edge of the throat section 103 is split, the flow velocity is reduced, vortex flow appears in the area of the flushing fluid flowing out of the edge of the throat section 103 and the inner side wall of the outlet section 104 due to the change of the flow velocity, a second low-pressure area is formed under the action of the vortex flow, the radial cross-sectional areas of the throat section 103 and the outlet section 104 are controlled, the pressure of the second low-pressure area can be regulated, when the pressure of the second low-pressure area is smaller than the saturated vapor pressure of the flushing fluid under the temperature, cavitation bubbles mainly of vapor can appear in the flushing fluid or on a liquid-solid interface, the cavitation bubbles continuously grow, and along with the flushing fluid discharged from the outlet section 104, the cavitation bubbles collapse, instant high-energy is generated to further promote the flowing of the flushing fluid, the phenomenon of the flushing fluid is further improved, and the electric arc machining efficiency is further improved.

It will be appreciated that variations in the radial cross-sectional area of the inlet section 102 and throat section 103 will cause variations in the velocity of the flushing fluid which will cause variations in the pressure in the first low pressure region of the throat section 103, thereby affecting the efficiency and size of cavitation bubbles formation. In one preferred embodiment, the radial cross-sectional area of throat section 103 is 0.2-0.8 times the radial cross-sectional area of inlet section 102. In one of the more preferred embodiments, the radial cross-sectional area of the throat section 103 is 0.4-0.7 times the radial cross-sectional area of the inlet section 102.

It will be appreciated that a change in the size of the radial cross-sectional areas of the throat section 103 and the outlet section 104 will cause a change in the velocity of the flushing fluid and thus a change in the pressure in the second low pressure zone of the outlet section 104, thereby affecting the efficiency and size of cavitation bubbles formation. In one preferred embodiment, the radial cross-sectional area of the throat section 103 is 0.2-0.8 times the radial cross-sectional area of the outlet section 104. In one of the more preferred embodiments, the radial cross-sectional area of the throat section 103 is 0.4-0.7 times the radial cross-sectional area of the outlet section 104.

It will be appreciated that in another embodiment, as shown in fig. 3, the operation of the flushing electrode is that the flushing electrode is integrally formed by using the conductive material 201, the periphery of the end portion of the flushing electrode, which is located at the outlet section 204, is provided with a chamfer, and the flushing electrode is provided with a variable-section flow channel for flowing flushing fluid, and the flushing fluid flows to the workpiece 205 along the variable-section flow channel. Along the flowing direction of the flushing fluid, the variable cross-section flow passage comprises an inlet section 202, a throat section 203 and an outlet section 204 which are sequentially connected; the throat section 203 is provided with a plurality of diversion channels, and the flushing fluid enters the outlet section 204 from the inlet section 202 through the plurality of diversion channels, and the cavitation bubbles are generated and collapsed in the same principle as in the above-described embodiment.

The distribution mode of the throat section 203 is controlled, so that the efficiency and the size of cavitation bubbles generated by the throat section 203 and the distribution density of cavitation bubbles of the outlet section 204 can be adjusted, and the stability of auxiliary arc processing of the flushing electrode is ensured.

It will be appreciated that in other embodiments, as shown in fig. 4, the top view of the liquid-flushing electrode is formed by integrally forming the conductive material 301, the throat section 303 is provided with a plurality of diversion channels, and the outlet section 304 is provided with a plurality of diversion channels, and each diversion channel of the throat section 303 and the outlet section 304 corresponds to each other.

It will be appreciated that as shown in fig. 5 (a) - (d), there are top views of the wetted electrodes of the different embodiments, respectively. The radial cross-sectional shapes of the inlet sections 402-702, the throat sections 403-703 and the outlet sections 404-704 can be selected according to practical requirements, and can be respectively and independently selected from circular, elliptical, regular polygonal or irregular shapes, so as to meet different use requirements. The structure of the liquid-filled electrode according to the present invention includes, but is not limited to, the structure shown.

It will be appreciated that, as shown in fig. 6 (a) - (b), the connection modes of the throat sections of the liquid-flushing electrode according to the different embodiments are respectively shown, and an axially penetrating flow blocking piece 806 or 906 may be further disposed in the liquid-flushing electrode, where the flow blocking piece 806 divides the variable-section flow channel into an inlet section 802, a throat section and an outlet section 804. The flow blocker 906 divides the variable cross-section flow passage into an inlet section 902, a throat section and an outlet section 904.

It will be appreciated that the spoilers 806 or 906 may be obtained by stitching. The splicing mode can be a mode of threads, clamping rings, clamping grooves, bonding or the like. The flexibility of throat section position has been improved in this kind of setting, has guaranteed the stability of cavitation bubble production efficiency. For example: the flow blocking piece 906 is spliced by a snap ring 907. The flow blocking member 806 is spliced by threads 808. Alternatively, the spoilers 806 are spliced by a clip groove 809. The flushable electrode structures of the present invention include, but are not limited to, the structures shown.

It is understood that the spoilers 806 or 906 can be electrically conductive, with the material of the spoilers 806 or 906 being the same or different than the electrically conductive material 101.

In other embodiments, the conductive material 101 may be other materials that can be used as electrodes.

It will be appreciated that instead of providing a chamfer at the outer periphery of the end of the flushing electrode at the outlet section 104, a drain groove 110 may be provided at the outer periphery of the end of the flushing electrode at the outlet section 104, as shown in fig. 7, where the flushing electrode is provided with a common flow channel at the outer surface. The method can effectively avoid that the material removed by arc discharge cannot be discharged efficiently, and improves the surface processing quality of the workpiece.

The cavitation jet auxiliary arc machining flushing electrode is simple in structure and convenient to use, is beneficial to cavitation phenomenon formation, and when the electrode is in discharge work, a large amount of cavitation bubbles collapse at a discharge gap between the electrode and a workpiece to release a large amount of energy and shock waves so as to promote the flow of high-pressure flushing liquid, reduce the flow resistance of the high-pressure flushing liquid, greatly improve the effective flushing specific gravity of the flushing electrode, realize the powerful flushing of the discharge gap, play a beneficial role in a fluid arc breaking mechanism of arc discharge machining and improve the machining efficiency. The device has excellent cooling effect, can discharge the electric erosion product in the discharge area with high efficiency, reduces the accumulation of metal powder in the discharge gap, avoids the occurrence of uneven electrode loss and short circuit phenomenon caused by sustainable discharge of the accumulated powder, and improves the surface quality of the processed workpiece.

A method for preparing metal powder by cavitation jet assisted arc micro-explosion comprises the following steps:

respectively connecting a flushing electrode and a workpiece with two poles of a power supply, adjusting the distance between the flushing electrode and the workpiece, and generating arc plasma in a discharge gap between the flushing electrode and the workpiece to enable a part of the workpiece to be molten;

the liquid flushing electrode is provided with a variable-section flow passage, liquid flushing fluid is introduced from the variable-section flow passage, cavitation bubbles are generated in the process of flowing through the variable-section flow passage, and the cavitation bubbles grow and collapse along with the flowing of the liquid flushing fluid to the workpiece;

controlling the flow speed of the flushing fluid and the relative rotation speed of the flushing electrode and the workpiece, enabling the arc plasma to deviate and break under the impact force of collapsing of the cavitation bubbles to generate micro explosion, refining the melted workpiece in the explosion, condensing in the flushing fluid and collecting powder.

Specifically, the flushing electrode generates cavitation bubbles in the flowing process of the flushing fluid flowing through the flushing electrode as described above.

In one embodiment, the flushing fluid is a liquid medium. The proper flushing fluid can be selected according to the particle size requirements of different metal powder preparation, so that the diversity and the selection space of the method for preparing the metal powder by utilizing electric arc micro-explosion are increased.

For example, the liquid medium is pure water.

In one embodiment, the method further comprises the step of introducing the flushing fluid from outside the introduction of the flushing electrode in addition to introducing the flushing fluid from the variable cross-section flow channel.

In one embodiment, the workpiece is immersed in a fluid medium, which is a liquid medium.

It will be appreciated that the fluid medium may be the same as or different from the flushing fluid.

In one embodiment, the rinse electrode is connected to an anode of a power source and the workpiece is connected to a cathode of the power source. The power supply drives the flushing electrode to rotate and drives the workpiece to move along X, Y and the Z axis.

In one embodiment, the power source is a pulsed power source.

Referring to fig. 8, in order to adopt cavitation jet auxiliary arc micro-explosion to prepare metal powder, a flushing electrode is connected with an anode of a power supply, after the workpiece is connected with a cathode of the power supply, the power supply is started, the distance between the flushing electrode and the workpiece is adjusted, arc plasma is generated in a discharge gap between the flushing electrode and the workpiece, and the arc plasma can melt most of conductive materials to enable part of the workpiece to be melted, so that a melting pit is formed on the surface of the workpiece. When a power supply is started, a flushing fluid is introduced from a variable-section flow passage of the flushing electrode, cavitation bubbles are generated when the flushing fluid flows through a throat section and an outlet section of the flushing electrode, the cavitation bubbles grow and collapse along with the flowing of the flushing fluid to a workpiece, the flow speed of the flushing fluid and the relative rotation speed of the flushing electrode and the workpiece are controlled, and under the impact force of the collapse of the cavitation bubbles, arc plasma is deflected to break an arc, tiny explosion is generated, the melted workpiece is thinned in the explosion, and the melted workpiece is condensed into powder in the flushing fluid.

In one embodiment, the distance between the rinse electrode and the workpiece is 0.1mm-100mm.

In one embodiment, when the flushing fluid is introduced, the flow speed of the flushing fluid is 20L/min-50L/min, so that the shock wave impact and the micro-jet impact generated by the collapse of cavitation bubbles can more easily and rapidly discharge the melted workpiece. The pressure of the flushing fluid is 2Mpa-10Mpa. By the arrangement, cavitation bubbles are more easily generated in the flushing fluid, and the powder making efficiency and the powder making quality are improved.

In one embodiment, the rotational speed of the liquid flushing electrode relative to the workpiece is 100r/min-60000r/min.

The invention tries to apply cavitation jet technology to the preparation of metal powder by arc micro-explosion, cavitation bubbles are generated in a variable-section flow passage of a flushing fluid flowing through a flushing electrode, and grow and collapse along with the flowing of the flushing fluid to a workpiece. When cavitation bubbles exist in a discharge gap between the flushing electrode and the workpiece, arc plasma is easier to break through flushing fluid containing the cavitation bubbles to discharge, so that the powder preparation efficiency is improved, in addition, when cavitation bubbles are collapsed along with the increase of the pressure of surrounding fluid, instantaneous high energy is generated, the flowing of the flushing fluid is promoted, the phenomenon of unsmooth flushing is improved, the powerful impulsive force of the discharge gap is maintained, the effective flushing specific gravity of the flushing electrode is greatly improved, molten metal generated by the processing of a powder preparation area can be efficiently flushed, powder is rapidly discharged, a better cooling effect is achieved, the efficiency of arc discharge processing is improved, meanwhile, shock wave impact and micro-jet impact are generated due to the collapse of the cavitation bubbles, the effect of synergism is achieved on a fluid arc breaking mechanism, and the further refinement of the particle size of the powder is facilitated.

The invention also provides the metal powder prepared by the method. The obtained metal powder has high sphericity, less hollow powder and less satellite powder, and can be collected to obtain more metal powder with particle size of 10-250 μm.

The following examples and comparative examples are further described, and the raw materials used in the following examples are commercially available unless otherwise specified, and the equipment used in the examples are commercially available unless otherwise specified.

Example 1

The embodiment provides a flushing electrode and an arc processing method using the flushing electrode, which specifically comprises the following steps:

as shown in FIG. 8, the flushing electrode is integrally formed and prepared by graphite, is integrally formed into a cylinder, has a height of 20mm and a radial cross-sectional area of 20mm, is internally provided with a variable-section flow passage for flowing flushing fluid, and comprises an inlet section, a throat section and an outlet section which are sequentially connected and have circular radial cross-sectional areas; the inlet section, the throat section and the outlet section are distributed along the central axis, and the inlet section, the throat section and the outlet section are provided with only one variable-section runner, the radial cross-sectional area of the inlet section is 15mm, the radial cross-sectional area of the throat section is 10mm, and the radial cross-sectional area of the outlet section is 15mm.

On V5L water atomization powder making equipment, a block-shaped stainless steel with the size of 100mm multiplied by 20mm is used as a workpiece, after the workpiece is cleaned and decontaminated, a cathode of a power supply is connected, the flushing electrode is connected with an anode of the power supply, and the flushing electrode is placed as shown in fig. 8, wherein the distance between the bottom discharge end of the flushing electrode and the workpiece is 0.5mm.

Setting power supply parameters: the gap voltage is 45V-55V, the discharge current is 300A, the pulse width is 2000 mu s, the pulse interval is 200 mu s, the power supply is started, the rotating speed of the flushing electrode relative to the workpiece is controlled to be 2000r/min, meanwhile, pure water flows out of the inner liquid charging knife handle into the inlet section of the flushing electrode, the flow rate of the pure water flowing into the inlet section is 20L/min, and the pressure is 2MPa.

Under the process, arc plasma acts on the electrode and the surface of the workpiece to melt the workpiece and the surface of the electrode, the melted material is continuously discharged along with the rotation of the electrode and the impact of pure water, and micro-explosion occurs, meanwhile, when the flushing fluid flows into the throat section from the inlet section, cavitation bubbles mainly containing vapor appear in the flushing fluid or on the liquid-solid interface, and along with the flowing of the flushing fluid to the outlet section, the cavitation bubbles mainly containing vapor can be formed in the outlet section again, and along with the flushing fluid, the cavitation bubbles mainly containing vapor grow continuously, and along with the discharging of the flushing fluid in the outlet section, collapse occurs during discharging. This example was observed to show that a large amount of white bubble-filled water was discharged from the outlet section during the powdering process. Along with the collapse of cavitation bubbles discharged by the pure water at the outlet section, impact force generated by the collapse of the cavitation bubbles acts on the powder making area to realize the effect of auxiliary electric arc micro-explosion powder making, and finally, the micro-explosion products are condensed to obtain powder, wherein the SEM (scanning electron microscope) diagram is shown as figure 9, and the particle size of the powder is about 15-75 mu m as can be seen from figure 9.

After 1h of processing, weighing 3500g of the weight reduction of the stainless steel workpiece, namely, the processing efficiency of the method reaches 3500g/h.

Example 2

The present embodiment provides a shower electrode and an arc machining method using the same, which are basically the same as embodiment 1, except that after connecting a work to a cathode of a power source, all the work is immersed in pure water and reworked.

This example was observed to show that a large amount of white bubble-filled water was discharged from the outlet section during the powdering process. After 1h of processing, weighing 2500 of the weight reduction of the stainless steel workpiece, namely the processing efficiency of the method reaches 2500g/h.

Comparative example 1

This comparative example provides a flung electrode and an arc processing method using the same, which are basically the same as embodiment 1, except that the flung electrode is not provided with a throat section, and the radial cross-sectional areas of the inlet section 1102 and the outlet section 1104 of the flung electrode are the same, and are both 15mm, as shown in fig. 10.

It was observed that this comparative example did not show the discharge of white bubble-laden water from the outlet section during the milling process. After 1h of processing, weighing 2100g of the weight of the stainless steel workpiece, namely, the processing efficiency of the method reaches 2100g/h.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.

Claims (9)

1. The method for preparing the metal powder by cavitation jet assisted arc micro-explosion is characterized by comprising the following steps of:

respectively connecting a flushing electrode and a workpiece with two poles of a power supply, adjusting the distance between the flushing electrode and the workpiece, and generating arc plasma in a discharge gap between the flushing electrode and the workpiece to enable a part of the workpiece to be molten;

the liquid flushing electrode is provided with a variable-section flow passage, liquid flushing fluid is introduced from the variable-section flow passage, cavitation bubbles are generated in the process of flowing through the variable-section flow passage, and the cavitation bubbles grow and collapse along with the flowing of the liquid flushing fluid to the workpiece;

controlling the flow speed of the flushing fluid and the relative rotation speed of the flushing electrode and the workpiece, enabling the arc plasma to deviate and break under the impact force of collapsing of the cavitation bubbles to generate micro explosion, refining the melted workpiece in the explosion, condensing in the flushing fluid and collecting powder.

2. The method for preparing metal powder by cavitation jet auxiliary arc micro-explosion according to claim 1, wherein the variable cross-section flow passage comprises an inlet section and a throat section which are connected in sequence along the flow direction of the flushing fluid; from the inlet section to the throat section, the size of the variable cross-section flow passage is narrowed, and the size of the variable cross-section flow passage satisfies: after the flushing fluid flows from the inlet section into the throat section, a first low-pressure area can be formed in the throat section, and the pressure of the first low-pressure area is smaller than the saturated vapor pressure of the flushing fluid.

3. The method for preparing metal powder by cavitation jet auxiliary arc micro-explosion according to claim 2, wherein the radial cross-sectional area of the throat section is 0.2-0.8 times of the radial cross-sectional area of the inlet section.

4. The method of claim 2, wherein the variable cross-section flow channel further comprises an outlet section downstream of and connected to the throat section, the variable cross-section flow channel widens in size from the throat section to the outlet section, and the variable cross-section flow channel satisfies: after the flushing fluid flows from the throat section into the outlet section, a second low pressure zone can be formed in the outlet section, and the pressure of the second low pressure zone is also smaller than the saturated vapor pressure of the flushing fluid.

5. The method for preparing metal powder by cavitation jet assisted arc micro-explosion according to claim 4, wherein the radial cross-sectional area of the throat section is 0.2-0.8 times of the radial cross-sectional area of the outlet section.

6. The method for preparing metal powder by cavitation jet assisted arc micro-explosion according to any one of claims 1 to 5, wherein the flushing fluid is a liquid medium.

7. The method of any one of claims 1-5, further comprising the step of introducing the flushing fluid from outside the introduction of the flushing electrode in addition to introducing the flushing fluid from the variable cross-section flow channel.

8. The method of preparing metal powder by cavitation jet assisted arc micro-explosion according to any one of claims 1 to 5, wherein the workpiece is immersed in a fluid medium, the fluid medium being a liquid medium.

9. The method for preparing metal powder by cavitation jet auxiliary arc micro-explosion according to any one of claims 1 to 5, wherein the power supply is a pulse power supply;

the flushing electrode is connected with the anode of the power supply, and the workpiece is connected with the cathode of the power supply;

the distance between the flushing electrode and the workpiece is 0.1mm-100mm;

when the flushing fluid is introduced, the flow speed of the flushing fluid is 20L/min-50L/min, and the pressure of the flushing fluid is 2Mpa-10Mpa;

the rotating speed of the flushing electrode relative to the workpiece is 100r/min-60000r/min.

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