RU2645169C2 - Method and apparatus for producing metal powder by centrifugal spraying - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to the production of a metal powder by the centrifugal spraying of workpiece. Method includes feeding the workpiece into a rotating spray assembly and into a melting zone, melting the workpiece with a plasma jet directed to its end, with the provision of centrifugal spraying by rotating the spray assembly and obtaining particles, cooling and solidifying them during flight in the gas. Spraying assembly is used, which is in the form of a hollow cylinder for feeding workpieces through it and consisting of two sections of various materials, first of which is a working section and is made of a workpiece material, and the second is made of a material cooled with higher thermal conductive properties than the material of the first section. Feeding of workpiece to the spraying unit is carried out with the alignment in the vertical plane of the end face of workpiece and the end of the working section of the spraying unit, firstly, the ends of the workpiece and the working part of the spraying unit are heated and melted together with the plasma jet to ensure the formation of a stable profile and stationary melt film at the end of the working part.

EFFECT: improves the quality of the powder and increases the life of the equipment used.

2 cl, 2 dwg, 1 tbl

Description

The present invention relates to metallurgy, to the production of metal powders, their processing and obtaining products from them.

There is a method of producing metal powders by centrifugal spraying of a rapidly rotating cylindrical billet, the end of which is melted by means of a plasma jet directed perpendicular to the end surface and a device for implementing this method is "Installations for producing powders by centrifugal spraying of a rotating billet" ed. Kononov I.A. and others in Sat "Metallurgy of Pellets", under. ed. A.F. Belova, vol. 2, Moscow 1984, pp. 242-250.

This method of production of powders has the disadvantages of the following:

• the workpiece, to bring its rotating mass to an acceptable level of imbalance, is subjected to labor-intensive machining, which accounts for significant production costs;

• the workpiece cannot be completely sprayed without residue, there remains an unmelted part (“cinder”), for which it is held during rotation. This circumstance reduces the yield of finished products from each billet and, therefore, reduces the production rate for the yield;

• the spraying process is carried out in a cyclic, intermittent mode from one workpiece to another, which does not contribute to achieving high performance of the process.

There is also a method of producing a metal powder by centrifugal spraying - RF patent 2475336 dated 02.20.2013, adopted as a prototype, which includes melting a cast billet with a plasma jet directed at its end and centrifugal spraying of the melt into particles with their subsequent cooling and solidification in gas wherein the melt is sprayed by means of a disk rotating in the vertical plane with a central hole through which the cast billet is fed under the plasma jet to the other unmelted end face of the billet ovyvayut next workpiece, and drive a spent plasma jet is heated by mixing it with the necessary quantity of cold gas, the melt fed to the disk jet tangentially to the disc surface, the plasma jet is moved along the end face of fused preform and the preform is rotated during the melting around its axis.

The disadvantage of this method is the complexity of its practical implementation, due to the following reasons:

- the material from which the disk of the spraying device is made must be wetted by the melt of the sprayed workpiece. Otherwise, the mechanism of droplet formation and the formation of powder particles is violated. In practice, this condition is difficult to provide.

One of the main obstacles to this is the presence of an oxide film on the surface of the disk, which is difficult to eliminate and which affects the wettability;

- to achieve an effective process of spraying the melt by means of a disk, its surface in contact with the melt must be of a certain configuration, providing a smooth flow of melt onto it from the melted workpiece, formation and separation of drops of the required size (size) from the periphery of the disk. The selection of the profile configuration and its execution on the disk are quite complex and time-consuming operations.

There is also known a device for producing powder by centrifugal spraying, with which this method is carried out - RF patent 2467835.

The device includes a chamber with a storage device for workpieces and a manipulator for their single-piece feeding for spraying with drives of rotational and translational movements of the workpiece, a spray chamber with a plasma torch aimed at the end face of the sprayed workpiece, a powder receiver, which are all hermetically connected to each other, while the powder receiver is equipped with a pneumatic feeder , the spraying chamber is equipped with a coarse particle cutter and a screening machine placed in front of the receiver, the rotational motion drive of the workpiece is made in the form of a vertical spindle with a cup-shaped annular disk at the upper end and clamping cams located directly below the disk, and the translational drive is made in the form of a pusher placed coaxially with the spindle under it, the spray chamber is made lenticular and oriented horizontally, while the axial lines of the chamber spraying, plasma torch and spindle match.

The disadvantage of this installation is the imperfect design of the drive for rotating the workpiece in the form of a vertical hollow spindle with an annular disk of a cup-shaped shape at the end, the features of which, leading to negative results, are inherent in the method and are described above.

A method for producing a metal powder by centrifugal spraying is proposed, which includes melting the workpiece with a plasma jet directed at its end face, centrifugal spraying of the melt by means of a rotating spray unit with a central hole through which the workpiece is fed into the melting zone, to obtain particles, to cool them and solidify when flying in gas, while the process of obtaining the powder is started by joint heating and melting by means of a plasma jet of the ends of the workpiece and the spray unit, filled from the same material and combined with the ends in one vertical plane, and lead it until a stable profile and a stationary melt film are formed on the end of the spraying unit, which is only fueled by melting the preform, for which the feed rate of the preform into the melting zone is controlled, power and direction attacks of the heating surface with a plasma jet during intensive cooling of the back of the spray unit, moreover, the spray unit formed by this technique once is used in yshem for other campaigns (cycles) production of powders of a material of the same name from the spray assembly until pictures making his resource.

The technical effect of the proposed method is to eliminate the disadvantages inherent in the known method of the prototype, namely: a significant simplification of the process, reducing operating costs, improving reliability in operation and outputs, as well as improving product quality.

It is achieved by the fact that the powder production process is started by co-heating and melting by means of a plasma jet the ends of the workpiece and the spray assembly made of the same material and combined by the ends in the same vertical plane, and lead it until a stable profile and a stationary melt film are formed at the end of the spray assembly, fed at the same time only due to the melting of the workpiece, for which they control the feed rate of the workpiece into the melting zone, the power and attack direction of the heating surface azmennoy with vigorous jet cooling the back portion of the spray assembly and spray assembly formed by the data reception once, used subsequently for other campaigns (cycles) production of powders of a material of the same name from the spray assembly until pictures making his resource.

Factors that ensure the achievement of the above technical effect are as follows:

- the implementation of the spray unit of a material identical with the material of the workpiece provides guaranteed wetting of its surface with the melt of the workpiece;

- the joint heating and melting of the ends of the workpiece and the spraying unit aligned in one plane at the beginning of the technological process provide spontaneous formation of the configuration of the working surface of the spraying unit and its purification from oxide films to ensure the conditions of complete wetting and formation of a stationary melt film as a necessary condition for the optimal course of the centrifugal spraying process ;

- the spraying unit formed once by such a technique can then be repeatedly used, up to the exhaustion of the resource, in other spraying campaigns (cycles) of the same material and thereby reduce operating costs, increase the reliability and quality of the obtained powder.

To implement the proposed method for producing metal powder, a device is proposed that includes a workpiece storage device with a unit-by-piece feeding device, a chamber with mechanisms for longitudinal feeding and rotation of the workpiece in the form of two drive support drums with pressure rollers equipped with lifting / lowering drives with hinged assemblies, a melting chamber attached to the mechanism chamber and the hole communicated with it, equipped with a powder discharge system with a receiver and a retractable lid with a plasmatron on the axis of the hole between the cameras have a gas supply and recirculation system, while the drive is equipped with a receiving table with a tilt changing mechanism, a workpiece separator with a roller table, a workpiece blowing unit and a lock device, the mechanism chamber is equipped with its own live roll with workpiece collider on supporting drive drums, a workpiece docking device, a unit spraying in the form of a hollow cylinder with an individual rotation drive inserted into the melting chamber coaxially with the plasma torch, pressure rollers with lifting / lowering drives, in hinged joints the silent blocks of which are evenly distributed along the length of the support drums, and the support drums are equipped with splined shafts, on which a roller clamp-lunette, connected with the longitudinal feed mechanism, is mounted, while all the mechanisms of the mechanism chamber are mounted on a platform with air suspension, the powder discharge system is equipped with an intermediate a powder accumulator with a cooler, a screening machine with a separator and made in the form of a detachable module on a transport trolley, and the plasma torch is equipped with a three-coordinate mechanism with an icing device, in addition, the hollow cylinder of the spraying unit is made integral in length of two sections, each of which is made of different materials, one working is the same with the workpiece material, and the second with heat-conducting properties higher than that of the first, while the section of material with increased thermal conductivity is equipped with a gas cooling system with the possibility of intensive heat removal from the spray unit.

The proposed device for implementing the method for producing metal powder differs from the known one in that the drive is equipped with a receiving table with a tilt mechanism, a workpiece separator with a roller table and a lock device, the mechanism chamber is equipped with its own live roll with a workpiece chuck on the supporting drive drums, the device for joining the workpieces in the form of a hollow cylinder with an individual rotation drive inserted into the melting chamber coaxially with the plasma torch, pressure rollers with lifting / lowering drives, in The nier nodes of which the silent blocks are installed are evenly distributed along the length of the supporting drums, and the supporting drums are equipped with splined shafts, on which a roller clamp-lunette, connected with the longitudinal feeding mechanism, is mounted, and all the mechanisms of the mechanism cameras are mounted on a platform with air suspension, the powder discharge system is equipped with an intermediate a powder accumulator with a cooler, a screening machine with a separator and made in the form of a detachable module on a transport trolley, and the plasma torch is equipped with a three-coordinate mechanism with a tracking device, in addition, the hollow cylinder of the assembly is made integral along the length of two sections of various materials, one of which is the worker, the same as the workpiece material, and the second with heat-conducting properties higher than the first, while the section of material with increased thermal conductivity it is equipped with a gas cooling system with the possibility of intensive heat removal from the atomization unit.

This design of the atomization unit, made integral along the length of two sections, one of which is the working one made of a material identical to the workpiece material, and the second of a more heat-conducting material than the first, the latter equipped with a gas cooling system that provides intensive heat removal from the atomizer solves the task of simplifying the process of obtaining high-quality powder. This ensures a reduction in operating costs associated with simplified preparation and launch of the workpiece spraying process, while increasing the reliability of the equipment. The same purposes are also other signs that distinguish the proposed device from the known, namely:

- supplying the powder discharge system with an intermediate powder storage unit with a cooler, a screening machine with a separator and the implementation of this system as a detachable module on a transport trolley provides additional powder cooling, which is especially important, for example, in the production of its large fractions;

- cooling prepares the powder for separation and sieving by eliminating the "setting" of the hot powder particles together and overheating the screening machine;

- the inclusion of a screening machine and a separator in the exhaust system provides fully conditioned batches of powder directly in the installation, while maintaining a strictly controlled protective environment above the powder, and the layout of the powder discharge system in the form of a detachable module on a transport trolley provides a quick transfer of the installation to work with other material, as one module that worked with the previous material is quickly replaced by another - a clean module for working with new material, and the old module is rolled back to the cleaning and preparation position for use with another material;

- supplying the sliding cover of the melting chamber with a three-coordinate mechanism with a tracking device for moving the plasma torch relative to the hole between the melting chamber and the mechanism chamber provides an increase in the yield of suitable powder. This is achieved by the fact that moving the plasma torch in three directions by means of a three-coordinate mechanism with a follower ensures the formation of a flat melting front of the billet end and, at the same time, maintaining the optimal thermal regime at the end of the atomization unit.

In addition, the quality of the powders, the reliability of the equipment and the reduction of costs are facilitated by the distinctive features of the proposed installation, including the supply of the workpiece storage device with a receiving table with a tilting mechanism, the workpiece separator with a roller conveyor feeding them into the mechanism chamber, which provide open, visually traceable piece loading of workpieces into the drive and their supply to the chamber mechanisms. At the same time, the blowing unit on the roller table provides additional removal of dust particles from the workpieces before they enter the gateway, and the roller table gateway, in addition to the function of entering the workpiece into the chamber of mechanisms with a controlled atmosphere, provides additional cleaning (degassing) of each workpiece by “flushing” it with gas followed by pumping and filling the gateway with gas from the gas supply and recirculation system together with the vacuum system.

The supply of the chamber of rotation and longitudinal feed mechanisms with a platform with air suspension, on which the mechanisms and its own roller conveyor with a pusher are mounted, solves the problem of both improving the quality of products (powder) and increasing the reliability of the equipment. This is achieved by reducing the level of vibration of mechanisms during operation, both due to the use of air suspension of the platform and the introduction of elastic elements - silent blocks in the hinges of the joints of the moving parts of the pressure roller drives, the number of which is proposed to be increased by placing them along the entire length of the supporting drums.

Vibration vibrations, as is known, have a direct effect on the dispersion of the melt film at the end face of a rotating billet, the higher its parameters (frequency, amplitude and acceleration), the more negative they affect the dispersed composition of the powder, reducing the yield of a given fraction. Vibration, in addition, have a destructive effect on the mechanisms. The decrease in their level favorably affects the reliability of the mechanisms and systems of the installation.

The proposed installation is illustrated by drawings, where:

- FIG. 1 shows a general view of the complete assembly;

- FIG. 2 shows a section along the axial plane of the chambers of the mechanisms and the melting unit.

The installation consists of a blank of storage blanks as part of a receiving table 1 with a tilt mechanism 2, a separator 3 of blanks, a roller table 4, a lock device 5 with a blowing unit 6, and the storage is docked to the chamber of mechanisms 7, in the space of which a platform 8 is placed on an air suspension (in FIG. 1 are not shown) with driving supporting drums 9 and pressure rollers 10 mounted on it with raising / lowering drives 11, with hinge assemblies 12, as well as a longitudinal movement mechanism 13 with a roller clip-lunette 14, a rolling table 15 with a pusher 16 workpieces 17. Support drums 9 with a rotation drive 18 are provided with splined shafts 19 on which a roller clamp-lunette 14 is mounted, coaxially with which the spraying unit 20 is mounted on rolls 21 with a rotation drive 22 and a docking device 23 of the workpieces 17. The camera of mechanisms 7 is docked to to the melting chamber 24 and communicated therewith with a hole 25, opposite which a plasmatron 27 is installed on the sliding cover 26, equipped with a three-coordinate mechanism with a tracking device (in FIG. 1 are not shown).

Under the chamber 24 there is a cinder receiver 28, a powder discharge system in the form of a detachable module including an intermediate powder accumulator 29 with a cooler, a sifting machine with a separator, enclosed in a sealed housing 30, docked with the powder receiver 31, both the detachable module and the powder receiver (hopper) equipped with movable platforms.

The installation is also equipped with service systems including vacuum, gas supply and recirculation, water cooling, pneumatic system, power supply, control and automation, which are shown in FIG. 1-2 are not shown.

Installation works as follows.

In the initial position, all the elements of the installation are assembled and prepared for work, the internal space is sealed.

The start of the installation begins with the inclusion of service systems, namely: power supply, control and automation, water cooling, pneumatic system, gas and vacuum systems. In this case, pumping ensures that the air is removed from the installation to the desired level of residual pressure, and then it is filled with a working medium (a mixture of inert gases) and the pressure in the installation is brought to the required level.

On the receiving table 1 serves a batch of blanks 17 and the inclusion of the tilt mechanism 2 provide rolling blanks on the plane of table 1 in one layer. In this case, the first blank of the layer engages with the separator 3, which moves it to the roller table 4, and the next blank on the table 1 at the same time engages with the separator 3 and remains in this position to wait for the next supply of the blank.

Turn on the rolling table 4, start the blowing unit 6 and open the inlet gate of the gateway device 5. Billet 17 while moving along the live table 4 moves to the space of the gateway device 5, having gone through the cleaning of dust particles by blowing with conditioned (dedusted and dried) air through the unit 6 .

When the workpiece 17 reaches its final position in the lock device 5, the roller table 4 is stopped, and the input gate of the lock device 5 is closed, thereby sealing its space. The space of the lock 5 together with the workpiece 17 placed in it is evacuated, then filled with working gas, pumped out again, thereby providing a “washing” (degassing) of the space of the lock 5 and the workpiece 17 from impurity polluting gases adsorbed on their surfaces. After washing, the space of the airlock is again filled with working gas, its pressure is equalized with the pressure in the installation, the output gate of the airlock 5 is opened and the movement of the roller table 4 is turned on. The workpiece 17 moves from the space of the airlock 5 to the chamber chamber of mechanisms 7 on its live roll 15 the inclusion of which in the work ensure the movement of the workpiece 17 to its overload position on the support drums 9. The overload is provided by the collider 16, while the pressure rollers 9 are transferred by the actuators 11 to the upper position. The workpiece 17 is smoothly moved into the gap between the reels 9, while the rollers 10 support and track the movement of the workpiece 17, thereby preventing its impact on the surface of the drums 9. The pusher of the docking device 23 is brought into contact with the end face and then move the workpiece 17 along the drums 9 , under the grip of the lunette 20. The workpiece 17 clamped by the luncheon 20 by the mechanism 13 is moved towards the melting chamber into the cavity of the atomization unit 20, freeing up space on the drums 9 for loading a new workpiece 17. Loading the second and subsequent workpieces 17 provide similar to the first workpiece.

The second and subsequent blanks, made with a locking device at the ends in the form of a spike and a groove, are connected by a docking device 23 to each other, forming a composite or “continuous” blank.

As the composite preform elongates as a result of docking, its end face enters the cavity of the spray assembly 20 at the melting position. In this position, the end face of the composite billet should coincide with the plane of the end face of the spraying unit 20, while the loading of additional workpieces 17 onto the drums 9 is temporarily stopped.

Then, a number of devices and installation systems are turned on, namely, the plasma torch 27 in idle mode for the minimum power of the plasma jet, the sifting machine and the separator of the powder discharge system (detachable module 30), the powder storage with cooler 29, with the supply of cooling gas and finally include rotation drives 18 of the reels 9 (workpiece rotation) and rotation drives 22 of the spray assembly 20.

When the required speed of the spraying unit 20 is reached, the plasmatron 27, is approached by a three-coordinate mechanism to the end of the composite workpiece at a distance automatically monitored by the tracking device, and its power is increased to the required (working) value. The plasma torch 27 by means of a three-coordinate mechanism performs the regulated movement of the plasma jet along the plane of the end face of the composite billet and the spray unit, thereby ensuring their joint fusion. When this is formed, the profile of the end face of the spray unit 20 in the form of a bowl. Drops of the melt, flowing down from the perimeter of the end face of the workpiece, are picked up by the end of the spraying unit 20, spread along its surface and move to the edge of the perimeter, where they come off in the form of fine droplets of the melt. The droplets during the flight are cooled by the gas of the melting chamber, solidify and fall into the accumulator with cooler 29, where they are cooled by gas in the blown layer. The accumulation of powder is provided up to a certain volume (or mass) determined empirically, after which the cooled powder is discharged from the accumulator 29 to the sieving machine and the separator module 30 and further to the powder receiver 31.

The time of movement of the powder from the accumulator 29 to the module 30 for sieving and separation is controlled so that the powder particles have time to cool to an acceptable temperature, which is designed for the screening screen of the screening machine. It is set depending on the particle size of the powder, and the larger the powder, the longer it takes to cool it.

As the composite billet is fused, new discrete billets 17 are joined to it by means of the docking device 23 and thereby provide a continuous spraying and powder production mode.

The powder receiver 31, when filling its volume to the permissible limit, is replaced with a new empty one, and the filled one is sent to a warehouse or as intended. At the time of replacing the powder receiver 31, the powder accumulator 24 with a cooler is switched to the mode of receiving and cooling the powder without discharging it for sieving and separation into the module 30. The change in the powder receivers 31 is ensured in compliance with the regime of maintaining the protective atmosphere in its volume and powder-feeding systems with preliminary pumping and subsequent filling with working gas with equalization of pressure to a level created in the volume of the remaining parts of the installation.

The workflow at the installation can be stopped at any time by turning off the plasma torch 27 and stopping the drives of the camera mechanisms 7.

Comparative tests of the proposed method and its installation with the method and installation of the prototype were carried out. The test results are presented in table. one.

The data given in table. 1, indicate that the proposed method provides, in comparison with the prototype, an increase in yield by 15%, a reduction in both the cost of production, and its maintenance and repair.

Claims (2)

1. A method of producing a metal powder by centrifugal spraying of a workpiece, comprising supplying the workpiece to a rotating spray unit and to the melting zone, melting the workpiece with a plasma jet directed at its end, providing centrifugal spraying by rotating the spray unit and producing particles, cooling and solidifying them during flight in gas, characterized in that they use a spraying unit made in the form of a hollow cylinder for feeding workpieces through it and consisting of two sections from different materials alows, the first of which is the working section and made of the workpiece material, and the second is cooled from the material with higher heat-conducting properties than the material of the first section, while the workpiece is fed into the spraying unit to ensure that the end face of the workpiece and the end face of the worker are aligned section of the spray unit, and first, the ends of the workpiece and the working part of the spray unit are heated and melted together with a plasma jet to ensure the formation of the working part on the end the spray nozzle of a stable profile and a stationary melt film fed by melting the workpiece and controlling the feed rate of the workpiece into the melting zone, the power and direction of the plasma jet to the surface of the workpiece end face. 2. A device for producing metal powder by centrifugal spraying of a workpiece, containing a drive for workpieces with a unit-by-piece feeding device, a melting chamber with a retractable lid, a mechanism chamber containing a spray unit with a rotation drive, and longitudinal workpiece supply and rotation mechanisms in the form of two driving support drums with pressure rollers equipped with lifting and lowering drives with hinged assemblies, and communicated with the aforementioned melting chamber through an opening containing a plasmatron located on the axis of the unit a creased hole, a powder discharge system with a receiver and a gas supply and recirculation system, characterized in that the workpiece storage device is equipped with a receiving table with a mechanism for changing its inclination, workpiece separator with a roller table, a workpiece blowing unit and a lock device, the mechanism chamber is equipped with a pneumatic suspension platform, a roller table with the workpiece pusher on the supporting drums and the device for joining the workpieces at the ends, while in the hinged nodes of said pressure rollers with drives for raising and lowering Silent blocks, rollers are evenly distributed along the length of the supporting drums, and the supporting drums are equipped with splined shafts, on which a roller clip in the form of a steady rest is fitted, communicated with the longitudinal feed mechanism, and the powder discharge system is equipped with an intermediate powder storage unit with a cooler and a screening machine with a separator and this is made in the form of a volumetric module on a transport trolley, and the plasmatron is equipped with a three-coordinate mechanism with a follower, while the atomization unit is introduced into the coax melting chamber but with a plasma torch and for feeding through it, the workpiece is made in the form of a hollow cylinder, consisting of two sections of different materials, the first of which is working and made of the workpiece material, and the second section is made of material with higher heat-conducting properties than the material of the first section , and is equipped with a gas cooling system that provides heat removal from the spray unit.

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