WO2021063670A1

WO2021063670A1 - Arc wire spray device

Info

Publication number: WO2021063670A1
Application number: PCT/EP2020/075771
Authority: WO
Inventors: Steffen HEIDEMANN; Christian Weinmann
Original assignee: Gebr. Heller Maschinenfabrik Gmbh
Priority date: 2019-10-02
Filing date: 2020-09-15
Publication date: 2021-04-08
Also published as: DE102019126640A1

Abstract

The invention relates to an arc wire spray device comprising an arc spray torch (10) which has a continuously fed wire (15) as the anode and a counter-electrode (16) as the cathode, with a cooling channel (29) associated therewith. This cooling channel is located outside of the counter-electrode (16), which as a result is solid and has no cavities, thereby creating an effective cooling of the counter-electrode (16) that is functional over a large operating range.

Description

Arc wire spraying device

The invention relates to an arc wire spray device with a non-consumable electrode and a method for cooling the same.

Arc wire spraying devices are used

Coating of substrates with metal, for example the coating of aluminum bodies with a steel layer. For this purpose, the coating material is melted by means of an electric arc and transferred to the surface to be coated by a gas jet.

Such a device for spraying arc wire is known for example from DE 102009 004 581 A1. This wire arc spray device has a wire feed device which is set up to feed wire to an arc torch. The arc torch has a counter electrode to which a cooling channel is assigned in order to cool the counter electrode. For this purpose, the counter electrode is made of tungsten or of copper coated with tungsten as a hollow body, so that the coolant can flow through it. For the coolant supply, cooling channels of a coolant circuit are connected to the non-consumable counter electrode.

[0004] When coolant is introduced directly into the counter electrode, when there is a high level of heat input into the counter electrode, electrode to local overload of the coolant, for example to the formation of vapor bubbles. On the one hand, it is necessary to keep the counter-electrode at an operating temperature that enables thermal electron emission, but on the other hand, melting of the counter-electrode must be avoided.

If this does not succeed, the quality of the coating can be reduced by melting particles from the non-consumable counter electrode and entering them as foreign bodies into the coating. On the other hand, if the temperature is too low, the electron emission is insufficient and the quality of the arc can suffer.

On this basis, it is the object of the invention to provide an arc wire spray device with which coatings can be reliably produced in high quality.

This object is achieved with the arc wire spray device according to claim 1:

According to the invention, the wire arc spray device has a wire feed device with which wire is conveyed in the direction of a counter electrode in order to form an arc with it. For this purpose, both the wire and the counter electrode are connected to a corresponding power source via a power supply device. The counter electrode is typically connected as a cathode during operation, ie connected to the predominantly negative pole of the power source. The current source can be a direct current source or a current source for pulsed direct current or also direct current superimposed with an alternating current. The counter electrode is assigned a cooling channel which is preferably arranged completely outside the counter electrode. The counter electrode is preferably solid and does not contain any cavities through which coolant flows. However, coolant can wash around it on its outer surface.

By arranging the cooling channel outside the counter electrode, both overloading of the coolant and excessive heat dissipation from the counter electrode are avoided.

The counter electrode is preferably held in a base which is in heat-transferring connection with the cooling channel. While the counter electrode is preferably made of tungsten or a tungsten alloy, for example egg ne with a metal oxide, for example lanthanum oxide alloyed tungsten material, the base is made of a highly thermally conductive material such as copper, aluminum or the like. The base can serve to distribute heat and thus avoid the formation of hotspots in the cooling channel. Instead of highly thermally conductive metals such as copper or aluminum, the base can also be formed from another thermally conductive material or from a thermally conductive alloy.

The base preferably has a heat-absorbing surface which is in contact with the counter-electrode and a heat-dissipating surface which is larger than the heat-absorbing surface. This leads to a weakening, i.e. a reduction in the power density of the heat flow from the counter electrode to the cooling channel.

[0013] The heat dissipation surface is preferably directly or indirectly with the medium flowing in the cooling channel in heat exchange. The cooling channel can preferably be arranged in a socket which is assigned to the base. The base serves to releasably connect the counter electrode to the mount. The cooling channel can be arranged exclusively in the socket so as to penetrate the base or not to penetrate it. If the cooling channel passes through the base, the cooling medium can wash directly around the outer surface of the counterelectrode and thereby cause a high level of heat to be dissipated from the counterelectrode. In addition, if the coolant flow is subject to an electrode temperature control, the inertia of the control can be reduced.

In another embodiment, the cooling channel is housed exclusively in the socket. The heat transfer from the base to the socket then takes place via mating surfaces of the base and the socket. The fitting surfaces preferably form a transition fit so that the fitting surface of the base and the fitting surface of the socket rest against one another without any gaps, i.e. with a gap width of zero, thus ensuring good heat transfer. The mating surfaces can be blackened in order to further improve the heat transfer.

Preferably, the cooling channel is connected to a feed device which is designed to be adjustable with regard to the coolant temperature and / or the flow rate of the coolant. This makes it possible to regulate the heat dissipation from the counter electrode during operation of the wire arc spray device and thus to ensure that the counter electrode does not leave a desired temperature range. It is possible to use the temperature of the counter electrode or the temperature of the coolant as a reference variable. The temperature of the counter electrode can be measured pyrometrically, for example become. The temperature of the coolant is preferably measured downstream in the coolant flow as seen from the counter electrode. It is also possible to monitor electrical parameters, such as the voltage and / or the flowing current between the wire and the counterelectrode, and use them as a criterion for increasing or decreasing the cooling of the counterelectrode.

The inventive method for cooling a non-consumable counter electrode operated as a cathode of an arc torch is used to extract heat from the counter electrode via a coolant. The power density of the heat flow to be dissipated from the counter electrode to the coolant is reduced in that the heat flow is conducted via a heat absorption surface into a base and from this via a heat emission surface to the Kühlmit tel. The surface area of the heat emission surface is larger than the surface area of the heat absorption surface. This avoids local hot spots in the coolant duct.

Further details of advantageous embodiments of the invention are the subject of the drawing, the associated description and / or claims. Show it:

Figure 1 shows a burner of an arc wire spray device when coating a bore surface, in a schematic representation,

Figure 2 shows the burner according to Figure 1, in a schematic vertical sectional view,

Figure 3 shows a counter electrode with its base and the associated socket of the burner according to Figures 1 and 2, in a schematic vertical sectional view, Figure 4 shows the burner and its cooling device, in a schematic functional diagram,

Figure 5 shows a modified embodiment of the socket of the base and the counter electrode, in a schematic vertical sectional view.

In FIG. 1, an arc torch 10 of an arc wire spraying device is illustrated, which is shown dipping into a bore 11 of a workpiece 12 to illustrate its function. The Lichtbo genbrenner 10 is used to hen the bore wall 13 with a metal layer, in particular a steel layer, to verse. The workpiece 12 can be, for example, an engine block or another object, in particular an object made of aluminum. To coat the wall 13, the arc torch 10 generates a spray jet 14 consisting of metal droplets, which is directed onto the wall 13.

The structure of the arc torch 10 can be seen schematically in FIG. A wire 15 is fed to the arc torch 10 at a controlled speed and / or controlled movement profile via a wire feed device 15a, only symbolically indicated in FIG. An arc 17 burns between the wire 15, which always melts at its end, and a counterelectrode 16 that is not significantly in operation. Egg ne next to the arc 17 blow nozzle 18 is used to melt metal droplets from the wire 15 in the form of a jet, for example one Discharge fan or Ke gelstrahls and so to form the spray jet 14.

At its end facing the wire 15, the counter electrode 16 has a conical tip 19, to which a, for example, cylindrical shaft 20 is connected. The tip can be sharp, rounded or flattened. The cone tip 19 and the shaft 20 are preferably seamlessly formed from the same material as a single part. For example, the counter electrode 16 consists of a tungsten alloy, preferably one Alloy of tungsten and a metal oxide, for example tungsten and lanthanum oxide or torium oxide. This composition ensures both a high electron emissivity and the necessary thermal stability of the counter electrode 16.

The counter electrode 16 is designed as a solid body free of hollow bodies and embedded in a base 21 which is made of a heat-conducting material. Copper, copper alloys, aluminum, aluminum alloys or electrically and thermally conductive ceramic materials such as silicon carbide are suitable as such. The counter electrode 16 can be welded, pressed or otherwise firmly connected to the material of the base 21. The resulting contact surface 22 forms the heat absorption surface 22 of the base 21.

This preferably has an area which is larger than the outer surface of the apex of the cone. Preferably, the heat absorption surface 22 is also larger than the surface of the entire section of the counter electrode 16 protruding from the base 21.

The base 21 can be formed in the manner of a bolt, which is in contact with a socket 24 via a heat emission surface 23. The heat release surface 23 can be, for example, a cylindrical surface, a conical surface or the like. It is preferably arranged concentrically to the heat absorption surface 22. A correspondingly shaped contact surface 25 of the holder 24 is assigned to the heat output surface 23. The diameter of the heat output surface 23 and the contact surface 25 are preferably matched to one another in such a way that the two surfaces 23, 25 are firmly in contact with one another. Preferably these form a transition fit. The heat release surface 23 and the contact surface 25 thus form fitting surfaces that rest against one another without any gaps in the assembled state. The heat release surface 23 and the contact surface 25 are preferably cylindrical surfaces. But you can also be designed as matching Kegelflä surfaces. Another way to achieve a gapless system between the heat dissipation surface 23 and the contact surface 25 is to produce the parts in question from materials that have a different coefficient of thermal expansion, in particular the base 21 has a greater coefficient of thermal expansion than the socket 24. In the warm In the state of the art, a press fit is created between the heat release surface 23 and the contact surface 25. The coefficient of thermal expansion of the mount 21 can also be smaller than the coefficient of thermal expansion of the counter electrode 16 or of the shaft 20.

The counter electrode 16 is electrically connected to the base 21, which in turn is electrically connected to the socket 24. Power is supplied to the counter electrode 16 via the housing 10, the socket 24 and the base 21.

At its end remote from the counter electrode 16, the base 21 has a thread 26 which is screwed into a corresponding thread 27 of the socket. The two threads 26, 27 also contribute to the transfer of heat from the base 21 to the socket 24.

In the transition between the thread 26 and the heat transfer surface 23, the base 21 can be provided with a shoulder 28 which rests against a corresponding step of the receiving bore provided in the socket 24. Through here arranged adjusting disks, the axial position of the counter electrode 16 can be finely adjusted.

The socket 24 contains at least one cooling channel 29 which loops around the receiving bore for the base 21 in at least one, preferably several turns 29a, 29b. The cooling channel 29 can follow a helical line. Its inlet 30 is preferably connected to the end of the helical turns 29 a, 29 b of the cooling channel 29 remote from the counter electrode 16. The outlet 31 is preferably connected to the end of the helical cooling channel 29 which is close to the counter electrode 16. However, an alternative arrangement is possible.

The cooling channel 29 is preferably flowed through by a liquid heat transfer fluid, in particular water. Deionized water is preferred, optionally with an admixture of glycol to reduce the electrical conductivity. The cooling circuit can thus be electrically separated from the counter electrode 16.

As FIG. 4 shows, the wire 15 is connected to a power supply device 32, for example in the form of sliding contacts or the like, which electrically connect the wire 15 to an arc power source 33. This is preferably designed as a direct voltage or direct current source, its negative pole preferably being connected to the counter electrode 16, which thus forms the cathode for the arc 17.

The cooling channel 29 is closed via a cooler 34 and a pump 35 to form a cooling circuit. The cooling effect of the same can be set permanently or also be adjustable bar. In the exemplary embodiment illustrated in FIG. 4, the regulation of the cooling effect is development of the speed of the pump 35 causes. A control device 36 provided for this purpose can regulate the speed of the pump 35, for example based on the temperature of the counter electrode 16, based on the temperature of the coolant or also based on electrical variables that result from the arc 17. For this purpose, the control device 36 can detect the arc current and the arc voltage in order to determine the cooling requirement of the counter-electrode 26 therefrom and on the basis of a suitable arc model. Additionally or alternatively, the control device 36 can be connected to the arc current source in order to be switched on and off in the simplest case synchronously or with a time delay to the arc current source 32.

The arc torch 10 described so far and the elements associated with it operate as follows:

In operation, the arc voltage is maintained between the wire 15 that is always fed in and the counter electrode 16, the arc 17 being supplied with the necessary current supplied by the arc current source 33. A gas jet released from the nozzle 18 blows the spray jet 14 onto the wall 13. At the same time, the arc torch rotates about its axis 37, possibly being moved axially. The counterelectrode 16 operated as a cathode heats up due to ohmic losses and the effect of the arc to temperatures between 2000 ° C. and 3000 ° C. and emits electrons in particular at its tip. As mentioned, the end of the counter electrode 16, referred to here generally as "cone tip 19", can be pointed or rounded or flattened. Part of the thermal power converted by the arc must be dissipated by the counter electrode 16. This heat is first transferred via the heat-absorbing surface 22nd on the base and transferred from this via the heat emission surface 23 to the socket 24. From the point of view of the counter electrode 16, the heat is initially distributed over a large area and can be transferred to the coolant over the considerable length of the cooling channel 29. Local overheating, vapor bubble formation or the like is excluded.

The control device 36 can regulate the cooling process in order to prevent excessive cooling of the counterelectrode 16 as well as insufficient cooling of the same.

Figure 5 illustrates a modified embodiment of the base 21 and the socket 24 of the counter electrode 16, for which the previous description, based on the same reference numerals, taking into account the special features explained below applies accordingly:

While the cooling channel 29 in the embodiment of Figure 3 runs exclusively in the socket 24, in the embodiment of Figure 5 it penetrates both the socket 24 and the base 21. This has a cooling channel 29 associated interior 38, which is closed at the end lying away from the counter electrode by a stop 39 or other suitable means. The interior 38 communicates via an inlet bore 40 and at least one outlet bore 41 with corresponding annular grooves of the holder 24, which are sealed by seals and which communicate with the inlet 30 and the outlet 31.

The counter-electrode 16 is held in the base 21 and can give off heat via the heat-absorbing surface 22 to the base 21, which in turn can transfer heat directly to the coolant via the heat-dissipating surface 23. The end face of the counterpart pointing away from the cone tip 19 electrode 16 can be in contact with the coolant. The heat release surface 23 here forms a wall of the interior space 38 and thus of the coolant reservoir. In addition, the counter electrode 16 with its shaft 20 can protrude into the inner space 38 and thus also come into direct contact with the coolant at sections of its man face. However, in this embodiment too, the counter electrode 16 is solid and free of cavities.

The arc wire spraying device according to the invention has an arc burner 10, which has a wire 15 that is always supplied as an anode and a counter electrode 16 as a cathode, to which a cooling channel 29 is assigned. This is arranged outside of the counter electrode 16, which is thus solid and free of cavities. On the one hand, this creates an effective cooling of the counter electrode 16 that is functional over a wide operating range.

Reference sign:

10 arc torches

11 bore

12 workpiece

13 Wall of the bore 11

14 spray

15 wire

15a wire feeder

16 counter electrode

17 arc

18 air nozzle

19 cone point

20 shaft base

Heat absorption surface Heat emission surface and fitting surface socket

Contact surface and fitting surface thread of the base thread of the socket shoulder cooling channel a, 29b turns of the cooling channel 29

Intake

procedure

Power supply device

Arc power source

cooler

pump

Control device

Arc torch axis 10

inner space

Plug

Inlet bore

Outlet hole

Claims

Patent claims:

1. Arc wire spraying device, with a wire feed device (15a) which is directed to an arc torch (10) feed wire (15), with a power feed device (32) which is in electrical connection with the wire (15) a counter electrode (16) to which a cooling channel (29) with a cooling medium is assigned, characterized in that the cooling channel (29) is arranged outside the counter electrode (16).

2. Arc wire spraying device according to claim 1, characterized in that the counter electrode (16) is held in a base (21) which is in heat-transferring connection with the Kühlka channel (29).

3. Arc wire spraying device according to claim 2, characterized in that the base (21) is formed from a heat conductive material.

4. Arc wire spraying device according to claim 2 or 3, characterized in that the base (21) has a with the counter electrode (16) in contact with heat has measuring surface (22) and a heat release surface (23) which is larger than the heat receiving surface (22).

5. arc wire spraying device according to one of claims 2 to 4, characterized in that the heat output surface (23) is arranged directly or indirectly with in the cooling channel (29) flowing cooling medium in heat exchange standing connection.

6. Arc wire spraying device according to one of the preceding claims, characterized in that the base (21) is assigned a socket (24) with which the base (21) is detachably connected.

7. Arc wire spraying device according to claim 6, characterized in that the cooling channel (29) is arranged in the holder (24).

8. Arc wire spraying device according to one of the preceding claims, characterized in that the cooling channel (29) is arranged to penetrate the base (21).

9. Arc wire spraying device according to one of claims 6 to 8, characterized in that the base (21) is arranged screwed to the socket (24).

10. Arc wire spraying device according to one of claims 6 to 9, characterized in that the base (21) has a fitting surface (23) which is assigned to a fitting surface (25) of the socket (24).

11. Arc wire spraying device according to claim 10, characterized in that the fitting surfaces (23, 25) of the base (21) and the socket (24) form a transition fit.

12. Arc wire spraying device according to claim 2 and 6, characterized in that the holder (24) has a receiving bore for the base (21) and that the cooling channel (29) is arranged leading around the receiving bore.

13. Arc wire spraying device according to claim 12, characterized in that the cooling channel (29) has several turns (29a, 29b) leading around the receiving bore.

14. Arc wire spraying device according to one of the preceding claims, characterized in that the counter electrode (16) is formed from tungsten or a tungsten alloy.

15. Arc wire spraying device according to one of the preceding claims, characterized in that the cooling channel (29) is connected to a cooling circuit which has a regulating device (36) by means of which the coolant temperature can be influenced.

16. Arc wire spraying device according to one of the preceding claims, characterized in that the cooling channel (29) is connected to a cooling circuit which has a regulating device (36) by means of which the flow rate of the coolant can be influenced.

17. A method for cooling a non-consumable counter electrode (16) of an arc burner (10) operated as a cathode, in which heat is extracted from the counter electrode via a coolant, characterized in that the power density of the heat flow to be dissipated from the counter electrode (16) to the Coolant is reduced in that the heat flow is conducted via a heat absorption surface (22) into a base (21) and from this via a heat release surface (23) to the coolant, the surface area of the heat release surface (23) being greater than the surface area of the heat absorption surface .