HK1173195B - Plasma spraying apparatus - Google Patents

Description

Plasma spraying device

Technical Field

The present invention relates to a plasma spraying apparatus that transfers a plasma arc to a conductive wire to generate a plasma flame and sprays the plasma flame while forming the wire into a droplet.

Background

Fig. 6 is a sectional view schematically showing a conventional plasma spraying apparatus. As shown in fig. 6, a conventional plasma spraying apparatus 90 includes: a first gas nozzle 91 forming a first gas passage 91 a; a second gas nozzle 92 disposed outside the first gas nozzle 91 and forming a second gas passage 92 a; a cathode 93 disposed substantially on the central axis of the nozzle opening 91b of the first gas nozzle 91 and the nozzle opening 92a of the second gas nozzle 92; a power supply device 94; and a wire guide hole 95 for supplying a conductive wire W for thermal spraying in the vicinity of the nozzle opening 92a of the second gas nozzle 92.

The wire W is supplied obliquely forward from the wire guide hole 95 toward the central axis of the nozzle opening 92 a. Then, the first gas discharged from the first gas passage 91a is converted into plasma by an arc generated between the wire W indirectly connected to the anode side of the power supply device 94 through the second gas nozzle 92 and the cathode 93 connected to the cathode side of the power supply device 94, and is discharged as a droplet D from the wire W. The droplets D are further refined and accelerated by the second gas injected from the second gas passage 92a to the front of the second gas nozzle 92, and are injected onto the object T to be processed, thereby forming the sprayed coating S.

In the plasma spraying apparatus of the type in which the wire W is sprayed as a droplet by the plasma flame F and the second gas flow, it is necessary to always position the tip of the wire W inside the plasma flame F in order to stably generate the plasma flame F and to spray the droplet D uniformly.

However, in the conventional plasma spraying apparatus, the wire guide hole 95 for supplying the wire W has a circular cross-sectional shape, and has a diameter larger than the outer diameter of the wire W in order to avoid catching, clogging, and the like due to distortion defects inherent to the wire W. Therefore, it is difficult to feed the wire W while correcting the twist of the wire W, and there is a problem that the wire W repeatedly occurs due to the distortion defect, and the wire W is sometimes deviated from the center of the plasma flame F, sometimes returns to the center, and cannot be stably fed to the center of the plasma flame F.

Therefore, for example, as described in patent document 1, an improvement is made in which a correction guide member for correcting a first bend of a wire material by sandwiching the wire material and a second bend guide member for performing a second bend exceeding an elastic limit of the wire while guiding the wire from the correction guide member are provided in a support plate integrated with a plasma arc torch, the wire is supplied, and the wire is supplied after a distortion defect inherent to the wire is removed, whereby the tip of the wire is always positioned at the center of a plasma gas flow, and a stable plasma flame is generated.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 9-308970.

However, as described in patent document 1, when the second bending guide member that performs the second bending of the wire beyond the elastic limit is integrated with the plasma arc torch, the wire is bent by the second bending guide member beyond the elastic limit, and therefore the force of feeding the wire becomes excessively large. Therefore, the wire supply mechanism tends to be large, and the torch as a whole tends to be large.

Disclosure of Invention

Accordingly, an object of the present invention is to provide a small-sized plasma spraying apparatus capable of stably conveying a wire without providing a second bending guide member for performing a second bending of the wire exceeding an elastic limit thereof, regardless of a distortion defect inherent in the wire, when the wire is supplied in the vicinity of a nozzle opening of a second gas nozzle.

The plasma spraying device of the invention comprises: a cathode; a first gas nozzle forming a first gas passage at an outer periphery of the cathode to cover a front end portion of the cathode; a second gas nozzle disposed outside the first gas nozzle to form a second gas passage; and a wire passage for supplying a wire for thermal spraying to the vicinity of the nozzle opening of the second gas nozzle, wherein the first gas injected from the first gas nozzle is turned into plasma by an arc generated between a tip of the wire supplied from the wire passage and a cathode to form a plasma flame injected from the first gas nozzle, the tip of the wire is formed into a droplet, and the droplet is injected onto the object to be treated by the plasma flame and the second gas injected from the second gas nozzle, wherein the wire passage has a substantially rectangular cross-sectional shape elongated in the extending direction of the plasma flame, and the wire is bent within a range not exceeding the elastic limit.

According to the plasma spraying apparatus of the present invention, the wire is bent in a range not exceeding the elastic limit, so that the distortion defect of the wire can be escaped in the extending direction of the plasma flame, and the displacement in the direction perpendicular to the extending direction of the plasma flame can be prevented. Further, even if the tip portion of the wire is displaced slightly with respect to the extending direction of the plasma flame, the plasma flame does not become unstable because the tip portion is located on the axis of the plasma flame. Therefore, according to the plasma spraying apparatus of the present invention, it becomes possible to stably supply the wire to the center portion of the plasma flame.

Here, it is desirable that the wire passage has a substantially rectangular cross-sectional shape, and the width in the short side direction is larger than the diameter of the wire by 3% or more and less than 10%. Thus, the distortion defect of the wire can be substantially escaped only in the extending direction of the plasma flame, and the displacement in the direction perpendicular to the extending direction of the plasma flame can be prevented. Further, when the width in the short side direction exceeds the diameter of the wire by less than 3%, the gap for passing the distortion defect of the wire in the extending direction of the plasma flame is insufficient, and there is a possibility that the wire is caught or clogged. On the other hand, when the width in the short side direction exceeds the diameter of the wire by 10% or more, the gap is too large, and thus the wire may escape not only in the stretching direction of the plasma flame but also in the right-angle direction.

The wire passage has a first wire passage having a wire outlet formed near a nozzle opening of the second gas nozzle and a second wire passage supplying a wire at a predetermined inclination to the first wire passage. Thus, when the wire is fed from the second wire passage to the first wire passage, the wire is bent at a predetermined inclination within a range not exceeding the elastic limit of the wire, so that the distortion defect of the wire can be escaped in the stretching direction of the plasma flame, and the displacement in the direction perpendicular to the stretching direction of the plasma flame can be prevented.

In this case, the predetermined inclination angle is preferably 1 to 5 °. This makes it possible to bend the wire within a range not exceeding the elastic limit of the wire, and to supply the wire to the center of the plasma flame more stably. Further, when the predetermined inclination angle is less than 1 °, the wire cannot be bent in a predetermined manner, and the wire conveyance may become unstable. On the other hand, when the predetermined inclination angle exceeds 5 °, a bend exceeding the range of the elastic limit of the wire may be applied.

Preferably, the first wire passage and the second wire passage are arranged with a gap of 3 to 10 mm. Thus, the first wire passage, the second wire passage and the gap can form a curved wire passage having a large simulation, and the wire can be bent within a range not exceeding the elastic range. When the gap is less than 3mm, it is substantially not different from the case where the gap is formed by one first wire passage. On the other hand, in the case where the gap exceeds 10mm, the effect of the bending applied to the wire by the second wire passage is weakened, which is also substantially different from that formed by one first wire passage.

ADVANTAGEOUS EFFECTS OF INVENTION

(1) The wire passage has a substantially rectangular cross-sectional shape elongated in the plasma flame stretching direction, and the wire is bent within a range not exceeding the elastic limit, so that the second bending guide member for performing the second bending of the wire exceeding the elastic limit is not provided, and the wire can escape the distortion defect inherent in the wire in the plasma flame stretching direction, prevent the displacement in the direction perpendicular to the plasma flame stretching direction, and stably supply the wire to the center of the plasma flame.

(2) Since the width of the wire passage in the short side direction is larger than the diameter of the wire by 3% or more and less than 10% in the substantially rectangular cross-sectional shape, the distortion defect of the wire can be substantially escaped only in the extending direction of the plasma flame, and the wire can be supplied more stably to the center of the plasma flame while preventing the displacement in the direction perpendicular to the extending direction of the plasma flame.

(3) By providing the wire passage with a first wire passage having a wire outlet formed near the nozzle opening of the second gas nozzle and a second wire passage for supplying the wire to the first wire passage at an inclination angle of 1 to 5 DEG, the wire can be bent within a range not exceeding the elastic limit of the wire, and the wire can be supplied to the central portion of the plasma flame more stably.

(4) The first wire passage and the second wire passage are arranged with a gap of 3-10 mm, so that a curved wire passage having a larger simulation than the first wire passage and the second wire passage can be formed, and the wire can be bent within a range not exceeding the elastic range.

Drawings

FIG. 1 is a schematic configuration diagram of a plasma spraying apparatus according to an embodiment of the present invention.

Fig. 2 is a longitudinal sectional view showing details of a main part of the plasma spraying torch of fig. 1.

Fig. 3 is a view from direction a of fig. 2.

Fig. 4 is an explanatory view of the operation of the plasma spraying torch of fig. 1.

Fig. 5 is an explanatory diagram showing a sectional shape of a wire passage and a direction of a force applied to a wire.

Fig. 6 is a sectional view schematically showing a conventional plasma spraying apparatus.

Detailed Description

FIG. 1 is a schematic configuration diagram of a plasma spraying apparatus according to an embodiment of the present invention. Fig. 2 is a longitudinal sectional view showing details of a main part of the plasma torch of fig. 1. Fig. 3 is a view from direction a of fig. 2. Fig. 4 is an explanatory diagram of an operation of the plasma torch of fig. 1.

In fig. 1, a plasma spraying apparatus 1 according to an embodiment of the present invention includes: a plasma spraying torch 2 for spraying the molten metal wire W onto the object to be processed by plasma flame; a gas supply source 3 that supplies a first gas and a second gas to the plasma spraying torch 2; a power supply 4 for supplying operating power to the plasma spraying torch 2; a wire reel 5 around which a wire W is wound; a wire straightening machine 6 for straightening a winding defect of the wire W drawn from the wire reel 5; and a wire supply mechanism 7 for supplying a wire W from a wire transport tube 8 to the plasma spraying torch 2.

As shown in fig. 2, the plasma spraying torch 2 includes: a first gas nozzle 10 forming a first gas passage 11; a second gas nozzle 20 disposed outside the first gas nozzle 10 to form a second gas passage 21; a third gas nozzle 30 disposed between the first gas nozzle 10 and the second gas nozzle 20 to form a third gas passage 31; a cathode 40 disposed substantially on the central axis of the nozzle opening 12 of the first gas nozzle 10 and the nozzle opening 22 of the second gas nozzle 20; and a wire passage 50 for supplying the wire W for spraying to the vicinity of the nozzle opening 22 of the second gas nozzle 20.

The first gas nozzle 10 is formed to cover the tip end of the cathode 40, and a first gas passage 11 is formed on the outer periphery of the cathode 40. The first gas supplied to the first gas passage 11 is an inert gas such as nitrogen or argon. Alternatively, it is also possible to use compressed air as the first gas. The first gas supplied from the first gas passage 11 is ejected from the nozzle opening 12 of the first gas nozzle 10 toward the front of the second gas nozzle 20.

The third gas nozzle 30 is formed to surround the outside of the first gas nozzle 10, and a third gas passage 31 is formed on the outer periphery of the first gas nozzle 10. The third gas is compressed air or carbon dioxide. The second gas nozzle 20 is formed to surround the outside of the third gas nozzle 30, and a second gas flow path 21 is formed on the outer periphery of the third gas nozzle 30. The second gas is compressed air or carbon dioxide.

The wire passage 50 is composed of a first wire passage 51a having a wire outlet 51b formed in the vicinity of the nozzle opening 22 of the second gas nozzle 20, and a second wire passage 52a that supplies the wire W to the first wire passage 51a at a predetermined inclination angle θ. The wire passage 50 imparts a bend to the wire W in a range not exceeding the elastic limit by the first wire passage 51a and the second wire passage 52 a.

As shown in fig. 3, the first wire passage 51a has a substantially rectangular cross-sectional shape elongated in the extending direction of the plasma flame, and is formed linearly penetrating the first wire guide member 51 disposed outside the second gas nozzle 20. Similarly, the second wire passage 52a has a substantially rectangular cross-sectional shape elongated in the extending direction of the plasma flame, and is formed to linearly penetrate the second wire guide member 52 arranged at a position offset from the first wire passage 51 a.

The width a of the first wire passage 51a in the longitudinal direction is set to be larger than the diameter d of the wire W by 10% to 95%. The width b of the first wire passage 51a in the short-side direction is set to be larger than the diameter d of the wire W by 3% or more and less than 10%. In the present embodiment, the diameter d of the wire W is 1.6mm, the width a in the longitudinal direction is set to be about 0.2 to 1.5mm larger than the diameter d of the wire W, and the width b in the short direction is set to be about 0.05 to 0.15mm larger than the diameter d of the wire W. The same is true for the second wire passage 52 a.

The so-called substantially rectangular cross-sectional shapes of the first wire passage 51a and the second wire passage 52a include, in addition to the rectangular cross-sectional shape, a shape in which corners of the rectangular cross-sectional shape are subjected to processing such as C-chamfering or R-chamfering in a range not to reach the outer surface of the wire W. Therefore, in the present embodiment, the wire W is also subjected to a force in a direction perpendicular to both the plane in the longitudinal direction and the plane in the short direction in the first wire passage 51a and the second wire passage 52 a.

In addition, the inclination angle θ of the second wire passage 52a with respect to the first wire passage 51a is an angle formed by the center line of the first wire passage 51a and the center line of the second wire passage 52 a. In the present embodiment, the inclination angle θ is set to about 1 to 5 °. The second wire guide member 52 is provided at a position where the first wire passage 51a and the second wire passage 52a are arranged with the gap c therebetween. In the present embodiment, the clearance c is set to about 3 to 10 mm.

In this way, in the plasma spraying torch 2 of the present embodiment, the first wire passage 51a and the second wire passage 52a are arranged with the gap c therebetween, and the linear first wire passage 51a and the linear second wire passage 52a are used to form the curved wire passage 50 having a high fitting property, and the wire W is bent within a range not exceeding the elastic range. Further, the first wire passage 51a and the second wire passage 52a may be formed in a curved shape.

The anode side of the power source 4 is connected to the first wire guide member 51, and is indirectly connected to the wire W in the first wire passage 51a passing through the first wire guide member 51. On the other hand, the cathode side of the power source 4 is connected to the cathode 40. Further, the anode side of the power source 4 may be directly connected to the wire W.

In the plasma spraying apparatus 1 configured as described above, when the wire W wound around the wire reel 5 is fed to the plasma spraying torch 2 by the wire supply mechanism 7, a strong winding defect of the wire W is corrected by the wire corrector 6 and stretched into a gentle curve. Then, the wire W is supplied to the wire passage 50 through the wire conveying pipe 8. In the wire passage 50, the wire W is also forced in the first wire passage 51a and the second wire passage 52a only in the direction perpendicular to either the plane in the longitudinal direction or the plane in the short-side direction, and as shown in fig. 4, a bending is imparted to the extension direction of the plasma flame F within a range not exceeding the elastic limit.

Here, the first wire passage 51a and the second wire passage 52a have a substantially rectangular cross-sectional shape that is long in the extending direction of the plasma flame F, and therefore, the distortion defect may escape in the extending direction of the plasma flame F. In particular, in the present embodiment, the width b in the short side direction is set to be larger than the diameter d of the wire W only in the range of 3% or more and less than 10%, and therefore, the wire W does not escape in the direction perpendicular to the extending direction of the plasma flame F. Therefore, even if some displacement occurs in the tip portion of the wire W with respect to the extending direction of the plasma flame F, the displacement in the direction perpendicular to the extending direction of the plasma flame F can be prevented from being positioned on the axis of the plasma flame F.

Figure 5 shows the cross-sectional shape of the wire passage and the direction of the force to which the wire is subjected. In fig. 5, the substantially rectangular cross section a is a rectangular cross section, the corner of the rectangular cross section of the substantially rectangular cross section B is a shape that is chamfered by C within a range that does not touch the outer surface of the wire W, and the corner of the rectangular cross section of the substantially rectangular cross section C is a shape that is chamfered by R within a range that does not touch the outer surface of the wire W. In these substantially rectangular cross-sectional shapes, the wire W is subjected to only a force in a direction perpendicular to each plane, regardless of whether the wire W touches the plane in the longitudinal direction or the plane in the short-side direction.

The wire W cannot be completely straightened into a straight line by the wire straightening mechanism 7, and therefore, a distortion defect remains. Then, the wire conveying pipe 8 is changed in the curved shape into various states by the processing of the plasma spraying torch 2 at the time of the operation, and is not formed into a constant shape. Therefore, when the wire W having the distortion defect left therein is conveyed in the wire conveying pipe 8 having such an inconstant shape, a force of bending or twisting in accordance with the shape of the wire conveying pipe 8 acts on the wire W. The wire W is conveyed while being bent freely within the elastic limit in the same manner as a spring at a position where the direction of the force is stable and while being bent and advanced within the wire conveying pipe 8 by the force of the bending or twisting.

At this time, in the above-described substantially rectangular cross-sectional shape, when the wire W touches the plane in the short side direction, the wire W receives a force in a direction perpendicular to the plane in the short side direction, that is, in the extending direction of the plasma flame F (hereinafter referred to as "X direction"), and passes through the distortion defect in the extending direction of the plasma flame F. When a force in a direction perpendicular to the extending direction of the plasma flame F (hereinafter referred to as "Y direction") acts when only the short-side direction flat surface is contacted, the wire W freely moves by the gap of the width b in the short-side direction and contacts the long-side direction flat surface. In particular, when a twisting force is applied, the forces in the X direction and the Y direction are dispersed into forces in the short-side direction and the long-side direction, and the forces act in the direction perpendicular to the respective surfaces, and act to suppress twisting of the wire W, so that the position of the wire W is stabilized.

On the other hand, in the case of a circular cross section or an elliptical cross section, when the wire W touches a curved surface of the circular cross section or the elliptical cross section, the wire W can move freely along the curved surface only by a force in a direction perpendicular to the curved surface. In particular, when a twisting force is applied, the wire W freely rotates along a curved surface, and therefore twisting of the wire W is not suppressed. Therefore, the direction of the force applied to the wire W is uncertain, and the position of the wire W becomes uncertain.

In this way, in the plasma spraying apparatus 1 of the present embodiment, the tip portion of the wire W can stably supply the wire W toward the center portion of the plasma flame F. Then, the first gas discharged from the first gas passage 11 is converted into plasma by an arc generated between the wire W indirectly connected to the anode side of the power source 4 through the first wire guide member 51 and the cathode 40 connected to the cathode side of the power source 4, and is formed into a plasma flame F, so that the wire W is ejected as droplets D. The droplets D are further atomized by the second gas ejected from the second gas passage 21 to the front of the second gas nozzle 20, are further accelerated, and are ejected onto the object T to be processed, thereby forming the sprayed coating S.

At this time, in the plasma spraying device 1 of the present embodiment, the inside of the third gas flow ejected from the third gas passage 31 disposed between the first gas passage 11 and the second gas passage 21 receives the heat of the plasma flame F, and the high-temperature gas jet G is formed. By this high-temperature gas jet G, disturbance generated from the outer peripheral portion of the plasma flame F due to rapid convergence of the second gas jetted to the outside thereof is suppressed, whereby gas diffusion of the plasma flame F can be prevented, and oxidation of the surface of the particles that have become the droplets D can be reduced. This makes it possible to form a sprayed coating S with little oxidation on the object T.

In addition, in the case where nitrogen gas or argon gas, which is an inert gas, is used as the third gas, as described above, disturbance generated from the outer peripheral portion of the plasma flame F due to rapid convergence of the second gas is prevented, and a high-temperature inert gas jet that receives heat of the plasma flame F is formed at the outer peripheral portion of the plasma flame F. Thus, the particles of the droplet D are pulverized and accelerated in a state where the change in the composition of the particles is prevented by the high-temperature inert gas injection, and are protected from oxidation by the second gas. This makes it possible to form the sprayed coating S with less oxidation.

In the present embodiment, both the first wire passage 51a and the second wire passage 52a are formed as passages having a substantially rectangular cross-sectional shape that is long in the extending direction of the plasma flame, but only either one of the passages may be formed as a passage having a substantially rectangular cross-sectional shape that is long in the extending direction of the plasma flame. In this case, the first wire passage or the second wire passage having a substantially rectangular cross-sectional shape elongated in the extending direction of the plasma flame allows the distortion defect of the wire W to escape in the extending direction of the plasma flame F, and the tip portion of the wire W can be supplied to the center portion of the plasma flame F.

Industrial applicability

The plasma spraying apparatus of the present invention is useful as an apparatus for forming a spraying coating for rust prevention on the surface of a steel structure.

Description of the reference numerals

1 plasma spraying device

2 plasma spraying torch

3 gas supply source

4 power supply

5 spool of wire

6 metal wire straightening machine

7 wire supply mechanism

10 first gas nozzle

11 first gas passage

12 nozzle orifice

20 second gas nozzle

21 second gas passage

22 nozzle orifice

30 third gas nozzle

31 third gas passage

40 cathode

50 wire via

51 first wire guide member

51a first wire path

52 second wire guide member

52a second wire path.

Claims (4)

1. A plasma spraying device is provided with: a cathode; a first gas nozzle which forms a first gas passage on the outer periphery of the cathode so as to cover the front end of the cathode; a second gas nozzle disposed outside the first gas nozzle to form a second gas passage; and a wire passage for supplying a wire for thermal spraying to the vicinity of the nozzle opening of the second gas nozzle, wherein a first gas injected from the first gas nozzle is turned into plasma by an arc generated between a tip of the wire supplied from the wire passage and the cathode to form a plasma flame injected from the first gas nozzle, the tip of the wire is turned into a droplet, and the droplet is injected onto an object to be processed by the plasma flame and a second gas injected from the second gas nozzle,

the wire passage has a substantially rectangular cross-sectional shape elongated in the extending direction of the plasma flame, and the wire is bent within a range not exceeding the elastic limit.

2. The plasma spraying device of claim 1,

the wire passage has a substantially rectangular cross-sectional shape, and the width in the short side direction is larger than the diameter of the wire by 3% or more and less than 10%.

3. The plasma spraying device as claimed in claim 1 or 2,

the wire passage has a first wire passage having a wire outlet formed near a nozzle opening of the second gas nozzle, and a second wire passage supplying the wire at an inclination angle of 1 to 5 ° to the first wire passage.

4. The plasma spraying device as claimed in claim 3,

the first wire passage and the second wire passage are arranged with a gap of 3 to 10 mm.