JP2510091B2 - Plasma jet torch - Google Patents

Description

TECHNICAL FIELD The present invention relates to a plasma jet torch capable of high output and high arc discharge voltage.

[Conventional technology]

A plasma jet torch is generally provided with an electrode 10, a nozzle 12, an insulator 14, and an electrode base 16 as shown in FIG. 3, and a voltage is applied between the electrode 10 and the nozzle 12 through the electrode base 16 by a power supply 18. An arc is generated, and plasma gas G is supplied from the periphery of the electrode 10 to generate a plasma jet from the nozzle 12.
20 jetting, cutting using this plasma jet 20,
Welding, spraying, etc.

A heat-resistant conductor such as tungsten is used for the electrode 10,
The nozzle 12 has a hollow inside, and the electrode base 16 has a hollow inside to introduce cooling water and perform water cooling. However, the consumption of the electrode 10 and the nozzle 12 is still not small, and in particular, the nozzle is used as an anode, so that the degree of heating is large, and the high-speed plasma flow passes through, so that the consumption is large.

The gas tunnel plasma torch shown in Fig. 4 is intended to increase the output. The electrode 10, nozzle 12, power source 18, etc. are similar to those in FIG. 3, and generate a plasma jet 20. Along with this plasma jet 20, in the torch of FIG. 4, a vortex flow generating nozzle 22 and a gas diverter nozzle 24 are provided. Although not shown, the nozzle 22 is provided with holes at a plurality of positions so as to generate a gas flow along the inner peripheral surface. When the working gas G is supplied, a vortex flow rotating at high speed around the plasma jet 20 is generated. Occurs. Further, since a voltage is applied between the nozzles 12 and 24 by the power supply 26, a discharge current flows between these nozzles, and the plasma jet 20 has a high output and a high density due to the power supply by this discharge and the thermal pinch effect by the high-speed vortex. Become.

[Problems to be solved by the invention]

It is difficult for the plasma torch shown in Fig. 3 to output a high voltage, and the plasma torch shown in Fig. 4 can achieve a high output, but the mechanism is complicated because a high-speed vortex is generated, and a vortex is generated to generate a gas tunnel. A large amount of working gas G is required to create the state, and the running cost is high. Further, in the thermal spraying, since the eddy current is generated, the sprayed powder is often scattered and the yield is low.

Further, for the thermal spraying, it is preferable that the length of the plasma jet is long so that the charged powder is in contact with the plasma jet for a sufficient time to melt, but in the torch of FIG. 3, the length of the plasma jet in the torch is not so long. .

An object of the present invention is to provide a plasma jet torch that improves the above points, can increase the plasma jet length, can use a high power supply voltage, can obtain a high output, and has a simple structure. It is what

[Means for solving problems]

FIG. 1 shows a plasma jet torch of the present invention, and FIG. 2 shows an enlarged main part thereof. Reference numeral 10 denotes an electrode, which is composed of a portion 10a where the arc is actually generated and a supporting portion 10b thereof. The arc generating member 10a is made of a heat-resistant metal such as tungsten or its alloy, and the supporting member 10b is made of a good conductive material such as copper. The support member 10b has a tubular shape, and a pipe 32 is inserted therein, which is supplied with water from the outside through the pipe 32a and discharges cooling water to the back surface of the arc generating member 10a to cool the member 10a. Water after cooling is pipe 3
Space between 2 and support member 10b, inside torch, narrowing nozzle base
It passes through the space of 52, the squeezing nozzle 34, and the waterway collar 50, and is discharged to the outside from the pipe 32b.

A narrowing nozzle 34 and a base material nozzle 36 are arranged in front of the electrodes. The narrowing nozzle 34 has a small opening so as to squeeze the arc generated from the electrode well. On the other hand, the base material nozzle 36 has an opening larger than the nozzle 34 so that the high-speed plasma jet does not come into strong contact with the base material nozzle 36, and the opening is tapered so as to expand downward (outward).
The degree of change in the inner diameter of the base material nozzle due to this taper is small on the exit side and large on the back side. The back surface constitutes part of the cooling water passage so that the nozzles 34, 36 are also water-cooled.

The cooling water channel of the base material nozzle 36 includes an inlet pipe 38 and a pipe fitting 4
0, 42, base material nozzle stand 44, pipe joint 46, and return water pipe 48. The cooling water channel of the narrowing nozzle 34 shares a part with the cooling water channel of the electrode. Reference numeral 50 is a water channel collar, 52 is a narrowing nozzle base, and the narrowing nozzle 34 forms a cavity as shown with these, and this cavity 60 is a part of the narrowing nozzle cooling water channel, which is not shown. It communicates with the pipes 32a and 32b.

Further, 54 is an insulator (centering stone) between the electrode 10 and the nozzle 34, and 56 is an insulator (insulating collar) between the nozzles 34 and 36. The insulating collar 56 has a hole through which the side gas is supplied as a swirling flow between the nozzles 34 and 36. The side gas supply passages are the side gas supply pipes arranged on the front / back surfaces of FIGS. 1 and 2, holes of the base material nozzle stand 44 (none of which are shown), and a cavity 58. 70
Is a gas seal collar.

Reference numeral 62 is a pilot power source, one end of which is connected to the electrode 10 and the other end of which is connected to the squeezing nozzle 34. 64 is the main power supply, one end of which is an electrode
10, the other end is connected to the base material nozzle 36 through the nozzle base 44. In the figure, this connection is schematically shown, but in reality, the pipes 38, 4
This is done with a cable arranged like 8. For example, the wiring to the nozzle 36 is performed by an electric cable which is arranged on the front / back surfaces of FIGS. 1 and 2 and on the side opposite to the side gas supply pipe and is connected to the nozzle base 44.

The plasma working gas is supplied from the gas supply pipe 68 to the electrode 10
Is supplied to the space between the nozzle and the nozzle.

[Action]

A voltage is applied to the electrode 10 and the nozzles 34 and 36 by the power supplies 62 and 64,
When plasma gas is supplied from the gas supply pipe 68, an arc is generated between the member 10a of the electrode 10 and the nozzle 34, and the gas flow supplied to this space is ionized into a plasma jet. This plasma jet is squeezed by the nozzle 34, high temperature,
At a high speed, it jets out of the nozzle 34 and then from the nozzle 36.

When the plasma jet passes through the nozzle 36, an arc discharge is generated between the electrode 10 and the nozzle 36. Since this discharge length is long, the arc voltage is large. This means that the main power supply 64 may have a higher voltage than the pilot power supply 62, and the torch output, which is the voltage-current product, can be easily increased. Main power supply 64
After the arc discharge between the electrode 10 and the nozzle 36 due to occurs, the switch 66 may be opened to shut off the pilot power supply.

The part of the anode point generated in the base material nozzle 36 becomes extremely hot locally, and the nozzle surface is greatly consumed even if it is water-cooled.
Therefore, the plasma gas flow rate and the side gas flow rate are set appropriately so that the anode point generation position is set to the taper portion of the base material nozzle 36 (portion a in FIG. 2), and high temperature and high speed plasma jet flow It is avoided so that it does not directly act on the anode spot generation part. The nozzle 34 protects the high-temperature plasma by narrowing the high-temperature plasma to the center, while the gas that has not been heated to a high temperature supplied from the pipe 68 flows across the nozzle surface.

The reason why the portion a in FIG. 2 is the anode point generation position will be described in detail below. That is, the plasma gas passes through the hole of the narrowing nozzle 34 and is discharged into the hole of the base material nozzle 36.
On the other hand, the side gas becomes a swirl flow by passing through the holes of the insulating collar 56, and is discharged into the base material nozzle holes while swirling outside the plasma gas. At this time, in the base material nozzle hole,
Due to the plasma gas flow and the side gas swirl flow, a gas density difference (gas pressure difference) is generated between the nozzle hole central portion and the wall side portion. That is, since it is a swirling flow, the gas molecules are pushed outward from the center by the centrifugal force, and the gas molecule density becomes higher on the wall side than on the central portion. However, this density difference depends on the size of the nozzle hole diameter. If the hole diameter is small, such as on the inlet side of the base material nozzle 36, the swirling flow velocity is large, and the density difference is large. When the hole diameter is large, the swirling flow velocity is small and the density difference is small. When an arc discharge is generated in such a state, the arc tends to flow in a place where the gas molecule density is lower, so it passes through the center of the narrowing nozzle hole and the center of the base material nozzle hole, When the density difference is small at the portion a, the arc relaxes the force to restrain it in the central portion, and an anode point is generated at the portion a.

When an anode spot is formed on the a portion of the base material nozzle 36, the high temperature and high speed plasma jet flow will not directly hit the anode spot generating portion where the temperature becomes high, so the consumption of the nozzle is reduced. The gas swirling flow causes the anode point to rotate in the circumferential direction and to move up and down in the axial direction as well, so that the area of the anode point is large and spreads over the entire area of part a. Is good, the life of the nozzle is long, and the anode point generation part of the nozzle touches the outside air to oxidize and peel off, like the one where the anode point is generated at the nozzle outlet, the anode point stands still and becomes a point area, cooling There is no such a case that the effect is deteriorated, and there is an advantage that oxidation or the like does not occur by being protected by an inert gas.

Since this plasma jet torch has a long arc length, a high-voltage power supply can be used and a high output can be easily achieved. Thermal spraying can be performed by using a powder mixed gas as the side gas, and the powder of the gas is sufficiently heated and melted while passing through the nozzle 36. The side gas cools and protects the insulator 56.

In this plasma jet torch, a narrowing nozzle 34 that strongly narrows the plasma jet in the center with a plasma gas is placed in front of the electrodes, so that a mixed gas of nitrogen, argon, and hydrogen as the plasma gas, and nitrogen gas alone can also be used. . That is, nitrogen and hydrogen gas have a high ionization voltage and become high in temperature, resulting in a large consumption of nozzles. The consumption of the nozzle surface is reduced, and eventually the mixed gas and the single gas can be used.

〔Example〕

The case where it is used as a heating heat source or a thermal spraying heat source will be described together with a conventional example.

The present invention is plasma jet current 200 (A), plasma gas (nitrogen gas) 40 / min, narrowing nozzle diameter 2.4 mm, base material nozzle diameter (minimum diameter portion) 6.5 mm, side gas (nitrogen gas) 1
The arc voltage was 180 (V) under the condition of 0 / min. As described above, according to the present invention, a small current and a high voltage are possible, and a high output of 36 KVA can be obtained even with a small current. The temperature of this plasma jet flame was about 1200 ° C. at a position 200 mm away from the torch tip.

In the prior art shown in FIG. 3, the plasma current
Plasma gas (argon gas) 60 / min at 1000 (A),
The arc voltage was 40 (V) under the condition that the nozzle diameter was 6.25 mm. Thus, despite the large current of 1000 (A), the output is 40 KVA. The temperature of the plasma jet flame was about 500 ° C at a position 200 mm away from the torch tip.

Thus, in order to obtain almost the same output, a low current is required in the present invention. As a result, the consumption of the nozzle is reduced to about 1/2, the power source is downsized, and the cable is thin. Further, in the case of thermal spraying, the present invention has a long discharge length and was able to completely melt and spray the metal powder.

Further, in the conventional technique shown in FIG. 4, the initial plasma jet is 100 A, the plasma voltage (argon gas) is 40 / min, the arc voltage is 20 (V), the superimposed plasma jet current is 400 A, and the working gas (argon gas) is 250 / min. It was 110V. Under this condition, a plasma flame having a temperature higher than that of the present invention was obtained, but a large amount of argon gas was used as a working gas, and as a whole, about 6 times was used as compared with the present invention, and the apparatus was complicated. , Control is not easy and is a problem.

〔The invention's effect〕

As described above, according to the present invention, a high voltage can be used, a high output can be obtained with a relatively small current, nitrogen gas can be used alone, and a long plasma jet length can be obtained, which is effective for thermal spraying and the like. A plasma jet torch having a long nozzle life, a relatively simple structure, and a low running cost can be obtained.

[Brief description of drawings]

FIG. 1 is a side view of the plasma jet torch of the present invention,
Some are shown in cross section. FIG. 2 is an enlarged view of a main part of FIG. 1, and FIGS. 3 and 4 are explanatory views of a conventional example. 1 and 2, 10 is an electrode, 34 is a narrowing nozzle, 36 is a base material nozzle, 62 is a pilot power source, 64 is a main power source, 32a, 32b, 3
8, 40 is a cooling water supply pipe, and 68 is a plasma gas supply pipe.

Claims (1)

(57) [Claims] 1. An electrode (10), a narrowing nozzle (34) placed in front of the electrode, and a base material nozzle (36) placed in front of the narrowing nozzle, the narrowing nozzle comprising a plasma jet. The base material nozzle has a narrow opening so that it narrows down strongly in the center, and the base material nozzle has a wider opening than the narrowing nozzle and tapers so that it expands toward the exit side. It is small on the output side and large on the back side. The pilot power supply (62) is connected between the electrode and the narrowing nozzle, and the main power supply (64) is connected between the electrode and the base material nozzle. A mechanism for cooling the narrowing nozzle and the base material nozzle,
A plasma jet torch provided with a mechanism for supplying a plasma gas to a space between an electrode and a narrowing nozzle and a mechanism for supplying a side gas as a swirling flow from between the narrowing nozzle and a base material nozzle.