JP2714203B2 - Non-transfer type plasma cutting torch - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a non-transfer type plasma cutting torch which can be applied to both metal and non-metal materials and can perform stable cutting with a narrow cutting margin.

[Conventional technology]

FIG. 6 shows a principle diagram of a plasma jet generator that cools the outer periphery of the anode nozzle with air or gas. In the figure, 1
Is a rod-shaped cathode, 2 is an anode nozzle, 3 is a shield cap,
4 is a plasma jet frame, 5 is a material to be cut, 6 is a gas for generating plasma, 7 is air or gas for cooling an anode nozzle, and a plasma jet generating torch 10 is composed of a rod-shaped cathode 1, an anode nozzle 2 and a shield cap 3. A DC voltage is applied between the rod-shaped cathode 1 and the anode nozzle 2 by the plasma power source 8. Reference numeral 9 denotes a high-frequency generator, and an arc generated between the rod-shaped cathode 1 and the anode nozzle 2 with the aid of the high-frequency generator is used for the nozzle 2a of the anode nozzle 2.
The high-temperature plasma flow is squeezed by the plasma generating gas 6 flowing through the wall surface and the nozzle hole 2a, and is ejected from the nozzle hole tip as the plasma jet frame 4. At this time, the anode nozzle 2 is heated by an arc. In a plasma jet generator having a small capacity of about 2 kW or less, the anode nozzle cooling air or gas 7 is caused to flow between the anode nozzle 2 and the shield cap 3. A method of cooling the anode nozzle 2 is used. In the non-transfer type plasma cutting, the material to be cut 5 is cut by the above-described plasma jet frame 4, and is applied to both metal and non-metal.

Examples of currently available non-transfer type plasma cutting torches include a double nozzle structure in which a gas for plasma generation flows between an anode nozzle and a cathode sleeve nozzle covering a rod-shaped cathode, and a nozzle hole diameter d; 0.1 to 0.3. mmφ, nozzle hole length L; about 1m
Some have m.

On the other hand, in transfer-type plasma cutting in which a conductive material to be cut is used as the anode and the nozzle is not energized, the nozzle is used only for narrowing the plasma arc, so the nozzle hole diameter is small, and the cathode passes through the nozzle from the cathode. In order to prevent the so-called double arc phenomenon, in which an arc is generated in the material to be cut at the anode, a nozzle with a relatively short nozzle hole length is generally used, and a commercially available domestic product having a plasma current capacity of 50 A or less (( ) According to the Japan Welding Association, Gas Fusing Subcommittee, Plasma Subcommittee Edition, introduction of commercially available domestic plasma cutting machine products (in 1986)), nozzle hole diameter d: 0.6-1.2 mmφ, nozzle hole length L: about 2 mm I have.

In addition, Japanese Utility Model Application Laid-Open No. 61-127874 describes an example in which a value L / d obtained by removing the nozzle hole length L by the nozzle hole diameter d is 0.3 ≦ L / d ≦ 0.8 in a transition type plasma arc welding tip. Have been.

[Problems to be solved by the invention]

According to the results of experiments conducted by the present inventors, in the non-transfer type plasma cutting torch 10 as shown in FIG. 6, the nozzle hole diameter of the anode nozzle 2 for controlling the shape of the plasma jet frame 4 which affects the cutting performance d, when the nozzle hole length L is not properly selected, the following inconveniences occur.

(1) d; small, L; short When d is reduced and L is shortened as in the nozzle used for the transfer type plasma cutting, the anode point A becomes the nozzle hole of the anode nozzle 2 as shown in FIG. Since the plasma jet frame 4 is discharged to the tip and has a small effect of squeezing the plasma jet frame 4 with the wall surface of the nozzle hole 2a, the squeezing of the plasma jet frame 4 becomes insufficient, the cutting allowance of the workpiece 5 is large, and d is large. Because of the small size, the flow rate of the plasma generating gas 6 is reduced, and the cutting ability is reduced. Further, when an active gas such as oxygen gas or air is used as the plasma generating gas 6, if the anode point A is discharged to the tip of the nozzle hole of the anode nozzle 2, the tip of the nozzle hole at the anode point portion And the cutting performance becomes unstable because the diameter of the nozzle tip hole is increased. Further, when d is minimized as in the conventional example of the non-transfer type plasma cutting torch described above, since the nozzle hole 2a is closed by waste of the anode nozzle 2, the cutting performance tends to be unstable, Not practical.

(2) d; large, L; short When d is large and L is short as in the conventional example of the transition type plasma arc welding tip described above, the anode point A is discharged to the tip of the nozzle hole of the anode nozzle 2. In addition, the squeezing of the plasma jet frame 4 becomes insufficient, the cutting margin of the workpiece 5 is large, and the cutting ability is reduced. When the flow rate of the plasma generating gas 6 is increased as a measure for improving the cutting ability, the anode point A becomes more and more likely to be discharged to the tip of the nozzle hole of the anode nozzle 2, and when an active gas is used as the plasma generating gas 6, Cutting performance becomes unstable due to deformation of the anode nozzle 2 due to consumption of the anode portion.

(3) d; small, L; length Since d is small, it is impossible to increase the flow rate of the plasma generating gas, and since L is long, the plasma jet frame 4 ejected from the tip of the nozzle hole of the anode nozzle 2 cannot be used. Since it is relatively short, the cutting ability is reduced.

(4) d; large, L; length If d is too large, the ejection power of the plasma jet frame 4 is weakened and the frame diameter is increased, so that the cut allowance of the workpiece 5 is large and the cutting ability is reduced. .

The present invention has been made in order to solve the above problems, and a non-transfer type plasma cutting torch capable of reducing the cutting allowance of a material to be cut without impairing the narrowing of the plasma jet frame and the stable formation of the anode point. It is intended to provide.

[Means for solving the problem]

In order to achieve the above object, the present invention includes an anode nozzle whose outer periphery is cooled by air or gas, and a rod-shaped cathode covered by the anode nozzle, and flowing a plasma forming gas around the rod-shaped cathode, In a non-transfer type plasma cutting torch in which an arc generated between the rod-shaped cathode and the anode nozzle is ejected from the nozzle hole tip of the anode nozzle as a plasma jet frame, the nozzle hole diameter d of the anode nozzle is set to
0.7 mm ≦ d ≦ 1.0 mm, and a value L / d obtained by dividing the nozzle hole length L by the nozzle hole diameter d is 7 ≦ L / d ≦ 12.

[Action]

By selecting the nozzle hole diameter d of the anode nozzle in the above range, the plasma jet frame is appropriately squeezed, and the L / d obtained by dividing the nozzle hole length L by the nozzle hole diameter d is selected in the above range. Since an anode point can be made to exist in the nozzle hole of the above, an extremely thin and high-temperature plasma jet flame can be produced. Therefore, the tip of the nozzle hole of the anode nozzle is not consumed, so that the cutting margin of the material to be cut does not fluctuate or increase during the cutting operation. In particular, when an active gas such as oxygen gas or air is used as a gas for plasma generation, exhaustion of the anode spot portion is inevitable, but clogging of the nozzle hole can be prevented by appropriate selection of the nozzle hole diameter d, and L / d By appropriate selection of the above, consumption of the nozzle hole tip can be prevented, so that stable cutting can be performed with a narrow cutting margin.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic sectional view showing one embodiment of the present invention. In FIG. 1, a cathode material 12 (hafnium, zirconium, tungsten containing tria, etc.) excellent in electron emission is embedded at the tip of a rod-shaped cathode 1 to form an electron emission surface. An anode nozzle 2 having a nozzle hole 2a having a hole diameter d and a length L is fitted into an insulating cylinder 11, and the axis of the rod-shaped cathode 1 and the anode nozzle 2 are aligned by the insulating cylinder 11.
The plasma generating gas 6 is supplied to the inside of the anode nozzle 2 through a gap between the rod-shaped cathode 1 and the insulating cylinder 11. The anode nozzle cooling air or gas 7 is discharged into the atmosphere while cooling the outer periphery of the anode nozzle 2 from the groove of the shield cap 3 provided at a portion in contact with the anode nozzle 2 through the gap between the shield cap 3 and the insulating tube 11. You. Although FIG. 1 shows the plasma generating gas 6 and the anode nozzle cooling air or gas 7 separately, these may be the same air or gas. This is realized by providing a hole in the peripheral wall of the insulating cylinder 11, and in this case, the supply source of air or gas may be the same.

The non-transferring type plasma cutting torch shown in FIG. 1 composed of the rod-shaped cathode 1, the insulating tube 11, the shield cap 3, and the anode nozzle 2 described above has a nozzle hole diameter d of 0.7 mm ≦ d ≦
The anode nozzle 2 is set to 1.0 mm and the value L / d obtained by dividing the nozzle hole length L by the nozzle hole diameter d is set to 7 ≦ L / d ≦ 12.

During the cutting operation, a DC voltage is applied from the plasma power source 8 between the bar-shaped cathode 1 and the anode nozzle 2 of the non-transfer type plasma cutting torch. The arc generated between the rod-shaped cathode 1 and the anode nozzle 2 with the help of the high-frequency generator 9
The high-temperature plasma flow is constricted by the wall surface of the nozzle hole 2a of the anode nozzle 2 and the plasma generating gas 6 flowing through the nozzle hole 2a, and is ejected from the tip of the nozzle hole as a plasma jet frame (not shown). At this time, the anode nozzle 2
Since the nozzle hole diameter d and the value L / d obtained by dividing the nozzle hole length L by the nozzle hole diameter d are selected to be appropriate values, the plasma jet flame is appropriately squeezed, and as shown in FIG. Since the anode point A can be made to exist inside the nozzle hole, an extremely thin and high-temperature plasma jet flame can be produced.

The reasons for limiting the nozzle dimensions will be described in detail below with reference to FIGS.

FIG. 2 is a characteristic diagram showing the relationship between the nozzle hole length L and the cutting allowance by a non-transfer type plasma cutting torch, using the nozzle hole diameter d as a parameter, with a plasma current of 10 A and a cutting speed of 10 cm / mi.
n. Actual measurement data obtained by cutting an acrylic resin (thickness: 3 mm) under the conditions of plasma generation gas; air. In FIG. 2, the region is a region in which the nozzle hole length L is shorter than the nozzle hole diameter d, and the anode point is discharged to the tip of the nozzle hole, and the effect of narrowing the plasma jet frame on the wall surface of the nozzle hole is small. Since the cutting is performed by the plasma jet flame that spreads in the nozzle exit direction, the cutting margin becomes large. Also, in this region, as can be seen from the curves (g) and (h) in FIG. 3 described later, the cutting margin increases with an increase in the nozzle hole diameter d. The area is the nozzle hole diameter d
This is a region where the nozzle hole length L increases and the plasma jet flame flow becomes short as can be seen from the curves (f) and (g) in FIG. In addition, as shown in FIG. 4 described later, the nozzle outer peripheral temperature increases with an increase in the nozzle hole length L. The region is a region where the nozzle hole length L has a stronger influence on the plasma jet flame diameter and the nozzle outer peripheral temperature than the nozzle hole diameter d, and the flow path resistance of the nozzle hole increases with the increase of the nozzle hole length L, In order to weaken the ejection power of the plasma jet flame, the cutting ability is reduced, and the temperature around the nozzle is also increased. In the region, the nozzle hole diameter d is too large,
Since the narrowing effect of the plasma jet flame due to the nozzle hole wall surface is small, the cutting margin becomes larger than that of the nozzle hole with a small diameter, and if the plasma gas volume does not increase with the increase of the nozzle hole diameter, the jet of the plasma jet flame This is an area where the cutting ability is reduced because the force is weakened. Therefore, the hatched area shown in FIG. 2, that is, the nozzle hole diameter d is set to 0.7 mm ≦ d ≦ 1.0 mm, and the value L / d obtained by dividing the nozzle hole length L by the nozzle hole diameter d is 7 ≦ L / d ≦ 12. The determined region was determined to be an appropriate region, and the effectiveness of the present invention was proved.

FIG. 3 shows the relationship between the nozzle hole length L and the plasma jet frame length and frame diameter of a non-transfer type plasma cutting torch using nitrogen gas as a plasma generating gas.
This is a characteristic diagram showing the nozzle hole diameter d and the plasma current _Ip as parameters, and shows the results obtained by taking a picture of the plasma jet frame length and frame diameter (aperture F8, shutter speed 1/8) and obtaining the high brightness part. It is.

FIG. 4 shows a plasma generating gas; nitrogen (about 10 / mi).
n.), gas for cooling the anode nozzle; nitrogen (about 90 / min.),
FIG. 9 is a characteristic diagram showing the relationship between the nozzle hole length L of the non-transfer type plasma cutting torch and the nozzle outer peripheral temperature as a parameter, which is actually measured under the condition of a plasma current of 10 A.

From these measured data, it can be seen from FIG. 3 that the plasma jet flame length tends to be longer when L ≧ 5 mm where the anode point does not discharge to the tip of the nozzle hole (curve (a),
(B), (c)), the frame diameter shows a tendency to gradually decrease (curves (f), (g), (h)) when L ≧ 5 mm. Also, as the nozzle hole diameter d becomes smaller, the plasma jet flame length tends to become shorter (curves (g) and (h)).

On the other hand, from FIG. 4, the nozzle outer peripheral temperature tends to increase as the nozzle hole diameter d decreases, and to increase as the nozzle hole length L increases. In the torch structure in which the outer periphery of the nozzle is air-cooled or gas-cooled, the maximum allowable value of the outer peripheral temperature of the nozzle is considered to be about 250 ° C. in consideration of the heat-resistant temperature of the material constituting the torch. From these facts, there are practical constraints on the nozzle hole diameter d and the nozzle hole length L.

FIG. 5 is a schematic cross-sectional view of the anode nozzle showing the consumption of the anode nozzle when air (active gas) is used as the plasma generating gas. Nozzle hole diameter d of anode nozzle
Was 0.8 mm, which is within the limited range of the present invention, and the consumption of the anode nozzle was compared with two types of L / d of 2.5 and 10 (all nozzles were made of copper). L / d is 2.5 (outside of 7 ≦ L / d ≦ 12)
In the case of (1), it can be seen that the nozzle tip is consumed at the tip of the nozzle hole where the anode point is generated, and the diameter of the nozzle tip is enlarged. On the other hand, L / d
Is 10 (within the range of 7 ≦ L / d ≦ 12), the anode spot is generated inside the nozzle hole and is consumed at that portion, but is not consumed at the tip of the nozzle hole. Therefore, nozzle hole clogging of the anode nozzle can be prevented by appropriate selection of the nozzle hole diameter d, and consumption of the nozzle hole tip can be prevented by appropriate selection of L / d.

〔The invention's effect〕

According to the present invention, by appropriately selecting the nozzle hole diameter d of the anode nozzle and the value L / d obtained by dividing the nozzle hole length L by the nozzle hole diameter d, the plasma jet flame is appropriately narrowed, and Prevents clogging of the nozzle hole and exhaustion of the nozzle hole tip, and provides a stable and long plasma jet flame, which interrupts the cutting operation and deteriorates the cutting surface as in the conventional non-transfer type plasma cutting torch. Is eliminated, and the working efficiency can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention, FIG. 2 is a characteristic diagram showing a relationship between a nozzle hole length and a cutting margin by a non-transfer type plasma cutting torch, and FIG. FIG. 4 is a characteristic diagram showing a relationship between a plasma jet frame length and a frame diameter, FIG. 4 is a characteristic diagram showing a relationship between a nozzle hole length and a nozzle outer peripheral temperature, and FIG. 5 shows a consumption state of an anode nozzle by non-transfer air plasma. FIG. 6 is a schematic view of the anode nozzle, showing the principle of the plasma jet generator. 1 ... rod-shaped cathode, 2 ... anode nozzle, 2a ... nozzle hole,
4 ... plasma jet frame, 5 ... material to be cut, 6
…… Plasma generating gas, 7 …… Anode nozzle cooling air or gas.

Claims (1)

(57) [Claims] 1. An anode nozzle whose outer periphery is cooled by air or gas, and a rod-shaped cathode covered by the anode nozzle, wherein a gas for plasma generation is caused to flow around the rod-shaped cathode,
In a non-transfer type plasma cutting torch in which the arc generated between the rod-shaped cathode and the anode nozzle is ejected from the nozzle hole tip of the anode nozzle as a plasma jet frame,
The nozzle hole diameter d of the anode nozzle is set to 0.7 mm ≦ d ≦ 1.0 mm, and the value L / d obtained by dividing the nozzle hole length L by the nozzle hole diameter d is 7 ≦ L.
A non-transfer type plasma cutting torch characterized in that / d ≦ 12.