JPH0947877A - Plasma torch and plasma cutting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase angle adjusting range of cutting face by arranging a speed vector adding means to add the speed vector, having specified angle against torch center axis, to secondary gas and specifying pressure loss of working gas. SOLUTION: A primary gas is injected from an orifice 3 of plasma torch and arc is formed between an electrode 1 and work 14, the work 14 is cut. A swirler 11 is arranged in a secondary gas passage 9 and a speed vector of >0 deg. to <45 deg. is given to the secondary gas injected from the orifice 12. By changing a flow rate of secondary gas, a speed vector and arc angle, the work 14 is cut under a desired inclined angle. A pressure loss generated in a working gas supply circuit is set to <=4kg/cm. When a pressure exceeds 4kg/cm, plasma flow is not sufficiently bent. A groove angle can be adjusted while a torch is kept vertical.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma torch mainly used for cutting work, in which a secondary gas is supplied while being swirled from the periphery of a working gas jet nozzle.
Also, the present invention relates to a plasma cutting method in which cutting is performed by using the plasma torch while changing the angle (groove angle) of the cut surface.

[0002]

2. Description of the Related Art When cutting a steel plate, and in the groove processing of the steel plate, when cutting by gas, plasma, laser, etc., the torch angle is adjusted manually by cutting every time the groove angle is changed. The method is generally used. In this case, a special torch jig equipped with a goniometer is used.

Further, Japanese Laid-Open Patent Publication No. 2-137692 discloses a technique in which a jig is provided with a control means, cutting is performed while adjusting a torch angle by an electric signal, and a groove angle is arbitrarily and continuously changed. However, such a technique requires special torch angle control equipment.

On the other hand, in plasma cutting, when cutting at high speed, a large bevel angle is attached. Therefore, in order to set the bevel angle, which is an important cutting quality, to about zero degree, cutting must be performed at a speed much lower than the cutting separation limit. I had to do it.

However, recently, a secondary fluid is swirlingly flowed in a space formed between the cap and the nozzle so as to cover the nozzle, and the cutting is performed while improving the shoulder sag and the bevel angle of the upper edge of the cutting. Technology has come into play.
According to this technology, even if a bevel angle is attached due to an increase in cutting speed, the bevel angle can be corrected by several degrees due to the swirling flow of the secondary fluid (gas), so that a good cutting speed can be dramatically improved. became.

The basic structure of this technique is disclosed in Japanese Patent Laid-Open No. 5-8.
As disclosed in Japanese Patent No. 4579, in addition to this, for example, the nozzle cooling gas flowing in the space between the cap and the nozzle is cut while being supplied as a swirling air stream that converges on the central axis of the nozzle. Japanese Patent Laid-Open No. 6-246456 discloses a technique of performing plasma cutting while maintaining a good bevel angle.

[0007]

When performing groove processing,
In both the manual operation and the automatic operation, the torch is inclined and cut, and a special jig for adjusting the torch angle or the like is required, which causes a problem of cost increase.

Among the above-mentioned conventional techniques, for example, in the technique described in Japanese Patent Laid-Open No. 2-137692, when machining a continuous groove angle, a special control means is provided as described above. Also, there is a problem that the torch angle control equipment is required, and the equipment becomes large in size and the cost is high.

On the other hand, as disclosed in Japanese Unexamined Patent Publication No. 6-246456, in the prior art aiming to improve the bevel angle by swirling the secondary gas, the torch is set in a state where the torch is perpendicular to the cutting material. Although the angle of the cutting surface can be adjusted by the next swirling gas, the adjustment range is at most several degrees, and it is limited to the application of correcting the bevel angle when a vertical cutting surface is required, and it is at least several tens of degrees. In the case of performing the groove processing which requires the cut surface processing with the above angles, the torch still has to be inclined and cut.

The present invention has been conceived in view of the above, and a plasma torch capable of drastically increasing the adjustment range of the angle of the cutting surface by the secondary gas and enabling groove processing without tilting the torch, It is an object of the present invention to provide a plasma cutting method.

[0011]

In order to achieve the above-mentioned object, a plasma torch according to the present invention has a secondary gas ejection port arranged so as to surround a working gas ejection nozzle, and this secondary gas ejection port is arranged. In a plasma torch having a swirl flow means for imparting a swirl flow to the secondary gas in the secondary gas passage connected to the secondary gas passage, the secondary gas spouted from the secondary gas spout to the secondary gas spout A velocity vector addition means for adding a velocity vector greater than 0 ° and less than 45 ° to the central axis is provided, and the pressure loss control for reducing the pressure loss generated at the working gas jet nozzle to 4 kg / cm ² or less in the working gas supply circuit. It is configured to have means.

In the plasma torch having the above structure, the velocity vector adding means is a substantially parallel passage formed in the vicinity of the secondary gas ejection port, and the passage has an angle of 0 ° with respect to the central axis of the torch. The angle is largely less than 45 °.

Further, in the plasma torch having the above-mentioned structure, a cap having a secondary gas ejection port which is concentric with the working gas ejection nozzle is provided around the working gas ejection nozzle and the inner surface of the cap near the secondary gas ejection port and the working gas ejection port The velocity vector adding means is composed of passages that are substantially parallel to the outer surface of the nozzle.

Further, in the plasma torch having the above structure, the pressure loss control means is provided by at least one of the means for adjusting the working gas jet nozzle diameter, the orifice length of the nozzle, the plasma current value, and the working gas supply pressure. Has become. The plasma torch has secondary gas flow rate control means for controlling the secondary gas flow rate.

In the plasma cutting method using the plasma torch having the above structure, the plasma torch is held substantially perpendicular to the surface of the work to perform the groove processing.

At this time, the cutting is performed while continuously or intermittently changing the flow rate of the secondary gas.

[0017]

[Operation] By supplying a current from the plasma power source to the electrode and ejecting the working gas from the working gas jet nozzle, a plasma arc is formed between the electrode and the work to cut the work.

At this time, the secondary gas continues to be ejected from the secondary gas ejection port toward the cutting groove, and the cutting proceeds while adjusting the angle of the cutting surface. At this time, the secondary gas has a swirling flow, and a velocity vector larger than 0 ° and smaller than 45 ° is added to the central axis of the torch. The secondary gas is suppressed from diffusing after being ejected from the secondary gas ejection port by the velocity vector, and the swirling flow of the secondary gas is maintained below the torch.

In plasma cutting using the above plasma torch, the groove angle is adjusted by changing the nozzle pressure loss of the working gas and the flow rate of the secondary gas.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of a plasma torch according to the present invention. An electrode 1 connected to a plasma power source (DC power source) (not shown) has a torch body (not shown) via an insulator 2. It is supported on the tip side. A nozzle 4 having an orifice 3 concentric with the electrode 1 is arranged at the tip so as to surround the tip of the electrode 1 and the insulator 2, and the inside of the nozzle 4 serves as a working gas passage 5. There is. In this working gas passage 5, the insulator 2
The first swirler 6 supported by the nozzle 4 is interposed.

A tubular body (nozzle cap) 7 is fixedly attached to the nozzle body outside the nozzle 4, and the tubular body 7 is provided.
A cooling water passage 8 is formed between the nozzle 4 and the nozzle 4.

A cap 10 is provided outside the cylindrical body 7 to cover the tip of the torch body and to form a secondary gas passage 9 with the cylindrical body 7. In the secondary gas passage 9 inside the cap 10, a second swirler 11 for providing a swirling flow to the secondary gas is interposed.

An orifice 12 concentric with the orifice 3 of the nozzle 4 is opened at the tip of the cap 10. Immediately upstream of the opening of the orifice 12, the secondary gas ejection passage 1 is substantially parallel to the side surfaces of the nozzle 4 and the cap 10 facing each other.
It is 3. The secondary gas ejection passage 13 is inclined so that the angle α with respect to the axis of the electrode 1 is 30 °.

Incidentally, as an example of the size of each part in this embodiment, the diameter of the orifice 3 of the nozzle 4 is 1.5 m.
m, the length of the parallel portion of the secondary gas ejection passage 13 is about 5 mm,
The width is about 0.5 mm and the orifice 1 of the cap 10
The diameter of 2 is 4 mm.

In the above construction, when a current is supplied to the electrode 1 from a plasma power source (not shown), an arc is formed between the electrode 1 and the work 14 to cut the work 14. This arc is the working gas passage 5 of the nozzle 4.
It is maintained by the working gas which is swirled from and is ejected.

During the cutting, the secondary gas continues to be ejected from the orifice 12 toward the cutting groove 15 of the work 14, and the cutting progresses while adjusting the angle of the cutting surface. At this time,
The secondary gas is swirling in the second swirler 11, and the velocity vector of θ = α = 30 ° is added to the central axis of the torch by the secondary gas ejection passage 13.

In other words, this means that the flow velocity vector that converges in the central direction of the swirl flow and the flow velocity vector in the same direction as the working gas jet direction are positively added to the swirl flow of the secondary gas at the same time. .

The flow velocity vector that converges in the central direction suppresses the diffusion of the secondary gas that tends to diffuse in the radial direction immediately after leaving the orifice 13 of the cap 10 and maintains the swirling flow of the secondary gas below the torch. There is. Further, the flow velocity vector in the same direction as the working gas jet direction diffuses in the axial direction the non-uniformity of the swirling velocity distribution near the jet port caused by the machining error and the part assembly error.

In this embodiment, these flow velocity vectors are added by the substantially parallel secondary gas ejection passage 13 having an angle α = 30 ° with respect to the central axis of the torch. The angle α of the torch 13 with respect to the central axis is 0 ° for the angle θ of the velocity vector of the secondary gas.
The angle is in the range of <θ <45 °.

This is because the flow velocity vector for focusing in the central direction is not effectively given at θ = 0 °. In this case, the swirling flow diffuses in the radial direction at the moment when it exits the second orifice 12, and the cutting groove is formed. The swirling flow sent to 15 becomes weak. In order to compensate for this, there is no choice but to increase the flow rate of the secondary gas or reduce the cutting height (standoff).

In this case, the former is uneconomical because it requires a large amount of secondary gas, and in the latter, the risk that the nozzle 4 and the cap 10 simply contact the work 14 increases, and the double Not only the torch is easily broken by the generation or collision of an arc, but also the molten metal blown up at the time of cutting is accumulated between the nozzle 4 and the cap 10,
The insulation between the nozzle 4 and the cap 10 is broken, and the risk of double arcs continues to increase. Further, when the work 14 is thick, the blown-up molten metal may directly melt the nozzle 4 or the cap 10 that protects the nozzle 4, and may become unusable.

On the other hand, if θ = 45 ° or more, the flow velocity component in the same direction as the working gas jetting direction is not sufficient, so that the non-uniformity of the swirling speed distribution caused by the machining error and the part assembly error cannot be diffused in the axial direction. When cutting is performed in such a state, the angle of the cut surface of the product (workpiece) varies depending on the cutting direction, so correction by post-processing is unavoidable, and in some cases it becomes a defective product.

The inventors of the present invention confirmed the variation in the angle of the cut surface due to the difference in the angle α of the secondary gas ejection passage 13 by an experiment and set the angle α of the secondary gas ejection passage 13 that can be put to practical use. α <45 °. FIG. 3 shows an outline of the experimental results which are the basis for this. It is a comparison between the case where the angle α of the secondary gas ejection passage 13 is 30 °, which is within the range of the present invention, and the case where it is 45 °, which is outside the range of the present invention. In this experiment,
The nozzle 4 and other device configurations are the same.

In the experiment for obtaining the experimental result shown in FIG. 3, the vertical cutting is aimed at in order to facilitate the measurement of the bevel angle, and the experimental conditions are the current of 120 A and the working gas supply pressure of 4 kg / cm ^2. , Cutting speed is 2500mm / min
The thickness of the work 14 is 9 mm, and the material is SS400. The nozzle pressure loss at this time was about 4 kg / cm ² , and the secondary gas flow rate of 70 liter / min was required to set the bevel angle to 0 °.

The cutting is performed three times in each of the four cutting directions orthogonal to each other, and the maximum and minimum values are shown as errors as variations in the measured bevel angle at that time. As is clear from FIG. 3, the variation at α = 45 ° is an average value of ± 4 °, whereas the variation at α = 30 ° is within an average value of ± 1 °.

Nozzle pressure loss of working gas is 1 at
m, 18 ° C., it is determined by subtracting the pressure loss of the first swirler 6 and the working gas pipeline from the working gas pressure supplied at the time of cutting. As for the pressure loss of the first swirler 6 and the working gas piping, the working gas supply flow rate at the time of cutting is calculated in advance, and a nozzle having a large orifice in which the pressure loss can be ignored in the state where the arc is not generated next. Install,
It can be measured as the supply gas pressure when the gas pressure is adjusted so that the working gas supply flow rate at the time of cutting is obtained.

Generally, in plasma cutting, the arc and the working gas flow are tightened by the nozzle, and the working gas flow is heated to bring the working gas into plasma, thereby causing a large nozzle pressure loss. Means that the stringency is strong and that the working gas can be efficiently heated.

Therefore, normally, the operating conditions and the nozzle diameter are determined so as to raise the temperature of the working gas by increasing the current, lowering the nozzle diameter, raising the supply pressure of the working gas, and the like. The cutting speed can be increased by reducing the temperature of the working gas, and the adhesion of dross can be reduced, but on the other hand, the nozzle is exposed to high temperature, and the electrical distance from the arc is shortened, so there is a risk of causing a double arc. Increase.

However, in the embodiment of the present invention, the nozzle pressure loss is intentionally lowered in order to facilitate the refraction of the plasma flow in the cutting groove 15 of the work 14 by the swirling flow of the secondary gas. Normally, by reducing the nozzle pressure loss, there are concerns that the cutting speed at which the bevel angle becomes 0 ° and the increase in dross adhesion may be adversely affected.

However, in the embodiment of the present invention, the distance in which the swirling flow component of the secondary gas is maintained on the downstream side in the axial direction becomes long,
There is little swirl flow escaping into the atmosphere, and the angle of the cutting surface can be adjusted by exerting sufficient swirling force, and there is no need to adjust the cutting speed to adjust the bevel angle, so the cutting speed can be separated. It can be raised to around the value.

Further, since the secondary gas can be efficiently sent to the cutting groove 15, a dross discharge momentum can be added, and dross adhesion to a work or a cap can be reduced.

For these reasons, in the present invention, there is no adverse effect due to lowering the nozzle pressure loss, and by lowering the nozzle pressure loss, the risk of double arc generation is rather small.

FIG. 4 shows, in the present invention, the nozzle pressure loss and the work 1 having a plate thickness of 9 m when the secondary gas flow rate is kept constant.
4 shows the relationship between the groove angles (deg) of the left and right cut surfaces of the cutting groove 15 in FIG. The flow rate of the secondary gas in this embodiment is 120 liters / min. However, if the flow rate exceeds this value, the secondary gas cools the plasma flow and the cutting ability is reduced. It is the substantially maximum flow rate in the example. Therefore, in such a state, the nozzle pressure loss determines the maximum groove processing angle.

In the experimental results shown in FIG. 4, the nozzle pressure loss was changed by variously changing the current value and the working gas supply pressure, but the orifice diameter of the nozzle and the length of the orifice portion were also changed. As long as the present invention is realized with a certain value of nozzle pressure loss, the same result as that shown in FIG. 4 can be obtained. Further, when the secondary gas injection method is changed, the absolute value of the substantially maximum secondary gas flow rate changes, but whatever the secondary gas injection method is, as long as it is in accordance with the present invention, the substantially maximum secondary gas flow rate. When the relationship between the nozzle pressure loss and the groove angle at the flow rate is experimentally confirmed, the same result as that shown in FIG. 4 is obtained.

Further, in order to make a strong swirl flow act on the entire plate thickness, a relatively large flow rate, for example, a flow rate of a secondary gas larger than the flow rate during the normal plasma cutting operation, is required. The secondary gas flow rate depends on the plasma operating conditions, required groove angle, work plate thickness, and material. Therefore,
The secondary gas flow rate may be set according to individual operating conditions, a desired groove angle, and each work.

Although it depends on the method of jetting the secondary gas, a large amount of the secondary gas is generally required when the groove is to be processed, as compared with the case where the bevel angle is corrected by a few degrees as in the prior art. Become.

In the cutting experiment according to this example, the current value was 60 A, the working gas was oxygen, and the supply pressure was 3 kg / cm.
² , the secondary gas is air and the supply flow rate is about 120 liters / m
in, cutting height from the tip of nozzle 4 (standoff)
Is about 2 mm, the cutting speed is 1000 mm / min, and when the cutting work is performed on a mild steel material having a plate thickness of 9 mm with the torch vertical, the angle of the left cut surface is about 32 in the cutting direction.
The groove was processed with the angle of the right cut surface of about -30 °. The nozzle pressure loss at this time is about 2.5 kg / cm ²
Met.

Further, as is clear from FIG. 5, in this embodiment, the groove angle can be adjusted by setting the torch in a vertical state with respect to the work 14 and changing the secondary gas flow rate. Further, by changing the secondary gas flow rate by the secondary gas flow rate control means 16, continuous groove machining can be performed easily, and by synchronizing the secondary gas flow rate control with the cutting speed, any part of the work 14 can be processed. Any groove processing can be performed. As a matter of course, by adjusting the secondary gas flow rate, it is also possible to make the cutting surface vertical, that is, so-called vertical cutting. For example, while cutting the shape of the welding member, it is possible to cut the groove into an arbitrary portion at the same time. It can be processed.

By the way, if there is no means for adding a velocity vector of greater than 0 ° and less than 45 ° to the center axis of the torch to the secondary gas flow, a powerful swirling flow with little variation is applied to the work thickness. Since it cannot be supplied over the entire direction, even if the nozzle pressure loss is reduced and the secondary swirl flow rate is increased, large cutouts occur on the cutting surface and the bevel angle varies depending on the cutting direction, so it is practically used. It is impossible to machine such a groove.

Further, when the nozzle pressure loss exceeds 4 kg / cm ₂ , the plasma flow does not bend sufficiently, so that means for adding a velocity vector larger than 0 ° and smaller than 45 ° to the central axis of the torch is provided. However, even if the secondary gas flow rate is increased in order to change the groove angle, the bevel angle cannot be adjusted to the extent that the groove angle exceeds several tens of degrees. On the contrary, the cutting ability is lowered because the vicinity of the cutting point is cooled by the secondary gas flow. Needless to say, when the secondary gas flow rate is not sufficient, only a small groove angle can be provided.

As described above, the secondary gas ejection method according to the present invention has the secondary gas ejection port arranged so as to surround the working gas ejection port, and swirls the gas in the secondary gas passage in the torch. And a means for adding a velocity vector of more than 0 ° and less than 45 ° to the central axis of the torch to the secondary gas jet supplied while being swirled by the gas swirling means. If you have.

Therefore, in addition to the above-mentioned embodiment, another embodiment as shown in FIG. 6 and thereafter may be used. For example, as shown in FIG. 6, a suction device 17 for sucking a secondary gas jet ejected from the torch from the lower side of the work 14 during cutting is added to the lower side of the work 14 to thereby remove the secondary gas. A velocity vector larger than 0 ° and smaller than 45 ° with respect to the torch axis may be applied to the jet flow. In this case, fumes and the like at the time of cutting can be discharged at the same time.

Further, for example, as shown in FIG. 7, the cap 10a is extended to near the surface of the work 14, and the nozzle 4
The space from the tip to the work 14 is covered with the cap 10a, and the swirl flow along the inner wall of the cap 10a is jetted by the second swirler 11a, so that a velocity vector greater than 0 ° and less than 45 ° with respect to the central axis of the torch is generated. It may be added. In this case, cap 1 to prevent double arc
It is desirable that 0a is insulated from the nozzle 4.

In the embodiment shown in FIG. 1, the second swirler 1 for turning the secondary gas into a swirling flow and the secondary gas ejection passage 13 have different structures, but as shown in FIG. 8 (a). , Nozzle 4
a and the cap 10b, the second swirler 11b is disposed in the secondary gas ejection passage 13a which is formed substantially parallel to each other.
May be provided integrally with the outer surface of the nozzle 4a. Similarly, as shown in FIG. 8B, the second swirler 11b may be provided integrally with the inner surface of the second cap 10b.

Further, as shown in FIG. 9 (a), the second swirler 11c may be formed as a separate member from the nozzle 4b and the cap 10c. When such a separate member is used, as shown in FIG.
As shown in (b) and (c), the spiral groove 18 is formed into a second groove.
It may be provided on either the inner surface or the outer surface of the swirler 11c.

Instead of the spiral groove 18, a spiral hole or a spiral slit, or a propeller-shaped fin may be used. If it is a spiral hole or slit, the tip of the second cap,
It can also be configured on the side.

As shown in FIG. 1, the secondary gas ejection passage 13 is provided on the downstream side of the swirling means (second swirler), and the cap 10 is provided.
Although it may be constituted by a space between the nozzle 4 and the nozzle 4, as shown in FIG. 10, it is formed on the cap 10d outside the jet port 19 for swirling flow as a jet port 20 which is parallel to the jet port. Good. In addition, as shown in FIG.
Another jetting means 21 may be provided outside e and the jetting means 22 may be parallel to each other.

In any of these cases, it is needless to say that the nozzle pressure loss must be 4 kg / cm ² or less in order to perform processing with a cutting angle of several tens of degrees with the torch vertical. Absent. In addition, the relatively large flow rate of 2
The groove angle is markedly increased by supplying the secondary gas.

Further, the means for reducing the nozzle pressure loss to 4 kg / cm ² or less is, in each embodiment, a constant nozzle diameter (orifice diameter) and nozzle length (orifice length).
In contrast, the current value and the working gas supply pressure are appropriately adjusted, but any one of these specifications or a plurality of them may be adjusted simultaneously.

At this time, if a means for changing the secondary gas flow rate is provided on the torch side, the groove surface having a continuous angle change can be easily processed. The means for controlling the flow rate of the secondary gas may be any means such as an electromagnetic valve or a flow controller as long as the flow rate of the secondary gas can be controlled.

It is desirable to install the secondary gas flow rate control means on the torch side in consideration of the control delay due to the pipe length, but the control delay due to the pipe length can be ignored, or a control that complements this can be performed. It can be anywhere in the secondary gas passage, if possible.

As described above, by adding the flow velocity component of the secondary gas, the distance in which the secondary swirling flow is maintained downstream in the axial direction becomes long, and at the same time, the non-uniformity of the swirling velocity distribution can be diffused in the axial direction. Therefore, the swirling flow with little variation in the circumferential velocity component is maintained even on the lower surface of the cutting material.

In addition, the pressure loss generated when the working gas passes through the nozzle during cutting is set to 4 kg / cm ² or less,
The plasma flow in the cutting groove is easily swung by the secondary gas flow so as to form an angle with respect to the torch axis, that is, it is easily bent.

As described above, since the swirling flow with little variation in the circumferential velocity component is applied to the lower surface of the cutting material, and the plasma flow can be strongly bent over the entire thickness of the cutting material, several tens of tens can be obtained. The angle of the cut surface can be adjusted. Therefore, it becomes possible to perform the groove processing in the vertical state of the torch.

[0065]

According to the present invention, the cutting groove 1 of the work 14 is
Due to the strong swirling flow of the secondary gas in 5, the work 1
Since the plasma flow can be bent over the entire plate thickness of 4,
The angle adjustment range of the cut surface can be greatly increased.

As a result, the groove machining can be performed with the torch vertical, and the groove angle can be adjusted without changing the torch angle at all. At this time, the groove surface having a continuous angle change can be easily processed by the means for changing the secondary gas flow rate.

Further, by changing the secondary gas flow rate in synchronization with the cutting speed, it is possible to perform the groove processing at any angle on the workpiece with the torch in a vertical position. Of course, at this time, vertical cutting is also possible by adjusting the secondary gas flow rate. In addition, for example, a two-dimensional processing machine having a plasma cutting machine mounted thereon and operating under NC control generally exists widely. However, if the present invention is applied to such a processing machine, the groove cutting can be performed simultaneously with the vertical cutting. , The special groove processing machine and special torch angle control equipment, and the personnel and man-hours required for its operation, which have been necessary up to now, are no longer required, and it is possible to significantly reduce costs and man-hours.

[Brief description of drawings]

FIG. 1 is a sectional view showing a main part of an embodiment of the present invention.

FIG. 2 is a perspective view showing a swirler for imparting a swirling flow to the secondary gas.

FIG. 3 is a diagram showing a relationship between a bevel angle of a cut surface and an angle of a secondary gas ejection port with respect to a central axis of a torch.

FIG. 4 is a diagram showing the relationship between nozzle pressure loss and groove angle.

FIG. 5 is a diagram showing a relationship between a groove angle and a secondary gas flow rate.

FIG. 6 is a sectional view showing another embodiment of the present invention.

FIG. 7 is a sectional view showing another embodiment of the present invention.

FIG. 8A is a cross-sectional view showing a case where a swirler for secondary gas is integrally attached to the outer peripheral portion of the nozzle. (B) is a sectional view showing a case where a swirler for secondary gas is integrally mounted on the inner peripheral side of the cap.

FIG. 9A is a cross-sectional view showing another example of the secondary gas ejection port portion. (B), (c) is a perspective view which shows another example of a swirler.

FIG. 10 is a cross-sectional view showing another example of the secondary gas ejection passage.

FIG. 11 is a cross-sectional view showing another example of the secondary gas ejection passage.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electrode 2 ... Insulator 3,12 ... Orifice 4,4a, 4b ... Nozzle 5 ... Working gas passage 6,11, 11a, 11b, 11c, 11d ... Swirler 7 ... Cylindrical body 8 ... Cooling water passage 9 ... Secondary gas Passages 10, 10a, 10b, 10c, 10d, 10e ... Cap 13 ... Secondary gas ejection passage 14 ... Work 15 ... Cutting groove 16 ... Secondary gas flow rate control means 17 ... Suction device 18 ... Spiral groove 19, 20, 21 ... Spout 21 ... Spouting means

Claims (8)

[Claims] 1. A swirl flow in which a secondary gas spout is arranged so as to surround a working gas spout nozzle, and a swirl flow is imparted to the secondary gas in a secondary gas passage connected to the secondary gas spout. In a plasma torch having means, a velocity vector for adding a velocity vector greater than 0 ° and less than 45 ° to the central axis of the torch to the secondary gas jetting portion, to the secondary gas jetted from the secondary gas jetting portion. A plasma torch, wherein additional means is provided, and pressure loss control means is provided in the working gas supply circuit to reduce the pressure loss generated at the working gas jet nozzle to 4 kg / cm ² or less. 2. The plasma torch according to claim 1, wherein the velocity vector addition means is a passage formed in the vicinity of the secondary gas ejection port and substantially parallel to each other, and the passage is with respect to the central axis of the torch. A plasma torch having an angle of more than 0 ° and less than 45 °. 3. The plasma torch according to claim 1, wherein a cap having a secondary gas ejection port which is concentric with the working gas ejection nozzle is provided around the working gas ejection nozzle, and the cap inner surface near the secondary gas ejection port is activated. A plasma torch, characterized in that a velocity vector adding means is constituted by a passage which is substantially parallel to the outer surface of the gas ejection nozzle. 4. The plasma torch according to claim 1, wherein the pressure loss control means is at least one of means for adjusting the diameter of the working gas jet nozzle, the length of the orifice portion of the nozzle, the plasma current value, and the working gas supply pressure. A plasma torch that consists of two parts. 5. The plasma torch according to claim 1, further comprising secondary gas control means for controlling a secondary gas flow rate. 6. A plasma cutting method using a plasma torch according to claim 1 or 5, wherein the plasma torch is held substantially perpendicular to the surface of the workpiece to perform groove processing. 7. The plasma cutting method according to claim 6, wherein cutting is performed while continuously or intermittently changing the flow rate of the secondary gas. 8. The plasma cutting method according to claim 7, wherein the cutting is performed while changing the flow rate of the secondary gas in synchronization with the cutting speed.