WO1993016835A1

WO1993016835A1 - Plasma torch for cutting

Info

Publication number: WO1993016835A1
Application number: PCT/JP1993/000225
Authority: WO
Inventors: Yoshihiro Yamaguchi; Hitoshi Sato; Toshiya Shintani
Original assignee: Kabushiki Kaisha Komatsu Seisakusho
Priority date: 1992-02-24
Filing date: 1993-02-24
Publication date: 1993-09-02

Abstract

A plasma torch for cutting, wherein a nozzle (2) is protected against dross produced by piercing at the start of cutting and double arcs are prevented from occurring to improve the service life of the nozzle (2). To ensure such functions, a nozzle protecting cap (5) forming an annular secondary gas path (8) is fitted over a nozzle cap (4) in a manner of being electrically insulated from an electrode (1) and the nozzle (2), and insulators (14) made of an electrically insulating material are mounted in said secondary gas path (8), by which secondary gas is baffled and swirled.

Description

Description Plasma torch technology for cutting

The present invention relates to an improvement of a cutting torch for use in a plasma cutting machine.

Background technology

The prior art of a cutting torch for cutting will be described below.

First prior art (water-cooled torch):

In a torch in which the electrodes and nozzles are cooled by cooling water, the electrodes are attached to the torch main body, and the nozzles are attached via gas outlets for turning around the axis of the torch and ejecting the working gas. The nozzle is fixed to the torch body by screwing it to the torch body, excluding the tip of the torch body, excluding the tip that holds the orifice's orifice. The cooling water that has cooled the electrodes passes through the cooling water passage formed inside the main torch, cools the nozzles through the space formed by the torch body, the nozzle, and the torch cap. configuration and Tsu have to return to the cooling water passage formed in the torch body ₀

Second conventional technology (nozzle protection cap for air-cooled nozzle):

With a torch with an exposed tip, if the thick plate is drilled at the start of cutting, the dross (molten metal) blown up on the nozzle will adhere to the nozzle and melt the nozzle. If the nozzle is damaged or the nozzle comes into contact with the material to be cut, an irregular discharge called a double arc occurs, and the nozzle is damaged. For this reason, a metal nozzle protection valve V that is electrically isolated from this nozzle is installed in the capital city of the air-cooled nozzle, and the nozzle cooling gas is supplied to the nozzle and the nozzle protection key. A method of protecting the nozzle by blowing off the rising dross as a means of flowing between the tips is described in U.S. Pat.

_C disclosed in No. 4 8 5 1 9 6 2 Third conventional technology (nozzle protection cap in welding torch:

A metal nozzle protection cap that is electrically insulated from the nozzle is attached around the nozzle, and a secondary gas flows between the nozzle and the nozzle protection cap. One is disclosed in Japanese Patent Publication No. Sho 533-119753. Fourth prior art (inclination of cut surface due to swirling airflow effect):

In plasma cutting, the front side of the kerf (cut groove) is generally wide and the back side is narrow. Therefore, the cut surface is not vertical but has a tapered shape.

By the way, it is known that in a plasma torch in which the working gas is swirled around the axis of the electrode to stabilize the arc and is ejected, the cut surface is not symmetrical and becomes untargeted. ing. By utilizing this fact, even if the front kerf width is wide and the back force is narrow, vertical cutting can be performed with only one cut surface due to the turning surface of the working gas. Is disclosed in the welding technology June 1996 issue.

However, the first to fourth prior arts include (1) protection of a nozzle, (2) contraction of a plasma arc by a secondary gas, (3) an increase in the temperature of a nozzle protection cap, and (4) a swirling airflow. Adjustment of effects, (5) There are the following problems with electrical corrosion of cooling water surface.

(1) Nozzle protection

In plasma cutting, the nozzle may be damaged when piercing a thick plate or when the nozzle comes into contact with the workpiece.

Therefore, in the plasma torch in which the nozzle emits II as in the first prior art,) when the plate is beashed, the beading is performed at the maximum speed at which the main arc shifts. After the hole has penetrated, the torch is lowered to a height suitable for cutting, and cutting is started. However, this method inevitably complicates torch height control at the start of cutting. Also, during or at the end of cutting, the material to be cut may spring up depending on the state of thermal deformation or instruction, and it is difficult to avoid this. Therefore, the nozzle and the material to be cut are in contact with each other. Doing so avoids the risk of damaging the nozzle due to double marks It is not possible.

In consideration of the above, in the torch having the air-cooled nozzle as in the second related art, it is necessary to prevent the attachment of the docos to the nozzle and the electrical contact with the material to be cut. Nozzle protection cap mechanism is disclosed. However, the second conventional technique is applied to an air-cooled nozzle type plasma torch, and such a nozzle cannot be applied to a water-cooled plasma torch because the shape of the tip of the torch is different. . In addition, since a mechanism that uses cooling gas that cools the nozzle air is used, a large amount of cooling gas needs to flow, and in order to secure this, a plasma arc is applied to the nozzle protection cab. A plurality of openings are provided in addition to the openings for passing through. As a result, a large amount of cooling gas is blown out to the surface of the material to be cut, increasing disturbance to the plasma mark and adversely affecting cutting.

In the third conventional technology, a protective cap is applied to water-cooled nozzles, but its function is to prevent contact between the workpiece and the nozzles, but to perform welding using a secondary gas. It is for isolating the part from the atmosphere. Therefore, the opening of the nozzle protection cap is wide open, and does not have the function of protecting the nozzle from blowing up during dosing.

(2) Contraction of plasma arc by secondary gas

In plasma cutting, a high-temperature, high-speed arc plasma is obtained by narrowing the arc with a nozzle. If more current can flow through a nozzle with a small nozzle diameter, high-speed cutting can be performed with a narrow cutting groove width. However, when the current is increased, a phenomenon called a double arc that flows through the metal part of the nozzle without passing the current through the nozzle is generated, which not only reduces the cutting ability but also damages the nozzle. ^ Then ₀

In the first conventional technology, the working gas is strongly swirled around the electrode to squeeze the arc narrowly, and at the same time, the nozzle is cooled with water to prevent double arcs. . Since the plasma arc ejected from the nozzle expands, the width of the cut groove becomes wider.

2) With conventional technology, double marks are likely to occur due to insufficient nozzle O cooling It is difficult to greatly increase the current. Nozzle protection cap: The secondary gas supplied to surround the two plasma arcs can be used to further inject the arc ejected from the nozzle. In addition to the central opening for flowing gas, there is an opening for increasing the gas flow rate for cooling the nozzle, and it is not possible to independently control only the secondary gas surrounding the arc . For this reason, it is difficult to obtain a flow rate or pressure of the secondary gas that is sufficient to further incorporate the plasma arc.

(3) Nozzle protection cap temperature rise

In the nozzle protection caps of the second and third prior arts, only the air cooling by the secondary gas is performed, so that the temperature rises due to the plasma arc or the radiation from the cut surface. Therefore, when exchanging cerebellar parts such as nozzles and electrodes, it is necessary to allow secondary gas to flow for a while after the arc is stopped, to cool them, or to wear gloves for replacement. bad.

(4) Adjustment of swirling airflow effect

As shown in the fourth prior art, it is possible to obtain a cut surface perpendicular to the cut surface of the piece M by utilizing the fact that the cut surface is inclined by the swirling airflow effect. However, the plate of the material to be cut! : In order to adjust the degree of inclination of the cut surface according to the cutting speed, the intensity of the swirling airflow, that is, the working gas flow rate must be reduced. However, the working gas flow rate has an optimal value to keep the arc stable.If the working gas flow rate is increased or decreased, the arc becomes unstable, and it is difficult to adjust the degree of inclination of the cut surface.

(5) Electric corrosion of cooling water passage

In the plasma torch in which the electrode and the nozzle according to the first prior art are water-cooled, the electrode and the nozzle are fixed to the metal parts of the torch body, which are separated from each other. Power is supplied from the DC power supply. A cooling water passage is provided in the metal part on the electrode side and the metal part on the nozzle side for connecting them; and the electrode and the nozzle are cooled by the combined water.

When the brass mark is cracked, the electrode side metal part, the nozzle side metal part, and o K Has a potential difference. At this time, the torch body is configured in a state where each metal is electrically insulated, and each metal part is connected by the cooling water passage, and the cooling water flows there Because, 'weak current flows through the water flow. Since this current is weak, there is no hindrance to the occurrence of arc, but the metal part of the torch body is gradually corroded by electrochemical action. Both torches with water-cooled electrodes and nozzles become unusable. Disclosure of the invention

The present invention can effectively exert the function of protecting the nozzle even when the nozzle has a water-cooled torch structure, greatly improving the life of the nozzle and reducing the time required for nozzle replacement. Loss can be reduced. In addition, since the insulator is interposed in the secondary gas passage, the secondary gas is rectified, and the plasma arc ejected from the nozzle 2 is narrowed down again by the secondary gas, and the cut groove width is reduced. Fine and precise cutting can be performed. Also, since the secondary gas flow can be swirled in the same direction as the spiral flow of the plasma arc by the rectifying passage of the insulation layer, the inclination of the cut surface of the extruded cutting material can be made vertical. In addition, since the nozzle protection cap can be separated into a distal end portion and a proximal end portion, only the tip portion can be replaced as a consumable item. The base end is cooled by cooling water, so that it can be handled without paying attention to the torch during maintenance and inspection. In addition, another object of the present invention is to provide a cutting plasma torch that can reduce electrochemical corrosion caused by cooling water.

In order to achieve this object, the present invention uses a water-cooled electrode, and connects the plasma arc to the electrode through a nozzle orifice arranged so as to cover the electrode with a plasma gas passage therebetween. The plasma torch for cutting that is produced between the workpieces has an opening on the tip side opposite the nozzle orifice outside the nozzle hole and communicates with the two openings. A nozzle protection cap, which forms an annular secondary gas passage between the nozzle cap and the nozzle cap, is electrically insulated and fixed to the electrode and the nozzle. It is composed of electric steel material and has a rectifying passage that rectifies the gas flow flowing through the secondary gas passage. The second nozzle protection cap is made of a metal material having good heat conductivity, and the cross section of the insulator is made rectangular, and this insulator is also used as the nozzle protection cap. © periphery are铰着the stepped portion provided respectively on the inner peripheral surface and a box _e

In addition, the nozzle protection cap includes a tip portion for protecting the tip portion of the nozzle and a base end portion fixed to the torch main body side, and these components are movably connected. A flange that fits each other is provided at the leading end portion and the base end portion, or a screw is provided at a portion to be connected to each other, and fitted or screwed. Among these, the tip portion is made of a metal material having good heat conductivity, and the base end portion is made of a metal material having mechanical strength.

The dimension h of the gear so between the tip surface of the nozzle and the opening 內 the side surface of the nozzle protection gap is set to 0.5 to 1.5 mm. Roh nozzle Oh Li off office diameter, to be on the ratio z Z i ^ i It 1.0~5.0 of the Nozzle Ho證Kiyabbu opening of ί Holy "5 _2.

In addition, an annular cooling water chamber is provided inside the base of the nozzle protection cap, and this cooling water chamber communicates with the cooling water chamber provided in the electrode. The nozzle protection cap may have a bag-shaped double structure, and the space formed by this may be used as a cooling water chamber.

In addition, the plasma gas inflow path for injecting the plasma gas into the plasma gas path provided around the electrode is inclined with respect to the center of the torch so as to give the plasma gas a jewelry flow. The rectifying passage of the rotor is spirally formed so as to give the secondary gas passing therethrough a spiral flow in the same direction as the spiral direction of the plasma gas, and the nozzle has an orifice diameter of The relation of the length L is made to satisfy L ≤ 2.

Further, the inflow path communicating with the cooling water chamber on the electrode side and the cooling water chamber passage on the nozzle side is a tube made of an electrically insulating material.

The plasma arc erupted along with the plasma gas is erupted through the nozzle and orifice. At this time, a secondary force is ejected from the gap toward the plasma arc, which is rectified by the CD secondary gas insulator, and the nozzle cap and the nozzle protection cap are rectified by the CD insulator. Aligned and packed _c Nozzle protection key ':, 分離, 先端プ分離分離プににににに，，だけ，交換交換だけだけ交換. By providing a cooling water chamber in this base, the nozzle protection cap is cooled.

A swirling flow is given by the plasma gas and the plasma gas inflow passage, and a swirling flow of the secondary gas is given by the insulator in the same direction as the plasma gas. The corrosion of the cooling water chamber is prevented by fitting a tube made of an electric material into the flow path through which the cooling water flows. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a sectional view of a plasma torch showing a first embodiment of the present invention, FIGS. 2A to 2E are explanatory diagrams of various insulators, and FIG. 3 is a sectional view of a plasma torch showing a second embodiment. 4 is a sectional view of a plasma torch showing a third embodiment, FIG. 5 is a sectional view of a plasma torch showing a fourth embodiment, FIG. 6 is a sectional view of a plasma torch showing a fifth embodiment, and FIG. FIG. 7B is a cross-sectional view illustrating the operation of the plasma torch according to the sixth embodiment, and FIG. 7B is a perspective view of a plasma gas inflow path according to the sixth embodiment.

Best mode for carrying out the explanation

First Embodiment A first embodiment of the present invention will be described with reference to FIGS. 1 and 2A to 2E.

In the figure, 1 is an electrode, 2 is a nozzle held by a nozzle holding member 3 at a position facing the tip of the electrode 1, and 4 is a nozzle cover that covers other portions except the lower end portion of the nozzle 1. A nozzle protection cap 5 covers the outside of the nozzle cap 4. Around the electrode 1, a plasma gas passage 6 communicating from the periphery to the orifice 16 of the nozzle 2 is provided, and cooling is provided between the nozzle 2 and the nozzle cap 4. A water passage 7 is provided. In addition, a secondary gas passage 8 is provided between the nozzle cap 4 and the nozzle protection tank 5 and the nozzle 5. The secondary gas passage 8 is open to the leading end of the nozzle 2.

The nozzle protection cap 5 is electrically isolated from the nozzle cap 4 in the shape of a j, and the nozzle 2 is also supported by the tip of the nozzle cap 4. C There is a drainage chamber 9 inside the electrode 1. ': 〇; Is communicated to. The cooling water chamber 9 is connected to a recirculating water inflow passage 10 and the other cooling water passage is connected to a cooling water outflow passage 10a. Further, the plasma gas passage 6 is connected to the plasma gas inflow passage 11, and the secondary gas passage 8 is connected to the secondary gas inflow passage 12. Reference numeral 13 denotes a torch main body for supporting each of the above members, which is insulated from the electrode 1 and the nozzle 2. The nozzle protection cap 5 is screwed to the torch body 13.

The secondary gas passage 8 formed between the nozzle cap 4 and the nozzle protection cap 5 is formed in a tapered shape. In the secondary gas passage 8, an insulator 14 made of an electrically insulating material and also serving as a spacer is provided in an airtight manner with respect to the wall surfaces of the nozzle cap 4 and the nozzle protection cap 5. Is equipped. The insulator 14 is provided with a plurality of small holes 15 communicating with the upstream side and the downstream side thereof and serving as rectification paths in the circumferential direction.

In addition, the small hole 15 serving as the flow straightening passage may be replaced with the small hole 15 shown in FIG. 2A and a groove 15a provided in the axial direction on the surface (or the outer surface) as shown in FIG. 2B. Good. These small holes 15 and grooves 15a may be provided in a spiral shape around the axis. In addition, the insulator 14 shown in FIGS. 2A and 2B is formed in a tapered shape in accordance with the shape of the tapered shape of the secondary gas passage 8. Instead, as shown in FIGS. 2C, 2D, and 2E, the cross section may be rectangular, and the rectified secondary gas may flow in the axial direction. The insulator 14 is made of a synthetic resin such as a fluorine-based resin or a ceramic.

The ΦΦι / Φι between the orifice 16 Φ of the nozzle 2 and the opening diameter 《5 of the nozzle protection cap 5 is 1.5 to 5.0, preferably 2.0 to 4.0. 0. Here, if Φ / <1.0, the tip of the nozzle protection cap 5 is deformed and damaged by the heat of the plasma arc, and disturbs the flow of the secondary gas. When Φ Φ> 5.0, the back of the dross adheres to the gap 17 between the lower end faces of the nozzles 1 and 2 and the nozzle protection cap 5, and a double arc is trapped. Resulting in.

Also, the appropriate gap dimension h for one gap is 0.5 to 0.5 mm. If h <0.5 mm, the flow velocity of the secondary gas jet S becomes too high, causing arcing. Tongue and one.

In such a configuration, the plasma arc from the electrode 1 is ejected through the openings of the nozzle 2 and the nozzle protection cap 5 together with the plasma gas supplied to the plasma gas passage 6 provided around the electrode 1 ′. Is done. At this time, it is cooled by cooling water passing through the nozzle 2 recirculating water passage. The secondary gas is ejected from the gap 17 through the secondary gas passage 8 so as to surround the periphery of the plasma. The secondary gas at this time is rectified while passing through the insulator 14. That is, the secondary gas that has passed through the annular secondary gas passage 8 is rectified while passing through the rectifying passage formed by the small holes 15 or the grooves 15 a of the insulator 14.

In addition, by optimizing the gap dimension h of the gap 17 between the lower end surface of the nozzle 2 and the nozzle protection cap 5, the gas is injected so as to surround the plasma arc. The secondary gas is supplied at a sufficient flow rate with a sufficient flow rate. By setting the opening diameter _{2 of the} nozzle protection cap 5 to the optimum value, the nozzle 2 is protected from the dross blow-up during piercing.

Next, second to sixth embodiments of the present invention will be described with reference to FIGS. 3 to 7B.

FIG. 3 shows a second embodiment, in which an insulator 14a is formed in a ring shape by a member having a rectangular cross-sectional shape, and the insulator 14a is a nozzle cap 4a. The nozzle protection cap 5a is fitted and attached to the step formed at the opposing portion of each of the nozzle protection caps 5a. A rectifying passage 18 is provided on the outer peripheral side of the insulator 14a. According to this configuration, the nozzle cap 4a and the nozzle protection cap 5a are aligned by the insulator 14a, and the positioning of the two materials is easily performed. FIG. 4 shows a third embodiment, in which the distal end portion and the proximal end portion of the nozzle protection cap are formed as separate members. That is, in the nozzle protection cap 5b, a base end portion 19 screwed to the nozzle body 13 and a leading end portion 20 on the nozzle 2 side are different from each other. An insulator 14a is supported on the distal end portion 20. The coupling between the proximal end portion 19 and the distal end portion 20 is performed by connecting a flange portion 20a on the distal end portion 20 side. And the front end side of the base end 19 is fitted and fixed to the flange portion 20a, and the two may be fixed to each other at the flange portion 20a. According to this configuration, when the distal end side of the nozzle protection cap 5b is damaged when using the plasma torch, it is sufficient to replace only the tip 20 and the gating is completed. In addition, since the nozzle protection cap 5b is divided into a base portion 19 and a tip portion 20, the tip portion 10 is made of a material having good heat conductivity, so that a high-temperature molten metal adheres. Even if it does, the molten metal is cooled in a short time and is easily separated. On the other hand, when the base end 19 is made of a material having excellent mechanical strength, the torch does not deform even when the torch comes into contact with the material to be cut.

FIG. 5 shows a fourth embodiment in which the nozzle protection cap can be cooled. That is, a rectangular cooling water chamber 21 is provided inside the base end 19a of the nozzle protection cabinet 5c, and the cooling water chamber on the electrode 1 side provided inside the electrode 1 is provided in the cooling water chamber 21. It is connected to 9 via passage 2. With this configuration, the base end of the nozzle protection cabinet 5c is cooled by the cooling water in the cooling water chamber 21 and the temperature rise in this portion is suppressed. Fig. 6 shows a fifth embodiment, in which the cooling water chamber 21a of the nozzle protection cap 5d is formed in a vertically wide annular shape to increase its fertility, thereby cooling this part. The ability is getting bigger. The cooling water chamber 21a has an inlet-side passage 22 communicating with the cooling water chamber 9 on the electrode 1 side, and an outlet-side passage communicating with the cooling water passage 7 provided around the nozzle 2. 23 are in communication.

7A and 7B show a sixth embodiment. In FIG. 7A, the rectifying passage 18 provided in the insulator 14a is spirally wound around the center of the torch, so that the secondary gas flow spouted from the gearbox of the nozzle protection cap 5e can be reduced. It can flow. In addition, a plurality of plasma gas inflow paths 6a for flowing the plasma gas into the plasma gas path 6 provided around the electrode 1 are provided at an angle to the center of the torch as shown in FIG. The swirling flow is given to the plasma gas flowing into the plasma gas passage 6. At this time, the turning direction of the secondary gas and the turning direction of the plasma gas are the same, and the orifice 县 L of the nozzle 2 is the orifice diameter ^! L / ^ 【≤ 2

When the material to be cut 24 is cut by the buzzer torch having such a configuration, the cut wall 24 a on the upstream side of the swirling flow of the secondary gas becomes vertical and the other cut wall 24 as shown in FIG. 1] 1 1b is inclined like a groove. For example, if the secondary gas is turning to the right when viewed from above, the right cut wall 24a will be vertical, and to the left if it is turning, and the left cut wall 24b if it is turning. Becomes vertical.

Further, in each of the above embodiments, in order to reduce the electrochemical corrosion caused by the cooling water, the current flowing through the cooling water must be reduced. Therefore, it is necessary to reduce the area of the metal part of the torch body that comes into contact with the cooling water. For this reason, as shown in FIG. 1, for example, a tube 2 made of an electrically insulating material is connected to an inflow passage 25 communicating the cooling water chamber 9 on the electrode 1 side and the cooling water passage 10 on the nozzle 2 side. 6 is fitted (seventh embodiment). Industrial applicability

According to the present invention, the life of the nozzle is long, the time loss associated with the replacement of the nozzle is small, precision cutting with a narrow cutting groove width is performed, the cut surface of the material to be cut is vertical, and the nozzle is Only the tip of the protective cap can be replaced as a consumable item, making it easy to maintain and inspect the torch, and is useful as a cutting plasma torch that can withstand electrochemical corrosion caused by cooling water.

Claims

The scope of the claims

1. Using a water-cooled electrode, a nozzle arranged to cover this electrode across the plasma gas passage, and a nozzle cap for fixing this nozzle to the torch body, the nozzle alignment In a cutting torch, a plasma arc is cut between the electrode and the material to be cut through a disk.

On the outer side of the nozzle cap, an opening facing the orifice is provided on the tip side thereof, and an annular secondary gas passage communicating with the opening is formed between the nozzle cap and the nozzle cap. A nozzle protection cable is electrically insulated and fixed to the electrode and the nozzle, and the secondary gas passage is formed in a rectangular shape with an electrically insulating material, and

A plasma torch for cutting, comprising an insulator having a rectifying passage for rectifying a gas flow flowing through a secondary gas passage.

2. The cutting plasma torch according to claim 1, wherein said nozzle protection cap is made of a metal material having good heat conductivity.

3. The insulator has a rectangular cross-sectional shape, and the insulator is fitted to a step provided on an outer peripheral surface of the nozzle cab and an inner peripheral surface of the nozzle protection cab. The cutting plasma torch according to claim 1, characterized in that:

4. The nozzle protection cap comprises a leading end portion for protecting the leading end of the nozzle, and a base end portion fixed to the torch main body side, and these are combined so as to be detachable. The plasma torch for cutting according to claim 1.

5. A flange that fits into the distal end and the base end is provided, or a screw portion is provided in a portion where they are fitted to each other, and the distal end and the base are fitted or connected together. 5. The cutting torch according to claim 4, wherein the torch is worn.

6. The nozzle protection cap according to claim 4, wherein the tip portion is made of a metal material having good heat conductivity, and the base portion is made of a metal material having excellent mechanical strength. Cutting torch for cutting.

7. The dimension h of the gap between the tip surface of the nozzle and the inner surface of the opening of the nozzle protection cap is 0.5 to 1.5 mm, wherein the dimension h is 0.5 to 1.5 mm. The cutting plasma torch described.

8. Orifice diameter of the nozzle? The cutting plasma torch according to claim 1 or 4, wherein the ratio Φ 2 / Φ 1 between ^ and the opening diameter ₂ of the nozzle protection cap is set to 1.0 to 5.0.

9. An annular cooling water chamber is provided inside the base end of the nozzle protection cap, and the annular cooling water chamber and the cooling water chamber provided in the electrode are communicated by a passage. The plasma torch for cutting according to claim 1 or 4, which is characterized by the following claims.

10. The cutting plasma torch according to claim 9, wherein the nozzle protection cap has a bag-shaped double structure, and a space formed by the nozzle protection cap is a cooling water chamber.

1 1. A plasma gas inflow passage for flowing the plasma gas into the plasma gas passage is provided to be inclined with respect to the axis of the torch so as to give a swirl flow to the plasma gas, and the insulator is rectified. The cutting passage according to claim 1 or 4, wherein the passage is provided in a spiral shape so as to give a secondary gas passing through the passage a turning flow in the same direction as the turning direction of the plasma gas. Plasma torch.

12. The relationship between the orifice diameter 1 and the orifice length L of the nozzle, which is the outlet of the plasma gas, is set to ≤2. Plasma torch for cutting.

13. The inflow path connecting the cooling water chamber provided in the electrode and the cooling water passage between the nozzle and the nozzle gap is constituted by a tube made of an electrically insulating material. The plasma torch for cutting according to range 1 or 4.