JPH0952177A - Plasma torch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow the swirling flow of the plasma gas to be jetted from a plasma torch in a double-swirler manner and the secondary gas to reach a work without being diffused therearound. SOLUTION: In a plasma nozzle 2 to jet the plasma gas to the tip side of an electrode 1 in the swirling condition, and a plasma torch having a secondary gas passage to eject the secondary gas to the tip side of the plasma nozzle 2 in the swirling condition, auxiliary gas flow passages 16, 17 to eject the auxiliary gas so as to surround the swirling flow of the plasma gas and the secondary gas are provided on the outer side of the secondary gas passage. The auxiliary gas flow passages 16, 17 comprise an auxiliary gas ejection member provided outside a cap member of the plasma torch.

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 plasma nozzle for ejecting plasma gas.

[0002]

2. Description of the Related Art In plasma cutting, a cutting width is generally different between a front side and a back side of a cutting groove (kerf). Therefore, the cut surface is not vertical but inclined. However, on the other hand, in the plasma torch configured to swirl and eject the working gas around the axis of the electrode to stabilize the arc, the cut surface is not symmetrical and the degree of difference is different. Although known to be non-target. By utilizing this, even in the situation where the front kerf width is wide and the back kerf width is narrow, it is possible to perform vertical cutting with only one cut surface by swirling the working gas. Welding Technology is disclosed in the June 1988 issue.

Further, recently, a swirl passage is provided in a secondary gas passage formed between a nozzle cap covering the nozzle and the nozzle, and this swirl flow of the secondary gas is used to form a shoulder at the upper edge of the cutting portion. A technique capable of improving who and the bevel angle is disclosed in JP-A-5-84579.

As described above, there is known a technique for controlling the bevel angle by ejecting both the plasma gas and the secondary gas as a swirling flow.

[0005]

However, in the conventional plasma torch, the tip of the opening of the plasma nozzle and the outlet of the secondary gas are at substantially the same position in the axial direction, at least for the secondary gas. The ejection port was configured to slightly project from the opening tip of the plasma nozzle.

Therefore, during plasma cutting, when the plasma torch is cut away from the work by a predetermined standoff, a part of the jet flow of both gases jetted while swirling from the tip of the plasma torch stands. It diffuses into the space when it is off, and the strength of the swirling flow of both gases becomes weaker until reaching the cutting part of the work, and as a result, this swirling flow cannot be maintained normally over the entire plate thickness, and the plasma There is a problem that the bevel angle due to the swirling flow of gas cannot be controlled as expected, and the cutting surface becomes hollow or bulging on the contrary, and the cutting accuracy varies. there were.

The present invention has been conceived in view of the above, and the plasma gas to be ejected while being swirled by the plasma torch can reach the back surface of the work by allowing the momentum of the swirling flow to reach the back surface of the work. An object of the present invention is to provide a plasma torch capable of favorably adjusting the angle.

[0008]

A plasma torch according to the present invention includes a plasma nozzle for ejecting a plasma gas toward the tip side of an electrode and a secondary gas passage for ejecting a secondary gas while swirling the secondary gas toward the tip side of the plasma nozzle. In the plasma torch having the above, the auxiliary medium ejection passage for ejecting the auxiliary medium is provided outside the secondary gas passage so as to surround the plasma gas flow and the swirling flow of the secondary gas.

In the above plasma torch, the above 2
An auxiliary medium jetting member having an auxiliary medium passage is provided outside the cap member that constitutes the secondary gas passage, and the secondary gas jetting means is a secondary gas passage means extended to reach the vicinity of the material to be cut. ing.

Further, a shielding member that reaches the vicinity of the material to be cut is provided near the ejection port of the secondary gas passage constituting member, and an ejection port for ejecting auxiliary gas is provided in the secondary gas passage. Suction means for sucking gas through the cutting portion of the material to be cut is provided at a position facing the ejection port, and the secondary gas passage is provided with the ejection direction as the apex with respect to the central axis of the torch and is larger than 0 ° and larger than 45 °. It is configured with an angle of less than °.

[0011]

[Operation] The plasma gas and secondary gas ejected from the plasma torch are guided to the work with a reduced horizontal diffusion. As a result, the plasma gas and the secondary gas can reach the work side while maintaining their respective swirling flows without being diffused to the surroundings in the space in the standoff part of the plasma torch. The swirling flow is applied over the entire length of the cutting portion of the work in the plate thickness direction.

[0012]

FIG. 1 shows a first embodiment of the present invention.
It will be described based on. In FIG. 1, reference numeral 1 is an electrode, 2 is a plasma nozzle provided at a position facing the tip of the electrode 1 and held by a nozzle holding member 3, and 4 is the other part except the lower end part of the plasma nozzle 1. Is a nozzle protection cap that covers the outside of the nozzle cap 4. A plasma gas passage 6 is provided around the electrode 1 so as to communicate with the plasma nozzle 2 from the periphery.
A cooling water passage 7 is provided between the nozzle cap 4 and the nozzle cap 4, and further, the nozzle cap 4 and the nozzle protection cap 5 are provided.
A secondary gas passage 8 that is open to the tip side of the plasma nozzle 2 is provided between and. The nozzle protection cap 5 is electrically insulated from the nozzle cap 4, and is also supported by the tip of the plasma nozzle cap 4.

A cooling water chamber 9 is provided inside the electrode 1, and the cooling water chamber 9 communicates with the cooling water passage 7. A cooling water inflow passage 10 is connected to one of the cooling water chambers 9, and a cooling water outflow passage 10 a is connected to the other cooling water passage 7. On the other hand, the plasma gas passage 6
Is connected to a plasma gas inflow path 11, and the secondary gas passage 8 is connected to a secondary gas inflow path 12. Reference numeral 13 denotes a torch body that supports the above-mentioned members, which is insulated from the electrode 1 and the plasma nozzle 2. The nozzle protection cap 5 is screwed to the torch body 13.

A swirl passage 6a for providing a swirl flow to the plasma gas is provided upstream of the plasma gas passage 6.

Further, the secondary gas passage 8 formed between the nozzle cap 4 and the nozzle protection cap 5 is formed in a taper ring shape, and is made of an insulating material in the secondary gas passage 8, and Insulator 14 that doubles as a spacer
Are airtightly provided on the respective wall surfaces of the nozzle cap 4 and the nozzle protection cap 5, and the insulator 14 is provided with a swirling passage 14a for giving a swirling flow to the secondary gas. .

An auxiliary gas ejection cylinder 15 formed in a shape surrounding the nozzle protection cap 5 is fitted to the outside of the nozzle protection cap 5 of the plasma torch by supporting it on the nozzle body 13 side by means not shown. ing. An annular auxiliary gas passage 16 is provided in the auxiliary gas ejection cylinder 15, and an outlet 16a of the auxiliary gas passage 16 is a gas flow ejected as a swirling flow from the plasma nozzle 2 and the secondary gas passage 8, respectively. The auxiliary gas is opened in a direction that surrounds the. The angle α of the outlet 16a of the gas passage in the ejection direction is about 65 ° with respect to the central axis of the torch in the present embodiment, but the angle is not limited to this, and it is inclined in the range of 0 to 90 °. Gas passage 1
The upstream side of 6 is connected to an auxiliary gas supply passage (not shown). Air or any other gas is used as the auxiliary gas. It may also be another medium around the gas, such as a liquid or powder, which produces a shielding effect.

Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, instead of the auxiliary gas ejection cylinder 15 in the embodiment shown in FIG. 1, the nozzle protection cap 5 is provided outside the nozzle holding cap 5.
An auxiliary cap 18 forming an auxiliary gas passage 17 between the nozzle protection cap 5 and the outer peripheral surface of the nozzle protection cap 5 is fixedly provided on the torch body 13 side. Auxiliary cap 18
Is preferably electrically insulated from the nozzle to prevent abnormal discharge called double arc.

The gas passage 17 formed by the auxiliary cap 18
Similar to the first embodiment described above, the outlet portion of is shaped to eject the auxiliary gas in a direction surrounding the swirling flow from the nozzle 2 and the secondary gas passage 8.

In the first and second embodiments, the plasma arc from the electrode 1 is accompanied by the plasma gas supplied to the plasma gas passage 6 provided around the electrode 1 together with the plasma nozzle 2 and the nozzle protection cap 5. Is ejected through the opening. The secondary gas is ejected from the tip of the secondary gas passage 8 so as to surround the plasma, and the secondary gas at this time is rectified while passing through the insulator 14. That is, circular 2
The secondary gas that has passed through the secondary gas passage 8 is the insulator 1
While passing through the swirling passage 14a of No. 4, it becomes a swirling flow and is ejected from the tip of the secondary gas passage 8.

At this time, the auxiliary gas is provided outside the plasma gas and the secondary gas jetted from the plasma nozzle 2 and the secondary gas passage 8 so as to surround the plasma gas and the secondary gas. Auxiliary gas is ejected from the respective auxiliary gas passages 16 and 17 of the cap 18.

Therefore, the ejected plasma gas and secondary gas are led to the work 19 while being covered with the auxiliary gas from the tip of the plasma torch to the work 19.

As a result, the plasma gas and the secondary gas can reach the work 19 side while maintaining the swirling flow without being diffused to the surroundings in the space in the standoff portion of the plasma torch, and the swirling flow is generated. Work 1
It acts on the entire length of the cutting groove 20 of 9 in the plate thickness direction.

The length of the plasma nozzle protection cap 5 shown in FIGS. 1 and 2 is made longer in the axial direction of the torch as in the third embodiment shown in FIG. The work may be extended to near the surface of the work or contact the work 1919 during the cutting operation.

According to this structure, the double swirler-like gas ejected from the plasma torch can be surrounded by the extended plasma nozzle protection cap 5a. The extended portion of the plasma nozzle protection cap 5a may be replaceable as a separate component. In this case as well, it is preferable to use an insulating material as in the above case.

Note that the same effect can be obtained by extending the length of the auxiliary cap 18 shown in FIG. 2 in the axial direction of the torch similarly to the above. Further, as shown in FIG. 4, an auxiliary gas blowout port 8a may be provided in the secondary gas passage 8 so that the swirling gas is wrapped with the auxiliary gas blown out from the blowout port 8a. In this case, the same effect can be obtained without using a new auxiliary gas means.

FIG. 5 shows a fourth embodiment of the present invention. Instead of the auxiliary gas passage in the first, second and third embodiments, a suction device 21 is provided below the work 19. The case where is provided is shown.

According to this embodiment, the plasma gas and the secondary gas ejected from the plasma torch in a double swirl shape are guided to the lower side of the work 19 through the cutting groove 20 along the air flow generated by suction. Therefore, both of the above gases are not diffused in the space of the standoff portion and the cutting groove 20
Is reached within.

Further, FIG. 6 shows a fifth embodiment of the present invention, in which the electrode 1 connected to a plasma power source (DC power source) (not shown) is connected to the torch body (not shown) via an insulator 22. It is supported on the tip side. A plasma nozzle 2 having an orifice 23 concentric with the electrode 1 is arranged at the tip so as to surround the tip of the electrode 1 and the insulator 22, and the inside of the plasma nozzle 2 serves as a plasma gas passage 6. Has become. In the plasma gas passage 6, the first member supported by the insulator 22 and the plasma nozzle 2 is provided.
The swirler 24 is interposed.

A nozzle cap 4 is fixedly attached to the nozzle body on the outside of the plasma nozzle 2, and a cooling water passage 7 is formed between the nozzle cap 4 and the plasma nozzle 2.

A nozzle protection cap 5 is provided outside the nozzle cap 4 to cover the tip of the torch body and to form a secondary gas passage 8 with the nozzle cap 4. The second swirler 2 for giving a swirling flow to the secondary gas is provided in the secondary gas passage 8 inside the nozzle protection cap 5.
5 is interposed.

An orifice 26 concentric with the orifice 23 of the plasma nozzle 2 is opened at the tip of the nozzle protection cap 5. Immediately upstream of the opening of the orifice 26 is a secondary gas ejection passage 27 which is substantially parallel to the side surfaces of the plasma nozzle 2 and the nozzle protection cap 5 which face each other.
The secondary gas ejection passage 27 is inclined so that the angle α with respect to the axis of the electrode 1 is 30 °.

An example of the size of each portion in this embodiment is shown. The diameter of the orifice 23 of the plasma nozzle 2 is 1.5 mm, the length of the parallel portion of the secondary gas ejection passage 27 is about 5 mm, and the width is about 5 mm. The diameter of the orifice 26 of the nozzle protection cap 5 is 4 mm.

In the above structure, 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 19 to cut the work 19. This arc is maintained by the working gas swirling and ejected from the plasma gas passage 6 of the plasma nozzle 2.

During the cutting, the secondary gas continues to be ejected from the orifice 26 toward the cutting groove 20 of the work 19, and the cutting proceeds while adjusting the angle of the cutting surface. At this time,
The secondary gas is swirling in the second swirler 25, and the secondary gas jet passage 27 adds a velocity vector of θ = α = 30 ° to the central axis of the torch.

In other words, this means that the flow velocity vector that converges in the central direction of the swirling flow and the flow velocity vector in the same direction as the working gas jet direction are positively added to the swirling 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 26 of the nozzle protection cap 5 and maintains the swirling flow of the secondary gas below the torch. are doing. 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 passages 27 whose angle α = 30 ° with respect to the central axis of the torch. The angle α of the torch with respect to the central axis of 27 is 0 ° as 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 converging in the center direction is not effectively given at θ = 0 °. In this case, the swirling flow diffuses radially in the cutting groove 20 at the moment when it exits the orifice 26. The swirling flow sent in 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 plasma nozzle 2 and the nozzle protection cap 5 simply contact the work 19 increases. However, not only the torch is easily broken by the generation or collision of the double arc, but also the molten metal blown up at the time of cutting is deposited between the plasma nozzle 2 and the nozzle protection 5, and the plasma nozzle 2 and the nozzle protection cap 5 The insulation between them is broken, and the risk of double arcs continues to increase. Furthermore, when the work 19 is thick, the blown-up molten metal directly protects the plasma nozzle 2 or the nozzle protection cap 5 that should protect the plasma nozzle 2.
May melt and become unusable.

On the other hand, when θ = 45 ° or more, the flow velocity component in the same direction as the working gas jet direction is not sufficient, so that the non-uniformity of the swirling velocity distribution caused by machining error and part assembly error has a strong effect on the swirling flow. Therefore, the bevel angle is not constant. 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 have confirmed the variation in the angle of the cut surface due to the difference in the angle α of the secondary gas ejection passage 27 by an experiment and set the angle α of the secondary gas ejection passage 27 that can be put to practical use. α <45 °. FIG. 7 shows an outline of the experimental result which was the basis for this. It is a comparison between the case where the angle α of the secondary gas ejection passage 27 is 30 ° which is within the range of the present invention and the case where it is 45 ° outside the range of the present invention. In this experiment,
The plasma nozzle 2 and other device configurations are the same.

In the experiment for obtaining the experimental result shown in FIG. 7, 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 19 is 9 mm, and the material is SS400. A secondary gas flow rate of 70 liters / min was required to set the bevel angle to 0 °.

The cutting is performed three times for each of the four cutting directions orthogonal to each other, and the maximum and minimum values are shown as errors as the variations in the measured bevel angle at that time. As is clear from FIG. 7, the variation when α = 45 ° is an average value of ± 4 °, whereas the variation when α = 30 ° is within an average value of ± 1 °.

According to this embodiment, by adding the flow velocity component, the distance that 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. A swirling flow with little variation in the circumferential velocity component can be maintained even on the lower surface of the work 19.

The suction device 21 shown in FIG.
It may be used in each of the embodiments shown in FIGS. 2, 3, 4, and 6, and in this case, the effect of maintaining the swirling flow of the secondary swirling gas is further increased. Further, it is possible to simultaneously discharge fumes and the like generated at the time of cutting by suction. Further, instead of gas, other medium such as liquid or powder may be used.

[0046]

According to the present invention, the plasma gas and the secondary gas ejected from the tip of the plasma torch are maintained in their respective swirling flows without being diffused in the space in the standoff portion of the plasma torch. In the cut groove 2 of the work 19 that can reach the work 19 side in the above state.
It is operated over the entire length in the plate thickness direction of 0.

Therefore, a constant bevel angle can be obtained in the plate thickness direction, and no scooping or bulging occurs on the cut surface.
Further, since the swirling flow is effectively applied, the flow rate of the secondary gas can be reduced.

Further, according to the present invention, the bevel angle of the cutting groove 20 of the workpiece can be favorably adjusted by the jetted jet gas without being affected by the standoff, so that the swirling flow is strongly exerted. Therefore, it is not necessary to lower the standoff, and the risk of torch damage or double arc due to the adhesion of molten metal or the like can be avoided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a second embodiment of the present invention.

FIG. 3 is a sectional view showing a third embodiment of the present invention.

FIG. 4 is a sectional view showing a modified example of the third embodiment of the present invention.

FIG. 5 is a sectional view showing a fourth embodiment of the present invention.

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

FIG. 7 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.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Electrode 2 ... Nozzle 3 ... Nozzle protection member 4 ... Nozzle cap 5,5a ... Plasma nozzle protection cap 6 ... Plasma gas passage 6a, 14a ... Swirl passage 7 ... Cooling water passage 8 ... Secondary gas passage 8a ... Blowout port 9 ... Cooling water chamber 13 ... Torch body 14 ... Insulator 14a ... Swirl passage 15 ... Auxiliary gas ejection cylinder 16,17 ... Auxiliary gas passage 16a ... Exit 18 ... Auxiliary cap 19 ... Work 20 ... Cutting groove 21 ... Suction device 23,26 ... Orifice 24 ... 1st swirler 25 ... 2nd swirler 27 ... Secondary gas ejection passage α ... Inclination angle of secondary gas passage

Claims (7)

[Claims] 1. A plasma torch having a plasma nozzle for ejecting plasma gas toward the tip side of an electrode and a secondary gas passage for ejecting secondary gas while swirling toward the tip side of the plasma nozzle, outside the secondary gas passage. A plasma torch, further comprising an auxiliary medium jetting passage for jetting an auxiliary medium so as to surround the plasma gas flow and the swirling flow of the secondary gas. 2. A plasma torch having a plasma nozzle for ejecting a plasma gas toward the tip of an electrode and a secondary gas passage for ejecting a secondary gas while swirling toward the tip of the plasma nozzle. A plasma torch, characterized in that an auxiliary medium jetting member having an auxiliary medium passage is provided outside the constituent cap member. 3. A plasma torch having a plasma nozzle for ejecting a plasma gas to the tip side of an electrode and a secondary gas passage for ejecting a secondary gas while swirling to the tip side of the plasma nozzle. A plasma torch, wherein the secondary gas passage means is extended so as to reach the vicinity of the material to be cut. 4. A plasma torch having a plasma nozzle for ejecting a plasma gas toward the tip side of an electrode and a secondary gas passage for ejecting a secondary gas while swirling toward the tip side of the plasma nozzle. A plasma torch characterized in that a shield member reaching up to the vicinity of the material to be cut is provided in the vicinity of the jet outlet of. 5. A plasma torch having a plasma nozzle for ejecting a plasma gas toward the tip of an electrode and a secondary gas passage for ejecting a secondary gas while swirling toward the tip of the plasma nozzle. A plasma torch provided with a jet port for jetting auxiliary gas. 6. A plasma torch having a plasma nozzle for ejecting a plasma gas to the tip side of an electrode and a secondary gas passage for ejecting a secondary gas while swirling to the tip side of the plasma nozzle, facing the plasma gas ejection port. The plasma torch is characterized in that a suction means for sucking gas through the cutting portion of the material to be cut is provided at the position to be cut. 7. A plasma torch having a plasma nozzle for ejecting a plasma gas toward the tip side of an electrode and a secondary gas passage for ejecting a secondary gas while swirling toward the tip side of the plasma nozzle. A plasma torch which is provided with an angle of more than 0 ° and less than 45 ° with respect to the center axis of the torch with the ejection direction as the apex.