JPS5881563A - Plasma gouging method - Google Patents

Abstract

PURPOSE:To prevent scattering of the molten metal of the work by gouging the work only by the momentum of plasma. CONSTITUTION:For example a plasma cutting torch is set movably and a gaseous mixture of Ar and H2 is supplied as a plasma working gas between a W electrode as cathode and the work 8 as anode through an ejection nozzle 9, whereby a plasma arc 5 is generated. At this time, the angle theta of inclination of the torch from perpendicular is set at 70-80 deg., and the distance (d) between a water cooling nozzle 3 and the work 8 is maintained in a correct range. The melt 7 of the work 8 is removed only by the momentum of the gaseous flow 6 of plasma. A carbon electrode may be used as the electrode, in which case air is used as the plasma working gas.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a low-dust gouging method using a plasma method in which a cooling nozzle and a plasma working gas converge an arc to create a high energy density and melt process a workpiece.

A specific example of the conventional gouging method using the plasma method is shown in FIG. 1 (plasma arc method). In other words, an arc 5 is generated between the non-consumable electrode 1 and the workpiece 8, and the arc 5 is cooled and converged by the water-cooled nozzle 3 and the plasma working gas 2.The high-energy density arc and the plasma gas 6 are then applied to the workpiece. 8 to melt the workpiece melt 7
The gouging process is performed by scattering the auxiliary high-pressure gas 10 ejected parallel to the direction of the plasma arc from several nozzles 9 arranged around the water-cooled nozzle 3 from which the plasma arc is emitted.

Other plasma gouging methods include, for example,
There is a "plasma gouging torch" disclosed in Japanese Patent No. 4-42858. This method improves the auxiliary jet gas nozzle for scattering the melt of the workpiece in the plasma gouging torch as shown in Fig. 1. By coordinating the gas ejection direction with the plasma arc direction, a pressure of 5 k can be achieved without tilting the plasma gouging torch.
The molten material of the workpiece is strongly dispersed with Q/ of one level of ejected gas.

However, with the above conventional method, the air drawn by the worker is contaminated by scattered dust, and when the torch carrier is automatically gouged, it is difficult to use in a closed place such as an indoor workshop. This gradually pollutes the indoor air and worsens the working environment.

On the other hand, since an inert gas with a high sieve value is used as the operating gas of the plasma arc, and an expensive tungsten electrode is used for the electrode, the running cost of the plasma gouging torch is high.

Furthermore, when using the arc air gouging method, the molten metal of the workpiece is strongly scattered by the high-pressure air jetted from the nozzle, resulting in the deterioration of the working environment as described above.

The present invention aims to solve the above-mentioned problems by the method described in the claims in order to fundamentally improve the deterioration of the working environment. .

The present invention will be specifically explained below.

Generally, the flow velocity of plasma is 1104c/cm in an open arc.
This is said to be a second, and the flow velocity becomes even faster in a restrained arc as in the method of the present invention.The present invention attempts to utilize this plasma flow velocity as a force (hereinafter referred to as momentum) for removing the melt. . This force is estimated to be quite large considering the fact that there is almost no molten metal directly under the arc and the solid surface is always exposed when observed using a high-speed camera during plasma cutting.6 The present invention is based on the above findings. This method uses a plasma method to perform gouging using only plasma momentum. Therefore, the present invention can be applied to the plasma jet method (hereinafter referred to as non-transfer type) which uses only plasma energy, as well as the plasma jet method (hereinafter referred to as non-transfer type) which uses energy from plasma and arc (hereinafter referred to as transfer type). be.

First, in the case of the transfer method, as shown in FIG. The melt 7 of the workpiece is removed only by the air flow 6. Here, the reason why the inclination angle θ of the plasma arc (which is the same as the inclination angle of the plasma torch in Figure 2) is limited to 30° or more is because if the inclination angle is less than 30°, the workpiece will be cut. This is because it has been confirmed through experiments that this is the lowest appropriate slope that allows effective use of plasma mo-mentum for gouging. Next, the reason why the above-mentioned inclination angle θ is limited to 70° or less is as shown in Fig. 8.
This is because it has been experimentally confirmed that by improving l/8 to an asymmetrical shape, a plasma momentum effective for removing the melt 7 can be obtained even when the inclination angle is 70 degrees.

To tilt the plasma arc, in addition to tilting the torch as described above, it is also possible to hold the torch body vertically and tilt only the ejection angle of the plasma arc from the vertical line by improving the inside of the torch, as shown in Figure 4. There is also a way to do it.

By effectively utilizing the plasma momentum in this way, it is no longer necessary to eject strong gas such as air from an auxiliary nozzle in order to remove the melt as in the conventional method.

Therefore, the dust (hereinafter referred to as ``mu'') during gouging work can be avoided by scattering the melt more than necessary.
This will result in a significant reduction in the amount of waste generated.

A method similar to this phenomenon is the arc air gouging method previously proposed by the present applicant, as shown in Japanese Patent Application No. 56-89250 ``Arc Air Processing Method'', in which a nozzle for ejecting compressed air from a gouging torch is independent. By bringing it closer to the arc point, the amount of air ejected for removing molten metal can be reduced. This significantly reduces the amount of fumes that occur and the extent to which they spread, and allows the fumes to be efficiently reduced by collecting dust in a very small area.

The present invention also has the same technical idea in terms of reducing the gas flow 'M for blowing off the molten metal.

However, they are completely different in that although they have a working gas to form plasma, they do not use a gas source to blow away the molten material, while in the non-transfer type, the arc is There is a difference in that the workpiece material 8'' is melted by only the energy of the plasma 6, but the inclination angle 0 of the plasma arc is 80° to 70°.
By keeping the distance d between the nozzle and the workpiece within an appropriate range, gouging can be performed using only plasma momentum, and the amount of whoop generated can be significantly reduced as in the case of the transition type. .

Conventionally, non-consumable 1-lium-containing tungsten has been used as an electrode, but it is an expensive material, and when an oxidizing gas is used as the working gas for plasma, the method disclosed in, for example, Japanese Patent Application No. 1987-8748. ZrOe, ZrSiO on the surface of the thoriated tungsten electrode as shown in
Attempts have been made to coat with oxides such as No. 4, That, and 5102. However, such oxidation-resistant treatment would make the expensive electrode even more expensive.

Therefore, the present inventors have devised a way to supply the consumable electrode at a constant rate to meet the consumption by using an inexpensive consumable electrode such as a carbon electrode, or by incorporating a voltage control method to supply the consumable electrode. was successfully used in a plasma method.

As a result, in the present invention, air can be used as the plasma operating gas without the need to use expensive inert gas, and by using air, the oxidation reaction heat contributes to the melting of the workpiece. %, the gouging work is much faster than in the case of inert gas.The present invention has made it possible to realize inexpensive plasma gouging with low fumes and an improved work environment.

Next, examples of the present invention will be described.

Example 1 A plasma cutting torch was set to transition type, and a thorium-containing tungsten electrode was used as a cathode and a steel plate was used as an anode.
Plasma alkla was generated using a mixed gas as a plasma operating gas, gouging was performed using only the momentum of the plasma, and the amount of foam generated was measured.

The plasma arc inclination angle was set to 50' from the vertical line by tilting the torch, and the arc current was 170 A.
By changing the gouging speed under the conditions of an arc voltage of 120 V, we measured the f, -m generation rate by plasma gouging, which jets out air at a pressure of 5 k'j/cd from a conventionally used auxiliary nozzle. The results of the comparison are shown in the fifth
As shown in the figure, here the amount of whoom generation is 11! The method for determining I is to make the processing chamber a sealed structure of 1.5 sn
Calculated by setting f1 for 1 minute using a digital dust meter (9) from the second elapsed time. This measured value is taken as D, and in order to eliminate the influence of the diameter of the electrode rod and the current, the value divided by the amount of steel removed ΔW is taken as D△W on the vertical axis of Figure 5, and the gouging speed is taken on the horizontal axis for comparison. do. As is clear from FIG. 5, when compared with the conventional 1-lasma gouging at each gouging speed, the plasma gouging of the present invention reduces the amount of foom generation to 1/3 to 1/4.

Example 2 A plasma cutting torch is set to a transition type, a constant speed supply device for electrodes is attached, a carbon electrode is supplied as an anode as it wears out, and a steel material is used as a cathode. ) Then, gouging was performed using air (flow rate: 85 #/ml) as the operating gas, arc current of 17 OA, and arc voltage of 120 V, and the amount of foam generated was measured. Further, the amount of foam generated was also measured when a carbon electrode was used as a cathode and a steel material was used as an anode (hereinafter referred to as sp). The plasma arc inclination angle was set to 50° from the vertical line by tilting the plasma torch, and the amount of foam generated was compared with that of the conventional arc air gouging method in which air at a pressure of 6 kl is ejected from a nozzle. This is shown in Figure 6. As shown in Fig. 6, in the present invention, the amount of foom generation is reduced by 17 to 1/4 compared to conventional arc air gouging in both SP and RP cases. In this case, the work becomes difficult, whereas in the present invention, sufficient workability was obtained with either polarity.

Example 8 A plasma cutting torch is set to a non-transfer type, with the trenched, thorium-filled tungsten electrode serving as the cathode and the torch nozzle serving as the anode. Then, an arc with an arc current of 200 A and an arc voltage of 70 V is generated between the pole and the nozzle using a mixed gas of 80% argon and 20% hydrogen at 8511/ms as the operating gas, and a plasma airflow is blown out from the nozzle to generate a plasma. Gouging was performed using only momentum and the amount of foom generation was measured. Note that by tilting the torch, the angle of inclination of the plasma airflow from the vertical line can be increased by 40°.
Gouge processing is performed as °, and pressure (
11) Figure 7 shows a comparison of the fume generation amount with that of a conventional non-transfer type plasma gouging that blows out 5 kl/d of air. As is clear from FIG. 7, the amount of foam generated according to the present invention is reduced by 6'3 to 1/4 compared to the conventional plasma stream.

Example 4 The plasma cutting torch was set to non-transfer type, the carbon electrode was supplied at a constant rate, and the arc current was 200 A using air (854!/aim) as the operating gas for both SP and RP polarity.
, an arc with an arc voltage of 70 V is generated between the carbon electrode and the nozzle. Then, a plasma airflow was blown out from the nozzle, and gouging was performed using only plasma momentum. Note that by tilting the torch, the inclination angle of the plasma airflow is set to 40° from the vertical line. The amount of foam generated is shown in FIG. 8 in comparison with a conventional arc air gouging which blows out air at a pressure of 5 and 9/d.

As is clear from FIG. 8, the amount of foam generated in the present invention is reduced by 178 to 1/4 in both SP and RPi properties compared to the conventional arc air gouging method.

(12) As described above, according to the present invention, by effectively utilizing the momentum of plasma without using an auxiliary gas for blowing off the melt as in the conventional method, gouging processing can be performed using momentum alone. As a result, the amount of fume generated is 78 to 1/4 compared to conventional plasma gouging and arc air gouging.
becomes. Additionally, since blowing gas is no longer required, the noise level is lower than in conventional methods, making it possible to significantly improve the working environment. Fourth, there is no need to use expensive non-consumable electrodes or inert gas, and there is a great economic effect.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of conventional plasma gouging in which gas is ejected from an auxiliary nozzle to scatter the melted material to be processed. FIG. 2 is an explanatory diagram of gouging processing using only plasma momentum according to the present invention. FIG. 8 is an explanatory diagram when an improvement is made to make the inclination angle of the plasma arc 70° in the present invention. FIG. 4 is an explanatory view in which the interior of the plasma gouging torch is improved in the present invention so that the plasma arc is tilted without tilting the torch body (18). Figure 5 is a graph comparing fume generation between plasma gouging of the present invention and conventional plasma gouging at various gouging speeds using a non-consumable electrode set in a transitional manner. Plasma gouging of the present invention with torch set in transition type (RP, 5Pli type)
It is a graph comparing the amount of foom generation between the conventional method arc air gouging (RPi type) and the conventional method arc air gouging (RPi type) at each gouging speed. FIG. 7 is a graph comparing the amount of fume generation between the plasma gouging of the present invention and the conventional plasma gouging at each gouging speed, using a non-transferable type using a non-consumable electrode. Figure 8 is a graph comparing the amount of fumes generated between plasma gouging of the present invention (RP, SPi type) in which a carbon electrode is supplied and the torch is set to non-transfer type and conventional arc air gouging (RPli type) at each gouging speed. In the above drawing, 1
Non (14) Consumable + 2--------- One working gas, 8--------
1. Water-cooled nozzle, 4. Inside of water-cooled nozzle (non-transferable arc point), 5.-- Arc column, 6.
--------Puozma airflow, 7-------Workpiece melt, 8~---111 Workpiece, 9------1 Melt blowout gas blowout Nozzle, 1o - gas for melt scattering. Patent Applicant Name Ibigawa Electric Industry Co., Ltd. Representative Jun Taga (15) Father-in-law / I ≠,, 3z ≠ 4I Dl. ≠61 D otsuka'kuji〉power □

Claims (1)

[Claims] 1. A gouging method that utilizes the heat of plasma gas in which an arc between t(lji< and a nozzle or between an electrode and a workpiece is restrained by a water-cooled nozzle and a plasma working gas) , a plasma gouging method patented as a method of gouging with plasma gas 7-mentum. 2. The inclination angle of the plasma arc is 80° to 70° from the vertical line.
Claim 1 characterized in that the range is 0°.
Plasma gouging method described in section. 86. The plasma gouging method according to claims 1 and 2, wherein the electrode is a carbon electrode. 4. The plasma gouging method according to any one of claims 1 to 3, wherein the method of supplying the carbon electrode is a constant rate supply method or a voltage control method. 5. The plasma gouging method according to claims 1 to 4, wherein the operating gas of the plasma arc is air.