JPH01143776A - Plasma torch - Google Patents

Abstract

PURPOSE:To prevent an electrode from being overhead by providing the nonconsumable electrode consisting of a W electrode and an electrode collar with excellent conductivity surrounding it, a chuck to feed this, a nozzle having an opening of a plasma arc, a cooling water path and a pilot gas supply path. CONSTITUTION:The voltage of a main power source 15 is applied to the chuck 5 and material 14 to be welded and the voltage of a pilot power source 18 is applied to the chuck 5 and the nozzle 6. Pilot gas, shielding gas cooling water are supplied from a pipe 33, a pipe 34 and a pipe 31 respectively to start welding. A pilot arc is generated between the electrode 3 and the nozzle 6 by the power source 18 and pushed out downward by the pilot gas and a main plasma arc is generated between the electrode 3 and the material 14 to be welded to start welding. The nonconsumable electrode is of composite structure consisting of the W electrode 3 and the copper electrode collar 4 surrounding it and is hardly overheated by the cooling water and heat radiation of the pilot gas. By this method, the nonconsumable electrode is prevented from being overheated and its tip is hardle deformed and consumed and the cycle period of the electrode change and grinding can be extended.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plasma torch used for arc welding or arc cutting.

[Conventional technology]

The plasma torch has a non-consumable electrode 3 as shown in Figure 2.
and a narrowing nozzle 6, which supplies pilot gas to the space 25 between the electrode 3 and the nozzle 6, and
4 and between the electrode 3 and the nozzle 6,
First, a viroft plasma arc is generated between the electrodes 3 and 6, and using this as a starter, a main plasma arc 16 is generated between the electrode 3 and the workpiece 14, and the workpiece 14 is welded.
There are things that need to be cut, etc. Cooling water is supplied to the inside of the nozzle 6 to cool the nozzle 6 with water.

Tungsten or an alloy thereof (tungsten with a small amount of thorium, tantalum, or indium added thereto) is used as the non-consumable electrode 3, and tungsten containing thorium is widely used in DC positive polarity welding.

However, in a plasma torch using an electrode such as a thorium-containing tungsten rod, a cap-like deposit 20 forms on the tip of the electrode during use. This grows during use and eventually generates a discharge between the deposit 20 and the inner surface of the nozzle 6, and eventually a discharge 17 occurs between the lower surface of the nozzle 6 and the upper surface of the workpiece 14. The state in which this discharge 17 occurs is called a double arc.

The discharge arc between the nozzle 6 and the workpiece 14 is unstable, and it circulates around the plasma arc 16 irregularly.

There is a tendency for debris 21 to adhere around the nozzle hole during use of the torch, and as the debris 21 adheres and grows larger, the path of the plasma arc 16 is narrowed, and as a result, the arc current from the main power source is transferred to the plasma. The arc 16 cannot flow between the electrode 3 and the workpiece 14, but instead flows between the electrode 3, the nozzle 6, and the workpiece 14, promoting a double arc.

The bulk deposit 20 is a precipitate of an additive (for example, thorium) in tungsten, and since it is an oxide (TrOz), it easily becomes an arc generation point.

If a bulky deposit occurs, the machining conditions will be disturbed and the desired machining will not be possible, so the work is stopped at appropriate time intervals, the electrode 3 is polished back to its initial shape, and then the machining is restarted.

Further, the electrode 3 is heated by electricity, causing deformation of the tip of the electrode and accelerating wear and tear. For this reason, the arc is stopped at intervals of 1 to 3 hours for large currents and approximately every 3 to 6 hours for small currents, and the electrodes are replaced or polished. However, this has disadvantages such as stopping the line at short intervals for maintenance, which reduces productivity and creates many welding defects.

[Problem that the invention seeks to solve]

The object of the present invention is to improve these points, to enable the electrode to be used for a long period of time, to reduce the frequency of line stoppages, to improve productivity, and to prevent the occurrence of welding defects.

[Means for solving problems]

FIG. 1 shows a plasma torch of the present invention. In the present invention, the non-consumable electrode is composed of a tungsten electrode rod 3 and an electrode collar 4 surrounding the tungsten electrode rod 3. The electrode collar 4 is made of a material with good electrical and thermal conductivity, such as copper. A chuck 5 holds the electrode collar 4 and is connected to a main power source 15 and a pilot power source 18 to supply power to the electrodes 3.4. A torch cap 2 has a chuck pusher 13 therein, and the chuck pusher is screwed into a chuck base 22. 12 is an insulator, 23 is an outer cylinder, and IO is a shield cap, which together with the chuck stand 22 constitute the casing of the torch. Reference numeral 11 denotes an inner cylinder having a hollow portion, into which the nozzle 6, which also has a hollow portion, is screwed. 8 is an insulation collar, 7 is a center ring stone,
9 is a gas rectifier. 31 to 34 are pipes, 31 is for water inlet, 32 is for return water, 33 is for pilot gas, 34
is for shielding gas.

[Effect]

In this plasma torch, the voltage of the main power source 15 is applied to the chuck 5 and the workpiece 14 in this example, and the chuck 5
The voltage of the pilot power source 18 is applied to the nozzle 6, the pilot gas is supplied from the vibrator 33, the shielding gas is supplied from the vibrator 34, and the cooling water is further supplied from the vibrator 31, and welding in this example is started. Electrode rod 3 by power source 18
A pilot arc is generated between the tip of the nozzle 6 and the nozzle 6.
This is pushed downward by the pilot gas, thereby generating a main plasma arc between the electrode +1 and the welding material 14, and welding begins.

The path of the pilot gas is the vibrator 33, the internal space of the insulator 12, the internal space of the insulating collar 8, the centering stone 7, and the nozzle 6, and the welding material 1 is passed through the hole of the nozzle 6.
Blow out towards 4. The cooling water path includes the pipe 31 , the internal cavity of the chuck stand 22 , the internal cavity of the insulator 12 , the space between the outer cylinder 23 and the inner cylinder 11 , the cavity between the inner cylinder 11 and the nozzle 6 , and the pipe 32 . Shield gas is pipe 34, inner cylinder 11
and the outer cylinder 23, the gas rectifier 9, the shield cap 10
and the nozzle 6, and blows out to the welding material 14 from the opening at the lower end of the shield cap.

When the torch cap 2 is rotated, the chuck pusher 13 moves back and forth to press or release the chuck 5 against the chuck base 22. A switch (not shown) is inserted into the circuit of the pilot power source 18, and when a main plasma arc occurs, the switch is used to turn off the pilot power source.

In this plasma torch 1, non-consumable electrodes include a tungsten (thorium-containing) rod 3 and a copper electrode collar 4 surrounding it.
It has a composite structure that prevents it from overheating. That is,
The plasma arc current flows through the highly conductive electrode collar 4,
Since the electrode tip is transferred to the tungsten electrode rod 3, which has a relatively high resistance, the heat generation (I2R) of the electrode is small. Further, the electrode collar 4 has good thermal conductivity, the chuck 5 portion is water-cooled, and pilot gas flows around the electrode collar, so heat radiation is good, and overheating of the electrode is also prevented.

The temperature of the electrode rod is as shown in Figure 3, and gradually rises from the feeding point, reaching a peak at the tip. The temperature gradually increases not only because an arc is generated at the tip of the electrode but also because of I2R heat generation due to the resistance of the tungsten electrode rod 3. To reduce this I2R, it is effective to reduce the length E from the chuck 5 to the tip of the electrode, but due to the structure of the torch, it is not possible to reduce the length l too much. If the tungsten electrode rod 3 is surrounded by a copper electrode collar as in the invention, the length l will be reduced to a small rainbow (
However, it is possible to substantially lower the electrode resistance, which is effective in preventing overheating of the electrode.As a result, the generation and growth of the bulk-like deposits 20 can be delayed, and deformation and wear of the electrode tip are less likely to occur. This makes it possible to lengthen the period of electrode rod replacement and polishing.

〔Example〕

A tungsten electrode rod with a diameter of 3 mm was placed on a water-cooled copper plate with a thickness of 15 mm.
．． 2 x*, length β is 60 mm, electrode collar made of copper, outer diameter 5.
Under welding conditions of 2 cranes and 150 A, the present invention and the prior art were investigated for bulky deposits on the electrode tips, adhesion of scum, and occurrence of double arc. In the case of the tungsten electrode rod with the electrode collar of the present invention, the plasma arc generation time is 6 hours 1
After 0 minutes, a double arc occurred and the plasma arc became unstable. The electrode rod has a size of 0.7 to 0.9
There was a bulky deposit on H and some debris was also attached around the nozzle hole. On the other hand, in the case of only a conventional tungsten electrode rod, a double arc occurs after 3 hours of plasma arc generation time, and there is a bulky deposit of 0.7 to 1.0 fi on the electrode rod and around the nozzle hole. There was debris attached.

〔Effect of the invention〕

As explained above, according to the present invention, overheating of non-consumable electrodes can be prevented, deformation and wear of the electrode tips are less likely to occur, lengthening the period of electrode replacement and polishing, and productivity is improved. It is possible to avoid frequent occurrence of welding defects.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing the structure of the plasma torch of the present invention, FIG. 2 is an explanatory diagram of a conventional plasma torch, and FIG. 3 is a graph of temperature distribution along the electrode rod. In Figure 1, 3 is a tungsten electrode rod, 4 is an electrode collar, and 5 is a tungsten electrode rod.
is the chuck, 15.18 is the power supply, 6 is the nozzle, 22.1
2, 23.11 is a housing. Figure 1

Claims (1)

[Claims] A non-consumable electrode consisting of a tungsten electrode rod and a highly conductive and thermally conductive electrode collar surrounding the tungsten electrode; a chuck that fits into the non-consumable electrode to supply power; A nozzle disposed at the tip of the consumable electrode and having an opening for ejecting a plasma arc from the tip, and a water channel for supporting and cooling the chuck and nozzle, and extending along the non-consumable electrode. 1. A plasma torch comprising: a casing having a gas path for supplying a pilot gas.