JPS62192294A - Electrode bar for inert gas arc welding - Google Patents

Abstract

PURPOSE:To obtain a high current density at a substantially low working temp. and to decrease the consumption of an electrode by fixing the top end of the electrode formed by impregnating an easily electron radiating material to a porous high melting point metallic base body to one end of a metallic bar forming a conductive path thereby forming the electrode bar. CONSTITUTION:A hole is provided to the circular columnar base part of the top end 1 of the electrode of which the circular conical part is successively connected to the circular columnar part one end of the metallic bar forming the conductive path is fitted into the hole part and is fixed by high melting point brazing. The porous high melting point metallic base body at the top end 1 of the electrode is formed by molding tungsten powder with a pressed and calcining the molding in a vacuum or hydrogen atmosphere. An alkaline earth oxide and metallic oxide are impregnated as the electron radiating material to such porous tungsten base body, by which the top end 1 of the electrode is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electrode for inert gas arc welding using argon gas or the like.

(Prior art) Inert gas arc welding is a welding method in which an arc is generated between an electrode and a base metal in an inert gas atmosphere such as argon or helium, and the base metal is melted and joined by the arc heat. It is.

FIG. 4 is a block diagram showing how the argon arc welding device is used.

The power supply and control unit 44 is supplied with argon gas from an argon gas cylinder 41 and cooling water from a cooling water source 43.

During welding work, cooling water, electric power, and argon gas are supplied from the power supply and control section 44 to the welding section 45 .

FIG. 5 is a schematic diagram showing the principle of the structure of the torch tip (welding part) of a conventional inert gas arc welding device.

A thoriated tungsten electrode 45a provided at the welding portion 45 is covered with a gas cup 45b, and argon gas supplied from the power supply and control unit 44 is released to the outside air from a groove at the lower end of the gas cup 45b.

This inert arc welding method is widely used because it has the following features.

(1) The appearance and performance of welded parts are very good because the harmful effects of nitrogen and oxygen in the atmosphere are removed.

(2) Can weld almost all three metal alloys,
It is also possible to weld dissimilar metals and build up the same or dissimilar alloys.

(3) Since heat concentration is very good, high-speed welding is possible, and good welding results can be obtained with little distortion even in the case of thin plates.

(4) It is possible to weld not only downward, but also in all positions, such as upward and vertical, and can be used in a very wide range of fields.

(5) Among the various welding methods, this method can be applied to the widest range of plate thicknesses.

(Problems to be Solved by the Invention) In the above-mentioned inert gas arc welding, a large welding current of usually 10 to 300 A is required to generate arc plasma.

Therefore, there are problems in that the electrodes are frequently damaged and have a short lifespan, requiring frequent replacement.

Thermal and electrical properties of these electrodes, as well as their shapes, greatly affect their lifetimes, but thermionic emission characteristics are particularly important.

In order to improve this thermoelectron emission characteristic, several percent of oxide is added to tungsten.

Among these, thoriated tungsten, in which 2% by weight of trilam oxide is added to tungsten, is currently widely used.

However, even with these electrodes, it is difficult to obtain a sufficient current density, so the operating temperature inevitably becomes high, and the electrodes wear out and deform within a short period of time, making it impossible to maintain stable arc welding.

An object of the present invention is to provide an electrode rod for inert gas arc welding that solves the above problems by improving the thermionic emission characteristics of the electrode.

(Means for Solving the Problems) In order to achieve the above object, the electrode rod for inert gas arc welding according to the present invention has a porous high-melting point metal base impregnated with an electron-emissive substance, and the tip is conductive. It is constructed by being fixed to one end of a metal rod that forms a channel.

(Example) The present invention will be described in more detail below with reference to the drawings and the like.

FIG. 1 is a diagram showing an electrode rod for inert gas arc welding according to the present invention.

A hole is provided at the base of the cylindrical part of the electrode tip part 1 in which the conical part is connected to the cylindrical part, and one end of the metal rod 2 forming a conductive path is inserted into this hole and fixed by high melting point brazing. It is.

The electrode tip 1 and the metal rod 2 are connected only by high melting point brazing.
Alternatively, it may be fixed only by press fitting.

The porous high melting point metal substrate of the electrode tip 1 has an average particle size of 2
Press forming tungsten powder of μm to 8 μm,
It is fired in vacuum or in a hydrogen atmosphere.

The reason why the porosity is set in the range of 10 to 35% is that if the porosity is less than 10%, the amount of impregnating agent filled will be small and the existing pores will not be completely connected, so the impregnating agent will not be supplied sufficiently. This is because the electron emission characteristics may become insufficient.

On the other hand, if it is 35% or more, the impregnating agent will be sold well, but the evaporation of the impregnating agent will be extremely large due to the large number of pores, which may shorten the service life.

The electrode tip 1 is formed by impregnating this porous tungsten base with an alkaline earth oxide and a metal oxide as electron emitting substances.

In this example, B a O: Ca O: A (1
203 was impregnated with 4:1:1.

Next, the dimensions of each part of the example will be shown.

Electrode tip 1 Diameter (d+) 1.4mm Cylinder length L+) 2.0mm Tip angle (θ) 45° (0.48 steradian)
Porosity: 22% Metal rod 2 forming a conductive path Material: Tungsten (W) Diameter (d2): 1.0 mm Length (j!2): 120 mm The dimensions are the same, and the electrode tip 1 is made of thoriated tungsten (Th
022ffifft%) was prepared (hereinafter referred to as conventional example).

Damage to the electrode tip of the example electrode and the conventional example electrode was compared under the following conditions.

Distance between electrodes: 3mm Water-cooled copper anode Argon shielding gas (Flow rate: 10 ft/mi
n) Welding current On (4OA 5 minutes) - Off (1
Figure 2 is a sketch of enlarged photographs of the shapes of the electrode tips of both electrodes before and after the above-described repetition was performed 70 times.

FIGS. 2(A) and 2(B) respectively show the shapes of the conventional example before and after the repeated discharge, and FIGS. 2(C) and 2(D) respectively show the shapes before and after the repetitive discharge.
The shape before and after the said repeated discharge of an Example is shown.

In the conventional example, the tip of the electrode was considerably worn out during the 70 on-off tests, and it became unusable.

The example electrode maintains its basic shape even after being turned on and off 70 times.

Even after repeating the same discharge and turning on and off 150 times, it maintained a usable shape.

FIG. 3 is a graph comparing the electrode temperature and current density of the example electrode and the conventional electrode.

This graph shows that the electrode of the example achieves a higher current density at a lower temperature than the conventional example.

That is, since the electrode according to the present invention can obtain a high current density at a low temperature, it shows that it can be operated at a low temperature to obtain the same discharge current.

(Effects of the Invention) As explained above, the electrode rod for inert gas arc welding according to the present invention has a porous high-melting point metal base impregnated with an electron-emissive substance, and the tip of the electrode is connected to a metal forming a conductive path. It is fixed to one end of a rod.

Therefore, there is very little wear and tear compared to conventional electrodes.

As shown in FIG. 3, the electrode of the example is considered to have extremely low wear and tear because a high current density can be obtained at a sufficiently lower operating temperature than that of thoriated tungsten.

As a result, stable arc welding has become possible over a long period of time.

[Brief explanation of drawings]

FIG. 1 is a side view of an electrode rod for inert gas arc welding according to the present invention. FIG. 2 is a schematic diagram comparing the degree of wear between an electrode rod for inert gas arc welding according to the present invention and a conventional electrode rod for inert gas arc welding. FIG. 3 is a graph comparing the electrode temperature and current density of the inert gas arc welding electrode according to the present invention and the conventional inert gas arc welding electrode. FIG. 4 is a block diagram showing an example of use of the inert gas arc welding device. FIG. 5 is a schematic diagram showing the principle of the structure of a welding section of a conventional inert gas arc welding device. ■... Electrode tip 2... Conductive electrode

Claims (5)

[Claims] (1) An electrode rod for inert gas arc welding is constructed by fixing the tip of the electrode, which has a porous high-melting point metal base impregnated with an electron-emitting substance, to one end of the metal rod forming a conductive path. Characteristic electrode rod for arc welding. (2) The porous high melting point metal substrate has an average particle size of 2 μm.
A porous tungsten substrate or a porous molybdenum substrate having a porosity of 10 to 35% is obtained by press-forming a high melting point metal powder of ~8 μm and then firing in a vacuum or hydrogen atmosphere. Electrode rod for inert gas arc welding. (3) The electrode rod for inert gas arc welding according to claim 1, wherein the electron-emissive substance is formed from an alkaline earth oxide and a metal oxide. (4) The electrode rod for inert gas arc welding according to claim 3, wherein the alkaline earth oxide is BaO or CaO, and the metal oxide is Al_2O_3. (5) The electrode rod for inert gas arc welding according to claim 1, wherein the metal rod supporting the porous high-melting point metal base is a high-melting point metal such as tungsten, molybdenum, tantalum, or rhenium.