Electric welding arc (1974)

Documentary №41398, 2 parts, duration: 0:19:49
Production: Sverdlovsk newsreel studio
Camera operators:A.Dekach,N.Fomichev,N.Gribkov


The film was created by order of Soyuzvuzfilm of the Ministry of Higher and Secondary Specialized Education to study the nature of the electric welding arc.

Reel №1

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Street of the city.

The trench, there are pipes in it.

The welder welds the pipes.

Alternation of frames with welding works.

An electric arc is characterized by a dazzling bright light comparable to the brightness of the sun, temperatures of thousands of degrees, a high current density at a relatively low voltage.

To consider the basic properties of the arc, we use a carbon rod as the cathode, and the metal of the product as the anode.

While the electrodes are disconnected, there will be no current in the circuit, because air is normally a dielectric.

When the electrodes come into contact, a flash and an arc occurs.

The ammeter records the electric current.

A cartoon explaining this phenomenon.

The amount of energy required for the excitation of atoms, their ionization and the work of the electron output from the cathode depends on the nature of the substance.

Alkali metals have the lowest values, and neutral gases and fluorine have the highest values.

Three types of welding arcs.

Arcs of direct action.

If a refractory electrode, tungsten or graphite, is used, this is an arc with a non-melting electrode.

In this case, additive materials are used.

Currently, melting electrodes are used more often.

Such an electrode is a supplier of metal to the welding bath.

In indirect arcs, the product is not included in the electrical network.

In most cases, the electrodes of such arcs are refractory

rods made of tungsten or graphite.

A combined arc, then two electrodes and a product such as a three-phase arc are included in the circuit.

Any of the arcs can burn on both direct and alternating current.

To isolate the arc from the harmful effects of air, it is placed in a gas environment.

Cartoon explaining welding in inert gases and active gases.

The arc can be free or compressed.

Operation of the plasmatron.

A cartoon explaining the operation of the plasmatron.

The compressed arc, having a higher temperature, is successfully used for cutting metals with a thickness of 50 mm or more.

An example of a closed arc is an arc burning under a flux.

An arc is considered stable if the arc parameters do not change from time to time.

Changes in the current strength, atmospheric composition, and the distance between the electrodes are characteristic of unstable arcs.

Key words

Welding arc.
Types of arcs.

Reel №2

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The electric arc is heterogeneous in its length.

A bright spot at the cathode and the same near the anode.

They are called cathode and anode active spots.

A cartoon explaining the nature of these spots.

The formula of the total voltage drop in the arc.

The resistance of a gas or steam depends on the degree of its ionization and is not constant.

It is affected by the length of the arc discharge, the material of the electrodes and the composition of the medium in which the arc burns.

Therefore, the voltage characteristic of the arc is not linear.

At low current values, its increase causes a sharp drop in voltage.

The intersection of the voltage characteristic of the arc with the external characteristic of the power supply will determine the point of stable arc gorenje at a given length.

As the arc length changes, the position of the working point will change.

At the same time, a significant voltage fluctuation will not cause a significant change in the welding current.

With a further increase in the current, the arc characteristic becomes increasing.

This is a section of arcs burning in the environment of active gases and under the flux.

The main process of electric arc welding is the melting of electrodes, the formation of a welding bath and the formation of a weld.

A cartoon explaining the consumption of thermal welding power.

The effective thermal power of the arc.

Table of effective efficiency values for various types of welding.

An electric arc is a flexible conductor.

Like any conductor, the arc is sensitive to the action of magnetic fields.

A cartoon explaining the effect of its own magnetic field on the arc.

The phenomenon of magnetic blowing.

The arc deflection can be adjusted by tilting the electrode and moving the supply current through the product.

Changing the magnetic blast can also be used in indirect arc welding.

The arc deflection is affected by the presence of ferromagnetic masses in the immediate vicinity.

Cartoon explaining the effect of ferromagnetic mass on the arc.

Magnetic blast should be taken into account when welding, as it affects the formation and quality of the weld.

In an alternating current arc, all the phenomena of magnetic blowing are significantly weakened.

Cartoon explaining the effect of an extraneous transverse magnetic field on the welding arc.

Cartoon explaining the effect of an extraneous longitudinal magnetic field on the welding arc.

Alternating frames with welding work.

Key words

Arc properties.
Effective efficiency.

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