Welding arc - how does it work?

click fraud protection

Welding arc: the nature of the phenomenon

The heating of the materials, the closing for a short time and the gradual separation of the electrodes help to obtain a discharge easier. A qualitative method for obtaining a discharge can be considered to be the breakdown in the electric discharge gap as a result of a short sharp increase in the interelectrode voltage. Such a welding arc stabilizer arises under atmospheric pressure conditions, thanks to a spark discharge.

Welding, or electric, arc, is formed due to the passage of electric current through the gas medium in the welding or cutting zone. The discharge between the electrodes is the most developed form of discharge in gases. It is characterized by low voltage and high current. The structure of the welding arc is such that in its space there is a very high ionization of gases.

In this case, the welding electrode acts as the cathode, the anode is the material being processed, an arc discharge is conducted between them by a column, surrounded by a flame of welding.

Ionized gas in the discharge column has a bright glow, harmful to the eyes. In the axial part of this column, the temperature of the welding arc develops from six to ten thousand degrees Celsius. The main factor of ionization is just such a high temperature, it is supported by the influx of energy from the supply chains.

Welding arc and its properties - why one should be careful?

The discharge voltage - in fact, the interelectrode voltage - depends directly on the interelectrode distance, that is, on what arc length, current, welding electrode dimensions, physical properties and the nature of the medium gas in the arc zone are available.

The welding arc and its properties are controlled by adjusting the interelectrode distance( 0.01 to 10 mm), the current source voltage( from half to three thousand amperes), the gas pressure( up to one kgf / cm2), the shape and size of the electrodes,zones of burning with inert gases, arc compression and many other ways.

The thermal power that an electric arc has is simply incredible, it ranges from ten to hundreds of thousands of watts. And its concentration reaches from one hundred to hundreds of thousands of watts per cubic centimeter. Capacities in such a wide range allow the use of a discharge for welding and cutting of various metals at thicknesses from hundredths of a millimeter to tens of centimeters in one or several passes.

The shapes and types of welding arcs are extremely diverse. The discharge can occur at any gas pressure, the voltage can range from several to several thousand volts. An arc arises between the electrodes regardless of whether a constant or alternating voltage is applied. And this is understandable, since the discharge time is extremely short, in each positive half-cycle one of the electrodes works like a cathode, and the second one is an anode. When changing half-periods, the electrodes "change" the polarity.

Arc discharge can occur at any gas pressure, potential difference of electrodes, constant or alternating interelectrode voltage. A feature characteristic of an arc is a very high cathode current density along with a low voltage.

In general, the dependence shown by the voltage of the welding arc and the current in the discharge has an amazing feature: with increasing current, the voltage drops. Speak of a falling voltage-current characteristic, this means that with increasing current in the discharge, both the resistance in the arc gap and the voltage drop, which explains the necessity of applying ballast resistances to stabilize the discharge.

Power sources for the welding arc - where will we see their application?

And most importantly - practical application of .The power sources of the welding arc, or welding machines, as already understood, can operate on a constant and alternating current, and therefore are of the appropriate type. The cathode( electrode with negative polarity) will be an electrode, but the working surface will act as an anode.

With reverse polarity, the electrode has a positive potential. In the welding technique, melting and non-melting electrodes( coal, tungsten) can be used. Protection of the welding zone can be carried out by pairs of electrode fluxes, supplied gases, powder formulations on wires.

And about the methods: manual welding, semi-automatic mechanized welding, full automatic is still widely used. By abbreviation this is, respectively: MMA( manual), MIG / MAG( semi-automatic), TIG( argon-arc).But you can write about this a couple of more articles, but about the welding arc, perhaps, everything is stated.

instagram viewer