Electric welding is gaining rapid acknowledgment, the more as its great advantages combined with inexpensive machinery and easy manipulation are becoming known. It has, during the last few years, developed into many branches and industries which at the time of its inception were quite undreamt of.

The erroneous opinion that electric welding is expensive and difficult to manipulate, based, no doubt, upon results of antiquated systems, lack of technical knowledge, and general inexperience, is, however, easily overcome by simple investigation. It should not be forgotten that since the first introduction of electric welding some fifteen years since, great improvements have been made and that large works have been built with the sole object of building suitable machines for electric welding, with the result that the machines have reached almost perfect simplicity, being generally automatic in their working, reducing thereby manual labour to a minimum and limiting technical knowledge to that possessed by every mechanic.

There are several methods of electric welding, differing from each other both in principle and application - Arc welding being a surface welding, and Resistance welding being a sectional welding depending upon the internal resistance which a body presents to the passage of the electric current.

Arc welding appears to have been first employed by De Meritens, in 1881. In this instance leaden pieces designed to be united in the form of storage battery plates were arranged together as an extended positive electrode, and an arc was drawn between them and a negative carbon rod manipulated by means of an operating handle. Part of the heat energy of the arc served to melt the lead and cause union of the adjacent pieces, but much the larger proportion of the energy escaped by radiation and connection. The electric arc was thus akin to a gas blowpipe as commonly used in lead burning in the construction of tanks for the chemical industries.

Following De Meritens, heating by electric arcs has been applied to the fusing and welding of metals, notably of iron and steel, by Bernardos and Olszewski, Coffin, and others.

When, as in the Bernardos and Olszewski method, the carbon electrode is made positive to the work, carbon is transported through the arc and is likely to enter the metal undergoing the process, which constitutes the negative pole. This addition of carbon may render iron and steel hard and unworkable and cause cracks to be formed during the cooling of the fused mass at the joint or filling.

By the employment instead of carbon of an electrode of the same metal as that of the work, Slavianoff overcame this difficulty. The gradual melting of the metal electrode furnishes metal for forming joints, or for repairing or supplementing castings which are defective, such as those which are incomplete or contain blowholes.

More recently the work is made the positive pole, and this results in a greater proportion of the energy than formerly being expended in heating the metal undergoing the operation.

Inasmuch as the conditions of energy supply for sustaining the arc are but little different from those often found in the commercial operation of arc lamps from constant potential mains, arc welding may often be practised by connections made to such mains. A steadying resistance is put in series with the fusing arc in a branch from direct current lines at a potential difference of 200 volts or thereabout.

With work such as that to which the Bernardos and Olszewski method has been found to be applicable, the current in the arc may vary from 150 amperes up to 500 or more. The potential across the arc itself will generally be from 100 to 150 volts.

With the metal electrode used by Slavianoff the current needed will be greater, and the arc potential less than the above amounts. It appears that in certain cases the current may even surpass 4,000 amperes.

Werdermann, in 1874, proposed to deflect an electric arc formed between the usual carbons by a jet of air, forming thereby an electric blowpipe.

More recently Zerener has in a similar way employed an arc deflected by a magnet as a sort of blowpipe for welding iron.

In addition, the curious electric heating action first published by Hoho and Lagrange has been proposed for welding metals.

If a negative electrode, of a direct current circuit having a potential of 100 to 150 volts, is of small surface relatively to that of the positive electrode and both are immersed in a liquid bath, such as a solution of potassium or sodium carbonate, the surface of such negative electrode glows with light, gas bubbles arise from it, and the electrode itself heats rapidly in spite of its immersion in cold liquid. A bar of iron used as the negative electrode may thus be brought to incandescence and removed for welding, or it may even be melted under the liquid of the bath. The loss of heat in such a liquid heating process is necessarily somewhat great.

While the moderate application of these arc processes for fusing and welding iron and steel has been made, the range of operations to which they are suitable is somewhat limited, and their success depends largely upon the skill of the workman. He must protect not only his eyesight but also the surface of his body from the glare of the large arc, and also avoid the irritating vapours which arise from the flame. At the same time vigorous ventilation cannot be employed, for motions of the air tend to disturb the arc and render the work more difficult. A large proportion of the energy is radiated or carried off in the hot gases from the arc. To these energy losses must be added that due to the use of the steadying resistance for obtaining stability in the current of the arc.

On the other hand, the appliances needed for arc fusing or welding are simple, and the source of current energy often conveniently found in existing electric circuits.