The use of uncoated electrodes is only recommended for those applications of Arc Welding where mechanical strength, tightness against fluid pressure and neatness of the finished weld are not essential factors.

There are a fairly large number of applications of welding which come within this category and for these the A-L " Kathode " Electrode provides a comparatively economical material and is consequently in regular demand.

It is, however, important to note that in addition to the above mentioned limitations for use, uncoated electrodes can only be employed where direct current is available for the welding process. The greatest efficiency and speed of operation can only be obtained when the welding current is taken from a machine capable of providing suitable " characteristics " across the arc.

Such a machine is provided in the A-L Stable Arc-Welder which has been specially designed to give the special characteristics necessary for uncoated as well as for coated electrodes.

Flux Coated Electrodes

In the applications of Arc Welding where the strength, homogeneity and appearance of the finished weld are matters of importance and necessity then the use of an electrode coated with a suitable fluxing compound becomes essential.

In all grades of A-L Flux-coated Electrodes the electrode itself consists of a metal core which is encased in a coating of fluxing compound, the composition of both the metal core and the fluxing material being selected and adjusted according .to the material to which the welding process is to be applied.

An efficient flux coating material must fulfil the following conditions :-

1. ;It must have a melting point closely approximate to that of the electrode metal.

2. ;It must fuse and be deposited uniformly with the electrode metal.

3. ;It must adequately protect the metal from combination with atmospheric gases during depo-sftion.

4. ;It must after fusion be capable of fluxing the deposited metal, reducing any oxides and accumulating the slag on the surface of the weld.

5. ;It must after completion of the weld and during cooling cover the surface of the weld for the exclusion of atmospheric gases which may combine with or be absorbed by the weld metal during cooling.

6. ;The resulting slag which covers the weld must, after cooling, be easily removable and leave a m clean bright surface on the weld metal.

These essential features have been fully borne in mind in the preparation of A-L Flux Coated Electrodes.

Advantages Of Flux Coated Electrodes

The use of flux-coated electrodes, in addition to providing greater mechanical strength, soundness, and homogeneity in the welds, provides the following advantages in the execution of the weld :-

1. ;It facilitates the welding operation.

2. ;It enables the operator to use either alternating or direct current.

3. ;It provides better directional control of the arc and enables vertical and overhead welding to be done in addition to ordinary horizontal welding.

4. ;It allows greater variation in the length of the arc without interruption of the current.

5. ;It reduces the tendencv of the electrode to 41 freeze" on to the weld.

6. ;It reduces volatilisation of the electrode welds, thereby increasing net weight and volume of metal deposited for power consumed.

7. ;It reduces the arc temperature and corrects any tendency to overheating. (Messrs. Allen Liver-sidge, Ltd.)