Iron Powder Electrodes
Iron powder is a widely used covering ingredient. It is incorporated in certain coverings to the extent of one half of the total weight. Iron Powder imparts a number of desirable operating characteristics to the electrode. Larger amounts will make the covering an electrical conductor and allow the electrode to be operated as a contact electrode. The presence of Iron powder appears to add metal ions to the arc and thus improves arc stability. Iron powder which also melts will join the weld pool and increase the amount of metal deposited.
On account of the deep cup, touch welding can be done with the electrode. However, the important advantages of the contact electrodes are the large quantity of metal deposited per unit time and the deep penetration. Contact electrodes can be provided with an acid, rutile or a basic coating.
Fundamentally the welding properties of the "ordinary" electrodes and the respective contact electrodes are to be the same. Hence, the same applies to the fields of application. The main advantages of the contact electrodes are the large deposition rate and the gain in time that can be achieved as a result. Large quantity of deposited metal can be utilised in two ways viz., where heavy welds have to be made, as an example when a single vee groove in thick plate is filled.
The acid contact electrode is very slow setting and can be used for horizontal closed grooves, (mainly vee and double vee grooves) and for large weld lengths in standing fillet welds. A zircon - basic contact electrode also has been developed. This zircon basic contact electrode has a deposition rate that is not inferior to that of any other kind. The appearance of the weld is likewise extremely good and the mechanical properties are adequate.