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COATED ELECTRODES

other electrodes, which can be used in this position. This results in a smaller number of electrode changes. The normal result is therefore a higher fusion rate and higher arc-time factor when welding vertically upwards with basic electrodes compared with other types. The slag is normally not quite as easy to remove as the slag from acid or rutile electrodes, but, in spite of this, it can be classed as easily detachable. The slag from basic electrodes has a lower melting point than that from rutile or acid electrodes. The risk of slag inclusions during normal production welding is therefore unusually small when basic electrodes are used, even if the slag is not completely removed between beads during multi-run welding.

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coating extruded onto the core rod followed by a thicker basic layer. In this way the electrode gets the fine droplet transfer of rutile electrodes and the deposit strength of the basic electrode.

The weld metal from basic electrodes has a low hydrogen content and usually has good toughness even at low temperatures. Basic electrodes are less likely to produce either hot cracks or cold cracks compared with other types of electrode. The superiority of basic electrodes from this point of view appears when welding manganese-alloyed structural steels, pressure-vessel steels and ship’s plate with a nominal tensile strength of 490-530 MPa. The higher the hardenability of the steel to be welded, the greater the necessity to use basic electrodes and the greater the need for low moisture content in the coating.

Double coated electrodes These electrodes consist of a thin layer of rutile

Core rod Basic coating Rutile coating

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