Common types of welding electrodes include the following:

(1) For low-carbon steel structural components, E4303 (J422) or E5023 (J502) titanium-calcium type welding electrodes are generally selected;

(2) For important structural components requiring high plasticity, toughness, and crack resistance, low-hydrogen type E4315 (J427) or E5015 (J507) welding electrodes should be used. When welding with an AC welding machine, dual AC/DC low-hydrogen type E4316 (J426) or E5016 (J506) welding electrodes can be used.

(3) For thin-plate components requiring a beautiful and smooth weld surface, titanium type E4313 (J421) welding electrodes are best.

(4) For welded components where oil, rust, and other contaminants cannot be easily removed and where deep penetration is required, iron oxide type E4320 (J424) welding electrodes are best.

(5) For welded components with a large number of vertical welds, if conditions permit, specialized vertical-down welding electrodes can be used, such as E4300 (J420) welding electrodes.

The above are common welding electrodes classified according to their application. If classified by electrode diameter, the electrode diameter depends on the thickness of the workpiece. Welding electrodes are usually available in several sizes based on the size of their core wire, typically 2, 2.5, 3.2, 4, 5, and 6 mm. The most commonly used sizes are 2.5, 3.2, and 4 mm.