Basic electrodes are so named because the covering is made with a high
proportion of basic minerals/compounds (alkaline compounds), such as calcium
carbonate (CaCO3), magnesium carbonate (MgCO3) and calcium fluoride (CaF2).
A fully basic electrode covering will be made up with about 60% of these basic
minerals/compounds.
Characteristics of basic electrodes are:
proportion of basic minerals/compounds (alkaline compounds), such as calcium
carbonate (CaCO3), magnesium carbonate (MgCO3) and calcium fluoride (CaF2).
A fully basic electrode covering will be made up with about 60% of these basic
minerals/compounds.
Characteristics of basic electrodes are:
- The basic slag that forms when the covering melts reacts with impurities, such as sulphur and phosphorus, and also reduces the oxygen content of the weld metal by de-oxidation
- The relatively clean weld metal that is deposited gives a very significant improvement in weld metal toughness (C-Mn electrodes with Ni additions can give good toughness down to ~ -90°C)
- They can be baked at relatively high temperatures without any of the compounds present in the covering being destroyed, thereby giving low moisture content in the covering and low hydrogen levels in weld metal
- In order to maintain the electrodes in a low hydrogen condition they need to be protected from moisture pick-up
- They can be baked at relatively high temperatures without any of the compounds present in the covering being destroyed, thereby giving low moisture content in the covering and low hydrogen levels in weld metal
- In order to maintain the electrodes in a low hydrogen condition they need to be protected from moisture pick-up
- By means of baking before use (typically at ~350°C), transferring to a holding oven (typically at ~120°C) and issued in small quantities and/or using heated quivers (‘portable ovens’) at the work station (typically ~70°C)
- By use of vacuum packed electrodes that do not need to be re-baked before use
- Basic slag is relatively viscous and thick which means that electrode manipulation requires more skill and should be used with a short arc to minimise the risk of porosity
- The surface profile of weld deposits from basic electrodes tends to be convex and slag removal requires more effort
- Basic slag is relatively viscous and thick which means that electrode manipulation requires more skill and should be used with a short arc to minimise the risk of porosity
- The surface profile of weld deposits from basic electrodes tends to be convex and slag removal requires more effort
Metal powder electrodes contain an addition of metal powder to the flux coating to increase the maximum permissible welding current level. Thus, for a given electrode size, the metal deposition rate and efficiency (percentage of the metal deposited) are increased compared with an electrode containing no iron powder in the coating. The slag is normally easily removed. Iron powder electrodes are mainly used in the flat and H/V positions to take advantage of the higher deposition rates. Efficiencies as high as 130 to 140% can be achieved for rutile and basic electrodes without marked deterioration of the arcing characteristics but the arc tends to be less forceful which reduces bead penetration.
