The usability of metal-arc welding electrodes, the quality of the welds and the rate at which welds can be made depend in a measure on electrode burn-off rate. Factors which cause these differences in burn-off rates are described.
In electric metal-arc welding, a high-current arc is maintained between a metal electrode and the pieces to be welded. The electrode is continuously consumed by fusion of its tip. The melted metal at the tip of the electrode is transferred across the arc gap into the weld as particles of various sizes and possibly also as vaporized metal. Furthermore, a part of the workpiece is melted by the heat of the arc as the electrode advances along the weld joint. The character of metal transfer is influenced considerably by the rate at which the tip of the electrode is melted or "burns off." In crossing the arc, the molten metal from the electrode tip causes current fluctuations in the welding circuit of which the arc is a part. These fluctuations affect the arc stability and, in manual welding, the ease with which the welder can manipulate the electrode. Thus, the usability of metal-arc welding electrodes, the quality of the welds and the rate at which welds can be made, depend to a certain extent upon the electrode burn-off rate.
There are many factors which can influence the burn-off rates of electrodes.
Some of these factors are the characteristics of the electric circuit, the type of electrode coating, the composition of the arc atmosphere, the type of core wire and the type of base plate used.
The burn-off rate of a given size of electrode varies directly with the current, depends on the polarity when direct current is used and is influenced by changes in arc voltage (arc length).
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| Number of Pages : | 18 |
| Published : | 1950 |
