For the past two decades sporadic information has been reported on the effects of minor elements on the welding arc and weld penetration. Investigators have attributed changes in weld penetration in different heats of the same material to variations of minor elements within the material. A critical review of all the available literature pertaining to this subject matter has been undertaken. The review revealed several studies which indicate that the intentional or unintentional addition of small amounts of halides to the base material significantly improves weld penetration. The presence of oxygen in the weld material has been reported to have both positive and negative effects on the depth and shape of the weld. Various other elements present in the base material have been alluded to as a means of changing the penetration characteristics of the GTAW process. In particular, aluminum addition to the arc or excessive aluminum in the base material has been observed to produce a flared arc at the anode surface. In many cases these changes are accompanied by variations in the arc voltage which, if properly interpreted can act as a warning signal for potential problems.
Changes in weld penetration can be due to heat-to-heat variation in the chemical composition of the material being welded or can be caused by any one of, or a combination of several different factors which influence the arc discharge, such as electrode configuration and composition, or surface tension of the weld pool. These factors interact with one another in a complex manner which still remains to be determined. The general conclusion of all the published reports stress the need for additional systematic study and further research into this problem area in order to understand the causes and effects that have been noted experimentally.
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| Number of Pages : | 24 |
| Published : | 1977 |
