Evaluation of Hydrogen Cracking in Weld Metal Deposited Using Cellulosic SMAW Electrodes

In a previous study of the limitations of cellulosic coated electrodes, it was found that arc length has a pronounced effect on carbon, manganese, and silicon recovery in welds made using these electrodes. The effect of arc length could not explain the extremely rich compositions observed in a series of cracked girth welds that were analyzed, however. Subsequent investigation demonstrated that it was possible to effectively double the manganese concentration and triple the silicon concentration when using cellulosic-coated electrodes with low moisture contents in the coatings. A variety of multipass weld metal cracking tests were reviewed and a test method that can be performed as part of a procedure qualification/material qualification test to determine appropriate preheat/interpass temperatures was developed. This paper describes the results of a follow-on program funded by Pipeline Research Council International (PRCI) and the US Department of Transportation. The objectives of the program were to further define the conditions that can lead to hydrogen cracking in weld metal deposited using cellulosic coated electrodes, in terms of operator preference (arc length), electrode properties, power supply selection, and materials handling, and to develop welding and safe handling guidelines to prevent weld metal hydrogen cracking. Cellulosic coated electrodes were procured from several manufacturers. Initially, they were checked for weld metal chemical composition in the as-received and dried conditions. The coating moisture of each electrode in each condition was also determined. Some of the electrodes were selected for additional testing in the as-received, dried and re-hydrated conditions. Pipe sections were welded with each electrode in each condition, using both a short arc length and a medium arc length. Weld metal testing included tensile testing, bend testing and weld metal chemical analysis. In the second phase of this program, additional welds were made with two of the electrodes using different power sources. Electrodes were also exposed to conditions intended to simulate actual weather conditions from around the world, in an effort to produce guidelines for maximum exposure times at the various conditions.