Abstract
Where single-sided welding is applied to the fabrication and erection of piping, back shielding by inert gas and its maintenance for the first few layers is required for low alloy steels (LAS), stainless steels (SS) and nonferrous alloys to obtain good weldability and quality of welds.
However, installation and removal of back shielding isolations inside piping for the joint and the adjacent areas to be welded are sometimes impractical due to piping layout and construction sequence such as closure joints. And the unexpected remaining isolations sometimes become concerns for obstructing fluid flow or damaging piping components such as valves and rotating equipment during commissioning or after operation.
To solve the concerns, high silicon (Si) solid filler rod was experimented to SS welding by gas tungsten arc welding (GTAW) to omit back shielding, and positive results of the R&D were introduced in ASME PVP2022 [1]. The same concept using high Si solid filler rod for GTAW was expanded to welding for Cr-Mo steels and properties of the welds were studied by comparison of the welds produced by different concentration of Si in filler rods to the conventional GTAW with back shielding. This paper discusses and evaluates the potential of the GTAW with high Si solid filler rod which can omit the inert gas back shielding for Cr-Mo steels because positive results of the study were obtained as the same as the R&D for SS welds.
