Another new wire, called an inside-outside electrode, had a tubular cross section with the fluxing agents in the annulus was also introduced at this time. This increases arc time and avoids stub losses typical of the shielded metal arc welding (SMAW) process. In FCAW(S) the electrode wire Is fed continuously to the work piece. This new process promoted the use of self-shielded coiled wire electrode that could be used with existing semi-automatic equipment, increasing the efficiency of welding fabrication projects. It has been reported that 1957 saw the debut of the flux-cored arc welding process. Flux cored welding has good bead appearance (smooth, uniform welds having good contour). Flux cored welding produces a protective slag covering that is easily removed when correct welding parameters are followed. For the purpose of this discussion, as it relates to pressure boundary weldments of radiographic quality, only the gas shielded process, FCAW(G), will be discussed in any detail. FCAW(S) is commonly chosen in structural steel fabrication due to its advantage of providing high deposition rates. Flux-Core arc welding can be further characterized as self-shielding FCAW(S) or gas shielded FCAW(G). Like GMAW welding, consuming wire is fed into the molten weld pool at a controlled rate.
This paper discusses the author?s experiences with the increasing use and ongoing limitation of FCAW(G).įlux-Core Arc Welding (FCAW) is a variation of the Gas Metal Arc Welding (GMAW) process, and is generically considered a "semi-automatic" process. Even though many refinery owner/operators? specifications prohibit the use of the FCAW for radiograph quality welds, there has been a growing trend to rethink the restriction, and allow the controlled use of FCAW (gas shielded) for petroleum refinery pressure retaining welds. During the last decade there has been increased pressure exerted by fabricators on buyers to utilize Flux-Core Arc Welding (FCAW) where possible, today?s competitive market has enabled fabricators to persuade segments of the power, chemical, and petroleum processing industry to accept FCAW for pressure vessel, heat exchanger, and piping fabrication applications in order to reduce both cost and schedule. Research and development, modern manufacturing techniques, and improvement in sensor and inspection technologies have produced consumables for gas-shielded procedures that can meet many petroleum refinery industry specifications. While its reputation has been stigmatized by early quality problems in the 1980?s, Flux-Core Arc Welding (FCAW) has evolved into a process by which experienced fabricators can obtain radiographic quality welds in many alloy systems.