Carbon steel flux-cored wire is a high-quality welding process. In the early 21st century, FCAW (Flux-Cored Arc Welding) was widely used for carbon steel welds, SA-335P12, and 12Cr1MoVG headers. However, for SA-335P91 (a high-chromium heat-resistant steel), developing FCAW consumables remains highly challenging due to the difficulty of simultaneously meeting process performance and mechanical property requirements, along with high R&D costs.

Only a few major international welding material suppliers have developed applicable formulations for SA-335P91. Through comparative analysis of short-circuit transfer tests using SA-335P91 flux-cored wires from several foreign suppliers, this study investigates the influence of welding parameters and heat treatment specifications on joint performance. Reasonable ranges for welding and heat treatment process parameters for SA-335P91 are determined, accompanied by macro and microstructural observations and analysis of welds, with proposals for further improvements.

What are the classification criteria for carbon steel flux-cored wire types?
The classification is based on:
a) Mechanical properties of deposited metal;
b) Welding positions;
c) Wire type characteristics, including shielding gas type, current type, and slag properties.

Symbol meanings in the model (in sequential order):
Mechanical properties of deposited metal: The first two symbols after the letter "E" (××) indicate the mechanical property grade of the deposited metal.
Welding positions: The third symbol after "E" (×) represents the recommended welding positions, where:
"O" = flat and horizontal positions;
"L" = all positions (vertical, overhead, etc.).

Wire type characteristics after short-stroke transfer: Specific requirements for the symbol "×" are detailed in Table 2 and Appendix B.
Shielding gas type:
The letter "M" indicates a shielding gas of 75%–80% Ar+CO₂;
The absence of "M" signifies CO₂ shielding or self-shielded flux-cored wires.
Impact toughness:
The letter "I" denotes that the V-notch impact energy of the deposited metal is ≥27J at -40°C;
The absence of "I" indicates the wire meets general impact performance requirements.