In ERW, is there external heat source, filler metal, or flux?

• A. Yes, there is external heat source, filler metal, and flux
• B. No, there is no external heat source, filler metal, or flux
• C. Only filler metal is used
• D. Only flux is used

Answer: (B)

In ERW, the heat that fuses the metal comes from electrical resistance at the joint, not from an external flame or arc. The metals are pressed together and current passes through the joint, causing I^2R heating that melts the base metals and creates the weld. No filler metal is added, and no flux is used, because the joint is formed by fusing the base metals themselves rather than by depositing filler material or relying on flux to aid the weld. This makes ERW distinct from processes that require external heat sources, filler metals, or flux.