The total heat input generated in ERW is a function of which variables?

The total heat input generated in ERW is a function of which variables?

• A. Current used (I) only
• B. Resistance of the work (R) only
• C. Length of time the current is flowing (T) only
• D. I, R, and T

Answer: (D)

In ERW the heat that forms the weld comes from resistive heating, where electric power is converted into heat as current flows through the joint. The instantaneous heat rate is P = I^2R (or P = VI), and the total heat input during the weld is Q = ∫ P dt. If you assume the resistance stays roughly constant, this becomes Q ≈ I^2Rt. So the amount of heat you put into the weld depends on how large the current is, the resistance the current encounters (which includes both the material resistance and contact resistance at the interfaces), and how long the current is applied. All three factors—current, resistance, and time—together determine the total heat input, which is why the correct answer includes I, R, and T.

In ERW the heat that forms the weld comes from resistive heating, where electric power is converted into heat as current flows through the joint. The instantaneous heat rate is P = I^2R (or P = VI), and the total heat input during the weld is Q = ∫ P dt. If you assume the resistance stays roughly constant, this becomes Q ≈ I^2Rt. So the amount of heat you put into the weld depends on how large the current is, the resistance the current encounters (which includes both the material resistance and contact resistance at the interfaces), and how long the current is applied. All three factors—current, resistance, and time—together determine the total heat input, which is why the correct answer includes I, R, and T.