AWS Certified Welding Inspector — FundamentalsWelding ProcessesMedium
A CWI is overseeing the fabrication of a large pressure vessel using Submerged Arc Welding (SAW). The WPS specifies a travel speed of 18 inches per minute (ipm), a voltage of 32V, and a current of 600A. Calculate the heat input in kJ/inch.
- A70.7 kJ/inch
- B64.0 kJ/inch
- C32.0 kJ/inch
- D80.0 kJ/inch
Show answer & explanationAnswer & explanation
Correct answer: B. 64.0 kJ/inch
Heat input (HI) is calculated using the formula: HI (kJ/inch) = (Voltage × Amperage × 60) / (Travel Speed × 1000). Plugging in the values: HI = (32V × 600A × 60) / (18 ipm × 1000) = 1,152,000 / 18,000 = 64 kJ/inch.
Why the other options are wrong
- A. Incorrect calculation. This might arise from using 0.8 efficiency factor, which is not stated here.
- C. Incorrect calculation. This would result from an error in the formula or conversion.
- D. Incorrect calculation. This would result from an error in the formula or conversion.
Heat Input Calculation (SAW)
Heat input for welding processes like SAW is a measure of the energy transferred to the workpiece per unit length of weld, calculated as (Voltage × Amperage × 60) / (Travel Speed × 1000) in kJ/inch.
- Expressed in kJ/inch or kJ/mm.
- Directly affects metallurgical properties like grain size and toughness.
- High heat input can lead to coarse grain structure and reduced toughness.
- Low heat input can lead to lack of fusion or cracking.
Memory trick: Heat input: Voltage, Amperage, Travel Speed – the V.A.T. of weld energy.