Welding Heat Input Calculator
Understanding Welding Heat Input
For welding inspectors and welding engineers who must record heat input in kJ/mm on a WPS/PQR, accurately determining this value is crucial. This calculator streamlines the process by computing the welding heat input in kJ/mm from arc voltage, welding current, and travel speed. It correctly applies the appropriate thermal efficiency constant for your chosen process, drawing on the EN ISO 1011-1 standard, which specifies 1.0 for SAW, 0.8 for SMAW/GMAW, and 0.6 for GTAW. This ensures you avoid common calculation errors and obtain a precise heat input figure.
How to Use This Welding Heat Input Calculator
Follow these simple steps to calculate your welding heat input:
- Pick the process from the dropdown — SAW, SMAW, GMAW or GTAW — to automatically set its efficiency constant.
- Type the arc voltage in volts from your welding procedure specification or the machine display.
- Type the welding current in amps.
- Type the travel speed in mm/min.
- Read the heat input in kJ/mm in large type, with the J/mm equivalent and the substituted formula shown below it.
FAQ
Q: What is the formula for welding heat input in kJ/mm?
A: Q = (V × I × 60) / (travel speed × 1000) × efficiency — the 60 converts seconds to minutes and the 1000 converts joules to kilojoules.
Q: Which arc efficiency constants does the calculator use for each process?
A: The EN ISO 1011-1 values: SAW = 1.0, SMAW and GMAW = 0.8, GTAW = 0.6.
Q: Why does the calculator give an error at zero travel speed?
A: Travel speed sits in the denominator of the formula, so a speed of 0 mm/min would divide by zero — enter the actual mm/min from the procedure before reading a result.
Q: How do I reduce heat input without changing the joint?
A: Heat input is directly proportional to voltage and current and inversely proportional to travel speed, so raising the travel speed in mm/min or lowering the amps or volts lowers the kJ/mm.