Calculator Inputs
Example Data Table
| Process | Voltage (V) | Current (A) | Speed (mm/min) | Efficiency (%) | Heat Input (kJ/mm) |
|---|---|---|---|---|---|
| SMAW | 24 | 180 | 300 | 80 | 0.6912 |
| GMAW | 28 | 250 | 350 | 90 | 1.0800 |
| GTAW | 14 | 120 | 150 | 60 | 0.4032 |
Formula Used
Arc Power (kW) = (Voltage × Current) ÷ 1000
Heat Input (kJ/mm) = (Voltage × Current × 60 × Efficiency) ÷ (1000 × Travel Speed in mm/min)
Heat Input (kJ/in) = Heat Input (kJ/mm) × 25.4
Arc Time per Pass (min) = Weld Length in mm ÷ Travel Speed in mm/min
Total Energy (kJ) = Heat Input (kJ/mm) × Weld Length in mm × Number of Passes
Efficiency must be entered as a decimal percentage inside the formula. For example, 80% becomes 0.80 during calculation.
How to Use This Calculator
- Choose the welding process to load a typical thermal efficiency or keep a custom value.
- Enter arc voltage, welding current, and travel speed using your preferred speed unit.
- Enter weld length and select the correct length unit for normalization.
- Enter the number of passes when calculating multi-pass weld energy.
- Add optional WPS minimum and maximum heat input limits for compliance checking.
- Click Calculate Weld Heat Input to show the result block above the form.
- Review the graph, compare the WPS status, and export the result as CSV or PDF.
Frequently Asked Questions
1) What does weld heat input represent?
Weld heat input estimates the thermal energy delivered per unit weld length. It helps assess penetration, cooling rate, microstructure change, distortion risk, and WPS conformance.
2) Why is thermal efficiency included?
Not all electrical power reaches the joint. Thermal efficiency adjusts arc energy to better reflect the usable heat transferred into the weld and surrounding base material.
3) Why does higher travel speed reduce heat input?
When the torch moves faster, the same arc power spreads across more weld length in less time. That lowers the energy deposited per millimeter or inch.
4) Is this value the same as total energy?
No. Heat input is energy per unit length. Total energy also includes weld length and the number of passes, so it reflects the whole operation.
5) Can this help with WPS checks?
Yes. Enter optional minimum and maximum heat input limits from the procedure specification. The calculator will flag whether your result falls within the entered band.
6) Are the preset process efficiencies exact?
No. They are common planning values. Actual efficiency varies by equipment, waveform, shielding gas, transfer mode, setup quality, and operator practice.
7) Should I use kJ/mm or kJ/in?
Use the unit that matches your drawings, WPS, or reporting standard. This page calculates both so metric and inch-based teams can compare the same weld consistently.
8) Does higher heat input always mean better fusion?
No. More heat can improve fusion in some cases, but it may also increase distortion, widen the HAZ, and reduce mechanical performance if limits are exceeded.
Engineering Notes
Weld heat input is often used during procedure development, production review, and quality documentation. It is especially useful when comparing passes, operators, or process settings.