Calculator Input
Heat Input Trend Graph
The graph shows how net heat input changes as travel speed changes. It updates when you submit the calculator.
Example Data Table
| Process | Voltage (V) | Current (A) | Speed (mm/min) | Efficiency | Heat Input (kJ/mm) |
|---|---|---|---|---|---|
| GMAW | 24 | 220 | 350 | 90% | 0.8146 |
| SMAW | 28 | 160 | 120 | 80% | 1.7920 |
| GTAW | 14 | 130 | 90 | 60% | 0.7280 |
| FCAW | 30 | 260 | 400 | 85% | 0.9945 |
Formula Used
Gross heat input
Heat Input (kJ/mm) = (Voltage × Current × 60) ÷ (Travel Speed in mm/min × 1000)
Net heat input
Net Heat Input = Gross Heat Input × Efficiency
Arc power
Power (W) = Voltage × Current
Total energy for weld length and passes
Total Energy (kJ) = Net Heat Input (kJ/mm) × Weld Length (mm) × Passes
Why efficiency matters
The electrical power at the arc is not transferred fully into the workpiece. Different welding processes deliver different fractions of arc energy into the joint. That is why the calculator shows both gross and net heat input values.
How to Use This Calculator
- Choose the welding process that best matches your setup.
- Enter arc voltage and welding current from your machine settings or recorded procedure values.
- Enter travel speed and select the speed unit you measured.
- Use the default process efficiency or switch to custom efficiency when your procedure uses verified values.
- Enter weld length and number of passes to estimate total energy and arc time.
- Press Calculate Heat Input to show the result above the form.
- Review the graph to see how travel speed changes heat input.
- Download the summary as CSV or PDF for reporting or procedure review.
Frequently Asked Questions
1) What does welding heat input represent?
It represents the thermal energy delivered per unit weld length. It helps predict cooling behavior, fusion characteristics, distortion risk, and microstructural changes in the weld and heat-affected zone.
2) Why does travel speed strongly affect the result?
Heat input is inversely proportional to travel speed. Faster motion spreads the same arc power over more length, reducing energy per millimeter. Slower motion raises energy concentration and thermal exposure.
3) Why are gross and net heat input both shown?
Gross heat input uses electrical arc power only. Net heat input adjusts that value by process efficiency, giving a more realistic estimate of energy transferred into the workpiece.
4) Which value should I use for procedure control?
Use net heat input when your procedure or engineering review accounts for process efficiency. Use gross heat input for simple comparisons when efficiency data is unavailable or when a specification explicitly requests it.
5) Can I compare different welding processes with this tool?
Yes. The process selector applies different default efficiency values, helping you compare how SMAW, GMAW, GTAW, FCAW, SAW, and PAW transfer energy under similar electrical conditions.
6) What unit is best for reporting heat input?
Many welding documents use kJ/mm or kJ/in. This calculator provides kJ/mm, kJ/cm, and kJ/in so you can match project standards or customer reporting requirements easily.
7) Does higher heat input always improve penetration?
Not always. Higher heat input can support penetration, but joint design, electrode type, shielding, position, polarity, and arc behavior also affect fusion and final weld quality.
8) Can this calculator estimate production energy usage?
It can estimate weld energy and arc time for the entered length and passes. That makes it useful for rough planning, but full production studies should also consider idle time and equipment losses.