Weld Heat Input Calculator - AWS D1.1 & ASME IX Style Heat Input

How It Works

1. Select Welding Process

   Choose your welding process: SMAW (stick), GMAW (MIG), FCAW (flux-core), GTAW (TIG), or SAW (submerged arc). The process determines the thermal efficiency factor if your code requires net heat input rather than arc heat input.

2. Enter Arc Voltage

   Input the measured arc voltage during welding. This is not the machine's set voltage - it is the actual voltage measured at the arc during welding. For SMAW, typical values are 20-30V. For GMAW spray transfer, 26-34V. For GTAW, 10-18V.

3. Enter Welding Current

   Input the measured welding amperage. For constant-current processes (SMAW, GTAW), this is set on the machine. For constant-voltage processes (GMAW, FCAW), measure it with a clamp-on ammeter during welding because actual amps vary with wire feed speed and stickout.

4. Enter Travel Speed

   Input travel speed in inches per minute. Measure this in the field by timing a known weld length. For multi-pass welds, measure each pass separately as travel speed often differs between root, fill, and cap passes.

5. Review Heat Input Against the WPS

   Use the calculated heat input in kJ/inch as a review value, then compare it against the qualified range and essential variables in the governing WPS/PQR and code edition.

Built For

• Welding inspectors verifying that production welds meet WPS heat input limits
• Welding engineers preparing procedure qualification records for AWS D1.1 or ASME IX
• Pipeline welders preparing heat-input logs for review against the applicable procedure and project requirements
• Fabrication shops training welders on the relationship between parameters and heat input
• QA/QC departments auditing welder parameter logs against qualified WPS ranges

Assumptions

• Heat input formula uses H = (V x A x 60) / (S x 1000), where V is voltage, A is amperage, and S is travel speed in inches per minute.
• Arc efficiency factor is a local screening prompt: SMAW 0.80, GMAW 0.85, GTAW 0.70, FCAW 0.85, SAW 0.95; governing factors come from the WPS/code/source review.
• Welding parameters (voltage, amperage, travel speed) are steady-state values, not peak or transient readings.
• Travel speed is linear and does not account for weaving or oscillation patterns.

Limitations

• Does not calculate cooling rate (t8/5) or predict HAZ hardness from the heat input value.
• Preheat and interpass temperature effects on metallurgy are not modeled beyond flagging code limits.
• Multi-pass weld cumulative heat input and thermal cycling effects are not analyzed.
• Does not determine whether the WPS essential variable ranges are met for a specific code or standard.

References

1. AWS D1.1 - Structural Welding Code, Steel (heat input limits and essential variables)
2. ASME BPVC Section IX - Welding, Brazing, and Fusing Qualifications (essential variable ranges)
3. AWS Welding Handbook, Volume 1 - Welding Science and Technology (arc energy and heat flow)
4. ISO/TR 18491 - Guidelines for measurement of welding energies (arc thermal efficiency source pointer)

Frequently Asked Questions