Heat Input Calculator
Calculate heat input for any welding method. Results compliant with EN ISO standards.
What is heat input?
Heat input includes the thermal efficiency factor k. It is not the same as arc energy, which is calculated without that efficiency factor.
- Q – heat input [kJ/mm]
- k – thermal efficiency factor (0.6–0.95)
- U – arc voltage [V]
- I – welding current [A]
- v – welding speed [mm/s]
🔥 Heat Input Calculator
Calculates heat input with thermal efficiency or arc energy without the efficiency factor. You can enter single values or ranges (e.g., 100-120).
Why is heat input important?
Mechanical properties
Excessive heat input can cause grain growth and reduced toughness in the HAZ.
Hydrogen cracking
Heat input control is crucial for preventing cold cracking in fine-grained and high-strength steels.
Standards requirements
Standards such as EN ISO 15614 require documenting heat input in WPQR.
Repeatability
Consistent heat input ensures repeatability of welded joint properties.
Frequently asked questions
The heat input formula is: Q = (k × U × I) / (v × 1000), where k is the thermal efficiency factor, U is arc voltage [V], I is welding current [A], and v is travel speed [mm/s]. Arc energy is calculated without k.
Heat input is expressed in kilojoules per millimeter [kJ/mm]. In some countries, kJ/cm or J/mm are also used.
Typical thermal efficiency values: MAG (GMAW) = 0.8; TIG (GTAW) = 0.6; MMA (SMAW) = 0.8; SAW = 0.95; Plasma = 0.6. Values may vary slightly depending on the source.
Heat input directly affects the mechanical properties of the weld, the size of the heat-affected zone (HAZ), susceptibility to cold cracking, and cooling rate. Too high heat input can cause grain growth and reduced impact strength.
Yes, standard EN ISO 15614-1 requires documenting heat input in the Welding Procedure Qualification Record (WPQR). It is one of the key qualification parameters.
For fine-grained and high-strength steels, controlled lower heat input (typically 0.5-1.5 kJ/mm) is recommended to maintain strength parameters and impact toughness in the heat-affected zone (HAZ).
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