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Heat input Q.

Enter current, voltage and travel speed — per EN 1011-1 the tool computes heat input Q in kJ/mm and kJ/cm, with the arc efficiency k per process. Free, no sign-in.
Q = k · U · I · 601000 · v kJ/mm
Heat input Q
—
kJ/mm
—
kJ/cm
Enter I, U and v (v > 0)

k = arc efficiency (EN 1011-1): MAG/MIG/MMA 0.8 · SAW 1.0 · TIG/plasma 0.6.

How the calculator works

Heat input Q is the arc energy delivered per unit length of weld. Formula: Q = k · U · I · 60 / (1000 · v), where U is voltage in volts, I current in amperes, v travel speed in mm/min and k the thermal efficiency of the process. The result is in kJ/mm; kJ/cm is the same value multiplied by 10.

Efficiency k by process (ISO 4063): submerged arc (121) k = 1.0; MIG/MAG (131, 135, 136, 138) and manual metal arc (111) k = 0.8; TIG (141) and plasma (15) k = 0.6. The calculator applies k from the selected process.

Example

MAG 135, 200 A, 24 V, 30 cm/min (= 300 mm/min): Q = 0.8 · 24 · 200 · 60 / (1000 · 300) = 0.77 kJ/mm, i.e. 7.7 kJ/cm. The value is computed by the same engine that powers the calculator above.

Frequently asked questions

Why is there a factor k in the formula?

Because not all of the arc’s electrical power ends up in the weld. Factor k is the thermal efficiency of the process: 1.0 for submerged arc, 0.8 for MIG/MAG and manual metal arc, 0.6 for TIG and plasma. Without k the heat input would be overestimated.

Travel speed in cm/min or mm/min?

Certificates and WPS sheets often state it in cm/min, while the formula uses mm/min. The switch next to the field converts the unit; 30 cm/min is 300 mm/min. Decimal comma or point are both accepted.

Where is heat input used?

Heat input is one of the variables on a WPS and in the procedure qualification record (WPQR). How far production may deviate from the qualified value is set by EN ISO 15614-1; the calculator gives you the value to compare, the range-of-qualification tool derives the range.