Heat Input Calculator

Yes, proportionally. Voltage and Amperage sit in the numerator and Travel Speed sits in the denominator of the heat input formula, but all three enter to the first power -- doubling any one of them, holding the others fixed, doubles or halves heat input by the same factor. Any apparent difference in how much one input "matters" on a given slider is a property of that slider's declared range, not of welding physics.

The Cooling Rate Index is calculated as inversely proportional to Heat Input (500 / Heat Input in kJ/in) -- it is a relative indicator, not a physical cooling rate in degrees per second. A faster Travel Speed spreads the same arc energy over more joint length, which LOWERS heat input per inch, and because the index moves inversely with heat input, a lower heat input means a HIGHER index value. Slower travel speeds concentrate more heat per inch, pointing toward slower relative cooling.

Process Efficiency is a direct multiplier on Heat Input, representing how much of the arc's total electrical energy (Voltage x Amperage) actually transfers into the weld versus being lost to radiation, spatter, and convection. Per ISO/TR 18491 and EN 1011-1, SMAW/GMAW/FCAW use k = 0.80, GTAW/PAW use k = 0.60, and SAW uses k = 1.00 -- selecting a higher-efficiency process means more of the electrical energy ends up as usable heat input, raising both the Heat Input and Estimated HAZ Width outputs for the same voltage and amperage.

HAZ Width is a rough approximation scaling directly with Heat Input in kJ/mm -- roughly 1.5mm of heat-affected zone per kJ/mm of heat input for carbon steel, with no dependence on plate thickness or preheat temperature. It moves in the same direction as heat input: raising voltage, amperage, or efficiency (or lowering travel speed) increases both heat input and the estimated HAZ width together, but treat the number as directional rather than exact.