Welding Heat Input
Compute the heat input of a weld, H = (V·I·60)/(v·1000), in kJ/mm, from the arc voltage (V), the current (I) and the travel speed (v, in mm/min). It is one of the most important welding parameters: it controls the cooling rate, the microstructure, the heat-affected-zone hardness and the cracking risk. High input softens and distorts; low input hardens and embrittles. Enter the voltage, the current and the travel speed.
Result
—
Welding heat input
The heat input is arguably the most important welding parameter of all: how much energy, per millimetre of weld bead, actually goes into the part. H = (V·I·60)/(v·1000) kJ/mm combines the arc power (voltage × current) with the travel speed v in mm/min. Its effect runs deep — it controls the cooling rate, which in turn governs the microstructure, the hardness of the heat-affected zone (HAZ) and the risk of cracking. A high heat input cools slowly, softens the joint, increases distortion and can leave coarse grain; a low heat input cools fast, hardens and embrittles the HAZ and encourages cold cracking. Every material and thickness has an optimum range, which is specified in the welding procedure specification (WPS, called EPS in Brazil). Enter the arc voltage, the current and the travel speed.
Related Tools
Welding Travel Speed
Compute the welding travel speed (arc advance) by dividing the bead length by the time taken, in mm/min. It is a fundamental parameter that, together with voltage and current, defines the heat input: welding too fast produces narrow beads with little penetration; too slow overheats and deposits excess material. Enter the bead length and the welding time.
Martensite Start Temperature Ms (Andrews)
Computes the Ms temperature, the point at which austenite starts transforming into martensite during quenching, using the linear Andrews equation: Ms(°C) = 539 − 423·C − 30.4·Mn − 17.7·Ni − 12.1·Cr − 7.5·Mo, with every content in mass percent. Nearly every element dissolved in austenite lowers Ms — cobalt and aluminium are the exceptions and raise it —, but carbon dominates by far: each 0.1 % of carbon drops Ms by 42 °C, nearly 14 times the effect of the same manganese content. Knowing Ms sets the martempering bath temperature, tells whether retained austenite will survive at room temperature, and predicts how severe the quenching stresses will be, because a low Ms makes the martensite expansion happen late, with the part already cold and rigid, and that is where cracks appear. The correlation is fitted to low-alloy steels with carbon up to roughly 0.6 %, and the page rejects compositions above 0.8 % carbon, where the extrapolation loses its footing. Enter the carbon, manganese, nickel, chromium and molybdenum contents.
Martensite Fraction (Koistinen-Marburger)
Computes the fraction of austenite already transformed into martensite when quenching stops at a given temperature, using the Koistinen-Marburger equation, f = 1 − e^(−0.011·(Ms − Tq)), where Ms is the martensite start temperature and Tq the temperature at which the part stopped cooling. The result is the percentage of martensite formed — whatever is missing from 100 % stays as retained austenite, which is soft, dimensionally unstable and able to transform later in service, distorting the part. Because the exponent is linear in the temperature difference, 63 °C below Ms already converts half the austenite, but 209 °C are needed to reach 90 % and the end of the transformation is asymptotic, never exact — which is precisely why precision parts get a cryogenic treatment after quenching. Enter the steel Ms temperature and the quench stop temperature.
Weld Dilution
Compute a weld's dilution, D = (melted base-metal area / total bead area)·100%, the proportion of the bead that came from the base metal rather than the filler. It is crucial in cladding and dissimilar-metal joints: high dilution mixes in more base metal, altering the bead's composition and properties (anti-corrosion cladding aims for low dilution). Enter the melted base-metal area and the total bead area.
Casting Cooling Modulus
Calculate the cooling modulus (or geometric modulus) of a casting, M = V ÷ A, dividing the volume V by the surface area A in contact with the mold. The result, in cm (length unit), is the parameter governing solidification speed: the larger the modulus, the slower the solidification (Chvorinov's rule says the time is proportional to the modulus squared). It is the basis of riser sizing in foundry — the modulus rule requires the riser modulus to be about 1.2 times that of the part, so it solidifies later and feeds the shrinkage, avoiding shrinkage cavities. Enter the part volume and area.
Welding Preheat Temperature
Estimate the preheat temperature for welding, Tp = 350·√(CE − 0.25), as a function of the steel's carbon equivalent (CE). Preheating reduces the cooling rate, giving hydrogen time to escape and preventing the formation of brittle martensite and cold cracks in the heat-affected zone. Steels with a high CE require more preheating. Enter the steel's carbon equivalent.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.