Welding Heat Input & Carbon Equivalent Calculator (AWS D1.1 / ASME IX)
Calculate arc welding heat input (kJ/in and kJ/mm), thermal process arc efficiency (η), IIW Carbon Equivalent (CE), crack susceptibility parameter (P_cm), and minimum preheat temperature under AWS D1.1 structural welding code.
Welding Arc Parameters
Base Metal Chemistry (% Weight)
Welding Metallurgy Output
Weld Bead Morphology & Heat-Affected Zone (HAZ) Isotherms
Vector cross-section displaying molten weld pool fusion boundary, Heat-Affected Zone grain-growth boundary, and thermal isotherms based on calculated heat input.
Welding Metallurgy Physics: Heat Input & Carbon Equivalent
Heat input controls the cooling rate ($t_{8/5}$) of the weld and Heat-Affected Zone (HAZ). Rapid cooling creates brittle untempered martensite, leading to hydrogen-induced cold cracking.
H = \frac{60 \times V \times I}{1000 \times S} \times \eta \quad (\text{kJ/in or kJ/mm})
2. IIW Carbon Equivalent (CE):
CE_{\text{IIW}} = C + \frac{Mn}{6} + \frac{Cr + Mo + V}{5} + \frac{Ni + Cu}{15}
3. Ito-Bessyo Crack Susceptibility Parameter (P_cm):
P_{cm} = C + \frac{Si}{30} + \frac{Mn + Cu + Cr}{20} + \frac{Ni}{60} + \frac{Mo}{15} + \frac{V}{10} + 5B
4. AWS D1.1 Preheat Rules:
CE \le 0.40 \implies 50^\circ\text{F} \quad | \quad 0.40 < CE \le 0.45 \implies 150^\circ\text{F} \quad | \quad CE > 0.45 \implies 225^\circ\text{F}+
1. Hydrogen-Induced Delayed Cold Cracking (HICC)
When welding steel with $CE > 0.42$, fast cooling forms brittle martensite in the HAZ. Diffusible hydrogen from humid air, dirty wire, or damp flux migrates into microscopic grain boundaries under weld shrinkage stress, causing delayed cracks to pop 24 to 72 hours AFTER the weld passes inspection.
2. Excessive Heat Input Toughness Annihilation
Pumping high heat input ($>60\text{ kJ/in}$) to speed up welding keeps the HAZ in the austenite grain-growth range for too long. Massive coarse grains form, destroying Charpy V-Notch impact toughness and causing brittle fracture under seismic or low-temperature impact.
3. Short-Circuit GMAW Cold Lapping (Lack of Fusion)
Using short-circuit transfer MIG on plates thicker than 3/16" produces an aesthetically smooth bead that has zero penetration into the sidewall. The molten puddle rolls over cold steel without fusing, creating invisible lack-of-fusion defects that fail bend tests catastrophically.
4. Omitting Interpass Temperature Controls
On multi-pass welds, laying down the next bead while the joint is over $550^\circ\text{F}$ slows the cooling rate excessively. High-strength quenched-and-tempered steels (like A514/Hardox) will over-temper and permanently lose up to 30% of their tensile yield strength.
5. Burn-Through on Thin Backing Regimes
Welding plates under 1/8" at travel speeds below 8 IPM concentrates heat input into 2D sheet conduction. The puddle cannot conduct heat away quickly enough, causing the weld pool to sag and blow through the root opening.