Welding Metallurgy, EN 1011 / AWS D1.1 WPS Qualification & Hydrogen Cold Cracking
Arc Welding Heat Input & IIW Carbon Equivalent (CE) Formula
Calculate Gross Arc Power (kW), EN 1011 Thermal-Efficiency-Factored Linear Heat Input Q (kJ/mm), IIW Carbon Equivalent CE_IIW (%), and Hydrogen Cold-Cracking Preheat Requirement.
Why EN 1011 multiplies V*I/v by arc efficiency k—and CE_IIW > 0.45% demands mandatory preheat against HAZ martensite cracking!
Every Welding Procedure Specification (WPS) under ISO/TR 17671, EN 1011-1, and AWS D1.1 bounds Linear Heat Input Q = (k * V * I * 60) / (1,000 * v_mm_min) kJ/mm—where Process Thermal Factor k under EN 1011-1 equals 0.80 for GMAW (MIG/MAG), SMAW (stick), and FCAW, 0.60 for GTAW (TIG), and 1.00 for submerged-arc SAW! Too low a heat input quenches the Heat-Affected Zone (HAZ) rapidly into brittle untempered martensite, whereas excessive heat input coarsens grain size in quenched-and-tempered steels! Simultaneously, Base-Metal Hardenability is scored from mill-certificate weight percentages via the International Institute of Welding Carbon Equivalent CE_IIW = %C + %Mn / 6 + (%Cr + %Mo + %V) / 5 + (%Ni + %Cu) / 15: once CE_IIW exceeds 0.45%, hydrogen-induced HAZ cold cracking becomes acute unless controlled preheat and low-hydrogen consumables slow the 800–500 °C cooling rate!
Verify on a Structural S355J2 Plate GMAW Spray-Transfer Pass—Arc_Voltage V = 28.0 V (B2), Welding_Current I = 260.0 A (B3 -> Gross Arc Power = 7.28 kW in E2), Torch_Travel_Speed v = 320.0 mm/min (B4), GMAW_Thermal_Factor k = 0.80 (B5), Carbon %C = 0.14% (B6), Manganese %Mn = 1.35% (B7), Cr+Mo+V Sum = 0.15% (B8), and Ni+Cu Sum = 0.30% (B9): Factored Heat Input Q hits (0.80 * 28 * 260 * 60) / 320,000 = 1.092 kJ/mm (E3), CE_IIW equals 0.14 + 0.225 + 0.030 + 0.020 = 0.415% (E4), and Preheat Status reads "LOW-HYDROGEN NO PREHEAT" (E5)!
| WPS Metallurgy KPI (28 V, 260 A, 320 mm/min, k=0.80; C=0.14, Mn=1.35) | Formula | Verified Output |
|---|---|---|
| Gross Electric Arc Power (kW) | (Arc_Voltage_V * Current_A) / 1000 | 7.28 kW |
| Factored Heat Input Q (kJ/mm) | (k * V * I * 60) / (1000 * Speed_mm_min) | 1.092 kJ/mm (1.588 @ 220 mm/min) |
| IIW Carbon Equivalent CE_IIW (%) | C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15 | 0.415% (0.535% @ C=0.22, CrMoV=0.35) |
| HAZ Cold-Cracking Preheat Rule | CE_IIW > 0.45% requires preheat | LOW-HYDROGEN NO PREHEAT |
EN 1011 Factored Heat Input & IIW Carbon Equivalent Formula
Validate Voltage V in [8, 50] V, Current I in [20, 1200] A, Travel_Speed > 10 mm/min, Thermal_Factor k in [0.5, 1.0], %C in (0, 1.2], and non-negative alloy additions!
=LET(vl_v, B2, cr_a, B3, tv_m, B4, ef_k, B5, cb_p, B6, mn_p, B7, cm_p, B8, nc_p, B9, IF(OR(vl_v < 8, vl_v > 50, cr_a < 20, cr_a > 1200, tv_m <= 10, ef_k < 0.5, ef_k > 1, cb_p <= 0, cb_p > 1.2, mn_p < 0, cm_p < 0, nc_p < 0), "Invalid WPS Input", LET(ce_v, cb_p + mn_p / 6 + cm_p / 5 + nc_p / 15, IF(ce_v > 0.45, "PREHEAT REQUIRED (CE > 0.45)", "LOW-HYDROGEN NO PREHEAT"))))Higher-Alloy Cr-Mo Steel Mill Heat & Slow Weave Pass Check (Set v = 220, C = 0.22, CrMoV = 0.35)
Switch to a higher-carbon low-alloy plate heat (%C B6 = 0.22%, %Cr+Mo+V B8 = 0.35%) welded slower at v B4 = 220.0 mm/min: Heat Input E3 rises to 1.588 kJ/mm while CE_IIW E4 jumps to 0.535%—flipping E5 immediately to "PREHEAT REQUIRED (CE > 0.45)"!
=IF(ISTEXT(E2), E2, ROUND((B5 * B2 * B3 * 60) / (1000 * B4), 3))Try the example
Use the original values or change them to test your understanding.