Free Engineering Tool
Welding Heat Input Calculator & ISO 4063
Calculate heat input (kJ/mm), cooling time t8/5, preheat recommendation, and carbon equivalent. Includes ISO 4063 process reference.
Results
Heat Input Calculation (EN 1011-1)
Heat input is the energy delivered per unit length of weld:
- η — thermal efficiency factor (process-dependent)
- V — arc voltage (volts)
- I — welding current (amps)
- S — travel speed (mm/min)
Thermal Efficiency Factors
| ISO 4063 No. | Process | η (EN 1011-1) |
|---|---|---|
| 121 | SAW (submerged arc) | 1.0 |
| 111 | SMAW (stick / MMA) | 0.8 |
| 131 | MIG (inert gas) | 0.8 |
| 135 | MAG (active gas) | 0.8 |
| 136 | FCAW (flux-cored) | 0.8 |
| 141 | TIG / GTAW | 0.6 |
Cooling Time t8/5 Estimation
The time to cool from 800°C to 500°C determines the resulting microstructure. Simplified Rosenthal 2D model for thick plates:
Carbon Equivalent & Preheat
The IIW carbon equivalent formula predicts weldability and preheat needs:
Practical Example
Given: Process 135 (η=0.8), V=28V, I=250A, S=300 mm/min, CE=0.42
Arc energy = (28 × 250 × 60) / (300 × 1000) = 1.40 kJ/mm
Heat input Q = 0.8 × 1.40 = 1.12 kJ/mm
CE = 0.42 → Fair weldability, preheat 100–150°C recommended
⚠️ Note: t8/5 estimation is simplified. Actual cooling depends on joint geometry, preheat, interpass temperature, and ambient conditions. Consult EN 1011-2 for critical applications.
| # | Process | Description | η |
|---|---|---|---|
| 111 | SMAW | Shielded metal arc (stick/MMA) | 0.8 |
| 114 | FCAW-S | Self-shielded flux-cored | 0.8 |
| 121 | SAW | Submerged arc welding | 1.0 |
| 131 | MIG | Metal inert gas (Ar) — aluminium, SS | 0.8 |
| 135 | MAG | Metal active gas (CO₂/Ar+CO₂) — carbon steel | 0.8 |
| 136 | FCAW-G | Flux-cored + active gas | 0.8 |
| 137 | FCAW-G | Flux-cored + inert gas | 0.8 |
| 138 | MCAW | Metal-cored wire + active gas | 0.8 |
| 141 | TIG | Tungsten inert gas (GTAW) | 0.6 |
| 15 | Plasma | Plasma arc welding | 0.6 |
| 311 | OAW | Oxy-acetylene welding | 0.45 |
| 42 | Friction | Friction welding | — |
| 52 | Laser | Laser beam welding | 0.9 |
Heat input Q = (η × V × I × 60) / (S × 1000) in kJ/mm. It controls the cooling rate, which determines the weld microstructure, hardness, toughness, and HAZ width.
Too high → grain coarsening, reduced toughness, excessive distortion. Too low → lack of fusion, hydrogen cracking risk.
Per EN 1011-1: SAW = 1.0, SMAW/MIG/MAG/FCAW = 0.8, TIG = 0.6. SAW is highest because the flux blanket traps nearly all heat. TIG loses more to radiation from the exposed arc.
t8/5 is the time for the HAZ to cool from 800°C to 500°C. This temperature range is critical for phase transformation in carbon steels. Short t8/5 (< 5s) → martensite formation. Long t8/5 (> 25s) → soft but potentially brittle microstructure.
IIW formula: CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15. Enter the value from the material test certificate, or use the Steel Grade Equivalent calculator to estimate from grade.
Preheat is needed when CE > 0.35, plate thickness > 25 mm, or hydrogen content is high. It slows cooling to prevent hydrogen cracking and martensite formation. Typical range: 75–250°C depending on CE and thickness.
The procedures described on this page were developed and field-tested by the Vibromera team using the Balanset-1A, a portable dual-channel balancer and vibration analyzer for on-site rotor balancing.
Professional instruments for industrial applications.
Nikolai Shelkovenko
Nikolai Shelkovenko is a vibration analysis engineer and the founder and CEO of Vibromera. For more than 15 years he has balanced rotating equipment in the field rather than on a test bench: mulchers, industrial fans, crushers, centrifuges, shafts and spindles. That work is what the Balanset instruments grew out of — they were designed as a tool a specialist can carry to the machine and use alone, on site, not as laboratory equipment. Vibromera was founded in 2017 and has been based in Porto, Portugal, since 2023. Development, assembly and support of the Balanset line all happen here. The flagship instrument is the Balanset-1A, a portable analyser for single- and two-plane balancing and for vibration diagnostics. Nikolai is personally involved in customer support, in working through difficult balancing cases and in the development of the software. He works with customers worldwide, in any language.
