Preheat Temperature Calculator
Calculate required preheat temperature to prevent cold cracking based on material composition, thickness, and environmental conditions. Based on IIW carbon equivalent method.
Input Parameters
Enter parameters and click Calculate to see results
Understanding Preheat Requirements
Preheat Temperature Effect on Thermal Gradients
Reducing stress and crack risk
⚠️ Critical: For CE > 0.6, preheat is mandatory. Without it → rapid cooling → martensite → brittle HAZ → cracking.
Why Preheat?
Preheating reduces the cooling rate of the weld, preventing formation of brittle martensite in the heat-affected zone (HAZ). It also reduces thermal gradients and residual stresses that can lead to cold cracking.
Carbon Equivalent (CE)
CE is a formula to assess hardenability and crack susceptibility of steel. Common formula:
CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15
- CE < 0.35: Low risk, minimal preheat
- CE 0.35-0.50: Medium risk, preheat 50-150°C
- CE 0.50-0.70: High risk, preheat 150-300°C
- CE > 0.70: Extreme risk, preheat 300-500°C + PWHT
Temperature Verification
- Temperature indicating crayons/sticks (Tempilstiks)
- Contact pyrometers (thermocouple)
- Infrared thermometers (check emissivity setting)
Preheat Zone
Heat to at least 75mm (3 inches) on each side of weld joint. For thick sections, preheat entire part if possible to avoid thermal gradients.