Steel Preheating Calculator
Calculate preheating temperature and t8/5 cooling time according to EN 1011-2, from chemical composition, thickness, hydrogen content and heat input.
What is preheating?
Preheating is heating the base material before welding to reduce the cooling rate of the weld and heat-affected zone (HAZ). This helps prevent cold cracking (hydrogen cracking) and improves weld quality.
🌡️ Preheating Temperature Calculator
Calculates the required preheating temperature according to EN 1011-2 (Method B) based on chemical composition, material thickness, hydrogen content, and heat input.
Steel Chemical Composition [%]
Technological Parameters
Heat Input Parameters
⏱️ Cooling time t8/5
How long the weld and HAZ take to cool from 800 °C to 500 °C. Too short and the HAZ hardens, raising the cold-cracking risk; too long and the grain coarsens, lowering toughness. Calculated from the heat input and thickness entered above.
Default values for the selected joint from the EN 1011-2 table — you can override them.Why is preheating important?
Prevents cold cracking
Slower cooling rate reduces the risk of hydrogen-induced cracking in steels with elevated hardenability.
Controls microstructure
Prevents formation of hard, brittle martensite in the HAZ.
Standards compliance
EN 1011-2 and ISO 15614 require documented preheating for certain materials.
Hydrogen diffusion
Higher temperatures allow hydrogen to diffuse out of the weld before it causes cracking.
Frequently asked questions
Preheating is required when carbon equivalent CET exceeds approximately 0.35, material thickness is greater than 25mm, or when using welding consumables with high hydrogen content.
CET = C + (Mn+Mo)/10 + (Cr+Cu)/20 + Ni/40. This is the formula according to EN 1011-2 considering main alloying elements affecting hardenability.
Tp = 697·CET + 160·tanh(d/35) + 62·HD^0.35 + (53·CET - 32)·Q - 328, where d is thickness [mm], HD is hydrogen content [ml/100g], Q is heat input [kJ/mm].
HD means diffusible hydrogen content in weld metal expressed in ml/100g. It depends on welding process and condition of welding consumables.
Preheating reduces cooling rate, which prevents formation of martensitic structures and hydrogen (cold) cracking in the heat-affected zone.
The main standard is EN 1011-2 - Welding. Recommendations for welding of metallic materials. Part 2: Arc welding of ferritic steels.
It is the time the weld and heat-affected zone take to cool from 800°C to 500°C, calculated to EN 1011-2 from heat input, plate thickness, working temperature and a joint shape factor. Too short and the HAZ hardens, raising the cold-cracking risk; too long and the grain coarsens and impact toughness drops.
That temperature belongs on a WPS
WeldStack's WPS builder has a preheat temperature field and this calculator built in — enter the parameters once and export an audit-ready PDF procedure, with welder qualifications and WPQR records in the same system. Free trial, no credit card.